Biomedical subjects

F Légaré

Publications and source records attributed to F Légaré.

11 recordsLinked to original sources

PubMed2005

Shakeup excitation during optical tunnel ionization.

Shakeup of a two-electron system is investigated in the strong infrared laser field limit, both theoretically and experimentally. During tunnel ionization the electron shakes up a second electron to an excited bound state. Theoretically, a complete analytical theory of shakeup in intense laser fields is developed. We predict that shakeup produces one excited sigma(u) D(+)(2) state in approximately 10(5) ionization events. Shakeup is measured experimentally by using the molecular clock provided by the internuclear motion. The number of measured events is found to be in excellent agreement with theory.

Journal Article↗

PubMed2004

The effects of flaxseed dietary supplement on lipid profile, bone mineral density, and symptoms in menopausal women: a randomized, double-blind, wheat germ placebo-controlled clinical trial.

Phytoestrogens are increasingly incorporated into the diet of menopausal women. However, there are limited data on the efficacy of flaxseed on the consequences of estrogen deficiency in menopausal women. The purpose of the study was to assess the effects of flaxseed incorporation into the diet of healthy menopausal women. One hundred and ninety-nine menopausal women were randomly assigned to consume 40 g flaxseed/d (n = 101) or wheat germ placebo (n = 98) for 12 months. At baseline and at month 12, serum levels of lipids, bone mineral density (BMD), and menopausal symptoms were evaluated. Statistical analysis was performed under the intention to treat principle. Flaxseed reduced serum total (-0.20 +/- 0.51 mmol/liter; P = 0.012) and high-density lipoprotein (-0.08 +/- 0.24 mmol/liter; P = 0.031) cholesterol concentrations compared with wheat germ placebo. BMD did not differ significantly between the two arms. Both flaxseed and wheat germ reduced (P < 0.0001) the severity scores of menopausal symptoms, but no statistical difference was found between the two arms. Our findings suggest that 1-yr incorporation of flaxseed into the diet produced a favorable, but not clinically significant, effect on blood cholesterol and caused no significant change in BMD or symptoms in healthy menopausal women.

Bone Density↗

PubMed2003

Time-resolved double ionization with few cycle laser pulses.

Ionization of D2 launches a vibrational wave packet on the ground state of D+2. Removal of the second electron places a pair of D+ ions onto a Coulombic potential. Measuring the D+ kinetic energy determines the time delay between the first and the second ionization. Caught between a falling ionization and a rapidly rising intensity, the typical lifetime of the D+2 intermediate is less than 5 fs when an intense 8.6 fs laser pulse is used. We simulate Coulomb explosion imaging of the ground state wave function of D2 by a 4 fs optical pulse and compare with our experimental observations.

Journal Article↗

PubMed2003

Probing molecular dynamics with attosecond resolution using correlated wave packet pairs.

Spectroscopic measurements with increasingly higher time resolution are generally thought to require increasingly shorter laser pulses, as illustrated by the recent monitoring of the decay of core-excited krypton using attosecond photon pulses. However, an alternative approach to probing ultrafast dynamic processes might be provided by entanglement, which has improved the precision of quantum optical measurements. Here we use this approach to observe the motion of a D2+ vibrational wave packet formed during the multiphoton ionization of D2 over several femtoseconds with a precision of about 200 attoseconds and 0.05 ångströms, by exploiting the correlation between the electronic and nuclear wave packets formed during the ionization event. An intense infrared laser field drives the electron wave packet, and electron recollision probes the nuclear motion. Our results show that laser pulse duration need not limit the time resolution of a spectroscopic measurement, provided the process studied involves the formation of correlated wave packets, one of which can be controlled; spatial resolution is likewise not limited to the focal spot size or laser wavelength.

Journal Article↗

PubMed2002

Sub-laser-cycle electron pulses for probing molecular dynamics.

Experience shows that the ability to make measurements in any new time regime opens new areas of science. Currently, experimental probes for the attosecond time regime (10(-18) 10(-15) s) are being established. The leading approach is the generation of attosecond optical pulses by ionizing atoms with intense laser pulses. This nonlinear process leads to the production of high harmonics during collisions between electrons and the ionized atoms. The underlying mechanism implies control of energetic electrons with attosecond precision. We propose that the electrons themselves can be exploited for ultrafast measurements. We use a 'molecular clock', based on a vibrational wave packet in H(2)(+) to show that distinct bunches of electrons appear during electron ion collisions with high current densities, and durations of about 1 femtosecond (10(-15) s). Furthermore, we use the molecular clock to study the dynamics of non-sequential double ionization.

Journal Article↗

PubMed2001

[Making a decision about hormone replacement therapy. A randomized controlled trial].

OBJECTIVE: To compare the efficacy of a decision-making aid with an information document from the Society of Obstetricians and Gynaecologists of Canada (SOGC) with regard to decisions about hormone replacement therapy (HRT). DESIGN: Randomized clinical trial. SETTING: Quebec city region. PARTICIPANTS: Menopausal Francophone women 45 to 69 years old. INTERVENTIONS: Subjects were given a manual and an audiocassette describing a six-step approach to making a decision about HRT. MAIN OUTCOME MEASURES: Amount of anxiety over the decision (main outcome), general knowledge of the risks and benefits of HRT, personal expectations and values concerning these risks and benefits, and women's views on HRT. RESULTS: Anxiety levels were significantly reduced in both groups, but the difference between the effectiveness of the two interventions was not significant (P = .77). Percentages of women whose general knowledge increased and of women with realistic expectations were significantly higher in the experimental group (P < .003 and P < .0001, respectively). Congruence between personal values and decisions about HRT increased significantly more in the experimental group (P < or = .003). CONCLUSION: The six-step approach to decision making was more helpful than the SOGC's information document in increasing subjects' knowledge of the risks and benefits of HRT, in creating more realistic expectations of HRT, and in increasing the congruence between subjects' personal values and their decisions on HRT.

Adult↗

PubMed2001

[Evaluation of medical web sites. Interobserver and intraobserver reliability of an evaluation tool].

OBJECTIVE: To develop and test the reliability of a tool for rating websites that provide information on evidence-based medicine. DESIGN: For each site, 60% of the score was given for content (eight criteria) and 40% was given for organization and presentation (nine criteria). Five of 10 randomly selected sites met the inclusion criteria and were used by three observers to test the accuracy of the tool. Each site was rated twice by each observer, with a 3-week interval between ratings. SETTING: Laval University, Quebec city. PARTICIPANTS: Three observers. MAIN OUTCOME MEASURES: The intraclass correlation coefficient (ICC) was used to rate the reliability of the tool. RESULTS: Average overall scores for the five sites were 40%, 79%, 83%, 88%, and 89%. All three observers rated the same two sites in fourth and fifth place and gave the top three ratings to the other three sites. The overall rating of the five sites by the three observers yielded an ICC of 0.93 to 0.97. An ICC of 0.87 was obtained for the two overall ratings conducted 3 weeks apart. CONCLUSION: This new tool offers excellent intraobserver and interobserver measurement reliability and is an excellent means of distinguishing between medical websites of varying quality. For best results, we recommend that the tool be used simultaneously by two observers and that differences be resolved by consensus.

Evaluation Studies as Topic↗

PubMed2000

Determinants of the intention to adopt hormone replacement therapy among premenopausal women.

OBJECTIVE: To identify the psychosocial factors that influence the intention to adopt hormone replacement therapy (HRT) at menopause. METHODS: Random Digit Dialing was used to recruit 644 premenopausal non-hysterectomized women aged 45-54. Data were collected using a telephone questionnaire previously developed according to the theory of planned behaviour. Variables measured were: intention to adopt HRT (INT); attitude towards HRT (Aact); perceived social norm (SN); perceived behavioural control (PBC); and personal normative belief (PNB). Socio-demographic data were also obtained. RESULTS: Stepwise multiple regression of INT on the theoretical variables yielded an R(2) of 0.70. The determinants were Aact (beta=0.39, P<0.001), PNB (beta=0.25, P<0.001), PBC (beta=0.23, P<0.001) and SN (beta=0.12, P<0.001). Women with a strong intention to adopt HRT represented 25% of the sample. These women were more likely to believe that adopting HRT would have the following positive consequences: an improvement in general well-being, the prevention of health problems, an improvement in interpersonal relationships, an increase in productivity, the regulation of mood swings and a reduction of hot flashes. They were also more likely to believe in the following negative consequences: side-effects, an increased risk of cancer, the likelihood of weight gain, and interference in the natural course of menopause (all at P<0.001). CONCLUSION: Actions that target behaviourial beliefs regarding HRT and perceived barriers to its adoption are most likely to influence adoption of HRT.

Attitude to Health↗

PubMed2000

[Rally-resources. The integration of community principles].

PROBLEM BEING ADDRESSED: Family medicine training programs are required to teach the four principles of family medicine, two of which deal with community responsibilities. Teachers in the Family Practice Unit at the Centre hospitalier de Québec, pavillon St-François d'Assise (UMF-SFA) have developed a learning activity that introduces residents to community agencies in the area. OBJECTIVE OF PROGRAM: To introduce family medicine residents to community aspects of the principles of family medicine, to help them identify community resources in the area served by UMF-SFA, to discuss these services so that they can use them effectively, and to offer new residents an opportunity to become better acquainted with these services and with the UMF-SFA team. MAIN COMPONENTS OF PROGRAM: In early September, a half-day is set aside for a rally during which mixed teams of supervisors and residents (four to eight to a team) visit about 10 community agencies in the vicinity of UMF-SFA. Walking from place to place, the teams spend 15 to 20 minutes with staff or users of each agency. The informal tone of the rally makes it easier for residents to understand these agencies. CONCLUSION: Each year for the past 10 years, all UMF-SFA members have taken part in a rally that introduces residents to the community-based resources of family medicine.

Attitude of Health Personnel↗

PubMed1999

[Recurrence and satisfaction levels following onysectomy with or without phenolization].

OBJECTIVE: To compare recurrence and satisfaction levels among patients undergoing onysectomy with phenolization (OP) and without phenolization (OS). DESIGN: Retrospective cohort study. SETTING: Family practice unit. PARTICIPANTS: All patients (N = 35) undergoing onysectomy between September 1992 and May 1993, and between January 1996 and February 1997. MAIN OUTCOME MEASURES: Type of onysectomy (OP or OS) was taken from the patient's medical record. A telephone interview was used to determine whether patients had experienced recurrence; satisfaction was measured retrospectively at diagnosis, at time of surgery, and after surgery using a five-point scale (very unsatisfied to very satisfied). RESULTS: Among the 30 patients interviewed by telephone, four of the six patients in the OS group experienced recurrence, and four of the 24 patients in the OP group experienced recurrence. (Fisher's exact test, P = .007). In the OS group, satisfaction levels at diagnosis, during surgery, and after surgery were 4.7, 4.5, and 4.2, respectively. In the OP group, satisfaction levels at these three points were 4.3, 4.2, and 4.4, respectively. Notwithstanding technique used, a connection was noted between recurrence and satisfaction level at the time of the telephone interview (repeated measures test, P = .036). CONCLUSION: In general medicine, onysectomy with phenolization could be the treatment of choice for ingrown toenails.

Adult↗

PubMed1998

[Factors influencing the adoption of hormone replacement therapy].

OBJECTIVE: To develop and test the metrologic qualities of a questionnaire for a survey on determining factors in initiating hormone replacement therapy (HRT), using Ajzen's planned behaviour theory. DESIGN: Semistructured interviews to collect the behavioural beliefs needed to develop the questionnaire and the test-retest. SETTING: Family medicine practices and the community. PARTICIPANTS: In two family medicine practices, 42 women completed semistructured interviews that yielded the beliefs needed to design the questionnaire for the core survey. Thirty other women from the community took part in the test-retest 2 weeks later. MAIN OUTCOME MEASURES: The internal consistency of the constructs (tendency of answers within a group of questions) was determined using Cronbach's alpha coefficient. Stability of the global constructs (proportion of subjects who had an absolute difference in their scores of less than 1 between the two measurements) was determined using the adjusted agreement coefficient (adjusted Po). RESULTS: Findings for 12 of the 14 global constructs were above the acceptance threshold of 0.60. In one case alpha could not be measured because there was only one question for measuring it. On the test-retest, 12 of the 14 adjusted Pos had a reliability rating at or above 80%. CONCLUSION: The questionnaire developed using Ajzen's planned behaviour theory had the requisite metrologic qualities for integration into the core survey on determining factors for initiating HRT.

Adult↗