Microplastics in Freshwater Systems: Analysis, Occurrence, and Sorption of Organic Contaminants

Synthetic polymers are one of the most significant pollutants in the aquatic environment, because of abilities such as buoyancy and extreme persistency. Serious effects are expected from so-called microplastics (particle size <5 mm) that are reported in rivers, lakes as well as the ocean and that accumulate in sediments worldwide. In this thesis the abundance of microplastics in river shore sediments in the Rhine-Main area of Germany was studied. Therefore, a new method was developed that is based on a sodium chloride density separation with subsequent destruction of natural debris, and identification of the plastic particles by microscopy or Fourier transform infrared spectroscopy (FTIR). Using the improved density separation, microplastics were separated from river shore sediments of 12 sites originating from the river Rhine, the river Main, and the stream Schwarzbach. Large amounts of microplastic particles of up to 1 g kg-1 or up to 4000 particles kg-1 were detected in the shore sediments. The identification by FTIR showed that polyethylene, polypropylene, and polystyrene were the most abundant polymer types in the sediments, covering over 75% of all plastics identified. Transport of microplastics from tributaries to main streams was indicated by the detection of identical pellets in the River Rhine and in the Main mouth. Comparable concentrations detected by sampling one site over a period of two years suggest a constant pollution of the river shore sediments with microplastics. For deeper insights into the sorption process of organic contaminants to synthetic polymers in freshwater systems, batch experiments in synthetic freshwater were conducted to determine sorption kinetics and sorption isotherms for four selected glass state polymers (polycarbonate, poly(methyl methacrylate), polystyrene, and polyvinyl chloride) and six different model substances (carbamazepine, hexachlorocyclohexane (β/γ), 17α-ethynilestradiol, chlorpyrifos, and o,p-dichlorodiphenyltrichlorethane). Sorption to the polymer particles was observed for all contaminants increasing with the KOW values of the contaminants. Because of losses of contaminants in control samples, sorption reaction models could be applied to four out of six contaminants, and isotherms were calculated for three contaminants. Furthermore, influences of the different polymer types used were observed in the experiments. Finally, microplastics separated from sediments were extracted and analyzed by GC/MS and LC-MS/MS using target screening methods and non-target approaches. Different pesticides were identified in the polymer particles, suggesting that microplastics can act as a sink for hydrophobic contaminants. Moreover, several plastic additives such as phthalates or chlorinated flame retardants were identified. For this reason, it is very likely that microplastics act as a direct source for these chemicals in aquatic systems. The results of this thesis stress the urgency for the mitigation of the plastic particles in the aquatic environment

Skyscraping Frontiers

As a space of extremes, the skyscraper has been continually constructed as an urban frontier in American cultural productions. Like its counterpart of the American wilderness, this vertical frontier serves as a privileged site for both subversion and excessive control. Beyond common metaphoric readings, this study models the skyscraper not only as a Foucauldian heterotopia, but also as a complex network of human and nonhuman actors while retracing its development from its initial assemblage during the 19th century to its steady evolution into a smart structure from the mid-20th century onward. It takes a close look at US-American literary and filmic fictions and the ways in which they sought to make sense of this extraordinary structure throughout the 20th and early 21st centuries. More traditional poststructuralist spatial theories are connected with concepts and methods of Actor-Network Theory in a compelling account of the skyscraper’s evolution as reflected in fictional media from early 20th-century short stories via a range of action, disaster and horror films to selected city novels of the 1990s and 2000s

El rugido de la modernidad: Los paisajes sonoros de la metrópolis y la construcción del sujeto moderno en Manhattan Transfer de John Dos Passos

This article explores the specificities and psychological effects of urban noise in John Dos Passos’ novel Manhattan Transfer. It seeks to elucidate how Manhattan’s soundscape is represented on the novel’s formal and content level and how it assumes an agency in its own right, when ceaselessly enveloping the novel’s characters. The city’s specific acoustic regimes, therefore, prove much more instrumental in constituting the characters as modern subjects than other sensorial dimensions. Within a thus enacted metropolitan panacousticon, the urban subject is crucially defined not only as a noise source in itself, but as always already overheard by a supposed other.Este artículo estudia las particularidades y los efectos psicológicos del ruido urbano en la novela Manhattan Transfer de John Dos Passos. Trata de esclarecer cómo el paisaje sonoro de Manhattan se representa en la forma y en el contenido de la novela y cómo asume un rol por derecho propio en la misma, al rodear de forma incesante a los personajes. Los regímenes acústicos específicos de las ciudad resultan por tanto mucho más decisivos en la creación de los personajes como sujetos modernos que otras dimensiones sensoriales. En un panacústico metropolitano así escenificado, el sujeto urbano se define fundamentalmente no solo como una fuente de sonido en sí mismo, sino como alguien a quien ya escucha un supuesto otro

Providing Multilingual Access to Health-Oriented Content

Finding health-related content is not an easy task. People have to know what to search for, which medical terms to use, and where to find accurate information. This task becomes even harder when people such as immigrants wish to find information in their country of residence and do not speak the national language very well. In this paper, we present a new health information system that allows users to search for health information using natural language queries composed of multiple languages. We present the technical details of the system and outline the results of a preliminary user study to demonstrate the usability of the system

Estimating Fiscal Multipliers by Combining Statistical Identification with Potentially Endogenous Proxies

Different proxy variables used in fiscal policy SVARs lead to contradicting conclusions regarding the size of fiscal multipliers. In this paper, we show that the conflicting results are due to violations of the exogeneity assumptions, i.e. the commonly used proxies are endogenously related to the structural shocks. We propose a novel approach to include proxy variables into a Bayesian non-Gaussian SVAR, tailored to accommodate potentially endogenous proxy variables. Using our model, we show that increasing government spending is a more effective tool to stimulate the economy than reducing taxes. We construct new exogenous proxies that can be used in the traditional proxy VAR approach resulting in similar estimates compared to our proposed hybrid SVAR model.Comment: 10 figure

Start-Up Financing in the Digital Age – A Systematic Review and Comparison of New Forms of Financing

Start-ups are seen as the leading force in dynamically growing economies. Limited financing opportunities often prevent entrepreneurs from realizing their innovative business ideas or taking growth opportunities. However, in the context of the technological revolution, a fundamental change in the entrepreneurial finance landscape is observed. Innovative, digital financial instruments such as Business Angel Networks, Crowdfunding, or Initial Coin Offerings provide young companies with attractive financing opportunities. Although a large number of studies focus on start-up financing in the digital age, the literature is still fragmented. By providing a systemic literature review of 85 high-quality peer-reviewed journal articles published between 1990 and 2019, we address the following purposes: First, we outline a holistic picture on the financing spectrum of start-ups in the digital age. Therefore, we classify the articles into two categories as traditional or novel financing instruments. Subsequently, we associate the different financing instruments into the various growth stages of start-ups and define them as equity or debt. Second, we evaluate the suitability of novel financing instruments based on the trade-off and pecking order theory. Third, we investigate whether new forms of financing are substitutes or complements to traditional financing forms. Furthermore, ideas for further research are suggested

Modeling Role-Based Systems with Exogenous Coordination

The concept of roles is a promising approach to cope with context dependency and adaptivity of modern software systems. While roles have been investigated in conceptual modeling, programming languages and multi-agent systems, they have been given little consideration within component-based systems. In this paper, we propose a hierarchical role-based approach for modeling relationships and collaborations between components. In particular, we consider the channel-based, exogenous coordination language Reo and discuss possible realizations of roles and related concepts. The static requirements on the binding of roles are modeled by rule sets expressed in many-sorted second-order logic and annotations on the Reo networks for role binding, context and collaborations, while Reo connectors are used to model the coordination of runtime role playing. The ideas presented in this paper may serve as a basis for the formalization and formal analysis of role-based software systems

Development and Production of Artificial Test Swarf to Examine Wear Behavior of Running Engine Components - Geometrically Derived Designs

Subtractive manufacturing processes are usually accompanied by the occurrence of tiny flakes and swarf, which later on cause severe wear and damage, especially in moving components such as rolling or sliding bearings, pistons, etc. However, up until now, such detrimental effects have hardly been investigated. One reason is the lack of a definition of a typical design of debris particle. Therefore, the main goal of the project described in this paper was to elaborate a draft that defines standardized test particles. It had to be evaluated whether test particles could be adequately reproduced and whether they would reveal significant damage potential. Taking into account future mass fabrication, Micro Powder Injection Molding (MicroPIM) was chosen as a production method. Five different 3D designs of geometrically defined test particles were developed. The maximum size of each design was 1167 mm in green state; however, all samples shrank in size during sintering. Specially tailored feedstocks containing 42CrMo4 steel powders were used and the related molding, debinding and sintering procedures were developed. All particle geometries and related mold inserts were developed using a commercial software routine for the layout of runner systems, gate locations and ejector positions. The damage potential of the test particles was evaluated based on trials using journal bearing and shift valve test rigs. Although only a moderate degree of damage potential could be ascertained up until now, it can be expected that the artificial swarf will enable standardized wear test procedures to be developed

Providing multilingual access to health-related content

Finding health-related content is not an easy task. People have to know what to search for, which medical terms to use, and where to find accurate information. This task becomes even harder when people such as immigrants wish to find information in their country of residence and do not speak the national language very well. In this paper, we present a new health information system that allows users to search for health information using natural language queries composed of multiple languages. We present the technical details of the system and outline the results of a preliminary user study to demonstrate the usability of the system