Channel rays

Several decades ago the number of elementary particles known was limited, and the system of elementary particles seemed to be comprehensible. Electrons had been known since 1858 as cathode rays, although the name electron was not used until 1881. Protons had been known since 1886 in the form of channel rays and since 1914 as constituents of hydrogen atoms. The discovery of the neutron in 1932 by Chadwick initiated intensive development in the field of nuclear science. In the same year positrons were discovered, which have the same mass as electrons, but positive charge. All these particles are stable with the exception of the neutron, which decays in the free state with a half-life of 10.25 min into a proton and an electron. In the following years a series of very unstable particles were discovered the mesons, the muons, and the hyperons. Research in this field was stimulated by theoretical considerations, mainly by the theory of nuclear forces put forward by Yukawa in 1935. The half-lives of mesons and muons are in the range up to 10 s, the half-lives of hyperons in the order of up to 10 s. They are observed in reactions of high-energy particles. 

Most of the chemical elements occur naturally not as a single species, but rather as a mixture of isotopes. The existence of isotopes was predicted already by de Marignac and discovered by Soddy in 1910 and Todd in 1912, respectively. Thomson found that neon forms isotopes with a mass of 20 and 22, when analyzing channel rays. Isotopes can be readily seen by means of a mass spectrometer, which... 

Channel Rays Descriptive term for energetic beams having the opposite electrical charge of cathode rays, emitted from electrically stimulated materials inside a vacuum tube, also identified by J. J. Thomson in 1897. 

The efficiency of gas turbines is limited by the maximum allowable turbine inlet temperature (TIT). The TIT may be increased by cooling of the blades and vanes of the high pressure turbine. Cooling channels can be casted into the components or may be drilled afterwards. Non-conventional processes like EDM, ECD or Laser are used for drilling. Radiographic examination of the drilled components is part of the inspection procedure. Traditional X-Ray film technique has been used. The consumable costs, the waste disposal and the limited capacity of the two film units lead to the decision to investigate the alternative of Real-Time X-Ray. 

Cromakalim (137) is a potassium channel activator commonly used as an antihypertensive agent (107). The rationale for the design of cromakalim is based on P-blockers such as propranolol (115) and atenolol (123). Conformational restriction of the propanolamine side chain as observed in the cromakalim chroman nucleus provides compounds with desired antihypertensive activity free of the side effects commonly associated with P-blockers. Enantiomerically pure cromakalim is produced by resolution of the diastereomeric (T)-a-meth5lben2ylcarbamate derivatives. X-ray crystallographic analysis of this diastereomer provides the absolute stereochemistry of cromakalim. Biological activity resides primarily in the (—)-(33, 4R)-enantiomer [94535-50-9] (137) (108). In spontaneously hypertensive rats, the (—)-(33, 4R)-enantiomer, at dosages of 0.3 mg/kg, lowers the systoHc pressure 47%, whereas the (+)-(3R,43)-enantiomer only decreases the systoHc pressure by 14% at a dose of 3.0 mg/kg. 

MIR), requires the introduction of new x-ray scatterers into the unit cell of the crystal. These additions should be heavy atoms (so that they make a significant contribution to the diffraction pattern) there should not be too many of them (so that their positions can be located) and they should not change the structure of the molecule or of the crystal cell—in other words, the crystals should be isomorphous. In practice, isomorphous replacement is usually done by diffusing different heavy-metal complexes into the channels of preformed protein crystals. With luck the protein molecules expose side chains in these solvent channels, such as SH groups, that are able to bind heavy metals. It is also possible to replace endogenous light metals in metal-loproteins with heavier ones, e.g., zinc by mercury or calcium by samarium. 

In other articles in this section, a method of analysis is described called Secondary Ion Mass Spectrometry (SIMS), in which material is sputtered from a surface using an ion beam and the minor components that are ejected as positive or negative ions are analyzed by a mass spectrometer. Over the past few years, methods that post-ion-ize the major neutral components ejected from surfaces under ion-beam or laser bombardment have been introduced because of the improved quantitative aspects obtainable by analyzing the major ejected channel. These techniques include SALI, Sputter-Initiated Resonance Ionization Spectroscopy (SIRIS), and Sputtered Neutral Mass Spectrometry (SNMS) or electron-gas post-ionization. Post-ionization techniques for surface analysis have received widespread interest because of their increased sensitivity, compared to more traditional surface analysis techniques, such as X-Ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES), and their more reliable quantitation, compared to SIMS. 

Adler and Axelrod,58 in their two-channel spectrograph, have taken the ultimate step in this direction by measuring the two intensities simultaneously. We may take for granted that the proper use of-an internal standard can eliminate the effect of different variations in equipment in different cases. It follows that care may be relaxed in connection with variations thus eliminated for example, approximate voltage regulation suffices for an x-ray source used to excite both analytical lines when these are measured simultaneously. 

Second, a multichannel x-ray spectrograph (9.8) has been modeled upon the Quantometer. Here the beam from a sample travels simultaneously along as many as 22 channels, each with its own crystal and detector. 

Fig. 9-10. Top-view schematic diagram of the Applied Research Laboratories Production X-ray Quantometer (PXQ). (a) Dual unit 22 dispersive channels (max), 1 nondispersive standard channel, (b) Single unit 12 dispersive channels (max), 1 nondispersive standard channel. (Courtesy of Davidson, Gilkerson, and Kemp, Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, March 1958.)...

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