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1.
Behaviour of a series of lubricant oils and the effect of a non stoichiometric inorganic compound, as solid extreme pressure additive, on rolling fatigue life are studied using the rolling four-ball accelerated service simulation test proposed by Barwell and Scott. The results show, in all tested cases, the remarkable efficacy of this type of additive. The Total Acidity Number (tan) was found to increase with performance time for the case of the base lubricant, while for the oils with additives, it remained at its constant low value. This led to a proposal of a possible mechanism of the additive performance in the rolling process. 相似文献
2.
Nanocrystalline TiO2 photosensitized with natural polymers with enhanced efficiency from 400 to 600 nm 总被引:1,自引:0,他引:1
Rodolfo Espinosa Inti Zumeta Jorge L. Santana Francisco Martínez-Luzardo Bernardo Gonzlez Sergilus Docteur Elena Vigil 《Solar Energy Materials & Solar Cells》2005,85(3):359-369
TiO2 sensitization for solar applications requires not only efficient but also stable and inexpensive sensitizers. Different condensed tannins extracted from bark wastes of tropical wood trees were studied as possible sensitizers of TiO2. These natural polymers adhere strongly to the TiO2 even from aqueous solutions. Absorption spectra are presented for 1 mM aqueous sensitizing solutions prepared with lyophilized condensed tannins which absorb light in the visible range. Spectral photocurrent measurements and I–V characterization show that no bias is required for electron injection to the TiO2 from all studied condensed tannins. Incident photon to current efficiency (IPCE) analysis indicates that surface complexation originates absorption bands with different electron injection efficiencies. These play a dominant role in determining IPCE spectral shape. We propose that surface modification by the sensitizer changes the surface trap density, thereby decreasing recombination losses. 相似文献
3.
Homer M.E. Hogan S.J. di Bernardo M. Williams C. 《Circuits and Systems II: Express Briefs, IEEE Transactions on》2004,51(10):511-516
In this brief, we consider methods to improve the performance of chaotic communication schemes. We study a system using a receiver which explicitly includes the presence of noise in the channel. We show how the choice of chaotic dynamical system generating the transmitted signal is crucial. We observe a large variation in bit error rate performance of the system as parameters in the maps are changed, and we propose a simple explanation for this variation. 相似文献
4.
A Complete and Highly Effective Mothproofing Agent Comprising a Pyrethroid and a Hexahydropyrimidine
Pyrethroids, considered as a general class of compounds, have been shown to provide effective protection from the larvae of the keratin-digesting insects Tineola bisselliella H., Tinea pellionella Linn., Hofmannophila pseudo-spretella Station and Attagenus piceus Oliv. The position regarding the susceptibility of the furniture carpet beetle to pyrethroids is less clear, however. It has been reported that both deltamethrin and permethrin are effective against Anthrenus flavipes Le Conte, whilst permethrin is also reported elsewhere to be effective against the same species. Results obtained in our laboratory, however, have indicated that pyrethroids may offer inadequate protection against Anthrenus vorax Waterh. [1, 2]. This latter species is identical to Anthrenus flavipes var. seminiveus Casey, a colour variety of Anthrenus flavipes Le Conte. The 1,3-disubstituted5-phenylcarbamoyl-2,4,6-trioxo- and 4,6-dioxo-2-thione-hexahydropyrimidine derivatives described in this paper exhibit a surprisingly high and selective toxicity to the Anthrenus species. Thus, a combination of an appropriate hexahydropyrimidine with a suitable pyrethroid, e.g. permethrin, provides complete control of a wide range of commonly encountered textile insect pests. The influence of substituents on the mothproofing activity is discussed. 相似文献
5.
The metabolism of 1-acyl-2-acetyl-sn-glycero-3-phosphocholine (1-acyl-PAF), a naturally occurring analogue of platelet activating factor (PAF), was investigated
in rabbit platelets. Our studies showed that 1-acyl-[3H]PAF (1-palmitoyl-2-acetyl-sn-glycero-3-phospho[N-methyl-3H]-choline) was converted by platelets into phosphatidyl-[3H]choline ([3H]PC) in a time-dependent fashion. The formation of [3H]PC occurred at a rate similar to that observed when lyso-[3H]PC (palmitoyl-sn-glycero-3-phospho[N-methyl-3H]choline) was used as substrate. In addition, a time-dependent increase in the level of water-soluble radioactivity was observed
during the incubation of platelets with either 1-acyl-[3H]PAF or lyso-[3H]PC. This increase was parallel to the formation of [3H]PC and was not observed in the presence of [14C]PAF (1-octadecyl-2-acetyl-sn-glycerol-3-phospho[N methyl-14C]choline). Analysis by thin-layer chromatography showed that the soluble radioactivity was mainly associated with glycerophosphocholine
(GPC). On the other hand, the preincubation of platelets with phenylmethylsulfonyl fluoride, an inhibitor of the acetylhydrolase,
reduced the hydrolysis of 1-acyl-[3H]PAF to [3H]GPC with a concomitant accumulation of radioactivity in 1-acyl-PAF. These findings suggest that 1-acyl-PAF is converted
into PC through deacetylation-reacylation with lysoPC as an obligatory intermediate. The findings also indicate that the lysoPC
resulting from 1-acyl-PAF is either reacylated to phosphatidylcholine (PC) or hydrolyzed to GPC by lysophospholipase. Finally,
we showed that the stimulation of platelets with PAF led to a time- and concentration-dependent increase in the conversion
of 1-acyl-[3H]PAF to [3H]PC. The stimulatory effect of PAF was not observed when platelets were lysed before incubation, suggesting that PAF enhances
the metabolism of 1-acyl-PAF, probably by accelerating its translocation through the plasma membrane. 相似文献
6.
We present a mechanism for reservations of bursty resources that is both truthful and robust. It consists of option contracts
whose pricing structure induces users to reveal the true likelihoods that they will purchase a given resource. Users are also
allowed to adjust their options as their likelihood changes. This scheme helps users save cost and the providers to plan ahead
so as to reduce the risk of under-utilization and overbooking. The mechanism extracts revenue similar to that of a monopoly
provider practicing temporal pricing discrimination with a user population whose preference distribution is known in advance. 相似文献
7.
Auletta Fabrizia Fiore Davide Richardson Michael J. diBernardo Mario 《Autonomous Robots》2022,46(3):469-481
Autonomous Robots - We propose a simple yet effective set of local control rules to make a small group of “herder agents” collect and contain in a desired region a large ensemble of... 相似文献
8.
E Parellada AM Catafau M Bernardo F Lome?a S Catarineu E González-Monclús 《Canadian Metallurgical Quarterly》1998,44(8):787-790
BACKGROUND: Functional neuroimaging findings of "hypofrontality" in schizophrenic patients is still controversial, due to the heterogeneity of methods and patient samples. This study tries to prevent some of these concerns by studying neuroleptic-naive (NN) and neuroleptic-free (NF) young female patients both in resting conditions and during a frontal cognitive activation task. METHODS: Regional cerebral blood flow (rCBF) was studied at rest and during the Wisconsin Card Sorting Test (WCST) in 25 young acute unmedicated schizophrenic female patients (14 NN and 11 NF) and 15 female controls, using single photon emission computed tomography. RESULTS: The schizophrenic and control groups did not differ in rCBF during the baseline condition, but the schizophrenic group failed to activate the frontal lobe during the WCST condition. In addition, the left anterior temporal rCBF at rest correlated with the Scale for the Assessment of Positive Symptoms total score. CONCLUSIONS: The results suggest that hypofrontality in young acute unmedicated schizophrenic patients is a result of an inability to activate frontal regions during cognition, rather than a baseline decrease in frontal activity. Furthermore, positive symptoms seem to be associated with left temporal cortex activity. 相似文献
9.
Bernardo Cordovez Aram J. Chung Michael Mak David Erickson 《Microfluidics and nanofluidics》2011,10(4):785-791
In this article, we explore a new fabrication process for a flexible, all polymer, active fluidic delivery system, incorporating
a fusion of laser micromachining and microfabrication techniques as well as rapid prototyping technology. Here, we show selective
fluidic delivery from isolated microchannels through an electrochemically driven pumping reaction, demonstrate the dispensing
of dose volumes up to 5.5 μl, and evaluate the device’s performance in terms of its delivery speed and ejection efficiency.
Finally, we move this work toward an implantable microfluidic drug delivery device by investigating the device’s biocompatibility
through a statistical approach that overviews the viability of bovine aortic endothelial cells on polyimide and silicon substrates. 相似文献
10.
In this paper we present adaptive algorithms for solving the uniform continuous piecewise affine approximation problem (UCPA)
in the case of Lipschitz or convex functions. The algorithms are based on the tree approximation (adaptive splitting) procedure.
The uniform convergence is achieved by means of global optimization techniques for obtaining tight upper bounds of the local
error estimate (splitting criterion). We give numerical results in the case of the function distance to 2D and 3D geometric
bodies. The resulting trees can retrieve the values of the target function in a fast way. 相似文献