Solar Reector Design

The design of solar panels is investigated. Different aspects of this problem are presented. A formula averaging the solar energy received on a given location is derived rst. The energy received by the collecting solar panel is then calculated using a specially designed algorithm. The geometry of the device collecting the energy may then be optimised using different algorithms. The results show that for a given depth, devices of smaller width are more energy efficient than those of wider dimensions. This leads to a more economically efficient design

Widespread movement of meltwater onto and across Antarctic ice shelves

Surface meltwater drains across ice sheets, forming melt ponds that can trigger ice-shelf collapse acceleration of grounded ice flow and increased sea-level rise. Numerical models of the Antarctic Ice Sheet that incorporate meltwater’s impact on ice shelves, but ignore the movement of water across the ice surface, predict a metre of global sea-level rise this century in response to atmospheric warming. To understand the impact of water moving across the ice surface a broad quantification of surface meltwater and its drainage is needed. Yet, despite extensive research in Greenland and observations of individual drainage systems in Antarctica, we have little understanding of Antarctic-wide surface hydrology or how it will evolve. Here we show widespread drainage of meltwater across the surface of the ice sheet through surface streams and ponds (hereafter ‘surface drainage’) as far south as 85° S and as high as 1,300 metres above sea level. Our findings are based on satellite imagery from 1973 onwards and aerial photography from 1947 onwards. Surface drainage has persisted for decades, transporting water up to 120 kilometres from grounded ice onto and across ice shelves, feeding vast melt ponds up to 80 kilometres long. Large-scale surface drainage could deliver water to areas of ice shelves vulnerable to collapse, as melt rates increase this century. While Antarctic surface melt ponds are relatively well documented on some ice shelves, we have discovered that ponds often form part of widespread, large-scale surface drainage systems. In a warming climate, enhanced surface drainage could accelerate future ice-mass loss from Antarctic, potentially via positive feedbacks between the extent of exposed rock, melting and thinning of the ice sheet

Displacement/Length Scaling Relationships for Normal Faults; a Review, Critique, and Revised Compilation

The relationship between normal fault displacement (D) and length (L) varies due to numerous factors, including fault size, maturity, basin tectonic history, and host rock lithology. Understanding how fault D and L relate is useful, given related scaling laws are often used to help refine interpretations of often incomplete, subsurface datasets, which has implications for hydrocarbon and low-carbon energy applications. Here we provide a review of D/L scaling laws for normal faults, discuss factors that could influence these relationships, including both geological factors and errors in measurement, and provide a critique of previously published D/L databases. We then present our newly assembled database of 4059 normal faults from 66 sources that include explicit information on: 1) fault length and displacement, 2) host rock lithology, 3) host basin tectonic history, and 4) maturity, as well as fault D and L through time when these data are available. We find an overall scaling law of D = 0.3L0.92, which is similar to previously published scaling equations and that varies in response to the aforementioned geological factors. Our data show that small faults (<1 m length) tend to be over-displaced compared to larger faults, active faults tend to be over-displaced compared to inactive faults, and faults with stiffer host rock lithologies, like igneous and carbonate rocks, tend to be under-displaced with respect to faults within softer, more compliant host rocks, like clastic sedimentary rocks. Our dynamic D/L through time data show that faults follow the hybrid fault growth model, i.e., they initially lengthen, during which time they will appear under-displaced, before accumulating displacement. To the best of our knowledge, this is the first comprehensive, integrated, critical study of D/L scaling laws for normal faults and the factors influencing their growth. These revised relationships can now be utilized for predicting fault length or displacement when only one variable is available and provide the basis for general understanding D/L scaling laws in the context of normal fault growth. This underpinning database is open-access and is available for analysis and manipulation by the broader structural geology community.publishedVersio

State-selective imaging of cold atoms

Atomic coherence phenomena are usually investigated using single beam techniques without spatial resolution. Here we demonstrate state-selective imaging of cold 85Rb atoms in a three-level ladder system, where the atomic refractive index is sensitive to the quantum coherence state of the atoms. We use a phase-sensitive diffraction contrast imaging (DCI) technique which depends on the complex refractive index of the atom cloud. A semiclassical model allows us to analytically calculate the detuning-dependent refractive index of the system. The predicted Autler-Townes splitting and our experimental measurements are in excellent agreement. DCI provided a quantitative image of the distribution of the excited-state fraction, and compared with on-resonance absorption and blue cascade fluorescence techniques, was found to be experimentally simple and robust

Influence of crop rotation and flutolanil on the diversity of fungi on peanut shells

Les agents pathogènes du sol qui affectent les arachides (Arachis hypogaea) survivent ou hivernent souvent sur les écales d'arachides laissées sur ou dans le sol. Les effets de diverses rotations de cultures sur la flore fongique des écales d'arachides ont été comparés par trois tests en champ menés en 1992 et en 1993. Dans deux des tests, les parcelles d'arachides cultivées de façon continue ont été traitées ou non traitées avec le fongicide flutolanil. Les pratiques de rotation ont varié avec la localisation, et les cultures en rotation avec les arachides étaient le coton (Gossypium hirsutum), le seigle (Secale céréale), l'herbe de Bahia (Paspalum notatum), et le maïs (Zea mays). Au total,31 genres de champignon ont été isolés des écales. Plus des deux tiers des isolats étaient des Deutéromycètes, suivis en fréquence par les Basidiomycètes, les Ascomycètes et les Phycomycètes. Les pratiques de rotation ont affecté l'incidence de plusieurs champignons pathogènes (par exemple, les Fusarium spp. et le Lasiodiplodia theobromae) sur les écales d'arachides, mais les résultats n'ont pas été cohérents entre les tests et les années. L'herbe de Bahia ou le maïs cultivés en rotation avec les arachides ont réduit la fréquence du Rhizoctonia solani AG-4 dans les écales. Le Rhizoctonia solani AG-2-2 et le Macrophomina phaseolina ont été isolés à des niveaux plus élevés dans la rotation herbe de Bahia-arachide. Quand les arachides étaient cultivées en rotation avec le coton avec ou sans une culture de couverture de seigle, les parcelles recouvertes de seigle avaient des taux d'isolement moindres pour les champignons totaux en 1992 que les parcelles sans seigle, mais aucune différence n'a été observée en 1993. De plus, plusieurs espèces de Fusarium ont été isolées plus fréquemment des écales provenant de parcelles en rotation avec le seigle. Le flutolanil a diminué significativement les taux d'isolement de plusieurs champignons, incluant le R. solani AG-4, dans un des essais en 1992. L'ensemble des champignons isolés (en combinant tous les isolats de champignon) sur les parcelles traitées au flutolanil étaient plus élevés en 1993, mais pas en 1992 sur un des sites. Les taux d'isolement pour les différents genres et espèces de champignon différaient sur les deux milieux utilisés (agar à l'extrait de malt et agar au sel de malt). En particulier, l’AIternaria alternata et des espèces de Fusarium ont été isolés plus fréquemment sur l'agar au sel de malt, tandis que L theobromae, R. solani AG-4 et Trichoderma spp. Étaient plus souvent rencontrés sur l'agar à l'extrait de malt.Soilborne pathogens of peanut (Arachis hypogaea) often survive or over winter on peanut shells left on or in the soil. The effects of different crop rotations on the peanut shell mycobiota were compared in three field trials in 1992 and repeated in 1993. In two of the trials, plots grown continuously to peanut were either treated with the fungicide flutolanil or left untreated. Rotation practices varied with location and the crops in rotation with peanut were cotton (Gossypium hirsutum), rye (Secale cereale), bahiagrass (Paspalum notatum), and corn (Zea mays). In total, 31 different gene of fungi were isolated from shells. Over two-thirds of the isolates were Deuteromycotina, followed in frequency by Basidiomycetes, Ascomycetes, and Phycomycetes. The rotation practices affected the incidence of several pathogenic fungi (e.g., Fusarium spp., and Lasiodiplodia theobromae) in the peanut shells, but the results were not consistent across trials or years. Bahiagrass or corn grown in rotation with peanut reduced the frequency of Rhizoctonia solani AG-4 in shells. Rhizoctonia solani AG-2-2 and Macrophomina phaseolina were isolated at a greater level in the bahiagrass-peanut rotation. Where peanut was rotated with cotton with or without a winter cover crop of rye, plots containing rye had lower isolation rates for total fungi in 1992 than those without rye, but there was no différence in 1993. Also, several species of Fusarium were isolated more frequently from shells from plots rotated with rye. Flutolanil significantly lowered isolation rates of several fungi, including R. solani AG-4, in one trial in 1992. Total fungi isolated (all fungal isolates combined) in the flutolanil-treated plots were greater in 1993, but not in 1992 at one site. Isolation rates for the different gene and species of fungi differed on the two media utilized (malt-extract agar and malt-salt agar). In particular, Alternaria alternata and species of Fusarium were isolated more frequently on malt-salt agar, whereas L theobromae, R. solani AG-4 and Trichoderma spp. were more common on malt-extract agar

Measurements of the production and transport of helium ash on the TFTR Tokamak

Helium ash production and transport have been measured in TFTR deuterium-tritium plasmas using charge-exchange recombination spectroscopy. The helium ash confinement time, including recycling effects, is 6--10 times the energy confinement time and is compatible with sustained ignition in a reactor. The ash confinement time is dominated by edge pumping rates rather than core transport. The measured evolution of the local thermal ash density agrees with modeling, indicating that alpha particle slowing-down calculations used in the modeling are reasonable

Long Pulse High Performance Plasma Scenario Development for the National Spherical Torus Experiment

The National Spherical Torus Experiment [Ono et al., Nucl. Fusion, 44, 452 (2004)] is targeting long pulse high performance, noninductive sustained operations at low aspect ratio, and the demonstration of nonsolenoidal startup and current rampup. The modeling of these plasmas provides a framework for experimental planning and identifies the tools to access these regimes. Simulations based on neutral beam injection (NBI)-heated plasmas are made to understand the impact of various modifications and identify the requirements for (1) high elongation and triangularity, (2) density control to optimize the current drive, (3) plasma rotation and/or feedback stabilization to operate above the no-wall limit, and (4) electron Bernstein waves (EBW) for off-axis heating/current drive (H/CD). Integrated scenarios are constructed to provide the transport evolution and H/CD source modeling, supported by rf and stability analyses. Important factors include the energy confinement, Zeff, early heating/H mode, broadening of the NBI-driven current profile, and maintaining q(0) and qmin>1.0. Simulations show that noninductive sustained plasmas can be reached at IP=800 kA, BT=0.5 T, 2.5, N5, 15%, fNI=92%, and q(0)>1.0 with NBI H/CD, density control, and similar global energy confinement to experiments. The noninductive sustained high plasmas can be reached at IP=1.0 MA, BT=0.35 T, 2.5, N9, 43%, fNI=100%, and q(0)>1.5 with NBI H/CD and 3.0 MW of EBW H/CD, density control, and 25% higher global energy confinement than experiments. A scenario for nonsolenoidal plasma current rampup is developed using high harmonic fast wave H/CD in the early low IP and low Te phase, followed by NBI H/CD to continue the current ramp, reaching a maximum of 480 kA after 3.4 s

Self Consistent 1/Nc1/N_c Expansion In The Presence Of Electroweak Interactions

In the conventional approach to the $1/N_c$ expansion, electroweak interactions are switched off and large $N_c$ QCD is treated in isolation. We study the self-consistency of taking the large $N_c$ limit in the presence of electroweak interaction. If the electroweak coupling constants are held constant, the large $N_c$ counting rules are violated by processes involving internal photon or weak boson lines. Anomaly cancellations, however, fix the ratio of electric charges of different fermions. This allows a self-consistent way to scale down the electronic charge $e$ in the large $N_c$ limit and hence restoring the validity of the large $N_c$ counting rules.Comment: 9 pages in REVTeX, no figure

Target-distractor synchrony affects performance in a novel motor task for studying action selection

The study of action selection in humans can present challenges of task design since our actions are usually defined by many degrees of freedom and therefore occupy a large action-space. While saccadic eye-movement offers a more constrained paradigm for investigating action selection, the study of reach-and-grasp in upper limbs has often been defined by more complex scenarios, not easily interpretable in terms of such selection. Here we present a novel motor behaviour task which addresses this by limiting the action space to a single degree of freedom in which subjects have to track (using a stylus) a vertical coloured target line displayed on a tablet computer, whilst ignoring a similarly oriented distractor line in a different colour. We ran this task with 55 subjects and showed that, in agreement with previous studies, the presence of the distractor generally increases the movement latency and directional error rate. Further, we used two distractor conditions according to whether the distractor's location changes asynchronously or synchronously with the location of the target. We found that the asynchronous distractor yielded poorer performance than its synchronous counterpart, with significantly higher movement latencies and higher error rates. We interpret these results in an action selection framework with two actions (move left or right) and competing 'action requests' offered by the target and distractor. As such, the results provide insights into action selection performance in humans and supply data for directly constraining future computational models therein

Core Poloidal Rotation and Internal Trnasport Barrier Formation in TFTR

Impurity poloidal rotation velocities have been measured in the core of TFTR plasmas using a new spectroscopic diagnostic. Two types of transitions to enhanced confinement in reversed shear plasmas are examined. A bifurcation in carbon poloidal rotation is observed to occur before the transition to enhanced confinement for one of these types, while other measured plasmas parameters remain constant. A narrow radial region with reversed poloidal rotation and rotational shear is established 60-100 ms before the transition, and is associated with a large negative radial electric field