Metal-Oxide Nanostructures Fabricated from Laser-Assisted Synthesis Technique

Background Rising levels of greenhouse gases in our atmosphere such as CO 2 are contributing to global rises in temperature, acidification of the oceans, and more extreme weather conditions. Hydrogenation of CO 2 to form carbon-based products is of great importance to reduce CO 2 levels and generate carbon-based compounds that can be used for industrial purposes. Copper- and nickel- based nanocatalysts have promising catalytic activity toward CO 2 hydrogenation, and have great interest to replace expensive and rare Pt- and Pd-based catalysts. Methods Focusing high powered laser pulses onto the surface of a silicon wafer immersed in liquid solutions containing nickel nitrate or copper nitrate in alkaline media leads to the formation of Cu, Ni or copper-nickel phyllosilicates (PS). The laser pulses remove Si atoms from the wafer, allowing them to interact with the surrounding liquid where the Cu 2+ or Ni 2+ ions incorporate themselves into the forming phyllosilicate structure. The well-dispersed Cu and Ni atoms throughout the structure lead to a highly catalytically active material. Results The Cu-PS and Ni-PS nanostructures were synthesized, and the formation mechanisms from different experimental parameters were investigated. The Cu-PS selectively converted CO 2 to methanol below 500ºC, and formed methanol and methane above 500ºC. Conclusions The synthesis of Cu-PS and Ni-PS nanostructured catalysts were achieved using a reactive laser ablation in liquid technique, and the products displayed catalytic activity toward the hydrogenation of CO 2 , with temperature-dependent selectivity toward methanol and methane.https://scholarscompass.vcu.edu/gradposters/1095/thumbnail.jp

Consequences of Categorical Labeling of Preschool Children

The use of categorical diagnostic labels prescribed in P.L. 94--142 with children below school age is examined in this article. National practices relative to categorical labeling are reviewed, and questions are posed concerning the consequences of categorical labeling for children from 3 to 6 years old. Data from the state of New Hampshire concerning the frequency of usage for specific categorical labels are presented and are found to be consistent with national trends. Data are presented on the number of children who transition from non-categorical early intervention programs serving children birth to 3 years into categorical preschool programs for children 3 through 5 years. Almost one-third of all children served in early intervention are found not to be eligible for preschool services because of the requirement for a categorical label. The roles of demographic factors related to place of residence, age, and local school policies in deciding who is eligible for services and what diagnostic category is assigned, were considered. Finally, the consequences of categorical labeling for children, parents, and programs are discussed

Distributed allocation of mobile sensing swarms in gyre flows

We address the synthesis of distributed control policies to enable a swarm of homogeneous mobile sensors to maintain a desired spatial distribution in a geophysical flow environment, or workspace. In this article, we assume the mobile sensors (or robots) have a "map" of the environment denoting the locations of the Lagrangian coherent structures or LCS boundaries. Based on this information, we design agent-level hybrid control policies that leverage the surrounding fluid dynamics and inherent environmental noise to enable the team to maintain a desired distribution in the workspace. We establish the stability properties of the ensemble dynamics of the distributed control policies. Since realistic quasi-geostrophic ocean models predict double-gyre flow solutions, we use a wind-driven multi-gyre flow model to verify the feasibility of the proposed distributed control strategy and compare the proposed control strategy with a baseline deterministic allocation strategy. Lastly, we validate the control strategy using actual flow data obtained by our coherent structure experimental testbed.Comment: 10 pages, 14 Figures, added reference

Novel microfluidic devices for aerosol analysis

2012 Spring.Includes bibliographical references.Widespread interest in microfluidic technology over the past 20 years has led to the development of microfluidic devices that are as varied in their complexity and capabilities as they are in the applications they are used for. This dissertation describes the development of two microfluidic devices, each designed for measurement of specific aerosol components. A microchip incorporating an interface between a continuous hydrodynamic sample flow and capillary electrophoresis separation was developed for analysis of atmospheric aerosols. The ability to separate and detect analytes from a continuous sample flow allows the microchip to be coupled to a particle-into-liquid aerosol sampler, providing a method for near real-time analysis of ionic aerosol components. Theoretical modeling of hydrodynamic and electroosmotic flows was used to predict flow behavior in the microchip and to optimize geometry. Separation and conductivity detection of common ionic aerosol components were carried out to observe device performance, and detection of nitrate and sulfate in Fort Collins air was accomplished with the coupled system. The simple design introduced here is the first example of a continuous flow microfluidic capillary electrophoresis device that incorporates conductivity detection, and is the first microfluidic device to be coupled to a continuous flow aerosol collector. A paper-based microfluidic device was also designed for the purpose of assessing occupational exposure to particulate metals. Assays were developed for colorimetric detection of metals on paper and these were employed in detection reservoirs of the device. A novel method was also developed for rapid digestion of particulate metals directly on a filter. Metal concentrations were quantified from color intensity images using a scanner in conjunction with image processing software. Finally, a standard incineration ash sample was aerosolized, collected on filters, and analyzed for the three metals of interest. This is the first paper-based device capable of multiplexed metal detection from a real, aerosolized sample

Roles of Free Electrons and H2O2 in the Optical Breakdown-Induced Photochemical Reduction of Aqueous [AuCl4]-

Free electrons and H2O2 formed in an optical breakdown plasma are found to directly control the kinetics of [AuCl4]− reduction to form Au nanoparticles (AuNPs) during femtosecond laser-assisted synthesis of AuNPs. The formation rates of both free electrons and H2O2 strongly depend on the energy and duration of the 800 nm laser pulses over the ranges of 10−2400 μJ and 30−1500 fs. By monitoring the conversion of [AuCl4]− to AuNPs using in situ UV−vis spectroscopy during laser irradiation, the first- and second-order rate constants in the autocatalytic rate law, k1 and k2, were extracted and compared to the computed free electron densities and experimentally measured H2O2 formation rates. For laser pulse energies of 600 μJ and lower at all pulse durations, the first-order rate constant, k1, was found to be directly proportional to the theoretically calculated plasma volume, in which the electron density exceeds the threshold value of 1.8 × 1020 cm−3. The second-order rate constant, k2, was found to correlate with the measured H2O2 formation rate at all pulse energies and durations, resulting in the empirical relationship k2 ≈ H2O20.5. We have demonstrated that the relative composition of free electrons and H2O2 in the optical breakdown plasma may be controlled by changing the pulse energy and duration, which may make it possible to tune the size and dispersity of AuNPs and other metal nanoparticle products synthesized with femtosecond laser-based methods

Portal vein thrombosis after laparoscopic splenectomy: an ongoing clinical challenge.

ObjectivesPortal vein thrombosis (PVT) following open splenectomy is a potentially lethal complication with an incidence of up to 6%. The objective of this report is to describe our management of a recent laparoscopic case, discuss current therapies, and consider antiplatelet therapy for prophylaxis.MethodsMedical records, laboratory studies, and imaging studies pertaining to a recent case of a laparoscopic splenectomy were examined. Current literature related to this topic was reviewed.ResultsA 16-year-old girl underwent laparoscopic splenectomy for idiopathic thrombocytopenic purpura. Her preoperative platelet count was 96K. She was discharged on postoperative day 1 after an uneventful operation including division of the splenic hilum with an endoscopic linear stapler. On postoperative day 20, she presented with a 5-day history of epigastric pain, nausea, and low-grade fevers without peritoneal signs. Her white blood cell count was 17.3; her platelets were 476K. Computed tomography demonstrated thrombosis of the splenic, superior mesenteric, and portal veins propagating into the liver. Heparinization was begun followed by an unsuccessful attempt at pharmacologic and mechanical thrombolysis by interventional radiology. Over the next 5 days, her pain resolved, she tolerated a full diet, was converted to oral anticoagulation and sent home. Follow-up radiographic studies demonstrated the development of venous collaterals and cavernous transformation of the portal vein.DiscussionNo standard therapy for PVT exists; several approaches have been described. These include systemic anticoagulation, systemic or regional medical thrombolysis, mechanical thrombolysis, and surgical thrombectomy. Unanswered questions exist about the most effective acute therapy, duration of anticoagulation, and the potential efficacy of routine prophylaxis with perioperative antiplatelet agents. PVT following splenectomy occurs with both the open and laparoscopic approach