1,767 research outputs found
EFFECTS OF RISK ON OPTIMAL NITROGEN FERTILIZATION DATES IN WINTER WHEAT PRODUCTION AS AFFECTED BY DISEASE AND NITROGEN SOURCE
Optimal fertilization dates were found for two nitrogen sources in the presence of two diseases for wheat farmers with different risk preferences. Risk was independent of fertilization date. Ammonium Nitrate and Urea-Ammonium Nitrate did not affect risk differently. Ammonium Nitrate applied on March 9 was optimal regardless of risk preferences.Crop Production/Industries,
EFFECTS OF RISK, DISEASE, AND NITROGEN SOURCE ON OPTIMAL NITROGEN FERTILIZATION RATES IN WINTER WHEAT PRODUCTION
Interactions among nitrogen (N) fertilization rate, N source, and disease severity can affect mean yield and yield variance in conservation tillage wheat production. A Just-Pope model was used to evaluate the effects of N rate, N source, and disease on the spring N-fertilization decision. Ammonium nitrate (AN) was the utility-maximizing N source regardless of risk preferences. The net-return-maximizing AN rate was 92 lb N/acre, providing 35.11/acre.Crop Production/Industries,
Palatini Variational Principle for an Extended Einstein-Hilbert Action
We consider a Palatini variation on a generalized Einstein-Hilbert action. We
find that the Hilbert constraint, that the connection equals the Christoffel
symbol, arises only as a special case of this general action, while for
particular values of the coefficients of this generalized action, the
connection is completely unconstrained. We discuss the relationship between
this situation and that usually encountered in the Palatini formulation.Comment: 14 pages, LaTe
Explorations, Vol. 2, No. 3
Cover image: Ezra Pound
Dedication: With affection and respect, this issue of EXPLORATIONS is dedicated to Carroll Terrell, Professor Emeritus of English.
Articles include: Carroll Terrell and the Great American Poetry Wars, by Burton Hatlen
Adventures in China, by H.Y. Forsythe, Jr.
Harry Kern and the Making of the New Japan, by Howard B. Schonberger
From the Dispatch Case: update on malnutrition in Maine, by Richard Cook
Changing Approaches to Protein Structure Determination, by Robert Anderegg
The Search of Effective Policy: Meeting the Challenge of an Aging Society, by Dennis A. Watkins and Julia M. Watkins
Citizen Survey of the Maine State Police, by Robert A. Stron
Continuum description of profile scaling in nanostructure decay
The relaxation of axisymmetric crystal surfaces with a single facet below the
roughening transition is studied via a continuum approach that accounts for
step energy g_1 and step-step interaction energy g_3>0. For diffusion-limited
kinetics, free-boundary and boundary-layer theories are used for self-similar
shapes close to the growing facet. For long times and g_3/g_1 < 1, (a) a
universal equation is derived for the shape profile, (b) the layer thickness
varies as (g_3/g_1)^{1/3}, (c) distinct solutions are found for different
g_3/_1, and (d) for conical shapes, the profile peak scales as
(g_3/g_1)^{-1/6}. These results compare favorably with kinetic simulations.Comment: 4 pages including 3 figure
The Grand Tour of the Ruby-East Humboldt Metamorphic Core Complex, Northeastern Nevada: Part 1-Introduction & Road Log
The purpose of this geological excursion is to provide an overview of the multiphase developmental history of the Ruby Mountains and East Humboldt Range, northeastern Nevada. Although these mountain ranges are commonly cited as a classic example of a Cordilleran metamorphic core complex developed through large-magnitude, mid-Tertiary crustal extension, a preceding polyphase Mesozoic contractional history is also well preserved in the ranges. An early phase of this history involved Late Jurassic two-mica granitic magmatism, high-temperature but relatively low-pressure metamorphism, and polyphase deformation in the central Ruby Mountains. In the northern Ruby Mountains and East Humboldt Range, a Late Cretaceous history of crustal shortening, metamorphism, and magmatism is manifested by fold-nappes (involving Archean basement rocks in the northern East Humboldt Range), widespread migmatization, injection of monzogranitic and leucogranitic magmas, all coupled with sillimanite-grade metamorphism.
Following Late Cretaceous contraction, a protracted extensional deformation partially overprinted these areas during the Cenozoic. This extensional history may have begun as early as the Late Cretaceous or as late as the mid-Eocene. Late Eocene and Oligocene magmatism occurred at various levels in the crust yielding mafic to felsic orthogneisses in the deep crust, a composite granitic pluton in the upper crust, and volcanic rocks at the surface. Movement along a west-rooted, extensional shear zone in the Oligocene and early Miocene led to core-complex exhumation. The shear zone produced mylonitic rocks about 1 km thick at deep crustal levels, and an overprint of brittle detachment faulting at shallower levels as unroofing proceeded.
Megabreccias and other synextensional sedimentary deposits are locally preserved in a tilted, upper Eocene through Miocene stratigraphic sequence. Neogene magmatism included the emplacement of basalt dikes and eruption of rhyolitic rocks. Subsequent Basin and Range normal faulting, as young as Holocene, records continued tectonic extension
Galactic dynamos with captured magnetic flux and an accretion flow
We examine the behaviour of an axisymmetric galactic dynamo model with a
radial accretion flow in the disc. We also introduce a vertical magnetic flux
through the galactic midplane, to simulate the presence of a large scale
magnetic field trapped by the galaxy when forming. The trapped vertical flux is
conserved and advected towards the disc centre by the radial flow. We confirm
that accretion flows of magnitude several km/s through a significant part of
the galactic disc can markedly inhibit dynamo action. Moreover, advection of
the vertical flux in general results in mixed parity galactic fields. However,
the effect is nonlinear and non-additive -- global magnetic field energies are
usually significantly smaller that the sum of purely dynamo generated and
purely advected field energies. For large inflow speeds, a form of
`semi-dynamo' action may occur.
We apply our results to the accumulation and redistribution, by a radial
inflow, of a vertical magnetic flux captured by the Galactic disc. Taking
representative values, it appears difficult to obtain mean vertical fields near
the centre of the Milky Way that are much in excess of 10 microgauss, largely
because the galactic dynamo and turbulent magnetic diffusion modify the
external magnetic field before it can reach the disc centre.Comment: 18 pages, 12 figures, LaTE
Stellar Proper Motions in the Galactic Bulge from deep HST ACS/WFC Photometry
We present stellar proper motions in the Galactic bulge from the Sagittarius
Window Eclipsing Extrasolar Search (SWEEPS) project using ACS/WFC on HST.
Proper motions are extracted for more than 180,000 objects, with >81,000
measured to accuracy better than 0.3 mas/yr in both coordinates. We report
several results based on these measurements: 1. Kinematic separation of bulge
from disk allows a sample of >15,000 bulge objects to be extracted based on
>6-sigma detections of proper motion, with <0.2% contamination from the disk.
This includes the first detection of a candidate bulge Blue Straggler
population. 2. Armed with a photometric distance modulus on a star by star
basis, and using the large number of stars with high-quality proper motion
measurements to overcome intrinsic scatter, we dissect the kinematic properties
of the bulge as a function of distance along the line of sight. This allows us
to extract the stellar circular speed curve from proper motions alone, which we
compare with the circular speed curve obtained from radial velocities. 3. We
trace the variation of the {l,b} velocity ellipse as a function of depth. 4.
Finally, we use the density-weighted {l,b} proper motion ellipse produced from
the tracer stars to assess the kinematic membership of the sixteen transiting
planet candidates discovered in the Sagittarius Window; the kinematic
distribution of the planet candidates is consistent with that of the disk and
bulge stellar populations.Comment: 71 pages, 30 figures, ApJ Accepte
Hubble Space Telescope NICMOS Polarization Observations of Three Edge-on Massive YSOs
Massive young stellar objects (YSOs), like low-mass YSOs, appear to be
surrounded by optically thick envelopes and/or disks and have regions, often
bipolar, that are seen in polarized scattered light at near-infrared
wavelengths. We are using the 0.2'' spatial resolution of NICMOS on Hubble
Space Telescope to examine the structure of the disks and outflow regions of
massive YSOs in star-forming regions within a few kpc of the Sun. Here we
report on 2 micron polarimetry of NGC 6334 V and S255 IRS1. NGC 6334 V consists
of a double-lobed bright reflection nebula seen against a dark region, probably
an optically thick molecular cloud. Our polarization measurements show that the
illuminating star lies ~ 2'' south of the line connecting the two lobes; we do
not detect this star at 2 micron, but there are a small radio source and a
mid-infrared source at this location. S255 IRS1 consists of two YSOs (NIRS1 and
NIRS3) with overlapping scattered light lobes and luminosities corresponding to
early B stars. Included in IRS1 is a cluster of stars from whose polarization
we determine the local magnetic field direction. Neither YSO has its scattered
light lobes aligned with this magnetic field. The line connecting the scattered
light lobes of NIRS1 is twisted symmetrically around the star; the best
explanation is that the star is part of a close binary and the outflow axis of
NIRS1 is precessing as a result of non-coplanar disk and orbit. The star NIRS3
is also offset from the line connecting its two scattered light lobes. We
suggest that all three YSOs show evidence of episodic ejection of material as
they accrete from dense, optically thick envelopes.Comment: 39 pages, 7 figures, 4 tables To be published in The Astrophysical
Journa
Convergence calls: multimedia storytelling at British news websites
This article uses qualitative interviews with senior editors and managers from a selection of the UK's national online news providers to describe and analyse their current experimentation with multimedia and video storytelling. The results show that, in a period of declining newspaper readership and TV news viewing, editors are keen to embrace new technologies, which are seen as being part of the future of news. At the same time, text is still reported to be the cornerstone for news websites, leading to changes in the grammar and function of news video when used online. The economic rationale for convergence is examined and the article investigates the partnerships sites have entered into in order to be able to serve their audience with video content. In-house video is complementing syndicated content, and the authors examine the resulting developments in newsroom training and recruitment practices. The article provides journalism and interactive media scholars with case studies on the changes taking place in newsrooms as a result of the shift towards multimedia, multiplatform news consumption
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