Interfacial-antiferromagnetic-coupling driven magneto-transport properties in ferromagnetic superlattices

We explore the role of interfacial antiferromagnetic interaction in coupled soft and hard ferromagnetic layers to ascribe the complex variety of magneto-transport phenomena observed in $La_{0.7}Sr_{0.3}MnO_3/SrRuO_3$ (LSMO/SRO) superlattices (SLs) within a one-band double exchange model using Monte-Carlo simulations. Our calculations incorporate the magneto-crystalline anisotropy interactions and super-exchange interactions of the constituent materials, and two types of antiferromagnetic interactions between Mn and Ru ions at the interface: (i) carrier-driven and (ii) Mn-O-Ru bond super-exchange in the model Hamiltonian to investigate the properties along the hysteresis loop. We find that the antiferromagnetic coupling at the interface induces the LSMO and SRO layers to align in anti-parallel orientation at low temperatures. Our results reproduce the positive exchange bias of the minor loop and inverted hysteresis loop of LSMO/SRO SL at low temperatures as reported in experiments. In addition, conductivity calculations show that the carrier-driven antiferromagnetic coupling between the two ferromagnetic layers steers the SL towards a metallic (insulating) state when LSMO and SRO are aligned in anti-parallel (parallel) configuration, in good agreement with the experimental data. This demonstrate the necessity of carrier-driven antiferromagnetic interactions at the interface to understand the one-to-one correlation between the magnetic and transport properties observed in experiments. For high temperature, just below the ferromagnetic $T_C$ of SRO, we unveiled the unconventional three-step flipping process along the magnetic hysteresis loop. We emphasize the key role of interfacial antiferromagnetic coupling between LSMO and SRO to understand these multiple-step flipping processes along the hysteresis loop.Comment: 13 pages and 11 figure

Fermionic representation for the ferromagnetic Kondo lattice model -- diagrammatic study of spin-charge coupling effects on magnon excitations

A purely fermionic representation is introduced for the ferromagnetic Kondo lattice model which allows conventional diagrammatic tools to be employed to study correlation effects. Quantum 1/S corrections to magnon excitations are investigated using a systematic inverse-degeneracy expansion scheme which incorporates correlation effects in the form of self-energy and vertex corrections, while explicitly preserving the continuous spin-rotation symmetry. Magnon self-energy is studied in the full range of interaction strength, and shown to result in strong magnon damping and anomalous softening for zone boundary modes, which accounts for several zone-boundary anomalies observed in recent spin-wave measurements of ferromagnetic manganites.Comment: 16 pages, 9 figure

Analysis of the prevalence, etiology, and risk factors of stillbirth from a teaching institute of North Eastern India- a retrospective study

Background: Stillbirth rate is considered a health index. The worldwide stillbirth rate is 18.4/1000 total birth. This study was aimed to evaluate the prevalence and risk factors of intrauterine fetal death in pregnant women in one of the teaching centers in Northeastern India.Methods: This was a retrospective study. All cases of intrauterine fetal death admitted in the department of obstetrics gynecology of our institute were included over two and half years. Information was gathered from the medical records of the patients and data were analyzed.Results: During two and half year’s period, the total number of deliveries was 2696 and the total numbers of stillbirths were 96, hence the stillbirth rate was 35.6/1000. 93 (96.87%) were antenatal stillbirths and 3 (3.12%) were intrapartum stillbirths. 82 (85.41%) women were unbooked. 85 (90.4%) belonged to low socioeconomic status. 67 (69.79%) were preterm. Maximum 39 (40.62%) belonged to 28-35 weeks of gestational age. The most common cause of Intrauterine death (IUD) was antepartum hemorrhage (17.7%). 14 (14.5%) were abruption and 3 were placenta previa. The second most common cause (14.5%) was the hypertensive disorder of pregnancy.Conclusions: The stillbirth rate in our institute is higher than the national average. The most common causes of IUD were antepartum hemorrhage, preeclampsia, prematurity, and malpresentation which can be diagnosed and managed by increasing uptake of antenatal care which will lead to timely identification and proper management of maternal and fetal complications eventually reducing the preventable stillbirths

Spin dynamics in the diluted ferromagnetic Kondo lattice model

The interplay of disorder and competing interactions is investigated in the carrier-induced ferromagnetic state of the Kondo lattice model within a numerical finite-size study in which disorder is treated exactly. Competition between impurity spin couplings, stability of the ferromagnetic state, and magnetic transition temperature are quantitatively investigated in terms of magnon properties for different models including dilution, disorder, and weakly-coupled spins. A strong optimization is obtained for T_c at hole doping p << x, highlighting the importance of compensation in diluted magnetic semiconductors. The estimated T_c is in good agreement with experimental results for Ga_{1-x}Mn_x As for corresponding impurity concentration, hole bandwidth, and compensation. Finite-temperature spin dynamics is quantitatively studied within a locally self-consistent magnon renormalization scheme, which yields a substantial enhancement in T_c due to spin clustering, and highlights the nearly-paramagnetic spin dynamics of weakly-coupled spins. The large enhancement in density of low-energy magnetic excitations due to disorder and competing interactions results in a strong thermal decay of magnetization, which fits well with the Bloch form M_0(1-BT^{3/2}) at low temperature, with B of same order of magnitude as obtained in recent squid magnetization measurements on Ga_{1-x}Mn_x As samples.Comment: 13 pages, 14 figure

Ferromagnetism in a dilute magnetic semiconductor -- Generalized RKKY interaction and spin-wave excitations

Carrier-mediated ferromagnetism in a dilute magnetic semiconductor has been studied using i) a single-impurity based generalized RKKY approach which goes beyond linear response theory, and ii) a mean-field-plus-spin-fluctuation (MF+SF) approach within a (purely fermionic) Hubbard-model representation of the magnetic impurities, which incorporates dynamical effects associated with finite frequency spin correlations in the ordered state. Due to a competition between the magnitude of the carrier spin polarization and its oscillation length scale, the ferromagnetic spin coupling is found to be optimized with respect to both hole doping concentration and impurity-carrier spin coupling energy $J$ (or equivalently $U$). The ferromagnetic transition temperature $T_c$, deteremined within the spin-fluctuation theory, corresponds closely with the observed $T_c$ values. Positional disorder of magnetic impurities causes significant stiffening of the high-energy magnon modes. We also explicitly study the stability/instability of the mean-field ferromagnetic state, which highlights the role of competing AF interactions causing spin twisting and noncollinear ferromagnetic ordering.Comment: 10 pages, 12 figure

Receptor for pre-Sl(21-47) component of hepatitis B virus on the liver cell: role in virus cell interaction

Attachment of hepatitis B virus to a hepatoblastoma cell line (HepG2) was examined using a synthetic peptide corresponding to the pre-S1 (21-47) region of the envelope protein. Scatchard analysis revealed a single class binding site of Kd 104 &#177; 27 nM/I and 5.4 &#177; 1.2 &#215; 10<SUP>5</SUP> sites per cell. Competition of HBV with pre-S1 peptides was dose dependent, and demonstrated it as the dominant binding site. In view of the suggested sequence homology between the peptide and IgA, cross-competition studies were carried out. The results indicate no direct role of IgA receptor in HBV binding. The receptor for the pre-S1 pep- tide was identified as a single major peptide of molecular weight 31 kD using in-situ ligand receptor crosslinking

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Not AvailableThis study was undertaken to document the gendered access to assets, to assess and improve the nutritional status of tribal women and children, to facilitate capacity building and skill upgradation through need based and sustainable interventions for improving livelihood and to document the impact. The sample of the study include 160 tribal families from two clusters of tribal villages in Shamakhunta block in Mayurbhanj district and R. Udayagiri block of Gajapati district in Odisha. The analysis of gendered access to assets revealed that 94% of the assets were with male; and almost 60% of the activities in crop production and 85% of activities in livestock management were performed by women. The project built the capacity of tribal families and grassroots institutions, enhance the access of poor tribal people to knowledge and innovations to increase the productivity of the resources in environmentally sustainable and socially equitable ways. Women from tribal communities were empowered with requisite knowledge and skills and trained in leadership. It was ensured that they are engaged in viable income generating activities through improved skills and livelihood support, and increased knowledge on household food and nutritional security. Outcome of this study would help in formulating gender based policy and services, enhancement of farm production for greater nutritional security of farm families, income and employment generation, drudgery reduction, improved health and nutritional status of women and children, empowerment of the tribal women, improvement in living standards, integrated development of the tribal families, and database having high practical utility for understanding the performance of gender based technological and social interventions in tribal ecosystem.ICAR-TSP Projec

Splenectomy in cirrhosis with hypersplenism: improvement in cytopenias, child's status and institution of specific treatment for hepatitis C with success

Introduction. Hypersplenism in cirrhosis is not infrequent and may compromise with quality of life and therapy. Splenectomy is a therapeutic option, but information on results of splenectomy is scarce.Material and methods. Consecutive patients with cirrhosis who underwent splenectomy between 2001-2010 were included in the study. Safety, efficacy of splenectomy and subsequent influence on therapy were evaluated.Results. Thirty three patients (mean age 30.9 ± 11.6 years, 19 men, viral 48.5%, autoimmune 15.1%, cryptogenic 36.4%) underwent splenectomy. Twenty were Child's A, 13 Child's B. Twenty patients had > 6 months follow up. Common indications were inability to treat with interferon, transfusion-dependent anemia, recurrent mucosal bleeds, and large spleen compromising quality of life. Median hospital stay was 7 (4-24) days. There was no splenectomy related mortality. Twenty three (70%) patients had post-operative complications, most commonly infections. Two patients required percutaneous drainage of post-operative collections, and 1 needed re-exploration for intra-abdominal bleed. Subsequent to splenectomy platelet count (44,000 to 151,000/mm3, p < 0.01) and TLC (2,500 to 13,400/mm3, p < 0.01) had sustained increase in all patients except one. Five HCV cirrhotics completed interferon and ribavirin therapy, 4 achieved sustained viral response. The quality of life improved and there was no recurrence of infections, mucosal bleed or anemia requiring transfusions in any patient. In patients on long term follow up (median duration 27 months), the median Child's score improved from 6 at baseline to 5 at follow up (p < 0.05).Conclusions. Splenectomy was safe and effective in patients with cirrhosis, and improved therapeutic options as well as Child's score