Bipolar Charge Distributions of Aerosol Particles in High-Purity Argon and Nitrogen

The bipolar diffusion charging has been studied for monodisperse sodium chloride and silver particles of 5–100 nm in atmospheric air, argon and nitrogen. The particles were bipolarly charged in a neutralizer by ions, produced by beta-rays from a Kr 85 source. The differently charged particle fractions were separated in a differential mobility analyzer and measured with an aerosol electrometer. The experimentally determined results in atmospheeric air are comparable with earlier measured asymmetric bipolar charge distributions. They show good agreement with the theoretically determined results based on the extended Fuchs model with four-input ion parameters: mobilities and masses of positive and negative ions. The experimentally determined bipolar charge distributions in argon and nitrogen are more asymmetric than in atmospheric air. The theoretically determined distributions, based on the extended Fuchs model, can be fitted to the experimental data. Furthermore, the extended Fuchs model is strongly dependent upon variations of the four input ion parameters. No differences for the experimentally determined bipolar charge distribution could be found between different gas purities and different particle materials.     

Design and Characterization of a Fluidized Bed Aerosol Generator: A Source for Dry,Submicrometer Aerosol

A fluidized bed aerosol generator has been designed and built for the purpose of generating a constant output of dry, submicrometer particles with a large number density. The output of the fluidized bed for generating aerosol particles from dry soot powder has been characterized using a differential mobility analyzer and a condensation particle counter. The particle size distribution is bimodal, with a mode in the submicrometer diameter size range and a mode in the supermicrometer diameter size range. The larger diameter mode is fully separated from the smaller mode and can thus be easily removed from the aerosol flow using impaction techniques. The distribution in the submicrometer size range is nearly log-normal, with a count median diameter falling between 0.1 and 0.3 micrometers. A number density of greater than 10⁵ particles cm^-3 of soot particles in the submicrometer range can be produced, constant to within 25% (1 standard deviation) over a 4 h time period. The number density of particles produced in the submicrometer range was found to vary with the ratio of soot to bronze beads in the bed mixture, whether or not a feed system was used, and nitrogen flow rate through the fluidized bed and feed system.     

Particle Charging and Transmission Efficiencies of Aerosol Charge Neutralizes

ABSTRACT

Diffusion losses and charging efficiency were measured for three types of charge neutralizers commonly used in aerosol research: two with ⁸⁵Kr and one with ²¹⁰Po as radiation sources. The diffusion losses were characterized at flows of 0.5 -6 1 min^?1 typically used in atmospheric aerosol physics measurements. All of the neutralizers tested exhibited high transmission efficiencies, with losses up to 25% at the smallest tested size of 3 nm, varying with size and flow in general agreement with diffusion loss theory. Charging efficiency was measured for a singly charged, monodisperse aerosol at the same flows and at concentrations of 10³-10⁴ particles cm^?3. Neither of the ⁸⁵Kr chargers brought the charge distribution close to equilibrium at 2 1 min^?1, except at concentrations ≤ 10³ cm^?3. The ²¹⁰Po charger produced the theoretically expected fraction of singly charged particles within the uncertainty of the experiment.     

Composition and Source Apportionment of Organic Aerosol in Beirut,Lebanon, During Winter 2012

Fine organic aerosols were collected at a semi-urban site in Beirut, Lebanon, from 28 January to 12 February 2012 as part of the Emission and Chemistry of Organic Carbon in East Mediterranean-Beirut (ECOCEM-Beirut). A total of 20 quartz filter samples were collected on a 12 h basis using a high-volume sampler and were analyzed using a GC/MS technique. Levoglucosan was the major most abundant single component with an average value of 306 ng.m^?3, followed by saturated and unsaturated carboxylic acids and sugars with average values of 234 and 118 ng.m^?3, respectively. Reported values for other carboxylic acids, polycyclic aromatic hydrocarbons, and biogenic secondary organic aerosols (BSOA) were 87, 33 and 21 ng.m^?3, respectively. Compared to a similar field campaign conducted in summer 2011, levoglucosan concentrations were lower in summer by a factor of 6, due to the use of wood burning for residential heating in winter. Concentrations of saturated and unsaturated carboxylic acids, other carboxylic acids, and BSOA were higher in summer by a factor of 3, 2, and 7, respectively. Higher concentrations observed for BSOA and other dicarboxylic acids during summer are due to higher biogenic emissions and greater photochemical activity in summer.

Copyright 2013 American Association for Aerosol Research     

The Los Angeles Aerosol Characterization and Source Apportionment Study: An Overview

The Los Angeles Aerosol Characterization and Source Apportionment Study (LA-ACSAS) is a decade-long laboratory and field study undertaken by the Southern California Edison Company (SCE) to characterize the chemical composition of fine (d _p < 3.5 μm) particles, PM_3,5, in the Los Angeles Basin, in terms of sulfate, nitrate, organic compounds and trace metals and apportion their sources. This paper provides an overview of the study results and summarizes the important conclusions regarding the composition and sources of PMJS in the Los Angeles Basin, especially regarding the organic fraction.     

光催化双极膜的制备及应用

以聚乙烯醇（PVA）和羧甲基纤维素钠（CMC）混合制成阳膜层材料,以聚乙烯醇和壳聚糖（CS）混合制成阴膜层材料。分别用氯化铬、戊二醛对阳膜、阴膜进行交联改性,并在阴阳膜层间加入具有光催化活性的纳米二氧化钛,得mCMC/TiO2/mCS双极膜。该双极膜在紫外光照射下,具有高的水解离效率,优良的亲水性能,双极膜阻抗小,工作电压低,并将该膜应用于合成乙醛酸和丁二酸体系中。     

Mechanism of Charge Transfer in the Transition Metal Ion Doped TiO2 with Bicrystalline Framework of Anatase and Rutile: Photocatalytic and Photoelectrocatalytic Activity

The high photocatalytic activity of the Mn²⁺ doped TiO₂ with bicrystalline framework of anatase and rutile is probed for the degradation of benzene under solar light with/without applied bias. The enhanced activity is attributed to the transfer of electrons from the rutile to electron trapping/lattice trapping sites of anatase and also to the impurity level created by the dopant which favours effective charge separation. The shallow detrapping nature of Mn²⁺ dopant additionally contributes to the overall enhancement in the photocatalytic activity especially in the presence of applied electric field.     

Antioxidant Activity of a Red Lentil Extract and Its Fractions

Phenolic compounds were extracted from red lentil seeds using 80% (v/v) aqueous acetone. The crude extract was applied to a Sephadex LH-20 column. Fraction 1, consisting of sugars and low-molecular-weight phenolics, was eluted from the column by ethanol. Fraction 2, consisting of tannins, was obtained using acetone-water (1:1; v/v) as the mobile phase. Phenolic compounds present in the crude extract and its fractions demonstrated antioxidant and antiradical activities as revealed from studies using a β-carotene-linoleate model system, the total antioxidant activity (TAA) method, the DPPH radical-scavenging activity assay, and a reducing power evaluation. Results of these assays showed the highest values when tannins (fraction 2) were tested. For instance, the TAA of the tannin fraction was 5.85 μmol Trolox^® eq./mg, whereas the crude extract and fraction 1 showed 0.68 and 0.33 μmol Trolox^® eq./mg, respectively. The content of total phenolics in fraction 2 was the highest (290 mg/g); the tannin content, determined using the vanillin method and expressed as absorbance units at 500 nm per 1 g, was 129. There were 24 compounds identified in the crude extract using an HPLC-ESI-MS method: quercetin diglycoside, catechin, digallate procyanidin, and p-hydroxybenzoic were the dominant phenolics in the extract.     

Centipede Venom: A Potential Source of Ion Channel Modulators

Centipedes are one of the most ancient and successful living venomous animals. They have evolved spooky venoms to deter predators or hunt prey, and are widely distributed throughout the world besides Antarctica. Neurotoxins are the most important virulence factor affecting the function of the nervous system. Ion channels and receptors expressed in the nervous system, including Na_V, K_V, Ca_V, and TRP families, are the major targets of peptide neurotoxins. Insight into the mechanism of neurotoxins acting on ion channels contributes to our understanding of the function of both channels and centipede venoms. Meanwhile, the novel structure and selective activities give them the enormous potential to be modified and exploited as research tools and biological drugs. Here, we review the centipede venom peptides that act on ion channels.     

Antioxidant Activity of Tannin Fractions Isolated from Buckwheat Seeds and Groats

Phenolic compounds were extracted with 80% (v/v) aqueous acetone from buckwheat seeds and groats. Tannin fractions were obtained from the crude extracts by Sephadex LH-20 column chromatography. Total phenolic contents of isolated fractions from buckwheat seeds and groats were 477 and 371 mg catechin equiv/g, respectively. The analyzed samples were characterized by electrophoretic separations using capillary zone electrophoresis. Both fractions exhibited strong antioxidant activity. The tannin fraction of buckwheat seeds reduced 1,1-diphenyl-2-picrylhydrazyl radicals (DPPH^·) and [2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid)] diammonium salt radical cations (ABTS^·+) stronger than the fraction of buckwheat groats. The EC₅₀ values amounted to 0.019 and 0.020 mg while Trolox equivalent antioxidant capacity values were 4.06 and 3.55 mmol Trolox equiv/g for tannin fractions of buckwheat seeds and groats, respectively. Similarly, antioxidant activity of the tannin fraction of buckwheat seeds measured by photochemiluminescence assay, was higher than antioxidant activity noted for the fraction obtained from groats. However, both fractions inhibited oxidation to the same extent in applied lipid models: β-carotene-linoleic acid emulsion and l-α-lecithin liposomes. In β-carotene-linoleic acid emulsion system, 1 mg of tannin fractions exhibited similar antioxidant activity to 0.5 mg butylated hydroxyanisole (BHA).     

Theory of Ion Exchange and Development of Charge in Kaolinite-Water Systems

Crystal-chemical concepts applied to cation adsorption on kaolinite crystals in a water medium permit the calculation of bond energies. These values place the cations in the proper sequence of replacing power. Comparison of bond energies with thermal energy makes possible the calculation of charge on the particle and explains much of the observed behavior of kaolin-water systems.     

Comment on the Calculation of the Steady-State Charge Distribution on Aerosols < 100 nm by Three Body Trapping Method in a Bipolar Ion Environment

The theory of Fuchs (1963) Fuchs, N. 1963. On the Stationary Charge Distribution on Aerosol Particles in a Bipolar Ionic Atmosphere. Geofis. Pura Appl., 56: 185–192. [Crossref] , [Google Scholar] is widely used for calculation of the steady-state charge distribution on (submicron) aerosol particles in a bipolar ion environment. Hoppel and Frick (1986) Hoppel, W. and Frick, G. 1986. Ion-Aerosol Attachment Coefficients and the Steady-State Charge Distribution on Aerosols in a Bipolar Environment. J. Aerosol Sci., 5: 1–21. [Taylor & Francis Online] , [Google Scholar] and others showed that the Fuchs theory is no longer valid for particle diameters in the order of magnitude of the ionic mean free path. In their 1986 and 1990 papers, Hoppel and Frick published a new calculation method based on the concept of thee-body trapping, which is applicable for small particles down to the size of ions. Some print and procedure mistakes were made in the named publications. Additionally some important calculation information was not given. In this article, the relevant equations are shown, corrected and appended. A recalculation of the charge distributions for small particles based on three-body trapping shows a pronounced difference in comparison to data calculated according to the theory of Fuchs.     

Antioxidative Effects of Oat Oil and its Fractions

The antioxidative properties of oat oil and its fractions were studied using the Rancimat method and lard, tallow and soybean oil as substrates. Oat oil extracted with isopropanol increased the induction time of oxidation of lard and tallow from 2 to 8-fold compared with the corresponding times without antioxidants, when applied at 1.0 to 5% concentrations. The same increase in stability was achieved with 0.25 to 1.5% concentrations of the separated fractions. The most effective fraction was the lecithin fraction isolated by supercritical CO₂ extraction. Almost equal results were achieved with a single-step ultrafiltration. Effects on the stability of soybean oil were similar but weaker.     

Ion Densities and Particle Charges for Alpha Ionization in an Aerosol Atmosphere: Columnar Recombination Corrections

Ionization by alpha sources in an environment containing small aerosol particles is of interest in aerosol neutralizes, particle chargers and atmospheric electricity. It is known that the conventional ion-balance equation is inadequate in describing the bulk ion densities for alpha sources in view of the columnar recombination process. An earlier self-consistent formulation to include this effect is extended to the case of unequal ionic mobilities and the consequent asymmetric charging of particles. Calculations for medium (Radon-222) and low (Thorium-232) energy sources commonly encountered indicate that the columnar recombination corrections lower the ion densities and the particle mean charges by a factor of about 2 for weak sources (strength < 10³ ions cm^?3 s^?1) and by a factor of 1.2 for strong sources (strength = 10⁹ ions cm^?3 s^?1). The paper presents a detailed study of the dependence of the correction factors as a function of particle concentration and the strength of the alpha sources.     

浅谈30DD350型离子膜电解槽的损坏和维修

介绍了30DD350电解槽的基本结构,总结了其损坏形式及维修方法。     

Charge Transport in Amorphous Organic Semiconductors: Effects of Disorder,Carrier Density,Traps, and Scatters

In real devices, organic semiconductors are largely amorphous. Because accurate molecular packing in them cannot be obtained, the relationship between the molecular structure and the material properties can be difficult to understand. Nevertheless, knowing the charge transport processes is essential to material and device engineering. In amorphous organic semiconductors, charge transport is often apprehended as a hopping process that can be described using the Marcus or Miller Abrahams equations. The intrinsic disorder and frequently present traps have a great influence on the charge mobility. Carrier density, which would affect the effective density of states and create space charge perturbations, is also one important factor in the charge transport process. Herein, recent advances in the charge transport mechanism in amorphous organic semiconductors are summarized. The influences of disorder, carrier density, traps, and scatters are discussed in detail.     

Investigation of a Novel Condensation Aerosol Generator: Solute and Solvent Effects

Part I of this article presents results of an experimental study on gas-phase nucleation for three model solutes and their solvent, propylene glycol (PG), with variables being solute concentration and the nature of the solute substance. A single manifestation of an aerosol generator, which forms condensation aerosols by cooling of hot vapor issuing from an electrically heated, pumped capillary, is described and used for all experiments. The effects of solute concentration and solute type were studied for deoxycorticosterone (DOC), benzil (BZ), and phenyl salicylate (PhS). Suppression of homogeneous nucleation and occurrence of heterogeneous condensation of the solvent was observed at different solute concentrations for BZ, PhS, and DOC. The nature and concentration of the solute dissolved in the solvent was shown to determine the final particle size distribution of the condensed aerosol. In the case of the least volatile solute, DOC, solute aerosol and total aerosol size distributions were identical at low solute concentrations. A transitional concentration region then existed in which a bimodal solute aerosol was formed, followed at high concentrations by increasing separation of the solvent-dominated aerosol size distribution and that of the solute. In Part II of this article, the effect of DOC dissolution in different solvents was studied at fixed solute concentration. The effects of six glycol solvents--i.e., PG, ethylene glycol (EG), dipropylene glycol (DPG), diethylene glycol (DEG), triethylene glycol (TEG), and tetraethylene glycol (TetEG)--and three nonglycol solvents--i.e., dimethyl sulfoxide (DMSO), formamide (FORM), and oleyl alcohol (OA)--were studied, as these affected the resultant aerosol sizes. Suppression of total aerosol mass median aerodynamic diameter (MMAD) was observed on dissolution of 0.5% w/w DOC in each solvent, although suppression occurred to different extents. It was shown that the boiling point or volatility of the solvent used to dissolve the less volatile DOC had an effect on the final particle size distribution of the condensed aerosol and whether the aerodynamic size distributions for the solute and the total aerosol were the same or different.     

Medical Aerosol Inhalers: Past,Present, and Future

The need to deliver pharmaceutical molecules to the respiratory tract has lead to the development of three major types of medical aerosol inhalers: The nebulizer, invented around the turn of the century, which uses aqueous solutions as its atomization substrate; the pressurized metered dose inhaler, invented in the mid-1950s, which uses a finely divided drug in a chlorofluorocarbon propellant suspension; and the dry powder inhaler, first commercialized in the early 1960s, which uses a powdered drug form. In general, these dosage forms have served the medical and patient community well, but recent advances in protein chemistry and the ozone depletion issues related to CFC propellants have lead to a renewed interest in the development of more efficient non-CFC inhalers. This article discusses the history of medical inhaler device technology and highlights the new technologies which may replace some of the existing delivery systems.     

潜艇舱室气溶胶的来源及监测技术的适艇性分析

结合检测数据和测点分布,分析了潜艇舱室气溶胶的来源及产生原因,提出了提高舰员个人卫生水平、避免二氧化碳吸收剂泄露、及时排出厨房油烟、有效防止废气泄露为控制潜艇舱室气溶胶的关键环节。对民用气溶胶监测技术进行了适艇性分析,通过对比现有监测技术的优缺点,明确现有检测手段存在的不足,为研发潜艇适用的气溶胶检测技术提供参考。