875 research outputs found
Dynamical Measurements of the Young Upper Scorpius Triple NTTS 155808-2219
The young, low-mass, triple system NTTS 155808-2219 (ScoPMS 20) was
previously identified as a ~17-day period single-lined spectroscopic binary
with a tertiary component at 0.21 arcseconds. Using high-resolution infrared
spectra, acquired with NIRSPEC on Keck II, both with and without adaptive
optics, we measured radial velocities of all three components. Reanalysis of
the single-lined visible light observations, made from 1987 to 1993, also
yielded radial velocity detections of the three stars. Combining visible light
and infrared data to compute the orbital solution produces orbital parameters
consistent with the single-lined solution and a mass ratio of q = 0.78 +/- 0.01
for the SB. We discuss the consistency between our results and previously
published data on this system, our radial-velocity analysis with both observed
and synthetic templates, and the possibility that this system is eclipsing,
providing a potential method for the determination of the stars' absolute
masses. Over the ~20 year baseline of our observations, we have measured the
acceleration of the SB's center-of-mass in its orbit with the tertiary.
Long-term, adaptive optics imaging of the tertiary will eventually yield
dynamical data useful for component mass estimates.Comment: 6 Tables, 8 Figures, updated to match published tex
Assessing the hidden impacts of hypothetical eruption events at Mount Etna
Abstract We estimate how the value and the spatial distribution of carbon storage, water yield and wild pollination services are expected to change with potential expansion of lava flow inundation at Mount Etna volcano (Sicily, Italy). We rely on a hazard map lava by flow inundation to simulate a set of three future land use/land cover (LU/LC) scenarios related to different hazard levels with a specific probability of occurrence. Our assessment used the Integrated Valuation of Environmental Services and Tradeoffs (InVEST) tool and GIS spatial analysis and indicates that changes in the delivery of all three ecosystem services are biophysically and economically sizeable. The variation between scenarios demonstrates that the carbon storage and wild pollination services will decrease because of the loss of woods and natural habitats. In contrast, the water yield capacity will increase for the creation of new naked land surfaces characterised by high permeability values. In the worst-case scenario, we estimate a loss of 17% and 10% for carbon storage and wild pollination services respectively, and an increase of approximately 10% for water yield
The impact of vehicle movement on exploitation parameters of roads and runways: a short review of the special issue
"The impact of vehicle movement on exploitation parameters of roads and runways: a short review of the special issue" Transport, 31(2), p. 127-13
Weak convergence of finite element approximations of linear stochastic evolution equations with additive noise II. Fully discrete schemes
We present an abstract framework for analyzing the weak error of fully
discrete approximation schemes for linear evolution equations driven by
additive Gaussian noise. First, an abstract representation formula is derived
for sufficiently smooth test functions. The formula is then applied to the wave
equation, where the spatial approximation is done via the standard continuous
finite element method and the time discretization via an I-stable rational
approximation to the exponential function. It is found that the rate of weak
convergence is twice that of strong convergence. Furthermore, in contrast to
the parabolic case, higher order schemes in time, such as the Crank-Nicolson
scheme, are worthwhile to use if the solution is not very regular. Finally we
apply the theory to parabolic equations and detail a weak error estimate for
the linearized Cahn-Hilliard-Cook equation as well as comment on the stochastic
heat equation
Semi-quantitative analysis of cannabinoids in hemp (Cannabis sativa L.) using gas chromatography coupled to mass spectrometry
Background
Hemp (Cannabis sativa L.) is a producer of cannabinoids. These organic compounds are of increasing interest due to their potential applications in the medicinal field. Advances in analytical methods of identifying and quantifying these molecules are needed.
Method
This study describes a new method of cannabinoid separation from plant material using gas chromatography-mass spectrometry (GC-MS) as the analytical tool to detect low abundance cannabinoids that will likely have implications for future therapeutical treatments. A novel approach was adopted to separate trichomes from plant material to analyse cannabinoids of low abundance not observed in raw plant extract. Required plant sample used for analysis was greatly reduced compared to other methods. Derivatisation method was simplified and deconvolution software was utilised to recognise unknown cannabinoid compounds of low abundance.
Results
The method produces well-separated spectra and allows the detection of major and minor cannabinoids. Ten cannabinoids that had available standards could be identified and quantified and numerous unidentified cannabinoids or pathway intermediates based on GC-MS spectra similarities could be extracted and analysed simultaneously with this method.
Conclusions
This is a rapid novel extraction and analytical method from plant material that can identify major and minor cannabinoids using a simple technique. The method will be of use to future researchers seeking to study the multitude of cannabinoids whose values are currently not understood
The sub-arcsecond hard X-ray structure of loop footpoints in a solar flare
The newly developed X-ray visibility forward fitting technique is applied to
Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) data of a limb
flare to investigate the energy and height dependence on sizes, shapes, and
position of hard X-ray chromospheric footpoint sources. This provides
information about the electron transport and chromospheric density structure.
The spatial distribution of two footpoint X-ray sources is analyzed using
PIXON, Maximum Entropy Method, CLEAN and visibility forward fit algorithms at
nonthermal energies from to keV. We report, for the first
time, the vertical extents and widths of hard X-ray chromospheric sources
measured as a function of energy for a limb event. Our observations suggest
that both the vertical and horizontal sizes of footpoints are decreasing with
energy. Higher energy emission originates progressively deeper in the
chromosphere consistent with downward flare accelerated streaming electrons.
The ellipticity of the footpoints grows with energy from at keV to at keV. The positions of X-ray emission are in
agreement with an exponential density profile of scale height ~km.
The characteristic size of the hard X-ray footpoint source along the limb is
decreasing with energy suggesting a converging magnetic field in the footpoint.
The vertical sizes of X-ray sources are inconsistent with simple collisional
transport in a single density scale height but can be explained using a
multi-threaded density structure in the chromosphere.Comment: 7 pages, 7 figures, submitted to Ap
The normal-to-planar superfluid transition in Helium 3
We study the nature of the Helium-3 superfluid transition from the normal to
the planar phase, which is expected to be stabilized by the dipolar
interactions. We determine the RG flow of the corresponding
Landau-Ginzburg-Wilson theory by exploiting two fixed-dimension perturbative
schemes: the massive zero-momentum scheme and the minimal-subtraction scheme
without expansion. The analysis of the corresponding six-loop and
five-loop series shows the presence of a stable fixed point in the relevant
coupling region. Therefore, we predict the transition to be continuous. We also
compute critical exponents. The specific-heat exponent is estimated as
, while the magnetic susceptibility and magnetization
exponents and for Helium 3 are ,
.Comment: 19 pages, 4 fig
Finding just the right recipe: nutrient requirements on Christmas Island
There is no history of large-scale agriculture on Christmas Island. As a result, there is a heavy reliance on imported produce
IR Detection of Low-Mass Secondaries in Spectroscopic Binaries
This paper outlines an infrared spectroscopic technique to measure the radial
velocities of faint secondaries in known single-lined binaries. The paper
presents our H-band observations with the CSHELL and Phoenix spectrographs and
describes detections of three low-mass secondaries in main-sequence binaries:
G147-36, G164-67, and HD144284 with mass ratios of 0.562+-0.011, 0.423+-0.042,
and 0.380+-0.013, respectively. The latter is one of the smallest mass ratios
derived to date
VLT/NACO adaptive optics imaging of the TY CrA system - A fourth stellar component candidate detected
We report the detection of a possible subsolar mass companion to the triple
young system TY CrA using the NACO instrument at the VLT UT4 during its
commissioning. Assuming for TY CrA a distance similar to that of the close
binary system HD 176386, the photometric spectral type of this fourth stellar
component candidate is consistent with an ~M4 star. We discuss the dynamical
stability of this possible quadruple system as well as the possible location of
dusty particles inside or outside the system.Comment: 4 pages, 2 figures postscrip
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