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Barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.] is a problematic weed that grows in rice (Oryza sativa L.) fields. Over-applying herbicide caused environmental pollution and the emergence of resistant weeds, and integrated weed management method can reduce the dependence on herbicides. The growth of E. crus-galli and rice seedlings could be significantly inhibited by high concentrations of fulvic acid (FA, C14H12O8) under flooding conditions (HF, 0.80 g/L) (p < 0.05). In contrast, the growth of seedlings could be promoted by the application of very low-concentration FA (LF, 0.02 g/L). The activities of glutathione S-transferase (GSTs) and antioxidant enzymes, including total superoxide dismutase (T-SOD), peroxidase (POD), and catalase (CAT) in E. crus-galli seedlings were enhanced by LF treatment; while the POD activity was decreased, the GSTs, T-SOD, and CAT activities were not significantly changed by HF treatment. The metabolomic and transcriptomic analyses showed that FA regulated E. crus-galli seedling growth by affecting the synthesis of indole derivatives and flavonoid compounds. Compared with the blank control (CK, 0 g/L), the levels of four indole derivatives were up-regulated under HF treatment, and the indole derivatives mentioned above were slightly down-regulated under LF treatment. The flavonoids, including naringenin, naringenin chalcone, eriodictyol, kaempferol, and epigallocatechin, were down-regulated under HF treatment, and the growth of E. crus-galli was restrained. In contrast, the metabolism and transcription of flavonoids were not significantly changed under LF treatment. Under the addition of 0.80 g/L FA, the growth of newly sprouted E. crus-galli was obviously inhibited, and the growth of rice was significantly promoted after eight days of rice planting (p < 0.05). The application of FA, therefore, might be a potential integrated weed management method to control the damage caused by E. crus-galli in paddy fields.
Hypertension represents one of the most common pre-existing conditions and comorbidities in Coronavirus disease 2019 (COVID-19) patients. To explore whether hypertension serves as a risk factor for disease severity, a multi-centre, retrospective study was conducted in COVID-19 patients. A total of 498 consecutively hospitalised patients with lab-confirmed COVID-19 in China were enrolled in this cohort. Using logistic regression, we assessed the association between hypertension and the likelihood of severe illness with adjustment for confounders. We observed that more than 16% of the enrolled patients exhibited pre-existing hypertension on admission. More severe COVID-19 cases occurred in individuals with hypertension than those without hypertension (21% vs. 10%, P = 0.007). Hypertension associated with the increased risk of severe illness, which was not modified by other demographic factors, such as age, sex, hospital geological location and blood pressure levels on admission. More attention and treatment should be offered to patients with underlying hypertension, who usually are older, have more comorbidities and more susceptible to cardiac complications.
To evaluate the epidemiological and clinical characteristics of severe acute respiratory coronavirus virus 2 (SARS-CoV-2) infection among healthcare workers (HCWs) in Hubei Province, China.
Retrospective cohort study.
Hubei Provincial Center for Disease Control and Prevention.
The participants in this study are cases identified by epidemiological investigation in Hubei Province, as of February 27, 2020, and were followed until March 7, 2020. In total, 1,989 HCWs and 41,137 other occupational cases were included for analysis.
We used descriptive statistics to summarize patient characteristics.
Of 1,989 laboratory-confirmed HCWs, 297 (14.93%) had severe or critical cases, 73 (3.67%) had asymptomatic infections, and 18 died of coronavirus disease 2019 (COVID-19). The case fatality rate was 0.9%. The proportion of severe or critical cases decreased from the beginning to the end of the outbreak (from 21.29% to 3.52%), and the proportion of asymptomatic cases increased from 0.0% to 47.18%. Nearly half of HCWs with confirmed COVID-19 reported no known contact with COVID-19 patients (969, 48.72%). Fever and cough were the most common symptoms at disease onset in both HCWs and other occupational cases; however, HCWs had higher rates of fatigue (30.90% vs 25.02%; P < .001) and myalgia (19.15% vs 13.43%; P < .001). Additionally, compared with other occupational groups, HCWs were associated with a lower risk of death after adjustment for potential confounders (odd ratio [OR], 0.50; 95% confidence interval [CI], 0.30–0.79).
Compared with COVID-19 cases in other occupational groups, HCWs with COVID-19 have half the risk of death, although they have been shown to have higher rates of fatigue and myalgia.
The manipulation of near-wall turbulent structures in a turbulent boundary layer (TBL) is an effective way to reduce the turbulent frictional drag. This paper demonstrates the effectiveness of a novel approach for the manipulation of near-wall structures in a TBL with Reynolds number (
) set to 1200. The manipulation is achieved by employing a sustainable wall-attached air-film array. The static and dynamic interface configuration of the air film can be modulated, which generates a dynamic slip boundary condition. For modulation frequencies within the TBL receptivity, this approach shows that it can effectively modify the TBL near-wall velocity/vorticity field. For a typical modulation frequency of 50 Hz, the near-wall mean streamwise velocity decreases and the wall-normal velocity increases when compared to the canonical flat plate TBL. The mean transverse vorticity is suppressed in the near-wall region and its peak is ‘pushed’ outward away from the wall. In the vicinity of modulated air-film array, the phase-locked velocity/vorticity field demonstrates harmonic motions such as a Stokes-type oscillatory motion. The distribution of shear stresses indicates suppressed momentum transfer toward the wall. Estimation of the wall skin friction via the Clauser chart method indicates a reduction of the wall skin friction up to 40 % in the downstream region of the air-film array. A control volume analysis shows that the TBL gains a significant amount of momentum over the oscillating air films, which suggests that the oscillating air film acts like a source of momentum. This pumping effect could potentially explain the observed wall skin friction reduction effect.