Infrared cut-off proposal for the holographic density

We propose an infrared cut-off for the holographic dark energy, which besides the square of the Hubble scale also contains the time derivative of the Hubble scale. This avoids the problem of causality which appears using the event horizon area as the cut-off, and solves the coincidence problem.     

Ferrotoroidic moment as a quantum geometric phase

We present a geometric characterization of the ferrotoroidic moment tau in terms of a set of Abelian Berry phases. We also introduce a fundamental complex quantity z munu, which provides an alternative way to calculate tau and its moments and is derived from the tensor T munu=2 under summation operator jrj muSj nu. This geometric framework defines a natural computational approach for density functional and many-body theories.     

Vortices trapped in the damaged surroundings of antidots in Nb films – Depinning transition

The depinning transition of Vortex Matter in the presence of antidots in superconducting Nb films has been investigated. The antidots were fabricated using two different techniques, resulting in samples with arrays of diverse pinning efficiency. At low temperatures and fields, the spatial arrangement of Vortex Matter is governed by the presence of the antidots. Keeping the temperature fixed, an increase of the field induces a depinning transition. As the temperature approaches T_c, the depinning frontier exhibits a characteristic kink at the temperature T_k, above which the phase boundary exhibits a different regime. The lower-temperature regime is adequately described by a power-law expression, whose exponent n was observed to be inversely proportional to the pinning capability of the antidot, a feature that qualifies this parameter as a figure of merit to quantify the pinning strength of the defect.     

Immobile Pore-Water Storage Enhancement and Retardation of Gas Transport in Fractured Rock

Wet tensile testing is a common method to assess the stability of bentonite-bonded moulding sands. For wet tensile testing, a specimen is first heated from above in order to simulate heat-driven moisture transport induced by the casting process. Then, tensile stress is applied until rupture. In this study, neutron radiography imaging was applied to moulding sands in situ during heating and wet tensile testing in order to investigate the effects of water kinematics on the tensile strength. Neutron radiography allowed the localization of the rupture plane and the quantitative determination of the local water content with sub-mm resolution. Quantification of the temperature at the rupture plane and of the heat kinematics within the specimen was accomplished by temperature measurements both in situ and ex situ. In this way, experimental data correlating the wet tensile strength with the specific conditions of moulding sands at the rupture plane were obtained for the first time. Series of experiments with different initial sand moisture contents were conducted. The results show that the weakest location within a sand profile can be pinpointed at the interface between evaporation and condensation zone (i.e. at the 100 \(^\circ \)C isotherm), where water vaporization starts and the water bridges connecting the sand grains collapse. This weakest location has maximum strength, if the local water content at the rupture plane is between 5 and 9 wt.%. Less water leads to a strong decrease of wet tensile strength. More water requires an initial water content above 5 wt.%, which leads to a decrease of the tensile strength of the unheated sand.     

On the isostructural and superprotonic Cs<Subscript>5</Subscript>H<Subscript>3</Subscript>(SO<Subscript>4</Subscript>)<Subscript>4</Subscript>·<Emphasis Type="Italic">x</Emphasis>H<Subscript>2</Subscript>O transformations: physical or chemical nature?

For over 20 years, researchers have agreed that when pentacesium trihydrogen tetrasulfate hydrate (Cs₅H₃(SO₄)₄·xH₂O) is heated through 141 °C, the observed conductivity increase corresponds to a physical transformation: a first-order superprotonic phase transition. A careful high-temperature phase behavior examination of this acid salt was performed by means of simultaneous thermogravimetric and differential scanning calorimetry, conventional and modulated differential scanning calorimetry, and impedance spectroscopy. The results present evidence that this transformation is of chemical, instead of physical nature. The conductivity increase is an exclusive consequence of a partial thermal decomposition, where liquid water (dissolving part of the surface salt) and hygroscopic cesium pyrosulfate (Cs₂S₂O₇), as decomposition products, behave like a polymer electrolyte membrane where the proton transport mechanism includes the vehicle type, using hydronium (H₃O⁺) as a charge carrier. Additionally, it was found that the intermediate temperature transformation (so-called isostructural phase transition) at around 87 °C is also of chemical nature.     

Implementation of atomic basis set composed of 1s Gaussian and 1s Slater-type orbitals to carry out quantum mechanics molecular calculations

A mixed atomic basis set formed with ls Slater-type orbitals and 1s floating spherical Gaussian orbitals is implemented. Evaluation of multicenter integrals is carried out using a method based on expansion of binary products of atomic basis functions in terms of a complete basis set, and a systematic analysis is performed. The proposed algorithm is very stable and furnishes fairly good results for total energy and geometry. An LCAO-SCF test calculation is carried out on LiH. The trends observed show that there are some combinations of mixed orbitals that are appropriate to describe the system. ©1999 John Wiley & Sons, Inc. J Comput Chem 20: 604–609, 1999     

ChemInform Abstract: Electronic Structure of AlO2, AlO2‐, Al3O5, and Al3O5‐ Clusters.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Imaging the Footprint of Nanoscale Electrochemical Reactions for Assessing Synergistic Hydrogen Evolution

This work proposes a novel method for measuring the intrinsic activity of single metal-based nanoparticles towards water reduction in neutral media at industrially relevant current densities. Instead of using gas nanobubbles as proxy, the method uses optical microscopy to track the local footprint of the reaction through the precipitation of metal hydroxide, which is associated to the local pH increase during electrocatalysis. The results show the electrocatalytic activities of different types of metal nanoparticles and bifunctionnal core-shell nanostructures made of Ni and Pt, and demonstrate the importance of metal hydroxide nano-shells in enhancing electrocatalysis. This method should be generalizable to any electrocatalytic reaction involving pH changes such as nitrate or CO₂ reduction.