The periodic table has been used by chemists to observe patterns and relationships between elements. There are 3 main groups in the Periodic Table; metals, metalloids, and nonmetals. For example, elements to the bottom and far left of the table are the most metallic, and elements on the top right are the least metallic. (e.g. cesium is much more metallic than helium). There are also many other patterns and relationships.
The periodic table was invented by the Russian chemist Dmitry Ivanovich Mendeleyev (18341907). In his honor, element 101 was named after him, mendelevium.
The version of the periodic table shown above is the one most used. Other widespread versions are shown below:
Physiology
Physiology is the study of how living things work. Physiologists can study how organs of an organism work together to make things happen. In human beings, for example, the digestion of food hormones and other chemicals are made by the stomach, liver, and pancreas. Muscle contraction happens because of chemical messages made by nerves of that muscle. By learning how the body functions normally, physiologists and physicians can better understand what happens when organs do not function normally. For example, an understanding of how the thyroid gland functions has helped in treating goitre. Studies of the circulatory system and the nervous system have helped physicians understand and treat such illnesses like heart disease, stroke, and high blood pressure.
The field is usually divided into human physiology, animal physiology, and plant physiology.
Planet
A planet is a large object such as Venus or Earth that orbits a star. Planets are smaller than stars, and they do not produce light. Jupiter is the biggest planet in the Solar System.
Planets are shaped like a slightly squashed ball (called a spheroid). Objects that orbit planets are called satellites. A star and everything which orbits it are called a star system.
There are eight planets in the Solar System. Pluto used to be called a planet, but in August 2006, the International Astronomical Union decided it was a dwarf planet instead. There are four more known dwarf planets in the Solar System, Ceres, Makemake, Eris and Haumea.
The name "planet" is from the Greek word "πλανήτης" ("planetes"), meaning "wanderers", or "things that move". Until the 1990s, people only knew of those in the Solar System. As of June 2017, we know of 3,610 other planets. These newly found planets are orbiting other stars: they are "extrasolar" planets. Sometimes people call them "exoplanets".
The planets are composed of material quite different from the Sun. The Sun is almost entirely composed of hydrogen, and some helium. Its energy comes from the conversion of hydrogen to helium. In contrast, the "terrestrial" planets are composed almost entirely of larger atoms and molecules which "cannot" have come from the Sun. It follows, therefore, that the material which forms those planets must have come from another source or sources. Those sources were the atoms formed in supernovae explosions by much larger and much shorter-lived stars in the Sun's neighbourhood as it moved in the galaxy. This material was captured by the Sun's gravity and pulled along to become the basic material out of which the planets condensed. The same considerations apply to other planetary systems in the galaxy.
The gas giants are composed of hydrogen gas from the same source as the Sun, plus (at their centres) higher "metallic" elements like the terrestrial planets. This is known from the drive-by data gathered by satellites, and by drive-into probes like the Galileo (spacecraft). There is a huge amount of data collected about each planet. The data is stored on computer files, and there are summary volumes in print.
The planets in the Solar System have names of Greek or Roman gods, apart from Earth, because people did not think Earth was a planet in old times. However, Earth is occasionally referred by the name of a Roman god: "Terra". Other languages, for example Chinese, use different names. Moons also have names of gods and people from classical mythology. The names of the moons of Uranus are from the plays written by Shakespeare.
Here is a list of planets in the Solar System. They are ordered by how close they are to the Sun, nearest first.
Astronomers speak about "major" (or true) planets, and minor planets, which are smaller objects that go around the Sun. Some examples of "minor planets" are asteroids, comets, and trans-Neptunian objects.
Planets in the Solar System are of three sorts:
Many objects in the Solar System that are not planets are also "icy". Examples are the icy moons of the outer planets of the Solar System (like Triton).
Political problems of China
Many people say the government stops people from having freedom of speech, freedom of religion and other political rights that people in other countries have. China still has one-party rule, and is not a democracy.
The following territories are claimed by China (PRC and/or ROC) and by another country or more.
Unequal treaties were forced onto Asian countries when European imperialism reached Asia.
The list includes claims from PRC and ROC, as well as unofficial historical claims.
"Note: Japan's and Korea's unequal treaties have been resolved since the end of WWII."
Police
Police are a group of people whose job is to enforce laws, help with emergencies, solve crimes and protect property. A person who carries out this duty is known as a police officer. They work out of a police station. Police are trained in first aid and rescue, because police officers are often one of the first people to get to a place where people are sick or injured, such as a car accident, or a fire.
A police agency may be called a "police force", "police department", "police service", "constabulary", "civil guard" or "protective service". A "gendarmerie" is a police force that is part of the military, although its members rarely do actual military work.
Most police forces in the United States name themselves as "[Place] Police Department", such as New York City Police Department. State police forces are usually known as either "[State] Highway Patrol" or "[State] State Police". In the United Kingdom, most are "[Place] Police" or "[Place] Constabulary". In Canada and other English-speaking countries, "[Place] Police Service" is common. Ireland's police are called the Garda Síochána.
A "law enforcement agency" is any agency that enforces the law. In the United States, there are some law enforcement agencies that are not called police forces but carry out similar work, such as the Federal Bureau of Investigations. One common type is a "sheriff's office" (also "sheriff's department"), an agency that is led by a "sheriff".
Those who carry out policing duties are known as "police officers". They may also be known as "policemen" (men only), "policewomen" (women only), "peace officers", "constables", "rangers" or "civil guards". In a sheriff's office, they are known as "sheriff's deputies" or "deputies" for short. In Ireland they are known by the Irish language word "gardaí" ("garda" if singular) or as "guards".
The police have different powers to help them do their job. These powers are different in different countries. Most police officers have the power to arrest people, search people, and search houses/properties. They sometimes carry equipment such as guns, batons, tasers, or pepper spray. The area where police officers can use these powers is called their jurisdiction. If officers are outside of their jurisdiction, another police force with jurisdiction can then use their powers.
The police deal with:
Most police departments have officers in two main groups: a "patrol" group with officers who wear uniforms, and a "detective" group with officers who wear normal clothing.