1,692 research outputs found
Unusual anisotropic magnetoresistance due to magnetization-dependent spin-orbit interactions
One of recent surprising discoveries is the unusual anisotropic
magnetoresistance (UAMR) that depends on two magnetization components
perpendicular to the current differently, in contrast to the conventional
anisotropic magnetoresistance (AMR) that predicts no change in resistance when
the magnetization varies in the plane perpendicular to the current. Using
density functional theory and Boltzmann transport equation calculations for bcc
Fe, hcp Co, and bcc FeCo alloys, we show that UAMR can be accounted by the
magnetization-dependent spin-orbit interactions (SOI): Magnetization-dependent
SOI modifies electron energy bands that, in turn, changes resistance. A
phenomenological model reveals the intrinsic connection between SOI and
order-parameters. Such a mechanism is confirmed by the strong biaxial stain
effect on UAMR. Our findings provide an efficient way of searching and
optimizing materials with large UAMR, important in the design of
high-performance spintronic devices.Comment: 4 figure
Management of Extracranial Carotid Artery Aneurysms:17 Years» Experience
AbstractObjectives:a retrospective review of seventeen-year (1980–1996) experience of the management of extracranial carotid artery aneurysms.Patients and methods:sixty-six aneurysms of extracranial carotid artery were seen in 63 patients. The diagnosis was confirmed by angiography in 51 patients and duplex ultrasonography in twelve. Twenty-eight (42%) patients had an atherosclerotic aneurysm, twenty-two (33%) had false aneurysms secondary to trauma, nine were congenital and seven were mycotic. All underwent aneurysm resection with saphenous-vein-graft interposition as the most common means of reconstruction.Results:one death occurred due to septicaemia in a diabetic patient with a mycotic aneurysm, giving an operative mortality of 1.5%. One patient had an immediate hemiparesis after carotid artery ligation, and three had a hemiparesis within 48 hours of operation (6.1%). After a change in technique to avoid a residual carotid stump, no further neurological problems were encountered in the following 28 patients.Conclusion:extracranial carotid aneurysms may be successfully managed with resection and reconstruction with autogenous saphenous vein. End-to-side anastomosis avoids a blind-ending stump which may be the source of emboli
The effects of a family non-universal Z-prime boson on B--->pipi decays
Motivated by the measured large branching ratio of
(the so-called "" puzzle), we investigate the effects of a family
non-universal model on the tree-dominated decays. We
find that the coupling parameter with a
nontrivial new weak phase , which is relevant to the
contributions to the QCD penguin sector , is needed
to reconcile the observed discrepancy. Combined with the recent fitting results
from , and decays, the
parameter spaces are severely reduced but still not excluded entirely, implying
that both the "" and "" puzzles could be accommodated
simultaneously within such a family non-universal model.Comment: 28 pages, 4 figures. References and discussions added. To appear in
IJMP
On Vanishing Theorems For Vector Bundle Valued p-Forms And Their Applications
Let be a strictly increasing function
with . We unify the concepts of -harmonic maps, minimal
hypersurfaces, maximal spacelike hypersurfaces, and Yang-Mills Fields, and
introduce -Yang-Mills fields, -degree, -lower degree, and generalized
Yang-Mills-Born-Infeld fields (with the plus sign or with the minus sign) on
manifolds. When and
the -Yang-Mills field becomes an ordinary Yang-Mills field,
-Yang-Mills field, a generalized Yang-Mills-Born-Infeld field with the plus
sign, and a generalized Yang-Mills-Born-Infeld field with the minus sign on a
manifold respectively. We also introduce the energy functional (resp.
-Yang-Mills functional) and derive the first variational formula of the
energy functional (resp. -Yang-Mills functional) with
applications. In a more general frame, we use a unified method to study the
stress-energy tensors that arise from calculating the rate of change of various
functionals when the metric of the domain or base manifold is changed. These
stress-energy tensors, linked to -conservation laws yield monotonicity
formulae. A "macroscopic" version of these monotonicity inequalities enables us
to derive some Liouville type results and vanishing theorems for forms with
values in vector bundles, and to investigate constant Dirichlet boundary value
problems for 1-forms. In particular, we obtain Liouville theorems for
harmonic maps (e.g. -harmonic maps), and Yang-Mills fields (e.g.
generalized Yang-Mills-Born-Infeld fields on manifolds). We also obtain
generalized Chern type results for constant mean curvature type equations for
forms on and on manifolds with the global doubling property
by a different approach. The case and is due to Chern.Comment: 1. This is a revised version with several new sections and an
appendix that will appear in Communications in Mathematical Physics. 2. A
"microscopic" approach to some of these monotonicity formulae leads to
celebrated blow-up techniques and regularity theory in geometric measure
theory. 3. Our unique solution of the Dirichlet problems generalizes the work
of Karcher and Wood on harmonic map
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Factors influencing the well-being of Asian American LGBT individuals across the lifespan: perspectives from leaders of community-based organizations
Background
Lesbian, gay, bisexual, and transgender (LGBT) individuals have documented disparities in mental health that are experienced across the life course. However, limited research has been conducted to identify the factors which contribute to evaluated risk for poor mental health among older Asian Americans who identify as LGBT. The purpose of this study was to determine the perspectives of leaders of community-based organizations about the mental health needs and concerns of their LGBT constituents from diverse Asian backgrounds.
Methods
Semi-structured qualitative interviews were conducted with leaders of community-based organizations serving the needs of LGBT individuals. A qualitative framework analysis approach was used to identify, analyze and report themes within the data.
Results
11 members of community organizations located in California (54.5%), Chicago (27.2%), and New York (18.1%) were interviewed. Chronic stress was identified as negatively impacting constituents’ lives and was attributed to social determinants of health, including inadequate housing, financial insecurity, discrimination, barriers to adequate health care, and immigration status. Ageism, social isolation, language barriers, and limited connections to cultural, religious, or LGBT communities were identified as factors impacting middle-aged and older adults. Participants identified homelessness, violence, and lack of parental acceptance as contributing to distress among youth and younger adults. The most vulnerable community members were identified as gender minorities, undocumented individuals, and individuals with limited English proficiencies. Organizational leaders described strategies to address social determinants.
Conclusions
Asian Americans who are LGBT are confronted with substantial risks for poor mental health that are linked to modifiable social determinants of health. Organizations serving these populations play a vital role in meeting the needs of a highly underserved population
Constraints on the nonuniversal Z^\prime couplings from B\to\pi K, \pi K^{\ast} and \rho K Decays
Motivated by the large difference between the direct CP asymmetries
and , we
combine the up-to-date experimental information on ,
and decays to pursue possible solutions with the nonuniversal
model. Detailed analyses of the relative impacts of different
types of couplings are presented in four specific cases. Numerically, we find
that the new coupling parameters, and with a common
nontrivial new weak phase , which are relevant to the
contributions to the electroweak penguin sector
and , are crucial to the observed " puzzle". Furthermore,
they are found to be definitely unequal and opposite in sign. We also find that
can put a strong constraint on the new
couplings, which implies the contributions to the coefficient of
QCD penguins operator involving the parameter required.Comment: 27 pages, 6 figures. References and a note adde
A Branch-and-Bound Algorithm for Minimizing the Energy Consumption in the PFS Problem
This paper considers the energy consumption minimization in permutation flow shop (PFS) scheduling problem. The energy consumption of each machine is decomposed into two parts: useful part which completes the operation at current stage and wasted part which is consumed during idle period. The objective considered here is to minimize the total wasted energy consumption which is a weighted summation of the idle time of each machine. To solve this new problem, a branch-and-bound algorithm is developed. Two lower bounds are proposed, and an initial upper bound by using a variant of NEH heuristic algorithm is applied. Compared with the makespan minimization criterion, this model deduces more energy-saving solutions. Experimental results also validate the efficiency of the proposed algorithm for problems with job number not larger than 15
Magnetic Excitations of Undoped Iron Oxypnictides
We study the magnetic excitations of undoped iron oxypnictides using a
three-dimensional Heisenberg model with single-ion anisotropy. Analytic forms
of the spin wave dispersion, velocities, and structure factor are given. Aside
from quantitative comparisons which can be made to inelastic neutron scattering
experiments, we also give qualitative criteria which can distinguish various
regimes of coupling strength. The magnetization reduction due to quantum zero
point fluctuations shows clear dependence on the c-axis coupling.Comment: 4 pages, 5 figures, to appear in Frontiers of Physics in China: a
special issue on Iron-based superconductor
Geometric Control of Human Stem Cell Morphology and Differentiation
During tissue morphogenesis, stem cells and progenitor cells migrate, proliferate, and differentiate, with striking changes in cell shape, size, and acting mechanical stresses. The local cellular function depends on the spatial distribution of cytokines as well as local mechanical microenvironments in which the cells reside. In this study, we controlled the organization of human adipose derived stem cells using micro-patterning technologies, to investigate the influence of multi-cellular form on spatial distribution of cellular function at an early stage of cell differentiation. The underlying role of cytoskeletal tension was probed through drug treatment. Our results show that the cultivation of stem cells on geometric patterns resulted in pattern- and position-specific cell morphology, proliferation and differentiation. The highest cell proliferation occurred in the regions with large, spreading cells (such as the outer edge of a ring and the short edges of rectangles). In contrast, stem cell differentiation co-localized with the regions containing small, elongated cells (such as the inner edge of a ring and the regions next to the short edges of rectangles). The application of drugs that inhibit the formation of actomyosin resulted in the lack of geometrically specific differentiation patterns. This study confirms the role of substrate geometry on stem cell differentiation, through associated physical forces, and provides a simple and controllable system for studying biophysical regulation of cell function
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