Polymorphic stages of the fresh water blue-green alga, Gomphosphaeria aponina

V. K. Dwivedi,Richa Tandon,G. L. Tiwari 한국조류학회I 2010 ALGAE Vol.25 No.3

The natural growth of a population of Gomphosphaeria aponina Kützing (Chroococcales, Cyanoprocaryota) was studied in a cemented freshwater tank in Allahabad, India. This population appeared to be a polymorphic species. Different species of the genus Gomphosphaeria have been segregated based on morphological features of colonies, cells and mucilage. However, these features are not well defined for different species. Our observations revealed many feature variations and, interestingly, certain features that have been described for different Gomphosphaeria species were seen in a single population. In this study, records of such variable morphological features were possible due to the availability of numerous specimens and continuous observations for more than two years. Further, this study revealed two points:(i) more detailed morphological studies are required both from nature as well as in culture to identify critical differences among the species, and (ii) molecular characterization of taxa appears to be necessary for final species settlement.

X-ray Absorption Spectroscopic Studies of Pulsed-Laser-Deposited Thin Films of Fe3O4 on Si(111) Substrate

P. Thakur,W. K. Choi,K. H. Chae,J.-Y. Kim,R. J. Choudhary,Shailja Tiwari,Ram Prakash,D. M. Phase,Ravi Kumar 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.6

We report on the growth and the characterization of magnetite thin films grown on Si(111) substrates by using pulsed laser deposition at different substrate temperatures (TS = 350, 450 and 550 ℃) by performing X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) experiments. The O K− and Fe L3,2−edge XAS spectra reveal that the couplings of the O 2p with Fe 3d orbitals highly rely on the growth processes. The XMCD data of well-characterized thin films exhibit characteristic contributions from Fe3+ A ions in tetrahedral sites and Fe2+ B and Fe3+ B ions in octahedral sites and have spectral features similar to those of the Fe3O4 single crystal. The temperature dependence of the XMCD line shape features remain unchanged below and above the Verwey transition. These investigations demonstrate the experimental conditions for controlled growth of Fe3O4 thin films on Si(111) substrates and suggest that the Fe3O4/Si(111) might a promising spintronic materials for future technology.

Cloning and characterization of a thermostable H₂O-forming NADH oxidase from Lactobacillus rhamnosus

Zhang, Y.W.,Tiwari, M.K.,Gao, H.,Dhiman, S.S.,Jeya, M.,Lee, J.K. IPC Science and Technology Press ; Elsevier Scienc 2012 Enzyme and microbial technology Vol.50 No.4

NADH oxidase (Nox) catalyzes the conversion of NADH to NAD<SUP>+</SUP>. A previously uncharacterized Nox gene (LrNox) was cloned from Lactobacillus rhamnosus and overexpressed in Escherichia coli BL21(DE3). Sequence analysis revealed an open reading frame of 1359bp, capable of encoding a polypeptide of 453 amino acid residues. The molecular mass of the purified LrNox enzyme was estimated to be ∼50kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and 100kDa by gel filtration chromatography, suggesting that the enzyme is a homodimer. The enzyme had optimal activity at pH 5.6 and temperature 65<SUP>o</SUP>C, and k<SUB>cat</SUB>/K<SUB>m</SUB> of 3.77x10<SUP>7</SUP>s<SUP>-1</SUP>M<SUP>-1</SUP>, the highest ever reported. Heat inactivation studies revealed that LrNox had high thermostability, with a half-life of 120min at 80<SUP>o</SUP>C. Molecular dynamics simulation studies shed light on the factors contributing to the high activity of LrNox. Although the properties of Nox from several microorganisms have been reported, this is the first report on the characterization of a recombinant H<SUB>2</SUB>O-forming Nox with high activity and thermostability. The characteristics of the LrNox enzyme could prove to be of interest in industrial applications such as NAD<SUP>+</SUP> regeneration.

ON pc-RINGS

Tiwary, A.K.,Paramhans, S.A. Department of Mathematics 1977 Kyungpook mathematical journal Vol.17 No.2

Gene delivery in conjunction with gold nanoparticle and tumor treating electric field

Tiwari, Pawan K.,Soo Lee, Yeon American Institute of Physics 2013 JOURNAL OF APPLIED PHYSICS - Vol.114 No.5

Modeling of Nanoparticle-Mediated Electric Field Enhancement Inside Biological Cells Exposed to AC Electric Fields

Tiwari, Pawan K.,Kang, Sung Kil,Kim, Gon Jun,Choi, Jun,Mohamed, A.-A. H.,Lee, Jae Koo IOP Publishing 2009 Japanese journal of applied physics Vol.48 No.r8

Synthesis of sulfur-co-polymer/porous long carbon nanotubes composite cathode by chemical and physical binding for high performance lithium-sulfur batteries

Tiwari, Vimal K.,Song, Hyeonjun,Oh, Yeonjae,Jeong, Youngjin Elsevier 2020 ENERGY Vol.195 No.-

<P><B>Abstract</B></P> <P>The composite cathode of sulfur-rich polymer and long cylindrical porous multiwalled carbon nanotubes (LCNT) is reported for high performance lithium-sulfur (Li–S) batteries through combining both chemical and physical binding strategies of sulfur, respectively. This technique efficiently exploits the synergistic effect of ability of stabilizing the polymeric sulfur. The role of uniform distribution of highly conductive LCNT network is optimized as a cathode host material by solution route. Annealed sulfur-co-polymer (S-co-poly) composites are homogeneously well attached via physisorption with LCNT submicron channel. The composite shows a high discharge capacity of 1040 mAh g<SUP>−1</SUP> in the 1st cycle of galvanostatic charge-discharge at 0.5C. Whereas, the cell maintains a reversible capacity of 610 mAh g<SUP>−1</SUP> after 200 cycles, showing good capacity rate. Therefore, solvent assisted both synthesis and further proper mixing enables high active material utilization whereas porous submicron channel of CNT network, which provides conducting pathway, adsorbs sulfur copolymer homogeneously for better electrochemical performance.</P> <P><B>Highlights</B></P> <P> <UL> <LI> S-co-poly-LCNT composite cathode was fabricated by inverse vulcanization through solution route. </LI> <LI> High discharge capacity and stable cyclability were achieved by combining chemical and physical binding strategies. </LI> <LI> S-co-poly-LCNT composite is a promising cathode material for high performance Li–S battery. </LI> </UL> </P>

Correlation between blood glucose and hematocrit: A new estimation methodology

Pawan K. Tiwari,남학현,손영수 한국바이오칩학회 2012 BioChip Journal Vol.6 No.3

The estimation of hematocrit in the enzy me and mediator configured blood glucose monitoring electrochemical strips is proposed conceptualizing an innovative data mining methodology. This methodology demonstrate assimilating the peak current(IP), and time(tP) to achieve the peak current of the amperometry; as a coordinate point in the indigenously nomenclated HMM(Hematocrit Monitoring Method) IP-tP Array. The array consists of onstructing a matrix(9×7 matrix) that could be extended to a matrix of appreciable size within the computational limitations. The computational results of hematocrit estimation are precise in the experimental range of 10-50% hematocrit volume. A mathematical model for the transient current emanating from an lectrochemical strip is also formulated corroborating our experimental results.

Raman Threshold Intensity of an Electromagnetic Wave in Cluster Plasmas

Pawan K. Tiwari,Chinook Mok,Chang-Mo Ryu,Changhwan Lim,Sung-Ki Hong 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.6

An electromagnetic wave instantly converts an atomic cluster into a microsphere plasma, resulting in a displacement of the electron and the ion clouds. The electron and the Coulomb pressure cause an atomic cluster to explode and expand hydrodynamically. A nonlinear theory has been formulated to investigate the threshold intensity in cluster plasmas. A laser intensity exceeding 10¹² W/㎠ and a pulse duration of less than 1 picoseconds causes the onset of a stimulated Raman backscattered wave. An electromagnetic wave instantly converts an atomic cluster into a microsphere plasma, resulting in a displacement of the electron and the ion clouds. The electron and the Coulomb pressure cause an atomic cluster to explode and expand hydrodynamically. A nonlinear theory has been formulated to investigate the threshold intensity in cluster plasmas. A laser intensity exceeding 10¹² W/㎠ and a pulse duration of less than 1 picoseconds causes the onset of a stimulated Raman backscattered wave.

Bi-axial and shear buckling of laminated composite rhombic hypar shells

Abhay K. Chaubey,Shubham Raj,Pratik Tiwari,Ajay Kumar,Anupam Chakrabarti,K.K. Pathak 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.74 No.2

The bi-axial and shear buckling behavior of laminated hypar shells having rhombic planforms are studied for various boundary conditions using the present mathematical model. In the present mathematical model, the variation of transverse shear stresses is represented by a second-order function across the thickness and the cross curvature effect in hypar shells is also included via strain relations. The transverse shear stresses free condition at the shell top and bottom surfaces are also satisfied. In this mathematical model having a realistic second-order distribution of transverse shear strains across the thickness of the shell requires unknown parameters only at the reference plane. For generality in the present analysis, nine nodes curved isoparametric element is used. So far, there exists no solution for the bi-axial and shear buckling problem of laminated composite rhombic (skew) hypar shells. As no result is available for the present problem, the present model is compared with suitable published results (experimental, FEM, analytical and 3D elasticity) and then it is extended to analyze bi-axial and shear buckling of laminated composite rhombic hypar shells. A C0 finite element (FE) coding in FORTRAN is developed to generate many new results for different boundary conditions, skew angles, lamination schemes, etc. It is seen that the dimensionless buckling load of rhombic hypar increases with an increase in c/a ratio (curvature). Between symmetric and anti-symmetric laminations, the symmetric laminates have a relatively higher value of dimensionless buckling load. The dimensionless buckling load of the hypar shell increases with an increase in skew angle.