Biomedical subjects

M Ahsan

Publications and source records attributed to M Ahsan.

33 records · Page 2Linked to original sources

PubMed2005

Measurement of the ratio of inclusive cross sections sigma(pp --> Z + b jet)/sigma(pp --> Z + jet) at square root(s) = 1.96 TeV.

Using the data collected with the D0 detector at square root(s) = 1.96 TeV, for integrated luminosities of about 180 pb(-1), we have measured the ratio of inclusive cross sections for pp --> Z + b jet to pp --> Z + jet production. The inclusive Z + b-jet reaction is an important background to searches for the Higgs boson in associated ZH production at the Fermilab Tevatron collider. Our measurement is the first of its kind, and relies on the Z --> e+ e- and Z --> mu+ mu- modes. The combined measurement of the ratio yields 0.021+/-0.005 for hadronic jets with transverse momenta pT > 20 GeV/c and pseudorapidities absolute value(eta) < 2.5, consistent with next-to-leading-order predictions of the standard model.

Journal Article↗

PubMed2005

Search for anomalous heavy-flavor quark production in association with W bosons.

We search for anomalous production of heavy-flavor quark jets in association with W bosons at the Fermilab Tevatron pp Collider in final states in which the heavy-flavor quark content is enhanced by requiring at least one tagged jet in an event. Jets are tagged using one algorithm based on semileptonic decays of b/c hadrons, and another on their lifetimes. We compare e+jets (164 pb(-1)) and mu+jets (145 pb(-1)) channels collected with the D0 detector at sqrt[s]=1.96 TeV to expectations from the standard model and set upper limits on anomalous production of such events.

Journal Article↗

PubMed2005

Measurement of the WW production cross section in pp collisions at square root[s]=1.96 TeV.

We present a measurement of the W boson pair-production cross section in pp collisions at a center-of-mass energy of sqrt[s]=1.96 TeV. The data, collected with the Run II D0 detector at Fermilab, correspond to an integrated luminosity of 224-252 pb(-1) depending on the final state (ee, emu, or mumu). We observe 25 candidates with a background expectation of 8.1+/-0.6(stat)+/-0.6(syst)+/-0.5(lum) events. The probability for an upward fluctuation of the background to produce the observed signal is 2.3x10(-7), equivalent to 5.2 standard deviations. The measurement yields a cross section of 13.8(+4.3)(-3.8)(stat)+1.2-0.9(syst)+/-0.9(lum) pb, in agreement with predictions from the standard model.

Journal Article↗

PubMed2005

Measurement of the Lambda0b lifetime in the decay lambda0b--> J/psiLambda0 with the D0 detector.

We present measurements of the Lambda(0)(b) lifetime in the exclusive decay channel Lambda(0)(b)--> J/psiLambda(0), with J/psi--> mu(+)mu(-) and Lambda(0)--> ppi(-), the B0 lifetime in the decay B0-->J/psiK(0)(S) with J/psi--> mu(+)mu(-) and K(0)(S)-->pi(+)pi(-), and the ratio of these lifetimes. The analysis is based on approximately 250 pb(-1) of data recorded with the D0 detector in pp collisions at sqrt[s] = 1.96 TeV. The Lambda(0)(b) lifetime is determined to be tau(Lambda(0)(b)) = 1.22(+0.22)(-0.18)(stat) +/- 0.04(syst) ps, the B0 lifetime tau(B0) = 1.40(+0.11)(-0.10)(stat) +/- 0.03(syst) ps, and the ratio tau(Lambda(0)(b))/tau(B0) = 0.87(+0.17)(-0.14)(stat) +/- 0.03(syst). In contrast with previous measurements using semileptonic decays, this is the first determination of the Lambda(0)(b) lifetime based on a fully reconstructed decay channel.

Journal Article↗

PubMed2005

Search for Wbb and WH production in pp collisions at square root [s]=1.96 TeV.

We present a search for Wbb production in pp collisions at sqrt[s]=1.96 TeV in events containing one electron, an imbalance in transverse momentum, and two b-tagged jets. Using 174 pb(-1) of integrated luminosity accumulated by the D0 experiment at the Fermilab Tevatron collider, and the standard-model description of such events, we set a 95% C.L. upper limit on Wbb production of 6.6 pb for b quarks with transverse momenta p(b)(T)>20 GeV and bb separation in pseudorapidity-azimuth space DeltaR(bb)>0.75. Restricting the search to optimized bb mass intervals provides upper limits on WH production of 9.0-12.2 pb for Higgs-boson masses of 105-135 GeV.

Journal Article↗

PubMed2005

Search for the flavor-changing neutral current decay B0s--> mu(+) mu(-) in pp Collisions at sqrt[s] = 1.96 TeV with the D0 detector.

We present the results of a search for the flavor-changing neutral current decay B(0)(s)--> mu(+) mu(-) using a data set with integrated luminosity of 240 pb(-1) of pp collisions at sqrt[s] = 1.96 TeV collected with the D0 detector in run II of the Fermilab Tevatron collider. We find the upper limit on the branching fraction to be B(B(0)(s)--> mu(+) mu(-)) < or= 5.0 x 10(-7) at the 95% C.L. assuming no contributions from the decay B(0)(d)--> mu(+) mu(-) in the signal region. This limit is the most stringent upper bound on the branching fraction B(0)(s)--> mu(+) mu(-) to date.

Journal Article↗

PubMed2004

Antioxidant micronutrient profile (vitamin E, C, A, copper, zinc, iron) of colostrum: association with maternal characteristics.

The study was conducted to investigate the micronutrient profile of human colostrum, and to assess the association of maternal characteristics to the micronutrients. Colostral concentrations of antioxidant vitamins E, C, and A were 21.34 +/- 8.47, 148.92 +/- 43.64, 0.79 +/- 0.42 micromol/l, respectively. The antioxidant minerals copper, zinc, and iron contents were 19.17 +/- 11.73, 63.69 +/- 12.82, 11.44 +/- 1.46 micromol/l, respectively. Maternal characteristics did not have any influence on the colostral micronutrients.

Adolescent↗

PubMed2001

Serum vitamin E, C and A status of the drug addicts undergoing detoxification: influence of drug habit, sexual practice and lifestyle factors.

BACKGROUND: The study was carried out on the hypothesis that drug addicts would have reduced vitamin E, C and A status which could be influenced by drug habit, sexual practice and lifestyle factors. METHOD: Serum concentrations of Vitamin E, C and A of male drug addicts and cohort controls were analysed, and influence of drug habit, sexual practice and lifestyle factors of the addicts on the vitamin status was assessed. The study was conducted among 253 drug addicts who sought detoxification voluntarily during the period of June 1997 to July 1998 at the Central Drug Addiction Treatment Hospital, Dhaka, and 100 cohort control men. Research instruments were questionnaire and blood specimens. HPLC and spectrophotometric methods were used to determine the vitamin levels in sera of drug addicts. RESULTS: alpha-Tocopherol (12.60+/-3.73 compared with 16.3+/-3.37 micromol/l; t=8.6, P=0.05), ascorbic acid (21.59+/-10.5 compared with 38.3+/-13.62 micromol/l; t=10.93, P=0.003) and retinol (1.15+/-0.39 compared with 1.33+/-0.30 micromol/l; t=5.28, P=0.048) in the drug addicts were significantly low as compared to those in the cohort controls. Use of multiple illicit drugs for a longer period of time did result in reduced levels of these vitamins. A significant reduction in retinol concentration was noted among the multiple drug users (F(2,250)=3.23, P=0.041). Duration of addiction had a significant linear correlation with the level of reduction in retinol (F(2,250)=3.23, P=0.041) and alpha-tocopherol (F(2,250)=3.06, P=0.049). Apart from having a significant negative correlation between number of sexual partners and retinol level (F(3,247)=2.65, P=0.049), sexual practice did not have any influence on the vitamin status of the addicts. Occupation did have a significant effect on the ascorbic acid level (F(4,248)=2.46, P=0.046), but other socioeconomic factors like income, age etc did not influence the vitamin E, C and A levels. Body mass index had a positive linear correlation with the vitamins, but it was significant only with vitamin C (F(2,250)=7.06, P=0.001). CONCLUSIONS: These results could have important implications for providing an antioxidant therapy to drug addicts and thus rehabilitating them into normal life. Risk of HIV infection and transmission (if any) could be reduced or inhibited.

Adolescent↗

PubMed2000

Constituents and cytotoxicity of Zanthoxylum rhesta stem bark.

3,5-Dimethoxy-4-geranyloxycinnamyl alcohol (1), 8-methoxy-N-methylflindersine (2), xanthyletin and sesamin have been isolated from petroleum ether extract of the stem bark of Zanthoxylum rhesta. The petroleum ether extract and 8-methoxy-N-methylflindersine showed cytotoxicity on brine shrimp nauplii.

Animals↗

PubMed2000

Sexual life style, drug habit and socio-demographic status of drug addicts in Bangladesh.

The sexual life style, drug habit and socio-demographic status of 253 male hospitalized drug addicts were investigated. This study was conducted during the period June 1997 to July 1998, and each case was selected by the random sampling method. The research instrument was an interviewer-administered questionnaire, the sexual habits, number and quality of sex partners, use of condoms, sexually transmitted diseases, etc., were considered as indicators of the sexual life style of the drug addicts. Eighty-eight percent (n=233) of the addicts were heterosexual. Bisexuality was found only in 7% (n=18) of the addicts. Eighty-seven percent (n=240) of the addicts have multiple sex partners of either commercial or residential category. Most of the drug addicts (72%,n=181) did not use condoms. Fifty-seven percent (n=145) of the addicts were observed to have sexual diseases. As indicators of a drug habit, starting drug, choice of drug, period of addiction, sharing of needles, etc., were included. Cannabis was the starting substance for 59% (n=149) of the addicts. Heroin was the drug of choice for 60% (n=157) addicts. A single drug was taken only by 8% (n=20) of the addicts and the remaining 92% (n=233) took multiple drugs. The drug addicts (n=97) who used mostly injection (87%,n=84) shared needles. Education, occupation, income, age, marital status, influencing factors for addiction were considered as socio-demographic characteristics. Young adults (79%,n=199), secondary educated (46%,n=116), low-mid income (60%,n=150), businessmen (46%,n=150) and married (60%,n=151) people were found highly involved in addiction. Self-curiosity and a friend's incitement were revealed as the most important influencing factors for taking drugs.

Adolescent↗

PubMed1997

Purification and characterization of the family J catalytic domain derived from the Clostridium thermocellum endoglucanase CelJ.

The Clostridium thermocellum endoglucanase CelJ contains two different catalytic domains in a polypeptide, i.e., a subfamily E1 catalytic domain and a family J catalytic domain [J. Bacteriol., 178, 5732-5740 (1996)]. The family J catalytic domain (CDJ-CelJ) was produced by a recombinant Escherichia coli and purified. The purified CDJ-CelJ gave a single band on SDS-polyacrylamide gel electrophoresis and the molecular weight of this enzyme (60,000) was consistent with the value (60,333) calculated from the DNA sequence. CDJ-CelJ hydrolyzed various cellulosic substrates, xylan, and lichenan but not p-nitrophenyl (PNP)-cellobioside, PNP-glucoside, or PNP-xyloside at all. CDJ-CelJ was active on Avicel, a microcrystalline cellulose, and the specific activity of CDJ-CelJ on Avicel (0.0078 U/mg protein) was comparable to that of CelS, which is recognized as the most important catalytic subunit of the C. thermocellum, cellulosome, suggesting that CelJ is also an important catalytic subunit in the cellulosome of this bacterium, in addition to CelS.

Amino Acid Sequence↗

PubMed1991

Efficacy of aqueous extract of garlic & allicin in experimental shigellosis in rabbits.

The aqueous extract of garlic (Allium sativum) and allicin both showed significant in vitro antibacterial activity against isolates of multiple drug-resistant Shigella dysenteriae 1, Sh. flexneri Y, Sh. sonnei and enterotoxigenic Escherichia coli. The minimum inhibitory concentrations of the aqueous extract and allicin against Sh. flexneri Y were 5 and 0.4 microliters/ml, respectively. The two agents also showed promising in vivo antibacterial activity against Sh. flexneri Y when tested in the rabbit model of experimental shigellosis, fully curing the infected rabbits within 3 days. On the contrary, 4 of the 5 rabbits in the control group died within 48 h. The rectal swab of rabbits of the experimental groups became free of the challenge bacteria on the second day of treatment. The antibacterial activity against the challenge strain was observed in the sera of the treated rabbits with 30-60 min of administration of the agents. The LD50 values of the aqueous extract and allicin in mice were 173.78 ml/kg and 204.17 microliters/kg of body weight, respectively. At the therapeutic dose, the two agents did not show any adverse effects on the standard biochemical profile of blood.

Animals↗

PubMed1990

Antibacterial activity of clove extracts against phagogenic strains including clinically resistant isolates of Shigella and Vibrio cholerae.

Clove extracts (petroleum ether, chloroform and ethanol extracts) were tested in vitro for their antibacterial activity against forty isolates of pathogenic bacteria including clinically resistant (resistant to ampicillin and nalidixic acid) strains of twenty-five Shigella and four Vibrio cholerae. All of the isolates except Pseudomonas aeruginosa showed promising sensitivity to the extracts.

Journal Article↗

PubMed1990

In vitro testing of the leaf extracts of Lawsonia alba for antimicrobial properties.

Leaf extracts (chloroform, ethanol and aqueous extracts) of Lawsonia elba were tested in vitro for their antimicrobial activity against seventeen strains of pathogenic bacteria and twelve fungi including seven pathogenic strains. Each of the extract showed good activity against most of the strains tested. The sensitivity of the bacteria and fungi to the extracts was compared to that of ampicillin, tetracycline, co-trimoxazole and griseofulvin sensidiscs.

Journal Article↗

PubMed1989

Antifungal activities of the oils of Nigella sativa seeds.

Antifungal activities of the oils of N. sativa seeds were tested against twenty fungi including pathogenic and industrial strains. All the oils were found to have significant activities against the fungi, but the volatile oil showed stronger and wider range of antifungal activities. MIC values of the volatile oil was also determined against three pathogenic fungi and lowest MIC was found against Aspergillus fumigatus.

Journal Article↗