Coulomb-Regulated Conductance Oscillations in a Disordered Quantum Wire

Wetensch. publicatieFaculteit der Wiskunde en Natuurwetenschappe

Three "universal" mesoscopic Josephson effects

1. Introduction 2. Supercurrent from Excitation Spectrum 3. Excitation Spectrum from Scattering Matrix 4. Short-Junction Limit 5. Universal Josephson Effects 5.1 Quantum Point Contact 5.2 Quantum Dot 5.3 Disordered Point Contact (Average supercurrent, Supercurrent fluctuations)Comment: 21 pages, 2 figures; legacy revie

Quantum Point Contacts and Coherent Electron Focusing

I. Introduction II. Electrons at the Fermi level III. Conductance quantization of a quantum point contact IV. Optical analogue of the conductance quantization V. Classical electron focusing VI. Electron focusing as a transmission problem VII. Coherent electron focusing (Experiment, Skipping orbits and magnetic edge states, Mode-interference and coherent electron focusing) VIII. Other mode-interference phenomenaComment: #3 of a series of 4 legacy reviews on QPC'

Oscillating Transverse Voltage in a Channel with Quantum Point Contact Voltage Probes

Wetensch. publicatieFaculteit der Wiskunde en Natuurwetenschappe

Unexpected features of branched flow through high-mobility two-dimensional electron gases

GaAs-based two-dimensional electron gases (2DEGs) show a wealth of remarkable electronic states, and serve as the basis for fast transistors, research on electrons in nanostructures, and prototypes of quantum-computing schemes. All these uses depend on the extremely low levels of disorder in GaAs 2DEGs, with low-temperature mean free paths ranging from microns to hundreds of microns. Here we study how disorder affects the spatial structure of electron transport by imaging electron flow in three different GaAs/AlGaAs 2DEGs, whose mobilities range over an order of magnitude. As expected, electrons flow along narrow branches that we find remain straight over a distance roughly proportional to the mean free path. We also observe two unanticipated phenomena in high-mobility samples. In our highest-mobility sample we observe an almost complete absence of sharp impurity or defect scattering, indicated by the complete suppression of quantum coherent interference fringes. Also, branched flow through the chaotic potential of a high-mobility sample remains stable to significant changes to the initial conditions of injected electrons.Comment: 22 pages, 4 figures, 1 tabl

An off-board quantum point contact as a sensitive detector of cantilever motion

Recent advances in the fabrication of microelectromechanical systems (MEMS) and their evolution into nanoelectromechanical systems (NEMS) have allowed researchers to measure extremely small forces, masses, and displacements. In particular, researchers have developed position transducers with resolution approaching the uncertainty limit set by quantum mechanics. The achievement of such resolution has implications not only for the detection of quantum behavior in mechanical systems, but also for a variety of other precision experiments including the bounding of deviations from Newtonian gravity at short distances and the measurement of single spins. Here we demonstrate the use of a quantum point contact (QPC) as a sensitive displacement detector capable of sensing the low-temperature thermal motion of a nearby micromechanical cantilever. Advantages of this approach include versatility due to its off-board design, compatibility with nanoscale oscillators, and, with further development, the potential to achieve quantum limited displacement detection.Comment: 5 pages, 5 figure

Universal Resistances of the Quantum RC circuit

We examine the concept of universal quantized resistance in the AC regime through the fully coherent quantum RC circuit comprising a cavity (dot) capacitively coupled to a gate and connected via a single spin-polarized channel to a reservoir lead. As a result of quantum effects such as the Coulomb interaction in the cavity and global phase coherence, we show that the charge relaxation resistance $R_q$ is identical for weak and large transmissions and it changes from $h/2e^2$ to $h/e^2$ when the frequency (times $\hbar$) exceeds the level spacing of the cavity; $h$ is the Planck constant and $e$ the electron charge. For large cavities, we formulate a correspondence between the charge relaxation resistance $h/e^2$ and the Korringa-Shiba relation of the Kondo model. Furthermore, we introduce a general class of models, for which the charge relaxation resistance is universal. Our results emphasize that the charge relaxation resistance is a key observable to understand the dynamics of strongly correlated systems.Comment: 12 pages, 3 figure

Seksueel overdraagbare aandoeningen, waaronder hiv, in Nederland in 2016

In 2016, the number of people who were tested at a Dutch STI clinic for a sexually transmitted infection (STI) increased, after a decrease in 2015. The percentage of people diagnosed with an STI has also increased, to 18.4 percent in 2016. It is estimated that the number of STI consultations at the general practitioner has decreased slightly. Chlamydia remains the most common STI in heterosexuals. Gonorrhoea is more common than chlamydia in men who have sex with men (MSM). STI clinics offer high-risk groups the opportunity for free STI testing. In 2016, a total of 143,139 consultations were registered at the STI clinics, an increase of 5 percent compared to 2015. The percentage of detected STIs varied per municipal health centre (GGD), ranging from 12.8 to 20.9 percent. Most STIs were detected in people infected with HIV, followed by people who had been notified for an STI. Chlamydia In 2016, 14.5 percent of STI clinic attendees were infected with chlamydia (20,698 diagnoses; an increase of 11 percent compared to the previous year). This increase can be explained in part because, since 2015, STI clinics more strictly prioritise people with a high risk of STI. The biggest increase was seen in heterosexual men (from 16.1 in 2015 to 18.0 percent in 2016). In women, the percentage of chlamydia diagnoses increased from 14.2 to 15.4. In MSM, the percentage has been stable around 10 percent for years. Gonorrhoea The number of gonorrhoea diagnoses at the STI clinics has risen in the past year with 13 percent, to 6,092 infections. The percentage of positive tests in heterosexual men (1.7 percent) and women (1.4 percent) remained stable, compared to previous years. In MSM, the percentage has increased from 10.7 percent in 2015 to 11.3 percent in 2016. The STI clinics have not yet found cases of gonorrhoea resistant to the first option antibiotic, Ceftriaxone. The number of gonorrhoea infections diagnosed by general practitioners in 2015 saw a slight decline among women, but an increase among men of 20 percent compared to 2014. Syphilis In 2016, the number of syphilis diagnoses increased by 30 percent compared to 2015, totalling 1,223 infections. This increase is mainly caused by an increase in the number of diagnoses in MSM, both those with and without HIV. Out of all syphilis infections, 95 percent was diagnosed in MSM. The percentage of positive diagnoses in heterosexual men and women remains very low; 0.19 and 0.07 percent of all consultations that tested for syphilis, respectively. HIV In 2016, 285 new HIV diagnoses were detected at the STI clinics, approximately the same number as in 2015 (288); 93 percent was detected in MSM. The percentage of HIV diagnoses in MSM decreased, from 2.8 percent in 2007 to 0.8 percent in 2016. The number of HIV patients that had their 'first care' encounter at a Dutch HIV treatment centre decreased again, from 1,033 cases in 2015 to 976 in 2016. Out of these people, 666 received their diagnosis in 2016Het aantal mensen dat zich bij een Centrum Seksuele Gezondheid (CSG) heeft laten testen op een seksueel overdraagbare aandoening (soa) is, na een daling in 2015, in 2016 weer toegenomen. Het percentage bij wie een soa werd vastgesteld is ook gestegen, tot 18,4 procent in 2016. Naar schatting is het aantal soa-consulten bij huisartsen licht gedaald. Chlamydia blijft de meest voorkomende soa onder heteroseksuelen. Onder mannen die seks hebben met mannen (MSM) werd vaker gonorroe dan chlamydia gevonden. De CSG's bieden hoog-risicogroepen de mogelijkheid om zich gratis te laten testen op soa's. In totaal zijn er in 2016 143.139 consulten geregistreerd bij de CSG's, een stijging van 5 procent ten opzichte van 2015. Het percentage gevonden soa's varieerde tussen de GGD-en; van 12,8 tot 20,9. De meeste soa's zijn gevonden bij mensen met hiv, gevolgd door mensen die waren gewaarschuwd voor een soa. Chlamydia In 2016 had 14,5 procent van de CSG-bezoekers een chlamydia-infectie (20.698 diagnoses; een toename van 11 procent ten opzichte van het jaar ervoor). Deze stijging is mogelijk deels te verklaren doordat GGD-en sinds 2015 eerder voorrang verlenen aan personen met hoog risico op soa. De grootste toename was te zien bij heteroseksuele mannen (van 16,1 in 2015 naar 18,0 procent in 2016). Bij vrouwen nam het percentage vastgestelde chlamydia toe van 14,2 naar 15,4. Onder MSM ligt dit percentage al jaren rond 10 procent. Gonorroe Het aantal gonorroe-diagnoses bij de CSG is het afgelopen jaar met 13 procent toegenomen tot 6.092 infecties. Het percentage positieven onder heteroseksuele mannen (1,7 procent) en vrouwen (1,4 procent) bleef stabiel ten opzichte van voorgaande jaren. Onder MSM is het percentage toegenomen van 10,7 procent in 2015 naar 11,3 procent in 2016. Bij CSG-bezoekers is nog steeds geen gonorroe resistent gevonden tegen het 'eerstekeus' antibioticum ceftriaxon. Het aantal gonorroe-infecties gediagnosticeerd door huisartsen in 2015 nam licht af onder vrouwen, maar steeg onder mannen met 20 procent ten opzichte van 2014. Syfilis In 2016 is het aantal diagnoses van syfilis met 30 procent gestegen ten opzichte van 2015, tot 1.223 infecties. Deze stijging komt voornamelijk door een toename in het aantal diagnoses onder MSM, zowel met als zonder hiv. Van alle syfilis-infecties werd 95 procent bij MSM vastgesteld. Het percentage positieve diagnoses onder heteroseksuele mannen en vrouwen blijft zeer laag; respectievelijk 0,19 en 0,07 procent van alle consulten waarin getest werd op syfilis. Hiv In 2016 zijn 285 nieuwe diagnoses van hiv gesteld bij de CSG, vrijwel evenveel als in 2015 (288). Drieënnegentig procent daarvan werd bij MSM vastgesteld. Het percentage hiv-diagnoses bij MSM is gedaald van 2,8 procent in 2007 tot 0,8 procent in 2016. Het aantal hiv-patiënten dat voor het eerst 'in zorg' was bij de Nederlandse hiv-behandelcentra daalde opnieuw, van 1.033 gevallen in 2015 tot 976 in 2016. Van hen hadden 666 personen de diagnose in 2016 gekregenMinisterie van VW

First patient-centred set of outcomes for pulmonary sarcoidosis: a multicentre initiative

Introduction Routine and international comparison of clinical outcomes enabling identification of best practices for patients with pulmonary sarcoidosis is lacking. The aim of this study was to develop a standard set of outcome measures for pulmonary sarcoidosis, using the valuebased healthcare principles. Methods Six expert clinics for interstitial lung diseases in four countries participated in a consensus-driven RANDmodified Delphi study. A mixed-method approach was applied for the identification of an outcome measures set and initial conditions for patients with pulmonary sarcoidosis. The expert team consisted of multidisciplinary professionals (n=14) from Cleveland Clinic, Cincinnati MC, Erasmus MC, Leuven UZ, Royal Brompton and St. Antonius Hospital. During a ranking process, participants were instructed to rank variables on a scale from 1 to 10 based on whether it has (1) impact of the outcome on quality of life, (2) impact of quality of care on the outcome and (3) the number of patients negatively affected by the outcome. Results An outcome measures set was defined consisting of seven outcome measures: mortality, pulmonary function, soluble interleukin-2 receptor change as an activity biomarker, weight gain, quality of life, osteoporosis and clinical outcome status. Discussion Collecting outcomes in pulmonary sarcoidosis internationally and the use of a broadly accepted set can enable international comparison. Differences in outcomes can potentially be used as a starting point for quality improvement initiatives

Temperature Dependence of Spin-Split Peaks in Transverse Electron Focusing

We present experimental results of transverse electron-focusing measurements performed using n-type GaAs. In the presence of a small transverse magnetic field (B⊥), electrons are focused from the injector to detector leading to focusing peaks periodic in B⊥. We show that the odd-focusing peaks exhibit a split, where each sub-peak represents a population of a particular spin branch emanating from the injector. The temperature dependence reveals that the peak splitting is well defined at low temperature whereas it smears out at high temperature indicating the exchange-driven spin polarisation in the injector is dominant at low temperatures