Design and development of an electrostatic sampler for bioaerosols with high concentration rate

Integration of bioaerosol sampling methods with modern analysis techniques, such as the polymerase chain reaction as well as our ability to detect low concentrations of airborne agents require samplers that are able not only to efficiently collect the biological particles, but also to concentrate them in small amounts of fluids. In this research, we began development of a novel bioaerosol sampler, where a combination of electrostatic collection mechanism with superhydrophobic (“Lotus leaf” type) collection surface allows for efficient particle collection, removal and concentration in water droplets as small as 5 μL. This new sampling concept allowed achieving very high sample concentration rates (up to 1 million and higher) and could be applied to detect low concentrations of bioaerosols in various environments.The prototype electrostatic precipitator with superhydrophobic surface had a shape of a half-pipe, where a top plate served as the ground electrode, while the collecting surface was 3.2 mm wide rectangular electrode coated with a superhydrophobic substance and positioned in a groove in the flat bottom surface. Airborne particles drawn into the sampler were positively charged and then by the action of an electrostatic field deposited onto the negatively charged electrode. The sampler was positioned at a ∼1° inclination angle to the horizontal, and the injected water droplets rolled off of electrode's surface removing deposited particles. Sampler's performance has been analyzed with polystyrene latex particles of five aerodynamic diameters (0.5, 1.2, 1.9, 3.2, and 5.1 μm), collecting droplet volumes ranging from 5 to 60 μL, and sampling flow rates of 2, 5, and 10 L/min. It was determined that vast majority of particles deposited onto the electrode are removed by the first rolling droplet, which for 3.2 μm particle and 20 μL droplet translated into a concentration rate of 3×10⁵. By narrowing the electrode to 2.1 mm and lowering the droplet volume to 5 μL we achieved the concentration rate as high as 1.2×10⁶. These concentration rates were sustained for sampling times as long as 60 min. This novel sampling concept demonstrates a great potential for sampling and detecting airborne microorganisms in low concentration environments.     

Length-dependent DNA degradation kinetic model: Decay compensation in DNA tracer concentration measurements

DNA is often used as a tracer in both environmental fluid flow characterization and in material tracking to avoid counterfeiting and ensure transparency in product value chains. The main drawback of DNA as a tracer is its limited stability, making quantitative analysis difficult. Here, we study length-dependent DNA decay at elevated temperatures and under sunlight by quantitative PCR and show that the stability of randomly generated DNA sequences is inversely proportional to the sequence length. By quantifying the remaining DNA length distribution, we present a method to determine the extent of decay and to account for it. We propose a correction factor based on the ratio of measured concentrations of two different length sequences. Multiplying the measured DNA concentration by this length-dependent correction factor enables precise DNA tracer quantification, even if DNA molecules have undergone more than 100-fold degradation. © 2018 American Institute of Chemical Engineers AIChE J, 65: 40–48, 2019     

Weight suppression and weight rebound in ex-smokers treated with fluoxetine.

Fluoxetine's effect (30 mg, 60 mg, and placebo) on postcessation weight gain was studied among participants from a randomized, double-blind 10-week smoking cessation trial who met strict criteria for abstinence and drug levels. It was hypothesized that (a) fluoxetine would dose-dependently suppress postcessation weight gain and (b) drug discontinuation would produce dose-dependent weight rebound. During the on-drug phase, placebo participants gained weight linearly (M?=?2.61 kg), exceeding both fluoxetine groups (30-mg M?=?1.33 kg, 60-mg M?=?1.25 kg). Weight suppression was initially greater for 60 mg than 30 mg, but both were followed by weight gain. Six months off-drug produced greater dose-dependent weight rebound for 60 mg than 30 mg or placebo. Considering both on- and off-drug phases, weight gain for 60 mg of fluoxetine (M?=?6.5 kg) was comparable with that for placebo (M?=?4.7 kg) but greater than that for 30 mg (M?=?3.6 kg). Fluoxetine appears to forestall postcessation weight gain, allowing time for the weight-conscious smoker to focus on quitting smoking rather than on preventing weight gain. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of an Ionic Air Cleaner on Indoor/Outdoor Particle Ratios in a Residential Environment

We tested a leading commercially available ionic air cleaner in a typical residential apartment to study the effect of the device on indoor/outdoor airborne particle number and mass concentration ratios. In addition, we also determined the indoor ozone and ion concentration levels. When measured during normal daily activity, the average indoor/outdoor mass concentration ratio was reduced from 1.03 to 0.73 and the number concentration ratios underwent reductions for most of the particle size fractions. However, due to a substantial inter-and intra-measurement variation in particle ratios, the observed average reductions were not statistically significant. When measurements were performed in a still room, the indoor/outdoor particle mass concentration ratio decreased from 0.9–1.4 to 0.3–0.4 in eight hours when the air cleaner was operating. Ambient ozone concentrations measured in the middle of the apartment were between 13–19 ppb during normal daily activity and the ozone levels increased to 77 ppb when measured in front of the ionic cleaner during still conditions. We also found that that there was a limited vertical diffusion of ions. The highest ion concentrations were measured at a 0.5 m height from the floor and decreased substantially with increasing measurement height. This finding may have implications for effective particle removal from a person's breathing zone. Overall, we found that the tested brand of commercially available ionic air cleaners may have the capability to remove some airborne particulate matter in actual residential settings, but its cleaning effect is reduced under normal daily activity.     

Hostility, the metabolic syndrome, and incident coronary heart disease.

This investigation examined the impact of hostility and the metabolic syndrome on coronary heart disease (CHD) using prospective data from the Normative Aging Study. Seven hundred seventy-four older, unmedicated men free of cardiovascular disease were included in the study. The total Cook-Medley Hostility (Ho) Scale score, anthropometric data, serum lipids, fasting insulin concentrations, blood pressure, cigarette smoking, alcohol consumption, and total dietary calories were used to predict incident CHD during a 3-year follow-up interval. Multivariate analysis indicated that only Ho positively predicted and high-density lipoprotein cholesterol level negatively predicted incident CHD. Ho's effects on CHD may be mediated through mechanisms other than factors that constitute the metabolic syndrome. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Efficacy of naltrexone in smoking cessation: a preliminary study and an examination of sex differences.

This double-blinded, placebo-controlled trial evaluated the efficacy of naltrexone as an adjunct to standard smoking cessation treatment. Participants (N = 110) were adult male and female nicotine-dependent smokers who expressed interest in quitting smoking. All subjects received six sessions of behavioral counseling (1 hr/session for 6 weeks), and 1 month of the nicotine patch (21 mg for the first 2 weeks, 14 mg the third week, 7 mg the fourth week). Subjects were randomly assigned to the naltrexone or placebo group. The naltrexone group started at 25 mg daily for 3 days prior to the quit date, and increased to 50 mg/day on the quit date and following 8 weeks. At the end of medication treatment, the naltrexone group had better quit rates versus the placebo group (48% quit on naltrexone vs. 41% on placebo), but this difference was not statistically significant. However, men and women differed on several measures: in the placebo group, women had significantly lower quit rates than men (39% vs. 67%, p<.05), but in the naltrexone group, women had quit rates comparable with those of men (58% vs. 62%, p = ns). Further examination revealed that naltrexone significantly reduced men's and women's cessation-related weight gain and selectively reduced women's urge to smoke to relieve negative affect and withdrawal. The results suggest continued examination of naltrexone as an adjunct in smoking cessation, particularly in female smokers, who have historically shown worse outcomes with traditional treatment methods.     

Performance Characteristics of the Aerosol Collectors of the Autonomous Pathogen Detection System (APDS)

This research analyzes the physical performance characteristics of the aerosol collectors of the autonomous pathogen detection system (APDS) that was recently developed by the Lawrence Livermore National Laboratory. The APDS is capable of continuous and fully autonomous monitoring for multiple airborne threat organisms and can be used as part of a monitoring network for urban areas and major public gatherings. The system has already been successfully tested with airborne Bacillus anthracis and Yersinia pestis biowarfare agents. The APDS aerosol collection system consists of a PM-style cap to remove large particles and a low-pressure drop virtual impactor preconcentrator positioned in front of a wetted-wall cyclone. The aerosol collectors operate at flow rates as high as 3750 l/min and collect airborne particles into 4 ml of liquid for subsequent detection. In our tests we determined the overall collection efficiency of the system by measuring the difference between inlet and outlet particle concentrations. The tests were performed with polydisperse oleic acid and monodisperse polystyrene latex (PSL) particles (0.6–3.1 µ m), and for three values of the major air flow rates in the virtual impactor (1760, 2530, and 3300 l/min), two values of the product, or cyclone, flow rates (375 and 450 l/min), and two different volumes of collection liquid (4 and 6 ml). We found that the cutoff size (d₅₀ ) of the entire collection system varied from 1.5 to 2.0 µ m when collecting PSL particles, with 3.1 µ m PSL particles being collected with efficiency of approximately 85%. When collecting oleic acid particles the d₅₀ of the entire system varied from 1.1 to 1.6 µ m. The concentration rates of the aerosol collection system were found to increase with increasing overall collection flow rate and approached one million per minute at the highest tested flowrates. Such high concentrating rates and high air sample volumes make the APDS collection system highly suitable for detecting low concentrations of airborne pathogens.     

Deposition Uniformity of Coal Dust on Filters and Its Effect on the Accuracy of FTIR Analyses for Silica

Miners are exposed to silica-bearing dust which can lead to silicosis, a potentially fatal lung disease. Currently, airborne silica is measured by collecting filter samples and sending them to a laboratory for analysis. Since this may take weeks, a field method is needed to inform decisions aimed at reducing exposures. This study investigates a field-portable Fourier transform infrared (FTIR) method for end-of-shift (EOS) measurement of silica on filter samples. Since the method entails localized analyses, spatial uniformity of dust deposition can affect accuracy and repeatability. The study, therefore, assesses the influence of radial deposition uniformity on the accuracy of the method. Using laboratory-generated Minusil and coal dusts and three different types of sampling systems, multiple sets of filter samples were prepared. All samples were collected in pairs to create parallel sets for training and validation. Silica was measured by FTIR at nine locations across the face of each filter and the data analyzed using a multiple regression analysis technique that compared various models for predicting silica mass on the filters using different numbers of “analysis shots.” It was shown that deposition uniformity is independent of particle type (kaolin vs. silica), which suggests the role of aerodynamic separation is negligible. Results also reflected the correlation between the location and number of shots versus the predictive accuracy of the models. The coefficient of variation (CV) for the models when predicting mass of validation samples was 4%–51% depending on the number of points analyzed and the type of sampler used, which affected the uniformity of radial deposition on the filters. It was shown that using a single shot at the center of the filter yielded predictivity adequate for a field method, (93% return, CV approximately 15%) for samples collected with 3-piece cassettes.

Copyright 2013 American Association for Aerosol Research     

N-PEG’ylation of chitosan via “click chemistry” reactions

N-azidated chitosan was prepared by four different methods: using azidated epichlorohydrin, sodium azide plius sodium nitrite, trifluoromethane sulfonyl azide or imidazole-1-sulfonyl azide hydrochloride. Using the two last reagents, the degree of azidation (DA) of chitosan was up to 40% and 65%, respectively. N-azidated chitosans with DA at about 60% were insoluble in aqueous and common organic solvents but dissolved in 5% LiCl solution in N-methyl-2-pyrrolidone, one of the very few solvents for chitin. Chitosan–methoxy poly(ethylene glycol) derivatives containing triazolyl moiety (chitosan-N-TMPEG comb copolymers) were prepared for the first time by coupling via 1,3-dipolar cycloaddition between pendant azide and end alkyne groups of chitosan and MPEG, respectively. Comb copolymers chitosan-N-TMPEG with degree of substitution (DS) of chitosan equal to DA of chitosan were synthesized at a certain excess of MPEG alkyne reaching DS up to 40%. “Clicking” of MPEG alkyne onto azidated chitosan was successful in binary mixture of water and methylene chloride but failed in 5% LiCl solution in N-methyl-2-pyrrolidone. Significant breakdown of chitosan backbone took place under “clicking” of MPEG in the presence of Cu(II)/ascorbate catalyst resulting in graft copolymers with bimodal MWD. Chitosan-N-TMPEG copolymers contained a certain residual amount of Cu and were soluble in acetate buffer (pH 3.7). Novel comb copolymers were characterized by FT-IR and ¹H NMR spectroscopy, SEC with triple detection, intrinsic viscosity, elemental and functional group analysis.