46,644 research outputs found
Richard-Sims/Sims_2023_OceanSODA-UNEXE: v1.0.0
No full textThis code relates to
Sims, R. P., Holding, T. M., Land, P. E., Piolle, J.-F., Green, H. L., and Shutler, J. D.: OceanSODA-UNEXE: A multi-year gridded Amazon and Congo River outflow surface ocean carbonate system dataset, Earth Syst. Sci. Data, https://doi.org/10.5194/essd-2022-294, 2023
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
Quantitative analysis of BN (C,O,Ar,H)-coatings using EPMA and SIMS
No full textS.141-147Electron probe microanalysis (EPMA) and secondary ion mass spectrometry (SIMS) are applied to the chemical characterization of boron nitride coatings with additional concentrations (1-20 at per cent) of H, C, O and Ar. Quantitative analysis of homogeneous films with a film thickness >0.3 mu m is carried out by conventional "bulk" EPMA with an accuracy of about 5 per cent relative. A similar degree of accuracy is obtained for the simultaneous determination of film thickness (0.1-0.5 mu m) and composition ("thin film" EPMA). SIMS based on monitoring MCs+ molecular secondary ions is demonstrated as a useful scheme for quantitative in-depth analysis of matrix elements. In the case of BN (H, C, O, Ar) materials a single standard (eg. defined by EPMA) is sufficient to establish a set of matrix-independent relative sensitivity factors.1
Are forecasting models usable for policy analysis?
No full textIn this article, Christopher A. Sims argues the answer to his title is yes. Sims explains that any decisionmaking model must incorporate some identifying assumptions to enable it to forecast the effects of alternative decisions. He argues that although all identifying assumptions in econometric policymaking models are of uncertain validity, those incorporated in vector autoregression (VAR) forecasting models have the advantage of allowing their uncertainty to be measured. Sims concludes by demonstrating a method for identifying a small macroeconomic VAR model so that it can be used to analyze monetary policyForecasting ; Economic policy
Synthesis of furanosesquiterpenoid natural products
No full textThe effect of addition of a catalytic quantity of a crown ether in the reaction of a phosphonate anion with a carbonyl compound (Wadsworth-Emmons reaction) has been studied and found to greatly facilitate this reaction. This modification of the Wadsworth-Emmons reaction, using a catalytic amount of 15-crown-5, has been employed in the synthesis of the naturally occurring furanosesquiterpene Pallescensin-E. The structure of this compound has been confirmed by comparison of its spectral data with that of the synthesised isomer, 4,l0-dihydro-7,8-dimethyl 10H-benzof4,5Jcycloheptafl,2-bJ furan.Homosesquirosefuran, an analogue of the naturally occurring furanosesquiterpene Sesquirosefuran, has been synthesised via the dianion of methylacetoacetate.An approach to the synthesis of Pinguisone (a component of the essential oil of the liverwort Aneura pinguis)has been attempted employing two Diels-Alder reactions to generate the four cis-methyl groups found in the natural product.In a study of the reaction of n-(2-methylallyl)nickel bromide complex with a range of epoxides, this complex was found not only to react with reactive epoxides (e.g. styrene epoxide) but also with less reactive propylene epoxide.Substrates for possible intramolecular n-allylnickel cyclisation to generate an a-methylene-6-valerolactone ring system have been prepared
Efficient p-Multigrid Based Solvers for Isogeometric Analysis on Multipatch Geometries
No full textIsogeometric Analysis can be considered as the natural extension of the Finite Element Method (FEM) to higher-order spline based discretizations simplifying the treatment of complex geometries with curved boundaries. Finding a solution of the resulting linear systems of equations efficiently remains, however, a challenging task. Recently, p-multigrid methods have been considered [18], in which a multigrid hierarchy is constructed based on different approximation orders p instead of mesh widths h as it would be the case in classical h-multigrid schemes [8]. The use of an Incomplete LU-factorization as a smoother within the p-multigrid method has shown to lead to convergence rates independent of both h and p for single patch geometries [19]. In this paper, the focus lies on the application of the aforementioned p-multigrid method on multipatch geometries having a C0-continuous coupling between the patches. The use of ILUT as a smoother within p-multigrid methods leads to convergence rates that are essentially independent of h and p, but depend mildly on the number of patches.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Numerical Analysi
An Operational Model of QuickPay
No full textIntroduction QuickPay is a micro payment scheme with prepayment 1, 6 . The customer must register with the broker to obtain an electronic carnet with value tokens before a sale may take place. It is possible to acquire additional value tokens, or to refresh the value tokens at any time. A merchant must also register with the broker to obtain an electronic till with authentication tokens. This will enable the merchant to validate the tokens presented by the customer. Once customer and merchant are registered, a sale may proceed as follows. First the customer presents one or more value tokens to the merchant. The merchant then authenticates himself with the broker and presents the customers value tokens to the broker for validation. The broker decides whether the customers tokens are valid. If the merchant is satisfied that the tokens are valid, goods/services may be delivered. The customer takes delivery but does not receive a receipt. The QuickPay philosophy is to make tran
A Multi-Sims Investigation of Water Content and D/H Ratios in Roberts Massif 04262 with Insight to Sources of Hydrogen in Maskelynite
No full textWe want to define the H2O content ([H2O]) and hydrogen (H) isotope composition of meteoritic material from Mars [1-3] with motivation to understand Mars volatile history, constrain geochemical signatures of interior water reservoirs (i.e. the Martian mantle) and explore effects of planetary (e.g. planet formation, magma ocean degassing) and local (e.g. volcanic degassing, impact melting and degassing) processes on H incorporated in minerals. Secondary ion mass spectrometry (SIMS) allows multiple avenues to address these questions. However, application to (1) precious astromaterials and (2) low level H measurements, pose specific challenges that are further complicated when combined. We present preliminary data of a multi-approach (SIMS vs. NanoSIMS) study of H in Roberts Massif 04262 (RBT 04262), an enriched lherzolitic shergottite with nonpoikilitic (NP) and poikilitic (P) lithologies [4]. We analyze olivine, pyrox-ene, and melt inclusions to compare indigenous mantle water, with impact-generated maskelynite to investigate H signatures due to shock
Exploiting energy sequencing of low energy SIMS to determine intrinsic chemical profiles with sub-nm precision
No full textIn the past, it has been proposed that secondary ion mass spectrometry (SIMS) depth profiling of a sample using a range of beam energies could be used as a means of estimating the intrinsic sample profile by extrapolating the measured profile parameters back to zero beam energy. In this paper, the authors address some of the issues that have hindered this approach and demonstrate a new metrology that exploits the idea of energy sequencing to yield intrinsic sample features with subnanometer precision. A significant reason why energy sequencing has not been exploited fully to date is because previous attempts failed to consider the convolution between the sample feature and response function parameters. Their new metrology overcomes this by utilizing a simultaneous fitting approach for which the sample feature is shared across all the profile fits and only the energy dependent response function parameters are varied between profiles using a power law dependence. The authors demonstrate how this approach now allows the intrinsic sample feature to be resolved robustly and with high precision. Additionally, the authors also show that once a specific matrix response function power law dependence has been established, as few as two SIMS profile energies would be sufficient to accurately determine the intrinsic sample feature. This new metrology approach is demonstrated using an atomically sharp SiGe/Si interface and was benchmarked against atomic resolution high angle annular dark field-scanning transmission electron microscopy
Observing temporally varying synoptic-scale total alkalinity and dissolved inorganic carbon in the Arctic Ocean
No full text<p>Arctic Ocean version of Sims et al. (2023) for evaluating and using empirical approaches for studying the surface marine carbonate system. All work builds on the methods and approaches developed within Land et al. (2019) and Sims et al. (2023).</p><p>Reference</p><p>Land PE, Findlay H, Shutler J, Ashton I, Holding T, Grouazel A, GIrard-Ardhuin F, Reul N, Piolle J-F, Chapron B, et al (2019). Optimum satellite remote sensing of the marine carbonate system using empirical algorithms in the Global Ocean, the Greater Caribbean, the Amazon Plume and the Bay of Bengal. Remote Sensing of Environment, doi: 10.1016/j.rse.2019.111469</p><p>Sims, R. P., Holding, T. M., Land, P. E., Piolle, J.-F., Green, H. L., and Shutler, J. D.: OceanSODA-UNEXE: a multi-year gridded Amazon and Congo River outflow surface ocean carbonate system dataset, Earth Syst. Sci. Data, 15, 2499–2516, https://doi.org/10.5194/essd-15-2499-2023, 2023</p><p> </p>
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