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Stellar contents and star formation in the young star cluster Be 59
Pandey, A. K.,Sharma, Saurabh,Ogura, K.,Ojha, D. K.,Chen, W. P.,Bhatt, B. C.,Ghosh, S. K. Blackwell Publishing Ltd 2008 Monthly notices of the Royal Astronomical Society Vol.383 No.3
<P>ABSTRACT</P><P>We present <I>UBV I</I><SUB><I>c</I></SUB> CCD photometry of the young open cluster Be 59 with the aim to study the star formation scenario in the cluster. The radial extent of the cluster is found to be ∼10 arcmin (2.9 pc). The interstellar extinction in the cluster region varies between <I>E</I>(<I>B</I>−<I>V</I>) ≃ 1.4 to 1.8 mag. The ratio of total-to-selective extinction in the cluster region is estimated as 3.7 ± 0.3. The distance of the cluster is found to be 1.00 ± 0.05 kpc. Using near-infrared (NIR) colours and slitless spectroscopy, we have identified young stellar objects (YSOs) in the open cluster Be 59 region. The ages of these YSOs range between <1 and ∼2 Myr, whereas the mean age of the massive stars in the cluster region is found to be ∼2 Myr. There is evidence for second-generation star formation outside the boundary of the cluster, which may be triggered by massive stars in the cluster. The slope of the initial mass function, Γ, in the mass range 2.5 < <I>M</I>/M<SUB>⊙</SUB>≤ 28 is found to be −1.01 ± 0.11 which is shallower than the Salpeter value (−1.35), whereas in the mass range 1.5 < <I>M</I>/M<SUB>⊙</SUB>≤ 2.5 the slope is almost flat. The slope of the <I>K</I>-band luminosity function is estimated as 0.27 ± 0.02, which is smaller than the average value (∼0.4) reported for young embedded clusters. Approximately 32 per cent of Hα emission stars of Be 59 exhibit NIR excess indicating that inner discs of the T Tauri star (TTS) population have not dissipated. The Midcourse Space Experiment (MSX) and <I>IRAS-HIRES</I> images around the cluster region are also used to study the emission from unidentified infrared bands and to estimate the spatial distribution of optical depth of warm and cold interstellar dust.</P>
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.
Singh, G.P.,Zeya, S.B.,Srivastava, A.K.,Ojha, N.G.,Suryanarayana, N. Korean Society of Sericultural Science 2008 International Journal of Industrial Entomology Vol.17 No.1
Pathogenic infection in tasar silkworm, Antheraea mylitta Drury is common and there is a breed specific response regarding tolerance. Hence, the tolerance level of three eco-races of tasar silkworm viz. Daba, Sarihan and Raily to Antheraea mylitta cytoplasmic polyhedrosis virus (AmCPV) infection was tested. The survival of Daba, Sarihan and Raily eco-races was significantly different (p<0.05) when challenged with the same concentration ($1{\times}10^5$ polyhedra/ml) of AmCPV. Daba eco-race was more tolerant to the AmCPV infection having higher survival (65.7%) and $LC_{50}$ values (1000893.17 polyhedra/ml) of AmCPV followed by Sarihan eco-race (50.7% survival and $LC_{50}$ value of AmCPV 187203.6168 polyhedra/ml) and Raily eco-race (24.3% survival and $LC_{50}$ value of AmCPV 5176.37 polyhedra/ml). The tolerance level of Daba and Sarihan eco-races against AmCPV was more than two times than Raily eco-race.
Natural convection of nanofluid flow between two vertical flat plates with imprecise parameter
Biswal, U.,Chakraverty, S.,Ojha, B.K. Techno-Press 2020 Coupled systems mechanics Vol.9 No.3
Natural convection of nanofluid flow between two vertical flat plates has been analyzed in uncertain environment.Anon-Newtonian fluid SodiumAlginate (SA) as base fluid and nanoparticles ofCopper(Cu) are taken into consideration. In thepresentstudy,we have takennanoparticle volume fraction as an uncertain parameterin terms offuzzy number. Fuzzy uncertainties are controlled by r-cut and parametric concept. Homotopy PerturbationMethod (HPM) has been used to solve the governing fuzzy coupleddifferential equationsforthe titled problem.Forvalidation, presentresults are comparedwith existingresultsforsome special casesviz. crisp case andthey are foundto be ingood agreement.
( G. P. Singh ),( S. B. Zeya ),( A. K. Srivastava ),( N. G. Ojha ),( N. Suryanarayana ) 한국잠사학회 2008 International Journal of Industrial Entomology Vol.17 No.1
Pathogenic infection in tasar silkworm, Antheraea mylitta Drury is common and there is a breed specific response regarding tolerance. Hence, the tolerance level of three eco-races of tasar silkworm viz. Daba, Sarihan and Raily to Antheraea mylitta cytoplasmic polyhedrosis virus (AmCPV) infection was tested. The survival of Daba, Sarihan and Raily eco-races was significantly different (p<0.05) when challenged with the same concentration (1 x 10(5) polyhedra/ml) of AmCPV. Daba eco-race was more tolerant to the AmCPV infection having higher survival (65.7%) and LC50 values (1000893.17 polyhedra/ml) of AmCPV followed by Sarihan eco-race (50.7% survival and LC50 value of AmCPV 187203.6168 polyhedra/ml) and Raily ecorace (24.3% survival and LC50 value of AmCPV 5176.37 polyhedra/ml). The tolerance level of Daba and Sarihan eco-races against AmCPV was more than two times than Raily eco-race.