2,849 research outputs found

    Doping and band-gap engineering of an intrazeolite tungsten(VI) oxide supralattice

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    New results are presented concerning the topotactic self-assembly, n-type doping and band-gap engineering of an intrazeolite tungsten(VI) oxide supralattice n(W03)-Na56Y, where 0 < η < 32, built-up of single size and shape (W03)2 dimers. In particular it has been found that the oxygen content of these dimers can be quantitatively adjusted by means of a thermal vacuum induced reversible reductive-elimination oxidative-addition of dioxygen. This provides access to new n(W03.x)-Na56Y materials (0 < χ ^ 1.0) in which the oxygen content, structural properties and electronic architecture of the dimers are changed. In this way one can precisely control the oxidation state, degree of η-doping and band-filling of a tungsten(VI) oxide supralattice through an approach which can be considered akin to, but distinct in detail to, that found in the Magneli crystallographic shear phases of non-stoichiometric bulk W03.x . Another discovery concerns the ability to alter local electrostatic fields experienced by the tungsten(VI) oxide moieties housed in the 13Ä supercages of 16(W03)-M36Y, by varying the ionic potential of the constituent supercage M + cations across the alkali metal series. This method provides the first opportunity to fine-tune the band-gap of a tungsten(VI) oxide supralattice. Α miniband electronic description is advanced as a qualitative first attempt to understand the origin of the above effects. The implications of these discoveries are that cluster size, composition and intrinsic electrostatic field effects can be used to "chemically manipulate" (engineer) the doping and band architecture of intrazeolite supralattices of possible interest in quantum electronics and nonlinear optics

    Tuning the effects of Landau-level mixing on anisotropic transport in quantum Hall systems

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    Electron-electron interactions in half-filled high Landau levels in two-dimensional electron gases in a strong perpendicular magnetic field can lead to states with anisotropic longitudinal resistance. This longitudinal resitance is generally believed to arise from broken rotational invariance, which is indicated by charge density wave (CDW) order in Hartree-Fock calculations. We use the Hartree-Fock approximation to study the influence of externally tuned Landau level mixing on the formation of interaction induced states that break rotational invariance in two-dimensional electron and hole systems. We focus on the situation when there are two non-interacting states in the vicinity of the Fermi level and construct a Landau theory to study coupled charge density wave order that can occur as interactions are tuned and the filling or mixing are varied. We examine in detail a specific example where mixing is tuned externally through Rashba spin-orbit coupling. We calculate the phase diagram and find the possibility of ordering involving coupled striped or triangular charge density waves in the two levels. Our results may be relevant to recent transport experiments on quantum Hall nematics in which Landau-level mixing plays an important role.Comment: 25 pages, 6 figure

    Age-related differences in inhibitory control in the early school years

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    The transition to school is associated with a greater requirement to inhibit irrelevant or inappropriate thought and behavior in order to concentrate on effective learning and to interact successfully with peers. Current knowledge of inhibitory control development in the early school years is limited due to a lack of normative data from age-appropriate, sensitive measures. In this study, three pictorial versions of the Stroop task were administered to investigate inhibitory control development in early school-aged children. Age-related trajectories of inhibition and effects of gender were examined in 80 children (42 boys) aged 5 to 8 years. All children were assessed with the Cognitive Assessment System Expressive Attention subtest (Big-Small Stroop), Fruit Stroop, and Boy-Girl Stroop. The Big-Small Stroop revealed substantial age-related improvement in inhibition from 5 to 7 years with a levelling of performance at 8 years of age, while the Fruit Stroop and Boy-Girl Stroop demonstrated clear but nonsignificant age trends. In particular, older children committed fewer errors and corrected their errors more frequently than younger children. Performance on all Stroop tasks correlated significantly, providing evidence that they tap similar cognitive abilities. Some gender differences were found. This study indicates that inhibitory skills develop rapidly in the early school years and suggests that error awareness may be a useful indicator of the development of cognitive inhibition for this age group

    Progress toward sonifying Napoleon’s march and fluid flow simulations through binaural horizons

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    Cross-modal data analytics—that can be rendered for experience through vision, hearing, and touch—poses a fundamental challenge to designers. Non-linguistic sonification is a well-researched means for non-visual pattern recognition but higher density datasets pose a challenge. Because human hearing is optimized for detecting locations on a horizontal plane, our approach recruits this optimization by employing an immersive binaural horizontal plane using auditory icons. Two case studies demonstrate our approach: A sonic translation of a map and a sonic translation of a computational fluid dynamics simulation

    The Relationship between Physical Health and Psychological Well-Being among Oldest-Old Adults

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    The purpose of this study was to evaluate the relationship between physical health and psychological well-being among oldest-old adults. Structural equation modeling was performed to examine health influences on psychological well-being among 306 octogenarians and centenarians from the Georgia Centenarian Study. Latent variables were created to reflect subjective health, as measured by self-ratings of health and objective health, as measured by physical health impairment (i.e., health problems, past and present diseases, hospitalization) and biomarkers (i.e., hemoglobin and albumin). Psychological well-being was measured by positive and negative affect. There were significant direct effects of subjective health on affect and significant indirect effects of objective health through subjective health on positive affect and negative affect. Subjective health took the role of a mediator between objective health and psychological well-being. These results highlight the status and perceptions of health as a critical indicator for well-being in extreme old age

    Exercise metabolism in non-obese patients with type 2 diabetes following the acute restoration of normoglycaemia

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    This study investigated how acute restoration of normoglycaemia affected energy metabolism during exercise in nonobese patients with type 2 diabetes. Six subjects (mean ± SEM) aged 56.2 ± 2.7 years, with a BMI of 24.5 ± 1.5 kg/m2 and a VO2 peak of 28.7 ml/kg/min, attended the lab on two randomised occasions for a four-hour resting infusion of insulin or saline, followed by 30 minutes cycling at 50% VO2 peak. During the 4 h resting infusion, there was a greater (P < 0 0001) reduction in blood glucose in insulin treatment (INS) (from 11.2 ± 0.6 to 5.6 ± 0.1 mmol/l) than in saline treatment/control (CON) (from 11.5 ± 0.7 to 8.5 ± 0.6 mmol/l). This was associated with a lower (P < 0 05) resting metabolic rate in INS (3.87 ± 0.17) than in CON (4.39 ± 0.30 kJ/min). During subsequent exercise, blood glucose increased significantly in INS from 5.6 ± 0.1 at 0 min to 6.3 ± 0.3 mmol/l at 30 min (P < 0 01), which was accompanied by a lower blood lactate response (P < 0 05). Oxygen uptake, rates of substrate utilization, heart rate, and ratings of perceived exertion were not different between trials. Insulin-induced normoglycaemia increased blood glucose during subsequent exercise without altering overall substrate utilization

    Drag in paired electron-hole layers

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    We investigate transresistance effects in electron-hole double layer systems with an excitonic condensate. Our theory is based on the use of a minimum dissipation premise to fix the current carried by the condensate. We find that the drag resistance jumps discontinuously at the condensation temperature and diverges as the temperature approaches zero.Comment: 12 pages, 1 Figure, .eps file attache

    Deep uncertainty, public reason, the conservation of biodiversity and the regulation of markets for lion skeletons

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    Public reason is a formal concept in political theory. There is a need to better understand how public reason might be elicited in making public decisions that involve deep uncertainty, which arises from pernicious and gross ignorance about how a system works, the boundaries of a system, and the relative value (or disvalue) of various possible outcomes. This article is the third in a series to demonstrate how ethical argument analysis—a qualitative decision-making aid—may be used to elicit public reason in the presence of deep uncertainty. The first article demonstrated how argument analysis is capable of probing deep into a single argument. The second article demonstrated how argument analysis can analyze a broad set of arguments and how argument analysis can be operationalized for use as a decision-making aid. This article demonstrates (i) the relevance of argument analysis to public reasoning, (ii) the relevance of argument analysis for decision-making under deep uncertainty, an emerging direction in decision theory, and (iii) how deep uncertainty can arise when the boundary between facts and values is inescapably entangled. This article and the previous two make these demonstrations using, as an example, the conservation and sustainable use of lions
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