230 research outputs found
Method of modeling the cognitive radio using Opnet Modeler
This article is a review of the first wireless standard based on cognitive radio networks. The necessity of wireless networks based on the technology of cognitive radio. An example of the use of standard IEEE 802.22 in Wimax network through which was implemented in the simulation software environment Opnet Modeler. Schedules to check the performance of HTTP and FTP protocols CR network. Simulation results justify the use of standard IEEE 802.22 in wireless networks.Ця стаття являє собою огляд першого бездротового стандарту, заснованого на мережах когнітивного радіо. У роботі були розглянуті основні елементи стандарту IEEE 802.22, такі як структура фізичного і канального рівнів, топологія системи, ємність системи і задане покриття системи. Також були визначені головні переваги та проблеми стандарту 802.22.Використовуючи пакетOpnetModeler, було промодульовано сегмент CR мережі через Wimax, використовуючи RIPng протокол
Spectral Asymptotics for Perturbed Spherical Schr\"odinger Operators and Applications to Quantum Scattering
We find the high energy asymptotics for the singular Weyl--Titchmarsh
m-functions and the associated spectral measures of perturbed spherical
Schr\"odinger operators (also known as Bessel operators). We apply this result
to establish an improved local Borg-Marchenko theorem for Bessel operators as
well as uniqueness theorems for the radial quantum scattering problem with
nontrivial angular momentum.Comment: 20 page
Holographic Recording Media based on Electron Donor Oligomers
For optical holographic recording by photothermoplastic technique reversible holographic media based on oligomers with hole type of conductivity are used. New carbazole containing radial tetrasubstituted silanes and germanes are described in the present work
Simulations of M87 and Sgr A* imaging with the Millimetron Space Observatory on near-Earth orbits
High resolution imaging of supermassive black holes shadows is a direct way
to verify the theory of general relativity at extreme gravity conditions. Very
Long Baseline Interferometry (VLBI) observations at millimeter/sub-millimeter
wavelengths can provide such angular resolution for supermassive black holes,
located in Sgr A* and M87. Recent VLBI observations of M87 with the Event
Horizon Telescope (EHT) has shown such capabilities. The maximum obtainable
spatial resolution of EHT is limited by Earth diameter and atmospheric phase
variations. In order to improve the image resolution longer baselines are
required. Radioastron space mission has successfully demonstrated the
capabilities of Space-Earth VLBI with baselines much larger than Earth
diameter. Millimetron is a next space mission of the Russian Space Agency that
will operate at millimeter wavelengths. Nominal orbit of the observatory will
be located around Lagrangian L2 point of the Sun-Earth system. In order to
optimize the VLBI mode, we consider a possible second stage of the mission that
could use near-Earth high elliptical orbit (HEO). In this contribution a set of
near-Earth orbits is used for the synthetic space-ground VLBI observations of
Sgr A* and M87 in joint Millimetron and EHT configuration. General-relativistic
magnetohydrodynamic models (GRMHD) for black hole environment of Sgr A* and M87
are used for static and dynamic imaging simulations at 230 GHz. A comparison
preformed between ground and space-ground baselines demonstrates that joint
observations with Millimetron and EHT significantly improve the image
resolution and allow the EHT+Millimetron to obtain snapshot images of Sgr A*
probing dynamics at fast timescales.Comment: 12 pages, 6 figure
Transmutations and spectral parameter power series in eigenvalue problems
We give an overview of recent developments in Sturm-Liouville theory
concerning operators of transmutation (transformation) and spectral parameter
power series (SPPS). The possibility to write down the dispersion
(characteristic) equations corresponding to a variety of spectral problems
related to Sturm-Liouville equations in an analytic form is an attractive
feature of the SPPS method. It is based on a computation of certain systems of
recursive integrals. Considered as families of functions these systems are
complete in the -space and result to be the images of the nonnegative
integer powers of the independent variable under the action of a corresponding
transmutation operator. This recently revealed property of the Delsarte
transmutations opens the way to apply the transmutation operator even when its
integral kernel is unknown and gives the possibility to obtain further
interesting properties concerning the Darboux transformed Schr\"{o}dinger
operators.
We introduce the systems of recursive integrals and the SPPS approach,
explain some of its applications to spectral problems with numerical
illustrations, give the definition and basic properties of transmutation
operators, introduce a parametrized family of transmutation operators, study
their mapping properties and construct the transmutation operators for Darboux
transformed Schr\"{o}dinger operators.Comment: 30 pages, 4 figures. arXiv admin note: text overlap with
arXiv:1111.444
The analysis of students' satisfaction with the educational process of the 5 th year of the pediatric faculty. Results of the questionnaire
conducting monitoring studies within the framework of the quality management system is the basis for improving the educational process, as a result of which top-level cadres are issued in practical public health. One of the tools for improving quality is the questioning of students, analysis and implementation of corrective measures. To assess the quality of teaching discipline Outpatient and Emergency Pediatrics at the Department of Outpatient Pediatrics and Pediatrics of the FPK and PP, 113 5-year students of the pediatric faculty who were trained in the IX and X semesters were surveyed. During the survey, it turned out that 98.2% of respondents are satisfied with the quality of teaching the discipline. However, the students, as the main consumers of the educational process, made a number of comments and suggestions to improve the quality of teaching the discipline, in accordance with which corrective measures are planned.проведение мониторинговых исследований в рамках системы менеджмента качества является основой для совершенствования образовательного процесса, в результате которого в практическое здравоохранение выпускаются кадры высшей квалификации. Одним из инструментов повышения качества является анкетирование студентов, анализ и проведение корректирующих мероприятий. Для оценки качества преподавания на кафедре Поликлинической педиатрии и педиатрии ФПК и ПП проведено анкетирование 113 студентов 5 курса педиатрического факультета, прошедших обучение в IX и X семестрах по дисциплине Поликлиническая и неотложная педиатрия. В ходе анкетирования выяснилось, что98,2 % респондентов удовлетворены качеством преподавания дисциплины. Однако, учащимися, как основными потребителями образовательного процесса, высказаны ряд замечаний и предложений по улучшению качества преподавания, в соответствии с которыми запланированы корректирующие мероприяти
Hybrid nanoparticles based on sulfides, oxides, and carbides
The methods for synthesis of hybrid nanoparticles based on sulfides, oxides, and carbides of heavy and transition metals were considered. The problem of the influence of the method of synthesis of the hybrid nanoparticles on their atomic structure, morphology of the nanomaterials, and functional properties was analyzed. The areas of practical use of the hybrid nanoparticles were proposed. © 2013 Springer Science+Business Media New York
Varespladib and cardiovascular events in patients with an acute coronary syndrome: the VISTA-16 randomized clinical trial
IMPORTANCE: Secretory phospholipase A2(sPLA2) generates bioactive phospholipid products implicated in atherosclerosis. The sPLA2inhibitor varespladib has favorable effects on lipid and inflammatory markers; however, its effect on cardiovascular outcomes is unknown. OBJECTIVE: To determine the effects of sPLA2inhibition with varespladib on cardiovascular outcomes. DESIGN, SETTING, AND PARTICIPANTS: A double-blind, randomized, multicenter trial at 362 academic and community hospitals in Europe, Australia, New Zealand, India, and North America of 5145 patients randomized within 96 hours of presentation of an acute coronary syndrome (ACS) to either varespladib (n = 2572) or placebo (n = 2573) with enrollment between June 1, 2010, and March 7, 2012 (study termination on March 9, 2012). INTERVENTIONS: Participants were randomized to receive varespladib (500 mg) or placebo daily for 16 weeks, in addition to atorvastatin and other established therapies. MAIN OUTCOMES AND MEASURES: The primary efficacy measurewas a composite of cardiovascular mortality, nonfatal myocardial infarction (MI), nonfatal stroke, or unstable angina with evidence of ischemia requiring hospitalization at 16 weeks. Six-month survival status was also evaluated. RESULTS: At a prespecified interim analysis, including 212 primary end point events, the independent data and safety monitoring board recommended termination of the trial for futility and possible harm. The primary end point occurred in 136 patients (6.1%) treated with varespladib compared with 109 patients (5.1%) treated with placebo (hazard ratio [HR], 1.25; 95%CI, 0.97-1.61; log-rank P = .08). Varespladib was associated with a greater risk of MI (78 [3.4%] vs 47 [2.2%]; HR, 1.66; 95%CI, 1.16-2.39; log-rank P = .005). The composite secondary end point of cardiovascular mortality, MI, and stroke was observed in 107 patients (4.6%) in the varespladib group and 79 patients (3.8%) in the placebo group (HR, 1.36; 95% CI, 1.02-1.82; P = .04). CONCLUSIONS AND RELEVANCE: In patients with recent ACS, varespladib did not reduce the risk of recurrent cardiovascular events and significantly increased the risk of MI. The sPLA2inhibition with varespladib may be harmful and is not a useful strategy to reduce adverse cardiovascular outcomes after ACS. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT01130246. Copyright 2014 American Medical Association. All rights reserved
Extended Thromboprophylaxis with Betrixaban in Acutely Ill Medical Patients
Background
Patients with acute medical illnesses are at prolonged risk for venous thrombosis. However, the appropriate duration of thromboprophylaxis remains unknown.
Methods
Patients who were hospitalized for acute medical illnesses were randomly assigned to receive subcutaneous enoxaparin (at a dose of 40 mg once daily) for 10±4 days plus oral betrixaban placebo for 35 to 42 days or subcutaneous enoxaparin placebo for 10±4 days plus oral betrixaban (at a dose of 80 mg once daily) for 35 to 42 days. We performed sequential analyses in three prespecified, progressively inclusive cohorts: patients with an elevated d-dimer level (cohort 1), patients with an elevated d-dimer level or an age of at least 75 years (cohort 2), and all the enrolled patients (overall population cohort). The statistical analysis plan specified that if the between-group difference in any analysis in this sequence was not significant, the other analyses would be considered exploratory. The primary efficacy outcome was a composite of asymptomatic proximal deep-vein thrombosis and symptomatic venous thromboembolism. The principal safety outcome was major bleeding.
Results
A total of 7513 patients underwent randomization. In cohort 1, the primary efficacy outcome occurred in 6.9% of patients receiving betrixaban and 8.5% receiving enoxaparin (relative risk in the betrixaban group, 0.81; 95% confidence interval [CI], 0.65 to 1.00; P=0.054). The rates were 5.6% and 7.1%, respectively (relative risk, 0.80; 95% CI, 0.66 to 0.98; P=0.03) in cohort 2 and 5.3% and 7.0% (relative risk, 0.76; 95% CI, 0.63 to 0.92; P=0.006) in the overall population. (The last two analyses were considered to be exploratory owing to the result in cohort 1.) In the overall population, major bleeding occurred in 0.7% of the betrixaban group and 0.6% of the enoxaparin group (relative risk, 1.19; 95% CI, 0.67 to 2.12; P=0.55).
Conclusions
Among acutely ill medical patients with an elevated d-dimer level, there was no significant difference between extended-duration betrixaban and a standard regimen of enoxaparin in the prespecified primary efficacy outcome. However, prespecified exploratory analyses provided evidence suggesting a benefit for betrixaban in the two larger cohorts. (Funded by Portola Pharmaceuticals; APEX ClinicalTrials.gov number, NCT01583218. opens in new tab.
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