Inference on Breakdown Frontiers

Given a set of baseline assumptions, a breakdown frontier is the boundary between the set of assumptions which lead to a specific conclusion and those which do not. In a potential outcomes model with a binary treatment, we consider two conclusions: First, that ATE is at least a specific value (e.g., nonnegative) and second that the proportion of units who benefit from treatment is at least a specific value (e.g., at least 50\%). For these conclusions, we derive the breakdown frontier for two kinds of assumptions: one which indexes relaxations of the baseline random assignment of treatment assumption, and one which indexes relaxations of the baseline rank invariance assumption. These classes of assumptions nest both the point identifying assumptions of random assignment and rank invariance and the opposite end of no constraints on treatment selection or the dependence structure between potential outcomes. This frontier provides a quantitative measure of robustness of conclusions to relaxations of the baseline point identifying assumptions. We derive $\sqrt{N}$-consistent sample analog estimators for these frontiers. We then provide two asymptotically valid bootstrap procedures for constructing lower uniform confidence bands for the breakdown frontier. As a measure of robustness, estimated breakdown frontiers and their corresponding confidence bands can be presented alongside traditional point estimates and confidence intervals obtained under point identifying assumptions. We illustrate this approach in an empirical application to the effect of child soldiering on wages. We find that sufficiently weak conclusions are robust to simultaneous failures of rank invariance and random assignment, while some stronger conclusions are fairly robust to failures of rank invariance but not necessarily to relaxations of random assignment.Comment: 65 pages. 26 page supplemental appendi

Analysis and calculation of macrosegregation in a casting ingot. MPS solidification model. Volume 1: Formulation and analysis

The physical and numerical formulation of a model for the horizontal solidification of a binary alloy is described. It can be applied in an ingot. The major purpose of the model is to calculate macrosegregation in a casting ingot which results from flow of interdendritic liquid during solidification. The flow, driven by solidification contractions and by gravity acting on density gradients in the interdendritic liquid, was modeled as flow through a porous medium. The symbols used are defined. The physical formulation of the problem leading to a set of equations which can be used to obtain: (1) the pressure field; (2) the velocity field: (3) mass flow and (4) solute flow in the solid plus liquid zone during solidification is presented. With these established, the model calculates macrosegregation after solidification is complete. The numerical techniques used to obtain solution on a computational grid are presented. Results, evaluation of the results, and recommendations for future development of the model are given. The macrosegregation and flow field predictions for tin-lead, aluminum-copper, and tin-bismuth alloys are included as well as comparisons of some of the predictions with published predictions or with empirical data

MPS solidification model. Analysis and calculation of macrosegregation in a casting ingot

Work performed on several existing solidification models for which computer codes and documentation were developed is presented. The models describe the solidification of alloys in which there is a time varying zone of coexisting solid and liquid phases; i.e., the S/L zone. The primary purpose of the models is to calculate macrosegregation in a casting or ingot which results from flow of interdendritic liquid in this S/L zone during solidification. The flow, driven by solidification contractions and by gravity acting on density gradients in the interdendritic liquid, is modeled as flow through a porous medium. In Model 1, the steady state model, the heat flow characteristics are those of steady state solidification; i.e., the S/L zone is of constant width and it moves at a constant velocity relative to the mold. In Model 2, the unsteady state model, the width and rate of movement of the S/L zone are allowed to vary with time as it moves through the ingot. Each of these models exists in two versions. Models 1 and 2 are applicable to binary alloys; models 1M and 2M are applicable to multicomponent alloys

Camp Reading: Logistics of a Revolutionary War Winter Encampment

No abstract is available at this time

Acute Otitis Media

Acute otitis media (AOM) is a common childhood illness that almost every child experiences by the time that they are five years of age. AOM is a self-limiting condition in which analgesics are thought to be efficient in treating the pain in these children. Literature was reviewed and the information that was compiled was presented as a PowerPoint presentationto a local group of mothers with children under the age of 6 years. This information explained the anatomy of the ear, the risk factors for AOM, treatment options, and preventative measures for AOM. As a future Nurse Practitioner, it is imperative that we understand what the needs of the parents are for the children that we are evaluating. It is our duty to provide the education needed and to share in the informed decision making process with the parents when a child is faced with an illness. We need to empower parents and providers to take a stand in a time where overprescribing is a global issue and leading us down a pathway of drug resistance. This is a multifactoral condition where guidelines are in place, but now must be revisited to ensure parents are aware of the treatment plans used to effectively manage AOM

Alien Registration- Poirier, Marie Helene A. (Greenville, Piscataquis County)

https://digitalmaine.com/alien_docs/8433/thumbnail.jp

Producer agency in decisions to hire foreign labour in the Saskatchewan apiary sector

Labour-intensive agricultural industries in Canada, and most recently in Saskatchewan, have become reliant on a foreign labour source as a means of ensuring survival within the structure of the global agricultural economy as domestic sources have declined or become too expensive. This study considers Anthony Giddens’ structuration theory in the examination of the hiring practices of producers operating within the apiary sector in Saskatchewan (1984). I argue that the inability of Saskatchewan apiarists to attract and retain an adequately sized and reliable labour force has caused producers to seek temporary foreign workers. In-depth interviews with producers were conducted in order to determine their reasons for shifting their recruiting and retention efforts to include foreign labour. Qualitative analysis of these interview data suggests that Saskatchewan producers have concluded that their only option is to take advantage of the opportunity to source labour from outside of the Canadian market