University of Zurich

About: University of Zurich is a education organization based out in Zurich, Switzerland. It is known for research contribution in the topics: Population & Medicine. The organization has 50842 authors who have published 124042 publications receiving 5304521 citations. The organization is also known as: UZH & Uni Zurich.

Stability of peakons

Abstract: The peakons are peaked solitary wave solutions of a certain nonlinear dispersive equation that is a model in shallow water theory and the theory of hyperelastic rods We give a very simple proof of the orbital stability of the peakons in the H1 norm © 2000 John Wiley & Sons, Inc

The Inner Structure of LambdaCDM Halos III: Universality and Asymptotic Slopes

Abstract: We investigate the mass profile of LambdaCDM halos using a suite of numerical simulations spanning five decades in halo mass, from dwarf galaxies to rich galaxy clusters. Our analysis confirms the proposal of Navarro, Frenk & White (NFW) that the shape of LambdaCDM halo mass profiles differs strongly from a power law and depends little on mass. The logarithmic slope of the spherically-averaged density profile, as measured by beta=-dln(rho)/dln(r), decreases monotonically towards the center and becomes shallower than isothermal (beta<2) inside a characteristic radius, r_{-2}. Although the fitting formula proposed by NFW provides a reasonably good approximation to the density and circular velocity profiles of individual halos, systematic deviations from the best NFW fits are also noticeable. Inside r_{-2}, the profile of simulated halos gets shallower with radius more gradually than predicted and, as a result, NFW fits tend to underestimate the dark matter density in these regions. This discrepancy has been interpreted as indicating a steeply divergent cusp, but our results suggest a different interpretation. We use the density and enclosed mass at our innermost resolved radii to place strong constraints on beta_{0}: density cusps as steep as r^{-1.5} are inconsistent with most of our simulations, although beta_{0}=1 is still consistent with our data. Our density profiles show no sign of converging to a well-defined asymptotic inner power law. We propose a simple formula that reproduces the radial dependence of the slope better than the NFW profile, and so may minimize errors when extrapolating our results inward to radii not yet reliably probed by numerical simulations.

Observation of Unconventional Quantum Spin Textures in Topological Insulators

Abstract: A topologically ordered material is characterized by a rare quantum organization of electrons that evades the conventional spontaneously broken symmetry–based classification of condensed matter. Exotic spin-transport phenomena, such as the dissipationless quantum spin Hall effect, have been speculated to originate from a topological order whose identification requires a spin-sensitive measurement, which does not exist to this date in any system. Using Mott polarimetry, we probed the spin degrees of freedom and demonstrated that topological quantum numbers are completely determined from spin texture–imaging measurements. Applying this method to Sb and Bi1–xSbx, we identified the origin of its topological order and unusual chiral properties. These results taken together constitute the first observation of surface electrons collectively carrying a topological quantum Berry's phase and definite spin chirality, which are the key electronic properties component for realizing topological quantum computing bits with intrinsic spin Hall–like topological phenomena.

IDH1 mutations are early events in the development of astrocytomas and oligodendrogliomas.

Abstract: IDH1 encodes isocitrate dehydrogenase 1, which participates in the citric acid cycle and was recently reported to be mutated in 12% of glioblastomas. We assessed IDH1 mutations in 321 gliomas of various histological types and biological behaviors. A total of 130 IDH1 mutations was detected, and all were located at amino acid residue 132. Of these, 91% were G→A mutations (Arg→His). IDH1 mutations were frequent in low-grade diffuse astrocytomas (88%) and in secondary glioblastomas that developed through progression from low-grade diffuse or anaplastic astrocytoma (82%). Similarly, high frequencies of IDH1 mutations were found in oligodendrogliomas (79%) and oligoastrocytomas (94%). Analyses of multiple biopsies from the same patient (51 cases) showed that there were no cases in which an IDH1 mutation occurred after the acquisition of either a TP53 mutation or loss of 1p/19q, suggesting that IDH1 mutations are very early events in gliomagenesis and may affect a common glial precursor cell population. IDH1 mutations were co-present with TP53 mutations in 63% of low-grade diffuse astrocytomas and with loss of heterozygosity 1p/19q in 64% of oligodendrogliomas; they were rare in pilocytic astrocytomas (10%) and primary glioblastomas (5%) and absent in ependymomas. The frequent presence of IDH1 mutations in secondary glioblastomas and their near-complete absence in primary glioblastomas reinforce the concept that despite their histological similarities, these subtypes are genetically and clinically distinct entities.