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81.
Leonid Churilov Audur Fridriksdottir Mahsa Keshtkaran Ian Mosley Andrew Flitman Helen M. Dewey 《Computers & Operations Research》2013
Stroke is the third most common cause of death and the sixth most common cause of disability worldwide. Treating acute ischemic stroke with thrombolytic therapy within 4.5 hours from symptom onset is effective in improving patient outcomes. The time from stroke onset to arrival to hospital has been identified as the single most important issue in determining patients' eligibility for stroke thrombolysis. There is a need for simultaneous systemic evaluation of multi-factorial interventions in pre-hospital acute care systems, aimed at increasing patients' eligibility for stroke thrombolysis. In this paper an OR solution is proposed in the form of a simulation model that provides clear measure of the relative benefit of alternative potential interventions, demonstrating how OR modeling can be used for providing decision support in pre-hospital stroke care operations and contributing to health OR literature. 相似文献
82.
Björn V. Adalbjörnsson Helen S. Toogood Dr. Anna Fryszkowska Dr. Christopher R. Pudney Dr. Thomas A. Jowitt Dr. David Leys Dr. Nigel S. Scrutton Prof. 《Chembiochem : a European journal of chemical biology》2010,11(2):197-207
We report the crystal structure of a thermophilic “ene” reductase (TOYE) isolated from Thermoanaerobacter pseudethanolicus E39. The crystal structure reveals a tetrameric enzyme and an active site that is relatively large compared to most other structurally determined and related Old Yellow Enzymes. The enzyme adopts higher order oligomeric states (octamers and dodecamers) in solution, as revealed by sedimentation velocity and multiangle laser light scattering. Bead modelling indicates that the solution structure is consistent with the basic tetrameric structure observed in crystallographic studies and electron microscopy. TOYE is stable at high temperatures (Tm>70 °C) and shows increased resistance to denaturation in water‐miscible organic solvents compared to the mesophilic Old Yellow Enzyme family member, pentaerythritol tetranitrate reductase. TOYE has typical ene‐reductase properties of the Old Yellow Enzyme family. There is currently major interest in using Old Yellow Enzyme family members in the preparative biocatalysis of a number of activated alkenes. The increased stability of TOYE in organic solvents is advantageous for biotransformations in which water‐miscible organic solvents and biphasic reaction conditions are required to both deliver novel substrates and minimize product racemisation. 相似文献
83.
Calear Alison L.; Christensen Helen; Mackinnon Andrew; Griffiths Kathleen M.; O’Kearney Richard 《Canadian Metallurgical Quarterly》2009,77(6):1021
The aim in the current study was to investigate the effectiveness of an online, self-directed cognitive–behavioral therapy program (MoodGYM) in preventing and reducing the symptoms of anxiety and depression in an adolescent school-based population. A cluster randomized controlled trial was conducted with 30 schools (N = 1,477) from across Australia, with each school randomly allocated to the intervention or wait-list control condition. At postintervention and 6-month follow-up, participants in the intervention condition had significantly lower levels of anxiety than did participants in the wait-list control condition (Cohen’s d = 0.15–0.25). The effects of the MoodGYM program on depressive symptoms were less strong, with only male participants in the intervention condition exhibiting significant reductions in depressive symptoms at postintervention and 6-month follow-up (Cohen’s d = 0.27–0.43). Although small to moderate, the effects obtained in the current study provide support for the utility of universal prevention programs in schools. The effectiveness of booster sessions should be explored in future research. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
84.
Drawing on and developing Kingdon’s multiple streams analysis, this article examines the development of one aspect of the UK’s low cost home ownership programme: shared ownership. We demonstrate how key human and non-human policy entrepreneurs were able to set the agenda from 1973–1983 in favour of shared ownership; they neutralized the alternatives, while retaining some of their instruments; and solved a number of early problems by bringing key players into the programme. Our data-sets include a range of archival material and elite interviews. The policy entrepreneurs included John Stanley (who was the housing minister in the First Thatcher government), the National Federation of Housing Associations, and the Building Societies Association. Our development of the multiple streams analysis is to argue that documents, including the lease, act as policy entrepreneurs in their own right. The lease was central to the development of shared ownership and its transformation into a model lease enrolled other organizations, most critically the building societies. 相似文献
85.
Andréia F. Zanette Rodrigo A. Barella Sibele B.C. Pergher Helen Treichel Débora Oliveira Marcio A. Mazutti Edson A. Silva J. Vladimir Oliveira 《Renewable Energy》2011,36(2):726-731
This work investigates the production of fatty acid methyl esters (FAME) from Jatropha curcas oil using a variety of heterogeneous catalysts: resins, zeolites, clays, hydrotalcites, aluminas and niobium oxide. For this purpose, a catalyst screening was first conducted in a batch reactor at the following operating conditions: oil to methanol molar ratio of 1:9, 6 h of reaction, 5 wt% catalyst, at 333 and 393 K. From the screening step, KSF clay and Amberlyst 15 catalysts were selected to carry out a 23 full factorial central composite rotatable design so as to elucidate the effects of process variables on FAME yield. The optimum reaction conditions for both catalysts were found to be oil to methanol molar ratio of 1:12, 5 wt% of catalyst, 433 K and 6 h of reaction with a FAME yield of about 70 wt%. A kinetic study was then experimentally performed and a semi-empirical model was built to represent the experimental data. Finally, catalyst re-utilization in five successive batch experiments was evaluated at the optimized conditions. 相似文献
86.
87.
Ran Bi Michael Schlaak Eike Siefert Richard Lord Helen Connolly 《Journal of Applied Electrochemistry》2010,40(6):1217-1223
The aim of the present study was to investigate the effect of a 10 Hz alternating current (10 Hz 1 V cm−1) and a 50 Hz alternating current (50 Hz 1 V cm−1) on the lettuce plant (Lactuca sativa) growing in a hydroponic (soil-free) culture. Thirty lettuce plants were pre-germinated, and then 15 of them were treated
with cadmium solution (CdCl2) of 5 mg/L in concentration. Ten plants (five plants with Cd and five plants without Cd) were subjected to a 10 Hz alternating
current (AC) electrical field; 10 plants were subjected to a 50 Hz AC field. The rest of the plants were used as a control.
The lettuce plants were harvested after a growth of 60 days. The chlorophyll content, biomass and metal content of the lettuce
plants were determined. The biomass of the plants growing in non-contaminated medium was 28 and 106% higher under the 10 and
the 50 Hz AC fields respectively compared to the control. Although the plant biomass was reduced by the presence of Cd in
the growth medium, the biomass of the plants growing in Cd contaminated medium was 40 and 63% higher respectively for 10 and
50 Hz AC field compared to the plant growing in Cd contaminated medium without electrical treatment. Increased uptake of Cd
in the plant shoot was found with the 50 Hz AC field. Significant accumulation and uptake of Cu in plant roots and shoots
was found under both electrical treatments. 相似文献
88.
Zhang Duyao Atkinson Helen V. Dong Hongbiao Zhu Qiang 《Metallurgical and Materials Transactions A》2017,48(10):4701-4712
Metallurgical and Materials Transactions A - There is a need to extend the application of semi-solid processing (SSP) to higher performance alloys such as 319s (Al-Si-Cu-Mg) and 201 (Al-Cu-Ag). The... 相似文献
89.
Helen Reveron Laurent Blanchard Yann Vitupier Emmanuelle Rivière Guillaume Bonnefont Gilbert Fantozzi 《Journal of the European Ceramic Society》2011,31(4):645-652
Many space systems such as satellite mirrors and their supporting structures require to be made from very low-thermal expansion materials combining both high hydrostability and relatively high mechanical properties. In this study, we have applied the “composite concept” in order to explore the possibility of fabricating near zero thermal expansion silicon nitride based ceramics. Consequently, a negative thermal expansion material belonged to the lithium aluminosilicate family (LAS powder crystallized under de β-eucryptite structure) was introduced in an alpha-silicon nitride fine powder (5 and 20 vol% of LAS) and the resulting composite system was sintered by Spark Plasma Sintering (SPS) at 1400 and 1500 °C. In the case of 20 vol% LAS compositions, relatively well-densified ceramics (94.4% of the theoretical density) were produced without adding any further sintering additive. The addition of yttria and alumina oxides allowed enhancing the densification level up to 98.2% (20 vol% LAS compositions) or from 62.3% up to 96.7% of the theoretical density in 5 vol% LAS materials. Nevertheless, it was impossible to full consolidate silicon nitride/LAS composite ceramics at temperatures lower than the temperature at which β-eucryptite melts, even by using SPS technology. Moreover, because of the relatively low temperatures involved in SPS, the α to β-Si3N4 transformation was avoided, resulting in microstructures composed of fine equiaxed α-Si3N4 grains (<200 nm) and of a glassy phase. Even if the effect of having a very large negative thermal expansion material was lost during the sintering step (because of the β-eucryptite melting), ceramics containing only 20 vol% of LAS-based phase exhibited very interesting values as regards of mechanical properties (strength, hardness, toughness, and Young's modulus), thermal conductivity and thermal expansion coefficient. We discuss in this work why we are so interested in developing dense silicon nitride/LAS ceramics sintered without any further additive addition, even though β-eucryptite is melted during the process and the transformation to the β phase is avoided. 相似文献
90.
Eunice Valduga Alexsandra Valério Pihetra Oliveira Tatsch Helen Treichel Agenor Furigo Jr. Marco Di Luccio 《Food and Bioprocess Technology》2009,2(2):234-238
The increasing demand for carotenoids by industries has drawn attention to their bio-production. Since pigments are intracellular,
extraction steps are then needed after cell cultivation. In this work, different strategies for extraction of carotenoid pigments
from Sporidiobolus salmonicolor (CBS 2636) were studied. Different solvents (dimethyl sulfoxide, petroleum ether, hexane, ethyl acetate, chloroform, and
acetone), liquid N2, and diatomaceous earth were used to disrupt the cell and thus release the intracellular carotenoids. The results of this
study showed that when multiple solvents were used, a synergistic effect on the extent of carotenoids recovery was obtained.
Maximum concentration of total carotenoids (913 μg/L) was obtained in the treatment using liquid N2 and dimethyl sulfoxide to disrupt the cell, followed by the extraction with a solution of acetone/methanol (7:3, v/v). 相似文献