Photodarkening and partial photobleaching: application to dichromated gelatin.

Photodarkening or partial photobleaching of photochromic solid media is described by means of an approximated analytical equation. The equation shows that the effective rate of the photochemical reaction is proportional to the square root of the final transmittance of the illuminated layer. The model is applied to describe the photodarkening of dichromated gelatin at 488 nm.

Photochromic behavior of spiropyran in polymer matrices.

The photoexcitation, relaxation, and optical erasure regimes of spiropyran- (SP-) doped polymer films were studied. Cellulose acetate, poly(vinyl acetate), and poly(methyl methacrylate) (PMMA) were used as host polymer matrices. We studied the character of the photoreaction for both coloring and bleaching processes. Reversible holographic recording in SP-PMMA films and the origin of the photochemical fatigue was studied upon repeated UV-visible irradiation cycles.

Reference values of plasma apolipoproteins A-I and B, and association with nonlipid risk factors in the populations of two Canadian provinces: Quebec and Saskatchewan. Canadian Heart Health Surveys Research Group.

OBJECTIVE: To determine the population distribution of apolipoproteins A-I and B, and the relationship of apolipoprotein B to lipid risk factors for coronary artery disease. DESIGN: A stratified random sample of men and women aged 18 to 74 years selected from the provinces of Saskatchewan and Quebec in 1989 and 1990. OUTCOME MEASURES: Plasma concentrations of apolipoproteins A-I and B, triglycerides, low density lipoprotein cholesterol, high density lipoprotein cholesterol and nonhigh density lipoprotein cholesterol for subjects who provided a fasting blood sample. MAIN RESULTS: Apolipoprotein B mean values increased with age from 0.80 g/L at age 18 to 24 years to a maximum of 1.16 g/L in the 45 to 54 year age group for men. For women, the values increased more gradually from 0.81 g/L for ages 18 to 24 to 1.19 g/L at ages 65 to 74 years. The distribution of apolipoprotein A-I was unrelated to age. Means for men varied from 1.35 g/L to 1.42 g/L and for women from 1.50 g/L to 1.61 g/L. Apolipoprotein B was strongly correlated with nonhigh density lipoprotein cholesterol (r2=0.89), and this was used to define apolipoprotein B concentrations less than 1.04 g/L as indicating low risk for coronary artery disease, from 1.04 g/L to less than 1.22 g/L as moderate risk, from 1.22 g/L to less than 1.40 g/L as high risk, and 1.40 g/L or greater as very high risk. The prevalence of high risk plasma apolipoprotein B levels was higher in men and women with triglycerides greater than 2.3 mmol/L. Apolipoprotein A-I was strongly correlated with high density lipoprotein cholesterol (r2=0.67), and this was use to identify apolipoprotein A-I concentrations of less than 1.20 g/L as a risk factor and 1.65 g/L or greater as an antirisk factor for coronary artery disease. The prevalence of apolipoprotein A-I of less than 1. 20 g/L was 19% in men and 6% in women, whereas the prevalence of apolipoprotein AI 1.65 g/L or greater was 9% in men and 28% in women. CONCLUSION: Reference values for plasma apolipoproteins A-I and B in a Canadian population random sample are given. Plasma apolipoprotein B and apolipoprotein A-I provide information that is complementary to that provided by low density lipoprotein and high density lipoprotein cholesterol levels.

Degenerate four-wave mixing geometry in thin-film waveguides for nonlinear material characterization.

We demonstrate experimentally a new degenerate four-wave mixing (DFWM) geometry in waveguides that permits the simultaneous determination of the nonlinear refractive index, the absorption, and the response time of the thin-film materials. The geometry consists of two guided pumps in a planar waveguide with an unguided probe. We achieve nonlinear characterization by measuring only the DFWM signal and the guided pump power at the waveguide output. The technique has been tested on a polymeric film (di-alkylaminonitro- stilbene).

[Medical books in the possession of Canadian health professionals in the seventeenth and eighteenth centuries]. / Le livre médical au sein du corps de santé canadien aux XVIIe et XVIIIe siècles.

This study, based on the data found in notarized inventories of the deceased, ex-libris or bookplates, and listings of books in institutional libraries, shows clearly that circulation of medical books, generally imported from Europe, was next to non-existent in the general public but growing steadily in the Canadian medical corps during the seventeenth and eighteenth centuries. This growth is proof of the increasing professionalization of the medical corps and institutionalization of medical know-how and expertise during that period.

Factors related to outcome following a work hardening program.

The purpose of this study was to determine factors related to a return to work following the completion of a work hardening program. Data from the Workers' Compensation Board of Alberta Millard Rehabilitation Centre for 1527 discharges, collected over 22 months, were examined retrospectively. Factors related to return to work were compared bivariately using logistic regression procedures. A multiple logistic regression model for return to work was also determined. The principle predictor of return to work was job-attached status to the pre-injury employer. Other factors related to return to work were education, primary diagnosis, injury to admission time, job attachment to the pre-accident employer, employer's annual payroll, and vocational direction. Due to the strength of the association between job-attached status to the pre-injury employer and a return to work, it was concluded that attempts to maintain this relationship should be a priority for rehabilitation providers and insurance carriers.

Physical characterization of unimplanted gel filled breast implants. Should old standards be revisited?

Physical characterization of unimplanted gel filled mammary prostheses was undertaken using both destructive and non-destructive test methods. Physical properties measured included mass, volume, optical transmittance, coefficient of kinetic friction, mechanical stiffness, dynamic response to a stationary random vibration, bursting strength, elasticity of the envelopes, and nuclear magnetic resonance relaxation times. The data obtained from this study will provide reference points for quantifying the rate of degradation of prostheses in past and current clinical use. Some of the test methods are suitable for use as routine quality control procedures to improve the uniformity of the properties and performance of breast prostheses. This investigation also showed that some currently used prostheses do not comply with the relevant American Society for Testing and Materials standards, or even with the manufacturers' own stated claims or specifications.

Computer-generated holograms on a metal ion-doped polymer system: contact copying.

Dichromated poly(acrylic acid) films with dimethyl formamide have been used as a real-time recording medium for volume transmission holograms. In this study a simple computer-generated holographic grating with a sinusoidal amplitude profile is copied onto this recording material by the contact-copying technique. The experimental setup for the contact copying of a computer-generated hologram (CGH) is explained, and the phase modulation is observed for a different exposure time. Theoretical and experimental diffraction efficiency values for the CGH copy are also evaluated. Photographs of the original and copy of the CGH on the photopolymer film are presented.

Modified holographic recording setup for photopolymerizable/flexible recording materials.

An improvement in the conventional holographic recording setup has been done for liquid (photopolymerizable) or flexible recording materials. The new vertical recording setup that comprises a horizontal substrate holder permits holographic recording on such materials without positioning them between two substrates, as has been done until now. This setup can be conveniently used for the fabrication of transmission, reflection, Fourier transform, and computer-generated holograms with few simple modifications as indicated.

Multiple beam generation using a stratified volume holographic grating.

The parameters of several stratified volume holographic gratings are optimized in order to obtain high diffraction efficiency beam spliters. Two-, three-, five-, seven-, and nine-beam fan-outs are theoretically studied and compared with what has been achieved by other means. With a simple optical setup, a fan-out element that generates seven beams of equal intensity is experimentally realized and a comparison with theory is made.

Smoking prevalence and associated risk factors in Canadian adults. Canadian Heart Health Surveys Research Group.

OBJECTIVE: To describe the prevalence and patterns of smoking among Canadian adults, the relation of smoking to other cardiovascular disease risk factors and the awareness of the causes of heart disease. DESIGN: Population-based cross-sectional surveys. SETTING: Nine Canadian provinces, from 1986 to 1990. PARTICIPANTS: A probability sample of 26,293 men and women aged 18 to 74 was selected from the health insurance registries in each province. Of these, 20,585 completed a questionnaire on smoking habits during a home interview. MAIN RESULTS: Approximately 29% of the Canadian population 18 years of age and over were regular cigarette smokers, and over 13% of regular smokers smoked more than 25 cigarettes per day. The proportion of women who had never smoked was higher (37%) than men (24%), except for young women aged 18 to 24. For all participants, there was a lower prevalence of high blood pressure and overweight among smokers than non-smokers. The prevalence of sedentary lifestyle, diabetes and elevated blood cholesterol was positively associated with smoking. The proportion of subjects who identified smoking as a cause of heart disease was higher among smokers, and over 90% believe that heart disease is preventable. CONCLUSION: Because smoking is positively associated with other cardiovascular risk factors, multifactorial and comprehensive approaches are needed in the implementation of cardiovascular disease prevention programs. Knowledge regarding the heart health hazards of smoking is high even among smokers. Motivational approaches that go beyond health risk messages are needed in cessation programs.

[Intervention framework of the Quebec Healthy Heart Demonstration Project]. / Le Cadre d'Intervention du Projet québécois de Démonstration en Santé du Coeur.

Cardiovascular diseases are Canada's primary cause of death and hospitalisation, and are the second major cause of restricted physical activity. Quebec province, with a mortality rate of 399/100,000, has figures even higher than the national average of 323/100,000, and 7 out of every 10 Quebecois present at least one of the major cardio-vascular risk factors. Following an exploratory task force on this question, the Canadian government initiated a partnership programme with the provinces wherein the federal government and provincial governments would each contribute one million Canadian dollars over a five year period for heart disease prevention programmes. Quebec province selected three different projects in which multifactorial, multisectorial community-based programmes were to be implemented. The sites chosen for the projects were: a rural region situated on the banks of the St. Laurence River, a Montreal suburban district, and a multi-ethnic, socio-economic disadvantaged community in downtown Montreal. Despite a common public health approach and the ultimate goal of improving heart health through the lowering of risk factors, each project had its own specific major intervention strategy and primary target population. The projects were linked by a study design to evaluate community and family mechanisms which favour the adoption of low risk behaviours. A coordinating committee was formed to supervise the overall project which included strategic planning, consultancy services to project staff, methodology, development and implementation, and evaluation. Each specific project team was free, however, to choose its particular orientations.(ABSTRACT TRUNCATED AT 250 WORDS)

A 12-month treatment of severe psoriasis with acitretin: results of a Canadian open multicenter study.

Both etretinate and its principal metabolite, acitretin, are efficacious in the treatment of psoriasis. Because patients with severe psoriasis often require chronic therapy, this study was undertaken to determine the efficacy, tolerability, and safety of acitretin in patients on continuous treatment for 12 months. The initial daily dose of 50 mg was taken for 4 weeks. Thereafter the dose was increased or decreased by 10 mg at monthly intervals (10 to 70 mg) to produce the optimal response with minimal toxicity. Seventy percent of the patients who completed 12 months of treatment showed marked improvement. All patients experienced adverse reactions; dry lips, hair loss, skin peeling, pruritus, and nail disorders were the most frequent. Fourteen patients were withdrawn from the study because of one or more intolerable adverse reactions.

Real time bleaching of methylene blue or thionine sensitized gelatin.

The kinetics of bleaching of methylene blue or thionine sensitized gelatin plates are investigated with a singlebeam exposure experiment. It is found that thionine bleaching can be modeled by a first-order theory; whereas, a higher-order theory is found necessary to explain methylene blue bleaching.

Real time hologram reinforcement demonstrated by thionine/PVA photoreducible thin layers.

Thionine dye dissolved in polyvinylalcohol matrix is a well-known photoreducible system that shows photochromism. Experiments on a real time hologram recording process performed by this system are presented here. During the reading process, a grating reinforcement was observed, and this phenomenon is qualitatively discussed.

Methylene blue sensitized gelatin: evidence of photodemethylation.

The dependence of diffraction efficiency of methylene blue sensitized gelatin gratings vs dye concentration is explained in terms of the aggregations tate of the dye.

Influence of the substrate temperature on the holographic properties of Se and SeGe thin films.

The effects of the substrate temperature (T(s)) on the optical constants of as-deposited Se and SeGe thin films and on the holographic recording properties of these films were investigated. The substrate temperature held between 35 degrees C and 50 degrees C during thin film deposition was identified as an appropriate means to improve the optical recording properties of these films.

Processing of holograms recorded in methylene blue sensitized gelatin.

The properties of gelatin films sensitized only with methylene blue are discussed, and a modified development process which gives higher diffraction efficiency for phase holograms recorded with a He-Ne laser is presented. The behavior of transmission and reflection gratings recorded in that medium is also studied.

Modulation transfer function measurements for thin layers of azo dyes in PVA matrix used as an optical recording material.

Diffraction efficiencies and characteristic erasure times were measured for two recording materials suitable for real-time holography and four-wave mixing. A study of real-time transmission volume grating formation was done in conjunction with polarization states of the writing beams for 30-microm thick layers. Modulation transfer function curves presented were obtained using a versatile device for which the spatial frequency domain was 500-4000 cycles/mm.