Monitoring the efficacy of aseptic sterilization processes by means of calorimetric and impedimetric sensing principles

Package sterilization is an essential step during aseptic packaging of food, pharmaceuticals or medical instruments to prevent microbiological contamination of the product. In food industries, the main objective is to produce consumer-safe and long-term stable food products. In recent years, the favored method to sterilize package material is by use of gaseous hydrogen peroxide (H2O2) at concentrations up to 10% v/v and elevated temperatures up to 300 °C. These process parameters enable a fast and effective, in chain sterilization of packages prior to filling with sterile products. Monitoring of this sensitive process is performed by predefined machine settings and laborious microbiological challenge tests, with earliest results after 72 hours. In previous works different sensors to monitor the packaging sterilization process have been developed, but till now there is no commercial system available to continuously monitor the final gas concentration or the microbial sterilization efficacy online within the package. In the present work, as a first approach the sensing principle of a calorimetric H2O2 gas sensor has been studied in more detail. The sensor is based on a differential set-up of one catalytically activated and one passivated temperature-sensing element. Surface characterizations have been performed to reveal the chemical reaction of H2O2 at the applied catalyst manganese(IV) oxide (MnO2). The surface characterization depicted a transition of the manganese oxidation state. Moreover, the treatment with H2O2 eliminates the polymeric layer on top of the catalyst, which has been applied as polymer matrix to attach the catalyst onto the sensing element. The calorimetric gas sensor has been further described by analytical expressions in order to evaluate the theoretical temperature rise. Thereby, different sensor scenarios (steady-state process, gas diffusion process and convective gas flow) have been described by the sensor's thermochemistry and physical transport mechanisms. These theoretical assumptions have been accompanied by surface and thermal characterizations of polymers applied as passivation materials. The characterizations demonstrate the suitability of the three investigated polymers (SU-8 photoresist, Teflon derivatives PFA and FEP), to act as a passivation against gaseous H2O2. As second approach of this work, a novel biosensor has been developed. This biosensor is based on interdigitated electrodes (IDE) on which a standardized test organism is immobilized. This test microorganism, spores of Bacillus atrophaeus, is commonly applied in industrial microbiological challenge tests to evaluate the efficacy of sterilization processes. Impedance measurements are applied to characterize the microbiological samples at the sensor surface before and after the gaseous H2O2 sterilization process. Thereby, a remaining change in impedance and phase has been observed. Numerical simulation tools have been employed to analyze the sensor signal, and to gather material parameters of the spores. Finally, the impedimetric and calorimetric sensor have been combined to serve as a miniaturized sensor system to analyze the efficacy of the gaseous sterilization process

Digital Competencies at Work

The digitalized work environment poses challenges to the workforce, such as the meaningful use of ever-new technological advances, dealing with increasingly complex tasks, or effective collaboration in dispersed work groups. The individual worker needs to adapt to rapidly increasing demands due to far-reaching changes in the workplace, to complete their everyday work tasks. However, there is an increasing discrepancy between the existing and required digital competencies in the workforce. Due to the urgent need to expand the scientific knowledge on this important topic, the main focus of this dissertation is on the development and measurement of the construct of digital competencies at work. In the scientific literature, a comprehensive framework that integrates the perspectives of prior research and practitioners in a work context has not been developed yet. Additionally, a common definition of digital competencies at work was still lacking although many wordings have been used for the concept. Modern work practices, such as the ubiquity of remote work for office workers emphasize the importance of digital communication and collaboration competencies at work. Yet, to date, there was no measurement tool for individual digital communication and collaboration competencies at work that is needed to conduct more scientific research on the construct. Another research gap derived from the results of the prior studies in this dissertation measuring digital competencies: The high mean values in all collected data sets led to the assumption that office workers might over-estimate their digital competencies. However, the research question of how the self-assessment of workers’ digital communication and collaboration competencies can be influenced by varying instructions has not yet been explored in an experimental study. Moreover, to further explore the nomological net of the construct, the relationship between digital communication and collaboration competencies and the motivation to train those were investigated. In my dissertation, I realized the collection of quantitative and qualitative data in nine samples and conducted a literature review to address the outlined research gaps. By integrating perspectives from research and practice and combining diverse methods, a coherent and detailed framework of digital competencies at work was created and a definition of the concept was provided in Paper 1. As depicted in Paper 2, building on the theoretical framework and prior research, digital communication and collaboration competencies were identified as dimensions with particular relevance to the challenges of today’s work environments. By using mixed methods, a measurement tool for digital communication and collaboration competencies was developed. The role of those competencies as potential resources in a gain spiral with social support, ultimately boosting work engagement in the unique setting of a pandemic that fundamentally altered the way of work worldwide based on the Job Demands-Resource model (Demerouti et al., 2001) and the conservation of resources theory (Hobfoll, 2011) was explored. Although results did not support the assumption of a gain spiral, we found that digital competencies, social support, and work engagement were stable and high during the crisis. The findings add knowledge about the motivational processes of workers in times of crisis. Subsequently, in Paper 3 the initial measurement tool was refined into a reliable and valid short-scale of digital communication and collaboration competencies at work. In several studies, the short-scale was validated and the nomological net of the constructs was explored. The last part of my dissertation is dedicated to the systematic examination of the effect that varying instructions have on workers’ self-assessment of digital communication and collaboration competencies and the motivation to train those. The results imply that the self-assessment of competencies and the motivation to train those cannot be influenced easily by varying instructions. Nevertheless, workers with high levels of digital communication and collaboration competencies also showed high motivation to train those. The findings of this dissertation provide a solid base for further theory building and extension in research on digital competencies at work. The insights gained from the studies of this dissertation comprise theoretical and practical implications for training development and human resource management. Overall, the results of this dissertation imply that digital competencies at work could be an important benefit in meeting the challenges of today’s digital work environments. The concept of digital competencies at work deserves more attention in future research

Open-Access-Tage (2007-2015)

[no abstract available

Promoting Open Access to librarians and researchers by the international information platform open-access.net

Open access has become an important publication form but the concept behind is not as well known as the public discussion makes us believe sometimes. Still today open access is equalized with electronic publication and often mixed with offers like google books. Researchers feel unsure when faced with open access and as a consequence often react conservatively. A German Research Foundation (DFG) funded project (2006-2010) attempts to structure and describe the concept of and the discussion about open access. With the libraries of the Universities of Bielefeld, Goettingen und Konstanz and the Institute of Qualitative Research in Berlin, four German experts in the area of open access took the initiative to create a now well known information platform www.open-access.net