Steam reforming of ethanol over bimetallic RhPt/La2O3: Long-term stability under favorable reaction conditions

Recently, the steam reforming of biofuels has been presented as a potential hydrogen source for fuel cells. Because this scenario represents an interesting opportunity for Colombia (South America), which produces large amounts of bioethanol, the steam reforming of ethanol was studied over a bimetallic RhPt/La2O3 catalyst under bulk mass transfer conditions. The effect of temperature and the initial concentrations of ethanol and water were evaluated at space velocities above 55,000 h−1 to determine the conditions that maximize the H2/CO ratio and reduce CH4 production while maintaining 100% conversion of ethanol. These requirements were accomplished when 21 mol% H2O and 3 mol% C2H5OH (steam/ethanol molar ratio = 7) were reacted at 600 °C. The catalyst stability was assessed under these reaction conditions during 120 h on stream, obtaining ethanol conversions above 99% during the entire test. The effect of both H2 and air flows as catalyst regeneration treatments were evaluated after 44 and 67 h on stream, respectively. The results showed that H2 treatment accelerated catalyst deactivation, and air regeneration increased both the catalyst stability and the H2 selectivity while decreasing CH4 generation. Fresh and spent catalyst samples were characterized by TEM/EDX, XPS, TPR, and TGA. Although the Rh and Pt in the fresh catalyst were completely reduced, the spent samples showed a partial oxidation of Rh and small amounts of carbonaceous residue. A possible Rh–Pt–Rh2O3 structure was proposed as the active site on the catalyst, which was regenerated by air treatment.

Non-covalent immobilization of RhDuphos on carbon nanotubes and carbon xerogels

The immobilization of the chiral complex RhDuphos, by electrostatic or π–π (adsorption) interactions, on carbon nanotubes and carbon xerogels is investigated. To promote such interactions, the supports were either oxidized or heat treated to create carboxylic type surface groups or an apolar surface, respectively. The catalysts were tested in the hydrogenation of methyl 2-acetamidoacrylate. The prepared hybrid catalysts are less active than the homogeneous RhDuphos, but most of them show a high enantioselectivity and the one prepared with the oxidized carbon xerogel is also reusable, being able to give a high substrate conversion, keeping as well a high enantioselectivity. The anchorage by electrostatic interactions is more interesting than the anchorage by π–π interactions, as the π–π adsorption method produces a modification of the metal complex structure leading to an active hybrid catalyst but without enantioselectivity. The creation of carboxylic groups on the support surface has led to some hindering of the complex leaching.

Prosperi Alpini... De praesagienda vita & morte aegrotantium, libri septem. In quibus ars tota Hippocratica praedicendi in aegrotis varios morborum eventus, cum ex veterum medicorum dogmatis, tum ex longa accurataque observatione, nova methodo elucescit.

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Asymmetric Bragg mirrors for the reduction of emission wavelength dependence on the viewing angle in organic microcavity light emitting diodes

Organic microcavity light emitting diodes typically exhibit a blue shift of the emitting wavelength with increasing viewing angle. While the wavelength shift can be reduced with the appropriate choice of organic materials and metal mirrors, for further reduction of the emission wavelength shift it is necessary to consider a mirror whose phase shift can partly compensate the effect of the change of optical path within the cavity. In this work, we used a genetic algorithm (GA) to design an asymmetric Bragg mirror in order to minimize the emission wavelength shift with viewing angle. Based on simulation results, the use of asymmetric Bragg mirrors represents a promising way to reduce the emission wavelength shift. Detailed comparison between GA optimized and conventional Bragg mirrors in terms of resonant wavelength dependence on the viewing angle, spectral narrowing, and brightness enhancement is given. (C) 2004 Elsevier B.V. All rights reserved.

The synthesis of a ferromagnetic polymer

The aim of this study was to prepare a ferromagnetic polymer using the design elements of molecular magnets. This involved the preparation of co-polyradicals of phenylacetylenes bearing nitronyl nitroxides and nitro/cyano groups. The magnetic properties of the materials were determined using a SQUID magnetometer. A novel rhodium catalyst, Rh(NBD)(NH3)Cl, was prepared in order to obtain good yields of polymerisation. A wide range of substituted phenylacetylenes were first homopolymerised in order to assess the efficiency of the catalyst. Yields were generally high, between 75% and 98%, and the time of polymerisation was short (one hour). SEC analysis revealed that the Mw of the polymers were in the range of 200,000 and 250,000. The discovery that phenylboronic acid acts a co-catalyst for the polymerisation served to increase the yields by 10% to 20% but the Mw of the polymers was reduced to approximately 100,000. Co-polyradicals were prepared in good to excellent yield using the new catalyst. The magnetic properties in the temperature range of 300K to 1.8K were investigated by SQUID, which revealed a spin glass system, antiferromagnets and possible dipolar magnets. Short-range ferromagnetic interactions between 300K and 100K were found in a co-polyradical containing nitronyl nitroxide and cyano substituted monomers. The magnetic properties were dependent upon both the type of monomers utilised and the ratio between them. The effects of ring substituents on the terminal alkyne have been studied by carbon-13 NMR. There was no correlation however, between the chemical shift of terminal alkyne and the polymerisability of the monomer.

Bifunctional organorhodium solid acid catalysts for methanol carbonylation

Robust, bifunctional catalysts comprising Rh(CO)(Xantphos) exchanged phosphotungstic acids of general formulas [Rh(CO)(Xantphos)]+n[H3–nPW12O40]n− have been synthesized over silica supports which exhibit tunable activity and selectivity toward direct vapor phase methanol carbonylation. The optimal Rh:acid ratio = 0.5, with higher rhodium concentrations increasing the selectivity to methyl acetate over dimethyl ether at the expense of lower acidity and poor activity. On-stream deactivation above 200 °C reflects Rh decomplexation and reduction to Rh metal, in conjunction with catalyst dehydration and loss of solid acidity because of undesired methyl acetate hydrolysis, but can be alleviated by water addition and lower temperature operation.

Decreased efficiency of trypsinization of cells following photodynamic therapy:evaluation of a role for tissue transglutaminase

Identifying the cellular responses to photodynamic therapy (PDT) is important if the mechanisms of cellular damage are to be fully understood. The relationship between sensitizer, fluence rate and the removal of cells by trypsinization was studied using the RIF-1 cell line. Following treatment of RIF-1 cells with pyridinium zinc (II) phthalocyanine (PPC), or polyhaematoporphyrin at 10 mW cm−2 (3 J cm−2), there was a significant number of cells that were not removed by trypsin incubation compared to controls. Decreasing the fluence rate from 10 to 2.5 mW cm−2 resulted in a two-fold increase in the number of cells attached to the substratum when PPC used as sensitizer; however, with 5,10,15,20 meso-tetra(hydroxyphenyl) chlorin (m-THPC) there was no resistance to trypsinization following treatment at either fluence rate. The results indicate that resistance of cells to trypsinization following PDT is likely to be both sensitizer and fluence rate dependent. Increased activity of the enzyme tissue-transglutaminase (tTGase) was observed following PPC-PDT, but not following m-THPC-PDT. Similar results were obtained using HT29 human colonic carcinoma and ECV304 human umbilical vein endothelial cell lines. Hamster fibrosarcoma cell (Met B) clones transfected with human tTGase also exhibited resistance to trypsinization following PPC-mediated photosensitization; however, a similar degree of resistance was observed in PDT-treated control Met B cells suggesting that tTGase activity alone was not involved in this process.

Análise imunoistoquímica após terapia fotodinâmica com cloro-alumínio ftalocianina em tecidos gengivais de humanos

Although photodynamic therapy have been used as a useful tool over the past 30 years in oncology, few clinical trials have been conducted in dentistry. Photodynamic therapy (PDT) uses non - toxic photosensitizers and selective which are administered in target cells followed by local application of visible light, producing reactive oxygen species capable of causing cell death by apoptosis or necrosis, injured the local vasculature, and exert important effects on the im mune system. New generations of photosensitizing agents, such as nanoparticulate phthalocyanines, has shown excellent results in antitumor and antibacterial activity . In this context, the present work constitutes the first clinical protocol of local appli cation of nanoemulsion chloro - aluminum phthalocyanine (AlClFc) followed by irradiation in human gingiva, and analyzed descriptively and comparatively , by means of immunohistochemistry , the expression of RANK , RANKL , OPG and VEGF in a split - mouth model . Eight healthy volunteers with clinical indication for extraction were included in the study . Seven days before the extraction, was injected in the gingiva of participants, 5 μ M of nanoemulsion AlClFc followed by irra diation with diode laser (660nm , 7 J/cm2 ), the contralateral side was used as control. Tissue specimens were removed seven days after the TFD is performed. Tissues sample were divided into two groups (test and con trol groups) for histological and immunohistochemical analysis. Patients were monitored at days, 0, 7, 14 and 30 to assess adverse effects of the therapy. Vascular alterations were seen in gingival samples that received PDT. Areas of edema and vascular con gestion, and intense vascularization were viewed . Additionally, dystrophic calcification in subepithelial region were observed in the test group. The results showed a similar pattern of immunostaining scores of RANK, RANKL and VEGF between the test and co ntrol groups, with no statistically significant difference (p = 0.317, p = 0.777, p = 0 .814, respectively). RANK and RANKL exhibited weak or absent immunostaining in most specimens analyzed. There was n o immunostaining for OPG. VEGF showed moderate to stro ng immunostaining in specimens from the test group. In addition, the clinical study showed that therapy was well tolerated by all patients. Adverse effects were short - time and completely reversible. Taken together, the results presented in this study showe d that PDT mediated by nanoemulsion containing AlClPc is safe for clinical application in gingival tissue and suggests that a strong immunostaining for VEGF after therapy .

Efeitos da terapia fotodinâmica com aluminio – cloro ftalocianina sobre a peroxidação lipídica e produtos antioxidantes em tecidos inflamados animais

Photodynamic therapy (PDT) consists of a non-toxic photosensitizing agent (FS) administration followed by a laser source resulting in a sequence of photochemical and photobiological processes that generate reactive oxygen species (ROS) that damaging cells. The present work evaluated the effects of PDT nanoemulsion-aluminum chloride phthalocyanine (AlClFc) mediated on malondialdehyde (MDA), glutathione (GSH), superoxide dismutase (SOD) and glutathione peroxidase (GPx) levels, which represent indicators involved in oxidative stress and antioxidant defenses. For this purpose, this study used 120 female rats of the Rattus norvegicus species, Wistar race, divided into 5 groups: Healthy (H), with periodontal disease (PD), with periodontal disease and treatment with FS (F), with periodontal disease and treatment with the laser (L); and periodontal disease and treatment with PDT (FL). An experimental model for represent periodontal disease (PD) was induced by ligature (split-mouth). Seven days later the induction of PD, the treatments were instituted according to the groups. In the group treated with PDT was applied 40μl FS (5μM) followed by laser irradiation diode InGaAlP (660nm, 100J / cm2). The rats were sacrificed on the 7th and 28th day after treatment and tissue specimens were removed and subjected to histological, immunohistochemical methods and enzymatic colorimetric measurements with detection by UV / VIS spectroscopy. Inflammatory changes, connective tissue disorganization and alveolar bone loss were displaying in groups with PD induced. The enzyme dosages showed that MDA levels were higher in PD induced groups, with no statistically significant differences (p> 0.05). High levels of GSH were found in groups L (p = 0.028) and FL (p = 0.028) compared with PD group, with statistically significant differences. Immunohistochemistry for SOD showed higher immunostaining in L and FL groups, compared to the PD group without statistically significant differences (p> 0.05). GPx showed lower immunoreactivity in the DP group when compared to the other groups and statistically significant differences were observed between the DPxL groups (p <0.05). TFD administered in this experiment did not induce elevation of MDA levels significantly increased the GSH levels and showed intense immunostaining pada SOD and GPx, showing that this therapy does not accentuated lipid peroxidation, however, it was able to induce effects on the antioxidant defenses processes. The LBI therapy appeared to show photomodulatory promoting effects reduction of the MDA levels, increasing GSH levels and with intense immunostaining for SOD and GPx, demonstrating that laser therapy induced antioxidant effects.

Geochemistry, chlorin concentrations and diatom abundance in sediments of lake Rotsee, Switzerland

The effects of eutrophication on short term changes in the microbial community were investigated using high resolution lipid biomarker and trace metal data for sediments from the eutrophic Lake Rotsee (Switzerland). The lake has been strongly influenced by sewage input since the 1850s and is an ideal site for studying an anthropogenically altered ecosystem. Historical remediation measures have had direct implications for productivity and microbial biota, leading to community composition changes and abundance shifts. The higher sewage and nutrient input resulted in a productivity increase, which led predominantly to a radiation in diatoms, primary producers and methanogens between about 1918 and 1921, but also affected all microorganism groups and macrophytes between about 1958 and 1972. Bacterial biomass increased in 1933, which may have been related to the construction of a mechanical sewage treatment plant. Biomarkers also allowed tracing of fossil organic matter/biodegraded oil contamination in the lake. Stephanodiscus parvus, Cyclotella radiosa and Asterionella formosa were the dominant sources of specific diatom biomarkers. Since the 1850s, the cell density of methanogenic Archaea (Methanosaeta spp.) ranged within ca. 0.5-1.8 x 10**9 cells/g dry sediment and the average lipid content of Rotsee Archaea was ca. 2.2 fg iGDGTs/cell. An altered BIT index (BITCH), indicating changes in terrestrial organic matter supply to the lake, is proposed.

Degradação de paracetamol empregando tecnologia oxidativa avançada baseada em fotocatálise heterogênea usando irradiação artificial e solar

In this work, the oxidation and mineralization of paracetamol, based in an advanced oxidative process promoted by heterogeneous photocatalysis, was evaluated. The action of two photocatalysts (titanium dioxide, and a composite based on the association between titanium dioxide and zinc phthalocyanine dye) was studied. First of all, experiments in laboratory scale were performed using as radiation font a 400 W high pressure mercury lamp. The mineralization of paracetamol, promoted by both photocatalysts, was evaluated working with 4L of solution containing 10 mg L-1 of paracetamol and 100 mg L-1 of photocatalyst. To find the best experimental conditions, the influence of hydrogen peroxide concentration and pH was evaluated for the reactions. The best results for the reactions in laboratory scale was obtained using 33,00 mg L-1 of hydrogen peroxide in natural pH (6,80). Under these conditions, 100% oxidation was reached in just 40 minutes of reaction using TiO2 P25, while the mineralization was 78%. Using the composite, the mineralization was 63% in 2 hours of reaction and a oxidation of almost 100% was reached after 60 minutes. A CPC reactor (compound parabolic concentrator) was employed in the expanded work scale, using the sun as irradiation source. In this case the experiments were performed using 50 L of aqueous solution containing 10 mg L-1 of paracetamol and 100 mg L-1 of photocatalyst. The assays were done at pH 3,00 and natural pH (6,80). The used concentration of hydrogen peroxide was 33,00 mg L-1, adopted after laboratory scale studies. The reaction at pH 3,00 shows to be more advantageous, since under natural pH (6,80), the use of deionized water was necessary to prepare the solutions, probably because the deleterious action of carbonate ions, known hydroxyl radical scavengers. Using solar irradiation, the reaction mediated by the composite was more efficient when compared with the assays under laboratory scale since the composite presents the advantage of promoting a better use of visible radiation. Under these conditions, the mineralization increased from 40% to 56% under pH 3,00. At natural pH the oxidation occurred more slowly and the mineralization decreased from 56% to 50%. Thus, the use of pH 3,00 will be more interesting in real scale applications, even if it is necessary the pH correction before the discard of the treated effluent to the environment.

Catalyst and substrate effects in enantioselective C–H insertion reactions of α-diazosulfones

This thesis describes a systematic investigation of the mechanistic and synthetic aspects of intramolecular reactions of a series of α-diazo-β-oxo sulfone derivatives using copper and, to a lesser extent, rhodium catalysts. The key reaction pathways explored were C–H insertion and cyclopropanation, with hydride transfer competing in certain instances. Significantly, up to 98% ee has been achieved in the C–H insertion processes using copper-NaBARF-bisoxazoline catalysts, with the presence of the additive NaBARF critical to the efficiency of the transformations. This novel synthetic methodology provides access to a diverse range of enantioenriched heterocyclic compounds including thiopyrans, sulfolanes, β- and γ-lactams, in addition to carbocycles such as fused cyclopropanes. The synthesis of the α-diazosulfones required for subsequent investigations is initially described. Of the twenty seven diazo sulfones described, nineteen are novel and are fully characterised in this work. The discussion is subsequently focused on a study of the copper and rhodium catalysed reactions of the α-diazosulfones with Chapter Four concentrated on highly enantioselective C–H insertion to form thiopyrans and sufolanes, Chapter Five focused on C–H insertion to form fused sulfolanes, Chapter Six focused on C–H insertion in sulfonyl α-diazoamides where both lactam formation and / or thiopyran / sulfolane formation can result from competing C–H insertion pathways, while Chapter Seven focuses on cyclopropanation to yield fused cyclopropane derviatives. One of the key outcomes of this work is an insight into the steric and / or electronic factors on both the substrate and the catalyst which control regio-, diastereo- and enantioselectivity patterns in these synthetically powerful transformations. Full experimental details for the synthesis and spectral characterisation of the compounds are included at the end of each Chapter, with details of chiral stationary phase HPLC analysis and assignment of absolute stereochemistry included in the appendix.

Color reflectance and XRF drill core scanner data of ANDRILL core AND-2A

The compositional record of the AND-2A drillcore is examined using petrological, sedimentological, volcanological and geochemical analysis of clasts, sediments and pore waters. Preliminary investigations of basement clasts (granitoids and metasediments) indicate both local and distal sources corresponding to variable ice-volume and ice-flow directions. Low abundance of sedimentary clasts (e.g., arkose, litharenite) suggests reduced contributions from sedimentary covers while intraclasts (e.g., diamictite, conglomerate) attest to intrabasinal reworking. Volcanic material includes pyroclasts (e.g., pumice, scoria), sediments and lava. Primary and reworked tephra layers occur within the Early Miocene interval (1093 to 640 metres below sea floor mbsf). The compositions of volcanic clasts reveal a diversity of alkaline types derived from the McMurdo Volcanic Group. Finer-grained sediments (e.g., sandstone, siltstone) show increases in biogenic silica and volcanic glass from 230 to 780 mbsf and higher proportions of terrigenous material c. 350 to 750 mbsf and below 970 mbsf. Basement clast assemblages suggest a dominant provenance from the Skelton Glacier - Darwin Glacier area and from the Ferrar Glacier - Koettlitz Glacier area. Provenance of sand grains is consistent with clast sources. Thirteen Geochemical Units are established based on compositional trends derived from continuous XRF scanning. High values of Fe and Ti indicate terrigenous and volcanic sources, whereas high Ca values signify either biogenic or diagenic sources. Highly alkaline and saline pore waters were produced by chemical exchange with glass at moderately elevated temperatures.

Geochemistry on manganese crusts from French Polynesia

The Tuamotu Archipelago in French Polynesia is a Co-rich ferromanganese crust province. The NODCO I survey (1986) provided detailed data on Co-rich crusts in this environment through the exploration of a restricted zone in the vicinity of Niau Island on the southern flank of the archipelago. This flat zone is a fossil atoll which, under the action of subsidence and tectonic movements, has collapsed to a water depth of 1000 m. The plateau is partially filled with coralline sediments. Outcrops of ferromanganese crusts, associated with rare nodules and slabs, are located on the inner side of the coral reef which bounds the ancient lagoon. The successive episodes of plateau history have been recorded in the different growth periods of the ferromanganese crusts. The crusts, nodules and slabs belong to the same morphological, mineralogical and geochemical family. Cobalt contents vary from 0.7 to 1.3%. The highest values belong to the thinnest ferromanganese crusts which are located on the flanks of the plateau. Average Ni contents are about 0.5% and Cu contents about 0.1%; Pt contents vary from 0.2 to 1.3 ppm. Platinum and Co are enriched in the outermost oxide zone of the crusts. Poorly crystallized -MnO2 is the dominant mineralogical phase. Cobalt enrichment seems to be related to -MnO2 particle size. The greatest contents are located in the finest material where the particle size is less than 0.1 m. Cobalt-rich crusts of the Niau Zone have the same characteristics as the Co-rich crusts from the Equatorial North Pacific. They differ in original setting: the reefal environment in the Niau Zone is superficial, overlying a volcanic substrate.