Life Sciences Commons^™

Uncertainty Assessment In Biomass Estimation, Isaac Lisle

Isaac Lisle

Elevated Co2 Induced Changes In The Chemistry Of Quaking Aspen (Populus Tremuloides Michaux) Leaf Litter: Subsequent Mass Loss And Microbial Response In A Stream Ecosystem, Steven Rier, Nancy Tuchman, Robert Wetzel, James Teeri

Nancy Tuchman

No abstract provided.

Tillage System Effects On 15-Year Carbon-Based And Simulated N Budgets In A Tile-Drained Iowa Field, Douglas L. Karlen, Ajay Kumar, Ramesh S. Kanwar, Cynthia A. Cambardella, Thomas S. Colvin

Douglas L Karlen

Tillage influences N fate and transport by changing soil structure, aeration, macropore continuity, plant-residue placement, and organic-matter mineralization rates. Our objective was to use 15-year N budgets to compare four primary tillage treatments for continuous corn (Zea mays L.) production on tile-drained Aquic Hapludolls (FAO: Haplic Phaeozems) in northeastern Iowa, USA. A carbon-based N budget used annual grain yield, grain-N concentrations measured in 1992, changes in surface-soil C content between 1977 and 1988 or 1992, surface-soil C : N ratios, and measurements of NO3–N lost in tile-drainage water. It accounted for 98, 104, 99, and 99% of the fertilizer N …

Sources Of Carbonaceous Aerosols And Deposited Black Carbon In The Arctic In Winter-Spring: Implications For Radiative Forcing, Q Wang, D J. Jacob, J A. Fisher, J Mao, E M. Leibensperger, C C. Carouge, P Le Sager, Y Kondo, J L. Jimenez, M J. Cubison, S J. Doherty

Jenny A Fisher

We use a global chemical transport model (GEOS-Chem CTM) to interpret observations of black carbon (BC) and organic aerosol (OA) from the NASA ARCTAS aircraft campaign over the North American Arctic in April 2008, as well as longer-term records in surface air and in snow (2007-2009). BC emission inventories for North America, Europe, and Asia in the model are tested by comparison with surface air observations over these source regions. Russian open fires were the dominant source of OA in the Arctic troposphere during ARCTAS but we find that BC was of prevailingly anthropogenic (fossil fuel and biofuel) origin, particularly …

Source Attribution And Interannual Variability Of Arctic Pollution In Spring Constrained By Aircraft (Arctas, Arcpac) And Satellite (Airs) Observations Of Carbon Monoxide, J A. Fisher, D J. Jacob, M T. Purdy, M Kopacz, P Le Sager, C C. Carouge, C D. Holmes, R M. Yantosca, R L. Batchelor, K Strong, G S. Diskin, H E. Fuelberg, J S. Holloway, E J. Hyer, W. W Mcmillan, J Warner, D G. Streets, Q Zhang, Y Yang, S Wu

Jenny A Fisher

We use aircraft observations of carbon monoxide (CO) from the NASA ARCTAS and NOAA ARCPAC campaigns in April 2008 together with multiyear (2003– 2008) CO satellite data from the AIRS instrument and a global chemical transport model (GEOS-Chem) to better understand the sources, transport, and interannual variability of pollution in the Arctic in spring. Model simulation of the aircraft data gives best estimates of CO emissions in April 2008 of 26 Tg month−1 for Asian anthropogenic, 9.4 for European anthropogenic, 4.1 for North American anthropogenic, 15 for Russian biomass burning (anomalously large that year), and 23 for Southeast Asian biomass …

Differential Effects Of Canopy Trimming And Litter Deposition On Litterfall And Nutrient Dynamics In A Wet Subtropical Forest, Steven J. Hall, Whendee L. Silver, Grizelle González

Steven J. Hall

Humid tropical forests have the highest rates of litterfall production globally, which fuels rapid nutrient recycling and high net ecosystem production. Severe storm events significantly alter patterns in litterfall mass and nutrient dynamics through a combination of canopy disturbance and litter deposition. In this study, we used a large-scale long-term manipulation experiment to explore the separate and combined effects of canopy trimming and litter deposition on litterfall rates and litter nutrient concentrations and content. The deposition of fine litter associated with the treatments was equivalent to more than two times the annual fine litterfall mass and nutrient content in control …

Characterisation Of Porous Freeze Dried Conducting Carbon Nanotube-Chitosan Scaffolds, Simon Moulton, Gordon Wallace, Luke Sweetman

Luke Sweetman

In this study, the fabrication and characterisation of highly porous yet conductive scaffolds was performed. The conductive component, namely single-walled carbon nanotubes (SWNTs), was incorporated into a chitosan bio-polymeric matrix utilising a dispersion-based freeze dry approach. The electroactive polymer poly(2-methoxy-5-sulfonic acid) (PMAS) was also successfully incorporated into scaffolds in an effort to improve the structural integrity of scaffolds in an aqueous, biologically relevant environment. Here, we report how the variation in dispersion and scaffold synthesis conditions, as well as the composition of constituent components, impact on scaffold properties.

Reactions Of Small Carbon-Bearing Radicals With Unsaturated Hydrocarbons: Product Detection And Low Temperature Kinetics, Adam Trevitt, Fabien Goulay, Stephen Leone

Adam Trevitt

We report on results from two experimental techniques concerned with the reactions of small carbon based radicals (CN and CH) with unsaturated hydrocarbons. First, low temperature (100-300K) kinetic studies using a pulse Laval nozzle technique probe the reactions of the CN radical with benzene and toluene. The CN + benzene is found to be a fast, barrierless reaction. But in the case of toluene, two reaction pathways are in competition, one of which back dissociates to the reactants. The implications for the atmosphere of Titan are discussed. Product detection studies undertaken at the Advanced Light Source (ALS) using synchrotron coupled …

Nanostructured Carbon Electrodes, Gordon G. Wallace, Jun Chen, Dan Li, Simon E. Moulton, Joselito M. Razal

Gordon Wallace

In its conducting form, carbon has proven to be a versatile, robust and high performing electrode material in areas such as energy conversion, energy storage and even medical bionics. In our laboratories we have been interested in the fabrication and utilization of nanostructured electrodes based on more recently discovered forms of carbon. These include carbon nanotubes and graphene.

Electrocatalytic Reduction Of Carbon Dioxide By Cobalt-Phthalocyanine-Incorporated Polypyrrole, Jun Chen, Gordon G. Wallace, Jiaxing Lu, Aijian Zhang, Weimin Zhang

Gordon Wallace

In the quest for catalysts for the electrocatalytic reduction of , a cobalt phthalocyanine/polypyrrole (CoPc/PPy) composite electrode has been developed. The electrode is prepared by drop casting CoPc onto the PPy film from the CoPc/tetrahydrofuran solution (1 mg/mL). The onset potential for reduction occurred at potentials 160 mV more positive than observed with a simple PPy electrode. Furthermore, in the potentiostatic electrolysis, the catalytic current for reduction at CoPc/PPy was very stable, with a higher current density and current efficiency when compared to the PPy electrode.

Controlled Deposition Of Polymer Carbon Nanotube Composites Through Inkjet Printing, William Small, Fatemeh Masdarolomoor, Gordon G. Wallace, Marc In Het Panhuis

Gordon Wallace

The controlled deposition of polyaniline carbon nanotube composites by inkjet printing is reported. It is demonstrated that the sheet resistance and transmittance can be expressed in amount of composite and MWNT material deposited. The most efficient way for improving the sheet resistance while keeping the cost in optical transparency to a minimum is by increasing the total amount of material deposited, rather than increasing MWNT loading fraction.

Carbon-Nanotube Biofiber Microelectrodes, Carol M. Lynam, Gordon G. Wallace, Willo Grosse

Gordon Wallace

All-biocompatible carbon-nanotube fibers were formed using wet spinning. In this process the spinning solutions used are carbon nanotubes dispersed using biomolecules such as hyaluronic acid and chitosan. We compare the effect of a coagulation bath containing either a polymer binder, e.g., polyethyleneimine, or simply a precipitating solvent system, e.g., acetone. The electrical, mechanical, and morphological properties of the resulting fibers were studied. Biocompatible electrode structures were generated suitable for a variety of biomedical applications, e.g.,in biosensors or in systems where the application of an electrical field is advantageous e.g., stimulation of electrically excitable cells such as nerve and muscle cells.

Photocatalytic Oxidation Of Methanol Using Titanium Dioxide/Single-Walled Carbon Nanotube Composite, Jun Chen, Carol M. Lynam, Chonlada Dechakiatkrai, Gordon G. Wallace, Sukon Phanichphant

Gordon Wallace

Titanium dioxide/single-walled carbon nanotube TiO2/SWNT composites were prepared for photocatalytic applications. Thecomposites were characterized using UV-visible and Raman spectroscopy, zeta-potential measurements, cyclic voltammetrycoupled with a photoreactor, scanning electron microscopy, and transmission electron microscopy coupled with energy dispersiveX-ray spectroscopy. The photocatalytic activity of TiO2 and the TiO2/SWNT composite was investigated using the photo-oxidationof methanol in sulfuric acid as supporting electrolyte. The results indicate that the TiO2/SWNT composite enhances the photocatalyticactivity compared to TiO2 alone. Electrochemical studies of the TiO2/SWNT composite were also carried out in varioussupporting electrolytes and the presence of SWNTs was shown to increase the current achieved in voltammetric …

Direct Ascorbic Acid Detection With Ferritin Immobilized On Single-Walled Carbon Nanotubes, Chonlada Dechakiatkrai, Jun Chen, Carol M. Lynam, Kwang Min Shin, Seon Jeong Kim, Sukon Phanichphant, Gordon G. Wallace

Gordon Wallace

Ferritin protein was noncovalently immobilized onto single-walled carbon nanotubes (SWNTs). This SWNT/ferritin composite was characterized using cyclic voltammetry, UV-visible spectroscopy, Raman spectroscopy, and high-resolution transmission electron microscopy. The use of the SWNT/ferritin film as an amperometric biosensor was demonstrated by sensing ascorbic acid in phosphate-buffered saline solution with a sensitivity of 767 uAmg. It demonstrated that ferritin protein bound to SWNTs enhances the oxidation reaction of ascorbic acid over 11-fold.

Sulfur-Mesoporous Carbon Composites In Conjunction With A Novel Ionic Liquid Electrolyte For Lithium Rechargeable Batteries, Jun Chen, Syed Ashraf, Sau Yen Chew, See How Ng, David Wexler, Jiazhao Wang, Hua Liu, Zhengwei Zhao, Shulei Chou

Shulei Chou

Sulfur coated mesoporous carbon (S-C) composites have been synthesized and physically characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and thermogravimetric analysis. Firstly, the electrochemical properties of the S-C composite cathode materials were tested in a conventional electrolyte consisting of 1 mol/L lithium bistrifluormethanesulfonimidate in poly(ethylene glycol) dimethyl ether to compare them with pure sulphur electrode. The capacity and cyclic stability of the S-C composite were improved. Then the S-C composites were tested in a novel ionic liquid electrolyte consisting of 1-ethyl-3-methylimidazolium bis(trifluromethanesulfonyl)imide and lithium

Flexible Free-Standing Carbon Nanotube Films For Model Lithium-Ion Batteries, Jun Chen, Sau Yen Chew, See How Ng, Jiazhao Wang, Hua Liu, P Novak, F Krumeich, Shulei Chou

Shulei Chou

No abstract provided.

The Loss Of Carbon Dioxide From Activated Perbenzoate Anions In The Gas Phase: Unimolecular Rearrangement Via Epoxidation Of The Benzene Ring, David G. Harman, Aravind Ramachandran, Michelle Gracanin, Stephen J. Blanksby

Stephen Blanksby

The unimolecular reactivities of a range of perbenzoate anions (X−C6H5CO3-), including the perbenzoate anion itself (X = H), nitroperbenzoates (X = para-, meta-, ortho-NO2), and methoxyperbenzoates (X = para-, meta-OCH3) were investigated in the gas phase by electrospray ionization tandem mass spectrometry. The collision-induced dissociation mass spectra of these compounds reveal product ions consistent with a major loss of carbon dioxide requiring unimolecular rearrangement of the perbenzoate anion prior to fragmentation. Isotopic labeling of the perbenzoate anion supports rearrangement via an initial nucleophilic aromatic substitution at the ortho carbon of the benzene ring, while data from substituted perbenzoates indicate that …

Towards Novel Entangled Carbon Nanotube Composite Electrodes, Gordon G. Wallace, P. Sherrell, J. Chen, A. Minett

Gordon Wallace

The commercialization of carbon nanotube electrodes is impeded by the lack of bulk processing techniques. One approach to overcome this impediment is the growth of macroscopic CNT composite architectures which do not require any extra processing. Unfortunately the fundamental growth mechanisms of these carbon composites is not currently understood. To probe this mechanism a systematic examination of the effect of certain growth parameters was undertaken. Within this paper we present the promising preliminary findings of this study revealing extremely complex relationships between variables during growth. We also present the performance of the produced architectures as capacitor electrodes and the further …

Top-Down Effects Of A Terrestrial Frog On Nutrient Dynamics, Karen H. Beard

Karen H. Beard

Many studies have found top-down effects of predators on prey, but few studies have linked top-down effects of vertebrate predators to nutrient cycling rates in terrestrial systems. In this study, large and significant effects of a terrestrial frog, Eleutherodactylus coqui (coqui), were recorded on nutrient concentrations and fluxes in a subtropical wet forest. In a manipulative experiment, coquis at natural densities were contained in or excluded from 1 m(3) enclosures for 4 months. Chemistry of leaf wash (throughfall), foliage, and decomposed leaf litter in the enclosures were measured as indicators of coqui effects on nutrient cycling. Coqui exclusion decreased elemental …

Organic Carbon Supply And Metabolism In A Shallow Groundwater Ecosystem, Michelle A. Baker

Michelle A. Baker

In groundwater ecosystems, in situ primary production is low, and metabolism depends on organic matter inputs from other regions of the catchment. Heterotrophic metabolism and biogeochemistry in the floodplain groundwater of a headwater catchment (Rio Calaveras, New Mexico, USA) were examined to address the following questions: (1) How do groundwater metabolism and biogeochemistry vary spatially and temporally? (2) What factors influence groundwater metabolism? (3) What is the energy source for groundwater metabolism?