Study of Complex Nitrogen and Oxygen-bearing Molecules toward the High-mass Protostar IRAS 18089–1732

The observation of oxygen(O)-and nitrogen(N)-bearing molecules gives an idea about the complex prebiotic chemistry in the interstellar medium.Recent millimeter and submillimeter wavelength observations have shown the presence of complex O-and N-bearing molecules in the star formation regions.So,the investigation of those molecules is crucial to understanding the chemical complexity in the star-forming regions.In this article,we present the identification of the rotational emission lines of N-bearing molecules ethyl cyanide(C_(2)H_(5)CN)and cyanoacetylene(HC_(3)N),and O-bearing molecule methyl formate(CH_(3)OCHO)toward high-mass protostar IRAS18089–1732 using the Atacama Compact Array.We also detected the emission lines of both the N-and O-bearing molecule formamide(NH_(2)CHO)in the envelope of IRAS 18089–1732.We have detected the v=0 and 1 state rotational emission lines of CH_(3)OCHO.We also detected the two vibrationally excited states of HC_(3)N(v7=1 and v7=2).The estimated fractional abundances of C_(2)H_(5)CN,HC_(3)N(v7=1),HC_(3)N(v7=2),and NH_(2)CHO toward IRAS 18089–1732 are(1.40±0.5)×10^(-10),(7.5±0.7)×10^(-11),(3.1±0.4)×10^(-11),and(6.25±0.82)×10^(-11)respectively.Similarly,the estimated fractional abundances of CH_(3)OCHO(v=0)and CH_(3)OCHO(v=1)are(1.90±0.9)×10^(-9)and(8.90±0.8)×10^(-10),respectively.We also created the integrated emission maps of the detected molecules,and the observed molecules may have originated from the extended envelope of the protostar.We show that C_(2)H_(5)CNand HC_(3)N are most probably formed via the subsequential hydrogenation of the CH_(2)CHCNand the reaction between C_(2)H_(2)and CN on the grain surface of IRAS 18089–1732.We found that NH_(2)CHO is probably produced due to the reaction between NH_(2)and H_(2)CO in the gas phase.Similarly,CH_(3)OCHO is possibly created via the reaction between radical CH_(3)O and radical HCO on the grain surface of IRAS 18089–1732.

关于YY/T1732-2020《口腔曲面体层X射线机专用技术条件》检测要点的探讨

目前,口腔医学的快速发展,口腔曲面全景体层X射线摄影在口腔诊断领域中起着特别重要的作用。口腔曲面体层定义是牙科X射线摄影中,由扇形X射线束和X射线影像接收器共同围绕患者头部协同运动获得的,其中X射线束运动取向为平行于患者的颅尾轴。它的原理是使X射线球管和影像接收器按照被检体的弧度从一侧颞下颌关节到另一侧颞下颌关节做相反方向运动,从而得到一张弧形的体层影像。这种摄影方式可清晰显示整口牙列、鼻腔、颌骨、上颌窦和颞下颌等解剖结构。市场上关于牙科X射线机的分类包括了固定式X射线机、移动式X射线机、壁挂式X射线机和数字全景X射线机以及口腔颌面锥形束计算机体层摄影设备,即口腔CT,市场上很多的三合一和四合一的机器是把几种形式综合到一起。口腔数字全景机是将整个口腔内的牙齿和颌骨的影像显示出来,通过X射线片能完整清晰地看到上下颌骨的全貌。因为需要精准地显示出上下颌骨、上下牙列、上下牙槽骨以及上颌窦,为医生准确诊断提供帮助,所以对全景机性能的判断和理解成为了检测工程师需要学习和钻研的问题。YY/T1732-2020《口腔曲面体层X射线机专用技术条件》这本标准是业内第一本适用于全景机的专用标准,并且已经于2021年6月1日实施。文章将结合本标准检测重点和目前的检测情况进行阐述。