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21.
Online social networks gained their popularity from relationships users can build with each other. These social ties play an important role in asserting users' behaviors in a social network. For example, a user might purchase a product that his friend recently bought. Such phenomenon is called social influence, which is used to study users' behavior when the action of one user can affect the behavior of his neighbors in a social network. Social influence is increasingly investigated nowadays as it can help spreading messages widely, particularly in the context of marketing, to rapidly promote products and services based on social friends' behavior in the network. This wide interest in social influence raises the need to develop models to evaluate the rate of social influence. In this paper, we discuss metrics used to measure influence probabilities. Then, we reveal means to maximize social influence by identifying and using the most influential users in a social network. Along with these contributions, we also survey existing social influence models, and classify them into an original categorization framework. Then, based on our proposed metrics, we show the results of an experimental evaluation to compare the influence power of some of the surveyed salient models used to maximize social influence. 相似文献
22.
Abstract. In this paper we consider the estimation of the degree of differencing d in the fractionally integrated autoregressive moving-average time series model ARFIMA ( p, d, q ). Using lag window spectral density estimators we develop a regression type estimator of d which is easy to calculate and does not require prior knowledge of p and q. Some large sample properties of the estimator are studied and the performance of the estimator for small samples is investigated using the simulation method for a range of commonly used lag windows. Some practical recommendations on the choice of lag windows and the choice of the window parameters are provided. 相似文献
23.
The use of polymeric materials for the administration of pharmaceuticals, and as biomedical devices has increased dramatically. This review focuses on synthetic biodegradable polymers of current interest for medical use, based on ester and anhydride bonds. Special attention is given to factors affecting biodegradation, including: polymer structure, morphology, molecular weight, radiation, and chemical treatment, as well as the effects of drugs and plasticizers added to the polymer mass. The toxicity and biocompatibility of the polymers and their current and future applications in medicine are also briefly reviewed. 相似文献
24.
The effects of linoleic, linolenic and columbinic acids fed as 4% of a high carbohydrate (50% glucose) diet on the activities
and the amounts of several enzymes associated with fatty acid synthesis in livers and mammary glands of lactating mice were
compared with those for stearic and oleic acids. Fatty acid synthesis, measured in vivo, was significantly lower in livers
of mice ingesting all 3 polyunsaturated fatty acids (PUFA), whereas in mammary glands synthesis was lower only in mice receiving
columbinic acid. The activities of fatty acid synthetase (FAS) and acetyl CoA carboxylase were significantly reduced in liver
by all 3 PUFA, as were activities of glucose-6-phosphate dehydrogenase, malic enzyme (ME) and citrate cleavage enzyme (CCE),
also associated with lipogenesis. In mammary gland, on the other hand, the activities of these enzymes were unaffected by
dietary PUFA. The tissue contents of FAS, ME and CCE, measured by rocket immunoelectrophoresis, were found to be significantly
reduced in liver by linoleate, linolenate and columbinate but were not significantly altered in mammary gland. The decrease
in hepatic lipogenesis observed was principally due to a decrease in the amounts of these enzymes induced by the dietary PUFA
but the inhibition in mammary gland caused by columbinate could not be accounted for by a reduction in enzyme contents and
therefore may be due to allosteric effects which occur when fatty acid synthesis is measured with3H2O. The fatty acid composition in liver and mammary gland of dams and in liver and kidney of pups completely reflected dietary
fatty acids. Columbinate made up ca. 20% of the total fatty acids in both tissues of the columbinic acid-fed mice and ca.
15% in the pup tissues. This suggests that columbinate is incorporated into milk lipids of dams and is easily absorbed by
pups. The elevated ratios of 16/16∶1 and 18/18∶1 in liver and mammary gland of dams and liver and kidney of the pups from
dams fed linoleate, linolenate and columbinate suggest that each of these polyunsaturated fatty acids in the diet can inhibit
the activity of Δ9 desaturase. 相似文献
25.
R. C. Wijesundera R. G. Ackman V. Abraham J. M. deMan 《Journal of the American Oil Chemists' Society》1988,65(9):1526-1530
A simple method for the determination of total sulfur content in vegetable and marine oils is described. The method involves
combustion of the oil sample in an oxygen bomb to convert all forms of sulfur to sulfate ions with subsequent determination
of the sulfate by ion chromatography and indirect ultraviolet detection. The ultraviolet system described is more sensitive
than conductivity detection and enables the method to be applied more widely.
Application of the method to a variety of vegetable and marine oils showed the general occurrence of sulfur in fats and oils,
albeit often at a low level. Among the samples examined, crude Canola oil had the highest sulfur content (25.0 mg/kg) followed
by the marine oils (5.8-15.2 mg/kg) and the non-Cruciferae vegetable oils (2.0-6.1 mg/kg).
To whom correspondence should be addressed. 相似文献
26.
A centrifugal sedimentation method (CSM) is proposed for the assessment of deformability of red blood cells. The method is based on the premise that a red blood cell (RBC) should deform in a centrifugal field due to the variation of the centrifugal acceleration with the distance from the center of rotation. This change in shape of the RBC leads to a change in the rate of sedimentation in the centrifugal field. The rate of sedimentation, which serves as a measure of deformability, is characterized by an apparent sedimentation coefficient (ASC) and its normalized value (NASC), which is calculated by comparison with a control group of normal RBCs. It has been shown that the NASC is sensitive to the speed of rotation, to treatments with glutaraldehyde, diamide, or chlorpromazine, to heat treatment and to osmotic pressure variations. 相似文献
27.
Sulfur compounds were added to refined and bleached canola oil before hydrogenation in the form of allyl, heptyl and 2-phenethyl
isothiocyanates, and the effects on hydrogenation rate, solid fat content and percentagetrans fatty acids were determined. The poisoning effect was most pronounced with allyl isothiocyanate and least with phenethyl
isothiocyanate. As the amount of added sulfur increased, the hydrogenation rate decreased. Of the three isothiocyanates used,
allyl isothiocyanate caused formation of larger amounts oftrans isomers. An increased sulfur level in the oil resulted in increased solid fat content andtrans isomer level. Allyl isothiocyanate also caused formation of larger amounts of solid fat than other isothiocyanates at all
levels of sulfur addition. 相似文献
28.
Fabienne Fay Isabelle Linossier Valérie Langlois Karine Vallee‐Rehel Michal Y. Krasko Abraham J. Domb 《应用聚合物科学杂志》2007,106(6):3768-3777
This article describes the synthesis and in vitro analysis of poly(ester anhydride) antimicrobial protection coatings. Poly(ester anhydride)s composed of ricinoleic acid, sebacic acid, terephthalic acid, and isophthalic acid were used in this study. The polymers were compatible with various fillers commonly used in paint preparation. The in vitro experiments showed that the polymers are able to release diuron, an antimicrobial agent, for months. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
29.
In addition to 2-methyl-4-heptanone, 6-methyl-5-hepten-2-one, and iridodials, the anal gland exudate of the dolichoderine ant,Tapinoma simrothi, contains 4-heptanone and 4-hydroxy-4-methyl-2-pentanone. The secretion functions as an alarm pheromone. 相似文献
30.
A mathematical model of fluid flow and mass transfer in a packed bed was derived and used to evaluate the liquid phase axial dispersion and mass transfer coefficients under high pressure conditions. The least-squares method was used to evaluate the rate parameters from experimental breakthrough curves, and the agreement between the concentration curves predicted from rate parameters and those measured experimentally was good. Experiments were performed at 20 and 200°C with water as a solvent and nonporous soda-lime glass beads as packing. Although the axial dispersion coefficient was independent of temperature and pressure, the mass transport parameters were found to be pressure dependent. 相似文献