Pressure effects on collective density fluctuations in water and protein solutions

Neutron Brillouin scattering and molecular dynamics simulations have been used to investigate protein hydration water density fluctuations as a function of pressure. Our results show significant differences between the pressure and density dependence of collective dynamics in bulk water and in concentrated protein solutions. Pressure-induced changes in the tetrahedral order of the water HB network have direct consequences for the high-frequency sound velocity and damping coefficients, which we find to be a sensitive probe for changes in the HB network structure as well as the wetting of biomolecular surfaces

LUIZ OTÁVIO DE SEIXAS QUEIROZ: UM PIONEIRO DA ANÁLISE DO COMPORTAMENTO NO BRASIL

This paper examines issues relating to the work of Luiz Otávio Seixas de Queiroz (1938-2003), a pioneer of the experimental analysis of behavior in Brazil. Emphasis is given to the wide ranging influence of his work, including participation in the institution of the personalized system of teaching in the Psychology course at the University of Brasilia, the Laboratory of the Experimental Analysis of Behavior in the  Pontificate Catholic University of Campinas, undergraduate teaching and utilization of applied behavioral analysis in the psychological clinic and to routines in a psychiatric hospital. His work as  an educator, researcher and clinician was effective for shaping and maintaining several generations of behavior analysts.Key words: Luiz Otávio de Seixas Queiroz, clinical psychology, applied behavior analysis, behavior analystO presente texto relata fatos e comentários que caracterizam Luiz Otávio Seixas de Queiroz (1938-2003) como um dos pioneiros da análise do comportamento no Brasil. Enfatiza-se a importância do âmbito de ação da sua atuação profissional, que abrangeu a instalação do curso de Psicologia com sistema de ensino programado individualizado na Universidade de Brasília e do Laboratório de Análise Experimental do Comportamento na Pontifícia Universidade Católica de Campinas, a formação de alunos, e a aplicação de princípios de análise comportamental à clínica e ao trabalho em hospital psiquiátrico. Como professor, pesquisador e clínico, estabeleceu as contingências efetivas para a formação de várias gerações de analistas do comportamento. Palavras-chave: Luiz Otávio de Seixas Queiroz, psicologia clínica, análise comportamental aplicada, analista do comportamento

The LISA beamline at ESRF.

This contribution provides a description of LISA, the new Italian Collaborating Research Group beamline operative at the European Synchrotron Radiation Facility. A presentation of the instruments available and optical devices is given as well as the main X-ray parameters (flux, energy resolution, focal spot dimensions, etc.) and comparison with theoretical calculations. The beamline has been open to users since April 2018 and will be ready at the opening of the Extremely Brilliant Source in late-2020

Vanadium based neutron beam monitor

A prototype quasiparasitic thermal neutron beam monitor based on isotropic neutron scattering from a thin natural vanadium foil and standard 3He proportional counters is conceptualized, designed, simulated, calibrated, and commissioned. The European Spallation Source designed to deliver the highest integrated neutron flux originating from a pulsed source is currently under construction in Lund, Sweden. The effort to investigate a vanadium based neutron beam monitor was triggered by a list of requirements for beam monitors permanently placed in the ESS neutron beams in order to provide reliable monitoring at complex beamlines low attenuation, linear response over a wide range of neutron fluxes, near to constant efficiency for neutron wavelengths in a range of 0.6 10 , calibration stability and the possibility to place the system in vacuum are all desirable characteristics. The scattering based prototype, employing a natural vanadium foil andstandard 3He proportional counters, was investigated at the V17 and V20 neutron beamlines of the Helmholtz Zentrum in Berlin, Germany, in several different geometrical configurations of the 3He proportional counters around the foil. Response linearity is successfully demonstrated for foil thicknesses ranging from 0.04 mm to 3.15 mm. Attenuation lower than 1 for thermal neutrons is demonstrated for the 0.04 mm and 0.125 mm foils. The geometries used for the experiment were simulated allowing for absolute flux calibration and establishing the possible range of efficiencies for various designs of the prototype. The operational flux limits for the beam monitor prototype were established as a dependency of the background radiation and prototype geometry. The herein demonstrated prototype monitors can be employed for neutron intensities ranging from 103 1010 n s

Time- and energy-resolved effects in the boron-10 based Multi-Grid and helium-3 based thermal neutron detectors

The boron-10 based Multi-Grid detector is being developed as an alternative to helium-3 based neutron detectors. At the European Spallation Source, the detector will be used for time-of-flight neutron spectroscopy at cold to thermal neutron energies. The objective of this work is to investigate fine time- and energy-resolved effects of the Multi-Grid detector, down to a few $\mu$eV, while comparing it to the performance of a typical helium-3 tube. Furthermore, it is to characterize differences between the detector technologies in terms of internal scattering, as well as the time reconstruction of ~ $\mu$s short neutron pulses. The data were taken at the Helmholtz Zentrum Berlin, where the Multi-Grid detector and a helium-3 tube were installed at the ESS test beamline, V20. Using a Fermi-chopper, the neutron beam of the reactor was chopped into a few tens of $\mu$s wide pulses before reaching the detector, located a few tens of cm downstream. The data of the measurements show an agreement between the derived and calculated neutron detection efficiency curve. The data also provide fine details on the effect of internal scattering, and how it can be reduced. For the first time, the chopper resolution was comparable to the timing resolution of the Multi-Grid detector. This allowed a detailed study of time- and energy resolved effects, as well as a comparison with a typical helium-3 tube.Comment: 37 pages, 21 figure

New perspectives onto the metal–to–non-metal transition in expanded liquid metals

The collective dynamics of liquid rubidium was measured by inelastic neutron scattering from melting up to 1673 K and 6.4 MPa to explore an electron gas instability, forecasted by theory at sufficient expansion. Pronounced variations are observed when the predicted conditions are approached. They comply with a scenario for the density-driven metal–to–non-metal transition suggested for fluid mercury where the liquid metal decomposes into a nanoemulsion of metallic and non-metallic domains and the metallic domains constantly disappear with ongoing expansion. Collective modes appear as an unambiguous signature of the metallic phase allowing to directly observe this process