Thermally Excited Resonating Membrane Mass Flow Sensor

A mass flow sensor based on the frequency shift of a resonating microstructure is being developed, using a measurement principle of the thermoanemometry type. The sensor is to be applied for mass flows up to 10 standard cubic centimeters per minute (sccm; 10sccm = 0.17 mg s-1), with a high sensitivity, a high resolution and a fast response. Here we report on the first prototype consisting of a 2 μm thick membrane: the temperature elevation of the thermally excited vibrating membrane affects its resonance frequency. The three-dimemsional heat transfer within the membrane and the mass flow is modeled, and expressions are derived for the resonance frequencies of initially curved and stressed membranes. Experiments have been carried out for nitrogen flows of up to 500 sccm passing over thermally excited membranes. Predicted and measured values for the shift of the resonance frequency agree well. The sensitivity of the average temperature elevation to the mass flow is quite small: at 10 sccm the cooling effect of the mass flow is only 0.2% of the heat loss by conduction to the substrate. At a resonance frequency of 5.0 kHz, and an average temperature elevation of the mebrane of 8°C, this still leads to a frequency change of 13 Hz in the mass flow range from zero to 10 sccm. Suggestions are presented for increasing the sensitivity of the sensor

Dynamic mode-I delamination of composite laminates using a drop-weight tower and optical data-acquisition

Impact events can hardly be called quasi-static. To test for relevant properties with quasi-static test methods thus seems to make little sense, especially when materials with a rate-sensitivity are the subject of testing. Therefore, a test setup is developed to obtain the trac-tion-separation behaviour and fracture toughness of composites in mode I delamination at impact rates of deformation. An optical technique is applied to obtain the load-deflection curve, allowing for contactless measurements

Enzyme localization can drastically affect signal amplification in signal transduction pathways

Push-pull networks are ubiquitous in signal transduction pathways in both prokaryotic and eukaryotic cells. They allow cells to strongly amplify signals via the mechanism of zero-order ultrasensitivity. In a push-pull network, two antagonistic enzymes control the activity of a protein by covalent modification. These enzymes are often uniformly distributed in the cytoplasm. They can, however, also be colocalized in space, for instance, near the pole of the cell. Moreover, it is increasingly recognized that these enzymes can also be spatially separated, leading to gradients of the active form of the messenger protein. Here, we investigate the consequences of the spatial distributions of the enzymes for the amplification properties of push-pull networks. Our calculations reveal that enzyme localization by itself can have a dramatic effect on the gain. The gain is maximized when the two enzymes are either uniformly distributed or colocalized in one region in the cell. Depending on the diffusion constants, however, the sharpness of the response can be strongly reduced when the enzymes are spatially separated. We discuss how our predictions could be tested experimentally.Comment: PLoS Comp Biol, in press. 32 pages including 6 figures and supporting informatio

The banking firm: the role of signaling with collaterals

In this paper we challenge basic results of signaling models. In our banking model each project of a borrower is described by a continuous density of outcomes. Different density functions are classified according to second stochastisch dominance. Combining these features we find that in a banking model collateral is no longer in a position to signal the degree of riskiness of the borrower to the lender. In most cases the equilibrium is a pooling equilibrium. --Signaling,collateral,perfect Bayesian equilibrium

An appropriate management strategy for informal settlements in mining areas: the case of smashblock, Thabazimbi

A thesis Submitted in Fulfillment of the degree of Masters Built Environment Housing to the Faculty of Engineering and Built Environment of the University of Witwatersrand, Johannesburg, August 2017This research report is about the appropriate management strategy for informal settlement in mining area, the case of Smashblock, Thabazimbi local municipality situated in Limpopo province. The research seek to understand the main problem of the rapid growth of unplanned informal settlements that results in poor living conditions for the residents of Smashblock. However, the key objective of the study is to understand the options for management of the informal settlement in Smashblock. The research comes up with an appropriate intervention and management strategy for Smashblock informal settlement. The research has explored the Smashblock informal settlement with regard to its specific nature and character, the role played by Thabazimbi municipality, sector departments and mining companies or other entities; improvement, relocation and / or upgrading plan(s), the engagement of the municipality, mining companies and other sector departments with regard to the informal settlement and approaches to informal settlement improvement and management that are offered through national or local policy. The research recommends interim improvements of Smashblock prior to full upgrading, e.g. about re-blocking, health and safety improvements, improved management or access to current water provision and sanitation.XL201