Erdalkalien

Ohne Zusammenfassung     

Bestimmung der Alkalien

Ohne Zusammenfassung     

Stickstoffbestimmung

Ohne Zusammenfassung     

Controlled excitations of the Belousov-Zhabotinsky reaction: Experimental procedures

The purpose of this research was to explore the unstirred, ferroin-catalyzed Belousov-Zhabotinsky (BZ) reaction as an experimental model for the response of excitable media to small perturbations (slightly larger than the threshold for excitations). Following Showalter et al. (Showalter, K.; Noyes, R. M.; Turner, H. J.Am. Chem. Soc. 1979, 101, 7463-69), we used a positively biased silver electrode to release silver ions into a BZ reaction mixture, removing bromide ions and causing an excitation if sufficient bromide was removed. We found (1) a scaling region in which the delay before activation increased linearly as the size of the perturbation decreased, qualitatively consistent with but not fully explained by the Oregonator of Field et al. (Field, R. J.; K?r?s, E.; Noyes, R. M. J. Am. Chem. Soc. 1972, 94, 8649-64); (2) evidence for a 10 s oligomerization time scale; and (3) that activations were always delayed until after the end of a pulse of current, with the delay essentially constant for sufficiently long pulses, an effect not seen in simple ODE models but consistent with the anomalously large current apparently required for activation (Showalter, K.; Noyes, R. M. J. Am. Chem. Soc. 1976, 98, 3730-31) and explainable by bromide transport. Overall, the BZ system appeared to be well-suited as an experimental prototype, despite its complexity.     

Search for differences in oscillation parameters for atmospheric neutrinos and antineutrinos at Super-Kamiokande

We present a search for differences in the oscillations of antineutrinos and neutrinos in the Super-Kamiokande-I, -II, and -III atmospheric neutrino sample. Under a two-flavor disappearance model with separate mixing parameters between neutrinos and antineutrinos, we find no evidence for a difference in oscillation parameters. Best-fit antineutrino mixing is found to be at (Δm2,sin2 2θ)=(2.0×10(-3) eV2, 1.0) and is consistent with the overall Super-K measurement.     

Discounting axioms imply risk neutrality

Although most applications of discounting occur in risky settings, the best-known axiomatic justifications are deterministic. This paper provides an axiomatic rationale for discounting in a stochastic framework. Consider a representation of time and risk preferences with a binary relation on a real vector space of vector-valued discrete-time stochastic processes on a probability space. Four axioms imply that there are unique discount factors such that preferences among stochastic processes correspond to preferences among present value random vectors. The familiar axioms are weak ordering, continuity and nontriviality. The fourth axiom, decomposition, is non-standard and key. These axioms and the converse of decomposition are assumed in previous axiomatic justifications for discounting with nonlinear intraperiod utility functions in deterministic frameworks. Thus, the results here provide the weakest known sufficient conditions for discounting in deterministic or stochastic settings. In addition to the four axioms, if there exists a von Neumann-Morgenstern utility function corresponding to the binary relation, then that function is risk neutral (i.e., affine). In this sense, discounting axioms imply risk neutrality.