Portable, low cost and sensitive cavity enhanced absorption (CEA) detection.

Absorption is a widely used technique for a range of different applications. It has lower sensitivity than many other techniques such as fluorescence which has 100 to 1000 times higher sensitivity than absorption. Optical cavity approaches have been developed where the light passes back and forth, within the sample, between two high reflectivity mirrors to increase the pathlength and sensitivity. These approaches have not yet, however, been widely used for analytical applications and for point-of-care diagnostics. Here we show a portable cavity enhanced absorption (CEA) spectrometer and a low cost point-of-care (POC) reader with CEA detection with mechanical elements fabricated using 3D printing. The CEA spectrometer can be used in both single pass and multi-pass cavity enhanced mode to provide measurements in the visible region that are very sensitive and over a wide dynamic range. The CEA mode was shown for Rhodamine B dye to increase the pathlength 57.8 fold over single pass measurements and an LOD of 7.1 × 10-11 M. The cost of the CEA POC reader was reduced by use of narrow band LEDs, photodiodes and removal of fibre optic coupling and with a 14 fold increase in the pathlength over conventional single pass microplate readers. The CEA POC reader was demonstrated for immunoassay of C-Reactive Protein (CRP), Procalcitonin (PCT) and Interleukin 6 (IL-6), towards a three biomarker panel to aid the diagnosis of sepsis. The CEA POC reader can be integrated with wireless connectivity for cloud based data sharing. We show here the potential for the wider use of optical cavity approaches where there is a need for sensitive absorption measurements and also for low cost point-of-care diagnostics.

Prescribing for hyperopia in childhood and teenage by academic optometrists.

PURPOSE: The purpose of this study was to examine the prescribing patterns of academic optometrists for infants, children, and teenagers with hyperopia and the factors that affected the decision to prescribe. A comparison was made to published guidelines for prescribing for hyperopia in children. METHODS: The Waterloo Eye Study (WatES) database is a database of all patients attending the Primary Care Clinic or the Pediatric Clinic at the School of Optometry, University of Waterloo, between February 2007 and January 2008. Records for 698 patients aged from birth to 19 years with hyperopia but without strabismus or significant anisometropia were extracted. They were analyzed to determine the factors that predicted whether a child was prescribed spectacles and the 50% prescribing points for hyperopia and astigmatism according to age. RESULTS: Univariate analysis showed that the level of hyperopia, astigmatism, age, distance, and near phoria and presence of symptoms were associated with the prescription of spectacles (p < 0.05). Multivariate analysis showed that the prescription of spectacles was predicted by age, highest sphere (either right or left eye), highest cylinder, the presence of symptoms, and distance phoria. Among 0 to 3 year olds, all the children with 5 D or more of hyperopia had been prescribed spectacles. Among the 4 to 6 year olds, this point was 3.25 D; and for the 7 to 19 year olds, it was 2.25 D. The levels at which 50% of the population had been prescribed spectacles was 3.7, 1.8, and 1.1 D for the 0 to 3 year olds, 4 to 6 year olds, and 7 to 19 year olds, respectively. There was frequently a difference between the refraction and the prescription such that the younger children, in particular, were often under corrected for both hyperopia and astigmatism. CONCLUSIONS: The optometrists in this academic setting appear to follow the available optometric guidelines for prescribing for hyperopia. They tend to prescribe for lower levels of hyperopia than U.S. ophthalmologists.

Toxicity of dispersed weathered crude oil to early life stages of Atlantic herring (Clupea harengus).

Reports of the chronic toxicity of dispersed crude oil to early life stages of fish perpetuate uncertainty about dispersant use. However, realistic exposures to dispersed oil in the water column are thought to be much briefer than exposures associated with chronic toxicity testing. To address this issue, the toxicity of dispersed weathered oil to early life stages of Atlantic herring (Clupea harengus) was tested for short exposure durations, ranging from 1 to 144 h. Toxicity was a function of concentration and duration of exposure, as well as of the life stage exposed. Medium South American crude oil dispersed with Corexit 9500 caused blue sac disease in embryos, but not in free-swimming embryos. The age of embryos was negatively correlated with their sensitivity to oil; those freshly fertilized were most sensitive. Sensitivity increased after hatch, with free-swimming embryos showing signs of narcosis. Gametes were also tested; dispersed oil dramatically impaired fertilization success. For exposures of less than 24 h, gametes and free-swimming embryos were the most sensitive life stages. For those of more than 24 h, young embryos (<1 d old) were most sensitive. The results are presented as statistical models that could assist decisions about dispersant use in the vicinity of fish spawning habitats.

Comparative toxicity of four chemically dispersed and undispersed crude oils to rainbow trout embryos.

The chronic toxicity of crude oil to fish embryos depends on the chemical constituents of the test oil and on factors that control the exposure of embryos to those constituents. The partitioning of chemicals from oil to water depends on the surface area of oil exposed to water and thus on the susceptibility of oil to be dispersed into droplets. The chronic toxicity of four different crude oils to embryos of rainbow trout (Oncorhynchus mykiss) was measured by exposure to the water-accommodated fraction (WAF; no droplet formation) and to the chemically enhanced WAF (CEWAF) of each oil. When effects were compared with the amount of WAF or CEWAF added to test solutions, chemical dispersion increased toxicity dramatically, by >35 to >300-fold, with the smallest difference measured for the lightest and least viscous oil. When effects were compared with measured concentrations of oil in test solutions, there were no differences in toxicity between WAF and CEWAF treatments, indicating that chemical dispersion promoted droplet formation and the partitioning of hydrocarbons from oil to water. On a dilution basis, the differences in toxicity among the four oils were correlated with the concentrations in oil of polynuclear aromatic hydrocarbons (PAH), particularly those with three to five rings, and with their viscosity, an index of dispersibility. However, when PAH concentrations were measured in solution, toxicity did not vary substantially among the four oils, suggesting that the PAH of each oil had equivalent toxicities and that differences in toxicity represented differences in dispersability.