Time-response, rapid

REAL TIME RESPONSE RAPIDITY OF SENSING PROCESSES LONG STABILITY - SHELF LIFETIME. OPERATIONAL LIFETIME... 

Unlike linear optical effects such as absorption, reflection, and scattering, second order non-linear optical effects are inherently specific for surfaces and interfaces. These effects, namely second harmonic generation (SHG) and sum frequency generation (SFG), are dipole-forbidden in the bulk of centrosymmetric media. In the investigation of isotropic phases such as liquids, gases, and amorphous solids, in particular, signals arise exclusively from the surface or interface region, where the symmetry is disrupted. Non-linear optics are applicable in-situ without the need for a vacuum, and the time response is rapid. 

For small K, i.e., K = 0.5 in Fig. 17, the response of the equilibrium to the depletion of species Red] in phase 1 is slow compared to diffusional mass transport, and consequently the current-time response and mass transport characteristics are close to those predicted for hindered diffusion with an inert interface. As K is increased, the interfacial process responds more rapidly to the electrochemical perturbation in phase 1. The transfer of the target species across the interface generates an enhanced flux to the UME, causing... 

Despite the considerable amount of information that has been garnered from more traditional methods of study it is clearly desirable to be able to generate, spectroscopically characterize and follow the reaction kinetics of coordinatively unsaturated species in real time. Since desired timescales for reaction will typically be in the microsecond to sub-microsecond range, a system with a rapid time response will be required. Transient absorption systems employing a visible or UV probe which meet this criterion have been developed and have provided valuable information for metal carbonyl systems [14,15,27]. However, since metal carbonyls are extremely photolabile and their UV-visible absorption spectra are not very structure sensitive, the preferred choice for a spectroscopic probe is time resolved infrared spectroscopy. Unfortunately, infrared detectors are enormously less sensitive and significantly slower... 

Wt-GFP was expressed in E. coli and purified as described in Ref. [4]. Time- and frequency resolved pump-probe transients were recorded with 40-fs, 400-nm excitation pulses and probe pulses with durations of approximately 40 fs throughout the visible spectral range. Since photo-conversion strongly alters the GFP response, rapid scan data acquisition was performed... 

For most measurement techniques a trade-off exists between time response and sensitivity. Instruments can be made to respond more rapidly, but then noise levels and detection limits increase. To fulfill certain measurement objectives for which sensitivity is not a problem, it may be useful to enhance the time response of the instrument and accept the decrease in sensitivity. In any event, careful consideration must be made in the design of any sampling program to ascertain what level of concentrations needs to be measured and what time-space resolution is required. These issues will determine the characteristics of the airborne platform and the instruments that will be used and will dictate how they will be deployed. 

Rapidity. Sampling and analysis times should be short compared with biological response times, response time in 90% of samples should be less than 30 s, and output should be RS232 or the equivalent. 

From frequency dependent dielectric loss measurements, the transitions associated with solvent dipole reorientations occur on a timescale of 10-n -10-13 s. By contrast, the time response of the electronic contribution to the solvent polarization is much more rapid since it involves a readjustment in electron clouds . The difference in timescales for the two types of polarization is of paramount importance in deciding what properties of the solvent play a role in electron transfer. The electronic component of the polarization adjusts rapidly and remains in equilibrium with the charge distribution while electron transfer occurs. The orientational component arising from solvent dipoles must adopt a non-equilibrium distribution before electron... 

A typical time response for a short-circuited photocurrent in the presence of hydroquinone ( Q) as an added solution redox species is shown in Figure 9. These photocurrents were stable for several hours. In the absence of in the electrolyte, the photocurrent also increased rapidly upon the onset of illumination, but subsequently decayed exponentially to 70% of its initial value in a half-decay time of ca. 25 s. This behavior is similar to that observed for chlorophyll monolayers deposited on SnC (12). Photocurrents under potentially-controlled conditions were also stable upon illumination, but exhibited slower decay characteristics when the light was turned off. This effect is unusual and is currently under further investigation. 

Acute Lasting a short time (test or exposure), severe enough to induce a response rapidly (stress or stimulus), having a sudden onset (effect) as opposed to chronic. Volume 1(1,2,3,5,10), Volume 2(5,8,11). 

In another example, the cyclometalated iridium complex [Ir(ppy)2(4-vinylpyridine)Cl] has been attached via hydrosilation see Hydrosilation) to hydride-terminated poly(dimethylsiloxane) to produce a luminescent material. Evaluation of this material as a luminescent oxygen sensor revealed significantly improved sensitivity over dispersions of the original vinyl pyridine complex in poly(dimethylsiloxane). The luminescent material was blended with polystyrene to give a new sensor that exhibited increased sensitivity and maintained short response times to rapid changes in air pressure. 

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