13,874 research outputs found
Statistical Analysis of Project Pyro Liquid Propellant Explosion Data
Statistical regression analysis of Project Pyro cryogenic propellant explosion test dat
Breaking the degeneracy between anisotropy and mass: The dark halo of the E0 galaxy NGC 6703
(abridged) We have measured line-of-sight velocity profiles (VPs) in the E0
galaxy NGC 6703 out to 2.6 R_e. From these data we constrain the mass
distribution and the anisotropy of the stellar orbits in this galaxy.
We have developed a non-parametric technique to determine the DF f(E,L^2)
directly from the kinematic data. From Monte Carlo tests using the spatial
extent, sampling, and error bars of the NGC 6703 data we find that smooth
underlying DFs can be recovered to an rms accuracy of 12%, and the anisotropy
parameter beta(r) to an accuracy of 0.1, in a given potential. An
asymptotically constant halo circular velocity v_0 can be determined with an
accuracy of +- \lta 50km/s.
For NGC 6703 we determine the true circular velocity at 2.6 R_e to be 250 +-
40km/s at 95% c.l., corresponding to a total mass in NGC 6703 inside 78'' (13.5
h_50^-1 kpc), of 1.6-2.6 x 10^11 h_50^-1 Msun. No model without dark matter
will fit the data; however, a maximum stellar mass model in which the luminous
component provides nearly all the mass in the centre does. In such a model, the
total luminous mass inside 78'' is 9 x 10^10 Msun and the integrated
M/L_B=5.3-10, corresponding to a rise from the center by at least a factor of
1.6.
The anisotropy of the stellar distribution function in NGC 6703 changes from
near-isotropic at the centre to slightly radially anisotropic (beta=0.3-0.4 at
30'', beta=0.2-0.4 at 60'') and is not well-constrained at the outer edge of
the data.
Our results suggest that also elliptical galaxies begin to be dominated by
dark matter at radii of \sim 10kpc.Comment: 19 pages LaTex, 18 figures. MNRAS, in press. Also available at
http://www.astro.unibas.ch/~gerhard/papers/dm6703.ps.g
A secondary ejecta explanation of a lunar seismogram
Secondary ejecta explanation to seismograph of Apollo 12 LM impac
Establishment of switchgrass in corn across a landscape gradient: Establishment, yield, and quality of biomass feedstock
Biofuel production in the United States is expected to offset a significant portion of current fuel use through continued use of corn (Zea mays L.) grain and increasingly from alternative feedstocks. Switchgrass (Panicum virgatum L.) is one such species with potential to be used as an alternative feedstock, but establishment is slow and requires long term commitment of land to reach maximum productivity. Switchgrass can be established while producing a corn crop using 2-4-D and atrazine herbicide and seeding switchgrass prior to corn planting, reducing the risk of producing switchgrass as a crop. Relative performance of both corn and switchgrass in the landscape can vary and can influence productivity. An experiment was conducted which examined performance of corn during establishment of `Cave-in-Rock\u27 and `Kanlow\u27 switchgrass, stand frequency in the following year, subsequent yield, and composition of harvested switchgrass biomass across a toposequence of landscape positions. Seeding switchgrass reduced yields from 11.6 Mg*ha-1 to 9.6 Mg*ha-1 and from 10.8 Mg*ha-1 to 8.3 Mg*ha-1, for grain and stover, respectively. Establishment stand frequencies were adequate in all landscape positions and frequencies ranging from 39 to 82 percent. Yield and cellulose concentration of subsequent year switchgrass biomass was greater for `Kanlow\u27. Nitrogen concentration was lower in `Kanlow\u27, but overall N removal was greater due to higher yield. Landscape position effect was demonstrated in the floodplain only, with floodplain position higher in total dry matter yield, ash content, N removal, and cellulose. Floodplain position biomass was lower in hemicellulose and total C. Switchgrass can be established in all landscape position when seeded prior to corn planting, subsequent composition of switchgrass varied by variety and landscape position. More years of data are needed to confirm these biomass quality differences between variety and landscape position
ISU Student Organic Farm* – 2008 Field Season
The ISU Student Organic Farm had a good learning year. This is the third year of the farm at its current location and much is happening. Our perennials are now fully established and include red raspberries, strawberries, asparagus, and rhubarb. The 10 surviving fruit trees in their third year of establishment should now begin bearing. The wet spring caused a slow start but we were able to plant a variety of vegetables in our 24, 4 ft Ă— 150 ft vegetable beds. Beds contained beans, peas, tomatoes, potatoes, eggplants, onions, various cucurbits, and various brassicas
Statistical Uncertainty in Quantitative Neutron Radiography
We demonstrate a novel procedure to calibrate neutron detection systems
commonly used in standard neutron radiography. This calibration allows
determining the uncertainties due to Poisson-like neutron counting statistics
for each individual pixel of a radiographic image. The obtained statistical
errors are necessary in order to perform a correct quantitative analysis. This
fast and convenient method is applied to data measured at the cold neutron
radiography facility ICON at the Paul Scherrer Institute. Moreover, from the
results the effective neutron flux at the beam line is determined
Invariant distributions, Beurling transforms and tensor tomography in higher dimensions
In the recent articles \cite{PSU1,PSU3}, a number of tensor tomography
results were proved on two-dimensional manifolds. The purpose of this paper is
to extend some of these methods to manifolds of any dimension. A central
concept is the surjectivity of the adjoint of the geodesic ray transform, or
equivalently the existence of certain distributions that are invariant under
geodesic flow. We prove that on any Anosov manifold, one can find invariant
distributions with controlled first Fourier coefficients. The proof is based on
subelliptic type estimates and a Pestov identity. We present an alternative
construction valid on manifolds with nonpositive curvature, based on the fact
that a natural Beurling transform on such manifolds turns out to be essentially
a contraction. Finally, we obtain uniqueness results in tensor tomography both
on simple and Anosov manifolds that improve earlier results by assuming a
condition on the terminator value for a modified Jacobi equation.This is the accepted manuscript. The final publication is available at Springer via http://dx.doi.org/10.1007/s00208-015-1169-0
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