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Biomedical subjects

J Ewing

Publications and source records attributed to J Ewing.

16 recordsLinked to original sources
PubMed2002

Performance assessment of NAPL remediation in heterogeneous alluvium.

Over the last few years, more than 40 partitioning interwell tracer tests (PITTs) have been conducted at many different sites to measure nonaqueous phase liquid (NAPL) saturations in the subsurface. While the main goal of these PITTs was to estimate the NAPL volume in the subsurface, some were specifically conducted to assess the performance of remedial actions involving NAPL removal. In this paper, we present a quantitative approach to assess the performance of remedial actions to recover NAPL that can be used to assess any NAPL removal technology. It combines the use of PITTs (to estimate the NAPL volume in the swept pore volume between injection and extraction wells of a test area) with the use of several cores to determine the vertical NAPL distribution in the subsurface. We illustrate the effectiveness of such an approach by assessing the performance of a surfactant/foam flood conducted at Hill Air Force Base, UT, to remove a TCE-rich NAPL from alluvium with permeability contrasts as high as one order of magnitude. In addition, we compare the NAPL volumes determined by the PITTs with volumes estimated through geostatistical interpolation of aquifer sediment core data collected with a vertical frequency of 5-10 cm and a lateral borehole spacing of 0.15 m. We demonstrate the use of several innovations including the explicit estimation of not only the errors associated with NAPL volumes and saturations derived from PITTs but also the heterogeneity of the aquifer sediments based upon permeability estimates. Most importantly, we demonstrate the reliability of the

Environmental Monitoring↗
PubMed2001

Paper-like electronic displays: large-area rubber-stamped plastic sheets of electronics and microencapsulated electrophoretic inks.

Electronic systems that use rugged lightweight plastics potentially offer attractive characteristics (low-cost processing, mechanical flexibility, large area coverage, etc.) that are not easily achieved with established silicon technologies. This paper summarizes work that demonstrates many of these characteristics in a realistic system: organic active matrix backplane circuits (256 transistors) for large ( approximately 5 x 5-inch) mechanically flexible sheets of electronic paper, an emerging type of display. The success of this effort relies on new or improved processing techniques and materials for plastic electronics, including methods for (i) rubber stamping (microcontact printing) high-resolution ( approximately 1 microm) circuits with low levels of defects and good registration over large areas, (ii) achieving low leakage with thin dielectrics deposited onto surfaces with relief, (iii) constructing high-performance organic transistors with bottom contact geometries, (iv) encapsulating these transistors, (v) depositing, in a repeatable way, organic semiconductors with uniform electrical characteristics over large areas, and (vi) low-temperature ( approximately 100 degrees C) annealing to increase the on/off ratios of the transistors and to improve the uniformity of their characteristics. The sophistication and flexibility of the patterning procedures, high level of integration on plastic substrates, large area coverage, and good performance of the transistors are all important features of this work. We successfully integrate these circuits with microencapsulated electrophoretic "inks" to form sheets of electronic paper.

Journal Article↗
PubMed2001

Investigation of surfactant-enhanced dissolution of entrapped nonaqueous phase liquid chemicals in a two-dimensional groundwater flow field.

Because of their low solubility, waste chemicals in the form of nonaqueous phase liquids (NAPLs) that are entrapped in subsurface formations act as long-term sources of groundwater contamination. In the design of remediation schemes that use surfactants, it is necessary to estimate the mass transfer rate coefficients under multi-dimensional flow fields that exit at field sites. In this study, we investigate mass transfer under a two-dimensional flow field to obtain an understanding of the basic mechanisms of surfactant-enhanced dissolution and to quantify the mass transfer rates. Enhanced dissolution experiments in a two-dimensional test cell were conducted to measure rates of mass depletion from entrapped NAPLs to a flowing aqueous phase containing a surfactant. In situ measurement of transient saturation changes using a gamma attenuation system revealed dissolution patterns that are affected by the dimensionality of the groundwater flow field. Numerical modeling of local flow fields that changed with time, due to depletion of NAPL sources, enabled the examination of the basic mechanisms of NAPL dissolution in complex groundwater systems. Through nonlinear regression analysis, mass transfer rates were correlated to porous media properties, NAPL saturation and aqueous phase velocity. Results from the experiments and numerical analyses were used to identify deficiencies in existing methods of analysis that uses assumptions of one-dimensional flow, homogeneity of aquifer properties, local equilibrium and idealized transient mass transfer.

Environmental Monitoring↗
PubMed2000

Murine B cell differentiation is accompanied by programmed expression of multiple novel beta-galactoside alpha2, 6-sialyltransferase mRNA forms.

ST6Gal I (beta-galactoside alpha2,6-sialyltransferase, ST6N) elaborates the ubiquitously expressed alpha2,6-sialyl linkage. A number of ST6Gal I mRNA isoforms, differing only in their 5'-UT regions, is transcribed from a single mouse gene, Siat1. In B-lineage cells, alpha2,6-sialic acid serves as extracellular ligand for CD22, a participant in cell activation via an intracellular signaling network of tyrosine kinases and SHP phosphastase. Activation and terminal differentiation of mature B cells into plasma cells is accompanied by the appearance of at least four distinct ST6Gal I mRNA isoforms. Resting splenic B-lymphocytes isolated from 8-12 wk C56Bl/6 mice expressed almost exclusively the Exons Q+O-containing form, which is the likely homolog to the previously documented human Y+Z and rat -1+0 forms. In vitro activation using recombinant CD40-ligand and conditioned media from T-helper cells resulted in a 2- to 3-fold elevation of overall ST6Gal I mRNA abundance by Day 3. This coincided with repression of the Q+O form, and appearance of three new isoforms containing 5'-untranslated sequences X(1), X(2), or X(3). The X(1)form persisted through Day 10, when the transition of B cells to plasma cells was completed as evidence by disappearance of CD22 mRNA. In contrast, the X(2)form only transiently appeared at Day 3 and declined to barely detectable levels by Day 7. Expression of the X(3)form, a minor mRNA form, paralleled the X(2)form. The divergent 5'-UT exons are dispersed over 69 kb of linear genomic space of Siat1. Mutually exclusive utilization of these 5'-UT exons in transcripts predicts separate and distinct promoter regulatory regions for each mRNA isoform.

Animals↗
PubMed1999

Hepatic acute phase induction of murine beta-galactoside alpha 2,6 sialyltransferase (ST6Gal I) is IL-6 dependent and mediated by elevation of exon H-containing class of transcripts.

Hepatic expression of CMP-NeuAc:Gal beta 1,4GlcNAc alpha 2,6-sialyltransferase (ST6Gal I) is induced as part of the acute phase response in mammals by mechanisms that remain poorly understood. Previous work suggests that murine liver ST6Gal I mRNA contains an additional and novel region that is not found on ST6Gal I mRNA from human HepG2 hepatoma cells and from rat liver. This novel region, residing 5' of the common Exon I sequence, is encoded by a discrete upstream exon, Exon H. Here we provide evidence that the Exon H-containing transcript is the murine counterpart of the human and rat ST6Gal I mRNAs transcribed from the hepatic-specific promoter, P1. Exon H-containing ST6Gal I mRNA is expressed in all three mice strains examined: balb/c, C57B46, and 129Sv. Furthermore, murine RNA tissue survey indicates that presence of Exon H-containing transcripts is restricted to the liver. When mice are subjected to subcutaneous injection of turpentine to elicit the hepatic acute phase response, greater than 4-fold elevation in liver ST6Gal I mRNA was observed. Consistent with the view that Exon H-containing transcripts is regulated by the murine P1 promoter, 5'-RACE analysis indicates that the majority of these transcripts contains the Exon H sequence. This is consistent with the view that Exon H-containing transcripts are regulated by the murine P1 region. To assess the mechanism of ST6Gal I response in the hepatic acute phase reaction, mice harboring lesions in both alleles of the IL-6 gene were examined. IL-6(-/-) animals expressed normal levels of ST6Gal I mRNA in liver, with Exon H-containing transcripts remaining the predominant mRNA isoform. However, hepatic ST6Gal I is not elevated upon turpentine injection in the IL-6(-/-) animals. These results indicate that ST6Gal I induction in mouse liver during the acute phase reaction is mediated predominantly by the IL-6 pathway, and results in the induction of the Exon H-containing class of ST6Gal I mRNA that is specific to the liver.

Acute-Phase Reaction↗
PubMed1998

Association of transcription factor IIA with TATA binding protein is required for transcriptional activation of a subset of promoters and cell cycle progression in Saccharomyces cerevisiae.

The general transcription factor IIA (TFIIA) interacts with the TATA binding protein (TBP) and promoter DNA to mediate transcription activation in vitro. To determine if this interaction is generally required for activation of all class II genes in vivo, we have constructed substitution mutations in yeast TFIIA which compromise its ability to bind TBP. Substitution mutations in the small subunit of TFIIA (Toa2) at residue Y69 or W76 significantly impaired the ability of TFIIA to stimulate TBP-promoter binding in vitro. Gene replacement of wild-type TOA2 with a W76E or Y69A/W76A mutant was lethal in Saccharomyces cerevisiae, while the Y69F/W76F mutant exhibited extremely slow growth at 30 degrees C. Both the Y69A and W76A mutants were conditionally lethal at higher temperatures. Light microscopy indicated that viable toa2 mutant strains accumulate as equal-size dumbbells and multibudded clumps. Transcription of the cell cycle-regulatory genes CLB1, CLB2, CLN1, and CTS1 was significantly reduced in the toa2 mutant strains, while the noncycling genes PMA1 and ENO2 were only modestly affected, suggesting that these toa2 mutant alleles disrupt cell cycle progression. The differential effect of these toa2 mutants on gene transcription was examined for a number of other genes. toa2 mutant strains supported high levels of CUP1, PHO5, TRP3, and GAL1 gene activation, but the constitutive expression of DED1 was significantly reduced. Activator-induced start site expression for HIS3, GAL80, URA1, and URA3 promoters was defective in toa2 mutant strains, suggesting that the TFIIA-TBP complex is important for promoters which require an activator-dependent start site selection from constitutive to regulated expression. We present evidence to indicate that transcription defects in toa2 mutants can be both activator and promoter dependent. These results suggest that the association of TFIIA with TBP regulates activator-induced start site selection and cell cycle progression in S. cerevisiae.

Cell Cycle↗
PubMed1997

Palliation of a malignant gastrocolic fistula by endoscopic human fibrin sealant injection.

We report the case of a female patient with Hodgkin's disease resistant to therapy who developed a gastrocolic fistula as a consequence of her disease, leading to distressing faeculent vomiting. This was not considered to be amenable to surgical resection and her symptoms were successfully palliated endoscopically using injection of human fibrin sealant into the gastric and colonic aspect of the fistula tract. Both mechanical sealing and promotion of healing by human fibrin sealant are likely to be responsible for its efficacy.

Adult↗
PubMed1994

The effect of hypothermia on transient focal ischemia in rat brain evaluated by diffusion- and perfusion-weighted NMR imaging.

The effect of moderate whole-body hypothermia (30 degrees C) on transient middle cerebral artery (MCA) occlusion in the rat was evaluated using diffusion- and perfusion-weighted magnetic resonance imaging. Two hours of transient MCA occlusion was induced by intracarotid insertion of a nylon filament under normothermic (n = 14) and hypothermic (n = 7) conditions. Diffusion- and perfusion-weighted imaging were performed before, during, and after focal ischemia from 30 min up to 7 days. In hypothermic animals, scattered neuronal necrosis was localized to select areas of the caudate putamen and the parietal and insular cortex. In contrast, the normothermic ischemic animals exhibited pan-necrosis and infarct encompassing the damaged area. The diffusion and perfusion data measured from caudate putamen indicate that hypothermia causes a significant reduction in the apparent diffusion coefficient of water (ADCw) and CBF values from normothermic control values (p < 0.01). In both normothermic and hypothermic animals after onset of MCA occlusion, ADCw and CBF values in the core of the ischemic region (striatum) significantly declined from the preischemic and homologous contralateral control ADCw and CBF values (p < 0.05). However, ADCw and CBF in the hypothermic group returned toward control more rapidly than in the normothermic group. These results suggest that the protective effect of hypothermia on ischemic cell damage is reflected in the early return of ADCw during reperfusion and the reduction of ischemic cell damage by hypothermia may be mediated by the improved CBF during acute reperfusion.

Animals↗
PubMed1994

Stem cell factor regulates human melanocyte-matrix interactions.

Stem cell factor (SCF) is hypothesized to play a critical role in the migration of melanocytes during embryogenesis because mutations in either the SCF gene, or its ligand, c-kit, result in defects in coat pigmentation in mice and in skin pigmentation in humans. In this report we directly show that SCF alters the adhesion and migration of human melanocytes to extracellular matrix (ECM) ligands and regulates integrin expression at the protein level. SCF decreased adhesion of neonatal and fetal cells to collagen IV, and increased attachment of fetal cells to laminin. Attachment of fetal cells to fibronectin was decreased, but was unchanged in neonatal cells. Flow cytometry analysis of neonatal melanocytes showed that SCF down-regulated the expression of the alpha 2 receptor, and up-regulated the expression of the alpha 3, alpha 5 and beta 1 integrin receptors. SCF down-regulated expression of alpha 2, alpha 5 and beta 1 integrins by fetal melanocytes, and up-regulated expression of the alpha v and alpha 3 integrin receptors. Analysis of melanocyte migration using time-lapse videomicroscopy showed that SCF significantly increased migration of neonatal, but not fetal, melanocytes on fibronectin (FN). We conclude that SCF regulates integrin expression at the protein level and that SCF has pleiotropic effects on melanocyte attachment and migration on ECM ligands. We suggest that this may be one mechanism by which SCF regulates melanocyte migration during development of the skin.

Cell Adhesion↗
PubMed1992

Lack of association between an RFLP near the D2 dopamine receptor gene and severe alcoholism.

Blum et al (1990) have recently examined a restriction fragment length polymorphism (RFLP) detected by TaqI RFLP to the dopamine D2 receptor gene (DRD2) in deceased alcoholics and nonalcoholics, and reported an association between alcoholism and the A1 allele. Subsequent studies, however, by other investigators have failed to confirm this. We have examined the DRD2 TaqI RFLP in 47 living Caucasian males with severe alcoholism. All alcoholic subjects were thoroughly characterized by a structured interview, and met DSM-III-R criteria for alcohol dependence. Only 9/47 (19%) (1990) of these alcoholics had the AI allele compared to 14/22 (64%) reported by Blum et al. This rate was not significantly different from the rates reported in control populations by Blum et al (1990), CEPH, or Bolos et al (1990), and differed only slightly from those reported by Grandy et al (1990). Alcoholics selected for severe medical complications also displayed a similar rate. Our data do not support an association between alcoholism and the D2 dopamine receptor gene in this population.

Adult↗
PubMed1989

Practice patterns and family life--a survey of Melbourne medical graduates.

To investigate sex differences in the professional achievements and personal life-styles of graduates, a questionnaire survey was conducted. The sample comprised surviving female medical graduates of the University of Melbourne and an equal number of male medical graduates who were matched by year of graduation. The final response rate was 70% (1764 subjects returned questionnaires) and was representative for both age and sex. This article describes the practice patterns and family lives of graduates. Considerable sex-related differences were found in the professional achievements and personal life-styles of the surveyed medical graduates. Women's professional careers tended to be more circumscribed than were those of male colleagues. Women were less involved in areas outside clinical practice such as teaching or lecturing, committees, medical administration, and research and its publication. Female doctors earned significantly (P less than 0.0001) less than did male doctors and were more likely to work as employees, locums or in sessional employment (P less than 0.0001). Women were more involved in all aspects of household activities, especially during midlife (40-60 years of age)--the peak career years for male doctors. The career underachievement of female doctors is likely to continue unless considerable changes are made to current postgraduate training schemes and career structures.

Adult↗
PubMed1986

Contraction stress test by nipple stimulation: efficacy and safety.

During a one-year period, 838 nonstress tests, 425 nipple stimulation contraction stress tests (NS-CSTs), and 115 spontaneous CSTs were done. Results were compared to those of NSTs and CSTs done by classic methods during a previous one-year period. The results revealed no hyperstimulation from contraction stress testing with nipple stimulation, and a significant reduction in the time to perform both tests conducted simultaneously when compared to the nonstress test plus classic oxytocin challenge test. The time to perform the combined tests compared to the routine nonstress test was not significantly different. Moreover, a cost-saving was also demonstrated. The combination of the NST and nipple stimulation CST appeared to be safe, efficacious, and cost-effective.

Breast↗