Structure-function relationship of Strong Metal-Support Interaction studied on supported Pd reference catalysts

Transition metal oxide supported, nano-scaled noble metal catalysts are known to show a variety of surface modifications when they are being reduced at increasing temperatures. Such processes involve for example (surface) alloying and the formation of partially reduced oxidic support overlayers that are both induced by the so-called strong metal-support interaction (SMSI). The present work investigated a series of oxide supported Palladium powder catalysts with a loading variation between 1-5 wt.-% on their structure-function relationship after reduction in different media and at different temperatures to create a reference system and explore the nature of SMSI. Hereby surface and bulk sensitive techniques like XPS, chemisorption, TEM, DRIFTS or XRD were applied to study the influence of electronic and structural modifications on the activity in catalytic oxidation of carbon monoxide which served as the main test reaction and was conducted at ambient pressure. The catalysts were synthesized reproducibly by a controlled co-precipitation approach and by impregnation. The investigated Pd/iron oxide system shows palladium surface decoration at comparably low reduction temperatures. The surface cover was found to be volatile in oxygen containing atmosphere and formed reversibly. Dependent on the Pd particle size it increases the CO oxidation activity. Alloy formation occurs at higher reduction temperatures. In case of the Pd/zinc oxide system reversible surface alloying takes place during reduction that is also beneficial for CO oxidation, but again deactivates fast. When being reduced at even higher temperatures the additional formation of an oxidic overlayer could be observed that does not further activate the system but leads to an overall reduction of active sites. Due to alloy formation, the zinc oxide system at higher conversions shows a different selectivity behavior in acetylene hydrogenation, compared to the iron oxide system. Also in case of the Pd/titania system, reversible surface decoration by partially reduced support happens during reduction. Different to the other investigated systems the surface-cover reversibly decreases CO oxidation activity however. The Pd/alumina system was studied as a less reducible reference. As expected, it does not show SMSI-induced modifications. In the end the work clearly shows that CO oxidation is a convenient method to study activity and stability of SMSI and decouple it from other involved processes. The effects of surface modification on the catalytic activity in this test reaction however strongly depend on the specific system and pre-conditioning and can either be of activating or deactivating nature. The basic principles involved in case of SMSI seem to apply both in UHV model systems and at powder systems at ambient pressure as found by the catalytic measurements.Übergangsmetalloxid geträgerte, nano-skalige Edelmetall-Katalysatoren sind bekannt dafür, eine Reihe von Oberflächen-Veränderungen zu erfahren, wenn sie bei erhöhter Temperatur reduziert werden. Diese Prozesse beinhalten beispielsweise (Oberflächen-) Legierungsbildung und die Ausblidung von teilweise reduzierten, oxidischen Träger- Schichten, in beiden Fällen hervorgerufen durch Starke Metall-Träger Wechselwirkung (Strong Metal-Support Interaction, SMSI). Die vorliegende Arbeit untersuchte eine Reihe von oxid-geträgerten Palladium Pulverkatalysatoren mit einer Variation der Beladung von 1- 5 Gewichts-% auf ihre Struktur-Eigenschafts Beziehungen nach Reduktion in verschiedenen Medien und bei veschiedenen Temperaturen, um ein Referenzsystem zu entwickeln und der Natur von SMSI auf den Grund zu gehen. Dabei kamen oberflächen- und volumensensitive Methoden wie XPS, Chemisorption, TEM, DRIFTS oder XRD zum Einsatz, um den Einfluss von elektronischen und strukturellen Veränderungen auf die Aktivität bei katalytischer Oxidation von Kohlenmonoxid zu untersuchen, welche als wichtigste Testreaktion bei Normaldruck durchgeführt wurde. Die Katalysatoren wurden auf reproduzierbare Weise durch kontrollierte Ko-Fällung und durch Imprägnierung hergestellt. Das untersuchte Pd/Eisenoxid System zeigt Bedeckung der Pd Oberfläche nach Reduktion bei vergleichsweise niedrigen Temperaturen. Diese Bedeckung war instabil in sauerstoffhaltiger Umgebung und bildete sich reversibel aus. Abhängig von der Pd Partikelgröße erhöht sie die Aktivität bei der CO-Oxidation. Legierungsbildung findet bei höheren Reduktionstemperaturen statt. Im Falle von Pd/Zinkoxid findet reversible Legierungsbildung an der Oberfläche statt, die ebenfalls die CO-Oxidation begünstigt, aber ebenfalls schnell deaktiviert. Nach Reduktion bei noch höheren Temperaturen konnte die zusätzliche Ausbildung einer oxidischen Überschicht beobachtet werden, die das System nicht weiter aktivierte, sondern insgesamt die Zahl der aktiven Plätze reduzierte. Wegen Legierungsbildung zeigt das Zinkoxid-System bei höheren Umsätzen in der Acetylenhydrierung ein anderes Selektivitätsverhalten als das Eisenoxid-System. Im Fall von Pd/Titanoxid kommt es während der Reduktion ebenfalls zu reversibler Oberflächen- Bedeckung durch teilweise reduzierten Träger. Anders als in den beiden anderen Fällen verringert diese Schicht hier jedoch die Aktivität in der CO-Oxidation. Pd/Aluminiumoxid wurde als schwer reduzierbares Referenz-System untersucht. Wie erwartet zeigt es keine durch SMSI hervorgerufenen Veränderungen. Schlussendlich konnte in dieser Arbeit gezeigt werden, dass CO-Oxidation eine einfache und geeignete Methode ist, SMSI zu untersuchen und ihren Einfluss auf Aktivität und Stabilität von dem anderer Prozesse zu trennen. Die Effekte von Oberflächenveränderungen auf die katalytische Aktivität dieser Test-Reaktion hängen jedoch stark vom entsprechenden System und der Vorbehandlung ab und können sowohl aktivierender als auch deaktivierender Natur sein. Die Grundlegenden Prinzipien, die bei SMSI eine Rolle spielen, scheinen sowohl im Fall von Modell-Systemen unter UHV-Bedingungen als auch bei Pulver-Systemen bei Normaldruck zu gelten, wie durch die katalytischen Messungen gezeigt wurde

Synopsis of the 6(th )Walker's Cay Colloquium on Cancer Vaccines and Immunotherapy

The 6(th )annual Cancer Vaccines and Immunotherapy Colloquium at Walker's Cay was held under the auspices of the Albert B. Sabin Vaccine Institute on March 10–13, 2004. The Colloquium consisted of a select group of 34 scientists representing academia, biotechnology and pharmaceutical industry. The main goal of this gathering was to promote in a peaceful and comfortable environment exchanges between basic and clinical science. The secondary benefit was to inspire novel bench to bedside ventures and at the same time provide feed back about promising and/or disappointing clinical results that could help re-frame some scientific question or guide the design of future trials. Several topics were covered that included tumor antigen discovery and validation, platforms for vaccine development, tolerance, immune suppression and tumor escape mechanisms, adoptive T cell therapy and dendritic cell-based therapies, clinical trials and assessment of response. Here we report salient points raised by speakers or by the audience during animated discussion that followed each individual presentation

Adjoint-Based Error Estimation and Mesh Adaptation for Problems with Output Constraints

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140439/1/6.2014-2576.pd

Aldehyde dehydrogenase and HSP90 co-localize in human glioblastoma biopsy cells.

The concept of a stem cell subpopulation as understood from normal epithelial tissue or bone marrow function has been extended to our understanding of cancer tissue and is now the target of treatment efforts specifically directed to this subpopulation. In glioblastoma, as well as in other cancers, increased expression of aldehyde dehydrogenase (ALDH) has been found localized within a minority sub-population of tumor cells which demonstrate stem cell properties. A separate body of research associated increased expression of heat-shock protein-90 (HSP90) with stem cell attributes. We present here results from our initial immunohistochemistry study of human glioblastoma biopsy tissue where both ALDH and HSP90 tended to be co-expressed in high amounts in the same minority of cells. Since 12% of all cells in the six biopsies studied were ALDH positive and 17% were HSP90 positive, by chance alone 2% would have been expected to be positive for both. In fact 7% of all cells simultaneously expressed both markers-a significant difference (p = 0.037). That two previously identified proteins associated with stem cell attributes tend to be co-expressed in the same individual glioblastoma cells might have clinical utility. Disulfiram, used to treat alcoholism for half-a century now, is a potent ALDH inhibitor and the old anti-viral drug ritonavir inhibits HSP90. These should be explored for the potential to retard aspects of glioblastoma stem cells' function subserved by ALDH and HSP90

Effect of Preexisting Neutralizing Antibodies on the Anti-tumor Immune Response Induced by Chimeric Human Papillomavirus Virus-like Particle Vaccines

AbstractChimeric human papillomavirus virus-like particles (HPV cVLPs) carrying HPV16 E7 protein are potent vaccines for inducing cell-mediated immunity (CMI) against HPV-induced tumors in animal models. We tested the hypothesis that virion-neutralizing antibodies generated during an initial vaccination might prevent effective boosting of CMI to the cVLPs. Mice with circulating HPV16-neutralizing antibodies, generated by direct immunization with wild-type VLPs or by passive transfer of hyperimmune anti-HPV16 VLP mouse sera, were subsequently vaccinated with HPV16 E7-containing cVLPs. Mice with preexisting neutralizing antibodies were not protected from HPV16 E7-positive TC-1 tumor challenge, compared to the protection seen in mice lacking these antibodies. Antibody-coated VLPs bound very inefficiently to receptor-positive cell lines, suggesting that one of the mechanisms of antibody interference is blocking of VLP binding to its receptor and thereby uptake of VLPs by antigen-presenting cells. Our results suggest that repetitive vaccination with a cVLP for induction of cellular immune responses to an incorporated antigen may be of limited effectiveness due to the presence of neutralizing antibodies against the capsid proteins induced after the first application. This limitation could potentially be overcome by boosting with cVLPs containing the same target antigen incorporated into other papillomavirus-type VLPs

Inflight Pharmacokinetic and Pharmacodynamic Responses to Medications Commonly Used in Spaceflight

Researchers do not know if medications act the same in the spaceflight environment as they do on Earth. Aspects of the spaceflight environment (low gravity, radiation exposure, closed environment, stress) have been shown to alter human physiology. Some of these physiological changes could be expected to alter either pharmacokinetics (PK, how the body absorbs, distributes, metabolizes and excretes administered medications) or pharmacodynamics (PD, receptors or signaling systems that are the targets of medication action). Anecdotal data has suggested that, at least for certain medications or indications, inflight medication efficacy is poor. In order to prepare for exploration missions where speedy evacuation to Earth may not be a possibility, the likelihood of unexpected medication action must be determined