4,050 research outputs found
Early sexual debut: Voluntary or coerced? Evidence from longitudinal data in South Africa â the Birth to Twenty Plus study
Background: Early sexual debut, voluntary or coerced, increases risks to sexual and reproductive health. Sexual coercion is increasingly receiving attention as an important public health issue owing to its association with adverse health and social outcomes.Objective: To describe voluntary and coerced experience at sexual debut.Methods: A longitudinal perspective among 2 216 adolescents (1 149 females, 1 067 males) in a birth cohort study in South Africa, analysing data collected on six occasions between 11 and 18 years.Results: The median age of sexual debut was 16 years for females and 15 for males. Reported coerced sexual debut included children <11 years of age. Males reported earlier sexual debut, with both voluntary and coerced sexual experience, than females (p<0.0001). Sexual coercion at early sexual debut among both male and female adolescents occurred mostly through sexual intercourse with older adolescents and partners of the same age.Conclusion: The identified time periods and age groups need to be targeted for interventions to delay sexual debut and prevent sexual coercion among young people. More research is needed to understand underlying predisposing risk factors for sexual coercion at sexual debut, both early and not early
Modeling Camera Effects to Improve Visual Learning from Synthetic Data
Recent work has focused on generating synthetic imagery to increase the size
and variability of training data for learning visual tasks in urban scenes.
This includes increasing the occurrence of occlusions or varying environmental
and weather effects. However, few have addressed modeling variation in the
sensor domain. Sensor effects can degrade real images, limiting
generalizability of network performance on visual tasks trained on synthetic
data and tested in real environments. This paper proposes an efficient,
automatic, physically-based augmentation pipeline to vary sensor effects
--chromatic aberration, blur, exposure, noise, and color cast-- for synthetic
imagery. In particular, this paper illustrates that augmenting synthetic
training datasets with the proposed pipeline reduces the domain gap between
synthetic and real domains for the task of object detection in urban driving
scenes
Even transient rapid infancy weight gain is associated with higher BMI in young adults and earlier menarche.
BACKGROUND: Early postnatal rapid 'catch-up' weight gain has been consistently associated with subsequent higher obesity risk and earlier pubertal development. In many low- and middle-income countries, infancy catch-up weight gain is transient and often followed by growth faltering. We explored the hypothesis that even transient catch-up weight gain during infancy is associated with later obesity risk and earlier puberty. METHODS: A total of 2352 (1151 male, 1201 female) black South African children in the birth to twenty prospective birth cohort study (Johannesburg-Soweto) underwent serial measurements of body size and composition from birth to 18 years of age. At the age of 18 years, whole-body fat mass and fat-free mass were determined using dual-energy X-ray absorptiometry. Pubertal development was assessed by the research team between ages 9 and 10 years, and it was recorded annually from the age of 11 years using a validated self-assessment protocol. RESULTS: Catch-up weight gain from birth to the age of 1 year, despite being followed by growth faltering between ages 1 and 2 years, was associated with greater mid-upper arm circumference (P=0.04) and skinfold thickness (P=0.048) at 8 years of age, and with higher weight (P<0.001) and body mass index (P=0.001) at 18 years of age after adjustment for sex, age, smoking during pregnancy, birth order, gestational age, formula-milk feeding and household socio-economic status. Infancy catch-up weight gain was also associated with younger age at menarche in girls (P<0.001). This association persisted after adjustment for smoking during pregnancy, birth order, gestational age, formula-milk feeding and household socio-economic status (P=0.005). CONCLUSION: Transient catch-up weight gain from birth to the age of 1 year among children born in a low-income area of South Africa was associated with earlier menarche and greater adiposity in early adulthood. This observation suggests that modifiable determinants of rapid infancy weight gain may be targeted in order to prevent later obesity and consequences of earlier puberty in girls.We are grateful to all study participants, their families and research assistants. Birth to twenty has been supported by The Wellcome Trust, Human Sciences Research Council, Medical Research Council, University of the Witwatersrand, the South African-Netherlands Programme on Alternative Development and the Anglo American Chairmanâs Fund.This is the author accepted manuscript. The final version is available via NPG at http://www.nature.com/ijo/journal/vaop/ncurrent/full/ijo201525a.html
Realizability of Polytopes as a Low Rank Matrix Completion Problem
This article gives necessary and sufficient conditions for a relation to be
the containment relation between the facets and vertices of a polytope. Also
given here, are a set of matrices parameterizing the linear moduli space and
another set parameterizing the projective moduli space of a combinatorial
polytope
Behavioral implications of shortlisting procedures
We consider two-stage âshortlisting proceduresâ in which the menu of alternatives is first pruned by some process or criterion and then a binary relation is maximized. Given a particular first-stage process, our main result supplies a necessary and sufficient condition for choice data to be consistent with a procedure in the designated class. This result applies to any class of procedures with a certain lattice structure, including the cases of âconsideration filters,â âsatisficing with salience effects,â and ârational shortlist methods.â The theory avoids background assumptions made for mathematical convenience; in this and other respects following Richterâs classical analysis of preference-maximizing choice in the absence of shortlisting
A universal tool for determining the time delay and the frequency shift of light: Synge's world function
In almost all of the studies devoted to the time delay and the frequency
shift of light, the calculations are based on the integration of the null
geodesic equations. However, the above-mentioned effects can be calculated
without integrating the geodesic equations if one is able to determine the
bifunction giving half the squared geodesic distance between
two points and (this bifunction may be called Synge's world
function). In this lecture, is determined up to the order
within the framework of the PPN formalism. The case of a stationary
gravitational field generated by an isolated, slowly rotating axisymmetric body
is studied in detail. The calculation of the time delay and the frequency shift
is carried out up to the order . Explicit formulae are obtained for the
contributions of the mass, of the quadrupole moment and of the internal angular
momentum when the only post-Newtonian parameters different from zero are
and . It is shown that the frequency shift induced by the mass
quadrupole moment of the Earth at the order will amount to
in spatial experiments like the ESA's Atomic Clock Ensemble in Space mission.
Other contributions are briefly discussed.Comment: 18 pages, To appear in: "Lasers, Clocks and Drag-Free control:
Exploration of Relativistic Gravity in Space", Springer Series on
Astrophysics and Space Science Library, vol 349, p 15
Talking South African fathers: a critical examination of menâs constructions and experiences of fatherhood and fatherlessness
The absence of biological fathers in South Africa has been constructed as a problem for children of both sexes but more so for boy-children. Arguably the dominant discourse in this respect has demonized non-nuclear, female-headed households. Fathers are constructed as either absent or âbadâ. Thus it has become important to explore more closely how male care-givers have been experienced by groups of men in South Africa. This article examines discourses of fatherhood and fatherlessness by drawing on qualitative interviews with a group of 29 men who speak about their reported experiences and understandings of being fathered or growing up without biological fathers. Two major and intertwined subjugated discourses about adult menâs experiences of being fathered that counter- balance the prevailing discourses about meaning of fatherhood and fatherlessness became evident, namely, âbeing always thereâ and âtalking fatherhoodâ. The importance of the experience of fatherhood as âbeing thereâ, which relates to a quality of time and relationship between child and father rather than physical time together, is illustrated. It is not only biological fathers who can âbe thereâ for their sons but also social fathers, other significant male role models and father figures who step in at different times in participantsâ lives when biological fathers are unavailable for whatever reason. Second, many positive experiences of fathers or father figures that resist a traditional role of authority and control and subscribe to more nurturant and non-violent forms of care, represented as âtalkingâ fathers, are underlined. If we are to better understand the impact of colonial and apartheid history and its legacy on family life in contemporary society, there is a need for more historically and contextually informed studies on the meaning of fatherhood and fatherlessness.Web of Scienc
Twenty Thousand-Year-Old Huts at a Hunter-Gatherer Settlement in Eastern Jordan
Ten thousand years before Neolithic farmers settled in permanent villages, hunter-gatherer groups of the Epipalaeolithic period (c. 22â11,600 cal BP) inhabited much of southwest Asia. The latest Epipalaeolithic phase (Natufian) is well-known for the appearance of stone-built houses, complex site organization, a sedentary lifestyle and social complexityâprecursors for a Neolithic way of life. In contrast, pre-Natufian sites are much less well known and generally considered as campsites for small groups of seasonally-mobile hunter-gatherers. Work at the Early and Middle Epipalaeolithic aggregation site of Kharaneh IV in eastern Jordan highlights that some of these earlier sites were large aggregation base camps not unlike those of the Natufian and contributes to ongoing debates on their duration of occupation. Here we discuss the excavation of two 20,000-year-old hut structures at Kharaneh IV that pre-date the renowned stone houses of the Natufian. Exceptionally dense and extensive occupational deposits exhibit repeated habitation over prolonged periods, and contain structural remains associated with exotic and potentially symbolic caches of objects (shell, red ochre, and burnt horn cores) that indicate substantial settlement of the site pre-dating the Natufian and outside of the Natufian homeland as currently understood
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