Biomedical subjects

Michael Rodgers

Publications and source records attributed to Michael Rodgers.

10 recordsLinked to original sources

PubMed2006

Biofilm growth and characteristics in an alternating pumped sequencing batch biofilm reactor (APSBBR).

A novel biofilm reactor-alternating pumped sequencing batch biofilm reactor (APSBBR)-was developed to treat synthetic dairy wastewater at a volumetric chemical oxygen demand (COD) loading rate of 487 g COD m(-3) d(-1) and an areal loading rate of 5.4 g COD m(-2) d(-1). This biofilm reactor comprised two tanks, Tanks 1 and 2, with two identical plastic biofilm modules in each tank. The maximum volume of bulk fluid in the two-tank reactor was the volume of one tank. The APSBBR was operated as a sequencing batch biofilm reactor with five operational phases-fill (25 min), anoxic (9 h), aerobic (9 h), settle (6 h) and draw (5 min). The fill, anoxic, settle and draw phases occurred in Tank 1. In the aerobic phase, the wastewater was circulated between the two tanks with centrifugal pumps and aeration was mainly achieved through oxygen absorption by micro-organisms in the biofilms when they were exposed to the air. In this paper, the biofilm growth and characteristics in the APSBBR were studied in a 98-day laboratory-scale experiment. During the course of the study, it was found that the biofilm thickness (delta) in Tank 1 ranged from 1.2 to 7.2 mm and that in Tank 2 from 0.5 to 2.2 mm; the biofilm growth against time (t) can be simulated as delta=0.07t0.99 (R2 = 0.97, P = 0.002) in Tank 1 and delta = 0.08t0.66 (R2 = 0.81, P = 0.04) in Tank 2. The biomass yield coefficient, Y, was 0.18 g volatile solids (VS) g(-1) COD removal. The biofilm density in both tanks, X, decreased as the biofilm thickness increased and can be correlated to the biofilm thickness, delta .

Absorption↗

PubMed2006

Small-scale domestic wastewater treatment using an alternating pumped sequencing batch biofilm reactor system.

An alternating pumped sequencing batch biofilm reactor (APSBBR) system was developed to treat small-scale domestic wastewater. This laboratory system had two reactor tanks, Reactor 1 and Reactor 2, with two identical plastic biofilm modules in each reactor. Reactor 1 of the APSBBR had five operational phases--fill, anoxic, aerobic, settle and draw. In the aerobic phase, the wastewater was circulated between the two reactor tanks with centrifugal pumps and aeration was mainly achieved through oxygen absorption by microorganisms in the biofilms when they were exposed to the air. This paper details the performance of the APSBBR system in treating synthetic domestic wastewater over 18 months. The effluent from the APSBBR system satisfied the European Wastewater Treatment Directive requirements, with respect to COD, ammonium-nitrogen and suspended solids. The biofilm growth in the two reactor tanks was different due to the difference in substrate loadings and growth conditions.

Biofilms↗

PubMed2006

Denitrification of a nitrate-rich synthetic wastewater using various wood-based media materials.

This laboratory study examined the use of various wood materials as a carbon source in horizontal flow filters to denitrify nitrate-nitrogen (NO3-N) from a synthetic wastewater. The filter materials were: sawdust (Pinus radiata), sawdust and soil, sawdust and sand, and medium-chip wood chippings and sand. Two influent concentrations of NO3-N, 200 mg L(-1) and 60 mg L(-1), loaded at 2.9 to 19.4 mg NO3-N kg(-1) mixture, were used. The horizontal flow filter with a wood chippings/sand mixture and an influent NO3-N concentration of 60 mg L(-1), which operated over a study duration of 166 days, performed best, yielding a 97% reduction in NO3-N at steady-state conditions.

Filtration↗

PubMed2004

Biochemical and physiological properties of the DNA binding domain of AraC protein.

Intact AraC protein is poorly soluble and difficult to purify, whereas its dimerization domain is the opposite. Unexpectedly, the DNA binding domain of AraC proved also to be soluble in cells when overproduced and is easily purified to homogeneity. The DNA binding affinity of the DNA binding domain for its binding site could not be measured by electrophoretic mobility shift because of its rapid association and dissociation rates, but its affinity could be measured with a fluorescence assay and was found to have a dissociation constant of 1 x 10(-8)M in 100 mM KCl. The binding of monomers of the DNA binding domain to adjacent half-sites occurs without substantial positive or negative cooperativity. A simple analysis relates the DNA binding affinities of monomers of DNA binding domain and normal dimeric AraC protein.

AraC Transcription Factor↗

PubMed2004

Biological nitrogen removal using a vertically moving biofilm system.

In this study, a biological nitrogen removal process using a vertically moving biofilm system was used to treat synthetic wastewater. The process consisted of two pre-denitrification units, one combined carbonaceous removal/nitrification unit and three nitrification units. Each unit employed biofilm growth on a plastic module. In the anoxic units, the modules were vertically moved, while always submerged, in the bulk fluid; in the aerobic units, they were moved vertically up into the air and down into the wastewater. Three small-scale experiments, having different recirculation ratios and influent loadings, were conducted at a controlled temperature of 11 degrees C. In this system, the carbonaceous removal efficiency was in the range of 94-96% and the total nitrogen removal efficiency was 77-82%. In the anoxic units, the denitrification efficiency was 94-98% and the areal denitrification rates, based on the surface area of the biofilm modules, were 2.9-3.8 g NO3-N/(m2 x d). The nitrification efficiency occurring in the aerobic tanks was up to 95% and the maximum areal ammonium removal rates were 1.3-1.8 g NH4-N/(m2 x d).

Bacteria↗

PubMed2004

Mixing characteristics and whey wastewater treatment of a novel moving anaerobic biofilm reactor.

A novel moving anaerobic biofilm reactor was used to treat whey wastewater. In this process, biofilm was grown on a plastic biofilm media module, which was vertically moved up and down in the bulk fluid. The objectives of the study were to investigate the mixing and performance characteristics of the new process in treating whey wastewater. The mixing efficiency was indicated by a dispersion number, D(L)/uL. D(L)/uL was up to 1.34, showing that the anaerobic reactor can be taken as a completely mixed reactor. At mesophilic conditions (35+/-2 degrees C), the admissible volumetric COD loading rate up to 11.6kg COD m(-3) day(-1) was achieved with the COD removal efficiency of 89% and the hydraulic retention time (HRT) of 1 day. When the HRT was 0.6 days, the volumetric COD loading rate was 15.2 kg COD m(-3) day(-1), but COD removal efficiency decreased to 81%. The percentage of methane (CH4) in the biogas was 63% on average and the yield of methane was 333.4 L CH4 kg(-1) COD removal at ambient conditions.

Bacteria, Anaerobic↗

PubMed2004

Laparoscopy in the management of colorectal cancer metastatic to the liver.

BACKGROUND: This investigation was undertaken to define the value of laparoscopy in the staging of patients with colorectal carcinoma metastatic to the liver. METHODS: The clinical details of 59 consecutive patients with colorectal liver metastases undergoing laparoscopy prior to planned hepatectomy were entered prospectively on a computerized database. All patients were staged preoperatively with thin slice (5-7 mm) helical computed tomography chest, abdomen and pelvis. Synchronous metastases were defined as those found during, or on imaging carried out within 1 month of, colorectal resection. Criteria for laparoscopic unresectability were: (i) histologically proven extrahepatic disease; (ii) bilateral inflow or outflow involvement; (iii) the presence of cirrhosis in patients requiring an extended resection (lobectomy or greater); or (iv) hepatic metastases involving more than six hepatic segments. RESULTS: In 24 patients with synchronous metastases (median age 65 years, range 32-81 years) all were resectable on laparoscopic criteria, of whom 21 were resected. Extrahepatic disease was found at laparotomy in three patients. In 35 patients with metachronous metastases (median age 64 years, range 32-81 years) laparoscopy could not be performed in five patients because of adhesions, and three patients were deemed unresectable on laparoscopic criteria. Of the remaining 27 patients, 25 underwent resection while two proved unresectable. Overall eight of 54 evaluable patients had unresectable disease and laparoscopy correctly identified three patients. CONCLUSIONS: Following computed tomography scan, 15% of patients with metastatic colorectal carcinoma will be found to have unresectable disease. Laparoscopy will identify approximately half. Laparoscopy is of no greater value in staging synchronous versus metachronous metastases.

Adult↗

PubMed2003

Ammonium removal using a vertically moving biofilm system.

Ammonium-nitrogen (NH4-N) removal using a vertically moving biofilm system was investigated at a temperature of 11 degrees C. The biofilms in this process were grown on biofilm modules, consisting of high surface area plastic media, which were vertically and repeatedly moved up into the air and down into the wastewater. The maximum NH4-N removal efficiency was up to 98.8% and the areal NH4-N removal rates, based on the surface area of the biofilm modules, were within the range of 0.68-1.94 g NH4-N m(-)2 day(-1). The kinetics of ammonium removal occurring after carbonaceous oxidation was completed can be simulated by using a zero-order empirical model. The ammonium removal rate was found to be proportional to the square root of the mass of biofilms on the modules. Monitoring DO concentrations in the bulk fluid showed that the vertically moving biofilm system possessed good aeration efficiency.

Biofilms↗

PubMed2002

Gall bladder cancer, extrahepatic bile duct cancer and ampullary carcinoma in New Zealand: Demographics, pathology and survival.

INTRODUCTION: The aim of present paper was to document the incidence of gall bladder cancer, cancer of the extrahepatic bile ducts and ampullary carcinoma in New Zealand. METHODS: Data were collected from the New Zealand Cancer Registry from 1980 to 1997 and combined with national census statistics to give crude and age standardized incidence rates. RESULTS: Over the 18-year study period, 226 carcinomas of the ampulla of Vater, 608 gall bladder cancers, and 486 extrahepatic cholangiocarcinomas were registered. The age standardized incidence rates for gall bladder carcinoma in all New Zealanders were 0.41/100 000 in men and 0.74/100 000 in women. The age standardized incidence rates for gall bladder cancer in Maori were 1.49/100 000 in Maori men and 1.59/100 000 in Maori women. The corresponding age standardized incidence rates for extrahepatic bile duct cancers were 0.67/100 000 in men and 0.45/100 000 in women. There were insufficient cases to calculate an age standardized incidence in Maori or Pacific Islanders. For carcinoma of the ampulla, the age standardized rates were 0.34/100 000 in men and 0.25/100 000 in women. There were insufficient cases to calculate an age standardized incidence rate for Maori or Pacific Islanders. When histology was defined adenocarcinoma was the most common form of cancer occurring in 66% of gall bladder cancers, 91% of extrahepatic bile duct cancers and 70% of ampullary cancers. Most tumours were advanced at presentation with regional or distant metastases present in 72% of gall bladder cancers, 63% of extrahepatic bile duct cancers and 69% of ampullary tumours at diagnosis. Survival was poor with median survivals of 86 days, 151 days and 440 days recorded for gall bladder cancer, extrahepatic bile duct cancer and ampullary cancer, respectively. CONCLUSIONS: The demographic profile, pathology and survival of patients with gall bladder cancer, extrahepatic bile duct cancer and ampullary carcinoma are similar in New Zealand to that of other Western countries. However New Zealand Maori have a relatively high incidence of gall bladder cancer, and the incidence is equal in both Maori men and women, while cancers of the extra-hepatic bile duct and ampulla of Vater are rare in Maori. In comparison, cancers of the gall bladder, extrahepatic bile ducts and ampulla are rare in Pacific Islanders.

Adenocarcinoma↗

PubMedDate not supplied

Solitary necrotic nodule of the liver: a riddle that is difficult to answer.

Solitary necrotic nodule of the liver is an unusual lesion that is often an incidental finding on abdominal imaging, intraoperative examination, or post mortem. Most reported cases of solitary necrotic nodule have been in males, and over three quarters of these lesions have occurred in the right lobe of the liver. Pathologically, solitary necrotic nodule is a benign lesion characterized by a completely necrotic core that is often partly calcified, surrounded by a dense hyalinized fibrous capsule containing elastin fibres. The ultrasound appearance of solitary necrotic nodule is usually of a "target" lesion with a hyperechoic center, while on CT scan they appear as non-enhancing hypodense lesions that are typical of metastatic adenocarcinoma or peripheral cholangiocarcinoma. The impression of malignancy is further enforced with the finding of necrotic cellular material on biopsy and the macroscopically hard and "gritty" nature of the nodules. Currently, permanent histopathology of solitary necrotic nodules is the only accurate method of diagnosis. However, solitary necrotic nodules are usually of a bilobed or lobulated shape that is unusual for malignant liver lesions, and they often lie in close proximity to hepatic inflow structures. Solitary necrotic nodule should be suspected in liver lesions with this configuration, location, and on a biopsy showing a large amount of necrosis.

Adult↗