Approaches and possible improvements in the area of multibody dynamics modeling

A wide ranging look is taken at issues involved in the dynamic modeling of complex, multibodied orbiting space systems. Capabilities and limitations of two major codes (DISCOS, TREETOPS) are assessed and possible extensions to the CONTOPS software are outlined. In addition, recommendations are made concerning the direction future development should take in order to achieve higher fidelity, more computationally efficient multibody software solutions

Fighting a losing battle: Vigorous immune response countered by pathogen suppression of host defenses in the chytridiomycosis-susceptible frog Atelopus zeteki

The emergence of the disease chytridiomycosis caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd) has been implicated in dramatic global amphibian declines. Although many species have undergone catastrophic declines and/or extinctions, others appear to be unaffected or persist at reduced frequencies after Bd outbreaks. The reasons behind this variance in disease outcomes are poorly understood: differences in host immune responses have been proposed, yet previous studies suggest a lack of robust immune responses to Bd in susceptible species. Here, we sequenced transcriptomes from clutchmates of a highly susceptible amphibian, Atelopus zeteki, with different infection histories. We found significant changes in expression of numerous genes involved in innate and inflammatory responses in infected frogs despite high susceptibility to chytridiomycosis. We show evidence of acquired immune responses generated against Bd, including increased expression of immunoglobulins and major histocompatibility complex genes. In addition, fungal-killing genes had significantly greater expression in frogs previously exposed to Bd compared with Bd-naïve frogs, including chitinase and serine-type proteases. However, our results appear to confirm recent in vitro evidence of immune suppression by Bd, demonstrated by decreased expression of lymphocyte genes in the spleen of infected compared with control frogs. We propose susceptibility to chytridiomycosis is not due to lack of Bd-specific immune responses but instead is caused by failure of those responses to be effective. Ineffective immune pathway activation and timing of antibody production are discussed as potential mechanisms. However, in light of our findings,suppression of key immune responses by Bd is likely an important factor in the lethality of this fungus

Large Interstellar Polarisation Survey. LIPS I: FORS2 spectropolarimetry in the Southern Hemisphere

Polarimetric studies of light transmitted through interstellar clouds may give constraints on the properties of the interstellar dust grains. Traditionally, broadband linear polarisation (BBLP) measurements have been considered an important diagnostic tool for the study of the interstellar dust, while comparatively less attention has been paid to spectropolarimetric measurements. However, spectropolarimetry may offer stronger constraints than BBLP, for example by revealing narrowband features, and by allowing us to distinguish the contribution of dust from the contribution of interstellar gas. Therefore, we have decided to carry out a Large Interstellar Polarisation Survey (LIPS) using spectropolarimetric facilities in both hemispheres. Here we present the results obtained in the Southern Hemisphere with the FORS2 instrument of the ESO Very Large Telescope. Our spectra cover the wavelength range 380--950\,nm at a spectral resolving power of about 880. We have produced a publicly available catalogue of 127 linear polarisation spectra of 101 targets. We also provide the Serkowski-curve parameters, as well as the wavelength gradient of the polarisation position angle for the interstellar polarisation along 76 different lines of sight. In agreement with previous literature, we found that the best-fit parameters of the Serkowski-curve are not independent of each other. However, the relationships that we obtained are not always consistent with what was found in previous studies.Comment: Accepted by A&A (replaced on 12 October 2017 simply to correct a Metadata error

More than skin deep: Functional genomic basis for resistance to Amphibian Chytridiomycosis

The amphibian-killing chytrid fungus Batrachochytriumdendrobatidis (Bd) is one of themost generalist pathogens known, capable of infecting hundreds of species globally and causing widespread population declines and extinctions. However, some host species are seemingly unaffected by Bd, tolerating or clearing infections without clinical signs of disease. Variation in host immune responses is commonly evoked for these resistant or tolerant species, yet to date,we have nodirect comparisonof amphibian species responses to infection at the level of gene expression. In this study,we challenged four CentralAmerican frog species that vary in Bd susceptibility, with a sympatric virulent strain of the pathogen. We compared skin and spleen orthologous gene expression using differential expression tests and coexpression gene network analyses.Wefound that resistant species have reduced skin inflammatory responses andincreased expressionofgenes involved inskin integrity. Incontrast, onlyhighly susceptible species exhibited suppressionof splenic T-cell genes. We conclude that resistance to chytridiomycosis may be related to a species’ ability to escape the immunosuppressive activity of the fungus. Moreover, our results indicate that within-species differences in splenic proteolytic enzyme gene expression may contribute to intraspecific variation in survival. This first comparison of amphibian functional immunogenomic architecture in response to Bd provides insights into key genetic mechanisms underlying variation in disease outcomes among amphibian species

Simulation of actively controlled spacecraft with flexible appendages

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76688/1/AIAA-25388-716.pd

Upwelling events, coastal offshore exchange, links to biogeochemical processes - Highlights from the Baltic Sea Sciences Congress at Rostock University, Germany, 19-22 March 2007

The Baltic Sea Science Congress was held at Rostock University, Germany, from 19 to 22 March 2007. In the session entitled"Upwelling events, coastal offshore exchange, links to biogeochemical processes" 20 presentations were given,including 7 talks and 13 posters related to the theme of the session.This paper summarises new findings of the upwelling-related studies reported in the session. It deals with investigationsbased on the use of in situ and remote sensing measurements as well as numerical modelling tools. The biogeochemicalimplications of upwelling are also discussed.Our knowledge of the fine structure and dynamic considerations of upwelling has increased in recent decades with the advent ofhigh-resolution modern measurement techniques and modelling studies. The forcing and the overall structure, duration and intensity ofupwelling events are understood quite well. However, the quantification of related transports and the contribution to the overall mixingof upwelling requires further research. Furthermore, our knowledge of the links between upwelling and biogeochemical processes is stillincomplete. Numerical modelling has advanced to the extent that horizontal resolutions of c. 0.5 nautical miles can now be applied,which allows the complete spectrum of meso-scale features to be described. Even the development of filaments can be describedrealistically in comparison with high-resolution satellite data.But the effect of upwelling at a basin scale and possible changes under changing climatic conditions remain open questions

Silent Springs: Why Are All the Frogs “Croaking”?

Amphibians are a fabulously successful group of animals; however, it is increasingly clear that they are experiencing extinction rates that far exceed those experienced by other classes of vertebrates. A new book examines the various reasons why amphibians are so threatened, and what can be done about it

MEN-2 Syndrome: The Value of Screening and Central Registration; A Study of Six Kindreds in The Netherlands

Since 1975, six families with the MEN-2A syndrome including 66 patients have been identified in The Netherlands. All these patients underwent thyroidectomy for C-cell hyperplasia and/or medullary thyroid carcinoma (MTC); eight were symptomatic (Group A), 51 were relatives of patients found to be affected (Group B), and seven had had a negative screening test that became positive (Group C). To assess the effect of screening, we compared these groups with respect to the occurrence of metastatic MTC at thyroidectomy and the results of the postoperative calcitonin (CT) tests. We found that 87% of Group A, 37% of Group B; and none of Group C had metastatic disease at surgery. The cure rates in these three groups with MEN-2A, as determined by stimulated CT measurement, was 0%, 51%, and 100%, respectively. From these results it may be concluded that screening can lead to the detection of MTC at an earlier stage which in turn could permit curative treatment and improvement of both prognosis and life expectancy. The need for supervision of affected families by central registration to guarantee the continuity of screening is stressed