期刊文献+
共找到13,192篇文章
< 1 2 250 >
每页显示 20 50 100
Comparison between Predicted and Measured X-Ray Output in Some Conventional Radiography Units 预览
1
作者 Calvin Didier Njiki Yolande Huguette Ebele Yigbedeck +1 位作者 Joseph Eric Martial Ndjaka Manyol Thierry Ndzana Ndah 《医学物理学、临床工程、放射肿瘤学(英文)》 2019年第4期204-210,共7页
This study aims to investigate how accurate are TASMICS and TASMIP models in predicting the X-ray output of some Conventional Radiology X-ray units with high frequency generators. The X-ray output in microgray per mil... This study aims to investigate how accurate are TASMICS and TASMIP models in predicting the X-ray output of some Conventional Radiology X-ray units with high frequency generators. The X-ray output in microgray per milliampere seconds (μGy/mAs) at 100 cm from the X-ray tube was determined for selected high voltages and taking into account the total filtration. The X-ray output was then measured directly with the multi-purpose detectors (MPD), Raysafe X2. The maximum relative error between measured and predicted values was found to be equal to 20%. The maximum relative error between measured and predicted values obtained demonstrates the difficulty of accurately predicting the X-ray tube output using TASMICS and TASMIP models since they are based on fixed anode angles and different composition of the tungsten anode. 展开更多
关键词 X-RAY SPECTRA TASMICS TASMIP
在线阅读 免费下载
An improved empirical green function method to extract microseismic signals
2
作者 Dayong Yu Pan Wang 《大地测量与地球动力学:英文版》 2019年第1期42-48,共7页
In mining, reservoir impoundment and hydraulic fracturing exploitation, the induced microseismic clusters may present complex waveforms at receivers since the individual events generally arrive very close. And the rou... In mining, reservoir impoundment and hydraulic fracturing exploitation, the induced microseismic clusters may present complex waveforms at receivers since the individual events generally arrive very close. And the routine methods for arrival picking are insufficiently efficient due to these strong influences. Here, we modified the empirical green function method and applied it to extract the green functions and the radiation coefficients of microseismic events with the largest energy in clusters.Multiple-channel records were used to estimate an 'average' source spectrum and then the 'average' source wavelet was removed from the records by deconvolution. We applied this method to the real data,and the result indicated clear improvement in extracting the dominant event of the clusters. 展开更多
关键词 Microseismic SIGNALS Empirical green FUNCTION SOURCE SPECTRA
Influence of annealing treatment on the luminescent properties of Ta:β-Ga2O3 single crystal
3
作者 余小威 崔慧源 +2 位作者 朱茂东 夏志林 赛青林 《中国物理B:英文版》 SCIE EI CAS CSCD 2019年第7期475-478,共4页
Ta5+doped β-Ga2O3 single crystals were grown by using the optical floating zone method, and then annealed in the air and nitrogen gas at 1400℃ for 20 hours.The transmittance spectra, photoluminescence(PL), x-ray irr... Ta5+doped β-Ga2O3 single crystals were grown by using the optical floating zone method, and then annealed in the air and nitrogen gas at 1400℃ for 20 hours.The transmittance spectra, photoluminescence(PL), x-ray irradiation spectra, and PL decay profiles of the samples were measured at room temperature.The relevant results show that the optical transmittance of the samples annealed in the air or nitrogen gas was improved.By drawing the(ahv)2–hv graph,it can be seen that the band gap decreased after being annealed in the air, but increased in nitrogen gas.The PL spectra and x-ray irradiation spectra show that the luminescent intensity of the sample annealed in the air increased substantially,while decreased for the sample annealed in nitrogen.The PL decay time of the Ta:β-Ga2O3 annealed in the air increased significantly compared with that of the Ta:β-Ga2O3 sample without annealing, but the tendency after annealing in nitrogen gas was opposite. 展开更多
关键词 Ta:β-Ga2O3 FLOATING zone method TRANSMITTANCE spectra ANNEALING
兴城地区岩石光谱特征与物性参数、金属元素间响应关系研究 预览
4
作者 杨长保 刘娜 郐开富 《光谱学与光谱分析》 SCIE EI CAS CSCD 北大核心 2019年第9期2953-2965,共13页
岩石物性参数、元素含量和光谱特征三者之间的相互关系并非独立存在,研究三者之间的相互关系,对于探索通过遥感信息进行岩石矿物成分、物性参数的定量反演方法奠定基础。采集了兴城地区590块岩样本,分析其物性参数(密度、介电常数、电... 岩石物性参数、元素含量和光谱特征三者之间的相互关系并非独立存在,研究三者之间的相互关系,对于探索通过遥感信息进行岩石矿物成分、物性参数的定量反演方法奠定基础。采集了兴城地区590块岩样本,分析其物性参数(密度、介电常数、电阻率、磁化率)、金属成分含量(Fe,Ti,V,Mn,Zr,Co,Zn,Nb,Bi,Pb)以及岩石光谱之间的关系。将各物化参数与原始光谱、光谱吸收深度、光谱小波包分解后的高低频做相关性分析,找出各物化参数影响光谱吸收和反射的特征波段,探究关系密切的参数。该研究为岩石岩性分类、某种金属元素和物理特性的反演以及用某种参数来预测关系密切的参数奠定了基础,取得如下结论:(1)获得了火成岩中Fe,Ti,Mn,V,Zn,Bi和Pb等元素的特征谱带,其中Fe元素含量更高,与光谱的相关性更显著。在0.4和0.54μm波段附近存在Fe的特征反射波段,1.0~1.5μm波段范围内存在Fe元素的特征吸收波段;在0.4~0.55和0.6~0.65μm波段范围内,Ti元素与光谱的相关性更显著,在2.28μm波段附近存在Ti的特征吸收波段;在0.41μm波段附近存在Mn的特征反射波段;火成岩、沉积岩V元素与光谱相关性差异性较大,在0.76,0.81,0.89,0.95μm波段附近可能存在火成岩的特征吸收波段和沉积岩的特征反射波段;沉积岩的Zn元素含量与光谱的相关性比火成岩要显著,在0.41,1.36,1.59μm波段附近可能存在火成岩Zn的特征反射波段,在2.34μm波段附近可能存在沉积岩Zn的特征波段;2.14μm波段附近,Bi元素对沉积岩光谱的吸收有一定的作用;Pb的特征谱带可能存在于0.45,0.54,2.29μm附近;(2)在岩石各物理特性和光谱的关系研究中,在0.57~0.85μm波段范围内,密度对光谱有很好的吸收反射特征,在0.53μm波段附近,磁化率使光谱有较强的反射,在1.08μm波段附近,磁化率使光谱产生较强的吸收;电阻率和光谱的相关关系与密度和光谱的� 展开更多
关键词 物性参数 金属元素 光谱 相关系数 高低频
在线阅读 下载PDF
Measurement of the prompt neutron spectrum from thermalneutron- induced fission in U-235 using the recoil proton meth 预览
5
作者 Tie He Pu Zheng Jun Xiao 《核技术:英文版》 SCIE CAS CSCD 2019年第7期68-76,共9页
A measurement of the ^235U prompt fission neutron spectrum (PFNS) by the recoil proton method was performed at the Institute of Nuclear Physics and Chemistry, China. Details of the method, which include the calculatio... A measurement of the ^235U prompt fission neutron spectrum (PFNS) by the recoil proton method was performed at the Institute of Nuclear Physics and Chemistry, China. Details of the method, which include the calculation and validation of the response matrix, are presented. The PFNS for ^235U in the energy range 1–12 MeV, induced by thermal neutrons, was obtained. The measured spectrum in the low-energy region was in good agreement with previous work and the ENDF/B-VII library, except for minor differences. In the high-energy region, however, the relative height of the measured spectrum was greater, and an analysis of the experiment indicated uncertainties of 13% at 10 MeV and 24% at 12 MeV. Experimental results showed that the recoil proton method could be used to measure prompt fission neutron spectra. Some directions for future work are included. 展开更多
关键词 PROMPT FISSION NEUTRON spectra RECOIL PROTON method Response matrix U-235
在线阅读 下载PDF
A zinc(Ⅱ) MOF based on secondary building units of infinite wavy-shaped chain exhibiting obvious luminescent sense effects
6
作者 Kai Li Kunhuan He +3 位作者 Quanwen Li Bin Xia Qinglun Wang Yinghui Zhang 《中国化学快报:英文版》 SCIE CAS CSCD 2019年第2期499-501,共3页
A new metal-organic framework (MOF),{[Zn7 (BPS)4 (OH)6 (H2O)2]·5 H2O]n}(1), (H2 BPS=4,4′-bibenzoic acid-2,2′-sulfone), based on a wavy and infinite chain-shaped secondary building units, has been synthesized un... A new metal-organic framework (MOF),{[Zn7 (BPS)4 (OH)6 (H2O)2]·5 H2O]n}(1), (H2 BPS=4,4′-bibenzoic acid-2,2′-sulfone), based on a wavy and infinite chain-shaped secondary building units, has been synthesized under solvothermal conditions and characterized by single crystal X-ray diffraction and further confirmed by PXRD, TGA and IR spectrum. The solid-state emission spectra reveal that compound 1 presents strong luminescence emission bands at room temperature. The fluorescent properties of compound 1 in diverse organic solvents indicated that 1 has palpable luminescent sense effects for DMF and DMAC. 展开更多
关键词 METAL-ORGANIC frameworks Secondary building unit SOLID-STATE emission spectra Fluorescent properties LUMINESCENT SENSE EFFECTS
Three-dimensional mapping of intertrochanteric fracture lines
7
作者 Ming Li Zhi-Rui Li +8 位作者 Jian-Tao Li Ming-Xing Lei Xiu-Yun Su Guo-Qi Wang Hao Zhang Gao-Xiang Xu Peng Yin Li-Cheng Zhang Pei-Fu Tang 《中华医学杂志:英文版》 SCIE CAS CSCD 2019年第21期2524-2533,共10页
Background:Available research about the anatomic patterns of intertrochanteric fractures is lacking,and fracture mapping has not previously been performed on intertrochanteric fractures.This study aimed to determine t... Background:Available research about the anatomic patterns of intertrochanteric fractures is lacking,and fracture mapping has not previously been performed on intertrochanteric fractures.This study aimed to determine the major trajectories of intertrochanteric fracture lines using computed tomography data from a series of surgically treated patients.Methods:In this study,504 patients with intertrochanteric fractures were retrospectively analyzed.Fracture patterns were graded according to Arbeitsgemeinschaft für Osteosynthesefragen(AO)classification.Fracture lines were transcribed onto proximal femoral templates and graphically superimposed to create a compilation of fracture maps that were subsequently divided into anterior,posterior,lateral,and medial fracture maps to create a three-dimensional(3D)pattern by reducing fragments in the 3D models.The fracture maps were then converted into frequency spectra.The major fracture patterns were assessed by focusing on the lateral femoral wall,lesser trochanter,intertrochanteric crest,and inner cortical buttress.Results:Anterior,posterior,lateral,and medial fracture maps were created.The majority of fracture lines(85.9%,433/504)on the anterior maps were along the intertrochanteric line where the iliofemoral ligament was attached.In the medial plane,the majority of fracture lines(49.0%,247/504)shown on the frequency spectrum included the turning point involving the third quadrant.In the posterior plane,the majority of fracture lines(52.0%,262/504)involved the intertrochanteric crest from the greater to the lesser trochanter.In the lateral plane,the majority of fracture lines(62.7%,316/504)involved the greater trochanter at the gluteus medius attachment.Conclusions:The fracture patterns observed in the present study might be used to describe morphologic characteristics and aid with management strategies.Further classifications or modifications that incorporate the fracture patterns identified in this study may be used in future research. 展开更多
关键词 Intertrochanteric fracture Fracture pattern Frequency spectra Computed tomography data CLASSIFICATION
Quantum Chemical Vibrational Study,FTIR and FT-Raman Spectra of 1,3-Diphenyl Propenone 预览
8
作者 Revathi Haldorai M.Thirumalaikumar +2 位作者 S.Sampathkrishnan C.Charanya N.Balamurugan 《光谱学与光谱分析》 SCIE EI CAS CSCD 北大核心 2019年第12期3932-3939,共8页
The Fourier Transform Infrared(FTIR)and Fourier transform Raman(FT-Raman)spectra of 1,3-Diphenyl Propenone were recorded in the regions 4000~400 and 4000~100 cm^-1,respectively,in the solid phase.Molecular electronic ... The Fourier Transform Infrared(FTIR)and Fourier transform Raman(FT-Raman)spectra of 1,3-Diphenyl Propenone were recorded in the regions 4000~400 and 4000~100 cm^-1,respectively,in the solid phase.Molecular electronic energy,geometrical structure,harmonic vibrational spectra was computed at the DFT/6-31G(d,p)and three parameter hybrid functional Lee-Yang-Parr/6-31G(d,p)levels of theory.The vibrational studies were interpreted in terms of potential energy distribution(PED).The results were compared with experimental values with the help of scaling procedures.Most of the modes have wave numbers in the expected range and are in good agreement with computed values and also the molecular properties of Mulliken population analysis have been calculated.Besides,thermodynamic properties were performed. 展开更多
关键词 FTIR FT-RAMAN Vibrational spectra PED
在线阅读 下载PDF
Temperature-dependent Raman scattering and photoluminescence in YBa2Cu3O7 doped with SiO2 and Zn0.95Mn0.05O nanoparticles:comparative study
9
作者 Munirah A. Al Messiere 《稀有金属:英文版》 SCIE EI CAS CSCD 2019年第8期754-763,共10页
A combined study examining the temperature dependencies of Raman scattering and photoluminescence(PL)of a YBa2 Cu3 O7(YBCO)matrix doped with SiO2(12 nm;0.01 wt%.,0.10 wt%)and Zn0.95Mn0.05O(20 nm;0.02 wt%,0.10 wt%)nano... A combined study examining the temperature dependencies of Raman scattering and photoluminescence(PL)of a YBa2 Cu3 O7(YBCO)matrix doped with SiO2(12 nm;0.01 wt%.,0.10 wt%)and Zn0.95Mn0.05O(20 nm;0.02 wt%,0.10 wt%)nanoparticles was presented.X-ray diffraction(XRD)analysis confirms that both YBCO types exhibit aperovskite structure with the orthorhombic Pmmm phase.The microstructure was examined using environmental scanning electron microscopy(ESEM).Raman scattering and photoluminescence measurements as functions of temperature were conducted in the 77-837 K range.The photoluminescence intensity is observed to decrease for the doped YBCO than for the pure YBCO,because of localized defects.The photoluminescence spectrum is primarily composed of three bands at 1.60,1.88,and 2.40 eV.A clearly pronounced correlation is observed between electronic and structural changes in the doped YBCO,which is due to the temperature,illumination,added oxygen or metal ions,and spectral parameters.The PL integrated intensity as a function of the inverse temperature was simulated using the Arrhenius model.This analysis reveals that the energy exchange between the different levels in the pure and doped YBCO was conducted via two vibration modes only,which are strongly linked to the oxygen and copper atoms in the YBCO matrix.The temperature dependencies of the modes at 340 and 500 cm-1 exhibit softening with temperature increase,resulting from microstructure control,which may be due to small concentrations of Si,Zn,and Mn substitutions at the chain Cu(1)and plane Cu(2)sites. 展开更多
关键词 Matrix YBA2CU3O7 NANOPARTICLES RAMAN scattering RAMAN modes PHOTOLUMINESCENCE spectra
Site dependent and spatially varying response spectra 预览
10
作者 Hakima Djilali Berkane Zamila Harichane +1 位作者 Erkan Celebi Sidi Mohammed Elachachi 《地震工程与工程振动:英文版》 SCIE EI CSCD 2019年第3期497-509,共13页
The goal of this study is to provide a stochastic method to investigate the eff ects of the randomness of soil properties due to their natural spatial variability on the response spectra spatial variation at sites wit... The goal of this study is to provide a stochastic method to investigate the eff ects of the randomness of soil properties due to their natural spatial variability on the response spectra spatial variation at sites with varying conditions. For this purpose, Monte Carlo Simulations are used to include the variability of both incident ground motion and soil parameters in the response spectra by mean of an appropriate coherency loss function and a site-dependent transfer function, respectively. The approach is built on the assumption of vertical propagation of SH type waves in soil strata with uncertain parameters. The response spectra are obtained by numerical integration of the governing equation of a single-degree-of-freedom (SDOF) system under non-stationary site-dependent and spatially varying ground motion accelerations simulated with non-uniform spectral densities and coherency loss functions. Numerical examples showed that randomness of soil properties signifi cantly aff ects the amplitudes of the response spectra, indicating that as the heterogeneity induced by the randomness of the parameters of the medium increases, the spectral ordinates attenuate. 展开更多
关键词 response SPECTRA RANDOMNESS SPECTRAL density MONTE Carlo
在线阅读 下载PDF
Effect of site amplifi cation on inelastic seismic response 预览
11
作者 Adhikary S Singh Y 《地震工程与工程振动:英文版》 SCIE EI CSCD 2019年第3期535-554,共20页
The available models for eff ective periods of site and structure are reviewed in context of frequency tuning in the inelastic seismic response of soil-structure system. The eff ect of seismic intensity and ductility ... The available models for eff ective periods of site and structure are reviewed in context of frequency tuning in the inelastic seismic response of soil-structure system. The eff ect of seismic intensity and ductility demand, on the eff ective periods, is investigated, and inelastic site amplifi cation is shown to be strongly correlated to the normalized eff ective period. Two non-dimensional parameters, analogous to the conventional site amplifi cation factors in codes, are defi ned to quantify the inelastic site amplifi cation. It is shown that the inelastic site amplifi cation factor (i.e. ratio of constant ductility spectral ordinates at soil site to those at rock outcrop) is able to represent the site eff ects more clearly, as compared to the inelastic site amplifi cation ratio (i.e. ratio of inelastic spectral ordinates at soil site to the corresponding elastic spectral ordinates at rock outcrop). Further, the peak in the amplifi cation factor corresponding to the eff ective site period diminishes rapidly with increasing ductility demand. 展开更多
关键词 SITE amplifi CATION normalized RESPONSE SPECTRA eff ective period INELASTIC SEISMIC RESPONSE INELASTIC SITE amplifi CATION factor
在线阅读 下载PDF
Optical phonon behavior and magnetism of columbite Zn0.8Co0.2Nb2O6
12
作者 李亮 王晓晗 +3 位作者 刘莹 李芳菲 周强 崔田 《中国物理B:英文版》 SCIE EI CAS CSCD 2019年第12期56-59,共4页
Columbite Zn0.8Co0.2Nb2O6 crystals were grown by optical floating zone methods. The x-ray diffraction(XRD) was used to check the structure information of the grown Zn0.8Co0.2Nb2O6 crystal. The room temperature and tem... Columbite Zn0.8Co0.2Nb2O6 crystals were grown by optical floating zone methods. The x-ray diffraction(XRD) was used to check the structure information of the grown Zn0.8Co0.2Nb2O6 crystal. The room temperature and temperature-dependent Raman spectra were tested to investigate the optical phonon behaviors of columbite Zn0.8Co0.2Nb2O6, which exhibited a temperature stable property. The magnetics properties of Zn0.8Co0.2Nb2O6, measured by a physical property measurement system(PPMS), were also presented in this work. 展开更多
关键词 columbite Zn0.8Co0.2Nb2O6 optical floating zone methods Raman spectra magnetics properties
Synthesis, Crystal Structure, Thermal Stability and Solid UV-Vis Absorption Spectra of One New Copper(Ⅱ) Coordination Polymer 预览
13
作者 薛丽平 《结构化学》 SCIE CAS CSCD 2019年第9期1537-1542,共6页
A new coordination polymer [Cu2(OH)(nbta)(tib)(H2 O)2]n(1, H3 nbta = 5-nitro-1,2,3-benzenetricarboxylic acid, tib = 1-(4 H-1,2,4-triazol-4-yl)-4-(imidazol-1-yl)benzene) constructed from dimeric Cu(Ⅱ) units has been s... A new coordination polymer [Cu2(OH)(nbta)(tib)(H2 O)2]n(1, H3 nbta = 5-nitro-1,2,3-benzenetricarboxylic acid, tib = 1-(4 H-1,2,4-triazol-4-yl)-4-(imidazol-1-yl)benzene) constructed from dimeric Cu(Ⅱ) units has been synthesized under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction analysis. The compound crystallizes in monoclinic system, space group I2/c, with a = 17.8474(9), b = 11.7588(6), c = 21.9221(11) ?, β = 104.419(5)°, V = 4455.7(4) ?3 and Z = 8. Compound 1 is a three-dimensional structure constructed from dimeric Cu(Ⅱ) units and presents a 2-nodal(3,5)-connected net. Moreover, the thermal stability and solid UV-Vis absorption spectra have been investigated. 展开更多
关键词 COPPER COORDINATION polymer crystal structure TOPOLOGY UV–Vis absorption SPECTRA
在线阅读 下载PDF
关于恒定列和矩阵谱隙的一个估计 预览
14
作者 何建锋 《湖北民族学院学报:自然科学版》 CAS 2019年第1期54-58,共5页
通过对恒定列(行)和矩阵性质的讨论,给出一个正恒定列和矩阵谱隙的估计式,该估计式的计算只涉及矩阵元素,计算简便.
关键词 矩阵 特征值 恒定列和
在线阅读 免费下载
Study on the Physical and Dissociation Properties of Disulfur Dichloride under Electric Fields 预览
15
作者 瞿荧飞 刘玉柱 +2 位作者 尹文怡 张启航 布玛丽亚·阿布力米提 《结构化学》 SCIE CAS CSCD 2019年第8期1241-1250,共10页
Disulfur dichloride is a hazardous substance, which is irritating to the eyes. It is significant to study the physical and dissociation properties under external electric fields. The bond length, energy, dipole moment... Disulfur dichloride is a hazardous substance, which is irritating to the eyes. It is significant to study the physical and dissociation properties under external electric fields. The bond length, energy, dipole moment, orbital energy level distribution, infrared spectra and dissociation properties of disulfur dichloride molecule under different external fields are obtained by using the density functional theory at the B3LYP/6-311++G(d, p) basis set level. In addition, ultraviolet-visible absorption spectra of the molecule in different electric fields are studied with configuration interaction-single excitation(CIS)/6-311++G(d, p) method. According to the results, it has been found that as the electric field exerted along the positive direction of the z-axis increases, the two sulfur-chlorine(S-Cl) bond lengths become longer and tend to break, while the sulfur-sulfur(S-S) bond length becomes shorter and the energy gap decreases. The infrared spectrum and ultraviolet-visible absorption spectra both exhibit red shift under electric field. Moreover, by scanning the potential energy surface of disulfur dichloride about S-Cl bond, the dissociation barrier decreases with the increase of positive electric field. When the external electric field arrives at 0.040 atomic units, the barrier disappears, meaning the dissociation of disulfur dichloride. The present results offer an important reference to further study of disulfur dichloride. 展开更多
关键词 disulfur DICHLORIDE DENSITY FUNCTIONAL theory EXTERNAL electric field SPECTRA DISSOCIATION
在线阅读 下载PDF
3种蝈螽鸣声结构的比较研究 预览
16
作者 孙雅梅 刘菲 陈刘生 《石河子大学学报:自然科学版》 北大核心 2019年第5期565-569,共5页
研究了优雅蝈螽Gampsocleis gratiosa、暗褐蝈螽Gampsocleis sedakovii及秃毛蝈螽Gampsocleis glabra 3种螽斯雄性的鸣声。优雅蝈螽鸣声是由振幅高低不同的2类脉冲组构成的脉冲序列,一系列的脉冲组间隔重复出现,其中,第1类脉冲组有9~10... 研究了优雅蝈螽Gampsocleis gratiosa、暗褐蝈螽Gampsocleis sedakovii及秃毛蝈螽Gampsocleis glabra 3种螽斯雄性的鸣声。优雅蝈螽鸣声是由振幅高低不同的2类脉冲组构成的脉冲序列,一系列的脉冲组间隔重复出现,其中,第1类脉冲组有9~10个脉冲,第2类脉冲组有10~11个脉冲,鸣声的主能峰频率约7.75 kHz,次能峰频率约4 kHz;暗褐蝈螽鸣声由一系列振幅高低不同的2类脉冲组构成,第1类脉冲组有2个脉冲,第2类脉冲组也有2个脉冲,鸣声的主能峰频率为10.50 kHz,次能峰频率为5.75 kHz;秃毛蝈螽鸣声由2类振幅高低不同的脉冲组构成,第1类脉冲组振幅较大,有1个脉冲,第2类振幅较小,有4~5个脉冲,鸣声的主能峰频率约9.1 kHz,次能峰频率不明显。 展开更多
关键词 蝈螽 鸣声结构 时域 频域
在线阅读 免费下载
Absorption Spectra Calculation of Torus-type C120 and Its Nitrogen Doped Derivatives 预览
17
作者 范广 周彩华 谢茹玉 《结构化学》 SCIE CAS CSCD 2019年第3期434-438,共5页
The absorption spectra of torus-type C120 and its derivatives doped by nitrogen(C119N, C118N2, C115N5) have been investigated based on the density functional theory. The longest absorption band of torus-type C120 can ... The absorption spectra of torus-type C120 and its derivatives doped by nitrogen(C119N, C118N2, C115N5) have been investigated based on the density functional theory. The longest absorption band of torus-type C120 can arrive at the near IR fields. For three derivatives doped by nitrogen, doped nitrogen atoms can induce the longer absorption band, and the more numbers of nitrogen atoms are doped in torus-type C120, the longer absorption band can be induced. 展开更多
关键词 torus-type C120 photodynamic therapy ABSORPTION SPECTRA
在线阅读 下载PDF
The Longnan MS5. 5 Earthquake on September 12, 2008:A Very Shallow Event Probably Triggered by the Wenchuan Earthquake 预览
18
作者 LUO Xinyu ZENG Xiangfang +3 位作者 DONG Peiyu ZHOU Yong WEI Xing CHENG Huihong 《中国地震研究:英文版》 CSCD 2019年第3期403-417,共15页
The 2008 Wenchuan earthquake has a significant impact on the seismicity of nearby regions. The Longnan earthquake which occurred on September 12,2008 in Gansu Province was out of the aftershock zone. Reliable source p... The 2008 Wenchuan earthquake has a significant impact on the seismicity of nearby regions. The Longnan earthquake which occurred on September 12,2008 in Gansu Province was out of the aftershock zone. Reliable source parameters are essential for understanding the seismogenic process of this earthquake. Therefore,three approaches are adopted to study the source parameters of this event. The focal mechanism is obtained with the g CAP method that takes non-Double-Couple(non-DC)component into account. The two fault planes are NP1:150°/45°/81° and NP2:342°/45°/98°,while the non-DC component is about 53%. The focal depth is 1. 6 km,which indicates the Longnan earthquake is a shallow event. Furthermore,this result is also in good agreement with results obtained with two other approaches:amplitude spectra of Rayleigh wave and surface displacement from In SAR measurement. To analyze the cause of the event,coulomb failure stress change caused by the Wenchuan earthquake on the Longnan earthquake fault plane is calculated. The result shows that coulomb stress change is 30 k Pa around the Longnan earthquake hypocenter,which exceeds the typical triggering threshold of 10 k Pa. The research indicates that the Wenchuan earthquake probably promote the happening of the Longnan earthquake. 展开更多
关键词 Longnan earthquake Source parameter Rayleigh wave amplitude spectra Surface displacement Coulomb failure stress
在线阅读 免费下载
Synthesis, Crystal Structure and DNA-Binding Property of a Mn(Ⅱ) Complex Based on 5-(Tri-fluoromethyl)pyridine-2-carboxylic Acid 预览
19
作者 王嘉恺 李冰 +2 位作者 武焕平 田晓燕 麻晓霞 《结构化学》 SCIE CAS CSCD 2019年第8期1349-1355,共7页
A new complex Mn(Htpc)2(H2O)2(1, Htpc = 5-(trifluoromethyl)pyridine-2-carboxylic acid) has been synthesized and characterized by elemental analysis, IR, TG and single-crystal X-ray diffraction. 1 belongs to triclinic ... A new complex Mn(Htpc)2(H2O)2(1, Htpc = 5-(trifluoromethyl)pyridine-2-carboxylic acid) has been synthesized and characterized by elemental analysis, IR, TG and single-crystal X-ray diffraction. 1 belongs to triclinic system, space group P■ with a = 5.0885(10), b = 6.5574(13), c = 14.016(3) ?, β = 90.67(3)o, V = 436.34(17) ?3, Z = 1, Dc = 1.793 g·cm-3, μ = 0.855 mm-1, Mr = 471.18, F(000) = 235, the final R = 0.0454 and wR = 0.1134 for 1998 observed reflections with I > 2σ(I). The Mn(Ⅱ) ion is coordinated by two N and two O atoms from two Htpc as well as two O atoms from two coordinated water molecules, forming a 0D motif with distorted octahedral coordinate geometry. The adjacent 0D units are linked into 1D chains through hydrogen bond O(1W)–H(1 WB)···O(2), and via the O(1 W)–H(1 WA)···O(1) hydrogen bond the neighboring 1D chains are connected into a 2D supramolecular layer. Moreover, the interactions between the ligand and its complex with CT-DNA were studied by EtBr fluorescence probe, which suggested that these compounds bind to CT-DNA through an intercalation mode. The binding constants were 0.41 and 0.64 for Htpc and complex 1, respectively. It indicates that the interaction between complex 1 and CT-DNA is stronger than Htpc. 展开更多
关键词 5-(trifluoromethyl)pyridine-2-carboxylic acid crystal structure DNA fluorescence SPECTRA
在线阅读 下载PDF
Ab initio investigation of excited state dual hydrogen bonding interactions and proton transfer mechanism for novel oxazoline compound
20
作者 王玉生 贾敏 +2 位作者 张巧丽 宋晓燕 杨大鹏 《中国物理B:英文版》 SCIE EI CAS CSCD 2019年第10期309-314,共6页
Owing to the importance of excited state dynamical relaxation, the excited state intramolecular proton transfer(ESIPT) mechanism for a novel compound containing dual hydrogen bond(abbreviated as "1-enol") is... Owing to the importance of excited state dynamical relaxation, the excited state intramolecular proton transfer(ESIPT) mechanism for a novel compound containing dual hydrogen bond(abbreviated as "1-enol") is studied in this work.Using density functional theory(DFT) and time-dependent density functional theory(TDDFT) method, the experimental electronic spectra can be reproduced for 1-enol compound. We first verify the formation of dual intramolecular hydrogen bonds, and then confirm that the dual hydrogen bond should be strengthened in the first excited state. The photo-excitation process is analyzed by using frontier molecular orbital(HOMO and LUMO) for 1-enol compound. The obvious intramolecular charge transfer(ICT) provides the driving force to effectively facilitate the ESIPT process in the S1 state. Exploration of the constructed S0-state and S1-state potential energy surface(PES) reveals that only the excited state intramolecular single proton transfer occurs for 1-enol system, which makes up for the deficiencies in previous experiment. 展开更多
关键词 excited state INTRAMOLECULAR PROTON TRANSFER potential energy surface INTRAMOLECULAR charge TRANSFER infrared VIBRATIONAL spectra
上一页 1 2 250 下一页 到第
使用帮助 返回顶部 意见反馈
新型冠状病毒肺炎防控与诊疗专栏