Intensive, task‐specific training enabled by a driven gait orthosis (DGO) may be a cost‐effective means of improving walking performance in children. A paediatric DGO has recently been developed. ...This study was the first paediatric trial aimed to determine the feasibility of robotic‐assisted treadmill training in children with central gait impairment (n=26; 11 females, 15 males; mean age 10y 1mo SD 4y; range 5y 2mo‐19y 5mo). Diagnoses of the study group included cerebral palsy (n=19; Gross Motor Function Classification System Levels I–IV), traumatic brain injury (n=1), Guillain‐Barré syndrome (n=2), incomplete paraplegia (n=2), and haemorrhagic shock (n=1), and encephalopathy (n=1). Sixteen children were in‐patients and 10 were outpatients. Twenty‐four of the 26 patients completed the training which consisted of a mean of 19 sessions (SD 2.2; range 13–21) in the in‐patient group and 12 sessions (SD 1.0; range 10–13) in the outpatient group. Gait speed and 6‐Minute Walking Test increased significantly (p<0.01). Functional Ambulation Categories and Standing dimension (in‐patient group p<0.01; outpatient group p<0.05) of the Gross Motor Function Measure improved significantly. DGO training was successfully integrated into the rehabilitation programme and findings suggest an improvement of locomotor performance.
Global vegetation models require the photosynthetic parameters, maximum carboxylation capacity (Vcm), and quantum yield (α) to parameterize their plant functional types (PFTs). The purpose of this ...work is to determine how much the scaling of the parameters from leaf to ecosystem level through a seasonally varying leaf area index (LAI) explains the parameter variation within and between PFTs. Using Fluxnet data, we simulate a seasonally variable LAIF for a large range of sites, comparable to the LAIM derived from MODIS. There are discrepancies when LAIF reach zero levels and LAIM still provides a small positive value. We find that temperature is the most common constraint for LAIF in 55% of the simulations, while global radiation and vapor pressure deficit are the key constraints for 18% and 27% of the simulations, respectively, while large differences in this forcing still exist when looking at specific PFTs. Despite these differences, the annual photosynthesis simulations are comparable when using LAIF or LAIM (r2 = 0.89). We investigated further the seasonal variation of ecosystem‐scale parameters derived with LAIF. Vcm has the largest seasonal variation. This holds for all vegetation types and climates. The parameter α is less variable. By including ecosystem‐scale parameter seasonality we can explain a considerable part of the ecosystem‐scale parameter variation between PFTs. The remaining unexplained leaf‐scale PFT variation still needs further work, including elucidating the precise role of leaf and soil level nitrogen.
Key Points
We present an analysis of the ecosystem photosynthetic parameter variation
The seasonal parameters are only partly explained by LAI
Key meteorological constraints are derived, which are useful as addition to PFTs
Despite recent evidence on an important role of volatile amines in the nucleation of particulate matter, very scarce information is available on their atmospheric abundance and source distribution. ...Previous measurements in animal housings had identified livestock husbandry as the main amine source, with trimethylamine (TMA) being the key component. This has led to the assumption that the agricultural sources for amines are similar as for ammonia, emitted throughout the cascade of animal excretion, storage and application in the field. In this study, we present the first micrometeorological flux measurements as well as dynamic enclosure experiments showing that the amine source strength from stored slurry is negligible, implying significant consequences for the global amine emission inventory. In the case of cattle, amine production is attributed to the animal's rumination activity and exhalation is suggested to be an important emission pathway, similar to the greenhouse gas methane. Fodder like hay and silage also emits volatile amines, potentially assigning these alkaloid compounds a key function in enhancing particle formation in remote areas.
Key Points
Assumptions on the main global amine sources are challanged by true measurements
Cattle amine production is attributed to rumination acitivity
Vegetation in senescent state (hay, silage) is an important global amine source
Past studies have suggested a statistical connection between explosive volcanic eruptions and subsequent El Niño climate events. This connection, however, has remained controversial. Here we present ...support for a response of the El Niño/Southern Oscillation (ENSO) phenomenon to forcing from explosive volcanism by using two different palaeoclimate reconstructions of El Niño activity and two independent, proxy-based chronologies of explosive volcanic activity from ad 1649 to the present. We demonstrate a significant, multi-year, El Niño-like response to explosive tropical volcanic forcing over the past several centuries. The results imply roughly a doubling of the probability of an El Niño event occurring in the winter following a volcanic eruption. Our empirical findings shed light on how the tropical Pacific ocean-atmosphere system may respond to exogenous (both natural and anthropogenic) radiative forcing.
The net annual NH3 exchange budget of a fertilised, cut grassland in Central Switzerland is presented. The observation-based budget was computed from semi-continuous micrometeorological fluxes over a ...time period of 16 months and using a process-based gap-filling procedure. The data for emission peak events following the application of cattle slurry and for background exchange were analysed separately to distinguish short-term perturbations from longer-term ecosystem functioning. A canopy compensation point model of background exchange is parameterised on the basis of measured data and applied for the purposes of gap-filling. The data show that, outside fertilisation events, grassland behaves as a net sink for atmospheric NH3 with an annual dry deposition flux of −3.0 kg N ha−1 yr−1, although small NH3 emissions by the canopy were measured in dry daytime conditions. The median Γs ratio in the apoplast (=NH4+/H+) estimated from micrometeorological measurements was 620, equivalent to a stomatal compensation point of 1.3 μg NH3 m−3 at 15 °C. Non-stomatal resistance to deposition Rw was shown to increase with temperature and decrease with surface relative humidity, and Rw values were among the highest published for European grasslands, consistent with a relatively high ratio of NH3 to acid gases in the boundary layer at this site. Since the gross annual NH3 emission by slurry spreading was of the order of +20 kg N ha−1 yr−1, the fertilised grassland was a net NH3 source of +17 kg N ha−1 yr−1. A comparison with the few other measurement-based budget values from the literature reveals considerable variability, demonstrating both the influence of soil, climate, management and grassland type on the NH3 budget and the difficulty of scaling up to the national level.
•O3 deposition fluxes: dynamic chamber technique compares well with eddy covariance.•Prerequisite are corrections for aerodynamic modifications and chemical reactions.•The relative error of fluxes ...measured by the dynamic chamber strongly depends on u*.•Considering the whole day, O3 is primarily deposited through a non-stomatal pathway.
Nowadays, eddy covariance is the state-of-the-art method to quantify turbulent exchange fluxes in the surface boundary layer. In the absence of instruments suitable for high-frequency measurements, fluxes can also be determined using e.g., chamber techniques. However, up to date fluxes of depositing compounds were rarely determined using chamber techniques, mainly due to a modification of the aerodynamic conditions for the trace gas transport within the chamber. In this study, we present ozone (O3) deposition fluxes measured by the dynamic chamber technique and validate them against the eddy covariance (EC) method for a natural grassland site in Germany. The chamber system presented in Pape et al. (2009) was used and optimized to (i) reduce the likelihood of non-stationarities, (ii) yield 30min averages of flux measurements, and (iii) supply simultaneous profile measurements. The raw O3 fluxes of the dynamic chamber were corrected for gas-phase chemistry in the chamber volume and for the modification of the aerodynamic and boundary layer resistances. Simultaneously measured carbon dioxide and water vapor fluxes by both methods compared well during daytime documenting an equal vegetation activity inside and outside the chambers. The final corrected O3 deposition fluxes of both methods deviated on average by only 11% during daytime. The findings demonstrate the capability of the dynamic chamber method to capture representative O3 deposition fluxes for grassland ecosystems, even when the canopy height is similar to the chamber height. The canopy resistance to O3 was assessed by both methods and showed a characteristic diurnal cycle with minimum hourly median values of 180sm−1 (chambers) and 150sm−1 (EC) before noon. During nighttime the fluxes and resistances showed a higher uncertainty for both methods due to frequent low wind associated with non-stationary conditions at the experimental site. Canopy resistances for nitrogen dioxide (NO2) deposition were determined analogously with the chambers and were on average 86% higher than for O3.
The input and loss of plant available nitrogen (reactive nitrogen: Nr) from/to the atmosphere can be an important factor for the productivity of ecosystems and thus for its carbon and greenhouse gas ...exchange. We present a novel converter for reactive nitrogen (TRANC: Total Reactive Atmospheric Nitrogen Converter), which offers the opportunity to quantify the sum of all airborne reactive nitrogen compounds (∑Nr) in high time resolution. The basic concept of the TRANC is the full conversion of all Nr to nitrogen monoxide (NO) within two reaction steps. Initially, reduced Nr compounds are being oxidised, and oxidised Nr compounds are thermally converted to lower oxidation states. Particulate Nr is being sublimated and oxidised or reduced afterwards. In a second step, remaining higher nitrogen oxides or those generated in the first step are catalytically converted to NO with carbon monoxide used as reduction gas. The converter is combined with a fast response chemiluminescence detector (CLD) for NO analysis and its performance was tested for the most relevant gaseous and particulate Nr species under both laboratory and field conditions. Recovery rates during laboratory tests for NH3 and NO2 were found to be 95 and 99%, respectively, and 97% when the two gases were combined. In-field longterm stability over an 11-month period was approved by a value of 91% for NO2. Effective conversion was also found for ammonium and nitrate containing particles. The recovery rate of total ambient Nr was tested against the sum of individual measurements of NH3, HNO3, HONO, NH4+, NO3−, and NOx using a combination of different well-established devices. The results show that the TRANC-CLD system precisely captures fluctuations in ∑Nr concentrations and also matches the sum of all individual Nr compounds measured by the different single techniques. The TRANC features a specific design with very short distance between the sample air inlet and the place where the thermal and catalytic conversions to NO occur. This assures a short residence time of the sample air inside the instrument, and minimises wall sorption problems of water soluble compounds. The fast response time (e-folding times of 0.30 to 0.35 s were found during concentration step changes) and high accuracy in capturing the dominant Nr species enables the converter to be used in an eddy covariance setup. Although a source attribution of specific Nr compounds is not possible, the TRANC is a new reliable tool for permanent measurements of the net ∑Nr flux between ecosystem and atmosphere at a relatively low maintenance and reasonable cost level allowing for diurnal, seasonal and annual investigations.
Introduction During the past years, new evidence has revealed the importance of the cerebellar-brain-inhibition (CBI) pathway on cognitive and sensory processing. The modulation of the cerebellar ...cortex through non-invasive stimulation techniques, as transcranial direct-current stimulation (tDCS), could contribute to the better understanding of neuronal mechanisms underlying the implication of cerebellar cortex in these processes. Objectives The aim of this study was to explore cerebro-cerebellar interactions affecting long-term plasticity in the somatosensory (SS) cortex by modulating cerebral and cerebellar cortical excitability in behaving mice. Materials and methods Mice were prepared for the chronic recording of local field potentials (LFPs) in the SS cortex in response to electrical whisker pad stimulation, as well as for simultaneous tDCS. Animals received tDCS over the cerebellum or the SS cortex at different current intensities with a duration of 5 s to asses immediate effects, and during 20 min to address after-effects on SS-LFPs. tDCS effects on long-term plasticity processes in the SS cortex were determined by using two conditioning protocols consisting of 8 and 50 Hz whisker stimulation with a duration of 10 min and 96 s, respectively. Each protocol was combined with the simultaneous presentation of tDCS or sham condition. Results Anodal increased and cathodal decreased in an immediate way the amplitude of SS-LFPs when applied to the ipsilateral SS cortex, whereas the opposite effects were obtained when tDCS was presented to the contralateral cerebellar cortex. Concerning long-term after-effects, cathodal tDCS over the SS cortex induced a long-term depression of LFPs whereas no effects were observed after anodal currents. Long-term potentiation of SS-LFPs was evoked by both cathodal and anodal cerebellar tDCS. Finally and as expected, long-term depression and long-term potentiation of SS-LFPs induced by 8 and 50 Hz whisker stimulation were modulated by simultaneous cerebellar tDCS. Conclusions The results demonstrate the capability of tDCS to modulate the excitability of SS and cerebellar cortices, as well as the potential role of the cerebellar cortex in the control of plastic changes occurring in the sensory cortex of behaving animals.
The results from 16 coupled atmosphere/ocean general circulation model (AOGCM) simulations are used to reduce internally generated noise and to obtain an improved estimate of the underlying response ...of 20th century global mean temperature to volcanic forcing. An upwelling diffusion energy balance model (UD EBM) with the same forcing and the same climate sensitivity as the AOGCM is then used to emulate the AOGCM results. The UD EBM and AOGCM results are in very close agreement, justifying the use of the UD EBM to determine the volcanic response for different climate sensitivities. The maximum cooling for any given eruption is shown to depend approximately on the climate sensitivity raised to power 0.37. After the maximum cooling for low‐latitude eruptions the temperature relaxes back toward the initial state with an e‐folding time of 29–43 months for sensitivities of 1–4°C equilibrium warming for CO2 doubling. Comparisons of observed and modeled coolings after the eruptions of Agung, El Chichón, and Pinatubo give implied climate sensitivities that are consistent with the Intergovernmental Panel on Climate Change (IPCC) range of 1.5–4.5°C. The cooling associated with Pinatubo appears to require a sensitivity above the IPCC lower bound of 1.5°C, and none of the observed eruption responses rules out a sensitivity above 4.5°C.
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