Most existing studies assign a polyynic and cumulenic character of chemical bonding in carbon-based chains relying on values of the bond lengths.Building on our recent work,in this paper we add further evidence on the...Most existing studies assign a polyynic and cumulenic character of chemical bonding in carbon-based chains relying on values of the bond lengths.Building on our recent work,in this paper we add further evidence on the limitations of such an analysis and demonstrate the significant insight gained via natural bond analysis.Presently reported results include atomic charges,natural bond order and valence indices obtained from ab initio computations for representative members of the astrophysically relevant neutral and charged HC_(2k/2k+1)H chain family.They unravel a series of counter-intuitive aspects and/or help naive intuition in properly understanding microscopic processes,e.g.,electron removal from or electron attachment to a neutral chain.Demonstrating that the Wiberg indices adequately quantify the chemical bonding structure of the HC_(2k/2k+1)H chains—while the often heavily advertised Mayer indices do not—represents an important message conveyed by the present study.展开更多
Density functional theory-based calculations have been carried out to study the bonding and reactivity in RB-As R(R=H,F,OH,CH3,CMe_3,CF_3,SiF_3,BO)systems.Our calculations demonstrated that all the studied systems ado...Density functional theory-based calculations have been carried out to study the bonding and reactivity in RB-As R(R=H,F,OH,CH3,CMe_3,CF_3,SiF_3,BO)systems.Our calculations demonstrated that all the studied systems adopted bent geometry(DR-B-As≈180°andDB-As-R≈90°or less).The reason for this bending was explained with the help of a valence-orbital model.The potential energy surfaces for three possible isomers of RB-As R systems were also generated,indicating that the RB-As R isomer was more stable than R_2B-As R when R=SiF_3,CMe_3,and H.The B-As bond character was analyzed using natural bond orbital(NBO)and Wiberg bond index(WBI)calculations.The WBI values for B-As bonds in F3Si B-As SiF_3 and HB-As H were 2.254 and 2.209,respectively,indicating that this bond has some triple-bond character in these systems.While the B centers prefer nucleophilic attack,the As centers prefer electrophilic attack.展开更多
Chemical reaction possibility was described quantitatively for the case of nitrotriazolam preparation with 2-clonazepam by using the data of two quantum chemical reactivity indices: net electrophilicity index and Wibe...Chemical reaction possibility was described quantitatively for the case of nitrotriazolam preparation with 2-clonazepam by using the data of two quantum chemical reactivity indices: net electrophilicity index and Wiberg bond order. Furthennore, relevant reaction mechanism was derived from tlie aspect of quantum chemistry. The results show that the indices used can quantitatively explain the chemical reactivity and reaction mechanism of the nitrotriazolam preparation. To validate the universal applicability of the proposed approach, the authors continued to use the quantum chemical reactivity indices to describe some classic chemical reactions, expecting to predict major issues related to physical organic chemistry, such as new chemical reactions and their mechanisms.展开更多
文摘分析全膝关节置换术（total knee arthroplastv,TKA）保留髌骨并行髌骨成形术后对膝前区疼痛及髌骨运动轨迹影响的疗效,为临床治疗提供参考。2007年1月~2011年1月,共随访类风湿关节炎保留髌骨全膝关节置换术患者226例383膝,其中男51例,女175例,年龄34~85岁。所有患者膝关节评分采用美国HSS评分系统,髌骨评分采用Feller等评分标准,随访时调查膝前痛,拍摄膝关节正、侧及髌骨90度轴位X射片。髌骨成形术：去除髌骨周围所有骨赘,磨平边缘,修整髌骨至Wiberg分型II型,用电刀切除髌骨周围软组织,试模复位后无拇指试验no thumb test阳性者松解髌骨支持带。结果显示患者术前、术后的HSS评分、髌骨评分、膝前痛评分、髌骨功能评分差异均有显著意义（P〈0.01）。类风湿关节炎保留髌骨的全膝关节置换术,术中对髌骨进行髌骨成形术处理,使髌骨形态恢复至Wiberg分型II型,术后髌骨运动轨迹良好,膝前痛的发生率低,术后疗效可靠。
基金financial support from the German Research Foundation(DFG Grant No.BA 1799/3-2)in the initial stage of this work and computational support by the state of Baden-Württemberg through bw HPC and the German Research Foundation through Grant No.INST 40/575-1 FUGG(bw Uni Cluster 2.0,bw For Cluster/MLS&WISO 2.0/HELIX,and JUSTUS 2.0 cluster)
文摘Most existing studies assign a polyynic and cumulenic character of chemical bonding in carbon-based chains relying on values of the bond lengths.Building on our recent work,in this paper we add further evidence on the limitations of such an analysis and demonstrate the significant insight gained via natural bond analysis.Presently reported results include atomic charges,natural bond order and valence indices obtained from ab initio computations for representative members of the astrophysically relevant neutral and charged HC_(2k/2k+1)H chain family.They unravel a series of counter-intuitive aspects and/or help naive intuition in properly understanding microscopic processes,e.g.,electron removal from or electron attachment to a neutral chain.Demonstrating that the Wiberg indices adequately quantify the chemical bonding structure of the HC_(2k/2k+1)H chains—while the often heavily advertised Mayer indices do not—represents an important message conveyed by the present study.
文摘Density functional theory-based calculations have been carried out to study the bonding and reactivity in RB-As R(R=H,F,OH,CH3,CMe_3,CF_3,SiF_3,BO)systems.Our calculations demonstrated that all the studied systems adopted bent geometry(DR-B-As≈180°andDB-As-R≈90°or less).The reason for this bending was explained with the help of a valence-orbital model.The potential energy surfaces for three possible isomers of RB-As R systems were also generated,indicating that the RB-As R isomer was more stable than R_2B-As R when R=SiF_3,CMe_3,and H.The B-As bond character was analyzed using natural bond orbital(NBO)and Wiberg bond index(WBI)calculations.The WBI values for B-As bonds in F3Si B-As SiF_3 and HB-As H were 2.254 and 2.209,respectively,indicating that this bond has some triple-bond character in these systems.While the B centers prefer nucleophilic attack,the As centers prefer electrophilic attack.
基金Project supported by the Key Laboratory for New Molecule Material Design and Function of Tianshui Normal University and the Scientific Research Projects of Young and Middle-aged in Tianshui Normal University(No.TSA1116)the Key Discipline of Tianshui Normal University,and the Fund of Educational Commission of Gansu Province(No.1108-03)~~
文摘Chemical reaction possibility was described quantitatively for the case of nitrotriazolam preparation with 2-clonazepam by using the data of two quantum chemical reactivity indices: net electrophilicity index and Wiberg bond order. Furthennore, relevant reaction mechanism was derived from tlie aspect of quantum chemistry. The results show that the indices used can quantitatively explain the chemical reactivity and reaction mechanism of the nitrotriazolam preparation. To validate the universal applicability of the proposed approach, the authors continued to use the quantum chemical reactivity indices to describe some classic chemical reactions, expecting to predict major issues related to physical organic chemistry, such as new chemical reactions and their mechanisms.
