1,066 research outputs found

    Observation and Prediction of Soil Water Under Different Types of Vegetation

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    Soil water trends were monitored during the 1971 growing season on the Anoka Sand Plain in east-central Minnesota. Soils were sampled under four vegetation densities, ranging from old field through increasing amounts of oak overstory. There was no difference over the sampled period in total soil water content (to 100 cm) on the four sites. Differences were found in water content of individual soil horizons, and especially in the surface horizon (0 to 10 cm). A model of evapotranspiration was used to simulate the observed trends and the prediction and observations were closely correlated (r2 ~ 0 .91)

    Status of Chemical Equilibrium in Relativistic Heavy Ion Collisions

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    Recent work on chemical equilibrium in heavy ion collisions is reviewed. The energy dependence of thermal parameters is discussed. The centrality dependence of thermal parameters at SPS energies is presented.Comment: 7 pages, 7 Postscript figure

    The Luminosity Function of Magnitude and Proper-Motion Selected Samples. The case of White-Dwarfs

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    The luminosity function of white dwarfs is a powerful tool for studies of the evolution and formation of the Milky Way. The (theoretical) white dwarf cooling sequence provides a useful indicator of the evolutionary time scales involved in the chronometry and star formation history of the galactic disk, therefore, intrinsically faint (& old) white dwarfs in the immediate solar neighborhood can be used to determine an upper limit for the age of the galactic disk. In this paper we examine the faint-end (MV>+14M_V > +14) behavior of the disk white dwarf luminosity function using the 1/Vmax1/V_{\rm max} method, but fully including the effects of realistic observational errors in the derived luminosity function. We employ a Monte Carlo approach to produce many different realizations of the luminosity function from a given data set with pre-specified and reasonable errors in apparent magnitude, proper-motions, parallaxes and bolometric corrections. These realizations allow us to compute both a mean and an expected range in the luminosity function that is compatible with the observational errors. We find that current state-of-the art observational errors, mostly in the bolometric corrections and trigonometric parallaxes, play a major role in obliterating (real or artificial) small scale fluctuations in the luminosity function. We also find that a better estimator of the true luminosity function seems to be the median over simulations, rather than the mean. When using the latter, an age for the disk of 10 Gyr or older can not be ruled out from the sample of Leggett, Ruiz, and Bergeron (1998).Comment: Manuscript AAS Latex macro v4.0, 33 pages, 13 postscript figures (Color in figs. 9 and 12). Accepted for publication in The Astrophysical Journal. Replaced by two-column version & indication of acceptance by the Ap

    Strange prospects for LHC energies

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    Strange quark and hadron production will be studied at the Large Hadron Collider (LHC) energies in order to explore the properties of both pp and heavy-ion collisions. The ALICE experiment will be specifically efficient in the strange sector with the identification of baryons and mesons over a wide range of transverse momentum. Dedicated measurements are proposed for investigating chemical equilibration and bulk properties. Strange particles can also help to probe kinematical regions where hard processes and pQCD dominate. We try to anticipate here several ALICE analyses to be performed as the first Pb--Pb and pp data will be available.Comment: 5 pages, 2 figures. To appear in the proceedings of Hot Quarks 2006, Villasimius, Italy, 15-20 May 200

    The continuum limit of quark number susceptibilities

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    We report the continuum limit of quark number susceptibilities in quenched QCD. Deviations from ideal gas behaviour at temperature T increase as the lattice spacing is decreased from T/4 to T/6, but a further decrease seems to have very little effect. The measured susceptibilities are 20% lower than the ideal gas values, and also 10% below the hard thermal loop (HTL) results. The off-diagonal susceptibility is several orders of magnitude smaller than the HTL results. We verify a strong correlation between the lowest screening mass and the susceptibility. We also show that the quark number susceptibilities give a reasonable account of the Wroblewski parameter, which measures the strangeness yield in a heavy-ion collision.Comment: 8 pages, 5 figure

    Soft Photoproduction Physics

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    Several topics of interest in soft photoproduction physics are discussed. These include jet universality issues (particle flavour composition), the subdivision into event classes, the buildup of the total photoproduction cross section and the effects of multiple interactions.Comment: 10 pages, LaTeX2e, no figures, to appear in the proceedings of the Durham Workshop on HERA Physics, ``Proton, Photon and Pomeron Structure'', 17--23 September 1995, Durham, U.

    Heavy Flavor Hadrons in Statistical Hadronization of Strangeness-rich QGP

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    We study b, c quark hadronization from QGP. We obtain the yields of charm and bottom flavored hadrons within the statistical hadronization model. The important novel feature of this study is that we take into account the high strangeness and entropy content of QGP, conserving strangeness and entropy yields at hadronization.Comment: v2 expended: 20 pages, 23 figures, 5 tables, in press EPJ-

    The X-ray spectra and spectral variability of intermediate type Seyfert galaxies: ASCA observations of NGC 4388 and ESO 103-G35

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    The X-ray spectra of two intermediate type Seyfert galaxies are investigated using ASCA observations separated by more than a year. Both NGC 4388 and ESO 103-G35 exhibit strong, narrow Fe K alpha line emission and absorption by cold neutral gas with a column density ~ 10^23 cm^-2, characteristic of the X-ray spectra of type 2 Seyfert galaxies. The power law continuum flux has changed by a factor of 2 over a time-scale of ~ 2 years for both objects, declining in the case of NGC 4388 and rising in ESO 103-G35. No variation was observed in the equivalent width of the Fe K alpha line in the spectra of NGC 4388, implying that the line flux declined with the continuum. We find that the strength of the line cannot be accounted for by fluorescence in line-of-sight material with the measured column density unless a `leaky-absorber' model of the type favored for IRAS 04575-7537 is employed. The equivalent width of the Fe K alpha emission line is seen to decrease between the observations of ESO 103-G35 while the continuum flux increased. The 1996 observation of ESO 103-G35 can also be fitted with an absorption edge at 7.4 ±\pm 0.2 keV due to partially ionized iron, and when an ionized absorber model is fitted to the data it is found that the equivalent column of neutral hydrogen rises to 3.5 x 10^23 cm^-2. The Fe K alpha line flux can be accounted by fluorescence in this material alone and this model is also a good representation of the 1988 and 1991 Ginga observations. There is then no requirement for a reflection component in the ASCA spectra of ESO 103-G35 or NGC 4388.Comment: 45 pages, 5 tables, 11 figures. Accepted for publication in the Astrophysical Journa
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