Facile Synthesis of 3-Alkyl-5-methyloxazolidine-2,4-diones and N-Lactoyl-N,N′-dialkylureas

The reaction between aliphatic amines and propylene carbonate can be performed in solventless conditions under microwave irradiation, becoming nearly complete within 15 min of irradiation. Oxidation of the formed mixture of 2-hydroxyethylcarbamates gives 3,5-methylalkyl-oxazolidine-2,4-diones. These compounds can react further with aliphatic primary amines to give N-lactoylureas.

Dynamic Complex‐to‐Complex Transformations of Heterobimetallic Systems Influence the Cage Structure or Spin State of Iron(II) Ions

Two new heterobimetallic cages, a trigonal‐bipyramidal and a cubic one, were assembled from the same mononuclear metalloligand by adopting the molecular library approach, using iron(II) and palladium(II) building blocks. The ligand system was designed to readily assemble through subcomponent self‐assembly. It allowed the introduction of steric strain at the iron(II) centres, which stabilizes its paramagnetic high‐spin state. This steric strain was utilized to drive dynamic complex‐to‐complex transformations with both the metalloligand and heterobimetallic cages. Addition of sterically less crowded subcomponents as a chemical stimulus transformed all complexes to their previously reported low‐spin analogues. The metalloligand and bipyramid incorporated the new building block more readily than the cubic cage, probably because the geometric structure of the sterically crowded metalloligand favours the cube formation. Furthermore it was possible to provoke structural transformations upon addition of more favourable chelating ligands, converting the cubic structures into bipyramidal ones.     

Argon cluster cleaning of Ga+ FIB-milled sections of organic and hybrid materials

Secondary ion mass spectrometry studies have been made of the removal of the degraded layer formed on polymeric materials when cleaning focused ion beam (FIB)-sectioned samples comprising both organic and inorganic materials with a 30-keV Ga⁺ FIB. The degraded layer requires a higher-than-expected Ar gas cluster ion beam (GCIB) dose for its removal, and it is shown that this arises from a significant reduction in the layer sputtering yield compared with that for the undamaged polymer. Stopping and Range of Ions in Matter calculations for many FIB angles of incidence on flat polymer surfaces show the depth of the damage and of the implantation of the Ga⁺ ions, and these are compared with the measured depth profiles for Ga⁺-implanted flat polymer surfaces at several angles of incidence using an Ar⁺ GCIB. The Stopping and Range of Ions in Matter depth and the measured dose give the sputtering yield volume for this damaged and Ga⁺-implanted layer. These, and literature yield values for Ga⁺ damaged layers, are combined on a plot showing how the changing sputtering yield is related to the implanted Ga density for several polymer materials. This plot contains data from both the model flat poly(styrene) surfaces and FIB-milled sections showing that these 2 surfaces have the same yield reduction. The results show that the damaged and Ga⁺-implanted layer's sputtering rate, after FIB sectioning, is 50 to 100 times lower than for undamaged polymers and that it is this reduction in sputtering rate, rather than any development of microtopography, that causes the high Ar⁺ GCIB dose required for cleaning these organic surfaces.     

Influence of dielectric barrier plasma treatment of ZnMgAl alloy-coated steel on the adsorption of organophosphonic acid monolayers

The adsorption of octadecyl phosphonic acid (ODPA) on oxide-covered surfaces of ZnMgAl alloy coatings is described as a function of a dielectric barrier discharge (DBD) pretreatment step. The ODPA monolayer formation enables the investigation of the influence of the DBD treatment on the resulting interfacial bond formation and surface coverage. Surface characterisation by means of surface spectroscopy (PM-IRRAS, XPS) and surface electrochemistry (cyclic voltammetry) showed that the DBD pretreatment with Ar, Ar/O₂ and Ar/H₂O gas mixtures leads to improved barrier properties of the adsorbed ODPA monolayer. Moreover, during ODPA monolayer formation from ethanolic solution, a partial etching of the surface oxide layer occurs.     

Long‐Lived Radical Cation Salts Obtained by Interaction of Monocyclic Arenes with Niobium and Tantalum Pentahalides at Room Temperature: EPR and DFT Studies

The 1:3 reactions of the alkoxy arenes 1,4‐(MeO)₂C₆H₄ and 1,4‐F₂‐2,5‐(MeO)₂C₆H₂ with TaF₅ in chloroform at 40–50 °C resulted in formation in about 35 % yield of the long‐lived radical cation salts [1,4‐(MeO)₂C₆H₄][Ta₂F₁₁] ( 2 a ) and [1,4‐F₂‐2,5‐(MeO)₂C₆H₂][Ta₂F₁₁] ( 2 b ), respectively. The non‐alkoxy‐substituted [arene][M₂X₁₁] [M=Ta, X=F: arene=C₆H₅Me ( 2 c ), 1,4‐C₆H₄Me₂ ( 2 d ), C₆H₅F ( 2 e ), C₆H₅NO₂ ( 2 f ); M=Nb, X=F: arene=C₆H₅Me ( 4 a ), 1,4‐C₆H₄Me₂ ( 4 b ), C₆H₅F ( 4 c ), C₆H₅NO₂ ( 4 d ); M=Ta, X=Cl: arene=1,4‐C₆H₄Me₂ ( 5 )] were obtained from the 3:1 reactions of MX₅ with the appropriate arene in chloroform at temperatures in the range 40–90 °C. Compounds 2 – 5 were detected by EPR spectroscopy (in CHCl₃) at room temperature, and their gas‐phase structures were optimized by DFT calculations. Formation of the M^IV species [MX₄(NCMe)₂] [M=Ta, X=F ( 3 a ); M=Nb, X=F ( 3 b ); M=Ta, X=Cl ( 3 c )] was ascertained by EPR spectroscopy on solutions obtained by treatment of the reaction mixtures with acetonitrile. Non‐selective reactions occurred upon combination of 1,4‐F₂‐2,5‐(MeO)₂C₆H₂ with AgNbF₆ (in CH₂Cl₂) and 1,4‐(MeO)₂C₆H₄ with SbF₅.     

Comparison of the Wetting Properties of Three Commonly Used Simulated Intestinal Fluids Used as Dissolution Media in the Characterization of Drugs

Simulated intestinal fluids (SIFs) are described in the United States Pharmacopoeia (USP) and the International Pharmacopoeia (IntPh) as recommended dissolution media for the characterization of solid drugs. This study was carried out to compare their wettability properties. Six different model substrates were used as surrogates for solid drugs. These surrogate solid substrates were characterized by the Lifshitz-van der Waals, electron donor and electron acceptor terms, which are the three components of the total surface energy obtained by the van Oss model, which is based upon Young’s equation. Contact angles of the SIFs on the surrogate solid-substrates were determined dynamically by image analysis up to five minutes after applying a drop of the fluid on the solid surface. Observed time-dependent spreading behavior was accounted for by a linear extrapolation of the experimental data to zero contact time to obtain the apparent equilibrium contact angle at zero time. Additionally, the pH, osmolality and buffer capacity of the SIFs were experimentally determined. Although some differences in osmolality and buffer capacity were observed, no statistically significant differences in the wetting properties of the three SIFs were detected. This confirms recent findings that there are no observed differences in dissolution behavior among these simulated intestinal fluids. Harmonization of these SIFs is thus recommended.     

Graphical Linking of MO Multicenter Bond Index and VB Structures. II- 5-c Rings and 6-c Heterocyclic Rings

Through the graphical method proposed, it is possible to create a link between an MO multicenter bond index and VB structures. The value of the index depends on the order of the atoms involved, if there are more than three. For 5-c rings, three basic structures are required; the eventually different values are 12. Unlike the 6-c case, it may happen that different pairs of basic structures are used to build the same polygon. For the 6-c rings, including heteroatoms, the original degeneracy of benzene splits, leading eventually to 60 different I_ring values.     

Effective Borel degrees of some topological functions

The focus of this paper is the incomputability of some topological functions (with respect to certain representations) using the tools of Borel computability theory, as introduced by V. Brattka in [3] and [4]. First, we analyze some basic topological functions on closed subsets of ?ⁿ , like closure, border, intersection, and derivative, and we prove for such functions results of Σ⁰₂‐completeness and Σ⁰₃‐completeness in the effective Borel hierarchy. Then, following [13], we re‐consider two well‐known topological results: the lemmas of Urysohn and Urysohn‐Tietze for generic metric spaces (for the latter we refer to the proof given by Dieudonné). Both lemmas define Σ⁰₂‐computable functions which in some cases are even Σ⁰₂‐complete. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Computing the asymptotic worst-case of bin packing lower bounds

This paper addresses the issue of computing the asymptotic worst-case of lower bounds for the Bin Packing Problem. We introduce a general result that allows to bound the asymptotic worst-case performance of any lower bound for the problem and to derive for the first time the asymptotic worst-case of the well-known bound L₃ by Martello and Toth. We also show that the general result allows to easily derive the asymptotic worst-case of several lower bounds proposed in the literature.