Mathematics

Mathematics (from Greek μάθημα máthēma, “knowledge, study, learning”) is the study of topics such as quantity (numbers),structure,space, and change. There is a range of views among mathematicians and philosophers as to the exact scope and definition of mathematics.

Mathematicians seek out patterns and use them to formulate new conjectures. Mathematicians resolve the truth or falsity of conjectures by mathematical proof. When mathematical structures are good models of real phenomena, then mathematical reasoning can provide insight or predictions about nature. Through the use of abstraction and logic, mathematics developed from counting, calculation, measurement, and the systematic study of the shapes and motions of physical objects. Practical mathematics has been a human activity for as far back as written records exist. The research required to solve mathematical problems can take years or even centuries of sustained inquiry.

Rigorous arguments first appeared in Greek mathematics, most notably in Euclid's Elements. Since the pioneering work of Giuseppe Peano (1858–1932), David Hilbert (1862–1943), and others on axiomatic systems in the late 19th century, it has become customary to view mathematical research as establishing truth by rigorous deduction from appropriately chosen axioms and definitions. Mathematics developed at a relatively slow pace until the Renaissance, when mathematical innovations interacting with new scientific discoveries led to a rapid increase in the rate of mathematical discovery that has continued to the present day.

Guest appearance

In show business, a guest appearance is the participation of an outsider performer (such as a musician or actor) in an event such as a music record or concert, show, etc., when the performer does not belong to the regular cast, band or other performing group. In music, such an outside performer is often referred to as a guest artist. In performance art, the terms guest role or guest star are also common, the latter term specifically indicating the guest appearance of a celebrity. The latter is often also credited as "special guest star" or "special musical guest star" by some production companies. A guest character is a character being portrayed within a fictional entertainment setting who is only involved as part of the plot once or a few times at most. A guest character has fewer appearances than main characters, supporting characters, and recurring characters.

In pop music, guest appearances are often described with the words featuring, with, or and. It is abbreviated in credit lists as feat., ft., f/, f.. In a television series, a guest star is an actor who appears in one or a few episodes. In radio and television shows, a guest star is a guest of the show who is a celebrity.

Scar

Scars are areas of fibrous tissue (fibrosis) that replace normal skin after injury. A scar results from the biological process of wound repair in the skin and other tissues of the body. Thus, scarring is a natural part of the healing process. With the exception of very minor lesions, every wound (e.g., after accident, disease, or surgery) results in some degree of scarring. An exception to this are animals with complete regeneration, which regrow tissue without scar formation.

Scar tissue is composed of the same protein (collagen) as the tissue that it replaces, but the fiber composition of the protein is different; instead of a random basketweave formation of the collagen fibers found in normal tissue, in fibrosis the collagen cross-links and forms a pronounced alignment in a single direction. This collagen scar tissue alignment is usually of inferior functional quality to the normal collagen randomised alignment. For example, scars in the skin are less resistant to ultraviolet radiation, and sweat glands and hair follicles do not grow back within scar tissues. A myocardial infarction, commonly known as a heart attack, causes scar formation in the heart muscle, which leads to loss of muscular power and possibly heart failure. However, there are some tissues (e.g. bone) that can heal without any structural or functional deterioration.

Bullet

A bullet is a projectile propelled by a firearm, sling, slingshot, or air gun. Bullets do not normally contain explosives, but damage the intended target by impact and penetration. The word "bullet" is sometimes colloquially used to refer to ammunition in general, or to a cartridge, which is a combination of the bullet, case/shell, powder, and primer. This use of 'bullet', when 'cartridge' is intended, leads to confusion when the components of a cartridge are discussed or intended.

Bullets fired from slings, slingshots, and many airguns (including BB guns) travel well below the speed of sound (about 343 m/s or 1126 ft/s in dry air at 20 °C or 68 °F). Low-power handguns have muzzle velocities generally less than the speed of sound (subsonic), while bullets fired from high-power handguns (such as a .44 Magnum) and from rifles have an initial speed faster than the speed of sound, meaning they are supersonic and thus can travel a substantial distance and even hit a target before a nearby observer hears the "bang" of the shot. Bullet speed through air depends on a number of factors such as barometric pressure, humidity, air temperature, and wind speed.

Coyote

The coyote (US /kaɪˈoʊtiː/ or /ˈkaɪ.oʊt/, UK /kɔɪˈjoʊteɪ/, or /kɔɪˈjoʊt/;Canis latrans) is a canid native to North America. It is a smaller, more basal animal than its close relative, the gray wolf, being roughly the North American equivalent to the Old World golden jackal, though it is larger and more predatory in nature. It is listed as "least concern" by the IUCN, on account of its wide distribution and abundance throughout North America, even southwards through Mexico and Central America. It is a highly versatile species, whose range has expanded amidst human environmental modification. This expansion is ongoing, and it may one day reach South America, as shown by the animal's presence beyond the Panama Canal in 2013.As of 2005, 19 subspecies are recognized.

The ancestors of the coyote diverged from those of the gray wolf, 1–2 million years ago, with the modern species arising in North America during the Middle Pleistocene. It is highly flexible in social organization, living either in nuclear families or in loosely knit packs of unrelated individuals. It has a varied diet consisting primarily of animal matter, including ungulates, lagomorphs, rodents, birds, reptiles, amphibians, fish, and invertebrates, though it may also eat fruit and vegetable matter on occasion. It is a very vocal animal, whose most iconic sound consists of a howl emitted by solitary individuals.Humans aside, cougars and gray wolves are the coyote's only serious enemies. Nevertheless, coyotes have on occasion mated with the latter species, producing hybrids colloquially called "coywolves".