Search results for "SHELL"
showing 10 items of 748 documents
Self-consistent continuum solvation (SCCS): the case of charged systems.
2013
The recently developed self-consistent continuum solvation model (SCCS) [O. Andreussi, I. Dabo, and N. Marzari, J. Chem. Phys. 136, 064102 (2012)] is applied here to charged species in aqueous solutions. Describing ions in solution represents a great challenge because of the large electrostatic interactions between the solute and the solvent. The SCCS model is tested over 106 monocharged species, both cations and anions, and we demonstrate its flexibility, notwithstanding its much reduced set of parameters, to describe charged species in solution. Remarkably low mean absolute errors are obtained with values of 2.27 and 5.54 kcal/mol for cations and anions, respectively. These results are co…
History of bioavailable lead and iron in the Greater North Sea and Iceland during the last millennium – A bivalve sclerochronological reconstruction
2014
We present the first annually resolved record of biologically available Pb and Fe in the Greater North Sea and Iceland during 1040-2004 AD based on shells of the long-lived marine bivalve Arctica islandica. The iron content in pre-industrial shells from the North Sea largely remained below the detection limit. Only since 1830, shell Fe levels rose gradually reflecting the combined effect of increased terrestrial runoff of iron-bearing sediments and eutrophication. Although the lead gasoline peak of the 20th century was well recorded by the shells, bivalves that lived during the medieval heyday of metallurgy showed four-fold higher shell Pb levels than modern specimens. Presumably, pre-indus…
Empirical calibration of the clumped isotope paleothermometer using calcites of various origins
2014
We present the first universal calibration of the clumped isotope thermometer for calcites of various mineralizing types. These are an eggshell of an ostrich, a tropical bivalve, a brachiopod shell, cold seep carbonate, and three foraminifera samples that grew between 9 and 38 C. CaCO3 was digested at 90 C using a common acid bath. Considering a difference in phosphoric acid fractionation factors between reaction at 25 and 90 C of 0.069& (Guo et al., 2009), the function between growth temperature T and the excess of 13 C– 18 O bonds in the evolved CO2 is expressed by a linear regression between 1/T 2 and absolute D47 (R 2 = 0.9915):
The mean square nuclear charge radius of
1996
We report on a collinear laser spectroscopy measurement of the nuclear charge radius of (I = 3/2), yielding . Within the experimental accuracy, the N = 20 neutron shell closure has no influence on the charge radii of the calcium isotopes.
Determining seasonality of mussel collection from an early historic Inuit site, Labrador, Canada: Comparing thin-sections with high-resolution stable…
2018
International audience; Stable oxygen isotope (delta O-18) analysis of mussels (Mytilus sp.) from a 16th to mid-18th century Inuit site in southern Labrador, Canada, indicates multiple seasons of shellfish collection, and by proxy, multiple seasons of site occupation. High-resolution delta O-18 sampling of shell permits a precise season of mussel collection since the temperature and freshwater signal of the local water is retained in the shell. Live-collected specimens of Mytilus sp. obtained from Labrador, were analyzed for stable oxygen isotopes and for growth patterns. These data were used to interpret results from the archaeological shells. Growth pattern analysis was conducted to test …
Le conchiglie di Lamarck come beni culturali
2012
Con questo contributo si è voluto ricordare che nella turbolenta Francia nel 1793 per la prima volta i beni naturali vengono ufficialmente riconosciuti anche come beni culturali facenti parte del patrimonio di un popolo, che li deve custodire e tutelare. Il tutto era scaturito dalla necessità di salvare dalla distruzione due acquasantiere costituite da 2 valve di tridacna, una conchiglia esotica, presenti nella Chiesa di S. Sulpice a Parigi. A questo importante evento partecipò attivamente anche Jean Baptiste Lamarck, Professore di Zoologia degli Insetti e dei Vermi presso il Museo Nazionale di Storia Naturale di Parigi. Proprio dallo studio delle conchiglie attuali, comparate con quelle fo…
Effects of pyrolysis conditions on the porous structure development of date pits activated carbon
2012
International audience; Activated carbons were prepared from biomass of Algerian date pits for developing efficient and cheap adsorbents in the aim to remove heavy metals from waste water. Carbon adsorbents were obtained following two successive treatments: pyrolysis under dry nitrogen flow and physical activation under wet nitrogen flow. Pyrolysis process was optimized by varying some operating parameters such as temperature, nitrogen flow, heating rate and pyrolysis hold time in order to determine their effects on the porous structure development of date pits activated carbon. Chars obtained from pyrolysis process were activated with the same operating conditions (activation temperature o…
Limiting transport properties of lanthanide and actinide ions in pure water
2003
Summary The limiting transport properties, i.e. the limiting ionic conductivity (λ°) and the limiting diffusion coefficient (D°), of lanthanide and actinide ions at 298.15K have been calculated by means of the microscopic version of the Stokes–Einstein law involving (i) the effective charge and the ionic radius of the ions and (ii) the ion micro-viscosity, i.e. the viscosity of the hydrated water molecules in the vicinity of the ion. The latter quantity was derived from the variation of the dynamic properties of the water molecules in the first hydration shell with the surface charge density of common mono-atomic cations of various charges. The obtained results were found to be consistent w…
Core–Shell Engineering to Enhance the Spectral Stability of Heterogeneous Luminescent Nanofluids
2017
This work was supported by the Spanish Ministerio de Educación y Ciencia (MAT2016-75362-C3-1-R) and by COST Action CM1403. L.L.-P. thanks the Universidad Autónoma de Madrid for the ‘‘Formación de Personal Investigador (FPI-UAM)’’program. P.H.-G. thanks the Spanish Ministerio de Economia y Competitividad for the Juan de la Cierva program (IJCI-2015-24551). M.P. and A.S. thank University of Verona (Italy) for financial support in the framework of the ‘‘Cooperint 2016’’ and “Ricerca di Base 2015” projects. The work of K.S. was supported by Latvian National Research Program IMIS2 (Grant No. 302/2012).
Étude théorique de la dynamique du réseau de PbTiO3 dans la phase quadratique
1999
Resume La dynamique du reseau du titanate de plomb PbTiO 3 est etudiee en phase quadratique a l'aide d'un modele a coquille tenant compte des polarisabilites electroniques des ions de la maille elementaire et des interactions a longue et a courte portee. Les resultats de nos calculs mettent en evidence le role important joue par l'anisotropie de la polarisabilite electronique de l'oxygene. Il est montre aussi que les courbes de dispersion des phonons calculees dans la premiere zone de Brillouin sont en bon accord avec l'experience.