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41.
The relative viscosity (RV) of polyvinylpyrrolidone (PVP) with different molecular weights was measured with a glass capillary viscometer and with a differential dual‐capillary viscometer in water at different concentrations. For the differential dual‐capillary viscometer, RV increases with a decreasing flow rate, especially for high molecular weight PVP at a 1% concentration. A good agreement in the RV between the two methods can be obtained for PVP with different molecular weights and at various concentrations if an appropriate flow rate is selected for the differential dual‐capillary viscometer. Special precaution is needed when using the differential dual‐capillary viscometer to measure the viscosity of a pure solvent. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1312–1315, 2002 相似文献
42.
43.
Louise M. Canfield Judy M. Hopkinson Anne F. Lima Gail S. Martin Kyoto Sugimoto Jeanne Burr Larry Clark Daniel L. McGee 《Lipids》1990,25(7):406-411
A quantitative method was developed for the assay of vitamin K in human colostrum and milk. The procedure combines preparative
and analytical chromatography on silica gel in a nitrogen atmosphere followed by reversed phase high performance liquid chromatography
(HPLC). Two HPLC steps were used: gradient separation with ultraviolet (UV) detection followed by isocratic separation detected
electrochemically. Due to co-migrating impurities, UV detection alone is insufficient for identification of vitamin K. Exogenous
vitamin K was shown to equilibrate with endogenous vitamin K in the samples. A statistical method was incorporated to control
for experimental variability. Vitamin K1 was analyzed in 16 pooled milk samples from 7 donors and in individual samples from 15 donors at 1 month post-partrum. Vitamin
K1 was present at 2.94±1.94 and 3.15±2.87 ng/mL in pools and in individuals, respectively. Menaquinones, the bacterial form
of the vitamin, were not detected. The significance of experimental variation to studies of vitamin K in individuals is discussed. 相似文献
44.
David Kritchevsky Larry M. Davidson Daniel A. Scott J. J. Van der Watt Dennis Mendelsohn 《Lipids》1988,23(3):164-168
Male Vervet monkeys (7/treatment) were fed a “Western” diet containing 46.2% calories as fat, 39.8% as carbohydrate and 14.0%
as protein. The diet was augmented with 10% cellulose or 10% pectin. A third (control) group of seven monkeys was fed a commercial
ration augmented with fruit and bread. After 34 weeks, serum cholesterol levels were elevated significantly in the two test
groups compared with the controls but there was no difference between the two fiber-fed groups. Serum triglycerides were unaffected.
Liver cholesterol levels were the same in all three groups but liver triglyceride levels were lower in the monkeys fed cellulose.
Biliary lipids were similar in all three groups as were the calculated lithogenic indices. The average aortic sudanophilia
(percent of total area) in the three groups was cellulose, 10.6±2.5; pectin, 8.1±2.5; and control, 1.1±0.4. One animal in
each of the groups fed “Western” diet exhibited an atherosclerotic plaque. The results indicate that there is no difference
between pectin and cellulose with regard to their effects on either lipidemia or aortic sudanophilia in Vervet monkeys fed
a Western-type diet. 相似文献
45.
Larry G. Butler David J. Riedl D. G. Lebryk H. J. Blytt 《Journal of the American Oil Chemists' Society》1984,61(5):916-920
The grain of some varieties of sorghum contains 2% or more condensed tannin; many other varieties contain no tannin at all.
Agronomic advantages, e.g., resistance to bird depredation, are associated with high-tannin sorghums, which have relatively
low nutritional value for nonruminants. The biological effects of tannin are a result of its propensity for binding proteins;
both hydrogen bonding and hydrophobic interactions are involved. Sorghum tannins can bind dietary proteins and reduce their
digestibility. Purified digestive enzymes are inhibited by tannin, but significant inhibition in vivo is unlikely. Proteins
differ greatly in their affinity for tannin. Those with highest affinity are large, have an open structure, contain no bound
carbohydrate and are rich in proline. Sorghum proteins of the alcohol-soluble prolamine fraction associate strongly with tannin,
are difficult to remove during tannin purification and are found combined with tannin in the indigestible residue after in
vitro digestion with pepsin. On germination, the seed may sacrifice a portion of these proteins to bind the tannin that might
otherwise interfere with metabolism by inhibiting seed enzymes. During seed development, tannin molecules are relatively short
and do not effectively precipitate proteins; as the seed dries, tannins undergo polymerization to an average of ca. 6 flavan-3-ol
units/molecule. The antinutritional effects of sorghum tannins can be eliminated by soaking the grain in dilute aqueous alkali,
but not by cooking. When rats are put on high-tannin sorghum diets, their parotid glands undergo hypertrophy and produce a
group of unique salivary proteins with extremely high affinity for tannin. These proteins contain over 40% proline and are
devoid of sulfur-containing and aromatic amino acids. This metabolic adaption may protect rats against tannin by binding and
inactivating it immediately when it enters the digestive tract.
Presented at the AOCS Meeting, May 11, 1983. 相似文献
46.
(Z)-11-Octadecenyl acetate (Z11–18Ac) and (Z)-11-eicosenyl acetate (Z11–20Ac) were identified as the aggregation pheromones ofDrosophila ananassae, andZ11–20Ac was identified as the aggregation pheromone ofDrosophila bipectinata. Z11–18Ac andZ11–20Ac were not attractive alone; however, in combination with fermenting food odors, the acetates attracted flies of both sexes in a wind-tunnel olfactometer. The pheromones were present in the ejaculatory bulb of sexually mature male flies and transferred to the female during mating. MaleD. bipectinata released little if anyZ11–20Ac to the food; however, recently mated females releasedZ11–20Ac to the surrounding surfaces in just a few hours after mating.D. ananassae males, on the other hand, appeared to release moreZ11–18Ac andZ11–20Ac to the surroundings than mated females. AlthoughD. bipectinata males had noZ11–18Ac, flies were as attracted toZ11–18Ac as to an equal quantity ofZ11–20Ac.D. ananassae were attracted toZ11–18Ac but not toZ11–16Ac orZ11–20Ac. However,Z11–20Ac in combination withZ11–18Ac was significantly more attractive thanZ11–18Ac alone. 相似文献
47.
P. Larry Phelan Caryn J. Roelofs Roger R. Youngman Thomas C. Baker 《Journal of chemical ecology》1991,17(3):599-613
Ovipositional host-finding in the navel orangeworm,Amyelois transitella (Walker), is brought about by an in-flight response to host odors. Wind-tunnel studies of the response of gravid females to almonds showed that this response is mediated primarily by long-chain fatty acids, particularly oleic acid and linoleic acid. Evidence for the behavioral activity of fatty acids is based on the fact that: (1) behavioral activity of almond oil was concentrated in a single liquid chromatographic fraction whose composition was predominantly long-chain fatty acids, (2) behavioral activity was lost when either almond oil or the active fraction of that oil was treated with diazomethane, (3) full activity was elicited by a selective extraction of free fatty acids from crude almond oil, and (4) upwind response by females was elicited by a blend of synthetic oleic and linoleic acids, albeit at a level less than that elicited by almond oil. Five fatty acids identified from the almond oil were: myristic acid (1%), palmitic acid (16%), stearic acid (3%), oleic acid (58%), and linoleic (22%). Attraction to various combinations of synthetic acids was observed only when oleic acid was present, and oleic acid elicited upwind flights to the source when presented alone; however, short-range responses were enhanced by the addition of linoleic acid, which elicited no long-range orientation by itself. Despite significant levels of attraction to synthetic blends, the percentage of females flying to the source was lower than that flying to acidulated almond oil, the best natural attractant tested. Thus, although longrange response may be mediated primarily by a blend of oleic and linoleic acids, additional and as yet unidentified components must also play an important role. Long-range chemically modulated host finding in this and other generalist plant feeders is discussed with respect to current models of the evolution of host finding, and it is argued that suggestions that long-range host finding should be correlated with narrowness of host utilization are logically flawed and are not supported by our current understanding of specific examples of host finding. 相似文献
48.
The chemical basis underlying orientation to fruit and fungal odors was investigated for the dried-fruit beetle,Carpophilus hemipterus (L.). In wind-tunnel bioassays of walking and flight response from 1.8 m, beetles were attracted to odors of the yeastSaccharomyces cerevisiae on agar, aseptic banana, or banana inoculated withS. cerevisiae, although both banana substrates elicited greater response than the yeast alone. When presented in a two-choice bioassay, the yeast-inoculated banana attracted approximately twice as many beetles as did the aseptic banana. GC-MS analysis of the headspace volatiles above these odor sources revealed a somewhat more complex and concentrated volatile profile for yeast-inoculated banana than for aseptic banana. The odor from yeast on agar had fewer components, and these were present at lower concentrations than the odors of either banana substrate. By blending mineral-oil or aqueous solutions of the 18 components of inoculated-banana odor in varying concentrations, it was possible to mimic closely the headspace profile of the natural odor. This synthetic odor also elicited beetle attraction in the wind tunnel at levels comparable to the inoculated banana. Through a series of bioassays in which individual components were subtracted from or added to a synthetic odor blend, it was determined that ethyl acetate, acetaldehyde, 2-pentanol, and 3-methylbutanol comprised the simplest blend of compounds evoking full behavioral response. However, 2-methylpropanol or butanol were apparently interchangeable with 3-methylbutanol in this blend, and comparable response could also be elicited by replacing acetaldehyde with a combination of both 2-pentanone and 3-hydroxy-2-butanone. Thus, our results suggest that this generalist insect herbivore locates its hosts by a long-range response to a variety of blends of common fruit volatiles, whose concentrations are enhanced by fungi. 相似文献
49.
Advances in fabricating superplastically formed and diffusion bonded components for aerospace structures 总被引:1,自引:0,他引:1
Larry D. Hefti 《Journal of Materials Engineering and Performance》2004,13(6):678-682
Superplastic forming and diffusion bonding (SPF/DB) production hardware is being fabricated today for aerospace applications.
Metal tooling is being used to bring the titanium sheets into contact so diffusion bonding can occur. However, due to material
sheet and tooling tolerances, good bond quality is difficult to achieve over large areas. A better method for achieving DB
is to use “stop-off” inside sealed sheets of titanium, which constitutes a pack, and then the pack is bonded using external
gas pressure. A good method for heating the pack for this process is to use induction heating. Components using “stop-off”
that were diffusion bonded first and then superplastically formed have shown much better bond quality than components that
were produced using matched metal tooling. This type of tooling has been successful at bonding small areas as long as the
exerted pressure is concentrated on the area where bonding is required. Finite element modeling is providing weight effect
solutions for titanium SPF/DB aerospace structures.
This paper was presented at the International Symposium on Superplasticity and Superplastic Forming, sponsored by the Manufacturing
Critical Sector at the ASM International AeroMat 2004 Conference and Exposition, June 8–9, 2004, in Seattle, WA. The symposium
was organized by Daniel G. Sanders, The Boeing Company. 相似文献
50.
Thermal stability of polyaniline 总被引:2,自引:0,他引:2
Thermal stability data for neutral (emeraldine base) and doped polyaniline with various counter anions are reported. The emeraldine base is a highly heat-stable polymer, with thermal stability up to 420 °C. The thermal stability of doped polyaniline is dependent on the counter anion. The methane sulfonic acid doped polyaniline is stable up to 250 °C. The decomposition of the doped polyaniline is seen as a two-step process. The first step is the loss of the dopant and the second step corresponds to the decomposition of the backbone. 相似文献