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41.
Prabir K. Dutt Santi R. Palit 《Journal of polymer science. Part A, Polymer chemistry》1970,8(1):15-24
Dihydrocivetone, a macrocyclic ketone, has been found to be a weak initiator of vinyl polymerization. Anhydrous zinc chloride strongly promotes this to form a novel initiating system. Monomers tried successfully are methyl methacrylate, acrylonitrile and α-methylstyrene. The characteristic feature of polymerization of α-methylstyrene differs greatly from those of other monomers and those have been discussed and compared. 相似文献
42.
Generation of fluorescent adducts of malondialdehyde and amino acids: toward an understanding of lipofuscin 总被引:2,自引:0,他引:2
Chowdhury PK Halder M Choudhury PK Kraus GA Desai MJ Armstrong DW Casey TA Rasmussen MA Petrich JW 《Photochemistry and photobiology》2004,79(1):21-25
Lipofuscin is a yellow-brown, highly fluorescent pigment that undergoes an age-related progressive accumulation in animal cells, mainly in postmitotic cells. It is a heterogeneous, high-molecular weight material associated with proteins, lipids and nucleic acids. Lipofuscin is implicated in many aspects of human health, including aging, oxidative stress, macular degeneration, lipid peroxidation, atherosclerosis, dementia (Alzheimer's Disease) and diseases associated with prions. Although the fluorescent properties of lipofuscin have long been recognized, neither histologists nor chemists have yet isolated the pigments themselves or characterized their optical properties. We have prepared lipofuscinlike species by reacting malondialdehyde (MDA) with cysteine (Cys). MDA:Cys adducts 3:2 and 2:2 are two of those that have been identified among the many that were present in the reaction. Whereas previous attempts to synthesize lipofuscinlike species resulted in compounds that were either nonfluorescent or emitted principally in the blue, the MDA:Cys adducts reported in this study are not only fluorescent but also emit over a broader range. 相似文献
43.
44.
A new tricyclic sesquiterpenoid 2‐(hydroxymethyl)‐5,5,9‐trimethyltricyclo[7.2.0.03,6]undecan‐2‐ol ( 1 ), was identified from the leaves of Ocimum sanctum, and its structure was elucidated by extensive NMR and ESI‐MS analyses. Compound 1 was found to have potent antiproliferative activity against the MCF‐7 cell line. 相似文献
45.
In the presence of diffusion, stability of three-layer Hele-Shaw flows which models enhanced oil recovery processes by polymer
flooding is studied for the case of variable viscosity in the middle layer. This leads to the coupling of the momentum equation
and the species advection-diffusion equation the hydrodynamic stability study of which is presented in this paper.
Linear stability analysis of a potentially unstable three-layer rectilinear Hele-Shaw flow is used to examine the effects
of species diffusion on the stability of the flow. Using a weak formulation of the disturbance equations, upper bounds on
the growth rate of individual disturbances and on the maximal growth rate over all possible disturbances are found. Analytically,
it is shown that a short-wave disturbance if unstable can be stabilized by mild diffusion of species, where as an unstable
long-wave disturbance can always be stabilized by strong diffusion of species. Thus, an otherwise unstable three-layer Hele-Shaw
flow can be completely stabilized by a large enough diffusion, i.e., by increasing enough the magnitude of the species diffusion
coefficient. The magnitude of this diffusion coefficient required to completely stabilize the flow will depend on the magnitude
of interfacial viscosity jumps and the viscosity gradient of the basic viscous profile of the middle layer. 相似文献
46.
Mukherjee PK 《The Journal of chemical physics》2011,135(13):134505
A phenomenological theory is presented, which describes the tricritical behavior of the R(I)-R(V) rotator phase transition in the mixture of alkanes with nanoparticles. The influence of the nanoparticles on the R(I)-R(V) transition in alkanes is discussed by varying the coupling between the order parameters of the rotator phases and nanoparticle. When nanoparticle solutes are added to pure alkanes, the R(I)-R(V) transition temperature is increased. It was observed from the theoretical calculations that for a particular value of the concentration of the nanoparticles, the first order R(I)-R(V) transition becomes second order at a tricritical point. Calculations based on this model agree qualitatively with experiment. 相似文献
47.
Continuous efforts have been made to process degraded iris images for enhancement of the iris recognition performance in unconstrained situations. Recently, many researchers have focused on developing the iris segmentation techniques, which can deal with iris images in a non-cooperative environment where the probability of acquiring unideal iris images is very high due to gaze deviation, noise, blurring, and occlusion by eyelashes, eyelids, glasses, and hair. Although there have been many iris segmentation methods, most focus primarily on the accurate detection of iris images captured in a closely controlled environment. The novelty of this research effort is that we propose to apply a variational level set-based curve evolution scheme that uses a significantly larger time step to numerically solve the evolution partial differential equation (PDE) for segmentation of an unideal iris image accurately, and thereby, speeding up the curve evolution process drastically. The iris boundary represented by the variational level set may break and merge naturally during evolution, and thus, the topological changes are handled automatically. The proposed variational model is also robust against poor localization and weak iris/sclera boundaries. In order to solve the size irregularities occurring due to arbitrary shapes of the extracted iris/pupil regions, a simple method is applied based on connection of adjacent contour points. Furthermore, to reduce the noise effect, we apply a pixel-wise adaptive 2D Wiener filter. The verification and identification performance of the proposed scheme is validated on three challenging iris image datasets, namely, the ICE 2005, the WVU Unideal, and the UBIRIS Version 1. 相似文献
48.
Prabir Kumar Chatterjee Asoke Nath Debnarayan Nath Mihir Chowdhury 《Chemical physics letters》1984,110(1):95-98
Low-temperature absorption and circular dichroism spectroscopy have been used to study single crystals of cubic potassium praseodymium double nitrate (anhydrous), K3Pr2(NO3)9. A model calculation of the optical activity has been performed to correlate the observed rotational strengths for crystal-field component-to-component transitions. 相似文献
49.
Strong Self-Similar Fluctuations of Target Fragments in Ring-like Events in Ultra-Relativistic Nuclear Collision 下载免费PDF全文
Dipak Ghosh Argha Deb Samabrata Sarkar Prabir Kumar Haldar 《中国物理快报》2006,23(11):2944-2947
The intermittent fluctuation of target evaporated particles is studied in both ring-like and jet-like events emitted in ^32 S-emulsion interactions at 200 A Ge V within the framework of multi-dimensional factorial moment methodology using the concept of the Hurst exponent. It is observed that the intermittent fluctuation in the ring-like event is self-similar, whereas in the jet-like event fluctuation is self-affine. However, study indicates that the strength of fluctuation in the ring-like events is much stronger than that in the jet-like events. 相似文献
50.
We propose a domain embedding method to solve second order elliptic problems in arbitrary two-dimensional domains. This method can be easily extended to three-dimensional problems. The method is based on formulating the problem as an optimal distributed control problem inside a rectangle in which the arbitrary domain is embedded. A periodic solution of the equation under consideration is constructed easily by making use of Fourier series. Numerical results obtained for Dirichlet problems are presented. The numerical tests show a high accuracy of the proposed algorithm and the computed solutions are in very good agreement with the exact solutions. 相似文献