1,670 research outputs found
Reciprocity - an indirect evolutionary analysis
This paper investigates strategic interaction between rational agents whose preferences evolve over time. Players face a pecuniary �game of life� comprising the ultimatum game and the dictator game. Utility may but need not be attached to the reciprocation of fair and unfair play by the opponent and equitable payoff distributions as proposed by Falk and Fischbacher (2001). Evolutionary fitness is determined solely by material success � regardless of the motives for its achievement. Agents cannot explicitly condition the social component of their preferences on whether they face the ultimatum or dictator game. Under these conditions, agents develop a strong preference for reciprocation but little interest in an equitable distribution as such. This corresponds to equitable ultimatum offers but full surplus appropriation by dictators. Adding an exogenous constraint on the possible divergence between preference for reciprocation and for an equitable distribution either makes ultimatum divisions asymmetric or dictators become generous depending on the relative frequency of ultimatum and dictator interaction.
Effects of virus infection on release of volatile organic compounds from insect-damaged bean, Phaseolus vulgaris
Insects can serve as important vectors of plant pathogens, especially viruses. Insect feeding on plants causes the systemic release of a wide range of plant volatile compounds that can serve as an indirect plant defense by attracting natural enemies of the herbivorous insect. Previous work suggests that the Mexican bean beetle (Epilachna varivestis) prefers to feed on plants infected by either of two viruses that it is known to transmit: Southern bean mosaic virus (SBMV) or Bean pod mottle virus (BPMV). A possible explanation for the preferred feeding on virus-infected tissues is that the beetles are attracted by volatile signals released from leaves. The purpose of this work was to determine whether volatile compounds from virus-infected plants are released differentially from those emitted by uninfected plants. To test the hypothesis, common bean plants (Phaseolus vulgaris cv. Black Valentine) were inoculated with either BPMV, SBMV, or a mixture of both viruses, and infected plants were compared to uninfected plants. An Ouchterlony assay was used with SBMVand BPMV-specific antisera to confirm the presence of virus in inoculated plants. RNA blot analysis was performed on tissue from each plant and indicated that a well-characterized defense gene, encoding phenylalanine ammonia-lyase (PAL), was not induced in systemic tissue following virus infection. Plant volatiles were collectedâand analyzed via gas chromatography (GC)âfrom plants that were either undamaged or beetle-damaged. In undamaged plants, there were no measurable differences in profiles or quantities of compounds released by uninfected and virus-infected plants. After Mexican bean beetles were allowed to feed on plants for 48 h, injured plants released several compounds that were not released from undamaged plants. Lower quantities of volatile compounds were released from virus-infected plants suggesting that enhanced release of plant-derived volatile organic compounds is not the cause for attraction of Mexican bean beetles to virus-infected plants
The initial temporal evolution of a feedback dynamo for Mercury
Various possibilities are currently under discussion to explain the observed
weakness of the intrinsic magnetic field of planet Mercury. One of the possible
dynamo scenarios is a dynamo with feedback from the magnetosphere. Due to its
weak magnetic field Mercury exhibits a small magnetosphere whose subsolar
magnetopause distance is only about 1.7 Hermean radii. We consider the magnetic
field due to magnetopause currents in the dynamo region. Since the external
field of magnetospheric origin is antiparallel to the dipole component of the
dynamo field, a negative feedback results. For an alpha-omega-dynamo two
stationary solutions of such a feedback dynamo emerge, one with a weak and the
other with a strong magnetic field. The question, however, is how these
solutions can be realized. To address this problem, we discuss various
scenarios for a simple dynamo model and the conditions under which a steady
weak magnetic field can be reached. We find that the feedback mechanism
quenches the overall field to a low value of about 100 to 150 nT if the dynamo
is not driven too strongly
Concerning the generation of geomagnetic giant pulsations by drift-bounce resonance ring current instabilities
Decomposing Service Definition in Predicate/Transition-Nets for Designing Distributed Systems
In this paper, we propose a new algorithm for the derivation of a protocol specification in Pr/T-nets, which is the specification of communicating N entities (N can be given), from a given service specification in Pr/T-nets and an allocation of the places of the service specification to the N entities. Our algorithm decomposes each transition of the service specification into a set of communicating Pr/T-subnets running on the N entities. Moreover, for the efficient control of conflict of shared resources, we present a timestamp-based mutual exclusion algorithm and incorporate it into the derivation algorithm
Passive, free-space heterodyne laser gyroscope
Laser gyroscopes making use of the Sagnac effect have been used as highly accurate rotation sensors for many years. First used in aerospace and defense applications, these devices have more recently been used for precision seismology and in other research settings. In particular, mid-sized (~1 m-scale) laser gyros have been under development as tilt sensors to augment the adaptive active seismic isolation systems in terrestrial interferometric gravitational wave detectors. The most prevalent design is the 'active' gyroscope, in which the optical ring cavity used to measure the Sagnac degeneracy breaking is itself a laser resonator. In this article, we describe another topology: a 'passive' gyroscope, in which the sensing cavity is not itself a laser but is instead tracked using external laser beams. While subject to its own limitations, this design is free from the deleterious lock-in effects observed in active systems, and has the advantage that it can be constructed using commercially available components. We demonstrate that our device achieves comparable sensitivity to those of similarly sized active laser gyroscopes
The composition of heavy molecular ions inside the ionopause of Comet Halley
The RPA2-PICCA instrument aboard the Giotto spacecraft obtained 10-210 amu mass spectral of cold thermal molecular ions in the coma of Comet Halley. The dissociation products of the long chain formaldehyde polymer polyoxymethylene (POM) have recently been proposed as the dominant complex molecules in the coma of Comet Halley; however, POM alone cannot account for all of the features of the high resolution spectrum. An important component of the dust at Comet Halley is particles highly enriched in carbon, hydrogen, oxygen, and nitrogen relative to the composition of carbonaceous chondrites. Since this dust could be a source for the heavy molecules observed by PICCA, a search was conducted for other chemical species by determining all the molecules with mass between 20 and 120 amu which can be made from the relatively abundant C, H, O, and N, without regard to chemical structure
Noncovalent Interactions by QMC: Speedup by One-Particle Basis-Set Size Reduction
While it is empirically accepted that the fixed-node diffusion Monte-Carlo
(FN-DMC) depends only weakly on the size of the one-particle basis sets used to
expand its guiding functions, limits of this observation are not settled yet.
Our recent work indicates that under the FN error cancellation conditions,
augmented triple zeta basis sets are sufficient to achieve a benchmark level of
0.1 kcal/mol in a number of small noncovalent complexes. Here we report on a
possibility of truncation of the one-particle basis sets used in FN-DMC guiding
functions that has no visible effect on the accuracy of the production FN-DMC
energy differences. The proposed scheme leads to no significant increase in the
local energy variance, indicating that the total CPU cost of large-scale
benchmark noncovalent interaction energy FN-DMC calculations may be reduced.Comment: ACS book chapter, accepte
Observations of the longitudinal spread of solar energetic particle events in solar cycle 24
With the twin STEREO spacecraft, significantly separated from L1-based satellites such as ACE, simultaneous multi-point measurements of solar energetic particle (SEP) events can be made for H-Fe ions from a few hundred keV/nuc to over 100 MeV/nuc and for electrons from tens to hundreds of keV. These observations allow studies of the longitudinal characteristics of SEP events to advance beyond statistical analysis of single point measurements. Although there have been few large SEP events thus far in cycle 24, there have been a number of smaller events that have been detected by more than one spacecraft. The composition of these SEP events, as indicated by the H/He and Fe/O abundance ratios, shows a dependence on longitudinal distance from the solar source in some events, at times with ratios varying by an order of magnitude. However, these variations are not organized by either the speed or width of the associated coronal mass ejections
Genetic analysis of seed traits in \u3ci\u3eSorghum bicolor\u3c/i\u3e that affect the human gut microbiome
Prebiotic fibers, polyphenols and other molecular components of food crops significantly affect the composition and function of the human gut microbiome and human health. The abundance of these, frequently uncharacterized, microbiome-active components vary within individual crop species. Here, we employ high throughput in vitro fermentations of pre-digested grain using a human microbiome to identify segregating genetic loci in a food crop, sorghum, that alter the composition and function of human gut microbes. Evaluating grain produced by 294 sorghum recombinant inbreds identifies 10 loci in the sorghum genome associated with variation in the abundance of microbial taxa and/or microbial metabolites. Two loci co-localize with sorghum genes regulating the biosynthesis of condensed tannins. We validate that condensed tannins stimulate the growth of microbes associated with these two loci. Our work illustrates the potential for genetic analysis to systematically discover and characterize molecular components of food crops that influence the human gut microbiome
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