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This cumulative dissertation examines the phenomenon of employee silence in professional service firms (PSFs). Although both research streams are independently well-established areas of organizational research, there has been a lack of research investigating the withholding of information, problems, or concerns in the knowledge-intensive context of PSFs. This thesis starts the academic and practitioner discourse about it and opens a multitude of further research opportunities.
The first manuscript draws on a literature-based and conceptual approach to examine the intersections of PSF and silence research. It identifies characteristics of PSFs that lead to employee silence and derives research propositions about the links between PSFs and silence. By applying a multi-method research approach, the second manuscript empirically investigates the extent to which employee silence is prevalent in PSFs. It determines PSF-specific antecedents fostering the unfavorable phenomenon and professionals' motives to remain silent. The third manuscript takes a grounded-theory approach to examine how employee silence in PSFs can be prevented or reduced. It develops overarching fields of action and concrete measures that help practitioners overcome employee silence.
Adopting a combination of Usage-based Construction Grammar and New Englishes approaches, the present study explores the constructional competition between preposition stranding (What is he talking about?) and pied-piping (About what is he talking?) in 12 varieties of English at different stages of Schneider’s (2007) Dynamic Model in order to gain more insights into the cognitive principles underlying the evolution of postcolonial Englishes. Analyzing 10,079 tokens from the International Corpus of English (ICE) and using mixed-effects logistic regression analysis, the study investigates whether the strength of processing factors and stylistic variables is correlated with Dynamic Model stages. Moreover, drawing on Hierarchical Configural Frequency Analysis (HCFA) and Large Number of Rare Events (LNRE) models, it tests Hoffmann’s (2021) Dynamic Model Productivity hypothesis, which predicts that more advanced varieties should exhibit a higher productivity of constructional slots, while varieties at lower stages of evolution should rely more on a small set of prototypical fillers.
The results are largely in line with Hoffmann’s (2011) analysis of preposition placement, which found that Kenyan English is more strongly affected by processing constraints than British English, while stylistic variables have a weaker effect in the L2 variety. Even though processing constraints turn out to strongly affect the constructional choices of speakers of all varieties, less advanced varieties are more likely to use pied-piped WH-interrogative constructions with adjunct PPs, which suggests that varieties at lower stages of evolution have a stronger preference for constructions that facilitate parsing in contexts in which the processing load is not maximal. Furthermore, in line with the frequent claim that New Englishes are characterized by a lack of register distinctions, the strength of stylistic variables turns out to be correlated with Dynamic Model stages. While Phases IV and V have formal pied-piped and informal stranded finite WH-relative clause constructions, Phase III only has the pied-piped variant. This effect can be attributed to two factors: the formal input that is typical of postcolonial Englishes, and the processing complexity of stranding constructions. That preposition stranding is less deeply entrenched in varieties at lower stages is also indicated by the fact that the slots of stranding constructions show a higher productivity in varieties at higher developmental stages, whereas less advanced varieties rely more on entrenched verb-preposition strings (e.g. refer to) and WH + P combinations (e.g. what…about). At the same time, earlier Dynamic Model phases exhibit more variation in the preposition slot of pied-piped finite WH-relative clause constructions, which can be attributed to the weaker entrenchment of constructions and a preference for explicit and transparent form-meaning pairings in these varieties. In sum, the results suggest that differences between the construction networks of varieties at different evolutionary stages result from a complex interplay of processing factors, input effects, second-language learning principles and, at least to a certain degree, cross-linguistic influence. In addition, the study shows that varieties of the same phase pattern very similarly in terms of their constructional choices, which provides support for Schneider’s (2007) classification of varieties according to Dynamic Model stages.
The study of nonlocal energy-based models has proliferated in the last decades
due to their relevance in applications and the novel mathematical challenges that they provide. Within this context, the thesis addresses a wide variety of aspects concerning variational problems involving nonlocal gradients. These have been proposed for modeling the emergence of cracks and cavitations in materials, and can be used in image denoising applications to preserve sharp features. The contributions of the thesis are concerned with several families of nonlocal gradients and can be divided into the following overarching themes:
(i) Development of nonlocal Sobolev spaces;
(ii) existence theories for minimizers of nonlocal integral functionals;
(iii) asymptotic analysis of parameter-dependent problems.
In the context of (i), we extend and unify the results established for the Riesz and finite-horizon fractional gradient by considering more general nonlocal gradients with radial kernels. Precisely, based on a delicate analysis of the Fourier symbol of the nonlocal gradient, we present minimal assumptions on the kernel function such that Poincaré inequalities and compact embeddings hold. Moreover, we provide sharp embeddings into Orlicz spaces and spaces with prescribed modulus of continuity, that refine the fractional Sobolev and Morrey inequalities.
With these tools at hand, the goal in (ii) is to establish rigorous existence results for minimizers of integral functionals depending on nonlocal gradients. We develop a translation mechanism that connects the nonlocal gradients with their local counterpart and use this to characterize the lower semicontinuity of the nonlocal functionals in terms of the classical notion of quasiconvexity. Based on this, we establish the existence of minimizers via the direct method under Dirichlet or novel Neumann-type boundary conditions. The latter conditions necessitate the study of functions with zero nonlocal gradient, which surprisingly constitute an infinite-dimensional vector space, and we employ recent results regarding pseudo-differential boundary-value problems to characterize them. We also tackle linear growth functionals, which lack the usual coercivity requirement, and provide an explicit formula for their relaxation in the space of functions with bounded fractional variation. This reveals insights about the behavior of minimizing sequences and is based on a careful analysis of the concentration effects of the fractional gradient by using tools from Young measure theory.
Building upon the existence results, the focus in (iii) lies on studying the dependence of the minimizers on parameters in the problem, specifically, the fractional parameter s and the interaction range δ. We establish using Gamma-convergence that the minimizers depend continuously on s and converge to the local solutions as s → 1. In parallel, we prove that localization also occurs in the vanishing horizon limit δ → 0, while the diverging horizon regime δ → ∞ leads to the models based on the Riesz fractional gradient. A crucial ingredient for the proofs of these results are uniform compactness statements, which are established by studying the dependence of the Fourier symbols on the respective parameters. In terms of applications, we develop an abstract framework for the well-posedness of bi-level optimization problems for parameter learning in image denoising. The results of the thesis show that the models involving nonlocal gradients fit into this framework, where the fractional parameter is tuned in order to obtain the optimal degree of smoothing.
The objective of this cumulative dissertation is to mitigate cognitive bias in human expert judgments intending to increase accuracy of judgments. The latter is important as it is known to be essential for business success. The approach for this purpose is to combine the strengths of humans and machines by giving the expert feedback generated by a statistical model (the machine) based on previous errors of the expert. Based on this concept of collaborative intelligence, a Decision Support System (DSS) is developed and tested in several experiments. The cumulative dissertation consists of three articles. Article 1 and Article 2 investigate different aspects of the DSS and Article 3 merges and supports the statements thereof. Article 1 considers the impact of personal error pattern feedback on further point estimates. The error feedback is based on personal prior judgments originating from different categories, assuming that experts selectively apply the feedback and are able to reduce bias and error. Thereby it is examined, how the feedback is used to change the direction of error and to reduce bias and error. This is investigated in general disregarding categories as well as selectively regarding difference between categories. Article 1 also covers the comparison between human corrected bias and machine auto-corrected bias. Article 2 deals with experiments with the same DSS, but focusing on certainty (confidence) interval estimation and decreasing overprecision (overconfidence) and over- and underestimation biases. Here, the DSS requires users to indicate a 90% certainty interval as an answer to estimation questions. It is investigated how feedback based on own error patterns can help to reduce overprecision by broadening certainty intervals. Moreover, aiming to mitigate over- and underestimation biases, shifts of the intervals are examined. Article 3 supports the statements of Article 1 and 2 by taking into account additional experiments with a larger sample size with the same categories as well as new categories to make the results more robust and generally valid. Article 3 also includes a further analysis regarding the comparison between human corrected bias and machine auto-corrected bias.
Unveiling the digital mindset: theoretical foundations, conceptualization and scale development
(2024)
This cumulative dissertation examines an individual’s digital mindset including its theoretical foundations. While the construct receives growing attention from academics and practitioners, research is still in its infancy with limited and heterogeneous conceptualizations.
The first manuscript conducts a systematic literature review on mindset definitions and conceptualizations prevalent in the management and business literature, contributing to the clarity of the mindset construct.
The second manuscript follows a multi-grounded theory approach to systematically define and conceptualize an individual’s digital mindset, posing an essential competency in the context of digital transformation.
The third manuscript builds on this definition and develops and validates a scale (DIMI-scale) to measure the construct throughout five phases.
The present cumulative thesis is based on 6 papers concerning 3 topics: Balian-Low theorems, exponential bases and neural network approximation.
Various extensions of the Balian-Low theorem are proved for Gabor spaces spanning strict subsets of the space of square-integrable functions on the real line.
Concerning exponential bases, we show that a partition of the unit interval into subintervals with rationally independent endpoints admits a so-called hierarchical Riesz spectral set.
Finally, in terms of neural network approximation, quantitative rates for the approximation of complex valued functions with Sobolev (real) regularity via complex valued neural networks are obtained. Additionally, a network architecture is provided for approximating classifier functions with Barron boundaries without the curse of dimensionality.
Sustainable food supply
(2024)
The present cumulative dissertation was written from 2020-2023 at the Professorship of Christian Social Ethics and Social Policy at the Business Faculty of the Catholic University of Eichstätt-Ingolstadt. All papers in this dissertation represent independent contributions to scientific journals in the fields of Sustainable Consumption, Sustainable Food, and Sustainable Consumer Behavior. They examine consumer behavior regarding sustainable food by analyzing various factors that influence consumers’ decision-making.
Paper I: Winterstein, J., & Habisch, A. (2021). Organic and local food consumption: A matter of age? Empirical evidence from the German market. ABAC Journal1, 41(1), 26-42.
Paper II: Winterstein, J. (2022). Nudging and Boosting towards Sustainable Food Choices–A Systematic Literature Review of Cognitively Oriented Measures. Products for Conscious Consumers: Developing, Marketing and Selling Ethical Products1, 113-132. https://doi.org/10.1108/978-1-80262-837-120221014
Paper III: Winterstein, J., Frank, F., & Habisch, A. (2024) Desire for exploration beats price: Empirical study on customer motives for using digital monetary food sharing platforms. International Journal of Innovation and Sustainable Development1,2. DOI: 10.1504/IJISD.2023.10055067
Paper IV: Winterstein, J., Zhu, B., & Habisch, A. (2024). How personal and social-focused values shape the purchase intention for organic food: Cross-country comparison between Thailand and Germany. Journal of Cleaner Production1,3, 434, 140313. https://doi.org/10.1016/j.jclepro.2023.140313
The existence of the common ash (Fraxinus excelsior L.) is acutely threatened by ash dieback, caused by the fungus Hymenoscyphus fraxineus. The disease may lead to reduced pollen flow due to crown damage and tree mortality, which affects the reproductive ecology of Fraxinus excelsior L. However, sexual reproduction in forest trees plays an essential role not only in species conservation and adaptive potential, but also in natural selection and the promotion of genetic diversity. The impending risk of reduced gene flow is therefore of serious concern and threatens the conservation of this valuable tree species. Therefore, it is critical to advance research on the effects of ash dieback on (effective) pollen transport and reproductive ecology of Fraxinus excelsior L. These results can be used to support forest management, such as maintaining ash genetic diversity and promoting the development of natural resistance. Therefore, this study will conduct extensive research in two seed orchards and one floodplain forest in Southern Germany from 2018 to 2021. The main objective of this dissertation was to improve our understanding of gene flow patterns by investigating (effective) pollen dispersal, pollen production and pollen and seed quality of ash trees in relation to their health status.
The main research questions were:
(1) How does ash (effective) pollen transport vary with stand density, ash abundance and meteorology?
(2) Is there a link between mating success and damage to the paternal tree?
(3) Does the health of the ash trees affect pollen and seed quality, as well as pollen quantity?
To answer these questions, different methods were used in the study areas, which differed in topography and degree of stocking. Therefore, not all parameters were examined at every site and in every year, depending on the issue concerned. The health status of the ash trees was assessed every year in July using a six-level vitality score. In addition, phenological observations were made annually in spring according to the BBCH code to determine different phenological stages such as beginning of flowering, full flowering, flower wilting and end of flowering.
Aerobiological pollen measurements were carried out in the two orchards in 2019 and 2020 using self-constructed gravimetric pollen traps of the Durham type. One of the traps was placed in the center of each orchard and up to five additional traps were placed at a maximum distance of 500 m from the orchard. Five vaseline-coated slides were attached to each trap (one in each cardinal di-rection and one horizontally) to measure pollen transport (N=4) and weekly cumulative pollen position (N=1). To study the influence of meteorological parameters, a climate station was placed in each orchard. In addition, other anemometers or data loggers for air temperature and relative humidity were installed.
For paternity analyses, cambium samples were collected for genotyping from branches and stumps of 251 ash trees in a seed orchard and floodplain forest. In addition, seeds were collected from 12 parent trees per site with different health status. Genetic analyses were performed to determine paternal trees using nuclear microsatellites. Paternities were assigned using the likelihood model implemented in Cervus 3.0.7 software.
Pollen viability of ash trees with different health status were studied at all three sites. Pollen production in the two seed orchards and seed quality in one orchard and the floodplain forest. For this purpose, inflorescences of 105 ash trees (pollen production), pollen of 125 ash trees (pollen viability) and seeds of 53 ash trees (seed quality) were collected. Pollen production was estimated from flower to tree level and pollen viability was determined using the TTC (2,3,5-triphenyltetrazolium chloride) test. In addition, pollen storage experiments were carried out to investigate the influence of meteorological factors on pollen viability. Pollen were stored for various periods at different temperatures and humidity conditions and their viability was determined. Seeds were analyzed for quantity and quality (solid, hollow grains, insect damage and germination) and seed quality was determined by both stratification and the TTC test.
The results on aerobiological pollen transport showed that pollen transport is related to meteorology, phenological development and the topography of the study site. The Schorndorf orchard, located on a slope, showed higher pollen levels at the downslope traps, likely due to the transport of pollen by cold air flow. The prevailing wind direction often corresponded with the compass direction in which the highest pollen deposition was measured. When analyzing the pollen data for individual traps, the highest pollen levels were measured outside the orchards in 2019, a year with low flower development. In contrast, most pollen were collected inside the orchard in the pollen-rich year 2020. This suggests that trees outside the orchard can potentially contribute more to pollination in a poor pollen year. In Emmendingen, minor difference in pollen quantity was found between traps at 1.5 m and 5 m height, but there were temporal differences indicating vertical variation in pollen availability. Ash pollen were found to be transported over a distance of more than 400 m, with the amount of pollen decreasing with increasing distance. About 50 % less pollen were measured at a distance of 200 m, but even at a distance of 500 m more than 10 % pollen were still detected.
The studies on effective pollen transport showed similar results: the average distance between father and mother tree was 76 m in the orchard and 166 m in the floodplain forest, with pollination success decreasing considerably with increasing distance. Despite the dense tree cover, the longest distances (> 550 m) were recorded in the floodplain forest. Based on this and the fact that 66.5 % cross-pollen input was recorded in the seed orchard, it can be assumed that pollination does not only involve local sources. However, self-pollination generally did not have a substantial effect on ash reproduction. In terms of health status, both healthy and slightly damaged parent trees showed similar mating success. However, in severely damaged trees almost no flowering could be documented. In general, it was demonstrated that both healthy and slightly diseased fathers sired more offspring than severely diseased ash trees.
The effect of ash dieback on pollen production showed no significant difference between healthy and diseased ash trees, although 53 % of severely diseased male ash trees did not produce flowers. In terms of pollen viability, there was a tendency for diseased ash trees to have less viable pollen than healthy ash trees. In addition, the viability experiments revealed a strong influence of prevailing temperatures on pollen viability, which decreased more rapidly under warmer conditions. There was also no statistical difference in seed quality between ash trees of different health status. However, non-viable seeds were often heavily infested with insects.
In summary, the studies show that a variety of factors influence the reproductive ecology and (effective) pollen transport of ash trees. However, the fact that severely affected ash trees are linked to a reduced flower production and lower pollen quality suggests that as health deteriorates, reproductive capacity also declines. It is therefore likely that severely diseased ash trees have a limited ability to pass on their genes to the next generation. Paternity analyses also suggest that high vigor has a positive effect on reproductive success and that pollen transport can occur over long distances. As susceptibility to ash dieback can be passed on from parents to offspring, these reactions to ash dieback may make ash populations less susceptible in the future.
Finance without foundations
(2022)
This thesis examines the role of financial inclusion by way of access to formal financial services such as savings, credit, transfers and payments, in supporting the lives of refugees in protracted displacement in Jordan. It asks if such access enables smoother financial and livelihood transitions as refugees arrive and integrate into their new environments in host countries. It critically evaluates the narrative presented by humanitarian actors supporting financial inclusion as a marketled intervention to support refugee self-reliance. It argues that the limited provision of financial services through mobile wallets and micro-credit is not sufficient to financially integrate refugees. Above all, it demonstrates through the in-depth qualitative research in Jordan that in a context where refugees’ livelihoods are constrained due to a lack of foundational economic rights, financial services can only marginally improve their lives by making it more convenient to receive remittances and humanitarian transfers.
The research is embedded in a larger project called “Finance in Displacement: Exploring and strengthening financial lives of forcibly displaced persons” (FIND), which was initiated in 2019 as a collaboration between the Katholische Universität Eichstätt-Ingolstadt, the Tufts University, and the International Rescue Committee. The project was supported by the German Federal Ministry for Economic Cooperation and Development (BMZ).
In children exposed to any traumatic experience, a conditional prevalence rate of 15.9% was estimated for posttraumatic stress disorder (PTSD; Alisic et al., 2014). In order to achieve best treatment outcomes, selecting evidence-based treatments is necessary (Durlak & DuPre, 2008). For pediatric PTSD, international guidelines recommend the use of manualized trauma-focused cognitive behavioral therapy (TF-CBT; Forbes, Bisson, Monson, & Berliner, 2020; National Institute for Health and Care Excellence, 2018; Phoenix Australia Centre for Posttraumatic Mental Health, 2013) and many effectiveness studies and initiatives (e.g. Goldbeck, Muche, Sachser, Tutus, & Rosner, 2016; Jensen et al., 2014; National Child Traumatic Stress Network, 2012) disseminated the TF-CBT manual of Cohen, Mannarino and Deblinger (2006, 2017; specific TF-CBT). However, the uptake of evidence-based treatments such as specific TF-CBT into practice is strongly affected by service providers’ attitudes toward evidence-based practice (EBP; Aarons, 2004; Aarons, Cafri, Lugo, & Sawitzky, 2012; Aarons, Sommerfeld, & Walrath-Greene, 2009; Moullin, Dickson, Stadnick, Rabin, & Aarons, 2019). These attitudes can be measured with the Evidence-Based Practice Attitudes Scale-36 (EBPAS-36; Rye, Torres, Friborg, Skre, & Aarons, 2017). In Germany, several effectiveness trials are underway further disseminating specific TF-CBT (Rosner, Barke, et al., 2020; Rosner, Sachser, et al., 2020) but a reliable and validated German version of the EBPAS-36 is missing. In addition, in terms of pooled effect sizes (ES), only one review evaluated specific TF-CBT 10 years ago (Cary & McMillen, 2012). Furthermore, little is known about the stability of its treatment effects, the concordance between children and adolescents’ and their caregivers’ ratings regarding the youths’ symptoms in this context as well as the influence of the heterogeneity of instruments used by individual studies.
Therefore, the aims of this dissertation were fourfold: Publication 1 pooled ES for specific TF-CBT regarding posttraumatic stress symptoms (PTSS) and secondary outcomes to provide an update of the literature. Large improvements were found across all outcomes and results were favorable for specific TF-CBT compared to all control conditions at post-treatment. Publication 2 pooled ES for specific TF-CBT at 12-month follow-up for the same outcomes to evaluate the stability of treatment effects and investigated concordance between participants and caregiver ratings. Again, large improvements were evident across all outcomes and TF-CBT was superior to active treatments and treatment as usual at 12-month follow-up. No significant differences were detected between participant and caregiver ratings with high reliability across almost all outcomes and assessment points. Publication 3 produced a validated German translation of the EBPAS-36 (EBPAS-36D) to facilitate EBP implementation research in Germany. Good psychometric properties and validity of the EBPAS-36D were confirmed. As additional content, this dissertation provides an unpublished report on the pooled ES of publication 1 differentiated by instruments used to assess the outcomes. ES did not differ by the instrument used to assess the respective outcome.
The conclusions that can be drawn from the studies as well as their limitations are discussed in the final section. While the EBPAS-36D was successfully validated and specific TF-CBT was strongly supported, several issues were identified that need further research attention.