Species with negative electron affinity and standard DFT methods. Finding the valence anions

Recently, we have shown that traditional bound-electron DFT models are reliable enough to reproduce negative electron affinities (EA) within a few meV, as long as the valence anion state is found, but they seem to fail in predicting the lowest EA when the ground anion state obtained is non-valence, which holds the extra electron in a diffuse orbital around the molecule; here we propose an alternative approach for finding the valence anion state, based on the stabilization exerted by a polar solvent; the methodology yields correct EA values (i.e. beyond the Koopman's theorem approximation) by gradually decreasing the dielectric constant of the medium.     

Poly(ether ester amide) microspheres for protein delivery: influence of copolymer composition on technological and biological properties

The production of PEEA microspheres with potential as carriers for protein oral delivery is described. PEEAs with different hydrophilicity were synthesized and characterized. Experiments showed that an increase in copolymer hydrophilicity gave particles less prone to cell interaction. BSA release profiles from PEEA microspheres demonstrated that an increase in polymer hydrophilicity was useful in limiting protein burst and modulating drug delivery rate by increasing PEEA degradability. These results show that fine-tuning of the hydrophilic/hydrophobic properties of PCL is essential for the formulation protein-loaded microspheres with specific properties.     

One‐pot synthesis of N2‐aminoprotected 6‐substituted and cycloalka[d] 4‐trifluoromethyl‐2‐acetylaminopyrimidines

The one‐pot synthesis of a novel series of amino‐protected 6‐alkyl‐, 6‐aryl‐, 6‐heteroaryl‐ and 5,6‐fused‐cycloalkane 4‐trifluoromethyl‐2‐acetylaminopyrimidines, where alkyl = Me; aryl = Ph, 4‐CH₃Ph, 4‐FPh, 4‐ClPh, 4‐BrPh, 4‐OCH₃Ph, 4‐NO₂Ph, 4,4′‐biphenyl, 1‐naphthyl; heteroaryl = 2‐thienyl, 2‐furyl and cycloalkyl = c‐C₆H₄, c‐C₇H₅ from the reaction of substituted 4‐methoxy‐1,1,1‐trifluoroalk‐3‐en‐2‐ones with 1‐acetylguanidine in acetonitrile or propan‐2‐ol as solvent, is reported. The acetylamino group of 2‐acetylaminopyrimidines was hydrolyzed under three different conditions to afford the corresponding free 2‐aminopyrimidines.     

Some approximation properties of a Durrmeyer variant of q‐Bernstein–Schurer operators

In this paper, we will propose a Durrmeyer variant of q‐Bernstein–Schurer operators. A Bohman–Korovkin‐type approximation theorem of these operators is considered. The rate of convergence by using the first modulus of smoothness is computed. The statistical approximation of these operators is also studied. Copyright © 2016 John Wiley & Sons, Ltd.     

The R<Subscript>2</Subscript>Pd<Subscript>3</Subscript>Ge<Subscript>5</Subscript> (R = La–Nd,Sm) germanides: synthesis,crystal structure and symmetry reduction

Direct synthesis and structural characterization of a series of polar rare earth palladium germanides of R₂Pd₃Ge₅ composition (R = La–Nd, Sm) is reported. The crystal structure of the Nd representative was determined by single-crystal X-ray diffraction analysis (U₂Co₃Si₅-type, SG: Ibam, oI40, Z = 4, a = 10.1410(6), b = 12.0542(8), c = 6.1318(4) Å, wR ₂ = 0.0306, 669 F ² values, 31 variables). The crystal structures of the other homologues were ensured by powder X-ray diffraction pattern analysis. A smooth variation of the cell dimensions is observed through the rare earth series. The structure of the studied compounds can be interpreted as consisting of a complex three-dimensional [Pd₃Ge₅]^δ? network spaced by the rare earth cations. Within the concept of symmetry reduction, a Bärnighausen tree is used to rationalize the related crystal structures of the RPd₂Ge₂, RPdGe₃ and R₂Pd₃Ge₅ ternary compounds, enriching the large family of the BaAl₄ derivatives. Moreover, syntheses with metal fluxes were performed, some of which were successful to obtain large crystals of La₂Pd₃Ge₅ (using Bi as solvent) and Nd₂Pd₃Ge₅ (using Pb as solvent) stoichiometry.     

An interlaboratory comparison on whole water samples

The European Water Framework Directive 2000/60/EC requires monitoring of organic priority pollutants in so-called whole water samples, i.e. in aqueous non-filtered samples that contain natural colloidal and suspended particulate matter. Colloids and suspended particles in the liquid phase constitute a challenge for sample homogeneity and stability. Within the joint research project ENV08 “Traceable measurements for monitoring critical pollutants under the European Water Framework Directive 2000/60/EC”, whole water test materials were developed by spiking defined amounts of aqueous slurries of ultra-finely milled contaminated soil or sediment and aqueous solutions of humic acid into a natural mineral water matrix. This paper presents the results of an European-wide interlaboratory comparison (ILC) using this type of test materials. Target analytes were tributyltin, polybrominated diphenyl ethers and polycyclic aromatic hydrocarbons in the ng/L concentration range. Results of the ILC indicate that the produced materials are sufficiently homogeneous and stable to serve as samples for, e.g. proficiency testing or method validation. To our knowledge, this is the first time that ready-to-use water materials with a defined amount of suspended particulate and colloidal matter have been applied as test samples in an interlaboratory exercise. These samples meet the requirements of the European Water Framework Directive. Previous proficiency testing schemes mainly employed filtered water samples fortified with a spike of the target analyte in a water-miscible organic solvent.     

Pretreatment processes for lignocellulosic biomass conversion to biofuels and bioproducts

Lignocellulosic materials, such as forestry, agricultural and agroindustrial residues, are among the most important sources of biomass for the production of fuels, chemicals and materials. However there are physical and chemical barriers in the lignin–carbohydrate supramolecular structure that render most plant cell wall components almost completely unavailable for conversion into commercial products. Thus successful conversion strategies must lead to the disruption of this structure and result in partial or total separation of the lignocellulosic components, increasing the accessibility of cellulose, hemicelluloses and lignins. It must also minimize the formation of by-products. Each pretreatment technology has its own characteristics and is usually applied to a specific source of carbohydrates and lignins. A general overview of the most important pretreatment methods for the production of platform chemicals and fermentable sugars are given in this paper.     

Complete assignment of 1H and 13C NMR spectra of some alpha-arylthio and alpha-arylsulfonyl substituted N-methoxy-N-methyl propionamides

The complete assignments of the 1H and 13C NMR spectra of the some alpha-arylthio and alpha-arylsulfonyl substituted N-methoxy-N-methyl propionamides, bearing methoxy, methyl, chloro, and nitro as substituents at the phenyl ring are reported.     

Effects of plant lactones on the production of biofilm of Pseudomonas aeruginosa

Sixteen plant sesquiterpene lactones, thirteen from four species of the Family Asteraceae, and three from a species of Hepaticae, as well as seven annonaceous acetogenins isolated from the seeds of the tropical tree Annona cherimolia (Family Annonaceae), were evaluated for their ability to inhibit or stimulate the production of biofilm by a strain of Pseudomonas aeruginosa. The tested compounds carry a gamma-lactone moiety in their structures. This structural feature is similar to the lactone moiety present in N-acyl homoserine lactones, compounds that play the important role of "quorum sensors" in the mechanisms of biofilm formation observed in many gram-negative bacteria. A special assay was employed to evaluate the influence of the tested plant compounds to inhibit or stimulate the production of biofilm in a P. aeruginosa wild strain. Most of the tested compounds affected the biofilm formation mechanism. Six sesquiterpene lactones isolated from Acanthospermum hispidum and one from Enydra anagallis as well as an acetogenin from Annona cherimolia strongly inhibited (69-77%) the biofilm formation when incorporated to a bacterial culture at a concentration of 2.5 microg/ml. However, one of the acetogenins, squamocin, stimulated the biofilm formation even at a concentration of 0.25 microg/ml. The study of substances affecting the biofilm formation can lead to the design of new strategies to control P. aeruginosa infections.