12,102 research outputs found
The Crane-Fly \u3ci\u3eTipula (Tipula)\u3c/i\u3e Oleracea (Diptera: Tipulidae) Reported From Michigan; A New Pest of Turfgrass in Eastern North America.
(excerpt)
The subgenus Tipula (Tipula) is an Old World group with two introduced species in North America, the European Crane Fly, Tipula (T.) paludosa Meigen and T. (T.) oleracea Linnaeus, sometimes called the Common Crane Fly (Oosterbroek, 2005). Tipula paludosa is better known in North America, long established in the Pacific Northwest (Jackson 1975) and Canadian Maritimes provinces (Alexander 1962), more recently in California (Umble and Rao 2004, S. Gaimari, California Dept. Food and Agriculture, pers. comm.). It is a leading insect pest of turf grass and pastures in these areas, including infestin
Nonparametric estimation of a convex bathtub-shaped hazard function
In this paper, we study the nonparametric maximum likelihood estimator (MLE)
of a convex hazard function. We show that the MLE is consistent and converges
at a local rate of at points where the true hazard function is
positive and strictly convex. Moreover, we establish the pointwise asymptotic
distribution theory of our estimator under these same assumptions. One notable
feature of the nonparametric MLE studied here is that no arbitrary choice of
tuning parameter (or complicated data-adaptive selection of the tuning
parameter) is required.Comment: Published in at http://dx.doi.org/10.3150/09-BEJ202 the Bernoulli
(http://isi.cbs.nl/bernoulli/) by the International Statistical
Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm
Estimation of a discrete monotone distribution
We study and compare three estimators of a discrete monotone distribution:
(a) the (raw) empirical estimator; (b) the "method of rearrangements"
estimator; and (c) the maximum likelihood estimator. We show that the maximum
likelihood estimator strictly dominates both the rearrangement and empirical
estimators in cases when the distribution has intervals of constancy. For
example, when the distribution is uniform on , the asymptotic
risk of the method of rearrangements estimator (in squared norm) is
, while the asymptotic risk of the MLE is of order .
For strictly decreasing distributions, the estimators are asymptotically
equivalent.Comment: 39 pages. See also
http://www.stat.washington.edu/www/research/reports/2009/
http://www.stat.washington.edu/jaw/RESEARCH/PAPERS/available.htm
Stellar Populations in Bulges
We present line strengths in the bulges and inner disks of 38 galaxies in the
local universe, including several galaxies whose bulges were previously
identified as being disk-like in their colors or kinematics, to see if their
spectral properties reveal evidence for secular evolution. We find that red
bulges of all Hubble types are similar to luminous ellipticals in their central
stellar populations. They have large luminosity-weighted ages, metallicities,
and alpha/Fe ratios. Blue bulges can be separated into a metal-poor class that
is restricted to late-types with small velocity dispersion and a young,
metal-rich class that includes all Hubble types and velocity dispersions.
Luminosity-weighted metallicities and alpha/Fe ratios are sensitive to central
velocity dispersion and maximum disk rotational velocity. Red bulges and
ellipticals follow the same scaling relations. We see differences in some
scaling relations between blue and red bulges and between bulges of barred and
unbarred galaxies. Most bulges have decreasing metallicity with increasing
radius; galaxies with larger central metallicities have steeper gradients.
Where positive age gradients (with the central regions being younger) are
present, they are invariably in barred galaxies. The metallicities of bulges
are correlated with those of their disks. While this and the differences
between barred and unbarred galaxies suggest that secular evolution cannot be
ignored, our results are generally consistent with the hypothesis that mergers
have been the dominant mechanism responsible for bulge formation.Comment: 30 pages, 21 figures; submitted to MNRA
Accounting for Multiplicity in Calculating Eta Earth
Using the updated exoplanet population parameters of our previous study,
which includes the planetary radius updates from Gaia DR2 and an inferred
multiplicity distribution, we provide a revised calculation.
This is achieved by sampling planets from our derived population model and
determining which planets meet our criterion for habitability. To ensure robust
results, we provide probabilities calculated over a range of upper radius
limits. Our most optimistic criterion for habitability provides an
value of . We also
consider the effects of multiplicity and the number of habitable planets each
system may contain. Our calculation indicates that of GK dwarfs
have more than one planet within their habitable zone. This optimistic
habitability criterion also suggests that of solar-like stars
will harbor 5 or more habitable planets. These tightly packed highly habitable
system should be extremely rare, but still possible. Even with our most
pessimistic criterion we still expect that of solar-like stars
harbor more than one habitable planet.Comment: 7 pages, 1 figure; Accepted for publication in MNRA
Fractional ac Josephson effect in p- and d-wave superconductors
For certain orientations of Josephson junctions between two p_x-wave or two
d-wave superconductors, the subgap Andreev bound states produce a 4pi-periodic
relation between the Josephson current I and the phase difference phi: I
sin(phi/2). Consequently, the ac Josephson current has the fractional frequency
eV/h, where V is the dc voltage. In the tunneling limit, the Josephson current
is proportional to the first power (not square) of the electron tunneling
amplitude. Thus, the Josephson current between unconventional superconductors
is carried by single electrons, rather than by Cooper pairs. The fractional ac
Josephson effect can be observed experimentally by measuring frequency spectrum
of microwave radiation from the junction. We also study junctions between
singlet s-wave and triplet p_x-wave, as well as between chiral p_x + ip_y-wave
superconductors.Comment: v. 5: minor update of references in proofs; v.4: minor improvements;
v.3: major expansion to 13 pages, 6 figures; v.2: significantly expanded to 6
pages; v.1: 4 pages, 2 figures, RevTeX
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