Showing papers by "Dublin City University published in 2000"

Omni-directional vision for robot navigation

Abstract: We describe a method for visual based robot navigation with a single omni-directional (catadioptic) camera. We show how omni-directional images can be used to generate the representations needed for two main navigation modalities: Topological Navigation and Visual Path Following. Topological Navigation relies on the robot's qualitative global position, estimated from a set of omni-directional images obtained during a training stage (compressed using PCA). To deal with illumination changes, an eigenspace approximation to the Hausdorff measure is exploited. We present a method to transform omni-directional images to Bird's Eye Views that correspond to scaled orthographic views of the ground plane. These images are used to locally control the orientation of the robot, through visual servoing. Visual Path Following is used to accurately control the robot along a prescribed trajectory, by using bird's eye views to track landmarks on the ground plane. Due to the simplified geometry of these images, the robot's pose can be estimated easily and used for accurate trajectory following. Omni-directional images facilitate landmark based navigation, since landmarks remain visible in all images, as opposed to a small field-of-view standard camera. Also, omni-directional images provide the means of having adequate representations to support both accurate or qualitative navigation. Results are described in the paper.

Fasciola hepatica infection downregulates Th1 responses in mice

Abstract: SUMMARY Immune responses induced with helminth parasites have been extensively studied, but there is limited information on those to Fasciola hepatica, especially on the subtype of T cell induced with this parasite. We investigated the local and systemic Tcell responses of different strains of mice following oral infection with doses of metacercariae fromF. hepatica. Spleen cells from BALB/c and 129Sv/Ev mice given a low-dose (5 metacercariae) infection exhibited a Th2 response, producing high levels of the cytokines IL-4 and IL-5, and low levels of IFN- g and IL-2. In contrast, C57BL/6 mice showed a mixed Th1/Th2 response. A more marked polarization to a Th2 response was observed in BALB/c, 129Sv/Ev exposed to a high-dose (15 metacercariae) infection and the C57BL/6 mice also exhibited a clear Th2 response. IL-4 defective (IL-4 π/π ) C57BL/6 mice infected with 5 metacercariae produced less IFN- g and more IL-5 compared to their wild-type C57BL/6 counterparts, suggesting that IL-4 is important in establishing the Th2 type response in murine fasciolosis. However, the secretion of IFN-g and IL-2 was completely suppressed in the high-dose infection and this was also observed in IL-4 π/π mice. Thus, liver flukes may secrete molecules that downregulate Th1 responses. T cell responses in the mesenteric (MLN) and hepatic lymph nodes (HLN) were also examined since newly excysted juveniles infect through the intestinal wall of their host before migrating to the hepatic tissue. Cells from both MLN and HLN secreted higher levels of IL-4 and IL-5 compared to spleen cells. We also observed a difference in cytokine profiles secreted by the MLN and HLN, which may reflect responses to antigens liberated by newly excysted juveniles and hepatic stage parasites, respectively.

Multivariate GARCH Modeling of Exchange Rate Volatility Transmission in the European Monetary System

Abstract: We construct a series of 3-, 4- and 5-variable multivariate GARCH models of exchange rate volatility transmission across the important European Monetary System (EMS) currencies including the French franc, the German mark, the Italian lira, and the European Currency Unit. The models are estimated without imposing the common restriction of constant correlation on both daily and weekly data from April 1979–March 1997. Our results indicate the importance of checking for specification robustness in multivariate Generalized Autoregressive Conditional Heleroskedasticity (GARCH) modeling, we find that increased temporal aggregation reduces observed volatility transmission, and that the mark plays a dominant position in terms of volatility transmission.

Development of surface plasmon resonance-based immunoassay for aflatoxin B1

Abstract: Aflatoxins are a group of highly toxic fungal secondary metabolites that occur in Aspergillus species and may contaminate foodstuffs and feeds. Two different anti-aflatoxin B1 antibodies were examined to develop a surface plasmon resonance (SPR)-based immunoassay to aflatoxin B1. A conjugate consisting of aflatoxin B1−bovine serum albumin (BSA) was immobilized on the dextran gel surface. Competition between immobilized aflatoxin B1 conjugate and free aflatoxin B1 in solution for binding to antibody injected over the surface formed the basis for the assay. Regeneration of the antibody from the immobilized conjugate surface is essential for the development of such an inhibitive immunoassay. Problems were encountered with the regeneration of the sensor surface, due to the high-affinity binding of the antibodies. Conventional regeneration solutions consisting of low concentrations of NaOH and HCl worked to a degree, but regeneration was at the expense of the integrity of the immobilized conjugate. A polyclona...

A micropower dry-electrode ECG preamplifier

Abstract: This paper describes the development of a very low-power preamplifier intended for use in pasteless-electrode recording of the human electrocardiogram. The expected input signal range is 100 /spl mu/V-10 mV from a lead-II electrode configuration. The amplifier provides a gain of 43 dB in a 3-dB bandwidth of 0.05 Hz-2 kHz with a defined high input impedance of 75 M/spl Omega/. It uses a driven common electrode to enhance rejection of common-mode interfering signals, including low-frequency motion artifact, achieving a common-mode rejection ratio (CMRR) of better than 80 dB over its entire bandwidth. The gain and phase characteristics meet the recommendations of the American Heart Association, ensuring low distortion of the output ECG signal and making it suitable for clinical monitoring. The amplifier has a power consumption of 30 /spl mu/W operating from a 3.3-V battery and is intended for use in small, lightweight, portable electrocardiographic equipment and heart-rate monitoring instrumentation.

John von Neumann and the evolutionary growth of complexity: looking backward, looking forward …

Abstract: In the late 1940s John von Neumann began to work on what he intended as a comprehensive "theory of [complex] automata." He started to develop a book length manuscript on the subject in 1952. However, he put it aside in 1953, apparently due to pressure of other work. Due to his tragically early death in 1957, he was never to return to it. The draft manuscript was eventually edited, and combined for publication with some related lecture transcripts, by Burks in 1966. It is clear from the time and effort that von Neumann invested in it that he considered this to be a very significant and substantial piece of work. However, subsequent commentators (beginning even with Burks) have found it surprisingly difficult to articulate this substance. Indeed, it has since been suggested that von Neumann's results in this area either are trivial, or, at the very least, could have been achieved by much simpler means. It is an enigma. In this paper I review the history of this debate (briefly) and then present my own attempt at resolving the issue by focusing on an analysis of von Neumann's problem situation. I claim that this reveals the true depth of von Neumann's achievement and influence on the subsequent development of this field, and further that it generates a whole family of new consequent problems, which can still serve to inform - if not actually define - the field of artificial life for many years to come.

The bfl-1 Gene Is Transcriptionally Upregulated by the Epstein-Barr Virus LMP1, and Its Expression Promotes the Survival of a Burkitt's Lymphoma Cell Line

Abstract: The recently identified bfl-1 gene (also known as A1 or GRS), a homologue of bcl-2, encodes an antiapoptotic protein that suppresses apoptosis induced by the p53 tumor suppressor protein and exhibits proliferative and potent cooperative transforming activities We show that elevated levels of bfl-1 mRNA are a feature of Epstein-Barr virus (EBV)-immortalized B-cell lines and Burkitt's lymphoma cell lines expressing the full spectrum of EBV latent proteins Using an EBV-negative Burkitt's lymphoma cell line in which the expression of EBV latent membrane protein 1 (LMP1) is inducibly regulated by tetracycline, we demonstrate that LMP1 expression coincides with a dramatic increase in the level of bfl-1 mRNA Also in this system, an increase in the level of Bcl-2 protein was seen to occur earlier than that of bcl-2 mRNA, suggesting that both transcriptional and translational mechanisms are involved in the control of Bcl-2 expression by LMP-1 We show that elevated bfl-1 mRNA stability can contribute to this effect of LMP-1, thus providing evidence of a novel mechanism of gene regulation by this EBV protein Upregulation of bfl-1 by LMP1 was not observed in the T-cell line Jurkat or the epithelial cell line C33A Ectopic expression of Bfl-1 in an EBV-positive cell line exhibiting a latency type I infection protects against apoptosis induced by growth factor deprivation, thereby providing a functional role for Bfl-1 in this cellular context and adding Bfl-1 to the list of antiapoptotic proteins whose expression is modulated by EBV This is the first report of the regulation of bfl-1 expression by a viral protein, and this novel finding may thus represent an important link between the EBV oncoprotein LMP1 and its cellular growth-transforming properties

Sol-gel immobilised ruthenium(II) polypyridyl complexes as chemical transducers for optical pH sensing

Abstract: A range of fluorescent ruthenium(II) polypyridyl complexes have been employed in an optical sensor device for pH analysis. The dye materials were immobilised in a sol–gel glass matrix and characterised upon exposure to aqueous buffer solutions. Changes of below 0.1 pH units were detectable using these dye-doped glass films, and linear ranges as large as pH 3–9 were observed. Sol–gel immobilisation effectively enhanced the operating range of these materials compared to solution. Interference from fluorescence quenching due to molecular oxygen was found to place important restrictions on the nature of dyes suitable for this application.

Does the Firm’s Technology and Marketing Profile Affect Foreign Market Entry?

Abstract: The authors examine the influence of the firm's technology and marketing profile on foreign market entry mode by testing hypotheses based on data from 105 firms in four European countries. Four tec...

When does explicit justification impair decision making

Abstract: The idea that careful analysis leads to better decisions is pervasive in research on decision making. Intriguingly, results raise the possibility that thinking about reasons for decisions before deciding may degrade decision quality. This paper reports the results of a laboratory study which examined whether task characteristics critically influence the effects of thinking about reasons on decision quality. We found that explicit reasoning degraded judgement quality, objectively measured, on an ‘intuitive’ task. However, we also found that explicit reasoning enhanced performance on an ‘analytic’ task. Copyright © 2000 John Wiley & Sons, Ltd.

Digital imaging as a detector for generic analytical measurements

Abstract: Digital imaging was investigated as a potential means of processing high density dot arrays for analytical purposes. Using a high resolution digital camera, a colour image of the dot array was taken and subsequently processed using in-house developed National Instruments LabVIEW® software to return numerical values for the red, green and blue components of the colour of each dot.

Theory of the radiation of dipoles placed within a multilayer system.

Abstract: A rigorous theory of radiation from dipoles embedded inside an arbitrary multilayer system is presented. In particular, we derive explicit expressions for the angular distribution of the electromagnetic field and the intensity radiated by the dipole into the surrounding media. Under the assumptions of mutual incoherence of the dipole radiation the calculations are extended to a layer of radiating dipoles. Special configurations corresponding to (i) a single dipole near a dielectric interface, (ii) a dipole layer surrounded by semi-infinite dielectric media, and (iii) a dipole layer placed on top of a waveguide layer are discussed in detail. This theoretical analysis has important consequences for the optimization of optical chemical sensors and biosensors that are based on fluorescence emission.

Electrochemiluminescent metallopolymer coatings: combined light and current detection in flow injection analysis.

Abstract: The application of thin films of the metallopolymer [Ru(bpy)2PVP10]2+ for the electrochemiluminescent (ECL) detection of oxalate in a flow injection analysis system is reported, where bpy is 2,2‘-bipyridyl and PVP is poly(4-vinylpyridine). Immobilization of the ECL reagent means that it can be regenerated in situ, eliminating the need to constantly deliver it to the reaction zone. Electrochemically generated Ru3+ reacts with the analyte to form the excited-state [Ru2+]*, which luminesces at 610 nm. The reaction is optimal at low pH, where the layer is swollen and homogeneous charge transport through the layer is more facile. Unlike traditional approaches, we simultaneously monitor both the amperometric and luminescent response of the modified electrode. The precision of both signals is similar at ∼2% (n = 10). However, the ECL response has a larger dynamic range extending from the low-micromolar to higmillimolar range and a lower limit of detection, ∼0.2 μM or 4 pmol of oxalate injected. The ECL approach ...

A comparison of classical scheduling approaches in power-constrained block-test scheduling

Abstract: Classical scheduling approaches are applied here to overcome the problem of unequal-length block-test scheduling under power dissipation constraints. List scheduling-like approaches are proposed first as greedy algorithms to tackle the fore mentioned problem. Then, distribution-graph based approaches are described in order to achieve balanced test concurrency and test power dissipation. An extended tree growing technique is also used in combination with these classical approaches in order to improve the test concurrency having assigned power dissipation limits. A comparison between the results of the test scheduling experiments highlights the advantages and disadvantages of applying different classical scheduling algorithms to the power-constrained test scheduling problem.

Bis(R-bipyridyl)ruthenium bibenzimidazole complexes (R = H, Me or But): supramolecular arrangement via hydrogen bonds, photo- and electro-chemical properties and reactivity towards carbon dioxide

Abstract: Complexes of the type [Ru(H2bibzim)(R-bpy)2X2·nH2O (R = H, 2,2′-bipyridine, bpy, X = CF3SO3−1; R = Me, 4,4′-dimethyl-2,2′-bipyridine, dmbpy, X = PF6−2; R = tert-butyl, 4,4′-di-tert-butyl-2,2′-bipyridine, tbbpy, X = Cl−3; H2bibzim = 1,1′-bibenzimidazole) containing two NH functions acting as hydrogen bond donors formed different spatially highly organised supramolecular assemblies with water. X-Ray investigation revealed that the nature of the counter ion influences the hydrogen bonding pattern and extent of spatial organisation. In 2 one dimensional chains of hydrogen bonded water could be found. In the deprotonated complex [Ru(bibzim)(tbbpy)2] 4 water molecules serve as hydrogen bond donors. The diastereomeric forms 5a/5b of the homodinuclear ruthenium complex [{Ru(tbbpy)2}2(bibzim)][PF6]2 could be separated. No differences in their photophysical properties could be detected. The X-ray investigation of 5a and [{Ru(bpy)2}2(bibzim)][PF6]26 showed little influence of peripheral substitution on structural properties. Complexes 3–5 exhibit activity in electrochemical CO2 reduction which can be tuned by variation of the degree of protonation of the bibenzimidazole.

Use of phosphonic acid as a generic hapten in the production of broad specificity anti-organophosphate pesticide antibody.

Abstract: Phosphonic acid (trans-4-phosphono-2-butenic acid; TPB) was used as a generic hapten in order to generate broad specificity antibodies against a group of organophosphorus pesticides. The polyclonal antiserum showed, in an indirect enzyme-linked immunosorbent assay (ELISA) format, preferential binding toward pesticides containing unsaturated diethyl-phosphate functionalities rather than the equivalent thiophosphate or dimethyl structures. The level of detection in the ELISA using a heterologous system was investigated and showed a 20-fold improvement when a conjugate for which the antibody had lower affinity was immobilized on the plate. Biosensor assays using parathion as a standard indicated that the antibody had a relatively high dissociation rate, and reproducible cycles of regeneration were achieved. The potential for using TPB as a generic hapten is discussed.