Weather

Weather is an all-encompassing term used to explain all of the many and varied phenomena that can occur in the atmosphere of a planet. The term is normally taken to mean the activity of these phenomena over short periods of time, typically no more than a few days in length. Average atmospheric conditions over significantly longer periods are known as climate. Usage of the two terms often overlaps and the concepts are obviously very closely connected. Weather phenomena result from temperature differences around the globe, which arise primarily because areas closer to the tropics, around the equator, obtain more energy from the Sun than more northern and southern regions, nearer to the Earth's poles.

A secondary cause of temperature differences on the Earth is that different surface areas have differing reflectivity, and therefore absorb and radiate dissimilar amounts of the solar energy they receive. Surface temperature differences cause vertical wind currents. A hot surface heats the air above it, and the air expands and rises, lowering the air pressure and drawing colder air into its place. Rising and expanding air gives up its heat and so cools, which causes it to shrink and sink, increasing air pressure and displacing the air already below it.

IP address

An IP address is a unique number that devices use in order to identify and communicate with each other on a computer network utilizing the Internet Protocol standard . Any participating network device — including routers, computers, time-servers, printers, Internet fax machines, and some telephones — must have its own unique address. An IP address can also be thought of as the equivalent of a street address or a phone number for a computer or other network device on the internet. Just as each street address and phone number uniquely identifies a building or telephone, an IP address can uniquely identify a specific computer or other network device on a network.

An IP address can appear to be shared by multiple client devices either because they are part of a shared hosting web server environment or because a proxy server acts as an intermediary agent on behalf of its customers, in which case the real originating IP addresses might be hidden from the server receiving a request. The analogy to telephone systems would be the use of predial numbers and extensions.

Antibiotic

An antibiotic is a drug that kills or slows the growth of bacteria. Antibiotics are one class of antimicrobials, a larger group which also includes anti-viral, anti-fungal, and anti-parasitic drugs. They are relatively harmless to the host, and therefore can be used to treat infections. The term, coined by Selman Waksman, originally described only those formulations derived from living organisms, in contrast to "chemotherapeutic agents", which are purely synthetic. Nowadays the term "antibiotic" is also applied to synthetic antimicrobials, such as the sulfa drugs. Antibiotics are generally small molecules with a molecular weight less than 2000. They are not enzymes. Some antibiotics have been derived from mould, for example the penicillin class.

Antibiotics can also be classified by the organisms against which they are effective, and by the type of infection in which they are useful, which depends on the sensitivities of the organisms that most commonly cause the infection and the concentration of antibiotic obtainable in the affected tissue.

Physical Model

A physical model is used in various contexts to mean a physical representation of some thing. That thing may be a single item or object a large system.The geometry of the model and the object it represents are often similar in the sense that one is a rescaling of the other; in such cases the scale is an important characteristic. However, in many cases the similarity is only approximate or even intentionally distorted. Sometimes the distortion is systematic with e.g. a fixed scale horizontally and a larger fixed scale vertically when modelling topography of a large area.

Physical models in science and technology allow us to simulate or visualize something about the thing it represents. A model in this sense is a physical object such as an architectural model of a projected building or an existing one.