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The sum of products of random variables arises in many applications, particularly in wireless communications. However, the analytical derivation of essential statistics, such as the probability density function and cumulative distribution function, still purveys significant challenges. The objective of this work is to derive exact formulations for the density and distribution of the sum of an arbitrary N instances, each comprising $L_{n}, n\in \{1,2,\ldots ,N\}$ products of independent Rayleigh-distributed variates. This renders our exact formulations rather flexible to comprise different fading scenarios. Based on our findings, we investigate the performance of a communication system employing a reconfigurable intelligent surface (RIS) by deriving key metrics, such as outage probability and average bit error rate. Also, we employ the central limit theorem to approximate the sum of envelope products and performance metrics. In addition, we conduct an asymptotic analysis to deepen our understanding of the system’s performance. Specifically, we obtain simple closed-form expressions for all the metrics derived here. Our analytical results are validated through Monte Carlo simulations.

The interest for functionally graded materials (FGM) has grown up during the last 2 decades owing to the possibility of developing pieces and devices with gradual variation of properties along one or more dimensions. This allows for an optimum performance as a function of the intended use. On the other hand, two stage sintering is a relative new sintering technique, where the shaped pieces are heated up to a relative density of 75–92 % of theoretical density, followed by a fast cooling step to an inferior temperature, where the piece in maintained up to the end of the densification process. This results in the development of finer microstructures, responsible for better mechanical properties. In this work, we characterized alumina-ytria-stabilized zirconia composites, with different amounts of 3Y-ZrO2 by dilatometry. After fitting thermal behavior of the different composites during sintering and determining temperature of maximum densification rate, co-pressed FGMs were produced. Then the samples were sintered by pressureless traditional technique and two stage sintering, with a peak temperature of 1450 °C and holding temperature of 1350 °C. Microstructure was studied by SEM and mechanical properties (microhardness and indentation toughness) were determined in order to compare pressureless sintered FGMs at 1500 °C and two-stage sintered FGMs.

Study Design:Cross-sectional.Objectives:To determine whether frequency of training is related to self-reported lower psychological distress, defined as depressive symptomology and perceived stress, among the US male wheelchair rugby athletes with tetraplegia.Setting:United States.Methods:Survey data were collected on a convenience sample at wheelchair rugby tournaments from January–April 2016. Participants self-reported depressive symptomology (CES-D-10), perceived stress scale (PSS), and frequency of rugby practice. Covariate-adjusted regression models were conducted among the full sample and a subsample of individuals who reported spinal cord injury (SCI) as the nature of their disability.Results:Participants included 150 males with tetraplegia, and 87% identified the nature of their disability as SCI. Participants were primarily Caucasian with an average age of ~35 years. Participants scored low on measures of depressive symptomology (mean=5.63; s.d.=4.35) and perceived stress (mean=4.63; s.d.=2.73). Sixty-seven percent of the participants practiced two or more times per week. Results of the main analyses indicated that practicing wheelchair rugby two times or more (compared to once a week or less) was significantly associated with lower depressive symptomology and perceived stress among the full sample and subsample of individuals with SCI.Conclusions:Greater frequency of wheelchair rugby participation was associated with lower levels of psychological distress. Future research should examine the directional and mechanistic relationship between frequency of sports participation and psychological distress to inform the benefits of adaptive sport.

Study design:Narrative review.Objectives:Review methods used to measure and classify obesity in individuals with spinal cord injuries (SCI). Outline the strengths and weaknesses of each method used to measure obesity in individuals with SCI.Setting:International.Methods:PubMed was used to identify articles before 2016. Search terms (‘obesity’ or ‘weight status’ and ‘spinal cord injury’). Filters: adults, English and human. Studies were retained that (1) included participants, 18 years or older, with SCI; (2) took place in inpatient, outpatient or community-based settings and (3) measured obesity status. Unique methods for classifying individuals with SCI as obese were identified and examples are presented.Results:Methods identified for classifying obesity were as follows: World Health Organization body mass index (BMI) cutoff⩾30 kg m−2, BMI cutoff ⩾25-29 kg m−2, and SCI-specific BMI cutoff ⩾22 kg m−2, waist circumference cutoff (women >102 cm, men >88 cm), percent body fat cutoffs ⩾25% using bioelectrical impedance analysis and dual-energy X-ray absorptiometry, computerized tomography scan visceral fat area ⩾100 cm2and percentage of ideal body weight.Conclusions:BMI is the most widely used measure of obesity in the SCI literature. Although some studies identified alternative cutoffs or other metrics, there is no standardized obesity classification in SCI. However, research is needed to determine and validate obesity classification specific to SCI due to physiological changes that occur following injury. We recommend that researchers and clinicians proceed with caution and use methodology based on the purpose of measurement.

Data are conflicting concerning risk for ischemic stroke associated with hyperhomocyst(e)inemia (hyper-Hcy) and a common polymorphism in the gene encoding 5,10-methylenetetrahydrofolate reductase (MTHFR 677C→T), which predisposes to hyper-Hcy in vivo.

Abstract: Several plant baits were tested to quantify Rhizoctonia inoculum density in Eucalyptus clonal garden soils. Experiments carried out with five types of plant baits in soils infested with R. solani showed that eucalypt twig segments were more readily colonised and allowed detection of the fungus at lower inoculum densities, showing high detection sensitivity across the tested clonal garden soils. Other baits had high colonisation levels, but varied greatly in sensitivity according to the tested soil. These results indicate that eucalypt twig segments were the most effective bait to estimate Rhizocronia inoculum density in clonal garden soils.

The antihypertensive mechanism of α2-adrenoceptor agonists, such as clonidine and rilmenidine, is not completely elucidated, although it is probably due to reduction of sympathetic tone mediated by stimulation of central α2-adrenoceptors. Because activation of α2-adrenoceptors on endothelial cells induces release of endothelium-derived relaxing factor (EDRF), we determined whether nitric oxide (NO) release is involved in the antihypertensive action of clonidine and rilmenidine. In chloralose-anesthetised Wistar rats, systolic and diastolic arterial blood pressures were recorded on a polygraph. Intravenous injection of clonidine or rilmenidine (control group) caused a rapid increase of arterial blood pressure, followed by a long-lasting hypotensive effect. The hypotensive effects, estimated as the area enclosed by the decrease in diastolic pressure during the 20 min after clonidine and rilmenidine injections, were 574 ± 60 and 410 ± 59 mm Hg/min, respectively. The delta decrease in diastolic arterial blood pressure observed 20 min after intravenous injections of clonidine and rilmenidine was 48 ± 5 and 34 ± 3 mm Hg, respectively. Clonidine and rilmenidine injected 5-10 min after intravenous pretreatment with L-NAME (2 and 1 mg/kg) or methylene blue (10 mg/kg) induced hypotensive effects that were significantly smaller than that observed for the control group. These results suggest that the antihypertensive effects of clonidine and rilmenidine also may be modulated by the NO-cyclic guanosine monophosphate (cGMP) pathway at the level of the central nervous system and/or at the vascular peripheral circulation.