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Microbial degradation of dissolved organic carbon (DOC) in aquatic environments can cause oxygen depletion, water acidification, and CO2 emissions. These problems are caused by labile DOC (LDOC) and not refractory DOC (RDOC) that resists degradation and is thus a carbon sink. For nearly a century, chemical oxygen demand (COD) has been widely used for assessment of organic pollution in aquatic systems. Here, we show through a multicountry survey and experimental studies that COD is not an appropriate proxy of microbial degradability of organic matter because it oxidizes both LDOC and RDOC, and the latter contributes up to 90% of DOC in high-latitude forested areas. Hence, COD measurements do not provide appropriate scientific information on organic pollution in natural waters and can mislead environmental policies. We propose the replacement of the COD method with an optode-based biological oxygen demand method to accurately and efficiently assess organic pollution in natural aquatic environments.

Two new compounds (1-2), including a bisabolane-type sesquiterpenoid (1), one new diphenyl ether derivative (2), together with 23 known compounds (3-25), were isolated from the fruits of Phyllanthus emblica. Their structures were elucidated by detailed spectroscopic analysis. All the isolated compounds were screened for the DPPH scavenging effects and cytoprotective effects against H2O2 induced PC12 cells injury. Compounds 12-15 showed significant DPPH scavenging effects with the IC50 values in the range of 3.25-4.18 μM. Among these potential antioxidants, compound 14 improved the survival of PC12 cells after H2O2 exposure without showing any cytotoxicity at the tested concentrations.

Neural stem cells (NSCs) are used to treat various nervous system diseases because of their self‐renewal ability and multidirectional differentiation potential. However, an insufficient ability to track their migration in vivo and poor control over their survival and differentiation efficiency are two major critical challenges for clinical application. Here, it is shown that when magnetic nanobubbles (MNBs), which are assembled from magnetic nanoparticles, are internalized by NSCs, intramembrane volumetric oscillation of the MNBs induces an increase in intracellular hydrostatic pressure and cytoskeleton force, resulting in the activation of the Piezo1‐Ca2+ mechanosensory channel. This subsequently triggers the BMP2/Smad biochemical signaling pathway, leading to differentiation of NSCs into the neuronal phenotype. Signaling through the Piezo1‐Ca2+‐BMP2/Smad pathway can be further accelerated by application of an external shear stress force using low‐intensity pulsed ultrasound. More importantly, magnetic resonance imaging and ultrasound imaging surveillance of NSCs based on MNB labeling can be leveraged to provide NSC therapeutic outcomes. Both the in vitro and in vivo findings demonstrate that a bubble nanostructure‐induced physical force can modulate and control the mechanical signaling pathway regulating stem cell development.

With the rapid growth in the use of wireless electronic devices, society urgently needs electromagnetic wave (EMW) absorbing material with light weight, thin thickness, wide effective absorbing band width, and strong absorption capacity. Herein, the multi-layer magnetic composite boards are fabricated by hot-pressing magnetic fiber boards and normal veneer layer-by-layer. The magnetic fibers obtained using in-situ chemical co-precipitation are used to fabricate magnetic fiber board by hot-pressing. The magnetic wave absorbing capacities of the magnetic fiber boards obtained with 72 h impregnation time exhibit strongest adsorption capacities of −51.01 dB with a thickness of 3.00 mm. It is proved that this outstanding EMW absorption property is due to the strongest dielectric loss, the optimal magnetic loss, and the dipole relaxation polarization. Meanwhile, the EMW absorbing capacities of the corresponding multi-layer composite magnetic board increases from −14.14 dB (3-layer) to −60.16 dB (7-layer). This is due to the generated multi-interfaces between magnetic fiber board and natural wood veneer in the EMW propagation direction, which significantly benefit multireflection and attenuation of the incident waves. The results obtained in this work indicate that natural wood fibers are of great potential in the fabrication of magnetic multi-layer boards treated as EMW absorbers via a low cost, green, and scalable method.

Herein, magnetic g-C 3 N 4 /g-carbon foams (CNFs) are fabricated via impregnating the as-prepared melamine−formaldehyde (MF) foams in iron acetylacetone (Fe(acac) 3 ) N,Ndimethylformamide (DMF) solutions with different concentrations followed by in situ pyrolysis. The corresponding electromagnetic wave (EMW) absorption behaviors are investigated. CNFs display solid 3D foam architectures with narrow and smooth skeletons, which consist of graphitic C 3 N 4 /carbon and CFe 15.1 . The in situ assynthesized α-Fe, Fe 3 O 4 , and Fe 3 C particles are dispersed on the skeleton surface. With the increase of Fe elemental content, the EMW absorption performance of CNFs is enhanced. Among them, the minimum reflection loss value of CNF-3 is as low as −52.17 dB, with a matching thickness (t m ) of 4.25 mm and a broad effective absorbing bandwidth of 9.37 GHz. Besides, CNF-3 exhibits potential simultaneously effective absorption performance from the X-band to the Ku-band. This superior absorption behavior is attributed to Maxwell−Wagner−Sillars polarization, residual loss effect, enriched interface polarization effect, and macroporous structures. Further research studies demonstrate the potential application of CNF-3 as a reinforcing agent for PCL-based 3D printing EMW absorbers with improved mechanical properties. The corresponding EMW absorption matching frequency can be adjusted by the number of 3D printing layers.