Modified spinel, Beta-manganous orthogermanate: stability and crystal structure

A new high-pressure polymorph with a modified spinel structure, beta-Mn(2)GeO(4), is stable in a pressure range intermediate between the field of the polymorph with the olivine structure and that of another high-pressure polymorph. Oxygen atoms are located approximately in cubic close packing with manganese and germanium atoms in octahedral and tetrahedral interstices, respectively, as in the spinel structure; however, germanium atoms form Ge(2)O(7) groups instead of isolated GeO(4) groups.     

Quenchable high-pressure polymorph of zinc selenate

A new quenchable high-pressure form of zinc selenate (ZnSeO(4)) was produced by subjecting the low-pressure modification to 40 kilobars at 400 degrees C for 30 minutes. The new form is orthorhombic, space group D(2h),(17)-Cmcm. The cell constants at 29 degrees C are: a, 5.511 angstroms; b, 8.110 angstroms; and c, 6.585 angstroms. The calculated density is 4.70 grams per cubic centimeter in comparison with 4.61 grams per cubic centimeter for the low-pressure modification. This implies a volume change of 2 percent at the transition.     

Lunar surface material: spacecraft measurements of density and strength

The relation of the density of the lunar surface layer to depth is probably best determined from spacecraft measurements of the bearing capacity as a function of depth. A comparison of these values with laboratory measurements of the bearing capacity of low-cohesion particulate materials as a function of the percentage of solid indicates that the bulk density at the lunar surface is about 1.1 grams per cubic centimeter and that it increases nearly linearly to about 1.6 grams per cubic centimeter at a depth of 5 centimeters.     

Superdense water ice

A new allotropic form of water ice with a density of 2.32 +/- 0.15 grams per cubic centimeter has been observed at very low pressures and for temperatures lower than 100 degrees K. It is most likely amorphous.     

Density of the Lunar Atmosphere

The minimum possible density of the lunar atmosphere at the surface is shown to be essentially the value for the interplanetary medium. This value, when combined with the observed maximum, places the particle density between 10(3) and 10(6) per cubic centimeter, while the electron density must be about 10(3) to 10(4) per cubic centimeter. These results are markedly different from those recently obtained by Firsoff.     

Ultragiant urban aerosol particles

Measurements taken 300 meters above ground level show surprisingly high concentrations of ultragiant aerosol particles both upwind and downwind of the St. Louis, Missouri, urban area. Assuming an average particle density of 2.0 grams per cubic centimeter, concentrations of particles with diameters between 5 and 55 micrometers sampled on 11 different days averaged 31 micrograms per cubic meter upwind and 55 micrograms per cubic meter downwind of the city.     

Thermal conductivity of monolithic organic aerogels

The total thermal conductivity lambda of resorcinol-formaldehyde aerogel monoliths has been measured as a function of density rho in the range from rho = 80 to 300 kilograms per cubic meter. A record-low conductivity value in air at 300 K of lambda approximately 0.012 watt per meter per kelvin was found for rho approximately 157 kilograms per cubic meter. Caloric measurements under variation of gas pressure as well as spectral infrared transmission measurements allowed the determination of solid conductivity, gaseous conductivity, and radiative conductivity as a function of density. The development of such low conductivity materials is of great interest with respect to the substitution of environmentally harmful insulating foams made from chlorofluorocarbons.     

Venus: density of upper atmosphere from measurements of drag on pioneer orbiter

Measurements of the changes in orbital period of the Pioneer Venus orbiter have yielded estimates of the density of the upper atmosphere of Venus at altitudes in the range from 150 to 200 kilometers. At the lower limit of this range, the density on the dayside of the terminator exhibits a temporal variation of amplitude near 4 x 10(-14) gram per cubic centimeter aboult a mean of approximately 1.4 x 10(-13) gram per cubic centimeter. The variation appears oscillatory, with a 4- to 5-day period, but barely one cycle was observed. The density on the nightside of the terminator, sampled inthe same 150-kilometer altitude range, fluctuates about a smaller mean of approximately 4 x 10(-14) gram per cubic centimeter. The density between the altitudes of 150 and 200 kilometers, sampled only on the dayside of the terminator, imply a scale height of between 15 and 20 kilometers. The interpretation of this estimate is uncertain, however, in view of the measurements at the different altitudes having been made at different times and, hence, at different values of solar phase.     

Herpesvirus antigens on cell membranes detected by centrifugation of membrane-antibody complexes

Herpesviruses specify new glycoproteins that bind to cell membranes and also appear in the envelope of the virion. Incubation of purified smooth membranes from infected cells with antiviral antibody results in an increase in the density of the membranes as determined by flotation in sucrose density gradients. The magnitude of this increase depends on the amount of antibody used; densities as high as 1.16 grams per cubic centimeter have been obtained (the density of the untreated membranes is 1.08 grams per cubic centimeter). Antiviral antibody does not increase the density of uninfected cell membranes nor do saline or normal rabbit serum change the densities of infected or uninfected cell mnembranes. Viral antigens-presumably the glycoproteins specified by the virus-are probably on the surface of the infected cell membranes and bind to them strongly enough to withstand the hydrodynamic forces applied to them in the sucrose gradient.     

Preparation of high-crystallinity polyethylene at low pressures

The preparation of highly crystalline polyethylene at low pressures is reported. With careful control of the substrate, the melting and crystallization schedule, and the physical state of the specimen (film thickness), it is possible to prepare polyethylene having a density in excess of 0.999 gram per cubic centimeter, a melting temperature of approximately 140 degrees C, and a heat of fusion in excess of 70 calories per gram. The approach appears to be general and should be applicable to a wide variety of polymers.     

Gallium, germanium, indium, and iridium in lunar samples

Neutron activation analyses of gallium, germanium, indium, and iridium in eight lunar samples and in meteorites and rocks (including four calciulnrich achondrites and five terrestrial basalts) with similar bulk compositions are reported. Lunar gallium concentrations are remarkably constant at about 5 parts per million, three times higher and four times lower than those in eucritic (calcium-rich) achondrites and terrestrial basalts, respectively. Lunar germanium concentrations range from 相似文献   

The Inner Core Translational Triplet and the Density Near Earth's Center

Four long records from superconducting gravimeters yield evidence of the triplet of translational oscillations of the solid inner core about its central position. Calculations of core oscillation modes allow identification of the three translational resonances at periods of 3.5820 +/- 0.0008, 3.7677 +/- 0.0006, and 4.015 +/- 0.001 hours by their rotational splitting. Each resonance is defined by approximately 20 successive spectral estimates. A new Earth model brings the computed periods into agreement with observation. It has a central density of 12.960 grams per cubic centimeter, inner core radius of 1221.1 kilometers, and a density jump at the inner core boundary of 0.407 grams per cubic centimeter.     

The Density of Hydrous Magmatic Liquids

Density measurements on several hydrous (相似文献   

Vertical structure of the ionosphere and upper neutral atmosphere of saturn from the pioneer radio occultation

Radio occultation measurements at S band (2.293 gigahertz) of the ionosphere and upper neutral atmosphere of Saturn were obtained during the flyby of the Pioneer 11 Saturn spacecraft on 5 September 1979. Preliminary analysis of the occultation exit data taken at a latitude of 9.5 degrees S and a solar zenith angle of 90.6 degrees revealed the presence of a rather thin ionosphere, having a main peak electron density of about 9.4 x 10/(3) per cubic centimeter at an altitude of about 2800 above the level of a neutral number density of 10(19) per cubic centimeter and a lower peak of about 7 x 10(3) per cubic centimeter at 2200 kilometers. Data in the neutral atmosphere were obtained to a pressure level of about 120 millibars. The temperature structure derived from these data is consistent with the results of the Pioneer 11 Saturn infrared radiometer experiment (for a helium fraction of 15 percent) and with models derived from Earth-based observations for a helium fraction by number of about 4 to 10 percent. The helium fraction will be further defined by mutual iteration with the infrared radiometer team.     

Long-range atmospheric transport of soil dust from Asia to the tropical north pacific: temporal variability

The concentration of airborne soil dust at Enewetak Atoll(11 degrees N, 162 degrees E) in April 1979 was 2.3 micrograms per cubic meter but decreased steadily to 0.02 microgram per cubic meter over the next 5 months. The spring dust is probably derived from China; its deposition rate ( approximately 0.3 millimeter per 1000 years) suggests that it may be a significant contributor to the deep-sea sediments of the North Pacific.     

Density-modulus relationship in graphite fibers made from acrylic yarns

Three types of polyacrylonitrile yarn were converted to graphite fibers. There was a linear relation between density and Young's modulus of the graphite fibers, the ranges observed being 1.58 to 2.18 grams per cubic centimeter and 25 to 112 x 10(6) pounds per square inch.     

A budget for continental growth and denudation

Oceanic crustal material on a global scale is re-created every 110 million years. From the data presented it is inferred that potential sialic material is formed at a rate of about 1.35 cubic kilometers per year, including hemipelagic volcanic sediments that accumulate at a rate of about 0.05 cubic kilometer per year. It is estimated that the influx of 1.65 cubic kilometers per year of terrigenous and biogenic sediment is deposited on the deep ocean, and this represents continental denudation. Because all this material is brought into a subduction zone, continental accretion rates, which could include all this material, may be as high as 3.0 cubic kilometers per year with a potential net growth for continents of 1.35 cubic kilometers per year.     

Plasma diagnosis from thermal noise and limits on dust flux or mass in comet giacobini-zinner

Thermal noise spectroscopy was used to measure the density and temperature of the main (cold) electron plasma population during 2 hours (1.5x10(5) kilometers perpendicular to the tail axis) around the point of closest approach of the International Cometary Explorer (ICE) to Comet Giacobini-Zinner. The time resolution was 18 seconds (370 kilometers) in the plasma tail and 54 seconds (1100 kilometers) elsewhere. Near the tail axis, the maximum plasma density was 670 per cubic centimeter and the temperature slightly above 1 electron volt. Away from the axis, the plasma density dropped to 100 per cubic centimeter (temperature, 2x 10(4) K) over 2000 kilometers, then decreased to 10 (1.5x 10(5)K) over 15,000 kilometers; outside that region (plasma tail), the density fluctuated between 10 and 30 per cubic centimeter and the temperature between 1x 10(5) and 4 x10(5) K. The relative density of the hot population rarely exceeded a few percent. The tail was highly asymmetrical and showed much structure. On the other antenna, shot noise was recorded from the plasma particle impacts on the spacecraft body. No evidence was found of grain impacts on the antennas or spacecraft in the plasma tail. This yields an upper limit for the dust flux or particle mass, indicating either fluxes or masses in the tail smaller than implied by the models or an anomalous grain structure. This seems to support earlier suggestions that these grains are featherlike. Outside the tail, and particularly near 10(5) kilometers from its axis, impulsive noises indicating plasma turbulence were observed.     

Discovery of sodium in the atmosphere of mercury

The spectrum of Mercury at the Fraunhofer sodium D lines shows strong emission features that are attributed to resonant scattering of sunlight from sodium vapor in the atmosphere of the planet. The total column abundance of sodium was estimated to be 8.1 x 10(11) atoms per square centimeter, which corresponds to a surface density at the subsolar point of about 1.5 x 10(5) atoms per cubic centimeter. The most abundant atmospheric species found by the Mariner 10 mission to Mercury was helium, with a surface density of 4.5 x 10(3) atoms per cubic centimeter. It now appears that sodium vapor is a major constituent of Mercury's atmosphere.     

金属锗在水稻体内的植物化研究

[目的]为重金属的植物化研究提供一定的基础。[方法]以3个水稻品种的幼苗为载体,研究金属锗在水稻体内的植物化过程。[结果]各个品种的水稻幼苗对锗毒性的抵抗能力存在差异。以拌土或浇灌的形式添加锗,0.060μg/ml的锗对吉丰3号、吉丰10号幼苗的农艺性状没有影响,但对吉丰47号幼苗的生长发育具有促进作用;1.00μg/ml的锗则对水稻幼苗的生长发育具有毒害作用。锗进入土壤后,能够迅速且大量地被水稻吸收并运往地上部分,其在水稻体内的积累规律为茎叶>根>糙米,并且茎叶中锗的含量远高于根和糙米中的锗含量。锗在水稻体内的最高允许浓度为0.060μg/ml。[结论]锗在水稻体内的植物化过程因水稻品种的不同而不同,0.060μg/ml锗的植物化效果最好。