Optisches Drehungsvermögen und Konformation, 3. Mitt.: Über die Verhältnisse beicis-Ringschlußreaktionen epimerer Aminoalkohole der Ephedrinreihe

Zusammenfassung (–)-Norephedrin, (–)-Ephedrin d. h.d _g-erythro-1-Phenyl-2-amino-bzw.-methylamino-propanole und deren rechtsdrehendethreo-Diastereomeren wurden durch Phosgen bzw. Chloracetylchlorid in die entsprechenden Oxazolidon-(2)- und Morpholon-(5)-Derivate umgewandelt. Die 3,4-Dimethyl-2-phenyl-morpholone wurden danach mit LiAlH₄ zu Morpholinderivaten reduziert. Der Unterschied zwischen dem Drehwert eineserythro--Aminoalkohols und irgendeines seiner cyclischen Derivate ist jeweils größer als in derthreo-Reihe. Das kann auf die größere Gesamtänderung in der Konformationsasymmetrie bei den Umwandlungen dererythro-Isomeren zurückgeführt werden. An Hand derBrewster-Methode waren Aussagen nur über die bevorzugten Konformationen der genannten sechsgliedrigen cyclischen Verbindungen möglich.Mit 2 Abbildungen.Herrn Prof. Dr.F. Wessely freundlichst zum 70. Geburtstag gewidmet.     

Excitation spectrum and thermodynamics of domain walls in the biaxial ferromagnet

The problem on spectrum of linear excitations in the presence of a moving domain wall in 1D Heisenberg ferromagnet with orthorhombic anisotropy is exactly solved. The explicit expressions for spin waves scattering on the domain wall are obtained. The phase shift of a spin wave, as the result of collision of spin wave with a moving wall, is exactly determined. The change in magnon density of states is calculated from this scattering data, and the contribution of domain walls to the classical low-temperature thermodynamics is found.     

Ultrasonic processing of dairy systems in large scale reactors

High intensity low frequency ultrasound was used to process dairy ingredients to improve functional properties. Based on a number of lab-scale experiments, several experimental parameters were optimised for processing large volumes of whey and casein-based dairy systems in pilot scale ultrasonic reactors. A continuous sonication process at 20 kHz capable of delivering up to 4 kW of power with a flow-through reactor design was used to treat dairy ingredients at flow rates ranging from 200 to 6000 mL/min. Dairy ingredients treated by ultrasound included reconstituted whey protein concentrate (WPC), whey protein and milk protein retentates and calcium caseinate. The sonication of solutions with a contact time of less than 1 min and up to 2.4 min led to a significant reduction in the viscosity of materials containing 18% to 54% (w/w) solids. The viscosity of aqueous dairy ingredients treated with ultrasound was reduced by between 6% and 50% depending greatly on the composition, processing history, acoustic power and contact time. A notable improvement in the gel strength of sonicated and heat coagulated dairy systems was also observed. When sonication was combined with a pre-heat treatment of 80 °C for 1 min or 85 °C for 30 s, the heat stability of the dairy ingredients containing whey proteins was significantly improved. The effect of sonication was attributed mainly to physical forces generated through acoustic cavitation as supported by particle size reduction in response to sonication. As a result, the gelling properties and heat stability aspects of sonicated dairy ingredients were maintained after spray drying and reconstitution. Overall, the sonication procedure for processing dairy systems may be used to improve process efficiency, improve throughput and develop value added ingredients with the potential to deliver economical benefits to the dairy industry.     

Reversible formation of glassy water in slowly cooling diluted drops

This letter presents experimental results obtained with a differential scanning calorimeter (DSC), which indicate that glassy water can be produced reversibly within slowly cooling diluted H2SO4/H2O drops.     

ChemInform Abstract: Endohedral Nickel,Palladium, and Platinum Atoms in 10‐Vertex Germanium Clusters: Competition Between Bicapped Square Antiprismatic and Pentagonal Prismatic Structures

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

On convexification of polygons by pops

Given a polygon P in the plane, a pop operation is the reflection of a vertex with respect to the line through its adjacent vertices. We define a family of alternating polygons, and show that any polygon from this family cannot be convexified by pop operations. This family contains simple as well as non-simple (i.e., self-intersecting) polygons, as desired. We thereby answer in the negative an open problem posed by Demaine and O’Rourke (2007) [9, Open Problem 5.3].     

Géométries Lorentziennes de dimension 3 : classification et complétude

We classify three-dimensional Lorentz homogeneous spaces G/I having a compact manifold locally modeled on them. We prove a completeness result: any compact locally homogeneous Lorentz threefold M is isometric to a quotient of a Lorentz homogeneous space G/I by a discrete subgroup Γ of G acting properly and freely on G/I. Moreover, if I is noncompact, G/I is isometric to a Lie group L endowed with a left invariant Lorentz metric, where L is isomorphic to one of the following Lie groups: