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排序方式: 共有1744条查询结果,搜索用时 15 毫秒
21.
Soujan Ghosh Swati Chowdhury Subrata Kundu Sudipta Sasmal Dimitrios Z. Politis Stelios M. Potirakis Masashi Hayakawa Suman Chakraborty Sandip K. Chakrabarti 《Entropy (Basel, Switzerland)》2022,24(1)
We focus on the possible thermal channel of the well-known Lithosphere–Atmosphere–Ionosphere Coupling (LAIC) mechanism to identify the behavior of thermal anomalies during and prior to strong seismic events. For this, we investigate the variation of Surface Latent Heat Flux (SLHF) as resulting from satellite observables. We demonstrate a spatio-temporal variation in the SLHF before and after a set of strong seismic events occurred in Kathmandu, Nepal, and Kumamoto, Japan, having magnitudes of 7.8, 7.3, and 7.0, respectively. Before the studied earthquake cases, significant enhancements in the SLHF were identified near the epicenters. Additionally, in order to check whether critical dynamics, as the signature of a complex phenomenon such as earthquake preparation, are reflected in the SLHF data, we performed a criticality analysis using the natural time analysis method. The approach to criticality was detected within one week before each mainshock. 相似文献
22.
Endophytes, being the co-evolution partners of green host plants, are factories of pharmaceutically valuable novel natural products. Cochliobolus sp. APS1, an endophyte of Andrographis paniculata (Green Chiretta), produces a plethora of natural bioactive compounds and the multipotent alkaloid Aziridine, 1-(2-aminoethyl)-, is the prime one among them. The isolate exhibited antibacterial, anti-biofilm, and antilarval potency. The MIC and MBC values of the ethyl-acetate culture extract ranged from 15.62 to 250 µg/mL against ten pathogenic microorganisms (including MRSA and VRSA). Killing kinetics data along with the leakage of macromolecules into the extracellular environment supports the cidal activity of the antibacterial principles. The broad spectrum antibacterial activity of Aziridine, 1-(2-aminoethyl)-, was optimized by a one-variable-at-a-time system coupled with response surface methodology, which led to a 45% enhancement of the antibacterial activity. The maximum response (22.81 ± 0.16 mm of zone of inhibition against MRSA) was marked in 250 mL Erlenmeyer flask containing 90 mL potato dextrose broth supplemented with (g%/L) glucose, 9.7; urea concentration, 0.74; with medium pH 6.48; after 8.76 days of incubation at 26 °C. APS1 strongly inhibited biofilm formation in the tested pathogenic microorganisms and acts as a larvicidal agent against the Dengue-vector Aedes aegypti. This is probably the first report of Aziridine, 1-(2-aminoethyl)-, from any endophytic source. Cochliobolus sp. APS1 possesses industrial importance for the production of bioactive alkaloids. 相似文献
23.
A simple electrochemical process has been implemented to fabricated fractal structured leaf-like metallic zinc. The fabricated material was structurally characterized using X-ray diffraction that reveals the hexagonal unit cell structure. Also the growth of the structure is anisotropic. Field emission scanning electron microscopic images revealed clearly the leaf-like morphology of the fabricated material is fern like and ∼500 μm in length, ∼50-60 μm wide and the platelets thickness is ∼5 μm. The growth of this structure is diffusion controlled and locally accomplished with the oriented attachment. Raman shift measurement revealed the existence of surface optical phonon modes which is very significant for surface defects. 相似文献
24.
Anirudh Pradhan Purnima Pandey Kanti Jotania Mahesh Kumar Yadav 《International Journal of Theoretical Physics》2007,46(11):2774-2787
Plane symmetric viscous fluid cosmological models of the universe with a variable cosmological term are investigated. The
viscosity coefficient of bulk viscous fluid is assumed to be a power function of mass density whereas the coefficient of shear
viscosity is to be proportional to rate of expansion in the model. We have also obtained a special model in which the shear
viscosity is assumed to be zero. The cosmological constant Λ is found to be a decreasing function of time and a positive which is supported by results from recent supernovae Ia observations.
Some physical and geometric properties of the models are also discussed. 相似文献
25.
A theoretical study of antioxidant activity of some Schiff bases derived from biologically important phenolic aldehydes and phenylenediamines 下载免费PDF全文
Romesh Borgohain Jyotirekha G. Handique Ankur Kanti Guha Sanjay Pratihar 《Journal of Physical Organic Chemistry》2018,31(2)
Because of their numerous biological as well as industrial importance, the study of Schiff bases is an emerging field for the researchers, in recent time. In this study, we have designed some Schiff bases derived from biologically important precursors. The antioxidant activities of the designed compounds are thoroughly studied theoretically using density functional theory taking various parameters like bond dissociation enthalpy, ionization enthalpy, proton dissociation enthalpy, and electron transfer enthalpy followed by the study of effects of solvent, spin density, and molecular orbital on antioxidant activity of the compounds. The comparison of antioxidant activity of the compounds with that of phenol and their parent aldehydes reveals the superior antioxidant activity of the designed compounds. This study contributes towards the information of an important bridge between bioorganic and computational chemistry. 相似文献
26.
27.
Jaya Chakraborty 《应用光谱学评论》2017,52(1):1-38
Microbes are the most fascinating group, with huge diversity devising myriad functional applications in the field of medicine, pharmaceuticals, environmental remediation, and industries. Quantitative and qualitative determination of biomolecules and microbial assisted phenomena by spectroscopy is a pioneer approach. It facilitates the study of atomic and molecular geometries, energy levels, chemical bonds, and interactions between molecules and microbes. It produces fingerprints of the microbial species serving to characterize, differentiate, and identify microorganisms, in both the environment and at single-cell level. Spectroscopy-based bioremediation techniques like Fourier transform infrared spectroscopy, mass spectroscopy, force spectroscopy, Raman spectroscopy, photoemission spectroscopy, and laser-induced breakdown spectroscopy have been very well represented and linked with the microbial applications. This review summarizes the traditional spectroscopic techniques used for the study of microbes and microbial-assisted products as well as illustrates its application in the field of microbial diversity and remediation. This will provide an outlook for the intricate characterization and dimension of microbes to be used for effective application in bioremediation. 相似文献
28.
Sumanta Chakraborty Soumitra SenGupta 《The European Physical Journal C - Particles and Fields》2017,77(8):573
We show that a possible resolution to the stabilization of an extra spatial dimension (radion) can be obtained solely in the context of gravitational dynamics itself without the necessity of introducing any external stabilizing field. In this scenario the stabilized value of the radion field gets determined in terms of the parameters appearing in the higher curvature gravitational action. Furthermore, the mass of the radion field and its coupling to the standard model fields are found to be in the weak scale implying possible signatures in the TeV scale colliders. Some resulting implications are also discussed. 相似文献
29.
Susanto Chakraborty Pranab Krishna Chanda Dipankar Ray 《International Journal of Theoretical Physics》1995,34(11):2223-2244
Under some assumptions and transformations of variables, Yang's equations forR-gauge fields on Euclidean space lead to conformally invariant equations permitting one to obtain infinitely many other solutions from any solution of these conformally invariant equations. These conformally invariant equations closely resemble the mathematically interesting generalized Lund-Regge equations. Some exact solutions of these conformally in variant equations are obtained. Except for some singular situations, these solutions are self-dual. 相似文献
30.
Sumana Chakraborty Yew Kam Ho 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,49(1):59-65
This work presents an investigation on the doubly excited 1S
e
autoionizing states of screened helium atom lying below the n = 4 threshold of the He+ ion. The potential generated in this system is represented by a Yukawa type potential. We have employed complex-coordinate
rotation method, as it is a powerful scheme to study high lying resonances. Hylleraas type wave function is used to consider
the correlation effect between all the charged particles. Our resonance parameters for the resonances lying below the He+ (n = 2) threshold agree well with those of the existing calculations by using the stabilization method. Resonances associated
with higher thresholds are new calculations. All the present results are well converged with basis length N = 444. 相似文献