Structural control of magnetic nanoparticles for positive nuclear magnetic resonance imaging

In addition to the tens of millions of medical doses consumed annually around the world,a vast number of nuclear magnetic resonance imaging(MRI)contrast agents are being deployed in MRI research and development,offering precise diagnostic information,targeting capabilities,and analyte sensing.Superparamagnetic iron oxide nanoparticles(SPIONs)are notable among these agents,providing effective and versatile MRI applications while also being heavy-metal-free,bioconjugatable,and theranostic.We designed and implemented a novel two-pronged computational and experimental strategy to meet the demand for the efficient and rigorous development of SPION-based MRI agents.Our MATLAB-based modeling simulation and magnetic characterization revealed that extremely small maghemite SPIONs in the 1-3 nm range possess significantly reduced transversal relaxation rates(R_(2))and are therefore preferred for positive(T_(1)-weighted)MRI.Moreover,X-ray diffraction and X-ray absorption fine structure analyses demonstrated that the diffraction pattern and radial distribution function of our SPIONs matched those of the targeted maghemite crystals.In addition,simulations of the X-ray near-edge structure spectra indicated that our synthesized SPIONs,even at 1 nm,maintained a spherical structure.Furthermore,in vitro and in vivo MRI investigations showed that our 1-nm SPIONs effectively highlighted whole-body blood vessels and major organs in mice and could be cleared through the kidney route to minimize potential post-imaging side effects.Overall,our innovative approach enabled a swift discovery of the desired SPION structure,followed by targeted synthesis,synchrotron radiation spectroscopic studies,and MRI evaluations.The efficient and rigorous development of our high-performance SPIONs can set the stage for a computational and experimental platform for the development of future MRI agents.

Influence of the Randomness of Longitudinal Resistance of Ballast Bed on Track-Bridge Interaction

To get the influence of the randomness of longitudinal resistance of ballast bed (LRBB) on track-bridge interaction, the statistical law of LRBB was studied with existing test data and the Shapiro-Wilk test. Based on the principle of track-bridge interaction, a rail-sleeper-bridge-pier integrated simulation model that could consider the randomness of LRBB was established. Taking a continuous beam bridge for the heavy-haul railway as an example, the effect of the randomness of LRBB on the mechanical behavior of continuous welded rail (CWR) on bridges under typical conditions was carefully examined with a random sampling method and the simulation model. The results show that the LRBB corresponding sleeper displacement of 2 mm obeys a normal distribution. When the randomness of LRBB is considered, the amplitudes of rail expansion force, rail bending force, rail braking force and rail broken gap all follow normal distribution. As the standard deviations of the four indexes are small, which indicates the randomness of LRBB has little effect on track-bridge interaction. The distributions of the four indexes make it possible to design CWR on bridges with the limit state method.

中美涉农高校普通化学课程比较与新农科背景下纯英文授课的初步探索和实践——以中国农业大学与康奈尔大学合作办学为例

以中国农业大学与康奈尔大学合作办学为契机,对中美涉农高校普通化学课程的培养目标、教学内容、教学方法、考核方式等方面进行了初步比较和探讨,并分享了笔者团队在纯英文授课中的初步探索实践与心得体会,力求打造一套兼具中国特色和国际化视野的世界一流农科大学普通化学的课程体系,为国内农林院校的本科普通化学课程的教学改革提供一定的参考。

A 31-year Global Diurnal Sea Surface Temperature Dataset Created by an Ocean Mixed-Layer Model

A dataset of hourly sea surface temperature(SST) from the period 1 January 1982 to 31 December 2012, and covering the global ocean at a resolution of 0.3°× 0.3°, was created using a validated ocean mixed-layer model(MLSST). The model inputs were heat flux and surface wind speed obtained from the Coupled Forecast System Reanalysis dataset. Comparisons with in-situ data from the Tropical Atmosphere Ocean array and the National Data Buoy Center showed that the MLSST fitted very well with observations, with a mean bias of 0.07℃, and a root-mean-square error(RMSE) and correlation coefficient of 0.37℃ and 0.98, respectively. Also, the MLSST fields successfully reproduced the diurnal cycle of SST in the in-situ data, with a mean bias of -0.005℃ and RMSE of 0.26℃. The 31-year climatology revealed that the diurnal range was small across most regions, with higher values in the eastern and western equatorial Pacific, northern Indian Ocean, western Central America, northwestern Australia, and several coastal regions. Significant seasonal variation of diurnal SST existed in all basins. In the Atlantic and Pacific basins, this seasonal pattern was oriented north–south, following the variation in solar insolation, whereas in the Indian basin it was dominated by monsoonal variability. At the interannual scale, the results highlighted the relationship between diurnal and interannual variations of SST, and revealed that the diurnal warming in the central equatorial Pacific could be a potential climatic indicator for ENSO prediction.

Effect of pH conditions on the depolymerization of Wucaiwan coal by mixed acids/ultrasound method and the product structures and performance

The cleavage of the aliphatic chain or ether bond connecting the polycyclic aromatic hydrocarbons in coal can be achieved by not only hydrogenation reduction but also oxidative acid treatment. In this paper, coal samples from Wucaiwan in Xinjiang were pretreated with HNO3 followed by mixed acids/ultrasound treatment. The depolymerized coal samples obtained under different pH conditions were then separated by fractional washing. The structures and properties of the resulting coal samples were studied by elemental analysis, FT-IR, XRD, TG-DTA, TEM, UV-Vis, and PL. The results showed that when pH = 0.012, the obtained coal samples were fragments stripped off from the raw coal samples by ultrasound in strong acid conditions, aliphatic hydrocarbons linked with oxygen-containing groups such as nitro group, a small amount of small aromatic molecules and mineral salts; when pH -- 1.99-4.09, the obtained coal samples were polycyclic aromatic hydrocarbons linked with oxygen-containing groups such as nitro group,possessing the annulus wall of multilayer graphene fragment structures built up by sp2 carbons, and they are typical fluorescent substances of carbon nanoparticle structure. The former has no solubility in organic solvents, while the latter can be well dissolved in polar solvents such as acetone. All the depolymerized coal samples obtained under different pH conditions exhibited good absorption and ability of fluorescence emission.

Recent improvements to the physical model of the Bohai Sea,the Yellow Sea and the East China Sea Operational Oceanography Forecasting System

In order to satisfy the increasing demand for the marine forecasting capacity,the Bohai Sea,the Yellow Sea and the East China Sea Operational Oceanography Forecasting System(BYEOFS)has been upgraded and improved to Version 2.0.Based on the Regional Ocean Modeling System(ROMS),a series of comparative experiments were conducted during the improvement process,including correcting topography,changing sea surface atmospheric forcing mode,adjusting open boundary conditions,and considering atmospheric pressure correction.(1)After the topography correction,the volume transport and meridional velocity maximum of Yellow Sea Warm Current increase obviously and the unreasonable bending of its axis around 36.1°N,123.5°E disappears.(2)After the change of sea surface forcing mode,an effective negative feedback mechanism is formed between predicted sea surface temperature(SST)by the ocean model and sea surface radiation fluxes fields.The simulation errors of SST decreased significantly,and the annual average of root-mean-square error(RMSE)decreased by about 18%.(3)The change of the eastern lateral boundary condition of baroclinic velocity from mixed Radiation-Nudging to Clamped makes the unreasonable westward current in Tsushima Strait disappear.(4)The adding of mean sea level pressure correction option which forms the mean sea level gradient from the Bohai Sea and the Yellow Sea to the western Pacific in winter and autumn is helpful to increasing the fluctuation of SLA and outflow of the Yellow Sea when the cold high air pressure system controls the Yellow Sea area.

Robot Interaction Force Estimation Using an Adaptive Sliding Mode Observer

In constrained motion control of a robot,the interaction force is an important variable,which directly describes the state of interaction.It is required in a number of algorithms for interaction control.Desirably,the interaction force has to be measured by force sensors.However,there are inherent limitations with force sensors,such as the cost,sensing noise,limited bandwidth,and the difficulty of physical location at the required place,which is dynamic.In the present paper,the interaction force is estimated by using high order sliding mode observers.An adaptive version of a high order sliding mode observer is developed to robustly reconstruct the interaction force.Experimental results are given to show the effectiveness of the developed algorithms.

Visual Avoidance of Collision with Randomly Moving Obstacles through Approximate Reinforcement Learning

In this research work,a hierarchical controller has been designed for an autonomous navigation robot to avoid unexpected moving obstacles where the state and action spaces are continuous.The proposed scheme consists of two parts:1)a controller with a high-level approximate reinforcement learning(ARL)technique for choosing an optimal trajectory in autonomous navigation;and 2)a low-level,appearance-based visual servoing(ABVS)controller which controls and execute the motion of the robot.A novel approach for path planning and visual servoing has been proposed by the combined system framework.The characteristics of the on-board camera which is equipped on the robot is naturally suitable for conducting the reinforcement learning algorithm.Regarding the ARL controller,the computational overhead is quite low thanks to the fact that a knowledge of obstacle motion is not necessary.The developed scheme has been implemented and validated in a simulation system of obstacle avoidance.It is noted that findings of the proposed method are successfully verified by obtaining an optimal robotic plan motion strategy.

Enhancing sensitivity of SERRS nanoprobes by modifying heptamethine cyanine-based reporter molecules

Surface enhanced resonance Raman scattering(SERRS)is a physical phenomenon that occurs when the energy of incident light is dose to that of electronic excitation of reporter molecules(RMs)attached on substrates.SERRS has showed great promise in healthcare applications such as tumor diagnosis,image guided tumor surgery and real-time evaluation of therapeutic response due to its ultra-sensitivity,manipulating convenience and easy acessibility.As the most widely used organic near-infrared(NIR)fuorophore,heptamethine cyanines possess the electronic ex-citation energy that is close to the plasmon absorption energy of the gold nano scafolds,which results in the extraordinary enhancement of the SERRS signal.However,the effect of hepta-methine cyanine structure and the gold nanoparticle morphology to the SERRS intensity are barely investigated.This work developed a series of SERRS nanoprobes in which two hepta-methine cyanine derivatives(IR783 and IR780)were used as the RM and three gold nanoparticles(nanorod,nanosphere and nanostar)were used as the substrates.Interestingly,even though IR780 and IR783 possess very similar chemical structure,SERRS signal produced by IR780 was determined as 14 times higher than that of IR783 when the RM concentration was6.5 × 10^(-6) M.In contrast,less than 4.0 fold SERRS signal intensity increase was measured by changing the substrate morphologies.Above experimental results indicate that finely tuning the chemical structure of the heptamethine cyanine could be a feasible way to develop robust SERRS probes to visualize tumor or guide tumor resection with high sensitivity and target to background ratio.

Goal Self-Concordance Model: What HaveWe Learned and Where are We Going

Goal self-concordance reflects self-generated personal goals aligning with people’s interests and core values in one’s implicit personality as organic components,which is measured by the“perceived locus of causality”PLOC.Pursuing and achieving self-concordant goals both predict diversified outcomes in need-satisfaction,mental and physical well-being,positive attitude and behavior,etc.Based on expounding and sorting out the concept and measurement about goal self-concordance,the author analyzes the differences among a series of goal self-concor-dance theories.This paper focuses on the latest research trends and summarizesfive influencing aspects of goal self-concordance:mental health,cognition,emotion,personal will,and behavioral outcomes.The mediating effects are discussed concerning antecedents and influence effects,the influence effects are shown in three aspects including the characteristics of individual,target,and environment.While the antecedent effects are respectively reflected in self-insight,personality,empowerment,and self-supported environment,content,and context of the goal itself.Finally,the author proposes several potential research interests from a broader perspective based on the current literature.

Robust Impedance Control of Robots Using an Adaptive Interaction Force Observer

For robot interaction control,the interaction force between the robot and the manipulated object or environment should be monitored.Impedance control is a type of interaction control.Specifically,in impedance control,the dynamic relationship between the interaction force and the resulting motion is controlled.In order to control the impedance of a mechanical system,typically,the interaction force has to be sensed.Due to the inherent limitations of direct force sensing at the interaction site,in the present work,the interaction force is observed using robust observers.In particular,to enhance the accuracy of impedance control,a first order sliding mode impedance controller is designed and incorporated in the present paper.Its advantage over positionbased interaction control algorithms is demonstrated through experimentation.Experimental results are given to show the effectiveness of the proposed algorithms.

情感治理与湾区融合——广州港澳创新创业基地案例

在粤港澳大湾区建设的背景下,如何使港澳青年融入国家发展大局成为备受关注的议题。港澳创新创业基地作为赴内地创业的港澳青年的活动载体,其被赋予着推动湾区融合的重任。本研究采用半结构式访谈、实地考察与网络文本分析的方法,以广州市港澳双创基地为研究对象,基于情感地理学理论,探讨港澳双创基地中的情感空间的构建过程,及其在湾区治理中的作用机制。研究发现:不同主体在港澳双创基地发展的过程中邂逅。通过基地物质景观的营造和各主体间的良好互动,基地被构建成一个积极正向的情感空间。伴随着港澳创业者在内地的流动、实践,情感空间实现尺度跃升。港澳创业者在内地积极的情感体验一方面增强其社会参与的热情,另一方面通过其在港澳本地的社会实践传递到当地,吸引更多港澳本地居民融入湾区发展,以一种柔性的、非正式的方式发挥着情感的力量。然而港澳创业者对内地的情感具有多元性,其对内地的归属感与其社会参与之间的关系也较为复杂,在内地的港澳创业者仍处于情感融入的状态;当前尚缺少关于如何发挥在内地的港澳创业者对港澳本地的辐射带动作用的顶层设计。上述结论丰富了湾区治理研究视角和尺度,揭示了当前湾区融合中存在的问题,也为湾区情感治理实践提供了有效思路。

Polarization-driven multifunctional organohydrogels with strain sensitivity toward electromagnetic wave absorption

Rapid advancements in flexible electronics and military applications necessitate high-performance electromagnetic wave(EMW)absorbers.While huge breakthroughs in achieving high-attenuation microwave absorption,conventional EMW absorbing materials have single function and ambiguous absorption mechanisms.Herein,numerous gel-type absorbers are fabricated by introducing“regulators”into poly(acrylamide-co-acrylic acid)(P(AM-co-AA))networks through radical polymerization in a glycerol-water mixed solvent.The dielectric constant and EMW absorption performance of the gels are precisely predicted by adjusting monomer concentration,the ratio of glycerol/water,and the content of the regulators.Notably,A_(6)G_(20)T_(20)-2 exhibits promising absorption performance with a minimum reflection loss(RL_(min))of-33.8 dB at 12.4 GHz.The effective absorption bandwidth(EAB)covers the entire X-band(8.2-12.4 GHz)at a thickness of 2.7 mm.A_(6)G_(20)T_(20)-2 also has sensitive deformation responses and excellent tensile strength,adhesiveness,self-healing and anti-freezing properties.Overall,this work not only provides insight into the polarization loss mechanism of the gels as the result of high correlation between EMW absorbing properties and molecular polarization,but also offers an important reference for developing functional protective materials because of the rich functionalities and efficient protective capabilities of the gels.

3D-printed MoS_(2)/Ni electrodes with excellent electro-catalytic performance and long-term stability for dechlorination of florfenicol

Here,we report the production of 3D-printed MoS_(2)/Ni electrodes(3D-MoS_(2)/Ni)with longterm stability and excellent performance by the selective laser melting(SLM)technique.As a cathode,the obtained 3D-MoS_(2)/Ni could maintain a degradation rate above 94.0%for forfenicol(FLO)when repeatedly used 50 times in water.We also found that the removal rate of FLO by 3D-MoS_(2)/Ni was about 12 times higher than that of 3D-printed pure Ni(3D-Ni),attributed to the improved accessibility of H^(*).In addition,the electrochemical characterization results showed that the electrochemically active surface area of the 3D-MoS_(2)/Ni electrode is about 3-fold higher than that of the 3D-Ni electrode while the electrical resistance is 4 times lower.Based on tert-butanol suppression,electron paramagnetic resonance and triple quadrupole mass spectrometer experiments,a“dual path”mechanism and possible degradation pathway for the dechlorination of FLO by 3D-MoS_(2)/Ni were proposed.Furthermore,we also investigated the impacts of the cathode potential and the initial pH of the solution on the degradation of FLO.Overall,this study reveals that the SLM 3D printing technique is a promising approach for the rapid fabrication of high-stability metal electrodes,which could have broad application in the control of water contaminants in the environmental field.

Development of MoS_(2)-stainless steel catalyst by 3D printing for efficient destruction of organics via peroxymonosulfate activation

Herein,a novel MoS_(2)-stainless steel composite material was first synthetized via a 3D printing method(3DP MoS_(2)-SS)for peroxymonosulfate(PMS)activation and organics degradation.Compared with MoS_(2)-SS powder/PMS system(0.37 g/(m^(2)/min)),4.3-fold higher k_(FLO)/S_(BET)value was obtained in 3DP MoS_(2)-SS/PMS system(1.60 g/(m^(2)/min),resulting from the superior utilization of active sites.We observed that 3DP MoS_(2)-SS significantly outperformed the 3DP SS due to the enhanced electron transfer rate and increased active sites.Moreover,Mo^(4+)facilitated the Fe^(2+)/Fe^(3+)cycle,resulting in the rapid degradation of florfenicol(FLO).Quenching experiments and electron paramagnetic resonance spectra indicated that·OH,SO_(4)·^(-),O_(2)·^(-)and^(1)O_(2)were involved in the degradation of FLO.The effect of influencing factors on the degradation of FLO were evaluated,and the optimized degradation efficiency of 98.69%was achieved at 1 mM PMS and pH of 3.0.Six degradation products were detected by UPLC/MS analyses and several possible degradation pathways were proposed to be the cleavage of C-N bonds,dechlorination,hydrolysis,defluorination and hydroxylation.In addition,3DP MoS_(2)-SS/PMS system also demonstrated superior degradation performance for 2-chlorophenol,acetaminophen,ibuprofen and carbamazepine.This study provided deep insights into the MoS_(2)-SS catalyst prepared by 3DP technology for PMS activation and FLO-polluted water treatment.

Multi-agent mobile networking observation experiment at the air-sea interface of ocean eddy

Current climate forecasting has advanced to the stage of investigating mesoscale air-sea interactions. Recent studies have identified significant structural differences between the cores and edges of mesoscale eddies;however, the effects of these structural variations on air-sea fluxes and the Marine Atmospheric Boundary Layer(MABL) remain underexplored. Traditional observations often fail to capture the detailed structures of eddies, necessitating enhanced observations at high spatiotemporal resolution for mesoscale eddies. To address this, efforts have been made to develop multi-agent platforms and expendable air-sea interface observation technologies. A task-oriented observation scheme was developed to monitor the spatial characteristics of mesoscale eddies. The South China Sea(SCS) is rich in mesoscale eddies with rapid motion changes, requiring enhanced observations of the air-sea interface using multi-agent mobile networking. An anticyclonic eddy was observed in the eastern region of the Xisha Islands in the SCS, and we examined variations in air-sea fluxes across different regions within the eddy.

Molecular dynamics study of water molecules nucleation for fine particle removal:Effects of wettability and aggregation modes and comparison with experiment Author links open overlay panel

Water vapor nucleation on particle's surface plays an important role in dust removal,cloud formation,and particle measurement.However,the selectivity of nucleation sites and the nucleation characteristic of water molecule on the particle's surface are still unclear,especially for the aggregated particles.In this paper,the effects of particle wettability and aggregation modes on the selectivity of nucleation sites and the nucleation characteristics were investigated using molecular dynamics simulation.The results were compared with our earlier experimental findings.It illustrates how the contact angle of clusters,the growth velocity,and the growth duration are all influenced by the interaction coefficient between water and particles.Moreover,the nucleation sites of water molecules on the particle aggregation surface exhibit a definite selectivity.The primary indicator of this selectivity is the preferential nucleation of water molecules at the interfaces of linear chain aggregation particles,at the inner side of non-linear chain aggregation particles,and at the centers of ring aggregation.These results are in good agreement with our previous experimental findings.More significantly,additional research has revealed that subcritical-size clusters typically aggregate on two-particle surfaces spacing when the spacing smaller than the critical cluster size.

“21世纪海上丝绸之路”海洋与气象灾害预警报现状和风险防范对策建议

2013年,习近平主席提出共建“丝绸之路经济带”和“21世纪海上丝绸之路”的重大倡议.“21世纪海上丝绸之路”以海洋为载体,主要包括西北太平洋、西南太平洋和印度洋等3个大洋及东海、南海、安达曼海、孟加拉湾、阿拉伯海、地中海等海域,沿线连接了亚洲、非洲、欧洲地区.2015年3月28日,国家发展和改革委员会、外交部、商务部联合发布《推动共建丝绸之路经济带和21世纪海上丝绸之路的愿景与行动》⑴(以下简称《愿景与行动》)。

生态哲学有机范式的二重性

面对全球性问题,在走向生态文明的过程中,人类亟须生态哲学的引导和支撑。“没有形而上的预想,就不可能有文明。”1由于怀特海有机哲学将人与自然关系看作自然参与人的生成(become)的内在关系,因此,可以将之视为生态哲学。一些论者试图将有机哲学作为“普遍”的生态哲学。但是,这种主张存在着一系列内在紧张,只是生态哲学的一种可能范式,可将之称为“生态哲学有机范式”,即按照有机哲学构建的一种生态哲学范式。只有立足于社会主义生态文明建设实践,坚持以人民为中心,坚持综合创新,才可能形成一种科学、普遍、有效的生态哲学。

长江流域林木资源的重要性及种质资源保护

中国长江流域有着丰富的林木资源,包含极高水平的物种多样性、特有性和遗传多样性。根据考古证据,在旧石器和新石器时代长江文明早期的孕育与发展中,林木在食物、能源、工具、建筑和舟船中的应用起到了关键作用。现在,长江流域和珠江流域逐渐成为国内木材供给的热点地区。面对木材供给总量不足和大径级木材结构性短缺问题,长江流域林木资源将是未来国内木材安全的重要保障。这使得林木种质资源的保护更加迫切。针对长江流域林木种质资源保护存在的家底不清和保存体系不完善问题,我们应尽快完成林木种质资源的全面调查和重要树种的多样性分析;完善原地、异地和设施保存相结合的保存体系。