238 research outputs found
Native and Introduced Forage Plants
The materials for this Bulletin have been collected and the analyses have been made during a period extending over several years. In reality this work is a continuation of that commenced in Bulletin No. 40 of this Station. Prof. Thomas A. Williams, now deceased, continued the collection of native grasses, etc., after Bulletin No. 40 was issued. Before he had severed his connection with this Station he had collected the following plants: Carex pennsylvanica, Stipa comata, Trifolium,alexandrium, Panicum miliacium, var. Sibericum, Polygonum ramosissimum, Ornithopus sativus, Festuca octiflora, Carex laxiflora, Elymus sibericus, Muhlenbergia ambigua, Spergula arvensis, Hordeum pusill um, Heirochloe borealis, Calamagrostis montanensis, Vicia villosa, Eragrostis abysinica, Lupinus luteus, and Spartina gracilis. The descriptions and analyses of these will appear in the· following pages excepting that of the Siberian Millet. Owing to the fact that the origin and authenticity of the seed sample are in question, the description is omitted
Probing Primordial Non-Gaussianity with Large-Scale Structure
We consider primordial non-Gaussianity due to quadratic corrections in the
gravitational potential parametrized by a non-linear coupling parameter fnl. We
study constraints on fnl from measurements of the galaxy bispectrum in redshift
surveys. Using estimates for idealized survey geometries of the 2dF and SDSS
surveys and realistic ones from SDSS mock catalogs, we show that it is possible
to probe |fnl|~100, after marginalization over bias parameters. We apply our
methods to the galaxy bispectrum measured from the PSCz survey, and obtain a
2sigma-constraint |fnl|< 1800. We estimate that an all sky redshift survey up
to z~1 can probe |fnl|~1. We also consider the use of cluster abundance to
constrain fnl and find that in order to be sensitive to |fnl|~100, cluster
masses need to be determined with an accuracy of a few percent, assuming
perfect knowledge of the mass function and cosmological parameters.Comment: 15 pages, 7 figure
DT/T beyond linear theory
The major contribution to the anisotropy of the temperature of the Cosmic
Microwave Background (CMB) radiation is believed to come from the interaction
of linear density perturbations with the radiation previous to the decoupling
time. Assuming a standard thermal history for the gas after recombination, only
the gravitational field produced by the linear density perturbations present on
a universe can generate anisotropies at low z (these
anisotropies would manifest on large angular scales). However, secondary
anisotropies are inevitably produced during the nonlinear evolution of matter
at late times even in a universe with a standard thermal history. Two effects
associated to this nonlinear phase can give rise to new anisotropies: the
time-varying gravitational potential of nonlinear structures (Rees-Sciama RS
effect) and the inverse Compton scattering of the microwave photons with hot
electrons in clusters of galaxies (Sunyaev-Zeldovich SZ effect). These two
effects can produce distinct imprints on the CMB temperature anisotropy. We
discuss the amplitude of the anisotropies expected and the relevant angular
scales in different cosmological scenarios. Future sensitive experiments will
be able to probe the CMB anisotropies beyong the first order primary
contribution.Comment: plain tex, 16 pages, 3 figures. Proceedings of the Laredo Advance
School on Astrophysics "The universe at high-z, large-scale structure and the
cosmic microwave background". To be publised by Springer-Verla
Is cosmology consistent?
We perform a detailed analysis of the latest CMB measurements (including
BOOMERaNG, DASI, Maxima and CBI), both alone and jointly with other
cosmological data sets involving, e.g., galaxy clustering and the Lyman Alpha
Forest. We first address the question of whether the CMB data are internally
consistent once calibration and beam uncertainties are taken into account,
performing a series of statistical tests. With a few minor caveats, our answer
is yes, and we compress all data into a single set of 24 bandpowers with
associated covariance matrix and window functions. We then compute joint
constraints on the 11 parameters of the ``standard'' adiabatic inflationary
cosmological model. Out best fit model passes a series of physical consistency
checks and agrees with essentially all currently available cosmological data.
In addition to sharp constraints on the cosmic matter budget in good agreement
with those of the BOOMERaNG, DASI and Maxima teams, we obtain a heaviest
neutrino mass range 0.04-4.2 eV and the sharpest constraints to date on gravity
waves which (together with preference for a slight red-tilt) favors
``small-field'' inflation models.Comment: Replaced to match accepted PRD version. 14 pages, 12 figs. Tiny
changes due to smaller DASI & Maxima calibration errors. Expanded neutrino
and tensor discussion, added refs, typos fixed. Combined CMB data, window and
covariance matrix at http://www.hep.upenn.edu/~max/consistent.html or from
[email protected]
Driving the resonant quantum kicked rotor via extended initial conditions
We study the resonances of the quantum kicked rotor subjected to an extended
initial distribution. For the primary resonances we obtain the dispersion
relation for the map of this system. We find an analytical dependence of the
statistical moments on the shape of the initial distribution. For the secondary
resonances we obtain numerically a similar dependence. This allows us to devise
an extended initial condition which produces an average angular momentum
pointing in a preset direction which increases with time with a preset ratio.Comment: 6 pages, 5 figures, send to EPJ
Quantum Mechanics from Focusing and Symmetry
A foundation of quantum mechanics based on the concepts of focusing and
symmetry is proposed. Focusing is connected to c-variables - inaccessible
conceptually derived variables; several examples of such variables are given.
The focus is then on a maximal accessible parameter, a function of the common
c-variable. Symmetry is introduced via a group acting on the c-variable. From
this, the Hilbert space is constructed and state vectors and operators are
given a clear interpretation. The Born formula is proved from weak assumptions,
and from this the usual rules of quantum mechanics are derived. Several
paradoxes and other issues of quantum theory are discussed.Comment: 26 page
Combined Aerostructural Wing and High-Lift System Optimization
A coupled-adjoint aerostrutctural wing optimization tool has been modified to include the optimization of high-lift devices from the start of the optimization process. The aerostructural tool couples a quasi-three-dimensional method with a finite beam element model. In this paper, the quasi-three-dimensional method is modified using a α method of Van Dam to enable high-lift aerodynamic analysis..
D* Production in Deep Inelastic Scattering at HERA
This paper presents measurements of D^{*\pm} production in deep inelastic
scattering from collisions between 27.5 GeV positrons and 820 GeV protons. The
data have been taken with the ZEUS detector at HERA. The decay channel
(+ c.c.) has been used in the study. The
cross section for inclusive D^{*\pm} production with
and is 5.3 \pms 1.0 \pms 0.8 nb in the kinematic region
{ GeV and }. Differential cross
sections as functions of p_T(D^{*\pm}), and are
compared with next-to-leading order QCD calculations based on the photon-gluon
fusion production mechanism. After an extrapolation of the cross section to the
full kinematic region in p_T(D^{*\pm}) and (D^{*\pm}), the charm
contribution to the proton structure function is
determined for Bjorken between 2 10 and 5 10.Comment: 17 pages including 4 figure
Observation of Scaling Violations in Scaled Momentum Distributions at HERA
Charged particle production has been measured in deep inelastic scattering
(DIS) events over a large range of and using the ZEUS detector. The
evolution of the scaled momentum, , with in the range 10 to 1280
, has been investigated in the current fragmentation region of the Breit
frame. The results show clear evidence, in a single experiment, for scaling
violations in scaled momenta as a function of .Comment: 21 pages including 4 figures, to be published in Physics Letters B.
Two references adde
Observation of hard scattering in photoproduction events with a large rapidity gap at HERA
Events with a large rapidity gap and total transverse energy greater than 5
GeV have been observed in quasi-real photoproduction at HERA with the ZEUS
detector. The distribution of these events as a function of the
centre of mass energy is consistent with diffractive scattering. For total
transverse energies above 12 GeV, the hadronic final states show predominantly
a two-jet structure with each jet having a transverse energy greater than 4
GeV. For the two-jet events, little energy flow is found outside the jets. This
observation is consistent with the hard scattering of a quasi-real photon with
a colourless object in the proton.Comment: 19 pages, latex, 4 figures appended as uuencoded fil
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