1,279 research outputs found
Security in Wireless Sensor Networks: Issues and Challenges
Wireless Sensor Network (WSN) is an emerging technology that shows great
promise for various futuristic applications both for mass public and military.
The sensing technology combined with processing power and wireless
communication makes it lucrative for being exploited in abundance in future.
The inclusion of wireless communication technology also incurs various types of
security threats. The intent of this paper is to investigate the security
related issues and challenges in wireless sensor networks. We identify the
security threats, review proposed security mechanisms for wireless sensor
networks. We also discuss the holistic view of security for ensuring layered
and robust security in wireless sensor networks.Comment: 6 page
All-optical coherent population trapping with defect spin ensembles in silicon carbide
Divacancy defects in silicon carbide have long-lived electronic spin states
and sharp optical transitions, with properties that are similar to the
nitrogen-vacancy defect in diamond. We report experiments on 4H-SiC that
investigate all-optical addressing of spin states with the zero-phonon-line
transitions. Our magneto-spectroscopy results identify the spin structure
of the ground and excited state, and a role for decay via intersystem crossing.
We use these results for demonstrating coherent population trapping of spin
states with divacancy ensembles that have particular orientations in the SiC
crystal.Comment: 28 page document: Pages 1-14 main text (with 3 figures); pages 15-28
supplementary information (with 5 figues). v2 has minor correction
Benefit Plan Design and Prescription Drug Utilization Among Asthmatics: Do Patient Copayments Matter?
Objective: The ratio of controller to reliever medication use has been proposed as a measure of treatment quality for asthma patients. In this study we examine the effects of plan level mean out-of-pocket asthma medication patient copayments and other features of benefit plan design on the use of controller medications alone, controller and reliever medications (combination therapy), and reliever medications alone. Methods: 1995-2000 MarketScan claims data were used to construct plan-level out-of-pocket copayment and physician/practice prescriber preference variables for asthma medications. Separate multinomial logit models were estimated for patients in fee-for-service (FFS) and non-FFS plans relating benefit plan design features, physician/practice prescribing preferences, patient demographics, patient comorbidities and county-level income variables to patient-level asthma treatment patterns. Results: We find that the controller reliever ratio rose steadily over 1995-2000, along with out-of-pocket payments for asthma medications, which rose more for controllers than for relievers. However, after controlling for other variables, plan level mean out-of-pocket copayments were not found to have a statistically significant influence upon patient-level asthma treatment patterns. On the other hand, physician practice prescribing patterns strongly influenced patient level treatment patterns. Conclusions: There is no strong statistical evidence that higher levels of out-of-pocket copayments for prescription drugs influence asthma treatment patterns. However, physician/practice prescribing preferences influence patient treatment.
Stabilizing nuclear spins around semiconductor electrons via the interplay of optical coherent population trapping and dynamic nuclear polarization
We experimentally demonstrate how coherent population trapping (CPT) for
donor-bound electron spins in GaAs results in autonomous feedback that prepares
stabilized states for the spin polarization of nuclei around the electrons. CPT
was realized by excitation with two lasers to a bound-exciton state.
Transmission studies of the spectral CPT feature on an ensemble of electrons
directly reveal the statistical distribution of prepared nuclear spin states.
Tuning the laser driving from blue to red detuned drives a transition from one
to two stable states. Our results have importance for ongoing research on
schemes for dynamic nuclear spin polarization, the central spin problem and
control of spin coherence.Comment: 5 pages, 4 figure
- …