23,861 research outputs found
Quenched Charge Disorder and Coulomb Interactions
We develop a general formalism to investigate the effect of quenched fixed
charge disorder on effective electrostatic interactions between charged
surfaces in a one-component (counterion-only) Coulomb fluid. Analytical results
are explicitly derived for two asymptotic and complementary cases: i)
mean-field or Poisson-Boltzmann limit (including Gaussian-fluctuations
correction), which is valid for small electrostatic coupling, and ii)
strong-coupling limit, where electrostatic correlations mediated by counterions
become significantly large as, for instance, realized in systems with
high-valency counterions. In the particular case of two apposed and ideally
polarizable planar surfaces with equal mean surface charge, we find that the
effect of the disorder is nil on the mean-field level and thus the plates
repel. In the strong-coupling limit, however, the effect of charge disorder
turns out to be additive in the free energy and leads to an enhanced long-range
attraction between the two surfaces. We show that the equilibrium inter-plate
distance between the surfaces decreases for elevated disorder strength (i.e.
for increasing mean-square deviation around the mean surface charge), and
eventually tends to zero, suggesting a disorder-driven collapse transition.Comment: 13 pages, 2 figure
Investigating the Effect of Stratospheric Radiation on Seed Germination and Growth
Three seed types: bean (Phaseolus vulgaris), corn (Zea mays) and radish (Raphanus sativus) were flown in a high altitude weather balloon into the mid-stratosphere to investigate the effects of high altitude radiation on germination success and seedling growth. After recovering and planting the seeds, the bean seeds showed lower germination success with exposure to high altitude radiation, and consequently stunted seedling growth. Cord and radish seeds experienced a statistically significant positive effect on germination success form radiation exposure compared to control seeds, but negative effect on seedling growth. Overall, the field experiments presented here support laboratory studies that show radiation exposure on vegetable seeds has a mixed effect on the germination success and negative effect on seedling growth on investigated seed types
Towards environmental sustainability in Russia: evidence from green universities
Environmental analysis; Environmental economics; Environmental management; Environmental pollution; Education; Sustainability; Environment; Universities; GM ranking; Fixed-effects, Random-effects; Russia © 2020Universities all over the world are increasingly recognizing the need for the attainment of environmental sustainability on campuses resulting in the adoption of several environmental sustainable initiatives by university management. This article, therefore, seeks to investigate the impact of campus-base management practices on environmental quality among Russian Universities. The study also explores the strengths and weaknesses against the best practices for campus sustainability as defined by the UI greenMetric world university ranking as well as the awareness of students about pro-environmental behaviours on campuses. Secondary data from the 2015 to 2019 world university ranking was sourced for the impact assessment as well as the strengths and weaknesses. The study also sourced primary data with the help of a structured questionnaire from student respondents to assess their awareness of pro-environmental behaviours. Fixed-effects, and random-effects models were used to assess the management impact on environmental quality. The result from the empirical models indicate that education and research, transportation and waste influence environmental quality on university campuses. The strengths and weaknesses of universities were assessed based on six (6) categories (setting and infrastructure, energy and climate change, waste, water, transport, and education and research). The study also assessed the perception of students on pro-environmental activities. While the results show an increasing trend of awareness among Russian universities (Management) in campus sustainability initiatives, most students appear to be unaware of environmental initiatives undertaken by their universities. The study, therefore, made some recommendations that can help improve campus sustainability levels while at the same time increase student participation. © 202
Quantum statistical properties of some new classes of intelligent states associated with special quantum systems
Based on the {\it nonlinear coherent states} method, a general and simple
algebraic formalism for the construction of \textit{`-deformed intelligent
states'} has been introduced. The structure has the potentiality to apply to
systems with a known discrete spectrum as well as the generalized coherent
states with known nonlinearity function . As some physical appearance of
the proposed formalism, a few new classes of intelligent states associated with
\textit{`center of-mass motion of a trapped ion'}, \textit{`harmonious states'}
and \textit{`hydrogen-like spectrum'} have been realized. Finally, the
nonclassicality of the obtained states has been investigated. To achieve this
purpose the quantum statistical properties using the Mandel parameter and the
squeezing of the quadratures of the radiation field corresponding to the
introduced states have been established numerically.Comment: 13page
Generation of spin currents via Raman scattering
We show theoretically that stimulated spin flip Raman scattering can be used
to inject spin currents in doped semiconductors with spin split bands. A pure
spin current, where oppositely oriented spins move in opposite directions, can
be injected in zincblende crystals and structures. The calculated spin current
should be detectable by pump-probe optical spectroscopy and anomalous Hall
effect measurement
Quantum Transport with Spin Dephasing: A Nonequilibrium Green's Function Approach
A quantum transport model incorporating spin scattering processes is
presented using the non-equilibrium Green's function (NEGF) formalism within
the self-consistent Born approximation. This model offers a unified approach by
capturing the spin-flip scattering and the quantum effects simultaneously. A
numerical implementation of the model is illustrated for magnetic tunnel
junction devices with embedded magnetic impurity layers. The results are
compared with experimental data, revealing the underlying physics of the
coherent and incoherent transport regimes. It is shown that small variations in
magnetic impurity spin-states/concentrations could cause large deviations in
junction magnetoresistances.Comment: NEGF Formalism, Spin Dephasing, Magnetic Tunnel Junctions,
Magnetoresistanc
A complete characterization of phase space measurements
We characterize all the phase space measurements for a non-relativistic
particle.Comment: 11 pages, latex, no figures, iopart styl
New limit on the mass of 9.4-keV solar axions emitted in an M1 transition in Kr nuclei
A search for resonant absorption of the solar axion by nuclei
was performed using the proportional counter installed inside the
low-background setup at the Baksan Neutrino Observatory. The obtained model
independent upper limit on the combination of isoscalar and isovector
axion-nucleon couplings allowed us to set
the new upper limit on the hadronic axion mass of eV (95\%
C.L.) with the generally accepted values =0.5 and =0.56.Comment: 5 pages, 2 figures, Proceedings of the 10th Patras Workshop on
Axions, WIMPs and WISP 29 June - 4 July 2014, CERN, Geneva, Switzerlan
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