Organocatalytic strategies for the construction of optically active imidazoles, oxazoles, and thiazoles

This study demonstrates the first enantioselective synthesis of hydroxyalkyl- and aminoalkyl-substituted imidazoles, oxazoles, and thiazoles. The approach developed utilizes a highly effective one-pot reaction cascade that consists of either an organocatalytic epoxidation or aziridination of α,β-unsaturated aldehydes coupled with a [3+2]-annulation, in which amidines, ureas, or thioureas act as effective 1,3-dinucleophilic species. The methodology described benefits from low catalyst loadings, commercially and readily available starting materials, and mild reaction conditions.     

RP-HPLC analysis of phenolic acids of selected Central European Carex L. (Cyperaceae) species and its implication for taxonomy

Eighteen species belonging to the Carex genus were checked for the presence and the amount of eight phenolic acids (p-hydroxybenzoic, vanillic, caffeic, syringic, protocatechuic, p-coumaric, sinapic, and ferulic) by means of HPLC. Both the free and bonded phenolic acids were analyzed. The majority of the analyzed acids occurred in the studied species in relatively high amounts. The highest concentrations found were caffeic acid and p-coumaric acid, for which the detected levels were negatively correlated. A very interesting feature was the occurrence of sinapic acid, a compound very rarely detected in plant tissues. Its distribution across the analyzed set of species can be hypothetically connected with the humidity of plants' habitats. Several attempted tests of aggregative cluster analysis showed no similarity to the real taxonomical structure of the genus Carex. Thus, the phenolic acids' composition cannot be considered as the major taxonomical feature for the genus Carex.     

UV emission properties of highly Pr3+-doped YAG epitaxial waveguides

In this work we present and discuss the dependence of ultraviolet (UV) photoluminescence of praseodymium ion (Pr³⁺):YAG crystalline waveguides, produced by liquid phase epitaxy, on activator concentration. Praseodymium level influence on UV fluorescence intensity, transition linewidth and dynamics was carefully investigated in order to better understand the nature of processes shaping both the interconfigurational d–f emission and intraconfigurational f–f emissions starting from the ³P₀ excited state. The pathways and the role of interconfiguration cross-relaxation in quenching of the UV 4f5d emission are analyzed.     

Evaluation of the UFXC32k photon‐counting detector for pump–probe experiments using synchrotron radiation

This paper presents the performance of a single‐photon‐counting hybrid pixel X‐ray detector with synchrotron radiation. The camera was evaluated with respect to time‐resolved experiments, namely pump–probe–probe experiments held at SOLEIL. The UFXC camera shows very good energy resolution of around 1.5 keV and allows the minimum threshold setting to be as low as 3 keV keeping the high‐count‐rate capabilities. Measurements of a synchrotron characteristic filling mode prove the proper separation of an isolated bunch of photons and the usability of the detector in time‐resolved experiments.     

Electrical and spectral properties of organic salts formed from BEDT-TTF and magnetic anions

Spectral and electrical investigations of the semiconducting (BEDT-TTF)₂W₆O₁₉ and the metal-like (BEDT-TTF)₆(Mo₈O₂₆)(DMF)₃ salts were performed. The vibrational and electronic spectra of the crystalline samples were analysed and assignment of the vibrational features was proposed. The temperature evolution of the vibrational spectra of the (BEDT-TTF)₂W₆O₁₉ salt was discussed.     

Bispalladium(II) Complexes of di-p-Pyrirubyrin Derivatives as Promising Near-Infrared Photoacoustic Dyes

The insertion of palladium(II) into di-p-pyrirubyrin results in mutually convertible bimetallic complexes. Post-synthetic functionalization of one of them yielded bispalladium(II) dioxo-di-p-pyrirubyrin and, after demetallation, dioxo-di-p-pyrirubyrin, introducing for the first time the α,β′-pyridin-2-one unit into the macrocyclic frame. Bispalladium(II) di-p-pyrirubyrin 6 , bispalladium(II) dioxo-di-p-pyrirubyrin 9 , and dioxo-di-p-pyrirubyrin 10 absorb and emit light around 1000 nm and are characterized by high photostability. Thus, they are promising candidates for near-infrared photoacoustic dyes, ideally targeting ( 9 ) the wavelength of Yb-based fiber lasers. The incorporation of an α,β′-pyridine moiety into expanded porphyrins opens a highly interesting area of research due to the attractive optical and coordination properties of the resulting molecules.     

Compressible Navier-Stokes equations with ripped density

We are concerned with the Cauchy problem for the two-dimensional compressible Navier-Stokes equations  supplemented with general H¹ initial velocity and bounded initial density not necessarily strictly positive: it may be the characteristic function of any set, for instance. In the perfect gas case, we establish global-in-time existence and uniqueness, provided the volume (bulk) viscosity coefficient is large enough. For more general pressure laws (like e.g., $P={\rho }^{\gamma }$ with $\gamma >1$), we still get global existence, but uniqueness remains an open question. As a by-product of our results, we give a rigorous justification of the convergence to the inhomogeneous incompressible Navier-Stokes equations when the bulk viscosity tends to infinity. In the three-dimensional case, similar results are proved for short time without restriction on the viscosity, and for large time if the initial velocity field is small enough.     

Versatility of potential biomedical use of functional polysuccinates

Polysuccinates with pendant allyl groups (PSAGE) were synthesized by melt copolymerization of succinic anhydride with allyl glycidyl ether and eventually other glycidyl ethers. It was found that PSAGE could be crosslinked by radical copolymerization with methyl methacrylate. Oxidized PSAGE considered as multifunctional epoxy resin was cured with use of glutaric anhydride to form solid material susceptible to hydrolytic degradation to water-soluble non-toxic products. Comb-like amphiphilic polysuccinates containing both pendant poly(oxyethylene) chains and epoxy groups have been synthesized as well and checked for their solubility in water. Properties of PSAGE-type polymers suggests their potential use as biomaterials and polymeric drug carries. Please note, in the print publication of D. Theis, T. Schmidt, K.-F. Arndt, Macromol. Symp. 210 (2004), 465, erroneously the DOI 10.1002/masy.200450651 is repeated. There, the DOI should read: 10.1002/masy.200450652     

Ultraweak spectrally resolved thermoluminescence in polymers

Spectrally resolved thermoluminescence (TL) measurements provide a lot of information concerning trapping and recombination states in various dielectric materials. As long-lived luminescence is typically weak, this technique requires a very sensitive apparatus. This paper describes the measurement system that is used for studying spectrally resolved TL and phosphorescence decay in polymers. Exemplary investigations are presented for poly(N-vinylcarbazole) (PVK) thin films. The obtained spectra clearly indicate the influence of solvents (dioxane, chlorobenzene) and excitation wavelengths on TL in PVK samples.