Multi-channel ALOHA and CSMA medium-access protocols: Markovian description and large deviations

We consider a multi-channel communication system under ALOHA and CSMA protocols, resepc- tively, in continuous time. We derive probabilistic formulas for the most important quantities: the numbers of sending attempts and the number of successfully delivered messages in a given time interval. We derive (1) explicit formulas for the large-time limiting throughput, (2) introduce an explicit and ergodic Markov chain for a deeper probabilistic analysis, and use this to (3) derive exponential asymptotics for rare events for these quantities in the limit of large time, via large-deviation principles

Impact of Active Layer Morphology, Density of States, Charge Carrier Concentration, and Local Charge Density Fluctuations on Bimolecular Recombination of Bulk Heterojunction Solar Cells: A Theoretical Perspective

We study the merits of a reaction-diffusion model to unravel the effects of active layer morphology and donor-acceptor interfacial roughness, density of states, charge carrier concentration, and local charge density fluctuations on the bimolecular recombination kinetics in bulk heterojunction organic semiconductors. We consider the cases of a single and composite electronic density of states (DoS) that consists of a superposition of a Gaussian and an exponential DoS. Using kinetic Monte Carlo (KMC) simulations, we apply the reaction-diffusion model in order to investigate the factors impacting bimolecular recombination (BMR) kinetics and rates at short and long time scales. We find that morphology, donor-acceptor interfacial roughness, and charge carrier concentration only affect BMR time, whereas DoS characteristics as well as local charge density fluctuations can significantly impact BMR kinetics and rates

Investigation on the relationship between diabetes mellitus type 2 and cognitive impairment.

Objective: The incidence of cognitive impairment is increasing with age; however, little is known about the role of hyperglycemia in cognitive impairment. This study focuses on investigating the relationship between diabetes mellitus type 2 and cognitive impairment. Methods: 60 diabetic patients, amongst whom, 30 had a well-controlled diabetes status and the other 30 had not. These patients were compared to 60 non-diabetic controls whose age, sex and educational class matched with the individuals of the first group. Patients with important risk factors for cognitive disorders (renal failure, major depressive disorders and psychoactive drug users, cerebrovascular accident history, etc.) were not included in the study. Modified Mini Mental Status examination (mMMSE) was done for all patients by a blinded expert examiner. Results: Subjects with diabetes (n = 60) had lower MMSE score than those without diabetes (P < .01). Diabetes was also associated with increased odds of cognitive decline as determined by MMSE scores (odds ratio = 1.9; CI = 95%, 1.01–3.6). A significant correlation between duration of disease and cognitive dysfunction was observed, P = 0.001. Also, the same correlation was found for quality of diabetes control, P = 0.002. Conclusion: Diabetes mellitus is associated with lower levels of cognitive functio

High strength lightweight aggregate concrete using blended coarse lightweight aggregate origin from palm oil industry

The benefits of using structural lightweight concrete in construction industry, particularly in high rise buildings, over normal weight concrete are numerous. The main method of producing structural lightweight concrete is the use of lightweight aggregates instead of ordinary aggregates in concrete. Due to the limited resources for natural and artificial lightweight aggregates, the alternative sources for lightweight aggregates should be discovered from industrial wastes. Oil palm shell (OPS) and oil-palm-boiler clinker (OPBC) are two solid wastes from palm oil industry and are available in abundance in tropical regimes. The use of just OPS as coarse lightweight aggregate in concrete mixture has some drawbacks for concrete. The aim of this study was to investigate engineering properties of a lightweight concrete containing both of these aggregates. For this purpose, in this study, 50% (by volume) of OPS was replaced with OPBC in an OPS lightweight concrete. The test results showed that when OPS was substituted with OPBC, significant improvement was observed in the compressive, splitting tensile and flexural strengths. In addition, initial and final water absorption as well as drying shrinkage strain of blended coarse lightweight aggregate concrete were significantly less than OPS concrete