Single-Name Credit Risk, Portfolio Risk, and Credit Rationing

This paper introduces non-diversifiable risk in the Stiglitz-Weiss adverse selection model, so that an increase in the average riskiness of the borrower pool causes higher portfolio risk. This opens up the possibility of equilibrium credit rationing. Comparative statics analysis shows that an increase in risk aversion turns a two-price equilibrium into a rationing equilibrium. A two-price equilibrium is more inefficient than a rationing equilibrium, and a usury law that rules out the higher of the two interest rates can be welfare-improving. Contrary to the common result, the equilibrium may be characterized by over-investment.asymmetric information; credit rationing

The Biodiversity and Geochemistry of Cryoconite Holes in Queen Maud Land, East Antarctica

Cryoconite holes are oases of microbial diversity on ice surfaces. In contrast to the Arctic, where during the summer most cryoconite holes are ‘open’, in Continental Antarctica they are most often ‘lidded’ or completely frozen year-round. Thus, they represent ideal systems for the study of microbial community assemblies as well as carbon accumulation, since individual cryoconite holes can be isolated from external inputs for years. Here, we use high-throughput sequencing of the 16S and 18S rRNA genes to describe the bacterial and eukaryotic community compositions in cryoconite holes and surrounding lake, snow, soil and rock samples in Queen Maud Land. We cross correlate our findings with a broad range of geochemical data including for the first time 13C and 14C analyses of Antarctic cryoconites. We show that the geographic location has a larger effect on the distribution of the bacterial community compared to the eukaryotic community. Cryoconite holes are distinct from the local soils in both 13C and 14C and their isotopic composition is different from similar samples from the Arctic. Carbon contents were generally low (≤0.2%) and older (6–10 ky) than the surrounding soils, suggesting that the cryoconite holes are much more isolated from the atmosphere than the soils

The microbial diversity and function of Arctic supraglacial biomes.

The main aim of this research project was to improve our understanding of the diversity, function and ecology of glacial microbiomes. Snow and ice algae are critical players in supraglacial habitats and form extensive blooms in spring and summer. Here I present results on the diversity and the function of snow and ice algae on 21 glaciers in 4 Arctic settings: Greenland, Iceland, Svalbard and Sweden. For the first time, I have evaluated the full microbial community composition (i.e., algae, bacteria, archaea) in the main supraglacial habitats, namely green snow, red snow, biofilms, dirty ice, and cryoconite holes. I have cross-correlated these data with metabolic analyses (i.e., metabolomics, pigments, fatty acids) and critical physico-chemical parameters. I found that snow and ice algae were the first communities to appear after the onset of melting and they showed positive net photosynthetic rates indicating accumulation of organic matter. Furthermore, for the first time I have described these communities in Iceland. My data reveal that red pigmented snow algae are cosmopolitan, and independent of location specific geochemical and mineralogical factors. Only six taxa made up >99% of the algal communities: two uncultured Chlamydomonadaceae, Chloromonas polyptera, Chloromonas nivalis, Chloromonas alpina and Raphidonema sempervirens. In contrast, the composition of green snow varied between the studied locations with higher relative abundance of Raphidonema sempervirens and Microglena sp. in Svalbard, and Chloromonas polyptera in Sweden. Furthermore, I show that green and red snow are not successive stages but two independent phenomena with different adaptation strategies. In all sites, bacteria were mostly represented by the phyla Bacteriodetes, Proteobacteria and Cyanobacteria. The bacterial community composition varied between the different habitats on the phylum level, whereas on the class level they also showed strong biogeography. Archaea showed overall low species diversity. The synthesis of pigments and fatty acids in snow and ice algae were mainly driven by nitrogen and less so by phosphorus limitation. This is especially important for pigments which cause a darkening of glacial surfaces. I show that snow and ice algae dramatically decrease surface albedo which will eventully result in higher melting rates of glaciers

Landauer's principle in the quantum domain

Recent papers discussing thermodynamic processes in strongly coupled quantum systems claim a violation of Landauer's principle and imply a violation of the second law of thermodynamics. If true, this would have powerful consequences. Perpetuum mobiles could be build as long as the operating temperature is brought close to zero. It would also have serious consequences on thermodynamic derivations of information theoretic results, such as the Holevo bound. Here we argue why these claims are erroneous. Correlations occurring in the strongly coupled, quantum domain require a rethink of how entropy, heat and work are calculated. It is shown that a consistent treatment solves the paradox

Microbial diversity on Icelandic glaciers and ice caps

Algae are important primary colonizers of snow and glacial ice, but hitherto little is known about their ecology on Iceland’s glaciers and ice caps. Due do the close proximity of active volcanoes delivering large amounts of ash and dust, they are special ecosystems. This study provides the first investigation of the presence and diversity of microbial communities on all major Icelandic glaciers and ice caps over a three year period. Using high-throughput sequencing of the small subunit ribosomal RNA genes (16S and 18S), we assessed the snow community structure and complemented these analyses with a comprehensive suite of physical-, geo- and biochemical characterizations of the aqueous and solid components contained in snow and ice samples. Our data reveal that a limited number of snow algal taxa (Chloromonas polyptera, Raphidonema sempervirens and two uncultured Chlamydomonadaceae) support a rich community comprising of other micro-eukaryotes, bacteria and archaea. Proteobacteria and Bacteroidetes were the dominant bacterial phyla. Archaea were also detected in sites where snow algae dominated and they mainly belong to the Nitrososphaerales, which are known as important ammonia oxidizers. Multivariate analyses indicated no relationships between nutrient data and microbial community structure. However, the aqueous geochemical simulations suggest that the microbial communities were not nutrient limited because of the equilibrium of snow with the nutrient-rich and fast dissolving volcanic ash. Increasing algal secondary carotenoid contents in the last stages of the melt seasons have previously been associated with a decrease in surface albedo, which in turn could potentially have an impact on the melt rates of Icelandic glaciers

Validity of Landauer's principle in the quantum regime

We demonstrate the validity of Landauer's erasure principle in the strong coupling quantum regime by treating the system-reservoir interaction in a consistent way. We show that the initial coupling to the reservoir modifies both energy and entropy of the system and provide explicit expressions for the latter in the case of a damped quantum harmonic oscillator. These contributions are related to the Hamiltonian of mean force and dominate in the strong damping limit. They need therefore to be fully taken into account in any low-temperature thermodynamic analysis of quantum systems.Comment: 4 pages, 2 figure

Novel insights in cryptic diversity of snow and glacier ice algae communities combining 18S rRNA gene and ITS2 amplicon sequencing

Melting snow and glacier surfaces host microalgal blooms in polar and mountainous regions. The aim of this study was to determine the dominant taxa at the species level in the European Arctic and the Alps. A standardized protocol for amplicon metabarcoding using the 18S rRNA gene and ITS2 markers was developed. This is important because previous biodiversity studies have been hampered by the dominance of closely related algal taxa in snow and ice. Due to the limited resolution of partial 18S rRNA Illumina sequences, the hypervariable ITS2 region was used to further discriminate between the genotypes. Our results show that red snow was caused by the cosmopolitan Sanguina nivaloides (Chlamydomonadales, Chlorophyta) and two as of yet undescribed Sanguina species. Arctic orange snow was dominated by S. aurantia, which was not found in the Alps. On glaciers, at least three Ancylonema species (Zygnematales, Streptophyta) dominated. Golden-brown blooms consisted of Hydrurus spp. (Hydrurales, Stramenophiles) and these were mainly an Arctic phenomenon. For chrysophytes, only the 18S rRNA gene but not ITS2 sequences were amplified, showcasing how delicate the selection of eukaryotic ‘universal’ primers for community studies is and that primer specificity will affect diversity results dramatically. We propose our approach as a ‘best practice’

"Pounded Earth and Heartbeats": 20thcentury Poetry by Native Women of North America

Apart from the lonely example of Emily Pauline Johnson’s (1861- 1913) works, published poetry by Native American women is a relatively new phenomenon starting in the late 1960s. A survey of 38 anthologies published between 1969 and 1997 rendered a total of 362 names of Native women poets in the USA and Canada, of whom only about 25 are published more continuously. The continuity of life between the forces of colonization and the ensuing struggle for decolonization emerges as an overriding paradigm in their poetry, encompassing topics like history, land, language, forms of geno- and ethnocide, cultural identity, abuses, family and community. New aesthetic strategies and self-determined forms of publication enhance their struggle for decolonization