Quantum oscillations observed in graphene at microwave frequencies

We have measured the microwave conductance of mechanically exfoliated graphene at frequencies up to 8.5 GHz. The conductance at 4.2 K exhibits quantum oscillations, and is independent of the frequency

Interfacial effects on the polarization of BiFeO3BiFeO_{3} films

By considering an interfacial layer between the electrode and the $BiFeO_{3}$($BFO$) layer, the polarization and the hysteresis behavior of $BFO$ film are simulated. It is found that the non-ferroelectric interface will increase the coercive field, and remarkably suppress the polarization of the ultrathin film under low applied fields. Due to the competition between the interfacial effect and the internal compressive stress, the maximum polarization on the P-E loop of a $BFO$ film can be independent on the film thickness under an adequate applied field.Comment: 3 pages, 2 figure

Access My Info: measuring data access rights around the world

In 2014, the Citizen Lab and Open Effect started Access My Info (AMI) a research project that uses data access requests and complementary policy, legal, and technical methods to learn about how private companies collect, retain, process, and disclose individuals’ personal data. Accompanying the research methodology is a web-based tool that helps members of the public generate data access requests based on templates tailored to different industries. AMI was first applied in Canada and resulted in tens of thousands of Canadians making DARs to telecommunication companies. The results of the study showed inconsistent responses across companies and documented consumers experiencing in significant barriers to accessing their data. Following the first AMI project in Canada, the Citizen Lab formed a working group to bring the research method to Asia and comparatively measure responses to DARs across the region. The working group includes academics, lawyers, advocates, and designers working in five jurisdictions: Hong Kong: Lokman Tsui (Chinese University of Hong Kong), Stuart Hargraves (Chinese University of Hong Kong), Keyboard Frontline (advocacy organization, Hong Kong), InMedia (media group, Hong Kong), Jason Li (Designer, Hong Kong) South Korea: Kelly Kim (OpenNet Korea), KS Park (Korea University) Australia: Adam Molnar (University of Waterloo / Deakin University) Indonesia: Sinta Dewi Rosadi (University of Padjadjaran) Malaysia: Sonny Zulhuda (International Islamic University Malaysia

Peripheral Fluorescein Angiographic Findings in Fellow Eyes of Patients with Branch Retinal Vein Occlusion

Introduction. Branch retinal vein occlusion (BRVO) is a common retinal vascular condition that results in intraocular inflammatory changes. Ultra wide field fluorescein angiography (UWFFA) is a retinal imaging device that can capture peripheral retinal findings. The purpose of this study was to look for peripheral findings in the fellow eye of patients with BRVO using UWFFA. Methods. Retrospective imaging review of patients diagnosed with BRVO that had both eyes imaged with UWFFA. Images were graded for peripheral findings in other quadrants of the same eye as well as in all quadrants of the fellow eye. Results. Of 81 patients, 14 (17%) patients had late vascular leakage in a quadrant other than the BRVO distribution. Five (6%) findings were in the same eye, 8 (10%) findings were in the fellow eye, and 1 (1%) finding was in both the same eye and the fellow eye. Of these 14 patients, 11 (80%) patients had hypertension. Conclusion. Late peripheral retinal leakage in the fellow eye of patients with BRVO was detected in this cohort of patients with UWFFA. This novel finding may represent underlying systemic inflammation, hypertension, or bilateral BRVOs

Collective Josephson Vortex Dynamics in Long Josephson Junction Stacks

We investigate the collective phase dynamics in conventional long Josephson junction (LJJ) stacks and in layered superconductors, exhibiting intrinsic LJJ behaviors. Using a theoretical model which accounts for both the magnetic induction effect and the breakdown of local charge neutrality (i.e., charging effect), we show that the collective motion of Josephson vortices, including the dispersion of Josephson plasma mode and the Swihart-type velocity, in an intrinsic LJJ stack such as Bi$_2$Sr$_2$CaCu$_2$O$_{8+y}$ (BSCCO) is significantly modified from those in a conventional LJJ stack. In BSCCO, the strength of the charging effect $\alpha$ is small (i.e., $\alpha \sim 0.1-0.4$), but it leads to notable changes in collective phase dynamics, including changes to the stability condition. Also, we show that splitting of the supercurrent branch in the resistive state is due to collective motion of Josephson vortices. The width of spread of these sub-branches in the linear current-voltage regime depends on $\alpha$, suggesting another way to measure the charging effect in BSCCO.Comment: 27 pages, 6 figures, to appear in Physica C (2002

Resting-State Glucose Metabolism Level Is Associated with the Regional Pattern of Amyloid Pathology in Alzheimer's Disease

It has been suggested that glucose metabolism within the brain's default network is directly associated with—and may even cause—the amyloid pathology of Alzheimer's disease (AD). Here we performed 2-[18F]fluoro-2-deoxy-D-glucose (FDG) and [11C]-labeled Pittsburgh Compound B (PIB) positron emission tomography (PET) on cognitively normal elderly subjects and on AD patients and conducted quantitative regional analysis of FDG- and PIB-PET images using an automated region of interest technique. We confirmed that resting glucose metabolism within the posterior components of the brain's default network is high in normal elderly subjects and low in AD patients, which is partially in agreement with the regional pattern of PIB uptake within the default network of AD patients. However, in several regions outside the default network, glucose metabolism was high in normal elderly subjects but was not depressed in AD patients, who exhibited significantly increased PIB uptakes in these regions. In contrast, the level of resting glucose metabolism in the default network and in regions outside the default network in normal elderly subjects was significantly correlated with the level of regional PIB uptake in AD patients. These results are discussed with experimental evidence suggesting that beta amyloid production and amyloid precursor protein regulation are dependent on neuronal activity

Experimental Test of the Inter-Layer Pairing Models for High-Tc Superconductivity Using Grazing Incidence Infrared Reflectometry

From measurements of the far-infrared reflectivity at grazing angles of incidence with p-polarized light we determined the c-axis Josephson plasma frequencies of the single layer high T_c cuprates Tl_2Ba_2CuO_6 and La_{2-x}Sr_xCuO_4. We detected a strong plasma resonance at 50 cm^{-1} for La_{2-x}Sr_xCuO_4 in excellent agreement with previously published results. For Tl_2Ba_2CuO_6 we were able to determine an upper limit of the unscreened c-axis Josephson plasma frequency 100 cm^{-1} or a c-axis penetration depth > 15 \mu m. The small value of $\omega_J$ stands in contrast to recent a prediction based on the inter-layer tunneling mechanism of superconductivity.Comment: 4 pages, Phys. Rev. B, in press, Revtex, 4 postscript figure

How people talk when teaching a robot

We examine affective vocalizations provided by human teach-ers to robotic learners. In unscripted one-on-one interac-tions, participants provided vocal input to a robotic dinosaur as the robot selected toy buildings to knock down. We find that (1) people vary their vocal input depending on the learner’s performance history, (2) people do not wait until a robotic learner completes an action before they provide in-put and (3) people näıvely and spontaneously use intensely affective vocalizations. Our findings suggest modifications may be needed to traditional machine learning models to better fit observed human tendencies. Our observations of human behavior contradict the popular assumptions made by machine learning algorithms (in particular, reinforcement learning) that the reward function is stationary and path-independent for social learning interactions. We also propose an interaction taxonomy that describes three phases of a human-teacher’s vocalizations: direction, spoken before an action is taken; guidance, spoken as the learner communicates an intended action; and feedback, spo-ken in response to a completed action