Characterization of surface deformation around Vickers indentations in InGaAsP epilayers on InP substrate

The deformation surrounding Vickers indentations on InGaAsP/InP epilayers have been studied in detail. The surface topography was characterized by using atomic force microscopy (AFM). The material pile-up and sink-in regions around the indentation impression was observed for the quaternary InGaAsP/InP epilayers. The sectional analysis mode of the AFM shows the depth profile at the indented region. Microindentation studies were carried out for different atomic fraction of the quaternary InGaAsP/InP compound semiconductor alloys. The microhardness values of InGaAsP/InP epilayers were found to be in the range of 5.08 and 5.73 GPa. These results show that the hardness value of the quaternary alloy drastically increases as the composition of As was increased by 0.01 atomic fraction and when the phosphorous concentration decreases from 0.4 to 0.38. The reason may be that the increase in As concentration hardens the lattice when phosphorous concentration was less and hardness decreases when phosphorous was increased.     

Critical phenomena in FINEMET alloy

The Fe_73.5Cu₁Nb₃Si_13.5B₉ FINEMET alloy has been prepared by the rapid solidification technique. The critical behaviour of this alloy in the amorphous as well as in its nanocrystalline states has been studied near their respective Curie temperatures. From the values of the critical exponents one can conclude that the alloy behaves like a 3D Heisenberg ferromagnet in the amorphous and nanocrystalline states. But there exists a slight increase in the value of β for the alloy annealed at 823 K (the nanocrystalline state) as observed in most of the amorphous alloys.     

Precise lattice parameter measurements in CsCl-Br solid solutions between room temperature and 90°K by powder x-ray diffraction

Solid solutions of CsCl-Br in five different concentrations were prepared in sealed quartz tubes by heating the mixture to 1123°K for 6–8 hr and quenching to room temperature. X-ray diffractograms were taken at eight different temperatures between room temperature and 90°K for these solid solutions using the YPC50NM powder diffractometer and a continuous flow cryostat. The observed lattice parameters for each sample at each temperature obtained from the powder diffractograms were then extrapolated to give the true lattice parameters using the least square method with Nelson-Riley extrapolation scheme. The values of the true lattice parameters at each concentration and at each temperature were tabulated and the results discussed. It is shown that the lattice parameters vs temperature for some concentrations exhibit an anomalous behaviour. Contribution No. 691     

A total synthesis of spiruchostatin A

We achieved the total synthesis of the histone deacetylase inhibitor spiruchostatin A, as the prelude to the preparation of a combinatorial library of its analogues. Two key reactions were an asymmetric acetate aldol reaction using a Zr-enolate and macrolactonization using the Shiina method.     

Mass spectrometry of heterocyclic compounds—III. Electron-impact-induced fragmentation of 1,2-benzisothiazole and some 3-substituted derivatives

The mass spectra of fifteen 1,2-benzisothiazoles are reported; their fragmentation patterns have been investigated by labelling experiments, high resolution mass measurements and defocused metastable ion detection. The parent compound of the series, 1,2-benzisothiazole, eliminates HCN after partial inter-ring hydrogen scrambling. The extent of scrambling has been determined for normal daughter ions produced at different electron beam energies and also for metastable daughter ions, and is compared with the data reported for benzothiazole. Some 3-substituted derivatives show unusual fragmentation patterns. The mechanisms of these processes are under further investigation.     

Globin chain separation by SDS polyacrylamide gel electrophoresis. Simple screening method for elongated hemoglobin chains

A simple method for the separation of hemoglobin chains from hemolysate or globin, by sodium dodecyl sulfate polyacrylamide gel electrophoresis, is described. The alpha, beta, and gamma chains can be clearly separated from each other. The alpha chain has the highest mobility, the beta chain has a slower mobility than the gamma chain, while the delta chain has about the same mobility as the beta chain. Hemoglobins with elongated chains can easily be detected by this method. Tak-beta, elongated by 11 residues, moves much more slowly than betaA but is much faster than alpha Constant Spring which is elongated by 31 residues. Screening of several individuals with slow-moving hemoglobins using this method led to the finding of a case with Hb Tak-beta thalassemia and other carriers of Hb Tak.     

Study of two diastereomeric pairs of regiosomeric 2-isoxazolines by tandem mass spectrometry with electron impact ionization

On electron impact (EI) ionization, two cis/trans pairs of 4-methyl-5-phenyl and 4-phenyl-5-methyl regioisomeric 3-carbethoxy-2-isoxazolines showed normal mass spectra and mass-analysed ion kinetic energy (MIKE) spectra of metastable (MI) and collision-activated (CA) molecule ions, allowing unequivocal differentiation of the regioisomers. The cis/trans stereoisomers of each regioisomer showed very similar normal mass spectra. Very interestingly, the cis- and trans-4-phenyl-5-methyl stereoisomers appeared reasonably differentiated by the molecule ion MIKE spectra, whereas the 4-methyl-5-phenyl regioisomeric pair of stereoisomers did not. The influence of the phenyl substituent to the fragmentation processes was notable. Some fragments of interest were studied by comparison of their MIKE spectra with those of model ions, generated by EI from suitable substrates, including (i) the isomeric α,β-unsaturated oxime, namely ethyl (Z)-2-(hydroxymino)-3-methyl-4-phenylbut-3-enoate, a by-product of importance for the mechanism(s) of the addition/cycloaddition reactions of nitrile oxides to alkenes and (ii) trans-β-methylstyrene, a dipolarophilic reactant in the same reactions. The favoured heterocyclic C(5)–O(1) bond cleavage occurred only for the ionized 4-methyl-5-phenyl 2-isoxazoline pair, leading to a distonic ion of relevance, as it can represent either a reasonable precursor for both the isomerization to the ionized α,β-unsaturated oxime and the EI-induced cycloreversion yielding ionized β-methylstyrene, or the ionized form of a zwitterionic intermediate, which had been proposed previously for the addition/cycloaddition mechanism(s) in the solution phase, currently under study.     

Rupture of thin stagnant films on a solid surface due to random thermal and mechanical perturbations

A generalized formalism for the rupture of a nondraining thin film on a solid support due to imposed random thermal and mechanical perturbations, modeled as a Gaussian white noise, is presented. The evolution of amplitude of perturbation is described by a stochastic differential equation. The average film rupture time is the average time for the amplitude of perturbation to equal to the film thickness and is calculated by employing a first passage time analysis for different amplitudes of imposed perturbations, wavenumbers, film thickness, van der Waals and electrostatic interactions and surface tensions. The results indicate the existence of an optimum wavenumber at which the rupture time is minimum. A critical film thickness is identified based on the sign of the disjoining pressure gradient, below which the film is unstable in that the rupture time is very small. The calculated values of rupture time as well as the optimum wavenumber in the present analysis agree well with the results of linear stability analysis for immobile as well as completely mobile gas-liquid film interfaces. For stable films, the rupture time is found to increase dramatically with film thickness near the critical film thickness. As expected, the average rupture time was found to be higher for smaller amplitudes of imposed perturbations, larger surface potentials, larger surface tensions and smaller Hamaker constants.     

Comparison of mass spectrometric methods for studying thermally labile compounds: Rifapentine

Results of 16 different mass spectrometric ionization and sample-introduction methods are compared for the case of a thermally very labile antibiotic, rifapentine. These suggest that extensive thermal decomposition occurs during evaporation when the sample can come into contact with hot metal parts, usually the source housing. The intensity of the molecular ion and the extent of fragmentation depend on various parameters, such as the ionization process, positive or negative-ion detection and the type of sample introduction. The most informative methods for rifapentine seem to be ‘in-beam’ electron impact, negative ionization with particle beam and direct liquid introduction interfaces and positive- and negative-ion fast atom bombardment.     

Regioselective synthesis of 3-alkylindoles mediated by zinc triflate

Zinc triflate was found to be an effective reagent for the C3-alkylation of indoles by alkyl halides in the presence of Hünig's base and tetrabutylammonium iodide. This new method for indole alkylation proceeds by a S(N)1-like pathway, and is general for allylic, benzylic, and tertiary halides.