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#126 2018-05-01 01:11:58

ganesh
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Re: Miscellany

110) Kiwi

Kiwi, any of five species of flightless birds belonging to the genus Apteryx and found in New Zealand. The name is a Maori word referring to the shrill call of the male. Kiwis are grayish brown birds the size of a chicken. They are related to the extinct moas. Kiwis are unusual in many respects: the vestigial wings are hidden within the plumage; the nostrils are at the tip (rather than the base) of the long, flexible bill; the feathers, which have no aftershafts, are soft and hairlike; the legs are stout and muscular; and each of the four toes has a large claw. The eyes are small and inefficient in full daylight, the ear openings are large and well developed, and very long bristles (perhaps tactile) occur at the base of the bill.

Dwelling in forests, kiwis sleep by day in burrows and forage for food—worms, insects and their larvae, and berries—by night. They can run swiftly when required; when trapped they use their claws in defense.

One or two large white eggs—up to 450 g (1 pound) in weight—are laid in a burrow and are incubated by the male for about 80 days. The egg is, relative to the size of the bird, the largest of any living species. The chick hatches fully feathered and with its eyes open; it does not eat for about a week.

Although no longer abundant, kiwis appear to be in no danger of extinction and may even be gradually adapting to semipastoral land.

The genus Apteryx forms the family Apterygidae, order Apterygiformes. Five species of kiwis are recognized: the tokoeka kiwi (A. australis), which includes the Haast tokoeka, Stewart Island tokoeka, Southern Fiordland tokoeka, and the Northern Fiordland tokoeka; the little spotted kiwi (A. oweni); the great spotted kiwi (A. haasti); the Okarito brown kiwi (A. rowi), also called the Rowi kiwi; and the brown kiwi (A. mantelli), also called the North Island brown kiwi.

rowi-kiwi-465-300x213.jpg


It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi. 

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#127 2018-05-03 03:53:13

ganesh
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Re: Miscellany

111) Mutation

Mutation, an alteration in the genetic material (the genome) of a cell of a living organism or of a virus that is more or less permanent and that can be transmitted to the cell’s or the virus’s descendants. (The genomes of organisms are all composed of DNA, whereas viral genomes can be of DNA or RNA; see heredity: The physical basis of heredity.) Mutation in the DNA of a body cell of a multicellular organism (somatic mutation) may be transmitted to descendant cells by DNA replication and hence result in a sector or patch of cells having abnormal function, an example being cancer. Mutations in egg or sperm cells (germinal mutations) may result in an individual offspring all of whose cells carry the mutation, which often confers some serious malfunction, as in the case of a human genetic disease such as cystic fibrosis. Mutations result either from accidents during the normal chemical transactions of DNA, often during replication, or from exposure to high-energy electromagnetic radiation (e.g., ultraviolet light or X-rays) or particle radiation or to highly reactive chemicals in the environment. Because mutations are random changes, they are expected to be mostly deleterious, but some may be beneficial in certain environments. In general, mutation is the main source of genetic variation, which is the raw material for evolution by natural selection.

The genome is composed of one to several long molecules of DNA, and mutation can occur potentially anywhere on these molecules at any time. The most serious changes take place in the functional units of DNA, the genes. A mutated form of a gene is called a mutant allele. A gene is typically composed of a regulatory region, which is responsible for turning the gene’s transcription on and off at the appropriate times during development, and a coding region, which carries the genetic code for the structure of a functional molecule, generally a protein. A protein is a chain of usually several hundred amino acids. Cells make 20 common amino acids, and it is the unique number and sequence of these that give a protein its specific function. Each amino acid is encoded by a unique sequence, or codon, of three of the four possible base pairs in the DNA (A–T, T–A, G–C, and C–G, the individual letters referring to the four nitrogenous bases adenine, thymine, guanine, and cytosine). Hence, a mutation that changes DNA sequence can change amino acid sequence and in this way potentially reduce or inactivate a protein’s function. A change in the DNA sequence of a gene’s regulatory region can adversely affect the timing and availability of the gene’s protein and also lead to serious cellular malfunction. On the other hand, many mutations are silent, showing no obvious effect at the functional level. Some silent mutations are in the DNA between genes, or they are of a type that results in no significant amino acid changes.

Mutations are of several types. Changes within genes are called point mutations. The simplest kinds are changes to single base pairs, called base-pair substitutions. Many of these substitute an incorrect amino acid in the corresponding position in the encoded protein, and of these a large proportion result in altered protein function. Some base-pair substitutions produce a stop codon. Normally, when a stop codon occurs at the end of a gene, it stops protein synthesis, but, when it occurs in an abnormal position, it can result in a truncated and nonfunctional protein. Another type of simple change, the deletion or insertion of single base pairs, generally has a profound effect on the protein because the protein’s synthesis, which is carried out by the reading of triplet codons in a linear fashion from one end of the gene to the other, is thrown off. This change leads to a frameshift in reading the gene such that all amino acids are incorrect from the mutation onward. More-complex combinations of base substitutions, insertions, and deletions can also be observed in some mutant genes.

Mutations that span more than one gene are called chromosomal mutations because they affect the structure, function, and inheritance of whole DNA molecules (microscopically visible in a coiled state as chromosomes). Often these chromosome mutations result from one or more coincident breaks in the DNA molecules of the genome (possibly from exposure to energetic radiation), followed in some cases by faulty rejoining. Some outcomes are large-scale deletions, duplications, inversions, and translocations. In a diploid species (a species, such as human beings, that has a double set of chromosomes in the nucleus of each cell), deletions and duplications alter gene balance and often result in abnormality. Inversions and translocations involve no loss or gain and are functionally normal unless a break occurs within a gene. However, at meiosis (the specialized nuclear divisions that take place during the production of gametes—i.e., eggs and sperm), faulty pairing of an inverted or translocated chromosome set with a normal set can result in gametes and hence progeny with duplications and deletions.

Loss or gain of whole chromosomes results in a condition called aneuploidy. One familiar result of aneuploidy is Down syndrome, a chromosomal disorder in which humans are born with an extra chromosome 21 (and hence bear three copies of that chromosome instead of the usual two). Another type of chromosome mutation is the gain or loss of whole chromosome sets. Gain of sets results in polyploidy—that is, the presence of three, four, or more chromosome sets instead of the usual two. Polyploidy has been a significant force in the evolution of new species of plants and animals.

Most genomes contain mobile DNA elements that move from one location to another. The movement of these elements can cause mutation, either because the element arrives in some crucial location, such as within a gene, or because it promotes large-scale chromosome mutations via recombination between pairs of mobile elements in different locations.

At the level of whole populations of organisms, mutation can be viewed as a constantly dripping faucet introducing mutant alleles into the population, a concept described as mutational pressure. The rate of mutation differs for different genes and organisms. In RNA viruses, such as the human immunodeficiency virus (HIV), replication of the genome takes place within the host cell using a mechanism that is prone to error. Hence, mutation rates in such viruses are high. In general, however, the fate of individual mutant alleles is never certain. Most are eliminated by chance. In some cases a mutant allele can increase in frequency by chance, and then individuals expressing the allele can be subject to selection, either positive or negative. Hence, for any one gene the frequency of a mutant allele in a population is determined by a combination of mutational pressure, selection, and chance.

Mutations_chart.jpg


It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi. 

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#128 2018-05-05 00:59:11

ganesh
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Re: Miscellany

112) Vitamin C

Vitamin C, also called ascorbic acid, water-soluble, carbohydrate-like substance that is involved in certain metabolic processes of animals. Although most animals can synthesize vitamin C, it is necessary in the diet of some, including humans and other primates, in order to prevent scurvy, a disease characterized by soreness and stiffness of the joints and lower extremities, rigidity, swollen and bloody gums, and hemorrhages in the tissues of the body. First isolated in 1928, vitamin C was identified as the curative agent for scurvy in 1932.

Vitamin C is essential for the synthesis of collagen, a protein important in the formation of connective tissue and in wound healing. It acts as an antioxidant, protecting against damage by reactive molecules called free radicals. The vitamin also helps in stimulating the immune system. It has been shown in animal trials that vitamin C has some anticarcinogenic activity.

Relatively large amounts of vitamin C are required—for instance, an adult man is said to need about 70 mg (1 mg = 0.001 gram) per day. Citrus fruits and fresh vegetables are the best dietary sources of the vitamin. Because vitamin C is easily destroyed by reactions with oxygen, especially in neutral or alkaline solution or at elevated temperatures, it is difficult to preserve in foods. The vitamin is added to certain fruits to prevent browning.

vitamin-c-benefit-skin-1.jpg


It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi. 

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#129 2018-05-07 02:20:14

ganesh
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Re: Miscellany

113) Aspirin

Aspirin, also called acetylsalicylic acid, derivative of salicylic acid that is a mild nonnarcotic analgesic useful in the relief of headache and muscle and joint aches. Aspirin is effective in reducing fever, inflammation, and swelling and thus has been used for treatment of rheumatoid arthritis, rheumatic fever, and mild infection. In these instances, aspirin generally acts on the symptoms of disease and does not modify or shorten the duration of a disease. However, because of its ability to inhibit the production of blood platelet aggregates (which may cut off the blood supply to regions of the heart or brain), it has also been used as an anticoagulant in the treatment of such conditions as unstable angina or following a minor stroke or heart attack.

Aspirin is sometimes used as a preventive agent for certain diseases. For example, daily intake of low-dose aspirin (75–300 mg) can reduce the risk of heart attack or stroke in high-risk individuals. Studies have also found that long-term use of low-dose aspirin can lower the risk of colon cancer in some persons and is associated with a reduced risk of death from several types of cancer, including certain forms of colon cancer as well as lung cancer and esophageal cancer.

Aspirin acts by inhibiting the production of prostaglandins, body chemicals that are necessary for blood clotting and are noted for sensitizing nerve endings to pain. The use of aspirin has been known to cause allergic reaction and gastrointestinal problems in some people. It has also been linked to the development in children (primarily those 2 to 16 years old) of Reye syndrome, an acute disorder of the liver and central nervous system that may follow viral infections such as influenza and chicken pox, and to the development of age-related macular degeneration (a blinding disorder) in some persons who use the drug regularly over many years. Like almost all drugs, aspirin is to be avoided during pregnancy.

media%2F037%2F037442eb-c883-42b6-8f89-2a71eb8019b3%2FphpyuEj0V.png


It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi. 

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#130 2018-05-08 23:23:35

ganesh
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Re: Miscellany

114) Anaconda

Anaconda, (genus Eunectes), either of two species of constricting, water-loving snakes found in tropical South America. The green anaconda (Eunectes murinus), also called the giant anaconda, sucuri, or water kamudi, is an olive-coloured snake with alternating oval-shaped black spots. The yellow, or southern, anaconda (E. notaeus) is much smaller and has pairs of overlapping spots.

Green anacondas live along tropical waters east of the Andes Mountains and on the Caribbean island of Trinidad. The green anaconda is the largest snake in the world. Although anacondas and pythons both have been reliably measured at over 9 metres (30 feet) long, anacondas have been reported to measure over 10 metres (33 feet) and are much more heavily built. Most individuals, however, do not exceed 5 metres (16 feet).

Green anacondas lie in the water (generally at night) to ambush caimans and mammals such as capybara, deer, tapirs, and peccaries that come to drink. An anaconda seizes a large animal by the neck and almost instantly throws its coils around it, killing it by constriction. Anacondas kill smaller prey, such as small turtles and diving birds, with the mouth and sharp backward-pointing teeth alone. Kills made onshore are often dragged into the water, perhaps to avoid attracting jaguars and to ward off biting ants attracted to the carcass. In the wild, green anacondas are not particularly aggressive. In Venezuela, they are captured easily during the day by herpetologists who, in small groups, merely walk up to the snakes and carry them off.

Green anacondas mate in or very near the water. After nine months, a female gives live birth to 14–82 babies, each more than 62 cm (24 inches) in length. The young grow rapidly, attaining almost 3 metres (10 feet) by age three.

Anacondas are members of the boa family (Boidae).

Anaconda-Pitbull-636816.jpg


It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi. 

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#131 2018-05-10 01:33:44

ganesh
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Re: Miscellany

115) Periscope

Periscope, optical instrument used in land and sea warfare, submarine navigation, and elsewhere to enable an observer to see his surroundings while remaining under cover, behind armour, or submerged.

A periscope includes two mirrors or reflecting prisms to change the direction of the light coming from the scene observed: the first deflects it down through a vertical tube, the second diverts it horizontally so that the scene can be viewed conveniently. Frequently there is a telescopic optical system that provides magnification, gives as wide an arc of vision as possible, and includes a crossline or reticle pattern to establish the line of sight to the object under observation. There may also be devices for estimating the range and course of the target in military applications and for photographing through the periscope.

The simplest type of periscope consists of a tube at the ends of which are two mirrors, parallel to each other but at 45° to the axis of the tube. This device produces no magnification and does not give a crossline image. The arc of vision is limited by the simple geometry of the tube: the longer or narrower the tube, the smaller the field of view. Periscopes of this type were widely used in World War II in tanks and other armoured vehicles as observation devices for the driver, gunner, and commander. When fitted with a small, auxiliary gunsight telescope, the tank periscope can also be used in pointing and firing the guns. By employing tubes of rectangular cross section, wide, horizontal fields of view can be obtained.

periscope.jpg


It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi. 

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#132 2018-05-10 15:53:30

ganesh
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Re: Miscellany

116) Acetic Acid

Acetic acid (CH3COOH), also called ethanoic acid, the most important of the carboxylic acids. A dilute (approximately 5 percent by volume) solution of acetic acid produced by fermentation and oxidation of natural carbohydrates is called vinegar; a salt, ester, or acylal of acetic acid is called acetate. Industrially, acetic acid is used in the preparation of metal acetates, used in some printing processes; vinyl acetate, employed in the production of plastics; cellulose acetate, used in making photographic films and textiles; and volatile organic esters (such as ethyl and butyl acetates), widely used as solvents for resins, paints, and lacquers. Biologically, acetic acid is an important metabolic intermediate, and it occurs naturally in body fluids and in plant juices.

Acetic acid has been prepared on an industrial scale by air oxidation of acetaldehyde, by oxidation of ethanol (ethyl alcohol), and by oxidation of butane and butene. Today acetic acid is manufactured by a process developed by the chemical company Monsanto in the 1960s; it involves a rhodium-iodine catalyzed carbonylation of methanol (methyl alcohol).

Pure acetic acid, often called glacial acetic acid, is a corrosive, colourless liquid (boiling point 117.9 °C [244.2 °F]; melting point 16.6 °C [61.9 °F]) that is completely miscible with water.

acetic%20acid.jpg


It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi. 

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#133 2018-05-12 01:03:48

ganesh
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Re: Miscellany

117) Pascal's Law

Pascal’s principle, also called Pascal’s law, in fluid (gas or liquid) mechanics, statement that, in a fluid at rest in a closed container, a pressure change in one part is transmitted without loss to every portion of the fluid and to the walls of the container. The principle was first enunciated by the French scientist Blaise Pascal.

Pressure is equal to the force divided by the area on which it acts. According to Pascal’s principle, in a hydraulic system a pressure exerted on a piston produces an equal increase in pressure on another piston in the system. If the second piston has an area 10 times that of the first, the force on the second piston is 10 times greater, though the pressure is the same as that on the first piston. This effect is exemplified by the hydraulic press, based on Pascal’s principle, which is used in such applications as hydraulic brakes.

Pascal also discovered that the pressure at a point in a fluid at rest is the same in all directions; the pressure would be the same on all planes passing through a specific point. This fact is also known as Pascal’s principle, or Pascal’s law.

variation_depth.jpg


It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi. 

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#134 2018-05-14 00:50:46

ganesh
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Re: Miscellany

118) Benzoic Acid

Benzoic acid, a white, crystalline organic compound belonging to the family of carboxylic acids, widely used as a food preservative and in the manufacture of various cosmetics, dyes, plastics, and insect repellents.

First described in the 16th century, benzoic acid exists in many plants; it makes up about 20 percent of gum benzoin, a vegetable resin. It was first prepared synthetically about 1860 from compounds derived from coal tar. It is commercially manufactured by the chemical reaction of toluene (a hydrocarbon obtained from petroleum) with oxygen at temperatures around 200° C (about 400° F) in the presence of cobalt and manganese salts as catalysts. Pure benzoic acid melts at 122° C (252° F) and is very slightly soluble in water.

Among the derivatives of benzoic acid are sodium benzoate, a salt used as a food preservative; benzyl benzoate, an ester used as a miticide; and benzoyl peroxide, used in bleaching flour and in initiating chemical reactions for preparing certain plastics.

benzoic-acid-250x250.jpg


It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi. 

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#135 2018-05-16 00:54:28

ganesh
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Re: Miscellany

119) Basil

Basil, (Ocimum basilicum), also called sweet basil, annual herb of the mint family (Lamiaceae), grown for its aromatic leaves. Basil is likely native to India and is widely grown as a kitchen herb. The leaves are used fresh or dried to flavour meats, fish, salads, and sauces; basil tea is a stimulant.

Basil leaves are glossy and oval-shaped, with smooth or slightly toothed edges that typically cup slightly; the leaves are arranged oppositely along the square stems. The small flowers are borne in terminal clusters and range in colour from white to magenta. The plant is extremely frost-sensitive and grows best in warm climates. Basil is susceptible to Fusarium wilt, blight, and downy mildew, especially when grown in humid conditions.

A number of varieties are used in commerce, including the small-leaf common basil, the larger leaf Italian basil, and the large lettuce-leaf basil. Thai basil (O. basilicum var. thyrsiflora) and the related holy basil (O. tenuiflorum) and lemon basil (O. ×citriodorum) are common in Asian cuisine. The dried large-leaf varieties have a fragrant aroma faintly reminiscent of anise and a warm, sweet, aromatic, mildly pungent flavour. The dried leaves of the common basil are less fragrant and more pungent in flavour.

The essential oil content is 0.1 percent, the principal components of which are methyl chavicol and d-linalool.

BasilSweetEO.jpg


It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi. 

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#136 2018-05-18 01:25:21

ganesh
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Re: Miscellany

120) Ear bone

Ear bone, also called Auditory Ossicle, any of the three tiny bones in the middle ear of all mammals. These are the malleus, or hammer, the incus, or anvil, and the stapes, or stirrup. Together they form a short chain that crosses the middle ear and transmits vibrations caused by sound waves from the eardrum membrane to the liquid of the inner ear. The malleus resembles a club more than a hammer, whereas the incus looks like a premolar tooth with an extensive root system. The stapes does closely resemble a stirrup. The top or head of the malleus and the body of the incus are held together by a tightly fitting joint and are seated in the attic, or upper portion, of the eardrum cavity. The handle of the malleus adheres to the upper half of the drum membrane. Three small ligaments hold the head of the malleus, and a fourth attaches a projection (called the short process) from the incus to a slight depression in the back wall of the cavity. The long process of the incus is bent near the lower end and carries a small knoblike bone that is jointed loosely to the head of the stapes—the third and smallest of the ossicles. The stapes lies in a horizontal position at right angles with the long process of the incus. There are two openings in the wall of the bony labyrinth and the stapes footplate fits perfectly in one of these openings—an oval-shaped window, where it is held in place by yet another ligament called the annular ligament.

There are two tiny muscles in the middle ear, which serve to alter the tension on the ear bones and thus the intensity (degree of loudness) of sounds. One, the tensor tympani, is attached to the handle of the malleus (itself attached to the eardrum membrane) and by its contraction tends to draw the malleus inward, thus increasing drum membrane tension. The second, called stapedius, tends to pull the footplate of the stapes out of the oval window. This is accomplished by tipping the stirrup, or stapes, backward.

figure%202.jpg


It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi. 

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#137 Today 00:50:39

ganesh
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Re: Miscellany

121) Spirogyra

Spirogyra, (genus Spirogyra), any member of a genus of some 400 species of free-floating green algae (division Chlorophyta) found in freshwater environments around the world. Named for their beautiful spiral chloroplasts, spirogyras are filamentous algae that consist of thin unbranched chains of cylindrical cells. They can form masses that float near the surface of streams and ponds, buoyed by oxygen bubbles released during photosynthesis. They are commonly used in laboratory demonstrations.

Each cell of the filaments features a large central vacuole, within which the nucleus is suspended by fine strands of cytoplasm. The chloroplasts form a spiral around the vacuole and have specialized bodies known as pyrenoids that store starch. The cell wall consists of an inner layer of cellulose and an outer layer of pectin, which is responsible for the slippery texture of the algae.

Spirogyra species can reproduce both sexually and asexually. Asexual, or vegetative, reproduction occurs by simple fragmentation of the filaments. Sexual reproduction occurs by a process known as conjugation, in which cells of two filaments lying side by side are joined by outgrowths called conjugation tubes. This allows the contents of one cell to completely pass into and fuse with the contents of the other. The resulting fused cell (zygote) becomes surrounded by a thick wall and overwinters, while the vegetative filaments die.

spirogyra.jpg


It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi. 

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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