A computational study on novel carbon-based lithium materials for hydrogen storage and the role of carbon in destabilizing complex metal hydrides

One of the major impediments in the way of the realization of hydrogen economy is the storage of hydrogen gas. This involves both the storage for stationary applications as well as that of storage onboard vehicles for transportation applications. For obvious reasons, the system targets for the automotive applications are more stringent. There are many approaches which are still being researched for the storage of hydrogen for vehicular applications. Among them are the high pressure storage of hydrogen gas and the storing of liquid hydrogen in super insulated cryogenic cylinders. While both of them have been demonstrated practically, the high stakes of their respective shortcomings is hindering the wide spread application of these methods. Thus different solid state storage materials are being looked upon as promising solutions. Metal hydrides are a class of solid state hydrogen storage materials which are formed by the reaction of metals or their alloys with hydrogen. These materials have very good gravimetric storage densities, but are very stable thermodynamically to desorp hydrogen at room temperatures. Research is going on to improve the thermodynamics and the reaction kinetics of different metal hydrides. This dissertation tries to address the problem of high thermodynamic stability of the existing metal hydrides in two ways. First, a novel carbon based lithium material is proposed as a viable storage option based on its promising thermodynamic heat of formation. Pure beryllium (Be) clusters and the carbon-beryllium (C-Be) clusters are studied in detail using the Density Functional Theory (DFT) computational methods. Their interactions with hydrogen molecule are further studied. The results of these calculations indicate that hydrogen is more strongly physisorbed to the beryllium atom in the C-Be cluster, rather than to a carbon atom. After these initial studies, we calculated the geometries and the energies of more than 100 different carbon based lithium materials with varying amounts of hydrogen. A detailed analysis of the heats of reactions of these materials using different reaction schemes is performed and based on the promising thermodynamic and gravimetric storage density, LiC4Be2H5 is divulged as a promising novel carbon based lithium material. In the later part, this dissertation performs a detailed study on the effect of carbon when it is used as a dopant in four different well known complex hydrides, lithium beryllium hydride (Li2BeH4), lithium borohydride (LiBH4), lithium aluminum hydride (LiAlH 4) and sodium borohydride (NaBH4). Initially, the unit cells of the crystal structure are fully resolved using the plane-wave pseudopotential implementation of DFT. The supercells of each of these are then constructed and optimized. Varying amounts of carbon is introduced as impurity in these crystals in different sites such as the top, subsurface and the bulk of the crystal lattice. Using the electronic structure calculations, it is established that (i) C-Be-H, C-B-H or C-Al-H compounds are formed respectively in the cases of Li2BeH4, LiBH4 and LiAlH4 when carbon is doped in them; (ii) and carbon dopant causes a decrease in the bond strengths of Be-H, B-H and Al-H in respective cases. This reduction in the bond strengths combined with the fact that there is a decrease in the ionic interaction between the cation and the anionic hydride units of these complex hydrides causes a destabilization effect

Neonatal Anesthesia and Oxidative Stress

Neonatal anesthesia, while often essential for surgeries or imaging procedures, is accompanied by significant risks to redox balance in the brain due to the relatively weak antioxidant system in children. Oxidative stress is characterized by concentrations of reactive oxygen species (ROS) that are elevated beyond what can be accommodated by the antioxidant defense system. In neonatal anesthesia, this has been proposed to be a contributing factor to some of the negative consequences (e.g., learning deficits and behavioral abnormalities) that are associated with early anesthetic exposure. In order to assess the relationship between neonatal anesthesia and oxidative stress, we first review the mechanisms of action of common anesthetic agents, the key pathways that produce the majority of ROS, and the main antioxidants. We then explore the possible immediate, short-term, and long-term pathways of neonatal-anesthesia-induced oxidative stress. We review a large body of literature describing oxidative stress to be evident during and immediately following neonatal anesthesia. Moreover, our review suggests that the short-term pathway has a temporally limited effect on oxidative stress, while the long-term pathway can manifest years later due to the altered development of neurons and neurovascular interactions

Neonatal Anesthesia and Oxidative Stress

Neonatal anesthesia, while often essential for surgeries or imaging procedures, is accompanied by significant risks to redox balance in the brain due to the relatively weak antioxidant system in children. Oxidative stress is characterized by concentrations of reactive oxygen species (ROS) that are elevated beyond what can be accommodated by the antioxidant defense system. In neonatal anesthesia, this has been proposed to be a contributing factor to some of the negative consequences (e.g., learning deficits and behavioral abnormalities) that are associated with early anesthetic exposure. In order to assess the relationship between neonatal anesthesia and oxidative stress, we first review the mechanisms of action of common anesthetic agents, the key pathways that produce the majority of ROS, and the main antioxidants. We then explore the possible immediate, short-term, and long-term pathways of neonatal-anesthesia-induced oxidative stress. We review a large body of literature describing oxidative stress to be evident during and immediately following neonatal anesthesia. Moreover, our review suggests that the short-term pathway has a temporally limited effect on oxidative stress, while the long-term pathway can manifest years later due to the altered development of neurons and neurovascular interactions

Learners’ Perspective towards E-Exams during COVID-19 Outbreak: Evidence from Higher Educational Institutions of India and Saudi Arabia

Online examinations, commonly referred to as e-exams (electronic examinations), underwent a considerable progression, getting adapted ubiquitously among higher education institutions worldwide. Their preferment was rapid due to the emergence of the COVID-19 pandemic. The process of conducting exams online is being opted as the appropriate way of assessment, ensuring the students’ safety and well-being. According to Warts et al., this form of examination has been pretty effective in the past when blended with the conventional assessment. However, at present, implemented as the singular way of assessment, e-exams have shown a more significant promise in being beneficial to the learners. As a matter of fact, a comprehensive analysis on understanding the learners’ perception towards the e-exams was not done earlier, particularly in the developing nations. Thus, it was pertinent to examine the pre-requisites of e-exams to promote it as a useful tool for the smooth conduct of exams in the aforesaid nations. Against such a backdrop, this study was conducted during January to March 2021 on 207 students enrolled in four universities, three situated in the National Capital Territory (NCT) of Delhi, India: Delhi University (DU), Jamia Millia Islamia (JMI), and Jawaharlal Nehru University (JNU), and one situated in Saudi Arabia, namely Saudi Electronic University (SEU). A quantitative approach was employed for the study, with the responses recorded via web questionnaires. Confirmatory -factor analysis (CFA) was applied in the study to examine whether the process of conducting online examinations is being chosen as the appropriate form of assessment, ensuring the safety and well-being of students through AMOS (version 24) software. For determining the reliability of the two latent constructs, namely “Perceptions of students towards E-exams (PSE)” and “Pre-requisites of E-exams (POE),” Cronbach’s alpha was used through SPSS (version 25) software in the study, and the results reveal that the strong internal consistency exists between all the measured variables. In addition, the mean and standard deviation were used by the researchers to find out the pre-requisites of the online examination system. The participants expressed their insights on the relative benefits of online examination. Their perception was based on pedagogy, validity and reliability, affective factors, practicality, and security. From their insights, it was concluded that online examination is more advantageous than conventional paper-based exams. The outcome also applies to the authenticity of grading and the overall efficiency concerning the time, effort, and expenditure on conducting the examination. Contrarily, the participating students also recognized numerous hurdles in implementing e-exams concerning security, validity, and impartiality. The conclusion further revealed that online examination is especially relevant for formative assessment of learning instead of summative assessment, provided authenticity, security, and flexibility are used as fundamental tenants in the proper implementation of e-exams. The outcome of the present study will facilitate higher education institutions and policymakers in taking the electronic examination system to the next level

Kinetic Monte Carlo simulations of the Fischer-Tropsch reaction

Kinetic Monte Carlo simulations were used to analyze the effect of barriers and the thermodynamics of the intermediates in the methanation reaction. Models on methanation representataive of different surfaces of transition metals as Ru or Co were presented. Trends in the methanation yield rate and the surface compositions as a function of temperatures and CO activation energies were put forward. Two different models that incorporate the C-C coupling in the formation of ethylene and ethane were also presented. The reaction rates were very sensitive to the activation energies of CO and rate of oxygen removal. This is an abstract of a paper presented at the 2011 AIChE Spring Meeting & 7th Global Congress on Process Safety (Chicago, IL 3/13-17/2011)

Faradic stimulation in the treatment of functional aphonia: A case series

Dissociative disorders have many clinical presentations, one of which is mutism. Hysterical mutism, or functional aphonia (FA), is a functional disorder of the vocal cords presenting as loss of voice with no change in the integrity of the anatomy or physiology of the voice box. Modern understanding of its etiology suggests a strong role for psychosocial stressors. Treatment modalities for this condition are aplenty and vary in mode of administration. This case series describes the use of faradic stimulation in the treatment of FA

Operations research on the female village-based family planning worker program of Pakistan

This article presents the results of a number of operations research studies (OR) of family planning services provided by a new cadre of female village-based family planning workers in Punjab Province, Pakistan. This cadre of workers, recruited nationwide, has been trained to visit women in their villages to provide information and family planning services. The studies were conducted as part of a broad program of technical assistance to the Government of Pakistan. Surveys investigated the quality of their training as well as attitudes among clients to the new program. They found that the program is developing well but there is room for improvement, particularly in counseling and training. Additional field studies are ongoing and recommendations for change have been incorporated in training and supervision. The program is expanding on a national scale

Electric Field Effects on Brain Activity: Implications for Epilepsy and Burst Suppression

Electric fields are now considered a major mechanism of epileptiform activity. However, it is not clear if another electrophysiological phenomenon, burst suppression, utilizes the same mechanism for its bursting phase. Thus, the purpose of this study was to compare the role of ephaptic coupling—the recruitment of neighboring cells via electric fields—in generating bursts in epilepsy and burst suppression. We used local injections of the GABA-antagonist picrotoxin to elicit epileptic activity and a general anesthetic, sevoflurane, to elicit burst suppression in rabbits. Then, we applied an established computational model of pyramidal cells to simulate neuronal activity in a 3-dimensional grid, with an additional parameter to trigger a suppression phase based on extra-cellular calcium dynamics. We discovered that coupling via electric fields was sufficient to produce bursting in scenarios where inhibitory control of excitatory neurons was sufficiently low. Under anesthesia conditions, bursting occurs with lower neuronal recruitment in comparison to seizures. Our model predicts that due to the effect of electric fields, the magnitude of bursts during seizures should be roughly 2–3 times the magnitude of bursts that occur during burst suppression, which is consistent with our in vivo experimental results. The resulting difference in magnitude between bursts during anesthesia and epileptiform bursts reflects the strength of the electric field effect, which suggests that burst suppression and epilepsy share the same ephaptic coupling mechanism

PERIOPERATIVE MEDICINE Relationship between Anesthetic Depth and Venous Oxygen Saturation during Cardiopulmonary Bypass

ABSTRACT Background: During cardiopulmonary bypass, mixed venous oxygen saturation (SvO 2 ) is frequently measured to assess circulatory adequacy. Fluctuations in SvO 2 not related to patient movement or inadequate oxygen delivery have been attributed clinically to increased cerebral oxygen consumption due to "light" anesthesia. To evaluate the relationship between anesthetic depth and SvO 2 , we prospectively measured bispectral index (BIS) and SvO 2 values in patients undergoing cardiac surgery with cardiopulmonary bypass. Methods: Adults scheduled for cardiac surgery with cardiopulmonary bypass were recruited for this prospective observational study. During bypass, BIS and SvO 2 values were recorded every 5 min. To control for confounding effects of changes in other variables known to affect SvO 2 , temperature, hematocrit, bypass pump flow, muscle relaxant use, and intravenous and inhaled anesthetic doses were also recorded. Only periods with limited variation in other variables affecting SvO 2 were analyzed. The relationship between BIS and SvO 2 was evaluated using mixed linear regression. Results: One thousand thirty-four data points were obtained in 41 patients. No overall association between BIS and SvO 2 was observed, either in unadjusted analysis or adjusted for covariates. In data points with temperatures less than the median (T Ͻ 34.1°C), a significant association between BIS and SvO 2 was observed both in unadjusted (␤ ϭ Ϫ0.32, P ϭ 0.01) and adjusted (␤ ϭ Ϫ0.27, P ϭ 0.04) analyses. Conclusions: In patients undergoing cardiopulmonary bypass, we found no overall association between BIS and SvO 2 . A weak but statistically significant association between BIS and SvO 2 was observed in patients with temperatures less than 34.1°C. These data suggest that low SvO 2 values on bypass are unlikely to be due to light or inadequate anesthesia. The relationship among temperature, BIS and SvO 2 deserves further study. D URING cardiopulmonary bypass, mixed venous oxygen saturation (SvO 2 ) is helpful for measuring circulatory adequacy. A decreased SvO 2 indicates inadequate oxygen delivery relative to oxygen consumption and suggests either that oxygen consumption has increased or that oxygen delivery has decreased. 1 In principle, during periods of cardiopulmonary bypass when oxygen delivery is constant and the anesthetized patient is at a constant temperature, SvO 2 should not change. However, SvO 2 values can vary in the absence of changes in temperature or oxygen delivery. One explanation cited in cardiac anesthesia textbooks for changes in SvO 2 is a change in anesthetic depth. 2,3 Existing data demonstrate that decreased anesthetic depth increases cerebral metabolic rate and cerebral oxygen consumption. 4 -6 Conversely, deeper levels of anesthesia decrease oxygen consumption. 7 Against a background of constant temperature, unchanged systemic oxygen delivery, and no patient movement, changes in SvO 2 may thus be potentially What We Already Know about This Topic ❖ Cardiac surgery caries a higher than normal risk for awareness ❖ During cardiopulmonary bypass, some clinicians consider lower than expected mixed venous oxygen saturation (SvO 2 ) to indicate possible awareness What This Article Tells Us That Is New ❖ In more than 1,000 data points in 41 patients, there was no relationship between the bispectral index as a measure of anesthetic depth and SvO 2 during cardiopulmonary bypass, suggesting that SvO 2 is not a good measure of anesthetic dept