5,245 research outputs found
The Impact of the Kansas Wheat Breeding Program on Wheat Yields, 1911–2006
This paper quantifies advances of the Kansas Agricultural Experiment Station (KAES) wheat breeding program for two time periods: (1) 1911 to 2006 and (2) 1977 to 2006. Using multiple regression, increases in yields of wheat varieties grown in Kansas are quantified, holding growing conditions and other improvements in productivity constant. Differences in KAES variety yields and those released by other public and private breeders are quantified. During the ‘‘new age’’ of wheat breeding (1977–2006), wheat breeding alone is found to have increased yields by 6.182 bushels per acre, or an average increase of 0.206 bushels per year.wheat yield, public wheat breeding, multiplicative heteroscedasticity, economic impact of technological change, Agribusiness, Farm Management, O13, Q16,
Equation of state of classical Coulomb plasma mixtures
We develop analytic approximations of thermodynamic functions of fully
ionized nonideal electron-ion plasma mixtures. In the regime of strong Coulomb
coupling, we use our previously developed analytic approximations for the free
energy of one-component plasmas with rigid and polarizable electron background
and apply the linear mixing rule (LMR). Other thermodynamic functions are
obtained through analytic derivation of this free energy. In order to obtain an
analytic approximation for the intermediate coupling and transition to the
Debye-Hueckel limit, we perform hypernetted-chain calculations of the free
energy, internal energy, and pressure for mixtures of different ion species and
introduce a correction to the LMR, which allows a smooth transition from strong
to weak Coulomb coupling in agreement with the numerical results.Comment: 6 pages, 7 figures; Phys. Rev. E. In v.2 after proofreading, minor
typos are fixe
Slow dynamics near glass transitions in thin polymer films
The -process (segmental motion) of thin polystyrene films supported
on glass substrate has been investigated in a wider frequency range from
10 Hz to 10 Hz using dielectric relaxation spectroscopy and thermal
expansion spectroscopy. The relaxation rate of the -process increases
with decreasing film thickness at a given temperature above the glass
transition. This increase in the relaxation rate with decreasing film thickness
is much more enhanced near the glass transition temperature. The glass
transition temperature determined as the temperature at which the relaxation
time of the -process becomes a macroscopic time scale shows a distinct
molecular weight dependence. It is also found that the Vogel temperature has
the thickness dependence, i.e., the Vogel temperature decreases with decreasing
film thickness. The expansion coefficient of the free volume is
extracted from the temperature dependence of the relaxation time within the
free volume theory. The fragility index is also evaluated as a function of
thickness. Both and are found to decrease with decreasing film
thickness.Comment: 9 pages, 7 figures, and 2 table
A simple two-module problem to exemplify building-block assembly under crossover
Theoretically and empirically it is clear that a genetic algorithm with crossover will outperform a genetic algorithm without crossover in some fitness landscapes, and vice versa in other landscapes. Despite an extensive literature on the subject, and recent proofs of a principled distinction in the abilities of crossover and non-crossover algorithms for a particular theoretical landscape, building general intuitions about when and why crossover performs well when it does is a different matter. In particular, the proposal that crossover might enable the assembly of good building-blocks has been difficult to verify despite many attempts at idealized building-block landscapes. Here we show the first example of a two-module problem that shows a principled advantage for cross-over. This allows us to understand building-block assembly under crossover quite straightforwardly and build intuition about more general landscape classes favoring crossover or disfavoring it
Preliminary interpretations of seafloor geomorphology from a near-shore multibeam sonar survey; Casey Station, East Antarctica
第6回極域科学シンポジウム[OG] 地圏11月16日(月) 国立極地研究所3階セミナー
GGD 37: An Extreme Protostellar Outflow
We present the first Spitzer-IRS spectral maps of the Herbig-Haro flow GGD 37 detected in lines of [Ne III], [O IV], [Ar III], and [Ne v]. The detection of extended [O IV] (55 eV) and some extended emission in [Ne v] (97 eV) indicates a shock temperature in excess of 100,000 K, in agreement with X-ray observations, and a shock speed in excess of 200 km s(-1). The presence of an extended photoionization or collisional ionization region indicates that GGD 37 is a highly unusual protostellar outflow.Jet Propulsion Laboratory, under NASA 1407NASA 1257184Jet Propulsion Laboratory (JPL) 960803University of Rochester 31419-5714Astronom
Heat capacity study of BaFeAs: effects of annealing
Heat-capacity, X-ray diffraction, and resistivity measurements on a
high-quality BaFeAs sample show an evolution of the
magneto-structural transition with successive annealing periods. After a 30-day
anneal the resistivity in the (ab) plane decreases by more than an order of
magnitude, to 12 cm, with a residual resistance ratio 36; the
heat-capacity anomaly at the transition sharpens, to an overall width of less
than K, and shifts from 135.4 to 140.2 K. The heat-capacity anomaly in both the
as-grown sample and after the 30-day anneal shows a hysteresis of 0.15 K,
and is unchanged in a magnetic field H = 14 T. The X-ray and
heat-capacity data combined suggest that there is a first order jump in the
structural order parameter. The entropy of the transition is reported
The IRAC Shallow Survey
The IRAC shallow survey covers 8.5 square degrees in the NOAO Deep Wide-Field
Survey in Bootes with 3 or more 30 second exposures per position. An overview
of the survey design, reduction, calibration, star-galaxy separation, and
initial results is provided. The survey includes approximately 370,000,
280,000, 38,000, and 34,000 sources brighter than the 5 sigma limits of 6.4,
8.8, 51, and 50 microJy at 3.6, 4.5, 5.8, and 8 microns respectively, including
some with unusual spectral energy distributions.Comment: To appear in ApJS, Spitzer special issue. For full resolution see
http://cfa-www.harvard.edu/irac/publication
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