Mechanisms Of Spread Research Articles

PATH-02. MESENCHYMAL-TYPE GENETIC MUTATIONS ARE LIKELY PRE-REQUISITE FOR GLIOBLASTOMA TO METASTASIZE OUTSIDE THE CENTRAL NERVOUS SYSTEM: AN ORIGINAL CASE SERIES AND SYSTEMATIC REVIEW OF THE LITERATURE

Abstract Glioblastoma multiforme (GBM) is locally aggressive, yet it metastasizes outside the central nervous system (CNS) in only 0.4% of cases. Little is known about what enables this subset of GBMs to survive outside the CNS, so we conducted a PRISMA-compliant systematic review of metastatic GBM wherein we reviewed 3579 search results and 1080 abstracts, ultimately analyzing data from 139 studies and 211 unique patients. Additionally, we analyzed four modern-day cases treated at our institution. In our patients, primary GBM lesions revealed consistent mutations in NF1, TERT, TP53, CDK4, and RB1/PTEN genes. Unique to the metastatic lesions were amplifications in integral cell-cycle regulating genes such as p53 and PDGFRA/KIT, as well as increased vimentin and Ki-67 expression. These data support the hypothesis that glial cells likely underwent mesenchymal-like mutations prior to extra-CNS involvement. How these cells reach the extra-axial environment is still under debate. In our systematic review, we found that metastases were discovered near previous surgical sites in at least 36.9% of cases, suggesting tumor seeding into the scalp during surgery may facilitate mesenchymal-type mutation in some cases. However, this is unlikely to be sole mechanism of spread as there are several reports of spread without surgery, and other hypothesized mechanisms include spontaneously circulating cells and glymphatics. Other sites of GBM metastasis included bone (47.9%), lung (25.6%), lymph nodes (25.1%), and liver (14.2%). On average, metastases were diagnosed 12.1 months after the most recent resection, and the mean survival from discovery was 5.7 months. In sum, there is strong evidence that GBMs acquire novel mutations to survive outside the CNS, are spread spontaneously or iatrogenically, and portend a poor prognosis once disseminated. Routine genetic and molecular characterization of both primary and metastatic GBMs and widespread reporting will help further characterize mechanisms of spread for this rare but deadly pathology.

Prion-like Spreading of Disease in TDP-43 Proteinopathies

TDP-43 is a ubiquitous nuclear protein that plays a central role in neurodegenerative disorders collectively known as TDP-43 proteinopathies. Under physiological conditions, TDP-43 is primarily localized to the nucleus, but in its pathological form it aggregates in the cytoplasm, contributing to neuronal death. Given its association with numerous diseases, particularly ALS and FTLD, the mechanisms underlying TDP-43 aggregation and its impact on neuronal function have been extensively investigated. However, little is still known about the spreading of this pathology from cell to cell. Recent research has unveiled the possibility that TDP-43 may possess prion-like properties. Specifically, misfolded TDP-43 aggregates can act as templates inducing conformational changes in native TDP-43 molecules and propagating the misfolded state across neural networks. This review summarizes the mounting and most recent evidence from in vitro and in vivo studies supporting the prion-like hypothesis and its underlying mechanisms. The prion-like behavior of TDP-43 has significant implications for diagnostics and therapeutics. Importantly, emerging strategies such as small molecule inhibitors, immunotherapies, and gene therapies targeting TDP-43 propagation offer promising avenues for developing effective treatments. By elucidating the mechanisms of TDP-43 spreading, we therefore aim to pave the way for novel therapies for TDP-43-related neurodegenerative diseases.

Targeting Endogenous Tau in Seeded Tauopathy Models Inhibits Tau Spread.

The transmission of tau pathology has been proposed as one of the major mechanisms for the spatiotemporal spreading of tau pathology in neurodegenerative diseases. Over the last decade, studies have demonstrated that targeting total or pathological tau using tau antibodies can mitigate the development of tau pathology in tauopathy or Alzheimer's disease (AD) mouse models, and multiple tau immunotherapy agents have progressed to clinical trials. Tau antibodies are believed to inhibit the internalization of pathologic seeds and/or block seed elongation after seed internalization. To further address the mechanism of tau antibody inhibition of pathological spread, we conducted immunotherapy studies in mouse primary neurons and wild-type mice (females) seeded with AD patient-derived tau to induce the formation and spreading of tau pathology. Notably, we evaluated the effect of a mouse tau-specific antibody (mTau8) which does not interact with AD-tau seeds in these models. Our results show that mTau8 crosses the blood-brain barrier at levels similar to other antibodies and effectively decreases AD-tau-seeded tau pathology in vitro and in vivo. Importantly, our data suggest that mTau8 binds to endogenous intraneuronal mouse tau, thereby inhibiting the elongation of internalized tau seeds. These findings provide valuable insights into the possible mechanism underlying antibody-based therapies for treating tauopathies.Significance Statement The transmission of tau pathology plays key role in the pathoclinical progression of tauopathy. Studies have shown that tau antibody treatment can mitigate tau pathology in transgenic and spreading models of tauopathy. To explore the mechanisms involved in this procedure, we conducted immunotherapy studies on human tau seeds induced tau spreading models using a mouse tau-specific antibody (mTau8), which does not interact with human-tau seeds. Our findings in the study enhance our understanding of antibody-based therapies for tauopathies.

Dynamic analysis and data-driven inference of a fractional-order SEIHDR epidemic model with variable parameters

To analyze and predict the evolution of contagion dynamics, fractional derivative modeling has emerged as an important technique. However, inferring the dynamical structure of fractional-order models with high degrees of freedom poses a challenge. In this paper, to elucidate the spreading mechanism and non-local properties of disease evolution, we propose a novel fractional-order SEIHDR epidemiological model with variable parameters, incorporating fractional derivatives in the Caputo sense. We compute the basic reproduction number by the next-generation matrix and establish local and global stability conditions based on this reproduction number. By using the fractional Adams–Bashforth method, we validate dynamical behaviors at different equilibrium points in both autonomous and non-autonomous scenarios, while qualitatively analyze the effects of fractional order on the dynamics. To effectively address the inverse problem of the proposed fractional SEIHDR model, we construct a fractional Physics-Informed Neural Network framework to simultaneously infer time-dependent parameters, fractional orders, and state components. Graphical results based on the COVID-19 pandemic data from Canada demonstrate the effectiveness of the proposed framework.

An Efficient Competitive Control Mechanism for Negative Information Spread in Online Social Networks

An Efficient Competitive Control Mechanism for Negative Information Spread in Online Social Networks

The pinning characteristics of droplets and the self-repair mechanism of lubricating film on nanoporous surface: A molecular dynamics perspective

The nanoscale pore gives rich dynamic information to the flow behavior of the droplets exuded on the SLIPS (Smooth Liquid-Infused Porous Surface). The key to realizing fast self-healing of lubricating film is to understand the dynamic law of droplets at nano-orifice. In this paper, a dynamics model of the exudation and spreading behavior is established by the non-equilibrium molecular dynamics simulation. The characteristics and the mechanism of pinning and spreading of nano-droplets were studied. We found that adjusting the wettability and pore diameter can change the liquid exudation and the pinning time of droplets at the orifice. The weaker wettability and larger pore diameter both can increase the exudation velocity and reduce the pinning time of the droplets, which then improves the spreading of exuded droplets and the self-repairing efficiency of the damaged liquid film. As the pore diameter increases, the spreading area of the droplets on the surface of the pore increases. The increase in the wettability also facilitates the spreading behavior, but the outflow rate of the liquid from the pore decreases. Under the combined effect of the two factors, the spreading area of droplets first increases and then decreases with the wettability increases. The results provide potential insights into the spreading mechanism of nanodroplets on porous surfaces.

Mechanisms of flame spread over convex polymethyl methacrylate building material

Polymethyl methacrylate (PMMA) is a widely used combustible building material in convex structures, such as highway sound barriers and building façades. However, most flame spread studies focus on flat surfaces. This study investigates flame spread along convex surfaces through a series of burning experiments with varying curvatures and widths. The average path flame spread rate increases along with a bigger curvature and width. By introducing a dimensionless average path flame spread rate, an empirical correlation linking the average path flame spread rate with sample width and curvature is proposed. In reality, flame spread over convex surface exhibits a distinct time-varying process. For a large curvature, the transition of the flame shape from a wall-fire regime to a pool-fire regime is observed during the process. Moreover, as curvature and width increase, the flame spread transitions from a two-stage process (regime I) to a three-stage process (regime II). In regime II, the transient flame spread rate initially decreases, then increases, and finally decreases again. This behavior is due to the shift from convection dominance to radiation dominance, although radiant heat transfer significantly influences regime I as well. During this transition, a two-peak phenomenon in radiant heat flux emerges, indicating the onset of regime II. Based on this phenomenon, a power-law correlation between curvature and sample width as the critical criterion for triggering regime II is determined. The results of this study have implications concerning the fire safety design of buildings.

3D mapping of direct VTA-CA2 circuit with potential involvement in Parkinson's disease degeneration.

Parkinson's disease dementia (PDD) is commonly developed in patients at the late stage of Parkinson's disease (PD) with unknown progression mechanisms. From the post-mortem tissues and animal models, the ventral tegmental area (VTA) and the CA2 regions are closely associated with dementia development in PDD. However, the structural connection between the two regions has not been fully traced. In this study, we applied tissue clearing and adeno-associated virus (AAV) tracing to map the neural circuits in a 3D manner. Hence, we have confirmed the direct connection between the regions with two dual AAV tracing systems and traced the VTA-CA2 circuit in 3D reconstruction. With the immunostaining, we have shown that the GABAergic neurons are the potential subtype of the postsynaptic CA2 neurons in the VTA-CA2 circuit. Under the 6-hydroxydopamine (6-OHDA), we have demonstrated the degeneration of the VTA-CA2 from the observation of fragmented axonal projections. Collectively, we have first traced the direct connection of the whole VTA-CA2 circuit in an intact 3D manner and monitored the fragmentation of this target circuit in the 6-OHDA model. This VTA-CA2 circuit can be a target for future studies of the pathological spreading and degeneration mechanism from PD to PDD.

Mechanisms of horizontal gene transfer and viral contribution to the fate of intracellular and extracellular antibiotic resistance genes in anaerobic digestion supplemented with conductive materials under ammonia stress

The addition of conductive materials (CMs) is an effective strategy for mitigating ammonia inhibition during anaerobic digestion (AD). However, the introduction of CMs can result in increased antibiotic resistance genes (ARGs) pollution, potentially facilitated by enhanced horizontal gene transfer (HGT). The complex dynamics of intracellular and extracellular ARGs (iARGs/eARGs) and the mechanisms underlying their transfer, mediated by CMs, in ammonia-stressed AD systems remain unclear. In this study, we investigated the effects of three commonly used CMs—nano magnetite (Mag), nano zero-valent iron (nZVI), and granular activated carbon (GAC)—on the fate of iARGs and eARGs during the AD of waste activated sludge under ammonia stress. The results revealed an unexpected enrichment of iARGs by 1.5 %–10.9 % and a reduction of eARGs by 14.1 %–25.2 % in CM-supplemented AD. This discrepancy in the dynamics of iARGs and eARGs may be attributed to changes in microbial hosts and the horizontal transfer of ARGs. Notably, CMs activated prophages within antibiotic-resistant bacteria (ARB) and their symbiotic partners involved in vitamin B12 provision, leading to the lysis of ARB and the subsequent release of eARGs for transformation. Additionally, the abundance of potentially mobile ARGs, which co-occurred with mobile genetic elements, increased by 56.6 %–134.5 % with CM addition, highlighting an enhanced potential for the HGT of ARGs. Specifically, Mag appeared to promote both transformation and conjugation processes, while nZVI only promoted conjugation. Moreover, none of the three CMs had any discernible impact on transduction. GAC proved superior to both nano Mag and nZVI in controlling the enrichment of iARGs, reducing eARGs, and limiting HGTs simultaneously. Overall, these findings provide novel insights into the role of viruses and the mechanisms of ARG spread in CM-assisted AD, offering valuable information for developing strategies to mitigate ARG pollution in practical applications.

Molecular epidemiology of extended-spectrum beta-lactamase-producing-Klebsiella species in East Tennessee dairy cattle farms.

The rising prevalence of Extended-Spectrum Beta-Lactamase (ESBL)-producing Klebsiella species (spp.) poses a significant threat to human and animal health and environmental safety. To address this pressing issue, a comprehensive study was undertaken to elucidate the burden and dissemination mechanisms of ESBL-Klebsiella spp. in dairy cattle farms. Fifty-seven Klebsiella species were isolated on CHROMagar™ ESBL plates and confirmed with MADLI-TOF MS and whole genome sequenced from 14 dairy farms. Six families of beta-lactamase (bla) (bla CTX-M, bla SHV, bla TEM, bla OXY, bla OXA, and bla SED) were detected in ESBL-Klebsiella spp. genomes. Most (73%) of isolates had the first three types of beta-lactamase genes, with bla SHV being the most frequent, followed by bla CTX-M. Most (93%) isolates harbored two or more bla genes. The isolates were genotypically MDR, with 26 distinct types of antibiotic resistance genes (ARGs) and point mutations in gyrA, gyrB, and parC genes. The genomes also harbored 22 different plasmid replicon types, including three novel IncFII. The IncFII and Col440I plasmids were the most frequent and were associated with bla CTXM-27 and qnrB19 genes, respectively. Eighteen distinct sequence types (STs), including eight isolates with novel STs of K. pneumoniae, were detected. The most frequently occurring STs were ST353 (n = 8), ST469 (n = 6), and the novel ST7501 (n = 6). Clusters of ESBL-Klebsiella strains with identical STs, plasmids, and ARGs were detected in multiple farms, suggesting possible clonal expansion. The same ESBL variant was linked to identical plasmids in different Klebsiella STs in some farms, suggesting horizontal spread of the resistance gene. The high burden and dual spread mechanism of ESBL genes in Klebsiella species, combined with the emergence of novel sequence types, could swiftly increase the prevalence of ESBL-Klebsiella spp., posing significant risks to human, animal, and environmental health. Immediate action is needed to implement rigorous surveillance and control measures to mitigate this risk.

Spreading of droplet impact on ribbed superhydrophobic surfaces with varying structure height

Hypothesis:Quantifying droplet spreading characteristics on ribbed superhydrophobic surfaces is challenging due to the complex fluid dynamics, limiting the practical applications. Droplet spreading dynamics are significantly influenced by the diameter ratio (rib diameter to droplet diameter) and height ratio (structure height to rib diameter) during impact. Experiment:Ribbed superhydrophobic surfaces with diameter ratios (0.18 to 0.75) and height ratios (0.125 to 0.5) underwent impact experiments with droplets at varied Weber numbers. Through simulations and analysis, we summarized the patterns of the maximum ribwise spreading coefficient, elucidated the droplet spreading mechanism on ribbed superhydrophobic surfaces. Findings:The findings revealed asymmetry in impact dynamics on ribbed superhydrophobic surfaces in the ribwise and radial directions. The maximum ribwise spreading coefficient initially decreases, followed by increase with increasing diameter ratio, decreasing in a slowing down trend with increasing height ratio. These observations indicated that maximum ribwise spreading coefficient can be minimize with critical ratios. Comparatively, the maximum spreading coefficient at critical height ratios is 72.7% to 92.3% of that on flat surfaces. To precisely forecast maximum ribwise spreading coefficient, two models are introduced for diameter ratios below and above critical range when height ratios below the critical range.

Effects of Acmella radicans Invasion on Soil Seed Bank Community Characteristics in Different Habitats.

To examine the effects of the recent Acmella radicans invasion on plant community and diversity in invaded habitats, the composition, density, species richness, diversity indices, and evenness index of the soil seed bank community of two different habitats (wasteland and cultivated land) in Yunnan Province, China, were analyzed through field sampling and greenhouse germination tests. A total of 28 species of plants belonging to 15 families and 28 genera, all annual herbs, were found in the soil seed bank. Seed densities and species number in the seed bank tended to be greater in April than in October; cultivated land also featured higher seed densities and species numbers compared to wasteland. With increased A. radicans cover, the seed bank population of A. radicans also significantly increased, but the seed bank populations of many other dominant species (e.g., Ageratum conyzoides and Gamochaeta pensylvanica) and native species (e.g., Laggera crispata and Poa annua) clearly declined. The germination of A. radicans seeds was concentrated during the period from the 4th to the 5th weeks. Vertically, the seed number of A. radicans was significantly different among the 0-5 cm, 5-10 cm and 10-20 cm layers that accounted for 80.7-90.6%, 9.4-16.1% and 0.0-3.2% of the total seed density in wasteland, respectively; and in cultivated land, A. radicans accounted for 56.8-64.9%, 26.7-31.8% and 8.1-13.5% of the total seed density, respectively. With reduced A. radicans cover, the species richness, Simpson index, Shannon-Wiener index, and Pielou indices of the weed community generally increased, and most diversity indices of weed communities in cultivated land were lower than in wasteland under the same cover of A. radicans. The results indicate that the invasion of A. radicans has negatively affected local weed community composition and reduced weed community diversity, and that these negative impacts in cultivated land may be enhanced by human disturbance. Our study was the first to elucidate the influence of A. radicans invasion on soil seed bank community characteristics in invaded habitats, providing a better understanding of its invasion and spread mechanisms in order to aid in developing a scientific basis for the prevention and control of this invader.

Metagenomics-resolved genomics provide novel ecological insights into resistome community coalescence of wastewater in river environment

The discharge of wastewater into rivers can lead to resistome coalescence, thereby enhancing the spread risk of antibiotic resistance genes (ARGs) through mixing of exogenous wastewater resistome communities with indigenous riverine communities. At present, the understanding on the role of resistome community coalescence in the dissemination of ARGs is still very limited, and little is known about the process and its ecological implications. To bridge the gap, this study has conducted field-based surveys and microcosm experiments to deeply dissect the coalescence of resistome community in wastewater within river environment, utilizing genome-centric metagenomic analysis approach. The field investigation suggests resistome coalescence enhances the abundance and diversity of ARGs in the receiving river. Furthermore, the microcosm experiments reveal the effect of mixing ratio on resistome coalescence in the water-sediment system and decipher the temporal attenuation dynamics of the coalesced resistome in the environment. The results show the higher proportion of wastewater has a greater impact on ARGs in the water, whereas the effect of mixing ratio is lesser in the sediments. Temporally, the source-specific ARGs originating from wastewater exhibit decreasing trends over the experimental duration, and relatively, the attenuation in the water is more pronounced than that in the sediments. Interestingly, natural light not only facilitates the attenuation of ARGs in the water but may also induce their deposition at the water-sediment interface. Variance partitioning analyses suggest the microbiome, mobilome, and abiotic factors collectively shape the coalescence of the resistome communities in the environment. The study provides empirical evidence on resistome coalescence in river systems, which is instrumental in gaining a better understanding of the spread mechanism of ARGs in the environment.

Virulence-Related Genes Expression in Planktonic Mixed Cultures of Candida albicans and Non-Albicans Candida Species

Introduction: Candida albicans is the most common opportunistic pathogen causing fungal infections worldwide, especially in high-risk patients. Its pathogenicity is related to virulence factors gene expression, such as hyphal growth (HWP1), cell adhesion (ALS3), and protease secretion (SAP1) during infection spreading mechanisms. In recent years, an increase in non-albicans Candida infections has been reported, which may present coinfection or competitive interactions with C. albicans, potentially aggravating the patient’s condition. This study aims to evaluate the expression of genes related to virulence factors of C. albicans and non-albicans Candida during planktonic stage. Methods: C. albicans (ATCC MYA-3573) as well as with three clinical strains (C. albicans DCA53, C. tropicalis DCT6, and C. parapsilosis DCP1) isolated from blood samples, were grown in 24-well plates at 37°C for 20 h, either in monocultures or mixed cultures. Quantitative real-time polymerase chain reaction was used to evaluate the expression levels of the genes HWP1, ALS3, and SAP1 in cells collected during the planktonic stage. In addition, hyphal filamentation was observed using a Scanning Electron Microscope. Results: The overexpression of HWP1 and ASL3 genes in mixed growth conditions between C. albicans and non-albicans Candida species suggests a synergistic relationship as well as an increased capacity for hyphal growth and adhesion. In contrast, C. parapsilosis versus C. tropicalis interaction shows an antagonistic relationship during mixed culture, suggesting a decreased virulence profile of C. parapsilosis during initial coinfection with C. tropicalis. Conclusion: The expression of HWP1, ALS3, and SAP1 genes associated with virulence factors varies under competitive conditions among species of the genus Candida during planktonic stage.

Mechanical force of uterine occupation enables large vesicle extrusion from proteostressed maternal neurons.

Large vesicle extrusion from neurons may contribute to spreading pathogenic protein aggregates and promoting inflammatory responses, two mechanisms leading to neurodegenerative disease. Factors that regulate the extrusion of large vesicles, such as exophers produced by proteostressed C. elegans touch neurons, are poorly understood. Here, we document that mechanical force can significantly potentiate exopher extrusion from proteostressed neurons. Exopher production from the C. elegans ALMR neuron peaks at adult day 2 or 3, coinciding with the C. elegans reproductive peak. Genetic disruption of C. elegans germline, sperm, oocytes, or egg/early embryo production can strongly suppress exopher extrusion from the ALMR neurons during the peak period. Conversely, restoring egg production at the late reproductive phase through mating with males or inducing egg retention via genetic interventions that block egg-laying can strongly increase ALMR exopher production. Overall, genetic interventions that promote ALMR exopher production are associated with expanded uterus lengths and genetic interventions that suppress ALMR exopher production are associated with shorter uterus lengths. In addition to the impact of fertilized eggs, ALMR exopher production can be enhanced by filling the uterus with oocytes, dead eggs, or even fluid, supporting that distention consequences, rather than the presence of fertilized eggs, constitute the exopher-inducing stimulus. We conclude that the mechanical force of uterine occupation potentiates exopher extrusion from proximal proteostressed maternal neurons. Our observations draw attention to the potential importance of mechanical signaling in extracellular vesicle production and in aggregate spreading mechanisms, making a case for enhanced attention to mechanobiology in neurodegenerative disease.

Mechanical force of uterine occupation enables large vesicle extrusion from proteostressed maternal neurons

Large vesicle extrusion from neurons may contribute to spreading pathogenic protein aggregates and promoting inflammatory responses, two mechanisms leading to neurodegenerative disease. Factors that regulate the extrusion of large vesicles, such as exophers produced by proteostressed C. elegans touch neurons, are poorly understood. Here, we document that mechanical force can significantly potentiate exopher extrusion from proteostressed neurons. Exopher production from the C. elegans ALMR neuron peaks at adult day 2 or 3, coinciding with the C. elegans reproductive peak. Genetic disruption of C. elegans germline, sperm, oocytes, or egg/early embryo production can strongly suppress exopher extrusion from the ALMR neurons during the peak period. Conversely, restoring egg production at the late reproductive phase through mating with males or inducing egg retention via genetic interventions that block egg-laying can strongly increase ALMR exopher production. Overall, genetic interventions that promote ALMR exopher production are associated with expanded uterus lengths and genetic interventions that suppress ALMR exopher production are associated with shorter uterus lengths. In addition to the impact of fertilized eggs, ALMR exopher production can be enhanced by filling the uterus with oocytes, dead eggs, or even fluid, supporting that distention consequences, rather than the presence of fertilized eggs, constitute the exopher-inducing stimulus. We conclude that the mechanical force of uterine occupation potentiates exopher extrusion from proximal proteostressed maternal neurons. Our observations draw attention to the potential importance of mechanical signaling in extracellular vesicle production and in aggregate spreading mechanisms, making a case for enhanced attention to mechanobiology in neurodegenerative disease.

Exploring the Frontier of Wheat Rust Resistance: Latest Approaches, Mechanisms, and Novel Insights.

Wheat rusts, including leaf, stripe, and stem rust, have been a threat to global food security due to their devastating impact on wheat yields. In recent years, significant strides have been made in understanding wheat rusts, focusing on disease spread mechanisms, the discovery of new host resistance genes, and the molecular basis of rust pathogenesis. This review summarizes the latest approaches and studies in wheat rust research that provide a comprehensive understanding of disease mechanisms and new insights into control strategies. Recent advances in genetic resistance using modern genomics techniques, as well as molecular mechanisms of rust pathogenesis and host resistance, are discussed. In addition, innovative management strategies, including the use of fungicides and biological control agents, are reviewed, highlighting their role in combating wheat rust. This review also emphasizes the impact of climate change on rust epidemiology and underscores the importance of developing resistant wheat varieties along with adaptive management practices. Finally, gaps in knowledge are identified and suggestions for future research are made. This review aims to inform researchers, agronomists, and policy makers, and to contribute to the development of more effective and sustainable wheat rust control strategies.

The Origin of the Problem: Characterization of Paraguayan Septoria steviae, Causal Agent of Septoria Leaf Spot of Stevia, Based on Multilocus Sequence Analysis.

Septoria leaf spot is a significant disease affecting cultivated stevia, potentially reducing yields by > 50%. The disease is caused by Septoria steviae, first identified in 1978 in Japan as a new pathogen of stevia. Understanding the origin of S. steviae could clarify how it spread to new production areas. To investigate this, 12 isolates of Septoria sp. were obtained from stevia's native range in the Amambay forests and field plantings in Paraguay from 2018 to 2020. These isolates underwent colony morphology and molecular characterization of Actin, β-Tubulin, Calmodulin, ITS, LSU, RPB2, and TEF1α loci. GenBank sequences from S. steviae isolates collected in France, Japan, and the United States were included. Multilocus sequence phylogenetic analysis generated a maximum likelihood (ML) tree. The morphological characteristics of Paraguayan isolates were similar to those of previously reported S. steviae type cultures from Japan. The ML analysis showed that Paraguayan isolates formed a monophyletic group with S. steviae isolates from France, Japan, and the United States. During blotter tests, pycnidia and cirri of S. steviae were observed on multiple stevia seed surfaces from different sources. Further characterization confirmed viable pathogenic conidia of S. steviae. This observation suggests that S. steviae could be associated with stevia seed, possibly spreading from the center of origin to other countries. This research is the first to genetically characterize S. steviae from Paraguay and propose its potential spread mechanism from the center of origin to the rest of the world.

Occurrence rate of equatorial Spread F and GPS ROTI in the ionospheric anomaly region over Vietnam

This paper presents the first observations of the occurrence rates of Spread F and GPS total electron content (TEC) index (ROTI) over Vietnam at the equatorial trough and the northern tropical crest of ionization anomaly in the Asian sector. The data have been examined for the monthly and nighttime variations in the occurrence of these two data at Bac Lieu (9.28°N, 105.73°E, dip: 1.73°N) and Phu Thuy (21.03°N, 105.95°E, dip: 14.49°N) during 2023. For Bac Lieu, the monthly variation in the occurrence of the range Spread F (RSF) has the maxima in the February, May, and September months, while the mixed Spread-F (MSF) and ROTI occurrences exhibit a semiannual asymmetry with peaks in March/April and October. For the nighttime variation, occurrence peaks at 1915-1930 LT for RSF, at about 1945-2100 LT for MSF, and between 2030-2330 LT for ROTI. Regarding the frequency Spread F (FSF) occurrence, the maximum values in the monthly variation are in April, and the nighttime variation peaks at about 2115-2315 LT. For Phu Thuy, the monthly variation of RSF, MSF, and ROTI occurrences also exhibit a semiannual asymmetry with peaks in March/April and October. These peak magnitudes are largest for ROTI, moderate for MSF, and smallest for RSF. The nighttime variation of RSF, MSF, and ROTI occurrence peaks show intense season changes from winter to autumn at pre-midnight, spring at post-midnight, and summer at post-midnight. The FSF occurrences are more significant in summer than in other seasons, mainly after midnight. The time order appearance of the Spread F types at Bac Lieu and Phu Thuy is first of RSF, then MSF, and finally FSF. This could reflect that the formation mechanisms of Spread F types are different and require further research. Our observations also showed that the post-midnight occurrence of Spread F is much larger than ROTI at Bac Lieu and Phu Thuy. The monthly variations in occurrence rates of Spread F and ROTI at Bac Lieu and Phu Thuy are similar, but these occurrence rates at Bac Lieu are usually larger than at Phu Thuy.

Comparative study on upward flame spread interactions and heat transfer over two parallel wires with various spacing distances in open space and vertical channel

Most previous work focused on the flame spread interactions and heat transfer over two parallel wires in open space, but few studies considered the vertical channel effects. Experiments were carried out to investigate the influence of vertical channel on the flame spread interactions and heat transfer over two parallel wires. Two types of polyethylene-insulated copper wires were used with spacing distance ranging from 0 mm to 52 mm. Whether for open space or vertical channel, four typical regimes of upward flame interactions are observed as a function of spacing distance, but the range of these regimes is affected by the vertical channel. For open space and vertical channel, the flame width, flame length and flame spread rate rise first and then drop, but these parameters for vertical channel are larger than that for open space due to the enhanced induced flow and the heat transfer. A heat transfer model is established for upward flame spread over two parallel wires taking the effects of spacing distance and vertical channel, in which the radiation from flame is considered, as well as the difference between the solid-phase and gas-phase heating lengths. The flame heat feedback is the dominant mechanism for upward flame spread over two parallel wires, and it for vertical channel is larger than that for open space.