Efficient and rapid experimental procedure for the synthesis of furan diol from d-glucal using ionic liquid

A new efficient and rapid experimental method and product isolation procedure as well as easy recyclable reaction media is expected to contribute to the development of a green strategy for the synthesis of furan diol from d-glucal. We determine the best conditions of reaction, minimizing the toxicity and finding an environmentally more acceptable process, using [Bmim][MSO₄]/InCl₃·3H₂O as a new solvent system under extremely mild conditions, providing high yields with a dramatic enhancement of reaction rate.     

Finite mixture modeling of censored and missing data using the multivariate skew-normal distribution

Advances in Data Analysis and Classification - Finite mixture models have been widely used to model and analyze data from a heterogeneous populations. Moreover, data of this kind can be missing or...     

Machine learning approach to discovery of small molecules with potential inhibitory action against vasoactive metalloproteases

Molecular Diversity - With the advancement of combinatorial chemistry and big data, drug repositioning has boomed. In this sense, machine learning and artificial intelligence techniques offer a...     

From linear to nonlinear PGD-based parametric structural dynamics

The present paper analyzes different integration schemes of solid dynamics in the frequency domain involving the so-called Proper Generalized Decomposition – PGD. The last framework assumes for the solution a parametric dependency with respect to frequency. This procedure allowed introducing other parametric dependences related to loading, geometry, and material properties. However, in these cases, affine decompositions are required for an efficient computation of separated representations. A possibility for circumventing such difficulty consists in combining modal and harmonic analysis for defining an hybrid integration scheme. Moreover, such a procedure, as proved in the present work, can be easily generalized to address nonlinear parametric dynamics, as well as to solve problems with non-symmetric stiffness matrices, always operating in the domain of low frequencies.     

Alkoxydiaminophosphine Ligands as Surrogates of NHCs in Copper Catalysis

A family of phosphine ligands containing a five-membered ring similar to the popular N-heterocyclic carbene ligands and an alkoxy third substituent has been developed. These alkoxydiaminophosphine ligands (ADAP) can be generated in one pot and reacted with a copper(I) source leading to the high yield isolation of complexes [(ADAP)CuX]₂ (X=Cl, Br). The dinuclear nature of these compounds has been established by means of X-ray studies and DOSY experiments. A screening of the catalytic properties of these complexes toward carbene-transfer reactions from diazocompounds to C−H bonds (alkane, arene), olefins or N−H bonds, as well as in CuAAC or nitrene transfer reactions have shown a performance at least similar, if not better, than their (NHC)CuCl analogues, opening a new window in copper catalysis with these readily tunable ADAP ligands.     

Consumption of calcium hydroxide and formation of C–S–H in cement pastes

The pozzolanic properties of the equilibrium catalyst (Ecat), an abundant waste from fluid catalytic cracking units of oil refineries, have been studied in cementitious matrices. The consumption of calcium hydroxide is usually taken as a means to assess the pozzolanicity of a material, ignoring the formation of C–S–H and other hydrates, the main product of the pozzolanic reaction. The use of thermal analysis methods allows the identification and quantification of the products of the hydration reaction, based on the loss of chemically combined water of phases present in a cementitious matrix. In the present study, TG/DTG techniques were used to quantify the amount of C–S–H + ettringite, C–A–S–H + C–A–H, and calcium hydroxide in cement–Ecat pastes, containing 0–40 % Ecat, aged for 1–28 days. The influence of the content of these phases on the mechanical properties of the resulting samples was also investigated by axial compression. The results further confirmed the pozzolanic activity of Ecat, so that the production of C–S–H and C–A–S–H increased with the aging time, but in a smaller amount than in the reference paste. The compressive strength test showed that the pastes containing 10 % Ecat, aged for 14 and 28 days, presented improved properties as compared to the corresponding references.     

Insights into molecular chemistry of Chiapas amber using infrared-light microscopy,PIXE/RBS,and sulfur K-edge XANES spectroscopy

Chiapas amber is a natural occurring fossil resin structurally composed of long macromolecule chains with semicrystalline phases associated with both fossil and polymerization process. The most conspicuous characteristic of this fossil polymer is that it preserves ancient organic inclusions. In the present work, PIXE/RBS spectrometry (particle-induced X-ray emission/Rutherford backscattering) were combined with complementary K-edge XANES spectroscopy (X-ray absorption near-edge structure) to identify the amount of sulfur in Chiapas amber. Initially, the amber samples were examined using infrared reflected photomicrography. Amber is transparent to infrared light and so embedded plants and animals are easily visible, showing them in extraordinary detail, as if they were immersed in a water-like solution. The PIXE/RBS data show that the proportion of sulfur in amber is significantly higher than that found in recently formed resins, consistent with the biogeochemical process that transforms the resin into amber during long-term burial in geological deposits. The sulfur K-edge XANES spectra from amber confirm the sulfur abundance and reveal sulfur species in the reduced and intermediate oxidation states in amber. Almost no oxidized sulfur was found, whereas the recent resins show mostly oxidized sulfur fractions. This indicates that labile oxidized sulfur decays during fossilization and resin maturation must occur under conditions of oxygen depletion. The implications of the presence of sulfur in amber for organic preservation is also discussed here. Sulfur compounds work as a polymer additive that promotes intense resin solidification. This restricts the early oxidant-specific biodegradation of the embedded biomatter and, over geological time, provides greater stability against chemical changes.     

Surface effects on the diagnostic of carbon/nitrogen low‐pressure plasmas studied by differentially pumped mass spectrometry

In this work, the characterization of the species produced in reactive plasmas by differentially pumped mass spectrometry is addressed. A H₂/CH₄/N₂ mixture (90 : 5 : 5) was fed into a direct current glow discharge and analysed by conventional and cryo‐trap assisted mass spectrometry. The gaseous mixture was chosen because of its particular relevance in the inhibition of tritium‐rich carbon film deposition in fusion plasmas (scavenger technique) and in the deposition of amorphous hydrogenated carbon films by plasma‐assisted chemical vapour deposition. Important changes in the composition of the detected species upon surface modification of the reactor walls (stainless steel or covered by an amorphous hydrogenated carbon layer) or in the way they are sampled (length and spatial configuration of the stainless steel duct) were detected. They are analysed in terms of radical formation and recombination on the reactor walls or into the sampling duct, thus providing some insight into the underlying chemistry. In general, when the reactor walls are covered by an amorphous hydrogenated carbon layer, more hydrocarbons are produced, but the radical production is lower and seem to be less reactive than in stainless steel. Also, two sources of oxygen contamination in the plasma have been identified, from the native oxide layer in stainless steel and from unintended water contamination in the chamber, which modify considerably the detected species. Copyright © 2014 John Wiley & Sons, Ltd.