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排序方式: 共有530条查询结果,搜索用时 15 毫秒
31.
Jyoti P. Gurung Moein Navvab Kashani Sanaz Agarwal Gonzalo Peralta Murat Gel Matthew A. B. Baker 《Biomicrofluidics》2021,15(3)
Many motile bacteria are propelled by the rotation of flagellar filaments. This rotation is driven by a membrane protein known as the stator-complex, which drives the rotor of the bacterial flagellar motor. Torque generation is powered in most cases by proton transit through membrane protein complexes known as stators, with the next most common ionic power source being sodium. Sodium-powered stators can be studied through the use of synthetic chimeric stators that combine parts of sodium- and proton-powered stator proteins. The most well studied example is the use of the sodium-powered PomA-PotB chimeric stator unit in the naturally proton-powered Escherichia coli. Here we designed a fluidics system at low cost for rapid prototyping to separate motile and non-motile populations of bacteria while varying the ionic composition of the media and thus the sodium-motive force available to drive this chimeric flagellar motor. We measured separation efficiencies at varying ionic concentrations and confirmed using fluorescence that our device delivered eightfold enrichment of the motile proportion of a mixed population. Furthermore, our results showed that we could select bacteria from reservoirs where sodium was not initially present. Overall, this technique can be used to implement the selection of highly motile fractions from mixed liquid cultures, with applications in directed evolution to investigate the adaptation of motility in bacterial ecosystems. 相似文献
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This study compares the instrumentation and analysis techniques used when determining the power expended pedalling a rope-braked
ergometer manufactured by Monark (Sweden) during a low intensity test. Power values were generated by eight subjects. The
instrumentation consisted of load cells to measure the rope brake forces, a tachometer to measure the flywheel velocity and
instrumented pedal cranks manufactured by Schoberer Rad Messtechnik (SRM). The subjects pedalled a rope-braked ergometer at
60 rev min-1, against a resistance of 3 kg, for 5 minutes. Three different measurements of the mean power were recorded and these were
compared with the value given by Monark. The SRM cranks provided two sets of results using different software packages supplied
with the cranks. SRM standard software is used for taking measurements during training and cycle races over long time periods.
An additional piece of software is provided by SRM called Ptnew, which gives readings of torque and pedal cadence over periods
up to 30 seconds. Using the values supplied by Monark each subject generated 180 W of power. The mean power for the eight
subjects, measured using the SRM cranks, was 170.36 W (SD 4.11) using the alternative SRM software (Ptnew) over a 30 second
period and 173.68 W (SD 2.21) using the standard SRM software. From the direct measurement of the brake forces and flywheel
velocity the mean power across the eight subjects was 148.90 W (SD 5.89). The SRM cranks measure the input power, whereas
the direct measurement system measures the power output excluding mechanical losses. These values give a figure for the mechanical
efficiency for the roped-braked ergometer of 88%. It was found that Monark overestimates the power generated by the subjects
when compared with both the SRM systems and the direct measurement instrumentation. 相似文献
34.
Measurement of ground reaction force (GRF) in running provides a direct indication of the loads to which the body is subjected
at each foot-ground contact, and can provide an objective explanation for performance outcomes. Traditionally, the collection
of three orthogonal component GRF data in running requires an athlete to complete a series of return loops along a laboratory
based runway, within which a force platform is embedded, in order to collect data from a discrete footfall. The major disadvantages
associated with this GRF data collection methodology include the inability to assess multiple consecutive foot contacts and
the fact that measurements are typically confined to the laboratory. The objective of this research was to investigate the
potential for wearable instrumentation to be employed, in conjunction with artificial neural network (ANN) and multiple linear
regression (MLR) models, for the estimation of GRF in middle distance running. A modular wearable data acquisition system
was developed to acquire in-shoe force (ISF) data. Matched data sets from wearable instrumentation (source data) and force
plate (target data) records were collected from elite middle-distance runners under controlled laboratory conditions for the
purposes of ANN and MLR model development (MD) and model validation (MV).
In terms of statistical measures of prediction accuracy the MLR model was found to provide a superior level of accuracy for
the prediction of the vertical and medio-lateral components of GRF and alternatively, the ANN model provided the most accurate
predictions of the anterior-posterior component of GRF. The prediction accuracy of each component of GRF was found to be governed
by the inherent signal variability, in which case the vertical and anterior-posterior components were more reliable and subsequently
predicted significantly more accurately than the medio-lateral component.
The emerging capability for obtaining continuous GRF records from wearable instrumentation has the potential to permit unprecedented
quantification of training stress and competition demands in running. 相似文献
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38.
This pilot study examined the effects of a short‐term music therapy program on the classroom behaviours of newly arrived refugee students who were attending an intensive ‘English as a Second Language’ secondary school. A cross‐over design with two five‐week intervention periods was employed with group music therapy sessions conducted one or two times per week. Data from the Behaviour Assessment Scale for Children were used to evaluate a range of positive and negative school behaviours. A significant decrease in externalising behaviours was found with particular reference to hyperactivity and aggression. No significant differences were found in other behaviours. Explanations and implications of these findings are discussed. 相似文献
39.
The article traces the Welsh origins of “translanguaging” from the 1980s to the recent global use, analysing the development and extension of the term. It suggests that the growing popularity of the term relates to a change in the way bilingualism and multilingualism have ideologically developed not only among academics but also amid changing politics and public understandings about bilingualism. The original pedagogic advantages of a planned use of translanguaging in pedagogy and dual literacy are joined by an extended conceptualisation that perceives translanguaging as a spontaneous, everyday way of making meaning, shaping experiences, and communication by bilinguals. A new conceptualisation of translanguaging is in brain activity where learning is through 2 languages. A tripartite distinction is suggested between classroom translanguaging, universal translanguaging, and neurolinguistic translanguaging. The article concludes with a summary of recent research into translanguaging with suggestions for future research. 相似文献
40.
Ryan S. Baker Arnon Hershkovitz Lisa M. Rossi Adam B. Goldstein Sujith M. Gowda 《学习科学杂志》2013,22(4):639-666
We present a new method for analyzing a student's learning over time for a specific skill: analysis of the graph of the student's moment-by-moment learning over time. Moment-by-moment learning is calculated using a data-mined model that assesses the probability that a student learned a skill or concept at a specific time during learning (Baker, Goldstein, & Heffernan, 2010, 2011). Two coders labeled data from students who used an intelligent tutoring system for college genetics. They coded in terms of 7 forms that the moment-by-moment learning curve can take. These labels are correlated to test data on the robustness of students’ learning. We find that different visual forms are correlated with very different learning outcomes. This work suggests that analysis of moment-by-moment learning curves may be able to shed light on the implications of students’ different patterns of learning over time. 相似文献