UNDERSTANDING THE EFFECTS OF EARLY MOTHERHOOD IN BRITAIN : THE EFFECTS ON MOTHERS

This paper examines the socio-economic consequences of teenage motherhood for a cohort of British women born in 1970. We employ a number of methods to control for observed and unobserved differences between women who gave birth as a teenager and those who do not. We present results from conventional linear regression models, a propensity score matching estimator, and an instrumental variable estimator that uses miscarriage data to control for unobserved characteristics influencing selection into teenage motherhood. We consider the effects on equivalised family income at age 30, and its constituent parts. We find significant negative effects of teenage motherhood using methods that control only for observed characteristics using linear regression or matching methods. However once unobserved heterogeneity is also taken into account, the evidence for large negative effects becomes much less clear-cut. We look at older and younger teenage mothers separately and find that the negative effects are not necessarily stronger for teenagers falling pregnant before age 18 compared with those falling pregnant between 18 and 20, which could further suggest that some of the negative effects of teenage motherhood are temporary.teenage pregnancy ; miscarriage ; instrumental variables

Trophic Complexity and the Adaptive Value of Damage-Induced Plant Volatiles.

Indirect plant defenses are those facilitating the action of carnivores in ridding plants of their herbivorous consumers, as opposed to directly poisoning or repelling them. Of the numerous and diverse indirect defensive strategies employed by plants, inducible volatile production has garnered the most fascination among plant-insect ecologists. These volatile chemicals are emitted in response to feeding by herbivorous arthropods and serve to guide predators and parasitic wasps to their prey. Implicit in virtually all discussions of plant volatile-carnivore interactions is the premise that plants “call for help” to bodyguards that serve to boost plant fitness by limiting herbivore damage. This, by necessity, assumes a three-trophic level food chain where carnivores benefit plants, a theoretical framework that is conceptually tractable and convenient, but poorly depicts the complexity of food-web dynamics occurring in real communities. Recent work suggests that hyperparasitoids, top consumers acting from the fourth trophic level, exploit the same plant volatile cues used by third trophic level carnivores. Further, hyperparasitoids shift their foraging preferences, specifically cueing in to the odor profile of a plant being damaged by a parasitized herbivore that contains their host compared with damage from an unparasitized herbivore. If this outcome is broadly representative of plant-insect food webs at large, it suggests that damage-induced volatiles may not always be beneficial to plants with major implications for the evolution of anti-herbivore defense and manipulating plant traits to improve biological control in agricultural crops

Fast Bayesian Record Linkage for Streaming Data Contexts

Record linkage is the task of combining records from multiple files which refer to overlapping sets of entities when there is no unique identifying field. In streaming record linkage, files arrive sequentially in time and estimates of links are updated after the arrival of each file. This problem arises in settings such as longitudinal surveys, electronic health records, and online events databases, among others. The challenge in streaming record linkage is to efficiently update parameter estimates as new data arrives. We approach the problem from a Bayesian perspective with estimates in the form of posterior samples of parameters and present methods for updating link estimates after the arrival of a new file that are faster than fitting a joint model with each new data file. In this paper, we generalize a two-file Bayesian Fellegi-Sunter model to the multi-file case and propose two methods to perform streaming updates. We examine the effect of prior distribution on the resulting linkage accuracy as well as the computational trade-offs between the methods when compared to a Gibbs sampler through simulated and real-world survey panel data. We achieve near-equivalent posterior inference at a small fraction of the compute time.Comment: 43 pages, 6 figures, 4 tables. (Main: 32 pages, 4 figures, 3 tables. Supplement: 11 pages, 2 figures, 1 table.) Submitted to Journal of Computational and Graphical Statistic

Generative Filtering for Recursive Bayesian Inference with Streaming Data

In the streaming data setting, where data arrive continuously or in frequent batches and there is no pre-determined amount of total data, Bayesian models can employ recursive updates, incorporating each new batch of data into the model parameters' posterior distribution. Filtering methods are currently used to perform these updates efficiently, however, they suffer from eventual degradation as the number of unique values within the filtered samples decreases. We propose Generative Filtering, a method for efficiently performing recursive Bayesian updates in the streaming setting. Generative Filtering retains the speed of a filtering method while using parallel updates to avoid degenerate distributions after repeated applications. We derive rates of convergence for Generative Filtering and conditions for the use of sufficient statistics instead of fully storing all past data. We investigate the alleviation of filtering degradation through simulation and Ecological species count data

Understanding the effects of early motherhood in Britain: the effects on mothers

This paper examines the socio-economic consequences of teenage motherhood for a cohort of British women born in 1970. We employ a number of methods to control for observed and unobserved differences between women who gave birth as a teenager and those who do not. We present results from conventional linear regression models, a propensity score matching estimator, and an instrumental variable estimator that uses miscarriage data to control for unobserved characteristics influencing selection into teenage motherhood. We consider the effects on equivalised family income at age 30, and its constituent parts. We find significant negative effects of teenage motherhood using methods that control only for observed characteristics using linear regression or matching methods. However once unobserved heterogeneity is also taken into account, the evidence for large negative effects becomes much less clear-cut. We look at older and younger teenage mothers separately and find that the negative effects are not necessarily stronger for teenagers falling pregnant before age 18 compared with those falling pregnant between 18 and 20, which could further suggest that some of the negative effects of teenage motherhood are temporary

Photography in architectural education: A tool for assessing social aspects of the built environment

AbstractArchitectural undergraduate education uses visual methods within both teaching and design processes. One method, photography, is mostly used for illustrative documentation. However, using photography more creatively offers rich potential for student engagement with the social environments they work within. In this study, students digitally photographed the built environment of Karaköy, Istanbul and went through a process of keywording and interpretation of their photographs. The results function in a documentary capacity, but also provide insights into the students’ social understandings of the built environment, which, in the context of architectural teaching and learning, has value for both students and instructors

A Combined Direct Analysis and Direct Strength Approach to Predict the Flexural Strength of Z-Purlins with Paired Torsion Braces

A series of 12 Base Tests for Z-section purlins with paired interior torsional braces and one flange attached to a flexible horizontal diaphragm are evaluated with the Direct Strength Method. Rather than use the conventional constrained bending stress approximation, a direct analysis philosophy is adopted where cross section stress distributions are calculated using a displacement compatibility approach. With a flexible diaphragm typical of a standing seam roof system, these stresses can deviate substantially from the constrained bending approximation and can significantly impact predicted local and distortional buckling behavior. The displacement compatibility approach incorporates estimates of load imbalances and second order effects that result from the standard base test procedure. Predicted local and distortional buckling strength shows good correlation to tested strength

Inducible plant responses linking above- and below-ground herbivory: ecological significance and underlying mechanisms

Above- and below-ground organisms can indirectly affect one another via several recently-described mechanisms, one such mechanism being herbivore-induced plant responses. Because plants leaves occur above-ground and roots below-ground, systemic plant responses to foliar- and root-feeding consumers can result in reciprocal interactions between above- and below-ground herbivory. To first address the broader theoretical context underlying plant-mediated herbivore interactions I conducted a meta-analytical review of interspecific interactions in phytophagous insects (Chapter 1). Using a data-set of 333 observations of interspecific herbivore interactions compiled from 145 independently published studies, I quantitatively assessed: (a) the overall importance of competition in the ecology of insect herbivores, and (b) whether plant-feeding insects conform to traditional competition paradigms. Despite finding frequent evidence for competition, I found very little evidence that phytophagous insects conform to theoretical predictions for interspecific competition. Notably, the strength of interactions between herbivores was largely unaffected by feeding guild, and occurred among distantly-related species that were spatially- and temporally-separated from one another. Moreover, in most cases plants mediated these indirect interactions. Next, I used the tobacco (Nicotiana tabacum) system to explore plant responses to foliar-feeding insects and root-feeding nematodes. I found that aboveground insect herbivores had limited impact on the secondary chemistry of roots, but belowground nematode herbivores strongly affected leaf chemistry (Chapter 2). However, the magnitude of leaf-root induction was also affected by vascular connectivity, with stronger induced responses among plant tissues that were more closely aligned (Chapter 3). Last, I assessed the impact of induced responses on the performance and abundance of foliar and root herbivores using manipulative greenhouse (Chapter 4) and field studies (Chapter 5). Overall, I documented that root-feeding nematodes positively affect leaf-chewing insects by interfering with aboveground nicotine dynamics, whereas aboveground insects benefit root-feeding nematodes via alteration of source-sink dynamics

Jasmonate-induced plant defenses and prey availability impact the preference and performance of an omnivorous stink bug, Podisus maculiventris

Many omnivorous insects are important biological control agents, and their success is influenced by both plant resistance and prey availability. The potential impact of these two factors is complicated by the fact that they may not be independent: Resistant plants also often support fewer herbivorous prey. We studied how lifetime development, growth, fecundity and preference of the omnivorous stink bug, Podisus maculiventris, was affected by jasmonate-induced plant defenses and amount of prey available. P. maculiventris survival was 70 % lower on high-resistance (jasmonate-overexpressing) plants compared to low-resistance (jasmonate-insensitive) plants. However, surviving P. maculiventris grew and achieved equal fecundity on low- and high-resistance plants. When given a choice, P. maculiventris preferred low-resistance plants, but did not differentiate between caterpillar prey reared on high- or low-resistance plants. Low prey availability impacted distinct aspects of P. maculiventris performance: Development time was lengthened, and nymphal and adult mass were reduced, but survival was not impacted. We did not detect any interactive effects between plant resistance and prey availability for any measure of P. maculiventris. Thus, we found remarkably compartmentalized impacts of plant resistance and prey availability for this omnivorous insect