Nima Afshar-Mohajer

Efficiency determination of an electrostatic lunar dust collector by discrete element method

Lunar grains become charged by the sun’s radiation in the tenuous atmosphere of the moon. This leads to lunar dust levitation and particle deposition which often create serious problems in the costly system deployed in lunar exploration. In this study, an electrostatic lunar dust collector (ELDC) is proposed to address the issue and the discrete element method (DEM) is used to investigate the effects of electrical particle-particle interactions, non-uniformity of the electrostatic field, and characteristics of the ELDC. The simulations on 20-μm-sized lunar particles reveal the electrical particle-particle interactions of the dust particles within the ELDC plates require 29% higher electrostatic field strength than that without the interactions for 100% collection efficiency. For the given ELDC geometry, consideration of non-uniformity of the electrostatic field along with electrical interactions between particles on the same ELDC geometry leads to a higher requirement of ∼3.5 kV/m to ensure 100% particle ...

Acute and chronic in vivo effects of exposure to nicotine and propylene glycol from an E-cigarette on mucociliary clearance in a murine model

Abstract Objective: To determine the effect of an acute (1 week) and chronic (3 weeks) exposure to E-cigarette (E-cig) emissions on mucociliary clearance (MCC) in murine lungs. Methods: C57BL/6 male mice (age 10.5 ± 2.4 weeks) were exposed for 20 min/day to E-cigarette aerosol generated by a Joyetech 510-T® E-cig containing either 0% nicotine (N)/propylene glycol (PG) for 1 week (n = 6), or 3 weeks (n = 9), or 2.4% N/PG for one week (n = 6), or 3 weeks (n = 9), followed by measurement of MCC. Control mice (n = 15) were not exposed to PG alone, or N/PG. MCC was assessed by gamma camera following aspiration of 99mtechnetium aerosol and was expressed as the amount of radioactivity removed from both lungs over 6 hours (MCC6hrs). Venous blood was assayed for cotinine levels in control mice and in mice exposed for 3-weeks to PG alone and N/PG. Results: MCC6hrs in control mice and in mice acutely exposed to PG alone and N/PG was similar, averaging (±1 standard deviation) 8.6 ± 5.2%, 7.5 ± 2.8% and 11.2 ± 5.9%, respectively. In contrast, chronic exposure to PG alone stimulated MCC6hrs (17.2 ± 8.0)% and this stimulation was significantly blunted following chronic exposure to N/PG (8.7 ± 4.6)% (p < .05). Serum cotinine levels were <0.5 ng/ml in control mice and in mice exposed to PG alone, whereas, N/PG exposed mice averaged 14.6 ± 12.0 ng/ml. Conclusions: In this murine model, a chronic, daily, 20 min-exposure to N/PG, but not an acute exposure, slowed MCC, compared to exposure to PG alone and led to systemic absorption of nicotine.

Evaluation of low-cost electro-chemical sensors for environmental monitoring of ozone, nitrogen dioxide, and carbon monoxide

ABSTRACT Development of an air quality monitoring network with high spatio-temporal resolution requires installation of a large number of air pollutant monitors. However, state-of-the-art monitors are costly and may not be compatible with wireless data logging systems. In this study, low-cost electro-chemical sensors manufactured by Alphasense Ltd. for detection of CO and oxidative gases (predominantly O3 and NO2) were evaluated. The voltages from three oxidative gas sensors and three CO sensors were recorded every 2.5 sec when exposed to controlled gas concentrations in a 0.125-m3 acrylic glass chamber. Electro-chemical sensors for detection of oxidative gases demonstrated sensitivity to both NO2 and O3 with similar voltages recorded when exposed to equivalent environmental concentrations of NO2 or O3 gases, when evaluated separately. There was a strong linear relationship between the recorded voltages and target concentrations of oxidative gases (R2 > 0.98) over a wide range of concentrations. Although a strong linear relationship was also observed for CO concentrations below 12 ppm, a saturation effect was observed wherein the voltage only changes minimally for higher CO concentrations (12–50 ppm). The nonlinear behavior of the CO sensors implied their unsuitability for environments where high CO concentrations are expected. Using a manufacturer-supplied shroud, sensors were tested at 2 different flow rates (0.25 and 0.5 Lpm) to mimic field calibration of the sensors with zero air and a span gas concentration (2 ppm NO2 or 15 ppm CO). As with all electrochemical sensors, the tested devices were subject to drift with a bias up to 20% after 9 months of continuous operation. Alphasense CO sensors were found to be a proper choice for occupational and environmental CO monitoring with maximum concentration of 12 ppm, especially due to the field-ready calibration capability. Alphasense oxidative gas sensors are usable only if it is valuable to know the sum of the NO2 and O3 concentrations.

Efficiency Evaluation of an Electrostatic Lunar Dust Collector

The accumulation of solar-based charges on lunar grains leads to levitation of the like charged particles. The lunar dust deposit on sensitive and costly surfaces of investigative equipment is a serious concern for lunar missions. Benefitting from the inherent trait of lunar particles which are naturally charged, an electrostatic lunar dust collector (ELDC) is hypothesized by this study as a highly efficient way for particle collection and equipment protection in the vacuum. The idea is a grid layer of charged conducting plates in front of the surface to be protected to provide the electrostatic field. Discrete Element Method (DEM) was applied to investigate the effect of electrical particle interactions on collection efficiency. Validation of this Lagrangian-based model was done by comparing to the analytical collection efficiency equation (Eulerian-based model) in the absence of electrical particle interactions. Then, electrostatic screening feature was turned on to address the difference in collection efficiency. The obtained results from Lagrangian-based method were close to the Eulerian-based solutions and indicated a small reduction in collection efficiency compared to the predicted analytical results. At the worst case scenario, all the 100-μm-sized particles would be collected by providing approximate electric field 6.4 kV/m. Both the Eulerian-based and Lagrangian-based methods confirm the adequacy of the proposed system for prospective applications.

Within-day and between-day reliability of thickness measurements of abdominal muscles using ultrasound during abdominal hollowing and bracing maneuvers

Ultrasonography imaging has been used as a non-invasive method to estimate the thickness and relative activities of the abdominal muscles in patients with lower back pain (LBP). However, the statistical reliability of US thickness measurements of abdominal muscles, including transversus abdominis (TrA), internal oblique (IO) and external oblique (EO) muscles during abdominal hollowing (AH) and abdominal bracing (AB) maneuvers has not been well-investigated. This study was performed on a total of 20 female subjects (10 with LBP and 10 without LBP) in the age range of 25-55 years to assess within-day and between-day reliability of the measurements. US measurements on maneuvers were repeated after two hours for the within-day reliability and after five days for the between-day reliability assessment. High intra-class correlation coefficient (ICC) values (>0.75) for within-day and between-day reliability assessments during AH maneuver were concluded. The ICC values were moderate for reliability assessment during AB. The ICC values for AH were greater than AB both for within- and between-day reliabilities. The small standard error of measurement and minimal detectable change values (0.16-0.78 and 0.44 to 2.15, respectively) were found for both AH and AB. We recommend real-time US imaging as a reliable way of determining the thicknesses of the TrA and IO muscle (and to some extent, EO muscle) for both healthy and LBP patients.

Source apportionment of atmospheric polycyclic aromatic hydrocarbons (PAHs) in Palm Beach County, Florida.

ABSTRACT Due to concerns about adverse health effects associated with inhalation of atmospheric polycyclic aromatic hydrocarbons (PAHs), 30 ambient air samples were obtained at an air quality monitoring station in Palm Beach County, Florida, from March 2013 to March 2014. The ambient PAH concentration measurements and fractional emission rates of known sources were incorporated into a chemical mass balance model, CMB8.2, developed by EPA, to apportion contributions of three major PAH sources including preharvest sugarcane burning, mobile vehicles, and wildland fires. Strong association between the number of benzene rings and source contribution was found, and mobile vehicles were identified to be the prevailing source (contribution ≥56%) for the observed PAHs concentration with lower molecular weights (four or fewer benzene rings) throughout the year. Preharvest sugarcane burning was the primary contributing source for PAHs with relatively higher molecular weights (five or more benzene rings) during the sugarcane burning season (from October to May of the next year). Source contribution of wildland fires varied among PAH compounds but was consistently lower than for sugarcane burning during the sugarcane harvest season. Determining the major sources responsible for ground-level PAHs serves as a tool to improving management strategies for PAH emitting sources and a step toward better protection of the health of residents in terms of exposure to PAHs. The results obtain insight into temporal dominance of PAH polluting sources for those residential areas located near sugarcane burning facilities and have implications beyond Palm Beach County, in areas with high concerns of PAHs and their linked sources. Implications: Source apportionment of atmospheric polycyclic hydrocarbons (PAHs) in Palm Beach County, Florida, meant to estimate contributions of major sources in PAH concentrations measured at Belle Glade City of Palm Beach County. Number of benzene rings was found to be the key parameter in determining the source with the prevailing contribution. Mobile vehicle sources showed a higher contribution for species with four or fewer benzene rings, whereas sugarcane burning contributed more for species with five or more benzene rings. Results from this study encourage more control for sugarcane burns and help to better manage authorization of the sugarcane burning incidents and more restrictive transportation plans to limit PAH emissions from mobile vehicles.

An efficient virus aerosol sampler enabled by adiabatic expansion

Abstract Protection of public health against pathogenic viruses transmitted through the airborne route requires effective sampling of airborne viruses for determination of their concentration and distribution. However, sampling viable airborne viruses is challenging as conventional bioaerosol sampling devices operate on inertia-based mechanisms that inherently have low sampling efficiency for virus aerosols in the ultrafine size range (< 100nm). Herein, a Batch Adiabatic-expansion for Size Intensification by Condensation (BASIC) approach was developed for efficient sampling of virus aerosols. The BASIC utilizes adiabatic expansion in a supersaturated container to activate condensation of water vapor onto virus aerosol particles, thus amplifying the size of the particles by orders of magnitude. Using aerosolized MS2 bacteriophage, the BASICs performance was evaluated and optimized both from the perspectives of physical size amplification as well as preservation of the viability of the MS2 bacteriophage. Experimental results show that one compression/expansion (C/E) cycle under a compression pressure of 103.5kPa and water temperature of 25°C was sufficient to increase the particle diameter from < 100nm to > 1µm; further increases in the number of C/E cycles neither increased particle number concentration nor diameter. An increase in compression pressure was associated with physical size amplification and a higher concentration of collected viable MS2. Water temperature of 40°C was found to be the optimal for size amplification as well as viability preservation. No significant effect on particle size enlargement was observed by changing the dwell time after expansion. The results illustrate the BASICs capability as a simple, quick and inexpensive tool for rapid sampling of viable airborne viruses.

Particle and Gas Emission Characterization from Oil and Oil-Dispersant Contaminated Sea Waters due to Breaking Waves

Crude oil spill incidents occur frequently, leaving seawater bodies with a verity of occupational, ecological and environmental issues from the local to global scale. Application of sub-surface dis...

Development of an In Vitro Exposure System for Live Visualization of the Health Impacts of Oily Marine Aerosol on the Human Respiratory System

Aerosolization of oily water droplets has recently been recognized as a potential respiratory health threat to oil spill cleanup workers, communities near spills, and marine mammals in oil-polluted waters. These sub-micron to millimeter scale droplets may be aerosolized by bursting bubbles, breaking waves, and splashing raindrops. Furthermore, dispersant applied to oil slicks also may become aerosolized as oil-water-dispersant emulsion droplets and subsequently inhaled, with unknown health consequences. With the goal of investigating the effects of inhaled oily marine aerosol on human lung health, we present the design of a novel in vitro bioreactor which mimics the conditions and exposures that human lungs might experience in the field. The bioreactor provides the ability to expose human lung cell cultures to laboratory-produced, well-characterized and chemically analyzed oily marine aerosols. A major advance over similar systems currently used to study the effects of smoking is the incorporation of opti...