谈毕达哥拉斯学派“数”理音乐思想

毕达哥拉斯是古希腊时期著名的哲学家、数学家和音乐理论家,以他的思想为中心形成了"毕达哥拉斯学派"。在音乐方面,毕达哥拉斯学派认为"音乐是数字,而宇宙是音乐",这种关于"音乐与数学"的观点一直影响着西方音乐的发展。本文将对毕达哥拉斯学派重要人物的"数"理音乐思想进行介绍,再结合现代音乐作品简析"数"理音乐思想对音乐发展的影响。

Rate Coefficients and Branching Ratio for Multi-Channel Hydrogen Abstractions from CH3OH by F

The hydrogen abstraction reaction F+CH3OH has two possible reaction pathways: HF+CH3O and HF+CH2OH. Despite the absence of intrinsic barriers for both channels, the former has a branching ratio comparable to the latter, which is far from the statistical limit of 0.25 (one out of four available H atoms). Furthermore, the measured branching ratio of the two abstraction channels spans a large range and is not quantitatively reproduced by previous theoretical predictions based on the transition-state theory with the stationary point information calculated at the levels of MФller-Plesset perturbation theory and G2. This work reports a theoretical investigation on the kinetics and the associated branching ratio of the two competing channels of the title reaction using a quasi-classical trajectory approach on an accurate full-dimensional potential energy surface (PES) fitted by the permutation invariant polynomial-neural network approach to ca. 1.21x10^5 points calculated at the explicitly correlated (F12a) version of coupled cluster singles doubles and perturbative triples (CCSD(T)) level with the aug-cc-pVDZ basis set. The calculated room temperature rate coeffcient and branching ratio of the HF+CH3O channel are in good agreement with the available experimental data. Furthermore, our theory predicts that rate coeffcients have a slightly negative temperature dependence, consistent with barrierless nature of the reaction.

Efficient Method to Extract Coupling Ratio and Round-trip Loss Parameters of Optical Waveguide Ring Resonator

Based on the measurement of the contrast ratios of the transmission spectra from the throughput and drop ports of ring resonator, an efficient method is proposed to extract the coupling ratio and round-trip loss of the integrated optical waveguide ring resonator. The parameters of a racetrack resonator prepared by ion-exchange technique in K9 optical glass substrate are examined, which demonstrates the validity of this method. The accuracy and applicable range of this method are also discussed.

Theoretical Investigations on Photodissociation Dynamics of Deuterated Alkyl Halides CD_(3)CH_(2)F

The product branching ratio between different products in multichannel reactions is as important as the overall rate of reaction,both in terms of practical applications(e.g.models of combustion or atmosphere chemistry)in understanding the fundamental mechanisms of such chemical reactions.A global ground state potential energy surface for the dissociation reaction of deuterated alkyl halide CD_(3)CH_(2)F was computed at the CCSD(T)/CBS//B3 LYP/aug-cc-p VDZ level of theory for all species.The decomposition of CD_(3)CH_(2)F is controversial concerning C-F bond dissociation reaction and molecular(HF,DF,H_(2),D_(2),HD)elimination reaction.RiceRamsperger-Kassel-Marcus(RRKM)calculations were applied to compute the rate constants for individual reaction steps and the relative product branching ratios for the dissociation products were calculated using the steady-state approach.At the different energies studied,the RRKM method predicts that the main channel for DF or HF elimination from1,2-elimination of CD_(3)CH_(2)F is through a four-center transition state,whereas D_(2) or H_(2) elimination from 1,1-elimination of CD_(3)CH_(2)F occurs through a direct three-center elimination.At 266,248,and 193 nm photodissociation,the main product CD_(2)CH_(2)+DF branching ratios are computed to be 96.57%,91.47%,and 48.52%,respectively;however,at 157 nm photodissociation,the product branching ratio is computed to be 16.11%.Based on these transition state structures and energies,the following photodissociation mechanisms are suggested:at 266,248,193 nm,CD_(3)CH_(2)F→absorption of a photon→TS5→the formation of the major product CD_(2)CH_(2)+DF;at 157 nm,CD_(3)CH_(2)F→absorption of a photon→D/F interchange of TS1→CDH_(2)CDF→H/F interchange of TS2→CHD_(2)CHDF→the formation of the major product CHD_(2)+CHDF.

血站核酸筛查模式对输血传播HBV残余风险影响的评估研究

目的初步评估探讨核酸筛查模式对献血人群乙型肝炎病毒(hepatitis B virus,HBV)传播残余风险度的影响。方法采用中国大陆执业比对工作组信息管理系统的相关数据,利用NAT单阳性率-窗口期比率数学模型(NAT yield/WP ratio model),对2015—2019年度我国18家血液中心的献血人群HBV传播的残余风险度进行趋势分析;同时分析比较2019年18家血液中心的ELISA联合核酸单检/混检(ELISA+ID-NAT/MP-NAT)和ELISA联合核酸混检(ELISA+MP-NAT)2种血液筛查(简称血筛)模式对残余风险度的影响。结果18家血液中心5年的HBV血筛残余风险度总体趋势经趋势卡方检验显示:核酸检测单阳性率趋势χ^(2)=39.42(P<0.01),残余风险度趋势χ^(2)=279.792(P<0.01);ELISA+ID-NAT/MP-NAT和ELISA+MP-NAT 2种不同血筛模式对残余风险度RR的影响差异有显著统计学意义,卡方检验显示χ^(2)=7.4(P<0.01)。结论自2015年我国将核酸检测用于血筛以来,HBV输血传播的残余风险度呈逐年下降趋势,目前主要的2种血筛模式对血液残余风险度有可能造成差别。