Phase extraction in speckle interferometry by a circle fitting procedure in the complex plane

In speckle interferometry (SI), temporal signals are amplitude- and frequency-modulated signals and exhibit a fluctuating background. Prior to phase computation, this background intensity must be eliminated. Here our approach is to build a complex signal from the raw one and to fit a circle through the points cloud representing its sampled values in the complex plane. The circle fit is computed from a set of points whose length is locally adapted to the signal. This procedure-new to our knowledge in SI-yields the background and the modulation depth and leads to the determination of the instantaneous frequency. The method, applied to simulated and experimental signals, is compared to empirical mode decomposition (EMD). It shows great robustness in the computation of the sought quantities in SI, especially with signals close to the critical sampling or, on the contrary, highly oversampled, situations where the background elimination by EMD is the most prone to errors.     

Chionanthus virginicus L.: phytochemical analysis and quality control of herbal drug and herbal preparations

Root barks of Chionanthus virginicus L. are used in homeopathic medicines in the treatment of icterus and hepatitis. The objective of this study is to identify novel secoiridoids and lignans and to develop a simple and reliable HPLC method for the determination of oleuropein, phillyrin, total secoiridoids and total lignans for quality control and stability studies of C. virginicus herbal drug and preparations. Secoiridoids and lignans were purified by preparative HPLC. Compounds previously described were identified by HPLC according to their retention times and UV spectra. Structures of new compounds were determined by NMR. Two compounds namely excelside B and acetoxypinoresinol-4"-O-beta-D-glucoside are described for the first time in the drug. HPLC separation was performed on Symmetry C18 (Waters) by gradient elution using acetonitrile and 0.2% aqueous phosphoric acid. The method was validated for specificity, linearity, precision, accuracy, limits of detection and quantification for simultaneous determination of secoiridoids and lignans in herbal drug and herbal preparations as mother tinctures. The proposed HPLC method is linear in the range studied (r2 > or = 0.9989) for all the analytes. The method is precise with intra- and inter-day variations of less than 4%. The mean recoveries of the analytes range from 99.65 to 102.81%. The method is successfully applied to the quantification of nine compounds belonging to secoiridoids and lignans and for the stability studies of these compounds. The study allowed completing the phytochemical knowledge of C. virginicus. This simple developed assay could be used as tools for routine quality control of C. virginicus herbal drug and herbal medicinal products.     

Testing the use of molecular dynamics to simulate fluorophore motions and FRET

Fluorescence resonance energy transfer (FRET) is commonly used to determine the proximity of fluorophores, but usually many assumptions are required to gain a quantitative relationship between the likelihood of energy transfer and fluorophore separation. Molecular Dynamics (MD) simulations provide one way of checking these assumptions, but before using simulations to study complex systems it is important to make sure that they can correctly model the motions of fluorophores and the likely FRET efficiency in a simple system. Here we simulate a well characterised situation of independent fluorophores in solution so that we can compare the predictions with expected values. Our simulations reproduce the experimental fluorescence anisotropy of Alexafluor488 and predict that of AlexaFluor568. At the ensemble level we are able to reproduce the expected isotropic and dynamic motion of the fluorophores as well as the FRET efficiency of the system. At the level of single donor-acceptor pairs, however, very long simulations are required to adequately sample the translational motion of the fluorophores and more surprisingly also the rotational motion. Our studies demonstrate how MD simulations can be used in more complex systems to check if the dynamic orientation averaging regime applies, if the fluorophores have isotropic orientational motion, to calculate the likely values of the orientation factor κ(2) and to determine the FRET efficiency of the system in both dynamic and static orientational averaging regimes. We also show that it is possible in some situations to create system specific relationships between FRET efficiency and fluorophore separation that can be used to interpret experimental data and find any correlations between κ(2) and separation that may influence distance measurements.     

Collisions of Vortex Filament Pairs

We consider the problem of collisions of vortex filaments for a model introduced by Klein et al. (J Fluid Mech 288:201–248, 1995) and Zakharov (Sov Phys Usp 31(7):672–674, 1988, Lect. Notes Phys 536:369–385, 1999) to describe the interaction of almost parallel vortex filaments in three-dimensional fluids. Since the results of Crow (AIAA J 8:2172–2179, 1970) examples of collisions are searched as perturbations of antiparallel translating pairs of filaments, with initial perturbations related to the unstable mode of the linearized problem; most results are numerical calculations. In this article, we first consider a related model for the evolution of pairs of filaments, and we display another type of initial perturbation leading to collision in finite time. Moreover, we give numerical evidence that it also leads to collision through the initial model. We finally study the self-similar solutions of the model.     

Neighbor Sum Distinguishing Index

We consider proper edge colorings of a graph G using colors of the set {1, . . . , k}. Such a coloring is called neighbor sum distinguishing if for any pair of adjacent vertices x and y the sum of colors taken on the edges incident to x is different from the sum of colors taken on the edges incident to y. The smallest value of k in such a coloring of G is denoted by ndi_Σ(G). In the paper we conjecture that for any connected graph G ≠ C ₅ of order n ≥ 3 we have ndi_Σ(G) ≤ Δ(G) + 2. We prove this conjecture for several classes of graphs. We also show that ndi_Σ(G) ≤ 7Δ(G)/2 for any graph G with Δ(G) ≥ 2 and ndi_Σ(G) ≤ 8 if G is cubic.     

Design and synthesis of new polyphosphorylated upper-rim modified calix[4]arenes as potential and selective chelating agents of uranyl ion

New upper-rim polyphosphorylated calix[4]arenes were designed for decorporation of uranium in case of nuclear contamination. A ligand system containing four preorganized 1-hydroxymethylene-1,1-bisphosphonic acid moieties anchored onto a calix[4]arene platform has been developed. Three calix[4]arene-bisphosphonates were efficiently prepared in multi-step syntheses with a variable carbon chain length between the bisphosphonate and the calix[4]arene. Affinity constants towards uranyl ion were determined and compared with those of bis(HEDP) and tris(HEDP) phosphonates, known as efficient ligands for uranyl.     

Screening of a minimal enriched P450 BM3 mutant library for hydroxylation of cyclic and acyclic alkanes

A minimal enriched P450 BM3 library was screened for the ability to oxidize inert cyclic and acyclic alkanes. The F87A/A328V mutant was found to effectively hydroxylate cyclooctane, cyclodecane and cyclododecane. F87V/A328F with high activity towards cyclooctane hydroxylated acyclic n-octane to 2-(R)-octanol (46% ee) with high regioselectivity (92%).     

A benchmark for cooperative coevolution

Cooperative co-evolution algorithms (CCEA) are a thriving sub-field of evolutionary computation. This class of algorithms makes it possible to exploit more efficiently the artificial Darwinist scheme, as soon as an optimisation problem can be turned into a co-evolution of interdependent sub-parts of the searched solution. Testing the efficiency of new CCEA concepts, however, it is not straightforward: while there is a rich literature of benchmarks for more traditional evolutionary techniques, the same does not hold true for this relatively new paradigm. We present a benchmark problem designed to study the behavior and performance of CCEAs, modeling a search for the optimal placement of a set of lamps inside a room. The relative complexity of the problem can be adjusted by operating on a single parameter. The fitness function is a trade-off between conflicting objectives, so the performance of an algorithm can be examined by making use of different metrics. We show how three different cooperative strategies, Parisian Evolution, Group Evolution and Allopatric Group Evolution, can be applied to the problem. Using a Classical Evolution approach as comparison, we analyse the behavior of each algorithm in detail, with respect to the size of the problem.     

Concise Multigram‐Scale Synthesis of Push–Pull Tricyanofuran‐Based Hemicyanines with Giant Second‐Order Nonlinearity: An Alternative for Electro‐optic Materials

Highly stable and highly soluble push–pull heptamethine hemicyanines based on the tricyanofuran electron‐accepting group can be prepared on a 15 g scale. The compounds display giant second‐order nonlinear figure of merit, μβ of up to 31 000×10^?48 esu, and lead to a poled material with a second‐order nonlinear response, r₃₃ of 90 pm V^?1 at 1.06 μm