Spectral Invariance of SG Pseudo-Differential Operators on L-P(R-n)

We prove the spectral invariance of SG pseudo-differential operators on L-P(R-n), 1 < p < infinity, by using the equivalence of ellipticity and Fredholmness of SG pseudo-differential operators on L-p(R-n), 1 < p < infinity. A key ingredient in the proof is the spectral invariance of SC pseudo-differential operators on L-2(R-n).

Cystine peptides. Disulfide conformations in fourteen membered loops investigated by Raman spectroscopy and circular dichroism

NHCH3 (X = Gly 1, Ala 2, Aib 3, Leu 4 and D-Ala 5), have been investigated by Raman and circular dichroism (CD) spectroscopy. Solid state Raman spectra are consistent with β-turn conformations in all five peptides. These peptides exhibit similar conformations of the disulfide segment in the solid state with a characteristic disulfide stretching frequency at 519 ± 3 cm-1, indicative of a trans-gauche-gauche arrangement about the Cα—Cβ—S—S—Cβ—Cα bonds. The results correlate well with the solid state conformations determined by X-ray diffraction for peptides 3 and 4. CD studies in chloroform and dimethylsulfoxide establish solvent dependent conformational changes for peptides 1, 3 and 5. Disulfide chirality has been derived using the quadrant rule. CD results together with previously reported nuclear magnetic resonance (n.m.r.) data suggest a conformational coupling between the peptide backbone and the disulfide segment

A microcomputer program to analyze the CD spectrum of proteins and nucleic acids—Use of LOTUS 1-2-3 spread sheet

A user friendly interactive computer program, CIRDIC, is developed which calculates the molar ellipticity and molar circular dichroic absorption coefficients from the CD spectrum. This, in combination with LOTUS 1-2-3 spread sheet, will give the spectra of above parameters vs wavelength. The code is implemented in MicroSoft FORTRAN 77 which runs on any IBM compatible PC under MSDOS environment.

A note on transient photocurrents at semiconductor electrodes

The imprint of the changing surface concentration of minority carriers in photocurrent transients is marginalized in “switch off” transients as compared to “switch on” transients. When the surface level is situated close to either one of the band edges, it is shown that in principle it must be possible to obtain the energy of the surface level from “switch off” transients.The time constants for the “switch on” and “switch off” cases behave differently with potential. While in “switch off”, transient plots, the magnitude of the slope decreases monotonically with increasing band bending potentials; for the “switch on” however, though it decreases and is identical to “switch off” initially, beyond a certain increase in potential the magnitude of the slope shows an increase.

Biochemical, histopathological and ultrastructural changes in rat liver induced by r-( + )-pulegone, a monoterpene ketone

Biochemical, histopathological and ultrastructural changes occurring at different time points after intraperitoneal administration of a single dose of pulegone (300 mg/kg) were studied. Significant decreases in the level of liver microsomal cytochrome P-450 (67%), heme (37%), aminopyrine N-demethylase (60%) and glucose-6-phosphatase (58%), were noticed 24 hr after pulegone treatment. Alanine amino transferase (ALT) levels increased in a time dependent manner, following exposure of rats to pulegone. Light microscopic studies of liver tissues showed dilation of central veins and distention of sinusoidal spaces 6 hr after pulegone treatment. Initial centrilobular necrosis was noticed at 12 hr. Centrilobular necrosis became severe at 18 hr and nuclear changes included karyorrhexis and karyolysis. Midzonal and periportal degenerative changes in addition to centrilobular necrosis was observed 24 hr after pulegone administration. Electron microscopic changes showed severe degeneration of endoplasmic reticulum, swelling of mitochondria and nuclear changes, 24 hr after administration of pulegone. The time course profile of the hepatocytes after treatment with pulegone indicates that endoplasmic reticulum is the organelle most affected, following which other degenerative changes occur ultimately leading to cell death.

Diastereoisomeric (η6-arene)ruthenium(II) chiral Schiff base complexes: crystal structure of a triphenylphosphine adduct

Reaction of [(eta-6-p-cymene)RuCl(L star)] with AgClO4 in Me2CO gives a perchlorate complex which on subsequent treatment with PPh3, gamma-picoline or Cl- yields adducts showing that there can be retention as well as inversion of configuration at the metal centre. The (R)Ru,(S)C absolute configurations of the chiral centres in the triphenylphosphine adduct have been established by an X-ray diffraction study [HL star, (S)-alpha-methylbenzylsalicylaldimine]. The CD spectral study reveals that there is an inversion of configuration during formation of the PPh3 adduct.

Crystal Chemistry of the Noncentrosymmetric Eulytites: A(3)Bi(XO4)(3) (X = V, A = Pb; X = P, A = Ca, Cd, Sr, Pb)

Eulytite compounds, A(3)Bi(XO4)(3) (X = P, A = Ca, Cd, Sr, Pb), belong to the noncentrosymmetric space group l (4) over bar 3d (No. 220) as determined by single-crystal X-ray diffraction studies. The crystals were grown from the melt-cool technique with considerable difficulty as the compounds melt incongruently at their melting temperature, except for the compound Pb3Bi(PO4)(3). The unit cell parameter a is 9.984(5), 9.8611(3), 10.2035(3), and 10.3722(2) angstrom for Ca3Bi(PO4)(3), Cd3Bi(PO4)(3), Sr3Bi(PO4)(3), and Pb3Bi(PO4)(3) respectively, and there are four formula units in the unit cell. The structure of Pb3Bi(VO4)(3), a unique eulytite with vanadium substitution, is compared with all these phosphorus substituted eulytites. The A(2+) and Bi3+ cations occupy the special position (16c) while the O anions occupy the general Wyckoff position (48e) in the crystal structure. Only one O position has been identified for Pb3Bi(PO4)(3) and Pb3Bi(VO4)(3), whereas two O atom sites were identified for Ca3Bi(PO4)(3), Cd3Bi(PO4)(3), and Sr3Bi(PO4)(3). The UV-vis diffuse reflectance spectra indicate large band gaps for all the phosphate eulytites while a lower band gap is observed for the vanadate eulytite. The feasibility of the use of these compounds in optoelectronic devices has been tested by measuring the second-harmonic generation (SHG) values which have been found to be of a magnitude equivalent to the commercially used KDP (KH2PO4).

Inelastic dynamic response of R.C. beam column joints by using B.E.M.

A BEM formulation to obtain the inelastic response of R.C. Beam-Column joints subjected to sinusoidal loading along the boundary is presented. The equations of motion are written along with kinematical and constitutive equations. The dynamic reciprocal theorem is presented and the temporal dependence is removed by assuming steady state response.

Numerical estimation of hotspot temperatures in electrodes subjected to pulsed electron beam heating in vacuum

A numerical solution for the transient temperature distribution in a cylindrical disc heated on its top surface by a circular source is presented. A finite difference form of the governing equations is solved by the Alternating Direction Implicit (ADI) time marching scheme. This solution has direct applications in analyzing transient electron beam heating of target materials as encountered in the prebreakdown current enhancement and consequent breakdown in high voltage vacuum gaps stressed by alternating and pulsed voltages. The solution provides an estimate of the temperature for pulsed electron beam heating and the size of thermally activated microparticles originating from anode hot spots. The calculated results for a typical 45kV (a.c.) electron beam of radius 2.5 micron indicate that the temperature of such spots can reach melting point and could give rise to microparticles which could initiate breakdown.

Open-circuit potential—time transients of alkaline porous iron electrodes at various states-of-charge

Open-circuit potential—time transients during the discharge of alkaline porous iron electrodes at various states-of-charge have been studied. From this, it has been possible to arrive at a correlation between the parameters of self-discharge kinetics of the electrode and observed open-circuit potential—recovery time constants. The study provides a method of estimate the state-of-charge of the rechargeable iron electrodes. As a hydrogen evolution reaction inevitably occurs on alkaline iron electrodes, the kinetics of the reaction have also been investigated.

Polyquinanes from (R)-(+)-limonene. Enantioselective total synthesis of the novel tricyclic sesquiterpene (-)-ceratopicanol

The first total synthesis of the biogenetically important and structurally novel triquinane sesquiterpene (-)-ceratopicanol has been accomplished.

Surface recombination at semiconductor electrodes: a single level study

The recombination and the faradaic fluxes are shown to be sensitive to the location of a single level recombination center, when it is located near the band edges. As the surface level is shifted deeper into the band gap from either of the band edges, the back emission terms are dominated by electron capture and hole capture terms, and the occupancy of the surface level is no longer determined by its location in the band gap. However, when one of the back emission terms determines the surface state occupancy, it is shown that there exists a simple relation between the value of the surface level and the recombination and the faradaic fluxes respectively. Expressions to this effect are derived and verified in the case of the recombination flux, which characterized by the potential at which it attains its maximum value. For the faradaic flux the results are qualitative.