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Resistive-pulse sensing (RPS), which is based on measuring the current pulse produced when a single particle transits a pore or channel, is an extremely versatile technique used to determine the size and concentration of cells and viruses and to detect single molecules. A major challenge to RPS is dynamic range: smaller particles in a heterogeneous sample can go undetected because of low signal-to-noise ratios (SNRs) and the fact that the pore size must be commensurate with that of the largest particles. Here, we describe a fundamentally different pore that provides an unprecedented dynamic detection range, from tens of nanometers to several microns in size, without the need for pre-sorting or filtration. Because of its unique geometry--nodes inserted along the channel--our pore produces distinct electronic signatures that overcome low SNRs. We demonstrate the power of our device by directly detecting and enumerating human immunodeficiency virus (HIV) in human plasma.

This paper deals with the analysis and.experimental implementation of a discrete time repetitive control scheme for robot manipulators. The repetitive control structure is designed to be easily implemented onto any system without modification to the existing controller. Simulation and experimental results show that the repetitive controller in conjunction with a computed torque control law, or a simple Proportional-Derivative (PD) control law, assured good tracking performance when the desired trajectory is periodic and the period is known.

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