Showing papers by "Dublin City University published in 1998"

Metal-Anion Sorption by Chitosan Beads: Equilibrium and Kinetic Studies

Abstract: Chitosan is a well-known biopolymer, whose high nitrogen content confers remarkable ability for the sorption of metal ions from dilute effluents. However, its sorption performance in both equilibrium and kinetic terms is controlled by diffusion processes. Gel bead formation allows an expansion of the polymer network, which improves access to the internal sorption sites and enhances diffusion mechanisms. Molybdate and vanadate recovery using glutaraldehyde cross-linked chitosan beads reaches uptake capacities as high as 7−8 mmol g-1, depending on the pH. The optimum pH (3−3.5) corresponded to the predominance range of hydrolyzed polynuclear metal forms and optimum electrostatic attraction. While for beads, particle size does not influence equilibrium, for flakes, increasing sorbent radius significantly decreases uptake capacities to 1.5 mmol g-1. Sorption kinetics are mainly controlled by intraparticle diffusion for beads, while for flakes the controlling mechanisms are both external and intraparticle diff...

Terms in context

Abstract: Terms in Context applies the methodology that has been developed over the last two decades in corpus linguistics to the relatively new and still little developed field of corpus-based terminography. While corpora are already being used by some terminologists for the identification of terms and retrieval of contextual fragments, this book describes the first attempt to use corpora for terminography in much the same way as large general reference corpora are already being used for general language lexicography. The author goes beyond the standard problem of identifying terms as opposed to non-terminological lexical items in text and focuses on identifying metalanguage patterns which point to the presence in text of (parts of) reusable definitions of terms. The author examines these patterns and shows how the information which they contain can be retrieved and used as input for terminological entries. Terms in Context should be of interest to ‘traditional’ terminologists who have not previously considered adopting a corpus-based approach to their work or at least not on the scale proposed here; to ‘modern’ terminologists who use text primarily for the identification of terms and the retrieval of contextual examples; to those in the corpus linguistic community who have hitherto used general language corpora for the purposes of lexicography and have not previously considered using special purpose corpora for more specific lexicography studies; and to academics in the ESP/LSP community who are interested in showing students how to use text as a means of ascertaining the meaning of terms.

Tailoring of sol-gel films for optical sensing of oxygen in gas and aqueous phase.

Abstract: Sol-gel-based optical sensors for both gas-phase and dissolved oxygen have been developed. Both sensors operate on the principle of fluorescence quenching of a ruthenium complex which has been entrapped in a porous sol-gel silica film. A comprehensive investigation was carried out in order to establish optimal film-processing parameters for the two sensing environments. Both tetraethoxysilane and organically modified sol-gel precursors such as methyltriethoxysilane and ethyltriethoxysilane were used. Film hydrophobicity increases as a function of modified precursor content, and this was correlated with enhanced dissolved oxygen (DO) sensor performance. Extending the aliphatic group of the modified precursor further improved DO sensitivity. The influence of water/precursor molar ratio, R, on the sol-gel film microstructure was investigated. R value tailoring of the microstructure and film surface hydrophobicity tailoring were correlated with oxygen diffusion behavior in the films via the Stern-Volmer constants for both gas phase and DO sensing. Excellent performance characteristics were measured for both gas-phase and DO oxygen sensors. The long-term quenching stability of DO sensing films was established over a period of 6 months.

Immunodiagnosis of Fasciola hepatica infection (fascioliasis) in a human population in the Bolivian Altiplano using purified cathepsin L cysteine proteinase.

Abstract: Cathepsin L1 (CL1), an immunogenic cysteine proteinase secreted by juvenile and adult Fasciola hepatica, was assessed for its potential as a diagnostic agent for the serologic detection of human fascioliasis. Using ELISAs, we compared the ability of liver fluke homogenates (LFH), excretory/secretory (ES) products, and CL1 to discriminate between seropositive (infected) and seronegative (noninfected) individuals within a population of 95 patients from the Bolivian Altiplano. A high prevalence of human fascioliasis has been reported in this region. The division between the seropositive and seronegative individuals was poorly defined when LFH was used as the antigen. A greater discrimination between these populations was achieved with both ES and CL1. A K-means cluster analysis using the combined ES and CL1 ELISA data identified a cluster of seropositive individuals. Cathepsin L1 detected a subset (20) of these seropositive individuals while ES detected all 26; however, ES detected nine additional individuals that were in the seronegative cluster. The ratio of the mean absorbance readings between seropositive and seronegative individuals was markedly improved by using conjugated second antibodies to IgG4, the predominant isotype elicited by infection. In these IgG4-ELISAs, CL1 again identified fewer individuals as seropositive than did ES, but improved the discrimination between the seropositive and seronegative individuals and thus provided a more conclusive diagnosis. Sera obtained from patients infected with schistosomiasis mansoni, cysticercosis, hydatidosis, and Chagas' disease were negative in these assays, which demonstrated the specificity of the IgG4-ELISA for detecting fascioliasis. Twenty of the 95 patients (21%) were seropositive for fascioliasis by the CL1 IgG4-ELISA, confirming the earlier reports of the high prevalence of disease in this region. A standardized diagnostic test for human fascioliasis, based on an ELISA that detects IgG4 responses to CL1, could be available to all diagnostic centers if sufficient quantities of recombinant CL1 can be produced.

Ultrahigh speed all-optical demultiplexing based on two-photon absorption in a laser diode

Abstract: The authors describe how the nonlinear process of two-photon absorption in a commercial laser diode may be used for all-optical demultiplexing in terabit per second optical time division multiplexing networks. Switching windows of 650 fs in duration have been observed, with corresponding switching energies of a few picojoules.

A point mass in an isotropic universe: existence, uniqueness, and basic properties

Abstract: Criteria which a space-time must satisfy to represent a point mass embedded in an open Robertson-Walker (RW) universe are given. It is shown that McVittie's solution in the case $k=0$ satisfies these criteria, but does not in the case $k=\ensuremath{-}1.$ The existence of a solution for the case $k=\ensuremath{-}1$ is proven and its representation in terms of an elliptic integral is given. The following properties of this and McVittie's $k=0$ solution are studied; uniqueness, the behavior at future null infinity, the recovery of the RW and Schwarzschild limits, the compliance with energy conditions, and the occurrence of singularities. The existence of solutions representing more general spherical objects embedded in a RW universe is also proven.

Leaching in sol–gel-derived silica films for optical pH sensing

Abstract: The effect of different processing parameters on the efficiency of entrapment of pH indicators in a sol–gel-derived silica film is reported. An evanescent wave absorption approach was used to monitor dopant-leaching from these films. The issues investigated include the effect on the rate of leaching of the water:alkoxide ratio, the pH of the leachant solution and the choice of silicon alkoxide. Results indicate that the most suitable sol–gel films in terms of leaching and response time are those prepared using tetraethoxysilane as precursor, acid catalysis and a water:alkoxide ratio of at least 4. Leaching is more pronounced for films used directly after preparation and varies for different pH environments. Implications of leaching for the long-term use of sol–gel based pH sensors are discussed.

Irish women accountants and career progression: a research note

Abstract: This article presents the findings of research into the career progression of Irish Chartered Accountants which compares the career progress of men and women and examines the obstacles to progression encountered by women. The research indicates that women face obstacles that are not encountered by their male counterparts and that career progression is frequently made at substantial cost to their personal lives.

Hysteresis in the E- to H-mode transition in a planar coil, inductively coupled rf argon discharge

Abstract: Inductively coupled rf discharges typically exhibit two modes of operation, namely, a low-density mode known as the E mode and a higher density mode known as the H mode. The transition between these modes exhibits hysteresis. Experimental observations of these transitions are presented. By means of a mixture of electromagnetic theory and circuit analysis and by invoking the requirement that the power absorbed and lost by the electrons should balance, the possible working points of an inductively coupled rf plasma source are identified in (P, ) space, where P is the power absorbed by the electrons, is the peak rf current in the induction coil and is the electron number density. Once the loci of the operating points have been identified in this manner, it is possible to construct a consistent explanation for all the experimental observations reported in the first part of the paper. In particular, it is possible to present an explanation for the hysteresis-like behaviour manifested by the mode transitions. Basically, the transitions occur when it is no longer possible to balance the power absorbed and lost by electrons.

Effects of ceria on the combustion activity and surface properties of Pt/Al2O3 catalysts

Abstract: The presence of Ce was found to be potentially beneficial for the iso-butane oxidation activity of 0.5 wt% Pt/Al 2 O 3 catalysts after reduction treatments. Temperature-programmed reduction (TPR) experiments showed that the addition of Ce to Pt/Al 2 O 3 resulted in a bimetallic surface interaction which affected surface reducibility. X-ray photoelectron spectroscopy (XPS) indicated that the nature of Pt–Ce interaction varied depending on the loading of Ce. After impregnation and calcination in air, the presence of Ce, at Ce:Pt≥8:1 atomic ratio, generally resulted in poorer oxidation activity relative to Pt/Al 2 O 3 with higher temperatures required to achieve the same level of i -C 4 H 10 conversion. At a lower Ce loading (Ce:Pt=0.5:1 atomic ratio), oxidation activity was not so adversely affected. In general, the activity of the Pt catalysts increased after initial testing in the reactant mixture. Reduction of a 0.5 wt% Pt/Al 2 O 3 catalyst resulted in considerable loss of activity. The addition of Ce appeared to help prevent this deactivation. TPR profiles indicated that the existence of an interaction between Pt and Ce in Pt–Ce/Al 2 O 3 samples was associated with improved activity following reduction.

The Cracked Looking Glass of Servants

Abstract: Translators working in minority languages have often been ignored in theoretical and historical debates on translation. If however ‘minority’ is treated as a dynamic as opposed to a static concept, then the experiences of minority languages have much to reveal to other languages in a world increasingly dominated by one global language. This article examines the role of minority languages in the context of scientific and technical translation, particularly with respect to the Internet and the emergence of Cyber-English. The effects of time-space compression on the practice of minority language translation and the working conditions of translators is discussed in the context of globalization and the ‘minoritization’ of all languages. The position of major/minor language translation in the light of debates on difference and universalism is considered and arguments are advanced for the more active incorporation of minority languages into translation studies research.

Plasmodium chabaudi chabaudi and P. falciparum: inhibition of aminopeptidase and parasite growth by bestatin and nitrobestatin.

Abstract: The major leucine aminopeptidase of the rodent malarial parasite Plasmodium chabaudi chabaudi was partially purified using a combination of high-pressure liquid chromatography on a size-exclusion column and affinity chromatography using the aminopeptidase-specific inhibitor bestatin as the ligand. The purified enzyme showed simple Michaelis-Menten kinetics when the fluorogenic peptide analogue leucyl-7-amino-4-methyl-courmarin served as the substrate, and it was strongly inhibited by both bestatin (K i= 50.7 ± 21.0 nM) and nitrobestatin (K i= 2.51 ± 0.2 nM) in a competitive manner. These inhibitors were also potent blockers of the growth of P. c. chabaudi and the human parasite P. falciparum in culture, and nitrobestatin was again the more potent. Therefore, the leucine aminopeptidase represents an important target to which novel anti-malarial agents could be directed.

The Challenges of Cross-Modal Translation: English-to-Sign-Language Translation in the Zardoz System

Abstract: The sign languages used by deaf communities around the world represent a linguistic challenge that natural-language researchers in AI have only recently begun to take up. This challenge is particularly relevant to research in Machine Translation (MT), as natural sign languages have evolved in deaf communities into efficient modes of gestural communication, which differ from English not only in modality but in grammatical structure, exploiting a higher dimensionality of spatial expression. In this paper we describe Zardoz, an on-going AI research system that tackles the cross-modal MT problem, translating English text into fluid sign language. The paper presents an architectural overview of Zardoz, describing its central blackboard organization, the nature of its interlingual representation, and the major components which interact through this blackboard both to analyze the verbal input and generate the corresponding gestural output in one of a number of sign variants.

The Concept of Learning in the Strategy Field Review and Outlook

Abstract: This article begins by looking at how the concept of learning has informed our understanding of competitiveness. It then goes on to examine the fresh perspective that the notion of learning opens u...