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Quasi-1D van der Waals materials, such as transition metal trichalcogenides, have strong covalent bonds in one direction and weaker bonds in cross-plane directions. They can be prepared as crystalline nanowires or nanoribbons consisting of 1D atomic threads, i.e., chains. We have examined the current carrying capacity of ZrTe3 nanoribbons using a set of structures fabricated by the shadow mask method. The bulk crystals were synthesized by the chemical vapor transport method and exfoliated onto Si/SiO2 substrates. It was found that ZrTe3 nanoribbons reveal an exceptionally high current density, on the order of ~100 MA/cm2, at the peak of the stressing DC current. The low-frequency noise was of 1/ ${f}$ type near room temperature ( ${f}$ is the frequency). The noise amplitude scaled with the resistance, following the trend established for other low-dimensional materials. The high current density in ZrTe3 can be attributed to the single-crystal nature of quasi-1D van der Waals materials. [ABSTRACT FROM AUTHOR]

There is widespread belief that our changing human relationships, nationally and globally, combined with huge advances in science and technology require public health to reassess its role and modus operandi. A key issue for public health is whether to focus on mechanisms relating to the health of individuals or to tackle the major determinants and problems. To achieve its goal of improving the health of the people, public health must develop the skills and attract the partners to address all factors that influence health.

About two-thirds of the world's population live in areas infested with dengue vectors, mainly Aedes aegypti. All four dengue viruses are circulating, sometimes simultaneously, in most of these areas. It is estimated that up to 80 million persons become infected annually although marked underreporting results in the notification of much smaller figures. Currently dengue is endemic in all continents except Europe and epidemic dengue haemorrhagic fever (DHF) occurs in Asia, the Americas and some Pacific islands. The incidence of DHF is much greater in the Asian countries than in other regions. In Asian countries the disease continues to affect children predominantly although a marked increase in the number of DHF cases in people over 15 years old has been observed in the Philippines and Malaysia during recent years. In the 1990's DHF has continued to show a higher incidence in South-East Asia, particularly in Viet Nam and Thailand which together account for more than two-thirds of the DHF cases reported in Asia. However, an increase in the number of reported cases has been noted in the Philippines, Lao People's Democratic Republic, Cambodia, Myanmar, Malaysia, India, Singapore and Sri Lanka during the period 1991-1995 as compared to the preceding 5-year period. In the Americas, the emergence of epidemic DHF occurred in 1981 almost 30 years after its appearance in Asia, and its incidence is showing a marked upward trend. In 1981 Cuba reported the first major outbreak of DHF in the Americas, during which a total of 344,203 cases of dengue were notified, including 10,312 severe cases and 158 deaths. The DHF Cuban epidemic was associated with a strain of dengue-2 virus and it occurred four years after dengue-1 had been introduced in the island causing epidemics of dengue fever. Prior to this event suspected cases of DHF or fatal dengue cases had been reported by five countries but only a few of them fulfilled the WHO criteria for diagnosis of DHF. The outbreak in Cuba is the most important event in the history of dengue in the Americas. Subsequently to it, in every year except 1983, confirmed or suspected cases of DHF have been reported in the Region. The second major outbreak in the Americas occurred in Venezuela in 1989 and since then this country has suffered epidemics of DHF every year. Between 1981 and 1996 a total of 42,246 cases of DHF and 582 deaths were reported by 25 countries in the Americas, 53% of which originated from Venezuela and 24% from Cuba. Colombia, Nicaragua and Mexico have each reported over 1,000 cases during the period 1992-1996. About 74% of the Colombian cases and 97% of the Mexican cases were reported during 1995-1996. A main cause of the emergence of DHF in the Americas was the failure of the hemispheric campaign to eradicate Aedes aegypti. Following a successful period that resulted in the elimination of the mosquito from 18 countries by 1962, the programme began to decline and as a result there was a progressive dissemination of the vector so that by 1997 with the exception of Canada, Chile and Bermuda, all countries in the Americas are infested. Other factors contributing to the emergence/re-emergence of dengue/DHF include the rapid growth and urbanization of populations in Latin America and the Caribbean, and increased travel of persons which facilitates dissemination of dengue viruses. Presently, all four dengue serotypes are circulating in the Americas, thus increasing the risk for DHF in this region.

With parental consent, we surveyed 942 students in grade 7 and 8 at the Ottawa Board of Education before the introduction of compulsory AIDS education. Television was seen as the most common and credible source of information about AIDS. Parents (by girls) and school nurse (by boys) were also seen as credible sources of information about AIDS. Boys seemed to know more about the transmission of AIDS than girls did. There was high awareness of condoms as an effective method of preventing the spread of AIDS. Avoidance of sexual intercourse as an effective preventive measure was less well known. AIDS education in school should emphasize abstinence as well as barrier methods as effective methods in preventing AIDS, and utilize the media, parents and family in educating students about AIDS.

In a random, mailed survey, 730 adolescents supplied information on their patterns and preferences for health care. The majority of respondents reported that they usually receive medical care from a private physician. Girls consulted physicians more frequently than boys, but there was no significant variation by age or social group. As the age of the respondent increased, the proportion visiting pediatricians decreased. When asked what they liked and disliked about their physician, respondents placed great emphasis upon the personal characteristics of the practitioner. Long waiting periods were the most common complaint. A significant proportion of adolescents with health concerns do not consult a health professional, even in cases where efficacious treatment may be available. Nervous/emotional problems, obesity, and birth control are concerns of adolescents which should be discussed with health professionals.

We conducted a telephone survey of 102 randomly selected Ottawa family physicians to determine their attitudes and practices regarding the treatment of hypercholesterolemia. Of the 102, 56% routinely measured serum cholesterol levels in all their patients over the age of 30 years, and 24% did so for patients in more restricted age ranges. The level at which they started dietary therapy averaged 6.95 mmol/L (270 mg/dl); for 25% it was less than 6.22 mmol/L (240 mg/dl). The level at which they started drug therapy averaged 8.9 mmol/L (345 mg/dl); for only 15% was it 7.23 mmol/L (280 mg/dl) or less. Two-thirds were unable to give numerical values to the serum cholesterol levels at which they started diet therapy, and 38% used the upper limits of laboratory normal values as an indication to start therapy. Our findings contrast markedly with results reported for US family physicians, who treat hypercholesterolemia much more aggressively. The variability in practices must be addressed if public campaigns to lower serum cholesterol levels are to be undertaken.

Health promotion and treatment programs for adolescents must be tailored to the unique concerns and needs of this population. A questionnaire was mailed to 1000 adolescents aged 12 to 20 years in the Ottawa-Carleton region; 729 responded, giving information on their health concerns and habits. The teenagers reported worrying mostly about chronic conditions such as acne, menstrual disorders, emotional problems, dental problems and being overweight. Some of these conditions can be treated if care is sought. The psychosocial problems most important to the adolescents were school and family problems. Girls tended to report health concerns more often than boys, but there was little variation by age or social group. Although the proportions of adolescents who were smoking cigarettes, drinking alcoholic beverages or using "recreational" drugs or who had ever had sexual intercourse were relatively high, the number of respondents who perceived such habits as health problems was low. There was a low level of concern about birth control among the respondents, including those who indicated that they had had sexual intercourse. The fact that significantly more girls than boys reported that they smoked and had engaged in sexual intercourse suggests specific targets for health promotion activities.