the-french-artist/wikipedia_20220301.simple_sentence_split huggingface dataset:
Cell testing
Lymphocytes are a type of white blood cell (or leukocyte).
They help an organism to fight infections.
They occur in the immune system of all vertebrates.
All lymphoctes have a large, blob-like nucleus.
large granular lymphocytes: these are part of the innate immune system, and are natural killer cells.
small lymphocytes: these lymphocytes are the main agents of the acquired immune system.
The two main types are:
T cells and
B cells.
Natural killer cells
Natural killer (NK) cells are a part of the immune system a person is born with.
They protect the organism from tumours and from cells infected by viruses.
Natural killer cells are made active by chemicals released by damaged cells called interferons.
Natural killer cells can tell the difference between infected cells, tumours, and normal cells.
They recognise changes in the level of a surface molecule called MHC (major histocompatibility complex) class I.
T and B cells
T cells (thymus cells) and B cells (bone cells) are the main cells of the adaptive immune response.
They tackle infections, and they cause the immune system to 'remember' the event.
The function of T cells and B cells is to recognize foreign antigens.
Antigens are surface molecules on a cell.
Once they have identified an invader, the cells respond to remove pathogens or pathogen-infected cells.
Some T cells, called T helper cells, produce cytokines that direct the immune response.
Cytokines signal to other immune cells that there is a foreign antigen present.
Other T cells, called cytotoxic T cells, produce toxic granules which cause the death of infected cells.
Once they are made active, B cells and T cells produce memory cells.
Throughout the lifetime of an animal, these cells will 'remember' each specific pathogen encountered, and are able to make a strong response if the pathogen is detected again.
Memory cells live a long time in the body, and are how vaccinations work.
Mammalian stem cells change or differentiate into several kinds of blood cell within the bone marrow.
This process is called haematopoiesis (= blood growth).
All lymphocytes come from a common basic lymphocyte cell before differentiating into their distinct lymphocyte types.
B cells mature into B lymphocytes in the bone marrow, while T cells migrate to and mature in a distinct organ, called the thymus.
After they mature, the lymphocytes enter the circulation and lymphoid organs (e.g. the spleen and lymph nodes) where they are able to sense invading pathogens and tumour cells.
In the circulatory system they move from lymph node to lymph node.
This contrasts with macrophages, which are rather stationary in the nodes.
Lymphocytes and disease
Human immunodeficiency virus (HIV) infects and destroys T cells.
Without the key defence that these T cells provide, the body becomes prone to infections that otherwise would not affect healthy people.
The extent of HIV progression is found by measuring the percentage of CD4+ T cells in the patient's blood.
The effects of other virus or lymphocyte disorders can also often be estimated by counting the numbers of lymphocytes present in the blood.
ja:白血球#リンパ球
An author is a person who writes  books, stories, poems, or other written work.
Their writing can be truth or fiction, short or long.
Often, author is a word for a professional writer, but any person who writes may also be called that.
Sometimes, a person who creates something that is not prose is called an author.
Someone who writes music may be called the author of that piece of music, though we would usually call that person a composer.
In the film world, the French word for author, auteur, is often used about someone who has been both the writer and director of a movie.
In copyright law, the author is the first owner of copyright.
Such laws also apply to other works of art such as pictures or music.
Networks of scientific papers
Pedipalps are the two appendages on the front of a spider's head.
Some spiders seem to have ten legs and not eight, because these pedipalps look like an extra pair of legs.
The pedipalps are used rather like arms.
Spiders often use them to hold insects (for example crickets) for them to eat.
Male spiders also use pedipalps for mating.
The male spiders make some silk, put sperm onto the silk, and then put their pedipalps into the sperm.
The pedipalps then hold the sperm, and the spider can use it to mate with a female by putting them inside her epigynum.
Diversity of pedipalps
The pedipalps of all chelicerates vary: Ricinulei, Thelyphonida, Amblypygi, some Opiliones, Schizomida, Scorpions and pseudoscorpions all have theirs as pincers, with the Amblypygi's being their entire pedipalps shaped like mantids.
The Palpigradi's pedipalps have some of the strangest roles of arachnids as they use theirs for locomotion.
The pedipalps of Solifugae act as antenna.
Close-up view of pedipalps on a large spider
Animal anatomy
In chemistry, an ionic compound is a compound made of ions.
They have strong ionic bonds between particles.
Lots of energy (heat) is required to break the bond apart, resulting in high melting and boiling points.
The ions join together because they have different charges.
Compounds of metals and non-metals are usually ionic.
They are made when two or more atoms come close together and an electron goes from one atom to the other atom.
The electron does this because both atoms want a full outer shell, similar to those of the noble gases.
Note 2: the elements in Group 0 do not react with other elements to form ions
sv:Jonförening
The ELISA method (Enzyme Linked Immuno-Sorbent Assay) is a technique used in biochemistry to determine if a certain substance--such as a specific cytokine or antigen--is present within a sample.
It is sometimes abbreviated as "EIA."
This technique uses special antibodies that attach themselves to the substance.
These antibodies generate a specific color.
The amount of color indicates the amount of substance present. (
Sometimes, the substance must be viewed under ultraviolet light for the antibodies to generate this color.)
Another set of antibodies are used to "capture" the substance.
These antibodies adhere to both the substance and the testing container, thus holding the substance in place.
An animated illustration of an ELISA assay
Image of a microtiter plate, such as is commonly used in ELISA tests
David Hume (7 May 1711 – 25 August 1776) was a philosopher and historian from Scotland.
When he was still alive, people thought of him as a historian.
He wrote a series of large books called The History of England.
But today, people think of Hume as an important philosopher.
In his books on philosophy, Hume said that many of our beliefs do not come from reason.
Instead, they come from our instincts or feelings.
For example, reason does not tell us that one thing causes another.
Instead, we see one thing and then we see another, and we feel a link between the two.
Similarly, reason does not tell us that someone is a good person.
Instead, we see that the person is kind and friendly, and we feel a special moral feeling.
Because Hume thought that these beliefs do not come from reason, people call him a "skeptical" or "anti-rationalist" philosopher.
Hume is famous for his 'Induction Fallacy'.
This draws attention to a common mistake people make.
People see something, and make claims that what they see will always be as they see it.
For example, people see only white swans and claim that all swans are white.
This is 'fallacious' or mistaken, because it is always possible that they then will see a black swan.
Hume was also skeptical about religion.
He was not a religious person and religious people did not like his opinions.
He did not believe in miracles.
He said that suicide wasn't always wrong, but never said whether or not he believed in God.
In 1776, when he was dying, his friends found him very calm about death, despite him not believing in an Afterlife.
Today, Hume's books are very important to philosophers who are interested in religion.
Another philosopher, Immanuel Kant, read some of Hume's books and changed his mind about some important things.
Kant said Hume had made him wake up from a sleeping dogmatism, the traditional metaphysics.
A Treatise of Human Nature: Being an Attempt to introduce the experimental Method of Reasoning into Moral Subjects. (
1739-40)
In this large book, Hume talks about the human mind and tries to figure out how it works.
He talks about knowledge, cause and effect, emotions, right and wrong, and many other things.
An Enquiry Concerning Human Understanding (1748)
In this small book, Hume talks about many of the same things from the Treatise, like knowledge and cause and effect.
He tried to make this book easy to read.
An Enquiry Concerning the Principles of Morals (1751)
This is another small book, and again, Hume tried to make it easy to read.
The book is about right and wrong.
Dialogues Concerning Natural Religion (after Hume died)
In this book, Hume has three characters who argue with each other about God.
1711 births
1776 deaths
A bath (UK English) or bathtub (US English) is a basin large enough for people sit in when washing their body.
The bath is usually in the bathroom.
A less common name for a bath is a washtub.
A bath is also a place where people can sit in water (or other liquids, often hot) for their health.
This is where the town name Bath comes from.
Public baths for relaxing were built in all parts of the Roman Empire.
Steam bath
A brush is a tool with bristles or wires or other filaments sticking out.
There are many kinds.
Most brushes have a long part at one end to hold (the handle), on the other end from the head that carries the bristles or filaments.
We use brushes for cleaning, making hair look good, painting, and other purposes.
Brushes for cleaning
Paint brushes
We use paint brushes for putting ink or paint on paper.
If a brush is dipped 1/3 to 1/4 of it’s length into a can of paint, a good brush will ideally pick up the perfect amount of paint and spread it on a surface in a film that is smooth and uniform and absent of any drips, dips, or brush marks.
Paint brushes typically come in two forms, synthetic, and natural.
Synthetic brushes are usually made from products such as nylon, while natural refers to bristles from an animal source.
Computer graphics uses digital paintbrushes for making pictures.
Round: The long, close-together bristles of these brushes mean they can hold more paint.
This is why many artists like them for painting large things and for color washes.
Flat: These are good for spreading paint.
Fan-shaped: These mix paint well.
Brush care
Clean paint from brushes after you use them.
This is very important for oil and acrylic paint because when the paint is dry, taking it off can break the brush.
Never leave brushes in water (etc.)
with the bristle end down.
This is because the bristles can change shape.
Sizes and materials
We can buy brushes in different sizes and materials.
Here are some sorts.
Decorators' brushes
The sizes of brushes used for painting and decorating (changing the colour or look of a room) are usually in millimeters or inches.
This shows how wide the head is.
1/8", 1/4", 3/8", 1/2", 5/8", 3/4", 7/8", 1", 1¼", 1½", 2", 2½", 3", 3½", 4".
10 mm, 20 mm, 30 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm.
We can buy brushes with natural or synthetic (man-made) bristles.
Handles (the part of the brush we hold) may be wood or plastic.
Artists' brushes
7/0 (also  0000000), 6/0, 5/0, 4/0, 000, 00, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 16, 18, 20, 22, 24, 25, 26, 28, 30.
We use sizes 000 to 20 most often.
Artists' brush handles (the part of the brush we hold) are often wooden, but the cheapest brushes may have plastic handles.
Many cheap handles are made of unfinished wood; better quality handles are of finished wood.
Starch is a complex carbohydrate.
It is made of many glucose units joined by chemical bonds.
This polysaccharide is produced by most green plants as an energy store.
It is the most common carbohydrate in human diets.
Pasta, potatoes, bread, and other starchy foods are made out of carbohydrates.
Starch in every day activities.
Starch in food
Some good food sources of starch are cereals, bread, potatoes, grains, peas, and beans.
Starch is also used for thickening sauces in cooking and thickening cold foods during a preheat.
Starch is a white powder that is tasteless and odourless.
Corn starch or cornflour is known as a popular kind of starch made from corn.
Foods with a lot of starch produce more energy than other foods.
However, if this energy is not used, it is turned into fat by the liver through de novo lipogenesis.
Laundry starch
There are also different kinds of starch, like laundry starch, which gives clothing a smooth and crisp feel.
Sweat and dirt from a person’s wrist and neck will stick to the starch on the clothes, not to the fibers of the clothes, and will wash away along with the starch.
Then, after each laundry load, the starch can be used again.
Other facts
Starch glues are used in wood, cotton, and bonding of paper.
Animals and humans have amylase, so they can digest starch.
Starch was used in Europe in the 16th and 17th centuries to stiffen the collars and ruffs of the fine linen which surrounded the neck.
Starch also requires heat to thicken.
The actual temperature depends on the type of starch.
Thomas Hobbes (5 April 1588 – 4 December 1679) was a philosopher from England.
His most famous book is Leviathan (1651).
Hobbes mainly wrote about government and law—he was a political philosopher.
He tried to show that the best kind of government has one in which society was organised under one authority.
All individuals in that society give up some rights for the sake of protection.
There is no doctrine of "separation of powers" in Hobbes's discussion.
According to him, the sovereign power must control civil, military, judicial, and ecclesiastical powers.
Looking at human nature, we will see that humans are very selfish and that we are willing to hurt each other if we think it will help us.
Naturally, humans are all equal because we are all strong enough to kill each other—even a child can kill a strong man while he sleeps.
Imagine what things would be like without a government.
It would be terrible—a "state of war".
There would not be enough stuff for everyone, and people would disagree about who got what.
Some people would fight each other, and everyone else would be very worried about their own safety.
No one would be able to trust anyone else or make plans for the future.
Life would be "solitary, poor, nasty, brutish, and short" (people would be alone, poor, mean, and would not live for long).
Next, Hobbes argues that it would be a good idea for everyone to stop fighting and choose a Sovereign which could be one man or an assembly of men.
Everyone should agree to obey the Sovereign, and give him all power of coercion or force of restraint under law.
Once the Sovereign is in place, everyone has to obey him, even those who disagree with him.
This is because everyone already agreed to obey him no matter what.
Hobbes says it's better to be mostly safe under an all-powerful Sovereign, than to be in a state of war.
Hobbes wanted his argument to be like math, with each step leading to the next.
However, many people disagreed with his argument.
Some said that Hobbes was in favor of rebellion, because he said that people were naturally equal.
Others said that humans are not as selfish as Hobbes thought.
Today, most people do not like the idea of an all-powerful government.
Nevertheless, Hobbes's argument was a very important one, and philosophers who are interested in government or political theory still study Hobbes's books very carefully.
1588 births
1679 deaths
17th-century English philosophers
Trevi (Latin: Trebiae), an old town and comune of Italy, in the province of Perugia in east central Umbria, 42°53N 12°45E, at 424 meters (1391 ft) above sea-level on the lower part of Mt. Serano above the wide plain of the Clitunno river.
It is 10 km (6 mi) S.S.E. of Foligno and 20 km (12 mi) N. of Spoleto.
The 2003 count of people by the government said that there were 7800 people living in the comune: about half of the people live in the town and the other people live in the country near town.
The frazioni of Trevi (the smaller towns that belong to Trevi) are Borgo, Bovara, Cannaiola, Coste, Pigge, Manciano, Matigge, Parrano, Picciche, S. Lorenzo, S. Maria in Valle.
Most of the town is densely built with many buildings predating the 18th century.
It crowns a summit and when one is in the centre the streets are mostly gently sloping.
From the town one can see one of the best views in Umbria, over 50 km (30 mi) to the west and on clear days as far as Perugia to the north and even Monte Amiata in southern Tuscany.
On the main train route from Rome to Ancona there is a station at the botton of Monte Serano servicing Trevi but the rapid Intercity services do not stop.
The train service from Florence to Rome by way of Perugia also stops there: Local bus connections are not frequent.
Trevi is a pleasant place to visit and of recent accommodation and good eating has become available; there are few restaurants, but they are good and more numerous than in other nearby small towns.
In Roman times, Pliny the Elder said Trevi was a city of the old Umbrians, and an old stone with Umbrian writing was found in the comune, at Bovara, in the 1950s. "
Treviae" is also listed in the 5th‑century Bordeaux Itinerary.
We do not know the history of Trevi in very old times, although some walls in the center part of the town on the hill are as old as the 1st century BC.
Trevi started to spread out away from the hill during the time of the Empire, when Hadrian fixed the main road in the area, the Via Flaminia; this made a small town in the plain grow, at a place now called Pietrarossa.
For hundreds of years people have been finding old things there: there were Roman baths that people were probably using in the time of St. Francis, who came here and told people to bathe in them.
In old times people say that Trevi ruled the valley below it, all the way to the Colli Martani, the line of mountains that run down the middle of Umbria.
Trevi had a bishop until the 11th century, and was an important place belonging to the Lombards (in Italian, a gastaldato).
At the beginning of the 13th century, Trevi made itself independent and became a free commune.
It often fought on the side of Perugia to defend itself against nearby Spoleto, and fought wars with other communes in the area, winning some and losing some.
It was invaded by Spoleto in the 14th century and by the Trinci, rulers of Foligno.
In 1438 Trevi became part of the lands belonging to the Church as part of the "legation" of Perugia: after that Trevi's history was as part of the States of the Church, then (1860) of the united Kingdom of Italy.
Trevi was at its most prosperous in the 15th century: the town was so important for those who wanted to buy and sell that people called it "il porto secco" — the dry port.
In 1470, with Foligno, Trevi became the fourth town in Italy to have a printing press, managed by the first known printing company.
Many big renaissance palazzi of the town indicate the contemporaneous prosperity.
Important old buildings
the Duomo Sant' Emiliano, a Romanesque building: it has a carved door and the back of the church has more sculpture.
The inside of the church was fixed in the 18th century and does not look old.
the Madonna delle Lacrime, a church from the Middle Ages, for monks, with big wall paintings painted to thank God for good things.
The best painting is the Adoration of the Magi by Perugino: it is the last painting he put his name and the date on.
S. Martino, has old Lombard stones and good paintings by Mezzastris
S. Francesco, a large Gothic building.
The country area around the town has many Romanesque churches: some of those on the plain were built on the Roman Via Flaminia and indicate the road's former route.
Some of the stone in these churches is old Roman and derives from buildings long gone.
Trevi's big museum is the Museo S. Francesco, next to the Gothic church S. Francesco, which is not used for worship any more.
It has a few Roman stones, but mostly many Umbrian paintings from the late Middle Ages to the 17th century: the best painting once was part of an altar, and it is by Lo Spagna.
There is a very interesting group of "ex‑votos" (paintings to thank God for saving a person from a sickness or an accident) painted by ordinary people, not famous artists, of the 16th‑ century to the 18th‑century.
The Museo della Civiltà dell' Olivo demonstrates the local olive culture: how they are planted, how they grow, and how they are made into oil.
The Flash Art Museum is dedicated to contemporary art and is the seat of an international art magazine.
Books to learn more about Trevi
The oldest big book on the history of Trevi is Historia universale dello Stato temporale ed ecclesiastico di Trevi, 1233 pages, by Durastante Natalucci, Trevi, 1745.
It was translated into a more modern and readable Italian by Carlo Zenobi, a local historian, between 1987 and 1994.
An important book for the plain below Trevi is Cannaiola, Memorie storiche raccolte negli anni 1873‑74 by Father (now the Blessed) Pietro Bonilli.
Trevi Tourist Office (Pro Trevi)
Bill Thayer's site
Towns in Italy
Settlements in Umbria
Nicomachos or Nicomachus is a Greek name.
Nicomachus of Gerasa, an ancient mathematician
Nicomachus, the father of Aristotle and court physician (doctor) to King Amyntas III of Macedon.
Nicomachus died when Aristotle was about 10.
Nicomachus wanted Aristotle to follow in his footsteps.
But Aristotle did not become a doctor but a philosopher.
Given names
A logo is a picture or drawing that is used by a person, group, or company to mark who they are.
A wordmark, or 'logotype', is a logo made entirely of a word or words.
It is usually the name of a product or organisation.
A company or group can use a 'logo' on the things that they make, like on the things they sell, on letters, and in advertisements.
When a person sees the logo picture, that person knows that the thing they see the logo on came from that company.
Logos can have letters and words in them.
Many logos have the name of the company or group in them.
Most logos are very simple drawings with only a small number of colors.
Some logos are only in black and white.
In many countries, companies and groups should tell their country's government about the logo they are using.
If they do this, the government can help stop a different company or group from using the same logo, so that every one can be sure that the logo is only used by the people who used it first.
This is sometimes called a 'trade mark'.
Logos are not used only by companies.
Many schools have logos.
Some cities have logos.
Clubs can have logos.
Even people can have their own logos if they want.
The heraldic badge is probably the oldest form of logo in the world.
A picture, also called an image, is a group of coloured points on a flat surface that looks the same as something else.
For example, a picture can look the same as an object or a person.
Pictures can also be drawings, paintings or photographs.
People who make such pictures are called artists, photographers or painters.
Pictures are very helpful.
Sometimes people say pictures are worth a thousand words.
Pictures and diagrams can be used to explain how to do things, and thus a picture is a kind of tool.
A moment captured in an image.
An image is something that can be seen, but it is not physically there.
It can be a photograph, a painting, or a picture on a television or computer screen.
A lens can make an image of an object appear somewhere else.
Cameras use this to make the image that becomes a photograph.
Making Pictures
Most pictures today are 'photographs'.
Photographs are made with cameras.
A camera makes a picture that looks very real.
When there were no cameras, people made pictures by using paint, brushes, pencils, crayons, pens, and other things that people can write or draw with.
Pictures made with paint and brush are called 'paintings'.
Before cameras, some artists were able to make very real looking pictures with just paint.
Sometimes pictures made with pencil or pen are called 'sketches', if they are made quickly and only look a little bit like the real thing.
Usually pictures are put on paper.
Pictures made with paint are usually put on a strong, rough fabric called 'canvas'.
Sometimes pictures can be put on walls or other things, even glass.
Some places, such as churches have pictures on windows made out of colored pieces of glass.
These are called stained glass.
Special types of Pictures
If people take a lot of pictures, and show them one at a time, very fast, they can make a picture that looks like it is moving.
This is called a "moving picture", or a movie.
A television shows people a moving picture by using light.
A projector shines light from a light bulb through a kind of transparent picture.
When light shines through this kind of picture onto a screen or another flat place, the picture can be seen on that flat place.
This is often used to show movies and slide shows to an audience.
Some people make pictures that do not look flat, by taking two regular flat pictures at the same time.
People have to move their eyes in a special way or use a stereoscope so they can see both pictures together.
When they look at the pictures using their binocular vision correctly, the picture does not look flat.
This is called '3D' or 'three dimensional'.
Building may be a noun or a verb.
Building is one of the most ancient human skills.
It is part of how we have survived and it is the clearest symbol of every civilization.
Although some other animals build simple structures, e.g. birds, ants and bees, humans have learned to build in a great many different ways to suit different needs and local conditions.
We build mostly for shelter.
Buildings can shelter people, or animals, or machinery, or anything.
The simplest building is just a roof to keep the space beneath dry, or shady.
Adding walls gives more shelter, from the wind or rain.
It also gives security.
By putting a window in a wall with or without glass, we let light inside the building.
We leave a hole somewhere big enough to go in and out, with a door which can be opened and closed.
Often the door will have a lock so the building can be left secure.
If a building is to last for a long time, it must have a solid foundation.
This foundation is like the root of a tree, which is sunk a bit deep into the ground and supports the walls.
If the ground is soft, the foundation must be very deep and strong so that the building can have a strong contact with the ground.
If a building is high enough, it can have more than one floor.
People can climb from one floor to the next by a staircase, or perhaps by a lift or elevator.
This is known as going upstairs, or downstairs.
Buildings can also have a floor under the ground.
This is usually called a cellar or basement.
Buildings can be beautiful or ugly, exciting or boring.
Architects are people trained to design buildings.
Their work is called architecture and it can be an art form.
Look at the building where you are reading this.
Look at the shapes and shadows.
Is there enough light?
Do some rooms make you feel like staying in them while others make you want to hurry away?
Do they have interesting features?
Think about how you could have made the building better.
Almost anybody can become an architect if they want to.
But only a good architect or a good builder can design or build a beautiful building.
Types of buildings
Shelters are places to live (residential buildings).
We also build places to work and to make things, places to store things, places to sell things, places where sick people can go to be treated, places to put people who break our laws.
We build to do many things.
Some buildings are meeting places.
A large number of people can gather at a temple or theater or stadium to worship god or to hear or see what other people say or do.
In Christendom they are called churches.
Until we began to build skyscrapers, religious buildings were usually the largest, tallest buildings in a town.
Fortresses and castles were also big but usually were not in town.
Big buildings require much work to make, thus can symbolize power.
They impress and they give a focus to cities.
Buildings are made of various materials.
Where wood is plentiful, it is much used.
Many very old buildings of stone exist.
Concrete is used almost everywhere.
Starting in the late 19th century, skyscrapers were made of steel, increasingly combined with glass.
Where people live or stay
Apartment or flat
Hotel (including motels and inns)
Where people work
School, Study hall, dormitory
Farm, barn, silo
Fire Station
Jail or prison
Culture and entertainment
Amphitheater
Movie Theatres
Arcades
A candle is a stick made of wax with a string (a thin piece of rope) straight in the middle.
If someone puts the string on fire, the flame burns slowly but for a long time.
Fire can burn string very fast.
But in a candle, the string does not burn fast, because the fire melts the wax instead.
The wax sometimes drips down the side of the candle.
When the melted wax is far from the flame, it gets hard again, and can be used again in a new candle.
The flame is very hot, since it is a very small, real fire.
The light blue part of the flame can be as hot as .
It can still burn people and things.
If the fire spreads, it can grow into a very big fire and even burn down a house or building.
If the flame is kept on the candle long enough, the candle will slowly get shorter and shorter until it is gone.
The fire on a candle can be put out by blowing air on it.
There is also a special tool called a "candle snuffer" that covers the fire with a small metal cup and puts it out.
Today, candle snuffers are usually only used in churches or in places where candles are up very high.
Stopping the fire stops the candle from burning until it is all gone.
Before light bulbs, candles were used so people could see at night.
Some people still use candles today when electricity is down, or because they like the little amount of light that candles make.
Some people also like candles because they look nice, or because they smell nice.
A special kind of candle called "citronella" can help keep bugs away.
Electric light
Christian symbols
Salamanders are amphibians.
They are the order Caudata (or Urodela).
There are about 500 different species.
Salamanders live in water and on land, and look rather like lizards, with four legs and a tail.
They hatch as larvae from eggs in the water.
At that stage, they have gills that stick out.
Most salamanders live on land when they are adults, after their change of shape (metamorphosis).
On land, salamanders live in moist habitats.
Their method of respiration varies.
Some salamanders stay in the water, but look like adults.
These are called newts.
Some salamanders retain gills into sexual maturity, such as the Axolotl.
This process is called neoteny.
Often, salamanders may have a chemical defence to predators; they are poisonous to eat.
In this case, they will have warning colouration.
Otherwise, if not poisonous, they will usually have camouflage.
Respiration differs between species of salamanders.
Species that lack lungs respire through gills.
In most cases, these are external gills, visible as tufts on either side of the head, although the amphiumas have internal gills and gill slits.
Some salamanders that are terrestrial have lungs that are used in respiration, although these are simple and sac-like, unlike the more complex organs found in mammals.
Many species, such as the Olm, have both lungs and gills as adults.
Some terrestrial species lack both lungs and gills and perform gas exchange through their skin, a process known as valerian respiration in which the capillary beds are spread throughout the epidermis, and inside the mouth.
Even some species with lungs can also respire through the skin in this manner.
The skin of salamanders secretes mucus.
This helps to keep the animal moist when on dry land, and maintains their salt balance while in water, as well as providing a lubricant during swimming.
Salamanders also secrete poison from glands in their skin, and some additionally have skin glands for secreting courtship pheromones.
Hunting is yet another unique aspect of salamanders.
In the lungless salamanders, muscles surrounding the hyoid bone contract to create pressure and actually "shoot" the hyoid bone out of the mouth along with the tongue.
The tip of the tongue is composed of a mucus which creates a sticky end to which the prey is captured.
Muscles in the pelvic region are used in order to reel the tongue and the hyoid back to its original position.
Many of the highly aquatic species, however, have no muscles in the tongue, and do not use it for capturing prey, while most other species have a mobile tongue, but without the adaptations to the hyoid bone.
Most species of salamander have small teeth in both the upper and lower jaws.
Unlike frogs, even the larvae of salamanders possess these teeth.
To find their prey, salamanders use trichromatic color vision in the ultraviolet range.
Permanently subterranean salamanders have reduced eyes, which may even be covered by a layer of skin.
The larvae, and the adults of some highly aquatic species, also have a lateral line organ, similar to that of fish, which can detect changes in water pressure.
Salamanders have no external ear, and only a vestigial middle ear.
Salamanders can drop their tail to escape predators.
The tail will drop off and wriggle around for a little while, and the salamanders will either run away or stay still enough to not be noticed while the predator is distracted.
Salamanders routinely regenerate complex tissues.
Within only a few weeks of losing a piece of limb, a salamander perfectly reforms the missing structure.
Caudata Culture
Salamander Video
Caudatamedia
Newts or efts are small amphibia.
They are in a subfamily of the salamanders.
They are found in North America, Europe, and North Asia.
Females lay eggs and leave them.
Tadpoles are born from those eggs.
Newts have three life stages.
First as a tiny aquatic larva, which gradually undergoes metamorphosis.
Then they leave the water for a year as a juvenile called an eft.
They go back in the water to breed as adults.
In some species the adults stay in water for the rest of their lives.
Others are land-based, but return to water each year to breed.
Many newts produce toxins in their skin secretions as a defence against predators.
They have bright skin colours as a warning to other animals.
Taricha newts of western North America are particularly toxic; the rough-skinned newt Taricha granulosa of the Pacific Northwest produces more than enough tetrodotoxin to kill an adult human.
Recently, a 29-year-old man in Coos Bay, Oregon, who had been drinking heavily, swallowed a rough-skin newt for a dare; he died later that day despite hospital treatment.
Most newts can be safely handled, provided that the toxins they produce are not ingested or allowed to come in contact with mucous membranes, or breaks in the skin.
After handling, proper hand-washing techniques should be followed due to the risk from the toxins they produce and bacteria they carry, such as salmonella.
It is illegal to handle or disturb great crested newts in the UK without a licence.
Are newts a related group?
The term "newt" has traditionally been used as a functional term for salamanders living in water, and not a systematic unit.
The relationship between the genera has been uncertain, though they may be a natural systematic unit.
Newer molecular analysis tend to suggest they actually do form a clade.
Some genera occasionally listed as Pleurodelinae are not newts (Salamandrina and Euproctus).
Poisons are substances which cause death or injury when taken in by a living thing.
It may be taken in as drink or food, or absorbed through the skin.
The damage is usually done by a chemical reaction.
The effect of the poison varies with the amount which is absorbed (taken in or inhaled).
Substances which are poisonous are called toxic, but any substance can be toxic if too much of it is consumed.
If poisoning causes death, it is lethal poison.
Legally, and in hazardous chemical labeling, poisons are especially toxic substances.
Less toxic substances are labeled "harmful", "irritant", or not labeled at all.
In medicine and zoology, toxins and venoms are different from poisons.
Toxins are the result of a biological process.
Venoms are substances which the organism uses to harm other species.
Certain organisms use venoms for hunting, or as a defense.
If an organism is poisonous, such as many mushrooms, it is harmful to eat.
If it is venomous, like snakes or honeybees, it has a harmful bite or sting.
For some very deadly bites humans have developed effective antivenoms.
Often it is only the quantity of a substance that makes the difference.
Drinking alcoholic drinks may lead to aggressive behaviour, problems with speech, and different forms of amnesia.
This effect is called intoxication.
People who drink even more may go into shock.
At the same time, alcohol can be used as a disinfectant.
Sometimes, poisons have an antidote.
The antidote of a poison will slow or reverse its effects.
The antidote may itself be a poison.
As an example, atropine can be used as an antidote against certain nerve gases, like tabun or sarin, or against certain insecticides.
It is also used as a medication.
In high doses, atropine is a poison.
Yet atropine is a core medicine in the World Health Organization's "essential drugs list".
There are other types of dangerous materials.
Carcinogens (cancer-causing poisons), like acrylamide, asbestos, and benzene
Mutagens (mutation-causing poisons) such as radiation and benzene
Teratogens (birth defect-causing poisons), like thalidomide and alcohol
In wars, some countries use poison gases against their enemies.
This is called chemical warfare.
Being poisoned by gas sometimes happens accidentally.
For example, a faulty furnace or heating system can cause carbon monoxide poisoning.
There are many types of poison gases.
For example, corrosive poison gases cause serious burns to the skin, eyes, and lungs.
Nerve agents are poisons that can kill by damaging the central nervous system.
Blister agents cause severe blisters on the inside and the outside of the body.
Choking agents make fluid build up in a person's lungs until they drown.
In 2010, poisoning resulted in about 180,000 deaths, down from 200,000 in 1990.
There were approximately 727,500 emergency department visits in the United States involving poisonings—3.3% of all injury-related encounters.
Exposure to toxins
Toxicity (how toxins affect the body)
NFPA 704 "fire diamond" (system that warns people how poisonous and dangerous a certain chemical is)
Powder is very small, dry pieces or grains.
When we press some dry solids very hard, or when we cut something up into lots of small pieces, we can sometimes make powder.
For example, people sometimes put face powder on their faces, when they want to look good.
Sometimes sports players put powder on their hands, to make them dry.
We put curry powder in our food, to make it taste stronger.
We put washing powder in the washing machine when we want to have clean clothes.
People use gunpowder to make bombs and fireworks.
Many animals develop in separate stages.
A larva (plural: larvae) develops from the egg in those animals.
It is a separate life stage from the adult reproductive stage.
A larva does not look like the adult animal, and changes shape (known as metamorphosis) as it grows up.
There may be several larval stages before the adult form.
Tadpoles, maggots and caterpillars are larvae.
Marine organisms with a larval stage often release large numbers of eggs and sperms into the water column.
After fertilisation, the eggs develop into tiny larvae.
The larvae develop and grow for some time before metamorphosing into adults.
Most marine invertebrates and many fish have a pelagic larval stage or pelagic eggs.
These live in the plankton, and may be transported long distances.
Evolutionary theory
Probably the most widely accepted theory explaining the evolution of larval stages is the need for dispersal.
Sessile organisms such as barnacles and tunicates, and sea-floor groups like mussels and crabs, need some way to move their young into new territory, since they cannot move long distances as adults.
Many species have relatively long pelagic larval stages (how long a larva is in the water column).
During this time, larvae feed and grow, and many species move through several stages of development.
For example, most barnacles moult through six nauplius larva stages before moulting to a cipris, when they look to settle.
The larvae eat different food from the adults, and disperse.
The other consideration is the small size of the eggs.
If animals lay many small eggs (and most do), then the young stages cannot live the life the adults lead.
They must live a separate life until they have the size and capability to live as an adult.
This is what the larvae do.
Origin of vertebrates
A long-standing theory is that in transformed larvae of sea-squirts (tunicates) lies the origin of vertebrates.
Tunicates are sessile, but their larvae are mobile, and have some features found in early vertebrates.
The process of paedomorphosis, where juvenile features are retained in the adult, is the proposed mechanism.
Genome analysis does show that the tunicates are the closest living relatives of vertebrates.
Amphibians are members of the class Amphibia.
The living ones are frogs (including toads), salamanders (including newts) and caecilians.
They are four-legged vertebrates which are cold blooded.
Amphibians lay their eggs in water, usually in a foam nest.
After hatching they are tadpoles, which live in the water and have gills.
The tadpoles change into adults in a process called metamorphosis.
When they are adult, they have lungs to breathe instead of gills, and legs.
Adult amphibians also use their skin to take in oxygen, and some species of salamanders do not have lungs.
The earliest amphibians evolved in the Devonian from lobe-finned fish which had jointed leg-like fins with digits.
They could crawl along the sea bottom.
Some had developed primitive lungs to help them breathe air when the stagnant pools of the Devonian swamps were low in oxygen.
They could also use their strong fins to hoist themselves out of the water and onto dry land if necessary.
For tens of millions of years, during the Carboniferous and early Permian, amphibia were top predators on land, especially in the low-lying tropical river systems.
In drier conditions, they were less effective, and the ancestors of mammals and reptiles (the Synapsids and Sauropsids) gradually took over the land.
They laid cleidoic eggs, which had hard shells, and could be laid out of water.
Most of the early large amphibians went extinct in the Triassic period; a few survived to the Lower Cretaceous.
The only living amphibiana today are the Lissamphibia.
These include the Anura (frogs and toads), Caudata (salamanders and newts) and Gymnophiona (caecilians).
They are all rather small, compared with mammals or reptiles.
The smallest frog and vertebrate in the world is the New Guinea frog (Paedophryne amauensis).
The biggest amphibian is the Chinese giant salamander (Andrias davidianus).
Amphibia are found everywhere in the world, except Antarctica, and there are about 5,565 different species: 88% of them are in the Anura.
In number of species, they are more successful than mammals, though they occupy a smaller range of habitats.
However, it is said that amphibian populations have been declining all over the world.
Conservation is therefore an important concern.
Living amphibia
Anura: Frogs (including toads)
Caudata: Salamanders (including newts)
Gymnophiona: Legless amphibia, similar to earthworms or snakes
Amphibians like to live near freshwater in warm weather.
There have also been species which live in forests, deserts and arctic conditions.
Adult amphibians use lungs, and they also get oxygen through their skin, so long as it is moist.
Amphibians may be camouflaged in brown and green, and if so they are prey for birds and reptiles.
Their colour gives them camouflage, which is their main defence.
Alternatively, many other amphibia have toxic skin, which is harmful to predators.
These are poisonous to eat.
This is an important defence against predation.
Connected to this is the use of warning colouration.
They may be in vivid colours of red, black, and yellow.
Research into the rough-skinned newt and the garter snake shows this is a typical case of co-evolution.
Where they live in the same area, the newts get more poisonous, and the snakes develop more resistance to the poison.
Amphibians have colour vision and depth of focus for clear sight.
They also have eyelids, glands and ducts which keep the eyes moist.
These are adaptations to life on land: amphibia were the first vertebrates to have these features.
Some amphibians, such as the common coquí, lay eggs out of water (in this case, on palm leaves).
The eggs develop directly into adult frogs, by-passing the tadpole stage.
Others, like mudpuppies and olms, have a different development.
In a process called neoteny, they become sexually developed as tadpoles, and continue to live in the water with gills.
The order Anura includes the frogs and toads.
There is no fundamental difference between frogs and toads.
Frogs have a short body, webbed digits (fingers or toes), protruding eyes, forked tongue and no tail.
They are exceptional jumpers: many of their features, particularly their long, powerful legs, are adaptations to improve jumping performance.
They often live in semi-aquatic or inhabit humid areas.
A popular distinction is often made between frogs and toads on the basis of their appearance.
Toads' warty skin is an adaptation for making their toxic slime.
Apart from these glands, their skin is dry, and that is an adaptation to drier habitats.
These features have evolved a number of times independently: convergent evolution.
The distinction has no taxonomic basis.
The only family exclusively given the common name "toad" is Bufonidae (the "true toads"), but many species from other families are commonly called "toads".
Caudata
Newts are salamanders which spend their life in the water even though they are adults.
They are classified in the subfamily Pleurodelinae of the family Salamandridae.
In most cases, these are external gills, visible as tufts on either side of the head.
Some terrestrial species lack both lungs and gills and perform gas exchange through their skin.
Even some species with lungs also respire through the skin in this manner.
This helps to keep the animal moist when on dry land, keeps their salt balance while in water, and lubricates during swimming.
Axolotls, from  the genus Ambystoma (or mole salamanders),  are neotenic amphibians.
This means they get to sexual maturity and reproduce while still in a larval form.
Defence mechanisms
Most salamanders and newts have some defence against predators, usually a poison which makes them uneatable.
Their bright colours are warning colouration.
If, instead, they are camouflaged, this means they are probably not protected by a toxin.
The second line of defence is to shed their tail, which can grow again.
The tail wriggles a bit, attracts the predator while the business part of the salamander moves off.
Other characteristics
There are over 350 lungless salamanders.
Most of them are terrestrial and are active in daytime.
Lungless salamanders may communicate with their nose.p168 Slender salamanders are found in the Pacific Coast.
They are sometimes called "worm salamanders".
This is because they have slimmer (skinny) bodies than most salamanders.p182 If touched, slender salamanders will bounce on the ground and then run away.
Gymnophiona
The order Gymnophiona includes the caecilians.
These are long, cylindrical, limbless animals that look like snakes or worms.
Their skin has circular folds, increasing their similarity to the segments of earthworms.
Some are aquatic, but most live underground in burrows they hollow out.
Many caecilians give birth to live young.
In species which lay eggs, the eggs may undergo metamorphosis before they hatch.
Caecilians are found in tropical Africa, Asia and Central and South America.
There are 171 different species.
Their skins make a mucus that makes them slippery enough to slip through the earth.
They can make a toxic material in their skins, as many frogs and toads do.