1,245 research outputs found
Monte Carlo critical isotherms for Ising lattices
Monte Carlo investigations of magnetization versus field, , at the
critical temperature provide direct accurate results on the critical exponent
for one, two, three and four-dimensional lattices:
=0, =0.0666(2)1/15,
=0.1997(4)1/5,
=0.332(5)1/3. This type of Monte Carlo data on
, which is not easily found in studies of Ising lattices in the current
literature, as far as we know, defines extremely well the numerical value of
this exponent within very stringent limits.Comment: 5 pages, 4 figures. Sent to Europhysics Letter
Extended Scaling for the high dimension and square lattice Ising Ferromagnets
In the high dimension (mean field) limit the susceptibility and the second
moment correlation length of the Ising ferromagnet depend on temperature as
chi(T)=tau^{-1} and xi(T)=T^{-1/2}tau^{-1/2} exactly over the entire
temperature range above the critical temperature T_c, with the scaling variable
tau=(T-T_c)/T. For finite dimension ferromagnets temperature dependent
effective exponents can be defined over all T using the same expressions. For
the canonical two dimensional square lattice Ising ferromagnet it is shown that
compact "extended scaling" expressions analogous to the high dimensional limit
forms give accurate approximations to the true temperature dependencies, again
over the entire temperature range from T_c to infinity. Within this approach
there is no cross-over temperature in finite dimensions above which
mean-field-like behavior sets in.Comment: 6 pages, 6 figure
Dissipation in Mesoscopic Superconductors with Ac Magnetic Fields
The response of mesoscopic superconductors to an ac magnetic field is
investigated both experimentally and with numerical simulations. We study small
square samples with dimensions of the order of the penetration depth. We obtain
the ac susceptibitity at microwave frequencies as a
function of the dc magnetic field . We find that the dissipation, given
by , has a non monotonous behavior in mesoscopic samples. In the
numerical simulations we obtain that the dissipation increases before the
penetration of vortices and then it decreases abruptly after vortices have
entered the sample. This is verified experimentally, where we find that
has strong oscillations as a function of in small squares of
Pb.Comment: 4 pages, 2 figure
Temperature dependence of an AlInP 63Ni betavoltaic cell
In this paper, the performance of an Al0.52In0.48P 63 Ni radioisotope cell is reported over the temperature range of −20 °C to 140 °C. A 400 μm diameter p+-i-n+ (2 μm i-layer) Al0.52In0.48P mesa photodiode was used as a conversion device in a novel betavoltaic cell. Dark current measurements on the Al0.52In0.48P detector showed that the saturation current increased increasing the temperature, while the ideality factor decreased. The effects of the temperature on the key cell parameters were studied in detail showing that the open circuit voltage, the maximum output power, and the internal conversion efficiency decreased when the temperature was increased. At −20 °C, an open circuit voltage and a maximum output power of 0.52 V and 0.28 pW, respectively, were measured
Minority Influence and Degrowth-Oriented Pro-environmental Conflict: When Emotions Betray Our Attachment to the Social Dominant Paradigm
If today the anthropogenic origin of climate change gathers almost total scientific consensus, human pro-environmental action is not changing with sufficient impact to keep global warming within the 1.5° limit. Environmental psychology has traditionally focused on the underlying barriers towards more pro-environmental behaviours. Emotions—like fear or anger—may act as such barriers especially in case of radical change (e.g., degrowth). While minority influence has been extensively applied to understand societal change, it has rarely been applied to understand the emotional responses that may hinder counter-normative pro-environmental messages. However, past literature on emotions shows that, in challenging situations—the likes of radical minority conflict—people will tend to use their emotional reaction to maintain societal status quo. Two studies investigated how participants emotionally react towards a counter-normative pro-environmental minority message (advocating degrowth). A qualitative (thematic analyses) and a quantitative (emotional self-report paradigm) studies showed that participants report emotions that allow them to realign themselves with the cultural backdrop of the social dominant paradigm (growth), thus resisting change. Specifically, although all participants tend to demonstrate higher proportions of control-oriented emotions, men do so more. These effects, as well as questions of cultural and ideological dominance, are discussed considering barriers towards pro-environmentalism
Social justice in education : how the function of selection in educational institutions predicts support for (non)egalitarian assessment practices
Educational institutions are considered a keystone for the establishment of a meritocratic
society. They supposedly serve two functions: an educational function that promotes learning
for all, and a selection function that sorts individuals into different programs, and ultimately
social positions, based on individual merit. We study how the function of selection relates to
support for assessment practices known to harm vs. benefit lower status students, through the
perceived justice principles underlying these practices. We study two assessment practices:
normative assessment-focused on ranking and social comparison, known to hinder the
success of lower status students-and formative assessment-focused on learning and
improvement, known to benefit lower status students. Normative assessment is usually
perceived as relying on an equity principle, with rewards being allocated based on merit and
should thus appear as positively associated with the function of selection. Formative
assessment is usually perceived as relying on corrective justice that aims to ensure equality of
outcomes by considering students' needs, which makes it less suitable for the function of
selection. A questionnaire measuring these constructs was administered to university students.
Results showed that believing that education is intended to select the best students positively
predicts support for normative assessment, through increased perception of its reliance on
equity, and negatively predicts support for formative assessment, through reduced perception
of its ability to establish corrective justice. This study suggests that the belief in the function
of selection as inherent to educational institutions can contribute to the reproduction of social
inequalities by preventing change from assessment practices known to disadvantage lowerstatus
student, namely normative assessment, to more favorable practices, namely formative
assessment, and by promoting matching beliefs in justice principles
Determination of Gd concentration profile in UO2-Gd2O3 fuel pellets
A transversal mapping of the Gd concentration was measured in UO2-Gd2O3
nuclear fuel pellets by electron paramagnetic resonance spectroscopy (EPR). The
quantification was made from the comparison with a Gd2O3 reference sample. The
nominal concentration in the pellets is UO2: 7.5 % Gd2O3. A concentration
gradient was found, which indicates that the Gd2O3 amount diminishes towards
the edges of the pellets. The concentration varies from (9.3 +/- 0.5)% in the
center to (5.8 +/- 0.3)% in one of the edges. The method was found to be
particularly suitable for the precise mapping of the distribution of Gd3+ ions
in the UO2 matrix.Comment: 10 pages, 5 figures, 2 tables. Submitted to Journal of Nuclear
Material
New extended high temperature series for the N-vector spin models on three-dimensional bipartite lattices
High temperature expansions for the susceptibility and the second correlation
moment of the classical N-vector model (O(N) symmetric Heisenberg model) on the
sc and the bcc lattices are extended to order for arbitrary N. For
N= 2,3,4.. we present revised estimates of the critical parameters from the
newly computed coefficients.Comment: 11 pages, latex, no figures, to appear in Phys. Rev.
Gallium arsenide 55Fe X-ray-photovoltaic battery
The effects of temperature on the key parameters of a prototype GaAs 55Fe radioisotope X-ray microbattery were studied over the temperature range -20 °C to 70 °C. A p-i-n GaAs structure was used to collect the photons from a 254 Bq 55Fe radioisotope X-ray source. Experimental results showed that the open circuit voltage and the short circuit current decreased with increased temperature. The maximum output power and the conversion efficiency of the device decreased at higher temperatures. For the reported microbattery, the highest maximum output power (1 pW, corresponding to 0.4 μW/Ci) was observed at -20 °C. A conversion efficiency of 9% was measured at -20 °C
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