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Ghoshal A.K.,Shibpur Dinobundhoo Institution College | Das N.,Indian Statistical Institute
ACM International Conference Proceeding Series | Year: 2017

Several community detection algorithms for large scale networks have been reported in the literature so far. But to the best of our knowledge none of these algorithms consider the diameter of the community as a key parameter. In this paper, we propose a new metric to measure the quality of the community structure identified in a network which is less computation intensive and more realistic. Also, we develop a new heuristic to identify community structures considering the diameter of the community as one of the determinant factors. To ensure good quality of the community structure, we restrict the diameter of a community, upper bounded by a certain value k ∗ D, the diameter of the original network. Comparison with existing algorithms by simulation on well-known graphs such as Zachary karate club, Dolphin network and Football club shows our algorithm performs better in terms of modularity of the community structure achieved. Also, it establishes the fact that the modularity parameter defined by us, can compare the community structures of a given network better. © 2017 ACM.


Guin P.S.,Shibpur Dinobundhoo Institution College | Mandal P.C.,Saha Institute of Nuclear Physics | Das S.,Jadavpur University
ChemPlusChem | Year: 2012

Anthracyclines are broad-spectrum antibiotics that are used against several human cancers. Hydroxy-9,10-anthraquinone compounds closely resemble anthracycline antibiotics from a structural and functional viewpoint. High cost and aspects of toxicity introduce limitations on its use. On complex formation the toxicities of anthracyclines decrease. A close analogue is sodium 1,4-dihydroxy-9,10-anthraquinone-2-sulphonate (AS), which is a comparatively cheaper molecule and resembles a good number of anthracycline derivatives. It forms a complex with Cu II, [Cu(AS) 2]. The complex interacts with calf thymus DNA that was studied by UV/Vis spectroscopy and cyclic vol-tammetry. The experimental data obtained from the two techniques was analyzed for binding constant and size of the binding site. These results not only corroborate each other but also justify earlier data obtained using fluorescence spectroscopy. An important aspect to this study was that nonlinear curve fitting, which is usually applied for analyzing DNA interaction using fluorescence and absorption spectroscopy, was used for the first time to analyze the interaction of the complex with DNA using cyclic voltammetry by monitoring the change in the reduction peak current (I p). The DNA binding data provides an insight into a probable mode of action of the hydroxy-9,10- anthraquinones within cells as modification of DNA that leads to cell death is an important aspect in cancer research. © 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.


Guin P.S.,Shibpur Dinobundhoo Institution College | Mandal P.C.,Jadavpur University | Mandal P.C.,Saha Institute of Nuclear Physics | Das S.,Jadavpur University
Radiation Physics and Chemistry | Year: 2013

Radiation-induced double-strand modification of DNA was studied in the absence and presence of sodium 1,4-dihydroxy-9,10-anthraquinone-2-sulfonate (NaQSH2) and its metal (Cu2+ and Ni2+) complexes in aerated, de-aerated (Argon saturated) and N2O saturated aqueous media at pH 7.4. Ethidium bromide, an established DNA intercalator was used to estimate DNA remaining after interaction with γ-radiation, by measuring loss of fluorescence of the ethidium bromide-DNA adduct. In de-aerated (Argon saturated) and N2O saturated aqueous media radiation-induced double-strand modification of calf thymus DNA was comparatively less in presence of NaQSH2 and its Ni(II) complex than standard control indicating the compounds behaved as radio-protectors. However, in presence of the Cu(II) complex radiation-induced double-strand modification increased significantly. In N2O saturated medium, double-strand modification of DNA was almost double in all cases than that observed in de-aerated (Argon saturated) medium indicating OH radicals played a major role in modifying DNA. That OH radicals were important was verified by repeating experiments using tertiary-butanol that showed significant decrease in DNA modification. Another important observation was in aerated medium NaQSH2, Ni(II)-NaQSH2 did not show radioprotection while Cu(II)-NaQSH2 was an almost equally effective radiosensitizer as that observed in N2O saturated medium. Role of molecular oxygen as radiosensitizer was thus realized. © 2013 Elsevier Ltd.


Guin P.S.,Shibpur Dinobundhoo Institution College | Mandal P.C.,Saha Institute of Nuclear Physics | Das S.,Jadavpur University
Journal of Coordination Chemistry | Year: 2012

The anthracycline drug adriamycin and its metal complexes are efficient in treating several forms of human cancers with recognized antineoplastic activity attributed to strong interactions with DNA within the target cells. The hydroxy-9,10-anthraquinone unit present in the molecule controls and regulates drug action. Metal ions when linked to adriamycin help to reduce the generation of radicals responsible for toxic side effects. A complex of adriamycin with Ni(II) was prepared and its physicochemical characteristics and DNA-binding ability were compared to a Ni(II) complex of sodium-1,4-dihydroxy-9,10- anthraquinone-2-sulphonate (NaLH 2), an analog of adriamycin. Interactions with calf thymus DNA of both complexes were studied by UV-Vis and fluorescence spectroscopy. Binding parameters determined for both complexes agree with each other. Binding of the Ni(II)-adriamycin complex to DNA was five to eight times stronger than for the Ni(II) complex of the hydroxy-9,10- anthraquinone analog, Na 2[Ni(NaLH) 2Cl 2] ·2H 2O, i.e., Ni(NaLH) 2. The difference in binding was attributed to the presence of sugar units in adriamycin and to its absence in NaLH 2. Although the Ni(II) complex of the hydroxy-9,10- anthraquinone analog of adriamycin [Ni(NaLH) 2] was slightly weaker in binding DNA than the drug and its Ni(II) complex, a much lower cost of the former justifies its consideration as a substitute for the anthracycline drugs that are now in use. © 2012 Taylor & Francis.


Roy S.,Shibpur Dinobundhoo Institution College | Mahali K.,Kalyani University | Dolui B.K.,Visva Bharati University
Asian Journal of Chemistry | Year: 2013

In this paper, the standard free energies (ΔGt 0(i)) and entropies (ΔSt 0(i)) of transfer of homologous α-amino acids viz. glycine (gly), DL-alanine (ala), from water to aqueous mixture of cationophilic dipolar aprotic N,N-dimethyl formamide (DMF) have been calculated from solubility measurements at five equidistant temperatures i.e., from 15-35 °C. The observed ΔGt0(i) and TΔSt0(i) versus composition profiles are complicated because of the various interactional effects. The chemical transfer Gibbs energies (ΔG0 t,ch(i)) and entropies (TΔS 0 t,ch(i)) have been determined after elimination of cavity effect, estimated by the scaled particle theory and dipole-dipole interaction effects, estimated by the use of Keesom-orientation expression. The chemical contributions of transfer energetics of glycine and DL-alanine are guided by the composite effects of increased dispersion interaction, basicity and decreased acidity, hydrogen bonding, hydrophobic and hydrophilic interaction effects of aqueous DMF as compared to that of reference solvent, water.


Mahali K.,Kalyani University | Roy S.,Shibpur Dinobundhoo Institution College | Dolui B.K.,Visva Bharati
Journal of the Chinese Chemical Society | Year: 2014

In this article, we reported the solubilities of the amino acid DL-nor-valine (VAL) at five equidistant temeratures i.e. from 15 to 35 °C in aqueous mixtures of N,N-dimethyl formamide (DMF). The Standard free energies (ΔG Ot (i)) and entropies (ΔS Ot (i)) of transfer of VAL from water to aqueous mixture of cationophilic dipolar aprotic DMF have been evaluated at 25 °C. The transfer of Gibbs energies (ΔG Ot,ch (i)) and entropies (TΔS Ot,ch (i)) due to the chemical effects have been obtained after elimination of cavity effect, estimated by the scaled particle theory and dipole-dipole interaction effects, computed by the used of Keesom-orientation expression. The chemical contribution of transfer energetics of DL-nor-valine (VAL) are mainly guided by the composite effects of increased dispersion interaction, basicity effect and decreased acidity, hydrogen bonding effects, hydrophilic hydration and hydrophobic hydration of aqueous DMF mixtures as compared to that of reference solvent, water. In this article the transfer energetics of DL-nor-Valine, having long aliphatic hydrophobic moiety are computed at 25 °C in aqueous mixture of N,N-dimethyl formamide. The chemical contribution of transfer energetics of it are guided by the composite effects of increased dispersion interaction, basicity and decreased acidity, H-bonding effects, hydrophilic and hydrophobic hydration of aqueous DMF mixtures compared to water. Copyright © 2014 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany.


Mahali K.,Kalyani University | Roy S.,Shibpur Dinobundhoo Institution College | Dolui B.K.,Visva Bharati
Journal of Chemical and Engineering Data | Year: 2015

In this article the standard free energies (ΔGt(i)) and entropies (ΔSt(i)) of transfer of four homologous α-amino acids including glycine (Gly), dl-alanine (dl-Ala), dl-α-amino butyric acid (dl-Aba.) and dl-nor-valine (dl-n-Val) from ethylene glycol (EG) to nonaqueous mixtures of ethylene glycol and dimethyl sulfoxide (DMSO) at 298.15 K are reported. The Gibbs energies of solutions have been determined from solubility measurements of each amino acid at different temperatures, that is, from 288.15 to 308.15 K by "formol titrimetry". The chemical parts of free energies (ΔGt,ch(i)) and entropies (TΔSt,ch(i)) of transfer of the homologous α-amino acids have been computed by subtracting the cavity effects and dipole-dipole interaction effects from the total transfer energies. The characteristics of the solvation thermodynamics of α-amino acids in EG-DMF and EG-ACN mixed solvent systems studied earlier are also discussed here for comparison. © 2015 American Chemical Society.


Roy S.,Shibpur Dinobundhoo Institution College | Mahali K.,Kalyani University | Dolui B.K.,Visva Bharati
Journal of Solution Chemistry | Year: 2013

The standard Gibbs energies δt G° (i)) and entropies δt S°) of transfer in aqueous mixtures of 1,2-dimethoxyethane (DME) containing 0, 20, 40, 60, 80, 100 wt-% DME have been determined from the solubility data of a series of homologous α-amino acids, evaluated by the formol titrimetric method. The observed result of Δt G (i) and TΔt S° (i) against DME concentration profiles are complicated due to the various interaction effects. The chemical effects on the transfer Gibbs energies δt- grant° ch (i)) and entropies of transfer Tδ tS°ch (i) have been obtained after elimination of the cavity effect, calculated by the scaled particle theory, and dipole-dipole interaction effects, estimated by the use of Keesom-orientation expression for total transfer Gibbs energies Δt G° (i) and entropies Δt S°, respectively. The chemical transfer energetics of the zwitterionic homologous α-amino acids are guided by the composite effects of increased dispersion interaction, basicity and decreased acidity, hydrogen bonding capacity and hydrophobic hydration of the DME mixed solvent as compared to that of reference solvent, water. © 2013 Springer Science+Business Media New York.


Roy S.,Shibpur Dinobundhoo Institution College | Guin P.S.,Shibpur Dinobundhoo Institution College
Journal of the Electrochemical Society | Year: 2015

The electrochemical behavior of 1-amino-4-hydroxy-9,10-anthraquinone (1-AHAQ) was studied in acetonitrile, dimethyl formamide and dimethyl sulfoxide. In such solvents 1-AHAQ undergoes successive two one-electron reduction forming semiquinone and quinone dianion respectively in which the first step is completely reversible and the second step is quasi-reversible. The reduction and oxidation potentials are dependent on the polarity of the media. The electrochemical parameters are evaluated and correlated with the polarity index of the media. During such reductions a comproportionation reaction operates between the quinone (1-AHAQ) and its dianion (1-AHAQ2-) to form a semiquinone radical (1-AHAQ•-). The apparent comproportionation constants are calculated to find a comparative account on the stability of the radical intermediate in such solvents. In the presence of benzoic acid the electrochemical behavior of 1-AHAQ is altered significantly which is determined in this study. Role of the polarity of the solvents, intra or intermolecular hydrogen bonding and acidic additives on the stability of the radical species is evaluated. In aqueous buffer the reduction of 1-AHAQ follows a one step two-electron process where a kinetic study was carried out to determine the apparent charge transfer rate constants at various scan rates. The results show that electrochemical behavior of 1-AHAQ in non-aqueous and aqueous media mimics the action of anthracycline anticancer drugs which may find a similarity in their biological activities at the cellular level. © 2014 The Electrochemical Society.


Das D.,Shibpur Dinobundhoo Institution College
Journal of Marine Science and Application | Year: 2015

There is a large class of problems in the field of fluid structure interaction where higher-order boundary conditions arise for a second-order partial differential equation. Various methods are being used to tackle these kind of mixed boundary-value problems associated with the Laplace’s equation (or Helmholtz equation) arising in the study of waves propagating through solids or fluids. One of the widely used methods in wave structure interaction is the multipole expansion method. This expansion involves a general combination of a regular wave, a wave source, a wave dipole and a regular wave-free part. The wave-free part can be further expanded in terms of wave-free multipoles which are termed as wave-free potentials. These are singular solutions of Laplace’s equation or two-dimensional Helmholz equation. Construction of these wave-free potentials and multipoles are presented here in a systematic manner for a number of situations such as two-dimensional non-oblique and oblique waves, three dimensional waves in two-layer fluid with free surface condition with higher order partial derivative are considered. In particular, these are obtained taking into account of the effect of the presence of surface tension at the free surface and also in the presence of an ice-cover modelled as a thin elastic plate. Also for limiting case, it can be shown that the multipoles and wave-free potential functions go over to the single layer multipoles and wave-free potential. © 2015, Harbin Engineering University and Springer-Verlag Berlin Heidelberg.

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