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T Bhattacharya

Publications and source records attributed to T Bhattacharya.

At least 19 recordsLinked to original sources
PubMed2004

Primary electron-transfer dynamics in 2-phenylindole-9-cyanoanthracene system. A comparative study with 2-methylindole.

Electrochemical measurements by cyclic voltammetry predict the possibility of occurrence of photoinduced electron-transfer (PET) reactions between the ground state of 2-phenylindole (2PI) (electron donor) and the excited singlet of 9-cyanoanthracene (9CNA) molecule acting as an electron acceptor. However, 2PI should be expected to behave as a relatively weaker electron donating agent than the structurally related donor 2-methylindole (2MI) as it possesses higher oxidation potential value. Both steady-state and time-resolved spectroscopic measurements in the polar acetonitrile (ACN) and ethanol (EtOH) solvents show that the fluorescence quenching phenomenon of 9CNA in presence of 2PI is primarily due to the involvement of dynamic process which in high probability should be PET. Nevertheless, in less polar tetrahydrofuran (THF) medium, the quenching of 9CNA results from the combined effect of dynamic and static modes. The transient absorption spectra, measured by using nanosecond laser flash photolysis, of 9CNA in presence of 2PI exhibit the signature of the bands of the anionic species of 9CNA, cation of the donor 2PI and the contact neutral radical. Observations of the transient absorption at the different delays infer that ion-recombination mechanism is responsible for production of the monomeric triplets of both 9CNA and 2PI. From the transient absorption decays in ACN medium, it has been demonstrated that the diffusional separation of ions from geminate ion-pair is facilitated in the case of 2MI-9CNA pair whereas for 2PI-9CNA system the energy wasting charge recombination dominates over the process of charge dissociation. From the above observations, the possibility of developing much potential photosynthetic model compounds with the donor 2MI, rather than with the other donor 2PI molecule has been hinted.

Anthracenes↗
PubMed2003

Non-radiative depletion of the excited electronic states of 9-cyanoanthracene in presence of tetrahydronaphthols.

Both steady state and time resolved spectroscopic measurements reveal that the prime process involved in quenching mechanism of the lowest excited singlet (S1) and triplet (T1) states of the well known electron acceptor 9-Cyanoanthracene (9CNA) in presence of 5,6,7,8-tetrahydro-1-naphthol (TH1N) or 5,6,7,8-tetrahydro-2-naphthol (TH2N) is H-bonding interaction. It has been confirmed that the fluorescence of 9CNA is not at all affected in presence of 5,6,7,8-tetrahydro-2-methoxy naphthalene (TH2MN) both in non-polar n-heptane (NH) and highly polar acetonitrile (ACN) media. This indicates that the H-bonding interaction is crucial for the occurrence of the quenching phenomenon observed in the present investigations with TH1N (or TH2N) donors and 9CNA acceptor. In ACN solvent both contact ion-pair (CIP) and solvent-separated (or dissociated) ions are formed due to intermolecular H-bonding interactions in the excited electronic states (both singlet and triplet). In NH environment due to stronger H-bonding interactions, the large proton shift within excited charge transfer (CT) or ion-pair complex, 1 or 3(D+-H...A-), causes the formation of the neutral radical, 3(D+H-A)*, due to the complete detachment of the H-atom. It is hinted that both TH1N and TH2N due to their excellent H-bonding ability could be used as antioxidants.

Anthracenes↗
PubMed2002

Preferential association of the heat-stable enterotoxin gene (stn) with environmental strains of Vibrio cholerae belonging to the O14 serogroup.

Toxigenic Vibrio cholerae O1 and O139 serogroups have the capacity of causing epidemic and pandemic cholera but are infrequently found in the environment. The other serogroups are abundant in aquatic environments but do not possess the virulence genes necessary for causing the disease. Of the 559 environmental strains of V. cholerae, collected during different periods from environmental samples in Calcutta, 9 (1.6%) harboured the heat-stable enterotoxin gene (stn). Six of the 9 strains belonged to the O14 serogroup. Thus, V. cholerae strains carrying the stn gene revealed preferential association with the O14 serogroup. Three of the six strains harboured the tcpA gene of the E1 Tor type, which is an unusual feature among environmental V. cholerae strains. A strain that possessed the E1 Tor type tcpA also had the CTX prophage. Pulsed field gel electrophoresis (PFGE) revealed that the stn gene positive O14 strains of V. cholerae were not clonal.

Animals↗
PubMed2001

Using human immunodeficiency virus type 1 sequences to infer historical features of the acquired immune deficiency syndrome epidemic and human immunodeficiency virus evolution.

In earlier work, human immunodeficiency virus type 1 (HIV-1) sequences were analysed to estimate the timing of the ancestral sequence of the main group of HIV-1, the virus that is responsible for the acquired immune deficiency syndrome pandemic, yielding a best estimate of 1931 (95% confidence interval of 1915-1941). That work will be briefly reviewed, outlining how phylogenetic tools were extended to incorporate improved evolutionary models, how the molecular clock model was adapted to incorporate variable periods of latency, and how the approach was validated by correctly estimating the timing of two historically documented dates. The advantages, limitations, and assumptions of the approach will be summarized, with particular consideration of the implications of branch length uncertainty and recombination. We have recently undertaken new phylogenetic analysis of an extremely diverse set of human immunodeficiency virus envelope sequences from the Democratic Republic of the Congo (the DRC, formerly Zaire). This analysis both corroborates and extends the conclusions of our original study. Coalescent methods were used to infer the demographic history of the HIV-1 epidemic in the DRC, and the results suggest an increase in the exponential growth rate of the infected population through time.

Acquired Immunodeficiency Syndrome↗
PubMed2001

Side bias and accidents: are they related?

This study purports to examine the role of different forms of side bias, handedness, footedness, eyedness, and earedness, in eliciting accident-proneness in individuals. A representative sample (N = 150) was administered a Side Bias Questionnaire (Handedness: 22 items, footedness: 5 items, eyedness: 5 items, earedness: 5 items) to ascertain their preferential bias. The questionnaire also required subjects to report the number of accidents committed during their lifetime while performing activities like sports, driving, household work, etc., that required attention of medical professionals. Regression analysis of data indicated that accident-prone behavior was significantly predicted from handedness. Analysis of variance, 3 (Accident groups: low, moderate, high) x 4 (Side bias: hand, foot, eye, ear), indicated that 'mixed' handers committed more accidents as compared with clear handers. The other forms of side bias, foot, ear, and eye were unrelated to frequency of accidents.

Accidents, Traffic↗
PubMed2000

Continuous quantum measurement and the emergence of classical chaos

We formulate the conditions under which the dynamics of a continuously measured quantum system becomes indistinguishable from that of the corresponding classical system. In particular, we demonstrate that even in a classically chaotic system the quantum state vector conditioned by the measurement remains localized and, under these conditions, follows a trajectory characterized by the classical Lyapunov exponent.

Journal Article↗
PubMed2000

Timing the ancestor of the HIV-1 pandemic strains.

HIV-1 sequences were analyzed to estimate the timing of the ancestral sequence of the main group of HIV-1, the strains responsible for the AIDS pandemic. Using parallel supercomputers and assuming a constant rate of evolution, we applied maximum-likelihood phylogenetic methods to unprecedented amounts of data for this calculation. We validated our approach by correctly estimating the timing of two historically documented points. Using a comprehensive full-length envelope sequence alignment, we estimated the date of the last common ancestor of the main group of HIV-1 to be 1931 (1915-41). Analysis of a gag gene alignment, subregions of envelope including additional sequences, and a method that relaxed the assumption of a strict molecular clock also supported these results.

Acquired Immunodeficiency Syndrome↗
PubMed2000

Expanding multiple antibiotic resistance among clinical strains of Vibrio cholerae isolated from 1992-7 in Calcutta, India.

Antimicrobial susceptibilities of Vibrio cholerae strains isolated from cholera patients admitted to the Infectious Diseases Hospital, Calcutta, India for 6 years were analysed to determine the changing trends; 840 V. cholerae strains isolated in 1992-1997 were included in this study. Among V. cholerae serogoup O1 and O139, ampicillin resistance increased from 1992 (35 and 70%, respectively) to 1997 (both serogroups 100%). Resistance to furazolidone and streptomycin was constantly high among V. cholerae O1 strains with gradual increase in resistance to other drugs such as ciprofloxacin, co-trimoxazole, neomycin and nalidixic acid. V. cholerae O139 strains exhibited susceptibilities to furazolidone and streptomycin comparable with those of O1 strains. However, after initial increase in resistance to chloramphenicol and co-trimoxazole, all the V. cholerae O139 strains became susceptible to these two drugs from 1995 onwards. Both V. cholerae O1 and O139 remained largely susceptible to gentamicin and tetracycline. V. cholerae non-O1, non-O139 strains, in contrast, exhibited high levels of resistance to virtually every class of antimicrobial agents tested in this study especially from 1995. Kruskal-Wallis one-way analysis showed that V. cholerae O1 Ogawa serogroup exhibited significant yearly increase in resistance to nine antibiotics followed by non-O1 non-O139 and O139 strains to six antibiotics and two antibiotics respectively. Interesting observation encountered in this study was the dissipation of some of the resistant patterns commonly found among V. cholerae non-O1 non-O139 or O1 serogroups to the O139 serogroup and vice versa during the succeeding years.

Cholera↗
PubMed1999

Fibrin sealant for treatment of cerebrospinal fluid leaks.

OBJECTIVE: Persistent cerebrospinal fluid leaks in the human population are rarely found in otherwise healthy individuals, but occur in patients with comorbid illnesses. These leaks are frequently resistant to dural suturing or closure of the defect site with connective tissue, cartilage, or plastic materials. In this study, fibrin sealant (ViGuard Fibrin Sealant was used to adhere muscle grafts to surgically created dural defects to close cerebrospinal fluid leaks in chinchillas. Histologic evaluation of the defect sites were conducted to assess healing and tissue response in the test and control groups. METHOD: In 20 chinchillas, after a skin incision, a 6 mm X 6 mm window was created in the right superior bulla exposing the underlying bony tegmen. Using a microcutting burr, a 3 mm X 3 mm area of tegmen was drilled out and the exposed dura was resected to create a large cerebrospinal fluid (CSF) leak. In the control group (n = 10), a small muscle graft from the surrounding tissue was placed into the defect site. In the test group (n = 10), the muscle graft was glued into the defect with ViGuard Fibrin Sealant. Bulla and skin were then closed. All animals were killed at 3 weeks into the experiment, and tissue was harvested for histologic examination. SETTING: The Department of Otolaryngology, Head and Neck Surgery Research Laboratory. University of Illinois, Chicago. RESULTS: Three weeks after surgery in the test group the tegmen defects were found to be closed by bone or connective tissue or both. Meninges had regrown, and the underlying brain appeared histologically normal. There was no evidence of CSF leak, toxicity, infection or other deleterious tissue reactions. In the control group, again the meningeal and bony tegmen defects were seen to be closed by connective tissue or bone or both. Brain tissues appeared histologically normal. There was no evidence of CSF leak, toxicity, or other deleterious tissue reactions. One animal of the test group died of unknown causes. On autopsy, no signs of meningitis or encephalitis could be detected and the cause of death was unapparent. CONCLUSION: Fibrin Sealant, made from pooled donor blood and treated with viral elimination procedures, was found in combination with muscle grafts to securely close induced CSF leaks in the chinchilla model. Inflammation, infection, or toxic reactions were not observed. We believe that ViGuard Fibrin Sealant has stronger bonding power compared with available autologous fibrin tissue adhesives.

Animals↗
PubMed1997

Evaluation of pooled fibrin sealant for ear surgery.

HYPOTHESIS: This study investigated the bonding strength and tissue toxicity of a commercially prepared dual-virally-inactivated pooled-blood fibrin tissue adhesive (ViGuard-FS; Melville Biologics, Inc., NY, U.S.A.) and compared it with an autologous fibrin tissue adhesive made by the precipitation of fibrinogen using ethanol and freezing (AFTA-E). METHODS: The bonding strength of FS was optimized by varying the concentrations of fibrinogen and human or bovine thrombin using three different surface media: inorganic (silastic), animal skin, and human dura mater. Furthermore, tissue reactions and duration of fibrin clots were studied by injecting FS into the auricles of rats. RESULTS: This study showed that optimized FS with human thrombin was superior in bonding strength to AFTA-E on all three surface media, and that FS does not produce any toxic tissue responses when injected into rat auricles. Minimal traces of the adhesive clot could be observed in a few auricles at 35 days after application. CONCLUSIONS: Because it is made from pooled-donor blood that has been treated with virus elimination procedures, FS is superior to autologous fibrin tissue adhesive in which fibrinogen is precipitated by the ethanol/freezing method. FS has not shown any undesirable tissue reactions when injected into live rat auricles. We believe that these results provide a rationale for further clinical development of ViGuard-FS as a tissue adhesive for otologic surgery.

Animals↗
PubMed1989

Influence of industrial pollutants on thyroid function in Channa punctatus (Bloch).

A 30 day exposure of C. punctatus to sublethal levels of phenol, ammonia, mercuric chloride, cadmium chloride and a mixture of the four resulted in an overall activation of guaiacol peroxidase and depression of iodide peroxidase (IPOD) activity and blood T4 titre. Interestingly enough, in case of 15 day ammonia and 1 day mercury exposures, an increase of IPOD activity was accompanied by a decrease in T4 titre. In general, phenol, mercury, cadmium and the mixture of pollutants were found to inhibit LP activity by 56% to 85% while ammonia inhibited lysosomal protease (LP) activity by 70%. Alterations in acid phosphatase (AP) activity indicate changes in the lysosomal membrane characteristics caused by these toxicants. Considering the concomitant alterations in IPOD, T4, LP and AP it is surmised that thyroid function in C. punctatus is influenced by the pollutants by two pathways, one via IPOD pathway affecting T4 synthesis and the other via lysosomal pathway affecting T4 release.

Ammonia↗