Mechanism of intraspecific toxin inhibition in Aspergillus flavus

Atoxigenic Aspergillus flavus was demonstrated by others as a promising biocontrol agent to minimize preharvest aflatoxins in susceptible crops. But the mechanism was unclear. A filter insert-well plate system was used to study the mechanism in lab. There was no inhibition when toxigenic A. flavus isolate 53 and inhibitory atoxigenic isolates were separated by 0.4 µm membrane, approximately 50% inhibition occurred when separated by 12 µm membrane, and complete inhibition occurred when a 74 µm membrane was used. This result suggested that touching or close physical interaction is needed for toxin inhibition and the nutrient competition hypothesis was not supported. Isolate 53 and inhibitory atoxigenic isolate 51 were used to study the timing of intraspecific toxin inhibition. The result showed that inhibition occurred when 0 - 4 day old isolate 51 was added within the first 16-hour growth of isolate 53. However, two-day old isolate 51 inhibited toxin production by two-day old isolate 53 and twenty-four hour old isolate 51 inhibited toxin production by 48-hour old isolate 53. These results suggested that there is a 16-hour “window” for the conidial inhibition ability of atoxigenic isolate but for mycelia, the “window” is expanded to 48 hours. Isolate Af70-GFP was acquired to microscopically examine the touch inhibition interaction. Surprisingly, none of the completely inhibitory atoxigenic isolates from our collection or NRRL 21882 inhibited toxin production by Af70-GFP. Isolate K49 and two Australian isolates were shown to be able to inhibit toxin production by Af70-GFP. The inhibitory abilities of additional atoxigenic isolates were tested with toxigenic isolates 53, Af70s-GFP and NRRL 3357. Different patterns were obtained among those three isolates. These results showed that there was specificity in the touch inhibition interaction. Af70-GFP and isolate K49 were used to continue microscopy work. The growth of Af70s-GFP appeared to be inhibited and vacuoles present in Af70s-GFP were absent when it was paired with K49. Biocontrol once thought to be due to competitive exclusion probably requires close physical growth or touching and displays specificity. Multiple atoxigenic isolates each specific to a subset of the toxigenic isolate population may be needed for an effective biocontrol application

A Simple Model for Elastic-Plastic Contact of Granular Geomaterials

We propose a simple elastic-plastic contact model by considering the interaction of two spheres in the normal direction, for use in discrete element method (DEM) simulations of geomaterials. This model has been developed by using the finite element method (FEM) and nonlinear fitting methods, in the form of power-law relation of the dimensionless normal force and displacement. Only four parameters are needed for each loading-unloading contact process between two spheres, which are relevant to material properties evaluated by FEM simulations. Within the given range of material properties, those four parameters can be quickly accessed by interpolating the data appended or by regression functions supplied. Instead of the Von Mises (V-M) yield criterion, the Drucker-Prager (D-P) criterion is used to describe the yield behavior of contacting spheres in this model. The D-P criterion takes the effects of confining pressure, the intermediate principal stress, and strain rate into consideration; thus, this model can be used for DEM simulation of geomaterials as well as other granular materials with pressure sensitivity

Gradual Enhancement of Stripe-Type Antiferromagnetism in Spin Ladder Material BaFe2_2S3_3 Under Pressure

We report pressure-dependent neutron diffraction and muon spin relaxation/rotation measurements combined with first-principles calculations to investigate the structural, magnetic, and electronic properties of BaFe$_2$S$_3$ under pressure. The experimental results reveal a gradual enhancement of the stripe-type ordering temperature with increasing pressure up to 2.6 GPa and no observable change in the size of the ordered moment. The ab initio calculations suggest that the magnetism is highly sensitive to the Fe-S bond lengths and angles, clarifying discrepancies with previously published results. In contrast to our experimental observations, the calculations predict a monotonic reduction of the ordered moment with pressure. We suggest that the robustness of the stripe-type antiferromagnetism is due to strong electron correlations not fully considered in the calculations

Smoking susceptibility and its predictors among adolescents in China: Evidence from Ningbo City

Susceptibility to smoking is a risk factor of actual adolescent smoking behaviors. This study aimed to estimate the rate of smoking susceptibility and its predictors in China with a sample of 4,695 junior high school students in Ningbo, China. Core questions from the Global Youth Tobacco Survey (GYTS) were adapted to the China context and administered to these students. The rate of smoking susceptibility, measured by “Do you foresee yourself taking up smoking in the next 12 months”, is 6.1%. Results from logistic regression suggested that among boys, adolescents’ health knowledge that smoking can cause lung cancer (OR=2.73), the belief that smoking can help people relax (OR=2.32), and self-report of never having seen anti-smoking information on campus (OR=1.80) predicted increased susceptibility to smoking. Conversely, the belief that boys who smoke are less attractive (OR=0.64), that parents will have a problem with their child smoking (OR=0.50), having no friends or classmates who smoke (OR=0.22), and not seeing teachers smoke in the previous week (OR=0.61) predicted decreased susceptibility to smoking. Findings for girls were similar. This study suggested the need for comprehensive programs aiming to improve family, peer, and school environments to decrease smoking susceptibility among adolescents

Smoking Experimentation among Elementary School Students in China: Influences from Peers, Families, and the School Environment

The aim of this study was to investigate experimentation with smoking among primary school students in China. Data were acquired from a recent survey of 4,073 students in grades 4 to 6 (ages 9–12) in 11 primary schools of Ningbo City. The questions were adapted from the Global Youth Tobacco Survey (GYTS). Results suggest that although the Chinese Ministry of Education (MOE) encourages smoke-free schools, experimentation with cigarettes remains a serious problem among primary school students in China. Peers, family members, and the school environment play important roles in influencing smoking experimentation among students. Having a friend who smoked, seeing a family member smoke, and observing a teacher smoking on campus predicted a higher risk of experimentation with smoking; the exposure to anti-tobacco materials at school predicted a lower risk of experimentation with smoking. The evidence suggests that public health practitioners and policymakers should seek to ensure the implementation of smoke-free policies and that intervention should target young people, families, and communities to curb the commencement of smoking among children and adolescents in China

Fermented Grains from Different Layers of Cellar in the First and Second Rounds of Fermentation of Maotai-Flavor Baijiu: Analysis of microbial community structure and Acid Composition as Well as Correlation between Them

In this study, the microbial community structure in fermented grains from the upper middle and lower layers of the cellar in the first and second rounds of fermentation of Maotai-flavor was analyzed by high-throughput sequencing, and the acid composition by ultra-high performance liquid chromatography (UPLC). Moreover, the correlation between them was investigated. The results showed that the total acid content of fermented grains was greater in the second round than the first round of fermentation. The radial distribution patterns of seven acidic compounds in different times and spaces of the cellar were different. The contents of lactic acid and acetic acid accounted for a large proportion in the two rounds of fermentation. For both rounds, the absolutely dominant bacterial genus was Limosilactobacillus, and the dominant fungal genera were Saccharomyces and Candida. As the fermentation time extended, there was a significant difference in the microbial community structure. The contents of total and individual acids were positively correlated with the relative abundance of Limosilactactacillacus, Schizosaccharomyces, Zygosaccharomyces, Candida and Kazachstania, and negatively correlated with the relative abundance of Lactobacillus, Saccharomyces, Paecilomyces and Torulaspora. This study provides a theoretical basis for further elucidating the fermentation mechanism of Maotai-flavor Baijiu cellar

Charge redistribution, charge order and plasmon in La2−x_{2-x}Srx_{x}CuO4_{4}/La2_{2}CuO4_{4} superlattices

Interfacial superconductors have the potential to revolutionize electronics, quantum computing, and fundamental physics due to their enhanced superconducting properties and ability to create new types of superconductors. The emergence of superconductivity at the interface of La$_{2-x}$Sr$_{x}$CuO$_{4}$/La$_{2}$CuO$_{4}$ (LSCO/LCO), with a T$_c$ enhancement of $\sim$ 10 K compared to the La$_{2-x}$Sr$_{x}$CuO$_{4}$ bulk single crystals, provides an exciting opportunity to study quantum phenomena in reduced dimensions. To investigate the carrier distribution and excitations in interfacial superconductors, we combine O K-edge resonant inelastic X-ray scattering and atomic-resolved scanning transmission electron microscopy measurements to study La$_{2-x}$Sr$_{x}$CuO$_{4}$/La$_{2}$CuO$_{4}$ superlattices (x=0.15, 0.45) and bulk La$_{1.55}$Sr$_{0.45}$CuO$_{4}$ films. We find direct evidence of charge redistribution, charge order and plasmon in LSCO/LCO superlattices. Notably, the observed behaviors of charge order and plasmon deviate from the anticipated properties of individual constituents or the average doping level of the superlattice. Instead, they conform harmoniously to the effective doping, a critical parameter governed by the T$_c$ of interfacial superconductors.Comment: 8 pages, 5 figure

Mammalian DNA2 helicase/nuclease cleaves G-quadruplex DNA and is required for telomere integrity

Efficient and faithful replication of telomeric DNA is critical for maintaining genome integrity. The G-quadruplex (G4) structure arising in the repetitive TTAGGG sequence is thought to stall replication forks, impairing efficient telomere replication and leading to telomere instabilities. However, pathways modulating telomeric G4 are poorly understood, and it is unclear whether defects in these pathways contribute to genome instabilities in vivo. Here, we report that mammalian DNA2 helicase/nuclease recognizes and cleaves telomeric G4 in vitro. Consistent with DNA2’s role in removing G4, DNA2 deficiency in mouse cells leads to telomere replication defects, elevating the levels of fragile telomeres (FTs) and sister telomere associations (STAs). Such telomere defects are enhanced by stabilizers of G4. Moreover, DNA2 deficiency induces telomere DNA damage and chromosome segregation errors, resulting in tetraploidy and aneuploidy. Consequently, DNA2-deficient mice develop aneuploidy-associated cancers containing dysfunctional telomeres. Collectively, our genetic, cytological, and biochemical results suggest that mammalian DNA2 reduces replication stress at telomeres, thereby preserving genome stability and suppressing cancer development, and that this may involve, at least in part, nucleolytic processing of telomeric G4

Transmission Roles of Symptomatic and Asymptomatic COVID-19 Cases: A Modelling Study

Coronavirus disease 2019 (COVID-19) asymptomatic cases are hard to identify, impeding transmissibility estimation. The value of COVID-19 transmissibility is worth further elucidation for key assumptions in further modelling studies. Through a population-based surveillance network, we collected data on 1342 confirmed cases with a 90-days follow-up for all asymptomatic cases. An age-stratified compartmental model containing contact information was built to estimate the transmissibility of symptomatic and asymptomatic COVID-19 cases. The difference in transmissibility of a symptomatic and asymptomatic case depended on age and was most distinct for the middle-age groups. The asymptomatic cases had a 66.7% lower transmissibility rate than symptomatic cases, and 74.1% (95% CI 65.9–80.7) of all asymptomatic cases were missed in detection. The average proportion of asymptomatic cases was 28.2% (95% CI 23.0–34.6). Simulation demonstrated that the burden of asymptomatic transmission increased as the epidemic continued and could potentially dominate total transmission. The transmissibility of asymptomatic COVID-19 cases is high and asymptomatic COVID-19 cases play a significant role in outbreaks