The electron mechanics of induction acceleration

The radial and axial motions of electrons in the betatron are described by means of a potential function of forces. Previously reported conditions of equilibrium, stability and damping of oscillations are derived for the region of parabolic variation of the potential. Extension of the analysis to, non-parabolic regions gives an account of the injection in conventional instruments in better agreement with experiment, particularly in regard to higher voltages of injection.Space charge limitations are discussed with the help of the Laplacian of the potential of forces.By means of an additional radial electric field electrons can be introduced as in the magnetron, without any asymmetry inherent in the conventional betatron circumferential injector. The analysis of the conditions of equilibrium and stability, greatly facilitated in this case by the notion of potential, shows that no substantial improvement in space charge limitations can be expected and that the required variations between the flux linking the electron orbits and the magnetic and electric fields at the orbits are difficult to realize on account of their complexity and narrow tolerances. The X-ray output of a small experimental double yoke instrument was measured by a phototube multiplier viewing an irradiated fluorescent screen and gave evidence of multiple group electron capture.     

网络教育资源在化学研究性学习中的应用

一、问题的提出 新一轮基础教育课程改革提出:"大力推进信息技术在教学过程中的普遍运用,促进信息技术与学科课程的整合,逐步实现教学内容的呈现方式、学生的学习方式和师生互动方式的变革,倡导以自主、合作、研究为主多元学习方式".     

Juggling competing activities: academic staff as doctoral candidates

ABSTRACT

This article explores the experiences of a group of established academic staff in New Zealand and the UK, as they undertake a doctorate in their home institutions. Our interest is in how individuals negotiate this dual status from a cultural-historical activity theory (CHAT) stance that explores how rules, tools, community and divisions of labour, and interacting activity systems, shape doctoral experiences. The focus in this article, having analysed their detailed narrative accounts, is on how academics experience three interdependent activity systems: those surrounding the thesis, the institutional context, and the home-life spheres. Issues related to time, workload and supervision issues, variability in collegial support and impact on personal priorities and time emerged. There is a range of particularities – from easy access to resources/supervisors to inflexible institutional regulations – applicable to this group of doctoral candidates. Negotiating life as an academic with concurrent doctoral candidature provides positive outcomes in terms of teaching, research confidence and general personal and professional development. However, a range of difficulties can also be encountered, particularly in relation to personal and professional relationships, and workload management.     

Remote effects of lower limb stretching: preliminary evidence for myofascial connectivity?

The skeletal muscles and the fibrous connective tissue form an extensive, body-wide network of myofascial chains. As fascia can modify its stiffness, strain transmission along these meridians is supposable. The goal of this trial therefore was to collect pilot data for potential remote effects of lower limb stretching on cervical range of motion (ROM). Twenty-six healthy participants (30 ± 6 years) were included in the matched-pairs intervention study. One group (n = 13) performed three 30 s bouts of static stretching for the gastrocnemius and the hamstrings, respectively. An age- and sex-matched control group (CG; n = 13) remained inactive. Pre- and post-intervention, maximal cervical ROM in flexion/extension was assessed. A repeated measures ANOVA revealed systematic differences between groups (P < .05). ROM increased following stretching (143.3 ± 13.9 to 148.2 ± 14°; P < .05) but remained unchanged in the CG (144.6 ± 16.8 to 143.3 ± 16.8°; P > .05). Our data point towards existence of a strain transfer along myofascial meridians. Further randomised controlled studies on conditions, factors and magnitude of tensile transmission are warranted.     

“Montrose” child life protection unit: A treatment and assessment model in child abuse intervention

In New South Wales, Australia, the Department of Youth and Community Services is empowered by statute to deal with cases of child abuse and neglect. Its child protection services include the Montrose Child Life Protection Unit which is designed to support and complement the work of both the Intake Service, Field Service and most importantly the work of child protective facilities in the community. The service has intake crisis counselling and call out resources; maintains a central register; provides a facility for crisis residential care for children and families, diagnostic assessment, and a day programme. The emphasis in service delivery in New South Wales in the area of child protection is on multidisciplinary intervention. The Department of Youth and Community Services is involved in promoting interagency cooperation and co-ordination. Over and above a philosophy that underlies service delivery is the Montrose Unit's involvement in sensitising the community to the difficult and often demanding role of parenting. Montrose represents an attempt to create an environment where parenting myths can be examined from a reality base and strategies implemented for reeducation.