5,316 research outputs found
Production functions and methods of specifying optimum fertilizer use under various uncertainty conditions for hay
Farmers who use fertilizer on a crop are concerned with at least two uncertainty problems relating to the amount of fertilizer that maximizes profits. Both of these problems arise, in part, from weather, a common underlying cause. First, crop yield is uncertain. Thus, a quantity of fertilizer applied, with the decision made before planting, may not be optimum for the yield actually obtained. Second, at the time of planting, future crop use or price may also be indefinite. The value of hay, for example, may differ according to the method of utilization. Hence, a particular amount of fertilizer applied in the spring may not provide the optimum value product at the end of the season.
This study is concerned with the estimation of production functions and the analysis of uncertainty problems as they relate to fertilization of alfalfa with P2O5 and K20. The basic data are taken from an experiment in which three hay cuttings were obtained during the 1952 growing season on Weller silt loam in Van Buren County, Iowa
3C459: A highly asymmetric radio galaxy with a starburst
Multifrequency radio observations of the radio galaxy 3C459 using MERLIN, VLA
and the EVN, and an optical HST image using the F702W filter are presented. The
galaxy has a very asymmetric radio structure, a high infrared luminosity and a
young stellar population. The eastern component of the double-lobed structure
is brighter, much closer to the nucleus and is significantly less polarized
than the western one. This is consistent with the jet on the eastern side
interacting with dense gas, which could be due to a merged companion or dense
cloud of gas. The HST image of the galaxy presented here exhibits filamentary
structures, and is compared with the MERLIN 5-GHz radio map. EVN observations
of the prominent central component, which has a steep radio spectrum, show a
strongly curved structure suggesing a bent or helical radio jet. The radio
structure of 3C459 is compared with other highly asymmetric, Fanaroff-Riley II
radio sources, which are also good candidates for studying jet-cloud
interactions. Such sources are usually of small linear size and it is possible
that the jets are interacting with clouds of infalling gas that fuel the radio
source.Comment: 10 pages, 6 figures, 2 table
Genetically predicted complement component 4A expression: effects on memory function and middle temporal lobe activation
Background The longstanding association between the major histocompatibility complex (MHC) locus and schizophrenia (SZ) risk has recently been accounted for, partially, by structural variation at the complement component 4 (C4) gene. This structural variation generates varying levels of C4 RNA expression, and genetic information from the MHC region can now be used to predict C4 RNA expression in the brain. Increased predicted C4A RNA expression is associated with the risk of SZ, and C4 is reported to influence synaptic pruning in animal models. Methods Based on our previous studies associating MHC SZ risk variants with poorer memory performance, we tested whether increased predicted C4A RNA expression was associated with reduced memory function in a large (n = 1238) dataset of psychosis cases and healthy participants, and with altered task-dependent cortical activation in a subset of these samples. Results We observed that increased predicted C4A RNA expression predicted poorer performance on measures of memory recall (p = 0.016, corrected). Furthermore, in healthy participants, we found that increased predicted C4A RNA expression was associated with a pattern of reduced cortical activity in middle temporal cortex during a measure of visual processing (p < 0.05, corrected). Conclusions These data suggest that the effects of C4 on cognition were observable at both a cortical and behavioural level, and may represent one mechanism by which illness risk is mediated. As such, deficits in learning and memory may represent a therapeutic target for new molecular developments aimed at altering C4’s developmental role
A new search for distant radio galaxies in the Southern hemisphere -- III. Optical spectroscopy and analysis of the MRCR--SUMSS sample
We have compiled a sample of 234 ultra-steep-spectrum(USS)-selected radio
sources in order to find high-redshift radio galaxies (HzRGs). The sample is in
the southern sky at -40 deg < DEC < -30 deg which is the overlap region of the
408-MHz Revised Molonglo Reference Catalogue, 843-MHz Sydney University
Molonglo Sky Survey (the MRCR--SUMSS sample) and the 1400-MHz NRAO VLA Sky
Survey. This is the third in a series of papers on the MRCR--SUMSS sample. Here
we present optical spectra from the ANU 2.3-m telescope, ESO New Technology
Telescope and ESO Very Large Telescope for 52 of the identifications from
Bryant et al. (2009, Paper II), yielding redshifts for 36 galaxies, 13 of which
have z>2. We analyse the K-z distribution and compare 4-arcsec-aperture
magnitudes with 64-kpc aperture magnitudes in several surveys from the
literature; the MRCR--SUMSS sample is found to be consistent with models for
10^{11}-10^{12} solar mass galaxies. Dispersions about the fits in the K-z plot
support passive evolution of radio galaxy hosts since z>3. By comparing
USS-selected samples in the literature, we find that the resultant median
redshift of the samples shown is not dependent on the flux density distribution
or selection frequency of each sample. In addition, our finding that the
majority of the radio spectral energy distributions remain straight over a wide
frequency range suggests that a k-correction is not responsible for the success
of USS-selection in identifying high redshift radio galaxies and therefore the
steep radio spectra may be intrinsic to the source or a product of the
environment. Two galaxies have been found to have both compact radio structures
and strong self-absorption in the Ly-alpha line, suggesting they are surrounded
by a dense medium...abridged.Comment: Accepted for MNRAS. 25 page
A new search for distant radio galaxies in the Southern hemisphere -- II. 2.2 micron imaging
We have compiled a sample of 234 ultra-steep-spectrum (USS) selected radio
sources in order to find high-redshift radio galaxies. The sample covers the
declination range -40deg < DEC < -30deg in the overlap region between the
1400-MHz NRAO VLA Sky Survey, 408-MHz Revised Molonglo Reference Catalogue and
the 843-MHz Sydney University Molonglo Sky Survey (the MRCR-SUMSS sample). This
is the second in a series of papers on the MRCR-SUMSS sample, and here we
present the K-band (2.2 micron) imaging of 173 of the sources primarily from
the Magellan and the Anglo-Australian Telescopes. We detect a counterpart to
the radio source in 93% of the new K-band images which, along with previously
published data, makes this the largest published sample of K-band counterparts
to USS-selected radio galaxies. The location of the K-band identification has
been compared to the features of the radio emission for the double sources. We
find that the identification is most likely to lie near the midpoint of the
radio lobes rather than closer to the brighter lobe, making the centroid a less
likely place to find the optical counterpart. 79% of the identifications are
less than 1 arcsec from the radio lobe axis. These results differ from studies
of low-redshift radio samples where the environments are typically not nearly
so dense and disturbed as those at high redshift. In contrast to some
literature samples, we find that the majority of our sample shows no alignment
between the near-infrared and radio axes. Several different morphologies of
aligned structures are found and those that are aligned within 10 degrees are
consistent with jet-induced star formation. ...abridged...Comment: Accepted for MNRAS. 28 pages. Due to file size constraints, low
resolution images have been used, and the high resolution versions are
available in the MNRAS published versio
Detailed Investigation of the Role of Common and Low-Frequency WFS1 Variants in Type 2 Diabetes Risk
OBJECTIVE: Wolfram syndrome 1 (WFS1) single nucleotide polymorphisms (SNPs) are associated with risk of type 2 diabetes. In this study we aimed to refine this association and investigate the role of low-frequency WFS1 variants in type 2 diabetes risk. RESEARCH DESIGN AND METHODS: For fine-mapping, we sequenced WFS1 exons, splice junctions, and conserved noncoding sequences in samples from 24 type 2 diabetic case and 68 control subjects, selected tagging SNPs, and genotyped these in 959 U.K. type 2 diabetic case and 1,386 control subjects. The same genomic regions were sequenced in samples from 1,235 type 2 diabetic case and 1,668 control subjects to compare the frequency of rarer variants between case and control subjects. RESULTS: Of 31 tagging SNPs, the strongest associated was the previously untested 3' untranslated region rs1046320 (P = 0.008); odds ratio 0.84 and P = 6.59 x 10(-7) on further replication in 3,753 case and 4,198 control subjects. High correlation between rs1046320 and the original strongest SNP (rs10010131) (r2 = 0.92) meant that we could not differentiate between their effects in our samples. There was no difference in the cumulative frequency of 82 rare (minor allele frequency [MAF] 100,000) or studies in ethnically diverse populations. Low frequency variants in WFS1 are unlikely to have a large impact on type 2 diabetes risk in white U.K. populations, highlighting the complexities of undertaking association studies with low-frequency variants identified by resequencing
The Multi-Object, Fiber-Fed Spectrographs for SDSS and the Baryon Oscillation Spectroscopic Survey
We present the design and performance of the multi-object fiber spectrographs
for the Sloan Digital Sky Survey (SDSS) and their upgrade for the Baryon
Oscillation Spectroscopic Survey (BOSS). Originally commissioned in Fall 1999
on the 2.5-m aperture Sloan Telescope at Apache Point Observatory, the
spectrographs produced more than 1.5 million spectra for the SDSS and SDSS-II
surveys, enabling a wide variety of Galactic and extra-galactic science
including the first observation of baryon acoustic oscillations in 2005. The
spectrographs were upgraded in 2009 and are currently in use for BOSS, the
flagship survey of the third-generation SDSS-III project. BOSS will measure
redshifts of 1.35 million massive galaxies to redshift 0.7 and Lyman-alpha
absorption of 160,000 high redshift quasars over 10,000 square degrees of sky,
making percent level measurements of the absolute cosmic distance scale of the
Universe and placing tight constraints on the equation of state of dark energy.
The twin multi-object fiber spectrographs utilize a simple optical layout
with reflective collimators, gratings, all-refractive cameras, and
state-of-the-art CCD detectors to produce hundreds of spectra simultaneously in
two channels over a bandpass covering the near ultraviolet to the near
infrared, with a resolving power R = \lambda/FWHM ~ 2000. Building on proven
heritage, the spectrographs were upgraded for BOSS with volume-phase
holographic gratings and modern CCD detectors, improving the peak throughput by
nearly a factor of two, extending the bandpass to cover 360 < \lambda < 1000
nm, and increasing the number of fibers from 640 to 1000 per exposure. In this
paper we describe the original SDSS spectrograph design and the upgrades
implemented for BOSS, and document the predicted and measured performances.Comment: 43 pages, 42 figures, revised according to referee report and
accepted by AJ. Provides background for the instrument responsible for SDSS
and BOSS spectra. 4th in a series of survey technical papers released in
Summer 2012, including arXiv:1207.7137 (DR9), arXiv:1207.7326 (Spectral
Classification), and arXiv:1208.0022 (BOSS Overview
Collapse of the world's largest herbivores
Large wild herbivores are crucial to ecosystems and human societies. We highlight the 74 largest terrestrial herbivore species on Earth (body mass ≥100 kg), the threats they face, their important and often overlooked ecosystem effects, and the conservation efforts needed to save them and their predators from extinction. Large herbivores are generally facing dramatic population declines and range contractions, such that ~60% are threatened with extinction. Nearly all threatened species are in developing countries, where major threats include hunting, land-use change, and resource depression by livestock. Loss of large herbivores can have cascading effects on other species including large carnivores, scavengers, mesoherbivores, small mammals, and ecological processes involving vegetation, hydrology, nutrient cycling, and fire regimes. The rate of large herbivore decline suggests that ever-larger swaths of the world will soon lack many of the vital ecological services these animals provide, resulting in enormous ecological and social costs
The Seventh Data Release of the Sloan Digital Sky Survey
This paper describes the Seventh Data Release of the Sloan Digital Sky Survey
(SDSS), marking the completion of the original goals of the SDSS and the end of
the phase known as SDSS-II. It includes 11663 deg^2 of imaging data, with most
of the roughly 2000 deg^2 increment over the previous data release lying in
regions of low Galactic latitude. The catalog contains five-band photometry for
357 million distinct objects. The survey also includes repeat photometry over
250 deg^2 along the Celestial Equator in the Southern Galactic Cap. A
coaddition of these data goes roughly two magnitudes fainter than the main
survey. The spectroscopy is now complete over a contiguous area of 7500 deg^2
in the Northern Galactic Cap, closing the gap that was present in previous data
releases. There are over 1.6 million spectra in total, including 930,000
galaxies, 120,000 quasars, and 460,000 stars. The data release includes
improved stellar photometry at low Galactic latitude. The astrometry has all
been recalibrated with the second version of the USNO CCD Astrograph Catalog
(UCAC-2), reducing the rms statistical errors at the bright end to 45
milli-arcseconds per coordinate. A systematic error in bright galaxy photometr
is less severe than previously reported for the majority of galaxies. Finally,
we describe a series of improvements to the spectroscopic reductions, including
better flat-fielding and improved wavelength calibration at the blue end,
better processing of objects with extremely strong narrow emission lines, and
an improved determination of stellar metallicities. (Abridged)Comment: 20 pages, 10 embedded figures. Accepted to ApJS after minor
correction
Searching for gravitational waves from known pulsars
We present upper limits on the amplitude of gravitational waves from 28
isolated pulsars using data from the second science run of LIGO. The results
are also expressed as a constraint on the pulsars' equatorial ellipticities. We
discuss a new way of presenting such ellipticity upper limits that takes
account of the uncertainties of the pulsar moment of inertia. We also extend
our previous method to search for known pulsars in binary systems, of which
there are about 80 in the sensitive frequency range of LIGO and GEO 600.Comment: Accepted by CQG for the proceeding of GWDAW9, 7 pages, 2 figure
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