On the anomalous sound propagation of nematics just above the clearing point

The sound attenuation coefficient due to the critical fluctuations of the order parameter is formulated in the isotropic phase of nematics by taking account of the mode-coupling effects between the order parameter and the hydrodynamic shear mode. The result is compared with the available experimental data.     

Exhaustive search of the configurational space of heat-shock protein 90 with its inhibitor by multicanonical molecular dynamics based dynamic docking

Multicanonical molecular dynamics based dynamic docking was used to exhaustively search the configurational space of an inhibitor binding to the N-terminal domain of heat-shock protein 90 (Hsp90). The obtained structures at 300 K cover a wide structural ensemble, with the top two clusters ranked by their free energy coinciding with the native binding site. The representative structure of the most stable cluster reproduced the experimental binding configuration, but an interesting conformational change in Hsp90 could be observed. The combined effects of solvation and ligand binding shift the equilibrium from a preferred loop-in conformation in the unbound state to an α-helical one in the bound state for the flexible lid region of Hsp90. Thus, our dynamic docking method is effective at predicting the native binding site while exhaustively sampling a wide configurational space, modulating the protein structure upon binding.     

Structure and properties of new olefin polymers

The relationship between molecular structures and physical properties of linear low density polyethylenes (LLDPEs) produced with single-site catalyst (SSC) was investigated. SSC polymerized LLDPE have excellent physical properties corresponding to its homogeneous molecular structure that had never been achieved by conventional Ziegler-Natta catalysts. It was found that some SSCs have the capability to produce LLDPEs with narrow molecular weight distribution but excellent melt properties. This result suggests that there exist long chain branches in these LLDPEs.     

Photoreactivating Enzyme for (6–4) Photoproducts in Cultured Goldfish Cells

We previously reported that when cultured goldfish cells are illuminated with fluorescent light, photorepair ability for both cyclobutane pyrimidine dimers and (6–4) photoproducts increased. In the present study, it was found that the duration of the induced photorepair ability for cyclobutane pyrimidine dimers was longer than that for (6–4) photoproducts, suggesting the presence of different photolyases for repair of these two major forms of DNA damage. A gel shift assay was then performed to show the presence of protein(s) binding to (6–4) photoproducts and its dissociation from (6–4) photoproducts under fluorescent light illumination. In addition, at 8 h after fluorescent light illumination of the cell, the binding of pro-tein(s) to (6–4) photoproducts increased. The restriction enzymes that have recognition sites containing TT or TC sequences failed to digest the UV-irradiated DNA pho-toreactivated by using Escherichia coli photolyase for cyclobutane pyrimidine dimers, indicating that restriction enzymes could not function because (6–4) photoproducts remained in recognition sites. But, when UV-irradiated DNA depleted of cyclobutane pyrimidine dimers was incubated with extract of cultured goldfish cells under fluorescent light illumination, it was digested with those restriction enzymes. These results suggested the presence of (6–4) photolyase in cultured goldfish cells as in Dro-sophila, Xenopus and Crotalus.     

Implementation of alpha-spectrometry for uranium isotopes in excreta samples

Summary The measurement of radioactivity concentrations in excreta is an important tool for the monitoring of possible radionuclide intakes by occupationally exposed workers. For this purpose, a radiochemical procedure for the determination of alpha-emitting isotopes of uranium in excreta has been optimized. The main steps involved in this procedure are pre-concentration, dissolution of sample, separation by ion-exchange resin, electrodeposition and alpha-spectroscopy. ²³²U tracer is used to monitor chemical recoveries and correct the results to improve precision and accuracy. The quality control of radiochemical analysis in urine and faecal samples has been performed with participation in intercomparison exercises. The results obtained from these samples, with chemical recoveries (80-95%), are shown to be highly consistent. The method offers good prospects to be applied in routine monitoring programme of workers.     

Syntheses of polymerizable viologens bearing a terminal vinyl group

Viologens that bore a terminal vinyl group were synthesized by four sequences of reactions: (1) N-vinylbenzyl-N′-n-propyl-4,4′-bipyridinium bromide chloride (V) was synthesized by the reaction of 4-(4′-pyrodyl)-N-n-propyl pyridinium bromide (III) with vinylbenzyl chloride; (2) N-β-acrylamidoethyl-N′-n-propyl-4,4′-bipyridinium dibromide (IX) was synthesized by the Menschutkin reaction of III with 2-aminoethyl bromide hydrobromide and subsequent reaction with acryloyl chloride; (3) N-β-methacryloyloxyethyl-N′-n-propyl-4,4′-bipyridinium dibromide and its analogs (XI) were synthesized by the reactions of III with the corresponding acyloxyalkyl bromides; and (4) N-vinyloxycarbonylmethyl-N′-n-propyl-4,4′-bipyridinium bromide chloride (XIII) was synthesized by the reaction of III with vinyl chloroacetate. With the exception of monomer XIII in which hydrolysis in large extent was observed during attempted polymerization, the synthesized monomers polymerized smoothly in aqueous solutions by a conventional radical procedure. Comparisons of the absorption peaks of the radical cations produced by reductions in aqueous solutions with those produced in films by ultraviolet (UV) irradiation indicate that the radical cations of polymers are associated intramolecularly in aqueous solutions.     

Effects of surface processing of lactose carrier particles on dry powder inhalation properties of salbutamol sulfate

The effects of the surface processing of lactose carrier particles on the dry powder inhalation properties of salbutamol sulfate were investigated. Lactose carrier particles were processed using a high-speed elliptical-rotor-type powder mixer (Theta-Composer). In the present study, drug/carrier powder mixtures were prepared, consisting of micronized salbutamol sulfate and coarse lactose carriers with various particle surface conditions prepared by surface processing. These powder mixtures were aerosolized by a Jethaler, and the in vitro inhalation properties of salbutamol sulfate were evaluated with a twin impinger. Compared with those of the powder mixed with unprocessed lactose carriers, the in vitro inhalation properties of the powder mixture prepared using the surface processed lactose carriers were significantly different, showing that the in vitro inhalation properties of salbutamol sulfate were improved. The in vitro inhalation properties increased with the rotor rotation rate. Using this surface processing system would thus be valuable for increasing the inhalation properties of dry powder inhalation with lactose carrier particles.     

Experimental analysis of thermal displacement and strain distributions in a small outline J-leaded electronic package by using wedged-glass phase-shifting moiré interferometry

To evaluate the influence of a printed wiring board (PWB) with a high coefficients of thermal expansion (CTE) on the thermal deformation of a small outline J-leaded electronic package (SOJ), a newly developed phase-shifting method was applied to moiré interferometry. This phase-shifting moiré interferometry method uses a wedged glass plate as a phase shifter to obtain displacement fields with a sensitivity of 100 nm/line. This technique also enabled the quantitative determination of strain distributions in all observation areas. Thermal loading was applied from room temperature (25 °C) to an elevated temperature (100 °C), and then the thermal strains of SOJ with and without the PWB were compared. The results showed that the concentrations of the longitudinal strains ε_xx and ε_yy became increasingly prominent when mounted on the PWB, and the shear strains γ_xy were concentrated at the corners of the silicon chip. The values of these strains increased by about 50% when the SOJ was mounted on the PWB.     

Semidirect Products of Association Schemes

In his 1996 work developing the theory of association schemes as a generalized group theory, Zieschang introduced the concept of the semidirect product as a possible product operation of certain association schemes. In this paper we extend the semidirect product operation into the entire set of association schemes. We then derive a way to decompose certain association schemes into smaller association schemes. We also investigate to what extent this product helps us to understand and characterize the structure of association schemes. We give some examples to show that the semidirect product produces many schemes that cannot be described as neither the direct product nor the wreath product of smaller schemes.This research was supported by Com²MaC-KOSEF, Korea.