2,533 research outputs found

    Externalities revisited: the use of an environmental equity account

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    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

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    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 [θl\theta_l, θi\theta_i, θa\theta_a] = [-33 +/- 4∘^{\circ}, 44 +/- 2∘^{\circ}, -15 +/- 15∘^{\circ}], 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 ΩP\Omega_P = 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

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    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

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    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

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    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

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    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

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    (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

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    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 k=−1k=-1 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 k=−1k=-1 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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