225 research outputs found
Front-end Electronics and Optimal Ganging Schemes for Single Photon Detection with Large Arrays of SiPMs in Liquid Argon
The operation of large arrays of silicon photomultipliers (SiPM) in tanks of
noble liquids requires low noise, low power front-end amplifiers, able to
operate reliably in the cryogenic environment. A suitable amplifier needs to be
paired with a proper SiPM ganging scheme, meaning the series/parallel
combination of SiPMs at its input. This paper presents a simple model to
estimate the ganging scheme that gives the best signal to noise ratio once the
basic electrical characteristics of the SiPM and amplifier are known. To prove
the validity of the model, we used an amplifier based on discrete components,
which achieves a white voltage noise in the 0.25-0.37 nV/Hz range at
liquid nitrogen temperature, while drawing 2-5 mW of power. Combined with the
optimal ganging scheme obtained with the model, the amplifier demonstrated
excellent single photon sensitivity up to 96 6x6 mm SiPMs (total area 34.6
cm, S/N 8-11). The measured results are in a good match with
calculated values, predicting the possibility to achieve a clear separation of
photoelectron peaks also with larger areas
Determination of the pKa value of phenolphthalein by means of absorbance measurements
We here report a laboratory protocol for the determination of the pKa value of an acid by means of determinations obtained with a spectrophotometer. Students determine the acidity constant (Ka) and the pKa associated with phenolphthalein from the absorbance values obtained from phenolphthalein solutions at different pHs. The present protocol for the determination of the pKa takes a very short time and is useful when teaching in conditions with limited equipment.Fil: Alonso, Manuel. Universidad de Buenos Aires. Facultad de Medicina. Departamento de Bioquímica Humana; ArgentinaFil: Chapela, Sebastián P.. Universidad de Buenos Aires. Facultad de Medicina. Departamento de Bioquímica Humana; ArgentinaFil: Cristaldo, María L.. Universidad de Buenos Aires. Facultad de Medicina. Departamento de Bioquímica Humana; ArgentinaFil: Nievas, Inés. Universidad de Buenos Aires. Facultad de Medicina. Departamento de Bioquímica Humana; ArgentinaFil: Burgos Oliver Gamondi, Hilda I.. Universidad de Buenos Aires. Facultad de Medicina. Departamento de Bioquímica Humana; ArgentinaFil: Stella, Carlos Alberto. Universidad de Buenos Aires. Facultad de Medicina. Departamento de Bioquímica Humana; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Scale-free movement patterns in termites emerge from social interactions and preferential attachments
As the number or density of interacting individuals in a social group increases, a transition can develop from uncorrelated and disordered behaviour of the individuals to a collective coherent pattern. We expand this observation by exploring the fine details of termite movement patterns to demonstrate that the value of the scaling exponent µ of a power-law describing the Lévy walk of an individual is modified collectively as the density of animals in the group changes. This effect is absent when termites interact with inert obstacles. We also show that the network of encounters and interactions among specific individuals is selective resembling a preferential attachment mechanism which is important for social networking. TeOur data suggest strongly that preferential attachments, a phenomenon not reported previously, and favourite interactions with a limited number of acquaintances are responsible for the generation of Lévy movement patterns in these social insects
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Rifabutin central nervous system concentrations in a rabbit model of tuberculous meningitis.
Tuberculous meningitis (TBM) has a high mortality, possibly due to suboptimal therapy. Drug exposure data of antituberculosis agents in the central nervous system (CNS) are required to develop more effective regimens. Rifabutin is a rifamycin equivalently potent to rifampin in human pulmonary tuberculosis. Here, we show that human-equivalent doses of rifabutin achieved potentially therapeutic exposure in relevant CNS tissues in a rabbit model of TBM, supporting further evaluation in clinical trials
Previsão probabilística de enchentes para uma pequena bacia hidrográfica do Pantanal.
O monitoramento para a previsão de cheias de pequenas bacias hidrográficas é de grande importância tendo em vista a relação dos recursos hídricos com a sociedade, pois pode garantir o uso sustentável às comunidades urbanas de cidades lindeiras à bacia. O rio Aquidauana está inserido na planície Pantaneira sendo considerado vulnerável à inundações, no entanto, falta de um sistema eficiente para previsões de cheias e inundações. Assim, este estudo propõe um sistema de previsão probalística de enchentes para a bacia do Rio Aquidauana. Para tanto foram utilizadas as redes neurais artificiais (RNAs) do tipo MultiLayer Perceptron (treinamento backpropagation) com parâmetros otimizados pelos Algoritmos Genéticos. A RNA foi treinada e avaliada com base em dados de chuva acumulada (mm) e nível de rio (cm) à montante entre os anos de 1995 a 2014. A previsão realizada foi de 1 a 5 dias, tendo como melhor desempenho o modelo para 1 dia de previsão, com resultado de coeficiente de determinação e erro quadrático médio de 0,93 e 30 (cm), respectivamente
The ESSnuSB design study: overview and future prospects
ESSnuSB is a design study for an experiment to measure the CP violation in
the leptonic sector at the second neutrino oscillation maximum using a neutrino
beam driven by the uniquely powerful ESS linear accelerator. The reduced impact
of systematic errors on sensitivity at the second maximum allows for a very
precise measurement of the CP violating parameter. This review describes the
fundamental advantages of measurement at the 2nd maximum, the necessary
upgrades to the ESS linac in order to produce a neutrino beam, the near and far
detector complexes, the expected physics reach of the proposed ESSnuSB
experiment, concluding with the near future developments aimed at the project
realization.Comment: 19 pages, 11 figures; Corrected minor error in alphabetical ordering
of the authors: the author list is now fully alphabetical w.r.t. author
surnames as was intended. Corrected an incorrect affiliation for two authors
per their reques
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