Electron paramagnetic resonance studies of photorefractive crystals II: Fe3+ doped Bi12SiO20 with copper vapour laser illumination in 10–100 K range

Photo-induced charge transfer and its kinetics were investigated in Bi₁₂SiO₂₀ in 10–300 K temperature range, using EPR of Fe³⁺ centre, underin situ illumination with copper vapour laser (CVL). The decay kinetics was found to follow double exponential behaviour. Relaxation of the photo-induced electron transfer to the preillumination condition occurred even at 10 K. Shallow traps were, therefore, associated with the electron trapping, leading to a better understanding of the fast photorefractive response of BSO.     

Error linear complexity measures for multisequences

Complexity measures for sequences over finite fields, such as the linear complexity and the k-error linear complexity, play an important role in cryptology. Recent developments in stream ciphers point towards an interest in word-based stream ciphers, which require the study of the complexity of multisequences. We introduce various options for error linear complexity measures for multisequences. For finite multisequences as well as for periodic multisequences with prime period, we present formulas for the number of multisequences with given error linear complexity for several cases, and we present lower bounds for the expected error linear complexity.     

Membrane Disruption and Enhanced Inhibition of Cell‐Wall Biosynthesis: A Synergistic Approach to Tackle Vancomycin‐Resistant Bacteria

Resistance to glycopeptide antibiotics, the drugs of choice for life‐threatening bacterial infections, is on the rise. In order to counter the threat of glycopeptide‐resistant bacteria, we report development of a new class of semi‐synthetic glycopeptide antibiotics, which not only target the bacterial membrane but also display enhanced inhibition of cell‐wall biosynthesis through increased binding affinity to their target peptides. The combined effect of these two mechanisms resulted in improved in vitro activity of two to three orders of magnitude over vancomycin and no propensity to trigger drug resistance in bacteria. In murine model of kidney infection, the optimized compound was able to bring bacterial burden down by about 6 logs at 12 mg kg^?1 with no observed toxicity. The results furnished in this report emphasize the potential of this class of compounds as future antibiotics for drug‐resistant Gram‐positive infections.     

Bismuth triflate catalyzed conjugate addition of indoles to α,β-enones

Reaction of indoles with electron deficient olefins under the influence of bismuth triflate has been studied at ambient temperature and affords the corresponding 3-alkylated indoles in excellent yields.     

Mean amplitudes of vibration and thermodynamic properties of methyl cyanide and methyl isocyanide

The mean amplitudes of vibration of methyl cyanide and methyl isocyanide have been calculated at 300°K, using the secular equation method based on symmetry coordinates. The thermodynamic properties of these molecules are also estimated for temperatures ranging from 200°K to 1000°K at 100° intervals.     

The nuclear magnetic resonance spectra of four spin systems

High resolution H¹ and F¹⁹ nuclear magnetic resonance spectra of 1-fluoro, 2, 4-dinitrobenzene were obtained and analyzed to determine all the parameters involved. As the spectrum of one of the protons is well separated from that of the other two, the secular equation has been solved in the first approximation. The analysis gives the following spin-spin coupling constants: J₀ ^HH = 8.7 ± 0.3 cps., J_m ^HH = 2.9 ± 0.2 cps., J_p ^HH = 0.6 ± 0.3 cps., J₀ ^HH = 10.4 ± 0.2 cps., and the two meta H-F coupling constants were found to be considerably different being 6.5 ± 0.3 cps. and 3.8 ± 0.3 cps. It has been found that theortho andmeta H-F coupling constants have the same sign as theortho andpara H-H coupling constants.     

Substitution of coordinated chlorides in cis-α and cis-β dichloro (triethylene tetramine) cobalt(III) chloride [Co(trien)Cl2]Cl by thiocyanate in aqueous medium

Substitution of coordinated chlorides in cis-α, and cis-β dichloro (triethylene tetramine) cobalt(III) chloride by thiocyanate was studied in aqueous medium in the pH range 3.8 to 4.0 at 25–26° C. Substitution, as in aquation, took place in two steps corresponding to the two chlorides, one step being faster than the other. Mechanisms have been discussed in the paper.     

Halogen nuclear magnetic resonance shifts

The nuclear magnetic resonance shifts (chemical shifts) of Cl³⁵ in aqueous solutions of alkali chlorides were determined using a High Resolution NMR Spectrometer. These small shifts probably represent the effect of the neighbouring atom even in the highly ionic state. A similarity of these results to the quadrupole coupling constants of the halogen atom in these molecules is pointed out.