Search

Abstract Background Vasoactive intestinal polypeptide secreting tumors(VIPomas) are rare endocrine tumors of the pancreas with an estimated incidence of 0.1 per million per year. The molecular mechanisms that mediate development of VIPomas are poorly investigated and require definition. Methods A genome- and gene expression analysis of specimens of a primary pancreatic VIPoma with hepatic metastases was performed. The primary tumor, the metastases, the corresponding healthy tissue of the liver, and the pancreas were compared with each other using oligonucleotide microarrays and loss of heterozygosity (LOH). Results The results revealed multiple LOH events and several differentially expressed genes. Our finding of LOH and downregulation was conspicuous in the microarray analysis for the mismatch repair gene MSH2 in the primary pancreatic VIPoma tumor, the hepatic metastasis but not in the corresponding healthy tissue. Further a strong overexpression of the chemokine CXCR4 was detected in the hepatic metastases compared to its pancreatic primary. With a review of the literature we describe the molecular insights of metastatic development in VIPoma. Conclusion In VIPoma, defects in the mismatch repair system especially in MSH2 may contribute to carcinogenesis, and increased CXCR4 may be associated with liver metastasis.

In Germany enrolment in majors is of considerable interest to academic departments, because their budget depends on the number of enrolled students. Besides observed factors, we presume that unobserved latent variables influence the major‐choice decision of students. Using stated preferences data from a discrete choice experiment among students pursuing a bachelor's degree in business administration at Hamburg Business School (HBS), we employ an integrated choice and latent variable model (ICLV). Thereby, we model the influence of a major‐specific latent variable, labeled image, on the major‐choice decision of the students. To identify the latent variables, we utilise ordered categorical indicators that we obtained from the assessment of major‐specific psychometric factors among students. Our findings reveal a significant impact of the latent variable image on the major‐choice decision. We further show the advantageous characteristic of an ICLV model by illustrating the cause‐and‐effect relationship compared to classic multinomial logit models. Based on our results, we examine practice‐oriented, requirements, research, and supervision to be the most relevant psychometric factors that lead to the identification of the latent variables and provide insights on how academic departments at HBS can raise their major's attractiveness from the student's perspective. Abstrakt: In Deutschland ist die Immatrikulation in den Studiengängen für die Fachbereiche von großem Interesse, da ihr Budget von der Anzahl der eingeschriebenen Studierenden abhängt. Neben den beobachteten Faktoren nehmen wir an, dass nicht beobachtete latente Variablen die Schwerpunktwahl der Studierenden beeinflussen. Auf der Grundlage von Präferenzdaten aus einem diskreten Auswahlexperiment unter den Studierenden des Bachelor‐Studiengangs der Betriebswirtschaftslehre an der Hamburg Business School (HBS) verwenden wir ein integriertes Wahl‐ und latente Variablenmodell (ICLV). Dabei modellieren wir den Einfluss einer Schwerpunkt‐spezifischen latenten Variable, die als Image bezeichnet wird, auf die Schwerpunktwahl der Studierenden. Um die latente Variable zu identifizieren, verwenden wir geordnete kategorische Indikatoren, die wir aus der Bewertung der Schwerpunkt‐spezifischen psychometrischen Faktoren erhalten haben. Unsere Ergebnisse zeigen einen signifikanten Einfluss der latenten Variable Image auf die Schwerpunktwahl. Wir zeigen ferner die vorteilhafte Eigenschaft eines ICLV‐Modells, indem wir die Ursache‐Wirkungs‐Beziehung im Vergleich zu klassischen multinomialen Logit‐Modellen veranschaulichen. Basierend auf unseren Ergebnissen untersuchen wir Praxisorientierung, Anforderung, Forschung und Betreuung als die relevantesten psychometrischen Faktoren, die zur Identifizierung der latenten Variable führen und Einblicke geben, wie die Schwerpunkte der HBS die Attraktivität ihres Studienfachs aus der Perspektive der Studierenden erhöhen können. [ABSTRACT FROM AUTHOR]

Titanium sheets were irradiated by free electron laser radiation in cw mode in pure nitrogen. Due to the interaction, nitrogen diffusion occurs and titanium nitride was synthesized in the tracks. Overlapping tracks have been utilized to create coatings in order to improve the tribological properties of the sheets. Caused by the local heating and the spatial dimension of the melt pool, convection effects were observed and related to the track properties. Stress, hardness, and nitrogen content were investigated with x-ray diffraction, nanoindention, and resonant nuclear reaction analysis. The measured results were correlated with the scan parameters, especially to the lateral track shift. Cross section micrographs were prepared and investigated by means of scanning electron microscopy. They show the solidification behavior, phase formation, and the nitrogen distribution. The experiments give an insight into the possibilities of materials processing using such a unique heat source. [ABSTRACT FROM AUTHOR]

With micro-Raman spectroscopy and x-ray diffraction (XRD), we studied ZnO crystals implanted with Mn, Fe, Co, and Ni, respectively, with implantation concentrations from 4 up to 16 at. %. Using thermal treatments in air up to 700 °C, we analyzed the annealing effect on the ZnO crystal lattice as well as the onset of secondary phases and their microstructure on the sample surface. While the 500 °C treatment induces a considerable annealing, secondary phases are observed for transition metal (TM) concentrations ≥8 at. % after the treatment at 700 °C. Their microstructure strongly depends on the TM species. Various stoichiometric and nonstoichiometric TM oxide precipitates as well as elemental TM clusters are identified by their Raman and XRD signatures and their possible magnetic impact is discussed. [ABSTRACT FROM AUTHOR]