Search PubMed⌕ Search

Biomedical subjects

P Pearce

Publications and source records attributed to P Pearce.

At least 19 recordsLinked to original sources
PubMed2007

Biomass effects on oxygen transfer in membrane bioreactors.

Ten biomass samples from both municipal and industrial pilot and full scale submerged membrane bioreactors (MBRs) with mixed liquor suspended solids concentrations (MLSS) ranging from 7.2 to 30.2g L(-1) were studied at six air-flow rates (0.7, 1.3, 2.3, 3, 4.4 and 6m(3)m(-3)h(-1)). Statistical analyses were applied to identify the relative impacts of the various bulk biomass characteristics on oxygen transfer. Of the biomass characteristics studied, only solids concentration (correlated with viscosity), the carbohydrate fraction of the EPS (EPS(c)) and the chemical oxygen demand (COD) concentration of the SMP (SMP(COD)) were found to affect the oxygen transfer parameters k(L)a(20) (the oxygen transfer coefficient) and alpha-factor. The relative influence on k(L)a(20) was MLSS>aeration>EPS(c)>SMP(COD) and on alpha-factor was MLSS>SMP(COD)>EPS(c)>aeration. Both k(L)a(20) and alpha-factor increased with increasing aeration and EPS(c) and decreased with increasing MLSS and SMP(COD). MLSS was found to be the main parameter controlling the oxygen transfer.

Biomass↗
PubMed2006

Ammonium removal from digested sludge liquors using ion exchange.

Liquors arising from the dewatering of digested sludge typically contain ammonium levels in the range 200-700mgl(-1) NH(4)(+)-N. These liquors are frequently recycled to the head of the wastewater treatment works (WwTW) untreated and can constitute >25% of the total nitrogen load entering the works at inlet. This paper investigates the use of a clay-based material, MesoLite, as an ion exchange medium for ammonium removal from recycle streams. Pilot-scale studies performed at Didcot WwTW, part of the Thames Water wastewater treatment network, indicate that MesoLite is highly selective for the ammonium ion. Results show that >95% of ammonium was removed from belt press liquors with an initial ammonium nitrogen concentration >600mgl(-1), with an overall ion exchange capacity >51g NH(4)(+)-Nkg(-1) medium and this resulted in an operating capacity in the range 27-36gNH(4)(+)-Nkg(-1).

Aluminum Silicates↗
PubMed2005

Occurrence and treatment trials of endocrine disrupting chemicals (EDCs) in wastewaters.

This study demonstrates that both synthetic and natural endocrine disrupting chemicals (EDCs) (e.g., bisphenol A, estrone and 17beta-estradiol) were found in the crude wastewaters from two wastewater treatment works (WwTWs). Conventional biological processes can lower EDCs concentrations to several tens to hundreds ngl(-1). Since natural EDCs (e.g., estrone and 17beta-estradiol) have biological activity and adverse impact on the environment at extremely low concentrations (several tens of ngl(-1)), further treatment after conventional biological processes is required. Preliminary trials with ferrate(VI) and electrochemical oxidation process demonstrated that both processes can effectively reduce EDCs to very low levels, ranging between 10 and 100ngl(-1), but the former is more effective than the latter to reduce COD concentration in wastewater for given studying conditions.

Benzhydryl Compounds↗
PubMed2005

A survey of endocrine disrupting chemicals in sewage and a preliminary treatment trial.

This paper demonstrates that synthetic endocrine disrupting chemicals (EDCs) (e.g. bisphenol-A) and natural EDCs (e.g. estrone and 17beta-estradiol) were found in the crude sewage from two sewage treatment works. Conventional biological processes can lower EDC concentrations to several hundred nanograms per litre. Because natural EDCs (e.g. estrone and 17beta1-estradiol) have biological activity and an adverse impact on the environment at extremely low concentrations (several tens of nanograms per litre), and because the existing wastewater/sewage treatment processes are not adequate to reduce natural EDC concentrations lower than 100 ng L(-1), further treatment after conventional biological processes is required. Preliminary trials with ferrate (VI) and electrochemical oxidation processes demonstrated that the former is more effective than the latter in reducing EDC concentrations, and that both the processes can effectively reduce EDCs to very low levels, ranging between 20 and 100 ng L(-1).

Benzhydryl Compounds↗
PubMed2004

Trickling filters for upgrading low technology wastewater plants for nitrogen removal.

Previous work through the 1990s in the Thames Water region in the UK has demonstrated the ability of the trickling filter process to produce fully nitrified effluents, reliably throughout the year. The original data used for the nitrification model derivations have been reanalysed, to investigate the degree of nitrogen removal across the process. Removals of total nitrogen ranging from 0% to over 50% were observed across the trickling filter process and calculated total nitrogen removals of 26-63% were obtained when primary treatment was included. The degree of nitrogen removal and biological denitrification (excluding cellular assimilation) was found to be strongly influenced by BOD load, irrigation velocity and media size. Regression models were produced which gave good predictive relationships for the data ranges used. The models produced worked for filters used with and without a recirculation of effluent nitrate which suggests that a significant degree of nitrification occurred in areas of high heterotroph activity (BOD removal). The simplicity and energy efficiency of the trickling filter process, combined with its capacity for full nitrification and partial denitrification, make the process attractive as a combined process used with pond systems in developing countries where nitrogen removal may be required. Some of these synergies have already been developed with the PETRO process in South Africa.

Filtration↗
PubMed2002

Potential phosphorus recovery by struvite formation.

Formation of struvite (MgNH4PO4 x 6H2O) at sewage treatment works can cause operational problems and decrease efficiency. Struvite has a commercial value and the controlled formation and recovery of it would be beneficial. A mass balance was conducted at full scale across the whole sewage treatment plant in order to identify a stream to conduct bench-scale struvite crystallisation studies. The most suitable stream was identified as the centrifuge liquors. The average flow of the liquor stream was 393 m3 d(-1) and the composition was as follows: 167 mg L(-1) phosphorus, 44 mg L(-1) magnesium, 615 mg L(-1) ammonium, 56 mg L(-1) calcium and 2580 mg L(-1) of alkalinity. The pH averaged at 7.6 and the stream had a predicted struvite precipitation potential of 140 mg L(-1). Struvite crystallisation occurred quickly during the trials, by raising the pH of the centrifuge liquors to 9.0 and dosing with magnesium. Up to 97% phosphorus removal as struvite was achieved. Struvite formation occurred when the molar ratio of magnesium:phosphorus was at least 1.05:1. Below this ratio phosphorus removals of 72% were observed, but not exclusively as struvite. Annual yields of struvite were calculated to be 42-100 tonnes a year, depending on the dose regime. Revenue from the sale of produced struvite could be between Pound Sterling8400 and Pound Sterling20,000 a year.

Costs and Cost Analysis↗
PubMed1995

Shigella isolates in stool.

A total of 447 Shigella strains were isolated from stool samples during 1989-1991. Of these 270 (60%) were from children. Among the different species and serotypes Sh. flexneri 60 (13.4%) and Sh. sonnei Phage 139 (65%) were the most frequently isolated strains. 154 (34.4%) strains were resistant to three and 179 (40%) to more than three antibiotics. Some strains of Shigella were found to be resistant to furazolidine and neomycin.

Adult↗
PubMed1994

Present status of the ovine gene map (Ovis aries); comparison with the bovine map (Bos taurus).

The status of the sheep map to the end of June 1993 is presented. Mapping information is available for a total of 107 loci comprising 16 anonymous DNA segments. This is an increase of 66 loci since 1990. No loci have been mapped on 10 of the 26 autosomes. Comparison of the cattle (350 loci) and sheep maps confirms their close evolutionary and genetic relationship and will reduce the effort required for their gene mapping.

Animals↗
PubMed1994

Steroid receptor binding and messenger RNA expression in fibroids from untreated and gonadotrophin-releasing hormone agonist pretreated women.

OBJECTIVE: The hypothesis of this study was that oestrogen may play a role in fibroid growth and that a lack of oestrogen may be the reason for gonadotrophin-releasing hormone agonist (GnRHa) induced fibroid shrinkage. Therefore our aims were (1) to investigate oestrogen receptor (ER) and progesterone receptor (PR) binding in fibroids and myometrium from untreated women and in fibroids from GnRHa pretreated women, (2) to evaluate the mRNA expression of ER and PR in these tissues, and (3) to examine whether a correlation existed between receptor binding and mRNA expression for ER and PR. DESIGN: Cytosolic ER and PR binding was assessed by the dextran-coated charcoal technique and ER and PR mRNA expression was assessed using Northern blots of total RNA. PATIENTS: Fibroid and corresponding myometrial specimens were obtained from 20 women undergoing hysterectomy while fibroid specimens only were obtained from 10 women undergoing myomectomy after at least 3 months pretreatment with GnRHa. RESULTS: We found that (1) ER binding was twice and PR binding was three times as great in fibroid as in myometrium and that there was no difference in binding for either receptor between fibroids from untreated and GnRHa pretreated women, (2) ER and PR mRNA abundances were similar in fibroids and myometrium from untreated women and in fibroids from untreated and GnRHa pretreated women, and (3) ER binding and ER mRNA abundance in both groups of fibroids and myometrium were independent of each other, but there was a positive correlation between PR binding and PR mRNA abundance in untreated fibroids and myometrium but not in GnRHa pretreated tumours. CONCLUSIONS: We conclude that (1) both oestrogen and progesterone may contribute to fibroid growth because of increased receptor binding in fibroids compared with myometrium and (2) in GnRHa treated women, fibroids may shrink because of a lowered circulating oestradiol level rather than because of a change in steroid receptor binding.

Adult↗
PubMed1994

Wound infection in total joint arthroplasty: effect of extended wound surveillance on wound infection rates.

OBJECTIVE: To determine the effects of a wound monitoring program on infection rates after total joint arthroplasty. DESIGN: Case series, comparing postoperative wound infection rates before and after hospital discharge. SETTING: A university-affiliated tertiary-care hospital. PATIENTS: A group of 865 patients who underwent primary or revision total hip or knee arthroplasty between September 1989 and September 1991 followed by in-hospital and post-discharge wound monitoring was compared with a baseline group of 204 patients who had undergone an arthroplasty procedure and in-hospital wound monitoring between March and September 1988; only 38 of these patients were selected for post-discharge monitoring. INTERVENTIONS: In the study group, wounds were monitored every 48 to 72 hours to the time of patient discharge and at 30 days post-discharge. Monthly reports of surgeon-specific and overall infection rates were sent to each surgeon during both baseline and study periods. MAIN OUTCOME MEASURES: Presence or absence of surgical wound infection. RESULTS: The initial overall wound infection rate was 9.9%. This decreased to 3.8% in the study group, after the wound monitoring program had been in place for at least 18 months. Post-discharge monitoring accounted for the majority of wound infections diagnosed. CONCLUSIONS: A wound monitoring program may be an important tool in lowering wound infection rates associated with total joint arthroplasty. Post-discharge monitoring is important in determining true wound infection rates.

Alberta↗
PubMed1993

Acute mountain sickness in a general tourist population at moderate altitudes.

OBJECTIVE: To determine the incidence of acute mountain sickness in a general population of visitors to moderate elevations, the characteristics associated with it, and its effect on physical activity. DESIGN: A cross-sectional study. SETTING: Resort communities located at 6300 to 9700 feet elevation in the Rocky Mountains of Colorado. PARTICIPANTS: Convenience sample of 3158 adult travelers, 16 to 87 years old (mean age [+/- SD], 43.8 +/- 11.8 years). RESULTS: Twenty-five percent of the travelers to moderate elevations developed acute mountain sickness, which occurred in 65% of travelers within the first 12 hours of arrival. Fifty-six percent of those with symptoms reduced their physical activity. The odds favoring acute mountain sickness were 3.5 times as large for visitors whose permanent residence was below 3000 feet elevation as for those whose residence was above 3000 feet; 2.8 times as large for visitors with previous symptoms of acute mountain sickness; and twice as large in travelers younger than 60 years. Women, obese persons, those in poor or average physical condition, and those with underlying lung disease also had a higher occurrence of acute mountain sickness (P < 0.05). CONCLUSIONS: Acute mountain sickness occurs in 25% of visitors to moderate altitudes and affects activity in most symptomatic visitors. Persons who are younger, less physically fit, live at sea level, have a history of acute mountain sickness, or have underlying lung problems more often develop these symptoms.

Acute Disease↗
PubMed1993

Prospective alterations in therapy for penetrating abdominal trauma.

In a double-blind, randomized study, 170 patients with traumatic perforation of the gastrointestinal tract were administered an advanced-generation cephalosporin. Patients were divided into infection risk groups (< or = 40%, low; 40% to 70%, mid; and > 70%, high) at surgical closure using a logistic regression formula based on four proved risk factors--age, blood replacement, ostomy, and the number of organs injured. Patients in the low group received 2 days of antibiotic therapy; those in the mid to high group received 5 days of antibiotic therapy. Those patients in the low to mid group had primary wound closure; those in the high group had their wounds packed open and closed later. Most of the patients (144 [85%]) were in the low group. Their major and minor infection rates (10% and 12%, respectively) were not significantly different from 145 historic control subjects receiving 5 days of antibiotic therapy (9% major; 14% minor). Patients in the mid to high group showed a greater incidence of major infections (46%) but a similar incidence of minor infections (12%). The results indicate that risk factors can be used to identify low-risk patients who require only short-term antibiotic therapy and primary wound closure. The remaining patients are at greater risk for infection despite prolonged antibiotic therapy and delayed wound closure.

Abdominal Injuries↗
PubMed1993

Prevention of epoxy resin dermatitis: failure of manufacturers to use available research information.

Research information is often recommended as a solution for occupational disease and injury. This study asks whether publicly available research information on prevention of a well-documented occupational hazard is acted on by an important sector in industry. The hazard, allergic contact dermatitis (ACD) caused by epoxy resins in paints, is particularly significant for painters, who may have to leave their jobs as a consequence of the condition. No evidence is found, according to a priori criteria, that paint manufacturers/suppliers acted on known prevention measures for epoxy resin ACD that are within their control to implement. The findings suggest that availability of research information alone fails to solve health and safety problems. Recommendations for avenues of direct and indirect enforcement where voluntary implementation is absent in the painting industry are suggested.

Australia↗
PubMed1993

Acinetobacter meningitis.

10,468 CSF samples from cases of meningitis in different age groups were cultured during 1988-1991. Acinetobacter calcoaceticus was isolated in 12 (5.6%) of 211 positive cultures. The strain were 100% resistant to ampicillin, cotrimoxazole and tetracycline 50% resistant to cephazolin gentamicin and kanamycin but 100% susceptible to chloramphenicol.

Acinetobacter↗
PubMed1991

Wound infections in orthopedic surgery: effect of extended surveillance on infection rate.

Substantial evidence now exists that ongoing surveillance of surgical wound infections can contribute to reduced infection rates. What is not yet determined is whether surveillance should be limited to the postoperative hospital stay or should be continued after patient discharge. To determine the number of infections occurring after discharge, the authors contacted a random sample of their patients who did not have wound infections during their hospitalization after orthopedic surgery. This was done 30 days after the procedure. The authors selected 273 patients of 1375 who underwent orthopedic surgery over a 7-month period and were able to contact 199 (73%). At the 30-day follow-up 23 patients (11.6%) had wound infections, as judged by wound discharge and physician prescription of antibiotics in 20 and the patient's description of pus issuing from the wound in 3. During the same period postoperative wound infections were found in only 19 (1.5%) of 1278 patients who were subjected to in-hospital surveillance. The authors conclude that, in patients who undergo orthopedic procedures, the majority of wound infections occur after discharge from the hospital and that infection rates based only on in-hospital surveillance greatly under represent true surgical wound infection rates for orthopedic procedures.

Alberta↗
PubMed1990

Surgical wound infections occurring in day surgery patients.

The occurrence of surgical wound infection in outpatient day surgery has not been extensively studied despite the increasing popularity of this mode of treatment. The present study was conducted to determine the frequency of surgical wound infections in a day surgery population. We randomly selected during a 6-month period 635 (25%) of 2540 patients undergoing a day surgery procedure in which a skin incision was made. The patients were telephoned 1 month after their procedure by an infection control practitioner. Infection was diagnosed if the patient reported that (1) their physician had made a diagnosis of a wound infection or (2) pus was or had been issuing from the wound. Of the 515 patients contacted, 72% had undergone a clean and 28% a clean-contaminated procedure. Patient risk factors for infection were almost completely absent in our day surgery patients. Twenty-six wound infections were diagnosed, 19 of which were identified by physicians' diagnosis and 7 by patient description, for a rate of 5.05%. Two patients required hospitalization for their infections, and 14 were treated with antibiotics. The clean wound infection rates were 4.62%, less than half the infection rate seen in our patients undergoing inpatient surgery at 1 month follow-up by the same surveillance technique. We conclude that day surgery infection rates are much lower than inpatient surgery infection rates at our facility, probably because of a relative absence of risk factors in the day surgery patients.

Ambulatory Surgical Procedures↗