Precession of the Earth as the Cause of Geomagnetism: Experiments lend support to the proposal that precessional torques drive the earth's dynamo

I have proposed that the precessional torques acting on the earth can sustain a turbulent hydromagnetic flow in the molten core. A gross balance of the Coriolis force, the Lorentz force, and the precessional force in the core fluid provided estimates of the fluid velocity and the interior magnetic field characteristic of such flow. Then these numbers and a balance of the processes responsible for the decay and regeneration of the magnetic field provided an estimate of the magnetic field external to the core. This external field is in keeping with the observations, but its value is dependent upon the speculative value for the electrical conductivity of core material. The proposal that turbulent flow due to precession can occur in the core was tested in a study of nonmagnetic laboratory flows induced by the steady precession of fluid-filled rotating spheroids. It was found that these flows exhibit both small wavelike instabilities and violent finite-amplitude instability to turbulent motion above critical values of the precession rate. The observed critical parameters indicate that a laminar flow in the core, due to the earth's precession, would have weak hydrodynamic instabilities at most, but that finite-amplitude hydromagnetic instability could lead to fully turbulent flow.     

“党建+”乡村治理模式探析——以Z村为例

乡村是国家治理的基本单元,乡村工作庞杂繁琐。在乡村治理中,基层党组织扮演着不可替代的角色。然而当前乡村社会普遍存在党组织软弱涣散等问题,严重制约乡村治理现代化进程。基于现状考虑,采用实地调研法和非结构式访谈法对 Z村进行调查,个案研究表明,为实现乡村有效治理,村庄应充分发挥党组织引领核心作用,结合村情概况适当压缩治理单元,采用刚性约束与柔性激励相结合的方式,理顺不同治理主体间的关系,形成平稳运行机制,并动员广大群众共同助力乡村可持续发展。     

Rotation and Magnetism of Earth's Inner Core

Three-dimensional numerical simulations of the geodynamo suggest that a super- rotation of Earth's solid inner core relative to the mantle is maintained by magnetic coupling between the inner core and an eastward thermal wind in the fluid outer core. This mechanism, which is analogous to a synchronous motor, also plays a fundamental role in the generation of Earth's magnetic field.     

基于2-模二部图的科研团队发现实证研究——以PIS研究领域的科研团队发现为例

以个性化信息服务（Persionalized Information Service,简写为PIS）研究领域的2008年-2017年中国学术文献网络出版总库中的7 426篇文献为研究样本,以Ucinet软件为分析工具,通过建立关键词--作者2-模二部图,挖掘该研究领域中几个有代表性的科研团队,并根据点度中心度这一网络特征指标对科研团队的核心人物及其主题研究热点进行探寻,为科研团队发现提供了一种新的视角和方法。     

Inner Core Anisotropy Due to the Magnetic Field--induced Preferred Orientation of Iron

Anisotropy of the inner core of the Earth is proposed to result from the lattice preferred orientation of anisotropic iron crystals during their solidification in the presence of a magnetic field. The resultant seismic anisotropy is related to the geometry of the magnetic field in the core. This hypothesis implies that the observed anisotropy (fast velocity along the rotation axis) indicates a strong toroidal field in the core, which supports a strong field model for the geodynamo if the inner core is made of hexagonal close-packed iron.     

Vortex core-driven magnetization dynamics

Time-resolved x-ray imaging shows that the magnetization dynamics of a micron-sized pattern containing a ferromagnetic vortex is determined by its handedness, or chirality. The out-of-plane magnetization in the nanometer-scale vortex core induces a three-dimensional handedness in the planar magnetic structure, leading to a precessional motion of the core parallel to a subnanosecond field pulse. The core velocity was an order of magnitude higher than expected from the static susceptibility. These results demonstrate that handedness, already well known to be important in biological systems, plays an important role in the dynamics of microscopic magnets.     

Pacific geomagnetic secular variation

We have considered several different types of records of long-period geomagnetic secular variation: direct measurements made in geomagnetic observatories; paleomagnetic measurements on Hawaiian lava flows with accurately known ages in the interval 0 to 200 years; paleomagentic measurements on Hawaiian lava flows with loosely determined ages within the interval 200 to 10,000 years ago; and worldwide paleomagnetic measurements of the average geomagnetic angular dispersion recorded in lava flows that formed during the past 0.7 million years. All these magnetic records indicate that, during this time, the nondipole component of the earth's field was lower in the central Pacific than elsewhere, as it is today. This, in turn, indicates that there is some type of inhomogeneity in the lower mantle which is coupled to the earth's core in such a way as to suppress the generation of the nondipole field beneath the central Pacific. With the present incomplete state of knowledge about the processes that give rise to the earth's field, it is uncertain whether undulations in the core-mantle interface or lateral variations in the composition and physical state of the lower mantle are ultimately responsible for the pattern of secular variation seen at the earth's surface.     

A Laboratory Model for Convection in Earth's Core Driven by a Thermally Heterogeneous Mantle

Thermal convection experiments in a rapidly rotating hemispherical shell suggest a model in which the convection in Earth's liquid outer core is controlled by a thermally heterogeneous mantle. Experiments show that heterogeneous boundary heating induces an eastward flow in the core, which, at a sufficiently large magnitude, develops into a large-scale spiral with a sharp front. The front separates the warm and cold regions in the core and includes a narrow jet flowing from the core-mantle boundary to the inner-core boundary. The existence of this front in the core may explain the Pacific quiet zone in the secular variation of the geomagnetic field and the longitudinally heterogeneous structure of the solid inner core.     

基于灰度直方图的图像增强算法

基于灰度直方图的图像增强技术是图像增强领域中的一个重要方面。本文介绍了两种基于灰度直方图的图像增强算法———直方图的均衡化算法和直方图的规定化算法的算法思想和算法应用。     

Equatorially dominated magnetic field change at the surface of Earth's core

Slow temporal variations in Earth's magnetic field originate in the liquid outer core. We analyzed the evolution of nonaxisymmetric magnetic flux at the core surface over the past 400 years. We found that the most robust feature is westward motion at 17 kilometers per year, in a belt concentrated around the equator beneath the Atlantic hemisphere. Surprisingly, this motion is dominated by a single wavenumber and persists throughout the observation period. This phenomenon could be produced by an equatorial jet of core fluid, by hydromagnetic wave propagation, or by a combination of both. Discrimination between these mechanisms would provide useful constraints on the dynamics of Earth's core.     

Earth's core and the geodynamo

Earth's magnetic field is generated by fluid motion in the liquid iron core. Details of how this occurs are now emerging from numerical simulations that achieve a self-sustaining magnetic field. Early results predict a dominant dipole field outside the core, and some models even reproduce magnetic reversals. The simulations also show how different patterns of flow can produce similar external fields. Efforts to distinguish between the various possibilities appeal to observations of the time-dependent behavior of the field. Important constraints will come from geological records of the magnetic field in the past.     

立足临床基础,培育核心能力——浅谈中医临床基础专业硕士研究生核心能力

培育和提高中医临床基础专业硕士研究生的核心能力,需要秉承中医药自身固有的特色,兼顾理论和实践两个方面,使专业名称中的“临床”与“基础”名副其实。中医药事业教育者和中医临床基础专业硕士研究生应从加强传统教育、锤炼实践技能和培育国际视野三方面入手,培育和提高中医临床基础专业硕士研究生的核心能力。     

Viscosity near Earth's solid inner core

Anomalous splitting of the two equatorial translational modes of oscillation of Earth's solid inner core is used to estimate the effective viscosity just outside its boundary. Superconducting gravimeter observations give periods of 3.5822 +/- 0.0012 (retrograde) and 4.0150 +/- 0.0010 (prograde) hours. With the use of Ekman layer theory to estimate viscous drag forces, an inferred single viscosity of 1.22 x 10(11) Pascal seconds gives calculated periods of 3.5839 and 4.0167 hours for the two modes, close to the observed values. The large effective viscosity is consistent with a fluid, solid-liquid mixture surrounding the inner core associated with the "compositional convection" that drives Earth's geodynamo.     

基于CiteSpace的全球竹林碳汇研究回顾及展望

随着全球气候变暖问题日益严重，竹林碳汇研究已经逐渐演化为碳汇相关研究领域的重要分支之一。本研究借助CiteSpace软件，对自《京都议定书》签订以来，Web of Science核心合集数据库中研究竹林碳汇的文献进行了回顾和梳理，结果表明:①竹林碳汇研究处于快速发展期，该领域正受到越来越多学者的密切关注；②发文作者之间合作紧密，核心作者发文能力较强，并且已经基本形成核心作者群，核心发文机构地域集聚性明显，对该领域贡献巨大；③现有研究主要集中于探讨竹林碳储量、竹林固碳能力、经营模式、竹制品碳储量、竹林增汇和增收效应等方面，主要观点包括竹林有着较高的碳储量、竹林固碳能力明显高于其他树林、经营模式对竹林固碳能力具有显著影响、竹制品具有较大的替代减排潜力、竹林具备增加森林碳汇和增加农户收益的双重功效等；④关键词的变迁与通过竹林碳汇应对全球气候变化，以及促进竹林可持续经营密切关联。未来应该扩大竹林碳汇领域的影响力，加强现实问题的对策类研究，以挖掘竹林碳汇减排和增收的双重效应。图2表2参39     

N₂reduction and hydrogenation to ammonia by a molecular iron-potassium complex

The most common catalyst in the Haber-Bosch process for the hydrogenation of dinitrogen (N(2)) to ammonia (NH(3)) is an iron surface promoted with potassium cations (K(+)), but soluble iron complexes have neither reduced the N-N bond of N(2) to nitride (N(3-)) nor produced large amounts of NH(3) from N(2). We report a molecular iron complex that reacts with N(2) and a potassium reductant to give a complex with two nitrides, which are bound to iron and potassium cations. The product has a Fe(3)N(2) core, implying that three iron atoms cooperate to break the N-N triple bond through a six-electron reduction. The nitride complex reacts with acid and with H(2) to give substantial yields of N(2)-derived ammonia. These reactions, although not yet catalytic, give structural and spectroscopic insight into N(2) cleavage and N-H bond-forming reactions of iron.     

地方农业院校内涵式发展的策略分析简

高等教育内涵式发展是贯彻《国家中长期教育改革和发展规划纲要（2010—2020年）》的客观要求,是高校尤其是地方农业院校的必然选择,其中特色发展是内涵式发展的核心。地方农业院校要想增强竞争力就必须树立特色理念、培养特色人才、构建特色队伍、建设特色学科、强化特色科研、培育特色文化。注重发展的特色性和行业性,才能增强地方农业院校发展的竞争力。     

Galileo Gravity Results and the Internal Structure of Io

Doppler data generated with the Galileo spacecraft's radio carrier wave were used to measure Io's external gravitational field. The resulting triaxial field is consistent with the assumption that Io is in tidal and rotational equilibrium. The inescapable conclusion is that it has a large metallic core. If the core is a eutectic mixture of iron and iron sulfide, it comprises 20.2 ± 7.4 percent of the satellite's total mass with a radius that is about 52 percent of Io's mean radius of 1821.3 kilometers; if the core is pure iron, it comprises 10.5 ± 3.7 percent of the total mass with a radius of about 36 percent of the mean radius.     

Ferroelectric columnar liquid crystal featuring confined polar groups within core-shell architecture

Ferroelectric liquid crystals are materials that have a remnant and electrically invertible polar order. Columnar liquid crystals with a ferroelectric nature have potential use in ultrahigh-density memory devices, if electrical polarization occurs along the columnar axis. However, columnar liquid crystals having an axial nonzero polarization at zero electric field and its electrical invertibility have not been demonstrated. Here, we report a ferroelectric response for a columnar liquid crystal adopting a core-shell architecture that accommodates an array of polar cyano groups confined by a hydrogen-bonded amide network with an optimal strength. Under an applied electric field, both columns and core cyano groups align unidirectionally, thereby developing an extremely large macroscopic remnant polarization.     

Saturn's Magnetic Field and Magnetosphere

The Pioneer Saturn vector helium magnetometer has detected a bow shock and magnetopause at Saturn and has provided an accurate characterization of the planetary field. The equatorial surface field is 0.20 gauss, a factor of 3 to 5 times smaller than anticipated on the basis of attempted scalings from Earth and Jupiter. The tilt angle between the magnetic dipole axis and Saturn's rotation axis is < 1 degrees , a surprisingly small value. Spherical harmonic analysis of the measurements shows that the ratio of quadrupole to dipole moments is < 10 percent, indicating that the field is more uniform than those of the Earth or Jupiter and consistent with Saturn having a relatively small core. The field in the outer magnetosphere shows systematic departures from the dipole field, principally a compression of the field near noon and an equatorial orientation associated with a current sheet near dawn. A hydromagnetic wake resulting from the interaction of Titan with the rotating magnetosphere appears to have been observed.