20W Output Broadband Amplifier with Automatic Gain Control and Thermal Protection

The requirement is to explore concept, design, fabrication and testing of a common source class B, cwrf amplifier by using readily available MOSFET that can withstand a load mismatch at all phase angles with more than a VSWR of 20:1. This amplifier must give an output of more than 20W with 13dB gain in the frequency range of 28 to 46MHz i.e. 37 ± 9MHz. This module will make one of the stages for a multistage cascaded high power cwrf solid state amplifier. The amplifier must be over current and over voltage protected by using external self-regulated dc power supply at the drain. The amplifier MOSFET device is presently to be biased at the gate with a variable dc supply. This arrangement will make it gain controlled. This will be feed backed from the cwrf output so as to make it automatic gain controlled in future. Various techniques of sampling forward and reflected power at the output must also be explored. A thermoswitch at the heat sink of MOSFET is to be added along with necessary circuitry to regulate the operating temperature, thereby protecting the device from overheating

Study On Nanoparticles Of ZnSe Synthesized By Chemical Method And Their Characterization

The properties of semiconductor nanoparticles depend mainly on their shape and size due to high surface-to-volume ratio. The II – VI semiconductors have many applications such as, LED, acousto-optical effects and biological sensors. The ZnSe nanoparticles have wide-ranging applications in laser, optical instruments etc. because it has wide band gap and transmittance range, high luminescence efficiency, low absorption coefficient. In recent years, much attention was paid on the preparation methods, performances and applications of ZnSe nanoparticles and thin solid films, and a lot of important accomplishments have been obtained. In the present study ZnSe nanoparticles were successfully prepared by reacting Zn(CH3COO)2·2H2O and Na2SeSO3 at 343 K. The size of the crystallite was estimated by X-ray diffraction and TEM, whereas EDAX has confirmed of no foreign impurity inclusion in ZnSe nanoparticles. XRD shows the crystallite size of 5.68 nm and TEM gives a distribution ranging from 20 nm to 71 nm. A SEM image shows that the particles are spherical in a shape. Quantum confinement has resulted in the blue shift compared to bulk ZnSe as observed from the absorption spectra of particles dispersed in DMF. We obtained the photoluminescence spectra on these particles with two different excitation wavelength which shows broad band emission peak at 573 nm. Photoluminescence spectra taken with other excitation wavelength also gives sharp emission peaks at 484 nm, 530 nm, 551 nm and 600 nm. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/967

Lattice QCD Calculations of the Sigma Commutator

As a direct source of information on chiral symmetry breaking within QCD, the sigma commutator is of considerable importance. With recent advances in the calculation of hadron masses within full QCD it is of interest to see whether the sigma commutator can be calculated directly from the dependence of the nucleon mass on the input quark mass. We show that provided the correct chiral behaviour of QCD is respected in the extrapolation to realistic quark masses one can indeed obtain a fairly reliable determination of the sigma commutator using present lattice data. Within two-flavour, dynamical-fermion QCD the value obtained lies in the range 45 to 55 MeV.Comment: 7 pages, 2 figure

Processing of aluminum-graphite particulate metal matrix composites by advanced shear technology

Copyright @ 2009 ASM International. This paper was published in Journal of Materials Engineering and Performance 18(9) and is made available as an electronic reprint with the permission of ASM International. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplications of any material in this paper for a fee or for commercial purposes, or modification of the content of this paper are prohibited.To extend the possibilities of using aluminum/graphite composites as structural materials, a novel process is developed. The conventional methods often produce agglomerated structures exhibiting lower strength and ductility. To overcome the cohesive force of the agglomerates, a melt conditioned high-pressure die casting (MC-HPDC) process innovatively adapts the well-established, high-shear dispersive mixing action of a twin screw mechanism. The distribution of particles and properties of composites are quantitatively evaluated. The adopted rheo process significantly improved the distribution of the reinforcement in the matrix with a strong interfacial bond between the two. A good combination of improved ultimate tensile strength (UTS) and tensile elongation (e) is obtained compared with composites produced by conventional processes.EPSR

Real-world efficacy of direct acting antiviral therapies in patients with HIV/HCV

The advent of direct-acting antiviral (DAA) therapies has dramatically transformed HCV treatment, with most recent trials demonstrating high efficacy rates (>90%) across all genotypes and special populations, including patients with HIV/HCV coinfection. The efficacy rates of HCV treatment are nearly identical between patients with HCV monofection and patients with HIV/HCV coinfection; however, there are limited studies to compare real-world efficacy with efficacy observed in clinical trials. Using a database from HIV clinics across the United States (US), we identified 432 patients with HIV/HCV coinfection who completed DAA therapy from January 1, 2014 to March 31, 2017 and were assessed for efficacy. Efficacy was evaluated as sustained virologic response (SVR) 12 weeks after DAA completion; furthermore, factors associated with achieving SVR12 were identified. In this analysis, we found DAA therapies to be effective, with 94% of the patients achieving SVR12 and 6% experiencing virologic failure. Baseline variables, including older age, HCV viral load <800K IU/ML, FIB-4 score <1.45, absence of depression, diabetes, substance abuse, and use of DAA regimens without ribavirin were significant predictors of achieving SVR12. Patients with fewer comorbidities, better liver health, and lower HCV viral loads at baseline were more likely to achieve treatment success. Our results were consistent with other real-world studies, supporting the use of HCV therapy in HIV/HCV coinfected patients

Spallation reactions. A successful interplay between modeling and applications

The spallation reactions are a type of nuclear reaction which occur in space by interaction of the cosmic rays with interstellar bodies. The first spallation reactions induced with an accelerator took place in 1947 at the Berkeley cyclotron (University of California) with 200 MeV deuterons and 400 MeV alpha beams. They highlighted the multiple emission of neutrons and charged particles and the production of a large number of residual nuclei far different from the target nuclei. The same year R. Serber describes the reaction in two steps: a first and fast one with high-energy particle emission leading to an excited remnant nucleus, and a second one, much slower, the de-excitation of the remnant. In 2010 IAEA organized a worskhop to present the results of the most widely used spallation codes within a benchmark of spallation models. If one of the goals was to understand the deficiencies, if any, in each code, one remarkable outcome points out the overall high-quality level of some models and so the great improvements achieved since Serber. Particle transport codes can then rely on such spallation models to treat the reactions between a light particle and an atomic nucleus with energies spanning from few tens of MeV up to some GeV. An overview of the spallation reactions modeling is presented in order to point out the incomparable contribution of models based on basic physics to numerous applications where such reactions occur. Validations or benchmarks, which are necessary steps in the improvement process, are also addressed, as well as the potential future domains of development. Spallation reactions modeling is a representative case of continuous studies aiming at understanding a reaction mechanism and which end up in a powerful tool.Comment: 59 pages, 54 figures, Revie

Cardiac magnetic resonance stress perfusion imaging for evaluation of patients with chest pain

Background: Stress cardiac magnetic resonance imaging (CMR) has demonstrated excellent diagnostic and prognostic value in single-center studies. Objectives: This study sought to investigate the prognostic value of stress CMR and downstream costs from subsequent cardiac testing in a retrospective multicenter study in the United States. Methods: In this retrospective study, consecutive patients from 13 centers across 11 states who presented with a chest pain syndrome and were referred for stress CMR were followed for a target period of 4 years. The authors associated CMR findings with a primary outcome of cardiovascular death or nonfatal myocardial infarction using competing risk-adjusted regression models and downstream costs of ischemia testing using published Medicare national payment rates. Results: In this study, 2,349 patients (63 ± 11 years of age, 47% female) were followed for a median of 5.4 years. Patients with no ischemia or late gadolinium enhancement (LGE) by CMR, observed in 1,583 patients (67%), experienced low annualized rates of primary outcome (4-fold higher annual primary outcome rate and a >10-fold higher rate of coronary revascularization during the first year after CMR. Patients with ischemia and LGE both negative had low average annual cost spent on ischemia testing across all years of follow-up, and this pattern was similar across the 4 practice environments of the participating centers. Conclusions: In a multicenter U.S. cohort with stable chest pain syndromes, stress CMR performed at experienced centers offers effective cardiac prognostication. Patients without CMR ischemia or LGE experienced a low incidence of cardiac events, little need for coronary revascularization, and low spending on subsequent ischemia testing. (Stress CMR Perfusion Imaging in the United States [SPINS]: A Society for Cardiovascular Resonance Registry Study; NCT03192891)

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC

Measurements of inclusive jet suppression in heavy ion collisions at the LHC provide direct sensitivity to the physics of jet quenching. In a sample of lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the anti-kt algorithm with values for the distance parameter that determines the nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp. Jet production is found to be suppressed by approximately a factor of two in the 10% most central collisions relative to peripheral collisions. Rcp varies smoothly with centrality as characterized by the number of participating nucleons. The observed suppression is only weakly dependent on jet radius and transverse momentum. These results provide the first direct measurement of inclusive jet suppression in heavy ion collisions and complement previous measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables, submitted to Physics Letters B. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02

Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV

Results are presented from a search for a W' boson using a dataset corresponding to 5.0 inverse femtobarns of integrated luminosity collected during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV. The W' boson is modeled as a heavy W boson, but different scenarios for the couplings to fermions are considered, involving both left-handed and right-handed chiral projections of the fermions, as well as an arbitrary mixture of the two. The search is performed in the decay channel W' to t b, leading to a final state signature with a single lepton (e, mu), missing transverse energy, and jets, at least one of which is tagged as a b-jet. A W' boson that couples to fermions with the same coupling constant as the W, but to the right-handed rather than left-handed chiral projections, is excluded for masses below 1.85 TeV at the 95% confidence level. For the first time using LHC data, constraints on the W' gauge coupling for a set of left- and right-handed coupling combinations have been placed. These results represent a significant improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe