Conductance fingerprint of Majorana fermions in the topological Kondo effect

We consider an interacting nanowire/superconductor heterostructure attached to metallic leads. The device is described by an unusual low-energy model involving spin-1 conduction electrons coupled to a nonlocal spin-1/2 Kondo impurity built from Majorana fermions. The topological origin of the resulting Kondo effect is manifest in distinctive non-Fermi-liquid (NFL) behavior, and the existence of Majorana fermions in the device is demonstrated unambiguously by distinctive conductance lineshapes. We study the physics of the model in detail, using the numerical renormalization group, perturbative scaling and abelian bosonization. In particular, we calculate the full scaling curves for the differential conductance in AC and DC fields, onto which experimental data should collapse. Scattering t-matrices and thermodynamic quantities are also calculated, recovering asymptotes from conformal field theory. We show that the NFL physics is robust to asymmetric Majorana-lead couplings, and here we uncover a duality between strong and weak coupling. The NFL behavior is understood physically in terms of competing Kondo effects. The resulting frustration is relieved by inter-Majorana coupling which generates a second crossover to a regular Fermi liquid.Comment: 17 pages, 8 figure

The Impacts of Wind Speed Trends and 30-Year Variability in Relation to Hydroelectric Reservoir Inflows on Wind Power in the Pacific Northwest

In hydroelectric dominated systems, the value and benefits of energy are higher during extended dry periods and lower during extended or extreme wet periods. By accounting for regional and temporal differences in the relationship between wind speed and reservoir inflow behavior during wind farm site selection, the benefits of energy diversification can be maximized. The goal of this work was to help maximize the value of wind power by quantifying the long-term (30-year) relationships between wind speed and streamflow behavior, using British Columbia (BC) and the Pacific Northwest (PNW) as a case study. Clean energy and self-sufficiency policies in British BC make the benefits of increased generation during low streamflow periods particularly large. Wind density (WD) estimates from a height of 10m (North American Regional Reanalysis, NARR) were correlated with cumulative usable inflows (CUI) for BC (collected from BC Hydro) for 1979–2010. The strongest WD-CUI correlations were found along the US coast (r ~0.55), whereas generally weaker correlations were found in northern regions, with negative correlations (r ~ -0.25) along BC’s North Coast. Furthermore, during the lowest inflow years, WD anomalies increased by up to 40% above average values for the North Coast. Seasonally, high flows during the spring freshet were coincident with widespread negative WD anomalies, with a similar but opposite pattern for low inflow winter months. These poorly or negatively correlated sites could have a moderating influence on climate related variability in provincial electricity supply, by producing greater than average generation in low inflow years and reduced generation in wet years. Wind speed and WD trends were also analyzed for all NARR grid locations, which showed statistically significant positive trends for most of the PNW and the largest increases along the Pacific Coast

Vaccine Cooler for the Global Poor

Cal Poly physics professors Peter Schwartz and Nathan Heston approached the Solar Freeze team with the problem that remote communities in Africa have limited access to modern-day medicine or vaccines. They suggested that we try and design a cooling device that can keep vaccines cold for multiple days at a time while the medicine is transported to remote villages. Currently, there are vaccine cooler products on the market, but most of them are very expensive or lack portability. Peter and Nate have tasked the Solar Freeze team to come up with a less expensive solution that is also portable and can handle the harsh environments of Africa. Due to the fact that Peter and Nate have done extensive research and laboratory experiments with using a solar panel to power thermo-electric coolers, they suggested that a thermo-electric cooler should be used to keep the cooler cold. The Solar Freeze team’s goal is to design a solar-powered vaccine cooler that utilizes thermo-electric coolers to freeze a phase change material and keep vaccines at optimal temperature

A Lyman Alpha Galaxy at Redshift z=6.944 in the COSMOS Field

Lyman-alpha emitting galaxies can be used to study cosmological reionization, because a neutral intergalactic medium scatters Lyman-alpha photons into diffuse halos whose surface brightness falls below typical survey detection limits. Here we present the Lyman-alpha emitting galaxy LAE J095950.99+021219.1, identified at redshift z=6.944 in the COSMOS field using narrowband imaging and followup spectroscopy with the IMACS instrument on the Magellan I Baade telescope. With a single object spectroscopically confirmed so far, our survey remains consistent with a wide range of IGM neutral fraction at redshift seven, but further observations are planned and will help clarify the situation. Meantime, the object we present here is only the third Lyman-alpha selected galaxy to be spectroscopically confirmed at redshift seven, and is 2--3 times fainter than the previously confirmed redshift seven Lyman alpha galaxies.Comment: 15 pages including 3 figures. Accepted for publication in The Astrophysical Journal Letter

Characterizing the Oldenburg ‘Butter Shale’ from the Upper Ordovician (Katian) Waynesville Formation along the Cincinnati Arch, USA

The Upper Ordovician (Katian) strata of the Cincinnati Arch contain numerous mudstone units known locally as ‘butter shales’ or ‘trilobite shales’. Most of these deposits are heavily collected for their excellently-preserved trilobites. The Oldenburg Butter Shale, however, is a previously-undescribed mudstone package from the Waynesville Formation, known only from limited exposure near Oldenburg, Indiana. The Oldenburg Shale is a 2 m-thick mudstone package with minor beds of shelly packstones, and calcisiltite-filled gutter casts. It contains abundant articulated trilobites. The mudstone portion contains illite, chlorite, quartz, calcite and traces of dolomite and pyrite. In outcrop, the shale exhibits no obvious bedding and breaks conchoidally. When cut and polished, the mudstone shows a mottled fabric, containing Lingulichnus and Chondrites trace fossils. The shelly units contain brachiopods, gastropods, and bryozoans. The gutter casts are 20 – 30 cm wide, display hummocky stratification, and contain Lingulichnus. Faunally, the Oldenburg is very unlike surrounding Waynesville strata. Instead of being dominated by brachiopods as is typical, the Oldenburg fauna consists of abundant bivalves (Modiolopsis, Ambonychia, and Caritodens), lingulid brachiopods, and the trilobites (Isotelus, and Flexicalymene, and rare Amphilichas in the upper 30 cm). Articulate brachiopods are represented in the shale to a limited extent by the genera Zygospira and Platystrophia. The shale also contains bryozoans, orthoconic cephalopods, rare crinoids and conulariids. Conodonts and scolecodonts are a major component of the microfauna. Taphonomy of the fossils, together with sedimentological features, indicates that this butter shale accumulated rapidly as a series of episodes of distal storm-generated mud and silt flows. Towards the top of the mudstone is a horizon of small concretions, about 7 cm wide. Overlying the butter shale is the pyrite crusted surface of the Mid-Richmondian Unconformity which removes the Oldenburg shale in most other locations. The concretions present at the top of the shale are the likely product of the prolonged sediment starvation accompanying this unconformity

Synthesis of 3-D coronal-solar wind energetic particle acceleration modules

1. Introduction Acute space radiation hazards pose one of the most serious risks to future human and robotic exploration. Large solar energetic particle (SEP) events are dangerous to astronauts and equipment. The ability to predict when and where large SEPs will occur is necessary in order to mitigate their hazards. The Coronal-Solar Wind Energetic Particle Acceleration (C-SWEPA) modeling effort in the NASA/NSF Space Weather Modeling Collaborative [Schunk, 2014] combines two successful Living With a Star (LWS) (http://lws. gsfc.nasa.gov/) strategic capabilities: the Earth-Moon-Mars Radiation Environment Modules (EMMREM) [Schwadron et al., 2010] that describe energetic particles and their effects, with the Next Generation Model for the Corona and Solar Wind developed by the Predictive Science, Inc. (PSI) group. The goal of the C-SWEPA effort is to develop a coupled model that describes the conditions of the corona, solar wind, coronal mass ejections (CMEs) and associated shocks, particle acceleration, and propagation via physics-based modules. Assessing the threat of SEPs is a difficult problem. The largest SEPs typically arise in conjunction with X class flares and very fast (\u3e1000 km/s) CMEs. These events are usually associated with complex sunspot groups (also known as active regions) that harbor strong, stressed magnetic fields. Highly energetic protons generated in these events travel near the speed of light and can arrive at Earth minutes after the eruptive event. The generation of these particles is, in turn, believed to be primarily associated with the shock wave formed very low in the corona by the passage of the CME (injection of particles from the flare site may also play a role). Whether these particles actually reach Earth (or any other point) depends on their transport in the interplanetary magnetic field and their magnetic connection to the shock

The Reliability of Parafoveal Cone Density Measurements

Background Adaptive optics scanning light ophthalmoscopy (AOSLO) enables direct visualisation of the cone mosaic, with metrics such as cone density and cell spacing used to assess the integrity or health of the mosaic. Here we examined the interobserver and inter-instrument reliability of cone density measurements. Methods For the interobserver reliability study, 30 subjects with no vision-limiting pathology were imaged. Three image sequences were acquired at a single parafoveal location and aligned to ensure that the three images were from the same retinal location. Ten observers used a semiautomated algorithm to identify the cones in each image, and this was repeated three times for each image. To assess inter-instrument reliability, 20 subjects were imaged at eight parafoveal locations on one AOSLO, followed by the same set of locations on the second AOSLO. A single observer manually aligned the pairs of images and used the semiautomated algorithm to identify the cones in each image. Results Based on a factorial study design model and a variance components model, the interobserver study\u27s largest contribution to variability was the subject (95.72%) while the observer\u27s contribution was only 1.03%. For the inter-instrument study, an average cone density intraclass correlation coefficient (ICC) of between 0.931 and 0.975 was calculated. Conclusions With the AOSLOs used here, reliable cone density measurements can be obtained between observers and between instruments. Additional work is needed to determine how these results vary with differences in image quality