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51.
The poisoning effect of various halogen compounds on a nickel-based hydrogenation catalyst has been investigated. While alkyl
monochlorides did not affect the catalyst activity, alkyl monobromide and-iodide had a strong poisonous effect. Vicinal dichlorides,
1,1-dichlorides, and HC1 also poisoned the catalyst. It is shown that with chlorine containing compounds, the poisoning mechanism
involves a fission of the carbon-chlorine bond with the formation of HC1, while bromine and iodine compounds adsorb to the
catalyst surface as such in a simple equilibrium reaction. A mackerel oil previously shown to exhibit three kinetically distinguishable
poisoning effects has been further examined, and it is shown that its content of halogens can probably account for the observed
poisoning pattern. 相似文献
52.
Dorota Johansson Björn Bergenståhl 《Journal of the American Oil Chemists' Society》1992,69(8):728-733
The influence of water on the interactions between fat and sugar crystals dispersed in triglyceride (vegetable) oils was qualitatively
estimated from sedimentation and rheological experiments. The experiments were performed both with and without food emulsifiers
(monoglycerides and lecithins) present in the oil. The effects of minor natural oil components (nontriglycerides) on the interactions
and on emulsifier adsorption to the crystals were examined by comparing a commercial refined oil and a chromatographically
purified oil. The results show that water generally increases the adhesion between fat and sugar crystals in oils and also
increases the surface activity of the oil-soluble food emulsifiers. Minor oil components give a small increase in the adhesion
between fat and sugar crystals in oils, but do not influence the adsorption of food emulsifiers in any systematic way. 相似文献
53.
Previous studies indicate a suppressive influence of fish oils on rodent malaria. The present work was carried out to study
(i) the dose-effect relation between dietary fish oils and lethality of primary malaria infection in mice; (iii) the modifying
influence of vitamin E; and (iii) the effect of previous fish oil feeding on parasitemia and lethality of a rechallenge infection.
For two or four weeks, groups of weanling male mice were fed a standard laboratory diet or one of eight purified diets containing
various amounts of fish oil (providing 6–21% of energy). The diets were prepared with and without vitamin E. After the two-or
four-week feeding period, the mice were injected intraperitoneally withPlasmodium yoelii yoelii-infected erythrocytes. Six months after the primary infection (four months after discontinuing fish oil feeding), the surviving
mice were again injected intraperitoneally with parasitized red blood cells (or even better—erythrocytes, erythrocytes are
used elsewhere). Primary malaria infection was lethal in mice fed standard diet alone or with fish oil and vitamin E added.
In contrast, feeding a fish oil-based diet without vitamin E improved survival to at least 70% if the mice had been fed these
diets for four weeks. Protection against malaria did not seem to be related to the fish oil dose used. Regardless of the previous
fish oil dose, all the mice surviving the primary infection survived the rechallenge infection with low parasitaemias. The
results suggest that the prooxidant nature of highly unsaturated fatty acids in fish oils may beneficially influence malaria
infection, and may also increase the resistance against reinfection for some time after discontinuing fish oil intake. 相似文献
54.
The absorption of tocopherols (α, γ, and σ) and fatty acids from rapeseed (RO), soybean (SOO), and sunflower (SUO) oil, both
from the natural oils and from the oils following moderate heating (180°C for 15 min), was measured in lymphcannulated rats.
Oils were administered as emulsions through a gastrostomy tube, and lymph samples were collected for 24 h. The composition
of tocopherols in oils and lymph fractions was measured by high-performance liquid chromatography, and fatty acids were measured
by gas-liquid chromatography. The highest accumulated transport of α-tocopherol was observed after SUO administration, the
lowest after SOO, with RO in between, corresponding to their relative contents (41.6±8.8, 32.7±5.0, and 24.9±4.3 μg at 24
h after administration of SUO, RO, and SOO, respectively). The calculated recoveries (in %) 24 h after oil administration
were 21.4±4.5, 45.7±7.0, and 78.8±13.5 for SUO, RO, and SOO, respectively, suggesting that the absorption efficiency decreased
when the α-tocopherol concentration increased. The recovery of α-tocopherol was higher than the recoveries of γ-and σ-tocopherol,
indicating that the different tocopherols were not absorbed to the same extent or with similar rates. No differences between
unheated and heated oils were observed in the absorption of tocopherols, whereas heating led to lower absorption of fatty
acids, thus showing no direct association between absorption of tocopherols and fatty acids. 相似文献
55.
Dehydrogenation of Light Alkanes Over Rhenium Catalysts on Conventional and Mesoporous MFI Supports 总被引:1,自引:0,他引:1
Anne Krogh Rovik Anke Hagen Iver Schmidt Søren Dahl Ib Chorkendorff Claus Hviid Christensen 《Catalysis Letters》2006,109(3-4):153-156
Recently, Re/HZSM-5 (Si/Al = 15) was shown to be an efficient catalyst for ethane dehydrogenation and aromatization at 823 K
and atmospheric pressure. In this reaction, the major initial products were benzene, toluene and xylene (BTX), but increasing
amounts of ethene were produced with time on stream due to deactivation of the catalyst. We show that by use of rhenium impregnated
MFI supports with very few or no acidic sites (Si/Al > 500), highly selective ethane dehydrogenation catalysts are obtained
with ethene selectivities of 98%. By use of mesoporous MFI supports (Si/Al >500) the lifetime of the catalyst appears to be
slightly improved compared to conventional MFI crystals. The beneficial effect of a mesoporous MFI support is convincingly
demonstrated in propane dehydrogenation, where both conversion and selectivities on the mesoporous MFI (Si/Al > 500) impregnated
with Re are significantly higher than on Re supported on a comparable conventional MFI support. 相似文献
56.
Desislava Bögner Frederike Schmachtl Björn Mayr Christopher P. Franz Sabine Strieben Gregor Jaehne 《臭氧:科学与工程》2019,41(2):105-117
Recirculating Aquaculture Systems (RAS) reduce water consumption by efficient filtration to maintain appropriate levels of accumulating compounds and sludge. Sludge is mechanically separated by drum filters and disposed of to the detriment of overall system water budgets. Dissolved nitrogen compounds are reduced via nitrification–denitrification filters, requiring commercial external carbon sources. The reuse of sludge after ozone pre-treatment may represent the next step in RAS optimization. The present study analyzes the content of sludge from RAS and tests ozonation as a pre-treatment for recycling as carbon source. The dissociative effect of ozone and the physicochemical changes due to ozonation lead to a significant increase in soluble carbon availability. Predominantly long-chain fatty acid (FA) (saturated and unsaturated) with 16 and 18 carbon atoms independently of the treatment were found in the profiles. Saturated FA concentrations in solution increased after 20, 40, and 60 min ozonation. The solid content of the sludge was practically unaffected by ozonation in terms of FA profile: only saturated FA slightly increases after 40 min treatment. The implications of these findings for denitrifying bacteria are discussed.
Abbreviations: Recirculating Aquaculture Systems (RAS); Advanced Oxidation Processes (AOPs) 相似文献
57.
Peter?S.?Piispanen Bj?rn?Hedman Torbj?rn?NorinEmail author 《Journal of surfactants and detergents》2002,5(2):165-168
The syntheses of derivatives of dehydroabietic acid suitable for further manipulation into surfactants are presented. The
compounds are produced at very high yields and purity. They contain several different functional groups, e.g., carboxylic
acid, amine, ester, alcohol, and an aromatic group. The functional groups are useful as the linking unit to the hydrophilic
part in synthesizing surfactants. 相似文献
58.
Activity coefficients for the ArN2, C2H6C2H4, and C3H6CO2 systems are calculated from published vapour-liquid equilibrium compositions at various pressures and temperatures. The activity coefficients are correlated using a two parameter model based on the principles of molecular thermodynamics. The method is used both in the normal liquid and critical regions. The parameters of the model are shown to be reasonably independent of the temperature for the three systems. 相似文献
59.
Marika Lüders Asbjørn Følstad Espen Waldal 《Journal of Computer-Mediated Communication》2014,19(3):446-462
Social media are often argued to change political communication, decreasing the distance between politicians and citizens, and increasing citizens' influence on policymaking. This paper presents findings from a study of how the Norwegian Labour Party uses social media, focusing on the community platform MyLabourParty. Interviews with politicians and a survey with citizens as respondents were conducted to examine the experiences of online political discussions. Findings show that citizens and politicians expect MyLabourParty to strengthen citizen participation. Yet, citizens still experience communication asymmetry and politicians may find it challenging to participate to the extent citizens expect. Means for bridging the gap between expectations and experiences are called for, in particular redefinition of the offering, changes of user‐practices, and system improvements. 相似文献
60.
Søren N. Sørensen René Sørensen Erik Lund 《Structural and Multidisciplinary Optimization》2014,50(1):25-47
This paper presents a gradient based topology optimization method for Discrete Material and Thickness Optimization of laminated composite structures, labelled the DMTO method. The capabilities of the proposed method are demonstrated on mass minimization, subject to constraints on the structural criteria; buckling load factors, eigenfrequencies, and limited displacements. Furthermore, common design guidelines or rules, referred to as manufacturing constraints, are included explicitly in the optimization problem as series of linear inequalities. The material selection and thickness variation are optimized simultaneously through interpolation functions with penalization. Numerical results for several parameterizations of a finite element model of a generic main spar from a wind turbine blade are presented. The different parameterizations represent different levels of complexity with respect to manufacturability. The results will thus give insight into the relation between potential weight saving and design complexity. The results show that the DMTO method is capable of solving the problems robustly with only few intermediate valued design variables. 相似文献