Search results for "Alite"

Atomically Precise, Thiolated Copper–Hydride Nanoclusters as Single-Site Hydrogenation Catalysts for Ketones in Mild Conditions

2019

Copper-hydrides are known catalysts for several technologically important reactions such as hydrogenation of CO, hydroamination of alkenes and alkynes, and chemoselective hydrogenation of unsaturated ketones to unsaturated alcohols. Stabilizing copper-based particles by ligand chemistry to nanometer scale is an appealing route to make active catalysts with optimized material economy; however, it has been long believed that the ligand-metal interface, particularly if sulfur-containing thiols are used as stabilizing agent, may poison the catalyst. We report here a discovery of an ambient-stable thiolate-protected copper-hydride nanocluster [Cu25H10(SPhCl2)18]3- that readily catalyzes hydrogen…

Template-free synthesis and structural evolution of discrete hydroxycancrinite zeolite nanorods from high-concentration hydrogels.

2017

We report the synthesis and characterization of hydroxycancrinite zeolite nanorods by a simple hydrothermal treatment of aluminosilicate hydrogels at high concentrations of precursors without the use of structure-directing agents. Transmission electron microscopy (TEM) analysis reveals that cancrinite nanorods, with lengths of 200-800 nm and diameters of 30-50 nm, exhibit a hexagonal morphology and are elongated along the crystallographic c direction. The powder X-ray diffraction (PXRD), Fourier transform infrared (FT-IR) and TEM studies revealed sequential events of hydrogel formation, the formation of aggregated sodalite nuclei, the conversion of sodalite to cancrinite and finally the gro…

Charge Transfer Plasmons in Dimeric Electron Clusters

2020

The tunability of the optical response of dimers of metal clusters and nanoparticles makes them ideal for many applications from sensing and imaging to inducing chemical reactions. We have studied charge transfer plasmons in separate and linked dimers of closed-shell electron clusters of 8 and 138 electrons using time-dependent density functional theory. The simple model clusters enable the systematic study of the charge transfer phenomenon from the electronic perspective. To identify the charge transfer plasmons, we have developed an index, the Charge Transfer Ratio, for quantifying the charge transfer nature of the excitations. In addition, we analyze the induced transition density and th…

Iron Mineralogy of Venus' Surface Investigated by M�ssbauer Spectroscopy

2000

Abstract We discuss the use of Mossbauer (MB) spectroscopy to study Fe-bearing minerals on Venus' surface. At present, there is no direct information about the mineralogy of Venus' surface, although in situ chemical analyses by X-ray fluorescence (XRF) spectroscopy have been done by the Venera 13, 14, and Vega 2 spacecraft at three landing sites. The XRF elemental analyses are sensitive to major rock-forming elements heavier than sodium and show the presence of several mass percent iron. Normative mineralogical calculations model the Fe mineralogy at the Venera 13, 14, and Vega 2 landing sites, but the actual Fe minerals present are unknown. We calculate synthetic MB spectra for the normati…

Density functional theory description of random Cu-Au alloys

2019

Density functional alloy theory is used to accurately describe the three core effects controlling the thermodynamics of random Cu-Au alloys. These three core effects are exchange correlation (XC), ...

Novel Methodologies to Model Charge Transport in Metal-Air Batteries

2018

Gradient estimates for heat kernels and harmonic functions

2020

Let $(X,d,\mu)$ be a doubling metric measure space endowed with a Dirichlet form $\E$ deriving from a "carr\'e du champ". Assume that $(X,d,\mu,\E)$ supports a scale-invariant $L^2$-Poincar\'e inequality. In this article, we study the following properties of harmonic functions, heat kernels and Riesz transforms for $p\in (2,\infty]$: (i) $(G_p)$: $L^p$-estimate for the gradient of the associated heat semigroup; (ii) $(RH_p)$: $L^p$-reverse H\"older inequality for the gradients of harmonic functions; (iii) $(R_p)$: $L^p$-boundedness of the Riesz transform ($p<\infty$); (iv) $(GBE)$: a generalised Bakry-\'Emery condition. We show that, for $p\in (2,\infty)$, (i), (ii) (iii) are equivalent, wh…

Tensorization of quasi-Hilbertian Sobolev spaces

2022

The tensorization problem for Sobolev spaces asks for a characterization of how the Sobolev space on a product metric measure space $X\times Y$ can be determined from its factors. We show that two natural descriptions of the Sobolev space from the literature coincide, $W^{1,2}(X\times Y)=J^{1,2}(X,Y)$, thus settling the tensorization problem for Sobolev spaces in the case $p=2$, when $X$ and $Y$ are infinitesimally quasi-Hilbertian, i.e. the Sobolev space $W^{1,2}$ admits an equivalent renorming by a Dirichlet form. This class includes in particular metric measure spaces $X,Y$ of finite Hausdorff dimension as well as infinitesimally Hilbertian spaces. More generally for $p\in (1,\infty)$ we…

Freshening of the Mediterranean Salt Giant: controversies and certainties around the terminal (Upper Gypsum and Lago-Mare) phases of the Messinian Sa…

2021

The late Miocene evolution of the Mediterranean Basin is characterized by major changes in connectivity, climate and tectonic activity resulting in unprecedented environmental and ecological disruptions. During the Messinian Salinity Crisis (MSC, 5.97-5.33 Ma) this culminated in most scenarios first in the precipitation of gypsum around the Mediterranean margins (Stage 1, 5.97-5.60 Ma) and subsequently > 2 km of halite on the basin floor, which formed the so-called Mediterranean Salt Giant (Stage 2, 5.60-5.55 Ma). The final MSC Stage 3, however, was characterized by a "low-salinity crisis", when a second calcium-sulfate unit (Upper Gypsum; substage 3.1, 5.55-5.42 Ma) showing (bio)geochemica…

Ages and stratigraphical architecture of late Miocene deposits in the Lorca Basin (Betics, SE Spain): New insights for the salinity crisis in margina…

2020

International audience; Unlike most Neogene basins of the Betic Cordillera where the Salinity Crisis is dated to the Messinian, a contradictory Tortonian dating was proposed for evaporites of the Lorca Basin. As a consequence, complex structural models have been proposed in the literature to explain this discrepancy in the timing of evaporites. In order to integrate the Lorca Basin into the geological context of the western Mediterranean domain during the Late Miocene, new sedimentological and stratigraphical studies coupled with new dating were performed, which allow us to propose a Messinian age for both diatomite-bearing deposits and evaporites of the Lorca Basin. These new ages challeng…