The Distribution and Origin of Bottom Sediments in Timbalier Bay, Louisiana, and the Adjacent Offshore Area

Paper by James I. Jones and Sam E. William

SPECIES II. Stellar parameters of the EXPRESS program giant star sample

As part of the search for planets around evolved stars, we can understand planet populations around significantly higher-mass stars than the Sun on the main sequence. This population is difficult to study any other way, particularly with radial-velocities since these stars are too hot and rotate too fast to measure precise velocities. Here we estimate stellar parameters for all of the giant stars from the EXPRESS project, which aims to detect planets orbiting evolved stars, and study their occurrence rate as a function of stellar mass. We analyse high resolution echelle spectra of these stars, and compute the atmospheric parameters by measuring the equivalent widths for a set of iron lines, using an updated method implemented during this work. Physical parameters are computed by interpolating through a grid of stellar evolutionary models, following a procedure that carefully takes into account the post-MS evolutionary phases. Probabilities of the star being in the red giant branch (RBG) or the horizontal branch (HB) are estimated from the derived distributions. Results: We find that, out of 166 evolved stars, 101 of them are most likely in the RGB phase, while 65 of them are in the HB phase. The mean derived mass is 1.41 and 1.87 Msun for RGB and HB stars, respectively. To validate our method, we compared our results with interferometry and asteroseismology studies. We find a difference in the radius with interferometry of 1.7%. With asteroseismology, we find 2.4% difference in logg, 1.5% in radius, 6.2% in mass, and 11.9% in age. Compared with previous spectroscopic studies, and find a 0.5% difference in Teff, 1% in logg, and 2% in [Fe/H]. We also find a mean mass difference with respect to the EXPRESS original catalogue of 16%. We show that the method presented here can greatly improve the estimates of the stellar parameters for giant stars compared to what was presented previously.Comment: 24 pages, 17 figures, 15 tables, accepted by A&

The Effects of Elevated Concentrations of Carbon Dioxide and Ozone on Potatoe (Solanum tuberosum L.) Yield

End of Project ReportPotatoes (Solanum tuberosum L. cv. Bintje) were grown in open top chambers at Teagasc, Crops Research Centre, Oak Park, Carlow and exposed to ambient and elevated concentrations of CO2 in combination with ambient and elevated concentrations of O3 in the 1998 and 1999 growing seasons. Exposure to elevated concentrations of O3 caused visual damage to the leaves of the potato plants in both years of the study. In 1999, ozone damage to leaves was significantly reduced in the presence of elevated concentrations of CO2. Stomatal conductance was reduced by elevated CO2 and was reduced further by the elevated O3 treatment under elevated CO2. Exposure to elevated CO2 increased tuber fresh weight yield by 32% in both years of the study. The yield increase was attributable to larger tuber sizes and not to an increase in the number of tubers. Tuber yield was unaffected by elevated O3 at ambient concentrations of CO2 in both years of the study. In 1999, the yield increase induced by elevated CO2 was substantially reduced by the presence of elevated O3

Experimental and numerical investigation of interface damage in composite L-angle sections under four-point bending

© The Author(s) 2020. Curved laminates in aero-structures, such as the L-angle sections where webs and flanges meet, are prone to delamination due to high interlaminar stresses in these regions. Some efforts to investigate delamination in these structures can be found in the literature but commonly structures are limited to unidirectional layups or modelling approaches are constrained to the cohesive element based methods. In this work, multi-directional L-angle laminates were manufactured using unidirectional prepregs and tested under four-point bending load conditions to examine the interface damage. Acoustic emission technique was used to assist the capture of damage initiation and propagation. Three interface modelling strategies for predicting delamination, namely cohesive element, cohesive surface and perfectly bonded interface were used in the numerical study. The interface damage behaviour was successfully predicted by the simulation methods and differences among the strategies were compared

Impacts of hemispheric solar geoengineering on tropical cyclone frequency

Solar geoengineering refers to a range of proposed methods for counteracting global warming by artificially reducing sunlight at Earth’s surface. The most widely known SG proposal is stratospheric aerosol injection (SAI) which has impacts analogous to those from volcanic eruptions. Observations following major volcanic eruptions indicate that aerosol enhancements confined to a single hemisphere effectively modulate North Atlantic tropical cyclone (TC) activity in the following years. Here we investigate the effects of both single-hemisphere and global SAI scenarios on North Atlantic TC activity using the HadGEM2-ES general circulation model and various TC identification methods. We show that a robust result from all of the methods is that SAI applied to the southern hemisphere would enhance TC frequency relative to a global SAI application, and vice versa for SAI in the northern hemisphere. Our results reemphasize the perils of regional geoengineering and should motivate policymakers to regulate large-scale unilateral geoengineering deployments

J-Band Infrared Spectroscopy of a Sample of Brown Dwarfs Using Nirspec on Keck II

Near-infrared spectroscopic observations of a sample of very cool, low-mass objects are presented with higher spectral resolution than in any previous studies. Six of the objects are L-dwarfs, ranging in spectral class from L2 to L8/9, and the seventh is a methane or T-dwarf. These new observations were obtained during commissioning of NIRSPEC, the first high-resolution near-infrared cryogenic spectrograph for the Keck II 10-meter telescope on Mauna Kea, Hawaii. Spectra with a resolving power of R=2500 from 1.135 to 1.360 microns (approximately J-band) are presented for each source. At this resolution, a rich spectral structure is revealed, much of which is due to blending of unresolved molecular transitions. Strong lines due to neutral potassium (K I), and bands due to iron hydride (FeH) and steam (H2O) change significantly throughout the L sequence. Iron hydride disappears between L5 and L8, the steam bands deepen and the K I lines gradually become weaker but wider due to pressure broadening. An unidentified feature occurs at 1.22 microns which has a temperature dependence like FeH but has no counterpart in the available FeH opacity data. Because these objects are 3-6 magnitudes brighter in the near-infrared compared to the I-band, spectral classification is efficient. One of the objects studied (2MASSW J1523+3014) is the coolest L-dwarf discovered so far by the 2-Micron All-Sky Survey (2MASS), but its spectrum is still significantly different from the methane-dominated objects such as Gl229B or SDSS 1624+0029.Comment: New paper, Latex format, 2 figures, accepted to ApJ Letter

The Calan-Hertfordshire Extrasolar Planet Search

The detailed study of the exoplanetary systems HD189733 and HD209458 has given rise to a wealth of exciting information on the physics of exoplanetary atmospheres. To further our understanding of the make-up and processes within these atmospheres we require a larger sample of bright transiting planets. We have began a project to detect more bright transiting planets in the southern hemisphere by utilising precision radial-velocity measurements. We have observed a constrained sample of bright, inactive and metal-rich stars using the HARPS instrument and here we present the current status of this project, along with our first discoveries which include a brown dwarf/extreme-Jovian exoplanet found in the brown dwarf desert region around the star HD191760 and improved orbits for three other exoplanetary systems HD48265, HD143361 and HD154672. Finally, we briefly discuss the future of this project and the current prospects we have for discovering more bright transiting planets.Comment: 4 pages, 2 figures, to appear in the conference proceedings "New Technologies for Probing the Diversity of Brown Dwarfs and Exoplanets" Shanghai 200

An experimental and numerical investigation into damage mechanisms in tapered laminates under tensile loading

Through-thickness thickness reductions in laminated composites are essential for weight and aerodynamic efficiency, but they can also be the site of damage initiation. Tensile failure mechanisms of modestly tapered laminates, loaded via gripping their thick and thin ends, and a severely tapered laminate, loaded by contact at its tapered section, were investigated via experiments and high-fidelity finite element modelling. The primary failure mode is by delamination, initiated from a terminated ply in the tapered region, which is quite sensitive to a small delamination defect at a ply drop location. Experimental measurements and FE predictions correlate very well in all cases for both location and load. In the severely tapered case, the contact stress influences the delamination and so a fibre failure criterion also needs to be considered, including both the fibre direction tensile stress and its interaction with through-thickness direct and shear stresses imposed by the contact