车轮对整车气动性能影响的试验与仿真研究

基于某款轿车通过风洞试验研究了5种轮胎和3种轮辋对整车气动性能的影响及其相互作用,并利用PIV(粒子成像测速)对车轮区域的流场进行了测量对比。结果表明,不同花纹轮胎产生的阻力和升力系数差别分别达到了0.003和0.026,且该差别因轮辋造型而异。其次利用图像识别测量了不同轮胎受力旋转时的变形,还原了真实的轮胎几何以进行仿真计算。通过对比仿真计算和试验结果,分析了不同花纹轮胎造成气动性能差异的原因,为车轮的空气动力学开发提供了参考。

Deep white matter hyperintensity is spatially correlated to MRI-visible perivascular spaces in cerebral small vessel disease on 7 Tesla MRI

Background The association between perivascular space(PVS)and white matter hyperintensity(WMH)has been unclear.Normal-appearing white matter(NAWM)around WMH is also found correlated with the development of focal WMH.This study aims to investigate the topological connections among PVS,deep WMH(dWMH)and NAWM around WMH using 7 Tesla(7T)MRI.Methods Thirty-two patients with non-confluent WMHs and 16 subjects without WMHs were recruited from our department and clinic.We compared the PVS burden between patients with and without WMHs using a 5-point scale.Then,the dilatation and the number of PVS within a radius of 1 cm around each dWMH were compared with those of a reference site(without WMH)in the contralateral hemisphere.In this study,we define NAWM as an area within the radius of 1 cm around each dWMH.Furthermore,we assessed the spatial relationship between dWMH and PVS.Results Higher PVS scores in the centrum semiovale were found in patients with>5 dWMHs(median 3)than subjects without dWMH(median 2,p=0.014).We found there was a greater dilatation and a higher number of PVS in NAWM around dWMH than at the reference sites(p<0.001,p<0.001).In addition,79.59%of the dWMHs were spatially connected with PVS.Conclusion dWMH,NAWM surrounding WMH and MRI-visible PVS are spatially correlated in the early stage of cerebral small vessel disease.Future study of WMH and NAWM should not overlook MRI-visible PVS.

Amplitude variation with offset and azimuth inversion to predict and evaluate coal seam fracture parameters

Amplitude variation with offset and azimuth(AVOA)inversion is a mainstream method for predicting and evaluating fracture parameters of conventional oil and gas reservoirs.However,its application to coal seams is limited because of the specificity of the equivalent media model for coal—also,the traditional seismic acquisition system employed in coal fields falls within a narrow azimuth.In this study,we initially derived a P‒P wave reflection coefficient approximation formula for coal seams,which is directly expressed in terms of fracture parameters using the Schoenberg linear-slide model and Hudson model.We analyzed the P‒P wave reflection coefficient’s response to the fracture parameters using a two-layer forward model.Accordingly,we designed a twostep inversion workflow for AVOA inversion of the fracture parameters.Thereafter,high-density wide-azimuth pre-stack 3D seismic data were utilized for inverting the fracture density and strike of the target coal seam.The inversion accuracy was constrained by Student’s tdistribution testing.The analysis and validation of the inversion results revealed that the relative fracture density corresponds to fault locations,with the strike of the fractures and faults mainly at 0°.Therefore,the AVOA inversion method and technical workflow proposed here can be used to efficiently predict and evaluate fracture parameters of coal seams.

Experimental study on NO_(x)emission characteristics under oxy-fuel combustion

This study focuses on the emission characteristics of NO_(x)under oxy-fuel combustion conditions.A comparative analysis with air combustion was performed.NO_(x)emission,control measures and influence factors under different working conditions were studied.Experiments were carried out on a 3-MWth test platform and a laboratory platform.The‘π’-type furnace was adopted,with the fur-nace width of 2.6 m,depth of 2.0 m and height of 10.5 m for the 3-MWth coal-fired boiler.NO_(x)emissions at different oxygen concen-trations and different air distribution were investigated;the effects of H2O and CO_(2)concentration on denitrification efficiency and SO_(2)/SO_(3)conversion rate were explored.Experiment results suggest that,compared with air combustion,NO concentration(volume basis)at the furnace outlet under oxy-fuel combustion is higher than that of air combustion,but the amount of NO_(x)emissions in the discharged gas significantly decrease compared to the air combustion conditions.In addition,the formation of NO_(x)can be effectively controlled through staged combustion.Furthermore,the selective catalytic reduction(SCR)denitrification efficiency and the con-version rate of SO_(2)to SO_(3)decreases when the CO_(2)concentration and the H2O content increase,indicating that CO_(2)and H2O have an adverse effect on the performance of the catalyst.Additionally,compared with CO_(2)concentration,H2O content has a greater effect on catalyst performance.

CCIN突变引起畸形精子症和男性不育

畸形精子症通常与精子变形缺陷相关,具有遗传异质性.之前的研究确定了一些致病基因,但大多数畸形精子症的病因仍然未知.该研究在畸形精子症患者中鉴定出CCIN^(H42L/H42L)和CCIN^(R432W/C447*)突变. CCIN编码细胞骨架蛋白Calicin,参与哺乳动物精子花萼结构的形成和维持,被推测在精子头部重塑过程中发挥作用.对携带上述CCIN突变位点的患者精子进行的形态学分析显示精子头部严重畸形.进一步的研究表明CCIN突变精子的Calicin蛋白显著降低.携带与患者相同突变位点的小鼠模型成功地再现了患者的不育表型.来自患者和突变小鼠的精子都无法黏附到卵子的透明带,这可能是CCIN突变导致雄性不育的主要原因.使用卵胞浆内单精子注射可以成功地克服这一缺陷,使患者及突变体小鼠获得子代.综上所述,该研究确定了Calicin在精子头部变形和男性生育中的功能,为遗传咨询和辅助生殖治疗提供了重要指导.

Pyroptotic macrophages stimulate the SARS-CoV-2-associated cytokine storm

Coronavirus disease 2019(COVID-19)is an unprecedented pandemic caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2).As of 22 February 2021,the worldwide pandemic has resulted in more than 110 million cases and 2.4 million deaths.1 Clinical investigation of COVID-19 patients has shown that a systemic cytokine storm can occur,especially in severe cases.2 Treatment of the SARS-CoV-2-associated cytokine storm with tocilizumab3 or anakinra4 has been shown to immediately improve the clinical outcome in most severe and critical COVID-19 patients.These data highlight the systemic cytokine storm as an important exacerbating event in severe COVID-19;however,our understanding of the molecular mechanisms involved in the initiation of the SARS-CoV-2-associated cytokine storm is limited.In the present study,we uncovered a reasonable explanation for cytokine storm initiation through the analysis of 13 autopsy samples from severe COVID-19 patients.

Seldom-segment versus multi-segment intramedullary spinal cord gliomas: a comparative clinical study

Dear Editor,Glial tumors (80%), astrocytomas, and ependymomas are the most frequent histological types of intramedullary spinal cord tumors (Bansal et al., 2013). Intramedullary tumors spanning three or more vertebral body levels are considered multi-segment intramedullary spinal cord tumors and have a much lower incidence than less involved tumors (Wang et al., 2012). We prospectively studied 81 consecutive patients who underwent resection of intramedullary spinal cord gliomas at a single medical center (The Neurosurgery Department of Peking University Third Hospital) between January 2010 and December 2015 to compare the neurological function and prognosis of patients with seldom-segment and multiple-segment intramedullary spinal cord gliomas.

Training the old dog new tricks: the applications of the Biginelli reaction in polymer chemistry

Recently, the Biginelli reaction, one of the most famous multicomponent reactions, has been introduced into the polymer chemistry to highly efficiently synthesize some interesting functional polymers. In this mini-review, several applications of the Biginelli reaction in polymer chemistry have been summarized, including polycondensation, post-polymerization modification,one-pot synthesis of well-defined polymer, etc. Meanwhile, the utilization of the Biginelli reaction in material science and chemical biology, and the future development of the Biginelli reaction in polymer chemistry have also been discussed.

Elevated Kir2.1/nuclear N2ICD defines a highly malignant subtype of non-WNT/SHH medulloblastomas

Medulloblastoma(MB)is one of the most common childhood malignant brain tumors(WHO grade IV),traditionally divided into WNT,SHH,Group 3,and Group 4 subgroups based on the transcription profiles,somatic DNA alterations,and clinical outcomes.Unlike WNT and SHH subgroup MBs,Group 3 and Group 4 MBs have similar transcriptomes and lack clearly specific drivers and targeted therapeutic options.The recently revised WHO Classification of CNS Tumors has assigned Group 3 and 4 to a provisional non-WNT/SHH entity.In the present study,we demonstrate that Kir2.1,an inwardly-rectifying potassium channel,is highly expressed in non-WNT/SHH MBs,which promotes tumor cell invasion and metastasis by recruiting Adam10 to enhance S2 cleavage of Notch2 thereby activating the Notch2 signaling pathway.Disruption of the Notch2 pathway markedly inhibited the growth and metastasis of Kir2.1-overexpressing MB cell-derived xenograft tumors in mice.Moreover,Kir2.1^(high)/nuclear N2ICD^(high)MBs are associated with the significantly shorter lifespan of the patients.Thus,Kir2.1^(high)/nuclear N2ICD^(high)can be used as a biomarker to define a novel subtype of non-WNT/SHH MBs.Our findings are important for the modification of treatment regimens and the development of novel-targeted therapies for non-WNT/SHH MBs.