Dioxygen activation at a single copper site: structure, bonding, and mechanism of formation of 1:1 Cu-O2 adducts

To evaluate the fundamental process of O(2) activation at a single copper site that occurs in biological and catalytic systems, a detailed study of O(2) binding to Cu(I) complexes of beta-diketiminate ligands L (L(1) = backbone Me; L(2) = backbone tBu) by X-ray crystallography, X-ray absorption spectroscopy (XAS), cryogenic stopped-flow kinetics, and theoretical calculations was performed. Using synchrotron radiation, an X-ray diffraction data set for L(2)CuO(2) was acquired, which led to structural parameters in close agreement to theoretical predictions. Significant Cu(III)-peroxo character for the complex was corroborated by XAS. On the basis of stopped-flow kinetics data and theoretical calculations for the oxygenation of L(1)Cu(RCN) (R = alkyl, aryl) in THF and THF/RCN mixtures between 193 and 233 K, a dual pathway mechanism is proposed involving (a) rate-determining solvolysis of RCN by THF followed by rapid oxygenation of L(1)Cu(THF) and (b) direct, bimolecular oxygenation of L(1)Cu(RCN) via an associative process.     

Reactivity of a 1:1 copper-oxygen complex: isolation of a Cu(II)-o-iminosemiquinonato species

While a 1:1 Cu-O2 adduct is generally unreactive with organic substrates, phosphines displace O2 via an associative process and added Cu(I) leads to a novel internal ligand oxidation to yield a Cu(II)-o-iminosemiquinone complex.     

Algorithmes mixtes asynchrones. Etude de convergence monotone

Summary In this paper we introduce two classes of iterative algorithms which we call Asynchronous mixed algorithms and we study their convergence under partial ordering. These algorithms can be implemented just as well on monoprocessors as on multiprocessors, and, along with their convergence study, constitute a generalization of the mixed classical Newton-relaxation algorithms.

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Résumé Nous introduisons dans cet article deux classes d'algorithmes itératifs que nous appelons «Algorithmes mixtes asynchrones» et nous en étudierons la convergence selon un ordre partiel. Ces algorithmes sont implémentables aussi bien sur les monoprocesseurs que sur les multiprocesseurs, et avec leur étude de convergence constituent une généralisation des algorithmes mixtes classiques «Newton-relaxation».

     

Synthesis of functionalized thiazoles via attack of heterocyclic nucleophiles on allenyl isothiocyanates

New examples of substituted thiazole derivatives carrying different heterocyclic ring systems at C-2 position were prepared via the reaction of several allenyl isothiocyanates with nucleophiles such as imidazoles, pyrazoles, benzimidazoles, indazole, 1,2,3-triazole, 1,2,4-triazole, and 1H-benzotriazole. Although these allenyl isothiocyanates are very reactive electrophiles and tend to polymerize, the yield of the thiazole products ranked between modest and very good. The regiochemistry of the reactions was proved by NMR and X-ray studies indicating that the attack of ambident nucleophiles proceeded very selectively. In some cases, however, the products were formed as mixtures of aromatic heterocycles and non-aromatic isomers. The latter could be rearranged to yield the uniform aromatic thiazoles.     

Vincamine Modulates the Effect of Pantoprazole in Renal Ischemia/Reperfusion Injury by Attenuating MAPK and Apoptosis Signaling Pathways

Pantoprazole has an antioxidant function against reactive oxygen species (ROS). Vincamine, a herbal candidate, is an indole alkaloid of clinical use against brain sclerosis. The aim of the present experiment is to evaluate, on a molecular level for the first time, the value of vincamine in addition to pantoprazole in treating experimentally induced renal ischemia/reperfusion injury (IRI). One-hundred-and-twenty-eight healthy male Wistar albino rats were included. Serum creatinine, blood urea nitrogen, and malondialdehyde levels were assessed. ELISA was used to estimate the pro-inflammatory cytokines. The expression of Bcl-2 and Bax genes was assessed by quantitative real-time PCR. ERK1/2, JNK1/2, p38, cleaved caspase-3, and NF-κB proteins expressions were estimated using western blot assay. The kidneys were also histopathologically studied. The IRI resulted in impaired cellular functions with increased creatinine, urea nitrogen, malondialdehyde, TNF-α, IL-6, and IL-1β serum levels, and up-regulated NF-ĸB, JNK1/2, ERK1/2, p38, and cleaved caspase-3 proteins. Furthermore, it down-regulated the expression of the Bcl-2 gene and upregulated the Bax gene. The treatment with vincamine, in addition to pantoprazole multiple doses, significantly alleviated the biochemical and histopathological changes more than pantoprazole or vincamine alone, whether the dose is single or multiple, declaring their synergistic effect. In conclusion, vincamine with pantoprazole multiple doses mitigated the renal IRI through the inhibition of apoptosis, attenuation of the extracellular signaling pathways through proinflammatory cytokines’ levels, and suppression of the MAPK (ERK1/2, JNK, p38)–NF-κB intracellular signaling pathway.     

Water‐based inorganic/polymer hybrid particles prepared via a multiple miniemulsion process

A universal method for the synthesis of water‐based inorganic–polymer hybrid particles was developed in which no organic solvent is required. To demonstrate the versatility of this process, zinc phosphate, calcium carbonate, and barium sulfate were chosen as different pigment examples which additionally can be utilized for functional coating applications. Furthermore, a complex polymeric composition based on epoxy–acrylic–styrene was chosen to illustrate the versatility from a soft matter point of view. The overall synthesis process was carried out by coemulsification of two inverse miniemulsions, containing two precursors, surrounded with a polymerizable continuous phase. This was then transferred to a direct miniemulsion by addition to a surfactant solution and subsequent homogenization followed by radical polymerization of the vinylic monomers. To our knowledge, this is the first work where a polymerizable continuous phase has been used in an inverse miniemulsion formation followed by transfer to a direct miniemulsion, followed by polymerization, so that the result is a water‐based dispersion. The resultant dispersion was characterized by dynamic light scattering; the particles were investigated via transmission electron microscopy with in situ determination of crystallinity using electron diffraction. Elemental analysis was also performed for the particles and the polymerized miniemulsions using X‐ray fluorescence and inductively coupled plasma‐optical emission spectroscopy, respectively. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Different Electro-Optical Modulators for High Transmission-Data Rates and Signal-Quality Enhancement

We show how to optimize design parameters for different electro-optical modulators where the effective refractive index plays an essential role in the evaluation of the bandwidth structure. We investigate the effect of operating parameters on the switching, modulating voltage, device performance index, and optical bandwidth for different material-based electro-optical modulators and evaluate the transmission bit rate using nonreturn-to-zero (NRZ) coding transmission technique. As well as lithium niobate (LiNbO3), gallium arsenide (GaAs), and polymethylmethacrylate (PMMA), polymer EOMs have been developed for extensive use in high-speed- and high-transmission-performance optical-fibertransmission systems. This is because they offer the advantages of modulation exceeding multi-Gbit/s combined with a low driving voltage.     

Maximization of repeater spacing in ultrawide-wavelength-division multiplexing optical communication systems based on multipumped laser diodes

We show that the amplifier bandwidth can be further increased and the gain spectrum can be tailored if one uses pumping with multiple laser wavelengths. We consider the wide-gain amplifier where four sets of multipumps are employed. We process two multiplexing techniques in long haul transmission cables where the number of channels is up to 9600 in ultrawide-wavelength-division multiplexing (UWWDM) with employment of the ultrawide-space-division multiplexing (UW-SDM) technique to merge the number of links up to 400 in the optical-fiber core over wide ranges of affecting sets of parameters. As well as the repeater spacing using a multi-pumping Raman amplifier, we investigate N _R pumps in the optical pumping wavelength (from 1.36 to 1.44 μm) to amplify optical channels where the optical wavelength range (1.45–1.65 μm) satisfies near infrared optical transmission region.     

Operation performance characteristics of vertical-cavity surface-emitting lasers (VCSELs) under high thermal neutron irradiated fields

To operate and read out even the innermost detectors under any particular conditions, electronics and optical components must be developed accordingly. For semiconductor lasers, on which we will concentrate here, it has been found that an inner temperature increase has a direct impact on the light power emitted by the device. It was found that the effects of radiation on the behavior of semiconductor lasers are convolved with those of temperature. An optimized coupling to the cooling of the laser device reduces the thermal effects in the material. Therefore, a test stand to qualify the effect of heat in the device and the adoption of the heat sink is realized. In this paper, we create a model describing the degradation of the light power and voltage characteristic of a semiconductor-laser undergoing irradiation where the high temperature effects are taken into account. This VCSEL-device model can be used to predict the behavior and operation-performance characteristics (rise time, 3 dB bandwidth, light power, resonance frequency, and transmission bit rate) of a laser being irradiated with different neutron doses. We check the robustness of the model against the high fluence (in excess of 10¹⁵ neutrons/cm²). We take into account the study of different semiconductor- and polymeric material-based VCSEL devices such as aluminum gallium arsenide (AlGaAs), indium gallium arsenide phosphors (InGaAsP), and polymeric polymethylmethacrylate (PMMA) under the same operating conditions.     

Steroidal glycoalkaloids from the berries of Solanum distichum

Two steroidal glycoalkaloids, Solanidine 3-O-[alpha-L-rhamnopyranosyl-(1' --> 4)-[alpha-L-rhamnopyranosyl-(1' --> 2)]-beta-D-glucopyranoside] (1) and Solanidine 3-O-[alpha-L-rhamnopyranosyl-(1' --> 4)-beta-D-glucopyranoside] (2) commonly known as alpha-chanonine and beta 2-chanonine, were isolated from the berries of Solanum distichum. The structures of the isolated compounds were studied by 1D and 2D NMR techniques and FAB MS analysis. The 13C NMR signal assignments and direct elucidation of the glycoside linkages were established. Glycoalkaloids level in the dried berries, determined by a simple colorimetric method, was found to be 5.08 +/- 0.18 g%.