11,917 research outputs found
Mechanisms of wave transformation in finite-depth water
Mechanisms of wave transformation in finite-depth water are investigated. The linear mechanisms ex- amined are percolation, bottom motion, shoaling, and refraction. The nonlinear mechanisms examined are wave-wave interaction and bottom friction. New exact computations of the nonlinear transfer for fi- nite-depth waves are presented for some directional wave spectra. These mechanisms are found to ex- plain satisfactorily wave decay observations obtained at several sites with different bottom sediment properties. The decay rates at these sites are found to be dominated by different mechanisms which are determined by the bottom conditions. As an example, detailed calculations are presented for data ob- tained at the Jonswap site
Correlations of center flux in SU(2) Yang-Mills theory
By using the method of center projection the center vortex part of the gauge
field is isolated and its propagator is evaluated in the center Landau gauge,
which minimizes the open 3-dimensional Dirac volumes of non-trivial center
links bounded by the closed 2-dimensional center vortex surfaces. The center
field propagator is found to dominate the gluon propagator (in Landau gauge) in
the low momentum regime and to give rise to an OPE correction to the latter of
.The screening mass of the center vortex field vanishes
above the critical temperature of the deconfinement phase transition, which
naturally explains the second order nature of this transition consistently with
the vortex picture. Finally, the ghost propagator of maximal center gauge is
found to be infrared finite and thus shows no signal of confinement.Comment: Presented at 23rd International Symposium on Lattice Field Field:
Lattice 2005, Trinity College, Dublin, Ireland, 25-30 Jul 200
Ionization by bulk heating of electrons in capacitive radio frequency atmospheric pressure microplasmas
Electron heating and ionization dynamics in capacitively coupled radio
frequency (RF) atmospheric pressure microplasmas operated in helium are
investigated by Particle in Cell simulations and semi-analytical modeling. A
strong heating of electrons and ionization in the plasma bulk due to high bulk
electric fields are observed at distinct times within the RF period. Based on
the model the electric field is identified to be a drift field caused by a low
electrical conductivity due to the high electron-neutral collision frequency at
atmospheric pressure. Thus, the ionization is mainly caused by ohmic heating in
this "Omega-mode". The phase of strongest bulk electric field and ionization is
affected by the driving voltage amplitude. At high amplitudes, the plasma
density is high, so that the sheath impedance is comparable to the bulk
resistance. Thus, voltage and current are about 45{\deg} out of phase and
maximum ionization is observed during sheath expansion with local maxima at the
sheath edges. At low driving voltages, the plasma density is low and the
discharge becomes more resistive resulting in a smaller phase shift of about
4{\deg}. Thus, maximum ionization occurs later within the RF period with a
maximum in the discharge center. Significant analogies to electronegative low
pressure macroscopic discharges operated in the Drift-Ambipolar mode are found,
where similar mechanisms induced by a high electronegativity instead of a high
collision frequency have been identified
Synthesis of Plastoquinone-9, α-Tocopherol and Phylloquinone (Vitamine K1) and its integration in chloroplast carbon metabolism of higher plants
Habitat width along a latitudinal gradient
We use the Chowdhury ecosystem model, one of the most complex agent-based
ecological models, to test the latitude-niche breadth hypothesis, with regard
to habitat width, i.e., whether tropical species generally have narrower
habitats than high latitude ones. Application of the model has given realistic
results in previous studies on latitudinal gradients in species diversity and
Rapoport's rule. Here we show that tropical species with sufficient vagility
and time to spread into adjacent habitats, tend to have wider habitats than
high latitude ones, contradicting the latitude-niche breadth hypothesis.Comment: 13 pages including all figures, draft for a biology journa
Introduction to the special issue: multiple jobholding in Europe
In a number of European countries there is a clear trend towards increased multiple jobholding. As things stand, however, little is known about the structure and the potential consequences of this increase, notably in terms of quality of work and social protection. This special issue focuses on contemporary forms of multiple jobholding in Europe. Have the structure, nature and dynamics of multiple jobholding changed over time? What are the roles of labour market flexibility, technological change and work fragmentation in the development of multiple jobholding? And do multiple jobholders benefit from similar and adequate employment terms, conditions and protections compared with single jobholders, or are they worse off as a consequence of their (fragmented) employment situation? What implications do these findings have for unions, policy-makers and the regulation of work? The collection of articles in this special issue adds to the literature on emerging forms of employment in the digital age and challenges for social protection, also in light of the COVID-19 pandemic. This introduction initiates a discussion of central debates on multiple jobholding and presents a synopsis of the articles in this issue
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