3,960 research outputs found
Surface Free Energies, Interfacial Tensions and Correlation Lengths of the ABF Models
The surface free energies, interfacial tensions and correlation lengths of
the Andrews-Baxter-Forrester models in regimes III and IV are calculated with
fixed boundary conditions. The interfacial tensions are calculated between
arbitrary phases and are shown to be additive. The associated critical
exponents are given by with in regime III
and with in regime IV. Our results are
obtained using general commuting transfer matrix and inversion relation methods
that may be applied to other solvable lattice models.Comment: 21 pages, LaTeX 2e, requires the amsmath packag
Interaction-Round-a-Face Models with Fixed Boundary Conditions: The ABF Fusion Hierarchy
We use boundary weights and reflection equations to obtain families of
commuting double-row transfer matrices for interaction-round-a-face models with
fixed boundary conditions. In particular, we consider the fusion hierarchy of
the Andrews-Baxter-Forrester models, for which we find that the double-row
transfer matrices satisfy functional equations with an su(2) structure.Comment: 48 pages, LaTeX, requires about 79000 words of TeX memory. Submitted
to J. Stat. Phy
Chandra and XMM-Newton Observations of the Double Cluster Abell 1758
Abell 1758 was classified as a single rich cluster of galaxies by Abell, but
a ROSAT observation showed that this system consists of two distinct clusters
(A1758N and A1758S) separated by approximately 8\arcmin (a projected
separation of 2 Mpc in the rest frame of the clusters). Only a few galaxy
redshifts have been published for these two clusters, but the redshift of the
Fe lines in the Chandra and XMM-Newton spectra shows that the recessional
velocities of A1758N and A1758S are within 2,100 km s. Thus, these two
clusters most likely form a gravitationally bound system, but our imaging and
spectroscopic analyses of the X-ray data do not reveal any sign of interaction
between the two clusters. The Chandra and XMM-Newton observations show that
A1758N and A1758S are both undergoing major mergers.
A1758N is in the late stages of a large impact parameter merger between two 7
keV clusters. The two remnant cores have a projected separation of 800 kpc.
Based on the measured pressure jumps preceding the two cores, they are receding
from one another at less than 1,600 km s. The two cores are surrounded
by hotter gas (--12 keV) that was probably shock heated during
the early stages of the merger. The gas entropy in the two remnant cores is
comparable with the central entropy observed in dynamically relaxed clusters,
indicating that the merger-induced shocks stalled as they tried to penetrate
the high pressure cores of the two merging systems.Each core also has a wake of
low entropy gas indicating that this gas was ram pressure stripped without
being strongly shocked (abridged). (A copy of the paper with higher resolution
images is available at http://asc.harvard.edu/~lpd/a1758.ps).Comment: paper plus 13 figure
Differing preferences of Antarctic soil nematodes for microbial prey
We tested the preferences of three nematode taxa, Geomonhystera villosa, Plectus spp. and Teratocephalus spp., extracted from moss at Signy Island in the Maritime Antarctic, for two microalgae, three microfungi and six heterotrophic bacteria, each also from soils at Signy Island. Choice test experiments on water agar medium, in which nematodes were enumerated in wells containing microbes at 24 and 48 h, indicated that there were differing preferences between nematodes for distinct prey. G. villosa was significantly attracted to the alga Chlorella cf. minutissima and the fungus Mortierella hyalina, and was more attracted to all algae and fungi than either of the other two nematodes. Both G. villosa and Teratocephalus spp. were attracted to an actinobacterium. Plectus spp. were significantly attracted to the alga Stichococcus bacillaris and bacteria with close taxonomic affinities to Arthrobacter, Pseudomonas and Polaromonas. Experiments using 0.5 μm diameter fluorescent beads indicated significantly increased ingestion by nematodes in the presence of each of these microbes compared with controls, except by Plectus spp. in the presence of S. bacillaris. We conclude that complex trophic interactions may occur in apparently simple Antarctic soil food webs
Integrative Risk Management for abrupt catastrophes destroying 10%- 20% of global food supply
Analysis of NCL Proteins from an Evolutionary Standpoint
The Neuronal Ceroid Lipofuscinoses (NCLs) are the most common group of neurodegenerative disorders of childhood. While mutations in eight different genes have been shown to be responsible for these clinically distinct types of NCL, the NCLs share many clinical and pathological similarities. We have conducted an exhaustive Basic Local Alignment Search Tool (BLAST) analysis of the human protein sequences for each of the eight known NCL proteins- CLN1, CLN2, CLN3, CLN5, CLN6, CLN7, CLN8 and CLN10. The number of homologous species per CLN-protein identified by BLAST searches varies depending on the parameters set for the BLAST search. For example, a lower threshold is able to pull up more homologous sequences whereas a higher threshold decreases this number. Nevertheless, the clade confines are consistent despite this variation in BLAST searching parameters. Further phylogenetic analyses on the appearance of NCL proteins through evolution reveals a different time line for the appearance of the CLN-proteins. Moreover, divergence of each protein shows a different pattern, providing important clues on the evolving role of these proteins. We present and review in-depth bioinformatic analysis of the NCL proteins and classify the CLN-proteins into families based on their structures and evolutionary relationships, respectively. Based on these analyses, we have grouped the CLN-proteins into common clades indicating a common evolving pathway within the evolutionary tree of life. CLN2 is grouped in Eubacteria, CLN1 and CLN10 in Viridiplantae, CLN3 in Fungi/ Metazoa, CLN7 in Bilateria and CLN5, CLN6 and CLN8 in Euteleostomi
Emerging spatial patterns in Antarctic prokaryotes
Recent advances in knowledge of patterns of biogeography in terrestrial eukaryotic organisms have led to a fundamental paradigm shift in understanding of the controls and history of life on land in Antarctica, and its interactions over the long term with the glaciological and geological processes that have shaped the continent. However, while it has long been recognized that the terrestrial ecosystems of Antarctica are dominated by microbes and their processes, knowledge of microbial diversity and distributions has lagged far behind that of the macroscopic eukaryote organisms. Increasing human contact with and activity in the continent is leading to risks of biological contamination and change in a region whose isolation has protected it for millions of years at least; these risks may be particularly acute for microbial communities which have, as yet, received scant recognition and attention. Even a matter apparently as straightforward as Protected Area designation in Antarctica requires robust biodiversity data which, in most parts of the continent, remain almost completely unavailable. A range of important contributing factors mean that it is now timely to reconsider the state of knowledge of Antarctic terrestrial prokaryotes. Rapid advances in molecular biological approaches are increasingly demonstrating that bacterial diversity in Antarctica may be far greater than previously thought, and that there is overlap in the environmental controls affecting both Antarctic prokaryotic and eukaryotic communities. Bacterial dispersal mechanisms and colonization patterns remain largely unaddressed, although evidence for regional evolutionary differentiation is rapidly accruing and, with this, there is increasing appreciation of patterns in regional bacterial biogeography in this large part of the globe. In this review, we set out to describe the state of knowledge of Antarctic prokaryote diversity patterns, drawing analogy with those of eukaryote groups where appropriate
The variation and visualisation of elastic anisotropy in rock forming minerals
Acknowledgements David Healy thanks John Wheeler (Liverpool) for discussions and Ross Angel (Padua) for discussions and a reprint. This paper is dedicated to the memory of John Frederick Nye (1923–2019), whose seminal text book, first published in 1957 (Physical Properties of Crystals: Their Representation by Tensors and Matrices; reprinted as Nye, 1985), has had a huge influence on the lead author. Financial support This research has been supported by the NERC (grant no. NE/N003063/1).Peer reviewedPublisher PD
Hydrothermal activity lowers trophic diversity in Antarctic sedimented hydrothermal vents
Sedimented hydrothermal vents are those in which hydrothermal fluid vents through sediment and are among the least studied deep-sea ecosystems. We present a combination of microbial and biochemical data to assess trophodynamics between and within hydrothermally active and off-vent areas of the Bransfield Strait (1050–1647 m depth). Microbial composition, biomass and fatty acid signatures varied widely between and within vent and non-vent sites and provided evidence of diverse metabolic activity. Several species showed diverse feeding strategies and occupied different trophic positions in vent and non-vent areas and stable isotope values of consumers were generally not consistent with feeding structure morphology. Niche area and the diversity of microbial fatty acids reflected trends in species diversity and was lowest at the most hydrothermally active site. Faunal utilisation of chemosynthetic activity was relatively limited but was detected at both vent and non-vent sites as evidenced by carbon and sulphur isotopic signatures, suggesting that the hydrothermal activity can affect trophodynamics over a much wider area than previously thought
Trehalose metabolism in the production of active dried Saccharomyces cerevisiae and its effect on retention of plasma-membrane activities
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