Showing papers by "University College Dublin published in 1998"

The Determinants of Corporate Debt Maturity Structure

Abstract: We examine the empirical determinants of debt maturity structure using a maturity structure measure that incorporates detailed information about all of a firm's liabilities. We find that larger, less risky firms, with longer-term asset maturities use longer-term debt. Additionally, debt maturity varies inversely with earnings surprises and a firm's effective tax rate, but there is only mixed support for an inverse relation with growth opportunities. We find strong support for the prediction of a non-monotonic relation between debt maturity and bond rating: firms with high or very low bond ratings use shorter-term debt.

Low Circulating Folate and Vitamin B6 Concentrations Risk Factors for Stroke, Peripheral Vascular Disease, and Coronary Artery Disease

Abstract: Background—A high plasma homocysteine concentration is a risk factor for atherosclerosis, and circulating concentrations of homocysteine are related to levels of folate and vitamin B6. This study was performed to explore the interrelationships between homocysteine, B vitamins, and vascular diseases and to evaluate the role of these vitamins as risk factors for atherosclerosis. Methods—In a multicenter case-control study in Europe, 750 patients with documented vascular disease and 800 control subjects frequency-matched for age and sex were compared. Plasma levels of total homocysteine (before and after methionine loading) were determined, as were those of red cell folate, vitamin B12, and vitamin B6. Results—In a conditional logistic regression model, homocysteine concentrations greater than the 80th percentile for control subjects either fasting (12.1 μmol/L) or after a methionine load (38.0 μmol/L) were associated with an elevated risk of vascular disease independent of all traditional risk factors. In a...

Bourdieu and Education: Acts of Practical Theory

Abstract: This text details the practical applications of Bourdieu's theories in a series of specific pedagogic research studies, showing how his ideas can be put into practice. Language, gender, career decision-making and the experience of higher education students are all covered. Questions are also raised concerning research methodology. The authors examine Bourdieu's interest in the position of the researcher within the research process. Bourdieu's influence is traced in aspects both of theory and practice. Finally, principles, approaches, methods and techniques that may be derived from Bourdieu are suggested, and assessed, for practical use in research.

The role of synchronization in digital communications using chaos. II. Chaotic modulation and chaotic synchronization

Abstract: For pt. I see ibid., vol. 44, p. 927-36 (1997). In a digital communications system, data are transmitted from one location to another by mapping bit sequences to symbols, and symbols to sample functions of analog waveforms. The analog waveform passes through a bandlimited (possibly time-varying) analog channel, where the signal is distorted and noise is added. In a conventional system the analog sample functions sent through the channel are weighted sums of one or more sinusoids; in a chaotic communications system the sample functions are segments of chaotic waveforms. At the receiver, the symbol may be recovered by means of coherent detection, where all possible sample functions are known, or by noncoherent detection, where one or more characteristics of the sample functions are estimated. In a coherent receiver, synchronization is the most commonly used technique for recovering the sample functions from the received waveform. These sample functions are then used as reference signals for a correlator. Synchronization-based coherent receivers have advantages over noncoherent receivers in terms of noise performance, bandwidth efficiency (in narrow-band systems) and/or data rate (in chaotic systems). These advantages are lost if synchronization cannot be maintained, for example, under poor propagation conditions. In these circumstances, communication without synchronization may be preferable. The theory of conventional telecommunications is extended to chaotic communications, chaotic modulation techniques and receiver configurations are surveyed, and chaotic synchronization schemes are described.

Assembly and Self-Organization of Silver Nanocrystal Superlattices: Ordered “Soft Spheres”

Abstract: Hydrophobic dodecanethiol-capped silver nanocrystals ranging from 50 to 80 A in diameter were synthesized using arrested growth methods. Size-selective precipitation was employed to isolate nanocrystals homogeneous in size and shape which exhibited close-packed structural order after drying on a carbon or mica substrate. Elemental analysis, H1 NMR and FTIR spectroscopies were used to characterize the compositional features of the adsorbed thiolate ligands on nanocrystals suspended in solution and condensed in nanocrystal films. Small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) were used to probe the structure of both individual nanocrystals and superlattices, and to estimate the energetic interactions between these sterically stabilized particles. In terms of these measurements, the effects of the capping ligand coverage, particle faceting and shape, and interparticle attractions on superlattice formation are elucidated. In particular, the concept of nanocrystals as “soft sphe...

Candida dubliniensis: Characteristics and Identification

Abstract: Candida dubliniensis is a recently described species of chlamydospore- and germ tube-positive yeast which has been recovered primarily from the oral cavities of human immunodeficiency virus (HIV)-infected individuals and AIDS patients. The organism has been recovered from patients in widespread

A genome-wide search for susceptibility genes in human systemic lupus erythematosus sib-pair families

Abstract: Systemic lupus erythematosus (SLE) is an autoimmune multisystem inflammatory disease characterized by the production of pathogenic autoantibodies. Previous genetic studies have suggested associations with HLA Class II alleles, complement gene deficiencies, and Fc receptor polymorphisms; however, it is likely that other genes contribute to SLE susceptibility and pathogenesis. Here, we report the results of a genome-wide microsatellite marker screen in 105 SLE sib-pair families. By using multipoint nonparametric methods, the strongest evidence for linkage was found near the HLA locus (6p11-p21) [D6S257, logarithm of odds (lod) = 3.90, P = 0.000011] and at three additional regions: 16q13 (D16S415, lod = 3.64, P = 0.000022), 14q21–23 (D14S276, lod = 2.81, P = 0.00016), and 20p12 (D20S186, lod = 2.62, P = 0.00025). Another nine regions (1p36, 1p13, 1q42, 2p15, 2q21–33, 3cent-q11, 4q28, 11p15, and 15q26) were identified with lod scores ≥1.00. These data support the hypothesis that multiple genes, including one in the HLA region, influence susceptibility to human SLE.

Solar disinfection of drinking water contained in transparent plastic bottles : characterizing the bacterial inactivation process

Abstract: series of experiments is reported to identify and characterize the inactivation process in operation when drinking water, heavily contaminated with a Kenyan isolate of Escherichia coli, is stored in transparent plastic bottles that are then exposed to sunlight. The roles of optical and thermal inactivation mechanisms are studied in detail by simulating conditions of optical irradiance, water turbidity and temperature, which were recorded during a series of solar disinfection measurements carried out in the Kenyan Rift Valley. Optical inactivation effects are observed even in highly turbid water (200 ntu) and at low irradiances of only 10 mW cm 2 . Thermal inactivation is found to be important only at water temperatures above 45 °C, at which point strong synergy between optical and thermal inactivation processes is observed. The results confirm that, where strong sunshine is available, solar disinfection of drinking water is an effective, low cost method for improving water quality and may be of particular use to refugee camps in disaster areas. Strategies for improving bacterial inactivation are discussed.

Asymptomatic synovitis precedes clinically manifest arthritis

Abstract: Objective It has been hypothesized that asymptomatic synovitis may precede clinical manifestations of arthritis in the earliest phase of rheumatoid arthritis (RA). To obtain more insight into this disease phase, we investigated the immunohistologic features of synovial tissue (ST) from the knee joints of rhesus monkeys with induced arthritis and from RA patients with both clinically involved and clinically uninvolved knee joints. Methods Serial ST biopsy specimens from the knee joints of 4 rhesus monkeys that had been immunized with type II collagen and ST from 10 RA patients were investigated. Eight patients without inflammatory joint disease served as controls. Results In ST from immunized monkeys, an influx of macrophages was observed well before the occurrence of arthritis. Signs of inflammation were also demonstrated in ST from clinically uninvolved knee joints of all RA patients evaluated. The ST was characterized in particular by infiltration with macrophages and by the expression of macrophage-derived cytokines. Conclusion The findings support the view that asymptomatic synovitis precedes clinically manifest arthritis in both early and established RA. This implies that the debut of RA already represents a chronic phase of the disease.

Confidence Limits Made Easy: Interval Estimation Using a Substitution Method

Abstract: The use of confidence intervals has become standard in the presentation of statistical results in medical journals. Calculation of confidence limits can be straightforward using the normal approximation with an estimate of the standard error, and in particular cases exact solutions can be obtained from published tables. However, for a number of commonly used measures in epidemiology and clinical research, formulae either are not available or are so complex that calculation is tedious. The author describes how an approach to confidence interval estimation which has been used in certain specific instances can be generalized to obtain a simple and easily understood method that has wide applicability. The technique is applicable as long as the measure for which a confidence interval is required can be expressed as a monotonic function of a single parameter for which the confidence limits are available. These known confidence limits are substituted into the expression for the measure--giving the required interval. This approach makes fewer distributional assumptions than the use of the normal approximation and can be more accurate. The author illustrates his technique by calculating confidence intervals for Levin's attributable risk, some measures in population genetics, and the "number needed to be treated" in a clinical trial. Hitherto the calculation of confidence intervals for these measures was quite problematic. The substitution method can provide a practical alternative to the use of complex formulae when performing interval estimation, and even in simpler situations it has major advantages.

Emulsification and microencapsulation properties of gum arabic

Abstract: Emulsions of gum arabic solutions (10% w/w) and soya oil at oil/gum ratios of 0.25−5.0 were prepared by homogenization at 20 MPa. The resulting emulsions were subsequently spray-dried to produce powders with oil contents ranging from 20 to 82% (w/w). Lipid globule size distributions and viscosities of the emulsions were determined, and particle size and percentage of extractable oil were determined for the spray-dried powders. The ability of the powders to redisperse in water was also examined. The average lipid globule size (D4,3) (0.57 μm) did not vary significantly (P > 0.05) as the oil/gum ratio was increased from 0.25 and 1.0, but it did increase at higher ratios to a maximum of 2.02 μm. The average particle size of the spray-dried emulsions was within the range 9−17 μm, and the microencapsulation efficiency decreased from 100 to 48% when the oil/gum ratio was increased from 0.25 to 5.0, respectively. Powders with an oil content <50% dispersed readily in water. Keywords: Gum arabic; emulsions; microe...

Simple, inexpensive, reliable method for differentiation of candida dubliniensis from candida albicans

Abstract: Candida dubliniensis is a recently described pathogenic species which shares many phenotypic features with Candida albicans, including the ability to form germ tubes and chlamydospores These similarities have caused significant problems in the identification of C dubliniensis by the average clinical mycology laboratory To facilitate the differentiation of these species, we investigated the growth of 120 isolates of C dubliniensis and 98 C albicans isolates at 42 and 45°C on Emmons’ modified Sabouraud glucose agar (SGA) and 10 isolates of each species in yeast-peptone-dextrose broth None of the C dubliniensis isolates grew on the agar or in the broth medium at 45°C, while 11 isolates were capable of growing on SGA at 42°C In contrast, all of the C albicans isolates but one grew at 45°C on or in either medium These reproducible results clearly demonstrate that the incubation of isolates suspected to be C dubliniensis or C albicans at 45°C provides a simple, reliable, and inexpensive method for the differentiation of the two species

Identification and expression of multidrug transporters responsible for fluconazole resistance in Candida dubliniensis.

Abstract: Candida dubliniensis is a recently described Candida species associated with oral candidosis in human immunodeficiency virus (HIV)-infected and AIDS patients, from whom fluconazole-resistant clinical isolates have been previously recovered. Furthermore, derivatives exhibiting a stable fluconazole-resistant phenotype have been readily generated in vitro from fluconazole-susceptible isolates following exposure to the drug. In this study, fluconazole-resistant isolates accumulated up to 80% less [3H] fluconazole than susceptible isolates and also exhibited reduced susceptibility to the metabolic inhibitors 4-nitroquinoline-N-oxide and methotrexate. These findings suggested that C. dubliniensis may encode multidrug transporters similar to those encoded by the C. albicans MDR1, CDR1, and CDR2 genes (CaMDR1, CaCDR1, and CaCDR2, respectively). A C. dubliniensis homolog of CaMDR1, termed CdMDR1, was cloned; its nucleotide sequence was found to be 92% identical to the corresponding CaMDR1 sequence, while the predicted CdMDR1 protein was found to be 96% identical to the corresponding CaMDR1 protein. By PCR, C. dubliniensis was also found to encode homologs of CDR1 and CDR2, termed CdCDR1 and CdCDR2, respectively. Expression of CdMDR1 in a fluconazole-susceptible delta pdr5 null mutant of Saccharomyces cerevisiae conferred a fluconazole-resistant phenotype and resulted in a 75% decrease in accumulation of [3H]fluconazole. Northern analysis of fluconazole-susceptible and -resistant isolates of C. dubliniensis revealed that fluconazole resistance was associated with increased expression of CdMDR1 mRNA. In contrast, most studies showed that overexpression of CaCDR1 was associated with fluconazole resistance in C. albicans. Increased levels of the CdMdr1p protein were also detected in fluconazole-resistant isolates. Similar results were obtained with fluconazole-resistant derivatives of C. dubliniensis generated in vitro, some of which also exhibited increased levels of CdCDR1 mRNA and CdCdr1p protein. These results demonstrate that C. dubliniensis encodes multidrug transporters which mediate fluconazole resistance in clinical isolates and which can be rapidly mobilized, at least in vitro, on exposure to fluconazole.

Inequality in Higher Education: a study of class barriers

Abstract: This paper is based on a study conducted among four groups of people who have direct experience of how social‐class position affects students’ access to, and participation in, higher education. Intensive interviews were undertaken with 122 people deliberately chosen from a range of counties, schools and higher educational institutions in Ireland. Interviews were undertaken with 40 low‐income working‐class second‐level students, 40 others at third level, 10 community workers who were both activists and parents in working‐class communities, 16 teachers and school principals including four from feepaying schools, and 16 second‐level students from fee‐paying secondary schools. The aim of the study was to examine the barriers experienced by low‐income working‐class students in accessing and succeeding in higher education. The study also set out to identify strategies for change as seen from the perspectives of the different groups, and to examine the ways in which more privileged students were able to...

Manufacturing of Thermoplastic Composites from Commingled Yarns-A Review:

Abstract: The use of commingled yarns is one of the more promising routes for producing structural thermoplastic composites. The textile processes available enable faster manufacturing and tailoring of the fiber architecture of preforms. Development of this technology is pushed by significant interest from, for example, the transportation industry. This paper reviews work done on commingled materials, including yarn manufacturing and preforming, modeling of impregnation and consolidation, and mechanical properties of the composites.

Effect of Calf Isolation on Follicular Wave Dynamics, Gonadotropin and Metabolic Hormone Changes, and Interval to First Ovulation in Beef Cows Fed Either of Two Energy Levels Postpartum

Abstract: The effects of postpartum energy intake, restricted suckling, and cow-calf isolation on concentrations of LH, FSH, growth hormone, and insulin-like growth factor-I (IGF-I) and on postpartum anestrous interval were determined by randomly allocating beef cows with a mean body condition score of 2.3 +/- 0.1 to receive either 80 MJ metabolizable energy (low-energy diet [L]; n = 51) or 120 MJ metabolizable energy (high-energy diet [H]; n = 52) per cow per day from calving. At 30 days postpartum, cows within diet were randomized to 1) have continued full access to their calves from birth to weaning (ad libitum suckling: ADLIB), 2) be suckled once-daily with their calves penned adjacent (restricted suckling, adjacent: RESADJ), 3) be isolated from all calves except for a once-daily suckling period (restricted suckling, isolated: RESISO). The mean postpartum interval was similar (p > 0.10) for L and H cows (62 and 63 days, respectively). RESADJ cows had a shorter (p 0.10) of diet. FSH secretion pattern was not affected by diet, suckling treatment, sequential follicle wave number, or follicle wave retrospectively realigned to emergence of first ovulatory wave. Within 5 days of suckling restriction and calf isolation, the number of LH pulses increased from 0.18 to 0.48 pulses per hour (p < 0.05). Both mean LH and the mean number of LH pulses increased linearly (p < 0.01) during the six follicle waves up to the first ovulatory wave. From 80 days before, until the time of, first ovulation, growth hormone decreased (p < 0.05) while IGF-I increased (p < 0.05), irrespective of treatment. The results indicate that the "suckling effect" in beef cows is the major factor affecting the duration of the postpartum interval and suggests that the maternal bond is more important than suckling in regulating LH pulse frequency, the key endocrine factor determining whether or not a dominant follicles ovulates. Removal of the suckling effect resulted in a rapid increase in LH pulse frequency, which was not dependent on level of postpartum nutrition, at least within the nutritional limits of this study. Mean concentrations of FSH, unlike LH, did not vary with follicle wave number, suggesting that lack of FSH is not a major factor delaying the resumption of ovulation in postpartum beef cows.

Michael White's narrative therapy

Abstract: A systematized description of a number of practices central to Michael Whites' narrative approach to therapy is given. These include collaborative positioning of the therapist, externalizing the problem, excavating unique outcomes, thickening the new plot, and linking the new plot to the past and the future. The practices of remembering and incorporation, using literary means to achieve therapeutic ends, and facilitating taking-it-back practices are also described. A number of questions are given which may be useful for those concerned with narrative therapy to address.

Apoptotic Regression of MCF-7 Xenografts in Nude Mice Treated with the Vitamin D3 Analog, EB1089

Abstract: 1,25-Dihydroxyvitamin D3 [1,25-(OH)2D3] and its synthetic analog EB1089 induce characteristic morphological features of apoptosis in MCF-7 cells in vitro that coincide with up-regulation of clusterin and cathepsin B, proteins associated with apoptosis in the mammary gland, and with down-regulation of Bcl-2, an antiapoptotic protein. To determine whether vitamin D3 compounds could mediate apoptosis of breast tumors in vivo, we treated nude mice carrying established MCF-7 xenografts with the low calcemic vitamin D3 analog EB1089 via daily injection or sustained release pellets for up to 5 weeks. The volume of tumors from mice treated with 45 pmol/day EB1089 was 4-fold lower than that of tumors from vehicle-treated control mice after 5 weeks. The reduced growth of tumors from EB1089-treated mice was associated with characteristic apoptotic morphology and a marked reduction in the proportion of epithelial cells to stroma. After 5 weeks of treatment with EB1089, MCF-7 tumors exhibited a 6-fold increase in DNA fragmentation (as measured by in situ end labeling) relative to that in control tumors. The enhanced rate of apoptosis in tumors from EB1089-treated mice was coupled to a 2-fold reduction in proliferation (as measured by expression of proliferating cell nuclear antigen) compared with that in tumors from control mice. The antitumor effects of EB1089 were evident at doses that had minimal effects on serum calcium and body weight. EB1089 treatment did not alter the growth of xenografts derived from a vitamin D3-resistant variant of MCF-7 cells (MCF-7(D3Res) cells), which display resistance to EB1089 in vitro, indicating that resistance to EB1089 is maintained in vivo. Tumors derived from both MCF-7 and MCF-7(D3Res) cells underwent apoptotic regression upon estradiol withdrawal, indicating comparable estrogen dependence of tumors with differential sensitivity to vitamin D3 compounds. These are the first studies to demonstrate apoptotic morphology and regression of human breast tumors in response to treatment with a vitamin D3 analog in vivo and support the concept that vitamin D3 compounds can effectively target human breast cancer.

Autocorrelated data in telemetry studies: time to independence and the problem of behavioural effects

Abstract: Independence of locational fixes, to reduce the effects of autocorrelation, is often deemed a prerequisite for estimation of home range size and utilization when using data derived from telemetric studies. Three methods of estimating times to independence using movement estimates, along with a statistical method of estimating the level of autocorrelation of locational data, were examined for two species of mammal. Attempts to achieve statistically independent data by subsampling resulted in severe redundancy in the data and significant underestimation of range size and rates of movement. Even a sample interval of one fix per week did not guarantee independence and also resulted in underestimation of range size despite range asymptotes being reached. It would appear that the correct strategy for the best possible estimation of range size and use from telemetry would be the repeated use of as short a sampling interval as is possible over an extended period of time. Statistical methods to measure levels of autocorrelation in locational data may be useful for comparing rates of range use between different populations of the same species or between species, as long as the same sample interval is used.

Modelling the Competence of Case-Bases

Abstract: The competence of a case-based system (the range of problems it can solve) depends critically on the cases in the case-base. However, the precise relationship between cases and overall competence is a complex one. For example, some cases can be critical to competence, while others may be largely redundant. In this paper we present, and evaluate, a new model of case competence. We argue that this model has an important role to play in areas such as the evaluation and benchmarking of case-based techniques, and we demonstrate a novel application of the model as a guide to case-base designers during the case authoring process.

Gas hydrate crystals may help build reefs

Abstract: During a recent cruise in the Porcupine Basin, off southwest Ireland, we discovered two extensive and hitherto largely unsuspected deep-water reef provinces, including a giant cluster of hundreds of buried mounds. The ring shapes of many reefs suggest that they are caused by an axial fluid expulsion at the sea bed, a transient flow well confined in space and time. We are exploring various hypotheses, but a stimulating avenue for research is opened by a glacially controlled growth pulse and subsequent decay of a shallow layer of gas hydrates as a methane buffer and probably indirectly as a ground for overlying biological communities.