Density imaging of volcanos with atmospheric muons

collaboration : TOMUVOLInternational audienceTheir capability to penetrate large depths of material renders high-energy atmospheric muons a unique probe for geophysical explorations. Provided the topography of the target is known, the measurement of the attenuation of the muon flux permits the cartography of matter density distributions revealing spatial and possibly also temporal variations in extended geological structures. A Collaboration between volcanologists, astroparticle- and particle physicists, TOMUVOL, was formed in 2009 to study tomographic muon imaging of volcanos with high-resolution tracking detectors. This contribution presents preparatory work towards muon tomography as well as flux measurements obtained after the first months of data taking at the Puy de Dˆome, an inactive lava dome volcano in the Massif Central in south-central France

Why school mathematics should be taught in a contemporary setting, (s.d.)

Documento com vinte e quatro páginas. O original pertence à professora Lydia Condé Lamparelli, fotografia autorizada pela mesma.Texto que discute tendências sobre o ensino de matemática

The Role of Equality and Equity in Social Preferences

Engelmann and Strobel (AER 2004) question the relevance of inequity aversion in simple dictator game experiments claiming that a combination of a preference for efficiency and a Rawlsian motive for helping the least well-off is more important than inequity aversion. We show that these results are partly based on a strong subject pool effect. The participants of the E&S experiments were undergraduate students of economics and business administration who self-selected into their field of study (economics) and learned in the first semester that efficiency is desirable. We show that for non-economists the preference for efficiency is much less pronounced. We also find a non-negligible gender effect indicating that women are more egalitarian than men. However, perhaps surprisingly, the dominance of equality over efficiency is unrelated to political attitudes.Social Preferences; Inequity Aversion; Efficiency Preferences

In Search of Homo Economicus: Behavioral Experiments in 15 Small-Scale Societies

We can summarize our results as follows. First, the canonical model is not supported in any society studied. Second, there is considerably more behavioral variability across groups than had been found in previous cross-cultural research, and the canonical model fails in a wider variety of ways than in previous experiments. Third, group-level differences in economic organization and the degree of market integration explain a substantial portion of the behavioral variation across societies: the higher the degree of market integration and the higher the payoffs to cooperation, the greater the level of cooperation in experimental games. Fourth, individual-level economic and demographic variables do not explain behavior either within or across groups. Fifth, behavior in the experiments is generally consistent with economic patterns of everyday life in these societies

Risk in Time: The Intertwined Nature of Risk Taking and Time Discounting

Standard economic models view risk taking and time discounting as two independent dimensions of decision making. However, mounting experimental evidence demonstrates striking parallels in patterns of risk taking and time discounting behavior and systematic interaction effects, which suggests that there may be common underlying forces driving these interactions. Here, we show that the inherent uncertainty associated with future prospects together with individuals’ proneness to probability weighting generates a unifying framework for explaining a large number of puzzling behavioral findings: delay-dependent risk tolerance, aversion to sequential resolution of uncertainty, preferences for the timing of the resolution of uncertainty, the differential discounting of risky and certain outcomes, hyperbolic discounting, subadditive discounting, and the order dependence of prospect valuation. Furthermore, all these phenomena can be accommodated by the same set of preference parameter values and plausible levels of inherent uncertainty

Social Preferences and the Efficiency of Bilateral Exchange

Under what conditions do social preferences, such as altruism or a concern for fair outcomes, generate efficient trade? I analyze theoretically a simple bilateral exchange game: Each player sequentially takes an action that reduces his own material payoff but increases the other player’s. Each player’s preferences may depend on both his/her own material payoff and the other player’s. I identify necessary conditions and sufficient conditions on the players’ preferences for the outcome of their interaction to be Pareto efficient. The results have implications for interpreting the rotten kid theorem, gift exchange in the laboratory, and gift exchange in the field

Ultrafast excited-state processes in the antiviral agent hypericin

Hypericin (Figure 1) has been shown by Lavieet al. toinactivate mature and properly assembled retroviruses, notably human immunodeficiency virus (HIV).\u27 Recently Kraus, Carpenter, and co-workers demonstrated the antiretroviral activity of hypericin against equine infectious anemia virus (EIAV), a lentivirus closely related to HIV, and have determined that light is required for activity.2 The requirement of light leads to the fundamental questions, what is the mechanism of action of hypericin and what is the role of light

Role of Solvent in Excited-State Proton Transfer in Hypericin

The excited-state proton transfer of hypericin is monitored by the rise time (-6-1 2 ps in the solvents investigated) of the component of stimulated emission corresponding to the formation of the long-lived (-5 ns) fluorescent tautomer. The assignment of this excited-state process to proton transfer has been verified by noting that a hypericin analog (mesonaphthobianthrone) lacking labile protons is not fluorescent unless its carbonyl groups are protonated. Recent experimental studies on other systems have suggested that three solvent properties play important roles in excited-state proton transfer: viscosity, hydrogen-bonding character, and dynamic solvation. We find that for hypericin, in a range of protic, aprotic, hydrogen-bonding, and non-hydrogen-bonding solvents in which the viscosity changes by a factor of 60 and the average solvation time changes by a factor of 100, the excited-state proton-transfer rate of hypericin is uncorrelated with these properties and varies not more than a factor of 2 (- 6-1 2 ps) at room temperature. The relative contribution of the bulk solvent polarity is considered, and the role of intramolecular vibrations of hypericin on the proton-transfer rate is discussed

Observation of Excited-State Tautomerization in the Antiviral Agent Hypericin and Identification of Its Fluorescent Species

The absorption spectra, fluorescence spectra, and fluorescence lifetimes of hypericin, an analog lacking hydroxyl groups, mesonaphthobianthrone, and hexamethylhypericin are obtained in aprotic and protic solvents. In aprotic solvents, mesonaphtobianthrone is nonfluorescent. In strong acids such as sulfuric or triflic acids, it becomes fluorescent. Furthermore, its spectrum is very similar to that of hypericin. Similarly, only in sulfuric acid does hexamethylhypericin afford absorption and emission spectra resembling those of hypericin. We therefore conclude that the fluorescent species of hypericin has one or both of its carbonyl groups protonated. The protonation equilibrium in both the ground and the excited state is discussed. The first detailed measurements of the primary processes in the antiviral agent, hypericin, are performed with picosecond resolution and a white-light continuum. Transient absorption measurements of hypericin with - 1-ps resolution indicate that upon optical excitation a new species is created that absorbs in the range of roughly 580-640 nm. This species exhibits a 6-1 2-ps decay, depending on the solvent. It is also observed that the stimulated emission signal, which arises from the fluorescent state, grows in with a time constant of 6-12 ps. Based upon the identification of the fluorescent species as hypericin with one or both carbonyl groups protonated, the rise time for the appearance of the stimulated emission signal is attributed to excited-state tautomerization