Real-time particulate emissions rates from active and passive heavy-duty diesel particulate filter regeneration.

Periodic regeneration is required to clean the diesel particulate filter (DPF) of heavy-duty diesel vehicle. In this study we analyze real-time particulate matter (PM) mass, particle number, and black carbon emissions during steady state driving active and passive diesel particulate filter (DPF) regenerations on a heavy-duty chassis dynamometer. Regeneration PM emissions were dominated by particles with count median diameter<100nm, with the majority <50nm.

High-global warming potential F-gas emissions in California: comparison of ambient-based versus inventory-based emission estimates, and implications of refined estimates.

To provide information for greenhouse gas reduction policies, the California Air Resources Board (CARB) inventories annual emissions of high-global-warming potential (GWP) fluorinated gases, the fastest growing sector of greenhouse gas (GHG) emissions globally. Baseline 2008 F-gas emissions estimates for selected chlorofluorocarbons (CFC-12), hydrochlorofluorocarbons (HCFC-22), and hydrofluorocarbons (HFC-134a) made with an inventory-based methodology were compared to emissions estimates made by ambient-based measurements. Significant discrepancies were found, with the inventory-based emissions methodology resulting in a systematic 42% under-estimation of CFC-12 emissions from older refrigeration equipment and older vehicles, and a systematic 114% overestimation of emissions for HFC-134a, a refrigerant substitute for phased-out CFCs.

Migration forces of transcatheter aortic valves in patients with noncalcific aortic insufficiency.

Objective: Transcatheter aortic valves have been successfully implanted into the calcified leaflets of patients with severe aortic stenosis. However, their stability in patients with noncalcified aortic insufficiency is unknown. Similar to thoracic and abdominal aortic stent grafts, transcatheter aortic valves are subjected to antegrade ejection forces during systole.

Effect of advanced aftertreatment for PM and NO(x) control on heavy-duty diesel truck emissions.

Emissions from four heavy-duty and medium-duty diesel vehicles were tested in six different aftertreatment configurations using a chassis dynamometer. The aftertreatment included four different diesel particle filters (DPF) and two prototype selective catalytic reduction (SCR) devices for NO(x) control. The goal of the project was to fully characterize emissions from various in-use vehicles meeting the 2007 particulate matter (PM) standard for the United States and California and to provide a snapshot of emissions from 2010 compliant vehicles.

Computational fluid dynamics simulation of transcatheter aortic valve degeneration.

Objectives: Studied under clinical trials, transcatheter aortic valves (TAV) have demonstrated good short-term feasibility and results in high-risk surgical patients with severe aortic stenosis. However, their long-term safety and durability are unknown. The objective of this study is to evaluate hemodynamic changes within TAV created by bioprosthetic leaflet degeneration.

Asymmetric mechanical properties of porcine aortic sinuses.

Background: Aortic sinuses are crucial components of the aortic root and important for aortic valve function. Mathematical modeling of various aortic valve or root replacements requires tissue material properties, and those of the aortic sinuses are unknown. The aim of this study is to compare the biaxial mechanical properties of the individual porcine aortic sinuses.

Computational fluid dynamics within bifurcated abdominal aortic stent-grafts.

Purpose: To assess the hemodynamic forces on a bifurcated abdominal aortic stent-graft under realistic conditions of flow, blood pressure, and sac pressure.

Methods: Computational fluid dynamics was used to study the temporal and spatial variations in surface pressure and shear through the cardiac cycle on models of bifurcated stent-grafts derived from computed tomography in 4 patients who had previously undergone endovascular repair of abdominal aortic aneurysm (AAA). The trunk, bifurcation, and limbs of the graft were analyzed separately and as parts of a unified whole.

Effects of engine speed and accessory load on idling emissions from heavy-duty diesel truck engines.

A nontrivial portion of heavy-duty vehicle emissions of NOx and particulate matter (PM) occurs during idling. Regulators and the environmental community are interested in curtailing truck idling emissions, but current emissions models do not characterize them accurately, and little quantitative data exist to evaluate the relative effectiveness of various policies. The objectives of this study were to quantify the effect of accessory loading and engine speed on idling emissions from a properly functioning, modern, heavy-duty diesel truck and to compare these results with data from earlier model year vehicles.

Modeling of polychlorinated biphenyl removal from contaminated soil using steam.

Microwave-generated steam technology shows promise as an effective remediation alternative for removal of polychlorinated biphenyls (PCBs) from contaminated soils, based on our laboratory-scale experiments. The overall process can be described by a nonisothermal, unsteady, coupled heat and multicomponent PCB mass-transport model in a multiphase, variably saturated, porous soil medium. In this paper, a multicomponent PCB mass-transport model is presented that assumes evaporation is an important removal mechanism and that is based on first-order mass transfer between the interface of PCB films and the bulk steam.