Zystische Adventitiadegeneration (CAD) als Ursache einer invalidisierenden Claudicatio intermittens

Zusammenfassung: Bei einem 45-jährigen Patienten mit wechselhaften Ischämiebeschwerden und initial limitierter Gehstrecke rechts von höchstens 50m führten die duplexsonographischen und angiographischen Abklärungen zur Verdachtsdiagnose einer zystischen Adventitiadegeneration. Intraoperativ zeigte sich ein zystisch aufgetriebenes Poplitealsegment mit Entleerung von gallertiger Flüssigkeit. Aufgrund der langstreckigen Veränderung erfolgte die Segmentresektion der A.poplitea und Rekonstruktion mittels eines autologen Veneninterponats. Die CAD ist ein seltenes Krankheitsbild, an das gerade bei jungen Patienten ohne systemische Arteriosklerose gedacht werden sollte. Die Therapie ist je nach Fall chirurgisch erhaltend durch Zystenresektion mittels "Exarterektomie" oder gefäßresezierend, insbesondere bei langstreckigen Veränderungen bzw. vollständiger Okklusion mittels Ersatz durch ein Veneninterpona

Structure of Extremely Nanosized and Confined In-O Species in Ordered Porous Materials

Perturbed-angular correlation, x-ray absorption, and small-angle x-ray scattering spectroscopies were suitably combined to elucidate the local structure of highly diluted and dispersed InOx species confined in porous of ZSM5 zeolite. These novel approach allow us to determined the structure of extremely nanosized In-O species exchanged inside the 10-atom-ring channel of the zeolite, and to quantify the amount of In2O3 crystallites deposited onto the external zeolite surface.Comment: 4 pages, 5 postscript figures, REVTEX4, published in Physical Review Letter

Mössbauer study of iron gall inks on historical documents

AL designed and coordinated the practical and scientific work, was involved in the evaluation and interpretation of the data and wrote various drafts of the paper. FEW designed and coordinated the practical and scientific work, performed the Mössbauer spectroscopy, evaluated and interpreted the data and wrote the final version of the manuscript. MD carried out the pH measurements of the papers and determined the nature of the papers and gave valuable hints to research on historical documents. TE provided the fragments of the two Spanish documents. JLPP proposed this investigation and gave valuable hints on the documents. All authors read and approved the final manuscript.Iron gall ink was used in the Western world as a permanent writing material already in late Roman times and throughout the Middle Ages, until it became obsolete in the twentieth century. There is much interest in experimental methods to determine the state of the ink and its degradation products on historical documents. Mossbauer spectroscopy with Fe-57 is such a method, and it has the particular advantage to be sensitive to the chemical bonding of iron, but this method has only rarely been applied to historical documents. In this paper we present Mossbauer data for two damaged documents from a Library in Granada and a handwritten German book from the eighteenth century. In addition to the inked parts of the manuscripts, ink-free parts were studied to determine the amount and chemical state of the iron in the papers. These new results are discussed in the context of previously published Mossbauer data. In one of the investigated documents Fe(II)-oxalate, FeC2O4 center dot 2H(2)O, was observed. The assignment of the various Fe3+ sites in the different documents is rather difficult and often there is a superposition of various species. Known forms of iron gallate are definitely not present on the inked papers. The observed ferric species can be remains of Fe3+ polyphenol complexes of the ink, complexes of Fe3+ with degradation products of the cellulose of the paper or gum arabic, or very small iron oxide or hydroxide nanoparticles

Computational studies for reduced graphene oxide in hydrogen-rich environment

We employ molecular dynamic simulations to study the reduction process of graphene-oxide (GO) in a chemically active environment enriched with hydrogen. We examine the concentration and pressure of hydrogen gas as a function of temperature in which abstraction of oxygen is possible with minimum damage to C-sp$^2$ bonds hence preserving the integrity of the graphene sheet. Through these studies we find chemical pathways that demonstrate beneficiary mechanisms for the quality of graphene including formation of water as well as suppression of carbonyl pair holes in favor of hydroxyl and epoxy formation facilitated by hydrogen gas in the environment.Comment: 9 pages and 9 figures. Animations and movies are available at: http://qmsimulatorgojpc.wordpress.com

Selective and low temperature transition metal intercalation in layered tellurides

Layered materials embrace rich intercalation reactions to accommodate high concentrations of foreign species within their structures, and find many applications spanning from energy storage, ion exchange to secondary batteries. Light alkali metals are generally most easily intercalated due to their light mass, high charge/volume ratio and in many cases strong reducing properties. An evolving area of materials chemistry, however, is to capture metals selectively, which is of technological and environmental significance but rather unexplored. Here we show that the layered telluride T2PTe2 (T=Ti, Zr) displays exclusive insertion of transition metals (for example, Cd, Zn) as opposed to alkali cations, with tetrahedral coordination preference to tellurium. Interestingly, the intercalation reactions proceed in solid state and at surprisingly low temperatures (for example, 80?°C for cadmium in Ti2PTe2). The current method of controlling selectivity provides opportunities in the search for new materials for various applications that used to be possible only in a liquid

Modeling of graphite oxide

Based on density functional calculations, optimized structures of graphite oxide are found for various coverage by oxygen and hydroxyl groups, as well as their ratio corresponding to the minimum of total energy. The model proposed describes well known experimental results. In particular, it explains why it is so difficult to reduce the graphite oxide up to pure graphene. Evolution of the electronic structure of graphite oxide with the coverage change is investigated.Comment: 12 pages, 7 figures. Discussion about reduction to pure graphene and several references added. Methodological part expanded. Accepted to J. Am. Chem. So

NMR-Based Structural Modeling of Graphite Oxide Using Multidimensional 13C Solid-State NMR and ab Initio Chemical Shift Calculations

Chemically modified graphenes and other graphite-based materials have attracted growing interest for their unique potential as lightweight electronic and structural nanomaterials. It is an important challenge to construct structural models of noncrystalline graphite-based materials on the basis of NMR or other spectroscopic data. To address this challenge, a solid-state NMR (SSNMR)-based structural modeling approach is presented on graphite oxide (GO), which is a prominent precursor and interesting benchmark system of modified graphene. An experimental 2D C-13 double-quantum/single-quantum correlation SSNMR spectrum of C-13-labeled GO was compared with spectra simulated for different structural models using ab initio geometry optimization and chemical shift calculations. The results show that the spectral features of the GO sample are best reproduced by a geometry-optimized structural model that is based on the Lerf-Klinowski model (Lerf, A. et al. Phys. Chem. B 1998, 102, 4477); this model is composed of interconnected sp(2), 1,2-epoxide, and COH carbons. This study also convincingly excludes the possibility of other previously proposed models, including the highly oxidized structures involving 1,3-epoxide carbons (Szabo, I. et al. Chem. Mater. 2006, 18, 2740). C-13 chemical shift anisotropy (CSA) patterns measured by a 2D C-13 CSA/isotropic shift correlation SSNMR were well reproduced by the chemical shift tensor obtained by the ab initio calculation for the former model. The approach presented here is likely to be applicable to other chemically modified graphenes and graphite-based systems

Longitudinal unzipping of carbon nanotubes to form graphene nanoribbons.

Published versio

Probing the Thermal Deoxygenation of Graphene Oxide using High Resolution In Situ X-Ray based Spectroscopies

Despite the recent developments in Graphene Oxide due to its importance as a host precursor of Graphene, the detailed electronic structure and its evolution during the thermal reduction remain largely unknown, hindering its potential applications. We show that a combination of high resolution in situ X-ray photoemission and X-ray absorption spectroscopies offer a powerful approach to monitor the deoxygenation process and comprehensively evaluate the electronic structure of Graphene Oxide thin films at different stages of the thermal reduction process. It is established that the edge plane carboxyl groups are highly unstable, whereas carbonyl groups are more difficult to remove. The results consistently support the formation of phenol groups through reaction of basal plane epoxide groups with adjacent hydroxyl groups at moderate degrees of thermal activation (~400 {\deg}C). The phenol groups are predominant over carbonyl groups and survive even at a temperature of 1000 {\deg}C. For the first time a drastic increase in the density of states (DOS) near the Fermi level at 600 {\deg}C is observed, suggesting a progressive restoration of aromatic structure in the thermally reduced graphene oxideComment: Pagona Papakonstantinou as Corresponding author, E-mail: [email protected]