Shock waves in liquids containing gas bubbles

Results of theoretical and experimental studies on shock wave propagation in boiling and nonboiling liquids with gas bubbles are reviewed. The structure of shock waves, their reflection and attenuation in two-phase gas-liquid media are considered.     

On the Topology of the Combinatorial Flag Varieties

We prove that the simplicial complex Ω _n of chains of matroids (with respect to the ordering by the quotient relation) on n elements is shellable. This follows from a more general result on shellability of the simplicial complex of W -matroids for an arbitrary finite Coxeter group W , and generalises the well-known results by Solomon—Tits and Bj?rner on spherical buildings. Received January 16, 2000, and in revised form October 7, 2000, and April 16, 2001. Online publication December 21, 2001.     

Sentence reception in noise from one versus two sources: effects of aging and hearing loss

Sentence reception thresholds (SRTs) and babble detection thresholds (BDTs) were measured for signals presented from loudspeakers located at 0 deg and 90 deg azimuth. In addition, the S/B ratios necessary to achieve SRT in the presence of a 12-talker babble were determined under three conditions in which the speech and babble were presented from the same or spatially separated loudspeakers. In the first experiment, normal-hearing subjects were tested on two occasions. The results were highly reliable, with standard errors of the test-retest differences of less than 1dB for all conditions. In the second experiment, SRTs, BDTs, and S/B ratios were measured for three normal-hearing groups (less than or equal to 39, 40-54, and greater than or equal to 55 years) and for a fourth group with presbycusis (greater than or equal to 55 years). Presbycusics had higher SRTs and BDTs than all other groups regardless of age, and the oldest normals had higher thresholds than younger subjects. Presbycusics required higher S/B ratios than any of the normal groups, and the oldest normal group needed a higher S/B ratio compared to the youngest group. All groups demonstrated a significant advantage in S/B ratio when the sentences and babble sources were spatially separated compared to when they were presented from the same loudspeaker. There was no significant difference in the magnitude of advantage due to spatial separation of speech and noise between the normal groups regardless of age, but the presbycusics had significantly smaller advantages than all normals.(ABSTRACT TRUNCATED AT 250 WORDS)     

Analysis of collision-broadened and overlapped spectral lines to obtain individual line parameters

Estimates of the statistical errors, correlations among the various fitting parameters and the accuracy of a simple approximation to a Voigt line profile are discussed in relation to the separation between adjacent lines. The computational procedure combined a series approximation with a nonlinear least-squares fitting routine to accurately fit the line profile and estimate the errors. Data were obtained for both simulated and experimental spectra as a means of testing the accuracy of the formalism and the effect of line separation.     

Pressure broadening in the 0–4 through 0–7 overtone bands of H35Cl and H37Cl

We have measured the pressure broadening coefficients of a number of rotation-vibration lines in the 0–4 through 0–7 overtone bands of HCl utilizing a Fourier transform spectrometer and a 409 m path length White cell. These data, when included with previous measurements on the fundamental and lower overtone bands, show a systematic variation of pressure broadening with increasing overtone band. This result reflects a change in the collision dynamics between molecules in the upper state of the transition with ground state molecules.     

« О Телах, Связанных С Обертывающими Алгебрами Алгебр Ли »

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? О Телах, Связанных С Обертывающими Алгебрами Алгебр Ли ?

     

Comparative genomics and functional annotation of bacterial transporters

Transport proteins are difficult to study experimentally, and because of that their functional characterization trails that of enzymes. The comparative genomic analysis is a powerful approach to functional annotation of proteins, which makes it possible to utilize the genomic sequence data from thousands of organisms. The use of computational techniques allows one to identify candidate transporters, predict their structure and localization in the membrane, and perform detailed functional annotation, which includes substrate specificity and cellular role.

We overview the main techniques of analysis of transporters' structure and function. We consider the most popular algorithms to identify transmembrane segments in protein sequences and to predict topology of multispanning proteins. We describe the main approaches of the comparative genomics, and how they may be applied to the analysis of transporters, and provide examples showing how combinations of these techniques is used for functional annotation of new transporter specificities in known families, characterization of new families, and prediction of novel transport mechanisms.     

Yttrium(III) and lanthanide(III) perchlorate complexes with the 2,2,6,6- tetramethylpiperidine nitroxide free radical

Summary 2,2,6,6-Tetramethylpiperidine nitroxide free radical (TMPNO) complexes with Y³⁺ and Ln³⁺ (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er or Yb) perchlorates were synthesized and characterized by means of i.r. and e.s.r. spectral, magnetic susceptibility and molar conductance studies. The new complexes are of the general type [M(TMPNO-)₂(OH₂)₃(OCIO₃)](ClO₄)₂ (M = Y or Ln), involving two TMPNO;, three aqua and one unidentate perchlorato ligand in the complex cation, and two anionic C10₄ groups. The NO bond-order in coordinated TMPNO is apparently two, as suggested by the i.r. evidence. The magnetic susceptibility and e.s.r. data were interpreted in terms of partial spin-spin coupling interaction between the unpaired electrons of the two TMPNO- ligands, as well as unpaired f electrons, in the case of paramagnetic lanthanide(Ill) ions. Severe steric hindrance, introduced during coordination of the free radical ligand through the NO oxygen atom, does not seem to allow accommodation of more than two TMPNO molecules in the inner coordination sphere of the central Y³⁺, or Ln³⁺ ion.To whom all correspondence should be directed.