Communications Biophysics

Contains reports on two research projects

Herbert Simon's decision-making approach: Investigation of cognitive processes in experts

This is a post print version of the article. The official published can be obtained from the links below - PsycINFO Database Record (c) 2010 APA, all rights reserved.Herbert Simon's research endeavor aimed to understand the processes that participate in human decision making. However, despite his effort to investigate this question, his work did not have the impact in the “decision making” community that it had in other fields. His rejection of the assumption of perfect rationality, made in mainstream economics, led him to develop the concept of bounded rationality. Simon's approach also emphasized the limitations of the cognitive system, the change of processes due to expertise, and the direct empirical study of cognitive processes involved in decision making. In this article, we argue that his subsequent research program in problem solving and expertise offered critical tools for studying decision-making processes that took into account his original notion of bounded rationality. Unfortunately, these tools were ignored by the main research paradigms in decision making, such as Tversky and Kahneman's biased rationality approach (also known as the heuristics and biases approach) and the ecological approach advanced by Gigerenzer and others. We make a proposal of how to integrate Simon's approach with the main current approaches to decision making. We argue that this would lead to better models of decision making that are more generalizable, have higher ecological validity, include specification of cognitive processes, and provide a better understanding of the interaction between the characteristics of the cognitive system and the contingencies of the environment

Optomechanical Cooling of a Macroscopic Oscillator by Homodyne Feedback

We propose a simple optomechanical model in which a mechanical oscillator quadrature could be "cooled" well below its equilibrium temperature by applying a suitable feedback to drive the orthogonal quadrature by means of the homodyne current of the radiation field used to probe its position.Comment: 9 pages, RevTeX, Figures available from authors, to appear in Phys. Rev. Let

Quantification of ferritin-bound iron in murine samples for Alzheimer's disease studies using species-specific isotope dilution mass spectrometry

Acknowledgments The project ReMiND 15HLT02 has received funding from the EMPIR programme co-financed by the Participating States and from the European Union's Horizon 2020 research and innovation programme. The authors gratefully thank Christoph Baumgartinger for his support with sample preparation as well as one independent referee for highly constructive comments.Peer reviewedPublisher PD

Iterated Binomial Sums and their Associated Iterated Integrals

We consider finite iterated generalized harmonic sums weighted by the binomial $\binom{2k}{k}$ in numerators and denominators. A large class of these functions emerges in the calculation of massive Feynman diagrams with local operator insertions starting at 3-loop order in the coupling constant and extends the classes of the nested harmonic, generalized harmonic and cyclotomic sums. The binomially weighted sums are associated by the Mellin transform to iterated integrals over square-root valued alphabets. The values of the sums for $N \rightarrow \infty$ and the iterated integrals at $x=1$ lead to new constants, extending the set of special numbers given by the multiple zeta values, the cyclotomic zeta values and special constants which emerge in the limit $N \rightarrow \infty$ of generalized harmonic sums. We develop algorithms to obtain the Mellin representations of these sums in a systematic way. They are of importance for the derivation of the asymptotic expansion of these sums and their analytic continuation to $N \in \mathbb{C}$. The associated convolution relations are derived for real parameters and can therefore be used in a wider context, as e.g. for multi-scale processes. We also derive algorithms to transform iterated integrals over root-valued alphabets into binomial sums. Using generating functions we study a few aspects of infinite (inverse) binomial sums.Comment: 62 pages Latex, 1 style fil

Accuracy of a method based on atomic absorption spectrometry to determine inorganic arsenic in food : Outcome of the collaborative trial IMEP-41

Peer reviewedPublisher PD

Quantum damping of position due to energy measurements

Quantum theory for measurements of energy is introduced and its consequences for the average position of monitored dynamical systems are analyzed. It turns out that energy measurements lead to a localization of the expectation values of other observables. This is manifested, in the case of position, as a damping of the motion without classical analogue. Quantum damping of position for an atom bouncing on a reflecting surface in presence of a homogeneous gravitational field is dealt in detail and the connection with an experiment already performed in the classical regime is studied. We show that quantum damping is testable provided that the same measurement strength obtained in the experimental verification of the quantum Zeno effect in atomic spectroscopy [W. M. Itano et al., Phys. Rev. A {\bf 41}, 2295 (1990)] is made available.Comment: 19 pages + 4 figures available upon request; Plain REVTeX; To be published in Phys. Rev.

Measurements of Lifetimes and a Limit on the Lifetime Difference in the Neutral D-Meson System

Using the large hadroproduced charm sample collected in experiment E791 at Fermilab, we report the first directly measured constraint on the decay-width difference Delta Gamma for the mass eigenstates of the D0-D0bar system. We obtain our result from lifetime measurements of the decays D0 --> K-pi+ and D0 --> K-K+, under the assumption of CP invariance, which implies that the CP eigenstates and the mass eigenstates are the same. The lifetime of D0 --> K-K+ (the CP-even final state is \tau_KK = 0.410 +/- 0.011 +/- 0.006 ps, and the lifetime of D0 --> K-pi+ (an equal mixture of CP-odd and CP-even final states is tau_Kpi = 0.413 +/- 0.003 +/- 0.004 ps. The decay-width difference is Delta Gamma = 2(Gamma_KK - Gamma_Kpi) = 0.04 +/- 0.14 +/- 0.05 ps^-1. We relate these measurements to measurements of mixing in the neutral D-meson system.Comment: 8 pages + 3 figures + 2 table

Iso-osmotic regulation of nitrate accumulation in lettuce (Lactuca sativa L.)

Concerns about possible health hazards arising from human consumption of lettuce and other edible vegetable crops with high concentrations of nitrate have generated demands for a greater understanding of processes involved in its uptake and accumulation in order to devise more sustainable strategies for its control. This paper evaluates a proposed iso-osmotic mechanism for the regulation of nitrate accumulation in lettuce (Lactuca sativa L.) heads. This mechanism assumes that changes in the concentrations of nitrate and all other endogenous osmotica (including anions, cations and neutral solutes) are continually adjusted in tandem to minimise differences in osmotic potential of the shoot sap during growth, with these changes occurring independently of any variations in external water potential. The hypothesis was tested using data from six new experiments, each with a single unique treatment comprising a separate combination of light intensity, N source (nitrate with or without ammonium) and nitrate concentration carried out hydroponically in a glasshouse using a butterhead lettuce variety. Repeat measurements of plant weights and estimates of all of the main soluble constituents (nitrate, potassium, calcium, magnesium, organic anions, chloride, phosphate, sulphate and soluble carbohydrates) in the shoot sap were made at intervals from about 2 weeks after transplanting until commercial maturity, and the data used to calculate changes in average osmotic potential in the shoot. Results showed that nitrate concentrations in the sap increased when average light levels were reduced by between 30 and 49 % and (to a lesser extent) when nitrate was supplied at a supra-optimal concentration, and declined with partial replacement of nitrate by ammonium in the external nutrient supply. The associated changes in the proportions of other endogenous osmotica, in combination with the adjustment of shoot water content, maintained the total solute concentrations in shoot sap approximately constant and minimised differences in osmotic potential between treatments at each sampling date. There was, however, a gradual increase in osmotic potential (ie a decline in total solute concentration) over time largely caused by increases in shoot water content associated with the physiological and morphological development of the plants. Regression analysis using normalised data (to correct for these time trends) showed that the results were consistent with a 1:1 exchange between the concentrations of nitrate and the sum of all other endogenous osmotica throughout growth, providing evidence that an iso-osmotic mechanism (incorporating both concentration and volume regulation) was involved in controlling nitrate concentrations in the shoot