1,795 research outputs found
Proximity of Iron Pnictide Superconductors to a Quantum Tricritical Point
We determine the nature of the magnetic quantum critical point in the doped
LaFeAsO using a set of constrained density functional calculations that provide
ab initio coefficients for a Landau order parameter analysis. The system turns
out to be remarkably close to a quantum tricritical point, where the nature of
the phase transition changes from first to second order. We compare with the
effective field theory and discuss the experimental consequences.Comment: 4 pages, 4 figure
Influence of vibrations on electron transport through nanoscale contacts
In this article we present a novel semi-analytical approach to calculate
first-order electron-vibration coupling constants within the framework of
density functional theory. It combines analytical expressions for the
first-order derivative of the Kohn-Sham operator with respect to nuclear
displacements with coupled-perturbed Kohn-Sham theory to determine the
derivative of the electronic density matrix. This allows us to efficiently
compute accurate electron-vibration coupling constants. We apply our approach
to describe inelastic electron tunneling spectra of metallic and molecular
junctions. A gold junction bridged by an atomic chain is used to validate the
developed method, reproducing established experimental and theoretical results.
For octane-dithiol and octane-diamine single-molecule junctions we discuss the
influence of the anchoring group and mechanical stretching on the inelastic
electron tunneling spectra.Comment: 13 pages, 5 figure
Why is cheating wrong?
Since cheating is obviously wrong, arguments against it (it provides an
unfair advantage, it hinders learning) need only be mentioned in passing. But
the argument of unfair advantage absurdly takes education to be essentially a
race of all against all; moreover, it ignores that many cases of unfair
(dis)advantages are widely accepted. That cheating can hamper learning does not
mean that punishing cheating will necessarily favor learning, so that this
argument does not obviously justify sanctioning cheaters.
-- Keywords: academic dishonesty, academic integrity, academic misconduct,
education, ethics, homework, plagiarismComment: 8 pages; new (completely rewritten) version; in Studies in Philosophy
and Education (2009
Cosmology with the Highly Redshifted 21cm Line
In addition to being a probe of Cosmic Dawn and Epoch of Reionization
astrophysics, the 21cm line at is also a powerful way to constrain
cosmology. Its power derives from several unique capabilities. First, the 21cm
line is sensitive to energy injections into the intergalactic medium at high
redshifts. It also increases the number of measurable modes compared to
existing cosmological probes by orders of magnitude. Many of these modes are on
smaller scales than are accessible via the CMB, and moreover have the advantage
of being firmly in the linear regime (making them easy to model theoretically).
Finally, the 21cm line provides access to redshifts prior to the formation of
luminous objects. Together, these features of 21cm cosmology at provide
multiple pathways toward precise cosmological constraints. These include the
"marginalizing out" of astrophysical effects, the utilization of redshift space
distortions, the breaking of CMB degeneracies, the identification of signatures
of relative velocities between baryons and dark matter, and the discovery of
unexpected signs of physics beyond the CDM paradigm at high redshifts.Comment: Science white paper submitted to Decadal 2020 surve
A DFT Study of Structural and Electronic Properties of ZnS Polymorphs and its Pressure-Induced Phase Transitions
A systematic first-principles investigation, by using the density functional formalism with the nonlocal B3LYP approximation including a long-range dispersion correction, has been performed to calculate the structural and electronic properties and phase transitions under pressure of the three phases of ZnS (cubic zinc blende, ZB, hexagonal wurtzite, W, and cubic rock salt, RS). Numerical and analytical fittings have been carried out to determine the equilibrium unit cell geometry and equation of state parameters for the ZnS phases. The band structures, energy gap, density of states, and vibrational frequencies and their pressure dependences are investigated. The present results illustrate that both phases, W and ZB, present very similar enthalpy and the RS phase becomes thermodynamically more stable than ZB and W structures at 15.0 and 15.5 GPa, respectively. These phase transitions are accompanied by an increase of the first shell coordination number of Zn atom and by a cell volume collapse of 13.9% and 14.3% for ZB and W phases, respectively. The atomic contributions of the conduction and valence bands, as well the binding energy for the Zn 3d orbital have been obtained.The authors gratefully acknowledge the financial support of the Brazilian agencies CAPES, CNPq (573636/2008-7) and FAPESP (2013/07296-2 and 2013/19289-0). J.A. also acknowledges Generalitat Valenciana for Prometeo/2009/053 project, Ministerio de Ciencia e Innovación for project CTQ-2012-36253-C03-01CTO, and Programa de Cooperación CientÃfica con Iberoamerica (Brasil), Ministerio de Educación (PHB2009-0065-PC)
A cross-national study on the antecedents of work–life balance from the fit and balance perspective
Drawing on the perceived work–family fit and balance perspective, this study investigates demands and resources as antecedents of work–life balance (WLB) across four countries (New Zealand, France, Italy and Spain), so as to provide empirical cross-national evidence. Using structural equation modelling analysis on a sample of 870 full time employees, we found that work demands, hours worked and family demands were negatively related to WLB, while job autonomy and supervisor support were positively related to WLB. We also found evidence that resources (job autonomy and supervisor support) moderated the relationships between demands and work–life balance, with high resources consistently buffering any detrimental influence of demands on WLB. Furthermore, our study identified additional predictors of WLB that were unique to some national contexts. For example, in France and Italy, overtime hours worked were negatively associated with WLB, while parental status was positively associated with WLB. Overall, the implications for theory and practice are discussed.Peer ReviewedPostprint (author's final draft
Routes for breaching and protecting genetic privacy
We are entering the era of ubiquitous genetic information for research,
clinical care, and personal curiosity. Sharing these datasets is vital for
rapid progress in understanding the genetic basis of human diseases. However,
one growing concern is the ability to protect the genetic privacy of the data
originators. Here, we technically map threats to genetic privacy and discuss
potential mitigation strategies for privacy-preserving dissemination of genetic
data.Comment: Draft for comment
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