The fatty acids of seed oils of the Flacourtiaceae,Hydnocarpus anthelmintica, Caloncoba echinata andTaraktogenus kurzii, have been examined by a combination of capillary gas chromatography, silver ion high performance liquid chromatography and
gas chromatography-mass spectrometry. In addition to the common range of cyclopentenyl fatty acids found in such oils, 13-cyclopent-2-enyltridec-4-enoic
acid was a major component ofH. anthelmintica and was identified by mass spectrometry as its picolinyl ester and dimethyldisulphide adduct. It has not previously been
found in nature. In the other seed oils, the isolated double bond in the corresponding fatty acid was in position 6, as expected.
Similarly,cis-4-hexadecenoic acid and C16 and C18 cyclopentyl fatty acids were identified for the first time inH. anthelmintica. Iso- andanteiso-methylbranched fatty acids were present in trace amounts. 相似文献
A computer model that treats ceramic-powder matrix–ceramic whisker composites as a percolative network of whiskers has been developed. The model calculates the critical fraction of whiskers at the percolation threshold for a two-dimensional random network of whiskers. The computed critical fraction was found to display an inverse dependence on whisker aspect ratio. In addition, the computed critical fraction (27 vol% for a whisker aspect ratio of 7) agreed well with the zero-shrinkage whisker fraction of 30 vol% in the densification of a colloid-pressed alumina–silicon carbide composite that exhibited a two-dimensional orientation of such whiskers. 相似文献
Early diagnosis of Alzheimer’s disease (AD) is essential if treatments are to be administered at an earlier point in time before neurons degenerate to a stage beyond repair. In order for early detection to occur tools used to detect the disorder must be sensitive to the earliest of cognitive impairments. Virtual reality technology offers opportunities to provide products which attempt to mimic daily life situations, as much as is possible, within the computational environment. This may be useful for the detection of cognitive difficulties. We develop a virtual simulation designed to assess visuospatial memory in order to investigate cognitive function in a group of healthy elderly participants and those with a mild cognitive impairment (MCI). Participants were required to guide themselves along a virtual path to reach a virtual destination which they were required to remember. The preliminary results indicate that this virtual simulation has the potential to be used for detection of early AD since significant correlations of scores on the virtual environment with existing neuropsychological tests were found. Furthermore, the test discriminated between healthy elderly participants and those with a MCI. 相似文献
Measurements of the cell have been used to determine activity coefficients of Na2O in molten NaCl, Na2SO4 and Na2CO3. Extreme negative deviations from Raoult's law were observed (γ < 10?3). In NaCl and Na2SO4, γ is independent of concentration below 1 m/o Na2O, but in Na2CO3, the activity is nearly independent of concentration, probably because the oxide reacts with dissolved O2 to form superoxide (O?2). 相似文献
The metabolism of α-linolenic acid from canola oil was studied in eight normolipidemic men. The 42-day study was divided into
three periods: a 6-day pre-experimental and two 18-day experimental. Approximately 75% of the dietary fat (28% of total energy)
was provided by a mixture of fats during the pre-experimental period and either canola oil (CO) or sunflower oil (SO) during
the experimental periods. The CO and SO diets were fed in a cross-over design. The ratios of linoleic to linolenic acid were
2.6∶1 and 73.9∶1 in the CO and SO diets, respectively. Dietary fat source had an effect on plasma phospholipid fatty acids:
18∶1n−9, 18∶3n−3 and 20∶5n−3 were higher (p<0.05), and 18∶2n−6 was lower in the phosphatidylcholine fraction; 18∶1n−9 was
higher and 20∶4n−6 lower in the phosphatidyl-ethanolamine fraction; and 18∶1n−9 and 20∶5n−3 were higher and 20∶4n−6 and 22∶6n−3
were lower in the alkenylacyl-ethanolamine phospholipid fraction on the CO diet as compared to the SO diet. Consumption of
the canola oil diet resulted in higher n−3 fatty acid levels and lower n−6 fatty acid levels in plasma phospholipids than
consumption of the sunflower oil diet. 相似文献
The oxygen nonstoichiometry, y, of La2– x Sr x CuO4– y (0 ≤ x ≤ 1) was determined as a function of temperature (800–1050°C) and oxygen partial pressure (10–4 to 1 atm) by a thermogravimetric technique. The results were interpreted in terms of a number of defect models. It was found that a model based on the defect reaction 4Cu×Cu+ 2 V ¨o+ O2(g)= 4Cu.Cu+ 2O×o described the results well when the x and y dependences of the partial molar enthalpy of oxygen in the solid were considered. The large defect concentrations observed in this system lead to defect interactions, possibly ordering on the oxygen sublattice. 相似文献
Acetic, propionic, butyric, isobutyric, valeric, and isovaleric acids have been identified in extracts of the excreta of the house cricket,Acheta domesticus (L.), by gas-liquid chromatography. Solutions of propionic acid applied to filter paper aggregated 1- to 2-week-old larvae, while solutions of acetic, butyric, valeric, and isovaleric acids were without effect. 相似文献
The pyrrolidide and picolinyl ester derivatives of the fatty acids in two natural lipid samples rich in unsaturated fatty
acids, pig testis lipids and cod liver oil were satisfactorily resolved on capillary columns of fused silica coated with stationary
phases of varying polarity. The picolinyl esters, in particular, when subjected to gas chromatography-mass spectrometry on
a column containing a cross-linked methyl silicone, gave distinctive mass spectra, which could be interpreted in terms of
both the numbers and positions of the double bonds. 相似文献
The high-temperature interaction between ~2.5 mg/cm2 of Na2SO4 and an atmospheric plasma sprayed (APS) Yb2Si2O7 topcoat–Si bond coat system on SiC CMC substrates was studied for times up to 240 h at 1000°C–1316°C in a 0.1% SO2–O2 gaseous environment. Yb2Si2O7 reacted with Na2SO4 to form Yb2SiO5 and an intergranular amorphous Na-silicate phase. Below 1200°C, the reaction was sluggish, needing days to cause morphological changes to the “splat microstructure” associated with APS coatings. The reaction was rapid at 1200°C and above, needing only a few hours for the entire topcoat to transform into a granulated microstructure consisting of Yb2SiO5 and Yb2Si2O7 phases. Na2SO4 deposits infiltrated the Yb2Si2O7 topcoat and transformed into an amorphous Na-silicate in less than 1 h at all exposure temperatures. Quantitative assessment of the Yb2SiO5 area fraction in the topcoat showed a linear decrease over time at 1316°C, attributed to reaction with the SiO2 thermally grown oxide (TGO) formed on the Si bond coat and rapid transport through the interpenetrating amorphous Na-silicate grain boundary phase. It was predicted that nearly 2 weeks is needed for complete removal of Yb2SiO5 from the topcoat at 1316°C for a single applied loading of Na2SO4. 相似文献
Hi Nicalon, Hi Nicalon S, Sylramic, and Sylramic iBN SiC fibers were exposed to ~60 μg/cm2 of Na2SO4 in a 0.1% SO2/O2 gaseous environment for times between 0.75 and 24 h at 1000°C. After exposure, the corrosion products were characterized using SEM, EDS, ICP-OES, TEM, and EFTEM to determine their high-temperature resistance to Na2SO4 and key reaction mechanisms. All SiC fiber types tested in this work exhibited little resistance to Na2SO4 deposit-induced attack relative to their behavior in dry O2 environments. It was found that Hi-Nicalon displayed the least resistance to Na2SO4 deposit-induced attack due to excess carbon content resulting in the formation of a highly porous crystalline oxide and promotion of basic corrosion conditions. All fiber types formed a crystalline SiO2 reaction product, either cristobalite or tridymite. Sylramic and Sylramic iBN formed a crystalline SiO2 reaction layer containing TiO2 needles due oxidation of TiB2 particles. Additionally, Na2SO4 deposits resulted in pitting of all fiber surfaces. 相似文献