5,363 research outputs found
Lung function decline in 4-monthly repeated spirometric measurements: Due to silt aerosol exposure or decreasing effort?
Background: Workers on dredgers and lighters on rivers are exposed to the inhalation of aerosols and dusts. Objective: The aim of this study was to investigate effects of river silt aerosol and dust exposure on the respiratory health of dredging employees. Methods: Six era mi nations were performed over a period of 2 years at 4-monthly intervals in 54 seamen with higher silt aerosol exposure and 36 controls of the same employer. Results: No significant differences could be observed between the groups at any time of the study but there was an unexpected significant decrease in the age-corrected expiratory vital capacity (FVC), forced expiratory volume in 1 s (FEV1) and midexpiratory flow rate (MMEF25/75) over the six series in both groups. This may indicate a loss of effort of the participants in re-examinations since biological and technical influences were highly unlikely to be the cause of these findings. Conclusions: Ignoring this possible decline of effort in frequently repeated measurements may result in overestimating potential effects of occupational exposure. Copyright (C) 2000 S. Karger AG, Basel
Effects of impurities on Tamm-like lanthanide-metal surface states
The effects of isolated residual-gas adsorbates on the local electronic
structure of the Dy(0001) surface were spatially mapped by scanning tunneling
microscopy and spectroscopy at 12 K. Less than 15 A away from an adsorbate, a
strong reduction of the intensity and a significant increase of the width of
the majority component of the surface state due to impurity scattering were
observed, with essentially no change of the minority component; this reflects a
high lateral localization of the Tamm-like surface state. Furthermore, an
adsorbate-induced state was found that behaves metastable.Comment: 5 pages, 4 figures, accepted as Brief Report for Physical Review
Optimization of perturbative similarity renormalization group for Hamiltonians with asymptotic freedom and bound states
A model Hamiltonian that exhibits asymptotic freedom and a bound state, is
used to show on example that similarity renormalization group procedure can be
tuned to improve convergence of perturbative derivation of effective
Hamiltonians, through adjustment of the generator of the similarity
transformation. The improvement is measured by comparing the eigenvalues of
perturbatively calculated renormalized Hamiltonians that couple only a
relatively small number of effective basis states, with the exact bound state
energy in the model. The improved perturbative calculus leads to a few-percent
accuracy in a systematic expansion.Comment: 6 pages of latex, 4 eps figure
The A-theoretic FarrellâJones conjecture for virtually solvable groups
We prove the A -theoretic FarrellâJones conjecture for virtually solvable groups. As a corollary, we obtain that the conjecture holds for S -arithmetic groups and lattices in almost connected Lie groups
Rigid unit modes in tetrahedral crystals
The 'rigid unit mode' (RUM) model requires unit blocks, in our case
tetrahedra of SiO_4 groups, to be rigid within first order of the displacements
of the O-ions. The wave-vectors of the lattice vibrations, which obey this
rigidity, are determined analytically. Lattices with inversion symmetry yield
generically surfaces of RUMs in reciprocal space, whereas lattices without this
symmetry yield generically lines of RUMs. Only in exceptional cases as in
beta-quartz a surface of RUMs appears, if inversion symmetry is lacking. The
occurence of planes and bending surfaces, straight and bent lines is discussed.
Explicit calculations are performed for five modifications of SiO_2 crystals.Comment: 18 pages, 6 figures, improved notatio
On moduli of vector bundles on p-adic curves and attached representations
In der vorliegenden Arbeit wird das von Deninger/Werner entwickelte p-adische Analogon der klassischen Narasimhan-Seshadri Theorie hinsichtlich der Formulierbarkeit in den Termen der Moduli von VektorbĂŒndeln und entsprechenden Darstellungen untersucht. Sei X eine glatte, projektive und zusammenhĂ€ngende Kurve ĂŒber QpBar. Einem VektorbĂŒndel E mit stark semistabiler Reduktion auf X_Cp ordnet das Ă©tale Paralleltransport unter anderem eine stetige endlich-dimensionale Darstellung der Ă©talen Fundamentalgruppe von X zu. Andererseits ist jedes VektorbĂŒndel mit stark semistabiler Reduktion ebenfalls semistabil, induziert also einen Cp-wertigen Punkt in dem Modulraum M_X, der semistabile VektorbĂŒndel von entsprechendem Rang und Grad parametrisiert. Es wird gezeigt, dass die Klasse der VektorbĂŒndel auf X_Cp (von festem Rang und Grad), die stark semistabile Reduktion ĂŒber ZpBar haben, im p-adischen Sinne eine offene Teilmenge in M_X(QpBar) induziert. Desweiteren beschreiben wir die obige Zuordnung der Darstellungen in den Termen der Moduli von VektorbĂŒndeln sowie zugeordneten Darstellungen. Wir zeigen, dass diese unter einer technischen Voraussetzung stetig ist
Equations of State for Nonlinear Sigma-Models II: Relations between Resummation Schemes, and Crossover Phenomena
It is shown how a recent method to systematically extrapolate and resum the
loop expansion for nonlinear sigma-models is related to solutions of the
renormalization group equation. This relation is used to generalize the
explicit equations of state obtained previously to models which display
crossover phenomena. As an example we discuss Wegner's localization model and
consider the crossover from symplectic to unitary symmetry.Comment: 14pp., REVTeX, 1 figur
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