Enhanced activity of an In-Fe2O3/H-ZSM-5 catalyst for NO reduction with methane

Selective reduction of NO by CH4 on an In-Fe2O3/H-ZSM-5 catalyst was investigated in the presence of excess oxygen. Compared with In/H-ZSM-5, the In-Fe2O3/H-ZSM-5 catalyst with high Fe2O3 contents showed higher activity in a wide range of reaction temperatures. It was found that the addition of Fe2O3 yielded a promotion effect on CH4 activation. The influence of water vapor on NO conversion was also investigated. The activity of the In/H-ZSM-5 catalyst has been found to be strongly inhibited by water vapor, while the In-Fe2O3/H-ZSM-5 catalyst remained fairly active in the presence of 3.3% steam. (C) 2000 Elsevier Science B.V. All rights reserved.

The use of Short Time on Stream (STOS) transient kinetics to investigate the role of hydrogen in enhancing NOx reduction over silver catalysts

The role of hydrogen in promoting the reduction by ammonia of NOx on silver catalysts has been investigated using a Short Time on Stream (STOS) technique to allow differentiation between potentially reactive intermediates and relatively inactive spectator species. Under these conditions, we have used DRIFTS to identify surface nitrate species that are formed and removed on a timescale of seconds. This is in contrast to nitrate species observed under normal steady-state conditions which can continue to form over many tens of minutes. Since this timescale of seconds is very similar to the response rate at which the NH3/NOx to N-2 reaction is accelerated when H-2 is added, or decelerated when H-2 is removed, we conclude that this fast-forming and fast disappearing nitrate species is most probably adsorbed on or close to the active Ag sites. The removal of such a blocking nitrate species from the active sites can explain the effect of H-2 in greatly increasing the rate of the overall de-NOx reaction. 

Mice lacking the gene encoding tissue-type plasminogen activator show a selective interference with late-phase long-term potentiation in both Schaffer collateral and mossy fiber pathways.

The gene encoding tissue-type plasminogen activator (t-PA) is an immediate response gene, downstream from CREB-1 and other constitutively expressed transcription factors, which is induced in the hippocampus during the late phase of long-term potentiation (L-LTP). Mice in which the t-PA gene has been ablated (t-PA-/-) showed no gross anatomical, electrophysiological, sensory, or motor abnormalities but manifest a selective reduction in L-LTP in hippocampal slices in both the Schaffer collateral-CA1 and mossy fiber-CA3 pathways. t-PA-/- mice also exhibit reduced potentiation by cAMP analogs and D1/D5 agonists. By contrast, hippocampal-dependent learning and memory were not affected in these mice, whereas performance was impaired on two-way active avoidance, a striatum-dependent task. These results provide genetic evidence that t-PA is a downstream effector gene important for L-LTP and show that modest impairment of L-LTP in CA1 and CA3 does not result in hippocampus-dependent behavioral phenotypes.

Plasmonic photocatalysts of supported gold nanoparticles for organic conversions

This thesis is a comprehensive study of plasmonic gold photocatalysts for organic conversions. It presents the advantages of plasmonic gold photocatalysts in the selective oxidation, reduction, and acetalisation. It is discovered that plasmonic gold photocatalysts exhibit better catalytic performance (higher selectivity or activity) in these organic conversions. The study in this thesis highlights the capacity of plasmonic gold photocatalysts in harvesting solar energy for converting organic raw materials to value-added chemicals, and the great potential of gold photocatalysts in chemical production.

Auditory context effects in picture naming investigated with event-related fMRI

Naming an object entails a number of processing stages, including retrieval of a target lexical concept and encoding of its phonological word form. We investigated these stages using the picture-word interference task in an fMRI experiment. Participants named target pictures in the presence of auditorily presented semantically related, phonologically related, or unrelated distractor words or in isolation. We observed BOLD signal changes in left-hemisphere regions associated with lexical-conceptual and phonological processing, including the midto-posterior lateral temporal cortex. However, these BOLD responses manifested as signal reductions for all distractor conditions relative to naming alone. Compared with unrelated words, phonologically related distractors showed further signal reductions, whereas only the pars orbitalis of the left inferior frontal cortex showed a selective reduction in response in the semantic condition. We interpret these findings as indicating that the word forms of lexical competitors are phonologically encoded and that competition during lexical selection is reduced by phonologically related distractors. Since the extended nature of auditory presentation requires a large portion of a word to be presented before its meaning is accessed, we attribute the BOLD signal reductions observed for semantically related and unrelated words to lateral inhibition mechanisms engaged after target name selection has occurred, as has been proposed in some production models.

Synthesis of both enantiomers of 1-phenylethane-1,2-diol via chirality transfer from bile acid derivatives

Both enantiomers of 1-phenylethane-1,2-diol were synthesized with good to excellent enantioselectivities via selective reduction of the phenylglyoxalates derived from bile acids, followed by reductive cleavage. (C) 2000 Elsevier Science Ltd. All rights reserved.

Enantiospecific Total Synthesis of (-)-Bengamide E

Total synthesis of the polyhydroxy caprolactam amide natural product, bengamide E, is accomplished starting from tartaric acid. Key reactions in the synthesis include desymmetrization of the bis(dimethylamide) unit of tartaric acid, Zn(BH4)2-mediated anti-selective reduction, and a HornerWadsworthEmmons olefination.

Bimetallic core-shell nanocomposites using weak reducing agent and their transformation to alloy nanostructures

An in situ seeding growth methodology towards the preparation of core-shell nanoparticles composed of noble metals has been developed by employing trimethylamine borane (TMAB) as the reducing agent. Being a weak reducing agent, TMAB is able to distinguish the smallest reduction potential window of any two metals which renders selective reduction of metal ions thus affording a core-shell architecture of the nanoparticles. A dramatic effect of solvent was noted during the reduction of Ag+ ions: an immediate reduction took place at room temperature when dry THF was used as solvent however, usage of wet THF (THF used directly from the bottle) brings out the reduction only at reflux conditions. In the case of Au and Pd nanoparticles, preparation was found to be independent of the quality of solvent used. Au nanoparticles are realized at room temperature whereas reflux conditions are required in the case of Pd nanoparticles. This difference in behavior of the monometallic nanoparticles was successfully exploited to construct different noble metal nanoparticles with core-shell architectures such as Au@Ag, Ag@Au, and Ag@Pd. Transformation of these core-shell nanoparticles to their thermodynamically stable alloy counterparts is also demonstrated under very mild conditions reported to date.

Use of pseudoephedrine as a practical chiral auxiliary for asymmetric synthesis

The use of pseudoephedrine as a practical chiral auxiliary for asymmetric synthesis is describe. Both enantiomers of pseudoephedrine are inexpensive commodity chemicals and can be N-acylated in high yields to form tertiary amides. In the presence of lithium chloride, the enolates of the corresponding pseudoephedrine amides undergo highly diastereoselective a1kylations with a wide range of alkyl halides to afford α-substituted products in high yields. These products can then be transformed in a single operation into highly enantiomerically enriched carboxylic acids, alcohols, and aldehydes. Lithium amidotrihydroborate (LAB) is shown to be a powerful reductant for the selective reduction of tertiary amides in general and pseudoephedrine amides in particular to form primary alcohols.

糖原酸酯合成方法的研究以及二环糖胺的合成

在糖化学中，糖原酸酯是一类重要的合成中间体，广泛运用于1,2-反式糖苷的合成，尤其对于寡糖的立体选择性合成具有重要的价值。目前文献报道的制备糖原酸酯的方法大多存在对环境不友好的问题。本文对传统的糖原酸酯制备方法进行了改进，通过研究发现无机碱也能够有效地催化合成糖原酸酯。以溴代糖和醇（或糖基受体）为原料，在无机碱、四丁基溴化铵、乙腈的体系中，合成了一系列简单醇糖原酸酯和糖-糖原酸酯。 聚乙二醇及其衍生物作为有机反应的溶剂和催化剂在有机化学中有广泛的应用。本文阐述了一种以溴代糖和醇（或糖基受体）为原料，在无机碱和聚乙二醇二甲醚反应体系中合成糖原酸酯的方法。该方法中，聚乙二醇二甲醚即作为绿色溶剂又作为催化剂，反应条件温和、环保、高效。 糖胺是一类重要的糖苷酶抑制剂，已在糖尿病和其他代谢紊乱等疾病的治疗中发挥了极其重要的作用。本文提供了一种合成一类具有潜在的糖苷酶抑制活性、结构新颖的二环糖胺的途径。该合成思路是以1-叠氮基-2-C-乙酰甲基-3,4,6-三-O-苄基-2-脱氧-β-D-葡萄糖为原料，经二环糖亚胺中间体，通过二环糖亚胺还原或加成得到一类二环糖胺。 Sugar orthoesters as one of the most important intermediates in carbohydrate chemistry, are used extensively in the synthesis of sugar 1,2-trans-glycosides, especially oligosaccharide. These methods in the literature are mostly eco-unfriendly. Herein we described a modified protocol for the preparation of sugar orthoesters using inorganic base, by improving the conventional method. Our method involves the treatment of peracetylated or perbenzotlated glycosyl bromides with alcohols in the presence of a quaternary ammonium salt and an inorganic alkali in acetonitrile solvent, affording both simple sugar orthoesters and sugar-sugar orthoesters. Polyethylene glycol and their derivatives as solvents or catalysts play a significant role in the organic reaction. We developed a novel and environmentally benign methodology towards the synthesis of sugar orthoesters, which are prepared by the reaction of peracetylated or perbenzotlated glycosyl bromides and alcohols in the presence of dimethyl ether of polyethylene glycol as either the reaction medium or catalyst. Glycosylamines and pseudo-glycosylamines have been tested against various glycosidases, and applied to the treatment of diabetes and other metabolic disorders. We presented a route of the synthesis of a bicyclic glycosylamine as a potential glycosidases inhibitor with unique structure. Reduction of 2-C-acetlymethyl-β-glucopyranosyl azide derivative firstly produced a bicyclic glycosylimine intermediate, and subsequently the bicyclic glycosylamine and its derivatives would be prepared through the selective reduction or addition the C=N double bond of the bicyclic glycosylimine intermediate.

Prussian Blue/Multiwalled Carbon Nanotube Hybrids: Synthesis, Assembly and Electrochemical Behavior

Prussian blue/carbon nanotube (PB/CNT) hybrids with excellent dispersibility in aqueous solutions were synthesized by adding CNTs to an acidic solution of Fe3+, [Fe(CN)(6)](3-) and KCl. Fourier transform infrared spectroscopy, UV-vis absorption spectroscopy and scanning electron microscopy were employed to confirm the formation of PB/CNT hybrids. The PB nanoparticles formed on the CNT surfaces exhibit a narrow size distribution and an average size of 40 nm. The present results demonstrate that the selective reduction of Fe3+ to Fe2+ by CNTs is the key step for PB/CNT hybrid formation. The subsequent fabrication of the PB/CNT hybrid films was achieved by layer-by-layer technique. The thus-prepared PB/CNT hybrid films exhibit electrocatalytic activity towards H2O2 reduction.

Enhanced myocardial relaxation in vivo in transgenic mice overexpressing the beta2-adrenergic receptor is associated with reduced phospholamban protein.

To assess the effect of targeted myocardial beta-adrenergic receptor (AR) stimulation on relaxation and phospholamban regulation, we studied the physiological and biochemical alterations associated with overexpression of the human beta2-AR gene in transgenic mice. These mice have an approximately 200-fold increase in beta-AR density and a 2-fold increase in basal adenylyl cyclase activity relative to negative littermate controls. Mice were catheterized with a high fidelity micromanometer and hemodynamic recordings were obtained in vivo. Overexpression of the beta2-AR altered parameters of relaxation. At baseline, LV dP/dt(min) and the time constant of LV pressure isovolumic decay (Tau) in the transgenic mice were significantly shorter compared with controls, indicating markedly enhanced myocardial relaxation. Isoproterenol stimulation resulted in shortening of relaxation velocity in control mice but not in the transgenic mice, indicating maximal relaxation in these animals. Immunoblotting analysis revealed a selective decrease in the amount of phospholamban protein, without a significant change in the content for either sarcoplasmic reticulum Ca2+ ATPase or calsequestrin, in the transgenic hearts compared with controls. This study indicates that myocardial relaxation is both markedly enhanced and maximal in these mice and that conditions associated with chronic beta-AR stimulation can result in a selective reduction of phospholamban protein.

An investigation of the thermal stability and sulphur tolerance of Ag/Y-Al2O3 catalysts for the SCR of NOx with hydrocarbons and hydrogen

The sulphur tolerance and thermal stability of a 2 wt% Ag/gamma-Al2O3 catalyst was investigated for the H-2-promoted SCR of NO, with octane and toluene. The aged catalyst was characterised by XRD and EXAFS analysis. It was found that the effect of ageing was a function of the gas mix and temperature of ageing. At high temperatures (800 degrees C) the catalyst deactivated regardless of the reaction mix. EXAFS analysis showed that this was associated with the Ag particles on the surface of the catalyst becoming more ordered. At 600 and 700 degrees C, the deactivating effect of ageing was much less pronounced for the catalyst in the H-2-promoted octane-SCR reaction and ageing at 600 degrees C resulted in an enhancement in activity for the reaction in the absence of H-2. For the toluene + H-2-SCR reaction the catalyst deactivated at each ageing temperature. The effect of addition of low levels of sulphur (1 ppm SO2) to the feed was very much dependent on the reaction temperature. There was little deactivation of the catalyst at low temperatures ( 500 degrees C). The results can be explained by the activity of the catalyst for the oxidation Of SO2 to SO3 and the relative stability of silver and aluminium sulphates. The catalyst could be almost fully regenerated by a combination of heating and the presence of hydrogen in the regeneration mix. The catalyst could not be regenerated in the absence of hydrogen. (c) 2006 Published by Elsevier B.V.

Abatement of nitrous oxide over natural and iron modified natural zeolites

The natural zeolite obtained from the Sivas-Yavu region in Turkey and iron modified forms were studied for the decomposition of N2O and selective catalytic reduction of N2O with NH3. The natural and iron modified zeolites were characterised by XRD, SEM, H-2-TPR, NH3-TPD and low temperature nitrogen sorption. The effect iron loading, precursor and valency on the catalytic performance of catalysts were studied. The catalytic activity of the zeolites increased up to about 7.0 wt.% Fe. Above this value, the activity decreased as a result of a reduction in the surface area and pore volume of the zeolite. The highest catalytic activity was observed using catalysts prepared with FeCl2 due to the formation of more reducible iron species in the zeolites. When FeSO4 was used as the iron precursor, sulphate remained on the surface even after extensive washing resulting in a decrease in the N2O decomposition activity and a shift the N2O reduction temperature to higher values. Since the natural and iron exchanged natural zeolites prepared using FeCl2 have comparable activity with synthetic zeolites, the offer a promising alternative catalyst for the abatement of N2O, particularly for the selective reduction of N2O with NH3. (C) 2011 Elsevier B.V. All rights reserved.

Controlling the Sulfur Poisoning of Ag/Al2O3 Catalysts for the Hydrocarbon SCR Reaction by Using a Regenerable SOx Trap

The deactivation of a silver-based hydrocarbon selective catalytic reduction catalyst by SOx and the subsequent regeneration under various operating conditions has been investigated. Using a sulfur trap based on a silica-supported catalyst it was found that, for a Ag/SiO2 + Ag/Al2O3 combination, the negative effect of SO2 on the n-octane-SCR reaction can be eliminated under normal operating conditions. The trap can be regenerated by hydrogen at low temperatures or at higher temperatures using a hydrocarbon reductant.