Scroll-shaped waves of chemical activity in three dimensions

Ferric ions catalyze the oxidation of malonate by bromate in acid solution, sometimes at a spatially uniform, steady rate, but sometimes in a self-regenerating three-dimensional wave which resembles a rotating scroll, often with its axis closed in a ring. In cross section perpendicular to the axis, one sees an involute spiral emerging from a thin cylindrical core. This "dissipative structure" organizes reaction stages periodically in space and time everywhere except along its rotation axis, which may therefore be a thermodynamically unique locus.     

Phototaxis of spiral waves

The drift of spiral waves toward regions of higher light intensity was observed experimentally in the ruthenium-catalyzed Belousov-Zhabotinsky reaction. A light gradient can thus be used to manipulate optical information in new computational systems based on photochemical media. The drift of a gradient that is rotationally invariant in space is three to four times as fast as that of a translationally invariant gradient. Simulations based on the use of a cellular automaton, which is made isotropic by a semirandom distribution of cells, are in agreement with the experimental results.     

Cassini discovers a kinematic spiral ring around Saturn

Since the time of the Voyager flybys of Saturn in 1980-1981, Saturn's eccentric F ring has been known to be accompanied on either side by faint strands of material. New Cassini observations show that these strands, initially interpreted as concentric ring segments, are in fact connected and form a single one-arm trailing spiral winding at least three times around Saturn. The spiral rotates around Saturn with the orbital motion of its constituent particles. This structure is likely the result of differential orbital motion stretching an initial cloud of particles scattered from the dense core of the F ring. Different scenarios of formation, implying ringlet-satellite interactions, are explored. A recently discovered moon candidate, S/2004 S6, is on an orbit that crosses the F-ring core at the intersection of the spiral with the ring, which suggests a dynamical connection between S/2004 S6 and the spiral.     

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RSM模型的螺旋管道内二次流特性分析

利用FLUENT流体力学软件,采用RSM模型对矩形截面螺旋管道紊流流动中的二次流进行数值模拟。分析研究表明,矩形螺旋管道不同管轴半径连接断面上明显出现一对二次涡,且两个二次涡位于中心略微偏向外边壁,其结果与目前所研究的二次涡所在位置有区别;而且随着雷诺数的增大,二次涡的位置变化不大;随着管道曲率的增加,二次流强度逐渐增大,而随着雷诺数的增大,二次流强度却有所减小。     

防堵式生物质颗粒水平螺旋进料器的设计

生物质快速热解过程中,连续不间断地供料是反应进行的关键.普通的螺旋进料器在输送生物质小颗粒时容易出现堵塞.通过对进料器两端轴承的受力分析并且观察在输料过程中出料口和进料口出现堵塞的情况,根据螺旋轴两端受力不同选择了不同的轴承,在出料口设计半圈或者一圈相反旋向的螺旋叶片,在进料口设计由凸轮-弹簧-导杆组成的防堵机构.所设计的防堵式水平螺旋进料器在实际运用中具有进料流畅、稳定均匀、密封性好等特点.     

螺旋式果园开沟装置的设计及土槽试验

针对现阶段果园开沟复杂的作业环境、人工开沟效率低、劳动强度大的生产实际,开发研制了一套与小型手扶拖拉机配套的圆柱型变螺距螺旋式果园开沟装置,分析了圆柱型变螺距螺旋的结构参数和主要运动参数,并借助高速数字化土槽试验平台开展了该装置的功能性试验.试验表明该开沟装置具有功耗低、集土壤切削、提升、抛撒于一体且矩形沟型的沟壁平整等显著特征.研究结果时实现果园机械化开沟装置的结构改进和优化设计具有重要的指导意义.     

Crossing the termination shock into the heliosheath: magnetic fields

Magnetic fields measured by Voyager 1 show that the spacecraft crossed or was crossed by the termination shock on about 16 December 2004 at 94.0 astronomical units. An estimate of the compression ratio of the magnetic field strength B (+/- standard error of the mean) across the shock is B2/B1 = 3.05 +/- 0.04, but ratios in the range from 2 to 4 are admissible. The average B in the heliosheath from day 1 through day 110 of 2005 was 0.136 +/- 0.035 nanoteslas, approximately 4.2 times that predicted by Parker's model for B. The magnetic field in the heliosheath from day 361 of 2004 through day 110 of 2005 was pointing away from the Sun along the Parker spiral. The probability distribution of hourly averages of B in the heliosheath is a Gaussian distribution. The cosmic ray intensity increased when B was relatively large in the heliosheath.     

起旋器出口断面流速分布与起旋效率

通过对 6种起旋器、4种流量工况的试验 ,对起旋器出口断面流速分布及起旋效率进行了分析。结果表明 ,起旋器出口断面轴向流速分布呈类对数型分布 ,它比平直流的流速分布更均匀 ,可以用平直流速分布公式与一个二次尾流函数来表示 ;起旋器出口断面周向流速分布在主流区近似呈线性分布。提出了起旋器的起旋效率计算式 ,公式表明要提高起旋效率 ,则必须减小阻力损失 ,即应对起旋器结构参数进行优化     

集中连片特困区旅游扶贫效率及旅游经济强度空间特征分析——基于Super-SBM模型和社会网络分析法

旅游扶贫是脱贫攻坚的有效途径之一，旅游扶贫效率是衡量旅游扶贫工作的核心指标，旅游经济强度是促进旅游发展的重要因素，二者彼此关联性对于开展旅游扶贫工作具有重要指导意义。以湖北大别山区16个县（区）为研究对象，运用Super-SBM模型，测度2011至2017年各县（区）旅游扶贫效率，并通过修正传统引力模型，构建各县（区）旅游强度关系矩阵，基于社会网络分析法，对16个县（区）2017年旅游经济强度空间特征进行可视化分析。结果表明：湖北大别山区旅游扶贫综合效率处于中等偏上水平(均值0.776)，整体呈现下降趋势；县（区）之间旅游联系强度较弱，具有明显的不均衡性，网络密度呈现“大分散，小聚集”的空间格局，核心区与边缘区之间连接密度较低，联系不够紧密，旅游经济联系地域空间格局分为东南，西北和中部三个主要派系。旅游扶贫效率与旅游经济强度呈现负相关性，边缘区旅游扶贫效率远比核心区旅游扶贫效率高，具体呈现高效率高强度、高效率低强度、低效率低强度、低效率高强度四种模式。提高旅游扶贫效率，优化旅游扶贫和旅游发展之间内生关系是当务之急，从改进旅游扶贫手段，优化扶贫管理模式；科学把握旅游规模，有效配置旅游资源；加强旅游经济联系，提升旅游扶贫效率等方面提出建议。     

Crystal structure of the RC-LH1 core complex from Rhodopseudomonas palustris

The crystal structure at 4.8 angstrom resolution of the reaction center-light harvesting 1 (RC-LH1) core complex from Rhodopseudomonas palustris shows the reaction center surrounded by an oval LH1 complex that consists of 15 pairs of transmembrane helical alpha- and beta-apoproteins and their coordinated bacteriochlorophylls. Complete closure of the RC by the LH1 is prevented by a single transmembrane helix, out of register with the array of inner LH1 alpha-apoproteins. This break, located next to the binding site in the reaction center for the secondary electron acceptor ubiquinone (UQB), may provide a portal through which UQB can transfer electrons to cytochrome b/c1.     

5TYJ-10A玉米种子脱粒机作业性能试验

为进一步探明脱粒装置结构参数对玉米种子果穗脱粒生产作业的影响,依托自行研制的5TYJ-10A玉米种子脱粒机,通过置换分别携有钉齿类、直板齿类、组合螺旋板齿类3类脱粒元件的脱粒装置,分析玉米种子脱粒装置工作性能,建立组合螺旋脱粒板齿几何参数相关数学模型,分析获得组合式螺旋板齿脱粒装置相关脱粒板齿半径、中心脱粒间距及板齿高度的设计参数。试验结果表明,选取出作业性能良好的组合螺旋板齿式脱粒装置,其脱净率为99.16%、含杂率为3.26%、破碎率为0.43%,对应实际生产率为11.6 t/h。采用脱粒板齿试验装置进行不同脱粒板齿螺旋角试验选取,结果表明,当组合螺旋板齿角为6°-12°时更适宜进行玉米种子脱粒作业。研究成果将为玉米种子脱粒生产装备的研发提供参考与借鉴。     

A high-resolution millennial record of the south asian monsoon from himalayan ice cores

A high-resolution ice core record from Dasuopu, Tibet, reveals that this site is sensitive to fluctuations in the intensity of the South Asian Monsoon. Reductions in monsoonal intensity are recorded by dust and chloride concentrations. The deeper, older sections of the Dasuopu cores suggest many other periods of drought in this region, but none have been of greater intensity than the greatest recorded drought, during 1790 to 1796 A.D. of the last millennium. The 20th century increase in anthropogenic activity in India and Nepal, upwind from this site, is recorded by a doubling of chloride concentrations and a fourfold increase in dust. Like other ice cores from the Tibetan Plateau, Dasuopu suggests a large-scale, plateau-wide 20th-century warming trend that appears to be amplified at higher elevations.     

Hydrogen 21-centimeter emission from a galaxy at cosmological distance

We have detected the neutral atomic hydrogen (HI) emission line at a cosmologically significant distance [redshift (z) = 0.18] in the rich galaxy cluster Abell 2218 with the Westerbork Synthesis Radio Telescope. The HI emission originates in a spiral galaxy 2.0 h65(-1) megaparsecs from the cluster core. No other significant detections have been made in the cluster, suggesting that the mechanisms that remove neutral gas from cluster galaxies are efficient. We infer that fewer than three gas-rich galaxies were accreted by Abell 2218 over the past 10(9) years. This low accretion rate is qualitatively consistent with low-density cosmological models in which clusters are largely assembled at z > 1.     

Orbital influence on Earth's magnetic field: 100,000-year periodicity in inclination

A continuous record of the inclination and intensity of Earth's magnetic field, during the past 2.25 million years, was obtained from a marine sediment core of 42 meters in length. This record reveals the presence of 100,000-year periodicity in inclination and intensity, which suggests that the magnetic field is modulated by orbital eccentricity. The correlation between inclination and intensity shifted from antiphase to in-phase, corresponding to a magnetic polarity change from reversed to normal. To explain the observation, we propose a model in which the strength of the geocentric axial dipole field varies with 100,000-year periodicity, whereas persistent nondipole components do not.     

Geomagnetic modulation of the 36Cl flux in the GRIP ice core, greenland

Geomagnetic field strength is expected to affect the production rate of cosmogenic isotopes such as beryllium-10, carbon-14, or chlorine-36. Chlorine-36 data from the Greenland Ice Core Project (GRIP) ice core agree well with a production rate calculation based on a paleomagnetic reconstruction for the past 100,000 years over both long- and short-term variations. A chlorine-36 peak at 38,000 years ago previously found in the beryllium-10 record from the Vostok ice core can be explained by a period of low geomagnetic field intensity.     

用X射线衍射法测定棉纤维次生胞壁的平均螺旋角

本文阐述应用X射线(002)面衍射弧测定棉纤维次生胞壁平均螺旋角(又称微纤丝角)的方法。该方法以X射线衍射强度分布为基础,而与分布曲线的峥值无关。     

汽爆系统中进料密封阀门的结构设计及稳定性分析

针对汽爆系统中进料口阀门进料效率低,容易漏气等问题,设计了一种集进料、密封和开启为一体的进料密封阀门。根据阀门的材质和使用环境,对阀门中的阀芯进行了理论分析,并利用ANSYS Workbench软件对其进行强度分析,得到了阀芯的最大变形量发生位置以及能够满足其稳定进料和密封时螺旋轴的最佳直径和最佳转速,经理论计算和强度校核,阀门在正常工作环境下,其阀芯的强度完全满足设计要求。对不同进料时间和转速对阀门的进料稳定性影响进行试验研究,确定150 kg玉米秸秆完成进料时的最佳转速为200 r·min-1,最佳进料时间为5 min。     

苯甲酸荧光法研究牛血酶解液锌螯合物清除羟自由基活性

研究牛血酶解液锌螯合物通过苯甲酸荧光法清除羟自由基的效果,为提高动物血液蛋白资源的利用和开发抗氧化活性新物质提供理论依据。建立了苯甲酸荧光光度法,确定使用该方法时苯甲酸的加入量和反应时间,研究H2O2用量对荧光强度的影响和牛血酶解液锌螯合物对羟自由基的清除效果。当苯甲酸浓度为0.6 mmol/L,反应时间为20 min时,荧光强度最大;当H2O2浓度在10~50 mmol/L时,H2O2浓度与产物的荧光强度呈线性关系;牛血酶解液锌螯合物有较强的羟自由基清除能力,达到80.8%(RSD=2.6%),比同浓度Vc溶液的清除效果好。苯甲酸荧光光度法操作简便,灵敏度高,重现性好,且不受水解液中血红素的干扰,可广泛用于水溶性有色抗氧化物质清除羟自由基能力的检测。     

复凝聚法制备苏云金杆菌微胶囊

[目的]探讨复凝聚法制备以明胶和阿拉伯胶为壁材的苏云金杆菌（Bacillus thuringiensis,简称Bt）微胶囊的工艺.[方法]通过单因素试验,研究了明胶浓度、阿拉伯胶浓度、芯壁比、pH、反应温度和转速对微胶囊包埋效率的影响,再通过正交优化试验确定最佳制备条件.利用光学显微镜、扫描电子显微镜和粒径测微仪对苏云金杆菌微胶囊形态及粒径分布进行表征.[结果]复凝聚法制备苏云金杆菌微胶囊最佳工艺条件为明胶浓度1.0％,阿拉伯胶浓度1.0％,芯壁比1∶1,复凝聚反应pH 3.6,温度40℃,搅拌速度550 r/min.在此条件下的包埋率达82.32％,粒径分布均匀且平均粒径在28.29 μm左右流动性好的球型固体微胶囊.[结论]该微胶囊符合实际应用需求,为杀虫剂的研制提供了理论依据.