A Comparison of Small Signal Modulation Parameter Extraction Techniques for Vertical-Cavity, Surface-Emitting Lasers

The small signal modulation characteristics of a vertical-cavity, surface-emitting laser (VCSEL) are determined using three different measurements: relative intensity noise, frequency response, and high resolution optical spectra. The resonant and damping frequencies were measured, and related rate equation parameters were extracted; excellent agreement was found both between experiment and theory, and amongst the different measurement techniques. The results and procedures are compared, and the findings are presented below

Technologies for restricting mould growth on baled silage

End of project reportSilage is made on approximately 86% of Irish farms, and 85% of these make some baled silage. Baled silage is particularly important as the primary silage making, storage and feeding system on many beef and smaller sized farms, but is also employed as a secondary system (often associated with facilitating grazing management during mid-summer) on many dairy and larger sized farms (O’Kiely et al., 2002). Previous surveys on farms indicated that the extent of visible fungal growth on baled silage was sometimes quite large, and could be a cause for concern. Whereas some improvements could come from applying existing knowledge and technologies, the circumstances surrounding the making and storage of baled silage suggested that environmental conditions within the bale differed from those in conventional silos, and that further knowledge was required in order to arrive at a secure set of recommendations for baled silage systems. This report deals with the final in a series (O’Kiely et al., 1999; O’Kiely et al., 2002) of three consecutive research projects investigating numerous aspect of the science and technology of baled silage. The success of each depended on extensive, integrated collaboration between the Teagasc research centres at Grange and Oak Park, and with University College Dublin. As the series progressed the multidisciplinary team needed to underpin the programme expanded, and this greatly improved the amount and detail of the research undertaken. The major objective of the project recorded in this report was to develop technologies to improve the “hygienic value” of baled silage

Dual-Mode Combustion Experiments with an Integrated Aeroramp-Injector/Plasma-Torch Igniter

Results from combustion experiments in a direct-connect supersonic combustor facility are presented. Successful ignition and sustained combustion of both hydrogen and ethylene fuels were achieved using an integrated aeroramp-injector/plasma-torch igniter configuration. A Mach 2 nozzle was used to obtain How simulating Mach approximate to 4 flight conditions at 27 km, at a total temperature of 1000 K and a static pressure of 42 kPa. Combustion was achieved at (global) equivalence ratios between 0.08 and 0.31 for hydrogen and 0.13 and 0.47 for ethylene, with corresponding maximum combustor pressure rises of about a factor of 4.0. One-dimensional performance analysis of the test data indicates combustion efficiencies as high as 75% for both fuels, in the leanest conditions tested. Off-design flight conditions were tested by varying the freestream air total temperature. Supersonic combustion was achieved at total temperatures as low as 530 K with hydrogen and 680 K with ethylene

Dual-Mode Combustion Experiments with an Integrated Aeroramp-Injector/Plasma-Torch Igniter

Results from combustion experiments in a direct-connect supersonic combustor facility are presented. Successful ignition and sustained combustion of both hydrogen and ethylene fuels were achieved using an integrated aeroramp-injector/plasma-torch igniter configuration. A Mach 2 nozzle was used to obtain How simulating Mach approximate to 4 flight conditions at 27 km, at a total temperature of 1000 K and a static pressure of 42 kPa. Combustion was achieved at (global) equivalence ratios between 0.08 and 0.31 for hydrogen and 0.13 and 0.47 for ethylene, with corresponding maximum combustor pressure rises of about a factor of 4.0. One-dimensional performance analysis of the test data indicates combustion efficiencies as high as 75% for both fuels, in the leanest conditions tested. Off-design flight conditions were tested by varying the freestream air total temperature. Supersonic combustion was achieved at total temperatures as low as 530 K with hydrogen and 680 K with ethylene

RydIQule: A Graph-based Paradigm for Modelling Rydberg and Atomic Systems

We describe a numerical technique and accompanying open-source Python software package called RydIQule. RydIQule uses a directional graph, relying on adjacency matrices and path-finding to generate a Hamiltonian for multi-level atomic systems. RydIQule then constructs semi-classical equations of motion (Bloch equations) into a tensor which can store an entire simulation consisting of varied system parameters. Using this framework, RydIQule returns solutions significantly faster than typical for interpreted programming languages. RydIQule extends beyond the capabilities of currently-available tools, facilitating rapid development in atomic and Rydberg spectroscopy. To demonstrate its utility, we use RydIQule to simulate a Doppler-broadened Rydberg atomic sensor that simultaneously demodulates five rf tones spanning from 1.7 to 116 GHz. Using RydIQule, this simulation can be solved in several hours on a commercial off-the-shelf desktop computer.Comment: 5 pages, 3 figure

Modelling the spatial demography of Atlantic cod (Gadus morhua) on the European continental shelf

Atlantic cod (Gadus morhua) stocks across the North Atlantic have been subject to intense fishing pressure during the 20th century, and some stocks have suffered well-documented collapses. On the European shelf, cod arewidely but heterogeneously distributed and are caught as part of a multispecies trawl fishery. There is a growing body of evidence that this stock is composed of substocks with potentially distinct demographic properties. As a first step towards the development of management methodologies that reflect this spatial and biological complexity, we present a spatially and physiologically explicit model describing the demography and distribution of cod on the European shelf. The computational efficiency of our implementation enables numerical parameter optimization, thus facilitating formal statistical tests of structural hypotheses. We use these methods to fit model variants embodying a variety of hypotheses about the movements of settled fish to a data set including spatial distribution information derived from International Bottom Trawl Surveys. The best-fit model emerging from this study is then used to investigate the potential effects oflong-term application of a series of regional fishing closure policies

Compositional Proteomics: Effects of Spatial Constraints on Protein Quantification Utilizing Isobaric Tags.

Mass spectrometry (MS) has become an accessible tool for whole proteome quantitation with the ability to characterize protein expression across thousands of proteins within a single experiment. A subset of MS quantification methods (e.g., SILAC and label-free) monitor the relative intensity of intact peptides, where thousands of measurements can be made from a single mass spectrum. An alternative approach, isobaric labeling, enables precise quantification of multiple samples simultaneously through unique and sample specific mass reporter ions. Consequently, in a single scan, the quantitative signal comes from a limited number of spectral features (≤11). The signal observed for these features is constrained by automatic gain control, forcing codependence of concurrent signals. The study of constrained outcomes primarily belongs to the field of compositional data analysis. We show experimentally that isobaric tag proteomics data are inherently compositional and highlight the implications for data analysis and interpretation. We present a new statistical model and accompanying software that improves estimation accuracy and the ability to detect changes in protein abundance. Finally, we demonstrate a unique compositional effect on proteins with infinite changes. We conclude that many infinite changes will appear small and that the magnitude of these estimates is highly dependent on experimental design