Improvement of tribological properties of co-acting elements by oil pockets creation on sliding surfaces

Sliding experiments were carried out using a block-on-ring friction machine. The tribosystem consists of the stationary block (counter-specimen) pressed at the required load P against the ring (specimen) rotating at the defined speed. The sliding was unidirectional. The block was a part of a bearing sleeve hardened EN-GJS 400-15 cast iron with a hardness value of 50 HRC. The ring samples, 35 mm in diameter, were made from hardened 42CrMo4 steel of hardness 32 HRC. Some variants of specimen surfaces were created by burnishing technique. Two kinds of experiments were done. Seizure tests were conducted at increasing pressure for sliding speeds in the range: 0.27–0.55 m/s. Wear resistance test was carried out under artificially increased dustiness conditions, too. It was found that surface texturing improved seizure resistance for the smallest sliding speed (0.27 m/s) comparing to untextured ground samples. The wear of steel rings with spherical dimples was smaller than of those having dimples of long drop shape for the pit-area ratio range of 7.5–20%.     

Isolation and confirmation of the proposed cleistanthol biogentic link from Croton insularis

The proposed cleistanthol biosynthetic intermediate en route to spruceanol, and other related family members, was isolated for the first time from Croton insularis, confirming the Jacobs-Reynolds hypothesis. Anticancer evaluation of the new isolates and their aerial oxidation products is also reported.     

New chiral P-N ligands for the regio- and stereoselective Pd-catalyzed dimerization of styrene

Two new chiral, enantiomerically pure, hybrid P-N ligands, namely (2R,5S)-2-phenyl-3-(2-pyridyl)-1,3-diaza-2-phosphanicyclo[3,3,0]octan-4-one (1) and (2R,5S)-2-phenyl-3-(2-pyridyl)-1,3-diaza-2-phosphanicyclo[3,3,0]octane (2), have been synthesized starting from L-proline. The two ligands differ in the presence or not of a carbonyl group in the diazaphosphane ring. Their coordination chemistry towards Pd(II) was studied by reacting them with [Pd(CH?)Cl(cod)]. A different behaviour was observed: ligand 2 shows the expected bidentate chelating behaviour leading to the mononuclear Pd-complex, while ligand 1 acts as a terdentate ligand giving a dinuclear species. The corresponding cationic derivatives were obtained from the palladium neutral complexes, both as mono- and dinuclear derivatives, and tested as precatalysts for styrene dimerization, yielding E-1,3-diphenyl-1-butene regio- and stereoselectively as the sole product. A detailed analysis of the catalytic behaviour is reported.     

One-step covalent grafting of Fe4 single-molecule magnet monolayers on gold

Iron(III)-based single-molecule magnets have been covalently grafted on Au(111) in one step using 1,2-dithiolan-3-yl side groups. Reaction with the substrate quantitatively affords a monolayer of electronically intact clusters doubly linked to the surface via Au-S bonds, as demonstrated by a combination of STM, XAS/XMCD and XPS studies.     

Intramolecular Michael reaction of tert-butylsulfinyl ketimines: asymmetric synthesis of 3-substituted indanones

Aromatic tert-butylsulfinyl ketimines bearing a suitable Michael acceptor at the ortho position readily undergo an intramolecular conjugate addition achieving indanone derivatives in good yields and complete diastereoselectivity.     

Base‐Dependent Stereodivergent Intramolecular Aza‐Michael Reaction: Asymmetric Synthesis of 1,3‐Disubstituted Isoindolines

The nucleophilic addition (A_N) / intramolecular aza‐Michael reaction (IMAMR) process on Ellman’s tert‐butylsulfinyl imines, bearing a Michael acceptor in the ortho position, is studied. This reaction affords 1,3‐disubstituted isoindolines with a wide range of substituents in good yields and diastereoselectivities. Interestingly, careful choice of the base for the aza‐Michael step allows either the cis or the trans diastereoisomers to be exclusively obtained. This stereodivergent cyclization has enabled the synthesis of C₂‐symmetric bisacetate‐substituted isoindolines. In addition, bisacetate isoindolines bearing two well‐differentiated ester moieties are also noteworthy because they may allow for the orthogonal synthesis of β,β′‐dipeptides using a single nitrogen atom as a linchpin.     

Long-lived emission from Eu3+:PbF2 nanocrystals distributed into sol–gel silica glass

This paper reports an optical investigation of Eu³⁺:PbF₂ nanocrystals distributed into silica glasses fabricated by sol–gel methods. The sample microstructure was investigated using scanning transmission electron microscopy. The β-cubic PbF₂ crystalline phase was identified using X-ray diffraction analysis. The observed emission bands correspond to ⁵D₀ → ⁷F_J (J = 0–4) transitions of Eu³⁺. The spectroscopic parameters for Eu³⁺ ions were determined based on excitation and emission measurements as well as luminescence decay analysis. Emission originating from ⁵D₀ state of Eu³⁺ ions in sample containing PbF₂ nanocrystals is long-lived in comparison to precursor sol–gel silica glasses.     

Modeling peptide binding to anionic membrane pores

Peptide‐induced pore formation in membranes can be dissected into two steps: pore formation and peptide binding to the pore. A computational method is proposed to study the second step in anionic membranes. The electrostatic potential is obtained from numerical solutions to the Poisson–Boltzmann equation and is then used in conjunction with IMM1 (implicit membrane model 1). A double charge layer model is used to incorporate the effects of the membrane dipole potential. Inhomogeneity of the charge density in the pore, characterized by explicit membrane simulations of toroidal pores, is included in the model. This approach was applied to two extensively studied peptides, magainin and melittin. In agreement with previous work, binding to toroidal pores is more favorable than binding to the flat membrane. The dependence of binding energy on anionic content exhibits different patterns for the two peptides, in correlation with the different lipid selectivity that has been observed experimentally. © 2013 Wiley Periodicals, Inc.     

Novel concepts of dissolving pulp production

Herein, we report about existing and novel dissolving pulp processes providing the basis for an advanced biorefinery. The SO₂–ethanol–water (SEW) process has the potential to replace the acid sulphite process for the production of rayon-grade pulps owing to a higher flexibility in the selection of the raw material source, substantially lower cooking times, and the near absence of sugar degradation products. Special attention is paid to developments that target toward the selective and quantitative fractionation of paper-grade pulps into hemicelluloses and cellulose of highest purity. This target has been accomplished by the IONCELL process where the entire hemicellulose fraction is selectively dissolved in an ionic liquid in which the H-bond basicity and acidity are adequately adjusted by the addition of a co-solvent. At the same time, pure hemicellulose can be recovered by further addition of the co-solvent, which then acts as a non-solvent. The residual pure cellulose fraction may then enter a Lyocell process for the production of regenerated cellulose products.     

O-Alkylation of Bioactive Phthalimide Derivatives Under Microwave Irradiation in Dry Media

In this paper we describe the synthesis of a new series of substituted 2-(4-alkoxy or 4-acyloxyphenethyl)-phthalimide derivatives (4--11). in good yields (58--87%), exploring the remarkable fast O-alkylation or O-acylation of 2-(4-hydroxyphenethyl)-phthalimide (3) in dry media under microwave irradiation.