The heat conductivity of liquid crystal phases of a soft ellipsoid string-fluid evaluated by molecular dynamics simulation

We have applied a nonequilibrium molecular dynamics heat flow algorithm to calculate the heat conductivity of a molecular model system, which forms uniaxial and biaxial nematic liquid crystals. The model system consists of a soft ellipsoid string-fluid where the ellipsoids interact according to a repulsive version of the Gay-Berne potential. On compression, this system forms discotic or calamitic uniaxial nematic phases depending on the dimensions of the molecules, and on further compression a biaxial nematic phase is formed. In the discotic nematic phase, the heat conductivity has two components, one parallel and one perpendicular to the director, where the last mentioned component is the largest one. This order of magnitudes is reversed in the calamitic nematic phase. In the biaxial nematic phase there are three components of the heat conductivity, one in the direction around which the long axes of the molecules are oriented, this is the largest component, another one in the direction around which the normals of the broadsides of the molecules are oriented, this is the smallest component, and one in the direction perpendicular to these two directions with a magnitude in between those of the first mentioned components. The relative magnitudes of the components of the heat conductivity span a fairly wide interval so it should be possible to use the model to parameterise experimental data.     

Comparison of short-range ion-ion correlations in the α, β and δ phases of Bi2O3

Neutron total scattering data for α-Bi₂O₃ and δ-Bi₂O₃, considering both the Bragg and diffuse components, have been analysed by the reverse Monte Carlo (RMC) method to extract experimental information concerning the short-range correlations between pairs of ions. These results complement the average structural information provided by conventional Rietveld refinement of the Bragg scattering alone. The radial and angular distribution functions in the stable ambient temperature α phase and superionic δ phase of Bi₂O₃ are presented and compared with the corresponding data for the metastable β phase reported previously. These data provide an important insight into the nature of the anion disorder within the highly conducting δ phase and the relationship between the δ phase and its ordered α and β counterparts.     

Application of accelerator mass spectrometry to macromolecules: preclinical pharmacokinetic studies on a polybisphosphonate

Data on the use of accelerator mass spectrometry (AMS) in conjunction with in vivo studies of macromolecular drugs are scarce. The present study shows the versatility of this technique when investigating the pharmacokinetics (PK) of a macromolecular drug candidate, a polybisphosphonate conjugate (ODX). The aforementioned is a polymer (molecular weight ~30 kDa) constituting a carbohydrate backbone with covalently linked ligands (aldendronate and aminoguanidine) and is intended for treatment of osteoporosis and the therapy of bone metastasis from prostate cancer. The conjugate is prepared through partial oxidation of the carbohydrate and sequential coupling of the ligands by reductive amination. ¹⁴ C was incorporated in the conjugate by means of coupling a commercially available ¹⁴ C‐lysine in the conjugation sequence. Fifteen rats were injected intravenously with ¹⁴ C‐labelled ODX (150 µg, 14 Bq/rat) and blood samples were collected at 1, 2, 4, 6, and 24 h post‐injection (3 rats/time point). Liver, spleen and kidney samples were collected at 4 and 24 h post‐injection. Blood from each time point (triplicate) were collected for AMS measurement determining the isotopic ratio (¹⁴ C/¹² C) and consequently the drug concentration in blood. ODX showed a transient presence in blood circulation; 93% of the total dose was cleared from the circulation within 1 h. The half‐life after 1 h was estimated to be about 3 h; 0.7% of the administered ¹⁴ C dose of ODX remained in circulation after 24 h. The major ¹⁴ C accumulation was in the liver, the spleen and the kidneys indicating the probable route of metabolism and excretion. This study demonstrates the versatility of AMS for pharmacological in vivo studies of macromolecules. Labelling with ¹⁴ C is relatively simple, inexpensive and the method requires minimal radioactivity, eliminating the need for radioprotection precautions in contrast to methods using scintillation counting. Copyright © 2011 John Wiley & Sons, Ltd.     

Study of the hadronic component of extensive air showers at the Carpet-2 EAS array

A method for the detection of hadrons with a muon detector at the Carpet-2 EAS array (Baksan Neutrino Observatory, Institute for Nuclear Research, Russian Academy of Sciences) has been described. Events induced by cosmic-ray hadrons have a signature that makes it possible to reliably distinguish them from muons. The characteristics of the hadronic component of extensive air showers with N _e ≥ 10⁵ have been presented.     

The pyrochlore structure and its relatives

The structures of pyrochlore, W₃Fe₃C, Sb₂O₃ (cub), KTaWO₆·H₂O, RbNbTeO₆, and Mg₃Cr₂Al₁₈ are discussed. Ideal atomic parameters are derived and compared with those observed.     

The Acoustic Characteristics of Professional Opera Singers Performing in Chorus Versus Solo Mode

In this study, members of a professional opera chorus were recorded using close microphones, while singing in both choral and solo modes. The analysis included computation of long-term average spectra (LTAS) for the two song sections performed and calculation of singing power ratio (SPR) and energy ratio (ER), which provide an indication of the relative energy in the singer's formant region. Vibrato rate and extent were determined from two matched vowels, and SPR and ER were calculated for these vowels. Subjects sung with equal or more power in the singer's formant region in choral versus solo mode in the context of the piece as a whole and in individual vowels. There was no difference in vibrato rate and extent between the two modes. Singing in choral mode, therefore, required the ability to use a similar vocal timbre to that required for solo opera singing.     

Density functional study of chlorine–oxygen compounds related to the ClO self-reaction

Geometrical parameters, vibrational frequencies, relative stabilities, and dissociation energies of the three stable Cl₂O₂ isomers and the OClO and ClOO radicals were investigated by density functional theory (DFT). The present analysis shows that DFT using hybrid functionals is capable of describing these systems to at least the same degree of accuracy as ab initio methods. The average absolute bond-length deviation of ClClO₂, ClOOCl, and ClO₂ from experimental results is 0.024/0.027 Å, with a maximum deviation for the dichlorine peroxide O(SINGLE BOND)O bond equal to 0.072/0.063 Å, for the B3PW91 and B3LYP functionals, respectively. The average absolute bond-angle deviation for the hybrid functionals is 0.8°. Harmonic vibrational frequencies calculated with DFT give for all Cl(SINGLE BOND)O compounds good agreement with experiments. The dissociation energies of ClOOCl, OClO, and ClOO were found to be in good agreement with experiments, the average error being less than 1.2 kcal/mol. The two isomers chloryl chloride (ClClO₂) and dichlorine peroxide (ClOOCl) were found to be approximately 9 kcal/mol more stable than the chlorine chlorite (ClOClO) isomer. The ClOO isomer is predicted to be 3.0 kcal/mol more stable than OClO, in accordance with the experimental value of 4 kcal/mol. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 66 : 203–217, 1998     

A graphical approach to permutation group representations for many-electron systems

A simple procedure is presented for obtaining the standard Young tableaux for the representation [(N/2) + S,(N/2) − S] of the permutation group ℒ_N for an N-electron system in spin state S directly from the spin branching diagram. We redefine the coordinate axes of the branching diagram to obtain a graph in terms of the partitions of the two-rowed Young diagram and define walks in this graph which yield directly the first rows of the allowed standard Young tableaux spanning a given representation when suitable weights have been assigned to the nodes in the graph. The allowed states are in a lexically ordered form and permit going easily from an index to an array and vice versa. © 1996 John Wiley & Sons, Inc.