46 research outputs found
Separating the effects of changes in land cover and climate: a hydro-meteorological analysis of the past 60 yr in Saxony, Germany
Understanding and quantifying the impact of changes in climate and land
use/land cover on water availability is a prerequisite to adapt water
management; yet, it can be difficult to separate the effects of these
different impacts. In this paper we illustrate a separation and attribution
method based on a Budyko framework. We assume that evapotranspiration (<i>E</i><sub>T</sub>) is limited
by the climatic forcing of precipitation (<i>P</i>) and evaporative demand (<i>E</i><sub>0</sub>),
but modified by land-surface properties. Impacts of changes in climate
(i.e., <i>E</i><sub>0</sub>/<i>P</i>) or land-surface changes on <i>E</i><sub>T</sub> alter the two
dimensionless measures describing relative water (<i>E</i><sub>T</sub>/<i>P</i>) and energy
partitioning (<i>E</i><sub>T</sub>/<i>E</i><sub>0</sub>), which allows us to separate and quantify
these impacts. We use the separation method to quantify the role of
environmental factors on <i>E</i><sub>T</sub> using 68 small to medium range river
basins covering the greatest part of the German Federal State of Saxony
within the period of 1950–2009. The region can be considered as a typical
central European landscape with considerable anthropogenic impacts. In the
long term, most basins are found to follow the Budyko curve which we
interpret as a result of the strong interactions of climate, soils and
vegetation. However, two groups of basins deviate. Agriculturally dominated
basins at lower altitudes exceed the Budyko curve while a set of high
altitude, forested basins fall well below. When visualizing the decadal
dynamics on the relative partitioning of water and energy the impacts of
climatic and land-surface changes become apparent. After 1960 higher forested
basins experienced large land-surface changes which show that the air
pollution driven tree damages have led to a decline of annual <i>E</i><sub>T</sub>
on the order of 38%. In contrast, lower, agricultural dominated areas show
no significant changes during that time. However, since the 1990s effective
mitigation measures on industrial pollution have been established and the
apparent brightening and regrowth has resulted in a significant increase of
<i>E</i><sub>T</sub> across most basins. In conclusion, data on both, the water and
the energy balance is necessary to understand how long-term climate and land
cover control evapotranspiration and thus water availability. Further, the
detected land-surface change impacts are consistent in space and time with
independent forest damage data and thus confirm the validity of the
separation approach
AKAPS act in a two-step mechanism of memory acquisition
Defining the molecular and neuronal basis of associative memories is based upon behavioral preparations that yield high performance due to selection of salient stimuli, strong reinforcement, and repeated conditioning trials. One of those preparations is the Drosophila aversive olfactory conditioning procedure where animals initiate multiple memory components after experience of a single cycle training procedure. Here, we explored the analysis of acquisition dynamics as a means to define memory components and revealed strong correlations between particular chronologies of shock impact and number experienced during the associative training situation and subsequent performance of conditioned avoidance. Analyzing acquisition dynamics in Drosophila memory mutants revealed that rutabaga (rut)-dependent cAMP signals couple in a divergent fashion for support of different memory components. In case of anesthesia-sensitive memory (ASM) we identified a characteristic two-step mechanism that links rut-AC1 to A-kinase anchoring proteins (AKAP)-sequestered protein kinase A at the level of Kenyon cells, a recognized center of olfactory learning within the fly brain. We propose that integration of rut-derived cAMP signals at level of AKAPs might serve as counting register that accounts for the two-step mechanism of ASM acquisition
A mock circulation loop to test extracorporeal CO2 elimination setups
Background: Extracorporeal carbon dioxide removal (ECCO2R) is a promising yet
limited researched therapy for hypercapnic respiratory failure in acute respiratory
distress syndrome and exacerbated chronic obstructive pulmonary disease. Herein,
we describe a new mock circuit that enables experimental ECCO2R research without
animal models. In a second step, we use this model to investigate three experimental
scenarios of ECCO2R: (I) the influence of hemoglobin concentration on CO2 removal. (II)
a potentially portable ECCO2R that uses air instead of oxygen, (III) a low-flow ECCO2R
that achieves effective CO2 clearance by recirculation and acidification of the limited
blood volume of a small dual lumen cannula (such as a dialysis catheter).
Results: With the presented ECCO2R mock, CO2 removal rates comparable to previous
studies were obtained. The mock works with either fresh porcine blood or diluted
expired human packed red blood cells. However, fresh porcine blood was preferred
because of better handling and availability. In the second step of this work, hemoglobin
concentration was identified as an important factor for CO2 removal. In the second
scenario, an air-driven ECCO2R setup showed only a slightly lower CO2 wash-out than the
same setup with pure oxygen as sweep gas. In the last scenario, the low-flow ECCO2R,
the blood flow at the test membrane lung was successfully raised with a recirculation
channel without the need to increase cannula flow. Low recirculation ratios resulted in
increased efficiency, while high recirculation ratios caused slightly reduced CO2 removal
rates. Acidification of the CO2 depleted blood in the recirculation channel caused an
increase in CO2 removal rate.
Conclusions: We demonstrate a simple and cost effective, yet powerful, “in-vitro”
ECCO2R model that can be used as an alternative to animal experiments for many
research scenarios. Moreover, in our approach parameters such as hemoglobin level can
be modified more easily than in animal models
Comparison of Circular and Parallel-Plated Membrane Lungs for Extracorporeal Carbon Dioxide Elimination
Extracorporeal carbon dioxide removal (ECCO2R) is an important technique to treat critical lung diseases such as exacerbated chronic obstructive pulmonary disease (COPD) and mild or
moderate acute respiratory distress syndrome (ARDS). This study applies our previously presented
ECCO2R mock circuit to compare the CO2 removal capacity of circular versus parallel-plated membrane lungs at different sweep gas flow rates (0.5, 2, 4, 6 L/min) and blood flow rates (0.3 L/min,
0.9 L/min). For both designs, two low-flow polypropylene membrane lungs (Medos Hilte 1000,
Quadrox-i Neonatal) and two mid-flow polymethylpentene membrane lungs (Novalung Minilung,
Quadrox-iD Pediatric) were compared. While the parallel-plated Quadrox-iD Pediatric achieved the
overall highest CO2 removal rates under medium and high sweep gas flow rates, the two circular
membrane lungs performed relatively better at the lowest gas flow rate of 0.5 L/min. The low-flow
Hilite 1000, although overall better than the Quadrox i-Neonatal, had the most significant advantage
at a gas flow of 0.5 L/min. Moreover, the circular Minilung, despite being significantly less efficient
than the Quadrox-iD Pediatric at medium and high sweep gas flow rates, did not show a significantly
worse CO2 removal rate at a gas flow of 0.5 L/min but rather a slight advantage. We suggest that
circular membrane lungs have an advantage at low sweep gas flow rates due to reduced shunting as
a result of their fiber orientation. Efficiency for such low gas flow scenarios might be relevant for
possible future portable ECCO2R devices
A Novel Mock Circuit to Test Full-Flow Extracorporeal Membrane Oxygenation
Extracorporeal membrane oxygenation (ECMO) has become an important therapeutic
approach in the COVID-19 pandemic. The development and research in this field strongly relies on
animal models; however, efforts are being made to find alternatives. In this work, we present a new
mock circuit for ECMO that allows measurements of the oxygen transfer rate of a membrane lung at
full ECMO blood flow. The mock utilizes a large reservoir of heparinized porcine blood to measure the
oxygen transfer rate of the membrane lung in a single passage. The oxygen transfer rate is calculated
from blood flow, hemoglobin value, venous saturation, and post-membrane arterial oxygen pressure.
Before the next measuring sequence, the blood is regenerated to a venous condition with a sweep
gas of nitrogen and carbon dioxide. The presented mock was applied to investigate the effect of a
recirculation loop on the oxygen transfer rate of an ECMO setup. The recirculation loop caused a
significant increase in post-membrane arterial oxygen pressure (paO2
). The effect was strongest for
the highest recirculation flow. This was attributed to a smaller boundary layer on gas fibers due to
the increased blood velocity. However, the increase in paO2 did not translate to significant increases
in the oxygen transfer rate because of the minor significance of physically dissolved oxygen for gas
transfer. In conclusion, our results regarding a new ECMO mock setup demonstrate that recirculation
loops can improve ECMO performance, but not enough to be clinically relevant
Land‐use intensity and biodiversity effects on infiltration capacity and hydraulic conductivity of grassland soils in southern Germany
Evidence from experimental and established grasslands indicates that plant biodiversity can modify the water cycle. One suspected mechanism behind this is a higher infiltration capacity (ν) and hydraulic conductivity (K) of the soil on species-rich grasslands. However, in established and agriculturally managed grasslands, biodiversity effects cannot be studied independent of land-use effects. Therefore, we investigated in established grassland systems how land-use intensity and associated biodiversity of plants and soil animals affect νB and K at and close to saturation. On 50 grassland plots along a land-use intensity gradient in the Biodiversity Exploratory Schwäbische Alb, Germany, we measured νB with a hood infiltrometer at several matrix potentials and calculated the saturated and unsaturated K. We statistically analysed the relationship between ν or K and land-use information (e.g., fertilising intensity), abiotic (e.g., soil texture) and biotic data (e.g., plant species richness, earthworm abundance). Land-use intensity decreased and plant species richness increased ν and K, while the direction of the effects of soil animals was inconsistent. The effect of land-use intensity on ν and K was mainly attributable to its negative effect on plant species richness. Our results demonstrate that plant species richness was a better predictor of ν and K at and close to saturation than land-use intensity or soil physical properties in the established grassland systems of the Schwäbische Alb