Exact Outage Probability Analysis of the Mixed RF/FSO System With Variable-Gain Relays

This paper presents a unified analysis of the mixed radio-frequency (RF)/free-space optics (FSO) relaying system, with multiple variable-gain amplify-and-forward relays. The partial relay selection (PRS) is employed to select the active relay for further re-transmission. Due to fast fading statistics of the first RF hop, it is assumed that the channel state information of the RF link is outdated, which is used for both the relay gain adjustment and the PRS procedure. The RF hops are subject to the Rayleigh fading, while the FSO hop is affected by the atmospheric turbulence and the pointing errors. The intensity fluctuations of the optical signal caused by atmospheric turbulence are modeled by the general Malaga (M) distribution, which takes into account the effect of multiple scattered components. An exact expression for the outage probability is derived. In addition, high-signal-to-noise-ratio approximations are provided, which can be used to efficiently determine the outage probability floor. Numerical results are validated by Monte Carlo simulations, which are used to examine the effects of the system and channel parameters on the RF/FSO system performance.Comment: Published in: IEEE Photonics Journa

Intrinsic and extrinsic decay of edge magnetoplasmons in graphene

We investigate intrinsic and extrinsic decay of edge magnetoplasmons (EMPs) in graphene quantum Hall (QH) systems by high-frequency electronic measurements. From EMP resonances in disk shaped graphene, we show that the dispersion relation of EMPs is nonlinear due to interactions, giving rise to intrinsic decay of EMP wavepacket. We also identify extrinsic dissipation mechanisms due to interaction with localized states in bulk graphene from the decay time of EMP wavepackets. We indicate that, owing to the unique linear and gapless band structure, EMP dissipation in graphene can be lower than that in GaAs systems.Comment: 5 page

Outage Probability Analysis of Mixed RF-FSO System Influenced by Fisher-Snedecor Fading and Gamma-Gamma Atmospheric Turbulence

In this paper, we investigate a dual-hop relaying system, composed of radio frequency (RF) and free-space optical (FSO) link. Decode-and-forward (DF) relay is employed to integrate the first RF link and the second line-of-sight FSO links. The RF channel is assumed to be subject to recently proposed Fisher-Snedecor fading model, which was shown to be convenient for modeling in realistic wireless communication scenarios. The FSO channel is affected by Gamma-Gamma distributed atmospheric turbulence. Expression for the outage probability is derived and utilized to present numerical results. Based on presented results, the effects of various RF and FSO channels parameters on the overall system performance are examined and discussed.Comment: Presented at 2018 26th Telecommunications Forum (TELFOR

Mixed RF-VLC Relaying System with Radio-Access Diversity

We present a statistical analysis of a mixed radio-frequency (RF)-visible light communications (VLC) relaying system, where outdoor millimeter wave based RF links are utilized to provide backhaul connectivity for indoor VLC broadcasting. The multiple RF links are assumed to communicate with the VLC access point through decode-and-forward relay. Novel closed-form outage probability and average bit error rate expressions are derived and utilized to obtain numerical results. Monte Carlo simulations validate presented numerical results, which are further used to examine the effects of system and channel parameters on system performance.Comment: Presented at 2019 28th Wireless and Optical Communications Conference (WOCC

Error rate and ergodic capacity of RF-FSO system with partial relay selection in the presence of pointing errors

This paper presents an analysis of a multiple dual-hop relaying system, which is composed of km-class radio frequency (RF)-free-space optical (FSO) links. Partial relay selection based on outdated channel state information (CSI) is employed in order to select active relay for further transmission. Amplify-and-forward relaying protocol is utilized. The RF links are assumed to be subject to Rayleigh fading, and the FSO links are influenced by both Gamma–Gamma atmospheric turbulence and pointing errors. On the basis of our previously derived expression for cumulative distribution function of the equivalent signal-to-noise ratio of the whole system, we derive novel analytical expressions for the average bit-error rate (BER) and ergodic capacity that are presented in terms of the Meijer’s G-function and extended generalized bivariate Meijer’s G-function, respectively. The numerical results are confirmed by Monte Carlo simulations. Considering the effect of time-correlation between outdated CSI and actual CSI related to the RF channel at the time of transmission, the average BER and the ergodic capacity dependence on various system and channel parameters are observed and discussed. The results illustrate that the temporal correlation between outdated and actual CSI has strong effect on system performance, particularly on BER values, when FSO hop is influenced by favorable conditions

Effects of placebos without deception compared with no treatment: a systematic review and meta-analysis

Aim Our aim was to address the clinical efficacy of open-label placebos compared with no treatment by systematic review, and meta-analysis where possible. Methods We searched the Cochrane Injuries Group's Specialised Register, The Cochrane Central Register of Controlled Trials (CENTRAL), Ovid MEDLINE(R) In-Process & Other NonIndexed Citations (OvidSP), EMBASE (OvidSP), and clinical trials registers and screened reference lists. We ran the most recent search on April 27 2015. All randomised controlled trials of any medical condition, which had both open-label placebo and no-treatment or treatment as usual groups were included. Two authors independently applied the selection criteria and extracted data. The risk of bias of included studies was assessed using the Cochrane criteria. We used random-effects model for meta-analysis. Results After removing duplicates we screened 348 publications, assessed 24 articles for eligibility and identified 5 trials (260 participants) that met our inclusion criteria. The clinical conditions were: irritable bowel syndrome (IBS), depression, allergic rhinitis, back pain and attention deficit hyperactivity disorder (ADHD). The overall risk of bias was moderate. All 5 trials were eligible for meta-analysis. We found a positive effect for non-deceptive placebos (standardized mean difference (SMD) 0.88, 95% CI 0.62 to 1.14, P<0.00001, I2= 1%). Conclusions Open-label placebos appear to have favorable clinical outcomes, compared to no treatment or no additional treatment. Caution is warranted when interpreting the results due to the limitations including the small number of trials and lack of blinding. Larger definitive trials are now warranted to explore the potential patient benefit of open-label placebos

In Vitro Aging of Human Skin Fibroblasts: Age-Dependent Changes in 4-Hydroxynonenal Metabolism

Evidence suggests that the increased production of free radicals and reactive oxygen species lead to cellular aging. One of the consequences is lipid peroxidation generating reactive aldehydic products, such as 4-hydroxynonenal (HNE) that modify proteins and form adducts with DNA bases. To prevent damage by HNE, it is metabolized. The primary metabolic products are the glutathione conjugate (GSH-HNE), the corresponding 4-hydroxynonenoic acid (HNA), and the alcohol 1,4-dihydroxynonene (DHN). Since HNE metabolism can potentially change during in vitro aging, cell cultures of primary human dermal fibroblasts from several donors were cultured until senescence. After different time points up to 30 min of incubation with 5 \ub5M HNE, the extracellular medium was analyzed for metabolites via liquid chromatography coupled with electrospray ionization mass spectrometry (LC/ESI-MS). The metabolites appeared in the extracellular medium 5 min after incubation followed by a time-dependent increase. But, the formation of GSH-HNL and GSH-DHN decreased with increasing in vitro age. As a consequence, the HNE levels in the cells increase and there is more protein modification observed. Furthermore, after 3 h of incubation with 5 \ub5M HNE, younger cells showed less proliferative capacity, while in older cells slight increase in the mitotic index was noticed