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91.
Embryogenic tissues of Dioscorea bulbifera were cryopreserved using the encapsulation-dehydration technique. Genetic stability of plants regenerated from cryopreserved embryogenic tissues was assessed using molecular, biochemical and morphological analysis. The random amplified polymorphic DNA (RAPD) analysis of 60 cryopreserved-derived and 20 in vitro grown (control) plantlets showed that 10 primers produced 62 clear reproducible DNA fragment profiles. The amplification products were monomorphic for all the plantlets except one. A total of 4960 DNA fragments were obtained from this study showing no variation in RAPD profiles. The diosgenin content of cryopreserved-derived plants, analyzed using HPLC, was similar to that of control plants. Morphology and the ability to form microtuber were also found to be unaltered in cryopreserved embryo-derived plantlets. Thus, the D. bulbifera plants regenerated from cryopreserved embryogenic tissues were genetically stable at the molecular, biochemical and morphological levels. 相似文献
92.
R.?K.?Roy S.?K.?Mandal D.?Bhattacharyya A.?K.?PalEmail author 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,34(1):25-31
Dielectric properties of silver/SiO2 nanocomposite thin films grown by high-pressure d.c. sputtering technique were studied by spectroscopic ellipsometry (300-800 nm). The dielectric behavior of the nanocomposite thin films largely depended on the particle size, its number density and the surrounding environments. The films showed semiconductor-like behavior up to a critical particle size and concentration, beyond which the films exhibited the typical surface plasmon resonance characteristics in their optical properties. The refractive index was also found to have a strong dependence on the particle size and its dispersion in the matrix. The results were found to be consistent with those obtained from UV-VIS optical absorbance data. Bruggeman effective medium theory was used to explain the experimental results.Received: 3 April 2002, Published online: 23 July 2003PACS:
78.67.-n Optical properties of nanoscale materials and structures
-
78.67.Bf Nanocrystals and nanoparticles 相似文献
93.
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
94.
John Kallikat Augustine Rajesha KumarAgnes Bombrun Ashis Baran Mandal 《Tetrahedron letters》2011,52(10):1074-1077
An efficient method for the Beckmann rearrangement of ketoximes to amides mediated by a catalytic amount (15 mol %) of propylphosphonic anhydride (T3P®) is described. Aldoximes underwent second order Beckmann rearrangement to provide the corresponding nitriles in excellent yields on reacting with T3P (15 mol %) at room temperature. The main advantages of this environmentally friendly protocol include procedural simplicity, and particularly ease of isolation of the products. 相似文献
95.
Midde SreekanthGavinolla Pranitha Bharatam JagadeeshTushar Kanti Chakraborty 《Tetrahedron letters》2011,52(14):1709-1712
Stereoselective construction of highly substituted five-membered carbocycles with multiple chiral centres is described. Sharpless kinetic resolution was applied as the key step to prepare the required 2,3-epoxy alcohols and a Ti(III) radical mediated opening of the epoxide ring followed by intramolecular trapping of the generated radical with a suitably placed α,β-unsaturated ester resulted in the formation of five-membered carbocycles with up to three consecutive new chiral centres stereoselectively fixed. 相似文献
96.
97.
Samit Mandal J Gerl H Geissel K Hauschild M Hellström Z Janas I Kojouharov Y Kopatch RC Lemmon P Mayet Z Podolyak PH Regan H Schaffner C Schlegel J Simpson HJ Wollersheim 《Pramana》2001,57(1):161-164
Feasibility of gamma-ray spectroscopy at relativistic energies with exotic heavy-ions and new generation of germanium detectors
(segmented Clover) is discussed. An experiment with such detector array and radioactive is discussed. 相似文献
98.
Swapan K. Bose † Krishnagopal Mandal Bireswar Chakrabarti 《Photochemistry and photobiology》1986,43(5):525-528
Abstract— Photolysis of α-crystallin in the presence of riboflavin under both aerobic and anaerobic conditions causes a rapid decrease in Trp emission; photooxidation most likely occurs via non-covalent complex formation between the sensitizer molecule and the substrate. However, the change in the tertiary structure of the protein, as manifested in the near-UV CD, is very different between aerobic and anaerobic photolysis. Riboflavin-sensitized reaction under aerobic condition causes a major change in the microenvironments of thiol groups as well as in the near-UV CD, whereas under anaerobic condition the change in the near-UV CD is much less and SH-group environments remain unaltered. The sensitizer in this photoinduced change in conformation of the protein is very selective and specific. 相似文献
99.
Sarifuddin Santabrata Chakravarty Prashanta Kumar Mandal Helge I. Andersson 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2009,56(Z2):299-323
The present investigation deals with a mathematical model representing the mass transfer to blood streaming through the arteries
under stenotic condition. The mass transport refers to the movement of atherogenic molecules, that is, blood-borne components,
such as oxygen and low-density lipoproteins from flowing blood into the arterial walls or vice versa. The blood flowing through
the artery is treated to be Newtonian and the arterial wall is considered to be rigid having differently shaped stenoses in
its lumen arising from various types of abnormal growth or plaque formation. The nonlinear unsteady pulsatile flow phenomenon
unaffected by concentration-field of the macromolecules is governed by the Navier–Stokes equations together with the equation
of continuity while that of mass transfer is controlled by the convection-diffusion equation. The governing equations of motion
accompanied by appropriate choice of the boundary conditions are solved numerically by MAC(Marker and Cell) method and checked
numerical stability with desired degree of accuracy. The quantitative analysis carried out finally includes the respective
profiles of the flow-field and concentration along with their distributions over the entire arterial segment as well. The
key factors like the wall shear stress and Sherwood number are also examined for further qualitative insight into the flow
and mass transport phenomena through arterial stenosis. The present results show quite consistency with several existing results
in the literature which substantiate sufficiently to validate the applicability of the model under consideration. 相似文献
100.
Gautam Mandal 《Physics letters. [Part B]》1989,220(4):533-538
We consider the implications of the existence of continuous families of classically degenerate vacua in constructing quantum string theory in compact toroidal spacetimes. We show that in the presence of unbroken supersymmetry when quantum corrections do not lift the degeneracy, symmetries of particular compactifications can be broken by the presence of the neighbouring vacua. We explicitly demonstrate this in case of the heterotic string where the gauge group SO(32) or E8×E8 breaks down to U(1)16 due to neighbouring configurations of arbitrary Wilson lines. 相似文献