Magnetic phase diagram of CePt3B1-xSix

We present a study of the main bulk properties (susceptibility, magnetization, resistivity and specific heat) of CePt_3B_(1-x)Si-x, an alloying system that crystallizes in a noncentrosymmetric lattice, and derive the magnetic phase diagram. The materials at the end point of the alloying series have previously been studied, with CePt_3B established as a material with two different magnetic phases at low temperatures (antiferromagnetic below T_N = 7.8 K, weakly ferromagnetic below T_C ~ 5 K), while CePt3Si is a heavy fermion superconductor (T_c = 0.75 K) coexisting with antiferromagnetism (T_N = 2.2 K). From our experiments we conclude that the magnetic phase diagram is divided into two regions. In the region of low Si content (up to x ~ 0.7) the material properties resemble those of CePt3B. Upon increasing the Si concentration further the magnetic ground state continuously transforms into that of CePt3Si. In essence, we argue that CePt_3B can be understood as a low pressure variant of CePt3Si.Comment: 7pages, 9figure

Partialsynthese maßgeschneiderter Photosensibilisatoren vom Chlorintyp und Studien zur pharmazeutischen Anwendung in der Photodynamischen Therapie

Photodynamic therapy is still in its initial stages. Non-acceptance in clinical application so far is due to the need for appropriate photosensitizers fulfilling several requirements. However, in the present state of research, amphiphilic chlorins without charges or ionic moieties are the most promising chromophores. Partial water-solubility or solubility in physiological solvents is important for a clinical application. This thesis deals with the synthesis of chlorin-carbohydrate-amides of various degrees of hydrophilicity, followed by the investigation of their photophysical and bio-medical properties. The synthesis is based on Deuteroporphyrin, which can be converted into chlorins with different alkyl chains by partial synthesis. Another approach is based on the substitution of the chromophores of chlorin e6 and its derivatives. Consequently, the carboxylic moieties were amidated successfully with acyclic sugar amines. The solubility of these amides ranges from moderate to good water-solubility. For all derivatives photophysical measurements showed enhanced absorption qualities compared to those of Photofrin, the currently best reviewed and medically most applied photosensitizer

Meaning Making with Art: Expert and Lay Perspectives in Understanding Artworks and Exhibition Concepts

In the present dissertation aesthetic meaning making is understood as a process combining perceptual, emotional and cognitive shares that can be experienced as more or less successful and satisfying in relation to the final understanding of a painting’s meaning. Referring to different scientific fields, such as philosophy, visual sciences, art history and psychology, it is explained that paintings represent meaning on different levels of abstraction that have to be considered in dependence to multiple contexts, such as personal previous knowledge and level of experience, or the social situation and physical setting in which a painting is viewed. It is discussed how expertise in art influences meaning making by presenting different models and frameworks of aesthetic processing: Developmental models describing identified skills and abilities of beholders in reference to different stages of visual literacy, and cognitive models conceptualizing meaning making as a sequence of perceptual, emotional and cognitive processes that take place while looking at a present work of art. Leder et al.’s cognitive model (2004) that describes aesthetic processing in five stages and considering possible influences of expertise and context is combined with Panofsky’s model of iconography and iconology (1975) that describes a systematic method of art historic art inquiry and built into an integrated model of meaning making used as basic framework for analyses in this dissertation. Studies of aesthetic psychology are reviewed and presented in accordance to Leder et al.’s (2004) and Panofsky’s (1975) model to discuss differences in meaning making of experts and laymen of art. These theoretical and analytical considerations are used to examine the special expertise of art historians in relation to meaning making with art. Referring to the form versus content approach in aesthetic psychology and using the integrated model of aesthetic processing as basic theoretical framework, the dissertation focused on experts’ and laymen’s use of content for meaning making when looking at representational art. Three studies were conducted to get deeper insights into the specific characteristics of art historian expertise (Study 1), to address the influence of social and physical context on meaning making when exploring a set of representational art chosen and arranged by an art historic professional (Study 2), and to specify expert-layman differences in using informative and less informative content for meaning making with single representational paintings (Study 3). Study 1, a focus group with art historians discussing about aims, skills and concepts according to their professional frameworks, indicates that the meaning potential of specific pictorial features and content is defined before actually engaging into viewing a painting by specific hypotheses that an art historian wants to test by analyzing a painting that determines the angle or perspective on a painting and is connected to the use of specific methods of art inquiry. According to the art historians of the focus group, meaning making itself is characterized by attempts of interpreting different features of a painting using asking questions and comparison as main strategies or tools of relating aspects in or between paintings. In Study 2, groups of students were videotaped while exploring a gallery space and engaging into card sorting tasks outside the gallery with paintings by the expressionist Edvard Munch. Meaning making was analyzed in relation to the exhibition concept and educational means of the exhibition curator, using socio cultural methods and discussing results according to the five stage model of aesthetic processing by Leder et al. (2004). Findings showed a mediating effect of the social and physical context of the exhibition context as well as task-specific mediation of comparison between paintings outside the gallery setting. Comparisons between paintings inside the gallery settings indicating an occupation with the curatorial concept behind the arrangement of the paintings could not be shown, indicating that participants were not aware of this meta-level of meaningful information provided by the curator in the gallery space. Finally, Study 3 explored differences in meaning making of experts and laymen of art history when viewing Renaissance portraits presented to them one by one on slides in a laboratory setting. Using eye tracking and simultaneous thinking aloud, participants’ perceptual and cognitive reference to content with high meaning potential compared to content less informative for meaning making was investigated. Findings show, that experts of art history look longer at symbolic content in relation to areas depicting human features. Further, in contrast to laymen, experts’ thinking aloud consists of a higher percentage of interpretation, reveals more often the meaning of symbolic objects and is more structured. In sum, the studies of this dissertation provide first evidence how meaning making with representational art understood as interlocked sequence of perceptual and cognitive processes is influenced by art historian expertise and the social and physical setting of art inquiry. Thus the present dissertation addresses a topic of great interest for both art education and museums that seek to provide situations, tools and different formats for laymen to engage into effective meaning making with art with the potential to learn and improve visual literacy according to the expert perspective of the art historian community.In der vorliegenden Dissertation wird die ästhetische Auseinandersetzung mit figurativer Kunst von Laien und Experten der Kunstgeschichte betrachtet. Bedeutsam für die Studien dieser Arbeit ist das kognitive Modell der ästhetischen Wahrnehmung und Verarbeitung von Leder et al. (2004), das in der Abfolge von fünf Verarbeitungsstufen Einflussfaktoren wie Expertise, Museumskontext und soziale Situation der Kunstbetrachtung berücksichtigt. Dieses Modell wird mit dem Ansatz der Ikonographie und Ikonologie des Kunsthistorikers Erwin Panofsky (1975) verknüpft. Panofsky beschreibt darin einen dreistufigen Verlauf der Bildanalyse in Abhängigkeit von bestimmten kunsthistorischen Fähigkeiten und Fertigkeiten. Die Integration beider Modelle dient als theoretische Grundlage für Konzeption und Analyse der Dissertationsstudien und wird dazu verwendet, Unterschiede zwischen Laien und Experten bei der Betrachtung von Bildern zu diskutieren. Drei Studien wurden durchgeführt, um (Studie 1) die charakteristischen Eigenschaften kunsthistorischer Expertise zu erfassen, (Studie 2) den Einfluss des sozialen und physischen Kontexts auf die Erfassung der Bedeutung eines Ausstellungskonzeptes zu untersuchen und (Studie 3) Experten-Laien Unterschiede im Gebrauch von informativem und weniger informativem Inhalt bei der perzeptuellen und kognitiven Analyse figurativer Bilder zu spezifizieren. Die Ergebnisse der Dissertation zeigen, dass Inhalt für die Erfassung von Bildbedeutung von Experten und Laien der Kunstgeschichte unterschiedlich genutzt wird. Die Debatte innerhalb der ästhetischen Psychologie den Bezug auf Form versus Inhalt eines Kunstwerks als herausragenden Unterschied zwischen Laien und Experten der Kunst zu betrachten, muss also neu geführt werden. Zukünftige Forschung sollte demnach stärkeren Fokus auf die Nutzung von inhaltlichen und formellen Aspekten für die Erfassung von Bildern auf höheren Bedeutungsebenen durch Laien und Experten legen. Die Ergebnisse der vorliegenden Arbeit sind aber auch für die museale Praxis von Bedeutung, da sie andere Herangehensweisen an die Kunstvermittlung im Museum empfiehlt, die Besucherinnen und Besuchern Situationen und Instrumente bereit stellen, in denen gemeinsam und vergleichend der Bedeutung von Bildern nachgegangen werden kann

Bioorthogonal protein-DNA conjugation methods for force spectroscopy.

Accurate and stable site-specific attachment of DNA molecules to proteins is a requirement for many single-molecule force spectroscopy techniques. The most commonly used method still relies on maleimide chemistry involving cysteine residues in the protein of interest. Studies have consequently often focused on model proteins that either have no cysteines or with a small number of cysteines that can be deleted so that cysteines can then be introduced at specific sites. However, many proteins, especially in eukaryotes, contain too many cysteine residues to be amenable to this strategy, and therefore there is tremendous need for new and broadly applicable approaches to site-specific conjugation. Here we present bioorthogonal approaches for making DNA-protein conjugates required in force spectroscopy experiments. Unnatural amino acids are introduced site-specifically and conjugated to DNA oligos bearing the respective modifications to undergo either strain-promoted azidealkyne cycloaddition (SPAAC) or inverse-electron-demand Diels-Alder (IE-DA) reactions. We furthermore show that SPAAC is compatible with a previously published peptide-based attachment approach. By expanding the available toolkit to tag-free methods based on bioorthogonal reactions, we hope to enable researchers to interrogate the mechanics of a much broader range of proteins than is currently possible

Modeling for nano risk assessment and management: The development of integrated governance tools and the potential role of technology assessment

In nano risk governance, we observe a trend toward coupling and integrating a variety of computational models into integrated risk governance tools. This article discusses the development and design of such integrated tools as ‘nano risk governance imaginaries in the making.’ Using an illustrative example, the SUNDS tool, we show how the tool manifests conceptual shifts from risk to innovation governance, a technocratic evidence culture based on the quantification of risks, and an envisioned application in industrial innovation management. This conceptualization runs the risk of narrowing the view of nano risks and cementing the widely lamented democratic deficit in risk governance. We therefore conclude that the development and application of integrated governance tools are highly relevant for technology assessment (TA) and TA should actively engage in their development processes

Standardizing DIRAC’s Cloud Interfaces

DIRAC is a widely used framework for distributed computing. It provides a layer between users and computing resources by offering a common interface to a number of heterogeneous resource providers. In these proceedings we describe a new implementation of the DIRAC to Cloud interface