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Search Results: 1 - 10 of 2184 matches for " Abhijit Saha "
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Synthesis and Spectral Studies of CdTe–Dendrimer Conjugates
Ghosh Srabanti,Saha Abhijit
Nanoscale Research Letters , 2009,
Abstract: In order to couple high cellular uptake and target specificity of dendrimer molecule with excellent optical properties of semiconductor nanoparticles, the interaction of cysteine-capped CdTe quantum dots with dendrimer was investigated through spectroscopic techniques. NH2-terminated dendrimer molecule quenched the photoluminescence of CdTe quantum dots. The binding constants and binding capacity were calculated, and the nature of binding was found to be noncovalent. Significant decrease in luminescence intensity of CdTe quantum dots owing to noncovalent binding with dendrimer limits further utilization of these nanoassemblies. Hence, an attempt is made, for the first time, to synthesize stable, highly luminescent, covalently linked CdTe–Dendrimer conjugate in aqueous medium using glutaric dialdehyde (G) linker. Conjugate has been characterized through Fourier transform infrared spectroscopy and transmission electron microscopy. In this strategy, photoluminescence quantum efficiency of CdTe quantum dots with narrow emission bandwidths remained unaffected after formation of the conjugate.
Electronic structure of random binary alloys : an augmented space formulation in reciprocal space
Kamal Krishna Saha,Abhijit Mookerjee
Physics , 2004,
Abstract: We present here a reciprocal space formulation of the Augmented space recursion (ASR) which uses the lattice translation symmetry in the full augmented space to produce configuration averaged quantities, such as spectral functions and complex band structures. Since the real space part is taken into account {\sl exactly} and there is no truncation of this in the recursion, the results are more accurate than recursions in real space. We have also described the Brillouin zone integration procedure to obtain the configuration averaged density of states. We apply the technique to Ni$_{50}$Pt$_{50}$ alloy in conjunction with the tight-binding linearized muffin-tin orbital basis. These developments in the theoretical basis were necessitated by our future application to obtain optical conductivity in random systems.
Optical properties of random alloys : A formulation
Kamal Krishna Saha,Abhijit Mookerjee
Physics , 2004,
Abstract: We present here a formulation for the calculation of the configuration-averaged optical conductivity in random alloys. Our formulation is based on the augmented-space theorem introduced by one of us [A. Mookerjee, J. Phys. C: Solid State Phys. 6, 1340 (1973)]. We show that disorder scattering renormalizes the electron and hole propagators as well as the transition amplitude. The corrections to the transition amplitude have been shown to be related to the self-energy of the propagators and vertex corrections.
Optical properties of random alloys : Application to Cu_{50}Au_{50} and Ni_{50}Pt_{50}
Kamal Krishna Saha,Abhijit Mookerjee
Physics , 2004, DOI: 10.1088/0953-8984/17/28/014
Abstract: In an earlier paper [K. K. Saha and A. Mookerjee, Phys. Rev. B 70 (2004) (in press) or, cond-mat/0403456] we had presented a formulation for the calculation of the configuration-averaged optical conductivity in random alloys. Our formulation is based on the augmented-space theorem introduced by one of us [A. Mookerjee, J. Phys. C: Solid State Phys. 6, 1340 (1973)]. In this communication we shall combine our formulation with the tight-binding linear muffin-tin orbitals (TB-LMTO) technique to study the optical conductivities of two alloys Cu_{50}Au_{50} and Ni_{50}Pt_{50}.
Block recursion and Green matrices
Kamal Krishna Saha,Abhijit Mookerjee
Physics , 2004,
Abstract: We present here generalization of the recursion method of Haydock et al [1] for the calculation of Green matrices (in angular momentum space). Earlier approaches concentrated on the diagonal elements, since the focus was on spectral densities. However, calculations of configuration averaged response functions or neutron scattering cross-sections require the entire Green matrices and self-energy matrices obtained from it. This necessitated the generalization of the recursion method presented here with examples.
Optimization of machining parameters of turning operations based on multi performance criteria
Abhijit Saha,N.K.Mandal
International Journal of Industrial Engineering Computations , 2013,
Abstract: The selection of optimum machining parameters plays a significant role to ensure quality of product, to reduce the manufacturing cost and to increase productivity in computer controlled manufacturing process. For many years, multi-objective optimization of turning based on inherent complexity of process is a competitive engineering issue. This study investigates multi-response optimization of turning process for an optimal parametric combination to yield the minimum power consumption, surface roughness and frequency of tool vibration using a combination of a Grey relational analysis (GRA). Confirmation test is conducted for the optimal machining parameters to validate the test result. Various turning parameters, such as spindle speed, feed and depth of cut are considered. Experiments are designed and conducted based on full factorial design of experiment.
Generalized uncertainty principle and black hole thermodynamics
Sunandan Gangopadhyay,Abhijit Dutta,Anirban Saha
Physics , 2013, DOI: 10.1007/s10714-013-1661-3
Abstract: We study the Schwarzschild and Reissner-Nordstr\"{o}m black hole thermodynamics using the simplest form of the generalized uncertainty principle (GUP) proposed in the literature. The expressions for the mass-temperature relation, heat capacity and entropy are obtained in both cases from which the critical and remnant masses are computed. Our results are exact and reveal that these masses are identical and larger than the so called singular mass for which the thermodynamics quantities become ill-defined. The expression for the entropy reveals the well known area theorem in terms of the horizon area in both cases upto leading order corrections from GUP. The area theorem written in terms of a new variable which can be interpreted as the reduced horizon area arises only when the computation is carried out to the next higher order correction from GUP.
Optical properties of perovskite alkaline earth titanates : a formulation
Kamal Krishna Saha,Tanusri Saha-Dasgupta,Abhijit Mookerjee,Sonali Saha,T. P. Sinha
Physics , 2002, DOI: 10.1088/0953-8984/14/15/301
Abstract: In this communication we suggest a formulation of the optical conductivity as a convolution of an energy resolved joint density of states and an energy-frequency labelled transition rate. Our final aim is to develop a scheme based on the augmented space recursion for random systems. In order to gain confidence in our formulation, we apply the formulation to three alkaline earth titanates CaTiO_3, SrTiO_3 and BaTiO_3 and compare our results with available data on optical properties of these systems.
Growth pattern of preterm and IUGR babies in an urban slum of Kolkata, West Bengal, India
Bobby Paul,Indranil Saha,Abhijit Mukherjee,Sima Roy
Internet Journal of Medical Update - EJOURNAL , 2011,
Abstract: The present study was carried out to analyze the growth pattern of preterm and IUGR infants from birth up to nine months of age. A longitudinal study was conducted in an urban slum of Chetla, Kolkata, India. Study population comprised of 36 low birth weight babies, out of which 13 were preterms and rest 23 were IUGR babies. Different anthropometric parameters like weight, length, head and chest circumference was measured and compared between two groups. During the entire follow up period, all the mean anthropometric parameters of the preterms lagged behind their IUGR counterparts; in contrast the growth potential of the preterms was more as revealed by their increased mean increments in terms of weight, length, head and chest circumference. Regular growth monitoring should be an essential component of care of both preterm and IUGR babies with more focused health care services for IUGR babies, so as to detect growth faltering at the earliest.
Structure, reactivity and electronic properties of V-doped Co clusters
Soumendu Datta,Mukul Kabir,Tanusri Saha-Dasgupta,Abhijit Mookerjee
Physics , 2009, DOI: 10.1103/PhysRevB.80.085418
Abstract: Structures, physical and chemical properties of V doped Co$_{13}$ clusters have been studied in detail using density functional theory based first-principles method. We have found anomalous variation in stability of the doped clusters with increasing V concentration, which has been nicely demonstrated in terms of energetics and electronic properties of the clusters. Our study explains the nonmonotonic variation in reactivity of Co$_{13-m}$V$_m$ clusters towards H$_2$ molecules as reported experimentally [J. Phys. Chem. {\bf 94}, 2744 (1990)]. Moreover, it provides useful insight into the cluster geometry and chemically active sites on the cluster surface, which can help to design better catalytic processes.
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