Background The United Arab Emirates (UAE) was the first country in the Middle East to report severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Serosurveys are essential to understanding the extent of virus transmission. This cross-sectional study aims to assess the seroprevalence of SARS-CoV-2 infection in the Emirate of Abu Dhabi. Methods Between 19 July and 14 August 2020, 4487 households were selected using a random sample stratified by region and citizenship of the head of household (UAE citizen or non-citizen). A cluster sample of 40 labour camps was selected. Data on socio-demographic characteristics, risk factors and symptoms compatible with coronavirus disease 2019 (COVID-19) were collected. Each participant was first tested by Roche Elecsys® Anti-SARS-CoV-2 assay, followed, when reactive, by the LIAISON® SARS-CoV-2 S1/S2 IgG assay. Results Among 8831 individuals from households, seroprevalence was 10·4% [95% confidence intervals (CIs) 9·5–11·4], with higher seroprevalence in Abu Dhabi and Al Ain regions compared with those in Al Dhafra. In households, we found no sex difference and UAE citizens had lower seroprevalence compared with those of other nationalities. Among 4855 workers residing in labour camps, seroprevalence was 68·6% (95% CI 61·7–74·7), with higher seroprevalence among workers from Southeast Asia. In households, individuals with higher body mass indexes demonstrated higher seroprevalences than individuals with normal weight. Anosmia and ageusia were strongly associated with seropositivity. Conclusions The majority of household populations in the Emirate of Abu Dhabi remained unexposed to SARS-CoV-2. In labour camps, SARS-CoV-2 transmission was high. Effective public health measures should be maintained.

<b><i>Background:</i></b> The burden of stroke weighs heavily in developing countries where recurrence rates clearly exceed that of developed countries. The impact of nonadherence to antithrombotic treatment within this context has been poorly investigated. <b><i>Objective:</i></b> The objective of this study was to evaluate patients with recurrent ischemic stroke in Egypt and Germany with focus on stroke subtype distribution and adherence to antithrombotic therapy. <b><i>Methods:</i></b> We conducted a comparative cross-sectional retrospective cohort study enrolling consecutive patients hospitalized for recurrent ischemic stroke in 2017 in 2 academic centers. Data were collected on demographics, risk factors, stroke subtypes, and medication adherence. Nonadherence to antithrombotic agents was analyzed at the time point of index stroke (recurrent stroke). Predictors of nonadherence were analyzed using logistic regression. <b><i>Results:</i></b> A total of 373 Egyptian and 468 German patients with ischemic stroke were included. The proportion of recurrent ischemic stroke among all patients was higher in the Egyptian cohort compared to the German cohort (33 vs. 10%, <i>p</i> &#x3c; 0.05). Small-vessel occlusion stroke was the most frequent subtype in Egyptians, with a significantly greater proportion than in Germans (45 vs. 26%, <i>p</i> &#x3c; 0.05). Nonadherence to antiplatelets at the time point of the recurrent stroke was higher in Egyptians than in Germans (82 vs. 19%, <i>p</i> &#x3c; 0.001). Low educational attainment among Egyptians (OR 0.14, 95% CI [0.00–0.19], <i>p</i> &#x3c; 0.01) and high comorbidity scores among Germans (OR 2.45, 95% CI [1.06–5.66], <i>p</i> &#x3c; 0.05) were found to be predictors of nonadherence to antithrombotic treatment. <b><i>Conclusions:</i></b> The large stroke recurrence burden in Egypt may be partly explained by differing adherence to secondary preventative antithrombotic pharmacotherapy. Predictors of medication nonadherence have to be addressed to reduce stroke recurrence disparities.

Signal cyclostationarity property is used for detection and signal's parameters estimation of the conventional orthogonal frequency division multiplexing (FT-OFDM). In this paper, cyclostationarity of fractional Fourier transform orthogonal frequency division multiplexing (FrFT -OFDM) is investigated. FrFT -OFDM has been proposed previously in order to alleviate the problem of high peak to average power ratio and its immunity to inter carrier interference. The cyclostationarity property of FrFT -OFDM can be considered an essential technique in performing signal's parameters estimation. A novel mathematical formula for the cyclic autocorrelation function of the FrFT -OFDM signal over A WGN is derived. This mathematical formula shows that the FrFT -OFDM signal has a cyclostationarity property and it is validated with the aid of extensive simulation results. Based on these simulations, it is shown that signal detection based on FrFT -OFDM cyclostationarity is feasible (as the FT OFDM) but its cyclic autocorrelation function magnitude is less than the conventional FT -OFDM at different values of signal to noise ratio (SNR).

In this paper the second order cyclo-stationarity property of Fractional Fourier Transform (FrFT) OFDM is investigated. A novel closed form analytical expression for the cyclic autocorrelation function of FrFT -OFDM signal is derived. The derived formula is achieved in the presence of multipath dispersive channel along with additive white Gaussian noise (A WGN). Extensive Simulations are performed in order to investigate the cyclo-stationarity property of FrFT-OFDM signal over fading channel. A comparison with the cyclo-stationarity property of the conventional FT -OFDM signal is presented. It is shown that the FrFT -OFDM signal can be detected based on its second order cyclo-stationarity feature. Also, the autocorrelation function of the FrFT-OFDM is mathematically proven to be periodic. Its magnitude is estimated at different signal to noise ratio and different fractional order values by the aid of simulation.

This paper characterizes the performance of direct sequence spread spectrum (DS-SS) signals from the detection probability point of view. The detection probability of DS-SS signals is estimated using wideband radiometer receiver over flat fading channel. Simulations are performed to evaluate detection probability of DS-SS signals over flat fading channel for various time bandwidth product values. The results are compared with the detection probability of DS-SS signals over AWGN channel. The results show that the fading parameter degrades the detection probability of DS-SS signals. The performance of DS will be discussed later in the presence of imperfect channel estimation errors.