Biomedical subjects
Publications and source records attributed to L Chevalier.
The ratio of the B+ and B0 meson lifetimes was measured using data collected in 2002-2004 by the D0 experiment in Run II of the Fermilab Tevatron Collider. These mesons were reconstructed in B-->mu(+)nuD(*-)X decays, which are dominated by B0 and B-->mu(+)nuD 0X decays, which are dominated by B+. The ratio of lifetimes is measured to be tau(+)/tau(0)=1.080+/-0.016(stat)+/-0.014(syst).
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.
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.
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.
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.
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.
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.
We report the results of a search for supersymmetry (SUSY) with gauge-mediated breaking in the missing transverse energy distribution of inclusive diphoton events using 263 pb(-1) of data collected by the D0 experiment at the Fermilab Tevatron Collider in 2002-2004. No excess is observed above the background expected from standard model processes, and lower limits on the masses of the lightest neutralino and chargino of about 108 and 195 GeV, respectively, are set at the 95% confidence level. These are the most stringent limits to date for models with gauge-mediated SUSY breaking with a short-lived neutralino as the next-to-lightest SUSY particle.
In order to better understand the risk factors and behaviour of a general sports population, a questionnaire was handed to 603 consecutive sportsmen of various disciplines during a specific sports medicine consultation and a half-marathon. Among the discovered risk factors, smoking was the most common (19.3% for the entire study population), predominantly in the youngest group (26%). A resting ECG had been performed very frequently within the previous year in those over 40 years (86.5%), but less often in the younger sportsmen (44.8%). An exercise test had also very often been performed in those aged over 40 years (69.2 vs 10.6%). Behaviour associated with cardiovascular risk was common. Undertaking physical activity while febrile (58%) and smoking just before or after exertion (13.1%) were widespread behaviours. This population appeared casual in its approach to possibly suspicious cardiac symptoms of exercise, particularly the females and paradoxically the subjects doing the most sport. Lastly, only a minority of sportsmen knew the telephone number for the emergency medical service (45%) or claimed to be competent at first aid (32%). This survey underlines a practice relatively in accordance with the recommendations for detecting cardiovascular pathology, but shows a failure of preventive education.
We report the observation of the X(3872) in the J/psipi(+)pi(-) channel, with J/psi decaying to mu(+)mu(-), in pp collisions at sqrt[s]=1.96 TeV. Using approximately 230 pb(-1) of data collected with the Run II D0 detector, we observe 522+/-100 X(3872) candidates. The mass difference between the X(3872) state and the J/psi is measured to be 774.9+/-3.1(stat)+/-3.0(syst) MeV/c(2). We have investigated the production and decay characteristics of the X(3872) and find them to be similar to those of the psi(2S) state.
A search for pair production of doubly charged Higgs bosons in the process pp -->H(++)H(--) -->mu(+)mu(+)mu(-)mu(-) is performed with the D0 run II detector at the Fermilab Tevatron. The analysis is based on a sample of inclusive dimuon data collected at an energy of sqrt[s]=1.96 TeV, corresponding to an integrated luminosity of 113 pb(-1). In the absence of a signal, 95% confidence level mass limits of M(H(+/-+/-)(L))>118.4 GeV/c(2) and M(H(+/-+/-)(R))>98.2 GeV/c(2) are set for left-handed and right-handed doubly charged Higgs bosons, respectively, assuming 100% branching into muon pairs.
The natural diet of Helix aspersa was studied in two populations by analysing faeces. Picris echioides, Carduus tenuifloris, Urtica dioica, Galium molugo (Dicotyledons) and Poaceae (Monocotyledons) were the principal resources of the studied populations. The species of Poaceae ingested by Helix aspersa in July were determined by analysing the phytoliths present in the faeces. Festuca rubra, Dactylis glomerata and Bromus hordeaceus seemed to be attractive for the snails whereas Elytrigia repens was rejected. These results were convergent with the ingestion rates of Poaceae in the laboratory but assimilation efficiencies did not explain these choices. Poaceae with the highest energetic values were not preferred to others. The texture, the mineral and organic contents of the Poaceae may be responsible for the snails feeding choices. The importance of Poaceae for this species is discussed.
Transformed callus cultures of Nicotiana tabacum were generated in which the SAM-1 gene from Arabidopsis thaliana encoding S-adenosylmethionine synthetase (SAM-S), under the control of the 35S promoter, had been integrated. The presence of the SAM-1 gene was detected in all tested transformants and the SAM-S activity correlated with the accumulation of SAM in the tobacco callus cultures. Three distinct phenotypic classes were identified among the transgenic cell lines in relation to growth of the cells, structure of the calli, and level of SAM. Transgene silencing was observed in several cultivated transgenic calli and this phenomenon was correlated directly with a low level of SAM-1 mRNA accompanied by a decrease of the SAM-S activity. The transgenic calli overexpressing the SAM-1 gene accumulated a high SAM level. The modifications in SAM-S activity were reflected in the pattern of secondary products present in the different cell lines, thereby demonstrating that the flux through the biosynthetic pathway of a plant secondary product can be modified by means of genetic engineering.
In this study, the efficiency of inducible promoters to switch on gene expression in the presence of inducer or to switch it off in its absence was evaluated in tobacco cell suspensions transformed with the gus gene coding sequence. Either plant (pats1A, pSalT, pIn2-2) or microbial (pMre, pTet) inducible promoters were used to drive gus expression. The inducers were light, abscisic acid, 2-CBSU, CuSO4, tetracycline, respectively. For each construct (inducible promoter-gus coding sequence), the optimal induction conditions were determined (inducer concentration, induction time, and age of cells in culture cycle before induction). The efficiency of the inducible promoter was then evaluated under optimal induction conditions. GUS-expression levels obtained under non-inducing and inducing conditions were systematically compared. Thirty or forty percent of the clones transformed with the pSalT-gus or pTet-gus construct, respectively, showed high induction rates (>1000) and GUS activities of the same order as those obtained with a constitutive system. However, basal GUS levels were always high for the pTet-gus cell lines. Seventy or eighty-five percent of the cell lines transformed with the pMre-gus or pln2-2-gus construct, respectively, had induction rates of 1.5 to 1000. The pats1A-gus construct gave very low induction rates-55% of cell lines had induction rates less than 1.5. Only the pSalt-gus construct gave both the highest induction rates and basal GUS-levels equivalent to the endogenous GUS background.
UNLABELLED: Between 1980 and 1995, we observed twenty-five patients (22 males, 3 females) at the mean age of 50.6 +/- 13 years, without previous myocardial infarction who presented exercise induced ST elevation on a bicycle stress test. METHODS: Significant ST elevation was defined as a > or = 1 mm change present in > or = 1 lead measured 0.08 sec after the J point and in 3 consecutive beats. All patients have undergone coronary angiography in the days following the exercise test. RESULTS: Most of patients (56%) presented a history of typical angina that was either purely exertional (8 pts) or also occurred at rest (6 pts). Others (36%) had non typical angina or no angina (8%); 78% of pts were smokers. Sixteen patients (group I) had ST elevation during exercise (exercise duration: 7.6 +/- 4 min; peak heart rate: 135.5 +/- 29 batt/min; ST = 3.5 +/- 1.5 mm) and nine (group II) during the recovery phase (exercise duration 16.3 +/- 1.6 min; p < 0.05; peak heart rate 168 +/- 22 batt/min; p < 0.05; ST: 5.8 +/- 3 mm; p < 0.05). In group I, 1 patient had no vessel disease, 12 had one vessel disease, 3 had multivessel disease with 6 cases of hypersevere coronary stenose (> 90%). In group II, 4 patients had normal coronary arteries, there was one vessel coronary artery disease in 4 patients and multivessel in one subject, without hypersevere coronary stenosis. Correlation between anatomic location of stenosis and electrocardiographic ST elevation was excellent, particularly in case of single vessel disease (100%). All patients underwent one or more new exercise tests after therapeutic intervention (surgery n = 3; angioplasty n = 7; medical treatment n = 15), only 2 patients had persistent exercise induced ST elevation. During follow-up (5 +/- 3 years), 3 patients died (2 cardiac deaths) and 3 had recurrent angina controlled by new treatment. CONCLUSION: Exercise-induced ST elevation is a rare phenomenon in patients without prior myocardial infarction. When occurring purely during exercise, coronary lesions are frequent and often servere, in the other hand ST elevation of the recovery phase is frequently associate with normal arteries or less severe lesions. In most cases, revascularisation or medical therapy can abolish clinical and electrocardiographic abnormalities.
BACKGROUND: Haemodynamic measurements taken at rest and during exercise showed that percutaneous transvenous mitral commissurotomy results in both acute and long-term improvement. However, the time lag before there is an increase in exercise and in peak oxygen uptake appears to be delayed and irregular. PATIENTS AND METHODS: To assess the potential of physical training to restore better physical capacity after percutaneous transvenous mitral commissurotomy, 26 patients with mitral stenosis were studied after the procedure. The group was split into two. Thirteen underwent a 3-month rehabilitation programme, and the other 13, who did not, acted as controls. RESULTS: The mitral valve orifice area increased similarly, from 1.12 +/- 0.17 to 1.88 +/- 0.28 cm2 in the training group and from 1.04 +/- 0.16 to 1.88 +/- 0.19 cm2 in the control group. Cardiopulmonary parameters were similar before percutaneous transvenous mitral commissurotomy (peak VO2: 19.9 +/- 2.4 vs 18.9 +/- 4.5 ml. min-1.kg-1; peak workload: 94.6 +/- 29.3 vs 96.1 +/- 25 watts; VO2 at anaerobic threshold: 17 +/- 3.4 vs 16.1 +/- 5.2 ml.min-1.kg-1; all P = ns). Three months later the results were higher in the training group 1 (peak VO2: 26.6 +/- 4.7 vs 21.6 +/- 3.8 ml.min-1.kg-1, P = 0.03; peak workload: 125.4 +/- 26.6 vs 108.5 +/- 23 watts, P = 0.03; VO2 at anaerobic threshold: 19.6 +/- 5.8 vs 15.8 +/- 2.9 ml.min-1.kg-1; P = 0.02). CONCLUSION: These results indicate that patients should take up exercise after successful percutaneous transvenous mitral commissurotomy for better functional improvement.
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We report the expression pattern of hemidesmosome-associated proteins laminin-5, composed of alpha 3 beta 3 gamma 2 chains, and HD1 in the developing mouse and human intestine, an organ in which variations in structure and function parallel morphogenesis and differentiation. Immunocytochemistry analysis revealed the coexpression of laminin-5 and HD1 at the basal pole of differentiating epithelial cells. Distinct noticeable variations occurring in the location of laminin alpha 3 chain in development of mouse gut were stressed by the reverse transcriptase-polymerase chain reaction data. A peculiar finding was also the location of laminin gamma 2 chain in the intestinal muscle coat. The cellular origin of laminin gamma 2 chain was examined by immunocytochemistry on interspecies hybrid intestines with specific antibodies recognizing mouse antigens. Complementary and sequential production of laminin gamma 2 chain was observed, by epithelial cells as establishment of the basement membrane occurs and by mesenchymal cells in the more differentiated organ. These results support the concept of mesenchymal involvement in deposition of basement membrane molecules, a crucial process for intestinal differentiation. Taken together these data provide the first evidence for the coexpression of hemidesmosome-associated proteins in the gut, a non-stratified tissue.