Generation of Nanoparticles with a Nebulizer-Cyclone System

A cyclone was used to modify the droplet output with a three-jet Collison nebulizer. The cyclone-nebulizer system was tested by producing ammonium fluorescein particles from a liquid suspension. The particle size distribution produced with the cyclone was smaller and narrower than that produced without the cyclone. Thus, the cyclone effectively removed the large droplets produced by the nebulizer. The nebulizer-cyclone system reduced the GSD of the output aerosol from 1.7 to 1.4. At the input pressures greater than 138 kPa, the concentration of 10–60 nm particles was greater with the cyclone than without the cyclone. These results are consistent with the shattering of large droplets within the cyclone and re-entrainment of these small secondary droplets. Optimization of the system using cyclone modeling to enhance the sharpness of cut, operational improvements, and decreased venting could maximize the output of tailored distributions of nanoparticles for various applications.     

Monoterpene Emissions from Lodgepole and Jack Pine Bark Inoculated with Mountain Pine Beetle‐Associated Fungi

Abstract

Relative monoterpene levels were analyzed from bark samples of lodgepole pine, jack pine, and their hybrids inoculated with mountain pine beetle (MPB)–associated fungi (Leptographium longiclavatum, Grosmannia clavigera, and Ophiostoma montium). Lodgepole pine showed the largest changes in relative emissions as a result of fungal inoculation. The relative emission of β‐phellandrene increased with fungal inoculation, making it the most abundant monoterpene for inoculated samples. Relative emissions of limonene and α‐pinene decreased in inoculated lodgepole pine. Lodgepole (5.6) and jack (146) pine differed in the ratio of α‐pinene to myrcene; two monoterpenes involved in pheromone synthesis by the MPB. These differences may contribute to the attractiveness of the two species as hosts for MPB; with jack pine potentially less attractive than lodgepole pine. Fungal inoculation reduced α‐pinene:myrcene ratios in lodgepole pine, which suggests one possible mechanism by which the fungi benefit the beetle.     

Direct computation of the performance of sequential procedures based on a sequence of t-statistics,with application to a confidence interval for μ/σ in a normal population

Formulas are derived for the direct computation — as opposed to simulation or approximation — of sequential procedures that are based on a sequence of t-statistics. This is applied to the numerical computation of the performance of a one-sided confidence interval for γ = μ/σ in a normal population, when the probability of covering the true value γ as well as the probability of covering the false value γ ? d, for given d > 0,is specified.     

Detection of Mercapturic Acids and Nucleoside Adducts in Blood,Urine and Feces of Rats Treated with Metabolites of Methylpyrene

The carcinogen 1-methylpyrene (MP) is metabolized via 1-hydroxymethylpyrene (HMP) to a sulfuric acid ester (SMP), which can covalently bind to nucleophiles such as glutathione and DNA. These primary reaction products may be processed to 1-methylpyrenyl mercapturic acid (MPMA) and free nucleoside adducts [e.g. N ²?(1-methylpyrenyl)-deoxyguanosine, MPdG], and then be excreted. MPMA may be considered as a marker for the amount of SMP which was detoxified, whereas MPdG represents that part which underwent uncontrolled reactions with tissue constituents. We have designed sensitive HPLC-MS/MS methods to determine levels of MPMA and MPdG in biological samples. Shortly after administration of HMP to rats, MPMA was detected in blood and was then excreted in urine (> 70 %) and feces (> 30 %), chiefly within 24 h. The level of urinary MPMA was higher in females than in males. MPdG was detected in urine of rat treated with SMP. Future investigations will focus on factors which modify the ratio of the excreted amounts of MPdG and MPMA in animals treated with MP or its metabolites.     

Carbon-Dioxide-Based Microsortation of Postconsumer Polyolefins and its Effect on Polyolefin Properties

Postconsumer polyolefin flake has been sorted using liquid carbon dioxide as a float-sink medium. This separation of PP and LDPE from HDPE was conducted at ambient temperature and a pressure that yielded a CO₂ specific gravity of 0.955, causing the HDPE to sink and the LDPE and PP to float. Although this process provided a high-purity (99+%) HDPE product stream, the effect of immersing the plastics in liquid carbon dioxide at these conditions was not previously measured. Therefore, six HDPE samples, two LDPE samples, and five PP samples were exposed to high-pressure carbon dioxide for 20 min. After this exposure, the polyolefins did not foam when the carbon dioxide was rapidly vented from the vessel. The weight reduction averaged 0.17%, which was attributed to the dissolution of low-molecular-weight additives or contaminants present on the surface of the plastics. No significant change in the melting point or latent heat of melting was observed, indicating that the degree of crystallinity was not affected by the exposure to carbon dioxide. No reduction was observed in the temperature at which the onset of thermal degradation occurred, because of the low solubility and degree of extraction of thermal stabilizers during the immersion in carbon dioxide. These results indicated that no deleterious effects on the polyolefin properties were associated with this separation technique.     

Optimizing Injection Molding Toward Multiple Quality and Cost Issues

Injection-molding part designers are frequently faced with multiple quality and cost issues. These issues are usually in conflict with each other; thus, a trade-off needs to be made to reach a final compromised solution. Because evaluation of part quality and cost via injection-molding simulation is very time-consuming, implementation of a conventional multicriteria optimization procedure for injection-molding problems is economically unfavorable. However, many injection-molding problems dealing with multiple quality and cost issues can be modeled as constrained problems, with the total cost as the objective function and quality quantities as the constraints. By introducing a concept of penalized total cost, such constrained problems are further simplified into bounded single-criterion problems. The bounded single-criterion problems are then optimized using a direct search-based optimization procedure. Strategies of modeling, transformation, and optimization for these problems are discussed in this article. A case study is provided.     

Evaluation of the Loading Characteristics of the EPA WINS PM2.5 Separator

The loading characteristics of the USEPA Well Impactor Ninety Six (WINS) PM_2.5 separator was an important design consideration during the separator's development. In recognition that all inertial separators eventually overload, the loading surface of the WINS was designed to be easily accessible, replaceable, and cleanable. Prior to promulgation of the method, the loading capacity of the WINS separator was evaluated by measuring its performance after repeated loading with laboratory-generated, high concentration, coarse-mode aerosol. For this purpose, a low flow rate loading wind tunnel was designed and constructed to artificially create coarse mode aerosols composed of Arizona Test Dust. This controlled test atmosphere was sampled by the PM_2.5 reference method sampling train, as specified in 40 CFR Part 50, Appendix L, at total aerosol mass concentrations averaging 332     

Evaluation of Elemental and Black Carbon Measurements from the GAViM and IMPROVE Networks

The GAViM program provides fine particulate and visibility data for several remote locations in Canada. Two long-term intercomparison studies between the GAViM and a major U.S. aerosol monitoring network, IMPROVE, were used to evaluate the uncertainty in the analytical data produced by proton induced x-ray emission (PIXE), proton elastic scattering analysis (PESA), and gravimetric analysis. GAViM and IMPROVE agreed well for elements from Fe to Zn where PIXE is the most sensitive; the relative difference between the 2 networks for Fe and Zn was <2%. Some lighter elements, e.g., sodium or sulphur, revealed a difference of 10-20%. Furthermore, an empiric conversion scheme for the GAViM absorption data produced by the laser integrated plate method (LIPM) was derived from the comparison to the IMPROVE thermal/optical reflectance (TOR) data. This conversion depends on the aerosol composition and is therefore site specific. It allows estimation of the elemental carbon concentrations from the historic raw light absorption values obtained by LIPM. If the mass attenuation coefficient of the fine aerosol collected at the 2 remote GAViM sites is assumed to be equal to 10 m 2 /g, then the results imply that the light absorption coefficient measured by LIPM is generally higher than the true value by up to a factor of 1.3 or 1.8, respectively. In both cases, LIPM overestimated the black carbon content, mostly for the lightly loaded samples.     

Influence of organic liquids on the nanostructure of precipitated cellulose

Organic liquids have been used in pretreatments to improve the digestibility of lignocellulosic biomass, ultimately reducing the amount of enzyme required to digest the material to its constituent sugars. To understand the influence of these solvents on cellulose nanostructure, phosphoric acid was used to solubilize cellulose (PAS cellulose) followed by washing of the PAS cellulose with organic liquids previously demonstrated to aid pretreatment. PAS cellulose washed using methanol, ethanol, and ethylene glycol had gel‐like properties with disrupted nanostructures. PAS cellulose washed with acetone, 2‐propanol, and water yielded an opaque white precipitate. Small‐angle neutron scattering indicated the formation of loosely bundled rods of cellulose in the gel‐like material. Fourier transform infrared resonance of solvent‐washed, flash‐dried PAS cellulose suggested an increase in interchain hydrogen bonds in the gel‐like precipitates relative to the more obvious precipitates formed in other solvents. The optimal wash liquid was determined to be 40% by volume ethanol in water to induce a highly digestible, gel‐like material. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of particle size and grafting density on the mechanical properties of polymer nanocomposites

End-grafting polymer chains to nanoparticles in polymer nanocomposite is a widely used method to disperse inorganic particles in a polymeric matrix in order to improve the material properties. While many fundamental studies have investigated how various factors influence the dispersion or aggregation of the nanoparticles, the effect of grafting on the resulting material properties has received considerably less attention. In particular, the effect of nanoparticle curvature and grafting density on the mechanical properties in polymer nanocomposites remains elusive. In this study, we develop a coarse-grained model of a polymer glass containing grafted nanoparticles and examine the resulting effects on the mechanical properties. By carefully designing the parameters of our polymer nanocomposites model, we can maintain dispersion of the nanoparticles whether they are grafted with polymer chains or not, which allows us to isolate the effect of end-grafting on the resulting mechanical properties. We examine how the nanoparticle size and grafting density affect the elastic constants, strain hardening modulus, as well as the mobility of the polymer segments during deformation. We find that the elastic constants and yield properties are enhanced nearly uniformly for all of our nanocomposite systems, while the strain hardening modulus depends weakly on the grafting density and the nanoparticle size.