A High-Pressure Test of Birch's Law     

Campbell AJ  Heinz DL 《Science (New York, N.Y.)》1992,257(5066):66-68

The compressional wave velocities of polycrystalline NaCl and KCl have been measured to over 17 gigapascals, with the use of Brillouin scattering and the diamond anvil cell. This pressure corresponds to 40% compression for NaCl and 60% compression for KCl (including the volume change across the B1-B2 transition). The data obey Birch's Law, which predicts that the velocity of each material is linear with density, except across the B1-B2 phase transition in KCl. This deviation from Birch's Law can be rationalized in terms of an interatomic potential model wherein the vibrational frequencies of the nearest neighbor bonds decrease when going to the eight-coordinated B2 structure from the six-coordinated B1 structure.  相似文献   

Real-space observation of molecular motion induced by femtosecond laser pulses     

Bartels L  Wang F  Möller D  Knoesel E  Heinz TF 《Science (New York, N.Y.)》2004,305(5684):648-651

Femtosecond laser irradiation is used to excite adsorbed CO molecules on a Cu110 surface; the ensuing motion of individual molecules across the surface is characterized on a site-to-site basis by in situ scanning tunneling microscopy. Adsorbate motion both along and perpendicular to the rows of the Cu110 surface occurs readily, in marked contrast to the behavior seen for equilibrium diffusion processes. The experimental findings for the probability and direction of the molecular motion can be understood as a manifestation of strong coupling between the adsorbates' lateral degrees of freedom and the substrate electronic excitation produced by the femtosecond laser radiation.  相似文献   

Control of crystal size and lattice formation by starmaker in otolith biomineralization     

Söllner C  Burghammer M  Busch-Nentwich E  Berger J  Schwarz H  Riekel C  Nicolson T 《Science (New York, N.Y.)》2003,302(5643):282-286

The stone-like otoliths from the ears of teleost fishes are involved in balance and hearing and consist of calcium carbonate crystallites embedded in a protein framework. We report that a previously unknown gene, starmaker, is required in zebrafish for otolith morphogenesis. Reduction of starmaker activity by injection of modified antisense oligonucleotides causes a change in the crystal lattice structure and thus a change in otolith morphology. The expression pattern of starmaker, along with the presence of the protein on the growing otolith, suggest that the expression levels of starmaker control the shape of the otoliths.  相似文献   

Probing high-barrier pathways of surface reactions by scanning tunneling microscopy     

Dürr M  Biedermann A  Hu Z  Höfer U  Heinz TF 《Science (New York, N.Y.)》2002,296(5574):1838-1841

The ability of scanning tunneling microscopy to probe the pathways of thermally activated high-barrier surface processes is frequently limited by competing low-barrier processes that can confuse measurement of the true initial and final configuration. We introduce an approach to circumvent this difficulty by driving the surface process with nanosecond laser heating. The method is applied to determine the pathway of recombinative desorption in the H/Si(001) system. The observed configuration of dangling bonds after laser heating reveals that the desorbed hydrogen molecules are not formed on single dimers, but rather from neighboring silicon dimers via an interdimer reaction pathway.  相似文献   

Validation of ELISA for the detection of potato virus antigen in sap of potato plant leaves     

Volker Zahn  Jörg Dahle  Karl‐Heinz Pastrik 《EPPO Bulletin》2011,41(1):30-38

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SOM fractionation methods: Relevance to functional pools and to stabilization mechanisms   总被引：2，自引：0，他引：2  

Margit von Lützow  Ingrid Kögel-Knabner  Heinz Flessa  Egbert Matzner 《Soil biology & biochemistry》2007,39(9):2183-2207

Soil organic matter (SOM) consists of various functional pools that are stabilized by specific mechanisms and have certain turnover rates. For the development of mechanistic models that predict changes in SOM storage, these pools have to be quantified and characterized. In the past, numerous fractionation schemes have been developed to separate and analyse such SOM fractions. In this review, the SOM fractions obtained with such operational fractionation procedures are described in terms of their pool sizes, chemical properties, and turnover rates. The main objective of this review is to evaluate these operationally defined fractions with respect to their suitability to describe functional SOM pools that could be used to parameterize SOM turnover models. Fractionation procedures include (1) physical separation of SOM into aggregate, particle size, and density fractions and fractions according to their magnetic susceptibility, and (2) various wet chemical procedures that fractionate SOM according to solubility, hydrolysability, and resistance to oxidation or by destruction of the mineral phase. Furthermore, combinations of fractionation methods are evaluated.The active SOM pool with turnover rates <10 years may best be represented by the soil microbial biomass and the light fraction (<1.6-2 g cm⁻³) obtained by density fractionation (if black carbon contents are considered). Most chemical and physical fractionations as well as combinations of methods yield SOM fractions that are not homogeneous in terms of turnover rates. It has proven to be particularly difficult to isolate functional fractions that represent the passive model pools in which the majority of soil SOM is stabilized. The available fractionation methods do not correspond to specific stabilization mechanisms and hence do not describe functional SOM pools. Another problem is that comprehensive data for turnover rates and data for whole soil profiles are only now becoming available, especially for new fractionation methods. Such information as well as the use of specific markers and compound-specific isotope analysis may be important for future differentiation and evaluation of functional SOM fractions.  相似文献   

Editorial: J. Plant Nutr. Soil Sci. 3/2006     

Karl‐Heinz Feger  Franz Wiesler  Franz Makeschin 《植物养料与土壤学杂志》2006,169(3):293-293

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Genetische Variabilität     

Joachim Dehne  Kurt Skiebe  Martin Stein  Hagen Herdam  Rolf Franke  Heinz Leike 《Genetic Resources and Crop Evolution》1988,36(1):247-274

Zusammenfassung Für die Pflanzenzüchtung ist die genetische Variabilität eine entscheidende Voraussetzung. Sie basiert auf Genmutationen, Chromosomenmutationen, Introgressionen, Autopolyploidie, Alloplasmie, transponiblen DNA-Elementen und der Kombination. Diese Variabilitätskomponenten werden charakterisiert. Außerdem wird anhand von Beispielen ihr Einfluß auf die Entwicklung der Kulturpflanzen demonstriert.Um effektiv in der Pflanzenzüchtung arbeiten zu können, bedarf es der Analyse von genetischer Variabilität. Dies geschieht mit Hilfe von Kreuzungsexperimenten und Parameterschätzungen. In zunehmendem Maße werden auch Marker bei der Analyse eingesetzt.Einen wichtigen Faktor zur zielgerichteten Beeinflussung der genetischen Variabilität stellt die Selektion dar. Sie führt zur Einschränkung der Kombination. Die Selektion ist für die Entwicklung von Sorten notwendig. Sie hat aber auch eine Verarmung an genetischer Information zur Folge.Für den weiteren Fortschritt in der Pflanzenzüchtung gilt es, eine genügende genetische Variabilität zu gewährleisten. Dazu bedarf es auch Maßnahmen zu ihrer Erhaltung. Genetische Variabilität muß außerdem verstärkt charakterisiert und analysiert werden.

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Genetic variability

Summary Genetic variability is a decisive prerequisite to plant breeding. It is based on gene mutations, chromosome mutations, introgressions, autopolyploidy, alloplasmy, transposible DNA elements and recombinations. These components of the genetic variability are illustrated and examples are given to demonstrate their contributions to the evolution of crop plants.Effective plant breeding requires the analysis of the genetic variation. It is analysed by hereditary studies and parameter estimations. The utilization of markers is continuously increasing in studies of the genetic variation.Selection is an important factor to a purposive influence on the genetic variability and leads to a restriction of the recombinations. Selection is necessary for the development of varieties but results also in an impoverishment of genetic information.For the continuous progress in plant breeding an adequate genetic variability is to secure. That includes also activities to its conservation. Furthermore the characterization and analysis of the genetic variability has to be intensified.

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Experimental liming of watersheds: an international cooperative effort between the United States and West Germany     

Robert W. Brocksen  Heinz W. Zoettl  Donald B. Porcella  Reinhard F. Huettl  Karl-Heinz Feger  Joe Wisniewski 《Water, air, and soil pollution》1988,41(1-4):455-471

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Einfluß der Fließstreckenlänge auf die Bodenumlagerung innerhalb einer erosionsgeschützten Kleinparzelle     

Heinz Peter Schrey 《植物养料与土壤学杂志》1987,150(4):235-240

Dependence of erosion from flow length within an erosion-protected plot On an Udalf derived from loess different micro-reliefs were formed to reduce erosion. Their effects on the spatial distribution of sand contents on bare soil after one vegetation period are described. At first erosion caused residuals of sand on unflooded areas and corresponding accumulation of finest material on flooded ones. Beds without flow barriers showed reduced clay and silt contents in the upper layer of about 2 mm. On beds with small dams there were no soil losses from the catchment areas between these flow barriers visible. Secondly the enriched sand was moved, too. This occured widely on flat beds. Within catchment areas there were only very small deposits of removed sand in front of the dams. In conclusion: Within the limits of a chosen risk, artificial microreliefs reduce completely erosion damages.  相似文献