878 research outputs found

    Really useful qualifications and learning? Exploring the policy effects of new sub-bachelors degree qualifications

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    The symposium paper addresses the conference theme of the relationship between policy, practice and research by critically examining policy discourse in lifelong learning and the role of research in understanding policy effects. Empirical and theoretical research on the rationale and practice of examples of short cycle HE including sub-bachelors degree level qualifications, such as Higher National Certificates and Diplomas and Foundation Degrees are the focus

    Cylindrical gravitational waves in expanding universes: Models for waves from compact sources

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    New boundary conditions are imposed on the familiar cylindrical gravitational wave vacuum spacetimes. The new spacetime family represents cylindrical waves in a flat expanding (Kasner) universe. Space sections are flat and nonconical where the waves have not reached and wave amplitudes fall off more rapidly than they do in Einstein-Rosen solutions, permitting a more regular null inifinity.Comment: Minor corrections to references. A note added in proo

    Fault-tolerant quantum computation with high threshold in two dimensions

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    We present a scheme of fault-tolerant quantum computation for a local architecture in two spatial dimensions. The error threshold is 0.75% for each source in an error model with preparation, gate, storage and measurement errors.Comment: 4 pages, 4 figures; v2: A single 2D layer of qubits (simple square lattice) with nearest-neighbor translation-invariant Ising interaction suffices. Slightly improved threshol

    Semiclassical Analysis of the Wigner 9J9J-Symbol with Small and Large Angular Momenta

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    We derive a new asymptotic formula for the Wigner 9j9j-symbol, in the limit of one small and eight large angular momenta, using a novel gauge-invariant factorization for the asymptotic solution of a set of coupled wave equations. Our factorization eliminates the geometric phases completely, using gauge-invariant non-canonical coordinates, parallel transports of spinors, and quantum rotation matrices. Our derivation generalizes to higher 3nj3nj-symbols. We display without proof some new asymptotic formulas for the 12j12j-symbol and the 15j15j-symbol in the appendices. This work contributes a new asymptotic formula of the Wigner 9j9j-symbol to the quantum theory of angular momentum, and serves as an example of a new general method for deriving asymptotic formulas for 3nj3nj-symbols.Comment: 18 pages, 16 figures. To appear in Phys. Rev.

    Prospective parents’ perspectives on antenatal decision making for the anticipated birth of a periviable infant

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    Objective: To examine prospective parents’ perceptions of management options and outcomes in the context of threatened periviable delivery, and the values they apply in making antenatal decisions during this period. Study design: Qualitative analysis of 46 antenatal interviews conducted at three tertiary-care hospitals with 54 prospective parents (40 pregnant women, 14 partners) who had received counseling for threatened periviable delivery (40 cases). Results: Participants most often recalled being involved in resuscitation, cerclage, and delivery mode decisions. Over half (63.0%) desired a shared decision-making role. Most (85.2%) recalled hearing about morbidity and mortality, with many reiterating terms like “brain damage”, “disability”, and “handicap”. The potential for disability influenced decision making to variable degrees. In describing what mattered most, participant spoke of giving their child a “fighting chance”; others voiced concerns about “best interest”, a “healthy baby”, “pain and suffering”, and religious faith. Conclusions: Our findings underscore the importance of presenting clear information on disability and eliciting the factors that parents deem most important in making decisions about periviable birth

    Energy-Efficient Multiprocessor Scheduling for Flow Time and Makespan

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    We consider energy-efficient scheduling on multiprocessors, where the speed of each processor can be individually scaled, and a processor consumes power sαs^{\alpha} when running at speed ss, for α>1\alpha>1. A scheduling algorithm needs to decide at any time both processor allocations and processor speeds for a set of parallel jobs with time-varying parallelism. The objective is to minimize the sum of the total energy consumption and certain performance metric, which in this paper includes total flow time and makespan. For both objectives, we present instantaneous parallelism clairvoyant (IP-clairvoyant) algorithms that are aware of the instantaneous parallelism of the jobs at any time but not their future characteristics, such as remaining parallelism and work. For total flow time plus energy, we present an O(1)O(1)-competitive algorithm, which significantly improves upon the best known non-clairvoyant algorithm and is the first constant competitive result on multiprocessor speed scaling for parallel jobs. In the case of makespan plus energy, which is considered for the first time in the literature, we present an O(ln11/αP)O(\ln^{1-1/\alpha}P)-competitive algorithm, where PP is the total number of processors. We show that this algorithm is asymptotically optimal by providing a matching lower bound. In addition, we also study non-clairvoyant scheduling for total flow time plus energy, and present an algorithm that achieves O(lnP)O(\ln P)-competitive for jobs with arbitrary release time and O(ln1/αP)O(\ln^{1/\alpha}P)-competitive for jobs with identical release time. Finally, we prove an Ω(ln1/αP)\Omega(\ln^{1/\alpha}P) lower bound on the competitive ratio of any non-clairvoyant algorithm, matching the upper bound of our algorithm for jobs with identical release time

    Stellar Iron Abundances at the Galactic Center

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    We present measurements of [Fe/H] for six M supergiant stars and three giant stars within 0.5 pc of the Galactic Center (GC) and one M supergiant star within 30 pc of the GC. The results are based on high-resolution (lambda / Delta lambda =40,000) K-band spectra, taken with CSHELL at the NASA Infrared Telescope Facility.We determine the iron abundance by detailed abundance analysis,performed with the spectral synthesis program MOOG.The mean [Fe/H] of the GC stars is determined to be near solar,[Fe/H] = +0.12 ±\pm 0.22. Our analysis is a differential analysis, as we have observed and applied the same analysis technique to eleven cool, luminous stars in the solar neighborhood with similar temperatures and luminosities as the GC stars. The mean [Fe/H] of the solar neighborhood comparison stars, [Fe/H] = +0.03 ±\pm 0.16, is similar to that of the GC stars. The width of the GC [Fe/H] distribution is found to be narrower than the width of the [Fe/H] distribution of Baade's Window in the bulge but consistent with the width of the [Fe/H] distribution of giant and supergiant stars in the solar neighborhood.Comment: 41 pages, 9 figures, ApJ, in pres

    Near-bed and surface flow division patterns in experimental river bifurcations

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    Understanding channel bifurcation mechanics is of great importance for predicting and managing multichannel river processes and avulsion in distributary river deltas. To date, research on river channel bifurcations has focused on factors determining the stability and evolution of bifurcations. It has recently been shown that, theoretically, the nonlinearity of the relation between sediment transport and flow discharge causes one of the two distributaries of a (slightly) asymmetrical bifurcation to grow and the other to shrink. The positive feedback introduced by this effect results in highly asymmetrical bifurcations. However, there is a lack of detailed insight into flow dynamics within river bifurcations, the consequent effect on bed load flux through bifurcating channels, and thus the impact on bifurcation stability over time. In this paper, three key parameters (discharge ratio, width-to-depth ratio, and bed roughness) were varied in order to examine the secondary flow field and its effect on flow partitioning, particularly near-bed and surface flow, at an experimental bifurcation. Discharge ratio was controlled by varying downstream water levels. Flow fields were quantified using both particle image velocimetry and ultrasonic Doppler velocity profiling. Results show that a bifurcation induces secondary flow cells upstream of the bifurcation. In the case of unequal discharge ratio, a strong increase in the secondary flow near the bed causes a larger volume of near-bed flow to enter the dominant channel compared to surface and depth-averaged flow. However, this effect diminishes with larger width-to-depth ratio and with increased bed roughness. The flow structure and division pattern will likely have a stabilizing effect on river channel bifurcations. The magnitude of this effect in relation to previously identified destabilizing effects is addressed by proposing an adjustment to a widely used empirical bed load nodal-point partition equation. Our finding implies that river bifurcations can be stable under a wider range of conditions than previously thought. Key Points Secondary flow in symmetrical bifurcations causes strong near-bed flow curvature A disproportional amount of near-bed flow enters the dominant downstream channel Flow curvature adds a stabilizing feedback on bifurcation evolution

    Abiotic and Biotic Soil Characteristics in Old Growth Forests and Thinned or Unthinned Mature Stands in Three Regions of Oregon

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    We compared forest floor depth, soil organic matter, soil moisture, anaerobic mineralizable nitrogen (a measure of microbial biomass), denitrification potential, and soil/litter arthropod communities among old growth, unthinned mature stands, and thinned mature stands at nine sites (each with all three stand types) distributed among three regions of Oregon. Mineral soil measurements were restricted to the top 10 cm. Data were analyzed with both multivariate and univariate analyses of variance. Multivariate analyses were conducted with and without soil mesofauna or forest floor mesofauna, as data for those taxa were not collected on some sites. In multivariate analysis with soil mesofauna, the model giving the strongest separation among stand types (P = 0.019) included abundance and richness of soil mesofauna and anaerobic mineralizable nitrogen. The best model with forest floor mesofauna (P = 0.010) included anaerobic mineralizable nitrogen, soil moisture content, and richness of forest floor mesofauna. Old growth had the highest mean values for all variables, and in both models differed significantly from mature stands, while the latter did not differ. Old growth also averaged higher percent soil organic matter, and analysis including that variable was significant but not as strong as without it. Results of the multivariate analyses were mostly supported by univariate analyses, but there were some differences. In univariate analysis, the difference in percent soil organic matter between old growth and thinned mature was due to a single site in which the old growth had exceptionally high soil organic matter; without that site, percent soil organic matter did not differ between old growth and thinned mature, and a multivariate model containing soil organic matter was not statistically significant. In univariate analyses soil mesofauna had to be compared nonparametrically (because of heavy left-tails) and differed only in the Siskiyou Mountains, where they were most abundant and species rich in old growth forests. Species richness of mineral soil mesofauna correlated significantly (+) with percent soil organic matter and soil moisture, while richness of forest floor mesofauna correlated (+) with depth of the forest floor. Composition of forest floor and soil mesofauna suggest the two groups represent a single community. Soil moisture correlated highly with percent soil organic matter, with no evidence for drying in sites that were sampled relatively late in the summer drought, suggesting losses of surface soil moisture were at least partially replaced by hydraulic lift (which has been demonstrated in other forests of the region)
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