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The majority of hot subdwarfs lie on or close to the helium main-sequence. Many have hydrogen-rich surfaces, but a substantial fraction have hydrogen-depleted or hydrogen-deficient surfaces. Amongst the former, three were known to show extraordinary overabundances of heavy elements including zirconium and lead. A limited survey with Subaru/HDS revealed three new lead-rich subdwarfs. A much wider survey is in progress using SALT. Discoveries include two new extreme helium stars, new intermediatedoi:10.5281/zenodo.1435126 fatcat:5sqpai6hlzcondzocji3wixbvu
more »... helium subdwarfs, and a new lead star. Analysis of the growing sample shows evidence of connections between hydrogen-deficient classes.
The brent geese were caught betw een N ovem ber 1991 and February 1993 either by cannon nets or dazzling at night. ... Methods Bird capture and marking D uring the three studies, 38 brent geese w ere fitted with radio transm itters ( Table 1 ). ...doi:10.2981/wlb.2001.011 fatcat:msld4rlz6faczha7brg24xctta
We would also like to thank Danil Lakens, Richard Lucas, Hal Pashler, and Daniel Simons for their helpful comments. ...doi:10.1027/1864-9335/a000204 fatcat:ply5sgctabevjdhs7fssj5od5u
We analyze the incidence of ad valorem and unit excise taxes in an oligopolistic industry with differentiated products and price-setting (Bertrand) firms. Both taxes may be passed on to consumers by more than 100 percent, and an increase in the tax rate can increase short run firm profits (and hence the long run number of firms). We provide summary conditions for these effects to arise. The conditions depend on demand curvatures and are written in elasticity form. Surprisingly, the analysisdoi:10.2139/ssrn.218272 fatcat:4ty3xb4tcnaitabcfwvpwyujlu
more »... ely corroborates Cournot results with homogeneous demand.
Modeling and Systems Engineering for Astronomy
The Terrestrial Planet Finder interferometer design concepts are large and complex systems that must operate in environments that are impractical to reproduce in preflight testing. The structurally-connected design is 36 meters longlonger than all but one thermal vacuum chamber in existence. The formation flying design will be comprised of up to five separate spacecraft, each with a sunshield over 15 meters on a side, and is designed to operate with formation sizes spanning over 100 meters todoi:10.1117/12.550265 fatcat:c2pc2c5ad5f6dckuvrgo45rldm
more »... ry close formations. System-level verification of the performance of the designs will need to rely on analytical modeling. The effort to model the many physical aspects of the designs under study is under way*. This paper describes the program of modeling for the TPF-I concepts. The program includes a number of types of models, such as the standard stand-alone optics, thermal, and structural models, as well as an endto-end performance model of the project system called the Observatory Simulation. Aspects of each model are discussed including the purpose, methods of implementation (software applications), and approaches to validation. Program-level considerations (such as model-to-model integration and configuration management) are also discussed. Given that there are at least seven different organizations contributing to model developments and more than twenty separate models, these are special challenges.
A medium- and high-resolution spectroscopic survey of helium-rich hot subdwarfs is being carried out using the Southern African Large Telescope (SALT). Objectives include the discovery of exotic hot subdwarfs and of sequences connecting chemically-peculiar subdwarfs of different types. The first phase consists of medium-resolution spectroscopy of over 100 stars selected from low-resolution surveys. This paper describes the selection criteria, and the observing, classification and analysisarXiv:2011.09523v1 fatcat:eklcip4q25a55ilie544b2rrua
more »... s. It presents 107 spectral classifications on the MK-like Drilling system and 106 coarse analyses (T_ eff, log g, log y) based on a hybrid grid of zero-metal non-LTE and line-blanketed LTE model atmospheres. For 75 stars, atmospheric parameters have been derived for the first time. The sample may be divided into 6 distinct groups including the classical 'helium-rich' sdO stars with spectral types (Sp) sdO6.5 - sdB1 (74) comprising carbon-rich (35) and carbon-weak (39) stars, very hot He-sdO's with Sp ≲ sdO6 (13), extreme helium stars with luminosity class ≲ 5 (5), intermediate helium-rich subdwarfs with helium class 25 – 35 (8), and intermediate helium-rich subdwarfs with helium class 10 - 25 (6). The last covers a narrow spectral range (sdB0 – sdB1) including two known and four candidate heavy-metal subdwarfs. Within other groups are several stars of individual interest, including an extremely metal-poor helium star, candidate double-helium subdwarf binaries, and a candidate low-gravity He-sdO star.
This paper considers the relative efficiency of ad valorem and unit taxes in imperfectly competitive markets. We provide a simple proof that ad valorem taxes are welfare-superior to unit taxes in the short run when production costs are identical across firms. The proof covers differentiated products and a wide range of market conduct. Cost asymmetries strengthen the case for ad valorem taxation under Cournot competition, but unit taxation may be welfare-superior under Bertrand competition withdoi:10.2139/ssrn.218273 fatcat:mq2helcs7fabra37v4rulvdayi
more »... roduct differentiation. Ad valorem taxation is superior with free entry under Cournot competition, but not necessarily under price competition when consumers value variety.
Changes in the slope of response curves of brent geese feeding activity in relation to fertilizer application rates (b = coefficient of regression of number of droppings deposited m −2 per day by brent ... The fields were selected specifically from the 22 available because of their similar size (4.1, S.D. ± 0.26 ha), similar summer cattle grazing densities, and regular use by 3500 wintering dark-bellied brent ...doi:10.1016/s0167-8809(00)00282-6 fatcat:5utx555cqjakbaht3vbd2kv6ya
Simon helped him with the statistical analysis. ...doi:10.1007/s11606-006-0245-2 pmid:16336619 pmcid:PMC1484667 fatcat:23c5ppalkzh4dfl67tbgzevd24
Annals of Glaciology
Ocean tides influence the flow of marine-terminating glaciers. Observations indicate that the large fortnightly variations in ice flow at Rutford Ice Stream in West Antarctica originate in the floating ice shelf. We show that nonlinear variations in ice shelf buttressing driven by tides can produce such fortnightly variations in ice flow. These nonlinearities in the tidal modulation of buttressing stresses can be caused by asymmetries in the contact stress from migration of the grounding linedoi:10.1017/aog.2017.22 fatcat:3vt23s72yvg4nbzoomsx3espmi
more »... d bathymetric pinning points beneath the ice shelf. Using a simple viscoelastic model, we demonstrate that a combination of buttressing and hydrostatic stress variations can explain a diverse range of tidal variations in ice shelf flow, including the period, phase and amplitude of flow variations observed at Rutford and Bindschadler Ice Streams.
Brent Polk (email@example.com). Materials availability This study did not generate new unique reagents. ...doi:10.1101/2021.06.02.446836 fatcat:3bz4yymv2ze2hiurjrpria77ne
Adaptive Optics Systems III
We present progress towards the development of a woofer-tweeter adaptive optics (AO) system using the first 37 actuators of a 91-actuator magnetic-liquid deformable mirror (MLDM) and a magnetic 97-actuator DM from ALPAO. The MLDM, which has both very large single-actuator and inter-actuator strokes, but a low bandwidth, is used as woofer, whereas the high bandwidth and lower stroke ALPAO DM is used as tweeter. The ALPAO DM should improve the bandwidth of the MLDM while the MLDM will allow correction of strong aberrations.doi:10.1117/12.925174 fatcat:6pm4dsgk6ndavhig6tiuxziwb4
Simons is a fellow of the American Geophysical Union. ... For example, Simons et al.  used the spatial pattern of low coherence to map the location of fault surface rupture due to the 1999 M w 7.1 Hector Mine, California earthquake. ...arXiv:2105.11544v1 fatcat:d4r4hrmdm5fthota3n36n2lhwy
."); Brent White, Putting Aside the Rule of Law Myth: Corruption and the Case for Juries in Emerging Democracies, 43 CORNELL INT'L L.J. 307, 309 (2010). 30 See, e.g., Richard H. ...doi:10.2139/ssrn.2230652 fatcat:kflxroxiozaovkvamatxqw44gq
This paper introduces a sharp-interface approach to simulating fluid-structure interaction involving flexible bodies described by general nonlinear material models and across a broad range of mass density ratios. This new flexible-body immersed Lagrangian-Eulerian (ILE) approach incorporates the geometrical and domain solution flexibility of the immersed boundary (IB) method with an accuracy comparable to body-fitted approaches that sharply resolve flows and stresses up to the fluid-structurearXiv:2204.12907v1 fatcat:at6kzy3jbvh5bepvmkrwjdxtze
more »... terface. Unlike many IB methods, our ILE formulation uses distinct momentum equations for the fluid and solid subregions with a Dirichlet-Neumann coupling strategy that connects fluid and solid subproblems through simple interface conditions. We use a penalty method involving two representations of the fluid-structure interface. These two representations are connected by approximate Lagrange multiplier forces that impose kinematic interface conditions. This approach also enables the use of multi-rate time stepping, which allows us to take different time step sizes for the fluid and structure subproblems. Our fluid solver relies on an immersed interface method for discrete surfaces to impose stress jump conditions along complex interfaces. The dynamics of the volumetric structural mesh are determined using a standard finite element approach to large-deformation nonlinear elasticity via a nearly incompressible solid mechanics formulation. This formulation also readily accommodates compressible structures for cases in which part of the solid boundary does not contact the incompressible fluid. Comparisons are made with computational and experimental benchmarks. We also demonstrate the capabilities of this methodology by applying it to model the transport and capture of a cylindrical blood clot in an inferior vena cava filter.
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