FEED: a feature selection method based on gene expression decomposition for single cell clustering.

Single-cell clustering is a critical step in biological downstream analysis. The clustering performance could be effectively improved by extracting cell-type-specific genes. The state-of-the-art feature selection methods usually calculate the importance of a single gene without considering the information contained in the gene expression distribution. Moreover, these methods ignore the intrinsic expression patterns of genes and heterogeneity within groups of different mean expression levels. In this work, we present a Feature sElection method based on gene Expression Decomposition (FEED) of scRNA-seq data, which selects informative genes to enhance clustering performance. First, the expression levels of genes are decomposed into multiple Gaussian components. Then, a novel gene correlation calculation method is proposed to measure the relationship between genes from the perspective of distribution. Finally, a permutation-based approach is proposed to determine the threshold of gene importance to obtain marker gene subsets. Compared with state-of-the-art feature selection methods, applying FEED on various scRNA-seq datasets including large datasets followed by different common clustering algorithms results in significant improvements in the accuracy of cell-type identification. The source codes for FEED are freely available at https://github.com/genemine/FEED.

High-Entropy Spinel Ferrites with Broadband Wave Absorption Synthesized by Simple Solid-Phase Reaction.

In this work, high-entropy (HE) spinel ferrites of (FeCoNiCrM)xOy (M = Zn, Cu, and Mn) (named as HEO-Zn, HEO-Cu, and HEO-Mn, respectively) were synthesized by a simple solid-phase reaction. The as-prepared ferrite powders possess a uniform distribution of chemical components and homogeneous three-dimensional (3D) porous structures, which have a pore size ranging from tens to hundreds of nanometers. All three HE spinel ferrites exhibited ultrahigh structural thermostability at high temperatures even up to 800 °C. What is more, these spinel ferrites showed considerable minimum reflection loss (RLmin) and significantly enhanced effective absorption bandwidth (EAB). The RLmin and EAB values of HEO-Zn and HEO-Mn are about -27.8 dB at 15.7 GHz, 6.8 GHz, and -25.5 dB at 12.9 GHz, 6.9 GHz, with the matched thickness of 8.6 and 9.8 mm, respectively. Especially, the RLmin of HEO-Cu is -27.3 dB at 13.3 GHz with a matched thickness of 9.1 mm, and the EAB reaches about 7.5 GHz (10.5-18.0 GHz), which covers almost the whole X-band range. The superior absorbing properties are mainly attributed to the dielectric energy loss involving interface polarization and dipolar polarization, the magnetic energy loss referring to eddy current and natural resonance loss, and the specific functions of 3D porous structure, indicating a potential application prospect of the HE spinel ferrites as EM absorbing materials.

Hyaluronic acid hydrogels, as a biological macromolecule-based platform for stem cells delivery and their fate control: A review.

Stem cell-based therapies offer numerous potentials to repair damaged or defective organs. The therapeutic outcomes of human studies, however, fall far short from what is expected. Enhancing stem cells local density and longevity would possibly maximize their healing potential. One promising strategy is to administer stem cells via injectable hydrogels. However, stem cells differentiation process is a delicate matter which is easily affected by various factors such as their interaction with their surrounding materials. Among various biomaterial options for hydrogels' production, hyaluronic acid (HA) has shown great promise. HA is a naturally occurring biological macromolecule, a polysaccharide of large molecular weight which is involved in cell proliferation, cell migration, angiogenesis, fetal development, and tissue function. In the current study we will discuss the applications, prospects, and challenges of HA-based hydrogels in stem cell delivery and fate control.

The Strengthening and Toughening of Biodegradable Poly (Lactic Acid) Using the SiO2-PBA Core-Shell Nanoparticle.

The balance of strengthening and toughening of poly (lactic acid) (PLA) has been an intractable challenge of PLA nanocomposite development for many years. In this paper, core-shell nanoparticles consisting of a silica rigid core and poly (butyl acrylate) (PBA) flexible shell were incorporated to achieve the simultaneous enhancement of the strength and toughness of PLA. The effect of core-shell nanoparticles on the tensile, flexural and Charpy impact properties of PLA nanocomposite were experimentally investigated. Scanning electron microscopy (SEM) and small-angle X-ray scattering (SAXS) measurements were performed to investigate the toughening mechanisms of nanocomposites. The experimental results showed that the addition of core-shell nanoparticles can improve the stiffness and strength of PLA. Meanwhile, its elongation at break, tensile toughness and impact resistance were enhanced simultaneously. These observations can be attributed to the cavitation of the flexible shell in core-shell nanoparticles and the resultant shear yielding of the matrix. In addition, a three-dimensional finite element model was also proposed to illustrate the damage processes of core-shell nanoparticle-reinforced polymer composites. It was found that, compared with the experimental performance, the proposed micromechanical model is favorable to illustrate the mechanical behavior of nanocomposites.

Tensile, Quasistatic and Dynamic Fracture Properties of Nano-Al2O3-Modified Epoxy Resin.

Epoxy resin, modified with different particle sizes (50 nm, 100 nm, 200 nm) and contents (1 wt %, 3 wt %, 5 wt %, 7 wt %) was manufactured. The mechanical behaviors of tensile, quasistatic fracture and dynamic fracture under SHPB (split Hopkinson pressure bar) loading were investigated. The dynamic fracture behaviors of the composites were evaluated by 2D-DIC (digital image correlation) and the strain gauge technique, and the fracture surface was examined by SEM (scanning electron microscope). According to the results, the tensile modulus and strength significantly increased for epoxy resin modified with 5 wt % Al2O3 of 50 nm. The quasistatic fracture toughness of modified epoxy resin increased with the particle content. However, the fracture toughness of epoxy resin modified with high content fillers decreased for particle agglomeration that existed in epoxy resin. The crack propagation velocity can be decreased for epoxy resin modified with particles under dynamic loading. The dynamic initiation fracture toughness of modified epoxy resin increases with both particle size and content, but when the fillers have a high content, the particle size effects are weak. For the composite under dynamic loading conditions, the toughening mechanism is also affected by particle size.

Thermal and Mechanical Properties of Bamboo Fiber Reinforced Epoxy Composites.

Bamboo fibers demonstrate enormous potential as the reinforcement phase in composite materials. In this study, in order to find suitable NaOH concentration for bamboo fiber treatment, bamboo fibers were treated with 2 wt.%, 6 wt.% and 10 wt.% NaOH solutions for 12 h, respectively. We determined that 6 wt.% NaOH treated bamboo fibers were optimal for the fabrication of bamboo fiber composites by single fiber tensile test, single fiber pull-out test, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The short length bamboo fibers treated with 6 wt.% NaOH solutions were well dispersed in the epoxy matrix by a new preparation method. The effect of fiber content and fiber length on the mechanical behavior of bamboo fiber reinforced epoxy composites was investigated. The results confirmed that fracture toughness and flexural modulus of the composites monotonically increased with fiber length and content. However, for all samples, composites showed negligible difference on the flexural strength. The fracture surfaces of the composites were observed by SEM, revealing that fiber breakage, matrix cracking, debonding, and fiber pull out were major failure types. In addition, thermogravimetric analysis (TGA) was carried out to investigate the thermal behavior of both bamboo fibers and composites.

The removal efficiency of constructed wetlands filled with the zeolite-slag hybrid substrate for the rural landfill leachate treatment.

The removal efficiencies of two horizontal subsurface flow constructed wetlands (HSSF CWs, down-flow (F1) and up-flow (F2)) filled with the zeolite-slag hybrid substrate for the rural landfill leachate treatment were investigated. The adsorption experiment was conducted to evaluate the potential of zeolite and slag as the wetland substrate. The effects of distance variations along the longitudinal profile of wetland bed on pollutant removal were assessed by sampling at four locations (inlet, outlet, 0.55 m, and 1.10 m from the inlet). During the operation time, the influent and effluent concentrations of chemical oxygen demand (COD), ammonia nitrogen (NH3-N), total nitrogen (TN), heavy metals, and polycyclic aromatic hydrocarbon (PAH) were measured. The results showed that the constructed wetlands were capable of removing COD, 20.5-48.2% (F1) and 18.6-61.2% (F2); NH3-N, 84.0-99.9% (F1) and 93.5-99.2% (F2); TN, 80.3-92.1% (F1) and 80.3-91.2% (F2); and heavy metals, about 90% (F1 and F2). The zeolite-slag hybrid substrate performed excellent removal efficiency for the nitrogen and heavy metals. The inlet area was the most active region of leachate removal. The up-flow constructed wetland (F2) has a higher removal efficiency for the PAH compounds. The significant removal efficiency illustrated that the rural landfill leachate can be treated using the horizontal subsurface flow constructed wetland filled with the zeolite-slag hybrid substrate.

Evaluation of the Possible Sources and Controlling Factors of Toxic Metals/Metalloids in the Florida Everglades and Their Potential Risk of Exposure.

The Florida Everglades is an environmentally sensitive wetland ecosystem with a number of threatened and endangered fauna species susceptible to the deterioration of water quality. Several potential toxic metal sources exist in the Everglades, including farming, atmospheric deposition, and human activities in urban areas, causing concerns of potential metal exposure risks. However, little is known about the pollution status of toxic metals/metalloids of potential concern, except for Hg. In this study, eight toxic metals/metalloids (Cd, Cr, Pb, Ni, Cu, Zn, As, and Hg) in Everglades soils were investigated in both dry and wet seasons. Pb, Cr, As, Cu, Cd, and Ni were identified to be above Florida SQGs (sediment quality guidelines) at a number of sampling sites, particularly Pb, which had a level of potential risk to organisms similar to that of Hg. In addition, a method was developed for quantitative source identification and controlling factor elucidation of toxic metals/metalloids by introducing an index, enrichment factor (EF), in the conventional multiple regression analysis. EFs represent the effects of anthropogenic sources on metals/metalloids in soils. Multiple regression analysis showed that Cr and Ni were mainly controlled by anthropogenic loading, whereas soil characteristics, in particular natural organic matter (NOM), played a more important role for Hg, As, Cd, and Zn. NOM may control the distribution of these toxic metals/metalloids by affecting their mobility in soils. For Cu and Pb, the effects of EFs and environmental factors are comparable, suggesting combined effects of loading and soil characteristics. This study is the first comprehensive research with a vast amount of sampling sites on the distribution and potential risks of toxic metals/metalloids in the Everglades. The finding suggests that in addition to Hg other metals/metalloids could also potentially be an environmental problem in this wetland ecosystem.