537 research outputs found
Deep-UV Light Emitting Diodes: An Experimental Investigation of Characterization and Optimization Techniques
Light emitting diodes (LEDs) and laser diodes (LDs) have many advantages over conventional light sources. Current commercial LEDs span the spectrum from IR to near- UV. There are a variety of applications for devices that extend into the deep-UV, including biological agent detection and optical storage. The nitride material system is a set of semiconducting compounds that have wavelengths that span a broad range, from yellow to deep-UV. AlGaN has a direct bandgap that extends into the deep-UV range; we will try to grow device-quality material, deposited epitaxially using metalorganic chemical vapor deposition on sapphire substrates
On the Assouad dimension of self-similar sets with overlaps
It is known that, unlike the Hausdorff dimension, the Assouad dimension of a
self-similar set can exceed the similarity dimension if there are overlaps in
the construction. Our main result is the following precise dichotomy for
self-similar sets in the line: either the \emph{weak separation property} is
satisfied, in which case the Hausdorff and Assouad dimensions coincide; or the
\emph{weak separation property} is not satisfied, in which case the Assouad
dimension is maximal (equal to one).
In the first case we prove that the self-similar set is Ahlfors regular, and
in the second case we use the fact that if the \emph{weak separation property}
is not satisfied, one can approximate the identity arbitrarily well in the
group generated by the similarity mappings, and this allows us to build a
\emph{weak tangent} that contains an interval. We also obtain results in higher
dimensions and provide illustrative examples showing that the
`equality/maximal' dichotomy does not extend to this setting.Comment: 24 pages, 2 figure
The Jurisdiction of the D.C. Circuit
The U.S. Court of Appeals for the D.C. Circuit is unique among federal courts, well known for an unusual caseload that is disproportionally weighted toward administrative law. What explains that unusual caseload? This Article explores that question. We identify several factors that “push” some types of cases away from the Circuit and several factors that “pull” other cases to it. We give particular focus to the jurisdictional provisions of federal statutes, which reveal congressional intent about the types of actions over which the D.C. Circuit should have special jurisdiction. Through a comprehensive examination of the U.S. Code, we identify several trends. First, the Congress is more likely to give the D.C. Circuit exclusive jurisdiction over the review of administrative rulemaking than over the review of agency decisions imposing a penalty. Second, the Congress is more likely to give the D.C. Circuit exclusive jurisdiction over the review of independent agency actions than over the review of executive agency actions. Finally, the Congress tends to grant the D.C. Circuit exclusive jurisdiction over matters that are likely to have a national effect. In sum, we explore what makes this court unique, from its history to its modern docket and jurisdiction
The Jurisdiction of the D.C. Circuit
The U.S. Court of Appeals for the D.C. Circuit is unique among federal courts, well known for an unusual caseload that is disproportionally weighted toward administrative law. What explains that unusual caseload? This Article explores that question. We identify several factors that “push” some types of cases away from the Circuit and several factors that “pull” other cases to it. We give particular focus to the jurisdictional provisions of federal statutes, which reveal congressional intent about the types of actions over which the D.C. Circuit should have special jurisdiction. Through a comprehensive examination of the U.S. Code, we identify several trends. First, the Congress is more likely to give the D.C. Circuit exclusive jurisdiction over the review of administrative rulemaking than over the review of agency decisions imposing a penalty. Second, the Congress is more likely to give the D.C. Circuit exclusive jurisdiction over the review of independent agency actions than over the review of executive agency actions. Finally, the Congress tends to grant the D.C. Circuit exclusive jurisdiction over matters that are likely to have a national effect. In sum, we explore what makes this court unique, from its history to its modern docket and jurisdiction
Inferring pandemic growth rates from sequence data
Using sequence data to infer population dynamics is playing an increasing role in the analysis of outbreaks. The most common methods in use, based on coalescent inference, have been widely used but not extensively tested against simulated epidemics. Here, we use simulated data to test the ability of both parametric and non-parametric methods for inference of effective population size (coded in the popular BEAST package) to reconstruct epidemic dynamics. We consider a range of simulations centred on scenarios considered plausible for pandemic influenza, but our conclusions are generic for any exponentially growing epidemic. We highlight systematic biases in non-parametric effective population size estimation. The most prominent such bias leads to the false inference of slowing of epidemic spread in the recent past even when the real epidemic is growing exponentially. We suggest some sampling strategies that could reduce (but not eliminate) some of the biases. Parametric methods can correct for these biases if the infected population size is large. We also explore how some poor sampling strategies (e.g. that over-represent epidemiologically linked clusters of cases) could dramatically exacerbate bias in an uncontrolled manner. Finally, we present a simple diagnostic indicator, based on coalescent density and which can easily be applied to reconstructed phylogenies, that identifies time-periods for which effective population size estimates are less likely to be biased. We illustrate this with an application to the 2009 H1N1 pandemic
Very high contrast IFU spectroscopy of AB Doradus C: 9 mag contrast at 0.2" without a coronagraph using spectral deconvolution
We present an extension of the spectral deconvolution method (Sparks & Ford
2002) to achieve very high contrast at small inner working radii. We apply the
method to the specific case of ground based adaptive optics fed integral field
spectroscopy (without a coronagraph). Utilising the wavelength dependence of
the Airy and speckle patterns, we make an accurate estimate of the PSF that can
be scaled and subtracted from the data cube. The residual noise in the
resulting spectra is very close to the photon noise from the starlight halo. We
utilise the technique to extract a very high SNR H & K band spectrum of AB Dor
C, the low mass companion to AB Dor A. By effectively eliminating all
contamination from AB Dor A, the extracted spectrum retains both continuum and
spectral features. The achieved 1 sigma contrast is 9 mag at 0.2", 11 mag at
0.5", in 20 mins exposure time, at an effective spectral bandwidth of 5.5 nm,
proving that the method is applicable even in low Strehl regimes.
The spectral deconvolution method clearly demonstrates the efficacy of image
slicer based IFUs in achieving very high contrast imaging spectroscopy at small
angular separations, validating their use as high contrast
spectrographs/imagers for extreme adaptive optics systems.Comment: 9 pages, 5 figures, accepted for publication in MNRAS. This is a
joint submission with astro-ph/0703564 by L. Close et a
Proteinase 3 contributes to endothelial dysfunction in an experimental model of sepsis
In sepsis-induced inflammation, polymorphonuclear neutrophils (PMNs) contribute to vascular dysfunction. The serine proteases proteinase 3 (PR3) and human leukocyte elastase (HLE) are abundant in PMNs and are released upon degranulation. While HLE’s role in inflammation-induced endothelial dysfunction is well studied, PR3’s role is largely uninvestigated. We hypothesized that PR3, similarly to HLE, contributes to vascular barrier dysfunction in sepsis. Plasma PR3 and HLE concentrations and their leukocyte mRNA levels were measured by ELISA and qPCR, respectively, in sepsis patients and controls. Exogenous PR3 or HLE was applied to human umbilical vein endothelial cells (HUVECs) and HUVEC dysfunction was assessed by FITC-dextran permeability and electrical resistance. Both PR3 and HLE protein and mRNA levels were significantly increased in sepsis patients (P \u3c 0.0001 and P \u3c 0.05, respectively). Additionally, each enzyme independently increased HUVEC monolayer FITC-dextran permeability (P \u3c 0.01), and decreased electrical resistance in a time- and dose-dependent manner (P \u3c 0.001), an effect that could be ameliorated by novel treatment with carbon monoxide-releasing molecule 3 (CORM-3). The serine protease PR3, in addition to HLE, lead to vascular dysfunction and increased endothelial permeability, a hallmark pathological consequence of sepsis-induced inflammation. CORMs may offer a new strategy to reduce serine protease-induced vascular dysfunction
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