Convective injection and photochemical decay of peroxides in the tropical upper troposphere: Methyl iodide as a tracer of marine convection

The convective injection and subsequent fate of the peroxides H2O2 and CH3OOH in the upper troposphere is investigated using aircraft observations from the NASA Pacific Exploratory Mission-Tropics A (PEM-Tropics A) over the South Pacific up to 12 km altitude. Fresh convective outflow is identified by high CH3I concentrations; CH3I is an excellent tracer of marine convection because of its relatively uniform marine boundary layer concentration, relatively well-defined atmospheric lifetime against photolysis, and high sensitivity of measurement. We find that mixing ratios of CH3OOH in convective outflow at 8-12 km altitude are enhanced on average by a factor of 6 relative to background, while mixing ratios of H2O2 are enhanced by less than a factor of 2. The scavenging efficiency of H2O2 in the precipitation associated with deep convection is estimated to be 55-70%. Scavenging of CH3OOH is negligible. Photolysis of convected peroxides is a major source of the HOx radical family (OH + peroxy radicals) in convective outflow. The timescale for decay of the convective enhancement of peroxides in the upper troposphere is determined using CH3I as a chemical clock and is interpreted using photochemical model calculations. Decline of CH3OOH takes place on a timescale of a 1-2 days, but the resulting HOx converts to H2O2, so H2O2 mixing ratios show no decline for ∼5 days following a convective event. The perturbation to HOx at 8-12 km altitude from deep convective injection of peroxides decays on a timescale of 2-3 days for the PEM-Tropics A conditions. Copyright 1999 by the American Geophysical Union

Exhaled breath profiling for diagnosing acute respiratory distress syndrome

The acute respiratory distress syndrome (ARDS) is a common, devastating complication of critical illness that is characterized by pulmonary injury and inflammation. The clinical diagnosis may be improved by means of objective biological markers. Electronic nose (eNose) technology can rapidly and non-invasively provide breath prints, which are profiles of volatile metabolites in the exhaled breath. We hypothesized that breath prints could facilitate accurate diagnosis of ARDS in intubated and ventilated intensive care unit (ICU) patients. Prospective single-center cohort study with training and temporal external validation cohort. Breath of newly intubated and mechanically ventilated ICU-patients was analyzed using an electronic nose within 24 hours after admission. ARDS was diagnosed and classified by the Berlin clinical consensus definition. The eNose was trained to recognize ARDS in a training cohort and the diagnostic performance was evaluated in a temporal external validation cohort. In the training cohort (40 patients with ARDS versus 66 controls) the diagnostic model for ARDS showed a moderate discrimination, with an area under the receiver-operator characteristic curve (AUC-ROC) of 0.72 (95%-confidence interval (CI): 0.63-0.82). In the external validation cohort (18 patients with ARDS versus 26 controls) the AUC-ROC was 0.71 [95%-CI: 0.54 - 0.87]. Restricting discrimination to patients with moderate or severe ARDS versus controls resulted in an AUC-ROC of 0.80 [95%-CI: 0.70 - 0.90]. The exhaled breath profile from patients with cardiopulmonary edema and pneumonia was different from that of patients with moderate/severe ARDS. An electronic nose can rapidly and non-invasively discriminate between patients with and without ARDS with modest accuracy. Diagnostic accuracy increased when only moderate and severe ARDS patients were considered. This implicates that breath analysis may allow for rapid, bedside detection of ARDS, especially if our findings are reproduced using continuous exhaled breath profiling. NTR2750, registered 11 February 201

Dormancy in white-grained wheat: Mechanisms and genetic control

Dissertação de Mestrado em Ecologia, apresentada ao Departamento de Ciências da Vida da Faculdade de Ciências e Tecnologia da Universidade de Coimbra

Development of a Fragment-Based in Silico Profiler for Michael Addition Thiol Reactivity

The Adverse Outcome Pathway (AOP) paradigm details the existing knowledge that links the initial interaction between a chemical and a biological system, termed the molecular initiating event (MIE), through a series of intermediate events, to an adverse effect. An important example of a well-defined MIE is the formation of a covalent bond between a biological nucleophile and an electrophilic compound. This particular MIE has been associated with various toxicological end points such as acute aquatic toxicity, skin sensitization, and respiratory sensitization. This study has investigated the calculated parameters that are required to predict the rate of chemical bond formation (reactivity) of a dataset of Michael acceptors. Reactivity of these compounds toward glutathione was predicted using a combination of a calculated activation energy value (Eact, calculated using density functional theory (DFT) calculation at the B3YLP/6-31G+(d) level of theory, and solvent-accessible surface area values (SAS) at the α carbon. To further develop the method, a fragment-based algorithm was developed enabling the reactivity to be predicted for Michael acceptors without the need to perform the time-consuming DFT calculations. Results showed the developed fragment method was successful in predicting the reactivity of the Michael acceptors excluding two sets of chemicals: volatile esters with an extended substituent at the β-carbon and chemicals containing a conjugated benzene ring as part of the polarizing group. Additionally the study also demonstrated the ease with which the approach can be extended to other chemical classes by the calculation of additional fragments and their associated Eact and SAS values. The resulting method is likely to be of use in regulatory toxicology tools where an understanding of covalent bond formation as a potential MIE is important within the AOP paradigm

Validation of a fragment-based profiler for thiol reactivity for the prediction of toxicity: skin sensitisation and tetrahymena pyriformis

This study outlines the use of a recently developed fragment-based thiol reactivity profiler for Michael acceptors to predict toxicity towards Tetrahymena pyriformis and skin sensitisation potency as determined in the Local Lymph Node Assay (LLNA). The results showed that the calculated reactivity parameter from the profiler, -log RC50(calc), was capable of predicting toxicity for both endpoints with excellent statistics. However, the study highlighted the importance of a well-defined applicability domain for each endpoint. In terms of Tetrahymena pyriformis this domain was defined in terms of how fast or slowly a given Michael acceptor reacts with thiol leading to two separate quantitative structure-activity models. The first, for fast reacting chemicals required only –Log RC50(calc) as a descriptor, whilst the second required the addition of a descriptor for hydrophobicity. Modelling of the LLNA required only a single descriptor, -log RC50(calc), enabling potency to be predicted. The applicability domain excluded chemicals capable of undergoing polymerisation and those that were predicted to be volatile. The modelling results for both endpoints, using the –log RC50(calc) value from the profiler, were in keeping with previously published studies that have utilised experimentally determined measurements of reactivity. This results demonstrate the output from the fragment-based thiol reactivity profiler can be used to develop quantitative structure-activity relationship models where reactivity towards thiol is a driver of toxicity

On the origin of tropospheric ozone and NOx over the tropical South Pacific

The budgets of ozone and nitrogen oxides (NOx = NO + NO2) in the tropical South Pacific troposphere are analyzed by photochemical point modeling of aircraft observations at 0-12 km altitude from the Pacific Exploratory Mission-Tropics A campaign flown in September-October 1996. The model reproduces the observed NO2/NO concentration ratio to within 30% and has similar success in simulating observed concentrations of peroxides (H2O2, CH3OOH), lending confidence in its use to investigate ozone chemistry. It is found that chemical production of ozone balances only half of chemical loss in the tropospheric column over the tropical South Pacific. The net loss is 1.8 x 1011 molecules cm-2 s-1. The missing source of ozone is matched by westerly transport of continental pollution into the region. Independent analysis of the regional ozone budget with a global three-dimensional model corroborates the results from the point model and reveals the importance of biomass burning emissions in South America and Africa for the ozone budget over the tropical South Pacific. In this model, biomass burning increases average ozone concentrations by 7-8 ppbv throughout the troposphere. The NOx responsible for ozone production within the South Pacific troposphere below 4 km can be largely explained by decomposition of peroxyacetylnitrate (PAN) transported into the region with biomass burning pollution at higher altitudes. Copyright 1999 by the American Geophysical Union

An algorithm for the generation of biofouled surfaces for applications in marine hydrodynamics

The adverse effects of marine biofouling on marine renewable energy devices are well established. In recent fundamental investigations on fluid flow over this type of surface roughness, marine biofouling has mainly been realized as ordered arrangements of roughness elements. These surfaces cannot be compared to realistic biofouled surfaces which show an irregular distribution of roughness features. In this work, a geometric algorithm for generating realistic surface roughness due to barnacle settlement is presented. The algorithm mimics the settlement behaviour of barnacles and allows the generation of a range of fouling states from very sparse rough surfaces to surfaces that are fully covered by barnacle colonies. The generated surfaces can be used in various applications, e.g. in CFD simulations to establish the fluid dynamic roughness effect of different fouling states or as 3D printed surface tiles for use in wind-tunnel and towing tank experiments

From uncertainty to reward: BOLD characteristics differentiate signaling pathways

<p>Abstract</p> <p>Background</p> <p>Reward value and uncertainty are represented by dopamine neurons in monkeys by distinct phasic and tonic firing rates. Knowledge about the underlying differential dopaminergic pathways is crucial for a better understanding of dopamine-related processes. Using functional magnetic resonance blood-oxygen level dependent (BOLD) imaging we analyzed brain activation in 15 healthy, male subjects performing a gambling task, upon expectation of potential monetary rewards at different reward values and levels of uncertainty.</p> <p>Results</p> <p>Consistent with previous studies, ventral striatal activation was related to both reward magnitudes and values. Activation in medial and lateral orbitofrontal brain areas was best predicted by reward uncertainty. Moreover, late BOLD responses relative to trial onset were due to expectation of different reward values and likely to represent phasic dopaminergic signaling. Early BOLD responses were due to different levels of reward uncertainty and likely to represent tonic dopaminergic signals.</p> <p>Conclusions</p> <p>We conclude that differential dopaminergic signaling as revealed in animal studies is not only represented locally by involvement of distinct brain regions but also by distinct BOLD signal characteristics.</p

Conventional and CT angiography in children: dosimetry and dose comparisons

Tremendous advances have been made in imaging in children with both congenital and acquired heart disease. These include technical advances in cardiac catheterization and conventional angiography, especially with advancements in interventional procedures, as well as noninvasive imaging with MR and CT angiography. With rapid advances in multidetector CT (MDCT) technology, most recently 64-detector array systems (64-slice MDCT), have come a number of advantages over MR. However, both conventional and CT angiography impart radiation dose to children. Although the presence of radiation exposure to children has long been recognized, it is apparent that our ability to assess this dose, particularly in light of the rapid advancements, has been limited. Traditional methods of dosimetry for both conventional and CT angiography are somewhat cumbersome or involve a potential for substantial uncertainty. Recent developments in dosimetry, including metal oxide semiconductor field effect transistors (MOSFET) and the availability of anthropomorphic, tissue-equivalent phantoms have provided new opportunities for dosimetric assessments. Recent work with this technology in state-of-the-art cardiac angiography suites as well as with MDCT have offered direct comparisons of doses in infants and children undergoing diagnostic cardiac evaluation. It is with these dose data that assessment of risks, and ultimately the assessment of risk-benefit, can be better achieved