Resonant electron transfer between quantum dots

An interaction of electromagnetic field with a nanostructure composed of two quantum dots is studied theoretically. An effect of a resonant electron transfer between the localized low-lying states of quantum dots is predicted. A necessary condition for such an effect is the existence of an excited bound state whose energy lies close to the top of the barrier separating the quantum dots. This effect may be used to realize the reversible quantum logic gate NOT if the superposition of electron states in different quantum dots is viewed as the superposition of bits 0 and 1.Comment: 8 pages, 1 EPS-figure, submitted to Phys. Rev.

cOOpD: Reformulating COPD classification on chest CT scans as anomaly detection using contrastive representations

Classification of heterogeneous diseases is challenging due to their complexity, variability of symptoms and imaging findings. Chronic Obstructive Pulmonary Disease (COPD) is a prime example, being underdiagnosed despite being the third leading cause of death. Its sparse, diffuse and heterogeneous appearance on computed tomography challenges supervised binary classification. We reformulate COPD binary classification as an anomaly detection task, proposing cOOpD: heterogeneous pathological regions are detected as Out-of-Distribution (OOD) from normal homogeneous lung regions. To this end, we learn representations of unlabeled lung regions employing a self-supervised contrastive pretext model, potentially capturing specific characteristics of diseased and healthy unlabeled regions. A generative model then learns the distribution of healthy representations and identifies abnormalities (stemming from COPD) as deviations. Patient-level scores are obtained by aggregating region OOD scores. We show that cOOpD achieves the best performance on two public datasets, with an increase of 8.2% and 7.7% in terms of AUROC compared to the previous supervised state-of-the-art. Additionally, cOOpD yields well-interpretable spatial anomaly maps and patient-level scores which we show to be of additional value in identifying individuals in the early stage of progression. Experiments in artificially designed real-world prevalence settings further support that anomaly detection is a powerful way of tackling COPD classification

The Form Factors of omega pi0 and pi+ pi- at psi(2S)

The measurements of psi(2S) -> omega pi0 and psi(2S) -> pi+ pi- in e+e- experiments are examined. It is found that the non-resonance virtual photon annihilation gives large contributions to the observed cross sections of these two processes. By including this contribution, the form factors and branching fractions of these two decay modes are revised.Comment: 6 pages, 1 figures(two diagrams), Phys. Lett. B557 (2003) 192-19

The Mass Definition in Hqet and a New Determination of Vcb_{\text{cb}}

Positive powers of the mass parameter in a physical quantity calculated with the help of heavy quark effective theory originate from a Wilson coefficient in the matching of QCD and HQET Green function. We show that this mass parameter enters the calculation as a well--defined running current mass. We further argue that the recently found ill--definition of the pole mass, which is the natural expansion parameter of HQET, does not affect a phenomenological analysis which uses truncated perturbative series. We reanalyse inclusive semileptonic decays of heavy mesons and obtain the $c$ quark mass $m_c^{\overline{\text{MS}}}(m_c) = (1.35\pm 0.20)\,\text{GeV}$ where the error is almost entirely due to scale--uncertainties. We also obtain $m_b^{\overline{\text{MS}}}(m_b) = (4.6\pm 0.3)\,\text{GeV}$ and $|V_{cb}|(\tau_B/1.49\,\text{ps})^{1/2} = 0.036\pm 0.005$ where the errors come from the uncertainty in the kinetic energy of the heavy quark inside the meson, in the experimental branching ratios, in QCD input parameters, and scale--uncertainties.Comment: 21 p., 5 figs, all style files incl., TUM-T31-56/R (Sec. 2 revised, phenomenological results unchanged

Повышение эффективности коррозионной защиты магистральных трубопроводов в грунтах с высокой коррозионной активностью

В работе изложен анализ существующих методов борьбы с коррозионными разрушениями трубопроводов в грунтах с высокой коррозионной активностью. В процессе исследования проводились: изучение теоретических основ процессов коррозионных разрушений; выявление факторов, оказывающих наибольшее влияние на возникновение коррозионных процессов; рассмотрение методов пассивной и активной защиты трубопроводов от коррозии. В результате исследования: произведен расчет электрохимической защиты. Область применения: линейная часть магистрального трубопровода.The article presents an analysis of existing methods for combating corrosion damage to pipelines in soils with increased corrosive activity. In the course of the research, the following were carried out: study of the theoretical foundations of corrosion destruction processes; identification of factors that have the greatest impact on the occurrence of corrosion processes; consideration of methods of passive and active protection of pipelines from corrosion. As a result of the research: the calculation of the electrochemical protection was made. Scope: linear part of the main pipeline

Biosensoren auf der Basis des Insektengeruchssinns als Routine-Instrument - Eine Machbarkeitsstudie

Die Leistungsfähigkeit des kürzlich entwickelten BioFET auf der Basis des Insektengeruchssinns hängt sowohl von den Eigenschaften der Insektenantenne und denen des Feldeffekttransistors als auch von der Güte der bioelektronischen Schnittstelle zwischen Insektenantenne und Feldeffekttransistor ab. Die von Seiten der Insektenantenne notwendigen Voraussetzungen sollen durch einen Vergleich der Tauglichkeit von Insektenantennen zweier verschiedener Insektenarten, dem Kartoffelkäfer (Leptinotarsa decemlineata) und dem Stahlblauen Kiefernprachtkäfer (Phaenops cyanea) für die Messung von Pflanzenschäden in unterschiedlichen Umgebungen veranschaulicht werden. Dabei steht der Abgleich der Eigenschaften der Biokomponenten hinsichtlich ihrer sensorischen Leistungsfähigkeit durch die Anwendung im Vordergrund. Für die praktische Anwendung des Biosensor-Systems im Routineeinsatz sind oftmals noch andere Eigenschaften, wie Verfügbarkeit des Sensorköpfe, zeitliche und räumliche Auflösung der Messungen sowie der Bedarf an Energie und ausgebildeten Arbeitskräften maßgeblich. Diese Parameter können durch Anzuchtbedingungen der Insekten, Lagerbarkeit der Bio- und der Halbleiterkomponente sowie technische Optionen des Biosensor-Systems beeinflusst werden. Die Fertigung eines Biosensors auf der Basis des Insektengeruchssinns nach Kundenwunsch erfordert eine sorgfältige Beschreibung der Sensor-Anwendung, die durch eine gründliche Kenntnis des biologischen Hintergrunds der verwendeten Insekten und der technischen Limitierungen bzw. Optionen von Transducer-Komponente und Biosensor-System ergänzt werden muss. Die Möglichkeit halbautomatischer Fertigungstechniken zur Herstellung der Sensorköpfe werden diskutiert und zukünftiges Entwicklungspotential aufgezeigt. Auf dieser Basis ist die Entwicklung von routinemäßig einsetzbaren Biosensoren auf der Basis des Insektengeruchssinns für die vor-Ort-Analytik von Duftstoffen in vielfältigen Anwendungen möglich

Reduction of anomalous heating in an in-situ-cleaned ion trap

Anomalous heating of trapped atomic ions is a major obstacle to their use as quantum bits in a scalable quantum computer. The physical origin of this heating is not fully understood, but experimental evidence suggests that it is caused by electric-field noise emanating from the surface of the trap electrodes. In this study, we have investigated the role that adsorbates on the electrodes play by identifying contaminant overlayers, developing an in situ argon-ion beam cleaning procedure, and measuring ion heating rates before and after cleaning the trap electrodes' surfaces. We find a reduction of two orders of magnitude in heating rate after cleaning.Comment: 7 pages, 1 figur

Opportunities for mesoscopics in thermometry and refrigeration: Physics and applications

This review presents an overview of the thermal properties of mesoscopic structures. The discussion is based on the concept of electron energy distribution, and, in particular, on controlling and probing it. The temperature of an electron gas is determined by this distribution: refrigeration is equivalent to narrowing it, and thermometry is probing its convolution with a function characterizing the measuring device. Temperature exists, strictly speaking, only in quasiequilibrium in which the distribution follows the Fermi-Dirac form. Interesting nonequilibrium deviations can occur due to slow relaxation rates of the electrons, e.g., among themselves or with lattice phonons. Observation and applications of nonequilibrium phenomena are also discussed. The focus in this paper is at low temperatures, primarily below 4 K, where physical phenomena on mesoscopic scales and hybrid combinations of various types of materials, e.g., superconductors, normal metals, insulators, and doped semiconductors, open up a rich variety of device concepts. This review starts with an introduction to theoretical concepts and experimental results on thermal properties of mesoscopic structures. Then thermometry and refrigeration are examined with an emphasis on experiments. An immediate application of solid-state refrigeration and thermometry is in ultrasensitive radiation detection, which is discussed in depth. This review concludes with a summary of pertinent fabrication methods of presented devices.Comment: Close to the version published in RMP; 59 pages, 35 figure