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Non-linear free vibrations and post-buckling analysis of shear flexible functionally graded beams
K. Sanjay Anandrao,R.K. Gupta,P. Ramchandran,G. Venkateswara Rao 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.44 No.3
Large amplitude free vibration and thermal post-buckling of shear flexible Functionally Graded Material (FGM) beams is studied using finite element formulation based on first order Timoshenko beam theory. Classical boundary conditions are considered. The ends are assumed to be axially immovable. The von-Karman type strain-displacement relations are used to account for geometric non-linearity. For all the boundary conditions considered, hardening type of non-linearity is observed. For large amplitude vibration of FGM beams, a comprehensive study has been carried out with various lengths to height ratios, maximum lateral amplitude to radius of gyration ratios, volume fraction exponents and boundary conditions. It is observed that, for FGM beams, the non-linear frequencies are dependent on the sign of the vibration amplitudes. For thermal post-buckling of FGM beams, the effect of shear flexibility on the structural response is discussed in detail for different volume fraction exponents, length to height ratios and boundary conditions. The effect of shear flexibility is observed to be predominant for clamped beam as compared to simply supported beam.
Reverse Bias Leakage Current Mechanism of AlGaN/InGaN/GaN Heterostructure
Apurba Chakraborty,Saptarsi Ghosh,Partha Mukhopadhyay,Sanjay K. Jana,Syed Mukulika Dinara,Ankush Bag,Mihir K. Mahata,Rahul Kumar,Subhashis Das,Palash Das,Dhrubes Biswas 대한금속·재료학회 2016 ELECTRONIC MATERIALS LETTERS Vol.12 No.2
The reverse bias leakage current mechanism of AlGaN/InGaN/GaNheterostructure is investigated by current-voltage measurement intemperature range from 298 K to 423 K. The Higher electric field acrossthe AlGaN barrier layer of AlGaN/InGaN/GaN double heterostructuredue to higher polarization charge is found to be responsible for strongFowler-Nordheim (FN) tunnelling in the electric field higher than3.66 MV/cm. For electric field less than 3.56 MV/cm, the reverse biasleakage current is also found to follow the trap assisted Frenkel-Poole(FP) emission in low negative bias region. Analysis of reverse FPemission yielded the barrier height of trap energy level of 0.34 eV withrespect to Fermi level.
Immobilization of Xylanase Using a Protein-Inorganic Hybrid System
( Ashok Kumar ),( Sanjay K. S. Patel ),( Bharat Mardan ),( Raviteja Pagolu ),( Rowina Lestari ),( Seong-hoon Jeong ),( Taedoo Kim ),( Jung Rim Haw ),( Sang-yong Kim ),( In-won Kim ),( Jung-kul Lee ) 한국미생물생명공학회(구 한국산업미생물학회) 2018 Journal of microbiology and biotechnology Vol.28 No.4
In this study, the immobilization of xylanase using a protein-inorganic hybrid nanoflower system was assessed to improve the enzyme properties. The synthesis of hybrid xylanase nanoflowers was very effective at 4°C for 72 h, using 0.25 mg/ml protein, and efficient immobilization of xylanase was observed, with a maximum encapsulation yield and relative activity of 78.5% and 148%, respectively. Immobilized xylanase showed high residual activity at broad pH and temperature ranges. Using birchwood xylan as a substrate, the V<sub>max</sub> and K<sub>m</sub> values of xylanase nanoflowers were 1.60 mg/ml and 455 μmol/min/mg protein, compared with 1.42 mg/ml and 300 μmol/min/mg protein, respectively, for the free enzyme. After 5 and 10 cycles of reuse, the xylanase nanoflowers retained 87.5% and 75.8% residual activity, respectively. These results demonstrate that xylanase immobilization using a proteininorganic hybrid nanoflower system is an effective approach for its potential biotechnological applications.
Production of Methanol from Methane by Encapsulated Methylosinus sporium
( Sanjay K. S. Patel ),( Jae-hoon Jeong ),( Sanjeet Mehariya ),( Sachin V. Otari ),( Bharat Madan ),( Jung Rim Haw ),( Jung-kul Lee ),( Liaoyuan Zhang ),( In-won Kim ) 한국미생물 · 생명공학회 2016 Journal of microbiology and biotechnology Vol.26 No.12
Massive reserves of methane (CH<sub>4</sub>) remain unexplored as a feedstock for the production of liquid fuels and chemicals, mainly because of the lack of economically suitable and sustainable strategies for selective oxidation of CH4 to methanol. The present study demonstrates the bioconversion of CH<sub>4</sub> to methanol mediated by Type I methanotrophs, such as Methylomicrobium album and Methylomicrobium alcaliphilum. Furthermore, immobilization of a Type II methanotroph, Methylosinus sporium, was carried out using different encapsulation methods, employing sodium-alginate (Na-alginate) and silica gel. The encapsulated cells demonstrated higher stability for methanol production. The optimal pH, temperature, and agitation rate were determined to be pH 7.0, 30oC, and 175 rpm, respectively, using inoculum (1.5 mg of dry cell mass/ml) and 20% of CH<sub>4</sub> as a feed. Under these conditions, maximum methanol production (3.43 and 3.73 mM) by the encapsulated cells was recorded. Even after six cycles of reuse, the Na-alginate and silica gel encapsulated cells retained 61.8% and 51.6% of their initial efficiency for methanol production, respectively, in comparison with the efficiency of 11.5% observed in the case of free cells. These results suggest that encapsulation of methanotrophs is a promising approach to improve the stability of methanol production.
Biological Methanol Production by a Type II Methanotroph Methylocystis bryophila
( Sanjay K. S. Patel ),( Primata Mardina ),( Sang-yong Kim ),( Jung-kul Lee ),( In-won Kim ) 한국미생물 · 생명공학회 2016 Journal of microbiology and biotechnology Vol.26 No.4
Methane (CH4) is the most abundant component in natural gas. To reduce its harmful environmental effect as a greenhouse gas, CH4 can be utilized as a low-cost feed for the synthesis of methanol by methanotrophs. In this study, several methanotrophs were examined for their ability to produce methanol from CH4; including Methylocella silvestris, Methylocystis bryophila, Methyloferula stellata, and Methylomonas methanica. Among these methanotrophs, M. bryophila exhibited the highest methanol production. The optimum process parameters aided in significant enhancement of methanol production up to 4.63 mM. Maximum methanol production was observed at pH 6.8, 30°C, 175 rpm, 100 mM phosphate buffer, 50 mM MgCl2 as a methanol dehydrogenase inhibitor, 50% CH4 concentration, 24 h of incubation, and 9 mg of dry cell mass ml-1 inoculum load, respectively. Optimization of the process parameters, screening of methanol dehydrogenase inhibitors, and supplementation with formate resulted in significant improvements in methanol production using M. bryophila. This report suggests, for the first time, the potential of using M. bryophila for industrial methanol production from CH4.
Immobilization of Laccase on SiO2 Nanocarriers Improves Its Stability and Reusability(s)
( Sanjay K. S. Patel ),( Vipin C. Kalia ),( Joon Ho Choi ),( Jung Rim Haw ),( In Won Kim ),( Jung Kul Lee ) 한국미생물 · 생명공학회 2014 Journal of microbiology and biotechnology Vol.24 No.5
Laccases have a broad range of industrial applications. In this study, we immobilized laccase on SiO2 nanoparticles to overcome problems associated with stability and reusability of the free enzyme. Among different reagents used to functionally activate the nanoparticles, glutaraldehyde was found to be the most effective for immobilization. Optimization of the immobilization pH, temperature, enzyme loading, and incubation period led to a maximum immobilization yield of 75.8% and an immobilization efficiency of 92.9%. The optimum pH and temperature for immobilized laccase were 3.5 and 45°C, respectively, which differed from the values of pH 3.0 and 40°C obtained for the free enzyme. Immobilized laccase retained high residual activities over a broad range of pH and temperature. The kinetic parameter Vmax was slightly reduced from 1,890 to 1,630 μmol/min/mg protein, and Km was increased from 29.3 to 45.6. The thermal stability of immobilized laccase was significantly higher than that of the free enzyme, with a half-life 11- and 18-fold higher at temperatures of 50°C and 60°C, respectively. In addition, residual activity was 82.6% after 10 cycles of use. Thus, laccase immobilized on SiO2 nanoparticles functionally activated with glutaraldehyde has broad pH and temperature ranges, thermostability, and high reusability compared with the free enzyme. It constitutes a notably efficient system for biotechnological applications.
Molecular Mechanism of Capsaicin in Pancreatic Cancer Prevention and Therapy
SANJAY K. SRIVASTAVA 한의병리학회 2015 대한동의병리학회 학술대회논문집 Vol.2015 No.10
Capsaicin, the pungent alkaloid of red pepper has been studied extensively for its anti-inflammatory and anti-oxidant properties. Several studies have shown significant chemopreventive effects of capsaicin against several mutagens and carcinogens. Recent studies indicated that capsaicin suppresses cancer growth by inhibiting cell proliferation and induces apoptosis. Although, capsaicin is a TRPV1 agonist, various reports indicated that the anti-cancer effect of capsaicin is independent of TRPV1. Our studies have shown that capsaicin suppresses the growth of various pancreatic cancer cells and induces apoptotic death. Interestingly, effects of capsaicin were more specific to cancer cells with little or no toxicity towards normal human pancreatic cells. By modulating mitochondrial electron transport complexes, capsaicin generates reactive oxygen species and disrupts mitochondrial functions of pancreatic cancer cells, resulting in the release of cytochrome c into the cytosol and activating caspase-3 cascade. In addition, capsaicin reduces the levels of cellular antioxidants like glutathione, thioredoxin and superoxide dismutase. Capsaicin also inhibits beta catenin pathway and acetylates FOXO-1 through CBP, leading to apoptosis. Oral administration of 5mg/kg capsaicin suppresses the growth of various pancreatic tumor cells in xenograft and orthotopic tumor model. In addition, 10 p.p.m. capsaicin in diet for eight weeks significantly suppresses chronic pancreatitis and progression of PanIN-1 to high grade PanIN-2 and PanIN-3 lesions in KRas<SUP>G12D</SUP>/Pdx-1 mouse model of pancreatic cancer. When given in combination, capsaicin significantly potentiates the anti-tumor effects of gemcitabine. In conclusion, capsaicin targets multiple survival pathways in pancreatic cancer cells resulting in overall tumor growth suppression. [Supported by R01 grant CA129038 awarded by the National Cancer Institute. NIH]