Quantum hydrodynamic models for semiconductors with and without collisions

In dieser Arbeit werden Quantum-Hydrodynamische (QHD) Modelle betrachtet, die ihren Einsatz besonders in der Modellierung von Halbleiterbauteilen finden. Das QHD Modell besteht aus den Erhaltungsgleichungen für die Teilchendichte, das Momentum und die Energiedichte, inklusive der Quanten-Korrekturen durch das Bohmsche Potential. Zu Beginn wird eine Übersicht über die bekannten Ergebnisse der QHD Modelle unter Vernachlässigung von Kollisionseffekten gegeben, die aus ein­em Schrödinger-System für den gemischten-Zustand oder aus der Wigner-Glei­chung hergeleitet werden können. Nach der Reformulierung der eindimensionalen QHD Gleichungen mit linearem Potential als stationäre Schrö­din­ger-Gleichung werden die semianalytischen Fassungen der QHD Gleichungen für die Gleichspannungs-Kurve betrachtet. Weiterhin werden die viskosen Stabilisierungen des QHD Modells be­rück­sich­tigt, sowie die von Gardner vorgeschlagene numerische Viskosität für das {sf upwind} Finite-Differenzen Schema berechnet. Im Weiteren wird das viskose QHD Modell aus der Wigner-Glei­chung mit Fokker-Planck Kollisions-Ope­ra­tor hergeleitet. Dieses Modell enthält die physikalische Viskosität, die durch den Kollision-Operator eingeführt wird. Die Existenz der Lösungen (mit strikt positiver Teilchendichte) für das isotherme, stationäre, eindimensionale, viskose Modell für allgemeine Daten und nichthomogene Randbedingungen wird gezeigt. Die dafür notwendigen Abschätzungen hängen von der Viskosität ab und erlauben daher den Grenzübergang zum nicht-viskosen Fall nicht. Numerische Simulationen der Resonanz-Tunneldiode modelliert mit dem nichtisothermen, stationären, eindimensionalen, viskosen QHD Modell zeigen den Einfluss der Viskosität auf die Lösung. Unter Verwendung des von Degond und Ringhofer entwickelten Quanten-Entropie-Minimierungs-Verfahren werden die allgemeinen QHD-Gleichungen aus der Wigner-Boltzmann-Gleichung mit dem BGK-Kollisions-Operator hergeleitet. Die Herleitung basiert auf der vorsichtige Entwicklung des Quanten-Max­well­ians in Potenzen der skalierten Plankschen Konstante. Das so erhaltene Modell enthält auch vertex-Terme und dispersive Terme für die Ge­schwin­dig­keit. Dadurch bleibt die Gleichspannungs-Kurve für die Re­so­nanz-Tunnel­diode unter Verwendung des allgemeinen QHD Modells in einer Dimension numerisch erhalten. Die Ergebnisse zeigen, dass der dispersive Ge­schwin­dig­keits-Term die Lösung des Systems stabilisiert.

Estimation of Quasi-Rational DSGE Models

Small-scale dynamic stochastic general equilibrium have been treated as the benchmark of much of the monetary policy literature, given their ability to explain the impact of monetary policy on output, inflation and financial markets. One cause of the empirical failure of New Keynesian models is partially due to the Rational Expectations (RE) paradigm, which entails a tight structure on the dynamics of the system. Under this hypothesis, the agents are assumed to know the data genereting process. In this paper, we propose the econometric analysis of New Keynesian DSGE models under an alternative expectations generating paradigm, which can be regarded as an intermediate position between rational expectations and learning, nameley an adapted version of the "Quasi-Rational" Expectatations (QRE) hypothesis. Given the agents' statistical model, we build a pseudo-structural form from the baseline system of Euler equations, imposing that the length of the reduced form is the same as in the `best' statistical model.

Stochastic foundations of dynamic trade and labor market models

This dissertation consists of three self-contained papers that are related to two main topics. In particular, the first and third studies focus on labor market modeling, whereas the second essay presents a dynamic international trade setup.rnrnIn Chapter "Expenses on Labor Market Reforms during Transitional Dynamics", we investigate the arising costs of a potential labor market reform from a government point of view. To analyze various effects of unemployment benefits system changes, this chapter develops a dynamic model with heterogeneous employed and unemployed workers.rn rnIn Chapter "Endogenous Markup Distributions", we study how markup distributions adjust when a closed economy opens up. In order to perform this analysis, we first present a closed-economy general-equilibrium industry dynamics model, where firms enter and exit markets, and then extend our analysis to the open-economy case.rn rnIn Chapter "Unemployment in the OECD - Pure Chance or Institutions?", we examine effects of aggregate shocks on the distribution of the unemployment rates in OECD member countries.rn rnIn all three chapters we model systems that behave randomly and operate on stochastic processes. We therefore exploit stochastic calculus that establishes clear methodological links between the chapters.

Hepatoprotective effect of tumour necrosis factor alpha blockade in psoriatic arthritis: a cross-sectional study

Objective To evaluate the impact of tumour necrosis factor α (TNFα) blockers on the presence of liver fibrosis in patients with rheumatoid arthritis (RA) and psoriatic arthritis (PsA) treated with methotrexate (MTX). Methods Participants were consecutive patients with RA and PsA who had undergone MTX treatment for at least 1 year ± TNF blockade for over 6 months. Liver fibrosis was assessed using non-invasive transient elastography (FibroScan). Regression models were used to compare FibroScan values of patients with RA and patients with PsA receiving TNFα blockers with those who were not. Results FibroScan assessments were performed on 51 patients with RA and 43 patients with PsA. Compared to patients with RA, those with PsA were predominantly young men, received lower cumulative dosages of MTX and exhibited a higher incidence of liver steatosis and hyperlipidaemia. An abnormal result was observed in 7.1% of the anti-TNFα-naïve and in 13% of the anti-TNFα-treated patients in the RA group and in 30% of the anti-TNFα-naïve and 4.3% of the anti-TNFα-treated patients in the PsA group (OR=0.11, 95% CI 0.02 to 0.98). Results of the PsA group were robust when adjusted for baseline characteristics. Conclusion The results suggest a protective effect of TNFα inhibitors against the development of liver fibrosis in patients with PsA.

Stroke, coronary and peripheral artery disease survey on antithrombotic treatment (START IT)

QUESTIONS UNDER STUDY: To determine the perception of primary care physicians regarding the risk of subsequent atherothrombotic events in patients with established cardiovascular (CV) disease, and to correlate this perception with documented antithrombotic therapy. METHODS: In a cross-sectional study of the general practice population in Switzerland, 381 primary care physicians screened 127 040 outpatients during 15 consecutive workdays in 2006. Perception of subsequent atherothrombotic events in patients with established CV disease was assessed using a tick box questionnaire allowing choices between low, moderate, high or very high risk. Logistic regression models were used to determine the relationship between risk perception and antithrombotic treatment. RESULTS: Overall, 13 057 patients (10.4%) were identified as having established CV disease and 48.8% of those were estimated to be at high to very high risk for subsequent atherothrombotic events. Estimated higher risk for subsequent atherothrombotic events was associated with a shift from aspirin monotherapy to clopidogrel, vitamin K antagonist or aspirin plus clopidogrel (p <0.001 for trend). Clopidogrel (12.7% vs 6.8%, p <0.001), vitamin K antagonist (24.5% vs 15.6%, p <0.001) or aspirin plus clopidogrel (10.2% vs 4.2%, p <0.001) were prescribed in patients estimated to be at high to very high risk more often than in those at low to moderate risk. CONCLUSIONS: Perception of primary care physicians regarding risk of subsequent atherothrombotic events varies in patients with CV disease, and as a result antithrombotic therapy is altered in patients with anticipated high to very high risk even though robust evidence and clear guidelines are lacking.

Gender inequity in the provision of care for hip disease: population-based cross-sectional study

Objectives To examine gender differences along the care pathway to total hip replacement. Methods We conducted a population-based cross-sectional study of 26,046 individuals aged 35 years and over in Avon and Somerset. Participants completed a questionnaire asking about care provision at five milestones on the pathway to total hip replacement. Those reporting hip disease were invited to a clinical examination. We estimated odds ratios (ORs) [95% confidence intervals (CI)] for provision of care to women compared with men. Results 3169 people reported hip pain, 2018 were invited for clinical examination, and 1405 attended (69.6%). After adjustment for age and disease severity, women were less likely than men to have consulted their general practitioner (OR 0.78, 95%-CI 0.61–1.00), as likely as men to have received drug therapy for hip pain in the previous year (OR 0.96, 95%-CI 0.74–1.24), but less likely to have been referred to specialist care (OR 0.53, 95%-CI 0.40–0.70), to have consulted an orthopaedic surgeon (OR 0.50, 95%-CI 0.32–0.78), or to be on a waiting list for total hip replacement (OR 0.41, 95%-CI 0.20–0.87). Differences remained in the 746 people who had sought care from their general practitioner, and after adjustment for willingness and fitness for surgery. Conclusions There are gender inequalities in provision of care for hip disease in England, which are not fully accounted for by gender differences in care seeking and treatment preferences. Differences in referral to specialist care by general practitioners might unwittingly contribute to this inequity. Accurate information about availability, benefits and risks of hip replacement for providers and patients, and continuing education to ensure that clinicians interpret and correct patients' assumptions could help reduce inequalities.

Methodology and models in erosion research: discussion and conclusions

This paper summarises the discussions which took place at the Workshop on Methodology in Erosion Research in Zürich, 2010, and aims, where possible, to offer guidance for the development and application of both in vitro and in situ models for erosion research. The prospects for clinical trials are also discussed. All models in erosion research require a number of choices regarding experimental conditions, study design and measurement techniques, and these general aspects are discussed first. Among in vitro models, simple (single- or multiple-exposure) models can be used for screening products regarding their erosive potential, while more elaborate pH cycling models can be used to simulate erosion in vivo. However, in vitro models provide limited information on intra-oral erosion. In situ models allow the effect of an erosive challenge to be evaluated under intra-oral conditions and are currently the method of choice for short-term testing of low-erosive products or preventive therapeutic products. In the future, clinical trials will allow longer-term testing. Possible methodologies for such trials are discussed.

Association between cam-type deformities and magnetic resonance imaging-detected structural hip damage: a cross-sectional study in young men

Objective Femoroacetabular impingement may be a risk factor for hip osteoarthritis in men. An underlying hip deformity of the cam type is common in asymptomatic men with nondysplastic hips. This study was undertaken to examine whether hip deformities of the cam type are associated with signs of hip abnormality, including labral lesions and articular cartilage damage, detectable on magnetic resonance imaging (MRI). Methods In this cross-sectional, population-based study in asymptomatic young men, 1,080 subjects underwent clinical examination and completed a self-report questionnaire. Of these subjects, 244 asymptomatic men with a mean age of 19.9 years underwent MRI. All MRIs were read for cam-type deformities, labral lesions, cartilage thickness, and impingement pits. The relationship between cam-type deformities and signs of joint damage were examined using logistic regression models adjusted for age and body mass index. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were determined. Results Sixty-seven definite cam-type deformities were detected. These deformities were associated with labral lesions (adjusted OR 2.77 [95% CI 1.31, 5.87]), impingement pits (adjusted OR 2.9 [95% CI 1.43, 5.93]), and labral deformities (adjusted OR 2.45 [95% CI 1.06, 5.66]). The adjusted mean difference in combined anterosuperior femoral and acetabular cartilage thickness was −0.19 mm (95% CI −0.41, 0.02) lower in those with cam-type deformities compared to those without. Conclusion Our findings indicate that the presence of a cam-type deformity is associated with MRI-detected hip damage in asymptomatic young men.

Electromyographic activity of the cervical flexor muscles in patients with temporomandibular disorders while performing the craniocervical flexion test: a cross-sectional study

Most patients with temporomandibular disorders (TMD) have been shown to have cervical spine dysfunction. However, this cervical dysfunction has been evaluated only qualitatively through a general clinical examination of the cervical spine.

Study protocol: Transition from localized low back pain to chronic widespread pain in general practice: identification of risk factors, preventive factors and key elements for treatment--a cohort study

Background Chronic localized pain syndromes, especially chronic low back pain (CLBP), are common reasons for consultation in general practice. In some cases chronic localized pain syndromes can appear in combination with chronic widespread pain (CWP). Numerous studies have shown a strong association between CWP and several physical and psychological factors. These studies are population-based cross-sectional and do not allow for assessing chronology. There are very few prospective studies that explore the predictors for the onset of CWP, where the main focus is identifying risk factors for the CWP incidence. Until now there have been no studies focusing on preventive factors keeping patients from developing CWP. Our aim is to perform a cross sectional study on the epidemiology of CLBP and CWP in general practice and to look for distinctive features regarding resources like resilience, self-efficacy and coping strategies. A subsequent cohort study is designed to identify the risk and protective factors of pain generalization (development of CWP) in primary care for CLBP patients. Methods/Design Fifty-nine general practitioners recruit consecutively, during a 5 month period, all patients who are consulting their family doctor because of chronic low back pain (where the pain is lasted for 3 months). Patients are asked to fill out a questionnaire on pain anamnesis, pain-perception, co-morbidities, therapy course, medication, socio demographic data and psychosomatic symptoms. We assess resilience, coping resources, stress management and self-efficacy as potential protective factors for pain generalization. Furthermore, we raise risk factors for pain generalization like anxiety, depression, trauma and critical life events. During a twelve months follow up period a cohort of CLBP patients without CWP will be screened on a regular basis (3 monthly) for pain generalization (outcome: incident CWP). Discussion This cohort study will be the largest study which prospectively analyzes predictors for transition from CLBP to CWP in primary care setting. In contrast to the typically researched risk factors, which increase the probability of pain generalization, this study also focus intensively on protective factors, which decrease the probability of pain generalization.

Rationale, scope, and 20-year experience of vascular surgical training with lifelike pulsatile flow models

Vascular surgical training currently has to cope with various challenges, including restrictions on work hours, significant reduction of open surgical training cases in many countries, an increasing diversity of open and endovascular procedures, and distinct expectations by trainees. Even more important, patients and the public no longer accept a "learning by doing" training philosophy that leaves the learning curve on the patient's side. The Vascular International (VI) Foundation and School aims to overcome these obstacles by training conventional vascular and endovascular techniques before they are applied on patients. To achieve largely realistic training conditions, lifelike pulsatile models with exchangeable synthetic arterial inlays were created to practice carotid endarterectomy and patch plasty, open abdominal aortic aneurysm surgery, and peripheral bypass surgery, as well as for endovascular procedures, including endovascular aneurysm repair, thoracic endovascular aortic repair, peripheral balloon dilatation, and stenting. All models are equipped with a small pressure pump inside to create pulsatile flow conditions with variable peak pressures of ~90 mm Hg. The VI course schedule consists of a series of 2-hour modules teaching different open or endovascular procedures step-by-step in a standardized fashion. Trainees practice in pairs with continuous supervision and intensive advice provided by highly experienced vascular surgical trainers (trainer-to-trainee ratio is 1:4). Several evaluations of these courses show that tutor-assisted training on lifelike models in an educational-centered and motivated environment is associated with a significant increase of general and specific vascular surgical technical competence within a short period of time. Future studies should evaluate whether these benefits positively influence the future learning curve of vascular surgical trainees and clarify to what extent sophisticated models are useful to assess the level of technical skills of vascular surgical residents at national or international board examinations. This article gives an overview of our experiences of >20 years of practical training of beginners and advanced vascular surgeons using lifelike pulsatile vascular surgical training models.

Towards a Variety of Family Models: Economic Contributions of Spouses and Family Power

In Western societies the increase in female employment (especially among married women) is seen as having brought about the crisis of the traditional model of the family, reinforcing the position of the "modern" model - the egalitarian family with two working spouses and a "dual-career" family. In contrast, the transitional situation in the post-communist countries during the 1990s is producing a crisis of the family with two working spouses (the basic type of the communist period) and leading to new power relations within the family. While the growth of dual-earner households in this century has implied modification of family models towards greater symmetry of responsibility for breadwinning and homemaking, there is considerable evidence that women's increased employment does not necessarily lead to a more egalitarian approach to gender roles within the family. The group set out to investigate the economic situation of families and economic power within the fame as a crucial factor in the transformation of families with two working spouses in order to reveal the specific patterns of gender contracts and power relations within the family that are emerging in response to the current political and economic transformation. They opted for a comparative approach, selecting the Czech Republic as a country where the very similar tendencies of a few years ago (almost 100% of women employed and the family as a realm of considerable private freedom where both women's and men's gender identities and the traditional distribution of family responsibilities were largely preserved) are combined with a very different experience in terms of economic inequalities during the 1990s to that of Russia. In the first stage of the study they surveyed 300 married couples (150 in each country) on the question of breadwinning. They then carried out in-depth interviews with 10 couples from each country (selected from among the educated layers of the population), focusing on the process of the social construction of gender, using breadwinning and homemaking as gender boundaries which distinguish men from women. By analysing changes in social position and the type of interpersonal interaction of spouses they distinguished two main types of family contracts: the neo-traditional "communal sharing" (with male breadwinner, traditional distribution of family chores and negotiated family power) and the modern one based on negotiated agreement. The most important pre-conditions of husband-wife agreement about breadwinning seemed to imply their overall gender ideology rather than the economic and/or family circumstances. In general, wives were more likely to express egalitarian views, supporting the blurring or even elimination of many gender boundaries. Husbands, on the other hand, more often gave responses calling for the continued maintenance of gender boundaries. The analysis showed that breadwinning is still an important gender boundary in these cultures, one that is assumed unless it is explicitly questioned and that is seen as part of what makes a man a "real man". The majority of respondents seemed to be committed to egalitarian ideology on gender roles and the distribution of family tasks, including decision making, but this is contradicted by the persistent idea of the husband as the breadwinner. This contradiction is more characteristic of the Russian situation than of the Czech. The quantitative study showed a difference in prevailing family models between the two countries, with a clearer shift towards the traditional family contract in the Russian case. The Czechs were more likely to consider their partnerships as based on negotiated agreement, while the Russians saw theirs as based on egalitarian contract, in both cases seeing this as the norm. The majority of couples said they felt satisfied with their marriage, although in both countries wives seemed to be less satisfied. There was however a difference in the issues that aroused dissatisfaction, with Czech women being more sensitive to issues such as self-realisation, personal independence, understanding and recognition in the family, and Russians to issues of love, understanding and recognition. The most disputed area for the majority of families was chores in the home, presumably because in many families both husband and wife were working hard outside the home and because a number of partners had differing views as to the ideal distribution of chores within the family. The distribution of power in the family seems to be linked to the level of well being. The analysis showed that in the dominant democratic model there is still an inverse connection between family leadership and well being: the more prominent the wife's position as head of the family is, the lower the level of family income. This may reflect both the husband's refusal to play the leading role in the family and even his rejection of any involvement in family issues in such a family. The qualitative research revealed that both men and women see the breadwinning role to be an essential part of masculine identity, a role which the female partner would take on temporarily to assist the male but not permanently since this would threaten the gender boundaries and the man's identity. At the same time, few breadwinners expressed a sense of job satisfaction and all considered their choice as imposed on them by the circumstances (i.e. having a family in difficult times). The group feel that family orientation and some loss of personal involvement in their profession is partly reflected in the fact that many of the men felt more comfortable and self-confident at home than at work. Women's work, on the other hand, was largely seen as a source of personal and self-realisation and social life. Eight out of ten of the Russian women interviewed were employed, although only two on a full-time basis, but none saw their jobs as adding substantially to the family budget. Both partners see the most important factor as the wife's wish to work or stay at home, and do not think it wise for the wife to work at the expense of her part of the "family contract", although husbands from the "egalitarian" relationships expressed more willingness to compromise. The analysis showed clearly that wives and husbands did not construct gender boundaries in isolation, with the interviews providing clear evidence of negotiation. At the same time, husbands' interpretations of their wives' employment were less susceptible to the influence of negotiation than were their gender attitudes and norms about breadwinning. One of the most interesting aspects of the spouses' negotiations was the extent to which they disagreed about what they seemed to have agreed upon. Most disagreements about the breadwinning boundaries, however, were over norms and were settled by changes in norms rather than in behavioural interpretation. Changes in norms were often a form of peace offering or were in response in changes in circumstances. The study did show, however, that many of the efforts at cooperation and compensation were more symbolic than real and the group found the plasticity of expressed gender ideology to be one of the most striking findings of their work. They conclude that the shift towards more traditional gednder distributions of incomes and domestic chores does not automatically mean the reestablishment of a patriarchal model of family power. On the contrary, it seems to be a compromise formation, relatively unstable, temporary and containing self-defeating forces as the split between the personal and professional value of work and its social value expressed in a money equivalent cannot be maintained for generations.

Complementary and conventional medicine in Switzerland: comparing characteristics of general practitioners

OBJECTIVES: Do structural characteristics of general practitioners (GPs) who practice complementary medicine (CAM) differ from those GPs who do not? Assessed characteristics included experience and professional integration of general practitioners (GPs), workload, medical activities, and personal and technical resources of practices. The investigated CAM disciplines were anthroposophic medicine, homoeopathy, traditional Chinese medicine, neural therapy and herbal medicine. MATERIAL AND METHODS: We designed a cross-sectional study with convenience and stratified samples of GPs providing conventional (COM) and/or complementary primary care in Switzerland. The samples were taken from the database of the Swiss medical association (FMH) and from CAM societies. Data were collected using a postal questionnaire. RESULTS: Of the 650 practitioners who were included in the study, 191 were COM, 167 noncertified CAM and 292 certified CAM physicians. The proportion of females was higher in the population of CAM physicians. Gender-adjusted age did not differ between CAM and COM physicians. Nearly twice as many CAM physicians work part-time. Differences were also seen for the majority of structural characteristics such as qualification of physicians, type of practice, type of staff, and presence of technical equipment. CONCLUSION: The study results show that structural characteristics of primary health care do differ between CAM and COM practitioners. We assumed that the activities of GPs are defined essentially by analyzed structures. The results are to be considered for evaluations in primary health care, particularly when quality of health care is assessed.

Opportunistic and systematic screening for chlamydia: a study of consultations by young adults in general practice

BACKGROUND: Opportunistic screening for genital chlamydia infection is being introduced in England, but evidence for the effectiveness of this approach is lacking. There are insufficient data about young peoples' use of primary care services to determine the potential coverage of opportunistic screening in comparison with a systematic population-based approach. AIM: To estimate use of primary care services by young men and women; to compare potential coverage of opportunistic chlamydia screening with a systematic postal approach. DESIGN OF STUDY: Population based cross-sectional study. SETTING: Twenty-seven general practices around Bristol and Birmingham. METHOD: A random sample of patients aged 16-24 years were posted a chlamydia screening pack. We collected details of face-to-face consultations from general practice records. Survival and person-time methods were used to estimate the cumulative probability of attending general practice in 1 year and the coverage achieved by opportunistic and systematic postal chlamydia screening. RESULTS: Of 12 973 eligible patients, an estimated 60.4% (95% confidence interval [CI] = 58.3 to 62.5%) of men and 75.3% (73.7 to 76.9%) of women aged 16-24 years attended their practice at least once in a 1-year period. During this period, an estimated 21.3% of patients would not attend their general practice but would be reached by postal screening, 9.2% would not receive a postal invitation but would attend their practice, and 11.8% would be missed by both methods. CONCLUSIONS: Opportunistic and population-based approaches to chlamydia screening would both fail to contact a substantial minority of the target group, if used alone. A pragmatic approach combining both strategies might achieve higher coverage.

Large Sample Theory for Semiparametric Regression Models with Two-Phase, Outcome Dependent Sampling

Outcome-dependent, two-phase sampling designs can dramatically reduce the costs of observational studies by judicious selection of the most informative subjects for purposes of detailed covariate measurement. Here we derive asymptotic information bounds and the form of the efficient score and influence functions for the semiparametric regression models studied by Lawless, Kalbfleisch, and Wild (1999) under two-phase sampling designs. We show that the maximum likelihood estimators for both the parametric and nonparametric parts of the model are asymptotically normal and efficient. The efficient influence function for the parametric part aggress with the more general information bound calculations of Robins, Hsieh, and Newey (1995). By verifying the conditions of Murphy and Van der Vaart (2000) for a least favorable parametric submodel, we provide asymptotic justification for statistical inference based on profile likelihood.