Towards New Robust Zn(II) Complexes for the Ring-Opening Polymerization of Lactide Under Industrially Relevant Conditions

The synthesis of bio-based and biodegradable plastics is a hot topic in research due to growing environmental problems caused by omnipresent plastics. As a result, polylactide, which has been known for years, has seen a tremendous increase in industrial production. Nevertheless, the manufacturing process using the toxic catalyst Sn(Oct)2 is very critical. As an alternative, five zinc acetate complexes have been synthesized with Schiff base-like ligands that exhibit high activity in the ring-opening polymerization of non-purified lactide. The systems bear different side arms in the ligand scaffold. The influence of these substituents has been analyzed. For a detailed description of the catalytic activities, the rate constants kapp and kp were determined using in-situ Raman spectroscopy at a temperature of 150 °C. The polymers produced have molar masses of up to 71 000 g mol−1 and are therefore suitable for a variety of applications. Toxicity measurements carried out for these complexes proved the nontoxicity of the systems. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA

Diseño de un manual de detección de ansiedad social en adolescentes

Curso de Especial InterésEl objetivo de este trabajo de grado ha sido diseñar un manual dirigido a padres y docentes, en el que se establezcan técnicas de detección de ansiedad social en adolescentes; el diseño de este manual permite un aprendizaje significativo de una forma diferente, en un lenguaje claro y preciso, en formato digital para un fácil acceso y portabilidad del material, logrando de esta forma, que la población adolescente sea beneficiada a través de las acciones que se emprenderán por parte de los padres de familia, docentes y profesionales.142 p.RESUMEN 1. JUSTIFICACIÓN 2. OBJETIVOS 3. ESTUDIO DEL MERCADO 4. PRESENTACIÓN DEL PRODUCTO 5. CLIENTES – SEGMENTACIÓN 6. COMPETENCIA 7. CANALES DE DISTRIBUCIÓN 8. RESULTADOS DEL ESTUDIO DE MERCADO 9. DISCUSIÓN DEL ESTUDIO DE MERCADO 10. PRESUPUESTO 11. RESULTADOS 12. CONCLUSIONES REFERENCIAS APÉNDICESPregradoPsicólog

Beiträge zum Wachstum und zur Textur dünner Goldfilme auf Steinsalz

This work investigates major aspects of crystallisation from the vapour phase, as llustrated by the deposition system of Au on NaCl . Following a briet review of models for the growth of thin crystalline films, problems relevant to the present work are dealt with in detail. Film growth and texture of gold films deposited under ultra-high vacuum conditions at substrate temperatures in the range 300 - 675 K haue been analyzed by ion backseattering (RBS), transmission e€eefron microscopy and various X-ray technigues. With respeet to film growth fron the vapour phase, this werk presents for the first time experlmental evidente for a continuous transition from 2-dimensional to 3-dimensional growth depending on the degree of supersaturation. This observation confirms theoreticai predictions by D. Kashchiev.The distribution of gold crystailites is found to be a fiber texture at low substrate temperatures. At higher temperatures, only a set of discrete crystallite orientations isobserved. The accompanying change in the symmetry of the texture is attributed to the emergence of anisotropic film forming processes at higher substrate temperatures. Anisotropic diffusion of aggregates on the substrates surface is suggested to be the dominant process involved in establishing the texture

Influence of the Particle Size Distribution on Surface Quality and Mechanical Properties in Additive Manufactured Stainless Steel Parts

A recent study confirmed that the particle size distribution of a metallic powder material has a major influence on the density of a part produced by SLM. Although it is possible to get high density values with different powder types, the processing parameters have to be adjusted accordingly, affecting the process productivity. However, the particle size distribution does not only affect the density but also the surface quality and the mechanical properties of the parts. Therefore, this study compares three different particle size distributions depending on the laser scan velocity and two layer thicknesses of 30μm and 45μm. By using an optimized powder material a low surface roughness can be obtained. A subsequent blasting process can further improve the surface roughness for all powder materials used in this study although this does not change the ranking of the powders with respect to the resulting surface quality.Mechanical Engineerin

Assessment of mismatched epitaxial layers by X-ray rocking curve measurements and simulations

In the design of heteroepitaxial systems the knowledge of composition, strain and thickness of the various layers involved is of great importance. The determination of these structural parameters is among the applications most common in high-resolution X-ray diffraction. Numerical simulation of rocking curves has emerged as an important aid in the determination of the relevant structural parameters. Based upon the dynamical theory of X-ray diffraction a FORTRAN program has been written to simulate and refine structural parameters from rocking curve data. X-ray rocking curve analysis has been used to develop and optimize MOCVD-growth of Ga(x)In(1-x)P/GaAs heteroepitaxial systems. We observed superlattice peaks in samples of low misfit. With the aid of computer simulations we attribute these to unintentional periodic compositional fluctuations (Ga/In) of the order of 1 per cent

Wirtschaftliches Herstellen gefüllter Polypropylen-Platten

Em neu entwickeltes Verfahren eimöglicht, mit bis zu 40 Gew.-% Talkum oder 40 Gew.-% Kreide geflilltes Polypropylen in einem Arbeitsgang aufzubereiten und zu Tafeln hoher Qualitat zu extrudieren, die mit oder ohne Teppichverkleidungfür den TiefziehprozeJl geeignet sind. Dabei ist die Zugabe von Rückware moglich. Mit zweiwelligen Schneckenknetern der Bauart ZSK können bei Schneckendurchmessern von 90mm 500 kg/h produziert werden; bei Verwendung von Maschinen mit 130 mm Schneckendurchmesser werden Durchsätze bis zu 1500 kg/h er wartet. Das Zusammenfassen von Compoundieren und Extrudieren in einem Arbeitsgangführt zu beachtlichen wirtschaftlichen Vorteilen gegenüber der konventionellen Herstell-Methode