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121.
Lipid metabolism was studied in rats fed diets containing corn oil, coconut oil, or medium-chain triglyceride (MCT), a glyceride
mixture containing fatty acids of 8 and 10 carbons in length. The ingestion of MCT-supplemented, cholesterolfree diets depressed
plasma and liver total lipids and cholesterol as compared with corn oil-supplemented diets. In rats fed cholesterol-containing
diets, plasma cholesterol levels were not influenced by dietary MCT, but liver cholesterol levels were significantly lower
than in animals fed corn oil. In vitro cholesterol synthesis from acetate-1-14C was lower in liver slices of rats that consumed MCT than in similar preparations from corn oil-fed rats. Studies of fatty
acid carboxyl labeling from acetate-1-14C and the conversion of palmitate-1-14C to C18 acids by liver slices showed that chain-lengthening activity is greater in the liver tissue of rats fed MCT than in the liver
of animals fed corn oil. The hepatic fatty acid desaturation mechanisms, evaluated by measuring the conversion of stearate-2-14C to oleate, was also enhanced by feeding MCT.
Adipose tissue of rats fed MCT converts acetate-1-14C to fatty acids at a much faster rate than does tissue from animals fed corn oil. Evidence is presented to show that the
enhanced incorporation of acetate into fatty acids by the adipose tissue of rats fed MCT represents de novo synthesis of fatty
acids and not chain-lengthening activity. Data are also presented on the fatty acid composition of plasma, liver, and adipose
tissue lipids of rats fed the different fats under study. 相似文献
122.
Campbell Charles T. Grant Ann W. Starr David E. Parker Stephen C. Bondzie Victor A. 《Topics in Catalysis》2000,14(1-4):43-51
Many industrially important catalysts consist of late transition metal particles supported on the surfaces of oxide materials. Our studies of such systems using model catalysts consisting of metal films vapor deposited onto the surfaces of single-crystalline oxides are reviewed here. Systems studied include Cu on ZnO, Pt on ZnO, Au on TiO2 and Cu, Ag and Pb on MgO. A unique adsorption microcalorimeter was developed to measure directly the energetic stability of the metal atoms on the oxide surfaces and the adhesion energy at the metal/oxide interface, which clarify the structural and chemisorption properties of the ultrathin metal particles. The structure of the oxide surface and the metal particles was elucidated by low-energy electron diffraction (LEED), low-energy ion scattering spectroscopy (ISS), angular-resolved X-ray photoelectron spectroscopy (XPS) and X-ray photoelectron diffraction (XPD). The electronic character of the metal particles was revealed by XPS, Auger electron spectroscopy (AES), band-bending and work function measurements. Sintering rates were measured by temperature-programmed ion scattering spectroscopy (TPISS). The chemisorption properties of these particles and their catalytic reactivity were monitored by mass spectroscopy and temperature-programmed desorption (TPD). 相似文献
123.
Eicosapentaenoic acid is primarily responsible for hypotriglyceridemic effect of fish oil in humans 总被引:4,自引:0,他引:4
The aim of this study was to determine whether eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA), or both, were responsible
for the triglyceride (TG)-lowering effects of fish oil. EPA (91% pure) and DHA (83% pure), a fish oil concentrate (FOC; 41%
EPA and 23% DHA) and an olive oil (OO) placebo (all ethyl esters) were tested. A total of 49 normolipidemic subjects participated.
Each subject was given placebo for 2–3 wk and one of the n-3 supplements for 3 wk in randomized, blinded trials. The target
n-3 fatty acid (FA) intake was 3 g/day in all studies. Blood samples were drawn twice at the end of each supplementation phase
and analyzed for lipids, lipoproteins, and phospholipid FA composition. In all groups, the phospholipid FA composition changed
to reflect the n-3 FA given. On DHA supplementation, EPA levels increased to a small but significant extent, suggesting that
some retroconversion may have occurred. EPA supplementation did not raise DHA levels, however, FOC and EPA produced significant
decreases in both TG and very low density lipoprotein (VLDL) cholesterol (C) levels (P<0.01) and increases in low density lipoprotein (LDL) cholesterol levels (P<0.05). DHA supplementation did not affect cholesterol, triglyceride, VLDL, LDL, or high density lipoprotein (HDL) levels,
but it did cause a significant increase in the HDL2/HDL3 cholesterol ratio. We conclude that EPA appears to be primarily responsible for TG-lowering (and LDL-C raising) effects of
fish oil. 相似文献
124.
Single-walled carbon nanotube (SWCNT)/silicone rubber composites that can be used in fabricating compliant electrodes are prepared by spraying a mixed solution of ionic-liquid-based SWCNT gel and silicone rubber onto an elastic substrate. Subsequently, the composites are exposed to nitric acid vapor. Scanning electron microscopy and atomic force microscopy images of the composites show that the SWCNTs are finely dispersed in the polymer matrix due to the addition of the ionic liquid. Doping of the SWCNTs by nitric acid can significantly lower the sheet resistance (Rs) of the composites; samples with 4 wt% of SWCNT content exhibit the lowest Rs value (50 Ω sq?1). This sheet resistance corresponds to a conductivity value of 63 S cm?1. In addition, the composites retain a high conductivity after several tensile strains are applied. Stretching the composite sample to 300% of the original length increased the Rs value to 320 Ω sq?1 (19 S cm?1). Even after 20th stretch/release/stretch cycle, the conductivity remains constant at a value of 18 S cm?1. These results provide a scalable route for preparing highly stretchable and conductive SWCNT composites with relatively low SWCNT concentrations. 相似文献
125.
Multilayer films for food packaging applications composed of polyvinyl alcohol (PVOH) as the core layer and polyhydroxyalkanoate (PHA) as the outer skin layers were produced by the co‐extrusion process. Rheological properties of PVOH and PHA were performed and analyzed before co‐extruding into a cast film. Analysis of the rheological data indicated the processing temperatures and grades of the PVOH and PHA polymers that would produce similar viscosity and melt flow properties. To improve adhesion of the layers, PHA was grafted with maleic anhydride using a dicumyl peroxide initiator to provide a tie layer material, which improved the peel strength of the PHA and PVOH layers by over 2×. Oxygen transmission rate (OTR) testing showed that the multilayer sample provided an OTR of 27 cc/m2‐day at 0% relative humidity (RH) and rates of 41 and 52 cc/m2‐day at relative humidity values of 60% and 90% RH, respectively. This indicates significant barrier performance enhancement over monolayer PVOH that provided an OTR of 60 cc/m2‐day at 0% RH and 999 cc/m2‐day at 60% RH. Biodegradation testing of the films in the marine environment showed that both the unmodified and maleated PHA polymers displayed high levels of mineralization, whereas the PVOH material did not. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
126.
Christopher Thellen Danielle Froio Jeanne Lucciarini Nandika Ann D'Souza 《Polymer》2005,46(25):11716-11727
Plasticized poly(l-lactide) (PLA) montmorillonite layered silicate (MLS) nanocomposites were compounded and blown-film processed using a co-rotating twin screw extruder. PLA was mixed with 10 wt% acetyltriethyl citrate ester plasticizer and 5 wt% of an organically modified montmorillonite at various screw speeds. Wide-angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM) determined that the compounded pellets and the blown film PLA/MLS nanocomposites were intercalated. The effect of processing screw speeds on the barrier, thermal, mechanical, and biodegradation properties of the nanocomposites were analyzed and compared to the neat polymer. Nanocomposite films show a 48% improvement in oxygen barrier and a 50% improvement in water vapor barrier in comparison to the neat PLA. The thermogravimetric analysis (TGA) showed an overall 9 °C increase in the decomposition temperature for all of the nanocomposites. Differential scanning calorimetry (DSC) has determined that the glass transition, cold crystallization and melting point temperatures were not significantly influenced by the presence of MLS. Mechanical properties of the nanocomposites showed that the Young's modulus increased by 20% and the ultimate elongation of the nanocomposites were not sacrificed in comparison to the neat samples. Biodegradation rates in soil were slightly greater for the PLA/MLS nanocomposite than the pure PLA. However, none of the PLA pure and nanocomposites achieved significant biodegradation levels after 180 days. 相似文献
127.
Removal of estrogenicity in Swedish municipal sewage treatment plants 总被引:17,自引:0,他引:17
The human estrogen receptor alpha-test, hosted in a yeast strain, was used to quantify estrogenicity in three-week composite samples of untreated and treated effluents from 20 Swedish municipal sewage treatment plants. The treatment plants were selected to represent different treatment processes regarding chemical precipitation and microbial procedures. The discharge from Swedish domestic sewage treatment plants contained estrogenic compounds corresponding to <0.1-15 ng estradiol equivalents/L. Low levels of estrogenic activity were also found in a river receiving municipal effluents, 3.5-35 km downstream the outlet from a sewage treatment works. The range of estrogenicity in untreated, raw sewage effluents was found to be 1-30 ng estradiol equivalents/L. Generally, wastewater treatment reduced the estrogenicity and extended biological treatment was most effective in its removal. Activated sludge treatment tended to be more effective than trickling filters, whereas chemical precipitation using iron or aluminium salts without biological treatment showed little effectivity. The study showed that treatment methods in current use are able to eliminate or largely reduce estrogenicity in domestic wastewater. 相似文献
128.
基于各向异性Gibbs随机场与高斯混合模型的脑MR图像分割算法 总被引:1,自引:1,他引:0
为了克服高斯混合模型(GMM)的局限性,利用 Gibbs 理论和图像结构信息构造各向异性 Gibbs 随机场,并将其引入到 GMM 框架中,完善 GMM 的分类效果,使其在克服噪声影响的同时,还能够保持细长拓扑结构区域信息以及角点区域信息.实验结果证明,文中算法可以得到较好的分类结果. 相似文献
129.
Liberalisation and privatisation have increased the need to gain more understanding into the management of hydro storage (HS) plants. We analyse what types of reservoir management policies enable an owner or a public authority to achieve their respective objectives. By “policy” we understand simple, easily applicable decision rules, which enable a decision maker to decide when and how much to produce based on currently available information. We use a stylised deterministic simulation model of a hydro-power producer (HP) who behaves strategically. We study a non-liberalised market, where the authorities aim to minimise the total electricity cost for customers and a liberalised market where the HP attempts to maximise his contribution. This enables us to evaluate the impact of the liberalisation of HS production decisions on production volumes and electricity prices. We conclude that imposing rigid policies with the aim of limiting the potential for strategic behaviour can create incentives to produce only at very high prices throughout the year. This can lead to very high total costs, especially when the producer has most flexibility (large reservoirs combined with large turbine capacity). More surprisingly, we observe lower total production in a non-liberalised market. 相似文献