Spectral-envelope-group-delay models for transients

Transient signals such as plosives in speech or Castanets in audio do not have a specific modulation or periodic structure in time domain. However, in the spectral domain they exhibit a prominent modulation structure, which is a direct consequence of their narrow time localization. Based on this observation, a spectral-domain AM-FM model for transients is proposed. The spectral AM-FM model is built starting from real spectral zero-crossings. The AM and FM correspond to the spectral envelope (SE) and group delay (GD), respectively. Taking into account the modulation structure and spectral continuity, a local polynomial regression technique is proposed to estimate the GD function from the real spectral zeros. The SE is estimated based on the phase function computed from the estimated GD. Since the GD estimation is parametric, the degree of smoothness can be controlled directly. Simulation results based on synthetic transient signals generated using a beta density function are presented to analyze the noise-robustness of the SEGD model. Three specific applications are considered: (1) SEGD based modeling of Castanet sounds; (2) appropriateness of the model for transient compression; and (3) determining glottal closure instants in speech using a short-time SEGD model of the linear prediction residue.

Cyclic AMP-dependent protein lysine acylation in mycobacteria regulates fatty acid and propionate metabolism

Acetylation of lysine residues is a posttranslational modification that is used by both eukaryotes and prokaryotes to regulate a variety of biological processes. Here we identify multiple substrates for the cAMP-dependent protein lysine acetyltransferase from Mycobacterium tuberculosis (KATmt). We demonstrate that a catalytically important lysine residue in a number of FadD (fatty acyl CoA synthetase) enzymes is acetylated by KATmt in a cAMP-dependent manner and that acetylation inhibits the activity of FadD enzymes. A sirtuin-like enzyme can deacetylate multiple FadDs, thus completing the regulatory cycle. Using a strain deleted for the KATmt ortholog in Mycobacterium bovis Bacillus Calmette-Guerin (BCG), we show for the first time that acetylation is dependent on intracellular cAMP levels. KATmt can utilize propionyl CoA as a substrate and, therefore, plays a critical role in alleviating propionyl CoA toxicity in mycobacteria by inactivating acyl CoA synthetase (ACS). The precision by which mycobacteria can regulate the metabolism of fatty acids in a cAMP-dependent manner appears to be unparalleled in other biological organisms and is ideally suited to adapt to the complex environment that pathogenic mycobacteria experience in the host.

Fourteen gene GBM prognostic signature identifies association of immune response pathway and mesenchymal subtype with high risk group

Background: Recent research on glioblastoma (GBM) has focused on deducing gene signatures predicting prognosis. The present study evaluated the mRNA expression of selected genes and correlated with outcome to arrive at a prognostic gene signature. Methods: Patients with GBM (n = 123) were prospectively recruited, treated with a uniform protocol and followed up. Expression of 175 genes in GBM tissue was determined using qRT-PCR. A supervised principal component analysis followed by derivation of gene signature was performed. Independent validation of the signature was done using TCGA data. Gene Ontology and KEGG pathway analysis was carried out among patients from TCGA cohort. Results: A 14 gene signature was identified that predicted outcome in GBM. A weighted gene (WG) score was found to be an independent predictor of survival in multivariate analysis in the present cohort (HR = 2.507; B = 0.919; p < 0.001) and in TCGA cohort. Risk stratification by standardized WG score classified patients into low and high risk predicting survival both in our cohort (p = <0.001) and TCGA cohort (p = 0.001). Pathway analysis using the most differentially regulated genes (n = 76) between the low and high risk groups revealed association of activated inflammatory/immune response pathways and mesenchymal subtype in the high risk group. Conclusion: We have identified a 14 gene expression signature that can predict survival in GBM patients. A network analysis revealed activation of inflammatory response pathway specifically in high risk group. These findings may have implications in understanding of gliomagenesis, development of targeted therapies and selection of high risk cancer patients for alternate adjuvant therapies.

Cyclic nucleotide signaling in intestinal epithelia: getting to the gut of the matter

The intestine is the primary site of nutrient absorption, fluid-ion secretion, and home to trillions of symbiotic microbiota. The high turnover of the intestinal epithelia also renders it susceptible to neoplastic growth. These diverse processes are carefully regulated by an intricate signaling network. Among the myriad molecules involved in intestinal epithelial cell homeostasis are the second messengers, cyclic AMP (cAMP) and cyclic GMP (cGMP). These cyclic nucleotides are synthesized by nucleotidyl cyclases whose activities are regulated by extrinsic and intrinsic cues. Downstream effectors of cAMP and cGMP include protein kinases, cyclic nucleotide gated ion channels, and transcription factors, which modulate key processes such as ion-balance, immune response, and cell proliferation. The web of interaction involving the major signaling pathways of cAMP and cGMP in the intestinal epithelial cell, and possible cross-talk among the pathways, are highlighted in this review. Deregulation of these pathways occurs during infection by pathogens, intestinal inflammation, and cancer. Thus, an appreciation of the importance of cyclic nucleotide signaling in the intestine furthers our understanding of bowel disease, thereby aiding in the development of therapeutic approaches.

Highly regioselective C2-alkenylation of indoles using the N-benzoyl directing group: an efficient Ru-catalyzed coupling reaction

A highly regioselective alkenylation of indole at the C2-position has been achieved using the Ru(II) catalyst by employing a directing group strategy. This strategy offers rare selectivity for the alkenylation N-benzoylindole at the C-2 position in the presence of the more active C3- and C7-position of indole and the ortho-positions of the benzoyl protecting group. A simple deprotection of the benzoyl group has also been exemplified, and the resulting product serves as a useful synthon for natural product syntheses.

Reduced-complexity partial-interference-cancellation group decoder for STBCs

In this letter, we propose a reduced-complexity implementation of partial interference cancellation group decoder with successive interference cancellation (PIC-GD-SIC) by employing the theory of displacement structures. The proposed algorithm exploits the block-Toeplitz structure of the effective matrix and chooses an ordering of the groups such that the zero-forcing matrices associated with the various groups are obtained through Schur recursions without any approximations. We show using an example that the proposed implementation offers a significantly reduced computational complexity compared to the direct approach without any loss in performance.

DETERMINATION OF THE STRONG COUPLING FROM HADRONIC TAU DECAYS USING RENORMALIZATION GROUP SUMMED PERTURBATION THEORY

Be the strong coupling constant alpha(s) from the tau hadronn width using a renormalization group summed (RGS) expansion of the QCD Adler lunction. The main theoretical uncertainty in the extraction of as is due to the manner in which renormalization group invariance is implemented, and the as yet uncalculated higher order terms in the QCD perturbative series. We show that new expansion exhibits good renormalization group improvement and the behavior of the series is similar to that of the standard RGS expansion. The value of the strong coupling in (MS) over bar scheme obtained with the RCS expansion is alpha(s) (M-tau(2)) = 0.338 +/- 0.010. The convergence properties of the new expansion can be improved by Bond transformation and analytic continuation in t he Bond plane. This is discussed elsewhere in these issues.

Redox regulation of protein tyrosine phosphatase 1B (PTP1B): Importance of steric and electronic effects on the unusual cyclization of the sulfenic acid intermediate to a sulfenyl amide

The redox regulation of protein tyrosine phosphatase 1B (PTP1B) via the unusual transformation of its sulfenic acid (PTP1B-SOH) to a cyclic sulfenyl amide intermediate is studied by using small molecule chemical models. These studies suggest that the sulfenic acids derived from the H2O2-mediated reactions o-amido thiophenols do not efficiently cyclize to sulfenyl amides and the sulfenic acids produced in situ can be trapped by using methyl iodide. Theoretical calculations suggest that the most stable conformer of such sulfenic acids are stabilized by n(O) -> sigma* (S-OH) orbital interactions, which force the -OH group to adopt a position trans to the S center dot center dot center dot O interaction, leading to an almost linear arrangement of the O center dot center dot center dot S-O moiety and this may be the reason for the slow cyclization of such sulfenic acids to their corresponding sulfenyl amides. On the other hand, additional substituents at the 6-position of o-amido phenylsulfenic acids that can induce steric environment and alter the electronic properties around the sulfenic acid moiety by S center dot center dot center dot N or S center dot center dot center dot O nonbonded interactions destabilize the sulfenic acids by inducing strain in the molecule. This may lead to efficient the cyclization of such sulfenic acids. This model study suggests that the amino acid residues in the close proximity of the sulfenic acid moiety in PTP1B may play an important role in the cyclization of PTP1B-SOH to produce the corresponding sulfenyl amide.

Horizontal pullout capacity of a group of two vertical plate anchors in clay

The horizontal pullout capacity of a group of two vertical strip plate anchors, placed along the same vertical plane, in a fully cohesive soil has been computed by using the lower bound finite element limit analysis. The effect of spacing between the plate anchors on the magnitude of total group failure load (P-uT) has been evaluated. An increase of soil cohesion with depth has also been incorporated in the analysis. For a weightless medium, the total pullout resistance of the group becomes maximum corresponding to a certain optimum spacing between the anchor plates which has been found to vary generally between 0.5B and B; where B is the width of the anchor plate. As compared to a single plate anchor, the increase in the pullout resistance for a group of two anchors becomes greater at a higher embedment ratio. The effect of soil unit weight has also been analyzed. It is noted that the interference effect on the pullout resistance increases further with an increase in the unit weight of soil mass.

Domains in complex surfaces with a noncompact automorphism group - II

Let X be an arbitrary complex surface and D subset of X a domain that has a noncompact group of holomorphic automorphisms. A characterization of those domains D that admit a smooth real analytic, finite type, boundary orbit accumulation point and whose closures are contained in a complete hyperbolic domain D' subset of X is obtained.

Cyclic AMP in Mycobacteria: the second messenger comes first

Cyclic AMP (cAMP) has emerged as a pivotal molecule for signalling in all life forms. Mycobacterial genomes have been found to encode for numerous proteins that are involved in cAMP generation, degradation and utilization. Many of these proteins have domain organizations unique to mycobacteria. This review summarizes recent advances in mechanisms of cAMP synthesis and degradation, focusing on the processes by which cAMP modulates mycobacterial signalling. We explore its impact on the physiology of the organism and on the discourse between M. tuberculosis and its host.

Group testing based spectrum hole search using a simple sub-nyquist sampling scheme

In this paper, we consider the problem of finding a spectrum hole of a specified bandwidth in a given wide band of interest. We propose a new, simple and easily implementable sub-Nyquist sampling scheme for signal acquisition and a spectrum hole search algorithm that exploits sparsity in the primary spectral occupancy in the frequency domain by testing a group of adjacent subbands in a single test. The sampling scheme deliberately introduces aliasing during signal acquisition, resulting in a signal that is the sum of signals from adjacent sub-bands. Energy-based hypothesis tests are used to provide an occupancy decision over the group of subbands, and this forms the basis of the proposed algorithm to find contiguous spectrum holes. We extend this framework to a multi-stage sensing algorithm that can be employed in a variety of spectrum sensing scenarios, including non-contiguous spectrum hole search. Further, we provide the analytical means to optimize the hypothesis tests with respect to the detection thresholds, number of samples and group size to minimize the detection delay under a given error rate constraint. Depending on the sparsity and SNR, the proposed algorithms can lead to significantly lower detection delays compared to a conventional bin-by-bin energy detection scheme; the latter is in fact a special case of the group test when the group size is set to 1. We validate our analytical results via Monte Carlo simulations.

Horizontal pullout resistance of a group of two vertical anchors in sand

The horizontal pullout capacity of a group of two vertical strip anchors placed along the same vertical plane in sand has been determined by using the upper bound finite elements limit analysis. The variation of the efficiency factor (xi (gamma) ) with changes in clear spacing (S) between the anchors has been established to evaluate the total group failure load for different values of (i) embedment ratio (H/B), (ii) soil internal friction angle (phi), and (iii) anchor-soil interface friction angle (delta). The total group failure load, for a given H/B, becomes always maximum corresponding to a certain optimal spacing (S-opt). The value of S-opt/B was found to lie in a range of 0.5-1.4. The maximum magnitude of xi (gamma) increases generally with increases in H/B, phi and delta.

Realistic coherent phantom track generation by a group of electronic combat aerial vehicles

We consider the problem of generating a realistic coherent phantom track by a group of ECAVs (Electronic Combat Aerial Vehicles) to deceive a radar network. The phantom track considered is the trajectory of a missile guided by proportional navigation. Sufficient conditions for the existence of feasible ECAV trajectories to generate the phantom track is presented. The line-of-sight guidance law is used to control the ECAVs for practical implementation. A performance index is developed to assess the performance of the ECAVS. Simulation results for single and multiple ECAVs generating the coherent phantom track are presented.

Generalization of deviated linear cyclic pursuit

Earlier work on cyclic pursuit systems has shown that using heterogeneous gains for agents in linear cyclic pursuit, the point of convergence (rendezvous point) can be chosen arbitrarily. But there are some restrictions on this set of reachable points. The use of deviated cyclic pursuit, as discussed in this paper, expands this set of reachable points to include points which are not reachable by any known linear cyclic pursuit scheme. The limits on the deviations are determined by stability considerations. Such limits have been analytically obtained in this paper along with results on the expansion in reachable set and the latter has also been verified through simulations.