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.

Al based ultra-fine eutectic with high room temperature plasticity and elevated temperature strength

Tiwary, C.S.,Kashyap, S.,Kim, D.H.,Chattopadhyay, K. Elsevier Sequoia 2015 Materials science & engineering. properties, micro Vol.639 No.-

Developments of aluminum alloys that can retain strength at and above 250<SUP>o</SUP>C present a significant challenge. In this paper we report an ultrafine scale Al-Fe-Ni eutectic alloy with less than 3.5at% transition metals that exhibits room temperature ultimate tensile strength of ~400 MPa with a tensile ductility of 6-8%. The yield stress under compression at 300<SUP>o</SUP>C was found to be 150 MPa. We attribute it to the refinement of the microstructure that is achieved by suction casting in copper mold. The characterization using scanning and transmission electron microscopy (SEM and TEM) reveals an unique composite structure that contains the Al-Al<SUB>3</SUB>Ni rod eutectic with spacing of ~90nm enveloped by a lamellar eutectic of Al-Al<SUB>9</SUB>FeNi (~140nm). Observation of subsurface deformation under Vickers indentation using bonded interface technique reveals the presence of extensive shear banding during deformation that is responsible for the origin of ductility. The dislocation configuration in Al-Al<SUB>3</SUB>Ni eutectic colony indicates accommodation of plasticity in α-Al with dislocation accumulation at the α-Al/Al<SUB>3</SUB>Ni interface boundaries. In contrast the dislocation activities in the intermetallic lamellae are limited and contain set of planner dislocations across the plates. We present a detailed analysis of the fracture surface to rationalize the origin of the high strength and ductility in this class of potentially promising cast alloy.

A Comparison of Pulsed and Continuous Atom Transfer between Two Magneto-optical Traps

S. P. Ram,S. K. Tiwari,S. R. Mishra 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.5

We present the experimental results for a comparison between pulsed and continuous transfer of cold 87Rb atoms between a vapor chamber magneto-optical trap (VC-MOT) and an ultra-highvacuum magneto-optical trap (UHV-MOT) when using a resonant push beam. We find that employing repetitive cycles of a pulsed and unfocused push beam on an unsaturated VC-MOT cloud results in a significantly higher number of atoms transferred to the UHV-MOT than the number obtained with a continuous push beam focused on a continuous VC-MOT. In pulsed transfer, we find that both the VC-MOT loading duration and the push beam duration play important roles in the transfer process and govern the number of atoms transferred to the UHV-MOT. The parameters and processes affecting the transfer have been investigated and are discussed.

Temperature and Phase-space Density of a Cold Atom Cloud in a Quadrupole Magnetic Trap

S. P. Ram,S. R. Mishra,S. K. Tiwari,H. S. Rawat 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.4

We present studies on modifications in the temperature, number density and phase-space densitywhen a laser-cooled atom cloud from optical molasses is trapped in a quadrupole magnetic trap. Theoretically, for a given temperature and size of the cloud from the molasses, the phase-spacedensity in the magnetic trap is shown first to increase with increasing magnetic field gradient andthen to decrease with it after attaining a maximum value at an optimum value of the magneticfieldgradient. The experimentally-measured variation in the phase-space density in the magnetictrap with changing magnetic field gradient is shown to exhibit a similar trend. However, theexperimentally-measured values of the number density and the phase-space density are much lowerthan the theoretically-predicted values. This is attributed to the experimentally-observed temperaturein the magnetic trap being higher than the theoretically-predicted temperature. Nevertheless,these studies can be useful for setting a higher phase-space density in the trap by establishing anoptimal value of the field gradient for a quadrupole magnetic trap.

Solar Science with the Atacama Large Millimeter/Submillimeter Array-A New View of Our Sun

Wedemeyer, S.,Bastian, T.,Brajš,a, R.,Hudson, H.,Fleishman, G.,Loukitcheva, M.,Fleck, B.,Kontar, E. P.,De Pontieu, B.,Yagoubov, P.,Tiwari, S. K.,Soler, R.,Black, J. H.,Antolin, P.,Scullion, E.,Gu Springer-Verlag 2016 Space science reviews Vol.200 No.1

<P>The Atacama Large Millimeter/submillimeter Array (ALMA) is a new powerful tool for observing the Sun at high spatial, temporal, and spectral resolution. These capabilities can address a broad range of fundamental scientific questions in solar physics. The radiation observed by ALMA originates mostly from the chromosphere-a complex and dynamic region between the photosphere and corona, which plays a crucial role in the transport of energy and matter and, ultimately, the heating of the outer layers of the solar atmosphere. Based on first solar test observations, strategies for regular solar campaigns are currently being developed. State-of-the-art numerical simulations of the solar atmosphere and modeling of instrumental effects can help constrain and optimize future observing modes for ALMA. Here we present a short technical description of ALMA and an overview of past efforts and future possibilities for solar observations at submillimeter and millimeter wavelengths. In addition, selected numerical simulations and observations at other wavelengths demonstrate ALMA's scientific potential for studying the Sun for a large range of science cases.</P>

ECR plasma etching of GaAs in CCl2F2/Ar/O2 discharge and IR studies of the etched surface

L. S. S. Singh,K. P. Tiwary,R. K. Purohit,Z. H. Zaidi,M. Husain 한국물리학회 2005 Current Applied Physics Vol.5 No.4

The etching of GaAs materials under electron cyclotron resonance conditions has been performed in an ECR etching system withrf biasing using the CCl2F2/Ar/O2 plasma chemistry. Etching experiments were carried out at a pressure between 0.015 and 0.020mbar, rf power 0.39 W/cm2, and dc bias voltage 200 V. The surface morphology and etch depth were taken by scanning electronmicroscopy and Dektek Prolometry respectively. The use of ECR conditions with additional rf biasing provides the good etchingof the surface and fast etch rates. Moreover, the surface of the GaAs material display smooth and stoichiometric surfaces at higherECR powers. The surface damages on the GaAs samples after the plasma exposure have been studied using IR spectroscopy..

Simulink 이용한 태양전지 MPPT 방법에 따른 출력특성 분석

백승학(S.H. Baek),임지혜(J.H. Im),티와리카필(K.R Tiwari),김대승(D.S. Kim),이강연(K.H. Lee),최연옥(Y.O. Choi),조금배(G.B. Cho),백형래(H.L. Baek) 대한전기학회 2010 대한전기학회 학술대회 논문집 Vol.2010 No.4

Nowadays has problem of energy resource shortage and environmental pollution. We are looking up various solution plans regarding this problem. Solar power is one of the solution to solve the energy shortage problem. But solar power is affected by the weather. So variation weather we can use Maximum Power Point Tracing device for solar PV system. In this paper, we compared Incremental Conductance method to Perturb & Observation(P&O) method about varying insolation. Two method were on the track of Maximum Power Point (MPP) using Matlab-Simulink.

Engineered Carbon-Nanomaterial-Based Electrochemical Sensors for Biomolecules

Tiwari, Jitendra N.,Vij, Varun,Kemp, K. Christian,Kim, Kwang S. American Chemical Society 2016 ACS NANO Vol.10 No.1

<P>The study of electrochemical behavior of bioactive molecules has become one of the most rapidly developing scientific fields. Biotechnology and biomedical engineering fields have a vested interest in constructing more precise and accurate voltammetric/amperometric biosensors. One rapidly growing area of biosensor design involves incorporation of carbon-based nanomaterials in working electrodes, such as one-dimensional carbon nanotubes, two-dimensional graphene, and graphene oxide. In this review article, we give a brief overview describing the voltammetric techniques and how these techniques are applied in biosensing, as well as the details surrounding important biosensing concepts of sensitivity and limits of detection. Building on these important concepts, we show how the sensitivity and limit of detection can be tuned by including carbon-based nanomaterials in the fabrication of biosensors. The sensing of biomolecules including glucose, dopamine, proteins, enzymes, uric acid, DNA, RNA, and 11202 traditionally employs enzymes in detection; however, these enzymes denature easily, and as such, enzymeless methods are highly desired. Here we draw an important distinction between enzymeless and enzyme-containing carbon-nanomaterial-based biosensors. The review ends with an outlook of future concepts that can be employed in biosensor fabrication, as well as limitations of already proposed materials and how such sensing can be enhanced. As such, this review can act as a roadmap to guide researchers toward concepts that can be employed in the design of next generation biosensors, while also highlighting the current advancements in the field.</P>

ON pc-RINGS

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

Effect of Nitrogen Gas Enriched Packing on Quality and Storage Life of Pearl Millet Based Fried Snack

( Tiwari Ajita ),( Jha S. K ) 한국농업기계학회 2017 바이오시스템공학 Vol.42 No.1

Purpose: The storage life of pearl millet-based, deep fried, ready-to-eat snacks, packaged in aluminum-laminated polyethylene having a thickness of 50 μm (with and without nitrogen) was evaluated under storage conditions of 38±2°C and 90% RH. Methods: The moisture content, free fatty acids (FFA), peroxide value, and crispness of the snack were evaluated throughout the storage period. The moisture content, FFA, and peroxide value increased with an increase in storage period, but the increase was less in packages flushed with nitrogen gas. The crispness decreased with an increase in the storage period, for snacks both with and without nitrogen packages. However, the decrease was less in nitrogen-flushed packages. FFA and peroxide values were strongly correlated with the moisture content of the snack. The storage life of the snack was found to be 60 and 45 days in packages with and without nitrogen respectively. Conclusions: The snack`s predicted storage life, for snacks with and without nitrogen packages, was determined as 294 and 254 days respectively.