4,487 research outputs found
The role of symmetry on interface states in magnetic tunnel junctions
When an electron tunnels from a metal into the barrier in a magnetic tunnel
junction it has to cross the interface. Deep in the metal the eigenstates for
the electron can be labelled by the point symmetry group of the bulk but around
the interface this symmetry is reduced and one has to use linear combinations
of the bulk states to form the eigenstates labelled by the irreducible
representations of the point symmetry group of the interface. In this way there
can be states localized at the interface which control tunneling. The
conclusions as to which are the dominant tunneling states are different from
that conventionally found.Comment: 14 pages, 5 figures, accepted in PRB, v2: reference 3 complete
Seeking the Real Adam Smith and Milton Friedman
In this paper we will analyze the relationship between free market principles and ethics through an exploration of how too many business managers often approach the ideas of Adam Smith and Milton Friedman. In doing so, we aim to provide a thoughtful foundation for future discussions of how we ought to navigate this intersection. We briefly examine questions such as: What is the relationship between the “best” economy in terms of efficiency and the common good for society? Is pursuing one’s individual economic advantage the same as promoting the general interest? As we analyze and discuss these questions, specifically in the context of Smith and Friedman, we also make some alternative normative assertions, grounded in social welfare, about adopting a broader societal perspective for the purpose of business
High resolution spectroscopy for Cepheids distance determination. II. A period- projection factor relation
The projection factor is a key quantity for the interferometric
Baade-Wesselink (hereafter IBW) and surface-brightness (hereafter SB) methods
of determining the distance of Cepheids. Indeed, it allows a consistent
combination of angular and linear diameters of the star. We aim to determine
consistent projection factors that include the dynamical structure of the
Cepheids' atmosphere. Methods. Hydrodynamical models of delta Cep and l Car
have been used to validate a spectroscopic method of determining the projection
factor. This method, based on the amplitude of the radial velocity curve, is
applied to eight stars observed with the HARPS spectrometer. The projection
factor is divided into three sub-concepts : (1) a geometrical effect, (2) the
velocity gradient within the atmosphere, and (3) the relative motion of the
"optical" pulsating photosphere compared to the corresponding mass elements
(hereafter fo-g). Both, (1) and (3) are deduced from geometrical and
hydrodynamical models, respectively, while (2) is derived directly from
observations. The Fe I 4896.439 A line is found to be the best one to use in
the context of IBW and SB methods. A coherent and consistent period-projection
factor relation (hereafter Pp relation) is derived for this specific spectral
line: p = [0.064 +- 0.020] log P + [1.376 +- 0.023]. This procedure is then
extended to derive dynamic projection factors for any spectral line of any
Cepheid. This Pp relation is an important tool for removing bias in the
calibration of the period-luminosity relation of Cepheids. Moreover, it reveals
a new physical quantity fo-g to investigate in the near future
Structural and magnetic properties of Fe/ZnSe(001) interfaces
We have performed first principles electronic structure calculations to
investigate the structural and magnetic properties of Fe/ZnSe(001) interfaces.
Calculations involving full geometry optimizations have been carried out for a
broad range of thickness of Fe layers(0.5 monolayer to 10 monolayers) on top of
a ZnSe(001) substrate. Both Zn and Se terminated interfaces have been explored.
Total energy calculations show that Se segregates at the surface which is in
agreement with recent experiments.
For both Zn and Se terminations, the interface Fe magnetic moments are higher
than the bulk bcc Fe moment.
We have also investigated the effect of adding Fe atoms on top of a
reconstructed ZnSe surface to explore the role of reconstruction of
semiconductor surfaces in determining properties of metal-semiconductor
interfaces. Fe breaks the Se dimer bond formed for a Se-rich (2x1)
reconstructed surface. Finally, we looked at the reverse growth i.e. growth of
Zn and Se atoms on a bcc Fe(001) substrate to investigate the properties of the
second interface of a magnetotunnel junction. The results are in good agreement
with the theoretical and experimental results, wherever available.Comment: 7 pages, 8 figures, accepted for publication in PR
Markov Chain Methods For Analyzing Complex Transport Networks
We have developed a steady state theory of complex transport networks used to
model the flow of commodity, information, viruses, opinions, or traffic. Our
approach is based on the use of the Markov chains defined on the graph
representations of transport networks allowing for the effective network
design, network performance evaluation, embedding, partitioning, and network
fault tolerance analysis. Random walks embed graphs into Euclidean space in
which distances and angles acquire a clear statistical interpretation. Being
defined on the dual graph representations of transport networks random walks
describe the equilibrium configurations of not random commodity flows on
primary graphs. This theory unifies many network concepts into one framework
and can also be elegantly extended to describe networks represented by directed
graphs and multiple interacting networks.Comment: 26 pages, 4 figure
A new interferometric study of four exoplanet host stars : {\theta} Cygni, 14 Andromedae, {\upsilon} Andromedae and 42 Draconis
Studying exoplanet host stars is of the utmost importance to establish the
link between the presence of exoplanets around various types of stars and to
understand the respective evolution of stars and exoplanets.
Using the limb-darkened diameter (LDD) obtained from interferometric data, we
determine the fundamental parameters of four exoplanet host stars. We are
particularly interested in the F4 main-sequence star, {\theta} Cyg, for which
Kepler has recently revealed solar-like oscillations that are unexpected for
this type of star. Furthermore, recent photometric and spectroscopic
measurements with SOPHIE and ELODIE (OHP) show evidence of a quasi-periodic
radial velocity of \sim150 days. Models of this periodic change in radial
velocity predict either a complex planetary system orbiting the star, or a new
and unidentified stellar pulsation mode.
We performed interferometric observations of {\theta} Cyg, 14 Andromedae,
{\upsilon} Andromedae and 42 Draconis for two years with VEGA/CHARA (Mount
Wilson, California) in several three-telescope configurations. We measured
accurate limb darkened diameters and derived their radius, mass and temperature
using empirical laws.
We obtain new accurate fundamental parameters for stars 14 And, {\upsilon}
And and 42 Dra. We also obtained limb darkened diameters with a minimum
precision of \sim 1.3%, leading to minimum planet masses of Msini=5.33\pm 0.57,
0.62 \pm 0.09 and 3.79\pm0.29 MJup for 14 And b, {\upsilon} And b and 42 Dra b,
respectively. The interferometric measurements of {\theta} Cyg show a
significant diameter variability that remains unexplained up to now. We propose
that the presence of these discrepancies in the interferometric data is caused
by either an intrinsic variation of the star or an unknown close companion
orbiting around it.Comment: 10 pages + 2 pages appendix, 16 figures, accepted for publication in
A&
The Deconfinement Phase Transition in One-Flavour QCD
We present a study of the deconfinement phase transition of one-flavour QCD,
using the multiboson algorithm. The mass of the Wilson fermions relevant for
this study is moderately large and the non-hermitian multiboson method is a
superior simulation algorithm. Finite size scaling is studied on lattices of
size , and . The behaviours of the
peak of the Polyakov loop susceptibility, the deconfinement ratio and the
distribution of the norm of the Polyakov loop are all characteristic of a
first-order phase transition for heavy quarks. As the quark mass decreases, the
first-order transition gets weaker and turns into a crossover. To investigate
finite size scaling on larger spatial lattices we use an effective action in
the same universality class as QCD. This effective action is constructed by
replacing the fermionic determinant with the Polyakov loop identified as the
most relevant Z(3) symmetry breaking term. Higher-order effects are
incorporated in an effective Z(3)-breaking field, , which couples to the
Polyakov loop. Finite size scaling determines the value of where the first
order transition ends. Our analysis at the end - point, , indicates
that the effective model and thus QCD is consistent with the universality class
of the three dimensional Ising model.
Matching the field strength at the end point, , to the
values used in the dynamical quark simulations we estimate the end point,
, of the first-order phase transition. We find which corresponds to a quark mass of about 1.4 GeV .Comment: LaTex, 25 pages, 18 figure
Social work and gender::An argument for practical accounts
This article contributes to the debate on gender and social work by examining dominant approaches within the field. Anti-discriminatory, woman-centered and intersectional accounts are critiqued for reliance upon both reification and isolation of gender. Via examination of poststructural, queer and trans theories within social work, the author then presents accounts based upon structural/materialist, ethnomethodological and discursive theories, in order to open up debates about conceptualization of gender. These are used to suggest that social work should adopt a focus on gender as a practical accomplishment that occurs within various settings or contexts
Potentially inappropriate medication in older participants of the Berlin Aging Study II (BASE-II) - Sex differences and associations with morbidity and medication use
INTRODUCTION:
Multimorbidity in advanced age and the need for drug treatment may lead to polypharmacy, while pharmacokinetic and pharmacodynamic changes may increase the risk of adverse drug events (ADEs).
OBJECTIVE:
The aim of this study was to determine the proportion of subjects using potentially inappropriate medication (PIM) in a cohort of older and predominantly healthy adults in relation to polypharmacy and morbidity.
METHODS:
Cross-sectional data were available from 1,382 study participants (median age 69 years, IQR 67-71, 51.3% females) of the Berlin Aging Study II (BASE-II). PIM was classified according to the EU(7)-PIM and German PRISCUS (representing a subset of the former) list. Polypharmacy was defined as the concomitant use of at least five drugs. A morbidity index (MI) largely based on the Charlson Index was applied to evaluate the morbidity burden.
RESULTS:
Overall, 24.1% of the participants were affected by polypharmacy. On average, men used 2 (IQR 1-4) and women 3 drugs (IQR 1-5). According to PRISCUS and EU(7)-PIM, 5.9% and 22.6% of participants received at least one PIM, while use was significantly more prevalent in females (25.5%) compared to males (19.6%) considering EU(7)-PIM (p = 0.01). In addition, morbidity in males receiving PIM according to EU(7)-PIM was higher (median MI 1, IQR 1-3) compared to males without PIM use (median MI 1, IQR 0-2, p<0.001).
CONCLUSION:
PIM use occurred more frequently in women than in men, while it was associated with higher morbidity in males. As expected, EU(7)-PIM identifies more subjects as PIM users than the PRISCUS list but further studies are needed to investigate the differential impact of both lists on ADEs and outcome.
KEY POINTS:
We found PIM use to be associated with a higher number of regular medications and with increased morbidity. Additionally, we detected a higher prevalence of PIM use in females compared to males, suggesting that women and people needing intensive drug treatment are patient groups, who are particularly affected by PIM use
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