The process of dimethyl carbonate to diphenyl carbonate: thermodynamics, reaction kinetics and conceptual process design

Diphenyl carbonate (DPC) is a precursor in the production of Polycarbonate (PC), a widely employed engineering plastic. To overcome the drawbacks of the traditional PC process - e.g. phosgene as a reactant and methylene chloride as solvent- a new process route starting from Dimethyl carbonate (DMC) via Methyl Phenyl carbonate (MPC) to DPC is investigated in this thesis.\ud First the general applicability of activities in reaction rate equations is examined, both theoretically and experimentally, for the system CO2-OH—salts. The results show that the activity based reaction rate yields fundamentally better results compared to the traditional concentration based approach and moreover establishes a fundamental link to the activity based description of chemical equilibria.\ud For the derivation of activity based reaction kinetics as well as chemical equilibria, activity coefficients are required. Hence, available VLE data of relevant carbonate systems has been taken from literature to fit corresponding UNIFAC parameters which have subsequently been used for the description of the relevant chemical equilibria and reaction kinetics.\ud The chemical equilibria encountered in the process from DMC to DPC have been experimentally determined thereby studying the influence of the molar reactant ratio DMC/phenol (0.25-3.0) and temperature (160-200C). The activity based and concentration based chemical equilibria have been compared to each other and the temperature dependence of the chemical equilibria has been described.\ud A comprehensive study has been performed to determine the kinetics of the three reactions involved in the carbonate system. The influence of the reactant ratio DMC/phenol (0.25-3.0), temperature (160-200C) and the catalyst amount has been investigated. The concept of a closed ideally stirred, isothermal batch reactor incorporating an activity based reaction rate model, has been used to fit kinetic parameters to the experimental data.\ud \ud For exploring the industrial production process of DPC from DMC using reactive distillation, a tray column model originating from the software package ChemSep was used. The influence of various parameters - feed location(s), number of stages, temperature and pressure - was studied and the results are \ud evaluated. First a process comprising of one reactive distillation column and then a process employing two reactive distillation columns has been investigated

Shared Histories of Co-evolution May Affect Trophic Interactions in a Freshwater Community Dominated by Alien Species

Interactions occurring between species in multiple invaded freshwater ecosystems are often difficult to observe and study. Studies on invasive alien species typically focus on single species, and, when the species community is exclusively composed of alien species, their interactions, eventual facilitation and hindering processes are very scarcely assessed. To investigate such a community, the species community in the Arno River (Tuscany, Italy) was examined as a model system using the combined approach of stable isotopes and dietary analyses. Established alien species have formed a pyramid shaped community with the European catfish Silurus glanis and the North American channel catfish Ictalurus punctatus in the apex position, followed by opportunistic predatory (Lepomis gibbosus) and omnivore (Alburnus alburnus, Cyprinus carpio, Barbus barbus, Pseudorasbora parva, Padogobius sp., Tinca tinca) species. These species were observed to feed on a variety of primary producers (Myriophyllum sp., Potamogeton sp., Phragmites australis) and consumers (aquatic insects, molluscs, Dikerogammarus villosus, Procambarus clarkii, Palaemon antennarius, tadpoles). Remarkably, the channel catfish Ictalurus punctatus showed an ontogenetic niche shift, with juveniles occupying a slightly higher trophic position than mature individuals. Pseudorasbora parva and A. alburnus showed a strong niche overlap, with the former having a wider niche. Such wide niches were also found for the invasive crustaceans D. villosus and P. clarkii. Outgoing from our findings, we suggest that life-history and geographic origin play a role in determining competition and interaction type among alien species, with species from the same geographic area showing a lower potential to compete than species from different areas, hence affecting their potential impact on native species

Is the number of non-native species in the European Union saturating?

Background Non-native species can have significant negative impacts on the environment, economies, and amongst others, also human Non-native species can have significant negative impacts on the environment, economies, and human Non-native species can have significant negative impacts on the environment, economies, and human well-being, among other factors. Globalisation and economic incentives have substantially facilitated the growth in the numbers of newly recorded non-native species in the European Union. The European Union’s diversity in terms of political and socio-economic differences across member states may have contributed to the introduction of non-native species. Results Data reported in the Alien Species First Record Database, however, suggests a decreasing trend in the number of non-native species recorded over the past three decades. InvaCost, a database of non-native species with economic impacts, similarly shows increasing numbers of reported non-native species with costs until the 2010s, which were, however, followed by a plateauing and ultimately decline. Although the recent trends in non-native species reports may be affected by a lag time in reporting and data allocation as well as possibly a disparity in research efforts, their impacts persist, leading to a growing ecological but also economic burden. We further identified substantial spatial differences as western European member states generally reported higher numbers of non-native species and non-native species with monetary impacts. Conclusions Without improved actions, biological invasions and their associated impacts will continue to rise, degrading natural capital and hampering sustainable development and sustainability targets. Therefore, improved coordinated efforts across the European Union are necessary to improve reporting of non-native species and a centralized collation of data through accessible databases should be considered

Parametrierung elektrischer Äquivalentschaltbilder von PEM Brennstoffzellen

In dieser Arbeit ist das statische und dynamische Klemmenspannungsverhalten von PEM Brennstoffzellen untersucht worden. Auf Grundlage der experimentellen Ergebnisse ist ein elektrisches Äquivalentschaltbild für statische und dynamische Zeitbereiche entwickelt und parametriert worden. &nbsp

Primarily neutral effects of river restoration on macroinvertebrates, macrophytes, and fishes after a decade of monitoring

Restoring river habitat heterogeneity is expensive and time consuming, yet often has little effect on aquatic biota. Such poor restoration outcomes could be partly caused by the predominance of short‐term studies, which do not account for natural temporal fluctuations nor changes in the effects of restoration through time. Consequently, research that examines the longer‐term dynamics of river restoration is crucial for providing a temporal perspective of restoration outcomes and for informing the effectiveness of restoration methods. We used the Nidda River in Germany as a case study of the temporal effects of river hydromorphological restoration on different aquatic taxa. We surveyed macroinvertebrate, macrophyte, and fish communities across three sites prerestoration (2008) and then monitored changes in one control versus two restored sites across 10 years (2010–2019). Overall, we found few effects of restoration on the macroinvertebrate and macrophyte communities, with no effects whatsoever on fishes. Restoration improved some components of the macroinvertebrate and macrophyte communities; however, these positive effects were temporally inconsistent and did not translate to improvements in river ecosystem health (based on an index of ecological quality). Our findings illustrate how allowing for more time for community development will not necessarily alter the fact that local‐scale river habitat restoration can elicit little to no change in aquatic communities. Combining local‐ with broad‐scale restoration efforts that address the primary drivers of hydroecological decline, in addition to long‐term monitoring, may therefore be required to ensure that river restorations successfully meet their ecological goals

Are the “100 of the world’s worst” invasive species also the costliest?

Biological invasions are increasing worldwide, damaging ecosystems and socioeconomic sectors. Two decades ago, the “100 of the world’s worst” invasive alien species list was established by the IUCN to improve communications , identifying particularly damaging ‘flagship’ invaders globally (hereafter, worst). Whilst this list has bolstered invader awareness, whether worst species are especially economically damaging and how they compare to other invaders (hereafter, other) remain unknown. Here, we quantify invasion costs using the most comprehensive global database compiling them (InvaCost). We compare these costs between worst and other species against sectorial, taxonomic and regional descriptors, and examine temporal cost trends. Only 60 of the 100 worst species had invasion costs considered as highly reliable and actually observed estimates (median: US$43 million). On average, these costs were significantly higher than the 463 other invasive species recorded in InvaCost (median: US$ 0.53 million), although some other species had higher costs than most worst species. Damages to the environment from the worst species dominated, whereas other species largely impacted agriculture. Disproportionately highest worst species costs were incurred in North America, whilst costs were more evenly distributed for other species; animal invasions were always costliest. Proportional management expenditures were low for the other species, and surprisingly, over twice as low for the worst species. Temporally, costs increased more for the worst than other taxa; however, management spending has remained very low for both groups. Nonetheless, since 40 species had no robust and/or reported costs, the “true” cost of “some of the world’s worst” 100 invasive species still remains unknown

When alien catfish meet—Resource overlap between the North American Ictalurus punctatus and immature European Silurus glanis in the Arno River (Italy)

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DEEP—A tool for differential expression effector prediction

High-throughput methods for measuring transcript abundance, like SAGE or microarrays, are widely used for determining differences in gene expression between different tissue types, dignities (normal/malignant) or time points. Further analysis of such data frequently aims at the identification of gene interaction networks that form the causal basis for the observed properties of the systems under examination. To this end, it is usually not sufficient to rely on the measured gene expression levels alone; rather, additional biological knowledge has to be taken into account in order to generate useful hypotheses about the molecular mechanism leading to the realization of a certain phenotype

Regulatory coordination of clustered microRNAs based on microRNA-transcription factor regulatory network

<p>Abstract</p> <p>Background</p> <p>MicroRNA (miRNA) is a class of small RNAs of ~22nt which play essential roles in many crucial biological processes and numerous human diseases at post-transcriptional level of gene expression. It has been revealed that miRNA genes tend to be clustered, and the miRNAs organized into one cluster are usually transcribed coordinately. This implies a coordinated regulation mode exerted by clustered miRNAs. However, how the clustered miRNAs coordinate their regulations on large scale gene expression is still unclear.</p> <p>Results</p> <p>We constructed the miRNA-transcription factor regulatory network that contains the interactions between transcription factors (TFs), miRNAs and non-TF protein-coding genes, and made a genome-wide study on the regulatory coordination of clustered miRNAs. We found that there are two types of miRNA clusters, i.e. homo-clusters that contain miRNAs of the same family and hetero-clusters that contain miRNAs of various families. In general, the homo-clustered as well as the hetero-clustered miRNAs both exhibit coordinated regulation since the miRNAs belonging to one cluster tend to be involved in the same network module, which performs a relatively isolated biological function. However, the homo-clustered miRNAs show a direct regulatory coordination that is realized by one-step regulation (i.e. the direct regulation of the coordinated targets), whereas the hetero-clustered miRNAs show an indirect regulatory coordination that is realized by a regulation comprising at least three steps (e.g. the regulation on the coordinated targets by a miRNA through a sequential action of two TFs). The direct and indirect regulation target different categories of genes, the former predominantly regulating genes involved in emergent responses, the latter targeting genes that imply long-term effects.</p> <p>Conclusion</p> <p>The genomic clustering of miRNAs is closely related to the coordinated regulation in the gene regulatory network. The pattern of regulatory coordination is dependent on the composition of the miRNA cluster. The homo-clustered miRNAs mainly coordinate their regulation rapidly, while the hetero-clustered miRNAs exert control with a delay. The diverse pattern of regulatory coordination suggests distinct roles of the homo-clustered and the hetero-clustered miRNAs in biological processes.</p