4,280 research outputs found
Marine resources and ocean surveys
Application of ERTS-1 remotely sensed multispectral imagery to marine resources and oceanic observations and surveys - Conferenc
Absence of magnetic long range order in YCrSbO: bond-disorder induced magnetic frustration in a ferromagnetic pyrochlore
The consequences of nonmagnetic-ion dilution for the pyrochlore family
Y()O ( = magnetic ion, = nonmagnetic
ion) have been investigated. As a first step, we experimentally examine the
magnetic properties of YCrSbO ( = 0.5), in which the magnetic
sites (Cr) are percolative. Although the effective Cr-Cr spin exchange
is ferromagnetic, as evidenced by a positive Curie-Weiss temperature,
= 20.1(6) K, our high-resolution neutron powder
diffraction measurements detect no sign of magnetic long range order down to 2
K. In order to understand our observations, we performed numerical simulations
to study the bond-disorder introduced by the ionic size mismatch between
and . Based on these simulations, bond-disorder ( 0.23)
percolates well ahead of site-disorder ( 0.61). This model
successfully reproduces the critical region (0.2 < < 0.25) for the N\'eel
to spin glass phase transition in Zn(CrGa)O, where
the Cr/Ga-sublattice forms the same corner-sharing tetrahedral network as the
-sublattice in Y()O, and the rapid drop in
magnetically ordered moment in the N\'eel phase [Lee , Phys. Rev. B
77, 014405 (2008)]. Our study stresses the nonnegligible role of bond-disorder
on magnetic frustration, even in ferromagnets
Triple trouble for XZ Tau : deep imaging with the Jansky Very Large Array
DF gratefully acknowledges support from STFC grant ST/J001422/1. RJI acknowledges support in the form of ERC Advanced Investigator programme, cosmicism. EI acknowledges funding from CONICYT/FONDECYT postdoctoral project no.: 3130504.We present new observations of the XZ Tau system made at high angular resolution (55 mas) with the Karl G. Jansky Very Large Array (VLA) at a wavelength of 7 mm. Observations of XZ Tau made with the VLA in 2004 appeared to show a triple-star system, with XZ Tau A resolved into two sources, XZ Tau A and XZ Tau C. The angular separation of XZ Tau A and C (0.09 arcsec) suggested a projected orbital separation of around 13 au with a possible orbital period of around 40 yr. Our follow-up observations were obtained approximately 8 yr later, a fifth of this putative orbital period, and should therefore allow us to constrain the orbital parameters of XZ Tau C, and evaluate the possibility that a recent periastron passage of C coincided with the launch of extended optical outflows from XZ Tau A. Despite improved sensitivity and resolution, as compared with the 2004 observations, we find no evidence of XZ Tau C in our data. Components A and B are detected with a signal-to-noise ratio greater than 10; their orbital motions are consistent with previous studies of the system, although the emission from XZ Tau A appears to be weaker. Three possible interpretations are offered: either XZ Tau C is transiting XZ Tau A, which is broadly consistent with the periastron passage hypothesis, or the emission seen in 2004 was that of a transient, or XZ Tau C does not exist. A fourth interpretation, that XZ Tau C was ejected from the system, is dismissed due to the lack of angular momentum redistribution in the orbits of XZ Tau A and XZ Tau B that would result from such an event. Transients are rare but cannot be ruled out in a T Tauri system known to exhibit variable behaviour. Our observations are insufficient to distinguish between the remaining possibilities, at least not until we obtain further VLA observations at a sufficiently later time. A further non-detection would allow us to reject the transit hypothesis, and the periastron passage of XZ Tau C as agent of XZ Tau A's outflows.Publisher PDFPeer reviewe
‘Our Global Family’: Using Storytelling to Develop Compassion and Acceptance of Cultural Others in Primary School Pupils
The aim of this project was to develop a teaching model that develops understanding, acceptance and compassion amongst primary school pupils towards others, particularly refugees and migrants
Bulletin No. 114 - The Movement of Nitric Nitrogen in Soil and its Relation to Nitrogen Fixation
In the spring of 1903, we commenced at the Utah Experiment Station a series of experiments, the purpose of which was to study the development and movement of nitrates in irrigated soil. The work was so outlined that it should give some very definite results, both as to the influence of water and the plant, upon the nitric nitrogen content of the soil
Ground-based detection of a cloud of methanol from Enceladus: When is a biomarker not a biomarker?
Saturn's moon Enceladus has vents emerging from a sub-surface ocean, offering
unique probes into the liquid environment. These vents drain into the larger
neutral torus in orbit around Saturn. We present a methanol (CH3OH) detection
observed with IRAM 30-m from 2008 along the line-of-sight through Saturn's
E-ring. Additionally, we also present supporting observations from the Herschel
public archive of water (ortho-H2O; 1669.9 GHz) from 2012 at a similar
elongation and line-of-sight. The CH3OH 5(1,1)-4(1,1) transition was detected
at 5.9 sigma confidence. The line has 0.43 km/s width and is offset by +8.1
km/s in the moon's reference frame. Radiative transfer models allow for gas
cloud dimensions from 1750 km up to the telescope beam diameter ~73000 km.
Taking into account the CH3OH lifetime against solar photodissociation and the
redshifted line velocity, there are two possible explanations for the CH3OH
emission: methanol is primarily a secondary product of chemical interactions
within the neutral torus that (1) spreads outward throughout the E-ring or (2)
originates from a compact, confined gas cloud lagging Enceladus by several
km/s. We find either scenario to be consistent with significant redshifted H2O
emission (4 sigma) measured from the Herschel public archive. The measured
CH3OH:H2O abundance (> 0.5 per cent) significantly exceeds the observed
abundance in the direct vicinity of the vents (~0.01 per cent), suggesting
CH3OH is likely chemically processed within the gas cloud with methane (CH4) as
its parent species.Comment: 16 pages, 4 figures, accepted for publication in the International
Journal of Astrobiology (IJA
Sub-arcsecond high sensitivity measurements of the DG~Tau jet with e-MERLIN
We present very high spatial resolution deep radio continuum observations at
5 GHz (6 cm) made with e-MERLIN of the young stars DG Tau A and B. Assuming it
is launched very close (~=1 au) from the star, our results suggest that the DG
Tau A outflow initially starts as a poorly focused wind and undergoes
significant collimation further along the jet (~=50 au). We derive jet
parameters for DG Tau A and find an initial jet opening angle of 86 degrees
within 2 au of the source, a mass-loss rate of 1.5x10^-8 solar masses/yr for
the ionised component of the jet, and the total ejection/accretion ratio to
range from 0.06-0.3. These results are in line with predictions from MHD
jet-launching theories.Comment: Accepted MNRAS Letter
The Removal of Artificially Generated Polarization in SHARP Maps
We characterize the problem of artificial polarization for the Submillimeter
High Angular Resolution Polarimeter (SHARP) through the use of simulated data
and observations made at the Caltech Submillimeter Observatory (CSO). These
erroneous, artificial polarization signals are introduced into the data through
misalignments in the bolometer sub-arrays plus pointing drifts present during
the data-taking procedure. An algorithm is outlined here to address this
problem and correct for it, provided that one can measure the degree of the
sub-array misalignments and telescope pointing drifts. Tests involving
simulated sources of Gaussian intensity profile indicate that the level of
introduced artificial polarization is highly dependent upon the angular size of
the source. Despite this, the correction algorithm is effective at removing up
to 60% of the artificial polarization during these tests. The analysis of
Jupiter data taken in January 2006 and February 2007 indicates a mean
polarization of 1.44%+/-0.04% and 0.95%+/-0.09%, respectively. The application
of the correction algorithm yields mean reductions in the polarization of
approximately 0.15% and 0.03% for the 2006 and 2007 data sets, respectively.Comment: 19 pages, 7 figure
Bulletin No. 274 - Influence of Rotation and Manure on the Nitrogen, Phosphorus, and Carbon of the Soil
All agricultural plants require carbon, hydrogen, oxygen, nitrogen, calcium, potassium, magnesium, sulfur, phosphorus, iron, and probably traces of other elements for their normal growth and fruition. The growth of farm crops is dependent upon an available supply of these elements, and the extent of growth is governed by the one present and available in least quantity in proportion to the plant\u27s needs. Of the essential elements, all plants secure two (carbon and oxygen) from the air, one (hydrogen) from the water, and the others from the soil. Most soils contain sufficient plant nutrients for normal plant production, with the exception of nitrogen, phosphorus, and potassium. These elements are used by the plants from the soil in the largest quantities and are generally the plant nutrients governing the productivity of a soil. In addition, the organic matter of the soil is of prime importance, for it is the matrix which holds the nitrogen and governs the structure and water-holding capacity of the soil. Probably most Utah soils contain sufficient potassium; consequently, the problem of Utah soil fertility resolves itself into maintaining an optimum concentration of nitrogen, phosphorus, and organic material in the soil. Therefore, this work represents a study of the influence of manure and crop rotation on the nitrogen, phosphorus, and carbon in the soil
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