630 research outputs found

    The experimental study of the Bi-Sn, Bi-Zn and Bi-Sn-Zn systems

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    The binary BiSn was studied by means of SEM (Scanning Electron Microscopy)/EDS (Energy-Dispersive solid state Spectrometry), DTA (Differential Thermal Analysis)/DSC (Differential Scanning Calorimetry) and RT-XRD (Room Temperature X-Ray Diffraction) in order to clarify discrepancies concerning the Bi reported solubility in (Sn). It was found that (Sn) dissolves approximately 10 wt% of Bi at the eutectic temperature. The experimental effort for the BiZn system was limited to the investigation of the discrepancies concerning the solubility limit of Zn in (Bi) and the solubility of Bi in (Zn). Results indicate that the solubility of both elements in the respective solid solution is approximately 0.3 wt% at 200 C. Three different features were studied within the BiSnZn system. Although there are enough data to establish the liquid miscibility gap occurring in the phase diagram of binary BiZn, no data could be found for the ternary. Samples belonging to the isopleths with w(Bi) 10% and w(Sn) 5%, 13% and 19% were measured by DTA/DSC. The aim was to characterize the miscibility gap in the liquid phase. Samples belonging to the isopleths with w(Sn) 40%, 58%, 77/81% and w(Zn) 12% were also measured by DTA/DSC to complement the study of BiSnZn. Solubilities in the solid terminal solutions were determined by SEM/EDS. Samples were also analyzed by RT-XRD and HT-XRD (High Temperature X-Ray Diffraction) confirming the DTA/DSC results for solid state phase equilibria

    Carbohydrate carbon sources induce loss of flocculation of an ale-brewing yeast strain

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    Aims: To identify the nutrients that can trigger the loss of flocculation under growth conditions in an ale-brewing strain, Saccharomyces cerevisiae NCYC 1195. Methods and Results: Flocculation was evaluated using the method of Soares, EX. and Vroman, A. [Journal of Applied Microbiology (2003) 95, 325]. Yeast growth with metabolizable carbon sources (glucose, fructose, galactose, maltose or sucrose) at 2% (w/v), induced the loss of flocculation in yeast that had previously been allowed to flocculate. The yeast remained flocculent when transferred to a medium containing the required nutrients for yeast growth and a sole nonmetabolizable carbon source (lactose). Transfer of flocculent yeast into a growth medium with ethanol (4% v/v), as the sole carbon source did not induce the loss of flocculation. Even the addition of glucose (2% w/v) or glucose and antimycin A (0.1 mg lˉ¹) to this culture did not bring about loss of flocculation. Cycloheximide addition (15 mglˉ¹) to glucose-growing cells stopped flocculation loss. Conclusions: Carbohydrates were the nutrients responsible for stimulating the loss of flocculation in flocculent yeast cells transferred to growing conditions. The glucose-induced loss of flocculation required de novo protein synthesis. Ethanol prevented glucose-induced loss of flocculation. This protective effect of ethanol was independent of the respiratory function of the yeast. Significance and Impact of the Study: This work contributes to the elucidation of the role of nutrients in the control of the flocculation cycle in NewFlo phenotype yeast strains.Instituto Politécnico do Porto (IPP) - Fundo de Apoio à Investigação - Project P24/96 , P24/97.Programa Plurianual de Unidades de I&D-CIEA/ ISEP

    Purification And N-terminal Sequencing Of Two Presynaptic Neurotoxic Pla2, Neuwieditoxin-i And Neuwieditoxin-ii, From Bothrops Neuwiedi Pauloensis (jararaca Pintada) Venom

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    Two presynaptic phospholipases A2 (PLA2), neuwieditoxin-I (NeuTX-I) and neuwieditoxin-II (NeuTX-II), were isolated from the venom of Bothrops neuwiedi pauloensis (BNP). The venom was fractionated using molecular exclusion HPLC (Protein-Pak 300SW column), followed by reverse phase HPLC (μBondapak C18 column). Tricine-SDS-PAGE in the presence or absence of dithiothreitol showed that NeuTX-I and NeuTX-II had a molecular mass of approximately 14 kDa and 28kDa, respectively. At 10μg/ml, both toxins produced complete neuromuscular blockade in indirectly stimulated chick biventer cervicis isolated preparation without inhibiting the response to acetylcholine, but NeuTX-II reduced the response to KCl by 67.0±8.0% (n=3; p<0.05). NeuTX-I and NeuTX-II are probably responsible for the presynaptic neurotoxicity of BNP venom in vitro. In fact, using loose patch clamp technique for mouse phrenic nerve-diaphragm preparation, NeuTX-I produced a calcium-dependent blockade of acetylcholine release and caused appearance of giant miniature end-plate potentials (mepps), indicating a pure presynaptic action. The N-terminal sequence of NeuTX-I was DLVQFGQMILKVAGRSLPKSYGAYGCYCGWGGRGK (71% homology with bothropstoxin-II and 54% homology with caudoxin) and that of NeuTX-II was SLFEFAKMILEETKRLPFPYYGAYGCYCGWGGQGQPKDAT (92% homology with Basp-III and 62% homology with crotoxin PLA2). The fact that NeuTX-I has Q-4 (Gln-4) and both toxins have F-5 (Phe-5) and Y-28 (Tyr-28) strongly suggests that NeuTX-I and NeuTX-II are Asp49 PLA2.131103121AIRD, S.D., KAISER II, LEWIS RV., KRUGGEL WG. A complete amino acid sequence for the basic subunit of crotoxin (1986) Arch. Biochem. Biophys, 249, pp. 296-300AIRD, S.D., KRUGGEL, W.G., KAISER II, Amino acid sequence of the basic subunit of Mojave toxin from the venom of the Mojave rattlesnake (Crotalus s. scutulatus) (1990) Toxicon, 28, pp. 669-673BEGHINI, D.G., TOYAMA, M.H., HYSLOP, S., SODEK, L., NOVELLO, J.C., MARANGONI, S., Enzymatic characterization of a novel phospholipase A2 from Crotalus durissus cascavella rattlesnake (maracambóia) venom (2000) J. Protein Chem, 19, pp. 603-607BORJA-OLIVEIRA, C.R., DURIGON, A.M., VALLIN, A.C.C., TOYAMA, M.H., SOUCCAR, C., MARANGONI, S., RODRIGUES-SIMIONI, L., The pharmacological effects of Bothrops neuwiedi pauloensis (jararaca-pintada) snake venom on avian neuromuscular transmission (2003) Braz. J. Med. Biol. Res, 36, pp. 617-624BORJA-OLIVEIRA, C.R., SOARES, A.M., ZAMUNER, S.R., HYSLOP, S., GIGLIO, J.R., PRADO-FRANCESCHI, J., RODRIGUES-SIMIONI, L., Intraspecific variation in the neurotoxic and myotoxic activities of Bothrops neuwiedi snake venoms (2002) J. Venom. Anim. Toxins, 8, pp. 88-101BUCARETCHI, F., HERRERA, S.R.F., HYSLOP, S., BARACAT, E.C.E., VIEIRA, R.J., Snakebites by Bothrops spp in children in Campinas, São Paulo, Brazil (2001) Rev. Inst. Med. Trop. São Paulo, 43, pp. 329-333CHO, W., KEZDY, F.J., Chromogenic substrate and assay of phospholipase A 2 (1991) Meth. Enzymol, 197, pp. 75-79CINTRA, A.C., MARANGONI, S., OLIVEIRA, B., GIGLIO, J.R., Bothropstoxin-I: Amino acid sequence and function (1993) J. Protein Chem, 12, pp. 57-64COGO, J.C., PRADO-FRANCESCHI, J., CRUZ-HÖFLING, M.A., CORRADO, A.P., RODRIGUES-SIMIONI, L., Effects of Bothrops insularis on the mouse and chick nerve-muscle preparation (1993) Toxicon, 31, pp. 1237-1247COGO, J.C., PRADO-FRANCESCHI, J., GIGLIO, J.R., CORRADO, A.P., CRUZ-HÖFLING, M.A., DONATO, J.L., LEITE, G.B., RODRIGUES-SIMIONI, L., An unusual presynaptic action of Bothrops insularis snake venom mediated by phospholipase A2 fraction (1998) Toxicon, 36, pp. 1323-1332DE SOUSA, M.V., MORHY, L., ARNI, R.K., WARD, R.J., GUTIÉRREZ, J.M., Amino acid sequence of a myotoxic Lys-49-phospholipase A2 homologue from the venom of Cerrophidion (Bothrops) godmani (1998) Biochim. Biophys. Acta, 1384, pp. 204-208DURIGON, A.M., BORJA-OLIVEIRA, C.R., DAL, B.C., OSHIMA-FRANCO, Y., COGO, J.C., LAPA, A.J., SOUCCAR, C., RODRIGUES-SIMIONI, L., Neuromuscular activity of Bothrops neuwiedi pauloensis snake venom in mouse nerve-muscle preparations (2005) J. Venom. Anim. Toxins incl. Trop. Dis, 11, pp. 22-33FONTES, M.R., SOARES, A.M., RODRIGUES, V.M., FERNANDES, A.C., DA SILVA, R.J., GIGLIO, J.R., Crystallization and preliminary X-ray diffraction analysis of a myotoxic phospholipase A(2) homologue from Bothrops neuwiedi pauloensis venom (1999) Biochim. Biophys. Acta, 1432, pp. 393-395FRANCIS, B., GUTIERREZ, J.M., LOMONTE, B., KAISER II, Myotoxin II from Bothrops asper (Terciopelo) venom is a lysine-49 phospholipase A 2 (1991) Arch. Biochem. Biophys, 284, pp. 352-359GEOGHEGAN, P., ANGULO, Y., CANGELOSI, A., DIAZ, M., LOMONTE, B., Characterization of a basic phospholipase A2-homologue myotoxin isolated from the venom of the snake Bothrops neuwiedii (yarara chica) from Argentina (1999) Toxicon, 37, pp. 1735-1746GINSBORG, B.L., WARRINER, J., The isolated chick biventer cervicis nerve-muscle preparation (1960) Brit. J. 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Toxicon, 1994, 32, 257-65HELUANY, N.F., HOMSI-BRANDEBURGO, M.I., GIGLIO, J.R., PRADO-FRANCESCHI, J., RODRIGUES-SIMIONI, L., Effects induced by bothropstoxin, a component from Bothrops jararacussu snake venom, on mouse and chick muscle preparations (1992) Toxicon, 30, pp. 1203-1210HOLZER, M., MACKESSY, S.P., An aqueous endpoint assay of snake venom phospholipase A2 (1995) Toxicon, 35, pp. 1149-1155HOMSI-BRANDEBURGO, M.I., QUEIROZ, L.S., SANTO-NETO, H., RODRIGUES-SIMIONI, L., GIGLIO, J.R., Fractionation of Bothrops jararacussu snake venom: Partial chemical characterization and biological activity of bothropstoxin (1988) Toxicon, 26, pp. 615-627JOHNSON, E.K., OWNBY, C.L., Isolation of a myotoxin from the venom of Agkistrodon contortrix laticinctus (broad-banded copperhead) and pathogenesis of myonecrosis induced by it in mice (1993) Toxicon, 31, pp. 243-255KAISER II, Gutierrez, J.M., Plummer, D., Aird, S.D., Odell, G.V., AIRD SD., ODELL GV. The amino acid sequence of a myotoxic phospholipase from the venom of Bothrops asper (1990) Arch. Biochem. Biophys, 278, pp. 319-325KATZ, B., MILEDI, R., The binding of acetylcholine to receptors and its removal from the synaptic cleft (1973) J. Physiol, 231, pp. 549-574KINI RM. Phospholipase A2 - A complex multifunctional protein puzzle. In: KINI RM. Ed., Venom phosholipase A2 enzymes. Structure, function and mechanism. New York: John Wiley &ampSons Inc Chichester, 1997, 1-28KONDO, K., NARITA, K., LEE, C.Y., Amino acid sequences of the two polypeptide chains in beta1-bungarotoxin from the venom of Bungarus multicinctus (1978) J. Biochem, 83, pp. 101-115KONDO, K., TODA, H., NARITA, K., LEE, C.Y., Amino acid sequence of β2-bungarotoxin from Bungarus multicinctus venom: The amino acid substitutions in the B chains (1982) J. 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    Modeling the Subsurface Structure of Sunspots

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    While sunspots are easily observed at the solar surface, determining their subsurface structure is not trivial. There are two main hypotheses for the subsurface structure of sunspots: the monolithic model and the cluster model. Local helioseismology is the only means by which we can investigate subphotospheric structure. However, as current linear inversion techniques do not yet allow helioseismology to probe the internal structure with sufficient confidence to distinguish between the monolith and cluster models, the development of physically realistic sunspot models are a priority for helioseismologists. This is because they are not only important indicators of the variety of physical effects that may influence helioseismic inferences in active regions, but they also enable detailed assessments of the validity of helioseismic interpretations through numerical forward modeling. In this paper, we provide a critical review of the existing sunspot models and an overview of numerical methods employed to model wave propagation through model sunspots. We then carry out an helioseismic analysis of the sunspot in Active Region 9787 and address the serious inconsistencies uncovered by \citeauthor{gizonetal2009}~(\citeyear{gizonetal2009,gizonetal2009a}). We find that this sunspot is most probably associated with a shallow, positive wave-speed perturbation (unlike the traditional two-layer model) and that travel-time measurements are consistent with a horizontal outflow in the surrounding moat.Comment: 73 pages, 19 figures, accepted by Solar Physic

    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 polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

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    This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio

    Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

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    The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter

    Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS

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    We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final version to appear in Physics Letters

    Measurement of the inclusive isolated prompt photon cross-section in pp collisions at sqrt(s)= 7 TeV using 35 pb-1 of ATLAS data

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    A measurement of the differential cross-section for the inclusive production of isolated prompt photons in pp collisions at a center-of-mass energy sqrt(s) = 7 TeV is presented. The measurement covers the pseudorapidity ranges |eta|<1.37 and 1.52<=|eta|<2.37 in the transverse energy range 45<=E_T<400GeV. The results are based on an integrated luminosity of 35 pb-1, collected with the ATLAS detector at the LHC. The yields of the signal photons are measured using a data-driven technique, based on the observed distribution of the hadronic energy in a narrow cone around the photon candidate and the photon selection criteria. The results are compared with next-to-leading order perturbative QCD calculations and found to be in good agreement over four orders of magnitude in cross-section.Comment: 7 pages plus author list (18 pages total), 2 figures, 4 tables, final version published in Physics Letters
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