7,272 research outputs found

    Associated production of a single heavy T-quark in the littlest and simplest little Higgs models

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    The colored SU(2)-singlet heavy T-quark is one of the most crucial ingredients in little Higgs models, which is introduced to cancel the largest contribution of the SM top quark to the Higgs boson mass at one-loop level. In two representative little Higgs models, the littlest Higgs model and the SU(3) simplest Higgs model, we comprehensively study the single heavy T-quark production at Large Hadron Collider (LHC). After presenting the possibility of relatively light (~500 GeV) T-quark in the simplest little Higgs model, we consider all the relevant processes, the 2->2 process of qb->q'T, the 2->3 process of qg->q'Tb, the s-channel process of q bar(q)'->T bar{b}, and the gluon fusion process of gg->T bar{t}. We found that the 2->3 process can be quite important, as its cross section is about 30% of the 2->2 one and it is dominant in high p_T distributions. The s-channel and the gluon fusion processes also show distinctive features in spite of their suppressed cross sections. In the gluon fusion process of the simplest little Higgs model, for example, the pseudo-scalar contribution is rather dominant over the Higgs contribution for relatively light M_T.Comment: 27 pages, using RevTeX; references adde

    Moving boundary and photoelastic coupling in GaAs optomechanical resonators

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    Chip-based cavity optomechanical systems are being considered for applications in sensing, metrology, and quantum information science. Critical to their development is an understanding of how the optical and mechanical modes interact, quantified by the coupling rate g0g_{0}. Here, we develop GaAs optomechanical resonators and investigate the moving dielectric boundary and photoelastic contributions to g0g_{0}. First, we consider coupling between the fundamental radial breathing mechanical mode and a 1550 nm band optical whispering gallery mode in microdisks. For decreasing disk radius from R=5R=5 μ\mum to R=1R=1 μ\mum, simulations and measurements show that g0g_{0} changes from being dominated by the moving boundary contribution to having an equal photoelastic contribution. Next, we design and demonstrate nanobeam optomechanical crystals in which a 2.52.5 GHz mechanical breathing mode couples to a 1550 nm optical mode predominantly through the photoelastic effect. We show a significant (30 %\%) dependence of g0g_{0} on the device's in-plane orientation, resulting from the difference in GaAs photoelastic coefficients along different crystalline axes, with fabricated devices exhibiting g0/2πg_{\text{0}}/2\pi as high as 1.1 MHz for orientation along the [110] axis. GaAs nanobeam optomechanical crystals are a promising system which can combine the demonstrated large optomechanical coupling strength with additional functionality, such as piezoelectric actuation and incorporation of optical gain media

    Mice as an Animal Model for Japanese Encephalitis Virus Research: Mouse Susceptibility, Infection Route, and Viral Pathogenesis

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    Japanese encephalitis virus (JEV), a zoonotic flavivirus, is principally transmitted by hematophagous mosquitoes, continually between susceptible animals and incidentally from those animals to humans. For almost a century since its discovery, JEV was geographically confined to the Asia-Pacific region with recurrent sizable outbreaks involving wildlife, livestock, and people. However, over the past decade, it has been detected for the first time in Europe (Italy) and Africa (Angola) but has yet to cause any recognizable outbreaks in humans. JEV infection leads to a broad spectrum of clinical outcomes, ranging from asymptomatic conditions to self-limiting febrile illnesses to life-threatening neurological complications, particularly Japanese encephalitis (JE). No clinically proven antiviral drugs are available to treat the development and progression of JE. There are, however, several live and killed vaccines that have been commercialized to prevent the infection and transmission of JEV, yet this virus remains the main cause of acute encephalitis syndrome with high morbidity and mortality among children in the endemic regions. Therefore, significant research efforts have been directed toward understanding the neuropathogenesis of JE to facilitate the development of effective treatments for the disease. Thus far, multiple laboratory animal models have been established for the study of JEV infection. In this review, we focus on mice, the most extensively used animal model for JEV research, and summarize the major findings on mouse susceptibility, infection route, and viral pathogenesis reported in the past and present, and discuss some unanswered key questions for future studies

    Effect of oxygen minimum zone formation on communities of marine protists

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    Author Posting. © The Author(s), 2012. This is the author's version of the work. It is posted here by permission of Nature Publishing Group for personal use, not for redistribution. The definitive version was published in The ISME Journal 6 (2012): 1586–1601, doi:10.1038/ismej.2012.7.Changes in ocean temperature and circulation patterns compounded by human activities are leading to oxygen minimum zone expansion with concomitant alteration in nutrient and climate active trace gas cycling. Here, we report the response of microbial eukaryote populations to seasonal changes in water column oxygen-deficiency using Saanich Inlet, a seasonally anoxic fjord on the coast of Vancouver Island British Columbia, as a model ecosystem. We combine small subunit ribosomal RNA gene sequencing approaches with multivariate statistical methods to reveal shifts in operational taxonomic units during successive stages of seasonal stratification and renewal. A meta-analysis is used to identify common and unique patterns of community composition between Saanich Inlet and the anoxic/sulfidic Cariaco Basin (Venezuela) and Framvaren Fjord (Norway) to show shared and unique responses of microbial eukaryotes to oxygen and sulfide in these three environments. Our analyses also reveal temporal fluctuations in rare populations of microbial eukaryotes, particularly anaerobic ciliates, that may be of significant importance to the biogeochemical cycling of methane in oxygen minimum zones.This work was performed under the auspices of the US Department of Energy's Office of Science, Biological and Environmental Research Program, and by the University of California, Lawrence Berkeley National Laboratory, Lawrence Livermore National Laboratory under Contract No., and Los Alamos National Laboratory (Contract No. DE-AC02-05CH11231, DE-AC52-07NA27344, DE-AC02-06NA25396), the Natural Sciences and Engineering Research Council (NSERC) of Canada 328256-07 and STPSC 356988, Canada Foundation for Innovation (CFI) 17444; Canadian Institute for Advanced Research (CIFAR), NSF MCB-0348407 to VE, NSF Center for Deep Energy Biosphere Investigations, and the Center for Bioinorganic Chemistry (CEBIC).2012-09-0

    Generation of Polyclonal Rabbit Antisera Specific to the Zika Virus Capsid Protein

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    Zika virus (ZIKV), a mosquito-borne flavivirus, is an emerging zoonotic pathogen closely related to Japanese encephalitis virus, West Nile virus, dengue virus, and yellow fever virus. Although ZIKV infection generally produces only mild symptoms in some infected individuals, it has recently been associated with a growing number of neurological diseases, including Guillain-Barré syndrome in ZIKV-infected adults and microcephaly in infants born to ZIKV-infected women. Like all flaviviruses, ZIKV has a plus-strand RNA genome encoding ten functional proteins (designated C, prM, E, NS1, NS2A, NS2B, NS3, NS4A, NS4B, and NS5). Of these ten, the C (capsid) protein is an essential structural protein required for the formation of infectious viral particles. In order to produce the antiserum specifically recognizing the ZIKV C protein in this study, we expressed and purified the ZIKV C protein as a glutathione-S-transferase (GST) fusion protein in E. coli. The ZIKV C protein-coding region was PCR-amplified using the genomic RNA of ZIKV PRVABC-59, and the amplicons were cloned into the pGEX-4T-1 E. coli expression vector. GST-C fusion proteins were purified using a glutathione sepharose column. Subsequently, the GST-C fusion proteins were used for immunization with rabbits. Western blot analysis using the ZIKV-infected Vero cell lysates were performed to examine the reactivity of the antisera to the ZIKV C protein. Thus, this study provides a useful reagent for the diagnosis and understanding of the viral morphogenesis in the ZIKV-infected cells

    Low Intensity Resistance Exercise Training with Blood Flow Restriction: Insight into Cardiovascular Function, and Skeletal Muscle Hypertrophy in Humans

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    Attenuated functional exercise capacity in elderly and diseased populations is a common problem, and stems primarily from physical inactivity. Decreased function and exercise capacity can be restored by maintaining muscular strength and mass, which are key factors in an independent and healthy life. Resistance exercise has been used to prevent muscle loss and improve muscular strength and mass. However, the intensities necessary for traditional resistance training to increase muscular strength and mass may be contraindicated for some at risk populations, such as diseased populations and the elderly. Therefore, an alternative exercise modality is required. Recently, blood flow restriction (BFR) with low intensity resistance exercise (LIRE) has been used for such special populations to improve their function and exercise capacity. Although BFR+LIRE has been intensively studied for a decade, a comprehensive review detailing the effects of BFR+LIRE on both skeletal muscle and vascular function is not available. Therefore, the purpose of this review is to discuss previous studies documenting the effects of BFR+LIRE on hormonal and transcriptional factors in muscle hypertrophy and vascular function, including changes in hemodynamics, and endothelial function

    Genetic Elements Involved in Zika Virus Neuropathogenesis

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    Zikavirus (ZIKV) is a mosquito-borne flavivirus(Fig. 1) that is closely related to Japanese encephalitis, West Nile, yellow fever, and dengue viruses. ZIKV was first discovered in Uganda in 1947, but it was not until recent outbreaks, such as through Micronesia in 2007 and through Brazil in 2015 (Fig. 2), that it has been found to be associated with neurological diseases such as Guillain-Barrésyndrome and microcephaly

    Variability of extracorporeal cardiopulmonary resuscitation utilization for refractory adult out-of-hospital cardiac arrest: an international survey study.

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    Objective: A growing interest in extracorporeal cardiopulmonary resuscitation (ECPR) as a rescue strategy for refractory adult out-of-hospital cardiac arrest (OHCA) currently exists. This study aims to determine current standards of care and practice variation for ECPR patients in the USA and Korea. Methods: In December 2015, we surveyed centers from the Korean Hypothermia Network (KORHN) Investigators and the US National Post-Arrest Research Consortium (NPARC) on current targeted temperature management and ECPR practices. This project analyzes the subsection of questions addressing ECPR practices. We summarized survey. Results: Overall, 9 KORHN and 4 NPARC centers reported having ECPR programs and had complete survey data available. Two KORHN centers utilized extracorporeal membrane oxygenation only for postarrest circulatory support in patients with refractory shock and were excluded from further analysis. Centers with available ECPR generally saw a high volume of OHCA patients (10/11 centers care for \u3e75 OHCA a year). Location of, and providers trained for cannulation varied across centers. All centers in both countries (KORHN 7/7, NPARC 4/4) treated comatose ECPR patients with targeted temperature management. All NPARC centers and four of seven KORHN centers reported having a standardized hospital protocol for ECPR. Upper age cutoff for eligibility ranged from 60 to 75 years. No absolute contraindications were unanimous among centers. Conclusion: A wide variability in practice patterns exist between centers performing ECPR for refractory OHCA in the US and Korea. Standardized protocols and shared research databases might inform best practices, improve outcomes, and provide a foundation for prospective studies

    Large Extra Dimension Effects on the Spin Configuration of the Top Quark Pair at e^+ e^- Colliders

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    Large extra dimension effects on the spin configuration of the top quark pair at the e+ettˉe^+ e^-\to t\bar{t} process are studied. It is shown that the TeV scale quantum gravity effects cause significant deviations from the Standard Model predictions for the spin configuration in the off-diagonal basis: they lead to substantial cross sections of the like-spin states of the top quark pair, which vanish in the SM; they weaken the pure dominance of the processes, the Up-Down (Down-Up) spin states for the left-handed (right-handed) beam. In addition it is shown that the angular cut 0.5<cosθ<0-0.5<\cos\theta<0 is very effective to determine the sign of the quantum gravity corrections.Comment: A discussion on the angular distribution is added with a tabl

    Variabilities and uncertainties in characterising water transport kinetics in glassy and ultraviscous aerosol

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    A comprehensive assessment of the accuracy with which water transport in viscous aerosol can be measured and predicted is provided.</p
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