Simulation and experimental determination of the online separation of blood components with the help of microfluidic cascading spirals     

Lisa Sprenger  Silvio Dutz  Thomas Schneider  Stefan Odenbach  Urs O. H?feli 《Biomicrofluidics》2015,9(4)

Microfluidic spirals were used to successfully separate rare solid components from unpretreated human whole blood samples. The measured separation ratio of the spirals is the factor by which the concentration of the rare component is increased due to the Dean effect present in a flow profile in a curved duct. Different rates of dilution of the blood samples with a phosphate-buffered solution were investigated. The diameters of the spherical particles to separate ranged from 2 μm to 18 μm. It was found that diluting the blood to 20% is optimal leading to a separation ratio up to 1.97. Using two spirals continuously placed in a row led to an increase in separation efficacy in samples consisting of phosphate-buffered solution only from 1.86 to 3.79. Numerical investigations were carried out to display the flow profiles of Newtonian water samples and the shear-thinning blood samples in the cross-section of the experimentally handled channels. A macroscopic difference in velocity between the two rheologically different fluids could not be found. The macroscopic Dean flow is equally present and useful to help particles migrate to certain equilibrium positions in blood as well as lower viscous Newtonian fluids. The investigations highlight the potential for using highly concentrated, very heterogeneous, and non-Newtonian fluidic systems in known microsystems for screening applications.  相似文献   

Dielectrophoretic capture of low abundance cell population using thick electrodes     

Julien Marchalot  Jean-Fran?ois Chateaux  Magalie Faivre  Hichem C. Mertani  Rosaria Ferrigno  Anne-Laure Deman 《Biomicrofluidics》2015,9(5)

Enrichment of rare cell populations such as Circulating Tumor Cells (CTCs) is a critical step before performing analysis. This paper presents a polymeric microfluidic device with integrated thick Carbon-PolyDimethylSiloxane composite (C-PDMS) electrodes designed to carry out dielectrophoretic (DEP) trapping of low abundance biological cells. Such conductive composite material presents advantages over metallic structures. Indeed, as it combines properties of both the matrix and doping particles, C-PDMS allows the easy and fast integration of conductive microstructures using a soft-lithography approach while preserving O₂ plasma bonding properties of PDMS substrate and avoiding a cumbersome alignment procedure. Here, we first performed numerical simulations to demonstrate the advantage of such thick C-PDMS electrodes over a coplanar electrode configuration. It is well established that dielectrophoretic force (F_DEP) decreases quickly as the distance from the electrode surface increases resulting in coplanar configuration to a low trapping efficiency at high flow rate. Here, we showed quantitatively that by using electrodes as thick as a microchannel height, it is possible to extend the DEP force influence in the whole volume of the channel compared to coplanar electrode configuration and maintaining high trapping efficiency while increasing the throughput. This model was then used to numerically optimize a thick C-PDMS electrode configuration in terms of trapping efficiency. Then, optimized microfluidic configurations were fabricated and tested at various flow rates for the trapping of MDA-MB-231 breast cancer cell line. We reached trapping efficiencies of 97% at 20 μl/h and 78.7% at 80 μl/h, for 100 μm thick electrodes. Finally, we applied our device to the separation and localized trapping of CTCs (MDA-MB-231) from a red blood cells sample (concentration ratio of 1:10).  相似文献   

Fuzzy flexible resource constrained project scheduling based on genetic algorithm     

查鸿  张连营 《天津大学学报(英文版)》2014,20(6):469-474

Both fuzzy temporal constraint and flexible resource constraint are considered in project scheduling. Inorder to obtain an optimal schedule, we propose a genetic algorithm integrated with concepts on fuzzy set theory aswell as specialized coding and decoding mechanism. An example demonstrates that the proposed approach can assistthe project managers to obtain the optimal schedule effectively and make the correct decision on skill training before aproject begins.  相似文献   

Social media effects on fostering online civic engagement and building citizen trust and trust in institutions     

Anne Marie Warren  Ainin Sulaiman  Noor Ismawati Jaafar 《Government Information Quarterly》2014

This paper tests the extent to which social media is shaping civic engagement initiatives to build trust among people and increase trust in their institutions, particularly the government, police and justice systems. A survey of 502 citizens showed that using social media for civic engagement has a significant positive impact on trust propensity and that this trust had led to an increase in trust towards institutions. Interestingly, while group incentives encouraged citizens to engage online for civic matters, it is civic publications through postings on social media that intensify the urge of citizens for civic action to address social issues. Post-hoc analysis via ten interviews with social activists was conducted to further examine their perceptions on trust towards institutions. The overall findings suggest that institutions, in their effort to promote a meaningful and trusting citizen engagement, need to enhance trust among the public by fostering social capital via online civic engagement and closing the public–police disengagement gap.  相似文献   

Teaching to the Test…or Testing to Teach: Exams Requiring Higher Order Thinking Skills Encourage Greater Conceptual Understanding     

Jamie?L.?JensenEmail author  Mark?A.?McDaniel  Steven?M.?Woodard  Tyler?A.?Kummer 《Educational Psychology Review》2014,26(2):307-329

In order to test the effect of exam-question level on fostering student conceptual understanding, low-level and high-level quizzes and exams were administered in two sections of an introductory biology course. Each section was taught in a high-level inquiry based style but was assigned either low-level questions (memory oriented) on the quizzes and exams, or high-level questions (application, evaluation, and analysis) on the quizzes and exams for the entirety of the semester. A final exam consisting of 20 low-level and 21 high-level questions was given to both sections. We considered several theoretical perspectives based on testing effect, test expectancy, and transfer-appropriate processing literature as well as the theoretical underpinnings of Bloom’s taxonomy. Reasoning from these theoretical perspectives, we predicted that high-level exams would encourage not only deeper processing of the information by students in preparation for the exam but also better memory for the core information (learned in the service of preparing for high-level questions). Results confirmed this prediction, with students in the high-level exam condition demonstrating higher performance on both the low-level final-exam items and the high-level final exam items. This pattern suggests that students who are tested throughout the semester with high-level questions acquire deep conceptual understanding of the material and better memory for the course information, and lends support to the proposed hierarchical nature of Bloom’s taxonomy.  相似文献   

Using technology pedagogical content knowledge development to enhance learning outcomes     

Douglas?D.?Agyei  Jared?KeengweEmail author 《Education and Information Technologies》2014,19(1):155-171

This paper describes an intervention in which pre-service teachers developed their TPACK through multiple data sources. Teachers’ self-reports of their TPACK knowledge were triangulated with performance-based assessment of their instructional practices and artifacts to give a better understanding and nature of pre-service teachers’ TPACK development. Although self reported measures did not correlate with pre-service teachers’ actual increased knowledge of technology integration, this study enhances better understanding of the pre-service teachers’ TPACK development through the multiple assessment measures. The learning outcome measures provide specific information and concrete representation of what pre-service teachers can actually do with technology in their TPACK development. The findings suggested multiple concerns about self-reported measures that are discussed in the framework of the TPACK instrument.  相似文献   

Probability,uncertainty and artificial intelligence     

James?CussensEmail author 《Metascience》2014,23(3):505-511

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Content and knowledge provision service – a way to build intellectual capital in learning organizations     

Sonja D?Radenkovi?Email author  Vladan?Deved?i?  Jelena?Jovanovi?  Zoran?Jeremic 《知识管理研究与实践》2014,12(3):297-309

This paper presents the concept and the implementation of the Content and/or Knowledge Provision (CKP) service. The service is developed as a part of research within Intelligent Learning Extended Organization, an 7th Framework Program for R&D project in the area of technology-enhanced learning. The project aimed at enhancing cross-organizational Learning and Knowledge Building (LKB) practices at workplaces, leading to continuous growth of organization’s intellectual capital. By using the CKP service, employees can upload different kinds of knowledge assets into a knowledge repository, annotate them and (re-)discover relevant ones by performing semantic search over the knowledge repository. Hence, the service effectively serves as a content and knowledge-sharing facility and semantic search engine within a learning organization. Furthermore, CKP enables collaborative manipulation and annotation of knowledge assets in the repository, thus supporting all three components of intellectual capital.  相似文献   

Ordering disorders; linking organization design and knowledge integration     

Paul H J?HendriksEmail author  Ben G M?Fruytier 《知识管理研究与实践》2014,12(1):48-61

Studies addressing the connections between knowledge and organization structures can be divided into two classes. One class holds that a perspective on knowledge signals shortcomings of classical design principles and calls for flatter hierarchy and less specification of the production structure. Another class maintains that a knowledge perspective on organizations is at odds with any design perspective, whether classical or not, because the emergent, thoroughly social and practice-based nature of knowledge as knowing in action makes knowledge a useless and even dangerous beacon to designers: ex ante, knowledge is said to be fundamentally indeterminate and any attempt to ‘structure around knowledge’ may effectively drive out knowledge. To explore differences and possible bridges between these two calls of studies, the paper explores how both elements of the equation, organization structure and organizational knowledge, are to be conceived to ensure a meaningful connection between them. It is argued that the grouping focus in both defines the meeting place of organization structures and organizational knowledge, but shows that the involved knowledge and grouping concepts are not mutually compatible. It leads to a view where organization structures are seen as the ‘seeding’ background for knowledge integration processes that, in turn, constitute the patterns of work relationships envisioned in the designer's organizational decomposition and grouping. For illustration purposes, the paper presents the example of the Max Planck Institute that describes one possible way through the conceptual model presented in the paper.  相似文献   

Paraoxonase 1 activity and phenotype distribution in premenopausal and postmenopausal women     

Dra?an Butorac  Ivana ?elap  Sanja Ka?kov  Vera Robi?  Tomislav Mileti?  Zlata Flegar Me?tri?  Andrea Hulina  Krunoslav Kuna  Tihana ?ani? Grubi?i?  Marija Grdi? Rajkovi? 《Biochemia medica : ?asopis Hrvatskoga dru?tva medicinskih biokemi?ara / HDMB》2014,24(2):273-280

Introduction

Postmenopausal women have higher risk of cardiovascular disease. One of the contributing factors could be reduced activity of anti-atherogenic enzyme paraoxonase 1 (PON1). The aim of this study was to examine differences in the lipid status, paraoxonase and arylesterase PON1 activities and PON1 phenotype in women with regular menstrual cycle and in postmenopausal women.

Materials and methods:

The study included 51 women in reproductive age (25 in follicular and 26 in luteal phase of the menstrual cycle) and 23 women in postmenopause. Lipid parameters in sera were determined using original reagents and according to manufacturer protocol. PON1 activity in serum was assessed by spectrophotometric method with substrates: paraoxon and phenylacetate. PON1 phenotype was determined by double substrate method.

Results:

Compared to the women in follicular and luteal phase, postmenopausal women have significantly higher concentration of triglyceride [0.9 (0.7–1.3), 0.7 (0.6–1.0) vs. 1.5 (0.9–1.7) mmol/L; P = 0.002], cholesterol [5.10 (4.78–6.10), 5.05 (4.70–5.40) vs. 6.30 (5.73–7.23) mmol/L; P < 0.001], LDL [3.00 (2.56–3.63), 3.00 (2.70–3.70) vs. 3.90 (3.23–4.50) mmol/L; P < 0.001], and apolipoprotein B [0.88 (0.75–1.00), 0.79 (0.68–1.00) vs. 1.07 (0.90–1.24) mmol/L; P = 0.002]. PON1 basal [104 (66–260), 106 (63–250) vs. 93 (71–165) U/L; P = 0.847] and salt-stimulated paraoxonase activity [210 (131–462), 211 (120–442) vs. 180 (139–296) U/L; P = 0.857] as well as arylesterase activity [74 (63–82), 70 (54–91) vs. 70 (60–81) kU/L; P = 0.906] and PON1 phenotype (P = 0.810) were not different in the study groups.

Conclusion:

There are no differences in PON1 activity and PON1 phenotype between women with regular menstrual cycle and postmenopausal women.  相似文献