Evaluating methane inventories by isotopic analysis in the London region.

A thorough understanding of methane sources is necessary to accomplish methane reduction targets. Urban environments, where a large variety of methane sources coexist, are one of the most complex areas to investigate. Methane sources are characterised by specific δ13C-CH4 signatures, so high precision stable isotope analysis of atmospheric methane can be used to give a better understanding of urban sources and their partition in a source mix. Diurnal measurements of methane and carbon dioxide mole fraction, and isotopic values at King's College London, enabled assessment of the isotopic signal of the source mix in central London. Surveys with a mobile measurement system in the London region were also carried out for detection of methane plumes at near ground level, in order to evaluate the spatial allocation of sources suggested by the inventories. The measured isotopic signal in central London (-45.7 ±0.5‰) was more than 2‰ higher than the isotopic value calculated using emission inventories and updated δ13C-CH4 signatures. Besides, during the mobile surveys, many gas leaks were identified that are not included in the inventories. This suggests that a revision of the source distribution given by the emission inventories is needed.

Marked long-term decline in ambient CO mixing ratio in SE England, 1997-2014: evidence of policy success in improving air quality.

Atmospheric CO at Egham in SE England has shown a marked and progressive decline since 1997, following adoption of strict controls on emissions. The Egham site is uniquely positioned to allow both assessment and comparison of 'clean Atlantic background' air and CO-enriched air downwind from the London conurbation. The decline is strongest (approximately 50 ppb per year) in the 1997-2003 period but continues post 2003. A 'local CO increment' can be identified as the residual after subtraction of contemporary background Atlantic CO mixing ratios from measured values at Egham. This increment, which is primarily from regional sources (during anticyclonic or northerly winds) or from the European continent (with easterly air mass origins), has significant seasonality, but overall has declined steadily since 1997. On many days of the year CO measured at Egham is now not far above Atlantic background levels measured at Mace Head (Ireland). The results are consistent with MOPITT satellite observations and 'bottom-up' inventory results. Comparison with urban and regional background CO mixing ratios in Hong Kong demonstrates the importance of regional, as opposed to local reduction of CO emission. The Egham record implies that controls on emissions subsequent to legislation have been extremely successful in the UK.

Measurements of δ13C in CH4 and using particle dispersion modeling to characterize sources of Arctic methane within an air mass.

A stratified air mass enriched in methane (CH4) was sampled at ~600 m to ~2000 m altitude, between the north coast of Norway and Svalbard as part of the Methane in the Arctic: Measurements and Modelling campaign on board the UK's BAe-146-301 Atmospheric Research Aircraft. The approach used here, which combines interpretation of multiple tracers with transport modeling, enables better understanding of the emission sources that contribute to the background mixing ratios of CH4 in the Arctic. Importantly, it allows constraints to be placed on the location and isotopic bulk signature of the emission source(s). Measurements of δ13C in CH4 in whole air samples taken while traversing the air mass identified that the source(s) had a strongly depleted bulk δ13C CH4 isotopic signature of -70 (±2.1)‰. Combined Numerical Atmospheric-dispersion Modeling Environment and inventory analysis indicates that the air mass was recently in the planetary boundary layer over northwest Russia and the Barents Sea, with the likely dominant source of methane being from wetlands in that region.

Blood pressure and cerebral oxygenation responses to skeletal muscle tension: a comparison of two physical maneuvers to prevent vasovagal reactions.

AIM: The present study compared blood pressure, heart rate, and cerebral oxygenation responses to two manipulations used to prevent vasovagal reaction -- skeletal muscle tensing alone and skeletal muscle tensing with leg crossing. METHODS AND RESULTS: Using a repeated measures within-subjects design, healthy young adults engaged in a brief laboratory protocol that included an initial 3 min resting baseline, 3 min of muscle tensing (or no-tensing control), and a 1 min orthostatic challenge. This sequence was repeated three times for each participant to allow for a direct comparison of physiological responses to two different muscle-tensing manipulations as compared to the no-tensing control condition. Results indicated that, relative to the no-tensing, both muscle tensing manipulations elicited significant increases in systolic blood pressure (8.7 +/- 1.1 mmHg), diastolic blood pressure (4.9 +/- 0.6 mmHg), and heart rate (10.9 +/- 0.9 bpm), while a significant increase in cerebral oxygenation was only observed in response to muscle tensing with legs crossed (0.8 +/- 0.2%). Blood pressure and heart rate responses to orthostatic challenge did not differ between the two tensing manipulations, although muscle tensing with legs crossed was followed by a more rapid recovery of cerebral oxygenation levels. CONCLUSION: These findings suggest that muscle tensing elicits physiological adaptations that may help reduce the risk of vasovagal reactions; however, the combination of lower body tension with the legs crossed is likely to be most effective as it was uniquely associated with significant increases in the flow of oxygenated blood to the brain.

Change mechanisms associated with combined relaxation/EMG biofeedback training for chronic tension headache.

Therapeutic mechanisms hypothesized to underlie improvements in tension headache activity achieved with combined relaxation and electromyographic (EMG) biofeedback therapy were examined. These therapeutic mechanisms included (1) changes in EMG activity in frontal and trapezii muscles, (2) changes in central pain modulation as indexed by the duration of the second exteroceptive silent period (ES2), and (3) changes in headache locus of control and self-efficacy. Forty-four young adults with chronic tension-type headaches were assigned either to six sessions of relaxation and EMG biofeedback training (N = 30) or to an assessment only control group (N = 14) that required three assessment sessions. Measures of self-efficacy and locus of control were collected at pre- and posttreatment, and ES2 was evaluated at the beginning and end of the first, third, and last session. EMG was monitored before, during, and following training trials. Relaxation/EMG biofeedback training effectively reduced headache activity: 51.7% of subjects who received relaxation/biofeedback therapy recorded at least a 50% reduction in headache activity following treatment, while controls failed to improve on any measure. Improvements in headache activity in treated subjects were correlated with increases in self-efficacy induced by biofeedback training but not with changes in EMG activity or in ES2 durations. These results provide additional support for the hypothesis that cognitive changes underlie the effectiveness of relaxation and biofeedback therapies, at least in young adult tension-type headache sufferers.

Enhancing the effectiveness of relaxation-thermal biofeedback training with propranolol hydrochloride.

This article evaluated the ability of propranolol to enhance results achieved with relaxation-biofeedback training. Thirty-three patients were randomized to relaxation-biofeedback training alone (administered in a limited-contact treatment format), or to relaxation-biofeedback training accompanied by long-acting propranolol (with dosage individualized at 60, 120, or 180 mg/day). Concomitant propranolol therapy significantly enhanced the effectiveness of relaxation-biofeedback training when either daily headache recordings (79% vs. 54% reduction in migraine activity) or neurologist clinical evaluations (90% vs. 66% reduction) were used to assess treatment outcome. Concomitant propranolol therapy also yielded larger reductions in analgesic medication use and greater improvements of quality of life measures than relaxation-biofeedback training alone but was more frequently associated with side effects.

[Keratomileusis without freezing--results with a 6-month follow-up]. / Kératomyleusis non gel--résultats avec un recul de 6 mois.

The authors describe the planar lamellar refractive keratoplasty without freezing and the results for six months.