Results of a Search for Sub-GeV Dark Matter Using 2013 LUX Data.

The scattering of dark matter (DM) particles with sub-GeV masses off nuclei is difficult to detect using liquid xenon-based DM search instruments because the energy transfer during nuclear recoils is smaller than the typical detector threshold. However, the tree-level DM-nucleus scattering diagram can be accompanied by simultaneous emission of a bremsstrahlung photon or a so-called "Migdal" electron. These provide an electron recoil component to the experimental signature at higher energies than the corresponding nuclear recoil. The presence of this signature allows liquid xenon detectors to use both the scintillation and the ionization signals in the analysis where the nuclear recoil signal would not be otherwise visible. We report constraints on spin-independent DM-nucleon scattering for DM particles with masses of 0.4-5 GeV/c^{2} using 1.4×10^{4} kg day of search exposure from the 2013 data from the Large Underground Xenon (LUX) experiment for four different classes of mediators. This analysis extends the reach of liquid xenon-based DM search instruments to lower DM masses than has been achieved previously.

Limits on Spin-Dependent WIMP-Nucleon Cross Section Obtained from the Complete LUX Exposure.

We present experimental constraints on the spin-dependent WIMP-nucleon elastic cross sections from the total 129.5 kg yr exposure acquired by the Large Underground Xenon experiment (LUX), operating at the Sanford Underground Research Facility in Lead, South Dakota (USA). A profile likelihood ratio analysis allows 90% C.L. upper limits to be set on the WIMP-neutron (WIMP-proton) cross section of σ_{n}=1.6×10^{-41} cm^{2} (σ_{p}=5×10^{-40} cm^{2}) at 35 GeV c^{-2}, almost a sixfold improvement over the previous LUX spin-dependent results. The spin-dependent WIMP-neutron limit is the most sensitive constraint to date.

First Searches for Axions and Axionlike Particles with the LUX Experiment.

The first searches for axions and axionlike particles with the Large Underground Xenon experiment are presented. Under the assumption of an axioelectric interaction in xenon, the coupling constant between axions and electrons g_{Ae} is tested using data collected in 2013 with an exposure totaling 95 live days ×118 kg. A double-sided, profile likelihood ratio statistic test excludes g_{Ae} larger than 3.5×10^{-12} (90% C.L.) for solar axions. Assuming the Dine-Fischler-Srednicki-Zhitnitsky theoretical description, the upper limit in coupling corresponds to an upper limit on axion mass of 0.12 eV/c^{2}, while for the Kim-Shifman-Vainshtein-Zhakharov description masses above 36.6 eV/c^{2} are excluded. For galactic axionlike particles, values of g_{Ae} larger than 4.2×10^{-13} are excluded for particle masses in the range 1-16 keV/c^{2}. These are the most stringent constraints to date for these interactions.

Results from a Search for Dark Matter in the Complete LUX Exposure.

We report constraints on spin-independent weakly interacting massive particle (WIMP)-nucleon scattering using a 3.35×10^{4} kg day exposure of the Large Underground Xenon (LUX) experiment. A dual-phase xenon time projection chamber with 250 kg of active mass is operated at the Sanford Underground Research Facility under Lead, South Dakota (USA). With roughly fourfold improvement in sensitivity for high WIMP masses relative to our previous results, this search yields no evidence of WIMP nuclear recoils. At a WIMP mass of 50 GeV c^{-2}, WIMP-nucleon spin-independent cross sections above 2.2×10^{-46} cm^{2} are excluded at the 90% confidence level. When combined with the previously reported LUX exposure, this exclusion strengthens to 1.1×10^{-46} cm^{2} at 50 GeV c^{-2}.

Improved Limits on Scattering of Weakly Interacting Massive Particles from Reanalysis of 2013 LUX Data.

We present constraints on weakly interacting massive particles (WIMP)-nucleus scattering from the 2013 data of the Large Underground Xenon dark matter experiment, including 1.4×10^{4} kg day of search exposure. This new analysis incorporates several advances: single-photon calibration at the scintillation wavelength, improved event-reconstruction algorithms, a revised background model including events originating on the detector walls in an enlarged fiducial volume, and new calibrations from decays of an injected tritium ß source and from kinematically constrained nuclear recoils down to 1.1 keV. Sensitivity, especially to low-mass WIMPs, is enhanced compared to our previous results which modeled the signal only above a 3 keV minimum energy. Under standard dark matter halo assumptions and in the mass range above 4 GeV c^{-2}, these new results give the most stringent direct limits on the spin-independent WIMP-nucleon cross section. The 90% C.L. upper limit has a minimum of 0.6 zb at 33 GeV c^{-2} WIMP mass.

Results on the Spin-Dependent Scattering of Weakly Interacting Massive Particles on Nucleons from the Run 3 Data of the LUX Experiment.

We present experimental constraints on the spin-dependent WIMP (weakly interacting massive particle)-nucleon elastic cross sections from LUX data acquired in 2013. LUX is a dual-phase xenon time projection chamber operating at the Sanford Underground Research Facility (Lead, South Dakota), which is designed to observe the recoil signature of galactic WIMPs scattering from xenon nuclei. A profile likelihood ratio analysis of 1.4×10^{4} kg day of fiducial exposure allows 90% C.L. upper limits to be set on the WIMP-neutron (WIMP-proton) cross section of σ_{n}=9.4×10^{-41} cm^{2} (σ_{p}=2.9×10^{-39} cm^{2}) at 33 GeV/c^{2}. The spin-dependent WIMP-neutron limit is the most sensitive constraint to date.

War, famine and excess child mortality in Africa: the role of parental education.

BACKGROUND: Civilian-targeted warfare and famine constitute two of the greatest public health challenges of our time. Both have devastated many countries in Africa. Social services, and in particular, health services, have been destroyed. Dictatorial and military governments have used the withholding of food as a political weapon to exacerbate human suffering. Under such circumstances, war and famine are expected to have catastrophic impacts on child survival. This study examines the role of parental education in reducing excess child mortality in Africa by considering Tigrai-Ethiopia, which was severely affected by famine and civil war during 1973--1991. METHODS: This study uses data from the 1994 Housing and Population Census of Ethiopia and on communities' vulnerability to food crises. Child mortality levels and trends by various subgroups are estimated using indirect methods of mortality estimation techniques. A Poisson regression model is used to examine the relationship between number of children dead and parental education. RESULTS: Although child mortality is excessively high (about 200 deaths per 1000 births), our results show enormous variations in child mortality by parental education. Child mortality is highest among children born to illiterate mothers and illiterate fathers. Our results also show that the role of parental education in reducing child mortality is great during famine periods. In the communities devastated by war, however, its impact was significant only when the father has above primary education. CONCLUSIONS Our findings suggest that both mother's and father's education are significantly and negatively associated with child mortality, although this effect diminishes over time if the crisis is severe and prolonged. The policy implications of our study include, obviously, reducing armed conflict, addressing food security in a timely manner, and expansion of educational opportunities.

Functional limitations and key indicators of well-being in children with disability.

OBJECTIVES: To compare measures of well-being in children with and without different types and severity of limitations. DESIGN: Nationally representative data for American children aged 5 to 17 years were drawn from the 1994 and 1995 National Health Interview Surveys on Disability (NHIS-D) (N = 41,300) and the Year 2000 Health Supplement to the 1994 NHIS-D (N = 9530). Family resources, safety, health status, and health access were measures of environment. The presence and severity of limitations were measured in the domains of mobility, self-care, communication, and learning. RESULTS: Children with functional limitations were more likely to live in families with limited resources and have greater exposure to secondhand smoke, less access to health care, and lower health status. Children with a limitation were not less likely to have a regular source of medical care, but they more often were delayed or prevented from getting necessary health care due to cost or insurance. CONCLUSIONS: Standard measures of child well-being were appropriate for children with functional limitations and showed their unfavorable situations. Children with functional limitations more often have unfavorable family resources, less healthy home environments, poorer health status, and less health service access than other children, making them more susceptible to developmental difficulties beyond those difficulties associated with the challenges of their specific functional limitations.

Sexual and fertility behaviors of American females aged 15-19 years: 1985, 1990, and 1995.

OBJECTIVES: This study characterized changes in sexual and reproductive behaviors from 1985 through 1995 among American females aged 15 to 19 years and related these changes to family factors. METHODS: Nationally representative sample survey data from the 1995 National Survey of Family Growth were analyzed with Weibull hazards models of age at first intercourse and first pregnancy and with logistic regression models of contraceptive use at first intercourse and pregnancy outcome. RESULTS: Improvements in the family socioeconomic situations of young women have lessened the risk of teen motherhood, while changes in family structure have increased the risk. Young women whose parents have more than a high school education, who live with both parents, and who attend church delay the timing of first sexual intercourse and are more likely to use a contraceptive. CONCLUSIONS: The trend of increases in teenage motherhood has ended owing to a halt in increases in the proportion of sexually active young women and substantial improvement in contraception, with the greatest improvements among those from advantageous family situations.

Family factors and social support in the developmental outcomes of very low-birth weight children.

This study used data that were representative of the normative population of all infants born in 1988 and were followed during the first 3 years of life. Large developmental delays and limitations in function were common among children weighing less than 1500 g at birth. Among very low-birth weight infants, minority status and living in a household headed by a single mother further worsen the disadvantages associated with a very low birth weight. Nor could the disadvantages associated with very low birth weight be accounted for by controls for other risk factors or buffering statuses and behaviors. Among all children (including those of very low birth weight) poverty, reliance on Medicaid and other government sources for health insurance, a history of risky behaviors, and inadequate prenatal care are the major risk factors for developmental delays, limitations in function, and impairment at birth. State program benefit levels have no obvious effects on child outcomes, taking into account participation in individual programs. An important finding in light of TANF is that maternal work, the use of child care, and the form and cost of child care did not influence developmental delay, limitation in function, or impairment, the outcomes that we were able to measure during the first 3 years of life. TANF eligibility requirements, however, may increase difficulty in obtaining prenatal and other medical services for mothers and children in need--factors shown here to be related strongly to increased risk of low birth weight and developmental delays, limitations, and impairments. Race and ethnicity, poverty status, and family structure are fundamental factors in early child development and function. Minority status, poverty, and single-parent households greatly increase the likelihood that a mother will engage in risky behaviors (smoking, alcohol use, illegal drug use) during pregnancy and receive inadequate prenatal care. Risky behaviors and inadequate prenatal care are the major risk factors for a baby of very low birth weight. When perinatologists first encounter a new patient who is of very low birth weight they often see an infant who is minority, in poverty, and in a single-parent household. Although such children did more poorly in development and function by age 3, the major effects of these variables were through the selectivity of such children into very low birth weight; the direct impact of these factors on development is somewhat muted. This research suggests there are a number of policies that can reduce development delays and functional limitations among children in the United States. Programs that are targeted to a mother and child (such as WIC, AFDC, health insurance coverage, and possibly the more recent TANF programs) significantly reduced the risk an infant will be of very low birth weight. Access and use of adequate prenatal care are essential. Programs designed to combat maternal behaviors that place the fetus at risk (smoking, alcohol, and illegal drug use) can be very successful in reducing the likelihood an infant will be of very low birth weight. An additional payoff from such programs comes after the birth, because even taking into account birth weight, these variables negatively impact on early childhood development and function. Single-parent family structure, race and ethnic minority status, and poverty status also are known to impact on kindergarten readiness, so that we expect a delayed impact of these variables on the child. The strength of this article is the use of normative population data to assess the role of birth weight in child outcome. We examined prenatal risk factors for a baby of very low birth weight, traced the manner by which these selective risks are reflected in the composition of very low-birth weight babies, demonstrated how a very low birth weight was fundamental to delays in development, and identified risk factors and potential buffers in this process. (ABSTRACT TRUNCATED)

Household organization, women's autonomy, and contraceptive behavior in southern Ethiopia.

The Southern Nations, Nationalities, and People's Region of Ethiopia (SNNPR) is home to 11 million people constituting more than 45 language and ethnic groups, most of whom live in extremely poor rural communities. Data for currently married, fecund women aged 15-49 from demographic surveys conducted in the SNNPR in 1990 and 1997 are used to investigate contraceptive knowledge and communication, and the use and future need for family planning services in this population. This study focuses on how these processes are affected by household organization and women's status, and on their implications for population policies and programs. Considerations of the implications of these results for understanding the fertility transition of a highly diverse African population under severe stress are presented. Although household extension and polygamy characterize one-third of the women sampled, they do not affect the women's contraceptive behavior. Women's literacy and autonomy are, by far, the most significant forces in the movement toward lower fertility in the region.

Improved disability population estimates of functional limitation among American children aged 5-17.

OBJECTIVES: This paper (a) creates and validates measures for population survey data to assess functional limitation in mobility, self-care, communication, and learning ability for school-age American children; (b) calculates rates of functional limitation using these measures, and provides population estimates of the number of children with limitations; and (c) examines these limitations as a function of socioeconomic factors. METHOD: The study is based on data for children aged 5-17 collected in the 1994 National Health Interview Survey on Disability. Ordinal values are assigned to survey items in the four functional areas and analyzed to produce scales of high reliability. These measures are used to identify within a 95% confidence interval the number of children with these limitations. Ordered logistic regression models measure the effects of functional limitations on disability and societal limitation. Socioeconomic differences are measured with an ordered logistic regression model that predicts severity and comorbidity. RESULTS: Limitations in learning ability (10.6%) and communication (5.5%) are the most common, with mobility (1.3%) and self-care (0.9%) occurring less often. Six percent of children have one serious functional limitation and 2.0% have two or more serious functional limitations. This corresponds to 4.0 million school-age American children with serious functional limitations. Functional limitation is strongly linked to socioeconomic disadvantage and to residence in single-mother households. CONCLUSIONS: Future population research should use multiple-item scales for four distinct areas of functional limitation, and a summary that takes into account both severity and comorbidity. The improved estimates of the number of school-age children with functional limitation in this paper may help contribute to a more informed scientific and policy discussion of functional limitation and disability among American school-age children. Future research on the disability process among children must consider the role of socioeconomic disadvantage and family structure.

Living arrangements of minority elders.

We used 1990 census data to examine differences in the current living arrangements of minority elderly. We found that differences among the minority populations in age, sex, and marital status account for only a small part of the observed differences in living arrangements. However, while minority groups as a whole differ substantially from the White population, national ethnic patterns within groups appear to be relatively small. Hispanic ethnic groups vary little once differences in marriage patterns are taken into account, although differences are greater within the Asian population.

Family networks in prenatal and postnatal health.

This paper examines the effects of kin access on prenatal health practices, birth outcome, and postnatal health practice for infants born to black and white mothers ages 21 to 28 in the U.S. during 1984-86. The data used for this research were compiled from three sources: (1) The National Longitudinal Survey of Youth; (2) The Children of the National Longitudinal Survey of Youth; (3) special kin access data files, which were created specifically for this study. Logistic regression procedures are used to assess the effects of kin proximity, maternal grandmother proximity, and presence of the child's father on health practices (N = 1,030) and birth outcome (N = 1,385), controlling for the mother's educational attainment, work experience, poverty, presence of the child's father, and birth order of the child. We find no evidence supporting the notion that kin access positively affects the prenatal and postnatal health practices of young mothers. The results suggest that young mothers who reside with their mothers or other adult kin, and those who are in close proximity to them, are no more likely to seek prenatal care during the first trimester, or to avoid smoking or drinking during pregnancy. Mothers who live with a sexual partner or husband are, however, somewhat more likely to seek prenatal care and to avoid alcohol use during pregnancy. Closer kin access is associated with a lower probability of breastfeeding. These results suggest that it will not be adequate to rely on kin networks or kin assistance to improve the prospect of healthy birth outcomes.

Women's status and infant mortality in rural Colombia.

This paper investigates the effects of maternal demographic characteristics and social and economic statuses on infant mortality in rural Colombia. Demographic characteristics include the age of the mother, parity and length of preceding interbirth interval, and sex of infant. Measures of women's status at the time of birth include education, wage labor and occupation, economic stratum, place of residence, and whether the mother is living with a husband. The life history data for the study (involving 4,928 births) were collected in 1986 from a representative sample of two cohorts of women resident in rural central Colombia. Overall differentials in infant mortality by measures of women's status are small and are in good part associated with the differing reproductive behaviors of the women and variations in breastfeeding practices. The sharp declines in infant mortality recorded in rural Colombia in recent years appear less related to improved status of women than to reductions in fertility that enhance infant survivorship and to public health interventions shared by all segments of the population.

PIP: As part of the demographic transition that has been unfolding in Colombia over the last 5 decades, both urban and rural areas have experienced substantial declines in infant mortality. This decline is generally attributed to extensive countrywide health campaigns during the 1950s and 60s aimed at the prevention of disease, government-supported child immunization campaigns during the 1970s and 80s, and improvements in the population's educational level. To investigate the dynamics behind the sharp decline in infant mortality, life history data were collected in 1986 from a representative sample of 2 cohorts of women living in rural central Colombia. 4928 births were available for analysis. The cohorts included women born in 1937-46, who were of reproductive age in the early 1960s when fertility began its decline, or 1955-61, who entered their reproductive period in the 1980s after the sharp decline in fertility. Measures of women's status and demographic characteristics at the time of each birth were reconstructed for the analysis. A total of 207 children born to the study subjects died before their 1st birthday, yielding a 0.042 probability of infant death. Substantial declines in this probability were observed over time, with 0.072 of infants born before 1960 dying compared to 0.050 of those born in 1960-72 and 0.033 of infants born after 1972. Logit model analysis of the life history data indicated that changes in the status of women, including educational attainment, have had only a slight impact on the sharp declines in infant mortality in rural Colombia. More important have been reductions in fertility that have cut the number of high parity and closely spaced births and the prevalence of breastfeeding among rural mothers.

Giving between generations in American families.

This paper documents the types and amounts of aid exchanged between adults and their non-coresidential parents. Data for the study are drawn from a representative national sample survey of Americans age 19 and older conducted in 1987-1988. Exchanges of monetary and material resources, childcare, household assistance, and companionship and advice are considered.Patterns of intergenerational exchange are found to differ by gender, family structure, age, ethnicity, and socioeconomic situation. Differences in exchange between males and females and between whites and Mexican-Americans are related to other life-course characteristics, and to the availability and proximity of kin. Blacks and persons living in poverty are shown to be less involved than other groups in intergenerational exchanges. Finally, patterns of prior assistance and the available needs and resources of the respondents and their parents are found to influence current patterns of exchange.

The social bases of declining infant mortality: lessons from a nineteenth-century Italian town.

PIP: A detailed study of the factors associated with the decline of infant mortality in the town of Casalecchio di Reno, near Bologna, Italy, from 1865-1921 was generated from household tax records, birth and death registers, census data, and a variety of scholarly sources. Infant mortality had been 400/1000 in 17th century, fell to about 250 in the mid 18th, to 186 from 1865-1880, to 100 in 1900, and 75 in 1910. Infant mortality was lower among merchant and sharecropper families who had decent housing, food and water, higher among daily wage workers who lived in filthy crowded apartments on marginal incomes, and much higher among women who worked in emerging textile factories who could not breastfeed and used animal milk (682/1000 in 1903). Results are expressed in terms of probability of an infant death for specific demographic or maternal characteristics. Infant deaths among wage working women began to fall after 1902 when the government regulated child and female labor, requiring post-partum leave and time to breastfeed. The fact that factory workers were literate and urbanized did not help their children survive until they received better water, sewage systems, free medical care, and better housing. Thus, infant mortality varied in subgroups, was not necessarily lower in "modern" urban classes, and its fall depended on direct government intervention.^ieng

Migration patterns during Italian urbanization, 1865-1921.

This study examines patterns of male migration in central Italy during its transformation from an agrarian to an urban-industrial society. The Italian population registers provide data on the extent and type of emigration among more than 3,500 men (ages 10 and over) who immigrated to the commune of Casalecchio di Reno, bordering the city of Bologna, from 1865 to 1915. Demographic and social differentials in overall rates of emigration and their relation to places of origin and destination are measured. The implications of these results for an understanding of population mobility are discussed.