Complex organic molecules in protoplanetary disks

Context. Protoplanetary disks are vital objects in star and planet formation, possessing all the material, gas and dust, which may form a planetary system orbiting the new star. Small, simple molecules have traditionally been detected in protoplanetary disks; however, in the ALMA era, we expect the molecular inventory of protoplanetary disks to significantly increase.

Aims. We investigate the synthesis of complex organic molecules (COMs) in protoplanetary disks to put constraints on the achievable chemical complexity and to predict species and transitions which may be observable with ALMA.

Methods. We have coupled a 2D steady-state physical model of a protoplanetary disk around a typical T Tauri star with a large gas-grain chemical network including COMs. We compare the resulting column densities with those derived from observations and perform ray-tracing calculations to predict line spectra. We compare the synthesised line intensities with current observations and determine those COMs which may be observable in nearby objects. We also compare the predicted grain-surface abundances with those derived from cometary comae observations.

Results. We find COMs are efficiently formed in the disk midplane via grain-surface chemical reactions, reaching peak grain-surface fractional abundances similar to 10(-6)-10(-4) that of the H nuclei number density. COMs formed on grain surfaces are returned to the gas phase via non-thermal desorption; however, gas-phase species reach lower fractional abundances than their grain-surface equivalents, similar to 10(-12)-10(-7). Including the irradiation of grain mantle material helps build further complexity in the ice through the replenishment of grain-surface radicals which take part in further grain-surface reactions. There is reasonable agreement with several line transitions of H2CO observed towards T Tauri star-disk systems. There is poor agreement with HC3(N) lines observed towards LkCa 15 and GO Tau and we discuss possible explanations for these discrepancies. The synthesised line intensities for CH3OH are consistent with upper limits determined towards all sources. Our models suggest CH3OH should be readily observable in nearby protoplanetary disks with ALMA; however, detection of more complex species may prove challenging, even with ALMA "Full Science" capabilities. Our grain-surface abundances are consistent with those derived from cometary comae observations providing additional evidence for the hypothesis that comets (and other planetesimals) formed via the coagulation of icy grains in the Sun's natal disk.

Women (Re)Negotiating Care across Family Generations: Intersections of Gender and Socioeconomic Status

Changing Generations, a study of intergenerational relations in Ireland undertaken between 2011 and 2013 by the Social Policy and Ageing Research Centre (SPARC), Trinity College, Dublin, and the Irish Centre for Social Gerontology (ICSG), NUI Galway, used the Constructivist Grounded Theory method to interrogate support and care provision between generations. This article draws on interviews with 52 women ages 18 to 102, allowing for simultaneous analysis of older and younger women’s perspectives. The intersectionality of gender and class emerged as central to the analysis. Socioeconomic positions shape contrasting forms of interdependency among family generations, ranging from “enmeshed” lives among lower socioeconomic groups to “freed” lives among higher socioeconomic groups. Women are initiating changes in how care and support flow across generations. Older women in higher socioeconomic groups are attuned to how emotional capital women expend across family generations can constrain (young) women’s lives. In an expression of solidarity, older women are renegotiating the place of care labor in their own lives and in the lives of younger women. A new reciprocity emerges that amounts to women “undoing gender.” This process is, however, deeply classed as it is women in higher socioeconomic groups whose resources best place them to renegotiate care.

Nonresident Father Involvement with Children and Divorced Women's Likelihood of Remarriage

Although remarriage is a relatively common transition, little is known about how nonresident fathers affect divorced mothers’ entry into remarriage. Using the 1979–2010 rounds of the National Longitudinal Study of Youth 1979, the authors examined the likelihood of remarriage for divorced mothers (N = 882) by nonresident father contact with children and payment of child support. The findings suggest that maternal remarriage is positively associated with nonresident father contact but not related to receiving child support.

A Note on Race, Ethnicity and Nativity Differences in Remarriage in the United States

The objectives of this study are to produce up-to-date estimates of race/ethnic/nativity differentials for remarriage and repartnership among women in the United States and to see if these differences are due to across-group differences in demographic characteristics. First, we produce lifetable estimates of remarriage and repartnering for white, black, U.S. born Latina and foreign born Latina women. Next, we estimate race/ethnic/nativity differentials for remarriage and repartnership using event-history analysis with and without controls for demographic characteristics. The results suggest a continued overall decline in remarriage rates, while many women repartner by cohabitating. Whites are more likely than blacks or Latinas to remarry and they are also more likely to repartner. Race/ethnic/nativity differentials remain even after accounting for variations in demographic characteristics. This suggests that race/ethnic/nativity differentials in remarriage and repartnering rates, rather than ameliorating disadvantages associated with divorce, reinforce these differentials.

Wanted and Unwanted Fertility in Bolivia:Does Ethnicity Matter?

CONTEXT: In Bolivia, the total fertility rate (TFR) among indigenous populations is higher than that among the nonindigenous population. It is important to investigate whether this difference is attributable to ethnic differences in wanted or unwanted fertility.
METHODS: Data from the 2003 Bolivian Demographic and Health Survey were used to estimate women's wanted and unwanted TFRs. Logistic regression analyses were conducted to examine whether women's, men's and couples' characteristics were associated with use of any contraceptive method and modern methods.
RESULTS: The TFRs for indigenous and nonindigenous women were 1.5 and 1.7, [corrected] respectively. The wanted fertility rate for indigenous women was nearly the same as that for nonindigenous women (2.8 and 1.4, [corrected] respectively); virtually all of the ethnic difference in the TFRs was attributable to the ethnic difference in unwanted fertility. The proportion of women in need of contraception was greater among indigenous women than among nonindigenous women (26% vs. 19%). In logistic regression analyses, male fertility preferences explained only a small part of the ethnic difference in contraceptive use.
CONCLUSION: Women's, men's and couples' preferences contribute only marginally to unwanted fertility, suggesting that structural factors act as obstacles to preventing unwanted fertility.

Nonresident Father Involvement with Children and Divorced Women's Likelihood of Remarriage

Although remarriage is a relatively common transition, we know little about how nonresident fathers affect divorced mothers’ entry into remarriage. Using the 1979-2010 rounds of the National Longitudinal Study of Youth 1979, we examined the likelihood of remarriage for divorced mothers (n=882) by nonresident father contact with children and payment of child support. The findings suggest that maternal remarriage is positively associated with nonresident father contact but not related to receiving child support.