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P. C. SRIVASTAVA,J. K. TRIPATHI 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2007 NANO Vol.2 No.2
Fe films (of ~50 nm) on p-silicon substrates have been deposited by electron beam evaporation technique to realize Fe/pSi devices. The devices have been irradiated from 100 MeV swift heavy ions of Fe7+ with a fluence of 1014 ions-cm-2. The morphological and structural characterization have been done from SEM, AFM and XRD facilities. Magnetic behavior has been studied from vibrating sample magnetometer (VSM) and SQUID facilities. SEM and AFM studies show the formation of a nanogranular structure. Further, XRD data has shown the formation of intermixed magnetic nanogranular silicide phase (Fe5Si3) having average grain size of 25 nm. M–H and ZFC (zero field-cooled)/FC (field-cooled) studies show the magnetic behavior of interacting magnetic particles. The observed results have been understood as a typical behavior of interacting magnetic nanograins.
Sarkar, P.,Kumar, H.,Rawat, M.,Varshney, V.P.,Goswami, T.K.,Yadav, M.C.,Srivastava, S.K. Asian Australasian Association of Animal Productio 2006 Animal Bioscience Vol.19 No.7
The efficacy of garlic extract and $PGF_2{\alpha}$ in the treatment of endometritis in cows was evaluated. A total of 26 parous cows affected with endometritis were randomly allocated into three groups. Group I (n = 10) animals were infused (IU) with 10 ml garlic extract mixed with 90 ml normal saline, three times at 12 h interval starting from the day of estrum, whereas the animals of Group II (n = 10) were treated with a single injection of $PGF_2{\alpha}$ (25 mg Lutalyse) on the $10^{th}$ to $12^{th}$ day after estrus, and group III (n = 6) remained as control. Cervico-vaginal mucus (CVM) was collected from each animal at pre- and post-treatment estrus and subjected to white side test, pH determination and total bacterial load. The clinical recovery of cows was assessed by negative white side test reaction, pH value and total bacterial count of CVM at subsequent estrus. The recovered animals were inseminated with frozen-thawed semen twice at 12 h intervals and pregnancy was confirmed at 45-60 days following insemination. A significant decline (p<0.05) in pH of CVM was observed in both the treatment groups at subsequent estrus. After treatment there was a significant (p<0.05) reduction in bacterial load, whereas, it was increased in control group. A total number of 65 isolates were identified in CVM samples comprising mostly of facultative anaerobic bacteria. Plasma $T_4$ and $T_3$ concentrations were increased in all the treated animals, whereas, a decline was observed in cortisol levels following treatment. The overall conception rate was 50% in treated groups as compared to nil pregnancy in the control.
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.
Magnetic Behaviour of Granular GdMnO3 Film
Negi, P.,Agrawal, H. M.,Singh, J. P.,Kumar, H.,Srivastava, R. C.,Asokan, K.,Chae, K. H. Springer Science + Business Media 2017 Journal of superconductivity and novel magnetism Vol.30 No.6
<P>The present study deals with the investigation of magnetic properties along with morphological and microstructure analyses of a multiferroic GdMnO3 film fabricated on Si(100) substrate by the pulsed laser deposition technique. Rutherford backscattering spectroscopic analysis suggests that the film is fabricated in the form of diffused layers having different stoichiometric proportions. Raman spectroscopy signifies that few modes present in the film are associated with MnO6 octahedra and some extra peaks indicating the mixed phase formation in tuning with the Rutherford backscattering spectroscopy. Atomic force microscopy confirms the granular nature of the film. Field-cooled and zero-field-cooled thermal magnetization curves show irreversible behaviour extending well above room temperature, which is associated with spin disorder. The presence of Gd+3 state and Mn+3/Mn+4 mixed states in the uppermost layers of the film was confirmed by near-edge X-ray absorption fine structure. Subsequently, in association with these observations, the film is a weak ferromagnetic at 5 K and even at room temperature.</P>
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.
Degradation of organic light emitting diode: Heat related issues and solutions
Tyagi, P.,Srivastava, R.,Giri, L.I.,Tuli, S.,Lee, C. Elsevier Sequoia] 2016 Synthetic metals Vol.216 No.-
Degradation of organic light emitting diodes (OLEDs) is the most serious obstacle towards their commercialization. OLED degrades due to various internal and external mechanisms. External degradation is mainly caused due to the instability of low work function cathode, pin-hole formation during fabrication which provides a path for oxygen and moisture infiltration. Operation of OLED also leads to degradation with major causes being morphological instability of organic layers, trap formation, indium or oxygen diffusion from anode, interface deterioration etc. Heat generation in the OLED also acts as a source of degradation. Most of the heat is generated instantaneously upon biasing of OLED due to resistive or Joule heating as a consequence of high resistance of organic layers and non-radiative recombination. Generated heat can be reduced by reducing the effects of the generation sources such as improving conductivity of organic layers by doping, using additional layers to improve charge injection, employing emissive layers with low recombination losses etc. However, these ways can only reduce the heat up to a certain amount. To further improve the lifetime of OLED, the generated heat can be dissipated by employing heat sinks using either thermally conducting substrate or encapsulation etc. We present a review on OLED degradation with a particular focus on heat generation, its consequences and ways of reduction.
A Distribution Automation System Simulator for Training and Research
Gupta R. P.,Srivastava S. C. The Korean Institute of Electrical Engineers 2005 KIEE International Transactions on Power Engineeri Vol.a5 No.2
This paper presents the design and development of a scaled down physical model for power Distribution Automation (DA) system simulation. The developed DA system simulator is useful in providing hands-on experience to utility engineers / managers to familiarize with the DA system and gain confidence in managing the power distribution system from the computer aided distribution control center. The distribution automation system simulator can be effectively used to carry out further research work in this area. This also helps the undergraduate and graduate students to understands the power distribution automation technology in the laboratory environment. The developed DA simulator has become an integral part of a distribution automation lab in the Electrical Engineering Department at Indian Institute of Technology Kanpur in India.