Ions Matter: Description of the Anomalous Electronic Behavior in Methylammonium Lead Halide Perovskite Devices

Carrier transport in methylammonium lead iodide (MAPbI₃)‐based hybrid organic–inorganic perovskites (HOIPs) is obscured by vacancy‐mediated ion migration. Thus, the nature of migrating species (cation/anion) and their effect on electronic transport in MAPbI₃ has remained controversial. Temperature‐dependent pulsed voltage–current measurements of MAPbI₃ thin films are performed under dark conditions, designed to decouple ion‐migration/accumulation and electronic transport. Measurement conditions (electric‐field history and scan rate) are shown to affect the electronic transport in MAPbI₃ thin films, through a mechanism involving ion migration and accumulation at the electrode interfaces. The presence of thermally activated processes with distinct activation energies (E_a) of 0.1 ± 0.001 and 0.41 ± 0.02 eV is established, and are assigned to electromigration of iodine vacancies and methylammonium vacancies, respectively. Analysis of activation energies obtained from electronic conduction versus capacitive discharge shows that the electromigration of these ionic species is responsible for the modification of interfacial electronic properties of MAPbI₃, and elaborates previously unaddressed issues of “fast” and “slow” ion migration. The results demonstrate that the intrinsic behavior of MAPbI₃ material is responsible for the hysteresis of the solar cells, but also have implications for other HOIP‐based devices, such as memristors, detectors, and energy storage devices.     

Automated adaptive cardiovascular flow simulations

We present an automatic adaptive procedure to perform blood flow simulations in the cardiovascular system. The procedure allows the user to start with subject-specific data collected through clinical measurements, like magnetic resonance imaging (MRI) data, and evaluate physiological parameters of interest, like flow distribution, pressure variations, wall shear stress, in an automatic and efficient manner. The process involves construction of geometric models of blood vessels, specification of flow conditions and application of an adaptive flow solver. The latter is based on incompressible Navier–Stokes equations using adaptive spatial discretization (meshing) techniques. In this article, we demonstrate the method on a model of a human abdominal aorta of a normal subject with geometry and flow rates assimilated from MRI data. The results obtained show that boundary layer mesh adaptivity offers a better alternative leading to more accurate predictions, especially for key physiological quantities like wall shear stress.     

Formulation Aspects and Effect of Critical Factors for Designing Extended Release Pellets: An Updated Review

Nowadays, pellets are playing a dominating role in the world of multiparticulate oral drug delivery. These pellets have many advantages over single-unit dosage forms like extended release. The present review highlights various formulation aspects for the designing of extended release pellets with a special emphasis on effect of key formulation variables. Design includes pellets–matrix and pellets–reservoir systems. Formulation variables such as effect of polymer, plasticizer, pore former, pH adjuster, antitacking agents, and wetting liquids are considered as key formulation variables. The authors lead to a conclusion that designing approaches and formulation factors should be considered and will assist while preparing extended release pellets.     

Generalized buckling analysis of laminated plates with random material properties using stochastic finite elements

A generalized layer-wise stochastic finite element formulation is developed for the buckling analysis of both homogeneous and laminated plates with random material properties. The pre-buckled stresses are considered in the derivation of geometric stiffness matrix and the effect of variation in these stresses on the mean and coefficient of variation of buckling strength is studied. The mean buckling strength of plates under uniform stress assumption exactly matches with those reported in the literature. However, it is shown that the actual mean buckling strength of plates can be significantly different based on the pre-buckled stress analysis which depends on boundary constraints, principal material directions, aspect and thickness ratios of plates. The statistics of buckling strength is determined using a Taylor series expansion based mean centered first order perturbation technique. The stochastic finite element solutions obtained using layer-wise plate theory is also validated with analytical solutions presented in this paper. Parametric studies are conducted for different aspect ratios, ply orientations and boundary conditions.     

On the synthesis of lithium boron nitride (Li3BN2)

Li₃BN₂ is a known lithium ion conductor and has been predicted lately to be a high capacity cathode for Li-ion batteries (Németh, 2014) [4]. In this study, we have investigated the synthesis of Li₃BN₂ through reactions between Li₃N and h-BN powders. Effects of the reaction temperature, holding time and reaction atmosphere on the formation of Li₃BN₂ have been evaluated. Rietveld refinement of X-ray diffraction patterns of all powders has been performed to quantify the percentage of each phase. The results show that both the reaction temperature and holding time affect strongly the percentage of Li₃BN₂ in the reaction product. Furthermore, a trace amount of oxygen in the reaction atmosphere can negatively impact the purity of the reaction product because of the high affinity of Li₃BN₂ towards oxidation.     

Palm fatty acid biodiesel: process optimization and study of reaction kinetics

The relatively high cost of refined oils render the resulting fuels unable to compete with petroleum derived fuel. In this study, biodiesel is prepared from palm fatty acid (PFA) which is a by-product of palm oil refinery. The process conditions were optimized for production of palm fatty acid methyl esters. A maximum conversion of 94.4% was obtained using two step trans-esterification with 1:10 molar ratio of oil to methanol at 65°C. Sulfuric acid and Sodium hydroxide were used as acid and base catalyst respectively. The composition of fatty acid methyl esters (FAME) obtained was similar to that of palm oil. The biodiesel produced met the established specifications of biodiesel of American Society for Testing and Materials (ASTM). The kinetics of the trans-esterification reaction was also studied and the data reveals that the reaction is of first order in fatty acid and methanol (MeOH) and over all the reaction is of second order.     

Effect of Moisture Content on Pitting and Milling Efficiency of Pigeon Pea Grain

Pitting is a premilling operation in which pigeon pea grain is passed through a dehulling machine quickly to crack the hull or partly dehull the grain. A study was conducted to investigate the effect of grain moisture content on pigeon pea hull during pitting. Pitting of the grain was done at 6%, 8%, 10%, 12%, and 14% moisture contents using dhal mill developed by Central Institute of Agricultural Engineering, Bhopal (India). Grains having a cracked hull or partly dehulled during pitting varied from 35.3% to 85.3% with maximum value at 10% moisture content and reduced with an increase in moisture content. Maximum finished product in the form of dehulled whole (gota) and dehulled splits (dhal) was also obtained at 10% moisture content. Pitted grains of pigeon pea were treated with 0.28% cottonseed oil to study the effect of moisture content and pitting on dehulling efficiency, which was maximum (86.7%) at 10% moisture content.     

Effect of improvement in anemia on electroneurophysiological markers (P300) of cognitive dysfunction in chronic kidney disease

Our aim is to study the effect of improvement in anemia on event-related potentials (ERPs; P300) as markers of cognitive dysfunction in predialysis and dialysis patients of chronic kidney disease (CKD). Thirty anemic patients of CKD (hemoglobin [Hb] < 9 g%), 15 in the predialysis group (Group A), and 15 patients on biweekly hemodialysis (Group B) were recruited for the study. Patients of uremic encephalopathy, dyselectrolytemia, and those with hearing problems were excluded. Both groups were given recombinant human erythropoietin (rhuEPO) 100 IU/kg biweekly for 6 weeks by the subcutaneous route. No intervention was performed in the third control group (Group C), which consisted of 30 normal healthy volunteers. The improvement in Hb was assessed every 2 weeks, and the amplitude and latency of the P300 component of the ERPs were studied before initiating treatment and after 6 weeks of rhuEPO administration. There was a significant increase in Hb in both the study groups without any significant alteration in kidney functions. A significant reduction in P300 latency was noted in both the study groups after intervention. Similarly, the amplitude of P300 also increased in both study groups, but attained statistical significance for the dialysis group only. No significant changes were observed in the control group. Administration of EPO in patients of anemia with CKD resulted in a significant improvement in the electrophysiological markers of cognitive function in the form of increased amplitudes and decreased latencies of P300 in both predialysis and dialysis patients.     

Effect of reaction temperature on crystallite size and sensing response of chromium oxide nanoparticles

Nanoparticles of chromium oxide have been synthesized following a precipitation technique at reaction temperatures 5, 27 and 65 °C. Synthesized powders were characterized using X-ray diffraction, transmission electron microscope and Brunauer–Emmett–Teller techniques to carry out structural and morphological analysis. The reaction temperature has been found to be playing a crucial role in controlling particle size. It has been observed that Cr₂O₃ nanoparticles synthesized at 27 °C were smaller as compared to those synthesized at 5 and 65 °C. Chromium oxide samples thus prepared were deposited as thick films on alumina substrates to act as gas sensors and their sensing response to ethanol vapour was investigated at different operable temperatures. It has been observed that all the sensors exhibited optimum response at 250 °C. The investigations revealed that sensing response of Cr₂O₃ nanoparticles synthesized at 27 °C was exceptionally higher than that of Cr₂O₃ nanoparticles synthesized at 5 and 65 °C.     

Two Techniques for Fast Computation of Constrained Shortest Paths

Computing constrained shortest paths is fundamental to some important network functions such as QoS routing, MPLS path selection, ATM circuit routing, and traffic engineering. The problem is to find the cheapest path that satisfies certain constraints. In particular, finding the cheapest delay-constrained path is critical for real-time data flows such as voice/video calls. Because it is NP-complete, much research has been designing heuristic algorithms that solve the epsiv-approximation of the problem with an adjustable accuracy. A common approach is to discretize (i.e., scale and round) the link delay or link cost, which transforms the original problem to a simpler one solvable in polynomial time. The efficiency of the algorithms directly relates to the magnitude of the errors introduced during discretization. In this paper, we propose two techniques that reduce the discretization errors, which allows faster algorithms to be designed. Reducing the overhead of computing constrained shortest paths is practically important for the successful design of a high-throughput QoS router, which is limited at both processing power and memory space. Our simulations show that the new algorithms reduce the execution time by an order of magnitude on power-law topologies with 1000 nodes. The reduction in memory space is similar.