Objectives:This study aimed to assess the effect of hearing and speech rehabilitation in patients with Nurotron■cochlear implants.Design:Ninety-eight paediatric patients with bilateral severe-to-profound sensorineura...Objectives:This study aimed to assess the effect of hearing and speech rehabilitation in patients with Nurotron■cochlear implants.Design:Ninety-eight paediatric patients with bilateral severe-to-profound sensorineural deafness who received cochlear implantation were divided into three groups according to age:group A(≤3 years),group B(4-7 years),and group C(8-16 years).All patients were followed up for one year for hearing and speech performance after the surgery.The comprehensive Auditory Perception Assessment,MAIS,CAP and SIR hearing and speech assessments and rating materials were used for assessment before the surgery and at 3,6,and 12 months after implant activation.Results:The scores of patients in the open-set speech assessment,Chinese Auditory Perception Assessment,MAIS,CAP and SIR significantly improved after cochlear implantation in all age groups.The younger the age at implantation,the better the results.Moreover,the hearing and speech performance of cochlear implant recipients gradually improved with the extension of rehabilitation time.Conclusions:Nurotron■Venus^TM cochlear implantation can improve the hearing and speech performance of patients with bilateral severe-to-profound sensorineural deafness.展开更多
In this paper, the effect of fluid in a tunnel of Corti （TC） on organ of Corti （OC） is studied. A three-dimensional OC model including basilar membrane （BM）, tectorial membrane （TM）, inner and outer hair cells...In this paper, the effect of fluid in a tunnel of Corti （TC） on organ of Corti （OC） is studied. A three-dimensional OC model including basilar membrane （BM）, tectorial membrane （TM）, inner and outer hair cells （OHCs）, and reticular lamina （RL） is established by COMSOL. An initial pressure is applied to the fluid in the TC. The frequency response of the structure is analyzed, and the displacement of the BM is achieved. The results are in good agreement with the experimental data, confirming validity of the finite element model. Based on the model, the effect of fluid in the TC on the OC is studied. The results show that, when the pressure gradient is absent in the fluid, with the increase of the initial fluid pressure, the displacement of the BM increases. However, when the initial fluid pressure increases to a certain value, the increase rate of the displacement of the BM becomes very slow. The movement of the fluid amplifies the BM movement. Furthermore, the movement of the fluid can strengthen the movement of the OHCs and the shear movement of the stereocilia, especially in the vicinity of the characteristic frequency at which the amplification effect reaches a peak. Nevertheless, a pressure gradient in the fluid affects the BM movement.展开更多
The Sinus Iridum region, the first choice for China＇s＂Lunar Exploration Project＂is located at the center of the lunar LQ-4 area and is the site of Chang＇e-3 （CE-3）＇s soft landing. To make the scientific explora...The Sinus Iridum region, the first choice for China＇s＂Lunar Exploration Project＂is located at the center of the lunar LQ-4 area and is the site of Chang＇e-3 （CE-3）＇s soft landing. To make the scientific exploration of Chang＇e-3 more targeted and scientific, and to obtain a better macro-level understanding of the geotectonic environment of the Sinus Iridum region, the tectonic elements in LQ-4 region have been studied and the typical structures were analyzed statistically using data from CE-1, Clementine, LRO and Lunar Prospector missions. Also, the mineral components and periods of mare basalt activities in the study area have been ascertained. The present study divides the tectonic units and establishes the major tectonic events and sequence of evolution in the study area based on morphology, mineral constituents, and tectonic element distribution.展开更多
Atmosphere–land interactions simulated by an LES model are evaluated from the perspective of heterogeneity propagation by comparison with airborne measurements. It is found that the footprints of surface heterogeneit...Atmosphere–land interactions simulated by an LES model are evaluated from the perspective of heterogeneity propagation by comparison with airborne measurements. It is found that the footprints of surface heterogeneity, though as 2D patterns can be dissipated quickly due to turbulent mixing, as 1D projections can persist and propagate to the top of the atmospheric boundary layer. Direct comparison and length scale analysis show that the simulated heterogeneity patterns are comparable to the observation. The results highlight the model＇s capability in simulating the complex effects of surface heterogeneity on atmosphere–land interactions.展开更多
According to the vibration characteristics of the organ of Corti （OC）, seven hypotheses are made to simplify the structure of the model, and a mechanical OC model is established. Using the variational principle, a d...According to the vibration characteristics of the organ of Corti （OC）, seven hypotheses are made to simplify the structure of the model, and a mechanical OC model is established. Using the variational principle, a displacement analytical expression is solved under a certain pressure. The results are in good agreement with experimental data, showing the validity of the formula. Combined with the damage caused by noise in clinic, it is found that the hardening of outer hair cells and outer stereocilia can lead to loss of hearing and generation of threshold shift. In addition, the results show that high frequency resonance occurs at the bottom of the basilar membrane （BM）, and low frequency resonance occurs at the top of the BM. This confirms the frequency selective characteristics of the BM. Further, using this formula can avoid interference of the envi- ronment and the technical level of the test personnel, and can evaluate performance of the OC objectively.展开更多
Permanent damage to hair cells(HCs)is the leading cause of sensory deafness.Supporting cells(SCs)are essential in the restoration of hearing in mammals because they can proliferate and differentiate to HCs.MDS1 and EV...Permanent damage to hair cells(HCs)is the leading cause of sensory deafness.Supporting cells(SCs)are essential in the restoration of hearing in mammals because they can proliferate and differentiate to HCs.MDS1 and EVI1 complex locus(MECOM)is vital in early development and cell differentiation and regulates the TGF-βsignaling pathway to adapt to pathophysiological events,such as hematopoietic proliferation,differentiation and cells death.In addition,MECOM plays an essential role in neurogenesis and craniofacial development.However,the role of MECOM in the development of cochlea and its way to regulate related signaling are not fully understood.To address this problem,this study examined the expression of MECOM during the development of cochlea and observed a significant increase of MECOM at the key point of auditory epithelial morphogenesis,indicating that MECOM may have a vital function in the formation of cochlea and regeneration of HCs.Meanwhile,we tried to explore the possible effect and potential mechanism of MECOM in SC proliferation and HC regeneration.Findings from this study indicate that overexpression of MECOM markedly increases the proliferation of SCs in the inner ear,and the expression of Smad3 and Cdkn2b related to TGF signaling is significantly down-regulated,corresponding to the overexpression of MECOM.Collectively,these data may provide an explanation of the vital function of MECOM in SC proliferation and trans-differentiation into HCs,as well as its regulation.The interaction between MECOM,Wnt,Notch and the TGF-βsignaling may provide a feasible approach to induce the regeneration of HCs.展开更多
Objective:To investigate the role of the periotic mesenchyme(POM)in the development of sensory cells of developing auditory epithelium.Methods:Developing auditory epithelium with or without periotic mesenchyme was iso...Objective:To investigate the role of the periotic mesenchyme(POM)in the development of sensory cells of developing auditory epithelium.Methods:Developing auditory epithelium with or without periotic mesenchyme was isolated from mice at embryonic days 11.5(E11.5),E12.5 and E13.5,respectively,and cultured in vitro to an equivalent of E18.5’s epithelium in vivo.Then,the explants were co-stained with antibodies targeting myosin VIIA,Sox2 and BrdU.Results:More hair cells in E11.5 t 7 DIV,E12.5 t 6 DIV and E13.5 t 5 DIV auditory epithelia were found upon culture with POM(225.90±62.44,476.94±100.81,and 1386.60±202.38,respectively)compared with the non-POM group(68.17±23.74,205.00±44.23,and 1266.80±38.84,respectively).Moreover,regardless of developmental stage,the mesenchymal tissue increased the amount of cochlear sensory cells as well as the ratio of differentiated hair cells to total sensory cells.Conclusions:The periotic mesenchyme promotes the development of cochlear sensory cells,and its effect depends on the developmental stage of the auditory epithelium.展开更多
The timing of the "Yanshanian Movement" and the tectonic setting that controlled the Yanshan fold-and-thrust belt during Jurassic time in China are still matters of controversy. Sediments that filled the int...The timing of the "Yanshanian Movement" and the tectonic setting that controlled the Yanshan fold-and-thrust belt during Jurassic time in China are still matters of controversy. Sediments that filled the intramontane basins in the Yanshan belt perfectly record the history of "Yanshanian Movement" and the tectonic background of these basins. Recognizing syn-tectonic sedimentation, clarifying its relationship with structures, and accurately defining strata ages to build up a correct chronostratigraphic framework are the key points to further reveal the timing and kinematics of tectonic deformation in the Yanshan belt from the Jurassic to the Early Cretaceous. This paper applies both tectonic and sedimentary methods on the fold-and-thrust belt and intramontane basins in the Zhangjiakou area, which is located at the intersection between the western Yanshan and northern Taihangshan. Our work suggests that the pre-defined "Jurassic strata" should be re-dated and sub-divided into three strata units: a Late Triassic to Early Jurassic unit, a Middle Jurassic unit, and a Late Jurassic to early Early Cretaceous unit. Under the control of growth fold-and-thrust structures, five types of growth strata developed in different growth structures: fold-belt foredeep type,thrust-belt foredeep type, fault-propagation fold-thrust structure type, fault-bend fold-thrust structure type, and fault-bend foldthrust plus fault-propagation fold composite type. The reconstructed "source-to-sink" systems of Late Triassic to Early Jurassic,Middle Jurassic and Late Jurassic to early Early Cretaceous times, which are composed of a fold-and-thrust belt and flexure basins, imply that the "Yanshanian Movement" in our study area started in the Middle Jurassic. During Middle Jurassic to early Early Cretaceous times, there have been at least three stages of fold-thrust events that developed "Laramide-type" basementinvolved fold-thrust structures and small-scale intramontane broken "axial basins". The westward migration of a "pair" of basement-involved fold-thrust belt and flexure basins might have been controlled by flat subduction of the western Paleo-Pacific slab from the Jurassic to the Early Cretaceous.展开更多
The northwestward subduction of the Izanagi Plate beneath the eastern Eurasian Plate during the Late Mesozoic caused a series of compressional deformation events in the Yanshan fold and thrust belt(YFTB), but the tect...The northwestward subduction of the Izanagi Plate beneath the eastern Eurasian Plate during the Late Mesozoic caused a series of compressional deformation events in the Yanshan fold and thrust belt(YFTB), but the tectonic deformation timing, tectonic properties and relationship between tectonic uplift and sediment accumulation in the intermontane basins continue to be debated. For this reason, the sedimentology, sediment provenance, and basin structure of the Qianjiadian Basin(QJB) in the northern Beijing region during the Late Jurassic and Early Cretaceous were studied in detail. The results suggest that a fault-propagation fold-type(FPFT) growth structure and growth strata developed on the western edge of the QJB and that the top part of Member 2 and Member 3 of the Tuchengzi Formation are growth strata controlled by the limb rotation mechanism. In two small thrust faults in the QJB, the Mesoproterozoic Xiamaling Formation is thrust over the Tuchengzi Formation, and these faults may have controlled the development of the fault-bend fold-type growth strata. An analysis of the "source-to-sink" process suggests that the hanging wall succession of the Shangyi-Pingquan fault(SPF) was the main source area of the Late Jurassic to early Early Cretaceous strata in the QJB. A zircon206 Pb/238 U age of 140.8±2.4 Ma for the volcanic rocks at the bottom of the FPFT growth strata represents the timing of the initiation of FPFT growth structure development. The discovery of the FPFT growth structure and growth strata in the QJB indicate that the QJB was an intermontane flexural basin controlled by fold and thrust structures during the early Early Cretaceous. Near the E-W-trending SPF, the NE-SW-trending Qianjiadian thrust fault(QJTF) and two small intrabasinal thrust faults may constitute a unified right-lateral strike-slip system that formed in response to the northwestward flat subduction of the Izanagi Plate beneath the East Asian continent during the Jurassic-Early Cretaceous.展开更多
A series of titanium amido complexes (1-Ti(NMe_(2))_(2) to 4-Ti(NMe_(2))_(2)) bearing NNO-tridentate ligands was synthesized from the reactions of phenoxy-imine-amine ligands with one equivalent of Ti(NMe_(2))_(4). Su...A series of titanium amido complexes (1-Ti(NMe_(2))_(2) to 4-Ti(NMe_(2))_(2)) bearing NNO-tridentate ligands was synthesized from the reactions of phenoxy-imine-amine ligands with one equivalent of Ti(NMe_(2))_(4). Subsequently, titanium dichloride complexes (1-TiCl_(2) to 4-TiCl_(2)) were prepared by treatment of titanium amido complexes with excess Me3SiCl in toluene. All metal complexes were characterized by 1H and 13C NMR spectroscopy, and the molecular structures of complexes of 2-Ti(NMe_(2))_(2), 2-TiCl_(2), and 4-TiCl_(2) in the solid state were determined by single-crystal X-ray diffraction. Upon activation with MAO, titanium dichloride complexes as single-site catalysts were extremely active toward ethylene homopolymerization with great control on molecular weight and distribution. In particular, 3-TiCl_(2)/MAO exhibited an activity as high as 1.35 × 108 g(PE)·mol−1(Ti)·h−1 at 70°C and produced polyethylene with high molecular weight (41.7 × 10^(4) g∙mol^(−1)) and very narrow distribution (Đ = 1.23). In the presence of 1-octene as comonomer, linear low-density polyethylenes (LLDPEs) with ultrahigh molecular weights (Mw = 136—326 × 10^(4) g∙mol^(−1)) and narrow distributions (Đ = 1.20—1.50) were successfully synthesized.展开更多
文摘Objectives:This study aimed to assess the effect of hearing and speech rehabilitation in patients with Nurotron■cochlear implants.Design:Ninety-eight paediatric patients with bilateral severe-to-profound sensorineural deafness who received cochlear implantation were divided into three groups according to age:group A(≤3 years),group B(4-7 years),and group C(8-16 years).All patients were followed up for one year for hearing and speech performance after the surgery.The comprehensive Auditory Perception Assessment,MAIS,CAP and SIR hearing and speech assessments and rating materials were used for assessment before the surgery and at 3,6,and 12 months after implant activation.Results:The scores of patients in the open-set speech assessment,Chinese Auditory Perception Assessment,MAIS,CAP and SIR significantly improved after cochlear implantation in all age groups.The younger the age at implantation,the better the results.Moreover,the hearing and speech performance of cochlear implant recipients gradually improved with the extension of rehabilitation time.Conclusions:Nurotron■Venus^TM cochlear implantation can improve the hearing and speech performance of patients with bilateral severe-to-profound sensorineural deafness.
基金Project supported by the National Natural Science Foundation of China(Nos.11272200 and 11572186)
文摘In this paper, the effect of fluid in a tunnel of Corti （TC） on organ of Corti （OC） is studied. A three-dimensional OC model including basilar membrane （BM）, tectorial membrane （TM）, inner and outer hair cells （OHCs）, and reticular lamina （RL） is established by COMSOL. An initial pressure is applied to the fluid in the TC. The frequency response of the structure is analyzed, and the displacement of the BM is achieved. The results are in good agreement with the experimental data, confirming validity of the finite element model. Based on the model, the effect of fluid in the TC on the OC is studied. The results show that, when the pressure gradient is absent in the fluid, with the increase of the initial fluid pressure, the displacement of the BM increases. However, when the initial fluid pressure increases to a certain value, the increase rate of the displacement of the BM becomes very slow. The movement of the fluid amplifies the BM movement. Furthermore, the movement of the fluid can strengthen the movement of the OHCs and the shear movement of the stereocilia, especially in the vicinity of the characteristic frequency at which the amplification effect reaches a peak. Nevertheless, a pressure gradient in the fluid affects the BM movement.
基金funded by the National Natural Science Foundation of China [grant numbers 42088101,42175158,41575072,41730962,41905075,42075158,and U1811464]the National Key Research and Development Program of China [grant numbers 2017YFA0604300 and 2016YFB0200801]supported by the National Key Scientific and Technological Infrastructure project entitled“Earth System Science Numerical Simulator Facility”(Earth-Lab)。
基金the key project (No. 2009AA122201) under the 863 program sponsored by Ministry of Science & Technology that has funded our research
文摘The Sinus Iridum region, the first choice for China＇s＂Lunar Exploration Project＂is located at the center of the lunar LQ-4 area and is the site of Chang＇e-3 （CE-3）＇s soft landing. To make the scientific exploration of Chang＇e-3 more targeted and scientific, and to obtain a better macro-level understanding of the geotectonic environment of the Sinus Iridum region, the tectonic elements in LQ-4 region have been studied and the typical structures were analyzed statistically using data from CE-1, Clementine, LRO and Lunar Prospector missions. Also, the mineral components and periods of mare basalt activities in the study area have been ascertained. The present study divides the tectonic units and establishes the major tectonic events and sequence of evolution in the study area based on morphology, mineral constituents, and tectonic element distribution.
基金supported by the DFG Transregional Cooperative Research Centre 32 "Patterns in Soil-Vegetation-Atmosphere-Systems: Monitoring, Modelling and Data Assimilation"
文摘Atmosphere–land interactions simulated by an LES model are evaluated from the perspective of heterogeneity propagation by comparison with airborne measurements. It is found that the footprints of surface heterogeneity, though as 2D patterns can be dissipated quickly due to turbulent mixing, as 1D projections can persist and propagate to the top of the atmospheric boundary layer. Direct comparison and length scale analysis show that the simulated heterogeneity patterns are comparable to the observation. The results highlight the model＇s capability in simulating the complex effects of surface heterogeneity on atmosphere–land interactions.
基金Project supported by the National Natural Science Foundation of China(Nos.11272200 and11572186)
文摘According to the vibration characteristics of the organ of Corti （OC）, seven hypotheses are made to simplify the structure of the model, and a mechanical OC model is established. Using the variational principle, a displacement analytical expression is solved under a certain pressure. The results are in good agreement with experimental data, showing the validity of the formula. Combined with the damage caused by noise in clinic, it is found that the hardening of outer hair cells and outer stereocilia can lead to loss of hearing and generation of threshold shift. In addition, the results show that high frequency resonance occurs at the bottom of the basilar membrane （BM）, and low frequency resonance occurs at the top of the BM. This confirms the frequency selective characteristics of the BM. Further, using this formula can avoid interference of the envi- ronment and the technical level of the test personnel, and can evaluate performance of the OC objectively.
基金was supported by the Chinese National Natural Science Foundation of China(grant number 81371089)the Research Project of Wannan Medical College(grant number WK202122).
文摘Permanent damage to hair cells(HCs)is the leading cause of sensory deafness.Supporting cells(SCs)are essential in the restoration of hearing in mammals because they can proliferate and differentiate to HCs.MDS1 and EVI1 complex locus(MECOM)is vital in early development and cell differentiation and regulates the TGF-βsignaling pathway to adapt to pathophysiological events,such as hematopoietic proliferation,differentiation and cells death.In addition,MECOM plays an essential role in neurogenesis and craniofacial development.However,the role of MECOM in the development of cochlea and its way to regulate related signaling are not fully understood.To address this problem,this study examined the expression of MECOM during the development of cochlea and observed a significant increase of MECOM at the key point of auditory epithelial morphogenesis,indicating that MECOM may have a vital function in the formation of cochlea and regeneration of HCs.Meanwhile,we tried to explore the possible effect and potential mechanism of MECOM in SC proliferation and HC regeneration.Findings from this study indicate that overexpression of MECOM markedly increases the proliferation of SCs in the inner ear,and the expression of Smad3 and Cdkn2b related to TGF signaling is significantly down-regulated,corresponding to the overexpression of MECOM.Collectively,these data may provide an explanation of the vital function of MECOM in SC proliferation and trans-differentiation into HCs,as well as its regulation.The interaction between MECOM,Wnt,Notch and the TGF-βsignaling may provide a feasible approach to induce the regeneration of HCs.
基金the Chinese National Natural Science Foundation of China(grant number 81371089)。
文摘Objective:To investigate the role of the periotic mesenchyme(POM)in the development of sensory cells of developing auditory epithelium.Methods:Developing auditory epithelium with or without periotic mesenchyme was isolated from mice at embryonic days 11.5(E11.5),E12.5 and E13.5,respectively,and cultured in vitro to an equivalent of E18.5’s epithelium in vivo.Then,the explants were co-stained with antibodies targeting myosin VIIA,Sox2 and BrdU.Results:More hair cells in E11.5 t 7 DIV,E12.5 t 6 DIV and E13.5 t 5 DIV auditory epithelia were found upon culture with POM(225.90±62.44,476.94±100.81,and 1386.60±202.38,respectively)compared with the non-POM group(68.17±23.74,205.00±44.23,and 1266.80±38.84,respectively).Moreover,regardless of developmental stage,the mesenchymal tissue increased the amount of cochlear sensory cells as well as the ratio of differentiated hair cells to total sensory cells.Conclusions:The periotic mesenchyme promotes the development of cochlear sensory cells,and its effect depends on the developmental stage of the auditory epithelium.
基金supported by National Natural Science Foundation of China(Grant Nos.41572189&91114203)National Key R&D Plan(Grant No.2017YFC0601405)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB18000000)
文摘The timing of the "Yanshanian Movement" and the tectonic setting that controlled the Yanshan fold-and-thrust belt during Jurassic time in China are still matters of controversy. Sediments that filled the intramontane basins in the Yanshan belt perfectly record the history of "Yanshanian Movement" and the tectonic background of these basins. Recognizing syn-tectonic sedimentation, clarifying its relationship with structures, and accurately defining strata ages to build up a correct chronostratigraphic framework are the key points to further reveal the timing and kinematics of tectonic deformation in the Yanshan belt from the Jurassic to the Early Cretaceous. This paper applies both tectonic and sedimentary methods on the fold-and-thrust belt and intramontane basins in the Zhangjiakou area, which is located at the intersection between the western Yanshan and northern Taihangshan. Our work suggests that the pre-defined "Jurassic strata" should be re-dated and sub-divided into three strata units: a Late Triassic to Early Jurassic unit, a Middle Jurassic unit, and a Late Jurassic to early Early Cretaceous unit. Under the control of growth fold-and-thrust structures, five types of growth strata developed in different growth structures: fold-belt foredeep type,thrust-belt foredeep type, fault-propagation fold-thrust structure type, fault-bend fold-thrust structure type, and fault-bend foldthrust plus fault-propagation fold composite type. The reconstructed "source-to-sink" systems of Late Triassic to Early Jurassic,Middle Jurassic and Late Jurassic to early Early Cretaceous times, which are composed of a fold-and-thrust belt and flexure basins, imply that the "Yanshanian Movement" in our study area started in the Middle Jurassic. During Middle Jurassic to early Early Cretaceous times, there have been at least three stages of fold-thrust events that developed "Laramide-type" basementinvolved fold-thrust structures and small-scale intramontane broken "axial basins". The westward migration of a "pair" of basement-involved fold-thrust belt and flexure basins might have been controlled by flat subduction of the western Paleo-Pacific slab from the Jurassic to the Early Cretaceous.
基金supported by the National Key Research and Development Project (Grant No. 2017YFC0601405)the National Natural Science Foundation of China (Grant Nos. 41572189 & 41820104004)the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB18030604)
文摘The northwestward subduction of the Izanagi Plate beneath the eastern Eurasian Plate during the Late Mesozoic caused a series of compressional deformation events in the Yanshan fold and thrust belt(YFTB), but the tectonic deformation timing, tectonic properties and relationship between tectonic uplift and sediment accumulation in the intermontane basins continue to be debated. For this reason, the sedimentology, sediment provenance, and basin structure of the Qianjiadian Basin(QJB) in the northern Beijing region during the Late Jurassic and Early Cretaceous were studied in detail. The results suggest that a fault-propagation fold-type(FPFT) growth structure and growth strata developed on the western edge of the QJB and that the top part of Member 2 and Member 3 of the Tuchengzi Formation are growth strata controlled by the limb rotation mechanism. In two small thrust faults in the QJB, the Mesoproterozoic Xiamaling Formation is thrust over the Tuchengzi Formation, and these faults may have controlled the development of the fault-bend fold-type growth strata. An analysis of the "source-to-sink" process suggests that the hanging wall succession of the Shangyi-Pingquan fault(SPF) was the main source area of the Late Jurassic to early Early Cretaceous strata in the QJB. A zircon206 Pb/238 U age of 140.8±2.4 Ma for the volcanic rocks at the bottom of the FPFT growth strata represents the timing of the initiation of FPFT growth structure development. The discovery of the FPFT growth structure and growth strata in the QJB indicate that the QJB was an intermontane flexural basin controlled by fold and thrust structures during the early Early Cretaceous. Near the E-W-trending SPF, the NE-SW-trending Qianjiadian thrust fault(QJTF) and two small intrabasinal thrust faults may constitute a unified right-lateral strike-slip system that formed in response to the northwestward flat subduction of the Izanagi Plate beneath the East Asian continent during the Jurassic-Early Cretaceous.
基金Financial support by NSFC(Nos.52073152,21871157)the 111 Project(No.D17004)+1 种基金the Shandong Province Natural Science Foundation(No.2021CXGC010902)the Taishan Scholar Constructive Engineering Foundation(No.tsqn20161031)is gratefully acknowledged.
文摘A series of titanium amido complexes (1-Ti(NMe_(2))_(2) to 4-Ti(NMe_(2))_(2)) bearing NNO-tridentate ligands was synthesized from the reactions of phenoxy-imine-amine ligands with one equivalent of Ti(NMe_(2))_(4). Subsequently, titanium dichloride complexes (1-TiCl_(2) to 4-TiCl_(2)) were prepared by treatment of titanium amido complexes with excess Me3SiCl in toluene. All metal complexes were characterized by 1H and 13C NMR spectroscopy, and the molecular structures of complexes of 2-Ti(NMe_(2))_(2), 2-TiCl_(2), and 4-TiCl_(2) in the solid state were determined by single-crystal X-ray diffraction. Upon activation with MAO, titanium dichloride complexes as single-site catalysts were extremely active toward ethylene homopolymerization with great control on molecular weight and distribution. In particular, 3-TiCl_(2)/MAO exhibited an activity as high as 1.35 × 108 g(PE)·mol−1(Ti)·h−1 at 70°C and produced polyethylene with high molecular weight (41.7 × 10^(4) g∙mol^(−1)) and very narrow distribution (Đ = 1.23). In the presence of 1-octene as comonomer, linear low-density polyethylenes (LLDPEs) with ultrahigh molecular weights (Mw = 136—326 × 10^(4) g∙mol^(−1)) and narrow distributions (Đ = 1.20—1.50) were successfully synthesized.
