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Physical Sciences and Mathematics Commons™

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Life Sciences

Iowa State University

2011

Articles 1 - 7 of 7

Full-Text Articles in Physical Sciences and Mathematics

Overview Of Corn-Based Fuel Ethanol Coproducts: Production And Use, Kurt A. Rosentrater Aug 2011

Overview Of Corn-Based Fuel Ethanol Coproducts: Production And Use, Kurt A. Rosentrater

Kurt A. Rosentrater

Modern societies face many challenges, including growing populations, increased demands for food, clothing, housing, consumer goods, and the raw materials required to produce all of these. Additionally, there is a growing need for energy, which is most easily met by use of fossil fuels (e.g., coal, natural gas, petroleum). For example, in 2008, the overall U.S. demand for energy was 99.3 x 1015 Btu (1.05 x 1014 MJ); 84% of this was supplied by fossil sources. Transportation fuels accounted for 28% of all energy consumed during this time, and nearly 97% of this came from fossil sources. Domestic production of …

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Net Exchanges Of Co2, Ch4, And N2o Between China's Terrestrial Ecosystems And The Atmosphere And Their Contributions To Global Climate Warming, Hanqin Tian, Xiaofeng Xu, Chaoqun (Crystal) Lu, Mingliang Liu, Wei Ren, Guangsheng Chen, Jerry Melillo, Jiyuan Liu Jun 2011

Net Exchanges Of Co2, Ch4, And N2o Between China's Terrestrial Ecosystems And The Atmosphere And Their Contributions To Global Climate Warming, Hanqin Tian, Xiaofeng Xu, Chaoqun (Crystal) Lu, Mingliang Liu, Wei Ren, Guangsheng Chen, Jerry Melillo, Jiyuan Liu

Chaoqun (Crystal) Lu

China's terrestrial ecosystems have been recognized as an atmospheric CO2 sink; however, it is uncertain whether this sink can alleviate global warming given the fluxes of CH4 and N2O. In this study, we used a process-based ecosystem model driven by multiple environmental factors to examine the net warming potential resulting from net exchanges of CO2, CH4, and N2O between China's terrestrial ecosystems and the atmosphere during 1961–2005. In the past 45 years, China's terrestrial ecosystems were found to sequestrate CO2 at a rate of 179.3 Tg C yr−1 with a 95% confidence range of (62.0 Tg C yr−1, 264.9 Tg …

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Impacts Of Tropospheric Ozone And Climate Change On Net Primary Productivity And Net Carbon Exchange Of China's Forest Ecosystems, Wei Ren, Hanqin Tian, Bo Tao, Arthur Chappelka, Ge Sun, Chaoqun (Crystal) Lu, Mingliang Liu, Guangsheng Chen, Xiaofeng Xu May 2011

Impacts Of Tropospheric Ozone And Climate Change On Net Primary Productivity And Net Carbon Exchange Of China's Forest Ecosystems, Wei Ren, Hanqin Tian, Bo Tao, Arthur Chappelka, Ge Sun, Chaoqun (Crystal) Lu, Mingliang Liu, Guangsheng Chen, Xiaofeng Xu

Chaoqun (Crystal) Lu

We investigated how ozone pollution and climate change/variability have interactively affected net primary productivity (NPP) and net carbon exchange (NCE) across China's forest ecosystem in the past half century. Using the dynamic land ecosystem model (DLEM) in conjunction with 10-km-resolution gridded historical data sets (tropospheric O3 concentrations, climate variability/change, and other environmental factors such as land-cover/land-use change (LCLUC), increasing CO2 and nitrogen deposition), we conducted nine simulation experiments to: (1) investigate the temporo-spatial patterns of NPP and NCE in China's forest ecosystems from 1961–2005; and (2) quantify the effects of tropospheric O3 pollution alone or in combination with climate variability …

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Developing Criteria For Evaluating The Sustainability Of Emerging Energy, Kurt A. Rosentrater, Elif Kongar Apr 2011

Developing Criteria For Evaluating The Sustainability Of Emerging Energy, Kurt A. Rosentrater, Elif Kongar

Kurt A. Rosentrater

Over the last decade, the interest in and production of biofuels has grown rapidly. Renewable transportation fuels can be produced from a variety of substrates, using various processing strategies. Feedstock preference and factory scale are geographic dependent. However, it is important to understand the implications of deploying these types of systems on a large scale, both throughout the U.S. as well as globally. To assess the sustainability of various biofuel options, it is crucial to evaluate their performance according to a number of attributes. This has been done using Life Cycle Assessment (LCA). Even so, comparisons among biofuel options are …

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Climate And Land Use Controls Over Terrestrial Water Use Efficiency In Monsoon Asia, Hanqin Tian, Chaoqun (Crystal) Lu, Guangsheng Chen, Xiaofeng Xu, Mingliang Liu, Wei Ren, Bo Tao, Ge Sun, Shufen Pan, Jiyuan Liu Mar 2011

Climate And Land Use Controls Over Terrestrial Water Use Efficiency In Monsoon Asia, Hanqin Tian, Chaoqun (Crystal) Lu, Guangsheng Chen, Xiaofeng Xu, Mingliang Liu, Wei Ren, Bo Tao, Ge Sun, Shufen Pan, Jiyuan Liu

Chaoqun (Crystal) Lu

Much concern has been raised regarding how and to what extent climate change and intensive human activities have altered water use efficiency (WUE, amount of carbon uptake per unit of water use) in monsoon Asia. By using a process-based ecosystem model [dynamic land ecosystem model (DLEM)], we examined effects of climate change, land use/cover change, and land management practices (i.e. irrigation and nitrogen fertilization) on WUE in terrestrial ecosystems of monsoon Asia during 1948–2000. Our simulations indicated that due to climate variability/change, WUE in the entire area decreased by 3·6% during the study period, with the largest decrease of 6·8% …

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Dead Zones In Porous Catalysts: Concentration Profiles And Efficiency Factors, Roger L. York, Kaitlin M. Bratlie, Lloyd R. Hile, Larry K. Jang Jan 2011

Dead Zones In Porous Catalysts: Concentration Profiles And Efficiency Factors, Roger L. York, Kaitlin M. Bratlie, Lloyd R. Hile, Larry K. Jang

Kaitlin M. Bratlie

This paper examines the conditions under which a dead zone, or a portion of the catalyst devoid of reactant, can form in a porous catalyst in which simultaneous reaction and diffusion are occurring. The condition that allows for the existence of a dead zone is defined by a critical Thiele modulus. When the Thiele modulus - the ratio of chemical reaction to diffusion - is greater than the critical Thiele modulus, a dead zone exists. This dead zone can be mathematically defined by a change of boundary conditions. We examine nth order reactions in isothermal infinite slabs, infinite cylinders, and …

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Measured And Predicted Temporal Changes In Soil Nitrate-N Levels From Late Summer To Early Spring In Montana, Andrew W. Lenssen, Clain Jones, Chengci Chen, Kent Mcvay, Bob Stougaard, Mal Westcott, Joyce Eckhoff, Jennifer Weeding, Mark Greenwood Jan 2011

Measured And Predicted Temporal Changes In Soil Nitrate-N Levels From Late Summer To Early Spring In Montana, Andrew W. Lenssen, Clain Jones, Chengci Chen, Kent Mcvay, Bob Stougaard, Mal Westcott, Joyce Eckhoff, Jennifer Weeding, Mark Greenwood

Andrew W. Lenssen

Most soil sampling is conducted from August to November in Montana because of better soil sampling conditions and because it provides more time for growers to make fertilizer decisions prior to application. Fertilizer guidelines in Montana are based on spring nitrate-N levels in the upper 2 ft because they are more indicative of growing season available N than fall nitrate-N levels. It is not known how much nitrate-N levels change between late summer and spring, nor is it known what factors affect these changes, and large changes could result in either over-application of N fertilizer or sub-optimal yields. A three-year …

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