Complete oxidation of methane at low temperature over Pt and Pd catalysts for the abatement of lean-burn natural gas fuelled vehicles emissions: influence of water and sulphur containing compounds

The catalytic activity of fresh Pd and Pt catalysts supported on γ-alumina in the complete oxidation of CH₄ traces under lean-burn conditions was studied in the presence or the absence of water or H₂S. Steam-aged catalysts were also studied in order to simulate long-term ageing in real lean-burn natural gas fuelled vehicles (NGVs) exhaust conditions. Without water or H₂S added to the feed, Pd catalysts exhibit a superior catalytic activity in methane oxidation compared to Pt ones, whatever the catalysts were fresh or aged. The addition of 10 vol.% water vapour to the feed strongly affects the activity of the fresh Pd catalyst, thus being only slightly more efficient than the fresh Pt one. H₂S has a strong poisoning effect on the catalytic activity of Pd catalysts, while Pt catalysts are more resistant. The fresh H₂S-poisoned Pd/Al₂O₃ catalyst was studied by TPD in O₂/He. Poisoning species decompose above 873 K as SO₂ and O₂ in relative concentrations consistent with the decomposition of surface sulphate species. However, a treatment in O₂/He at temperatures as high as 923 K does not allow the complete regeneration of the catalytic activity of H₂S-poisoned Pd/Al₂O₃. A mechanism involving the poisoning of PdO by sulphate species is proposed. Different diffusion processes by which these sulphate species can migrate back and forth between PdO and the support, depending on the experimental conditions, are suggested.     

Working Memory Capacity and the Antisaccade Task: Individual Differences in Voluntary Saccade Control.

Performance on antisaccade trials requires the inhibition of a prepotent response (i.e., don't look at the flashing cue) and the generation and execution of a correct saccade in the opposite direction. The authors attempted to further specify the role of working memory (WM) span differences in the antisaccade task. They tested high- and low-span individuals on variants of prosaccade and antisaccade trials in which an eye movement is the sole requirement. In 3 experiments, they demonstrated the importance of WM span differences in both suppression of a reflexive saccade and generation of a volitional eye movement. The results support the contention that individual differences in WM span are not exclusively due to differences in inhibition but also reflect differences in directing the focus of attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

一种新型声波降粘防蜡装置

新型声波降粘防措装置由上、下接头、振动簧片和收缩喷嘴构成。装置安装在抽油泵泵简之下，尾管之上，在压差作用下井下流体以较大速度从装置的喷嘴射出，冲击振动簧片，产生机械振动声波，油水混合液在声波中产生相应的声波力学效应和分散乳化作用等，使混合液在油管内的粘度降低，蜡晶不易聚集长大，从而达到降粘防蜡延长油井热洗周期的目的。室内试验及现场近20口井的应用情况表明，这种装置具有结构简单、成本低廉、应用方便等特点，具有明显的降粘防蜡效果。     

Sodium silicate as a coke inhibitor during naphtha pyrolysis

Rates of coke formation during steam pyrolysis of naphtha have been investigated in a jet-stirred reactor both for sodium silicate coated and uncoated Inconel 600 surfaces in the temperature range of 1078–1108 K. Coke formation rates were significantly reduced on sodium silicate coated plates due to the passivation of the metal surface. However, the coking rates gradually increased with successive decokings of the coated surface.     

The effects of induction conditions on production of a soluble antitumor sFv in Escherichia coli

CC49 is a second generation monoclonal antibody(mAb) with highaffinity to a pancarcinoma antigen, TAG-72. A single-chain Fv(sFv)ofCC49 may have a role in managing human carcinomas. Most reportedsFvs have been expressed as insoluble products that must besolubilized and renatured. Soluble sFv expression is advantageousas activity can be assayed directly from the periplasmic fraction.Also, gene-level immunoconjugates may not be amenable to refoldingprotocols. Using a vector that carries the tac promoter andomp A signal, we have examined the effects of four variableson the expression and accumulation of soluble CC49 sFv: (i)linker sequence joining VL and VH, (ii) isopropylthio-ß-D-galactosideconcentration for induction, (iii) temprature, and (iv) theaddition of nonmetabolizable sugars to the medium. We have beenable to demonstrate, using rapidly prepared periplasmic extracts,that the yield of soluble sFv improves by the addition of 0.4Msucrose to the medium and by inducing expression with a verylow concentration of IPTG (0.02–0.03 mM). Under theseinduction conditions periplasmic extracts demonstrate increasedexpression of the sFv, as shown by the larger amount of a 27kDa band on SDS-polyacrylamide gel, and an increased abilityto inhibit binding of the mAb CC49 to immobilized tumor extracts.     

Inhibition of nitrification in the packed bed reactors by selected organic compounds

The effect of methanol, acetone, formalin and glucose on the nitrification process in the packed bed reactors has been investigated. For the utilized compounds the inhibition constant K_i was determined according to Dixon's method. The determined values were as follows: methanol K_i = 116.0 mg l^?1; acetone K_i = 804.2 mg l^?1; formalin K_i = 61.5 mg l^?1. The value of K_i for glucose has not been determined because glucose in applied concentration up to 11,325 mg l^?1 had no effect on the nitrification course.     

Quantification of Factors Which Influence Nisin's Inhibition of CIostridium botulinum 56A in a Model Food System

We modeled nisin's anticlostridial activity and assessed the antagonistic or potentiating influences of food ingredients. The model systems contained yeast extract, proteose peptone, and glucose; were supplemented with protein (0.075, 0.75, 7.5% w/v), phospholipid (0.075, 0.75, 7.5% w/v), or soluble starch (5, 17.5, 30% w/v); and were adjusted to pH 5.5, 6.0, or 6.5. Samples inoculated with 10⁴/mL spores were incubated at 15, 25, or 35°C. Statistical analysis developed an equation (r²= 0.76) that modeled the response and identified temperature as the most significant (α 0.001) variable. Nisin lost effectiveness with increasing temperature. Nisin concentration had significant positive and phospholipid negative, linear effects. Many interactive effects were significant (α 0.20). Nisin inhibited C. botulinum until its residual level dropped below a threshold, which decreased from 154 IU/mL at 35°C to 12 IU/mL at 15°C.     

Adsorption and inhibitive properties of benzimidazole derivatives in acid mild steel corrosion

Eight diazoles were investigated as corrosion inhibitors of mild steel in 1 M hydrochloric acid using gravimetric and polarization techniques. It was found that the inhibition efficiency increased with the increase of organic substrate concentration, while the adsorption followed the Frumkin isotherm. A correlation between the electronic parameters (induction and mesomeric effects of the substituents, ionization potential values) as well as those of the chemical structure (molecular area) of diazoles molecules and their inhibiting properties was looked for. The results obtained show that a definite interdependence exists but it is not as simple and straightforward as might be expected.     

Motivated attention and prepulse inhibition of startle in rats: Using conditioned reinforcers as prepulses.

In humans, prepulse inhibition (PPI) of startle is greater during attended prestimuli than it is during ignored prestimuli, whereas in rats, most work has focused on passive PPI, which does not require attention. In the work described in this article, researchers developed a paradigm to assess attentional modification of PPI in rats using motivationally salient prepulses. Water-deprived rats were either conditioned to attend to a conditioned stimulus (CS; 1-s, 7-dB increase in white noise) paired with water (CS+ group), or they received uncorrelated presentations of white noise and water (CSo group). After 10 conditioning sessions, startle probes (50 ms, 115 dB) were introduced, with the CS serving as a continuous prepulse. Three experiments examined PPI across a range of prepulse intensities (4-10 dB) and stimulus onset asynchronies (SOAs; 30-960 ms). PPI was consistently reduced in the CS+ group, particularly with a 10-dB prepulse and a 60-ms SOA. Thus, PPI in rats differed between attended and ignored prestimuli, but the effect was reversed in the results of research with humans. A fourth study eliminated the group difference by reversing the CS-water contingency. Methodological and motivational hypotheses regarding the current findings are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inhibition of sulfide on the simultaneous removal of nitrate and p‐cresol by a denitrifying sludge

BACKGROUND: Many industrial discharges, such as those generated from petrochemical refineries, contain large amounts of sulfurous, nitrogenous and organic contaminants. Denitrification has emerged as a suitable technology for the simultaneous removal of these pollutants in a single reactor unit; however, more evidence is demanded to clarify the limitations of denitrification on the simultaneous removal of sulfide and phenolic contaminants and to optimize the biological process. The aim of this study was to evaluate the capacity of a denitrifying sludge to simultaneously convert sulfide and p‐cresol via denitrification. RESULTS: Sulfide was the preferred electron donor over p‐cresol, imposing a 5 h lag phase (required for complete sulfide removal) on organotrophic denitrification. Addition of sulfide (20 mg S^2? L^?1) to p‐cresol‐amended denitrifying cultures also decreased the reduction rate of nitrate and nitrite, as well as the production rate of nitrogen gas. Nitrite reduction rate was the most affected step by sulfide, decreasing from 35 to 21 mg N (g VSS d)^?1. A synergistic inhibitory effect of nitrate and sulfide was also observed on nitrite reduction. Despite the effects of sulfide on the respiratory rates monitored, complete removal of nitrate, sulfide and p‐cresol could be achieved after 48 h of incubation. CONCLUSION: Our results suggest that simultaneous removal of sulfide and p‐cresol could be achieved in denitrifying reactors, but a large hydraulic residence time may be required to sustain an efficient process due to inhibitory effects of sulfide. Copyright © 2008 Society of Chemical Industry