Physical probes

The nature of the DM basic constituents is still unknown. Among the viable competitors for having a cosmologically relevant DM species (see, e.g., Gon-dolo in these Proceedings), the leading candidate is the lightest supersymmetric 

The x annihilation rate in a DM halo is R = nx(r)(aV)A, where nx(r) = nx,og(r) is the neutralino number density and ( tV)a is the annihilation cross section averaged over a thermal velocity distribution at freeze-out temperature (see, e.g., Gondolo in these Proceedings). Although the annihilation cross section is a non-trivial function of the mass and physical composition of the neutralino, to our purpose it suffices to recall that the relic density is approximately given by  

The time evolution of the electron spectrum is given by the transport equation  

It has been recently proposed (Colafrancesco 2004b) that the unavoidable Compton Scattering of CMB photons by the secondary electrons produced in XX annihilation also provides an additional source of SZ effect, that we call here SZ dm, with specific spectral and spatial features. According to these results, the DM induced spectral distortion can be written as 

The nature of Dark Matter, despite its overwhelming evidence, is still intangible. It is nonetheless appealing, in these respects, that some astrophysical features of galaxy clusters and of galaxies might give information on the fundamental properties of the DM particles. 

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Laser Raman diagnostic teclmiques offer remote, nonintnisive, nonperturbing measurements with high spatial and temporal resolution [158], This is particularly advantageous in the area of combustion chemistry. Physical probes for temperature and concentration measurements can be debatable in many combustion systems, such as furnaces, internal combustors etc., since they may disturb the medium or, even worse, not withstand the hostile enviromnents [159]. Laser Raman techniques are employed since two of the dominant molecules associated with air-fed combustion are O2 and N2. Flomonuclear diatomic molecules unable to have a nuclear coordinate-dependent dipole moment caimot be diagnosed by infrared spectroscopy. Other combustion species include CFl, CO2, FI2O and FI2 [160]. These molecules are probed by Raman spectroscopy to detenuine the temperature profile and species concentration m various combustion processes. 

Ever since Pasteur s work with enantiomers of sodium ammonium tartrate, the interaction of polarized light has provided a powerful, physical probe of molecular chirality [18]. What we may consider to be conventional circular dichroism (CD) arises from the different absorption of left- and right-circularly polarized light by target molecules of a specific handedness [19, 20]. However, absorption measurements made with randomly oriented samples provide a dichroism difference signal that is typically rather small. The chirally induced asymmetry or dichroism can be expressed as a Kuhn g-factor [21] defined as ... 

The results of the EXAFS studies on supported bimetallic catalysts have provided excellent confirmation of earlier conclusions (21-24) regarding the existence of bimetallic clusters in these catalysts. Moreover, major structural features of bimetallic clusters deduced from chemisorption and catalytic data (21-24), or anticipated from considerations of the miscibility or surface energies of the components (13-15), received additional support from the EXAFS data. From another point of view, it can also be said that the bimetallic catalyst systems provided a critical test of the EXAFS method for investigations of catalyst structure (17). The application of EXAFS in conjunction with studies employing ( mical probes and other types of physical probes was an important feature of the work (25). 

Investigations utilizing EXAFS have the very important feature of yielding information in an environment of the kind actually encountered in catalysis. We have recently demonstrated the feasibility of making measurements while a catalytic reaction is actually occurring. One can anticipate that measurements of this type will receive Increased emphasis in the future. For studies of the structures of highly dispersed metal catalysts, EXAFS may well be the most generally applicable physical probe currently available. 

The crystallographic structure of rubredoxin from Clostridium pasteurianum at 2.5 A, a resolution sufficient to reveal the sequence of several of the bulky amino acid side chains, shows the iron coordinated to two pairs of cysteine residues located rather near the termini of the polypeptide chain (Fig. 1). A related rubredoxin, with a three times larger molecular weight, from Pseudomonas oleovorans is believed to bind iron in a similar fashion. This conclusion is based on physical probes, especially electron paramagnetic resonance spectroscopy, all of which indicate that the iron is in each case situated in a highly similar environment however, the proteins display some specificity in catalytic function. 

M. Sinha, Ph. D. Physics Probing Polymer Networks Using Pulse Propagation and Brillouin Light Scattering Techniques. University of Cincinnati, 2000. 

Geometric structure of the bare metal clusters and the complexes formed by reaction are unknown and present a significant experimental challenge. Chemical studies are starting to imply something about the structure of the products and will be invaluable until more direct chemical physics probes are available. 

The experimental techniques for obtaining data suitable for a LFER are relatively simple, but the number of necessary measurements is large, in comparison with most physical probes for which the opposite is usually true. However, the otherwise inaccessible information gained makes the task worthwhile this may stimulate the development of methods for rapid or automated accumulation of data. 

In the distant past, measurements of the attenuation of the (3 spectrum from a newly discovered isotope were used to identify the energy of the (3 decay. Recently, the attenuation of strong sources has been used to monitor the thickness of materials during manufacturing processes. Notice that the monitoring can be continuous, nondestructive, and a physical probe does not need to touch the material being measured. 

Some Physical Probes of Enzyme Structure in Solution Serge N. Timasheff... 

A recent summary of the history and dynamics of the theoretical models of benzene39 cites a view that even though the current molecular orbital (MO) view of benzene seems complete and ultimate while the valence bond (VB) view seems obsolete, the recent findings about zr-distortivity in benzene indicate that the benzene story is likely to take additional twists and turns that will revive the VB viewpoint (see footnote 96 in ref 39). What the present review will show is that the notion of delocalized zr-systems in Scheme 1 is an outcome of both VB and MO theories, and the chemical manifestations are reproduced at all levels. The use of VB theory leads, however, to a more natural appreciation of the zr-distortivity, while the manifestations of this ground state s zr-distortivity in the excited state of delocalized species provides for the first time a physical probe of a Kekule structure .3... 

It should be noted that near-field scanning optical microscopy (NSOM) (discussed at the beginning of this chapter) is often grouped alongside other SPM techniques. However, for our discussion, we will focus on AFM and STM since these use physical probes to interrogate a surface, rather than focused light. 

This mechanism has been confirmed by reacting a series of onium chloride salts with phenol using 35q NMR determination as physical probe as shown in table 2-2. 

Another source of confusion had its origin in the twin carbonyl stretching band found in the IR spectrum of furfuraldehyde. The double peak was assumed to arise from the two species, oxygen-cis and oxygen-trans, even though the results were difficult to fit to those revealed by other physical probes. The same phenomenon occurs in the thiophene series where it was eventually traced to Fermi resonance between the carbonyl and the C(5)—H vibrations.360 That Fermi resonance is also responsible in the furan series has been demonstrated by showing that there is only one carbonyl band in furfuraldehyde when position 5 is deuterated.361... 

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