Multivariate Decomposition for Hazard Rate Models

We develop a regression decomposition technique for hazard rate models, where the difference in observed rates is decomposed into components attributable to group differences in characteristics and group differences in effects. The baseline hazard is specified using a piecewise constant exponential model, which leads to convenient estimation based on a Poisson regression model fit to person-period, or split-episode data. This specification allows for a flexible representation of the baseline hazard and provides a straightforward way to introduce time-varying covariates and time-varying effects. We provide computational details underlying the method and apply the technique to the decomposition of the black-white difference in first premarital birth rates into components reflecting characteristics and effect contributions of several predictors, as well as the effect contribution attributable to race differences in the baseline hazard.Poisson regression, hazard rates, decomposition, piecewise constant exponential model

Necessary conditions for joining optimal singular and nonsingular subarcs

Necessary conditions for optimality of junctions between singular and nonsingular subarcs for singular optimal control problem

The Role of Silicate in the Parasitism of Pleurosigma sp. Diatoms by the Thraustochytrid Phycophthorum isakeiti

The recently described thraustochytrid diatom parasite Phycophthorum isakeiti has been isolated from the marine system of northern Norway (Hassett, 2020). Protist P. isakeiti’s ecological role, biodiscovery potential, and interactions with a possible diatom host, Pleurosigma sp. remain largely unexplored. Here I present culturing experiments to test whether P. isakeiti is an obligate parasite. To supplement this analysis, incidence of infection and division was explored in a P. isakeiti-Pleurosigma sp. model system and assessed as a function of time in the presence of standard and reduced silicate conditions. Nutrient analysis and cell counting experiments spanning 15 to 31 days were conducted to investigate rates of free silicate uptake, free nitrate uptake, and the effect of P. isakeiti on rates of Pleurosigma sp. division and infection. Resin and ethyl acetate extractions were performed to characterize and screen for allelopathic chemicals involved in diatom defense or thraustochytrid parasitism. Lastly, bioassays were undertaken to detect whether any primary or secondary metabolites produced during host parasitism had biotechnologically relevant activities. Contrary to my hypothesis that P. isakeiti would be able to grow in the absence of its diatom host due to its presence in highly seasonal, light limited climates like northern Norway, I found no evidence to support a facultative strategy of P. isakeiti in a variety of tested medium. In coculturing experiments, the proportion of host Pleurosigma sp. cells dividing increased over time in the presence of the parasite, P. isakeiti. The silicate was depleted in media to a greater extent in parasitized cultures compared to non-parasitized cultures suggesting greater uptake of silicate in parasitized diatom populations. Two compounds, C17H27NO2 (4.2422 min; 278.20923 m/z) and C23H16O2 (9.2357min, 325.12084 m/z), were detected through liquid chromatography mass spectrophotometry exclusively in Pleurosigma sp. cultures parasitized by P. isakeiti. Limited bioactivity was detected in anti-bacterial assays against gram-positive Staphylococcus aureus and in the inhibition of TNF-a production during the anti-inflammation screening. No bioactivity was observed in the anti-cancer or biofilm assays. Experiments and observations in this thesis characterize the role of silicate in the parasitism of Pleurosigma sp. by P. isakeiti. The present research is multidisciplinary, spanning the fields of ecology and biodiscovery to yield novel, fundamental knowledge on a newly described species, P. isakeiti and to describe the interaction with its host, Pleurosigma sp., an ecologically important diatom species

Many Low Income Women In Texas Do Not Get the Effective Contraception They Want After Giving Birth

Population Research Cente

Language of Interview and the Subjectively-Rated Health of Hispanic Mothers and their Children

Hispanics tend to be as healthy as non-Hispanic whites across a number of indicators, yet they consistently rate their health as worse than non-Hispanic whites. This incongruous finding has been tied both to levels of acculturation and Spanish-language use, questioning the validity of self-reported health for Spanish speakers in the United States. Furthermore, in the same way that Hispanic adults interviewed in Spanish have worse self-rated health, when asked in Spanish mothers rate their children’s health as worse than those mothers who answer in English. The exact reasons for this relationship, though, are unclear. Frequently this language effect has been taken as an indicator of acculturation; as such, the assumption is that as time progresses Hispanics become more acculturated and answer questions regarding their health more similarly to non-Hispanic whites. However, up until this point there has been no longitudinal research examining the relationship between rated health and language of interview. Using three waves of data on Hispanic mothers and their children from the Fragile Families and Child Well-being Study, this paper addresses the following questions: 1. Is Spanish language interview predictive of worse rated health for both mothers and children, and do these relationships change over time? 2. Does the effect of language on rated health persist after controlling for potential mediators? By employing two-level generalized linear models, we find that on average, those who were interviewed in Spanish are more likely to rate their and their children’s health as worse than those who answered in English. The effect of language of interview on reported health persists over time, even after controlling for measures of acculturation, physical and mental health, and access to health care. Contrary to what some have proposed, we see no discernable change over time in the way women rate their own health or that of their children.

Local unitary cocycles of E0-semigroups

AbstractThis paper concerns the structure of the group of local unitary cocycles, also called the gauge group, of an E0-semigroup. The gauge group of a spatial E0-semigroup has a natural action on the set of units by operator multiplication. Arveson has characterized completely the gauge group of E0-semigroups of type I, and as a consequence it is known that in this case the gauge group action is transitive. In fact, if the semigroup has index k, then the gauge group action is transitive on the set of (k+1)-tuples of appropriately normalized independent units. An action of the gauge group having this property is called (k+1)-fold transitive. We construct examples of E0-semigroups of type II and index 1 which are not 2-fold transitive. These new examples also illustrate that an E0-semigroup of type IIk need not be a tensor product of an E0-semigroup of type II0 and another of type Ik