Constraints on oceanic methane emissions west of Svalbard from atmospheric in situ measurements and Lagrangian transport modeling

Methane stored in seabed reservoirs such as methane hydrates can reach the atmosphere in the form of bubbles or dissolved in water. Hydrates could destabilize with rising temperature further increasing greenhouse gas emissions in a warming climate. To assess the impact of oceanic emissions from the area west of Svalbard, where methane hydrates are abundant, we used measurements collected with a research aircraft (Facility for Airborne Atmospheric Measurements) and a ship (Helmer Hansen) during the Summer 2014 and for Zeppelin Observatory for the full year. We present a model-supported analysis of the atmospheric CH₄ mixing ratios measured by the different platforms. To address uncertainty about where CH₄ emissions actually occur, we explored three scenarios: areas with known seeps, a hydrate stability model, and an ocean depth criterion. We then used a budget analysis and a Lagrangian particle dispersion model to compare measurements taken upwind and downwind of the potential CH₄ emission areas. We found small differences between the CH₄ mixing ratios measured upwind and downwind of the potential emission areas during the campaign. By taking into account measurement and sampling uncertainties and by determining the sensitivity of the measured mixing ratios to potential oceanic emissions, we provide upper limits for the CH₄ fluxes. The CH₄ flux during the campaign was small, with an upper limit of 2.5 nmol m^-2 s^-1 in the stability model scenario. The Zeppelin Observatory data for 2014 suggest CH₄ fluxes from the Svalbard continental platform below 0.2 Tg yr^-1. All estimates are in the lower range of values previously reported.

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.

A longitudinal examination of psychosocial impairment across the anxiety disorders

BACKGROUND

Anxiety disorders are highly prevalent disorders associated with substantial psychosocial impairment, but few studies have examined impairment within specific anxiety disorders. Furthermore, it is unclear how change in different types of anxiety has an impact on change in impairment, particularly given high rates of co-morbidity. The current study assessed the temporal associations of impairment and symptoms of three common anxiety disorders in a large, diagnostically heterogeneous clinical sample.

METHOD

Data were collected from 606 treatment-seeking individuals at an anxiety clinic, most of whom subsequently enrolled in cognitive-behavioral therapy. Symptoms of panic, social anxiety and generalized anxiety disorder (GAD), as well as levels of impairment, were assessed three times over 2 years. In addition to examining levels of impairment across diagnostic groups, latent growth modeling was used to evaluate the longitudinal associations of anxiety symptoms and impairment.

RESULTS

Those with a principal diagnosis of GAD reported higher levels of impairment in some domains at baseline; however, at follow-up assessments individuals with social anxiety disorder reported greater impairment than those with panic disorder. Anxiety symptoms and impairment both declined over time. Change in all three anxiety symptoms was closely associated with change in impairment, but only GAD remained a significant (positive) predictor of change in impairment after accounting for co-morbidity.

CONCLUSIONS

Impairment and all three anxiety disorders were closely associated, both cross-sectionally and longitudinally. Because change in GAD was most specifically related to change in impairment, treatment for those with multiple anxiety disorders could focus on treating GAD symptoms first or treating transdiagnostic processes.

The atmospheric chemistry of trace gases and particulate matter emitted by different land uses in Borneo

We report measurements of atmospheric composition over a tropical rainforest and over a nearby oil palm plantation in Sabah, Borneo. The primary vegetation in each of the two landscapes emits very different amounts and kinds of volatile organic compounds (VOCs), resulting in distinctive VOC fingerprints in the atmospheric boundary layer for both landscapes. VOCs over the Borneo rainforest are dominated by isoprene and its oxidation products, with a significant additional contribution from monoterpenes. Rather than consuming the main atmospheric oxidant, OH, these high concentrations of VOCs appear to maintain OH, as has been observed previously over Amazonia. The boundary-layer characteristics and mixing ratios of VOCs observed over the Borneo rainforest are different to those measured previously over Amazonia. Compared with the Bornean rainforest, air over the oil palm plantation contains much more isoprene, monoterpenes are relatively less important, and the flower scent, estragole, is prominent. Concentrations of nitrogen oxides are greater above the agro-industrial oil palm landscape than over the rainforest, and this leads to changes in some secondary pollutant mixing ratios (but not, currently, differences in ozone). Secondary organic aerosol over both landscapes shows a significant contribution from isoprene. Primary biological aerosol dominates the super-micrometre aerosol over the rainforest and is likely to be sensitive to land-use change, since the fungal source of the bioaerosol is closely linked to above-ground biodiversity.

Challenges in quantifying biosphere-atmosphere exchange of nitrogen species

Recent research in nitrogen exchange with the atmosphere has separated research communities according to N form. The integrated perspective needed to quantify the net effect of N on greenhouse-gas balance is being addressed by the NitroEurope Integrated Project (NEU). Recent advances have depended on improved methodologies, while ongoing challenges include gas-aerosol interactions, organic nitrogen and N(2) fluxes. The NEU strategy applies a 3-tier Flux Network together with a Manipulation Network of global-change experiments, linked by common protocols to facilitate model application. Substantial progress has been made in modelling N fluxes, especially for N(2)O, NO and bi-directional NH(3) exchange. Landscape analysis represents an emerging challenge to address the spatial interactions between farms, fields, ecosystems, catchments and air dispersion/deposition. European up-scaling of N fluxes is highly uncertain and a key priority is for better data on agricultural practices. Finally, attention is needed to develop N flux verification procedures to assess compliance with international protocols.

Street canyon aerosol pollutant transport measurements

Current understanding of dispersion in street canyons is largely derived from relatively simple dispersion models. Such models are increasingly used in planning and regulation capacities but are based upon a limited understanding of the transport of substances within a real canyon. In recent years, some efforts have been made to numerically model localised flow in idealised canyons (e.g., J. Appl. Meteorol. 38 (1999) 1576-89) and stepped canyons (Assimakopoulos V. Numerical modelling of dispersion of atmospheric pollution in and above urban canopies. PhD thesis, Imperial College, London, 2001) but field studies in real canyons are rare. To further such an understanding, a measurement campaign has been conducted in an asymmetric street canyon with busy one-way traffic in central Manchester in northern England. The eddy correlation method was used to determine fluxes of size-segregated accumulation mode aerosol. Measurements of aerosol at a static location were made concurrently with measurements on a platform lift giving vertical profiles. Size-segregated measurements of ultrafine and coarse particle concentrations were also made simultaneously at various heights. In addition, a small mobile system was used to make measurements of turbulence at various pavement locations within the canyon. From this data, various features of turbulent transport and dispersion in the canyon will be presented. The concentration and the ventilation fluxes of vehicle-related aerosol pollutants from the canyon will be related to controlling factors. The results will also be compared with citywide ventilation data from a separate measurement campaign conducted above the urban canopy.

Adjunctive color Doppler ultrasonography in second-trimester transabdominal amnioinfusion

Transabdominal amnioinfusion improves the diagnostic accuracy of ultrasonography in pregnancies complicated by second-trimester oligohydramnios. Needle localization may be difficult because of patient obesity or the absence of an acoustic window. The two cases presented demonstrate that color Doppler imaging facilitates amnioinfusion by visualizing the injection jet of free-flowing infusate, confirming intraamniotic needle placement.

The effect of sulphur chemistry on the scattering properties of particles

A model has been developed of the interaction of aerosol with shallow layer clouds. The model includes aqueous phase chemical processes, particularly the oxidation of sulphur dioxide (SO 2 ) occurring in droplets formed on cloud condensation nuclei of known chemical composition. The cloud microphysics as a function of height above cloud base is predicted along with changes to the aerosol size distribution and hygroscopic properties after a single cycle through cloud. The predictions of the model are compared with observations from a hill cap cloud experiment for a single cloud pass. A stratocumulus cloud model then examines the changes in the cloud microphysics and aerosol population arising as the modified aerosol distribution undergoes a further passage through cloud. The cycling process is repeated a further nine times. We show that the cloud processing of the aerosol results in a strongly bimodal aerosol size distribution which can significantly affect the direct radiative forcing of the aerosol. The processing is strongly oxidant-limited and forced entrainment of hydrogen peroxide through cloud top is required to maintain the oxidation. A strong surface source of ammonia substantially enhances the observed modification. The processing affects the cloud condensation nucleus spectrum, initially increasing the number of droplets activated. However, multiple cycling has a tendency to stabilize the droplet number.

Complicated right subclavian artery pseudoaneurysm after central venipuncture

Life-threatening complications of central venipuncture are rare. We report an unusual case of a patient in whom a large right subclavian pseudoaneurysm developed, causing pressure necrosis of the membranous trachea and esophagus, after right internal jugular vein cannulation. The patient underwent oversewing of the proximal and distal ends of the subclavian artery and primary tracheal repair. An esophageal leak that presented on the sixth postoperative day was treated by primary suture repair with proximal and distal diversion.

Fetal heart rate accelerations, fetal movement, and fetal behavior patterns in twin gestations

OBJECTIVE

Previous studies have shown that twins, when monitored simultaneously, show a remarkably high incidence of coincident fetal heart rate accelerations (about 58%). The current study examines synchrony of behavior patterns in twins.

STUDY DESIGN

We examined 37 fetal monitor strips from 15 sets of twins with simultaneous fetal heart rate and fetal movement recorded by means of Doppler techniques (Toitu MT-430 fetal actocardiograph). The strips were analyzed for coincidence of fetal heart rate accelerations and fetal movement episodes and then conceptually for synchrony of fetal behavior patterns on the basis of descriptions of behavioral states by Prechtl.

RESULTS

Thirty-six percent of fetal heart rate accelerations were found to be simultaneous. Forty-three percent of movement epochs were considered simultaneous. We found that twins exhibited synchronous behavior patterns (basically sleep or awake state) 94.7% of the time.

CONCLUSION

Twin-twin interactions are more consistently related than suspected when observation is limited to heart rate alone, and the synchrony and role of fetal behavior states must be considered when twin interactions and behavior are studied.

Emergent applications of cardiopulmonary support: a multiinstitutional experience

The use of emergent portable bypass systems is increasing. Because of limited patient use in any one institution, a combined experience can better determine the applicability of these systems. A total of 187 patients from 17 centers were analyzed. Causes leading to bypass initiation were cardiac arrest (125 patients), cardiogenic shock (44), profound hypothermia (7), pulmonary insufficiency (9), and miscellaneous (2). Weaning from bypass was successful in 30.5% (57 patients). Sixty-four patients (34.2%) were transferred to standard bypass or other modes of circulatory assist. Of the total population, 40 patients (21.4%) were alive greater than 30 days. There were no survivors of unwitnessed arrests. Major diagnostic or therapeutic interventions were carried out on bypass in 74.9% of all patients. In survivors, 77.1% (37/48) had major therapeutic interventions as compared with 50.0% (67/135) of nonsurvivors. Emergency portable bypass systems can successfully resuscitate and support cardiac hemodynamics, although the underlying causes necessitating bypass remain difficult to correct. When corrective intervention can be performed, there is an increased chance of survival. Unwitnessed arrest, prolonged cardiopulmonary resuscitation, and lack of treatment options are relative contraindications. Appropriate patient selection and early application of these systems should lead to improved survival.

Measurements and modelling of cloudwater deposition to moorland and forests

The objective of the study was to measure the size dependence of cloudwater deposition and associated average ionic fluxes to vegetated surfaces. Measurements were made over a forest canopy at Dunslair heights in south Scotland and a moorland site, Great Dun Fell, in northern England. Measurements were made using the gradient and eddy correlation techniques. Eddy correlation measurements were made using an ultrasonic anemometer, a Knollenberg forward scattering spectrometer probe (to measure liquid water fluxes and fluxes of droplets in 1 microm size intervals) and a GSI particulate volume monitor (to measure liquid-water fluxes). Measurements were made at Great Dun Fell of the size dependence of droplet deposition velocity, using the gradient technique with two Knollenberg probes. Simultaneous gradient and eddy correlation measurements were also made at Great Dun Fell of average cloud-water fluxes, together with chemical analysis of cloud water composition, using a continuous analysis system. At Dunslair Heights, eddy correlation measurements were made using both the Knollenberg and Gerber Scientific Instruments (GSI) probes, while simultaneous gradient measurements using two GSI probes were also attempted. Samples of cloud water were collected at Dunslair Heights, using passive string collectors for chemical analysis by ion chromatography. The major findings of the study were: 1. The droplet deposition velocities measured by the two techniques were similar. 2. The deposition velocities were a strong function of droplet size. Considerable resistance to deposition was evident for droplets of less than 5 microm radius. Deposition velocities for particles from about 6 to 8 microm exceeded those for momentum. 3. Except when the droplets were very small or the winds very light, bulk cloud-water deposition velocities were about 80% or more of the momentum deposition velocities to forests.

A field study of the generation of nitrate in a hill cap cloud

A field experiment to investigate the formation of nitrate as an airstream passes through a hill cap cloud has been performed at the UMIST field station on Great Dun Fell. It has been shown that the aerosol nitrate concentration increased by about 0.5 microg m(-3) as the airstream passed through the cloud during the night. At sunrise the nitrate production disappeared. It is suggested that the most likely mechanism for this nitrate production was due to the solution of N2O5 and NO3 formed from the reaction of NO2 with O3. These higher oxides build up overnight in the absence of short wave radiation to photolyse them. Other possible mechanisms of nitrate production are also discussed.

Cervical pregnancy. A report of two cases

Cervical pregnancy is a rarely occurring form of ectopic pregnancy. Given its rarity, the identification of risk factors is based on anecdotal case reports and occasional summarizing reviews. We managed two additional cases with a new, conservative approach. The trend is away from radical therapy and toward conservation of reproductive function.

Intraoperative assessment of tricuspid valve function after conservative repair

It is desirable to repair coexistent tricuspid valve pathology at the time of mitral valve corrections. Conservative tricuspid repair may consist of commissurotomy, annuloplasty, or both. It is important that the repair be appropriate or tricuspid valve replacement may be necessary. A simple reproducible method of intraoperative testing for tricuspid valve insufficiency has been developed and used in 25 patients. Fifteen patients have been recatheterized, and the correlation between the intraoperative and postoperative findings has been consistent.

The topical myocardial cooling device: Correlation of its effectiveness with method of cannulation and core temperature of the patient

The Topical Cooling Device(R)(*) (TCD) is a closed system that circulates sterile saline solution at 4 degrees C in the pericardium. The system's ability to maintain cardiac hypothermia under clinical conditions depends on the method of cannulation and the core temperature of the patient. After studies were done in ten groups of patients, with at least three patients in each group, the effects of these two variables on TCD performance were then observed in a series of over 250 coronary artery bypass cases and are summarized in the following report.

The anatomic basis for the occasional failure of transfemoral balloon catheter thromboembolectomy

A Fogarty balloon catheter was advanced from the common femoral artery through the popliteal artery and its branches in 15 cadavers. The catheter passed into the peroneal branch 89% of the time. In all 15 cadavers, the peroneal artery was the direct continuation of the popliteal artery and the arterior tibial and posterior tibial arteries branched off at varying angles from the popliteal. This provides an anatomic explanation for the occasional failure of transfemoral Fogarty catheter embolectomy of the leg. Our study suggests that if the patient's foot does not improve after Fogarty embolectomy, the popliteal artery should be exposed and the catheter directed into the shank arteries using vascular forceps.