High-throughput sorting of drops in microfluidic chips using electric capacitance

We analyze a recently introduced approach for the sorting of aqueous drops with biological content immersed in oil, using a microfluidic chip that combines the functionality of electrowetting with the high throughput of two-phase flow microfluidics. In this electrostatic sorter, three co-planar electrodes covered by a thin dielectric layer are placed directly below the fluidic channel. Switching the potential of the central electrode creates an electrical guide that leads the drop to the desired outlet. The generated force, which deflects the drop, can be tuned via the voltage. The working principle is based on a contrast in conductivity between the drop and the continuous phase, which ensures successful operation even for drops of highly conductive biological media like phosphate buffered saline. Moreover, since the electric field does not penetrate the drop, its content is protected from electrical currents and Joule heating. A simple capacitive model allows quantitative prediction of the electrostatic forces exerted on drops. The maximum achievable sorting rate is determined by a competition between electrostatic and hydrodynamic forces. Sorting speeds up to 1200 per second are demonstrated for conductive drops of 160 pl in low viscosity oil.     

Auswirkungen einer Intervention auf die Auseinandersetzung und Arbeit mit Bildungsstandards bei Mathematik-Lehrkräften

The introduction of educational standards in Germany forced teachers to change their perspective in order to achieve competence-oriented teaching. The initial representative surveys throughout Germany indicated that a short time after the introduction of the educational standards, teachers in various school forms were still very slow to implement the idea of competence-oriented teaching in their everyday school life. This article presents the effects of a newly developed intervention programme in which mathematics teachers familiarised themselves with educational standards for the first time. The teacher data and the performance data of the pupils of the schools participating in the project are compared in a longitudinal study with the data of schools which were not included in the intervention programme. The results indicate that after the intervention programme has run for one year, mathematics teachers in the project schools are more competence-oriented in their teaching and reflect more intensively on the concept of the educational standards than mathematics teachers in the comparison schools.     

Choice based diffusion model for predicting sales of mobile phones using conjoint analysis

The modeling of understanding consumers buying behavior requires a technique, which does not only incorporate the preferences of the consumers but also have the ability to trade-off between multi-characteristics products and services. This study is supported by evaluating a framework via a marketing research technique of Conjoint Analysis wherein we have shown how certain attributes of mobile phones when studied jointly can affect the overall buying behavior of the youth towards various brands taken into consideration. Further, customers' choice probabilities of the mobile phones, based on preferences have been evaluated and potential market size is determined. Also, this study has determined and forecasted the sales on the basis of choice probability and utility obtained via conjoint analysis. Customers of the mobile phone located in Delhi have been targeted for this study.