NASA airframe structural integrity program

NASA initiated a research program with the long-term objective of supporting the aerospace industry in addressing issues related to the aging of the commercial transport fleet. The program combines advanced fatigue crack growth prediction methodology with innovative nondestructive examination technology with the focus on multi-stage damage (MSD) at rivited connections. A fracture mechanics evaluation of the concept of pressure proof testing the fuselage to screen for MSD was completed. A successful laboratory demonstration of the ability of the thermal flux method to detect disbonds at rivited lap splice joints was conducted. All long-term program elements were initiated, and the plans for the methodology verification program are being coordinated with the airframe manufacturers

Evaluation of the concept of pressure proof testing fuselage structures

The FAA and NASA have recently completed independent technical evaluations of the concept of pressure proof testing the fuselage of commercial transport airplanes. The results of these evaluations are summarized. The objectives of the evaluations were to establish the potential benefit of the pressure proof test, to quantify the most desirable proof test pressure, and to quantify the required proof test interval. The focus of the evaluations was on multiple-site cracks extending from adjacent rivet holes of a typical fuselage longitudinal lap splice joint. The FAA and NASA do not support pressure proof testing the fuselage of aging commercial transport aircraft. The argument against proof testing is as follows: (1) a single proof test does not insure an indefinite life; therefore, the proof test must be repeated at regular intervals; (2) for a proof factor of 1.33, the required proof test interval must be below 300 flights to account for uncertainties in the evaluation; (3) conducting the proof test at a proof factor of 1.5 would considerably exceed the fuselage design limit load; therefore, it is not consistent with accepted safe practices; and (4) better safety can be assured by implementing enhanced nondestructive inspection requirements, and adequate reliability can be achieved by an inspection interval several times longer than the proof test interval

A review of nonlinear constitutive models for metals

Over the past two decades a number of thermomechanical constitutive theories have been proposed for viscoplastic metals. These models are in most cases similar in that they utilize a set of internal state variables which provide locally averaged representations of microphysical phenomena such as dislocation rearrangement and grain boundary sliding. The state of development of several of these models is now at the point where accurate theoretical solutions can be obtained for a wide variety of structural problems at elevated temperatures. The fundamentals of viscoplasticity are briefly reviewed and a general framework is outlined. Several of the more prominent models are reviewed, and predictions from models are compared to experimental results

Social Change and the Family

This paper explores the social change of the past 40 years through reporting the results of a restudy. It argues that social change can be understood, culturally, as involving a process of de-institutionalisation and, structurally, as involving differentiation within elementary family groups as well as within extended family networks. Family change is set in the context of changes in the housing and labour markets and the demographic, industrial and occupational changes of the past 40 years. These changes are associated with increases in women\'s economic activity rates and a decrease in their \'degree of domesticity\'. They are also associated with increasing differentiation within families such that occupational heterogeneity is now found at the heart of the elementary family as well as within kinship groupings as was the case 40 years ago. Thus the trend towards increased differentiation identified in the original study (Rosser and Harris: The Family and Social Change) has continued into the 21st century. This is associated with a de-institutionalisation of family life and an increasing need for partners to negotiate participation in both productive and reproductive work.De-Institutionalisation, Social Change, Restudy, Occupational Differentiation, Extended Family

Glucocorticoid receptor action in metabolic and neuronal function [version 1; referees: 3 approved]

Glucocorticoids via the glucocorticoid receptor (GR) have effects on a variety of cell types, eliciting important physiological responses via changes in gene expression and signaling. Although decades of research have illuminated the mechanism of how this important steroid receptor controls gene expression using in vitro and cell culture–based approaches, how GR responds to changes in external signals in vivo under normal and pathological conditions remains elusive. The goal of this review is to highlight recent work on GR action in fat cells and liver to affect metabolism in vivo and the role GR ligands and receptor phosphorylation play in calibrating signaling outputs by GR in the brain in health and disease. We also suggest that both the brain and fat tissue communicate to affect physiology and behavior and that understanding this “brain-fat axis” will enable a more complete understanding of metabolic diseases and inform new ways to target them

A micromechanics model of the stiffness and strength of laminates with fiber waviness

A mathematical model based on the Euler-Bernoulli beam theory is proposed for predicting the effective Young's moduli of piecewise isotropic composite laminates with local ply curvatures in the main load-carrying layers. Strains in corrugated layers, In-Phase layers, Out-of-Phase layers are predicted for various geometries and material configurations by assuming matrix layers as elastic foundations of different spring constants. The effective Young's moduli measured from corrugated aluminum specimens and aluminum/epoxy specimens with In-Phase and Out-of-Phase wavy patterns coincide very well with the model predictions. Moire fringe analysis of an In-Phase specimen and an Out-of-Phase specimen are also presented confirming the main assumption of the model related to the elastic constraint due to the matrix layers. The present model is also compared with the experimental results and other models, including the micro-buckling models, published in the literature. The results of the present study show that even a very small scale local ply curvature produces a noticeable effect on the mechanical constitutive behavior of a laminated composite

Social Media For Social Good: A Guide To New Media For College Activists

In a world of Tweets and status updates, how do we take all those hours perusing social networks and put them to good use? In my thesis project, Social Media for Social Good: A Guide to New Media For College Activists, I explore the uses of these networks to activate people towards building positive social change. It is my opinion that college is the best time to be an activist. How do college students communicate? Social Media. From the campus to the global scale, social media can be effectively used to mobilize people to take action on a wide array of issues. Navigating all of the services, and their uses for the student activist is complicated, and therefore my guide presents some insight on how we can take Facebook and Twitter past FarmVille and updates on your morning breakfast to a useful set of tools for organizing and mobilization. The work concludes with a look at some emerging social media for the organizer to pay attention to that will shape of the world of tomorrow, along with the work they do

Glucocorticoid Receptor and Adipocyte Biology.

Glucocorticoids are steroid hormones that play a key role in metabolic adaptations during stress, such as fasting and starvation, in order to maintain plasma glucose levels. Excess and chronic glucocorticoid exposure, however, causes metabolic syndrome including insulin resistance, dyslipidemia, and hyperglycemia. Studies in animal models of metabolic disorders frequently demonstrate that suppressing glucocorticoid signaling improves insulin sensitivity and metabolic profiles. Glucocorticoids convey their signals through an intracellular glucocorticoid receptor (GR), which is a transcriptional regulator. The adipocyte is one cell type that contributes to whole body metabolic homeostasis under the influence of GR. Glucocorticoids' functions on adipose tissues are complex. Depending on various physiological or pathophysiological states as well as distinct fat depots, glucocorticoids can either increase or decrease lipid storage in adipose tissues. In rodents, glucocorticoids have been shown to reduce the thermogenic activity of brown adipocytes. However, in human acute glucocorticoid exposure, glucocorticoids act to promote thermogenesis. In this article, we will review the recent studies on the mechanisms underlying the complex metabolic functions of GR in adipocytes. These include studies of the metabolic outcomes of adipocyte specific GR knockout mice and identification of novel GR primary target genes that mediate glucocorticoid action in adipocytes

Copper Mining and Environmental Costs in Dominica

A proposal from an international mining company to establish a copper mining operation in the Caribbean island of Dominica could be highly favourable, given the potential for financial benefits associated with such a project. On the downside, such projects are often associated with environmental damage. The area targeted for this copper mine was a rainforest in the north-eastern portion of Dominica occupying around 12 percent of the island’s total land area. A critical question is therefore whether copper mining could be a viable alternative to agrarian uses of the targeted area, if both financial and environmental costs are taken into consideration. A Contingent Valuation Survey of Dominicans and Visitors allowed for inclusion of non-market costs in the analysis. Cost-Benefit and sensitivity analyses were carried out to assess project feasibility. The results indicated that NPV was negative under conservative assumptions. NPV was sensitive to changes in the price of copper and the inclusion of environmental costs did affect the level of price increase required to make NPV positive.Copper mining, Dominica, environmental costs, sensitivity analysis, cost-benefit, Agribusiness, Environmental Economics and Policy, Financial Economics,