Monte Carlo simulation of salt effect on water structure through 3D mechanistic potentials

Highly concentrated electrolyte solutions were studied through a Monte Carlo-based simulator, developed to consider the water molecules not a homogeneous dielectric as usual, but as dipoles that can move and rotate within a 3D lattice. This approach allowed fast calculations of detailed interactions between the particles, which were described from mechanistic potentials including dipole–dipole, ion–dipole, ion–ion, and hydrogen bonding (HB) interactions. A good agreement was found between experimental data and simulated results. The study also provides new insights about the balance of the different interactions in systems with or without electrolytes, and the effects of the electrolytes addition on the original water structure. The proposed model was also compared with previous explicit models.     

Syntheses, structures and intermolecular interactions of tetraorganoammonium, -phosphonium and -stibonium dimethyl- and diphenyltetrahaloantimonates

The syntheses and spectroscopic (NMR, MS) investigations of the antimonates [Ph₄P]⁺[Me₂SbCl₄]⁻ (1), [Me₄Sb]⁺[Me₂SbCl₄]⁻ (2), [Et₄N]⁺[Ph₂SbCl₄]⁻ (3), [Bu₄N]⁺[Ph₂SbCl₄]⁻ (4), [Me₄Sb]⁺[Ph₂SbCl₄]⁻ (5), [Et₃MeSb]⁺[Ph₂SbCl₄]⁻ (6), [Et₄N]⁺[Ph₂SbF₄]⁻ (7) and [Et₄N]⁺[Ph₂SbBr₄]⁻ (8) are reported. Halogen scrambling reactions of Et₄NBr or Ph₄EBr (E = P, Sb) with R₂SbCl₃ (R = Me, Ph) produce mixtures of compounds from which crystals of [Et₄N]⁺[Ph₂SbBr_1.24Cl_2.76]⁻ (9), [Et₄N]⁺[Ph₂SbBr_2.92Cl_1.08]⁻ (10) or [Ph₄Sb]⁺[Me₂SbCl₄]⁻ (11) were isolated. The crystal and molecular structures of 1 and 3-11 are reported.     

Protein–Inorganic Array Construction: Design and Synthesis of the Building Blocks

Herein we describe the design and synthesis of the first series of di‐functional ligands for the directed construction of inorganic‐protein frameworks. The synthesized ligands are composed of a metal‐ion binding moiety (terpyridine‐based) conjugated to an epoxysuccinyl peptide, known to covalently bind active cysteine proteases through the active‐site cysteine. We explore and optimize two different conjugation chemistries between the di‐functionalized metal‐ion ligand and the epoxysuccinyl‐containing peptide moiety: peptide‐bond formation (with limited success) and Cu^I‐catalysed click chemistry (with good results). Further, the complexation of the synthesized ligands with Fe^II and Ni^II ions is investigated: the di‐functional ligands are confirmed to behave similarly to the parent terpyridine. As designed, the peptidic moiety does not interfere with the complexation reaction, in spite of the presence of two triazole rings that result from the click reaction. ES‐MS together with NMR and UV/Vis studies establish the structure, the stoichiometry of the complexation reactions, as well as the conditions under which chemically sensitive peptide‐containing polypyridine ligands can undergo the self‐assembly process. These results establish the versatility of our approach and open the way to the synthesis of di‐functional ligands containing more elaborated polypyridine ligands as well as affinity labels for different enzyme families. As such, this paper is the first step towards the construction of robust supramolecular species that cover a size‐regime and organization level previously unexplored.     

Polymers with spatial or topological constraints: Theoretical and computational results

In this review, we provide an organized summary of the theoretical and computational results that are available for polymers subject to spatial or topological constraints. Because of the interdisciplinary character of the topic, we provide an accessible, non-specialist introduction to the main topological concepts, polymer models, and theoretical/computational methods used to investigate dense and entangled polymer systems. The main body of our review deals with (i) the effect that spatial confinement has on the equilibrium topological entanglement of one or more polymer chains and (ii) the metric and entropic properties of polymer chains with fixed topological states. These problems have important technological applications and implications for life sciences. Both aspects, especially the latter, are amply covered. A number of selected open problems are finally highlighted.     

Dynamic-susceptibility studies of the interplay between the Néel and Brown magnetic relaxation mechanisms

We have used temperature- and frequency-resolved ac-susceptibility measurements to investigate the magnetic relaxation of a Co_0.2Fe_2.8O₄ magnetic fluid above the freezing point of the liquid carrier. Our data show that both the Néel and the Brown relaxation mechanisms are operative at temperatures in the vicinity of the out-of-phase (imaginary) susceptibility peak. We separate the contributions of the two mechanisms to the overall relaxation time, and demonstrate that Brownian relaxation plays a dominant role at all temperatures within this high-dissipation regime.     

Approximation in weighted p-mean by RBF networks of Delsarte translates

We give conditions on the kernel function (or activation function) for the family of radial basis function (RBF) neural networks obtained upon replacing the usual translation by the Delsarte one, with not necessarily the same smoothing factor in all kernel nodes, to have the universal approximation property in suitable weighted L^p$L^p$-spaces (1?p<∞)$(1?p<\infty )$. A complete characterization of such kernels for p=1$p=1$ and p=2$p=2$ is provided.     

Optimizing the Electrocatalytic Activity of Surface Confined Co Macrocyclics for the Electrooxidation of Thiocyanate at pH 4

We have studied the trends in catalytic activity of several Co macrocyclics confined on the surface graphite electrodes for the oxidation of thiocyanate. A plot of log i (at constant E) versus the formal potential of the catalyst gives a volcano correlation, indicating that the Co(II/I) redox potential needs to be tuned, in order to achieve maximum reactivity. Graphite electrodes modified with Co phthalocyanine at pH 4 exhibit linear amperometric response for thiocyanate concentration in the range 10^?7 and 10^?3 M. Theoretical calculations show that electrocatalytic activity (as log i at constant E) plotted versus the energy of the LUMO of the Co complex also gives a volcano correlation.     

Periodic Solutions of Pendulum-Like Perturbations of Singular and Bounded $${\phi}$$-Laplacians

In this paper we study the existence and multiplicity of periodic solutions of pendulum-like perturbations of bounded or singular f{\phi}-Laplacians. Our approach relies on the Leray-Schauder degree and the upper and lower solutions method.     

Solutions for the storage and handling of SPINE standard pucks

Currently there is no rack system for the long‐term storage of SPINE pucks in spite of their commercial availability and heavy usage at the ESRF. The only way to store pucks is in transport dewar canisters which presents a number of limitations and drawbacks. Here a simple affordable rack for storing SPINE pucks is described, which we believe is accessible to not only synchrotrons but also both academic and industrial research laboratories.