85 research outputs found
Papermaking in Maine: Economic Trends from 1894 to 2000
This essay reviews the major economic trends in Maine’s paper industry since the late nineteenth century. It sets the context at national and regional levels, offers a broad statistical picture of the industry’s production in Maine, and concludes with a focus on Maine’s “mill towns.” Paper production is a branch of a larger industry that converts primary fiber — logs, chips, wastepaper, rags, or market pulp — into paper
Precision Masses of the low-mass binary system GJ 623
We have used Aperture Masking Interferometry and Adaptive Optics (AO) at the
Palomar 200'' to obtain precise mass measurements of the binary M dwarf GJ 623.
AO observations spread over 3 years combined with a decade of radial velocity
measurements constrain all orbital parameters of the GJ 623 binary system
accurately enough to critically challenge the models. The dynamical masses
measured are m_{1}=0.371\pm0.015 M_{\sun} (4%) and m_{2}=0.115\pm0.0023
M_{\sun} (2%) for the primary and the secondary respectively. Models are not
consistent with color and mass, requiring very low metallicities.Comment: 7 pages, 5 figures. Accepted for Ap
Direct Detection of the Brown Dwarf GJ 802B with Adaptive Optics Masking Interferometry
We have used the Palomar 200" Adaptive Optics (AO) system to directly detect
the astrometric brown dwarf GJ 802B reported by Pravdo et al. 2005. This
observation is achieved with a novel combination of aperture masking
interferometry and AO. The dynamical masses are 0.1750.021 M and
0.0640.032 M for the primary and secondary respectively. The
inferred absolute H band magnitude of GJ 802B is M=12.8 resulting in a
model-dependent T of 1850 50K and mass range of
0.057--0.074 M.Comment: 4 Pages, 5 figures, emulateapj format, submitted to ApJ
Born Again Protoplanetary Disk Around Mira B
The Mira AB system is a nearby (~107 pc) example of a wind accreting binary
star system. In this class of system, the wind from a mass-losing red giant
star (Mira A) is accreted onto a companion (Mira B), as indicated by an
accretion shock signature in spectra at ultraviolet and X-ray wavelengths.
Using novel imaging techniques, we report the detection of emission at
mid-infrared wavelengths between 9.7 and 18.3 m from the vicinity of Mira
B but with a peak at a radial position about 10 AU closer to the primary Mira
A. We interpret the mid-infrared emission as the edge of an optically-thick
accretion disk heated by Mira A. The discovery of this new class of accretion
disk fed by M-giant mass loss implies a potential population of young planetary
systems in white-dwarf binaries which has been little explored, despite being
relatively common in the solar neighborhood.Comment: Accepted for Ap
Planets Around Low-Mass Stars (PALMS). II. A Low-Mass Companion to the Young M Dwarf GJ 3629 Separated By 0.2"
We present the discovery of a 0.2" companion to the young M dwarf GJ 3629 as
part of our high contrast adaptive optics imaging search for giant planets
around low-mass stars with the Keck-II and Subaru telescopes. Two epochs of
imaging confirm the pair is co-moving and reveal signs of orbital motion. The
primary exhibits saturated X-ray emission, which together with its UV
photometry from GALEX point to an age younger than ~300 Myr. At these ages the
companion lies below the hydrogen burning limit with a model-dependent mass of
46 +/- 16 Mjup based on the system's photometric distance of 22 +/- 3 pc.
Resolved YJHK photometry of the pair indicates a spectral type of M7 +/- 2 for
GJ 3629 B. With a projected separation of 4.4 +/- 0.6 AU and an estimated
orbital period of 21 +/- 5 yr, GJ 3629 AB is likely to yield a dynamical mass
in the next several years, making it one of only a handful of brown dwarfs to
have a measured mass and an age constrained from the stellar primary.Comment: Accepted for publication in Ap
The Expanding Fireball of Nova Delphini 2013
A classical nova occurs when material accreting onto the surface of a white
dwarf in a close binary system ignites in a thermonuclear runaway. Complex
structures observed in the ejecta at late stages could result from interactions
with the companion during the common envelope phase. Alternatively, the
explosion could be intrinsically bipolar, resulting from a localized ignition
on the surface of the white dwarf or as a consequence of rotational distortion.
Studying the structure of novae during the earliest phases is challenging
because of the high spatial resolution needed to measure their small sizes.
Here we report near-infrared interferometric measurements of the angular size
of Nova Delphini 2013, starting from one day after the explosion and continuing
with extensive time coverage during the first 43 days. Changes in the apparent
expansion rate can be explained by an explosion model consisting of an
optically thick core surrounded by a diffuse envelope. The optical depth of the
ejected material changes as it expands. We detect an ellipticity in the light
distribution, suggesting a prolate or bipolar structure that develops as early
as the second day. Combining the angular expansion rate with radial velocity
measurements, we derive a geometric distance to the nova of 4.54 +/- 0.59 kpc
from the Sun.Comment: Published in Nature. 32 pages. Final version available at
http://www.nature.com/nature/journal/v515/n7526/full/nature13834.htm
Establishing Alpha Oph as a Prototype Rotator: Improved Astrometric Orbit
The nearby star Alpha Oph (Ras Alhague) is a rapidly rotating A5IV star
spinning at ~89% of its breakup velocity. This system has been imaged
extensively by interferometric techniques, giving a precise geometric model of
the star's oblateness and the resulting temperature variation on the stellar
surface. Fortuitously, Alpha Oph has a previously known stellar companion, and
characterization of the orbit provides an independent, dynamically-based check
of both the host star and the companion mass. Such measurements are crucial to
constrain models of such rapidly rotating stars. In this study, we combine
eight years of Adaptive Optics imaging data from the Palomar, AEOS, and CFHT
telescopes to derive an improved, astrometric characterization of the companion
orbit. We also use photometry from these observations to derive a model-based
estimate of the companion mass. A fit was performed on the photocenter motion
of this system to extract a component mass ratio. We find masses of
2.40^{0.23}_{0.37} solar masses and 0.85^{0.06}_{0.04} solar masses for Alpha
Oph A and Alpha Oph B, respectively. Previous orbital studies of this system
found a mass too high for this system, inconsistent with stellar evolutionary
calculations. Our measurements of the host star mass are more consistent with
these evolutionary calculations, but with slightly higher uncertainties. In
addition to the dynamically-derived masses, we use IJHK photometry to derive a
model-based mass for Alpha Oph B, of 0.77 +/- 0.05 solar masses marginally
consistent with the dynamical masses derived from our orbit. Our model fits
predict a periastron passage on 2012 April 19, with the two components having a
~50 milliarcsec separation from March to May 2012. A modest amount of
interferometric and radial velocity data during this period could provide a
mass determination of this star at the few percent level.Comment: Accepted to ApJ, 6 pages, 4 figure
Removing Algebraic Data Types from Constrained Horn Clauses Using Difference Predicates
We address the problem of proving the satisfiability of Constrained Horn
Clauses (CHCs) with Algebraic Data Types (ADTs), such as lists and trees. We
propose a new technique for transforming CHCs with ADTs into CHCs where
predicates are defined over basic types, such as integers and booleans, only.
Thus, our technique avoids the explicit use of inductive proof rules during
satisfiability proofs. The main extension over previous techniques for ADT
removal is a new transformation rule, called differential replacement, which
allows us to introduce auxiliary predicates corresponding to the lemmas that
are often needed when making inductive proofs. We present an algorithm that
uses the new rule, together with the traditional folding/unfolding
transformation rules, for the automatic removal of ADTs. We prove that if the
set of the transformed clauses is satisfiable, then so is the set of the
original clauses. By an experimental evaluation, we show that the use of the
differential replacement rule significantly improves the effectiveness of ADT
removal, and we show that our transformation-based approach is competitive with
respect to a well-established technique that extends the CVC4 solver with
induction.Comment: 10th International Joint Conference on Automated Reasoning (IJCAR
2020) - version with appendix; added DOI of the final authenticated Springer
publication; minor correction
Marine Volcaniclastic Record of Early Arc Evolution in the Eastern Ritter Range Pendant, Central Sierra Nevada, California
Marine volcaniclastic rocks in the Sierra Nevada preserve a critical record of silicic magmatism in the early Sierra Nevada volcanic arc, and this magmatic record provides precise minimum age constraints on subduction inception and tectonic evolution of the early Mesozoic Cordilleran convergent margin at this latitude. New zircon Pb/U ages from the Ritter Range pendant and regional correlations indicate arc inception no later than mid‐Triassic time between 37 and 38°N. The regional first‐order felsic magma eruption rate as recorded by marine volcanic arc rocks was episodic, with distinct pulses of ignimbrite emplacement at ca. 221 to 216 Ma and 174 to 167 Ma. Ignimbrites range from dacite to rhyolite in bulk composition, and are petrographically similar to modern arc‐type, monotonous intermediate dacite or phenocryst‐poor, low‐silica rhyolite. Zircon trace element geochemistry indicates that Jurassic silicic melts were consistently Ti‐ and light rare earth‐enriched and U‐depleted in comparison to Triassic melts of the juvenile arc, suggesting Jurassic silicic melts were hotter, drier, and derived from distinct lithospheric sources not tapped in the juvenile stage of arc construction. Pulses of ignimbrite deposition were coeval with granodioritic to granitic components of the underlying early Mesozoic Sierra Nevada batholith, suggesting explosive silicic volcanism and batholith construction were closely coupled at one‐ to two‐million‐year time scales
Better Palliative Care for people with a Dementia: Summary of InterdisciplinaryWorkshop Highlighting Current Gaps and Recommendations for Future Research
Background: Dementia is the most common neurological disorder worldwide and is a life-limiting condition, but very often is not recognised as such. People with dementia, and their carers, have been shown to have palliative care needs equal in extent to those of cancer patients. However, many people with advanced dementia are not routinely being assessed to determine their palliative care needs, and it is not clear why this is so. Main body: An interdisciplinary workshop on "Palliative Care in Neurodegeneration, with a focus on Dementia", was held in Cork, Ireland, in May 2016. The key aim of this workshop was to discuss the evidence base for palliative care for people with dementia, to identify 'gaps' for clinical research, and to make recommendations for interdisciplinary research practice. To lead the discussion throughout the day a multidisciplinary panel of expert speakers were brought together, including both researchers and clinicians from across Ireland and the UK. Targeted invitations were sent to attendees ensuring all key stakeholders were present to contribute to discussions. In total, 49 experts representing 17 different academic and practice settings, attended. Key topics for discussion were pre-selected based on previously identified research priorities (e.g. James Lind Alliance) and stakeholder input. Key discussion topics included: i. Advance Care Planning for people with Dementia; ii. Personhood in End-of-life Dementia care; iii. Topics in the care of advanced dementia at home. These topics were used as a starting point, and the ethos of the workshop was that the attendees could stimulate discussion and debate in any relevant area, not just the key topics, summarised under iv. Other priorities. Conclusions: The care experienced by people with dementia and their families has the potential to be improved; palliative care frameworks may have much to offer in this endeavour. However, a solid evidence base is required to translate palliative care into practice in the context of dementia. This paper presents suggested research priorities as a starting point to build this evidence base. An interdisciplinary approach to research and priority setting is essential to develop actionable knowledge in this area
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