On the 2-extendability of planar graphs

AbstractSome sufficient conditions for the 2-extendability of k-connected k-regular (k⩾3) planar graphs are given. In particular, it is proved that for k⩾3, a k-connected k-regular planar graph with each cyclic cutset of sufficiently large size is 2-extendable

The Sexual health of pupils in years 4 to 6 of primary schools in rural Tanzania

Background/objectives: There is an urgent need for effective interventions to improve the sexual and\ud reproductive health of adolescents. Reliable data on the sexual health of adolescents are needed to guide\ud the development of such interventions. The aim was to describe the sexual health of pupils in years 4 to 6 of\ud 121 rural primary schools in north western Tanzania, before the implementation of an innovative sexual\ud health intervention in 58 of the schools.\ud Methods: A cross sectional survey of primary school pupils in rural Tanzania was carried out. The study\ud population comprised pupils registered in years 4 to 6 of 121 primary schools in 20 rural communities in\ud 1998. Basic demographic information was collected from all pupils seen. Those born before 1 January\ud 1985 (aged approximately 14 years and over) were invited to participate in the survey, and asked about\ud their knowledge and attitudes towards sexual health issues, and their sexual experience. A urine specimen\ud was requested and tested for HIV, Chlamydia trachomatis (CT), Neisseria gonorrhoeae (NG) and, for\ud females, pregnancy.\ud Results: 9283 pupils born before 1 January 1985 were enrolled and provided demographic information\ud and a urine sample. Male pupils were significantly older than females (mean age 15.5 years v 14.8 years,\ud p,0.001), but all other demographic characteristics were similar between the sexes. 14 (0.2%) of the\ud enrolled pupils (four male and 10 female) were HIV positive, 83 (0.9%) were positive for CT, and 12\ud (0.1%) for NG. 32 female pupils (0.8%) were positive by pregnancy test. Sexual experience was reported\ud by one fifth of primary school girls, and by almost half of boys. Only 45/114 (39%) girls with biological\ud markers of sexual activity reported having had sex.\ud Conclusions: HIV, CT, NG, and pregnancy were present though at relatively low levels among pupils in\ud years 4 to 6 of primary school. A high proportion of pupils with a biological marker of sexual activity\ud denied ever having had sex. Alternative ways of collecting sensitive data about the sexual behaviour of\ud school pupils should be explored

“Seek any means, and keep it your secret”: Young women’s attempts to control their reproduction through contraceptive and fertility practices in rural Tanzania

This study examined young women’s attempts to control reproduction through contraception and fertility protection or promotion in rural Tanzania. It drew on participant observation in nine villages, group discussions and interviews in three others, and 16 health facility simulated patient visits from 1999-2002. Fertility was highly valued, but out-of-wedlock pregnancies were stigmatized. Many girls used traditional contraception, such as wearing charms or drinking ash solutions. Young single mothers sometimes used modern contraception, including Depo Provera, because injections were accessible, private, and infrequent. However, use was ambivalent and inconsistent for fear of side effects, such as infertility (hormonal contraceptives) and reduced male pleasure (condoms). Newly married women tried to conceive immediately. Traditional treatments were used for infertility, miscarriage, or difficult deliveries. These were attributed to physical causes (sexually transmitted infections; contraception; abortion) and/or supernatural causes (God’s will; witchcraft; ancestral punishment). Improved reproductive health education and services are greatly needed. The potential of condoms to protect future fertility should be emphasised

Vertical structure of stratospheric water vapour trends derived from merged satellite data

Stratospheric water vapour is a powerful greenhouse gas. The longest available record from balloon observations over Boulder, Colorado, USA shows increases in stratospheric water vapour concentrations that cannot be fully explained by observed changes in the main drivers, tropical tropopause temperatures and methane. Satellite observations could help resolve the issue, but constructing a reliable long-term data record from individual short satellite records is challenging. Here we present an approach to merge satellite data sets with the help of a chemistry–climate model nudged to observed meteorology. We use the models’ water vapour as a transfer function between data sets that overcomes issues arising from instrument drift and short overlap periods. In the lower stratosphere, our water vapour record extends back to 1988 and water vapour concentrations largely follow tropical tropopause temperatures. Lower and mid-stratospheric long-term trends are negative, and the trends from Boulder are shown not to be globally representative. In the upper stratosphere, our record extends back to 1986 and shows positive long-term trends. The altitudinal differences in the trends are explained by methane oxidation together with a strengthened lower-stratospheric and a weakened upper stratospheric circulation inferred by this analysis. Our results call into question previous estimates of surface radiative forcing based on presumed global long-term increases in water vapour concentrations in the lower stratosphere

Brief Report: Randomized, Double-Blind Comparison of Tenofovir Alafenamide (TAF) vs Tenofovir Disoproxil Fumarate (TDF), Each Coformulated with Elvitegravir, Cobicistat, and Emtricitabine (E/C/F) for Initial HIV-1 Treatment: Week 144 Results

In 2 double-blind phase 3 trials, 1733 antiretroviral-naive adults were randomized to tenofovir alafenamide (TAF) or tenofovir disoproxil fumarate (TDF), each coformulated with elvitegravir/cobicistat/emtricitabine (E/C/F). At 144 weeks, TAF was superior to TDF in virologic efficacy, with 84.2% vs 80.0% having HIV-1 RNA <50 copies/mL (difference 4.2%; 95% confidence interval: 0.6% to 7.8%). TAF had less impact than TDF on bone mineral density and renal biomarkers. No participants on TAF had renal-related discontinuations vs 12 on TDF (P < 0.001), with no cases of proximal tubulopathy for TAF vs 4 for TDF. There were greater increases in lipids with TAF vs TDF, with no difference in the total cholesterol to high-density lipoprotein ratio. For initial HIV therapy, E/C/F/TAF is superior to E/C/F/TDF in efficacy and bone and renal safety

Terrestrial habitat requirements of nesting freshwater turtles

Because particular life history traits affect species vulnerability to development pressures, cross-species summaries of life history traits are useful for generating management guidelines. Conservation of aquatic turtles, many members of which are regionally or globally imperiled, requires knowing the extent of upland habitat used for nesting. Therefore, we compiled distances that nests and gravid females had been observed from wetlands. Based on records of \u3e 8000 nests and gravid female records compiled for 31 species in the United States and Canada, the distances that encompass 95% of nests vary dramatically among genera and populations, from just 8 m for Malaclemys to nearly 1400 m for Trachemys. Widths of core areas to encompass varying fractions of nesting populations (based on mean maxima across all genera) were estimated as: 50% coverage = 93 m, 75% = 154 m, 90% = 198 m, 95% = 232 m, 100% = 942 m. Approximately 6–98 m is required to encompass each consecutive 10% segment of a nesting population up to 90% coverage; thereafter, ca. 424 m is required to encompass the remaining 10%. Many genera require modest terrestrial areas (\u3c200 m zones) for 95% nest coverage (Actinemys, Apalone, Chelydra, Chrysemys, Clemmys, Glyptemys, Graptemys, Macrochelys, Malaclemys, Pseudemys, Sternotherus), whereas other genera require larger zones (Deirochelys, Emydoidea, Kinosternon, Trachemys). Our results represent planning targets for conserving sufficient areas of uplands around wetlands to ensure protection of turtle nesting sites, migrating adult female turtles, and dispersing turtle hatchlings

Dense Stellar Populations: Initial Conditions

This chapter is based on four lectures given at the Cambridge N-body school "Cambody". The material covered includes the IMF, the 6D structure of dense clusters, residual gas expulsion and the initial binary population. It is aimed at those needing to initialise stellar populations for a variety of purposes (N-body experiments, stellar population synthesis).Comment: 85 pages. To appear in The Cambridge N-body Lectures, Sverre Aarseth, Christopher Tout, Rosemary Mardling (eds), Lecture Notes in Physics Series, Springer Verla

The Physics of Star Cluster Formation and Evolution

© 2020 Springer-Verlag. The final publication is available at Springer via https://doi.org/10.1007/s11214-020-00689-4.Star clusters form in dense, hierarchically collapsing gas clouds. Bulk kinetic energy is transformed to turbulence with stars forming from cores fed by filaments. In the most compact regions, stellar feedback is least effective in removing the gas and stars may form very efficiently. These are also the regions where, in high-mass clusters, ejecta from some kind of high-mass stars are effectively captured during the formation phase of some of the low mass stars and effectively channeled into the latter to form multiple populations. Star formation epochs in star clusters are generally set by gas flows that determine the abundance of gas in the cluster. We argue that there is likely only one star formation epoch after which clusters remain essentially clear of gas by cluster winds. Collisional dynamics is important in this phase leading to core collapse, expansion and eventual dispersion of every cluster. We review recent developments in the field with a focus on theoretical work.Peer reviewe