18,101 research outputs found
The spiral spin state in a zigzag spin chain system
We considered a spin chain with nearest neighbor and next nearest neighbor
exchange interactions, anisotropic exchange interaction and
Dzyaloshinskii-Moriya interaction. The conditions of the spiral spin state as
the ground state were analyzed. Our method was to build the connection between
the spiral state and the fully polarized state with a unitary transformation.
Under this transformation, anisotropic exchange interaction and
Dzyaloshinskii-Moriya interaction can be transformed to each other. Then we
used positive semi-definite matrix theorem to identify the region of fully
polarized state as the ground state for the transformed Hamiltonian, and it is
the region of spiral spin state as the ground state of the original
Hamiltonian. We also found that the effect of Dzyaloshinskii-Moriya interaction
is important. Its strength is related to the pitch angle of spiral spins. Our
method can be applied to coupled spin chains and two dimensional triangular
lattice systems. The result can be compared with experiment data.Comment: 12 pages, 9 figure
Marginally Trapped Surfaces in the Nonsymmetric Gravitational Theory
We consider a simple, physical approach to the problem of marginally trapped
surfaces in the Nonsymmetric Gravitational Theory (NGT). We apply this approach
to a particular spherically symmetric, Wyman sector gravitational field,
consisting of a pulse in the antisymmetric field variable. We demonstrate that
marginally trapped surfaces do exist for this choice of initial data.Comment: REVTeX 3.0 with epsf macros and AMS symbols, 3 pages, 1 figur
Hall effect and geometric phases in Josephson junction arrays
Since effectively the local contact vortex velocity dependent part of the Magnus force in a Josephson junction array is zero in the classical limit, we predict zero classical Hall effect. In the quantum limit because of the geometric phases due to the finite superfluid density at superconductor grains, rich and complex Hall effect is found in this quantum regime due to the Thouless-Kohmoto-Nightingale-den-Nijs effect
Spin relaxation in a GaAs quantum dot embedded inside a suspended phonon cavity
The phonon-induced spin relaxation in a two-dimensional quantum dot embedded
inside a semiconductor slab is investigated theoretically. An enhanced
relaxation rate is found due to the phonon van Hove singularities. Oppositely,
a vanishing deformation potential may also result in a suppression of the spin
relaxation rate. For larger quantum dots, the interplay between the spin orbit
interaction and Zeeman levels causes the suppression of the relaxation at
several points. Furthermore, a crossover from confined to bulk-like systems is
obtained by varying the width of the slab.Comment: 5 pages, 4 figures, to apper in Phys. Rev. B (2006
Trends in the prevalence, incidence and surgical management of carpal tunnel syndrome between 1993 and 2013: an observational analysis of UK primary care records
OBJECTIVES: To describe the prevalence, incidence and surgical management of carpal tunnel syndrome (CTS), between 1993 and 2013, as recorded in the Clinical Practice Research Datalink (CPRD). DESIGN: We completed a series of cross-sectional epidemiological analyses to observe trends over time. SETTING: Primary care data collected between 1993 and 2013, stored in the CPRD. POPULATION: Individuals aged ≥18 years were selected. Prevalent and incident episodes of CTS and episodes of surgical intervention were identified using a list of preidentified Read codes. ANALYSIS: We defined incident episodes as those with no preceding diagnostic code for CTS in the past 2 years of data. Episodes of surgery were expressed as a percentage of the prevalent population during the same calendar year. Joinpoint regression was used to determine significant changes in the underlying trend. RESULTS: The prevalence of CTS increased over the study period, with a particular incline between 2000 and 2004 (annual percentage change 7.81). The female-to-male prevalence ratio reduced over time from 2.74 in 1993 to 1.93 in 2013. The median age of females and males with CTS were noted to increase from 49 and 53 years, respectively in 1993 to 54 and 59 years, respectively in 2013. Incidence was also noted to increase over time. After an initial increase between 1993 and 2007, the percentage of prevalent patients with a coded surgical episode began to decrease after 2007 to 27.41% in 2013 (annual percentage change -1.7). CONCLUSION: This study has demonstrated that the prevalence and incidence of CTS increased over the study period between 1993 and 2013. Rates of surgery for CTS also increased over the study period; however after 2007, the per cent of patients receiving surgery showed a statistically significant decline back to the rate seen in 2004
Predicting surgical intervention in patients presenting with carpal tunnel syndrome in primary care.
Purpose: Carpal tunnel syndrome (CTS) is a symptomatic compression neuropathy of the median nerve. This study investigated the value of candidate prognostic factors (PFs) in predicting carpal tunnel release surgery. Patients and methods: This is a retrospective cohort study set in the Clinical Practice Research Datalink. Patients ≥18 years presenting with an incident episode of CTS were identified between 1989 and 2013. Candidate PF's defined in coded electronic patient records were identified following literature review and consultation with clinicians. Time to first carpal tunnel release surgery was the primary end point. A manual backward stepwise selection procedure was used to obtain an optimal prediction model, which included all the significant PFs. Results: In total, 91,412 patients were included in the cohort. The following PFs were included in an optimal model (C-statistic: 0.588 [95% CI 0.584-0.592]) for predicting surgical intervention: geographical region; deprivation status; age hazard ratio (HR 1.02 per year, 95% CI 1.01-1.02); obesity (HR 1.23, 95% CI 1.19-1.27); alcohol drinker (HR 1.05, 95% CI 1.00-1.10); smoker (HR 1.06, 95% 1.03-1.10); inflammatory condition (HR 1.13, 95% CI 0.98-1.29); neck condition (HR 1.13, 95% CI 1.03-1.23); and multisite pain (HR 1.10, 95% CI 1.05-1.15). Although not included in the multivariable model, pregnancy (if gender female) within 1 year of the index consultation, reduced the risk of surgery (HR 0.24, 95% CI 0.21-0.28). Conclusion: This study shows that patients who are older and who have comorbidities including other pain conditions are more likely to have surgery, whereas patients presenting with CTS during or within a year of pregnancy are less likely to have surgery. This information can help to inform clinicians and patients about the likely outcome of treatment and to be aware of which patients may be less responsive to primary care interventions
Laser anneal of oxycarbosilane low-k film
Submilisecond laser anneal has been experimentally investigated for porogen removal and its ability to improve the mechanical strength in oxycarbosilane ultra low-k films compromised due to the introduction of porosity. We report the occurrence of extensive bond rearrangements inferred from Fourier-transform infra-red (FTIR) spectroscopy, elastic recoil detection (ERD) and spectroscopic ellipsometry (SE) in the energy range of 1.4-8 eV. The laser anneal affects most notably the organic content of the organosilicate matrix leading to depletion and reorganization. Nevertheless, the tested conditions reveal a processing window which allows for 13% improvement of Young’s modulus as compared to the reference film, annealed in a conventional furnace at 400°C for 2 h, while not impacting the relative dielectric constant of 2.25
Entanglement detection via condition of quantum correlation
We develop a novel necessary condition of quantum correlation. It is utilized
to construct -level bipartite Bell-type inequality which is strongly
resistant to noise and requires only analyses of measurement outcomes
compared to the previous result . Remarkably, a connection between
the arbitrary high-dimensional bipartite Bell-type inequality and entanglement
witnesses is found. Through the necessary condition of quantum correlation, we
propose that the witness operators to detect truly multipartite entanglement
for a generalized Greenberger-Horne-Zeilinger (GHZ) state with two local
measurement settings and a four-qubit singlet state with three settings.
Moreover, we also propose the first robust entanglement witness to detect
four-level tripartite GHZ state with only two local measurement settings
- …