Haldia Government College

Purba, India

Haldia Government College

Purba, India
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Nath S.,Kalyani University | Nath S.,Krishnagar Government College | Mondal N.S.,Haldia Government College | Ghosh N.K.,Kalyani University
Journal of Superconductivity and Novel Magnetism | Year: 2017

We consider the Hubbard-Holstein model on a 2D tilted eight-site square lattice at quarter fillings having on-site (λ1) and inter-site (λ2) electron-phonon (EP) interactions and inter-site Coulomb repulsion (V ). Mobility of electrons decreases, and hence, localization of electrons is favored by λ1 as well as inter-site Coulomb repulsion in the non-interacting limit (U/t = 0.0). In the interacting case (U/t = 8.0), an initial delocalization effect observed due to the competition between on-site Coulomb repulsion and EP interaction λ1 though V favors localization. For smaller λ1, the competition between λ2 and V increases the delocalization effect. As λ2 increases further, localization occurs. In the interacting case, localization occurs at much higher values of λ2 due to the additional delocalization effect of U. On-site (S0) and/or large bipolarons are formed with λ1 in the presence of V, and inter-site Coulomb repulsion effectively increases λ1. Thus, V favors the formation of S0 bipolarons. However, the formation of S1 bipolarons is suppressed by inter-site Coulomb repulsion. An existence of critical λ2 = λ2c is observed for the formation of on-site (S0) and neighboring-site (S1) bipolarons. © 2017 Springer Science+Business Media New York

Sahoo S.,Haldia Government College | Sengupta D.,Indian Statistical Institute
Computational Statistics and Data Analysis | Year: 2016

Tests designed to detect increasing hazard ratio against the proportional hazards hypothesis are generally consistent for other alternatives also. This article provides a test of the null hypothesis of increasing hazard ratio. The test is based on the separation between an empirical version of the relative trend function and its greatest convex minorant. The proportional hazards model, the least favorable null model for large samples, is used to produce simulation based cutoffs. A simulation study shows reasonable performance of the proposed test in small samples. The analytical test, together with a graphical version, is illustrated through two real life examples. © 2017 Elsevier B.V.

Konar S.,University of Calcutta | Jana A.,University of Calcutta | Das K.,Haldia Government College | Ray S.,University of Calcutta | And 2 more authors.
Inorganica Chimica Acta | Year: 2013

Three new zig-zag 1D coordination polymers and a binuclear complex of Cu(II) involving pyrazole based tri- and pentadentate schiff base ligands (Z)-2-(2-(5-methyl-1H-pyrazole-3-carbonyl)hydrazono)-2- phenylacetic acid (L'1) and (Z)-2-(2-(5-methyl-1-(pyridin-2-yl)-1H-pyrazole-3-carbonyl) hydrazono)-2- phenylacetic acid (L'2) are reported in this work. The ligand precursors L1 and L2 have been transformed into L1' and L2' during the course of reaction with metal ions in which the ester groups have been changed to carboxylate group. The 1D coordination polymers, namely, [Cu(L'1)(ClO4) 2(H2O)]n (1), [Cu(L'2)(- ClO 4)]n (3), [Cu(L'2)(NO3)]n (4) and a binuclear complex [Cu2(L'1)2Cl2] (2) have been synthesized. The complexes 1-3 are of distorted octahedral geometry and the complex 2 is distorted square pyramidal. Interestingly, these structural variations are dependent on counterions and substituent on the pyrazole ring. These have been characterized by elemental analyses, UV, IR, single crystal X-ray diffraction, electrochemical and photoluminescence studies. L'1 serves as tridentate NNO donor where pyrazole nitrogen, azomethine nitrogen and ligand carboxylate group are coordinatively active, leaving the carbonyl oxygen of carbohydrazide part inactive. The same situation (coordination modes) arises in another pentadentate NNNOO donor L'2 where extra pyridine nitrogen is coordinated. The complexes 3 and 4 have considerable fluorescence emission while the rest of the complexes and the ligand molecules are fluorescent silent. © 2012 Elsevier B.V. All rights reserved.

Dhara A.,University of Calcutta | Jana A.,University of Calcutta | Konar S.,University of Calcutta | Ghatak S.K.,University of Calcutta | And 5 more authors.
Tetrahedron Letters | Year: 2013

A novel rhodamine-based chemosensor, 3′,6′-bis(diethylamino)-2- ((2,7-dimethoxy-9H-fluoren-9-ylidene)amino)spiro[isoindoline-1,9′-xanthen] -3-one (1) for aluminum ion, was designed and synthesized. Compound 1 is an orange colored, weak fluorescent compound which was synthesized via one-step facile reaction of rhodamine B hydrazide with 2,7-dimethoxy-9H-fluoren-9-one in MeOH. When Al3+ salt was added in methanol:water (30:70, v/v) solution then spirolactum ring of 1 was opened. The absorbance and fluorescence of the mixed solution were increased dramatically because of the opening of the lactum ring. Thus, signal transduction occurred via reversible CHEF (chelation-enhanced fluorescence) mechanism in the range 580-584 nm. © 2013 Elsevier Ltd. All rights reserved.

Manna S.K.,Haldia Government College | Mondal S.K.,Haldia Government College | Ahmed A.,Indian Institute of Technology Kharagpur | Mandal A.,Haldia Government College | And 4 more authors.
RSC Advances | Year: 2014

An efficient one pot synthesis of polycyclic benzimidazole derivatives has been developed (up to 90% yield). The protocol is very mild, metal-free, and not restricted to anhydrous conditions. It also demonstrates an example of preferential electrocyclic reaction over Michael reaction. These new benzimidazole derivatives are highly fluorescent and show a dramatic change with pH; The characteristic bright bluish fluorescence was observed in MeOH (UV-light, 366 nm) but the intensity was totally diminished at pH = 2.5. © 2014 The Royal Society of Chemistry.

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.

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.

Pal P.J.,Dumkal Institute of Engineering and Technology | Saha T.,Haldia Government College | Sen M.,Indian Institute of Technology Kanpur | Banerjee M.,Indian Institute of Technology Kanpur
Nonlinear Dynamics | Year: 2012

In this paper, we consider a delayed predator-prey system with intraspecific competition among predator and a strong Allee effect in prey population growth. Using the delay as bifurcation parameter, we investigate the stability of coexisting equilibrium point and show that Hopf-bifurcation can occur when the discrete delay crosses some critical magnitude. The direction of the Hopf-bifurcating periodic solution and its stability are determined by applying the normal form method and the centre manifold theory. In addition, special attention is paid to the global continuation of local Hopf bifurcations. Using the global Hopf-bifurcation result of Wu ({Trans. Am. Math. Soc.} 350:4799-4838, 1998) for functional differential equations, we establish the global existence of periodic solutions. Numerical simulations are carried out to validate the analytical findings. © 2011 Springer Science+Business Media B.V.

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.

Sources of sediments have been identified through study of mineral composition of sediments in the lower reach of the Rupnarayan River, West Bengal, India by X-ray diffraction (XRD) technique to understand the causes and mechanisms of sedimentation. Collected sediment samples are washed by hot and distilled water, dried and disaggregated manually with a mortar and pestle. Sediment samples are scanned at 7°–45°2θ interval by XPERT-PRO diffractometer. Diffractograms generated from XRD analysis reveals that the entire reach under study shows the dominance of minerals including quartz, illite, chlorite, chloritoid, anatase, goethite, oligoclase, sillimanite and corundum, having their origin in the upper and middle catchment with little contribution from lower catchment and river banks. Statistical test indicates that except tourmaline and anatase, all the minerals show steady trend in concentration in sediments. PCA reveals that five Eigen values account for 82.092% of the total variation of the distribution of minerals. There is no conspicuous trend in the spatial distribution of the minerals in the study area. The minerals drained from upper catchment are caught up in the estuary and again redistributed upstream by stronger flood tide. This leads to an unsystematic and irregular distribution of minerals in the study area. © 2016 Elsevier Ltd

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