Magnetic field dependence of resistivity minima in amorphous LaGdAu alloys with high Gd content

Magnetoresistivity measurements have been performed in fields up to 40 kOe on some concentrated amorphous LaGdAu alloys exhibiting characteristics of a spin-glass. The negative magnetoresistivity at low temperature is found to be roughly proportional to the square of the magnetization. The resistivity minima in these alloys are attributed to a mechanism of electron scattering from magnetic clouds coupled by RKKY interactions, in qualitative agreement with analysis of our remanent magnetization data.     

Optical rectification in tellurium from 10.6 μm

Optical rectification in single crystals of tellurium produced by infra-red radiation at 10.6 μm has been observed. The value of |χ⁰ ₁₁₁| is found to be 0.9×10⁻⁶ esu. Preliminary experiments to test the usefulness of the effect to monitor mode-locked infra-red laser pulses have been inconclusive.     

Fed-Batch Strategies for Production of PHA Using a Native Isolate of <Emphasis Type="Italic">Halomonas venusta</Emphasis> KT832796 Strain

In this study, polyhydroxyalkanoates (PHA) accumulation by Halomonas venusta KT832796, a moderate halophilic bacteria isolated from marine source was studied. Both nutritional requirements and process parameters for submerged cultivation of the organism in bioreactor have been standardized. From the shake flask studies, glucose and ammonium citrate as carbon and nitrogen source produced maximum PHA at a ratio 20 with 3.52 g/L of dry cell weight and 70.56% of PHA content. However, ammonium sulfate as the nitrogen source was found to be more suitable for fed-batch cultivation. Several feeding strategies including pH-based fed-batch and variants of pulse feeding were studied to improve the PHA levels. pH-based feeding, although improved PHA level to 26 g/L, most of the carbon flux was diverted towards biomass formation; hence, the percent PHA was only 39.15% of the dry cell weight. Maximum PHA of 33.4 g/L, which corresponded to 88.12% of the dry cell, was obtained from high concentration single pulse method. There was a net 8.65-fold increase in PHA using this feeding strategy when compared to batch studies. According to our knowledge, this is the highest amount of PHA reported for a Halomonas venusta strain.     

Synthesis of heteroarylated ketones via bismuth(III) triflate-promoted regioselective 1,4- and 1,6-additions of electron-rich heteroarenes to cyclic enones and dienones

The development and optimization of bismuth(III) triflate-promoted regioselective 1,4- and 1,6-additions of electron-rich heteroarenes to cyclic, β,β-disubstituted enones and dienones is described. Additions of a range of heteroarenes, including furan, thiophene, pyrrole, and indole nucleophiles, to cyclic, β,β-disubstituted enones occur to form all-carbon quaternary centers in up to 88% yield. In addition, regioselective 1,6-additions of electron-rich heteroarenes to 3-vinyl-2-cyclohexenone occur to produce a variety of δ-heteroarylated, β,β-disubstituted enones in up to 93% yield. The high 1,6-selectivity for these reactions is attributed to the increased steric bulk at the β-position relative to the δ-position, and no competing 1,4-conjugate addition is observed.     

On infinite K-clan geometry

We discuss infinite elation generalized quadrangles as group coset geometries and use this approach to deal with the special case of those associated with flocks of quadratic cones of PG(3,K).This research begun while the second author was a C.N.R. visiting professor in Italy during May–June 1996.     

Picosecond-resolution study of nonlinear scattering in carbon black suspensions in water and ethanol

The physical origin of the nonlinear scattering of light induced by focusing of intense laser pulses onto carbon black suspensions (CBS's) is discussed through the interpretation of limitation, time-resolved pump-probe transmission, and angularly and time-resolved scattering experiments performed with picosecond resolution. Comparison of the experimental results performed on two different solutions of CBS's in water and in ethanol leads us to the conclusion that the scattering phenomenon begins most probably with growing microplasmas and that the influence of the solvent is significant only at longer times.     

A hexagonal polymorph of Fe(HPO3H)3

Iron tri(hydrogenphosphite), Fe(HPO₃H)₃, crystallizes in both a monoclinic and a hexagonal space group. In this report the structure determination of the hexagonal variant is described: space group P6₃, a = 8.1690(2) Å, c = 6.9300(2) Å. The structure is slightly disordered, Fe³⁺ being partially replaced by Al³⁺, and is very close to that of Fe₂(HPO₃)₃. The only significant difference is that one half of the FeO₆ octahedra is missing and that its density is reduced by one half.