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Biswas A.,University of Calcutta | Das T.K.,University of Calcutta | Salasnich L.,University of Padua | Salasnich L.,University of Maribor | Chakrabarti B.,Lady Brabourne College
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2010

We investigate the structure and stability of Bose-Einstein condensates of Li7 atoms with realistic van der Waals interactions by using the potential harmonic expansion method. Besides the known low-density metastable solution with a contact δ-function interaction, we find a stable branch at a higher density which corresponds to the formation of an atomic cluster. Comparison with the results of a nonlocal effective interaction is also presented. We analyze the effect of trap size on the transition between the two branches of solutions. We also compute the loss rate of a Bose condensate due to two- and three-body collisions. © 2010 The American Physical Society.


Haldar S.K.,Lady Brabourne College | Chakrabarti B.,Kalyani University | Chakrabarti B.,University of Sao Paulo
International Journal of Modern Physics B | Year: 2013

We calculate Shannon information entropy of trapped interacting bosons in both the position and momentum spaces, Sr and Sk, respectively. The total entropy maintains the functional form S = a + b ln N for repulsive bosons. At the noninteracting limit the lower bound of entropic uncertainty relation is also satisfied whereas the diverging behavior of S r and Sk at the critical point of collapse for attractive condensate accurately calculates the stability factor. Next we study the dynamics of Shannon information entropy with varying interparticle potential. We numerically solve the time-dependent Gross-Pitaevskii equation and study the influence of increasing nonlinearity in the dynamics of entropy uncertainty relation (EUR). We observe that for small nonlinearity the dynamics is regular. With increase in nonlinearity although Shannon entropy shows large variation in amplitude of the oscillation, the EUR is maintained throughout time for all cases and it confirms its generality. We also study the dynamics in a very tight trap when the condensate becomes highly correlated and strongly inhomogeneous. Time evolution of total entropy exhibits aperiodic and fluctuating nature in very tight trap. We also calculate Landsberg's order parameter for various interaction strengths which supports earlier observation that entropy and order are decoupled. © 2013 World Scientific Publishing Company.


Biswas A.,University of Calcutta | Chakrabarti B.,University of Sao Paulo | Chakrabarti B.,Lady Brabourne College | Das T.K.,University of Calcutta | Salasnich L.,University of Padua
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2011

We study coherence of a trapped bosonic cloud with attractive finite-range interaction in a tight harmonic trap. One-body density and pair-distribution function in the ground state for different trap sizes are calculated. We also calculate healing length and the correlation length which signify the presence of high spatial coherence in a very tight trap leading to the destruction of the condensate for a fixed particle number. This is in marked variance with the usual collapse of the attractive metastable condensate when N>Ncr. Thus we investigate the critical frequency and critical size of the trap for the existence of attractive Bose-Einstein condensation. The finite-range interaction gives a nonlocal effect in the effective many-body potential, and we observe a high-density stable branch besides the known metastable branch. Moreover, the new branch shows universal behavior even in the very tight trap. © 2011 American Physical Society.


Bhattacharyya S.,Deys Medical Stores Manufacturing Ltd | Datta S.,University of Calcutta | Mallick B.,Lady Brabourne College | Dhar P.,University of Calcutta | Ghosh S.,University of Calcutta
Journal of Agricultural and Food Chemistry | Year: 2010

Three different cultivars of marigold flowers (Tagetes patula L.) (marigold orange, marigold yellow, and marigold red) were analyzed for the lutein ester contents, and the in vitro antioxidative activities of the flower extracts were compared. The total antioxidant capacity, reducing power, hydroxyl, DPPH, and ABTS•+ radical scavenging activities, iron chelation capacity, and inhibition of lipid peroxidation in a linoleic acid emulsion system were measured. Iron-mediated Fenton reaction was carried out to evaluate the protective effect of leutin against DNA damage. The marigold orange (MGO) variety contains the maximum amount of lutein. It also had the highest DPPH radical scavenging activity and ABTS radical scavenging activity, with an EC50 value of 0.344 mg/mL. It was also the most effective against lipid peroxidation and hydroxyl radical scavenging activities. The MGO extract has the maximum reducing power. Hepatic cell damage in iron-mediated Fenton reaction caused by free radicals was reduced by the marigold extracts. Marigold flowers of Indian variety can be effectively utilized to produce lutein ester, which can be used as a food supplement or as an accessible source of natural antioxidants. © 2010 American Chemical Society.


Chakrabarti B.,University of Sao Paulo | Chakrabarti B.,Lady Brabourne College | Biswas A.,University of Calcutta | Kota V.K.B.,Physical Research Laboratory | And 2 more authors.
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2012

It is a well-established fact that statistical properties of energy-level spectra are the most efficient tool to characterize nonintegrable quantum systems. The statistical behavior of different systems such as complex atoms, atomic nuclei, two-dimensional Hamiltonians, quantum billiards, and noninteracting many bosons has been studied. The study of statistical properties and spectral fluctuations in interacting many-boson systems has developed interest in this direction. We are especially interested in weakly interacting trapped bosons in the context of Bose-Einstein condensation (BEC) as the energy spectrum shows a transition from a collective nature to a single-particle nature with an increase in the number of levels. However this has received less attention as it is believed that the system may exhibit Poisson-like fluctuations due to the existence of an external harmonic trap. Here we compute numerically the energy levels of the zero-temperature many-boson systems which are weakly interacting through the van der Waals potential and are confined in the three-dimensional harmonic potential. We study the nearest-neighbor spacing distribution and the spectral rigidity by unfolding the spectrum. It is found that an increase in the number of energy levels for repulsive BEC induces a transition from a Wigner-like form displaying level repulsion to the Poisson distribution for P(s). It does not follow the Gaussian orthogonal ensemble prediction. For repulsive interaction, the lower levels are correlated and manifest level-repulsion. For intermediate levels P(s) shows mixed statistics, which clearly signifies the existence of two energy scales: external trap and interatomic interaction, whereas for very high levels the trapping potential dominates, generating a Poisson distribution. Comparison with mean-field results for lower levels are also presented. For attractive BEC near the critical point we observe the Shnirelman-like peak near s=0, which signifies the presence of a large number of quasidegenerate states. © 2012 American Physical Society.


Roy K.,Lady Brabourne College | Chakrabarti B.,Kalyani University | Kota V.K.B.,Physical Research Laboratory
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2013

It is a well-known fact that the statistical behaviors of level fluctuation and level correlation in the energy-level spectra are the most efficient tool to characterize quantum chaos in nonintegrable quantum systems. The system of interacting trapped bosons is a complex system where the low-lying energy levels are highly influenced by the level repulsion. In this case, interatomic interaction is a dominating fact with strong level correlation between distant levels. Here we numerically calculate the correlation function, number variance, and Dyson-Mehta least-square deviation for the low-lying levels for a few thousand interacting trapped bosons, and our data show good analogy with the Gaussian orthogonal ensemble (GOE) results with a signature of chaos. In the next part of our study, the energy spectrum of these low-lying levels is considered as a discrete signal and the fluctuation of the excitation energy is considered as discrete time series. Then we calculate numerically the height-height correlation function for different order of momentum. In our study logarithmic correlation structure is found instead of multiscaling structure, and we observe that spectral statistics are compatible with those of GOE. © 2013 American Physical Society.


Debnath P.K.,Santoshpur Sri Gouranga Vidyapith H.S. | Chakrabarti B.,Lady Brabourne College
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2010

We study the instability of collective excitations of a three-dimensional Bose-Einstein condensate with repulsive and attractive interactions in a shallow trap designed as a quadratic plus a quartic potential. By using a correlated many-body theory, we determine the excitation modes and probe the critical behavior of collective modes, having a crucial dependence on the anharmonic parameter. We examine the power-law behavior of monopole frequency near criticality. In Gross-Pitaevskii variational treatment the power-law exponent is determined as one-fourth power of (1-AAcr), A is the number of condensate atoms and Acr is the critical number near collapse. We observe that the power-law exponent becomes 16 in our calculation for the pure harmonic trap and it becomes 17, for traps with a small anharmonic distortion. However for large anharmonicity the power law breaks down. © 2010 The American Physical Society.


Saha A.,All India Institute of Hygiene and Public Health | Nag Chaudhury A.,Lady Brabourne College | Bhowmik P.,All India Institute of Hygiene and Public Health | Chatterjee R.,Lady Brabourne College
Asian Pacific Journal of Cancer Prevention | Year: 2010

In the absence of any nationwide cervical screening program, cancer of cervix remains a major public health problem for India. We here assessed knowledge levels of female college students about cervical cancer, its risk factors, the human papillomavirus (HPV) etiologic agent and Pap (Papanicolaou) smear testing for screening. We conducted a questionnaire survey of the students (N=630), aged 17 to 24 years, in Kolkata, India. Only 20% correctly identified cervix cancer as the most prevalent female cancer in India, while 43% were aware of the ages of occurrence. Though 41% thought sexual activity to be associated with cervical cancer, its risk factors, like, 'smoking', 'having multiple sex partners', 'cervical infections', 'early onset of sexual intercourse', 'multiple parity' were recognized by 29%, 3%, 4%, 13% and 15%, respectively. The terms 'Pap test' and HPV had been heard by 11% and 15 % of the students, respectively, and 75% of the students desired to have protective vaccination. Bivariate analysis revealed that educational stream, standard of the college and family size were significantly associated with knowledge levels. Additionally, multivariate regression analysis indicated city students were more knowledgeable than those from outside the city. It is imperative that women gather adequate knowledge on cervical cancer for the success of any program to control the disease. Wide and effective spreading of awareness about the disease among women must form an integral part of public health policy of government.


Mondal A.K.,Vidyasagar University | Parui S.M.,Lady Brabourne College
African Journal of Biotechnology | Year: 2011

Comparative banding pattern of the seed protein of 17 taxa belonging to the three families Mimosaceae, Caesalpiniaceae and Fabaceae was studied with the aim of testing the proposed delimitation of the order Leguminales (Fabales) into the three families or subfamilies and to assess the phylogenetic relationships within the three families. Cluster and pairing affinity or similarity index analysis of the data from total protein grouped the 17 taxa into three discrete clusters based on their families. Considerable amount of homology was observed in the banding pattern between the different taxa. © 2011 Academic Journals.


Ganguly P.,Lady Brabourne College
Journal of Molecular Liquids | Year: 2010

The absorption and fluorescence spectra of Acridine Orange and Safranin O (both cationic dyes) have been studied in solutions of different classes of surfactants - cationic (CTAB), anionic (SDS) and non-ionic (Triton X-100). The spectral changes of the dyes were observed in varying amounts of Triton X-100, CTAB and SDS and indicated the formation of charge-transfer dye-surfactant complex between the dyes and Triton X-100 caused by incorporation of the dye molecules to micelles. It was observed that there were two types of interactions between the dyes and micelles: hydrophobic and electrostatic. While the hydrophobic interactions play a dominant role in binding of the dyes to neutral Triton X-100, the electrostatic interactions explain the binding of dyes to anionic SDS. The binding of dyes to cationic CTAB may be explained in terms of a dominant role played by hydrophobic interactions over electrostatic repulsions. The spectral studies (both absorption and fluorescence) of dyes have also been carried out in different polar and non-polar solvents, and the corresponding Stokes' shifts of fluorescence from the absorption have been calculated. The Stokes' shifts have been found to increase with increasing polarity of the solvents. An attempt has been made to ascertain the polarity of the microenvironment of the dyes in micellar media from the photophysical characteristics of the dyes in solvents of known polarity. © 2009.

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