Dominant Mechanisms that Shape the Airborne Particle Size and Composition Distribution in Central California

The size and composition of ambient airborne particulate matter is reported for winter conditions at five locations in (or near) the San Joaquin Valley in central California. Two distinct types of airborne particles were identified based on diurnal patterns and size distribution similarity: hygroscopic sulfate/ammonium/nitrate particles and less hygroscopic particles composed of mostly organic carbon with smaller amounts of elemental carbon. Daytime PM₁₀ concentrations for sulfate/ammonium/nitrate particles were measured to be 10.1 μ g m^?3, 28.3 μ g m^?3, and 52.8 μ g m^?3 at Sacramento, Modesto and Bakersfield, California, respectively. Nighttime concentrations were 10–30% lower, suggesting that these particles are dominated by secondary production. Simulation of the data with a box model suggests that these particles were formed by the condensation of ammonia and nitric acid onto background or primary sulfate particles. These hygroscopic particles had a mass distribution peak in the accumulation mode (0.56–1.0 μ m) at all times. Daytime PM₁₀ carbon particle concentrations were measured to be 9.5 μ g m^?3, 15.1 μ g m^?3, and 16.2 μ g m^?3 at Sacramento, Modesto, and Bakersfield, respectively. Corresponding nighttime concentrations were 200–300% higher, suggesting that these particles are dominated by primary emissions. The peak in the carbon particle mass distribution varied between 0.2–1.0 μ m. Carbon particles emitted directly from combustion sources typically have a mass distribution peak diameter between 0.1–0.32 μ m. Box model calculations suggest that the formation of secondary organic aerosol is negligible under cool winter conditions, and that the observed shift in the carbon particle mass distribution results from coagulation in the heavily polluted concentrations experienced during the current study. The analysis suggests that carbon particles and sulfate/ammonium/nitrate particles exist separately in the atmosphere of the San Joaquin Valley until coagulation mixes them in the accumulation mode.     

Advances in the stabilization of flexible PVC by using a liquid calcium‐zinc technology

The global market for liquid mixed‐metal stabilizers is migrating toward heavy‐metal‐free products, Historically, these systems have not been performance and cost competitive. High efficiency calcium‐zinc stabilizers have the potential to replace heavy‐metal‐based products. The intrinsic value of non‐phenolic lubricating calcium intermediates and calcium‐zinc stabilizers is discussed.     

Low‐velocity impact of nanocomposite and polymer plates

Nanocomposites are more widely studied today because of higher stiffness, decreased permeability, thermal stability, and many other properties superior to those of regular polymers. However, manufacturers are concerned about implementing nanocomposites because of their lower impact properties with respect to the base polymer. This study focused on low‐velocity impact tests of a thermoplastic olefin by itself and with 5 wt % nanoclay. The impact tests were conducted at ?40, 23.9, and 65.6°C until the polymer and nanocomposite plates experienced complete striker penetration. The force–time and force–deflection responses obtained from the impact testing provided a means of comparing the impact performances of the two materials. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2309–2315, 2005     

Bisphenol S Impairs Invasion and Proliferation of Extravillous Trophoblasts Cells by Interfering with Epidermal Growth Factor Receptor Signaling

The placenta supports fetal growth and is vulnerable to exogenous chemical exposures. We have previously demonstrated that exposure to the emerging chemical bisphenol S (BPS) can alter placental endocrine function. Mechanistically, we have demonstrated that BPS interferes with epidermal growth factor receptor (EGFR) signaling, reducing placenta cell fusion. Extravillous trophoblasts (EVTs), a placenta cell type that aids with vascular remodeling, require EGF to invade into the maternal endometrium. We hypothesized that BPS would impair EGF-mediated invasion and proliferation in EVTs. Using human EVTs (HTR-8/SVneo cells), we tested whether BPS could inhibit the EGF response by blocking EGFR activation. We also evaluated functional endpoints of EGFR signaling, including EGF endocytosis, cell invasion and proliferation, and endovascular differentiation. We demonstrated that BPS blocked EGF-induced phosphorylation of EGFR by acting as a competitive antagonist to EGFR. Transwell assay and a three-dimensional microfluidic chip invasion assay revealed that BPS exposure can block EGF-mediated cell invasion. BPS also blocked EGF-mediated proliferation and endovascular differentiation. In conclusion, BPS can prevent EGF-mediated EVT proliferation and invasion through EGFR antagonism. Given the role of EGFR in trophoblast proliferation and differentiation during placental development, our findings suggest that maternal exposure to BPS may contribute to placental dysfunction via EGFR-mediated mechanisms.     

Sex Attractant Pheromone of the Luna Moth, <Emphasis Type="Italic">Actias luna</Emphasis> (Linnaeus)

Giant silk moths (Lepidoptera: Saturniidae) typically are not well represented as larvae or adults in community level inventories of Lepidoptera, and as a result, little is known about their population dynamics. Furthermore, in recent years, many species of silk moths appear to have experienced population declines. Volatile sex pheromones are powerful sampling tools that can be used in operational conservation and monitoring programs for insects. Here, we describe the identification of the sex attractant pheromone of a giant silk moth, the luna moth Actias luna. Coupled gas chromatography-electroantennographic detection and gas chromatography-mass spectrometric analyses of extracts from pheromone glands of female luna moths supported the identification of (6E,11Z)-6,11-octadecadienal (E6,Z11–18:Ald), (6E)-6-octadecenal (E6–18:Ald), and (11Z)-11-octadecenal (Z11–18:Ald) as the compounds in extracts that elicited responses from antennae of male moths. These identifications were confirmed by synthesis, followed by testing of blends of the synthetic compounds in field trials in Ontario, Canada, and Kentucky, USA. Male moths were attracted to synthetic E6,Z11–18:Ald as a single component. Attraction appeared to be enhanced by addition of E6–18:Ald but not Z11–18:Ald, suggesting that the luna moth pheromone consists of a blend of E6,Z11–18:Ald and E6–18:Ald.     

Molybdenum carbide catalysts for water–gas shift

Molybdenum carbide (Mo₂C) was demonstrated to be highly active for the water–gas shift of a synthetic steam reformer exhaust stream. This catalyst was more active than a commercial Cu–Zn–Al shift catalyst under the conditions employed (220–295°C and atmospheric pressure). In addition, Mo₂C did not catalyze the methanation reaction. There was no apparent deactivation or modification of the structure during 48 h on‐stream. The results suggest that high surface area carbides are promising candidates for development as commercial water–gas shift catalysts. This revised version was published online in July 2006 with corrections to the Cover Date.     

Freeze-form extrusion fabrication of functionally graded materials

Presented in this paper is a novel additive manufacturing technology for making three-dimensional parts with functionally graded materials (FGMs), called Freeze-form Extrusion Fabrication (FEF). The system development included a triple-extruder mechanism, extruder modeling and control, pastes extrusion planning for desired composition gradients, and software coding for motion and extrusion control. The effectiveness of the developed FEF system was demonstrated first by fabricating limestone (CaCO₃) parts with graded colors and then by fabricating ‘green’ parts with graded compositions between alumina (Al₂O₃) and zirconia (ZrO₂). The fabricated part went through post-processing, and the sintered part was analyzed using energy dispersive spectroscopy (EDS) to determine its material compositions.     

Host Recognition by the Specialist Hoverfly <Emphasis Type="Italic">Microdon mutabilis</Emphasis>, a Social Parasite of the Ant <Emphasis Type="Italic">Formica lemani</Emphasis>

The larva of the hoverfly Microdon mutabilis is a specialist social parasite of the ant Formica lemani that is adapted to local groups of F. lemani colonies but mal-adapted to colonies of the same species situated only a few hundred meters away. At a study site in Ireland, F. lemani shares its habitat with four other ant species. All nest under stones, making the oviposition choice by M. mutabilis females crucial to offspring survival. In this study, we tested the hypothesis that, as an extreme specialist, M. mutabilis should respond to cues derived from its host rather than from its microenvironment, a phenomenon that has hitherto only been addressed in the context of herbivorous insects and their parasitoids. In behavioral assays, M. mutabilis females reacted to volatiles from F. lemani colonies by extending their ovipositors, presumably probing for an oviposition substrate. This behavior was not observed toward negative controls or volatiles from colonies of Myrmica scabrinodis, the host ant of the closely related Microdon myrmicae. Coupled gas chromatography-electroantennography (GC-EAG) that used antennal preparations of M. mutabilis located a single physiologically active compound within an extract of heads of F. lemani workers. Coupled GC-mass spectrometry (GC-MS) tentatively identified the compound as a methylated methylsalicylate. GC co-injection of the extract with authentic samples showed that of the four possible isomers (methyl 3-, 4-, 5-, and 6-methylsalicylate), only methyl 6-methylsalicylate co-eluted with the EAG-active peak. Furthermore, the response to methyl 6-methylsalicylate was four times higher than to those of the other isomers. Coupled GC-EAG and GC-MS also revealed physiological responses to two constituents, 3-octanone and 3-octanol, of the M. scabrinodis alarm pheromone. However, the behavioral trials did not reveal any behavior that could be attributed to these compounds. Results are discussed in the context of four phases of host location behavior, and of the characteristics, which volatile cues should provide to be useful for an extreme specialist such as M. mutabilis.     

Inhibition of dicing of guanosine-rich shRNAs by quadruplex-binding compounds

RNA interference is triggered by small hairpin precursors that are processed by the endonuclease dicer to yield active species such as siRNAs and miRNAs. To regulate the RNAi-mediated suppression of gene expression, we imagined a strategy that relies on the sequence-specific inhibition of shRNA precursor processing by immediate RNA-small molecule interactions. Here, we present a first step in this direction by augmenting shRNAs with guanosine-rich sequences that are prone to fold into four-stranded structures. The addition of small molecules that selectively bind to such quadruplex sequences should allow for the specific inhibition of dicing of shRNAs that contain suitable G-rich elements. In an attempt to find compounds that protect against dicer processing, we have examined the effects of quadruplex-binding compounds on the dicer processing of shRNAs containing G-quadruplexes. Although a variety of small molecules that are known to bind to quadruplexes inhibited in vitro dicing of shRNAs, only two substance classes, namely certain porphyrazines and bisquinolinium compounds, showed selective inhibition of G-rich shRNAs compared to control sequences lacking guanine-rich elements. The G-rich shRNAs displayed a potent knockdown of gene expression in mammalian cell culture, but the effect was not influenced by addition of the respective quadruplex-binding compounds.