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排序方式: 共有451条查询结果,搜索用时 31 毫秒
171.
Hermes M Hagemann D Britz P Lieser S Rock J Naumann E Walter C 《Magma (New York, N.Y.)》2007,20(2):103-115
Background Continuous arterial spin labeling (CASL) is a non-invasive technique for the measurement of cerebral blood flow (CBF). The
aim of the present study was to examine the reproducibility of CASL measurements and its suitability to consistently detect
differences between groups, regions, and resting states.
Materials and methods Thirty-eight healthy subjects (19 female) were examined at 1.5 T on two measurement occasions that were seven weeks apart.
Resting CBF was measured with eyes open and eyes closed.
Results In different regions of interest (ROIs) the repeatability estimates varied between 9 and 19 ml/100 g/min. There were no significant
mean differences between occasions in all ROIs (P > 0.05). Greater CBF in the eyes-open than in the eyes-closed state was consistently present in the primary and secondary
visual areas. Furthermore, CBF was consistently greater in the right than in the left hemisphere (P < 0.05) and differed between lobes and between arterial territories (P < 0.001). Finally, we consistently observed greater CBF in women than in men (P < 0.001).
Conclusion This study demonstrates the suitability of CASL to consistently detect differences between groups, regions, and resting states
even after seven weeks. This emphasizes its usefulness for longitudinal designs. 相似文献
172.
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174.
Mesoporous silicates (MPS) possess ordered pore structures with pore diameters sufficiently large to accommodate a range of enzymes. The successful immobilization of an enzyme on MPS usually requires modification of the surface of MPS to optimize the interactions between the support and the enzyme. Recent developments on the functionalization of MPS for the immobilization of enzymes are described in this review. 相似文献
175.
The effects of omega‐3 polyunsaturated fatty acids and genetic variants on methylation levels of the interleukin‐6 gene promoter 下载免费PDF全文
176.
James A. Howard Patrick A. Walsh Edmond J. Walsh 《International Journal of Heat and Mass Transfer》2011,54(21-22):4752-4761
This paper investigates a two-phase non-boiling slug flow regime for the purposes of enhancing heat transfer in microchannel heat sinks or compact heat exchangers. The primary focus is upon understanding the mechanisms leading to enhanced heat transfer and the effect of using different Prandtl number fluids, leading to variations in Capillary number. Experimental work was conducted using Infrared thermography and results are presented in the form of Graetz solution, spanning both the thermal entrance and fully developed flow regions. Nusselt numbers enhancements were observed throughout when data was reduced to account for void fraction. However, the gaseous void was also noted to demonstrate an artificial increase with greater thicknesses of the liquid film, due to higher Capillary numbers. Up to 600% enhancement in heat transfer rates were observed over conventional Poiseuille flow. This was verified through Nusselt number measurements over inverse Graetz number ranges from 10?4 to 1 and slug length to channel diameter ratios from 0.88 to 32. Varying Prandtl and Capillary numbers caused notable effects in the transition region between entrance and fully developed flows. Significant Nu oscillations were observed for low Pr fluids due to internal circulation within the slug. However, these oscillations are observed to be damped out when higher Prandtl number fluids are employed. The thickness of the liquid film surrounding the gas bubbles is shown to have a significant influence on heat transfer performance. Overall, this study provides a greater understanding of the mechanisms leading to significant enhancements in heat exchange devices employing two-phase gas–liquid flows without boiling. 相似文献
177.
F Gottsauner-Wolf EL Egger A Giurea M Antosch D Olsen MG Rock FH Sim 《Canadian Metallurgical Quarterly》1999,(358):101-110
An Achilles tendon allograft with its bony insertion was used to bridge a Titanium implant, containing an endoprosthetic tendon anchor, and the sheep biceps muscle. Twelve sheep were operated on unilaterally and followed up clinically and histologically for 2, 4 (n = 2), 8, and 12 months (n = 4). Full function of the front limb was regained after 8 to 12 weeks. There were no signs of mechanical loosening at all times. The morphologic changes at the bone block and implant fixation site were an initial revascularization of the allograft bone, which was observed at 2 months and enhanced at 4 months but occurred without any evidence of bone remodeling. This was changed in all specimens taken at 8 and 12 months where intensive new bone development, remodeling, and bone ingrowth in the titanium implant was found. Bone mass was shifted significantly to the tendon insertion half of the bone block because of a creeping substitution of the cancellous allograft bone and bone ingrowth to the implant. Overall bone mass slightly decreased with time but resorption of allograft bone outweighed new bone development only at lesser loaded areas. Transplantation of a bone and tendon allograft to an implant resulted in a revitalized, mechanically stable, and biologically anchored compound. 相似文献
178.
Knowledge Mapping: Getting Started with Knowledge Management 总被引:21,自引:0,他引:21
Edmond F. Vail III 《Information Systems Management》1999,16(4):1-8
Knowledge mapping can be a powerful tool for CIOs in implementing knowledge management in their organizations. A knowledge map can bridge the gap between business and information technology (IT) people. It can also capture and integrate the knowledge collected in an initial knowledge management identification process. the value of these initial knowledge maps can then be extended to incorporate the rest of the intellectual capital of an enterprise. 相似文献
179.
Jihane Abou Rached Christelle El Hayek Eliane Dahdah Cédric Gennequin Samer Aouad Haingomalala Lucette Tidahy Jane Estephane Bilal Nsouli Antoine Aboukaïs Edmond Abi-Aad 《International Journal of Hydrogen Energy》2017,42(17):12829-12840
NixMg6?xAl1.8Ce0.2 (with 0 ≤ x ≤ 6) mixed oxides catalysts were prepared by hydrotalcite route. All the oxides were calcined at 800 °C and characterized by different physico-chemical methods. The catalysts are then reduced before their use in the steam reforming of toluene. The XRD and TG/DTA confirmed the formation of the hydrotalcite structure for the non-calcined samples. The N2 adsorption/desorption results revealed that all catalysts correspond to mesoporous materials. The study by temperature programmed reduction (H2-TPR) showed that the reducibility of the catalysts is influenced by the nickel content. The CO2-TPD results showed that the catalyst with high magnesium content present the highest basicity. The Ni2Mg4Al1.8Ce0.2 shows the best toluene conversion among all the catalysts and it was then compared to a non-promoted catalyst. The spent catalysts were characterized by TPO, TG/DTA and XRD and they didn't reveal any coke formation. 相似文献
180.
Chui Michael H.; Papanikolaou Yanni; Fontaine-Bisson Bénédicte; Turcotte Josée; Wolever Thomas M. S.; El-Sohemy Ahmed; Chiasson Jean-Louis; Rabasa-Lhoret Remi; Maheux Pierre; Ryan Edmond; Greenwood Carol E. 《Canadian Metallurgical Quarterly》2007,121(3):619
Inflammatory markers predict memory dysfunction in elderly patients, but their contribution to memory deficits in adults with Type 2 diabetes mellitus (T2DM) is less well understood. The present study determined whether specific single-nucleotide polymorphisms in the promoter region of tumor necrosis factor-alpha (TNF-α) predict verbal memory in older patients with T2DM. Immediate and delayed verbal memory were assessed using word list and paragraph recall tests in a cohort of subjects with T2DM during 2 sessions, separated by 48 weeks. The presence of the TNF-α-238A allele, which has been shown to decrease gene expression, consistently predicted better baseline performance and protected against memory decline over a period of 48 weeks. Therefore, inflammatory mediators may be important modulators of memory function in individuals with T2DM. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献