Quantum monte carlo study of the energetics of small hydrogenated and fluoride lithium clusters

An investigation of the energetics of small lithium clusters doped either with a hydrogen or with a fluorine atom as a function of the number of lithium atoms using fixed‐node diffusion quantum Monte Carlo (DMC) simulation is reported. It is found that the binding energy (BE) for the doped clusters increases in absolute values leading to a more stable system than for the pure ones in excellent agreement with available experimental measurements. The BE increases for pure, remains almost constant for hydrogenated, and decreases rapidly toward the bulk lithium for the fluoride as a function of the number of lithium atoms in the clusters. The BE, dissociation energy as well as the second difference in energy display a pronounced odd–even oscillation with the number of lithium atoms. The electron correlation inverts the odd–even oscillation pattern for the doped in comparison with the pure clusters and has an impact of 29%–83% to the BE being higher in the pure cluster followed by the hydrogenated and then by the fluoride. The dissociation energy and the second difference in energy indicate that the doped cluster Li₃H is the most stable whereas among the pure ones the more stable are Li₂, Li₄, and Li₆. The electron correlation energy is crucial for the stabilization of Li₃H. © 2016 Wiley Periodicals, Inc.     

Ag Doped Titanium Dioxide Nanocomposite‐modified Glassy Carbon Electrode as Electrochemical Interface for Catechol Sensing

The electrochemical sensing of catechol (CC) on a glassy carbon electrode modified with the ionothermal assisted synthesis of Ag doped TiO₂ a nanoparticle has been successfully demonstrated for the first time.Ag doped TiO₂ nanoparticles composite modified glassy carbon electrode exhibits higher electrocatalytic activity towards oxidation of catechol than glassy carbon electrode itself. The modified electrode also exhibits high selectivity towards this analyte in the presence of some of the metal ions and some of the biological compounds. Linear ranges and the limit of detections with the above electrode are 1–15 µM and 0.0249 µM respectively. The optimized protocol has been utilized for monitoring the catechol in some of the natural samples like apple juice and green tea and in industrial effluents.     

Synthesis and cytotoxic activity of some 3-benzyl-5-arylidenefuran-2(5H)-ones

3-Benzyl-furan-2(5H)-one (2a) and 3-(4-bromobenzyl)-furan-2(5H)-one (2b) were treated with TBDMSOTf and converted into the corresponding tert-butyldimethyl-silylfuran ethers. These furans were further condensed with several aromatic aldehydes affording compounds 5-14 with general 3-benzyl-5-arylidene-furan-2(5H)-one structures in 31% to 98% yields. Such compounds are analogues of the naturally occurring nostoclide lactones, reported to present moderate cytotoxic activity. Compounds 5-14 were submitted to an in vitro bioassay against the HL-60, HCT-8, SF295 and MDA-MB-435 cancer cell lines using the MTT cytotoxicity assay.     

Simultaneous distillation-extraction of high-value volatile compounds from Cistus ladanifer L

The present paper describes a procedure to isolate volatiles from rock-rose (Cistus ladanifer L.) using simultaneous distillation-extraction (SDE). High-value volatile compounds (HVVC) were selected and the influence of the extraction conditions investigated. The effect of the solvent nature and extraction time on SDE efficiency was studied. The best performance was achieved with pentane in 1 h operation. The extraction efficiencies ranged from 65% to 85% and the repeatability varied between 4% and 6% (as a CV%).The C. ladanifer SDE extracts were analysed by headspace solid phase microextraction (HS-SPME) followed by gas chromatography with flame ionization detection (GC-FID). The HS-SPME sampling conditions such as fiber coating, temperature, ionic strength and exposure time were optimized. The best results were achieved with an 85 μm polyacrylate fiber for a 60 min headspace extraction at 40 °C with 20% (w/v) of NaCl. For optimized conditions the recovery was in average higher than 90% for all compounds and the intermediate precision ranged from 4 to 9% (as CV %). The volatiles α-pinene (22.2 mg g⁻¹ of extract), 2,2,6-trimethylcyclohexanone (6.1 mg g⁻¹ of extract), borneol (3.0 mg g⁻¹ of extract) and bornyl acetate (3.9 mg g⁻¹ of extract) were identified in the SDE extracts obtained from the fresh plant material.     

Critical fluctuations of a binary fluid mixture confined in a porous medium

We have performed small angle neutron scattering experiments on the binary fluid mixture n-C₆H₁₄+n-C₈F₁₈ imbibed inside porous Vycor glass in the thermodynamic region corresponding to the bulk critical one. The resulting structure can be represented as the sum of a temperature dependent Lorentzian term and a term describing the interference between the porous matrix, a shell part richer in one component coating the glass surface, and a core part richer in the other component. We observe critical fluctuations extending over distances markedly larger than the mean pore size. Received 20 May 1999     

Feasibility of non-invasive temperature estimation by the assessment of the average gray-level content of B-mode images

This paper assesses the potential of the average gray-level (AVGL) from ultrasonographic (B-mode) images to estimate temperature changes in time and space in a non-invasive way.     

A supramolecular zigzag chain of organometallic dipoles mediated by PF6− anions

The title compound, (η⁵‐cyclo­penta­dienyl)(4‐nitro­benzo­nitrile‐κN)(trimethyl­phosphine‐κP)(triphenyl­phosphite‐κP)iron(II) hexa­fluoro­phosphate, [Fe(C₅H₅)(C₇H₄N₂O₂)(C₁₈H₁₅O₃P)(C₃H₉P)]PF₆, has been characterized by spectroscopic and X‐ray diffraction in order to evaluate the tuning of the electron density at the metal centre and the extension of the π delocalization on the mol­ecule due to the presence of phosphite and phosphine co‐ligands. The compound crystallizes in the centrosymmetric space group P2₁/c, which destroys the possibility of exhibiting any quadratic non‐linear optical properties. The packing shows a supramolecular zigzag chain of antiparallel cations connected via the PF₆⁻ anions through C—H⋯F^δ− inter­actions, with H⋯F distances ranging from 2.39 to 2.67 Å. Each zigzag chain is composed of isomeric organometallic fragments containing either R or S mol­ecules. These chains are connected through weak inter­molecular C—H⋯C inter­actions, forming a two‐dimensional plane parallel to (101).     

Ellipses Percolation

We define a continuum percolation model that provides a collection of random ellipses on the plane and study the connectivity behavior of the covered set and the vacant set, the one obtained by removing all ellipses. Our model generalizes a construction that appears implicitly in the Poisson cylinder model of Tykesson and Windisch. The ellipses model has a parameter \(\alpha > 0\) associated with the tail decay of the major axis distribution; we only consider distributions \(\rho \) satisfying \(\rho [r, \infty ) \asymp r^{-\alpha }\). We prove that this model presents a double phase transition in \(\alpha \). For \(\alpha \in (0,1]\) the plane is completely covered by the ellipses, almost surely. For \(\alpha \in (1,2)\) the vacant set is not empty but does not percolate for any positive density of ellipses, while the covered set always percolates. For \(\alpha \in (2, \infty )\) the vacant set percolates for small densities of ellipses and the covered set percolates for large densities. Moreover, we prove for the critical parameter \(\alpha = 2\) that there is a non-degenerate interval of densities for which the probability of crossing boxes of a fixed proportion is bounded away from zero and one. In this interval neither the covered set nor the vacant set percolate, a behavior that is similar to critical independent percolation on \(\mathbb {Z}^2\).