Synthesis, magnetic and Mossbauer spectroscopic studies of Cr doped lithium ferrite nanoparticles

Srivastava, M.,Layek, S.,Singh, J.,Das, A.K.,Verma, H.C.,Ojha, A.K.,Kim, N.H.,Lee, J.H. Elsevier Sequoia 2014 JOURNAL OF ALLOYS AND COMPOUNDS Vol.591 No.-

Lithium-based ferrites are promising and potential magnetic materials for microwave applications. They possess a spinel (AB<SUB>2</SUB>O<SUB>4</SUB>) type crystal structure, where the distributions of metal cations over the tetrahedral (A) and octahedral (B) voids play a crucial role for exhibiting different physical properties. Among various parameter of synthesis, pH is an important factor that influences the cation distribution over A and B voids, overall growth of the nanoparticles and different physical properties. In the present work single phase Cr substituted lithium ferrite nanoparticles have been synthesized by the sol-gel method at different pH. The phase identification and crystallite size have been probed by X-ray diffraction studies. The crystallite size changes by 44.2-48.8nm upon varying the pH from 3.5 to 11.5. In order to investigate the cations distribution at A/B sites, Mossbauer spectroscopic measurements were done. The values of magnetic hyperfine field obtained from the Mossbauer data for the A and B sites are ~49.5T and 51T, respectively. Moreover, it is observed that the area ratio of B site to A site increases with increasing the pH. This observation further suggests that the B site is more preferable for Fe<SUP>3+</SUP> cations at higher pH than the A site. The magnetic parameter such as saturation magnetization (M<SUB>s</SUB>), remanent magnetization (M<SUB>r</SUB>), coercive field (H<SUB>C</SUB>) and squareness (S) are determined by vibrating sample magnetometer (VSM) measurements, which show a consistent increase with increasing pH. The reason for the variation in magnetic properties has been explained on the basis of increased Fe<SUP>3+</SUP> cation occupancies at the B site and size effect, which is well supported by Mossbauer spectroscopic and XRD studies.

Implications of Site‐specific Mass Absorption Cross‐section (MAC) to Black Carbon Observations at a High‐altitude Site in the Central Himalaya

Priyanka Srivastava,Manish Naja,T. R. Seshadri,Hema Joshi,U. C. Dumka,Mukunda M. Gogoi,S. Suresh Babu 한국기상학회 2022 Asia-Pacific Journal of Atmospheric Sciences Vol.58 No.1

Accurate estimation of black carbon (BC) from the widely used optical attenuation technique is important for the reliable assessment of their climatic impact. The optical instruments use Mass Absorption Cross-section (MAC) for converting light attenuation records to BC mass concentrations and Aethalometer is a widely used optical instrument for BC estimation. Several studies have shown large variability inMAC values. It is thus necessary to examine the accuracy and consistency ofMAC values obtained using Aethalometer over distinct geographic locations and seasons. In the present study, MAC values are derived using simultaneous observations (2014–2017) from an EC-OC analyzer and an Aethalometer (AE-42) over a high altitude central Himalayan site at Nainital (29.4oN, 79.5oE, 1958 a.m.s.l). The observations reveal that the annual mean value of MAC (5.03 ± 0.03 m2g− 1 at 880nm) is significantly lower than the constant value used by the manufacturer (16.6 m2g− 1 at 880nm). The estimated MAC values also showed significant seasonal variation, spanning over a range from 3.7 to 6.6 m2g− 1. It is found that the seasonal variability of elemental carbon (EC), air mass variation and meteorological parameters play an important role in the changes in MAC values over this region. Multi-wavelength determination of MAC shows the contribution of absorption by species other than EC at shorter wavelengths.MAC does not show a clear diurnal variation, unlike EC and absorption coefficient. The slope of EC vs. corrected equivalent black carbon (eBC) showed a significant improvement during all seasons when compared with uncorrected eBC. This lends credibility to the fact that the use of site-specific MAC leads to more reliable estimates of eBC over the central Himalayan region. It is found that, instead of using the site specific MAC value, had we used the one supplied by the instrument, we would have underestimated the radiative forcing by about 7.8Wm− 2 which amounts to a reduction by 24 %.

Novel Withanolides from the Flowers of Datura tatula

Srivastava, Anjani,Manickam, M.,Sinha-Bagchia, A.,Sinhaa, S.C.,Ray, A.B. The Korean Society of Pharmacognosy 1996 Natural Product Sciences Vol.2 No.1

Three new withanolides, designated as withatatulins B, C, and D, were isolated from the fresh flowers of Datura tatula Linn. Detailed spectral analysis of these compounds permitted advancement of their structures respectively, as $5{\beta},6{\beta}-epoxy-12{\beta}$,21-dihydroxy-1-oxo-witha-2,24-dienolide (2), $6{\beta},12{\beta},21-trihydroxy-1-oxowitha$ 2, 4,24-trienolide (3) and $5{\beta},6{\beta},12{\beta}$,21-tetrahydroxy-1-oxo-witha-2,24-dienolide (4a). Withanolides with oxygen functions both at 12 and 21-positions are rare and first reported from Datura species.

Irradiation induced modifications in morphology and magnetic property of Mn/Si structure

M.K. Srivastava,V. Ganesan,P.C. Srivastava 한국물리학회 2010 Current Applied Physics Vol.10 No.4

Mn films of ~50 nm has been deposited by electron beam evaporation technique on cleaned and etched Si [(1 0 0), 8–10 Ω cm] substrates to realize a Mn/Si interfacial structures. The structures have been irradiated from energetic (~100 MeV) ion beam from Mn side. The irradiated and unirradiated structures have been characterized from atomic force microscopy, X-ray diffractometry, magnetic force microscopy,and vibrating sample magnetometer facilities. It has been found that surface/interfacial granular silicide phases (of MnxSiy) are formed before and after the irradiation with a irradiation induced modifications of surface morphology and magnetic property. The surface/interface roughness has been found to increase on the irradiation from the atomic force microscopy data. The magnetic property on the irradiation shows an interesting and significant feature of an increased coercivity and a ferromagnetic like behavior in the Mn–Si structure. The observed increased coercivity has been related to the increased roughness on the irradiation. The ferromagnetism after the irradiation is a curious phenomenon which seems due to the formation of Mn–C–Si compound from the carbon dissolved in silicon.

Alteration of pharmacokinetics of oxytetracycline following oral administration of Piper longum in hens

C.Varshneya,M. Singh,R.S. Telang,A.K. Srivastava 대한수의학회 2005 Journal of Veterinary Science Vol.6 No.3

The pharmacokinetic profile of orally administered oxytetracycline (10mg/kg body weight) was studied 7 days post oral treatment of Piper longum (15 mg equivalent/kg) in White Leghorn hens (2-2.8 kg). On the day 8, oxytetracycline (OTC) was administered orally and blood samples were collected from the wing vein in heparinised vials for plasma separation at 0 (pre-treatment), 15, 30, 60, 120, 240, 360, 480 and 600 minutes post OTC administration. Plasma OTC concentrations were determined by microbial assay technique using Bacillus cereus var. mycoides (ATCC 11778) as test organism. The plasma levels of OTC against time were adequately described by one compartment open model. The pharmacokinetic data revealed that P. longum treated animals had significantly higher area under curve (AUC), area under the first moment of plasma drug concentration-time curve (AUMC) and mean residential time (MRT). Prior treatment of P. longum significantly reduced elimination rate constant (β) and increased elimination half life (t½β). The total body clearance (ClB)reduced by 21% whereas total duration of pharmacological effect (td) increased by 29%. The treatment with P. longum reduced loading and maintenance dose by 33.3 and 39%,respectively.

Enhanced Antibiotic Production by Streptomyces sindenensis Using Artificial Neural Networks Coupled with Genetic Algorithm and Nelder-Mead Downhill Simplex

( Tripathi C. K. M. ),( Mahvish Khan ),( Vandana Praveen ),( Saif Khan ),( Akanksha Srivastava ) 한국미생물 · 생명공학회 2012 Journal of microbiology and biotechnology Vol.22 No.7

Antibiotic production with Streptomyces sindenensis MTCC 8122 was optimized under submerged fermentation conditions by artificial neural network (ANN) coupled with genetic algorithm (GA) and Nelder-Mead downhill simplex (NMDS). Feed forward back-propagation ANN was trained to establish the mathematical relationship among the medium components and length of incubation period for achieving maximum antibiotic yield. The optimization strategy involved growing the culture with varying concentrations of various medium components for different incubation periods. Under non-optimized condition, antibiotic production was found to be 95 μg/ml, which nearly doubled (176 μg/ml) with the ANN-GA optimization. ANN-NMDS optimization was found to be more efficacious, and maximum antibiotic production (197 μg/ml) was obtained by cultivating the cells with (g/l) fructose 2.7602, MgSO4 1.2369, (NH4)2PO4 0.2742, DL-threonine 3.069%, and soyabean meal 1.952%, for 9.8531 days of incubation, which was roughly 12% higher than the yield obtained by ANN coupled with GA under the same conditions.

Bio-reduction of graphene oxide using drained water from soaked mung beans (Phaseolus aureus L.) and its application as energy storage electrode material

Jana, M.,Saha, S.,Khanra, P.,Murmu, N.C.,Srivastava, S.K.,Kuila, T.,Lee, J.H. Elsevier 2014 Materials science and engineering B. Advanced Func Vol.186 No.-

Green reduction of graphene oxide (GO) using drained water from soaked mung beans (Phaseolus aureus L.) has been demonstrated. In comparison to the toxic and hazardous reducing chemicals, the drained water from soaked mung beans (P. aureus L.) is completely green reducing agent, the reduction process is very simple and cost effective. The removal of oxygen containing functional groups of GO has been confirmed by UV-vis, Fourier transform infrared and X-ray photoelectron spectroscopy analysis. Morphological characterization of rGO has been performed by atomic force and transmission electron microscopy analysis. Electrochemical performances of rGO have been evaluated by cyclic voltammetry (CV), charge-discharge and electrochemical impedance spectroscopy techniques. The specific capacitance (SC) of rGO has been found to be 137Fg<SUP>-1</SUP> at a current density of 1.3Ag<SUP>-1</SUP>. The retention in SC is more than 98% after 1000 charge-discharge cycles suggesting long-term electrochemical cyclic stability as supercapacitor electrode materials.

Structural and magnetic study of dysprosium substituted cobalt ferrite nanoparticles

Kumar, H.,Srivastava, R.C.,Pal Singh, J.,Negi, P.,Agrawal, H.M.,Das, D.,Hwa Chae, K. North-Holland Pub. Co 2016 Journal of magnetism and magnetic materials Vol.401 No.-

The present work investigates the magnetic behavior of Dy<SUP>3+</SUP> substituted cobalt ferrite nanoparticles. X-ray diffraction studies reveal presence of cubic spinel phases in these nanoparticles. Raman spectra of these nanoparticles show change in intensity of Raman bands, which reflects cation redistribution in cubic spinel lattice. Saturation magnetization and coercivity decrease with increase of Dy<SUP>3+</SUP>concentration in these nanoparticles. Room temperature Mossbauer measurements show the cation redistribution in these nanoparticles and corroborates the results obtained from Raman Spectroscopic measurements. Decrease in magnetization of Dy<SUP>3+</SUP> substituted cobalt ferrite is attributed to the reduction in the magnetic interaction and cation redistribution.

Effect of Certain Immunomodulators on Uterine Infections and Fertility in Post Partum Buffaloes

Kumar, Puneet,Srivastava, S.K.,Rawat, Mayank,Yadav, M.C.,Kumar, H. Asian Australasian Association of Animal Productio 2004 Animal Bioscience Vol.17 No.7

The present study was aimed to study the effect of aqueous extract of Tinospora cordifolia and autologous plasma on uterine infections. Buffaloes in estrus, 40 days and above postpartum were checked for uterine infections. Animals having uterine infections were randomly divided into three groups of six animals each. Buffaloes in group I, II and III (control) were given intrauterine infusion of aqueous extract of Tinospora cordifolia (3,000 mg total dose), autologous plasma (150 ml) and phosphate buffer saline (150 ml) respectively, in three divided doses, once daily for three consecutive days, starting from the day of estrus. A fourth group (IV) comprising of six buffaloes having no uterine infection was also included in the present study. Buffaloes were inseminated artificially on next estrus following treatment and confirmed for pregnancy 60 days later. Bacterial population in CVM of buffaloes in group I, II and III was significantly (p<0.05) higher than group IV. After treatment there was a significant (p<0.01) reduction in bacterial population in group I (83.496$\pm$7.755%) and group II 80.233$\pm$5.799%) than group in III 7.557$\pm$33.551%) at next estrus. There was non-significant improvement in first service conception rate (CR, 33.33%) and overall conception rate (OCR, 27.27%) in group I, in comparison to group III (first service CR-16.67%; OCR-20.0%). No significant improvement was seen in OCR (22.22%) in-group II also in comparison to group III. The improvement in group I was however, nonsignificantly lower than normal animals of group IV (First service CR-16.67%; OCR-36.33%).

Edge-Directed Error Diffused Digital Halftoning : A Steerable Filter Approach

Pardeep Garg,Abhinav Gupta,M.C. Srivastava,Ankur Gupta,Nikunj Agarwal 보안공학연구지원센터(IJSIP) 2009 International Journal of Signal Processing, Image Vol.2 No.3