Search results for " shell"
showing 10 items of 307 documents
The Coordination of Uranyl in Water: A Combined Quantum Chemical and Molecular Simulation Study
2005
The coordination environment of uranyl in water has been studied using a combined quantum mechanical and molecular dynamics approach. Multiconfigurational wave function calculations have been performed to generate pair potentials between uranyl and water. The quantum chemically determined energies have been used to fit parameters in a polarizable force field with an added charge transfer term. Molecular dynamics simulations have been performed for the uranyl ion and up to 400 water molecules. The results show a uranyl ion with five water molecules coordinated in the equatorial plane. The U-O(H(2)O) distance is 2.40 A, which is close to the experimental estimates. A second coordination shell…
Crystal fabrics and element impurities (Sr/Ca, Mg/Ca, and Ba/Ca) in shells of Arctica islandica—Implications for paleoclimate reconstructions
2013
Sr/Ca, Mg/Ca and Ba/Ca values are heterogeneously distributed in shells of Arctica islandica. These patterns are largely associated with crystal fabrics (size, habit and orientation of crystals) or the processes controlling them. The outer sublayer of the outer shell layer (oOSL; homogenous and irregular simple prismatic crystal fabrics,) contained element/Ca values up to 62% higher than the inner sublayer (iOSL; crossed-acicular, crossed-lamellar, fine crossed-lamellar and irregular simple prismatic crystal fabrics). A gradual decrease in Sr/Ca and Mg/Ca values was observed from the outer portions of the oOSL toward the oOSL/iOSL transition zone. This chemical shift was accompanied by a gr…
Thermochemical properties of small open-shell systems: experimental and high-levelab initioresults for NH2and
2006
The first adiabatic ionization energy and the first singlet–triplet splitting of the amidogen radical (NH2) have been determined by high-level ab initio quantum chemistry based on the coupled-cluster approach (90 041 and 10 319 cm−1, respectively) and by high-resolution pulsed-field-ionization zero-kinetic-energy (PFI-ZEKE) photoelectron spectroscopy (90 083.8 ± 1.0 and 10 222.0 ± 1.3 cm−1, respectively). A comparison between the theoretical and experimental values demonstrates the predictive powers of high-level ab initio theory in the derivation of the thermochemical properties of small molecular systems. The absolute accuracy of better than 100 cm−1 alleviates the experimental search for…
No-core configuration-interaction model for the isospin- and angular-momentum-projected states
2016
[Background] Single-reference density functional theory is very successful in reproducing bulk nuclear properties like binding energies, radii, or quadrupole moments throughout the entire periodic table. Its extension to the multi-reference level allows for restoring symmetries and, in turn, for calculating transition rates. [Purpose] We propose a new no-core-configuration-interaction (NCCI) model treating properly isospin and rotational symmetries. The model is applicable to any nucleus irrespective of its mass and neutron- and proton-number parity. It properly includes polarization effects caused by an interplay between the long- and short-range forces acting in the atomic nucleus. [Metho…
Molecular bases of anorexia nervosa, bulimia nervosa and binge eating disorder: shedding light on the darkness
2017
International audience; Eating-disorders (EDs) consequences to human health are devastating, involving social, mental, emotional, physical and life-threatening aspects, concluding on impairment and death in cases of extreme anorexia nervosa. It also implies that people suffering an ED need to find psychiatric and psychological help as soon as possible to achieve a fully physical and emotional recovery. Unfortunately, to date, there is a crucial lack of efficient clinical treatment to these disorders. In this review, we present an overview concerning the actual pharmacological and psychological treatments, the knowledge of cells, circuits, neuropeptides, neuromodulators and hormones in the h…
Our Friend and Mathematician Karl Strambach
2020
This paper is dedicated to Karl Strambach on the occasion of his 80th birthday. Here we want to describe our work with Prof. Karl Strambach.
Naftas un gāzes nozares ieguves darbības un veiksmīgu faktoru analīze apvienošanās un pārņemšanas
2018
Bakalaura darba tiek izpētīts naftas un dabasgāzes jomas Royal Dutch Shell un BG group kompanijas apvienošanas vai pārņemšanas darījuma pieredze, kas ir viens no attīstības stratēģijas veidiem, un dod iespēju uzņēmumiem ne tikai saglabāt savu tirgus pozīciju, bet arī attīstīties. Darba mērķis ir analizēt un novērtēt apvienošanās un pārņemšanas efektivitāti, un izstrādāt ieteikumus, lai uzlabotu darījumus šajā jomā. Pirmajā nodaļā ir aprakstīti apvienošanās un pārņemšanas ekonomiskā būtība, darījuma veidi, riski un principi. Otrajā nodaļā ir sniegts naftas un gāzes nozares raksturojums un tā saistība ar apvienošanas vai pārņemšanas procesu, ka arī pasaules pieredze šajā jomā. Trešajā nodaļā …
The Basics of Nuclear Chemistry and Radiochemistry: An Introduction to Nuclear Transformations and Radioactive Emissions
2019
Radiopharmaceutical chemistry and nuclear medicine make use of radioactive elements and compounds labeled with them. This chapter describes the fundamentals of radioactivity in the context of life sciences. It addresses principal questions such as: What is the composition of an atomic nucleus and what are the forces which hold nucleons bound within the nucleus? Even so, some nuclei are stable, and many others are not—why? The fate of unstable nuclei is transforming into more stable nucleon configurations—but what are the basic pathways to do so? What’s going on inside the nucleus? What are the energetics and velocities of these transformations? And finally, the various changes inside the nu…
Further comments on the origin of oysters
2006
In his comment to our recent paper (Marquez-Aliaga et al. 2005), Hautmann (2006) raises two interesting questions: (a) the ambivalent attachment to the substrate recognized in the species cristadifformis Schlotheim, 1820 and spondyloides Schlotheim, 1820, which we include into the Ostreoidae genus Umbrostrea, is in conflict with the sinistral attachment usually recognized as an autapomorphy of the group and (b) antimarginal ribs are not valid as a character linking Prospondylus acinetus Newell and Boyd, 1970 and early oysters (our proposal of derivation), because they appear in several unrelated families of bivalves. Moreover, Hautmann (2005), finds additional difficulties in accepting our …
Evolution and biomineralization of pteropod shells
2021
12 pages; International audience; Shelled pteropods, known as sea butterflies, are a group of small gastropods that spend their entire lives swimming and drifting in the open ocean. They build thin shells of aragonite, a metastable polymorph of calcium carbonate. Pteropod shells have been shown to experience dissolution and reduced thickness with a decrease in pH and therefore represent valuable bioindicators to monitor the impacts of ocean acidification. Over the past decades, several studies have highlighted the striking diversity of shell microstructures in pteropods, with exceptional mechanical properties, but their evolution and future in acidified waters remains uncertain. Here, we re…