Mechanical Properties of Nanostructured Materials Determined Through Molecular Modeling Techniques

The potential for gains in material properties over conventional materials has motivated an effort to develop novel nanostructured materials for aerospace applications. These novel materials typically consist of a polymer matrix reinforced with particles on the nanometer length scale. In this study, molecular modeling is used to construct fully atomistic models of a carbon nanotube embedded in an epoxy polymer matrix. Functionalization of the nanotube which consists of the introduction of direct chemical bonding between the polymer matrix and the nanotube, hence providing a load transfer mechanism, is systematically varied. The relative effectiveness of functionalization in a nanostructured material may depend on a variety of factors related to the details of the chemical bonding and the polymer structure at the nanotube-polymer interface. The objective of this modeling is to determine what influence the details of functionalization of the carbon nanotube with the polymer matrix has on the resulting mechanical properties. By considering a range of degree of functionalization, the structure-property relationships of these materials is examined and mechanical properties of these models are calculated using standard techniques

"She is my teacher and if it was not for her I would be dead": Exploration of rural South African community health workers' information, education and communication activities

Community health workers (CHWs) are important resources in health systems affected by the HIV/AIDS pandemic. International guidelines on task-shifting recommend that CHWs can provide diverse HIV services, ranging from HIV prevention to counselling patients for lifelong antiretroviral therapy. There is, however, little evidence on the experiences with CHW delivery of these services in Africa. This qualitative study included 102 interviews that explored experiences with information, education and communication (IEC) activities provided by CHWs within rural South Africa. Semi- structured interviews were conducted with CHWs (n = 17), their clients (n = 33) and the primary caregivers of these clients (n = 30), allowing for data source triangulation. Twenty-two follow-up interviews explored emergent themes from preliminary interviews. Despite limited formal education and training, CHWs in this study were significant providers of IEC, including provision of generic health talks and HIV-specific information and facilitation to support clients’ entry and maintenance in the formal health system. They often incorporated local knowledge and understanding of illness in their communication. CHWs in this study were able to bridge the lifeworlds of the community and the formal services to expedite access and adherence to local clinics and other services. As mediators between the two worlds, CHWs reinterpreted health information to make it comprehensible in their communities. With growing formalisation of CHW programmes in South Africa and elsewhere, CHWs’ important role in health service access, health promotion and health maintenance must be recognised and supported in order to maximise impact.Web of Scienc

Junctions and thin shells in general relativity using computer algebra I: The Darmois-Israel Formalism

We present the GRjunction package which allows boundary surfaces and thin-shells in general relativity to be studied with a computer algebra system. Implementing the Darmois-Israel thin shell formalism requires a careful selection of definitions and algorithms to ensure that results are generated in a straight-forward way. We have used the package to correctly reproduce a wide variety of examples from the literature. We present several of these verifications as a means of demonstrating the packages capabilities. We then use GRjunction to perform a new calculation - joining two Kerr solutions with differing masses and angular momenta along a thin shell in the slow rotation limit.Comment: Minor LaTeX error corrected. GRjunction for GRTensorII is available from http://astro.queensu.ca/~grtensor/GRjunction.htm

High Spatial Resolution Fast-Neutron Imaging Detectors for Pulsed Fast-Neutron Transmission Spectroscopy

Two generations of a novel detector for high-resolution transmission imaging and spectrometry of fast-neutrons are presented. These devices are based on a hydrogenous fiber scintillator screen and single- or multiple-gated intensified camera systems (ICCD). This detector is designed for energy-selective neutron radiography with nanosecond-pulsed broad-energy (1 - 10 MeV) neutron beams. Utilizing the Time-of-Flight (TOF) method, such a detector is capable of simultaneously capturing several images, each at a different neutron energy (TOF). In addition, a gamma-ray image can also be simultaneously registered, allowing combined neutron/gamma inspection of objects. This permits combining the sensitivity of the fast-neutron resonance method to low-Z elements with that of gamma radiography to high-Z materials.Comment: Also published in JINST: http://www.iop.org/EJ/abstract/1748-0221/4/05/P0501

Navigation and Exploration in 3D-Game Automated Play Testing

To enable automated software testing, the ability to automatically navigate to a state of interest and to explore all, or at least sufficient number of, instances of such a state is fundamental. When testing a computer game the problem has an extra dimension, namely the virtual world where the game is played on. This world often plays a dominant role in constraining which logical states are reachable, and how to reach them. So, any automated testing algorithm for computer games will inevitably need a layer that deals with navigation on a virtual world. Unlike e.g. navigating through the GUI of a typical web-based application, navigating over a virtual world is much more challenging. This paper discusses how concepts from geometry and graph-based path finding can be applied in the context of game testing to solve the problem of automated navigation and exploration. As a proof of concept, the paper also briefly discusses the implementation of the proposed approach

Reasoning About a Service-oriented Programming Paradigm

This paper is about a new way for programming distributed applications: the service-oriented one. It is a concept paper based upon our experience in developing a theory and a language for programming services. Both the theoretical formalization and the language interpreter showed us the evidence that a new programming paradigm exists. In this paper we illustrate the basic features it is characterized by

Pushouts in software architecture design

A classical approach to program derivation is to progressively extend a simple specification and then incrementally refine it to an implementation. We claim this approach is hard or impractical when reverse engineering legacy software architectures. We present a case study that shows optimizations and pushouts--in addition to refinements and extensions--are essential for practical stepwise development of complex software architectures.NSF CCF 0724979NSF CNS 0509338NSF CCF 0917167NSF DGE-1110007FCT SFRH/BD/47800/2008FCT UTAustin/CA/0056/200

Resemblances of Parents and Twins in Sport Participation and Heart Rate

A model to analyze resemblances of twins and parents using LISREL is outlined and applied to sports participation and heart-rate data. Sports participation and heart rate were measured in 44 monozygotic and 46 dizygotic adolescent twin pairs and in their parents. Genetic factors influence variation in both sports behavior and heart rate, while there is no evidence for transmission from parental environment to offspring environment. For sports participation the data support a model in which there is a high positive correlation between environments of spouses and between environments of female twins. This correlation is absent for male twins and negative for opposite sex twins. For heart rate, a positive correlation between environmental influences was observed for all twins; there is no evidence for assortative mating. The proposed model can also handle data sets where parents and twins have been measured on more than one variable. This is illustrated by an application to the observed association of sports participation and heart rate

Cognitive bias modification training in adolescents: effects on interpretation biases and mood

BACKGROUND: Negative biases in the interpretation of ambiguous material have been linked to anxiety and mood problems. Accumulating data from adults show that positive and negative interpretation styles can be induced through cognitive bias modification (CBM) paradigms with accompanying changes in mood. Despite the therapeutic potential of positive training effects, training paradigms have not yet been explored in adolescents. METHODS: Eighty-two healthy adolescents (aged 13-17 years) were randomly allocated to either positive or negative CBM training. To assess training effects on interpretation bias, participants read ambiguous situations followed by test sentences with positive or negative interpretations of the situation. Participants rated the similarity of these sentences to the previously viewed ambiguous situations. Training effects on negative and positive affect were assessed using visual analogue scales before and after training. RESULTS: After training, adolescents in the negative condition drew more negative and fewer positive interpretations of new ambiguous situations than adolescents in the positive condition. Within the positive condition, adolescents endorsed more positive than negative interpretations. In terms of mood changes, positive training resulted in a significant decrease in negative affect across participants, while the negative condition led to a significant decrease in positive affect among male participants only. CONCLUSION: This is the first study to demonstrate the plasticity of interpretation bias in adolescents. The immediate training effects on mood suggest that it may be possible to train a more positive interpretation style in youth, potentially helping to protect against anxiety and depressive symptoms

Precision measurements of the top quark mass from the Tevatron in the pre-LHC era

The top quark is the heaviest of the six quarks of the Standard Model. Precise knowledge of its mass is important for imposing constraints on a number of physics processes, including interactions of the as yet unobserved Higgs boson. The Higgs boson is the only missing particle of the Standard Model, central to the electroweak symmetry breaking mechanism and generation of particle masses. In this Review, experimental measurements of the top quark mass accomplished at the Tevatron, a proton-antiproton collider located at the Fermi National Accelerator Laboratory, are described. Topologies of top quark events and methods used to separate signal events from background sources are discussed. Data analysis techniques used to extract information about the top mass value are reviewed. The combination of several most precise measurements performed with the two Tevatron particle detectors, CDF and \D0, yields a value of \Mt = 173.2 \pm 0.9 GeV/$c^2$.Comment: This version contains the most up-to-date top quark mass averag