Hydrogels containing redispersible spray-dried melatonin-loaded nanocapsules: a formulation for transdermal-controlled delivery

The aim of the present study was to develop a transdermal system for controlled delivery of melatonin combining three strategies: nanoencapsulation of melatonin, drying of melatonin-loaded nanocapsules, and incorporation of nanocapsules in a hydrophilic gel. Nanocapsules were prepared by interfacial deposition of the polymer and were spray-dried using water-soluble excipients. In vitro drug release profiles were evaluated by the dialysis bag method, and skin permeation studies were carried out using Franz cells with porcine skin as the membrane. The use of 10% (w/v) water-soluble excipients (lactose or maltodextrin) as spray-drying adjuvants furnished redispersible powders (redispersibility index approximately 1.0) suitable for incorporation into hydrogels. All formulations showed a better controlled in vitro release of melatonin compared with the melatonin solution. The best controlled release results were achieved with hydrogels prepared with dried nanocapsules (hydrogels > redispersed dried nanocapsules > nanocapsule suspension > melatonin solution). The skin permeation studies demonstrated a significant modulation of the transdermal melatonin permeation for hydrogels prepared with redispersible nanocapsules. In this way, the additive effect of the different approaches used in this study (nanoencapsulation, spray-drying, and preparation of semisolid dosage forms) allows not only the control of melatonin release, but also transdermal permeation.     

Zum Einfluss baulicher Randbedingungen auf das dynamische Verhalten von WIB‐Eisenbahnbrücken

Die Weiterentwicklung des europäischen Eisenbahnnetzes ist unter anderem durch den vermehrten Einsatz von Hochgeschwindigkeitszügen und eine signifikante Anhebung der Betriebsgeschwindigkeiten gekennzeichnet. Um die Auswirkungen von Zugbeanspruchungen auf Eisenbahnbrücken im Rahmen einer dynamischen Bemessung hinreichend genau vorhersagen zu können, ist die Kenntnis der wesentlichen dynamischen Systemeigenschaften erforderlich. Nur so können bemessungsrelevante Resonanzeffekte, die bei hohen Geschwindigkeiten grundsätzlich nicht auszuschließen sind, rechnerisch auf zuverlässige Weise erfasst werden. Messungen insbesondere an WIB‐Überbauten zeigen jedoch, dass eine realistische rechnerische Abschätzung von Brückeneigenfrequenzen schwierig ist. Tatsächliche und rechnerische Werte weichen in vielen Fällen erheblich voneinander ab. Als ursächlich wird hierfür unter anderem eine unzureichende Berücksichtigung baulicher Randbedingungen angesehen, die teilweise erheblichen Einfluss auf die Steifigkeits‐ und Dämpfungseigenschaften der Brücke haben. Der vorliegende erste Teil des Beitrags führt in die Problematik ein und präsentiert Ergebnisse aus Messuntersuchungen an WIB‐Eisenbahnbrücken, die von der Deutschen Bahn durchgeführt wurden. Im folgenden zweiten Teil des Beitrags wird auf Grundlage numerischer Studien gezeigt, wie sich einzelne bauliche Randbedingungen auf das dynamische Verhalten von WIB‐Überbauten auswirken. Abschließend werden die Untersuchungsergebnisse dazu genutzt, Vorschläge für eine genauere dynamische Bemessung abzuleiten. On the influence of constructional elements on the dynamic behaviour of filler beam railway bridges — Part 1: Introduction and measurements on filler beam bridges. Enhancements of the European railway system are amongst other things mainly characterized by increased usage of high speed trains and significantly raised operating speeds. To predict effects of train loading on railway bridges for a dynamic design adequately, knowledge of the system’s significant dynamic characteristics is required. Only this ensures that resonance effects, which generally cannot be screened out for high speeds, can be covered analytically by reliable values. Measurements especially carried out on filler beam bridges have shown though that a realistic estimation of eigenfrequencies of bridges is difficult. Actual values and measured ones differ significantly in many cases. In particular non‐consideration of structural constraints is seen as reason for this, given that they have an immense effect on a bridge’s stiffness and damping characteristics. This first part of the contribution gives a brief survey on the dynamics of high‐speed railway bridges. Furthermore results from measurements on filler beam railway decks are presented. In the forthcoming second part of the contribution the influence of particular constructional elements on the dynamic behaviour of filler beam bridges is investigated, supported by numerical studies. Finally the main outcomes are discussed and proposals for an improved dynamic bridge design are made.     

Intraoral defect coverage with muscle flaps

PURPOSE: This study investigated whether wound healing after the use of purely muscular flaps for intraoral defect coverage is negatively influenced by insipient muscular atrophy and the absence of a covering layer. MATERIALS AND METHODS: In an experimental study, microsurgical transplantation of muscle flaps from the anterior abdominal wall was carried out in 18 Lewis rats. A nerve anastomosis for motor reinnervation was not performed. Atrophy of the muscle flaps was determined by measuring the reduction of their size and weight after 3, 8, and 20 weeks. In the clinical part of the study, free muscle transplants from different donor regions (vastus lateralis, pectoralis major, internal oblique, and temporalis muscles) were used for defect coverage in various areas of the oral cavity. To study epithelization, punch biopsy specimens from the muscle surface were taken at periods of 2 to 4 weeks up to 6 months for histologic evaluation. Final evaluation of reconstruction results with special regard to speech, tongue mobility, mouth opening, chewing, and swallowing took place after 6 months. RESULTS: In the experimental study, average weight loss of the muscle flaps was 67% after 20 weeks, and the remaining surface area was 71%. The number of myocytes was only about 30% compared with control muscles, and parts of the flap appeared as a thin fibrous membrane. Clinically, this atrophy led to restricted mobility in such areas as the floor of the mouth, the buccal plane, and the tongue. Muscle flaps covering solid structures such as bones or reconstruction plates adapted well to the transplant bed, and the atrophy of the muscle led to no constriction of the surrounding tissue. Atrophy also did not have a negative effect when muscle flaps were placed in the region of the pharyngeal wall. Epithelization started from the edges after 2 weeks and was concluded after 8 weeks in all transplants if no additional radiation was performed. The muscle tissue was sufficiently resistant so that infection, fistulization, and necrosis did not occur. CONCLUSIONS: Muscle flaps undergo considerable atrophy with a cicatricial transformation and reduction of flexibility. Despite these disadvantages they can be used in the hard palate, the alveolar crest, and in the pharyngeal wall without causing functional restriction. Because of constriction of the surrounding tissues, mobile areas such as the buccal plane, the floor of the mouth, and the tongue are not suitable as sites for muscle transplants.     

Pancreatic colon stenoses

Benign colonic stenosis may be caused by pancreatitis. Colonic obstruction arising during the acute stage of pancreatitis is mostly found to be reversible. Persistant colonic stenosis after acute or relapsing pancreatitis may point to an adjacent abscess. Two patients with pancreatitic colonic stenosis illustrate those different courses of the disease.     

An area-efficient bit-serial integer and GF(2) multiplier

This paper presents the design of a new multiplier architecture for normal integer multiplication of positive and negative numbers as well as for multiplication in finite fields of order 2ⁿ. It has been developed to increase the performance of algorithms for cryptographic and signal processing applications on implementations of the Instruction Systolic Array (ISA) parallel computer model [M. Kunde, H.W. Lang, M. Schimmler, H. Schmeck, H. Schröder, Parallel Computing 7 (1988) 25-39, H.W. Lang, Integration, the VLSI Journal 4 (1986) 65-74]. The multiplier operates least significant bit (LSB)-first for integer multiplication and most significant bit ( )-first for finite field multiplication. It is a modular bit-serial design, which on the one hand can be efficiently implemented in hardware and on the other hand has the advantage that it can handle operands of arbitrary length.     

Grundsätzliche Überlegungen zur Entstehung der Kristallseigerung und der eutektischen Zweitphasenausscheidung in Dreistoffsystemen

Erörterung über den Erstarrungsablauf und über die Ausscheidung zweier eutektischer Verbindungen in Dreistofflegierungen anhand eines angenommenen Zustandsschaubildes. Quantitative Darstellung von Rechenergebnissen über die Kristallseigerung primärer Mischkristalle bei veränderten Gesamtlegierungsgehalten mit Aussagen über den Legierungseinfluß auf die Kristallseigerung. Angaben über die Zusammenhänge zwischen Zustandsschaubild, Verteilungskoeffizient und Kristallseigerung. Behandlung des Mechanismus für eine Zweitphasenausscheidung. Hinweise auf die praktische Bedeutung der seigerungsbedingten Schmelzpunkterniedrigung.