Sliding Window Spectrum Sensing for Full-Duplex Cognitive Radios with Low Access-Latency

In a cognitive radio system the failure of secondary user (SU) transceivers to promptly vacate the channel can introduce significant access-latency for primary or high-priority users (PU). In conventional cognitive radio systems, the backoff latency is exacerbated by frame structures that only allow sensing at periodic intervals. Concurrent transmission and sensing using self-interference suppression has been suggested to improve the performance of cognitive radio systems, allowing decisions to be taken at multiple points within the frame. In this paper, we extend this approach by proposing a sliding-window full-duplex model allowing decisions to be taken on a sample-by-sample basis. We also derive the access-latency for both the existing and the proposed schemes. Our results show that the access-latency of the sliding scheme is decreased by a factor of 2.6 compared to the existing slotted full-duplex scheme and by a factor of approximately 16 compared to a half-duplex cognitive radio system. Moreover, the proposed scheme is significantly more resilient to the destructive effects of residual self-interference compared to previous approaches.Comment: Published in IEEE VTC Spring 2016, Nanjing, Chin

Quantum Error Correction on Linear Nearest Neighbor Qubit Arrays

A minimal depth quantum circuit implementing 5-qubit quantum error correction in a manner optimized for a linear nearest neighbor architecture is described. The canonical decomposition is used to construct fast and simple gates that incorporate the necessary swap operations. Simulations of the circuit's performance when subjected to discrete and continuous errors are presented. The relationship between the error rate of a physical qubit and that of a logical qubit is investigated with emphasis on determining the concatenated error correction threshold.Comment: 4 pages, 5 figure

Spatial Multiplexing of QPSK Signals with a Single Radio: Antenna Design and Over-the-Air Experiments

The paper describes the implementation and performance analysis of the first fully-operational beam-space MIMO antenna for the spatial multiplexing of two QPSK streams. The antenna is composed of a planar three-port radiator with two varactor diodes terminating the passive ports. Pattern reconfiguration is used to encode the MIMO information onto orthogonal virtual basis patterns in the far-field. A measurement campaign was conducted to compare the performance of the beam-space MIMO system with a conventional 2-by-?2 MIMO system under realistic propagation conditions. Propagation measurements were conducted for both systems and the mutual information and symbol error rates were estimated from Monte-Carlo simulations over the measured channel matrices. The results show the beam-space MIMO system and the conventional MIMO system exhibit similar finite-constellation capacity and error performance in NLOS scenarios when there is sufficient scattering in the channel. In comparison, in LOS channels, the capacity performance is observed to depend on the relative polarization of the receiving antennas.Comment: 31 pages, 23 figure

Enantioselective construction of the tricyclic core of curcusones A–D via a cross-electrophile coupling approach

Herein we report our recent progress toward the enantioselective total synthesis of the diterpenoid natural products curcusones A–D by means of complementary Stetter annulation or ring-closing metathesis (RCM) disconnections. Using the latter approach, we have achieved the concise construction of the 5–7–6 carbocyclic core embedded in each member of the curcusone family. Essential to this route is the use of a cross-electrophile coupling strategy, which has not previously been harnessed in the context of natural product synthesis

Critical Junctures in Assistive Technology and Disability Inclusion

It is clear from the events of the last 18 months that while technology has a huge potential for transforming the way we live and work, the entire ecosystem—from manufacturing to the supply chain—is vulnerable to the vagaries of that ecosystem, as well as having the potential to exacerbate new and existing inequalities [...

Vascular Dysfunction and Posttraumatic Stress Disorder: Examining the Role of Oxidative Stress and Sympathetic Activity

Purpose: The physiological manifestations of posttraumatic stress disorder (PTSD) have been associated with an increase in risk of cardiovascular disease (CVD) independent of negative lifestyle factors. The goal of the study was to better elucidate the mechanisms behind the increased CVD risk by examining peripheral vascular function, a precursor to CVD. Moreover, this study sought to determine the role of oxidative stress and sympathetic nervous system (SNS) activity in PTSD-induced vascular dysfunction. Methods: Sixteen individuals with PTSD (10 women, 6 men; age 24 ± 4 years), and twenty-four healthy controls (CTRL; 15 women, 9 men, 24 ± 4 years), participated in the study. The PTSD group participated in two visits, consuming either a placebo or antioxidant cocktail (AO - vitamins C and E and alpha lipoic acid) prior to their visits, in a randomized order. Arm vascular function was assessed via the reactive hyperemia- induced flow mediated dilation of the brachial artery (BAFMD) technique and evaluated with Doppler ultrasonography. Brachial artery and arm microvascular function were determined by percent change of diameter from baseline normalized for BA shear rate (BAD/Shear), and blood flow area under the curve (BF AUC), respectively. Heart rate variability (HRV) was used to assess autonomic nervous system activity. Results: BF AUC was significantly lower (p = 0.02) and SNS activity was significantly higher (p = 0.02) in the PTSD group when compared to the CTRL group. BAD/Shear was not different between groups. Following the acute AO supplementation, BF AUC was augmented to which it was no longer significantly different (p = 0.16) when compared to the CTRL group. SNS activity within the PTSD group was significantly reduced (p=.007) following the AO supplementation when compared to the PL condition, and the difference between PTSD and CTRL was no longer significant (p=.41). Conclusion: Young individuals with PTSD demonstrated lower arm microvascular, but not brachial artery, function as well as higher sympathetic activity when compared to healthy controls matched for age, sex, and physical activity level. Furthermore, this microvascular dysfunction and SNS activity was attenuated by an acute AO supplementation to the level of the healthy controls. Taken together, this study revealed that the modulation of oxidative stress, via an acute AO supplementation, improved vascular dysfunction in individuals with PTSD, potentially by reducing the substantial SNS activity associated with this disorder.https://scholarscompass.vcu.edu/gradposters/1084/thumbnail.jp

Maximum entanglement of formation for a two-mode Gaussian state over passive operations

We quantify the maximum amount of entanglement of formation (EoF) that can be achieved by continuous-variable states under passive operations, which we refer to as EoF-potential. Focusing, in particular, on two-mode Gaussian states we derive analytical expressions for the EoF-potential for specific classes of states. For more general states, we demonstrate that this quantity can be upper-bounded by the minimum amount of squeezing needed to synthesize the Gaussian modes, a quantity called squeezing of formation. Our work, thus, provides a new link between non-classicality of quantum states and the non-classicality of correlations.Comment: Revised versio

Elemental bio-imaging of trace elements in teeth using laser ablation-inductively coupled plasma-mass spectrometry

Objectives: In this study we present the application of a novel laboratory method that employs laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to construct two-dimensional maps of trace elements in teeth. Methods: Teeth were sectioned longitudinally, embedded in resin and polished to a smooth surface. Data were generated by laser ablating the entire sectioned tooth surface. Elemental images were constructed using custom-built software. Results: Quantified images of 66Zn, 88Sr, 111Cd and 208Pb, with a spatial resolution of 30 μm2, were generated from three teeth. Concentrations were determined by single-point calibration against NIST SRM 1486 (bone meal). Zn and Sr concentrations were determined in the μg g-1 range and Cd and Pb in the ng g -1 range. Concentrations of Pb, Zn and Cd were higher in dentine particularly in regions adjacent the pulp. Conclusions: Elemental bio-imaging employing LA-ICP-MS is a novel method for constructing μm-scale maps of trace elements in teeth. This simple imaging method displays the heterogeneity of trace elements throughout the tooth structure that correspond to specific structural and developmental features of teeth. As a preliminary study, this work demonstrates the capabilities of LA-ICP-MS imaging in dental research. © 2011 Elsevier Ltd. All rights reserved