Synthesis of naturally occurring diene and trienes by Te/Li exchange on (1Z,3Z)-butyltelluro-4-methoxy-1,3-butadiene

(1Z,3Z)-Butyltelluro-o-4-methoxy-1,3-butadiene 2 was obtained by the hydrotelluration of(Z)-1-methoxy-but-1-en-3-ynes 1. The butadienyllithium 3 obtained by the Te/Li exchange reaction in the (1Z,3Z)-1-butyltelluro-4-methoxy-1.3-butadiene 2 reacted with aldehydes to form the corresponding alcohols 4a-d with total retention of configuration. The alcohols formed undergo hydrolysis, resulting in the alpha,beta,gamma,delta-unsaturated aldehydes of (E,E) configuration, which are precursors of trienes obtained from natural sources. The products of this reaction were employed in the synthesis of methyl-(2E,4E)-decadienoate 7, which is a component of the flavor principles of ripe Bartlett pears. Performing the Wittig reaction of the methyl triphenylphosphorane with the deca-(2E,4E)-dienal 5a, we were able to synthesize the undeca-(1,3E,5E)-triene 6a. This compound is a sex-pheromone component of the marine brown algae Fucus serratus, Dictyopteris plagiograma, and Dictyopteris australis. Performing the Wittig reaction of methyl triphenylphosphorane with the octa-(2E,4E)-dienal 5c, the nona-(1,3E,5E)-triene 6b was synthesized. The compound obtained is a sex-pheromone component of the marine brown alga Sargassum horneri. The octa-( 1,3E,5E)-triene 6c was easily obtained from hepta-(2E,4E)-dienal 5d by the Wittig reaction with methyl triphenylphophorane. This compound is a sex-pheromone component of the marine brown alga Fucus serratus. (C) 2010 Elsevier Ltd. All rights reserved.

Modeling volatile organic compounds (voc`s) adsorption onto cup-stacked carbon nanotubes (cscnt) using the linear driving force model

Modeling volatile organic compounds (voc`s) adsorption onto cup-stacked carbon nanotubes (cscnt) using the linear driving force model. Volatile organic compounds (VOC`s) are an important category of air pollutants and adsorption has been employed in the treatment (or simply concentration) of these compounds. The current study used an ordinary analytical methodology to evaluate the properties of a cup-stacked nanotube (CSCNT), a stacking morphology of truncated conical graphene, with large amounts of open edges on the outer surface and empty central channels. This work used a Carbotrap bearing a cup-stacked structure (composite); for comparison, Carbotrap was used as reference (without the nanotube). The retention and saturation capacities of both adsorbents to each concentration used (1, 5, 20 and 35 ppm of toluene and phenol) were evaluated. The composite performance was greater than Carbotrap; the saturation capacities for the composite was 67% higher than Carbotrap (average values). The Langmuir isotherm model was used to fit equilibrium data for both adsorbents, and a linear driving force model (LDF) was used to quantify intraparticle adsorption kinetics. LDF was suitable to describe the curves.

Jacobsen catalyst immobilized on chitosan membrane as interface catalyst in organic/aqueous system for alkene oxidation

The Jacobsen catalyst, Mn(salen), was immobilized in chitosan membrane. The obtained Mn(salen)-Chit was characterized by thermogravimetric analysis (TC), differential thermal analysis (DTA), differential scanning calorimetry (DSC), infrared spectroscopy (FT-IR), degree of N-acetylation by (1)H NMR, and UV-vis spectroscopy. The UV-vis absorption spectrum of the encapsulated catalyst displayed the typical bands of the Jacobsen catalyst, and the FT-IR presented an absorption band characteristic of the imines present in the Jacobsen catalyst. The chitosan membranes were available, in a biphasic system, as a catalytic barrier between two different phases: an organic substrate phase (cyclooctene or styrene) and an aqueous solution of either m-CPBA, t-BuOOH or H(2)O(2), and dismissing the need for phase transfer agents and leading to better product yields compared with the catalyst in homogeneous medium. This new catalyst did not leach from the support and was reused many times, leading to high turnover frequencies. (C) 2009 Elsevier B.V. All rights reserved.

Interfacial interactions and structure of organic-inorganic nanohybrids

Understanding the interfacial interactions and structure is important to better design and application of organic-inorganic nanohybrids. This paper presents our recent molecular dynamic studies on organoclays and polymer nanocomposites, including the layering behavior of organoclays, structural and dynamic properties of dioctadecyldimethyl ammoniums in organoclays, and interfacial interactions and structure of polyurethane nanocomposites. The results demonstrate that the layering behaviors of organoclays are closely related to the chain length of quaternary alkyl ammoniums and cation exchangeable capacity of clays. In addition to typical layered structures such as monolayer, bilayer and pseudo-trilayer, a pseudo-quadrilayer structure was also observed in organoclays modified with dioctadecyldimethyl ammoniums (DODDMA). In such a structure, alkyl chains do not lie flat within a single layer but interlace, and also jump to the next layer or even the next nearest layer. Moreover, the diffusion constants of nitrogen and methylene atoms increase with the temperature and methelene towards the tail groups. For polyurethane nanocomposite, the van der Waals interaction between apolar alkyl chains and soft segments of polyurethane predominates the interactions between organoclay and polyurethane. Different from most bulk polyurethane systems, there is no distinct phase-separated structure for the polyurethane.

Magnetic field effects on the conductivity of organic bipolar and unipolar devices at room temperature

Magnetic field effects on the conductivity of different types of organic devices: undoped and dye doped aluminium (III) 8-hydroxyquinoline (Alq(3))-based organic light emitting diodes (OLEDs), electron-only Alq(3)-based diodes, and a hole-only N,N`-diphenyl-N,N`-bis(1-naphthyl)1,1`-biphenyl-4,4`-diamine (alpha-NPD)-based diode were studied at room temperature. Only negative magnetoresistance (MR) was observed for the Alq(3)-based devices. The addition of a rubrene dye in Alq(3)-based OLEDs quenches the MR by a factor of 5. The alpha-NPD hole-only device showed only positive MR. Our results are discussed with respect to the actual models for MR in organic semiconductors. Our results are in good agreement with the bipolaron model. (C) 2009 Elsevier B.V. All rights reserved.

Luminescent Langmuir-Blodgett film of a new amphiphilic Eu(3+) beta-diketonate

This work reports on the synthesis and characterization of the ligand 3-hexadecylpentane-2,4-drone (Hhdacac) and its Eu(3+) complexes Eu(hdacac)(6) center dot 2H(2)O, Eu(hdacac)(6) center dot phen and Eu(hdacac)(6) center dot tta, where phen and tta denote 1,10-phenanthroline and thenoyltrifluoroacetone, respectively. These new compounds present long carbon chains and their expected miscibility into non-polar ambients is confirmed by the emission spectra of Eu(hdacac)6 center dot tta in hexane. Moreover, the amphiphilic properties of Eu(hdacac)6 complexes allow the obtainment of thin luminescent films by the Langmuir-Blodgett technique. In both cases (solids and films), the typical antenna effect of beta-diketonates is observed. The alluring characteristics of these compounds raise great interest in many fields of Materials Science, like photo- and electro-luminescent materials (mainly thin ""organic"" films), metal catalysts or probes in non-polar solutions, and Langmuir-Blodgett films of several compositions. For the characterization of these products, nuclear magnetic resonance spectroscopy ((1)H NMR), thermogravimetric analysis, elementary analyses (C, H), scanning electron microscopy (energy dispersive X-ray spectroscopy), absorption (UV-vis/FT-IR) and photoluminescence spectroscopies were used. (c) 2008 Elsevier B.V. All rights reserved.

Ferromagnetism, paramagnetism, and a Curie-Weiss metal in an electron-doped Hubbard model on a triangular lattice

Motivated by the unconventional properties and rich phase diagram of NaxCoO2 we consider the electronic and magnetic properties of a two-dimensional Hubbard model on an isotropic triangular lattice doped with electrons away from half-filling. Dynamical mean-field theory (DMFT) calculations predict that for negative intersite hopping amplitudes (t < 0) and an on-site Coulomb repulsion, U, comparable to the bandwidth, the system displays properties typical of a weakly correlated metal. In contrast, for t > 0 a large enhancement of the effective mass, itinerant ferromagnetism, and a metallic phase with a Curie-Weiss magnetic susceptibility are found in a broad electron doping range. The different behavior encountered is a consequence of the larger noninteracting density of states (DOS) at the Fermi level for t > 0 than for t < 0, which effectively enhances the mass and the scattering amplitude of the quasiparticles. The shape of the DOS is crucial for the occurrence of ferromagnetism as for t > 0 the energy cost of polarizing the system is much smaller than for t < 0. Our observation of Nagaoka ferromagnetism is consistent with the A-type antiferromagnetism (i.e., ferromagnetic layers stacked antiferromagnetically) observed in neutron scattering experiments on NaxCoO2. The transport and magnetic properties measured in NaxCoO2 are consistent with DMFT predictions of a metal close to the Mott insulator and we discuss the role of Na ordering in driving the system towards the Mott transition. We propose that the Curie-Weiss metal phase observed in NaxCoO2 is a consequence of the crossover from a bad metal with incoherent quasiparticles at temperatures T > T-* and Fermi liquid behavior with enhanced parameters below T-*, where T-* is a low energy coherence scale induced by strong local Coulomb electron correlations. Our analysis also shows that the one band Hubbard model on a triangular lattice is not enough to describe the unusual properties of NaxCoO2 and is used to identify the simplest relevant model that captures the essential physics in NaxCoO2. We propose a model which allows for the Na ordering phenomena observed in the system which, we propose, drives the system close to the Mott insulating phase even at large dopings.

Improved VDC casting of aluminium alloys through an understanding of the surface properties of the molten metal

Vertical direct chill (VDC) casting of aluminium alloys is a mature process that has evolved over many decades through gradual change to both equipment design and casting practice. Today, air-pressurised, continuous lubrication, hot top mould systems with advanced station automation are selected as the process of choice for producing extrusion billet. Specific sets of operating parameters are employed on these stations for each alloy and size combination to produce optimal billet quality. The designs and parameters are largely derived from past experience and accumulated know-how. Recent experimental work at the University of Queensland has concentrated on understanding the way in which the surface properties of liquid aluminium alloys, e.g., surface tension, wetting angle and oxide skin strength, influence the size and shape of the naturally-stab le meniscus for a given alloy, temperature and atmosphere. The wide range of alloy-and condition-dependent values measured has led to the consideration of how these properties impact the stability of the enforced molten metal meniscus within the hot top mould cavity. The actual shape and position of the enforced meniscus is controlled by parameters such as the upstream conduction distance (UCD) from sub-mould cooling and the molten metal head. The degree of deviation of this actual meniscus from the predicted stable meniscus is considered to be a key driver in surface defect formation. This paper reports on liquid alloy property results and proposes how this knowledge might be used to better design VDC mould systems and casting practices.

A quantitative coronary angiography-matched comparison between a prospective randomised multicentre cutting balloon angioplasty and bare metal stent trial (REDUCE III) and the Rapamycin-Eluting Stent Evaluation At Rotterdam Cardiology Hospital (RESEARCH) study

Aims: There remains significant concern about the long-term safety of drug-eluting stents (DES). However, bare metal stents (BMS) have been used safely for over two decades. There is therefore a pressing need to explore alternative strategies for reducing restenosis with BMS. This study was designed to examine whether IVUS-guided cutting balloon angioplasty (CBA) with BMS could convey similar restenosis rates to DES. Methods and results: In the randomised REstenosis reDUction by Cutting balloon angioplasty Evaluation (REDUCE III) study, 521 patients were divided into four groups based on device and IVUS use before BMS (IVUS-CBA-BMS: 137 patients; Angio-CBA-BMS: 123; IVUS-BA-BMS: 142; and Angio-BA-BMS: 119). At follow-up, the IVUS-CBA-BMS group had a significantly lower restenosis rate (6.6%) than the other groups (p=0.016). We performed a quantitative coronary angiography (QCA) based matched comparison between an IVUS-guided CBA-BMS strategy (REDUCE III) and a DES strategy (Rapamycin-Eluting-Stent Evaluation At Rotterdam Cardiology. Hospital, the RESEARCH study). We matched the presence of diabetes, vessel size, and lesion severity by QCA. Restenosis (>50% diameter stenosis at follow-up) and target vessel revascularisation (TVR) were examined. QCA-matched comparison resulted in 120-paired lesions. While acute gain was significantly greater in IVUS-CBA-BMS than DES (1.65 +/- 0.41 mm vs. 1.28 +/- 0.57 mm, p=0.001), late loss was significantly less with DES than with IVUS-CBA-BMS (0.03 +/- 0.42 mm vs. 0.80 +/- 0.47 mm, p=0.001). However, no difference was found in restenosis rates (IVUS-CBA-BMS: 6.6% vs. DES: 5.0%, p=0.582) and TVR (6.6% and 6.6%, respectively). Conclusions: An IVUS-guided CBA-BMS strategy yielded restenosis rates similar to those achieved by DES and provided an effective alternative to the use of DES.

Finite element analysis of mechanical properties in discontinuously reinforced metal matrix composites with ultrafine microstructure

This investigation focused on the finite element analyses of elastic and plastic properties of aluminium/alumina composite materials with ultrafine microstructure. The commonly used unit cell model was used to predict the elastic properties. By combining the unit cell model with an indentation model, coupled with experimental indentation measurements, the plastic properties of the composites and the associated strengthening mechanism within the metal matrix material were investigated. The grain size of the matrix material was found to be an important factor influencing the mechanical properties of the composites studied. (C) 1997 Elsevier Science S.A.

Major histocompatibility complex (MHC) class II-positive dendritic cells in the rat iris - In situ development from MHC class II-negative precursors

Purpose. To examine the postnatal development of major histocompatibility complex (MHC) class II-positive dendritic cells (DC) in the iris of the normal rat eye. Methods. Single-and double-color immunomorphologic studies were performed on whole mounts prepared from rat iris taken at selected postnatal ages (2 to 3 days to 78 weeks). Immunopositive cells were enumerated, using a quantitative light microscope, and MHC class II expression on individual cells was assessed by microdensitometric analysis. Results. Major histocompatibility class II-positive DCs in the iris developed in an age-dependent manner and reached adult-equivalent density and structure at approximately 10 weeks of age, considerably later than previously described in other DC populations in the rat. In contrast, the anti-rat DC monoclonal antibody OX62 revealed a population of cells present at adult-equivalent levels as early as 3 weeks after birth. Dual-color immunostaining and microdensitometric analysis demonstrated that during postnatal growth, development of the network of MHC class II-positive DCs was a consequence of the progressive increase in expression of MHC class II antigen by OX62-positive cells. Conclusions. During postnatal growth, the DC population of the iris develops initially as an OX62-positive-MHC class II-negative population, which then develops increasing MHC class II expression in situ and finally resembles classic DC populations in other tissue sites. Maturation of the iris DC population is temporally delayed compared with time to maturation in other tissue sites in the rat.

Effects of oxide promoters on metal dispersion and metal-support interactions in Ni catalysts supported on activated carbon

Various oxide-promoted Ni catalysts supported on activated carbon were prepared, and the effect of promoters on the surface structure and properties of Ni catalysts was studied. Physical adsorption (Na adsorption), thermogravimetric analysis (TGA), temperature-programmed desorption (TPD), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used to characterize the catalysts. It is found that nickel is fairly uniformly distributed in the pores of the carbon support. Addition of promoters produces a more homogeneous distribution of nickel ion in carbon. However, distributions of promoters in the pores are varying. Addition of promoters increases the dispersion of nickel in carbon. Promoters also change the interaction between the carbon and Ni, resulting in significantly different behaviors of catalysts under various environments. CaO and MgO promoters improve the reactivity of nickel catalysts with O-2 but retard the interaction between nickel oxide and carbon. La2O3 shows some inhibiting effect on the interactions between nickel oxide and oxygen as well as carbon.