228 research outputs found

    Formation of Subtropical Mode Water in a high-resolution ocean simulation of the Kuroshio Extension region

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    Author Posting. © Elsevier B.V., 2007. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Ocean Modelling 17 (2007): 338-356, doi:10.1016/j.ocemod.2007.03.002.A high-resolution numerical model is used to examine the formation and variability of the North Pacific Subtropical ModeWater (STMW) over a 3-year period. The STMW distribution is found to be highly variable in both space and time, a characteristic often unexplored because of sparse observations or the use of coarse resolution simulations. Its distribution is highly dependent on eddies, and where it was renewed during the previous winter. Although the potential vorticity fluxes associated with down-front winds can be of the same order of magnitude or even greater than the diabatic ones due to air-sea temperature differences, the latter dominate the potential vorticity budget on regional and larger scales. Air-sea fluxes, however, are dominated by a few strong wind events, emphasizing the importance of short time scales in the formation of mode waters. In the Kuroshio Extension region, both advection and mixing play important roles to remove the STMW from the formation region.This work was sponsored by the National Science Foundation OCE-0220161 (S.J.) and OCE-0221781/0549225 (J.M.), the Office of Naval Research (J.M., M.M.), Department of Energy/CCPP (M.M.), and the Office of Science (BER), US Department of Energy, Grant No. DE-FG02-05ER64119 (J.M.)

    Preoperative biliary drainage for biliary tract and ampullary carcinomas

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    We posed six clinical questions (CQ) on preoperative biliary drainage and organized all pertinent evidence regarding these questions. CQ 1. Is preoperative biliary drainage necessary for patients with jaundice? The indications for preoperative drainage for jaundiced patients are changing greatly. Many reports state that, excluding conditions such as cholangitis and liver dysfunction, biliary drainage is not necessary before pancreatoduodenectomy or less invasive surgery. However, the morbidity and mortality of extended hepatectomy for biliary cancer is still high, and the most common cause of death is hepatic failure; therefore, preoperative biliary drainage is desirable in patients who are to undergo extended hepatectomy. CQ 2. What procedures are appropriate for preoperative biliary drainage? There are three methods of biliary drainage: percutaneous transhepatic biliary drainage (PTBD), endoscopic nasobiliary drainage (ENBD) or endoscopic retrograde biliary drainage (ERBD), and surgical drainage. ERBD is an internal drainage method, and PTBD and ENBD are external methods. However, there are no reports of comparisons of preoperative biliary drainage methods using randomized controlled trials (RCTs). Thus, at this point, a method should be used that can be safely performed with the equipment and techniques available at each facility. CQ 3. Which is better, unilateral or bilateral biliary drainage, in malignant hilar obstruction? Unilateral biliary drainage of the future remnant hepatic lobe is usually enough even when intrahepatic bile ducts are separated into multiple units due to hilar malignancy. Bilateral biliary drainage should be considered in the following cases: those in which the operative procedure is difficult to determine before biliary drainage; those in which cholangitis has developed after unilateral drainage; and those in which the decrease in serum bilirubin after unilateral drainage is very slow. CQ 4. What is the best treatment for postdrainage fever? The most likely cause of high fever in patients with biliary drainage is cholangitis due to problems with the existing drainage catheter or segmental cholangitis if an undrained segment is left. In the latter case, urgent drainage is required. CQ 5. Is bile culture necessary in patients with biliary drainage who are to undergo surgery? Monitoring of bile cultures is necessary for patients with biliary drainage to determine the appropriate use of antibiotics during the perioperative period. CQ 6. Is bile replacement useful for patients with external biliary drainage? Maintenance of the enterohepatic bile circulation is vitally important. Thus, preoperative bile replacement in patients with external biliary drainage is very likely to be effective when highly invasive surgery (e.g., extended hepatectomy for hilar cholangiocarcinoma) is planned

    Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV

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    Results are presented from a search for a W' boson using a dataset corresponding to 5.0 inverse femtobarns of integrated luminosity collected during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV. The W' boson is modeled as a heavy W boson, but different scenarios for the couplings to fermions are considered, involving both left-handed and right-handed chiral projections of the fermions, as well as an arbitrary mixture of the two. The search is performed in the decay channel W' to t b, leading to a final state signature with a single lepton (e, mu), missing transverse energy, and jets, at least one of which is tagged as a b-jet. A W' boson that couples to fermions with the same coupling constant as the W, but to the right-handed rather than left-handed chiral projections, is excluded for masses below 1.85 TeV at the 95% confidence level. For the first time using LHC data, constraints on the W' gauge coupling for a set of left- and right-handed coupling combinations have been placed. These results represent a significant improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe

    Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV

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    A search for a Higgs boson decaying into two photons is described. The analysis is performed using a dataset recorded by the CMS experiment at the LHC from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross section of the standard model Higgs boson decaying to two photons. The expected exclusion limit at 95% confidence level is between 1.4 and 2.4 times the standard model cross section in the mass range between 110 and 150 GeV. The analysis of the data excludes, at 95% confidence level, the standard model Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The largest excess of events above the expected standard model background is observed for a Higgs boson mass hypothesis of 124 GeV with a local significance of 3.1 sigma. The global significance of observing an excess with a local significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is estimated to be 1.8 sigma. More data are required to ascertain the origin of this excess.Comment: Submitted to Physics Letters

    Measurement of the Lambda(b) cross section and the anti-Lambda(b) to Lambda(b) ratio with Lambda(b) to J/Psi Lambda decays in pp collisions at sqrt(s) = 7 TeV

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    The Lambda(b) differential production cross section and the cross section ratio anti-Lambda(b)/Lambda(b) are measured as functions of transverse momentum pt(Lambda(b)) and rapidity abs(y(Lambda(b))) in pp collisions at sqrt(s) = 7 TeV using data collected by the CMS experiment at the LHC. The measurements are based on Lambda(b) decays reconstructed in the exclusive final state J/Psi Lambda, with the subsequent decays J/Psi to an opposite-sign muon pair and Lambda to proton pion, using a data sample corresponding to an integrated luminosity of 1.9 inverse femtobarns. The product of the cross section times the branching ratio for Lambda(b) to J/Psi Lambda versus pt(Lambda(b)) falls faster than that of b mesons. The measured value of the cross section times the branching ratio for pt(Lambda(b)) > 10 GeV and abs(y(Lambda(b))) < 2.0 is 1.06 +/- 0.06 +/- 0.12 nb, and the integrated cross section ratio for anti-Lambda(b)/Lambda(b) is 1.02 +/- 0.07 +/- 0.09, where the uncertainties are statistical and systematic, respectively.Comment: Submitted to Physics Letters

    Search for new physics in events with opposite-sign leptons, jets, and missing transverse energy in pp collisions at sqrt(s) = 7 TeV

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    A search is presented for physics beyond the standard model (BSM) in final states with a pair of opposite-sign isolated leptons accompanied by jets and missing transverse energy. The search uses LHC data recorded at a center-of-mass energy sqrt(s) = 7 TeV with the CMS detector, corresponding to an integrated luminosity of approximately 5 inverse femtobarns. Two complementary search strategies are employed. The first probes models with a specific dilepton production mechanism that leads to a characteristic kinematic edge in the dilepton mass distribution. The second strategy probes models of dilepton production with heavy, colored objects that decay to final states including invisible particles, leading to very large hadronic activity and missing transverse energy. No evidence for an event yield in excess of the standard model expectations is found. Upper limits on the BSM contributions to the signal regions are deduced from the results, which are used to exclude a region of the parameter space of the constrained minimal supersymmetric extension of the standard model. Additional information related to detector efficiencies and response is provided to allow testing specific models of BSM physics not considered in this paper.Comment: Replaced with published version. Added journal reference and DO

    Measurement of isolated photon production in pp and PbPb collisions at sqrt(sNN) = 2.76 TeV

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    Isolated photon production is measured in proton-proton and lead-lead collisions at nucleon-nucleon centre-of-mass energies of 2.76 TeV in the pseudorapidity range |eta|<1.44 and transverse energies ET between 20 and 80 GeV with the CMS detector at the LHC. The measured ET spectra are found to be in good agreement with next-to-leading-order perturbative QCD predictions. The ratio of PbPb to pp isolated photon ET-differential yields, scaled by the number of incoherent nucleon-nucleon collisions, is consistent with unity for all PbPb reaction centralities.Comment: Submitted to Physics Letters

    Flowcharts for the management of biliary tract and ampullary carcinomas

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    No strategies for the diagnosis and treatment of biliary tract carcinoma have been clearly described. We developed flowcharts for the diagnosis and treatment of biliary tract carcinoma on the basis of the best clinical evidence. Risk factors for bile duct carcinoma are a dilated type of pancreaticobiliary maljunction (PBM) and primary sclerosing cholangitis. A nondilated type of PBM is a risk factor for gallbladder carcinoma. Symptoms that may indicate biliary tract carcinoma are jaundice and pain in the upper right area of the abdomen. The first step of diagnosis is to carry out blood biochemistry tests and ultrasonography (US) of the abdomen. The second step of diagnosis is to find the local extension of the carcinoma by means of computed tomography (CT), magnetic resonance imaging (MRI), magnetic resonance cholangiopancreatography (MRCP), percutaneous transhepatic cholangiography (PTC), and endoscopic retrograde cholangiopancreatography (ERCP). Because resection is the only way to completely cure biliary tract carcinoma, the indications for resection are determined first. In patients with resectable disease, the indications for biliary drainage or portal vein embolization (PVE) are checked. In those with nonresectable disease, biliary stenting, chemotherapy, radiotherapy, and/or best supportive care is selected

    Measurement of the mass difference between top quark and antiquark in pp collisions at root s=8 TeV

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    Studies of azimuthal dihadron correlations in ultra-central PbPb collisions at=2.76 TeV

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