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Biomedical subjects

D W Smith

Publications and source records attributed to D W Smith.

At least 19 recordsLinked to original sources
PubMed2006

Natural freezing as a wastewater treatment method: E. coli inactivation capacity.

Inactivation capacity of E. coli (strain ATCC 15597) in water by natural freezing was examined via two freezing methods: spray freezing and freezing in a freezer. The effect of freezing temperature (-5, -15 and -35 degrees C), storage time, freeze-thaw cycles on the survival of the test organism were investigated. In addition, the number of cells injured by the freezing process was also examined by using different growth media. The bacteria frozen at the warmer temperature (-5 degrees C) was most sensitive to storage and freeze-thaw cycles as compared to those frozen at -15 and -35 degrees C. In general, greater inactivation efficiencies were achieved under longer storage time and warmer freezing temperature conditions. Freezing and thawing caused cell injury. More cells were injured when frozen at -15 degrees C. The percentage of cells injured decreased as freeze-thaw cycles increased. The spray-freezing process was found more effective in killing the cells. On average, the log reduction rate for the spray ice with two-day storage time was about 4 log units higher than those without any storage after freezing. The results indicated that the natural freezing processes are not only cost-effective techniques for chemical and physical contaminant removal from wastewater or enhancing sludge dewaterability in cold regions but also effective in reducing E. coli concentration.

Colony Count, Microbial↗
PubMed2006

Neural networks modelling of streamflow, phosphorus, and suspended solids: application to the Canadian Boreal forest.

Sediment has long been identified as an important vector for the transport of nutrients and contaminants such as heavy metals and microorganisms. The respective nutrient loading to water bodies can potentially lead to dissolved oxygen depletion, cyanobacteria toxin production and ultimately eutrophication. This study proposed an artificial neural network (ANN) modelling algorithm that relies on low cost readily available meteorological data for simulating streamflow (Q), total suspended solids (TSS) concentration, and total phosphorus (TP) concentration. The models were applied to a 130-km2 watershed in the Canadian Boreal Plain. Our results demonstrated that through careful manipulation of time series analysis and rigorous optimization of ANN configuration, it is possible to simulate Q, TSS, and TP reasonably well. R2 values exceeding 0.89 were obtained for all modelled data cases. The proposed models can provide real time predictions of the modelled parameters, can answer questions related to the impact of climate change scenarios on water quantity and quality, and can be implemented in water resources management through Monte Carlo simulations.

Geologic Sediments↗
PubMed2005

Murray valley encephalitis mimicking herpes simplex encephalitis.

We describe a patient with serologically proven Murray Valley encephalitis (MVE), whose presentation was clinically and radiologically characteristic of Herpes simplex encephalitis (HSE). The reports of MRI abnormalities in MVE, and the closely related Japanese Encephalitis and West Nile virusii are mostly of bilateral thalamic or grey matter involvement. The MRI scan findings in this case instead showed the typical temporal lobe changes of HSE. Our case report highlights that MVE can mimic HSE, both clinically and radiologically. Therefore it is important to collect an accurate and detailed travel history from patients where there is a risk of exposure to MVE virus. If suspected, antibody testing of serum and CSF, and CSF for MVE-RNA if available, should be undertaken. This case also highlights the potential under-diagnosis of Murray Valley encephalitis.

Adult↗
PubMed2005

Safety of low-dose low-molecular-weight-heparins in thrombocytopenic stem cell transplantation patients: a case series and review of the literature.

Few attempts have been made to examine the feasibility of safely administering low-molecular-weight-heparins (LMWHs) in the presence of concurrent thrombocytopenia. We retrospectively investigated the safety of low-dose LMWH in BMT patients, a population at risk of bleeding. In total, 26 patients received at least one dose of low-dose enoxaparin (ie <1 mg/kg/day) during thrombocytopenia. s.c. enoxaparin 40 mg once daily was given in 85% of the cohort. The mean number of platelet days <55 x 10(9) and <20 x 10(9)/l were 16.5 days (95% CI=8.04-24.96) and 4.14 days (95% CI=2.35-5.93), respectively. The mean number of low-dose enoxaparin administration days when platelet <55 x 10(9) and 20 x 10(9)/l were 9.89 days (95% CI=3.26-16.53) and 2.25 days (95% CI=0.57-3.93), respectively. Minor bleeding occurred in four patients (15%) whereas major episodes developed in two patients (8%). The latter two events occurred during the transition between full therapeutic (ie 1.5-2 mg/kg/day) and low-dose enoxaparin close to the onset of thrombocytopenia. The present case series, along with the discussed literature, descriptively suggests that low-dose enoxaparin may be safely administered at a platelet count in the range of 20 and 55 x 10(9)/l in BMT patients who weigh >55 kg.

Adult↗
PubMed2004

Dynamics of {beta}-amyloid reductions in brain, cerebrospinal fluid, and plasma of {beta}-amyloid precursor protein transgenic mice treated with a {gamma}-secretase inhibitor.

gamma-Secretase inhibitors are one promising approach to the development of a therapeutic for Alzheimer's disease (AD). gamma-Secretase inhibitors reduce brain beta-amyloid peptide (Abeta), which is believed to be a major contributor in the etiology of AD. Transgenic mice overexpressing the human beta-amyloid precursor protein (APP) are valuable models to examine the dynamics of Abeta changes with gamma-secretase inhibitors in plaque-free and plaque-bearing animals. BMS-299897 2-[(1R)-1-[[(4-chlorophenyl)sulfony](2,5-difluorophenyl)amino]ethyl]-5-fluorobenzenepropanoic acid, a gamma-secretase inhibitor, showed dose- and time dependent reductions of Abeta in brain, cerebrospinal fluid (CSF), and plasma in young transgenic mice, with a significant correlation between brain and CSF Abeta levels. Because CSF and brain interstitial fluid are distinct compartments in composition and location, this correlation could not be assumed. In contrast, aged transgenic mice with large accumulations of Abeta in plaques showed reductions in CSF Abeta in the absence of measurable changes in plaque Abeta in the brain after up to 2 weeks of treatment. Hence, CSF Abeta levels were a valuable measure of gamma-secretase activity in the central nervous system in either the presence or absence of plaques. Transgenic mice were also used to examine potential side effects due to Notch inhibition. BMS-299897 was 15-fold more effective at preventing the cleavage of APP than of Notch in vitro. No changes in the maturation of CD8(+) thymocytes or of intestinal goblet cells were observed in mice treated with BMS-299897, showing that it is possible for gamma-secretase inhibitors to reduce brain Abeta without causing Notch-mediated toxicity.

Aging↗
PubMed2004

Removal of coliphages in secondary effluent by microfiltration-mechanisms of removal and impact of operating parameters.

The efficacy of a microfiltration (MF) pilot plant in removing somatic coliphages (referred hereafter as coliphages) present in the secondary effluent was evaluated during this study. The impact of operating parameters such as feed coliphage concentrations, permeate flux and membrane fouling on the removal of coliphages by the MF plant was investigated. The study showed that membrane fouling was beneficial for removing coliphages by MF. It was also shown that the removal of coliphages by MF was initially governed by adsorption on membrane surface or in membrane pores. As the membrane fouled, however, the removal of coliphages was primarily governed by direct interception on the cake layer formed on the surface of the membrane. Increases in feed coliphage concentrations resulted in the passage of larger numbers of coliphages when the MF was clean but had little impact on the passage of coliphages when the membrane became fouled. Increasing permeate flux lowered log-removal values (LRVs) for the clean membrane but resulted in an initial increase in LRVs for the fouled membrane followed by a drop in LRVs with further increases in permeate flux.

Coliphages↗
PubMed2004

Treatment of pulp mill and oil sands industrial wastewaters by the partial spray freezing process.

The spray freezing process, a natural freezing technology, was used to treat pulp mill effluent and oil sands tailings pond water. The wastewaters froze partially or completely (i.e. with or without runoff generation) during the spraying operation. Greater than 60% impurity reduction in the spray ice was obtained when 30% of the total volume of the sprayed water was released as runoff. Organic and inorganic contaminants were rejected with different efficiencies. The impurities were uniformly distributed within the ice columns when the spray ice was produced without generating any runoff. While a significant increase in impurity concentration was observed at the bottom of the ice formed with runoff production. The spray freezing process is an effective and economically feasible technique for wastewater treatment in cold regions. To achieve higher impurity removal efficiency, the wastewater should be only partially frozen during spray ice production.

Freezing↗
PubMed2004

Ozonation of biologically treated landfill leachate: treatment efficiency and molecular size distribution analysis.

A wide range of ozone doses were used to oxidise biologically treated Clover Bar landfill leachate, and results were compared to those of a previous study that involved aged raw leachate. The COD, BOD5 and colour of the leachate were measured prior to and after ozonation. The molecular size distribution of each sample was also analysed. At an ozone dose of 2.6 g l(-1), COD and colour removal efficiencies were 47% and 91%, respectively, while BOD5 increased by 324%. The BOD5/COD ratio increased from 0.02 prior to ozonation to approximately 0.2 following an ozone dose of 5.5 g l(-1), indicating improvement in the leachate biodegradability. Ozonation was very effective in reducing the concentration of organic compounds with molecular weights larger than 300 Dalton. After ozonation, no new peaks representing small molecules were observed. Relationships representing ozone dose, COD, BOD5, and the BOD5/COD ratio, as functions of total peak area of molecular size distribution, were determined.

Environmental Monitoring↗
PubMed2004

Aciclovir or ganciclovir universal prophylaxis of cytomegalovirus infection in liver transplantation: an economic analysis.

BACKGROUND: Cytomegalovirus (CMV) following orthotopic liver transplantation can result in significant morbidity and mortality. Prophylaxis with oral aciclovir (ACV) or ganciclovir (GCV) for all transplant recipients (universal prophylaxis) may be beneficial, but which agent is more cost-effective is unknown. METHODS: A single centre, retrospective study of all patients who had OLT at the Western Australian Liver Transplantation Service was performed. Patients received ACV from 1992 to 1998, and GCV from 1999 to 2001. A comparative cost-effectiveness analysis for the two groups was performed based on the mean total cost of the number of cases of CMV infection and disease as the clinical end-point. RESULTS: The ACV group comprised of 55 patients and there were 24 in the GCV group. The incidence of CMV disease was 7% and 4% for the ACV and GCV groups, respectively (P > 0.05). For CMV infection it was 16% and 8%, respectively (P > 0.05). GCV prevented more cases of CMV infection and disease than ACV but at an incremental cost of dollars A20,000 (dollars US10,172) per case prevented. Overall, ACV was more cost-effective than GCV by dollars A2200 (dollars US1119) per person. The cost benefit of ACV was derived principally through a reduced pharmaceutical cost. Both agents were well tolerated without development of antiviral resistance. CONCLUSIONS: Universal prophylaxis of CMV infection-following liver transplantation with aciclovir is more cost-effective than with ganciclovir.

Acyclovir↗
PubMed2003

Antibody-dependent enhancement of Murray Valley encephalitis virus virulence in mice.

Enhancement of flavivirus infection in vitro in the presence of subneutralizing concentrations of homologous or heterologous antiserum has been well described. However, the importance of this phenomenon in the enhancement of flavivirus infection in vivo has not been established. In order to study antibody-mediated enhancement of flavivirus infection in vivo, we investigated the effect of passive immunization of mice with Japanese encephalitis virus (JE) antiserum on the outcome of infection with Murray Valley encephalitis virus (MVE). We show that prior treatment of mice with subneutralizing concentrations of heterologous JE antiserum resulted in an increase in viraemia titres and in mortality following challenge with wild-type MVE. Our findings support the hypothesis that subneutralizing concentrations of antibody may enhance flavivirus infection and virulence in vivo. These findings are of potential importance for the design of JE vaccination programs in geographic areas in which MVE co-circulates. Should subneutralizing concentrations of antibody remain in the population following JE vaccination, it is possible that enhanced disease may be observed during MVE epidemics.

Animals↗
PubMed2002

Application of a dynamic 2-D mixing model to assess the impact of chemical spills on raw water quality.

A non-steady-state two-dimensional river mixing model was used in conjunction with the Hec-2 water surface profile model to develop a "spill model" by which impact of chemical spills on the raw water quality of a water treatment plant can be assessed. The dynamic 2-D mixing model was applied to the North Saskatchewan River between Devon and the Rossdale Water Treatment Plant in Edmonton, Alberta. Hec-2 compatible data were used to estimate surface water elevations for the river under varying discharge conditions. To ensure accurate estimates of the surface water elevations, Hec-2 was calibrated using the high water mark data, which were collected by the Alberta Environment during the 1986 Edmonton flood. The calibrated Hec-2 model was then used to estimate surface water elevations using flowrates from 50 m3 s1 to 5000 m3 s1. The dynamic mixing model was modified so it could utilize the cross sectional geometry data and estimated water surface elevations obtained from the Hec-2 model. Several input files were prepared for the mixing model, representing various discharge conditions of the river. A user-friendly interface was developed allowing operators easy manipulation of the mixing model. Provisions were also incorporated to allow input of required spill data such as the location of the spill, types of chemicals involved, and the magnitude of the spill. The two-dimensional mixing model estimates the concentration of a conservative chemical(s) at any point downstream of the chemical spill.

Accidents↗
PubMed2002

Modeling a full-scale primary sedimentation tank using artificial neural networks.

Modeling the performance of full-scale primary sedimentation tanks has been commonly done using regression-based models, which are empirical relationships derived strictly from observed daily average influent and effluent data. Another approach to model a sedimentation tank is using a hydraulic efficiency model that utilizes tracer studies to characterize the performance of model sedimentation tanks based on eddy diffusion. However, the use of hydraulic efficiency models to predict the dynamic behavior of a full-scale sedimentation tank is very difficult as the development of such models has been done using controlled studies of model tanks. In this paper, another type of model, namely artificial neural network modeling approach, is used to predict the dynamic response of a full-scale primary sedimentation tank. The neuralmodel consists of two separate networks, one uses flow and influent total suspended solids data in order to predict the effluent total suspended solids from the tank, and the other makes predictions of the effluent chemical oxygen demand using data of the flow and influent chemical oxygen demand as inputs. An extensive sampling program was conducted in order to collect a data set to be used in training and validating the networks. A systematic approach was used in the building process of the model which allowed the identification of a parsimonious neural model that is able to learn (and not memorize) from past data and generalize very well to unseen data that were used to validate the model. Theresults seem very promising. The potential of using the model as part of a real-time process control system isalso discussed.

Forecasting↗
PubMed2002

Theoretical analysis and experimental verification of ozone mass transfer in bubble columns.

Modeling the performance of ozone bubble columns for water and wastewater treatment was carried out using two models: the axial dispersion model and the back flow cell model (BFCM). Expressing these two models in terms of dimensionless operating parameters allowed the examination of their predictions of dissolved ozone, gaseous ozone, and superficial gas velocity profiles along the bubble column height. Pilot-scale experimental data from the literature were used to test the models' predictions of the dissolved ozone profiles for water treatment applications. The models have demonstrated reliable predictions of the dissolved ozone concentration profiles along the bubble column for water treatment conditions in the co-current and the counter-current flow modes. The axial dispersion model and the back flow cell model have proved to be adequate for describing the performance of ozone bubble columns, however, the BFCM was easier to formulate and solve.

Gases↗
PubMed2002

The diagnosis of chlamydia, gonorrhoea, and trichomonas infections by self obtained low vaginal swabs, in remote northern Australian clinical practice.

OBJECTIVE: To examine the diagnostic performance of self obtained low vaginal swabs (SOLVS) and polymerase chain reaction (PCR) techniques in the diagnosis of Chlamydia trachomatis (CT), Neisseria gonorrhoeae (NG), and Trichomonas vaginalis (TV) infection in a variety of clinical practice settings in remote north western Australia. DESIGN: A cross sectional field study of microbiological collection techniques in women undergoing gynaecological investigation in remote settings performed by a variety of practitioner types over 10 months. PARTICIPANTS AND SETTING: 349 women from remote towns and communities in the Kimberley region of north west Western Australia having gynaecological examinations for clinical reasons, well women screening, antenatal screening, and sexual health examinations. RESULTS: The overall prevalence of infection in the study population based on any positive conventional sample was 9.2%, 7.6%, and 16.1% for CT, NG, and TV respectively. The detection rates for CT and NG by SOLVS were 89% and 96% respectively, compared with 79% and 91% for endocervical swabs and 79% and 83% for first void urine. SOLVS had a sensitivity of 93% for TV detection, equal to that of clinician obtained low vaginal swabs. None of these differences reached statistical significance. A combination of SOLVS and first void urine detected 96% of the CT cases, 100% of the NG cases, and 96% of TV cases. CONCLUSIONS: Self obtained low vaginal swabs are an acceptable, simple and sensitive diagnostic sample for the detection of CT, NG, and TV, and have particular applications in remote clinical practice and as a screening technique.

Adult↗
PubMed2002

Model-based advanced process control of coagulation.

The drinking water treatment industry has seen a recent increase in the use of artificial neural networks (ANNs) for process modelling and offline process control tools and applications. While conceptual frameworks for integrating the ANN technology into the real-time control of complex treatment processes have been proposed, actual working systems have yet to be developed. This paper presents development and application of an ANN model-based advanced process control system for the coagulation process at a pilot-scale water treatment facility in Edmonton, Alberta, Canada. The system was successfully used to maintain a user-defined set point for effluent quality, by automatically varying operating conditions in response to changes in influent water quality. This new technology has the potential to realize significant operational cost saving for utilities when applied in full-scale applications.

Alberta↗
PubMed2001

Studies on the resistance/reactivation of Giardia muris cysts and Cryptosporidium parvum oocysts exposed to medium-pressure ultraviolet radiation.

The ex vivo and in vivo reactivation of Giardia muris cysts and Cryptosporidium parvum oocysts after exposure to different doses of ultraviolet (UV) radiation was determined using animal infectivity. The infectivity of UV-treated parasites stored for 1-4 days (G. muris) or 1-17 days (C. parvum) at room temperature in the dark was similar to that of organisms administered immediately after UV treatment, indicating that the parasites did not reactivate ex vivo. In contrast, we observed in vivo reactivation of G. muris in three of seven independent animal infectivity experiments, when parasites were treated with relatively low doses of medium-pressure UV (<25 mJ/cm(2)). Our observations indicate that G. muris cysts and C. parvum oocysts exposed to medium-pressure UV doses of 60 mJ/cm(2) or higher did not exhibit resistance to and/or reactivation following treatment. This suggests that when appropriate doses of UV are used, significant and permanent inactivation of these parasites may be achieved.

Animals↗