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Search Results: 1 - 10 of 3902 matches for " Saha Sanjay "
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Systematic investigations on the reduction of 4-aryl-4-oxoesters to 1-aryl-1,4-butanediols with methanolic sodium borohydride
Subrata Kumar Chaudhuri,Manabendra Saha,Amit Saha,Sanjay Bhar
Beilstein Journal of Organic Chemistry , 2010, DOI: 10.3762/bjoc.6.94
Abstract: 4-Aryl-4-oxoesters undergo facile reduction of both the keto and the ester groups with methanolic NaBH4 at room temperature to yield the corresponding 1-aryl-1,4-butanediols whereas 4-alkyl-4-oxoesters furnish the corresponding 1,4-butanolides via selective reduction of the keto moiety. Results of a detailed and systematic investigation of the reaction are described.
“On-Water” Catalyst-Free Ecofriendly Synthesis of the Hantzsch Dihydropyridines
Amit Pramanik,Manabendra Saha,Sanjay Bhar
ISRN Organic Chemistry , 2012, DOI: 10.5402/2012/342738
Abstract:
“On-Water” Catalyst-Free Ecofriendly Synthesis of the Hantzsch Dihydropyridines
Amit Pramanik,Manabendra Saha,Sanjay Bhar
ISRN Organic Chemistry , 2012, DOI: 10.5402/2012/342738
Abstract: An eco-friendly “on-water” protocol for efficient catalyst-free synthesis of the Hantzsch dihydropyridines from aryl, heteroaryl, alkyl, and vinylogous aldehydes has been developed with minimum auxiliary substances, toxic reagents, organic solvents, and disposal problems. 1. Introduction 4-Substituted 1,4-dihydropyridine framework has emerged as one of the most prolific chemotypes in the recent computational analysis of medicinal chemistry database due to its multifarious pharmaceutical applications. They serve as important analogues of NADH coenzymes [1] exhibiting neuroprotectant [2] and platelet anticoagulatory activity [3]. These compounds often act as cerebral anti-ischemic [3] agents in the treatments of Alzheimer’s disease and as chemosensitizers [4] in tumour therapy. Due to their high efficiency as Ca2+ channel blockers, the Hantzsch dihydropyridines also find immense applications in the treatment of cardiovascular disorders and hypertension [5]. 1,4-Dihydropyridine skeleton is also present in many vasodilator, bronchodilator, antiatherosclerotic, antitumor, antidiabetic, geroprotective, and hepatoprotective agents. Moreover, these compounds serve as important synthetic intermediates [6, 7] for the preparation of various pyridine derivatives through oxidative aromatization sequences. A number of synthetic protocols for the construction of the dihydropyridine skeleton are available in the literature using ammonia [8], refluxing ammonium hydroxide in a closed vessel microwave synthesizer [9], urea-silica gel [10], ammonium acetate in ethanol under microwave irradiation [11], ammonium hydroxide in ethanol [12], 2,4,6-trichloro-1,3,5-triazine [13], magnesium nitride [14] in water at an elevated temperature in a sealed vessel using stoichiometric excess of organic reactants, and many others. Many of the aforesaid protocols use expensive and toxic reagents (often in excess amounts than required for reaction stoichiometry), have complicated reaction setup, require long reaction times, and form byproducts due to various side reactions. Often these reactions are performed in various organic solvents posing a serious threat of fire hazard, especially when they are carried out under microwave irradiation. Several solvent-free protocols [10] have been developed using supported reagents, but still they require toxic organic solvents during product isolation. Also the disposal of the left-over inorganic supports remains problematic [10] which causes perturbation in the environment. In recent times, ammonium acetate has been judiciously utilized [15, 16] as a
A study of cluster behavioral abnormalities in down syndrome
Bhattacharyya Ranjan,Sanyal Debasish,Roy Krishna,Saha Sanjay
Indian Journal of Medical Sciences , 2009,
Abstract: Background :The behavioral phenotype in Down syndrome follows a characteristic pattern. Aims: To find the incidence of behavioral abnormalities in Down syndrome, to compare these findings with other causes of intellectual disability and normal population and to cluster these abnormalities. Settings :One hundred forty mentally challenged people attending at tertiary care set up and from various non-governmental organizations were included in the study. Patients from both rural and urban set up participated in the study. The age-matched group from normal population was also studied for comparison. Design :The study design is a cross-sectional survey done independently by four observers. Materials and Methods :A semi-structured proforma for demographic profile has been used. The behavioral abnormalities are assessed by using DASH II (Diagnostic Assessment for the Severely Handicapped second modified version) scale. Statistical Analysis :Demographic comparison has been done by analysis of variance. Correlation matrix has been run to identify correlation between individual items. Principal component analysis has been used for grouping the behavioral pattern. Results :Behavioral abnormalities as expected are more common in people having intellectual disability than the normal population. The Down syndrome group unlike other causes of intellectual disability shows higher scores in Stereotypy. Impulse control and Mania subscales. Factor analysis yields five characteristic factor structures, namely, hyperactive-impulsive, biological functions, affective, neurotic and organic-pervasive developmental disorder clusters. Conclusions :Contrary to the conventional belief of docile-fun and music loving prototype, individuals diagnosed with Down syndrome show clusters of behavioral abnormalities and management can vary depending on these target symptoms.
Net Charge Fluctuations as a signal of QGP from Polyakov-Nambu-Jona-Lasinio model
Abhijit Bhattacharyya,Supriya Das,Sanjay K. Ghosh,Sibaji Raha,Rajarshi Ray,Kinkar Saha,Sudipa Upadhaya
Physics , 2012,
Abstract: We report the first model study of the net charge fluctuations in terms of D-measure within the framework of the Polyakov-Nambu-Jona-Lasinio model. Net charge fluctuation is estimated from the charge susceptibility evaluated using PNJL model. A parameterization of the freeze-out curve has been used to obtain D as a function of sqrt(s). We have discussed our results vis-a-vis recent experimental findings from ALICE collaboration.
Shear Viscosity and Phase Diagram from Polyakov$-$Nambu$-$Jona-Lasinio model
Sanjay K. Ghosh,Sibaji Raha,Rajarshi Ray,Kinkar Saha,Sudipa Upadhaya
Physics , 2014, DOI: 10.1103/PhysRevD.91.054005
Abstract: We discuss a detailed study of the variation of shear viscosity, $\eta$, with temperature and baryon chemical potential within the framework of Polyakov$-$Nambu$-$Jona-Lasinio model. $\eta$ is found to depend strongly on the spectral width of the quasi-particles present in the model. The variation of $\eta$ across the phase diagram has distinctive features for different kinds of transitions. These variations have been used to study the possible location of the Critical End Point (CEP), and cross-checked with similar studies of variation of specific heat. Finally using a parameterization of freeze-out surface in heavy-ion collision experiments, the variation of shear viscosity to entropy ratio has also been discussed as a function of the center of mass energy of collisions.
Polyakov--Nambu--Jona-Lasinio model in finite volumes
Abhijit Bhattacharyya,Sanjay K. Ghosh,Rajarshi Ray,Kinkar Saha,Sudipa Upadhaya
Physics , 2015,
Abstract: We discuss the 2+1 flavor Polyakov loop enhanced Nambu--Jona-Lasinio model in a finite volume. The main objective is to check the volume scaling of thermodynamic observables for various temperatures and chemical potentials. We observe the possible violation of the scaling with system size in a considerable window along the whole transition region in the $T-\mu_q$ plane.
A Time History Method for Analysing Operational Piping Vibrations  [PDF]
Subrata Saha
World Journal of Mechanics (WJM) , 2012, DOI: 10.4236/wjm.2012.26038
Abstract: Vibration failure of piping is a serious problem and a matter of concern for safety and reliability of plant operations. Fatigue is the main cause of such failures. Due to the complexity of the phenomenon no closed form design solutions are available. In our study an analytical technique based on the theory of vibrations in the time domain has been presented. Using the inverse theory, the problem has been reduced to a system of Volterra Integral equations to be solved simultaneously at every time step. The solution of the inverse problem may be used in the conventional method to calculate stresses and end reactions which are important from the perspective of engineering design and condition monitoring. The method is robust, simple and can be easily adopted by practicing engineers.
Logarithmic operators in SL(2, R) WZNW model, Singletons and AdS_3/(L)CFT_2 correspondence
Sanjay
Physics , 2000, DOI: 10.1088/0305-4470/35/46/311
Abstract: We discuss the role of singletons and logarithmic operators in AdS_3 string theory in the context of AdS_3/CFT_2 correspondence.
On direct and crossed channel asymptotics of four-point functions in AdS/CFT correspondence
Sanjay
Physics , 1999, DOI: 10.1142/S0217732399001516
Abstract: We analyse the leading logarithmic singularities in direct and crossed channel limit of the four-point functions in dilaton-axion sector of type IIB supergravity on $AdS_{5}$ in AdS/CFT correspondence. Logarithms do not cancel in the full correlator in both channels.
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