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In this study, a LCC-VSC hybrid HVDC transmission system was taken as an example. The valve and neutral overvoltage of the hybrid HVDC system were simulated and then calculated at the VSC converter station by installing a blocking diode and a DC circuit breaker, as well as by grounding after neutral bus outage. The isolation effect of the blocking diode and the DC circuit breaker on the VSC converter station in the protection and the effect on the DC overvoltage were compared, and the difference was analyzed by complying with the mechanism of overvoltage. The effect of different locations of the blocking diode on the overvoltage suppression was compared, and it was concluded that different locations of blocking diode could raise different requirements for the insulation coordination of the converter valve. By analyzing energy sources of the neutral bus overvoltage at different stages, it was further concluded that the energy stored in the distributed inductance of the metal return line could be a vital source of neutral bus overvoltage energy. On that basis, an overvoltage suppression strategy for grounding neutral bus directly after the stop of the converter station was proposed.

Root temperature is an important ecological factor affecting plant growth. A solar greenhouse with an active solar heating system was built in Jinan, in the cold climate zone of northern China. Experiments encompassing the complete cycle of heat collection, heat storage, and heat release were carried out. Using the experimental data, the numerical simulation of soil heat storage with a variable heat flow was executed using the ANSYS (ANSYS Inc., Pittsburgh, PA, USA) Fluent software. Soil temperature fields were studied on typical sunny days and typical cloudy days in the transition season and winter. The solar collector efficiency and coefficient of performance of the system were investigated. The applicability of this active solar soil heating system with soil heat storage for cold areas was evaluated. The results showed that the system effectively maintained suitable ground temperatures to prevent plant growth inhibition caused by low ground temperatures in winter. During the experimental period, the solar collector efficiency was 47% and the system's coefficient of performance was 67.70. The thermal performance of the system was much better than a traditional energy system. This study showed that this active solar heating system with soil heat storage is an economic and feasible way to increase soil temperatures in solar greenhouses in cold areas. [ABSTRACT FROM AUTHOR]

The consumption of probiotics and fermented foods has been very popular in recent decades. The primary aim of our study was to evaluate the effect of probiotics on the gut microbiota and the changes in inflammatory cytokines after an average of 6.7 weeks of probiotic administration among normal pregnant women. Thirty-two healthy pregnant women at 32 weeks of gestation were recruited and divided into two groups. The probiotic group ingested combined probiotics until after birth. The base characteristics of the probiotics and control groups showed no significant differences. The structure of the fecal microbiota at the genus level varied during the third trimester, and administration of probiotics had no influence on the composition of the fecal microbiota however, many highly abundant taxa and core microbiota at the genus level changed in the probiotic group when compared to the control group. The analysis of cytokines showed that IL-5, IL-6, TNF-α, and GM-CSF had equal levels between the baseline and control groups but were significantly increased after probiotic administration (baseline = control < probiotics). Additionally, levels of IL-1β, IL-2, IL-12, and IFN-γ significantly increased among the three groups (baseline < control < probiotics). This result demonstrated that probiotics helped to shift the anti-inflammatory state to a pro-inflammatory state. The correlation analysis outcome suggested that the relationship between the microbiota and the cytokines was not strain-dependent. The gut microbiota varied during the third trimester. The probiotics demonstrated immunomodulation effects that helped to switch over to a pro-inflammatory immune state in the third trimester, which was important for labor. [ABSTRACT FROM AUTHOR]

The combination of reversible addition-fragmentation chain transfer (RAFT) polymerization and Click Chemistry was employed as a new approach to synthesize polyvinyltetrazole resin from acrylonitrile. The chemical composition and structure of the polyvinyltetrazole resin was studied by Fourier-transform infrared spectrometry and UV-Vis spectroscopies. Elemental analysis indicated the higher tetrazole content of the polyvinytetrazole resin. The polyvinyltetrazole resin exhibited excellent adsorption for metal ions and the maximum adsorption capacity for Hg(II) was 5.79 mmol/g. The resin could be reused stably in the adsorption of heavy metal ions. [ABSTRACT FROM PUBLISHER]

The present study analyzed the characteristics of switching overvoltage, and discussed in detail the main influencing factors and worst-case conditions of switching overvoltage in the \pm 1100-kV ultra-high-voltage direct-current (UHVDC) converter station. The results showed that ac bus overvoltage was produced by oscillation, and would not be a threat to the equipment in the converter station. The results also showed there were two cases for overvoltage on related valves. In the first case, the valve overvoltage was on converter valves in the upper three-pulse group of the 12-pulse converter, and was caused by the voltage difference between the dc line and ac bus at the valve side under a specific fault. In the second case, the overvoltage was on other valves, and was caused by a phase-to-phase switching surge that penetrated into the valve hall. Other results were that overvoltage on the dc bus was mainly caused by the full reflection of the wave, and overvoltage on the neutral bus was caused by high-voltage sources, such as the dc source creating stress on the neutral bus under specific faults, or the freewheeling current of the metal return line and the smoothing reactors. [ABSTRACT FROM AUTHOR]

Zincpowder was used as both reducing agent and supplemental activatorfor atom transfer radical polymerization via activators regeneratedby electron transfer (ARGET ATRP) to prepare polyacrylonitrile (PAN).Zinc powder was found to be an excellent additional agent with bettercontrolled behavior, higher monomer conversion, and faster polymerizationrate in comparison with ascorbic acid (VC). The effects of catalyst,ligand, and initiator on polymerization rate and molecular weightof PAN were investigated in detail. The resulting PAN was modifiedand employed as an adsorbent for removal of metal ions. Compared withCu(II) and Pb(II), the modified PAN showed an excellent adsorptionperformance toward Hg(II). [ABSTRACT FROM AUTHOR]

Emulsion templating of high internal phase emulsion was used to synthesize high oil-absorption resins with hexadecyl methacrylate and methyl methacrylate as monomers. Effects of cross-linking agent, emulsifier, initiator and porogen, polymerization temperature, polymerization time, the water/oil volume ratio, and the dosage of co-monomer on the properties of high oil-absorption resins were discussed. The optimum polymerization conditions for synthesis of high oil-absorbing resin were obtained. The highest oil absorbency in trichloromethane was 34 g/g. The oil absorbency of the resin remained constant after three times recovery. [ABSTRACT FROM AUTHOR]

ABSTRACT A novel catalyst system based on La(0)/hexamethylenetetramine (HMTA) complexes is used for single electron transfer-living radical polymerization (SET-LRP) of acrylonitrile (AN) in the presence of ascorbic acid (VC) with carbon tetrachloride (CCl4) as a initiator and N, N-dimethylformamide (DMF) as a solvent. Compared with SET-LRP of AN in the absence of VC, monomer conversion is markedly increased. SET-LRP of AN in the presence of VC is also conducted in the presence of air. The kinetic studies show that the polymerizations both in the absence of oxygen and in the presence of air proceed in a well-controlled manner. With the respect to the polymerization in the absence of oxygen, the polymerization in the presence of air provides slower reaction rate and broader polydispersity. Effects of amount of VC, La, CCl4, and are investigated in detail. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4088-4094 [ABSTRACT FROM AUTHOR]

Porous butyl methacrylate/octadecyl acrylate (BMA/OA) copolymers were first synthesized by suspended emulsion polymerization and evaluated for oil absorbency application. Effects of initiator, cross-linking agent, precipitator, dispersant agent, and emulsifier, water/oil ratio on oil absorbency of BMA/OA copolymers were studied in detail. The maximum oil absorbency to toluene was 23.5 g/g. [ABSTRACT FROM AUTHOR]

Oil-absorption resins are considered one of the effective materials to separate organic chemical compounds from oily water. In this work, well-defined high oil-absorption resins of poly(methyl methacrylate-butyl methacrylate) grafted onto silica gel were prepared by surface-initiated atom transfer radical polymerization using activators regenerated by electron transfer mediated by FeCl3/iminodiacetic acid. The grafted polymers were grown in a controlled manner. By considering the effect of different polymerization conditions, we prepared novel high oil-absorption resins. The chemical structures of the resins were determined by Fourier transform IR spectroscopy. SEM and TGA were also used to characterize the resins. It was found that the resins had good heat-resistant quality, higher oil absorbency and better oil retention and regeneration properties. The resins can absorb 31.2 g g−1 for tricholoromethane and 23.3 g g−1 for toluene. Copyright © 2012 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

In recent years, it has become evident that early-life intestinal flora plays a pivotal role in determining human health. Consequently, it is imperative to explore the establishment of neonatal intestinal flora and its influencing factors. Early neonatal intestinal flora is influenced by a multitude of factors, including maternal and infant-related factors, as well as external environment. This review summarizes the colonization mechanism of intestinal flora in the early life of newborns and discussed their influence on the establishment of neonatal intestinal flora, taking into account factors such as delivery mode, gestational age and feeding mode. Additionally, this review delves into the natural or artificial reconstruction of intestinal flora colonization defects in infants born via cesarean section and premature infants, with the goal of establishing a theoretical foundation for preventing and treating issues related to neonatal intestinal flora colonization and associated diseases., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Ma, Shi, Meng, Fan, Tang, Luo, Wang, Zhou and Xiao.)

Background: Probiotic supplementation has been popular and widespread, yet we still lack a comprehensive understanding of how probiotic supplementation during pregnancy affects the gut microbial networks of pregnant women and infants. In this study, we firstly used network analysis to compare the gut microbiota of pregnant women with and without probiotic supplementation, as well as their infants., Methods: Thirty-one pairs of healthy pregnant women and infants were recruited and randomly divided into the probiotic group (15 mother-infant pairs) and the control group (16 mother-infant pairs). Pregnant women in the probiotic group consumed combined probiotics from 32 weeks to delivery. Fecal samples were collected from pregnant women and infants at several time points. Gut microbiota was evaluated using 16S rRNA gene sequencing. Intestinal microbial network and topological properties were performed using the molecular ecological network analysis., Results: No significant difference was found between the probiotic and control groups on the microbial alpha and beta diversity. As the gestational age increased, the total links, average degree, average clustering coefficient, robustness, and the proportion of positive correlations were increased in pregnant women with probiotics administration. In contrast, these indices were decreased in infants in the probiotic group., Conclusion: Probiotic supplement does not change the microbial diversity of pregnant women and infants, but significantly alters the intestinal microbial network structure and properties. Although pregnant women have more complicated and stable networks after probiotic administration, their infants have less stable networks., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Huang, Li, Tye, Chan, Tang, Luo, Wang, Zhou, Duan and Xiao.)

Background: The influence of different delivery modes on the mother-to-child transmission (MTCT) rate of pregnant women with high hepatitis B viremia was investigated., Methods: A retrospective analysis was performed on data for 855 hepatitis- B -virus (HBV) carrier mothers who received regular prenatal care and delivered at the First Affiliated Hospital of Jinan University from January 2011 to October 2015. The neonates were classified into three groups according to the delivery mode: eutocia (438 cases), Non-parturient cesarean delivery (371 cases), and parturient cesarean delivery (46 cases). The neonatal HBV surface antigen (HBsAg) positive rates of the three delivery groups were comparatively analyzed to determine the influence of the delivery mode on HBV MTCT. Of the 855 HBV-carrier mothers, 480 mothers and respective newborns were tested for HBV-DNA and classified into four groups: HBV DNA≥10 7 copies/mL (96 cases), 10 5 ≤HBV DNA<10 7 copies/mL (37 cases), 10 3 ≤HBV DNA<10 5 copies/mL (85 cases), and HBV DNA<10 3 copies/mL (262 cases). The effect of the HBV DNA titers of these pregnant women on HBV MTCT was analyzed., Results: Statistically significant (P<0.05) differences were found among the HBsAg positive rates of neonates of HBV-carrier pregnant women delivered by the three methods from HBV-carrier pregnant women with HBV DNA≥107 copies/mL. No statistically significant (P>0.05) differences among the HBsAg positive rates were found for neonates delivered by the three methods from HBV-carrier pregnant women with HBV DNA<10 7 copies/mL., Conclusions: The delivery mode may influence the risk of HBV maternal-to-infant vertical transmission for HBV-carrier pregnant women with HBV DNA≥10 7 copies/mL. That is, elective cesarean section may reduce the HBV maternal-to-infant vertical transmission., (Copyright © 2020 Elsevier Masson SAS. All rights reserved.)

Sweet potato starch residue (SPSR) was used as starting material to prepare an eco-friendly adsorbent. SPSR was modified by bromoacetyl bromide to obtain a macroinitiator for surface-initiated single electron transfer-living radical polymerization (SI-SET-LRP) of acrylonitrile (AN) catalyzed by La(0)/hexamethylenetetramine (HMTA) in N,N-dimethylformamide (DMF) in the presence of ascorbic acid (VC). The amidoxime (AO) adsorbent was prepared by the reaction of the graft copolymer bromoactylated sweet potato starch (BSPS)/polyacrylonitrile (BSPS-g-PAN) with hydroxylamine. The maximum adsorption capacity for Hg(II) was 4.03 mmol·g(-1). This simple method provided a novel approach to recycle and reuse agricultural residues for controlling heavy metal pollution.