1,081 research outputs found
Reply to 'Comment on "Extending Hirshfeld-I to bulk and periodic materials" '
The issues raised in the comment by T.A. Manz are addressed through the
presentation of calculated atomic charges for NaF, NaCl, MgO, SrTiO and
LaCeO, using our previously presented method for calculating
Hirshfeld-I charges in Solids [J. Comput. Chem.. doi: 10.1002/jcc.23088]. It is
shown that the use of pseudo-valence charges is sufficient to retrieve the full
all-electron Hirshfeld-I charges to good accuracy. Furthermore, we present
timing results of different systems, containing up to over atoms,
underlining the relatively low cost for large systems. A number of theoretical
issues is formulated, pointing out mainly that care must be taken when deriving
new atoms in molecules methods based on "expectations" for atomic charges.Comment: 7 pages, 2 Tables, 2 figure
Extending Hirshfeld-I to bulk and periodic materials
In this work, a method is described to extend the iterative Hirshfeld-I
method, generally used for molecules, to periodic systems. The implementation
makes use of precalculated pseudo-potential based charge density distributions,
and it is shown that high quality results are obtained for both molecules and
solids, such as ceria, diamond, and graphite. The use of such grids makes the
implementation independent of the solid state or quantum chemical code used for
studying the system. The extension described here allows for easy calculation
of atomic charges and charge transfer in periodic and bulk systems.Comment: 11 pages, 4 Tables, 5 Figures, pre-referee draft only, much extended
post referee version only available at publishe
Continuous-feed nanocasting process for the synthesis of bismuth nanowire composites
We present a novel, continuous-feed nanocasting procedure for the synthesis
of bismuth nanowire structures embedded in the pores of a mesoporous silica
template. The immobilization of a bismuth salt inside the silica template from
a diluted metal salt solution yields a sufficiently high loading to obtain
electrically conducting bulk nanowire composite samples after reduction and
sintering the nanocomposite powders. Electrical resistivity measurements of
sintered bismuth nanowires embedded in the silica template reveal
size-quantization effects
Interpretando la Mina Rica (PulpĂ, Almeria): estructura, mineralogĂa y geoquĂmica.
En este trabajo se presenta la estructura, mineralogĂa y geoquĂmica de la Mina Rica, un excelente ejemplo de la metalogenia del SE peninsular. Para ello se ha realizado la cartografĂa geolĂłgica detallada de las galerĂas, el estudio etrogrĂĄfico de las zonas mineralizadas y no mineralizadas y el anĂĄlisis isotĂłpico de los sulfatos y sufuros
The origin of large gypsum crystals in the Geode of PulpĂ (AlmerĂa, Spain)
The Geode of PulpĂ (AlmerĂa, Spain) is an âŒ11 m3 ovoid cavity, the walls of which are covered with meter-sized idiomorphic and highly transparent gypsum (CaSO4â2H2O) crystals. We performed a thorough study based on field work, and petrographic and geochemical data collection, which aimed to reconstruct the geological history leading to the formation of this geode. The geode is hosted in mineralized Triassic carbonate rocks with a discontinuous mineral sequence from iron-carbonates and barite to celestine and finally gypsum (microcrystalline and selenite). Data from fluid inclusions show that barite precipitated above 100 °C, celestine at âŒ70 °C, and gypsum below 25 °C. All ÎŽ34S sulfate phases fall between Triassic and Tertiary evaporite values. Barite and gypsum, either microcrystalline or large selenite crystals, show variable ÎŽ34S and ÎŽ18O compositions, whereas celestine and centimetric selenite gypsum have homogeneous values. We propose that the growth of the large selenite crystals in the Geode of PulpĂ was the result of a self-feeding mechanism consisting of isovolumetric anhydrite replacement by gypsum at a temperature of 20 ± 5 °C, episodically contributed by a ripening process enhanced by temperature oscillations due to climatic change
New determination of gypsum isotope fractionation factor
Gypsum is a low temperature mineral of relevance for the understanding of evaporitic and late hydrotermal scenarios. Gypsum deposits are spread all over the geological record and their crystals may contain important information about the history of the seas
Messenger RNA electroporation: an efficient tool in immunotherapy and stem cell research.
Over the last decades medicine has developed tremendously, but still many diseases are incurable. The last years, cellular (gene) therapy has become a hot topic in biomedical research for the potential treatment of cancer, AIDS and diseases involving cell loss or degeneration. Here, we will focus on two major areas within cellular therapy, cellular immunotherapy and stem cell therapy, that could benefit from the introduction of neo-expressed genes through mRNA electroporation for basic research as well as for clinical applications. For cellular immunotherapy, we will provide a state-of-the-art on loading antigen-presenting cells with antigens in the mRNA format for manipulation of T cell immunity. In the area of stem cell research, we will highlight current gene transfer methods into adult and embryonic stem cells and discuss the use of mRNA electroporation for controlling guided differentiation of stem cells into specialized cell lineages
Unraveling the sulfate sources of (giant) gypsum crystals using gypsum isotope fractionation factors.
We combine newly determined isotope fractionation factors of gypsum precipitated in the laboratory with the isotopic compositions of natural anhydrite and gypsum to unravel the sulfate sources of the giant selenite crystals in the Naica mine (Chihuahua, Mexico). Gypsum was precipitated in the laboratory from CaSO4-NaCl-H2O solutions across a broad temperature range to establish the isotopic fractionation behavior of the sulfate molecule between the solid and dissolved phase. Oxygen isotopes show a significant fractionation dependence on temperature, with the solid phase more depleted in light isotopes with decreasing temperature. Sulfur isotopes display only a weak but similar dependence on temperature. At high salinity (4.5 M NaCl) no temperature dependence was found for the isotope composition. Based on this fractionation behavior, we attempt to elucidate the origin of the sulfate source(s) responsible for the formation of the (giant) gypsum crystals in the Naica mine. Detailed analysis of the isotopic composition of anhydrite, gypsum, and water samples strongly suggests that different types of anhydrite (of hypogenic and sedimentary origin) were dissolved to form these unique gypsum formations. The homogeneous isotopic composition of most gypsum crystals analyzed reveals an effective hydrodynamic mixing and a slow kinetics of precipitation fed by solutions of calcium sulfate from different anhydrite sources
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