Titanium dioxide nanoparticles (TiO2 NPs) are one of the most widely used nanomaterials in the consumer products, agriculture, and energy sectors. Their large demand and widespread applications will ...inevitably cause damage to organisms and ecosystems. A better understanding of TiO2 NP toxicity in living organisms may promote risk assessment and safe use practices of these nanomaterials. This review summarizes the toxic effects of TiO2 NPs on multiple taxa of microorganisms, algae, plants, invertebrates, and vertebrates. The mechanism of TiO2 NP toxicity to organisms can be outlined in three aspects: The Reactive Oxygen Species (ROS) produced by TiO2 NPs following the induction of electron–hole pairs; cell wall damage and lipid peroxidation of the cell membrane caused by NP-cell attachment by electrostatic force owing to the large surface area of TiO2 NPs; and TiO2 NP attachment to intracellular organelles and biological macromolecules following damage to the cell membranes.
Display omitted
2D hierarchically porous carbon (2D-HPC) nanosheets with unique advantages are highly desired as host materials for lithium sulfur (Li–S) batteries and other energy storage devices. Herein, we ...propose a self-template and organic solvent-free approach to synthesize nanosheets of monoclinic ZIF-8 at room temperature from which 2D-HPC nanosheets (ZIF-8 nanosheets carbon denoted as ZIF-8-NS-C) are derived to be an efficient sulfur immobilizer for Li–S batteries for the first time. The anisotropic nanosheets are believed to relate to the symmetry of the monoclinic structure. The 2D ZIF-8-NS-C nanosheets with embedded hierarchical pores construct an effective conductive network through “plane-to-plane” modes to endow superior electron transfer and fast electrochemical kinetics. Moreover, the nitrogen-rich feature of ZIF-8-NS-C can increase the affinity/interaction of carbon host with lithium polysulfides, favoring the cyclic performance. The sulfur/ZIF-8-NS-C (S/ZIF-8-NS-C) cathode shows a superior rate capability with high capacities of 1226 mA h g–1 at 0.2 C and 785 mA h g–1 at 2 C, and a sustainable cycling stability with a capacity attenuation of 0.12% per cycle at 0.5 C for 300 cycles. The approach proposed here pioneers the controllable design of MOF-based structures to inspire the exploration of more variable MOF-derived porous materials for energy storage applications.
Three types of CuMAl layered double hydroxides (LDHs, M=Mg, Zn, Ni) were successfully synthesized by coprecipitation. Powder X-ray diffraction (XRD), inductively coupled plasma atomic emission ...spectrometry (ICP-AES) and UV–Vis diffuse reflectance spectrum (UV–vis) were used to confirm the formation of as-synthesized solids with good crystal structure. The photocatalytic activity of those LDH materials for CO{sub 2} reduction under visible light was investigated. The experimental results show that CuNiAl-LDHs with narrowest band gap and largest surface areas behave highest efficiency for methanol generation under visible light compared with CuMgAl-LDHs and CuZnAl-LDHs. The CuNiAL-LDH showed high yield for methanol production i.e. 0.210 mmol/g h, which was high efficient. In addition, the influence of the different M{sup 2+} on the structures and stability of the CuMAl-LDHs was also investigated by analyzing the geometric parameters, electronic arrangement, charge populations, hydrogen-bonding, and binding energies by density functional theory (DFT) analysis. The theoretical calculation results show that the chemical stability of LDH materials followed the order of CuMgAl-LDHs>CuZnAl-LDHs>CuNiAl-LDHs, which is just opposite with the photocatalytic activity and band gaps of three materials. - Graphical abstract: The host–guest calculation models and XRD patterns of CuMAl-LDHs: CuMgAl-LDHs (a), CuZnAl-LDHs (b) and CuNiAl-LDHs (c). - Highlights: • Three types of CuMAl layered double hydroxides (LDHs, M=Mg, Zn, Ni) has been synthesized. • CuMgNi shows narrower band gap and more excellent textural properties than other LDHs. • The band gap: CuMgAl<CuZnAl<CuNiAl based on result from UV–vis analysis. • CuMgAl shows the highest stability and lowest photocatalytic activity, while CuNiAl just opposite.
Thermoplastic carbon fibre reinforced polyetheretherketone (CF/PEEK) and thermoset CF/epoxy composites have been widely applied in various industries. However, there is still a lack of knowledge ...concerning the milling performance and residual mechanical behavior of these two types of composites. To address this issue, we conducted a comprehensive investigation of the machinability during milling of both composites, with a focus on cutting force, machining temperature, chip characteristics, and milling-induced damages. To our knowledge, this is the first report documenting the correlation between surface integrity under different cutting conditions and residual tensile behaviour in both composites. The results demonstrate that CF/PEEK exhibits better machining quality than CF/epoxy due to its ductile matrix and strong interface bonding with fibres. Furthermore, down-milling was found to be preferable to up-milling for minimizing top layer surface damage, while petal-shaped chips with good integrity were found to be generated by CF/PEEK during milling. Moreover, CF/PEEK exhibited a significantly higher residual tensile strength (12.05%–63.22%) compared to CF/epoxy.
•This study provides the investigation of milling performance in CF/PEEK and CF/epoxy, filling a knowledge gap.•The effects of two milling strategies on damages were systematically investigated to obtain preferable milling strategy.•The findings on residual tensile strength indicated that CF/PEEK has significantly higher resilience compared to CF/epoxy.
Early faults in rolling bearings tend to result in periodic impulse components in the collected vibration signals. However, these fault features are always distorted by noise interferences. Feature ...extraction from vibration signals is an effective means to detect early defects in rolling bearings. A new morphological filter (MF), called enhanced difference morphological filter (EDMF) is proposed for vibration signal processing and then implementing bearing fault diagnosis. EDMF is capable of depressing noise and preserving effective impulsive components, where four new basic morphological operators are integrated effectively. The experimental results on simulation and bearing vibration signals verify that EDMF is effective for defect detection of rolling bearings. The comparison results show that the new MF can extract fault features more effectively from vibration signals with much noise than other typical MFs.
Cystatin C, the full name of cystatin C, is one of the most potent cathepsin inhibitors currently known, which can strongly inhibit cathepsin in lysosomes and regulate the level of intracellular ...proteolysis. Cystatin C plays a very broad role in the body. High temperature-induced brain injury leads to very serious damage to brain tissue, such as cell inactivation, brain tissue edema, etc. At this time, cystatin C can play a crucial role. Based on the research on the expression and role of cystatin C in high temperature-induced brain injury in rats, this paper draws the following conclusions: high temperature can cause very serious damage to the brain tissue of rats, which can seriously lead to death. Cystatin C has a protective effect on brain cells and cerebral nerves. When the brain is damaged by high temperature, cystatin C can relieve the damage of high temperature to the brain and protect brain tissue. In this paper, a detection method for cystatin C with more outstanding performance is proposed, and compared with the traditional detection method, the detection method in this paper is verified to have more accurate accuracy and excellent stability through comparative experiments. Compared with traditional detection methods, it is more worthwhile to use and is a better detection method.
LiFexMn2-xO4 (x=0.0, 0.1 and 0.2) with superior rate and cycling performance is synthesized using a sol – gel method by combining citric acid and glucose as the chelating agent. For the first time Fe ...is found to basically occupy the 16d site. Fe doping decreases the occupancies of Mn at the 8a site considerably, and reduces the variations of the lattice volume before and after charge significantly, and suppresses the formation of the lower valence manganese surface phases. The structure - related factors other than the conventional morphology and size lead to the drastically enhanced performance of the Fe - doped samples. The combination of the decreased occupancies of Mn on the 8a site, and the only occupation of Fe on the 16d site, and the suppression of the surface phases of manganese ions with the lower valences and the alleviation of the Jahn - Teller effect due to the partial replacement of Mn3+ by Fe3+ result in both the improved electronic and ionic conductivities, and thus the drastically enhanced performance. The capacity of 66 mAh g−1 for x = 0.2 is delivered for 300C discharge with 1C charge. The capacity retentions after 1500 cycles for 100C discharge and 10C charge at room temperature (RT) and 60°C are 90% and 83%, respectively. The present study opens a feasible way to obtain the high performance manganese spinel cathode by controlling the lattice site occupation of an alien element and manganese and the formation of low valence manganese surface phases.
A full PDMS micro-droplet chip for 3D cell culture was prepared by using SLA light-curing 3D printing technology. This technology can quickly customize various chips required for experiments, saving ...time and capital costs for experiments. Moreover, an injection molding method was used to prepare the full PDMS chip, and the convex mold was prepared by light-curing 3D printing technology. Compared with the traditional preparation process of micro-droplet chips, the use of 3D printing technology to prepare micro-droplet chips can save manufacturing and time costs. The different ratios of PDMS substrate and cover sheet and the material for making the convex mold can improve the bonding strength and power of the micro-droplet chip. Use the prepared micro-droplet chip to carry out micro-droplet forming and manipulation experiments. Aimed to the performance of the full PDMS micro-droplet chip in biological culture was verified by using a solution such as chondrocyte suspension, and the control of the micro-droplet was achieved by controlling the flow rate of the dispersed phase and continuous phase. Experimental verification shows that the designed chip can meet the requirements of experiments, and it can be observed that the micro-droplets of sodium alginate and the calcium chloride solution are cross-linked into microspheres with three-dimensional (3D) structures. These microspheres are fixed on a biological scaffold made of calcium silicate and polyvinyl alcohol. Subsequently, the state of the cells after different time cultures was observed, and it was observed that the chondrocytes grew well in the microsphere droplets. The proposed method has fine control over the microenvironment and accurate droplet size manipulation provided by fluid flow compared to existing studies.
Polycrystalline SnSe bulks were synthesized by a simple and rapid High Pressure and High Temperature (HPHT) method in pressure range of 1–5 GPa, and the thermoelectric performances were assessed ...after high pressure was released. HPHT can not only sharply shorten synthetic time to 25 min, but also tune thermoelectric properties in a broad range. More importantly, the beneficial thermoelectric properties under high pressure are effectively retained to ambient conditions via “quenching” procedure. The intrinsically high electrical resistivity of SnSe is remarkably reduced by HPHT, which is ascribed to pressure-induced band gap narrowing. A minimum electrical resistivity of 0.1 Ω cm at 5 GPa and maximum power factor of 1 × 10−4 Wm−1K−2 at 3 GPa for SnSe0.98Te0.02 are achieved at ambient conditions. Besides, the first principle calculations reveal that high pressure can fundamentally shrink interatomic distances and lattice parameters, which thus lead to a decreased band gap. The pressure coefficient of band gap dEg/dP = −0.074 eV/GPa is obtained. The variations of electronic structure under high pressure are in accordance with the trend in measured thermoelectric properties.
Display omitted
•HPHT a simple and rapid synthetic method (from elements to bulk in 25 min).•HPHT can distinctly reduce the intrinsically high electrical resistivity of SnSe.•The high pressure effects are retained to ambient conditions.•The calculations verify the interatomic distance shrinkage and band gap narrowing.
The physical environment of classrooms has a strong relationship with student learning performance and health. Since the outbreak of COVID-19 in 2019, almost all universities have begun implementing ...closed instructional management, which has forced students to spend a much longer amount of time inside the classroom. This has also led to an increasing problem of thermal comfort in classroom indoor environments. In this paper, classrooms evolved from three dominant teaching modes at Zhejiang Sci-Tech University (ZSTU), located in the Hot Summer and Cold Winter (HSCW) zone of China, were selected as experimental spaces. Meanwhile, 12 learning groups with 60 students (30 of each sex) were selected as the tested samples. The relationship between thermal comfort and learning efficiency of the tested students was established through thermal comfort questionnaires and learning efficiency tests under the typical natural conditions in transition seasons. Based on this, improvement strategies were proposed for the current state of the classroom environment, providing a database for optimizing the environmental conditions of university classrooms in HSCW zone on the basis of improving students’ learning efficiency.
PDF
