Räumliche Spannungsmessungen mit dem Stress State Transducer (SST) in ungesättigten aggregierten Böden - theoretische Betrachtungen und erste Ergebnisse     

Rainer Horn  Clarence  Johnson  Harald Semmel  Robert Schafer  Matthias Lebert 《植物养料与土壤学杂志》1992,155(4):269-274

Stress measurements in undisturbed unsaturated soils with a Stress State Transducer (SST) - theory and first results A method to quantify the spatial stress distribution will be introduced and first results will be discussed. This method allows the detailed analysis of principal and shear stresses as well as the determination of the direction angle of principal stresses and the octahedral shear stress angle. The described Stress State Transducer (SST) is composed of six single strain gage sensors that enable the accurate and reproducable recording of stresses in six directions in a wide load range. Their data form the base for calculation of spatial stress distribution. Some first results show that in a luvisol derived from loess wheeling at a wheel load of 4.0 Mg induces high shear stresses in a depth of 30 cm. This probably causes plastic soil deformation.  相似文献   

Primer-directed enzymatic amplification of DNA with a thermostable DNA polymerase   总被引：2172，自引：0，他引：2172  

R K Saiki  D H Gelfand  S Stoffel  S J Scharf  R Higuchi  G T Horn  K B Mullis  H A Erlich 《Science (New York, N.Y.)》1988,239(4839):487-491

A thermostable DNA polymerase was used in an in vitro DNA amplification procedure, the polymerase chain reaction. The enzyme, isolated from Thermus aquaticus, greatly simplifies the procedure and, by enabling the amplification reaction to be performed at higher temperatures, significantly improves the specificity, yield, sensitivity, and length of products that can be amplified. Single-copy genomic sequences were amplified by a factor of more than 10 million with very high specificity, and DNA segments up to 2000 base pairs were readily amplified. In addition, the method was used to amplify and detect a target DNA molecule present only once in a sample of 10(5) cells.  相似文献   

Imprinting: lasting effects on uracil incorporation into chick brain   总被引：4，自引：0，他引：4  

P P Bateson  S P Rose  G Horn 《Science (New York, N.Y.)》1973,181(99):576-578

On the first day after hatching, domestic chicks were trained for 20, 60, 120, or 240 minutes with an imprinting stimulus. On the second day, they were all retrained for 60 minutes. The greater the chicks' experience on the first day, the lower the rate of incorporation of tritiated uracil into macromolecules in the anterior part of the forebrain roof on the second day. Such effects were not found in other brain regions, nor in any brain region of chicks that received similar treatment on the first day but were not retrained on the second.  相似文献   

Imaging of intermittency in ripple-wave turbulence     

WB Wright  R Budakian  DJ Pine  SJ Putterman 《Science (New York, N.Y.)》1997,278(5343):1609-1612

The dynamics of a fluid surface filled with high-amplitude ripples were studied with a technique (diffusing light photography) that resolves the height at all locations instantaneously. Even when nonlinearities are strong enough to generate a (Kolmogorov) cascade from long wavelength (where energy is input) to shorter wavelength, the resulting turbulent state contains large coherent spatial structures. The appearance of these structures in a thermal equilibrium state (with the same average energy) would be highly improbable.  相似文献   

Rutile-bearing refractory eclogites: missing link between continents and depleted mantle   总被引：9，自引：0，他引：9  

Rudnick RL  Barth M  Horn I  McDonough WF 《Science (New York, N.Y.)》2000,287(5451):278-281

A mass imbalance exists in Earth for Nb, Ta, and possibly Ti: continental crust and depleted mantle both have subchondritic Nb/Ta, Nb/La, and Ti/Zr, which requires the existence of an additional reservoir with superchondritic ratios, such as refractory eclogite produced by slab melting. Trace element compositions of minerals in xenolithic eclogites derived from cratonic lithospheric mantle show that rutile dominates the budget of Nb and Ta in the eclogites and imparts a superchondritic Nb/Ta, Nb/La, and Ti/Zr to the whole rocks. About 1 to 6 percent by weight of eclogite is required to solve the mass imbalance in the silicate Earth, and this reservoir must have an Nb concentration >/= 2 parts per million, Nb/La >/= 1.2, and Nb/Ta between 19 and 37-values that overlap those of the xenolithic eclogites. As the mass of eclogite in the continental lithosphere is significantly lower than this, much of this material may reside in the lower mantle, perhaps as deep as the core-mantle boundary.  相似文献   

Binary Pulsar PSR 1913 + 16: Model for Its Origin     

Van Horn HM  Sofia S  Savedoff MP  Duthie JG  Berg RA 《Science (New York, N.Y.)》1975,188(4191):930-933

The existing observational data for the binary pulsar PSR 1913 + 16 are sufficient to give a rather well-defined model for the system. On the basis of evolutionary considerations, the pulsar must be a neutron star near the upper mass limit of 1.2 solar masses (M.). The orbital inclination is probably high, i>/= 700, and the mass of the unseen companion probably lies close to the upper limit of the range 0.25 M. to 1.0 M.. The secondary cannot be a main sequence star and is probably a degenerate helium dwarf. At the 5.6-kiloparsec distance indicated by the dispersion measure, the magnetic dipole model gives an age of approximately 4 x 104 years, a rate of change of the pulsar period of P approximately 2 nanoseconds per day, and a surface magnetic field strength approximately (1/3) that of the Crab pulsar. The pulsar is fainter than an apparent magnitude V approximately + 26.5 and is at least approximately 80 times fainter than the Crab pulsar in the x-ray band. The companion star should be fainter than V approximately + 30, and a radio supernova remnant may be detectable near the position of the pulsar at a flux level of 相似文献   

Response     

Morris CE  Horn R 《Science (New York, N.Y.)》1991,253(5021):801

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Dense astrophysical plasmas     

VAN Horn HM 《Science (New York, N.Y.)》1991,252(5004):384-389

Degenerate bodies composed primarily of dense hydrogen and helium plasmas range from giant planets to the so far hypothetical brown dwarfs. More massive objects begin their lives as nondegenerate stars and may end as white dwarfs, composed primarily of carbon and oxygen, or as neutron stars, with solid crusts of iron or heavier elements and cores of neutron matter. The physical properties of dense plasmas that are necessary to construct theoretical models of such degenerate stars include the equation of state, transport properties, and nuclear reaction rates.  相似文献   

Auswirkung unterschiedlicher Bodenbearbeitung auf die mechanische Belastbarkeit von Ackerböden     

R. Horn 《植物养料与土壤学杂志》1986,149(1):9-18

Effect of different tillage systems on the mechanical compressibility of arable soils The influence of different tillage systems (Zero-tillage, minimum tillage with rotary tiller and conventional tillage with moldboard plow) on the mechanical compressibility of two soils, a Regosol from loess-colluvium, and a Vertisol from mesocoic clay has been investigated as well as the causes and consequences for penetration resistance and air permeability. In addition the bulk density and the pore size distribution of aggregates have been investigated with regard to a possible explanation for the often described difference in stability in untilled or minimum tilled soils when compared to tilled ones. The results clearly demonstrate the higher mechanical stability of the untilled or minimum tilled soils as compared to tilled soils, which may result in better growing condition for plants. The higher stability is the result of a more vertical oriented pore geometry and stress distribution and can be explained by measured differences in the bulk density and pore size distribution within the aggregates too.  相似文献   

Fiedler,H.J.: Bodennutzung und Bodenschutz. VEB Gustav Fischer Verlag,Jena, 1990; 268 S., 34 Abb., 48 Tab., 10 Übersichten,DM 70,-. ISBN 3-334-00302-7.     

R. Horn 《植物养料与土壤学杂志》1991,154(3):237-237

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