Quantum Spin Hall Insulator State in HgTe Quantum Wells

Recent theory predicted that the Quantum Spin Hall Effect, a fundamentally novel quantum state of matter that exists at zero external magnetic field, may be realized in HgTe/(Hg,Cd)Te quantum wells. We have fabricated such sample structures with low density and high mobility in which we can tune, through an external gate voltage, the carrier conduction from n-type to the p-type, passing through an insulating regime. For thin quantum wells with well width d < 6.3 nm, the insulating regime shows the conventional behavior of vanishingly small conductance at low temperature. However, for thicker quantum wells (d > 6.3 nm), the nominally insulating regime shows a plateau of residual conductance close to 2e^2/h. The residual conductance is independent of the sample width, indicating that it is caused by edge states. Furthermore, the residual conductance is destroyed by a small external magnetic field. The quantum phase transition at the critical thickness, d = 6.3 nm, is also independently determined from the magnetic field induced insulator to metal transition. These observations provide experimental evidence of the quantum spin Hall effect.Comment: 16 pages, 5 figure

Response to combination therapy with interferon alfa-2a and ribavirin in chronic hepatitis C according to a TNF-alpha promoter polymorphism

Background. Tumor necrosis factor-alpha (TNF-alpha) is involved in the pathogenesis of chronic active hepatitis C. Polymorphisms in the promoter region of the TNF-alpha gene can alter the TNF-alpha expression and modify the host immune response. The present study aimed at the correlation of the G308A TNF-alpha polymorphism with the response to antiviral combination therapy in chronic hepatitis C. Patients and Methods: 62 patients with HCV and 119 healthy unrelated controls were genotyped for the G308A TNF-alpha promoter polymorphism. The patients received 3 x 3 million units of interferon alfa-2a and 1,0001,200 mg ribavirin daily according to their body weight. A response was defined as absence of HCV-RNA and normalization of S-ALT after 6 months of combination therapy. Results:With respect to the allele and genotype frequency, a significant difference was not observed between controls and patients with chronic hepatitis C. Furthermore, such a difference was also not observed if responders and non-responders to antiviral therapy were compared. Conclusions: The promoter polymorphism of the TNF-alpha gene investigated herein is equally distributed in healthy individuals and patients with hepatitis C and does not seem to predict the response to therapy with interferon alfa-2a and ribavirin. Copyright (C) 2003 S. Karger AG, Basel

A semi-automatic verification tool for software requirements specification documents

Most software problems arise from deficiencies in the manner in which software requirements are elicited and expressed. Ensuring that the Software Requirements Specification document (SRS) has the necessary quality is crucial to the success of any software development project, since its information is used across all project stages. In this paper, we present a semiautomatic verification tool for SRS documents based on a comprehensive quality model.Sociedad Argentina de Informática e Investigación Operativ

Evaluation of aircraft microwave data for locating zones for well stimulation and enhanced gas recovery

Imaging radar was evaluated as an adjunct to conventional petroleum exploration techniques, especially linear mapping. Linear features were mapped from several remote sensor data sources including stereo photography, enhanced LANDSAT imagery, SLAR radar imagery, enhanced SAR radar imagery, and SAR radar/LANDSAT combinations. Linear feature maps were compared with surface joint data, subsurface and geophysical data, and gas production in the Arkansas part of the Arkoma basin. The best LANDSAT enhanced product for linear detection was found to be a winter scene, band 7, uniform distribution stretch. Of the individual SAR data products, the VH (cross polarized) SAR radar mosaic provides for detection of most linears; however, none of the SAR enhancements is significantly better than the others. Radar/LANDSAT merges may provide better linear detection than a single sensor mapping mode, but because of operator variability, the results are inconclusive. Radar/LANDSAT combinations appear promising as an optimum linear mapping technique, if the advantages and disadvantages of each remote sensor are considered

Fiber-optical analogue of the event horizon

The physics at the event horizon resembles the behavior of waves in moving media. Horizons are formed where the local speed of the medium exceeds the wave velocity. We use ultrashort pulses in microstructured optical fibers to demonstrate the formation of an artificial event horizon in optics. We observed a classical optical effect, the blue-shifting of light at a white-hole horizon. We also show by theoretical calculations that such a system is capable of probing the quantum effects of horizons, in particular Hawking radiation.Comment: MEDIA EMBARGO. This paper is subject to the media embargo of Scienc

Collaboration in Bipartite Networks, with an Application to Coauthorship Networks

This paper studies the impact of collaboration on research output. First, we build a micro-founded model for scientific knowledge production, where collaboration between researchers is represented by a bipartite network. The equilibrium of the game incorporates both the complementarity effect between collaborating researchers and the substitutability effect between concurrent projects of the same researcher. Next, we develop a Bayesian MCMC procedure to estimate the structural parameters, taking into account the endogenous matching of researchers and projects. Finally, we illustrate the empirical relevance of the model by analyzing the coauthorship network of economists registered in the RePEc Author Service

Performance-based contracting in the defence industry: Exploring triadic dynamics between government, OEMs and suppliers

This study takes a rare longitudinal perspective to examine performance-based contracting (PBC) in the context of the development of a major capital defence project. It employs a triadic framework to examine changes in actors and their roles over time in fulfilling the project. The triads involve both contractors as suppliers and government entities. More specifically, using a historical narrative method the study suggests that over the 30 year span of the new warship’s development, different parties occupy the nodes of triads where the roles or functions of the principal and agents in the contract change over time. Our use of a triadic perspective enables us to trace both the withdrawal of the government customer from a position of authority and the specific strategy of one supplier to occupy the vacated role as systems integrator. The study makes three distinct contributions: firstly, to our understanding of PBC through tracing the development of the conditions that enable PBC in largescale long-term public-private contracting such as clear role delineation. Second, it adds to understanding of principal-agent behaviour in triadic public-private projects, suggesting that customer and supplier roles need to be perceived as supply network dynamics. Third, it suggests reasons why this defence acquisition underperformed, focusing on the mediation of the customer’s value requirement through powerful players seeking to extend their control. We argue PBC must be re-assessed in complex environments to include less direct financial measures such as long-term market share and adopt a more nuanced approach to contractual management than simply transferring risk.We wish to acknowledge the financial assistance provided by the Chartered Institute of Purchasing & Supply and the Institute of Supply Management

Introduction: Celebrating the Mound City Bar Association Centennial: Looking Back, Leading Forward

In 2022, the Mound City Bar Association in St. Louis, one of the first Black bar associations in the country, celebrates its 100th anniversary. In this volume of the Washington University Journal of Law & Policy, distinguished authors look back at a century of contributions of Mound City Bar Association lawyers, judges, and allies, documenting their efforts to eliminate racial discrimination and break down barriers to equal justice. The volume is a testament to the work of countless individuals in the fight for civil rights since the beginning of the association in 1922. The authors also anticipate and examine the challenges ahead and the work yet to be done to achieve equal justice for all in our city, the region, and the country in the years to come

304Nuclear targeting apelin induces phenotypic transition of vascular smooth muscle cells

Background: Apelin, and its receptor APJ, are a peptidic system playing a crucial role in vascular diseases. However, the role of apelin in atherogenesis and smooth muscle cell (SMC) proliferation remains unclear. We isolated 2 distinct SMC phenotypes from porcine coronary artery: spindle-shaped (S) and rhomboid (R). Biological features of R-SMCs (i.e. enhanced proliferative and migratory activities as well as poor level of differentiation) explain their capacity to accumulate into the intima. S100A4 is a marker of R-SMCs in vitro and of intimal SMCs, both in pig and human. S100A4 is a Ca2+-binding protein that can also be secreted; it has extracellular functions probably via the receptor for advanced glycation end products (RAGE). Purpose: Investigate the effects of apelin on SMC phenotypic transition and S100A4 expression and release. Methods and Results: We observed that apelin was highly expressed in R-SMCs particularly in their nucleus. P-SORT software analysis of preproapelin sequence suggested that N-terminal truncated apelin may target the nucleus, and we confirmed this in SMCs by overexpression of mutated preproapelin-His-tag. Transfection of mutated preproapelin-His-tag encoding plasmid in differentiated S-SMCs induced a transition towards a R-phenotype associated with increased proliferative activity, downregulation of SMC differentiation markers (i.e. alpha-smooth muscle actin), and increased nuclear expression and release of S100A4. In contrast, transfection of S-SMCs with wild type preproapelin-His-tag encoding plasmid did not induce nuclear targeting of Apelin or S100A4, and did not change the S-phenotype. Stimulation of S-SMCs with PDGF-BB, known to induce a transition to the R-phenotype, yielded nuclear targeting of both apelin and S100A4. In vivo, Apelin was expressed in SMC nuclei of stent-induced intimal thickening while its expression in the media was mainly cytoplasmic. Conclusions: Our results suggest that nuclear targeting of apelin in SMCs acts on S100A4 expression and release, cell proliferation and differentiation. The pathophysiological consequences of this retargeting could be instrumental in the understanding of artherosclerosi