Soziales Kapital als Determinante der Kundenbeziehung

In der Marketingliteratur liegen bis dato keine wissenschaftlichen Untersuchungen vor, die den Effekt des Sozialen Kapitals als Determinante der Kundenbeziehung empirisch nachweisen. Daher besteht ein Forschungsdefizit, welchem mit der vorliegenden Untersuchung begegnet werden soll. Der Analyse liegt die Annahme zugrunde, daß Virtuelle Gemeinschaften Soziales Kapital bereitstellen. Die Erklärung dieses aus der Soziologie stammenden Konstrukts erfolgt im Rahmen dieser Arbeit anhand der Determinanten Qualität des sozialen Netzwerks, Normen sowie Social Trust. Hierbei handelt es sich um hypothetische Konstrukte, die im Hinblick auf die Empirie konzeptualisiert und mit zentralen Elementen des Beziehungsmanagements (Zufriedenheit, Vertrauen, Commitment) in Verbindung gesetzt werden. Durch die abschließende kausalanalytischen Untersuchung mittels des LISREL-Ansatzes gelingt es, ein Modell zu identifizieren, woran kundenbindende Effekte Virtueller Gemeinschaften festgemacht werden können. Obwohl die Stichprobe nur in einer Community (Puschkin Bar) generiert wurde, lassen sich Trendaussagen bezüglich der Gestaltung und des Managements dieses Marketinginstruments treffen

A microsatellite study in the Łęgucki Młyn/Popielno hybrid zone reveals no genetic differentiation between two chromosome races of the common shrew (Sorex araneus)

This study investigated a chromosome hybrid zone between two chromosomal races of the common shrew (Sorex araneus). Gene flow and genetic structure of the hybrid zone, located in the northeast of Poland, were studied using seven polymorphic autosomal microsatellite loci (L9, L14, L33, L45, L67, L68, L97) and a Y-linked microsatellite locus (L8Y). Seventy-five animals (46 of the Łęgucki Młyn race and 29 of the Popielno race) from nine different localities were examined and the data were analyzed using hierarchical AMOVA and F-statistic. The studied microsatellite loci and races (divided into nine geographical populations) were characterized by observed heterozygosity (HO), expected heterozygosities within (HS), and between (HT) populations, inbreeding coefficient (FIS), fixation index (FST), and average allelic richness (A). We found that genetic structuring within and between the two chromosome races were weak and non-significant. This finding and unconstrained gene flow between the races indicates a high level of migration within the Łęgucki Młyn/Popielno hybrid zone, suggesting that evolutionarily important genetic structuring does not occur in interracial zones where races which are not genetically distinct come into contact

External quality assessment of trans-European multicentre antigen determinations (enzyme-linked immunosorbent assay) of urokinase-type plasminogen activator (uPA) and its type 1 inhibitor (PAI-1) in human breast cancer tissue extracts.

High levels of urokinase-type plasminogen activator (uPA) and plasminogen activator inhibitor type 1 (PAI-1) in breast cancer tissue extracts have been associated with rapid disease progression. In these studies, different enzyme-linked immunosorbent assay (ELISA) kits have been applied for the quantification, and consequently the ranges of uPA and PAI-1 levels reported differ considerably. Therefore, the Receptor and Biomarker Study Group (RBSG) of the European Organization for Research and Treatment of Cancer (EORTC) and a consortium of the BIOMED-1 project 'Clinical Relevance of Proteases in Tumor Invasion and Metastasis' initiated three collaborative between-laboratory assessment trials aimed at controlling uPA and PAI-1 antigen analyses. For this purpose, two control preparations were produced from different sources: pooled human breast cancer specimens (QC-240893) and human breast cancer xenografts raised in nude mice (QC-101094). The lyophilized preparations were stable for prolonged times (at least 3 and 27 months respectively) at 4 degrees C. Furthermore, a good parallelism following dilution was found for uPA and PAI-1. The data from QC trial no. 1 clearly indicated that acceptable between-laboratory coefficients of variation (CVs) for uPA (<8.2%) and PAI-1 (<16.6%) in QC-240893 could be achieved when the same type of ELISA kit (American Diagnostica) was used. From the second trial, in which ten EORTC laboratories each received five identical lyophilized QC-101094 samples, it appeared that the within-laboratory variations for uPA and PAI-1 determinations obtained by 'experienced' laboratories were lower (<12.9%) than those from non-experienced laboratories (<36.4%). In a third QC trial, five BIOMED-1 laboratories, all of which employed ELISA procedures for uPA and PAI-1, participated in six subsequent quality assessment rounds receiving five samples of QC-101094. Although for each laboratory the within-run CVs for uPA as well as for PAI-1 were low (<7.8%), the between-run CVs were found to be considerably higher (up to 56.2% for uPA and to 27.6% for PAI-1). Consequently, because of the different ELISA formats used, the absolute analyte values measured in the different laboratories varied substantially. The use of 'common external standards' in the different ELISAs resulted in a significant reduction of the between-laboratory CVs from 61.3% to 15.7% (uPA) and from 42.1% to 19.1% (PAI-1). The present data demonstrate that in multicentre studies the same ELISA kit should be used, and that external quality assurance (QA) is mandatory. Furthermore, it appears from the present study that standardization of the protein assay as a tissular parameter is imperative

Soluble urokinase receptor released from human carcinoma cells: a plasma parameter for xenograft tumour studies

The urokinase plasminogen activator receptor (uPAR) plays a critical role in urokinase-mediated plasminogen activation and thereby in the process leading to invasion and metastasis. Soluble urokinase receptor (suPAR) is released from tumours, and in cancer patients the blood level of soluble receptor is increased. Using an enzyme-linked, immunosorbent assay (ELISA)-specific for the human urokinase receptor, release of soluble receptor was measured in cultures of human breast carcinoma cells, in tumour extracts and in plasma from mice with xenografted human tumours. Soluble human urokinase receptor (shuPAR) was released into culture supernatant during the growth of the human breast cancer cell line MDA-MB-231 BAG, and the level of shuPAR in conditioned medium determined by ELISA was a linear function of both viable cell number and time of incubation. Western blotting showed that the form of shuPAR measured by ELISA in conditioned medium consisted virtually exclusively of the three-domain full-length protein, while uPAR in cell lysates consisted of full-length uPAR as well as the domains (2+3) cleavage product. shuPAR was also released into the plasma of nude mice during growth of MDA-MB-231 BAG, MDA-MB-435 BAG and HCT 116 cells as subcutaneously xenografted tumours. Western blotting demonstrated that the shuPAR released from the xenografted human tumours into plasma consisted of the three-domain full-length protein, despite the finding of some cleaved uPAR in detergent extracts of tumour tissue. The levels of shuPAR determined by ELISA in the plasma of host mice during the growth of xenografted cell lines were highly correlated with tumour volume. © 1999 Cancer Research Campaig

Response of the XENON100 Dark Matter Detector to Nuclear Recoils

Results from the nuclear recoil calibration of the XENON100 dark matter detector installed underground at the Laboratori Nazionali del Gran Sasso (LNGS), Italy are presented. Data from measurements with an external 241AmBe neutron source are compared with a detailed Monte Carlo simulation which is used to extract the energy dependent charge-yield Qy and relative scintillation efficiency Leff. A very good level of absolute spectral matching is achieved in both observable signal channels - scintillation S1 and ionization S2 - along with agreement in the 2-dimensional particle discrimination space. The results confirm the validity of the derived signal acceptance in earlier reported dark matter searches of the XENON100 experiment