Fučík spectra for vector equations

Let $L:\hbox{dom} L\subset L^2(\Omega;R^N)\rightarrow L^2(\Omega;R^N)$ be a linear operator, $\Omega$ being open and bounded in $R^M$. The aim of this paper is to study the Fu\v c\'\i k spectrum for vector problems of the form $Lu=\alpha Au^+ -\beta Au^-$, where $A$ is an $N\times N$ matrix, $\alpha, \beta$ are real numbers, $u^+$ a vector defined componentwise by $(u^+)_i=\max\{u_i,0\}$, $u^-$ being defined similarly. With $\lambda^*$ an eigenvalue for the problem $Lu=\lambda Au$, we describe (locally) curves in the Fučík spectrum passing through the point $(\lambda^*,\lambda^*)$, distinguishing different cases illustrated by examples, for which Fučík curves have been computed numerically

Relation entre humidité relative et performances pour des Assemblages Membrane Electrodes de pile PEM à base d'aérogels de carbone - Impact de l'ajout de PTFE dans la couche catalytique

National audiencePour améliorer les performances des piles PEM (Proton Exchange Membrane Fuel Cells), il est nécessaire de mieux comprendre les phénomènes qui apparaissent lors de leur fonctionnement. L'objectif de cette étude est d'étudier différents paramètres jouant un rôle dans la gestion de l'eau en utilisant les matériaux modèles que sont les aérogels de carbone comme support de catalyseur. Pour cela, nous avons synthétisé trois aérogels de carbone d'architectures différentes que nous avons utilisés comme supports de catalyseur et mis en oeuvre en Assemblage Membrane Electrodes (AME). Dans ce travail, nous avons également étudié l'impact du taux d'humidité relative cathodique et de l'utilisation de PTFE dans la couche catalytique cathodique. Les tests des différents AME sur un banc monocellule montrent l'importance du contrôle de l'architecture du support carboné. Par ailleurs, les performances des AME peuvent être améliorées en utilisant du PTFE et en diminuant l'humidité relative à la cathod

Influence of carbon aerogel texture on PEMFC performances

International audienceTo improve Proton Exchange Membrane Fuel Cells (PEMFC), it is necessary to understand the phenomena occurring in operating conditions. The objective of this study is to determine how carbon support architecture can impact PEMFC performances, particularly diffusive limitations. In this context, as they have a controllable texture, carbon aerogels were used as catalyst supports in PEM fuel cell cathodes. Three carbon aerogels with different morphologies were synthesized. Fuel cell measurements show that the carbon support architecture has a significant impact on diffusive limitations. Moreover, they confirm that Nafion® loading must be optimized in order to preserve the catalytic layers architecture. This work finally highlights the impact of the catalytic layers architecture on the PEMFC performances

Faculty Development Initiatives in Medical Education in German-Speaking Countries : I. State of affairs

Maßgeblich unter dem wachsenden externen Druck hat die didaktische Qualifizierung in den medizinischen Fakultäten an Bedeutung gewonnen. Im Rahmen der Professionalisierung der medizinischen Aus-, Fort- und Weiterbildung ist eine pädagogisch-didaktische Ausbildung der Lehrenden unumgänglich. Um Orientierung und Argumentationshilfe zu geben, werden in einer dreiteiligen Artikelfolge Stellenwert der Medizindidaktik, Anforderungsprofil der Angebote und Konzepte zur Implementierung und zur Erfolgsmessung für den deutschsprachigen Raum beleuchtet. In Teil I geben wir eine Bestandsaufnahme zur Medizindidaktik. Aktuell gibt es bundesweit ein breit gefächertes Qualifizierungsangebot. Es reicht von einfachen unstrukturierten Kurzfortbildungen wie zum Beispiel Vorträgen und Seminaren, die inhaltlich, formal und qualitativ eine große Beliebigkeit zeigen, bis hin zu umfassenden mehrjährigen (Aufbau-)Studiengängen mit "Master-Degree". Im internationalen Vergleich fehlt in Deutschland ein allgemein verbindliches "Basis-Programm", das die täglich Lehrenden systematisch auf ihre Ausbildungsaufgaben vorbereitet. Dies ist bisher nur lokal umgesetzt wie zum Beispiel in Baden-Württemberg mit dem ministeriell zertifizierten Programm der Medizindidaktischen Qualifikation I und II. Vergleichbares ist in Nordrhein-Westfalen und Bayern im Aufbau.In recent years, quality management of educational skills of medical teachers has gained increasing relevance, predominantly triggered by rising external pressure. Meanwhile, a consensus is reached that a professional training in pedagogical methods and didactic skills is essential for medical teachers in UGME and PGME. A series of three articles intends to provide not only a brief overview, but also detailed argumentative support concerning pedagogical aspects of medical education, the conceptual design and the implementation of faculty development programs in medical education. Additionally the important topic of how the effectiveness of staff development programs can be demonstrated will be addressed. The goal of the first article is to outline the present situation, conditions and recognition of teacher's training programs in German-speaking countries. At present, a variety of faculty development programs and activities have been designed and implemented. These activities include e.g. non-structured short courses and lectures, workshops and seminars of one to six days, as well as longitudinal programs up to national, two-year postgraduate programs to achieve the degree of a "Master of Medical Education" in Swiss and Germany. Compared to the international situation, in Germany is a lack of a mandatory basic program for all teaching staff members, which systematically provides a broad range of teaching and learning strategies for diverse settings. Only one regional faculty development program has been established so far in the federal state of Baden-Wurttemberg, which has been certified as "Medical Education Qualification, Step I and II" by the federal state ministry responsible for higher education. Two comparable programs are on the way in the federal states of Bavaria and North-Rhine-Westfalia

Faculty development initiatives in medical education in German-speaking countries : II. needs assessment and quality criteria

Maßgeblich unter dem wachsenden externen Druck hat die didaktische Qualifizierung in den medizinischen Fakultäten an Bedeutung gewonnen. Im Rahmen der Professionalisierung der medizinischen Aus-, Fort- und Weiterbildung ist eine pädagogisch-didaktische Ausbildung der Lehrenden unumgänglich. Um Orientierung und Argumentationshilfe zu geben, werden in einer dreiteiligen Artikelfolge Stellenwert der Medizindidaktik, Anforderungsprofil der Angebote und Konzepte zur Implementierung und zur Erfolgsmessung für den deutschsprachigen Raum beleuchtet. In Teil II beleuchten wir den Ausbildungsbedarf und erstellen ein Anforderungsprofil für ein strukturiertes systematisches Qualifizierungsangebot. Der Hauptbedarf besteht in der Qualifizierung der Lehrenden, die den täglichen Unterricht durchführen. Insbesondere sie brauchen das Handwerkszeug, das ihnen erlaubt, ihre verschiedenen Lehraufgaben effizienter zu bewältigen. Seitens der Fakultät und der Studierenden bestehen Ansprüche an qualifizierte Lehrende; ebenso bestehen Forderungen seitens der Lehrenden an adäquat qualifizierende Kurse. Zur Umsetzung dieser berechtigten Ansprüche sind modular aufgebaute Programme nötig, die eine zumindest national qualitativ und quantitativ vergleichbare Ausbildung gewährleisten. Anforderungen an derartige Kurse sind bereits definiert und lokal zum Beispiel in Baden-Württemberg und zum Teil auch in Nordrhein-Westfalen umgesetzt. Es gilt nun, diese auf breiter Basis in die Praxis umzusetzen.In recent years, quality management of didactic skills of medical teachers has gained increasing relevance, predominately triggered by rising external pressure. Meanwhile, a consensus is reached that a professional training in pedagogical methods and didactic skills is essential for medical teachers in UGME and PGME. A triple series of articles intends to provide not only a brief overview, but also detailed argumentative support concerning pedagogical aspects of medical education, the conceptual design and the implementation of faculty development programs in medical education. Additionally the important topic of how the effectiveness of staff development programs can be demonstrated will be addressed. The goal of the first article was to outline the actual situation, conditions and acknowledgment of teacher's training programs in German-speaking countries. The second article focuses on the needs assessment and on quality criteria of a systematic and comprehensive teachers' training. The most urgent necessity is the preparation of faculty members that cover the daily teaching routine. The teachers require a broad range of teaching and learning strategies that can be used in diverse settings and that enable them to fulfill their multiple roles more efficiently and effectively. Both medical school and students demand for qualified teachers; and faculty members call for professional opportunities to acquire the essential teaching skills and tools. Modular-designed training programs are necessary, which keep at least national minimal standards: A catalogue of quality criteria for such training programs has been defined and already implemented in Baden-Württemberg, and partly in North-Rhine-Westfalia. These criteria are described to make them adoptable for other places

Doped TiO2 aerogels as alternative catalyst supports for proton exchange membrane fuel cells: A comparative study of Nb, V and Ta dopants

International audienceNb, Ta and V-doped TiO2 aerogels and xerogels have been synthesized as possible new alternatives to carbon blacks for Proton Exchange Membrane Fuel Cells catalyst supports. A comparative study of different dopants was realized in a single study. Nb, Ta and V showed different behaviors with respect to the final material structure and morphology, composition and electronic conductivity. They are all prone to surface segregation, to different extents. V-doped TiO2 apart, the rutile structure could only be obtained after calcination in a reducing atmosphere at 800 °C for Nb or Ta-doped TiO2. The electronic conductivity exhibited a maximum at 10 at.% for Nb and Ta, 5 at.% for V. Nb revealed to be the most appropriate dopant to increase the electronic conductivity of TiO2, followed by Ta and V. 4 to 5 orders of magnitude were gained after Nb doping for xerogels conductivity to reach almost 0.1 S cm−1. The role of point defects was discussed to account for phase transition and evolution of conductivity

Biomechanische Untersuchungen zum dynamischen Verhalten und zur Gelenkstabilität von Dual-Mobility Implantatsystemen unter physiologischen Randbedingungen

Das Ziel der vorliegenden Dissertation bestand in der experimentellen und analytischen Charakterisierung des dynamischen Verhaltens von konzentrischen und exzentrischen Dual-Mobility-Systemen unter physiologischen Randbedingungen. Zusätzlich wurde die Gelenkstabilität (Luxationsverhalten) von Dual-Mobility-Implantatsystemen gegenüber einer klassischen Endoprothese mit gleichem Kopfaußendurchmesser experimentell erfasst. Hierbei stellten insbesondere exzentrische Dual-Mobility-Systeme ein wirkungsvolles Therapiekonzept für den Einsatz an Patienten mit einem erhöhten Luxationsrisiko dar.The aim of the present study was to analyse the dynamic behavior of concentric and eccentric dual-mobility systems under physiological conditions using experimental and analytical techniques. Additionally, hip joint stability was investigated and compared with a standard total hip replacement. In conclusion, the high resisting torque against dislocation and the large range of motion substantiated the use of eccentric dual-mobility systems in case of hip joint instability

Faculty development initiatives in Medical Education in German-Speaking Countries : III. Aspects of successful implementation

Eine erfolgreiche Implementierung medizindidaktischer Qualifizierungsmaßnahmen setzt zwingend voraus, dass die Fakultäten nicht nur für entsprechende Angebote, sondern mittelfristig auch für lehrförderliche Rahmenbedingungen sorgen. Dabei müssen sowohl institutionelle Aspekte, die sich aus der Struktur und Funktion der Fakultät als Organisation ergeben als auch individuelle Aspekte der Zielgruppe der Lehrenden berücksichtigt werden. Von institutioneller Seitemuss vor allem Dermatologie und Deutschland die für alle sichtbare Unterstützung des Programms sichergestellt werden. Ebenfalls von zentraler Bedeutung ist die Bereitschaft, die medizindidaktische Qualifikation als einen wesentlichen Baustein der akademischen Laufbahn zu bewerten. Im Hinblick auf die Lehrenden geht es vor allem darum, das Angebot bekannt zu machen und seinen Nutzen herauszustellen, was mit Hilfe karrierebezogener Anreize naturgemäß leichter ist.To implement faculty development programs successfully it is absolutely essential that medical schools do not only provide adequate courses but do also offer surrounding conditions conducive to teaching. Institutional aspects that arise from structure and function of the medical school as an organisation as well as individual aspects that refer to the target group of medical teachers have to be taken into account. Looking at the institutional aspects it is especially important that official support of the program is assured and visible for everybody. Another institutional requirement is that expertise in teaching is regarded as an integral component of academic careers in medical education. Regarding medical teachers it is important to make faculty development programs known to them and to emphasise their benefit which is of course a lot easier by means of career incentives

Comparison of platinum deposit methods on carbon aerogels used in Proton Exchange. Membrane Fuel Cells (PEMFC)

International audienceWith the rarefaction and price increase of fossil fuels along with the consequences of greenhouse effect, many challenges have to be taken up. Consequently, a strong research effort is devoted to cleaner energy converters like fuel cells. In the car industry, Proton Exchange Membrane Fuel Cells (PEMFC) are chosen by a majority. But, remaining problems must be solved before a development at a large scale, among which: reducing the costs and increasing the power density and durability. Costs reduction mostly implies both diminishing the platinum quantity required for the oxygen reduction reaction at the cathode and increasing its activity. For these reasons, researches are devoted to the impact study of various methods of platinum deposit on the performances of new electrocatalysts and to the understanding of phenomena occurring in fuel cells

Acute Cerebrovascular Disease in the Young The Stroke in Young Fabry Patients Study

Background and Purpose-Strokes have especially devastating implications if they occur early in life; however, only limited information exists on the characteristics of acute cerebrovascular disease in young adults. Although risk factors and manifestation of atherosclerosis are commonly associated with stroke in the elderly, recent data suggests different causes for stroke in the young. We initiated the prospective, multinational European study Stroke in Young Fabry Patients (sifap) to characterize a cohort of young stroke patients. Methods-Overall, 5023 patients aged 18 to 55 years with the diagnosis of ischemic stroke (3396), hemorrhagic stroke (271), transient ischemic attack (1071) were enrolled in 15 European countries and 47 centers between April 2007 and January 2010 undergoing a detailed, standardized, clinical, laboratory, and radiological protocol. Results-Median age in the overall cohort was 46 years. Definite Fabry disease was diagnosed in 0.5% (95% confidence interval, 0.4%-0.8%; n=27) of all patients; and probable Fabry disease in additional 18 patients. Males dominated the study population (2962/59%) whereas females outnumbered men (65.3%) among the youngest patients (18-24 years). About 80.5% of the patients had a first stroke. Silent infarcts on magnetic resonance imaging were seen in 20% of patients with a first-ever stroke, and in 11.4% of patients with transient ischemic attack and no history of a previous cerebrovascular event. The most common causes of ischemic stroke were large artery atherosclerosis (18.6%) and dissection (9.9%). Conclusions-Definite Fabry disease occurs in 0.5% and probable Fabry disease in further 0.4% of young stroke patients. Silent infarcts, white matter intensities, and classical risk factors were highly prevalent, emphasizing the need for new early preventive strategies