The Jahn-Teller effect: a case of incomplete theory for d4 complexes?

We present relativistic calculations at the four-component Dirac-DFT level for the geometries of the series of group 9 monoanionic hexafluorides MF(6)(-), M = Co, Rh, Ir. Highly correlated four-component relativistic CCSD(T) energies were also calculated for the optimized geometries. Spin-orbit coupling effects influence the geometrical preferences for molecular structures: relativistic calculations predict ground states with octahedral symmetries O(h)* for all hexafluorides in this study, while at the nonrelativistic limit, a structural deviation toward D(4h) ground state symmetries is predicted. Our findings suggest that relativistic effects have an important role in molecular structure preferences for the title hexafluorides.     

Electronic speckle pattern interferometry using vortex beams

We show that it is possible to perform electronic speckle pattern interferometry (ESPI) using, for the first time to our knowledge, vortex beams as the reference beam. The technique we propose is easy to implement, and the advantages obtained are, among others, environmental stability, lower processing time, and the possibility to switch between traditional ESPI and spiral ESPI. The experimental results clearly show the advantages of using the proposed technique for deformation studies of complex structures.     

Topological study of the periodic system

We carried out a topological study of the Space of Chemical Elements, SCE, based on a clustering analysis of 72 elements, each one defined by a vector of 31 properties. We looked for neighborhoods, boundaries, and other topological properties of the SCE. Among the results one sees the well-known patterns of the Periodic Table and relationships such as the Singularity Principle and the Diagonal Relationship, but there appears also a robustness property of some of the better-known families of elements. Alkaline metals and Noble Gases are sets whose neighborhoods have no other elements besides themselves, whereas the topological boundary of the set of metals is formed by semimetallic elements.     

In Vitro and In Silico Anti-Arboviral Activities of Dihalogenated Phenolic Derivates of L-Tyrosine

Despite the serious public health problem represented by the diseases caused by dengue (DENV), Zika (ZIKV) and chikungunya (CHIKV) viruses, there are still no specific licensed antivirals available for their treatment. Here, we examined the potential anti-arbovirus activity of ten di-halogenated compounds derived from L-tyrosine with modifications in amine and carboxyl groups. The activity of compounds on VERO cell line infection and the possible mechanism of action of the most promising compounds were evaluated. Finally, molecular docking between the compounds and viral and cellular proteins was evaluated in silico with Autodock Vina^®, and the molecular dynamic with Gromacs^®. Only two compounds (TDC-2M-ME and TDB-2M-ME) inhibited both ZIKV and CHIKV. Within the possible mechanism, in CHIKV, the two compounds decreased the number of genome copies and in the pre-treatment strategy the infectious viral particles. In the ZIKV model, only TDB-2M-ME inhibited the viral protein and demonstrate a virucidal effect. Moreover, in the U937 cell line infected with CHIKV, both compounds inhibited the viral protein and TDB-2M-ME inhibited the viral genome too. Finally, the in silico results showed a favorable binding energy between the compounds and the helicases of both viral models, the NSP3 of CHIKV and cellular proteins DDC and β2 adrenoreceptor.     

Influence of nitrogen partial pressure on the microstructure and morphological properties of sputtered RuN coatings

In this work, the production of RuN thin films using the reactive direct current magnetron sputtering technique is presented. Samples were grown with varying Ar/N₂ ratio with values of 60/40, 80/20, 85/15, 90/10, 95/5, and 100/0. X‐ray photoelectron spectroscopy was employed to determine the presence of RuN before and after a sputtering etching process. According to the high‐resolution of N1s spectra, 3 peaks were identified at 397.4 ± 0.3 eV, 398.3 ± 0.3 eV, and 398.8 ± 0.3 eV binding energies, corresponding to hybridizations of nitrogen with transition metals, oxynitrides, and oxycarbides. X‐ray diffraction analyses were performed, showing the coexistence of the RuN face‐centered cubic and Ru hexagonal compact packed phases. After the etching process, the samples grown at nitrogen flow rates greater than 15% continued to show the RuN face‐centered cubic phase. Atomic force microscope analyses showed that as the nitrogen concentration increased, the grain size and roughness also tended to increase.     

The Mutation of the “Nobel Prize in Chemistry” into the “Nobel Prize in Chemistry or Life Sciences”: Several Decades of Transparent and Opaque Evidence of Change within the Nobel Prize Program

Over the past several decades, the Nobel Prize program has slowly but steadily been modified in both transparent and opaque ways. A transparent change has been the creation of the Nobel Prize in Economic Sciences, officially known as the Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel. An opaque change has been the mutation of the Nobel Prize in Chemistry into what is effectively the “Nobel Prize in Chemistry or Life Sciences.” This paper presents a detailed study of this opaque change, including evidence that the disciplines of chemistry and biochemistry cover, today, intellectually quite distinct and generally scientifically‐unrelated intellectual territory. This paper supports the evolution of the Nobel Prizes, and encourages the Nobel Prize program to move from opaque to transparent change processes for the next generations of achievement in the sciences.     

Dissecting Bonding Interactions in Cysteine Dimers

Neutral (n) and zwitterionic (z) forms of cysteine monomers are combined in this work to extensively explore the potential energy surfaces for the formation of cysteine dimers in aqueous environments represented by a continuum. A simulated annealing search followed by optimization and characterization of the candidate structures afforded a total of 746 structurally different dimers held together via 80 different types of intermolecular contacts in 2894 individual non-covalent interactions as concluded from Natural Bond Orbitals (NBO), Quantum Theory of Atoms in Molecules (QTAIM) and Non-Covalent Interactions (NCI) analyses. This large pool of interaction possibilities includes the traditional primary hydrogen bonds and salt bridges which actually dictate the structures of the dimers, as well as the less common secondary hydrogen bonds, exotic X⋯Y (X = C, N, O, S) contacts, and H⋯H dihydrogen bonds. These interactions are not homogeneous but have rather complex distributions of strengths, interfragment distances and overall stabilities. Judging by their Gibbs bonding energies, most of the structures located here are suitable for experimental detection at room conditions.     

Improved mixing condition on the grid for counting and sampling independent sets

The hard-core model has received much attention in the past couple of decades as a lattice gas model with hard constraints in statistical physics, a multicast model of calls in communication networks, and as a weighted independent set problem in combinatorics, probability and theoretical computer science. In this model, each independent set I in a graph G is weighted proportionally to λ^|I|, for a positive real parameter λ. For large λ, computing the partition function (namely, the normalizing constant which makes the weighting a probability distribution on a finite graph) on graphs of maximum degree Δ ≥ 3, is a well known computationally challenging problem. More concretely, let ${\lambda_c(\mathbb{T}_\Delta)}$ denote the critical value for the so-called uniqueness threshold of the hard-core model on the infinite Δ-regular tree; recent breakthrough results of Weitz (Proceedings of the 38th Annual ACM Symposium on Theory of Computing (STOC), pp. 140–149, 2006) and Sly (Proceedings of the 51st Annual IEEE Symposium on Foundations of Computer Science (FOCS), pp. 287–296, 2010) have identified ${\lambda_c(\mathbb{T}_\Delta)}$ as a threshold where the hardness of estimating the above partition function undergoes a computational transition. We focus on the well-studied particular case of the square lattice ${\mathbb{Z}^2}$ , and provide a new lower bound for the uniqueness threshold, in particular taking it well above ${\lambda_c(\mathbb{T}_4)}$ . Our technique refines and builds on the tree of self-avoiding walks approach of Weitz, resulting in a new technical sufficient criterion (of wider applicability) for establishing strong spatial mixing (and hence uniqueness) for the hard-core model. Our new criterion achieves better bounds on strong spatial mixing when the graph has extra structure, improving upon what can be achieved by just using the maximum degree. Applying our technique to ${\mathbb{Z}^2}$ we prove that strong spatial mixing holds for all λ < 2.3882, improving upon the work of Weitz that held for λ < 27/16 = 1.6875. Our results imply a fully-polynomial deterministic approximation algorithm for estimating the partition function, as well as rapid mixing of the associated Glauber dynamics to sample from the hard-core distribution.     

Determination of the optimum parameters in the high resolution thermogravimetric analysis (HRTG) for cementitious materials

In this article, the methodology to implementation of high resolution thermogravimetric analysis (HRTG) for construction materials like Portland cement pastes is presented. The aim of this technique is to make easier the identification of the decomposition reactions that frequently are overlapping on conventional thermogravimetric analysis (TG) like is the case of some mineral phases in the cement pastes. The optimum parameters related to sample mass and purge flow gas were established. It is necessary carried out the analysis with high quantity of sample (60 mg in this case) and without purge gas in order to get better results and excellent reproducibility. The tests have average heating rate higher than 3 °C min⁻¹ in the temperature range studied (35–300 °C), showing that the HRTG is not time-expensive technique.