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Murano glass
Murano glass - History of Murano Glassmaking
Murano glass - The Art of Glassmaking
Murano glass - References

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The Zohar posits that the human soul has three elements, the nefesh, ru’ach, and neshamah. The nefesh is found in all humans, and enters the physical body at birth. It is the source of one’s physical and psychological nature. The next two parts of the soul are not implanted at birth, but can be developed over time; their development depends on the actions and beliefs of the individual. They are said to only fully exist in people awakened spiritually. A common way of explaining the three parts of the soul is as follows:

• Nefesh (נפש) - the lower part, or “animal part”, of the soul. It is linked to instincts and bodily cravings.

• Ruach (רוח) - the middle soul, the “spirit”. It contains the moral virtues and the ability to distinguish between good and evil.

• Neshamah (נשמה) - the higher soul, or “super-soul”. This separates man from all other lifeforms. It is related to the intellect, and allows man to enjoy and benefit from the afterlife. This part of the soul is provided both to Jew and non-Jew alike at birth. It allows one to have some awareness of the existence and presence of God.

The Raaya Meheimna, a section of related teachings spread throughout the Zohar, discusses the two other parts of the human soul, the chayyah and yehidah (first mentioned in the Midrash Rabbah). Gershom Scholem writes that these “were considered to represent the sublimest levels of intuitive cognition, and to be within the grasp of only a few chosen individuals”. The Chayyah and the Yechidah do not enter into the body like the other three - thus they received less attention in other sections of the Zohar.

• Chayyah (חיה) - The part of the soul that allows one to have an awareness of the divine life force itself.

• Yehidah (יחידה) - the highest plane of the soul, in which one can achieve as full a union with God as is possible.

Both rabbinic and kabbalistic works posit that there are also a few additional, non-permanent states to the soul that people can develop on certain occasions. These extra souls, or extra states of the soul, play no part in any afterlife scheme, but are mentioned for completeness:

• Ruach HaKodesh (רוח הקודש) - (”spirit of holiness”) a state of the soul that makes prophecy possible. Since the age of classical prophecy passed, no one (outside of Israel) receives the soul of prophesy any longer. See the teachings of Abraham Abulafia for differing views of this matter.

• Neshamah Yeseira - The “supplemental soul” that a Jew can experience on Shabbat. It makes possible an enhanced spiritual enjoyment of the day. This exists only when one is observing Shabbat; it can be lost and gained depending on one’s observance.

• Neshamah Kedosha - Provided to Jews at the age of maturity (13 for boys, 12 for girls), and is related to the study and fulfillment of the Torah commandments. It exists only when one studies and follows Torah; it can be lost and gained depending on one’s study and observance.

Among its many pre-occupations, Kabbalah teaches that every Hebrew letter, word, number, even the accent on words of the Hebrew Bible contains a hidden sense; and it teaches the methods of interpretation for ascertaining these meanings. One such method is as follows:

Kabbalah
Kabbalah - Use of term
Kabbalah - Origins
Kabbalah - Origin of Jewish mysticism
Kabbalah - Textual antiquity of esoteric mysticism
Kabbalah - Mystic doctrines in Talmudic times
Kabbalah - Kabbalah of the Middle Ages
Kabbalah - The Ban Against Studying Kabbalah
Kabbalah - Lurianic Kabbalah in Early Modern history
Kabbalah - Kabbalah of the Sefardim and Mizrahim
Kabbalah - Kabbalah of the Maharal
Kabbalah - The failure of Sabbatian mysticism
Kabbalah - Spread of Kabbalah during the 1700s
Kabbalah - The modern world
Kabbalah - Primary texts
Kabbalah - Theodicy: explanation for the existence of evil
Kabbalah - Kabbalistic understanding of God
Kabbalah - The human soul in Kabbalah
Kabbalah - Number-Word mysticism
Kabbalah - Divination and clairvoyance
Kabbalah - Practical applications
Kabbalah - Gnosticism and Kabbalah
Kabbalah - Criticisms
Kabbalah - Debate about Kabbalah in Judaism
Kabbalah - Kabbalah in non-Jewish society
Kabbalah - References

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While many sea animals produce exoskeletons, usually only those of mollusks (also spelled “mollusc”) are normally considered to be “sea shells”. The majority of shell-forming mollusks belong to the classes Gastropoda (univalves, or snails) or Bivalvia. Three other shell-bearing classes are Scaphopoda (tusk shells), Polyplacophora (segmented chitons) and Monoplacophora (single-shelled chiton-like animals, also called Tryblidia). Some species of Cephalopoda also build shells, including the primitive Nautilus order which produces the famous “chambered Nautilus” shell; although some taxa of cephalopods such as octopi and squid only form small internal shells.

Malacology, the scientific study of mollusks as living organisms, has a branch devoted to shells, called conchology - although it should be noted that these terms are sometimes used interchangeably, even by scientists (this is more common in Europe).

The shell will grow over time as the animal inside adds its building material to the leading edge near the opening. This causes the shell to become longer and wider to better accommodate the growing animal inside. A mollusc shell is formed, repaired and maintained by a part of the mollusc called the mantle. Injuries to or abnormal conditions of the mantle are often reflected in the shell they form and tend. When the animal encounters harsh conditions which limit its food supply or otherwise cause it to become dormant for a while, the mantle often ceases to produce the shell substance. When conditions improve again and the mantle resumes its task, a “growth line” which extends the entire length of the shell is produced, and the pattern and even the colors on the shell after these dormant periods are sometimes quite different from previous colors and patterns.

The majority of shells are made of nacre, an organic mixture of outer layers of horny conchiolin (a scleroprotein), followed by an intermediate layer of calcium carbonate (CaCO3) as either calcite or aragonite in the form of platy crystals. Shells of the class Polyplacophora are made of a softer calcium carbonate compound called chiton.

Nacre is secreted by the epithelial cells (formed by the germ layer ectoderm) of the mantle tissue of certain species of mollusk. Mollusk blood is rich in dissolved calcium. In these mollusks the calcium is concentrated out from the blood where it can crystallize as calcium carbonate. The individual crystals of each layer differ in shape and orientation. Nacre is continually deposited onto the inner surface of the animal’s shell (the iridescent nacreous layer also known as mother of pearl), both as a means to smooth the shell itself and as a defense against parasitic organisms and damaging detritus.

When a mollusk is invaded by a parasite or is irritated by a foreign object that the animal cannot eject, a process known as encystation entombs the offending entity in successive, concentric layers of nacre. This process eventually forms what we call pearls and continues for as long as the mollusk lives. Almost any species of bivalve or gastropod is capable of producing pearls, but only a few, such as the famous pearl oysters, are highly prized.

Mollusc shells (especially those formed by marine species) are very durable and outlast the otherwise soft-bodied animals that produce them by a very long time (sometimes thousands of years). They fossilize easily, and fossil mollusc shells date all the way back to the Cambrian period. Large amounts of shells may form sediment and become compressed into limestone.

Shells of marine molluscs (some of which wash up on beaches or live in the intertidal or sub-tidal zones and are therefore easily found without specialized equipment) are called “seashells”, and are collected by a large number of enthusiasts (who collect “specimen shells” - shells which come with information about them such as how, when, where and in what habitat they were collected), especially in the tropical and sub-tropical areas of our planet, where there are more species of colorful, large and intertidal seashells than in regions further north.

Other molluscs

There are of course fresh-water shell-bearing molluscs, and the class Gastropoda (”snails”) contains many species which live on land, without any need of bodies of water: these are appropriately called “land snails” and are also highly prized by many collectors. It is a little known fact that there are actually more species of land snails than there are marine: they cannot disperse very quickly, so populations are frequently isolated from each other, resulting in situations where adjacent islands and even valleys separated by hills or mountains, contain closely-related but clearly separate species of land snails.

Animal shell
Animal shell - Mollusks of the sea, traditional “sea shells”
Animal shell - Shells in other animals

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Dictionary of Woodworking Tools - Salaman, R.A. 1975 and 1989, ISBN 0-942391-51-9

Hatchet
Hatchet - Types of Hatchets
Hatchet - References

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• Adhesives

• Air cushion

• Buckle

• Counterfort

• Eyelet

• Heel

• Hook

• Insole

• Laces

• Reinforcement tape

• Sole

• Steel shank

• Tack

• Toe puff

• Tread

• Welt

Footwear
Footwear - Footwear materials
Footwear - Footwear components
Footwear - Types of footwear

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Ethiopia has historically had one of the best economies in the world, which had continued on during reign of Haile Selassie, during which the value of the Ethiopian dollar was equivalent to the US Dollar. But soon, Emperor Haile Selassie couldn’t reform economic policies and failed to improve the living condition of the people. In 1972 and 1973, more than 200,000 people died in the Wallo famine. The Emperor Haile Sellasie tried to hide the famine but university students revealed the drought to the world. After the 1974 revolution, the economy of Ethiopia was run as Command economy. Stronger state controls were implemented, and a large part of the economy was transferred to the public sector, including all agricultural land and urban rental property, and all financial institutions. The bad weather also continued to harm the agriculture sector. However since Mengistu Haile Mariam’s relationship with the west was bad, the government hid the famine in Tigray and Wallo region causing the death of more than 250,000 Ethiopians. When the government finally allowed UN workers to witness the condition, one of the worst humanitarian crisis of the decade was revealed. Together with flawed relocation project and the Red Terror around 1,500,000 Ethiopians were killed under Mengistu Haile Mariam. Also six million people were in more famine before the EPRDF-led government overthrew the Derg regime. Then a lot of economic reforms were carried. Since mid-1991, the economy has evolved toward a decentralized, market-oriented economy, emphasizing individual initiative, designed to reverse a decade of economic decline. In 1993, gradual privatization of business, industry, banking, agriculture, trade, and commerce was underway.

Nevertheless, Ethiopia is still privatized. Many government owned properties during the previous regime have now been transferred to these EPRDF owned enterprises in the name of privatization. Furthermore, the Ethiopian constitution defines the right to own land as belonging only to “the state and the people,” but citizens may only lease land (up to 99 years), unable to mortgage, sell, or own it.

Agriculture accounts for almost 41 percent of the gross domestic product (GDP), 80 percent of exports, and 80 percent of the labor force. Many other economic activities depend on agriculture, including marketing, processing, and export of agricultural products. Production is overwhelmingly of a subsistence nature, and a large part of commodity exports are provided by the small agricultural cash-crop sector. Principal crops include coffee, pulses (e.g., beans), oilseeds, cereals, potatoes, sugarcane, and vegetables. Exports are almost entirely agricultural commodities, and coffee is the largest foreign exchange earner. Ethiopia’s livestock population is believed to be the largest in Africa, and as of 1987 accounted for about 15 percent of the GDP.

Ethiopia
Ethiopia - The Name Ethiopia
Ethiopia - History
Ethiopia - Politics
Ethiopia - Geography
Ethiopia - Deforestation
Ethiopia - Administrative divisions
Ethiopia - Economy
Ethiopia - Demographics
Ethiopia - Culture
Ethiopia - Sports
Ethiopia - Archaeology

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Wires and cables for electrical purposes are covered with various insulating materials, such as cotton, rubber, or plastic, wrapped in concentric fashion and further protected with, substances such as paraffin, some kind of preservative compound, bitumen or lead sheathing or steel taping. The stranding or covering machines employed in this work are designed to carry supplies of material and wind it on to the wire which is passing through at a rapid rate. Some of the smallest machines for cotton covering have a large drum, which grips the wire and moves it through toothed gears at a definite speed; the wire passes through the centre of disks mounted above a long bed, and the disks carry each a number of bobbins varying from six to twelve or more in different machines. A supply of covering material is wound on each bobbin, and the end is led on to the wire, which occupies a central position relatively to the bobbins; the latter being revolved at a suitable speed bodily with their disks, the cotton is consequently served on to the wire, winding in spiral fashion so as to overlap. If a large number of strands are required the disks are duplicated, so that as many as sixty spools may be carried, the second set of strands being laid over the first.

For the heavier cables, used for electric light and power, and submarine cables, the machines are somewhat different in construction. The wire is still carried through a hollow shaft, but the bobbins or spools of covering material are set with their spindles at right angles to the axis of the wire, and they lie in a circular cage which rotates on rollers below. The various strands coming from the spools at various parts of the circumference of the cage all lead to a disk at the end of the hollow shaft. This disk has perforations through which each of the strands pass, thence being immediately wrapped on the cable, which slides through a bearing at this point. Toothed gears having certain definite ratios are used to cause the winding drum for the cable and the cage for the spools to rotate at suitable relative speeds which do not vary. The cages are multiplied for stranding with a large number of tapes or strands, so that a machine may have six bobbins on one cage and twelve on the other.

Rubber covering of wires and cables is done by passing them through grooved rollers simultaneously with rubber strips above and below, so that the rubber is crushed on to the wires, the latter emerging as a wide band. The separate wires are parted forcibly, each retaining its rubber sheathing. Vulcanizing is afterwards done in steam-heated drums. However, the conductor needed to be tinned to provide some relief to stripping away the natural rubber. Since the mid 1960s, the insulation has been plastic or polymers exhibiting properties similar to rubber.

Many auxiliary machines are necessary in connection with wire and cable-covering, as plant for preparing the rubber and paper, etc., cutting it into strips, winding it, measuring lengths, etc.

Wire
Wire - History
Wire - Production
Wire - Finishing, covering, and insulating
Wire - Examples of Wire
Wire - Pre-wire

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Liquid ammonia is the best-known and most widely studied non-aqueous ionizing solvent. Its most conspicuous property is its ability to dissolve alkali metals to form highly coloured, electrically conducting solutions containing solvated electrons. Apart from these remarkable solutions, much of the chemistry in liquid ammonia can be classified by analogy with related reactions in aqueous solutions. Comparison of the physical properties of NH3 with those of water shows that NH3 has the lower melting point, boiling point, density, viscosity, dielectric constant and electrical conductivity; this is due at least in part to the weaker H bonding in NH3 and the fact that such bonding cannot form cross-linked networks since each NH3 molecule has only 1 lone-pair of electrons compared with 2 for each H2O molecule. The ionic self-dissociation constant of liquid NH3 at −50 °C is approx. 10-33 mol2•l-2.

Solubility of salts

Liquid ammonia is an ionizing solvent, although less so than water, and dissolves a range of ionic compounds including many nitrates, nitrites, cyanides and thiocyanates. Most ammonium salts are soluble, and these salts act as acids in liquid ammonia solutions. The solubility of halide salts increases from fluoride to iodide. A saturated solution of ammonium nitrate contains 0.83 mol solute per mole of ammonia, and has a vapour pressure of less than 1 bar even at 25 °C.

Solutions of metals

Liquid ammonia will dissolve the alkali metals and other electropositive metals such as calcium, strontium, barium, europium and ytterbium. At low concentrations (<0.06 mol/L), deep blue solutions are formed: these contain metal cations and solvated electrons, free electrons which are surrounded by a cage of ammonia molecules.

These solutions are very useful as strong reducing agents. At higher concentrations, the solutions are metallic in appearance and in electrical conductivity. At low temperatures, the two types of solution can coexist as immiscible phases.

Redox properties of liquid ammonia

The range of thermodynamic stability of liquid ammonia solutions is very narrow, as the potential for oxidation to dinitrogen, E° (N2 + 6NH4+ + 6e− ⇌ 8NH3), is only +0.04 V. In practice, both oxidation to dinitrogen and reduction to dihydrogen are slow. This is particularly true of reducing solutions: the solutions of the alkali metals mentioned above are stable for several days, slowly decomposing to the metal amide and dihydrogen. Most studies involving liquid ammonia solutions are done in reducing conditions: although oxidation of liquid ammonia is usually slow, there is still a risk of explosion, particularly if transition metal ions are present as possible catalysts.

Ammonia
Ammonia - History
Ammonia - Synthesis and production
Ammonia - Biosynthesis
Ammonia - Properties
Ammonia - Uses
Ammonia - Ammonia’s role in biologic systems and human disease
Ammonia - Liquid ammonia as a solvent
Ammonia - Detection and determination
Ammonia - Safety precautions

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List of ethnic slurs
List of ethnic slurs - 0-9
List of ethnic slurs - A
List of ethnic slurs - B
List of ethnic slurs - C
List of ethnic slurs - D
List of ethnic slurs - E
List of ethnic slurs - F
List of ethnic slurs - G
List of ethnic slurs - H
List of ethnic slurs - I
List of ethnic slurs - J
List of ethnic slurs - K
List of ethnic slurs - L
List of ethnic slurs - M
List of ethnic slurs - N
List of ethnic slurs - O
List of ethnic slurs - P
List of ethnic slurs - Q
List of ethnic slurs - R
List of ethnic slurs - S
List of ethnic slurs - T
List of ethnic slurs - U
List of ethnic slurs - V
List of ethnic slurs - W
List of ethnic slurs - X
List of ethnic slurs - Y
List of ethnic slurs - Z

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There are two main methods to produce synthetic diamond. The original method is High Pressure High Temperature (HPHT) and is still the most widely used method because of its relative low cost. It uses large presses that can weigh a couple of hundred tons to produce a pressure of 5 GPa at 1,500 degrees Celsius to reproduce the conditions that create natural diamond inside the Earth. The second method, using chemical vapor deposition or CVD, was invented in the 1980s, and is basically a method creating a carbon plasma on top of a substrate onto which the carbon atoms deposit to form diamond.

High pressure, high temperature, HPHT

There are two main press designs used to supply the pressure and temperature necessary to produce synthetic diamond. These basic designs are the belt press and the cubic press. There are a number of other designs, but none of them are used for industrial scale manufacturing.

The original GE invention by H. Tracy Hall, uses the belt press, wherein upper and lower anvils supply the pressure load and heating current to a cylindrical volume. This internal pressure is confined radially by a belt of pre-stressed steel bands. A variation of the belt press uses hydraulic pressure to confine the internal pressure, rather than steel belts. Belt presses are still used today by the major manufacturers at a much larger scale than the original designs.

The second type of press design is the cubic press. A cubic press has six anvils which provide pressure simultaneously onto all faces of a cube-shaped volume. The first multi-anvil press design was actually a tetrahedral press, using only four anvils to converge upon a tetrahedron-shaped volume. The cubic press was created shortly thereafter to increase the pressurized volume. A cubic press is typically smaller than a belt press and can achieve the pressure and temperature necessary to create synthetic diamond faster. However, cubic presses cannot be easily scaled up to larger volumes. To illustrate, one could increase the pressurized volume by either increasing the size of the anvils, thereby increasing by a factor of 6 the amount of force needed on the anvils to achieve a similar pressurization, or by decreasing the surface area to volume ratio of the pressurized volume by using more anvils to converge upon a different platonic solid (such as a dodecahedron), but such a press would be unnecessarily complex and not easily manufacturable.

Chemical Vapor Deposition, CVD

Chemical vapor deposition of diamond has received a great deal of attention in the materials sciences because it allows many new applications of diamond that had previously been either too expensive to implement or too difficult to make economical. CVD diamond growth typically occurs under low pressure (1 to 27 Pa) and involves feeding varying amounts of gases into a chamber, energizing them and providing conditions for diamond growth on the substrate. The gases always include a carbon source, and typically include hydrogen as well, though the amounts used vary greatly depending on the type of diamond being grown. Energy sources include hot filament, microwave power, and arc discharges, among others. The energy source is intended to generate a plasma in which the gases are broken down and more complex chemistries occur. The actual chemical process for diamond growth is still under study and is complicated by the very wide variety of diamond growth processes used.

The advantages to CVD diamond growth include the ability to grow diamond over large areas, the ability to grow diamond on a substrate, and the control over the properties of the diamond produced. In the past, when high pressure high temperature (HPHT) techniques were used to produce diamond, the diamonds were typically very small free standing diamonds of varying sizes. With CVD diamond growth areas of greater than fifteen centimeters (six inches) diameter have been achieved and much larger areas are likely to be successfully coated with diamond in the future. Improving this ability is key to enabling several important applications.

The ability to grow diamond directly on a substrate is important because it allows the addition of many of diamond’s important qualities to other materials. Since diamond has the highest thermal conductivity of any material, layering diamond onto high heat producing electronics (such as optics and transistors) allows the diamond to be used as a heat sink,. Diamond films are being grown on valve rings, cutting tools, and other objects that benefit from diamond’s hardness and exceedingly low wear rate. In each case the diamond growth must be carefully done to achieve the necessary adhesion onto the substrate.

The most important attribute of CVD diamond growth is the ability to control the properties of the diamond produced. In the area of diamond growth the word “diamond” is used as a description of any material primarily made up of sp3 bonded carbon, and there are many different types of diamond included in this. By regulating the processing parameters—especially the gases introduced, but also including the pressure the system is operated under, the temperature of the diamond, and the method of generating plasma—many different materials that can be considered diamond can be made. Single crystal diamond can be made containing various dopants. Polycrystalline diamond consisting of grain sizes from several nanometers to several micrometers can be grown,. Some polycrystalline diamond grains are surrounded by thin, non-diamond carbon, while others are not. These different factors affect the diamond’s hardness, smoothness, conductivity, optical properties and more.

There are several problems facing CVD diamond growth in the future. First, because research in the area is so heavily application oriented, there are basic questions which have had very little work done on them, and this continues to be a problem for the field. This problem is exacerbated by the fact that small changes in chemistry can require a great deal of research to understand. Another problem is that while CVD diamond growth occurs over large areas compared to other methods of diamond growth, these areas are still too small for some applications, such as large scale transistor manufacturing. There is no better method of producing semiconducting, doped diamond than CVD, but until large scale wafers can be efficiently produced CVD electronics will only have niche applications. CVD diamond growth has had historically low growth rates, usually a few micrometers an hour. While growth rates have been improved dramatically in a few very specific areas, in most applications they are still very slow. The biggest problem with CVD diamond growth is cost; cheaper alternatives are used instead of CVD diamonds whenever possible.

The Carnegie Institute’s Geophysical Laboratory can produce 10 carat (2 g) single-crystal diamonds rapidly (28 nm/s) by CVD, as well as colorless single-crystal diamonds. Growth of colorless diamonds up to 60 g (300 carats) is believed achievable using their method.

Synthetic diamond
Synthetic diamond - History
Synthetic diamond - Manufacturing technologies
Synthetic diamond - Synthetic diamond types
Synthetic diamond - Applications
Synthetic diamond - Synthetic gems

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