Conventional energy conversion architectures in photovoltaic (PV) systems are often forced to tradeoff conversion efficiency and power production. This paper introduces an energy conversion approach ...that enables each PV element to operate at its maximum power point (MPP) while processing only a small fraction of the total power produced. This is accomplished by providing only the mismatch in the MPP current of a set of series-connected PV elements. Differential power processing increases overall conversion efficiency and overcomes the challenges associated with unmatched MPPs (due to partial shading, damage, manufacturing tolerances, etc.). Several differential power processing architectures are analyzed and compared with Monte Carlo simulations. Local control of the differential converters enables distributed protection and monitoring. Reliability analysis shows significantly increased overall system reliability. Simulation and experimental results are included to demonstrate the benefits of this approach at both the panel and subpanel level.
Persons with subacromial impingement syndrome (SIS) have an imbalance in scapular muscle recruitment. To avoid humeral head compression against the coracoacromial arch during the early stages of ...rehabilitation, physical therapists recommend movements targeting scapular retraction, shoulder depression, and arm extension such as the inverted row (IR) exercise. The purposes of this study were to describe: (1) scapular balance ratios during an IR and (2) the magnitudes of recruitment of spinal stabilizer muscles. Scapular muscle balance ratios from 26 healthy participants were calculated from electromyographic (EMG) activity of the upper trapezius (UTP), lower trapezius (LTP), middle trapezius (MTP), serratus anterior (SA), posterior deltoid (PD), latissimus dorsi (LD), and biceps brachii (BB) during an IR on stable and unstable support surfaces. Balance ratios were obtained by dividing normalized EMG activity of the UTP by the normalized EMG values from each of the other six muscles. Four median scapular balance ratios (UTP/MTP, UTP/PD, UTP/LD, and UTP/BB) ranged from 0.9 to 2.2, whereas the UTP/LTP ratio ranged from 1.6 to 2.2 and the UTP/SA ratio ranged from 1 to 4.7. Activation of seven muscles promoted safe containment of the humeral head within the glenoid fossa during the IR in healthy persons and potentially people with the tendency for development of SIS. Four spinal stabilizer muscles were examined: longissimus thoracis (LT), multifidus (MF), rectus abdominis (RA), and external oblique (EO). Spinal stabilizer EMG activation values ranged from 34% to 40% maximum voluntary isometric contraction (MVIC) for the RA and EO and from 54% to 66% MVIC for the LT and MF.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, OILJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK, VSZLJ
Approaches based on organismal DNA found in the environment (eDNA) have become increasingly utilized for ecological studies and biodiversity inventories as an alternative to traditional field survey ...methods. Such DNA-based techniques have largely been used to establish the presence of free-living organisms, but have much potential for detecting and quantifying infectious agents in the environment, which is necessary to evaluate disease risk. We developed an eDNA method to examine the distribution and abundance of the trematode
Ribeiroia ondatrae
, a pathogenic parasite known to cause malformations in North American amphibians. In addition to comparing this eDNA approach to classical host necropsy, we examined the detectability of
R. ondatrae
in water samples subject to different degradation conditions (time and temperature). Our test exhibited high specificity and sensitivity to
R. ondatrae
, capable of detecting as little as 14 fg (femtograms) of this parasite's DNA (1/2500th of a single infectious stage) from field water samples. Compared to our results from amphibian host necropsy, quantitative PCR was ~90% concordant with respect to
R. ondatrae
detection from 15 field sites and was also a significant predictor of host infection abundance. DNA was still detectable in lab samples after 21 days at 25°C, indicating that our method is robust to field conditions. By comparing the advantages and disadvantages of eDNA vs. traditional survey methods for determining pathogen presence and abundance in the field, we found that the lower cost and effort associated with eDNA approaches provide many advantages. The development of alternative tools is critical for disease ecology, as wildlife management and conservation efforts require reliable establishment and monitoring of pathogens.
Growing interest in ecology has recently focused on the hypothesis that community diversity can mediate infection levels and disease ('dilution effect'). In turn, biodiversity loss--a widespread ...consequence of environmental change--can indirectly promote increases in disease, including those of medical and veterinary importance. While this work has focused primarily on correlational studies involving vector-borne microparasite diseases (e.g. Lyme disease, West Nile virus), we argue that parasites with complex life cycles (e.g. helminths, protists, myxosporeans and many fungi) offer an excellent additional model in which to experimentally address mechanistic questions underlying the dilution effect. Here, we unite recent ecological research on the dilution effect in microparasites with decades of parasitological research on the decoy effect in macroparasites to explore key questions surrounding the relationship between community structure and disease. We find consistent evidence that community diversity significantly alters parasite transmission and pathology under laboratory as well as natural conditions. Empirical examples and simple transmission models highlight the diversity of mechanisms through which such changes occur, typically involving predators, parasite decoys, low competency hosts or other parasites. However, the degree of transmission reduction varies among diluting species, parasite stage, and across spatial scales, challenging efforts to make quantitative, taxon-specific predictions about disease. Taken together, this synthesis highlights the broad link between community structure and disease while underscoring the importance of mitigating ongoing changes in biological communities owing to species introductions and extirpations.
We report a measurement of the positive muon lifetime to a precision of 1.0 ppm; it is the most precise particle lifetime ever measured. The experiment used a time-structured, low-energy muon beam ...and a segmented plastic scintillator array to record more than 2×10(12) decays. Two different stopping target configurations were employed in independent data-taking periods. The combined results give τ(μ(+)) (MuLan)=2 196 980.3(2.2) ps, more than 15 times as precise as any previous experiment. The muon lifetime gives the most precise value for the Fermi constant: G(F) (MuLan)=1.166 378 8(7)×10(-5) GeV(-2) (0.6 ppm). It is also used to extract the μ(-)p singlet capture rate, which determines the proton's weak induced pseudoscalar coupling g(P).
Synthetic MR imaging enables reconstruction of various image contrasts from 1 scan, reducing scan times and potentially providing novel information. This study is the first large, prospective ...comparison of synthetic-versus-conventional MR imaging for routine neuroimaging.
A prospective multireader, multicase noninferiority trial of 1526 images read by 7 blinded neuroradiologists was performed with prospectively acquired synthetic and conventional brain MR imaging case-control pairs from 109 subjects (mean, 53.0 ± 18.5 years of age; range, 19-89 years of age) with neuroimaging indications. Each case included conventional T1- and T2-weighted, T1 and T2 FLAIR, and STIR and/or proton density and synthetic reconstructions from multiple-dynamic multiple-echo imaging. Images were randomized and independently assessed for diagnostic quality, morphologic legibility, radiologic findings indicative of diagnosis, and artifacts.
Clinical MR imaging studies revealed 46 healthy and 63 pathologic cases. Overall diagnostic quality of synthetic MR images was noninferior to conventional imaging on a 5-level Likert scale (
< .001; mean synthetic-conventional, -0.335 ± 0.352; Δ = 0.5; lower limit of the 95% CI, -0.402). Legibility of synthetic and conventional morphology agreed in >95%, except in the posterior limb of the internal capsule for T1, T1 FLAIR, and proton-density views (all, >80%). Synthetic T2 FLAIR had more pronounced artifacts, including +24.1% of cases with flow artifacts and +17.6% cases with white noise artifacts.
Overall synthetic MR imaging quality was similar to that of conventional proton-density, STIR, and T1- and T2-weighted contrast views across neurologic conditions. While artifacts were more common in synthetic T2 FLAIR, these were readily recognizable and did not mimic pathology but could necessitate additional conventional T2 FLAIR to confirm the diagnosis.
Cosmic-ray electrons and positrons (CREs) at GeV-TeV energies are a unique probe of our local Galactic neighborhood. CREs lose energy rapidly via synchrotron radiation and inverse-Compton scattering ...processes while propagating within the Galaxy, and these losses limit their propagation distance. For electrons with TeV energies, the limit is on the order of a kiloparsec. Within that distance, there are only a few known astrophysical objects capable of accelerating electrons to such high energies. It is also possible that the CREs are the products of the annihilation or decay of heavy dark matter (DM) particles. VERITAS, an array of imaging air Cherenkov telescopes in southern Arizona, is primarily utilized for gamma-ray astronomy but also simultaneously collects CREs during all observations. We describe our methods of identifying CREs in VERITAS data and present an energy spectrum, extending from 300 GeV to 5 TeV, obtained from approximately 300 hours of observations. A single power-law fit is ruled out in VERITAS data. We find that the spectrum of CREs is consistent with a broken power law, with a break energy at 710±40stat±140syst GeV.
Brivanib is a dual inhibitor of vascular-endothelial growth factor and fibroblast growth factor receptors that are implicated in the pathogenesis of hepatocellular carcinoma (HCC). Our multinational, ...randomized, double-blind, phase III trial compared brivanib with sorafenib as first-line treatment for HCC.
Advanced HCC patients who had no prior systemic therapy were randomly assigned (ratio, 1:1) to receive sorafenib 400 mg twice daily orally (n = 578) or brivanib 800 mg once daily orally (n = 577). Primary end point was overall survival (OS). Secondary end points included time to progression (TTP), objective response rate (ORR), disease control rate (DCR) based on modified Response Evaluation Criteria in Solid Tumors (mRECIST), and safety.
The primary end point of OS noninferiority for brivanib versus sorafenib in the per-protocol population (n = 1,150) was not met (hazard ratio HR, 1.06; 95.8% CI, 0.93 to 1.22), based on the prespecified margin (upper CI limit for HR ≤ 1.08). Median OS was 9.9 months for sorafenib and 9.5 months for brivanib. TTP, ORR, and DCR were similar between the study arms. Most frequent grade 3/4 adverse events for sorafenib and brivanib were hyponatremia (9% and 23%, respectively), AST elevation (17% and 14%), fatigue (7% and 15%), hand-foot-skin reaction (15% and 2%), and hypertension (5% and 13%). Discontinuation as a result of adverse events was 33% for sorafenib and 43% for brivanib; rates for dose reduction were 50% and 49%, respectively.
Our study did not meet its primary end point of OS noninferiority for brivanib versus sorafenib. However, both agents had similar antitumor activity, based on secondary efficacy end points. Brivanib had an acceptable safety profile, but was less well-tolerated than sorafenib.
A method to synchronize and control a system of parallel single-phase inverters without communication is presented. Inspired by the phenomenon of synchronization in networks of coupled oscillators, ...we propose that each inverter be controlled to emulate the dynamics of a nonlinear dead-zone oscillator. As a consequence of the electrical coupling between inverters, they synchronize and share the load in proportion to their ratings. We outline a sufficient condition for global asymptotic synchronization and formulate a methodology for controller design such that the inverter terminal voltages oscillate at the desired frequency, and the load voltage is maintained within prescribed bounds. We also introduce a technique to facilitate the seamless addition of inverters controlled with the proposed approach into an energized system. Experimental results for a system of three inverters demonstrate power sharing in proportion to power ratings for both linear and nonlinear loads.
Genomic sequencing is essential to track the evolution and spread of SARS-CoV-2, optimize molecular tests, treatments, vaccines, and guide public health responses. To investigate the global ...SARS-CoV-2 genomic surveillance, we used sequences shared via GISAID to estimate the impact of sequencing intensity and turnaround times on variant detection in 189 countries. In the first two years of the pandemic, 78% of high-income countries sequenced >0.5% of their COVID-19 cases, while 42% of low- and middle-income countries reached that mark. Around 25% of the genomes from high income countries were submitted within 21 days, a pattern observed in 5% of the genomes from low- and middle-income countries. We found that sequencing around 0.5% of the cases, with a turnaround time <21 days, could provide a benchmark for SARS-CoV-2 genomic surveillance. Socioeconomic inequalities undermine the global pandemic preparedness, and efforts must be made to support low- and middle-income countries improve their local sequencing capacity.
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