Search tips
Search criteria

Results 1-11 (11)

Clipboard (0)

Select a Filter Below

Year of Publication
Document Types
1.  Optical manipulation of single flux quanta 
Nature Communications  2016;7:12801.
Magnetic field can penetrate into type II superconductors in the form of Abrikosov vortices, which are magnetic flux tubes surrounded by circulating supercurrents often trapped at defects referred to as pinning sites. Although the average properties of the vortex matter in superconductors can be tuned with magnetic fields, temperature or electric currents, handling of individual Abrikosov vortices remains challenging and has been demonstrated only with sophisticated scanning local probe microscopies. Here we introduce a far-field optical method based on local heating of the superconductor with a focused laser beam to realize a fast and precise manipulation of individual vortices, in the same way as with optical tweezers. This simple approach provides the perfect basis for sculpting the magnetic flux profile in superconducting devices like a vortex lens or a vortex cleaner, without resorting to static pinning or ratchet effects.
Manipulation of individual superconducting vortices remains challenging and has been demonstrated only in a sophisticated way. Here, Veshchunov et al. realize a fast and precise manipulation of individual vortices using a far-field optical method, providing a simple way towards optical control of Josephson transport.
PMCID: PMC5052701  PMID: 27677835
2.  Key Beliefs for Targeted Interventions to Increase Physical Activity in Children: Analyzing Data from an Extended Version of the Theory of Planned Behaviour 
Given the high prevalence of overweight and low levels of physical activity among children, a better understanding of physical activity behaviour is an important step in intervention planning. This study, based on the theory of planned behaviour, was conducted among 313 fifth graders and their parents. Children completed a computer-based questionnaire to evaluate theoretical constructs and behaviour. Additional information was obtained from parents by means of a questionnaire. Correlates of children's physical activity were intention and self-identity. Determinants of intention were self-efficacy, self-identity, and attitude. Parental variables were mediated through cognitions. Among girls, practicing sedentary activities was an additional negative determinant of intention. Key beliefs of boys and girls were related to time management and difficulties associated with physical activity. For girls, social identification as an active girl was another important belief related to positive intention. This study provides theory-based information for the development of more effective interventions aimed at promoting physical activity among children.
PMCID: PMC2905955  PMID: 20652005
3.  Seeking medical advice if HIV symptoms are suspected. Qualitative study of beliefs among HIV-negative gay men. 
Canadian Family Physician  2000;46:861-868.
OBJECTIVE: To identify beliefs associated with seeking medical advice promptly when symptoms of HIV infection are suspected among HIV-negative gay men. DESIGN: Qualitative study of beliefs among focus group participants. SETTING: Quebec city, Que, metropolitan area. PARTICIPANTS: Referred sample of 20 HIV-negative gay men 18 to 45 years old who attended bars, university, or gay associations in Quebec city. METHOD: Three focus groups of five to seven subjects were formed and each 2-hour session was tape-recorded. MAIN OUTCOME FINDINGS: Participants thought that seeking medical advice promptly when symptoms of HIV are suspected would help them be informed about their health status and would eliminate unnecessary anxiety and fear, but would force them to face reality and make major changes. Barriers were the quality of the relationship with their physicians and concern about discussing their sexual lives. Normative beliefs were sought from members of community groups, circles of close friends, health providers, and the media. CONCLUSIONS: Several beliefs could influence the motivation of seronegative gay men to seek medical advice promptly when symptoms of HIV infection are suspected. These beliefs should be integrated into programs promoting early consultation with physicians and into clinical counseling, as integration could facilitate early treatment and care. Physicians should give special attention to establishing relationships of trust with these patients.
PMCID: PMC2144804  PMID: 10790818
4.  Les facteurs influant sur l'adoption de l'hormonothérapie de remplacement. 
Canadian Family Physician  1998;44:1280-1286.
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.
PMCID: PMC2278266  PMID: 9640522
5.  Hypercholesterolemia screening. Does knowledge of blood cholesterol level affect dietary fat intake? 
Canadian Family Physician  1998;44:1289-1297.
OBJECTIVE: To assess whether knowing blood cholesterol test results influences people's intention to lower their dietary fat intake and to assess changes in diet after 3 months. DESIGN: Randomized clinical study. SETTING: Two hospital-based family medicine centres. PARTICIPANTS: A total of 526 patients aged 18 to 65, without prior knowledge of their blood cholesterol levels, were recruited. Seventy did not appear for their appointments, and 37 did not meet study criteria, leaving 419 participants. From that group, 391 completed the study. INTERVENTIONS: Patients submitted to cholesterol screening were randomly assigned to one of two groups, completing the study questionnaires either before (control group) or after (experimental group) being informed of their screening test results. All participants were called 3 months after transmission of test results to assess their dietary fat intake at that time. MAIN OUTCOME MEASURES: Differences in intention to adopt a low-fat diet reported between the experimental and control groups and differences in dietary fat intake modification after 3 months between patients with normal and abnormal blood cholesterol test results. RESULTS: Knowledge of test results influenced patients' intentions to adopt low-fat diets (F1,417 = 5.4, P = .02). Patients reported lower mean dietary fat intake after 3 months than at baseline (P < .0001). The reduction was greater in patients with abnormal screening results (F2,388 = 3.6, P = .03). CONCLUSIONS: Being informed of personal blood cholesterol levels effects an immediate change in eating habits that translates into reduced dietary fat intake.
PMCID: PMC2278249  PMID: 9640523
6.  [Fréquence des maladies transmises sexuellement chez des étudiants universitaires.] 
OBJECTIVE: To estimate the incidence rate of sexually transmitted diseases (STDs) among university students and evaluate the associated sociodemographic factors. DESIGN: Mail survey in April 1990. Included in the questionnaire were questions about the subjects' STD experience since their admission to the university and the type and date of the infection. SUBJECTS: Of the 19,682 undergraduate students 2920 subjects, in 10 groups of 292, were randomly selected. A total of 1731 (59.4%) completed the questionnaire. MAIN OUTCOME MEASURES: Estimated annualized incidence rates of genital human papillomavirus infection and Chlamydia infection. RESULTS: The estimated annualized incidence rates of genital human papillomavirus and Chlamydia infections were 2.2% and 1.5% respectively. Among the students who indicated being infected with genital human papillomavirus 59% were 18 to 21 years old (p < 0.05), 76% were women (p < 0.01) and 69% had more than one sexual partner (p < 0.01). No statistically significant associations were observed between age, sex and Chlamydia infection. On the other hand, 95% of the cases of Chlamydia infection were found among those who had more than one sexual partner (p < 0.01). CONCLUSION: University students continue to have sexual activities at risk for STDs and should be specifically targetted by general practitioners and health services in an effort to slow the spread of STDs.
PMCID: PMC1485833  PMID: 8388772
7.  Predicting and reinforcing children's intentions to wear protective helmets while bicycling. 
Public Health Reports  1992;107(3):283-289.
The researchers undertook to identify the factors that are most likely to influence children's intentions to use bicycle helmets. To determine the most important intention influencing factors, a random sample of 797 students in grades 4 through 6 completed a self-administered questionnaire concerning their beliefs about helmet use. They were asked about their perceptions of the risk of riding bicycles unprotected, the severity of possible head injuries, and about other bicycle-safety related behaviors. Factors that best predicted the student's intentions to use bicycle helmets involved both behavioral beliefs and normative beliefs. Analysis of factors influencing those with low intentions to use helmets, compared to those with high intentions, suggests the most effective messages that health planners can provide preadolescents to influence them to use helmets. They are that helmet use is fun and attractive, helmets provide a new look and a sporting image, and friends approve of and value this behavior. Parents, and particularly mothers, can reinforce their children's intentions to use helmets and their involvement should be encouraged.
PMCID: PMC1403648  PMID: 1594738
8.  Factors influencing intentions of pregnant women to exercise after giving birth. 
Public Health Reports  1989;104(2):188-195.
The aim of this study was to identify factors that may influence a pregnant woman's decision to exercise after giving birth. A sample of 98 pregnant women were asked to complete a questionnaire investigation attitudes, social norms, perceived barriers to exercise, and intention regarding exercising after giving birth. Also determined were age, education level, exercise habits, number of months elapsed since onset of present pregnancy, and number of children. The regressions of intentions to exercise on all variables yielded R2 of 0.52 for nulliparous and 0.60 for pluriparous pregnant women. Important differences in variables that explained intentions were found between both groups of women, with perceived barriers to exercise being a key predictor that was, in turn, influenced by previous experience with pregnancy. It is suggested that the experience of the postnatal period modifies the interrelation between the variables explaining intentions regarding exercise after giving birth. Consequently, the programs should take into account the impact that the birth of a first child will have on the perceived barriers to exercise.
PMCID: PMC1580036  PMID: 2495554
9.  The cognitive profile of those who intend to exercise but do not. 
Public Health Reports  1986;101(5):521-526.
The purpose of this study was to identify the cognitive profile of people who intend to exercise but fail to carry out this intention. A theoretical framework was adopted to study the attitudinal beliefs of these persons about exercise, their evaluation of the associated consequences, and their normative beliefs and motivation to comply with these norms. Subjects were classified according to the congruence between stated intention and self-reported exercise behavior 2 months later in this way: positive intention and congruent behavior (CONG+, N = 74). positive intention and incongruent behavior (INCONG-, N = 45). negative intention and congruent behavior (CONG-, N = 42). negative intention and incongruent behavior (N = 2, not analyzed). MANOVA analysis indicated little difference between the cognitive profiles of inactive and active positive intenders. Relative to the CONG+ group, the INCONG- group perceived that regular exercise would be "tiring" (P less than 0.001) and "time consuming" (P less than 0.001); they also placed less value on the consequence of "being healthy" (P less than 0.05). Both groups differed from the CONG- group. As would be expected, those with positive intentions to exercise identified more advantages to being physically active. It appears that sedentary positive intenders perceived the exercise behavior as physically demanding and had difficulty in reconciling the time demands of an exercise program with their weekly schedules. This observation suggests that these two beliefs should be considered for the promotion of physical activity as well as the investigation of influential social and environmental variables.
PMCID: PMC1477759  PMID: 3094084
10.  Plasma lipoprotein levels and the prevalence of hyperlipoproteinemia in a Canadian working population 
The lipids and lipoproteins — cholesterol (C), triglyceride (TG) and high-density, low-density, very-low-density and sinking pre-β-lipoprotein cholesterol (HDL-C, LDL-C, VLDL-C and SPB-C) — in plasma samples from 1620 fasting white adults and children from the Toronto—Hamilton area were analysed. The mean concentration of HDL-C was about 45 mg/dl in men and about 60 mg/dl in women, and the levels were constant throughout adult life in both sexes. Boys had higher mean HDL-C levels than men, but girls had lower mean HDL-C levels than women. Mean LDL-C levels, like total C levels, increased with age, from about 87 mg/dl in boys to 136 mg/dl in men, and from about 91 mg/dl in girls to 145 mg/dl in women. The mean levels of VLDL-C followed the TG patterns for age and sex, rising from about 7 mg/dl in boys to 26 mg/dl in men, and from about 11 mg/dl in girls to 19 mg/dl in women. SPB-C was detectable visually in 39% of the population and with the aid of densitometry in 54%; the levels were not related to age, sex or oral contraceptive use, and the median level was 3 mg/dl.
Prevalence estimates of hyperlipoproteinemia showed that type IV was the most common, and it was found more than three times as often in men as in women. This was in part due to the customary use of plasma TG cut-off points that do not reflect the large difference in TG levels between males and females. Type IIA hyperlipoproteinemia was found in about 2% of the adults and type IIb in a further 1%. Types I, III and V were all rare. The prevalence of types II and IV hyperlipoproteinemia was four times greater in women using oral contraceptives than in nonusers in the same age range.
PMCID: PMC1801586  PMID: 7363194
11.  Normative standards of plasma cholesterol and triglyceride concentrations in Canadians of working age. 
Canadian Medical Association Journal  1977;117(9):1020-1024.
Fasting plasma cholesterol and triglyceride concentrations were determined for 6407 working Canadian adults aged 20 to 69 years in Toronto and Hamilton. Means, medians and 5th and 95th percentiles were ascertained from the data for men, women taking oral contraceptives or estrogen preparations, and women not taking such medication. Mean plasma cholesterol values (mg/dL) ranged in men from 168.3 at ages 20 to 24 years to 211.5 at ages 45 to 49 years, and in women using hormone preparations from 180.3 at ages 20 to 24 years to 224.2 at ages 50 to 54 years; corresponding values in women not using these preparations were 164.9 and 220.6. Plasma triglyceride means (mg/dL) ranged in men from 108.7 at ages 20 to 24 years to 166.7 at ages 40 to 44 years, in women using hormone preparations from 115.4 at ages 20 to 24 years to 145.3 at ages 45 to 59 years, and in women not using these preparations from 77.5 at ages 20 to 24 years to 112.4 at ages 50 to 54 years.
PMCID: PMC1880192  PMID: 912626

Results 1-11 (11)