8,282 research outputs found
Properties of holographic dark energy at the Hubble length
Full text linkWe consider holographic cosmological models of dark energy in which the
infrared cutoff is set by the Hubble's radius. We show that any interacting
dark energy model, regardless of its detailed form, can be recast as a non
interacting model in which the holographic parameter evolves slowly
with time. Two specific cases are analyzed. We constrain the parameters of both
models with observational data, and show that they can be told apart at the
perturbative level.Comment: 4 pages, 6 figures. Contribution to the Proceedings ERE201
The examination of Na-Ca effect on some qualitative and quantitative characters in durum wheat plants
Get PDFThe effect of salt stress (NaCl) on shoot height (cm), root length (cm), dry and fresh weight (g), chlorophyll a and b, total chlorophyll (mg-1) and carotenoid amount was investigated in this study. In addition, the positive effects of Ca+2 (20 mM) were also investigated. Triticum durum Desf. Mirzabey, Kunduru-1149, and DH-6 and DH-8, derived from Kunduru-1149 using wide hybridization, were used as plant materials in this study. Arnon-Hoagland solution was used as food source for the plants and various NaCl concentrations (0, 50, 150 and 200 mM) and Ca+2 (as CaCl2) were added to Arnon-Hoagland solution. The research was completed at the end of the fifth week and the effect of NaCl on the root length of genotypes was found to be significant (P<0.05). Ca+2 caused an increase in root length in all NaCl applications, except for the 200 mM NaCl, whereas shoot height decreased with increasing salt concentration, except for the 50 mM NaCl. This character also increased with Ca+2 application significantly. Dry and fresh weight of the plant decreased with increasing salt concentration. Ca+2 ameliorated dry and fresh weight of the plant at 50 mM NaCl in all the genoypes and NaCl doses, except for the Kunduru-1149 and DH-6. The highest increase in total chlorophyll amount was found in 50 mM NaCl + CaCl2 in DH-8 (from 17.29 to 20.14 mg g-1). However, the rate of increase in the amount of carotenoid by the addition of Ca+2 was also determined for each genotype.Key words: Triticum durum Desf., salinity, calcium, chlorophyll, carotenoid
Fast Hierarchical Clustering and Other Applications of Dynamic Closest Pairs
Full text linkWe develop data structures for dynamic closest pair problems with arbitrary
distance functions, that do not necessarily come from any geometric structure
on the objects. Based on a technique previously used by the author for
Euclidean closest pairs, we show how to insert and delete objects from an
n-object set, maintaining the closest pair, in O(n log^2 n) time per update and
O(n) space. With quadratic space, we can instead use a quadtree-like structure
to achieve an optimal time bound, O(n) per update. We apply these data
structures to hierarchical clustering, greedy matching, and TSP heuristics, and
discuss other potential applications in machine learning, Groebner bases, and
local improvement algorithms for partition and placement problems. Experiments
show our new methods to be faster in practice than previously used heuristics.Comment: 20 pages, 9 figures. A preliminary version of this paper appeared at
the 9th ACM-SIAM Symp. on Discrete Algorithms, San Francisco, 1998, pp.
619-628. For source code and experimental results, see
http://www.ics.uci.edu/~eppstein/projects/pairs
Physiological Correlates of Choice‐Induced Dissonance: An Exploration of HPA‐Axis Responses
Full text linkChoice can produce a negatively arousing cognitive conflict (called dissonance), which is thought to motivate the chooser to spread their preferences for the relevant options (called Spreading of Alternatives, or SA). The current work aimed to determine the relationship between HPA‐axis activity and both choice‐induced dissonance and its reduction (i.e. SA) among individuals with varying cultural backgrounds. European–Americans and Asians made a choice between two equally attractive CDs either in the presence of a cue indicative of social eyes (i.e. public‐choice condition) or in the absence thereof (i.e. private‐choice condition). As predicted, European–Americans and Asians showed a reliable SA primarily in the private and public choice conditions, respectively. Importantly, a sharp decline of salivary cortisol was observed over the span of 30 min, and, moreover, this decline was reliably predicted by the magnitude of SA regardless of either culture or the choice being private vs. public. These results suggest that although choice‐induced dissonance is too weak to elicit an HPA‐axis stress response, SA is associated with variability in the decline of salivary cortisol during the laboratory task. Copyright © 2015 John Wiley & Sons, Ltd.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/113729/1/bdm1845.pd
Size segregation and convection
Full text linkThe size segregation of granular materials in a vibrating container is
investigated using Molecular Dynamics. We find that the rising of larger
particles is accompanied by the existence of convection cells even in the case
of the lowest possible frequencies. The convection can, however, also be
triggered by the larger particle itself. The possibility of rising through this
mechanism strongly depends on the depth of the larger particle.Comment: 7 pages, 4 figure
Performance-based fi nancing at the Global Fund to Fight AIDS, Tuberculosis and Malaria: an analysis of grant ratings and funding, 2003–12
Get PDFBackground Performance-based fi nancing can be used by global health funding agencies to improve programme
performance and thus value for money. The Global Fund to Fight AIDS, Tuberculosis and Malaria was one of the fi rst
global-health funders to deploy a performance-based fi nancing system. However, its complex, multistep system for
calculating and paying on grant ratings has several components that are subjective and discretionary. We aimed to test
the association between grant ratings and disbursements, an indication of the extent to which incentives for
performance are transmitted to grant recipients.
Methods We obtained publicly available data for 508 Global Fund grants from 2003 to 2012 with performance ratings
and corresponding disbursements, merged with other datasets that contained data for relevant country characteristics.
We used regression analysis to identify predictors of grant disbursements in phase 2 (typically the latter 3 of 5 years
of a grant), using two dependent variables: whether a grant had any phase-2 disbursements, and the phase-2
disbursement amount. In a separate analysis, we also investigated the predictors of grant performance ratings.
Findings Grant performance rating in phase 1 was positively associated with having any disbursements in phase 2,
but no association was seen between phase-1 ratings and phase-2 disbursement amounts. Further more, performance
ratings are not replicable by external observers, both because subjective and discretionary decisions are made in the
generation of performance measures and because the underlying data are not available.
Interpretation The Global Fund’s present performance-based funding system does not adequately convey incentives
for performance to recipients, and the organisation should redesign this system to explicitly link a portion of the
funds to a simple performance measure in health coverage or outcomes, measured independently and robustly
Gene therapy restores vision in rd1 mice after removal of a confounding mutation in Gpr179
Get PDFThe rd1 mouse with a mutation in the Pde6b gene was the first strain of mice identified with a retinal degeneration. However, AAV-mediated gene supplementation of rd1 mice only results in structural preservation of photoreceptors, and restoration of the photoreceptor-mediated a-wave, but not in restoration of the bipolar cell-mediated b-wave. Here we show that a mutation in Gpr179 prevents the full restoration of vision in rd1 mice. Backcrossing rd1 with C57BL6 mice reveals the complete lack of b-wave in a subset of mice, consistent with an autosomal recessive Mendelian inheritance pattern. We identify a mutation in the Gpr179 gene, which encodes for a G-protein coupled receptor localized to the dendrites of ON-bipolar cells. Gene replacement in rd1 mice that are devoid of the mutation in Gpr179 successfully restores the function of both photoreceptors and bipolar cells, which is maintained for up to 13 months. Our discovery may explain the failure of previous gene therapy attempts in rd1 mice, and we propose that Grp179 mutation status should be taken into account in future studies involving rd1 mice
Subdiffusive axial transport of granular materials in a long drum mixer
Full text linkGranular mixtures rapidly segregate radially by size when tumbled in a
partially filled horizontal drum. The smaller component moves toward the axis
of rotation and forms a buried core, which then splits into axial bands. Models
have generally assumed that the axial segregation is opposed by diffusion.
Using narrow pulses of the smaller component as initial conditions, we have
characterized axial transport in the core. We find that the axial advance of
the segregated core is well described by a self-similar concentration profile
whose width scales as , with . Thus, the
process is subdiffusive rather than diffusive as previously assumed. We find
that is nearly independent of the grain type and drum rotation rate
within the smoothly streaming regime. We compare our results to two
one-dimensional PDE models which contain self-similarity and subdiffusion; a
linear fractional diffusion model and the nonlinear porous medium equation.Comment: 4 pages, 4 figures, 1 table. Submitted to Phys Rev Lett. For more
info, see http://www.physics.utoronto.ca/nonlinear
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