The growing importance of covering payment risks in the chemical industry

The first dark clouds are gathering on the economic horizon of the chemical industry and may cause an unattractive dip in otherwise impressive growth.With the oil price remaining high, concerns that global economic growth is cooling and ever fiercer competition, the outlook is gloomy. There is also uncertainty about the reform of the European Community Regulation on chemicals, REACH, the financial impact ofwhich is still impossible to predict formost companies. Such lists of possible causes of an economic slowdown often fail to mention the risk of bad debts,whichmay result in considerable financial difficulties for companies or, in the worst case scenario, lead to insolvency. However, providing security against the risk of payment default should always be on the agenda. This is particularly relevant in viewof the growing importance of trade credit, a fact reflected by the winter 2007 Payment Practices Barometer recently published byAtradius. In addition, payment practices have deteriorated in some countries and sectors in Europe

Biomimetische Strukturierung von Silikonmaterialien für die Beeinflussung von Zellverhalten und für dehnungsversteifende Materialien

In the first part of this thesis research, an artificial extra-cellular matrix formed the basis for experiments with a pathogenic species of amoeba, Acanthamoeba castellanii. In order to find new therapeutic approaches to fighting diseases caused by this species, the migratory behavior of Acanthamoeba castellanii in micro-pillar structures made of silicone, which were used to mimic the confined environment of an extra-cellular matrix, was explored. For the experiments, amoebae ingested microparticles of varying shapes. While it was found that sphere-shaped particles with a diameter smaller than the distance between the micro-pillars did not impact migration behavior, absorption of larger particles by Acanthamoeba castellanii caused migration to be strongly reduced. However, in some instances, it appeared that Acanthamoeba castellanii was nonetheless able to successfully navigate the pillar structures. These observations could serve as a basis for developing methods aimed at capturing amoebae before they can enter the human body. In the second part of this thesis, the focus was on developing a material with specific mechanical properties geared at mimicking an intra-cellular effect, namely the cross-linking of fibers within the cytoskeleton as a reaction to deformation of the cell and thereby increasing its stiffness. Emulating this effect, a strain-stiffening material was developed using a flexible, slat-structured silicone. When the material is elongated, these slats touch, thereby leading to a stiffening of the material. Employing finite element analysis, the degree to which various geometrical factors of the structure and friction between the slats affect the material’s stiffening behavior was examined, and the results were verified using tensile tests. The structure that resulted from my efforts yields a stiffening behavior that is material-independent, speed-independent and reversible, and that occurs also when the material is elongated.Eine künstliche extrazelluläre Matrix war die Basis für Experimente mit der pathogenen Amöbenspezies Acanthamoeba castellanii im ersten Teil der Arbeit. Auf der Suche nach neuartigen therapeutischen Ansätzen gegen Krankheiten, die von dieser Spezies verursacht werden, wurde deren Migrationsverhalten in mikrostrukturieren Säulenstrukturen aus flexiblem Silikon, die die beengende Umgebung der extrazellulären Matrix darstellen sollten, untersucht. Im Rahmen der Experimente haben die Amöben Mikropartikel mit verschiedenen Geometrien aufgenommen. Kugelförmige Partikel mit einem Durchmesser, der kleiner als der Abstand zwischen den Säulen ist, beeinflussten die Migration in den Strukturen nicht. In den Fällen, in denen Acanthamoeba castellanii größere Partikel aufgenommen hat, war die Migration in den Strukturen stark reduziert. In einigen Fällen konnten jedoch alternative Herangehensweisen beobachtet werden, die trotzdem Migration durch die Säulenstrukturen erlaubten. Die Imitation eines intrazellulären Effektes war die Grundlage für die Entwicklung eines Materials mit definierten mechanischen Eigenschaften im zweiten Teil der Arbeit. Die Fähigkeit von Zellen, als Reaktion auf eine Deformation Fasern im Zytoskelett zu vernetzen und somit ihre Steifigkeit zu erhöhen, wurde in dehnungsversteifenden Materialien nachgestellt. Es wurde eine Struktur aus flexiblem Silikon entwickelt, die eine Lamellenstruktur enthält. Diese Lamellen berühren sich im Fall einer Elongation des Materials und führen zu einer Versteifung des Materials. Es wurde mit Hilfe von Finite Elemente Analysen der Einfluss sowohl diverser geometrische Faktoren der Struktur, als auch der Reibung zwischen den Lamellen auf das Versteifungsverhalten des Materials untersucht. Die Ergebnisse wurden mit Hilfe von realen Zugversuchen verifiziert. Die entwickelte Struktur bietet ein materialunabhängiges, geschwindigkeitsunabhängiges, reversibles Versteifungsverhalten, das zudem auch bei einer Elongation des Materials auftritt

(4R,4aR,6S,7S,7aS)-6-Hydroxy-7-hy- droxymethyl-4-methylperhydrocyclo- penta[c]pyran-1-one chloroform solvate from Valeriana laxiflora

The structure of an iridolactone isolated from Valeriana laxiflora was established as (4R,4aR,6S,7S,7aS)-6-hydroxy-7-hydroxy­methyl-4-methyl­per­hydro­cyclo­penta­[c]­pyran-1-one chloro­form solvate, C10H16O4·CHCl3. The two rings are cis-fused. The [delta]-lactone ring adopts a slightly twisted half-chair conformation with approximate planarity of the lactone group and the cyclo­pentane ring adopts an envelope conformation. The hydroxy group, the hydroxymethyl group and the methyl group all have [beta] orientations. The absolute configuration was determined using anomalous dispersion data enhanced by the adventitious inclusion of a chloro­form solvent mol­ecule. Hydro­gen bonding, crystal packing and ring conformations are discussed in detail.The structure of the title compound was determined in the Molecular Structure Laboratory of the Department of Chemistry, University of Arizona. The diffractometer was obtained with funds provided by the NSF (grant No. CHE9610374). This study was supported by NIH grant No. 5U01TW00316-10 awarded to BNT

(ÿ)-Fern-7-en-3a-ol from Sebastiania brasiliensis

The structure of a fernane isolated from S. brasiliensis was established as fern-7en-3[alpha]-ol, C30H50O. Rings A and D assume a chair conformation, while rings B and C adopt a twist-boat conformation. Rings A/B, C/D, and D/E are trans fused. The relative orientation of the hydroxy group and that of the iso­propyl group is [alpha].This structure was determined in the Molecular Structure Laboratory of the Department of Chemistry, University of Arizona, Tucson, AZ 85721, USA. The SMART1000 diffractometer was gratefully obtained with funds provided by NSF grant CHE9610374. This study was supported by NIH grant 5U01TW00316-10 awarded to BNT. This study was undertaken as part of the required course work for the class CHEM 517 offered by Dr J. H. Enemark at the University of Arizona. The authors thank Liliya Yatsunyk for her help in this study

Reactive Flow Simulation of Micromixers Based On Grid Deformation Techniques

Process intensification of engineering applications in the framework of reacting flows in micromixer devices attracts the attention of engineers and scientists from various fields. With the steadily increasing available computational resources the traditional experimentally supported investigations may be extended by computational ones. For this purpose, a simulation framework based on state of the art numerical techniques extended with special grid deformation techniques has been developed. Its validation in terms of comparison with computational and experimental results in reacting, as well as in non-reacting frameworks has been performed on the basis of the T-mixer, and SuperFocus mixer, respectively. The computational efficiency of the developed tool is shown to be applicable for optimization tasks, such as reverse engineering purposes

Tarapacol 15-Acetate, a New Diterpenoid from Grindelia tarapacana Phil.

In the title compound, 15-acetoxy-14(S)-hydroxy-13-epi-manoyl oxide {IUPAC systematic name: 2-(dodecahydro-3,4a,7,7,10a-pentamethyl-1H-naphtho[2,1-b]pyran-3-yl)-2-hydroxyethyl acetate}, C22H38N4, rings A and B have chair conformations. Ring C adopts a boat conformation with the 16-methyl group in an axial position and the bulky glycol monoacetate group in an equatorial position. Ring systems A/B and B/C (conventional IUPAC labdane diterpenoid nomenclature) are trans fused about the C(5)-C(10) and C(8)-C(9) bonds, respectively. The present study establishes the relative stereochemistry at the C(14) position.This work was supported by a grant to the American Association for the Advancement of Science from the John D. and Catherine T. MacArthur Foundation, awarded to BNT. The structure was determined in the Molecular Structure Laboratory of the Department of Chemistry as a special class project in Chemistry 517

Modeling Ice Shelf/Ocean Interaction in Antarctica: A Review

The most rapid loss of ice from the Antarctic Ice Sheet is observed where ice streams flow into the ocean and begin to float, forming the great Antarctic ice shelves that surround much of the continent. Because these ice shelves are floating, their thinning does not greatly influence sea level. However, they also buttress the ice streams draining the ice sheet, and so ice shelf changes do significantly influence sea level by altering the discharge of grounded ice. Currently, the most significant loss of mass from the ice shelves is from melting at the base (although iceberg calving is a close second). Accessing the ocean beneath ice shelves is extremely difficult, so numerical models are invaluable for understanding the processes governing basal melting. This paper describes the different ways in which ice shelf/ocean interactions are modeled and discusses emerging directions that will enhance understanding of how the ice shelves are melting now and how this might change in the future