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   

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   

MEMBERS OF THE NATIONAL COUNCIL FOR JEWISH EDUCATION     

Walter I. Ackerman  Samuel M. Blumenfield  Abraham P. Gannes  Alexander Schindler  Isaac Toubin  Charles Zibbell 《Journal of Jewish Education》2013,79(3):176-177

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THE WRONG WAY STILL: WRONG IN 1889 AND WRONG IN 1995     

Dr. Hanan A. Alexander 《Journal of Jewish Education》2013,79(2):15-20

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Towards an American Jewish Education     

Alexander M. Dushkin 《Journal of Jewish Education》2013,79(1):17-22

My function is to analyze a survey of adult Jewish education and to present briefly some of my own views on the subject. The survey was planned and conducted under the direction of the National Advisory Council on Adult Jewish Education of the American Association for Jewish Education. The Advisory Council includes the directors or representatives of a number of important religious and lay national Jewish agencies which sponsor adult Jewish education. The responses to the questionnaires were analyzed and the Survey Report was written by Rabbi Samuel I. Cohen.  相似文献   

Democracy and Jewish Education     

Alexander M. Dushkin 《Journal of Jewish Education》2013,79(2):94-100

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The Jewish Educational System—A Plea for Organic Unity     

Alexander M. Dushkin 《Journal of Jewish Education》2013,79(2):76-80

This article analyzes the career commitments and retention patterns among graduates of the DeLeT program (Day School Leadership Through Teaching) who were prepared for day-school teaching at Brandeis University and Hebrew Union College-Jewish Institute of Religion. Employing t-tests to analyze survey responses, we identify factors that shape and support teachers' career commitments to Jewish day schools. Our findings suggest that those who stay in Jewish day school teaching are likely to do so because of more commitment to the Jewish community, greater perception of effective teacher preparation experience, and better school support in comparison to those who leave teaching in this setting. These findings are consistent with a multi-layered understanding of teachers' lives and career commitments, which is illustrated in the interaction between person, program, and setting.  相似文献