Preparation, Air Filtration Performance of a Fluorinated Polyimide/Polyacrylonitrile Nanofibrous Membrane by Electrospinning.

This paper reports the successful fabrication of a new nanofibrous membrane, F-PI/PAN, through electrospinning of polyacrylonitrile (PAN) and fluorinated polyimide (F-PI). The nanofibrous membrane exhibits comprehensive properties for high-temperature filtration and robust PM2.5 (particulate matter with an aerodynamic equivalent diameter of 2.5 microns or less) removal. The introduction of F enhances the hydrophobicity of the PI. The relationship between the hydrophobic performance and the filtration performance of particles is investigated. The chemical group of the composite membrane was demonstrated using FITR, while the surface morphology was investigated using field emission scanning electron microscopy. The TGA results indicated good thermal stability at 300 °C. Various ratios of F-PI membranes were prepared to characterize the change in properties, with the optimal mass ratio of F-PI being 20 wt%. As the proportion of F-PI increases, its mechanical and filtration efficiency properties and hydrophobicity become stronger. The contact angle reaches its maximum of 128 ± 5.2° when PAN:F-PI = 6:4. Meanwhile, when PAN:F-PI = 8:2, the filtration efficiency reaches 99.4 ± 0.3%, and the elongation at break can reach 76%. The fracture strength can also reach 7.1 MPa, 1.63 times that of the pure PAN membrane.

An ARF gene mutation creates flint kernel architecture in dent maize.

Dent and flint kernel architectures are important characteristics that affect the physical properties of maize kernels and their grain end uses. The genes controlling these traits are unknown, so it is difficult to combine the advantageous kernel traits of both. We found mutation of ARFTF17 in a dent genetic background reduces IAA content in the seed pericarp, creating a flint-like kernel phenotype. ARFTF17 is highly expressed in the pericarp and encodes a protein that interacts with and inhibits MYB40, a transcription factor with the dual functions of repressing PIN1 expression and transactivating genes for flavonoid biosynthesis. Enhanced flavonoid biosynthesis could reduce the metabolic flux responsible for auxin biosynthesis. The decreased IAA content of the dent pericarp appears to reduce cell division and expansion, creating a shorter, denser kernel. Introgression of the ARFTF17 mutation into dent inbreds and hybrids improved their kernel texture, integrity, and desiccation, without affecting yield.

Application of Glasses-Free Augmented Reality Localization in Neurosurgery.

OBJECTIVE: The accurate localization of intracranial lesions is critical in neurosurgery. Most surgeons locate the vast majority of neurosurgical sites through skull surface markers, combined with neuroimaging examination and marking lines. This project's primary purpose was to develop an augmented reality (AR) technology or tool that can be used for surgical positioning using the naked eye. METHODS: Brain models were predesigned with intracranial lesions using computerized tomography scan, and Digital Imaging and Communications in Medicine data were segmented and modeled by 3D slicer software. The processed data were imported into a smartphone 3D viewing software application (Persp 3D) and were used by a Remebot surgical robot. The localization of intracranial lesions was performed, and the AR localization error was calculated compared with standard robot localization. RESULTS: After mastering the AR localization registration method, surgeons achieved an average localization error of 1.39 ± 0.82 mm. CONCLUSIONS: The error of AR positioning technology in surgical simulation tests based on brain modeling was millimeter level, which has verified the feasibility of clinical application. More efficient registration remains a need that should be addressed.

Interfacial Engineering of Copper-Nickel Selenide Nanodendrites for Enhanced Overall Water Splitting in Alkali Condition.

Fabricating heterogeneous interfaces is an effective approach to improve the intrinsic activity of noble-metal-free catalysts for water splitting. Herein, 3D copper-nickel selenide (CuNi@NiSe) nanodendrites with abundant heterointerfaces are constructed by a precise multi-step wet chemistry method. Notably, CuNi@NiSe only needs 293 and 41 mV at 10 mA cm-2 for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively. Moreover, the assembled CuNi@NiSe system just requires 2.2 V at 1000 mA cm-2 in anion exchange membrane (AEM) electrolyzer, which is 2.0 times better than Pt/C//IrO2 . Mechanism studies reveal Cu defects on the Cu2-x Se surface boost the electron transfer between Cu atoms and Se atoms of Ni3 Se4 via Cu2-x Se/Ni3 Se4 interface, largely lowering the reaction barrier of rate-determining step for HER. Besides, the intrinsic activity of Ni atoms for in situ generated NiOOH is largely enhanced during OER because of the electron-modulating effect of Se atoms at Ni3 Se4 /NiOOH interface. The unique 3D structure also promotes the mass transfer during catalysis process. This work emphasizes the essential role of interfacial engineering for practical water splitting.

Initiating Fluorine Chemistry in Polycyclic Aromatic Hydrocarbon-Derived Carbon for New Cluster-Mode Na Storage with Superhigh Capacity.

Carbon materials are widely accepted as promising candidates for sodium-ion batteries (SIBs) anodes due to their chemical stability and conductivity, while the capacity is still unsatisfactory. Here, this work reports the superhigh capacity Na storage through initiating fluorine chemistry (CF bonds) in carbon synthesized by the dehydrogenation and fluorination of polycyclic aromatic hydrocarbon such as pitch. Experimental and theoretical investigations uncover that CF bonds exist at the form of dangling bonds (CFx ), which generates the coexistence of graphitic and defective nanodomains. It delivers a superhigh capacity of 450 mAh g-1 , far surpassing most of current SIBs carbon anodes. Theoretical calculation attributes this performance to a new Na storage mechanism that Na can be accommodated in the form of cluster rather than a single ion at each host site with F-doping. This work highlights the significance of carbon material chemistry in establishing the novel ion storage manner in SIBs and other batteries.

Investigation of sludge disintegration using vortex cavitation circulating fluidised grinding technology.

Waste-activated sludge (WAS) is regarded as a source of hazardous waste pollution from sewage treatment plants. To efficiently deal with WAS, vortex cavitation circulating fluidised grinding technology (VCCFGT) was proposed as a novel circulating fluidisation technology (CFT) to disintegrate WAS. To be specific, we investigated the effects of disintegration duration, pressure, and filling ratio of mill balls on sludge disintegration. The results of chemical and physical evaluation showed that the values of soluble chemical oxygen demand (SCOD), disintegration degree (DDSCOD), DNA, protein, carbohydrate, and NH4+-N increased with the increase in the filling ratio of the mill balls. Under a pressure and filling ratio of 0.30 MPa and 1.6%, respectively, the maximum effect was achieved after 60 min of treatment. Compared to those in the treatment without mill balls, the values of SCOD, DDSCOD, DNA, protein, carbohydrate, and NH4+-N in the treatment using mill balls increased by 218, 229, 230, 177, 371, and 190%, respectively. As a result of this technology, the temperature of the sludge dramatically increased, rising approximately 42.9 °C. Compared to that of the raw sludge, the sludge particle size after treatment was reduced by 83.25% at most, and the morphology of the sludge comprised smaller flocs. Compared to that of the ball-milling method, the mill balls filling ratio of VCCFGT reduced by 93.60-98.12%. Compared to that of sludge disintegration by the vortex cavitation method, VCCFGT indicating good disintegration degree (increased by 229%) and economic feasibility. VCCFGT has good application prospects for sludge disintegration. The main mechanisms of sludge disintegration and organic release include centrifugal force, grinding, shear force, cavitation, and cyclic fatigue effects, among which grinding plays a leading role. This study concluded that CFT can effectively disintegrate sludge flocs and disrupt bacterial cell walls.

One-Step Approach for Constructing High-Density Single-Atom Catalysts toward Overall Water Splitting at Industrial Current Densities.

The construction of highly active, durable, and cost-effective catalysts is urgently needed for green hydrogen production. Herein, catalysts consisting of high-density Pt (24 atoms nm-2 ) and Ir (32 atoms nm-2 ) single atoms anchored on Co(OH)2 were constructed by a facile one-step approach. Remarkably, Pt1 /Co(OH)2 and Ir1 /Co(OH)2 only required 4 and 178 mV at 10 mA cm-2 for hydrogen evolution reaction and oxygen evolution reaction, respectively. Moreover, the assembled Pt1 /Co(OH)2 //Ir1 /Co(OH)2 system showed mass activity of 4.9 A mgnoble metal -1 at 2.0 V in an alkaline water electrolyzer, which is 316.1 times higher than that of Pt/C//IrO2 . Mechanistic studies revealed that reconstructed Ir-O6 single atoms and remodeled Pt triple-atom sites enhanced the occupancy of Ir-O bonding orbitals and improved the occupation of Pt-H antibonding orbital, respectively, contributing to the formation of the O-O bond and the desorption of hydrogen. This one-step approach was also generalized to fabricate other 20 single-atom catalysts.

THP9 enhances seed protein content and nitrogen-use efficiency in maize.

Teosinte, the wild ancestor of maize (Zea mays subsp. mays), has three times the seed protein content of most modern inbreds and hybrids, but the mechanisms that are responsible for this trait are unknown1,2. Here we use trio binning to create a contiguous haplotype DNA sequence of a teosinte (Zea mays subsp. parviglumis) and, through map-based cloning, identify a major high-protein quantitative trait locus, TEOSINTE HIGH PROTEIN 9 (THP9), on chromosome 9. THP9 encodes an asparagine synthetase 4 enzyme that is highly expressed in teosinte, but not in the B73 inbred, in which a deletion in the tenth intron of THP9-B73 causes incorrect splicing of THP9-B73 transcripts. Transgenic expression of THP9-teosinte in B73 significantly increased the seed protein content. Introgression of THP9-teosinte into modern maize inbreds and hybrids greatly enhanced the accumulation of free amino acids, especially asparagine, throughout the plant, and increased seed protein content without affecting yield. THP9-teosinte seems to increase nitrogen-use efficiency, which is important for promoting a high yield under low-nitrogen conditions.

Hierarchical Amplitude-Aware Permutation Entropy-Based Fault Feature Extraction Method for Rolling Bearings.

In order to detect the incipient fault of rolling bearings and to effectively identify fault characteristics, based on amplitude-aware permutation entropy (AAPE), an enhanced method named hierarchical amplitude-aware permutation entropy (HAAPE) is proposed in this paper to solve complex time series in a new dynamic change analysis. Firstly, hierarchical analysis and AAPE are combined to excavate multilevel fault information, both low-frequency and high-frequency components of the abnormal bearing vibration signal. Secondly, from the experimental analysis, it is found that HAAPE is sensitive to the early failure of rolling bearings, which makes it suitable to evaluate the performance degradation of a bearing in its run-to-failure life cycle. Finally, a fault feature selection strategy based on HAAPE is put forward to select the bearing fault characteristics after the application of the least common multiple in singular value decomposition (LCM-SVD) method to the fault vibration signal. Moreover, several other entropy-based methods are also introduced for a comparative analysis of the experimental data, and the results demonstrate that HAAPE can extract fault features more effectively and with a higher accuracy.

Preparation, filtration, and photocatalytic properties of PAN@g-C3N4 fibrous membranes by electrospinning.

Particulate matter and formaldehyde (HCHO) in closed indoor environments are seriously harmful to human health; hence, techniques for the improvement of air quality have attracted significant attention. PAN@g-C3N4 fibrous membranes with high efficiency, low resistance, and photocatalytic activity were prepared by electrospinning with polyacrylonitrile (PAN) and graphite carbon nitride (g-C3N4), followed by the high-temperature polycondensation of melamine. The addition of g-C3N4 to the nanofibrous membrane effectively improved the filtration efficiency of PM2.5. When the amount of added g-C3N4 was 3 wt%, the filtration efficiency of PM2.5 was 99.76 ± 0.3%, the filtration efficiency was stable for 24 hours at a continuous high concentration, and the filtration cycle stability was good. As a photocatalytic material, g-C3N4 causes the photocatalytic degradation of HCHO, and thus, significantly improves the filtration efficiency of the nanofibrous membrane to HCHO. When the amount of added g-C3N4 was 3 wt%, the filtration efficiency of the nanofibrous membrane to HCHO reached 78.0 ± 1.8%. The mechanism of catalytic degradation showed that the PAN fibres first adsorbed and intercepted the HCHO molecules. Under simulated sunlight irradiation, the photogenerated holes generated by the g-C3N4 nanosheets in the fibres oxidised and decomposed the adsorbed HCHO molecules. This study has broad application potential for high-efficiency filters to improve indoor air quality.

Image Reconstruction Under Contact Impedance Effect in Micro Electrical Impedance Tomography Sensors.

Contact impedance has an important effect on micro electrical impedance tomography (EIT) sensors compared to conventional macro sensors. In the present work, a complex contact impedance effect ratio ξ is defined to quantitatively evaluate the effect of the contact impedance on the accuracy of the reconstructed images by micro EIT. Quality of the reconstructed image under various ξ is estimated by the phantom simulation to find the optimum algorithm. The generalized vector sampled pattern matching (GVSPM) method reveals the best image quality and the best tolerance to ξ. Moreover, the images of yeast cells sedimentary distribution in a multilayered microchannel are reconstructed by the GVSPM method under various mean magnitudes of contact impedance effect ratio |ξ|. The result shows that the best image quality that has the smallest voltage error UE = 0.581 is achieved with measurement frequency f = 1 MHz and mean magnitude |ξ| = 26. In addition, the reconstructed images of cells distribution become improper while f < 10 kHz and mean value of |ξ| > 2400.

Effect of cooking methods on nutritional quality and volatile compounds of Chinese chestnut (Castanea mollissima Blume).

This study aimed to evaluate the effects of different cooking methods on the content of important nutrients and volatiles in the fruit of Chinese chestnut. The nutritional compounds, including starch, water-soluble protein, free amino acids, reducing sugar, sucrose, organic acids and total flavonoids, of boiled, roasted and fried chestnuts were significantly (P<0.05) lower than those of fresh chestnuts after cooking, while the amylose, fat, crude protein and total polyphenol content varied slightly (P>0.05). L-Aspartic acid, L-glutamic acid and L-arginine were found to be the main reduced free amino acids in cooked chestnuts. The main aromatic compositions in fresh chestnuts were aldehydes and esters, while ketones, furfural and furan were formed in cooked chestnuts due to the Maillard reaction and degradation of saccharides, amino acids and lipids. Principle component analysis demonstrated that roasting and frying had a similar effect on the nutritional composition of chestnuts, which differed from that of the boiling process.

On the properties of Se⋯N interaction: the analysis of substituent effects by energy decomposition and orbital interaction.

The nature and strength of intermolecular Se⋯N interaction between selenium-containing compounds HSeX (X = CH3, NH2, CF3, OCH3, CN, OH, NO2, Cl, F), and NH3 have been investigated at the MP2/aug-cc-pVDZ level. The Se⋯N interaction is found to be dependent on the substituent groups, which greatly affect the positive electrostatic potential of Se atoms and the accepting electron ability of X-Se σ(∗) antibonding orbital. Energy decomposition of the Se ⋯N interaction reveals that electrostatic and induction forces are comparable in the weak-bonded complexes and induction becomes more significant in the complexes with strong electron-withdrawing substituents. Natural bond orbital (NBO) analysis indicates that the primary source of the induction is the electron transfer from the N lone pair to the X-Se σ(∗) antibonding orbital. The geometry of the complex and the interaction directionality of NH3 to X-Se bond can be regarded as a consequence of the exchange-repulsion. The topological analysis on the electron density reveals the nature of closed-shell interaction in these X-Se⋯N contacts. The Se⋯N interaction in the complexes with the strong electron-withdrawing substituent has a partly covalent character.

Spatio-temporal Variation of Sediment Methanotrophic Microorganisms in a Large Eutrophic Lake.

Aerobic methane-oxidizing bacteria (MOB) play a crucial role in mitigating the methane emission from lake ecosystems to the atmosphere. However, the distribution of methanotrophic community in shallow and eutrophic lake and its influential factors remain essentially unclear. The present study investigated sediment methanotrophic microorganisms at different sites in eutrophic freshwater Dianchi Lake (China) in two different seasons. The abundance, diversity, and structure of sediment methanotrophic community showed a profound spatial and seasonal variation. The pmoA gene copy number in lake sediments ranged from 8.71 ± 0.49 × 10(4) to 2.09 ± 0.03 × 10(7) copies per gram of dry sediment. Sediment methanotrophic communities were composed of Methylococcus and Methylobacter (type I methanotrophs) and Methylosinus (type II methanotrophs), while type I MOB usually outnumbered type II MOB. Moreover, ammonia nitrogen was found to be a potential determinant of methanotrophic community structure in Dianchi Lake.

Spatial distribution characteristics of volatile halogenated hydrocarbons in unsaturated zone of Xiaodian sewage irrigation area, Taiyuan, China.

Sewage irrigation is one of the best options to reduce the stress on limited fresh water and to meet the nutrient requirement of crops. Environment pollution caused by volatile halogenated hydrocarbons (VHCs) associated with sewage irrigation has received increasing attention due to the toxicological importance in ecosystem. The aim of this study was to discuss the spatial distribution characteristics of VHCs in unsaturated zone under sewage irrigation and their migration in the environment. Soil samples were collected from XiaoDian district of TaiYuan city and measured for the major VHCs including of chloroform (CHCl3), tetrachloromethane (CCl4), trichloroethylene (C(2)HCl(3)), tetrachloroethylene(C(2)Cl(4)), pentachlorobenzene (C(6)HCl(5)), hexachlorobenzene (C(6)Cl(6)). Results showed that VHCs were accumulated in the unsaturated zone with long-term sewage irrigation. The contents of VHCs in the unsaturated zone of the study area were 34, 2, 3, 1.5, 8.3, 4.8 times higher than the background value respectively. Soils with long-term irrigation of sewage showed higher contents of VHCs than that with short-term irrigation of sewage. Not only the irrigation time, soil physical properties (e.g. soil texture) also played an important role on VHCs accumulation in soil.

Microbial quantities and enzyme activity in soil irrigated with sewage for different lengths of time.

Sewage is widely used on agricultural soils in peri-urban areas of developing countries to meet shortages of water resource. Although sewage is a good source of plant nutrients, it also increases the heavy metals loads to soils. Microbial responses to these contaminants may serve as early warning indicators of adverse effects of sewage irrigation on soil quality. The purpose of this study was to assess the effect of time of sewage irrigation on soil microbial indicators. Soil samples were collected from seven soil sites (S1-S7) irrigated with 0 years, 16 years, 23 years, 25 years, 27 years, 32 years and 52 years, respectively in Shijiazhuang of China and analyzed. For each soil sample, we determined the quantities of bacteria, fungi and actinomycete, and enzyme activities of urease, sucrase, phosphatase, dehydrogenase and catalase. Our results showed that the soils of S2-S7 irrigated with sewage effluents for different times (ranged between 16 and 52 years) exhibited higher densities of bacteria, actinomycete, urease, sucrase and phosphatase but lower densities of fungi when compared with S1 irrigated with sewage effluents for 0 years. The soil S7 irrigated with sewage effluents for longest times (52 years) contained lowest activities of catalase when compared with the soils of S1-S6. The densities of bacteria (R = 0.877, p < 0.01), actinomycete (R = 0.875, p < 0.01), sucrase (R = 0.858, p < 0.01) and phosphatase (R = 0.804, p < 0.05) were significantly correlated in a positive manner with time of sewage irrigation. Soil fungi quantities and urease, dehydrogenase and catalase activities did not change significantly with irrigation time. This study confirms that sewage irrigation had negative effects on microbial properties including fungi, catalase and dehydrogenase in the long term, so there is a need for continuous monitoring for sustainable soil health.