3,404 research outputs found
Contaminants in manure - a problem for organic farming?
This work addresses possible ways in which animal manure might become contaminated by undesirable elements and how such manure might pose a risk to the health of soil organisms, animals, plants and humans. Research has shown that the pathways of organic compounds such as veterinary medicines and pesticides may be unpredictable and that undesirable elements can be transferred to the food chain. The basic principles of organic farming, in this case specially related to the principles of health, ecology and care, imply that special attentionshould be given to precaution and responsibility. These are key concerns in the management of organic farming. Taking these principles seriously, would mean a more restrictive practice on the use of animal manure from conventional farming. Through identifying which compounds might be present, their environmental properties and their residue levels in manure and environment, the authorities will be able to establish restricted practice based on knowledge
The Transition between Nonorthogonal Polarization Modes in PSR B2016+28 at 1404 MHz
Polarization observations of the radio emission from PSR B2016+28 at 1404 MHz
reveal properties that are consistent with two, very different, interpretations
of the pulsar's viewing geometry. The pulsar's average polarization properties
show a rapid change in position angle (PA) near the pulse center, suggesting
that the observer's sightline nearly intersects the star's magnetic pole. But
single pulse, polarization observations of the pulsar show nearly orthogonal
modes of polarization following relatively flat and parallel PA trajectories
across the pulse, suggesting that the sightline is far from the pole.
Additionally, PA histograms reveal a "modal connecting bridge", of unknown
origin, joining the modal PA trajectories over much of the pulse and following
the rapid PA change shown in the average data. The nonorthogonality of
polarization modes is incorporated in a statistical model of radio polarization
to account for the deviations from mode orthogonality that are observed in the
pulsar. The model is used to interpret the rapid PA change and modal connecting
bridge as a longitudinally-resolved transition between modes of nonorthogonal
polarization. Thus, the modal PA trajectories are argued to reflect the
pulsar's true viewing geometry. This interpretation is consistent with the
pulsar's morphological classification, preserves the Radhakrishnan & Cooke
model of pulsar radio emission, and avoids the complication that the modal
connecting bridge might be produced by some other emission mechanism. The
statistical model's ability to simulate the rich variety of polarization
properties observed in the emission lends additional support to the model's
applicability and its underlying assumption that the polarization modes occur
simultaneously.Comment: Accepted for publication in Ap
Ellipticity and Deviations from Orthogonality in the Polarization Modes of PSR B0329+54
We report on an analysis of the polarization of single pulses of PSR B0329+54
at 328 MHz. We find that the distribution of polarization orientations in the
central component diverges strongly from the standard picture of orthogonal
polarization modes (OPMs), making a remarkable partial annulus on the Poincare
sphere. A second, tightly clustered region of density appears in the opposite
hemisphere, at a point antipodal to the centre of the annulus. We argue that
this can be understood in terms of birefringent alterations in the relative
phase of two elliptically polarized propagation modes in the pulsar
magnetosphere (i.e. generalised Faraday rotation). The ellipticity of the modes
implies a significant charge density in the plasma, while the presence of both
senses of circular polarization, and the fact that only one mode shows the
effect, supports the view that refracted ordinary-mode rays are involved in the
production of the annulus. At other pulse longitudes the polarization
(including the circular component) is broadly consistent with an origin in
elliptical OPMs, shown here quantitatively for the first time, however
considerable non-orthogonal contributions serve to broaden the orientation
distribution in an isotropic manner.Comment: 13 pages, 5 figures, to appear in A&
A Review of High School Level Astronomy Student Research Projects over the last two decades
Since the early 1990s with the arrival of a variety of new technologies, the
capacity for authentic astronomical research at the high school level has
skyrocketed. This potential, however, has not realized the bright-eyed hopes
and dreams of the early pioneers who expected to revolutionise science
education through the use of telescopes and other astronomical instrumentation
in the classroom. In this paper, a general history and analysis of these
attempts is presented. We define what we classify as an Astronomy Research in
the Classroom (ARiC) project and note the major dimensions on which these
projects differ before describing the 22 major student research projects active
since the early 1990s. This is followed by a discussion of the major issues
identified that affected the success of these projects and provide suggestions
for similar attempts in the future.Comment: Accepted for Publication in PASA. 26 page
The solar nebula origin of (486958) Arrokoth, a primordial contact binary in the Kuiper Belt
The New Horizons spacecraft’s encounter with the cold classical Kuiper Belt object (486958) Arrokoth (provisional designation 2014 MU₆₉) revealed a contact-binary planetesimal. We investigate how Arrokoth formed, finding it is the product of a gentle, low-speed merger in the early Solar System. Its two lenticular lobes suggest low-velocity accumulation of numerous smaller planetesimals within a gravitationally collapsing cloud of solid particles. The geometric alignment of the lobes indicates they were a co-orbiting binary that experienced angular momentum loss and subsequent merger, possibly due to dynamical friction and collisions within the cloud or later gas drag. Arrokoth’s contact-binary shape was preserved by the benign dynamical and collisional environment of the cold classical Kuiper Belt, so informs the accretion processes that operated in the early Solar System
The Formation of the Collisional Family around the Dwarf Planet Haumea
Haumea, a rapidly rotating elongated dwarf planet (~ 1500 km in diameter),
has two satellites and is associated with a "family" of several smaller Kuiper
Belt objects (KBOs) in similar orbits. All members of the Haumea system share a
water ice spectral feature that is distinct from all other KBOs. The relative
velocities between the Haumea family members are too small to have formed by
catastrophic disruption of a large precursor body, which is the process that
formed families around much smaller asteroids in the Main Belt. Here we show
that all of the unusual characteristics of the Haumea system are explained by a
novel type of giant collision: a graze-and-merge impact between two comparably
sized bodies. The grazing encounter imparted the high angular momentum that
spun off fragments from the icy crust of the elongated merged body. The
fragments became satellites and family members. Giant collision outcomes are
extremely sensitive to the impact parameters. Compared to the Main Belt, the
largest bodies in the Kuiper Belt are more massive and experience slower
velocity collisions; hence, outcomes of giant collisions are dramatically
different between the inner and outer solar system. The dwarf planets in the
Kuiper Belt record an unexpectedly large number of giant collisions, requiring
a special dynamical event at the end of solar system formation.Comment: Accepted for publication in ApJ, 12 pages, 4 figures, 2 tables
Photometric and proper motion study of neglected open cluster NGC 2215
Optical UBVRI photometric measurements using the Faulkes Telescope North were
taken in early 2011 and combined with 2MASS JHK and WISE infrared
photometry as well as UCAC4 proper motion data in order to estimate the main
parameters of the galactic open cluster NGC 2215 of which large uncertainty
exists in the current literature. Fitting a King model we estimate a core
radius of 1.120.04 (0.240.01pc) and a limiting radius of
0.5 (0.940.11pc) for the cluster. The results of isochrone
fits indicates an age of with a distance of
pc, a metallicity of dex and a reddening of
. A proportion of the work in this study was undertaken by
Australian and Canadian upper secondary school students involved in the Space
to Grow astronomy education project, and is the first scientific publication to
have utilized our star cluster photometry curriculum materials.Comment: 10 pages, 9 Figures, 3 Table
Self-aligned fabrication process for silicon quantum computer devices
We describe a fabrication process for devices with few quantum bits (qubits),
which are suitable for proof-of-principle demonstrations of silicon-based
quantum computation. The devices follow the Kane proposal to use the nuclear
spins of 31P donors in 28Si as qubits, controlled by metal surface gates and
measured using single electron transistors (SETs). The accurate registration of
31P donors to control gates and read-out SETs is achieved through the use of a
self-aligned process which incorporates electron beam patterning, ion
implantation and triple-angle shadow-mask metal evaporation
Confirmatory factor analysis of two self-efficacy scales for astronomy understanding and robotic telescope use
This paper presents the results of a confirmatory factor analysis on two self-efficacy scales designed to probe the self-efficacy of college-level introductory astronomy (Astro-101) students (n=15181) from 22 institutions across the United States of America and Canada. The students undertook a course based on similar curriculum materials, which involved students using robotic telescopes to support their learning of astronomical concepts covered in the traditional Astro-101 courses. Previous research by the authors using these self-efficacy scales within a pre-/post-test approach showed both high reliabilities and very high construct validities. However, the scale purporting to measure students\u27 self-efficacy in relation to their use of the astronomical instrumentation associated with online robotic telescopes was particularly skewed and required further investigation. This current study builds on the previous work and shows how a slight adjustment of the survey items presents an improved and robust scale for measuring self-efficacy
- …