Pre‐symptomatic transmission of novel coronavirus in community settings

We used contact tracing to document how COVID‐19 was transmitted across 5 generations involving 10 cases, starting with an individual who became ill on January 27. We calculated the incubation period of the cases as the interval between infection and development of symptoms. The median incubation period was 6.0 days (interquartile range, 3.5‐9.5 days). The last two generations were infected in public places, 3 and 4 days prior to the onset of illness in their infectors. Both had certain underlying conditions and comorbidity. Further identification of how individuals transmit prior to being symptomatic will have important consequences.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/163478/2/irv12773.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/163478/1/irv12773_am.pd

Effect of Cooling Rate on Microstructure Evolution and Mechanical Properties of SCM435 Steel

The microstructural evolution of SCM435 cold heading steel at different cooling rates was investigated by means of scanning electron microscopy, TEM, XRD, and electron backscatter diffraction. The results show that the cooling rate has a significant effect on the microstructure of the experimental steel. With an acceleration in the cooling, the microstructure of the steel gradually changed from ferrite and pearlite to ferrite, pearlite, and granular bainite; finally, the pearlite disappeared, and the microstructure changed to acicular ferrite, bainite, and martensite. With an increase in the cooling rate, the morphology of the carbide underwent an evolution from sheet carbide to short-rod carbide, granular carbide, and ultimately thin-strip carbide. With the acceleration in cooling, the proportion of large-angle grain boundaries gradually decreased, and the area of small-angle grain boundaries gradually increased. When the cooling rate was 0.1 °C/s, the proportion of large-angle grain boundaries was as high as 52.8%, and the dislocation density was only 1.91 × 1012 cm−2. When the cooling rate was 2.0 °C/s, the proportion of large-angle grain boundaries was only 27.1%, and the dislocation density increased to 5.38 × 1012 cm−2. With the increase in the cooling rate, the depth of the decarbonization layer and the thickness of the scale oxide gradually decreased, the proportion of the FeO phase in the scale phase gradually decreased, and the proportion of the Fe3O4 phase and Fe2O3 phase gradually increased. The tensile strength increased monotonously with the increase in cooling rate, whereas the elongation and area reduction first decreased, then increased, and then decreased. When the cooling rate was 1.0 m/s, the short rod and granular bainite in the material structure endowed the SCM435 steel with excellent strength and toughness matching, and the tensile strength and elongation of the steel reached 895 MPa and 24%, respectively

Time series analysis and prediction model of percentage of influenza-like illness （ILI） cases in Shanghai

ObjectiveTo predict the incidence trend of influenza-like illness proportion （ILI%） in Shanghai using the seasonal autoregressive integrated moving average model （SARIMA）， and to provide an important reference for timely prevention and control measures.MethodsTime series analysis was performed on ILI% surveillance data of Shanghai Municipal Center for Disease Control and Prevention from the 15th week of 2015 to the 52nd week of 2019， and a prediction model was established. Seasonal autoregressive integrated moving average （SARIMA） model was established using data from the foregoing 212 weeks， and prediction effect of the model was evaluated using data from the latter 36 weeks.ResultsFrom the 15th week of 2015 to the 52nd week of 2019， the average ILI% in Shanghai was 1.494%， showing an obvious epidemic peak. SARIMA（1，0，0） （2，0，0） 52 was finally modeled. The residual of the model was white noise sequence， and the true values were all within the 95% confidence interval of the predicted values.ConclusionSARIMA（1，0，0） （2，0，0） 52 can be used for the medium term prediction of ILI% in Shanghai， and can play an early warning role for the epidemic and outbreak of influenza in Shanghai

Clinical Features and Risk Factors of Active Tuberculosis in Patients with Behçet’s Disease

To investigate the clinical features and potential risk factors of active tuberculosis (ATB) in Behçet’s disease (BD), we conducted a case-control study on hospitalized BD patients in our institute from 2010 to 2019. BD patients with ATB were enrolled as the case group. The control group was selected by random number sampling from the remaining BD patients, including those with latent tuberculosis infection, previous tuberculosis, or without tuberculosis. Finally, we reviewed 386 BD patients and identified 21 (5.4%) ATB cases, including four (19.0%) microbiologically confirmed and 17 (81.0%) clinically diagnosed. We found that BD patients with ATB were more prone to have systemic symptoms (fever, night sweating, and unexplained weight loss) and/or symptoms related to the infection site. Multivariate logistic regression analysis revealed that erythrocyte sedimentation rate ESR>60 mm/h (OR=13.710, 95% CI (1.101, 170.702)), increased IgG (OR=1.226, 95% CI (1.001, 1.502)), and positive T-SPOT.TB (OR=7.793, 95% CI (1.312, 48.464), for 24-200 SFC/106PBMC; OR=17.705 95% CI (2.503, 125.260), for >200 SFC/106PBMC) were potential risk factors for ATB in BD patients. Our study suggested that when BD patients have systemic symptoms with significantly elevated TB-SPOT, the diagnosis of ATB should be considered

Corrosion mechanism and microstructure evolution of yttrium-doped marine steel

The effects of Yttrium dosage and heat treatment process on the microstructure, inclusions, and corrosion resistance of marine steel, as well as the electrochemical parameters on corrosion behavior were studied in this work. The results show that Yttrium mainly exists in Yttrium oxide and Yttrium sulfide. In the process of the optimal heat treatment temperature (800°C-5h), the movement of grain boundaries is hindered by the nailing action of Y2O3, which makes the grain size refined. Yttrium can refine the corrosion products and improve the adhesion ability between the corrosion layer and the substrate, which can effectively improve the corrosion resistance of marine steel. The electrochemical parameters mainly affect the proportion and structure of α-FeOOH and α-Fe2O3 in the corrosion layer by affecting the ion diffusion rate or oxygen content, thus affecting the corrosion resistance property. With the increase of temperature, the diffusion coefficient of oxygen in solution increases, and the limiting current density also increases, which is not conducive to the formation of dense corrosion layer and will lead to faster corrosion speed

Effect of Rare Earth Yttrium on Inclusion Characteristics of Grain-Oriented Silicon Steel

To investigate the influence of heavy rare earth element yttrium on the type, morphology, and quantity distribution of inclusions in grain-oriented silicon steel, thermodynamic calculation was carried out on the typical rare earth inclusions in grain-oriented silicon steel containing yttrium. The main inclusions in the experimental steels with and without yttrium were observed and analyzed using field emission scanning electron microscope (FESEM, Zeiss Gemini SEM 300) and energy dispersive spectrometer (EDS, OXFORD Ultim Extreme). The electron backscatter diffraction (EBSD, OXFORD Symmetry) was used to analyze the local average misorientation of the hot-rolled plate. The results show that the inclusions in the Y-free steel are mainly long MnS, irregular Al2O3 and MnS-Al2O3. The inclusions in the Y-bearing steel are spherical rare earth compounds. The number of inclusions in Y-bearing steel decreases and the size increases compared with Y-free steel. The mean value of local average misorientation and the dislocation density of Y-bearing steel are smaller compared with Y-free steel, which could avoid the cracking problem caused by dislocation accumulation during hot rolling. After heating the rough-rolling sample to 1350 °C, there is no obvious difference in the inclusions type between the Y-free steel and Y-bearing steel. However, the area fraction of inclusions in Y bearing steel increases slightly. According to the thermodynamic calculation results, there are mainly three kinds of rare earth inclusions, YS, Y2S3 and Y2O2S, in Y-bearing steel, among which YS has the strongest stability and the stability of Y2O2S is the weakest. The rare earth element yttrium can effectively modify the inclusions, transforming the irregular Al2O3 inclusions, formed during the deoxidation of silicon steel into spherical rare earth inclusions, which suppress the precipitation of long MnS inclusions. Thus, the formability of the steel could be improved

Effect of drying procedures on the physicochemical properties and antioxidant activities of polysaccharides from <i>Crassostrea gigas</i> - Fig 1

<p>Photographs the polysaccharides from <i>C</i>. <i>gigas</i> (A: FDCGP; B: SDCGP; C: REDCGP).</p

Scavenging effects of polysaccharides by different methods on ABTS radical.

<p>The results were presented as the mean ± SD (n = 3).</p