A tomographic technique for the simultaneous imaging of temperature, chemical species, and pressure in reactive flows using absorption spectroscopy with frequency-agile lasers

This paper proposes a technique that can simultaneously retrieve distributions of temperature, concentration of chemical species, and pressure based on broad bandwidth, frequency-agile tomographic absorption spectroscopy. The technique holds particular promise for the study of dynamic combusting flows. A proof-of-concept numerical demonstration is presented, using representative phantoms to model conditions typically prevailing in near-atmospheric or high pressure flames. The simulations reveal both the feasibility of the proposed technique and its robustness. Our calculations indicate precisions of ∼70 K at flame temperatures and ∼0.05 bars at high pressure from reconstructions featuring as much as 5% Gaussian noise in the projections.This work was supported by the Seventh Framework Program (Grant Agreement No. PIIF-GA-2012-330840) of the European Union and was performed using the Darwin Supercomputer of the University of Cambridge High Performance Computing Service.Copyright 2014 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The article appeared in Applied Physics Letters 104, 034101 (2014) and may be found at (http://scitation.aip.org/content/aip/journal/apl/104/3/10.1063/1.4862754)

Some preliminary findings on Hong Kong business cycles

This paper presents some preliminary quantitative findings on the characteristics of business cycles in Hong Kong. The recently developed "approximate bandpass filter" is used to extract the fluctuations at business cycle frequencies (8 to 32 quarters) of macroeconomic time series. Based on the filtered time series, the paper identifies the cyclical turning points, describes the pattern of output fluctuations, and examines the co-movement of various macroeconomic variables.postprin

A numerical investigation of high-resolution multispectral absorption tomography for flow thermometry

Multispectral absorption tomography (MAT) is now a well-established technique that can be applied for the simultaneous imaging of temperature, species concentration, and pressure of reactive flows. However, only intermediate spatial resolution, on order of 15×15 grid points, has so far been achievable in previous demonstrations. The aim of the present work is to provide a numerical validation of our MAT algorithm for thermometry of combusting flows, but with greatly improved spatial resolution to motivate its experimental realization in practical environments. We demonstrate a grid resolution that is comparable to that of classical absorption tomography (CAT) containing 80×80 elements from only two orthogonal projections, which is impractical to realize with CAT but especially desirable for applications where optical access is limited. This is achieved using the smoothness assumption, which holds true under most combustion conditions. The study shows that better spatial resolution can be obtained through a simple increase in the spatial sampling frequency for the two available projections, as the smoothness condition becomes more reliable on smaller spatial scales. Our work also demonstrates the first application of MAT for full volumetric reconstructions. The studies thus provide robust guidelines for the implementation of MAT over large spatial scales and lay solid foundations for its development and application in complex technical combustion scenarios, where spatial resolution is crucial to investigate the interaction of flow phenomena with chemical reactions.This work was funded by the European Commission under Grant No. ASHTCSC 330840 and was partly performed using the Darwin Supercomputer of the University of Cambridge High Performance Computing Service. Clemens F. Kaminski also wishes to acknowledge EPSRC for funding (grant EP/L015889/1).This is the final published version of a paper published in Applied Physics B, February 2015, DOI 10.1007/s00340-015-6012-

A Rapid Dynamical Monte Carlo Algorithm for Glassy Systems

In this paper we present a dynamical Monte Carlo algorithm which is applicable to systems satisfying a clustering condition: during the dynamical evolution the system is mostly trapped in deep local minima (as happens in glasses, pinning problems etc.). We compare the algorithm to the usual Monte Carlo algorithm, using as an example the Bernasconi model. In this model, a straightforward implementation of the algorithm gives an improvement of several orders of magnitude in computational speed with respect to a recent, already very efficient, implementation of the algorithm of Bortz, Kalos and Lebowitz.Comment: RevTex 7 pages + 4 figures (uuencoded) appended; LPS preprin

Drilling process monitoring for a wealth of extra factual data from drillhole site investigation

This paper presents a method for obtaining valuable additional information from automatic drilling process monitoring in conventional drillhole site investigation. A digital drilling process monitor (DPM) is developed and used to automatically and continuously monitor and record the operational process while a hole is being drilled in ground using a hydraulic rotary machine. The DPM data are examined in detail for an enhanced recording and understanding of the ground profile while drilling. The extra information from the DPM is validated with information from conventional manual drillhole logging. The DPM results can improve geotechnical knowledge and engineering practice in Hong Kong and other mountainous regions.published_or_final_versio

Oral immunization with a dam mutant of Yersinia pseudotuberculosis protects against plague.

Inactivation of the gene encoding DNA adenine methylase (dam) has been shown to attenuate some pathogens such as Salmonella enterica serovar Typhimurium and is a lethal mutation in others such as Yersinia pseudotuberculosis strain YPIII. In this study the dam methylase gene in Yersinia pseudotuberculosis strain IP32953 was inactivated. Unlike the wild-type, DNA isolated from the mutant could be digested with MboI, which is consistent with an altered pattern of DNA methylation. The mutant was sensitive to bile salts but not to 2-aminopurine. The effect of dam inactivation on gene expression was examined using a DNA microarray. In BALB/c mice inoculated orally or intravenously with the dam mutant, the median lethal dose (MLD) was at least 10(6)-fold higher than the MLD of the wild-type. BALB/c mice inoculated with the mutant were protected against a subcutaneous challenge with 100 MLDs of Yersinia pestis strain GB and an intravenous challenge with 300 MLDs of Y. pseudotuberculosis IP32953

Substrate Specificity and Biochemical Characteristics of an Engineered Mammalian Chondroitinase ABC.

Chondroitin sulfate proteoglycans inhibit regeneration, neuroprotection, and plasticity following spinal cord injury. The development of a second-generation chondroitinase ABC enzyme, capable of being secreted from mammalian cells (mChABC), has facilitated the functional recovery of animals following severe spinal trauma. The genetically modified enzyme has been shown to efficiently break down the inhibitory extracellular matrix surrounding cells at the site of injury, while facilitating cellular integration and axonal growth. However, the activity profile of the enzyme in relation to the original bacterial chondroitinase (bChABC) has not been determined. Here, we characterize the activity profile of mChABC and compare it to bChABC, both enzymes having been maintained under physiologically relevant conditions for the duration of the experiment. We show that this genetically modified enzyme can be secreted reliably and robustly in high yields from a mammalian cell line. The modifications made to the cDNA of the enzyme have not altered the functional activity of mChABC compared to bChABC, ensuring that it has optimal activity on chondroitin sulfate-A, with an optimal pH at 8.0 and temperature at 37 °C. However, mChABC shows superior thermostability compared to bChABC, ensuring that the recombinant enzyme operates with enhanced activity over a variety of physiologically relevant substrates and temperatures compared to the widely used bacterial alternative without substantially altering its kinetic output. The determination that mChABC can function with greater robustness under physiological conditions than bChABC is an important step in the further development of this auspicious treatment strategy toward a clinical application