Stability Analysis of a Delayed Rumor Propagation Model with Nonlinear Incidence Incorporating Impulsive Vaccination.

The presence of information asymmetry can hinder the public's ability to make well-informed decisions, resulting in unwarranted suspicion and the widespread dissemination of rumors. Therefore, it is crucial to provide individuals with consistent and dependable scientific education. Regular popular science education is considered a periodic impulsive intervention to mitigate the impact of information asymmetry and promote a more informed and discerning public. Drawing on these findings, this paper proposes a susceptible-hesitant-infected-refuting-recovered (SHIDR) rumor-spreading model to explain the spread of rumors. The model incorporates elements such as time delay, nonlinear incidence, and refuting individuals. Firstly, by applying the comparison theorem of an impulsive differential equation, we calculate two thresholds for rumor propagation. Additionally, we analyze the conditions of global attractiveness of the rumor-free periodic solution. Furthermore, we consider the condition for the rumor's permanence. Finally, numerical simulations are conducted to validate the accuracy of our findings. The results suggest that increasing the proportion of impulsive vaccination, reducing the impulsive period, or prolonging the delay time can effectively suppress rumors.

Powdery Mildew Caused by Erysiphe sedi on Crassula capitella in China.

Crassula capitella Thunb. is a succulent used ornamentally in gardens and landscapes. In August 2019, severe powdery mildew infection was observed on C. capitella in a plant nursery, 1000m2 in area, in Xining (36°42'44.39" N, 101°44'50.50″E, alt. 2330 m), China. Approximately 35% of the leaves on a plant were symptomatic, and 80% of the plants were affected. The disease seriously reduced the ornamental value. A voucher specimen was deposited in the Herbarium of Plant Pathology at Qinghai University under accession no. QHU2019150. The pathogen formed superficial mycelia on leaves and stems producing conspicuous white colonies followed by necrosis of the leaf tissues and defoliation. Mycelia were amphigenous, white, effuse or in patches, persistent with lobed appressoria. The pathogen produced conidia singly on 2- to 3-celled conidiophores occurring on the ectophytic hyphae. Conidia were subcylindrical, measured 22 to 41 × 10 to 16 (n = 50) µm, and were produced singly on the tip of conidiophores. Conidiophores were erect and up to 110 µm long, foot-cells straight, cylindrical and 22 to 53 × 8 to 10 (n = 50) µm, followed by one to three shorter cells. Chasmothecia were not found. The fungus was identified as Erysiphe sedi based on morphology (Braun and Cook 2012). To confirm the identification, the ITS region was amplified. The ITS5/P3 and PM5/ITS4 primers were used to amplify the ITS region by nested PCR, and the cloned fragments were sequenced (Takamatsu and Kano 2001). The aligned ITS region sequences were deposited in GenBank (accession no. MT178769). A BLAST search analysis of the two sequences revealed 99.84% identity with E. sedi infecting Sedum aizoon in Russia (LC010045). A phylogenetic tree was constructed in MEGA6 with 15 ITS sequences using the neighbor-joining method with the Kimura 2-parameter substitution model. The sequence retrieved from powdery mildew on Crassula capitella in China clustered together with the sequences obtained from E. sedi on Sedum spp. with nearly 100 % concordance, placing it in the Erysiphe aquilegiae complex as defined by Takamatsu et al. (2015) and recently critically discussed by Shin et al. (2019). This complex comprises numerous Erysiphe spp. insufficiently resolved, especially when based only on ITS data. However, for the time being we follow Götz et al. (2019) and recognize E. sedi as a species of its own and identify the Chinese collection on Crassula capitella as E. sedi because of the morphological agreement and concordant ITS data. Pathogenicity tests were completed by gently pressing infected leaves onto five healthy leaves of C. capitella, Inoculated and non-inoculated plants were maintained separately in different rooms of a greenhouse at 22 to 25°C. Inoculated plants developed signs and symptoms after 12 days, whereas control plants remained symptomless. The morphology of the fungus on inoculated leaves was identical to that originally observed on diseased plants. To our knowledge, this is the first report of powdery mildew caused by Erysiphe sedi on C. capitella in China and worldwide, although E. sedi is reported to infect many Crassulaceous or Crassulaceae hosts (Cho et al. 2012, Götz et al. 2019).

[Effect of degradation succession process on the temperature sensitivity of ecosystem respiration in alpine Potentilla fruticosa scrub meadow].

Grazing is one of the main artificial driving forces for the degradation succession process of alpine meadow. In order to quantitatively study the temperature sensitivity of alpine meadow ecosystem respiration in different degradation stages, we conducted the research in Haibei Alpine Meadow Ecosystem Research Station, CAS from July 2003 to July 2004. The static chamber-chromatography methodology was used to observe the seasonal changes of alpine scrub ecosystem respiration flux during different degradation stages. The results showed that: (1) The seasonal changes of ecosystem respiration flux in different degradation stages of alpine shrub presented a unimodal curve. The maximum appeared in August and the minimum appeared during the period from October to next April. The degradation succession process significantly decreased the ecosystem respiratory CO2 release rate. The respiratory rate ranges of alpine Potentilla fruticosa scrub (GG), Kobresia capillifolia meadow (GC) and bare land (GL) were 34.21-1 168.23, 2.30-1 112.38 and 20.40-509.72 mg (m2 x h)(-1), respectively. The average respiration rate of GG was 1.29 and 2.56 times of that of GC and GL, respectively; (2) Temperature was the main factor that affected the ecosystem respiration rate, and contributed 25% - 79% of the variation of the ecosystem respiration. The degradation succession process significantly changed the correlation between ecosystem respiration rate and temperature. The correlation (R2) between ecosystem respiration rate and each temperature indicator (T(s), T(d) and T(a)) was reduced by 47.23%, 46.95% and 55.28%, respectively when the ground vegetation disappeared and the scrub was degraded into secondary bare land; (3) The difference of Q10 between warm and cool seasons was significant (P < 0.05), and the value of cold season was larger than that of warm season. Degradation succession process apparently changed the temperature sensitivity of ecosystem respiration. The Q10 values of GG, GC and GL were 2.38, 2.91 and 1.62, respectively. Q10 of GC was increased by 22.26% and that of GL was decreased by 31.93% compared with that of GG.