Spectral- and frequency-encoded fluorescence imaging

A method for obtaining fluorescence images with a high number of resolvable points by using spectral and frequency encoding is presented. Broadband excitation light is encoded with a wavelength-dependent frequency modulation and dispersed onto the sample with a grating to simultaneously illuminate an entire image line. The Fourier transform of the frequency-encoded fluorescence emission provides one line of the image. Mechanical scanning along a direction orthogonal to the wavelength-encoded axis allows creation of the two-dimensional fluorescent image. This method is applicable for developing submillimeter diameter endoscopes. The principles of the technique are validated by imaging indocyanine green fluorescence in microfluidic channels.     

Single and double metallic layer-containing ruthenium dendrimers. Synthesis and catalytic properties

The reaction of a series of phosphanyl-terminated carbosilane dendrimers displaying only one phosphorus ligand per arm with [RuCl(2)(p-cymene)](2) resulted in the grafting of RuCl(p-cymene) moieties on the periphery of the dendrimer. In these species, the chloride ligand is easily displaced by the organic bases pyridine, 4-cyanopyridine and 4,4[prime or minute]-bipyridine to afford new cationic metallodendrimers. NMR studies have confirmed the chirality of the ruthenium centre. The species containing 4,4[prime or minute]-bipyridine reacts through the uncoordinated pyridyl nitrogen with a new equivalent of [RuCl(2)(p-cymene)](2) or [RhCl(CO)(2)](2) to lead to homo- or hetero-bimetallic layer-containing dendrimeric systems. The ruthenodendrimers were tested as catalysts in the transfer hydrogenation of cyclohexanone by propan-2-ol and their activity compared with that of some analogous mononuclear ruthenium(ii) complexes.     

Alpha,omega-bis(thioacetyl)oligophenylenevinylene chromophores from thioanisol precursors

The selective cleavage of arylmethyl thioethers provides a convenient protocol for the synthesis of all-E isomers of alpha, omega-bis(thioacetyl)oligophenyenevinylene molecules (OPVs). The S-methyl group is tolerant of Wittig-type and Heck-type reactions for forming OPV structures and can be converted to the S-acetyl group by treatment with sodium thiomethoxide and acetyl chloride. The thermal conditions of the deprotection/reprotection step concurrently isomerize the conjugated chromophore to the all-E isomer, regardless of the stereochemistry of the starting olefins. This approach is demonstrated for a variety of linear and [2.2]paracyclophane containing OPVs, which have been characterized by electrochemical and spectroscopic techniques. Additionally, these S-acetyl-terminated OPVs self-assemble on gold surfaces. Monolayers containing these molecules were characterized by water contact angle measurements, ellipsometry, and X-ray photoelectron spectroscopy.     

In vivo human retinal imaging by ultrahigh-speed spectral domain optical coherence tomography

An ultrahigh-speed spectral domain optical coherence tomography (SD-OCT) system is presented that achieves acquisition rates of 29,300 depth profiles/s. The sensitivity of SD-OCT and time domain OCT (TD-OCT) are experimentally compared, demonstrating a 21.7-dB improvement of SD-OCT over TD-OCT. In vivo images of the human retina are presented, demonstrating the ability to acquire high-quality structural images with an axial resolution of 6 microm at ultrahigh speed and with an ocular exposure level of less than 600 microW.     

Improved signal-to-noise ratio in spectral-domain compared with time-domain optical coherence tomography

A signal-to-noise ratio (SNR) analysis is presented for optical coherence tomography (OCT) signals in which time-domain performance is compared with that of the spectral domain. A significant SNR gain of several hundredfold is found for acquisition in the spectral domain. The SNR benefit is demonstrated experimentally in a hybrid time-domain-spectral-domain OCT system.     

De Rham and Infinitesimal Cohomology in Kapranov's Model for Non commutative Algebraic Geometry

The title refers to the nilcommutative or NC-schemes introduced by M. Kapranov in Noncommutative Geometry Based on Commutator Expansions, J. Reine Angew. Math 505 (1998) 73–118. The latter are noncommutative nilpotent thickenings of commutative schemes. We also consider the parallel theory of nil-Poisson or NP-schemes, which are nilpotent thickenings of commutative schemes in the category of Poisson schemes. We study several variants of de Rham cohomology for NC- and NP-schemes. The variants include nilcommutative and nil-Poisson versions of the de Rham complex as well as of the cohomology of the infinitesimal site introduced by Grothendieck in Crystals and the de Rham Cohomology of Schemes, Dix exposés sur la cohomologie des schémas, Masson, Paris (1968), pp. 306–358. It turns out that each of these noncommutative variants admits a kind of Hodge decomposition which allows one to express the cohomology groups of a noncommutative scheme Y as a sum of copies of the usual (de Rham, infinitesimal) cohomology groups of the underlying commutative scheme X (Theorems 6.1, 6.4, 6.7). As a byproduct we obtain new proofs for classical results of Grothendieck (Corollary 6.2) and of Feigin and Tsygan (Corollary 6.8) on the relation between de Rham and infinitesimal cohomology and between the latter and periodic cyclic homology.     

Low Dimension Dynamics in the EPRB Experiment with Random Variable Analyzers

The Einstein–Podolsky–Rosen–Bohm (EPRB) experiment performed with random variable and spatially separated analyzers is a milestone test in the controversy between Objective Local Theories (OLT) and Quantum Mechanics (QM). Only a few OLT are still possible. Some of the surviving OLT (specifically, the so called non-ergodic theories) would be undetectable in the averaged statistical values, but they may leave their trace in the time dynamics. For, while QM predicts random processes, the OLT of this kind predict the existence of regularities that may be revealed as a low dimensional object in the phase space. We perform a numerical analysis of the time-resolved data recorded in that experiment to unveil any hypothetical low dimensional dynamics that may be present. We find no consistent indication of such dynamics except for one data file, the longest of all in the real time. The possible causes of these dynamics are discussed.      

Atomistic modeling of segregation and bulk ordering in Ag-Au alloys

The bulk and surface properties of Ag-Au alloys, for the whole range of concentration and as a function of temperature, is studied by means of a simple modeling scheme using the Bozzolo-Ferrante-Smith method for alloys. Evidence for short-range order is found and explained, as well as its relationship with the experimentally observed segregation behavior.     

Determination of β-glucosidase activity in soils with a bioanalytical sensor modified with multiwalled carbon nanotubes

Soil microorganisms and enzymes are the primary mediators of soil biological processes, including organic matter degradation, mineralization, and nutrient recycling. They play an important role in maintaining soil ecosystem quality and functional diversity. Moreover, enzyme activities can provide an indication of quantitative changes in soil organic matter. β-Glucosidase (β-Glu) activity has been found to be sensitive to soil management and has been proposed as a soil quality indicator because it provides an early indication of changes in organic matter status and its turnover. The aims of the present study were to test and use a simple and convenient procedure for the assay of β-Glu activity in agricultural soil. The method described here is based on the enzymatic degradation of cellobiose by β-Glu present in the soil sample and the subsequent determination of glucose produced by the enzymatic reaction using screen-printed carbon electrodes modified with multiwalled carbon nanotubes (SPCE-CNT) equipped with coimmobilized glucose oxidase and horseradish peroxidase enzymes. The potential applied to the SPCE-CNT detection was −0.15 V versus a Ag/AgCl pseudo-reference electrode. A linear calibration curve was obtained in the range 2.7–11.3 mM with a correlation coefficient. In the present study, an easy and effective SPCE-CNT-modified electrode allowed an improved amperometric response to be achieved and this is attributed to the increased surface area upon electrode modification.