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排序方式: 共有2647条查询结果,搜索用时 10 毫秒
81.
Biodegradable Ethylene‐Bis(Propyl)Disulfide‐Based Periodic Mesoporous Organosilica Nanorods and Nanospheres for Efficient In‐Vitro Drug Delivery 下载免费PDF全文
82.
Coubard Olivier A.; Ferrufino Lena; Boura Marine; Gripon Alice; Renaud Mélanie; Bherer Louis 《Canadian Metallurgical Quarterly》2011,25(3):353
Objective: Attentional control, the ability to maintain goal-directedness in the face of distraction, has been shown to decline in normal aging (NA) and Alzheimer's disease (AD), yet the nature and extent of deficits is under debate. This study investigated attentional control in NA and AD compared to healthy young adults in several tasks such as setting, suppressing, switching, and preparing attention. Method: Fifty-two participants (17 AD, 17 NA, and 18 young participants) underwent the Tower of London, the Zoo map test, the Stroop test, letter verbal fluency, a computerized version of the Rule shift cards tests, the Trail making test, the Plus-minus test, and a reaction time task with variable preparatory intervals. Results: Analyses of variance showed that NA as compared to young participants were impaired in the Tower of London, the Stroop test, and the Rule shift cards tests. AD as compared to NA participants were impaired in all tests except the Stroop test. Principal component analysis in young adults confirmed the modularity of attentional tasks, which was reduced in NA and AD participants. Principal component analysis in all populations showed a decline of attentional control with NA and AD regardless of the tasks, with an increase in between-participants variability only between young and NA participants. Conclusions: Attentional control dysfunction is different in NA and AD: NA affects suppressing attention, switching attention for unpredictable but not predictable events, and preparing attention for unpredictable events, whereas AD affects setting, suppressing, switching, and preparing attention with less specificity. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
83.
Norberto Labrador Delia Gutiérre-Campos Olivier Rapaud Hélène Ageorges Alexandre Maitre 《Ceramics International》2019,45(9):11677-11685
High-purity nanocrystalline aluminum nitride powders were synthesized by using a 12?kW non-transferred arc plasma. The synthesis was conducted in a versatile, new designed, one-chamber thermal plasma reactor (TPR). The novel experimental assembly incorporated better working conditions like: high temperature gradient between the crucible and reactor's wall, and high super-saturation of the system by nitrogen and carbon. Thermodynamic modelling of the synthesis was conducted in order to achieve the best conditions for AlN formation. In this study, aluminum discs of Al 1100 were used as precursor material and pure nitrogen was the only gas used as reagent and plasmogenic gas.Nanopowders collected from reactor's wall were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-Ray diffraction (XRD). Synthesized h-AlN nano-powders were found to be free of oxides and aluminum metal. A thin carbon-layer around the particles was detected. TEM results indicated that the carbon-layer was around 5 and 10?nm. This outcome could make a significant difference with other synthesis reported in the literature since the occurrence of the carbon-layer, could delay AlN oxidation, prevent hydration, and could avoid the agglomeration of the particles. 相似文献
84.
By means of ADE-FDTD method, this paper investigates the electromagnetic modelling of a rib-loaded waveguide composed of a
Nd3+ doped Silicon Rich Silicon Oxide active layer sandwiched between a SiO2 bottom cladding and a SiO2 rib. The Auxilliary Differential Equations are the rate equations which govern the levels populations. The Finite Difference
Time Domain (FDTD) scheme is used to solve the space and time dependent Maxwell equations which describe the electromagnetic
field in a copropagating scheme of both pumping (λ
pump
= 488 nm) and signal (λ
signal
= 1064 nm) waves. Such systems are characterized by extremely different specific times such as the period of electromagnetic
field ~ 10-15 s and the lifetimes of the electronic levels between ~ 10-10s and ~ 10-4 s. The time scaling method is used in addition to specific initial conditions in order to decrease the computational time.
We show maps of the Poynting vector along the propagation direction as a function of the silicon nanograin (Si-ng) concentrations.
A threshold value of 1024 Si-ng m-3 is extracted below which the pump wave can propagate so that a signal amplication is possible. 相似文献
85.
Olivier Boutin Axel De Nadaï Antonio Garcia Perez Jean-Henry Ferrasse Marina Beltran Elisabeth Badens 《Chemical Engineering Research and Design》2011,89(11):2477-2484
The supercritical oil extraction from oleaginous seeds (sunflower and rapeseeds) is presented here through experimental and modelling results. The experimental setup allows an accurate following of the mass of the oil extracted and to derive the experimental influences of pressure, temperature and supercritical CO2 flowrate on the extraction curves. These parameters are very sensitive and highlight the necessity of precise optimisation of experimental conditions. In order to complete the behaviour of supercritical fluids extraction, an improved modelling is proposed. The modelling basic equations are based on others modelling published previously. In this work, the determination of several parameters comes from correlations and the other constants are fitted with all the experimental results. Thus the modelling is more representative and predictive as other ones. The modelling results present a good agreement with the experimental results, and hence it can be used for the dimensioning of some extraction autoclaves. 相似文献
86.
Pourceau G Chevolot Y Goudot A Giroux F Meyer A Moulés V Lina B Cecioni S Vidal S Yu H Chen X Ferraris O Praly JP Souteyrand E Vasseur JJ Morvan F 《Chembiochem : a European journal of chemical biology》2011,12(13):2071-2080
Influenza neuraminidases hydrolyze the ketosidic linkage between N-acetylneuraminic acid and its adjacent galactose residue in sialosides. This enzyme is a tetrameric protein that plays a critical role in the release of progeny virions. Several methods have been described for the determination of neuraminidase activity, usually based on colorimetric, fluorescent, or chemiluminescent detection. However, only a few of these tests allow discrimination of the sialyl-linkage specificity (i.e., α2-3- versus α2-6-linked sialyllactosides) of the neuraminidase. Herein we report a glycoarray-based assay and a MALDI-TOF study for assessing the activity and specificity of two influenza neuraminidases on whole viruses. The human A(H3N2) and avian A(H5N2) neuraminidase activities were investigated. The results from both approaches demonstrated that α2-3 sialyllactoside was a better substrate than α2-6 sialyllactoside for both viruses and that H5N2 virus had a lower hydrolytic activity than H3N2. 相似文献
87.
The microstructure and mechanical properties of melt-spun isotactic polypropylene (iPP) fibers were studied for different take-up velocities and throughputs with a combination of small- and wide-angle X-ray scattering, calorimetry and tensile tests. With the increase of take-up velocity the mesomorphic fraction of the fibers steadily decreases while the crystalline fraction increases. The addition of an alpha-nucleating agent led to an increase of crystallinity and a slight decrease of the orientation factor. By contrast, a beta-nucleator resulted in a complete suppression of the fiber crystallinity. The orientation factor of the mesophase and/or crystalline phase is found to have a one-to-one correlation with the fiber tenacity and deformation at break. At the same time, the absolute values of crystallinity and/or mesomorphicity are fully uncorrelated with these mechanical characteristics. The observed correlations can be used for example to design and control the fiber mechanical properties by tuning the processing conditions such as take-up velocity, throughput and addition of nucleating agents. 相似文献
88.
Roland Oltra Alexandre Zimmer Claire Sorriano Fabien Rechou Céline Borkowski Olivier Néel 《Electrochimica acta》2011,(20):7038
Some constituent intermetallic (IMPs) particles at the surface of aluminium alloys are considered as preferential sites for the initiation of structural corrosion resulting in localized trenching around the particles and the surrounding Al matrix. In this work, a modified scanning electrochemical microscope (SECM) experiment was used to induce such phenomena via a local alcalinisation on 200 nm thick aluminium coatings promoting their local dissolution in an aerated 0.1 M NaCl electrolyte. The local alcalinisation was induced by the oxygen reduction reaction on the tip of a SECM which mimics the surface of an isolated IMP. From a phenomenological point of view, reproducible cylindrical damage develops in front of the platinum ultramicroelectrode (UME). Using a 2D finite element modelling to simulate the SECM experiments, the role of the local alcalinisation was validated and the calculated Al dissolution rate was found in agreement with the experimental evaluation. 相似文献
89.
Yann Battie Olivier Ducloux Philippe Thobois Nelly Dorval Jean Sébastien Lauret Brigitte Attal-Trétout Annick Loiseau 《Carbon》2011,49(11):3544-3552
A comparative study was made of sorted semi-conducting single walled carbon nanotube (SWCNT) films and unsorted SWCNT films for gas sensing applications. The transmission line method is used to monitor separately the SWCNTs film resistance and the contact resistance between electrodes and the SWCNTs, thus revealing that the sensing mechanism mainly relies on a modification of the tube conductivity during gas exposure. The fabricated sensors demonstrate a detection limit of 20 ppb NO2 and 600 ppb NH3 mainly attributed to experimental setup limitations. Moreover, semi-conducting nanotubes happened to be 2.5 times more sensitive to NH3 than unsorted ones, thus proving that selectivity can be improved by sorting the SWCNTs. The temperature dependence of the sensor sensitivity was studied, and a good agreement was found between experimental results and the Langmuir adsorption model. 相似文献