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Biomedical subjects

P Meredith

Publications and source records attributed to P Meredith.

At least 19 recordsLinked to original sources
PubMed2004

A first-principles density-functional calculation of the electronic and vibrational structure of the key melanin monomers.

We report first-principles density-functional calculations for hydroquinone (HQ), indolequinone (IQ), and semiquinone (SQ). These molecules are believed to be the basic building blocks of the eumelanins, a class of biomacromolecules with important biological functions (including photoprotection) and with the potential for certain bioengineering applications. We have used the difference of self-consistent fields method to study the energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital, Delta(HL). We show that Delta(HL) is similar in IQ and SQ, but approximately twice as large in HQ. This may have important implications for our understanding of the observed broadband optical absorption of the eumelanins. The possibility of using this difference in Delta(HL) to molecularly engineer the electronic properties of eumelanins is discussed. We calculate the infrared and Raman spectra of the three redox forms from first principles. Each of the molecules have significantly different infrared and Raman signatures, and so these spectra could be used in situ to nondestructively identify the monomeric content of macromolecules. It is hoped that this may be a helpful analytical tool in determining the structure of eumelanin macromolecules and hence in helping to determine the structure-property-function relationships that control the behavior of the eumelanins.

Benzoquinones↗
PubMed2004

Postsynthesis stabilization of free-standing mesoporous silica films.

Mixed ammonia-water vapor postsynthesis treatment provides a simple and convenient method for stabilizing mesostructured silica films. X-ray diffraction, transmission electron microscopy, nitrogen adsorption/desorption, and solid-state NMR (13C, 29Si) were applied to study the effects of mixed ammonia-water vapor at 90 degrees C on the mesostructure of the films. An increased cross-linking of the silica network was observed. Subsequent calcination of the silica films was seen to cause a bimodal pore-size distribution, with an accompanying increase in the volume and surface area ratios of the primary (d = 3 nm) to secondary (d = 5-30 nm) pores. Additionally, mixed ammonia-water treatment was observed to cause a narrowing of the primary pore-size distribution. These findings have implications for thin film based applications and devices, such as sensors, membranes, or surfaces for heterogeneous catalysis.

Adsorption↗
PubMed2004

Absorption and fluorescence spectroscopy of rhodamine 6G in titanium dioxide nanocomposites.

A comparison has been made between the spectroscopic properties of the laser dye rhodamine 6G (R6G) in mesostructured titanium dioxide (TiO(2)) and in ethanol. Steady-state excitation and emission techniques have been used to probe the dye-matrix interactions. We show that the TiO(2)-nanocomposite studied is a good host for R6G, as it allows high dye concentrations, while keeping dye molecules isolated, and preventing aggregation. Our findings have important implications in the context of solid state dye-lasers and microphotonic device applications.

Coloring Agents↗
PubMed2004

A two-step sol-gel method for synthesis of nanoporous TiO2.

This article reports a study of the effects of synthesis parameters on the preparation and formation of mesoporous titania nanopowders by employing a two-step sol-gel method. These materials displayed crystalline domains characteristic of anatase. The first step of the process involved the hydrolysis of titanium isopropoxide in a basic aqueous solution mediated by neutral surfactant. The solid product obtained from step 1 was then treated in an acidified ethanol solution containing the same titanium precursor to thicken the pore walls. Low pH and higher loading of the Ti precursor in step 2 produced better mesoporosity and crystallinity of titanium dioxide polymorphs. The resultant powder exhibited a high surface area (73.8 m2/g) and large pore volume (0.17 cm3/g) with uniform mesopores. These materials are envisaged to be used as precursors for mesoporous titania films as a wide band gap semiconductor in dye-sensitized nanocrystalline TiO2 solar cells.

Crystallization↗
PubMed2000

Hospital admissions. Just the ticket.

Pilot schemes for direct booking of hospital appointments have won support from the consultants involved. Skilled leadership has been crucial to managing changes that enable direct booking to be put into practice. The nursing role is central to the system, particularly in pre-operative assessment clinics. For direct booking to become widespread, management of all acute hospital resources will have to be reviewed.

Admitting Department, Hospital↗
PubMed2000

The NHS patient information lottery: it is whom you see rather than what you need.

OBJECTIVE: To examine the current scale of provision of patient information materials by consultant surgeons in UK NHS and private sector hospitals. DESIGN: Secondary analysis of the responses of 12,555 surgical patients to surveys evaluating surgical services provided by specific consultants. SETTING: 7 NHS Trusts and one private sector hospital distributed throughout the UK. MAIN OUTCOME MEASURES: Provision of information materials by hospital, surgeon, and case-mix. Comparison of this service with patients' evaluations of surgeons' verbal communication in the outpatient clinic. RESULTS: Great variation exists between surgeons of the same specialty, and between hospital surgical directorates as a whole in the routine provision of supportive information materials to patients undergoing surgery. This variation cannot be explained solely by clinical need. Patients treated in private hospitals were less likely to receive information materials compared to patients treated within the NHS. CONCLUSIONS: Provision of printed information materials to patients by clinicians appears to be arbitrary. With the prospect of national performance frameworks in the foreseeable future, it is reasonable to assume that not only will the content of patient information be determined by quality standards but, in addition, its availability will be decided by clinical need rather than the clinician's preferences or interests.

Aftercare↗
PubMed2000

Achieving quality 24-h blood pressure control with candesartan cilexetil.

Epidemiological evidence suggests that optimal blood pressure control requires strategies that lower blood pressure consistently and fully throughout 24 h. In order to maximize compliance, antihypertensive agents also need to be well tolerated and effective when administered at a convenient once-daily dose. The new angiotensin II type 1 (AT1) receptor blocker candesartan binds tightly to, and dissociates slowly from, the AT1-receptor and thereby provides long-lasting suppression of the renin-angiotensin system. This is likely to explain its pronounced antihypertensive efficacy, which is maintained smoothly over 24 h. The trough-to-peak ratio is a useful measure of the persistence of antihypertensive efficacy at the end of the dosing interval. This ratio was found to be close to the ideal of 1.0 for candesartan cilexetil, 8 and 16 mg, whereas it was 0.7 for the prototype AT1-receptor blocker losartan, 50 mg. The antihypertensive effect of candesartan cilexetil, 16 mg, was also significantly greater than that of losartan, 100 mg, as demonstrated by ambulatory blood pressure measurements 0-36 h after dosing and by clinic measurements 48 h after dosing. By controlling blood pressure well beyond the normal dosing interval, candesartan cilexetil provides cardiovascular protection even in those patients who may occasionally miss doses.

Angiotensin Receptor Antagonists↗
PubMed1999

Do pharmacologic differences among antihypertensive agents point to clinical benefits?

On the basis of results of long-term trials, to date, it is reasonable to conclude that blood pressure lowering, per se, rather than the identity of the antihypertensive regimen, is associated with reducing risk for stroke and coronary heart disease in patients with hypertension. Clinicians should identify drugs within each antihypertensive class that reduce blood pressure consistently over a 24-hour period and have a duration appropriate for once-daily administration. Candesartan cilexetil is an appropriate choice among angiotensin II receptor blockers (ARBs); it has a trough: peak ratio of 0.9-1.1, which fully justifies once-daily dosing. Once genuinely long-acting antihypertensive medications are used routinely, it will be possible to evaluate whether the different drug classes provide ancillary benefits beyond blood pressure lowering.

Antihypertensive Agents↗
PubMed1999

Clinical pharmacokinetics of doxazosin in a controlled-release gastrointestinal therapeutic system (GITS) formulation.

AIMS: A controlled-release gastrointestinal therapeutic system (GITS) formulation of doxazosin mesylate, a long-acting selective alpha1-adrenoceptor antagonist, was developed to enhance the pharmacokinetic profile and simplify the titration schedule by precisely controlling drug delivery rate, permitting an initial dose of 4 mg once daily, compared with standard doxazosin, which is initiated at 1 mg day-1 and titrated to a higher therapeutically effective dose. The aim of the present work was to evaluate the pharmacokinetics and bioavailability of doxazosin GITS with respect to the effect of food, age and gender, and multiple dosing. In addition, in vitro performance was assessed in conditions simulating the gastrointestinal environment. METHODS: A three-way crossover study in 24 subjects assessed the comparative bioavailability of doxazosin GITS under fed and fasting conditions and doxazosin standard under fasting condition. A multiple-dose, two-way crossover study in 35 subjects assessed the comparative pharmacokinetics and bioavailability of doxazosin GITS and doxazosin standard 4 and 8 mg upon multiple dosing. A multiple-dose, four-parallel-group study was conducted to determine the steady-state pharmacokinetics and bioavailability of doxazosin GITS 4 mg in 41 young and elderly male and female subjects. The release-rate profiles of doxazosin GITS were determined in artificial gastric fluid (pH=1.2), intestinal fluid (pH=7.5), and water. The effect of agitation on the dissolution characteristics of doxazosin GITS in artificial gastric fluid was studied at stirring rates of 50, 75, and 100 rev min-1. RESULTS: In vitro studies demonstrated that release rates for the GITS tablet are independent of pH in the range of 1.2 (gastric) to 7. 5 (intestinal), and of stirring rates simulating gastrointestinal motility. Clinical pharmacology studies showed that doxazosin GITS had a lower maximum plasma concentration, prolonged time to reach maximum plasma concentration, and a higher minimum plasma concentration compared with doxazosin standard. Thus, the GITS formulation results in a more gradual absorption of doxazosin, and a reduced plasma doxazosin concentration peak-to-trough fluctuation ratio. The relative bioavailability of doxazosin GITS is approximately 60%. With a high-fat meal, the maximum plasma concentration and area under the concentration-time curve were 31% and 18% higher, respectively (P<0.05). Bioequivalence was established between the dose strengths of two 4 mg doxazosin GITS tablets and one 8 mg doxazosin GITS tablet. For both young adult and elderly subjects, and males and females, the pharmacokinetics of doxazosin GITS once daily for 7 days were comparable. Doxazosin GITS was well tolerated in the subjects studied, including young and elderly males and females. CONCLUSIONS: The GITS formulation of doxazosin enhances the pharmacokinetic profile compared with doxazosin standard, allowing more gradual absorption of doxazosin, and a reduced plasma doxazosin peak-to-trough concentration ratio. Thus, doxazosin GITS therapy can be initiated at a therapeutic dose of 4 mg with reduced haemodynamic side-effects.

Adult↗
PubMed1998

Patient surveys. There for the asking.

The government's proposal to survey 100,000 patients a year in order to improve services faces considerable organisational problems. We estimate it will cost 200,000 pounds a year. The simple opinion poll approach should be avoided in favour of a detailed questionnaire. A rolling programme of surveys in specific service areas might be more meaningful than a comprehensive annual survey. The aims of capturing patients' views and comparing performance across the country could prove incompatible.

Government↗
PubMed1998

Inquiry into the potential value of an information pamphlet on consent to surgery to improve surgeon-patient communication.

OBJECTIVES: To find out how patients recently undergoing surgery experienced the consenting process and the response of these patients to a pamphlet on consent to surgery. To test the reaction of health professionals to the pamphlet. DESIGN: A pilot pamphlet was produced and a questionnaire was sent to patients inquiring about their consenting experience, and how the pamphlet might have helped them through the consent procedure. A pamphlet and a questionnaire were also sent to a random sample of the health professionals serving these patients. SUBJECTS: Patients and health professionals. RESULTS: 61% of patients returned the questionnaire. Knowledge about the consent procedure was shown to be limited. 49% were unaware that they had the right to insist that the surgeon could only perform the specified operation and nothing more. 83% were unaware that they could add something in writing to the consent form before signing. 28% of health professionals returned their questionnaire, most of whom thought that the pamphlet provided a useful contribution to surgeon-patient communication. CONCLUSION: Evidence shows that patients are not well informed about consenting to surgery and further information would provide much needed guidance on understanding their role in the consent procedure. The low response from the health professional study is perhaps an indication that at present this is an issue which is not seen as a priority.

Comprehension↗
PubMed1996

Freeze-drying: in situ observations using cryoenvironmental scanning electron microscopy and differential scanning calorimetry.

The quality of a freeze-dried product and the ease with which it can be reconstituted depend upon the morphology which develops during freezing and upon solvent sublimation. In this paper, the use of an environmental scanning electron microscope (ESEM) with a cryostage attachment is reported as a means of studying such structural evolution during the sublimation process. Results indicate that cryo-ESEM can provide a useful addition to techniques already used for the development of freeze-drying cycles, such as differential scanning calorimetry and light microscopy.

Acetates↗
PubMed1996

Aspects of patient satisfaction with communication in surgical care: confirming qualitative feedback through quantitative methods.

This paper reviews the results of a two-phase study of patient satisfaction with surgical services. Phase one adopted a qualitative approach using interviews and observation of surgeons and patients. Phase two was based on a questionnaire survey using questions generated by the qualitative study. Selected data reported here focus on the principal areas of concern for surgical patients and the importance of a patient's medical condition in accounts of satisfaction with care. The results reveal the importance of interview data as a means to explain the meanings behind questionnaire responses. However, where personal accounts are not sustained statistically, it may be necessary to reconsider the assumption that such methodologies may simply be "triangulated" to elicit an identical patient perspective and agenda. This is important in view of the fact that health research is increasingly reliant on standardized measures of quality-of-life, symptom-scoring and patient satisfaction, all of which use questionnaires whose claim to validity is their equivalence to the results of prior interviewing.

Adolescent↗
PubMed1996

Errors in trough: peak ratio determinations induced by patient behaviour.

BACKGROUND: Trough: peak ratio is often used to evaluate the duration of antihypertensive action. Whatever the method of measurement chosen, trough effect has to be measured 24 h after the last drug intake for a once daily regimen. Peak effect is usually measured 4-6 h after drug intake. If patients' compliance to therapeutic instructions is perfect, then the 'intrinsic' trough: peak ratio of the drug is equal to the measured trough: peak ratio. Some patients do not follow these instructions, leading to biases in the evaluation of the ratio. For trough evaluation, all patients (N) are supposed to take the last dose of the drug the day before blood pressure measurement. However, if some patients (n1) wrongly take the drug in the morning of the visit, they will be evaluated at peak (type A error). For peak evaluation, all patients (N) are supposed to take the drug a few hours before blood pressure measurement. If some patients (n2) miss their morning dose, they will be evaluated at trough (type B error). METHODS: In the MACH 1 study, the use of an electronic pill count monitor allowed us to quantify n1/N and n2/N. A total of 452 hypertensive patients were randomly assigned to two groups. Patients in group 1 received written instructions to take their last dose during the morning of the day before the visit, whereas patients of group 2 had to take their last dose on the morning of the visit. RESULTS: Electronic pill-box recording revealed that 32.9%: of patients in group 1 committed type A error, whereas 27.7% of patients in group 2 committed type B error. The resulting 'pill-box corrected' trough: peak ratio was lower (87.5% for diastolic blood pressure and 93.1% for systolic blood pressure) than the uncorrected trough: peak ratio (95.2% for diastolic blood pressure and 96.0% for systolic blood pressure) of the population. CONCLUSION: The random behaviour of patients, with respect to treatment compliance, results in a systematic overestimation of the measured trough: peak ratio. The computation of this ratio may be optimized by improving patient compliance. Alternatively, only data from a patient subpopulation that complies with the therapeutic protocol, as reported by readings from electronic pill boxes, should be taken into account for its calculation.

Journal Article↗
PubMed1996

But was the operation worth it? The limitations of quality of life and patient satisfaction research in health-care outcome assessment.

There is increasing recognition that clinically-derived measures of surgical outcome must be reconciled with patients' own perception of their post-treatment condition. Recently developed quality-of-life and symptom-score measures of outcome have drawn upon patients' own reports of functional status, in contrast to traditional, clinically-derived observations or technical measurements. Patient satisfaction research has been an independent growth industry whose focus has been patient feedback on quality of care received. This paper proposes that the research designs of neither tradition take full account of the personal significance, value or social meaning of a treatment for the patient, although the subject straddles both effectiveness and satisfaction. This begs the question of the value to clinicians of feedback on how worthwhile patients feel a procedure has been in their own cost-benefit terms? If this is also an important dimension of outcome assessment, the range of measures currently available cannot account for it. This paper explores possible reasons why existing patient-oriented measures address what is important to the clinician rather than the patient.

Attitude of Health Personnel↗