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Topic: Effective atomic number

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complex number

natural number

prime number

atomic number

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	Effective atomic number - Wikipedia, the free encyclopedia
		Effective atomic number has two different meanings: one that is the effective nuclear charge of an atom, and one that calculates the average atomic number for a compound or mixture of materials.
		Effective atomic numbers are useful not only in understanding why electrons further from the nucleus are so much more weakly bound than those closer to the nucleus, but also because they can tell us when to use simplified methods of calculating other properties and interactions.
		Effective atomic number is important for predicting how X-rays interact with a substance, as certain types of x-ray interactions depend on the atomic number.
	en.wikipedia.org /wiki/Effective_atomic_number (676 words)

	Atomic number - Wikipedia, the free encyclopedia
		In chemistry and physics, the atomic number (Z) is the number of protons found in the nucleus of an atom.
		The atomic number originally meant the number of an element's place in the periodic table.
		The atomic number is closely related to the mass number (although they should not be confused) which is the number of protons and neutrons in the nucleus of an atom.
	en.wikipedia.org /wiki/Atomic_number (305 words)

	Glossary
		Atomic Number--The number of protons in the nucleus of a neutral atom of a nuclide.
		The "effective atomic number" is calculated from the composition and atomic numbers of a compound or mixture.
		Mass Numbers (A)--The number of nucleons (protons and neutrons) in the nucleus of an atom.
	www.fas.org /man/dod-101/sys/land/docs/du/mr1018.7.gloss.html (3409 words)

	[No title] (Site not responding. Last check: 2007-11-06)
		Because of this a single effective atomic number for a sample of coal may not be sufficient to determine the percentage of coal that is ash.
		As the percentage of silicon and aluminium in the ash decreases the percentage of elements with a higher atomic number increases and the scanner overestimates the percentage ash in the coal.
		The scanner calculated result was calculated using the effective atomic number calculated directly from the output of the dual energy x-ray absorption scanner and a supplementary measurement of the percentage of silicon and aluminium in the coal.
	www.wipo.int /cgi-pct/guest/getbykey5?KEY=01/09596.010208&ELEMENT_SET=DECL (4689 words)

	[No title] (Site not responding. Last check: 2007-11-06)
		This method reduces the number of slices necessary to be taken by the CT scanner, including the number of slices taken through metal, to detect a target object and increases the accuracy with which target objects are detected.
		To determine the effective atomic number for a particular object, all pixels within the object are compared to pixels surrounding the object and a histogram is created, where the mode (peak of the histogram) represents the effective atomic number.
		atomic number and mass values represent a probability or range of probabilities that the atomic number and mass data are correct.
	www.wipo.int /cgi-pct/guest/getbykey5?KEY=03/67770.030814&ELEMENT_SET=DECL (6076 words)

	Category:Atomic physics - Wikipedia, the free encyclopedia
		Atomic physics is the field of physics that studies atoms as isolated systems comprised of electrons and an atomic nucleus.
		It is primarily concerned with the arrangement of electrons around the nucleus and the processes by which these arrangements change.
		As with many scientific fields, strict delineation can be highly contrived and atomic physics is often considered in the wider context of atomic, molecular and optical physics.
	en.wikipedia.org /wiki/Category:Atomic_physics (135 words)

	International Union of Pure and Applied Chemistry
		Effective molecular symmetry group - The appropriate group in which the energy levels of molecules undergoing rearrangements on a given experimental time scale are to be classified.
		An extension of the rule to transition metal cluster compounds is known as the effective atomic number rule.
		(r), of an atomic or molecular system (in the latter case the term molecular electrostatic potential is commonly used) and a positive unit point charge located at r.
	www.iupac.org /reports/1999/7110minkin/e.html (1852 words)

	Mass attenuation coefficient
		The mass attenuation coefficient tends to increase with increasing atomic number at the same photon energy, so materials with high atomic numbers (and, hence, high mass attenuation coefficients) are normally chosen to shield x and gamma radiation.
		The molar extinction coefficient is not related to the effective atomic number, but to the orbital electronic structure of the atoms or molecules used as an absorber.
		Total light attenuation for a given absorber thickness at a particular wavelength depends on the molar concentration of absorber (the number of molecules per unit volume)—hence the name, molar extinction coefficient.
	www.hps.org /publicinformation/ate/q1632.html (531 words)

	Sheet detection system - Patent 6301326
		Since.mu..sub.pe is a function of atomic number/energy and.mu..sub.es is a function of atomic mumber, these expressions can be solved for atomic number by using two different X-ray energy levels, e.g., 40 Kev and 90 Kev.
		Within target envelope 90 the atomic number of the material increases from the organic boundary to the inorganic boundary as indicated by vector 108 and an increasing thickness of the material detected increases generally parallel to the organic boundary 94 as indicated by vector 110.
		This is accomplished by using the store frame equivalent atomic number circuit 122 which stores the equivalent atomic number output from look-up table 80 for each scan in the frame.
	www.freepatentsonline.com /6301326.html (4009 words)

	illumin : article : The Design and Use of Soybean Oil-Filled Breast Implants in Augmentation Mammioplasty
		Radiolucency is determined by a material's effective atomic number, which is the relative amount of photoelectric interaction between different materials and a radiation beam; the resulting amount of interaction produces the contrast in radiographic images (Brucker 2108).
		Because saline and silicone implant fillers have atomic numbers that are higher than that of the breast tissue, they are radiopaque on a mammogram (Brucker 2108).
		Soybean oil filled implants, however, are radiolucent on a mammogram because they have an effective atomic number near that of breast tissue (Brucker 2108).
	illumin.usc.edu /article.php?articleID=41&page=2 (540 words)

	Article : Retrieval of True Color of the Internal Organ of CT Images and Attempt to Tissue Characterization by ... (Site not responding. Last check: 2007-11-06)
		CT or attenuation number represents the linear coefficient of attenuation of various organic tissue in relation to water and expressed in Hounsfield unit (HU) [10,11,12,13] CT No. of the non contrast image is mainly taken.
		In general, the CT number of any material will shift as a function of the difference between the atomic number of that material and the atomic number of water.
		CT number determines directly the effective atomic number or electron density of the tissue instead of the attenuation coeeficient [7].
	www.ijri.org /articles/archives/2002-12-2/Radiation_169.htm (3923 words)

	Nat' Academies Press, The Practicality of Pulsed Fast Neutron Transmission Spectroscopy for Aviation Security (1999)
		Attenuation is a function of energy, density, and average atomic number.
		The significance of the photoelectric effect is greater for materials composed of elements with a high atomic number (Z), such as metals or other inorganic materials.
		Although the effective atomic number is not enough to completely characterize a material, it does provide discrimination capability above and beyond characterization by a physical density metric alone.
	www.nap.edu /openbook/030906449X/html/9.html (2333 words)

	Alpha, beta, and gamma detectors
		This process can continue and multiply the number of ionization events (the ionization process propagates along the entire central wire anode) by a large factor and result in a very large electronic pulse when the ions are collected at the electrodes.
		Because the likelihood of gamma-ray interactions depends strongly on the atomic number of the material the gamma rays are interacting with, the detection efficiency of germanium is considerably lower than that of NaI(Tl) because germanium has a lower effective atomic number.
		There are a number of other less popular semiconductor detectors with poorer energy resolution than germanium and silicon, but that have been used in some applications in gamma-ray measurements.
	hps.org /publicinformation/ate/q534.html (3265 words)

	Radiation Safety Manual - Chapter 10 (Site not responding. Last check: 2007-11-06)
		The most effective shielding materials are those that have a low effective atomic number (Z) since brehmsstrahlung production increases linearly with the Z of the absorber.
		Beta absorption is relatively independent of atomic number so plastic, glass, wood and other low-Z materials provide shielding which is just as effective at stopping P-32 beta particles as an equal mass of lead or iron, producing fewer X-rays in the process.
		The most effective P-32 shield is one which utilizes a low-Z inner shield to absorb the beta particles and minimize X-ray production, and an outer layer of lead or iron to absorb the x rays produced in the inner shield.
	bfa.sdsu.edu /ehs/radch10.htm (2336 words)

	chemdefinitions.htm
		This number defines the type of atom it is; for example, any atom with an atomic number of 8 must always be oxygen.
		, where A is a cation with a coordination number of 12, exhibiting cuboctahedral symmetry with the X anion, and B and B' are cations with a coordination number of 6, exhibiting octahedral symmetry with the X anions.
		mass number-the number of protons and neutrons in the nucleus of an atom.
	www.chemistry.ohio-state.edu /~pbarnes/oldwebs/chemdefinitions.htm (2286 words)

	OccultAtoms (Site not responding. Last check: 2007-11-06)
		The illustrations there given of atomic combination are entirely wrong and misleading, but if the stovepipe run through the centre of the single atom be removed, the picture may be taken as correct, and will give some idea of the complexity of this fundamental unit of the physical universe.
		The respective numbers of ultimate atoms contained in a chemical atom of these two bodies are thus seen to closely correspond with their accepted weight numbers.
		Thus the Occult Chemists might be excused for conceiving a random set of atomic pictures and associating them with elements known to chemistry on the basis of their effective atomic weights (number of anu / 18).
	www.chem.yale.edu /~chem125/125/history99/8Occult/OccultAtoms.html (8425 words)

	CHARGED PARTICLE INTERACTIONS
		The straggling peak is approximately Gaussian shaped, with a width that increases with the ratio Z/A. In other words, at lower atomic numbers (where the Z/A ratio is higher) we have wider widths.
		For mixtures of elements, one determines the "effective atomic number", Z(eff).
		The atomic number part is the approximation and the guts of the Bragg-Kleeman rule.
	www.med.harvard.edu /JPNM/physics/didactics/physics/charged/lect.html (2511 words)

	Average atomic number...
		In light of these findings, we anticipate the absorption, or attenuation, coefficient to depend somewhat linearly on atomic number, Z. A strict linear dependence would be expected for Compton scattering of essentially mono-energetic radiation at energies which preclude contributions from additional scattering mechanisms.
		Firstly, many so-called plastic explosives possess effective Z values which are somewhat larger than ordinary luggage items [8]; consequently, the probability of encountering an explosive is in some way related to Z of the sample in question.
		Currently, we are evaluating the inclusion of such a probability in a correlation analysis, which yields a single explosive probability from a 2-dimensional array of attenuation spectra corresponding to a given piece of luggage.
	darkwing.uoregon.edu /~lefevre/NIMB.doc.html (2402 words)

	Energy variables (Site not responding. Last check: 2007-11-06)
		Although the effective number of electrons is a concept which has appeared in the literature since the early twentieth century, it has not been adequately defined.
		NEFFIN is the effective number of electrons in the atom, but all the electrons may not be equally polarizable.
		Let Z be the "effective atomic number" for the species with a complete outer shell of electrons, and adjust in the same way to give the "modified atomic number" z.
	www.moldiscovery.com /docs/grid/c40.html (2653 words)

	COMMERCIAL AIRCRAFT SECURITY: WHERE IS THE TECHNOLOGY TODAY
		We also might want to look for the average atomic number and molecular structure.
		If you measure the effective atomic number and density, you find that most explosives cluster around an effective atomic number of 7 or 8, because of the amount of nitrogen.
		But the atomic number itself gets obscured if things are stacked on top of each other.
	web.mit.edu /ssp/spring98/lanza.htm (1022 words)

	CHM 401 Lecture 31 Summary (Site not responding. Last check: 2007-11-06)
		Effective Atomic Number Rule (EAN): complexes with 18 (sometimes 16) electrons are stable (analogous to octet rule for main group elements)
		EAN is most effective for low oxidation states and organometallic complexes
		Unlike the main group, d orbital lone pairs are generally not stereochemically active so the geometries of these compounds normally are determined solely by the number of ligands.
	bilbo.chm.uri.edu /CHM401/lecture31.html (155 words)

	The Radioactive Boy Scout - Ken Silverstein
		David's Atomic Energy merit-badge pamphlet was brazenly pro-nuclear, which is no surprise since it was prepared with the help of Westinghouse Electric, the American Nuclear Society, and the Edison Electric Institute, a trade group of utility companies, some of which run nuclear power plants.
		This "atomic number" determines the element's chemical properties and position in the periodic table.
		In beta decay, either a neutron is converted into a proton, and the atomic number rises, or the opposite occurs, pushing the atomic number down.
	www.wesjones.com /silverstein1.htm (7208 words)

	CBU CHEM422 E1 2001
		Describe and explain the trends in the periodic table for the atomic radius.
		The atomic radius decreases left to right across a period and increases top to bottom down a family.
		Going across a period, the effective atomic number increases as the electrons are added as individual charges whereas the nucleus acts as point charge.
	www.cbu.edu /~mcondren/c422e101.htm (516 words)

	Predicition Coordination Numbers (Site not responding. Last check: 2007-11-06)
		We know that common numbers are 2, 4, and 6, and that often it is two times the oxidation number of the metal.
		There is an old model, put forward by N. Sidgwick in 1927 that uses a term called the Effective Atomic Number (EAN).
		He suggested that when the total number of valence electrons (s+p+d+f) of the metal plus the coordination ligands (2 electrons per ligand) summed to a closed shell number [ e.g.
	www.newton.dep.anl.gov /askasci/chem00/chem00341.htm (187 words)

	Hydrogen(1) (Site not responding. Last check: 2007-11-06)
		It is also known that an electron can interact with an electromagnetic field resulting in a transition from an excited state to a lower energy state and the emission of a photon.
		Certain nuclei can occasionally de-excite by internal conversion, which is a process whereby the excitation energy is transferred directly to one of the atomic electrons, causing it to be ejected from the atom.
		Apply conservation laws to determine the number and energies of photons produced when annihilation occurs from each of these possible ground states.
	electron6.phys.utk.edu /phys594/archives/quantum/Hydrogen/hydrogen1.htm (943 words)

	Contour Plots for Atomic Orbitals Tutorial (Site not responding. Last check: 2007-11-06)
		The effective nuclear charges "seen" by the electrons in the 2p and 3p atomic orbitals are required for the plots.
		Enter 14 for the "atomic number" of silicon and 7 for the seven OTHER electrons in the 2s2p group that "screen" the eighth electron in the group.
		However, the size of the contour plot - the area in which there is a 99% chance of finding the electron - is much larger for the 3p atomic orbital than the 2p atomic orbital.
	www.chm.davidson.edu /ronutt/che115/Density/Density_Tutor.htm (272 words)

	The Phantom Laboratory
		These phantoms are constructed with a natural human skeleton cast inside a proprietary urethane material that has the same effective atomic number as the body's soft tissue.
		The lungs' lower density is duplicated with the special atomically correct material used in our RANDO® Phantom lungs, which has an atomic number and specific gravity of human lungs at a median respiratory state.
		This material is formed to the contours of the rib cage.
	www.phantomlab.com /sectional_phantoms.html (484 words)

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