14,100 research outputs found
Helium ionization detection apparatus
In a gas chromatograph apparatus comprising a gas supply (He carrier gas), a sample injection apparatus, a chromatograph column, a He ion detector, and connecting tubes, a foreign gas (other than He) injection apparatus is installed between the sample injection apparatus and the detector. Mixing of the sample gas and foreign gas takes place readily, the sample gas is always maintained at a stable concentrator range, and accurate measurements are possible, especially at low sample gas concentrations
The Effect of Baryons on Halo Shapes
Observational evidence indicates a mismatch between the shapes of
collisionless dark matter (DM) halos and those of observed systems. Using
hydrodynamical cosmological simulations we investigate the effect of baryonic
dissipation on halo shapes. We show that dissipational simulations produce
significantly rounder halos than those formed in equivalent dissipationless
simulations. Gas cooling causes an average increase in halo principal axis
ratios of ~ 0.2-0.4 in the inner regions and a systematic shift that persists
out to the virial radius, alleviating any tension between theory and
observations. Although the magnitude of the effect may be overestimated due to
overcooling, cluster formation simulations designed to reproduce the observed
fraction of cold baryons still produce substantially rounder halos. Subhalos
also exhibit a trend of increased axis ratios in dissipational simulations.
Moreover, we demonstrate that subhalos are generally rounder than corresponding
field halos even in dissipationless simulations. Lastly, we analyze a series of
binary, equal-mass merger simulations of disk galaxies. Collisionless mergers
reveal a strong correlation between DM halo shape and stellar remnant
morphology. In dissipational mergers, the combination of strong gas inflows and
star formation leads to an increase of the DM axis ratios in the remnant. All
of these results highlight the vital role of baryonic processes in comparing
theory with observations and warn against over-interpreting discrepancies with
collisionless simulations on small scales.Comment: 8 pages, 3 figures. To appear in the proceedings of the XXIst IAP
Colloquium "Mass Profiles and Shapes of Cosmological Structures", Paris 4-9
July 2005, France, (Eds.) G. Mamon, F. Combes, C. Deffayet, B. Fort, EAS
Publications Serie
Bilinear Equations and B\"acklund Transformation for Generalized Ultradiscrete Soliton Solution
Ultradiscrete soliton equations and B\"acklund transformation for a
generalized soliton solution are presented. The equations include the
ultradiscrete KdV equation or the ultradiscrete Toda equation in a special
case. We also express the solution by the ultradiscrete permanent, which is
defined by ultradiscretizing the signature-free determinant, that is, the
permanent. Moreover, we discuss a relation between B\"acklund transformations
for discrete and ultradiscrete KdV equations.Comment: 11 page
National and International Factors in Pickle Markets
This report presents global and domestic information regarding production, trade and market developments for pickled cucumbers. U.S. cucumber production and trade are commonly divided into two categories: fresh and pickling. Michigan is the largest producer of pickling cucumbers in the country, accounting for 18 percent of total U.S. production. Like many agri-food industries, this processed product sector has gone through numerous changes in the past decade which have influenced production and marketing trends, and assessing the influence of individual factors is difficult. However, using production and trade data it is possible to infer some possible drivers of trends and outcomes for the industry. Year-round supply from other countries, quality products at more competitive prices, changing consumer preferences, and more service-oriented business models have introduced new marketing structures likely to continue driving future trade and production patterns. The information presented in this report is important in order to assess competitiveness and develop a broad and well-informed perspective for the pickling industry in Michigan. The report is structured as follows: first, we present information on global volume produced in the period 1992 to 2004, including rates of change in production and shares of total world production by country. Second, we compare total acreage trends in the U.S and production and acreage trends in Michigan during the late 1990s and early 2000s. Third, we highlight information on pickled cucumber import and export volumes by country. Finally, we present a brief description of historic trends in food marketing and globalization that are likely to continue influencing the pickling industry in the future.Crop Production/Industries, International Relations/Trade,
Geometrical characterization of textures consisting of two or three discrete colorings
Geometrical characterization for discretized contrast textures is realized by computing the Gaussian and mean curvatures relative to the central pixel of a clique and four neighboring pixels, these four neighbors either being first or second order neighbors. Practical formulae for computing these curvatures are presented. Curvatures based on the central pixel depend upon the brightness configuration of the clique pixels. Therefore the cliques are classified into classes by configuration of pixel contrast or coloring. To look at the textures formed by geometrically classified cliques, we create several textures using overlapping tiling of cliques belonging to a single curvature class. Several examples of hyperbolic textures, consisting of repeated hyperbolic cliques surrounded by non-hyperbolic cliques, are presented with the nonhyperbolic textures. We also introduce a system of 81 rotationally and brightness shift invariant geo-cliques that have shared curvatures and show that histograms of these 81 geo-cliques seem to be able to distinguish isotrigon textures
Missing Thermal Energy of the Intracluster Medium
The Sunyaev-Zel'dovich (SZ) effect is a direct probe of thermal energy
content of the Universe, induced in the cosmic microwave background (CMB) sky
through scattering of CMB photons off hot electrons in the intracluster medium
(ICM). We report a 9-sigma detection of the SZ signal in the CMB maps of
Wilkinson Microwave Anisotropy Probe (WMAP) 3yr data, through study of a sample
of 193 massive galaxy clusters with observed X-ray temperatures greater than 3
keV. For the first time, we make a model-independent measurement of the
pressure profile in the outskirts of the ICM, and show that it closely follows
the profiles obtained by X-ray observations and numerical simulations. We find
that our measurements of the SZ effect would account for only half of the
thermal energy of the cluster, if all the cluster baryons were in the hot ICM
phase. Our measurements indicate that a significant fraction (35 +/- 8 %) of
baryonic mass is missing from the hot ICM, and thus must have cooled to form
galaxies, intracluster stars, or an unknown cold phase of the ICM. There does
not seem to be enough mass in the form of stars or cold gas in the cluster
galaxies or intracluster space, signaling the need for a yet-unknown baryonic
component (at 3-sigma level), or otherwise new astrophysical processes in the
ICM.Comment: 9 pages, 4 figures, references added, a mismatch between X-ray and SZ
properties of simulated clusters is corrected, marginally increasing the
significance of missing baryon fraction, Accepted for publication in MNRA
The Cluster-Merger Shock in 1E 0657-56: Faster than the Speeding Bullet?
Shock waves driven in the intergalactic medium during the merging of galaxy
clusters have been observed in X-ray imaging and spectroscopy. Fluid motions
inferred from the shock strength and morphology can be compared to the cold
dark matter (CDM) distribution inferred from gravitational lensing. A detailed
reconstruction of the CDM kinematics, however, must take into account the
nontrivial response of the fluid intracluster medium to the collisionless CDM
motions. We have carried out two-dimensional simulations of gas dynamics in
cluster collisions. We analyze the relative motion of the clusters, the bow
shock wave, and the contact discontinuity and relate these to X-ray data. We
focus on the "bullet cluster," 1E 0657-56, a near head-on collision of
unequal-mass clusters, for which the gas density and temperature jumps across
the prominent bow shock imply a high shock velocity 4,700 km/s. The velocity of
the fluid shock has been widely interpreted as the relative velocity of the CDM
components. This need not be the case, however. An illustrative simulation
finds that the present relative velocity of the CDM halos is 16% lower than
that of the shock. While this conclusion is sensitive to the detailed initial
mass and gas density profile of the colliding clusters, such a decrease of the
inferred halo relative velocity would increase the likelihood of finding 1E
0657-56 in a LambdaCDM universe.Comment: 4 pages, 4 figure
Determination of nuclear parton distribution functions and their uncertainties at next-to-leading order
Nuclear parton distribution functions (NPDFs) are determined by global
analyses of experimental data on structure-function ratios F_2^A/F_2^{A'} and
Drell-Yan cross-section ratios \sigma_{DY}^A/\sigma_{DY}^{A'}. The analyses are
done in the leading order (LO) and next-to-leading order (NLO) of running
coupling constant \alpha_s. Uncertainties of the NPDFs are estimated in both LO
and NLO for finding possible NLO improvement. Valence-quark distributions are
well determined, and antiquark distributions are also determined at x<0.1.
However, the antiquark distributions have large uncertainties at x>0.2. Gluon
modifications cannot be fixed at this stage. Although the advantage of the NLO
analysis, in comparison with the LO one, is generally the sensitivity to the
gluon distributions, gluon uncertainties are almost the same in the LO and NLO.
It is because current scaling-violation data are not accurate enough to
determine precise nuclear gluon distributions. Modifications of the PDFs in the
deuteron are also discussed by including data on the proton-deuteron ratio
F_2^D/F_2^p in the analysis. A code is provided for calculating the NPDFs and
their uncertainties at given x and Q^2 in the LO and NLO.Comment: 15 pages, LaTeX, 22 eps files, to appear in PRC. A code for
calculating our nuclear parton distribution functions and their uncertainties
can be obtained from http://research.kek.jp/people/kumanos/nuclp.htm
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