Preparation of flexible and elastic poly(trimethylene carbonate) structures by stereolithography

3D porous and non-porous structures are designed and prepared by stereolithography using resins based on PTMC macromers. Tough, flexible network films prepared in this manner show E moduli of ≈3.8 MPa and high elongations at break >900%; tensile strengths are ≈4.2 MPa. These values increase with increasing PTMC macromer molecular weight. To reach suitable viscosities for processing, up to 45 wt% propylene carbonate is added as non-reactive diluent. The solid specimens have compression moduli of 3.1-4.2 MPa, similar to the values determined in tensile testing. The built porous structures show porosities of 53-66% and average pore sizes of 309-407 μm. The compression moduli of the porous structures are significantly lower than those of the solid structures.     

Redox properties of 8-quinolinol and implications for its mode of action

8-Quinolinol (oxine, 8-hydroxyquinoline) is a simple aromatic alkaloid with allelopathic, antibacterial, antifungal, and cytotoxic activities. Generally, it is assumed that 8-quinolinol toxicity depends on transition metal chelation that negatively affects their availability for metalloenzymes in the cell or reactive oxygen species generation (ROS), which are formed following reduction of molecular oxygen by autoxidation of the redox active metal central atom of the 8-quinolinol complex. On the contrary, beneficial effects of 8-quinolinol and its derivatives in the medication of certain degenerative diseases are known. In this context, the activity of 8-quinolinol derivatives is attributed to their antioxidant activity following iron complex formation. To address this controversial issue, we explore the possible anti- or pro-oxidant effects of 8-quinolinol and its iron complexes in the deoxyribose degradation assay, by cyclic voltammetry and in a biological assay. The antibacterial effects of 8-quinolinol and its complex with iron were evaluated on Curtobacterium flaccumfacies and Paenibacillus amylolyticus. 8-Quinolinol showed strong antioxidant activity in the deoxyribose degradation assay. This activity may not depend exclusively on iron chelation, but probably more on the notable reducing properties of 8-quinolinol; it proved to be a more efficient antioxidant than the flavonoids catechin and quercetin. By contrast, 8-quinolinol showed no pro-oxidative effects in the deoxyribose degradation assay, both in free form and in complex with iron, as it may occur with redox cyclers. Cyclic voltammetry confirmed this too. 8-Quinolinol significantly inhibited bacterial growth and respiration. Idiosyncratically, its 50:1 mixture with iron(III) ions was less active compared with free 8-quinolinol; it even caused a U-shaped nonlinear hormetic effect on growth and failed to inhibit respiration as totally as the pure mixture; the respiration was even accelerated compared with the control as a result of lower stress. Our results support the notion that complex formation with either iron or other transition metals affects the reducing power of 8-quinolinol, but, in contrast to general assumptions, this study finds no support that complex formation with iron represents the major mode of action.     

Realization of cartesian closed topological hulls

The cartesian closed topological (CCT) hull of a concrete categoryK is the smallest full CCT extension ofK. A general method for describing the CCT hulls is presented and applied to render unified proofs for the basic examples ofK: topological spaces, uniform spaces, pretopological spaces, compact T₂ spaces, metrizable spaces, and completely regular spaces.     

Die Synthese von 3β-Acetoxy-24-aza-24-desoxa-xysmalogenin,. Partialsynthetische Versuche in der Reihe der Herzgifte. 12. Mitteilung,

Synthesis of 3β-acetoxy-24-aza-24-desoxa-xymalogenin Starting from the pregnenolone-derivative 1 we report the synthesis of the possibly cardiac-active compound 24-aza-24-desoxa-xysmalogenin 15 .     

Theoretical investigation of the cyclic conformer of ozone

Ab initio SCF and CI calculations are reported which find the cyclic conformer of ozone to lie 16 kcal/mole above the preferred (open-chain) form of this substance. Polarization functions in the AO basis set are found to be quite important in this determination, strongly favoring the cyclic species. The possible experimental significance of such a relatively stable ring conformer of ozone is assessed.     

Aluminium

Ohne Zusammenfassung