Dealing with Dust Entrained in the Nitrogen Plume Demonstration.

Water condensation plumes produced by the addition of iron powder to liquid nitrogen can be contaminated with small quantities of particulate matter. Variations on the plume demonstration, including those using noisemakers, are described to help minimize the release of particulates into the air.

Plumes from Using Iron to Boil Liquid Nitrogen to Illustrate the Importance of Surface Area.

The relationship between surface area and dynamics of processes can be demonstrated by adding iron at room temperature to liquid nitrogen. The rate at which the liquid nitrogen boils to produce gas is related to the surface area of the iron. Adding iron in the form of consistent units that have measurable sizes can be readily connected to observable differences in rates of nitrogen gas production. For example, samples of smaller iron spheres with their greater surface area transfer heat more quickly than do larger spheres of the same volume to liquid nitrogen causing it to boil faster, but more briefly, and produce larger plumes of nitrogen gas from a container vent. The plumes are essentially comprised of nitrogen and water, which make them potentially safer than plumes from other demonstrations such as the "genie in a bottle", based on hydrogen peroxide decomposition. These simple activities can be used as stand-alone demonstrations or as the basis of laboratory activities.

Infrared Spectroscopic Analysis of the Adsorption of Pyridine Carboxylic Acids on Colloidal Ceria.

Surface adsorption of a homologous series of pyridine carboxylic acids on a hydrated colloidal cerium dioxide (ceria) film is characterized using the combination of experimental and computationally determined infrared (IR) spectra. Experimental analyses employ attenuated total reflectance (ATR) IR spectroscopy of deposited colloidal ceria thin films equilibrated with three pyridine carboxylic acids at pH 3.0, 5.5, and 8.5. The corresponding computational IR spectra for the energy-minimized intermediate and base forms of the pyridine carboxylic acids use density functional theory calculations at the B3LYP/6-311++G** level of theory. Solvent effects are modeled using both the COSMO implicit solvation model and the inclusion of explicit water molecules. Experimental IR spectra show that the adsorptive interactions between the pyridine carboxylic acids and ceria surface are due to the outer-sphere coordination of cerium ions in the films. Vibrational assignments based on combined experimental and computational results indicate that both pyridyl ring nitrogen and carboxylate functional groups account for the interaction of pyridine carboxylic acids at ceria surfaces. Experimentally determined Langmuir constants point to the intermediate form of picolinic acid (pyridine-2-carboxylic acid) as having the strongest adsorption to ceria compared to the other pyridine carboxylic acids investigated. The enhanced adsorption of picolinic acid is attributed to the adjacency of the protonated pyridyl nitrogen and the carboxylate group relative to nicotinic acid (pyridine-3-carboxylic acid) and isonicotinic acid (pyridine-4-carboxylic acid).

Synthesis of palladium colloids within polydimethylsiloxane and their use as catalysts for hydrogenation.

The presence of unreacted silanes within cured polydimethylsiloxane (PDMS) leads to the reduction of tetrachloropalladate(II) ions, generating encapsulated palladium colloids. The resulting colloids had varied morphology and were typically less than 80 nm in size. The Pd/PDMS vessels, which contained 0.10±0.01% Pd, were effective catalysts for the hydrogenation of carbon-carbon multiple bonds for at least ten successive runs with no loss of catalytic activity, and the catalyst does not exhibit the same pyrophoric behavior as Pd on carbon after use in hydrogenation reactions. In addition, storage of previously used Pd/PDMS vessels for 6 months in air did not affect the catalytic activity, and the overall morphology of the catalysts after use was the same as those that have not been involved in catalytic reactions.

Characterization of a virion occlusion-defective Autographa californica multiple nucleopolyhedrovirus mutant lacking the p26, p10 and p74 genes.

Nucleopolyhedroviruses (NPVs), family Baculoviridae, are insect-specific viruses with the potential to control insect pests in agriculture and forestry. NPVs are occluded in polyhedral occlusion bodies. Polyhedra protect virions from inactivation in the environment as well as assisting virions in horizontal transmission in the insect population. The process of virion occlusion in the polyhedra is undefined and the genes that regulate the virion occlusion process have not been well investigated yet. An Autographa californica multiple nucleopolyhedrovirus (AcMNPV) mutant (AcDef) that has a 2136 bp DNA deletion, including p26, p10 and p74 genes, has been isolated. No virions were detected in the polyhedra of AcDef. Restoration of all the missing sequences into AcDef led to proper virion occlusion. Individual gene deletion of either p10 or p26 could not abolish virion occlusion in the polyhedra of AcMNPV, but p10 deletion reduced virion occlusion efficiency more than threefold compared with the wild-type AcMNPV. Previous studies by other research groups on deletion of AcMNPV gene p74 suggested that p74 is a per os infectivity factor, and deletion of the p74 gene did not eliminate virion occlusion. Collectively, the three genes (p26, p10 and p74) may act in concert to regulate the virion occlusion process. Therefore, p26, p10 and p74 are all required for proper virion occlusion in the polyhedra of AcMNPV.