3,349 research outputs found
Gate-controllable spin-battery
We propose a gate-controllable spin-battery for spin current. The
spin-battery consists of a lateral double quantum dot under a uniform magnetic
field. A finite DC spin-current is driven out of the device by controlling a
set of gate voltages. Spin-current can also be delivered in the absence of
charge-current. The proposed device should be realizable using present
technology at low temperature.Comment: 3 pages, 3 figures, accepted by Appl. Phys. Let
Source monitoring for continuous-variable quantum key distribution
The noise in optical source needs to be characterized for the security of
continuous-variable quantum key distribution (CVQKD). Two feasible schemes,
based on either active optical switch or passive beamsplitter are proposed to
monitor the variance of source noise, through which, Eve's knowledge can be
properly estimated. We derive the security bounds for both schemes against
collective attacks in the asymptotic case, and find that the passive scheme
performs better.Comment: The first version. 9 pages and 4 figure
Weakly nonlinear quantum transport: an exactly solvable model
We have studied the weakly non-linear quantum transport properties of a
two-dimensional quantum wire which can be solved exactly. The non-linear
transport coefficients have been calculated and interesting physical properties
revealed. In particular we found that as the incoming electron energy
approaches a resonant point given by energy , where the transport is
characterized by a complete reflection, the second order non-linear conductance
changes its sign. This has interesting implications to the current-voltage
characteristics. We have also investigated the establishment of the gauge
invariance condition. We found that for systems with a finite scattering
region, correction terms to the theoretical formalism are needed to preserve
the gauge invariance. These corrections were derived analytically for this
model.Comment: 15 pages, LaTeX, submitted to Phys. Rev.
Chaos control in random Boolean networks by reducing mean damage percolation rate
Chaos control in Random Boolean networks is implemented by freezing part of
the network to drive it from chaotic to ordered phase. However, controlled
nodes are only viewed as passive blocks to prevent perturbation spread. This
paper proposes a new control method in which controlled nodes can exert an
active impact on the network. Controlled nodes and frozen values are
deliberately selected according to the information of connection and Boolean
functions. Simulation results show that the number of nodes needed to achieve
control is largely reduced compared to previous method. Theoretical analysis is
also given to estimate the least fraction of nodes needed to achieve control.Comment: 10 pages, 2 figure
Testing Spatial Noncommutativity via Magnetic Hyperfine Structure Induced by Fractional Angular Momentum of Rydberg System
An approach to solve the critical problem of testing quantum effects of
spatial noncommutativity is proposed. Magnetic hyperfine structures in a
Rydberg system induced by fractional angular momentum originated from spatial
noncommutativity are discussed. The orders of the corresponding magnetic
hyperfine splitting of spectrum lie within the
limits of accuracy of current experimental measurements. Experimental tests of
physics beyond the standard model are the focus of broad interest. We note that
the present approach is reasonable achievable with current technology. The
proof is based on very general arguments involving only the deformed
Heisenberg-Weyl algebra and the fundamental property of angular momentum. Its
experimental verification would constitute an advance in understanding of
fundamental significance, and would be a key step towards a decisive test of
spatial noncommutativity.Comment: 11 pages, no figure
Statistical Analysis for Hospital Length-of-Stay and Readmission Rate Study
Hospital readmission rate has become a major indicator of quality of care, with penalties given to hospitals that have high rates of readmission. At the same time, insurers are applying increasing pressure to improve efficiency and reduce costs, including decreasing hospital lengths of stay. We analyze these trends to determine if reducing lengths of stay (LOS) may actually worsen readmission rates. All records of patients admitted to the neurosurgical service at one hospital from October 2007 through June 2014 were aggregated and analyzed for several variables, including initial length of stay, readmission occurrence, and length of stay, admitting diagnosis, admission priority and discharge disposition. Any trends over time were also noted. 925 out of 9,409 patient encounters are readmissions. Readmission rate and average length of stay were found significantly negative correlated. Besides linear regression which directly connecting average length of stay and readmission rate, survival analysis methods with Cox proportional hazard ratio model were employed to determine which factors were associated with a higher risk of readmission. There was a clear increase in readmissions over the study period, but LOS remained relatively constant, suggesting that increasing medical complexity confounded efforts to decrease LOS and was responsible for increased readmission rates. This study can help providers avoid readmissions by focusing on effective management of comorbidities
Hospital Length of Stay and Readmission Rate for Neurosurgical Patients
BACKGROUND
Hospital readmission rate has become a major indicator of quality of care, with penalties given to hospitals with high rates of readmission. At the same time, insurers are increasing pressure for greater efficiency and reduced costs, including decreasing hospital lengths of stay (LOS).
OBJECTIVE
To analyze the authors’ service to determine if there is a relationship between LOS and readmission rates.
METHODS
Records of patients admitted to the authors’ institution from October 2007 through June 2014 were analyzed for several data points, including initial LOS, readmission occurrence, admitting and secondary diagnoses, and discharge disposition.
RESULTS
Out of 9409 patient encounters, there were 925 readmissions. Average LOS was 6 d. Univariate analysis indicated a higher readmission rate with more diagnoses upon admission (P < .001) and an association between insurance type and readmission (P < .001), as well as decreasing average yearly LOS (P = .0045). Multivariate analysis indicated statistically significant associations between longer LOS (P = .03) and government insurance (P < .01).
CONCLUSION
A decreasing LOS over time has been associated with an increasing readmission rate at the population level. However, at the individual level, a prolonged LOS was associated with a higher risk of readmission. This was attributed to patient comorbidities. However, this increasing readmission rate may represent many factors including patients’ overall health status. Thus, the rate of readmission may represent a burden of illness rather than a valid metric for quality of care
Commensurate lock-in and incommensurate supersolid phases of hardcore bosons on anisotropic triangular lattices
We investigate the interplay between commensurate lock-in and incommensurate
supersolid phases of the hardcore bosons at half-filling with anisotropic
nearest-neighbor hopping and repulsive interactions on triangular lattice. We
use numerical quantum and variational Monte Carlo as well as analytical
Schwinger boson mean-field analysis to establish the ground states and phase
diagram. It is shown that, for finite size systems, there exist a series of
jumps between different supersolid phases as the anisotropy parameter is
changed. The density ordering wavevectors are locked to commensurate values and
jump between adjacent supersolids. In the thermodynamic limit, however, the
magnitude of these jumps vanishes leading to a continuous set of novel
incommensurate supersoild phases.Comment: 5 pages, 5 figures, added new results, changed title and conclusio
Current conservation in two-dimensional AC-transport
The electric current conservation in a two-dimensional quantum wire under a
time dependent field is investigated. Such a conservation is obtained as the
global density of states contribution to the emittance is balanced by the
contribution due to the internal charge response inside the sample. However
when the global partial density of states is approximately calculated using
scattering matrix only, correction terms are needed to obtain precise current
conservation. We have derived these corrections analytically using a specific
two-dimensional system. We found that when the incident energy is near the
first subband, our result reduces to the one-dimensional result. As
approaches to the -th subband with , the correction term diverges. This
explains the systematic deviation to precise current conservation observed in a
previous numerical calculation.Comment: 12 pages Latex, submitted to Phys. Rev.
Role of Phagocyte Oxidase in UVA-Induced Oxidative Stress and Apoptosis in Keratinocytes
Chronic exposure to ultraviolet radiation including ultraviolet A (315–400 nm) (UVA) may cause photocarcinogenesis and photoaging. The UVA-induced production of reactive oxygen species (ROS) and the resultant oxidative stress exposure play an important role in these biological processes. Here we have investigated the role of phagocyte oxidase (PHOX, gp91phox) in the production of ROS, redox status change, and apoptosis after UVA exposure by using gp91phox-deficient (gp91phox-/-) primary keratinocytes. UVA radiation resulted in increased ROS production and oxidation of reduced glutathione (GSH) to its oxidized form (GSSG). The presence of diphenylene iodonium (DPI) inhibited ROS production by UVA. In comparison with wild-type cells, gp91phox-/- cells produced slightly less ROS and GSH oxidation. UVA radiation induced apoptosis in wild-type keratinocytes as detected by phosphatidylserine (PS) translocation, caspase activation, and DNA fragmentation. As compared with wild-type cells, UVA induced less PS translocation in gp91phox-deficient cells. No difference, however, was observed in caspase activation and DNA fragmentation after UVA exposure in wild-type and gp91phox-/- cells. These findings suggest that gp91phox plays a limited role in the UVA-induced ROS production, oxidative stress, and therefore the PS translocation, but has no effect on UVA-induced caspase activation and DNA fragmentation during apoptosis
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