A new oxovanadium(IV)-cucurbit[6]uril complex: Properties and potential for confined heterogeneous catalytic oxidation reactions

This work presents a new oxovanadium(IV)-cucurbit[6]uril complex, which combines the catalytic properties of the metal ion with the size-excluding properties of the macrocycle cavity. In this coordination compound, the VO(2-) ions are coordinated to the oxygen atoms located at the rim of the macrocycle in slightly distorted square-pyramidal configurations, which are in fact C(2v) symmetries. This combination results in a size-selective heterogeneous catalyst, which is able to oxidize linear alkanes like n-pentane at room temperature, but not styrene, cyclohexane or z-cyclooctene, which are too big to enter the cucurbit[6]uril cavity. The results presented here contribute to understanding the mechanism of alkane catalytic oxidation by oxovanadium(IV) complexes. (C) 2010 Elsevier Ltd. All rights reserved.

One-pot synthesis of mixed (Z)-1,2-bis(organylchalcogene)-1-alkenes precursors of the novel beta-organylthio vinyllithium intermediates

One-pot hydrochalcogenation of 1-phenylthioacetylenes using organylselenolate and organyltellurolate anions generated by the insertions of selenium and tellurium in n-organyl lithium produced (Z)-1,2-bis(organylchalcogene)-1-alkenes. The chemical reactivity of these mixed 1,2-bis(organylchalcogene)-1-alkenes was studied by Te/Li and Se/Li stereoretentive exchanges carried out with n-butyl lithium, furnishing the new intermediate species (Z)-beta-organylthio vinyllithium anions, which were trapped with aldehydes, to give the (Z)-3-hydroxy vinyl thioethers with total control of the regio- and stereochemistry. (c) 2010 Elsevier Ltd. All rights reserved.

Electrochemical oxidation of synthetic tannery wastewater in chloride-free aqueous media

The electrochemical treatment of a synthetic tannery wastewater, prepared with several compounds used by finishing tanneries, was studied in chloride-free media. Boron-doped diamond (Si/BDD), antimony-doped tin dioxide (Ti/SnO(2)-Sb), and iridium-antimony-doped tin dioxide (Ti/SnO(2)-Sb-Ir)were evaluated as anode. The influence of pH and current density on the treatment was assessed by means of the parameters used to measure the level of organic contaminants in the wastewater; i.e., total phenols, chemical oxygen demand (COD), total organic carbon (TOC), and absorbance. Results showed that faster decrease in these parameters occurred when the Si/BDD anode was used. Good results were obtained with the Ti/SnO(2)-Sb anode, but its complete deactivation was reached after 4h of electrolysis at 25 mA cm(-2), indicating that the service life of this electrode is short. The Ti/SnO(2)-Sb-Ir anode is chemically and electrochemically more stable than the Ti/SnO(2)-Sb anode, but it is not suitable for the electrochemical treatment under the studied conditions. No significant changes were observed for electrolyses performed at different pH conditions with Si/BDD, and this electrode led to almost complete mineralization after 4 h of electrolysis at 100mAcm(-2). The increase in current density resulted in faster wastewater oxidation, with lower current efficiency and higher energy consumption. Si/BBD proved to be the best electrodic material for the direct electrooxidation of tannery wastewaters. (C) 2010 Elsevier B.V. All rights reserved.

Characterization and voltammetric behavior of Pt(y)Mo(z)O(x)/C electrodes prepared by the thermal decomposition of polymeric precursors

Carbon-supported catalysts containing platinum and molybdenum oxide are prepared by thermal decomposition of polymeric precursors. The Pt(y)Mo(z)O(x)/C materials are characterized by energy dispersive X-ray spectroscopy, transmission electron microscopy, and X-ray diffraction. The catalysts present a well-controlled stoichiometry and nanometric particles. Molybdenum is present mainly as the MoO(3) orthorhombic structure, and no Pt alloys are detected. The voltammetric behavior of the electrodes is investigated; a correlation with literature results for PtMo/C catalysts prepared by other methods is established. The formation of soluble species and the aging effect are discussed. (C) 2009 Elsevier B.V. All rights reserved.

Biomimetic Oxidation of Piperine and Piplartine Catalyzed by Iron(III) and Manganese(III) Porphyrins

Synthetic metalloporphyrins, in the presence of monooxygen donors, are known to mimetize various reactions of cytochrome P450 enzymes systems in the oxidation of drugs and natural products. The oxidation of piperine and piplartine by iodosylbenzene using iron(III) and manganese(III) porphyrins yielded mono- and dihydroxylated products, respectively. Piplartine showed to be a more reactive substrate towards the catalysts tested. The structures of the oxidation products were proposed based on electrospray ionization tandem mass spectrometry.

Tetra-crowned porphyrin as P450 biomimetic model for carbamazepine oxidation

A substituted porphyrin bearing four crown ether units, H(2)(TCP), was synthesized from the reaction between (5,10,15,20-tetra(o-aminophenyl) porphyrin) and the acyl derivative of the ether (4-carboxy-18-crown-6). The free-base porphyrin was characterized by C, N, and H elemental analysis; UV-vis and IR spectroscopies; and (1)H NMR. The corresponding ironporphyrin, Fe(TCP)Cl, was obtained via iron insertion into H(2)(TCP). Fe(TCP)Cl was employed as catalyst for carbamazepine (CBZ) oxidation by iodosylbenzene (PhIO), 3-chloroperoxybenzoic acid (m-CPBA) or sodium hypochlorite (NaOCl), in methanol or in a biphasic water/dichloroethane system. The crowned ironporphyrin proved to be a highly efficient and selective catalyst for CBZ epoxidation even in the biphasic dichloroethane /H(2)O system, with no need for an additional phase transfer agent.

Electrochemical oxidation of acid black 210 dye on the boron-doped diamond electrode in the presence of phosphate ions: Effect of current density, pH, and chloride ions

The electrochemical oxidation of acid black 210 dye (AB-210) on the boron-doped diamond (BDD) was investigated under different pH conditions. The best performance for the AB-210 oxidation occurred in alkaline phosphate solution. This is probably due to oxidizing agents such as phosphate radicals and peroxodiphosphate ions, which can be electrochemically produced with good yields on the BDD anode, mainly in alkaline solution. Under this condition, the COD (chemical oxygen demand) removal was higher than that obtained from the model proposed by Comninellis. Electrolyses performed in phosphate buffer and in the presence of chloride ions resulted in faster COD and color removals in acid and neutral solutions, but in alkaline phosphate solution, a better performance in terms of TOC removal was obtained in the absence of chloride. Moreover, organochloride compounds were detected in all electrolyses performed in the presence of chloride. The AB-210 electrooxidation on BDD using phosphate as supporting electrolyte proved to be interesting since oxidizing species generated from phosphate ions were able to completely degrade the dye without producing organochloride compounds. (C) 2009 Elsevier Ltd. All rights reserved.

Signature of mott-insulator transition with ultracold fermions in a one-dimensional optical lattice

Using the exact Bethe ansatz solution of the Hubbard model and Luttinger liquid theory, we investigate the density profiles and collective modes of one-dimensional ultracold fermions confined in an optical lattice with a harmonic trapping potential. We determine a generic phase diagram in terms of a characteristic filling factor and a dimensionless coupling constant. The collective oscillations of the atomic mass density, a technique that is commonly used in experiments, provide a signature of the quantum phase transition from the metallic phase to the Mott-insulator phase. A detailed experimental implementation is proposed.

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.

Activity of the medial prefrontal cortex and amygdala underlies one-trial tolerance of rats in the elevated plus-maze

The anxiolytic effects of benzodiazepines are reduced after a single exposure of rats to elevated plus-maze test (EPM). Midazolam showed an anxioselective profile in animals submitted to one session (T1) but did not change the usual exploratory behavior of rats exposed twice (T2) to the EPM. In this study we examined further the one-trial tolerance by performing a factor analysis of the exploratory behavior of rats injected with saline before both trials as well as an immunohistochemistry study for quantification of Fos expression in encephalic structures after these sessions. Factor analysis of all behavioral categories revealed that factor I consisted of anxiety-related categories in T1 whereas these same behavioral categories loaded on factor 2 in T2. Risk assessment was also dissociated as it loaded stronger on T2 (factor 3) than on T1 (factor 4). Locomotor activity in T1 loaded on factor 5. Immunohistochemistry analyses showed that Fos expression predominated in limbic structures in T1 group. The medial prefrontal cortex and amygdala were the main areas activated in T2 group. These data suggest that anxiety and risk assessment behaviors change their valence across the EPM sessions. T2 is characterized by the emergence of a fear factor, more powerful risk assessment and medial prefrontal cortex activation. The amygdala functions as a switch between the anxiety-like patterns of T1 to the cognitive control of fear prevalent in T2. The EPM retest session is proposed as a tool for assessing the cognitive activity of rodents in the control of fear. (c) 2007 Elsevier B.V. All rights reserved.

Finite-temperature correlations and density profiles of an inhomogeneous interacting one-dimensional Bose gas

We calculate the density profiles and density correlation functions of the one-dimensional Bose gas in a harmonic trap, using the exact finite-temperature solutions for the uniform case, and applying a local density approximation. The results are valid for a trapping potential that is slowly varying relative to a correlation length. They allow a direct experimental test of the transition from the weak-coupling Gross-Pitaevskii regime to the strong-coupling, fermionic Tonks-Girardeau regime. We also calculate the average two-particle correlation which characterizes the bulk properties of the sample, and find that it can be well approximated by the value of the local pair correlation in the trap center.

Amphiphilic cerium(III) beta-diketonate as a catalyst for reducing diesel/biodiesel soot emissions

This work reports on the synthesis, characterization and applications of the new cerium(III) beta-diketonate Ce(hdacac)(3)(Hhdacac)(3)center dot 2H(2)O (where hdacac and Hhdacac denote, respectively, the hexadecylpentane-2,4-dionate and hexadecylpentane-2,4-dione ligands) as catalyst for the reduction of automotive emissions. Due to its amphiphilic character, this complex can be solubilized in non-polar fuels, thus generating cerium(IV) oxide particles, which efficiently catalyze the oxidation of diesel/biodiesel soot. The synthesized complex was characterized by microanalysis (C, H), thermal analysis, and infrared spectroscopy. Scanning electron microscopy, X-ray diffractometry, and specific surface area measurements attested that the complex can act as a soluble precursor of homogeneous CeO(2) spherical nanoparticles. The efficiency of this compound as catalyst for the reduction of soot emission was evaluated through static studies (comprising carbon black oxidation), which confirmed that increasing concentrations of the complex result in lower carbon black oxidation temperatures and lower activation Gibbs free energies. Dynamic studies, which embraced the combustion of diesel/biodiesel blends containing different amounts of the solubilized complex in a stationary motor, allowed a comparative evaluation of the soot emission through diffuse reflectance spectroscopy. These analyses provided very emphatic evidences of the efficiency of this new cerium complex for the control of soot emission in diesel/biodiesel motors. (c) 2009 Published by Elsevier B.V.

Thoracic aorta calcification detected by electron beam tomography predicts all-cause mortality

Background: The presence of coronary artery calcium (CAC) is an independent marker of increased risk of cardiovascular disease (CVD) events and mortality. However, the predictive value of thoracic aorta calcification (TAC), which can be additionally identified without further scanning during assessment of CAC, is unknown. Methods: We followed a cohort of 8401 asymptomatic individuals (mean age: 53 +/- 10 years, 69% men) undergoing cardiac risk factor evaluation and TAC and CAC testing with electron beam computed tomography. Multivariable Cox proportional hazards models were developed to predict all-cause mortality based on the presence of TAC. Results: During a median follow-up period of 5 years, 124 (1.5%) deaths were observed. Overall survival was 96.9% and 98.9% for those with and without detectable TAC, respectively (p < 0.0001). Compared to those with no TAC, the hazard ratio for mortality in the presence of TAC was 3.25 (95% CI: 2.28-4.65, p < 0.0001) in unadjusted analysis. After adjusting for age, gender, hypertension, dyslipidemia, diabetes mellitus, smoking and family history of premature coronary artery disease, and presence of CAC the relationship remained robust (HR 1.61, 95% CI: 1.10-2.27, p = 0.015). Likelihood ratio chi(2) statistics demonstrated that the addition of TAC contributed significantly in predicting mortality to traditional risk factors alone (chi(2) = 13.62, p = 0.002) as well as risk factors + CAC (chi(2) = 5.84, p = 0.02) models. Conclusion: In conclusion, the presence of TAC was associated with all-cause mortality in our study; this relationship was independent of conventional CVD risk factors as well as the presence of CAC. (C) 2009 Elsevier Ireland Ltd. All rights reserved.

Molecular orbital calculations of two-electron states for P-donor solid-state spin qubits

We theoretically study the Hilbert space structure of two neighboring P-donor electrons in silicon-based quantum computer architectures. To use electron spins as qubits, a crucial condition is the isolation of the electron spins from their environment, including the electronic orbital degrees of freedom. We provide detailed electronic structure calculations of both the single donor electron wave function and the two-electron pair wave function. We adopted a molecular orbital method for the two-electron problem, forming a basis with the calculated single donor electron orbitals. Our two-electron basis contains many singlet and triplet orbital excited states, in addition to the two simple ground state singlet and triplet orbitals usually used in the Heitler-London approximation to describe the two-electron donor pair wave function. We determined the excitation spectrum of the two-donor system, and study its dependence on strain, lattice position, and interdonor separation. This allows us to determine how isolated the ground state singlet and triplet orbitals are from the rest of the excited state Hilbert space. In addition to calculating the energy spectrum, we are also able to evaluate the exchange coupling between the two donor electrons, and the double occupancy probability that both electrons will reside on the same P donor. These two quantities are very important for logical operations in solid-state quantum computing devices, as a large exchange coupling achieves faster gating times, while the magnitude of the double occupancy probability can affect the error rate.

Combined Laser and Intravitreal Triamcinolone for Proliferative Diabetic Retinopathy and Macular Edema: One-year Results of a Randomized Clinical Trial

PURPOSE: To evaluate laser combined with intravitreal triamcinolone acetonide (IVTA) for the management of patients with proliferative diabetic retinopathy (PDR) and clinically significant macular edema (CSME). DESIGN: Randomized clinical trial. METHODS: SETTINGS: Single center. STUDY POPULATION: Twenty-two patients with bilateral treatment,naive moderate PDR and CSME. INTERVENTION: Laser (panretinal and macular) photocoagulation was performed in each eye, followed by IVTA in one randomly assigned eye. Best,corrected visual acuity (BCVA), fundus photography, and optical coherence tomography were performed at baseline and at months 1, 3, 6, 9, and 12. MAIN OUTCOME MEASURES:. Changes in BCVA, central macular thickness (CMT), and total macular volume (TMV). RESULTS: The mean logarithm of the minimal angle of resolution (logMAR) BCVA improved significantly, and mean CMT and TMV were significantly reduced in the IVTA group compared with the laser,only group (controls) at all study follow-up visits (P < .001). The mean logMAR BCVA (Snellen equivalent) was 0.44 (20/50(-2)) for the IVTA group and 0.38 (20/50(+1)) for the controls at baseline, and 0.12 (20/25(-1)) for the IVTA group and 0.32 (20/40(-1)) for the controls at 12 months (P < .001.). The mean CMT and TMV were, respectively, 360 mu m and 8.59 mm(3) for the IVTA group and 331 mu m and 8.44 mm(3) for the controls at baseline, and 236 mu m and 7.32 mm(3) for the IVTA group and 266 mu m and 7.78 mm(3) for the controls at 12 months (P < .001). CONCLUSIONS: The combination of laser photocoagulation with IVTA was associated with improved BCVA and decreased CMT and TMV when compared with laser photocoagulation alone for the treatment of moderate PDR with CSME. (Am J Ophthalmol 2009;147:291-297. (C) 2009 by Elsevier Inc. All rights reserved.)