The chemical bonding nature of rare earth（RE） elements can be studied by a quantitative analysis of electron domain of an atom. The outer electrons of RE elements are within the valence shell 4f^（0-14）5d^（0-1）6s...The chemical bonding nature of rare earth（RE） elements can be studied by a quantitative analysis of electron domain of an atom. The outer electrons of RE elements are within the valence shell 4f^（0-14）5d^（0-1）6s^2, which are involved in all chemical bonding features. We in this work found that the chemical bonding characteristics of 4f electrons are a kind of hybridizations, and classified them into three types of chemical bonding of 4f^（0-14）5d^（0-1）6s^2, furthermore, the coordination number ranging from 2 to 16 could thus be determined. We selected Y（NO_3）_3, La（NO_3）_3, Ce（NO_3）_3, YCl_3, LaCl_3, and CeCl_3 as examples to in-situ observe their IR spectra of chemical bonding behaviors of Y^（3＋）, La^（3＋） and Ce^（3＋） cations, which could show different chemical bonding modes of 4f and 5d electrons. In the present study, we obtained the direct criterion to confirm whether 4f electrons can participate in chemical bonding, that is, only when the coordination number of RE cations is larger than 9.展开更多
Magnetotactic bacteria(MTB)are morphologically and phylogenetically diverse prokaryotes commonly able to produce magnetic nanocrystals within intracellular membrane-bound organelles(i.e.,magnetosomes)and to swim along...Magnetotactic bacteria(MTB)are morphologically and phylogenetically diverse prokaryotes commonly able to produce magnetic nanocrystals within intracellular membrane-bound organelles(i.e.,magnetosomes)and to swim along geomagnetic field lines.We studied the diversity of MTB in the samples collected from a mangrove area in the Sanya River,Hainan,South China,using microscopic and microbial phylogenetic methods.Results of microanalysis and observation in microscopy and energy dispersive X-ray spectroscopy(EDXS)reveal a highly morphological diversity of MTB including unicellular cocci,vibrios,rod-shaped bacteria,and three morphotypes of multicellular magnetotactic prokaryotes(MMPs).In addition,analysis of the 16S rRNA gene showed that these MTB were clustered into 16 operational taxonomic units affi liated to the Alpha-,Delta-,and Gamma-proteobacteria classes within the Proteobacteria phylum.Meanwhile,by using the coupled fluorescence and transmission electron microscopy analysis,rodshaped bacteria,vibrio,and cocci were phylogenetically and structurally identified at the single-cell level.This study demonstrated highly diverse MTB communities in the mangrove ecosystem and provide a new insight into the overall diversity of MTB.展开更多
The study of various oxidation states of chromium with Sargassum <i>sp</i>. is of particular interest since hexavalent chromium </span><span style="font-size:10.0pt;font-family:""&g...The study of various oxidation states of chromium with Sargassum <i>sp</i>. is of particular interest since hexavalent chromium </span><span style="font-size:10.0pt;font-family:"">is </span><span style="font-size:10.0pt;font-family:"">reduced to trivalent chromium in </span><span style="font-size:10.0pt;font-family:"">an </span><span style="font-size:10.0pt;font-family:"">aqueous solution. In this study, a systematic density functional theory (DFT) calculations were performed to study the interactions of transition metal chromium ion with different oxidation states and spin states with the <i>Sar</i></span><i><span style="font-size:10.0pt;font-family:"">gassum sp</span></i><span style="font-size:10.0pt;font-family:"">. decorated with carboxylate</span><span style="font-size:10.0pt;font-family:""> </span><span style="font-size:10.0pt;font-family:"">(acetate) at the wB97XD/6-311++</span><span style="font-size:10.0pt;font-family:""> </span><span style="font-size:10.0pt;font-family:"">G(d,p)</span><span style="font-size:10.0pt;font-family:""> </span><span style="font-size:10.0pt;font-family:"">level of theory. The structures and binding energies of chromium met<span>al</span></span><span style="font-size:10.0pt;font-family:"">-</span><span style="font-size:10.0pt;font-family:"">carboxylate complexes at various oxidation states and spin states in gas</span><span style="font-size:10.0pt;font-family:""> phase were examined. The coordination strength of Cr(VI) with the acetate <span>ligand was predominantly the strongest compare</span></span><span style="font-size:10.0pt;font-family:"">d</span><span style="font-size:10.0pt;font-family:""> to the other oxidation</span><span style="font-size:10.0pt;font-family:""> states. <span>Vibrational frequency analysis, for the homoleptic monomers of tris</span> <span>[</span><span>Cr<sup>III</sup>(AC)<sub>3</sub>]<sup>0</sup> and </span>[Cr<sup>VI</sup>(AC)<sub>3</sub>]<sup>3+</sup> complexes, illustrate good harmony with the experimental and<span> theoretical calculated frequencies. Using the time</span></span><span style="font-size:10.0pt;font-family:"">-</span><span style="font-size:10.0pt;font-family:"">dependent DFT</span><span style="font-size:10.0pt;font-family:""> (TD-DFT) at the level of CAM-B3LYP/6-311++G(d,p), the vertical excitation energies were obtained. The stabilization energies derived using the second order perturbation </span><span style="font-size:10.0pt;font-family:"">theory, <i>E</i><sub>ij</sub><sup>(2)</sup>, of NBO analysis confirmed the greater charge transfer for the</span><span style="font-size:10.0pt;font-family:""> observed trends in the metal binding. The calculated binding </span><span style="font-size:10.0pt;font-family:"">energies</span><span style="font-size:10.0pt;font-family:""> </span><span style="font-size:10.0pt;font-family:"">(ΔE) and interactions energies </span><span style="font-size:10.0pt;font-family:Symbol;">S</span><i><span style="font-size:10.0pt;font-family:"">E</span></i><sub><span style="font-size:10.0pt;font-family:"">ij</span></sub><sup><span style="font-size:10.0pt;font-family:"">(2)</span></sup><span style="font-size:10.0pt;font-family:""> favor</span><span style="font-size:10.0pt;font-family:""> </span><span style="font-size:10.0pt;font-family:"">the formation of</span><span style="font-size:10.0pt;font-family:""> [Cr<sup>VI</sup>(AC)<sub>3</sub>]<sup>3+</sup> complexes. The findings of this study identify efficient electronic factors as major contributors to the metal binding affinities, with promising possibilities for the design of metal-ligand complexes and sensing of the metal ions.展开更多
The silicon-strip tracker of the China Seismo-Electromagnetic Satellite（CSES） consists of two doublesided silicon strip detectors（DSSDs） which provide incident particle tracking information.A low-noise analog ASIC...The silicon-strip tracker of the China Seismo-Electromagnetic Satellite（CSES） consists of two doublesided silicon strip detectors（DSSDs） which provide incident particle tracking information.A low-noise analog ASIC VA140 was used in this study for DSSD signal readout.A beam test on the DSSD module was performed at the Beijing Test Beam Facility of the Beijing Electron Positron Collider（BEPC） using a 400–800 MeV/c proton beam.The pedestal analysis results,RMSE noise,gain correction,and intensity distribution of incident particles of the DSSD module are presented.展开更多
基金supported by the National Natural Science Foundation of China(51125009,91434118,21401185,21521092)Hundred Talents Program of Chinese Academy of SciencesJilin Province Science and Technology Development Project(20170101092JC,20160520006JH)
文摘The chemical bonding nature of rare earth（RE） elements can be studied by a quantitative analysis of electron domain of an atom. The outer electrons of RE elements are within the valence shell 4f^（0-14）5d^（0-1）6s^2, which are involved in all chemical bonding features. We in this work found that the chemical bonding characteristics of 4f electrons are a kind of hybridizations, and classified them into three types of chemical bonding of 4f^（0-14）5d^（0-1）6s^2, furthermore, the coordination number ranging from 2 to 16 could thus be determined. We selected Y（NO_3）_3, La（NO_3）_3, Ce（NO_3）_3, YCl_3, LaCl_3, and CeCl_3 as examples to in-situ observe their IR spectra of chemical bonding behaviors of Y^（3＋）, La^（3＋） and Ce^（3＋） cations, which could show different chemical bonding modes of 4f and 5d electrons. In the present study, we obtained the direct criterion to confirm whether 4f electrons can participate in chemical bonding, that is, only when the coordination number of RE cations is larger than 9.
基金Supported by the Project of Academy Locality Science and Technology Cooperation of Sanya City,China(No.2014YD02)the National Natural Science Foundation of China(No.41920104009)。
文摘Magnetotactic bacteria(MTB)are morphologically and phylogenetically diverse prokaryotes commonly able to produce magnetic nanocrystals within intracellular membrane-bound organelles(i.e.,magnetosomes)and to swim along geomagnetic field lines.We studied the diversity of MTB in the samples collected from a mangrove area in the Sanya River,Hainan,South China,using microscopic and microbial phylogenetic methods.Results of microanalysis and observation in microscopy and energy dispersive X-ray spectroscopy(EDXS)reveal a highly morphological diversity of MTB including unicellular cocci,vibrios,rod-shaped bacteria,and three morphotypes of multicellular magnetotactic prokaryotes(MMPs).In addition,analysis of the 16S rRNA gene showed that these MTB were clustered into 16 operational taxonomic units affi liated to the Alpha-,Delta-,and Gamma-proteobacteria classes within the Proteobacteria phylum.Meanwhile,by using the coupled fluorescence and transmission electron microscopy analysis,rodshaped bacteria,vibrio,and cocci were phylogenetically and structurally identified at the single-cell level.This study demonstrated highly diverse MTB communities in the mangrove ecosystem and provide a new insight into the overall diversity of MTB.
文摘The study of various oxidation states of chromium with Sargassum <i>sp</i>. is of particular interest since hexavalent chromium </span><span style="font-size:10.0pt;font-family:"">is </span><span style="font-size:10.0pt;font-family:"">reduced to trivalent chromium in </span><span style="font-size:10.0pt;font-family:"">an </span><span style="font-size:10.0pt;font-family:"">aqueous solution. In this study, a systematic density functional theory (DFT) calculations were performed to study the interactions of transition metal chromium ion with different oxidation states and spin states with the <i>Sar</i></span><i><span style="font-size:10.0pt;font-family:"">gassum sp</span></i><span style="font-size:10.0pt;font-family:"">. decorated with carboxylate</span><span style="font-size:10.0pt;font-family:""> </span><span style="font-size:10.0pt;font-family:"">(acetate) at the wB97XD/6-311++</span><span style="font-size:10.0pt;font-family:""> </span><span style="font-size:10.0pt;font-family:"">G(d,p)</span><span style="font-size:10.0pt;font-family:""> </span><span style="font-size:10.0pt;font-family:"">level of theory. The structures and binding energies of chromium met<span>al</span></span><span style="font-size:10.0pt;font-family:"">-</span><span style="font-size:10.0pt;font-family:"">carboxylate complexes at various oxidation states and spin states in gas</span><span style="font-size:10.0pt;font-family:""> phase were examined. The coordination strength of Cr(VI) with the acetate <span>ligand was predominantly the strongest compare</span></span><span style="font-size:10.0pt;font-family:"">d</span><span style="font-size:10.0pt;font-family:""> to the other oxidation</span><span style="font-size:10.0pt;font-family:""> states. <span>Vibrational frequency analysis, for the homoleptic monomers of tris</span> <span>[</span><span>Cr<sup>III</sup>(AC)<sub>3</sub>]<sup>0</sup> and </span>[Cr<sup>VI</sup>(AC)<sub>3</sub>]<sup>3+</sup> complexes, illustrate good harmony with the experimental and<span> theoretical calculated frequencies. Using the time</span></span><span style="font-size:10.0pt;font-family:"">-</span><span style="font-size:10.0pt;font-family:"">dependent DFT</span><span style="font-size:10.0pt;font-family:""> (TD-DFT) at the level of CAM-B3LYP/6-311++G(d,p), the vertical excitation energies were obtained. The stabilization energies derived using the second order perturbation </span><span style="font-size:10.0pt;font-family:"">theory, <i>E</i><sub>ij</sub><sup>(2)</sup>, of NBO analysis confirmed the greater charge transfer for the</span><span style="font-size:10.0pt;font-family:""> observed trends in the metal binding. The calculated binding </span><span style="font-size:10.0pt;font-family:"">energies</span><span style="font-size:10.0pt;font-family:""> </span><span style="font-size:10.0pt;font-family:"">(ΔE) and interactions energies </span><span style="font-size:10.0pt;font-family:Symbol;">S</span><i><span style="font-size:10.0pt;font-family:"">E</span></i><sub><span style="font-size:10.0pt;font-family:"">ij</span></sub><sup><span style="font-size:10.0pt;font-family:"">(2)</span></sup><span style="font-size:10.0pt;font-family:""> favor</span><span style="font-size:10.0pt;font-family:""> </span><span style="font-size:10.0pt;font-family:"">the formation of</span><span style="font-size:10.0pt;font-family:""> [Cr<sup>VI</sup>(AC)<sub>3</sub>]<sup>3+</sup> complexes. The findings of this study identify efficient electronic factors as major contributors to the metal binding affinities, with promising possibilities for the design of metal-ligand complexes and sensing of the metal ions.
文摘The silicon-strip tracker of the China Seismo-Electromagnetic Satellite（CSES） consists of two doublesided silicon strip detectors（DSSDs） which provide incident particle tracking information.A low-noise analog ASIC VA140 was used in this study for DSSD signal readout.A beam test on the DSSD module was performed at the Beijing Test Beam Facility of the Beijing Electron Positron Collider（BEPC） using a 400–800 MeV/c proton beam.The pedestal analysis results,RMSE noise,gain correction,and intensity distribution of incident particles of the DSSD module are presented.
