Ventilation and posture effects on inhalation exposures to volatile cleaning ingredients in a simulated domestic worker cleaning environment

Associations between cleaning chemical exposures and asthma have previously been identified in professional cleaners and healthcare workers. Domestic workers, including housecleaners and caregivers, may receive similar exposures but in residential environments with lower ventilation rates. Study objectives were to compare exposures to occupational exposure limits (OELs), to determine relative contributions from individual cleaning tasks to overall exposure, and to evaluate the effects of ventilation and posture on exposure. Airborne chemical concentrations of sprayed cleaning chemicals (acetic acid or ammonia) were measured during typical cleaning tasks in a simulated residential work environment. Whole-house cleaning exposures (18 cleaning tasks) were measured using integrated personal sampling methods. Individual task exposures were measured with a sampling line attached to subjects' breathing zones, with readings recorded by a ppbRAE monitor, equipped with a photoionization detector calibrated for ammonia and acetic acid measurements. Integrated sampling results indicated no exposures above OELs occurred, but 95th percentile air concentrations would require risk management decisions. Exposure reductions were observed with increased source distance, with lower exposures from mopping floors compared to kneeling. Exposure reductions were also observed for most but not all tasks when ventilation was used, with implications that alternative exposure reduction methods may be needed.     

Poly(ethylene glycol)s 2000-8000 in water may be planar: A small-angle neutron scattering (SANS) structure study

Poly(ethylene glycol)s of all molecular weights are highly soluble in water. Small-Angle Neutron Scattering (SANS) data has been collected on buffered ionic D₂O solutions of PEGs of nominal molecular weights 2000, 4000, and 8000 Da at a low concentration of 0.5% (w/v). The radii of gyration R_g vary as approximately M_w^0.5, which is consistent with both a Gaussian chain and a flat plate. Numerous types of experiments indicate flaws in the interpretation as a Gaussian chain. When the alternative interpretation is used, the structures in these dilute solutions are found to have a constant area stoichiometry of 1:1 water:-CH₂CH₂O- and are consistent with the data when monomeric molecules are plates of packed chains one chain thick.     

The Sixth Toe: The Modern Culinary Role of the Guinea Pig In Southern Peru

In Peru modern perceptions of class, ethnicity, and social identity dictate whether the domesticated guinea pig (cuy) is considered a delicacy or an unpalatable indigenous food item. In the southern Peruvian city of Moquegua the breeding of cuyes, including the occurrence of many polydactyl individuals, the location of restaurants that serve cuy, meal costs, and behavior associated with cuy consumption attest to the animal's value beyond its dietary role. Partaking of a restaurant-prepared cuy reinforces social bonds and low sierra cultural identity. However, for some upper-class residents in Moquegua and for the majority of residents in the nearby industrial port city of Ilo, the cuy is considered an anomalous food item associated with indigenous culture and is not consumed. Food trends involving either the popularity or the rejection of a traditional Andean meat source reflect ongoing cultural change within sierra and coastal societies in Peru and have implications for other geographic areas.     

On the Substrate Binding of Linoleate 9-Lipoxygenases

Lipoxygenases (LOX; linoleate:oxygen oxidoreductase EC 1.13.11.12) consist of a class of enzymes that catalyze the regio- and stereo specific dioxygenation of polyunsaturated fatty acids. Here we characterize two proteins that belong to the less studied class of 9-LOXs, Solanum tuberosum StLOX1 and Arabidopsis thaliana AtLOX1. The proteins were recombinantly expressed in E. coli and the product specificity of the enzymes was tested against different fatty acid substrates. Both enzymes showed high specificity against all tested C18 fatty acids and produced (9S)-hydroperoxides. However, incubation of the C20 fatty acid arachidonic acid with AtLOX1 gave a mixture of racemic hydroperoxides. On the other hand, with StLOX1 we observed the formation of a mixture of products among which the (5S)-hydroperoxy eicosatetraenoic acid (5S-H(P)ETE) was the most abundant. Esterified fatty acids were no substrates. We used site directed mutagenesis to modify a conserved valine residue in the active site of StLOX1 and examine the importance of space within the active site, which has been shown to play a role in determining the positional specificity. The Val576Phe mutant still catalyzed the formation of (9S)-hydroperoxides with C18 fatty acids, while it exhibited altered specificity against arachidonic acid and produced mainly (11S)-H(P)ETE. These data confirm the model that in case of linoleate 9-LOX binding of the substrate takes place with the carboxyl-group first. Sequence data: The nucleotide sequences reported in this paper are annotated in the GenBank/EMBL data bank under the accession numbers Q06327 and S73865.     

High‐Energy Density Dielectrics and Capacitors for Elevated Temperatures: Ca(Zr,Ti)O3

The Ca(Zr_1?xTi_x)O₃ (CZT) solid solution system is a linear dielectric that is of interest for high‐temperature power capacitor applications. This dielectric was synthesized by conventional solid‐state processes and prototyped into single‐layer CZT capacitors, which were fabricated with interdigitated electrodes cofired between dielectric layers ~10‐μm thick. The dielectric properties of these capacitors were extensively investigated as a function of Zr/Ti ratio on the CaZrO₃ side of the solid solution. The electrostatic energy density and breakdown strength of the CZT capacitors were investigated by measuring polarization–electric field curves as a function of temperature from room temperature to 250°C. The Ca(Zr_0.80Ti_0.20)O₃ capacitors show high electrostatic energy density of 4 J/cm³ at 250°C. Highly accelerated life testing (HALT) was also performed on these dielectrics, and we quantified the thermal stimulated depolarization current (TSDC) to access the major point defects in the CZT system.