Does PGA external stenting reduce compliance mismatch in venous grafts?

Background: Autogenous vein grafting is widely used in regular bypassing procedures. Due to its mismatch with the host artery in both mechanical property and geometry, the graft often over expands under high arterial blood pressure and forms a step-depth where eddy flow develops, thus causing restenosis, fibrous graft wall, etc. External stents, such as sheaths being used to cuff the graft, have been introduced to eliminate these mismatches and increase the patency. Although histological and immunochemical studies have shown some positive effects of the external stent, the mechanical mismatch under the protection of an external stent remains poorly analyzed. Methods: In this study, the jugular veins taken from hypercholesterolemic rabbits were transplanted into the carotid arteries, and non-woven polyglycolic acid (PGA) fabric was used to fabricate the external stents to study the effect of the biodegradable external stent. Eight weeks after the operation, the grafts were harvested to perform mechanical tests and histological examinations. An arc tangent function was suggested to describe the relationship between pressure and cross-sectional area to analyse the compliance of the graft. Results: The results from the mechanical tests indicated that grafts either with or without external stents displayed large compliance in the low-pressure range and were almost inextensible in the high-pressure range. This was very different from the behavior of the arteries or veins in vivo. The data from histological tests showed that, with external stents, collagen fibers were more compact, whilst those in the graft without protection were looser and thicker. No elastic fiber was found in either kind of grafts. Furthermore, grafts without protection were over-expanded which resulted in much bigger cross-sectional areas. Conclusion: The PGA external extent contributes little to the reduction of the mechanical mismatch between the graft and its host artery while remodeling develops. For the geometric mismatch, it reduces the cross-section area, therefore matching with the host artery much better. Although there are some positive effects, conclusively the PGA is not an ideal material for external stent.

Identification of a class of non-linear systems

This paper considers the on-line identification of a non-linear system in terms of a Hammerstein model, with a zero-memory non-linear gain followed by a linear system. The linear part is represented by a Laguerre expansion of its impulse response and the non-linear part by a polynomial. The identification procedure involves determination of the coefficients of the Laguerre expansion of correlation functions and an iterative adjustment of the parameters of the non-linear gain by gradient methods. The method is applicable to situations involving a wide class of input signals. Even in the presence of additive correlated noise, satisfactory performance is achieved with the variance of the error converging to a value close to the variance of the noise. Digital computer simulation establishes the practicability of the scheme in different situations.

Non-Gaussian Cosmological Perturbations from Hybrid Inflation and Preheating

This thesis consists of four research papers and an introduction providing some background. The structure in the universe is generally considered to originate from quantum fluctuations in the very early universe. The standard lore of cosmology states that the primordial perturbations are almost scale-invariant, adiabatic, and Gaussian. A snapshot of the structure from the time when the universe became transparent can be seen in the cosmic microwave background (CMB). For a long time mainly the power spectrum of the CMB temperature fluctuations has been used to obtain observational constraints, especially on deviations from scale-invariance and pure adiabacity. Non-Gaussian perturbations provide a novel and very promising way to test theoretical predictions. They probe beyond the power spectrum, or two point correlator, since non-Gaussianity involves higher order statistics. The thesis concentrates on the non-Gaussian perturbations arising in several situations involving two scalar fields, namely, hybrid inflation and various forms of preheating. First we go through some basic concepts -- such as the cosmological inflation, reheating and preheating, and the role of scalar fields during inflation -- which are necessary for the understanding of the research papers. We also review the standard linear cosmological perturbation theory. The second order perturbation theory formalism for two scalar fields is developed. We explain what is meant by non-Gaussian perturbations, and discuss some difficulties in parametrisation and observation. In particular, we concentrate on the nonlinearity parameter. The prospects of observing non-Gaussianity are briefly discussed. We apply the formalism and calculate the evolution of the second order curvature perturbation during hybrid inflation. We estimate the amount of non-Gaussianity in the model and find that there is a possibility for an observational effect. The non-Gaussianity arising in preheating is also studied. We find that the level produced by the simplest model of instant preheating is insignificant, whereas standard preheating with parametric resonance as well as tachyonic preheating are prone to easily saturate and even exceed the observational limits. We also mention other approaches to the study of primordial non-Gaussianities, which differ from the perturbation theory method chosen in the thesis work.

Compliance verification methodology for renewable generation integration. Application to island power grids

261 p.

O Estado como investidor institucional: a disciplina jurídica de uma atuação estatal não interventiva na economia

Em um contexto de demandas sociais tendencialmente crescentes, uma das alternativas para o aumento da arrecadação de receitas pelo Estado reside no manejo de aplicações financeiras. Os investimentos financeiros estatais, a rigor, já acontecem, mas nem sempre o objetivo claro e explícito de obtenção de resultados financeiramente interessantes e, eventualmente ou mesmo por isso , sob gestão economicamente ineficiente. Às vezes, até se enxerga o foco na obtenção de rendimentos relevantes na ação estatal, mas sem uma disciplina específica, o que pode abrir espaço a uma gestão de ativos desqualificada ou mesmo fraudulenta, com sérios prejuízos aos cofres públicos e, em situações extremas, ampliação ainda maior das despesas públicas. O objetivo desta tese, portanto, é reconhecer que nem sempre o Estado atua na economia com propósito interventivo e que, na qualidade de investidor institucional vale dizer, de ente que tem o dever de proceder aos investimentos e às aplicações financeiras que digam com as melhores práticas de administração dos ativos públicos , precisa atuar sob o jugo de normas jurídicas claras, que permitam ao Estado ampliar suas receitas dentro de limites razoáveis de exposição a risco financeiro e disponibilizem aos órgãos de fiscalização e controle da Administração Pública as ferramentas necessárias para, também quanto a esse aspecto, aferir a eficiência da ação estatal. Para tanto, têm-se como pressupostos o anacronismo da resistência cultural às aplicações financeiras dos entes da Administração Pública e a noção de que quaisquer ferramentas de obtenção de receitas pelo Estado estão sujeitas a algum grau de risco. Com base nas bem-sucedidas experiências nacionais e internacionais, será possível concluir, ao final, que é admissível, do ponto de vista constitucional e legal, a ação do Estado como investidor nos mercados financeiro e de capitais e que é viável a formulação de parâmetros gerais para a disciplina jurídica do Estado investidor.

Linear quadratic game and non-cooperative predictive methods for potential application to modelling driver-AFS interactive steering control

This paper is concerned with the modelling of strategic interactions between the human driver and the vehicle active front steering (AFS) controller in a path-following task where the two controllers hold different target paths. The work is aimed at extending the use of mathematical models in representing driver steering behaviour in complicated driving situations. Two game theoretic approaches, namely linear quadratic game and non-cooperative model predictive control (non-cooperative MPC), are used for developing the driver-AFS interactive steering control model. For each approach, the open-loop Nash steering control solution is derived; the influences of the path-following weights, preview and control horizons, driver time delay and arm neuromuscular system (NMS) dynamics are investigated, and the CPU time consumed is recorded. It is found that the two approaches give identical time histories as well as control gains, while the non-cooperative MPC method uses much less CPU time. Specifically, it is observed that the introduction of weight on the integral of vehicle lateral displacement error helps to eliminate the steady-state path-following error; the increase in preview horizon and NMS natural frequency and the decline in time delay and NMS damping ratio improve the path-following accuracy. © 2013 Copyright Taylor and Francis Group, LLC.

Using participant or non-participant observation to explain information behaviour

Cooper, J., Lewis, R. & Urquhart, C. (2004). Using participant or non-participant observation to explain information behaviour. Information Research, 9(4). Retrieved August 3, 2006 from http://informationr.net/ir/9-4/paper184.html Sponsorship: AHRC (Cooper).

Non-anonymous ballot aggregation: an axiomatic generalization of Approval Voting

We study axiomatically situations in which the society agrees to treat voters with different characteristics distinctly. In this setting, we propose a set of intuitive axioms and show that they jointly characterize a new class of voting procedures, called Type-weighted Approval Voting. According to this family, each voter has a strictly positive and finite weight (the weight is necessarily the same for all voters with the same characteristics) and the alternative with the highest number of weighted votes is elected. The implemented voting procedure reduces to Approval Voting in case all voters are identical or the procedure assigns the same weight to all types. Using this idea, we also obtain a new characterization of Approval Voting.

Impact of non-optimal grounding of the CC2420 RFIC on a 802.15.4 Tyndall sensor wireless mote

The performance of an RF output matching network is dependent on integrity of the ground connection. If this connection is compromised in anyway, additional parasitic elements may occur that can degrade performance and yield unreliable results. Traditionally, designers measure Constant Wave (CW) power to determine that the RF chain is performing optimally, the device is properly matched and by implication grounded. It is shown that there are situations where modulation quality can be compromised due to poor grounding that is not apparent using CW power measurements alone. The consequence of this is reduced throughput, range and reliability. Measurements are presented on a Tyndall Mote using a CC2420 RFIC todemonstrate how poor solder contact between the ground contacts and the ground layer of the PCB can lead tothe degradation of modulated performance. Detailed evaluation that required the development of a new measurement definition for 802.15.4 and analysis is presented to show how waveform quality is affected while the modulated output power remains within acceptable limits.

Reliability of antitransglutaminase antibodies as predictors of gluten-free diet compliance in adult celiac disease.

OBJECTIVE: Strict lifelong compliance to a gluten-free diet (GFD) minimizes the long-term risk of mortality, especially from lymphoma, in adult celiac disease (CD). Although serum IgA antitransglutaminase (IgA-tTG-ab), like antiendomysium (IgA-EMA) antibodies, are sensitive and specific screening tests for untreated CD, their reliability as predictors of strict compliance to and dietary transgressions from a GFD is not precisely known. We aimed to address this question in consecutively treated adult celiacs. METHODS: In a cross-sectional study, 95 non-IgA deficient adult (median age: 41 yr) celiacs on a GFD for at least 1 yr (median: 6 yr) were subjected to 1) a dietician-administered inquiry to pinpoint and quantify the number and levels of transgressions (classified as moderate or large, using as a cutoff value the median gluten amount ingested in the overall noncompliant patients of the series) over the previous 2 months, 2) a search for IgA-tTG-ab and -EMA, and 3) perendoscopic duodenal biopsies. The ability of both antibodies to discriminate celiacs with and without detected transgressions was described using receiver operating characteristic curves and quantified as to sensitivity and specificity, according to the level of transgressions. RESULTS: Forty (42%) patients strictly adhered to a GFD, 55 (58%) had committed transgressions, classified as moderate (< or = 18 g of gluten/2 months; median number 6) in 27 and large (>18 g; median number 69) in 28. IgA-tTG-ab and -EMA specificity (proportion of correct recognition of strictly compliant celiacs) was 0.97 and 0.98, respectively, and sensitivity (proportion of correct recognition of overall, moderate, and large levels of transgressions) was 0.52, 0.31, and 0.77, and 0.62, 0.37, and 0.86, respectively. IgA-tTG-ab and -EMA titers were correlated (p < 0.001) to transgression levels (r = 0.560 and R = 0.631, respectively) and one to another (p < 0.001) in the whole patient population (r = 0.834, N = 84) as in the noncompliant (r = 0.915, N = 48) group. Specificity and sensitivity of IgA-tTG-ab and IgA-EMA for recognition of total villous atrophy in patients under a GFD were 0.90 and 0.91, and 0.60 and 0.73, respectively. CONCLUSIONS: In adult CD patients on a GFD, IgA-tTG-ab are poor predictors of dietary transgressions. Their negativity is a falsely secure marker of strict diet compliance.

Strategic non-cooperation as soft balancing: Why Iraq was not just about Iraq

Many commentators explain recent transatlantic rifts by pointing to diverging norms, interests and geopolitical preferences. This paper proceeds from the premise that not all situations of conflict are necessarily due to underlying deadlocked preferences. Rather, non-cooperation may be a strategic form of soft balancing. That is, more generally, if they believe that they are being shortchanged in terms of influence and payoffs, weaker states may deliberately reject possible cooperation in the short run to improve their influence vis-à-vis stronger states in the long run. This need not be due to traditional relative gains concern. States merely calculate that their reputation as a weak negotiator will erode future bargaining power and subsequently their future share of absolute gains. Strategic non-cooperation is therefore a rational signal of resolve. This paper develops the concept of strategic non-cooperation as a soft balancing tool and applies it to the Iraq case in 2002-2003. © 2005 Palgrave Macmillan Ltd.

Through the portal – improving the flow of information on non-native marine species in Great Britain.

Abstract: The UK Government funded, GB Non-Native Species Information Portal (GBNNSIP) collects and collates data on non-native species in Great Britain making information available online. Resources include a comprehensive register of non-native species and detailed fact sheets for a sub-set, significant to humans or the environment. Reporting of species records are linked to risk analyses, rapid responses and horizon scanning to support the early recognition of threats (Figure 12). The portal has improved flow of new and existing distributional data to the National Biodiversity Network (NBN) to generate distribution maps for the portal. The project is led by the Biological Records Centre and the Marine Biological Association is responsible for marine non-native species within this scheme. The INTERREG IV funded project Marinexus has included professional research and citizen science work, which has fed directly into the portal. The portal outputs and the work of Marinexus have a range of marine governance applications, including supporting work towards MSFD compliance.

To what extent do children with cerebral palsy participate in everyday life situations?

The aims of the study are to describe participation of children with cerebral palsy in everyday life situations, to investigate the relationship between participation (primary outcome variable) with child and parent characteristics (independent variables) and to compare the frequency of participation (secondary outcome variable) of children with cerebral palsy with children without disabilities. A cross-sectional survey of parents of children with cerebral palsy in Northern Ireland was undertaken in families’ homes using standard questionnaires. Children with cerebral palsy born between 31/8/1991 and 1/4/1997 were identified from a case register of people with the condition. A total of 102 parents opted in (51% response rate). Questionnaires included the Life Habits Questionnaire (Life-H) to measure difficulties in participation and The Frequency of Participation Questionnaire (FPQ), to measure frequency of participation with comparative data for children without disability. Overall, children with cerebral palsy participated less often than their non-disabled peers across a number of lifestyle and cultural pursuits. Among the 102 children with cerebral palsy, participation in ‘relationships’ was the least disrupted area of everyday life and aspects of ‘school’, ‘personal care’ and ‘mobility’ were the most disrupted. Children with cerebral palsy and severe co-impairments were significantly less likely to experience higher levels of participation in most areas of everyday life when compared to children with cerebral palsy and no severe co-impairments. Child physical and psychological well-being did not influence participation although higher parenting stress was significantly related to lower child participation in ‘community activities’. Participation is an important health outcome for children with cerebral palsy and should be incorporated in routine clinical practice. Professionals have a role to play both at the level of addressing individual child and family needs as well as influencing legislation and policy to ensure improved access to services and local communities.

User behaviour, best practice and the risks of non-target exposure associated with anticoagulant rodenticide use

Usage of anticoagulant rodenticides (ARs) is an integral component of modern agriculture and is essential for the control of commensal rodent populations. However, the extensive deployment of ARs has led to widespread exposure of a range of non-target predatory birds and mammals to some compounds, in particular the second-generation anticoagulant rodenticides (SCARS). As a result, there has been considerable effort placed into devising voluntary best practice guidelines that increase the efficacy of rodent control and reduce the risk of non-target exposure. Currently, there is limited published information on actual practice amongst users or implementation of best practice. We assessed the behaviour of a typical group of users using an on-farm questionnaire survey. Most baited for rodents every year using SGARs. Most respondents were apparently aware of the risks of non-target exposure and adhered to some of the best practice recommendations but total compliance was rare. Our questionnaire revealed that users of first generation anticoagulant rodenticides rarely protected or checked bait stations, and so took little effort to prevent primary exposure of non-targets. Users almost never searched for and removed poisoned carcasses and many baited for prolonged periods or permanently. These factors are all likely to enhance the likelihood of primary and secondary exposure of non-target species. (C) 2010 Published by Elsevier Ltd.

Teachers’ reflections on non standard students work

One of the tasks of teaching (Ball, Thames, & Phelps, 2008) concerns the work of interpreting student error and evaluating alternative algorithms used by students. Teachers’ abilities to understand nonstandard student work affects their instructional decisions, the explanations they provide in the classroom, the way they guide their students, and how they conduct mathematical discussions. However, their knowledge or their perceptions of the knowledge may not correspond to the actual level of knowledge that will support flexibility and fluency in a mathematics classroom. In this paper, we focus on Norwegian and Portuguese teachers’ reflections when trying to give sense to students’ use of nonstandard subtraction algorithms and of the mathematics imbedded in such. By discussing teachers’ mathematical knowledge associated with these situations and revealed in their reflections, we can perceive the difficulties teachers have in making sense of students’ solutions that differ from those most commonly reached.