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Particle flux determined from traps in the Canary Island region 全文
1997
Neuer, Susanne | Ratmeyer, Volker | Davenport, Robert | Fischer, Gerhard | Wefer, Gerold
We present a 3 year record of deep water particle flux at the recently initiated ESTOC (European Station for Time-series in the Ocean, Canary Islands) located in the eastern subtropical North Atlantic gyre. Particle flux was highly seasonal, with flux maxima occurring in late winter-early spring. A comparison with historic CZCS (Coastal Zone Colour Scanner) data shows that these flux maxima occurred about 1 month after maximum chlorophyll was observed in surface waters in a presumed primary source region 100 km * 100 km northeast of the trap location. The main components of the particles collected with the traps were mineral particles and carbonate, both correlating strongly with organic matter sedimentation. Mineral particles in the sinking matter are indicative of the high aeolian input from the African desert regions. Comparing particle fluxes at 1 km and 3 km depth, we find that particle sedimentation increased substantially with depth. Yearly organic carbon sedimentation was 0.6 g m**-2 at 1 km depth compared with 0.8 g m**-2 at 3 km. We hypothesize that higher phytoplankton biomass observed further north could be a source of laterally advecting particles that interact with fast sinking particles originating from the primary source region. This hypothesis is also supported by the differences in size distribution of lithogenic matter found at the two trap depths.
显示更多 [+] 显示较少 [-]Eficiencia de uso de nitrogeno en el cultivo de maiz bajo distintos metodos de aplicacion.
1997
Larios L. | Gordon R. | Obando R. | Osorio M. | Lopez G. | Bolanos J.A.
Diversos estudios han mostrado que la eficiencia de absorcion de los fertilizantes es baja en los sistemas de produccion de maiz de la region. Una mejoria en la eficiencia de absorcion significaria un impacto significativo en la rentabilidad de los sistemas de produccion de maiz. Este trabajo reporta los resultados de 19 ensayos durante 1993-94 a traves de la region de Centro America y el Caribe, para evaluar la eficiencia de absorcion de urea-N en maiz bajo diversas practicas de aplicacion (voleo vs chuzeado) y fraccionamiento (2 vs 3 aplicaciones), un testigo absoluto sin aplicacion de N y el testigo del agricultor. Todos los ensayos recibieron 100 kg de N y dosis de 20 kg P/ha y se uso la mejor variedad de maiz recomendada para cada zona. Los datos muestran una eficiencia de absorcion cercana al 30 porciento para todos los tratamientos de aplicacion de N. Comparaciones entre aplicaciones al voleo vs chuzeado mostraron una respuesta significante en rendimiento de grano al chuzeado (de 0.39 t/ha P<0.001), sin detectarse una mejoria por el fraccionamiento de 2 a 3 aplicaciones. Se detecto una relacion fuerte y significativa entre el rendimiento final y el contenido de N en la hoja de la mazorca a la floracion, estimada con clorofil6metros. Se esperaba que enterrar la urea (chuzeado) incrementaria la eficiencia de uso de N mas que la mejoria detectada.
显示更多 [+] 显示较少 [-][Question about the correct calculation of sugar determined losses in exhausted cossettes]
1997
Walerianczyk, E. | Zero, M. (Instytut Przemyslu Cukrowniczego, Warszawa (Poland))
[Nitrogen use efficiency in maize as determined by the method of application]
1997
Larios, L. | Gordon, R. | Obando, R. | Osorio, M. | Lopez, G. | Bolanos, J.A.
Diversos estudios han mostrado que la eficiencia de absorcion de los fertilizantes es baja en los sistemas de produccion de maiz de la region. Una mejoria en la eficiencia de absorcion significaria un impacto significativo en la rentabilidad de los sistemas de produccion de maiz. Este trabajo reporta los resultados de 19 ensayos durante 1993-94 a traves de la region de Centro America y el Caribe, para evaluar la eficiencia de absorcion de urea-N en maiz bajo diversas practicas de aplicacion (voleo vs chuzeado) y fraccionamiento (2 vs 3 aplicaciones), un testigo absoluto sin aplicacion de N y el testigo del agricultor. Todos los ensayos recibieron 100 kg de N y dosis de 20 kg P/ha y se uso la mejor variedad de maiz recomendada para cada zona. Los datos muestran una eficiencia de absorcion cercana al 30 porciento para todos los tratamientos de aplicacion de N. Comparaciones entre aplicaciones al voleo vs chuzeado mostraron una respuesta significante en rendimiento de grano al chuzeado (de 0.39 t/ha P0.001), sin detectarse una mejoria por el fraccionamiento de 2 a 3 aplicaciones. Se detecto una relacion fuerte y significativa entre el rendimiento final y el contenido de N en la hoja de la mazorca a la floracion, estimada con clorofil6metros. Se esperaba que enterrar la urea (chuzeado) incrementaria la eficiencia de uso de N mas que la mejoria detectada.
显示更多 [+] 显示较少 [-]Separation power of the 95 substrates of the BIOLOG system determined in various soils
1997
Hitzl, W. | Rangger, A. | Sharma, S. | Insam, H.
The separation power of the 95 substrates of the BIOLOG GN plates was tested using soil from Denmark, Germany and Italy. The data set comprised 420 BIOLOG plates, 195 of them incubated at 14 degrees C and 225 incubated at 30 degrees C. We calculated the ratio of the between soil variation to the within soil variation of each substrate to obtain two lists of carbon sources ranked according to their separation power. These results suggest that the use of a reduced set of discriminating carbon sources, with a higher number of replicates on each plate, would be a better approach because statistical tests like MANOVA and related techniques can be applied.
显示更多 [+] 显示较少 [-]Distribution of Xylella fastidiosa in southern Ontario as determined by the polymerase chain reaction 全文
1997
Goodwin, P.H. | Zhang, S.
Trees were surveyed in 1994 and 1995 in southern Ontario for symptoms of leaf scorching and infection by Xylella fastidiosa. Samples were collected from 114 trees in 48 locations, and DNA was extracted from leaf veins and petioles of affected leaves. The DNA was used in the polymerase chain reaction (PCR) with primers that amplify a 733 base-pair fragment from isolates of X. fastidiosa. Several samples yielded PCR products of varying sizes, but only three samples from American elm (Ulmus americana) yielded the 733 base pair fragment characteristic of X. fastidiosa that also hybridized with the PCR product of a strain isolated from a tree infected with the bacterium. These trees were all located within the Niagara Peninsula. This is the first report of X. fastidiosa in Ontario and represents the most northerly distribution of X. fastidiosa-infected trees in eastern North America.
显示更多 [+] 显示较少 [-]The prevalance of Fasciola hepatica in its snail intermediate host determined by DNA probe assay
1997
Kaplan, R.M. | Dame, J.B. | Reddy, G.R. | Courtney, C.H.
Accurate snail intermediate host infection prevalence data have the potential to be extremely useful in determining seasonal transmission dynamics of Fasciola hepatica. Because the microscopic techniques currently used lack the sensitivity and specificity necessary to obtain meaningful infection prevalence data, we developed a highly accurate and efficient DNA probe assay. The assay has a sensitivity of 100%, a specificity of > 99%, easily detects a single miracidia and does not cross-hybridize with DNA of Fascioloides magna, Paramphistomum liorchis or Heterobilharzia americana, trematodes that share the same intermediate host and enzootic range as Fasciola hepatica. Using this assay, we determined the prevalence of F. hepatica in its snail intermediate host, Fossaria cubensis, during the second year of a 2-year study on the epizootiology of Fasciola hepatica in Florida. The overall infection prevalence of snails assayed in this study (n = 5246) was 1.5% and ranged from 0.1% to 3.1% for individual cattle ranches. Additionally, infection prevalence differed significantly for successive size groupings of snails, varying from 0% for 1-mm snails to 18.5% for 9- and 10-mm snails. The accuracy and efficiency of the DNA probe assay reported here for determining snail infection prevalence offers an inexpensive alternative to tracer animal studies for determining the epizootiology of F. hepatica.
显示更多 [+] 显示较少 [-]Kinetics of the oxygen evolution step in plants determined from flash-induced chlorophyll a fluorescence
1997
Shinkarev, V.P. (Illinois Univ., Urbana, IL (USA). Dept. of Plant Biology) | Xu, C. | Govindjee | Wraight, C.A.
Seasonal changes in copepod production between the Sanriku and Boso, Japan determined using the Ikeda-Motoda method
1997
Okumura, Y. (National Research Inst. of Fisheries Science, Yokohama (Japan)) | Shimoda, T. | Sasaki, K.
The fibrillar orientation in the S2-layer of wood fibres as determined by X-ray diffraction analysis
1997
Sahlberg, U. | Salmen, L. | Oscarsson, A.
It is the fibrillar orientation in the S2-layer which to a great extent determines the mechanical properties of the wood fibre, with regard both to strength and stiffness and to swelling properties. Measurements of the average fibril angle of fibres are not however easy and the results differ between the methods used. In order to evaluate in more detail how the fibril angle varies in spruce wood, an X-ray method based on diffraction from the 040-plane was developed. By comparison with microscopic examination it is concluded that reliable results relating to the fibrillar orientation in the S2-layer are obtained with the X-ray technique. It is shown that the fibril angle of mature wood is rather constant with regard to both age of the annual ring and its position in the height of the tree. The fibril angle of the earlywood is found to be only slightly higher than that of latewood fibres. It is also shown that compression wood may be easily identified by virtue of the fact that its fibril angle is much higher than that of normal mature wood.
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