Information & explanations, latest texts & monographs on
Atomic_nucleus (including recent related patents.)
Atomic nucleusThe center of an atom is called the nucleus. It is composed of one or more protons and usually some neutrons as well. The number of protons in an atom's nucleus is called the atomic number, and determines which element the atom is (for example hydrogen, carbon, oxygen, etc.). Though the positively charged protons exert a repulsive electromagnetic force on each other, the distances between nuclear particles are small enough that the strong interaction (which is stronger than the electromagnetic force but decreases more rapidly with distance) predominates. (The gravitational attraction is negligible, being a factor 1036 weaker than this electromagnetic repulsion.) See also: The discovery of the electron was the first indication that the atom had internal structure. This structure was initially imagined according to the "raisin cookie" or "plum pudding" model, in which the small, negatively charged electrons were embedded in a large sphere containing all the positive charge. Ernest_Rutherford and Marsden, however, discovered in 1911 that alpha particles from a radium source were sometimes scattered backwards from a gold foil, which led to the acceptance of a planetary model, in which the electrons orbited a tiny nucleus in the same way that the planets orbit the sun. A heavy nucleus can contain hundreds of nucleons (neutrons and protons), which means that to some approximation it can be treated as a classical system, rather than a quantum-mechanical one. In the resulting liquid-drop model, the nucleus has an energy which arises partly from surface tension and partly from electrical repulsion of the protons. The liquid-drop model is able to reproduce many features of nuclei, including the general trend of binding energy with respect to mass number, as well as the phenomenon of nuclear fission. Superimposed on this classical picture, however, are quantum-mechanical effects, which can be described using the nuclear shell model, developed in large part by Maria Goeppert-Mayer. Nuclei with certain numbers of neutrons and protons (the magic numbers 2, 8, 20, 50, 82, 126, ...) are particularly stable, because their shells are filled. Since some nuclei are more stable than others, it follows that energy can be released by nuclear reactions. The sun is powered by nuclear fusion, in which two nuclei collide and merge to form a larger nucleus. The opposite process is fission, which powers nuclear power plants. Because the binding energy per nucleon is at a maximum for medium-mass nuclei (around iron), energy is released either by fusing light nuclei or by fissioning heavier ones. The elements up to iron are created in a star during a series of fusion stages. First hydrogen fuses with itself to form helium, then helium fuses with itself twice to make carbon, and further fusings proceed to make heavier elements, until the series of fusions make iron which will not fuse further. If the star explodes in a supernova, the high energy neutrinos streaming from the supernova will bombard the escaping elements to form substantial portions of the elemental neuclei heavier than iron. Hence, during stellar evolution through the progression of stages in fusing succeedingly heavier elements, the death of a star in a supernova can create the elements necessary for life. Nuclear reactions occur naturally on earth. Except in manmade conditions, such as atomic explosions, temperatures and pressures on earth are not high enough to overcome the electrical repulsion between nuclei and allow fusion. But heavy nuclei such as uranium may undergo fission and alpha decay, and beta decay can also occur. Alpha decay can be considered as an extremely asymmetric case of fission, in which one fragment is a helium nucleus (alpha particle). In beta decay, either a proton is converted into a neutron (with the emission of an antielectron and a neutrino) or a neutron is converted into a proton (emitting an electron and an antineutrino). Much of current research in nuclear physics relates to the study of nuclei under extreme conditions. The heaviest of all nuclei are neutron stars. Nuclei may also be characterized by extreme shapes (like footballs) or by extreme neutron-to-proton ratios. Experimenters can also use artificially induced fusion at high energies to create nuclei at very high temperatures, and there are signs that these experiments have produced a phase transition from normal nuclear matter to a new state, the quark-gluon plasma, in which the quarks mingle with one another, rather than being segregated in triplets as neutrons and protons. See also: List of particlesThis article is adapted from from Wikipedia All Wikipedia article text is available under the terms of the GNU Free Documentation License Nucleus: The History of Atomic Energy of Canada Limited by Robert Bothwell The Atomic Nucleus. by Robley Dunglison, Evans From Nucleons to the Atomic Nucleus. Perspectives in Nuclear Physics by Kris Heyde Knowing the Atomic Nucleus by R. Hobart Ellis Knowing the Atomic Nucleus by R. Hobart Ellis The atomic nucleus by J. M. Reid The Atomic Nucleus by John McArthur Reid Atomic Nucleus by Robley Dunglison Evans The Atomic Nucleus As a Relativistic System (Texts and Monographs in Physics) by L. N. Savushkin Vom Atomkern zum Kernkraftwerk = From atomic nucleus to nuclear power plant by Dietrich Bünemann The atomic nucleus and chemistry by Larry A. Haskin What do we know about the atomic nucleus by Mike Allan The Fundamental Nucleus: a Study of the Impact of the British Atomic Energy Project on Basic Research (Reports) by AEA Technology Plc What do we know about the atomic nucleus by Mike Allan Recent Atomic_nucleus related patents From USPTO: 6717407: Method for evaluating magnetic resonance data containing spectroscopic information, by analysis of a frequency difference between spectrum spikes 6710090: Inhibitory or blocking agents of molecular generating and/or inducing functions 6690961: Apparatus and method for transition between fluoro-mode and diagnostic mode magnetic resonance imaging 6686879: Method and apparatus for transmitting and receiving signals having a carrier interferometry architecture 6686739: Method for operating a magnetic resonance device for producing a magnetic resonance spectrum 6657432: Gradient coils for MRI systems having multiple current density zones 6632020: Method and apparatus for calibrating an imaging system 6631391: Parallel computer system and parallel computing method 6624777: Fast A/D conversion signal processor, RF receiver circuit, digital receiver front end circuit, MRI apparatus, and fast A/D conversion device 6615069: Magnetic resonance imaging device 6613924: Silver precursors for CVD processes 6610977: Security system for NBC-safe building 6597172: Water and fat separation image forming method, magnetic resonance imaging apparatus, reference peak phase detecting method and reference peak position detecting method 6593421: Flooring adhesives based on styrene-butadiene copolymers 6572987: Light-emitting device 6566878: Magnetic resonance imaging device and method therefor 6563906: X-ray compton scattering density measurement at a point within an object 6563159: Substrate of semiconductor integrated circuit 6552539: Method of correcting resonance frequency variation and MRI apparatus 6534981: MR imaging method and MRI apparatus 6528996: Diffusion-weighted imaging method and apparatus for fast pulse sequence with MPG pulses 6517799: Isolation of small-bandgap fullerenes and endohedral metallofullerenes 6508652: Chemblox educational molecular models 6504373: Magnetic resonance imaging apparatus 6504248: Thin film circuit substrate and manufacturing method therefor 6489638: Light emitting device 6489080: Positive resist composition 6489041: Magnetic body formed by quantum dot array using non-magnetic semiconductor 6486666: Method and apparatus for measuring the degree of polarization of polarized gas 6485883: Positive photoresist composition 6472681: Quantum computer 6456869: Solid state beta-sensitive surgical probe 6452992: Method and device for measuring the relative proportions of plutonium and uranium in a body 6451337: Chitosan-based nitric oxide donor compositions 6444994: Apparatus and method for processing the components of a neutron lens 6433547: Method of determining the direction of application of gradient magnetic field for the detection of diffusive motion, method of measuring the diffusion coefficient, and MRI apparatus 6429434: Transmission attenuation correction method for PET and SPECT 6423076: Laser directed portable MRI stereotactic system 6373250: Method of magnetic resonance imaging 6357075: Hair brush 6355225: Fullerene contrast agent for magnetic resonance imaging and spectroscopy 6346551: Inhibitory or blocking agents of molecular generating and/or inducing functions 6344818: Apparatus and method for the detection of materials 6329657: Coincidence transmission source 6303016: Isolation of small-bandgap fullerenes and endohedral metallofullerenes 6297506: System and method for reducing pile-up errors in multi-crystal gamma ray detector applications 6284933: TFPX synthesis 6266289: Method of toroid write and read, memory cell and memory device for realizing the same 6261594: Chitosan-based nitric oxide donor compositions |