Volatile organic compounds (VOCs) play an important role in the formation of ozone and aerosols in the atmosphere. In an increasing number of field campaigns the proton-transfer-reaction mass ...spectrometer (PTR-MS) has proven to be a useful and fast tool for measuring VOCs and studying the relevant atmospheric processes. This work describes laboratory and field measurements with two different versions of the PTR-MS and presents important instrument specific features. The temperature stabilization and the change of the gasket material in the newer version significantly improved the performance of the instrument, as demonstrated by periodical background measurements under field conditions. The investigation of the mass discrimination illustrated the necessity of an elaborate verification. The humidity dependence of benzene was substantially lower than in former studies, which used higher drift tube pressures, but it is still higher than predicted by a simple dimer/monomer equilibrium model. An instrument comparison with a fluorescent technique was performed for formaldehyde and showed differences between pure formaldehyde calibration gases and complex ambient air samples. An intercomparison of two PTR-MSs measuring ambient air yielded satisfactory results after calibration for most of the considered masses. Comparing PTR-MS and gas chromatograph measurements of aromatic compounds, revealed a good agreement for conditions of fresh anthropogenic emissions. In photochemically aged air, many masses detected by the PTR-MS are not only influenced by anthropogenically and biogenically emitted but also oxidized VOCs.
Measuring arm and hand function of the affected side is vital in stroke rehabilitation. Therefore, the Virtual Peg Insertion Test (VPIT), an assessment combining virtual reality and haptic feedback ...during a goal-oriented task derived from the Nine Hole Peg Test (NHPT), was developed. This study aimed to evaluate (1) the concurrent validity of key outcome measures of the VPIT, namely the execution time and the number of dropped pegs, with the NHPT and Box and Block Test (BBT), and (2) the test-retest-reliability of these parameters together with the VPIT's additional kinetic and kinematic parameters in patients with chronic stroke. The three tests were administered on 31 chronic patients with stroke in one session (concurrent validity), and the VPIT was retested in a second session 3-7 days later (test-retest reliability). Spearman rank correlation coefficients (ρ) were calculated for assessing concurrent validity, and intraclass correlation coefficients (ICCs) were used to determine relative reliability. Bland-Altman plots were drawn and the smallest detectable difference (SDD) was calculated to examine absolute reliability.
For the 31 included patients, 11 were able to perform the VPIT solely via use of their affected arm, whereas 20 patients also had to utilize support from their unaffected arm. For n = 31, the VPIT showed low correlations with the NHPT (ρ = 0.31 for time (Texs); ρ = 0.21 for number of dropped pegs (Ndp)) and BBT (ρ = -0.23 for number of transported cubes (Ntc); ρ = -0.12 for number of dropped cubes (Ndc)). The test-retest reliability for the parameters Texs, mean grasping force (FggoN), number of zero-crossings (Nzc1/sgo/return) and mean collision force (FcmeanN) were good to high, with ICCs ranging from 0.83 to 0.94. Fair reliability could be found for Fgreturn (ICC = 0.75) and trajectory error (Etrajgocm) (0.70). Poor reliability was measured for Etrajreturncm (0.67) and Ndp (0.58). The SDDs were: Tex = 70.2 s, Ndp = 0.4 pegs; Fggo/return = 3.5/1.2 Newton; Nzc1/sgo/return = 0.2/1.8 zero-crossings; Etrajgo/return = 0.5/0.8 cm; Fcmean = 0.7 Newton.
The VPIT is a promising upper limb function assessment for patients with stroke requiring other components of upper limb motor performance than the NHPT and BBT. The high intra-subject variation indicated that it is a demanding test for this stroke sample, which necessitates a thorough introduction to this assessment. Once familiar, the VPIT provides more objective and comprehensive measurements of upper limb function than conventional, non-computerized hand assessments.
Concentrations and fluxes of methanol were measured above two differently managed grassland fields (intensive and extensive) in central Switzerland during summer 2004. The measurements were performed ...with a proton-transfer-reaction mass-spectrometer and fluxes were determined by the eddy covariance method. The observed methanol emission showed a distinct diurnal cycle and was strongly correlated with global radiation and water vapour flux. Mean and maximum daily emissions were found to depend on grassland species composition and, for the intensive field, also on the growing state. The extensive field with a more complex species composition had higher emissions than the graminoid-dominated intensive field, both on an area and on a biomass basis. A simple parameterisation depending on the water vapour flux and the leaf area index allowed a satisfying simulation of the temporal variation of methanol emissions over the growing phase. Accumulated carbon losses due to methanol emissions accounted for 0.024 and 0.048% of net primary productivity for the intensive and extensive field, respectively. The integral methanol emissions over the growing periods were more than one order of magnitude higher than the emissions related to cut and drying events.
At a cropland and a grassland site field scale ammonia (NH3) emissions from slurry application were determined simultaneously by two approaches based on (i) eddy covariance (EC) flux measurements ...using high temperature Chemical Ionisation Mass Spectrometry (HT-CIMS) and on (ii) backward Lagrangian Stochastic (bLS) dispersion modelling using concentration measurements by three optical open path Fourier Transform Infrared (FTIR) systems. Slurry was spread on the fields in sequential tracks over a period of one to two hours. In order to calculate field emissions, measured EC/HT-CIMS fluxes were combined with flux footprint analysis of individual slurry spreading tracks to parameterise the NH3 volatilisation with a bi-exponential time dependence. Accordingly, track-resolved concentration footprints for the FTIR measurements were calculated using bLS. A consistency test with concentrations measured by impingers showed very low systematic deviations for the EC/HT-CIMS results (<8%) but larger deviations for the bLS/FTIR results. For both slurry application events, the period during fertilisation and the subsequent two hours contributed by more than 80% to the total field emissions. Averaged over the two measurement methods, the cumulated emissions of the first day amounted to 17 ± 3% loss of applied total ammoniacal nitrogen over the cropland and 16 ± 3% over the grassland field.
Physical exercise seems to be a safe and effective intervention in patients with inflammatory myopathy (IM). However, the optimal training intervention is not clear. To achieve an optimum training ...effect, physical exercise training principles must be considered and to replicate research findings, FITT components (frequency, intensity, time, and type) of exercise training should be reported. This review aims to evaluate exercise interventions in studies with IM patients in relation to (1) the application of principles of exercise training, (2) the reporting of FITT components, (3) the adherence of participants to the intervention, and (4) to assess the methodological quality of the included studies. The literature was searched for exercise studies in IM patients. Data were extracted to evaluate the application of the training principles, the reporting of and the adherence to the exercise prescription. The Downs and Black checklist was used to assess methodological quality of the included studies. From the 14 included studies, four focused on resistance, two on endurance, and eight on combined training. In terms of principles of exercise training, 93 % reported
specificity
, 50 %
progression
and
overload
, and 79 %
initial values
.
Reversibility
and
diminishing returns
were never reported. Six articles reported all FITT components in the prescription of the training though no study described adherence to all of these components. Incomplete application of the exercise training principles and insufficient reporting of the exercise intervention prescribed and completed hamper the reproducibility of the intervention and the ability to determine the optimal dose of exercise.
Fast response optical analyzers based on laser absorption spectroscopy are the preferred tools to measure field-scale mixing ratios and fluxes of a range of trace gases. Several state-of-the-art ...instruments have become commercially available and are gaining in popularity. This paper aims for a critical field evaluation and intercomparison of two compact, cryogen-free and fast response instruments: a quantum cascade laser based absorption spectrometer from Aerodyne Research, Inc., and an off-axis integrated cavity output spectrometer from Los Gatos Research, Inc. In this paper, both analyzers are characterized with respect to precision, accuracy, response time and also their sensitivity to water vapour. The instruments were tested in a field campaign to assess their behaviour under various meteorological conditions. The instrument's suitability for eddy covariance flux measurements was evaluated by applying an artificial flux of CH4 generated above a managed grassland with otherwise very low methane exchange. This allowed an independent verification of the flux measurements accuracy, including the overall eddy covariance setup and data treatment. The retrieved fluxes were in good agreement with the known artificial emission flux, which is more than satisfactory, given that the analyzers were attached to separate sonic anemometers placed on individual eddy towers with different data acquisition systems but similar data treatment that are specific to the best practice used by the involved research teams.
We studied the impact of climate change on the dynamics of soil organic carbon (SOC) stocks in productive grassland systems undergoing two types of management, an intensive type with frequent ...harvests and fertilizer applications and an extensive system without fertilization and fewer harvests. Simulations were conducted with a dedicated newly developed model, the Oensingen Grassland Model. It was calibrated using measurements taken in a recently established permanent sward in Central Switzerland, and run to simulate SOC dynamics over 2001-2100 under various climate change scenarios assuming different elements of IPCC A2 emission scenarios. We found that: (1) management intensity dominates SOC until approximately 20 years after grassland establishment. Differences in SOC between climate scenarios become significant after 20 years and climate effects dominate SOC dynamics from approximately 50 years after establishment. (2) Carbon supplied through manure contributes about 60 % to measured organic C increase in fertilized grassland. (3) Soil C accumulates particularly in the top 10 cm of the soil until 5 years after establishment. In the long-term, C accumulation takes place in the top 15 cm of the soil profile, while C content decreases below this depth. The transitional depth between gains and losses of C mainly depends on the vertical distribution of root senescence and root biomass. We discuss the importance of previous land use on carbon sequestration potentials that are much lower at the Oensingen site under ley-arable rotation with much higher SOC stocks than most soils under arable crops. We further discuss the importance of biomass senescence rates, because C balance estimations indicate that these may differ considerably between the two management systems.
Abstract
The introduction of proton transfer reaction mass spectrometry (PTR‐MS) for fast response measurements of volatile organic compounds (VOC) has enabled the use of eddy covariance methods to ...investigate VOC fluxes on the ecosystem scale. In this study PTR‐MS flux measurements of VOC were performed over agricultural grassland during and after a cut event. Selected masses detected by the PTR‐MS showed fluxes of methanol, acetaldehyde, and acetone. They were highest directly after cutting and during the hay drying phase. Simultaneously, significant fluxes of protonated ion masses 73, 81, and 83 were observed. Due to the limited identification of compounds with the PTR‐MS technique, GC‐MS and GC‐FID‐PTR‐MS techniques were additionally applied. In this way, ion mass 73 could be identified as 2-butanone, mass 81 mainly as (Z)-3-hexenal, and mass 83 mainly as the sum of (Z)-3-hexenol and hexenyl acetates. Hexenal, hexenols, and the hexenyl acetates are mostly related to plant wounding during cutting. It was found that legume plants and forbs emit a higher number of different VOC species than graminoids.
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