Chemical control of polar behavior in bicomponent short-period superlattices

Using first-principles density functional calculations, we study the interplay of ferroelectricity and polar discontinuities in a range of 1-1 oxide superlattices, built out of ferroelectric and paraelectric components. Studies have been carried out for a varied choice of chemical composition of the components. We find that, when polar interfaces are present, the polar discontinuities induce off- centric movements in the ferroelectric layers, even though the ferroelectric is only one unit cell thick. The distortions yield non-switchable polarizations, with magnitudes comparable to those of the corresponding bulk ferroelectrics. In contrast, in superlattices with no polar discontinuity at the interfaces, the off-centric movements in the ferroelectric layer are usually suppressed. The details of the behavior and functional properties are, however, found to be sensitive to epitaxial strain, rotational instabilities and second-order Jahn-Teller activity, and are therefore strongly in uenced by the chemical composition of the paraelectric layer.Comment: 7 pages, 2 figure

Origin of Magnetism and trend in TcT_{c} in Cr-based double perovskites: Interplay of two driving mechanisms

Employing first principles density functional calculations, together with solution of the low-energy, model Hamiltonian constructed in a first principles manner, we explored the origin of magnetism and $T_c$ trend in Cr-based double perovskite series, Sr$_2$CrB$'$O$_6$ (B$'$=W/Re/Os). Our study shows that the apparently puzzling $T_c$ trend in Sr$_2$CrB$'$O$_6$ (B$'$=W/Re/Os) series can be understood in terms of the interplay of the hybridization driven mechanism and the super-exchange mechanism.Comment: to be appeared in Phys. Rev.

Size control of Charge-Orbital Order in Half-Doped Manganite, La0.5_{0.5}Ca0.5_{0.5}MnO3_3

Motivated by recent experimental results, we study the effect of size reduction on half-doped manganite, La$_{0.5}$Ca$_{0.5}$MnO$_3$, using the combination of density functional theory (DFT) and dynamical mean field theory (DMFT). We find that upon size reduction, the charge-ordered antiferromagnetic phase, observed in bulk, to be destabilized, giving rise to the stability of a ferromagnetic metallic state. Our theoretical results, carried out on defect-free nanocluster in isolation, establish the structural changes that follow upon size reduction to be responsible for this. Our study further points out the effect of size reduction to be distinctively different from application of hydrostatic pressure. Interestingly, our DFT+DMFT study, additionally, reports the correlation-driven stability of charge-orbitally ordered state in bulk La$_{0.5}$Ca$_{0.5}$MnO$_3$, even in absence of long range magnetic order.Comment: 5 pages, 3 figures; to appear in Physical Review Letter

Electronic Structure, Phonons and Dielectric Anomaly in Ferromagnetic Insulating Double Perovskite La2NiMnO6

Using first-principles density functional calculations, we study the electronic and magnetic properties of ferromagnetic insulating double-perovskite compound La2NiMnO6, which has been reported to exhibit interesting magnetic field sensitive dielectric anomaly as a function of temperature. Our study reveals existence of very soft infra-red active phonons that couple strongly with spins at the Ni and Mn sites through modification of the super-exchange interaction. We suggest that these modes are the origin for observed dielectric anomaly in La2NiMnO6.Comment: 4 pages,3 figure

Prevalence and characteristics of polycystic ovarian syndrome in women attending in outpatient department of obstetrics and gynecology of Bangabandhu Sheikh Mujib Medical University, Dhaka, Bangladesh

Background: Polycystic ovary syndrome (PCOS) is a heterogenous, multifactorial, complex genetic disorder. Most commonly, it affects the females of reproductive age. This is one of the most widespread diseases across the world and if left untreated, may result in infertility and even uterine cancer. Methods: A cross sectional observation study of 100 PCOS patients was carried out from August 2018 to July 2019 in gynecology out-patient department of Bangabandhu Sheikh Mujib medical university, Dhaka. In this study clinical, biochemical and hormonal profile of these patients were analyzed and correlation was done between clinical features and biochemical and hormonal profile. Results: The prevalence of PCOS was 6.11% in the gynecology out-patient visits and 35.39% among infertile women. The mean age group of the patients was 24.3±5.16 SD. The mean BMI was 24.66±5.34 SD. The mean duration of infertility was 5.17 years. The prevalence of metabolic syndrome in our study was 15.0%. In this study menstrual irregularity was the most common complaint. Spearman’s correlation between various clinical and laboratory parameters showed positive correlation exists between BMI and testosterone (r=0.4824; p<0.0001).Conclusions: The study showed that most of our polycystic ovary syndrome subjects were present with oligomenorrhea. Hirsutism and central obesity were also common presentation. Obese women with PCOS had more severe ovulatory dysfunction and need more attention for their appropriate management.

An L0_0L1_1-norm compressive sensing paradigm for the construction of sparse predictive lattice models using mixed integer quadratic programming

First-principles based lattice models allow the modeling of ab initio thermodynamics of crystalline mixtures for applications such as the construction of phase diagrams and the identification of ground state atomic orderings. The recent development of compressive sensing approaches for the construction of lattice models has further enabled the systematic construction of sparse physical models without the need for human intuition other than requiring the compactness of effective cluster interactions. However, conventional compressive sensing based on L1-norm regularization is strictly only applicable to certain classes of optimization problems and is otherwise not guaranteed to generate optimally sparse and transferable results, so that the method can only be applied to some materials science applications. In this paper, we illustrate a more robust L0L1-norm compressive-sensing method that removes the limitations of conventional compressive sensing and generally results in sparser lattice models that are at least as predictive as those obtained from L1-norm compressive sensing. Apart from the theory, a practical implementation based on state-of-the-art mixed-integer quadratic programming (MIQP) is proposed. The robustness of our methodology is illustrated for four different transition-metal oxides with relevance as battery cathode materials: Li2xTi2(1-x)O2, Li2xNi2yO2, MgxCr2O4, and NaxCrO2. This method provides a practical and robust approach for the construction of sparser and more predictive lattice models, improving on the compressive sensing paradigm and making it applicable to a much broader range of applications.Comment: 25 pages, 3 figure

Reducing unsafe menstrual regulation through medication in Bangladesh

The Population Council and Marie Stopes Bangladesh, in collaboration with the Directorate General of Family Planning and with funding from the World Health Organization, tested the feasibility of introducing menstrual regulation with medication (MRM) in Bangladesh and assessed the acceptability of providing MRM using the combination drug regimen mifepristone and misoprostol in urban and rural public health facilities. As reported in this policy brief, the study demonstrates that it is feasible and safe to introduce MRM in rural and urban public health facilities. Given the choice, almost two-thirds of women preferred MRM to manual vacuum aspiration and women receiving MRM reported being satisfied or very satisfied with their quality of care. The report recommends that the Ministry of Health and Family Welfare and its partners work together to train providers and to procure the medical commodities to introduce MRM as an option for menstrual regulation in health facilities nationwide

Risk factors associated with post cesarean surgical site wound infection in Bangabandhu Sheikh Mujib medical university, Bangladesh

Background: Caesarean section is one of the most commonly performed surgical procedures in hospitals. Surgical site infections are a common complication after a caesarean section (C-section) and mainly responsible for increased maternal mortality and morbidity, the dissatisfaction of patients, longer hospital stays as well as higher treatment costs. Methods: This prospective cohort was conducted at Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka, Bangladesh included 400 women (247 emergency CS, 153 elective CS) from September 2019 to August 2020. Data were collected through consent, medical record reviews, and questionnaires. SSI risk factors were assessed, and wound examinations were conducted before discharge. STATA 14.0 was used for analysis. Participants were educated about SSI symptoms and monitored for 30 days post-operation. Results: Nulliparous individuals were more common in the emergency CS group (61.5% vs. 32% in Elective CS). Ruptured membranes were higher in emergency CS (71.7% vs. 2.6% in elective CS). Prophylactic antibiotic usage differed significantly (88.7% in emergency CS vs. 3.9% in elective CS). Post-discharge wound infections were more prevalent in emergency CS (10.53% vs. 2.61% in elective CS). No significant differences were found in other parameters. High-risk factors included BMI >30 and operation time ≥45 min. Conclusion: SSI rates may be underestimated with limited hospital observation. Prolonged operation times (>38 min) and high BMI (>30) significantly increased SSI risk. Identifying high-risk subgroups and administering antibiotics accordingly can help prevent SSI and reduce unnecessary antibiotic use