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101.
Immobilization of lipase B from Candida antarctica on epoxy‐functionalized silica: characterization and improving biocatalytic parameters 下载免费PDF全文
102.
Energy is essential for present societies. In particular, transportation systems depend on petroleum-based fuels. That world oil production is set to pass a peak is now a reasonably accepted concept, although its date is far from consensual. In this work, we analyze the true expectations of the oil market participants about the future availability of this fundamental energy source. We study the evolution through time of the curves of crude oil futures prices, and we conclude that the market participants, among them the crude oil producers, already expect a near-term peak of oil production. This agrees with many technical predictions for the date of peak production, including our own, that point to peak dates around the end of the present decade. If this scenario is confirmed, it can cause serious social and economical problems because societies will have little time to perform the necessary adjustments. 相似文献
103.
Aline G. Cunha Angelo A. T. da Silva Mateus G. Godoy Rodrigo V. Almeida Alessandro B. C. Simas Denise M. G. Freire 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2013,88(2):205-211
BACKGROUND: The response surface methodology was successfully applied to the optimization of the reaction variables for the kinetic resolution of a precursor of high‐value myo‐inositols, ( ± )‐1,2‐O‐isopropylidene‐3,6‐di‐O‐benzyl‐myo‐inositol (( ± )‐1), by Novozym 435. The resolutions were run separately, with two acylating agents, ethyl acetate and vinyl acetate, in a solvent‐free system. The variables analyzed were reaction temperature, substrate concentration, water concentration and enzyme activity. A statistical model was employed for the evaluation of the influence of the variables on conversion and enantiomeric excess (ee). RESULTS: The optimal conditions for this resolution using vinyl acetate as acylating agent were 45 °C, 5 mg mL?1 of substrate, 71 U of enzyme activity and 0%w/w of water concentration. The high conversion (49.2 %) and ee (>99%) reached in the chemoenzymatic synthesis of acylated product, L‐(?)‐5‐O‐Acetyl‐3,6‐di‐O‐benzyl‐1,2‐O‐isopropylidene‐myo‐inositol, secure the efficient synthesis of the D enantiomorph present in the original racemic mixture (( ± )‐1) as well. CONCLUSIONS: The use of the experimental design strategy was productive, leading to a 14‐fold increase in the productivity of the reaction compared with the non‐optimized conditions. Both derivative L‐(?)‐2 and remaining substrate D‐(+)‐1 were obtained at high ee. © 2012 Society of Chemical Industry 相似文献
104.
Fan and chiller energy savings achievable in commercial buildings with adjustable-speed drives are described. The savings are estimated with the aid of parametric simulations from a sophisticated, hourly building-energy simulation model. Two prototypes-a single-zone retail store and a multizone medium-sized office building-are simulated for five US locations. The model incorporates part-load performance curves for both inlet vane and adjustable-speed drive controls for fans and centrifugal chillers. The results identify economic conditions that justify the added expense of adjustable-speed drives 相似文献
105.
This paper proposes an olfaction based methodology to automatically cover an unknown area enabling the decoupled cooperation
of a group of floor cleaning mobile robots. This method is based on the utilisation of low cost chemical sensors in cleaning
mobile robots, in order to differentiate clean from dirty areas. The experimental results show that the use of olfactory capabilities
allows to efficiently cover and clean a certain area, and demonstrate the possibility of coordinating several mobile robots
without the need of expensive sensing capabilities, map building or complex algorithms for task scheduling. 相似文献
106.
Modeling and querying moving objects in networks 总被引:11,自引:0,他引:11
Ralf Hartmut Güting Victor Teixeira de Almeida Zhiming Ding 《The VLDB Journal The International Journal on Very Large Data Bases》2006,15(2):165-190
Moving objects databases have become an important research issue in recent years. For modeling and querying moving objects,
there exists a comprehensive framework of abstract data types to describe objects moving freely in the 2D plane, providing
data types such as moving point or moving region. However, in many applications people or vehicles move along transportation networks. It makes a lot of sense to model the
network explicitly and to describe movements relative to the network rather than unconstrained space, because then it is much
easier to formulate in queries relationships between moving objects and the network. Moreover, such models can be better supported
in indexing and query processing. In this paper, we extend the ADT approach by modeling networks explicitly and providing
data types for static and moving network positions and regions. In a highway network, example entities corresponding to these
data types are motels, construction areas, cars, and traffic jams. The network model is not too simplistic; it allows one
to distinguish simple roads and divided highways and to describe the possible traversals of junctions precisely. The new types
and operations are integrated seamlessly into the ADT framework to achieve a relatively simple, consistent and powerful overall
model and query language for constrained and unconstrained movement. 相似文献
107.
D Ili? EA Almeida DD Schlaepfer P Dazin S Aizawa CH Damsky 《Canadian Metallurgical Quarterly》1998,143(2):547-560
In many malignant cells, both the anchorage requirement for survival and the function of the p53 tumor suppressor gene are subverted. These effects are consistent with the hypothesis that survival signals from extracellular matrix (ECM) suppress a p53-regulated cell death pathway. We report that survival signals from fibronectin are transduced by the focal adhesion kinase (FAK). If FAK or the correct ECM is absent, cells enter apoptosis through a p53-dependent pathway activated by protein kinase C lambda/iota and cytosolic phospholipase A2. This pathway is suppressible by dominant-negative p53 and Bcl2 but not CrmA. Upon inactivation of p53, cells survive even if they lack matrix signals or FAK. This is the first report that p53 monitors survival signals from ECM/FAK in anchorage- dependent cells. 相似文献
108.
109.
J Tonkiss JS Shumsky PL Shultz SS Almeida JR Galler 《Canadian Metallurgical Quarterly》1995,17(5):601-608
The separate and combined effects of prenatal cocaine exposure and malnutrition on mother-pup interactions in rats were assessed daily from postnatal day 2 to day 21. Sprague-Dawley dams were fed a diet of low protein content (6% casein), an isocaloric diet of adequate protein content (25% casein, control), or a laboratory chow diet prior to mating and throughout pregnancy. Within each diet group, rats received either cocaine injections (30 mg/kg IP two times per week prior to mating and then 30 mg/kg SC daily from days 3 to 18 of pregnancy) or saline injections. Litters were fostered on the day of birth to control mothers (i.e., nondrug-exposed dams fed the control or chow diet). Foster mothers fed the 25% casein diet showed increased contact with cocaine-exposed pups compared with nondrug-exposed pups in the second postnatal week but lower levels as the pups approached weaning. Passive nursing was increased in dams caring for prenatally malnourished, cocaine-exposed pups compared with those caring for similar pups with no drug exposure. Chow-fed mothers did not differ in their behavior towards pups with or without prenatal cocaine treatment. Prenatal cocaine and malnutrition independently compromised birth weight and various reflexive milestones but the attainment of physical milestones was affected only by prenatal cocaine. There were no additive effects of the two prenatal insults on any measure of mother-pup interaction or pup development. 相似文献
110.
This paper describes the observation of the structural behaviour of two of the largest docks in the world, the Setenave docks,
as well as the experimental techniques developed by LNEC for observing this type of structures.
This work was considered of fundamental importance not only for checking the safety conditions of the dock structural behaviour,
but also for the progress of design methods of these structures, especially as concerns the interaction between soil, piles
and bottom slabs.
In accordance with the programme of observation, we had the opportunity to appreciate the behaviour of the sunk docks under
the following conditions: during the elevation of the ground-water level, which had been lowered for the construction of the
docks; during successive filling and emptying operations in docks for the repair of several ships; and also during the simultaneous
flooding of the two docks up to the level +4.2 m above the land area for the launching of a ship constructed in the shipbuilding dock.
Résumé Cet article rend compte de l'observation du comportement de deux des docks les plus importants du monde, les docks Setenave, ainsi que des techniques expérimentales mises au point par le LNEC pour l'observation de ce type de structure. Cette étude a été considérée comme étant d'une importance fondamentale non seulement pour vérifler les conditions de sécurité du comportement structurel des docks mais aussi pour le progrès des méthodes de conception de ce type de structure, particulièrement en ce qui concerne l'interaction entre le sol, les piliers et les dalles de fondation. En correspondance avec ce programme d'observation, on a pu estimer le comportement des docks immergés dans les conditions suivantes: au cours de l'élévation du niveau de l'eau souterraine qui avait été abaissé pour la construction des docks; au cours des opérations de remplissage et de vidage successives des docks pour la réparation des navires; également au cours du remplissage simultané des deux docks jusqu'au niveau+4.2 m au-dessus du sol pour le lancement d'un navire dans le dock de construction.相似文献