Mixing with the radiofrequency single-electron transistor

By configuring a radio-frequency single-electron transistor as a mixer, we demonstrate a unique implementation of this device, that achieves good charge sensitivity with large bandwidth about a tunable center frequency. In our implementation we achieve a measurement bandwidth of 16 MHz, with a tunable center frequency from 0 to 1.2 GHz, demonstrated with the transistor operating at 300 mK. Ultimately this device is limited in center frequency by the RC time of the transistor's center island, which for our device is ~ 1.6 GHz, close to the measured value. The measurement bandwidth is determined by the quality factor of the readout tank circuit.Comment: Submitted to APL september 200

Mechanically probing coherent tunnelling in a double quantum dot

We study theoretically the interaction between the charge dynamics of a few-electron double quantum dot and a capacitively-coupled AFM cantilever, a setup realized in several recent experiments. We demonstrate that the dot-induced frequency shift and damping of the cantilever can be used as a sensitive probe of coherent inter-dot tunnelling, and that these effects can be used to quantitatively extract both the magnitude of the coherent interdot tunneling and (in some cases) the value of the double-dot T_1 time. We also show how the adiabatic modulation of the double-dot eigenstates by the cantilever motion leads to new effects compared to the single-dot case.Comment: 6 pages, 2 figure

“Perhaps she only had a banana available to throw”: Habitus, racial prejudice, and whiteness on Australian Football League message boards

This article presents the findings of 2,415 posts collected from two prominent Australian Football League message boards that responded to a racist incident involving a banana being thrown at Adelaide Crows player, Eddie Betts, in August 2016. It adopts Bourdieu’s concept of habitus to examine the online practice of fans for evidence of racist discourse and the extent to which this was supported or contested by fellow fans. The overall findings are that online debates about race in Australian Rules Football and wider Australian society remain divided, with some posters continuing to reflect racial prejudice and discrimination towards non-whites. However, for the vast majority, views deemed to have racist connotations are contested and challenged in a presentation centering on social change and racial equality

High-Frequency Nanofluidics: An Experimental Study using Nanomechanical Resonators

Here we apply nanomechanical resonators to the study of oscillatory fluid dynamics. A high-resonance-frequency nanomechanical resonator generates a rapidly oscillating flow in a surrounding gaseous environment; the nature of the flow is studied through the flow-resonator interaction. Over the broad frequency and pressure range explored, we observe signs of a transition from Newtonian to non-Newtonian flow at $\omega\tau\approx 1$, where $\tau$ is a properly defined fluid relaxation time. The obtained experimental data appears to be in close quantitative agreement with a theory that predicts purely elastic fluid response as $\omega\tau\to \infty$

A macro-realism inequality for opto-electro-mechanical systems

We show how to apply the Leggett-Garg inequality to opto-electro-mechanical systems near their quantum ground state. We find that by using a dichotomic quantum non-demolition measurement (via, e.g., an additional circuit-QED measurement device) either on the cavity or on the nanomechanical system itself, the Leggett-Garg inequality is violated. We argue that only measurements on the mechanical system itself give a truly unambigous violation of the Leggett-Garg inequality for the mechanical system. In this case, a violation of the Leggett-Garg inequality indicates physics beyond that of "macroscopic realism" is occurring in the mechanical system. Finally, we discuss the difficulties in using unbound non-dichotomic observables with the Leggett-Garg inequality.Comment: 9 pages, 2 figures. Added additional figure (2b), and associated conten

The Effect of Mechanical Resonance on Josephson Dynamics

We study theoretically dynamics in a Josephson junction coupled to a mechanical resonator looking at the signatures of the resonance in d.c. electrical response of the junction. Such a system can be realized experimentally as a suspended ultra-clean carbon nanotube brought in contact with two superconducting leads. A nearby gate electrode can be used to tune the junction parameters and to excite mechanical motion. We augment theoretical estimations with the values of setup parameters measured in the samples fabricated. We show that charging effects in the junction give rise to a mechanical force that depends on the superconducting phase difference. The force can excite the resonant mode provided the superconducting current in the junction has oscillating components with a frequency matching the resonant frequency of the mechanical resonator. We develop a model that encompasses the coupling of electrical and mechanical dynamics. We compute the mechanical response (the effect of mechanical motion) in the regime of phase bias and d.c. voltage bias. We thoroughly investigate the regime of combined a.c. and d.c. bias where Shapiro steps are developed and reveal several distinct regimes characteristic for this effect. Our results can be immediately applied in the context of experimental detection of the mechanical motion in realistic superconducting nano-mechanical devices.Comment: 18 pages, 11 figure

Effects of oral L-Carnitine supplementation on insulin sensitivity indices in response to glucose feeding in lean and overweight/obese males

Infusion of carnitine has been observed to increase non-oxidative glucose disposal in several studies but the effect of oral carnitine on glucose disposal in non-diabetic lean vs. overweight/obese humans has not been examined. This study examined the effects of 14 days L-Carnitine L-Tartrate oral supplementation (LC) on blood glucose, insulin, NEFA and GLP-1 responses to an oral glucose tolerance test (OGTT). Sixteen male participants were recruited (lean (n=8) and overweight/obese (n=8)). After completing a submaximal predictive exercise test, participants were asked to attend three experimental sessions. These three visits were conducted, in the morning to obtain fasting blood samples and to conduct 2hr OGTT’s. The first visit was a familiarisation trial and the final two visits were conducted two weeks apart following 14 days of ingestion of placebo (PL, 3g glucose/day) then LC (3g LC/day) ingested as 2 capsules 3x/day with meals. On each visit blood was drawn at rest, at intervals during the OGTT for analysis of glucose, insulin, non-esterified fatty acids (NEFA) and total glucagon-like peptide-1 (GLP-1). Data obtained were used for determination of usual insulin sensitivity indices (HOMA-IR, AUC glucose, AUC insulin, 1st phase and 2nd phase β-cell function, estimated insulin sensitivity index, and estimated metabolic clearance rate). Data were analysed using RMANOVA and post-hoc comparisons where appropriate. There was a significant difference between groups for body mass, % fat and BMI with no significant difference in age and height. Mean (SEM) plasma glucose concentration at 30 minutes was significantly lower (