Probing Ultrafast Dissociation Dynamics of Chloroiodomethane in the B Band by Time-Resolved Mass Spectrometry

Ultrafast dissociation dynamics of chloroiodomethane （CH2ICl） in the B band is studied by femtosecond time- resolved time-of-flight （TOF） mass spectrometry. Time-resolved TOF mass signal of parent ion （CH2ICl＋） and main daughter ion （CH2Cl＋） are obtained. The curve for the transient signal of CH2ICl＋ is simple and can be well fitted by an exponential decay convoluted with a Gaussian function. The decay constant determined to be less than 35 fs reflects the lifetime of the B band. Significant substituent effects on photodissociation dynamics of CH2IC1 compared with CH3I are discussed. The dissociation time from the parent ion CH2IC1＋ to the daughter ion CH2Cl＋ is determined in the experiment. The optimized geometry of the ionic state of CH2ICl and the ionization energy are calculated for further analysis of the measurements. In addition, compared with the parent ion, a new decay component with time constant of -596 fs is observed for CH2Cl＋, and reasonable mechanisms are proposed for the explanation.

A New kHz Velocity Map Ion/Electron Imaging Spectrometer for Femtosecond Time-Resolved M olecular Reaction Dynamics Studies

A new velocity map imaging spectrometer is constructed for molecular reaction dynamics studies using time-resolved photoelectron/ion spectroscopy method. By combining a kHz pulsed valve and an ICCD camera, this velocity map imaging spectrometer can be run at a repetition rate of 1 kHz, totally compatible with the fs Ti：Sapphire laser system, facilitating time-resolved studies in gas phase which are usually time-consuming. Time-resolved velocity map imaging study of NH3 photodissociation at 200 nm was performed and the time-resolved total kinetic energy release spectrum of H＋NH~ products provides rich information about the dissociation dynamics of NH3. These results show that this new apparatus is a powerful tool for investigating the molecular reaction dynamics using time-resolved methods.

Analysis of Turbulence Structure in the Stirred Tank with a Deep Hollow Blade Disc Turbine by Time-resolved PIV

The turbulence structure in the stirred tank with a deep hollow blade(semi-ellispe) disc turbine(HEDT) was investigated by using time-resolved particle image velocimetry(TRPIV) and traditional PIV.In the stirred tank,the turbulence generated by blade passage includes the periodic components and the random turbulent ones.Traditional PIV with angle-resolved measurement and TRPIV with wavelet analysis were both used to obtain the random turbulent kinetic energy as a comparison.The wavelet analysis method was successfully used in this work to separate the random turbulent kinetic energy.The distributions of the periodic kinetic energy and the random turbulent kinetic energy were obtained.In the impeller region,the averaged random turbulent kinetic energy was about 2.6 times of the averaged periodic one.The kinetic energies at different wavelet scales from a6 to d1 were also calculated and compared.TRPIV was used to record the sequence of instantaneous velocity in the impeller stream.The evolution of the impeller stream was observed clearly and the sequence of the vorticity field was also obtained for the identification of vortices.The slope of the energy spectrum was approximately-5/3 in high frequency representing the existence of inertial subrange and some isotropic properties in stirred tank.From the power spectral density(PSD) ,one peak existed evidently,which was located at f0(blade passage frequency) generated by the blade passage.

Simultaneous measurements of global vibrational spectra and dephasing times of molecular vibrational modes by broadband time-resolved coherent anti-Stokes Raman scattering spectrography

In broadband coherent anti-Stokes Raman scattering （CARS） spectroscopy with supercontinuum （SC）, the simultaneously detectable spectral coverage is limited by the spectral continuity and the simultaneity of various spectral components of SC in an enough bandwidth. By numerical simulations, the optimal experimental conditions for improving the SC are obtained. The broadband time-resolved CARS spectrography based on the SC with required temporal and spectral distributions is realised. The global molecular vibrational spectrum with well suppressed nonresonant background noise can be obtained in a single measurement. At the same time, the measurements of dephasing times of various molecular vibrational modes can be conveniently achieved from intensities of a sequence of time-resolved CARS signals. It will be more helpful to provide a complete picture of molecular vibrations, and to exhibit a potential to understand not only both the solvent dynamics and the solute-solvent interactions, but also the mechanisms of chemical reactions in the fields of biology, chemistry and material science.

Spectrum-effect relationship between HPLC fingerprints and bioactive components of Radix Hedysari on increasing the peak bone mass of rat

The traditional Chinese medicine of Radix Hedysari plays an important role in invigorating gas for ascending, benefiting blood for promoting production of fluid, and promoting circulation for removing obstruction in collaterals, which is consistent with the principle of treatment for osteoporosis. This study is designed to investigate the bioactive components on increasing peak bone mass (PBM) by exploring the spectrum-effect relationship between chromatography fingerprints and effect. Multiple indicators are selected to evaluate the pharmacological activity. In fingerprints, 21 common peaks are obtained, five of which are identified. Furthermore, gray relational analysis (GRA) is a quantitative method of gray system theory and is used to describe the correlation degree of common peaks and pharmacological activities with relational value. 21 components are then divided into three different regions, of which ononin and calycosin play an extremely significant role in increasing PBM. In addition, factor analysis and hierarchical cluster analysis (HCA) are used to screen the optimal producing area for Radix Hedysari. This provides a comprehensive and efficient method to improve the quality evaluation of Radix Hedysari, confirming the bioactive components for PBM-enhancement and further develop its medicinal value.

Dependence of Decamethylcyclopentasiloxane (DMCPS) Dissociation on Ionized Energy by Using Quadrupole Mass Spectrum

Dependence of decamethylcyclopentasiloxane （DMCPS） organosilicon dissociation on ionized energy in the energy range of 25 eV to 70 eV is investigated by using a quadrupole mass spectrometry. At the ionized energy below 55 eV, the dissociation of DMCPS is dominant. As the ionized energy is above 55 eV, the DMCPS dissociation achieves the maximum cross section, while the fragments from the DMCPS dissociation can further dissociate, which leads to a different ingredient of fragments. At the lower ionized energy of 25 eV, the main fragments are SiOC2H＋, SiCH＋, Si＋, O＋ and CH＋ ions, which shows an important effect on the SiCOH low-k film deposition.

Towards the understanding of 1^1 p1 meson mass spectrum

Based on the meson-meson mixing and Regge trajectory, this paper establishes the mass relations which can describe the mass spectrum of 1^1 P1 meson state. Using these mass relations, it obtains the mass of K1B, hi （1380） and hc（1P） to be 1358.5MeV, 1468 MeV and 3543.9 MeV, respectively. The results are compared with other theoretical results and should be tested by experiments in the future.

Thermal-induced Unfolding of β-Crystallin and Disassembly of its Oligomers Revealed by Temperature-Jump Time-Resolved Infrared Spectroscopy

β-Crystallins are the major structural proteins existing in the vertebrate lens, and their conformational stability is critical in maintaining the life-long transparency and refraction index of the lens. Seven subunits of β-crystallins naturally assemble into various heteroge- neous oligomers with different sizes. Here, we systematically investigated the thermal sta- bility of the different secondary structures present in β-Crystallins and then the dynamic process for the thermal-induced unfolding of β-crystallins by Fourier transform infrared spectroscopy-monitored thermal titration and temperature-jump nanosecond time-resolved IR difference absorbance spectra. Our results show that the N-terminal anti-parallel β-sheets in β-crystallin are the most unstable with a transition midpoint temperature at 36.0-2.1℃, leading to the formation of an intermediate consisting vastly of random coil structures. This intermediate structure is temporally assigned to that of the monomer generated by the thermal-induced disassembly of β-crystallin oligomers with a transition midpoint tempera- ture of 40.4-0.7℃. The global unfolding of β-crystallins that leads to denaturation and aggregation indicated by the formation of intermolecular anti-parallel β-sheets has a transi- tion midpoint temperature determined as 72.4-0.2 ℃. Temperature-jump time-resolved IR absorbance difference spectroscopy analysis further reveals that thermal-induced unfolding of β-crystallins occurs firstly in the anti-parallel β-sheets in the N-terminal domains with a time constant of 50 ns.

Ultrafast Decay Dynamics of N-Ethylpyrrole Excited to the S_(1)Electronic State:A Femtosecond Time-Resolved Photoelectron Imaging Study

N-ethylpyrrole is one of ethylsubstituted derivatives of pyrrole and its excited-state decay dynamics has never been explored.In this work,we investigate ultrafast decay dynamics of N-ethylpyrrole excited to the S_(1)electronic state using a femtosecond time-resolved photoelectron imaging method.Two pump wavelengths of 241.9 and 237.7 nm are employed.At 241.9 nm,three time constants,5.0±0.7 ps,66.4±15.6 ps and 1.3±0.1 ns,are derived.For 237.7 nm,two time constants of 2.1±0.1 ps and 13.1±1.2 ps are derived.We assign all these time constants to be associated with different vibrational states in the S_(1)state.The possible decay mechanisms of different S_(1)vibrational states are briefly discussed.

Ultrafast Dynamics of Water Molecules Excited to Electronic ■ States:A Time-Resolved Photoelectron Spectroscopy Study

The ultrafast dynamics of water molecules excited to the two F states is studied by combining two-photon excitation and time-resolved photoelectron imaging techniques. The lifetimes of the F1A1 and F1B1 states of H2O (D2O) were derived to be 1.0±0.3 (1.9±0.4) and 10±3 (30±10) ps, respectively. We propose that the F1A1 state mainly decays through the D state, due to the nonadiabatic coupling between them, while the F1B1 state decays through the F1A1 state via Coriolis interaction.

Vector Boson Mass Spectrum from Extra Dimension

Based on the mechanism for mass creation in the space-time with extradimensions proposed in our previous work, (arXiv: 1301.1405 [hep-th] 2013) we consider now the mass spectrum of vector bosons in extradimensions. It is shown that this spectrum is completely determined by some function of compactification length and closely related to the metric of extradimensions.

Mass Spectrum of Dirac Equation with Local Parabolic Potential

In this paper, we solve the eigen solutions to the Dirac equation with local parabolic potential which is approximately equal to the short distance potential generated by spinor itself. The energy spectrum is quite different from that with Coulomb potential. The mass spectrum of some bary-ons is similar to this one. The angular momentum-mass relation is quite similar to the Regge trajectories. The parabolic potential has a structure of asymptotic freedom near the center and confinement at a large distance. So, the results imply that, the local parabolic potential may be more suitable for describing the nuclear potential. The procedure of solving can also be used for some other cases of Dirac equation with complicated potential.

铁路标准桥梁典型减隔震体系响应行为与谱分析方法

基于铁路标准桥梁3种典型减隔震设计体系,分析了结构的地震响应行为,重点研究了墩身质量的动力效应和减隔震体系的振型效应.结果显示:铁路标准桥梁墩身质量对桥墩的地震响应存在显著的动力效应,忽视该效应会导致墎顶位移和墎底弯矩的平均相对误差约达11%~32%,对主梁的地震位移影响较小,平均相对误差不超过5%;桥墩的地震响应主要受计算方向上的前2阶振型控制,其中第2阶振型以桥墩自振形态为主,振型阻尼可偏于安全地按结构阻尼比考虑;基于2阶振型效应的SRSS组合可以较好地考虑减隔震铁路标准桥梁的墩身质量动力效应,其预测墩底弯矩平均相对误差可下降至7.5%;AASHTO规范建议的多振型反应谱法适用于铁路标准桥梁典型减隔震体系的地震响应分析.

基于TMD的大跨度斜拉桥风致随机振动控制研究

本文开展基于TMD的大跨度桥梁风致随机振动控制研究.建立了随机风荷载作用下桥梁—TMD系统随机振动响应分析的虚拟激励分析程序.提出了随机振动响应控制的TMD参数优化方法.以西固黄河大桥为背景,开展了实际桥梁的风致振动控制分析.结果表明:基于本文方法TMD参数优化后振动控制效率可提高近9倍,横向随机位移响应的控制效率可达到28.83%,横向随机加速度响应的控制效率可达到28.8%.

改进的高压气枪震源气泡物理模型及其应用

基于可压缩气泡动力学理论,建立改进的高压气枪震源气泡物理模型,其中考虑气枪气泡系统之间的物质输运效应、气液热传导等多种影响因素.改进模型的计算结果与实验数据吻合良好,且优于传统模型.在此基础上,本文分别探究了特征参数对单枪和双枪气泡动力学特性及流场压力波的影响规律.研究表明气枪开口方式是模拟压力波首脉冲的关键因素,但是对于后续的气泡溃灭脉动压力影响较小;气枪平移运动对气泡的影响可忽略不计;气枪非同步激发可在保证压力波低频段能量不降低的前提下,在一定程度上削弱高频段能量.本研究旨在为深海资源勘探新型气枪的设计提供参考.

基于声发射频谱的次生胶结岩体加卸载损伤特性

斜坡岩体裂隙中广泛存在后期次生胶结物,地震过程中次生胶结岩体极易发育密集微裂纹。开展单轴静荷载和加卸载试验,通过声发射频谱演化特征研究荷载条件下次生胶结物对岩体微裂纹扩展过程的影响。研究结果表明:静荷载下小尺度裂纹、微小裂纹、沿晶裂纹和穿晶裂纹贯穿整个试验过程,低频高频信号对应的大尺度裂纹主要产生在不稳定扩展阶段,加卸载条件下声发射主频演化类型受到次生胶结物面积的影响,次生胶结物对岩体损伤起主要控制作用,降低了造成岩体损伤的应力阈值,加卸载作用下次生胶结物与岩石性质差异造成的非协调变形是造成损伤的根本原因。

茉莉酸调控马铃薯离体块茎发育的主要代谢物变化

【目的】茉莉酸(jasmonic acid,JA)是马铃薯块茎发育过程中重要调控激素之一,研究JA调控块茎发育机理将为块茎产量及品质性状形成提供重要理论基础。【方法】采用马铃薯离体匍匐茎作为供试材料,外源添加JA(0、0.5、5和50μmol·L^(-1))处理,分析JA诱导离体块茎表型形态、组织显微结构、碳水化合物积累及蛋白质组变化。【结果】随JA处理浓度升高,单个匍匐茎形成块茎数目、块茎直径及干鲜重、环髓区细胞面积、淀粉及可溶性糖含量在0.5和5μmol·L^(-1)JA处理后逐渐增加(P<0.05),而50μmol·L^(-1)JA处理后块茎直径及干鲜重、淀粉含量显著减少(P<0.05);脂氧合酶活性随JA浓度升高逐渐降低(P<0.05)。采用双向凝胶电泳(2-DE)和MALDI-TOF/TOF-MS质谱技术鉴定到JA调控块茎发育密切相关的35个差异表达蛋白质(P<0.05且差异表达倍数≥2.5倍),主要涉及生物能量与代谢(28.6%)、细胞防御(28.6%)、蛋白质生物合成与贮藏(11.4%)、信号转导(8.6%)、转录(8.6%)、未知功能(8.6%)和混杂(5.6%)。通过聚类分析将这些蛋白质差异表达模式聚为三类:第一类包括17个蛋白质,在0.5μmol·L^(-1)JA处理后下调表达,而在5μmol·L^(-1)JA处理后上调表达,主要参与生物能量与代谢、蛋白质生物合成与贮藏、信号转导、转录;第二类包括10个蛋白质,随JA浓度升高上调表达,主要参与细胞防御、生物能量与代谢、转录;第三类包括8个蛋白质,JA处理后均下调表达,主要参与生物能量与代谢、细胞防御、蛋白质生物合成与贮藏。【结论】低浓度JA(0.5和5μmol·L^(-1))主要通过诱导块茎环髓区细胞膨大、细胞内蔗糖及多糖积累、细胞防御能力来促进块茎形态建成,而高浓度JA(50μmol·L^(-1))则表现为抑制作用。

六种常用农药成分在茄子中残留降解动态

本研究旨在探索啶虫脒、噻虫胺、噻虫嗪、哒螨灵、联苯菊酯和高效氟氯氰菊酯在茄子中的残留降解动态,以支持食品安全和生态环境保护。通过气相色谱—三重四极杆质谱法和液相色谱—三重四极杆质谱法,检测了这些农药在茄子中的降解情况,并采用一级动力学模型拟合了降解曲线,得到了农药组分的半衰期。结果表明,农药残留降解受到农药种类、环境条件和作物种类等多重因素的影响,不同农药在茄子中的残留期有所差异。部分农药的降解需结合二级动力学模型进行深入分析,从而得到了新的拟合降解方程。本研究为茄子种植中农药的合理施用及减少农药残留提供了科学指导。

亚铁活化过硫酸盐体系对水体溶解性有机质分子转化的影响

亚铁活化过硫酸盐(PS/Fe^(2+))高级氧化是修复有机污染水体的常用技术,在修复过程中会诱导水体中溶解性有机质(DOM)分子结构转变。为研究PS/Fe^(2+)体系中DOM的分子转化特性,选取腐殖酸(HA)、富里酸(FA)和天然有机质(NOM)3种不同种类的DOM为研究对象,利用光谱和高分辨率质谱对比分析了PS/Fe^(2+)反应前后DOM的理化特性和分子结构特征。结果表明:①与热或碱活化PS体系相比,PS/Fe^(2+)反应后DOM芳香度、分子数和分子量显著下降。②反应后,DOM中残留了含C、H和O的木质素和单宁类物质,去除了O/C<0.6的低氧化程度分子,生成了富含氮和硫的高氧化程度分子。③PS/Fe^(2+)体系去除了DOM中的不饱和态分子(49.3%~94.0%),生成饱和态物质的数量、类型因DOM种类表现出明显差异。研究显示,PS/Fe^(2+)体系在自由基氧化与络合作用的共同介导下显著增加了DOM的分子转化程度,进而可能影响共存污染物的环境行为。

基于MassARRAY平台的人血小板抗原基因分型的质谱检测方法

目的:建立基于MassARRAY质谱iPLEX分析技术的人血小板抗原(human platelet antigen,HPA)基因分型方法。方法:通过文献检索HPA1-29W系统的单核苷酸多态性突变或缺失位点的信息,确定35个目的基因突变位点,按MassARRAY突变位点标示方法、引物设计固定格式和引物设计软件在线设计90条引物(正、反向扩增引物和延伸引物各30条),以12个插入HPA1-29W野生型和突变型序列的合成质粒以及50例已知HPA分型的献血者样本进行扩增和质谱检测,分析灵敏度、特异度和重复性,随机抽取15例样本的一代测序和质谱分型结果进行对比验证,建立检测方法。结果:基于MassARRAY平台的HPA基因分型的质谱检测方法与测序法检测结果相符合,灵敏度为100%,特异度为100%,重复性为100%。结论:成功建立基于MassARRAY平台的HPA1-29W系统的质谱分型方法,适合中国人群HPA分型,具有临床应用前景。