55 research outputs found

    Adsorptive stripping voltammetric determination of trace level Ricin in castor seeds using a boron-doped diamond electrode.

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    Ricin, (Ricinus communis agglutinin, RCA) is one of the most poisonous of naturally occurring substances and has great potential for bioterrorism because no antidote exists. Fast detection at low concentrations is a challenge, and vital to the development of proper countermeasures. In this study, a square wave adsorptive stripping voltammetric (SWAdSV) method for determining RCA using a cathodically polarized boron-doped diamond (BDD) electrode is presented. An irreversible electrochemical RCA oxidation peak was identified on the BDD electrode by different voltammetric techniques using both direct and adsorptive stripping modes. An adsorption-controlled (slope log Ip vs log v of 0.80) pHdependent process was observed. For values of 1.0pH 9.0, the numbers of protons and electrons associated with the oxidation reaction were estimated (ca. 1.0) by differential pulse voltammetry. The RCA oxidation step may correspond to the oxidation of tryptophan amino acid residues, and occurs in a complex mechanism. The excellent analytical performance of the cathodically polarized BDD electrode in combination with the stripping mode ramp was verified with RCA by using a short deposition time in an open circuit potential (120 s). Under optimized analysis conditions, a linear response in the range of (3.3?94.0)3109 mol L1 (r2=0.9944) and a limit of detection of 6.231010 mol L1 were estimated. This LOD is lower than several methods found in the literature. For example, it is 168 times lower than that obtained by using square wave voltammetric with a glassy carbon electrode. Moreover, an even lower LOD might be achieved by using the SWAdSV method with a higher pre-concentration time. In addition, trace levels of RCA were successfully determined in different castor seed cultivars with an overall average recovery from 99.2 1.6% for the three different RCA-A concentration levels. The high accuracy of the analytical data highlights the use of the proposed method for determining RCA in other samples

    Intermediate mass dimuon production in Indium-Indium collisions at the CERN SPS

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    We present preliminary results on the production of intermediate mass dimuons in 158 A·GeV In-In collisions at the CERN SPS. NA38 and NA50 observed a strong excess in this region in S-U and Pb-Pb interactions with respect to the dimuon production rate expected from p-A data. Thanks to the use of a pixel vertex tracker, NA60 can separate the prompt dimuons from the pairs resulting from open charm decays and show that the excess dimuons are of prompt origin

    Study of the production of charged pions, kaons, and protons in pPb collisions at √SNN=5.02 TeV

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    Evidence for light-by-light scattering and searches for axion-like particles in ultraperipheral PbPb collisions at root s(NN)=5.02 TeV

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    Evidence for the light-by-light scattering process, gamma gamma -> gamma gamma, in ultraperipheral PbPb collisions at a centre-of-mass energy per nucleon pair of 5.02 TeV is reported. The analysis is conducted using a data sample corresponding to an integrated luminosity of 390 mu b(-1) recorded by the CMS experiment at the LHC. Light-by-light scattering processes are selected in events with two photons exclusively produced, each with transverse energy E-T(gamma) > 2 GeV, pseudorapidity vertical bar eta(gamma)vertical bar 5 GeV, diphoton transverse momentum p(T)(gamma gamma) gamma gamma) = 120 +/- 46(stat) +/- 28(syst) +/- 12(theo) nb, is consistent with the standard model prediction. The m(gamma gamma) distribution is used to set new exclusion limits on the production of pseudoscalar axion-like particles, via the gamma gamma -> a -> gamma gamma process, in the mass range m(a) = 5-90 GeV. (C) 2019 The Author(s). Published by Elsevier B.V.Peer reviewe

    Search for dark matter and unparticles produced in association with a Z boson in proton-proton collisions at root s=8 TeV

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    Correction: DOI 10.1103/PhysRevD.97.099903Peer reviewe

    Photodynamic Inactivation of Yeast and Bacteria by Extracts of Alternanthera brasiliana

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    Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)This study was undertaken to evaluate the effect of Alternathera brasiliana (Amaranthaceae) extracts as photosensitizing agents in photodynamic antimicrobial therapies (PACT) against Staphylococcus aureus, Staphylococcus epidermidis and Candida dubliniensis. The crude hexane and ethanol extracts were obtained from A. brasiliana whole plant and showed absortion from 650 to 700nm. Also, singlet molecular oxygen (O-1(2)) production (type II photosensitization reaction) was examined, and the results show that 1,3-diphenylisobenzofuran photodegradation was greatly enhanced in the presence of the A. brasiliana extracts. One plate in each assay was irradiated while the other was not irradiated, the number of colony-forming units per milliliter (CFU/mL) was obtained, and data analyzed by the Tukey test. The chemical composition of the extracts was determined by chromatographic and spectrometric techniques; steroids, triterpenes, and flavonoids were identified. Laser irradiation alone at 685nm using diode laser, output power of 35mW, and energy of 28 J/cm(2), or non-irradiated crude extracts in sub-inhibitory concentration did not reduce the number of CFU/mL significantly, whereas irradiated hexane and ethanol extracts, in sub-inhibitory concentrations, inhibited the growth of these microorganisms. The photoactivation of hexane and ethanol extracts of A. brasiliana, in sub-inhibitory concentrations, using red laser radiation at 685nm had an antimicrobial effect.14910151022Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAEPEX-UNICAMPFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

    Progress control in iterated local search for nurse rostering

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    This paper describes an approach in which a local search technique is alternated with a process which ‘jumps’ to another point in the search space. After each ‘jump’ a (time-intensive) local search is used to obtain a new local optimum. The focus of the paper is in monitoring the progress of this technique on a set of real world nurse rostering problems. We propose a model for estimating the quality of this new local optimum. We can then decide whether to end the local search based on the predicted quality. The fact that we avoid searching these bad neighbourhoods enables us to reach better solutions in the same amount of time. We evaluate the approach on five highly constrained problems in nurse rostering. These problems represent complex and challenging real world rostering situations and the approach described here has been developed during a commercial implementation project by ORTEC bv
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