The 10 most recently published documents
In order to support both the provision of clean drinking water and the preservation of biodiversity in aquatic ecosystems, a comprehensive scientific understanding of the identity, concentration, and behavior of anthropogenic pollutants in the aquatic environment is essential. Organic micropollutants constitute a large group of anthropogenic pollutants and originate from all areas of daily human life: pharmaceuticals are part of the daily routine for many people, pesticides are crucial for food production, and organic chemicals are used in the industrial production of paper, plastics, paints, and many other products. These micropollutants enter the water cycle, either in their parent form or as transformation products, where they can lead to potentially harmful effects. In addition to target methods, non-target approaches have been established as powerful tools for comprehensively investigating these compounds in the water cycle. Beyond the analytical challenges of instrumentally detecting these compounds, the prioritization and evaluation of the large datasets generated by non-target pose both chemical and data science challenges, forming the overarching theme of this work.
The work comprises three studies demonstrating the development and application of non-target screening (NTS) methodologies. In an NTS using high-performance liquid chromatography (HPLC) coupled with high-resolution mass spectrometry (QTOF-MS/MS), 112 samples from the river Nidda and seven of its tributaries were analyzed. On average, approximately 2700 signals, or features, were detected per sample. To filter these extensive data and prioritize unknown compounds, a method was first developed to reliably assign adducts, isotopologues, source fragments and other ionization products to a common component based on retention time and peak shape. In the next step, the prioritization of unknown compounds was achieved by highlighting features that were detected specifically at individual sites under investigation, but which were not typically considered to originate from municipal wastewater. This was accomplished by comparing the data from the Nidda river system with NTS data from municipal wastewater treatment plant effluents. Only the highlighted, Nidda-specific features were considered further. As a result, an average data prioritization of 7% across all samples was achieved, leading to the identification of nine compounds. Among these were the industrial compound Nylostab S-EED™, which had not been previously observed in the environment and three algal toxins, whose occurrence resulted from the algal bloom of a nearby water body.
In the second study, investigations focused on permanently cationic compounds in suspended particulate matter samples from the rivers Rhine and Saar. The data prioritization was based on the specific physicochemical properties of this substance group. Following extraction, a two-step procedure was applied, relying on interactions with strong ion exchangers and chromatography using deuterated solvents. This resulted in 5% of the detected NTS signals being labeled as potentially cationic compounds. Based on this, 22 compounds were identified, four of which were previously unknown. Trend analyses covering the period from 2005/2006 to 2018, along with an assessment of the ecotoxicological risks based on semi-quantitatively determined concentrations, suggest that identified compounds such as Basic Yellow 28 and Fluorescent Brightener 363 may have a high ecotoxicological relevance.
The third study focused on the analysis of samples from disconnected, inter-regional river systems. In collaboration with the local environmental authorities, a three-year study was conducted, analyzing 524 samples from 79 sites along rivers across Saxony. For this purpose, a method was developed that allowed for the characterization of sites based on five categories, considering both known and unknown compounds to assess their chemical contamination. The results were classified by calculating the modified z-scores within each category. The method was validated based on the results of target analysis in the same samples. As a result of the study, 13 sites were classified as anomalous due to high z-scores, as elevated levels of pharmaceuticals, industrial chemicals but also unclassified unknown compounds were detected. At two potentially industrially contaminated sites, the Münzbach and Dorfbach Oberschindmaas, nine compounds were identified and their concentrations were estimated using a 1-point calibration. For the compound hexa(methoxymethyl)melamine, a concentration in the range of 300 µg/L was determined, suggesting a considerable risk for the environment (risk quotient: 5.6).
Microplastics (MP) (1 μm to 5 mm) enter riverine environments in various ways. Point sources (e. g. industrial plants) can be differentiated from diffuse sources (e. g. erosion). Once MP has entered river systems, it underlies hydrodynamic processes and is finally transported towards the oceans. Due to fragmentation, MP particles decrease in size during transport. MP particles are highly heterogeneous considering density and shape, which makes spatially and temporally high resolved sampling difficult and thus hampers the quantification of annual loads in rivers. Within this thesis, we conducted a spatially and temporally high resolved monitoring in the River Rhine with the aim to quantify an annual MP load at our study site, Koblenz.
With a literature review we exposed that most studies present their results by means of particle number instead of particle mass. Also, many studies did not consider spatial nor temporal aspects within their sampling design. For the first time, we presented a compilation of global annual load values within river systems, partly using innovative methodological approaches to convert MP items to MP mass. Hereby, a correlation between catchment area and annual MP load could be detected. Global loads showed a large range (< 1 kg/y – 1533 t/y).
To estimate the annual MP load of the River Rhine at the study site Koblenz, we performed a temporally high resolved sampling using sedimentation boxes (SB, time-integrated samples over months) and a continuous flow centrifuge (CFC, discrete sampling). Via thermal degradation procedures, polymer concentration in mg/g was estimated for PP, PE, PS and PVC. Hereby, annual loads of 400 t (SB) and 60 t (CFC) were calculated. Deviation of both methods was more pronounced for polymers with lower density (PP and PE), whereas PVC loads were comparable. This led to further laboratory experiments, which showed that particle retention efficiency of the SB was varying with the particle’s properties. Thus, the SB sample might not be representative for the river’s conditions. Furthermore, the CFC had difficulties in retaining polymers with lower density (losses up to > 50 % were noticed). Nevertheless, the calculated MP loads do fit well into our compilation of global MP load values. An extensive quantification of retention efficiencies for several polymer types and particle sizes (SB) or an additional sampling step for the clearwater of the CFC for low-dense MP particles could lead to more robust MP concentration values in the future.
Depth-distributed sampling campaigns with a filter cascade and filter nets revealed strong density-dependant vertical gradients within the water column. These gradients were even apparent within the smallest particle size classes and thus were larger than a theoretical determination based on the Rouse number would have suggested. Both, filter cascade and filter net showed a positive correlation between river discharge and MP concentration. This correlation allows for a first speculation on MP sources within the River Rhine: The main source of MP seems, in congruence with suspended sediments, to be a diffuse entry which rises with rising water level. In contrast, a constant entry from a point source would lead to lower concentrations during flood events due to dilution.
Within this work we could point out that extensive research is needed considering the understanding of different sampling devices and their sampling efficiencies. First approaches for an improvement of these limitations have been shown. Still, a combination of sampling techniques is necessary to cover the portfolio of potential issues regarding MP research. For a more precise quantification of annual MP loads, standardisation of procedures on all working steps is urgently needed.
Promotionsordnung des Fachbereichs 2:
Philologie / Kulturwissenschaften der Universität Koblenz
Promotionsordnung des Fachbereichs 3:
Mathematik / Naturwissenschaften der Universität Koblenz
Promotionsordnung des Fachbereichs 4:
Informatik der Universität Koblenz
Ordnung für die Eignungsprüfung Musik der Universität Koblenz
Promotionsordnung des Fachbereichs 1:
Bildungswissenschaften der Universität Koblenz
This study investigated the acquisition of skills by future maths teachers in Rhineland-Palatinate during
their final internship phase before entering the so-called `Vorbereitungsdienst´, a kind of in-depth in-
ternship/ practical training.
In order to record the students' learning progress, a pre/post-test approach was chosen in which the
participants each analysed five short teaching sequences in an online questionnaire and then answered
questions on mathematical argumentation. So the test reflected a central content of the internship,
the observation and reflection of maths lessons.
All video sequences were focussed on aspects of mathematical argumentation in the classroom. Ma-
thematical reasoning not only describes one of the general competences laid down in the educational
standards and curricula for the subject of mathematics, but also goes beyond the other general com-
petences in terms of its fundamental importance for mathematics lessons.
In the test group, a total of 54 trainees was surveyed at the beginning and at the end of their in-depth
internship in four internship periods in 2022 and 2023. The control group consisted of 28 student tea-
chers of mathematics, who were also surveyed twice at 3-week intervals without completing a school
placement in the meantime.
The collected data sets, which essentially consist of free text responses, were analysed using the qua-
litative content analysis method. In addition, the interpretative uncertainty that arises here was mini-
mised through backward testing. In this way, the quantity and quality of the video analysis as well as
the knowledge and understanding of mathematical argumentation could be determined and com-
pared for each respondent in both tests.
As a result, the study confirms previous findings regarding the perception of teaching by experts and
novices and also the fundamental increase in knowledge through practical phases. In addition the
study shows that both quantitative and qualitative response behaviour improved after the practical
training and the test participants were able to identify aspects of argumentation in the lesson excerpts
and justify their importance for good mathematics teaching. This was more successful in teaching si-
tuations that are not very dynamic than in teaching situations that are very dynamic, such as those
arising from conversational situations. In addition, a deeper understanding of the competence `ma-
thematical argumentation´ could be demonstrated after the internship and it could be seen that the
didactic knowledge and the ability to analyse videos correlate more strongly with each other in the
post-test than in the pre-test.
The effects described were only evident in the test group, but not in the control group without the
work placement.
Positron Emission Tomography (PET) is becoming more and more important in clinical routine
applications. One of the major limitations is the sensitivity to patient motion especially in the thorax
to periodic respiratory movement. Another open point of discussion is the method how to define the
tumor volume, especially when the precise knowledge of the tumor borders is important as in
radiation treatment planning. Therefore, in this work these two topics to improve quantification in
PET imaging have been addressed. First a new motion correction algorithm was implemented using
image deblurring including movement information of a 4D Computed Tomography (CT). This method,
which has the advantage of not increasing the PET acquisition time as other motion correction
techniques, was applied to phantom and patient data and showed promising result in improvement of lesion quantification. In phantom studies an improvement of up to 49% in lesion volume and in
patient studies of up to 33.3% could be demonstrated.
In the second part of this work, a new segmentation method based on textural parameters was
implemented and validated as well in phantom and patient data. In the latter a validation with
histopathological data was performed showing a very good performance of the new algorithms,
especially in larger lesions. Best result could be shown in phantom data and patient data for the
segmentation algorithm based in the local entropy.
In summary, two algorithms were implemented and validated which can improve quantification of
PET imaging furthermore
Seit mehr als 10 Jahren forscht und lehrt das Team des Centers for Enterprise Research (CEIR) an der Universität Koblenz im Bereich der digitalen Unterstützung kollaborativer Arbeit in Unternehmen (Enterprise Collaboration) und untersucht den Aufbau und die Nutzung von Kollaborationstechnologie für den Digitalen Arbeitsplatz.
Der vorliegende CEIR Report mit dem Titel „Collaborative Actions on Documents Ontology (ColActDOnt)“ beschreibt die Entwicklung einer Ontologie für Benutzeraktionen an Content in Kollaborationssystemen (englisch: Enterprise Collaboration Systems). Die Arbeit an der Ontologie erfolgte im Rahmen eines DFG-Projekts mit dem Titel „Social Process Mining“. In diesem Projekt wurde eine Methode für das sogenannte „Cross-System Process Mining“ entwickelt. Cross-System Process Mining erlaubt die Analyse von Arbeitsprozessen, deren Ablauf von mehreren, heterogenen Kollaborationslösungen (z.B. HCL Connections, Alfresco, Skype) unterstützt werden. Aufgrund der Heterogenität der involvierten Systeme müssen die Logfiles der unterschiedlichen Softwaresysteme zunächst in einen gemeinsamen, harmonisierten Event-Log überführt werden. Die ColActDOnt stellt die notwendige Systematik für diese Harmonisierung zur Verfügung.
Die Ontologie wurde entwickelt in einer Reihe von interaktiven Workshops mit den Projektbeteiligten (Prof. Dr. Petra Schubert, Dr. Florian Schwade, Julian Mosen) unter der Leitung von Martin Just, der die Ergebnisse anschließend im Rahmen seiner Masterarbeit dokumentierte. Anschließend wurden die wichtigsten Teile in gekürzter Form in dem vorliegenden CEIR-Report veröffentlicht.
Mit den CEIR-Reports möchten wir ausgewählte wissenschaftliche Ergebnisse einem breiteren Publikum zur Verfügung stellen. Die in dieser Arbeit dargestellten Informationen sind für Unternehmen interessant, die an einer gezielten (Weiter-)Entwicklung ihrer Enterprise Collaboration Platform interessiert sind.