Defining Geographic Communities

The purpose of this paper is to provide a guide to concepts, ideas, and measurements of geographic communities. The paper investigates the various concepts of geographic communities found in the literature and reviews existing studies to determine how researchers measure geographic communities in practice.Geographic communities, Local labour markets

Defining Geographic Communities

The purpose of this paper is to provide a guide to concepts, ideas, and measurements of geographic communities. The paper investigates the various concepts of geographic communities found in the literature and reviews existing studies to determine how researchers measure geographic communities in practice.Geographic communities, Local labour markets

Exons, introns and DNA thermodynamics

The genes of eukaryotes are characterized by protein coding fragments, the exons, interrupted by introns, i.e. stretches of DNA which do not carry any useful information for the protein synthesis. We have analyzed the melting behavior of randomly selected human cDNA sequences obtained from the genomic DNA by removing all introns. A clear correspondence is observed between exons and melting domains. This finding may provide new insights in the physical mechanisms underlying the evolution of genes.Comment: 4 pages, 8 figures - Final version as published. See also Phys. Rev. Focus 15, story 1

Propfan Test Assessment (PTA)

The objectives of the Propfan Test Assessment (PTA) Program were to validate in flight the structural integrity of large-scale propfan blades and to measure noise characteristics of the propfan in both near and far fields. All program objectives were met or exceeded, on schedule and under budget. A Gulfstream Aerospace Corporation GII aircraft was modified to provide a testbed for the 2.74m (9 ft) diameter Hamilton Standard SR-7 propfan which was driven by a 4475 kw (600 shp) turboshaft engine mounted on the left-hand wing of the aircraft. Flight research tests were performed for 20 combinations of speed and altitude within a flight envelope that extended to Mach numbers of 0.85 and altitudes of 12,192m (40,000 ft). Propfan blade stress, near-field noise on aircraft surfaces, and cabin noise were recorded. Primary variables were propfan power and tip speed, and the nacelle tilt angle. Extensive low altitude far-field noise tests were made to measure flyover and sideline noise and the lateral attenuation of noise. In coopertion with the FAA, tests were also made of flyover noise for the aircraft at 6100m (20,000 ft) and 10,668m (35,000 ft). A final series of tests were flown to evaluate an advanced cabin wall noise treatment that was produced under a separate program by NASA-Langley Research Center

A simple model for DNA denaturation

Following Poland and Scheraga, we consider a simplified model for the denaturation transition of DNA. The two strands are modeled as interacting polymer chains. The attractive interactions, which mimic the pairing between the four bases, are reduced to a single short range binding term. Furthermore, base-pair misalignments are forbidden, implying that this binding term exists only for corresponding (same curvilinear abscissae) monomers of the two chains. We take into account the excluded volume repulsion between monomers of the two chains, but neglect intra-chain repulsion. We find that the excluded volume term generates an effective repulsive interaction between the chains, which decays as $1/r^{d-2}$. Due to this long-range repulsion between the chains, the denaturation transition is first order in any dimension, in agreement with previous studies.Comment: 10 page

Helix or Coil? Fate of a Melting Heteropolymer

We determine the probability that a partially melted heteropolymer at the melting temperature will either melt completely or return to a helix state. This system is equivalent to the splitting probability for a diffusing particle on a finite interval that moves according to the Sinai model. When the initial fraction of melted polymer is f, the melting probability fluctuates between different realizations of monomer sequences on the polymer. For a fixed value of f, the melting probability distribution changes from unimodal to a bimodal as the strength of the disorder is increased.Comment: 4 pages, 5 figure

Ephemeral active regions and coronal bright points: A solar maximum Mission 2 guest investigator study

A dominate association of coronal bright points (as seen in He wavelength 10830) was confirmed with the approach and subsequent disappearance of opposite polarity magnetic network. While coronal bright points do occur with ephemeral regions, this association is a factor of 2 to 4 less than with sites of disappearing magnetic flux. The intensity variations seen in He I wavelength 10830 are intermittent and often rapid, varying over the 3 minute time resolution of the data; their bright point counterparts in the C IV wavelength 1548 and 20 cm wavelength show similar, though not always coincident time variations. Ejecta are associated with about 1/3 of the dark points and are evident in the C IV and H alpha data. These results support the idea that the anti-correlation of X-ray bright points with the solar cycle can be explained by the correlation of these coronal emission structures with sites of cancelling flux, indicating that, in some cases, the process of magnetic flux removal results in the release of energy. That the intensity variations are rapid and variable suggests that this process works intermittently

The Phase Structure of Supersymmetric Sp(2N_c) Gauge Theories with an Adjoint

We study the phase structure of N = 1 supersymmetric Sp(2N_c) gauge theories with 2N_f fundamentals, an adjoint, and vanishing superpotential. Using a-maximization, we derive analytic expressions for the values of N_f below which the first several gauge-invariant operators in the chiral ring violate the unitarity bound and become free fields. In doing so we are able to explicitly check previous conjectures about the behavior of this theory made by Luty, Schmaltz, and Terning. We then compare this to an analysis of the first two 'deconfined' dual descriptions based on the gauge groups Sp(2N_f+2) x SO(2N_c+5) and Sp(2N_f+2) x SO(4N_f+4) x Sp(2N_c+2), finding precise agreement. In particular, we find no evidence for non-obvious accidental symmetries or the appearance of a mixed phase in which one of the dual gauge groups becomes free.Comment: 18 pages, 2 figures; v2: added references to match JHEP versio

Higgs Boson Decays to Neutralinos in Low-Scale Gauge Mediation

We study the decays of a standard model-like MSSM Higgs boson to pairs of neutralinos, each of which subsequently decays promptly to a photon and a gravitino. Such decays can arise in supersymmetric scenarios where supersymmetry breaking is mediated to us by gauge interactions with a relatively light gauge messenger sector (M_{mess} < 100 TeV). This process gives rise to a collider signal consisting of a pair of photons and missing energy. In the present work we investigate the bounds on this scenario within the minimal supersymmetric standard model from existing collider data. We also study the prospects for discovering the Higgs boson through this decay mode with upcoming data from the Tevatron and the LHC.Comment: 18 pages, 5 figures, added references and discussion of neutralino couplings, same as journal versio