5,399 research outputs found
DIE ROLLE DER INSTRUMENTALEN ANALYTIK IN DER TECHNOLOGISCHEN FORSCHUNG ZUR HERSTELLUNG VON Câ - Cââ AROMATEN DURCH KATALYTISCHES BENZIN-REFORMING
BILDUNG VON HĂHEREN ALKYLBENZOLEN BEI DER REFORMING VON BENZINFRAKTIONEN AN EINEM BIMETALLISCHEN KATALYSATOR
AMOC Recovery in a Multicentennial Scenario Using a Coupled AtmosphereâOceanâIce Sheet Model
We simulate the two Coupled Model Intercomparison Project scenarios RCP4.5 and RCP8.5, to assess the effects of meltâinduced fresh water on the Atlantic meridional overturning circulation (AMOC). We use a newly developed climate model with high resolution at the coasts, resolving the complex ocean dynamics. Our results show an AMOC recovery in simulations run with and without an included ice sheet model. We find that the ice sheet adds a strong decadal variability on the freshwater release, resulting in intervals in which it reduces the surface runoff by high accumulation rates. This compensating effect is missing in climate models without dynamic ice sheets. Therefore, we argue to assess those freshwater hosing experiments critically, which aim to parameterize Greenland's freshwater release. We assume the increasing net evaporation over the Atlantic and the resulting increase in ocean salinity, to be the main driver of the AMOC recovery
The Epsilon Calculus and Herbrand Complexity
Hilbert's epsilon-calculus is based on an extension of the language of
predicate logic by a term-forming operator . Two fundamental
results about the epsilon-calculus, the first and second epsilon theorem, play
a role similar to that which the cut-elimination theorem plays in sequent
calculus. In particular, Herbrand's Theorem is a consequence of the epsilon
theorems. The paper investigates the epsilon theorems and the complexity of the
elimination procedure underlying their proof, as well as the length of Herbrand
disjunctions of existential theorems obtained by this elimination procedure.Comment: 23 p
A general model to optimise CuII labelling efficiency of double-histidine motifs for pulse dipolar EPR applications
JLW is supported by the BBSRC DTP Eastbio. We thank the Leverhulme Trust for support (RPG-2018-397). This work was supported by equipment funding through the Wellcome Trust (099149/Z/12/Z) and BBSRC (BB/R013780/1). We gratefully acknowledge ISSF support to the University of St Andrews from the Wellcome Trust.Electron paramagnetic resonance (EPR) distance measurements are making increasingly important contributions to studies of biomolecules underpinning health and disease by providing highly accurate and precise geometric constraints. Combining double-histidine (dH) motifs with CuII spin labels shows promise for further increasing the precision of distance measurements, and for investigating subtle conformational changes. However, non-covalent coordination-based spin labelling is vulnerable to low binding affinity. Dissociation constants of dH motifs for CuII-nitrilotriacetic acid were previously investigated via relaxation induced dipolar modulation enhancement (RIDME), and demonstrated the feasibility of exploiting the double histidine motif for EPR applications at sub-ÎŒM protein concentrations. Herein, the feasibility of using modulation depth quantitation in CuII-CuII RIDME to simultaneously estimate a pair of non-identical independent KD values in such a tetra-histidine model protein is addressed. Furthermore, we develop a general speciation model to optimise CuII labelling efficiency, in dependence of pairs of identical or disparate KD values and total CuII label concentration. We find the dissociation constant estimates are in excellent agreement with previously determined values, and empirical modulation depths support the proposed model.Publisher PDFPeer reviewe
From AMANDA to IceCube
The first string of the neoteric high energy neutrino telescope IceCube
successfully began operating in January 2005. It is anticipated that upon
completion the new detector will vastly increase the sensitivity and extend the
reach of AMANDA to higher energies. A discussion of the IceCube's discovery
potential for extra-terrestrial neutrinos, together with the prospects of new
physics derived from the ongoing AMANDA research will be the focus of this
paper. Preliminary results of the first antarctic high energy neutrino
telescope AMANDA searching in the muon neutrino channel for localized and
diffuse excess of extra-terrestrial neutrinos will be reviewed using data
collected between 2000 and 2003. Neutrino flux limits obtained with the
all-flavor dedicated UHE and cascade analyses will be described. A first
neutrino spectrum above one TeV in agreement with atmospheric neutrino flux
expectations and no extra-terrestrial contribution will be presented, followed
by a discussion of a limit for neutralino CDM candidates annihilating in the
center of the Sun.Comment: 15 pages, 8 figures Invited talk contribution at 5th International
Conference on Non-accelerator New Physics (NANP 05), Dubna, Russia, 20-25 Jun
200
Study of the variability of Blazars gamma-ray emission
The gamma-ray emission of blazar jets shows a pronounced variability and this
feature provides limits to the size and to the speed of the emitting region. We
study the gamma-ray variability of bright blazars using data from the first 18
months of activity of the Large Area Telescope on the Fermi Gamma-Ray Space
Telescope. From the daily light-curves of the blazars characterized by a
remarkable activity, we firstly determine the minimum variability time-scale,
giving an upper limit for the size of the emitting region of the sources,
assumed to be spheroidal blobs in relativistic motion. These regions must be
smaller than ~10^-3 parsec. Another interesting time-scale is the duration of
the outbursts. We conclude that they cannot correspond to radiation produced by
a single blob moving relativistically along the jet, but they are either the
signature of emission from a standing shock extracting energy from a modulated
jet, or the superposition of a number of flares occurring on a shorter
time-scale. We also derive lower limits on the bulk Lorentz factor needed to
make the emitting region transparent for gamma-rays interacting through
photon-photon collisions.Comment: 11 pages, 7 figures, accepted for publication on Advances in Space
Research. Poster presented at COSPAR 2010 (Bremen), event E11 (Time
variability at high energies: a probe of AGN physics
- âŠ