Covariant nucleon electromagnetic form factors from the Goldstone-boson-exchange quark model

We present a study of proton and neutron electromagnetic form factors for the recently proposed Goldstone-boson-exchange constituent quark model. Results for charge radii, magnetic moments, and electric as well as magnetic form factors are reported. The calculations are performed in a covariant framework using the point-form approach to relativistic quantum mechanics. All the predictions by the Goldstone-boson-exchange constituent quark model are found in remarkably good agreement with existing experimental data.Comment: LATEX, 10 pages, including 4 ps-figures, slightly modified, one additional referenc

Mindful breath awareness meditation facilitates efficiency gains in brain networks: A steady-state visually evoked potentials study

The beneficial effects of mindfulness-based therapeutic interventions have stimulated a rapidly growing body of scientific research into underlying psychological processes. Resulting evidence indicates that engaging with mindfulness meditation is associated with increased performance on a range of cognitive tasks. However, the mechanisms promoting these improvements require further investigation. We studied changes in behavioural performance of 34 participants during a multiple object tracking (MOT) task that taps core cognitive processes, namely sustained selective visual attention and spatial working memory. Concurrently, we recorded the steady-state visually evoked potential (SSVEP), an EEG signal elicited by the continuously flickering moving objects, and indicator of attentional engagement. Participants were tested before and after practicing eight weeks of mindful breath awareness meditation or progressive muscle relaxation as active control condition. The meditation group improved their MOT-performance and exhibited a reduction of SSVEP amplitudes, whereas no such changes were observed in the relaxation group. Neither group changed in self-reported positive affect and mindfulness, while a marginal increase in negative affect was observed in the mindfulness group. This novel way of combining MOT and SSVEP provides the important insight that mindful breath awareness meditation may lead to refinements of attention networks, enabling more efficient use of attentional resources

An economic assessment of pre-vaccination screening for hepatitis A and B.

OBJECTIVE: The availability of a single vaccine active against hepatitis A and B may facilitate prevention of both infections, but complicates the question of whether to conduct pre-vaccination screening. The authors examined the cost-effectiveness of pre-vaccination screening for several populations: first-year college students, military recruits, travelers to hepatitis A-endemic areas, patients at sexually transmitted disease clinics, and prison inmates. METHODS: Three prevention protocols were examined: (1) screen and defer vaccination until serology results are known; (2) screen and begin vaccination immediately to avoid a missed vaccination opportunity; and (3) vaccinate without screening. Data describing pre-vaccination immunity, vaccine effectiveness, and prevention costs borne by the health system (i.e., serology, vaccine acquisition, and administration) were derived from published literature and U.S. government websites. Using spreadsheet models, the authors calculated the ratio of prevention costs to the number of vaccine protections conferred. RESULTS: The vaccinate without screening protocol was most cost-effective in nine of 10 analyses conducted under baseline assumptions, and in 69 of 80 sensitivity analyses. In each population considered, vaccinate without screening was less costly than and at least equally as effective as screen and begin vaccination. The screen and defer vaccination protocol would reduce costs in seven populations, but effectiveness would also be lower. CONCLUSIONS: Unless directed at vaccination candidates with the highest probability of immunity, pre-vaccination screening for hepatitis A and B immunity is not cost-effective. Balancing cost reduction with reduced effectiveness, screen and defer may be preferred for older travelers and prison inmates

Predicted Effects of a New Combination Vaccine on Childhood Immunization Coverage Rates and Vaccination Activities

Introduction: A new combination vaccine, diphtheria-tetanus-acellular pertussis (DTaP)-hepatitis B (HepB)-inactivated poliovirus vaccine (IPV) [DTaP-HepB-IPV], recently became available for use in the US primary infant-vaccination series. Our objectives were to estimate its effects on immunization-coverage rates, vaccination activities, and health-system costs in US dollars (2003 values). Methods: A model was developed and applied to medical records of 775 children born in mid-2001 who received primary care at 32 private pediatrics centers. DTaP-HepB-IPV use was predicted by applying decision rules to selectively substitute it for component vaccines, in compliance with the Advisory Committee on Immunization Practices' minimum age and time interval criteria. The model considered effects of DTaP-HepB-IPV on use of HepB at ageDTaP-hepatitis-B-poliovirus-vaccine, Immunisation-coverage, Vaccines

Valuation of Symptomatic Hepatitis A in Adults: Estimates Based on Time Trade-Off and Willingness-To-Pay Measurement

Background: The cost effectiveness of hepatitis A prevention is typically assessed by comparing vaccination costs with the number of life-years saved. This endpoint does not consider the benefits of preventing nonfatal yet symptomatic infections. Nearly as many days of healthy life are lost to hepatitis A morbidity as mortality. Objective: To investigate the value American adults place on preventing hepatitis A symptoms by using the willingness-to-pay and time trade-off metrics. Methods: We provided a written description of hepatitis A symptoms to 181 American adults, who judged the amounts of money and lifespan they would forego to avoid them. The description made no reference to the possibility of fatality, and respondents were asked not to consider costs of medical care and work loss. We investigated relationships between demographic characteristics and each metric, the relationship between the two metrics, and the test/re-test reliability of the metrics. Results: Respondents would pay a median of $US2000 (inter-quartile range,$US500 to 5000; 2001 values) for risk-free prevention of hepatitis A symptoms. Alternatively, they would forego a median of 28 days survival (inter-quartile range, 6 to 40 days) for cost-free prevention. There was modest correlation between willingness-to-pay and time trade-off responses (r = 0.24, pHepatitis A, Pharmacoeconomics, Willingness to pay