分类: 生物学 >> 植物学 >> 应用植物学 提交时间: 2020-05-31 合作期刊: 《干旱区科学》
摘要: The vegetation ecosystem of the Qinghai–Tibet Plateau in China, considered to be the ′′natural laboratory′′ of climate change in the world, has undergone profound changes under the stress of global change. Herein, we analyzed and discussed the spatial-temporal change patterns and the driving mechanisms of net primary productivity (NPP) in the Qinghai–Tibet Plateau from 2000 to 2015 based on the gravity center and correlation coefficient models. Subsequently, we quantitatively distinguished the relative effects of climate change (such as precipitation, temperature and evapotranspiration) and human activities (such as grazing and ecological construction) on the NPP changes using scenario analysis and Miami model based on the MOD17A3 and meteorological data. The average annual NPP in the Qinghai–Tibet Plateau showed a decreasing trend from the southeast to the northwest during 2000–2015. With respect to the inter-annual changes, the average annual NPP exhibited a fluctuating upward trend from 2000 to 2015, with a steep increase observed in 2005 and a high fluctuation observed from 2005 to 2015. In the Qinghai–Tibet Plateau, the regions with the increase in NPP (change rate higher than 10%) were mainly concentrated in the Three-River Source Region, the northern Hengduan Mountains, the middle and lower reaches of the Yarlung Zangbo River, and the eastern parts of the North Tibet Plateau, whereas the regions with the decrease in NPP (change rate lower than –10%) were mainly concentrated in the upper reaches of the Yarlung Zangbo River and the Ali Plateau. The gravity center of NPP in the Qinghai–Tibet Plateau has moved southwestward during 2000–2015, indicating that the increment and growth rate of NPP in the southwestern part is greater than those of NPP in the northeastern part.Further, a significant correlation was observed between NPP and climate factors in the Qinghai–Tibet Plateau. The regions exhibiting a significant correlation between NPP and precipitation were mainly located in the central and eastern Qinghai–Tibet Plateau, and the regions exhibiting a significant correlation between NPP and temperature were mainly located in the southern and eastern Qinghai–Tibet Plateau. Furthermore, the relative effects of climate change and human activities on the NPP changes in the Qinghai–Tibet Plateau exhibited significant spatial differences in three types of zones, i.e., the climate change-dominant zone, the human activity-dominant zone, and the climate change and human activity interaction zone. These research results can provide theoretical and methodological supports to reveal the driving mechanisms of the regional ecosystems to the global change in the Qinghai–Tibet Plateau.
分类: 医学、药学 >> 临床医学 提交时间: 2023-07-25 合作期刊: 《中国全科医学》
摘要: 背景 近年来移动智慧医疗在心血管疾病的筛查、干预、救治、管理中的优势愈加突出。其中单导联可穿戴心电设备在院外应用于心律失常患者的前期筛查、诊断中的应用价值得到了学者及临床的认可。但因其导联和匹配的云平台功能的单一性,限制了其在基层医疗机构中对慢病患者风险筛查及长期随访管理中的应用。目的 本研究立足分级诊疗,从慢性病防控的视角,以单导联可穿戴心电设备为载体,探索移动智慧医疗在基层老年慢病患者中心血管病风险防控中的应用价值。方法 选取 2022 年 18 月宁夏地区 20 家基层医疗机构收治的 3 000 例 65 岁以上慢性病患者为研究对象,其中男 1 202 例、女 1 798 例;平均年龄(71.35.0)岁。基层医生借助手机 APP 及患者管理云平台录入患者资料,给患者佩戴单导联可穿戴心电设备采集 72 h 心电数据上传至患者管理云平台。由专业心电图医生分别对数据进行心律失常、心率变异性(HRV)、阻塞性睡眠呼吸暂停综合征(OSAHS)分析及风险分层,并综合 3 种分析方法的分层结果将心血管疾病综合风险符合低、中及高危的数据在云平台勾选相应的标识。云平台对高、中危患者以短信形式通知基层医生对患者进行不同流程的管理。统计 3 种分析方法不同风险分层患者检出例数,低、中、高危心血管病风险患者检出例数及按流程管理率。结果 检出心律失常符合正常、阳性及重大阳性者分别为 1 526 例(50.86%)、1 349 例(44.97%)、125 例(4.17%);HRV 符合轻度、中度及重度降低者分别为 2 330 例(78.5%)、630 例(21.21%)、8 例(0.27%);OSAHS 符合轻度、中度、重度异常者分别 1 769 例(65.57%)、573 例(19.31%)、626 例(21.09%)。心血管疾病综合风险为低、中、高危患者分别为 744 例(24.80%)、1 640 例(54.67%)、616 例(30.53%)。心血管疾病综合风险为高、中、低危患者按流程管理率分别为 94.49%(703 例)、88.10%(1 445 例)、100.00%(616 例)。结论 移动智慧医疗技术与心律失常、HRV 及 OSAHS 分析方法联合应用于基层老年慢病患者心血管疾病防控,不但可提高患者心血管疾病风险检出率,还能提高其管理率,有利于基层老年慢性病患者心血管疾病防控体系的建立。
分类: 天文学 >> 天文学 提交时间: 2023-06-07 合作期刊: 《天文学进展》
摘要: 小质量 X 射线双星系统中的辐射涵盖射电到伽马射线波段。通常认为 X 射线辐射来自吸积盘内区,射电辐射主要由喷流贡献,而紫外、光学以及近红外 (UV/OPT/NIR) 辐射可能由多种辐射机制贡献。确定 X 射线双星系统中 UV/OPT/NIR 辐射的主导机制可以对吸积过程的研究提供非常重要的信息。分析不同波段辐射流量之间的相关性是一种重要的研究方法。前人通过分析 UV/OPT/NIR 辐射与 X 射线辐射之间的幂律相关性,研究了 UV/OPT/NIR 辐射的主要起源。总结了不同源中存在的幂律相关性的观测结果,并介绍了用于解释 UV/OPT/NIR 辐射起源的理论模型。
分类: 医学、药学 >> 临床医学 提交时间: 2023-07-26 合作期刊: 《中国全科医学》
摘要: 背景 建立统一的全科医学诊断术语和编码集是提升我国社区卫生服务机构服务水平和推动全科医学体系建设的重要手段,但一直以来缺乏适合我国全科医学发展现状的规范化诊断术语和编码,导致全科医师的诊断不规范、不标准,严重阻碍了我国全科医学的发展。目的 构建社区卫生服务全科医学诊断术语和编码集,并验证诊断术语和编码集的有效性,促进社区全科诊断标准化和规范化。方法 通过文献学习和专家咨询法,结合社区常见健康问题谱和疾病谱,基于 ICD-10 构建社区卫生服务适用的全科诊断术语和编码集;于 2021 年 9 月2022 年 2 月在深圳市两个行政区的 259 家社区健康服务中心试点运行所研制的全科诊断术语和编码集以进行实证研究,以社区健康服务信息系统后台诊断数据和以社区全科医师为样本的问卷调研为基本数据,分析试点实施情况,验证诊断术语和编码集的合理性和有效性。结果 编制完成全科医学诊断术语和编码集,其中全科诊断分类 41 种,含标准化全科诊断术语和编码 6 629 项。深圳市两区试点结果显示,规范化干预区域的诊断名称规范化构成比较非试点区高86.13%~95.38%;试点区该时段涉及的诊断名称同比下降 96.60%,规范化干预使全科常用诊断大为聚焦,且跟社区疾病谱基本一致,社区常见疾病诊断归集度高。问卷调查结果显示,87.31%(227/260)的调查对象认为编码集对社区诊断规范化有促进作用,77.31%(201/260)的调查对象支持编码集的上线应用。结论 本研究初步建立规范化和标准化的全科医学诊断术语和编码集,形成了社区全科诊断术语字典,解决数据分析时一义多词的难题,同时兼顾上下转诊和医保对接,有效提高了社区诊疗效率和规范化水平,对基层卫生事业发展产生积极地推动作用。
分类: 天文学 >> 天文学 提交时间: 2023-06-07 合作期刊: 《天文学进展》
摘要: 光学窄波段观测能够表征发射线天体清晰的结构,是研究发射线天体的重要手段,对恒星形成区、类星体窄线区、星系 H II 区、星际介质等方面的研究具有重要意义。消除窄波段图像的连续谱是常用的搜寻发射线天体的方法,传统上连续谱扣除的解决方法是根据像素位置、方向和强度来调整图像对齐,然后进行两幅图像的相减,但是其过程繁琐不适合用于巡天大数据减连续谱。基于窄波段巡天项目 (narrow band survey, NBS) [S II] 波段数据,提出一种通过自动匹配宽、窄波段流量数据与星像轮廓方法。该方法自动匹配图像天文位置,避免了图像像素对齐过程中像素位置调整和图像选择。通过快速探测宽、窄视场图像的流量和星像,完成相应匹配,提高图像相减效率。根据实验结果,减完连续谱的图像中大概 70% 亮星能被扣除干净,并且能够获取到较清晰的发射线天体结构。目前该方法已用于搜寻 Herbig-Haro 天体 (简称 HH 天体),超新星遗迹候选体选取等工作中。
提交时间: 2017-05-02
摘要: Crystalline silicon thin film [c-Si TF] solar cells with an active layer thickness of a few micrometers may provide a viable pathway for further sustainable development of photovoltaic technology, because of its potentials in cost reduction and high effic
分类: 生物学 >> 生态学 提交时间: 2017-11-17
摘要: In recent years, immunotherapies, such as those involving chimeric antigen receptor (CAR) T cells, have become increasingly promising approaches to non-small-cell lung cancer (NSCLC) treatment. In this study, we explored the antitumor potential of prostate stem cell antigen (PSCA)-redirected CAR T and mucin 1 (MUC1)-redirected CAR T cells in tumor models of NSCLC. First, we generated patient-derived xenograft (PDX) mouse models of human NSCLC that maintained the antigenic profiles of primary tumors. Next, we demonstrated the expression of PSCA and MUC1 in NSCLC, followed by the generation and confirmation of the specificity and efficacy of PSCA-and MUC1-targeting CAR T cells against NSCLC cell lines in vitro. Finally, we demonstrated that PSCA-targeting CAR T cellscould efficiently suppress NSCLC tumor growth in PDX mice and synergistically eliminate PSCA(+)MUC1(+) tumors when combined with MUC1-targeting CAR Tcells. Taken together, our studies demonstrate that PSCA and MUC1 are both promising CAR T cell targets in NSCLC and that the combinatorial targeting ofthese antigens could further enhance the antitumor efficacy of CAR T cells.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: Among the heavy metal ions, copper(II) can cause eye and liver damage at high uptake. The existence of copper ions (Cu2+) even with an ultralow concentration of less than 0.1 μg g−1 can be toxic to living organisms. Thus, it is highly desirable to develop efficient adsorbents to remove Cu2+ from aqueous solu- tions. In this work, without any surface functionalization or pretreatment, a water-stable zeolitic imidazo- late framework (ZIF-8) synthesized at room temperature is directly used as a highly efficient adsorbent for removal of copper ions from aqueous solutions. To experimentally unveil the adsorption mechanism of Cu2+ by using ZIF-8, we explore various effects from a series of important factors, such as pH value, contact time, temperature and initial Cu2+ concentration. As a result, ZIF-8 nanocrystals demonstrate an unexpected high adsorption capacity of Cu2+ and high removal efficiency for both high and low concen- trations of Cu2+ from water. Moreover, ZIF-8 nanocrystals possess fast kinetics for removing Cu2+ with the adsorption time of less than 30 min. In addition, the pH of the solution ranging from 3 to 6 shows little effect on the adsorption of Cu2+ by ZIF-8. The adsorption mechanism is proposed for the first time and systematically verified by various characterization techniques, such as TEM, FTIR, XPS, XRD and SEM.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: Two types of fibers were prepared by using bio- based materials: a mono-filament made from poly(3- hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) and a multi-filament made from poly(3-hydroxybutyrate-co-3- hydroxyvalerate) (PHBV) and polylactic acid (PLA) blend. The two fibers were evaluated for mechanical properties, biocompatibility and degradability for the potential appli- cation as medical sutures. The PHBHHx fiber showed remarkable biocompatibility by H.E. Stainning, with very little impact to the surrounding tissues. The degradation of the fiber was observed by SEM after implantation for 36 weeks, and the major degradation product was detected after 96 weeks. Consistently, the PHBHHx fiber main- tained more than half of the mechanical properties after 96 weeks. The other fiber was prepared by twisting PHBV/PLA blend strands to a bunch, and showed high biocom- patibility and relatively high degradability. The bunched structure loosed after 36 weeks of implantation. These low- cost and easily prepared fibers have great potential in medical applications, since they could avoid the formation of fibrous capsule, reduce the size of scar, and degrade into non-toxic and even beneficial products.
提交时间: 2017-05-02
摘要: Template-free synthesis of TiO2 architectures with controlled morphology evolution has been developed through solvothermal reaction in 1,4-dioxane. By simply varying the molar ratio of the concentrated HCl over Titanium isopropoxide [TTIP] from 0 to 5.0,
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: In the preliminary design process of switched reluctance machine (SRM), adjusting the number of wingding turns or cross-sectional area of conductor to optimize windings design has dramatic effects on the performances like torque density, efficiency and thermal dissipation and so on. However, the difficulty exists on how to guarantee these performances while optimizing winding design. This paper proposes an analytical optimization design method based on an regulation model of ampere density and coil space factor, which can directly determine the optimal number of winding turns, the cross- sectional area of conductor, the ampere density and the coil space factor. And a MATLAB pre-design program has been developed to provide two design schemes respectively with and without the optimization model. The comparison analysis has been further carried out with finite element analysis (FEA). The simulation results verify that the performances can be highly improved with the proposed optimization model.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: Antireflection (AR) coatings that exhibit multi- functional characteristics, including high transparency, robust resistance to moisture, high hardness, and antifogging proper- ties, were developed based on hollow silica−silica nano- composites. These novel nanocomposite coatings with a closed-pore structure, consisting of hollow silica nanospheres (HSNs) infiltrated with an acid-catalyzed silica sol (ACSS), were fabricated using a low-cost sol−gel dip-coating method. The refractive index of the nanocomposite coatings was tailored by controlling the amount of ACSS infiltrated into the HSNs during synthesis. Photovoltaic transmittance (TPV) values of 96.86− 97.34% were obtained over a broad range of wavelengths, from 300 to 1200 nm; these values were close to the theoretical limit for a lossy single-layered AR coating (97.72%). The nanocomposite coatings displayed a stable TPV, with degradation values of less than 4% and 0.1% after highly accelerated temperature and humidity stress tests, and abrasion tests, respectively. In addition, the nanocomposite coatings had a hardness of approximately 1.6 GPa, while the porous silica coatings with an open-pore structure showed more severe degradation and had a lower hardness. The void fraction and surface roughness of the nanocomposite coatings could be controlled, which gave rise to near-superhydrophilic and antifogging characteristics. The promising results obtained in this study suggest that the nanocomposite coatings have the potential to be of benefit for the design, fabrication, and development of multifunctional AR coatings with both omnidirectional broadband transmission and long-term durability that are required for demanding outdoor applications in energy harvesting and optical instrumentation in extreme climates or humid conditions.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: A new strategy to synthesize hierarchical, porous titania/carbon [TiO2/C] hybrid microspheres via solvothermal reaction in N,N′-dimethyl formamide [DMF] has been developed. In situ formed polystyrene [PS] colloids have been used as templating agent and carbon source, through which TiO2/PS microspheres with a diameter of ca. 1 μm are built by packed TiO2 nanoparticles of tens of nanometers. The TiO2/PS microspheres are converted to TiO2/C microspheres with different amounts of carbon under controlled calcination condition. The mechanism investigation unveils that the introduction of concentrated HCl creates surface tension between PS and DMF, leading to the formation of PS colloids in solution. The solvothermal treatment further promotes the formation of PS colloids and integration of the titania nanoparticles within the PS colloids. The morphology, crystallinity, nature and content of carbon, UV–Vis absorption, carbon doping, pore size distribution, pore volume, and BET surface area of the TiO2 microspheres with different amounts of carbon have been measured. The applications of the TiO2/C hybrid microspheres as photo catalyst for water splitting and lithium-ion battery anode have been demonstrated. Superior photo catalytic activity for hydrogen conversion under both full spectrum and visible light illumination compared to commercial P25 has been observed for the TiO2/C microspheres with 2 wt% of carbon. Besides, the TiO2/C microspheres with 8 wt% of carbon as lithium-ion battery anode showed a much higher capacity than the bare TiO2 microsphere anode. The origin for the enhanced performance as photo catalyst and lithium-ion battery anode is discussed.
分类: 物理学 >> 核物理学 提交时间: 2016-09-14
摘要: By regularly monitoring the most stable millisecond pulsars over many years, pulsar timing arrays (PTAs) are positioned to detect and study correlations in the timing behaviour of those pulsars. Gravitational waves (GWs) from supermassive black hole binaries (SMBHBs) are an exciting potentially detectable source of such correlations. We describe a straight-forward technique by which a PTA can be "phased-up" to form time series of the two polarisation modes of GWs coming from a particular direction of the sky. Our technique requires no assumptions regarding the time-domain behaviour of a GW signal. This method has already been used to place stringent bounds on GWs from individual SMBHBs in circular orbits. Here, we describe the methodology and demonstrate the versatility of the technique in searches for a wide variety of GW signals including bursts with unmodeled waveforms. Using the first six years of data from the Parkes Pulsar Timing Array, we conduct an all-sky search for a detectable excess of GW power from any direction. For the lines of sight to several nearby massive galaxy clusters, we carry out a more detailed search for GW bursts with memory, which are distinct signatures of SMBHB mergers. In all cases, we find that the data are consistent with noise.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: A new facile scalable method has been developed to synthesize silicon oxycarbide (SiOC)/carbon nanohybrids using difunctional dental methacrylate monomers as solvent and carbon source and the silane coupling agent as the precursor for SiOC. The content (from 100% to 40% by mass) and structure (ratio of disor- dered carbon over ordered carbon) of the free carbon matrix have been systematically tuned by varying the mass ratio of methacryloxy- propyltrimethoxysilane (MPTMS) over the total mass of the resin monomers from 0.0 to 6.0. Compared to the bare carbon anode, the introduction of MPTMS significantly improves the electrochemical performance as a lithium-ion battery anode. The initial and cycled discharge/charge capacities of the SiOC/C nanohybrid anodes reach maximum with the MPTMS ratio of 0.50, which displays very good rate performance as well. Detailed structures and electrochemical performance as lithium-ion battery anodes have been systematically investigated. The structure−property correlation and corresponding mechanism have been discussed.
提交时间: 2017-05-02
摘要: Carbon monoxide clathrate hydrate is a potentially important constituent in the solar system. In contrast to the well-established relation between the size of gaseous molecule and hydrate structure, previous work showed that carbon monoxide molecules pref
提交时间: 2017-05-02
摘要: Two types of flexible terahertz metamaterials were fabricated on polyethylene naphthalate [PEN] substrates. The unit cell of one type consists of two identical split-ring resonators [SRRs] that are arranged face-to-face [i.e., FlexMetaF]; the unit cell of
提交时间: 2017-05-02
摘要: White TiO2 nanoparticles [NPs] have been widely used for cancer photodynamic therapy based on their ultraviolet light-triggered properties. To date, biomedical applications using white TiO2 NPs have been limited, since ultraviolet light is a well-known mu