Spot theory

The analytical concepfs and sfrafegies developed by Ekins and his coworkers (1990) to improve the sensitivity of the immunoassay heralded the appearance 

An altemahve approach is the mass-sensing multianalyte microarray immunoassay first described by researchers at Beckman Coulter, Fullerton, CA (Silzel et al., 1998). As early as 1991, other groups at Beckman Coulter had adapted commercially available ink-jet printers (e.g., the Hewlett Packard Deskjet) for deposihng oligonucleohdes or proteins such as streptavidin onto substrates to create arrays (Matson, xmpublished data). Piezoelectric 

Adsorbed monolayers of antibodies (IgG) can be achieved in the range of 130 to 650 ng/cm or from 10 to lO molecules/mm, depending upon the solid phase. Thus, antibody microspots having diameters of 50 to 120 p would be sufficient. For a weaker binding antibody, -10 °, the ambient 

Sapsford etal. (2001) examined microarray-based antibody-antigen binding kinetics in real time to determine the effect of spot size. Capture antibodies were immobilized in an array pattern onto silver-clad microscope slides. Antimouse IgG was directly attached to the surface or attached via neutravidin capture of the biotinylated antibody. Cy5-labeled mouse IgG capture was monitored based upon the signal generated from the excitation of an evanescent wave guide (slide) with a 635-nm laser source detection was achieved by a charge-coupled device (CCD) camera system. Both static and flow-through conditions were employed. 

The binding kinetics were characterized in terms of the apparent time constant (K pp = kf C + k ) where C = analyte concentration kf = association rate constant and k = dissociation rate constant. In closed loop experiments, a plateau value for K pp of 0.0024/s was reached at a linear flow rate of 2.67 mL/min. K ppWas foxmd to decrease with decreasing antigen concentration (C), with equilibrium achieved only at the highest level (1 pg/mL). The association rate constant Kf was calculated at 3.6 x 10 M/s for IgG binding. 

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Some of the quantitative consequences of hot spot theory were presented in Ref 19. A qualitative discussion of heat flow in a compressed gas bubble hot spot was also presented in Ref 19. The necessity of having enough, but not too much, liquid or solid spray or foam within a compressed gas bubble (in order to have sufficient heat flow from the bubble to the surrounding condensed explosive) provides another hard-to-control variable in impact testing and thus increases the variability of test results... 

Phung (Ref 201) attempted to apply the thermal hot-spot theory to pulsed-electron... 

According to the hot-spot theory (Neppiras Noltingk 1950), the homogeneous ultrasound reaction takes place in the collapsing cavitation bubble and in the superheated (ca. 2,000 K) liquid shell around it. Species with sufficient vapor pressure diffuse into the cavity, where they undergo the effect of adiabatic collapse. 

The generally accepted explanation for the origin of sonochemistry and sonoluminescence is the hot-spot theory, in which the potential energy given to the bubble as it expands to maximum size is concentrated into a heated gas core as the bubble implodes. The oscillations of a gas bubble driven by an acoustic field are well described by the Rayleigh-Plesset equation.7... 

The hot-spot theory, expounded by Bowden and Yoffe in their earlier work [2], is the foundation for most of their interpretations of initiation experiments. Heat (certainly), shock, friction, and intense electron beams were aU described as causing localized heating, such that if the region grows beyond a critical size the rate of heat generation exceeds the rate of heat loss and explosion occurs. 

Behind the alternatives there lay uncertainties about the identity of the processes being initiated. Nevertheless, the validity of the hot-spot theory, at least with respect to carefully circumscribed situations, was confirmed by several ingenious experiments which proved to have a striking relevance to many practi-... 

Studies of slow thermal decomposition, when combined with the hot-spot theory, proved to have particularly interesting consequences for understanding the sensitivity of the azides and their troublesome and seemingly temperamental response to some stimuli. 

Thus, within the thermal or hot-spot theory, there existed a rationale for describing not only how azides respond to various stimuli, but considering the many possible parameters involved in the energy transfer from an external stimulus to the molecules of a crystal, a basis for the erratic behavior of samples. 

In addition, unlike most solids to which the heat transfer equation has been applied, the azides are sensitive to shocks of such low intensity that the average temperature rise generated is of the order of tens of degrees (not large enough to initiate a fast reaction). Some alternative mechanism for localizing the energy must therefore be found if the hot spot theory is to apply. 

The nature of the extreme conditions which produce radicals in sonicated media is still a matter of debate in spite of numerous cases of "compelling" evidence. From the historical and scientific points of view, SL was studied because of the possible correlation of the appearance phase of SL flashes with bubble dynamics.6,136 It is generally thought that recombination of radicals is responsible for SL. However, it is not firmly established that SL exclusively arises from such a process. A survey of the literature also reveals that for multi-bubble fields, SL and sonochemistry (SC) are not necessarily coupled. Therefore, SL should not be systematically used as a tool for an estimation of the extreme conditions at the root of sonochemistry. Three kinds of hypotheses might explain radical formation, i.e., the hot-spot theory, 2 the shock-wave model, and the electrical theories.1 8/1 9... 

Carbon tetrafluoride has a low y value and should be less effective than argon. An interpretation based only on the "hot-spot" theory seems unsatisfactory, and the mechanism can be more complex than a simple pyrolysis. On the other hand, CF4 is an effective energy carrier in plasma chemistry, giving support to the existence of electrical phenomena. It can be suggested that a reaction takes place between species derived from the gas molecule (an excited state, a radical ion ) and the alkyl halide, which cleaves in a second step, in analogy with chlorocarbon radiolysis. However, the question is open for future investigations. 

It is surprising to see the apparent parsimonious interest of sonochemists in the Diels-Alder addition. This reaction with a large negative activation volume is frequently carried out in heated sealed tubes. Then, from the sonochemist s viewpoint, the high pressures and temperatures produced by the cavitational collapses should activate the reaction, provided the reactants are able to penetrate into the bubble. Non-volatile reagents should not be activated since the pressures and temperatures decrease sharply outside the bubble. Thus, the hot-spot theory predicts that the sonochemical Diels-Alder reactivity should more or less be related to the volatility of the partners. 

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