Reducing the Surface Degradation of Aluminum Extrusion Dies During Preheating

Aluminum extrusion dies are usually made from H13 steel that is ferritically nitrocarburized to minimize wear and pick-up. Before being placed in the extrusion press, the dies are preheated to minimize thermal shock at the start of the extrusion cycle. During the preheating time, the nitrocarburized layer oxidizes. Some of this layer can break away during extrusion leaving marks on the product. Although inerting the preheat furnaces with nitrogen has been found to reduce the oxidation, it does not solve the problem completely. Experiments have shown that a small addition of ammonia to the preheating protective atmosphere could eliminate oxidation and prevent nitrogen loss from the surface nitride layer.     

Amino Alcohol Acrylonitriles as Activators of the Aryl Hydrocarbon Receptor Pathway: An Unexpected MTT Phenotypic Screening Outcome

Lead (Z)-N-(4-(2-cyano-2-(3,4-dichlorophenyl)vinyl)phenyl)acetamide, 1 showed MCF-7 GI₅₀=30 nM and 400-fold selective c.f. MCF10A (normal breast tissue). Acetamide moiety modification ( 13 a - g ) to introduce additional hydrophobicity was favoured with MCF-7 breast cancer cell activity enhanced at 1.3 nM. Other analogues were potent against the HT29 colon cancer cell line at 23 nM. Textbook SAR data was observed in the MCF-7 cell line, in an MTT assay, via the ortho ( 17 a ), meta ( 17 b ) and para ( 13 f ). The amino alcohol -OH moiety was pivotal, but no stereochemical preference noted. But, these data did not fit our homology modelling expectations. Aberrant MTT ((3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) screening results and metabolic interference confirmed by sulforhodamine B (SRB) screening. Interfering analogues resulted in 120 and 80-fold CYP1A1 and CYP1A2 amplification, with no upregulation of SULT1A1. This is consistent with activation of the AhR pathway. Piperidine per-deuteration reduced metabolic inactivation. 3-OH / 4-OH piperidine analogues showed differential MTT and SRB activity supporting MTT assay metabolic inactivation. Data supports piperidine 3-OH, but not the 4-OH, as a CYP substrate. This family of β-amino alcohol substituted 3,4-dichlorophenylacetonitriles show broad activity modulated via the AhR pathway. By SRB analysis the most potent analogue was 23 b , (Z)-3-(4-(3-(4-phenylpiperidin-1-yl)-2-hydroxypropoxy)phenyl)-2-(3,4-dichlorophenyl)-acrylonitrile.     

Laboratory and Ambient Particle Density Determinations using Light Scattering in Conjunction with Aerosol Mass Spectrometry

A light scattering module has been integrated into the current AMS instrument. This module provides the simultaneous measurement of vacuum aerodynamic diameter (d _va) and scattered light intensity (R_LS) for all particles sampled by the AMS above ～180 nm geometric diameter. Particle counting statistics and correlated chemical ion signal intensities are obtained for every particle that scatters light. A single calibration curve converts R_LS to an optical diameter (d _o). Using the relationship between d _va and d _o the LS-AMS provides a real-time, per particle measurement of the density of the sampled aerosol particles. The current article is focused on LS-AMS measurements of spherical, non-absorbing aerosol particles. The laboratory characterization of LS-AMS shows that a single calibration curve yields the material density of spherical particles with real refractive indices (n) over a range from 1.41 < n < 1.60 with an accuracy of about ±10%. The density resolution of the current LS-AMS system is also shown to be 10% indicating that externally mixed inorganic/organic aerosol distributions can be resolved. In addition to the single particle measurements of d _va and R_LS, correlated chemical ion signal intensities are obtained with the quadrupole mass spectrometer. A comparison of the particle mass derived from the physical (R_LS and d _va) and chemical measurements provides a consistency check on the performance of the LS-AMS. The ability of the LS-AMS instrument to measure the density of ambient aerosol particles is demonstrated with sample results obtained during the Northeast Air Quality Study (NEAQS) in the summer of 2004.     

Development of an Aerosol Mass Spectrometer for Size and Composition Analysis of Submicron Particles

The importance of atmospheric aerosols in regulating the Earth's climate and their potential detrimental impact on air quality and human health has stimulated the need for instrumentation which can provide real-time analysis of size resolved aerosol, mass, and chemical composition. We describe here an aerosol mass spectrometer (AMS) which has been developed in response to these aerosol sampling needs and present results which demonstrate quantitative mea surement capability for a laboratory-generated pure component NH₄ NO₃ aerosol. The instrument combines standard vacuum and mass spectrometric technologies with recently developed aerosol sampling techniques. A unique aerodynamic aerosol inlet (developed at the University of Minnesota) focuses particles into a narrow beam and efficiently transports them into vacuum where aerodynamic particle size is determined via a particle time-of-flight (TOF) measurement. Time-resolved particle mass detection is performed mass spectrometrically following particle flash vaporization on a resistively heated surface. Calibration data are presented for aerodynamic particle velocity and particle collection efficiency measurements. The capability to measure aerosol size and mass distributions is compared to simultaneous measurements using a differential mobility analyzer (DMA) and condensation particle counter (CPC). Quantitative size classification is demonstrated for pure component NH₄ NO₃ aerosols having mass concentrations 0.25_mu g m -3. Results of fluid dynamics calculations illustrating the performance of the aerodynamic lens are also presented and compared to the measured performance. The utility of this AMS as both a laboratory and field portable instrument is discussed.     

A Numerical Characterization of Particle Beam Collimation by an Aerodynamic Lens-Nozzle System: Part I. An Individual Lens or Nozzle

Particle beams have traditionally been produced by supersonic expansion of a particle-laden gas through a single nozzle to vacuum. However, it has been shown that, by passing the particle-laden gas through a series of axi-symmetric subsonic contractions and expansions (an aerodynamic lens system) prior to the supersonic expansion to vacuum through a single nozzle, beam divergence can be significantly reduced. In this paper, particle motion in expansions of a gas-particle suspension through either a single lens or a single nozzle have been investigated numerically. Since the single aerodynamic lens and the isolated nozzle are the elementary components of any aerodynamic lens-nozzle inlet system, a fundamental understanding of these components is essential for designing an inlet system with the desired sampling rate, collimation, and transmission properties. If a gas undergoes subsonic contraction and expansion through an orifice, the associated particles would follow the fluid streamlines if the particles were inertialess. However, real particles may either experience a displacement toward the axis of symmetry or may impact on the front surface of the lens. The first of these effects leads to collimation of the particles near the axis, but the second effect leads to particle loss. It is found that the maximum particle displacement occurs at a particle Stokes number, St, near unity and significant impact loss also begins at St ; 1. The lens dimensionless geometry and the Reynolds number of the flow are other important parameters. When a gas containing suspended particles undergoes supersonic expansion through a nozzle to vacuum from the lens working pressure (～300 Pa), it is found that particle beam divergence is a function of Reynolds number, nozzle geometry, and particle Stokes number. More specifically, it is found that a stepped nozzle generally helps to reduce beam divergence and that particle velocity scales with the speed of sound.     

Particulate Emissions from in-use Commercial Aircraft

Particulate emission indices (per kg fuel) have been determined by sampling the advected plumes of in-use commercial aircraft at two different airports using a novel approach. Differences are observed in the number, magnitude, and composition of the particle emissions between idle and take-off. At the first airport, Electrical Low Pressure Impactor (ELPI) data indicate that number based emission indices (EI _n ) vary by an order of magnitude for take-off plumes from different aircraft. Additionally, EI _n values for idle plumes are greater than take-off. At the second airport, EI _n values derived from condensation particle counter (CPC) measurements span ～ an order of magnitude (3–50 × 10 ¹⁵ particles per kg fuel). The median values of the idle and take-off plumes were 1.8 × 10 ¹⁶ and 7.6 × 10 ¹⁵ particles per kg fuel, respectively. For take-off plumes, the magnitude of the particulate emission index is not correlated with NO _x at either airport. The surface properties of the particulate emissions in take-off and idle plumes differ significantly as measured by diffusion charging (DC) and photoelectric aerosol sensor (PAS) instruments. Results indicate that take-off plumes are characterized by particles with photoelectric-active surfaces, presumably elemental carbon, whereas idle plumes are composed of non-photoelectric-active constituents and coated soot particles. Measurements of the particulate size distribution (ELPI) show evidence for two modes, one at ～ 90 nm aerodynamic diameter and a second mode at or below the instrument cutoff ( < 30 nm).     

Improved hysteresis band current controller

A new hysteresis band current controller for voltage source inverters is presented. This new technique, which has been experimentally verified, is based on the use of a second input current error derivative for the selection of the zero voltage vectors V_0,7 , which greatly reduces the inverter switching frequency     

Crazy Quilt Queens

Spreading out over almost 120 square miles on the northwest corner of Long Island, across the East River from Manhattan, Queens is physically the largest borough in the City of New York, and the second most populous and most ethnically diverse county in the us. Its 2.2 million residents come from 81 different countries, and nearly half are foreign-born. Writer Jayne Merkel and photographer Julian Olivas describe the architectural diversity of Queens - a combination in which architectural and ethnic characteristics rarely coincide. Most of the borough's residents and institutions occupy structures built by those that came before them. Queens is in almost perpetual flux. Copyright © 2005 John Wiley & Sons, Ltd.     

Development and Characterization of a Fast-Stepping/Scanning Thermodenuder for Chemically-Resolved Aerosol Volatility Measurements

Numerous sources of liquid aerosols are to be found in industrial environments. Such aerosols may, for instance, be cutting fluids, pesticides, etc., that are harmful or even toxic to humans. To control and reduce worker exposure to potentially toxic aerosols, these latter are usually filtered through fibrous filters. When non-saturated air traverses a clogged filter, however, the drops deposited on the fibers may evaporate. Consequently, workers are exposed to greater amounts of more concentrated vapors than the initial state of the filtered aerosol. Furthermore, exposure readings are distorted by an artifact that may be significant. This study offers an experimental approach to long-term monitoring of the evaporation of a semi-volatile n-hexadecane liquid aerosol deposited on filters of varying efficiency. Results were modeled using two semi-empirical models for identifying the basic parameters of liquid aerosol evaporation on fibers. For the first time ever it has been demonstrated that the Fick's first law, as previously suggested by models proposed in the literature, does not control evaporation kinetic.