Genetic variation and acid tolerance in the Nemouridae (Insecta: Plecoptera)

An electrophoretic survey of sixteen enzyme loci in nine of the eleven British Nemouridae (Insecta: Plecoptera) was carried out in order to assess their systematic relationships and to determine the level of genetic variation in these primitive insects. [Continues.

cath-resolve-hits: A new tool that resolves domain matches suspiciously quickly

Motivation. Many bioinformatics areas require us to assign domain matches onto stretches of a query protein. Starting with a set of candidate matches, we want to identify the optimal subset that has limited/no overlap between matches. This may be further complicated by discontinuous domains in the input data. Existing tools are increasingly facing very large data-sets for which they require prohibitive amounts of CPU-time and memory. Results. We present cath-resolve-hits (CRH), a new tool that uses a dynamic-programming algorithm implemented in open-source C++ to handle large datasets quickly (up to ∼1 million hits/second) and in reasonable amounts of memory. It accepts multiple input formats and provides its output in plain text, JSON or graphical HTML. We describe a benchmark against an existing algorithm, which shows CRH delivers very similar or slightly improved results and very much improved CPU/memory performance on large datasets

Local Change Point Detection and Signal Cleaning using EEMD with applications to Acoustic Shockwaves

The Ensemble Empirical Mode Decomposition (EEMD) has become a preferred technique to decompose nonlinear and non-stationary signals due to its ability to create time-varying basis functions. However, current EEMD signal cleaning techniques are unable to deal with situations where a signal only occurs for a portion of the entire recording length. By combining change point detection and statistical hypothesis testing, we demonstrate how to clean a signal to emphasize unique local changes within each basis function. This not only allows us to observe which frequency bands are undergoing a change, but also leads to improved recovery of the underlying information. Using this technique, we demonstrate improved signal cleaning performance for acoustic shockwave signal detection. The technique is implemented in R via the LCDSC package

A compact microwave microfluidic sensor using a re-entrant cavity

A miniaturized 2.4 GHz re-entrant cavity has been designed, manufactured and tested as a sensor for microfluidic compositional analysis. It has been fully evaluated experimentally with water and common solvents, namely methanol, ethanol, and chloroform, with excellent agreement with the expected behaviour predicted by the Debye model. The sensor’s performance has also been assessed for analysis of segmented flow using water and oil. The samples’ interaction with the electric field in the gap region has been maximized by aligning the sample tube parallel to the electric field in this region, and the small width of the gap (typically 1 mm) result in a highly localised complex permittivity measurement. The re-entrant cavity has simple mechanical geometry, small size, high quality factor, and due to the high concentration of electric field in the gap region, a very small mode volume. These factors combine to result in a highly sensitive, compact sensor for both pure liquids and liquid mixtures in capillary or microfluidic environment

Dual mode microwave microfluidic sensor for temperature variant liquid characterization

A dual mode, microstrip, microfluidic sensor was designed, built, and tested, which has the ability to measure a liquid's permittivity at 2.5 GHz and, simultaneously, compensate for temperature variations. The active liquid volume is small, only around 4.5 μL. The sensor comprises two quarter ring microstrip resonators, which are excited in parallel. The first of these is a microfluidic sensor whose resonant frequency and quality factor depend on the dielectric properties of a liquid sample. The second is used as a reference to adjust for changes in the ambient temperature. To validate this method, two liquids (water and chloroform) have been tested over a temperature range from 23 °C to 35 °C, with excellent compensation results

Doherty amplifier structures for modern microwave communication systems

The Power Amplifier (PA) is a critical component in any mobile communications system with performance that is very sensitive to RF envelope dynamics. Achieving the required linearity demanded by evolving communications systems invariably involves increasing PA complexity at the cost of reducing PA efficiency the consequences of which are severe and include for example reduced operational time for portable communications devices and perhaps less obviously the significant running, capital and thermal management costs associated with mobile communication system base-stations. The Doherty PA is one of a number of elegant architectures that have been developed to address this problem, and although conceived and patented in the 1930's, has only recently become established as a means of enhancing efficiency in microwave PA applications. The Doherty is renowned for its elegant simplicity however, the realisation of functional Doherty PAs using modern microwave devices is problematical and hindered by many hidden complexities, which are in general brought about by the complex, 'load-pulling' action of two active devices that conspire to cause a variety of performance related problems. Although harmonic behaviour is important, understanding device interaction at a fundamental level has been found to be the critical factor in achieving good overall Doherty performance. With this in mind, this thesis concentrates initially on developing an extensive understanding of fundamental device interaction through the use of a novel Doherty measurement approach which involves replacing the classical Doherty's symmetrical input power division arrangement with independent, phase-coherent excitations. The resulting insight has meant that it has been possible to introduce more focused measurement techniques including harmonic analysis and waveform engineering in order to further explore individual device behaviour. The extensive use of harmonic load-pull measurement systems and the direct synthesis of the impedance environments that exist within the Doherty have allowed a number of device technologies to be considered within the application environment resulting in the realisation of GaAs and GaN Doherty prototypes. As a direct result of this analysis, a number of optimisation approaches have been identified that involve the dynamic adjustment of relative input magnitude, relative input phase and relative device bias, which has in turn exposed the various design trade-offs that exist between linearity and efficiency within the Doherty. Other work includes the development of modulated measurement systems and specialised excitations that allow the meaningful comparison between measured single-tone and modulated performance, as well as allowing more comprehensive investigations into Doherty linearity under varying IF impedance conditions

Simplified analysis of the effect of load variation in common Doherty power amplifier architectures

This paper describes the effect of load variation on Doherty power amplifier performance. A simplified analysis that considers three common Doherty amplifier architectures allows the evaluation of how load variation translates into variation of load at the devices' current generator plane. Under the assumption that system counter-measures are used to avoid drain voltage clipping, the average efficiency and power are evaluated and compared among the different architectures. While, at the centre design frequency, similar results can be observed, it can be seen that an intrinsically broadband design leads to better average power and efficiency over frequency vs. load variation

Non-linear explosion tremor at Sangay, Volcano, Ecuador

A detailed analysis of discrete degassing pulses, chugs, at Sangay volcano, was performed on seismic and infrasonic records to determine the physics of the conduit. Infrasonic chugging signals appear as repetitive pulses with small variations in amplitude and time lag. An automated time-domain analysis was developed to measure with high precision time intervals and amplitudes at different wave arrivals, reducing the possibility error associated with hand picking. Using this automated method, a strong positive correlation of acoustic amplitude with repose time between individual pulses on chugging signals of Sangay was found on numerous oscillating sequences. Frequency gliding of apparent harmonic frequencies generally trends from high to low frequency at Sangay, in contrast to trends at Karymsky Volcano, Russia. A new description of chugging events using wavelet transform methods, appropriate for non-stationary signals, shows subtle changes in the waveforms relate to physical processes in the volcano. A system of non-linear feedback, based on choked flow at the vent, is postulated as the most likely source of this volcanic tremor

Simplified analysis of the effect of load variation in common Doherty power amplifier architectures

This paper describes the effect of load variation on Doherty power amplifier performance. A simplified analysis that considers three common Doherty amplifier architectures allows the evaluation of how load variation translates into variation of load at the devices' current generator plane. Under the assumption that system counter-measures are used to avoid drain voltage clipping, the average efficiency and power are evaluated and compared among the different architectures. While, at the centre design frequency, similar results can be observed, it can be seen that an intrinsically broadband design leads to better average power and efficiency over frequency vs. load variation

Improving efficiency, linearity and linearisability of an asymmetric doherty power amplifier by modulating the peaking amplifier’s supply voltage

Envelope tracking and asymmetric Doherty power amplifiers are two techniques that can be used to achieve high average efficiencies when amplifying signals with high peak-toaverage power ratios, e.g. those employed in modern wireless communication standards. In this paper, a combination of the two techniques, the modulation of the drain voltage of the peaking amplifier in an asymmetric Doherty power amplifier, is described. It is demonstrated how this combination can increase the efficiency in the high-power range while reducing the AM/PM distortion of the DPA. Additionally, the degrees of freedom in terms of efficiency, linearity, and linearisability when designing the shaping function is discussed. Measurements of an asymmetric 2.4 GHz DPA using 10 W and 25 W GaN HEMTs prove the concept and demonstrate the achievable improvements in terms of efficiency, linearity, and linearisability