Passive Filtration of Airborne Particles from Buildings Ventilated by Natural Convection: Design Procedures and a Case Study at the Buddhist Cave Temples at Yungang,China

Air exchange between interior spaces and the outdoor atmosphere can occur due to a variety of processes, including wind-driven flows and natural convectiondriven flows. As air is exchanged with the outdoors, airborne particles can be brought inside. Depending on the use of the indoor space, the presence of particles in indoor air could be a nuisance to the occupants or could be damaging to materials kept indoors. While one obvious solution to such problems is to install a mechanical air filtration system, that is not always practical. In particular, the character of some historical houses and some archaeological sites would be degraded by the presence of a mechanical air distribution system, and in some parts of the world the reliable electrical power supply needed for such a filtration system may not be available. In the present paper we consider principles for the design of passive filtration systems in which air motion through the filter material is induced by a natural convection flow rather than by a mechanical fan. A fluid mechanical model first is described for predicting the air flow through an interior space that acts as a thermal siphon. The effect of placing filter material in the path of such air flows is examined next. The indoor-outdoor air quality model of Nazaroff and Cass (1989a) is matched to the natural convection air exchange model, and calculations are performed to determine the relationship between the outdoor particle size distribution and indoor particle size distributions and particle deposition rates given a passive filtration system. Example calculations are worked for the case of a passive particle filtration system that could be installed to protect the interior of the Buddhist cave temples at Yungang, China. These are a collection of manmade cave temples dating from the 5th century AD, now situated in the middle of one of China's largest coal-mining regions with its accompanying air pollution problems.     

Use of Difunctional Compounds During Rapid Steam Hydrolysis (Rash) Pretreatment

Mixed hardwood chips were treated with difunctional compounds as catalysts to study the reaction of wood with steam. The Rapid Steam Hydrolysis (RASH) pretreatment process was used for steam treatment. The difunctional compounds studied were maleic anhydride, phthalic anhydride, isophthalic acid, and terephthalic acid at 1.5% concentration based on dry wood weight. RASH pretreatment was performed for one minute at 180°C, 200°, 220°C, 230°C, 240°C, and 260°C. These compounds strongly modified the RASH pretreated material, especially the physical structure. Overall recovery of the pretreated catalyzed and uncatalyzed solids decreased with an increase in RASH temperatures. Catalyst addition did not make a difference on the recovery of pretreated solids. Cellulose degradation increased with temperature for catalyzed systems. Hemicellulose solubilization and degradation were extremely sensitive to the type of catalyst and RASH temperatures. Almost all of the hemicellulose was lost at higher temperatures. Lignin losses did not appear to be affected by the addition of catalyst except at 260°C. Enzymatic rates were improved by addition of the catalysts, especially at the lower temperatures. The maleic anhydride gave the highest enzymatic rates at all temperatures, and phthalic anhydride gave the second highest. The water solubles generally followed the same trends as the enzymatic hydrolysis rates and increased with the addition of catalysts, especially maleic anhydride.     

Numerical Simulation of Anisotropic Shrinkage in a 2D Compact of Elongated Particles

Microstructural evolution during simple solid-state sintering of two-dimensional compacts of elongated particles packed in different arrangements was simulated using a kinetic, Monte Carlo model. The model used simulates curvature-driven grain growth, pore migration by surface diffusion, vacancy formation, diffusion along grain boundaries, and annihilation. Only the shape of the particles was anisotropic; all other extensive thermodynamic and kinetic properties such as surface energies and diffusivities were isotropic. We verified our model by simulating sintering in the analytically tractable cases of simple-packed and close-packed, elongated particles and comparing the shrinkage rate anisotropies with those predicted analytically. Once our model was verified, we used it to simulate sintering in a powder compact of aligned, elongated particles of arbitrary size and shape to gain an understanding of differential shrinkage. Anisotropic shrinkage occurred in all compacts with aligned, elongated particles. However, the direction of higher shrinkage was in some cases along the direction of elongation and in other cases in the perpendicular direction, depending on the details of the powder compact. In compacts of simple-packed, mono-sized, elongated particles, shrinkage was higher in the direction of elongation. In compacts of close-packed, mono-sized, elongated particles and of elongated particles with a size and shape distribution, the shrinkage was lower in the direction of elongation. The results of these simulations are analyzed, and the implication of these results is discussed.     

Synthesis and structure-activity relationship of the isoindolinyl benzisoxazolpiperidines as potent,selective, and orally active human dopamine D4 receptor antagonists

A new class of potent dopamine D(4) antagonists was discovered with selectivity over dopamine D(2) and the alpha-1 adrenoceptor. The lead compound was discovered by screening our compound collection. The structure-activity relationships of substituted isoindoline rings and the chirality about the hydroxymethyl side chain were explored. The isoindoline analogues showed modest differences in potency and selectivity. The S enantiomer proved to be the more potent enantiomer at the D(4) receptor. Several analogues with greater than 100-fold selectivity for D(4) over D(2) and the alpha-1 adrenoreceptor were discovered. Several selective analogues were active in vivo upon oral or intraperitoneal administration. A chiral synthesis starting from either D- or L-O-benzylserine is also described.     

Brillouin-Scattering Study of the Elastic Constants of ErVO4

The room-temperature elastic constants of ErVO₄ were considerably smaller than those of isostructural silicate and phosphate analogs. The generally "less-rigid" crystalline lattice and weaker metal-oxygen bond-strength in the RVO₄ (R = rare earth elements) phases indicates that these materials are of interest for potential applications as an interphase component in toughened oxide ceramic composites.     

An improved accelerated weathering protocol to anticipate Florida exposure behavior of coatings

A new accelerated weathering protocol has been developed which closely replicates the performance of automotive and aerospace coating systems exposed in South Florida. IR spectroscopy was used to verify that the chemical composition changes that occurred during accelerated weathering in devices with a glass filter that produced a high fidelity reproduction of sunlight’s UV spectrum matched those that occurred during natural weathering. Gravimetric water absorption measurements were used to tune the volume of water absorption during accelerated weathering to match that which occurred during natural weathering in South Florida. The frequency of water exposure was then scaled to the appropriate UV dose. A variety of coating systems were used to verify the correlation between the physical failures observed in the accelerated weathering protocol and natural weathering in South Florida. The new accelerated weathering protocol correctly reproduced gloss loss, delamination, cracking, blistering, and good performance in a variety of diverse coating systems. For automotive basecoat/clearcoat paint systems, the new weathering protocol shows significant acceleration over both Florida and previous accelerated weathering tests. For monocoat aerospace systems, the new weathering protocol showed less acceleration than for automotive coatings, but was still an improvement over previous accelerated tests and was faster than Florida exposure.     

Automated High-Throughput Fatty Acid Analysis of Umbilical Cord Serum and Application to an Epidemiological Study

Large population studies show that polyunsaturated fatty acids are important for human health, but determining relationships between the health benefits and the fatty acid content has been hampered by the unavailability of labor-effective high-throughput technologies. An automated high throughput fatty acid analysis was developed from a previous procedure based on direct transesterification including the automation of chemical procedures, data acquisition and automatic data processing. The method was validated and applied to umbilical cord serum samples in an epidemiological study. The method was linear in the range of 1–600 μg/mL serum with r ² ≥0.99. The within-run CV was <5.4% for 23 fatty acids and a range of recoveries over three concentrations were 76–119% in a low-lipid matrix with the exception of 14:0. The fatty acid concentration as measured by the robotic method for human plasma was in good agreement with the Lepage & Roy method. The fatty acid profile in umbilical cord serum from American subjects (n = 287) showed an average of 38.0, 24.9, 32.0 and 4.6% of total fatty acids for saturates, monounsaturates, n-6 and n-3 polyunsaturates, respectively. This is the first report of a complete, validated, cost-effective, automated, high throughput fatty acid measurement method along with application to a population-based study. Automated fatty acid analysis coupled with automated data processing greatly facilitates the high throughput, 72 samples transesterified in 6 h, required for large population-based studies.     

Ultrarapid Phase Conversion in β-Alumina Tubes

β-Alumina, the electrolyte of choice of sodium/sulfur and sodium/metal chloride batteries and alkali-metal thermal-electric converters, was sintered from precursor phases to high β-phase purity in less than 15 s from the onset of densification by rapid pass-through rf induction coupled plasma sintering. The maximum instantaneous shrinkage rate was 1.8%/s. The resistivity was measured to be 13.8 ± 1.4 Ω·cm. The rapid conversion found is a significant improvement over conventional processing of β-alumina, which requires extended postsintering annealing times to obtain high β-phase purity.