期刊文献+
共找到36,778篇文章
< 1 2 250 >
每页显示 20 50 100
More Peripheral Visualization of Hepatic Arteries by Using Respiratory-Triggered 3D True Steady-State Free-Precession Projection Magnetic Resonance Angiographic Sequences with Time-Spatial Labeling Inversion Pulse
1
作者 Daisuke Tsuge Ryohei Kuwatsuru +3 位作者 Tatsuro Inoue Yuki Yamashiro Kazuhiro Suzuki Akihiko Shiraishi 《Open Journal of Radiology》 2014年第4期314-321,共8页
Purpose: To evaluate respiratory-triggered three-dimensional (3D) true steady-state free-precession (SSFP) projection magnetic resonance angiographic sequences with time-spatial labeling inversion pulse (Time-SLIP) fo... Purpose: To evaluate respiratory-triggered three-dimensional (3D) true steady-state free-precession (SSFP) projection magnetic resonance angiographic sequences with time-spatial labeling inversion pulse (Time-SLIP) for visualizing the hepatic arteries and to optimize the image acquisition protocol. Materials and Methods: A 1.5-T clinical magnetic resonance imager was used to perform abdominal magnetic resonance angiography (MRA) in 25 consecutive patients before transcatheter arterial chemoembolization or surgery. We compared two selective space-labeling inversion pulse (tag pulse) patterns (Patterns I and II, oblique and parallel tag pulses, respectively). Two experienced radiologists evaluated the number of hepatic arterial branches visible on the acquired MRA images, and the results were referenced with those on images from intra-arterial digital subtraction angiography. Results: Images were acquired from all patients. The two radiologists clearly visualized branches of the left and right hepatic arteries. More peripheral hepatic arterial branches were identified in MRA images captured by using tag pulse Pattern I than in those acquired by using Pattern II (P P > 0.05). Conclusion: Non-contrast-enhanced Time-SLIP hepatic MRA with true SSFP allowed selective visualization of peripheral hepatic vessels. 展开更多
关键词 Hepatic Artery Non-Contrast Magnetic Resonance ANGIOGRAPHY time-spatial LABELING INVERSION PULSE TRUE SSFP ANGIOGRAPHY
暂未订购
A round-trip journey of electrons:Electron catalyzed direct fixation of N_(2)to azos 被引量:2
2
作者 Baijing Wu Jinrui Li +5 位作者 Xiaoxue Luo Jingtian Ni Yiting Lu Minhua Shao Cunpu Li Zidong Wei 《Chinese Journal of Catalysis》 2025年第1期386-393,共8页
The triple bond in N_(2)has an extremely high bond energy and is thus difficult to break.N_(2)is commonly converted into NH3 artificially via the Haber-Bosch process,and NH_(3)can be utilized to produce other nitrogen... The triple bond in N_(2)has an extremely high bond energy and is thus difficult to break.N_(2)is commonly converted into NH3 artificially via the Haber-Bosch process,and NH_(3)can be utilized to produce other nitrogen-containing chemicals.Here,we developed an electron catalyzed method to directly fix N_(2)into azos,by pushing and pulling the electron into and from the aromatic halide with the cyclic voltammetry method.The round-trip journey of electron can successfully weaken the triple bond in N_(2)through the electron pushing-induced aryl radical via a“brick trowel”transition state,and then produce the diazonium ions by pulling the electron out from the diazo radical intermediate.Different azos can be synthesized with this developed electron catalyzed approach.This approach provides a novel concept and practical route for the fixation of N_(2)at atmospheric pressure into chemical products valuable for industrial and commercial applications. 展开更多
关键词 fixed N_(2) AZO Electron catalyzed strategy "Brick trowel"transition state Arylradicals
在线阅读 下载PDF
The(Homotopy)Fixed Point Set of S^(1)-Actions on Rationally Elliptic 4-Manifolds
3
作者 Chen Huimin Liu Xiugui 《南开大学学报(自然科学版)》 北大核心 2025年第3期32-37,共6页
Let X be a closed simply connected rationally elliptic 4-manifold.The rational homotopy type of homotopy fixed point sets X^(hS^(1))is determined,and based on some relations between X^(hS^(1))and X^(S^(1)),the rationa... Let X be a closed simply connected rationally elliptic 4-manifold.The rational homotopy type of homotopy fixed point sets X^(hS^(1))is determined,and based on some relations between X^(hS^(1))and X^(S^(1)),the rational homotopy type of the fixed point set X^(S^(1))is determined. 展开更多
关键词 rationally elliptic 4-manifolds rational homotopy type homotopy fixed point set fixed point set
原文传递
Coincidence Point and Common Fixed Point Theorems on b-Metric-like Spaces
4
作者 LUO Ting 《应用数学》 北大核心 2025年第3期831-840,共10页
In this paper,we establish common fixed point theorems for expansive map?pings on b-metric-like space and coincidence point for f-weakly isotone increasing mappings in partially ordered b-metric-like space.The main re... In this paper,we establish common fixed point theorems for expansive map?pings on b-metric-like space and coincidence point for f-weakly isotone increasing mappings in partially ordered b-metric-like space.The main results generalize and extend several well-known comparable results from the existing literature.Moreover,some examples are provided to illustrate the main results. 展开更多
关键词 b-metric-like space Partially ordered b-metric-like space Expansive mapping f-weakly isotone mapping Coincidence point Common fixed point
在线阅读 下载PDF
Fixed Neural Network Image Steganography Based on Secure Diffusion Models
5
作者 Yixin Tang Minqing Zhang +2 位作者 Peizheng Lai Ya Yue Fuqiang Di 《Computers, Materials & Continua》 2025年第9期5733-5750,共18页
Traditional steganography conceals information by modifying cover data,but steganalysis tools easily detect such alterations.While deep learning-based steganography often involves high training costs and complex deplo... Traditional steganography conceals information by modifying cover data,but steganalysis tools easily detect such alterations.While deep learning-based steganography often involves high training costs and complex deployment.Diffusion model-based methods face security vulnerabilities,particularly due to potential information leakage during generation.We propose a fixed neural network image steganography framework based on secure diffu-sion models to address these challenges.Unlike conventional approaches,our method minimizes cover modifications through neural network optimization,achieving superior steganographic performance in human visual perception and computer vision analyses.The cover images are generated in an anime style using state-of-the-art diffusion models,ensuring the transmitted images appear more natural.This study introduces fixed neural network technology that allows senders to transmit only minimal critical information alongside stego-images.Recipients can accurately reconstruct secret images using this compact data,significantly reducing transmission overhead compared to conventional deep steganography.Furthermore,our framework innovatively integrates ElGamal,a cryptographic algorithm,to protect critical information during transmission,enhancing overall system security and ensuring end-to-end information protection.This dual optimization of payload reduction and cryptographic reinforcement establishes a new paradigm for secure and efficient image steganography. 展开更多
关键词 Image steganography fixed neural network secure diffusion models ELGAMAL
在线阅读 下载PDF
MEMS microwave power detection chip based on fixed beams and its model
6
作者 Qirui Xu Zhiyin Ding Debo Wang 《Journal of Semiconductors》 2025年第6期87-95,共9页
In order to solve the problems of low overload power in MEMS cantilever beams and low sensitivity in traditional MEMS fixed beams,a novel MEMS microwave power detection chip based on the dual-guided fixed beam is desi... In order to solve the problems of low overload power in MEMS cantilever beams and low sensitivity in traditional MEMS fixed beams,a novel MEMS microwave power detection chip based on the dual-guided fixed beam is designed.A gap between guiding beams and measuring electrodes is designed to accelerate the release of the sacrificial layer,effectively enhanc-ing chip performance.A load sensing model for the MEMS fixed beam microwave power detection chip is proposed,and the mechanical characteristics are analyzed based on the uniform load applied.The overload power and sensitivity are investi-gated using the load sensing model,and experimental results are compared with theoretical results.The detection chip exhibits excellent microwave characteristic in the 9-11 GHz frequency band,with a return loss less than-10 dB.At a signal fre-quency of 10 GHz,the theoretical sensitivity is 13.8 fF/W,closely matching the measured value of 14.3 fF/W,with a relative error of only 3.5%.These results demonstrate that the proposed load sensing model provides significant theoretical support for the design and performance optimization of MEMS microwave power detection chips. 展开更多
关键词 detection chip dual-guided fixed beam MEMS load sensing model sensitivity
在线阅读 下载PDF
Fixed Point Results for Extended Contractions with Various Weak Conditions in Generalized Metric Spaces
7
作者 HAN Yan DONG Yanshou +1 位作者 DUAN Jiangmei XU Shaoyuan 《Wuhan University Journal of Natural Sciences》 2025年第6期540-548,共9页
In this work,we investigate several fixed point theorems in double controlled metric spaces by providing some new definitions,which serve as a natural extension of the existing notions.Moreover,we establish its variou... In this work,we investigate several fixed point theorems in double controlled metric spaces by providing some new definitions,which serve as a natural extension of the existing notions.Moreover,we establish its various characterizations by some typical examples.Specifically,these examples hold in double-controlled metric-like spaces instead of usual b-metric spaces.The fixed point theorems are obtained under these new concepts,without appealing to the completeness of the spaces or the continuity of the mappings.Furthermore,we prove that the completeness in double-controlled metric-like spaces is necessary if the extended Kannan-type contractions have a fixed point in the spaces.The results contribute to a deeper understanding of Kannan-type contractions and their applicability in the context of fixed point theory in double-controlled metric spaces. 展开更多
关键词 double controlled metric-like spaces COMPLETENESS asymptotic regularity fixed point
原文传递
Validation Analysis of Gas Chromatography Method for Determining 8 Benzene Derivatives in Fixed Pollution Source Exhaust Gas
8
作者 Wenshuai XU Juan LI Ziyan LIN 《Meteorological and Environmental Research》 2025年第4期37-39,42,共4页
Benzene derivatives are volatile organic compounds commonly present in the atmospheric environment,which are toxic and complex in composition.They have become a key regulatory object in China s atmospheric environment... Benzene derivatives are volatile organic compounds commonly present in the atmospheric environment,which are toxic and complex in composition.They have become a key regulatory object in China s atmospheric environment management.In this paper,Shimadzu Nexis GC-2030 gas chromatography was used to simultaneously detect eight benzene derivatives.According to the Environmental Monitoring—Technical Guideline on Drawing and Revising Analytical Method Standards(HJ 168-2010),the monitoring methods for benzene,toluene,ethylbenzene,p-xylene,m-xylene,isopropylbenzene,o-xylene,and styrene in the Stationary Source Emission—Determination of Benzene and Its Analogies—Bags Sampling/Direct Injection—Gas Chromatography(HJ 1261-2022)are verified,and their linear relationships,detection limits,precision and accuracy are analyzed. 展开更多
关键词 Benzene derivatives fixed pollution source exhaust gas Method validation
在线阅读 下载PDF
Fixed point results for asymptotically regular mappings in abstract metric spaces
9
作者 HAN Yan DAI Ting-ting XU Shao-yuan 《Applied Mathematics(A Journal of Chinese Universities)》 2025年第3期632-644,共13页
In this paper,various extended contractions are introduced as generalizations of some existing contractions given by Kannan,Ciric,Reich and Gornicki,et al.Then,several meaningful results about asymptotically regular m... In this paper,various extended contractions are introduced as generalizations of some existing contractions given by Kannan,Ciric,Reich and Gornicki,et al.Then,several meaningful results about asymptotically regular mappings in cone metric spaces over Banach algebras are obtained,weakening the completeness of the spaces and the continuity of the mappings.Moreover,some nontrivial examples are showed to verify the innovation of the new concepts and our fxed point theorems. 展开更多
关键词 asymptotic regularity fixed point cone metric spaces over Banach algebras
在线阅读 下载PDF
Relativistic non-Fermi liquid fixed point in(2+1)-dimensional birefringent Dirac fermions interacting with electromagnetic fields
10
作者 Wan-Zi Sun Kai Liu +1 位作者 Wu-Ming Liu Cheng-Xi Li 《Chinese Physics B》 2025年第5期524-532,共9页
The system consisting of(2+1)-dimensional quasirelativistic birefringent Dirac fermions with Coulomb interactions and retarded current–current interactions is described by a quantum field theory similar to reduced qu... The system consisting of(2+1)-dimensional quasirelativistic birefringent Dirac fermions with Coulomb interactions and retarded current–current interactions is described by a quantum field theory similar to reduced quantum electrodynamics.We used the perturbative renormalization group method to study the low-energy behavior of the system and found that it flows to a fixed point of the non-Fermi liquid composed of relativistic pseudospin-1/2 Dirac fermions in the deep infrared limit.At the fixed point,the fermion Green function exhibits a finite anomalous dimension,and the residue of the quasiparticle pole vanishes in a power-law fashion.Our research provides new theoretical perspectives for understanding the origin of spin-1/2 fermions in the standard model. 展开更多
关键词 non-Fermi liquid fixed point birefringent Dirac fermions perturbative renormalization group Fermi velocity renormalization
原文传递
Investigation of flight stability for fixed canard dual-spin projectile via CFD/RBD coupled method
11
作者 Gang Wang Tengyue Zhang +2 位作者 Tianyu Lin Haizhen Lin Ke Xi 《Defence Technology(防务技术)》 2025年第11期1-18,共18页
In this paper,a high-fidelity computational fluid dynamics(CFD)and rigid body dynamics(RBD)coupled platform for virtual flight simulation is developed to investigate the flight stability of fixed canard dual-spin proj... In this paper,a high-fidelity computational fluid dynamics(CFD)and rigid body dynamics(RBD)coupled platform for virtual flight simulation is developed to investigate the flight stability of fixed canard dual-spin projectile.The platform's reliability is validated by reproducing the characteristic resonance instability of such projectiles.By coupling the solution of the Unsteady Reynolds-Averaged Navier-Stokes equations and the seven-degree-of-freedom RBD equations,the virtual flight simulations of fixed canard dual-spin projectiles at various curvature trajectories are achieved,and the dynamic mechanism of the trajectory following process is analyzed.The instability mechanism of the dynamic instability during trajectory following process of the fixed canard dual-spin projectile is elucidated by simulating the rolling/coning coupled forced motion,and subsequently validated through virtual flight simulations.The findings suggest that an appropriate yaw moment can drive the projectile axis to precession in the tangential direction of the trajectory,thereby enhancing the trajectory following stability.However,the damping of the projectile attains its minimum value when the forward body equilibrium rotational speed(-128 rad/s)is equal to the negative of the fast mode frequency of the projectile.Insufficient damping leads to the fixed canard dual-spin projectile exiting the dynamic stability domain during the trajectory following,resulting in weakly damped instability.Keeping the forward body not rotating or increasing the spin rates to-192 rad/s can enhance the projectile's damping,thereby improving its dynamic stability. 展开更多
关键词 fixed canard dual-spin projectile CFD/RBD coupled method Virtualflight simulation Following stability Dynamic stability
在线阅读 下载PDF
Fractional Discrete-Time Analysis of an Emotional Model Built on a Chaotic Map through the Set of Equilibrium and Fixed Points
12
作者 Shaher Momani Rabha W.Ibrahim Yeliz Karaca 《Computer Modeling in Engineering & Sciences》 2025年第4期809-826,共18页
Fractional discrete systems can enable the modeling and control of the complicated processes more adaptable through the concept of versatility by providing systemdynamics’descriptions withmore degrees of freedom.Nume... Fractional discrete systems can enable the modeling and control of the complicated processes more adaptable through the concept of versatility by providing systemdynamics’descriptions withmore degrees of freedom.Numerical approaches have become necessary and sufficient to be addressed and employed for benefiting from the adaptability of such systems for varied applications.A variety of fractional Layla and Majnun model(LMM)system kinds has been proposed in the current work where some of these systems’key behaviors are addressed.In addition,the necessary and sufficient conditions for the stability and asymptotic stability of the fractional dynamic systems are investigated,as a result of which,the necessary requirements of the LMM to achieve constant and asymptotically steady zero resolutions are provided.As a special case,when Layla and Majnun have equal feelings,we propose an analysis of the system in view of its equilibrium and fixed point sets.Considering that the system has marginal stability if its eigenvalues have both negative and zero real portions,it is demonstrated that the system neither converges nor diverges to a steady trajectory or equilibrium point.It,rather,continues to hover along the line separating stability and instability based on the fractional LMM system. 展开更多
关键词 Fractional difference system fractional differential operators fractional calculus chaotic map EQUILIBRIUM fixed point sets nyquist plot routh-Hurwitz criterion
在线阅读 下载PDF
2.1 billion fixed assets landing,Xinao shares reveal new growth points for textile enterprises
13
作者 Qiu Shuchen 《China Textile》 2025年第6期32-34,共3页
Xin'ao Co.,Ltd.(603889),Iocated in Jiaxing City,Zhejiang Province,is a wellestablished enterprise in the wool textile industry.It focuses on the entire wool textile supply chain,integrating wool procurement,wool t... Xin'ao Co.,Ltd.(603889),Iocated in Jiaxing City,Zhejiang Province,is a wellestablished enterprise in the wool textile industry.It focuses on the entire wool textile supply chain,integrating wool procurement,wool top production,wool top modification,dyeing and finishing,and spinning,After more than thirty years of development,it has gradually formed a large-scale,market-oriented textile eco-system with Xin'ao Co.,Ltd. as the core,with its subsidia ries specializing in different production and sales functions. 展开更多
关键词 fixed assets wool top production wool textile industry supply chain procurement textile enterprises production sales functions growth points
在线阅读 下载PDF
Fixed-Time Stability of Random Nonlinear Systems
14
作者 Fuyong Wang Jiayi Gong +1 位作者 Zhongxin Liu Fei Chen 《IEEE/CAA Journal of Automatica Sinica》 2025年第7期1507-1509,共3页
Dear Editor,This letter embarks on an examination of fixed-time stability(FxTS)for random nonlinear systems(RNSs)governed by random differential equations.This endeavor encompasses a multifaceted analysis of FxTS,comm... Dear Editor,This letter embarks on an examination of fixed-time stability(FxTS)for random nonlinear systems(RNSs)governed by random differential equations.This endeavor encompasses a multifaceted analysis of FxTS,commencing with its rigorous definition and its integration with Lyapunov theory,along which a consequential corollary emerges.Particularly,the positive definiteness of the expectation of settling time is established,and a less conservative upper bound is derived.The effectiveness of the proposed fixed-time theorem is verified by an example. 展开更多
关键词 settling time integration lyapunov theoryalong Lyapunov theory random nonlinear systems rnss governed upper bound random differential equations fixed time stability random nonlinear systems
在线阅读 下载PDF
腰髂固定联合INFIX治疗Tile B型骨盆骨折的临床研究
15
作者 徐耀宁 黄森 +2 位作者 池伟东 张彬 吴俊哲 《系统医学》 2025年第3期104-106,110,共4页
目的分析腰髂固定联合内置固定架(internal fixator,INFIX)治疗Tile B型骨盆骨折的临床疗效。方法回顾性选取2021年1月—2024年6月中山市中医院收治的55例Tile B型骨盆骨折患者的临床资料。根据治疗方法分为两组,对照组(28例)采用骶髂... 目的分析腰髂固定联合内置固定架(internal fixator,INFIX)治疗Tile B型骨盆骨折的临床疗效。方法回顾性选取2021年1月—2024年6月中山市中医院收治的55例Tile B型骨盆骨折患者的临床资料。根据治疗方法分为两组,对照组(28例)采用骶髂关节螺钉联合外固定架治疗,观察组(27例)采用腰髂固定联合INFIX治疗。比较两组临床疗效、疼痛评分、骨盆功能恢复情况及并发症发生情况。结果观察组的总有效率达96.29%(26/27),较对照组的71.43%(20/28)更高,差异有统计学意义(χ^(2)=4.527,P<0.05)。观察组的疼痛评分低于对照组,且其Majeed骨盆功能评分高于对照组,差异均有统计学意义(P均<0.05)。观察组并发症的发生率低于对照组,差异有统计学意义(P<0.05)。结论腰髂固定联合INFIX治疗Tile B型骨盆骨折在临床疗效、疼痛缓解、功能恢复及安全性方面优于骶髂关节螺钉联合外固定架。 展开更多
关键词 骨盆骨折 Tile B型 腰髂固定 内置固定架 疗效 并发症
暂未订购
Enhancing Coating Inoculation for Improved Nitrogen-Fixing Efficiency of Rhizobia in Soybean (Glycine max L.)
16
作者 Anne Nora Ndokon Bikang Liliane Meguekam Tekam +1 位作者 Alain-Martial Sontsa-Donhoung Dieudonné Nwaga 《American Journal of Plant Sciences》 2025年第2期245-262,共18页
Plant biofertilization involves introducing compounds containing living mi-croorganisms into the coating medium to sustainably enhance plant production and soil health. This is a complex process that undergoes multipl... Plant biofertilization involves introducing compounds containing living mi-croorganisms into the coating medium to sustainably enhance plant production and soil health. This is a complex process that undergoes multiple stages of development before yielding a final product. The final biofertilizer is used by legumes-protein-rich crops in symbiosis with rhizobia to enable biological nitrogen fixation increasing natural soil fertility. This study aims to determine the optimal formulation of a rhizobial biofertilizer to improve the performance of soybean (Glycine max L. cv. Docko). To this end, soybean seeds obtained from IRAD were coated with different formulations derived from locally sourced materials. Palm kernel oil was used as an adhesive in one group, while corn powder served as an adhesive in another. The coated seeds were then sown in the field. The results indicate that the combination of pigeon pea powder + sugarcane molasses, with palm kernel oil as an adhesive, produced the best nodulation (nitrogen fixation). This formulation also led to significant improvements in growth (+350%) and total nitrogen content (+1100%) compared to the bacterial broth inoculum control (B0) (P ≤ 0.01). These findings represent a significant advancement in improving nitrogen-fixing bacterial inoculants and enhancing soil fertility for the sustainable cultivation of soybeans in this tropical soil. 展开更多
关键词 FORMULATION BIOFERTILIZER N-fixing RHIZOBIA COATING Growth
在线阅读 下载PDF
精准播种与定点抛栽对水稻秧苗素质与产量的影响
17
作者 王志刚 黄颂迪 +7 位作者 章文斌 陈惠哲 张玉屏 向镜 张义凯 徐逸文 王亚梁 陈叶平 《中国稻米》 北大核心 2026年第1期94-96,101,共4页
本试验以籼粳杂交稻甬优31为材料,研究了两种不同播种方式(撒播与精准播种)和两种抛秧方式(人工撒抛与定点抛栽)对水稻秧苗素质及产量的影响。结果显示,精准播种处理的秧苗在株高、叶龄、根长、茎基宽以及干质量等方面均优于撒播处理,... 本试验以籼粳杂交稻甬优31为材料,研究了两种不同播种方式(撒播与精准播种)和两种抛秧方式(人工撒抛与定点抛栽)对水稻秧苗素质及产量的影响。结果显示,精准播种处理的秧苗在株高、叶龄、根长、茎基宽以及干质量等方面均优于撒播处理,除株高和干质量外,其余各项指标的差异均达到显著或极显著水平,这表明精准播种处理的秧苗素质明显优于撒播处理;产量及其构成因子两者尽管差异不显著,但精准播种处理的总体表现优于撒播处理。对于抛秧方式方面,定点抛栽处理的穗长、每穗实粒数、千粒重和产量分别比人工撒抛处理显著高5.39%、6.11%、2.74%和5.14%。精准播种与定点抛栽相结合的处理相较撒播与人工撒抛相结合的处理,显著增产7.38%。由此可见,精准播种与有序抛栽对于培育健壮秧苗以及实现水稻高产具有重要意义。 展开更多
关键词 水稻 精准播种 定点抛栽 有序种植 产量
在线阅读 下载PDF
干旱区含氟地下水微生物群落特征及其环境响应
18
作者 李玲 范廷玉 +2 位作者 周金龙 杨长德 宫云晓 《中国环境科学》 北大核心 2026年第1期354-364,共11页
为查明干旱区含氟地下水中微生物群落结构、功能特征及其与水化学环境因子之间的作用关系,以和田河流域绿洲区LF组(ρ(F^(-))≤1.0mg/L)、MF组(1.0mg/L<ρ(F^(-))≤2.0mg/L)、HF组(ρ(F^(-))>2.0mg/L)3组地下水为研究对象,采用16s... 为查明干旱区含氟地下水中微生物群落结构、功能特征及其与水化学环境因子之间的作用关系,以和田河流域绿洲区LF组(ρ(F^(-))≤1.0mg/L)、MF组(1.0mg/L<ρ(F^(-))≤2.0mg/L)、HF组(ρ(F^(-))>2.0mg/L)3组地下水为研究对象,采用16s RNA高通量测序技术探究不同氟(F^(-))含量水平下地下水细菌群落多样性、结构及功能差异.结果表明:(1)3组地下水中细菌群落多样性指数受F^(-)含量影响较小,但群落结构差异明显.(2)变形菌门是3组地下水的优势菌门,相对丰度分别为67.61%(LF组)、52.02%(MF组)、41.34%(HF组);嘉利翁氏菌属、氢噬胞菌属、硝化螺旋菌属、Ferritrophicum等在LF组或MF组的相对丰度远高于HF组;鞘脂菌属是HF组的优势菌属,在LF组和MF组中相对丰度很低.(3)F^(-)、HCO_(3)^(-)、Ca^(2+)、NO_(3)^(-)和Cl~-为影响含氟地下水细菌群落结构的关键化学指标.(4)根据PICRUSt2功能预测,3组地下水中主要功能基因均为新陈代谢功能,与LF组相比,HF组的细菌在参与辅因子丰度和维生素代谢的途径中活性显著降低.(5)HF组相对丰度较高的嘉利翁氏菌属、氢噬胞菌属、硝化螺旋菌属等化能自养型固碳微生物均与F^(-)和HCO_(3)^(-)含量呈显著负相关性,与Ca^(2+)含量呈显著正相关(P<0.01).绿洲区地下水中微生物群落结构、功能差异及其与环境因子的相关性,体现了干旱区含氟地下水中化能自养型固碳微生物对F^(-)的迁移与转化过程有显著影响,其相对丰度同时也受到F^(-)含量的影响. 展开更多
关键词 含氟地下水 群落结构 功能预测 化能自养型固碳微生物
在线阅读 下载PDF
不同杀青方式对扁形绿芽茶风味品质形成的影响
19
作者 杨娟 陈善敏 +6 位作者 王杰 袁林颖 李解 张玉来 张莹 刘行 李明红 《食品工业科技》 北大核心 2026年第2期59-69,共11页
为探究不同杀青方式对扁形绿芽茶风味品质形成的影响,采用高效液相色谱(High performance liquid chromatography,HPLC)及顶空固相微萃取(Headspace solid phase microextraction,HS-SPME)联用气相色谱-质谱技术(Gas chromatography-mas... 为探究不同杀青方式对扁形绿芽茶风味品质形成的影响,采用高效液相色谱(High performance liquid chromatography,HPLC)及顶空固相微萃取(Headspace solid phase microextraction,HS-SPME)联用气相色谱-质谱技术(Gas chromatography-mass spectrometry,GC/MS)检测分析加工过程生化成分及香气变化。结果表明,微波补杀有利于改善扁形绿芽茶汤色、香气、滋味品质,对后期成茶中茶多酚、游离氨基酸及可溶性糖转化生成有利,同时有利于加工过程儿茶素(Catechin,C)、没食子儿茶素(Gallocatechin,GC)、表儿茶素(Epicatechin,EC)的后期生成。从对照组(CK)和微波补杀组(WB)中分别检测出972、966种挥发性代谢物,两组杀青处理中鲜叶、杀青叶及成茶间挥发性代谢物特征差异明显,微波补杀有利于丰富茶叶香气化合物种类,杀青叶与成茶间差异代谢物显著多于杀青叶与鲜叶间差异代谢物。对差异代谢物相对气味活度值(relative odor activity value,rOAV)分析,分别从CK组和WB组注释到6种、9种rOAV>1的差异代谢物,推测是不同杀青处理中各工序香气变化的关键呈香物质。其中具有似橙类水果香气风味表现的1-癸醇、(E)-3,7-二甲基-2,6-辛二醛、柠檬醛以及具有温和愉快芳香气、橙香、花香风味表现的对伞花烃、邻氨基苯甲酸甲酯、邻伞花烃可能是引起不同杀青处理成茶香气品质差异的主要物质。本研究为川渝地区扁形绿芽茶品质特征形成成因及加工工艺优化提供理论参考。 展开更多
关键词 扁形绿芽茶 杀青方式 成分 香气 品质
在线阅读 下载PDF
透明矫治技术研究新进展
20
作者 陈嵩 《华西口腔医学杂志》 北大核心 2026年第1期29-33,共5页
本文系统梳理了透明矫治技术在材料学、临床治疗效果及对口腔健康影响方面的最新研究进展。在材料学领域,研究聚焦于膜片的生物相容性、生物/智能复合矫治器的研发及直接打印透明矫治器技术。尽管主流材料总体安全,但部分仍存在细胞毒... 本文系统梳理了透明矫治技术在材料学、临床治疗效果及对口腔健康影响方面的最新研究进展。在材料学领域,研究聚焦于膜片的生物相容性、生物/智能复合矫治器的研发及直接打印透明矫治器技术。尽管主流材料总体安全,但部分仍存在细胞毒性隐患;智能复合材料通过集成传感器或添加抗菌成分,为监测和预防釉质脱矿提供了新策略;直接打印透明矫治器技术则因其可定制化和高精度展现出巨大潜力。临床疗效方面,对于轻中度错[牙合]畸形,透明矫治器与固定矫治器疗效相当,但在复杂拔牙病例中其效率与效果稍逊。具体牙移动控制上,扩弓主要通过牙冠倾斜移动实现,效果低于设计预期;磨牙远移的实现度也有限;同时,研究否定了其具有特异性的“[牙合]垫效应”,并能导致下颌逆旋的观点。对于儿童骨性Ⅱ类错[牙合]畸形,结合功能矫治模块的透明矫治器显示出良好的应用前景,但证据等级仍需提高。在对口腔健康的影响上,与固定矫治器相比,透明矫治器能有效降低釉质脱矿风险,减少菌斑堆积,改善牙周健康状况。透明矫治技术正朝着更精准、高效和个性化的方向发展,但医生需明确其工具属性,成功治疗的根本仍在于全面的诊断、恰当的治疗计划与细致的临床操作。 展开更多
关键词 正畸治疗 透明矫治器 固定矫治器
暂未订购
上一页 1 2 250 下一页 到第
使用帮助 返回顶部