Better band gaps for wide-gap semiconductors from a locally corrected exchange-correlation potential that nearly eliminates self-interaction errors

This work constitutes a comprehensive and improved account of electronic-structure and mechanical properties of silicon-nitride (Si3N4) polymorphs via van Leeuwen and Baerends (LB) exchange-corrected local density approximation (LDA) that enforces the exact exchange potential asymptotic behavior. The calculated lattice constant, bulk modulus, and electronic band structure of Si3N4 polymorphs are in good agreement with experimental results. We also show that, for a single electron in a hydrogen atom, spherical well, or harmonic oscillator, the LB-corrected LDA reduces the (self-interaction) error to exact total energy to ~10%, a factor of three to four lower than standard LDA, due to a dramatically improved representation of the exchange-potential.Comment: 6 pages, 3 figure

Revealing the nature of antiferro-quadrupolar ordering in Cerium Hexaboride: CeB6_6

Cerium-hexaboride (CeB$_6$) f-electron compound displays a rich array of low-temperature magnetic phenomena, including `magnetically hidden' order, identified as multipolar in origin via advanced x-ray scattering. From first-principles electronic-structure results, we find that the \emph{antiferro-quadrupolar} (AFQ) ordering in CeB$_{6}$ arises from crystal-field splitting and yields band structure in agreement with experiments. With interactions of $p$-electrons between Ce and B$_{6}$ being small, the electronic state of CeB$_{6}$ is suitably described as Ce(4$f^{1}$)$^{3+}$(e$^{-}$)(B$_{6}$)$^{2-}$. The AFQ state of orbital spins is caused by an exchange interaction induced through spin-orbit interaction, which also splits J=5/2 state into $\Gamma_{8}$ ground state and $\Gamma_{7}$ excited state. Within the smallest antiferromagnetic (111) configuration, an orbital-ordered AFQ state appears during charge self-consistency, and supports the appearance of `hidden' order. Hydrostatic pressure (either applied or chemically induced) stabilizes the AFM (AFQ) states over a ferromagnetic one, as observed at low temperatures.Comment: 6 pages, 4 figure

Comparative study between levobupivacaine with clonidine and levobupivacaine with fentanyl in epidural labour analgesia in rural set up

Background: Neuraxial techniques are the gold standard for intrapartum labour analgesia. Neuraxial labour analgesia using new local anaesthetics such as levobupivacaine has become very popular by virtue of the safety and lesser motor blockade caused by these agents. Multiple randomized controlled trials comparing epidural analgesia with systemic opioids, nitrous oxide or both have demonstrated lower internal pain scores and higher maternal satisfaction with neuraxial analgesia. The purpose of this study is to compare fentanyl and clonidine combination with levobupivacaine in terms of effect of epidural labour analgesia on fetal outcome and incidence of instrumental or caesarean delivery and duration of second stage of labour.Methods: A total of 50 primiparous with singleton pregnancy and vertex presentation and cervical dilatation of 3-5 cm were enrolled for the study in our hospital in department of obstetrics and gynecology. They were divided into group 1 and group 2 (25 patients in each group). Group 1 received 10 ml. of 0.125% isobaric levobupivacaine with 25µg fentanyl and group 2 received 10 ml of 0.125% isobaric levobupivacaine with 60 µg clonidine. Parturients were given epidural analgesia on numerical rating scale (NRS) Score >3. Breakthrough pain supplemented with 3-5 ml of 0.125% levobupivacaine. Data collected were demographic profile of the patients, analgesic qualities, 1st and 2nd stage labour duration, side effects and feto-maternal outcome.Results: Post treatment mean NRS were almost similar between two groups at all periods except at 15 minutes when it was significantly lower for group 2 (2.64±0.49). Onset of analgesia was earlier in group 2 (13.68±0.94) in comparison to group 1 (15.36±1.18) and was statistically significant.Conclusions: In conclusion Group 2 (levobupivacaine with clonidine) showed significant difference in early onset of analgesia but did not show any significant difference in duration of labour, maternal and fetal outcome and mode of delivery

Prediction of morbidity and mortality in middle and old aged surgical patients-comparison of standard scoring system and addition of echocardiography with hemodynamic indices

Background: A prospective study was carried out in our hospital to predict morbidity and mortality in middle and old aged surgical patients by adding echocardiography to standard scoring system with hemodynamic studies.Methods: A total of 50 patients of either sex ranging from 40-70 years of ASA grade 1 & 2 scheduled for various types of noncardiac surgeries were enrolled for the study in our hospital. Patients were divided in two groups according to echocardiographic examinations. The patients with normal echocardiographic values were kept in control group and the patients with abnormal values were kept under study group. The patients in study group were further divided in three groups according to LVEF. Group1-LEVF≥60%, Group2-LVEF≥50-59%, Gr3≥40-49% Tab lorazepam was given to all the patients’ orally prior night of surgery. All the patients were induced with same type inducing agents according to body weight. All the patients were maintained on IPPV by anaesthesia machine with supplemental fentanyl, N2O, O2 and muscle relaxant. SPO2, electrocardiograph (ECG), Non-invasive/invasive blood pressure (BP), Spirometry, Capnography and temperature were monitored. At the end of the research project data’s were compiled systematically and were subjected to statistical analysis using odd’s ratio(OR),95% confidence interval (CI), z value and p value, two statistical software programme were used.Results: Significant difference in the results seen between the three study groups (Gr1, Gr2, Gr3) for perioperative ischemic changes, CHF and arrhythmias.Conclusions: In conclusion preoperative TTE before non-cardiac surgery can predict the risk of perioperative cardiac complications in known or suspected cases of cardiac disease patients.