MANUFACTURING TECHNIQUES FOR TITANIUM ALUMINIDE BASED ALLOYS AND METAL MATRIX COMPOSITES

Dual phase titanium aluminides composed vastly of gamma phase (TiAl) with moderate amounts of alpha2 phase (Ti3Al) have been considered for several high temperature aerospace and automobile applications. High specific strength coupled with exceptional high temperature performance in the areas of creep and oxidation resistance makes titanium aluminides "materials of choice" for next generation propulsion systems. Titanium aluminides are primarily being considered as potential replacements for Ni-based superalloys in gas turbine engine components with the aim of developing more efficient and leaner engines with high thrust-to-weight ratio. As titanium aluminides lack room temperature ductility, traditional manufacturing techniques such as casting, forging and rolling are more expensive to perform. To overcome this, research over the past decade has examined powder metallurgy techniques such as hot-isostatic pressing, sintering and hot-pressing to produce titanium aluminides parts. Enhancements in these powder metallurgy techniques has produced near-net shape parts of titanium aluminides possessing a homogeneous and refined microstructure and thereby exhibiting better mechanical performance. This study presents a novel powder metallurgy approach to consolidate titanium aluminide powders. Traditional powder consolidation processes require exposure to high temperatures over a lengthy duration. This exposure leads to grain growth in the consolidated part which adversely affects its mechanical properties. A rapid consolidation process called Plasma Pressure Compaction (P2C) has been introduced and utilized to consolidate titanium aluminide powders to produce titanium aluminide parts with minimal grain growth. The research also explores the role of small alloying additions of Nb and Cr to enhance ductility of the consolidated parts. The grain size of the consolidated parts is further reduced in the sub-micrometer range by milling the as-received powders. Finally, a metal matrix composite with TiAl matrix reinforced with TiB was developed by first blending the matrix and the reinforcement powders and then consolidating the powder blend

A Nearly Tight Sum-of-Squares Lower Bound for the Planted Clique Problem

We prove that with high probability over the choice of a random graph $G$ from the Erd\H{o}s-R\'enyi distribution $G(n,1/2)$, the $n^{O(d)}$-time degree $d$ Sum-of-Squares semidefinite programming relaxation for the clique problem will give a value of at least $n^{1/2-c(d/\log n)^{1/2}}$ for some constant $c>0$. This yields a nearly tight $n^{1/2 - o(1)}$ bound on the value of this program for any degree $d = o(\log n)$. Moreover we introduce a new framework that we call \emph{pseudo-calibration} to construct Sum of Squares lower bounds. This framework is inspired by taking a computational analog of Bayesian probability theory. It yields a general recipe for constructing good pseudo-distributions (i.e., dual certificates for the Sum-of-Squares semidefinite program), and sheds further light on the ways in which this hierarchy differs from others.Comment: 55 page

The power of sum-of-squares for detecting hidden structures

We study planted problems---finding hidden structures in random noisy inputs---through the lens of the sum-of-squares semidefinite programming hierarchy (SoS). This family of powerful semidefinite programs has recently yielded many new algorithms for planted problems, often achieving the best known polynomial-time guarantees in terms of accuracy of recovered solutions and robustness to noise. One theme in recent work is the design of spectral algorithms which match the guarantees of SoS algorithms for planted problems. Classical spectral algorithms are often unable to accomplish this: the twist in these new spectral algorithms is the use of spectral structure of matrices whose entries are low-degree polynomials of the input variables. We prove that for a wide class of planted problems, including refuting random constraint satisfaction problems, tensor and sparse PCA, densest-k-subgraph, community detection in stochastic block models, planted clique, and others, eigenvalues of degree-d matrix polynomials are as powerful as SoS semidefinite programs of roughly degree d. For such problems it is therefore always possible to match the guarantees of SoS without solving a large semidefinite program. Using related ideas on SoS algorithms and low-degree matrix polynomials (and inspired by recent work on SoS and the planted clique problem by Barak et al.), we prove new nearly-tight SoS lower bounds for the tensor and sparse principal component analysis problems. Our lower bounds for sparse principal component analysis are the first to suggest that going beyond existing algorithms for this problem may require sub-exponential time

Upregulated wnt-11 and mir-21 expression trigger epithelial mesenchymal transition in aggressive prostate cancer cells

Prostate cancer (PCa) is the second-leading cause of cancer-related death among men. microRNAs have been identified as having potential roles in tumorigenesis. An oncomir, miR-21, is commonly highly upregulated in many cancers, including PCa, and showed correlation with the Wnt-signaling axis to increase invasion. Wnt-11 is a developmentally regulated gene and has been found to be upregulated in PCa, but its mechanism is unknown. The present study aimed to investigate the roles of miR-21 and Wnt-11 in PCa in vivo and in vitro. First, different Gleason score PCa tissue samples were used; both miR-21 and Wnt-11 expressions correlate with high Gleason scores in PCa patient tissues. This data then was confirmed with formalin-fixed paraffin cell blocks using PCa cell lines LNCaP and PC3. Cell survival and colony formation studies proved that miR-21 involves in cells’ behaviors, as well as the epithelial-mesenchymal transition. Consistent with the previous data, silencing miR-21 led to significant inhibition of cellular invasiveness. Overall, these results suggest that miR-21 plays a significant role related to Wnt-11 in the pathophysiology of PCa

Use of OTSC Device System for Closure of Fistulas in the Alimentary Tract – A Case Series

AbstractObjectiveWe report our experience – a case series with the Over the Scope Clip (OTSC), Bear claw, a novel and new tool for the endoscopic entrapment of tissue for closure of fistula and perforations.DesignSingle-center.SettingTertiary referral academic gastroenterology unit and center for advanced therapeutic endoscopy.Patient Case I – referred for endoscopic treatment for the closure of gastrocutaneous fistula (GC).Case II – referred for endoscopic treatment for the closure of colo-vaginal fistula.Case III – referred for endoscopic treatment for the closure of GC fistula.InterventionThe OTSC system was mounted on the tip of the scope and passed down to the level of the fistula. The targeted site of the fistula was grasped with the tissue anchoring tripod and pulled into the cap with concomitant scope channel suction. Once the tissue was trapped in the cap, the Bear claw was deployed.Main outcome measurementsNA.ResultsAll patients recovered. No complication or recurrence noted. Case I showed successful results with closure of the fistula. Case II fistula was not closed due to the cavity beneath the fistula probably abscess formation – which prevented the healing of the fistula site despite of the closure with OTSC. Case III fistula did not close successfully due to the larger diameter of the fistula which was greater than 1 cm.ConclusionWith several new devices being introduced, it is difficult to judge the implementation of one tool over the others. This device has shown promising results for fistula closure if used knowing the limitation of the product

Optimize the contribution of design to innovation performance in Indian SMEs–What roles for culture, tradition, policy and skills?

This paper examines the historic growth and development of the design sector in India, and evaluates the potential of the industry to contribute to innovation performance as the country’s manufacturing sector continues its expansion via a comparative analysis of design policies in advanced economies and those in India, and an evaluation of the performance of design promotional initiatives, the paper identifies lessons that might be incorporated sensitively into the future elaboration of Indian design policy. The paper concludes that design inputs can contribute to both social and economic development (and to innovation performance in both traditional craft and hi-tech manufacturing). However, it also argues that policy to support intelligent growth, diffusion and take-up of design must be attuned to both qualitative issues of culture, diversity and tradition, and to ‘harder’ issues of location, infrastructure, skills, investment and demand.</p

DEVELOPMENT AND VALIDATION OF RP-HPLC METHOD FOR SIMULTANEOUS ESTIMATION OF AZILSARTAN MEDOXOMIL AND CHLORTHALIDONE IN BULK AND TABLET DOSAGE FORM

Objective: A simple, precise, accurate method was developed for the simultaneous estimation of azilsartan and chlorthalidone in bulk and tablet dosage form by RP-HPLC technique.Methods: Acetonitrile and water in the ratio of (70:30) pH 2.8 used as mobile phase run through (Cosmosil C18 (4.6ID x 250 mm, Particle size: 5 micron) column with a flow rate of 0.9 ml/min. The temperature of the column oven was maintained at 30 °C. Wavelength was selected 244 nm. Stock and working solutions were prepared by using the diluents water and acetonitrile in the ratio of 50:50. Runtime was fixed to 9 min.Results: Chlorthalidone and azilsartan were eluted at 2.02 and 3.92 with good resolution the plate count, tailing factor and all system suitability parameters are within ICH range. Azilsartan Medoxomil and Chlorthalidone were found to be linear low in concentration range of 80-400μg/ ml and 25-125μg/ ml respectively in the linearity study, regression equation and coefficient of correlation for Azilsartan Medoxomil and Chlorthalidone were found to be (y = 28695x+15397 r²=0.995) and (y=13444+27405 r² = 0.996) Percentage recovery for both Azilsartan Medoxomil and Chlorthalidone was found in range of 99.89%-99.96% indicating accuracy of the proposed work. Assay of the tablet was performed and found as 100.15%.Conclusion: All the parameters were within the ICH guidelines, and the method was economical and simple as retention times were less than in literature and decreased run time

Top Management Team Heterogeneity and SME Export Performance: Investigating the Role of Environmental Uncertainty

Research has generally found that firm competing in high uncertainty environments gain advantages from having diverse (heterogeneous) management teams (TMTs). Employing a national survey of 70 small- and medium-sized enterprises (SMEs), the present study examined whether TM T heterogeneity in functional background, international work experience, and foreign language proficiency had a stronger relationship with  export performance for firms competing in high than those competing in low uncertainty environments. Results were generally weak when market and industry factors contributing to uncertainty were examined  separately;  however,  additional  analysis  showed  that  the hypothesized relationship did exist when uncertainty was measured employing both factors simultaneously

ORIENTING IN 3D SPACE: BEHAVIORAL AND NEUROPHYSIOLOGICAL STUDIES IN BIG BROWN BATS

In their natural environment, animals engage in a wide range of behavioral tasks that require them to orient to stimuli in three-dimensional space, such as navigating around obstacles, reaching for objects and escaping from predators. Echolocating bats, for example, have evolved a high-resolution 3D acoustic orienting system that allows them to localize and track small moving targets in azimuth, elevation and range. The bat’s active control over the features of its echolocation signals contributes directly to the information represented in its sonar receiver, and its adaptive adjustments in sonar signal design provide a window into the acoustic features that are important for different behavioral tasks. When bats inspect sonar objects and require accurate 3D localization of targets, they produce sonar sound groups (SSGs), which are clusters of sonar calls produced at short intervals and flanked by long interval calls. SSGs are hypothesized to enhance the bat’s range resolution, but this hypothesis has not been directly tested. We first, in Chapter 2, provide a comprehensive comparison of SSG production of bats flying in the field and in the lab under different environmental conditions. Further, in Chapter 3, we devise an experiment to specifically compare SSG production under conditions when target motion is predictable and unpredictable, with the latter mimicking natural conditions where bats chase erratically moving prey. Data from both of these studies are consistent with the hypothesis that SSGs improve the bat’s spatio-temporal resolution of target range, and provide a behavioral foundation for the analysis and interpretation of neural recording data in chapters 4 and 6. The complex orienting behaviors exhibited by animals can be understood as a feedback loop between sensing and action. A primary brain structure involved in sensorimotor integration is the midbrain superior colliculus (SC). The SC is a widely studied brain region and has been implicated in species-specific orienting behaviors. However, most studies of the SC have investigated its functional organization using synthetic 2D (azimuth and elevation) stimuli in restrained animals, leaving gaps in our knowledge of how 3D space (azimuth, elevation and distance) is represented in the CNS. In contrast, the representation of stimulus distance in the auditory systems of bats has been widely studied. Almost all of these studies have been conducted in passively listening bats, thus severing the loop between sensing and action and leaving gaps in our knowledge regarding how target distance is represented in the auditory system of actively echolocating bats. In chapters 4, 5 and 6, we attempt to fill gaps in our knowledge by recording from the SC of free flying echolocating bats engaged in a naturalistic navigation task where bats produce SSGs. In chapter 4, we provide a framework to compute time-of-arrival and direction of the instantaneous echo stimuli received at the bats ears. In chapters 5 and 6, we provide an algorithm to classify neural activity in the SC as sensory, sensorimotor and premotor and then compute spatial receptive fields of SC neurons. Our results show that neurons in the SC of the free-flying echolocating bat respond selectively to stimulus azimuth, elevation and range. Importantly, we find that SC neuron response profiles are modulated by the bat’s behavioral state, indicated by the production of SSG. Broadly, we use both behavior and electrophysiology to understand the action-perception loop that supports spatial orientation by echolocation. We believe that the results and methodological advances presented here will open doors to further studies of sensorimotor integration in freely behaving animals