A method for the analysis of hot-film anemometer signals in two-phase flows

The authors discuss the application of hot-film anemometers in gas-liquid two-phase flow. Having stored the digitized record of the anemometer output signal on magnetic tape, methods are discussed that permit the identification of the vapour-phase using electronic computer programs. Methods are described to identify large vapour slugs and small bubbles. The authors propose an extension of these methods to the treatment of two-phase flows containing both large and small bubbles.     

Buchbesprechungen

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Lateralization based on interaural phase differences: effects of frequency, amplitude, duration, and shape of rise/decay

Experiments in lateralization were performed to evaluate the relative contribution of envelope and phase cues in binaural hearing with particular reference to the effects of frequency, amplitude, shape of rise/decay, and duration of peak amplitude. Pure-tone signals were presented with interaural phase shifts ranging between 90 degrees and 360 degrees. For a given value of phase shift, the leading signal was presented randomly to the right or left ear over a block of 100 trials, and the laterality of the resultant image was judged. Rise/decay time was varied from 5 to 200 ms across blocks. The results confirmed our previous finding that a rise/decay time of at least 200 ms is required to secure a psychophysically steady-state signal. This value will, however, depend on the values chosen for the other signal parameters. Within limits, decreasing intensity could be compensated for by decreasing rise/decay, suggesting the psychophysical importance of the initial segment of the signal (precedence effect). For low frequencies of 650 to 1250 Hz, performance is sensitive to interaural phase shift and largely independent of frequency. For higher frequencies of 1500 and 2000 Hz, lateralization is independent of the phase cue and also largely insensitive to change in rise/decay time. Finally, performance remains unchanged with variation in peak duration ranging from 25 to 200 ms.     

A specificity switch in selected cre recombinase variants is mediated by macromolecular plasticity and water

The basis for the altered DNA specificities of two Cre recombinase variants, obtained by mutation and selection, was revealed by their cocrystal structures. The proteins share similar substitutions but differ in their preferences for the natural LoxP substrate and an engineered substrate that is inactive with wild-type Cre, LoxM7. One variant preferentially recombines LoxM7 and contacts the substituted bases through a hydrated network of novel interlocking protein-DNA contacts. The other variant recognizes both LoxP and LoxM7 utilizing the same DNA backbone contact but different base contacts, facilitated by an unexpected DNA shift. Assisted by water, novel interaction networks can arise from few protein substitutions, suggesting how new DNA binding specificities might evolve. The contributions of macromolecular plasticity and water networks in specific DNA recognition observed here present a challenge for predictive schemes.     

A variable temperature H NMR study of stereochemical non-rigidity in group VI metal pentacarbonyl complexes of 1,3,5,7-Tetrathian; [M(CO)5( H2)] (M=Cr OR W)

Stereochemical non-rigidity in the complexes [M(CO)₅( H₂)] (M = Cr or W) has been studied by dynamic nuclear magnetic resonance spectroscopy. In the temperature range ca. −100 to 120°C two intramolecular processes were observed, namely pyramidal atomic inversion about sulphur atoms, and a commutation of the M(CO)₅ moiety between coordination sites on different sulphur atoms. Accurate energy barriers for both processes have been obtained by detailed computer simulations of the static and the dynamic spectra. The magnitudes of ΔG≠ (298.15 K) are compared with those reported for related complexes. The exact nature of the M(CO)₅ shift cannot be unambiguously assigned from the observed spectral line-shape changes. Two possible mechanisms are proposed and discussed.     

Anderson localization for Bernoulli and other singular potentials

We prove exponential localization in the Anderson model under very weak assumptions on the potential distribution. In one dimension we allow any measure which is not concentrated on a single point and possesses some finite moment. In particular this solves the longstanding problem of localization for Bernoulli potentials (i.e., potentials that take only two values). In dimensions greater than one we prove localization at high disorder for potentials with Hölder continuous distributions and for bounded potentials whose distribution is a convex combination of a Hölder continuous distribution with high disorder and an arbitrary distribution. These include potentials with singular distributions.We also show that for certain Bernoulli potentials in one dimension the integrated density of states has a nontrivial singular component.Partially supported by NSF grant DMS 85-03695Partially supported by NSF grant DMS 83-01889Partially supported by G.N.F.M. C.N.R.     

Zum System H2O2, Fe2+-, Fe3+-Ion

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Adaptation and implementation of the RAYGUN gamma-ray analysis code on the IBM PC

The RAYGUN gamma-ray analysis code (a descendant of GAMANAL and GRPANL) has been converted from FORTRAN IV to RATFOR and ported to the IBM PC environment. The history of the code and some of the problems encountered during the conversion are discussed. The converted code was then used to analyze the IAEA G-1 Intercomparison Spectra as one measure of the codes performance. The results of the analyses showed that although the intrinsic peak finding and multiplet resolution capabilities of the code are a bit weak, the UPPER-LIMIT and LIBRARY-SEARCH options work quite well. When appropriate gamma-ray libraries are created, the overall performance of the code is quite satisfactory. The RAYGUN code runs on an IBM PC or clone with 256 Kbytes of RAM.     

Zincsulphate induced metallothionein in pancreatic islets and protected against the diabetogenic toxin streptozotocin

A new azoamino reagent amido black diazoaminoazobenzene (ABDAB) has been synthesized, and found to be a good chromogenic reagent for cadmium. In pH 10.4 Na(2)B(4)O(7)NaOH buffer solution cadmium reacts with ABDAB to form an orange-red chelate (1:2), exhibiting an absorption maximum at 520 nm. The apparent molar absorptivity is 1.62x10(5) l mol(-1) cm(-1). Beer's law is obeyed in the range 0-8 mug/25 ml Cd. The method is simple and rapid, with high sensitivity and good selectivity and is applied to the determination of trace amounts of cadmium in waste water and metal materials with satisfactory results.