Relativistic Hydrodynamics and Quasiperiodic Oscillations

MATHEWS GRANT J.,FRAGILE P. CHRIS,WILSON JANES R. The Korean Astronomical Society 2001 Journal of The Korean Astronomical Society Vol.34 No.4

We present preliminary numerical simulations of tilted-disk accretion around a rotating black hole. Our goal is to explore whether hydrodynamic instabilities near the Bardeen-Petterson radius could be responsible for generating moderate-frequency quasi-periodic oscillations in X-ray binaries. We review the relevant general relativistic hydrodynamic equations, and discuss preliminary results on the structure and dynamics of a thin, Keplerian disk.

C?H bond arylation of anilides inside copper-exchanged zeolites

Mathew, B.P.,Yang, H.J.,Jeon, H.,Lee, J.H.,Kim, J.C.,Shin, T.J.,Myung, K.,Kwak, S.K.,Kwak, J.H.,Hong, S.Y. Elsevier 2016 Journal of molecular catalysis Chemical Vol.417 No.-

<P>Syntheses of fine-chemicals using heterogeneous catalysts have tremendous industrial potentials, yet C-H functionalization studies have been largely focused on homogeneous catalysis. We report here the first meta-selective C-H bond arylation of anilides inside copper-exchanged zeolites. Mid- or large-pore zeolite frameworks are selected as supports to access large organic molecules, and atomically distributed copper catalysts exhibit high activities (84-90% conversions) toward direct arylation of anilides with diphenyliodonium salt on 0.5 mol% copper concentration. Computational studies indicate the well fitted copper-aryl complexes inside zeolite frameworks. Electron micrographs, elemental analyses, and reusability study show no observable leaching of catalytically active copper species during the reactions tested. These results demonstrate the practical synthetic potential of copper-exchanged zeolites as promising supported molecular catalysts to afford biaryl motifs-containing compounds with high catalytic activity, chemical stability, and recyclability. (C) 2016 Elsevier B.V. All rights reserved.</P>

CONSTRAINTS ON PRE-INFLATION COSMOLOGY AND DARK FLOW

MATHEWS, GRANT J.,LAN, N.Q.,KAJINO, T. The Korean Astronomical Society 2015 天文學論叢 Vol.30 No.2

If the present universe is slightly open then pre-inflation curvature would appear as a cosmic dark-flow component of the CMB dipole moment. We summarize current cosmological constraints on this cosmic dark flow and analyze the possible constraints on parameters characterizing the pre-inflating universe in an inflation model with a present-day very slightly open ${\Lambda}CDM$ cosmology. We employ an analytic model to show that for a broad class of inflation-generating effective potentials, the simple requirement that the observed dipole moment represents the pre-inflation curvature as it enters the horizon allows one to set upper and lower limits on the magnitude and wavelength scale of pre-inflation fluctuations in the inflaton field and the curvature parameter of the pre-inflation universe, as a function of the fraction of the total initial energy density in the inflaton field. We estimate that if the current CMB dipole is a universal dark flow (or if it is near the upper limit set by the Planck Collaboration) then the present constraints on ${\Lambda}CDM$ cosmological parameters imply rather small curvature ${\Omega}_k{\sim}0.1$ for the pre-inflating universe for a broad range of the fraction of the total energy in the inflaton field at the onset of inflation. Such small pre-inflation curvature might be indicative of open-inflation models in which there are two epochs of inflation.

Particle Size Effect of Anatase TiO[sub 2] Nanocrystals for Lithium-Ion Batteries

Kang, J. W.,Kim, D. H.,Mathew, V.,Lim, J. S.,Gim, J. H.,Kim, J. The Electrochemical Society 2011 Journal of the Electrochemical Society Vol.158 No.2

High rate performance of a NaTi2(PO4)3/rGO composite electrode via pyro synthesis for sodium ion batteries

Song, J.,Park, S.,Gim, J.,Mathew, V.,Kim, S.,Jo, J.,Kim, S.,Kim, J. Royal Society of Chemistry 2016 Journal of Materials Chemistry A Vol.4 No.20

<P>The present study reports on a highly rate capable NASICON-structured NaTi2(PO4)(3)/reduced graphene oxide (NTP/rGO) composite electrode synthesized by polyol-assisted pyro synthesis for Na-ion batteries (NIBs). X-ray diffraction (XRD) studies confirmed the presence of a rhombohedral NaTi2(PO4)(3) phase in the composite while Raman spectroscopy studies helped to identify the existence of rGO in the composite. Electron microscopy studies established that NaTi2(PO4)(3) nanoparticles of average sizes ranging between 20 and 30 nm were uniformly distributed and embedded in the GO sheets. When tested for sodium storage properties, the obtained NTP/rGO composite electrode registered high rate capacities (95 mA h g(-1) at 9.2C and 78 mA h g(-1) at 36.8C) when compared to that of the NTP/C electrode (similar to 1 mA h g(-1) at 9.2 and 36.8C). Further, the NTP/rGO composites delivered a reversible capability of 62 mA h g(-1) at 20C after 1000 cycles. The enhanced performance of the composite electrode can be attributed to the nano-sized NaTi2(PO4)(3) particles with shorter diffusion path lengths. These particles embedded in the rGO sheets with enhanced electrolyte/electrode contact areas ultimately lead to an improvement in the electrical conductivity at high current densities. Ex situ XANES studies confirmed reversible Na-ion intercalation/de-intercalation into/from NTP/rGO. The study thus demonstrates that the NaTi2(PO4)(3)/rGO nanocomposite electrode is a promising candidate for the development of high power/energy density anodes for NIBs.</P>

MARKING FOR LIBRARIES AND INFORMATION AGENCIES

Anne J. Mathews 덕성여자대학교 도서관학회 1988 도서관학회지 Vol.2 No.1

Structure and Li⁺ ion transport in a mixed carbonate/LiPF₆ electrolyte near graphite electrode surfaces: a molecular dynamics study

Boyer, Mathew J.,Vilč,iauskas, Linas,Hwang, Gyeong S. The Royal Society of Chemistry 2016 Physical chemistry chemical physics Vol.18 No.40

<P>Electrolyte and electrode materials used in lithium-ion batteries have been studied separately to a great extent, however the structural and dynamical properties of the electrolyte–electrode interface still remain largely unexplored despite its critical role in governing battery performance. Using molecular dynamics simulations, we examine the structural reorganization of solvent molecules (cyclic ethylene carbonate : linear dimethyl carbonate 1 : 1 molar ratio doped with 1 M LiPF<SUB>6</SUB>) in the vicinity of graphite electrodes with varying surface charge densities (<I>σ</I>). The interfacial structure is found to be sensitive to the molecular geometry and polarity of each solvent molecule as well as the surface structure and charge distribution of the negative electrode. We also evaluated the potential difference across the electrolyte–electrode interface, which exhibits a nearly linear variation with respect to <I>σ</I> up until the onset of Li<SUP>+</SUP> ion accumulation onto the graphite edges from the electrolyte. In addition, well-tempered metadynamics simulations are employed to predict the free-energy barriers to Li<SUP>+</SUP> ion transport through the relatively dense interfacial layer, along with analysis of the Li<SUP>+</SUP> solvation sheath structure. Quantitative analysis of the molecular arrangements at the electrolyte–electrode interface will help better understand and describe electrolyte decomposition, especially in the early stages of solid-electrolyte-interphase (SEI) formation. Moreover, the computational framework presented in this work offers a means to explore the effects of solvent composition, electrode surface modification, and operating temperature on the interfacial structure and properties, which may further assist in efforts to engineer the electrolyte–electrode interface leading to a SEI layer that optimizes battery performance.</P> <P>Graphic Abstract</P><P>The reorganization of solvent molecules in response to the excess charge on the anode is theoretically analyzed, which helps to better understand and describe the initial stages of SEI formation. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c6cp05140e'> </P>

Morbidity Patterns among Menopausal Women in Rural Uttar Pradesh, India: A Cross-Sectional Study

( Debora J. Mathew ),( Sandip Kumar ),( Pankaj Kumar Jain ),( Dhiraj Kumar Srivastava ),( Vaibhav Singh ),( Kiran Krishnappa ) 대한폐경학회 2021 대한폐경학회지 Vol.27 No.1

Objectives: The quality of life declines gradually as women enter menopause, owing to the various problems associated with estrogen deficiency and aging, which adds to their morbidities. This study aimed to investigate the patterns of morbidity among rural menopausal women and compare the morbidity patterns among menopausal transition group and post-menopausal women. Methods: This community-based cross-sectional study included menopausal women aged 45-55 years from rural areas of the Etawah district, Uttar Pradesh, India. To select blocks and villages of the district, multistage random sampling was performed. According to a pretested, semistructured schedule, data were collected through interviews. Results: A total of 315 women participated in the study. The most frequent complaints among the participants were of feeling tired and worn out (85.1%) and of muscle and joint pains (67.6%). Poor memory (P = 0.046) and diabetes (P = 0.024) were more common in women who were in the menopause transition phase than in those who were in the postmenopausal phase. Conclusions: This study showed that majority of the menopausal women suffered from physical problems. Lifestyle modification and awareness programs will be beneficial among women in menopausal transition, to reduce the morbidity later in post-menopausal stage. Behaviour change communication, family and community support are essential in post-menopausal women, to help them cope with various morbid conditions.

High rate capability of LiFePO₄ cathodes doped with a high amount of Ti

Kim, S.,Mathew, V.,Kang, J.,Gim, J.,Song, J.,Jo, J.,Kim, J. Ceramurgica ; Elsevier Science Ltd 2016 CERAMICS INTERNATIONAL Vol.42 No.6

A Li-ion battery cathode with target stoichiometry LiTi<SUB>0.08</SUB>Fe<SUB>0.92</SUB>PO<SUB>4</SUB> was prepared by doping a high amount of Ti<SUP>4+</SUP> into the olivine structure using solid-state reaction at 700<SUP>o</SUP>C. Synchrotron X-ray diffraction studies confirmed the presence of a major olivine phase and NASICON-type ion-conducting Li<SUB>3</SUB>Fe<SUB>2</SUB>(PO)<SUB>4</SUB> and Li<SUB>2</SUB>TiFe(PO<SUB>4</SUB>)<SUB>3</SUB> impurities. Further, the calculated lattice parameter values appear to confirm Ti-doping in LiFePO<SUB>4</SUB>. Electron microscopy and particle distribution studies not only revealed a slightly increased average particle-size and particle fragmentation but also confirmed a fair distribution of Ti<SUP>4+</SUP> ions in the prepared sample. The LiTi<SUB>0.08</SUB>Fe<SUB>0.92</SUB>PO<SUB>4</SUB> cathode delivered high specific capacities and good capacity retentions (@?2% capacity loss after 50 cycles) for lithium battery applications. Besides, the cathode delivered impressive rate capabilities as specific capacities of 160 and 110mAhg<SUP>-1</SUP> at 0.2 and 11.4C, respectively, were retained. Although the average particle-size was slightly higher, the presence of ion-conducting NASICON-type species appear to contribute to the enhanced electrical conductivity and hence to the cathode performance of LiTi<SUB>0.08</SUB>Fe<SUB>0.92</SUB>PO<SUB>4</SUB>.

Electronic and optical properties of strain-locked metallic Ti2O3 films

Lahneman D.J.,Kim H.,Jiang H.,Mathews S.A.,Lock E.,Prestigiacomo J.,Qazilbash M.M.,Rohde C.,Piqué A. 한국물리학회 2023 Current Applied Physics Vol.47 No.-

We successfully grow corundum structured Ti2O3 films on c-plane sapphire substrates using pulsed laser deposition. Temperature dependent resistivity measurements show that a metal to insulator transition (MIT) is suppressed, showing conducting behavior at all temperatures. Samples still show an increase in resistivity as temperature is decreased, a characteristic indicative of a semiconducting phase. Our films exhibit grain size on the order of 30 nm which induce a strain consistent with nanoparticle Ti2O3 showing a (c/a) ratio of 2.7. The imposed strain causes an increase in the c-axis length as the temperature is decreased, and thereby suppresses the transition to an insulating phase. Our optical data agrees with this result, showing the lack of a band gap and the electronic structure consistent with bulk high temperature metallic Ti2O3 with the a1g - eπg interband transition shifted down to 0.7 eV from its bulk insulating value of ~1 eV.