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Am Beispiel von Flüchtlingsintegration werden institutionelle Entwicklungen im Mehrebenensystem aus einer länderübergreifenden Perspektive analysiert. Insgesamt hat der Grad der Verwaltungsverflechtung und vertikalen Koordination in diesem Bereich zugenommen und die Rolle der Kommunen wurde – ungeachtet unterschiedlicher Ausprägungen der (De-)Zentralisierung – gestärkt. Während die starke fluchtbedingte Zuwanderung als äußerer Faktor dieser Entwicklung Vorschub geleistet hat, nehmen historische Pfadabhängigkeiten und die jeweiligen Verwaltungskulturen nach wie vor erheblichen Einfluss auf die genannten Entwicklungen.
Back to bureaucracy?
(2024)
In this contribution, the emergence of the neo-Weberian state (NWS) is analyzed with regard to German public administration. Drawing on the concept of a governance space, which consists of a hierarchy, markets, and networks, we distinguish between four empirical manifestations of the NWS, namely, the NWS as (1) come back of the public/ re-municipalization; (2) re-hierarchization; (3) de-agencification; (4) de-escalation in performance management. These movements can, on the one hand, be interpreted as a (partial) reversal of New Public Management (NPM) approaches and a “swinging back of the pendulum” (see Kuhlmann & Wollmann, 2019) toward public and classical Weberian principles (e.g., hierarchy, regulation, institutional re-aggregation). This reversal re-strengthened the hierarchy within the overall governance space to the detriment of, but without completely replacing, market mechanisms and networks. NPM’s failure to deliver what it promised and its inappropriateness as a response to more recent challenges connected to crises and wicked problems have engendered a partial return of the public and a move away from the economization logic of NPM. On the other hand, post-NPM reversals and managerial de-escalation gave rise to hybrid models that merge NPM and classic Weberian administration. While some well-functioning combinations of NPM and Weberianism exist, the hybridization of “old” and “neo” elements has also provoked ambivalent and negative assessments regarding the actual functioning of the NWS in Germany. Our analysis suggests that the NWS is only partially suitable as a model for reform and future administrative modernization, largely depending on the context surrounding reform and implementation practices.
The global drylands cover nearly half of the terrestrial surface and are home to more than two billion people. In many drylands, ongoing land-use change transforms near-natural savanna vegetation to agricultural land to increase food production. In Southern Africa, these heterogenous savanna ecosystems are also recognized as habitats of many protected animal species, such as elephant, lion and large herds of diverse herbivores, which are of great value for the tourism industry. Here, subsistence farmers and livestock herder communities often live in close proximity to nature conservation areas. Although these land-use transformations are different regarding the future they aspire to, both processes, nature conservation with large herbivores and agricultural intensification, have in common, that they change the vegetation structure of savanna ecosystems, usually leading to destruction of trees, shrubs and the woody biomass they consist of.
Such changes in woody vegetation cover and biomass are often regarded as forms of land degradation and forest loss. Global forest conservation approaches and international programs aim to stop degradation processes, also to conserve the carbon bound within wood from volatilization into earth’s atmosphere. In search for mitigation options against global climate change savannas are increasingly discussed as potential carbon sinks. Savannas, however, are not forests, in that they are naturally shaped by and adapted to disturbances, such as wildfires and herbivory. Unlike in forests, disturbances are necessary for stable, functioning savanna ecosystems and prevent these ecosystems from forming closed forest stands. Their consequently lower levels of carbon storage in woody vegetation have long been the reason for savannas to be overlooked as a potential carbon sink but recently the question was raised if carbon sequestration programs (such as REDD+) could also be applied to savanna ecosystems. However, heterogenous vegetation structure and chronic disturbances hamper the quantification of carbon stocks in savannas, and current procedures of carbon storage estimation entail high uncertainties due to methodological obstacles. It is therefore challenging to assess how future land-use changes such as agricultural intensification or increasing wildlife densities will impact the carbon storage balance of African drylands.
In this thesis, I address the research gap of accurately quantifying carbon storage in vegetation and soils of disturbance-prone savanna ecosystems. I further analyse relevant drivers for both ecosystem compartments and their implications for future carbon storage under land-use change. Moreover, I show that in savannas different carbon storage pools vary in their persistence to disturbance, causing carbon bound in shrub vegetation to be most likely to experience severe losses under land-use change while soil organic carbon stored in subsoils is least likely to be impacted by land-use change in the future.
I start with summarizing conventional approaches to carbon storage assessment and where and for which reasons they fail to accurately estimated savanna ecosystem carbon storage. Furthermore, I outline which future-making processes drive land-use change in Southern Africa along two pathways of land-use transformation and how these are likely to influence carbon storage. In the following chapters, I propose a new method of carbon storage estimation which is adapted to the specific conditions of disturbance-prone ecosystems and demonstrate the advantages of this approach in relation to existing forestry methods. Specifically, I highlight sources for previous over- and underestimation of savanna carbon stocks which the proposed methodology resolves. In the following chapters, I apply the new method to analyse impacts of land-use change on carbon storage in woody vegetation in conjunction with the soil compartment. With this interdisciplinary approach, I can demonstrate that indeed both, agricultural intensification and nature conservation with large herbivores, reduce woody carbon storage above- and belowground, but partly sequesters this carbon into the soil organic carbon stock. I then quantify whole-ecosystem carbon storage in different ecosystem compartments (above- and belowground woody carbon in shrubs and trees, respectively, as well as topsoil and subsoil organic carbon) of two savanna vegetation types (scrub savanna and savanna woodland). Moreover, in a space-for-time substitution I analyse how land-use changes impact carbon storage in each compartment and in the whole ecosystem. Carbon storage compartments are found to differ in their persistence to land-use change with carbon bound in shrub biomass being least persistent to future changes and subsoil organic carbon being most stable under changing land-use. I then explore which individual land-use change effects act as drivers of carbon storage through Generalized Additive Models (GAMs) and uncover non-linear effects, especially of elephant browsing, with implications for future carbon storage. In the last chapter, I discuss my findings in the larger context of this thesis and discuss relevant implications for land-use change and future-making decisions in rural Africa.
Laser induced switching offers an attractive possibility to manipulate small magnetic domains for prospective memory and logic devices on ultrashort time scales. Moreover, optical control of magnetization without high applied magnetic fields allows manipulation of magnetic domains individually and locally, without expensive heat dissipation. One of the major challenges for developing novel optically controlled magnetic memory and logic devices is reliable formation and annihilation of non-volatile magnetic domains that can serve as memory bits in ambient conditions. Magnetic skyrmions, topologically nontrivial spin textures, have been studied intensively since their discovery due to their stability and scalability in potential spintronic devices. However, skyrmion formation and, especially, annihilation processes are still not completely understood and further investigation on such mechanisms are needed. The aim of this thesis is to contribute to better understanding of the physical processes behind the optical control of magnetism in thin films, with the goal of optimizing material parameters and methods for their potential use in next generation memory and logic devices.
First part of the thesis is dedicated to investigation of all-optical helicity-dependent switching (AO-HDS) as a method for magnetization manipulation. AO-HDS in Co/Pt multilayer and CoFeB alloys with and without the presence of Dzyaloshinskii-Moriya interaction (DMI), which is a type of exchange interaction, have been investigated by magnetic imaging using photo-emission electron microscopy (PEEM) in combination with X-ray magnetic circular dichroism (XMCD). The results show that in a narrow range of the laser fluence, circularly polarized laser light induces a drag on domain walls. This enables a local deterministic transformation of the magnetic domain pattern from stripes to bubbles in out-of-plane magnetized Co/Pt multilayers, only controlled by the helicity of ultrashort laser pulses. The temperature and characteristic fields at which the stripe-bubble transformation occurs has been calculated using theory for isolated magnetic bubbles, using as parameters experimentally determined average size of stripe domains and the magnetic layer thickness.
The second part of the work aims at purely optical formation and annihilation of magnetic skyrmions by a single laser pulse. The presence of a skyrmion phase in the investigated CoFeB alloys was first confirmed using a Kerr microscope. Then the helicity-dependent skyrmion manipulation was studied using AO-HDS at different laser fluences. It was found that formation or annihilation individual skyrmions using AO-HDS is possible, but not always reliable, as fluctuations in the laser fluence or position can easily overwrite the helicity-dependent effect of AO-HDS. However, the experimental results and magnetic simulations showed that the threshold values for the laser fluence for the formation and annihilation of skyrmions are different. A higher fluence is required for skyrmion formation, and existing skyrmions can be annihilated by pulses with a slightly lower fluence. This provides a further option for controlling formation and annihilation of skyrmions using the laser fluence. Micromagnetic simulations provide additional insights into the formation and annihilation mechanism.
The ability to manipulate the magnetic state of individual skyrmions is of fundamental importance for magnetic data storage technologies. Our results show for the first time that the optical formation and annihilation of skyrmions is possible without changing the external field. These results enable further investigations to optimise the magnetic layer to maximise the energy gap between the formation and annihilation barrier. As a result, unwanted switching due to small laser fluctuations can be avoided and fully deterministic optical switching can be achieved.
Wars and the world
(2024)
This book offers a descriptive analysis of the Soviet/Russian wars in Afghanistan, Chechnya, and Georgia, as well as an in-depth exploration of the ways in which these wars are framed in the collective consciousness created by global popular culture. Russian and Western modalities of remembrance have been, and remain, engaged in a world war that takes place (not exclusively, but intensively) on the level of popular culture. The action/reaction dynamic, confrontational narratives and othering between the two "camps" never ceased. The Cold War, in many ways and contrary to the views of many others who hoped for the end of history, never really ended.
The trace elements copper, iron, manganese, selenium and zinc are essential micronutrients involved in various cellular processes, all with different responsibilities. Based on that importance, their concentrations are tightly regulated in mammalian organisms. The maintenance of those levels is termed trace element homeostasis and mediated by a combination of processes regulating absorption, cellular and systemic transport mechanisms, storage and effector proteins as well as excretion. Due to their chemical properties, some functions of trace elements overlap, as seen in antioxidative defence, for example, comprising an expansive spectrum of antioxidative proteins and molecules. Simultaneously, the same is true for regulatory mechanisms, causing trace elements to influence each other’s homeostases. To mimic physiological conditions, trace elements should therefore not be evaluated separately but considered in parallel. While many of these homeostatic mechanisms are well-studied, for some elements new pathways are still discovered. Additionally, the connections between dietary trace element intake, trace element status and health are not fully unraveled, yet. With current demographic developments, also the influence of ageing as well as of certain pathological conditions is of increasing interest. Here, the TraceAge research unit was initiated, aiming to elucidate the homeostases of and interactions between essential trace elements in healthy and diseased elderly. While human cohort studies can offer insights into trace element profiles, also in vivo model organisms are used to identify underlying molecular mechanisms. This is achieved by a set of feeding studies including mice of various age groups receiving diets of reduced trace element content. To account for cognitive deterioration observed with ageing, neurodegenerative diseases, as well as genetic mutations triggering imbalances in cerebral trace element concentrations, one TraceAge work package focuses on trace elements in the murine brain, specifically the cerebellum. In that context, concentrations of the five essential trace elements of interest, copper, iron, manganese, selenium and zinc, were quantified via inductively coupled plasma-tandem mass spectrometry, revealing differences in priority of trace element homeostases between brain and liver. Upon moderate reduction of dietary trace element supply, cerebellar concentrations of copper and manganese deviated from those in adequately supplied animals. By further reduction of dietary trace element contents, also concentrations of cerebellar iron and selenium were affected, but not as strong as observed in liver tissue. In contrast, zinc concentrations remained stable. Investigation of aged mice revealed cerebellar accumulation of copper and iron, possibly contributing to oxidative stress on account of their redox properties. Oxidative stress affects a multitude of cellular components and processes, among them, next to proteins and lipids, also the DNA. Direct insults impairing its integrity are of relevance here, but also indirect effects, mediated by the machinery ensuring genomic stability and its functionality. The system includes the DNA damage response, comprising detection of endogenous and exogenous DNA lesions, decision on subsequent cell fate and enabling DNA repair, which presents another pillar of genomic stability maintenance. Also in proteins of this machinery, trace elements act as cofactors, shaping the hypothesis of impaired genomic stability maintenance under conditions of disturbed trace element homeostasis. To investigate this hypothesis, a variety of approaches was used, applying OECD guidelines Organisation for Economic Co-operation and Development, adapting existing protocols for use in cerebellum tissue and establishing new methods. In order to assess the impact of age and dietary trace element depletion on selected endpoints estimating genomic instability, DNA damage and DNA repair were investigated. DNA damage analysis, in particular of DNA strand breaks and oxidatively modified DNA bases, revealed stable physiological levels which were neither affected by age nor trace element supply. To examine whether this is a result of increased repair rates, two steps characteristic for base excision repair, namely DNA incision and ligation activity, were studied. DNA glycosylases and DNA ligases were not reduced in their activity by age or trace element depletion, either. Also on the level of gene expression, major proteins involved in genomic stability maintenance were analysed, mirroring results obtained from protein studies. To conclude, the present work describes homeostatic regulation of trace elements in the brain, which, in absence of genetic mutations, is able to retain physiological levels even under conditions of reduced trace element supply to a certain extent. This is reflected by functionality of genomic stability maintenance mechanisms, illuminating the prioritization of the brain as vital organ.
A new challenger seeks to enter the German party system: Bündnis Sahra Wagenknecht (BSW). With her new party, former Die Linke politician Sahra Wagenknecht combines a left-authoritarian profile (economically left-leaning, but culturally conservative) with anti-US, pro-Russia and anti-elitist stances. This article provides the first large-n academic study of the voter potential of this new party by using a quasi-representative sample (n = 6,000) drawn from a Voting Advice Application-like dataset that comes from a website designed to explore the Bündnis Sahra Wagenknecht’s positions. The results show that congruence with foreign policy positions and anti-elitism are strong predictors of the propensity to vote for the Bündnis Sahra Wagenknecht. In contrast, social/welfare and immigration policies are less predictive for assessing the party’s potential. Among the different socio-demographic groups, the Bündnis Sahra Wagenknecht has a strong potential among baby boomers, the less educated and East Germans. Regarding party voters, the Bündnis Sahra Wagenknecht is favoured by supporters of some minor parties like dieBasis, Freie Wähler and Die PARTEI, but also non-voters. Among the established parties, the party’s potential is high among Die Linke voters and, to a lesser extent, voters of the Social democrats (SPD) and Alternative for Germany (AfD). A potential below the average is reported for the supporters of the Liberals (FDP) and Christian Democrats (CDU/CSU) and most clearly for Green and Volt voters.
Hardy inequalities on graphs
(2024)
The dissertation deals with a central inequality of non-linear potential theory, the Hardy inequality. It states that the non-linear energy functional can be estimated from below by a pth power of a weighted p-norm, p>1. The energy functional consists of a divergence part and an arbitrary potential part. Locally summable infinite graphs were chosen as the underlying space. Previous publications on Hardy inequalities on graphs have mainly considered the special case p=2, or locally finite graphs without a potential part.
Two fundamental questions now arise quite naturally: For which graphs is there a Hardy inequality at all? And, if it exists, is there a way to obtain an optimal weight? Answers to these questions are given in Theorem 10.1 and Theorem 12.1. Theorem 10.1 gives a number of characterizations; among others, there is a Hardy inequality on a graph if and only if there is a Green's function. Theorem 12.1 gives an explicit formula to compute optimal Hardy weights for locally finite graphs under some additional technical assumptions. Examples show that Green's functions are good candidates to be used in the formula.
Emphasis is also placed on illustrating the theory with examples. The focus is on natural numbers, Euclidean lattices, trees and star graphs. Finally, a non-linear version of the Heisenberg uncertainty principle and a Rellich inequality are derived from the Hardy inequality.
Resolving the evolutionary history of two hippotragin antelopes using archival and ancient DNA
(2024)
African antelopes are iconic but surprisingly understudied in terms of their genetics, especially when it comes to their evolutionary history and genetic diversity. The age of genomics provides an opportunity to investigate evolution using whole nuclear genomes. Decreasing sequencing costs enable the recovery of multiple loci per genome, giving more power to single specimen analyses and providing higher resolution insights into species and populations that can help guide conservation efforts. This age of genomics has only recently begun for African antelopes. Many African bovids have a declining population trend and hence, are often endangered. Consequently, contemporary samples from the wild are often hard to collect. In these cases, ex situ samples from contemporary captive populations or in the form of archival or ancient DNA (aDNA) from historical museum or archaeological/paleontological specimens present a great research opportunity with the latter two even offering a window to information about the past. However, the recovery of aDNA is still considered challenging from regions with prevailing climatic conditions that are deemed adverse for DNA preservation like the African continent. This raises the question if DNA recovery from fossils as old as the early Holocene from these regions is possible.
This thesis focuses on investigating the evolutionary history and genetic diversity of two species: the addax (Addax nasomaculatus) and the blue antelope (Hippotragus leucophaeus). The addax is critically endangered and might even already be extinct in the wild, while the blue antelope became extinct ~1800 AD, becoming the first extinct large African mammal species in historical times. Together, the addax and the blue antelope can inform us about current and past extinction events and the knowledge gained can help guide conservation efforts of threatened species. The three studies used ex situ samples and present the first nuclear whole genome data for both species. The addax study used historical museum specimens and a contemporary sample from a captive population. The two studies on the blue antelope used mainly historical museum specimens but also fossils, and resulted in the recovery of the oldest paleogenome from Africa at that time.
The aim of the first study was to assess the genetic diversity and the evolutionary history of the addax. It found that the historical wild addax population showed only limited phylogeographic structuring, indicating that the addax was a highly mobile and panmictic population and suggesting that the current European captive population might be missing the majority of the historical mitochondrial diversity. It also found the nuclear and mitochondrial diversity in the addax to be rather low compared to other wild ungulate species. Suggestions on how to best save the remaining genetic diversity are presented. The European zoo population was shown to exhibit no or only minor levels of inbreeding, indicating good prospects for the restoration of the species in the wild. The trajectory of the addax’s effective population size indicated a major bottleneck in the late Pleistocene and a low effective population size well before recent human impact led to the species being critically endangered today.
The second study set out to investigate the identities of historical blue antelope specimens using aDNA techniques. Results showed that six out of ten investigated specimens were misidentified, demonstrating the blue antelope to be one of the scarcest mammal species in historical natural history collections, with almost no bone reference material. The preliminary analysis of the mitochondrial genomes suggested a low diversity and hence low population size at the time of the European colonization of southern Africa.
Study three presents the results of the analyses of two blue antelope nuclear genomes, one ~200 years old and another dating to the early Holocene, 9,800–9,300 cal years BP. A fossil-calibrated phylogeny dated the divergence time of the three historically extant Hippotragus species to ~2.86 Ma and demonstrated the blue and the sable antelope (H. niger) to be sister species. In addition, ancient gene flow from the roan (H. equinus) into the blue antelope was detected. A comparison with the roan and the sable antelope indicated that the blue antelope had a much lower nuclear diversity, suggesting a low population size since at least the early Holocene. This concurs with findings from the fossil record that show a considerable decline in abundance after the Pleistocene–Holocene transition. Moreover, it suggests that the blue antelope persisted throughout the Holocene regardless of a low population size, indicating that human impact in the colonial era was a major factor in the blue antelope’s extinction.
This thesis uses aDNA analyses to provide deeper insights into the evolutionary history and genetic diversity of the addax and the blue antelope. Human impact likely was the main driver of extinction in the blue antelope, and is likely the main factor threatening the addax today. This thesis demonstrates the value of ex situ samples for science and conservation, and suggests to include genetic data for conservation assessments of species. It further demonstrates the beneficial use of aDNA for the taxonomic identification of historically important specimens in natural history collections. Finally, the successful retrieval of a paleogenome from the early Holocene of Africa using shotgun sequencing shows that DNA retrieval from samples of that age is possible from regions generally deemed unfavorable for DNA preservation, opening up new research opportunities. All three studies enhance our knowledge of African antelopes, contributing to the general understanding of African large mammal evolution and to the conservation of these and similarly threatened species.
Background: Societies worldwide have become more diverse yet continue to be inequitable. Understanding how youth growing up in these societies are socialized and consequently develop racial knowledge has important implications not only for their well-being but also for building more just societies. Importantly, there is a lack of research on these topics in Germany and Europe in general.
Aim and Method: The overarching aim of the dissertation is to investigate 1) where and how ethnic-racial socialization (ERS) happens in inequitable societies and 2) how it relates to youth’s development of racial knowledge, which comprises racial beliefs (e.g., prejudice, attitudes), behaviors (e.g., actions preserving or disrupting inequities), and identities (e.g., inclusive, cultural). Guided by developmental, cultural, and ecological theories of socialization and development, I first explored how family, as a crucial socialization context, contributes to the preservation or disruption of racism and xenophobia in inequitable societies through its influence on children’s racial beliefs and behaviors. I conducted a literature review and developed a conceptual model bridging research on ethnic-racial socialization and intergroup relations (Study 1). After documenting the lack of research on socialization and development of racial knowledge within and beyond family contexts outside of the U.S., I conducted a qualitative study to explore ERS in Germany through the lens of racially marginalized youth (Study 2). Then, I conducted two quantitative studies to explore the separate and interacting relations of multiple (i.e., family, school) socialization contexts for the development of racial beliefs and behaviors (Study 3), and identities (Studies 3, 4) in Germany. Participants of Study 2 were 26 young adults (aged between 19 and 32) of Turkish, Kurdish, East, and Southeast Asian heritage living across different cities in Germany. Study 3 was conducted with 503 eighth graders of immigrant and non-immigrant descent (Mage = 13.67) in Berlin, Study 4 included 311 early to mid-adolescents of immigrant descent (Mage= 13.85) in North Rhine-Westphalia with diverse cultural backgrounds.
Results and Conclusion: The findings revealed that privileged or marginalized positions of families in relation to their ethnic-racial and religious background in society entail differential experiences and thus are an important determining factor for the content/process of socialization and development of youth’s racial knowledge. Until recently, ERS research mostly focused on investigating how racially marginalized families have been the sources of support for their children in resisting racism and how racially privileged families contribute to transmission of information upholding racism (Study 1). ERS for racially marginalized youth in Germany centered heritage culture, discrimination, and resistance strategies to racism, yet resistance strategies transmitted to youth mostly help to survive racism (e.g., working hard) by upholding it instead of liberating themselves from racism by disrupting it (e.g., self-advocacy, Study 2). Furthermore, when families and schools foster heritage and intercultural learning, both contexts may separately promote stronger identification with heritage culture and German identities, and more prosocial intentions towards disadvantaged groups (i.e., refugees) among youth (Studies 3, 4). However, equal treatment in the school context led to mixed results: equal treatment was either unrelated to inclusive identity, or positively related to German and negatively related to heritage culture identities (Studies 3, 4). Additionally, youth receiving messages highlighting strained and preferential intergroup relations at home while attending schools promoting assimilation may develop a stronger heritage culture identity (Study 4). In conclusion, ERS happened across various social contexts (i.e., family, community centers, school, neighborhood, peer). ERS promoting heritage and intercultural learning, at least in one social context (family or school), might foster youth’s racial knowledge manifesting in stronger belonging to multiple cultures and in prosocial intentions toward disadvantaged groups. However, there is a need for ERS targeting increasing awareness of discrimination across social contexts of youth and teaching youth resistance strategies for liberation from racism.