Optimized detection of particulates from liquid samples in the aerosol phase: Focus on black carbon

Operational parameters for a single particle soot photometer (SP2) and a CETAC Marin-5 nebulizer were optimized for detection of particulates aerosolized from liquid samples. The sensitivity of nebulization efficiency on nebulizer input gas pressure, liquid sample flow rate, and alcohol doping of the sample were explored. The nebulization efficiency of the Marin-5 was found to be roughly independent of applied gas pressure once above a minimum pressure. The nebulization efficiency changed by ～50% for an order of magnitude change in liquid sample flow. Doping the sample with isopropyl alcohol at a 1:1 ratio results in a ～50% relative increase in nebulization efficiency over a broad range of liquid flows. These results should apply to all particulate materials in the size range studied. SP2 operational parameters including sheath and sample flow were explored to optimize detection of refractory black carbon (rBC) specifically via coupling to the nebulizer. The SP2 tested samples up to 5 cc s?1 with 100% detection of rBC in its size range of detection, with increased sample jet spread and corresponding lack of detected rBC in the air at higher flows, leading to a total undetected rBC mass fraction of ～15% at 16 cc s?1. Varying sheath flow does not improve this result, which is significant because under reasonable Marin-5 operating conditions, the SP2 only samples a fraction of the total air flow out of the nebulizer. Recommended operational parameters for cases of sample with low rBC loadings are presented: first, when very little liquid sample is available; second, when considerable sample is available.

© 2017 American Association for Aerosol Research     

Large deformation mechanical behavior of gelatin–maltodextrin composite gels

The large deformation failure behavior of gelatin–maltodextrin composite gels was assessed. All the studied compositions were selected to lie within the incompatibility domain of the gelatin–maltodextrin phase diagram at 60°C, which produced gelatin continuous (maltodextrin included) and maltodextrin continuous (gelatin included) composites. Composite microstructural evaluation was performed using confocal laser scanning microscopy (CLSM). The large deformation mechanical behavior was measured in tension and compression experiments. Crack–microstructure interactions were investigated by dynamic experiments on the CLSM. The gelatin continuous composites exhibited pseudo-yielding behavior during tension and compression testing, and there was a significant decrease in modulus that arose from interfacial debonding. Conversely, the maltodextrin continuous composites exhibited an essentially brittle failure behavior, and there was an approximately linear increase in stress with increasing strain until fracture (which occurred at significantly lower strains than for the gelatin continuous composites). The CLSM observation of the failure of the notched samples also demonstrated interfacial debonding in the crack path; however, this occurred at significantly smaller strains than for the gelatin continuous samples with minimal elastic–plastic deformation of the maltodextrin matrix. The Poisson ratio was estimated to be close to 0.5 for these composites for all examined compositions. Compositions corresponding to a tie line of the phase diagram were also investigated to assess the influence of the relative phase volume (for constant phase compositions) on the failure behavior. The majority of the parameters subsequently extracted from the stress–strain curves were apparently functions of the individual phase volumes. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 124–135, 2001     

The effect of the previous crop on the growth,nitrogen uptake and yield of winter barley intended for malting

Winter barley which received a range of nitrogen rates, was grown at Rothamsted as a test crop after winter oats, winter barley, winter beans, oilseed rape or potatoes, to compare the effects of previous crop on growth and N uptake. In the autumn following the first year crops, the largest amount of residual inorganic N found in the soil was after potatoes, the smallest after oats. Throughout the second season the heaviest crops of barley, which also contained the most N, were after potatoes, and the lightest were after barley. To produce grain with a N concentration of less than 1.8% N (w/w, dry wt), acceptable for malting, it was found that not more than 75 kg N ha⁻¹ after barley and 125 kg N ha⁻¹ after oats, 100 kg N ha⁻¹ after beans and 50 kg N ha⁻¹ after rape or potatoes could be applied. The results demonstrated that barley of acceptable quality for malting can be grown after a break crop, providing that the rate of N fertiliser is suitably adjusted to take account of the residual fertility, but the results do not suggest that residual soil N affects the grain N concentration differently to N applied as fertiliser early in the season.     

(2<Emphasis Type="Italic">S</Emphasis>,8<Emphasis Type="Italic">Z</Emphasis>)-2-Butyroxy-8-heptadecene: Major Component of the Sex Pheromone of Chrysanthemum Gall Midge, <Emphasis Type="Italic">Rhopalomyia longicauda</Emphasis>

The sex pheromone of the chrysanthemum gall midge, Rhopalomyia longicauda (Diptera: Cecidomyiidae), the most important insect pest in commercial plantations of chrysanthemum, Dendranthema morifolium (Ramat.) Tzvel., in China, was identified, synthesized, and field-tested. Volatile chemicals from virgin females and males were collected on Porapak in China and sent to the United Kingdom for analysis. Coupled gas chromatographic–electroantennographic detection (GC-EAG) analysis of volatile collections from females revealed two compounds that elicited responses from antennae of males. These compounds were not present in collections from males. The major EAG-active compound was identified as 2-butyroxy-8-heptadecene by gas chromatographic (GC) retention indices, mass spectra, in both electron impact and chemical ionization modes, hydrogenation, epoxidation, and derivatization with dimethyldisulfide. The lesser EAG-active compound was identified as the corresponding alcohol. The ratio of butyrate to alcohol in the collections was 1:0.26. Racemic (Z)-8-heptadecen-2-ol and the corresponding butyrate ester were synthesized from (Z)-7-hexadecenyl acetate, and the synthetic compounds found to have identical GC retention indices and mass spectra to those of the natural, female-specific components. Analysis of the volatile collections on an enantioselective cyclodextrin GC column showed the natural pheromone contained (2S,8Z)-2-butyroxy-8-heptadecene. Field tests showed that rubber septa containing racemic (Z)-2-butyroxy-8-heptadecene were attractive to R. longicauda males. The (naturally occurring) S-enantiomer was equally as attractive as the racemate, while the R-enantiomer was not attractive to males, and did not inhibit the activity of the S-enantiomer. The attractiveness of the butyrate was significantly reduced by the presence of even small amounts of the corresponding alcohol.     

The distribution of calcium in apples with watercore

The transverse distribution of calcium across median slices of Cox's Orange Pippin apples affected by watercore was compared with that in slices from the remaining bulked sound fruit in samples at harvest. Concentrations of calcium were lower in all zones of apples with watercore. In affected apples, proportions of calcium were higher in the outer zones and much lower in the core zones.     

A Facile Strategy for the Fabrication of Cell-Laden Porous Alginate Hydrogels based on Two-Phase Aqueous Emulsions

Porous alginate (Alg) hydrogels possess many advantages as cell carriers. However, current pore generation methods require either complex or harsh fabrication processes, toxic components, or extra purification steps, limiting the feasibility and affecting the cellular survival and function. In this study, a simple and cell-friendly approach to generate highly porous cell-laden Alg hydrogels based on two-phase aqueous emulsions is reported. The pre-gel solutions, which contain two immiscible aqueous phases of Alg and caseinate (Cas), are cross-linked by calcium ions. The porous structure of the hydrogel construct is formed by subsequently removing the Cas phase from the ion-cross-linked Alg hydrogel. Those porous Alg hydrogels possess heterogeneous pores ≈100 µm and interconnected paths. Human white adipose progenitors (WAPs) encapsulated in these hydrogels self-organize into spheroids and show enhanced viability, proliferation, and adipogenic differentiation, compared to non-porous constructs. As a proof of concept, this porous Alg hydrogel platform is employed to prepare core-shell spheres for coculture of WAPs and colon cancer cells, with WAP clusters distributed around cancer cell aggregates, to investigate cellular crosstalk. This efficacious approach is believed to provide a robust and versatile platform for engineering porous-structured Alg hydrogels for applications as cell carriers and in disease modeling.