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Medinīpur, India

Sahoo S.,Haldia Government College | Sengupta D.,Indian Statistical Institute
Statistics in Medicine | Year: 2016

In this paper, we present a class of graphical tests of the proportional hazards hypothesis for two-sample censored survival data. The proposed tests are improvements over some existing tests based on asymptotic confidence bands of certain functions of the estimated cumulative hazard functions. The new methods are based on the comparison of unrestricted estimates of the said functions and their restricted versions under the hypothesis. They combine the rigour of analytical tests with the descriptive value of plots. Monte Carlo simulations suggest that the proposed asymptotic procedures have reasonable small sample properties. The power is much higher than existing graphical tests and comparable with existing analytical tests. The method is then illustrated through the analysis of a data set on bone marrow transplantation for Leukemia patients. © 2016 John Wiley & Sons, Ltd. Source


Ray S.,University of Calcutta | Konar S.,University of Calcutta | Jana A.,University of Calcutta | Das K.,Haldia Government College | And 3 more authors.
Polyhedron | Year: 2013

One binuclear Cu(II) complex, [Cu2(L1) 2(N3)2] (1), and a trinuclear Cu(II) complex, [Cu3(L2)3(μ1,1N3) 2](ClO4) (2), of two potentially tridentate NNO-donor Schiff base ligands, [2-(1-(2-(4,6-dimethylpyrimidin-2-yl)hydrazono)ethyl) phenol] (HL1) and [2-((2-(4,6-dimethyl pyrimidin-2-yl) hydrazono) methyl) phenol] (HL2), have been synthesized and characterized by elemental analyses, UV-Vis IR spectroscopy, DFT and single crystal X-ray crystallography. The ligands HL1 and HL2 are [1 + 1] condensation products of 2-hydrazino-4,6-dimethylpyrimidine with 2-hydroxy acetophenone and salicylaldehyde respectively. In 1, the two Cu(II) centers are bridged by μ-phenoxo groups. In 2, the three Cu(II) centers are held together by two μ1,1 bridging azide ions and a phenoxo oxygen atom which binds the three metal centers and behaves as a μ3-O atom. The geometries of the complexes have been optimized using the UB3LYP level of theory. The calculation confirms that all the copper centers are five coordinate with distorted square pyramidal geometries, which is consistent with the experimental data. © 2012 Elsevier Ltd. All rights reserved. Source


Chattopadhyay B.,Indian Association for The Cultivation of Science | Chattopadhyay B.,Free University of Colombia | Das U.,Haldia Government College | Das U.,Jadavpur University | And 2 more authors.
CrystEngComm | Year: 2013

Crystal structures of two benzyloxybenzoic acids (1 and 2) and two benzyloxyanilines (3 and 4) have been solved from laboratory X-ray powder diffraction data using the direct space methodology. The refinements of structures 1, 2, 3 and 4 have been carried out following the Rietveld method. The nature of intermolecular interactions in 1-4 has been analyzed through the Hirshfeld surfaces and 2D fingerprint plots. The COOH functional group generates a cyclic R22(8) synthon via intermolecular O-H⋯O hydrogen bonds in 1 and 2. An interplay of O-H⋯O and C-H⋯O hydrogen bonds, and C-H⋯π interactions in 1 and 2 facilitates the formation of three-dimensional supramolecular frameworks in 1 and a one-dimensional step-like architecture in 2. While the combination of N-H⋯π and C-H⋯π interactions link the molecules in 3 into parallel columns along the [100] direction, no such molecular assembly has been observed in 4. Hirshfeld surface analyses of 1-4 as well as a few related benzyloxybenzoic acid and benzyloxyaniline derivatives retrieved from the Cambridge structural database (CSD) indicate that about 90% of Hirshfeld surface areas in this class of compounds are due to H⋯H, C⋯H and O⋯H contacts. © 2013 The Royal Society of Chemistry. Source


Das U.,Haldia Government College | Das U.,Jadavpur University | Chattopadhyay B.,Indian Association for The Cultivation of Science | Mukherjee M.,Indian Association for The Cultivation of Science | Mukherjee A.K.,Jadavpur University
Chemical Physics Letters | Year: 2011

Crystal structures of three derivatives of phenylpropionic acid, 2, 3 and 4 with hydroxyl, methyl and methoxy substitutions at the 2, 4 positions have been determined from X-ray powder diffraction data and their electronic structures were calculated at the DFT level. The optimized molecular geometries agree closely to that obtained from the crystallographic analysis. Intermolecular O-H...O hydrogen bonds generate R22(8) rings, which are further connected through O-H...O and C-H...O hydrogen bonds into two-dimensional framework in 2 and 4, and a step like architecture in 3. The HOMO-LUMO energy gap (>4.0 eV) indicates a high kinetic stability of the three compounds. © 2010 Elsevier B.V. All rights reserved. Source


Das U.,Haldia Government College | Das U.,Jadavpur University | Chattopadhyay B.,Indian Association for The Cultivation of Science | Mukherjee M.,Indian Association for The Cultivation of Science | Mukherjee A.K.,Jadavpur University
Crystal Growth and Design | Year: 2012

The structure determination of 3-phenylpropionic acid (1), 3-(3-methylphenyl) propionic acid (5), and 3-(3- methoxyphenyl) propionic acid (6), all three compounds crystallizing in the monoclinic space group P2 1/a (or P2 1/n) with Z′ = 2, has been accomplished from laboratory X-ray powder diffraction data following the direct space approach. The nature of intermolecular interactions in 1, 5, and 6 has been analyzed using the Hirshfeld surfaces and 2D fingerprint plots. While the two molecules (A and B) in the crystallographic asymmetric unit of 6 display almost identical conformation, those in 1 and 5 are significantly different due a rotation about the C-C bond linking the planar aromatic ring and propionic acid fragments. The presence of the COOH functional group in the compounds promotes the formation of cyclic R 2 2(8) synthons via intermolecular O-H•••O hydrogen bonds. Further linking of molecules through intermolecular C-H•••O and C-H•••π hydrogen bonds generates a three-dimensional supramolecular architecture in 1 and 5 and a two-dimensional molecular sheet in 6. Hirshfeld surface analyses of 1, 5, and 6 as well as a few substituted phenylpropionic acids retrieved from the Cambridge Structure Database (CSD) indicate that 94-99% of Hirshfeld surface areas in this class of compounds are due to H•••H, O•••H, and C•••H contacts. © 2011 American Chemical Society. Source

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