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Carlson R.K.,Bethel University | Lee R.A.,Bethel University | Assam J.H.,Bethel University | King R.A.,Bethel University | Nagel M.L.,Penn State Greater Allegheny
Molecular Physics | Year: 2015

We report the results of a joint theoretical and experimental investigation into the copolymerisation of acrylamides and acrylates with α-olefins in free-radical processes. The transition-state structures of models for free-radical homo- and copolymerisation involving acrylamide, methylacrylamide, methacrylate, methyl methacrylate, and ethylene have been determined using density functional theory. The reaction energies and barrier heights comport with the experimentally observed properties, including the prevalence of monomer alternation, the realised stereospecificity, and the reaction yield. Continuum solvation models have been applied to determine the sensitivity of the relative energies to the bulk solvent properties. Experimentally, a Lewis acid catalyst is demonstrated to increase the incorporation of nonpolar 1-alkenes in copolymerisations with polar acrylamides and acrylates. In the presence of the Lewis acid, scandium (III) trifluoromethanesulfonate, the copolymerisation of 1-hexene and acrylamide results in an 8.5 mol % incorporation, up from 3.9 mol % in the absence of the Lewis acid. Computations incorporating Mg2+ as a model Lewis acid elucidate the mechanism of this catalysis. In the addition of methacrylate to a methyl methacrylate radical terminated polymer, the Lewis acid binds to the carbonyls on both promoting isotactic addition, while for the addition of an alkene to the same polymer, the Lewis acid binds to the polymer, reducing the barrier for alkenyl addition inductively by withdrawing electron density. We have demonstrated the ability of computational studies to aid experimentalists in the synthesis of new copolymers with desired properties. © 2015 Taylor & Francis.

Lindsey B.A.,Penn State Greater Allegheny | Liu A.Y.,Georgetown University
American Journal of Physics | Year: 2013

Many studies have separately documented the benefits of research-based curricula and pedagogical methods. Here, we report on the effects of adopting a reform curriculum (Matter and Interactions) in conjunction with a pedagogical tool designed and validated in the context of a traditional treatment of mechanics (Tutorials in Introductory Physics). We document the need for targeted interactive engagement materials (such as the tutorials) even in a course with a population of students who are extremely well-prepared in physics. We describe the modifications necessary to successfully incorporate Tutorials in Introductory Physics into a course using Matter and Interactions, and we present data documenting the success of this approach. © 2013 American Association of Physics Teachers.

Miracolo M.A.,Carnegie Mellon University | Hennigan C.J.,Carnegie Mellon University | Ranjan M.,Carnegie Mellon University | Nguyen N.T.,Carnegie Mellon University | And 5 more authors.
Atmospheric Chemistry and Physics | Year: 2011

Field experiments were performed to investigate the effects of photo-oxidation on fine particle emissions from an in-use CFM56-2B gas turbine engine mounted on a KC-135 Stratotanker airframe. Emissions were sampled into a portable smog chamber from a rake inlet installed one-meter downstream of the engine exit plane of a parked and chocked aircraft. The chamber was then exposed to sunlight and/or UV lights to initiate photo-oxidation. Separate tests were performed at different engine loads (4, 7, 30, 85 %). Photo-oxidation created substantial secondary particulate matter (PM), greatly exceeding the direct PM emissions at each engine load after an hour or less of aging at typical summertime conditions. After several hours of photo-oxidation, the ratio of secondary-to-primary PM mass was on average 35 ± 4.1, 17 ± 2.5, 60 ± 2.2, and 2.7 ± 1.1 for the 4, 7, 30, and 85 % load experiments, respectively. The composition of secondary PM formed strongly depended on load. At 4 % load, secondary PM was dominated by secondary organic aerosol (SOA). At higher loads, the secondary PM was mainly secondary sulfate. A traditional SOA model that accounts for SOA formation from single-ring aromatics and other volatile organic compounds underpredicts the measured SOA formation by ∼60 % at 4 % load and ∼40 % at 85 % load. Large amounts of lower-volatiliy organic vapors were measured in the exhaust; they represent a significant pool of SOA precursors that are not included in traditional SOA models. These results underscore the importance of accounting for atmospheric processing when assessing the influence of aircraft emissions on ambient PM levels. Models that do not account for this processing will likely underpredict the contribution of aircraft emissions to local and regional air pollution. © 2011 Author(s).

Nagel M.L.,Penn State Greater Allegheny | Lindsey B.A.,Penn State Greater Allegheny
Chemistry Education Research and Practice | Year: 2015

This paper describes an interdisciplinary investigation of students' usage of ideas about energy from physics in the context of introductory chemistry. We focus on student understanding of the idea that potential energy is a function of distance between interacting objects, a concept relevant to understanding potential energy in both physical and chemical contexts. Data from student responses to written surveys and focus-group interviews reveal that students do not spontaneously make connections between ideas they have about energy from physics classes and the understanding of energy that they develop in chemistry. We describe the development of a sequence of questions that appears to aid students in drawing these connections appropriately. We also document students' as they are confronted with and struggle to resolve the mismatch between their energy ideas from physics and chemistry. © 2015 The Royal Society of Chemistry.

Drozd G.T.,Carnegie Mellon University | Miracolo M.A.,Carnegie Mellon University | Presto A.A.,Carnegie Mellon University | Lipsky E.M.,Penn State Greater Allegheny | And 3 more authors.
Energy and Fuels | Year: 2012

Particle and gaseous emissions from a T63 gas-turbine engine were characterized using three fuels: standard military jet fuel (JP-8), Fischer-Tropsch (FT) synthetic fuel, and a 50:50 blend of each. Primary emissions were sampled using a dilution tunnel and sampling trains with both filters and sorbent tubes. Primary particulate matter (PM) and gaseous emissions for the neat FT and blend fuels were reduced relative to emissions when using JP-8 fuel at both idle and cruise loads. At idle load, PM mass emissions are reduced by 65% with neat FT fuel and by 50% for the 50:50 blend compared to neat JP-8 fuel. The JP-8/FT blend thus decreases emissions beyond the linear average of the emissions for the individual fuels. At idle load, FT fuel reduced total hydrocarbon emissions by 20%, while the blend showed no significant change compared to neat JP-8. At cruise load, neat FT fuel resulted in an 80% reduction in primary PM emissions and a 30% reduction in total hydrocarbon emissions compared to neat JP-8. Decreases in PM emissions at idle load come from lower elemental carbon (EC) and primary organic aerosol (POA), while at cruise load emissions, reductions are driven mainly by EC. Gas chromatography-mass spectrometry (GC-MS) and thermo-optical analysis of filter samples indicate that engine oil comprises a significant fraction of the POA emissions. When using FT fuel, POA emissions appear to be largely engine oil, but emissions with JP-8 fuel have a large fraction of partially oxidized organic material. The differences in POA composition may be due to both the presence of partially oxidized fuel as well as greater EC/soot levels when using JP-8 fuel. Thermodenuder and GC-MS measurements indicate that the POA emissions are semi-volatile; therefore, dynamic gas-particle partitioning will alter the contribution of primary emissions to ambient PM. Total gas-phase hydrocarbon emissions greatly outweigh POA emissions, and applying even moderate yields of secondary organic aerosol (SOA) will dominate over POA emissions. A high abundance of unsaturated volatile organic compounds (VOCs) in the gaseous emissions will enhance oxidation chemistry in the exhaust plume and promote the formation of SOA. © 2012 American Chemical Society.

Presto A.A.,Carnegie Mellon University | Nguyen N.T.,Carnegie Mellon University | Ranjan M.,Carnegie Mellon University | Reeder A.J.,Carnegie Mellon University | And 5 more authors.
Atmospheric Environment | Year: 2011

Staged tests were conducted to measure the particle and vapor emissions from a CFM56-2B1 gas-turbine engine mounted on a KC-135T Stratotanker airframe at different engine loads. Exhaust was sampled using a rake inlet installed 1-m downstream of the engine exit plane of a parked and chocked aircraft and a dilution sampler and portable smog chamber were used to investigate the particulate matter (PM) emissions. Total fine PM mass emissions were highest at low (4%) and high (85%) load and lower at intermediate loads (7% and 30%). PM mass emissions at 4% load are dominated by organics, while at 85% load elemental carbon is dominant. Quantifying the primary organic aerosol (POA) emissions is complicated by substantial filter sampling artifacts. Partitioning experiments reveal that the majority of the POA is semivolatile; for example, the POA emission factor changed by a factor of two when the background organic aerosol concentration was increased from 0.7 to 4μgm-3. Therefore, one cannot define a single non-volatile PM emission factor for aircraft exhaust. The gas- and particle-phase organic emissions were comprehensively characterized by analyzing canister, sorbent and filter samples with gas-chromatography/mass-spectrometry. Vapor-phase organic emissions are highest at 4% load and decrease with increasing load. Low-volatility organics (less volatile than a C12 n-alkane) contributed 10-20% of the total organic emissions. The low-volatility organic emissions contain signatures of unburned fuel and aircraft lubricating oil but are dominated by an unresolved complex mixture (UCM) of presumably branched and cyclic alkanes. Emissions at all loads contain more low-volatility organic vapors than POA; thus secondary organic aerosol formation in the aging plume will likely exceed POA emissions. © 2011 Elsevier Ltd.

Nagel M.L.,Penn State Greater Allegheny
Journal of Chemical Education | Year: 2013

A trip to the mall is used as a classroom demonstration to illustrate the fundamentals of separations without the need for chemicals or any chemistry background. Student volunteers are the "mixture", and depending on the shopping list they have been given, they spend varying amounts of time in the "stores" versus moving through and out of the "mall", as the instructor reads all of the possible shopping stops aloud. In less than 10 minutes, the students observe the separation of the "mixture" into distinct groups, see how this can be represented graphically, and may then apply the knowledge to chemical separations. © 2012 The American Chemical Society and Division of Chemical Education, Inc.

Miracolo M.A.,Carnegie Mellon University | Drozd G.T.,Carnegie Mellon University | Jathar S.H.,Carnegie Mellon University | Presto A.A.,Carnegie Mellon University | And 3 more authors.
Environmental Science and Technology | Year: 2012

A series of smog chamber experiments were performed to investigate the effects of fuel composition on secondary particulate matter (PM) formation from dilute exhaust from a T63 gas-turbine engine. Tests were performed at idle and cruise loads with the engine fueled on conventional military jet fuel (JP-8), Fischer-Tropsch synthetic jet fuel (FT), and a 50/50 blend of the two fuels. Emissions were sampled into a portable smog chamber and exposed to sunlight or artificial UV light to initiate photo-oxidation. Similar to previous studies, neat FT fuel and a 50/50 FT/JP-8 blend reduced the primary particulate matter emissions compared to neat JP-8. After only one hour of photo-oxidation at typical atmospheric OH levels, the secondary PM production in dilute exhaust exceeded primary PM emissions, except when operating the engine at high load on FT fuel. Therefore, accounting for secondary PM production should be considered when assessing the contribution of gas-turbine engine emissions to ambient PM levels. FT fuel substantially reduced secondary PM formation in dilute exhaust compared to neat JP-8 at both idle and cruise loads. At idle load, the secondary PM formation was reduced by a factor of 20 with the use of neat FT fuel, and a factor of 2 with the use of the blend fuel. At cruise load, the use of FT fuel resulted in no measured formation of secondary PM. In every experiment, the secondary PM was dominated by organics with minor contributions from sulfate when the engine was operated on JP-8 fuel. At both loads, FT fuel produces less secondary organic aerosol than JP-8 because of differences in the composition of the fuels and the resultant emissions. This work indicates that fuel reformulation may be a viable strategy to reduce the contribution of emissions from combustion systems to secondary organic aerosol production and ultimately ambient PM levels. © 2012 American Chemical Society.

Gordon T.D.,Carnegie Mellon University | Gordon T.D.,National Oceanic and Atmospheric Administration | Gordon T.D.,University of Colorado at Boulder | Presto A.A.,Carnegie Mellon University | And 13 more authors.
Atmospheric Chemistry and Physics | Year: 2014

The effects of photochemical aging on emissions from 15 light-duty gasoline vehicles were investigated using a smog chamber to probe the critical link between the tailpipe and ambient atmosphere. The vehicles were recruited from the California in-use fleet; they represent a wide range of model years (1987 to 2011), vehicle types and emission control technologies. Each vehicle was tested on a chassis dynamometer using the unified cycle. Dilute emissions were sampled into a portable smog chamber and then photochemically aged under urban-like conditions. For every vehicle, substantial secondary organic aerosol (SOA) formation occurred during cold-start tests, with the emissions from some vehicles generating as much as 6 times the amount of SOA as primary particulate matter (PM) after 3 h of oxidation inside the chamber at typical atmospheric oxidant levels (and 5 times the amount of SOA as primary PM after 5 × 106 molecules cm-3 h of OH exposure). Therefore, the contribution of light-duty gasoline vehicle exhaust to ambient PM levels is likely dominated by secondary PM production (SOA and nitrate). Emissions from hot-start tests formed about a factor of 3-7 less SOA than cold-start tests. Therefore, catalyst warm-up appears to be an important factor in controlling SOA precursor emissions. The mass of SOA generated by photooxidizing exhaust from newer (LEV2) vehicles was a factor of 3 lower than that formed from exhaust emitted by older (pre-LEV) vehicles, despite much larger reductions (a factor of 11-15) in nonmethane organic gas emissions. These data suggest that a complex and nonlinear relationship exists between organic gas emissions and SOA formation, which is not surprising since SOA precursors are only one component of the exhaust. Except for the oldest (pre-LEV) vehicles, the SOA production could not be fully explained by the measured oxidation of speciated (traditional) SOA precursors. Over the timescale of these experiments, the mixture of organic vapors emitted by newer vehicles appears to be more efficient (higher yielding) in producing SOA than the emissions from older vehicles. About 30% of the nonmethane organic gas emissions from the newer (LEV1 and LEV2) vehicles could not be speciated, and the majority of the SOA formed from these vehicles appears to be associated with these unspeciated organics. By comparing this study with a companion study of diesel trucks, we conclude that both primary PM emissions and SOA production for light-duty gasoline vehicles are much greater than for late-model (2007 and later) on-road heavy-duty diesel trucks. © 2014 Author (s).

Lindsey B.A.,Penn State Greater Allegheny | Heron P.R.L.,University of Washington | Shaffer P.S.,University of Washington
American Journal of Physics | Year: 2012

Choosing a system of interest and identifying the interactions of the system with its environment are crucial steps in applying the relation between work and energy. Responses to problems that we administered in introductory calculus-based physics courses show that many students fail to recognize the implications of a particular choice of system. In some cases, students do not believe that particular groupings of objects can even be considered to be a system. Some errors are more prevalent in situations involving gravitational potential energy than elastic potential energy. The difficulties are manifested in both qualitative and quantitative reasoning. © 2012 American Association of Physics Teachers.

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