ETH Zurich

About: ETH Zurich is a education organization based out in Zurich, Switzerland. It is known for research contribution in the topics: Population & Computer science. The organization has 48393 authors who have published 122408 publications receiving 5111383 citations. The organization is also known as: Swiss Federal Institute of Technology in Zurich & Eidgenössische Technische Hochschule Zürich.

Prion (PrPSc)-specific epitope defined by a monoclonal antibody.

Abstract: Prions are infectious particles causing transmissible spongiform encephalopathies (TSEs). They consist, at least in part, of an isoform (PrPSc) of the ubiquitous cellular prion protein (PrPC). Conformational differences between PrPC and PrPSc are evident from increased beta-sheet content and protease resistance in PrPSc. Here we describe a monoclonal antibody, 15B3, that can discriminate between the normal and disease-specific forms of PrP. Such an antibody has been long sought as it should be invaluable for characterizing the infectious particle as well as for diagnosis of TSEs such as bovine spongiform encephalopathy (BSE) or Creutzfeldt-Jakob disease (CJD) in humans. 15B3 specifically precipitates bovine, murine or human PrPSc, but not PrPC, suggesting that it recognizes an epitope common to prions from different species. Using immobilized synthetic peptides, we mapped three polypeptide segments in PrP as the 15B3 epitope. In the NMR structure of recombinant mouse PrP, segments 2 and 3 of the 15B3 epitope are near neighbours in space, and segment 1 is located in a different part of the molecule. We discuss models for the PrPSc-specific epitope that ensure close spatial proximity of all three 15B3 segments, either by intermolecular contacts in oligomeric forms of the prion protein or by intramolecular rearrangement.

The zCOSMOS 10k-Bright Spectroscopic Sample

Abstract: We present spectroscopic redshifts of a large sample of galaxies with I_(AB) < 22.5 in the COSMOS field, measured from spectra of 10,644 objects that have been obtained in the first two years of observations in the zCOSMOS-bright redshift survey. These include a statistically complete subset of 10,109 objects. The average accuracy of individual redshifts is 110 km s^(–1), independent of redshift. The reliability of individual redshifts is described by a Confidence Class that has been empirically calibrated through repeat spectroscopic observations of over 600 galaxies. There is very good agreement between spectroscopic and photometric redshifts for the most secure Confidence Classes. For the less secure Confidence Classes, there is a good correspondence between the fraction of objects with a consistent photometric redshift and the spectroscopic repeatability, suggesting that the photometric redshifts can be used to indicate which of the less secure spectroscopic redshifts are likely right and which are probably wrong, and to give an indication of the nature of objects for which we failed to determine a redshift. Using this approach, we can construct a spectroscopic sample that is 99% reliable and which is 88% complete in the sample as a whole, and 95% complete in the redshift range 0.5 < z < 0.8. The luminosity and mass completeness levels of the zCOSMOS-bright sample of galaxies is also discussed.

Fast and scalable layer four switching

Abstract: In Layer Four switching, the route and resources allocated to a packet are determined by the destination address as well as other header fields of the packet such as source address, TCP and UDP port numbers. Layer Four switching unifies firewall processing, RSVP style resource reservation filters, QoS Routing, and normal unicast and multicast forwarding into a single framework. In this framework, the forwarding database of a router consists of a potentially large number of filters on key header fields. A given packet header can match multiple filters, so each filter is given a cost, and the packet is forwarded using the least cost matching filter.In this paper, we describe two new algorithms for solving the least cost matching filter problem at high speeds. Our first algorithm is based on a grid-of-tries construction and works optimally for processing filters consisting of two prefix fields (such as destination-source filters) using linear space. Our second algorithm, cross-producting, provides fast lookup times for arbitrary filters but potentially requires large storage. We describe a combination scheme that combines the advantages of both schemes. The combination scheme can be optimized to handle pure destination prefix filters in 4 memory accesses, destination-source filters in 8 memory accesses worst case, and all other filters in 11 memory accesses in the typical case.

Partial melting of two amphibolites: contrasting experimental results under fluid-absent conditions

Abstract: A large portion of the lower continental crust may be amphibolitic in composition and without a free fluid phase. As a consequence, H2O-undersaturated or fluid-absent melting of amphibolites may be responsible for the formation of some granites and migmatites produced during major orogenic events. In an attempt to determine the systematics of melting under fluid-absent conditions, a series of piston-cylinder experiments was conducted on two natural amphibolites; one, a meta-alkali basalt (ABA) with a total water content of ∼ wt% contained in hornblende, and the other, a meta-island-arc tholeiite (IAT) which has ∼1–1.3 wt% water contained in hornblende, cummingtonite and biotite. The experimentally determined melting ranges of the two amphibolites showed that the solidus temperatures, and sta temperature interval over which amphibole was stable, were controlled by the amphibolites' different bulk compositions and their resulting metamorphic assemblages. The volume % of melt produced by melting of the two amphibolites were compared with estimated amounts, based on Burnham's (1979) water-melt solubility model and the fluid-absent melting model presented by Clemens and Vielzeuf (1987). The observed melt volumes were greater than estimated. As the water content of melt largely detemines the volume % of melt produced, independent measurements of the water-content of the glass formed during partial melting in the ABA were made by thermogravimetric analyses. The water content of the ABA glass is ∼2 wt%, which is less than the assumed “melt-water” content (water content of the melt) used in previous modeling of fluidabsent anatexis in mafic lithologies. As a consequence, more melt can be expected during fluid-absent partial melting of mafic lower crust, as is observed in the experiments. A modification of the Clemens and Vielzeuf (1987) fluid-absent melting model for mafic compositions has been made using the experimental data available on melting in basaltic systems and is presented here for pressures of 5, 8 and 10 kbar. Tectonic scenarios in which the crust is thickened (i.e. by collision) then undergoes extension or where a previously thinned crust is later rethickened, provide enough heat so that amphibolite melting under fluid-absent conditions can become importan and hence responsible for some melts produced during post-collisional magmatism. The results may also have applications to melting in hydrated oceanic crust in subduction zones and in island arc terains.

Effects of climate extremes on the terrestrial carbon cycle: concepts, processes and potential future impacts

Abstract: Extreme droughts, heat waves, frosts, precipitation, wind storms and other climate extremes may impact the structure, composition and functioning of terrestrial ecosystems, and thus carbon cycling and its feedbacks to the climate system. Yet, the interconnected avenues through which climate extremes drive ecological and physiological processes and alter the carbon balance are poorly understood. Here, we review the literature on carbon cycle relevant responses of ecosystems to extreme climatic events. Given that impacts of climate extremes are considered disturbances, we assume the respective general disturbance-induced mechanisms and processes to also operate in an extreme context. The paucity of well-defined studies currently renders a quantitative meta-analysis impossible, but permits us to develop a deductive framework for identifying the main mechanisms (and coupling thereof) through which climate extremes may act on the carbon cycle. We find that ecosystem responses can exceed the duration of the climate impacts via lagged effects on the carbon cycle. The expected regional impacts of future climate extremes will depend on changes in the probability and severity of their occurrence, on the compound effects and timing of different climate extremes, and on the vulnerability of each land-cover type modulated by management. Although processes and sensitivities differ among biomes, based on expert opinion, we expect forests to exhibit the largest net effect of extremes due to their large carbon pools and fluxes, potentially large indirect and lagged impacts, and long recovery time to regain previous stocks. At the global scale, we presume that droughts have the strongest and most widespread effects on terrestrial carbon cycling. Comparing impacts of climate extremes identified via remote sensing vs. ground-based observational case studies reveals that many regions in the (sub-)tropics are understudied. Hence, regional investigations are needed to allow a global upscaling of the impacts of climate extremes on global carbon-climate feedbacks.