A centrifugo-magnetically actuated gas micropump

This paper describes a novel gas micropump on a centrifugal microfluidic platform. The pump is integrated on a passive and microstructured polymer disk which is sealed with an elastomer lid featuring paramagnetic inlays. The rotational motion of this hybrid disk over a stationary magnet induces a designated sequence of volume displacements of the elastic lid, leading to a net transport of gas. The pumping pressure scales linearly with the frequency, with a maximum observable pressure of 4.1 kPa. The first application of this rotary device is the production of gas-liquid flows by pumping ambient air into a continuous centrifugal flow of liquid. The injected gas volume segments the liquid stream into a series of liquid compartments. Apart from such multi-phase flows, the new pumping technique supplements a generic air-to-liquid sampling method to centrifugal microfluidic platforms

Properties of Tailored Granular Media

The macroscopic behavior of granular media is determined by interactions at the grain scale. While some phenomena in granular media can be explained by hard sphere models, experiments always deal with friction, van-der-Waals forces, liquid bridge formation and tribocharging. In how far these interactions determine the macroscopic behavior and the relative strength of each interaction in a real experiment are often difficult to estimate. In this thesis, we investigate how changes at the surfaces of granular spheres can influence the macroscopic behavior of a granular medium. In a first experiment, we measure the rheological properties of surface modified granular particles. Such modifications necessarily influence multiple factors at once and so we measure the influence of the surface modifications on friction, wettability and triboelectric charging behavior and then correlate the changes at the grain scale to the macroscopic behavior. In a second experiment, we investigate in how far charging effects due to tribocharging can determine the packing structure of a granular packing. In the context of controlling the triboelectric effect, we investigate the stochastic nature of exchanged charges in collisions of granular particles and investigate the effect of surface treatments on triboelectric charging behavior. We show that triboelectric charging can indeed define the packing structure and lead to ordered structures in which electrostatic potential is minimized. The effect of boundary conditions is also investigated. Finally, we show that wall friction and piston shape influence the force propagation and displacements in a two dimensional granular medium

Alginate micro-bead fabrication on a centrifugal microfluidics platform

We present a novel method for the direct, centrifugally induced fabrication of small alginate beads displaying adjustable diameters between 180 mum and 800 mum by polymer-tube micronozzles. The size distribution features a CV of 7 - 16 % for the main peak. Up to 600 beads per second and channel are issued from the micronozzle through an air gap towards a standard lab tube ("Eppi") attached to the rotor spinning and containing a curing agent. At spinning frequencies between 5 Hz and 28 Hz, the tubes align horizontally under rotation and return to a vertical position as soon as the rotor is at rest. The hardened beads are collected within the tube for further processing or characterization. This method is considered as a low cost technology for micro encapsulation technologies

The Emergence of the Actively Managed ETF

Since the first exchange-traded fund began trading in 1993, the ETF form has attracted enormous investment flows. However, this triumph of the ETF has been overwhelmingly limited to the world of passive investment. Due to a mix of recent market innovation and regulatory change, this state of affairs is changing today. As I explain in this Article, there is much reason to believe that the actively managed ETF is now set to emerge as a significant feature of the investment landscape. And this emergence has important implications for, among others, the main parties that play key roles in protecting investors (namely, the Securities and Exchange Commission as well as investment intermediaries)

A New Market-Based Approach to Securities Law

Modern securities regulation has three main areas, each of which is plagued by a core problem. Mandatory disclosure law leaves society with suboptimal disclosure, as the government calls for too little of some information (for example, management analysis of company prospects) and too much of other information (for example, data about trivial executive perks). Securities fraud law (specifically, its central fraud-on-the-market theory of reliance) yields damages at odds with any reasonable theory of compensation and deterrence. And insider trading law fails to achieve its ends because incentives to police illegal trading and tipping by executives are currently weak. In this Article, we propose fixing these fundamental flaws of securities law by shifting much of the regulatory focus from firms to information. In particular, we introduce the idea of building the law around a well-regulated market for the public-company information that sits at the center of each of the three main areas of securities law. Deploying this market, we argue, would trigger incentives for firms to disclose more information of value while also motivating them to more rigorously police illegal trading and tipping by their agents. Additionally, it would help regulators identify when the law requires disclosure that is not socially valuable and assist in the identification of a class of securities fraud plaintiffs that is more in line with the goals of the anti-fraud regime

Atmospheric Conditions Associated with Lightning during Snow and Ice Events

The purpose of this research was to find the atmospheric mechanisms associated with lightning in snow and ice events. The specific mechanisms that were examined were low-level wind shear, upper level divergence, surface temperature, low-level temperature, the -10 ° C level, and precipitable water. A chi-squared dependency test showed the strong association of low-level wind shear to each precipitation type (snow, sleet/freezing rain, rain) in two separate studies. Surface temperature appeared to have a relationship to lightning in all precipitation categories, while no significant relationship to lightning in all precipitation categories, while no significant relationship was found with upper level divergence, the -10 ° C level, or the precipitable water. From examination of the vertical soundings, temperatures above freezing are found in the low levels for all precipitation types meaning that different types of hydrometeors are present in the clouds. The mixing of these due to the turbulent effects of low-level shear may explain how the thunderclouds (mostly stratiform) are charged. Graupel and snow pellet interaction are also believed to be mechanisms for cloud charging