Spin reorientation in antiferromagnetic Dy2FeCoO6 double perovskite.

We explored the electronic and magnetic properties of the lanthanide double perovskite Dy2FeCoO6 by combining magnetization, Raman and Mössbauer spectroscopy and neutron diffraction along with density functional theory (DFT) calculations. Our magnetization measurements revealed two magnetic phase transitions in Dy2FeCoO6. First, a paramagnetic to antiferromagnetic transition at T N = 248 K and subsequently, a spin reorientation transition at T SR = 86 K. In addition, a field-induced magnetic phase transition with a critical field of H c ≈ 20 kOe is seen at 2 K. Neutron diffraction data suggested cation-disordered orthorhombic structure for Dy2FeCoO6 in Pnma space group which is supported by Raman scattering results. The magnetic structures ascertained through representational analysis indicate that at T N, a paramagnetic state is transformed to Γ5(Cx, Fy, Az) antiferromagnetic structure while, at T SR, Fe/Co moments undergo a spin reorientation to Γ3(Gx, Ay, Fz). The refined magnetic moment of (Fe/Co) is 1.47(4) µ B at 7 K. The antiferromagnetic structure found experimentally is supported through the DFT calculations which predict an insulating electronic state in Dy2FeCoO6.

A novel nonlinear sliding mode controller for a single stage grid-connected photovoltaic system.

A nonlinear sliding mode controller is proposed for a single stage grid-connected photovoltaic system with a novel nonlinear sliding surface. The proposed controller is designed to ensure maximum power extraction with unity power factor. There are two main advantages of the proposed sliding surface. The new surface will results in a first order sliding mode controller. The second advantage is that maximum power extraction is achieved by tracking DC-link voltage (Vdc) of the PV system. The proposed controller is also compared with the existing sliding mode controller in terms of both numerical simulation and experimental results. It is found that, the proposed controller's performance is better than the existing controller in terms of power extraction and more robust when there are uncertainties and disturbance in PV system.

Spin reorientation and disordered rare earth magnetism in Ho2FeCoO6.

We report the experimental observation of spin reorientation in the double perovskite Ho2FeCoO6. The magnetic phase transitions in this compound are characterized and studied through magnetization and specific heat, and the magnetic structures are elucidated through neutron powder diffraction. Two magnetic phase transitions are observed in this compound-one at [Formula: see text] K, from paramagnetic to antiferromagnetic, and the other at [Formula: see text] K, from a phase with mixed magnetic structures to a single phase through a spin reorientation process. The magnetic structure in the temperature range 200-45 K is a mixed phase of the irreducible representations [Formula: see text] and [Formula: see text], both of which are antiferromagnetic. The phase with mixed magnetic structures that exists in Ho2FeCoO6 gives rise to a large thermal hysteresis in magnetization that extends from 200 K down to the spin reorientation temperature. At T N2, the magnetic structure transforms to [Formula: see text]. Though long-range magnetic order is established in the transition metal lattice, it is seen that only short-range magnetic order prevails in the Ho3+ lattice. Our results should motivate further detailed studies on single crystals in order to explore the spin reorientation process, spin switching and the possibility of anisotropic magnetic interactions giving rise to electric polarization in Ho2FeCoO6.

Incidentally Detected Elevated Liver Enzymes: From Liver to Muscle.

We describe 8 children - with incidentally detected isolated elevation of liver enzymes aspartate aminotansferase and alanine aminotransferase - who were extensively evaluated for hepatic causes before finally being diagnosed to have muscular dystrophy. Serum creatinine phosphokinase levels, if performed early during the work-up, may help in diagnosis of muscle disease and avoid unnecessary investigations for liver disease.

Magnetic glass state and magnetoresistance in SrLaFeCoO6 double perovskite.

Unusual features in magnetization resembling the kinetic arrest of a magnetic glass state are observed in the La-doped double perovskite, SrLaFeCoO6. Neutron powder diffraction experiments confirm the presence of antisite disorder as well as a lack of long-range magnetic order down to 4 K in this double perovskite which displays spin glass-like features in dc and ac susceptibilities. Magnetic relaxation observed through cooling and heating under unequal fields (CHUF) point towards unusual domain dynamics which is supported by a broad memory effect. Among the two anomalies that are observed at [Formula: see text] 75 K and at [Formula: see text] 250 K in the magnetic measurements, the former is associated with a spin-freezing temperature below which the magnetic glass state is experimentally verified. The magnetometric experiments detailed in the paper bring out the non-equilibrium metastable magnetic states in this disordered magnetic system. The magnetic glass state described above manifests in the electrical resistivity [Formula: see text] through the formation of a 'hard gap' because of the spin-exchange energy following the formation of magnetic glass. It is observed that the combination of disorder and magnetic glass state leads to a large, negative magnetoresistance (MR) of ≈47[Formula: see text] at 5 K in 8 T.

Long term follow-up study to evaluate immunogenicity and safety of a single dose of live attenuated hepatitis a vaccine in children.

Worldwide, viral hepatitis continues to be a cause of considerable morbidity and mortality. Mass immunization with a single dose of live attenuated HAV has been shown to significantly reduce disease burden in the community. This was a phase IV, 5-year follow up study carried out at 4 centers (Kolkata, Delhi, Mumbai and Chennai) across India. The subjects with antibody titer <20 mIU/mL at baseline were evaluated for long term immunogenicity. Of the 503 subjects enrolled, 349 subjects were baseline seronegative with an anti-HAV antibody titer <20 mIU/mL. Overall, 343 subjects could be followed up at some point of time during this 5 y post vaccination period. In the last year (60 months) of follow-up, 108 subjects (97.3%) of 111 subjects (who came for follow-up at the end of 5 y) had a protective antibody titer (anti-HAV antibody titer >20 mIU/mL). The seroconversion rates considering seroprotection levels of anti-HAV antibody titer >20 mIU/mL, following vaccination starting from 6 weeks, 6 months, 12 months, 24 months, 36 months, 48 months and 60 months were 95.1%, 97.9%, 98.3%, 96.2%, 97.8%, 92.6% and 97.3%, respectively. The geometric mean concentration (GMC) over the years increased from 64.9 mIU/mL at 6 weeks to 38.1 mIU/mL and 135.2 mIU/mL at 6 months and 12 months, respectively and was maintained at 127.1 mIU/mL at 60 months. In conclusion, the result of this 5-year follow up study showed that the single dose of live attenuated vaccine is well tolerated and provides long-term immunogenicity in healthy Indian children.

Magnetic and magnetocaloric properties of nanocrystalline Pr(1-x)A(x)Mn(1-y)Co(y)O3 (A = Ca, Sr) (x = 0.3; y = 0.5) manganites.

Structural, magnetic and magnetocaloric properties of sol-gel prepared, nanocrystalline oxides Pr(1-x)A(x)Mn(1-y)Co(y)O3 (A = Ca, Sr) (x = 0.3; y = 0.5) (cubic, space group Fm3m) have been studied. From the X-ray data, the crystallite size of Pro.7Ca0.3Mn0.5Co0,503 and Pr0.7Sr0.3Mn0.5Co0.5O3 samples is found to be approximately 24 nm and approximately15 nm respectively. High resolution transmission electron microscopy image shows average particle size of approximately 34 nm and approximately 20 nm. Magnetization measurements indicate a Curie temperature of approximately 153 K and approximately172 K in applied magnetic field of 100 Oe for Pr0.7Ca0.3Mn0.5Co0.5O3 and Pr0.7Sr0.3Mn0.5Co0.O3 compounds. The magnetization versus applied magnetic field curves obtained at temperatures below 150 K show significant hysteresis and magnetization is not saturated even in a field of 7 T. The magnetocaloric effect is calculated from M versus H data obtained at various temperatures. Magnetic entropy change shows a maximum near T(c) for both the samples and is of the order approximately 2.5 J/kg/K.

Ionic Transport Properties in Nanocrystalline Ce0.8A0.2O2-δ (with A = Eu, Gd, Dy, and Ho) Materials.

The ionic transport properties of nanocrystalline 20 mol% Eu, Gd, Dy, and Ho doped cerias, with average grain size of around 14 nm were studied by correlating electrical, dielectric properties, and various dynamic parameters. Gd-doped nanocrystalline ceria shows higher value of conductivity (i.e., 1.8 × 10-4 S cm-1 at 550°C) and a lower value of association energy of oxygen vacancies with trivalent dopants Gd3+ (i.e., 0.1 eV), compared to others. Mainly the lattice parameters and dielectric constants (ε∞) are found to control the association energy of oxygen vacancies in these nanomaterials, which in turn resulted in the presence of grain and grain boundary conductivity in Gd- and Eu-doped cerias and only significant grain interior conductivity in Dy- and Ho-doped cerias.

Magnetic behaviour in Dy(1-x)Mm(x)Co2 compounds.

The magnetic behaviour in Dy(1-x)Mm(x)Co(2) (x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5; Mm = mischmetal) compounds is reported using temperature and field dependence of magnetization (M-T and M-H respectively) measurements. A strong composition dependent irreversibility is observed in both the M-T and M-H scans below the magnetic ordering temperature (T(C)). A clear change of the first-order magnetic transition of DyCo(2) to a second-order one in Dy(0.5)Mm(0.5)Co(2) is evidenced by M-T and a series of Arrott (M(2) versus H/M) plots, obtained from the M-H isotherms around T(C). The variation in induced moments of the Co sublattice is estimated. It is found that the Mm substitution can only lead to a considerable reduction in the T(C), saturation magnetization, and Co moment. The observed behaviour of M-T and M-H plots with increasing Mm content is discussed in detail.

Immunogenicity and safety of live attenuated hepatitis A vaccine: a multicentric study.

OBJECTIVE: To evaluate immunogenicity and tolerability of single dose live attenuated injectable hepatitis A vaccine in four metropolitan cities of India. METHODS: Live attenuated hepatitis A vaccine was administered to 505 children aged 18 to 60 months in four centers across India. Immunogenicity of the vaccine was assessed by estimation of anti-HAV antibody titer at 6 weeks and 6 months following administration of the vaccine. Safety evaluation of the vaccine was also done during the visits. RESULTS: At 6 weeks, 480 subjects (95%) came for the follow-up and 411 (81.4%) subjects reported at the end of 6 months. The geometric mean titer (GMT) of anti-HAV antibody of the subjects who did not have the seroprotective titer at the baseline were assessed at 6 weeks and 6 months which was 81.04 mIU/ml and 150.66 mIU/ml respectively. At 6 weeks, 95.1 % seroconverted and at the end of 6 months, 97.9 % had seroconverted. Both solicited and unsolicited vaccine-induced local and systemic adverse events were insignificant at all the centers, except swelling and induration in a few. CONCLUSION: Live attenuated injectable hepatitis A vaccine was immunogenic and tolerable with minimal reactogenecity, in this study of single dose schedule. Safety profile was also satisfactory in the study population.

Study on dosimetric parameters for stereotactic radiosurgery and intensity-modulated radiotherapy.

This study is an attempt to compare the dosimetric parameters of intensity-modulated radiation therapy (IMRT) and stereotactic radiosurgery (SRS) using patient data. Radiosurgery was delivered through circular tertiary collimators attached to a linear accelerator. Six patients who were treated with SRS were replanned and evaluated with the IMRT planning system. Contouring of all structures, including target volume, was done on the IMRT system to closely match the SRS system. Treatment plans were generated after specifying the goals in the prescription module. The NOMOS BEAK collimator attached to the NOMOS MIMiC delivery device was chosen for treatment delivery. Various parameters such as conformity index, homogeneity index, target volume coverage, nontarget tissue, and brainstem doses were calculated and compared between the IMRT and SRS systems. Patient data were divided into 2 groups based on the complexity of the lesion and the number of isocenters used for radiosurgery. Analysis was done for each group and for the cumulative data. Superior conformality and homogeneous dose distribution in IMRT for multiple isocenter cases were observed. In addition, critical structure volumes for 50%, 70%, and 90% of the prescribed dose were lower in IMRT compared to SRS treatment. However, nontarget tissue received significantly higher doses with IMRT plans. Results show that IMRT treatment modality produces similar results as radiosurgery for small, spherical lesions, whereas it is found to be superior to SRS for irregular lesions in terms of critical structure sparing and better dose homogeneity.

Management of acute diarrhoea in children.

Acute diarrhoeal disease is one of the major killers in children in the developing countries. A management protocol consisting of "Triple A" (assessment, analysis of clinical presentation and action plan protocol) approach has been found to be rewarding in our set-up. The matter has been dealt with by the authors in this article in its proper perspective.

Clinical and viral marker pattern of acute sporadic hepatitis in children in Madras, South India.

One hundred and twenty-seven children who presented with features of acute hepatitis during the period February 1995 to January 1996 were studied. Specific aetiologic agents were identified in 89 per cent. Of these, 67.7 per cent were due to a single virus, whereas 21.3 per cent were due to two or more hepatitis viruses. Hepatitis A virus (HAV) was the sole infecting agent in 38.6 per cent of cases, hepatitis B virus (HBV) in 13.4 per cent of cases, and hepatitis E virus (HEV) in 15.7 per cent of cases. Mixed infections were due to HAV and HBV co-infection (7.1 per cent), HAV and HEV (13.4 per cent), and the combination of HAV, HBV, and HEV (0.8 per cent). In 11 per cent, none of the markers (HAV to HEV) were identified. Acute sporadic hepatitis in children can occur due to a single hepatitis virus type or, at times, due to co-infection with a combination of two enterally transmitted viruses or enteral and parenterally transmitted viruses. Improving personal hygiene and active immunization are essential in the prevention of these viral illnesses. This study was done in a referral centre and hence we report a higher morbidity (13.4 per cent) and mortality (12.6 per cent) rate in all groups of infection. Hence, apart from the viruses, factors such as the age of the child, nutritional status, and treatment taken prior to hospitalization should be taken into consideration to predict the prognosis in a given child.

Role of Candida in indirect pathogenesis of antibiotic associated diarrhoea in infants.

One hundred and thirty seven isolates of Candida species were isolated from antibiotic associated diarrhoea cases and were examined to study the role of Candida in the pathogenesis of diarrhoea in infants. The quantitative estimation of yeast population by simple gram stain smear revealed more than 70% of the cases had 3+ score. The isolates further screened for detection of beta-lactamases. Among the isolated Candida sp, beta-lactamases was secreted by C. albicans, C. tropicalis, C. krusei and C. parapsilosis. Further, 46% of the Candida isolates were found to be produced 741-1110 mU/ml of beta-lactamases, suggesting that these enzyme would inactivate penicillin group of drugs and cause failure in the therapy directed against other diarrhoegenic bacteria.

Multiple drug resistant non typhoidal Salmonella spp associated with acute diarrheal disease.

Rectal swabs/stool specimens from 115 children (0-5 years) suffering with acute diarrhea were screened for non typhoidal salmonella species. 7 (6%) patients were found to be positive for non typhoidal salmonella. 4 (3.47%) were positive for S. paratyphi B and 3 (2.6%) were positive for S. typhimurium. Multidrug resistance was seen in 57 percent of the strains. All strains were sensitive to Ciprofloxacin. All strains were resistant to Ampicillin followed by Ciprofloxacin. All strains were resistant to Ampicillin followed by Gentamycin (43%), Kanamycin (43%), Tetracycline (43%), Streptomycin (28.5%) and Chloramphenicol (28.5%).

Risk factors for persistent diarrhea among children under 2 years of age. Case control study.

A case control study was done at the Institute of Child Health, Madras, among prospectively recruited children aged 1-23 months to identify the risk factors for persistent diarrhea. Cases were children with diarrhea persisting for > 14 days. Controls were children with acute diarrhea who had recovered within 7 days. Two controls for each case, matched for age were recruited. The total number of cases and controls recruited were 170 and 340. Fifteen risk factors for association with persistent diarrhea were studied. When the factors were adjusted for covariables by logistic regression, only 6 factors were found to be significant, namely, malnutrition (OR 2.9; 95% CI 1.9-4.5), dysenteric stools (OR 2.4; 95% CI 1.3-4.3), indiscriminate use of antimicrobials (OR 2.4; 95% CI 1.6-3.9), associated illnesses (OR 2.1; 95% CI 1.5-3.1), stools > 10/day (OR 1.8; 95% CI 1.2-2.8) and persistence of dehydration (OR 1.4; 95% CI 1.2-1.7). However, when invasive diarrhea was excluded, weight loss during study period became a significant factor. It is concluded that all children with acute diarrhea should be investigated for associated illnesses and treated adequately, indiscriminate use of antimicrobials should be avoided and nutritional support should be provided.

Comparative evaluation of the antipyretic efficacy of ibuprofen and paracetamol.

An open multicentric trial was conducted on 175 patients to compare the antipyretic efficacy of ibuprofen (7 mg/kg) and paracetamol (8 mg/kg). Children between the age of 4 months and 12 years with fever were admitted to the study, 85 in the ibuprofen group and 90 in the paracetamol group. The axillary temperatures were recorded at half hourly intervals for 2 hours. The mean fall in temperature at 1, 1.5 and 2 hours was similar in both groups and the differences were not statistically significant (p greater than 0.05). At half hour, the fall in temperature (mean +/- SEM) for ibuprofen was 0.1975 +/- 0.0409 and for paracetamol was 0.3843 +/- 0.0490. This absolute difference of 0.19 degrees C was statistically significant (p less than 0.05). We conclude that ibuprofen has antipyretic activity comparable to that of paracetamol and that it could be a valuable alternative antipyretic in clinical practice. There is a need to repeat this trial with higher doses of ibuprofen, to establish a dose response of the drug, if any, and to find an optimally effective dose.