Clusters of galaxies : observational properties of the diffuse radio emission

Clusters of galaxies, as the largest virialized systems in the Universe, are ideal laboratories to study the formation and evolution of cosmic structures...(abridged)... Most of the detailed knowledge of galaxy clusters has been obtained in recent years from the study of ICM through X-ray Astronomy. At the same time, radio observations have proved that the ICM is mixed with non-thermal components, i.e. highly relativistic particles and large-scale magnetic fields, detected through their synchrotron emission. The knowledge of the properties of these non-thermal ICM components has increased significantly, owing to sensitive radio images and to the development of theoretical models. Diffuse synchrotron radio emission in the central and peripheral cluster regions has been found in many clusters. Moreover large-scale magnetic fields appear to be present in all galaxy clusters, as derived from Rotation Measure (RM) studies. Non-thermal components are linked to the cluster X-ray properties, and to the cluster evolutionary stage, and are crucial for a comprehensive physical description of the intracluster medium. They play an important role in the cluster formation and evolution. We review here the observational properties of diffuse non-thermal sources detected in galaxy clusters: halos, relics and mini-halos. We discuss their classification and properties. We report published results up to date and obtain and discuss statistical properties. We present the properties of large-scale magnetic fields in clusters and in even larger structures: filaments connecting galaxy clusters. We summarize the current models of the origin of these cluster components, and outline the improvements that are expected in this area from future developments thanks to the new generation of radio telescopes.Comment: Accepted for the publication in The Astronomy and Astrophysics Review. 58 pages, 26 figure

MicroMotility: State of the art, recent accomplishments and perspectives on the mathematical modeling of bio-motility at microscopic scales

Mathematical modeling and quantitative study of biological motility (in particular, of motility at microscopic scales) is producing new biophysical insight and is offering opportunities for new discoveries at the level of both fundamental science and technology. These range from the explanation of how complex behavior at the level of a single organism emerges from body architecture, to the understanding of collective phenomena in groups of organisms and tissues, and of how these forms of swarm intelligence can be controlled and harnessed in engineering applications, to the elucidation of processes of fundamental biological relevance at the cellular and sub-cellular level. In this paper, some of the most exciting new developments in the fields of locomotion of unicellular organisms, of soft adhesive locomotion across scales, of the study of pore translocation properties of knotted DNA, of the development of synthetic active solid sheets, of the mechanics of the unjamming transition in dense cell collectives, of the mechanics of cell sheet folding in volvocalean algae, and of the self-propulsion of topological defects in active matter are discussed. For each of these topics, we provide a brief state of the art, an example of recent achievements, and some directions for future research

Prognostic model to predict postoperative acute kidney injury in patients undergoing major gastrointestinal surgery based on a national prospective observational cohort study.

Background: Acute illness, existing co-morbidities and surgical stress response can all contribute to postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery. The aim of this study was prospectively to develop a pragmatic prognostic model to stratify patients according to risk of developing AKI after major gastrointestinal surgery. Methods: This prospective multicentre cohort study included consecutive adults undergoing elective or emergency gastrointestinal resection, liver resection or stoma reversal in 2-week blocks over a continuous 3-month period. The primary outcome was the rate of AKI within 7 days of surgery. Bootstrap stability was used to select clinically plausible risk factors into the model. Internal model validation was carried out by bootstrap validation. Results: A total of 4544 patients were included across 173 centres in the UK and Ireland. The overall rate of AKI was 14·2 per cent (646 of 4544) and the 30-day mortality rate was 1·8 per cent (84 of 4544). Stage 1 AKI was significantly associated with 30-day mortality (unadjusted odds ratio 7·61, 95 per cent c.i. 4·49 to 12·90; P < 0·001), with increasing odds of death with each AKI stage. Six variables were selected for inclusion in the prognostic model: age, sex, ASA grade, preoperative estimated glomerular filtration rate, planned open surgery and preoperative use of either an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker. Internal validation demonstrated good model discrimination (c-statistic 0·65). Discussion: Following major gastrointestinal surgery, AKI occurred in one in seven patients. This preoperative prognostic model identified patients at high risk of postoperative AKI. Validation in an independent data set is required to ensure generalizability

Diffusion characteristics in the Cu-Ti system

The formation and growth of intermetallic compounds by diffusion reaction of Cu and Ti were investigated in the temperature range 720-860 degrees C using bulk diffusion couples. Only four, out of the seven stable intermediate compounds of the Cu-Ti system, were formed in the diffusion reaction zone in the sequence CuTi, Cu4Ti, Cu4Ti3 and CuTi2. The activation energies required for the growth of these compounds were determined. The diffusion characteristics of Cu4Ti, CuTi and Cu4Ti3 and Cu(Ti) solid solution were evaluated. The activation energies for diffusion in these compounds were 192.2, 187.7 and 209.2 kJ mol(-1) respectively, while in Cu(Ti), the activation energy increased linearly from 201.0 kJ mol(-1) to 247.5 kJ mol(-1) with increasing concentration of Ti, in the range 0.5-4.0 at.%. The impurity diffusion coefficient of Ti in Cu and its temperature dependence were also estimated. A correlation between the impurity diffusion parameters for several elements in Cu matrix has been established

A kinetic model for iron aluminide coating by low pressure chemical vapor deposition: Part II. Model formulation

Formation of aluminide diffusion coatings on iron, nickel and cobalt by pack cementation and chemical vapor deposition (CVD) involves a series of similar steps, the slowest among them are the transport of aluminum bearing species from the vapor phase to the substrate by gas-phase diffusion and the solid-phase diffusion of aluminum into the substrate to form the aluminide phases. The former increases the surface concentration of aluminum in the coating while the latter decreases it. Modeling of the process is based on the observation that the surface composition of the coating tends to reach a steady state value in a short time after the commencement of the process, at which stage the rates of the above two processes are equal. However, in the case of iron aluminide coatings produced by low pressure chemical vapor deposition (1.33±0.13 kPa), the rate of transport of aluminum to the substrate is much faster than the solid phase diffusion of aluminum into the iron substrate since the diffusion coefficients of the vapor species are inversely proportional to pressure and the diffusion layer thickness is reduced considerably at low pressures. Under this condition, the vapor transport is no longer a rate-determining step and the composition of the aluminide coating is decided by the kinetics of the solid phase diffusion. This model could explain the kinetics of the process, surface composition and concentration profile of the coating.© Elsevie

Microstructural evolution during reactive brazing of alumina to Inconel 600 using Ag-based alloy

A metal ceramic bonding process was developed to produce vacuum tight alumina Inconel 600 joints using an Ag-based active metal brazing alloy that can withstand continuous operating temperature up to 560 degrees C. The microstructure and microchemistry of the braze zone was examined using extensive microanalysis of the constituent phases and a mechanism for the interfacial reactions responsible for the bonding is proposed. Prolonged heat treatment at 400 and 560 degrees C under simulated in-service conditions revealed that the microstructure of braze zone of the joints was stable and maintained leak-tightness and strength. The bond strength of the interface was high enough to cause failure in the alumina side of the joints. Failure of the joints was caused by initiation of crack on the surface of alumina as a result of high tensile residual stress adjacent to the metal ceramic interface. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved

Stability of microstructure and its evolution during solid-state annealing of Al(2)O(3)-Inconel 600 brazed couples

The stability of the microstructure of alumina-Inconel 600 brazed joints was investigated under simulated in-service conditions by subjecting them to prolonged heat treatment at 400 and 560 degrees C. The evolution of the microstructure and microchemistry of the brazing zone was examined using extensive microanalysis of the constituent phases. The layered structure of the brazing zone transformed to homogeneous, near-equilibrium, two-phase microstructure after heat treatment at 560 C. Solid-state interdiffusion was identified as a primary factor responsible for such copious modification of the microstructure. Intermediate temperature heat treatment at 400 degrees C revealed that the mechanism of transformation of the microstructure was globulization of the Ni overlayer and dissolution of Mo from the metallization layer into the Ni-rich phase. The migration behavior of each of the elements, in response to heat treatment, was analyzed. Cr was found to diffuse out of Inconel and form a layer of Cr(2)O(3) at the alumina-brazing alloy interface. The bond strength of the interface was high enough to cause cohesive failure in the alumina side of the joints. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved

Origin of hard and soft zone formation during cladding of austenitic/duplex stainless steel on plain carbon steel

Weld cladding of corrosion resistant materials is an attractive alternative to bulk usage. Such processes are generally associated with potential deterioration of mechanical properties at the clad/metal interface, often attributed to the formation of hard and soft zones which is usually minimised by control of dilution and use of a buffer layer. To ascertain the origin of the hard and soft zones, weld cladding of austenitic stainless steel (309L) was attempted on plain carbon (0-28 wt-%) steel base metal at various heat inputs, and correspondingly different dilution percentages for the weld metal were obtained. The formation of hard and soft zones was observed mainly on the austenitic stainless steel (i.e. weld metal) side. Typically close to the welding interface (i.e. visible fusion line) a hard zone was observed, followed, but only at higher dilution, by a soft zone. In general, with increasing dilution, the peak hardness and width of the hard zone increased, and the chromium and nickel concentrations of the soft zone significantly decreased. The hard zones were martensitic regions which, at higher dilution, contained chromium carbide precipitates. These precipitates may explain the chromium depletion in the adjacent soft zone. The nickel depletion may be a result of the positive interaction coefficient between nickel and carbon. Since hard/soft zone formation was least at lower dilution, cladding of duplex and superduplex stainless steel was conducted on the same plain carbon base with and without a 309L buffer at an optimum dilution of about 15%. Even at this dilution, direct cladding always resulted in hard and soft zone formation, which was significantly reduced or eliminated by indirect cladding. The hard zones were identified as regions with extensive carbide precipitation (no evidence of martensite formation was found), which occurred in duplex/superduplex grades even at 15% dilution. (C) 2001 IoM Communications Ltd

Novel platinum&ndash;palladium bimetallic nanoparticles synthesized by Dioscorea bulbifera: anticancer and antioxidant activities

Sougata Ghosh,1 Rahul Nitnavare,1 Ankush Dewle,1 Geetanjali B Tomar,1 Rohan Chippalkatti,1 Piyush More,1 Rohini Kitture,2 Sangeeta Kale,2 Jayesh Bellare,3 Balu A Chopade4 1Institute of Bioinformatics and Biotechnology, University of Pune, 2Department of Applied Physics, Defense Institute of Advanced Technology, Pune, 3Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, 4Department of Microbiology, University of Pune, Pune, India Abstract: Medicinal plants serve as rich sources of diverse bioactive phytochemicals that might even take part in bioreduction and stabilization of phytogenic nanoparticles with immense therapeutic properties. Herein, we report for the first time the rapid efficient synthesis of novel platinum&ndash;palladium bimetallic nanoparticles (Pt&ndash;PdNPs) along with individual platinum (PtNPs) and palladium (PdNPs) nanoparticles using a medicinal plant, Dioscorea bulbifera tuber extract (DBTE). High-resolution transmission electron microscopy revealed monodispersed PtNPs of size 2&ndash;5 nm, while PdNPs and Pt&ndash;PdNPs between 10 and 25 nm. Energy dispersive spectroscopy analysis confirmed 30.88%&plusmn;1.73% elemental Pt and 68.96%&plusmn;1.48% elemental Pd in the bimetallic nanoparticles. Fourier transform infrared spectra indicated strong peaks at 3,373 cm-1, attributed to hydroxyl group of polyphenolic compounds in DBTE that might play a key role in bioreduction in addition to the sharp peaks at 2,937, 1,647, 1,518, and 1,024 cm-1, associated with C&ndash;H stretching, N&ndash;H bending in primary amines, N&ndash;O stretching in nitro group, and C&ndash;C stretch, respectively. Anticancer activity against HeLa cells showed that Pt&ndash;PdNPs exhibited more pronounced cell death of 74.25% compared to individual PtNPs (12.6%) or PdNPs (33.15%). Further, Pt&ndash;PdNPs showed an enhanced scavenging activity against 2,2-diphenyl-1-picrylhydrazyl, superoxide, nitric oxide, and hydroxyl radicals. Keywords: Dioscorea bulbifera, platinum nanoparticles, palladium nanoparticles, platinum&ndash;palladium bimetallic nanoparticles, anticancer, antioxidan