cahya/simple-wikipedia huggingface dataset:
San Francisco Bay is a shallow, productive estuary through which water draining about forty percent of California, flowing in the Sacramento and San Joaquin rivers from the Sierra Nevada mountains and Central Valley, enters the Pacific Ocean. Technically, both rivers flow into Suisun Bay, which help flows through the Carquinez Strait to meet with the Napa River at the entrance to San Pablo Bay, which connects at its south end to San Francisco Bay, although the entire group of interconnected bays are often referred to as "the San Francisco Bay."

San Francisco Bay lies in the US state of California and is surrounded by a region known as the San Francisco Bay Area, that is near the big cities of San Francisco, Oakland, and San Jose.

The Bay covers somewhere between 400  and 1,600  square miles (1,040 to 4,160 square kilometres), depending on which sub-bays (such as San Pablo Bay), estuaries, wetlands, and so on are included in the measurement.

Photography

References 
 1999 Grolier Multimedia Encyclopedia.
 1988 Encyclopædia Britannica.

Other websites 
 San Francisco Bay: Portrait of an Estuary, David Sanger and John Hart, University of California Press
 Barging In - A Short History of Liveaboards on the Bay 
 Army Corps of Engineers Bay Model: Working scale model of the Bay 
 BoatingSF.com: Photos of SF Bay and its boats, plus online cruising guide
 SF Estuary Institute: San Francisco Bay Historical View Maps

San Francisco Bay Area
Bodies of water of California
Bays of the United States
Alameda County, California
Santa Clara County, California
Contra Costa County, California
Solano County, California
San Mateo County, California
Marin County, California
Ahmed Yassin (January 1, 1937 – March 22, 2004) was a spiritual leader of the militant Palestinian group Hamas. Yassin's birth date is in dispute. He claimed he was born 1/1/1938, however, his passport indicated 1/1/1937. To some he was a hero, to some he was a notorious member of a terrorist organization. He was also a symbolic figure for Palestinians to fight against Israel. 

Yassin was born in al-Jura, British Mandate of Palestine. He helped create Hamas and became its spiritual leader in 1987. To other members of Hamas he was a hero but he was blamed by the Israeli government for planning suicide bombings and other attacks against Israel. He claimed that was the only way of fighting occupation. He was confined to a wheelchair because he was paralyzed since age 12, he was also nearly blind and could barely hear. He was very powerful and influential. He was assassinated in an airstrike in Gaza City by the Israeli Army after he left a mosque in Gaza in the early morning hours.

Other websites 
 Israel Bombing of Refugee Camp 
 Yassin killed, Ahmed Yassin biography 
 Yassin's letter and kids named after him

1937 births
2004 deaths
Deaths by airstrike
Assassinated people
Muslim terrorists
Palestinian Muslims
Palestinian nationalists
Palestinian terrorists
In physics, a field means that a physical quantity is assigned to every point in space (or, more generally, spacetime). A field is seen as extending throughout a large region of space so that it influences everything. The strength of a field usually varies over a region. Michael Faraday became the first to coin the term "field", in 1849.

For some fields, there is a number for each point in space. They are called scalar fields. For more complicated fields, there are more than one number for each point in space. They are called vector fields or tensor fields. For example, one can model a gravitational field by a vector field where a vector indicates the acceleration a mass would experience at each point in space. Other examples are temperature fields or air pressure fields, which are often illustrated on weather reports by isotherms and isobars by joining up the points of equal temperature or pressure respectively.

Types of fields

Classical fields 
Newtonian gravitation: describes the gravitational force as a mutual interaction between two masses.
Electromagnetism:  electric and magnetic fields are not only fields of force which dictate the motion of particles, but also have an independent physical reality because they carry energy.
Gravitation in general relativity: this is Einstein's theory of gravity. 
Waves as fields

Quantum fields 
It is now believed that quantum mechanics should underlie all physical phenomena.

Field theory 
A field theory is a physical theory that describes how one or more physical fields interact with matter.

Related pages 
 Elasticity
 Fluid dynamics
 General relativity
 Maxwell's equations
 Particle physics

References 

 Landau, Lev D. and Lifshitz, Evgeny M. 1971. Classical theory of fields. 3rd ed, London: Pergamon.  Vol. 2 of the Course of Theoretical Physics.

Basic physics ideas
In vector calculus, the gradient of a multivariate function measures how steep a curve is. On a graph of the function, it is the slope of the tangent of that curve. More generally, it is a vector that points in the direction in which the function grows the fastest. Its coordinates are partial derivatives of that function. The gradient of a function f is often written as  or .

Related pages 

 Laplace operator

References 

Mathematics
Calculus
An archer is someone who practices archery (shooting with bows and arrows). 

Archer can also mean:

Fictional characters
 Sean Archer, character portrayed by John Travolta/Nicolas Cage in the movie Face/Off
 Danny Archer, character portrayed by Leonardo DiCaprio in the movie Blood Diamond

Other
 Jeffrey Archer, Baron Archer of Weston-super-Mare, British author, former politician
 Archer River, one of the best-known rivers in Cape York Peninsula, Australia
 Archer (horse) - an Australian racehorse that won the first two Melbourne Cups
Archery is the practice of using a bow to shoot arrows. Archery has historically been used in hunting and combat and has become a precision sport. A person practicing archery is called an archer, and one who enjoys or is an expert at archery is sometimes called an toxophilite.

History

The earliest evidence of archery dates back more than 9,000 years. The bow probably was used in hunting first and later adopted as a tool of warfare. It was one of the earliest forms of artillery. 

Classical civilizations, notably the Persians, Macedonians, Nubians, Greeks, Parthians, Indians, Japanese, Chinese, and Koreans, had large numbers of archers in their armies. Archers in chariots were especially important in armies of ancient Egypt. Arrows were very destructive against massed formations, and the use of archers helped win battles. The army of the Mongol Empire was mostly archers on horseback.

Other websites 

 Archery Interchange UK The UK's largest online archery community.
 The Great Northwood Bowmen  Medieval Longbow Archery and re-enactment Society, re-enacting the 15th century, based in London. 
 Bowhunting Basics
 Archery Information
 Archery Pictures

       
 
War
Summer Olympic sports
A signal transduction in biology is a  cellular mechanism. It converts a stimulus into a response in the cell. There are two stages in this process:
A signalling molecule attaches to a receptor protein on the cell membrane.
A second messenger transmits the signal into the cell, and a change takes place in the cell.
So, signal transduction starts with a signal to a cell receptor, and ends with a change in cell function. In either step, the signal can be amplified. Thus, one signalling molecule can cause many responses.

Receptors are in the cell membrane, with part of the receptor outside and part inside the cell.  The  chemical signal binds to the outer portion of the receptor, changing its shape. This causes another signal inside the cell.  Some chemical messengers, such as testosterone, can pass through the cell membrane, and bind directly to receptors in the cytoplasm or nucleus.

Sometimes there is a cascade of signals within the cell. With each step of the cascade, the signal can be amplified, so a small signal can result in a large response. Eventually, the signal creates a change in the cell, either in the expression of the DNA in the nucleus or in the activity of enzymes in the cytoplasm.

Most often, ordered sequences of biochemical reactions inside the cell are involved. These are carried out by enzymes and linked through second messengers. So a "second messenger pathway" is produced. These things usually happen quickly, sometimes very quickly. They may last from milliseconds (in the case of ion flux) to days for gene expression.

The number of proteins and other molecules that take part increases during the process. So a 'signal cascade' develops and a relatively small stimulus may cause a large response.

In bacteria and other single-cell organisms, the transduction processes a cell has limits the number of ways it can respond to its environment. In multicellular organisms, lots of different signal transduction processes are used to coordinate the behavior of individual cells. By this means the function of the organism as a whole is organized. The more complex the organism, the more complex the repertoire of signal transduction processes the organism must possess.

Thus, sensing of both the external and internal environment at the cellular level, relies on signal transduction. Many disease processes such as diabetes, heart disease, autoimmunity and cancer arise from defects in signal transduction pathways. This highlights the critical importance of signal transduction to biology and medicine.

These systems of communication between cells are extremely ancient, and are found in all metazoa.

Related pages 
Transduction (physiology)
Ligand
Cytokine

References

Other websites 

 [http://stke.sciencemag.org/ Science'''s STKE - Signal transduction knowledge environment], from Science'', published by AAAS.
 Cosma Shalizi's Signal transduction notebook

Cell biology
Molecular biology
Flux is a term in physics and mathematics. It is broadly defined as "How much stuff goes through a thing" (or into an area). The word "flux" is similar to "flow".

For instance, imagine a butterfly net. The amount of air passing through the net is the flux.

Movement of substances 
In the study of transport phenomena (heat transfer, mass transfer and fluid dynamics), flux is defined as flow per unit area, where flow is the movement of some quantity per time. Flux, in this definition, is a vector.
 
There are many fluxes used in the study of transport phenomena. Each type of flux has its own distinct unit of measurement along with distinct physical constants. Six of the most common forms of flux from the transport literature are defined as:
Momentum flux, the rate of transfer of momentum across a unit area (N·s·m−2·s−1). (Newtonian fluid, viscous flow)
Heat flux, the rate of heat flow across a unit area (J·m−2·s−1). (Fourier's Law) (This definition of heat flux fits Maxwell's original definition.)
Chemical flux, the rate of movement of molecules across a unit area (mol·m−2·s−1). (Fick's law of diffusion)
Volumetric flux, the rate of volume flow across a unit area (m3·m−2·s−1). (Darcy's law)
Mass flux, the rate of mass flow across a unit area (kg·m−2·s−1). (Either an alternate form of Fick's law that includes the molecular mass, or an alternate form of Darcy's law that includes the density).
Radiative flux, the amount of energy moving in the form of photons at a certain distance from the source per steradian per second (J·m−2·s−1). Used in astronomy to study and classify stars.  Also acts as a generalization of heat flux, which is equal to the radiative flux when restricted to the infrared spectrum.
Magnetic flux, the density of a magnetic field.

Electromagnetism 

In the field of electromagnetism, flux is usually the integral of a vector quantity over a finite surface. The result of this integration is a scalar quantity. The magnetic flux is thus the integral of the magnetic vector field over a surface, and the electric flux is defined similarly. Using this definition, the flux of the Poynting vector over a specified surface is the rate at which electromagnetic energy flows through that surface. Confusingly, the Poynting vector is sometimes called the power flux,  which is an example of the first usage of flux, above. It has units of watts per square metre (W/m2).

Related pages 
Fluid dynamics

References

Further reading

Physical quantity
Mathematics
Flux comes from Latin and means flow; it may mean:
 Flux, a scientific term describing the rate of flow of something through a surface
 Flux (software), a free for non-commercial usage suite of VRML/X3D viewing/authoring software
 Flux (metallurgy), a material that aids in smelting and soldering by assisting the flow of the molten metal
 Flow (psychology), often referred to as flux
 Flux (biochemistry), the rate of turnover of molecules through a metabolic pathway
 Flux (novel), a book by Stephen Baxter
 Flux Magazine (US), a short-lived American music, comic book & video game magazine from the mid-1990s
 Flux Of Pink Indians, the name of a British anarcho-punk band, originally known as Flux of Pink Indians
 Fluxx, a card game
 Flux Capacitor, a fictional device from Back to the Future that "makes time travel possible"
 Fluxus, an art movement
 Flux Wildly, one of the main characters from the computer game Toonstruck
 Flux (magazine), a magazine published by students at the University of Oregon journalism school
 Flux (magazine), a magazine published in the United Kingdom
Neuroscience (or neurobiology) is the scientific study of the nervous system. It is the branch of biology which investigates every aspect of the brain and nervous system.

The nervous system is made of billions of neurons connected together and to other systems in the body.  The central nervous system includes the brain, spinal cord and retina. It is connected to the rest of the body via the peripheral nervous system.

Research themes 
Neuroscience research focusses on a set of themes and questions.  
 Behavior/cognition/language
 Biological rhythms
 Brain imaging or neuroimaging
 Cell biology
 Cell imaging & Electrophysiology
 Learning/memory
 Signal transduction
 Neurobiology of the neuron
 Sensation and perception
 Sleep
 Autonomic nervous system and homeostasis
 Arousal, attention and emotion
 Genetics of the nervous system
Developmental biology of the nervous system 
Diseases of the nervous system

Related pages 

 Biology
 Cognitive neuropsychology
 Ethology
 Neurology
 Neuropsychology
 Psychiatry

References

Textbooks 

Squire, L. et al. (2003). Fundamental Neuroscience, 2nd edition. Academic Press; 
Byrne and Roberts (2004). From Molecules to Networks. Academic Press; 
Sanes, Reh, Harris (2005). Development of the Nervous System, 2nd edition. Academic Press; 
Siegel et al. (2005). Basic Neurochemistry, 7th edition. Academic Press; 
Rieke, F. et al. (1999). Spikes: Exploring the Neural Code. The MIT Press; Reprint edition

Online textbooks 
Neuroscience 2nd ed. Dale Purves et al. Published by Sinauer Associates, Inc., 2001.
Basic Neurochemistry: Molecular, Cellular, and Medical Aspects 6th ed. by George J. Siegel et al. Published by Lippincott, Williams & Wilkins, 1999.

Popular works
 
 Damasio, A. R. (1994). Descartes' Error: Emotion, Reason, and the Human Brain. New York, Avon Books.  (Hardcover)  (Paperback)
 Gardner, H. (1976). The Shattered Mind: The Person After Brain Damage. New York, Vintage Books, 1976 
 Luria, A. R. (1997). The Man with a Shattered World: The History of a Brain Wound. Cambridge, Massachusetts, Harvard University Press.  (Hardcover)  (Paperback)
 Sacks, O. The Man Who Mistook His Wife for a Hat. Summit Books  (Hardcover)  (Paperback)
 Sacks, O. (1990). Awakenings. New York, Vintage Books. (See also Oliver Sacks)  (Hardcover)  (Paperback)
 Sternberg, E. (2007) Are You a Machine? The Brain, the Mind and What it Means to be Human. Amherst, NY: Prometheus Books.

Other websites 
 High-Resolution Cytoarchitectural Primate Brain Atlases 
 Society for Neuroscience
 Neural Plasticity-Open Access Journal (Hindawi Publishing)
 Neuroscience. 2nd ed. by Purves et al. (online textbook)
 Neuroscience for Kids
The resting potential of a cell is the membrane potential that would be maintained if there were no action potentials, synaptic potentials, or other active changes in the membrane potential. In most cells the resting potential has a negative value, which by convention means that there is excess negative charge inside compared to outside. The resting potential is mostly determined by the concentrations of the ions in the fluids on both sides of the cell membrane and the ion transport proteins that are in the cell membrane. How the concentrations of ions and the membrane transport proteins influence the value of the resting potential is outlined below.

Other websites 
Neuroscience - online textbook by Purves, et al.
 Basic Neurochemistry Molecular, Cellular, and Medical Aspects by Siegel, et al.
 Bertil Hille Ion channels of excitable membranes, 3rd ed., Sinauer Associates, Sunderland, MA (2001). 
 Generation of resting membrane potential Wright, S.H., Advances in Physiology Education, 28(1-4): 139-142, 2004,

Biochemistry
A fable is a type of story which shows something in life or has a meaning to a word. A fable teaches a lesson or suggests a moral from it. A fable starts in the middle of the story, that means, jumps into the main event without detailed introduction of characters. The characters of a fable may be animals, plants and legendary creatures. When animals are used in fables, they think and talk like people, even though they act like animals. For example, in a fable a clay pot might say that it is frightened of being broken.

The stories told by fables are usually very simple. To understand a fable, the reader or listener does not need to know all about the characters, only one important thing. For this reason animals are often used in fables in a way that is easily understood because it is always the same. They keep the same characteristics from story to story.
 A lion is noble
 A rooster is boastful
 A peacock is proud
 A fox is cunning
 A wolf is fierce
 A horse is brave
 A donkey is hard-working

The most famous fables are those attributed to Aesop (6th century B.C.). Many fables are so well-known that their morals have become English sayings.

For example:
 If a person says "sour grapes!" then they are referring to "The Fox and the Grapes". This fable is about a fox who saw a beautiful bunch of grapes hanging on a vine. He wanted to eat them but they were high up. He tried and tried to jump high enough to pull them down. When he was too tired to jump anymore, he went away saying "I'll bet those grapes were sour!"

So, if a person sees a beautiful thing that they want, but cannot have, sometimes they say "I don't want it, anyway! I'll bet it is really no good!" This way of thinking is called "sour grapes".

"Crying wolf" is another well-known English saying. This comes from "The Boy Who Cried Wolf". This fable is about a boy who was sent to mind the sheep. The boy got lonely while minding the sheep, so he shouted "Wolf! Wolf!"  The people came running. The next day, he did it again and they were very angry. On the third day the boy saw a wolf. He cried "Wolf! Wolf!" but no one came and the wolf ate him.

So if a person always makes a great fuss to get attention, or if a person says something bad has happened when it has not, then it is called "crying wolf" and people will stop bothering to pay attention, even when things go really wrong.

Related pages
 Children's literature
 Jean de La Fontaine
 Myth
 Fairy tale

Other websites

 Animal Symbolism List of frequently described animals and their characteristics
 The Dragon-Tyrant
 Fables - Collection and guide to fables for children 
 Imaginexus  A collection of interconnected stories that anyone can edit
 Beast Fable Society  An academic society focused on fables and related genres

Fairy tales
Drainage is the natural or artificial removal of surface and sub-surface water from a given area.  Many agricultural soils need drainage to improve production or to manage water supplies.

Early history
The earliest archaeological record of an advanced system of drainage comes from the  Indus Valley Civilization from around 3100 BC in what is now Pakistan and North India. The ancient Indus systems of sewerage and drainage that were developed and used in cities throughout the civilization were far more advanced than any found in contemporary urban sites in the Middle East and even more efficient than those in some areas of modern Pakistan and India today. All houses in the major cities of Harappa and Mohenjo-daro had access to water and drainage facilities. Waste water was directed to covered drains, which lined the major streets.

Reasons for artificial drainage 

Wetland soils may need drainage to be used for agriculture. In the northern USA and Europe, glaciation created numerous small lakes which gradually filled with humus to make marshes. Some of these were drained using open ditches and trenches.

The largest project of this type in the world has been in process for centuries in the Netherlands. The area between Amsterdam, Haarlem and Leiden was, in prehistoric times swampland and small lakes. Turf cutting (Peat mining), subsidence and shoreline erosion gradually caused the formation of one large lake, the Haarlemmermeer, or lake of Haarlem. The invention of wind powered pumping engines in the 15th century permitted drainage of some of the marginal land, but the final drainage of the lake had to await the design of large, steam powered pumps and agreements between regional authorities. The elimination of the lake occurred between 1849 and 1852, creating thousands of km2 of new land.

Other websites 

WebCom Systems, software created for designing soakaways and filter trenches.
NDS , drainage calculator.
Ancient drains, a series of images of the earliest drainage systems in the ancient Indus city of Mohenjo daro
Stormwater DesignInformation on stormwater design 
Draining for Profit, and Draining for Health by George E. Waring, 1867, from Project Gutenberg
 Drainage photos 

Agriculture
Engineering
Empoldering is a method of reclaiming land from the sea, and a way to control floods.  Empoldering involves the use of a polder, a piece of land in a low-lying area that has been reclaimed from a body of water by building dikes and drainage canals.

Although empoldering is usually carried out in low-lying coastal areas, it can also be dome in inland areas such as lakes and rivers.  It is common in countries like the Netherlands, where much of the country is below sea level and subject to flooding.  About one-fifth of the land in the Netherlands has been reclaimed from the sea.  Their largest and most successful project is the Zuider Zee project.

Polders have two distinct features.  Firstly, they are enclosed by dikes to keep the water out.  The dikes also serve to protect the polder from erosion.  Secondly, polders are continually maintained by systems of drainage canals and pumps which prevent them from becoming waterlogged and hence, suitable for cultivation.

Process 

Stage 1: Dike constructed around the area to be reclaimed to keep water from coming in.

Stage 2: The area is drained using pumps and drainage canals.

Stage 3: "Reeds" (a type of salt tolerant plant) are sown by aircraft to help the soil form.

Stage 4: After 3 years, reeds are burnt and the ash is used as fertilizers for the soil.

Stage 5: After a period of up to 15 years, the polder is ready for growing crops, building houses and constructing roads.

Limits of land reclamation 

1. Cost of reclaiming from deeper waters 

2. Availability of sand 

3. Dispute over territorial boundaries

Physical geography
The Doctor of Philosophy, (PhD, Ph.D., DPhil or D.Phil.) is a degree a person gets from a university by finishing a doctorate program. In many areas of study, the PhD/DPhil is the highest degree that a person can earn (this is called the "terminal degree"). There are PhD/DPhil degrees for many different fields, such as PhDs/DPhils in literature, philosophy, history, science, mathematics, and engineering. Some PhD/DPhil degrees have existed for hundreds of years, such as the PhD/DPhil in Canon Law. Other PhD/DPhil degrees were developed in the 1970s and 1980s, such as the PhD/DPhil in Computer Science.

Requirements for degree
To be admitted to a PhD/DPhil program, a person usually has to have completed their Bachelor's degree or master's degree that is related to the PhD/DPhil degree. For example, a person applying to be admitted to a PhD/DPhil degree in Theater would normally have to have a master's degree such as a Master of Arts (MA) degree in Theater, English Literature, or a related area.

Elements of a PhD/DPhil degree
The PhD/DPhil degree usually takes between three and six years of full-time study to complete. They may or may not require a master's degree beforehand. Many PhD/DPhil degrees begin with a period of graduate courses. After the PhD/DPhil student has taken these courses, they take examinations to test what the student knows about their area of study. After the student passes the exams, they begin to do original research. The product is a long research report called a dissertation (or a "thesis"). Some PhD/DPhil degrees also require students to pass exams in languages (such as French, German, or other languages). Many PhD/DPhil students teach undergraduate students or assist professors with research during their PhD/DPhil studies.

As a requirement for university teaching 
Requirements for university teaching vary in different subjects and in different countries. A PhD/DPhil is necessary or usual to become a university professor in many fields, especially in science. However, many famous professors have not had higher degrees, though that is less common today. In some fields, there is no PhD/DPhil, and so another degree is required to become a university professor. For example, the highest degree in Fine Arts fields such as printmaking or graphic design is the Master of Fine Arts (MFA) degree. A person with an MFA degree can become a university professor in some Fine Arts fields.

Other websites 
 The Mathematics PhD in the United Kingdom: Notes on its History Contains information/links of more general relevance than mathematics.

Academia
Academic degrees
In geography, a marsh is a type of wetland. It has grasses, rushes, reeds, typhas, sedges, and other herbaceous plants (possibly with low-growing woody plants) in a context of shallow water.  A marsh is different from a swamp, which has a greater proportion of open water surface, which is generally deeper than a marsh. In the US, the term 'swamp' is used for wetland dominated by trees rather than grasses and low herbs.

The water of a marsh can be fresh, brackish or saline. Coastal marshes may be associated with estuaries and along waterways between coastal barrier islands and the inner coast.  Estuarine marshes often are based on soils consisting of sandy bottoms or bay muds.

Marshes are critically important wildlife habitat, often serving as breeding grounds for a wide variety of animal life.

Related pages
Fen
Swamp
Ecoregion

Other websites 
 Marshes of the Lowcountry (South Carolina) -- Beaufort County Library

Wetlands
Ulan-Ude (Russian:Ула́н-Удэ́; Buryat: Улаан-Үдэ), formerly Verkhneudinsk (), the capital city of the Buryat Republic, Russia. The city is located about 100 km south-east of Lake Baikal. It sits at the foot of the Khamar-Daban and Khrebet Ulan-Burgasy mountain ranges, next to the confluence of the Selenga River and its tributary, the Uda. The city is divided into two parts by the Uda. Population 359,391 (2002 Census); 352,530 (1989 Census). It is the third largest city in East Siberia.  It is served by Ulan-Ude Airport (Mukhino) as well as the smaller Ulan-Ude Vostochny Airport.

Ulan-Ude was founded in 1666 by the Russian Cossacks. Due to its geographical position, the city grew rapidly and became a large trade centre which connected Russia with China and Mongolia. There are old merchants' mansions richly decorated with wood and stone carving in the historical center of Ulan-Ude, along the river banks. They represent beautiful examples of Russian classicism.  There is also a large and highly unusual head of Lenin in the central square.

Gallery

Sources

Other websites

Siberia
The pelagic zone is the open sea or ocean that is not near the coast. The name comes from the Greek πέλαγος (pélagos), which might be translated as "open sea".

To make this clear, seas around continents have continental crust beneath them. They are shallow. Seas away from continents can be very deep, and do not have continental shelves beneath them.

Sub-zones 
The pelagic (or open ocean) zone is divided into a number of sub-zones:

 Epipelagic (surface to 200m): the illuminated surface zone where there is enough light for photosynthesis. Because of this, plankton, and the food chain which feeds on it, are in this zone. The top predators are fish such as tuna and many sharks.
 Mesopelagic (from 200m to 1000m): the twilight zone.  Although some light penetrates this deep, it is insufficient for photosynthesis. The name comes from Greek μέσον, middle. 
 Bathyal zone (from 1000m to 4000m): by this depth the ocean is almost entirely dark (with only the occasional bioluminescent organism). There are no living plants, and most animals survive by consuming the snow of detritus falling from the zones above, or (like the marine hatchetfish) by preying upon others. Giant squid live at this depth, and here they are hunted by deep-diving sperm whales. From Greek βαθύς (bathys), deep.
 Abyssal zone (from 4000m to the ocean floor): no light penetrates to this depth, and some creatures are blind and colourless. Bioluminescence also occurs in this zone. 
 Hadal zone (the deep water in ocean trenches) – the name comes from Hades, the classical Greek underworld. This zone is less well known. Very few species live in the open areas, but many organisms live in hydrothermal vents.

The last three zones are similar in character, and some marine biologists count them as a single zone or consider the latter two to be the one zone. Some define the hadopelagic as waters below 6000 meters, whether in a trench or not.

Other features of the deep ocean 
Seamounts
Ocean ridges

Other websites 
 The Deep Sea pages at Oceanlink 

Biological oceanography
Ecology
Biomes
Vitamin A is a vitamin, a group of organic chemicals including retinal and several carotenoids. The human body does not make these chemicals, and must take them from food. Egg yolks and liver are both rich in vitamin A. Many parts of the body need vitamin A. For example, vitamin A helps sight and is good for the immune system. It is also important for a growing embryo.

β-carotene, a provitamin found in foods like carrots can be converted to vitamin A. The efficiency of the conversion depends on genetics and fat consumption.

Too little vitamin A is dangerous to health. People who do not get enough of the vitamin may lose the ability to see in poor light and suffer from a weakened immune system. They may also have problems with memory, because vitamin A is important for the brain. People with malnutrition often have too little vitamin A. This is common in poor countries.

Hypervitaminosis A 
Too much vitamin A is also dangerous to one's health. It is a condition known as hypervitaminosis. Vitamin A is not soluble in water, and the human body can not get rid of the excess vitamin A easily by urination.  Too much vitamin A can make someone very sick.  People may get too much vitamin A from taking too many vitamin pills or from eating too much A-rich food like liver.

What applies to humans applies to all mammals at least. Some large predators, such as the big cats, seem not to eat their preys' livers. On the other hand, polar bears apparently do so, and they store vitamin A in their liver cells. However, they have long, sometimes very long, periods between kills. In contrast, African big cats kill about every three or four days, and they do seem to avoid eating the preys' livers.

References 

Fat-soluble vitamins
Vitamin D is a hormone. It is a steroid which is made in the body under the right conditions. Its making by the body needs sunlight, which acts on the lower layers of the skin. 

However, if the body does not make enough, it can be found from food sources in tiny amounts.  In fact, many countries add it automatically to certain foods like milk. Supplements can be easily found in most developed countries.

Vitamin D is a fat-soluble nutrient. This means that any portion not used immediately is stored in fat tissue for future use.

What it does
As a hormone, Vitamin D does many things in the body.  It was first discovered as the substance which could prevent and cure rickets. It controls the levels of calcium ions and phosphates in the blood, as well as calcium and magnesium absorption in the intestines. It helps bones grow and form. It is also good for the immune system.

Different kinds
In total, there are 5 different forms, D1 to D5. The most common ones are D2 and D3 (see images).

D3 (also called cholecalciferol) is the kind produced by the body. It is also found naturally in marine oils and in lanolin (oil from sheep's wool), the most common source for supplements.

D2 (also called ergocalciferol) is produced by fungi. It is similar to D3, but not exactly the same.

Getting enough
D3 is made in the skin from cholesterol, and changed into a more active form by the liver. However, the skin will not make it unless enough ultraviolet light shines on it. As sunlight contains ultraviolet light, getting enough sun is one way of getting enough D3.

Many things can keep the skin from making enough D3. Winter sunlight may be too weak. Melanin, which protects skin from damage, also keeps it from making D3, which is why people with darker skin are more prone to deficiency. Older people are also prone, because aging skin makes less D3, even with enough sunlight. Clothing, glass, sunscreens and sunblocks also shield the skin from getting enough ultraviolet light to make D3.

It is hard to know how much supplemental Vitamin D, if any, is needed. Less than 25 micrograms (1000 IU) per day, but up to 100 mcg (4000 IU) per day is considered safe. A recent panel of Vitamin D researchers concluded that at least 20-25 mcg (800-1000 IU) per day would help most adults.

Few foods naturally contain much D3. Fish do, especially oily ones, such as salmon, sardine and mackerel. Many kinds of edible mushrooms contain some D2, like shiitake. Mushrooms grown in full sunlight tend to have more.

References

Other websites 
Benefits and sources of Vitamin D 
Benefits of Vitamin D 
Factsheet on Vitamin D
FDA takes Vitamin D drugs and feeds them to prisoners 

Fat-soluble vitamins
Steroid hormones
The B vitamin complex (also called B vitamins) are a group of 8 vitamins. They have an important job in the metabolism of cells. Each B vitamin is a cofactor (a coenzyme) for some key metabolic processes or it is a precursor needed to make one.

Originally, people thought they were just different forms of one vitamin (as with Vitamin D, for example). Later it turned out that they are separate vitamins that often can be found together. They are Vitamin B1/Thiamine, Vitamin B2/Riboflavin, Vitamin B3/Vitamin P/Vitamin PP/Niacin,Vitamin B5/Pantothenic acid, Vitamin B6, Vitamin B7/Vitamin H/Biotin, Vitamin B9/Vitamin M/Vitamin B-c/Folate and Vitamin B12. They are required for growth, and proper functioning of nerves and muscles. B vitamins are found in meat, milk, whole grains and fresh vegetables.

Vitamin B deficiencies have been shown to cause the following symptoms:

mental problems
heart palpitations
heart arrhythmias
exhaustion
paranoia, vague fears, fear that something dreadful is about to happen, nervousness, ADD (attention deficiency), inability to concentrate
thoughts of dying
frustration
inability to sleep
restlessness
tingling in hands
tingling fingers and toes
crying spells, inability to cope
soreness all over

Well-known medical syndromes caused by thiamine deficiency are beri-beri, Wernicke–Korsakoff syndrome (WKS), and optic neuropathy.

References
A claw is a sharp object. It is found at the end of a toe or finger in many mammals, birds, and some reptiles. The word "claw" is also used in reference to an invertebrate. For example, the chelae of crabs and lobsters are often called claws or pincers. 

A claw is made of hard protein called keratin. They are used by some meat eating mammals such as cats to catch and hold prey, but they may also be used for other things such as digging, climbing trees, and so on, in those and other species.

Similar appendages that are flat and do not come to a sharp point are called nails instead.

Arthropods 
The correct name for an arthropod's 'claw' is chela (plural chelae). Legs that have a chela are called chelipeds. Chelae are also called pincers.

Tetrapods
In tetrapods, claws are made of keratin and have two layers.  The unguis is the outside hard layer, which has keratin fibers arranged perpendicular to the direction of growth and in layers at an angle. The subunguis is the soft, flaky layer, and the grain is parallel to the direction of growth. The claw grows outward from the nail matrix at the base of the unguis and the subunguis grows thicker while traveling across the nail bed. The unguis grows outward faster than the subunguis to make a curve and the thinner sides of the claw wear away faster than their thicker middle, making a more or less sharp point. Tetrapods use their claws in many ways, such as grasping or killing prey, digging, climbing, and hanging.

Birds 
A talon is the claw of a bird of prey, which it uses to hunt. The talons are very important, and if they did not have them, those birds would not be able to catch their food.

Mammals 
A nail is similar to a claw but it is flatter and has a curved edge instead of a point. A nail that is big enough to hold weight is called a 'hoof'. 

Every so often, the growth of claws stops and restarts, just like the growth of hair. In hair, this causes the hair to fall out and it is replaced by a new one. In claws, this results in an old layer, and it breaks off. This takes several months for human thumbnails. Cats are often seen working old layers off on wood or on boards made for the purpose. Ungulates' hooves trim themselves when they walk on the ground. Domesticated equids (horses, donkeys and mules) usually need regular trimming by a farrier.

Many predatory mammals have claws that can hide inside the animal's paw, especially animals such as the cat.

Primates

A primate's nail only has the unguis; the subunguis has disappeared. Similar to the tail, the claw in apes is not needed. However, in some primates, the subunguis has redeveloped to make a claw-like structure. These certain animals do not have actual claws; instead the unguis appears normal along with a thick growth of subunguis.  Some lemurs have a toilet-claw.

Other websites 

The Horse's Hoof Anatomy 
Rat's Claws, also explains much about mammalian claws in general.

Animal anatomy
Max and Moritz (German: Max und Moritz) are two naughty little boys in a story by Wilhelm Busch.  The stories were written in 1865 and are still extremely popular in Germany.

Wilhelm Busch was an artist as well as a writer.  He wrote a lot of stories in rhyme and made drawings to go with them.  Max and Moritz are stories like these.  The two boys get up to lots of naughty pranks.  There are seven stories (seven pranks).  In the final prank they are caught and come to a sad end.  In the 19th century writers had to show that bad behaviour would be punished in the end.  The seven stories are stories with a moral.

The seven stories 

In the first story the boys tie pieces of bread onto pieces of string and put it down where an old woman, Widow Bolte, keeps her hens.  The hens each try to swallow a piece of bread, which sticks in their throats and they end up hanging in the tree and die.

In the second story Widow Bolte, who is still crying, decides she might as well roast the hens.  The boys take fishing rods, climb onto the roof and pull the frying chickens up with their rods.  Widow Bolte finds the chickens gone, thinks her little dog has eaten them, and gives the poor dog a beating.

In the third story they take a saw and make a hole in the tiny wooden bridge outside the tailor’s house.  They shout at the tailor, calling him names.  He is furious and comes running out, the bridge breaks and he falls into the stream.  Two flying geese save him.  He has a terrible tummy ache but his wife puts a hot iron on his tummy and he feels better.

In the fourth story the boys put gunpowder in the pipe of the schoolmaster while he is in church.  When he lights his pipe there is an explosion.

In the fifth story the boys collect beetles and put them under the mattress in their uncle’s bed.  In the middle of the night, when the uncle is asleep, the beetles creep up on him.  He wakes up and fights with them until he has killed them all.

In the sixth story the boys try to steal some pretzels (German rolls) from the bakery, but they fall into the tub of dough.  The baker comes in and finds them.  He bakes them in the oven, but when they are taken out they eat their way through the dough and escape.

In the seventh story the boys cut a hole in the farmer’s sacks.  When the miller picks one of these sacks up he realizes the grain is spilling.  He sees the boys, puts them in the sack and takes them to the mill, where the miller grinds them into corn and feeds them to his ducks.

Comics
Fictional characters
Sexual abstinence is the practice of not having sex. It is a choice that some people make. As well as sex itself, they may also choose to abstain from other sexual activities. Sexual abstinence has been debated since ancient history, both in terms of same-sex and opposite-sex relationships. Some people take anaphrodisiacs to help them stay abstinent. Someone who decides to avoid sex is called a celibate or volcel.

Culture
Abstaining from sex before marriage is usually called chastity. In some countries, it is illegal to have sex before marriage. Many religious and ethical systems proscribe sexual activities between a person and anyone other than a spouse of that person, including most denominational variations of Judaism, Christianity, and Islam, as have, historically, many legal systems and societal norms. People who are abstinent even though they do not want to be are sometimes called incels or TFL (true forced loneliness). One form of sexual abstinence is fapstinence, avoiding masturbation.

Reasons
People may choose to do this for any reason. A common reason is because of the person's religious or philosophical beliefs. When done for religious reasons, it is called celibacy. Other people may choose abstinence in order to prevent pregnancy or sexually transmitted diseases. When someone is abstinent from sex but they don't want to be, its sometimes called incel, short for involuntary celibacy.

Related pages
Fornication
Asexuality

References

Other websites 
 Chastity in Catholic Encyclopedia — a Christian view on chastity

Human sexuality
The Council of Jerusalem or apostolic council is a common name for a meeting of early Christian leaders reported in the Acts of the Apostles chapter .  The meeting must have happened about  the year 50, at the latest some time before the death of James the Just in 62.

The issues 
A common interpretation is that the council came together because there was disagreement within the Early Christian community between those who believed the church must observe the rules of traditional Judaism, and Paul of Tarsus, who believed there was no such necessity. The "rules of traditional Judaism," the Halakha of Rabbinic Judaism, were not finished at this time.

The central issue was circumcision, as the author of Acts relates the initial confrontation in Antioch, where Paul had been preaching:
"And certain men which came down from Judaea taught the brethren, [and said], Except ye be circumcised after the manner of Moses, ye cannot be saved." (Acts 15:1) KJV

Footnotes

Other websites 
 Acts 15 
 JersualemCouncil.org
 NA26 Greek Acts 15 
 Catholic Encyclopedia: Judaizers
 Catholic Encyclopedia: Apostolic Canons
 Didache
 Apostolic Constitutions
 Didascalia Apostolorum
 Jewish Antiquities 20 
 New Perspective on Paul
 Early Christian Writings
 Jewish Encyclopedia: Hillel v. Shammai
 Jewish Encyclopedia: Didascalia
 Gentiles and Circumcision

Further reading 
 Ehrman, Bart D. Lost Christianities: The Battle for Scripture and the Faiths We Never Knew 2003
 Eisenman, Robert, 1997. James the Brother of Jesus : The Key to Unlocking the Secrets of Early Christianity and the Dead Sea Scrolls.  A cultural historian's dissenting view based on contemporary texts.
 Westerholm, Stephen. Perspectives Old and New on Paul: The "Lutheran" Paul and His Critics 2003 

Jerusalem
Jerusalem
New Testament
1st century
Central European Summer Time is the name for a time zone. Some of the countries that have Central European Time shift their clocks forward one hour, during the summer months. And shift it one hour backwards during winter months.

Time zones
Mohammed Jihad Ahmed Jibril (March 3, 1961 in Damascus - May 20, 2002 in Beirut) was the son of Ahmed Jibril, founder of the Popular Front for the Liberation of Palestine-General Command (PFLP-GC). He was killed by a car bomb. He was assassinated on May 20, 2002. 

Jihad Ahmed Jibril was the leader of the military wing of the PFLP-GC and was the heir apparent of the organization before he was killed in a car bombing in Beirut in 2002. The assassination was blamed on Israel, although Jibril had many other enemies, including the Lebanese Christian militia and other Palestinian nationalist organizations.  

Ahmed Jibril was co-leader of the militant Popular Front for the Liberation of Palestine-General Command. Israeli radio reports said that the son, Jihad Ahmed Jibril, was involved in smuggling arms and explosives to Palestinian militants in the West Bank and Gaza Strip.
But there was no evidence to directly link him with terrorist attacks.

Ahmed Jibril accused the Israeli intelligence agency, Mossad, of responsibility for the killing, but a spokesman for Defense Minister Benjamin Ben-Eliezer said Israel was not involved.

In mid-June 2006, Lebanon authorities arrested a group of alleged spies who reportedly confessed to working for Israel and carrying out the attacks.

1961 births
2002 deaths
Assassinated people
Muslim terrorists
Palestinian Muslims
Palestinian nationalists
Palestinian terrorists
People from Damascus
The Acts of the Apostles (Greek Praxeis Apostolon) is a book of the Bible, which now is the fifth in the New Testament. It is often simply called Acts.

Acts tells the story of the Early Christian church, with particular interest for the ministry of the Twelve Apostles and of Paul of Tarsus. The early chapters in Jerusalem, report Jesus's Resurrection, his Ascension, the Day of Pentecost, and the start of the Twelve Apostles' ministry. The later chapters report Paul's conversion, his ministry, and finally his arrest and imprisonment and trip to Rome.
 
Most people think that the author of Acts also wrote the Gospel of Luke, as Acts 1:1 refers to 'the former treatise have I made, Theophilus, of all that Jesus began both to do and teach'. The traditional view is that both the two books were written c. 60 by a companion of Paul named Luke. Many theologians still think so. But some think the books were written by an unknown author at a later date, sometime between 80 and 150.

References

Other websites 
 Bible Gateway 35 languages/50 versionsy at GospelCom.net
 Dating Acts 
 Unbound Bible 100+ languages/versions at Biola University
 Online Bible at gospelhall.org
 Book of Acts at Bible Gateway
 Acts from the Biblical Resource Database 
 The Apostle Paul's Shipwreck: An Historical Investigation of Acts 27 and 28 
 Catholic Encyclopedia: Acts of the Apostles
 Encyclopedia Britannica: Acts of the Apostles
 Jewish Encyclopedia: New Testament - The Acts of the Apostles
 Tertullian.org: The Western Text of the Acts of the Apostles (1923) J. M. WILSON, D.D.

New Testament books
A Firebreak is a way to fight fires. In a firebreak, there is no vegetation, or other material that can burn. This makes it hard for a fire to jump across the break. Therefore, the spread of a possible fire is delayed.

Firefighting