Vertical microbubble column–A photonic lab-on-chip for cultivation and online analysis of yeast cell cultures     

Stefanie Demming  Gena Peterat  Andreu Llobera  Hannah Schmolke  Alexander Bruns  Michael Kohlstedt  Ala‘aldeen Al-Halhouli  Claus-Peter Klages  Rainer Krull  Stephanus Büttgenbach 《Biomicrofluidics》2012,6(3)

This paper presents a vertically positioned microfluidic system made of poly(dimethylsiloxane) (PDMS) and glass, which can be applied as a microbubble column (μBC) for biotechnological screening in suspension. In this μBC, microbubbles are produced in a cultivation chamber through an integrated nozzle structure. Thus, homogeneous suspension of biomass is achieved in the cultivation chamber without requiring additional mixing elements. Moreover, blockage due to produced carbon dioxide by the microorganisms—a problem predominant in common, horizontally positioned microbioreactors (MBRs)—is avoided, as the gas bubbles are released by buoyancy at the upper part of the microsystem. The patterned PDMS layer is based on an optimized two-lithographic process. Since the naturally hydrophobic PDMS causes problems for the sufficient production of microbubbles, a method based on polyelectrolyte multilayers is applied in order to allow continuous hydrophilization of the already bonded PDMS-glass-system. The μBC comprises various microelements, including stabilization of temperature, control of continuous bubble formation, and two optical configurations for measurement of optical density with two different sensitivities. In addition, the simple and robust application and handling of the μBC is achieved via a custom-made modular plug-in adapter. To validate the scalability from laboratory scale to microscale, and thus to demonstrate the successful application of the μBC as a screening instrument, a batch cultivation of Saccharomyces cerevisiae is performed in the μBC and compared to shake flask cultivation. Monitoring of the biomass growth in the μBC with the integrated online analytics resulted in a specific growth rate of 0.32 h⁻¹, which is almost identical to the one achieved in the shake flask cultivation (0.31 h⁻¹). Therefore, the validity of the μBC as an alternative screening tool compared to other conventional laboratory scale systems in bioprocess development is proven. In addition, vertically positioned microbioreactors show high potential in comparison to conventional screening tools, since they allow for high density of integrated online analytics and therefore minimize time and cost for screening and guarantee improved control and analysis of cultivation parameters.  相似文献   

The planarity of the stickface motion in the field hockey hit     

Willmott AP  Dapena J 《Journal of sports sciences》2012,30(4):369-377

The field hockey hit is an important but poorly understood stroke. In this study, we investigated the planarity of the stickface motion during the downswing to better characterize the kinematics and to assess the suitability of planar pendulum models for simulating the hit. Thirteen experienced female field hockey players were filmed executing hits with a single approach step, and the kinematics of the centre of the stickface were measured. A method was developed for identifying how far back from impact the stickface motion was planar. Orthogonal regression was used to fit least-squares planes to the stickface path during sections of the downswing of varying length, with each section ending at impact. A section was considered planar if the root mean square residual between the stickface path and the fitted plane was less than 0.25% of the distance travelled by the stickface during that period. On average, the stickface motion was planar for the last 83 ± 12% of its downswing path, with the length of the planar section ranging from 1.85 m to 2.70 m. The suitability of a planar model for the stickface motion was supported, but further investigation of the stick and arm kinematics is warranted.  相似文献   

Variability of inter-team distances associated with match events in elite-standard soccer     

W Frencken  Hd Poel  C Visscher  K Lemmink 《Journal of sports sciences》2012,30(12):1207-1213

Abstract In soccer, critical match events like goal attempts can be preceded by periods of instability in the balance between the two teams' behaviours. Therefore, we determined periods of high variability in the distance between the teams' centroid positions longitudinally and laterally in an international-standard soccer match and evaluated corresponding match events. Position data were collected with AMISCO Pro?. Inter-team distance variability was calculated over a 3-s moving window. Out of the 242 match periods that exceeded the variability criterion, 51 were dead-ball situations. Match events identified through longitudinal inter-team distance primarily related to defending players moving forward-backward after a longitudinal pass. Match events identified through lateral inter-team distance mainly corresponded with defending players moving laterally following sideways passing. One of two goals and two of fourteen goal-attempts were preceded by a period of high variability. Together, periods of highly variable inter-team distance were associated with collective defensive actions and team reorganisation in dead-ball moments rather than goals or goal attempts. Inter-team dynamics quantified (mutual) reorganisation of the teams and marked teams' collective defensive ability to respond to attacking explorations.  相似文献   

A faster running speed is associated with a greater body weight loss in 100-km ultra-marathoners     

Knechtle B  Knechtle P  Wirth A  Alexander Rüst C  Rosemann T 《Journal of sports sciences》2012,30(11):1131-1140

In 219 recreational male runners, we investigated changes in body mass, total body water, haematocrit, plasma sodium concentration ([Na(+)]), and urine specific gravity as well as fluid intake during a 100-km ultra-marathon. The athletes lost 1.9 kg (s = 1.4) of body mass, equal to 2.5% (s = 1.8) of body mass (P < 0.001), 0.7 kg (s = 1.0) of predicted skeletal muscle mass (P < 0.001), 0.2 kg (s = 1.3) of predicted fat mass (P < 0.05), and 0.9 L (s = 1.6) of predicted total body water (P < 0.001). Haematocrit decreased (P < 0.001), urine specific gravity (P < 0.001), plasma volume (P < 0.05), and plasma [Na(+)] (P < 0.05) all increased. Change in body mass was related to running speed (r = -0.16, P < 0.05), change in plasma volume was associated with change in plasma [Na(+)] (r = -0.28, P < 0.0001), and change in body mass was related to both change in plasma [Na(+)] (r = -0.36) and change in plasma volume (r = 0.31) (P < 0.0001). The athletes consumed 0.65 L (s = 0.27) fluid per hour. Fluid intake was related to both running speed (r = 0.42, P < 0.0001) and change in body mass (r = 0.23, P = 0.0006), but not post-race plasma [Na(+)] or change in plasma [Na(+)] (P > 0.05). In conclusion, faster runners lost more body mass, runners lost more body mass when they drank less fluid, and faster runners drank more fluid than slower runners.  相似文献   

Creatine kinase activity weakly correlates to volume completed following upper body resistance exercise     

Machado M  Willardson JM  Silva DR  Frigulha IC  Koch AJ  Souza SC 《Research quarterly for exercise and sport》2012,83(2):276-281

In the current study, we examined the relationship between serum creatine kinase (CK) activity following upper body resistance exercise with a 1- or 3-min rest between sets. Twenty men performed two sessions, each consisting of four sets with a 10-repetition maximum load. The results demonstrated significantly greater volume for the 3-min condition (M = 4156 kg, SD = 867, for 3 min; vs. M = 3503 kg SD = 759, for 1 min; p < .001), with no significant differences in delta CK activity between conditions (p = .574). Nevertheless, there was a weak correlation between the delta CK activity and total volume of exercise completed (r = .55 with a 1-min rest, and r = .45 with a 3-min rest). Therefore, the volume following upper body resistance exercise correlates weakly with serum CK levels, irrespective of rest interval length between sets.  相似文献   

Robust block second order sliding mode control for a quadrotor     

L. Luque-Vega  B. Castillo-Toledo  Alexander G. Loukianov 《Journal of The Franklin Institute》2012,349(2):719-739

This paper presents the design of a controller based on the block control technique combined with the super twisting control algorithm for trajectory tracking of a quadrotor helicopter. A first order exact differentiator is used in order to estimate the virtual control inputs, which simplifies the control law design. In addition, the wind parameter resulting from the aerodynamic forces is also estimated in order to ensure robustness against these unmatched perturbations. The stability and finite time convergence of the exact differentiator have been recently proved by means of Lyapunov functions, and therefore the stability analysis of the proposed controller has been carried out along the same lines. The performance and effectiveness of the proposed controller are tested in a simulation study taking into account external disturbances.  相似文献   

“What could be” in Canadian sport facility environmental sustainability     

Cheryl Mallen  Chris Chard 《Sport Management Review》2012,15(2):230-243

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Comparison of 2D video and electrogoniometry measurements of knee flexion angle during a countermovement jump and landing task     

Erich Petushek  Chris Richter  David Donovan  William P. Ebben  Phillip B. Watts  Randall L. Jensen 《Sports Engineering》2012,15(3):159-166

Quantifying countermovement jump (CMJ) and landing knee flexion angle is important for performance and injury risk assessment. The purpose of the study was to compare electrogoniometer (El-Gon)- and video-derived CMJ and landing knee flexion angle. Twenty-two adults performed three CMJs while knee flexion angle was simultaneously assessed using an El-Gon and video. The average systematic offset (RMSE) of the El-Gon-derived knee flexion angle throughout the entire movement was 7.03°?±?2.69°. Excellent reliability was demonstrated by the El-Gon (ICCavg?=?0.92). Countermovement knee flexion angle, maximum landing knee flexion angle and flexion angle at maximum vertical ground reaction force were 12.0°, 10.9°, and 5.7° higher, respectively, when assessed using El-Gon (p?<?0.001), compared to video. Errors between instruments are likely due to El-Gon crosstalk, misalignment and/or axis determination. The El-Gon is a cost-effective and time-efficient alternative to video analysis for the assessment of knee flexion angle if the error is accounted for and the sensor is precisely attached.  相似文献   

DNS白名单会阻碍IPv6的实施吗？     

John rzozowski  Comcast  洪丹  陈树生 《中国教育网络》2010,(7):31-33

什么是DNS白名单？在当今的公共互联网上使用IPv4地址时,解析程序可以向权威的域名服务器查询并接收IPv4的地址A记录。当一位权威DNS的管理员为指定域添加IPv6地址AAAA记录时,它将像A记录和其他RR一样被解析程序查询和接收。  相似文献   

Learning to use the Internet as a study tool: a review of available resources and exploration of students' priorities     

Bond CS  Fevyer D  Pitt C 《Health information and libraries journal》2006,23(3):189-196

BACKGROUND: The Internet is a valuable information tool, but users often struggle to locate good quality information from within the vast amount of information available. OBJECTIVE: The aim of the study was to identify the online information resources available to assist students develop Internet searching skills, and to explore the students' priorities in online guides. METHODS: A qualitative approach was adopted with two phases. The first was a structured search of available online study skills resources. The second comprised 10 group interviews with a total of 60 students at all stages of five undergraduate health and social care related courses at a UK university. RESULTS: The study found that there were good online guides available, but that, perversely, the better guides tended to require the best searching skills to locate them. A few students were enthusiastic about using online support, however the majority felt that if they had the skills to locate such resources they wouldn't use a study guide to improve these skills, and if they did not have the skills they would not think of using an online guide to develop them. CONCLUSIONS: Students wanted assistance when they had problems or questions, rather than sites that offered structured learning experiences. Personal support rather than virtual support was also considered to be most important to the students in this study.  相似文献