STOCHASTIC CHARGE TRANSPORT IN MULTI-ISLAND SINGLE-ELECTRON TUNNELING DEVICES

The physics of the operation of singe-electron tunneling devices (SEDs) and singe-electron tunneling transistors (SETs), especially of those with multiple nanometer-sized islands, has remained poorly understood in spite of some intensive experimental and theoretical research. This computational study examines the current-voltage (IV) characteristics of multi-island single-electron devices using a newly developed multi-island transport simulator (MITS) that is based on semi-classical tunneling theory and kinetic Monte Carlo simulation. The dependence of device characteristics on physical device parameters is explored, and the physical mechanisms that lead to the Coulomb blockade (CB) and Coulomb staircase (CS) characteristics are proposed. Simulations using MITS demonstrate that the overall IV characteristics in a device with a random distribution of islands are a result of a complex interplay among those factors that affect the tunneling rates that are fixed a priori (e.g. island sizes, island separations, temperature, gate bias, etc.), and the evolving charge state of the system, which changes as the source-drain bias (VSD) is changed. With increasing VSD, a multi-island device has to overcome multiple discrete energy barriers (up-steps) before it reaches the threshold voltage (Vth). Beyond Vth, current flow is rate-limited by slow junctions, which leads to the CS structures in the IV characteristic. Each step in the CS is characterized by a unique distribution of island charges with an associated distribution of tunneling probabilities. MITS simulation studies done on one-dimensional (1D) disordered chains show that longer chains are better suited for switching applications as Vth increases with increasing chain length. They are also able to retain CS structures at higher temperatures better than shorter chains. In sufficiently disordered 2D systems, we demonstrate that there may exist a dominant conducting path (DCP) for conduction, which makes the 2D device behave as a quasi-1D device. The existence of a DCP is sensitive to the device structure, but is robust with respect to changes in temperature, gate bias, and VSD. A side gate in 1D and 2D systems can effectively control Vth. We argue that devices with smaller island sizes and narrower junctions may be better suited for practical applications, especially at room temperature.

Konstruktion und Concetto. Die römischen Katafalke für Kardinal Alessandro Farnese (1589), Papst Sixtus V. (1591) und Principe Carlo Barberini (1630)

In Rom entstand im ausgehenden 16. Jahrhundert die Gattung des „Tempietto-Katafalks“, eines Trauergerüsts in Form eines überkuppelten Zentralbaus, der anlässlich der feierlichen Exequien eines hochrangigen Verstorbenen die symbolische Totenbahre als anspruchsvolle ephemere Kleinarchitektur überfängt. Anhand dreier herausragender Beispiele, der Katafalke für Kardinal Alessandro Farnese, Papst Sixtus V. und Principe Carlo Barberini, sollen die architektonische Gestalt der Funeraltempietti und ihre symbolische Aussage näher beleuchtet werden. Dabei soll weniger die Ikonographie der figürlichen Ausstattung im Mittelpunkt stehen als vielmehr die “Sprachfähigkeit” der gewählten architektonischen Formen, die bei den hier vorgestellten römischen Katafalken ein zentraler Teil der Gesamtkonzepts ist. Dabei sind sowohl der Festanlass – die Memoria des verstorbenen Würdenträgers – als auch die Architektur selbst zum Thema gemacht.

L'oeuvre de Sade et le conte. Le retour refoulé de Barbe-Bleue

Cet article s’intéresse aux différentes fonctions que l’on peut attribuer aux éléments fabuleux dans les œuvres du marquis de Sade. Il s’agit en particulier d’éclaircir les liens intertextuels entre Barbe-Bleue et un conte allégorique que le marquis publie, en 1800, dans la série de ses Crimes de l’amour, sous le titre de Rodrigue ou la tour enchantée. Dans ce texte, la chambre interdite renvoie aussi à un passé criminel, mais elle ne réveille pas la mauvaise conscience et ne suscite aucun remords. Sade semble vouloir faire du conte de Barbe-Bleue le paradigme d’un refoulement manqué, la figure d’une rechute malencontreuse dans un passé archaïque et indigne d’être examiné moralement. Or, les œuvres de Sade ne peuvent plus admettre l’univers surnaturel des contes de fées, considéré comme tout aussi révolu que cette conscience morale qui s’exprime par le remords.

BENCHMARKING AND IMPLEMENTATION OF A NEW INDEPENDENT MONTE CARLO DOSE CALCULATION QUALITY ASSURANCE AUDIT TOOL FOR CLINICAL TRIALS

Introduction Commercial treatment planning systems employ a variety of dose calculation algorithms to plan and predict the dose distributions a patient receives during external beam radiation therapy. Traditionally, the Radiological Physics Center has relied on measurements to assure that institutions participating in the National Cancer Institute sponsored clinical trials administer radiation in doses that are clinically comparable to those of other participating institutions. To complement the effort of the RPC, an independent dose calculation tool needs to be developed that will enable a generic method to determine patient dose distributions in three dimensions and to perform retrospective analysis of radiation delivered to patients who enrolled in past clinical trials. Methods A multi-source model representing output for Varian 6 MV and 10 MV photon beams was developed and evaluated. The Monte Carlo algorithm, know as the Dose Planning Method (DPM), was used to perform the dose calculations. The dose calculations were compared to measurements made in a water phantom and in anthropomorphic phantoms. Intensity modulated radiation therapy and stereotactic body radiation therapy techniques were used with the anthropomorphic phantoms. Finally, past patient treatment plans were selected and recalculated using DPM and contrasted against a commercial dose calculation algorithm. Results The multi-source model was validated for the Varian 6 MV and 10 MV photon beams. The benchmark evaluations demonstrated the ability of the model to accurately calculate dose for the Varian 6 MV and the Varian 10 MV source models. The patient calculations proved that the model was reproducible in determining dose under similar conditions described by the benchmark tests. Conclusions The dose calculation tool that relied on a multi-source model approach and used the DPM code to calculate dose was developed, validated, and benchmarked for the Varian 6 MV and 10 MV photon beams. Several patient dose distributions were contrasted against a commercial algorithm to provide a proof of principal to use as an application in monitoring clinical trial activity.

Why Monte Carlo Simulations are Inferences and not Experiments

Monte Carlo simulations arrive at their results by introducing randomness, sometimes derived from a physical randomizing device. Nonetheless, we argue, they open no new epistemic channels beyond that already employed by traditional simulations: the inference by ordinary argumentation of conclusions from assumptions built into the simulations. We show that Monte Carlo simulations cannot produce knowledge other than by inference, and that they resemble other computer simulations in the manner in which they derive their conclusions. Simple examples of Monte Carlo simulations are analysed to identify the underlying inferences.

More than just Good Luck. How to Explain the Success of Monte Carlo Simulations

Monte Carlo simulation is a powerful method in many natural and social sciences. But what sort of method is it? And where does its power come from? Are Monte Carlo simulations experiments, theories or something else? The aim of this talk is to answer these questions and to explain the power of Monte Carlo simulations. I provide a classification of Monte Carlo techniques and defend the claim that Monte Carlo simulation is a sort of inference.

Replica ai pareri del rabbino J. Costa e di altri rabbini sulla validità del testamento del fu conte Caid Nissim Samama

[David Castelli]

Ein Wort zur Zeit bei der ersten im neuen israelitischen Cultus-Tempel vorgenommenen Confirmation am 22. Juni 1858 durch Adolph Jellinek

Verf. von Isaak Grünberger

Chrétiens ›Roman de Perceval ou le Conte du Graal‹ und Wolframs ›Parzival‹. Ihre Überlieferung und textkritische Erschließung

This article discusses the manuscript transmission of Chrétien’s Roman de Perceval ou le Conte du Graal and Wolfram’s Parzival in terms of their textual tradition and editorial criticism. It shows that the most recent edition of the Old French Perceval (K. Busby 1993) can be viewed as a landmark of the art of conventional editing that appeared at the peak of the discussion of ‘New Philology’ and took its own position in this context. At the same time, the Perceval was subject of critical studies based on the principle of ‘unrooted trees’ that questioned the genealogical concept of traditional ‘Lachmannian’ stemmatology. Conversely, a new edition of Wolfram’s Parzival, based on all known manuscripts, remained a desideratum for decades in German studies. Specific research on the textual tradition played a rather marginal role for a long time, but has been reinforced in the recent years in the context of a new critical edition presenting the totality of manuscripts as well as different textual versions in electronic form. The concept of ‘unrooted trees’ visualizing relationships of manuscript readings can be integrated in this concept. The article gives an overview of these methods, presents examples of editorial techniques, and develops ideas on how to combine the research on the manuscript tradition of both the German text and its French counterpart.