7,697 research outputs found

    K^0-\bar{K}^0 mixing in the Standard Model from Nf=2+1+1 Twisted Mass Lattice QCD

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    We present preliminary results at {\beta} = 1.95 (a = 0.077 fm) on the first unquenched N_f=2+1+1 lattice computation of the B_K parameter which controls the neutral kaon oscillations in the Standard Model. Using N_f=2+1+1 maximally twisted sea quarks and Osterwalder-Seiler valence quarks we achieve O(a) improvement and a continuum-like renormalization pattern for the four-fermion operator. Our results are extrapolated/interpolated to the physical light/strange quark mass but not yet to the continuum limit. The computation of the relevant renormalization constants is performed non perturbatively in the RI'-MOM scheme using dedicated simulations with N_f=4 degenerate sea quark flavours produced by the ETM collaboration. We get B_K^{RGI} (a = 0.077) = 0.747(18), which when compared to our previous unquenched N_f=2 determination and most of the existing results, suggests a rather weak B_K^{RGI} dependence on the number of dynamical flavours. We are at the moment analysing lattice data at two additional {\beta} values which will allow us to perform an extrapolation to the continuum limit.Comment: 7 pages, 8 figures, Proceedings of Lattice 2011, XXIX International Symposium on Lattice Field Theory, Squaw Valley, Lake Tahoe, Californi

    K^0-\bar{K}^0 Mixing Beyond the SM from Nf=2 tmQCD

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    We present preliminary results on the of neutral kaon oscillations in extensions of the Standard Model. Using Nf=2 maximally twisted sea quarks and Osterwalder-Seiler valence quarks, we achieve both O(a)-improvement and continuum-like renormalization pattern for the relevant four-fermion operators. We perform simulations at three values of the lattice spacing and extrapolate/interpolate our results to the continuum limit and physical light/strange quark mass. The calculation of the renormalization constants of the complete operator basis is performed non- perturbatively in the RI-MOM scheme.Comment: 7 pages, 2 figures; presented at the XXVIII International Symposium on Lattice Field Theory Villasimius, Sardinia, Ital

    Kaon oscillations in the Standard Model and Beyond using Nf=2 dynamical quarks

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    We compute non-perturbatively the B-parameters of the complete basis of four-fermion operators needed to study the Kaon oscillations in the SM and in its supersymmetric extension. We perform numerical simulations with two dynamical maximally twisted sea quarks at three values of the lattice spacing on configurations generated by the ETMC. Unwanted operator mixings and O(a) discretization effects are removed by discretizing the valence quarks with a suitable Osterwalder-Seiler variant of the Twisted Mass action. Operators are renormalized non-perturbatively in the RI/MOM scheme. Our preliminary result for BK(RGI) is 0.73(3)(3).Comment: 7 pages, 3 figures, 1 table, proceedings of the XXVII Int'l Symposyum on Lattice Field Theory (LAT2009), July 26-31 2009, Peking University, Beijing (China

    Precision scans of the pixel cell response of double sided 3D pixel detectors to pion and x-ray beams

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    hree-dimensional (3D) silicon sensors offer potential advantages over standard planar sensors for radiation hardness in future high energy physics experiments and reduced charge-sharing for X-ray applications, but may introduce inefficiencies due to the columnar electrodes. These inefficiencies are probed by studying variations in response across a unit pixel cell in a 55μm pitch double-sided 3D pixel sensor bump bonded to TimePix and Medipix2 readout ASICs. Two complementary characterisation techniques are discussed: the first uses a custom built telescope and a 120GeV pion beam from the Super Proton Synchrotron (SPS) at CERN; the second employs a novel technique to illuminate the sensor with a micro-focused synchrotron X-ray beam at the Diamond Light Source, UK. For a pion beam incident perpendicular to the sensor plane an overall pixel efficiency of 93.0±0.5% is measured. After a 10o rotation of the device the effect of the columnar region becomes negligible and the overall efficiency rises to 99.8±0.5%. The double-sided 3D sensor shows significantly reduced charge sharing to neighbouring pixels compared to the planar device. The charge sharing results obtained from the X-ray beam study of the 3D sensor are shown to agree with a simple simulation in which charge diffusion is neglected. The devices tested are found to be compatible with having a region in which no charge is collected centred on the electrode columns and of radius 7.6±0.6μm. Charge collection above and below the columnar electrodes in the double-sided 3D sensor is observed

    Energy Demand in Sugarcane Residue Collection and Transportation

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    Sugarcane production system is in transition, mainly due to its harvesting process. Harvest through burning has been gradually replaced by mechanized processes, providing another by-product to be explored: sugarcane trash. In Brazil, through of the sugarcane trash, São Paulo state itself produces around 210.4 million BOE – barrel of oil equivalent (1,251,952 TJ ), which could supply consumers through cogeneration or for further second generation ethanol. For the sugarcane trash to be collected, mechanized processes are required, such as windrowing, gathering, and transporting. In agricultural production systems, embodied energy is affected by the mechanization level. In order to assess environmental performance by the energy point-of-view, analysis of energy flows provides subsidies for the decision makers. Thus, this study aimed to determine the material and energy flows for sugarcane trash collection and to identify its critical steps. The sugarcane variety grown was RB855113, spaced between rows 1.4 m, in the second cut, and yield of 108 Mg ha-1. The following mechanized operations were evaluated: windrowing, gathering, and transport, using material and energy flow as supporting tools. Regarding the energy balance, sugarcane trash collection system is feasible. Among evaluated operations, gathering is the one that presented higher energy demand. Fuel in harvesting is the main factor that affects energy demand for having sugarcane trash available.   Keywords: material flow, mechanized harvest, bioenergy, biofue

    Optimal cutoff-value of Siemens cardiac troponin I assay in patients with kidney disease for the early diagnosis of acute myocardial infarction

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    Purpose: The recent introduction of more sensitive cardiac troponin (cTn) assays improved the early diagnosis of acute myocardial infarction (AMI). However, its diagnostic utility has never been tested in patients with kidney disease (KD), who are known to have elevated levels of cTn already in the absence of AMI, which may lead to a lower diagnostic value of more sensitive cTn in this high-risk subgroup. Methods: We conducted an international multicenter study to examine the diagnostic accuracy of the Siemens cTnI Ultra assay in 1997 consecutive patients presenting to the emergency department with symptoms suggestive of AMI, of whom 343 (17%) were determined to have KD (MDRD GFR <60ml/min/1.73m2) and to derive the optimal cutoff-value for the diagnosis of AMI in patients with KD. The diagnostic accuracy was further compared to a conventional cTn assay (Roche Troponin T fourth generation). The final diagnosis was adjudicated by two independent cardiologists based on hs-cTnT. Results: AMI was the final diagnosis in 35% (n=120) of all KD-patients as compared to 18% in patients with normal kidney function (p<0.001). Among KD-patients with other diagnoses than AMI, baseline hs-cTnI-levels were elevated above the 99thpercentile in 20%, In patients with KD the diagnostic accuracy at presentation, quantified by the area under the receiver-operator-characteristic curve (AUC), was significantly greater for Siemens cTnI as compared to the standard cTnT assay (AUC for cTnI, 0.88 vs. AUC for the standard assay, 0.82, p=0.013). In patients presenting within three hours after the onset of chest pain, the superiority of Siemens cTnI over conventional cTnT was even more pronounced (AUC 0.86 vs. 0.72, p=0.005). In KD, the optimal hs-cTnI cutoff derived from the ROC curve was 46 ng/l compared to 19 ng/l in patients with normal kidney function (standard 99th percentile 40 ng/l, provided by the manufacturer). Conclusions: The Siemens cTnI Ultra assay has a very high diagnostic accuracy also in KD-patients and is superior to a conventional cTnT-assay. Mild cTnI elevations are common in non-AMI patients. The optimal cutoff-level in KD-patients seems to be around the 99th percentile of a standard population, whereas the optimal cutoff-level in patients with normal kidney function tends to be only half of the suggested cutoff-value. ClinicalTrials.gov number, NCT0047058

    Could GLUT12 be a Potential Therapeutic Target in Cancer Treatment? A Preliminary Report

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    Background: Recent studies proposed GLUT12 to be a major glucose transporter involved in the glycolytic metabolism of cancer cells. Methods: GLUT12 expression was determined by immunohistochemistry in a selection of cancer cell lines and a tumour spheroid model. Results: GLUT12 expression was high in A549 and RH-36; low in HT29; and absent in NB-EB cancer cell lines. GLUT12 expression was located in the necrotic centre of HT29 spheroids, which is characterised by anaerobic metabolism. Conclusion: The data supports the involvement of GLUT12 in the glycolytic metabolism of cancer cells and therefore, its potential as a novel therapeutic target for cancer treatment

    B-physics computations from Nf=2 tmQCD

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    We present an accurate lattice QCD computation of the b-quark mass, the B and Bs decay constants, the B-mixing bag-parameters for the full four-fermion operator basis, as well as estimates for \xi and f_{Bq}\sqrt{B_q} extrapolated to the continuum limit and the physical pion mass. We have used Nf = 2 dynamical quark gauge configurations at four values of the lattice spacing generated by ETMC. Extrapolation in the heavy quark mass from the charm to the bottom quark region has been carried out using ratios of physical quantities computed at nearby quark masses, having an exactly known infinite mass limit.Comment: 7 pages, 4 figures, presented at the 31st International Symposium on Lattice Field Theory (Lattice 2013), 29 July - 3 August 2013, Mainz, German
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