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Vivien M Johnston 《British journal of educational technology : journal of the Council for Educational Technology》1985,16(3):188-198
The organizational problems and decisions associated with introducing the microcomputer into the English curriculum are considered. The factors influencing decisions concerning how many machines to use are identified as availability; the classroom environment, in terms of its physical properties, patterns of use, and availability of resources; resources of teacher time, including previewing materials, organizing equipment, and lesson time. The attitudes of teachers and pupils are contrasted. The organization of classroom activities must facilitate learning through small-group discussion, and so accepted English teaching practices at secondary level are challenged by the introduction of the microcomputer. 相似文献
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Contingency in innovation and the role of national systems: taxol and taxotère in the USA and France
A very rich collection of archival material is used to compare two anticancer drugs commercialised by multinationals collaborating with public sector research, one in the USA and one in France. The framework of national innovation systems is used to compare the innovative environments for each development (different institutional structures, research programmes, financing, industry-academic-government relationships, environmental concern, and intellectual property regimes). The empirical work was able to bring out the nuances and subtleties of each environment, the way in which innovation took place in practice, and some striking differences from what stereotypical accounts of innovation in each country would have suggested. 相似文献
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Vivien Rolfe 《British journal of educational technology : journal of the Council for Educational Technology》2011,42(4):701-710
New students face the challenge of making a smooth transition between school and university, and with regards to academic practice, there are often gaps between student expectations and university requirements. This study supports the use of the plagiarism detection service Turnitin to give students instant feedback on essays to help improve academic literacy. A student cohort (n = 76) submitted draft essays to Turnitin and received instruction on how to interpret the ‘originality report’ themselves for feedback. The impact of this self‐service approach was analysed by comparing the writing quality and incidence of plagiarism in draft and final essays, and comparing the results to a previous cohort (n = 80) who had not used Turnitin formatively. Student and staff perceptions were explored by interview and questionnaire. Using Turnitin formatively was viewed positively by staff and students, and although the incidence of plagiarism did not reduce because of a worsening of referencing and citation skills, the approach encouraged students to develop their writing. To conclude, students were positive of their experience of using Turnitin. Further work is required to understand how to use the self‐service approach more effectively to improve referencing and citation, and narrow the gap between student expectations and university standards. 相似文献
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Anil Haraksingh Thilsted Vahid Bazargan Nina Piggott Vivien Measday Boris Stoeber 《Biomicrofluidics》2012,6(4)
A flow redirection and single cell immobilization method in a microfluidic chip is presented. Microheaters generated localized heating and induced poly(N-isopropylacrylamide) phase transition, creating a hydrogel that blocked a channel or immobilized a single cell. The heaters were activated in sets to redirect flow and exchange the fluid in which an immobilized cell was immersed. A yeast cell was immobilized in hydrogel and a 4′,6-diamidino-2-phenylindole (DAPI) fluorescent stain was introduced using flow redirection. DAPI diffused through the hydrogel and fluorescently labelled the yeast DNA, demonstrating in situ single cell biochemistry by means of immobilization and fluid exchange.The ability to control microfluidic flow is central to nearly all lab-on-a-chip processes. Recent developments in microfluidics either include microchannel based flow control in which microvalves are used to control the passage of fluid,1 or are based on discrete droplet translocation in which electric fields or thermal gradients are used to determine the droplet path.2, 3 Reconfigurable microfluidic systems have certain advantages, including the ability to adapt downstream fluid processes such as sorting to upstream conditions and events. This is especially relevant for work with individual biomolecules and high throughput cell sorting.4 Additionally, reconfigurable microfluidic systems allow for rerouting flows around defective areas for high device yield or lifetime and for increasing the device versatility as a single chip design can have a variety of applications.Microvalves often form the basis of flow control systems and use magnetic, electric, piezoelectric, and pneumatic actuation methods.5 Many of these designs require complicated fabrication steps and can have large complex structures that limit the scalability or feasability of complex microfluidic systems. Recent work has shown how phase transition of stimuli-responsive hydrogels can be used to actuate a simple valve design.6 Beebe et al. demonstrated pH actuated hydrogel valves.7 Phase transition of thermosensitive poly(N-isopropylacrylamide) (PNIPAAm) using a heater element was demonstrated by Richter et al.8 Phase transition was also achieved by using light actuation by Chen et al.9 Electric heating has shown a microflow response time of less than 33 ms.11 Previous work10 showed the use of microheaters to induce a significant shift in the viscosity of thermosensitive hydrogel to block microchannel flow and deflect a membrane, stopping flow in another microchannel. Additionally, Yu et al.12 demonstrated thermally actuated valves based on porous polymer monoliths with PNIPAAm. Krishnan and Erickson13 showed how reconfigurable optically actuated hydrogel formation can be used to dynamically create highly viscous areas and thus redirect flow with a response time of ～ 2?s. This process can be used to embed individual biomolecules in hydrogel and suppress diffusion as also demonstrated by others.15, 16 Fiddes et al.14 demonstrated the use of hydrogels to transport immobilized biomolecules in a digital microfluidic system. While the design of Krishnan and Erickson is highly flexible, it requires the use of an optical system and absorption layer to generate a geometric pattern to redirect flow.This paper describes the use of an array of gold microheaters positioned in a single layer polydimethylsiloxane (PDMS) microfluidic network to dynamically control microchannel flow of PNIPAAm solution. Heat generation and thus PNIPAAm phase transition were localized as the microheaters were actuated using pulse width modulation (PWM) of an applied electric potential. Additionally, hydrogel was used to embed and immobilise individual cells, exchange the fluid parts of the microfluidic system in order to expose the cells to particular reagents to carry out an in situ biochemical process. The PDMS microchannel network and the microheater array are shown in Figure Figure11.Open in a separate windowFigure 1A sketch of the electrical circuit and a microscope image of the gold microheaters and the PDMS microchannels. The power to the heaters was modulated with a PWM input through a H-bridge. For clarity, the electrical circuit for only the two heaters with gelled PNIPAAm is shown (H1 and V2). There are four heaters (V1-V4) in the “vertical channels” and three heaters (H1-H3) in the “horizontal” channel.The microchannels were fabricated using a patterned mould on a silicon wafer to define PDMS microchannels, as described by DeBusschere et al.17 and based on previous work.10 A 25 × 75 mm glass microscope slide served as the remaining wall of the microchannel system as well as the substrate for the microheater array. The gold layer had a thickness of 200 nm and was deposited and patterned using E-beam evaporation and photoresist lift-off.21 The gold was patterned to function as connecting electrical conductors as well as the microheaters.It was crucial that the microheater array was aligned with an accuracy of ～ 20μm with the PDMS microchannel network for good heat localization. The PDMS and glass lid were treated with plasma to activate the surface and alignment was carried out by mounting the microscope slide onto the condenser lens of an inverted microscope (TE-2000 Nikon Instruments). While imaging with a 4× objective, the x, y motorized stage aligned the microchannels to the heaters and the condenser lens was lowered for the glass substrate to contact the PDMS and seal the microchannels.Local phase transition of 10% w/w PNIPAAm solution in the microchannels was achieved by applying a 7 V potential through a H-bridge that received a PWM input at 500 Hz which was modulated using a USB controller (Arduino Mega 2650) and a matlab (Mathworks) GUI. The duty cycle of the PWM input was calibrated for each microheater to account for differences in heater resistances (25?Ω to 52?Ω) due to varying lengths of on-chip connections and slight fabrication inconsistencies, as well as for different flow conditions during device operation. Additionally, thermal cross-talk between heaters required decreasing the PWM input significantly when multiple heaters were activated simultaneously. This allowed confining the areas of cross-linked PNIPAAm to the microheaters, allowing the fluid in other areas to flow freely.By activating the heaters in sets, it was possible to redirect the flow and exchange the fluid in the central area. Figure Figure22 demonstrates how the flow direction in the central microchannel area was changed from a stable horizontal flow to a stable vertical flow with a 3 s response time, using only PNIPAAm phase transition. Constant pressures were applied to the inlets to the horizontal channel and to the vertical channels. Activating heaters V1-4 (Figure (Figure2,2, left) resulted in flow in the horizontal channel only. Likewise, activating heaters H1 and H2 allowed for flow in the vertical channel only. In this sequence, the fluid in the central microchannel area from one inlet was exchanged with fluid from the other inlet. Additionally, by activating heater H3, a particle could be immobilised during the exchange of fluid as shown in Figure Figure33 (top).Open in a separate windowFigure 2Switching between fluid from the horizontal and the vertical channel using hydrogel activation and flow redirection with a response time of 3 s. A pressure of 25 mbar was applied to the inlet of the horizontal channel and a pressure of 20 mbar to the vertical channel. The flow field was determined using particle image velocimetry, in which the displacement of fluorescent seed particles was determined from image pairs generated by laser pulse exposure. Processing was carried out with davis software (LaVision).Open in a separate windowFigure 3A series of microscope images near heater H3 showing: (1a)-(1c) A single yeast cell captured by local PNIPAAm phase transition and immobilized for 5 min before being released. (2a) A single yeast cell was identified for capture by embedding in hydrogel. (2b) The cell as well as the hydrogel displayed fluorescence while embedded due to the introduction of DAPI in the surrounding region. (2c) The diffusion of DAPI towards the cell as the heating power of H3 is reduced after 15 min, showing a DAPI stained yeast cell immobilized.Particle immobilisation in hydrogel and fluid exchange in the central area of the microfluidic network were used to carry out an in situ biochemical process in which a yeast cell injected through one inlet was stained in situ with a 4′,6-diamidino-2-phenylindole (DAPI) solution (Invitrogen), which attached to the DNA of the yeast cell.18 A solution of yeast cells with a concentration of 5 × 107cells/ml suspended in a 10% w/w PNIPAAm solution was injected through the horizontal channel. A solution of 2μg/l DAPI in a 10% w/w PNIPAAm solution was injected through the vertical channel. A single yeast cell was identified and captured near the central heater, and by deactivating the heaters in the vertical channel, DAPI solution was introduced in the microchannels around the hydrogel. After immobilising the cell for 15 min, the heater was deactivated, releasing the cell in the DAPI solution. This process is shown in Figure Figure33 (bottom). The sequence of the heater activation and deactivation in order to immobilize the cell and exchange the fluid is outlined in the supplementary material.21Eriksen et al.15 demonstrated the diffusion of protease K in the porous hydrogel matrix,19 and it was therefore expected that DAPI fluorescent stain (molecular weight of 350 kDa, Ref. 20) would also diffuse. DAPI diffusion is shown in Figure 3(2b) in which the yeast cell shows fluorescence while embedded in the hydrogel. The yeast cell was released by deactivating the central heater and activating all the others to suppress unwanted flow in the microchannel. As a result, the single cell was fully immersed in the DAPI solution. Immobilization of a single cell allows for selection of a cell that exhibits a certain trait and introduction of a new fluid while maintaining the cell position in the field of view of the microscope such that a biochemical response can be imaged continuously.In summary, a microfluidic chip capable of local heating was used to induce phase transition of PNIPAAm to hydrogel, blocking microchannel flow, and thereby allowing for reconfigurable flow. Additionally, the hydrogel was used to embed and immobilise a single yeast cell. DAPI fluorescent stain was introduced using flow redirection, and it stained the immobilized cell, showing diffusion into the hydrogel. The versatile design of this microfluidic chip permits flow redirection, and is suitable to carry out in situ biochemical reactions on individual cells, demonstrating the potential of this technology for forming large-scale reconfigurable microfluidic networks for biochemical applications. 相似文献
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Motivation beliefs of secondary school teachers in Canada and Singapore: A mixed methods study 总被引：1，自引：0，他引：1
Robert M. Klassen Wan Har Chong Vivien S. Huan Isabella Wong Allison Kates Wanwisa Hannok 《Teaching and Teacher Education》2008
A mixed methods approach was used to explore secondary teachers’ motivation beliefs in Canada and Singapore. Results from Study 1 revealed that socio-economic status (SES) was the strongest predictor of school climate in Canada, and that collective efficacy mediated the effect of SES on school climate in Singapore, but not in Canada. In Study 2, interviews were conducted with 10 teachers in Canada and 14 teachers in Singapore. Teachers in both settings discussed students’ social and behavior problems, but the range of the social problems was greater in Canada than in Singapore, and had a stronger impact on teachers’ motivation beliefs. 相似文献
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Mumba Frackson Pottmeyer Laura Ochs Chabalengula Vivien M. 《Research in Science Education》2021,51(5):1247-1267
Research in Science Education - Most studies on inquiry have focused on student outcomes, teachers’ conceptions of inquiry, implementation of inquiry in science classrooms, and inquiry... 相似文献
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