Polyurethane Ionomers,a New Class of Block Polymers

Linear polyurethanes containing ionic centers at wide intervals are heteropolymers having a pronounced segment structure, i.e. ionomers. As a result of interactions between chains (Coulomb forces and hydrogen bonds), their properties are similar to those of crosslinked elastomers. They are strongly associated both in organic and in aqueous solutions. Polyurethane ionomers in polar organic solvents spontaneously form stable aqueous dispersions on addition of water, with the ionomer as the disperse phase. The particle size can be varied between 20 nm and 1 mm.     

Stress-fit applications to experimental shell analyses

The stress-fit method is a procedure for determining complete stress distribution in shells from experimental data. Displacement, slope and shearing-force distributions may also be calculated. The method is applicable to all shell configurations for which closed-form solutions have been formulated and may be applied to certain asymmetrically loaded shells as well as those loaded axisymmetrically. Application to cylindrical and spherical shells is discussed in detail, and the procedure is shown to be verfied experimentally.     

Fusion properties of certain steroid hormones and related compounds

Summary The fusion properties of threecorpus luteum, six testes, five steroid estrogens, two gluco corticoids, one adrenal cortex, and two unclassified steroids were determined. These data afford rapid and positive identification of these compounds and only minute amounts of material are required.

---

Zusammenfassung Das charakteristische Verhalten der Schmelzen von 3 GelbkörperSteroiden, 6 Keimdrüsen-Steroiden, 5 östrogenen Steroiden, 2 glucocorticoiden Steroiden, 1 Nebennierenrinden-Steroid und von 2 nicht klassifizierten Steroiden wurde bestimmt. Diese Daten ermöglichen die rasche und einwandfreie Identifizierung dieser Verbindungen mit nur ganz geringen Mengen.

---

Résumé On a déterminé les propriétés au cours de la fusion de trois stéroïdes du corps jaune, six steroïdes des testicules, cinq stéroïdes oestrogènes, deux gluco-corticostéroïdes, un stéroïde cortico-surrénal et deux stéroïdes non classés. Ces données permettent l'identification rapide et positive de ces composés et n'exigent que des quantités minimes de substance.

     

Novel beta-lactam antibiotics synthesized by amination of catechols using fungal laccase

Novel cephalosporins, penicillins, and carbacephems were synthesized by amination of catechols with amino-beta-lactams like cefadroxil, amoxicillin, ampicillin and the structurally related carbacephem loracarbef using laccase from Trametes sp. All isolated monoaminated products inhibited the growth of several Gram positive bacterial strains in the agar diffusion assay, among them methicillin-resistant Staphylococcus aureus strains and vancomycin-resistant Enterococci. Observed differences in the cytotoxicity and in vivo activity in a "Staphylococcus-infected, immune suppressed mouse" model are discussed.     

On the Global Existence and Stability of a Multi-Dimensional Supersonic Conic Shock Wave

We establish the global existence and stability of a three-dimensional supersonic conic shock wave for a compactly perturbed steady supersonic flow past an infinitely long circular cone with a sharp angle. The flow is described by a 3-D steady potential equation, which is multi-dimensional, quasilinear, and hyperbolic with respect to the supersonic direction. Making use of the geometric properties of the pointed shock surface together with the Rankine–Hugoniot conditions on the conic shock surface and the boundary condition on the surface of the cone, we obtain a global uniform weighted energy estimate for the nonlinear problem by finding an appropriate multiplier and establishing a new Hardy-type inequality on the shock surface. Based on this, we prove that a multi-dimensional conic shock attached to the vertex of the cone exists globally when the Mach number of the incoming supersonic flow is sufficiently large. Moreover, the asymptotic behavior of the 3-D supersonic conic shock solution, which is shown to approach the corresponding background shock solution in the downstream domain for the uniform supersonic constant flow past the sharp cone, is also explicitly given.