Browsing by Author "Newman, Jeffrey D."
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Item Open Access Amperometric biosensor for formic acid in air(Elsevier, 2000-11-01) Sandström, K. J. Mattias; Newman, Jeffrey D.; Sunesson, Anna-Lena; Levina, Jan-Olof; Turner, Anthony P. F.The possibility of developing a simple, inexpensive and specific personal passive ”real-time” air sampler based on biosensor technology was investigated. Formic acid was used as a model substance. The sensor is based on the enzymatic reaction between formic acid and formate dehydrogenase with NAD+ as a cofactor and Meldola’s blue as mediator. An effective way to immobilise the enzyme, cofactor and Meldola’s blue on screen-printed electrodes was found to be in a mixture of glycerol and phosphate buffer covered with a gas-permeable membrane. When the sensor was introduced into an atmosphere containing formic acid, it gave a distinct and rapid amperometric response.Item Open Access The clinical utility and cost-effectiveness of non-bone mineral density based prognostic tests for osteoporotic fracture(Cranfield University, 2012-06) Poku, Ernest Kofi; Newman, Jeffrey D.This thesis investigated a number of aspects of the clinical utility and cost-effectiveness of clinical risk factors, online multivariate algorithms, DXA and a nail-based Raman spectroscopy test, BQT for fracture risk using archived nail samples, and questionnaire data from the Nurses’ Health Study which followed women for up to 23 years. The results showed that the BQT in combination with CRFs improved the results over CRFs alone, using logistic regression and Cox’s proportional hazards analysis. The improvement seen was larger using the Cox model, indicating that time is an important factor. The multivariate algorithms, FRAX and QFractureScores were compared in retrospective and cohort models and found to be predictive, but the relative performance of the two algorithms was highly dependent on the input data. Reclassification is an exciting new approach to evaluating the addition of new biomarkers in multivariate algorithms and was found in the Nurses’ Health Study to provide better discrimination than AUC. Cost-effectiveness analysis using Markov and decision tree approaches showed that the BQT with a low cut-off in combination with DXA was consistently on the cost-effective frontier, indicating that this new biomarker would be an integral part of any mass screening strategy. In conclusion, it is clear that the use of the BQT can enhance the performance of clinical risk factors and, with further improvements, the combination may offer a cost-effective alternative to the use of DXA for mass screening in multivariate algorithms.Item Open Access Development fo electrochemical sensors for heavy metal ions detection in environmental samples(2004-01) Kadara, Rashid; Tothill, Ibtisam E.; Newman, Jeffrey D.The work presented in this thesis was concerned with the development of single-use drop-on sensors incorporating a three-electrode configuration (graphite carbon- working electrode, carbon-counter electrode and silver/silver chloride - reference electrode) for on-site detection of toxic heavy metals in various environmental matrices. The fabricated three-electrode configuration system was coupled with square-wave anodic stripping voltammetry (SWASV) or constant current stripping chronopotentiometry (CCSCP) in order to provide a means of a relatively inexpensive on-site detector for trace levels of lead (II), copper (II) and cadmium (II). Detections and determinations of these metals were carried out on bare screen-printed carbon electrodes (SPCEs), mercury film SPCE, bismuth film SPCE and SPCEs modified with Nafion, 2,5- Dimercapto-1, 3, 4- thiadiazole (DMTD), bismuth oxide (Bi₂O₃) and polyethyleneimine (PEI) using the optimised procedures developed for measurements. With the optimised working conditions, the results obtained indicate that the screen-printed electrochemical sensors are sensitive and reproducible enough for the CCSCP and SWASV determination of lead, copper and cadmium in the microgram per litre - milligram per litre range. Limits of detection below 20 µg I¯¹ were estimated for the trace metal detection of lead, copper and cadmium on both the bismuth and mercury film electrodes. For the bare SPCE, detection limits of 35, 45 and 59 µg I¯¹ were obtained for lead, cadmium and copper detection using CCSCP. The reproducibility of the measurements, which also contributed to the interest in developing the electrochemical sensing devices for metal ions, was below 15 % for the bare SPCE, bismuth film SPCE, and mercury film SPCE. Modifications of SPCEs with an ion-exchanger (Nafion) and a complexing agent (DMTD) provided means of increasing the sensitivity of stripping response obtained at the bare SPCE. Detection limits of 20 and 22 µg I¯¹ were estimated for lead (II) measurements at the Nafion modified SPCE and at the screen-printed DMTD modified electrode, respectively. The application of the various electrodes to real samples is demonstrated and proved successful for both water and soil extracted samples including in situ measurements at a contaminated site.Item Open Access Electrochemical method for the determination of arsenic 'in the field' using screen-printed grid electrodes(Cranfield University, 2008-02) Dudeney, Richard; Setford, S.; Newman, Jeffrey D.; Tothill, Ibtisam E.This project describes development and problem solving efforts to realise a viable portable sensor for arsenic, applicable to drinking water. The work is the first dedicated effort towards this goal, after the preliminary investigations previously conducted at Cranfield University (Cooper, 2004 and Noh, 2005). Using polymeric gold ink BQ331 (DuPont Microcircuit Materials, Bristol, UK) as working electrode on screen printed strips, the electrochemical procedure was studied. Due to the wealth of research on electrochemical and non electrochemical methods for arsenic determination, this project attempts to capitalise on the unique advantages of the screen-printed gold surface. In particular, the issues surrounding the performance of the sensor were evaluated by electrochemical and spectroscopic means (including infrared, nuclear magnetic resonance and X-ray photoelectron spectroscopy). A number of custom screen printed electrodes were prepared in house comparing sensor performance on compositional factors. An interference coming from silver interaction with chloride in the reference electrode was identified. As such, the design of the sensor needs to change to include either an immobilising layer, such as Nafion, over the silver, or to omit screen-printed silver altogether. The Nafion was presumed to work by excluding (or at least much reducing) the passage of negatively charged chloride ions to the silver surface preventing formation of soluble silver chloride complexes. The design of the sensor was considered in light of performance and sensitivity. The screen-printed electrodes were cut to facilitate a microband design lending favourable diffusive to capacitive current characteristics. With this design, As(III) detection was demonstrated comfortably at 5 ppb (in a copper tolerant 4 M HCl electrolyte) without electrode need for additional preparation procedures. This is below the World Health Organisation (WHO) guideline and United States Environmental Protection Agency (USEPA) regulation level of 10 ppb in drinking water. The electrode materials are already mass manufacturable at an estimated cost less than £ 0.5 per electrode. Themicroband design could, in principle, be applied to mercury and other metal ions. The procedure for As(V) either with chemical or electrochemical reduction and determination still needs to be assessed. However, the presented electrode system offers a viable alternative to the colorimetric test kits presently employed around the world for arsenic in drinking water. Also, the Nicholson Method (Nicholson, 1965a), used for characterising electron transfer kinetics at electrode surfaces, was extended for application to rough surfaces using a fractal parameter introduced by Nyikos and Pajkossy (1988). This work includes mathematical derivation and numerical evaluation and gives a number of predictions for electrochemical behaviour. These predictions could not be tested experimentally, as yet, since the physical conditions must be carefully controlled.Item Open Access Estimating measurement uncertainty in the medical laboratory(Cranfield University, 2016-09) Placido, Rui; Newman, Jeffrey D.; Gomes, Maria AdelinaMedical Laboratories Accreditation is covered by ISO 15189:2012 - Medical Laboratories — Requirements for Quality and Competence. In Portugal, accreditation processes are held under the auspices of the Portuguese Accreditation Institute (IPAC), which applies the Portuguese edition (NP EN ISO 15189:2014). Accordingly, Medical Laboratories accreditation processes now require the estimate of measurement uncertainty (MU) associated to the results. The Guide to the Expression of Uncertainty in Measurement (GUM) describes the calculation of MU, not contemplating the specific aspects of medical laboratory testing. Several models have been advocated, yet without a final consensus. Given the lack of studies on MU in Portugal, especially on its application in the medical laboratory, it is the objective of this thesis to reach to a model that fulfils the IPAC’s accreditation regulations, in regards to this specific requirement. The study was based on the implementation of two formulae (MU-A and MU-B), using the Quality Management System (QMS) data of an ISO 15189 Accredited Laboratory. Including the laboratory’s two Cobas® 6000–c501 (Roche®) analysers (C1 and C2) the work focused three analytes: creatinine, glucose and total cholesterol. The MU-B model formula, combining the standard uncertainties of the method’s imprecision, of the calibrator’s assigned value and from the pre-analytical variation, was considered the one best fitting to the laboratory's objectives and to the study's purposes, representing well the dispersion of values reasonably attributable to the measurand final result. Expanded Uncertainties were: Creatinine - C1 = 9,60%; C2 = 5,80%; Glucose - C1 = 8,32%; C2 = 8,34%; Cholesterol - C1 = 4,00%; C2 = 3,54 %. ...[cont.].Item Open Access Evaluation of health outcomes associated with medication in southern Portugal using a novel approach for medication review: ReMeD study(2017-06) Espirito Santo, Margarida de Fatima Neto; Newman, Jeffrey D.Currently, a large portion of the world's population uses medication on a regular basis and uses health services frequently, mainly due to the increase of longevity and the growing number of chronic diseases (CD). Consequently, a correct medication management is needed in order to improve the responsible use of medicines and health outcomes. Portugal shows a high prevalence of CD such as hypertension, obesity, dyslipidaemia and diabetes. Moreover, the Algarve region presents some shortcomings in accessibility to healthcare. Therefore, this research project arises with the main aim of establishing a methodology to analyse the outcomes of the process of medication use (MU) through medication review (MR) , in a clinical practice setting in Southern Portugal (AEDMADA clinic), applied in the ReMeD study. Patient´s data was collected individually and then systematically analysed considering the humanistic, economic and clinical outcomes. A questionnaire (SAHL-S&E) was previously adapted for the Portuguese language aimimg to identify subjects with low health literacy (HL), which was then used during the MR. The ReMeD study was conducted in 118 patients, mainly 65 years, hypertense, diabetic, dyslipidemic and presenting a very high cardiovascular risk. Humanistic outcomes showed 25.4% of patients having low medication knowledge, 43.2% with low HL and about 25% being non-adherent to medication. Economic outcomes revealed that most patients were polymedicated (73.8%) and monitored by 2-3 Physicians, and about 15% suffering hospitalization in the last year. Negative clinical outcomes (NCO) were identified in 99.2% of patients, and 74.6% presented risks of developing NCO. As a whole, the ReMeD methodology seems appropriate to identify situations from the process of MU, useful to outline new strategies aimed to improve patient's MU and the empowerment for disease management. Applying this novel approach enables the conduction of MR in a clinical setting, allowing to pinpoint modifiable situations, contributing to improve health outcomes.Item Open Access Glycaemic control: The role of nutritional intake, postprandial glycaemia, nutrition therapy adherence, and diabetes complications(Cranfield University, 2014-07-14) Pinto, Ezequiel; Newman, Jeffrey D.This thesis analysed the associations between several clinical and psychometric variables that can determine glycaemic control: nutritional intake, barriers to nutrition therapy adherence, postprandial glycaemia, and diabetes complications perception. A group of 66 patients previously diagnosed with type 2 diabetes mellitus was recruited and categorized into patients with HbA1c below 7% (proper glycaemic control) and patients with HbA1c of 7% or above (poor glycaemic control). All subjects were interviewed and offered a nutritionally controlled breakfast. The glucose response to the experimental breakfast was monitored for 120 minutes after the meal, in order to record postprandial glycaemia levels The results show that subjects with adequate glycaemic control have a better compliance of nutrition recommendations, but all patients have excess intakes of energy, total cholesterol, saturated fatty acids, and sugars. There are no significant differences in postprandial glycaemia between patients with adequate glycaemic control and those with poor glycaemic control, which may imply that some subjects are unaware that they exceed the recommended rise in postprandial glucose, and thus may be at a higher than expected risk for macro and microvascular events. As self-monitoring is the only practical way to detect postprandial hyperglycaemia, efforts should be made to promote regular glucose self-monitoring. Patients with poor glycaemic control have a more biased opinion of their likelihood of personal disease risk. Additionally, exposures such as medical tests, air pollution, pesticides, or household chemicals, are considered as likely to cause health problems as several known and common diabetes complications, like high blood pressure or cardiovascular disease. Younger age, high body mass index, and biased personal disease risk perceptions are important predictors of glycaemic control and should be addressed by education interventions. Health professionals need to consider specific patient characteristics in order to provide proper continued medical care, and nutrition education should be tailored to the perceptions of patients and should positively discriminate subjects above or below the internationally proposed HbA1c cut-points for glycaemic control.Item Open Access Home blood glucose biosensors: a commercial perspective(Elsevier, 2005-06-15) Newman, Jeffrey D.; Turner, Anthony P. F.Twenty years on from a review in the first issue of this journal, this contribution revisits glucose sensing for diabetes with an emphasis on commercial developments in the home blood glucose testing market. Following a brief introduction to the needs of people with diabetes, the review considers defining technologies that have enabled the introduction of commercial products and then reviews the products themselves. Drawing heavily on the performance of actual instruments and publicly available information from the companies themselves, this work is designed to complement more conventional reviews based on papers published in scholarly journals. It focuses on the commercial reality today and the products that we are likely to see in the near future.