Dielectric properties of some MM′O4 and MTiM′O6 (M=Cr, Fe, Ga; M′=Nb, Ta, Sb) rutile-type oxides

We describe an investigation of the structure and dielectric properties of MM'O-4 and MTiM'O-6 rutile-type oxides for M = Cr, Fe, Ga and M' = Nb. Ta and Sb. All the oxides adopt a disordered rutile structure (P4(2)/mnm) at ambient temperature. A partial ordered trirutile-type structure is confirmed for FeTaO4 from the low temperature (17 K) neutron diffraction studies While both the MM'O-4 oxides (CrTaO4 and FeTaO4) investigated show a normal dielectric property MTiM'O-6 oxides for M = Fe, Cr and M' = Nb/Ta/Sb display a distinct relaxor/relaxor-like response. Significantly the corresponding gallium analogs, GaTiNbO6 and GaTiTaO6, do not show a relaxor response at T<500K (C) 2010 Elsevier Inc All rights reserved

Genetic characterization of Indian type O FMD virus 3A region in context with host cell preference

The 3A region of foot-and-mouth disease virus has been implicated in host range and virulence. For example, amino acid deletions in the porcinophilic strain (O/TAW/97) at 93-102 aa of the 153 codons long 3A protein have been recognized as the determinant of species specificity. In the present study, 18 type 0 FMDV isolates from India were adapted in different cell culture systems and the 3A sequence was analyzed. These isolates had complete 3A coding sequence (153 aa) and did not exhibit growth restriction in cells based on species of origin. The 3A region was found to be highly conserved at N-terminal half (1-75 aa) but exhibited variability or substitutions towards C-terminal region (80-153). Moreover the amino acid substitutions were more frequent in recent Indian buffalo isolates but none of the Indian isolates showed deletion in 3A protein, which may be the reason for the absence of host specificity in vitro. Further inclusive analysis of 3A region will reveal interesting facts about the variability of FMD virus 3A region in an endemic environment. (C) 2010 Elsevier B.V. All rights reserved.

Asymptotic behaviour and boundedness of linear systems with time varying coefficients

Motivated by developments in spacecraft dynamics, the asymptotic behaviour and boundedness of solution of a special class of time varying systems in which each term appears as the sum of a constant and a time varying part, are analysed in this paper. It is not possible to apply standard textbook results to such systems, which are originally in second order. Some of the existing results are reformulated. Four theorems which explore the relations between the asymptotic behaviour/boundedness of the constant coefficient system, obtained by equating the time varying terms to zero, to the corresponding behaviour of the time varying system, are developed. The results show the behaviour of the two systems to be intimately related, provided the solutions of the constant coefficient system approach zero are bounded for large values of time, and the time varying terms are suitably restrained. Two problems are tackled using these theorems.

Type I seesaw mechanism for quasi-degenerate neutrinos

We discuss symmetries and scenarios leading to quasi-degenerate neutrinos in type I seesaw models. The existence of degeneracy in the present approach is not linked to any specific structure for the Dirac neutrino Yukawa coupling matrix y(D) and holds in general. Basic input is the application of the minimal flavour violation principle to the leptonic sector. Generalizing this principle, we assume that the structure of the right-handed neutrino mass matrix is determined by y(D) and the charged lepton Yukawa coupling matrix y(l) in an effective theory invariant under specific groups G(F) contained in the full symmetry group of the kinetic energy terms. G(F) invariance also leads to specific structure for the departure from degeneracy. The neutrino mass matrix (with degenerate mass m(0)) resulting after seesaw mechanism has a simple form Mv approximate to m(0)(I - py(l)y(l)(T)) in one particular scenario based on supersymmetry. This form is shown tolead to correct description of neutrino masses and mixing angles. The thermal leptogenesis after inclusion of flavour effects can account for the observed baryon asymmetry of the universe within the present scenario. Rates for lepton flavour violating processes can occur at observable levels in the supersymmetric version of the scenario. (c) 2010 Elsevier B.V. All rights reserved.

Hardness of approximation results for the problem of finding the stopping distance in Tanner graphs

Tanner Graph representation of linear block codes is widely used by iterative decoding algorithms for recovering data transmitted across a noisy communication channel from errors and erasures introduced by the channel. The stopping distance of a Tanner graph T for a binary linear block code C determines the number of erasures correctable using iterative decoding on the Tanner graph T when data is transmitted across a binary erasure channel using the code C. We show that the problem of finding the stopping distance of a Tanner graph is hard to approximate within any positive constant approximation ratio in polynomial time unless P = NP. It is also shown as a consequence that there can be no approximation algorithm for the problem achieving an approximation ratio of 2(log n)(1-epsilon) for any epsilon > 0 unless NP subset of DTIME(n(poly(log n))).

SPSA algorithms with measurement reuse

Four algorithms, all variants of Simultaneous Perturbation Stochastic Approximation (SPSA), are proposed. The original one-measurement SPSA uses an estimate of the gradient of objective function L containing an additional bias term not seen in two-measurement SPSA. As a result, the asymptotic covariance matrix of the iterate convergence process has a bias term. We propose a one-measurement algorithm that eliminates this bias, and has asymptotic convergence properties making for easier comparison with the two-measurement SPSA. The algorithm, under certain conditions, outperforms both forms of SPSA with the only overhead being the storage of a single measurement. We also propose a similar algorithm that uses perturbations obtained from normalized Hadamard matrices. The convergence w.p. 1 of both algorithms is established. We extend measurement reuse to design two second-order SPSA algorithms and sketch the convergence analysis. Finally, we present simulation results on an illustrative minimization problem.

Trishanku, a novel regulator of cell-type stability and morphogenesis in Dictyostelium discoideum

We have identified a novel gene, trishanku (triA), by random insertional mutagenesis of Dictyostelium discoideum. TriA is a Broad complex Tramtrack bric-a-brac domain-containing protein that is expressed strongly during the late G2 phase of cell cycle and in presumptive spore (prespore (psp)) cells. Disrupting triA destabilizes cell fate and reduces aggregate size; the fruiting body has a thick stalk, a lowered spore: stalk ratio, a sub-terminal spore mass and small, rounded spores. These changes revert when the wild-type triA gene is re-expressed under a constitutive or a psp-specific promoter. By using short- and long-lived reporter proteins, we show that in triA(-) slugs the prestalk (pst)/psp proportion is normal, but that there is inappropriate transdifferentiation between the two cell types. During culmination, regardless of their current fate, all cells with a history of pst gene expression contribute to the stalk, which could account for the altered cell-type proportion in the mutant.

The Hybrid Consumer: Exploring the Drivers of a New Consumer Behaviour Type

A dramatically different consumption pattern seems to be emerging among a vast group of consumers. This may mean that conventional consumer stereotypes and segmentation theory are becoming outdated. The so called hybrid consumers seem to increasingly opt for both premium and budget alternatives in various product and service categories while mid-priced alternatives are losing share in their consumption basket. Although this type of polarisation, or dispersion, is already recognized as an important change, hybrid behaviour is still largely under-researched. The present study aims to analyze the possible drivers of hybrid consumption and by identifying typical categories and situations of trading up versus trading down derive tentative characteristics of hybrid consumption for further research on the topic. A tentative pattern of hybrid consumption was identified, which relates trading up to high-involvement, discretional spending and trading down to low-involvement necessities. However, it was also found that hybrid consumption transcends product category boundaries and may thus be less straightforward than previously perhaps assumed. In addition, a purchase pattern continuum was developed, accounting for various degrees of hybrid consumption.

Trapped waves in the neighborhood of a sonic-type singularity

A model equation is derived to study trapped nonlinear waves with a turning effect, occurring in disturbances induced on a two-dimensional steady flow. Only unimodal disturbances under the short wave assumption are considered, when the wave front of the induced disturbance is plane. In the neighbourhood of certain special points of sonic-type singularity, the disturbances are governed by a single first-order partial differential equation in two independent variables. The equation depends on the steady flow through three parameters, which are determined by the variations of velocity and depth, for example (in the case of long surface water waves), along and perpendicular to the wave front. These parameters help us to examine various relative effects. The presence of shocks in a continuously accelerating or decelerating flow has been studied in detail.

Characterization of human symptomatic rotavirus isolates MP409 and MP480 having ‘long’ RNA electropherotype and subgroup I specificity, highly related to the P6[1],G8 type bovine rotavirus A5, from Mysore, India

In an epidemiological study of symptomatic human rotaviruses in Mysore, India during 1993 and 1994, isolates MP409 and MP480 were isolated from two children suffering from severe, acute dehydrating diarrhea. Both isolates exhibited 'long' RNA pattern and subgroup I specificity suggesting the likelihood of their animal origin. Both isolates did not react with monoclonal antibodies (MAbs) specific for serotypes G1 to G6 as well as CIO. To determine the genetic origin of these isolates, complete nucleotide sequences of genes encoding the outer capsid proteins VP4 and VP7, nonstructural proteins NSP1 and NSP3 and viral enterotoxin protein NSP4 from MP409 and partial sequences of genes from MP480 were determined. Comparison of the 5' and 3' terminal sequences of 250 nucleotides revealed complete identity of the gene sequences in both strains suggesting that MP409 and MP480 are two different isolates of a single strain. Comparison of the nucleotide and deduced amino acid sequences of VP4, VP7, NSP1 and NSP3 of MP409 with published sequences of strains belonging to different serotypes revealed that both outer capsid proteins VP4 and VP7 and NSP1 are highly related to the respective proteins from the P6[1], G8 type bovine rotavirus A5 isolated from a calf with diarrhoea in Thailand and that the NSP3 is highly homologous to that of bovine rotaviruses. The NSP 1 protein showed greatest sequence identity with NSP4s belonging to the KUN genetic group to which NSP4s from human G2 type strains and bovine rotaviruses belong. MP409 and MP480 likely signify interspecies transmission of P6[1], G8 type strains from cattle to humans and represent the first P6[1] type rotaviruses isolated in humans. These and our previous studies on the asymptomatic neonatal strain I321 are of evolutionary and epidemiological significance in the context of close association of majority of the Indian population with cattle.

Peptide hairpin nucleation with the obligatory Type I' beta-turn Aib-(D)Pro segment

The alpha-aminoisobutyric acid-D-proline (Aib-(D)Pro) dipeptide is an obligatory Type I' beta-turn forming segment that nucleates hairpin formation.

New type of high field electrooptic response in nematics

We have made concurrent measurements of ionic current and optical transmission between crossed polarisers on several nematics with positive dielectric anisotropy under the action of applied low frequency (< 1KHz) square wave voltages. When the field E is low, the measured current is linear in E and there is no electrooptic response. Beyond some value of the field (E(0)similar to 100 esu), the current becomes independent of the field (phenomenon of limiting current). Further an electrooptic signal is measured at twice the frequency of the applied voltage, which exhibits a peak as a function of the field. The width of the peak is 3 to 4 times the value of E-0, and the signal level at the peak decreases as the frequency is increased. These measurements have been made on three highly polar compounds with cyano end groups. Careful observations do not show any evidence of electrohydrodynamic instabilities in the sample. It is argued that the observations can be understood if at the onset of the phenomenon of the limiting current, a strong electric field gradient is established near one of the electrodes due to the sweeping of an ionic species with high mobility. The field gradient produces a flexoelectric deformation of the director field, which in turn gives rise to the electrooptic effect. At higher fields, the stabilising dielectric torque takes over to suppress this instability.

Simultaneous Measurement of Strain and Temperature using Type I and Pre-strained Fiber Bragg Gratings

Strain and temperature sensitivities of a type I Bragg grating inscribed in a germania doped silica fiber, fabricated under normal conditions and zero strain, are compared with that of a Bragg grating inscribed under pre-strained condition. The results obtained reveal that the strain and temperature sensitivities of the two gratings are different. Based on these results, we demonstrate a technique which enables discrimination of strain and temperature in a Fiber Bragg Grating (FBG) with a linear response. The present technique allows for an easy implementation of the sensor by providing a direct access to the grating region in the fiber and demands only a simple interrogation system.