1,590 research outputs found
Planet formation, orbital evolution and planet-star tidal interaction
We consider several processes operating during the late stages of planet
formation that can affect observed orbital elements. Disk-planet interactions,
tidal interactions with the central star, long term orbital instability and the
Kozai mechanism are discussed.Comment: 26 pages, TeX, 3 figures (2 in color), 2 style files (ppiv-style.tex
and epsf.sty), to be published in "Protostars and Planets IV," eds. A. Boss,
V. Mannings, and S. Russel
Predicting the frequencies of diverse exo-planetary systems
Extrasolar planetary systems range from hot Jupiters out to icy comet belts
more distant than Pluto. We explain this diversity in a model where the mass of
solids in the primordial circumstellar disk dictates the outcome. The star
retains measures of the initial heavy-element (metal) abundance that can be
used to map solid masses onto outcomes, and the frequencies of all classes are
correctly predicted. The differing dependences on metallicity for forming
massive planets and low-mass cometary bodies are also explained. By
extrapolation, around two-thirds of stars have enough solids to form Earth-like
planets, and a high rate is supported by the first detections of low-mass
exo-planets.Comment: 5 pages, 2 figures; accepted by MNRA
Herschel Observations and Updated Spectral Energy Distributions of Five Sunlike Stars with Debris Disks
Observations from the Herschel Space Observatory have more than doubled the
number of wide debris disks orbiting Sunlike stars to include over 30 systems
with R > 100 AU. Here we present new Herschel PACS and re-analyzed Spitzer MIPS
photometry of five Sunlike stars with wide debris disks, from Kuiper belt size
to R > 150 AU. The disk surrounding HD 105211 is well resolved, with an angular
extent of >14" along the major axis, and the disks of HD 33636, HD 50554, and
HD 52265 are extended beyond the PACS PSF size (50% of energy enclosed within
radius 4.23"). HD 105211 also has a 24-micron infrared excess that was
previously overlooked because of a poorly constrained photospheric model.
Archival Spitzer IRS observations indicate that the disks have small grains of
minimum radius ~3 microns, though the minimum grain gradius is larger than the
radiation pressure blowout size in all systems. If modeled as
single-temperature blackbodies, the disk temperatures would all be <60 K. Our
radiative transfer models predict actual disk radii approximately twice the
radius of model blackbody disks. We find that the Herschel photometry traces
dust near the source population of planetesimals. The disk luminosities are in
the range 0.00002 <= L/L* <= 0.0002, consistent with collisions in icy
planetesimal belts stirred by Pluto-size dwarf planets.Comment: Accepted for publication in ApJ. 18 pages, including 10 figures and 3
table
Development and application of an innovative approach to predicting pollutant concentrations in highway runoff
Recognising the challenges and limitations of current methodologies to predict highway runoff concentrations, this paper presents a novel approach based on the derivation of pollutant emission factors for twelve different types of vehicle. Published emission factor data and properties of differing vehicles types are combined with annual average daily traffic volume (AADT), highway characteristics and rainfall data to determine the pollutant distributions associated with differing highway and traffic types. In this paper, the method is applied to 126 sections of highway in the Greater London Borough of Enfield (United Kingdom; UK) and results are comparable with values reported in the literature. The approach is used to identify the level of AADT predicted to result in an exceedance of environmental quality standards (EQS), with results suggesting that runoff from highways experiencing AADT values as low as 5000 may require treatment prior to discharge to receiving waters. Future scenario analyses indicate that the impact of progressively replacing petrol and diesel vehicles with electric vehicles will have negligible impact on concentrations of zinc (Zn), copper (Cu), cadmium (Cd) and total suspended solids discharging from highway environments. The approach enables identification and ranking of urban highways in terms of their pollution runoff potential and provides an important support to users in prioritising locations for the installation of sustainable drainage options in order to protect receiving water environments. [Abstract copyright: Copyright © 2021. Published by Elsevier B.V.
People with Dementia, Contributing to Learning and Teaching in Higher Education: Innovative Practice
Patients and service users have a well-established role in teaching and learning on professional qualifying programmes such as such as social work and nursing. However, the role of people with dementia in contributing to educational initiatives at higher educational level remains under explored. Four people with dementia were recruited as Expert by Lived Experience Tutors for the Foundation Degree in Dementia Studies at a University in the United Kingdom. They met students regularly to support their learning. We were interested in researching whether and how this enhanced the ability of students to enable people to live well with dementia. However, we also discovered that the initiative gave insight into psychosocial aspects of dementia, and a new opportunity to explore personhood, co-production and social citizenship. That is the focus of this article
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