Numerical Characterization of Particle Beam Collimation: Part II Integrated Aerodynamic-Lens–Nozzle System

As a sequel to our previous effort on the modeling of particle motion through a single lens or nozzle, flows of gas–particle suspensions through an integrated aerodynamic-lens–nozzle inlet have been investigated numerically. It is found that the inlet transmission efficiency (η_t) is unity for particles of intermediate diameters (D_p ～ 30–500 nm). The transmission efficiency gradually diminishes to ～40% for large particles (D_p > 2500 nm) because of impact losses on the surface of the first lens. There is a catastrophic reduction of η_t to almost zero for very small particles (D_p ≤ 15 nm) because these particles faithfully follow the final gas expansion. We found that, for very small particles, particle transmission is mainly controlled by nozzle geometry and operating conditions. A lower upstream pressure or a small inlet can be used to improve transmission of very small particles, but at the expense of sampling rate, or vice versa. Brownian motion exacerbates the catastrophic reduction in η_t for small particles; we found that the overall particle transmission efficiency can be roughly calculated as the product of the aerodynamic and the purely Brownian efficiencies. For particles of intermediate diameters, Brownian motion is irrelevant, and the modeling results show that the transmission efficiency is mainly controlled by the lenses. Results for an isolated lens or nozzle are used to provide guidance for the design of alternative inlets. Several examples are given, in which it is shown that one can configure the inlet to preferentially sample large particles (with η_t > 50% for D_p = 50–2000 nm) or ultrafine particles (with η_t > 50% for D_p = 20–1000 nm). Some of the results have been compared with experimental data, and reasonable agreement has been demonstrated.     

Deep hydration: Poly(ethylene glycol) Mw 2000–8000 Da probed by vibrational spectrometry and small-angle neutron scattering and assignment of ΔG° to individual water layers

Aqueous solutions of poly(ethylene glycol) (PEG) exhibit some remarkable properties, among which is the small changes in water activity compared to the volumes occupied by the PEG: For example, the water in a 20% mass fraction solution of 6000 Da PEG has an activity of 0.9939. We have investigated PEGs with molecular weights 200, 400, 1000, 2000, 4000, and 8000 Da in the concentration range 1% to 17% mass fraction at neutral pH and with added KCl concentrations of 10 mmol L^?1 in aqueous solutions–conditions near those for promoting protein crystallization. These solutions exhibit a structural change at around 6% mass fraction as seen in the solution viscosities, compressibilities, and infrared spectra. Raman spectroscopy shows that the PEGs remain in the same structural form over the concentration range, and the infrared spectra indicate that the change must be due to a local shift in the water structure. Modeling of the results from small-angle neutron scattering (SANS) on the solutions suggests that the structures of the PEGs in the molecular mass range 2000 Da to 8000 Da are paired in the solution, and the separation distance decreases with increasing PEG concentration. From the structure, it becomes clear that the small effect on water activity occurs because of screening by the more weakly bound outer layers. From the bulk measurement of a_w and with reasonable assumptions, a free energy ΔG° can be assigned to each of the fourth, third, and second hydration layers.     

Thermal analysis of novel underfill materials with optimum processing characteristics

This work encompasses the development of low‐viscosity cyclic oligomer underfill formulations that cure without heat evolution. Boron nitride, silica‐coated aluminum nitride, and alumina ceramic powders were used as fillers in cyclic butylene terephthalate oligomer melts. The melts were heated with a suitable catalyst to induce polymerization. The effects of the filler type and composition on the thermal and mechanical properties of the poly(butylene terephthalate)/filler composites were examined with differential scanning calorimetry, temperature‐modulated differential scanning calorimetry, thermogravimetric analysis, thermomechanical analysis, and dynamic mechanical analysis. Scanning electron microscopy was employed to elucidate the morphology of these composites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1300–1307, 2005     

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.     

Copper(I)-Dioxygen Adducts and Copper Enzyme Mechanisms

Primary copper(I)-dioxygen (O₂) adducts, cupric-superoxide complexes, have been proposed intermediates in copper-containing dioxygen-activating monooxygenase and oxidase enzymes. Here, mechanisms of C−H activation by reactive copper-(di)oxygen intermediates are discussed, with an emphasis on cupric-superoxide species. Over the past 25 years, many synthetically derived cupric-superoxide model complexes have been reported. Due to the thermal instability of these intermediates, early studies focused on increasing their stability and obtaining physical characterization. More recently, in an effort to gain insight into the possible substrate oxidation step in some copper monooxygenases, several cupric-superoxide complexes have been used as surrogates to probe substrate scope and reaction mechanisms. These cupric superoxides are capable of oxidizing substrates containing weak O−H and C−H bonds. Mechanistic studies for some enzymes and model systems have supported an initial hydrogen-atom abstraction via the cupric-superoxide complex as the first step of substrate oxidation.     

The effects of long‐term exposure of flax fiber reinforced polymer to salt solution at high temperature on tensile properties

Most research on natural fiber composites has been primarily conducted on randomly‐oriented fibers. This study is focused on the short‐ and long‐term performances of flax fiber‐reinforced polymer (Flax‐FRP) made from continuous unidirectional fiber mats, and compares it to Glass‐FRP composite. The study looked into the effect of number of layers on properties, comparing wet layup (WL) to vacuum bag (VB) molding, and aging in a 3.5% salt solution for up to 365 days at 23, 40, and 55°C. Results show that Flax‐FRP has a tensile strength and modulus of one third the values of Glass‐FRP. Using the VB process, Flax‐FRP showed a strength and modulus 18 and 36% higher, respectively, than WL specimens. As the number of layers increased from one to five, the strength and modulus also increased but stabilized at three layers. After 365 days of conditioning at 23, 40, and 55°C, WL specimens showed a strength retention of 81, 73, and 69%, respectively. Using the Arrhenius relationship, it was estimated that both WL and VB Flax‐FRP would retain 60% of their tensile strength after 100 years of saltwater exposure at an annual mean temperature of 10°C. POLYM. COMPOS., 37:3234–3244, 2016. © 2015 Society of Plastics Engineers     

Fire Injury Reduces Inducible Defenses of Lodgepole Pine against Mountain Pine Beetle

We examined the effect of wildfire injury on lodgepole pine chemical defenses against mountain pine beetle. We compared the constitutive phloem chemistry among uninjured, lightly-, moderately-, and severely-injured trees, and the induced chemistry elicited by simulated beetle attack, among these same categories. We also compared the entry rates of caged female beetles into trees of these categories. The volatiles we studied included thirteen monoterpene hydrocarbons, four allylic monoterpene alcohols, one ester, and one phenyl propanoid, of which the monoterpene hydrocarbons always comprised 96% or more of the total. Fire injury reduced the total concentration of these compounds in the induced but not constitutive phloem tissue of lodgepole pines. Fire injury also affected the relative composition of some volatiles in both induced and constitutive phloem. For example, increased fire injury reduced 4-allylanisole, a host compound that inhibits mountain pine beetle aggregation. Increased fire injury also increased (−) α-pinene, which can serve as precursor of pheromone communication. However, it also reduced myrcene and terpinolene, which can serve as stimulants and synergists of pheromone communication. Beetle entry did not show statistical differences among fire injury categories, although there was a trend to increased entry with fire injury. These results suggest that the reduced ability of trees to mobilize induced chemical defenses is an important mechanism behind the higher incidence of attack on fire-injured trees in the field. Future studies should concentrate on whether beetles that enter fire-injured trees are more likely to elicit aggregation, based on the differences we observed in volatile composition.     

Poly(styrene-b-isobutylene-b-styrene) block copolymer ionomers (BCPI) and BCPI/silicate nanocomposites. 2. NaBCPI sol-gel polymerization templates

Polystyrene (PS) blocks in poly(styrene-b-isobutylene-b-styrene) (PS-PIB-PS) block copolymers were partially sulfonated and the acid groups converted to Na⁺SO₃⁻ groups to create ionomers. Then, dimethylacetamide was used to selectively swell the ionic PS domains and the swollen films were exposed to sol-gel reactive tetraethylorthosilicate solutions. (EtO)_4−xSi(OH)_x monomers then permeated films so that sol-gel reactions occurred within/around the ionic PS domains. Environmental scanning electron microscopy/energy dispersive X-ray spectroscopy investigations showed that silicate structures can be incorporated within the interior of the ionomer films. Differential scanning calorimetry studies indicated that there is no variance in the PIB block T_g with respect to ionomer formation, or with respect to silicate loading of the ionomer at low levels, which suggests that the silicate component does not reside in the PIB phase. ²³Na solid state NMR spectroscopy detected isolated Na⁺SO₃⁻ groups as well as aggregated SO₃⁻Na⁺ ion pairs for ‘as cast’ and ‘dry’ non-silicate containing ionomer samples. In a hydrated sample, almost all Na⁺ ions were solvent-separated. AFM analysis showed that phase separation exists, but that the degree of order is significantly less than that for hybrids based on the corresponding benzyltrimethylammonium ionomer. This frustrated morphology was also seen in the results of small angle X-ray scattering experiments. Given the scale of organic/inorganic heterogeneity, these hybrids are properly classified as nanocomposites.     

Towards an Environmentally Acceptable Heterogeneous Catalytic Method of Producing Adipic Acid by the Oxidation of Hydrocarbons in Air

A survey is given of the catalytic methods potentially available for the production of adipic acid by the oxidation of readily available hydrocarbon precursors under environmentally benign conditions. Encouraging results are reported using H₂O₂ as oxidant and microporous FeAlPO-5 as catalyst at moderate temperatures.