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Structural and functional connectivity of the whole brain and subnetworks in individuals with mild traumatic brain injury:predictors of patient prognosis
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作者 Sihong Huang Jungong Han +4 位作者 Hairong Zheng Mengjun Li Chuxin Huang Xiaoyan Kui Jun Liu 《Neural Regeneration Research》 SCIE CAS CSCD 2024年第7期1553-1558,共6页
Patients with mild traumatic brain injury have a diverse clinical presentation,and the underlying pathophysiology remains poorly understood.Magnetic resonance imaging is a non-invasive technique that has been widely u... Patients with mild traumatic brain injury have a diverse clinical presentation,and the underlying pathophysiology remains poorly understood.Magnetic resonance imaging is a non-invasive technique that has been widely utilized to investigate neuro biological markers after mild traumatic brain injury.This approach has emerged as a promising tool for investigating the pathogenesis of mild traumatic brain injury.G raph theory is a quantitative method of analyzing complex networks that has been widely used to study changes in brain structure and function.However,most previous mild traumatic brain injury studies using graph theory have focused on specific populations,with limited exploration of simultaneous abnormalities in structural and functional connectivity.Given that mild traumatic brain injury is the most common type of traumatic brain injury encounte red in clinical practice,further investigation of the patient characteristics and evolution of structural and functional connectivity is critical.In the present study,we explored whether abnormal structural and functional connectivity in the acute phase could serve as indicators of longitudinal changes in imaging data and cognitive function in patients with mild traumatic brain injury.In this longitudinal study,we enrolled 46 patients with mild traumatic brain injury who were assessed within 2 wee ks of injury,as well as 36 healthy controls.Resting-state functional magnetic resonance imaging and diffusion-weighted imaging data were acquired for graph theoretical network analysis.In the acute phase,patients with mild traumatic brain injury demonstrated reduced structural connectivity in the dorsal attention network.More than 3 months of followup data revealed signs of recovery in structural and functional connectivity,as well as cognitive function,in 22 out of the 46 patients.Furthermore,better cognitive function was associated with more efficient networks.Finally,our data indicated that small-worldness in the acute stage could serve as a predictor of longitudinal changes in connectivity in patients with mild traumatic brain injury.These findings highlight the importance of integrating structural and functional connectivity in unde rstanding the occurrence and evolution of mild traumatic brain injury.Additionally,exploratory analysis based on subnetworks could serve a predictive function in the prognosis of patients with mild traumatic brain injury. 展开更多
关键词 cognitive function CROSS-SECTION FOLLOW-UP functional connectivity graph theory longitudinal study mild traumatic brain injury prediction small-worldness structural connectivity subnetworks whole brain network
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Connecting parameters optimization on unsymmetrical twin-tower structure linked by sky-bridge 被引量:1
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作者 孙黄胜 刘默涵 朱宏平 《Journal of Central South University》 SCIE EI CAS 2014年第6期2460-2468,共9页
Based on a simplified 3-DOF model of twin-tower structure linked by a sky-bridge,the frequency response functions,the displacement power spectral density(PSD)functions,and the time-averaged total vibration energy were... Based on a simplified 3-DOF model of twin-tower structure linked by a sky-bridge,the frequency response functions,the displacement power spectral density(PSD)functions,and the time-averaged total vibration energy were derived,by assuming the white noise as the earthquake excitation.The effects of connecting parameters,such as linking stiffness ratio and linking damping ratio,on the structural vibration responses were then studied,and the optimal connecting parameters were obtained to minimize the vibration energy of either the independent monomer tower or the integral structure.The influences of sky-bridge elevation position on the optimal connecting parameters were also discussed.Finally,the distribution characteristics of the top displacement PSD and the structural responses,excited by El Centro,Taft and artificial waves,were compared in both frequency and time domain.It is found that the connecting parameters at either end of connection interactively affect the responses of the towers.The optimal connecting parameters can greatly improve the damping connections on their seismic reduction effectiveness,but are unable to reduce the seismic responses of the towers to the best extent simultaneously.It is also indicated that the optimal connecting parameters derived from the simplified 3-DOF model are applicable for two multi-story structures linked by a sky-bridge with dampers.The seismic reduction effectiveness obtained varies from 0.3 to 1.0 with different sky-bridge mass ratio.The displacement responses of the example structures are reduced by approximately 22% with sky-bridge connections. 展开更多
关键词 twin-tower connected structure sky-bridge connecting parameter optimization seismic response
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Formation and thermal stability of connected hard skeleton structure in ATX525 cast alloys 被引量:1
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作者 Ke-qiang Qiu Hui-han Zhang +2 位作者 Yan Re Ying-lei Ren Rong-de Li 《China Foundry》 SCIE 2015年第6期412-417,共6页
The formation and the thermal stability of a connected hard skeleton structure(CHSS) in the matrix of Mg-5Al-2Sn-5Ca(ATX525) alloy were investigated by using X-ray diffractometer, scanning electron microscopy, differe... The formation and the thermal stability of a connected hard skeleton structure(CHSS) in the matrix of Mg-5Al-2Sn-5Ca(ATX525) alloy were investigated by using X-ray diffractometer, scanning electron microscopy, differential scanning calorimeter, creep tester and isothermal treatment method. The results indicated that the CHSS composed of Mg2(Al,Ca) and Al2 Ca intermetallics was formed into a typical eutectic structure and no obvious change occurred when the samples were isothermally treated at 250 °C for 96 h and 350 °C for 72 h, respectively. It became a chained structure when isothermally treated at 450 °C for 48 h. The dissolution and reconstruction processes, however, were observed for the CHSS when the processing temperature was up to 550 °C. The creep life at the stress-temperature condition of 50MPa/200°C for the alloy treated at 450 °C for 48 h was as high as 510 h, and the strain at creep time of 100 h was as low as 0.03%, which indicated that the present alloy has not only a good thermal stability, but also a better heat resistance. 展开更多
关键词 Mg cast alloy connected hard skeleton structure isothermal treatment thermal stability heat resistance
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Structural Analysis and Design of Steel Connections Using Component-Based Finite Element Model
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作者 Lubomir Sabatka Frantisek Wald +2 位作者 Jaromir Kabelac Drahoslav Kolaja Martin Pospisil 《Journal of Civil Engineering and Architecture》 2015年第8期895-901,共7页
This paper introduces CBFEM (component-based finite element model) which is a new method to analyze and design connections of steel structures. Design focused CM (component model) is compared to FEM (finite eleme... This paper introduces CBFEM (component-based finite element model) which is a new method to analyze and design connections of steel structures. Design focused CM (component model) is compared to FEM (finite elements models). Procedure for composition of a model based on usual production process is used in CBFEM. Its results are compared to those obtained by component method for portal frame eaves moment connection with good agreement. Design of moment resistant column base is demonstrated by a case loaded by two directional bending moments and normal force. Interaction of several connections in one complex joint is explained in the last example. This paper aims to provide structural engineers with a new tool to effectively analyze and design various joints of steel structures. 展开更多
关键词 Steel structures structural connections finite element model component model analytical model design model.
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A Modifi ed Molecular Structure Mechanics Method for Analysis of Graphene
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作者 华军 LI Dongbo +3 位作者 ZHAO Dong LIANG Shengwei LIU Qinlong JIA Ruiyan 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2015年第6期1172-1178,共7页
Based on molecular mechanics and the deformation characteristics of the atomic lattice structure of graphene, a modifi ed molecular structure mechanics method was developed to improve the original one, that is, the se... Based on molecular mechanics and the deformation characteristics of the atomic lattice structure of graphene, a modifi ed molecular structure mechanics method was developed to improve the original one, that is, the semi-rigid connections were used to model the bond angle variations between the C-Cbonds in graphene. The simulated results show that the equivalent space frame model with semi-rigid connections for graphene proposed in this article is a simple, efficient, and accurate model to evaluate the equivalent elastic properties of graphene. Though the present computational model of the semi-rigid connected space frame is only applied to characterize the mechanical behaviors of the space lattices of graphene, it has more potential applications in the static and dynamic analyses of graphene and other nanomaterials. 展开更多
关键词 graphene molecular structure mechanics semi-rigid connections mechanical properties
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Study of Finite Element Analysis on Launch Vehicle Connection Structural Strength
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作者 WU Hao WANG Jingchao +10 位作者 RUI Xing ZHANG Ling ZHU Zhentao YANG Fan WANG Bin CHEN Youwei ZHANG Dengyu WANG Shuai YANG Ruisheng YU Long WANG Zhuoqun 《Aerospace China》 2021年第2期59-64,共6页
The strength of the connection structure has always been a key issue in the structural design of a launch vehicle.In this paper,the finite element analysis method is used for the strength of typical connection structu... The strength of the connection structure has always been a key issue in the structural design of a launch vehicle.In this paper,the finite element analysis method is used for the strength of typical connection structures of a new launch vehicle.The research scope includes the inter-stage connection structure and the bundle connection structure.Aiming at establishing the strength of these two connection structures under flight conditions,we built a refined finite element model,simulated the bolt tensile test and obtained a calculation criteria,and carried out finite element analysis of the connection structures under flight conditions.As a result,we not only established the analysis and evaluation method of the connection structures based on the refined finite element modeling analysis,but also provided a fast numerical simulation design method for the development of the launch vehicle’s connection structures,which greatly improved the design efficiency and reduced the design risk. 展开更多
关键词 launch vehicle connection structure finite element analysis
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Research on Medial Temporal Lobe Epilepsy by Combining Structural and Functional MRI
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作者 YU Min TAO Ling QIAN Zhi-yu 《Chinese Journal of Biomedical Engineering(English Edition)》 2013年第2期61-69,共9页
Epilepsy is a common neurological disorder, and its electrophysiology characteristic is abnormally high excitability and synchronization of the neural activity. This paper focuses on the study of medial temporal lobe ... Epilepsy is a common neurological disorder, and its electrophysiology characteristic is abnormally high excitability and synchronization of the neural activity. This paper focuses on the study of medial temporal lobe epilepsy with hippocampal sclerosis. The hippocampus plays an important role in short-term memory. However, little is known about the connectivity between hippocampal structures and adjacent brain regions. The functional and structural connectivity between patients and controls was investigated by using the techniques of functional magnetic resonance imaging and diffusion tensor imaging in the paper. Three pairs of ROIs related to working memory from BOLD-fMRI data were chosen. These ROIs were registrated from MNI space to individual space and the fiber bundle between two ROIs were traced in the DTI images. The results show that the number of fiber bundle of patients reduce among these ROIs, such as left hippocampus and right hippocampus, left hippocampus and left thalamus, left hippocampus and left frontal lobe and so on. And the number of fiber bundle of patients increase among these ROIs, such as left thalamus and right thalamus, right hippocampus and right thalamus. And the FA values of the fiber bundles of patients in some regions related to left hippocampus decrease. The cause of abnormal functional and structural connections due to the damage of hippocampus in medial temporal lobe epilepsy is studied from a new perspective. 展开更多
关键词 medial temporal lobe epilepsy hippocampal sclerosis structural connection fiber bundle trace
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Structural connection with predetermined discrete variable friction forces
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作者 Kaixin Chen Georgios Tsampras Kyoungyeon Lee 《Resilient Cities and Structures》 2023年第1期1-17,共17页
This paper presents a simple and practical structural connection able to develop predetermined discrete variable friction forces at target design displacement levels. The innovative connection is termed Modified Fricti... This paper presents a simple and practical structural connection able to develop predetermined discrete variable friction forces at target design displacement levels. The innovative connection is termed Modified Friction Device ( Modified FD ). Modified FDs are used to transfer the seismic induced horizontal forces from the floors to the core wall seismic force-resisting system of a building. The schematics of the physical embodiment of the Modified FD are presented. The components and the assembly of the Modified FD are discussed. The mechanics of the Modified FD are explained. Results from static structural analyses of two types of finite element models of the Modified FD are presented. The first model is developed using solid finite elements and it is used to assess the expected kinematics and the expected force-displacement response of the Modified FD. The second model is developed using a truss finite element and it can be used to effciently simulate the force-displacement response of the Modified FD in numerical earthquake simulations of structural systems. The force-displacement response of the Modified FD computed using a numerical earthquake simulation of an eighteen-story reinforced concrete core wall building model is presented. The seismic response of the building model with Modified FDs is compared with the seismic response of the building model with monolithic connections and the seismic response of the building model with friction devices with constant friction forces. The results presented in this paper show that it is possible to develop a simple and practical structural connection with predetermined discrete variable forcedisplacementresponse to limit the seismic induced horizontal forces transferred between the floors of the flexible gravity load resisting system and the core wall piers in high-performance earthquake resilient buildings. 展开更多
关键词 Friction devices structural connections Core wall buildings Earthquake resilience
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The Mechanism Analysis of Seafloor Silt Liquefaction Under Wave Loading 被引量:8
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作者 Yang Shaoli , Shen Weiquan Yang Zuosheng \Assistant, The Institute of Estuarine and Coastal Studies, Ocean University of Qingdao, Qingdao 266003 . Professor, The Institute of Estuarine and Coastal Studies, Ocean University of Qingdao, Qingdao 266003 《China Ocean Engineering》 SCIE EI 1995年第4期375-386,共12页
The sediment in Chengbei area of the Huanghe (Yellow River) subaqueous delta is the object of a reseach project in this article. The accumulating and dissipating effects following the change of time are considered fir... The sediment in Chengbei area of the Huanghe (Yellow River) subaqueous delta is the object of a reseach project in this article. The accumulating and dissipating effects following the change of time are considered first in the study area and the distributing curves of excess pore water pressure along with time and depth in the soil stratum are gained; the possibility of silt liquefaction is evaluated using the computing values and the affecting depth of liquefaction is given. This paper quantitatively analyzes the dynamic response of seafloor soil under the cyclic loading of waves and makes an inquiry into the instable mechanism of soil. 展开更多
关键词 dynamic water pressure cyclic shear stress excess pore water pressure LIQUEFACTION structure connection
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A brain structural connectivity biomarker for autism spectrum disorder diagnosis in early childhood
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作者 Xi Jiang Xiao-Jing Shou +24 位作者 Zhongbo Zhao Yuzhong Chen Fan-Chao Meng Jiao Le Tian-Jia Song Xin-Jie Xu Weitong Guo Xiaoyan Ke Xiao-E Cai Weihua Zhao Juan Kou Ran Huo Ying Liu Hui-Shu Yuan Yan Xing Ji-Sheng Han Song-Ping Han Yun Li Hua Lai Lan Zhang Mei-Xiang Jia Jing Liu Xuan Liu Keith M.Kendrick Rong Zhang 《Psychoradiology》 2023年第1期171-181,共11页
Background:Autism spectrum disorder(ASD)is associated with altered brain development,but it is unclear which specific structural changes may serve as potential diagnostic markers,particularly in young children at the ... Background:Autism spectrum disorder(ASD)is associated with altered brain development,but it is unclear which specific structural changes may serve as potential diagnostic markers,particularly in young children at the age when symptoms become fully estab-lished.Furthermore,such brain markers need to meet the requirements of precision medicine and be accurate in aiding diagnosis at an individual rather than only a group level.Objective:This study aimed to identify and model brain-wide differences in structural connectivity using diffusion tensor imaging(DTI)in young ASD and typically developing(TD)children.Methods:A discovery cohort including 93 ASD and 26 TD children and two independent validation cohorts including 12 ASD and 9 TD children from three different cities in China were included.Brain-wide(294 regions)structural connectivity was measured using DTI(fractional anisotropy,FA)together with symptom severity and cognitive development.A connection matrix was constructed for each child for comparisons between ASD and TD groups.Pattern classification was performed on the discovery dataset and the resulting model was tested on the two independent validation datasets.Results:Thirty-three structural connections showed increased FA in ASD compared to TD children and associated with both autistic symptom severity and impaired general cognitive development.The majority(29/33)involved the frontal lobe and comprised five different networks with functional relevance to default mode,motor control,social recognition,language and reward.Overall,clas-sification achieved very high accuracy of 96.77%in the discovery dataset,and 91.67%and 88.89%in the two independent validation datasets.Conclusions:Identified structural connectivity differences primarily involving the frontal cortex can very accurately distinguish novel individual ASD from TD children and may therefore represent a robust early brain biomarker which can address the requirements of precision medicine. 展开更多
关键词 autism spectrum disorder diffusion tensor imaging fractional anisotropy brain structural connectivity individual diag-nosis early childhood
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Fibrous Structure of Connective Tissue of Normal Human Lamina Cribrosa.
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作者 Ren Zeqin. Dept Ophthal, the First Teaching Hospital, BMU, Beijing 100034 《Chinese Medical Journal》 SCIE CAS CSCD 1995年第7期78-78,共1页
Fibrous components and structural morphology of the connective tissue of the lamina cribrosa obtained from 35 normal human autopsy eyes were examined by histochemical staining, transmission electron microscopic and co... Fibrous components and structural morphology of the connective tissue of the lamina cribrosa obtained from 35 normal human autopsy eyes were examined by histochemical staining, transmission electron microscopic and computer- 展开更多
关键词 Fibrous structure of Connective Tissue of Normal Human Lamina Cribrosa
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BUILDING WITH BAMBOO: A REVIEW OF CULM CONNECTION TECHNOLOGY
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作者 Kira Disén Peggi L.Clouston 《Journal of Green Building》 2013年第4期83-93,共11页
Interest in the engineering performance of bamboo is on the rise primarily due to its rapid regenerative qualities and high strength-to-weight ratio.It has been a standard,sustainable building material for thousands o... Interest in the engineering performance of bamboo is on the rise primarily due to its rapid regenerative qualities and high strength-to-weight ratio.It has been a standard,sustainable building material for thousands of years in Asia and South America,where it grows naturally.Although there are many examples of magnificent bamboo structures,standards and documentation on safe and reliable bamboo design are scarce,particularly for connection design.Traditional connections involve friction-tight lashings(eg.ropes and cords of dried grasses)and pin-and-socket connections such as dowels and pegs,but more recent advances have involved integration with steel hardware and concrete.This paper presents bamboo as a feasible alternative building material and presents a review of past,current and emerging technologies to join hollow bamboo culms in structural applications.The paper’s intent is to give an overview of the current state of bamboo connection technology and to promote developments in the emerging field of bamboo engineering.Recent technological advances and visionary architects have proven that it is possible to create safe structures that are not only sustainable but have tremendous potential for use in disaster relief and quick-build scenarios. 展开更多
关键词 bamboo structural connections natural building material mechanical properties
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The Brain Connectome for Chinese Reading 被引量:2
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作者 Wanwan Guo Shujie Geng +1 位作者 Miao Cao Jianfeng Feng 《Neuroscience Bulletin》 SCIE CAS CSCD 2022年第9期1097-1113,共17页
Chinese,as a logographic language,fundamentally differs from alphabetic languages like English.Previous neuroimaging studies have mainly focused on alphabetic languages,while the exploration of Chinese reading is stil... Chinese,as a logographic language,fundamentally differs from alphabetic languages like English.Previous neuroimaging studies have mainly focused on alphabetic languages,while the exploration of Chinese reading is still an emerging and fast-growing research field.Recently,a growing number of neuroimaging studies have explored the neural circuit of Chinese reading.Here,we summarize previous research on Chinese reading from a connectomic perspective.Converging evidence indicates that the left middle frontal gyrus is a specialized hub region that connects the ventral with dorsal pathways for Chinese reading.Notably,the orthography-to-phonology and orthography-to-semantics mapping,mainly processed in the ventral pathway,are more specific during Chinese reading.Besides,in addition to the left-lateralized language-related regions,reading pathways in the right hemisphere also play an important role in Chinese reading.Throughout,we comprehensively review prior findings and emphasize several challenging issues to be explored in future work. 展开更多
关键词 Brain connectome Chinese reading Word recognition Reading comprehension structural connectivity Functional connectivity
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Hybrid beamforming with discrete phase shifters for millimeter wave backhaul networks 被引量:1
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作者 Yuan Jiangwei Li Xiaohui +1 位作者 Pu Wenjuan Yang Xu 《The Journal of China Universities of Posts and Telecommunications》 EI CSCD 2018年第5期31-38,共8页
Hybrid beamforming( HBF) technology becomes one of the key technologies in the millimeter wave( mm Wave)mobile backhaul systems,for its lower complexity and low power consumption compared to full digital beamform... Hybrid beamforming( HBF) technology becomes one of the key technologies in the millimeter wave( mm Wave)mobile backhaul systems,for its lower complexity and low power consumption compared to full digital beamforming( DBF). Two structures of HBF exist in the mm Wave mobile backhaul system,namely,the fully connected structures( FCS) and partially connected structures( PCS). However,the existing methods cannot be applied to both structures. Moreover,the ideal phase shifter is considered in some current HBF methods,which is not realistic. In this paper,a HBF algorithm for both structures based on the discrete phase shifters is proposed in the mm Wave mobile backhaul systems. By using the principle of alternating minimization,the optimization problem of HBF is decomposed into a DBF optimization problem and an analog beamforming( ABF) optimization problem.Then the least square( LS) method is enabled to solve the optimization model of DBF. In addition,the achievable data rate for both structures with closed-form expression which can be used to convert the optimization model into a single-stream beamforming optimization model with per antenna power constraint is derived. Therefore,the ABF is easily solved. Simulation results show that the performance of the proposed HBF method can approach the full DBF by using a lower resolution phase shifter. 展开更多
关键词 millimeter wave backhanl networks fully connected structure partially connected structure hybrid beamforming limited phase shiftersresolution
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A Volumetric and Functional Connectivity MRI Study of Brain Arginine-Vasopressin Pathways in Autistic Children 被引量:6
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作者 Xiao-Jing Shou Xin-Jie Xu +8 位作者 Xiang-Zhu Zeng Ying Liu Hui-Shu Yuan Yan Xing Mei-Xiang Jia Qing-Yun Wei Song-Ping Han Rong Zhang Ji-Sheng Han 《Neuroscience Bulletin》 SCIE CAS CSCD 2017年第2期130-142,共13页
Dysfunction of brain-derived arginine-vasopressin(AVP) systems may be involved in the etiology of autism spectrum disorder(ASD). Certain regions such as the hypothalamus, amygdala, and hippocampus are known to con... Dysfunction of brain-derived arginine-vasopressin(AVP) systems may be involved in the etiology of autism spectrum disorder(ASD). Certain regions such as the hypothalamus, amygdala, and hippocampus are known to contain either AVP neurons or terminals and may play an important role in regulating complex social behaviors.The present study was designed to investigate the concomitant changes in autistic behaviors, circulating AVP levels, and the structure and functional connectivity(FC) of speci?c brain regions in autistic children compared with typically developing children(TDC) aged from 3 to5 years. The results showed:(1) children with ASD had a signi?cantly increased volume in the left amygdala and left hippocampus, and a signi?cantly decreased volume in the bilateral hypothalamus compared to TDC, and these were positively correlated with plasma AVP level.(2) Autistic children had a negative FC between the left amygdala and the bilateral supramarginal gyri compared to TDC. The degree of the negative FC between amygdala and supramarginal gyrus was associated with a higher score on the clinical autism behavior checklist.(3) The degree of negative FC between left amygdala and left supramarginal gyrus was associated with a lowering of the circulating AVP concentration in boys with ASD.(4) Autistic children showed a higher FC between left hippocampus and right subcortical area compared to TDC.(5) The circulating AVP was negatively correlated with the visual and listening response score of the childhood autism rating scale.These results strongly suggest that changes in structure and FC in brain regions containing AVP may be involved in the etiology of autism. 展开更多
关键词 Autism Children Arginine-vasopressin MRI structure Connectivity Behavior
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Increasing loss of mature boreal forests around protected areas with red-listed forest species
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作者 Aino‑Maija Määttänen Raimo Virkkala +1 位作者 Niko Leikola Risto K.Heikkinen 《Ecological Processes》 SCIE EI 2022年第1期319-331,共13页
Background:Protected areas(PA)are central to biodiversity,but their efficiency is challenged by human‑induced habitat loss and fragmentation.In the Fennoscandian boreal region,forestry with clearcutting is a threat to... Background:Protected areas(PA)are central to biodiversity,but their efficiency is challenged by human‑induced habitat loss and fragmentation.In the Fennoscandian boreal region,forestry with clearcutting is a threat to biodiversity causing the loss of mature forest elements and deterioration of ecological processes in forest landscapes,ultimately affecting PAs via declined structural connectivity.This paper aims to(1)determine PAs with high,red‑listed species concentrations;(2)estimate the change in forest habitat around these PAs on different spatial scales;and(3)determine if forest management intensity is higher around biologically most valuable PAs.Occurrences of red‑listed forest‑dwelling species in Finland were used to identify PAs harbouring these species and to produce site‑specific importance indices.CORINE landcover data was used as a baseline for the distribution of forests to assess the cover of clear‑cuttings from 2001 to 2019 with the Global Forest Change(GFC)data set in three buffer areas around the PAs with occurrences of red‑listed species.Results:The largest proportion of clear‑cuts occurred in 1 km and 10 km buffers around the PAs in the southern and middle boreal zones,being ca.20%.This indicates that the forest habitat is degrading fast at regional and landscape levels.On the positive side,the change in forest cover was lower around the biologically most important PAs compared to other PAs with red‑listed species.Conclusions:Open and free satellite‑data based assessments of the cover and change of forests provide reliable estimates about the rates at which mature and old‑growth forests are being converted into young managed ones in Finland mainly via clear‑cuts on different scales around PAs.The rate of clear‑cuts was lowest in adjacent buffer areas next to the most species‑rich PAs,which provides opportunities for biodiversity conservation efforts to be targeted to the remaining mature and old‑growth forests found in the vicinity of these areas. 展开更多
关键词 Biodiversity conservation Boreal forest Change detection Global Forest Watch Habitat loss structural connectivity
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New Construction of Complex Manifold via Conifold Transition
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作者 Jin Xing XU 《Acta Mathematica Sinica,English Series》 SCIE CSCD 2012年第7期1347-1368,共22页
For a generic anti-canonical hypersurface in each smooth toric Fano 4-fold with rank 2 Picard group, we prove there exist three isolated rational curves in it. Moreover, for all these 4-folds except one, the contracti... For a generic anti-canonical hypersurface in each smooth toric Fano 4-fold with rank 2 Picard group, we prove there exist three isolated rational curves in it. Moreover, for all these 4-folds except one, the contractions of generic anti-canonical hypersurfaces along the three rational curves can be deformed to smooth threefolds which is diffeomorphic to connected sums of S3 ~ S~. In this manner, we obtain complex structures with trivial canonical bundles on some connected sums of S^3 × S^3. This construction is an analogue of that made by Friedman [On threefolds with trivial canonical bundle. In: Complex Geometry and Lie Theory, volume 53 of Proc. Sympos. Pure Math., Amer. Math. Soc., Providence, RI, 1991, 103-134], Lu and Tian [Complex structures on connected sums of S^3× S^3. In: Manifolds and Geometry, Pisa, 1993, 284 293] who used only quintics in P^4. 展开更多
关键词 Calabi Yau threefolds conifold transitions complex structures on connected sums of S^3× S^3
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