Oberflächenfunktionalisierung einer degradierbaren Magnesiumlegierung

In this thesis a new technique for surface modification of biodegradable magnesium alloys is presented and characterized. With a view to the functionalization of bioabsorbable coronary metal stents, the main focus of this work is on the covalent bonding of organofunctional silanes that offer a wide range of possible surface modifications and allow further bonding to a vast variety of substances. Common methods of silanization are applied to the magnesium alloy WE43 for the first time. In addition a new three step silanization technique has been developed. The stability and passivating effect of these silane films are demonstrated. The experiments are carried out on WE43 substrates. Therefore new preparation methods for magnesium alloys have been developed that produce a smooth and clean surface of reproducible quality. The WE43 surface was characterized with energy dispersive X-ray spectroscopy. The organofunctional silanes used for the surface treatment are 3-Aminopropyltriethoxysilane (APTES), n-Octadecyltrimethoxysilane (ODTMS) and n-Octadecyltriethoxysilane (ODTES). In addition two bifunctional silanes were used: Bis[3-(triethoxysilyl)propyl]tetrasulfide (BTES) and Bis(trimethoxysilylpropyl) amine (BTMA). The silanes were applied with a dip-coating process and analyzed with reflection-absorption-infrared-spectroscopy. These spectra contain the typical silane peaks, signals from the intact functional groups and reveal the structural changes due to condensation reactions. Moreover free silanols were found that can be used for multilayer formation. The covalent character of the silane bonding to the magnesium substrate and to the coronary stent surface was demonstrated with fluorescence microscopy. The effects of the surface treatment of coronary stents made of a magnesium alloy in respect to the corrosion protection were examined in the simulated body fluids PBS and eSBF-H. The new three step silanization technique – a serial silanization with BTES, BTMA and again with BTES – improves the corrosion resistance compared to single layer silane films and untreated stents. In addition the silane films were used as coupling agents for the polymer PLLA. The pre-treatment with the organofunctional silane ODTMS as well as with the bifunctional silanes had a positive effect on the corrosion resistance of a PLLA top-coating.In dieser Arbeit wird ein Verfahren zur Oberflächenfunktionalisierung für biodegradable Magnesiumlegierungen entwickelt und charakterisiert. Insbesondere in Hinblick auf die Beschichtung von biodegradablen Koronarstents liegt der Schwerpunkt auf der kovalenten Anbindung von funktionellen Organosilanen. Diese erlauben eine vielfältige Manipulation der Oberfläche und die Anbindung eines breiten Spektrums von Substanzen. Gängige Silanisierungsmethoden wurden dabei erstmals auf die Magnesiumlegierung WE43 übertragen. Zudem wurde ein neuartiges dreistufiges Silanisierungsverfahren entwickelt und die Stabilität und passivierende Wirkung der so aufgebrachten Silanfilme nachgewiesen. Gegenstand der Experimente bilden Flachproben aus WE43, die mikroskopisch spiegelnd glatt, rückstandsfrei und reproduzierbar präpariert und mit energiedispersiver Röntgenspektroskopie charakterisiert wurden. Zu diesem Zweck wurden neue und effektive Präparationsmethoden speziell für Magnesiumlegierungen entwickelt. Für die Funktionalisierung wurden folgende monovalente Organosilane verwendet: 3-Aminopropyltriethoxysilan (APTES) und n-Octadecyltrimethoxysilan (ODTMS) bzw. n-Octadecyltriethoxysilan (ODTES). Zusätzlich kamen bivalente Silane zum Einsatz: Bis[3-(triethoxysilyl)propyl]tetrasulfid (BTES) und Bis(trimethoxysilylpropyl) amin (BTMA). Die nasschemisch aufgebrachten Silanfilme wurden mittels Reflexions-Absorptions-Infrarotspektroskopie auf der Legierungsoberfläche analysiert. Die Spektren zeigen die silantypischen Peaks, die intakten funktionellen Gruppen und die strukturellen Veränderungen aufgrund von Kondensationsreaktionen der Silanmoleküle. In den Silanfilmen wurden auch freie Silanolgruppen gefunden, die eine Multilagenbeschichtung mit verschiedenen Silanen erlauben. Der kovalente Charakter der Silananbindung auf WE43 Flachproben und Koronarstents aus Magnesium wurde mittels Fluoreszenzmikroskopie nachgewiesen. Die Auswirkungen der Funktionalisierung von Magnesiumstents auf das Korrosionsverhalten wurde mit Auslagerungsversuchen in den körperähnlichen Modellelektrolyten PBS und eSBF-H untersucht. Das neuartige dreistufige Beschichtungsverfahren, bei dem Koronarstents mit BTES, BTMA und nochmals mit BTES silanisiert werden, verbessert die Korrosionsbeständigkeit im Vergleich zu einfachen Silanisierungen oder unbeschichteten Stents. Zudem wurde die Wirkung der Silane als Haftvermittler durch eine zusätzliche Polymerbeschichtung mit PLLA demonstriert. Sowohl mit dem monovalenten Silan ODTMS, als auch mit verschiedenen Bis-Silan-Beschichtungen ist ein positiver Effekt auf die Korrosionsbeständigkeit von PLLA-beschichteten Stents zu beobachten

Sex Industry and Sex Workers in Nevada

Timeworn but true, it is undeniable that “sex sells” and perhaps nowhere is this more evident than in Las Vegas, the symbolic center of the commercial sex industry and America’s own “Sin City.” To understand the commercial sex industry in Las Vegas and the Nevada sex industry more generally, we need to understand how local patterns reflect the larger trends in the nation and the world

Premier: The Magazine of the UNLV Harrah College of Hospitality

Of the countless hospitality programs around the world, why does the Harrah College of Hospitality consistently rank at the top? I believe the college\u27s excellence stems from our ability to leverage our strengths with those of our partners to do great things. It\u27s that simple. This approach has certainly been in play as we\u27ve navigated the difficulties of the past two years. We\u27ve worked with our friends in industry and academia to bolster our internship and mentorship programs, research, and interdisciplinary projects, all with the intent of expanding the knowledge base of the hospitality discipline and building a pipeline of much-needed talent for the industry. In the pages that follow, you\u27ll find example after example of these partnerships at work: our catering team\u27s unprecedented collaboration with UNLV Athletics; a new wine and music course that combines the expertise of the Hospitality College with the expertise of the UNLV Music Department; researchers from our college and around the world coming together to address tough industry challenges; and donors, such as Andrew and Peggy Cherng and the San Manuel Band of Mission Indians, helping the college bring innovative hospitality programs into higher ed. Perhaps the college\u27s most impactful partnership over the years has been with the hospitality companies in Las Vegas. We provide the smart and well-prepared student talent; they provide opportunities for students to work and intern in the industry. Our ongoing internship collaboration with Resorts World Las Vegas (pg. 24), which benefits 20+ UNLV students each semester, is but one example of how collaborations can lead to greatness. When the college and our partners share our time, expertise, and resources, there\u27s simply no limit to what we can accomplish. Together, we are stronger and more resilient, and our students are primed to carry the spirit of partnership forward into their lives and careers

Lignin Biosynthesis Gene Expression Is Associated with Age-related Resistance of Winter Squash to Phytophthora capsici

The Oomycete plant pathogen, Phytophthora capsici, causes root, crown, and fruit rot of winter squash (Cucurbita moschata) and limits production. Some C. moschata cultivars develop age-related resistance (ARR), whereby fruit develop resistance to P. capsici 14 to 21 days postpollination (DPP) because of thickened exocarp; however, wounding negates ARR. We uncovered the genetic mechanisms of ARR of two C. moschata cultivars, Chieftain and Dickenson Field, that exhibit ARR at 14 and 21 DPP, respectively, using RNA sequencing. The sequencing was conducted using RNA samples from ‘Chieftain’ and ‘Dickenson Field’ fruit at 7, 10, 14, and 21 DPP. A differential expression and subsequent gene set enrichment analysis revealed an overrepresentation of upregulated genes in functional categories relevant to cell wall structure biosynthesis, cell wall modification/organization, transcription regulation, and metabolic processes. A pathway enrichment analysis detected upregulated genes in cutin, suberin monomer, and phenylpropanoid biosynthetic pathways. A further analysis of the expression profile of genes in those pathways revealed upregulation of genes in monolignol biosynthesis and lignin polymerization in the resistant fruit peel. Our findings suggest a shift in gene expression toward the physical strengthening of the cell wall associated with ARR to P. capsici. These findings provide candidate genes for developing Cucurbita cultivars with resistance to P. capsici and improve fruit rot management in Cucurbita species

Epidemiology and Population Biology of Pseudoperonospora cubensis: A Model System for Management of Downy Mildews

The resurgence of cucurbit downy mildew has dramatically influenced production of cucurbits and disease management systems at multiple scales. Long-distance dispersal is a fundamental aspect of epidemic development that influences the timing and extent of outbreaks of cucurbit downy mildew. The dispersal potential of Pseudoperonospora cubensis appears to be limited primarily by sporangia production in source fields and availability of susceptible hosts and less by sporangia survival during transport. Uncertainty remains regarding the role of locally produced inoculum in disease outbreaks, but evidence suggests multiple sources of primary inoculum could be important. Understanding pathogen diversity and population differentiation is a critical aspect of disease management and an active research area. Underpinning advances in our understanding of pathogen biology and disease management has been the research capacity and coordination of stakeholders, scientists, and extension personnel. Concepts and approaches developed in this pathosystem can guide future efforts when responding to incursions of new or reemerging downy mildew pathogens.Keywords: disease management, mating type, pathotype, Bayesian prediction, risk assessment, genomic

Analysis of cryptic, systemic Botrytis infections in symptomless hosts

Botrytis species are generally considered to be aggressive, necrotrophic plant pathogens. By contrast to this general perception, however, Botrytis species could frequently be isolated from the interior of multiple tissues in apparently healthy hosts of many species. Infection frequencies reached 50% of samples or more, but were commonly less, and cryptic infections were rare or absent in some plant species. Prevalence varied substantially from year to year and from tissue to tissue, but some host species routinely had high prevalence. The same genotype was found to occur throughout a host, representing mycelial spread. B. cinerea and B. pseudocinerea are the species that most commonly occur as cryptic infections, but phylogenetically distant isolates of Botrytis were also detected, one of which does not correspond to previously described species. Sporulation and visible damage occurred only when infected tissues were stressed, or became mature or senescent. There was no evidence of cryptic infection having a deleterious effect on growth of the host, and prevalence was probably greater in plants grown in high light conditions. Isolates from cryptic infections were often capable of causing disease (to varying extents) when spore suspensions were inoculated onto their own host as well as on distinct host species, arguing against co-adaptation between cryptic isolates and their hosts. These data collectively suggest that several Botrytis species, including the most notorious pathogenic species, exist frequently in cryptic form to an extent that has thus far largely been neglected, and do not need to cause disease on healthy hosts in order to complete their life-cycles