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1.
Igor Rochlin Yonatan Aumann David Sarne Luba Golosman 《Autonomous Agents and Multi-Agent Systems》2016,30(3):526-552
We consider team-work settings where individual agents incur costs on behalf of the team. In such settings it is frequently the custom to reimburse agents for the costs they incur (at least in part) in order to promote fairness. We show, however, that when agents are self-interested, such reimbursement can result in degradation in efficiency—at times severe degradation. We thus study the relationship between efficiency and fairness in such settings, distinguishing between ex-ante and ex-post fairness. First, we analyze reimbursement policies that reimburse solely based on purchase receipts (as is customary), and show that with such policies the degradation in both efficiency and fairness can be unbounded. We thus introduce two other families of reimbursement policies. The first family guarantees optimal efficiency and ex-ante fairness, but not ex-post fairness. The second family improves (at times) on ex-post fairness, but at the expense of efficiency, thus providing a tradeoff between the two. 相似文献
2.
Yun Tu David Kingston Judy Kung Luba S. Kotlyar Bryan D. Sparks Keng H. Chung 《Petroleum Science and Technology》2006,24(3):327-338
The effectiveness of commercial oilsands separation processes relies on the water wettability of the solids. Consequently, the interaction between the mineral and organic matter types present in oilsands is of interest. In this work, we report results related to the adsorption of a pentane insoluble fraction from bitumen on kaolinite and illite, the major clay types present in oilsands. We determined adsorption from toluene solution by illite and kaolinite and use a combination of spectroscopic techniques to probe the organic coated clay surfaces to different depths. The results are compared with similar data for equivalent natural fractions from oilsands. 相似文献
3.
Maxim Stolyarchuk Julie Ledoux Elodie Maignant Alain Trouv Luba Tchertanov 《International journal of molecular sciences》2021,22(2)
Redox (reduction–oxidation) reactions control many important biological processes in all organisms, both prokaryotes and eukaryotes. This reaction is usually accomplished by canonical disulphide-based pathways involving a donor enzyme that reduces the oxidised cysteine residues of a target protein, resulting in the cleavage of its disulphide bonds. Focusing on human vitamin K epoxide reductase (hVKORC1) as a target and on four redoxins (protein disulphide isomerase (PDI), endoplasmic reticulum oxidoreductase (ERp18), thioredoxin-related transmembrane protein 1 (Tmx1) and thioredoxin-related transmembrane protein 4 (Tmx4)) as the most probable reducers of VKORC1, a comparative in-silico analysis that concentrates on the similarity and divergence of redoxins in their sequence, secondary and tertiary structure, dynamics, intraprotein interactions and composition of the surface exposed to the target is provided. Similarly, hVKORC1 is analysed in its native state, where two pairs of cysteine residues are covalently linked, forming two disulphide bridges, as a target for Trx-fold proteins. Such analysis is used to derive the putative recognition/binding sites on each isolated protein, and PDI is suggested as the most probable hVKORC1 partner. By probing the alternative orientation of PDI with respect to hVKORC1, the functionally related noncovalent complex formed by hVKORC1 and PDI was found, which is proposed to be a first precursor to probe thiol–disulphide exchange reactions between PDI and hVKORC1. 相似文献
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5.
Teresa M. Ignasiak Luba Kotlyar Nicolar Samman Douglas S. Montgomery Otto P. Strausz 《Fuel》1983,62(3):363-369
Athabasca asphaltene has been separated according to molecular weight on Bio-Beads SX-1 gel. The number-average molecular weights of the five arbitrary fractions obtained by this fractionation range from 1200 to 17000. The chemical, spectral and thermal properties of the fractions are all similar but their polymer-forming propensities are markedly different. The significance of this latter property, which is defined in terms of the amount of CH2Cl2-insoluble material produced upon thermolysis at 300 °C, increases rapidly with increasing molecular weight of the fraction. In contrast the whole asphaltene does not form polymer at 300 °C under the same conditions and it is concluded that the chain propagating steps are terminated by a variety of inhibitors that are contained in the asphaltene agglomerate. During gel permeation chromatography separation the clay present in the asphaltene concentrates in the higher-molecular-weight fractions. This affinity to attract the clay is thought to be related to the physical, and not the chemical, properties of these higher-molecular-weight materials. The clay also exerts a catalytic effect on the polymerization of the asphaltene fractions which is most pronounced in the highest-molecular-weight fraction and gradually decreases with decreasing molecular weight. 相似文献
6.
David Semyonov Ory Ramon Zoya Kaplun Luba Levin-Brener Nadya Gurevich Eyal Shimoni 《Food research international (Ottawa, Ont.)》2010,43(1):193-202
This study evaluates the implementation of a new process: spray freeze drying (SFD), to produce dry micro-capsules of Lactobacillus paracasei with high viability. The study concentrated on determining the survival of the cells, encapsulated in a matrix of maltodextrin and trehalose. SFD was compared with the conventional bulk freeze drying (BFD). Overall it was shown that SFD is a successful method to generate dry micro-capsules of probiotic cells with high viability (>60%). The spraying stage did not affect the viability of the bacteria. In the freezing stage, high osmotic pressures originated by elevated trehalose concentrations, helped preserving the cells viability. It was also found that the lower the maltodextrin molecular weight, the larger the beads volume and solids concentration, the higher is the bacteria survival during the freezing and drying stages. In the drying stage, trehalose concentration was also the critical factor that increased final probiotic viability. 相似文献
7.
This paper focuses on structures observed by scanning and transmission electron microscopy and atomic force microscopy upon and within the abdominal cuticle of the Oriental hornet, Vespa orientalis. Taken together, these structures form an 'organ' whose function is the absorption ef sunlight and storage of the resultant electrical energy. In principle, this organ resembles a solar cell. The gaster of the hornet is cone-shaped and comprised of the following components: (i) structures protruding from the epicuticular surface, which are arranged lengthwise and generally parallel to one another like furrows; (ii) these furrows overlie straight, terrace-like flat surfaces, which are shaped like imperfect polygons, each about 100 microm2 in area; (iii) each terrace abuts an area that is positioned lower than it, the juncture between the two is comprised of a stripe, which is vertical to the topmost polygonal flat and perpendicular to the furrows; (iv) between the juncture stripes, at distances of 10-100 microm apart, there are smooth flat surfaces reminiscent of a parabolic mirror of about 20 microm2, each possessing a rounded, eccentric area recessed to a depth of about 7.5 microm (i.e. a heat sinking housing), underneath which can be seen the upper part of the peripheral photoreceptor (PP); (v) cuticular lamellae, about 30 in number, create a pore between them in the PP region, fold in vertical fashion and enwrap the entire PP down to its broad base which is immersed in a yellow bacterial layer and where the cuticular layers are very thin. Presumably the light energy impinges vertically upon the individual terraced flat surfaces while the hornet is in flight, creating such situations for a fraction of a second at a time. The insolation is absorbed more intensively in the furrows, owing to their shape. The picked up solar energy is now transmitted as electric charges from the furrows to the conduction stripes between abutting terraces, and thence to: (a) the rhodopsin pigment in the PP (the smaller moiety), or (b) the numerous cuticular layers, depending on the energy level of the picked up photons (the larger moiety), and (c) finally to the bacterial layer for storage in its walls. The latter region will be a p-type as compared to the energy stored in the layers of brown cuticle. The cuticle thus was found to contain many PPs but within the cuticle they are dispersed in contrast to the situation in the compound eye, where the many photoreceptors are concentrated. 相似文献
8.
Teresa M. Ignasiak Luba Kotlyar Frederick J. Longstaffe Otto P. Strausz Douglas S. Montgomery 《Fuel》1983,62(3):353-362
Athabasca bitumen separated from the associated mineral matter by Soxhlet extraction contains fine clay particles and inherent ash. Empirical relations have been developed to estimate the percentage of clay and inherent ash present in the asphaltene fraction which concentrates in large measure the mineral constituents present in the bitumen. The ash level, Y, of the asphaltenes is related to the weight per cent of clay, Ct, by an expression of the form Y = 0.872Ct + 0.582. The ash level of the asphaltene fraction is also correlated with the infrared absorbance. A, at 1032 cm?1 which gives an approximate empirical relation of the form A = 0.0648Y + 0.294. Greater accuracy at low ash levels can be achieved by measuring A at 1040 cm?1 above the base line drawn from 960 to 1140 cm?1. This results in the equation A = 0.0709Y + 0.0124 when a standard KBr pellet thickness of 0.833 mm and concentration of 2 mg asphaltene per 300 mg KBr is used. X-ray diffraction used to characterize the clay minerals shows decreasing crystallinity as the particle size diminishes. The infrared absorbance of this mineral matter indicates decreasing intensity of the band at 2930 cm?1, associated with adsorbed and occluded organic matter, relative to the two characteristic clay bands at 3697 and 3620 cm?1 as the particle size decreases. Trace element analysis of the asphaltene inherent ash, by inductively coupled argon plasma, shows the major metallic constituents to be vanadium, nickel and iron with minor amounts of calcium, potassium, aluminium and sodium. 相似文献
9.
Suoqi Zhao Bryan D. Sparks Luba S. Kotlyar Keng H. Chung 《Petroleum Science and Technology》2002,20(9):1071-1085
X-ray photoelectron spectroscopy (XPS) was used to determine sulphur species and their distribution in fractions of fluid coking residue (CK) and hydro-cracking residue (HC) derived from an Athabasca bitumen pitch (ABP). The major sulphur species were sulphides/mercaptans and thiophenes in each case. No sulphoxides and sulphones were detected in any non-oxidised samples. Each residua was separated into between 9 and 15 front-cut samples and a single end-cut fraction by supercritical fluid extraction and fractionation (SFEF). This approach has been used to produce different molecular weight fractions, depending on the severity of separation conditions. In the fractions from the parent Athabasca bitumen pitch about 65-80 wt% of the total sulphur occurs as thiophenes with the remainder being sulphide species. The reactivity of the sulphur species in the parent pitch was determined under mild conditions using a standard technique for selective oxidation. In this procedure sulphides are preferentially oxidized to sulphoxides while thiophenic sulphur remains unchanged; under the same reaction conditions the degree of sulphide conversion generally declined with increasing molecular weight of the fractions. Commercial catalytic hydrocracking completely removed sulphides from the front-cut fractions of the parent pitch. However, the composition of the end-cut fraction from the residua produced by this process was virtually the same as that for the comparable fraction from fluid coking. This observation demonstrates that hydrocracking has little effect on intractable heavy ends. Also, hydrocracking removed only a relatively small proportion of thiophenic sulphur. On the other hand, while commercial fluid coking removed most of the sulphides from the parent pitch the residue was enriched with thiophene compared to the parent feed. This observation demonstrates the partitioning effect occurring during coking reactions. 相似文献
10.
Nelson Fong Samson Ng Keng H. Chung Yun Tu Zaifeng Li Bryan D. Sparks Luba S. Kotlyar 《加拿大化工杂志》2004,82(4):782-793
To overcome the compositional variability inherent to natural oil sands we use extraction tests with model oil sands (MOS) systems in a systematic, experimental design study. Eight significant variables from screening tests in earlier work are tested here. Namely, concentrations of bitumen, silica fines, sodium kaolinite, illite and montmorillonite. In addition, we tested different concentrations of Ca2+, Mg2+, and Na+ in the synthetic process water used with bitumen separation tests. A two level, fractional factorial experimental design allowed testing of the selected variables using only 16 runs. In addition, sodium hydroxide was added as a ninth variable and four repeat tests allowed evaluation of precision. The resulting bitumen recovery model explained 94% of the data variation. The associated parameter estimates were in general agreement with previous experimental observations and with actual operational experience. 相似文献