Particle-tracking microrheology is an in situ technique that allows quantification of biofilm material properties. It overcomes the limitations of alternative techniques such as bulk rheology or force spectroscopy by providing data on region specific material properties at any required biofilm location and can be combined with confocal microscopy and associated structural analysis. This article describes single particle tracking microrheology combined with confocal laser scanning microscopy to resolve the biofilm structure in 3 dimensions and calculate the creep compliances locally. Samples were analysed from Pseudomonas fluorescens biofilms that were cultivated over two timescales (24 h and 48 h) and alternate ionic conditions (with and without calcium chloride supplementation). The region-based creep compliance analysis showed that the creep compliance of biofilm void zones is the primary contributor to biofilm mechanical properties, contributing to the overall viscoelastic character.

The paper describes a CMOS voltage reference design that uses the temperature dependence of NMOS and PMOS threshold voltages to form a temperature-insensitive reference. No diodes or parasitic bipolar transistors are used. The circuit architecture accommodates a wide range of output voltages. A test chip is fabricated using a 0.5 mm CMOS process. The prototype achieves a temperature coefficient of 32 ppm/1C for a temperature range of À101C to 801C and a supply voltage sensitivity of 10 mV/V.

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This paper is concerned with the initial-boundary value problem of scalar conservation laws with weak discontinuous flux, whose initial data are a function with two pieces of constant and whose boundary data are a constant function. Under the condition that the flux function has a finite number of weak discontinuous points, by using the structure of weak entropy solution of the corresponding initial value problem and the boundary entropy condition developed by Bardos-Leroux-Nedelec, we give a construction method to the global weak entropy solution for this initial-boundary value problem, and by investigating the interaction of elementary waves and the boundary, we clarify the geometric structure and the behavior of boundary for the weak entropy solution.

This paper proposes a fast settling reference amplifier for use with a current-steering Digital-to-Analog Converter (DAC). The reference amplifier utilizes an open loop architecture, resulting in a bandwidth of 2.5 GHz, small chip area and low power. The wide bandwidth of the reference amplifier is shown to be important for fast settling of DAC current output. The reference amplifier is also able to generate a reference current that tracks fast changes of reference voltage, thus is useful in applications such as multiplying DACs and transversal filters. The proposed design was fabricated using a 1 µm GaAs HBT process. The prototype reference amplifier achieves a temperature coefficient of 92 ppm/ • C over a temperature range of 0-100 • C and the reference current changes only ±2.14% when the power supply varies ±0.2 V.