D. Dubé

Developments in metallic biodegradable stents

Interest in metallic degradable biomaterials research has been growing in the last decade. Both scientific journals and patent databases record a high increase in publications in this area. Biomedical implants with temporary function, such as coronary stents, are the targeted applications for this novel class of biomaterials. It is expected that stents made of degradable biomaterials, named biodegradable stents, will provide a temporary opening into a narrowed arterial vessel until the vessel remodels and will progressively disappear thereafter. Biodegradable stents made of metal have recently been progressed into preclinical tests in humans after their first introduction in early 2000s. By referring to patents and journal publications, this paper reviews the developments in biodegradable stents, with emphasis on those made of metals, starting from the first design ideas to validation testing.

Prevalence of pathological gambling and related problems among College students in the Quebec metropolitan area

The prevalence of pathological gambling and problems associated with it were measured among 1,471 students of three colleges in the Quebec city metropolitan area. Almost 90% of the students had gambled and 21.7% of the students engage in this behaviour once a week or more. The prevalence of pathological gamblers was found to be 2.8% for the entire sample. The percentage of pathological gamblers was much higher among males (5.7%) than females (0.6%). The results indicate that pathological gambling is associated with economic, professional and interpersonal problems. The discussion addresses the implications of the present findings and suggests avenues for future research.

Iron–manganese: new class of metallic degradable biomaterials prepared by powder metallurgy

Abstract An Fe–35 wt-%Mn alloy, aimed to be used as a metallic degradable biomaterial for stent applications, was prepared via a powder metallurgy route. The effects of processing conditions on the microstructure, mechanical properties, magnetic susceptibility and corrosion behaviour were investigated and the results were compared to those of the SS316L alloy, a gold standard for stent applications. The Fe35Mn alloy was found to be essentially austenitic with fine MnO particles aligned along the rolling direction. The alloy is ductile with a strength approaching that of wrought SS316L. It exhibits antiferromagnetic behaviour and its magnetic susceptibility is not altered by plastic deformation, providing an excellent MRI compatibility. Its corrosion rate was evaluated in a modified Hanks solution, and found superior to that of pure iron (slow in vivo degradation rate). In conclusion, the mechanical, magnetic and corrosion characteristics of the Fe35Mn alloy are considered suitable for further development of a new class of degradable metallic biomaterials.

Mechanical properties and microstructure of new magnesium-lithium base alloys

Magnesium-lithium base alloys containing aluminum, silicon and rare-earth additions have been prepared by melting and solidification in a low-carbon steel crucible, homogenized at 350°C and extruded at the same temperature. The distribution of alloying elements in homogenized specimens was determined and the microstructure of these alloys characterized. The mechanical properties were measured and compared with those of similar alloys.

Degradable metallic biomaterials: Design and development of Fe–Mn alloys for stents

Designing materials having suitable mechanical properties and targeted degradation behavior is the key for the development of biodegradable materials for medical applications, including stents. A series of Fe-Mn alloys was developed with the objective to obtain mechanical properties similar to those of stainless steel 316L and degradation behavior more suited than pure iron. Four alloys with Mn content ranging between 20 and 35 wt % were compared in this study. Their microstructure, mechanical properties, magnetic properties as well as degradation behavior were carefully investigated. Results show that their microstructure is mainly composed of gamma phase with the appearance of epsilon phase in alloys having a lower Mn content. The yield strength and elongation of alloys was comprised between 234 MPa and 32% for Fe-35%Mn alloy to 421 MPa and 7.5% for the Fe-20%Mn alloy. All alloys show similar magnetic susceptibility ( approximately 1.8 x 10(-7) m(3)/kg) in the quenched condition. This magnetic susceptibility remains constant after plastic deformation for all the tested alloys except for the Fe-20%Mn alloy. The corrosion rate was higher than pure iron. Among the alloys studied in this work, the Fe-35%Mn alloy shows mechanical properties and degradation behavior closely approaching those required for biodegradable stents application.

Gambling among primary school students.

This study identifies the gambling behavior of 1,320 primary school students aged 8 to 12 of the 4th, 5th and 6th grades. Eighty-six percent admitted to having, at some time or another, bet money. Lotteries are the most popular form of gambling for this age group. Sixty-one percent of these students gamble with lotteries. In descending order of popularity, other games played by students were: bingo, card-playing for money, bets on sports, wagering on specific events, video gambling (video poker and slot machines), and finally betting on games of skill. Gambling behaviors differed according to gender. More than 40% of respondents reported gambling once a week or more for at least one game. Because of the early development of gambling behavior in children, prevention programs for pathological gambling should be implemented as early as the fourth grade.

Characterization and performance of laser melted AZ91D and AM60B

Laser melting can be used to alter the surface of alloys and produce a fine microstructure, usually improving corrosion resistance. In the present work, a pulsed Nd:YAG laser was used to melt and rapidly quench the surface of die cast AZ91D and AM60B magnesium alloys with the objective of improving the corrosion resistance in salt-water (NaCl) solution. The corrosion of AZ91D and AM60B was not significantly reduced by laser melting even though the microstructure of both alloys was refined but a close examination of corroded surfaces gave indications about some corrosion enhancing factors. The physical aspect of corroded surfaces and the microstructure of laser melted specimens are presented along with the results of corrosion tests.

Correction of inflated responsibility in the treatment of obsessive-compulsive disorder

This study evaluates the efficacy of a cognitive treatment for obsessive-compulsive disorder (OCD). Four patients with OCD whose major complaints were checking rituals were treated in a multiple baseline across subjects design. Cognitive correction targeted inflated responsibility, without any exposure or response prevention. All subjects reported a clinically significant decrease in interference caused by rituals, a 52-100% reduction in Y-BOCS scores, and a decrease in perceived responsibility. Therapeutic gains were maintained at follow-up (6 and 12 months) for three patients. Results suggest that cognitive therapy targeting inflated responsibility is a promising alternative to exposure-based treatment.

Degradation Behaviour of Metallic Biomaterials for Degradable Stents

The short-term need of scaffolding function of stent and the prevention of potential longterm complication of permanently implanted stent have directed to the original idea of biodegradable stent. Selecting and developing materials showing appropriate mechanical and degradation properties are key steps for the development of this new class of medical devices. Therefore, the study of their in vitro degradation behaviour is mandatory for the selection of potential candidate materials suited in vivo. In this work, the degradation behaviour of current studied biodegradable metals including three magnesium alloys (Mg, AM60B and AZ91D), pure iron and Fe-35Mn was investigated. The tests were performed in a simulated blood plasma solution at 37±0.1 oC, using three different methods; potentiodynamic polarization, static immersion, and dynamic test in a test-bench which mimics the flow condition in human coronary artery. Degradation rate was determined as ion release rate measured by using atomic adsorption spectroscopy (AAS) and also estimated from weight loss and corrosion current. Surface morphology and chemical composition of corroded specimens were analyzed by using SEM/EDS. The three degradation methods provide consistent results in corrosion tendency, where Mg showed the highest corrosion rate followed by AZ91D, AM60B, Fe-35Mn and iron. Potentiodynamic polarization gives a rapid estimation of corrosion behaviour and rate. Static immersion test shows the effect of time on the degradation rate and behaviour. Dynamic test provides the closest approach to the environment after stent implantation and its results show the effect of the flow on the materials degradation. In conclusion, the three investigated methods can be applied for screening, selecting and validating materials for degradable stent application before going further to in vivo assessments.

Psychological Characteristics of Volunteers in Studies on Gambling

Advertisements were published in local newspapers asking for volunteers to participate in a study on gambling. A battery of eleven questionnaires was mailed to the subjects assessing pathological gambling behavior, sociodemographic characteristics, motivation to gamble, erroneous perceptions about gambling, superstitious beliefs, depressive symptoms, social anxiety and avoidance, alcohol and drug abuse, problem-solving skills, and marital satisfaction. Subjects received