A new Venus‐ESD‐Chamber (VEC) and peripheral systems were designed and built to simulate Venus lightning. It consists of three subsystems (a) electrostatic discharge (ESD) generation, (b) ...environmental pressure, temperature, gas composition control & monitoring, and (c) optical and non‐optical sensors. We conducted arc discharge experiments in air, in CO2, and in Venus major gas mixture (CO2‐N2, 96.5% ± 1.5%:3.5% ± 1.5%) under 10, 350, 700, and 1,000 mbar pressures, that correspond to the 50–75 km altitude range in the cloud layer of Venus. Plasma and Raman spectra, plus gas sensors, and GC‐MS were used to identify the ESD products and to semi‐quantify CO and O3 generated by ESD. We have found all species of free radicals that have been found in previous simulation studies using different discharge technologies, including some important species in CO2‐N2 system, nitrogen oxides and CN. In addition, we found three species (O3, N2+, and C2) that have not been previously reported. Our results suggest that electron flux and kinetic energy are the determining factors for the type of generated free radical species and gas pressure plays a less important role. We found that the quantity of CO changes with the type of ESD. The detection of O3 in this study suggests that lightning might be one of the sources of O3 observed in the Venusian atmosphere. OI emission line at 777.4 nm is the most prominent line in our plasma spectra of FD, consistent with the intense optical flash observed by the Lightning and Airglow Camera (LAC) on the Akatsuki mission.
Plain Language Summary
Lightning is a common phenomenon on Earth and plays an important role in atmospheric chemistry as well as in atmosphere‐surface interaction. The thick atmosphere and strong convective activities in Venus cloud layers could ignite lightning. Evidence of lightning on Venus (optical and electric types) has been reported since the 1970s, including the observation made by the most recent mission Akatsuki in 2020. Here, we report the detection of 15 types of free radicals generated during a set of arc‐type electric discharges in simulated Venus atmosphere with two major Venus gases (CO2 & N2) and in a pressure range corresponding to the Venus cloud layer (50–75 km altitude range). These free radicals are ions and neutral atoms/molecules in excited states, which have extremely high chemical reactivity and high kinetic energy. They could play crucial roles in Venus atmospheric chemistry and might be helpful to interpret some past mission observations for example, nitrogen oxides and O3.
Key Points
Building a Venus‐ESD chamber enables simulation of Venus lightning and radical sensing
Arc discharge was realized to simulate lightning in the cloud layer of Venus
15 types of free radicals and excited atoms/molecules were characterized using four sensors
The high dehydrogenation temperature of magnesium hydride MgH2 is still the main obstacle to its practical application as a solid-state hydrogen storage medium. Using experimental and ...first-principles calculations approaches, we, for the first time, investigate the catalytic effect and mechanism of nickel phthalocyanine on the dehydrogenation properties of MgH2. The results display that a small amount of nickel phthalocyanine can promote MgH2 dehydrogenation at significantly decreased temperatures by more than 90 °C relative to milled pristine or graphene-added MgH2 system. However, the agglomeration of MgH2 particles is not evidently alleviated through nickel phthalocyanine addition. When MgH2 is milled with graphene firstly and then the obtained mixture is further milled with nickel phthalocyanine, the dehydrogenation properties and agglomeration of MgH2 particles can be synergistically improved to some extent. The first-principles calculations of dehydrogenation enthalpy and binding energy account for the experimental differences in catalysis and aggregation-resistance abilities of nickel phthalocyanine and graphene on MgH2 particles. Notably, the NiN4-inserted graphene is predicted to be an ideal additive for MgH2, which combines the synergetic catalysis-confinement effect of nickel phthalocyanine and graphene on MgH2 particles. Analysis of electronic structures reveals that the excellent catalytic effect of nickel phthalocyanine on MgH2 can be ascribed to the more electron transfer between nickel phthalocyanine and MgH2, which induces the significantly weakened bond strength of MgH and decreased dehydrogenation enthalpy of MgH2.
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•NiPc exhibits superior catalytic effect on MgH2 dehydrogenation.•Multi-addition of NiPc and G can improve dehydrogenation and agglomeration of MgH2.•Dehydrogenation enthalpy and binding energy of MgH2-NiPc system are calculated.•Catalytic effect of NiPc on MgH2 is associated with electron transfer between them.•NiN4-inserted G is predicted to be an ideal catalysis-confinement additive for MgH2.
1. This study investigated the effect of dietary calcium (Ca) levels on growth performance, bone development and Ca transporter gene expression levels in the small intestine of broiler chickens.
2. ...On the day of hatch, 350, Ross 308 male broilers were randomly allotted to one of five treatments with five replicate pens each and 14 birds per pen. Dietary Ca levels in feed were 5.0, 7.0, 9.0, 11.0 and 13.0 g/kg, in which 9.0 g/kg was in the control diet. All diets contained 4.5 g/kg non-phytate phosphorus (NPP).
3. The increase in dietary Ca levels from 5.0 to 13.0 g/kg did not affect the growth performance of 1- to 18-day-old broilers (P > 0.05).
4. Increasing the Ca levels linearly increased the ash weight and the contents of ash, Ca and phosphorus (P) in the tibia of broilers at 18 days of age (P < 0.05). The contents of ash, Ca and P in broilers fed with 9.0 g/kg Ca were higher than those in birds fed with 5.0 g/kg Ca (P < 0.05).
5. Increasing the Ca levels linearly decreased mRNA expression levels of the Ca-binding protein 28-kDa (CaBP-D28k), plasma membrane Ca-transporting ATPase 1b (PMCAlb), sodium (Na)/Ca exchanger 1 (NCX1), nuclear vitamin D receptor (nVDR) and membrane vitamin D receptor (mVDR) in the duodenum of broilers at 18 d of age (P < 0.05). Similar results were seen in the jejunum and ileum. Broilers fed 9.0-13.0 g/kg Ca in feed had lower mRNA expression levels of CaBP-D28k and PMCAlb in the small intestine than birds fed 5.0 g/kg Ca in feed (P < 0.05).
6. The data indicated that low levels of dietary Ca stimulated its transporter gene transcription and promoted absorption, but high levels of Ca inhibited transporter gene expression and prevented excessive absorption in the small intestine of broiler chickens.
Microorganisms present a global public health problem and are the leading cause of hospital-acquired infections. Therefore, it is essential to study the prevalence of microorganisms in hospital ...environments. The conclusion from such a study can contribute to identify the areas most likely to be contaminated in a hospital and appropriate measures that can decrease the exposure risk.
The prevalence of microorganisms in hospital air was examined in different departments by obtaining air samples with an impactor before and during the SARS-CoV-2 pandemic. A total of 2145 microorganisms were identified, and the corresponding data were jointly analyzed by area, sampling period, and concentration.
The most frequently detected microorganisms in hospital air were Staphylococcus, Micrococcus, Neisseria, and fungi, and the more polluted departments were the hemodialysis department, respiratory department, treatment room, and toilet. Significant differences were found between the concentration of bacteria and fungi before and during the pandemic, which could be related to multiple environmental conditions. Furthermore, SARS-CoV-2 was negative in all the air samples.
Overall, this study confirmed the existence and dynamic characteristics of airborne microorganisms in a hospital. The results contribute to the adaptation of specific measures which can decrease the exposure risk of patients, visitors, and staff.
The magnetic and mechanical properties of sintered Nd–Fe–B magnets prepared by different sintering processes were investigated. The results showed that the intrinsic coercivity and fracture toughness ...of sintered Nd–Fe–B magnets first increased, and then declined with increasing annealing temperature. The optimum magnetic properties and fracture toughness of sintered Nd–Fe–B magnets were obtained at the annealing temperature of 540°C. Sintering temperature increasing from 1047°C to 1071°C had hardly effect on the magnetic properties of sintered Nd–Fe–B magnets. The variation of Vickers hardness and fracture toughness was not the same with increasing sintering temperature, and the effect of sintering temperature on the mechanical properties was complex and irregular. The reasons for the variation on magnetic and mechanical properties were analyzed, and we presumed that the effect of microstructure on the mechanical properties was more sensitive than the magnetic properties through analyzing the microstructure of sintered Nd–Fe–B magnets.
•The optimum fracture toughness of sintered Nd–Fe–B magnets was obtained at 540°C.•The effect of sintering temperature on mechanical properties was irregular.•Sintering temperature had hardly effect on the magnetic properties in this paper.•The effect of microstructure on mechanical properties was more sensitive.
Magnesium based hydride (MgH2) is a promising hydrogen storage material. However, the sluggish sorption rate impedes its practical applications. To improve the dehydrogenation kinetics of MgH2, the ...influences of external strains with different dimension (uniaxial/biaxial/triaxial), direction (tensile/compressive) and magnitude (−3% ∼ +3%) on H atom diffusion properties within MgH2 lattice are investigated for the first time using first-principles calculations method. In addition, the synergistic effects of strain and doping of transition metal Nb are further studied. The results show that the diffusion energy barrier of H atom is sensitive to the strain applied to MgH2 lattice. The energy barrier value decreases significantly upon no matter uniaxial, biaxial or triaxial strain, leading to the remarkable increase of H atom diffusion rate. By contrast, the uniaxial tensile strains of ε ≥ 0.5% along 100 or 010 crystal direction, biaxial and triaxial compressive strains of ε ≤ −2% are more beneficial to improving the dehydrogenation kinetics of MgH2. What's more, the strain and Nb doping play the synergistic enhancement effect in increasing H atom diffusion rate, which is superior to their separate role. Analysis of electronic structures reveals that the dehydrogenation kinetics of different MgH2 systems is associated with the energy gap value near Fermi level and the covalent bond strength between hydrogen and metal ions within MgH2 lattice. These results prompt a new insight to enhance the dehydrogenation kinetics of MgH2 by synergistically introducing external strain and transition metal catalysts.
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•The strain and doping effects on dehydrogenation kinetics of MgH2 are studied.•Uniaxial, biaxial and triaxial strains all can increase H atom diffusion rate.•The strain and Nb doping play the synergistic enhancement effect.•The strain and Nb doping alter the electronic structures of MgH2.•A new insight to enhance the dehydrogenation kinetics of MgH2 is proposed.
Internationally, geopolymerisation technique has gradually been one of the most popular methods to dispose wastes due to effective immobilization of toxic metals. However, few studies were conducted ...on the wastes containing many different heavy metals and determined the factors affecting the immobilization of these heavy metals. In this paper, a series of fly ash-based geopolymeric matrices containing Cd(II), Cu(II), Pb(II) and Cr(III) were investigated. The results show that these heavy metals can be effectively immobilized into the geopolymeric matrices. In addition, the concentrations of alkali activator and different kinds of heavy metals have fairly impact on the immobilization behavior to one metal in the same system, and the heavy metals seem to have fairly large effect on the chemical and physical characteristics of the final products.
1. Enhancing bone strength to solve leg disorders in poultry has become an important goal in broiler production. Bone morphogenetic protein 7 (BMP7), a member of the BMP family, represents an ...attractive therapeutic target for bone regeneration in humans and plays critical roles in skeletal development.
2. The objective of this study was to investigate the relationship between BMP7 gene expression, single-nucleotide polymorphisms (SNPs) and growth traits in chickens. Here, a SNP (c.1995T>C) in the chicken (Gallus gallus) BMP7 gene was identified, that was associated with growth and carcass traits.
3. Genotyping revealed that the T allele occurred more frequently in breeds with high growth rates, whereas the C allele was predominant in those with low growth rates. The expression level of BMP7 in the thigh bone of birds with the TT genotype was significantly higher than in those with the CC genotype at 21, 42 and 91 d of age.
4. These findings suggest that selecting the birds with the TT genotype of SNP c.1995T>C could improve bone growth, could reduce leg disorders in fast-growing birds. The SNP c.1995T>C may serve as a selective marker for improving bone growth and increasing the consistency of body weights in poultry breeding.
Origin‐destination (OD) pattern is a highly useful means for transportation research since it summarizes urban dynamics and human mobility. However, existing visual analytics are insufficient for ...certain OD analytical tasks needed in transport research. For example, transport researchers are interested in path‐related movements across congested roads, besides global patterns over the entire domain. Driven by this need, we propose waypoints‐constrained OD visual analytics, a new approach for exploring path‐related OD patterns in an urban transportation network. First, we use hashing‐based query to support interactive filtering of trajectories through user‐specified waypoints. Second, we elaborate a set of design principles and rules, and derive a novel unified visual representation called the waypoints‐constrained OD view by carefully considering the OD flow presentation, the temporal variation, spatial layout and user interaction. Finally, we demonstrate the effectiveness of our interface with two case studies and expert interviews with five transportation experts.
Origin‐destination (OD) pattern is a highly useful means for transportation research since it summarizes urban dynamics and human mobility. However, existing visual analytics are insufficient for certain OD analytical tasks needed in transport research. For example, transport researchers are interested in path‐related movements across congested roads, besides global patterns over the entire domain. Driven by this need, we propose waypoints‐constrained ODvisual analytics, a new approach for exploring path‐related OD patterns in an urban transportation network. First, we use hashing‐based query to support interactive filtering of trajectories through user‐specified waypoints.
We have used polymerase chain reaction (PCR) based on 16/18S rRNA sequences, followed by denaturing gradient gel electrophoresis (DGGE) to describe the effect of different types of phenolic acid on ...soil microbial populations. Further, we suggest a potential mechanism by which these acids selectively enhance specific microbial populations in soil, leading to the development of shifted communities with differing qualitative and quantitative compositions. Microbial biomass carbon (MBC) and basal soil respiration (BSR) were also measured to assess changes in quantitative estimation and the activity of the total microbial biomass. In this study, two types of phenolic acids, – phenol 2,4-di-tert-butylphenol (PEDT) and vanillic acid (VA) – were used. The results revealed that a significant effect on the microbial biomass and activity. The addition of PEDT and VA resulted in stimulation of microbial biomass at low concentrations and inhibition at high concentrations. In addition, DGGE analysis revealed that the two phenolic acid applications, VA in particular, could have a considerable impact on microbial communities. These results suggest that PEDT and VA play important roles in soybean allelopathy; this may be important for understanding the relationship between allelopathy and barriers in soybean monocropping.
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