1,921 research outputs found
Public perceptions of potential adaptations for mitigating heat stress on Australian dairy farms
Selfishness, fraternity, and other-regarding preference in spatial evolutionary games
Spatial evolutionary games are studied with myopic players whose payoff
interest, as a personal character, is tuned from selfishness to other-regarding
preference via fraternity. The players are located on a square lattice and
collect income from symmetric two-person two-strategy (called cooperation and
defection) games with their nearest neighbors. During the elementary steps of
evolution a randomly chosen player modifies her strategy in order to maximize
stochastically her utility function composed from her own and the co-players'
income with weight factors and Q. These models are studied within a wide
range of payoff parameters using Monte Carlo simulations for noisy strategy
updates and by spatial stability analysis in the low noise limit. For fraternal
players () the system evolves into ordered arrangements of strategies in
the low noise limit in a way providing optimum payoff for the whole society.
Dominance of defectors, representing the "tragedy of the commons", is found
within the regions of prisoner's dilemma and stag hunt game for selfish players
(Q=0). Due to the symmetry in the effective utility function the system
exhibits similar behavior even for Q=1 that can be interpreted as the "lovers'
dilemma".Comment: 7 two-column pages, 8 figures; accepted for publication in J. Theor.
Bio
Quantum rings for beginners: Energy spectra and persistent currents
Theoretical approaches to one-dimensional and quasi-one-dimensional quantum
rings with a few electrons are reviewed. Discrete Hubbard-type models and
continuum models are shown to give similar results governed by the special
features of the one-dimensionality. The energy spectrum of the many-body states
can be described by a rotation-vibration spectrum of a 'Wigner molecule' of
'localized' electrons, combined with the spin-state determined from an
effective antiferromagnetic Heisenberg Hamiltonian. The persistent current as a
function of the magnetic flux through the ring shows periodic oscillations
arising from the 'rigid rotation' of the electron ring. For polarized electrons
the periodicity of the oscillations is always the flux quantum Phi_0. For
nonpolarized electrons the periodicity depends on the strength of the effective
Heisenberg coupling and changes from Phi_0 first to Phi_0/2 and eventually to
Phi_0/N when the ring gets narrower.Comment: 27 pages, 22 figure
Recent developments in German corporate governance.
This paper provides an overview of the German corporate governance system. We review the governance role of large shareholders, creditors, the product market and the supervisory board. We also discuss the importance of mergers and acquisitions, the market in block trades, and the lack of a hostile takeover market. Given that Germany is often referred to as a bank-based economy, we pay particular attention to the role of the universal banks (Hausbanken). We show that the German system is characterised by a market for partial corporate control, large shareholders and bank/creditor monitoring, a two-tier (management and supervisory) board with co-determination between shareholders and employees on the supervisory board, a disciplinary product-market, and corporate governance regulation largely based on EU directives but with deep roots in the German codes and legal doctrine. Another important feature of the German system is its corporate governance efficiency criterion which is focused on the maximisation of stakeholder value rather than shareholder value. However, the German corporate governance system has experienced many important changes over the last decade. First, the relationship between ownership or control concentration and profitability has changed over time. Second, the pay-for-performance relation is influenced by large shareholder control: in firms with controlling blockholders and when a universal bank is simultaneously an equity- and debtholder, the pay-for-performance relation is lower than in widely-held firms or blockholder-controlled firms. Third, since 1995 several major regulatory initiatives (including voluntary codes) have increased transparency and accountability
90 GHz Continuum Observations of Messier 66
Radio emission at around 90 GHz from star-forming galaxies is expected to be
strongly dominated by the free-free component due to ionising radiation from
massive, short-lived, stars. We present high surface-brightness sensitivity
observations at 90 GHz of the nearby star-forming galaxy Messier 66 with
resolution of about 9 arcsec (corresponding to a physical scale of about 500
pc) and analyse these observations in combination with archival lower frequency
radio and mid-infrared measurements. For the four regions for which the
observations support our models we find that the free-free component indeed
dominates the emission at 90 GHz, making up 76--90 per cent of the luminosity
at this frequency but with the data also consistent with all of the emission
being due to free-free. The estimates of free-free luminosities are also
consistent, within measurement and decomposition errors, with star-formation
rates derived from lower radio frequencies and mid-infrared observations. In
our analysis we consider both power-law and curved spectra for the synchrotron
component but do not find evidence to support the curved model in preference to
the power-law.Comment: 7 pages, 5 figures. Submitted to MNRAS. Further information, plots,
links to software are available at
http://www.mrao.cam.ac.uk/~bn204/galevol/2012-90ghz-m66.htm
Electron-hole bilayer quantum dots: Phase diagram and exciton localization
We studied a vertical ``quantum dot molecule'', where one of the dots is
occupied with electrons and the other with holes. We find that different phases
occur in the ground state, depending on the carrier density and the interdot
distance. When the system is dominated by shell structure, orbital degeneracies
can be removed either by Hund's rule, or by Jahn-Teller deformation. Both
mechanisms can lead to a maximum of the addition energy at mid-shell. At low
densities and large interdot distances, bound electron-hole pairs are formed.Comment: 10 pages, 3 figure
The slope of the mass profile and the tilt of the fundamental plane in early-type galaxies
We present a survey, using the Chandra X-ray observatory, of the central
gravitating mass profiles in a sample of 10 galaxies, groups and clusters,
spanning ~2 orders of magnitude in virial mass. We find the total mass
distributions from ~0.2--10Re, where Re is the optical effective radius of the
central galaxy, are remarkably similar to powerlaw density profiles. The
negative logarithmic slope of the mass density profiles, alpha, systematically
varies with Re, from alpha=2, for systems with Re~4kpc to alpha=1.2 for systems
with Re>30kpc. Departures from hydrostatic equilibrium are likely to be small
and cannot easily explain this trend. We show that the conspiracy between the
baryonic (Sersic) and dark matter (NFW/ Einasto) components required to
maintain a powerlaw total mass distribution naturally predicts an
anti-correlation between alpha and Re that is very close to what is observed.
The systematic variation of alpha with Re implies a dark matter fraction within
Re that varies systematically with the properties of the galaxy in such a
manner as to reproduce, without fine tuning, the observed tilt of the
fundamental plane. We speculate that establishing a nearly powerlaw total mass
distribution is therefore a fundamental feature of galaxy formation and the
primary factor which determines the tilt of the fundamental plane.Comment: 10 pages, 5 figures, 2 tables. Accepted for publication in MNRAS.
Minor revisions to match accepted versio
AfrOBIS: a marine biogeographic information system for sub-Saharan Africa
AfrOBIS is one of 11 global nodes of the Ocean Biogeographic Information System (OBIS), a freely accessible network of databases collating marine data in support of the Census of Marine Life. Versatile graphic products, provided by OBIS, can be used to display the data. To date, AfrOBIS has loaded about3.2 million records of more than 23 000 species located mainly in the seas around southern Africa. This forms part of the 13.2 million records of more than 80 000 species currently stored in OBIS. Scouting for South African data has been successful, whereas locating records in other African countries has been much less so
Residents' support for tourism development: The role of residents' place image and perceived tourism impacts
Drawing on the triple bottom line approach for tourism impacts (economic, socio-cultural and environmental) and adopting a non-forced approach for measuring residents' perception of these impacts, this study explores the role of residents' place image in shaping their support for tourism development. The tested model proposes that residents' place image affects their perceptions of tourism impacts and in turn their support for tourism development. The results stress the need for a more flexible and resident oriented measurement of tourism impacts, revealing that more favorable perceptions of the economic, socio-cultural and environmental impacts lead to greater support. Moreover, while residents' place image has been largely neglected by tourism development studies, the findings of this study reveal its significance in shaping residents' perception of tourism impacts as well as their level of support. The practical implications of the findings for tourism planning and development are also discussed
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