Climatic changes are altering Earth's hydrological cycle, resulting in altered precipitation amounts, increased interannual variability of precipitation, and more frequent extreme precipitation events. These trends will likely continue into the future, having substantial impacts on net primary productivity (NPP) and associated ecosystem services such as food production and carbon sequestration. Frequently, experimental manipulations of precipitation have linked altered precipitation regimes to changes in NPP. Yet, findings have been diverse and substantial uncertainty still surrounds generalities describing patterns of ecosystem sensitivity to altered precipitation. Additionally, we do not know whether previously observed correlations between NPP and precipitation remain accurate when precipitation changes become extreme. We synthesized results from 83 case studies of experimental precipitation manipulations in grasslands worldwide. We used meta-analytical techniques to search for generalities and asymmetries of aboveground NPP (ANPP) and belowground NPP (BNPP) responses to both the direction and magnitude of precipitation change. Sensitivity (i.e., productivity response standardized by the amount of precipitation change) of BNPP was similar under precipitation additions and reductions, but ANPP was more sensitive to precipitation additions than reductions; this was especially evident in drier ecosystems. Additionally, overall relationships between the magnitude of productivity responses and the magnitude of precipitation change were saturating in form. The saturating form of this relationship was likely driven by ANPP responses to very extreme precipitation increases, although there were limited studies imposing extreme precipitation change, and there was considerable variation among experiments. This highlights the importance of incorporating gradients of manipulations, ranging from extreme drought to extreme precipitation increases into future climate change experiments. Additionally, policy and land management decisions related to global change scenarios should consider how ANPP and BNPP responses may differ, and that ecosystem responses to extreme events might not be predicted from relationships found under moderate environmental changes.
International audienceThis study has for objective the determination of thermal, mechanical and acoustical properties of insulating bio-based composite made with chitosan and sunflower's stalks particles. An experimental design was established to find the size grading of particles, the ratio chitosan/sunflower particles and the stress of compaction influencing the thermal and mechanical properties. Composites with a thermal conductivity $(\kappa)$ of 0.056 W/m/K, a maximum stress $(\sigma_{\text{max}})$ of 2 MPa and an acoustic coefficient of absorption $(\alpha)$ of 0.2 were obtained with a ratio of chitosan of 4.3% (w/w) and a size grading of particles higher to 3 mm. These mechanical and thermal performances are competitive with those of other insulating bio-based materials available on the market
Montmorillonite (MMT)-supported Ag/TiO(2) composite (Ag/TiO(2)/MMT) has been prepared through a one-step, low-temperature solvothermal technique. Powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) reveal that the Ag particles coated with TiO(2) nanoparticles are well-dispersed on the surface of MMT in the composite. As a support for the Ag/TiO(2) composite, the MMT prevents the loss of the catalyst during recycling test. This Ag/TiO(2)/MMT composite exhibits high photocatalytic activity and good recycling performance in the degradation of E. coli under visible light. The high visible-light photocatalytic activity of the Ag/TiO(2)/MMT composite is ascribed to the increase in surface active centers and the localized surface plasmon effect of the Ag nanoparticles. The Ag/TiO(2)/MMT materials with excellent stability, recyclability, and bactericidal activities are promising photocatalysts for application in decontamination.
The successful tissue
integration of a biomedical material is mainly
determined by the inflammatory response after implantation. Macrophage
behavior toward implanted materials is pivotal to determine the extent
of the inflammatory response. Hydrogels with different properties
have been developed for various biomedical applications such as wound
dressings or cell-loaded scaffolds. However, there is limited investigation
available on the effects of hydrogel mechanical properties on macrophage
behavior and the further host inflammatory response. To this end,
methacrylate–gelatin (GelMA) hydrogels were selected as a model
material to study the effect of hydrogel stiffness (2, 10, and 29
kPa) on macrophage phenotype in vitro and the further host inflammatory
response in vivo. Our data showed that macrophages seeded on stiffer
surfaces tended to induce macrophages toward a proinflammatory (M1)
phenotype with increased macrophage spreading, more defined F-actin
and focal adhesion staining, and more proinflammatory cytokine secretion
and cluster of differentiation (CD) marker expression compared to
those on surfaces with a lower stiffness. When these hydrogels were
further subcutaneously implanted in mice to assess their inflammatory
response, GelMA hydrogels with a lower stiffness showed more macrophage
infiltration but thinner fibrotic capsule formation. The more severe
inflammatory response can be attributed to the higher percentage of
M1 macrophages induced by GelMA hydrogels with a higher stiffness.
Collectively, our data demonstrated that macrophage behavior and the
further inflammatory response are mechanically regulated by hydrogel
stiffness. The macrophage phenotype rather than the macrophage number
predominately determined the inflammatory response after the implantation,
which can provide new insights into the future design and application
of novel hydrogel-based biomaterials.
Summary
Emerging technologies in stem cell engineering have produced sophisticated organoid platforms by controlling stem cell fate via biomaterial instructive cues. By micropatterning and differentiating human induced pluripotent stem cells (hiPSCs), we have engineered spatially organized cardiac organoids with contracting cardiomyocytes in the center surrounded by stromal cells distributed along the pattern perimeter. We investigated how geometric confinement directed the structural morphology and contractile functions of the cardiac organoids and tailored the pattern geometry to optimize organoid production. Using modern data-mining techniques, we found that pattern sizes significantly affected contraction functions, particularly in the parameters related to contraction duration and diastolic functions. We applied cardiac organoids generated from 600 μm diameter circles as a developmental toxicity screening assay and quantified the embryotoxic potential of nine pharmaceutical compounds. These cardiac organoids have potential use as an
in vitro
platform for studying organoid structure-function relationships, developmental processes, and drug-induced cardiac developmental toxicity.
Design and construction of artificial photoresponsive protocells based on the encapsulation and activation of metallized peptide/porphyrin self-assembled nanofilaments within silica-nanoparticle-stabilized colloidosomes.
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