How to make water run uphill

A surface having a spatial gradient in its surface free energy was capable of causing drops of water placed on it to move uphill. This motion was the result of an imbalance in the forces due to surface tension acting on the liquid-solid contact line on the two opposite sides ("uphill" or "downhill") of the drop. The required gradient in surface free energy was generated on the surface of a polished silicon wafer by exposing it to the diffusing front of a vapor of decyltrichlorosilane, Cl(3)Si(CH(2))(9)CH(3). The resulting surface displayed a gradient of hydrophobicity (with the contact angle of water changing from 97 degrees to 25 degrees ) over a distance of 1 centimeter. When the wafer was tilted from the horizontal plane by 15 degrees , with the hydrophobic end lower than the hydrophilic, and a drop of water (1 to 2 microliters) was placed at the hydrophobic end, the drop moved toward the hydrophilic end with an average velocity of approximately 1 to 2 millimeters per second. In order for the drop to move, the hysteresis in contact angle on the surface had to be low (相似文献   

THE TRIPLE POINT OF WATER

(1) A common error in text-books on physical chemistry is pointed out. It is hoped that the correct value for the triple point temperature, +.0098 degrees C, will be given in new books and in succeeding editions of the books surveyed above. (2) Inconsistencies in the vapor pressure values for ice and for liquid water near 0 degrees C are pointed out. (3) The equilibrium vapor pressures for ice and liquid water under two different sets of equilibrium conditions are compared with the triple point pressure.     

散叶莴苣幼苗高温胁迫下生理生化变化的研究

以3个耐热品种(“意大利全能生菜”、“耐抽薹生菜”和“辛普森-精英”)和3个不耐热品种(“生菜王”、“大速生”和“嫩绿奶油生菜”)为试验材料,研究散叶莴苣在人工模拟高温胁迫下的热害情况、细胞膜透性、保护酶相对活性变化以及丙二醛相对含量的变化。结果表明,幼苗热害指数是鉴定散叶莴苣的耐热性的理想指标,高温导致相对电导率和丙二醛含量升高,过氧化物酶、超氧化物歧化酶活性下降,过氧化氢酶活性升高。     

甘蔗种质资源的研究

对 2 64个国内外栽培甘蔗品种及福建省内野生甘蔗“割手密”的特征特性等进行了研究 ,结果表明 :“割手密”的体细胞染色体数有 2n =72、80、84、88、92、96、1 0 2等 7种类型 ,酯酶同工酶有 1 9种类型 ;印度培育的甘蔗品种产量高 ,澳大利亚培育的甘蔗品种锤度高 ;从国外引进的品种中筛选出 3个生长特快的高产品种 (“C1 55-76”、“My5462”和“My5770”)和 2个高纤维含量的高产品种 (“FCP86-2 61”和“FCP86-2 63”)。对上述甘蔗种质资源进行了创新利用 ,已初步选育出特高糖品种“闽糖 91 -2 2 1”及高生物量品系“闽糖 92 -1 1 7”和“闽糖 92 -2 2 5”等     

Ross ice shelf sea temperatures

Two temperature profiles recorded by a sensitive bathythermograph at the Ross Ice Shelf Project site (82 degrees 22.5'S, 168 degrees 37.5'W) are presented. From the shape of the profiles it is concluded that an inflow of water at intermediate depths provides a source of heat to drive a regime in which ice is melted from the interface at a depth of 360 meters. Melting maintains the temperature of a thick layer under the ice at about -2.14 degrees C, close to the ambient freezing temperature. A very well mixed layer about 35 meters thick was found at the seabed.     

Freezing resistance in polar fishes

Arctic and antarctic fishes, living in contact with sea ice at -1.9 degrees C, have plasma equilibrium freezing points near -1.2 degrees C which are dependent on salt concentrations. These supercooled fishes have plasma protein concentrations much higher than other polar animals have, and the proteins impede ice propagation at temperatures down to -2 degrees C. Plasma protein concentration increases as environmental water temperature decreases.     

瓶插液对储藏后牡丹“洛阳红”切花瓶插品质的影响

以经过储藏12d、24d、36d的牡丹品种“洛阳红”为试材,通过测定切花瓶插期间的瓶插寿命、花径变化、鲜重变化率、水分平衡值和乙烯释放率等指标,研究了瓶插液(3%蔗糖 0.2g/LHQS 2mmolSTS)对“洛阳红”切花瓶插品质的影响。结果表明:瓶插液(3%蔗糖 0.2g/LHQS 2mmolSTS)可以显著延长“洛阳红”切花的瓶插寿命、提高其水分平衡值和花径、降低其鲜重损失和乙烯释放,提高‘洛阳红’切花的瓶插观赏品质。     

江西稻米品质现状及加速优质稻开发的对策

依据国家标准GB/T1 7891 -1 999《优质稻谷》中的 8项涉及品种特性的品质性状指标 ,江西省主栽的杂交籼稻中 ,没有 1个组合达到国家标准 ,其主要原因是胶稠度、垩白度和垩白率不合格。主栽的常规稻品种中 ,只有一个早稻品种 (“湘早籼 31号”)和两个晚稻品种 (“赣晚籼 30号”和“赣晚籼 1 9号”)分别达到国家 3、3、2级优质稻谷标准 ,但没有一个达国家一级标准 ,差距表现在直链淀粉含量不是偏高就是偏低。因此 ,提出了加速江西优质稻开发的对策 ,即建立优质稻生产基地 ,发挥龙头企业的作用 ,实施优化栽培技术。     

Amorphous ice: density and reflectivity

Amorphous ice prepared under a wide range of conditions has a density, determined from its buoyancy in liquid oxygen, of 0.94+/-0.02 gram per cubic centimeter, the same as that of ordinary hexagonal ice, with no indication of the glassy superdense ice (2.32 grams per cubic centimeter) reported recently. The diffuse reflectivity shows a small increase as the ice crystallizes at 153 degrees K. This increase is followed by a much larger increase (probably associated with crystal growth) as the sample warms, and the reflectivity reaches a maximum well below the melting temperature. Although the ice deposits appear translucent, the specular reflectivity is low, thus indicating a dull rather than a glassy surface.     

Electrons in finite-sized water cavities: hydration dynamics observed in real time

We directly observed the hydration dynamics of an excess electron in the finite-sized water clusters of (H2O)n- with n = 15, 20, 25, 30, and 35. We initiated the solvent motion by exciting the hydrated electron in the cluster. By resolving the binding energy of the excess electron in real time with femtosecond resolution, we captured the ultrafast dynamics of the electron in the presolvated ("wet") and hydrated states and obtained, as a function of cluster size, the subsequent relaxation times. The solvation time (300 femtoseconds) after the internal conversion [140 femtoseconds for (H2O)35-] was similar to that of bulk water, indicating the dominant role of the local water structure in the dynamics of hydration. In contrast, the relaxation in other nuclear coordinates was on a much longer time scale (2 to 10 picoseconds) and depended critically on cluster size.     

Liquid water in frozen tissue: study by nuclear magnetic resonance

Nuclear magnetic resonance (NMR) spectroscopy was used to examine the behavior and extent of liquid water in postrigor-frozen tissue of cod at temperatures below 0 degrees C. A liquid-water phase persists in the tissue down to about -70 degrees C; the extent of the phase decreases rapidly between 0 degrees and -10 degrees C and slowly at lower temperatures. That the NMR absorption peak of the liquid water increases in width, with decreasing temperature, suggests loss of mobility or structuring of the phase. A technique for introducing geometrically uniform cores of muscle into the probe of the high-resolution spectrometer permits quantitative determinations of liquid water.     

Discovery of till deposition at the grounding line of Whillans Ice Stream

We report on the discovery of a grounding-line sedimentary wedge ("till delta") deposited by Whillans Ice Stream, West Antarctica. Our observation is that grounding-line deposition serves to thicken the ice and stabilize the position of the grounding line. The ice thickness at the grounding line is greater than that of floating ice in hydrostatic equilibrium. Thus, the grounding line will tend to remain in the same location despite changes in sea level (until sea level rises enough to overcome the excess thickness that is due to the wedge). Further, our observation demonstrates the occurrence of rapid subglacial erosion, sediment transport by distributed subglacial till deformation, and grounding-line sedimentation, which have important implications for ice dynamics, numerical modeling of ice flow, and interpretation of the sedimentation record.     

Formation of glasses from liquids and biopolymers

Glasses can be formed by many routes. In some cases, distinct polyamorphic forms are found. The normal mode of glass formation is cooling of a viscous liquid. Liquid behavior during cooling is classified between "strong" and "fragile," and the three canonical characteristics of relaxing liquids are correlated through the fragility. Strong liquids become fragile liquids on compression. In some cases, such conversions occur during cooling by a weak first-order transition. This behavior can be related to the polymorphism in a glass state through a recent simple modification of the van der Waals model for tetrahedrally bonded liquids. The sudden loss of some liquid degrees of freedom through such first-order transitions is suggestive of the polyamorphic transition between native and denatured hydrated proteins, which can be interpreted as single-chain glass-forming polymers plasticized by water and cross-linked by hydrogen bonds. The onset of a sharp change in ddT( is the Debye-Waller factor and T is temperature) in proteins, which is controversially indentified with the glass transition in liquids, is shown to be general for glass formers and observable in computer simulations of strong and fragile ionic liquids, where it proves to be close to the experimental glass transition temperature. The latter may originate in strong anharmonicity in modes ("bosons"), which permits the system to access multiple minima of its configuration space. These modes, the Kauzmann temperature T(K), and the fragility of the liquid, may thus be connected.     

Ion penetration of the water-Oil interface

Ions typically pass with difficulty from water into organic phases because of water's superior solvation power. This inhibits such processes as ion transport in batteries or in lipid bilayers of cells. Ion penetration across such an interface was studied with unusual structural control. Hydronium ions were soft-landed at 1 electron volt on cold films of 3-methylpentane ("oil") on a metal substrate. The field produced by these ions drove them through the films when warmed. Coadsorption of water (0.14 to 35 bilayers) inhibited the ion penetration by creating a solvation energy trap. A Born solvation model successfully predicted the trapping energies (0 to 38 kilojoules per mole).     

Rutherford backscattering to study the near-surface region of volatile liquids and solids

Here we describe the use of Rutherford backscattering spectrometry (RBS) to measure quantitative in situ elemental profiles with high depth resolution, online and nondestructively, in volatile substances (liquid and frozen acids, ice). Samples for analysis are held in a chamber with controlled temperature and partial pressures designed to match conditions for aerosols in Earth's atmosphere. This technique is demonstrated in studies of water solubility in sulfuric acid, hydrochloric acid (HCl) on ice surfaces, the formation of a HCl-hexahydrate surface layer on evaporating HCl-doped ice, and the diffusion of water through this layer.     

Planet Within a Planet: Rotation of the Inner Core of Earth

The time dependence of the orientation of Earth's inner core relative to the mantle was determined using a recently discovered 10-degree tilt in the axis of symmetry of the inner core's seismic-velocity anisotropy. Two methods of analyzing travel-time variations for rays traversing the inner core, on the basis of 29 years of data from the International Seismological Centre (1964-1992), reveal that the inner core appears to rotate about 3 degrees per year faster than the mantle. An anomalous variation in inner-core orientation from 1969 to 1973 coincides in time with a sudden change ("jerk") in the geomagnetic field.     

Scheiner's Halo: Evidence for Ice Ic in the Atmosphere

Refraction of sunlight at the angle of minimum deviation between octahedral faces of crystals of ice Ic in the upper atmosphere could produce a halo around the sun or the moon at 27.46 degrees . Crystals of hexagonal ice having low-index faces cannot produce a halo of this radius. It is therefore suggested that Scheiner's halo, which has been reported at least four times since 1629 at 28 degrees from the sun, is due to ice Ic. If this is correct, it is apparently the first evidence that ice Ic occurs naturally and that liquid water can freeze to ice Ic.     

Microorganisms in the accreted ice of Lake Vostok, Antarctica

Analysis of a portion of Vostok ice core number 5G, which is thought to contain frozen water derived from Lake Vostok, Antarctica (a body of liquid water located beneath about 4 kilometers of glacial ice), revealed between 2 x 10(2) and 3 x 10(2) bacterial cells per milliliter and low concentrations of potential growth nutrients. Lipopolysaccharide (a Gram-negative bacterial cell biomarker) was also detected at concentrations consistent with the cell enumeration data, which suggests a predominance of Gram-negative bacteria. At least a portion of the microbial assemblage was viable, as determined by the respiration of carbon-14-labeled acetate and glucose substrates during incubations at 3 degrees C and 1 atmosphere. These accreted ice data suggest that Lake Vostok may contain viable microorganisms.     

A mid-brunhes climatic event: long-term changes in global atmosphere and ocean circulation

A long-term climatic change 4.0 x 10(5) to 3.0 x 10(5) years ago is recorded in deep-sea sediments of the Angola and Canary basins in the eastern Atlantic Ocean. In the Angola Basin (Southern Hemisphere) the climatic signal shows a transition to more humid ("interglacial") conditions in equatorial Africa, and in the Canary Basin (Northern Hemisphere) to more "glacial" oceanic conditions. This trend is confirmed by comparison with all well-documented marine and continental records from various latitudes available; in the Northern Hemisphere, in the Atlantic north of 20 degrees N, climate merged into more "glacial" conditions and in equatorial regions and in the Southern Hemisphere to more "interglacial" conditions. The data point to a more northern position of early Brunhes oceanic fronts and to an intensified atmosphere and ocean surface circulation in the Southern Hemisphere during that time, probably accompanied by a more zonal circulation in the Northern Hemisphere. The mid-Brunhes climatic change may have been forced by the orbital eccentricity cycle of 4.13 x 10(5) years.     

新复方中药制剂“沙大净”对鸡红细胞免疫功能的影响

为了解研究新复方中药制剂(“沙大净”口服液)对蛋鸡红细胞免疫功能的影响,试验选用35周龄的海兰白蛋鸡80只,随机分成4组,1%“沙大净”组、0.5%“沙大净”组、0.25%“沙大净”组和对照组,每组20只。结果表明:1%“沙大净”组、0.5%“沙大净”组的RBC-C3bRR、RFER都极显著(P<0.01)高于对照组,而RBC-ICR显著低于(P<0.05)对照组。因此,“沙大净”对鸡红细胞的免疫功能有较明显的促进作用。