Throughfall deposition of ammonium and sulphate during ammonia fumigation of a scots pine forest     

J. N. Cape  L. J. Sheppard  J. Binnie  P. Arkle  C. Woods 《Water, air, and soil pollution》1995,85(4):2247-2252

The estimation of the dry deposition of sulphur dioxide to forests is confounded by the possibility of co-deposition of SO₂ with NH₃ on leaf surfaces. A sector of Scots pine forest was selectively fumigated with NH₃ to give average concentrations up to 15 ppbV (nL L^–1) above ambient, in order to test the hypothesis that increased air concentrations of NH₃ would enhance the dry deposition of SO₂, and the consequent amounts of SO₄ ^2– measured in throughfall below the forest canopy. Ammonia gas, generated by evaporation of concentrated aqueous solution, was released above the canopy in proportion to wind speed when the wind direction was between south and west. Concentrations of NH₃ at canopy height were measured using passive diffusion tubes; throughfall was preserved with thymol and measured weekly. Meteorological data and SO₂ concentrations were recorded continuously, to permit the estimation of dry deposition input. Deposition of NH₄ ⁺ in throughfall over 8 months was increased by up to 40 meq m^–2 relative to control sites upwind of the NH₃ release point, with largest values closest to the release point. Deposition of SO₄ ^2– in throughfall was also enhanced in the fumigated area, by up to 20 meq m^–2, even though average ambient SO₂ concentrations were 2.3 ppbV. The results are discussed in terms of the factors controlling SO₂ deposition on forest surfaces, the development of appropriate deposition models, and their relevance to using throughfall as an estimate of total S deposition.  相似文献   

Local positive feedback regulation determines cell shape in root hair cells     

Takeda S  Gapper C  Kaya H  Bell E  Kuchitsu K  Dolan L 《Science (New York, N.Y.)》2008,319(5867):1241-1244

The specification and maintenance of growth sites are tightly regulated during cell morphogenesis in all organisms. ROOT HAIR DEFECTIVE 2 reduced nicotinamide adenine dinucleotide phosphate (RHD2 NADPH) oxidase-derived reactive oxygen species (ROS) stimulate a Ca2+ influx into the cytoplasm that is required for root hair growth in Arabidopsis thaliana. We found that Ca2+, in turn, activated the RHD2 NADPH oxidase to produce ROS at the growing point in the root hair. Together, these components could establish a means of positive feedback regulation that maintains an active growth site in expanding root hair cells. Because the location and stability of growth sites predict the ultimate form of a plant cell, our findings demonstrate how a positive feedback mechanism involving RHD2, ROS, and Ca2+ can determine cell shape.  相似文献   

Individual lipids and proximate analysis of various foods. 2. Frankfurters and other meat and poultry products     

D R Newkirk  A J Sheppard  W D Hubbard  T Osgood 《Journal of agricultural and food chemistry》1978,26(2):349-350

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Development of Chemical Index as a Measure of In-Stream Water Quality in Response to Land-Use and Land Cover Changes     

T. Tsegaye  D. Sheppard  K. R. Islam  W. Tadesse  A. Atalay  L. Marzen 《Water, air, and soil pollution》2006,174(1-4):161-179

Water pollution in response to accelerated land-use/land cover changes has drawn concerns because of public health and environmental impacts. The study was conducted to evaluate the impact of land use/land cover changes, seasonal, and location on water quality of streams within the Wheeler Lake Watershed basin in northern Alabama. Temporal water samples from 18 sheppard streams were randomly collected in 2000 and 2001, processed and analyzed for pH, and total nitrogen (TN), dissolved (Dp), particulate (Pp) and total phosphorus (Tp), dissolved oxygen (DO) and soluble lead (Pb) concentration, employing standard methods of analysis. The data were normalized and integrated into a simple index (WQC_Index) to evaluate stream water quality. Results showed that the urban proportion of the total watershed basin had increased from 2.9 to 14.7% with an associated loss of agricultural (8.9%) and wetland (4.8%) covers from 1992 to 2000. A change in land-use/land covers in association with seasonal and location variation significantly affected stream water quality. Total nitrogen concentration in stream water had a peak during the summer at 34% above the annual mean. While both Pp and Tp concentrations peaking during the summer at 24% above the annual mean and about 25% below the annual mean during spring, the DO concentrations were 46% above the annual mean during the fall and 18 to 26% below annual mean during summer. The WQC_Index had responded very seasonal and showed significant identical trends, with 21% degradation in water quality during the summer above the annual mean and improvement during the spring at 20% above the annual mean. Upstream water had a significantly greater Pp and Tp (21 to 28%) concentration than at down- and middle streams water. Location and seasonal variations had significant interactive effects on Pp, Tp and DO concentration of stream water. Total amount of seasonal rainfall significantly accounted 99.6% of the variations in WQC_Index. Increasing seasonal mean relative humidity, air and soil temperature, evaporation and solar radiation had positive relationship with the variations in WQC_Index. Among the water quality parameters, both Pp and Tp were correlated (r ² = 0.998^?*?) to each other, and accounted for more than 80% variability of the WQC_Index. Highly significant positive linear relationship between Pp and Tp concentration suggested that 99.8% of the P in stream water is in Pp form which probably transported with sediments in surface runoff. In other words, Pp is the main pollutant responsible for degradation of stream water quality in the Wheeler lake basin. Routine measurement of either Pp or Tp concentration could be used as sensitive and early indicator of temporal changes in stream water quality even when the other parameters changed negligibly or remain unchanged.  相似文献   

Applications of pedigree-based genome mapping in wheat and barley breeding programs   总被引：1，自引：0，他引：1  

Mandy Christopher  Emma Mace  David Jordan  David Rodgers  Paul McGowan  Ian Delacy  Phillip Banks  John Sheppard  David Butler  David Poulsen 《Euphytica》2007,154(3):307-316

The aim of the pedigree-based genome mapping project is to investigate and develop systems for implementing marker assisted selection to improve the efficiency of selection and increase the rate of genetic gain in breeding programs. Pedigree-based whole genome marker application provides a vehicle for incorporating marker technologies into applied breeding programs by bridging the gap between marker–trait association and marker implementation. We report on the development of protocols for implementation of pedigree-based whole genome marker analysis in breeding programs within the Australian northern winter cereals region. Examples of applications from the Queensland DPI&F wheat and barley breeding programs are provided, commenting on the use of microsatellites and other types of molecular markers for routine genomic analysis, the integration of genotypic, phenotypic and pedigree information for targeted wheat and barley lines, the genomic impacts of strong selection pressure in case study pedigrees, and directions for future pedigree-based marker development and analysis.  相似文献   

Measles virus matrix protein synthesized in a subacute sclerosing panencephalitis cell line   总被引：4，自引：0，他引：4  

R D Sheppard  C S Raine  M B Bornstein  S A Udem 《Science (New York, N.Y.)》1985,228(4704):1219-1221

Measles virus generally produces acute illness. Rarely, however, persistent infection of brain cells occurs, resulting in a chronic and fatal neurological disease, subacute sclerosing panencephalitis (SSPE). Evidence indicates that expression of the measles virus matrix protein is selectively restricted in this persistent infection, but the mechanism underlying this restriction has not been identified. Defective translation of matrix messenger RNA has been described in one SSPE cell line. This report presents evidence that in a different SSPE tissue culture cell line IP-3-Ca, the matrix protein is synthesized but fails to accumulate. A general scheme is proposed to reconcile the different levels at which restriction of matrix protein has been observed.  相似文献   

Clinical and biochemical changes in sheep inoculated with Leptospira interrogans serotype pomona.     

K R Millar  R T Hodges  A D Sheppard  M W Hammington 《New Zealand veterinary journal》1977,25(8):203-207

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Detection of infectious laryngotracheitis virus in chickens using a non-radioactive DNA probe.   总被引：3，自引：0，他引：3  

L Keam  J J York  M Sheppard  K J Fahey 《Avian diseases》1991,35(2):257-262

A DNA hybridization assay using a non-radioactive probe has been developed for the detection of infectious laryngotracheitis virus (ILTV) DNA. A 1.4-kilobase pair BamHI fragment of ILTV genomic DNA was cloned and then labeled by one of two methods; nick translation using 32P-dATP or non-radioactive labeling using a commercially available DNA labeling and detection kit. The non-radioactive DNA labeling method proved to be as sensitive as the radioactive method. Using the non-radioactive probe, ILTV DNA was readily detected in tracheal samples from acutely infected chickens and also from convalescent chickens at a time when viral antigen could no longer be detected by the enzyme-linked immunosorbent assay or the virus could no longer be reisolated. This technique provides a safe and effective means of identifying field outbreaks of ILTV and also may detect latent ILTV infections relatively quickly and inexpensively.  相似文献   

Factors affecting orderly establishment and growth of a broiler industry in Northwestern Epirus, Greece     

E E Sheppard  A Donos 《World's poultry science journal》1967,23(4):315-320

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Irregular recurrence of large earthquakes along the san andreas fault: evidence from trees     

Jacoby GC  Sheppard PR  Sieh KE 《Science (New York, N.Y.)》1988,241(4862):196-199

Old trees growing along the San Andreas fault near Wrightwood, California, record in their annual ring-width patterns the effects of a major earthquake in the fall or winter of 1812 to 1813. Paleoseismic data and historical information indicate that this event was the "San Juan Capistrano" earthquake of 8 December 1812, with a magnitude of 7.5. The discovery that at least 12 kilometers of the Mojave segment of the San Andreas fault ruptured in 1812, only 44 years before the great January 1857 rupture, demonstrates that intervals between large earthquakes on this part of the fault are highly variable. This variability increases the uncertainty of forecasting destructive earthquakes on the basis of past behavior and accentuates the need for a more fundamental knowledge of San Andreas fault dynamics.  相似文献