Integrability and Ergodicity of Classical Billiards in a Magnetic Field

We consider classical billiards in plane, connected, but not necessarily bounded domains. The charged billiard ball is immersed in a homogeneous, stationary magnetic field perpendicular to the plane. The part of dynamics which is not trivially integrable can be described by a "bouncing map". We compute a general expression for the Jacobian matrix of this map, which allows to determine stability and bifurcation values of specific periodic orbits. In some cases, the bouncing map is a twist map and admits a generating function which is useful to do perturbative calculations and to classify periodic orbits. We prove that billiards in convex domains with sufficiently smooth boundaries possess invariant tori corresponding to skipping trajectories. Moreover, in strong field we construct adiabatic invariants over exponentially large times. On the other hand, we present evidence that the billiard in a square is ergodic for some large enough values of the magnetic field. A numerical study reveals that the scattering on two circles is essentially chaotic.Comment: Explanations added in Section 5, Section 6 enlarged, small errors corrected; Large figures have been bitmapped; 40 pages LaTeX, 15 figures, uuencoded tar.gz. file. To appear in J. Stat. Phys. 8

Temporary Intervention and Long Term Legacy: Lessons from London Case Studies

The paper explores the issue of temporary projects on vacant land focusing on London in the 2007-2012 downturn. Using a case study approach, a link has been identified between the success of temporary projects and a longer-term vision, as well as a move toward better integration between temporary occupants and developer/land-owner. Within this paradox the whole idea of temporariness is put under question, as is the traditional mainstream depiction of bottom-up in opposition to top-down action. These trends are contextualised within the dynamics of recession that has triggered new types of creative conversations between parties traditionally considered in opposition and may contribute to reframing urban development as an incremental, organic and collaborative process

Constraints and prospects for contraceptive service provision to young people in Uganda: providers' perspectives

<p>Abstract</p> <p>Background</p> <p>Unintended pregnancies lead to unsafe abortions, which are a leading cause of preventable maternal mortality among young women in Uganda. There is a discrepancy between the desire to prevent pregnancy and actual contraceptive use. Health care providers' perspectives on factors influencing contraceptive use and service provision to young people aged 15-24 in two rural districts in Uganda were explored.</p> <p>Methods</p> <p>Semi-structured questionnaires were used for face- to-face interviews with 102 providers of contraceptive service at public, private not-for-profit, and private for-profit health facilities in two rural districts in Uganda. Descriptive and inferential statistics were used in the analysis of data.</p> <p>Results</p> <p>Providers identified service delivery, provider-focused, structural, and client-specific factors that influence contraceptive use among young people. Contraceptive use and provision to young people were constrained by sporadic contraceptive stocks, poor service organization, and the limited number of trained personnel, high costs, and unfriendly service. Most providers were not competent enough to provide long-acting methods. There were significant differences in providers' self-rated competence by facility type; private for-profit providers' competence was limited for most contraceptives. Providers had misconceptions about contraceptives, they had negative attitudes towards the provision of contraceptives to young people, and they imposed non-evidence-based age restrictions and consent requirements. Thus, most providers were not prepared or were hesitant to give young people contraceptives. Short-acting methods were, however, considered acceptable for young married women and those with children.</p> <p>Conclusion</p> <p>Provider, client, and health system factors restricted contraceptive provision and use for young people. Their contraceptive use prospects are dependent on provider behavior and health system improvements.</p

Impact of Antiretroviral Therapy on Incidence of Pregnancy among HIV-Infected Women in Sub-Saharan Africa: A Cohort Study

A multicountry cohort study in sub-Saharan Africa by Landon Myer and colleagues reveals higher pregnancy rates in HIV-infected women on antiretroviral therapy (ART)

Quality of Care in Contraceptive Services Provided to Young People in Two Ugandan Districts: A Simulated Client Study

BACKGROUND: Low and inconsistent use of contraceptives by young people contributes to unintended pregnancies. This study assessed quality of contraceptive services for young people aged 15-24 in two rural districts in Uganda. METHODS: Five female and two male simulated clients (SCs) interacted with 128 providers at public, private not-for-profit (PNFP), and private for profit (PFP) health facilities. After consultations, SCs were interviewed using a structured questionnaire. Six aspects of quality of care (client's needs, choice of contraceptive methods, information given to users, client-provider interpersonal relations, constellation of services, and continuity mechanisms) were assessed. Descriptive statistics and factor analysis were performed. RESULTS: Means and categorized quality scores for all aspects of quality were low in both public and private facilities. The lowest quality scores were observed in PFP, and medium scores in PNFP facilities. The choice of contraceptive methods and interpersonal relations quality scores were slightly higher in public facilities. Needs assessment scores were highest in PNFP facilities. All facilities were classified as having low scores for appropriate constellation of services. Information given to users was suboptimal and providers promoted specific contraceptive methods. Minority of providers offered preferred method of choice and showed respect for privacy. CONCLUSIONS: The quality of contraceptive services provided to young people was low. Concurrent quality improvements and strengthening of health systems are needed

Women's sexual health and contraceptive needs after a severe obstetric complication ("near-miss"): a cohort study in Burkina Faso

BACKGROUND: Little is known about the reproductive health of women who survive obstetric complications in poor countries. Our aim was to determine how severe obstetric complications in Burkina Faso affect reproductive events in the first year postpartum. METHODS: Data were collected from a prospective cohort of women who either experienced life threatening (near-miss) pregnancy-related complications or an uncomplicated childbirth, followed from the end of pregnancy to one year postpartum or post-abortum. Documented outcomes include menses resumption, sexual activity resumption, dyspareunia, uptake of contraceptives, unmet needs for contraception and women's reproductive intentions.Participants were recruited in seven hospitals between December 2004 and March 2005 in six towns in Burkina Faso. RESULTS: Reproductive events were associated with pregnancy outcome. The frequency of contraceptive use was low in all groups and the method used varied according to the presence or not of a live baby. The proportion with unmet need for contraception was high and varied according to the time since end of pregnancy. Desire for another pregnancy was highest among near-miss women with perinatal death or natural abortion. Women in the near-miss group with induced abortion, perinatal death and natural abortion had significantly higher odds of subsequent pregnancy. Unintended pregnancies were observed mainly in women in the near-miss group with live birth and the uncomplicated delivery group. CONCLUSIONS: Considering the potential deleterious impact (on health and socio-economic life) of new pregnancies in near-miss women, it is important to ensure family planning coverage includes those who survive a severe complication

Limits to modern contraceptive use among young women in developing countries: a systematic review of qualitative research

<p>Abstract</p> <p>Background</p> <p>Improving the reproductive health of young women in developing countries requires access to safe and effective methods of fertility control, but most rely on traditional rather than modern contraceptives such as condoms or oral/injectable hormonal methods. We conducted a systematic review of qualitative research to examine the limits to modern contraceptive use identified by young women in developing countries. Focusing on qualitative research allows the assessment of complex processes often missed in quantitative analyses.</p> <p>Methods</p> <p>Literature searches of 23 databases, including Medline, Embase and POPLINE^®, were conducted. Literature from 1970–2006 concerning the 11–24 years age group was included. Studies were critically appraised and meta-ethnography was used to synthesise the data.</p> <p>Results</p> <p>Of the 12 studies which met the inclusion criteria, seven met the quality criteria and are included in the synthesis (six from sub-Saharan Africa; one from South-East Asia). Sample sizes ranged from 16 to 149 young women (age range 13–19 years). Four of the studies were urban based, one was rural, one semi-rural, and one mixed (predominantly rural). Use of hormonal methods was limited by lack of knowledge, obstacles to access and concern over side effects, especially fear of infertility. Although often more accessible, and sometimes more attractive than hormonal methods, condom use was limited by association with disease and promiscuity, together with greater male control. As a result young women often relied on traditional methods or abortion. Although the review was limited to five countries and conditions are not homogenous for all young women in all developing countries, the overarching themes were common across different settings and contexts, supporting the potential transferability of interventions to improve reproductive health.</p> <p>Conclusion</p> <p>Increasing modern contraceptive method use requires community-wide, multifaceted interventions and the combined provision of information, life skills, support and access to youth-friendly services. Interventions should aim to counter negative perceptions of modern contraceptive methods and the dual role of condoms for contraception and STI prevention should be exploited, despite the challenges involved.</p

A 3-year multicentre randomized controlled trial of etonogestrel- and levonorgestrel-releasing contraceptive implants, with non-randomized matched copper-intrauterine device controls

STUDY QUESTION Is there any difference in the clinical performance of the 3-year one-rod etonogestrel (ENG)- and the 5-year two-rod levonorgestrel (LNG)-releasing contraceptive implants during 3 years of insertion, and between implant and intrauterine device (IUD) contraception, in particular complaints possibly related to hormonal contraceptives? SUMMARY ANSWER The cumulative contraceptive effectiveness after 3 years and method continuation through 2.5 years were not significantly different between ENG and LNG implants, but both outcomes were significantly worse in the non-randomized age-matched group of IUD users than in the combined implant group. WHAT IS KNOWN ALREADY ENG- and LNG-releasing implants are safe and highly efficacious contraceptives with pregnancy rates reported to be 0.0-0.5 per 100 women-years (W-Y). No head-to-head comparative study of the two implants has been undertaken, and little information is available on comparisons of complaints of side effects of implant and copper IUD users. STUDY DESIGN, SIZE, DURATION This was an open parallel group RCT with 1:1 allocation ratio of the ENG and the LNG implants with non-randomized control group of women choosing TCu380A IUD to address lack of reliable data on common side effects typically attributed to the use of progestogen-only contraceptives. After device(s) placement, follow-ups were at 2 weeks, 3 and 6 months, and semi-annually thereafter for 3 years or until pregnancy, removal or expulsion of the implant/IUD occurred. PARTICIPANTS, SETTING, METHODS The study took place in family planning clinics in Brazil, Chile, Dominican Republic, Hungary, Thailand, Turkey and Zimbabwe. Women seeking long-term contraception were enlisted after an eligibility check and informed consent, and 2982 women were enrolled: 1003, 1005 and 974 in the ENG-implant, LNG-implant and IUD groups, respectively; 995, 997 and 971, respectively, were included in the per protocol analysis reported here. MAIN RESULTS AND THE ROLE OF CHANCE ENG and LNG implants each had the same 3-year cumulative pregnancy rate of 0.4 per 100 W-Y [95% confidence interval (CI) 0.1-1.4]. A weight of ≥70 kg at admission was unrelated to pregnancy. Method continuation rates for ENG and LNG implants at 2.5 years were 69.8 (95% CI 66.8-72.6) and 71.8 per 100 W-Y (68.8-74.5), and at 3 years 12.1 (95% CI 5.2-22.0) and 52.0 per 100 W-Y (95% CI 41.8-61.2), respectively. Bleeding disturbances, the most frequent reason for method discontinuation, were significantly more common in the ENG group [16.7 (95% CI 14.4-19.3)] than in the LNG group [12.5 (95% CI 10.5-14.9)] (P 0.019). The 3-year cumulative loss to follow-up was lower in the ENG- than in the LNG-implant group, 8.1 (95% CI 6.4-10.2) and 14.4 per 100 W-Y (95% CI 12.1-17.1), respectively. The median duration of implant removal was 50 s shorter among women with ENG than among women with LNG implant (P < 0.0001). In the observational comparison between IUD and implant users, the 3-year relative risk for pregnancy in IUD group compared with the combined implant group was 5.7 per 100 W-Y (95% CI 4.4-7.3) (P = 0.0003). The 3-year expulsion rate of the IUD was 17.8 per 100 W-Y (95% CI 14.5-21.9), while the discontinuation rate for bleeding disturbances was 8.5 (95% CI 6.7-10.9). Frequency of complaints of headache and dizziness was not significantly different between implant and IUD users (P = 0.16 and 0.77, respectively), acne and bleeding irregularities were more frequent among implant users (P < 0.0001), while heavy bleeding and lower abdominal pain occurred more often among IUD than implant users (P < 0.0001). LIMITATIONS, REASONS FOR CAUTION Few women were ≤19 years old or nulligravida, the proportion of implant users ≥70 kg was <20% and <8% were obese. WIDER IMPLICATIONS OF THE FINDINGS Findings of the study can inform policy makers and clinicians about choice of implant, but also about TCu380A IUD in relation to implants. STUDY FUNDING/COMPETING INTEREST(S) UNDP/UNFPA/WHO/UNICEF/World Bank Special Programme of Research, Development and Research Training in Human Reproduction (HRP), Department of Reproductive Health and Research (RHR), World Health Organization (WHO). This report contains the views of an international expert group and does not necessarily represent the decisions or the stated policy of the WHO. TRIAL REGISTRATION ISRCTN33378571 registered on 22 March 2004. The first participant was enrolled on 12 May 200

Non-pharmacological management of osteoporosis: a consensus of the Belgian Bone Club

This consensus article reviews the various aspects of the non-pharmacological management of osteoporosis, including the effects of nutriments, physical exercise, lifestyle, fall prevention, and hip protectors. Vertebroplasty is also briefly reviewed. Non-pharmacological management of osteoporosis is a broad concept. It must be viewed as an essential part of the prevention of fractures from childhood through adulthood and the old age. The topic also includes surgical procedures for the treatment of peripheral and vertebral fractures and the post-fracture rehabilitation. The present document is the result of a consensus, based on a systematic review and a critical appraisal of the literature. Diets deficient in calcium, proteins or vitamin D impair skeletal integrity. The effect of other nutriments is less clear, although an excessive consumption of sodium, caffeine, or fibres exerts negative effects on calcium balance. The deleterious effects of tobacco, excessive alcohol consumption and a low BMI are well accepted. Physical activity is of primary importance to reach optimal peak bone mass but, if numerous studies have shown the beneficial effects of various types of exercise on bone mass, fracture data as an endpoint are scanty. Fall prevention strategies are especially efficient in the community setting, but less evidence is available about their effectiveness in preventing fall-related injuries and fractures. The efficacy of hip protectors remains controversial. This is also true for vertebroplasty and kyphoplasty. Several randomized controlled studies had reported a short-term advantage of vertebroplasty over medical treatment for pain relief, but these findings have been questioned by recent sham-controlled randomized clinical studies