RESUMEN
A method to characterize macroscopically homogeneous rigid frame porous media from impedance tube measurements by deterministic and statistical inversion is presented. Equivalent density and bulk modulus of the samples are reconstructed with the scattering matrix formalism, and are then linked to its physical parameters via the Johnson-Champoux-Allard-Lafarge model. The model includes six parameters, namely the porosity, tortuosity, viscous and characteristic lengths, and static flow and thermal permeabilities. The parameters are estimated from the measurements in two ways. The first one is a deterministic procedure that finds the model parameters by minimizing a cost function in the least squares sense. The second approach is based on statistical inversion. It can be used to assess the validity of the least squares estimate, but also presents several advantages since it provides valuable information on the uncertainty and correlation between the parameters. Five porous samples with a range of pore properties are tested, and the pore parameter estimates given by the proposed inversion processes are compared to those given by other characterization methods. Joint parameter distributions are shown to demonstrate the correlations. Results show that the proposed methods find reliable parameter and uncertainty estimates to the six pore parameters quickly with minimal user input.
RESUMEN
OBJECTIVE: To describe postoperative complications and visual outcomes after immediately sequential bilateral cataract surgery (ISBCS) and to assess whether additional risk is incurred by operating on the fellow eye immediately following the first. ANIMALS STUDIED: A retrospective review of 128 dogs (256 eyes) that underwent ISBCS in three veterinary ophthalmology centers between May 2007 and December 2011 was performed. PROCEDURE: Visual status at final evaluation was recorded and intra- and postoperative complications were recorded and analyzed. Data for the first operated eye (FE) and then the second eye (SE) were statistically analyzed to assess whether performing surgery on the SE immediately after the FE resulted in any negative consequences for the second eye. RESULTS: No serious intraoperative anesthetic incident occurred due to prolonged surgery. Phacoemulsification times were significantly shorter for the SE than for the FE. On final examination, 239 eyes out of 256 (93.36%) exhibited functional vision (score 2), and three dogs were completely blind due to long-term bilateral postoperative complications. The most common postoperative complications were uveitis (58 eyes, 22.66%), postoperative ocular hypertension (POH; nine eyes, 3.5%), glaucoma (nine eyes, 3.5%) and total retinal detachment (seven eyes, 2.73%). No case of endophthalmitis was reported. These results were no worse than those typically reported for unilateral phacoemulsification. In addition, the risk of blindness and other postoperative complications was not significantly increased in the SE. CONCLUSIONS: The results of this study suggest that ISBCS is not associated with an increased incidence of intra- or postoperative complications compared to classic unilateral cataract surgery and might be a viable option for selected patients. The risk of blindness or postoperative complications was not higher in SEs than in FEs.
