1,716 research outputs found

    Mars high-resolution mapping

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    A series of photomosaics of high-resolution Viking Orbiter images of Mars is being prepared and published to support the Mars 1:500,000 scale geologic mapping program. More than 100 of these photomosaics were made manually, but for the last several years they have all been made digitally. The digital mosaics are published on the Mars Transverse Mercator (MTM) system, and they are also available to the appropriate principal investigators as digital files in the mosaicked digital image model (MDIM) format. The mosaics contain Viking Orbiter images with the highest available resolution: in some areas as high as 10 m/pixel. This resolution, where it exists, will support a 1:100,000 map scale. The full resolution of a mosaic is preserved in a digital file, but conventional lithographic publication of such large-scale inset maps will be done only if required by the geologic map author. When high-resolution images do not full the neatlines of an MTM quadrangle, the medium-resolution (1/256 degrees/pixel, or 231 m/pixel) MDIM is used. The mosaics are tied by image-matching to the planetwide MDIM, in which random errors as large as 5 km (10 mm at 1:500,000 scale) are common; a few much larger, worst-case errors also occur. Because of the distribution of the errors, many large discrepancies appear along the cutlines between frames with very different resolutions. Furthermore, each block of quadrangles is compiled on its own local control system, and adjacent blocks, compiled later, are unlikely to match. Selection of areas to be mapped is based on geologic mapping proposals reviewed and recommended by the Mars 1:500,000 scale geologic mapping review panel. There is no intention to map the entire planet at this scale

    A Wien Filter Energy Loss Spectrometer for the Dedicated Scanning Transmission Electron Microscope

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    A Wien filter electron spectrometer has been added to a VG Microscopes, Ltd. HB501 STEM to improve the energy resolution and accuracy of energy loss analysis combined with a high spatial resolution. An energy resolution of 130meV is obtained with a 2mR collection angle at the specimen. The 0.28eV wide field emission energy profile therefore dominates the energy resolution for the device. The energy axis is automatically calibrated by the electrostatic method of scanning, yielding an accuracy and stability of 30meV. A preliminary energy resolution of 0.5eV is demonstrated for 20mR full collection angles at the specimen. Results of experiments suggest that, even with a 0.3eV energy resolution, interband losses below 1.5eV will be hard to observe due to the long exponentially decaying field emission profile. Deconvolution procedures will probably be necessary as a result

    A cryopump for cooling objects at a distance

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    Design and construction of cryopump is reported that feeds from primary source to cool component up to 30 ft from source. Liquid oxygen or nitrogen is gravity fed through loop system to copper fibers enclosing component at room temperature where fluid boils, cools object, vaporizes and recycles through tubing loop

    Physical mechanisms of interface-mediated intervalley coupling in Si

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    The conduction band degeneracy in Si is detrimental to quantum computing based on spin qubits, for which a nondegenerate ground orbital state is desirable. This degeneracy is lifted at an interface with an insulator as the spatially abrupt change in the conduction band minimum leads to intervalley scattering. We present a theoretical study of the interface-induced valley splitting in Si that provides simple criteria for optimal fabrication parameters to maximize this splitting. Our work emphasizes the relevance of different interface-related properties to the valley splitting.Comment: 4 pages, revised versio

    Relating the Time Complexity of Optimization Problems in Light of the Exponential-Time Hypothesis

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    Obtaining lower bounds for NP-hard problems has for a long time been an active area of research. Recent algebraic techniques introduced by Jonsson et al. (SODA 2013) show that the time complexity of the parameterized SAT(\cdot) problem correlates to the lattice of strong partial clones. With this ordering they isolated a relation RR such that SAT(RR) can be solved at least as fast as any other NP-hard SAT(\cdot) problem. In this paper we extend this method and show that such languages also exist for the max ones problem (MaxOnes(Γ\Gamma)) and the Boolean valued constraint satisfaction problem over finite-valued constraint languages (VCSP(Δ\Delta)). With the help of these languages we relate MaxOnes and VCSP to the exponential time hypothesis in several different ways.Comment: This is an extended version of Relating the Time Complexity of Optimization Problems in Light of the Exponential-Time Hypothesis, appearing in Proceedings of the 39th International Symposium on Mathematical Foundations of Computer Science MFCS 2014 Budapest, August 25-29, 201

    Electron energy loss spectroscopy of single silicon nanocrystals: The conduction band

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    Spatially resolved electron energy loss spectroscopy has been performed on single, H-terminated, Si nanocrystals in the size range 25–500 Å. The particles were prepared via the gas-phase photolysis of a dilute Si2H6/He mixture in a gas flow cell, and deposited on a holey carbon grid for analysis. Energy loss within a few eV of the core 2p ionization edge reveals information about the conduction band states at Δ1 and L1 in the Brillouin zone. The conduction band edge is observed to shift to higher energy as the inverse square of the particle radius. In addition, a strong increase in the oscillator strength for these transitions is observed for decreasing particle sizes below 60 Å

    Moral Hypocrisy and Acting for Reasons: How Moralizing Can Invite Self-Deception

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    According to some, contemporary social psychology is aptly described as a study in moral hypocrisy. In this paper we argue that this is unfortunate when understood as establishing that we only care about appearing to act morally, not about true moral action. A philosophically more interesting interpretation of the “moral hypocrisy”-findings understands it to establish that we care so much about morality that it might lead to (1) self-deception about the moral nature of our motives and/or (2) misperceptions regarding what we should or should not do in everyday or experimental situations. In this paper we argue for this claim by elaborating on a fascinating series of experiments by Daniel Batson and his colleagues who have consistently contributed to the moral hypocrisy findings since the late nineties, and showing in what way they contribute to a better understanding of moral agency, rather than undermine the idea that we are moral agents

    Visual Bias Predicts Gait Adaptability in Novel Sensory Discordant Conditions

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    We designed a gait training study that presented combinations of visual flow and support-surface manipulations to investigate the response of healthy adults to novel discordant sensorimotor conditions. We aimed to determine whether a relationship existed between subjects visual dependence and their postural stability and cognitive performance in a new discordant environment presented at the conclusion of training (Transfer Test). Our training system comprised a treadmill placed on a motion base facing a virtual visual scene that provided a variety of sensory challenges. Ten healthy adults completed 3 training sessions during which they walked on a treadmill at 1.1 m/s while receiving discordant support-surface and visual manipulations. At the first visit, in an analysis of normalized torso translation measured in a scene-movement-only condition, 3 of 10 subjects were classified as visually dependent. During the Transfer Test, all participants received a 2-minute novel exposure. In a combined measure of stride frequency and reaction time, the non-visually dependent subjects showed improved adaptation on the Transfer Test compared to their visually dependent counterparts. This finding suggests that individual differences in the ability to adapt to new sensorimotor conditions may be explained by individuals innate sensory biases. An accurate preflight assessment of crewmembers biases for visual dependence could be used to predict their propensities to adapt to novel sensory conditions. It may also facilitate the development of customized training regimens that could expedite adaptation to alternate gravitational environments
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