456 research outputs found
Spin degree of freedom in two dimensional exciton condensates
We present a theoretical analysis of a spin-dependent multicomponent
condensate in two dimensions. The case of a condensate of resonantly
photoexcited excitons having two different spin orientations is studied in
detail. The energy and the chemical potentials of this system depend strongly
on the spin polarization . When electrons and holes are located in two
different planes, the condensate can be either totally spin polarized or spin
unpolarized, a property that is measurable. The phase diagram in terms of the
total density and electron-hole separation is discussed.Comment: 4 pages, 3 figures, Accepted for publication in Physical Review
Letter
Dynamical effects of an unconventional current-phase relation in YBCO dc-SQUIDs
The predominant d-wave pairing symmetry in high temperature superconductors
allows for a variety of current-phase relations in Josephson junctions, which
is to a certain degree fabrication controlled. In this letter we report on
direct experimental observations of the effects of a non-sinusoidal
current-phase dependence in YBCO dc-SQUIDs, which agree with the theoretical
description of the system.Comment: 4 pages, 4 ps figures, to apprear in Phys. Rev. Let
Enhancing Light-Matter Interactions in MoS\u3csub\u3e2\u3c/sub\u3e by Copper Intercalation
The intercalation of layered compounds opens up a vast space of new host–guest hybrids, providing new routes for tuning the properties of materials. Here, it is shown that uniform and continuous layers of copper can be intercalated within the van der Waals gap of bulk MoS2 resulting in a unique Cu–MoS2 hybrid. The new Cu–MoS2 hybrid, which remains semiconducting, possesses a unique plasmon resonance at an energy of ≈1eV, giving rise to enhanced optoelectronic activity. Compared with high‐performance MoS2 photodetectors, copper‐enhanced devices are superior in their spectral response, which extends into the infrared, and also in their total responsivity, which exceeds 104 A W−1. The Cu–MoS2 hybrids hold promise for supplanting current night‐vision technology with compact, advanced multicolor night vision
Engineering Superfluidity in Electron-Hole Double Layers
We show that band-structure effects are likely to prevent superfluidity in
semiconductor electron-hole double-layer systems. We suggest the possibility
that superfluidity could be realized by the application of uniaxial pressure
perpendicular to the electron and hole layers.Comment: 4 pages, includes 3 figure
Semiclassical theory of shot noise in ballistic n+-i-n+ semiconductor strucutres: relevance of Pauli and long range Coulomb correlations
We work out a semiclassical theory of shot noise in ballistic n+-i-n+
semiconductor structures aiming at studying two fundamental physical
correlations coming from Pauli exclusion principle and long range Coulomb
interaction. The theory provides a unifying scheme which, in addition to the
current-voltage characteristics, describes the suppression of shot noise due to
Pauli and Coulomb correlations in the whole range of system parameters and
applied bias. The whole scenario is summarized by a phase diagram in the plane
of two dimensionless variables related to the sample length and contact
chemical potential. Here different regions of physical interest can be
identified where only Coulomb or only Pauli correlations are active, or where
both are present with different relevance. The predictions of the theory are
proven to be fully corroborated by Monte Carlo simulations.Comment: 15 pages, 11 figures. Title changed and Introduction rewritten.
Accepted for publication in Physical Review
Suppression of non-Poissonian shot noise by Coulomb correlations in ballistic conductors
We investigate the current injection into a ballistic conductor under the
space-charge limited regime, when the distribution function of injected
carriers is an arbitrary function of energy F_c(epsilon). The analysis of the
coupled kinetic and Poisson equations shows that the injected current
fluctuations may be essentially suppressed by Coulomb correlations, and the
suppression level is determined by the shape of F_c(epsilon). This is in
contrast to the time-averaged quantities: the mean current and the spatial
profiles are shown to be insensitive to F_c(epsilon) in the leading-order terms
at high biases. The asymptotic high-bias behavior for the energy resolved
shot-noise suppression has been found for an arbitrary (non-Poissonian)
injection, which may suggest a new field of investigation on the optimization
of the injected energy profile to achieve the desired noise-suppression level.Comment: extended version 4 -> 8 pages, examples and figure adde
Suppression of non-Poissonian shot noise by Coulomb correlations in ballistic conductors
We investigate the current injection into a ballistic conductor under the
space-charge limited regime, when the distribution function of injected
carriers is an arbitrary function of energy F_c(epsilon). The analysis of the
coupled kinetic and Poisson equations shows that the injected current
fluctuations may be essentially suppressed by Coulomb correlations, and the
suppression level is determined by the shape of F_c(epsilon). This is in
contrast to the time-averaged quantities: the mean current and the spatial
profiles are shown to be insensitive to F_c(epsilon) in the leading-order terms
at high biases. The asymptotic high-bias behavior for the energy resolved
shot-noise suppression has been found for an arbitrary (non-Poissonian)
injection, which may suggest a new field of investigation on the optimization
of the injected energy profile to achieve the desired noise-suppression level.Comment: extended version 4 -> 8 pages, examples and figure adde
Managing Coastal Resources In The 21St Century
Coastal ecosystems are increasingly dominated by humans. Consequently, the human dimensions of sustainability science have become an integral part of emerging coastal governance and management practices. But if we are to avoid the harsh lessons of land management, coastal decision makers must recognize that humans are one of the more coastally dependent species in the biosphere. Management responses must therefore confront both the temporal urgency and the very real compromises and sacrifices that will be necessary to achieve a sustainable coastal ecosystem, one that is economically feasible, socially just, and ecologically sound
Modelling and simulating change in reforesting mountain landscapes using a social-ecological framework
Natural reforestation of European mountain landscapes raises major environmental and societal issues. With local stakeholders in the Pyrenees National Park area (France), we studied agricultural landscape colonisation by ash (Fraxinus excelsior) to enlighten its impacts on biodiversity and other landscape functions of importance for the valley socio-economics. The study comprised an integrated assessment of land-use and land-cover change (LUCC) since the 1950s, and a scenario analysis of alternative future policy. We combined knowledge and methods from landscape ecology, land change and agricultural sciences, and a set of coordinated field studies to capture interactions and feedback in the local landscape/land-use system. Our results elicited the hierarchically-nested relationships between social and ecological processes. Agricultural change played a preeminent role in the spatial and temporal patterns of LUCC. Landscape colonisation by ash at the parcel level of organisation was merely controlled by grassland management, and in fact depended on the farmer's land management at the whole-farm level. LUCC patterns at the landscape level depended to a great extent on interactions between farm household behaviours and the spatial arrangement of landholdings within the landscape mosaic. Our results stressed the need to represent the local SES function at a fine scale to adequately capture scenarios of change in landscape functions. These findings orientated our modelling choices in the building an agent-based model for LUCC simulation (SMASH - Spatialized Multi-Agent System of landscape colonization by ASH). We discuss our method and results with reference to topical issues in interdisciplinary research into the sustainability of multifunctional landscapes
Factors influencing patient satisfaction with dental appearance and treatments they desire to improve aesthetics
Background: We assessed factors influencing patients’ satisfaction with their dental appearance and the
treatments they desired to improve dental aesthetics.
Methods: A cross-sectional study was performed out among 235 adult patients who visited the Hospital Universiti
Sains Malaysia dental clinic. A structured, interviewer-guided questionnaire was used to identify patient satisfaction
with their general dental appearance, cosmetic elements and desired treatments.
Results: The 235 patients consisted of 70 males (29.8%) and 165 females (70.2%), of mean age 31.5 years (SD 13.0).
Of these patients, 124 (52.8%) were not satisfied with their general dental appearance. In addition, 132 patients
(56.2%) were not happy with the color of their teeth, 76 (32.3%), regarded their teeth were poorly aligned, 62
(26.4%), as crowded and 56 (23.4%) protruded. Dissatisfaction with tooth color was significantly higher in female
than in male patients (odds ratio [OR] of 1.99 (95% confidence interval [CI] 1.13-3.50). Tooth whitening was the
treatment most desired by patients (48.1%). Results of multiple logistic regression analysis showed that patient
dissatisfaction with general dental appearance was significantly associated with female gender (OR = 2.18; 95% CI:
1.18-4.03), unhappiness with tooth color (OR = 3.05; 95% CI: 1.74-5.34) and the opinion that their teeth protruded
(OR = 2.91, 95% CI: 1.44-5.91)
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