Molecular weight segregation on surfaces of polyethylene blended films as estimated from nanoscratch tests using scanning probe microscopy

Nanoscratch tests using scanning probe microscopy (SPM) were performed on films prepared from two polyethylene (PE) materials polymerized by using a metallocene catalyst system with different molecular weights (MWs). Blended samples were prepared by dissolving both PE materials at various ratios in hot p-xylene. The pure and blended samples were compression molded into films at 180 degrees C for different holding times in the molten state. The results of SPM nanoscratch tests with an applied load of 30 nN indicated that the lower-MW surface could be easily plowed with wear debris but the higher-MW surface was less deformed. However, the deformation pattern of the blended film surface was similar to that of the lower-MW surface. These results suggest that MW segregation occurs during holding in the molten state as lower-MW components rise to the film surface.     

Determination of gallopamil in human plasma by selected ion monitoring

A gas chromatographic mass spectrometric procedure using selected ion monitoring is described for the quantification of gallopamil in human plasma. Gas chromatographic separation of gallopamil from phenolic metabolite isomers is made possible by treatment with ethyl chloroformate. The detection limit for the quantitation by the present method is 0.09 ng/ml of plasma. The method has sufficient sensitivity to permit pharmacokinetic studies with human subjects following the oral administration of gallopamil hydrochloride.     

A note on Gersten's conjecture for logarithmic Hodge-Witt sheaves

We prove a purity theorem for logarithmic Hodge-Witt sheaves and construct a complex, which gives thep-part of the reciprocity sequence for a function field over a finite field of characteristicp.     

Application of biosynthetic 13C-enrichment using [1-13C]-, [2-13C]- and [1,2-13C2]-acetate as precursor for 13C NMR spectral assignment of higher plant metabolites. The assignments of some bryonolic acid derivatives

The ¹³C NMR spectra of some derivatives of bryonolic acid (1) (D:C-friedoolean-8-en-3β-ol-29-oic acid) were assigned by means of ¹³C-enrichment, lanthanide-induced shifts (LIS) and comparison of chemical shift data between derivatives. The ¹³C-enriched species of 1, i.e., 1a, 1b and 1c were biosynthesized by Luffa cylindrica (Cucurbitaceae) callus fed with [1-¹³C]-, [2-¹³C]- or [1,2-¹³C₂]-acetate, respectively. Methyl acetylbryonolates 2, 2a, 2b and 2c, methyl bryonolates 3, 3a, 3b and 3c, methyl bryononates 4 and 4a, diacetyl-3β,29-diols (3,29-diacetyl-D:C-friedoolean-8-en-β,29-diol) 5, 5a, 5b and 5c, and 3-acetyl-3β,29-diols 6, 6a and 6b were prepared from 1, 1a, 1b and 1c, and their ¹³C NMR spectra were recorded. The ¹³C concentration of the ¹³C-enriched species was high enough to exhibit the satellite peaks clearly, and the analysed data were very useful for this study. Thus, total assignments for 2, 3, 4, 5 and 6 were established. It was found that conversion of the methoxycarbonyl group at C-29 into an acetoxymethyl group caused complex changes in the chemical shifts of the C, D- and E-ring carbons and those of the methyl carbons linked to these rings.     

Radiation-induced emulsion polymerization of ethylene. I. Effect of reaction conditions on the polymerization

The effect of reaction conditions on the rate of radiation-induced emulsion polymerization of ethylene was studied by use of a 500-ml autoclave. Among various kinds of emulsifiers, a series of potassium salts of fatty acids gave high rates of the polymerization. The polymerization was inhibited by the presence of oxygen, but the rate of polymerization followed by the induction period was not influenced by the initial presence of oxygen. Stirring rate and the monomer: water ratio did not affect the rate of polymerization. The rate of polymerization was maximum at about 80°C, and number-average molecular weight was influenced by the temperature in a similar manner as the rate of polymerization. This suggests that the change of mobility of propagating radical in the polymer particle changes the rate of termination reaction. The rate of polymerization was proportional to the 1.7 power of the reaction pressure.     

Facile synthesis of Gramicidin S via cyclication of a linear pentapeptide

Azide and N-hydroxysuccinimide ester of five pentapeptides related to gramicidin S (cyclic decapeptide) were cyclized to determine the ratio of dimer to monomer in the cyclization product, the pentapeptide derivative with D-Phe as C-terminus giving the dimer in good yield.     

Preparation of optically active peralkyldiphosphines and their use, as the rhodium(I) complex, in the asymmetric catalytic hydrogenation of ketones

Two types of the optically active peralkyldiphosphine, 2,3-O-isopropylidene-2,3-dihydroxy-1,4-bis(dialkylphosphino)butane (Rdiop 3) and N-(N′-substituted carbamoyl-4-dicyclohexylphosphino-2-dicyclohexylphosphinomethylpyrrolidine (R-Cycapp 8), have been prepared by various synthetic methods. Rhodium(I) complexes of 3 and 8 showed high catalytic activity for hydrogenation of various kinds of prochiral ketones, which were reduced smoothly to the corresponding optically active hydroxy compounds, under hydrogen at atmospheric pressure and ambient temperature. The neutral rhodium(I) complexes (diphosphine-Rh^N) hydrogenated -ketoamides and -ketopantolactone in fairly high optical yields (66–77%ee). In the hydrogenation of N-(-ketoacyl)--amino esters, the Cydiop-Rh^N catalyst showed a marked contrast to the diop-Rh^N system; in the hydrogenation of the methyl ester of N-(phenylglyoxyl)-(S)--phenylalanine, 72%de was attained with little double asymmetric induction by the chiral center in the substrate.     

Emulsifier-free emulsion polymerization of tetrafluoroethylene by radiation. V. Effect of reaction conditions on the stability of polytetrafluoroethylene latex

The stability of PTFE latex prepared in the absence of emulsifier by radiation-induced polymerization was investigated by electrophoresis and conductometric titration. The storage stability depends on total dose rather than dose rate, and the stable latex can be obtained in the region log D > 0.026 V₁ ? 0.6, where D is the total dose (10⁴ rad) and V₁ is a polymer concentration in latex (g/liter). The stability increases only during polymerization in the presence of enough TFE monomer. The ζ potential of the latex particles lies in the region from ?25 to ?50 mV in an as-polymerized state (near pH 3) and from ?50 to ?65 mV at pH 10. The number of carboxyl end groups and surface charge density were examined by conductometric titration with NaOH and calculation from the G values of radiolysis of water. All the surface charge densities measured by conductometric titration are larger than those calculated from the G values. These results suggest that some acids have been formed on the surface of the particles. The acids may be the carboxyl end groups of polymer chains or hydrofluoric acid (HF) adsorbed on the surface. PTFE particles prepared in this polymerization system are stabilized mainly due to the carboxyl end groups and adsorptions of OH? and HF on the particles.     

Sensitive and simple analysis of sorbic acid using liquid chromatography with electrospray ionization tandem mass spectrometry

Sorbic acid (SA: CH(3)-CH=CH-CH=CH-COOH) and its salts are widely used as preservatives in foodstuff because of their growth inhibitory effects on mold, yeast and a wide range of bacteria. However, it is still unclear whether SA and its salts are actually incorporated in these organisms and a higher organisms like mammalian cells. Acidic compounds such as SA are usually analyzed by HPLC with eluents containing acetic acid, formic acid and their ammonium acetates, but such acidic buffers may suppress the ionization efficiency of the acidic compounds in negative-mode electrospray ionization (ESI). In this study, we present a sensitive and simple method for analysis of SA by HPLC with non-acidic solvents such as CH(3)CN/CH(3)OH-H(2)O by negative ion mode ESI-LC/MS. As a result, SA at less as 30 fmol was selectively determined by the selected reaction monitoring (SRM) mode. It was defined as the peak area with a signal-to-noise ratio (S/N) of 3. Good linearity was obtained in the range from 55 fmol (S/N 3) to 500 fmol (r(2)=0.9968) for SA by using LC/MS with the SRM mode. We also show that the method is useful to analyze SA level in the cytosol of mastocytoma cells, which were pretreated with SA. These results suggest the applicability of this method for the highly sensitive determination of SA in the mammalian tissues and cells.