Microphysical explanation of the RH-dependent water affinity of biogenic organic aerosol and its importance for climate.

A large fraction of atmospheric organic aerosol (OA) originates from natural emissions that are oxidized in the atmosphere to form secondary organic aerosol (SOA). Isoprene (IP) and monoterpenes (MT) are the most important precursors of SOA originating from forests. The climate impacts from OA are currently estimated through parameterizations of water uptake that drastically simplify the complexity of OA. We combine laboratory experiments, thermodynamic modeling, field observations, and climate modeling to (1) explain the molecular mechanisms behind RH-dependent SOA water-uptake with solubility and phase separation; (2) show that laboratory data on IP- and MT-SOA hygroscopicity are representative of ambient data with corresponding OA source profiles; and (3) demonstrate the sensitivity of the modeled aerosol climate effect to assumed OA water affinity. We conclude that the commonly used single-parameter hygroscopicity framework can introduce significant error when quantifying the climate effects of organic aerosol. The results highlight the need for better constraints on the overall global OA mass loadings and its molecular composition, including currently underexplored anthropogenic and marine OA sources.

Criegee intermediates in the indoor environment: new insights.

Criegee intermediates are formed in the ozonolysis of alkenes and play an important role in indoor chemistry, notably as a source of OH radicals. Recent studies have shown that these Criegee intermediates react very quickly with NO2 , SO2 , and carbonyls, and in this study, steady-state calculations are used to inspect the potential impact of these data on indoor chemistry. It is shown that these reactions could accelerate NO3 formation and SO2 removal in the indoor environment significantly. In addition, reaction between Criegee intermediates and halogenated carbonyls could provide a significant loss process indoors, where currently one does not exist.

The relationship between aerosol concentration and atmospheric potential gradient in urban environments.

Urban aerosol is a growing concern for people living within cities; aerosol have been implicated in many ill health conditions, including that of the lung and of the heart. Atmospheric potential gradient is a consequence of charge carried to the ionosphere through thunderstorms, and its value depends on highly electrically mobile ion concentrations, hence local conductivity of the air. Ions attach to aerosol in the atmosphere, reducing their mobility and therefore increasing the potential gradient, and so potential gradient measurements have been suggested as a proxy for aerosol measurements. Particle number count, size distribution and potential gradient were measured for two campaigns in Manchester, U.K., and one campaign in Bristol, U.K. Using a factor based on size distribution to account for preferential attachment at larger sizes provided the best relationship with potential gradient, but particle count alone showed a weaker, but similar relationship. The increase in particle count caused by annual bonfire and fireworks celebrations (November) was evidenced in both potential gradient and particle numbers. Daily regression or correlation did not show a consistent relationship. In the larger Bristol data set, increasing humidity led to a reduction of potential gradient, while increasing particle number led to an increase.

Criegee intermediates and their impacts on the troposphere.

Criegee intermediates (CIs), carbonyl oxides formed in ozonolysis of alkenes, play key roles in the troposphere. The decomposition of CIs can be a significant source of OH to the tropospheric oxidation cycle especially during nighttime and winter months. A variety of model-measurement studies have estimated surface-level stabilized Criegee intermediate (sCI) concentrations on the order of 1 × 104 cm-3 to 1 × 105 cm-3, which makes a non-negligible contribution to the oxidising capacity in the terrestrial boundary layer. The reactions of sCI with the water monomer and the water dimer have been found to be the most important bimolecular reactions to the tropospheric sCI loss rate, at least for the smallest carbonyl oxides; the products from these reactions (e.g. hydroxymethyl hydroperoxide, HMHP) are also of importance to the atmospheric oxidation cycle. The sCI can oxidise SO2 to form SO3, which can go on to form a significant amount of H2SO4 which is a key atmospheric nucleation species and therefore vital to the formation of clouds. The sCI can also react with carboxylic acids, carbonyl compounds, alcohols, peroxy radicals and hydroperoxides, and the products of these reactions are likely to be highly oxygenated species, with low vapour pressures, that can lead to nucleation and SOA formation over terrestrial regions.

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.

Physical and chemical processes of air masses in the Aegean Sea during Etesians: Aegean-GAME airborne campaign.

High-resolution measurements of gas and aerosols' chemical composition along with meteorological and turbulence parameters were performed over the Aegean Sea (AS) during an Etesian outbreak in the framework of the Aegean-GAME airborne campaign. This study focuses on two distinct Etesian patterns, with similarities inside the Marine Atmospheric Boundary Layer (MABL) and differences at higher levels. Under long-range transport and subsidence the pollution load is enhanced (by 17% for CO, 11% for O3, 28% for sulfate, 62% for organic mass, 47% for elemental carbon), compared to the pattern with a weaker synoptic system. Sea surface temperature (SST) was a critical parameter for the MABL structure, turbulent fluxes and pollutants' distribution at lower levels. The MABL height was below 500 m asl over the eastern AS (favoring higher accumulation), and deeper over the western AS. The most abundant components of total PM1 were sulfate (40-50%) and organics (30-45%). Higher average concentrations measured over the eastern AS (131 ± 76 ppbv for CO, 62.5 ± 4.1 ppbv for O3, 5.0 ± 1.1 µg m(-3) for sulfate, 4.7 ± 0.9 µg m(-3) for organic mass and 0.5 ± 0.2 µg m(-3) for elemental carbon). Under the weaker synoptic system, cleaner but more acidic air masses prevailed over the eastern part, while distinct aerosol layers of different signature were observed over the western part. The Aitken and accumulation modes contributed equally during the long-range transport, while the Aitken modes dominated during local or medium range transport.

Transcutaneous monitoring of oxygen tension during one-lung anesthesia.

Twenty adult patients were monitored with a transcutaneous oxygen tension sensor during one-lung ventilation. Anesthesia was maintained with enflurane-oxygen or isoflurane-oxygen. The transcutaneous oxygen tension values accurately followed the trend of arterial oxygen tension (r = 0.94, n = 96, transcutaneous oxygen tension = 4.8 + 0.78 X arterial oxygen tension). The transcutaneous oxygen tension values averaged 80% of the arterial oxygen tension values (transcutaneous oxygen tension index = transcutaneous oxygen tension/arterial oxygen tension = 0.80 +/- 0.18) (mean +/- standard deviation). When one-lung ventilation was initiated, there was a progressive drop in transcutaneous oxygen tension which reached a minimum of 19 +/- 10 minutes. The mean of the minimum transcutaneous oxygen tension and arterial oxygen tension values was 66 +/- 44 torr and 83 +/- 43 respectively. This resulted in a mean alveolar-arterial oxygen gradient of 515 +/- 152 torr during one-lung ventilation. In eight patients, the arterial oxygen tension fell below 60 torr, 45 +/- 9 torr. When two-lung ventilation was resumed, the transcutaneous oxygen tension and arterial oxygen tension values promptly rose to mean values of 342 +/- 121 torr and 411 +/- 103 torr, respectively in 9 +/- 3 minutes. The transcutaneous oxygen tension monitor provided a continuous assessment of the patient's oxygenation, gave early warning of potentially hazardous hypoxia, and permitted nearly real-time assessment of the efficacy of corrective therapies.

Added inspiratory work of breathing during CPAP ventilation: comparison of two demand-valve devices with a continuous flow-system.

Measurements of added inspiratory work (AIW) of breathing imposed by three different CPAP systems were performed in 10 patients. One system was a continuous flow system while the two others were demand flow systems separated from respirators (Ohmeda VD 101 and Draeger CPAP 800 devices). AIW was calculated from pressure and flow signals recorded at the mouthpiece level. The AIW calculated with the two demand-flow systems was found to be the same as the AIW calculated with the continuous flow system although the results obtained by the Draeger device were less constant. The results obtained with the Ohmeda device in our patients conflicted with data previously published using a lung model.

Intravesical ethanol as quantitative measure of bladder hyperpermeability.

BACKGROUND AND PURPOSE: Bladder surface hyperpermeability may be a factor in the etiology of interstitial cystitis (IC). We evaluated the intravesical instillation of ethanol as a quantitative measure of bladder hyperpermeability in an experimental model in male New Zealand White rabbits. MATERIALS AND METHODS: In two study groups (N = 4 each), the glycosaminoglycan (GAG) layer on the bladder surface was disrupted via a 10-minute exposure to 10% protamine sulfate (PS). The study groups then underwent bladder instillation of 10% (group 1) and 20% (group 2) ethanol. The control groups underwent bladder instillation of either 10% (N = 2) or 20% ethanol (N = 2) without exposure to PS. Ten minutes after ethanol instillation, venous blood was sampled, and the ethanol concentration was determined by mass spectrometry. Study group animals were sacrificed after blood sampling. Control animals were sacrificed at 2 weeks and 4 weeks for histologic examination of the bladder. RESULTS: The blood alcohol concentration was 0 in the control animals exposed to 10% or 20% ethanol, 14.5+/-2.2 ng/dL in the 10% ethanol study group, and 25.6+/-3.6 ng/dL in the 20% ethanol study group. Histologic examination of bladder tissue revealed no ethanol-induced abnormalities in the control animals. CONCLUSION: Intravesical instillation of 10% and 20% ethanol is a safe and reliable quantitative measure of bladder hyperpermeability in an animal model. Clinical trials are ongoing to evaluate the utility of the intravesical ethanol test for diagnosing IC and monitoring the response to therapy.

Pentosanpolysulfate coating of silicone reduces encrustation.

BACKGROUND AND PURPOSE: A significant problem associated with catheterization in the urinary tract is the encrustation of the catheter materials. One approach to reducing encrustation is to alter the surface properties of the catheters. We evaluated the effectiveness of coating with pentosanpolysulfate (PPS), a semisynthetic polysaccharide similar to heparin, in reducing encrustation and the foreign-body inflammatory response to silicone stents in the bladders of male New Zealand White rabbits. MATERIALS AND METHODS: Sixteen rabbits were divided into three groups to receive placement in their bladders of uncoated (N = 7), PPS-coated (N = 7), or sham matrix-processed silicone rings (N = 2) via open cystotomy. After 50 days of maintenance on normal food and water, all rabbits were sacrificed, and the air-dried, unfixed silicone ring surfaces were examined by scanning electron microscopy. Bladders and remaining silicone rings were removed and preserved separately. Silicone rings, cleaned of all encrustation, were stained with toluidene blue to determine the presence or absence of PPS coating on the surface. RESULTS: Histologic examination revealed normal tissue in bladder sections exposed to coated silicone rings and an inflammatory response in sections from bladders having uncoated silicone rings. Coating with PPS was associated with an eightfold reduction in the amount of encrustation of silicone and a marked reduction in the inflammatory response of the bladder wall to the foreign body. CONCLUSIONS: A PPS coating may be useful in reducing the encrustation of long-term indwelling silicone stents or catheters in the human urinary tract.

[Continuous measurement of gas exchange during artificial ventilation]. / Mesure en continu des échanges gazeux au cours de la ventilation artificielle.

A system for on-line measurement of respiratory gas exchange in patients undergoing artificial ventilation is described. Fractional concentrations were measured by a mass spectrometer and expired flow by a pneumotachometer; signals processing was carried out by a microcomputer. The accuracy of the measurement of the burning methanol RQ was within 1.6% at FIO2 lower or equal to 0.4. When compared to a reference method (the Douglas bag method), correlation was found to be excellent. The major problem in measuring gas exchange in a ventilated patient is that physiological signals are contaminated by artefacts which may lead to erroneous computations. An algorithm was developed in order to identify and disregard artefacted periods or ventilatory unsteady state in the patients. The technique used for data processing gave reliable continuous measurements of respiratory gas exchange for periods up to 24 h, without interfering with the nursing of the ventilated patients.

Contribution of depression and anxiety to impaired health-related quality of life following first myocardial infarction.

BACKGROUND: The extent to which depression impairs health-related quality of life (HRQoL) in the physically ill has not been clearly established. AIMS: To quantify the adverse influence of depression and anxiety, assessed at the time of first myocardial infarction and 6 months later, on the physical aspect of HRQoL 12 months after the infarction. METHOD: In all, 260 in-patients, admitted following first myocardial infarction, completed the Hospital Anxiety and Depression Scale and the Medical Outcomes Study SF-36 assessment before discharge and at 6- and 12-month follow-up. RESULTS: Depression and anxiety 6 months after myocardial infarction predicted subsequent impairment in the physical aspects of HRQoL (attributable adjusted R(2)=9%, P<0.0005). These negative effects of depression and anxiety on outcome were mediated by feelings of fatigue. Depression and anxiety present before myocardial infarction did not predict HRQoL 12 months after myocardial infarction. CONCLUSIONS: Detection and treatment of depression and anxiety following myocardial infarction improve the patient's health-related quality of life.

Layer guided-acoustic plate mode biosensors for monitoring MHC-peptide interactions.

The transduction signals from the immobilisation of a class I heavy chain, HLA-A2, on a layer guided acoustic plate mode device, followed by binding of beta(2)-microglobulin and subsequent selective binding of a target peptide are reported.

Structural analysis of oligomeric molecules formed from the reaction products of oleic acid ozonolysis.

The products arising from the ozonolysis of oleic acid (cis-9-octadecenoic acid) in solution have been studied using negative ion mode electrospray ionization ion trap mass spectrometry. Oleic acid is an important component of atmospheric organic aerosol and is a key model species in predicting aerosol physical and chemical characteristics. The four predicted reaction products, 1-nonanal, nonanoic acid, 9-oxononanoic acid, and azelaic acid, were all observed in roughly equal yields. In addition to these products a large number of higher molecular weight compounds were detected with m/z ratios of up to 1000 Daltons. Tandem mass spectrometry of these larger ions revealed thatthey represented a complex mixture of linear alpha-acyloxyalkyl hydroperoxides, secondary ozonides, and cyclic diperoxides, formed by reactions between ozonolysis products and Criegee intermediates. These comprise the first directly elucidated structures of large oligomeric species from oleic acid ozonolysis. The degree of oligomerization and hence molecular weight distribution was observed to increase with reaction time in solution.

Oxygen delivery and uptake in the adult respiratory distress syndrome. Lack of relationship when measured independently in patients with normal blood lactate concentrations.

This study was designed to determine whether acute alterations in oxygen delivery (DO2) induced by the institution of positive end-expiratory pressure (PEEP) would affect oxygen uptake (VO2) in patients with adult respiratory distress syndrome (ARDS). In 8 patients with ARDS who exhibited normal blood lactate concentrations, we evaluated the relationship between DO2 and VO2 during 3 consecutive periods: intermittent positive pressure ventilation (IPPV), continuous positive pressure ventilation (CPPV) with a 10 cm H2O PEEP, and finally CPPV with volume loading. Oxygen uptake was measured directly with a mass spectrometer system. Oxygen delivery was calculated as the product of cardiac output (thermodilution) and arterial blood oxygen content (Lex-O2-Con analyzer). By comparison with the IPPV period, application of PEEP led to a decrease of DO2, which returned to baseline values when volume loading was added to PEEP. In none of the patients did VO2 parallel the changes of DO2. They demonstrated, therefore, a properly enhanced oxygen extraction during the PEEP-induced decrease of DO2. We conclude that, when measured independently, DO2 and VO2 are not correlated in patients with ARDS with normal blood lactate who are mechanically ventilated with PEEP.

Arterial-alveolar oxygen partial pressure ratio: a theoretical reappraisal.

The relationship between the arterial-alveolar oxygen partial pressure ratio (PaO2/PAO2) and different fractions of inspired oxygen (FIO2) was studied using a bicompartmental computer model. PaO2/PAO2 was found to be less stable than in previous clinical works probably because the venous admixture varied with changes in the FIO2.

Molecular imprinted polymer coated QCM for the detection of nandrolone.

An acoustic wave sensor coated with an artificial biomimetic recognition element has been developed to selectively screen for nandrolone in the liquid phase. A highly specific covalently imprinted polymer (MIP) was spin coated onto one electrode of a quartz crystal microbalance (QCM) as a thin permeable film. Selective rebinding of the nandrolone was observed as a frequency shift in the QCM for concentrations up to 0.2 ppm with the sensor binding shown to favour nandrolone over analogous compounds.

Detection of polycyclic aromatic hydrocarbons using quartz crystal microbalances.

A chemically coated piezoelectric sensor has been developed for the determination of PAHs in the liquid phase. An organic monolayer attached to the surface of a gold electrode of a quartz crystal microbalance (QCM) via a covalent thiol-gold link complete with an ionically bound recognition element has been produced. This study has employed the PAH derivative 9-anthracene carboxylic acid which, once bound to the alkane thiol, functions as the recognition element. Binding of anthracene via pi-pi interaction has been observed as a frequency shift in the QCM with a detectability of the target analyte of 2 ppb and a response range of 0-50 ppb. The relative response of the sensor altered for different PAHs despite pi-pi interaction being the sole communication between recognition element and analyte. It is envisaged that such a sensor could be employed in the identification of key marker compounds and, as such, give an indication of total PAH flux in the environment.