Optimization of the direct LSC method for determination of biogenic component in liquids by applying 14C

Journal of Radioanalytical and Nuclear Chemistry - Determination of fraction of biogenic component in liquid fuels by a direct radiocarbon measurement in liquid scintillation counter (direct-LSC...     

Triblock Terpolymers by Simultaneous Tandem Block Polymerization (STBP)

A route of synthesizing triblock terpolymers in a one‐pot, “one‐step” polymerization approach is presented. The combination of two distinct polymerization techniques through orthogonal catalyst/initiator functionalities attached to a polymeric linker furnishes novel pathways to ABC‐terpolymers. Both polymerizations have to be compatible regarding mechanisms, chosen monomers, and solvents. Here, an α,ω‐heterobifunctional poly(ethylene glycol) serves as poly­meric catalyst/initiator to obtain triblock terpolymers of poly(norbornene)‐b‐poly(ethylene glycol)‐b‐poly(l ‐lactic acid) PNB‐PEG‐PLLA via simultaneous ring opening metathesis poly­merization and ring opening polymerization in a fast one‐pot polymerization. Structural characterization of the polymers is provided via ¹H‐, DOSY‐, and ¹H,¹H‐COSY‐NMR, while solution and thin film self‐assembly are investigated by dynamic light scattering and atomic force microscopy.

     

Spherical Polyolefin Particles from Olefin Polymerization in the Confined Geometry of Porous Hollow Silica Particles

Porous hollow silica particles (HSPs) are presented as new templates to control the product morphology in metallocene‐catalyzed olefin polymerization. By selectively immobilizing catalysts inside the micrometer‐sized porous hollow silica particles, the high hydraulic forces resulting from polymer growth within the confined geometries of the HSPs cause its supporting shell to break up from the inside. As the shape of the support is replicated during olefin polymerization, perfectly spherical product particles with very narrow size distribution can be achieved by using HSPs exhibiting a monomodal size distribution. Furthermore, the size of the obtained product particles can be controlled not only by the polymerization time but also by the size of the support material.

     

Spectra of some block operator matrices and application to transport operators

In this paper a new concept for a 3×3 block operator matrix is studied on a Banach space. It is shown that, under certain conditions, it defines a closable operator and its essential spectra are determined. Application to transport operators in L₁-space is given.     

On the first polyarsenic organic compound from nature: arsenicin A from the New Caledonian marine sponge Echinochalina bargibanti

Reported here is the first polyarsenic compound ever found in nature. Denominated arsenicin A, it was isolated along a bioassay-guided fractionation of the organic extract of the poecilosclerid sponge Echinochalina bargibanti collected from the north-eastern coast of New Caledonia. In defining an adamantine-type polyarsenic structure for this compound, deceptively simple NMR spectra were complemented by extensive mass spectral analysis. However, it was only the synthesis of a model compound that provided the basis to discriminate structure 4 from other spectrally compatible structures for arsenicin A; to this end, a comparative ab initio simulation of IR spectra for the natural and the synthetic compounds was decisive. Arsenicin A is endowed with potent bactericidal and fungicidal activities on human pathogenic strains. All this may revive pharmacological interest in arsenic compounds while prompting us to rethink the arsenic cycle in nature.     

Determination of calibration function in thermal field flow fractionation under thermal field programming

A new procedure for determining the calibration function able to relate retention and operative parameters to molecular weight of the species in thermal field flow (ThFFF) under thermal field programming (TFP) conditions is presented. The procedure involves determining the average values of retention parameters under TFP and determining a numerical function related to the temperature variations that occur during TFP. The calibration parameters are obtained by a procedure fitting the retention and operative parameters that hold true at the beginning of the TFP. The procedure is closely related to the one previously developed to calibrate the retention time axis under TFP ThFFF and, together, they constitute a full calibration procedure. Experimental validation was performed with reference to polystyrene (PS)-decalin and PS-THF systems. The calibration functions here obtained were compared to those derived by the classical procedure at constant thermal field ThFFF to obtain the calibration function at variable cold wall temperatures. Excellent agreement was found in all cases proving "universality" of the ThFFF calibration concept, i.e. it is independent of the particular system on which it was determined and can thus be extended to ThFFF operating under TFP. The new procedure is simpler than the classical one since it requires less precision in setting the instrumentation and can be obtained with fewer experiments. The potential applications for the method are discussed.     

Differential proteome analysis of tonsils from children with chronic tonsillitis or with hyperplasia reveals disease-associated protein expression differences

A proteomic approach has been used to establish a proteome map and differentiate between the protein composition of tonsils from patients with chronic tonsillitis (CT) and that of tonsils with hyperplasia (HPL). Two-dimensional gel analysis was performed with material from four patients with HPL and five patients with CT. An average of approximately 600 spots were detected in each gel. A total of 127 different proteins were identified in 158 spots analyzed by mass spectrometry. Our study revealed disease-associated differences between protein abundance for two protein spots, an HSP27 isoform and UMP-CMP kinase. Both protein spots were more abundant in the CT group. HSP27 ELISA was performed for 32 patients, 12 belonging to the HPL group and 20 to the CT group. ELISA could not be used to differentiate HSP27 isoforms nor to distinguish CT from HPL. HSP27 was found to migrate to two further protein spots in the 2D gels. The differently expressed HSP27 isoform migrated as the most acidic of all the HSP27 isoforms detected, indicating the highest degree of phosphorylation. The sum of all three HSP27 abundances in the gels from the CT group was not different from that of the HPL group, consistent with the ELISA results. Our results suggest that phosphorylation differences caused the observed migration differences of HSP27. Together with the UMP-CMP kinase abundance differences, we conclude that kinase and/or phosphatase activity are different in CT and HPL. This paper was presented at the 38th Annual Meeting of the German Society for Mass Spectrometry (DGMS) held in March 2005 in Rostock, Germany.     

Luminescent Properties of a Silicone-Carbazolyl Polyfluorene Hybrid Material for Device Applications

In the present work, bilayered hybrids obtained by hydrosilylation of polysiloxane with carbazolyl moieties (Sil-Cz) and polyfluorene (Sil-PFO) had their photophysical behavior, morphological characteristics and interaction properties studied for applications in electroluminescent devices. Fluorescence spectra of the Sil-Cz did not show emission in the excimer/aggregate region (from 400 to 500 nm). This is an unexpected behavior since most of the carbazole-based materials present excimer and aggregation. Nonetheless, this unusual observation was also predicted by geometry optimization calculations. Fluorescence spectra were taken for both compounds separately and for the bilayered system show some evidence of interaction between carbazolyl and polyfluorene moieties, giving rise to the supposition that the can form a system with tunable luminescent properties.     

Anodic oxidation of organometallic sandwich complexes using [Al(OC(CF3)3)4] or [AsF6] as the supporting electrolyte anion

Anodic voltammetry and electrolysis of the metallocenes ferrocene, ruthenocene, and nickelocene have been studied in dichloromethane containing two different fluorine-containing anions in the supporting electrolyte. The perfluoroalkoxyaluminate anion [Al(OC(CF₃)₃)₄]⁻ has very low nucleophilicity, as shown by its inertness towards the strong electrophile [RuCp₂]⁺ and by computation of its electrostatic potential in comparison to other frequently used electrolyte anions. The low ion-pairing ability of this anion was shown by the large spread in E_1/2 potentials (ΔE_1/2 = 769 mV) for the two one-electron oxidations of bis(fulvalene)dinickel. The hexafluoroarsenate anion [AsF₆]⁻, on the other hand, reacts rapidly with the ruthenocenium ion and is much more strongly ion-pairing towards oxidized bis(fulvalene)dinickel (ΔE_1/2 = 492 mV). In terms of applications of these two anions to the anodic oxidation of organometallic sandwich complexes, the behavior of [Al(OC(CF₃)₃)₄]⁻ is similar to that of other weakly-coordinating anions such as [B(C₆F₅)₄]⁻, whereas that of [AsF₆]⁻ is similar to the more traditional electrolyte anions such as [PF₆]⁻ and [BF₄]⁻. Additionally, the synthesis and crystal structure of [Cp₂Fe][Al(OC(CF₃)₃)₄] are reported.