265 research outputs found
Long-term shifts in water quality show scale-dependent bioindicator responses across Russia – Insights from 40 year-long bioindicator monitoring program
Scale-related assessment strategies are important contributions to successful ecosystem management. With varying impact of environmental drivers from local to regional scales, a focal task is to understand scale-de- pendent responses when assessing the state of an ecosystem. In this study we use large-scale monitoring data, spanning 40 years and including four aquatic bioindicator groups (phytoplankton, zooplankton, periphyton, zoobenthos) to expose the long-term changes of water quality across Russia. We include four hierarchical spatial scales (region, basin, waterbody and observation point) to identify the relative importance of different spatio- temporal scales for the variation of each bioindicator and patterns of co-variation among the bioindicators at different hierarchical levels. We analysed the data with Hierarchical Modelling of Species Communities (HMSC), an approach that belongs to the framework of joint species distribution models. We performed a cross validation to reveal the predictive power of modelled bioindicator variation, partitioned explained variance among the fixed effects (waterbody type, and influence of human population density) and the random effects (spatial and spatio-temporal variation at the four hierarchical scales), and examined the co-variation among bioindicators at each spatio-temporal scale. We detected generally decreasing water quality across Russian freshwaters, yet with region and bioindicator specific trends. For all bioindicators, the dominating part of the variation was attributed the largest (region) and smallest (observation point) hierarchical scales, the region particularly important for benthic and the observation point for pelagic bioindicators. All bioindicators captured the same spatial variation in water quality at the smallest scale of observation point, with phytoplankton, zooplankton and periphyton being associated positively to each other and negatively to zoobenthos. However, at larger spatial scales and at spatio-temporal scales, the associations among the bioindicators became more complex, with phytoplankton and zooplankton showing opposite trends over time. Our study reveals the sensitivity of bioindicators to spatial and temporal scales. While delivering unidirectional robust water quality assessments at the local scale, bioindicator co-variation is more complex over larger geographic scales and over time.Peer reviewe
Water-Blown Polyurethane Foams Showing a Reversible Shape-Memory Effect
Water-blown polyurethane (PU) foams are of enormous technological interest as
they are widely applied in various fields, i.e., consumer goods, medicine,
automotive or aerospace industries. The discovery of the one-way shape-memory
effect in PU foams provided a fresh impetus for extensive investigations on
porous polymeric actuators over the past decades. High expansion ratios during
the shape-recovery are of special interest when big volume changes are
required, for example to fill an aneurysm during micro-invasive surgery or
save space during transportation. However, the need to program the foams
before each operation cycle could be a drawback impeding the entry of shape-
memory polymeric (SMP) foams to our daily life. Here, we showed that a
reversible shape-memory effect (rSME) is achievable for polyurethane water-
blown semicrystalline foams. We selected commercially available crystallizable
poly(ε-caprolactone)-diols of different molecular weight for foams synthesis,
followed by investigations of morphology, thermal, thermomechanical and shape-
memory properties of obtained compositions. Densities of synthesized foams
varied from 110 to 180 kg∙m−3, while peak melting temperatures were
composition-dependent and changed from 36 to 47 °C, while the melting
temperature interval was around 15 K. All semicrystalline foams exhibited
excellent one-way SME with shape-fixity ratios slightly above 100% and shape-
recovery ratios from the second cycle of 99%. The composition with broad
distribution of molecular weights of poly(ε-caprolactone)-diols exhibited an
rSME of about 12% upon cyclic heating and cooling from Tlow = 10 °C and Thigh
= 47 °C. We anticipate that our experimental study opens a field of systematic
investigation of rSMEs in porous polymeric materials on macro and micro scale
and extend the application of water-blown polyurethane foams to, e.g.,
protective covers with zero thermal expansion or even cushions adjustable to a
certain body shape. View Full-Tex
BK virus-induced nephritis and cystitis after matched unrelated donor stem cell transplantation: A case report
Currently, there is no standard therapy for a BK virus infection of the urogenital tract in immunocompromised, stem cell transplanted patients, so that early diagnosis and introduction of supportive measures have the highest response rates to date. © 2020 The Authors. Clinical Case Reports published by John Wiley & Sons Ltd
Investigation of a Second Exhaust Valve Lift to Improve Combustion in a Methane - Diesel Dual-Fuel Engine
In recent years, the utilization of dual-fuel combustion has gained
popularity in order to improve engine efficiency and emissions. With
its high knock resistance, methane allows operation in high
compression diesel engines with lower risk of knocking. With the use
of diesel fuel as an ignition source, it is possible to exploit the
advantages of lean combustion without facing problems to provide
the high amount of ignition energy necessary to burn methane under
such operating conditions. Another advantage is the variety of
sources from which the primary fuel can be obtained. In addition to
fossil sources, methane can also be produced from biomass or
electrical energy.
As the rate of substitution of diesel by methane increases, the trade-
off between nitrogen oxide and soot is mitigated. However, emissions
of carbon monoxide and unburned methane increase. Since carbon
monoxide is toxic and methane has 25 times the global warming
potential of carbon dioxide, these emission components pose a
problem. Because of the stability of the molecule, methane catalysts
require an exhaust gas temperature of over 500 °C in order to work
effectively.
In this work, the effect of conventional cooled external exhaust gas
recirculation (EGR) and additional hot internal EGR are investigated
for different substitution rates in a nonroad tractor engine converted
to dual-fuel operation. The internal EGR rate is controlled by a
variable second exhaust valve lift during the intake stroke – an
approach which promises to benefit dual-fuel engines by increasing
the in-cylinder gas temperature, thus favoring more complete
combustion. A simulation model of the engine is used to determine
the internal EGR rates and in-cylinder temperatures based on the
experimental data. When internal EGR is used in combination with
external EGR, the resulting emissions show additional reductions in
nitrogen oxide (up to -51 %), carbon monoxide (up to -18 %) and
methane (up to -28 %) with increasing internal EGR, while still
maintaining low soot levels due to the substitution of diesel fuel for
methane
GAMER-MRIL identifies Disability-Related Brain Changes in Multiple Sclerosis
Objective: Identifying disability-related brain changes is important for
multiple sclerosis (MS) patients. Currently, there is no clear understanding
about which pathological features drive disability in single MS patients. In
this work, we propose a novel comprehensive approach, GAMER-MRIL, leveraging
whole-brain quantitative MRI (qMRI), convolutional neural network (CNN), and an
interpretability method from classifying MS patients with severe disability to
investigating relevant pathological brain changes. Methods:
One-hundred-sixty-six MS patients underwent 3T MRI acquisitions. qMRI
informative of microstructural brain properties was reconstructed, including
quantitative T1 (qT1), myelin water fraction (MWF), and neurite density index
(NDI). To fully utilize the qMRI, GAMER-MRIL extended a gated-attention-based
CNN (GAMER-MRI), which was developed to select patch-based qMRI important for a
given task/question, to the whole-brain image. To find out disability-related
brain regions, GAMER-MRIL modified a structure-aware interpretability method,
Layer-wise Relevance Propagation (LRP), to incorporate qMRI. Results: The test
performance was AUC=0.885. qT1 was the most sensitive measure related to
disability, followed by NDI. The proposed LRP approach obtained more
specifically relevant regions than other interpretability methods, including
the saliency map, the integrated gradients, and the original LRP. The relevant
regions included the corticospinal tract, where average qT1 and NDI
significantly correlated with patients' disability scores (=-0.37 and
0.44). Conclusion: These results demonstrated that GAMER-MRIL can classify
patients with severe disability using qMRI and subsequently identify brain
regions potentially important to the integrity of the mobile function.
Significance: GAMER-MRIL holds promise for developing biomarkers and increasing
clinicians' trust in NN
Early mortality and loss to follow-up in HIV-infected children starting antiretroviral therapy in Southern Africa.
BACKGROUND: Many HIV-infected children in Southern Africa have been started on antiretroviral therapy (ART), but loss to follow up (LTFU) can be substantial. We analyzed mortality in children retained in care and in all children starting ART, taking LTFU into account. PATIENTS AND METHODS: Children who started ART before the age of 16 years in 10 ART programs in South Africa, Malawi, Mozambique, and Zimbabwe were included. Risk factors for death in the first year of ART were identified in Weibull models. A meta-analytic approach was used to estimate cumulative mortality at 1 year. RESULTS: Eight thousand two hundred twenty-five children (median age 49 months, median CD4 cell percent 11.6%) were included; 391 (4.8%) died and 523 (7.0%) were LTFU in the first year. Mortality at 1 year was 4.5% [95% confidence interval (CI): 2.8% to 7.4%] in children remaining in care, but 8.7% (5.4% to 12.1%) at the program level, after taking mortality in children and LTFU into account. Factors associated with mortality in children remaining in care included age [adjusted hazard ratio (HR) 0.37; 95% CI: 0.25 to 0.54 comparing > or =120 months with <18 months], CD4 cell percent (HR: 0.56; 95% CI: 0.39 to 0.78 comparing > or =20% with <10%), and clinical stage (HR: 0.12; 95% CI: 0.03 to 0.45 comparing World Health Organization stage I with III/IV). CONCLUSIONS: In children starting ART and remaining in care in Southern Africa mortality at 1 year is <5% but almost twice as high at the program level, when taking LTFU into account. Age, CD4 percentage, and clinical stage are important predictors of mortality at the individual level
Model-Informed Machine Learning for Multi-component T2 Relaxometry
Recovering the T2 distribution from multi-echo T2 magnetic resonance (MR)
signals is challenging but has high potential as it provides biomarkers
characterizing the tissue micro-structure, such as the myelin water fraction
(MWF). In this work, we propose to combine machine learning and aspects of
parametric (fitting from the MRI signal using biophysical models) and
non-parametric (model-free fitting of the T2 distribution from the signal)
approaches to T2 relaxometry in brain tissue by using a multi-layer perceptron
(MLP) for the distribution reconstruction. For training our network, we
construct an extensive synthetic dataset derived from biophysical models in
order to constrain the outputs with \textit{a priori} knowledge of \textit{in
vivo} distributions. The proposed approach, called Model-Informed Machine
Learning (MIML), takes as input the MR signal and directly outputs the
associated T2 distribution. We evaluate MIML in comparison to non-parametric
and parametric approaches on synthetic data, an ex vivo scan, and
high-resolution scans of healthy subjects and a subject with Multiple
Sclerosis. In synthetic data, MIML provides more accurate and noise-robust
distributions. In real data, MWF maps derived from MIML exhibit the greatest
conformity to anatomical scans, have the highest correlation to a histological
map of myelin volume, and the best unambiguous lesion visualization and
localization, with superior contrast between lesions and normal appearing
tissue. In whole-brain analysis, MIML is 22 to 4980 times faster than
non-parametric and parametric methods, respectively.Comment: Preprint submitted to Medical Image Analysis (July 14, 2020
Adjusting Mortality for Loss to Follow-Up: Analysis of Five ART Programmes in Sub-Saharan Africa
Evaluation of antiretroviral treatment (ART) programmes in sub-Saharan Africa is difficult because many patients are lost to follow-up. Outcomes in these patients are generally unknown but studies tracing patients have shown mortality to be high. We adjusted programme-level mortality in the first year of antiretroviral treatment (ART) for excess mortality in patients lost to follow-up
- …