In Situ Investigations of Mechanochemical One‐Pot Syntheses

We present an in situ triple coupling of synchrotron X‐ray diffraction with Raman spectroscopy, and thermography to study milling reactions in real time. This combination of methods allows a correlation of the structural evolution with temperature information. The temperature information is crucial for understanding both the thermodynamics and reaction kinetics. The reaction mechanisms of three prototypical mechanochemical syntheses, a cocrystal formation, a C?C bond formation (Knoevenagel condensation), and the formation of a manganese‐phosphonate, were elucidated. Trends in the temperature development during milling are identified. The heat of reaction and latent heat of crystallization of the product contribute to the overall temperature increase. A decrease in temperature occurs via release of, for example, water as a by‐product. Solid and liquid intermediates are detected. The influence of the mechanical impact could be separated from temperature effects caused by the reaction.     

Array of electrodeposited Ru-decorated TiO<Subscript>2</Subscript> nanotubes with enhanced photoresponse

Although TiO₂ anatase phase has been widely chosen as the main photocatalyst, it presents high electron/hole recombination rate. However, today, what is sought is a semiconductor material with enhanced photocatalytic activity with higher photon to electron conversion efficiency by introduction of electrons trap dopants. In this paper, TiO₂ nanotubes arrays obtained by anodization of Ti substrates were decorated with Ru via electrodeposition, and their photo-response was investigated. First, voltammetric experiments were performed to elucidate the route of Ru reduction on the TiO₂ surface and to select the range of potentials for Ru deposition. The reduction potentials were used for controlling the amount of Ru distributed all over the surface. Although Ru was electrodeposited at potentials over the range from ??0.025 to ??0.188 V vs. Ag/AgCl, the deposition of 3.7 mC cm^?2 at ??0.100 V for 30 min resulted in a tenfold greater photocurrent when compared to the recorded photocurrent for the undecorated TiO₂ nanotubes array. Next, Ru-decorated TiO₂ nanotubes with a length of 323?±?18 nm and inner and outer diameters of 91 and 104 nm, respectively, were characterized using SEM-WDS, SEM-FEG, XRD, and XPS. UV-Vis-NIR diffuse reflectance spectroscopy and photoluminescence (PL) measurements, which revealed a maximum PL emission at 445 nm, showed that for the array of Ru-decorated TiO₂ nanotubes, the electron-hole recombination may be effectively inhibited by the presence of ruthenium electrodeposited, which can make this photocatalyst even more attractive for environmental applications. The performances of the TiO₂ and Ru-decorated TiO₂ catalysts were compared in heterogeneous photocatalysis experiments for color removal of an azo-dye, which presented a pseudo-first-order rate constant more than twofold greater for the Ru-decorated TiO₂ catalysts.     

Representation theory of generalized deformed oscillator algebras

The representation theory of the generalized deformed oscillator algebras (GDOA's) is developed. GDOA's are generated by the four operators {1, a, a , N}. Their commutators and Hermiticity properties are those of the boson oscillator algebra, except for [a, a ] _q = G(N), where [a, b] _q = ab – q ba and G(N) is a Hermitian, analytic function. The unitary irreductible representations are obtained by means of a Casimir operator C and the semi-positive operator a a. They may belong to one out of four classes: bounded from below (BFB), bounded from above (BFA), finite-dimentional (FD), unbounded (UB). Some examples of these different types of unirreps are given.     

Random Walks on Trees and an Inequality of Means

We define trees generated by bi-infinite sequences, calculate their walk-invariant distribution and the speed of a biased random walk. We compare a simple random walk on a tree generated by a bi-infinite sequence with a simple random walk on an augmented Galton-Watson tree. We find that comparable simple random walks require the augmented Galton-Watson tree to be larger than the corresponding tree generated by a bi-infinite sequence. This is due to an inequality for random variables with values in [1, [ involving harmonic, geometric and arithmetic mean.     

Weak chemiluminescence emission during base induced rearrangement of G-factors

A rearrangement in basic medium of the natural endoperoxide G3-factor extracted from Eucalyptus grandis is described. Evidence to support a 1,2-dioxetane intermediate that decomposes with weak luminescence emission (quantum yield) is presented.     

Expeditive synthesis of glycodendrimer scaffolds based on versatile TRIS and mannoside derivatives

A new family of glycodendrimer scaffolds containing 12 and 18 peripheral alpha-d-mannopyranosidic units has been synthesized by Cu(I)-catalyzed [1,3]-dipolar cycloadditions using sulfurated dendritic scaffolds bearing alkyne functionalities and novel TRIS derivatives.     

Homophymine A, an anti-HIV cyclodepsipeptide from the sponge Homophymia sp

A new anti-HIV cyclodepsipeptide, homophymine A, was isolated from a New Caledonian collection of the marine sponge Homophymia sp. The structure of homophymine A was determined by interpretation of spectroscopic data, acid hydrolysis, and LC-MS analysis. Homophymine A contains 11 amino acid residues and an amide-linked 3-hydroxy-2,4,6-trimethyloctanoic acid moiety. Along with four D-, two L-, and one N-methyl amino acids, it also contains four unusual amino acid residues: (2S,3S,4R)-3,4-diMe-Gln, (2R,3R,4S)-4-amino-2,3-dihydroxy-1,7-heptandioic acid, L-ThrOMe, and (2R,3R,4R)-2-amino-3-hydroxy-4,5-dimethylhexanoic acid. In a cell-based XTT assay, homophymine A exhibited cytoprotective activity against HIV-1 infection with a IC50 of 75 nM.     

Liquid and gas chromatography coupled to isotope ratio mass spectrometry for the determination of 13C-valine isotopic ratios in complex biological samples

On-line gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) is commonly used to measure isotopic ratios at natural abundance as well as for tracer studies in nutritional and medical research. However, high-precision (13)C isotopic enrichment can also be measured by liquid chromatography-isotope ratio mass spectrometry (LC-IRMS). Indeed, LC-IRMS can be used, as shown by the new method reported here, to obtain a baseline separation and to measure (13)C isotopic enrichment of underivatised amino acids (Asp, Thr-Ser, Glu, Pro, Gly, Ala, Cys and Val). In case of Val, at natural abundance, the SD(delta(13)C) reported with this method was found to be below 1 per thousand . Another key feature of the new LC-IRMS method reported in this paper is the comparison of the LC-IRMS approach with the conventional GC-C-IRMS determination. To perform this comparative study, isotopic enrichments were measured from underivatised Val and its N(O, S)-ethoxycarbonyl ethyl ester derivative. Between 0.0 and 1.0 molar percent excess (MPE) (delta(13)C= -12.3 to 150.8 per thousand), the calculated root-mean-square (rms) of SD was 0.38 and 0.46 per thousand and the calculated rms of accuracy was 0.023 and 0.005 MPE, respectively, for GC-C-IRMS and LC-IRMS. Both systems measured accurately low isotopic enrichments (0.002 atom percent excess (APE)) with an SD (APE) of 0.0004. To correlate the relative (delta(13)C) and absolute (atom%, APE and MPE) isotopic enrichment of Val measured by the GC-C-IRMS and LC-IRMS devices, mathematical equations showing the slope and intercept of the curves were established and validated with experimental data between 0.0 to 2.3 MPE. Finally, both GC-C-IRMS and LC-IRMS instruments were also used to assess isotopic enrichment of protein-bound (13)C-Val in tibial epiphysis in a tracer study performed in rats. Isotopic enrichments measured by LC-IRMS and GC-C-IRMS were not statistically different (p>0.05). The results of this work indicate that the LC-IRMS was successful for high-precision (13)C isotopic measurements in tracer studies giving (13)C isotopic enrichment similar to the GC-C-IRMS but without the step of GC derivatisation. Therefore, for clinical studies requiring high-precision isotopic measurement, the LC-IRMS is the method of choice to measure the isotopic ratio.