Development and Optimization of NOx Reduction Catalysts using Statistical Analysis

Work placed 3rd at Denman Undergraduate Research ForumIncreasing regulation and a push towards fuel-efficient automobile engines has driven the development of new NOx emission removal technology for natural gas reciprocating engines and diesel engines. While many technologies have been developed, one of the more promising advances has been the patented dual catalyst approach, which both oxidizes and reduces NOx in the presence of a reducing agent. The system operates by first oxidizing nitrogen monoxide to nitrogen dioxide over a cobalt-based catalyst, and then reducing the nitrogen dioxide to nitrogen over a reducing palladium-based catalyst under the presence of methane (reducing agent). The process is based on findings that it is thermodynamically easier to reduce nitrogen dioxide than nitrogen monoxide and the dual catalyst has shown experimentally to obtain nitrogen yields of close to 90% when operating under simulated exhaust conditions. While the approach has been effective in reducing NOx under dry conditions, the reduction catalyst has shown to deactivate in the presence of water vapor, a common component in engines. This report focuses on the development of new, water-resistant, reduction catalyst formulations that are active for NOx reduction with the emphasis on activity. Two pathways were chosen for the synthesis of new catalysts. The first pathway focused on modifying the preparation technique from incipient wetness impregnation to sol-gel technique, which changed the preparation from a physical route to a chemical route. Several levels of alkoxide concentration and nominal sulfuric acid loading were studied to see how these sol-gel parameters impacted surface area, pore volume, and activity. ANOVA and regression modeling were used as a method to determine parameter significance and for optimization work. Results indicated that the nominal sulfate loading heavily impacted the surface area and pore volume with a maximum occurring in the system that may be linked to monolayer surface coverage of sulfate. The alkoxide concentration was less important but the analysis indicated the presence of an interaction effect between the sulfate and alkoxide concentration. XPS data taken on these indicates that samples prepared with an alkoxide concentration/sulfuric acid ratio (sulfate ratio) of 2 retained the most sulfur after calcination, which was in disagreement with the best-obtained surface area and pore volume. Activity testing ran the new reduction catalysts across a nitrogen dioxide, oxygen, and methane stream to test for nitrogen yield. Results showed that temperature was the primary effect in NOx selective catalytic reduction with alkoxide concentration and sulfate ratio following. Significant interactions were present with a change in one factor affecting others. The sample with a sulfate ratio of 2 and an alkoxide concentration of 1 molar had the best yield though ANOVA showed this point to be a statistical outlier, which added emphasis to the XPS data of maximum sulfur retention. In general, the model showed that increases in alkoxide concentration and increases in the nominal sulfate loading increased NOx reduction activity, though the interactions complicated this system. The second pathway focused on changing the catalytic support from zirconia to ceria on incipient wetness prepared Pd-based catalysts. Ceria has been shown to be more hydrophobic that zirconia and has been active in other catalyzed reactions. Several catalysts were prepared that varied the palladium loading and sulfate loading on the samples to see how these parameters impacted nitrogen dioxide reduction. Results indicated that all samples failed to show activity and further work is being accomplished to change the formulation.No embarg

Dyslipidemia impairs mitochondrial trafficking and function in sensory neurons

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154247/1/fsb2fj201700206r.pd

Electron-hole crossover in gate-controlled bilayer graphene quantum dots

Electron and hole Bloch states in gapped bilayer graphene exhibit topological orbital magnetic moments with opposite signs near the band edges, which allows for tunable valley-polarization in an out-of-plane magnetic field. This intrinsic property makes electron and hole quantum dots (QDs) in bilayer graphene interesting for valley and spin-valley qubits. Here we show measurements of the electron-hole crossover in a bilayer graphene QD, demonstrating the opposite sign of the orbital magnetic moments associated with the Berry curvature. Using three layers of metallic top gates, we independently control the tunneling barriers of the QD while tuning the occupation from the few-hole regime to the few-electron regime, crossing the displacement-field controlled band gap. The band gap is around 25 meV, while the charging energies of the electron and hole dots are between 3-5 meV. The extracted valley g-factor is around 17 and leads to opposite valley polarization for electron and hole states at moderate B-fields. Our measurements agree well with tight-binding calculations for our device

A phase II evaluation of nanoparticle, albumin-bound (nab) paclitaxel in the treatment of recurrent or persistent platinum-resistant ovarian, fallopian tube, or primary peritoneal cancer: A Gynecologic Oncology Group Study

Nab-paclitaxel is a novel Cremophor®-free nanoparticle of albumin-stabilized paclitaxel, which has favorable efficacy and toxicity characteristics relative to other solvent-based taxanes, such as paclitaxel and docetaxel

Catching Element Formation In The Act

Gamma-ray astronomy explores the most energetic photons in nature to address some of the most pressing puzzles in contemporary astrophysics. It encompasses a wide range of objects and phenomena: stars, supernovae, novae, neutron stars, stellar-mass black holes, nucleosynthesis, the interstellar medium, cosmic rays and relativistic-particle acceleration, and the evolution of galaxies. MeV gamma-rays provide a unique probe of nuclear processes in astronomy, directly measuring radioactive decay, nuclear de-excitation, and positron annihilation. The substantial information carried by gamma-ray photons allows us to see deeper into these objects, the bulk of the power is often emitted at gamma-ray energies, and radioactivity provides a natural physical clock that adds unique information. New science will be driven by time-domain population studies at gamma-ray energies. This science is enabled by next-generation gamma-ray instruments with one to two orders of magnitude better sensitivity, larger sky coverage, and faster cadence than all previous gamma-ray instruments. This transformative capability permits: (a) the accurate identification of the gamma-ray emitting objects and correlations with observations taken at other wavelengths and with other messengers; (b) construction of new gamma-ray maps of the Milky Way and other nearby galaxies where extended regions are distinguished from point sources; and (c) considerable serendipitous science of scarce events -- nearby neutron star mergers, for example. Advances in technology push the performance of new gamma-ray instruments to address a wide set of astrophysical questions.Comment: 14 pages including 3 figure

Lymphatic Mapping and Sentinel Lymph Node Biopsy in Women With Squamous Cell Carcinoma of the Vulva: A Gynecologic Oncology Group Study

To determine the safety of sentinel lymph node biopsy as a replacement for inguinal femoral lymphadenectomy in selected women with vulvar cancer

Is bilateral lymphadenectomy for midline squamous carcinoma of the vulva always necessary? An analysis from Gynecologic Oncology Group (GOG) 173

To determine which patients with near midline lesions may safely undergo unilateral groin dissection based on clinical exam and lymphoscintigraphy (LSG) results

Language endangerment and language documentation in Africa

Non peer reviewe