1,119 research outputs found
Crystal-field splittings in CeX (X= N, P, As, Sb, Bi) compounds
The unusual and interesting physical properties of rare earth intemetallic
compounds have their origin in the combination of strongly correlated 4f states
and their hybridization with the conduction electron sea, which gives rise to
their complex low temperature Kondo behavior. In particular, Ce compounds are
very sensitive to the crystalline and chemical environment, as compared to
other rare earth systems. The interaction of the 4f state with the conduction
band plays an important role in the determination of the different magnetic,
structural and transport properties of these systems. Among the cerium
compounds, those of the type CeX, which crystallize in the rock salt structure,
exhibit extremely unusual magnetic properties. By making use of the mixed
LDA-NCA calculation technique we analyse the crystal-field splittings of CeX
compounds (X=N, P, As, Sb, Bi). The obtained ab-initio hybridization functions
are taken as imputs to calculate the crystal-field splittings within NCA (non
crossing approximation) and the tendencies are contrasted with experiments. KEY
WORDS: Highly correlated systems, crystal fields, p-electron.Comment: 8 pages, 2 figure
Regression of tricuspid regurgitation after two-stage arterial switch operation for failing systemic ventricle after atrial inversion operation
AbstractThe cases of five patients with previous Senning ( n = 4) or Mustard ( n = 1) operations and failing systemic ventricles in whom banding of the pulmonary artery was performed as an interim step toward an arterial switch procedure are reported. The rise in the ratio of left to right mean systolic ventricular pressure, from 0.35 before operation to 0.90 during operation and 0.80 on the first postoperative day, caused a shift of the ventricular septum from a leftward to a midline or nearly midline position. This shift was associated with a reduction of tricuspid regurgitation. At a median interval of 5.1 months after pulmonary artery banding, the mean left ventricular posterior wall thickness had increased to 8.2 mm, versus 5 mm before operation, and the mean left ventricular myocardial mass index had increased to 90 gm/m2, versus 55.6 gm/m2 before operation. After the arterial switch operation, which was performed in four patients, the tricuspid regurgitation decreased to a trivial amount ( n = 1) or disappeared completely ( n = 3). (J THORAC CARDIOVASC SURG 1996;111:342-7
Outskirts of Distant Galaxies In Absorption
QSO absorption spectroscopy provides a sensitive probe of both the neutral
medium and diffuse ionized gas in the distant Universe. It extends 21cm maps of
gaseous structures around low-redshift galaxies both to lower gas column
densities and to higher redshifts. Combining galaxy surveys with
absorption-line observations of gas around galaxies enables comprehensive
studies of baryon cycles in galaxy outskirts over cosmic time. This Chapter
presents a review of the empirical understanding of the cosmic neutral gas
reservoir from studies of damped Lya absorbers (DLAs). It describes the
constraints on the star formation relation and chemical enrichment history in
the outskirts of distant galaxies from DLA studies. A brief discussion of
available constraints on the ionized circumgalactic gas from studies of lower
column density Lya absorbers and associated ionic absorption transitions is
presented at the end.Comment: 45 pages, 7 figures, invited review, Book chapter in "Outskirts of
Galaxies", Eds. J. H. Knapen, J. C. Lee and A. Gil de Paz, Astrophysics and
Space Science Library, Springer, in pres
Fermi edge singularities in X-ray spectra of strongly correlated fermions
We discuss the problem of the X-ray absorption in a system of interacting
fermions and, in particular, those features in the X-ray spectra that can be
used to discriminate between conventional Fermi-liquids and novel "strange
metals". Focusing on the case of purely forward scattering off the core-hole
potential, we account for the relevant interactions in the conduction band by
means of the bosonization technique. We find that the X-ray Fermi edge
singularities can still be present, although modified, even if the density of
states vanishes at the Fermi energy, and that, in general, the relationship
between the two appears to be quite subtle.Comment: Latex, 16 pages, Princeton preprin
Food for thought: association between dietary tyrosine and cognitive performance in younger and older adults
The fact that tyrosine increases dopamine availability that, in turn, may enhance cognitive performance has led to numerous studies on healthy young participants taking tyrosine as a food supplement. As a result of this dietary intervention, participants show performance increases in working memory and executive functions. However, the potential association between habitual dietary tyrosine intake and cognitive performance has not been investigated to date. The present study aims at clarifying the association of episodic memory (EM), working memory (WM) and fluid intelligence (Gf), and tyrosine intake in younger and older adults. To this end, we acquired habitual tyrosine intake (food frequency questionnaire) from 1724 participants of the Berlin Aging Study II (1383 older adults, 341 younger adults) and modelled its relations to cognitive performance assessed in a broad battery of cognitive tasks using structural equation modeling. We observed a significant association between tyrosine intake and the latent factor capturing WM, Gf, and EM in the younger and the older sample. Due to partial strong factorial invariance between age groups for a confirmatory factor analysis on cognitive performance, we were able to compare the relationship between tyrosine and cognition between age groups and found no difference. Above and beyond previous studies on tyrosine food supplementation the present result extend this to a cross-sectional association between habitual tyrosine intake levels in daily nutrition and cognitive performance (WM, Gf, and EM). This corroborates nutritional recommendations that are thus far derived from single-dose administration studies
ROSAT PSPC observations of nearby spiral galaxies - II. Statistical properties
We present a statistical analysis of the largest X-ray survey of nearby
spiral galaxies in which diffuse emission has been separated from discrete
source contributions. Regression and rank-order correlation analyses are used
to compare X-ray properties such as total, source and diffuse luminosities, and
diffuse emission temperature, with a variety of physical and multi-wavelength
properties, such as galaxy mass, type and activity, and optical and infrared
luminosity. The results are discussed in terms of the way in which hot gas and
discrete X-ray sources scale with the mass and activity of galaxies, and with
the star formation rate. We find that the X-ray properties of starburst
galaxies are dependent primarily on their star-forming activity, whilst for
more quiescent galaxies, galaxy mass is the more important parameter. One of
the most intriguing results is the tight linear scaling between far-infrared
and diffuse X-ray luminosity across the sample, even though the hot gas changes
from a hydrostatic corona to a free wind across the activity range sampled
here.Comment: 13 pages, latex file, 18 postscript figures, to appear in MNRA
Power spectrum of many impurities in a d-wave superconductor
Recently the structure of the measured local density of states power spectrum
of a small area of the \BSCCO (BSCCO) surface has been interpreted in terms of
peaks at an "octet" of scattering wave vectors determined assuming weak,
noninterfering scattering centers. Using analytical arguments and numerical
solutions of the Bogoliubov-de Gennes equations, we discuss how the
interference between many impurities in a d-wave superconductor alters this
scenario. We propose that the peaks observed in the power spectrum are not the
features identified in the simpler analyses, but rather "background" structures
which disperse along with the octet vectors. We further consider how our
results constrain the form of the actual disorder potential found in this
material.Comment: 5 pages.2 figure
The future of work in shaping the employment inclusion of young adults with disabilities:a qualitative study
Purpose: The world of work is changing and creating challenges and opportunities for the employment inclusion of young people with disabilities. In this article, the perceptions held by young adults with disabilities regarding participation in the future of work are examined. Design/methodology/approach: One-on-one interviews were conducted with Canadian young adults (ages 18–36 years) living with a disability. Participants were asked about their thoughts regarding the impact of the changing nature of work on their labor market involvement and career aspirations. A thematic analysis was performed to identify and examine emergent salient themes. Findings: In total, 22 young adults were interviewed; over half held secure employment. Career aspirations and work-related decisions were primarily shaped by a participant's health needs. The future of work was seen as a more proximal determinant to employment. Digital technologies were expected to impact working conditions and create barriers and facilitators to employment. Participants who indicated being securely employed held positive expectations regarding the impact of digital technology on their work. Participants working precariously held negative appraisals regarding the impact of digital technologies on employment opportunities. The role of technological and soft skills was critical to participating in a labor market reliant on advanced technology. Participants reported barriers to developing job skills related to their disability and their work arrangements. Originality/value: This research highlights the importance of considering changes in the future of work, especially the digital transformation of the economy, in the design of initiatives which promote the employment inclusion of young adults with disabilities. Despite the significance of the changing nature of work, supporting health needs and encouraging access to secure work arrangements also remain paramount.</p
Anomalous Superconducting Properties and Field Induced Magnetism in CeCoIn5
In the heavy fermion superconductor CeCoIn5 (Tc=2.3K) the critical field is
large, anisotropic and displays hysteresis. The magnitude of the critical-field
anisotropy in the a-c plane can be as large as 70 kOe and depends on
orientation. Critical field measurements in the (110) plane suggest 2D
superconductivity, whereas conventional effective mass anisotropy is observed
in the (100) plane. Two distinct field-induced magnetic phases are observed: Ha
appears deep in the superconducting phase, while Hb intersects Hc2 at T=1.4 K
and extends well above Tc. These observations suggest the possible realization
of a direct transition from ferromagnetism to Fulde-Ferrel-Larkin-Ovchinnikov
superconductivity in CeCoIn5.Comment: 4 pages, 3 figure
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