Pulse model

The effects of IL-1 in this pulse model have been confirmed and extended to show that actinomycin D prevents IL-1-induced potentiation of glucose-stimu-... 

The phenomenological pulse model [18], which has the following functional form ... 

Since that work, more quantitative s-process calculations have been done in conjunction with the detailed numerical thermal-pulse model calculations by Becker [BEK81], leading to the same conclusion [TAK85b]. It is worth noting that the observed Tc abundance relative to Zr, Nb, Mo and Ru [SMI83] can be well accounted for even if the "Tc B-decay half-life is as short as a few years at 3x10 K. 

So far the bimolecular ionization of photoexcited molecules was theoretically investigated assuming a huge excess of quenchers and the weakest light pumping. The latter was usually represented as either a short pulse modeled as a 5 function or quasistationary excitation that is switched on as a ( pulse ... 

In the pulse model, as in the previous models, it is assumed that the time between the radical-solvent collisions, during which the scalar interaction can occur, is a random variable. Thus the variation of the scalar interaction experienced by a nucleus as a function of time will have the generalized form illustrated in Fig. 6. The rate of change of this scalar interaction will depend on the geometry of the interaction between the I and the 5 spins. For example, different radicals S) may approach different / spins with preferred orientations with the result that the electron orbital overlap with the nucleus may be described by different functions in each case, so that the existence of different functions for the scalar interaction seems justifiable on a purely physical basis. Several pictorial examples of different pulses... 

The validity of using a pulse model is based upon the simple diffusion equation for a liquid, which implies a Poisson process of fluctuations with time, with an average jump rate, x For the case of the scalar interaction Xp may be identified as the mean time between successive encounters of a given I spin and the S spins. 

The merit of the pulse model is that it is capable of yielding quite different forms of the scalar interaction from the same physical concept. Undoubtedly other stochastic processes that can be explained on a... 

This again uses the random translational diffusion model for the dipolar interaction and the pulse model for the scalar interaction. 

Most of the models involve many more adjustable parameters than in the case of the relatively simple sticking and diffusion models. For example, in the case of the pulse model it may be necessary to assume that the scalar interaction is described by a combination of the pulses shown in Fig. 7. Thus finding a unique fit to the experimental results is tedious and requires the use of a computer. 

Fig. 10. Plot of p versus Wj for CgF /TTBP I, generalized sticking modeP° II, pulse model.

The chemometric principle was used to derive a guideline for obtaining a simple yes or no answer about the sterility of food particulates heated at aseptic processing temperatures. A quadratic temperature pulse model was used to estimate bacterial destruction from the fractional yield of thermally produced chemical marker compounds (2,3-dihydro-3,5-dihydroxy-6-methyl-4(H)-pyran-4-one, M-1, and 4-hydroxy-5-methyl-3(2H)-furanone, M-2) and the rate constants and the activation energies of the chemical and bacterial systems. The model yielded a conservative estimate of lethality at the center of meat-balls heated under different time-temperature conditions. A scheme for determining the minimum marker yield for a designated F -value is provided. 

In Lakestani (10) modelling work performed within the PISC III project is validated against experiments. Figure 1 shows the pulse echo response from the lower edge of a 10 mm vertical strip-like crack at centre depth 55 mm. The probe has the size 20 mm by 22 ram, is of SV type with angle 45 and has centre frequency 2.2 MHz and an assumed bandwidth of 2 MHz. The calibration is perfomed by a side-drilled hole of diameter 9.5 mm and centre depth 60 mm (the... 

Standard procedures that are used for testing of construction materials are based on square pulse actions or their various combinations. For example, small cyclic loads are used for forecast of durability and failure of materials. It is possible to apply analytical description of various types of loads as IN actions in time and frequency domains and use them as analytical deterministic models. Noise N(t) action as a rule is represented by stochastic model. 

An idea of investigation of AE response of the material to different types of loads and actions seems to be useful for building up a dynamic model of the material. In this ease AE is representing OUT data, and it is possible to take various AE parameters for this purpose. It is possible to consider a single AE pulse in time or frequency domain or AE pulses sequence as... 

Accurate modelling of the field radiated by ultrasonic transducers is an essential step forward considering the final goal of the complete simulation of pulse echo experiments. 

The Champ-Sons model has been developed to quantitatively predict the field radiated by water- or solid wedge- eoupled transdueers into solids. It is required to deal with interfaces of complex geometry, arbitrary transducers and arbitrary excitation pulses. It aims at computing the time-dependent waveform of various acoustical quantities (displacement, velocity, traction, velocity potential) radiated at a (possibly large) number of field-points inside a solid medium. 

The Champ-Sons model is a most effieient tool allowing quantitative predictions of the field radiated by arbitrary transducers and possibly complex interfaces. It allows one to easily define the complete set of transducer characteristics (shape of the piezoelectric element, planar or focused lens, contact or immersion, single or multi-element), the excitation pulse (possibly an experimentally measured signal), to define the characteristics of the testing configuration (geometry of the piece, transducer position relatively to the piece, characteristics of both the coupling medium and the piece), and finally to define the calculation to run (field-points position, acoustical quantity considered). 

Figure Al.6,8 shows the experimental results of Scherer et al of excitation of I2 using pairs of phase locked pulses. By the use of heterodyne detection, those authors were able to measure just the mterference contribution to the total excited-state fluorescence (i.e. the difference in excited-state population from the two units of population which would be prepared if there were no interference). The basic qualitative dependence on time delay and phase is the same as that predicted by the hannonic model significant interference is observed only at multiples of the excited-state vibrational frequency, and the relative phase of the two pulses detennines whether that interference is constructive or destructive.

Figure Al.6.25. Modulus squared of tire rephasing, (a), and non-rephasing, R., (b), response fiinetions versus final time ifor a near-eritieally overdamped Brownian oseillator model M(i). The time delay between the seeond and third pulse, T, is varied as follows (a) from top to bottom, J= 0, 20, 40, 60, 80, 100,...

The electron-spm echo envelope modulation (ESEEM) phenomenon [37, 38] is of primary interest in pulsed EPR of solids, where anisotropic hyperfme and nuclear quadnipole interactions persist. The effect can be observed as modulations of the echo intensity in two-pulse and three-pulse experiments in which x or J is varied. In liquids the modulations are averaged to zero by rapid molecular tumbling. The physical origin of ESEEM can be understood in tenns of the four-level spin energy diagram for the S = I = model system... 

Two different types of dynamic test have been devised to exploit this possibility. The first and more easily interpretable, used by Gibilaro et al [62] and by Dogu and Smith [63], employs a cell geometrically similar to the Wicke-Kallenbach apparatus, with a flow of carrier gas past each face of the porous septum. A sharp pulse of tracer is injected into the carrier stream on one side, and the response of the gas stream composition on the other side is then monitored as a function of time. Interpretation is based on the first two moments of the measured response curve, and Gibilaro et al refer explicitly to a model of the medium with a blmodal pore... 

Solution of the model equations shows that, for a linear isothermal system and a pulse injection, the height equivalent to a theoretical plate (HETP) is given by... 

Nuclear Magnetic Resonance. The iateraction of a nucleus with Bq is usually described usiag vector notation and models as ia Figure 2 where the bulk magnetization, Af, and the static field Bq are initially parallel to A radio frequency pulse is appHed ia the xy plane for a duration of t p.s,... 

L. Burkhart, A. Survey of Simulated Methods for Modeling Pulsed Sieve-Plate Extraction Columns, UCRL-15101, Ames Laboratory, Iowa State University, Ames, Iowa, 1979. 

Oxidation Catalyst. An oxidation catalyst requires air to oxidize unbumed hydrocarbons and carbon monoxide. Air is provided with an engine driven air pump or with a pulse air device. Oxidation catalysts were used in 1975 through 1981 models but thereafter declined in popularity. Oxidation catalysts may be used in the future for lean bum engines and two-stroke engines. 

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