1,859 research outputs found
Reactions of exotic nuclei with the quark-meson coupling model
No full textThe nucleon-nucleon interaction is an important requirement for investigations of nuclear structure and reactions, as well as for astrophysical models such as r-process nucleosynthesis and neutron stars. The traditional approach to low-energy nuclear physics is to treat nucleons as immutable objects interacting via phenomenological forces. The use of phenomenological interactions, rather than one derived from a microscopic theory, raises questions as to the reliability of predictions for exotic regions of the nuclear chart. The quark-meson coupling (QMC) model uses a relativistic mean-field approach to provide a microscopically derived nucleon-nucleon interaction, which takes into account the quark structure of the nucleon. The Skyrme energy density functional is a popular phenomenological tool in studies of nuclear structure and reactions. In this work, the QMC density functional was used to produce a set of Skyrme parameterisations, in the hopes that they will give more reliable predictions for exotic nuclei. In conjunction with Hartree-Fock-Bogoliubov (HFB) calculations, the Skyrme-QMC (SQMC) parameterisations have been used to model the ground-state properties of individual nuclei and nucleus-nucleus potentials for Ca + Sn reactions. The SQMC parameterisation performs with an accuracy comparable to modern phenomenological functionals. From this, one can investigate the importance of the isovector terms of the nucleon-nucleon interaction, which are particularly significant for exotic, neutron-rich regions of the nuclear chart. One of the notable successes of the QMC model is its derivation of nuclear spin-orbit coupling. The isovector dependence of the spin-orbit equation of state is remarkably similar to that of the modern UNEDF1 phenomenological density functional. HFB calculations along the Sn isotopic chain reveal that the isovector properties of the spin-orbit term impact binding energies to a level that will be significant for astrophysical r-process modelling.E. McRae, C. Simenel, E.C. Simpson, and A.W. Thoma
Afropean Journeys: A Conversation with E.C. Osondu
No full textNigeria-born and US resident author E.C. Osondu debuted with the short story collection Voice of America (2010), followed by the novel This House is Not for Sale (2015) and Alien Stories (2020). His latest novel, When the Sky is Ready the Stars Will Appear, the compelling tale of an African boy’s journey towards Rome in search of a better life, was first published in translation in Italy with the title Quando il cielo vuole spuntano le stelle (2020). Only one year later, the original version of the novel was published in Nigeria. This piece, based on a conversation with the author within the context of the “Afropean Bridges” 2021 Series, introduces E.C. Osondu and his works to the Italian audience
A numerical model study of the stratocumulus-topped marine boundary layer
No full textA one-dimensional model with second order turbulence closure has been developed and used to investigate processes in the cloud-topped marine atmospheric boundary layer. Model developments were required to correctly apply surface flux terms near the sea surface, poor representation of which is common to several models from the recent literature. The improved surface forcing is shown to affect the predicted boundary layer structure. Other developments included the implementation of a fully implicit numerical code, which generated less numerical noise than that originally used in the model, and an improved initialisation procedure. The new model code was then shown to quantitatively reproduce processes in the stratocumulus topped boundary layer using measurements of atmospheric turbulence from aircraft from the North Sea and the subtropical North Atlantic and North Pacific. The model is robust to changes in the mixing length coefficients used in the turbulence closure and to perturbations in the initial profiles. The model is used to simulate conditions that occur as winds circulate from the subtropics towards the tradewind regions. The observed transition from a shallow stratocumulus layer to a deeper stratocumulus layer interacting with cumulus clouds beneath is simulated in response to realistic external forcing. The final stages of transition, from cumulus under stratocumulus to shallow cumulus is however not observed in the simulation; possible reasons for this are discussed. The model shows in detail the interaction between the stratocumulus layer and cumulus clouds beneath. The cumulus clouds thicken, moisten and cool the stratocumulus layer and therefore act to maintain the layer, but can also drive entrainment. The peaks inturbulent kinetic energy in the stratocumulus layer which follow cumulus penetrations of the stratocumulus layer can be large enough to directly cause the boundary layer to entrain air from above the boundary layer and grow in height. The entrained air is warmer and drier than the boundary layer air and tends to dissipate the stratocumulus layer. The model is then used to show how the imposed environmental conditions affect processes within the boundary layer. An important model prediction is that cloud top entrainment instability may act to promote mixing between the surface and cloud in deep-decoupled boundary layers. The mixing acts to replenish the cloud liquid water and sustain the cloud. Cloud top entrainment instability has previously been thought to have the capacity to lead to rapid erosion of the cloud, although this has not been observed in practice. This mechanism could help to explain the observed persistence of stratocumulus clouds under these conditions
Ships Observing Marine Climate: a catalogue of the VOS participating in the VSOP-NA
No full textOur present knowledge of the marine climate, as represented by data sets such as COADS (Woodruff et al., 1987), is based on meteorological observations from the Voluntary Observing Ships (VOS). Because the VOS are merchant ships, rather than specially designed meteorological platforms, errors and biases exist in the data. However there is little information readily available to the climatologist either on the nature of the VOS fleet or on the observing practises which are used. This report, describing the forty-six ships that participated in the Voluntary Observing Ships' Special Observing Project - North Atlantic (VSOP-NA), therefore serves two purposes:(i) it provides a reference document to aid analysis of the VSOP-NA data set,(ii) it gives a detailed description of a subset of the VOS, which will be of value in the interpretation of marine climate data sets.This report is in two parts, Part 1 is an overall summary of the ship characteristics, Part 2 is a ship by ship description. The next section will briefly describe the VSOP-NA project, followed by a summary of the characteristics of the VSOP-NA ships (Section 3). Since these ships were specially selected (Section 2.2), the degree to which they are representative of the whole VOS fleet will be carefully considered. The meteorological instrumentation used by the VOS varies depending on which meteorological agency recruited the ships. That used on the chosen VSOP-NA ships is typical of VOS recruited by the countries bordering the North Atlantic, and will be described in Section 4. Section 5 is a summary of Part 1 of the report.Part 2 presents the VSOP-NA ship catalogue. This includes, for each ship, diagrams of the layout (indicating in particular the exposure of the sensors), a summary of the geographical positions at which observations were obtained, and details of the instrumentation used.<br/
Services in Europe: a policy for the '90s. Europe: Magazine of the European Community No. 263, January-February 1987
No full textAlice Colson, right, seeing off Ted Colson, centre, and Eringa Peter, left, on their trip across the Simpson Desert, Abminga, South Australia, 1936 [picture].
No full textTitle devised by cataloguer from inscription and reference sources.; In album: Central Australia photograph album.; Inscriptions: "From Ted Colson to A. Wiley - My plant & Black boy (Peter) as I was about to start on my attempt to cross the Simpson Desert. My wife sees us off. E.C."--Below image and in ink on verso; "With Compliments A. J. Wylie from E. A. Colson"--In ink on verso; "A.J. Wiley, Prospect, South Aust."--Stamp on verso.; Condition: Folds, creases, faded, yellowing.; Also available in an electronic version via the Internet at: http://nla.gov.au/nla.pic-vn4927468
A comparison of data-driven internal multiple elimination strategies and their consequences for imaging
No full textWe compare two data-driven internal multiple reflection elimination schemes derived from regular Marchenko equations and Inverse Scattering Series (ISS). The scheme derived from regular Marchenko equations creates a new data set without internal multiple reflections. The scheme derived from ISS is equal to the result after the second iteration of the Marchenko-based scheme. It can attenuate internal multiple reflections with residuals. We evaluate the success of two schemes with a 2D complex numerical example. It is shown that Marchenko-based data-driven scheme is relatively more robust for internal multiple reflection elimination.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.Applied Geophysics and Petrophysic
Análisis de las dos líneas de transmisión del tratado de Tudmīr (94 H./713 e.C.)
No full textThe two main texts of the transmission lines of the treaty of Tudmīr (94 H/713 e.C. ), included by al- ‘Uḏrī and al-Ḍabbī in their respective works, are edited and translated on the basis of an new reading of the manuscripts that contain them, and after that, we reach some conclusions about its process of copy. There are compared the two texts, and are listed its textual differences. As conclusion, we propose that Al- ‘Uḏrī’s text is the oldest, because its author has copied them from the original document of the 8th. c. (or a copy transfer of this). The transmission of al-Ḍabbī is more recent and it was based in an oral transmission of the text.Análisis de las dos líneas de transmisión del tratado de Tudmīr (94 H./713 e.C.)Los dos textos principales de las líneas de transmisión del tratado de Tudmīr (94 H/713 e.C.), incluidos por al-‘Uḏrī y al-Ḍabbī en sus respectivas obras, son editados y traducidos en base a la relectura de los manuscritos que los contienen y de ello se extraen una serie de conclusiones sobre su proceso de copia. Luego son comparados los dos textos entre sí y se enumeran una serie de diferencias textuales. Finalmente, como hipótesis interpretativa se propone que el texto de al-‘Uḏrī es el más antiguo, y habría sido copiado de un traslado del original por su autor, mientras que la transmisión de al-Ḍabbī habría sido más reciente y se habría fundado en otra fuente más antigua que habría puesto por escrito un relato oral del texto
A study of phytochrome, its isolation, structure and photochemical transformations
No full textApplied Science
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