A dual frequency microstrip antenna for Ka band

For fixed satellite communication systems at Ka band with downlink at 17.7 to 20.2 GHz and uplink at 27.5 to 30.0 GHz, the focused optics and the unfocused optics configurations with monolithic phased array feeds have often been used to provide multiple fixed and multiple scanning spot beam coverages. It appears that a dual frequency microstrip antenna capable of transmitting and receiving simultaneously is highly desirable as an array feed element. This paper describes some early efforts on the development and experimental testing of a dual frequency annular microstrip antenna. The antenna has potential application for use in conjunction with a monolithic microwave integrated circuit device as an active radiating element in a phased array of phased array feeds. The antenna is designed to resonate at TM sub 12 and TM sub 13 modes and tuned with a circumferential microstrip ring to vary the frequency ratio. Radiation characteristics at both the high and low frequencies are examined. Experimental results including radiating patterns and swept frequency measurements are presented

Critical electrical aspects of alternating-current power source for Centaur space vehicle

Reliability of silicon rectifiers as inverters for alternating current power source for Atlas Centaur launch vehicle

Trends in antibiotic susceptibility patterns and epidemiology of MRSA isolates from several hospitals in Riyadh, Saudi Arabia

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA), is associated with high morbidity and mortality rates with rapid development of resistance. METHODS: A total of 512 MRSA isolates were procured from 6 major hospitals in Riyadh, Saudi Arabia and antibiotic susceptibilities and MICs were documented against several antibiotics and vancomycin. SPSS version 10 was used for statistical analysis. RESULTS: The prevalence of MRSA in the study hospitals ranged from 12% to 49.4%. Mean patient age was 44 years with males constituting 64.4% and females 35.6%. Approximately 41.5% of the isolates came from patients in the extreme age groups. MIC for vancomycin was in the susceptible range for all isolates ranging from 0.25 to 3 ug/ml. The overall susceptibility of MRSA to the various antibiotics tested was: fusidic acid 4.3%, sulfamethoxazole/trimethoprim 33.8%, gentamicin 39.6%, mupirocin 77.0%, gatifloxacin 78.9%, chloramphenicl 80.7%, linezolid 95.1%, quinupristin/dalfopristin 100%. Some differences were noted in the resistance of isolates among the participating hospitals reflecting antibiotic usage. On the whole, inpatient isolates (accounting for 77.5% of the isolates) were more resistant than outpatient isolates (22.5%) except for linezolid. Quinupristin-dalfopristin and linezolid are the most effective antibiotics tested against inpatient isolates while quinupristin-dalfopristin and gatifloxacin seem to be the most effective against outpatient isolates. Approximately one forth of the isolates are no longer susceptible to mupirocin used for eradication of the carrier state reflecting resistance developing after widespread use. Trends over time show a tendency towards decreased susceptibility to gatifloxacin and linezolid with increasing susceptibility to gentamicin and sulfamethoxazole/trimethoprim. CONCLUSION: Quinupristin/dalfopristin and linezolid are two valuable additions to our antimicrobial armamentarium, but resistance has already been described. To preserve their value, their use should be limited to those rare cases where they are clearly needed. Fusidic acid, the local antibiotic, gentamicin and trimethoprim/sulfamethoxazole should not be relied upon for treatment of MRSA infections, at least empirically as the percentage of susceptible isolates is very low

Sex-Specific Effects of a Wartime-Like Radiation Exposure on Cognitive Function.

Evaluating the risk for central nervous system (CNS) effects after whole-body or partial-body irradiation presents challenges due in part to the varied exposure scenarios in the context of occupational, accidental or wartime releases. Risk estimations are further complicated by the fact that robust changes in brain function are unlikely to manifest until significantly late post exposure times. Collectively, the current data regarding CNS radiation risk are conflicting in humans and a survey of the animal model data shows that it is similarly inconsistent. Due to the sparseness of such data, the current study was conducted using male and female mice to evaluate the brain for the delayed effects of a 2 Gy whole-body exposure to c rays starting six months postirradiation. Behavioral testing indicated sex-specific differences in the induction of anxiety-like behaviors and in the ability to abolish fear memories. Molecular analyses showed alterations in post-synaptic protein levels that might affect synaptic plasticity and increased levels of global DNA methylation, suggesting a potential epigenetic mechanism that might contribute to radiation-induced cognitive dysfunction. These data add to the understanding of the CNS response to whole-body irradiation and may lead to improved risk assessment and provide guidance in the development of effective radiation countermeasures to protect military personnel and civilians alike

COMBINED LOADING OF A WAVE AND SURFACE CURRENT ON A FIXED VERTICAL SLENDER CYLINDER

ABSTRACT A study on the loading of an oblique surface wave and a surface current field on a fixed vertical slender cylinder in a 3D flow frame is illustrated in the present paper. The three dimensional expressions describing the characteristics of the combined wave-current field in terms of mass, momentum and energy flux conservation equations are formulated. The parameters before the interaction of the oblique wave-free uniform current and current-free wave are used to formulate the kinematics of the flow field. These expressions are also employed to formulate and calculate the loads imparted by the wave-current fluid flow on a bottom mounted slender vertical cylinder. The surface current considered in this report, is assumed uniform and acting over a layer of fluid that extends from the free surface to a specified finite depth. Prior work assumes that uniform currents existed over the total depth of the fluid domain. In this paper we extend the approach considered in Zaman and Baddour (2004) for the wave-current analysis. Morison et al equation is deployed for the load computations in all cases. The above model is utilized to compute the loads on a slender cylinder for a wave with varying range of incidence current field. Computations of the moments are also done for the case when current is existed over the whole water depth of the domain. INTRODUCTION Fluid motion in the sea is a blend of wave and current of different forms. The coexistence of waves and currents and consequently their interaction play an essential role in most ocean dynamic processes and are important topics for ocean engineers and related scientists. In order to evaluate the performance of any ocean structure it is an important task for the designer to account for the effects resulting from the interaction of a combined wave-current field with any ocean structure. The computation of loads exerted by waves and currents is an important task in the study of the stability/integrity of any ocean structure. In the present formulation it is assumed that the flow fields are irrotational and inviscid. This allows the estimation of the flows characteristics needed in a Morison et al equation context. Velocity potentials are adopted to express the oblique flow fields in 3D for: (i) a wave field in the absence of current; (ii) a current field in the absence of wave and (iii) the wavecurrent combined field after the interaction of both a currentfree wave and a wave-free current. These three distinct flow fields are first introduced for collinear flows in For the computation of the parameters of the wave-current field, we have developed three-dimensional expressions describing the characteristics of the combined flow in terms of mass, momentum and energy transport conservation equations and the given before-interaction parameters of a wave-free uniform current and current-free wave. These equations are efficient in describing the combined wave-current field parameters. The relations obtained in satisfying the conservation of mass, momentum, energy flux and a dispersion relation generate a system of nonlinear equations that ar

Why are we seeing an increasing incidence of infective endocarditis in the UK?

The increasing incidence of infective endocarditis in England is real, and education is critical to ensure swift diagnosis and best clinical outcomes. Factors responsible remain speculative, but multiple explanations are likely

The cost-effectiveness of antibiotic prophylaxis for patients at risk of infective endocarditis

Background: In March 2008, the National Institute for Health and Care Excellence (NICE) recommended stopping antibiotic prophylaxis (AP) for those at risk of infective endocarditis (IE) undergoing dental procedures in the UK, citing a lack of evidence of efficacy and cost-effectiveness. We have performed a new economic-evaluation of AP based on contemporary estimates of efficacy, adverse events and resource implications. Methods: A decision analytic cost-effectiveness model was used. Health service costs and benefits (measured as Quality Adjusted Life Years, QALYs) were estimated. Rates of IE before and after the NICE guidance were available to estimate prophylactic efficacy. AP adverse event rates were derived from recent UK data and resource implications were based on English Hospital Episode Statistics. Results: AP was less costly and more effective than no AP for all patients at risk of IE. The results are sensitive to AP efficacy, but efficacy would have to be substantially lower for AP not to be costeffective. AP was even more cost-effective in patients at high-risk of IE. Only a marginal reduction in annual IE rates (1.44 cases in high-risk and 33 cases in all at-risk patients) would be required for AP to be considered cost-effective at £20,000 ($26,600) per QALY. Annual cost savings of £5.5-8.2m ($7.3-10.9m) and health gains >2,600 QALYs could be achieved from reinstating AP in England. Conclusions: AP is cost-effective for preventing IE, particularly in those at high-risk. These findings support the cost-effectiveness of guidelines recommending AP use in high-risk individuals

A Case of Scopulariopsis brevicaulis

Scopulariopsis is a genus of mold that is usually associated with onychomycosis and rarely causes complicated infection in immunocompetent persons. We describe a case of an immunocompetent 65-year-old male with a history of mitral valve repair with prosthetic ring placement who developed acute left posterior knee pain. Imaging showed a left popliteal artery aneurysm and thrombus, and further evaluation with transesophageal echocardiogram demonstrated two large, mobile mitral valve vegetations. He underwent debridement and replacement of the mitral valve, followed by debridement of the left popliteal artery with peroneal artery bypass. The intraoperative cultures grew Scopulariopsis brevicaulis. Due to the resistant nature of the organism, he was initially treated with combination antifungals including liposomal amphotericin B, caspofungin, and voriconazole and was continued on chronic suppression with posaconazole with no evidence of recurrence. Scopulariopsis is a rare cause of fungal endocarditis. Treatment of Scopulariopsis endocarditis is challenging and is not well understood due to its rarity

The role of statins in prevention and treatment of community acquired pneumonia: a systematic review and meta-analysis.

BACKGROUND: Emerging epidemiological evidence suggests that statins may reduce the risk of community-acquired pneumonia (CAP) and its complications. PURPOSE: Performed a systematic review to address the role of statins in the prevention or treatment of CAP. DATA SOURCE: Ovid MEDLINE, Cochrane, EMBASE, ISI Web of Science, and Scopus from inception through December 2011 were searched for randomized clinical trials, cohort and case-control studies. STUDY SELECTION: Two authors independently reviewed studies that examined the role of statins in CAP. DATA EXTRACTION: Data about study characteristics, adjusted effect-estimates and quality characteristics was extracted. DATA SYNTHESIS: Eighteen studies corresponding to 21 effect-estimates (eight and 13 of which addressed the preventive and therapeutic roles of statins, respectively) were included. All studies were of good methodological quality. Random-effects meta-analyses of adjusted effect-estimates were used. Statins were associated with a lower risk of CAP, 0.84 (95% CI, 0.74-0.95), I(2) = 90.5% and a lower short-term mortality in patients with CAP, 0.68 (95% CI, 0.59-0.78), I(2) = 75.7%. Meta-regression did not identify sources of heterogeneity. A funnel plot suggested publication bias in the treatment group, which was adjusted by a novel regression method with a resultant effect-estimate of 0.85 (95% CI, 0.77-0.93). Sensitivity analyses using the rule-out approach showed that it is unlikely that the results were due to an unmeasured confounder. CONCLUSIONS: Our meta-analysis reveals a beneficial role of statins for the risk of development and mortality associated with CAP. However, the results constitute very low quality evidence as per the GRADE framework due to observational study design, heterogeneity and publication bias