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Search Results: 1 - 10 of 19170 matches for " Richard Sicher "
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Responses of Metabolites in Soybean Shoot Apices to Changing Atmospheric Carbon Dioxide Concentrations
Richard Sicher
International Journal of Agronomy , 2012, DOI: 10.1155/2012/309153
Abstract: Soybean seedlings were grown in controlled environment chambers with CO2 partial pressures of 38 (ambient) and 72 (elevated) Pa. Five or six shoot apices were harvested from individual 21- to 24-day-old plants. Metabolites were analyzed by gas chromatography and, out of 21 compounds, only sucrose and fructose increased in response to CO2 enrichment. One unidentified metabolite, Unk-21.03 decreased up to 80% in soybean apices in response to elevated CO2. Levels of Unk-21.03 decreased progressively when atmospheric CO2 partial pressures were increased from 26 to 100?Pa. Reciprocal transfer experiments showed that Unk-21.03, and sucrose in soybean apices were altered slowly over several days to changes in atmospheric CO2 partial pressures. The mass spectrum of Unk-21.03 indicated that this compound likely contained both an amino and carboxyl group and was structurally related to serine and aspartate. Our findings suggested that CO2 enrichment altered a small number of specific metabolites in soybean apices. This could be an important step in understanding how plant growth and development are affected by carbon dioxide enrichment. 1. Introduction Atmospheric CO2 partial pressures are increasing due to human activities that include industrialization, fossil fuel combustion, and deforestation [1]. Since CO2 is an important substrate for photosynthesis, elevated atmospheric CO2 has the potential to alter the productivity of terrestrial plants and that of natural or managed ecosystems [2]. Single leaf gas exchange rates of higher plants were affected by CO2 enrichment, and this often resulted in larger plants with increased reproductive capacity [3–5]. Due to accelerated rates of net CO2 assimilation, concentrations of various leaf components including starch, soluble carbohydrates, amines, organic acids, pigments, and important photosynthetic proteins were affected by plant growth in CO2-enriched atmospheres [6–8]. Increased biomass accumulation in response to CO2 enrichment impacted the demand for soil nutrients, and in some cases this resulted in nutritionally limited growth conditions [9]. Nutrient limitations under CO2 enrichment also decreased leaf photosynthetic capacity and further altered leaf constituents [8]. In comparison to source leaves, much less attention has been given to the effects of elevated CO2 on the growth and development of sinks. Sink organs are dependent upon source leaves for assimilates to provide the carbon, nitrogen, and energy needed for growth and development. In general, metabolite levels in sink tissues were altered in concert
Daily changes of amino acids in soybean leaflets are modified by CO2 enrichment
Richard Charles Sicher
International Journal of Plant Biology , 2010, DOI: 10.4081/pb.2010.e18
Abstract: The effects of CO2 enrichment on plant growth and on nitrogen partitioning were examined using soybean [Glycine max (L.) Merr. cv. Clark] leaflets. Plants were grown from single seeds in matching controlled environment chambers. Continuous ambient CO2 partial pressures were from 38 to 40 Pa and elevated CO2 treatments were 68 to 70 Pa. Total above ground biomass, total leaf area and specific leaf weight of soybean were increased 78%, 58% and 33%, respectively, in response to CO2 enrichment when measured 25 days after sowing. Total chlorophyll (a+b) was 25% greater in third trifoliolate soybean leaflets in response to CO2 enrichment but total soluble protein did not differ between treatments. These and other measurements indicated that soybean plants were nitrogen sufficient in this study. Variations of total soluble amino acids were observed in soybean leaflets and these were enhanced by CO2 enrichment when measurements were performed mid-day. However, concentrations of total amino acids were similar in both CO2 treatments by end of the photoperiod. Glycine was lower in the elevated compared to the ambient CO2 treatment suggesting that rates of photorespiration were diminished by elevated CO2. Alanine increased 20% in response to CO2 enrichment. Overall, changes of soluble amino acids in response to CO2 enrichment were smaller than in other crop species and a temporal shift occurred in the daily accumulation of amino acids in soybean leaflets.
Physiological Traits and Metabolites of Cacao Seedlings Influenced by Potassium in Growth Medium  [PDF]
Yan-Mei Li, Marshall Elson, Dapeng Zhang, Richard C. Sicher, Hang Liang, Lyndel W. Meinhardt, Virupax Baligar
American Journal of Plant Sciences (AJPS) , 2013, DOI: 10.4236/ajps.2013.45133
Abstract:

Cacao (Theobroma cacao L.) is of significant economic importance in several tropical countries but its yield potentials are low mainly because of poor soil fertility especially low levels of potassium (K). Cacao has a high demand for K to maintain healthy growth and production. Knowledge of K use in cacao will help the development of suitable crop management practices and will aid breeding varieties adapted to environments with a limited soil K supply. Using a plant growth chamber, we investigated the growth and physiological traits among three cacao varieties at three levels of growth medium K (52, 156, and 469 mg·plant-1). Significant K effects were observed on growth traits including stem diameter, root length, chlorophyll b, and the ratio of chlorophyll a/b. Significant K effect was also found on carbohydrate metabolites, such as fructose, glucose, myo-inositol, raffinose and starch. However, no K effect was observed in other growth and physiological indicators, including biomass of seedling and net photosynthetic rate. There were significant genotype differences on seedling growth indicators, including stem diameter, stem height, total biomass, leaf biomass, leaf area, root length, chlorophyll a + b and carotenoids. Genotype difference was also found on all measured carbohydrate and starch metabolites, except maltose and raffinose. Results of this study indicate that although K plays a critical role in cacao tree growth and productivity, cacao may be less sensitive to K deficiency during the seedling stage. The present results improved our understanding about K and plants interaction in cacao seedlings, which is useful for crop management and germplasm utilization.

Drought Responses of Foliar Metabolites in Three Maize Hybrids Differing in Water Stress Tolerance
Jinyoung Y. Barnaby, Moon Kim, Gary Bauchan, James Bunce, Vangimalla Reddy, Richard Charles Sicher
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0077145
Abstract: Maize (Zea mays L.) hybrids varying in drought tolerance were treated with water stress in controlled environments. Experiments were performed during vegetative growth and water was withheld for 19 days beginning 17 days after sowing. Genotypic comparisons used measured changes of leaf water potential or results were expressed by time of treatment. Total dry matter of the drought tolerant hybrid on the final harvest was 53% less than that of the intermediate and susceptible maize hybrids when plants were water sufficient. This showed that maize hybrids selected for extreme drought tolerance possessed a dwarf phenotype that affected soil water contents and leaf water potentials. Changes of shoot and root growth, leaf water potential, net photosynthesis and stomatal conductance in response to the time of water stress treatment were diminished when comparing the drought tolerant to the intermediate or susceptible maize hybrids. Genotypic differences were observed in 26 of 40 total foliar metabolites during water stress treatments. Hierarchical clustering revealed that the tolerant maize hybrid initiated the accumulation of stress related metabolites at higher leaf water potentials than either the susceptible or intermediate hybrids. Opposite results occurred when changes of metabolites in maize leaves were expressed temporally. The above results demonstrated that genotypic differences were readily observed by comparing maize hybrids differing in drought tolerance based on either time of treatment or measured leaf water potential. Current findings provided new and potentially important insights into the mechanisms of drought tolerance in maize.
Efficient moves for global geometry optimization methods and their application to binary systems
Michael Sicher,Stephan Mohr,Stefan Goedecker
Physics , 2010, DOI: 10.1063/1.3530590
Abstract: We show that molecular dynamics based moves in the Minima Hopping (MH) method are more efficient than saddle point crossing moves which select the lowest possible saddle point. For binary systems we incorporate identity exchange moves in a way that allows to avoid the generation of high energy configurations. Using this modified Minima Hopping method we reexamine the binary Lennard Jones (BLJ) benchmark system with up to 100 atoms and we find a large number of new putative global minima structures.
Glassy clusters: Relations between their dynamics and characteristic features of their energy landscape
Sandip De,Bastian Schaefer,Ali Sadeghi,Michael Sicher,D. G. Kanhere,Stefan Goedecker
Physics , 2013,
Abstract: Based on a recently introduced metric for measuring distances between configurations, we in- troduce distance-energy (DE) plots to characterize the potential energy surface (PES) of clusters. Producing such plots is computationally feasible on the density functional (DFT) level since it re- quires only a set of a few hundred stable low energy configurations including the global minimum. By comparison with standard criteria based on disconnectivity graphs and on the dynamics of Lennard- Jones clusters we show that the DE plots convey the necessary information about the character of the potential energy surface and allow to distinguish between glassy and non-glassy systems. We then apply this analysis to real systems on the DFT level and show that both glassy and non-glassy clusters can be found in simulations. It however turns out that among our investigated clusters only those can be synthesized experimentally which exhibit a non-glassy landscape.
On the Prevention of Obesity and a Philosophy for Healthy Living  [PDF]
Richard Visser
Food and Nutrition Sciences (FNS) , 2012, DOI: 10.4236/fns.2012.37128
Abstract: Overweight and obesity have now reached historical, maximal peak values, with nearly one-third of world population suffering from these conditions. We are now witnessing the impact of this epidemic upon the global health status, with non-communicable diseases on the rise. We have also witnessed the shortcomings and failures of past actions taken when obesity is already present. In this essay the author reviews efforts made in the past regarding identification and treatment of obesity, and propose that actions should be taken before the onset of this disease, by motivating people to make intelligent, healthy choices when it comes to food and physical activity. A philosophy for healthy living should become central to the intervention actions, for them to be successful and sustained. Prevention of obesity should involve all those concerned irregardless of their position in society and curricular training, in order to create a multi-lateral, multi-national effort that will protect our families and our children from the consequences of this epidemic.
A Supportive Approach to Supervising Students Reading for a Phd in Systems and Software Engineering  [PDF]
Richard Lai
Creative Education (CE) , 2012, DOI: 10.4236/ce.2012.326138
Abstract: Supervising a PhD student is a complex teaching task as it involves a very unstructured environment and many intellectual challenges and stimuli, and it often requires a compatible student/supervisor relationship for successful outcomes. It is therefore not surprising that it has been reported that an aspect of teaching and learning that has been overlooked in higher education is research student supervision. Typical problems of poor supervision include: high rates of dissatisfaction with supervisors and high attrition rates and slow rates of completion for students. It has also been reported that there is no set prescription on appropriate and successful supervision; rather, the interactions between quality and style of supervision, and the field of study have all to be considered. It is not easy to know what a student and his/her supervisor should be doing in order to succeed. We are thus motivated to present in this paper our approach to supervising students reading for a PhD in systems and software engineering. This approach is centered on motivating students to learn and to do research by having supervisory activities that support their development throughout their candidature.
The Evolution of Curriculum Development in the Context of Increasing Social and Environmental Complexity  [PDF]
Richard Plate
Creative Education (CE) , 2012, DOI: 10.4236/ce.2012.38192
Abstract: The history of curriculum development has been characterized and a series of “crises” with the pendulum shifting between traditionalists’ call for getting back to the basics and the progressives’ focus on the learner. However, tracing this history, one can see a common theme in the criticisms expressed by both parties: the failure of the existing curriculum to meet the demands presented by an increasingly complex society. I follow this theme in order to provide historical context for contemporary calls by scientists and educators for wider use of systems-oriented curricula (i.e. curricula designed to improve systems thinking) at primary, secondary, and tertiary levels of education. With this context, one can view these current calls not as a radical shift of direction, but as a logical next stage in the evolution of curriculum. I conclude with a call for more research assessing the effectiveness of systems-oriented instruction and provide guidelines for enhancing the usefulness of such research in the current United States system.
Sino-French Engineering Curriculums: An Ongoing Process for Elitist Education?  [PDF]
Richard Mariom
Creative Education (CE) , 2012, DOI: 10.4236/ce.2012.37B048
Abstract: Here is a multisite case-study paper presenting Sino-French engineering education reform cooperation process. This questions the consequences for the introduction of a hybrid framework in a both dynamic and dichotomous innovation context such as Chinese one.
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