538 research outputs found
Belief Change and Memory for Previous Beliefs after Comprehension of Contentious Scientific Information
We explored the relationship between belief change and recollection of previous beliefs. Subjects reported beliefs about TV violence. Later, subjects read a one-sided, belief inconsistent text. We manipulated whether subjects reported beliefs after reading first, or recollected previous beliefs first. A third group was told their previous beliefs before reporting current beliefs. Recollections were not improved when subjects recollected beliefs first. When told previous beliefs, belief change was reduced, suggesting a desire to appear consistent
Spin currents and spin dynamics in time-dependent density-functional theory
We derive and analyse the equation of motion for the spin degrees of freedom
within time-dependent spin-density-functional theory (TD-SDFT). Results are (i)
a prescription for obtaining many-body corrections to the single-particle spin
currents from the Kohn-Sham equation of TD-SDFT, (ii) the existence of an
exchange-correlation (xc) torque within TD-SDFT, (iii) a prescription for
calculating, from TD-SDFT, the torque exerted by spin currents on the spin
magnetization, (iv) a novel exact constraint on approximate xc functionals, and
(v) the discovery of serious deficiencies of popular approximations to TD-SDFT
when applied to spin dynamics.Comment: now includes discussion of OEP and GGA; to appear in Phys. Rev. Let
Reduction of nickel oxide particles by hydrogen studied in an environmental TEM
In situ reduction of nickel oxide (NiO) particles is performed under 1.3 mbar of hydrogen gas (H-2) in an environmental transmission electron microscope (ETEM). Images, diffraction patterns and electron energy-loss spectra (EELS) are acquired to monitor the structural and chemical evolution of the system during reduction, whilst increasing the temperature. Ni nucleation on NiO is either observed to be epitaxial or to involve the formation of randomly oriented grains. The growth of Ni crystallites and the movement of interfaces result in the formation of pores within the NiO grains to accommodate the volume shrinkage associated with the reduction. Densification is then observed when the sample is nearly fully reduced. The reaction kinetics is obtained using EELS by monitoring changes in the shapes of the Ni L-2,L-3 white lines. The activation energy for NiO reduction is calculated from the EELS data using both a physical model-fitting technique and a model-independent method. The results of the model-fitting procedure suggest that the reaction is described by Avrami models (whereby the growth and impingement of Ni domains control the reaction), in agreement with the ETEM observations
Aspects of the breeding biology of Janaira gracilis Moreira & Pires (Crustacea, Isopoda, Asellota)
The biological aspects of incubating females of Janaira gracilis Mbreira & Pires, are described. The marsupium is formed by 4 pairs of oostegites arising from pereopods I-IV. The oostegites appear for the first time at the post-marsupial stage 7 (preparatory stage 1), growing successively at each moult until stage 9 (brooding stage 1), when they reach fully development. The sizes of the eggs increase with the body size of the females. The number of eggs, per female, is a linear function of the body volume, i.e., the fecundity increases with the female's body size. The number of eggs, embryos and juveniles decrease during the marsupial development. This decrease in brood number is higher between the last two marsupial stages, i.e., from stage C to D, than between the preceding marsupial stages. The average and overall brood mortality rate is of 38.95%.São descritos, no presente trabalho, vários aspectos relacionados à biologia de fêmeas grávidas de Janaira gracilis Moreira & Pires. O marsúpio é formado por 4 pares de oostégitos, que partem dos pereópodos I-IV. Os oostégitos, que surgem pela primeira vez no estádio 7 do desenvolvimento pós-marsupial (estágio preparatório 1), crescem nas sucessivas mudas, atingindo no estágio 9 (estágio reprodutor 1) seu pleno desenvolvimento. O tamanho dos ovos é proporcional ao tamanho das fêmeas. O número de ovos, por fêmeas, e proporcional ao volume das fêmeas, isto é, a fecundidade é mais elevada nos exemplares de maior comprimento. O número de ovos, embriões e jovens decresce com o desenvolvimento marsupial, sendo este decréscimo maior entre os dois últimos estágios marsupials (i.é., entre os estágios C e D) do que entre os estágios precedentes. A taxa média de mortalidade marsupial é de 38.95%
Graphene-based ultrathin flat lenses
Flat lenses when compared to curved surface lenses have the advantages of being aberration free and they offer a compact design necessary for a myriad of electro-optical applications. In this paper we present flat and ultra-thin lenses based on graphene, the world’s thinnest known material. Monolayers and low number multilayers of graphene were fabricated into Fresnel zones to produce Fresnel zone plates which utilize the reflection and transmission properties of graphene for their operation. The working of the lens and their performance in the visible and terahertz regimes was analyzed computationally. Experimental measurements were also performed to characterize the lens in the visible regime and a good agreement was obtained with the simulations. The work demonstrates the principle of atom thick graphene-based lenses, with perspectives for ultra-compact integration.HB would like to thank The Leverhulme Trust for the research funding. QD is supported by Bureau of International Cooperation, Chinese Academy of Sciences (121D11KYSB20130013).This is the accepted manuscript. The final version is available from ACS at http://pubs.acs.org/doi/abs/10.1021/ph500197j
Astrocyte-mediated short-term synaptic depression in the rat hippocampal CA1 area: two modes of decreasing release probability
<p>Abstract</p> <p>Background</p> <p>Synaptic burst activation feeds back as a short-term depression of release probability at hippocampal CA3-CA1 synapses. This short-term synaptic plasticity requires functional astrocytes and it affects both the recently active (< 1 s) synapses (post-burst depression) as well as inactive neighboring synapses (transient heterosynaptic depression). The aim of this study was to investigate and compare the components contributing to the depression of release probability in these two different scenarios.</p> <p>Results</p> <p>When tested using paired-pulses, following a period of inactivity, the transient heterosynaptic depression was expressed as a reduction in the response to only the first pulse, whereas the response to the second pulse was unaffected. This selective depression of only the first response in a high-frequency burst was shared by the homosynaptic post-burst depression, but it was partially counteracted by augmentation at these recently active synapses. In addition, the expression of the homosynaptic post-burst depression included an astrocyte-mediated reduction of the pool of release-ready primed vesicles.</p> <p>Conclusions</p> <p>Our results suggest that activated astrocytes depress the release probability via two different mechanisms; by depression of vesicular release probability only at inactive synapses and by imposing a delay in the recovery of the primed pool of vesicles following depletion. These mechanisms restrict the expression of the astrocyte-mediated depression to temporal windows that are typical for synaptic burst activity.</p
AWAKE: A Proton-Driven Plasma Wakefield Acceleration Experiment at CERN
The AWAKE Collaboration has been formed in order to demonstrate proton-driven plasma wakefield acceleration for the first time. This acceleration technique could lead to future colliders of high energy but of a much reduced length when compared to proposed linear accelerators. The CERN SPS proton beam in the CNGS facility will be injected into a 10 m plasma cell where the long proton bunches will be modulated into significantly shorter micro-bunches. These micro-bunches will then initiate a strong wakefield in the plasma with peak fields above 1 GV/m that will be harnessed to accelerate a bunch of electrons from about 20 MeV to the GeV scale within a few meters. The experimental program is based on detailed numerical simulations of beam and plasma interactions. The main accelerator components, the experimental area and infrastructure required as well as the plasma cell and the diagnostic equipment are discussed in detail. First protons to the experiment are expected at the end of 2016 and this will be followed by an initial three-four years experimental program. The experiment will inform future larger-scale tests of proton-driven plasma wakefield acceleration and applications to high energy colliders
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