Influence of amorphous solid Dispersions of Paracetamol and PVP VA 64 on the thermoresponsive Behaviour of the Polymer

The dissolution of spray-dried amorphous solid dispersions consisting of paracetamol and PVP VA 64 at room temperature leads to the formation of different systems, depending on the drug/polymer ratio. Aqueous systems at room temperature with poor paracetamol/PVP VA 64 ratio are transparent solutions, while higher drug loads lead to phase separation of the solution. PVP VA 64 is known as thermoresponsive polymer. The aim of the study was to investigate the dissolution behaviour of these amorphous solid dispersions in water and their influence on the thermoresponsive behaviour of this polymer. Therefore, the demixing temperature was determined using DSC, since a change in the system constitutes an endothermic process. It could be shown that PVP VA 64 has lower critical solution temperature (LCST) behaviour around 70 °C, which decreases with increasing content of paracetamol due to the complex formation between the polymer and paracetamol

Entwicklung porciner und humaner organotypischer cornealer Zellkulturmodelle für in vitro Permeationsuntersuchungen

Die vorliegende Arbeit entstand unter dem Aspekt, ausgehend von porcinen und humanen cornealen Zellkulturen, durch Geweberekonstruktion eine Alternative zu exzidierten Hornhäuten von Versuchs- und Schlachttieren für in vitro Permeationsuntersuchungen zu entwickeln. Neben der Isolierung und Charakterisierung der porcinen Corneazellen und der Entwicklung eines porcinen Cornea-Konstruktes gelang der Aufbau eines Corneaäquivalentes aus humanen Zellen. Hierbei konnten histologische Gemeinsamkeiten zur Cornea in vivo sowie die Expression corneaspezifischer Merkmale in den Gewebekonstrukten mittels Immunhistologie, Rasterelektronenmikroskopie, SDS-Gelelektrophorese und Western-Blot Untersuchungen gezeigt werden. Zur Bestimmung der Barriereeigenschaften der Konstrukte wurden Permeationsuntersuchungen mit verschiedenen Arzneistoffen und Formulierungen durchgeführt und mit Untersuchungen an exzidierten porcinen Hornhäuten verglichen. Es zeigte sich eine erhöhte Permeabilität der Konstrukte wobei der Unterschied von Konstrukt zur exzidierten Cornea im Falle des porcinen Konstruktes etwa Faktor 2-4 und für das humane Konstrukt nur etwa 1,7 betrug. Die Ergebnisse dieser Arbeit zeigen die Möglichkeiten des Einsatzes der entwickelten porcinen und humanen Cornea-Konstrukte als alternative in vitro Modelle für transcorneale Permeationsuntersuchungen.The aim of the present contribution was to isolate and culture the different corneal cell types (endothelial, stomal and epithelial cells) from original excised porcine and human cornea and to build a cornea-construct by tissue engineering as an alternative for in vitro permeation studies. After successful isolation and cultivation of corneal cells an organotypic porcine and human cornea equivalent was reconstructed. It showed histological similarities to the cornea in vivo and the expression of specific corneal characteristics in the cultivated construct were confirmed by immunohistological studies, scanning electron microscopy, gel electrophoresis and Western immunoblotting. To determine the barrier properties of the constructs permeation studies with different formulations containing three different ophthalmic drugs as donor were performed and resultant permeation coefficients were compared with data obtained with excised porcine cornea. The cornea-constructs showed increased permeability. For the porcine construct permeation coefficients were higher by factor 2-4 and for the human construct by factor 1,6-1,8 in comparison with excised porcine cornea. The good comparability of data from both porcine and human cornea construct with data from excised animal cornea shows that the cultivated corneal equivalents as in vitro model for permeation studies could be helpful to predict drug absorption into human eye

Tunable Charge Detectors for Semiconductor Quantum Circuits

Nanostructures defined in high-mobility two-dimensional electron systems offer a unique way of controlling the microscopic details of the investigated device. Quantum point contacts play a key role in these investigations, since they are not only a research topic themselves, but turn out to serve as convenient and powerful detectors for their electrostatic environment. We investigate how the sensitivity of charge detectors can be further improved by reducing screening, increasing the capacitive coupling between charge and detector and by tuning the quantum point contacts' confinement potential into the shape of a localized state. We demonstrate the benefits of utilizing a localized state by performing fast and well-resolved charge detection of a large quantum dot in the quantum Hall regime

Functionalization and Subsequent Chemical Reactions of Polypnictogen Ligand Complexes

In summary, this dissertation deals with the synthesis and functionalization of polypnictogen ligand complexes. Besides the successful realization of the latter with organic nucleophiles and electrophiles, a conceptually new way for the preparation of phosphines could be found. For the first time, a functionalized phosphorus atom could be removed from the coordination sphere of a transition metal. This finding was transferred to other substituents and the versatility of this method was demonstrated

A General Pathway to Heterobimetallic Triple‐Decker Complexes

A systematic study on the reactivity of the triple-decker complex [(Cp'''Co)(2)(mu,eta(4):eta(4)-C7H8)] (A) (Cp'''=1,2,4-tritertbutyl-cyclopentadienyl) towards sandwich complexes containing cyclo-P-3, cyclo-P-4, and cyclo-P-5 ligands under mild conditions is presented. The heterobimetallic triple-decker sandwich complexes [(Cp*Fe)(Cp'''Co)(mu,eta(5):eta(4)-P-5)] (1) and [(Cp'''Co)(Cp'''Ni)(mu,eta(3):eta(3)-P-3)] (3) (Cp*=1,2,3,4,5-pentamethylcyclopentadienyl) were synthesized and fully characterized. In solution, these complexes exhibit a unique fluxional behavior, which was investigated by variable temperature NMR spectroscopy. The dynamic processes can be blocked by coordination to {W(CO)(5)} fragments, leading to the complexes [(Cp*Fe)(Cp'''Co)(mu(3),eta(5):eta(4):eta(1)-P-5){W(CO)(5)}] (2 a), [(Cp*Fe)(Cp'''Co)(mu(4),eta(5):eta(4):eta(1):eta(1)-P-5){(W(CO)(5))(2)}] (2 b), and [(Cp'''Co)(Cp'''Ni)(mu(3),eta(3):eta(2):eta(1)-P-3){W(CO)(5)}] (4), respectively. The thermolysis of 3 leads to the tetrahedrane complex [(Cp'''Ni)(2)(mu,eta(2):eta(2)-P-2)] (5). All compounds were fully characterized using single-crystal X-ray structure analysis, NMR spectroscopy, mass spectrometry, and elemental analysis

Increasing the {\nu} = 5 / 2 gap energy: an analysis of MBE growth parameters

The fractional quantized Hall state (FQHS) at the filling factor {\nu} = 5/2 is of special interest due to its possible application for quantum computing. Here we report on the optimization of growth parameters that allowed us to produce two-dimensional electron gases (2DEGs) with a 5/2 gap energy up to 135 mK. We concentrated on optimizing the MBE growth to provide high 5/2 gap energies in "as-grown" samples, without the need to enhance the 2DEGs properties by illumination or gating techniques. Our findings allow us to analyse the impact of doping in narrow quantum wells with respect to conventional DX-doping in AlxGa1-xAs. The impact of the setback distance between doping layer and 2DEG was investigated as well. Additionally, we found a considerable increase in gap energy by reducing the amount of background impurities. To this end growth techniques like temperature reductions for substrate and effusion cells and the reduction of the Al mole fraction in the 2DEG region were applied

The migration to NGN from a regulatory perspective

Telecommunication networks around the world develop towards All-IP next generation networks (NGN). This migration is driven by higher economies of scale and scope, price reductions for IP network elements, opportunities for new services and an improved experience for the end users. As the telecommunication markets are typically regulated and governments around the world have issued policies for the sector, the developments towards NGN networks have outcomes on regulation and government policies. This paper assesses the technological development towards NGN and the question on how and which initiatives regulatory authorities have implemented with regard to this development. With NGN, the development in the core networks is assessed, while the development in access networks (Next Generation Access Networks) is excluded..

Nucleophilic Attack at Pentaarsaferrocene [Cp*Fe(η5‐As5)]‐The Way to Larger Polyarsenide Ligands

By the reaction of [Cp*Fe(η5-As5)] (I) (Cp*=C5Me5) with main group nucleophiles, unique functionalized products with η4-coordinated polyarsenide (Asn) units (n=5, 6, 20) are obtained. With carbon-based nucleophiles such as MeLi or KBn (Bn=CH2Ph), the anionic organo-substituted polyarsenide complexes, [Li(2.2.2-cryptand)][Cp*Fe(η4-As5Me)] (1 a) and [K(2.2.2-cryptand)][Cp*Fe{η4-As5(CH2Ph)}] (1 b), are accessible. The use of KAsPh2 leads to a selective and controlled extension of the As5 unit and the formation of the monoanionic compound [K(2.2.2-cryptand][Cp*Fe(η4-As6Ph2)] (2). When I is reacted with [M]As(SiMe3)2 (M=Li ⋅ THF; K), the formation of the largest known anionic polyarsenide unit in [M′(2.2.2-cryptand)]2[(Cp*Fe)4{μ5-η4:η4:η3:η3:η1:η1-As20}] (3) occurred (M′=Li (3 a), K (3 b))

Nukleophiler Angriff am Pentaarsaferrocen [Cp*Fe(η5‐As5)] – Der Weg zu größeren Polyarsenid‐Liganden

Durch die Reaktion von [Cp*Fe(η5-As5)] (I) (Cp*=C5Me5) mit Hauptgruppenelement-Nukleophilen werden einzigartige funktionalisierte Produkte mit η4-koordinierten Polyarsenid-(Asn)-Einheiten (n=5, 6, 20) erhalten. Mit kohlenstoffbasierten Nukleophilen wie beispielsweise MeLi oder KBn (Bn=CH2Ph) sind die anionischen organo-substituierten Polyarsenidkomplexe [Li(2.2.2-Kryptand)][Cp*Fe(η4-As5Me)] (1 a) und [K(2.2.2-Kryptand)][Cp*Fe{η4-As5(CH2Ph)}] (1 b) zugänglich. Die Verwendung von KAsPh2 führt zu einer selektiven und kontrollierten Erweiterung der As5-Einheit und unter Bildung der monoanionischen Verbindung [K(2.2.2-Kryptand][Cp*Fe(η4-As6Ph2)] (2). Wird I mit [M]As(SiMe3)2 (M=Li ⋅ THF; K) zur Reaktion gebracht, kommt es zur Bildung der größten bekannten anionischen Polyarsenid-Einheit in [M′(2.2.2-Kryptand)]2[(Cp*Fe)4{μ5-η4:η4:η3:η3:η1:η1-As20}] (3)(M′=Li (3 a), K (3 b))