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Biomedical subjects

S K Ong

Publications and source records attributed to S K Ong.

12 recordsLinked to original sources
PubMed2003

Cold weather nitrogen removal deficiencies of aerated lagoons.

Aerated lagoons are widely used throughout the state of Iowa, USA by small communities, due to their relatively low costs and maintenance requirements. Although aerated lagoons were not initially designed for ammonia removal many of these facilities have been assigned effluent ammonia limits in recent years Since widespread monitoring began, it has been found that aerated lagoons tend to have problems with high effluent ammonia concentrations during the winter and early spring. This study collected and analyzed data from 10 aerated lagoon facilities in central Iowa to determine the factors governing cold weather nitrogen removal in aerated lagoons. The factors found to affect performance were temperature and detention time. None of the following factors were found to significantly affect performance: dissolved oxygen (DO), pH, CBOD5 loading, total nitrogen loading, aerated cell depth and design standards governing the design. It should be noted that DO and pH were relatively constant and generally favorable for nitrification. Increased mixing energy was correlated with poorer performance, but this correlation may not be correct as the expected benefit of more intense mixing conditions may masked by the overwhelming benefit of long detention times.

Ammonia↗
PubMed2001

Air sparging effectiveness: laboratory characterization of air-channel mass transfer zone for VOC volatilization.

Air sparging in conjunction with soil vapor extraction is one of many technologies currently being applied for the remediation of groundwater contaminated with volatile organic compounds (VOCs). Mass transfer at the air-water interface during air sparging is affected by various soil and VOC properties. In this study with a single air-channel apparatus, mass transfer of VOCs was shown to occur within a thin layer of saturated porous media next to the air channel. In this zone, the VOCs were found to rapidly deplete during air sparging resulting in a steep concentration gradient while the VOC concentration outside the zone remained fairly constant. The sizes of the mass transfer zone were found to range from 17 to 41 mm or 70d(50) and 215d(50) (d(50)=mean particle size) for low organic carbon content media (<0.01% OC). The size of the mass transfer zone was found to be proportional to the square root of the aqueous diffusivity of the VOC, and was affected by the mean particle size, and the uniformity coefficient. Effects of the volatility of the VOCs as represented by the Henry's law constants and the airflow rates on the mass transfer zone were found to be negligible but VOC mass transfer from air-water interface to bulk air phase seems to play a role. A general correlation for predicting the size of the mass transfer zone was developed. The model was developed using data from nine different VOCs and verified by two other VOCs. The existence of the mass transfer zone provides an explanation for the tailing effect of the air phase concentration under prolonged air sparging and the rebound in the VOC air phase concentration after the sparging system is turned off.

Air Movements↗
PubMed2001

Use of solvents to enhance PAH biodegradation of coal tar-contaminated soils.

Bioremediation of coal tar-contaminated soils containing polycyclic aromatic hydrocarbons (PAHs) is highly challenging because of the low solubility and strong sorption properties of PAHs. Five coal tar-contaminated soils from former manufactured gas plant (MGP) sites were pretreated with two solvents, acetone and ethanol to enhance the bioavailability of the PAH compounds. The biodegradation of various PAHs in the pretreated soils was assessed using soil slurry reactors. The total PAH degradation rates for soils pretreated with solvents were estimated to be about two times faster than soils that were not pretreated with solvents. For example, the total PAH first order degradation rate constants were 0.165+/-0.032, 0.147+/-0.020, and 0.076+/-0.009 day(-1) for Vandalia (EXC) soil that were pretreated with acetone, ethanol, and with no solvent, respectively. A distinctive advantage for soils pretreated with solvents was the enhanced removal of 5-ring PAH compounds such as benzo(a)pyrene and to a limited extent 4-ring compounds such as chrysene. Even for soils with 3.5% or more organic carbon content (two soils out of five), the degradation rate constants of chrysene were found to be two times faster than soils that were not pretreated. The degradation rate constants of benzo(a)pyrene were enhanced by 2-6 times for all five contaminated soils that were pretreated with solvents. To further elucidate trends that control the solvent treatment, the percent improvement in degradation rate constants (100 x rate constants for pretreated soils/rate constants for non-treated soils) for 16 PAHs were found to correlate well with the PAH partition coefficients (K(oc)). Except for phenanthrene and the clay fraction of the soil, correlations between the percent improvement in degradation rates constants and several physical properties of the soils were poor and sporadic. This implies that the enhancement in PAH availability using solvent treatment was driven by the distribution of the PAHs between the solvent and the adsorbed PAHs.

Adsorption↗
PubMed2000

Immunoglobulin D multiple myeloma in our hospital--a rare occurrence.

Immunoglobulin (Ig) D multiple myeloma is a rare presentation, usually with an aggressive course and a poorer prognosis. It accounts for about 1-2% of newly diagnosed mulitple myeloma patients. Due to its rarity, reports on Ig D multiple myeloma are limited in the literature. We therefore present 4 cases of Ig D multiple myeloma in our hospital over a period of 8 years between 1990 to 1998. The average age of presentation of our patients was 44 years old with a female preponderance. Common presenting symptoms were appetite and weight loss and bone pain. Two patients presented with neurological symptoms and 2 with renal impairment. Three patients had an associated lambda paraproteinaemia and the fourth had a kappa paraproteinaemia. A common finding in Ig D myeloma is a small or no spike seen on serum electrophoresis together with heavy Bence Jones proteinuria. A review of the literature on Ig D myeloma is also presented.

Adult↗
PubMed1997

Pre-operative chemotherapy for squamous cell carcinoma of the oesophagus: do histological assessment and p53 overexpression predict chemo-responsiveness?

Pre-operative chemotherapy is increasingly used in the treatment of oesophageal carcinoma. However, no features have been identified which can reliably predict a positive response to chemotherapy. The aim of this study was to examine whether histological features and p53 overexpression could predict such response. Prechemotherapy endoscopic biopsies from 55 patients, who subsequently completed two courses of chemotherapy followed by surgical resection, were studied. Patients were classified into responders and non-responders according to clinical and pathological findings. Pathological features of the endoscopic biopsies examined included adequacy of the tumour tissue, histological grade, degree of keratinisation, histologic patterns, mitotic rates and nuclear pleomorphism. Biopsy specimens were also tested for p53 overexpression using p53 protein specific mouse monoclonal antibody DO-7 on paraffin sections. Histologic features and p53 expression were correlated to chemoresponsiveness. 76% (42 of 55) of patients had sufficient biopsy tissue for assessment. Response to chemotherapy was evident in 64% (n = 27) of patients. None of the non-responders had tumours with high-grade nuclear pleomorphism compared with 37% (10 of 27) of responders (P = 0.01). All patients with high-grade nuclear pleomorphism responded to chemotherapy. No significant differences were found between the responders and non-responders with respect to tumour differentiation (P = 0.7), degree of keratinisation (P = 0.3) and mitotic rates (P = 0.8). Overall, p53 overexpression was noted in 67% (28 of 42) of patients. This was more prevalent in non-responders (12/15) compared to responders (16/27), but this was not statistically significant (P = 0.08). The degree of p53 overexpression had no significant relationship with responsiveness to chemotherapy. High-grade nuclear pleomorphism, identified on pretreatment biopsy specimens, correlated with response to chemotherapy, whereas p53 overexpression did not correlate with response. Improved tissue sampling and further investigations should be done so that the assessment of prechemotherapeutic endoscopic biopsies can have significant impact on clinical decision making.

Aged↗
PubMed1992

A rapid in situ respiration test for measuring aerobic biodegradation rates of hydrocarbons in soil.

An in situ test method to measure the aerobic biodegradation rates of hydrocarbons in contaminated soil is presented. The test method provides an initial assessment of bioventing as a remediation technology for hydrocarbon-contaminated soil. The in situ respiration test consists of ventilating the contaminated soil of the unsaturated zone with air and periodically monitoring the depletion of oxygen (O2) and production of carbon dioxide (CO2) over time after the air is turned off. The test is simple to implement and generally takes about four to five days to complete. The test was applied at eight hydrocarbon-contaminated sites of different geological and climatic conditions. These sites were contaminated with petroleum products or petroleum fuels, except for two sites where the contaminants were primarily polycyclic aromatic hydrocarbons. Oxygen utilization rates for the eight sites ranged from 0.02 to 0.99 percent O2/hour. Estimated biodegradation rates ranged from 0.4 to 19 mg/kg of soil/day. These rates were similar to the biodegradation rates obtained from field and pilot studies using mass balance methods. Estimated biodegradation rates based on O2 utilization were generally more reliable (especially for alkaline soils) than rates based on CO2 production. CO2 produced from microbial respiration was probably converted to carbonate under alkaline conditions.

Aerobiosis↗
PubMed1982

Termination of pregnancy in cases of intrauterine fetal death, missed abortion, molar and anencephalic pregnancy with intramuscular administration of 2a 2b dihomo 15(S) 15 methyl PGF2 alpha methyl ester--a multicentre study.

2a 2b dihomo 15(S) 15 methyl PGF2 alpha methyl ester (dihomo 15 me PGF2 alpha) in intramuscular doses of 0.5 mg 8 hourly was used in 631 patients with abnormal intrauterine pregnancy comprising 282 cases of intrauterine fetal death, 233 cases of missed abortion, 34 and 82 cases respectively anencephalic and molar pregnancies. The study was carried out as a collaborative project between the University Departments of Obstetrics and Gynaecology in Singapore (Singapore), Medan (Indonesia) and Kuala Lumpur (Malaysia) during the period June 1974 and November 1979. Six hundred patients (95.1%) aborted or delivered in a mean time of 11.3 hours (S.D. +/- 7.0) with an average of 1.8 injections of the prostaglandin analogue per patient. Side effects included vomiting (23.6%; mean 0.45 episodes per patient), diarrhoea (44.4%; mean 1.00 episode per patient), cold and shivering (11.9%) and pyrexia (12.4%). One patient sustained a cervical laceration which did not require repair. There were no complications.

Abortion, Missed↗
PubMedDate not supplied

African Burkitt's lymphoma: a new perspective.

High titres of antibody to Epstein-Barr virus (EBV) late genes identify individuals at risk of developing endemic Burkitt's lymphoma (eBL). Viral lytic cycle early and intermediate-early gene expression in BL is associated with a favourable tumour response to chemotherapy. Our study investigated whether serological data identifying antibody expression to zta, a viral function that activates lytic-cycle gene expression, correlate with expression of its gene in tumours, and could have prognostic value. Studies on 10 Malawian patients, with presumed BL on clinical grounds, showed good correlations, suggesting that serum antibody responses might predict treatment responsiveness. The results with 1 patient were particularly striking. When admitted in January 1998, prognosis was poor as he was unable to walk, and had tumour cells, characteristic of stage IV disease, in his bone marrow. Laboratory investigations showed particularly high levels both of serum zta antibodies and of gene expression in his tumour. Follow-up confirmed him alive 6 months after hospital discharge. Among the EBV-positive cases, 2 were ultimately diagnosed as rhabdomyosarcoma, a tumour not previously associated with this virus. The findings from this small study, if confirmed, should have value for future BL management in resource-poor parts of the world.

Antibodies, Viral↗
PubMedDate not supplied

Registration based on projective reconstruction technique for augmented reality systems.

In AR systems, registration is one of the most difficult problems currently limiting their application. In this paper, we propose a simple registration method using projective reconstruction. This method consists of two steps: embedding and tracking. Embedding involves specifying four points to build the world coordinate system on which a virtual object will be superimposed. In tracking, a projective reconstruction technique is used to track these four specified points to compute the model view transformation for augmentation. This method is simple, as only four points need to be specified at the embedding stage and the virtual object can then be easily augmented onto a real scene from a video sequence. In addition, it can be extended to a scenario using the projective matrix that has been obtained from previous registration results using the same AR system. The proposed method has three advantages: 1) It is fast because the linear least square method can be used to estimate the related matrix in the algorithm and it is not necessary to calculate the fundamental matrix in the extended case. 2) A virtual object can still be superimposed on a related area even if some parts of the specified area are occluded during the whole process. 3) This method is robust because it remains effective even when not all the reference points are detected during the whole process, as long as at least six pairs of related reference points correspondences can be found. Some experiments have been conducted to validate the performance of the proposed method.

Algorithms↗
PubMedDate not supplied

Registration using natural features for augmented reality systems.

Registration is one of the most difficult problems in augmented reality (AR) systems. In this paper, a simple registration method using natural features based on the projective reconstruction technique is proposed. This method consists of two steps: embedding and rendering. Embedding involves specifying four points to build the world coordinate system on which a virtual object will be superimposed. In rendering, the Kanade-Lucas-Tomasi (KLT) feature tracker is used to track the natural feature correspondences in the live video. The natural features that have been tracked are used to estimate the corresponding projective matrix in the image sequence. Next, the projective reconstruction technique is used to transfer the four specified points to compute the registration matrix for augmentation. This paper also proposes a robust method for estimating the projective matrix, where the natural features that have been tracked are normalized (translation and scaling) and used as the input data. The estimated projective matrix will be used as an initial estimate for a nonlinear optimization method that minimizes the actual residual errors based on the Levenberg-Marquardt (LM) minimization method, thus making the results more robust and stable. The proposed registration method has three major advantages: 1) It is simple, as no predefined fiducials or markers are used for registration for either indoor and outdoor AR applications. 2) It is robust, because it remains effective as long as at least six natural features are tracked during the entire augmentation, and the existence of the corresponding projective matrices in the live video is guaranteed. Meanwhile, the robust method to estimate the projective matrix can obtain stable results even when there are some outliers during the tracking process. 3) Virtual objects can still be superimposed on the specified areas, even if some parts of the areas are occluded during the entire process. Some indoor and outdoor experiments have been conducted to validate the performance of this proposed method.

Algorithms↗
PubMedDate not supplied

Degradation and metabolite production of tylosin in anaerobic and aerobic swine-manure lagoons.

Watershed contamination from antibiotics is becoming a critical issue because of increased numbers of confined animal-feeding operations and the use of antibiotics in animal production. To understand the fate of tylosin in manure before it is land-applied, degradation in manure lagoon slurries at 22 degrees C was studied. Tylosin disappearance followed a biphasic pattern, where rapid initial loss was followed by a slow removal phase. The 90% disappearance times for tylosin, relomycin (tylosin D), and desmycosin (tylosin B) in anaerobically incubated slurries were 30 to 130 hours. Aerating the slurries reduced the 90% disappearance times to between 12 and 26 hours. Biodegradation and abiotic degradation occur, but strong sorption to slurry solids was probably the primary mechanism of tylosin disappearance. Dihydrodesmycosin and an unknown degradate with molecular mass of m/z 934.5 were detected. Residual tylosin remained in slurry after eight months of incubation, indicating that degradation in lagoons is incomplete and that residues will enter agricultural fields.

Animal Husbandry↗