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21.
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
22.
When contributors to a common cause (or public good) are uncertain about each others’ valuations, early contributors are likely
to be cautious in free-riding on future contributors. Contrary to the case of complete information, when contributors have
independent private valuations for the public good, the expected total contribution generated in a sequential move game may
be higher than in a simultaneous move game. This is established in a conventional framework with quasi-linear utility where
agents care only about the total provision of the public good (rather than individual contribution levels) and there is no
non-convexity in the provision of the public good. We allow for arbitrary number of agents and fairly general distribution
of types. 相似文献
23.
The purpose of this paper is to introduce some new generalized double difference sequence spaces using summability with respect
to a two valued measure and an Orlicz function in 2-normed spaces which have unique non-linear structure and to examine some
of their properties. This approach has not been used in any context before. 相似文献
24.
K.C. Majumdar Randhir Kumar Sinha Santanu Chakravorty 《Journal of Physics and Chemistry of Solids》2009,70(8):1171-915
The miscibility of a rod-shaped (R) and a bent-shaped (BC) compound forming an induced B1 phase is reported. B1 phase is not present in both R and BC in the entire phase sequence. R exhibits partially bilayered smectic Ad phase with cholesteric and TGB while BC shows a B2 phase. It is interesting to show that the B2 phase is totally diminished in low composition (weight%) of BC, B1 phase is induced at lower temperature range (~90-135 °C). A dielectric study is also incorporated to confirm the induction of B1 phase in the binary mixture. 相似文献
25.
Prevalent visualization tools exploit gray value distribution in images through modified histogram equalization and matching technique, referred to as the window width/window level-based method, to improve visibility and enhance diagnostic value. The window width/window level tool is extensively used in magnetic resonance (MR) images to highlight tissue boundaries during image interpretation. However, the identification of different regions and distinct boundaries between them based on gray-level distribution and displayed intensity levels is extremely difficult because of the large dynamic range of tissue intensities inherent in MR images. We propose a soft-segmentation visualization scheme to generate pixel partitions from the histogram of MR image data using a connectionist approach and then generate selective visual depictions of pixel partitions using pseudo color based on an appropriate fuzzy membership function. By applying the display scheme in clinical examples in this study, we could demonstrate additional overlapping regions between distinct tissue types in healthy and diseased areas (in the brain) that could help improve the tissue characterization ability of MR images. 相似文献
26.
We report measurements of birefringence
of several nematic liquid crystals having transverse as well as longitudinal dipole moments in thin (1.4 to
) and thick (7 to
cells. Rubbed polyimide-coated glass plates are used to get planar alignment of the nematic director in these cells. We find significant enhancement (6 to
) of
(
, where S is the orientational order parameter) in thin cells in all compounds with aromatic cores even at temperatures far (
C) below the nematic-isotropic transition point. The enhancement is larger in compounds having several phenyl rings and lower if the number of phenyl rings is reduced. In a compound that does not have an aromatic core no significant enhancement is observed, implying that the strength of the surface potential depends on the aromaticity of the cores. Assuming a perfect orientational order at the surface, calculations based on the Landau-de Gennes theory show that the thickness averaged enhancement of S is sharply reduced as the temperature is lowered in the nematic phase. The measured order parameter S is further enhanced in thin cells because of the stiffening of the elastic constant which reduces the thermal fluctuations of the nematic director. The combined effect is however too small at low temperatures to account for the experimental data.Received: 22 February 2004, Published online: 24 May 2004PACS:
61.30.-v Liquid crystals - 61.30.Pq Microconfined liquid crystals: droplets, cylinders, randomly confined liquid crystals, polymer dispersed liquid crystals, and porous systems - 61.30.Hn Surface phenomena: alignment, anchoring, anchoring transitions, surface-induced layering, surface-induced ordering, wetting, prewetting transitions, and wetting transitionsSurajit Dhara: Present address: Department of Physics, Birla Institute of Technology and Science, Pilani 333 031, India. 相似文献
27.
P. Santhana Raman K.G.M. Nair R. Kesavamoorthy B.K. Panigrahi S. Dhara V. Ravichandran 《Applied Physics A: Materials Science & Processing》2007,87(4):709-713
Indium nanoclusters are synthesized in an amorphous silica matrix using an ion-implantation technique. Indium ions (In2+) with energy of 890 keV are implanted on silica to fluences in the range of 3×1016–3×1017 cm-2. The formation of indium nanoclusters is confirmed by optical absorption spectrometry and glancing incidence X-ray diffraction
studies. A low frequency Raman scattering technique is used to study the growth of embedded indium nanoclusters in the silica
matrix as a function of fluence and post-implantation annealing duration. Rutherford backscattering spectrometry studies show
the surface segregation of implanted indium. Photoluminescence studies indicate the formation of a small quantity of indium
oxide phase in the ion-implanted samples.
PACS 85.40.Ry; 78.67.Bf; 73.20.Mf; 82.75.Fq 相似文献
28.
Krishna C. Majumdar Buddhadeb Chattopadhyay Santanu Chakravorty Nilasish Pal Randhir Kumar Sinha 《Tetrahedron letters》2008,49(50):7149-7152
The synthesis and characterization of a homologous series of Schiff bases consisting of an N-methyldiphenylamine moiety as the central core is reported, which exhibits smectic A phase and transitions from the partial bilayer SmAd phase to the bilayer SmA2 phase as the temperature is lowered. 相似文献
29.
In this paper we report a new geometry for diode laser pumping. We show that an efficient moving-disc laser can be designed which can operate at 20 kW of average power with existing diode laser technology. 相似文献
30.
Santanu Mandal Ashok Kumar Rout Anupam Ghosh Guillaume Pilet Debasis Bandyopadhyay 《Polyhedron》2009,28(17):3858-3862
Two new mononuclear complexes of manganese(III) viz. [MnL2(LH)2]ClO4 (1) and [MnL2(N3)]·0.5CH3OH (2) have been synthesized by reacting manganese perchlorate with furfurylamine and salicylaldehyde (plus sodium azide in 2) where L = (2-hydroxybenzyl-2-furylmethyl)imine, an asymmetric bidentate Schiff base formed in situ to bind the Mn(III) ion. The complexes have been characterized by elemental analysis, IR spectroscopy, TGA and single crystal X-ray diffraction studies. Structural studies reveal that the complexes 1 and 2 adopt an octahedral and a square pyramidal geometry, respectively. The antibacterial activity of the complexes has been tested against Gram(+) and Gram(?) bacteria. 相似文献