STRETCHY ELECTRONICS. Hierarchically buckled sheath-core fibers for superelastic electronics, sensors, and muscles.

Superelastic conducting fibers with improved properties and functionalities are needed for diverse applications. Here we report the fabrication of highly stretchable (up to 1320%) sheath-core conducting fibers created by wrapping carbon nanotube sheets oriented in the fiber direction on stretched rubber fiber cores. The resulting structure exhibited distinct short- and long-period sheath buckling that occurred reversibly out of phase in the axial and belt directions, enabling a resistance change of less than 5% for a 1000% stretch. By including other rubber and carbon nanotube sheath layers, we demonstrated strain sensors generating an 860% capacitance change and electrically powered torsional muscles operating reversibly by a coupled tension-to-torsion actuation mechanism. Using theory, we quantitatively explain the complementary effects of an increase in muscle length and a large positive Poisson's ratio on torsional actuation and electronic properties.

Childhood and adolescent leukaemia in a North American population.

OBJECTIVE: This was to describe and analyse incidence and survival data on childhood leukaemias. SAMPLE: Incident leukaemia cases aged 0-19 from the cancer registry holdings of the province of Saskatchewan for the 60-year period 1932-1991 are the subject of this descriptive report. METHODS: Age-adjusted, age-specific, histologic-type specific, sex-specific, and cohort-specific incidence trends were reviewed. Univariate and multivariate survival analyses explored the effects of time period, age at diagnosis, gender, and histologic type. RESULTS: Acute lymphocytic leukaemia (ALL) occurred more commonly in males and before the age of five; the 1982-1991 age-adjusted incidence is 3.1/100,000. Increasing incidence has been consistently noted, but has attenuated since 1971. The relative risk of developing ALL in the first 9 years of life, using children born from 1944 to 1948 as baseline, increased with each successive 5-year birth cohort until 1969-1973; since then the risk has been stable. Other histologic types were rare; over 60 years there were only 85 cases that could be grouped as acute non-lymphocytic leukaemias (ANLL); the 1982-1991 age-adjusted ANLL incidence is 0.6/100,000. A dramatic improvement in survival was seen over the last six decades, primarily for ALL. In ALL, children under five have better survival than older children and adolescents; the reverse is true for ANLL. CONCLUSIONS: ALL and ANLL are distinctive diseases clinically and the epidemiological findings are likewise distinctive. Our current ALL patterns are consonant with a number of other published reports. However, our small numbers of ANLL limit inferences.

Assessing needs for palliative care education of primary care physicians: results of a mail survey.

The purpose of this study was to determine continuing education needs in the area of palliative care, as defined by family practice physicians. The methodology consisted of an anonymous questionnaire mailed in October, 1991, to all family practitioners in the city of Regina, Saskatchewan having admission privileges at any of the city's three hospitals. Replies were received from 31.1% of that population; the worst-case estimate is that about half of the city's palliative care caseload in 1991 was under the care of these respondents. In a priority-ranking format, physicians rated pain assessment and management as the patients' greatest need and their greatest continuing education need. Although emotional support and communication were highly ranked among other needs of patients, they were not highly ranked among education needs. Grand rounds was indicated as the educational venue of preference. Longer, more intensive educational formats were not selected. Communication of palliative status, including "Do not resuscitate" status, has reportedly become a routine practice. We have concluded that palliative care education should focus on the felt needs of family practice physicians for technical competence in pain assessment and management, using abbreviated formats. Cautious introduction of content areas and educational methods more likely to address patient needs is warranted. A one- or two-day workshop devoted to bereavement guidance might be a concrete focus for communication-oriented continuing education.