Effects of Estrogen on Mucosal Structure and Numbers and Distribution of Intraepithelial Lymphocytes and Goblet Cells in Small Intestine of Rats

To study the effects of estrogen on the structure of the intestinal mucosal barrier, 18 healthy female Wistar Rats underwent estrus synchronization. In diestrus, they were divided into three groups: one sham operated control group (SHAM); one ovariectomized group (OVX); and one ovariectomized plus estradiol benzoate group (OVX+E2). Intestinal mucosal epithelial cells, intraepithelial lymphocytes (IEL), and goblet cells (GCs) were observed by light microscope. The results showed that in the OVX group, the intestinal mucosa damaged obviously, the villus atrophied, the ratio of villus height to crypt depth reduced, and the number of IELs and GCs reduced. The indicators of OVX+E2 group were significantly higher than OVX group, but some indicators were lower than SHAM. These indicated that the function of intestinal mucosal barrier was greatly damaged in ovariectomied rat, and proper dosage of estradiol benzoate would improve the function of small intestinal mucosal barrier in ovariectomied rat to some degree.

Development and validation of a nomogram to predict failure of 14-day negative nucleic acid conversion in adults with non-severe COVID-19 during the Omicron surge: a retrospective multicenter study

Background With the variability in emerging data,guidance on the isolation duration for patients with coronavirus disease 2019(COVID-19)due to the Omicron variant is controversial.This study aimed to determine the predictors of prolonged viral RNA shedding in patients with non-severe COVID-19 and construct a nomogram to predict patients at risk of 14-day PCR conversion failure.Methods Adult patients with non-severe COVID-19 were enrolled from three hospitals of eastern China in Spring 2022.Viral shedding time(VST)was defined as either the day of the first positive test or the day of symptom onset,whichever was earlier,to the date of the first of two consecutively negative PCR tests.Patients from one hospital(Cohort I,n=2033)were randomly grouped into training and internal validation sets.Predictors of 14-day PCR conversion failure were identified and a nomogram was developed by multivariable logistic regression using the training dataset.Two hospitals(Cohort II,n=1596)were used as an external validation set to measure the performance of this nomogram.Results Of the 2033 patients from Cohort I,the median VST was 13.0(interquartile range:10.0-16.0)days;716(35.2%)lasted>14 days.In the training set,increased age[per 10 years,odds ratio(OR)=1.29,95%confidence interval(CI):1.15-1.45,P<0.001]and high Charlson comorbidity index(OR=1.25,95%CI:1.08-1.46,P=0.004)were independent risk factors for VST>14 days,whereas full or boosted vaccination(OR=0.63,95%CI:0.42-0.95,P=0.028)and antiviral therapy(OR=0.56,95%CI:0.31-0.96,P=0.040)were protective factors.These predictors were used to develop a nomogram to predict VST>14 days,with an area under the ROC curve(AUC)of 0.73 in the training set(AUC,0.74 in internal validation set;0.76 in external validation set).Conclusions Older age,increasing comorbidities,incomplete vaccinations,and lack of antiviral therapy are risk factors for persistent infection with Omicron variant for>14 days.A nomogram based on these predictors could be used as a prediction tool to guide treatment and isolation strategies.

Effects of tooth bending damage on the leakage performance and rotordynamic coefficients of labyrinth seals

Tooth bending damage resulting from an intense impact by the rotor sometimes occurs in the transient operation.To investigate the influence of after-damage clearance and tooth bending length on the leakage performance and rotordynamic coefficients of labyrinth seals,three tooth bending damages were taken into consideration,including the unbent tooth damage(abbreviated as Unbent),the partial tooth bending damage(abbreviated as Pbent)and the complete tooth bending damage(abbreviated as Cbent).The transient CFD solution was utilized to calculate the leakage flow rates and rotordynamic coefficients of labyrinth seals with clearances of 0.3,0.4,0.5,0.6 mm for three tooth bending damages.The obtained result shows that the Unbent tooth damage leaks least while the Pbent tooth bending damage leaks most,and an increase of 6.1%for Cbent tooth bending damage and an increase of 19.4%for Pbent tooth bending damage are discovered at the tooth clearance of 0.6 mm in comparison with the Unbent tooth damage.Compared to the Unbent tooth damage,the effective damping for Pbent tooth bending damage and Cbent tooth bending damage is lower and drops by 9.7%–33.6%and 8.5%–22.6%respectively at the tooth clearance of 0.6 mm,suggesting that Pbent tooth bending damage or Cbent tooth bending damage tends to weaken the seal stability when compared to the Unbent tooth damage.

Effects of swirl brake axial arrangement on the leakage performance and rotor stability of labyrinth seals

Swirl brakes are usually introduced at the seal entrance in industry to improve the seal stability,especially for labyrinth seals suffering low seal clearance and high inlet preswirl ratio.However,how to arrange swirl brakes at the seal entrance to obtain better seal stability retains unknown,such as the axial distance between the brake trailing edge and the first tooth.To this end,the effects of the distance between brakes and the first tooth on the leakage flow rate and seal rotordynamic coefficients were numerically investigated at typical inlet preswirl ratios of 0.45 and0.8,and the predicted results were in comparison with the results for no-brake configuration.The obtained results disclose that the brake configuration arranged against the first tooth produces lower circumferential velocity in the downstream of the brakes as a result of the larger counterclockwise vortex moving from the brake trailing edge to the brake leading edge when compared to the brake configuration away from the first tooth.Besides,the dropped circumferential velocity in the downstream of brakes will cause larger pressure fluctuation in the circumferential direction and thus generates larger tangential force to restrain the rotor forward whirl.On the other hand,the effective damping is further increased when the distance between brakes and the first tooth decreases to zero,that is,the crossover frequency is even disappeared at the inlet preswirl ratio of 0.45 and successfully drops from 69.9 Hz to 32.7 Hz at the preswirl ratio of 0.8.