13,993 research outputs found
Computing semidefinite programming lower bounds for the (fractional) chromatic number via block-diagonalization.
Exercise-Derived Microvesicles: A Review of the Literature
Initially suggested as simple cell debris, cell-derived microvesicles (MVs) have now gained acceptance as recognized players in cellular communication and physiology. Shed by most, and perhaps all, human cells, these tiny lipid-membrane vesicles carry bioactive agents, such as proteins, lipids and microRNA from their cell source, and are produced under orchestrated events in response to a myriad of stimuli. Physical exercise introduces systemic physiological challenges capable of acutely disrupting cell homeostasis and stimulating the release of MVs into the circulation. The novel and promising field of exercise-derived MVs is expanding quickly, and the following work provides a review of the influence of exercise on circulating MVs, considering both acute and chronic aspects of exercise and training. Potential effects of the MV response to exercise are highlighted and future directions suggested as exercise and sports sciences extend the realm of extracellular vesicles
Stable soft extrapolation of entire functions
Soft extrapolation refers to the problem of recovering a function from its
samples, multiplied by a fast-decaying window and perturbed by an additive
noise, over an interval which is potentially larger than the essential support
of the window. A core theoretical question is to provide bounds on the possible
amount of extrapolation, depending on the sample perturbation level and the
function prior. In this paper we consider soft extrapolation of entire
functions of finite order and type (containing the class of bandlimited
functions as a special case), multiplied by a super-exponentially decaying
window (such as a Gaussian). We consider a weighted least-squares polynomial
approximation with judiciously chosen number of terms and a number of samples
which scales linearly with the degree of approximation. It is shown that this
simple procedure provides stable recovery with an extrapolation factor which
scales logarithmically with the perturbation level and is inversely
proportional to the characteristic lengthscale of the function. The pointwise
extrapolation error exhibits a H\"{o}lder-type continuity with an exponent
derived from weighted potential theory, which changes from 1 near the available
samples, to 0 when the extrapolation distance reaches the characteristic
smoothness length scale of the function. The algorithm is asymptotically
minimax, in the sense that there is essentially no better algorithm yielding
meaningfully lower error over the same smoothness class. When viewed in the
dual domain, the above problem corresponds to (stable) simultaneous
de-convolution and super-resolution for objects of small space/time extent. Our
results then show that the amount of achievable super-resolution is inversely
proportional to the object size, and therefore can be significant for small
objects
Mendocino power plant site ecological study, Quarterly Report No. 1; July 1 - September 30, 1971
This report is the first quarterly report submitted in
partial fulfillment of Research Contract No. S-1902 between the Department of Fish and Game and the Pacific Gas and
Electric Company. Through this contract the Department of Fish and Game is to conduct a pre-operational ecological
study to establish a base line inventory of the marine
biota with special reference to fish and to abalone, including food chains.
Quarterly reports will be followed by annual reports. The
first annual report will cover all work from September 1971 through December 1972. Full tables and species lists will be included in each annual report
On and Off-diagonal Sturmian operator: dynamic and spectral dimension
We study two versions of quasicrystal model, both subcases of Jacobi
matrices. For Off-diagonal model, we show an upper bound of dynamical exponent
and the norm of the transfer matrix. We apply this result to the Off-diagonal
Fibonacci Hamiltonian and obtain a sub-ballistic bound for coupling large
enough. In diagonal case, we improve previous lower bounds on the fractal
box-counting dimension of the spectrum.Comment: arXiv admin note: text overlap with arXiv:math-ph/0502044 and
arXiv:0807.3024 by other author
The merger of two-dimensional radially stratified high-Froude-number vortices
We investigate the influence of density inhomogeneities on the merger of two corotating two-dimensional vortices at infinite Froude number. In this situation, buoyancy effects are negligible, yet density variations still affect the flow by pure inertial effects through the baroclinic torque. We first re-address the effects of a finite Reynolds number on the interaction between two identical Gaussian vortices. Then, by means of direct numerical simulations, we show that vortices transporting light fluid in a heavier counterpart merge from further distances than vortices in a uniform density medium. On the other hand, heavy vortices only merge from small separation distances. We measure the critical distance a/b0 of the vortex radii to their initial separation distance. It departs from the homogeneous threshold of 0.22 in response to increasing density contrasts between the vortices and their surroundings. An analysis of the contribution of the baroclinic vorticity to the dynamics of the flow is detailed and explains the observed behaviour. This analysis is completed by a simple model based on point vortices that mimics the flow. It is concluded that vortices carrying light fluid are more likely to generate large-scale structures than heavy ones in an inhomogeneous fluid
Environmental policy, innovation and performance : new insights on the Porter hypothesis
Jaffe and Palmer (1997) present three distinct variants of the so-called Porter Hypothesis. The āweakā version of the hypothesis posits that environmental regulation will stimulate certain kinds of environmental innovations. The ānarrowā version of the hypothesis asserts that flexible environmental policy regimes give firms greater incentive to innovate than prescriptive regulations, such as technology-based standards.Finally, the āstrongā version posits that properly designed regulation may induce cost-saving innovation that more than compensates for the cost of compliance. In this paper, we test the significance of these different variants of the Porter Hypothesis using data on the four main elements of the hypothesised causality chain (environmental policy, research and development, environmental performance and commercial performance). The analysis is based upon a unique database which includes observations from approximately 4200 facilities in seven OECD countries. In general, we find strong support for the āweakā version, qualified support for the ānarrowā version, and qualified support for the āstrongā version as well.PORTHER HYPOTHESIS;ENVIRONMENTAL POLICY;INNOVATION;ENVIRONMENTAL PERFORMANCE;BUSINESS PERFORMANCE
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