Observation of relaxation modes in room temperature ferroelectric liquid crystal mixtures

The dielectric measurements in SmC* and SmA phases of a room temperature ferroelectric liquid crystal mixture FLC-6980 in the cells of different thickness in planer alignment have been carried out in the frequency range 100 Hz to 1 MHz. A relaxation mode (called NRM) whose dielectric increment is less than the Goldstone mode has been observed in the SmC* phase. This mode appears due to the surface effect. Goldstone mode and the soft mode was observable in the vicinity of SmC*-SmA transition temperature (T _C*A). The dielectric parameters of the Goldstone mode, new mode and the soft mode have been studied as a function of frequency and temperature. The calculated values for f_NRM, δε^NRM and distribution parameter α_NRM are found to be 325 kHz, 6 and 0.156 for 5μm thick planer cell at 37°C. It is seen that in the vicinity of theT _C*A, soft mode obeys the Curie-Weiss law given by mean field theory. The results have been compared with materials of large spontaneous polarization.     

The <Emphasis Type="Italic">np</Emphasis> interaction effects on the double-beta decay nuclear matrix elements for medium-mass nuclei

The quality of Hartree-Fock-Bogolyubov wave functions is tested by comparing the theoretically calculated results with the available experimental data for a number of spectroscopic properties like yrast spectra, reduced B(E2) transition probabilities, quadrupole moments, and g factors for the nuclei involved in 2νββ decay. It is observed that the np interactions vis-à-vis the deformations of the intrinsic ground states of medium-mass nuclei play a crucial role in the fine tuning of the nuclear matrix elementsM_2ν.     

Sensitivity degradation due to fibre dispersion-induced PM-AM noise in optically preamplified direct detection systems

It is well known that sensitivities as good as 45 photons/bit can be achieved when direct detection systems use ideal optical preamplifiers. We study the degradation in this sensitivity due to the presence of PM-AM noise that is caused by the laser phase noise and fibre dispersion. The results form a basis for the optimum design of optically preamplified direct detection systems by selection of a suitable laser source and fibre.     

Scanning tunneling microscopy of sputtered aluminum particles

The scanning tunneling microscope is an ideal tool to study the local geometric and electronic structure of single supported metal clusters. Our experimental setup consists of an extraction type ion gun combined with a quadrupol mass spectrometer to deposit mass-selected metal cluster. ions. First results showing scanning tunneling microscopy pictures of sputtered aluminum clusters are presented.     

On certain double integrals

We evaluate certain double integrals involving H-functions of two variables. These integrals are quite general and are capable of yielding a number of integrals as particular cases.     

Exact solution of a meiman problem with an application to the pionic contribution to the muon magnetic moment

An exact solution is obtained tp the follpwing problem: given a form factor F(t) analytic in the cut t plane, to find a lower bpund to a weighted ontegral over |F(t)|² over the cut in the presence of space-like data and also time-like data on both the modulus and the phase of F(t). The solution is used to obtain a lower bound on the pionic contribution to the muon magnetic moment (a_μ(ππ)). We obtain a_μ(ππ) ≥ 41.8 × 10^?9.     

Structural,dielectric and conductivity behaviours of cetyltrimethylammonium bromide/ethylene glycol-based quenched lyotropic mesophases

The present study highlights the effect of quenching on the structural, textural and dielectric dynamics of cetyltrimethylammonium bromide/ethylene glycol binary mixtures of varying concentrations 30:70, 50:50 and 75:25 wt.%. No mesomorphism is seen in the as-prepared binary mixtures as X-ray diffraction and polarisation optical microscopy studies reveal the crystalline-like structures for the studied concentrations. With the effect of quenching, lyotropic hexagonal phase is obtained at 30:70, 50:50 wt.% concentration; however, mixture with higher 75:25 wt.% concentrations exhibit crystalline-like phase. The obtained hexagonal lyotropic phases restrain the mesomorphism up to ≈340 K and then show crystalline-like structures with the further increase in the temperature. Dielectric and relaxation behaviours of hexagonal lyotropic phases are presented in this study. The relaxation parameters of lyotropic phases are also discussed. Interestingly, the hexagonal lyotropic phases obtained for 30:70 and 50:50 wt.% concentrations exhibit ac conductivity of the order of 10^–5 S/m, which can be seen as a significant result of this study.     

Enhanced stability of the columnar matrix in a discotic liquid crystal by insertion of ZnO nanoparticles

An experimental characterisation of dispersions of ZnO nanoparticles (NPs) in the columnar matrix of a discotic liquid crystal has been carried out. Thermophysical properties have been investigated by absorbance spectroscopy, differential scanning calorimetry, polarising optical microscopy, dielectric measurements, dc conductivity, X-ray diffraction and infrared (IR) dichroism technique. The experimental results show that inclusion of ZnO NPs into the columnar matrix enhances the orientational order in the columnar phase and does not affect the two-dimensional hexagonal lattice. The alignment in homeotropic samples is also found to be better with the addition of the NPs. The real (?′) and imaginary parts (?′′) of the permittivity increase by a small amount in the dispersions. The order parameter measured using the IR dichroism technique in the face-on geometry (homeotropic alignment) shows an enhancement for the composite system. The dc conductivity is also found to increase by an order of magnitude by addition of the NPs. These results suggest an improved stacking of the disc-like molecules within the columns by the insertion of the ZnO NPs possessing high charge mobility. Such composite systems would be highly beneficial for potential applications such as organic conductors.     

Crystallization and X-Ray Diffraction Studies of Salmonella Invasion Protein D (SipD), Insight Tip Component of Salmonella typhi Type III Secretion System

Crystallography Reports - Many pathogenic gram-negative bacteria including Salmonella typhi utilize type III secretion systems (T3SSs) to inject bacterial proteins into host cells and to initiate...