16,651 research outputs found
Micromagnetic simulations of sweep-rate dependent coercivity in perpendicular recording media
The results of micromagnetic simulations are presented which examine the
impact of thermal fluctuations on sweep rate dependent coercivities of both
single-layer and exchange-coupled-composite (ECC) perpendicular magnetic
recording media. M-H loops are calculated at four temperatures and sweep rates
spanning five decades with fields applied normal to the plane and at 45
degrees. The impact of interactions between grains is evaluated. The results
indicate a significantly weaker sweep-rate dependence for ECC media suggesting
more robustness to long-term thermal effects. Fitting the modeled results to
Sharrock-like scaling proposed by Feng and Visscher [J. Appl. Phys. 95, 7043
(2004)] is successful only in the case of single-layer media with the field
normal to the plane.Comment: 7 pages, 14 figure
Quantum field theoretic approach to neutrino oscillations in matter
We consider neutrino oscillations in non-uniform matter in a quantum field
theoretic (QFT) approach, in which neutrino production, propagation and
detection are considered as a single process. We find the conditions under
which the oscillation probability can be sensibly defined and demonstrate how
the properly normalized oscillation probability can be obtained in the QFT
framework. We derive the evolution equation for the oscillation amplitude and
discuss the conditions under which it reduces to the standard
Schr\"odinger-like evolution equation. It is shown that, contrary to the common
usage, the Schr\"odinger-like evolution equation is not applicable in certain
cases, such as oscillations of neutrinos produced in decays of free pions
provided that sterile neutrinos with eV exist.Comment: LaTeX, 24 pages + 16 pages of appendices, 1 figure. V2: typos
correcte
Mass hierarchy, 2-3 mixing and CP-phase with Huge Atmospheric Neutrino Detectors
We explore the physics potential of multi-megaton scale ice or water
Cherenkov detectors with low ( GeV) threshold. Using some proposed
characteristics of the PINGU detector setup we compute the distributions of
events versus neutrino energy and zenith angle , and study
their dependence on yet unknown neutrino parameters. The
regions are identified where the distributions have the highest sensitivity to
the neutrino mass hierarchy, to the deviation of the 2-3 mixing from the
maximal one and to the CP-phase. We evaluate significance of the measurements
of the neutrino parameters and explore dependence of this significance on the
accuracy of reconstruction of the neutrino energy and direction. The effect of
degeneracy of the parameters on the sensitivities is also discussed. We
estimate the characteristics of future detectors (energy and angle resolution,
volume, etc.) required for establishing the neutrino mass hierarchy with high
confidence level. We find that the hierarchy can be identified at --
level (depending on the reconstruction accuracies) after 5 years of
PINGU operation.Comment: 39 pages, 21 figures. Description of Fig.3 correcte
Tailoring Gold Nanoparticle Characteristics and the Impact on Aqueous-Phase Oxidation of Glycerol
Poly(vinyl alcohol) (PVA)-stabilized Au nanoparticles (NPs) were synthesized by colloidal methods in which temperature variations (−75 to 75 °C) and mixed H2O/EtOH solvent ratios (0, 50, and 100 vol/vol) were used. The resulting Au NPs were immobilized on TiO2 (P25), and their catalytic performance was investigated for the liquid phase oxidation of glycerol. For each unique solvent system, there was a systematic increase in the average Au particle diameter as the temperature of the colloidal preparation increased. Generation of the Au NPs in H2O at 1 °C resulted in a high observed activity compared with current Au/TiO2 catalysts (turnover frequency = 915 h–1). Interestingly, Au catalysts with similar average particle sizes but prepared under different conditions had contrasting catalytic performance. For the most active catalyst, aberration-corrected high angle annular dark field scanning transmission electron microscopy analysis identified the presence of isolated Au clusters (from 1 to 5 atoms) for the first time using a modified colloidal method, which was supported by experimental and computational CO adsorption studies. It is proposed that the variations in the populations of these species, in combination with other solvent/PVA effects, is responsible for the contrasting catalytic properties
Designing Inclusive Reflective Learning with Digital Democratic Dialogue Across Boundaries and Diversities
A new approach to spherically symmetric junction surfaces and the matching of FLRW regions
We investigate timelike junctions (with surface layer) between spherically
symmetric solutions of the Einstein-field equation. In contrast to previous
investigations this is done in a coordinate system in which the junction
surface motion is absorbed in the metric, while all coordinates are continuous
at the junction surface.
The evolution equations for all relevant quantities are derived. We discuss
the no-surface layer case (boundary surface) and study the behaviour for small
surface energies. It is shown that one should expect cases in which the speed
of light is reached within a finite proper time.
We carefully discuss necessary and sufficient conditions for a possible
matching of spherically symmetric sections.
For timelike junctions between spherically symmetric space-time sections we
show explicitly that the time component of the Lanczos equation always reduces
to an identity (independently of the surface equation of state).
The results are applied to the matching of FLRW models. We discuss `vacuum
bubbles' and closed-open junctions in detail. As illustrations several
numerical integration results are presented, some of them indicate that the
junction surface can reach the speed of light within a finite time.Comment: new version - corrected boundary surface discussion, improved
presentation, and corrected reference 22 pages, many figure
30 days wild: development and evaluation of a large-scale nature engagement campaign to improve well-being
There is a need to increase people’s engagement with and connection to nature, both for human well-being and the conservation of nature itself. In order to suggest ways for people to engage with nature and create a wider social context to normalise nature engagement, The Wildlife Trusts developed a mass engagement campaign, 30 Days Wild. The campaign asked people to engage with nature every day for a month. 12,400 people signed up for 30 Days Wild via an online sign-up with an estimated 18,500 taking part overall, resulting in an estimated 300,000 engagements with nature by participants. Samples of those taking part were found to have sustained increases in happiness, health, connection to nature and pro-nature behaviours. With the improvement in health being predicted by the improvement in happiness, this relationship was mediated by the change in connection to nature
Exciton entanglement in two coupled semiconductor microcrystallites
Entanglement of the excitonic states in the system of two coupled
semiconductor microcrystallites, whose sizes are much larger than the Bohr
radius of exciton in bulk semiconductor but smaller than the relevant optical
wavelength, is quantified in terms of the entropy of entanglement. It is
observed that the nonlinear interaction between excitons increases the maximum
values of the entropy of the entanglement more than that of the linear coupling
model. Therefore, a system of two coupled microcrystallites can be used as a
good source of entanglement with fixed exciton number. The relationship between
the entropy of the entanglement and the population imbalance of two
microcrystallites is numerically shown and the uppermost envelope function for
them is estimated by applying the Jaynes principle.Comment: 16 pages, 6 figure
Synthesis of nanocrystals by discharges in liquid nitrogen from Si-Sn sintered electrode
International audienceThe synthesis feasibility of silicon-tin nanocrystals by discharges in liquid nitrogen is studied using a Si-10 at % Sn sintered electrode. Time-resolved optical emission spectroscopy shows that silicon and tin melt almost simultaneously. The presence of both vapours does not lead to the synthesis of alloyed nanocrystals but to the synthesis of separate nanocrystals of silicon and tin with average sizes of 10 nm. These nanocrystals are transformed into amorphous silicon oxide (am-SiO2) and beta-SnO2 by air oxidation, after evaporation of the liquid nitrogen. The synthesis of an am-Si0.95Sn0.05 phase around large silicon crystals (similar to 500 nm) decorated by beta-Sn spheroids is achieved if the current flowing through electrodes is high enough. When the sintered electrode is hit by powerful discharges, some grains are heated and tin diffuses in the large silicon crystals. Next, these grains are shelled and fall into the dielectric liquid
Quantum Sine(h)-Gordon Model and Classical Integrable Equations
We study a family of classical solutions of modified sinh-Gordon equation,
$\partial_z\partial_{{\bar z}} \eta-\re^{2\eta}+p(z)\,p({\bar z})\
\re^{-2\eta}=0p(z)=z^{2\alpha}-s^{2\alpha}Q(\alpha>0)(\alpha<-1)$ models.Comment: 35 pages, 3 figure
- …