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Cell Biology/Cell types/Eukaryotes

Eukaryotes house a distinct nucleus, a structure in which the genetic material (DNA) is contained, surrounded by a membrane much like the outer cell membrane. Eukaryotic cells are found in most algae, protozoa, all multicellular organisms (plants and animals) including humans. The genetic material in the nucleus forms multiple chromosomes that are linear and complexed with proteins that help the DNA 'pack' and are involved in regulation of gene expression.

The cells of higher plants differ from animal cells in that they have large vacuoles, a cell wall, chloroplasts, and a lack of lysosomes, centrioles, pseudopods, and flagella or cilia. Animal cells do not have the chloroplasts, and may or may not have cilia, pseudopods or flagella, depending on the type of cell.

Comparing Prokaryotic and Eukaryotic Cells
All cells have several basic features in common: they are all bounded by a selective barrier, plasma membrane. Cytosol is a jellylike substance that is semifluid. All cells contain chromosomes which carry genes in the form of DNA, and ribosomes that make proteins according to instructions from the gene. The major difference between prokaryotic and eukaryotic cells is the location of their DNA. In eukaryotic cell, DNA is found at the nucleus, which is bounded by a double membrane. (the word eukaryotic is from the Greek eu, true, and karyon, kernel, here referring to the nucleus).

Eukaryotic cells are much larger than prokaryotic cells; size is general aspect of cell structure that relates to function. The logistics of carrying out cellular metabolism sets limits on cell size. At the lower limit, the smallest cells, known are bacteria called mycoplasmas have diameters between 0.1 and 1.0mm. These are the smallest packages with enough DNA to program metabolism and enough enzymes and other cellular equipment to carry out the activities necessary for a cell to sustain itself and reproduce.

Metabolic requirements also impose theoretical upper limits on the size that is practical for a single cell. Plasma membrane functions as a selective barrier that allows sufficient passage of oxygen, nutrients, and wastes to service the entire cell. For each square micrometer of membrane, only a limited amount of a particular substance can cross per second, so the ratio of surface area to volume is critical. As a cell increases in size, its volume grows proportionately more than its surface area. Area is proportional to a linear dimension squared, whereas volume is proportional to the linear dimension cubed. Therefore a smaller object has a greater ration of surface area to volume.

The need for a surface area sufficiently large to accommodate the volume helps explain the microscopic size of most cells, and the narrow, elongated shapes of others, such as nerve cells. Larger organisms has more cells compare to smaller cells. High ratio of surface area to volume is especially important in cells that exchange a lot of material with their surroundings such as intestinal cells. Such cells may have many long, thin projections from their surface called microvilli, which increase surface area without an appreciable increase in volume.

Animal Cells
Flagellum: locomotion organelle present in some animal cells; composed of a cluster of microtubules within an extension of the plasma membrane.

Centrosome: region where the cell's microtubules are initiated contains a pair of centrioles which function is unknown.

Cytoskeleton: reinforces cell's shape, functions in cell movement components are made of protein. It includes microfilaments, intermediate filaments, and microtubules.

Microvilli: projections that increase the cell's surface area.

Peroxisome: organelle with carious specialized metabolic functions; produces hydrogen peroxide as a by-product, then converts it to water.

Mitochondrion: organelle where cellular respiration occurs and most ATP is generated.

Lysosome: digestive organelle where macromolecules are hydrolyzed.

Golgi apparatus: organelle active in synthesis, modification, sorting, and secretion of cell products.

Ribosomes: complexes (small brown dots) that make proteins; free in cytosol or bound to rough ER or nuclear envelope.

Plasma membrane: membrane enclosing the cell

Endoplasmic Reticulum (ER): network of membraneous sacs and tube; active in membrane synthesis and other synthetic and metabolic processes; has rough (ribosome-studded) and smooth regions. (Rough ER, and Smooth ER)

Nucleus: nucleus contains: Nuclear envelope: double membrane enclosing the nucleus; perforated by pores; continuous with ER                 Nucleolus: structure involved in production of ribosomes; a nucleus has one or more nucleoli Chromatin: material consisting of DNA and proteins; visible as individual chromosomes in a dividing cell

In animal cells, lysosomes, centrosomes with centrioles, and flagella are present but not in plant cells.

Plant Cell
Cell Wall: outer layer that maintains cell's shape and protects cell from mechanical damage; made of cellulose, other polysaccharide, and protein.

Plasmodesmata: channels through cell walls that connect the cytoplasms of adjacent cells.

Chloroplast: photosynthetic organelle; converts energy of sunlight to chemical energy stored in sugar molecules.

 Central vacuole: prominent organelle in older plant cells; functions include storage, breakdown of waste products, hydrolysis of macromolecules; enlargement of vacuole is a major mechanism of plant growth.

Nucleus: nucleus contains: Nuclear envelope: double membrane enclosing the nucleus; perforated by pores; continuous with ER                 Nucleolus: structure involved in production of ribosomes; a nucleus has one or more nucleoli Chromatin: material consisting of DNA and proteins; visible as individual chromosomes in a dividing cell

Golgi apparatus: organelle active in synthesis, modification, sorting, and secretion of cell products.

Endoplasmic Reticulum (ER): network of membraneous sacs and tube; active in membrane synthesis and other synthetic and metabolic processes; has rough (ribosome-studded) and smooth regions. (Rough ER, and Smooth ER)

Ribosomes: complexes (small brown dots) that make proteins; free in cytosol or bound to rough ER or nuclear envelope.

Cytoskeleton: reinforces cell's shape, functions in cell movement components are made of protein. It includes microfilaments, intermediate filaments, and microtubules.

In plant cell, chloroplasts, central vacuole, cell wall, and plasmodesmata are present but not in animal cells. Chromatin in the plant cell is a primary protein

Nucleus
The nucleus contains most of the genes in the eukaryotic cell; some genes are located in mitochondria and chloroplast. It is generally the most conspicuous organelle in a eukaryotic cell. The nuclear envelope encloses the nucleus, sparating its contents from the cytoplasm. The nuclear envelope is a double membrane, each a lipid bilayer with associated proteins. The envelope is perforated by pore structure that are about 100nm in diameter. At the lip of each pore, the inner and outer membranes of the nuclear envelope are continuous. Pore complex lines each pore and regulates the entry and exit of most proteins and RNAs, as well as large complexes of macromolecules. Except at the pores, the nuclear side of the envelope is lined by the nuclear lamina, a netlike array of protein filaments that maintains the shape of the nucleus by mechanically supporting the nuclear envelope. Also nuclear matrix, a framework of fibers extending throughout the nuclear interior, present.

Chromosomes are organized DNA units that carry the genetic information. Each chromosome is made up of material called chromatin, a complex of proteins and DNA. Stained chromatic usually appears as a diffuse mass, byt as a cell prepares to divide, the thin chromatin fibers coil up and condense thick enough to be distinguished as chromosomes. Each eukaryotic species has a characteristic number of chromosomes. For example human has 46 chromosomes.

Nucleolus is a prominent structure within the nondividing nucleus. Ribosomal RNA (rRNA) is synthesized from instructions in the DNA; in nucleolus, proteins imported from the cytoplasm are assembled with rRNA into large and small ribosomal subunits. Theses subunits then exit the nucleus through the nuclear pores to the cytoplasm, where a large and a small subunit can assemble into a ribosome. the number depends on the species and the stage in the cell's reproductive cycle.

The Nucleus directs protein synthesis by synthesizing messenger RNA (mRNA) according to instructions provided by the DNA. The mRNA is then transported to the cytoplasm via the nuclear pores. Once an mRNA molecule reaches the cytoplasm, ribosomes translate the mRNA's genetic message into the primary structure of a specific poly peptide.

Ribosomes
Ribosomes are complexes made of ribosomal RNA and protein; ribosomes are the cellular components that carry out proteins synthesis, also known as protein factories. Cells that have high rates of protein synthesis have particularly large number of ribosomes. Cells active in protein synthesis also have prominent nucleoli. Ribosomes build proteins in two cytoplasmic locales. Free ribosomes are suspended in the cytosol, while bound ribosomes are attached to the outside of the endoplasmic reticulum or nuclear envelope. Bound and free ribosomes are structurally identical, and ribosomes can alternate between the two roles. Most of proteins are made on free ribosomes function within the cytosol. Bound ribosomes generally make proteins that are destined for insertion into membranes, for packaging within certain organelles such as lysosomes, or for export from the cell (secretion).

The Endomembrane System
Endomembrane system carries out a variety of tasks in the cell. These tasks include synthesis of proteins and their transport into membranes and organelles or out of the cell, metabolism and movement of lipids, and detoxification of poisons. The membrane of this system are related either through direct physical continuity or by the transfer of membrane segments as tiny vesicles. The various membranes are not identical in structure and function; the thickness, molecular composition, and types of chemical reactions carried out in a given membrane are not fixed but modified several times during the membrane's life. The endomembrane system includes the nuclear envelope, the endoplasmic reticulum, the Golgi apparatus, lysosomes, various kinds of vacuoles, and the plasma membrane.

Endoplasmic Reticulum (ER)
Endoplasmic reticulum (ER) is an extensive network of membrane that it accounts for more than half the total membrane in many eukaryotic cells. The word endoplasmic means "within the cytoplasm", and reticulum is Latine for "little net". The ER consists of a network of membranous tubules and sacs called cisternae. The ER membrane separates the internal compartment of the ER, ER lumen (cavity) or cisternal space, from the cytosol. Since ER membrane is continuous with the nuclear envelope, the space between the two membranes of the envelope is continuous with the lumen of the ER. Smooth ER lacks ribosomes on its outer surface, and Rough ER has ribosomes on the outer surface of the membrane. Ribosomes are also attached to the cytoplasmic side of the nuclear envelope's outer membrane.

Smooth ER- The smooth ER functions in diverse metabolic processes, which vary with cell type. These processes include synthesis of lipids, metabolism of carbohydrates, and detoxification of drugs and poisons. Enzymes of the smooth ER are important in the synthesis of lipids, including oils, phospholipids, and steroids. Sex hormones of vertebrates and the various steroid hormones are produced by the smooth ER in animal cells. Other enzymes of the smooth ER help detoxify drugs and poisons in liver cells. Detoxification involves adding hydroxyl groups to drug molecules, making them more soluble and easier to flush from the body. For example, sedative phenobarbital and other barbiturates are the drugs that metabolized in this manner by smooth ER in liver cells. Barbiturates, alcohol, and many other drugs induce the proliferation of smooth ER and its associated detoxification enzymes, therefore, increasing tolerance to the drugs; in other words, higher doses are required to achieve a particular effect. Also, because some of the detoxification enzymes have relatively broad action, the proliferation of smooth ER in response to one drug can increase tolerance to other drugs as well. The smooth ER also stores calcium ions; in muscle cells, a specialized smooth ER membrane pumps calcium ions from the cytosol into the ER lumen. When a muscle cell is stimulated by a nerve impulse, calcium ions rush back across the ER membrane into the cytosol and trigger contraction of the muscle cell.

Rough ER- Many times of cells secrete proteins produced by ribosomes attached to rough ER. As a polypeptide chain grows from a bound ribosomes, it is threaded into the ER lumen through a pore formed by a protein complex in the ER membrane. As the new protein enters the ER lumen, it folds into its native shape. Most secretory proteins are glycoproteins, which have carbohydrates covalently bonded to them. After secretory proteins are formed, the ER membrane keeps them separate from proteins that are produced by free ribosomes and will remain in the cytosol. Secretory proteins depart from the ER wrapped in the membranes of vesicles that bud like bubbles from a specialized region called transitional ER. Transport vesicles are the vesicles in transit from one part of the cell to another. Rough ER is also a membrane factory for the cell; it grows in place by adding membrane proteins and phospholipids to its own membrane. As polypeptide destined to be membrane proteins grow from the ribosomes, they are inserted into the ER membrane and are anchored there by their hydrophobic portions. The rough ER makes its own membrane phospholipids; enzymes build into the ER membrane assemble phospholipids from precursors in the cytosol. The ER membrane expands and is transferred in the form of transport vesicles to other components of the endomembrane system.

Golgi Apparatus
Golgi is a center of manufacturing, warehousing, sorting, and shipping. The products of the ER are modified and stored and then sent to other destinations. Golgi apparatus is extensive in cells specialized for secretion. The Golgi apparatus consists of flattened membranous sac, cisternae. The membrane of each cisterna in a stack separates ints internal space from the cytosol. Besicles concentrated in the vicinity of the Golgi apparatus are engaged in the transfer of material between parts of the Golgi and other structures. Golgi stack has a distinct structural polarity with the membrane of cisternae on opposite side of the stack different in thickness and molecular composition. The two poles of a Golgi stack are referred to as the cis face and the trans face; cis is the receiving and trans is shipping departments of the Golgi apparatus. The cis face is usually located near ER. Transport vesicles move material from the ER to the Golgi apparatus. A vesicle that buds from the ER can add its membrane and the contents of its lumen to the cis face by fusing with a Golgi membrane. The trans face give rise to vesicles, which pinch off and travel to other sites. The products of ER are usually modified during their transit from the cis region to the trans region of the Golgi. Various Golgi enzymes modify the carbohydrate portions of glycoproteins; carbohydrates are first added to proteins in the rough ER during the process of polypeptide synthesis. The carbohydrate on the resulting glycoprotein is then modified as it passes through the rest of the ER and the Golgi. The Golgi removes some sugar monomers and substitutes other, producing a large variety of carbohydrates. In addition, the Golgi apparatus manufactures certain macromolecules by itself. Many polysaccharides secreted by cells are Golgi products, including pectins and certain other non-cellulose polysaccharides made by plant cells and incorporated along with cellulose into their cell walls. Similar to secretory proteins, non-protein Golgi products will be secreted depart from the trans face of the Golgi inside transport vesicles that eventually fuse with the plasma membrane.

The Golgi manufactures and refines its products in stages, with different cisternae containing unique teams of enzymes. Recent research has give rise to a new model of the Golgi as a more dynamic structure; According to the cisternal maturation model, the cisternae of the Golgi actually progress forward from the cis to the tras face of the Golgi, carrying and modifying their cargo as they move. Before a Golgi stack dispatches its products by budding vesicles fromt he trans face, it sorts these products and targets them for various parts of the cell. Molecular identification tags, such as phosphate groups added to the Golgi products, aid in sorting. Transport vesicles budded fromt he Golgi may have external molecules on their membranes that recognize "docking site" on the surface of specific organelles or on the plasma membrane, therefore, targeting the vesicle appropriately.

Lysosomes
Lysosome is a membranous sac of hydrolytic enzymes that an animal cell uses to digest macromolecules. Lysosomal enzymes work best in the acidic environment found in lysosomes. If a lysosome breaks open or leaks its contents, the released enzymes are not very active because the cytosol has a neutral pH. However, excessive leakage from a large number of lysosomes can destroy a cell by autodigestion. Hydrolytic enzymes and lysosomal membrane are made by rough ER and then transferred to the Golgi apparatus for further processing. Proteins of the inner surface of the lysosomal membrane and the digestive enzymes are spared from destruction by having three dimensional shapes that protect vulnerable bonds from enzymatic attack.

Phagocytosis is a process that amoebas and many other protists eat by engulfing smaller organisms or other food particles. The food vacuole formed, and then fuses with a lysosome and digests the food. Digestion products pass into cytosol and become nutrients for the cell. In human body, white blood cell helps defend the body by engulfing and destroying bacteria and other invaders.

Lysosome use their hydrolytic enzymes to recycle the cell's own organic material; this is called autophagy. During autophagy, damaged organelle or small amount of cytosol become surrounded by a double membranes, and lysosome fuses with the outer membrane of their vesicle. The lysosomal enzymes dismantle the enclosed material, and the organic monomers are returned to the cytosol for reuse. The lysosomes become engorged with indigestible substrates, which begin to interfere with other cellular activities.

Vacuoles
Vacuoles are membrane-bounded vesicles whose functions vary in different kinds of cells. Food vacuoles are formed by phagocytosis. Many freshwater protists have contractile vacuoles that pump excess water out of the cell, thereby maintaining a suitable concentration of ions and molecules inside the cell. In plants and fungi, which lacks lysosomes, vacuoles carry out hydrolysis;

The central vacuole develops by the coalescence of smaller vacuoles, themselves derived from the endoplasmic reticulum and Golgi apparatus. The vacuolar membrane is selective in transportin solutes. As result, the solution inside the central vacuole is called cell sap, is different in composition from the cytosol. It can hold reserves of important organic compounds such as proteins stockpiled in the vacuoles of storage cells in seeds. Also it is the plant cell's main repository of inorganic ions, such as potassium and chloride. Many plant cells use their vacuoles contain pigments that color the cells. Vacuoles may also help protect the plant against predators by containing compounds that are poisonous or unpalatable to animals. The vacuole has a major role in the growth of plant cells, which enlarge as their vacuoles absorb water, enabling the cell to become larger with a minimal investment in new cytoplasm.

Mitochondria and Chloroplasts
Mitochondria and chloroplasts are the organelles that convert energy to forms that cells can use for work. Mitochondria are the site of cellular respiration, the metabolic process that generates ATP by extracting energy from sugars, fats, and other fuels with the help of oxygen. Chloroplasts, are found in plants and algae, and they are the sites of photosynthesis. They convert solar energy to chemical energy by absorbing sunlight and using it to drive the synthesis of organic compounds such as sugar from carbon dioxide and water. Both of them are not part of endomembrane system. Mitochondria have two membrane separating their innermost space from the cytosol, and chloroplasts have three. The membrane proteins of mitochondria and chloroplasts are made not by ribosomes bound to the ER, but by free ribosomes in the cytosol and by ribosomes contained within these organelles themselves. They also contain small amount of DNA that programs the synthesis of the proteins made on the organelle's ribosomes. Mitochondria and chloroplasts are semiautonomous organelles that grow and reproduce within the cell.

Mitochondria Mitochondria are found in all eukaryotic cells; Some cells have a single large mitochondrion, but more often a cell has hundreds or thousands of mitochondria. The number correlates with the cell's level of metabolic activity. The mitochondrion is enclosed by two membranes, each a phospholipid bilayer with a unique collection of embedded proteins. The outer membrane is smooth, but the inner membrane is convoluted, with infolding called cristae. The inner membrane divides the mitochondrion into two internal compartments : the first is the inter-membrane space, the narrow region between the inner and outer membranes and the second compartment, the mitochondrial matrix, is enclosed by the inner membrane. the matrix contains many different enzymes as well as the mitochondrial DNA and ribosomes. Enzymes in the matrix catalyze some steps of cellular respiration. Other proteins that function in respiration, including the enzyme that makes ATP are built into the inner membrane, As highly folded surface, the cristae give the inner mitochondrial membrane a large surface ares, thus enhancing the productivity of cellular respiration.

Chloroplasts The chloroplast is a specialized member of related plant organelles called plastids. Chloroplasts contain the green pigment chlorophyll, along with enzymes and other molecules that function in the photosynthetic production of sugar. Its shape is lens-shaped and found in leaves. The contents of a chloroplast are partitioned from the cytosol by an envelope consisting of two membranes separated by a very narrow intermembrane space. Inside the chloroplast is another membranous system in the form of flattened, inter-connected sacs called thylakoids. Thylakoids are stacked like poker ships, and each stack is called granum. The fluid outside the thylakoids is the stroma which contains the chloroplast DNA and ribosomes as well as many enzymes. The membranes of the chloroplast divide the chloroplast space into three compartments: the intermembrane space, the stroma, and the thylakoid space.

Cytoskeleton
Cytoskeleton is a network of fibers extending throughout the cytoplasm. It plays a major role in organizing the structure and activities of the cell. It is composed of three types of molecular structure: microtubules, microfilaments, and intermediate filaments. The main function of the cytoskeleton is to give mechanical support to the cell and maintain its shape. Cytoskeleton is stabilized by balance between opposing forces exerted by its elements. The cytoskeleton is more dynamic than an animal skeleton; it can be quickly dismantled in one part of the cell and reassembled in a new location, changing the shape of the cell. Also several types of cell motility involve the cytoskeleton. the cell motility encompasses both changes in cell location and more limited movements of parts of the cell. Cell motility require the interaction of the cytoskeleton with motor proteins. Cytoskeletal elements and motor proteins work together with plasma membrane molecules to allow whole cells to move along fibers outside the cell. The cytoskeleton is also involved in regulating biochemical activities in the cell in response to mechanical stimulation forces exerted by extracellular molecules via cell-surface proteins are apparently transmitted into the cell by cytoskeletal elements, and the forces may even reach the nucleus.

Microtubules- thickest

All eukaryotic cells have microtubules; the wall of the hollow tube is constructed from a globular protein called tubulin. Each tubulin protein is a dimer, a molecule made up of two subunits. A tubulin dimer consists of two slightly different polypeptides, alpha-tublin, and beta-tubulin. Microtubules grow in length by adding tubulin dimers. Due to the architecture of a microtubules, its two ends are slightly different; one end can accumulate or release tubulin dimers at a much higher rate than the other, therefore, growing and shrinking significantly during cellular activities. This is called the "plus end", not because it can only add tubulin proteins but because it's the end where both "on" and "off" rates are much higher. Microtubules shape and support the cell and also serve as tracks along which organelles equipped with other proteins can move.

In animal cells, microtubules grow out from a centrosomes, a region that is often located near the nucleus and considered a "microtubule-organizing center". Theses microtubules function as compression-resisting girders of the cytoskeleton. Within the centrosome are a pair of centrioles, each composed of nine sets of triplet microtubules arrange in a ring. Before division, the centrioles replicate; although centrosomes with centrioles may help organize microtubule assembly in animal cell,s they are not essential for this function in all eukaryotes.

Also specialized arrangement of microtubules is responsible for the beating of flagella and cilia. There are microtubule containing extensions that project from some cells. When cilia or flagella extend from cells that are held in place as part of a tissue layer, they can move fluid over the surface of the tissue. Flagella and cilia different in their beating patterns. A flagellum has an undulating motion that generates force in the same direction as the flagellum's axis. However cilia work more like oars, with alternating power and recovery strokes generating force in a direction perpendicular to the cilium's axis. A cillium may also act as a signal-receiving "antenna" for the cell. Cilia that have this function are nonmotile, and there is only one per cell. Membrane proteins on this kind of cilium transmit molecular signals from the cell's movement to its interior, triggering signaling pathways that may lead to changes in the cell's activities. Cillia-based signaling appears to be crucial to brain function and to embryonic development. Motile cilia and flagella share a common ultrastructure; each has a core of microtubules sheathed in an extension of the plasma membrane. Nine doublets of microtubules, the members of each parit sharing part of their walls, are arranged in a ring. This arrangement, referred to as the "9+2" pattern, is found in all eukaryotic flagella and motile cilia. Non-motile primary cilia have "9+0" pattern, lacking the central pari of microtubules. The microtubule assembly of a cilium or flagellum is anchored in the cell by a basal body, which is structurally very similar to a centriole.

In flagella and motile cilia, flexible cross-linking proteins, evenly spaced along the length of the cilium or flagellum, connect the outer doublets to each other and to the two central microtubules Each outer doublet also has paris of protruding proteins spaced along its length and reaching toward the neighboring doublet; These are large motor proteins called dyneins, composed of several polypeptides. Dyneins are responsible for the bending movements of the organelle. A dynein molecule performs a complex cycle of movements cause by changes in these shape of the proteins, with ATP providing the energy for these changes. The mechanics of dynein-based bending involve a process that resembles walking. A typical dynein protein has two "feet" that "walk" along the microtubule of the adjacent doublet, one foot maintaining contact while the other releases and reattaches one step further along the microtubules. Without any restraints ont he movement of the microtubules doublets, one doublet would continue to "walk" along and slide past the surface of the other, elongating the cilium or flagellum rather than bending it.

Microfillaments- thinnest

Microfilaments are solid rods about 7nm in diameter. They are also called as actin filaments because they are build from molecules of actin, a globular protein. A microfilament si a twisted double chain of actin subunits. Microfilaments can form structural networks, due to the presence of proteins that bind along the side of an actin filament and allow a new filament to extend as a branch. The structure role of microfilaments in the cytoskeleton is to bear tension. A cortical microfilaments, a three-dimensional network formed by microfilaments just inside the plasma membrane, helps support the cell's shape. This network give the outer cytoplasmic layer of a cell called the cortex.

In animal cells specialized for transporting materials across the plasma membrane, such as intestinal cells, bundles of microfilaments make up the core of microvilli. Microfillaments are well known for their role in cell motility, particularly as part of the contractile apparatus of muscle cells (myosin). Localized contraction brought about by actin and myosin also plays a role in amoeboid movement, which a cell such as an amoeba crawls along a surface by extending and flowing into cellular extension called pseudopodia. pseudopodia extend and contract through the reversible assembly of actin subunits nto microfilaments and of microfilaments into networks that convert cytoplasm fro a sol to a gel. The pseudopodium extends until the actin reassembles into a network.

In plant cells, both actin-myosin interactions and sol-gel transformations brought about by actin may be involved in cytoplasmic streaming, a circular flow of cytoplasm within cells.

intermediate filaments- middle range intermediate filaments are larger than the diameter of microfilaments but smaller than that of microtubules. Specialized for bearing tension (like microfilaments), intermediate filaments are a diverse class of cytoskeletal elements. Each type is constructed from a different molecular subunit such as keratins. Intermediate filaments are more permanent fixture of cells than are microfilaments and microtubules. Even after the death of the cell, intermediate filament networks often persist. Intermediate filaments are important in reinforcing the shape of a cell and fixing the position of certain organelles. For instance, the nucleus commonly sits within a cage made of intermediate filaments, fixed in location by braches of the filaments that extend into the cytoplasm. Other intermediate filaments make p the nuclear lamina that lines the interior of the nuclear envelope. In case where the shape of the entire cell is correlated with function, intermediate filaments support that shape.

Cell Wall
Cell wall is an extracellular structure of plant cell that distinguishes them from animal cells. The wall protects the plant cell, maintains its shape, and prevents excessive uptake of water. The strong walls of specialized cells hold the plant up against the force of gravity. Plant cell walls are much thicker than the plasma membrane, and the exact chemical composition of the wall varies from species to species and even from one cell type to another in the same plant, but basic design of the wall is consistent. Microfibrils made of the polysaccharide cellulose are synthesized by an enzyme called cellulose synthase and secreted to the extracellular space, where they become embedded in a matrix of other polysaccharides and proteins. This combination of materials, strong fibers in a "ground substance" (matrix), is the same basic architectural design found in steel-reinforced concrete and in fiberglass.

A young plant cell first secrets a thins and flexible wall called the primary cell wall; as the cell grows, the cellulose fibrils are oriented at right angles to the direction of cell expansion, possibly affecting the growth pattern. Between primary walls of adjacent cell is the middle lamella, which is a thin layer rich in sticky polysaccharides pectins. The middle lamella flues adjacent cells together. When the cell mature and stops growing, it strengthens its wall. Some plant cells do this simply by secreting hardening substances into the primary wall, but other cells add a secondary cell wall between the plasma membrane and the primary wall. Then secondary wall, often deposited in several laminated layer, has a strong and durable matrix that afford the cell protection and support.

title: Cell Biology/Cell types/Eukaryotes


text:
Wikipedia:Articles for deletion/TPS Pakistan

The result was keep. Jo-Jo Eumerus (talk, contributions) 19:04, 26 September 2017 (UTC)

TPS Pakistan

 * – ( View AfD View log  Stats )

No in-depth coverage found. Fails WP:NCORP.  Greenbörg  (talk)  12:59, 19 September 2017 (UTC)
 * Note: This debate has been included in the list of Pakistan-related deletion discussions. Mark the trainDiscuss 15:54, 19 September 2017 (UTC)
 * Note: This debate has been included in the list of Companies-related deletion discussions. Mark the trainDiscuss 15:54, 19 September 2017 (UTC)

 * Keep Meets WP:GNG, see the following coverage in refs:         and others.  Mar4d  ( talk ) 12:41, 20 September 2017 (UTC)
 * Keep Just edited the article. Replaced individual company references with newspaper references. Removed previous promotional content as best as I could. Will continue soon as more references become available.---Ngrewal1 (talk) 00:17, 22 September 2017 (UTC)
 * Keep - Apart from the refs already in the article, here are more: PakObserver & Pakistan Today. - Mfarazbaig (talk) 09:42, 23 September 2017 (UTC)

source: wikimedia

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


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User:Michael Joseph Chiderah

Michael Joseph Chiderah, the first son in the family of eight, born in the 24th January, 1998; born and bred in the city of Aba and I'm from Isiala Ngwa North in Abia State, I study mathematics and statistics, in Nekede, Owerri, Imo State, Nigeria. . ..

title: User:Michael Joseph Chiderah


text:
Robotics/Components/Actuation Devices/Air muscle

The concept of a fully autonomous, mission capable, legged robot has for years been a Holy Grail of roboticists. Development of such machines has been hampered by actuators and power technology and control schemes that cannot hope to compete with even some of the “simplest” systems found in the natural world.

Biomimetics
Faced with such a daunting task, it is not surprising that more and more researchers are beginning to look toward biological mechanisms for inspiration.

Biology provides a wealth of inspiration for robot design. There are millions of species of animals that have evolved efficient solutions to locomotion and locomotion control.

Legs, wheels, treads
Insects in particular are well known not only for their speed and agility but also for their ability to traverse some of the most difficult terrains imaginable; insects can be found navigating rocky ground, walking upside down, climbing vertical surfaces, or even walking on water. Furthermore, insects almost instantly respond to injury or removal of legs by altering stance and stepping pattern to maintain efficient locomotion with a reduced number of legs [1]. Given the ultimate goal of autonomy, this ability to reconfigure locomotion strategies will be crucial to the robustness of autonomous robots [2].

There are of course other mechanisms capable of producing locomotion, most notably wheels and caterpillar treads. While these devices are admittedly much easier to design and implement, they carry with them a set of disadvantages that inhibits their use in military or exploratory applications. Primary amongst these limitations is the simple fact that wheels, and to a lesser extent treads, are not capable of traversing terrain nearly as complex as that which a legged vehicle is capable of maneuvering over [2]. Even wheeled and tracked vehicles designed specifically for harsh terrains cannot maneuver over an obstacle significantly shorter than the vehicle itself; a legged vehicle on the other hand could be expected to climb an obstacle up to twice its own height, much like a cockroach can. This limitation on mobility alone means that in any environment without fairly flat, continuous terrain, a walking vehicle is far preferable to a wheeled or tracked one. Legged vehicles are also inherently more robust than those dependent on wheels or tracks. The loss of a single leg on a hexapod will result in only minimal loss in maneuverability; on a wheeled vehicle a damaged wheel could spell the end of mobility, and a damaged caterpillar tread almost always results in catastrophic failure. Finally, legged vehicles are far more capable of navigating an intermittent substrate—such as a slatted surface—than wheeled vehicles [3].

Given the preceding argument for the use of legged locomotion in certain environments, one is left with the daunting task of actually designing an efficient legged robot. While such a task is difficult to say the least, nature has provided us—literally—with a world full of templates. Animals can be found that are capable of navigation over almost any surface, and it is from these natural solutions to locomotion problems that engineers are more and more often seeking inspiration.

Actuators
2. Actuator Selection The selection of actuators plays a pivotal role in any mobile robot design, as the shape, size, weight and strength of an actuator must all be taken into account, and the power source of the actuators often provides the greatest constraint on a robot’s potential abilities. Actuators perform like muscles and joints of a robot to bring about motion.

Muscle
Biological organisms have a great advantage over mechanical systems in that muscle, nature’s actuator of choice, has a favorable force-to-weight ratio and requires low levels of activation energy. Their tunable passive stiffness properties are also well suited for energy efficient legged locomotion. The most frequently used actuators, electric motors and pneumatic/hydraulic cylinders, are far from equivalent to their biological counterparts.

Electric motor
Electric motors are probably the most commonly used actuation and control devices in modern day robotics, and with good reason. Motors in a wide range of sizes are readily available and they are very easy to control. These devices are also fairly easy to implement, normally requiring just a few electrical connections. However, electric motors have several disadvantages. Most importantly, their force-to-weight ratio is far lower than that of pneumatic and hydraulic devices, and in a field such as legged robotics, where weight is of the utmost importance, this makes them unsuitable for many applications. Typically, electric systems have a power to weight ratio of 50-100 W/kg (including only motor and gear reducer, operating at rated power), whereas fluid systems produce 100-200 W/kg (including actuator and valve weights) [4] and biological muscle, which varies widely in properties, produces anywhere from 40-250 W/kg [5]. In addition, when trying to take advantage of an animal’s efficient biomechanical design, the drastic difference between the rotary motion of most electric motors and the linear motion of muscle can cause complications.

Pneumatic and hydraulic cylinder
Pneumatic and hydraulic cylinder systems eliminate some of the problems associated with electric motors [6]. As a general rule, they provide a significantly higher force-to-weight ratio than motors; an advantage that in itself often leads to their use, even given the increased complexity and weight of control valves and pressurized fluid lines required for operation. These actuators also produce linear motion, which makes them more suitable to serving a role equivalent to muscle. Unfortunately, air cylinders are better suited to “bang-bang” operation; that is, motion from one extreme to another with mechanical stops to halt motion. Smooth walking motion requires a much larger range of states, and the stiction present in most pressure cylinders makes even coarse position control difficult. Fluid pressure devices are still quite massive; for example, almost seventy-five percent of CWRU’s Robot III’s weight is composed of its actuators and valves [7].

Braided pneumatic actuator
Braided pneumatic actuators (BPAs) provide a number of advantages over conventional actuation devices, and share some important characteristics with biological muscle. These devices consist of two major components: an inflatable bladder around which is wrapped an expandable fiber mesh (Figure 1). The resulting actuator is significantly lighter than a standard air cylinder; however, the braided pneumatic actuator is actually capable of producing greater forces (and thus possesses a much higher force-to weight-ratio) than its heavier counterpart. When the bladder is filled with pressurized air, its volume tends to increase. Because of the constant length of the mesh fibers, this can only be accomplished by the actuator expanding radially while simultaneously contracting along its axis. The result is a muscle-like contraction that produces a force-length curve akin to the rising phase of actual muscle [8].

Figure 1: A placeholder An important property of BPA to note is that at maximum contraction (L/Lo≈0.69) the actuator is incapable of producing force; conversely, the maximum possible force is produced when the actuator is fully extended. Therefore, similar to muscle, the force output of these actuators is self-limited by nature. While an electric motor controller could conceivably become unstable and drive a system until failure of either the structure or the motor, a braided pneumatic actuator driven by an unstable controller is less likely to be driven to the point of damaging itself or the surrounding structure. Because of this property, braided pneumatic actuators are well suited for the implementation of positive load feedback, which is known to be used by animals including cockroaches, cats and humans [9].

BPAs are also known as McKibben artificial muscles [10], air muscles, and rubbertuators. They were patented in 1957 by Gaylord and used by McKibben in orthotic devices [11]. Like biological muscle, BPAs are pull-only devices. This means that they must be used in opposing pairs, or opposing some other antagonist. This property is of significant importance for useful application of these devices, for although it requires the use of two actuators or sets of actuators at each joint, it allows the muscle-like property of co-contraction, also known as stiffness control. If one considers a joint in the human body, such as the elbow or knee, it should be obvious that whatever position the joint is in the muscles that control that joint can be activated (flexed) without changing the joint angle. From an engineering standpoint, this is accomplished by increasing the force produced by each muscle in such a way that the net moment produced at the joint is zero. As a result, the joint angle remains the same but perturbations, such as the application of an outside force, result in less disturbance. From a practical standpoint, this means that the joint can be varied through a continuum of positions and compliances independently. The resulting joint can be stiff when needed, such as when bearing weight while walking, or compliant, as in cases of heel strike where compensation for uneven terrain may be needed.

The greatest impediment to widespread use of BPAs has been their relatively short fatigue life. Under operating conditions such as we desire, these devices are capable of a service life on the order of 10,000 cycles as they were originally designed. A significant improvement to these devices has been made by the Festo Corporation, which has recently introduced a new product called fluidic muscle. This operates on the same principles as a standard BPA, with the critical difference being that the fiber mesh is impregnated inside the expandable bladder. The resulting actuators have a demonstrated fatigue life on the order of 10,000,000 cycles at high pressure.

3. Previous Robots

Two previous robots developed at CWRU have provided significant insight and impetus for the design of Robot V. Both of these cockroach-based robots are non-autonomous, and rely on off board controllers and power supplies for operation.

Robot III was the first pneumatically powered robot built at CWRU, and relied on conventional pneumatic cylinders for actuation. This 15 kilogram robot was powerful, and was demonstrated to be capable of easily lifting payloads equivalent to its own weight. The fundamental failing of this robot was the difficulty inherent in the control of the pneumatic cylinders; although capable of maintaining stance robustly and cycling its legs in a cockroach manner, to date this robot has not demonstrated smooth locomotion [12].

Kinematically similar to its predecessor, Robot IV implemented braided pneumatic actuators in place of Robot III’s pneumatic cylinders. This robot was underpowered; it was barely able to lift itself, the valves were moved off-board for walking experiments. However, this robot was significantly easier to control, in large part because the valves allowed air to be trapped inside the actuators, so that joint stiffness could be varied as well as joint position. Using an open-loop controller, this robot was able to locomote [13]

4. Overview of Robot V

Design Case Western Reserve University’s most recent robot, Robot V (Ajax) like its predecessors Robot IV and Robot III is based on the death head cockroach Blaberus discoidalis. Although it is not feasible to capture the full range of motion exhibited by the insect—up to seven degrees of freedom per leg—analysis of leg motion during locomotion suggests that this is not necessary. This is because in many cases joints demonstrate only a small range of motion, while the majority of a leg’s movement is produced by a few joints. We have determined that three joints in the rear legs, four in the middle legs, and five in the front legs are sufficient to produce reasonable and robust walking [7] [14]. The different number of DOF in each set of limbs represents the task-oriented nature of each pair of legs. On the insect, the front legs are relatively small and weak, but highly dexterous (Figure 2), and are thus able to effectively manipulate objects or navigate difficult terrain. This dexterity is attained in the robot through three joints between the body and coxa. These joints are referred to (from most proximal to most distal) as γ, with an axis parallel to the intersection of the median and coronal planes (in the z direction); β, with an axis parallel to the median and transverse planes (in the y direction); and α, with

Figure 2: Schematic of front leg with axes of joint rotation

an axis parallel to the coronal and transverse planes (in the x direction). The two remaining joints are between the coxa and femur and the femur and tibia. The middle legs on the insect play an important role in weight support, and are critical for turning and climbing (rearing) functions; however they sacrifice some dexterity for power. On Robot V, the middle legs have only two degrees of freedom—α and β—between the body and coxa, and retain the single joint between the coxa and femur and the femur and tibia. Finally, the cockroach uses its rear legs primarily for locomotion, and although these limbs are not as agile as the others, they are larger and much more powerful; likewise, the rear legs of the robot have only one joint between each of the segments. The body-coxa joint uses of only the β joint. Although each leg has a unique design, one component they have in common is the tarsus, or foot, construction. This consists of a compliant member attached to the end of the tibia and a pair of claws. The compliant element is capable of bending to maintain contact with the ground, thus providing traction. The claws are angled differently on each leg to assist in its specific task; for example, the claws on the rear leg are angled backwards like spines, allowing the foot additional traction when propelling the robot forward.

4.1 Valves

Each joint is driven by two opposing sets of actuators, allowing for controlled motion in both directions (previous robots have used a single actuator set paired with a spring) [15]. Each actuator set is driven by two two-way valves; one for air inlet and one for air exhaust. This scheme doubles the number, and thus the weight, of valves as compared to Robot III; however, it allows for the implementation of stiffness control, or co-contraction. Because the pressures in opposing actuators can be independently varied, the same joint angle can be achieved using different combinations of actuator pressures; all that is required is that the moments on a given joint sum to zero at the desired position. As a result, a joint can be made very stiff by pressurizing both sets of actuators, or very compliant, by pressurizing one actuator only enough to overcome the mass properties of the limb to reach a desired position.

4.2 Stance bias

The actuators onboard a legged robot can generally be subdivided into two classes: those used to move the limb through the swing phase and those required to maintain stance and generate locomotion. One of the fundamental differences between these two types of actuators is the load that is required of them. The swing actuators need only provide the force necessary to overcome the weight and inertia of the limb, whereas the stance actuators must support not only a significant portion of the entire mass of the robot, but also provide the force necessary for locomotion. This disparity between operational demands can potentially lead to large, powerful stance actuators and small swing actuators (as can be seen in the human body with powerful quadriceps muscles which maintain stance, and the respectively weaker hamstring muscles, which are used for swing); however, because of limited options for robot actuator sizes, it is more often the case that the swing actuators are overpowered, whereas the stance actuators are either underpowered or just capable of meeting the demands placed on them. On Robot V this problem was resolved through the placement of torsion springs at some critical load bearing joints (specifically the coxa-femur and β joints) to provide a bias in the direction of stance. As a result, the forces required of the stance actuators are significantly reduced while the swing actuators must produce greater forces, but still remain within their operational range.

5. Initial Trials

Robot V, like Robot IV, was designed as an exoskeleton, where the structural members are placed outside and around the actuators. Not only did this allow a significant reduction in weight, but it also provided a limited protection for the actuators, which are susceptible to puncture and abrasion (Figure 3). The vast majority of the structural elements were made of 6061-T6 Aluminum, although axles and actuator mounting shafts were made of 1018 steel, and fasteners were made from stainless steel. All joint axles were mounted in nylon journal bearings.

Figure 3: Robot V (Ajax)

Whenever possible, actuators were directly mounted to both their insertion and their origin. This precluded the need for tendons, allowing the maximum possible length of actuator to be used. This in turn maximized the force and stroke available for each individual joint. The notable exception to this strategy was the β actuators, which were attached to a tendon and mounted parallel to the body. This was done to reduce the overall height of the robot. The first legs to be built were the middle legs. These were chosen for initial tests because they must be dexterous and forceful to maintain stance in a tripod gait. After completion of the first leg the range of motion (ROM) of each of its joints was measured and compared to the design values. These data are summarized below:

Joint ROM Desired ROM β 20° 30° α 25 40 c-f (coxa-femur) 40 50 f-t (femur-tibia) 75 75

These tests were performed at both 5.5 and 6.25 bar, with no significant difference between the results of the two, suggesting that at these pressures the actuators had reached their full contraction. Although the desired ROMs were not reached, the measured ROMs are in excess of those demonstrated by animal. The demonstrated ROM’s of the leg were deemed sufficient for walking and climbing. A gantry was constructed to support the middle legs for preliminary stance and motion tests. With only horizontal support—to prevent tipping—the legs were able to maintain stance while supporting their weight (three kilos) plus the weight of the valves for the actuators (one half kilo) and a gantry element (one kilo) without any pressurized air in the actuators. This capability, a result of the aforementioned stance bias, clearly demonstrates the ability of these legs to support not only the weight of the robot, but a significant payload as well. An open loop controller was then used to cycle the legs through “push-ups”; raising themselves from a minimum to a maximum height. In this fashion, the legs were able to lift the body approximately 6 cm. This process was repeated with additional payloads (beyond valve and gantry weight) of two and a half and five kilograms using 6 bar air. In both cases, the legs were able to attain the same height.

6. Ajax

Fully assembled—including valves—Robot V weighs 15 kilograms. Range of motion tests have been performed for all joints, and are summarized below. In many cases, specifically the femur-tibia joints of all legs, these ranges of motion are in excess of the desired ROM. In all cases, they are sufficient for walking and climbing.

JOINT ROM Front Leg γ 35° β 45 α 25 c-f 40 f-t 75 Middle Leg β 20 α 25 c-f 40 f-t 75 Rear Leg β 25 c-f 50 f-t 80

Ajax demonstrates a propensity to stand due to the preloads placed on the torsion springs; even without pressure in the actuators, the middle and rear

Figure 4: Robot V without activated actuators (top) and standing (bottom). Note that even when the actuators are un-pressurized, they maintain a near-stance position, with only the feet contacting the surface.

Legs maintain a near-stance position. Initial tests of the robot have shown that it is capable of supporting its weight in a standing position and of achieving stance both unloaded and with a five kilogram payload (Figure 4).

Further tests have shown that the robot is able to achieve a tripod stance and alternate between tripods, which is important for walking. These tasks were achieved using a simple open loop controller. Furthermore, the passive properties of the BPA’s are clearly highlighted in the robot’s ability to return to its desired position after suffering perturbations without the use of any form of active posture control. Using a feed forward controller with absolutely no feedback, the robot can produce reasonable forward locomotion. Although this is by no means the robust, agile walking that is the ultimate goal of this project, it is a clear demonstration of not only the robot’s capabilities, but also the advantages offered by the BPA’s. The ability to move using only an open loop controller is in large part a result of the passive properties of the actuators, which provide compensation for any instabilities in the controller itself and immediate response to perturbations without the need for controller intervention.

This can be contrasted with Robot III, which, even with kinematic and force feedback, was not able to walk. This failure of Robot III is attributed to the inability of both the pneumatic cylinders and posture controller to deal with the sudden changes in load associated with locomotion.

In short, the BPA’s act as filters, providing immediate response to perturbation; a task the controller is incapable of. This same process occurs in biological muscle, which responds nearly instantaneously to perturbation, but only slowly to neurological input [16]. With the addition of a biologically inspired closed loop controller in the future, Ajax is expected to display robust, insect-like locomotion.

7. Future Work

Although the mechanical aspects of this robot have been completed, the control system is still in its infancy. Because the mechanics of a system are inextricably linked to its control circuits, Ajax’s controller is expected to benefit from the close relationship between its design and that of the actual insect. This relationship is perhaps most prominent in the muscle-like nature of the braided pneumatic actuators.

Sensors will be added to provide not only joint position feedback, but force feedback as well. Joint angle can easily be determined with a potentiometer, as has been done on our previous robots. Force feedback will be attained through pressure measurements from the actuators, which, given actuator length, can be used to determine actuator force. Although strain gauges properly placed on the mounting elements of the actuators can produce sufficient force feedback, previous work has shown many desirable characteristics inherent in pressure transducers: they have much cleaner signals, do not require amplifiers, and do not exhibit cross talk; all disadvantages of strain gauges. In addition, strain gauges must be mounted directly adjacent to the actuator they are recording from; this requires more weight at distal points of the limb, (thusly increasing the moment of inertia of the limb) and generally reduces the usable available stroke of the actuator. We have demonstrated that a pressure transducer located down-line from an actuator produces a sufficient signal to determine actuator force.

An insect-inspired controller was developed for Robot III, and this will be modified for use on Robot V. It is a distributed hierarchical control system. The local to central progression includes circuits that control joint position and stiffness, inter-leg coordination and reflexes, intra-leg gait coordination, and body motion. The inter-leg coordination circuit solves the inverse kinematics problem for the legs and the centralized posture control system solves the force distribution problem.


text:
Jack Epps

Jack Epps may refer to:

 * Jack Epps (American football) (born 1963), former professional American football player
 * Jack Epps Jr. (born 1949), American screenwriter, co-writer of Top Gun

title: Jack Epps


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User:Vuara/Decoding Egyptian hieroglyphs

Call number 493.18242 MCD Author McDermott, Bridget. Title Decoding Egyptian hieroglyphs : how to read the secret language of the pharaohs / Bridget McDermott ; foreword by Joann Fletcher. Publication info San Francisco : Chronicle Books, 2001. Physical descrip 171 p. : col ill. ; 24 cm. Bibliography note Includes bibliographical references (p. 171) and index. Subject term Egyptian language--Writing, Hieroglyphic. DBCN (Sirsi) AED-5639 ISBN<PHONE_NUMBER> (pbk.) Read a chapter or excerpt Author Biography Bridget McDermott is at work on her doctoral thesis on the ancient Egyptian military, and is also a media consultant on Egyptian archaeology. She lives in England Joann Fletcher, Ph.D., is director of the NILE educational organization, as well as a frequent university lecturer. She divides her time between Egypt and her home in England Distributed by Syndetic Solutions, Inc. Summary The French linguist who decoded the Rosetta Stone took 14 years to do so; amateur translators would find the task much simpler with Decoding Egyptian Hieroglyphs: How to Read the Secret Language of the Pharaohs by British doctoral student Bridget McDermott. For instance: "a water pot on a human leg, a bread loaf and a flesh sign together" means "meat." The colorful text, a marriage between coffee-table picture book and high school language workbook, offers photographs of ancient inscriptions with sidebars clarifying their meaning as well as pronunciation and grammar guides, magic spells, maps, mythology and basic Egyptian history. Copyright 2001 Cahners Business Information. Distributed by Syndetic Solutions, Inc.

Table of Contents Foreword Dr Joann Fletcher 6 Chapter 1 First Steps 8 Discovery and Decipherment 10 The Rosetta Stone 11 The History of the Language 12 The Scribal Legacy 14 The Role of the Scribe 15 How Hieroglyphs Work 18 The Arrangement of Signs 19 Spelling and Pronunciation 20 The Alphabet 22 Determinatives 24 Chapter 2 Origins of the Signs 26 Signs from Nature 28 On the Banks of the Nile 28 Bodies Human and Divine 30 The Animal World 34 Hosts of the Air 36 Reeds and Flowers 38 The Divine Elements of Life 41 Life on Earth 44 Dwellings of Men and Gods 45 The Harvest of the Fields 50 Eating and Drinking 53 Recreation and Sport 56 Chapter 3 The Sacred Art Of Writing 58 The Magical Dimension 60 Worship of the Gods 60 The Art of Magic 64 Tomb Inscriptions 66 Reading a Tomb Inscription 68 The Pyramid Texts 70 Coffin Texts 72 The Book of the Dead 74 How to Read Objects 76 Statues 76 Jewelry 78 Weapons of War 80 The Power of Names 82 The King's Titles 82 Gods and Goddesses 86 Reading a Temple Inscription 90 Chapter 4 Realms of Meaning 92 A Healthy Life 94 The Body Beautiful 94 The Healing Arts 96 Death and the Afterlife 98 Relationships 104 Generations 104 Expressing Emotions 106 Love and Family Life 108 Trades and Skills 110 Mining 111 Servants of the Gods 112 Servants of the State 115 A Life of Work 118 Soldiers 120 Weapons and War 122 The Force of Egypt 122 Military Records 124 Egypt and Beyond 126 The Black Land 126 The Forty-Two Nomes 128 Sacred Sites 130 Peoples Beyond the Black Land 134 Calculation and Measurement 138 Time 138 The Seasons of the Year 140 Mathematics 142 Celestial Worlds 144 Creation Myths 145 Day and Night 146 The Waters of Heaven 148 Chapter 5 Reference File 150 The Grammar of Hieroglyphs 152 Sample Translations 160 Sign Index 166 Index 172 Acknowledgments 176 Distributed by Syndetic Solutions, Inc.

Review The French linguist who decoded the Rosetta Stone took 14 years to do so; amateur translators would find the task much simpler with Decoding Egyptian Hieroglyphs: How to Read the Secret Language of the Pharaohs by British doctoral student Bridget McDermott. For instance: "a water pot on a human read more... Appeared in: Library Journal, Nov 01, 2002 (c) Copyright 2003, Cahners Business Information, a division of Reed Elsevier, Inc. All Rights Reserved.

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Chapter One

DISCOVERY & DECIPHERMENT

In 1799 a French officer at Fort Julien in el-Rashîd in Egypt uncovered a granitic rock carved with three scripts: hieroglyphs, demotic or popular Egyptian, and ancient Greek. The slab was the key to deciphering hieroglyphs.

THE ROSETTA STONE

The officer was a member of a French expeditionary force to Egypt, and copies of the inscription on the slab — later called the Rosetta Stone after European versions of el- Rashîd — were sent to Paris. By examining the Greek text on the slab, scholars saw that the carving commemorated the coronation of Ptolemy V and had been commissioned by priests of Memphis in 196BCE. But it was years before the fourteen lines of Egyptian hieroglyphs were deciphered.

Jean-François Champollion, a precocious French linguist, obtained a copy of the Rosetta Stone inscription in 1808 when he was only eighteen. Fluent in ancient Greek, he compared the hieroglyphs in oval enclosures — which were believed to contain royal names — to the royal names listed in the Greek section of the inscription. Other scholars had identified Ptolemy in Greek and Egyptian. Champollion assumed that the name should be read alphabetically and that each hieroglyph represented a separate letter, and by reading from right to left established the name p-t-o-l-m-y-s. He was able to draw up a small alphabet.

When he saw a copy of an inscription containing the name Cleopatra, he made a longer sign list that enabled him to read names on other monuments. He realized that hieroglyphs used signs that represented both sounds and ideas and he examined the grammar of the language, making his findings public in 1822.

THE HISTORY OF THE LANGUAGE

Around 3000BCE developments in trade brought about crosscultural relationships between Egypt, Mesopotamia and neighbouring countries. The Sumerians of Mesopotamia had developed a system of writing that used pictograms or picture signs and for many years scholars believed that this system was the basis of Egyptian writing. Recent excavations at Abydos, however, have revealed that Egypt had used a pictorial language several hundred years before Mesopotamia.

The oldest surviving examples of written Egyptian date from c.3250BCE. At first the pictorial script was used primarily to record royal possessions but by the Old Kingdom (2625-2130BCE) the script appeared mainly in religious or commemorative inscriptions on palaces, temples and tombs, on statues, coffins and sarcophagi and on amulets and jewelry. For this reason the Greeks who ruled Egypt after the death of Alexander the Great in 323BCE called the writing "hieroglyphics" from the Greek words hieros (meaning "sacred") and gluphe ("carving"). Hieroglyphic writing was in use for more than 3,000 years from the fourth millennium BCE to the fourth century of the Christian era, when — in a Roman-dominated Egypt — it faded into obscurity. The latest known inscriptions in hieroglyphs date from 24 August 394CE and were discovered on the island of Philae in the River Nile in southern Egypt, where a temple to the goddess Isis was still in use in the sixth century CE.

Hieroglyphic signs were written in columns and rows and read from right to left, from left to right or from top to bottom — but never from bottom to top (see page 19). A simplified form of hieroglyphic writing probably first appeared shortly after the introduction of the original hieroglyphs. In the Old Kingdom this simplified form was used for secular administrative papyri as well as for temple accounts and religious texts. In the Greco-Roman period (332BCE-CE395), however, it was used only by priests and in religious contexts — the Greeks named it "hieratic", from hieratikos ("priestly"). Scribes wrote hieratic in columns and rows; in rows it read from right to left.

A more rapid form of writing — best described as a shorthand used for administrative documents — first appeared in 724-712BCE and continued in use until the late Roman period (fourth century CE). The Egyptians identified it by a phrase meaning "writing of documents", but it is widely known as "demotic" from the Greek demotikos ("popular"), because it was used in secular writing.

A fourth form of written Egyptian was Coptic. This was written in the Greek alphabet but retained seven characters from the ancient Egyptian language. While earlier forms of Egyptian used only consonants in their alphabets (see pages 22-23), Coptic used vowels as well and has helped scholars reconstruct the vowel sounds of hieroglyphic writing. The earliest Coptic texts, which date from the first and second centuries CE, were Egyptian magical writings. The name comes from the Greek Aiguptia, "Egypt". After the Arab conquest of Egypt in 640-642CE, Arabic largely replaced Coptic in Egypt.

The language of Egypt is divided by historians into Old, Middle and Late Egyptian. Old Egyptian is dated to 3180-2240BCE and was used in official, funerary and biographical inscriptions. Middle Egyptian (2240-1990BCE) was developed in literary compositions of the Middle Kingdom and continued in use well into the Eighteenth Dynasty (1539-1292BCE). Because it is grammatically consistent, Middle Egyptian is the best place to start when learning to read hieroglyphs. Late Egyptian, dating to 1573-715BCE, is found in official documents, inscriptions and letters.

THE SCRIBAL LEGACY

In ancient Egypt, those able to read or write the elaborate hieroglyphic script were held in great esteem, and often became prominent figures in the religious, military or political realms. Literacy was limited to members of the élite. Highly trained scribes used hieroglyphs to facilitate the administration of the state and to document political and religious events.

THE ROLE OF THE SCRIBE

From the age of seven, boys from Egypt's upper classes attended school at temple, where they practised their writing on ostraca (fragments of pottery or limestone) or on wooden writing boards that were coated with gypsum. Pupils probably also learned words and phrases by heart by chanting them. Boys are also known to have studied literary compositions including stories and wisdom texts.

It is thought that Egyptian further education began between the ages of thirteen and fifteen, when students were expected to embark on an apprenticeship. Among the many trades open to educated young men, the military and scribal professions were particularly highly regarded. Those who chose to become scribes enjoyed promising prospects — qualified scribes could expect to graduate to prestigious administrative positions in a range of sectors. Military scribes were responsible for recruiting and organizing the army and its supplies. Some scribes acted as architects, while others designed the plans for decorating royal tombs and temples with hieroglyphs and pictures, and supervised the artists and craftsmen who carried the plans out.

Individual scribes, even if they came from relatively humble backgrounds, were sometimes promoted to positions of high office. Imhotep, the scribe and architect of the step pyramid at Saqqara, was even worshipped as a god after his death, as was another famous scribe, Amenhotep son of Hapu (see page 17).

The ancient Egyptians revered literacy, and even élite men who were not scribes sometimes commissioned statues of themselves kneeling crosslegged on the ground in the pose that characterized the profession. The scribe is usually depicted with rolls of writing material stretched across his knees. The Egyptians wrote on bone, clay, ivory, linen, metal and vellum, but ostraca and papyrus were more widely used. Scribes selected small rectangular sections or rolls of papyrus, which were several metres in length. Egyptian books, in the form of scrolls, were usually stored in boxes or jars.

The hieroglyphic word for "scribe" ?? ss/sesh (see pages 20-23 for transliteration and pronunciation of hieroglyphs) starts with an image of the scribal palette and tools; the determinative sign (see page 24) is a kneeling male figure that represents a scribe at work. The scribal palette consisted of black and red inks that were used to distinguish between sections of text. The black pigment was derived from carbon, while the red was extracted from two types of iron oxide and ochre. Both pigments were moulded into small cakes which were mixed with gum and water. Pens and brushes were crafted from the firm, straight stems of reeds or from slivers of wood which were bruised at one end until the fibres separated and formed bristles. The word "to write" ?? ss/sesh is almost identical to the word for "scribe", and was pronounced in the same way. It shows the scribal palette and pen followed by the image of a sealed papyrus roll.

HOW HIEROGLYPHS WORK

For centuries hieroglyphs were an unbreakable code because scholars were misled by the ancient Egyptians' use of symbols in writing. To break the code modern readers had to understand — as Jean-François Champollion did — that the symbols represent both sounds and ideas (see page 20). The first step of all, however, is to examine how scribes arranged the hieroglyphs.

THE ARRANGEMENT OF SIGNS

Ancient Egyptian scribes wrote hieroglyphs in both rows and columns with no spaces between the words. Inscriptions can be read from left to right or from right to left along a row and in a column from top to bottom.

When reading a row you can work out in which direction to read because signs containing humans, animals or birds always face toward the beginning of the inscription. For example, when the word for "drink" is written like this ?? it should be read from the left because the human figure and the bird are facing toward the left. If it is written in this way ?? it is read from the right.

When a row of hieroglyphs appears vertically reading should begin at the top, for hieroglyphs were never written from the bottom to the top of a column. Within a row if two signs are put together vertically — as the bird and the mouth sign are in "drink" — the upper one should be read first. The signs in "drink" should therefore be read in this order ?? (folded cloth) ?? (sparrow), ?? (mouth), ?? (reed), ?? (water ripples) and ?? (man).

The signs reproduced in this book are printed as we are accustomed to read English — in a straight line from left to right. However, scribes used hieroglyphs as part of the decorative scheme of the monument, tomb or other object on which they were writing, often arranging the signs in the way most pleasing to the eye. When carving an inscription on a monument, they would group the signs to fill the space available. Sometimes they repeated pieces of text in opposing directions for symmetrical effect.

SPELLING AND PRONUNCIATION

Before Jean-François Champollion made his inspired breakthrough in the decoding of hieroglyphs (see page 11), scholars believed that all hieroglyphic symbols stood for concepts or things and that none was used to represent sounds in the way that the letters of the English alphabet are used. In fact hieroglyphic writing, as Champollion understood, combines ideograms (signs that represent ideas and things) and phonograms (signs that represent sounds).

Many signs depict recognizable creatures or things — for example, ?? (bull), ?? (horse) or ?? (child). Many depict stylized versions of the thing to which they refer, as in ?? (lotus pool), ?? (lotus flower) or ?? (palm branch stripped of leaves). Sometimes a sign is used as the word for the object it depicts. For instance, the word for "mouth" ?? consists of the mouth sign written with a single stroke that indicates, among other things, that this word refers to the thing that is represented. Similarly the words for "sun" ?? and "arm" ?? are written with the signs that represent those objects. More usually, however, hieroglyphic signs represent sounds in the Egyptian language — they are used as phonograms. Two picture signs representing different sounds can be put together to make a new word, which often has nothing to do with the things represented by the picture signs themselves. A hypothetical English equivalent usually quoted by scholars would be to write "belief" by combining the images of a bee and a tree's leaf: bee-leaf. If you were trying to decode this hypothetical English hieroglyph and expected the resulting word to relate to bees, leaves, honey or trees, you would be heading in entirely the wrong direction.

By careful comparison of the use of hieroglyphic signs in different contexts, scholars have identified specific signs with individual sounds. Where possible they have matched these sounds with the letters of the English alphabet. But some sounds in ancient Egyptian do not have exact equivalents in English and so cannot be represented using letters of the alphabet; in these cases scholars have developed a set of signs to represent the sounds (see pages 22-23). The translation of hieroglyphic pictures into sounds is called "transliteration". Ancient Egyptian hieroglyphs did not represent vowel sounds (a,e,i,o,u) and so only consonants are used in transliteration.

In the word for "house" ?? the rectangle represents a house; the pronunciation of the word combined the consonant sounds p and r — and the sign is transliterated using those letters: pr. The word for "to go forth" ?? made the same sound combination. In this context the sign of the house works to represent the sound combination pr(i); the mouth sign reinforces this, because it represents the sound r; the sign for walking legs helps to distinguish between the house symbol used as an ideogram in ?? and the same symbol used as a phonogram in "to go forth" — the leg sign indicates that the word is to do with movement and is an example of a determinative (see page 24).

Scholars do not know for certain how the ancient Egyptians pronounced the words represented by hieroglyphs, but they have a good idea based on comparative research in Coptic (see page 13). As well as transliterating hieroglyphic signs into recognizable letters (but using only consonants), we can write out the word's probable pronunciation complete with vowel sounds. The word house ??, transliterated pr, was probably pronounced "pair". In this book the hieroglyphic words cited are followed firstly by the transliteration, then the pronunciation, thus: "house" ?? pr/pair; "mistress of the house" ?? ?? nbt-pr/nebet -pair; the ancient name for Egypt ("the black land") ?? ?? ?? kmt/Kemet.

THE ALPHABET

Ancient Egyptian used a standard alphabet of twenty-four "letters" each of which represented a single consonant. The letters are shown in the box below alongside their transliteration (see pages 20-21) — either a letter from the English alphabet or a transliteration sign devised by scholars — and their probable pronunciation.

The sounds represented by the transliteration signs given in the alphabet box below are as follows: 3 — glottal stop, similar to "thro'le" (for "throttle") in Cockney English; i — like "y"; ?? — guttural "ah" sound; h — emphatic "h"; h — similar to "ch" in Scottish "loch"; h — similar to "ch" in German "ich"; š — "sh" as in "shimmy"; k — "kw" like "q" in "queen"; t — similar to to "t" in "tube"; d -"dj" similar to "j" in "joker".

The language also used a number of signs that represented combinations of two consonants (these are known as "biliteral signs") or combinations of three consonants (known as "triliteral signs"). A list of biliteral signs and a selection of triliteral signs is given on pages 158-9 in the Reference File section at the end of this book.

DETERMINATIVES

Two English words can sound identical but have different meanings — for example, "pear" and "pair". In hieroglyphs, where no vowels were written, words commonly shared a spelling. The adjective ?? "old" and the noun ?? "praise" both read i3w/ah-oo. When words looked alike in this way, Egyptian scribes added what scholars call determinatives — ideograms used to determine or make clear the meaning. The determinative for ?? "old" is a stooping, elderly man while the determinative for "praise" is a figure raising hands in worship. Determinatives do not have a phonetic function — they represent no sound. Ideograms of a man ?? or parts of the male anatomy including the penis ?? and ?? were used to determine words with male aspects: for example, ?? s3/sar "son" and ?? h3y/hay "husband". Ideograms of a woman ?? were used to determine words with female aspects such as ?? mwt/moot "mother".

(Continues...) distributed by Syndetic Solutions, Inc.


text:
Raboso

Raboso may refer to:

 * San Juan Raboso, Puebla, a town sometimes called Raboso
 * Raboso (grape)

title: Raboso


text:
Talk:The periodic table

What should go here?
Do we want a list of the elements in atomic order, or do we want them arranged in the actual periodic table? Should someone create this image-wise? Mathboy965 17:49, 21 September 2006 (UTC)

 * Let's make it so all the elements are clickable. That could be really useful. --HappyCamper 21:42, 26 September 2006 (UTC)

 * If I make them clickable, what should they link to? --Mathboy965 23:15, 26 September 2006 (UTC)

 * For now, I guess, just link back to the Wikipedia articles on the elements, say Calcium. The idea on Wikiversity is that we want to create learning materials, so the idea is more geared towards telling someone how to use the periodic table, and get the information they need. --HappyCamper 14:36, 27 September 2006 (UTC)

 * I would like to ask, how did you manage to create the periodic table in a single edit? That was some massive editing you did there! --HappyCamper 14:41, 27 September 2006 (UTC)

 * I kept edited and saving to a text file instead of to the wiki page. When I finished, I saved to the wiki page and created the periodic table.  --Mathboy965 17:07, 28 September 2006 (UTC)

Adding things
I have just put a few things under the sections. I will expand these later, but don't have much time at the moment. --Mathboy965 17:05, 28 September 2006 (UTC)

 * So I do not pretend to have any particle physics background - I have just created the nonmetals page and a few elements. Just some very basic research to get things started so smarter people can take over ;) Markco1 18:20, 10 September 2010 (UTC)

Colour contrast
Hi, If you are going to use two different colours in a square there needs to be good contrast between them for the text to be readable. Blue on a purple background is one of several that I can't see and I'm sure some others can't either. WereSpielChequers 12:39, 2 June 2011 (UTC)
 * Thank you for the changes, it looks much improved! --HappyCamper 02:56, 3 June 2011 (UTC)

A Requirement
The number of electrons in each of the shells of the atom is required. In that way, more information can be extracted from it.--M1234 19:01, 17 October 2011 (UTC)
 * That should be included in their own pages. ---Atcovi (Talk - Contribs) 01:37, 19 January 2016 (UTC)

Groups
I find it peculiar that Groups are mentioned in the text but omitted from the table which only shows columns. For reasons with which I'm unfamiliar (perhaps inconsistent usage), it seems to be fashionable to replace the traditional groups with 18 column headings. If we're going that way with the table, why not the text?

title: Talk:The periodic table


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Wikipedia:Articles for deletion/Michele Martinez (2nd nomination)

The result was delete. Jo-Jo Eumerus (talk, contributions) 18:54, 27 September 2019 (UTC)

Michele Martinez
AfDs for this article:
 * – ( View AfD View log  Stats )

Previously deleted at Articles for deletion/Michele Martinez, the subject still fails to meet WP:POLITICIAN. Kudpung กุดผึ้ง (talk) 13:18, 20 September 2019 (UTC)
 * Note: This discussion has been included in the list of People-related deletion discussions. Kudpung กุดผึ้ง (talk) 13:18, 20 September 2019 (UTC)
 * Note: This discussion has been included in the list of Politicians-related deletion discussions. Shellwood (talk) 13:22, 20 September 2019 (UTC)
 * Note: This discussion has been included in the list of California-related deletion discussions. Shellwood (talk) 13:22, 20 September 2019 (UTC)

 * Delete per consensus at the last AFD. I can't see what's changed to make her more notable per WP:POLITICIAN since then. Tracy Von Doom (talk) 13:45, 20 September 2019 (UTC)
 * Delete. As a city council member, subject fails WP:NPOL. CASSIOPEIA(talk) 13:55, 20 September 2019 (UTC)
 * Delete. Santa Ana is not a global city for the purposes of handing its city councillors an automatic free pass over WP:NPOL #2, so her only path into Wikipedia is to be referenceable to a depth and range and volume of reliable source coverage that marks her out as much more special than most other city councillors — but the ability to cite a handful of local coverage in her own local media market does not do that, because every city councillor everywhere can always show a handful of local coverage in their own local media market. People are also not notable for running as candidates in elections they did not win, so neither running for mayor nor running for the state legislature boosts her notability at all — and having been named in a "top 40" listicle is also not a notability claim in and of itself, so a 111-word blurb in the Huffington Post's "40 Under 40: Latinos in American Politics" is not the magic ticket either. Nothing stated in the article is "inherently" notable enough to exempt her from having to have a lot more than just one blurb of extralocal coverage. Bearcat (talk) 14:43, 20 September 2019 (UTC)
 * Delete WP:NPOLITICIAN --qedk (t 桜 c) 20:44, 20 September 2019 (UTC)
 * Delete - fails both WP:GNG and WP:NPOL. Onel 5969  TT me 12:38, 22 September 2019 (UTC)
 * Note: This discussion has been included in the list of Women-related deletion discussions. Coolabahapple (talk) 07:21, 24 September 2019 (UTC)

 * Delete, largely per Bearcat: WP:NPOLITICIAN is clearly not met, which leaves WP:GNG, but GNG requires in depth coverage of the article's subject within (ideally at least a handful of) reliable, independent sources. The closest we have to in-depth coverage focused upon the proposed article's subject comes from the HuffPost article, and even that source contains merely a three sentence paragraph regarding Ms. Martinez.  Unfortunately, despite the fact that there are technically nearly a dozen citation in the article, collectively, the content within them that is directed to the subject does not meet the notability threshold, even when we aggregate them. Further, if this is the second time we have had to delete the article in three years, we may want to consider salting the title. That would be a shame, in that its possible this woman's profile could raise in the coming years, and then there will be hoops to be jumped through to get a (then justified) article into existence, but given there is a possibility that the subject's supporters may re-add the article again without meeting notability standards, it may be called for. Snow let's rap 07:48, 26 September 2019 (UTC)

 * The above discussion is preserved as an archive of the debate. Please do not modify it. Subsequent comments should be made on the appropriate discussion page (such as the article's talk page or in a deletion review). No further edits should be made to this page.


text:
User:Mhzrr

''Bone Marrow Transplant now FREE in Sindh. Earlier, # SindhGovt launched FREE health services at NICVD, Jinnah & SIUT.''

title: User:Mhzrr


text:
Talk:Santa Teresa (rum)

More sources
The article is ok, but it needs more reliable sources for backing.--MaoGo (talk) 09:29, 23 September 2019 (UTC)

title: Talk:Santa Teresa (rum)


text:
Talk:Anthony Selway

External links modified
Hello fellow Wikipedians,

I have just modified 1 one external link on Anthony Selway. Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:
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title: Talk:Anthony Selway


text:
Graphic Design/Type

=Typography=

Typeforms are an integral part of modern communication. Since the invention of the printing press, people have used printed —and more recently— electronic type to communicate. Could you imagine a newspaper or magazine where all the articles were handwritten and copied? Imagine how difficult it would be to compose an e-mail or use desktop publishing software to create party invitations without the existence of typefaces.

Typefaces are used in print and electronic media not just to communicate a legible message, but as an expressive tool of the author or designer. Each typeface can be used to convey a different style or atmosphere. There are typefaces evocative of Art Deco, The old American West, Weddings and other traditionally formal ceremonies, childhood, The Middle Ages, handwritten text, and an endless variety of other styles.

It is almost imperative as a graphic designer, and absolutely imperative as a typographer, to develop an appreciation and understanding of both modern and historic typography. In everyday life, one should pay attention to the stylistic and practical uses of typefaces in various kinds of media. Note what feelings the designer was hoping to convey, or what style they were attempting to mimic.

Classification
A typeface is a style of lettering, such as Helvetica or Times. A font is the set of a typeface, used to produce the letters. On a computer, it is a file used by the system. People often confuse "font" with "typeface". For example, Helvetica, point 12 is a different font from Helvetica, point 14, even though both are of the same typeface.

A set of similar typefaces is called a "family." Within a family, typefaces are categorized as parent (e.g. Times, Helvetica) or relative (e.g. bold, italic). Typefaces are categorized also according to style (e.g. italic, book), weight (e.g. bold or light), and width (e.g. expanded).

Type is measured in points, from top to bottom of the letters' invisible bounding boxes. Since each letter fills up a percentage of that bounding box, when the size of the box is increased, the letter size increases.

The divisions you may already be familiar with are the serif and sans-serif fonts. Serif fonts, like Times, have the little feet and variable line width characters which make them easy to read. Sans-serif fonts, like Helvetica and Verdana, are drawn with more even-width lines and don't have the little feet, which gives them a clean, modern feel.

Usage in Design
Text can have a number of different purposes in a design. It can be used for pure graphic appeal —or aesthetically— a case in which legibility may be less important than aesthetics. An example of graphical use of text is possibly that of major titles. Text may also, more commonly, be used for communication on a linguistic basis rather than visual, in which case, legibility is always the priority of the designer. A few examples of usage of text for linguistic communication are: the body text of an article or book, the text of a restaurant menu, or in product descriptions in a catalog.

A font may be used either successfully or poorly, depending on its degree of relevance in the project and the skill of the designer. The designer must pay careful attention to letter, word, and line spacing as well as the size of the typeface and its stylistic contribution to the overall aesthetic of the project. He or she must optimize the properties of the text for its purpose in the overall design (aesthetic or communicative) and maintain legibility where it is necessary, and the designer is also expected to add visual variety with formatting and layout, as well as possible font changes where applicable.

Choosing a Font
A designer has to choose a font that is not only appropriate to the mood of the design, but that is appropriate for the text's purpose in the design. For example, there are many kinds of decorative typefaces that one would not want to set an entire article in. This is because a purely decorative typeface tends to be distracting to the content of the message and tire the reader's eyes when used in large portions. Our eyes are most comfortable reading less idiosyncratic typefaces. Decorative typefaces are better suited for display type (greater than 14 points), while simpler type is better used for text (less than 14 points). To maintain readability in large blocks of text —such as in an article— stay consistent, and use only one family.

Readability in Different Media
Standard graphic design wisdom holds that of the categories of serif and sans-serif, serif fonts are easier to read. This is because when reading, the eye quickly scans the tops of the letterforms, and a serif font has more immediately recognizable features thanks to the tiny 'eye-holds' provided by the serifs. There is a notion slowly gaining acceptance, that, for the purposes of purely electronic design, the reverse is sometimes true. Sans-serif fonts are more readable in this case because a screen has a lower resolution than a printed page, so the serifs only serve to smudge the letter forms.

Some typefaces such as Times, originally designed for the London Times newspaper, or Futura, designed as a letterpress (raised plate) type for printing on paper, were intended for the printed page. Others such as Georgia and Verdana were designed for the lower resolution of text on a screen. The shapes of these typefaces are developed to optimize visibility in smaller sizes on a computer monitor. In larger sizes, these differences don't matter as much.

For maximum readability on the page: Serif; On the screen: Sans.

Typeface Sizing
Keep the typeface at a reasonable size for reading. The numbered size of a typeface may reflect the overall height of the lines that stick out of the type, but not the readability size that relates to the inner dimensions of the letters. The type size should be chosen on a visual basis, and not purely on that of font size numbers. Usually, type that is proportioned so that the lower case size is larger in proportion to the overall height of the font, can produce a greater amount of legible words into an equivalent space.

Typeface Spacing
Word spacing should be so that the reader is aware of the beginnings and endings of words with little or no difficulty. Experiment with spacing settings to find the best one. Letter spacing and line spacing may be used to expand on the expressivity of the font. Leave enough space between the lines so that the text is legible. Experimentation is important here, too. The reader's eyes should be pulled to the next word as they read, not to the lines above and below. The letter spacing should be that so the reader can easily differentiate between different characters. Yet again: experiment, experiment, experiment.

 * Kerning
 * Kerning is the horizontal spacing between exactly 2 glyphs. When you are hand kerning text (logotype or headline text usually) try to imagine that the baseline and glyph shapes make a container, and imagine pouring water in. Try to make the negative space between each pair of glyphs hold the same amount of water.

 * Tracking
 * Tracking is the horizontal space added to or subtracted from the space between each and every pair of glyphs in a selection. In other words tracking adds to or subtracts from the kerning of all pairs of glyphs in a selection.

 * Leading
 * Leading is the vertical spacing between separate lines of type. There is a relationship between the length of the line and the amount of leading needed for easy legibility. Longer lines need more leading to prevent the reader's eye from slipping up or down when moving from the end of one line to the beginning of the next. It then logically follows that short lines are preferable if information density is important as in a newspaper.

 * Typographic Color
 * Typographic Color is something of a misnomer in that it is only concerned with one aspect of color: value. The darkness or lightness of a block of text on average is the typographic color of that block of text. Typographic color is strongly influenced by spacing. Consider the difference in the emotions aroused by a dark block of text (long lines with little tracking and leading as seen in many legal agreements) and a light block of text with lots of space.

When to Break Rules
With text used purely for graphical or display purposes, spacing, fonts, or colors that would be considered otherwise unreasonable can be utilized to create a visually appealing effect. The legibility rules that are extremely important in body text aren't as critical to effect the larger typeface size. Make sure that before deciding to use more untraditional methods of formatting text, you consider the desires of your client, and/or the stylistic effect the formatting will have on the overall design. Is it supposed to be a classic, elegant wedding invitation, or is this a layout for a skateboarding magazine article? Consider the circumstances and break or follow the rules of tradition appropriately. Remember that a common amateur mistake is to break too many —or the wrong— formatting rules in rebellion of the idea that aesthetics have constraints. Then, they end up with a horrible mess of a design that looks good under no circumstances. The purpose of a graphic designer is to merge optimal form and function. Remember: anything can be art, but not anything can look good!

Layout
A good layout is one that shows good use of the elements and principles of design. Most importantly, a designer should use the principles of design to draw the reader's eye both to and through the design easily. The elements of design are: color, value, texture, shape, form, space, and line. The principles of design are: contrast, emphasis, balance, unity, pattern, movement, and rhythm. The specifics of both the principles and elements vary from source to source, but the idea remains the same. If you haven't studied the principles and elements of design before, read more in the chapter Principles of Design, or scroll down to view the external links.

=External Links=
 * Books on Typography The Type Directors Club

 * Five Simple Steps to Better Typography -- Mark Boulton

 * Books on Typography -- By Index Book publishing.

 * Typographica. A Journal of Typography.

 * The Principles of Design -- Digital Web Magazine

 * The Elements of Design -- Digital Web Magazine

 * Design examples -- Design Examples Online Magazine

title: Graphic Design/Type


text:
User:Amoore2479/Sample page

Anthony John Moore

Author, British Army Veteran to the Army Catering Corps

Born 21st September 1960, Kingston, Jamaica.

Son of

Lorna Whisken (Moore) (King) (Chaddock)

and John William Moore

Siblings -

Jamie Travis Tony Roger Moore

Richard Jason Micheal Robert Moore

Kristian Levi Lewis Anthony Moore

Robin Matthew Ryan Moore

Abigail Maddison Moore

title: User:Amoore2479/Sample page