Charge transport in thin metallic films

In dieser Arbeit wurden die verschiedenen mikroskopischen Beiträge des elektrischen Widerstands zum makroskopischen Widerstand in einem elektrischen Leiter auf Nanometerskala untersucht. Dabei wurde der Transport der Elektronen parallel und senkrecht zur Oberfläche betrachtet. Um den elektronischen Transport parallel zur Oberfläche zu analysieren, wurde die Rastertunnel-Potentiometrie verwendet. Mit ihr lassen sich die mikroskopischen Widerstandsbeiträge lokal auflösen und vom elektrischen Gesamtwiderstand isoliert untersuchen. Als elektrische Leiter wurden Wismut- und Silberfilme verwendet, die mit einer Dicke von bis zu 20 Monolagen auf einem Silizium-Substrat epitaktisch gewachsen sind. In den epitaktischen Bereichen der Wismut- und Silberfilme ist ein mikroskopischer Beitrag zum elektrischen Widerstand durch Stöße der Elektronen mit Phononen gegeben. Weitere wichtige Beiträge zum elektrischen Widerstand ergeben sich durch Streuung der Elektronen an Stufen des Silizium-Substrats und an Korngrenzen im Metallfilm. Aus der Analyse wurde ein spez. Stufen- und Korngrenzenwiderstand bestimmt. In einem weiteren System, der leitfähigen Si(111)- -Ag rekonstruierten Oberfläche, wird der elektrische Widerstand durch Streuung der Elektronen an atomaren Substratstufen und an Domänengrenzen dominiert. Für die Analyse des elektronischen Transports senkrecht zur Oberfläche wurde die Ballistische Elektronen Emissions Mikroskopie (BEEM) verwendet. Es wurde gezeigt, dass das System Wismut auf Si(100) für BEEM Experimente sehr gut geeignet ist. Mit dieser Methode konnte der ballistische Transport durch die beiden organischen Moleküle C60 und PTCDA untersucht werden, die auf dem Wismutfilm aufgebracht wurden. Hierdurch konnten die spezifischen Pfade der ballistischen Elektronen durch die Moleküle erstmalig identifiziert werden. Eine Signatur im BEEM Strom konnte für beide Moleküle auf den LUMO + 1 Zustand zurückgeführt werden. Es wurden einzelne C60 Moleküle identifiziert, bei denen die Transmission der ballistischen Elektronen genauso groß ist wie auf den unbedeckten Wismutbereichen.In this work, the different microscopic contributions to the macroscopic resistivity in an electric conductor were analysed on the nanometer scale. It was distinguished whether the transport of electrons occurs parallel or perpendicular to the surface. To analyse the electronic transport parallel to the surface, Scanning Tunneling Potentiometry was performed. This method allows to resolve the local microscopic contributions to the resistivity and to isolate their contribution from the global electric resistivity. As electric conductor, thin epitaxial bismuth and silver films with a thickness of up to 20 monolayers grown on a silicon single crystal were analysed. The microscopic contributions to the electric resistivity in the epitaxial regions of the film were dominated by electron-phonon scattering. It turned out that scattering of the electrons at substrate steps and at grain boundaries within the metal film contribute to the resistivity as well. A specific step and grain boundary resistivity was determined. For an additional system, the conducting Si(111)- -Ag surface reconstruction, the electric resistivity was dominated by scattering of the electrons at atomic substrate steps and domain boundaries. For the analysis of the electronic transport perpendicular to the surface, Ballistic Electron Emission Microscopy (BEEM) was applied. It could be shown that bismuth on a (100) oriented silicon single crystal substrate is a well suited system for BEEM experiments. This method was used to study the ballistic transport of electrons through the organic molecules C60 and PTCDA, deposited onto the bismuth film. Specific pathways for the ballistic transport of electrons could be identified. The contribution in the BEEM current could be attributed to the LUMO + 1 state for both molecules. Individual C60 molecules could be identified; they exhibit a transmission for the ballistic electrons which is almost as high as for the bare bismuth surface

Validation of Neural Network Controllers for Uncertain Systems Through Keep-Close Approach: Robustness Analysis and Safety Verification

Among the major challenges in neural control system technology is the validation and certification of the safety and robustness of neural network (NN) controllers against various uncertainties including unmodelled dynamics, non-linearities, and time delays. One way in providing such validation guarantees is to maintain the closed-loop system output with a NN controller when its input changes within a bounded set, close to the output of a robustly performing closed-loop reference model. This paper presents a novel approach to analysing the performance and robustness of uncertain feedback systems with NN controllers. Due to the complexity of analysing such systems, the problem is reformulated as the problem of dynamical tracking errors between the closed-loop system with a neural controller and an ideal closed-loop reference model. Then, the approximation of the controller error is characterised by adopting the differential mean value theorem (DMV) and the Integral Quadratic Constraints (IQCs) technique. Moreover, the Relative Integral Square Error (RISE) and the Supreme Square Error (SSE) bounded set are derived for the output of the error dynamical system. The analysis is then performed by integrating Lyapunov theory with the IQCs-based technique. The resulting worst-case analysis provides the user a prior knowledge about the worst case of RISE and SSE between the reference closed-loop model and the uncertain system controlled by the neural controller. The suitability of the proposed technique is demonstrated by the results obtained on a nonlinear single-link robot system with a NN trained to control the movement of this mechanical system while keeping close to an ideal closed-loop reference model.Comment: 19 pages, 10 figures, Journal Paper submitted to IEEE Transactions on Control Systems Technolog

Recurrence of Uterine Rupture in a Pseudo-Unicornuate Uterus at 17 Weeks of Amenorrhea: Case Report and Literature Review

Pregnancy in a rudimentary horn is a very rare condition. It is responsible for several complications. Prognosis is reserved because the natural evolution generally leads to a cataclysmic uterine rupture at the beginning of the second trimester. Classically, the treatment after foetal extraction consists of ablation of the rudimentary horn and associated fallopian tube. We report the obstetric outcome of a patient with history of rudimentary uterine horn rupture, the treatment of which was ablation of the rudimentary horn

Eyelid fat grafting: indications, operative technique and complications; a systematic review

International audienceIntroduction - Many recent studies concerning autologous fat grafting in the eyelids have been published, mostly consisting of case reports and retrospective case series. However, no study on the overall complication or satisfaction rate associated with the various grafting techniques exists. We performed a comprehensive literature review to determine the outcomes and complications of eyelid fat grafting, as well as patient satisfaction.Methods - A systematic review of the literature using the PRISMA criteria was conducted. This protocol was registered at the Prospective Register of Systematic Reviews at the National Institute for Health Research.Results - Sixteen studies, representing 1,159 patients and published between June 2004 and December 2014, were included. Satisfactory results, judged by clinical examination, were observed in all studies. Few postoperative complications were reported.Conclusions - We demonstrated that the procedures were easy to perform, and achieved satisfactory and sustainable results with few complications in both reconstructive and cosmetic surgery. However, a wide disparity exists in the various fat harvesting, fat purification, and reinjection techniques. Further studies are required to assess the long-term outcomes. Our conclusions should be accepted cautiously due to the small number of articles and the lack of evidence in published studies.<br

Cystadénome Papillaire de L’épididyme: Un Nouveau Cas

Le cystadénome papillaire de l’épididyme est une tumeur paratesticulaire bénigne rare. Se présentant comme une masse épididymaire uni ou bilatérale. Son association avec le syndrome de Von Hippel-Lindau est fréquente, en particulier dans les lésions bilatérales. Nous rapportons l’observation d’un patient âgé de 36 ans, qui présentait depuis un an des douleurs scrotales gauches, une grosse bourse chronique, sans fièvre ni signes fonctionnels urinaires. L’examen avait mis en évidence une masse testiculaire dure, irrégulière et indolore sans adénopathies inguinales ni masse abdominale. L’échographie scrotale avait montré une masse testiculaire gauche solide hypoéchogène bien limitée de 3 x 2,5 x 2,2 cm. Les marqueurs tumoraux étaient normaux (ßHCG : 2 UI/j, AlphaFoetoProteine : 2,94 UI/l). La masse testiculaire a été explorée à travers une incision inguinale gauche. A la palpation, c’était une tumeur testiculaire dure. Une orchidectomie gauche a été réalisée. L’examen anatomopathologique de la pièce d’exérèse avait conclu à un aspect morphologique et immunohistochimique d’un cystadénome papillaire séreux borderline paratesticulaire sans signe d’invasion. A travers notre observation et les données de la littérature, nous proposons de mieux définir le diagnostic clinique et anatomopathologique ainsi que le traitement de ces tumeurs testiculaires rares.Mots clés : épididyme, cystadénome papillaire

Impact of body mass index on post-thyroidectomy morbidity

BACKGROUND: The impact of obesity on total thyroidectomy (TT) morbidity (recurrent laryngeal nerve palsy and hypocalcaemia) remains largely unknown. METHODS: In a prospective study (NCT01551914), patients were divided into five groups according to their body mass index (BMI): underweight, normal weight, overweight, obese, and severely obese. Preoperative and postoperative serum calcium was measured. Recurrent laryngeal nerve (RLN) function was evaluated before discharge, and if abnormal, at 6 months. RESULTS: In total 1310 patients were included. Baseline characteristics were similar across BMI groups except for age and sex. Postoperative hypocalcaemia was more frequent in underweight compared to obese patients but the difference was not statistically significant in multivariate analysis. There was no difference between groups in terms of definitive hypocalcaemia, transient and definitive RLN palsy, and postoperative pain. CONCLUSION: Obesity does not increase intraoperative and postoperative morbidity of TT, despite a longer duration of the procedure

Building block libraries and structural considerations in the self-assembly of polyoxometalate and polyoxothiometalate systems

Inorganic metal-oxide clusters form a class of compounds that are unique in their topological and electronic versatility and are becoming increasingly more important in a variety of applications. Namely, Polyoxometalates (POMs) have shown an unmatched range of physical properties and the ability to form structures that can bridge several length scales. The formation of these molecular clusters is often ambiguous and is governed by self-assembly processes that limit our ability to rationally design such molecules. However, recent years have shown that by considering new building block principles the design and discovery of novel complex clusters is aiding our understanding of this process. Now with current progress in thiometalate chemistry, specifically polyoxothiometalates (POTM), the field of inorganic molecular clusters has further diversified allowing for the targeted development of molecules with specific functionality. This chapter discusses the main differences between POM and POTM systems and how this affects synthetic methodologies and reactivities. We will illustrate how careful structural considerations can lead to the generation of novel building blocks and further deepen our understanding of complex systems

Green function techniques in the treatment of quantum transport at the molecular scale

The theoretical investigation of charge (and spin) transport at nanometer length scales requires the use of advanced and powerful techniques able to deal with the dynamical properties of the relevant physical systems, to explicitly include out-of-equilibrium situations typical for electrical/heat transport as well as to take into account interaction effects in a systematic way. Equilibrium Green function techniques and their extension to non-equilibrium situations via the Keldysh formalism build one of the pillars of current state-of-the-art approaches to quantum transport which have been implemented in both model Hamiltonian formulations and first-principle methodologies. We offer a tutorial overview of the applications of Green functions to deal with some fundamental aspects of charge transport at the nanoscale, mainly focusing on applications to model Hamiltonian formulations.Comment: Tutorial review, LaTeX, 129 pages, 41 figures, 300 references, submitted to Springer series "Lecture Notes in Physics