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Background: While the use of plastic materials has generated huge societal benefits, the "plastic age" comes with downsides: One issue of emerging concern is the accumulation of plastics in the aquatic environment. Here, so-called microplastics (MP), fragments smaller than 5 mm, are of special concern because they can be ingested throughout the food web more readily than larger particles. Focusing on freshwater MP, we briefly review the state of the science to identify gaps of knowledge and deduce research needs.
State of the science: Environmental scientists started investigating marine (micro)plastics in the early 2000s. Today, a wealth of studies demonstrates that MP have ubiquitously permeated the marine ecosystem, including the polar regions and the deep sea. MP ingestion has been documented for an increasing number of marine species. However, to date, only few studies investigate their biological effects. The majority of marine plastics are considered to originate from land-based sources, including surface waters. Although they may be important transport pathways of MP, data from freshwater ecosystems is scarce. So far, only few studies provide evidence for the presence of MP in rivers and lakes. Data on MP uptake by freshwater invertebrates and fish is very limited.
Knowledge gaps: While the research on marine MP is more advanced, there are immense gaps of knowledge regarding freshwater MP. Data on their abundance is fragmentary for large and absent for small surface waters. Likewise, relevant sources and the environmental fate remain to be investigated. Data on the biological effects of MP in freshwater species is completely lacking. The accumulation of other freshwater contaminants on MP is of special interest because ingestion might increase the chemical exposure. Again, data is unavailable on this important issue.
Conclusions: MP represent freshwater contaminants of emerging concern. However, to assess the environmental risk associated with MP, comprehensive data on their abundance, fate, sources, and biological effects in freshwater ecosystems are needed. Establishing such data critically depends on a collaborative effort by environmental scientists from diverse disciplines (chemistry, hydrology, ecotoxicology, etc.) and, unsurprisingly, on the allocation of sufficient public funding.
In recent years, interest in the environmental occurrence and effects of microplastics (MPs) has shifted towards our inland waters, and in this chapter we provide an overview of the issues that may be of concern for freshwater environments. The term ‘contaminant of emerging concern’ does not only apply to chemical pollutants but to MPs as well because it has been detected ubiquitously in freshwater systems. The environmental release of MPs will occur from a wide variety of sources, including emissions from wastewater treatment plants and from the degradation of larger plastic debris items. Due to the chemical makeup of plastic materials, receiving environments are potentially exposed to a mixture of micro- and nano-sized particles, leached additives, and subsequent degradation products, which will become bioavailable for a range of biota. The ingestion of MPs by aquatic organisms has been demonstrated, but the long-term effects of continuous exposures are less well understood. Technological developments and changes in demographics will influence the types of MPs and environmental concentrations in the future, and it will be important to develop approaches to mitigate the input of synthetic polymers to freshwater ecosystems.
Micromorphology is a suitable method to study the contents and stratigraphic relationships of pit fills. Within the ramparts of Corneşti-Iarcuri, fill layers of a pit were sampled. Th e pit fill was macroscopically divided into primary and secondary fill due to striking differences. These differences could be verified and concretized micromorphologically.
The Cueva del Azufre in Tabasco, Mexico, is a nutrient-rich cave and its inhabitants need to cope with high levels of dissolved hydrogen sulfide and extreme hypoxia. One of the successful colonizers of this cave is the poeciliid fish Poecilia mexicana, which has received considerable attention as a model organism to examine evolutionary adaptations to extreme environmental conditions. Nonetheless, basic ecological data on the endemic cave molly population are still missing; here we aim to provide data on population densities, size class compositions and use of different microhabitats. We found high overall densities in the cave and highest densities at the middle part of the cave with more than 200 individuals per square meter. These sites have lower H2S concentrations compared to the inner parts where most large sulfide sources are located, but they are annually exposed to a religious harvesting ceremony of local Zoque people called La Pesca. We found a marked shift in size/age compositions towards an overabundance of smaller, juvenile fish at those sites. We discuss these findings in relation to several environmental gradients within the cave (i.e., differences in toxicity and lighting conditions), but we also tentatively argue that the annual fish harvest during a religious ceremony (La Pesca) locally diminishes competition (and possibly, cannibalism by large adults), which is followed by a phase of overcompensation of fish densities.
Microglia, the primary immune cells of the central nervous system, hold a multitude of tasks in order to ensure brain homeostasis and are one of the best predictors of biological age on a cellular level. We and others have shown that these long-lived cells undergo an aging process that impedes their ability to perform some of the most vital homeostatic functions such as immune surveillance, acute injury response, and clearance of debris. Microglia have been described as gradually transitioning from a homeostatic state to an activated state in response to various insults, as well as aging. However, microglia show diverse responses to presented stimuli in the form of acute injury or chronic disease. This complexity is potentially further compounded by the distinct alterations that globally occur in the aging process. In this review, we discuss factors that may contribute to microglial aging, as well as transcriptional microglia alterations that occur in old age. We then compare these distinct phenotypic changes with microglial phenotype in neurodegenerative disease.
The German savings and cooperative banks of the 19th century were precursors of modern microfinance. They provided access to financial services for the majority of the German population, which was formerly excluded from bank funding. Furthermore, they did this at low costs for themselves and affordable prices for their clients. By creating networks of financially viable and stable financial institutions covering the entire country, they contributed significantly to building a sound and “inclusive” financial infrastructure in Germany. A look back at the history of German savings and cooperative banks and combining these experiences with the lessons learned from modern microfinance can guide current policy and be valuable for present and future models of microfinance business.
Access to loans and other financial services is extremely valuable for micro-, small- and medium-sized enterprises in developing and transition countries as it enables their owners as well as their employees to exploit their economic potential and to increase their income. Although this insight has lead development aid institutions to undertake many attempts to create sustainable microfinance institutions, only a small fraction of these has been successful so far. This article analyses what determines the success of attempts to provide financial services in general, and credit in particular, to low income target groups in these countries. We argue that it is crucial to understand, and to mitigate or even eliminate in practice, the serious and numerous incentive problems at the level of the lending operations as well as those at the levels of the human resource management and the governance of microfinance institutions. We attempt to show moreover, that unsolved incentive problems at only one level will ultimately undermine any potential success at the other levels. In our paper, we first analyse information and incentive problems from a theoretical perspective, using and extending the well-known Stiglitz-Weiss model of credit rationing, and derive theoretical requirements for solutions of these problems. In the light of these considerations, we then discuss how problems are solved in practice. Section 3 deals with the credit relationship. Section 4 extends the argument by showing how incentive problems within the institution can be handled, and section 5 analyses corporate governance-related problems of development finance institutions as incentive problems. In section 6 it is demonstrated why, and how, the incentive problems at the different levels, as well as their solutions, are interrelated. From this we derive the proposition that, as the institutional devices for dealing with these problems constitute a complementary system, any sustainable solution requires consistent arrangements of all elements and at all levels of the system. In the last section we will show the potential of strategic networks to set up institutions which we consider to be consistent systems for successfully solving the problems at all three levels simultaneously.
This thesis presents microstructural investigations of rock salt from the central part of the Gorleben salt dome (Northern Germany). The main emphasis was to characterize the rock salt microfabrics, to identify operating deformation mechanisms in halite and anhydrite and to decipher the macro- and microstructural distribution of hydrocarbons, which have been encountered during the underground exploration of the salt dome. The microfabrics of the Knäuel- and the Streifensalz formation indicate that strain-induced grain boundary migration has been active during deformation of halite. Crystal plastic deformation of halite is further documented by lattice bending, subgrain formation and minor subgrain rotation. Evidence for pressure solution of halite has not been found, but cannot be excluded because of the small grain size, the lack of LPO and the low differential stress (1.1 - 1.3 MPa) as deduced from subgrain-size piezometry. Solution precipitation creep was proven for intercalated anhydrite layers and clusters, which have been deformed in the brittle-ductile regime. Brittle deformation of anhydrite in terms of boudinage and fracturing was counteracted by viscous creep of halite which caused a re-sealing of fractures and a reestablishing of the characteristic sealing capacity of rock salt. Hydrocarbons are mainly located along cross cut 1 West of the Gorleben exploration mine and are heterogeneously distributed in the rock salt. They are incorporated in the rock salt foliation in the form of streaks, dispersed clouds, clusters and isolated patches. On the micro-scale, hydrocarbons are trapped along grain boundaries of halite and/or anhydrite, in micro-capillary tubes of anhydrite and in pore space of the rare rock salt with elevated porosity (< 1.26 vol.-%). Such elevated porosities correlate with elevated hydrocarbon concentrations of several hundred ppm. The overall concentrations of hydrocarbons, however, are very low (< 0.05 wt.-%). Elevated porosity is depicted to be a remnant originating from an early stage of salt uplift when fluid and hydrocarbons have migrated and spread from the Staßfurt Karbonat (z2SK) into the superjacent Gorleben Hauptsalz. During halokinesis and the strong reworking of the salt body hydrocarbons have been redistributed and dismembered resulting in the isolated present-day occurrences. The distribution of hydrocarbons shows no relation to local variations in the rock salt fabric. The microstructures of hydrocarbon-bearing and hydrocarbon-free Gorleben rock salt are not distinguishable from each other. Likewise, the presence of hydrocarbons should not have influenced the mechanical behavior or the rock salt as indicated by the microfabrics studied and by geomechanical data. The pure amounts of hydrocarbons are too low for any detectable impact on the barrier properties of this part of rock salt. Although hydrocarbons have migrated into the Gorleben Hauptsalz during an early stage of salt uplift when the sealing capacity of rock salt was diminished, the major implication of their isolated distribution patterns is that the Gorleben rock salt was able to regain its sealing capacity during subsequent deformation and re-equilibration. Former migration pathways for fluid and hydrocarbons have been healed and do not exist anymore. The application of X-ray computed tomography (CT) allows the 3D visualization and quantification of anhydrite, pore space and fluid phases located along grain-boundaries or trapped as intracrystalline inclusions. The 3D reconstruction of anhydrite clusters and pore space for the same sample reveals different spatial distribution patterns. This fact implies that anhydrite is not responsible for such elevated pore space in the rock salt studied, which has been largely closed during the polyphase deformation history of the Gorleben salt dome. High-resolution nanoCT scans (≤ 1 μm voxel size) of single intra- and intercrystalline fluid inclusions in rock salt enable a characterization of gaseous, solid and liquid phases inside single fluid inclusions and give exact information on morphology and shape. The 3D reconstruction of grain boundary fluid inclusions allows the amount, volumes, surface areas or diameters of various types to be determined. Non-destructive X-ray CT imaging is presented as very useful tool to characterize the structural inventory of rock salt. This non-destructive technique offers new perspectives for microstructural studies and for a wide range of research in structural geology, in general.
Microenvironmental regulation of tumor progression and therapeutic response in brain metastasis
(2019)
Cellular and non-cellular components of the tumor microenvironment (TME) are emerging as key regulators of primary tumor progression, organ-specific metastasis, and therapeutic response. In the era of TME-targeted- and immunotherapies, cancer-associated inflammation has gained increasing attention. In this regard, the brain represents a unique and highly specialized organ. It has long been regarded as an immunological sanctuary site where the presence of the blood brain barrier (BBB) and blood cerebrospinal fluid barrier (BCB) restricts the entry of immune cells from the periphery. Consequently, tumor cells that metastasize to the brain were thought to be shielded from systemic immune surveillance and destruction. However, the detailed characterization of the immune landscape within border-associated areas of the central nervous system (CNS), such as the meninges and the choroid plexus, as well as the discovery of lymphatics and channels that connect the CNS with the periphery, have recently challenged the dogma of the immune privileged status of the brain. Moreover, the presence of brain metastases (BrM) disrupts the integrity of the BBB and BCB. Indeed, BrM induce the recruitment of different immune cells from the myeloid and lymphoid lineage to the CNS. Blood-borne immune cells together with brain-resident cell-types, such as astrocytes, microglia, and neurons, form a highly complex and dynamic TME that affects tumor cell survival and modulates the mode of immune responses that are elicited by brain metastatic tumor cells. In this review, we will summarize recent findings on heterotypic interactions within the brain metastatic TME and highlight specific functions of brain-resident and recruited cells at different rate-limiting steps of the metastatic cascade. Based on the insight from recent studies, we will discuss new opportunities and challenges for TME-targeted and immunotherapies for BrM.
Microeconometric evidence on demand-side real rigidity and
implications for monetary non-neutrality
(2016)
To model the observed slow response of aggregate real variables to nominal shocks, most macroeconomic models incorporate real rigidities in addition to nominal rigidities. One popular way of modelling such a real rigidity is to assume a non-constant demand elasticity. By using a homescan data set for three European countries, including prices and quantities bought for a large number of goods, in addition to consumer characteristics, we provide estimates of price elasticities of demand and on the degree of demand-side real rigidities. We find that price elasticites of demand are about 4 in the median. Furthermore, we find evidence for demand-side real rigidities. These are, however, much smaller than what is often assumed in macroeconomic models. The median estimate for demand-side real rigidity, the super-elasticity, is in a range between 1 and 2. To quantitatively assess the implications of our empirical estimates, we calibrate a menu-cost model with the estimated super-elasticity. We find that the degree of monetary non-neutrality doubles in the model including demand-side real rigidity, compared to the model with only nominal rigidity, suggesting a multiplier effect of around two. However, the model can explain only up to 6% of the monetary non-neutrality observed in the data, implying that additional multipliers are necessary to match the behavior of aggregate variables.