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Guwāhāti, India

Bujarborua D.,Pragjyoti Eye Care and Research Center | Nagpal P.N.,Retina Foundation | Deka M.,Arya Vidyapeeth College
Graefe's Archive for Clinical and Experimental Ophthalmology | Year: 2010

Background: To study the demography, various morphological patterns and fluid dynamics of the smokestack leak by fluorescein angiography (FA) in central serous chorioretinopathy (CSC). Methods: Part I (clinical): review of the medical records and angiographic documents of 69 consecutive cases of CSC with smokestack leak. Part II (experimental): documentation of the movement of various concentrations of fluorescein dye due to convection currents in a laboratory model that roughly represents a closed chamber similar to that of CSC in human eyes. Results: The clinical study (Part I) revealed that 14.40% of 479 consecutive cases had smokestack leak, of which 70% occurred in first acute episode (p-value: <0.001), 27.14% in acute recurrent episodes (50% fresh leak) and 2.85% in chronic stage. Patients were predominantly male (84.05%) with a median age of 34.00±8.14 years. The median symptom duration excluding the chronic cases was 15±34.28 days. This type of leak was mostly (48.57%) seen in medium-sized CSC, and the majority were in the parafoveal superonasal quadrant (31.42%). The ascending type of leak was predominant (94.28%). In four eyes, an atypical pattern and in two eyes more than one smokestack leak were seen within the same detached area. The experimental study (Part II) demonstrated that fluid containing a low concentration of fluorescein ascended due to convection currents, whereas highly concentrated dye descended. Conclusions: The clinical study revealed smokestack leaks to be significantly more common in a primary acute episode, and they usually develop in the early part of the acute phase of the disease (average duration 15±34.28 days). Rarely, this type of leak can occur in the chronic stage, and multiple leaks may develop in the same detached space. The various patterns of dye movement due to convection currents in the experimental model resembled the dye movement in certain cases of CSC of the present series. The experimental study also hinted at the probability of drainage of unbound fluorescein molecules along with protein-laden heavy fluid in downward spread of the leak. © 2009 Springer-Verlag.

Bhattacharyya P.K.,Arya Vidyapeeth College
Computational and Theoretical Chemistry | Year: 2016

Reactivity, aromaticity and absorption spectra of Perylo[1,12-b,c,d] thiophene tetraester doped with B, N, O Se and BN have been discussed in the light of Density Functional Theory (DFT) and Time Dependent Density Functional Theory (TDDFT). Doping with electron rich and electron deficient centres affects the reactivity and aromaticity of the thiophene tetraesters. A significant shift in the absorption spectra is observed in case of B and BN doped species. Aromaticity of the species is gauged by nucleus independent chemical shift (NICS). Results show that the doped species vary in their reactivity and aromaticity. N, O or Se doped species exhibit almost comparable excitation energies and absorption peaks. © 2016.

Purkayastha J.,Arya Vidyapeeth College | Matsui M.,Kyoto University
Asian Herpetological Research | Year: 2012

A new Dicroglossid species is described from Mawphlang, Meghalaya, northeastern India. The new species differs from all the congeners occurring in this region in body size and call characteristics. It is larger than Fejervarya syhadrensis and F. nepalensis, but smaller than F. teraiensis. It overlaps F. pierrei in snout-vent length, but clearly differs from it in advertisement call, with much shorter note duration, much longer inter note interval, and much lower dominant frequency. Paucity of genetic information and underestimation of species diversity in this region are discussed.

Deka B.C.,Arya Vidyapeeth College | Bhattacharyya P.K.,Arya Vidyapeeth College
Computational and Theoretical Chemistry | Year: 2015

We described density functional study carried out in order to delve into the interaction between chitosan, a gene carrier and nucleobases. Our study asserts the pivotal role played by hydrogen bonding in chitosan-nucleobase adduct formation. Incorporation of aqueous medium is found to bring about a significant impact on the interaction between the two. Thermochemical analysis suggests the presence of strong thermodynamic driving force for adduct formation in gas phase while no such driving force is observed in aqueous phase. Moreover, except adenine, aromaticity of nucleobases is enhanced by adduct formation with chitosan. Protonation of the nucleobases leads to dissociation of the two constituents of the adducts. © 2014 Elsevier B.V.

Bania K.K.,Tezpur University | Guha A.K.,Dibrugarh University | Bhattacharyya P.K.,Arya Vidyapeeth College | Sinha S.,Arya Vidyapeeth College
Dalton Transactions | Year: 2014

A DFT and ab initio quantum chemical study has been carried out at different theoretical levels to delve into the role of the cation-π interaction within the main group metal cations (Li+, Na+ and K+), substituted benzene and borazine. The effects of electron withdrawing and electron donating groups on these non-covalent forces of interaction were also studied. The excellent correlation between Hammett constants and binding energy values indicates that the cation-π interaction is influenced by both inductive and resonance effects. Electron donating groups (EDG) such as -CH3 and -NH2 attached to benzene at the 1, 3 and 5 position and the three boron atoms of borazine were found to strengthen these interactions, while electron withdrawing groups (EWG) such as -NO 2 did the reverse. These results were further substantiated by topological analysis using the quantum theory of atoms in molecules (QTAIM). The polarized continuum model (PCM) and the discrete solvation model were used to elucidate the effect of solvation on the cation-π interaction. The size of the cations and the nature of the substituents were found to influence the enthalpy and binding energy of the systems (or complex). In the gas phase, the cation-π interaction was found to be exothermic, whereas in the presence of a polar solvent the interaction was highly endothermic. Thermochemical analysis predicts the presence of thermodynamic driving forces for borazine and benzene substituted with EDG. DFT based reactivity descriptors, such as global hardness (η), chemical potential (μ) and the electrophilicity index (ω) were used to elucidate the effect of the substituent on the reactivity of the cation-π complexes. This journal is © The Royal Society of Chemistry.

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