307 research outputs found
Intermanifold similarities in partial photoionization cross sections of helium
Using the eigenchannel R-matrix method we calculate partial photoionization
cross sections from the ground state of the helium atom for incident photon
energies up to the N=9 manifold. The wide energy range covered by our
calculations permits a thorough investigation of general patterns in the cross
sections which were first discussed by Menzel and co-workers [Phys. Rev. A {\bf
54}, 2080 (1996)]. The existence of these patterns can easily be understood in
terms of propensity rules for autoionization. As the photon energy is increased
the regular patterns are locally interrupted by perturber states until they
fade out indicating the progressive break-down of the propensity rules and the
underlying approximate quantum numbers. We demonstrate that the destructive
influence of isolated perturbers can be compensated with an energy-dependent
quantum defect.Comment: 10 pages, 10 figures, replacement with some typos correcte
Mirror Position Determination for the Alignment of Cherenkov Telescopes
Imaging Atmospheric Cherenkov Telescopes (IACTs) need imaging optics with
large apertures to map the faint Cherenkov light emitted in extensive air
showers onto their image sensors. Segmented reflectors fulfill these needs
using mass produced and light weight mirror facets. However, as the overall
image is the sum of the individual mirror facet images, alignment is important.
Here we present a method to determine the mirror facet positions on a segmented
reflector in a very direct way. Our method reconstructs the mirror facet
positions from photographs and a laser distance meter measurement which goes
from the center of the image sensor plane to the center of each mirror facet.
We use our method to both align the mirror facet positions and to feed the
measured positions into our IACT simulation. We demonstrate our implementation
on the 4 m First Geiger-mode Avalanche Cherenkov Telescope (FACT).Comment: 11 figures, small ray tracing performance simulation, and
implementation demonstratio
FACT -- the First Cherenkov Telescope using a G-APD Camera for TeV Gamma-ray Astronomy (HEAD 2010)
Geiger-mode Avalanche Photodiodes (G-APD) bear the potential to significantly
improve the sensitivity of Imaging Air Cherenkov Telescopes (IACT). We are
currently building the First G-APD Cherenkov Telescope (FACT) by refurbishing
an old IACT with a mirror area of 9.5 square meters and construct a new, fine
pixelized camera using novel G-APDs. The main goal is to evaluate the
performance of a complete system by observing very high energy gamma-rays from
the Crab Nebula. This is an important field test to check the feasibility of
G-APD-based cameras to replace at some time the PMT-based cameras of planned
future IACTs like AGIS and CTA. In this article, we present the basic design of
such a camera as well as some important details to be taken into account.Comment: Poster shown at HEAD 2010, Big Island, Hawaii, March 1-4, 201
Quantifying understorey vegetation in the US Lake States: a proposed framework to inform regional forest carbon stocks
The contribution of understorey vegetation (UVEG) to forest ecosystem biomass and carbon (C) across diverse forest types has, to date, eluded quantification at regional and national scales. Efforts to quantify UVEG C have been limited to field-intensive studies or broad-scale modelling approaches lacking field measurements. Although large-scale inventories of UVEG C are not common, species-and community-level inventories of vegetation structure are available and may prove useful in quantifying UVEG C stocks. This analysis developed a general framework for estimating UVEG C stocks by employing per cent cover estimates of UVEG from a region-wide forest inventory coupled with an estimate of maximum UVEG C across the US Lake States (i.e. Michigan, Minnesota and Wisconsin). Estimates of UVEG C stocks from this approach reasonably align with expected C stocks in the study region, ranging from 0.86+0.06 Mg ha 21 in red pine-dominated to 1.59+0.06 Mg ha 21 for aspen/birch-dominated forest types. Although the data employed here were originally collected to assess broad-scale forest structure and diversity, this study proposes a framework for using UVEG inventories as a foundation for estimating C stocks in an often overlooked, yet important ecosystem C pool
The Kondo Resonance in Electron Spectroscopy
The Kondo resonance is the spectral manifestation of the Kondo properties of
the impurity Anderson model, and also plays a central role in the dynamical
mean-field theory (DMFT) for correlated electron lattice systems. This article
presents an overview of electron spectroscopy studies of the resonance for the
4f electrons of cerium compounds, and for the 3d electrons of V_2O_3, including
beginning efforts at using angle resolved photoemission to determine the
k-dependence of the resonance. The overview includes the comparison and
analysis of spectroscopy data with theoretical spectra as calculated for the
impurity model and as obtained by DMFT, and the Kondo volume collapse
calculation of the cerium alpha-gamma phase transition boundary, with its
spectroscopic underpinnings.Comment: 32 pages, 11 figures, 151 references; paper for special issue of J.
Phys. Soc. Jpn. on "Kondo Effect--40 Years after the Discovery
Onset of magnetism in B2 transition metals aluminides
Ab initio calculation results for the electronic structure of disordered bcc
Fe(x)Al(1-x) (0.4<x<0.75), Co(x)Al(1-x) and Ni(x)Al(1-x) (x=0.4; 0.5; 0.6)
alloys near the 1:1 stoichiometry, as well as of the ordered B2 (FeAl, CoAl,
NiAl) phases with point defects are presented. The calculations were performed
using the coherent potential approximation within the Korringa-Kohn-Rostoker
method (KKR-CPA) for the disordered case and the tight-binding linear
muffin-tin orbital (TB-LMTO) method for the intermetallic compounds. We studied
in particular the onset of magnetism in Fe-Al and Co-Al systems as a function
of the defect structure. We found the appearance of large local magnetic
moments associated with the transition metal (TM) antisite defect in FeAl and
CoAl compounds, in agreement with the experimental findings. Moreover, we found
that any vacancies on both sublattices enhance the magnetic moments via
reducing the charge transfer to a TM atom. Disordered Fe-Al alloys are
ferromagnetically ordered for the whole range of composition studied, whereas
Co-Al becomes magnetic only for Co concentration >0.5.Comment: 11 pages with 9 embedded postscript figures, to be published in
Phys.Rev.
Electronic and structural properties of vacancies on and below the GaP(110) surface
We have performed total-energy density-functional calculations using
first-principles pseudopotentials to determine the atomic and electronic
structure of neutral surface and subsurface vacancies at the GaP(110) surface.
The cation as well as the anion surface vacancy show a pronounced inward
relaxation of the three nearest neighbor atoms towards the vacancy while the
surface point-group symmetry is maintained. For both types of vacancies we find
a singly occupied level at mid gap. Subsurface vacancies below the second layer
display essentially the same properties as bulk defects. Our results for
vacancies in the second layer show features not observed for either surface or
bulk vacancies: Large relaxations occur and both defects are unstable against
the formation of antisite vacancy complexes. Simulating scanning tunneling
microscope pictures of the different vacancies we find excellent agreement with
experimental data for the surface vacancies and predict the signatures of
subsurface vacancies.Comment: 10 pages, 6 figures, Submitted to Phys. Rev. B, Other related
publications can be found at http://www.rz-berlin.mpg.de/th/paper.htm
Simultaneous measurements of electronic conduction and Raman response in molecular junctions
Electronic conduction through single molecules is affected by the molecular
electronic structure as well as by other information that is extremely
difficult to assess, such as bonding geometry and chemical environment. The
lack of an independent diagnostic technique has long hampered single-molecule
conductance studies. We report simultaneous measurement of the conductance and
the Raman spectra of nanoscale junctions used for single-molecule electronic
experiments. Blinking and spectral diffusion in the Raman response of both
para-mercaptoaniline and a fluorinated oligophenylyne ethynylene correlate in
time with changes in the electronic conductance. Finite difference time domain
calculations confirm that these correlations do not result from the conductance
modifying the Raman enhancement. Therefore, these observations strongly imply
that multimodal sensing of individual molecules is possible in these
mass-producible nanostructures.Comment: 16 pages, 5 figures + supporting material of 15 pages, 10 figure
AFM study of morphology and mechanical properties of a chimeric 2 spider silk and bone sialoprotein protein for bone regeneration
Atomic force microscopy (AFM) was used to assess a
new chimeric protein consisting of a fusion protein of the consensus
repeat for Nephila clavipes spider dragline protein and bone sialoprotein
(6merĂŸBSP). The elastic modulus of this protein in film
form was assessed through force curves, and film surface roughness
was also determined. The results showed a significant difference
among the elastic modulus of the chimeric silk protein, 6merĂŸBSP,
and control films consisting of only the silk component (6mer). The
behavior of the 6merĂŸBSP and 6mer proteins in aqueous solution in
the presence of calcium (Ca) ions was also assessed to determine
interactions between the inorganic and organic components related
to bone interactions, anchoring, and biomaterial network formation.
The results demonstrated the formation of protein networks in the
presence of Ca2ĂŸ ions, characteristics that may be important in the
context of controlling materials assembly and properties related to
bone formation with this new chimeric silk-BSP protein.Silvia Games thanks the Foundation for Science and Technology (FCT) for supporting her Ph.D. grant, SFRH/BD/28603/2006. This work was carried out under the scope of the European NoE EXPERTISSUES (NMP3-CT-2004-500283), the Chimera project (PTDC/EBB-EBI/109093/2008) funded by the FCT agency, the NIH (P41 EB002520) Tissue Engineering Resource Center, and the NIH (EB003210 and DE017207)
Effectiveness and safety of opicapone in Parkinson's disease patients with motor fluctuations: The OPTIPARK open-label study
BACKGROUND: The efficacy and safety of opicapone, a once-daily catechol-O-methyltransferase inhibitor, have been established in two large randomized, placebo-controlled, multinational pivotal trials. Still, clinical evidence from routine practice is needed to complement the data from the pivotal trials. METHODS: OPTIPARK (NCT02847442) was a prospective, open-label, single-arm trial conducted in Germany and the UK under clinical practice conditions. Patients with Parkinsonâs disease and motor fluctuations were treated with opicapone 50âmg for 3 (Germany) or 6 (UK) months in addition to their current levodopa and other antiparkinsonian treatments. The primary endpoint was the Clinicianâs Global Impression of Change (CGI-C) after 3âmonths. Secondary assessments included Patient Global Impressions of Change (PGI-C), the Unified Parkinsonâs Disease Rating Scale (UPDRS), Parkinsonâs Disease Questionnaire (PDQ-8), and the Non-Motor Symptoms Scale (NMSS). Safety assessments included evaluation of treatment-emergent adverse events (TEAEs) and serious adverse events (SAEs). RESULTS: Of the 506 patients enrolled, 495 (97.8%) took at least one dose of opicapone. Of these, 393 (79.4%) patients completed 3âmonths of treatment. Overall, 71.3 and 76.9% of patients experienced any improvement on CGI-C and PGI-C after 3âmonths, respectively (full analysis set). At 6âmonths, for UK subgroup only (nâ=â95), 85.3% of patients were judged by investigators as improved since commencing treatment. UPDRS scores at 3âmonths showed statistically significant improvements in activities of daily living during OFF (meanâ±âSD change from baseline: ââ3.0â±â4.6, pâ<â0.0001) and motor scores during ON (ââ4.6â±â8.1, pâ<â0.0001). The meanâ±âSD improvements of ââ3.4â±â12.8 points for PDQ-8 and -6.8â±â19.7 points for NMSS were statistically significant versus baseline (both pâ<â0.0001). Most of TEAEs (94.8% of events) were of mild or moderate intensity. TEAEs considered to be at least possibly related to opicapone were reported for 45.1% of patients, with dyskinesia (11.5%) and dry mouth (6.5%) being the most frequently reported. Serious TEAEs considered at least possibly related to opicapone were reported for 1.4% of patients. CONCLUSIONS: Opicapone 50âmg was effective and generally well-tolerated in PD patients with motor fluctuations treated in clinical practice. TRIAL REGISTRATION: Registered in July 2016 at clinicaltrials.gov (NCT02847442)
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