1,495 research outputs found
Need, Greed and Noise: Competing Strategies in a Trading Model
We study an economic model where agents trade a variety of products by using
one of three competing rules: "need", "greed" and "noise". We find that the
optimal strategy for any agent depends on both product composition in the
overall market and composition of strategies in the market. In particular, a
strategy that does best on pairwise competition may easily do much worse when
all are present, leading, in some cases, to a "paper, stone, scissors" circular
hierarchy.Comment: 10 pages, 6 figure
Physics of Fashion Fluctuations
We consider a market where many agents trade many different types of products
with each other. We model development of collective modes in this market, and
quantify these by fluctuations that scale with time with a Hurst exponent of
about 0.7. We demonstrate that individual products in the model occationally
become globally accepted means of exchange, and simultaneously become very
actively traded. Thus collective features similar to money spontaneously
emerge, without any a priori reason.Comment: 9 pages RevTeX, 5 Postscript figure
Scaling in Fracture and Refreezing of Sea Ice
Sea ice breaks up and regenerates rapidly during winter conditions in the
Arctic. Analyzing satellite data from the Kara Sea, we find that the average
ice floe size depends on weather conditions. Nevertheless, the frequency of
floes of size is a power law, , where ,
for less than approximately 100 . This scale-invariant behaviour
suggests a competition between fracture due to strains in the ice field and
refreezing of the fractures. A cellular model for this process gives results
consistent with observations.Comment: Physica A (in press
Correlation of mixed lymphocyte culture with chronic graft-versus-host disease following allogeneic stem cell transplantation
The purpose of the present study was to evaluate the mixed lymphocyte culture as a predictive assay of acute and chronic graft-versus-host disease (GVHD). We studied 153 patients who received a first bone marrow transplantation from human leukocyte antigen-identical siblings. Acute GVHD was observed in 26 of 128 (20.3%) patients evaluated and chronic GVHD occurred in 60 of 114 (52.6%). One-way mixed lymphocyte culture (MLC) assays were performed by the standard method. MLC results are reported as the relative response (RR) from donor against patient cells. The responses ranged from -47.0 to 40.7%, with a median of 0.5%. The Kaplan-Meier probability of developing GVHD was determined for patients with positive and negative MLC. There was no significant difference in incidence of acute GVHD between the groups studied. However, the incidence of chronic GVHD was higher in recipients with RR >4.5% than in those with RR 4.5%), 2.9 for those who received peripheral blood progenitor cells as a graft, and 2.2 for patients who developed previous acute GVHD. MLC was not useful for predicting acute GVHD, but MLC with RR >4.5% associated with other risk factors could predict the development of chronic GVHD, being of help for the prevention and/or treatment of this late complication.56757
Be Stars: Rapidly Rotating Pulsators
I will show that Be stars are, without exception, a class of rapidly rotating
stars, which are in the majority of cases pulsating stars as well, while none
of them does possess a large scale (i.e. with significant dipolar contribution)
magnetic field.Comment: Review talk given at "XX Stellar Pulsation Conference Series: Impact
of new instrumentation and new insights in stellar pulsations", Granada, 5-9
September 2011, in press in AIP Conf. Se
Mass Parameterizations and Predictions of Isotopic Observables
We discuss the accuracy of mass models for extrapolating to very asymmetric
nuclei and the impact of such extrapolations on the predictions of isotopic
observables in multifragmentation. We obtain improved mass predictions by
incorporating measured masses and extrapolating to unmeasured masses with a
mass formula that includes surface symmetry and Coulomb terms. We find that
using accurate masses has a significant impact on the predicted isotopic
observables.Comment: 12 pages, 4 figure
Strumigenys fairchildi brown, 1961 (Formicidae, myrmicinae): First record of this rarely collected ant from Brazil
Strumigenys fairchildi Brown, 1961 is recorded for the first time in Brazil. This ant species was previously known only from a few specimens collected in Costa Rica, Panama and Ecuador. The worker S. fairchildi was collected at the Parque Estadual do Cristalino, a continuous area of Amazon tropical rain forest protected for biodiversity conservation in the municipality of Novo Mundo, Mato Grosso state. In addition, we present a distribution map and high-resolution images of the worker. © 2016 Check List and Authors
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