3,064 research outputs found
Peierls distorted chain as a quantum data bus for quantum state transfer
We systematically study the transfer of quantum state of electron spin as the
flying qubit along a half-filled Peierls distorted tight-binding chain
described by the Su-Schrieffer-Heeger (SSH) model, which behaves as a quantum
data bus. This enables a novel physical mechanism for quantum communication
with always-on interaction: the effective hopping of the spin carrier between
sites and connected to two sites in this SSH chain can be induced by
the quasi-excitations of the SSH model. As we prove, it is the Peierls energy
gap of the SSH quasi-excitations that plays a crucial role to protect the
robustness of the quantum state transfer process. Moreover, our observation
also indicates that such a scheme can also be employed to explore the intrinsic
property of the quantum system.Comment: 10 pages, 6 figure
Patterned growth and cathodoluminescence of conical boron nitride nanorods
We demonstrate a simple and effective approach for growing large-scale, high-density, and well-patterned conical boron nitride nanorods. A catalyst layer of Fe(NO3)3 was patterned on a silicon substrate by using a copper grid as a mask. The nanorods were grown via annealing milled boron carbide powders at 1300 °C in a flow of nitrogen gas. The as-grown nanorods exhibit uniform morphology and the catalyst pattern precisely defines the position of nanorod deposition. Cathodoluminescence (CL) spectra of the nanorods show two broad emission bands centered at 3.75 and 1.85 eV. Panchromatic CL images reveal clear patterned structure<br /
A Cosmological Model with Dark Spinor Source
In this paper, we discuss the system of Friedman-Robertson-Walker metric
coupling with massive nonlinear dark spinors in detail, where the thermodynamic
movement of spinors is also taken into account. The results show that, the
nonlinear potential of the spinor field can provide a tiny negative pressure,
which resists the Universe to become singular. The solution is oscillating in
time and closed in space, which approximately takes the following form
g_{\mu\nu}=\bar R^2(1-\delta\cos t)^2\diag(1,-1,-\sin^2r ,-\sin^2r
\sin^2\theta), with light year, and
. The present time is about .Comment: 13 pages, no figure, to appear in IJMP
Event history analysis of dynamic communication networks
Statistical analysis on networks has received growing attention due to demand from various emerging applications. In dynamic networks, one of the key interests is to model the event history of time-stamped interactions among nodes. We model dynamic directed networks via multivariate counting processes. A pseudo partial likelihood approach is exploited to capture the network dependence structure. Asymptotic results are established. Numerical experiments are performed to demonstrate the effectiveness of our proposal
Disease burden of urinary tract infections among type 2 diabetes mellitus patients in the U.S.
AbstractAimsType 2 diabetes is a reported risk factor for more frequent and severe urinary tract infections (UTI). We sought to quantify the annual healthcare cost burden of UTI in type 2 diabetic patients.MethodsAdult patients diagnosed with type 2 diabetes were identified in MarketScan administrative claims data. UTI occurrence and costs were assessed during a 1-year period. We examined UTI-related visit and antibiotic costs among patients diagnosed with UTI, comparing those with versus without a history of UTI in the previous year (prevalent vs. incident UTI cases). We estimated the total incremental cost of UTI by comparing all-cause healthcare costs in patients with versus without UTI, using propensity score-matched samples.ResultsWithin the year, 8.2% (6,014/73,151) of subjects had ≥1 UTI, of whom 33.8% had a history of UTI. UTI-related costs among prevalent versus incident cases were, respectively, 447 (p=0.033) for outpatient services, 1,819 (p=NS) for hospitalizations, and 35 (p<0.0001) for antibiotics. UTI was associated with a total all-cause incremental cost of $7,045 (95% CI: 4,130, 13,051) per patient with UTI per year.ConclusionsUTI is common and may impose a substantial direct medical cost burden among patients with type 2 diabetes
Semiparametric Multivariate Accelerated Failure Time Model with Generalized Estimating Equations
The semiparametric accelerated failure time model is not as widely used as
the Cox relative risk model mainly due to computational difficulties. Recent
developments in least squares estimation and induced smoothing estimating
equations provide promising tools to make the accelerate failure time models
more attractive in practice. For semiparametric multivariate accelerated
failure time models, we propose a generalized estimating equation approach to
account for the multivariate dependence through working correlation structures.
The marginal error distributions can be either identical as in sequential event
settings or different as in parallel event settings. Some regression
coefficients can be shared across margins as needed. The initial estimator is a
rank-based estimator with Gehan's weight, but obtained from an induced
smoothing approach with computation ease. The resulting estimator is consistent
and asymptotically normal, with a variance estimated through a multiplier
resampling method. In a simulation study, our estimator was up to three times
as efficient as the initial estimator, especially with stronger multivariate
dependence and heavier censoring percentage. Two real examples demonstrate the
utility of the proposed method
Corrections to Scaling for the Two-dimensional Dynamic XY Model
With large-scale Monte Carlo simulations, we confirm that for the
two-dimensional XY model, there is a logarithmic correction to scaling in the
dynamic relaxation starting from a completely disordered state, while only an
inverse power law correction in the case of starting from an ordered state. The
dynamic exponent is .Comment: to appear as a Rapid commu. in Phys. Rev.
- …