Properties of low-molecular-weight polyethylene treated with gas plasma

Polyethylene films were evaporated in gas plasmas of Ar, N₂, O₂, and H₂O. The deposits were analyzed by infrared (IR) spectroscopy to determine the concentration of characteristic functional groups. The deposit prepared in Ar-atmosphere had a rather high concentration of methyl group and many double bonds were produced in the film. The deposits prepared in Ar- and N₂-plasmas produced similar spectra, which showed twice the concentration of methyl group than the deposit in Ar-atmosphere and also contained a few carbonyl and hydroxyl groups. The film treated in O₂-plasma contained the largest amount of carbonyl group and the lowest number of double bonds among the plasma-treated deposits. Dielectric loss curves against temperature for the deposits treated in these plasmas showed a broad peak near 20°C. For O₂-plasma-treated film the loss tangent curves showed a sharp maximum. The activation energy for the relaxation of Ar-, O₂-, and H₂O-plasma-treated films had the same value of 50.6 kcal/mol. The observed relaxation in the films prepared in gas plasmas was considered due to the β process and was attributed to the motion of oxidized branched polyethylene.     

Synthesis, solid-state and solution structures of tris[(2-methoxymethyl)phenyl]germanes with a substituent on germanium

A series of tris[(2-methoxymethyl)phenyl]germanes with a substituent on germanium was prepared and their solid-state and solution structures were investigated by means of X-ray crystallography and NMR spectroscopy to elucidate the effect of the substituent on the hypercoordination of the germanium atom in triarylgermanes. It was shown that when the substituent is a halogen, the triarylgermanes tend to be pentacoordinated trigonal bipyramidal while the triarylgermane is tetrahedral with no coordination when the substituent is a phenyl group. The methyl derivative is a monocapped tetrahedron.     

Structural Study of Methyl Acrylate in a Nematic Liquid Crystal by 1H NMR with 13C Satellites

The molecular structure and conformation of methyl acrylate have been determined by analyzing the ¹H NMR spectrum with ¹³C satellites of the molecules dissolved in the liquid crystal ZLI 1132. In the structural analysis, direct coupling constants have been corrected for molecular vibrations and converted to those in the r structure. The correlation between reorientational motion and internal rotation has been taken into account by using the mean external potential described in terms of bond interaction tensors. The potential for the internal rotation about the bond has been represented as V() = (V ₁/2) (1 – cos ) + (V ₂/2)(1 – cos 2), where is zero for the s-cis configuration, and the determined values of V ₁ and V ₂ are 2.7(1) and 8.4(13) kJ mol^–1, respectively. The relative abundance of the s-cis conformer, 76(1)%, agrees with a gas-phase value, 67(11)%, determined by electron diffraction within experimental errors.     

α-hydroperoxy sulfide in sulfide photooxidation. Formation and isolation in the photooxidation of thiazolidine derivatives in aprotic media

In the photooxidation of 3-acyl-2,2-dimethyl-4(R)-substituted thiazolidine derivatives, 5(R)-hydroxy derivative obtained was found to be derived from the 5-hydroperoxy derivative which was isolated and characterized.     

New synthetic method for aromatic polyketones from bis(arylsilane)s and aromatic dicarboxylic acid chlorides

A new synthetic method for aromatic polyketones was developed through Friedel–Crafts polycondensation of bis(arylsilane) monomers with aromatic dicarboxylic acid chlorides. The solution polycondensation of these monomer pairs in the presence of aluminum chloride in 1,2‐dichloroethane readily afforded aromatic polyketones having inherent viscosities up to 0.37 dL/g with the elimination of chlorotrimethylsilane. The polycondensation proceeded through aromatic electrophilic ipso substitution, the mechanism of which is very similar to that of normal Friedel–Crafts acylation. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2729–2735, 2002     

Redispersible dry emulsion system as novel oral dosage form of oily drugs: in vivo studies in beagle dogs.

The absorption characteristics of vitamin E acetate (VEA) formulated into a dry emulsion system after its oral administration to beagle dogs were determined and compared to those of two different dosage forms (an oily mixture of the drug with cottonseed oil and an oil (drug)-in-water emulsion). The three dosage forms were administered in a crossover fashion to six nonfasting subjects, and the drug absorption was assessed from the plasma concentration of the major metabolite (free vitamin E). VEA formulated in the dry emulsion was rapidly absorbed, which suggested that a considerable amount was released as reformed emulsion droplets in the gastrointestinal tract as well as in water in vitro. Based on the analysis of variance, no significant differences in bioavailability parameters (AUC, Cmax or Tmax) were observed among the three dosage forms.     

An improved algorithm for the analytical computation of solvent-excluded volume. The treatment of singularities in solvent-accessible surface area and volume functions

An algorithm for the analytical computation of solvent-excluded volume is presented as part of our efforts to develop an improved computational model for a solvent effect term, in which the work required to create a cavity in the solvent is expressed as a function of the solvent-excluded volume. In this article we describe mathematical developments in the analytical integration of solvent-accessible surface (SAS) area, the singularities in SAS area and volume functions, and the procedures required to detect and treat singularities. Techniques to increase algorithm performance are presented, which improve computational speed by about five times, on the average. The accuracy of the analytical method for volume computation is compared with the accuracy of two numerical methods: the numerical integration of SAS area and the point-by-point scanning method. This algorithm calculates the volume of the spheres confined among their intersection planes and resembles a numerical integration of surface area by summing up volume layers. These characteristics make the algorithm useful in analytically calculating the work required to create a convex cavity in a solvent and the work (pΔV) associated with a change in the solvent-excluded volume of the solute due to solvent pressure. © 1995 by John Wiley & Sons, Inc.     

ON THE TWO FORMS OF INTERMEDIATE M OF BACTERIORHODOPSIN

Abstract— The decay time course of intermediate M of bacteriorhodopsin was investigated by flash spectrophotometry. The decay was composed of two exponentials showing the existence of two forms of intermediate absorbing around 410 nm. The two were very different in kinetic character whereas the absorption spectra were almost the same. The relative yield of the two components was a function of the intensity of the exciting flash and the slower component disappeared when the flash intensity was made very small. A model based on the trimeric cluster structure of bacteriorhodopsin is proposed.     

The phase transformation of copper-oxinate crystals observed by electron microscopy

Summary The transformation of copper-oxinate dihydrates was studied by electron microscopy and electron diffraction method. The replica method was also applied. The mechanism by which the unstable α-form is transformed into the stable β-form is as follows. The deposition of unstable needle-like α-form crystal → internal transformation of the α-form and the formation of intermediate fine particles, (γ-form) → inter- and intra-particle condensation aggregation of the γ-form → formation of the plate like β-form crystal by internal transformation of the aggregates and by the cementation of dissolved part.

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Zusammenfassung Die Umwandlung von Kupferoxynat-Dihydraten wurde mit Elektronenmikroskop und Elektronenbeugung studiert. Es wurde die Abdruckmethode angewendet. Der Mechanismus, durch welchen die instabile Alphaform in die stabile Betaform übergeht, wird verfolgt. Der Abbau der instabilen nadelf?rmigen Alphaform-Kristalle zu interner Umwandlung der Alphaform und der Bildung von einer intermedi?ren aus feinen Partikeln bestehenden Gammaform in die inter- und intrapartikul?re Kondensationsaggregation der Gammaform und schlie?lich die Bildung der pl?ttchen?hnlichen Betaform-Kristalle durch interne Umwandlung der Aggregate und durch Verkittung der gel?sten Teile wird gezeigt.

     

Interstitial Zn atoms do the trick in thermoelectric zinc antimonide, Zn4Sb3: a combined maximum entropy method X-ray electron density and ab initio electronic structure study

The experimental electron density of the high-performance thermoelectric material Zn4Sb3 has been determined by maximum entropy (MEM) analysis of short-wavelength synchrotron powder diffraction data. These data are found to be more accurate than conventional single-crystal data due to the reduction of common systematic errors, such as absorption, extinction and anomalous scattering. Analysis of the MEM electron density directly reveals interstitial Zn atoms and a partially occupied main Zn site. Two types of Sb atoms are observed: a free spherical ion (Sb3-) and Sb2(4-) dimers. Analysis of the MEM electron density also reveals possible Sb disorder along the c axis. The disorder, defects and vacancies are all features that contribute to the drastic reduction of the thermal conductivity of the material. Topological analysis of the thermally smeared MEM density has been carried out. Starting with the X-ray structure ab initio computational methods have been used to deconvolute structural information from the space-time data averaging inherent to the XRD experiment. The analysis reveals how interstitial Zn atoms and vacancies affect the electronic structure and transport properties of beta-Zn4Sb3. The structure consists of an ideal A12Sb10 framework in which point defects are distributed. We propose that the material is a 0.184:0.420:0.396 mixture of A12Sb10, A11BCSb10 and A10BCDSb10 cells, in which A, B, C and D are the four Zn sites in the X-ray structure. Given the similar density of states (DOS) of the A12Sb10, A11BCSb10 and A10BCDSb10 cells, one may electronically model the defective stoichiometry of the real system either by n-doping the 12-Zn atom cell or by p-doping the two 13-Zn atom cells. This leads to similar calculated Seebeck coefficients for the A12Sb10, A11BCSb10 and A10BCDSb10 cells (115.0, 123.0 and 110.3 microV K(-1) at T=670 K). The model system is therefore a p-doped semiconductor as found experimentally. The effect is dramatic if these cells are doped differently with respect to the experimental electron count. Thus, 0.33 extra electrons supplied to either kind of cell would increase the Seebeck coefficient to about 260 microV K(-1). Additional electrons would also lower sigma, so the resulting effect on the thermoelectric figure of merit of Zn4Sb3 challenges further experimental work.