577,132 research outputs found
Word Up! Directed motor action improves word learning [Abstract]
Can simple motor actions help people expand their vocabulary? Here we show that word learning depends on where students place their flash cards after studying them. In Experiment 1, participants learned the definitions of âalien wordsâ with positive or negative emotional valence. After studying each card, they placed it in one of two boxes (top or bottom), according to its valence. Participants who were instructed to place positive cards in the top box, consistent with Good is Up metaphors, scored about 10
Photosynthesis and calcification in the calcifying algae Halimeda discoidea studied with microsensors
With microsensors, we measured the steadyâstate microprofiles of O2, pH and Ca2+ on the topside of young segments of Halimeda discoidea, as well as the surface dynamics upon lightâdark shifts. The effect of several inhibitors was studied. The steadyâstate measurements showed that under high light intensity, calcium and protons were taken up, while O2 was produced. In the dark, O2 was consumed, the pH decreased to below seawater level and Ca2+ uptake was reduced to 50%. At low light intensity (12âmmolâphotonsâmâ2âsâ1), Ca2+ efflux was observed. Upon lightâdark shifts, a complicated pattern of both the pH and calcium surface dynamics was observed. Illumination caused an initial pH decrease, followed by a gradual pH increase: this indicated that the surface pH of H. discoidea is determined by more than one lightâinduced process. When photosynthesis was inhibited by dichlorophenyl dimethyl urea (DCMU), a strong acidification was observed upon illumination. The nature and physiological function of this putative pump is not known. The calcium dynamics followed all pH dynamics closely, both in the presence and absence of DCMU. The Caâchannel blockers verapamil and nifedipine had no effect on the Ca2+ dynamics and steadyâstate profiles. Thus, in H. discoidea, calcification is not regulated by the alga, but is a consequence of pH increase during photosynthesis. Acetazolamide had no effect on photosynthesis, whereas ethoxyzolamide inhibited photosynthesis at higher light intensities. Therefore, all carbonic anhydrase activity is intracellular. Carbonic anhydrase is required to alleviate the CO2 limitation. Calcification cannot supply sufficient protons and CO2 to sustain photosynthesis
Adaptive drivers in a model of urban traffic
We introduce a simple lattice model of traffic flow in a city where drivers
optimize their route-selection in time in order to avoid traffic jams, and
study its phase structure as a function of the density of vehicles and of the
drivers' behavioral parameters via numerical simulations and mean-field
analytical arguments. We identify a phase transition between a low- and a
high-density regime. In the latter, inductive drivers may surprisingly behave
worse than randomly selecting drivers.Comment: 7 pages, final versio
Quantum critical behaviour of the plateau-insulator transition in the quantum Hall regime
High-field magnetotransport experiments provide an excellent tool to
investigate the plateau-insulator phase transition in the integral quantum Hall
effect. Here we review recent low-temperature high-field magnetotransport
studies carried out on several InGaAs/InP heterostructures and an InGaAs/GaAs
quantum well. We find that the longitudinal resistivity near the
critical filling factor ~ 0.5 follows the universal scaling law
, where . The critical exponent equals ,
which indicates that the plateau-insulator transition falls in a non-Fermi
liquid universality class.Comment: 8 pages, accepted for publication in Proceedings of the Yamada
Conference LX on Research in High Magnetic Fields (August 16-19, 2006,
Sendai
On the strategy frequency problem in batch Minority Games
Ergodic stationary states of Minority Games with S strategies per agent can
be characterised in terms of the asymptotic probabilities with which
an agent uses of his strategies. We propose here a simple and general
method to calculate these quantities in batch canonical and grand-canonical
models. Known analytic theories are easily recovered as limiting cases and, as
a further application, the strategy frequency problem for the batch
grand-canonical Minority Game with S=2 is solved. The generalization of these
ideas to multi-asset models is also presented. Though similarly based on
response function techniques, our approach is alternative to the one recently
employed by Shayeghi and Coolen for canonical batch Minority Games with
arbitrary number of strategies.Comment: 17 page
MHD Simulations of the ISM: The Importance of the Galactic Magnetic Field on the ISM "Phases"
We have carried out 1.25 pc resolution MHD simulations of the ISM, on a
Cartesian grid of kpc size in the galactic plane and kpc into the halo, thus being able to fully trace the
time-dependent evolution of the galactic fountain. The simulations show that
large scale gas streams emerge, driven by SN explosions, which are responsible
for the formation and destruction of shocked compressed layers. The shocked gas
can have densities as high as 800 cm and lifetimes up to 15 Myr. The
cold gas is distributed into filaments which tend to show a preferred
orientation due to the anisotropy of the flow induced by the galactic magnetic
field. Ram pressure dominates the flow in the unstable branch T K, while for T K (stable branch) magnetic pressure takes
over. Near supernovae thermal and ram pressures determine the dynamics of the
flow. Up to 80% of the mass in the disk is concentrated in the thermally
unstable regime T K with of the disk mass
enclosed in the T K gas. The hot gas in contrast is controlled by
the thermal pressure, since magnetic field lines are swept towards the dense
compressed walls.Comment: 8 pages, 8 figures (in jpeg format) that include 2 simulations images
and 6 plots. Paper accepted by the referee for publication in the proceedings
of ``Magnetic fields and star formation: theory versus observations'', kluwe
- âŠ