Review: Biosensors for the detection of Escherichia coli

The supply of safe potable water, free from pathogens and chemicals, requires routine  analyses and the application of several diagnostic techniques. Apart from being  expensive, many of the detection methods require trained personnel and are often time-consuming. With drastic climate changes, severe droughts, increases in  population and pollution of natural water systems, the need to develop ultrasensitive, low-cost and hand-held, point-of-use detection kits to monitor water quality is critical. Although Escherichia coli is still considered the best indicator of water quality, cell numbers may be below detection limits, or the cells may be non-culturable and thus only detected by DNA amplification. A number of different biosensors have been developed to detect viable, dead or non-culturable microbial cells and chemicals in water. This review discusses the differences in these biosensors and evaluates the application of microfluidics in the design of ultra-sensitive nano-biosensors.Keywords: Biosensors, microfluidics, nano-biosensors, E. coli detectio

Observation of shapiro-steps in AFM-plough micron-size YBCO planar constrictions

Using an Atomic Force Microscope (AFM), we successfully ploughed micron size planar constriction type junctions on YBa3Cu30 7-x thin films. The 100 nanometer (nm) thin films are deposited on MgO substrates by an Inverted Cylindrical Magnetron (ICM) sputtering technique. The films are then patterned into 8-10 micron size strips, using photolithography and dry etching. A diamond coated tip was used with the AFM in this process. We were able to observe well defined current-voltage (I-V) characteristics and Shapiro-steps, successfully demonstrating a possible Josephson effect in these constrictions. © 2009 IEEE.Using an Atomic Force Microscope (AFM), we successfully ploughed micron size planar constriction type junctions on YBa3Cu30 7-x thin films. The 100 nanometer (nm) thin films are deposited on MgO substrates by an Inverted Cylindrical Magnetron (ICM) sputtering technique. The films are then patterned into 8-10 micron size strips, using photolithography and dry etching. A diamond coated tip was used with the AFM in this process. We were able to observe well defined current-voltage (I-V) characteristics and Shapiro-steps, successfully demonstrating a possible Josephson effect in these constrictions. © 2009 IEEE.Conference PaperConference Pape

Effect of mutual coupling between RF SQUID's in distributed Josephson inductance phase shifters

A brief overview of the principles behind the behavior of the recently reported distributed Josephson inductance phase shifter is given. Simulation results of a typical phase shifter are presented. A model for the mutual flux coupling between adjacent RF SQUID sections is derived and the results are used to predict the effect of the coupling on the phase shift of the device. Distortion of the output signal is related to the time variation of the dynamic inductance of the transmission line.Articl

CALCULATION OF MAXIMUM BULK ELECTRIC FIELD IN HIGH-VOLTAGE DIODES WITH SMALL AND INTERMEDIATE NEGATIVE BEVEL ANGLES.

The letter describes the extension of an existing method for calculating the maximum bulk electric field for semiconductor diodes with large negative bevel angles to include diodes with smaller negative bevel angles, and to take into account a shift of the position where the electric field reaches a maximum.Articl

NOVEL METHOD FOR CALCULATING MAXIMUM BULK ELECTRIC FIELD IN HIGH-VOLTAGE DIODES WITH LARGE NEGATIVE BEVEL ANGLES.

The letter describes a simple method for calculating the maximum bulk electric field in high-voltage semiconductor diodes with large bevel angles. It is based on the notion of a characteristic length, which is defined. The resulting model is a useful design aid.Articl

Complementary output switching logic: A superconducting voltage-state logic family operating at microwave frequencies

The development of a new superconducting logic family, Complementary Output Switching Logic (COSL), is described. It is described how the two main problems inhibiting superconducting operation at microwave frequencies, namely magnetic flux trapping and large variations of the nominal component values due to the fabrication process, are solved. A brief overview of the operation of the basic logic gate and the layout process is given. Measured results of the basic gates are given for frequencies up to 18 GHz. The measured results of more complex circuits, such as a code converter and a pseudo-random bit sequence generator, are also presented.Articl

On using genetic algorithms to optimize high frequency superconducting digital circuits for optimal yield

Even simple superconducting logic gates can contain tens of inductors, resistors and Josephson junctions. In order to increase the yield and reliability of such circuits to acceptable levels, it is often needed to adjust all the element values. The search space is therefore very large, and genetic algorithms have been used with remarkable success to optimize such gates.Conference Pape

Yield optimization of high frequency superconducting digital circuits with genetic algorithms

Even simple superconducting logic gates can contain tens of inductors, resistors and Josephson junctions. In order to increase the yield and reliability of such suboptimal circuits to acceptable levels, it is often needed to adjust all the element values. The search space is therefore very large, and genetic algorithms have been used with remarkable success to optimize such gates. Copyright © 2002 IEEE.Conference Pape

An RSFQ DC-resettable latch for building memory and reprogrammable circuits

A new RSFQ latch, the DC-Resettable Latch (DCRL), is introduced. The DCRL functions like a standard nondestructive readout register (NDRO), except that it requires a dc current or current pulse to reset. This allows the DCRL to be used as a memory element in large memory blocks, where the entire block can be erased with a current pulse from a single threaded current line instead of unwieldy pulse distribution circuitry. The reset current can be applied by off-chip control logic, or on-chip bipolar current elements such as HUFFLEs. However, the DCRL is most useful as the base building block of complex reprogrammable RSFQ circuitry. © 2005 IEEE.Conference Pape

Modified quasi-one-junction squid and read-out system as a comparator for high speed analog-to-digital conversion

We have designed and simulated a comparator, based on the Quasi-One-Junction Superconducting Quantum Interference Device (SQUID) and a non-symmetrical Two-Junction SQUID read-out system. This comparator can be utilized to construct an n-bit Analog-to-Digital Convertor with only n comparators. The theoretical input bandwidth is in the GHz range.Conference Pape