1,099 research outputs found

    Quartic Gauge Boson Couplings and Tree Unitarity in the SU(3)_C X SU(3)_L X U(1)_N Models

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    The quartic gauge boson couplings in the SU(3)C⊗SU(3)L⊗U(1)N{SU(3)}_C \otimes {SU(3)}_L \otimes {U(1)}_N models are presented. We find that the couplings of four {\it differrent} gauge bosons may have unusual Lorentz structure and the couplings sastify the tree unitarity requirement at high energy limit.Comment: 13 pages, Latex, axodraw.st

    Exchange bias effect in Au-Fe3O4 nanocomposites

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    We report exchange bias (EB) effect in the Au-Fe3O4 composite nanoparticle system, where one or more Fe3O4 nanoparticles are attached to an Au seed particle forming 'dimer' and 'cluster' morphologies, with the clusters showing much stronger EB in comparison with the dimers. The EB effect develops due to the presence of stress at the Au-Fe3O4 interface which leads to the generation of highly disordered, anisotropic surface spins in the Fe3O4 particle. The EB effect is lost with the removal of the interfacial stress. Our atomistic Monte Carlo studies are in excellent agreement with the experimental results. These results show a new path towards tuning EB in nanostructures, namely controllably creating interfacial stress, and opens up the possibility of tuning the anisotropic properties of biocompatible nanoparticles via a controllable exchange coupling mechanism

    Density functional theory calculations of the carbon ELNES of small diameter armchair and zigzag nanotubes: core-hole, curvature and momentum transfer orientation effects

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    We perform density functional theory calculations on a series of armchair and zigzag nanotubes of diameters less than 1nm using the all-electron Full-Potential(-Linearised)-Augmented-Plane-Wave (FPLAPW) method. Emphasis is laid on the effects of curvature, the electron beam orientation and the inclusion of the core-hole on the carbon electron energy loss K-edge. The electron energy loss near-edge spectra of all the studied tubes show strong curvature effects compared to that of flat graphene. The curvature induced π−σ\pi-\sigma hybridisation is shown to have a more drastic effect on the electronic properties of zigzag tubes than on those of armchair tubes. We show that the core-hole effect must be accounted for in order to correctly reproduce electron energy loss measurements. We also find that, the energy loss near edge spectra of these carbon systems are dominantly dipole selected and that they can be expressed simply as a proportionality with the local momentum projected density of states, thus portraying the weak energy dependence of the transition matrix elements. Compared to graphite, the ELNES of carbon nanotubes show a reduced anisotropy.Comment: 25 pages, 15 figures, revtex4 submitted for publication to Phys. Rev.

    Unconventional anomalous Hall effect in 3d/5d multilayers mediated by the nonlocal spin-conductivity

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    We evidenced unconventionnal Anomalous Hall Effects (AHE) in 3d/5d (Co0.2nm/Ni0.6nm)N multilayers grown on a thin Pt layer or thin Au:W alloy. The inversion observed on AHE originates from the opposite sign of the spin-orbit coupling of Pt compared to Ni. Via advanced simulations methods for the description of the spin-current profiles based on the spin-dependent Boltzmann formalism, we extracted the spin Hall angle (SHA) of Pt and (Co/Ni) as well as the relevant transport parameters. The extracted SHA for Pt, +20%, is opposite to the one of (Co/Ni), giving rise to an effective AHE inversion for thin (Co/Ni) multilayers (N < 17). The spin Hall angle in Pt is found to be larger than the one previously measured in combined spin-pumping inverse spin-Hall effect experiments in a geometry of current perpendicular to plane. Whereas magnetic proximity effects cannot explain the effect, spin-current leakage and anisotropic electron scattering at Pt/(Co,Ni) interfaces fit the experiments.Comment: 7 pages, 2 figure

    Bilepton contributions to the neutrinoless double beta decay in the economical 3-3-1 model

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    Possible contributions of the bilepton to the neutrinoless double beta (ββ)0ν(\beta\beta)_{0\nu} decay in the economical 3-3-1 model are discussed. We show that the (ββ)0ν(\beta\beta)_{0\nu} decay in this model is due to both sources--Majorana L_{L} and Dirac D_{D} neutrino masses. If the mixing angle between charged gauge bosons, the standard model WW and bilepton YY, is in range of the ratio of neutrino masses L/<Mν>D_{L}/< M_{\nu}>_{D}, both the Majorana and Dirac masses simultaneously give contributions dominant to the decay. As results, constraints on the bilepton mass are also given.Comment: 9 pages, 6 figure

    Asymptomatic giant coronary aneurysm in an adolescent with Behcet's syndrome

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    <p>Abstract</p> <p>Objective</p> <p>Behcet's is an idiopathic multi-organ syndrome, which may have onset during childhood. Vascular involvement is uncommon, with rarely reported coronary aneurysm formation. We present a case report of a teenager girl who developed recalcitrant life-threatening Behcet's vasculitis, involving both small and large venous and arterial systems including a giant coronary aneurysm.</p> <p>Case report</p> <p>De-identified data were collected retrospectively in case report format. Although our sixteen year old female with Behcet's vasculitis had resolution of many arterial aneurysms, she had persistent venous thrombosis of large vessels, as well as persistent, giant arterial aneurysms requiring intra-arterial coiling of a lumbar artery and coronary bypass grafting despite intensive immunosuppression including glucocorticoids, cyclophosphamide, infliximab, methotrexate, azathioprine and intravenous immunoglobulin.</p> <p>Conclusions</p> <p>Vascular manifestations may be seen in Behcet's syndrome, including asymptomatic coronary aneurysm, which may be refractory to immunosuppression and ultimately require surgical intervention. Increased awareness is essential for prompt diagnosis and management.</p

    Epidemiologic application of verbal autopsy to investigate the high occurrence of cancer along Huai River Basin, China

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    <p>Abstract</p> <p>Background</p> <p>In 2004, the media repeatedly reported water pollution and "cancer villages" along the Huai River in China. Due to the lack of death records for more than 30 years, a retrospective survey of causes of death using verbal autopsy was carried out to investigate cancer rates in this area.</p> <p>Methods</p> <p>An epidemiologic study was designed to compare numbers of deaths and causes of death between the study areas with water pollution and the control areas without water pollution in S County and Y District in 2005. The study areas were selected based on the distribution of the Huai River and its tributaries. Verbal autopsy was used to assist cause of death (COD) diagnoses and to verify mortality rates. The standard mortality rates (SMRs) of cancer in the study area were compared with those in the control areas. In order to verify the difference between mortality rates due to cancers in the study and the control areas, patients who reported having cancer in the survey received a second diagnosis by national and provincial oncologists with pathological and laboratory examinations. Comparisons were made to determine if differential cancer prevalence rates in the study and control areas were similar to the difference in mortality due to cancer in these study and control areas. Mortality rates of cancers in study and control areas were also compared with national statistics for the rural population of China.</p> <p>Results</p> <p>Over five years, 3,301 deaths were identified, including 1,158 cancer deaths. The annual average SMRs of cancer in the study areas of S County and Y District were 277.8/100,000 and 223.6/100,000, respectively, which is three to four times higher than those in the control areas. In addition, a total of 626 cases of cancer in the study and control areas were confirmed. The prevalence rates of cancer were 545/100,000 and 128.1/100,000 per year in the study and control areas in S County, respectively, and 440.9/100,000 and 200/100,000 per year in the study and control areas in Y District, respectively. The mortality and prevalence rates of digestive cancers were higher in the study areas than the control areas. In 2000, the SMR for cancer in rural areas nationwide was 120.9/100,000, and in study areas in S County and Y District, the excess rates of deaths were 184/100,000 and 138.8/100,000, respectively.</p> <p>Conclusions</p> <p>The death rates of digestive cancers were much higher in the study areas of S County and Y District. The patterns for between-area differences in prevalence and mortality rates of cancer were similar. Verbal autopsy is shown to be a useful tool in retrospective mortality surveys in low-resource areas with limited access to health care.</p

    Rapid integrated assessment of food safety and nutrition related to pork consumption of regular consumers and mothers with young children in Vietnam

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    Pork is the most common and widely consumed meat product in Vietnam. The study aimed to assess nutrition and food safety risks and opportunities associated with pork value chains in Vietnam. Twenty-nine focus group discussions (FGD) were conducted in Hung Yen and Nghe An provinces with 164 participants who were both regular pork consumers and mothers with young children. In each province, three districts were selected, and in each district we selected one commune. To assess the quality of pork, we took 30 swab samples of pig carcasses at slaughterhouses, 90 pork samples at slaughterhouses and markets and analysed all samples for total bacterial count (TBC), coliforms, water holding capacity and pH. The results showed that pork was the main livestock product consumed and women are responsible for buying and preparing food for daily meals. Pork was the main animal sourced food (ASF) for Vietnamese consumers, for 50–60% of ASF. There was little knowledge of zoonotic diseases. The findings suggest further studies to address consumers’ concern on chemical contamination. Most market pork samples were not within the allowable range of limits standards of Vietnam for bacterial contamination: 90% of samples were above the official permissible limit for TBC and 98% did not meet standards for coliforms. Fifty percent of samples had acceptable pH but only 5% had acceptable water holding capacity. There were no significant differences in pork quality between intensifying Hung Yen and traditional Nghe An provinces, although there was a tendency for samples from Hung Yen to have better compliance. This rapid assessment revealed considerable interest and knowledge on pork nutrition and safety and found some behavioural but few quality and safety differences between traditional and intensifying systems. This indicated marketed pork is of low quality and safety, and a lack of support to consumers in making good choices
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