Strategies of Growth: Forms, Characteristics and Returns

Using a sample of retail firms that have different product lines and a variety of geographic scopes, the study assesses the effect of geographic scope and breadth of product on economic performance

Use of operational analyses to study the dynamics of troposphere-stratosphere interactions in polar regions

Operational analyses produced by large weather centers have been used in the past to monitor various aspects of the general circulation as well as address dynamical questions. For a number years researchers have been monitoring National Meteorological Center (NMC) analyses at 100 millibars because it is the level from which stratospheric analyses are built. In particular, they closely examined the pressure-work term at that level which is an important parameter related to the forcing of the stratosphere by the troposphere. Rapid fluctuations typically seen in this quanity during the months of July-November, and similarly noted by Randel et al., (1987) may raise some concern about the quality of the analyses. Researchers investigated the behavior of the term mainly responsible for these variations, namely the eddy flux of heat, and furthermore have corroborated the presence of these variations in contemporaneous analyses produced by the European Centre for Medium Range Forecasts (ECMWF). Researchers demonstrated that fluctuations in standing eddy heat fluxes, related to the forcing of the stratosphere by the troposphere, agree in two largely independent meteorological analyses. Researchers believe, that these fluctuations are mostly real

The Outer Limits of Galaxy Clusters: Observations to the Virial Radius with Suzaku, XMM, and Chandra

The outskirts of galaxy clusters, near the virial radius, remain relatively unexplored territory and yet are vital to our understanding of cluster growth, structure, and mass. In this presentation, we show the first results from a program to constrain the state of the outer intracluster medium (ICM) in a large sample of galaxy clusters, exploiting the strengths of three complementary X-ray observatories: Suzaku (low, stable background), XMM-Newton (high sensitivity), and Chandra (good spatial resolution). By carefully combining observations from the cluster core to beyond r_200, we are able to identify and reduce systematic uncertainties that would impede our spatial and spectral analysis using a single telescope. Our sample comprises nine clusters at z ~ 0.1-0.2 fully covered in azimuth to beyond r_200, and our analysis indicates that the ICM is not in hydrostatic equilibrium in the cluster outskirts, where we see clear azimuthal variations in temperature and surface brightness. In one of the clusters, we are able to measure the diffuse X-ray emission well beyond r_200, and we find that the entropy profile and the gas fraction are consistent with expectations from theory and numerical simulations. These results stand in contrast to recent studies which point to gas clumping in the outskirts; the extent to which differences of cluster environment or instrumental effects factor in this difference remains unclear. From a broader perspective, this project will produce a sizeable fiducial data set for detailed comparison with high-resolution numerical simulations.Comment: 8 pages, 6 figures. To appear in the proceedings of the Suzaku 2011 Conference, "Exploring the X-ray Universe: Suzaku and Beyond.

Spatial intensity distribution analysis quantifies the extent and regulation of homodimerization of the secretin receptor

Previous studies have indicated that the G protein-coupled secretin receptor is present as a homo-dimer, organized through symmetrical contacts in transmembrane domain IV, and that receptor dimerization is critical for high potency signalling by secretin. However, whether all of the receptor exists in the dimeric form or if this is regulated, is unclear. We used measures of quantal brightness of the secretin receptor tagged with monomeric enhanced green fluorescent protein (mEGFP) and Spatial Intensity Distribution Analysis to assess this. Calibration using cells expressing plasma membrane-anchored forms of mEGFP initially allowed demonstration that the Epidermal Growth Factor receptor is predominantly monomeric in the absence of ligand and whilst wild type receptor was rapidly converted to a dimeric form by ligand, a mutated form of this receptor remained monomeric. Equivalent studies showed that at moderate expression levels the secretin receptor exists as a mixture of monomeric and dimeric forms, with little evidence of higher-order complexity. However, sodium butyrate induced up-regulation of the receptor resulted in a shift from monomeric towards oligomeric organization. By contrast, a form of the secretin receptor containing a pair of mutations on the lipid-facing side of transmembrane domain IV was almost entirely monomeric. Down-regulation of the secretin receptor-interacting G protein Gαs did not alter receptor organization, indicating that dimerization is defined specifically by direct protein-protein interactions between copies of the receptor polypeptide, whilst short term treatment with secretin had no effect on organization of the wild type receptor but increased the dimeric proportion of the mutated receptor variant

On some sequencing problems in finite groups

AbstractA finite group is called Z-sequenceable if its non-identity elements can be listed x1, x2, …, xn so that xixi+1 for i = 1, 2, …, n − 1. Various necessary and sufficient conditions are determined for such sequencings to exist. In particular, it is proved that if n ⩾ 3, then the symmetric group Sn is not Z-sequenceable

Kansas refraction profiles

Historically, refraction surveys have been conducted in hopes of mapping distinct layers within the earth. Refraction is a useful tool provided its limitations and the assumption that layers increase in seismic velocity with increasing depth are kept in mind. A traditional reversed-refraction profile was conducted along a 500-km (300- mi)-long east-west line extending from Concordia, Kansas, to Agate, Colorado. Analysis of the data showed an average crustal velocity of 6.1 kmlsec (3.7 milsec) and an average upper-mantle P phase velocity of 8.29 kmlsec (4.97 milsec) with a Moho depth calculated to be 36 km (23 mi) on the eastern end and 46 km (29 mi) on the western end. Some evidence suggests velocities as high as 7.2 kmlsec (4.3 milsec) in the crust at various locations along the survey line. The strong east-west regional gravity gradient of -0.275 mgalb supports the seismically drawn conclusion of a thinning of crust in north-central Kansas. In order to supplement the data from this refraction survey, we took advantage of the Kansas earthquake seismograph network. A crustal study using earthquakes as energy sources and a regional earthquake network as seismometer locations resulted in a crustal-velocity model that will improve determination of local earthquake locations. A large anomalous body in the upper mantle/lower crust, assumed to be related to the Precambrian-aged Midcontinent Geophysical Anomaly (MGA), resulted in early Pwave arrivals from refracted energy from the Moho recorded at Concordia, Salina, Tuttle Creek, and Milford. An omnidirectional positive P residual zone near El Dorado may be related to the Wichita geomagnetic low. Some evidence suggests the presence of a lower velocity material on the western and eastern flanks of the MGA, possibly representing the Rice Formation. A P velocity of 8.25 krn/sec±0.1k m/sec (4.95 mi/sec+0.09m i/sec) with the crust thinning from west to east and an apparent thinning from the north and from the south was determined from the 16 regional earthquakes studied. Crustal thickness from central Kansas through western Missouri seems to be relatively consistent