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The Horizontal Branch Population of NGC 1851 as Revealed by the Ultraviolet Imaging Telescope (UVIT)
Subramaniam, Annapurni,Sahu, Snehalata,Postma, Joseph E.,Cô,té,, Patrick,Hutchings, J. B.,Darukhanawalla, N.,Chung, Chul,Tandon, S. N.,Rao, N. Kameswara,George, K.,Ghosh, S. K.,Girish, V.,M American Astronomical Society 2017 The Astronomical journal Vol.154 No.6
<P>We present the UV photometry of the globular cluster NGC 1851 using images acquired with the Ultraviolet Imaging Telescope (UVIT) onboard the ASTROSAT satellite. Point-spread function fitting photometric data derived from images in two far-UV (FUV) filters and one near-UV (NUV) filter are used to construct color-magnitude diagrams (CMDs), in combination with HST and ground-based optical photometry. In the FUV, we detect only the bluest part of the cluster horizontal branch (HB); in the NUV, we detect the full extent of the HB, including the red HB, blue HB, and a small number of RR Lyrae stars. UV variability was detected in 18 RR Lyrae stars, and three new variables were also detected in the central region. The UV/optical CMDs are then compared with isochrones of different age and metallicity (generated using Padova and BaSTI models) and synthetic HB (using helium-enhanced Y2 models). We are able to identify two populations among the HB stars, which are found to have either an age range of 10-12. Gyr, or a range in Y-ini of 0.23-0.28, for a metallicity of [Fe/H] = -1.2 to -1.3. These estimations from the UV CMDs are consistent with those from optical studies. The almost-complete sample of the HB stars tends to show a marginal difference in spatial/azimuthal distribution among the blue and red HB stars. Thus, this study showcases the capability of UVIT, with its excellent resolution and large field of view, to study the hot stellar population in Galactic globular clusters.</P>
Design curves for prestressed concrete rectangular beam sections based on BS 8110
Subramaniam, Kolluru V.L.,Sinha, S.N. Techno-Press 1995 Structural Engineering and Mechanics, An Int'l Jou Vol.3 No.6
Design curves have been prepared for prestressed rectangular beam section based on BS 8110, for determining area of steel for any given cross section, for stresses in concrete and steel and for the design moment. The design moment and the area of steel have been expressed in dimensionless form in terms of cross sectional dimensions and the characteristic strength of concrete. The choice and combination of design parameters result in considerably less number of curves as aid for design of rectangular prestressed beam sections, than those reported in CP 110 (Part 3).
Subramaniam Chandrasekar,Palanisamy Kasi Viswanathan,Periyayya Uthirakumar,Gian Carlo Montanari 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.1
The extensive use of mineral oil for high voltage insulation applications has directed to widespread research works targeted at improving its dielectric and thermal characteristics. The present study investigates a novel nanofuid insulation prepared using carbon quantum dots (CQD) which is used for the surface treatment of SiO2 nanoparticles added to commercially available mineral oil. The proposed nanofuid referred as CQD–SiO2 nanofuid is tested for its insulation properties such as AC breakdown voltage (BDV), partial discharge (PD), lightning impulse (LI), dissipation factor (Tan-delta), volume resistivity, viscosity and thermal characteristics such as fash and fre point. The tests were conducted for three diferent nanofuid concentrations, that is, 0.01%wt, 0.05%wt and 0.1%wt. Weibull distribution analysis is carried out for breakdown data of BDV test and LI test. Results of CQD–SiO2 nanofuid are compared with mineral oil with and without SiO2 nanofllers. The results show that inclusion of CQD covered SiO2 nanoparticles have the capability to improve the AC breakdown strength by more than 100%, partial discharge inception voltage by 50%, lightning impulse withstand capabilities up to 20% and volume resistivity by 50%. It has also the tendency to slightly improve the fash point and fre point properties than the mineral oil. Signifcant reduction of PD magnitude and Tan-delta values are noticed with CQD–SiO2 nanofuid. Such results indicate that the CQD–SiO2 nanofuid can be a suitable candidate for MV insulation applications.
Subramaniam, Perumal,Selvi, Natesan Thamil,Devi, Soundarapandian Sugirtha Korean Chemical Society 2014 대한화학회지 Vol.58 No.1
The oxidative decarboxylation of phenylsulfinylacetic acid (PSAA) by Cr(VI) in 20% acetonitrile -80% water (v/v) medium follows overall second order kinetics, first order each with respect to [PSAA] and [Cr(VI)] at constant [$H^+$] and ionic strength. The reaction is acid catalysed, the order with respect to [$H^+$] is unity and the active oxidizing species is found to be $HCrO_3^+$. The reaction mechanism involves the rate determining nucleophilic attack of sulfur atom of PSAA on chromium of $HCrO_3^+$ forming a sulfonium ion intermediate. The intermediate then undergoes ${\alpha}$,${\beta}$-cleavage leading to the liberation of $CO_2$. The product of the reaction is found to be methyl phenyl sulfone. The operation of substituent effect shows that PSAA containing electron-releasing groups in the meta- and para-positions accelerate the reaction rate while electron withdrawing groups retard the rate. An excellent correlation is found to exist between log $k_2$ and Hammett ${\sigma}$ constants with a negative value of reaction constant. The ${\rho}$ value decreases with increase in temperature evidencing the high reactivity and low selectivity in the case of substituted PSAAs.
Subramaniam Thatchaneshkanth,최광식 한국해양과학기술원 2023 Ocean and Polar Research Vol.45 No.4
Commonly occurring on a shallow subtidal coarse sand bottom in the northwest Pacific region, the Jedo Venus clam Leucoma (=Protothaca) jedoensis (Lischke, 1874) is one of the valuable shellfish resources supporting the local fisheries industry on the south coast of Korea. In this study, we surveyed the pathologic condition of L. jedoensis from a shallow subtidal sand flat in Gamakman Bay on the south coast using histology and Ray’s fluid thioglycollate medium (RFTM) assay to diagnose infection by the protozoan pathogen Perkinsus olseni. In September 2022, a total of 200 clams with shell length (SL) ranging from 29 to 50 mm were obtained from Gamakman Bay, and each clam was subjected to histology and RFTM assay. Histology revealed that all clams collected in September were in the resting stage, indicating that L. jedoensis in the study area completed spawning before September. Perkinsus olseni and unidentified trematode in the sporocysts stage were observed in histology with a low prevalence of 1.5% and 1%, respectively. Contrary to the histology, the RFTM assay indicated that 4.5% of the Jedo Venus clams examined in this survey were infected with P. olseni, with an average infection intensity of 1.1 x 104 cells/g gill, highlighting the presence of P. olseni in the area. The histology and RFTM assay suggested that P. olseni may not exert a substantial impact on Jedo Venus clam health, compared to Manila clams, the host of P. olseni occurring in the south coast exhibiting extremely high levels of P. olseni infection intensities and prevalence.
CONTROLLABILITY OF STOCHASTIC VOLTERRA INTEGRODIFFERENTIAL SYSTEMS
Subramaniam, R,Balachandran, K. 한국전산응용수학회 2002 The Korean journal of computational & applied math Vol.9 No.2
In this paper, sufficient conditions for the controllability of stochastic integrodifferential systems in Banach spaces are established. The results are obtained by using a fixed point theorem. An example is provided to illustrate the theory.