土壤环境中粘粒的分散-凝聚行为及其影响因素

本文研究了一般无机离子,重金属离子,表面活性剂和高分子化合物对土壤粘粒分散凝聚行为的影响,以期为土壤环境的保护与管理提供理论依据。结果表明i:)一般无机离子可通过对粘粒表面扩散双电层的压缩作用导致粘粒凝聚,且离子价数越高压缩作用越强i;i)重金属离子在粘粒上的专性吸附,导致其对扩散双电层的压缩作用更强i;ii)阳离子表面活性剂在较低浓度时可形成粒间疏水性表面胶束使粘粒凝聚,而在较高浓度时可形成粒内亲水性表面胶束使粘粒分散i;v)阳离子型高分子化合物在较低浓度时对粘粒的架桥作用可使粘粒凝聚,而在较高浓度时的静电斥力可使粘粒分散;v)随着pH的升高,粘粒由于表面负电荷的增加而趋于分散。以上说明:双电层的压缩、专性吸附、粒间疏水性表面胶束和架桥作用等均可使土壤粘粒凝聚,降低其稳定性。     

影响刨花对流干燥的因素分析

该文通过对刨花干燥过程中影响因素的研究,以期为刨花干燥工艺的优化设计和过程控制提供理论依据.研究表明,随着气流温度的升高,刨花平均干燥速率增大,单位能耗也相应增加;随着气流速度的提高,刨花平均干燥速率增大,单位能耗逐渐降低;随着刨花初含水率的升高,刨花平均干燥速率加大,单位能耗增加;随着装载量的增大,刨花平均干燥速率大幅减小,单位能耗基本不变,总能耗急剧增加;转筒的运动影响了刨花的干燥,其自转可提高平均干燥速率.实际生产中应根据产量和生产成本,选择合适的干燥条件进行生产.     

磁场中电解质内胶态粒子的电荷分布

为了探求磁处理技术防垢的机理，应用电学与统计力学的理论和数学分析的方法。对电解质内胶态粒子周围的电荷分布进行了研究，计算了磁场对这种电荷分布的影响，给出了在温度较高及稀溶液情况下磁场对胶态粒子周围电荷分布影响的公式。认为电解质内的胶态粒子周围带有一层离子电荷，其厚度取决于温度与离子的浓度。当离子浓度离子大时，离子层变薄，促使胶粒之间发生凝聚；当温度增高时，离子层变厚，阻碍胶粒之间发生凝聚。当电解质     

Extraparticulate chain interaction between different electron transport particles

Interaction or cross-linking between the respiratory chains of the electron transport particles of bacterial origin occurs with a mixture of active and inactive particles. Interaction between bacterial particles and liver sub-mitochondrial particles also occurs. Irradiation of the bacterial particles at 360 nanometers resulted in the destruction of quinone and consequent loss of ability of reduced nicotinamide adenine, dinucleotides to reduce cytochromes b, c(1), c, and a plus a(3). A mixture of both irradiated and untreated particles in the presence of the reduced dinucleotide resulted in the reduction of cytochromes c and a plus a(3), in an amount equivalent to the total concentration of these cytochromes in both types of particles. In contrast, the amount of cytochrome b reduced was equivalent to half the particle concentration or to that observed with the active particles alone. The rate of reduction of cytochromes c and a plus a(3) with the mixture of particles was similar to that with the active particles alone. The interaction or cross-linking between the particulate respiratory chains of bacteria or of bacterial and mammalian systems occurs after cytochrome b and before or at cytochrome c.     

华南地区桑园和荒地生境内红火蚁食物组成研究

通过对红火蚁觅食搬运的和弃尸堆中的动植物残片取样和鉴定,研究了华南地区桑园和荒地两种生境中红火蚁的食物组成。结果表明:在桑园和荒地中,红火蚁的食物残片无论是在觅食搬运中还是在弃尸堆中均以动物残片为主,分别高达94.92%和68.44%以上,而且两种生境红火蚁食物组成种类相近,只是各类群所占比例略有不同。红火蚁觅食搬运的食物残片种类比弃尸堆中的丰富,在桑园和荒地中,觅食残片共收集到的类群数比弃尸堆残片的类群多8个。     

The role of surface chemistry in filter feeding by zooplankton

Surface chemistry of both particles and animals is important in filter feeding at low Reynolds number. Daphnia magna, fed mixtures of three sizes of polystyrene particles, retained particles that were smaller than the mesh size of the animals (1.0 micrometer) at greater efficiencies than predicted by a sieving model. Retention efficiency of the smallest particles (0.5 micrometer) was increased when negative surface charge on the particles was neutralized, and retention was decreased when a nonionic surfactant was, added to reduce wettability.     

Composition of saturnian stream particles

During Cassini's approach to Saturn, the Cosmic Dust Analyser (CDA) discovered streams of tiny (less than 20 nanometers) high-velocity (approximately 100 kilometers per second) dust particles escaping from the saturnian system. A fraction of these impactors originated from the outskirts of Saturn's dense A ring. The CDA time-of-flight mass spectrometer recorded 584 mass spectra from the stream particles. The particles consist predominantly of oxygen, silicon, and iron, with some evidence of water ice, ammonium, and perhaps carbon. The stream particles primarily consist of silicate materials, and this implies that the particles are impurities from the icy ring material rather than the ice particles themselves.     

Planets and Comets: Role of Crystal Growth in Their Formation

The application of crystal growth theory to the formation of smoke particles from the primordial solar nebula indicates that solid particles with filamentary structures would form. Such particles would facilitate successive aggregation into planets, comets, and asteroids. The difficulties associated with the aggregation of spherical smoke particles would thus be avoided.     

春小麦病毒病的鉴定——Ⅰ.电镜观察及病细胞超微结构分析

小麦病叶中观察到大小为50～55nm×330～450nm的病毒粒体,粒体大多为弹状,少数为两端削平的杆状;粒体横切面有3层同心环结构;本病毒粒体主要存在于感病细胞的细胞质中及细胞核的周围;在个别细胞的核质中发现无被膜粒体。细胞质中的病毒粒体常聚集成团粒体结构,此结构的外缘有膜状物包围。未成熟的筛管分子中和胞间连丝附近的病毒粒体呈散乱无规则分布。观察到病毒粒体通过胞间连丝运转的状态及粒体运转对胞间连丝的影响,还发现高尔基体囊胞增生现象和粒体在细胞质中的出芽现象。将电镜观察结果同已报道的有关文献进行比较,认为该病毒为北方禾谷花叶病毒(国内称小麦丛矮病毒)(NCMV)。     

Particle Sorting by Repeated Freezing and Thawing

If a hetrogeneous mixture of particles of various sizes is frozen and thawed repeatedly, the particles are sorted into relatively uniformn groups by size. The movement of particles depends on the amount of water between the ice-water interface and the particle, the rate of freezing, the distribution of the particles by size, and the orientation of the freeze-thaw plane.     

Magnetic particles extracted from manganese nodules: suggested origin from stony and iron meteorites

On the basis of x-ray diffraction and electron microprobe data, spherical and ellipsoidal particles extracted from manganese nodules were divided into three groups. Group 1 particles are believed to be derived from iron meteorites, and Group 11 particles from stony meteorites. Group III particles are believed to be volcanic in origin.     

Particle capture by a pacific brittle star: experimental test of the aerosol suspension feeding model

Ophiopholis aculeata, a suspension feeding brittle star, is capable of removing artificial particles from seawater by some mechanism or mechanisms other than sieving; the animal can capture a finite proportion of particles in all size classes available from at least 30 to 360 micrometers in diameter. A marked shift in the size distribution of particles caught by the animal toward larger particle sizes agrees with predictions derived from aerosol filtration theory. Adhesion of particles to the tube feet is strongly dependent on the presence of fixed charged groups on the surface of the particles.     

Oxygen isotopes in refractory stratospheric dust particles: proof of extraterrestrial origin

The oxygen and magnesium isotopic compositions of five individual particles that were collected from the stratosphere and that bear refractory minerals were measured by secondary ion mass spectrometry. Four of the particles exhibit excesses of oxygen-16 similar to those observed in anhydrous mineral phases of carbonaceous chondrites and thus are extraterrestrial. The oxygen and magnesium isotopic abundances of one corundum-rich particle are consistent with a terrestrial origin. Magnesium in the four extraterrestrial particles is isotopically normal. It is unlikely that these particles are derived from carbonaceous chondrites and thus such particles probably represent a new type of collected extraterrestrial material.     

土壤颗粒和肥力关系的研究进展

阐述了土壤微粒的形成机制和不同微粒在土壤肥力上的作用，并从一个新的角度运用更细小的颗粒分级理论(即纳米微粒)对土壤肥力的影响进行了展望．     

土壤无机纳米微粒对土壤肥力的影响

从土壤中不同微粒及不同大小粒径等对土壤肥力的影响方面进行了阐述,进而引入了土壤中的超微粒子——无机纳米微粒对土壤肥力的影响,并且对其发展前景进行了展望。     

表面活性剂在土壤粒子上的吸附及影响因素综述

综述了表面活性剂在土壤粒子上吸附及其影响因素的国内外研究进展。研究表明,表面活性剂可通过静电引力、离子交换和氢键等方式吸附在土壤粒子上。表面活性剂的类型与结构组成、土壤的理化特性以及环境条件对其在土壤粒子上的吸附具有非常重要的影响。混合表面活性剂比单一表面活性剂的吸附机理更为复杂。最后,指出目前研究中存在的不足,提出应加强开展混合表面活性剂和特殊表面活性剂在土壤粒子上吸附研究的建议。     

生态核不育大麦花粉的扫描电镜观察

对生态核不育大麦不育株和可育株的成熟花粉以及对照品种８９０９和鄂啤２号的成熟花粉进行了扫描电镜观察，发现生态核不育大麦不育株和可育株均含有空秕状和圆形、饱满两类花粉；两对照品种的花粉为圆形、饱满类型。生态核不育大麦可育株的圆形花粉与对照品种花粉一样，其萌发孔有明显突出的孔盖；而生态核不育大麦不育株的圆形花粉则无孔盖。因此，可认为萌发孔孔盖的有无是生态核不育大麦可育与不育花粉的典型鉴别特征。     

颗粒滚动摩擦系数对颗粒堆内部受力的影响

为探究贮存过程中不同形状玉米颗粒与镀锌钢板间滚动摩擦系数对颗粒堆基底接触力分布的影响,采用离散元法数值模拟标定球形、锥形和矩形玉米颗粒间滚动摩擦系数。玉米颗粒形状越不规则,滚动摩擦系数越大,其中锥形玉米颗粒间滚动摩擦系数最大。以3种形状玉米颗粒与镀锌钢板间滚动摩擦系数为因素,以玉米颗粒与基底法向、切向接触力平均值为指标,作3因素5水平二次正交旋转组合模拟试验,运用Design-Expert8.0.6软件数据处理,基于结合响应曲面法分析试验结果。随玉米颗粒与镀锌钢板间滚动摩擦系数增加,玉米颗粒与基底间法向和切向接触力平均值均先增大后趋于稳定,且模拟试验得玉米颗粒与基底法向接触力分布规律与物理试验结果基本一致。研究结果可为粮仓设计及结构优化提供理论参考。     

Phagocytosis of inhaled plutonium oxide-239pu particles by pulmonary macrophages

Pulmonary macrophages and plutonium particles were removed by washing the lungs of rats that had inhaled plutonium oxide-(239)Pu. A significant amount of plutonium was found in multiple washings of the same lung. The removal of toxic particles by washing is of potential therapeutic value. Particles were phagocytized by macrophages during the first 3 hours and retained within these cells for up to 25 days. Nearly all particles in washings were found in macrophages after the second day. The percent of macrophages with engulfed particles increased with increasing amounts of plutonium deposited in the lungs. The ability of pulmonary macrophages to rapidly phagocytize and retain plutonium particles deposited in the lungs has been shown.     

Streptomycin resistance mutation in Escherichia coli: altered ribosomal protein

Reconstitution of 30S ribosomal particles was performed with 16S ribosomal RNA, "core" proteins, and "split" proteins from 30S particles derived from streptomycin-sensitive and streptomycin-resistant Escherichia coli cells in various combinations. Analysis of streptomycin sensitivity of the reconstituted particles has shown that the alteration induced by the resistance mutation resides in the core proteins, and not in the RNA or in the split proteins of the 30S particles.