Seasonal variation and human impacts of the river biofilm bacterial communities in the Shiting River in southeastern China.

Bacterial communities in epilithic biofilm plays an important role in biogeochemistry processes in freshwater ecosystems. Nevertheless, our understanding of the geographical and seasonal variations of the composition of bacterial communities in the biofilm of gravels on river bed is still limited. Various anthropogenic activities also influence the biofilm bacteria in gravel rivers. By taking the Shiting River in the upper Yangtze River basin in Sichuan Province as an example, we studied the geographical and seasonal variations of epilithic bacteria and the impacts of weirs and other human activities (e.g., sewage pollution). The river has experienced severe degradation since the Ms 8.0 Wenchuan Earthquake, and weirs were constructed to prevent bed erosion. We collected epilithic biofilms samples at 17 sites along ~ 30 km river reach of the Shiting River in the autumn of 2021 and the summer of 2022, respectively. We applied 16S rRNA gene high-throughput sequencing technology and Functional Annotation of Prokaryotic Taxa (FAPROTAX) to analyze the seasonal and biogeographic patterns and potential functions of the biofilm bacterial communities. The results showed that epilithic bacteria from the two surveys exhibited variation in community composition, bacterial diversity and potential functions. The bacteria samples collected in the autumn have much higher alpha diversity and richness than those collected in the summer. Bacterial richness and diversity were lower downstream of the weirs than upstream. Low diversity was observed at a sampling site influenced by sewage inflow, which contains high level of nitrogen-related chemicals.

In Vivo High-Contrast Biomedical Imaging in the Second Near-Infrared Window Using Ultrabright Rare-Earth Nanoparticles.

Intravital luminescence imaging in the second near-infrared window (NIR-II) enables noninvasive deep-tissue imaging with high spatiotemporal resolution of live mammals because of the properties of suppressed light scattering and diminished autofluorescence in the long-wavelength region. Herein, we present the synthesis of a downconversion luminescence rare-earth nanocrystal with a core-shell-shell structure (NaYF4@NaYbF4:Er,Ce@NaYF4:Ca). The structure efficiently maximized the doping concentration of the sensitizers and increased Er3+ luminescence while preventing cross relaxation. Furthermore, Ce3+ doping in the middle layer efficiently limited the upconversion pathway and increased downconversion by 24-fold to produce bright 1550 nm luminescence under 975 nm excitation. Finally, optimizing the inert shell coating of NaYF4:Ca and liposome encapsulation reduced the luminescence quenching impact by water and improved biological metabolism. Thus, our synthesized biocompatible, ultrabright NIR-II probes provide high contrast and resolution for through-scalp and through-skull luminescence imaging of mice cerebral vasculature without craniotomy as well as imaging of mouse hindlimb microvessels.

Effect of ionic surfactants on the settling behavior of silt.

Ionic surfactants are easily adsorbed by silt and clay particles, thus affecting the flocculation characteristics and settling behavior. The settling velocity, typical size, Zeta potential and surface tension of silt flocs were measured in the presence of two different kinds of ionic surfactants. The results indicated that the cetyltrimethylammonium bromide (CTAB, a typical cationic surfactant) can dramatically accelerate the settling of slit particles, while the linear alkylbenzene sulfonate (LAS, a typical anionic surfactant) slightly retarded silt sedimentation to some extent. In still water, the representative settling velocity dramatically increased from 0.36 cm s-1 to 0.43 cm s-1 with the increase of CTAB concentration, which increased by more than 20%. Oppositely, the sedimentation rate decreased from 0.36 cm s-1 to 0.33 cm s-1 with the increase of LAS concentration. In flowing water, as the flow rate increased from 0 to 20 cm s-1 and the ionic surfactant concentration increased from 0 to 10 mg L-1, the sedimentation rate decreased to 57% and 89% in the presence of CTAB and LAS respectively, which was due to an enhanced dispersion of silt particles and a breaking of flocs. The SEM image test shows that the floc particle size increased 1.5 times of the primary particle size under the high CTAB concentration. The flocculation induced by ionic surfactants greatly influences the sediment size as well as the law of settling velocity. The intrinsic influence mechanism was also discussed based on the variations of silt particle properties. This systematic study can be used for further development of flocculation models and particle size distribution of fine-grained soil.

Snapshot temporal compressive light-sheet fluorescence microscopy via deep denoising and total variation priors.

We present a snapshot temporal compressive light-sheet fluorescence microscopy system to capture high-speed microscopic scenes with a low-speed camera. A deep denoising network and total variation denoiser are incorporated into a plug-and-play framework to quickly reconstruct 20 high-speed video frames from a short-time measurement. Specifically, we can observe 1,000-frames-per-second (fps) microscopic scenes when the camera works at 50 fps to capture the measurement. The proposed method can potentially be applied to observe cell and tissue motions in thick living biological specimens.

Spatial and temporal characteristics, influencing factors and prediction models of water quality and algae in early stage of Middle Route of South-North Water Diversion Project.

The Middle Route (MR) of the South-to-North Water Diversion Project (SNWDP) of China is one of the world's largest inter-basin water diversion projects. As an important source of drinking water in North China, its water quality safety determines the success or failure of a sizable water supply. At present, there is a lack of in-depth and systematic understanding of the interaction between hydrodynamics and the water environment as well as water ecological processes in the main canal at the early stages of operation. It is not currently possible to accurately predict water quality and algae status at the early stage of canal ecosystem succession. Change trends and distribution characteristics of the main water ecological environment elements in the main canal at the early MR stage are analyzed in this study. The main factors influencing algae are investigated by principal component analysis (PCA) to characterize the water quality and algae transport distribution in the main MR canal under the complex multi-sluice joint dispatching conditions. The relationship between environmental factors, hydrodynamic, water quality, and algae in the coupled canal-sluice system in the SNWDP MR is determined. Algae distributions under different water transmission conditions in a typical canal section are predicted accordingly. CODMn and algal density in the main canal are shown to increase from south to north along the canal. DO decreases from south to north; other water quality indexes do not significantly differ from north to south. Algal density along the canal differs to the greatest extent in summer, followed by spring and autumn, and is the weakest in winter. The predicted algae densities in the main canal under different water conveying conditions show that single sluice control and strong water flow from Taocha Head Section increase the flow velocity after passing through the sluice with a fixed opening. Algal density decreases flow rate increases under single sluice regulation conditions. The maximum rate of algal density change reaches 22.13% and 29.55% under double sluice and four sluice scheduling. Algae control effects grow significantly as the number of control sluices increases. The results of this work may provide technical support for water quality forecasting and algae risk warning in the SNWDP MR as well as a workable reference for similar projects.

Isomeric Ir(iii) complexes for tracking mitochondrial pH fluctuations and inducing mitochondrial dysfunction during photodynamic therapy.

Mitochondrial pH is known to be alkaline (near 8.0) and has emerged as a potential factor for mitochondrial function and disorder. Here we investigate two pairs of isomeric phosphorescent Ir(iii) complexes (1-4) that show mitochondrial pH-responsive properties and induce mitochondrial dysfunction during photodynamic therapy. These complexes are designed to function by controlling the protonation of the benzimidazole and carboxyl groups. 1 and 2 exhibit enhanced emission intensity and a blue-shift emission change in response to pH alterations from 6.0 to 8.0. They have ideal pKa values (7.49 for 1 and 7.41 for 2) and show mitochondria-specific phosphorescence staining in situ, thereby allowing the monitoring of mitochondrial pH in live cells. 3 and 4 produce abundant intracellular ROS and exhibit high phototoxicities against cancer cells. Interestingly, these pH-responsive probes can be utilized to monitor the change in mitochondrial pH and mitochondrial damage during photodynamic therapy (PDT), which provides a convenient method for the in situ monitoring of therapeutic effects and the assessment of treatment outcomes.

Genipin-crosslinked polyvinyl alcohol/silk fibroin/nano-hydroxyapatite hydrogel for fabrication of artificial cornea scaffolds-a novel approach to corneal tissue engineering.

Design of artificial corneal scaffolds substitute is crucial for replacement of impaired cornea. In this paper, porous polyvinyl alcohol/silk fibroin/nano-hydroxyapatite (PVA/SF/n-HA) composite hydrogel was prepared via the genipin (GP) cross-linking, the pore diameter of the hydrogel ranged from 8.138 nm and 90.269 nm, and the physical and physiological function of hydrogel were investigated. The resulting hydrogel exhibited favourable physical properties. With the GP content increasing, the structural regularity of PVA/SF/n-HA composite hydrogel was enhanced and the thermal stability was improved. The moisture content was slightly decreased and generally maintained at approximately 70%. The tensile strength was heightened up to 0.64 MPa, while the breaking elongation was decreased slightly. Moreover, the biofunction was investigated. The in vitro degradation test demonstrated that with the addition of GP, the stability of the composite hydrogels in protease XIV solution was promoted and the three-dimensional porosity structure of composite hydrogels was maintained as ever. And the human corneal fibroblasts (HCFs) were employed to examine the cells cytotoxicity of the PVA/SF/n-HA composite hydrogels with different GP content by CCK-8 assay. Based on confocal laser scanning microscope (CLSM) and scanning electron microscope (SEM), HCFs had individually commendable adhesion and proliferation on PVA/n-HA/SF composite hydrogel. HCFs proliferated and grew into the pores of composite hydrogel. The results of biocompatibility experiments of composite hydrogel suggested that it was no acute toxicity, in vitro cytotoxicity was 0 or 1 grade. Overall, results from this paper, PVA/n-HA/SF composite hydrogel was a qualified medical material which conformed to the national standard, could be a promising alternative for artificial cornea scaffold material-a novel approach to corneal tissue engineering.

A phosphorescent iridium probe for sensing polarity in the endoplasmic reticulum and in vivo.

The polarity of a cell is the feedback of a series of complex mechanisms that establish and maintain functionality of particular domains. Many cellular processes involved in the spatial arrangement and protein composition such as differentiation, localized membrane growth, activation of the immune response, directional cell migration, and vectorial transport of molecules across cell layers may lead to changes and development of polarity. In this work, a phosphorescent iridium complex was reported for sensitively probing environmental and cellular polarity. This probe exclusively targeted the endoplasmic reticulum (ER) and successfully in situ tracked polarity variations during ER stress in living cells. Importantly, the blood of diabetic mice in the presence of this probe appears to have distinguished phosphorescence compared with the blood of normal mice, indicating that the probe probably monitors blood polarity in diabetes.

Resolution improvement of multifocal structured illumination microscopy with sparse Bayesian learning algorithm.

Multifocal structured illumination microscopy (MSIM) is the parallelized version of image scanning microscopy (ISM), which uses multiple diffraction limited spots, instead of a single diffraction limited spot, to increase the imaging speed. By adding pinhole, contraction and deconvolution, a twofold resolution enhancement could be achieved in theory. However, this resolution improvement is difficult to be attained in practice. In this work, without any modification of the experimental setup, we propose to use multiple measurement vector (MMV) model sparse Bayesian learning (MSBL) algorithm (MSIMMSBL) as the reconstruction algorithm of MSIM, which does not need to estimate the illumination patterns but treat the reconstruct process as an MMV signal reconstruction problem. We compare the reconstructed super-resolution images of MSIMMSBL and MSIM by using simulation and experimental raw images. The results prove that by using the MSBL algorithm, the MSIM can obtain a higher than twofold resolution enhancement compared with the wide field image. This outstanding imaging resolution combining with the primary advantages of MSIM, such as the high imaging speed, could promote the application of MSIM in super-resolution microscopy imaging technology.

Synthesis and nonlinear optical properties of single-crystalline KNb3O8 nanowires.

Single-crystalline KNb(3)O(8) nanowires with widths of 100-300 nm and lengths up to tens of microns were synthesized by calcining Nb(2)O(5) powders in molten KCl and K(2)SO(4). The phase of the products was determined by means of x-ray diffraction, and the morphology and structure were characterized by using scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy and selected area electron diffraction techniques. The growth direction of the KNb(3)O(8) obtained was determined to be the [001] crystallographic direction. Meanwhile, the polarization response of the second-harmonic generation (SHG) response was investigated. The as-synthesized nanowires clearly exhibited a SHG response, which means that the nanowires were an efficient nanoscale second-harmonic light source. The excellent nonlinear optical property of KNb(3)O(8) shows potential for application in nano-optical devices.