PbTiO₃/SrTiO₃ interface: Energy band alignment and its relation to the limits of Fermi level variation

The interface formation between PbTiO₃ and SrTiO₃ has been studied by in situ photoelectron spectroscopy. A valence band offset of 1.1±0.1eV, corresponding to a conduction band offset of 1.3±0.1eV, is determined. These values are in good agreement with the band offsets estimated from measured ionization potentials of SrTiO₃ and PbTiO₃ surfaces. The observed band offsets are also in line with a ~1.1eV difference in barrier heights of PbTiO₃ in contact with different electrode materials as compared to barrier heights of SrTiO₃ with the same electrode materials. The results indicate that the band alignment is not strongly affected by Fermi level pinning and that the barrier heights are transitive. The limits of Fermi level variation observed from a number of thin films prepared on different substrates with different conditions are the same for both materials when these are aligned following the experimentally determined band offsets. By further comparing electrical conductivities reported for SrTiO₃ and PbTiO₃, it is suggested that the range of Fermi level position in the bulk of these materials, which corresponds to the range of observed conductivities, is comparable to the range of Fermi level position at interfaces with different contact materials. In particular the possibly low barrier height for electron injection into SrTiO₃ is consistent with the metallic conduction of donor doped or reduced SrTiO₃, while barrier heights ≳1eV for PbTiO₃ are consistent with the high resistivity even at high doping concentrations. The variation of barrier heights at interfaces therefore provides access to the range of possible Fermi level positions in the interior of any, including insulating, materials, which is relevant for understanding defect properties

Surface states, surface potentials, and segregation at surfaces of tin-doped In₂O₃

Surfaces of In₂O₃ and tin-doped In₂O₃ (ITO) were investigated using photoelectron spectroscopy. Parts of the measurements were carried out directly after thin film preparation by magnetron sputtering without breaking vacuum. In addition samples were measured during exposure to oxidizing and reducing gases at pressures of up to 100Pa using synchrotron radiation from the BESSY II storage ring. Reproducible changes of binding energies with temperature and atmosphere are observed, which are attributed to changes of the surface Fermi level position. We present evidence that the Fermi edge emission observed at ITO surfaces is due to metallic surface states rather than to filled conduction band states. The observed variation of the Fermi level position at the ITO surface with experimental conditions is accompanied by a large apparent variation of the core level to valence band maximum binding energy difference as a result of core-hole screening by the free carriers in the surface states. In addition segregation of Sn to the surface is driven by the surface potential gradient. At elevated temperatures the surface Sn concentration reproducibly changes with exposure to different environments and shows a correlation with the Fermi level position

Lewis A. Coser: a stranger within more than one gate

This article presents a short portrait of Lewis A. Coser (1913–2003), the American sociologist who became renowned as one of the founders of ‘conflict sociology’. Born in Berlin, Coser had to leave his homeland for political reasons and he spent the years before Nazi Germany’s invasion of France in Paris. Coser then fled to the United States and started his academic career there at the College of the University of Chicago. An abridged version of the PhD thesis he wrote at Columbia University was published as The Functions of Social Conflict, which earned him recognition, a promotion, and made him a figure of authority for sociologists in the 1960s. In this article the author draws on archival materials to examine Coser’s life, major publications and achievements. His intellectual trajectory from Marxism to Mertonian Functionalism, his strong commitment to a Weberian view of the separation of politics from scholarship, the breadth of his erudition in literature and classical sociological theory, and his lifelong place in New York intellectual circles and intellectual magazines made him an extraordinary figure even amongst his contemporaries

MCL-1 antagonism enhances the anti-invasive effects of dasatinib in pancreatic adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) remains one of the deadliest malignancies. It is phenotypically heterogeneous with a highly unstable genome and provides few common therapeutic targets. We found that MCL1, Cofilin1 (CFL1) and SRC mRNA were highly expressed by a wide range of these cancers, suggesting that a strategy of dual MCL-1 and SRC inhibition might be efficacious for many patients. Immunohistochemistry revealed that MCL-1 protein was present at high levels in 94.7% of patients in a cohort of PDACs from Australian Pancreatic Genome Initiative (APGI). High MCL1 and Cofilin1 mRNA expression was also strongly predictive of poor outcome in the TCGA dataset and in the APGI cohort. In culture, MCL-1 antagonism reduced the level of the cytoskeletal remodeling protein Cofilin1 and phosphorylated SRC on the active Y416 residue, suggestive of reduced invasive capacity. The MCL-1 antagonist S63845 synergized with the SRC kinase inhibitor dasatinib to reduce cell viability and invasiveness through 3D-organotypic matrices. In preclinical murine models, this combination reduced primary tumor growth and liver metastasis of pancreatic cancer xenografts. These data suggest that MCL-1 antagonism, while reducing cell viability, may have an additional benefit in increasing the antimetastatic efficacy of dasatinib for the treatment of PDAC

Indications for a metatheoretic foundation of meaning in biosemiotics. Some philosophical remarks as an introduction to the Gatherings in Biosemiotic 6, Salzburg, Austria, 5-9 July 2006

Biosemiotics is the study of meaning in living systems; it is about context dependent communication and signification on all levels of biological organization. Thereby, biosemiotics perceives the concept of meaning as an essential, non-reducible characteristic of the living world; without it, the latter cannot be understood in a reasonable way. But this position is in conflict with the standard classical stance of natural science (though, of course, not with the one of social sciences). Accord-ing to this perspective, the idea of meaning can only be consid-ered as a kind of metaphorical use of language (due to our cognitive inability in terms of a complete reduction). This article gives some indications, how biosemiotics can defend and justify its position form a metatheoretic and philosophic point of view. Though, meaning is so evident and, hence, a basically real fact in living systems, we nevertheless need a sound scientific foundation for its argumentation

Kathodenzerstäubte(Ba,Sr)TiO3-Dünnschichten für steuerbare Mikrowellenkomponenten Material-, Bauteil- und Grenzflächeneigenschaften

In dieser Arbeit wurde der Einfluss der Präparationsbedingen auf die Zusammensetzung, Struktur und die elektronischen Eigenschaften von kathodenzerstäubten (Ba,Sr)TiO3 Dünnschichten untersucht und mit den Bauteileigenschaften von auf diesen Schichten aufbauenden Varaktoren in Metall/Isolator/Metall-Topographie in Zusammenhang gebracht. Des Weiteren wurden die bauteilrelevanten Kontakteigenschaften zwischen Dielektrikum und Metallisierung mittels in-situ Photoelektronenspektroskopie untersucht. Hierbei wurde eine starke Abhängigkeit der Schottky-Barrierenhöhe von der Grenzflächendefektkonzentration am Kontakt gefunden und die Defekte Sauerstoffleerstellen zugeordnet