2,533 research outputs found
Externalities revisited: the use of an environmental equity account
This exploratory paper attempts to restart a debate about the incorporation of environmental
externalities into the cost structure of the organisation. A number approaches are considered;
regulation together with all that would follow such as audit and policing; pollution permits, which
probably can only be used with a sinking lid application; and other charging mechanisms such as
making the private sector pay for public sector capital funding. The fourth alternative, the use of an
environmental equity account, has not been widely considered in the literature.
The paper proposes the use of an environmental equity account (after Boone and Rubenstein,
1997) with the express intent of generating a charge for environmental impact based on the cost of
control. That is, the cost of implementing state of the art technology compared to that currently in
use within the organisation, is used as a balance which may be either paid as a capital sum or
carried as a balance sheet entry upon which dividend payments would have to be made. It is
envisaged that both capital sums and dividend payments would go to an agency responsible for
environmental remediation activity
A Slowly Precessing Disk in the Nucleus of M31 as the Feeding Mechanism for a Central Starburst
We present a kinematic study of the nuclear stellar disk in M31 at infrared
wavelengths using high spatial resolution integral field spectroscopy. The
spatial resolution achieved, FWHM = 0."12 (0.45 pc at the distance of M31), has
only previously been equaled in spectroscopic studies by space-based long-slit
observations. Using adaptive optics-corrected integral field spectroscopy from
the OSIRIS instrument at the W. M. Keck Observatory, we map the line-of-sight
kinematics over the entire old stellar eccentric disk orbiting the supermassive
black hole (SMBH) at a distance of r<4 pc. The peak velocity dispersion is
381+/-55 km/s , offset by 0.13 +/- 0.03 from the SMBH, consistent with previous
high-resolution long-slit observations. There is a lack of near-infrared (NIR)
emission at the position of the SMBH and young nuclear cluster, suggesting a
spatial separation between the young and old stellar populations within the
nucleus. We compare the observed kinematics with dynamical models from Peiris &
Tremaine (2003). The best-fit disk orientation to the NIR flux is [,
, ] = [-33 +/- 4, 44 +/- 2, -15 +/-
15], which is tilted with respect to both the larger-scale galactic
disk and the best-fit orientation derived from optical observations. The
precession rate of the old disk is = 0.0 +/- 3.9 km/s/pc, lower than
the majority of previous observations. This slow precession rate suggests that
stellar winds from the disk will collide and shock, driving rapid gas inflows
and fueling an episodic central starburst as suggested in Chang et al. (2007).Comment: accepted by Ap
Spectral and Spin Measurement of Two Small and Fast-Rotating Near-Earth Asteroids
In May 2012 two asteroids made near-miss "grazing" passes at distances of a
few Earth-radii: 2012 KP24 passed at nine Earth-radii and 2012 KT42 at only
three Earth-radii. The latter passed inside the orbital distance of
geosynchronous satellites. From spectral and imaging measurements using NASA's
3-m Infrared Telescope Facility (IRTF), we deduce taxonomic, rotational, and
physical properties. Their spectral characteristics are somewhat atypical among
near-Earth asteroids: C-complex for 2012 KP24 and B-type for 2012 KT42, from
which we interpret the albedos of both asteroids to be between 0.10 and 0.15
and effective diameters of 20+-2 and 6+-1 meters, respectively. Among B-type
asteroids, the spectrum of 2012 KT42 is most similar to 3200 Phaethon and 4015
Wilson-Harrington. Not only are these among the smallest asteroids spectrally
measured, we also find they are among the fastest-spinning: 2012 KP24 completes
a rotation in 2.5008+-0.0006 minutes and 2012 KT42 rotates in 3.634+-0.001
minutes.Comment: 4 pages, 3 figures, accepted for publication in Icaru
Only connect: addressing the emotional needs of Scotland's children and young people
A report on the SNAP (Scottish Needs Assessment Programme) Child and Adolescent Mental Health Phase Two survey. It describes a survey of a wide range of professionals working with children and young people in Scotland, and deals with professional perspectives on emotional, behavioural and psychological problems. Conclusions and recommendations are presented
Incorporating Physical Knowledge into Machine Learning for Planetary Space Physics
Recent improvements in data collection volume from planetary and space
physics missions have allowed the application of novel data science techniques.
The Cassini mission for example collected over 600 gigabytes of scientific data
from 2004 to 2017. This represents a surge of data on the Saturn system.
Machine learning can help scientists work with data on this larger scale.
Unlike many applications of machine learning, a primary use in planetary space
physics applications is to infer behavior about the system itself. This raises
three concerns: first, the performance of the machine learning model, second,
the need for interpretable applications to answer scientific questions, and
third, how characteristics of spacecraft data change these applications. In
comparison to these concerns, uses of black box or un-interpretable machine
learning methods tend toward evaluations of performance only either ignoring
the underlying physical process or, less often, providing misleading
explanations for it. We build off a previous effort applying a semi-supervised
physics-based classification of plasma instabilities in Saturn's magnetosphere.
We then use this previous effort in comparison to other machine learning
classifiers with varying data size access, and physical information access. We
show that incorporating knowledge of these orbiting spacecraft data
characteristics improves the performance and interpretability of machine
learning methods, which is essential for deriving scientific meaning. Building
on these findings, we present a framework on incorporating physics knowledge
into machine learning problems targeting semi-supervised classification for
space physics data in planetary environments. These findings present a path
forward for incorporating physical knowledge into space physics and planetary
mission data analyses for scientific discovery.Comment: 25 pages, 7 figures, accepted for publication in Frontiers in
Astronomy and Space Sciences for the Research Topic of Machine Learning in
Heliophysics at https://www.frontiersin.org/articles/10.3389/fspas.2020.0003
Nonlinear software sensor for monitoring genetic regulation processes with noise and modeling errors
Nonlinear control techniques by means of a software sensor that are commonly
used in chemical engineering could be also applied to genetic regulation
processes. We provide here a realistic formulation of this procedure by
introducing an additive white Gaussian noise, which is usually found in
experimental data. Besides, we include model errors, meaning that we assume we
do not know the nonlinear regulation function of the process. In order to
illustrate this procedure, we employ the Goodwin dynamics of the concentrations
[B.C. Goodwin, Temporal Oscillations in Cells, (Academic Press, New York,
1963)] in the simple form recently applied to single gene systems and some
operon cases [H. De Jong, J. Comp. Biol. 9, 67 (2002)], which involves the
dynamics of the mRNA, given protein, and metabolite concentrations. Further, we
present results for a three gene case in co-regulated sets of transcription
units as they occur in prokaryotes. However, instead of considering their full
dynamics, we use only the data of the metabolites and a designed software
sensor. We also show, more generally, that it is possible to rebuild the
complete set of nonmeasured concentrations despite the uncertainties in the
regulation function or, even more, in the case of not knowing the mRNA
dynamics. In addition, the rebuilding of concentrations is not affected by the
perturbation due to the additive white Gaussian noise and also we managed to
filter the noisy output of the biological systemComment: 21 pages, 7 figures; also selected in vjbio of August 2005; this
version corrects a misorder in the last three references of the published
versio
A Multi-Frequency Radio Study of Supernova Remnant G292.0+1.8 and its Pulsar Wind Nebula
(Abridged) We present a detailed radio study of the young supernova remnant
(SNR) G292.0+1.8 and its associated pulsar PSR J1124-5916, using the Australia
Telescope Compact Array at observing wavelengths of 20, 13 and 6 cm. We find
that the radio morphology of the source consists of three main components: a
polarized flat-spectrum central core coincident with the pulsar J1124-5916, a
surrounding circular steep-spectrum plateau with sharp outer edges and,
superimposed on the plateau, a series of radial filaments with spectra
significantly flatter than their surroundings. HI absorption argues for a lower
limit on the distance to the system of 6 kpc.
The core clearly corresponds to radio emission from a pulsar wind nebula
powered by PSR J1124-5916, while the plateau represents the surrounding SNR
shell. The plateau's sharp outer rim delineates the SNR's forward shock, while
the thickness of the plateau region demonstrates that the forward and reverse
shocks are well-separated. Assuming a distance of 6 kpc and an age for the
source of 2500 yr, we infer an expansion velocity for the SNR of ~1200 km/s and
an ambient density ~0.9 cm^-3. We interpret the flat-spectrum radial filaments
superimposed on the steeper-spectrum plateau as Rayleigh-Taylor unstable
regions between the forward and reverse shocks of the SNR. The flat radio
spectrum seen for these features results from efficient second-order Fermi
acceleration in strongly amplified magnetic fields.Comment: 11 pages of text, plus 7 embedded EPS figures. Accepted to ApJ. Added
missing units on x-axis of Fig
Topology and Fragility in Cosmology
We introduce the notion of topological fragility and briefly discuss some
examples from the literature. An important example of this type of fragility is
the way globally anisotropic Bianchi V generalisations of the FLRW model
result in a radical restriction on the allowed topology of spatial sections,
thereby excluding compact cosmological models with negatively curved
three-sections with anisotropy. An outcome of this is to exclude chaotic mixing
in such models, which may be relevant, given the many recent attempts at
employing compact FLRW models to produce chaotic mixing in the cosmic
microwave background radiation, if the Universe turns out to be globally
anisotropic.Comment: 12 pages, LaTex file, to appear in Gen. Rel. Grav. (1998
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