Study Flow

Bergeat A, Calvo T, Dorthe G and Loison J-C 1999 Fast-flow study of the OH + OH reaction products J. Phys. Chem. A 103 6360-5... 

Hoover W G, Ladd A J C and Moran B 1982 High strain rate plastic flow studied via nonequilibrium molecular dynamics Phys. Rev.L 48 1818-20... 

Laser Doppler Velocimeters. Laser Doppler flow meters have been developed to measure Hquid or gas velocities in both open and closed conduits. Velocity is measured by detecting the frequency shift in the light scattered by natural or added contaminant particles in the flow. Operation is conceptually analogous to the Doppler ultrasonic meters. Laser Doppler meters can be appHed to very low flows and have the advantage of sensing at a distance, without mechanical contact or interaction. The technique has greatest appHcation in open-flow studies such as the deterrnination of engine exhaust velocities and ship wake characteristics. 

Most polymer processing methods involve heating and cooling of the polymer melt. So far the effect of the surroundings on the melt has been assumed to be small and experience in the situations analysed has proved this to be a reasonable assumption. However, in most polymer flow studies it is preferable to consider the effect of heat transfer between the melt and its surroundings. It is not proposed to do a detailed analysis of heat transfer techniques here, since these are dealt with in many standard texts on this subject. Instead some simple methods which may be used for heat flow calculations involving plastics are demonstrated. 

In flow studies of fast reactions streams of two reactant solutions are forced under pressure to meet in a mixing chamber, from which the mixed solution passes to an... 

Figure 4-12. Stopped-flow study of the pyridine-catalyzed hydrolysis of acetic anhydride, showing the formation and decay of the acetylpyridinium ion intermediate. Initial concentrations were 0.087 M pyridine, 2.1 x im M acetic anhydride the pH was 5.5 ionic strength, 1.0 M temperature, 25 C. Five hundred data points tabsorbance at 280 nm) were measured in I s. The smooth curve is a ht to Eq. (3-27). Source Data of D. Khossravi and S.-F. Hsu, University of Wisconsin.

Figure 4-12 shows a stopped-flow study of the pyridine-catalyzed hydrolysis of acetic anhydride. The absorbance-time curve reveals tbe formation and decay of the reactive intermediate acetylpyridinium ion. 

Hewitt, G. F. Int. J. Multiphase Flow, 9 (1983) 715-749. Two-phase flow studies in the United Kingdom. 

The time required to pass through the high shear zone will be proportional to the volume of the vessel divided by the flow from the turbine. This will be porportional to 1/ND. With a turbine in turbulent flow, turnover is relatively rapid and all the fluid will pass through the impeller region in a relatively short period of time. The flow regime in an anchor or helically agitated vessel can be inferred from the flow studies by Smith and Peters (], 13j. These indicated... 

A stopped-flow study of the formation of CrOs yielded the following rate law for acidities of 0.01 to 0.05 M... 

Mn(III) perchlorate in HCIO4 oxidises H2O2 with a stoichiometry of 2 Mn(III) 1 H202 . Stopped-flow studies show the reaction to be approximately first-order in both reactants but that the second-order rate coefficient k2 varies as follows... 

A second recent stopped-flow study indicated some enhancement of the initial absorption of Mn(III) at 470 nm on mixing with H2O2, and a complex of formula MnH02 is incorporated into the reaction scheme. The decomposition of this constitutes the rate-determining step (Atj = 80 sec at 25 °C with p. = 4.0 M). k is independent of initial [Mn(riI)]/[H202], of acidity (between 0.5 and 3.7 M) and of temperature. No dependence on [Mn(II)] was looked for. 

A stopped-flow study of the Ce(IV) sulphate oxidations of several of these substances to the corresponding disulphide produced a general rate law... 

A recent stopped-flow study of the autoxidation of the complexes Cu(NH3)2 and Cu(imidazole)2 in aqueous acetonitrile indicates a common rate law ... 

K. L. McCarthy, L. Odberg, R. L. Powell 1994, (Turbulent pipe-flow studied by time-averaged NMR imaging - measurements of velocity profile and turbulent intensity), Magn. Reson. Imag. 12, 923. 

Microfabrication techniques with the features of integration, reproduction and precision are particularly suitable for the implementation of miniaturized designs and significant reduction in product costs. A miniaturized magnetic resonance probe for on-line/in-line flow studies can be microfabricated by combining an rf coil [45, 46] with microfabricated gradients [47] and electronics [48] around a small tube/capillary. 

With the rare exception of xenon gas NMR of fluidized beds, which we discuss later, granular flow studies by NMR detect signals from the particles and not the surrounding medium. Because it is technically easier to obtain NMR signals from liquids rather than solids, the majority of granular NMR studies so far use solid particles containing liquids. 

ZT Chowhan, YP Chow. Powder flow studies I. Powder consolidation ratio and its relationship to capsule-filling weight variation. Int J Pharm 4 317, 1980. 

Regarding submerged plants, sorption of Cu(II) by Myriophyllum spicatum L. (Eurasian water milfoil) has been shown to be fast and fits isotherm models such as Langmuir, Temkin, and Redlich-Peterson. The maximum sorption capacity (c/lll l j ) of copper onto M. spicatum L. was 10.80 mg/g, while the overall sorption process was best described by the pseudo-second-order equation.115 Likewise, Hydrilla verticillata has been described as an excellent biosorbent for Cd(II). In batch conditions, the qmsx calculated was 15.0 mg/g. Additionally, II. verticillata biomass was capable of decreasing Cd(II) concentration from 10 to a value below the detection limit of 0.02 mg/L in continuous flow studies (fixed-bed column). It was also found that the Zn ions affected Cd(II) biosorption.116... 

Lassen NA and Ingvar DH (1980). Blood flow studies in the aging normal brain and in senile dementia. Aging of the brain and dementia. Aging, 13, 91-98. 

Cold flow studies have several advantages. Operation at ambient temperature allows construction of the experimental units with transparent plastic material that provides full visibility of the unit during operation. In addition, the experimental unit is much easier to instrument because of operating conditions less severe than those of a hot model. The cold model can also be constructed at a lower cost in a shorter time and requires less manpower to operate. Larger experimental units, closer to commercial size, can thus be constructed at a reasonable cost and within an affordable time frame. If the simulation criteria are known, the results of cold flow model studies can then be combined with the kinetic models and the intrinsic rate equations generated from the bench-scale hot models to construct a realistic mathematical model for scale-up. 

In an effort to put powder flow studies and hopper design on a more fundamental basis, Jenike [45] developed a powder shear tester and methodology that permits an assessment of powder flow properties as a function of consolidation load and time as well as powder-hopper material interactions. The methodology has been used extensively in the study of pharmaceutical materials [39,58-61]. From the yield loci obtained using this method, several parameters can be determined that influence powder flow, and discussions of these points are well documented in the literature [49,62,63]. 

One of the most prominent positive symptoms in schizophrenia is the auditory hallucinations that are perceived as distinct voices emanating from outside the individual. Regional cerebral-blood-flow studies in patients experiencing auditory hallucinations reveal activation of the associational auditory cortex during the episodes of hallucinations, but not in their absence. One theory holds that auditory hallucinations occur as a consequence of the inability of individuals with schizophrenia to monitor effectively their inner speech. fMRI studies suggest that... 

Gas ionization detectors are widely used in radiochemistry and X-ray spectrometry. They are simple and robust in construction and may be employed as static or flow detectors. Flow studies have received attention in the interfacing of radioactive detectors with gas chromatographs. A radio-gas chromatograph (Figure 10.9) uses a gas flow proportional counter to monitor the effluent from the gas chromatography column. To achieve... 

A flow study of the reaction between oxygen atoms and chlorine at high pressures (Bradley et al, J Chem Soc Trans Faraday Soc 1 1251, 1973) produced... 

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