SINGLE PHOTONS ARE SUFFICIENT TO TRIGGER MOVEMENT RESPONSES IN Chlamydomonas reinhardtii

Abstract— The unicellular green alga Chlamy domonas reinhardtii shows two distinct movement responses upon changes in green light irradiance: These are direction changes and stop responses. The dependence of both responses on the intensity of applied flashes was measured and analysed with the help of Poisson statistics. In dark-adapted cells both responses were 'single-photon' events. Preillumination of cells or background irradiation decreased the sensitivity for the stop response, now requiring two or more photons to trigger it. In the blind, carotenoid-negative mutant FN 68 the light-sensitivity for a stop-response was reconstituted by addition of all trans retinal. This result indicated that not only the receptor for phototaxis but also that for the stop response is a retinal protein. In addition, stimulus-response curves from the literature were analysed by Poisson statistics.     

Selection of internal standards for quantitative analysis by matrix-assisted laser desorption-ionization (MALDI) time-of-flight mass spectrometry

 The selection of an appropriate internal standard (IS) for quantification by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry is critical for the successful application of quantitative MALDI. Selection of the IS depends on the chemical similarity of the analyte and IS and the mass separation of the analyte and IS as a function of instrumental peak resolution. For the quantification of bovine insulin, a series of internal standards including horse heart cytochrome C, bovine insulin chain B, des-pentapeptide human insulin, and des-octapeptide porcine insulin was investigated. Des-pentapeptide human insulin was found to be the most appropriate internal standard (relative standard deviation of the standard curve slope=2.99%, correlation coefficient=0.988 in the range of 0.5–0.4 μmol/L). Two methods for measuring of the MALDI signal intensity were evaluated, direct peak integration following subtraction of a linear background and non-linear least squares curve fitting. The results obtained with these methods were equivalent. Received: 10 November 1995 / Revised: 4 March 1996 / Accepted: 6 March 1996     

(5,10,15,20‐Tetraphenylporphyrinato‐κ4N)bis(l‐valine‐κN methyl ester)iron(III) trifluoromethylsulfonate dichloromethane solvate

The title compound, [Fe(C₄₄H₂₈N₄)(C₆H₁₃NO₂)₂](CF₃O₃S)·­CH₂Cl₂, is the first amino ester complex of iron porphyrins to be investigated using X‐ray diffraction and it can be considered as a model complex of cytochrome f. The Fe atom is six‐coordinate to four N atoms of the porphyrin ring and to two N atoms of the axial amino ester ligands.     

Structure and conformation of cyclobutylsilane: an electron diffraction and ab initio study

A gas electron diffraction study of cyclobutylsilane results in a mixture of equatorial and axial conformers, with the equatorial confomer slightly more stable (Δ G = 0.8 ± 0.4 kJ mol⁻¹). The cyclobutyl ring is distorted with the adjacent bonds longer (C₁---C₂ = 1.573 (4) Å) than the opposite bonds (C₂---C₃ = 1.557 (4) Å). The experimental values for the energy difference between the two conformers and for the geometric parameters are reproduced very well by ab initio calculations. The importance of silicon 3d orbitals in the interpretation of ring distortion is ambiguous, but on the basis of the ab initio calculations the participation of silicon 3d functions is negligible.     

Structural analysis and probing the conformational space of dansylamide by means of gas-phase electron diffraction and quantum chemistry

Dansylamide is perhaps the most ubiquitous fluorophore due to its donor-acceptor bifunctionality and its ability to form intra- and intermolecular hydrogen bonding. Among the diversity of its applications is the development of new generation of biosensors for the in vivo monitoring of traces of metals. The structure and conformational stability of dansylamide in the gas phase were investigated for the first time by a combined gas-phase electron diffraction-mass spectrometry (GED/MS), complemented by quantum chemical calculations. GED data indicate that different skewed conformers exist at T?=?464 K, which are characterized by the deviation of two S–N bonds from the perpendicular orientation relative to the naphthalene plane. Maybe the most indicative structural parameters for electronic interactions between the donor-acceptor substituents and the aromatic naphthalene and the subsequent stabilization of the favorable skewed eclipsed-syn conformer are the dihedral angles C₉–C₁–S–N and C₁₀–C₅–N–C with the experimentally determined values of 66.8° (32) and 68.1° (72), respectively. The role of –SO₂NH₂ by forming intramolecular hydrogen bonds was scrutinized by employing the natural bond orbital approach (NBO), quantum theory atoms in molecules (QTAIM), and molecular electrostatic potential (MESP). The non-planarity of the naphthalene skeleton due to the electronic interactions with the substituents and its consequence for the fluorescence activity of dansylamide have been discussed.     

The complexity of advice‐giving

Advice‐giving about personal problems is a common form of human interaction. However, an open question is whether there is an abstract and general logic that explains how advice‐giving works. In this study, we addressed this question from the perspective of dynamical systems. We measured the nonlinear dynamics of advice‐giving by using recurrence quantification analysis. Analyzing 600 texts of request for advice and the advice given, our results uncover a typical logic of advice‐giving, and suggest that advice‐giving may be understood as a dynamic manipulation of perspective‐taking. © 2009 Wiley Periodicals, Inc. Complexity 2009     

The Wiener-Khinchin theorem and recurrence quantification

The Wiener-Khinchin theorem states that the power spectrum is the Fourier transform of the autocovariance function. One form of the autocovariance function can be obtained through recurrence quantification. We show that the advantage of defining the autocorrelation function with recurrences can demonstrate higher dimensional dynamics.     

Soliton solutions of shallow water wave equations by means of G′/G expansion method

In this work, we investigate the traveling wave solutions for some generalized nonlinear equations: The generalized shallow water wave equation and the Whitham-Broer-Kaup model for dispersive long waves in the shallow water small-amplitude regime. We use the $G'/G$ expansion method to determine different soliton solutions of these models. The conditions of existence and uniqueness of exact solutions are also presented.     

An analytical framework of 2D diffusion,wave-like,telegraph, and Burgers’ models with twofold Caputo derivatives ordering

The purpose of the current work is to provide an analytical solution framework based on extended fractional power series expansion to solve 2D temporal–spatial fractional differential equations. For this purpose, we first present a new trivariate expansion endowed with twofold Caputo-fractional derivatives ordering, namely \(\alpha ,\,\beta \in (0,1]\), to study the combined effect of fractional derivatives on both temporal and spatial coordinates. Then, by virtue of this expansion, a parallel scheme of the Taylor power series solution method is utilized to extract both closed-form and supportive approximate series solutions of 2D temporal–spatial fractional diffusion, wave-like, telegraph, and Burgers’ models. The obtained closed-form solutions are found to be in harmony with the exact solutions exist in the literature when \(\alpha =\beta =1\), which exhibits the legitimacy and the validity of the proposed method. Moreover, the accuracy of the approximate series solutions is validated using graphical and tabular tools. Finally, a version of Taylor’s Theorem that associated with our proposed expansion is derived in terms of mixed fractional derivatives.     

A historical review of recurrence plots

In the last two decades recurrence plots (RPs)were introduced in many different scientific disciplines. It turned out how powerful this method is. After introducing approaches of quantification of RPs and by the study of relationships between RPs and fundamental properties of dynamical systems, this method attracted even more attention. After 20 years of RPs it is time to summarise this development in a historical context.