Platinum particle size and support effects in NO(x) mediated carbon oxidation over platinum catalysts

Platinum metal was dispersed on microporous, mesoporous, and nonporous support materials including the zeolites Na-Y, Ba-Y, Ferrierite, ZSM-22, ETS-10, and AIPO-11, alumina, and titania. The oxidation of carbon black loosely mixed with catalyst powder was monitored gravimetrically in a gas stream containing nitric oxide, oxygen, and water. The carbon oxidation activity of the catalysts was found to be uniquely related to the Pt dispersion and little influenced by support type. The optimum dispersion is around 3-4% corresponding to relatively large Pt particle sizes of 20-40 nm. The carbon oxidation activity reflects the NO oxidation activity of the platinum catalyst, which reaches an optimum in the 20-40 nm Pt particle size range. The lowest carbon oxidation temperatures were achieved with platinum loaded ZSM-22 and AIPO-11 zeolite crystallites bearing platinum of optimum dispersion on their external surfaces.     

Antibiofilm activity of the essential oil of citronella (Cymbopogon nardus) and its major component,geraniol, on the bacterial biofilms of Staphylococcus aureus

Food Science and Biotechnology - Medicinal plants with antimicrobial action have been investigated for uses against biofilms, among which, Cymbopogon nardus, citronella, stands out as a promising...     

小麦适度碾皮一种提高面粉品质及附加值的技术

提高原料小麦利用效率及其面粉品质,始终是制粉业需要不断解决的根本问题.为此,制粉业的加工设备和工艺一直在不断地创新. 制粉的小麦最好能够在碾磨之前除去其外皮,然而,采取常规的技术和工艺,这是不可能的.     

Optimizing contaminant desorption and bioavailability in dense slurry systems. 2. PAH bioavailability and rates of degradation

The effects of mechanical mixing on rates of polycyclic aromatic hydrocarbon (PAH) biodegradation in dense geosorbent slurry (67% solids content, w/w) systems were evaluated using laboratory-scale intermittently mixed batch bioreactors. A PAH-contaminated soil and a phenanthrene-sorbed mineral sorbent (alpha-Al2O3) were respectively employed as slurry solids in aerobic and anaerobic biodegradation studies. Both slurries exhibited a characteristic behavior of pseudoplastic non-Newtonian fluids, and the impeller revolution rate and its diameter had dramatic impacts on power and torque requirements in their laminar flow mixing. Rates of phenanthrene biodegradation were markedly enhanced by relatively low-level auger mixing under both aerobic and anaerobic (denitrifying) conditions. Parameters for empirical models correlating biodegradation rate coefficient (k(b)) values to the degree of mixing were similar to those for correlations between mass transfer (desorption) rate coefficient (k(r)) values for rapidly desorbing fractions of soil organic matter and degree of mixing reported in a companion study, supporting a conclusion that performance-efficient and cost-effective enhancements of PAH mass transfer (desorption) and its biodegradation processes can be achieved by the introduction of optimal levels of reactor-scale mechanical mixing.     

Halogenated natural products in five species of Antarctic sponges: compounds with POP-like properties?

Purified extracts of five species of Antarctic sponges (Demospongiae: Kirkpatrickia variolosa, Artemisina apollinis, Phorbas glaberrima, and Halichondria sp. and Calcarea: Leucetta antarctica) from King George Island were analyzed by GC/MS for the presence of persistent and lipophilic halogenated compounds to identify bioaccumulative halogenated natural products. Sample extracts were prepared using methods identical for the determination of POPs, namely, microwave-assisted extraction with organic solvents, gel permeation chromatography, and column chromatography on deactivated silica. In addition, samples were treated with sulfuric acid to remove acid-destructible compounds. PCBs were not detectable and only traces of lindane, p,p'-DDE, and alpha-HCH were detected in these samples in decreasing order of abundance, underscoring their uncontaminated state. In contrast, 146 brominated compounds were identified by correct isotopic ratios m/z 79 and 81, 50% of which eluted prior to lindane including the most abundant peaks. Each sponge sample contained > or = 35 brominated compounds of natural origin, 14 of which were detected in all species. Estimated concentrations ranged from the high ng/kg to mg/kg (air-dried weights) and relative distributions of the same compounds in different sponges were highly variable. The high abundance of these compounds relative to known anthropogenic pollutants strongly suggests a natural origin. Multiple mode (EI-, ECNI-, and PCI-) GC/MS enabled identification of an aliphatic ketone tentatively identified as 1,1,2-tribromo-oct-1-en-3-one, present in all species but highest in Phorbas glaberrima. Several halogenated phenols including 2,4,6-tribromophenol were also abundant in Phorbas glaberrima as were halogenated anisoles in lower relative abundances. The halogenated phenols were analyzed without derivatization. The sample of Halichondria sp. contained the dibromotrichloro monoterpene MHC-1, a recently described environmental contaminant in fish and seals. Retrospective analysis of other marine samples confirmed that 2,4,6-tribromophenol was present in seal blubber from both the Arctic and the Antarctic. The presence of naturally occurring organohalogens such as 2,4,6-tribromophenol and MHC-1 in Antarctic marine invertebrates thus provides a link to their occurrence in marine mammals.     

Transformation and removal of bisphenol A from aqueous phase via peroxidase mediated oxidative coupling reactions: efficacy, products, and pathways

A systematic investigation of the feasibility of and mechanisms for transformation and removal of bisphenol A (BPA) from aqueous phase via oxidative coupling mediated by horseradish peroxidase is described. It is demonstrated that BPA can be effectively transformed into precipitable solid products in HRP-mediated oxidative coupling reactions. A total of 13 reaction intermediates and products are identified using LC/MS and GC/MS techniques, and with the help of ab initio molecular modeling, detailed reaction pathways are proposed. It is postulated that two BPA radicals are coupled primarily by the interaction of an oxygen atom on one radical and propyl-substituted aromatic carbon atom on another, followed by elimination of an isopropylphenol carboncation. All intermediates or products detected can be interpreted as resulting from either coupling or substitution reactions between BPA and other intermediates or products. The efficacy of the reaction at low substrate concentrations is demonstrated using a sensitive analytical procedure involving solid-phase extractions. The results suggest that catalyzed oxidative coupling reactions may be important natural transformation pathways for estrogenic phenolic compounds and indicate their potential use as an efficient means for removal of estrogenicity from waters and wastewaters.     

Physiologically based persistent organic pollutant accumulation in pig tissues and their edible safety differences: An in vivo study

As one of the most important animal food sources, pigs are an important model in the assessment of human exposure to persistent organic pollutants (POPs). In the present study, the distribution of the administrated polychlorodibenzo-p-dioxin/furan (PCDD/F)–polychlorinated biphenyl (PCB) mixture and polybrominated diphenyl ethers (PBDEs) in the different tissues of pigs, including liver, lung, kidney, subcutaneous fat, mesentery and muscle, for understanding the physiologically based pollutant accumulation in these tissues and their edible safety was investigated. It was found that liver had a much higher potential to accumulate PCDD/Fs and dioxin-like pollutants like PCB-126 than the other tissues, but it did not specifically concentrate PBDE congeners as compared to the other tissues. The different PCDD/F congeners and PCB-126 followed a similar distribution pattern in the different tissues; also the different PBDE congeners have the similar pattern in these tissues. The liver’s higher concentrating potency for dioxin-like pollutants may result from its detoxification function, however, it can concentrate dioxin-like pollutants but not PBDEs may suggest that it is the toxicity but not lipophilic property of these POPs dominated their accumulation in liver tissues. Also the result suggested that liver is a high-risk edible tissue for dioxin-like pollutants. In conclusion, the present study suggested that physiologically based assessments are necessary for evaluating edible tissue safety in animal source foods.     

Studies on the formation of lysinomethylalanine and histidinomethylalanine in milk products

From reaction mixtures consisting ofN-acetyldehydroaminobutyric acid methyl ester andN -acetyl-l-lysine orN -acetyl-l-histidine, respectively, distinct amounts of the cross-link amino acidsN -(2-amino-2-carboxy-l-methylethyl)-l-lysine (lysinomethylalanine, LMeAL) andN -(2-amino-2-carboxy-1-methyl-ethyl)-l-histidine (histidinomethylalanine, HMeAL) were isolated via preparative ion-exchange chromatography and identified by¹H- and¹³C-nuclear magnetic resonance. In the amino acid chromatogram, both compounds eluted clearly separated from other basic amino acids. However, neither LMeAL nor HMeAL could be detected in numerous acid hydrolysates of a range of milk products. In model studies, threonine showed a significantly lower tendency for an alkali-induced -elimination reaction compared to serine. The reactivity of the resulting dehydroaminobutyric acid towards nucleophiles was more than tenfold lower as compared to dehydroalanine. Thus, the formation of LMeAL as well as of HMeAL during food processing is negligible.

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Studien zur Bildung von Lysinomethylalanin und Histidinomethylalanin in Milchprodukten

Zusammenfassung Aus Reaktionsansätzen bestehend ausN-Acetyldehydroaminobuttersäurenthylester undN -Acetyl-l-lysin beziehungsweiseN -Acetyl-l-histidin konnten die Crosslink-AminosäurenN -(2-Amino-2-carboxy-1-methyl-ethyl)-l-lysin (Lysinomethylalanin, LMeAL) undN -(2 amino-2-carboxy-2 -methyl-ethyl)-l-histidin (Histidinomethylalanin, HMeAL) durch präparative Ionenaustauschchromatographie isoliert und anschließend durch 1H-und¹³C-NMR identifiziert werden. Das Aminosäurechromatogramm zeigte eine eindeutige Trennung beider Aminosäurederivate von anderen basischen Aminosäuren. Dennoch konnten in einer großen Zahl von Säurehydrolysaten der verschiedensten Milchprodukte weder LMeAL noch HMeAL nachgewiesen werden. In Modelluntersuchungen erfolgte die -Elimination an Threonin im Vergleich zu Serin in einem deutlich geringeren Maße. Die Reaktivität der dabei entstehenden Dehydroaminobuttersäure gegenüber Nucleophilen war mehr als zehnfach geringer als die von Dehydroalanin. Damit kann die Bildung sowohl von LMeAL als auch von HMeAL bei der Verarbeitung von Nahrungsmitteln als vernachlässigbar gering eingeschätzt werden.

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Dedicated to Prof. Dr. W. Baltes on the occasion of his 65th birthday     

Facing the issues.

Replies to P. L. Wachtel (see PA, Vol. 51:Issue 5) stating that efforts to achieve integration between psychodynamic and behavioral approaches are appealing, but are unlikely to succeed unless the empirical issues are faced without distortion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)