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21.
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
22.
Schindler P Barreiro JT Monz T Nebendahl V Nigg D Chwalla M Hennrich M Blatt R 《Science (New York, N.Y.)》2011,332(6033):1059-1061
The computational potential of a quantum processor can only be unleashed if errors during a quantum computation can be controlled and corrected for. Quantum error correction works if imperfections of quantum gate operations and measurements are below a certain threshold and corrections can be applied repeatedly. We implement multiple quantum error correction cycles for phase-flip errors on qubits encoded with trapped ions. Errors are corrected by a quantum-feedback algorithm using high-fidelity gate operations and a reset technique for the auxiliary qubits. Up to three consecutive correction cycles are realized, and the behavior of the algorithm for different noise environments is analyzed. 相似文献
23.
Hafezparast M Klocke R Ruhrberg C Marquardt A Ahmad-Annuar A Bowen S Lalli G Witherden AS Hummerich H Nicholson S Morgan PJ Oozageer R Priestley JV Averill S King VR Ball S Peters J Toda T Yamamoto A Hiraoka Y Augustin M Korthaus D Wattler S Wabnitz P Dickneite C Lampel S Boehme F Peraus G Popp A Rudelius M Schlegel J Fuchs H Hrabe de Angelis M Schiavo G Shima DT Russ AP Stumm G Martin JE Fisher EM 《Science (New York, N.Y.)》2003,300(5620):808-812
Degenerative disorders of motor neurons include a range of progressive fatal diseases such as amyotrophic lateral sclerosis (ALS), spinal-bulbar muscular atrophy (SBMA), and spinal muscular atrophy (SMA). Although the causative genetic alterations are known for some cases, the molecular basis of many SMA and SBMA-like syndromes and most ALS cases is unknown. Here we show that missense point mutations in the cytoplasmic dynein heavy chain result in progressive motor neuron degeneration in heterozygous mice, and in homozygotes this is accompanied by the formation of Lewy-like inclusion bodies, thus resembling key features of human pathology. These mutations exclusively perturb neuron-specific functions of dynein. 相似文献
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Helmut Saucke Britta Schultz Rainer Wedemeyer Nadine Liebig Olaf Zimmermann Peter Katz 《Gesunde Pflanzen》2011,63(4):183-189
The cabbage whitefly,Aleyrodes proletella, has developed to a key pest in brassica vegetable crops throughout Germany. In a 3-year project we investigated a biotechnical approach employing netting (0.8?×?0.8 mm meshsize) in combination with the native parasitoidEncarsia tricolor in an inoculative-inundative approach in organic Brussels sprouts under field conditions. In small scale plot experiments continuous netting from transplanting in May till October alone reduced whitefly larval densities by 77 % at peak infestation in all years. Remaining whitefly infestation under net was associated with the necessity of temporary net removal for the purpose of mechanical weeding, which caused primary whitefly infestation. Release of mass rearedE. tricolour under net at the first signs of larval infestation significantly increasedA. proletella-parasitation and reduced infestation compared to netted controls without release. Furthermore, at highest dosage in 2009,E. tricolor had a significant enhancing effect on raw yield and the quality level of marketable yield. Additional on-farm experiments without netting in 2008 and 2009 confirmed the control potential ofE. tricolor. Although the most important project mile stones have been achieved, namely (a)E. tricolour-establishment under net and in the open field, (b) enhanced parasitation corresponding with pest density decline and (c) a positive impact on yield and quality parameters, further research will be necessary. The focus should be on the initial infestation period, optimizing the timing, frequency and required dosage. 相似文献
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Marion A. Sonnleitner Madeleine S. Günthardt-Goerg Inga K. Bucher-Wallin Werner Attinger Sybille Reis Rainer Schulin 《Water, air, and soil pollution》2001,126(3-4):271-290
Sixteen open-top chambers, each equipped with two non-weighablegravity-drained lysimeter compartments, were used to investigate the impacts of elevated atmospheric carbon dioxide (CO2) concentration and nitrogen (N) deposition on the water relations and growth of young model forest ecosystems on two different types of soils. The same vegetation of a mixed spruce and beech overstorey and various herbs in the understorey was planted in all treatments on both soils. The soils were repacked on top of a drainage layer. Four combinations of treatments were applied in four replicates each: ambient (370 cm3 m-3) CO2 + low (7 kg N ha-1 a-1) N deposition, ambient CO2 + high(70 kg N ha-1 a-1) N deposition, elevated (590 cm3 m-3) CO2 + low N deposition, and elevated CO2 + high N deposition. After canopy closure, treatment effects on evapotranspiration and growth during the third year of study were very different for the two soils.On the acidic sandy loam, elevated CO2 enhanced growth(leaf biomass +21%, roots +27%) at reduced evapotranspiration (–9%). High N deposition increased aboveground growth even more strongly (+50%), but also increased evapotranspiration (+16%). Together, elevated CO2 and high N had a more than additive fertilizer effect on growth, while their effects on evapotranspirationcompensated. On the calcareous loamy sand, elevated CO2not only tended to enhance growth (leaf biomass +17%, roots +20%), but also increased evapotranspiration (+5%).On this soil, aboveground growth was stimulated by N only incombination with elevated CO2, but less than on the acidic soil, while evapotranspiration (–6.5%) and root growth into the subsoil (–54%) were decreased by increased N deposition at both CO2 concentrations, in contrast to the N treatments on the acidic sandy loam. The influence of the soil on the observed ecosystem responses canbe interpreted in terms of the concept of optimal resource allocation. 相似文献
28.
Methods for evaluating human impact on soil microorganisms based on their activity,biomass, and diversity in agricultural soils 总被引:10,自引:0,他引:10
The present review is focused on microbiological methods used in agricultural soils accustomed to human disturbance. Recent developments in soil biology are analyzed with the aim of highlighting gaps in knowledge, unsolved research questions, and controversial results. Activity rates (basal respiration, N mineralization) and biomass are used as overall indices for assessing microbial functions in soil and can be supplemented by biomass ratios (C : N, C : P, and C : S) and eco‐physiological ratios (soil organic C : microbial‐biomass C, qCO2, qNmin). The community structure can be characterized by functional groups of the soil microbial biomass such as fungi and bacteria, Gram‐negative and Gram‐positive bacteria, or by biotic diversity. Methodological aspects of soil microbial indices are assessed, such as sampling, pretreatment of samples, and conversion factors of data into biomass values. Microbial‐biomass C (µg (g soil)–1) can be estimated by multiplying total PLFA (nmol (g soil)–1) by the FPLFA‐factor of 5.8 and DNA (µg (g soil)–1) by the FDNA‐factor of 6.0. In addition, the turnover of the soil microbial biomass is appreciated as a key process for maintaining nutrient cycles in soil. Examples are briefly presented that show the direction of human impact on soil microorganisms by the methods evaluated. These examples are taken from research on organic farming, reduced tillage, de‐intensification of land‐use management, degradation of peatland, slurry application, salinization, heavy‐metal contamination, lignite deposition, pesticide application, antibiotics, TNT, and genetically modified plants. 相似文献
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A new method for permanent registration of pH value in mineral soil input of an acid forest soil The organic top layers of acid forest soils in low mountain ranges of Germany which receive acid precipitation are of special ecological interest to the observation for their saisonal chemical behaviour. Root systems of young spruce forests tend to accumulate in these layers because of Al-toxicity in mineral soil. Conventional procedures for a weekly sampling of soil solution do not account for short term events. Thus, a measuring device for permanent pH-logging of soil solution in mineral soil input was developed. A microprocessor controls the vacuum in the ceramic cups containing pH-glass electrodes in order to maintain steady water flux into the cups. The accuracy of the measured pH was tested with a theoretical equilibrium modell concerning CO2-degassing and with a laboratory experiment. Below pH 4.7 no influence of CO2-losses on the pH inside the cups occurs. Permanent measurements in mineral soil of a spodosol in The Fichtelgebirge showed fluctuations of higher pH values immediately after precipitation and decreasing values later on. In late spring this behaviour is not yet pronounced. 相似文献