778 research outputs found

    From Spectrum Pooling to Space Pooling: Opportunistic Interference Alignment in MIMO Cognitive Networks

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    We describe a non-cooperative interference alignment (IA) technique which allows an opportunistic multiple input multiple output (MIMO) link (secondary) to harmlessly coexist with another MIMO link (primary) in the same frequency band. Assuming perfect channel knowledge at the primary receiver and transmitter, capacity is achieved by transmiting along the spatial directions (SD) associated with the singular values of its channel matrix using a water-filling power allocation (PA) scheme. Often, power limitations lead the primary transmitter to leave some of its SD unused. Here, it is shown that the opportunistic link can transmit its own data if it is possible to align the interference produced on the primary link with such unused SDs. We provide both a processing scheme to perform IA and a PA scheme which maximizes the transmission rate of the opportunistic link. The asymptotes of the achievable transmission rates of the opportunistic link are obtained in the regime of large numbers of antennas. Using this result, it is shown that depending on the signal-to-noise ratio and the number of transmit and receive antennas of the primary and opportunistic links, both systems can achieve transmission rates of the same order.Comment: Submitted to IEEE Trans. in Signal Processing. Revised on 23-11-0

    National and Local Antibiotic Prescribing Trends and Prescribing Appropriateness in Older Adults

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    Background: Antibiotic overuse/misuse has been documented in several reports to increase the risk of Clostridioides difficile (C.diff) infection and antibiotic resistance. The older adult population is more prone to use antibiotic medications than any other age group due to decreased immune function, use of urinary catheters, ventilation during hospitalization and other factors. Antibiotic resistance and C.diff are major public health problems. However, studies examining the trends of antibiotic use and the association between the antibiotic use and negative health outcomes among older adults in the outpatient and emergency department settings are limited. Objectives: The main objectives of this dissertation were to: 1) calculate the national antibiotic trends among community-dwelling older adults in the United State; 2) evaluate the antibiotic trends and antibiotic appropriateness among older adult patients visiting the geriatrics clinic and adult internal ambulatory care clinic at VCU Health; and 3) examine the antibiotic trends and antibiotic appropriateness among older adult patients and middle-aged patients visiting the emergency department at VCU Health. Methods: For the first objective, data were obtained from Medical Expenditure Panel survey (MEPS) a nationally representative dataset (2011-2015). Descriptive analyses were conducted and multiple logistic regression was performed to assess the association between the antibiotic use and demographic and sociodemographic characteristics. In the second objective, data were obtained from VCU Health outpatient clinics (geriatrics, and Internal medicine ambulatory care clinic only). Descriptive statistics were calculated and multiple logistic regression was performed to assess the association between antibiotic appropriateness and type of clinics and other demographic characteristics. In the third objective, the emergency department electronic medical records at VCU were used. Trend analysis was performed across the dissertation studies using the Cochran–Armitage test. All variables were considered statistically significant at an α level of 0.05. All the statistical analyses were conducted using the Statistical Analysis Software Version 9.4 (SAS v.9.4), (SAS Institute Inc, Cary, NC). Results: There were 105,762,134 prescriptions dispensed to older adults in the outpatient setting in the US from 2011 to 2015. Antibiotic prescriptions were more common among women (18%) compared to men (12%). White participants received more antibiotics (27%) than African Americans (1.77%) and others (1.4%). Among the 3,515 patients who visited either Geriatrics or Internal Medicine ambulatory clinic at VCU Health from 2012-2017, 1,534 antibiotics were prescribed. Potentially inappropriate antibiotic prescriptions were similar between the two clinics (30% in Geriatrics clinic and 28% in Internal Medicine ambulatory clinic) with p-value of 0.08. In addition, 6,343 middle-aged or older adult patients were dispensed and prescribed an antibiotic in the ED at VCU Health from (2012 to 2017). Eighteen percent of the antibiotic prescriptions received by middle age group were considered potentially inappropriate, compared to 9% among the older adult patient (p \u3c 0.0001). Conclusions: The rate of antibiotic use overall remains unchanged despite the national and international efforts to reduce antibiotic prescriptions and eventually to reduce antibiotic resistance. The changes in the patterns of use in some of the antibiotic categories appear to be driven more by the safety concerns rather than reducing overall use. Future research is needed to strengthen antibiotic stewardship programs for older adults in outpatient settings

    The Prevalence of Dietary Supplement Use Among Older Adult Population Using National Health And Nutrition Examination Survey (NHANES) 2009-2012

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    Background: Dietary supplements (DS) use has increased in the U.S. in the past 20 years. More than half of the U.S. population reported using DS. There are few studies to our knowledge that have assessed DS use specifically for older adults. In this study we purposed to evaluate the trend of using DS among older adults and to test the association between using DS and several demographics, socioeconomics and health characteristics. The second objective was to evaluate the reasons behind using DS among older adults using a nationally representative database. Methods: This is a cross sectional study using the most recent National Health and Nutrition Examination Survey (NHANES) database 2009-2012. It is a nationally representative sample of noninstitutionalized adults in the U.S. Frequency and weighted percentage (standard error) were reported for dichotomous variables. Multiple logistic regressions model analyses were used to evaluate the predictors of DS use after testing model assumptions, multicollinearity, and outliers. P values 0.05 were considered significant. All the statistical analyses were conducted using SAS software version 9.4. Results: Out of 2625 older adult participants (65 years and older) 70.5% of them reported using DS in the past 30 days. Female, non-hispanic white, obese, overweight and excellent and very good self-reported health status participants were more likely to use DS. Multivitamin-multiminerals (MVMM), calcium and vitamin D were the most commonly reported supplements among older adults. 71% of oldest old (80≥ years) reported taking DS and prescription medication in the past 30 days concomitantly and 73% of polypharmacy users reported using DS. To stay healthy, to improve overall health and for bone health were the most commonly reported reasons behind using DS. Conclusion: majority of older adult participants reported using DS in the past 30 days. Health care professionals need to evaluate the dietary supplement information from older adults in order to improve health care

    Composition-tuned smeared phase transitions

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    Phase transitions in random systems are smeared if individual spatial regions can order independently of the bulk system. In this paper, we study such smeared phase transitions (both classical and quantum) in substitutional alloys A1x_{1-x}Bx_x that can be tuned from an ordered phase at composition x=0x=0 to a disordered phase at x=1x=1. We show that the ordered phase develops a pronounced tail that extends over all compositions x<1x<1. Using optimal fluctuation theory, we derive the composition dependence of the order parameter and other quantities in the tail of the smeared phase transition. We also compare our results to computer simulations of a toy model, and we discuss experiments.Comment: 6 pages, 4 eps figures included, final version as publishe

    Anomalous elasticity in a disordered layered XY model

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    We investigate the effects of layered quenched disorder on the behavior of planar magnets, superfluids, and superconductors by performing large-scale Monte-Carlo simulations of a three-dimensional randomly layered XY model. Our data provide numerical evidence for the recently predicted anomalously elastic (sliding) intermediate phase between the conventional high-temperature and low-temperature phases. In this intermediate phase, the spin-wave stiffness perpendicular to the layers vanishes in the thermodynamic limit while the stiffness parallel to the layers as well as the spontaneous magnetization are nonzero. In addition, the susceptibility displays unconventional finite-size scaling properties. We compare our Monte-Carlo results with the theoretical predictions, and we discuss possible experiments in ultracold atomic gases, layered superconductors and in nanostructures.Comment: 6 pages, 4 eps figures included, proceedings of FQMT11, final version as publishe

    Beirut: The City as a Body Politic

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    Israeli bombs completely destroyed Beirut’s neighbourhood Haret Hreik in the summer of 2006. Because Hizbullah’s headquarters is located in the neighbourhood, Israeli war planners considered its destruction of particular symbolic and strategic relevance. For the same reasons, authority of reconstruction carried heightened symbolism and led to contestation between the central government and Hizbullah. In the intersection of these two powerful actors there remains little room for local residents to have a voice in the re-organization of their living spaces

    THE CHALLENGES AND PROBLEMS FACED BY STUDENTS IN THE EARLY STAGE OF WRITING RESEARCH PROJECTS IN L2, UNIVERSITY OF BISHA, SAUDI ARABIA

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    Research, by its nature, is a critical challenging task requires in depth knowledge of the subject matter, planning, care, and hard work. From the students’ point of view, this paper attempts to explore the challenges that are faced by undergraduates when they are writing proposals and research projects at the early stages. The study target group comprised undergraduates in the final year in the College of Science and Arts, Al-Namas, University of Bisha, Saudi Arabia. Around 60 subjects participated in this study and they were from Department of English and Department of Computer Science who conducted their research projects in English as Second Language (ESL). The Research tools of the study include questionnaire and informal interviews with students and teachers of the target groups. Clearly, the results from study showed that around 70 % of the participants who are writing research or conducting research projects in English is one of the predominant challenges for them. Around 50% prefer to conduct their research in L1. The study explored various and common challenges/difficulties during writing the research proposals and projects such as: difficulty in deciding the topic for research, lack of good knowledge of the methodology, inability of finding modern, specialized and related references, lack of interest in research, lack of understanding of the subject matter, lack of time, and research guiding. The study also attempts to give some suggestions/recommendations for developing the process of writing research proposals and research projects.  Article visualizations
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