Excimer laser pumped by an intense, high-energy heavy-ion beam

High-energy heavy ions are an ideal tool to generate homogeneously excited, extended volumes of nonthermal plasmas. Here, the high-energy loss (dE/dx) and absolute power deposition of heavy ions interacting with matter has been used to pump an ultraviolet laser. A pulsed 70 MeV/u 238U beam with up to 2.5 x 10(9) particles in approximately 100 ns beam bunches was stopped in a 1.2 m long laser cell filled with a 1.6 bar Ar-Kr-F2 mixture (typically 50%:49.9%:0.1%). Laser effect on the 248 nm KrF* excimer transition is clearly demonstrated.     

A covalent organic cage compound acting as a supramolecular shadow mask for the regioselective functionalization of C60

A trigonal-bipyramidal covalent organic cage compound serves as an efficient host to form stable 1 : 1-complexes with C₆₀ and C₇₀. Fullerene encapsulation has been comprehensively studied by NMR and UV/Vis spectroscopy, mass spectrometry as well as single-crystal X-ray diffraction. Exohedral functionalization of encapsulated C₆₀via threefold Prato reaction revealed high selectivity for the symmetry-matched all-trans-3 addition pattern.

The taming of the Prato reaction: a covalent organic cage compound serves as a supramolecular template for the regioselective functionalization of C₆₀.     

Two sub-pixel processing algorithms for high accuracy particle centre estimation in low seeding density particle image velocimetry

This article presents two algorithms for spatial processing of low seeding density PIV (particle image velocimetry) images which lead to sub-pixel precision in particle positioning. The particle centres are estimated to accuracies of the order of 0.1 pixel, yielding 1% error in velocity calculation. The first algorithm discriminates valid particles from the rest of the image and determines their centres in Cartesian coordinates by using a two-dimensional Gaussian fit. The second algorithm performs local correlation between particle pairs and determines instantaneous two-dimensional velocities. The methods have been applied initially to simulated data. Gaussian noise and distortion has then been added to simulate experimental conditions. It is shown that, in comparison with conventional methods, the new algorithms offer up to an order of magnitude higher accuracy for particle centre estimation. Finally, the Gaussian fit approach has been used to map an experimental transonic flow field from the stator trailing edge wake region of a cascade with an estimated error of 1%. The experimental results are found to be in good agreement with previous theoretical steady-state viscous calculations.     

Boundedness of the first eigenvalue of the -Laplacian

We prove that for any 1$">, any compact manifold of three or more dimensions carries Riemannian metrics of volume one with the first eigenvalue of the -Laplacian arbitrarily large.

     

Thermal analysis of new glycopolymers derived from monosaccharides

A novel monomer carrying carbohydrate moiety was prepared by simple reaction of methacrylic acid with 3-O-(2′,3′-epoxy-propyl)-1,2:5,6-di-O-isopropylidene-α-d-glucofuranose. Another d-glucose oligomer was synthesized by the polycondensation of a dicarboxylic acid including the carbohydrate residue into the main polymeric chain, 3-O-benzyl-5,6-(bis-O-(acryloyloxy))-1,2-di-O-isopropylidene-α-d-glucofuranose, with propane-1,3-diol using p-toluenesulfonic acid as catalyst. These products were copolymerized with styrene and 2-hydroxypropyl methacrylate, respectively, at different mass ratios, using benzoyl peroxide as initiator. Differential scanning calorimetry was performed in order to study the copolymerization process of the monomer and oligomer into the chosen co-monomers, respectively, and the activation energy of this process was evaluated using Kissinger–Akahira–Sunose (KAS) method. The storage and loss modulus of the obtained glycopolymers were evaluated using dynamic mechanical analysis. The thermal stability of the obtained products was studied via thermogravimetry.     

Capsaicin and Gut Microbiota in Health and Disease

Capsaicin is a widespread spice known for its analgesic qualities. Although a comprehensive body of evidence suggests pleiotropic benefits of capsaicin, including anti-inflammatory, antioxidant, anti-proliferative, metabolic, or cardioprotective effects, it is frequently avoided due to reported digestive side-effects. As the gut bacterial profile is strongly linked to diet and capsaicin displays modulatory effects on gut microbiota, a new hypothesis has recently emerged about its possible applicability against widespread pathologies, such as metabolic and inflammatory diseases. The present review explores the capsaicin–microbiota crosstalk and capsaicin effect on dysbiosis, and illustrates the intimate mechanisms that underlie its action in preventing the onset or development of pathologies like obesity, diabetes, or inflammatory bowel diseases. A possible antimicrobial property of capsaicin, mediated by the beneficial alteration of microbiota, is also discussed. However, as data are coming mostly from experimental models, caution is needed in translating these findings to humans.     

Analytical performance of an r.f. capacitively coupled plasma for atomic emission with tip-ring electrode geometry

A low to medium power radiofrequency capacitively coupled plasma is characterized as spectral source for atomic emission. The signal to background ratio and the limits of detection were determined for 19 elements as a function of the plasma torch geometry and the observation point.     

Role of nanomechanical properties in the tribological performance of phospholipid biomimetic surfaces

The role of phospholipid bilayers in controlling and reducing frictional forces between biological surfaces is investigated by three complementary experiments: friction forces are measured using a homemade tribometer, mechanical resistance to indentation is measured by AFM, and lipid bilayer degradation is controlled in situ during friction testing using fluorescence microscopy. DPPC lipid bilayers in the solid phase generate friction coefficients as low as 0.002 (comparable to that found for cartilage) that are stable through time. DOPC bilayers formed by the vesicle fusion method or the adsorption of mixed micelles generate higher friction coefficients. These coefficients increased through time, during which the bilayers degraded. The friction coefficient is correlated with the force needed to penetrate the bilayer with the AFM tip. With only one bilayer in the contact region, the friction increased to a similar value of about 0.08 for the DPPC and DOPC. Our study therefore shows that good mechanical stability of the bilayers is essential and suggests that the low friction coefficient is ensured by the hydration layers between adjacent lipid bilayers.     

Amyloid–β peptides time-dependent structural modifications: AFM and voltammetric characterization

The human amyloid beta (Aβ) peptides, Aβ_1-40 and Aβ_1-42, structural modifications, from soluble monomers to fully formed fibrils through intermediate structures, were investigated, and the results were compared with those obtained for the inverse Aβ_40-1 and Aβ_42-1, mutant Aβ_1-40Phe¹⁰ and Aβ_1-40Nle³⁵, and rat Aβ_1-40Rat peptide sequences. The aggregation was followed at a slow rate, in chloride free media and room temperature, and revealed to be a sequence-structure process, dependent on the physicochemical properties of each Aβ peptide isoforms, and occurring at different rates and by different pathways. The fibrilization process was investigated by atomic force microscopy (AFM), via changes in the adsorption morphology from: (i) initially random coiled structures of ∼0.6 nm height, corresponding to the Aβ peptide monomers in random coil or in α-helix conformations, to (ii) aggregates and protofibrils of 1.5–6.0 nm height and (iii) two types of fibrils, corresponding to the Aβ peptide in a β-sheet configuration. The reactivity of the carbon electrode surface was considered. The hydrophobic surface induced rapid changes of the Aβ peptide conformations, and differences between the adsorbed fibrils, formed at the carbon surface (beaded, thin, <2.0 nm height) or in solution (long, smooth, thick, >2.0 nm height), were detected. Differential pulse voltammetry showed that, according to their primary structure, the Aβ peptides undergo oxidation in one or two steps, the first step corresponding to the tyrosine amino acids oxidation, and the second one to the histidine and methionine amino acids oxidation. The fibrilization process was electrochemically detected via the decrease of the Aβ peptide oxidation peak currents that occurred in a time dependent manner.