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Biomedical subjects

J Britton

Publications and source records attributed to J Britton.

At least 37 records · Page 2Linked to original sources
PubMed2005

Public health measures to reduce smoking prevalence in the UK: how many lives could be saved?

OBJECTIVE: To estimate the number of deaths that could be prevented in the UK by implementing population strategies to reduce smoking prevalence. DESIGN: A prospective analysis of future mortality using recent national smoking prevalence data and relative risks of mortality in current smokers, ex-smokers, and never-smokers. POPULATION: Smokers in the UK. INTERVENTIONS: Population measures of proven effectiveness assumed to reduce smoking prevalence by 1 percentage point per year for 10 years, or alternatively by 13% over 19 years (1 percentage point per annum for seven years, 0.5 percentage point per annum for 12 years) as considered to be achievable in a recent report to the UK Chancellor of the Exchequer. MAIN OUTCOME MEASURE: Estimated deaths from smoking prevented in the 35-75 year age group. RESULTS: Reducing the prevalence of smoking by 1 percentage point each year for 10 years would prevent 69 049 deaths at ages between 35 and 74 years during that period. The model of reduction by 13% over 19 years would prevent 54 308 and 194 493 deaths in 10 and 19 years, respectively. Continued prevalence reductions at the current rate of 0.4 percentage points each year will prevent 23 192 deaths over 10 years. CONCLUSIONS: Full implementation of simple population measures to encourage smoking cessation could prevent substantial numbers of deaths in the UK.

Adult↗
PubMed2005

Use of nicotine replacement therapy and the risk of acute myocardial infarction, stroke, and death.

OBJECTIVE: To determine whether nicotine replacement therapy (NRT) is associated with an increased risk of acute myocardial infarction, acute stroke, or death. DESIGN: Self control case series analysis of data from The Health Improvement Network (THIN) to estimate the relative incidence of myocardial infarction and stroke in four 14 day periods before and after the first prescription for NRT. SETTING: THIN is a computerised general practice database. SUBJECTS: Patients contributing data to THIN. INTERVENTIONS: Observational study of NRT. MAIN OUTCOMES: Acute myocardial infarction, acute stroke, and death. RESULTS: 33,247 individuals had been prescribed NRT, of whom 861 had had a myocardial infarction and 506 a stroke. There was a progressive increase in the incidence of first myocardial infarction in the 56 days leading up to the first NRT prescription (overall incidence ratio 5.55, 95% confidence interval (CI) 4.42 to 6.98), but the incidence fell after this time and was not increased in the 56 days after starting NRT (incidence ratio 1.27, 95% CI 0.82 to 1.97). The results were similar for second myocardial infarction and stroke, and for subgroups of people with pre-existing angina and hypertension. There were 960 deaths in our cohort during a mean follow up period of 2.6 years after starting NRT, with no evidence of an increased mortality in the 56 days after the NRT prescription (incidence ratio 0.86, 95% CI 0.60 to 1.23). CONCLUSIONS: The use of NRT is not associated with any increase in the risk of myocardial infarction, stroke, or death.

Adult↗
PubMed2004

Realization of quantum error correction.

Scalable quantum computation and communication require error control to protect quantum information against unavoidable noise. Quantum error correction protects information stored in two-level quantum systems (qubits) by rectifying errors with operations conditioned on the measurement outcomes. Error-correction protocols have been implemented in nuclear magnetic resonance experiments, but the inherent limitations of this technique prevent its application to quantum information processing. Here we experimentally demonstrate quantum error correction using three beryllium atomic-ion qubits confined to a linear, multi-zone trap. An encoded one-qubit state is protected against spin-flip errors by means of a three-qubit quantum error-correcting code. A primary ion qubit is prepared in an initial state, which is then encoded into an entangled state of three physical qubits (the primary and two ancilla qubits). Errors are induced simultaneously in all qubits at various rates. The encoded state is decoded back to the primary ion one-qubit state, making error information available on the ancilla ions, which are separated from the primary ion and measured. Finally, the primary qubit state is corrected on the basis of the ancillae measurement outcome. We verify error correction by comparing the corrected final state to the uncorrected state and to the initial state. In principle, the approach enables a quantum state to be maintained by means of repeated error correction, an important step towards scalable fault-tolerant quantum computation using trapped ions.

Journal Article↗
PubMed2004

Quantum dense coding with atomic qubits.

We report the implementation of quantum dense coding on individual atomic qubits with the use of two trapped 9Be+ ions. The protocol is implemented with a complete Bell measurement that distinguishes the four operations used to encode two bits of classical information. We measure an average transmission fidelity of 0.85(1) and determine a channel capacity of 1.16(1).

Journal Article↗
PubMed2004

Deterministic quantum teleportation of atomic qubits.

Quantum teleportation provides a means to transport quantum information efficiently from one location to another, without the physical transfer of the associated quantum-information carrier. This is achieved by using the non-local correlations of previously distributed, entangled quantum bits (qubits). Teleportation is expected to play an integral role in quantum communication and quantum computation. Previous experimental demonstrations have been implemented with optical systems that used both discrete and continuous variables, and with liquid-state nuclear magnetic resonance. Here we report unconditional teleportation of massive particle qubits using atomic (9Be+) ions confined in a segmented ion trap, which aids individual qubit addressing. We achieve an average fidelity of 78 per cent, which exceeds the fidelity of any protocol that does not use entanglement. This demonstration is also important because it incorporates most of the techniques necessary for scalable quantum information processing in an ion-trap system.

Journal Article↗
PubMed2004

Toward Heisenberg-limited spectroscopy with multiparticle entangled states.

The precision in spectroscopy of any quantum system is fundamentally limited by the Heisenberg uncertainty relation for energy and time. For N systems, this limit requires that they be in a quantum-mechanically entangled state. We describe a scalable method of spectroscopy that can potentially take full advantage of entanglement to reach the Heisenberg limit and has the practical advantage that the spectroscopic information is transferred to states with optimal protection against readout noise. We demonstrate our method experimentally with three beryllium ions. The spectroscopic sensitivity attained is 1.45(2) times as high as that of a perfect experiment with three non-entangled particles.

Journal Article↗
PubMed2004

A case-control study of dietary and erythrocyte membrane fatty acids in asthma.

BACKGROUND: Epidemiological evidence suggests that increased dietary omega-6 and reduced omega-3 fatty acid intake, may have contributed to the rising prevalence of asthma, but these hypotheses have not been tested in studies comparing both dietary intake and objective measures of polyunsaturated fatty acids. OBJECTIVE: To assess whether a higher intake of omega-6 or a lower intake of omega-3 fatty acids increases the risk of asthma, by measuring dietary fatty acid intake by a food frequency questionnaire (FFQ) and erythrocyte membrane fatty acids, as an objective biomarker of intake. METHODS: We have compared individual fatty acid intake estimated by FFQ and by mass spectrometry of fasting erythrocyte cell membranes in 89 cases of asthma and 89 community-matched controls. RESULTS: The odds of asthma were increased in relation to intake of the omega-3 fatty acids eicosapentaenoic acid (odds ratio (OR) for difference between the 25th and 75th centiles of intake= 1.89, 95% CI 1.15-3.11) and docosahexaenoic acid (OR = 2.11, 95% CI 1.19-3.74). There was no evidence of any difference in erythrocyte membrane levels of omega-3 fatty acids, while the odds of asthma were reduced in relation to linoleic acid (omega-6) membrane levels (OR = 0.45, 95% CI 0.21-0.95). CONCLUSION: These findings suggest that dietary omega-3 fatty acids do not play a major role in protecting against asthma, and that higher levels of erythrocyte membrane linoleic acid are associated with a lower risk of asthma.

Adult↗
PubMed2004

Prevalence and associated factors of atopic dermatitis symptoms in rural and urban Ethiopia.

BACKGROUND: Allergic diseases, including atopic dermatitis (AD), are increasingly becoming a clinical problem in developing countries. OBJECTIVE: We investigated the prevalence of AD symptoms and the effects of potential environmental aetiologies in rural and urban areas of Jimma in southwestern Ethiopia. METHODS: Information on allergic disease symptoms and lifestyle factors was gathered in an interviewer-led cross-sectional questionnaire-based population survey of 9844 urban and 3032 rural participants of all ages. A one-in-four subsample underwent skin prick testing for hypersensitivity to Dermatophagoides pteronyssinus, mixed threshings, and aspergillus. RESULTS: Around 95% of those eligible took part in the survey. Lifetime cumulative prevalence of AD symptoms was generally low with an overall prevalence of 1.2%, but was higher in the urban (1.5%) than in the rural area (0.3%; odds ratio (OR)=4.45 [95% CI 2.34-8.47]). AD symptoms were strongly associated with wheeze (adjusted OR=22.03 [15.45-31.42]) and rhinitis symptoms (61.94 [42.66-89.95]). Of several environmental exposures assessed, residence in a house made of brick (rather than mud) walls with wooden (rather than clay) floor, exposure to cigarette smoke as a child, having lived outside of Jimma in the past, and being of the Tigrean ethnic group were associated with an increased risk of AD symptoms. CONCLUSION: Although the overall prevalence of AD symptoms was low in this Ethiopian population, a marked urban-rural gradient was evident. Lifestyle factors linked to urbanization were associated with an increased risk of AD symptoms.

Adolescent↗
PubMed2004

A study of smoking and smoking cessation on the curricula of UK medical schools.

OBJECTIVES: To identify current practice in teaching on smoking and smoking cessation in UK medical schools, and establish whether newly qualified UK doctors feel prepared to deliver smoking cessation interventions. DESIGN: Search of published curricula from all UK medical schools; questionnaire surveys of all UK medical school deans and UK qualified pre-registration house officers (PRHOs). PARTICIPANTS: Deans or nominated representatives from all 24 UK medical schools with current undergraduates, and all UK qualified PRHOs. MAIN OUTCOME MEASURES: Inclusion and organisation in curriculum of 15 predefined core topics related to smoking (deans); perceived readiness to deliver smoking cessation interventions (PRHOs). RESULTS: There was no mention of smoking or smoking cessation in the published curriculum material of 10 (42%) medical schools. Deans reported compulsory teaching on a mean (SD) of 9.5 (2.8) core topics, while PRHOs recalled compulsory teaching in only 6.6 (3.2). Training in clinical aspects of smoking cessation was particularly neglected, with 60% of PRHOs reporting that they graduated unable to deliver smoking cessation interventions in accordance with national guidelines. Only 17% of PRHOs felt well prepared to deliver advice on using nicotine replacement therapy, and 5% on bupropion. CONCLUSIONS: Teaching on smoking cessation in UK medical schools is inadequate.

Curriculum↗
PubMed2004

Vitamin E supplements in asthma: a parallel group randomised placebo controlled trial.

BACKGROUND: Increased dietary vitamin E intake is associated with a reduced incidence of asthma, and combinations of antioxidant supplements including vitamin E are effective in reducing ozone induced bronchoconstriction. A study was undertaken to investigate the effect of supplementation with vitamin E for 6 weeks on bronchial hyperresponsiveness in atopic adults with asthma. METHODS: 72 participants from a clinical trial register of adults with asthma were randomised to receive 500 mg natural vitamin E or matched placebo for 6 weeks in a placebo controlled, double blind parallel group clinical trial. Inclusion criteria included age 18-60 years, maintenance treatment of at least one dose of inhaled corticosteroid per day, a positive skin prick test to one of three common allergens, and bronchial hyperresponsiveness to methacholine (defined as a dose provoking a 20% fall in forced expiratory volume in 1 second (FEV(1)) (PD(20)) of 12.25 micromol). Secondary outcomes were FEV(1), forced vital capacity, mean morning and evening peak flow, symptom scores, bronchodilator use, and serum immunoglobulin E levels. RESULTS: In the primary intention to treat analysis the change in PD(20) was similar in the vitamin E and placebo groups with a mean difference of +0.25 doubling doses of methacholine (95% confidence interval -0.67 to +1.16 greater with vitamin E). There was no effect of vitamin E supplementation on any other measure of asthma control, either in the intention to treat or per protocol analysis. There was also no effect of vitamin E supplementation on serum immunoglobulin levels. CONCLUSION: Dietary supplementation with vitamin E adds no benefit to current standard treatment in adults with mild to moderate asthma.

Adolescent↗
PubMed2004

Amino acids and asthma: a case-control study.

Amino acids contribute to various anti-oxidant and immunological activities relevant to asthma pathogenesis, raising the possibility that differences in amino acids may be involved in asthma aetiology. The authors hypothesised that cystine reduces the risk of asthma via glutathione metabolism. Methionine, glutamine, glutamic acid and glycine may have potential protective effects, whilst arginine, phenylalanine and tryptophan may have adverse effects in asthma. Fasting plasma levels of amino acids were compared in a case-control study. A total of 89 adults, aged 18-65 yrs, with asthma controlled by inhaled corticosteroids, were recruited from a volunteer database and local primary care registers, and compared with 89 controls individually matched for age, sex and primary care centre. Contrary to the primary hypothesis, cases had higher fasting plasma cystine levels than controls, and there was no difference between cases and controls in any of the other amino acids tested, with the exception of plasma glycine, which was associated with a strongly reduced risk of asthma (odds ratio for the highest tertile compared to lowest 0.30 (95% confidence interval (0.11-0.82)). This study negates the hypothesis that higher fasting plasma cystine levels have a protective effect on the risk of asthma, although the inverse correlation with plasma glycine deserves further investigation.

Adolescent↗
PubMed2003

Quantum information processing with trapped ions.

Experiments directed towards the development of a quantum computer based on trapped atomic ions are described briefly. We discuss the implementation of single-qubit operations and gates between qubits. A geometric phase gate between two ion qubits is described. Limitations of the trapped-ion method such as those caused by Stark shifts and spontaneous emission are addressed. Finally, we describe a strategy to realize a large-scale device.

Journal Article↗
PubMed2003

Experimental demonstration of a robust, high-fidelity geometric two ion-qubit phase gate.

Universal logic gates for two quantum bits (qubits) form an essential ingredient of quantum computation. Dynamical gates have been proposed in the context of trapped ions; however, geometric phase gates (which change only the phase of the physical qubits) offer potential practical advantages because they have higher intrinsic resistance to certain small errors and might enable faster gate implementation. Here we demonstrate a universal geometric pi-phase gate between two beryllium ion-qubits, based on coherent displacements induced by an optical dipole force. The displacements depend on the internal atomic states; the motional state of the ions is unimportant provided that they remain in the regime in which the force can be considered constant over the extent of each ion's wave packet. By combining the gate with single-qubit rotations, we have prepared ions in an entangled Bell state with 97% fidelity-about six times better than in a previous experiment demonstrating a universal gate between two ion-qubits. The particular properties of the gate make it attractive for a multiplexed trap architecture that would enable scaling to large numbers of ion-qubits.

Journal Article↗
PubMed2003

Experimental demonstration of a technique to generate arbitrary quantum superposition states of a harmonically bound spin-1/2 particle.

Using a single, harmonically trapped 9Be(+) ion, we experimentally demonstrate a technique for generation of arbitrary states of a two-level particle confined by a harmonic potential. Rather than engineering a single Hamiltonian that evolves the system to a desired final state, we implement a technique that applies a sequence of simple operations to synthesize the state.

Journal Article↗
PubMed2003

Comparison of parent knowledge, therapy utilization and severity of atopic eczema before and after explanation and demonstration of topical therapies by a specialist dermatology nurse.

BACKGROUND: The failure of patients to take medicines in a way that leads to clinical benefit is a major challenge. A consensus has emerged that, on average, compliance sufficient to obtain therapeutic objectives occurs about half the time, with noncompliance contributing to therapeutic failure in the other half. These figures refer to simple oral regimens. There has been little work assessing compliance/concordance with complex treatment regimens for atopic eczema. Asthma schools led by specialist nurses have been shown to improve knowledge, use of therapies and clinical outcome. OBJECTIVES: To determine the effect of education and demonstration of topical therapies by specialist dermatology nurses on therapy utilization and severity of atopic eczema. METHODS: Fifty-one children with atopic eczema attending a paediatric dermatology clinic were followed for up to 1 year. At each visit the parent's knowledge about atopic eczema and its treatment and therapy utilization was recorded. The severity of the eczema was recorded using the six area, six sign atopic dermatitis severity score (SASSAD) and parental assessment of itch, sleep disturbance and irritability. At the first visit a specialist dermatology nurse explained and demonstrated how to use all of the topical treatments. This education was repeated at subsequent visits depending on the knowledge of the parent. RESULTS: At baseline less than 5% of parents had received/recalled receiving any explanation of the causes of eczema or demonstration of how to apply topical treatments. The eczema was poorly controlled in all children (mean SASSAD 42.9). Of the children, 24% were not being treated with any emollient cream/ointment; the mean use was 54 g weekly. Of the children, 25% were being inappropriately treated with potent or very potent topical steroids. Following repeated education and demonstration of topical therapies by a specialist dermatology nurse, there was an 89% reduction in the severity of the eczema. The main change in therapy utilization was an 800% increase in the use of emollients (to 426 g weekly of emollient cream/ointment) and no overall increase in the use of topical steroids, accounting for potency and quantity used. CONCLUSIONS: This study reinforces the importance of specialist dermatology nurses in the management of atopic eczema. It also confirms the opinion of patients, patient support groups, dermatologists and best practice guidelines that the most important intervention in the management of atopic eczema is to spend time to listen and explain its causes and demonstrate how to apply topical therapies.

Administration, Topical↗