Browsing by Subject "PART II"

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  • Andersson, Stefan S.; Wagner, Thomas; Jonsson, Erik; Fusswinkel, Tobias; Whitehouse, Martin J. (2019)
    This study explores the suitability of apatite as a tracer of the source(s), chemistry, and evolution of ore-forming hydrothermal fluids. This is tested by analysing the halogen (F, Cl, Br, and I), stable Cl isotopic, and trace element compositions of fluorapatite from the regional-scale Olserum-Djupedal rare earth element (REE) phosphate mineralisation in SE Sweden, which is dominated by monazite-(Ce), xenotime-(Y), and fluorapatite. The primary hydrothermal fluid flow system is recorded in a sequence from proximal granite-hosted to distal metasediment-hosted fluorapatite. Along this sequence, primary fluorapatite shows a gradual increase of Cl and Br concentrations and in (Gd/Yb)(N), a decrease of F and I concentrations, a decrease in delta Cl-37 values, in (La/Sm)(N), and partly in (La/Yb)(N) and (Y/Ho)(N). Local compositional differences of halogen and trace element concentrations have developed along rims and in domains adjacent to fractures of fluorapatite due to late-stage partial reaction with fracture fluids. These differences are insignificant compared to the larger deposit-scale zoning. This suggests that apatite can retain the primary record of the original ore-forming fluid despite later overprinting fluid events. The agreement between Br/Cl and I/Cl ratios of apatite and those of co-existing fluid inclusions at lower temperatures indicates that only a minor fractionation of Br from I occurs during apatite precipitation. The halogen ratios of apatite can thus be used as a first-order estimate for the composition of the ore-forming fluid. Taking the small fractionation factors for Cl isotopes between apatite and co-existing fluid at high temperatures into account, we propose that the Cl isotopic composition of apatite and the halogen ratios derived from the apatite composition can be used jointly to trace the source(s) of ore-forming fluids. By contrast, most trace elements incorporated in apatite are affected by the host rock environment and by fluid-mineral partitioning due to growth competition between co-crystallising minerals. Collectively, apatite is sensitive to changing fluid compositions, yet it is also able to record the character of primary ore-forming fluids. Thus, apatite is suitable for tracing the origin, chemistry, and evolution of fluids in hydrothermal ore-forming settings. (C) 2019 Elsevier Ltd. All rights reserved.
  • Thelin, Eric P.; Raj, Rahul; Bellander, Bo-Michael; Nelson, David; Piippo-Karjalainen, Anna; Siironen, Jari; Tanskanen, Päivi; Hawryluk, Gregory; Hasen, Mohammed; Unger, Bertram; Zeiler, Frederick A. (2020)
    Current accepted cerebrovascular reactivity indices suffer from the need of high frequency data capture and export for post-acquisition processing. The role for minute-by-minute data in cerebrovascular reactivity monitoring remains uncertain. The goal was to explore the statistical time-series relationships between intra-cranial pressure (ICP), mean arterial pressure (MAP) and pressure reactivity index (PRx) using both 10-s and minute data update frequency in TBI. Prospective data from 31 patients from 3 centers with moderate/severe TBI and high-frequency archived physiology were reviewed. Both 10-s by 10-s and minute-by-minute mean values were derived for ICP and MAP for each patient. Similarly, PRx was derived using 30 consecutive 10-s data points, updated every minute. While long-PRx (L-PRx) was derived via similar methodology using minute-by-minute data, with L-PRx derived using various window lengths (5, 10, 20, 30, 40, and 60 min; denoted L-PRx_5, etc.). Time-series autoregressive integrative moving average (ARIMA) and vector autoregressive integrative moving average (VARIMA) models were created to analyze the relationship of these parameters over time. ARIMA modelling, Granger causality testing and VARIMA impulse response function (IRF) plotting demonstrated that similar information is carried in minute mean ICP and MAP data, compared to 10-s mean slow-wave ICP and MAP data. Shorter window L-PRx variants, such as L-PRx_5, appear to have a similar ARIMA structure, have a linear association with PRx and display moderate-to-strong correlations (r ~ 0.700, p 
  • Sabbatini, Simone; Mammarella, Ivan; Arriga, Nicola; Fratini, Gerardo; Graf, Alexander; Hoertriagl, Lukas; Ibrom, Andreas; Longdoz, Bernard; Mauder, Matthias; Merbold, Lutz; Metzger, Stefan; Montagnani, Leonardo; Pitacco, Andrea; Rebmann, Corinna; Sedlak, Pavel; Sigut, Ladislav; Vitale, Domenico; Papale, Dario (2018)
    The eddy covariance is a powerful technique to estimate the surface-atmosphere exchange of different scalars at the ecosystem scale. The EC method is central to the ecosystem component of the Integrated Carbon Observation System, a monitoring network for greenhouse gases across the European Continent. The data processing sequence applied to the collected raw data is complex, and multiple robust options for the different steps are often available. For Integrated Carbon Observation System and similar networks, the standardisation of methods is essential to avoid methodological biases and improve comparability of the results. We introduce here the steps of the processing chain applied to the eddy covariance data of Integrated Carbon Observation System stations for the estimation of final CO2, water and energy fluxes, including the calculation of their uncertainties. The selected methods are discussed against valid alternative options in tenns of suitability and respective drawbacks and advantages. The main challenge is to warrant standardised processing for all stations in spite of the large differences in e.g. ecosystem traits and site conditions. The main achievement of the Integrated Carbon Observation System eddy covariance data processing is making CO2 and energy flux results as comparable and reliable as possible, given the current micrometeorological understanding and the generally accepted state-of-the-art processing methods.
  • Auvinen, Mikko; Boi, Simone; Hellsten, Antti; Tanhuanpaa, Topi; Jarvi, Leena (2020)
    This study examines the statistical predictability of local wind conditions in a real urban environment under realistic atmospheric boundary layer conditions by means of Large-Eddy Simulation (LES). The computational domain features a highly detailed description of a densely built coastal downtown area, which includes vegetation. A multi-scale nested LES modelling approach is utilized to achieve a setup where a fully developed boundary layer flow, which is also allowed to form and evolve very large-scale turbulent motions, becomes incident with the urban surface. Under these nonideal conditions, the local scale predictability and result sensitivity to central modelling choices are scrutinized via comparative techniques. Joint time-frequency analysis with wavelets is exploited to aid targeted filtering of the problematic large-scale motions, while concepts of information entropy and divergence are exploited to perform a deep probing comparison of local urban canopy turbulence signals. The study demonstrates the utility of wavelet analysis and information theory in urban turbulence research while emphasizing the importance of grid resolution when local scale predictability, particularly close to the pedestrian level, is sought. In densely built urban environments, the level of detail of vegetation drag modelling description is deemed most significant in the immediate vicinity of the trees.
  • Dahoun, Tarik; Pardinas, Antonio F.; Veronese, Mattia; Bloomfield, Michael A. P.; Jauhar, Sameer; Bonoldi, Ilaria; Froudist-Walsh, Sean; Nosarti, Chiara; Korth, Carsten; Hennah, William; Walters, James; Prata, Diana; Howes, Oliver D. (2018)
    Whilst the role of the Disrupted-in-Schizophrenia 1 (DISC1) gene in the aetiology of major mental illnesses is debated, the characterization of its function lends it credibility as a candidate. A key aspect of this functional characterization is the determination of the role of common non-synonymous polymorphisms on normal variation within these functions. The common allele (A) of the DISCI single-nucleotide polymorphism (SNP) rs821616 encodes a serine (ser) at the Ser704Cys polymorphism, and has been shown to increase the phosphorylation of extracellular signal-regulated protein Kinases 1 and 2 (ERK1/2) that stimulate the phosphorylation of tyrosine hydroxylase, the rate-limiting enzyme for dopamine biosynthesis. We therefore set out to test the hypothesis that human ser (A) homozygotes would show elevated dopamine synthesis capacity compared with cysteine (cys) homozygotes and heterozygotes (TT and AT) for rs821616. [F-18]-DOPA positron emission tomography (PET) was used to index striatal dopamine synthesis capacity as the influx rate constant K-i(cer) in healthy volunteers DISC1 rs821616 ser homozygotes (N = 46) and healthy volunteers DISC1. rs821616 cys homozygotes and heterozygotes (N = 56), matched for age, gender, ethnicity and using three scanners. We found DISC1 rs821616 ser homozygotes exhibited a significantly higher striatal K-i(cer) compared with cys homozygotes and heterozygotes (P = 0.012) explaining 6.4% of the variance (partial eta(2) = 0.064). Our finding is consistent with its previous association with heightened activation of ERK1/2, which stimulates tyrosine hydroxylase activity for dopamine synthesis. This could be a potential mechanism mediating risk for psychosis, lending further credibility to the fact that DISC1. is of functional interest in the aetiology of major mental illness.
  • Kurppa, Mona; Hellsten, Antti; Auvinen, Mikko; Raasch, Siegfried; Vesala, Timo; Jarvi, Leena (2018)
    Buildings and vegetation alter the wind and pollutant transport in urban environments. This comparative study investigates the role of orientation and shape of perimeter blocks on the dispersion and ventilation of traffic-related air pollutants, and the street-level concentrations along a planned city boulevard. A large-eddy simulation (LES) model PALM is employed over a highly detailed representation of the urban domain including street trees and forested areas. Air pollutants are represented by massless and passive particles (non-reactive gases), which are released with traffic-related emission rates. High-resolution simulations for four different city-block-structures are conducted over a 8.2 km domain under two contrasting inflow conditions with neutral and stable atmospheric stratification corresponding the general and wintry meteorological conditions. Variation in building height together with multiple cross streets along the boulevard improves ventilation, resulting in 7-9% lower mean concentrations at pedestrian level. The impact of smaller scale variability in building shape was negligible. Street trees further complicate the flow and dispersion. Notwithstanding the surface roughness, atmospheric stability controls the concentration levels with higher values under stably stratified inflow. Little traffic emissions are transported to courtyards. The results provide urban planners direct information to reduce air pollution by proper structural layout of perimeter blocks.
  • Virman, Meri; Bister, Marja; Sinclair, Victoria; Räisänen, Jouni; Järvinen, Heikki (2020)
    A recent study based on observations has shown that after precipitation over tropical oceans rather shallow temperature structures occur in the lower troposphere and that their magnitude depends on climatological low- to midtropospheric humidity. As any process that produces temperature perturbations in the lower troposphere can be of great significance for the formation of atmospheric deep convection, the vertical temperature structure associated with evaporation of stratiform precipitation and its sensitivity to low- to midtropospheric humidity are studied by conducting three-dimensional, high-resolution, idealized simulations with the Advanced Research version of the Weather Research and Forecasting (WRF) Model. In the simulations, rainwater with mixing ratio and number concentration characteristic of stratiform precipitation associated with mesoscale convective systems is added in a large round area at roughly 560 hPa. Evaporative cooling and subsidence warming below result in a cold anomaly at roughly 560–750 hPa and, especially, a warm anomaly at roughly 750–900 hPa. The cold-over-warm anomalies are stronger with smaller low- to midtropospheric relative humidity in the initial conditions, with the maximum magnitude of the warm anomaly ranging between 0.7 and 1.2 K. The temperature anomalies propagate to the environment and still remain present after precipitation stops. The results show that evaporation of stratiform precipitation alone can lead to temperature structures, which are on the same order of magnitude as the observed ones, that potentially inhibit subsequent convection by increasing convective inhibition. Therefore, the representation of microphysical processes affecting the location, amount, and vertical and horizontal distribution of stratiform precipitation and its evaporation in numerical models requires special attention.