2,300 research outputs found
Selection for Biomass Yield in Upland, Lowland, and Hybrid Switchgrass
Switchgrass (Panicum virgatum L.) is a candidate for cellulosic bioenergy feedstock development in many parts of North America, Europe, and Asia. Breeding for increased biomass yield is a viable and desirable research objective to improve both economic and energy yields per hectare. The objectives of this study were to estimate progress from (i) selection for biomass yield in upland switchgrass, (ii) selection for winter survival, biomass yield, and biomass quality in lowland switchgrass, and (iii) advanced-generation heterosis effects in four upland Ă— lowland hybrid switchgrass populations. Selection for increased biomass yield in upland switchgrass resulted in mean genetic gains for of 0.71 Mg ha-1 per cycle (8% per cycle = 4% yr-1) for biomass yield. Selection for increased biomass yield in lowland switchgrass resulted in mean genetic gains of 0.89 Mg ha-1 (18% = 1% yr-1) for biomass yield. Mean high-parent heterosis between upland and lowland ecotypes was 3.57 Mg ha-1 (43%). These gains in biomass yield resulted in significant increases in ethanol production for a fermentation platform or high heating value for a combustion platform. Biomass yield is a moderately heritable trait in switchgrass and it can be readily improved in both upland and lowland populations using conventional breeding methods
Switchgrass
Switchgrass (Panicum virgatum L.) is a tall, erect, warm-season perennial native to the tall grass prairie, oak savanna, and associated ecosystems of North America. It can be found in prairies, open woodlands, and brackish marshes east of the Rocky Mountains and generally south of 55° north latitude (Hitchcock 1951; Stubbendieck et al. 1991). Less than 1% of these ecosystems exist today, but these prairie and savanna remnants have served as in situ gene banks, preserving a vast amount of genetic diversity within switchgrass and many other plant species. Switchgrass has a diversity of uses as well, including pasture, hay production, biomass for energy production, soil and water conservation, carbon sequestration, and wildlife habitat
Temperature dependence of spatially heterogeneous dynamics in a model of viscous silica
Molecular dynamics simulations are performed to study spatially heterogeneous
dynamics in a model of viscous silica above and below the critical temperature
of the mode coupling theory, . Specifically, we follow the evolution
of the dynamic heterogeneity as the temperature dependence of the transport
coefficients shows a crossover from non-Arrhenius to Arrhenius behavior when
the melt is cooled. It is demonstrated that, on intermediate time scales, a
small fraction of oxygen and silicon atoms are more mobile than expected from a
Gaussian approximation. These highly mobile particles form transient clusters
larger than that resulting from random statistics, indicating that dynamics are
spatially heterogeneous. An analysis of the clusters reveals that the mean
cluster size is maximum at times intermediate between ballistic and diffusive
motion, and the maximum size increases with decreasing temperature. In
particular, the growth of the clusters continues when the transport
coefficients follow an Arrhenius law. These findings imply that the structural
relaxation in silica cannot be understood as a statistical bond breaking
process. Though the mean cluster sizes for silica are at the lower end of the
spectrum of values reported in the literature, we find that spatially
heterogeneous dynamics in strong and fragile glass formers are similar on a
qualitative level. However, different from results for fragile liquids, we show
that correlated particle motion along quasi one-dimensional, string-like paths
is of little importance for the structural relaxation in this model of silica,
suggesting that string-like motion is suppressed by the presence of covalent
bonds.Comment: 13 pages, 11 figure
Inner Molecular Rings in Barred Galaxies: BIMA SONG CO Observations
Although inner star-forming rings are common in optical images of barred
spiral galaxies, observational evidence for the accompanying molecular gas has
been scarce. In this paper we present images of molecular inner rings, traced
using the CO (1-0) emission line, from the
Berkeley-Illinois-Maryland-Association Survey of Nearby Galaxies (BIMA SONG).
We detect inner ring CO emission from all five SONG barred galaxies classified
as inner ring (type (r)). We also examine the seven SONG barred galaxies
classified as inner spiral (type (s)); in one of these, NGC 3627, we find
morphological and kinematic evidence for a molecular inner ring. Inner ring
galaxies have been classified as such based on optical images, which emphasize
recent star formation. We consider the possibility that there may exist inner
rings in which star formation efficiency is not enhanced. However, we find that
in NGC 3627 the inner ring star formation efficiency is enhanced relative to
most other regions in that galaxy. We note that the SONG (r) galaxies have a
paucity of CO and H alpha emission interior to the inner ring (except near the
nucleus), while NGC 3627 has relatively bright bar CO and H alpha emission; we
suggest that galaxies with inner rings such as NGC 3627 may be misclassified if
there are significant amounts of gas and star formation in the bar.Comment: To be published in the Astrophysical Journal, July 2002 A version of
the paper with full resolution figures is available at:
http://www.astro.umd.edu/~mregan/ms.ps.g
Selection Signatures in Four Lignin Genes from Switchgrass Populations Divergently Selected for \u3ci\u3eIn Vitro\u3c/i\u3e Dry Matter Digestibility
Switchgrass is undergoing development as a dedicated cellulosic bioenergy crop. Fermentation of lignocellulosic biomass to ethanol in a bioenergy system or to volatile fatty acids in a livestock production system is strongly and negatively influenced by lignification of cell walls. This study detects specific loci that exhibit selection signatures across switchgrass breeding populations that differ in in vitro dry matter digestibility (IVDMD), ethanol yield, and lignin concentration. Allele frequency changes in candidate genes were used to detect loci under selection. Out of the 183 polymorphisms identified in the four candidate genes, twenty-five loci in the intron regions and four loci in coding regions were found to display a selection signature. All loci in the coding regions are synonymous substitutions. Selection in both directions were observed on polymorphisms that appeared to be under selection. Genetic diversity and linkage disequilibrium within the candidate genes were low. The recurrent divergent selection caused excessive moderate allele frequencies in the cycle 3 reduced lignin population as compared to the base population. This study provides valuable insight on genetic changes occurring in short-term selection in the polyploid populations, and discovered potential markers for breeding switchgrass with improved biomass quality
Genetic Diversity, Plant Adaptation Regions, and Gene Pools for Switchgrass
Switchgrass (Panicum virgatum L.) is a perennial grass native to the North American tallgrass prairie and broadly adapted to the central and eastern USA. Transfer of germplasm throughout this region creates the potential of contaminating local gene pools with genes that are not native to a locale. The objective of this study was to identify structural patterns and spatial variation for molecular markers of switchgrass populations from the northern and central USA. Forty six prairie-remnant populations and 11 cultivars were analyzed for random amplified polymorphic DNA (RAPD) markers. Although there was significant population differentiation, little of this variation was associated with geographic regions. A small amount of population differentiation was associated with hardiness zones and ecoregions, suggesting that a recent proposal to use these two criteria for defining plant adaptation regions has merit for defining gene pools and seed-transfer zones of switchgrass. Cultivars of switchgrass cannot be differentiated from prairie-remnant populations in the northern and central USA on the basis of RAPD markers, indicating that they are still highly representative of natural germplasm. Seed sources of switchgrass can be moved considerable distance within hardiness zones and ecoregions without causing significant contamination, pollution, swamping, or erosion of local gene pools
Environmental Marketing
Foremost in the minds of most customers are quality images at a reasonable cost. But customers are becoming increasingly concerned with the environmental impacts of their print jobs. Effective marketing of
your environmental protection efforts may provide you with a keen competitive advantage. As general environmental awareness continues to sharpen, environmental marketing will play a larger role in attracting and retaining customers.Ope
Plate Developing Pollution Prevention Fact Sheet
Many plate developers are solvent-based, and therefore may be potentially hazardous. Some can be flammable, have a high biological oxygen demand (BOD)(1) or very high or low pH. Opportunities to reduce waste from platemaking processes can save money through reduced waste disposal costs. Two ways to prevent pollution from plate developing
are aqueous-based plate developing systems and electronic prepress technology.Ope
Facts about Paper
For most printers, paper represents one of the largest input costs. But because paper prices can fluctuate suddenly and unpredictably, printers of all sizes can feel the strain of the paper industry's boom-bust cycles. The good news is that environmental considerations provide opportunities to improve efficiency and reduce costs. While printers often must defer to customers' specifications, they can play a major role in shaping those specifications. The key is staying abreast of the changes in the paper demand and manufacture, and learning how to help influence the changes. This fact sheet highlights some of the facts about paper related to the printing industry.Ope
- …