The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
Lucas Neas - One of the best experts on this subject based on the ideXlab platform.
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Characterization of a spatial gradient of nitrogen dioxide across a United States-Mexico border city during winter.
The Science of the total environment, 2005Co-Authors: Melissa Gonzales, Clifford Qualls, Edward Hudgens, Lucas NeasAbstract:A gradient of ambient nitrogen dioxide (NO(2)) concentration is demonstrated across metropolitan El Paso, Texas (USA), a city located on the international border between the United States and Mexico. Integrated measurements of NO(2) were collected over 7 days at 20 elementary schools and 4 air quality monitoring stations located throughout the city during typical winter atmospheric conditions. Replicate passive monitors were co-located with chemiluminescence analyzers at the monitoring stations for two consecutive 7-day periods. The passive measurements correlated with the analyzer measurements (R(2)=0.74) with precision of 2.5+/-2.2 ppb. Nitrogen dioxide concentrations ranged from 11.0 to 37.5 ppb (mean 20.6+/-7.1 ppb). In a multivariate regression model, the Site Elevation and distances to a main highway and to an international port of entry from Mexico explained 81% of the variance in the passive measurements. The results of this pilot study indicate that proximity to vehicle-related sources of NO(2) and Site Elevation are key predictors for future, more detailed assessments of vehicle-related air pollution exposure in the El Paso region.
Kevin F. Bronson - One of the best experts on this subject based on the ideXlab platform.
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Multispectral Reflectance of Cotton Related to Plant Growth, Soil Water and Texture, and Site Elevation
Agronomy Journal, 2001Co-Authors: Robert J. Lascano, J. D. Booker, L. Ted Wilson, Kevin F. Bronson, Edward M. Barnes, Eduardo SegarraAbstract:Radiometric data can be useful to determine the impact of field heterogeneity, irrigation, and fertilization on plant water and N use. A 2-yr (1998-1999) study was conducted on the South Texas High Plains to investigate cotton (Gossypium hirsutum L.) spectral and agronomic responses to irrigation and N fertilization and to determine the simple and cross correlation among cotton reflectance, plant growth, N uptake, lint yield, Site Elevation (SE), and soil water and texture. The treatments were irrigation at 50 and 75% of calculated cotton evapotranspiration (ET) and N rates of 0, 90, and 135 kg ha -1 arranged in an incomplete block of size-2 design. Plant and soil spectral properties were investigated within a wavelength of 447 to 1752 nm. Near-infrared (NIR) reflectance was positively correlated with plant biomass and N uptake. Reflectance in the red and midinfrared band increased with SE. The mixed-model analysis showed that cotton NIR reflectance, normalized difference vegetative index (NDVI), soil water, N uptake, and lint yield were significantly affected by irrigation (P < 0.0012). The N treatment had no effect on spectral parameters, and interaction between irrigation and N fertilizer was significant on NIR reflectance (P < 0.0027). All spectral and agronomic parameters measured were associated with SE. The red and NIR reflectance and NDVI were cross-correlated with soil water, sand, clay, and SE across a distance of 60 to 80 m. Characterization of plant and soil reflectance and their spatial structure can be the basis for variable N application on heterogeneous fields to increase N use efficiency.
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Cotton lint yield variability in a heterogeneous soil at a landscape scale
Soil & Tillage Research, 2001Co-Authors: Robert J. Lascano, J. D. Booker, L. Ted Wilson, Kevin F. BronsonAbstract:Abstract Landscape variability associated with topographic features affects the spatial pattern of soil water and N redistribution, and thus N uptake and crop yield. A landscape-scale study was conducted in a center pivot irrigated field on the southern High Plains of Texas in 1999 to assess soil water, soil NO 3 -N, cotton ( Gossypium hirsutum L.) lint yield, and N uptake variability in the landscape, and to determine the spatial correlation between these landscape variables using a state-space approach. The treatments were irrigation at 50 and 75% cotton potential evapotranspiration (ET). Neutron access tubes were placed at a 15-m interval along a 710 m (50% ET) and 820 m (75% ET) transect across the field. Soil NO 3 -N in early spring was autocorrelated at a distance varying between 60 and 80 m. Measured soil volumetric water content (WC), total N uptake, and lint yield were generally higher on lower landscape positions. Cotton lint yield was significantly correlated to soil WC ( r =0.76), soil NO 3 -N ( r =0.35), and Site Elevation ( r =−0.54). Differences of Site Elevation between local neighboring points explained the soil water, NO 3 -N and lint yield variability at the micro-scale level in the landscape. Soil WC, cotton lint yield, N uptake, and clay content were crosscorrelated with Site Elevation across a lag distance of ±30–40 m. The state-space analysis showed that cotton lint yield was positively weighted on soil WC availability and negatively weighted on Site Elevation. Cotton lint yield state-space models give insights on the association of soil physical and chemical properties, lint yield, and landscape processes, and have the potential to improve water and N management at the landscape-scale.
Emily Lena Jones - One of the best experts on this subject based on the ideXlab platform.
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Compositional variability in Mediterranean archaeofaunas from Upper Paleolithic Southwest Europe
Quaternary Science Reviews, 2018Co-Authors: Emily Lena JonesAbstract:Abstract Recent meta-analyses of Upper Paleolithic Southwestern European archaeofaunas (Jones, 2015, 2016) have identified a consistent “Mediterranean” cluster from the Last Glacial Maximum through the early Holocene, suggesting similarities in environment and/or consistency in hunting strategy across this region through time despite radical changes in climate. However, while these archaeofaunas from this cluster all derive from Sites located within today's Mediterranean bioclimatic region, many of them are from locations far from the Mediterranean Sea – Atlantic Portugal, the Spanish Meseta – which today differ significantly from each other in biotic composition. In this paper, I explore clustering (through cluster analysis and non-metric multidimensional scaling) within the Mediterranean archaeofaunal group. I test for the influence of sample size as well as the geographic variables of Site Elevation, latitude, and longitude on variability in the large mammal portions of archaeofaunal assemblages. ANOVA shows no relationship between cluster-defined groups and Site Elevation or longitude; instead, Site latitude appears to be a primary contributor to patterning. However, the overall compositional similarity of the Mediterranean archaeofaunas in this dataset suggests more consistency than variability in Upper Paleolithic hunting strategy in this region.
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Subsistence change, landscape use, and changing Site Elevation at the Pleistocene-Holocene transition in the Dordogne of southwestern France
Journal of Archaeological Science, 2007Co-Authors: Emily Lena JonesAbstract:The dramatic topography of the Dordogne Valley region of southwestern France has long been recognized as an influence on prehistoric human settlement and subsistence patterns. Previous research on late Pleistocene settlement patterns in this region implies that, as cold-adapted higher-ranked resources became scarce in the lowlands, Site location in the Dordogne and adjacent river valleys should shift towards higher-Elevation areas during the period from 18,000 to 6500 years BP. This study employs a GIS-based analysis to evaluate the changing settlement patterns in the Dordogne region at this time. While no significant changes in Elevation were found during this period, Site Elevation variance does appear to increase significantly between the Magdalenian and the Sauveterrian. Explanations for this finding are explored using zooarchaeological data from Moulin du Roc, one of the Sites in the data set. Results suggest that the Magdalenian period in the Dordogne may not have been as resource-rich as is often assumed.
L. Krishnamurthy - One of the best experts on this subject based on the ideXlab platform.
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Screening Rhizobium spp. strains associated with Gliricidia sepium along an altitudinal transect in Veracruz, Mexico
Agroforestry Systems, 1999Co-Authors: J. I. Melchor-marroquín, J. Jesús Vargas-hernández, R. Ferrera-cerrato, L. KrishnamurthyAbstract:In order to characterize Rhizobium strains naturally associated with Gliricidia sepium (Jacq.) Walp. and to determine their effectiveness for seedling inoculation, morphologic traits of G. sepium nodules and Rhizobium strains isolated from them, collected along on altitudinal transect (10—970 m above sea level) in northern Veracruz were studied. The Rhizobium strains isolated (three from each of eight sampling Sites) were evaluated in terms of dry matter production, total nitrogen and nodulation capability on six month-old G. sepium seedlings inoculated under greenhouse conditions. Even though all isolated strains belong to the Hup^+ group, differences in both morphological and physiological traits of nodules and Rhizobium strains were observed, associated to Site Elevation. Nodules from low Elevation Sites (< 100 m) were spherical and smooth, with Rhizobium strains tolerant to salinity (5% NaCl), and those from high Elevation Sites (> 500 m) were branched, with strains sensitive to salt. Thirteen strains (two from Sites below 100 m and 11 from Sites above 100 m) significantly increased seedling biomass, and nine of them also increased nitrogen content without negatively affecting the physiological nitrogen use efficiency (PEI) as compared to control seedlings. The relative effectiveness index (REI) of these Rhizobium strains varied between 2.0 and 2.4. However, no significant trend (r = 0.25) was found between PEI values of strains and Site Elevation. Nodular mass (NM) varied from 1.1 up to 1.7 mg dry weight with significant differences among strains, even though no significant Elevational trend was found in this trait.
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Screening Rhizobium spp. strains associated with Gliricidia sepium along an altitudinal transect in Veracruz, Mexico
Agroforestry Systems, 1999Co-Authors: J. I. Melchor-marroquín, J. Jesús Vargas-hernández, R. Ferrera-cerrato, L. KrishnamurthyAbstract:In order to characterize Rhizobium strains naturally associated with Gliricidia sepium (Jacq.) Walp. and to determine their effectiveness for seedling inoculation, morphologic traits of G. sepium nodules and Rhizobium strains isolated from them, collected along on altitudinal transect (10—970 m above sea level) in northern Veracruz were studied. The Rhizobium strains isolated (three from each of eight sampling Sites) were evaluated in terms of dry matter production, total nitrogen and nodulation capability on six month-old G. sepium seedlings inoculated under greenhouse conditions. Even though all isolated strains belong to the Hup+ group, differences in both morphological and physiological traits of nodules and Rhizobium strains were observed, associated to Site Elevation. Nodules from low Elevation Sites ( 500 m) were branched, with strains sensitive to salt. Thirteen strains (two from Sites below 100 m and 11 from Sites above 100 m) significantly increased seedling biomass, and nine of them also increased nitrogen content without negatively affecting the physiological nitrogen use efficiency (PEI) as compared to control seedlings. The relative effectiveness index (REI) of these Rhizobium strains varied between 2.0 and 2.4. However, no significant trend (r = 0.25) was found between PEI values of strains and Site Elevation. Nodular mass (NM) varied from 1.1 up to 1.7 mg dry weight with significant differences among strains, even though no significant Elevational trend was found in this trait.
Melissa Gonzales - One of the best experts on this subject based on the ideXlab platform.
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Characterization of a spatial gradient of nitrogen dioxide across a United States-Mexico border city during winter.
The Science of the total environment, 2005Co-Authors: Melissa Gonzales, Clifford Qualls, Edward Hudgens, Lucas NeasAbstract:A gradient of ambient nitrogen dioxide (NO(2)) concentration is demonstrated across metropolitan El Paso, Texas (USA), a city located on the international border between the United States and Mexico. Integrated measurements of NO(2) were collected over 7 days at 20 elementary schools and 4 air quality monitoring stations located throughout the city during typical winter atmospheric conditions. Replicate passive monitors were co-located with chemiluminescence analyzers at the monitoring stations for two consecutive 7-day periods. The passive measurements correlated with the analyzer measurements (R(2)=0.74) with precision of 2.5+/-2.2 ppb. Nitrogen dioxide concentrations ranged from 11.0 to 37.5 ppb (mean 20.6+/-7.1 ppb). In a multivariate regression model, the Site Elevation and distances to a main highway and to an international port of entry from Mexico explained 81% of the variance in the passive measurements. The results of this pilot study indicate that proximity to vehicle-related sources of NO(2) and Site Elevation are key predictors for future, more detailed assessments of vehicle-related air pollution exposure in the El Paso region.