Sensitivity probe

In Vivo Biosensing. In vivo biosensing involves the use of a sensitive probe to make chemical and physical measurements in living, functioning systems (60—62). Thus it is no longer necessary to decapitate an animal in order to study its brain. Rather, an electrochemical biosensor is employed to monitor interceUular or intraceUular events. These probes must be small, fast, sensitive, selective, stable, mgged, and have a linear response. 

The longest wavelengths of the electromagnetic spectmm are sensitive probes of molecular rotation and hyperfine stmcture. An important appHcation is radio astronomy (23—26), which uses both radio and microwaves for chemical analysis on galactic and extragalactic scales. Herein the terrestrial uses of microwave spectroscopy are emphasized (27—29). 

PL can be used as a sensitive probe of oxidative photodegradation in polymers. After exposure to UV irradiation, materials such as polystyrene, polyethylene, polypropylene, and PTFE exhibit PL emission characteristic of oxidation products in these hosts. The effectiveness of stabilizer additives can be monitored by their effect on PL efficiency. 

The reactivity of substituted aromatic compounds, more than that ol any other class of substances, is intimately tied to their exact structure. As a result, aromatic compounds provide an extraordinarily sensitive probe for studying the relationship between structure and reactivity We ll examine that relationship in this and the next chapter, and we ll find that the lessons learned are applicable to all other organic compounds, including such particularly important substances as the nucleic acids that control our genetic makeup. 

Inertial sensors are useful devices in both science and industry. Higher precision sensors could find practical scientific applications in the areas of general relativity (Chow et ah, 1985), geodesy and geology. Important applications of such devices occur also in the field of navigation, surveying and analysis of earth structures. Matter-wave interferometry has recently shown its potential to be an extremely sensitive probe for inertial forces (Clauser, 1988). First, neutron interferometers have been used to measure the Earth rotation (Colella et ah, 1975) and the acceleration due to gravity (Werner et ah, 1979) in the end of the seventies. In 1991, atom interference techniques have been used in... 

X-ray absorption near edge structure (XANES) spectroscopy is a non-destructive and sensitive probe of the coordination number and geometry as well as of the effective charge of a chosen atom within a molecule and therefore also of the formal oxidation number. Recently, there have been a number of XANES studies at the sulfur K-edge demonstrating the sensitivity of... 

A qualitatively different approach to probing multiple pathways is to interrogate the reaction intermediates directly, while they are following different pathways on the PES, using femtosecond time-resolved pump-probe spectroscopy [19]. In this case, the pump laser initiates the reaction, while the probe laser measures absorption, excites fluorescence, induces ionization, or creates some other observable that selectively probes each reaction pathway. For example, the ion states produced upon photoionization of a neutral species depend on the Franck-Condon overlap between the nuclear configuration of the neutral and the various ion states available. Photoelectron spectroscopy is a sensitive probe of the structural differences between neutrals and cations. If the structure and energetics of the ion states are well determined and sufficiently diverse in... 

Electrical conductivity is an easily measured transport property, and percolation in electrical conductivity appears a sensitive probe for characterizing microstructural transformations. A variety of field (intensive) variables have been found to drive percolation in reverse microemulsions. Disperse phase volume fraction has been often reported as a driver of percolation in electrical conductivity in such microemulsions [17-20]. 

Exponential decay often occurs in measurements of diffusion and spin-relaxation and both properties are sensitive probes of the electronic and molecular structure and of the dynamics. Such experiments and analysis of the decay as a spectrum of 7i or D, etc., are an analog of the one-dimensional Fourier spectroscopy in that the signal is measured as a function of one variable. The recent development of an efficient algorithm for two-dimensional Laplace inversion enables the two-dimensional spectroscopy using decaying functions to be made. These experiments are analogous to two-dimensional Fourier spectroscopy. 

The attractive nature of XB causes D- -X distances shorter than the sum of van der Waals radii of involved atoms the stronger the interaction, the shorter the D- -X interaction lengths. Consistent with the rationalization of XB as an electron donation from D to the antibonding X-Y orbital [59], XB formation results in an elongation of the X-Y covalent bond. The D- -X interaction length is usually a more sensitive probe for XB strength than the X - Y covalent bond elongation (Table 3). 

As mentioned in the Introduction, the observation of a nonzero EDM of an electron would be a signature of behavior beyond that described by the standard model (SM) of physics [9]. It would be a more sensitive probe of the SM than the neutron EDM, which could have nonzero EDM due to CP violation in the QCD sector of the SM. 

Kramer, B., Krusius, P., Schroder, W. and Schiilke, W. (1977) Fourier-transformed Compton profiles a sensitive probe for the microstructure of semiconductors, Phys. Rev. Lett., 38, 1227-1230. 

New tank systems are also equipped with leak monitoring devices that take advantage of the double-walled construction. Leakage can be reported in real time and more accurately using these detection devices, which include water- or product-sensitive probes, or pressure detection devices if the space between the two walls is designed to remain under vacuum. 

In this section, we present a unified picture of the different electronic effects that combine to determine methyl rotor potentials in the S0, Sp and D0 electronic states of different substituted toluenes. Our approach is based on analysis of ab initio wavefunctions using the natural bond orbitals (NBOs)33 of Weinhold and cowork-ers. We will attempt to decompose the methyl torsional potential into two dominant contributions. The first is repulsive steric interactions, which are important only when an ortho substituent is present. The second is attractive donor-acceptor interactions between CH bond pairs and empty antibonding orbitals vicinal to the CH bonds. In the NBO basis, these attractive interactions dominate the barrier in ethane (1025 cm-1) and in 2-methylpropene (1010 cm-1) see Figure 3. By analogy, donor-acceptor attractions are important in toluenes whenever there is a substantial difference in bond order between the two ring CC bonds adjacent to the C-CH3 bond. Viewed the other way around, we can use the measured methyl rotor potential as a sensitive probe of local ring geometry. 

Sahoo D, Narayanaswami V, Kay CM, Ryan RO (2000) Pyrene excimer fluorescence a spatially sensitive probe to monitor lipid-induced helical rearrangement of apolipophorin III. Biochemistry 39 6594-6601... 

Kostenko E, Dobrikov M, Phshnyi D, Petyuk V (2001) 5 -Bis-pyrenylated oligonucleotides displaying excimer fluorescence provide sensitive probes of RNA sequence and structure. Nucleic Acids Res 29 3611-3620... 

A Ca2+-specific fluorescent chemosensor 25 in aqueous buffer signals Ca2+ via a decrease in fluorescence intensity, whereas excess of Mg2+ ions has no effect on the emission [85]. This probe has limited solubility in aqueous solution after binding to Ca2+. A Zn2+ sensitive probe 26 showing different fluorescence responses depending on the complexation stoichiometry is described in [86],... 

Squaraine dyes 10b, 39a, 39b, 41a, 41c, 41d, and 41e were used to measure different proteins such as BSA, HSA, ovalbumin, avidin from hen egg white, lysozyme, and trypsin (Fig. 12) [58]. It is difficult to predict correlations between the dyes structures and the affinity or sensitivity of the dyes for different proteins. All squaraine probes exhibit considerable fluorescence increases in the presence of BSA. Dicyanomethylene-squaraine 41c is the brightest fluorescent probe and demonstrates the most pronounced intensity increase (up to 190 times) in presence of BSA. At the same time, the fluorescent response of the dyes 10b, 39a, 39b, 41a, 41c, 41d, and 41e in presence of other albumins (HSA and ovalbumin) is, in general, significantly lower (intensity increases up to 24 times). Dicyanomethylene-squaraine 41a and amino-squaraines 39a and 39b are the most sensitive probes for ovalbumin. Dyes 41d, 10b, and 41e containing an A-carboxyalky I -group demonstrate sufficient enhancement (up to 16 times) in the presence of avidin. Nevertheless, the presence of hydrolases like lysozyme or trypsin has only minor effects on the fluorescence intensity of squaraine dyes. 

Fig. 23 Extended styryl fluorescent dyes as DNA sensitive probes...

CHD Re (CO) j. are very close to the gas phase positions and the shift (Mn to Re) is almost identical in gas phase and matrix. Thus, V(C-H). in the matrix will provide information on the C-H bond length. On generation of the unstable 1 2 complexes, there is a downward shift in V(C-H). of 11-14 cm implying a bond lengthening of. 0011-.00 X. This is clearly a very sensitive probe of the effect of slight electronic perturbation of the metal centre and is likely to be useful for other systems. 

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