radiation

X-ray crystallography

... liquid nitrogen . Freezing crystals both reduces radiation damage incurred during data collection and decreases thermal motion within the crystal. Crystals are placed on a diffractometer , a machine that emits a beam of x-rays. The x-rays diffract off the electrons in the crystal, and the pattern of diffra...

Wavelength

...cy of the wave. When dealing with electromagnetic radiation in a vacuum, this speed is the speed of light c , for signals (waves) in air, this is the speed of sound in air. The relationship is given by: where: λ = wavelength of a sound wave or electromagnetic wave c = speed of li...

Optical spectrum

...h is the reason the sky is blue). Electromagnetic radiation outside the optical wavelength range is almost entirely absorbed by the atmosphere. Contents showTocToggle("show","hide") 1 Historical use of the term 2 Explanation of Newton's experiment 3 Spectroscopy 4 See also Hist...

Thermoregulation

... the faeces and urine, respiration, conduction and radiation from the skin, and by evaporation of perspiration....e about 3, respiration about 20, skin (conduction, radiation and evaporation) about 77. Hence it is clear the chief means of loss are the skin and the lungs. The...

Speciation

...n is also related to a process known as adaptive radiation . Speciation mechanisms Ernst Mayr proposed a speciation mechanism called allopatry . Allopatry begins when subpopulations of a species become isolated geographically (for example, by habitat fragmentation or migration). The isolated popul...

Skin

...entation which absorbs the potentially dangerous radiation contained therein. Human skin pigmentation varies across populations in a visually dramatic manner. This has sometimes led to the classification of people(s) on the basis of skin color. See the article on human skin color for more information. M...

Punctuated equilibrium

... and Alfred Russel Wallace . See also: Adaptive radiation References Eldredge, Niles, and Gould, Stephen Jay:"Punctuated equilibria: an alternative to phyletic gradualism" in: T.Schopf (Hrsg.), Models in Paleobiology, 82-115, Freeman, Cooper and Co., San Francisco, (1972); reprinted in: N.Eldredge, ...

Prion

...g Creutzfeldt-Jakob disease resisted ultraviolet radiation (which breaks down nucleic acids), yet responded to agents that disrupt proteins. Initially, this hypothesis was highly controversial, because it seemed to contradict the " central dogma of modern biology ", which asserts that all living organisms us...

Photon

...hotons are the building blocks of electromagnetic radiation : that is, a photon is a "particle" of light , al...s: that is, the smallest amount of electromagnetic radiation that can exist is one photon whatever its wavelength , frequency , energy , or momentum . Photon...

Photobiology

...rocessing , circadian rhythms , and ultraviolet radiation effects. There are numerous professional societies devoted to the study of photobiology, the largest of which are the American Society for Photobiology and the European Society for Photobiology ....

Mutagen

...l. Mutagens are usually chemical compounds or radiation . The Ames test is one method to determine how mutagenic an agent is. See also DNA repair Genetics Teratogen...

Magnetic resonance imaging

...nt patients from associating the examination with radiation exposure. Scientists still use NMR when discu...t utilizes strong magnetic fields and non-ionizing radiation in the radio frequency range. Compare this to CT scans and traditional X-rays which involve dose...

Molecular evolution

...aterial during cell division and by exposure to radiation , chemicals, or viruses , or can occur deliberately under cellular control during the processes such as meiosis or hypermutation . Mutations are considered the driving force of evolution , where less favorable (or deleterious ) mutations are re...

Microorganism

... vacuum , and some can be unusually resistant to radiation . Microorganisms are used in brewing , baking , biotechnology , recycling of other organisms' remains and waste products, and many other processes. They can also be harmful as pathogens when, as parasites , they cause infections . Microorg...

Lyon hypothesis

...le she was studying the genetic consequences of radiation exposure, and therefore bears her name . See also XY sex-determination system Dosage compensation Reference Carrel L, Willard HF. X-inactivation profile reveals extensive variability in X-linked gene expression in females. . Natu...

Immunology

...with chemotherapy ( drugs ) and radiotherapy ( radiation ). However, immunotherapy is also often used in the immunosuppressed (such as HIV patients) and people suffering from other immune deficiencies or autoimmune diseases. Diagnostic immunology The specificity of the bond between antibody and antig...

Human

...n part because of human vulnerability to ionizing radiation , starting with Yuri Gagarin 's space flight in 1961 . Between 1969 and 1974 , up to two humans at a time spent brief intervals on the Moon . As of 2004 , no other celestial body has been visited by human beings, although there has been a co...

Fick's law of diffusion

...ne, D . Fick's first law is also important in radiation transfer equations. However, in this context it b...ccurate when the diffusion constant is low and the radiation becomes limited by the speed of light rather than by the resistance of the material the radiation is...

Evolution

...aterial during cell division and by exposure to radiation , chemicals, or viruses , or can occur deliberately under cellular control during processes such as meiosis or hypermutation . In multicellular organisms, mutations can be subdivided into germline mutations, which can be passed on to progeny an...

Cold-blooded

...argely on external sources of heat, such as solar radiation . As the environmental temperature increases, the animal's metabolic rate will increase. Lizards, fish, and amphibians are examples of ectotherms.Whereas an endotherm, or warm-blooded animal will use up to 98% of its energy for heat production, ...

Electrical energy

...eld , or in any volume containing electromagnetic radiation . The SI unit of electrical energy is the joul...he fields propagating in space as electromagnetic radiation . The amount of electrical energy surrounding a conductor or travelling through a waveguide may be ...

Diffusion

...ransport phenomenon : compare it, for example, to radiation . All diffusion can be modelled quantitatively using the diffusion equation , the solutions of which go by different names depending on the physical situation. Steady state bi-molecular diffusion is governed by Fick's first law . Steady-state th...

Dialysis

...ds include microwaves , heating pads and solar radiation (often using the dashboard of a car, for instance while travelling). The patient, who performs the entire procedure themselves, dons a disposable surgical mask , scrubs their hands using antibacterial soap, and tucks a clean towel into the waist...

Computed axial tomography

...ments in CT technology have meant that the overall radiation dose has decreased, scan times have decreased and ...ferent angle) has increased over time. Still, the radiation dose from CT scans is several times higher than conventional X-ray scans. Presently , the cost of...

Cancer

...ncer can be treated by surgery , chemotherapy , radiation therapy or other methods. The choice of therapy ... use of a certain type of energy (called ionizing radiation ) to kill cancer cells and shrink tumors. Radiation therapy injures or destroys cells in the area be...

Botany

... and taxonomy . Plant responses to ultraviolet radiation can help us monitor problems like the holes in the ozone layer . Analysing pollen deposited by plants thousands or millions of years ago can help scientists to reconstruct past climates and predict future ones, an essential part of climate c...

Autoradiograph

...an image produced on a photographic film by the radiation from a radioactive substance....

Adaptive radiation

Adaptive radiation describes the rapid speciation of a single or a...n by mutation and natural selection . Adaptive radiation often occurs when a species is introduced to a new ecosystem , or when a species can survive in an ...

Absorption spectrum

...am depicting the wavelengths of electromagnetic radiation absorbed by a material, usually a gas . It can b...der white light, which consists of electromagnetic radiation at all frequencies, passing through a sample of cold gas. For any collection of atoms or molecule...