High on-chip gain spiral Al2O3:Er3+ waveguide amplifiers.

We demonstrate reactively sputtered Al2O3:Er3+ waveguide amplifiers with an erbium concentration of 3.9 × 1020 ions/cm3, capable of achieving over 30 dB small signal net gain at 1532 nm using bidirectional pumping at 1480 nm. We observe on chip output powers of 10.2-13.6 dBm of amplified signal power at 1532 nm for a 12.9 cm waveguide amplifier considering -25.4 dB of lumped coupling losses per facet. Annealing was used to improve the performance of the devices, which were patterned using electron beam lithography and reactive ion etching. This result, to our knowledge, represents record breaking on-chip internal net gain for Al2O3:Er3+ waveguide amplifiers, which show promise over other technologies due to wafer scalability and promise of easy monolithic integration with other material platforms to support a wide variety of applications.

Analysis of the Budget Impact of Fractional Exhaled Nitric Oxide Monitoring in the Management of Childhood Asthma: The Colombian National Health System Perspective.

BACKGROUND: Fractional exhaled nitric oxide (FeNO) testing is a simple, noninvasive approach to assessing airway inflammation with minimal discomfort that provides results within a few minutes. For policy makers, the economic impact of this technology is the main concern, especially in developing countries. We evaluated the budget impact of asthma management using FeNO monitoring in patients aged between 4 and 18 years in Colombia. METHODS: A budget impact analysis was performed to evaluate the potential cost of FeNO monitoring. The analysis was based on a 5-year time horizon and performed from the perspective of the Colombian National Health System. The incremental budget impact was calculated by subtracting the cost of the new treatment, in which FeNO is reimbursed, from the cost of conventional treatment without FeNO (management based on clinical symptoms [with or without spirometry/peak flow] or asthma guidelines [or both] for asthma-related cases). Univariate 1-way sensitivity analyses were performed. RESULTS: In the base case analysis the 5-year costs associated with FeNO and non-FeNO were estimated to be €469 904 130 and €480 485 149, respectively, indicating savings for the Colombian National Health System of €10 581 019 if FeNO is adopted for the routine management of patients with persistent asthma. This result proved to be robust in the univariate 1-way sensitivity analysis. CONCLUSION: FeNO monitoring generated cost savings in emergency settings for infants with persistent asthma. This evidence can be used by decision makers in Colombia to improve clinical practice guidelines and should be replicated to validate the results in other middle-income countries.

Analysis of the Budget Impact of Fractional Exhaled Nitric Oxide Monitoring in the Management of Childhood Asthma: The Colombian National Health System Perspective

Background: Fractional exhaled nitric oxide (FeNO) testing is a simple, noninvasive approach to assessing airway inflammation withminimal discomfort that provides results within a few minutes. For policy makers, the economic impact of this technology is the mainconcern, especially in developing countries. We evaluated the budget impact of asthma management using FeNO monitoring in patientsaged between 4 and 18 years in Colombia.Methods: A budget impact analysis was performed to evaluate the potential cost of FeNO monitoring. The analysis was based on a5-year time horizon and performed from the perspective of the Colombian National Health System. The incremental budget impact wascalculated by subtracting the cost of the new treatment, in which FeNO is reimbursed, from the cost of conventional treatment withoutFeNO (management based on clinical symptoms [with or without spirometry/peak flow] or asthma guidelines [or both] for asthma-relatedcases). Univariate 1-way sensitivity analyses were performed.Results: In the base case analysis the 5-year costs associated with FeNO and non-FeNO were estimated to be €469 904 130 and€480 485 149, respectively, indicating savings for the Colombian National Health System of €10 581 019 if FeNO is adopted for theroutine management of patients with persistent asthma. This result proved to be robust in the univariate 1-way sensitivity analysis.Conclusion: FeNO monitoring generated cost savings in emergency settings for infants with persistent asthma. This evidence can be used bydecision makers in Colombia to improve clinical practice guidelines and should be replicated to validate the results in other middle-income countries (AU)

Antecedentes: El óxido nítrico en aire exhalado es una medición simple y no invasiva de la inflamación de las vías respiratorias cuyosresultados están disponibles en pocos minutos. Para los responsables de la formulación de políticas sanitarias, la principal preocupaciónes el impacto económico que implica la adaptación de esta tecnología, muy especialmente en los países en desarrollo. Este estudiotiene como objetivo evaluar el impacto presupuestario, en el sistema Nacional de Salud de Colombia, del manejo del asma mediante lamonitorización de óxido nítrico exhalado en pacientes entre 4 y 18 años.Métodos: Se realizó un análisis de impacto presupuestario para evaluar el posible impacto financiero derivado de la implementación de lamonitorización óxido nítrico exhalado fraccionado en el asma. El análisis consideró un horizonte temporal de 5 años y la perspectiva delSistema Nacional de Salud de Colombia. El impacto presupuestario incremental se calculó restando el coste del nuevo tratamiento, en elque se reembolsa el FeNO, del coste del tratamiento convencional sin FeNO (manejo basado en síntomas clínicos (con o sin espirometría /flujo máximo) o guías de asma (o ambos), para los relacionados con el asma). Se realizaron análisis de sensibilidad univariantes de una vía.Resultados: En el análisis del caso base, los costos a 5 años asociados a FeNO y no FeNO se estimaron en 469.904.130 € y 480.485.149 €respectivamente, lo que indica un ahorro para la Salud Nacional de Colombia de 10.581.019 € si se adopta la monitorización de FeNOen el manejo rutinario de pacientes con asma persistente. La solidez de este resultado fue confirmada en el análisis de sensibilidadunivariante, unidireccional.Conclusión: El óxido nítrico exhalado fraccionado ahorró costos en los entornos de emergencia en población pediátrica con asma persistente.Esta evidencia puede ser utilizada por los tomadores de decisiones en nuestro país para mejorar las guías de práctica clínic

Predictors for the prescription of albuterol in infants hospitalized for viral bronchiolitis.

INTRODUCTION AND OBJECTIVES: Despite the recommendation against routine use of inhaled bronchodilators in infants with viral bronchiolitis given in the main clinical practice guidelines (CPGs) on viral bronchiolitis, albuterol is widely prescribed to patients with this disease. The aim of this study was to identify predictors of prescription of albuterol in a population of infants hospitalized for viral bronchiolitis. MATERIAL AND METHODS: An analytical cross-sectional study performed during the period from March 2014 to August 2015, in a random sample of patients <2 years old hospitalized in the Fundacion Hospital La Misericordia, a hospital located in Bogota, Colombia. After reviewing the electronic medical records, we collected demographic, clinical, and disease-related information, including prescription of albuterol at any time during the course of hospitalization as the outcome variable. RESULTS: For a total of 1365 study participants, 1042 (76.3%) were prescribed with albuterol therapy. After controlling for potential confounders, it was found that age (OR 1.11; CI 95% 1.08-1.15; p<0.001), and a prolonged length of stay (LOS) (OR 1.93; CI 95% 1.44-2.60; p<0.001) were independent predictors of prescription of albuterol in our sample of patients. By contrast, albuterol prescription was less likely in the post-guideline assessment period (OR 0.41; CI 95% 0.31-0.54; p<0.001), and in infants with RSV isolation (OR 0.71; CI 95% 0.52-0.97; p=0.035). CONCLUSIONS: Albuterol was highly prescribed in our population of inpatients with the disease. The independent predictors of prescription of albuterol in our sample of patients were age, implementation of a CPG on viral bronchiolitis, RSV isolation, and LOS.

Direct medical costs of RSV-related bronchiolitis hospitalizations in a middle-income tropical country.

INTRODUCTION AND OBJECTIVES: With the objective of making informed decisions on resource allocation, there is a critical need for studies that provide accurate information on hospital costs for treating respiratory syncytial virus (RSV)-related bronchiolitis, mainly in middle-income countries (MICs). The aim of the present study was to evaluate the direct medical costs associated with bronchiolitis hospitalizations caused by infection with RSV in Bogota, Colombia. MATERIAL AND METHODS: We reviewed the available electronic medical records (EMRs) for all infants younger than two years of age who were admitted to the Fundacion Hospital de La Misericordia with a discharge principal diagnosis of RSV-related bronchiolitis over a 24-month period from January 2016 to December 2017. Direct medical costs of RSV-related bronchiolitis were retrospectively collected by dividing the infants into three groups: those requiring admission to the pediatric ward (PW) only, those requiring admission to the pediatric intermediate care unit (PIMC), and those requiring to the pediatric intensive care unit (PICU). RESULTS: A total of 89 patients with a median (IQR) age of 7.1 (3.1-12.2) months were analyzed of whom 20 (56.2%) were males. Overall, the median (IQR) cost of infants treated in the PW, in the PIMC, and in the PICU was US$518.0 (217.0-768.9) vs. 1305.2 (1051.4-1492.2) vs. 2749.7 (1372.7-4159.9), respectively, with this difference being statistically significant (p<0.001). CONCLUSIONS: The present study helps to further our understanding of the economic burden of RSV-related bronchiolitis hospitalizations among infants of under two years of age in a middle-income tropical country.

Direct medical costs of pediatric asthma exacerbations requiring hospital attendance in a middle-income country.

INTRODUCTION AND OBJECTIVES: With the aim of making informed decisions on resource allocation, there is a critical need for studies that provide accurate information on hospital costs for treating pediatric asthma exacerbations, mainly in middle-income countries (MICs). The aim of the present study was to evaluate the direct medical costs associated with pediatric asthma exacerbations requiring hospital attendance in Bogota, Colombia. PATIENTS AND METHODS: We reviewed the available electronic medical records (EMRs) for all pediatric patients who were admitted to the Fundacion Hospital de La Misericordia with a discharge principal diagnosis pediatric asthma exacerbation over a 24-month period from January 2016 to December 2017. Direct medical costs of pediatric asthma exacerbations were retrospectively collected by dividing the patients into four groups: those admitted to the emergency department (ED) only; those admitted to the pediatric ward (PW); those admitted to the pediatric intermediate care unit (PIMC); and those admitted to the pediatric intensive care unit (PICU). RESULTS: A total of 252 patients with a median (IQR) age of 5.0 (3.0-7.0) years were analyzed, of whom 142 (56.3%) were males. Overall, the median (IQR) cost of patients treated in the ED, PW, PIMC, and PICU was US$38.8 (21.1-64.1) vs. US$260.5 (113.7-567.4) vs. 1212.4 (717.6-1609.6) vs. 2501.8 (1771.6-3405.0), respectively: this difference was statistically significant (p<0.001). CONCLUSIONS: The present study helps to further our understanding of the economic burden of pediatric asthma exacerbations requiring hospital attendance among pediatric patients in a MIC.

Video-oculography eye tracking towards clinical applications: A review.

Most neurological diseases are usually accompanied by a broad spectrum of oculomotor alterations. Being able to record and analyze these different types of eye movements would be a valuable tool to understand the functional integrity of brain structures. Nowadays, video-oculography is the most widely used eye-movements assessing method. This paper presents a study of the existing eye tracking video-oculography techniques and also analyzes the importance of measuring slight head movements for diseases diagnosis. In particular, two types of methods are reviewed and compared, including appearance-based and feature-based methods which are further subdivided into 2D-mapping and 3D model-based approaches. In order to demonstrate the advantages and disadvantages of these different eye tracking methods for disease diagnosis, a series of comparisons are conducted between them, addressing the complexity of the system, the accuracy achieved, the ability to measure head movements and the external conditions for which they have been designed. Lastly, it also highlights the open challenges in this research field and discusses possible future directions.

Variations of B cell subpopulations in peripheral blood of healthy Mexican population according to age: Relevance for diagnosis of primary immunodeficiencies.

BACKGROUND: Peripheral blood B cells include lymphocytes at various stages of differentiation, each with a specific function in the immune response. All these stages show variations in percentage and absolute number throughout human life. The numbers and proportions of B subpopulation are influenced by factors such as gender, age, ethnicity, and lifestyle. This study establishes reference values according to age of peripheral blood B cell subtypes in healthy Mexican population. METHODS: Peripheral blood from healthy new-borns and adults were analysed for total B cell subpopulations, using surface markers such as CD19, IgM, IgD, CD21, CD24, CD27, and CD38, to identify naïve, memory with and without isotype switch, double-negative, transitional, and plasmablast cells. RESULTS: We observed a significant variation in terms of frequency and absolute counts between all groups analysed. Values from each B cell subpopulation show variations according to age. CONCLUSIONS: In order to attempt to elucidate reference values for B cell subpopulation, the present study evaluated a population sample of healthy blood donors from this region. Values reported here can also be used as a tool for diagnosis of diseases in which B cell maturation is affected.

Effects of zinc supplementation in the prevention of respiratory tract infections and diarrheal disease in Colombian children: A 12-month randomised controlled trial.

BACKGROUND: Among the preventive strategies for lowering the incidence of upper respiratory tract infections (URTI) and acute diarrhoea episodes, two of the most common diseases in children, zinc supplementation has received special interest. However, there is a need for additional studies that determine the preventive effects of different doses of zinc on URTI and diarrhoeal disease episodes in children. METHODS: In a randomised, triple-blind clinical trial, we evaluated the efficacy of 12 months of daily zinc supplementation in the incidence of URTI and acute diarrhoea in a population of healthy children aged between 6 and 12 months living in Bogota, Colombia. The outcomes analysed were incidence of URTI, acute diarrhoeal disease episodes, and side effects of the interventions. RESULTS: Between 2010 and 2013, a total of 355 children underwent randomisation, with 174 assigned to the zinc supplementation group and 181 to the control group. In the multivariate analyses, having been randomised to the non-supplemented control group (IRR 1.73, 95% CI 1.52-1.97, p<0.001), and nursery attendance (IRR 1.41, 95% CI 1.07-1.87, p=0.016) were independently linked to the number of URTI. Likewise, having been randomised to the non-supplemented group (IRR 1.43, 95% CI 1.20-1.71, p<0.001), and lower socioeconomic status (IRR 1.86, 95% CI 1.11-3.13, p=0.018) were independently associated to the number of diarrhoeal disease episodes. CONCLUSIONS: Daily supplementation of 5mg of zinc during 12 months significantly decreased the incidence of URTI and diarrhoeal disease episodes in a healthy population of children aged between 6 and 12 months.

Zn, Cd, S and trace metal bioaccumulation in willow (Salix spp.) cultivars grown hydroponically.

Willows (Salix spp.) can be used to phytoremediate soils contaminated by Zn and Cd under certain conditions. In this study, the ability of 14 Salix cultivars to concentrate Cd, Zn and S in leaves was measured in hydroponic culture with 10 and 200 µM Cd and Zn, respectively, in the nutrient medium. The cultivars showed a wide range of biomass yields, tolerance to metals, and foliar concentrations of Zn and Cd, with some cultivars accumulating up to 1000 mg kg(-1) Zn, 70 mg kg(-1) Cd and 10,000 mg kg(-1) S with only mild phytotoxicity symptoms attributable to excess Zn. Cultivars with higher foliar Zn concentrations tended to have higher foliar Cd concentrations as well, and competition between Zn and Cd for uptake was observed. Exposure of Salix cultivars to Cd and Zn did not affect foliar concentrations of secondary metabolites such as polyphenols, but trace metal concentrations in leaves were significantly reduced (Fe and Cu) or increased (Mn) by exposure to excess Zn and Cd. Sulfur-XANES spectroscopy showed foliar S to be predominantly in highly oxidized (sulfate plus sulfonate) and reduced (thiol) forms, with oxidized S more prevalent in willows with the highest total S content.

Epidemic activity of respiratory syncytial virus is related to temperature and rainfall in equatorial tropical countries.

Although viral acute lower respiratory infections (ALRIs) are a major public health problem in tropical low- and middle-income countries (LMICs), and there is growing evidence showing their relationship with meteorological parameters, studies performed in these countries are scarce. In an analytical cross-sectional study, we determined which of the main meteorological parameters (temperature, absolute humidity, rainfall, wind speed, and solar radiation) predicted respiratory syncytial virus (RSV) activity in a population of hospitalized children with ALRI during a 5-year period, from January 2009 to December 2013. Out of a total of 4559 children included in the study (mean age 9·2 ± 8·5 months), 2953 (64·8%) presented RSV infection during the 3-month period from March to May. In the multivariate analysis, after controlling for absolute humidity, wind speed, and solar radiation, temperature [incidence rate ratio (IRR) 2·25, 95% confidence interval (CI) 1·11-4·53, P = 0·024], and rainfall (IRR 1·01, 95% CI 1·00-1·02, P = 0·044) were independently associated with the monthly number of RSV infections. In conclusion, in Bogota, the capital of a tropical LMIC lying slightly above the equator, RSV activity peaks in the 3-month period from March to May, the main rainy period of the year in the city. In addition, rainfall and temperature are the two most important meteorological parameters that are independently associated with RSV activity in hospitalized children with ALRI in the city.

Relationship between meteorological conditions and respiratory syncytial virus in a tropical country.

This study aimed to determine which meteorological conditions are associated with respiratory syncytial virus (RSV) isolates in a population of children hospitalized with acute lower respiratory infection (ALRI) in Bogota, Colombia. In an analytical cross-sectional study, links were examined between the number of monthly RSV infections and monthly average climatic variation (temperature, relative humidity, rainfall, wind speed, solar radiation) between 1 January 2010 and 30 April 2011 in a population of hospitalized children aged <3 years with ALRI caused by RSV. Out of a total of 1548 children included in the study (mean age 9·2 ± 8·5 months), 1194 (77·1%) presented RSV infection during the 3-month period from March to May. In the multivariate analysis, after controlling for wind speed, relative humidity, and solar radiation, monthly average temperature [incident rate ratio (IRR) 3·14, 95% confidence interval (CI) 1·56-6·30, P = 0·001] and rainfall (IRR 1·008, 95% CI 1·00-1·01, P = 0·048) were independently associated with the monthly number of RSV infections. In conclusion, in Bogota, a tropical Latin American city, average temperature and rainfall are the meteorological variables most strongly associated with RSV isolation in children hospitalized with ALRI in the city.

Allergic rhinitis and associated factors in schoolchildren from Bogota, Colombia.

BACKGROUND: Allergic rhinitis is one of the most frequent chronic diseases among children. The objective of the study was to assess the prevalence of and the factors associated with self-reported allergic rhinitis symptoms in schoolchildren from Bogota, Colombia. METHODOLOGY/PRINCIPAL: We followed the International Study of Asthma and Allergies in Childhood (ISAAC) methodology. Our sample included 3,256 children aged 6 - 7 and 3,830 adolescents aged 13 - 14 years. RESULTS: The prevalence of self-reported allergic rhinitis symptoms was 30.8% among children and 36.6% among adolescents. Factors associated with self-reported allergic rhinitis among children included current asthma and atopic dermatitis symptoms; use of acetaminophen in the first year of life and in the last 12 months; antibiotic use in the first year of life; high- school and university maternal education; smokers at home; and caesarean delivery. Among adolescents, associated factors included current asthma and atopic dermatitis symptoms; current acetaminophen use once per month; frequent fast-food consumption; cat exposure at home; and smoking. CONCLUSION: Further exploration of factors associated with allergic rhinitis symptoms is needed.

Factors associated to recurrent visits to the emergency department for asthma exacerbations in children: implications for a health education programme.

INTRODUCTION: Recurrent emergency department (ED) visits for asthma exacerbations produce anxiety as well as high costs to the health system and the family. OBJECTIVE: To identify factors associated with recurrent ED visits for asthma exacerbations in children in Bogotá, Colombia. METHODS: Data obtained from a survey of parents of 223 patients with asthma (mean +/- SD: 4.8+/-3.5 years of age) attending an asthma clinic were analysed. Demographic data and a broad asthma knowledge and attitudes questionnaire were completed by the parents. RESULTS: Of the 223 asthmatic patients enrolled, 60 (26.9 %) had 3 or more visits to the ED for asthma in the last 6 months ("recurrent ED visits"). After controlling by age, educational level of the father, and severity of the disease; parents of children with "recurrent ED visits" were more prone to report that they attended ED because the asthma exacerbations were severe enough to go to the primary care physician (OR, 2.45; CI 95 %, 1.13-5.30; p=0.02); that asthma medications should be administered only when the children are symptomatic (OR, 3.26; CI 95 %, 1.45-7.36; p=0.004), and conversely they were less prone to have knowledge that asthma exacerbations can be avoided if medications are administered in the asymptomatic periods (OR, 0.31; CI 95 %, 0.14-0.68; p=0.003). CONCLUSIONS: An educational programme intended to reduce the recurrent ED visits for asthma exacerbations should consider the inclusion of an explanation about the chronic nature of the disease and the importance of long-term therapy.

Postnatal manganese exposure alters dopamine transporter function in adult rats: Potential impact on nonassociative and associative processes.

In the present study, we examined whether exposing rats to a high-dose regimen of manganese chloride (Mn) during the postnatal period would depress presynaptic dopamine functioning and alter nonassociative and associative behaviors. To this end, rats were given oral supplements of Mn (750 microg/day) on postnatal days (PD) 1-21. On PD 90, dopamine transporter (DAT) immunoreactivity and [3H]dopamine uptake were assayed in the striatum and nucleus accumbens, while in vivo microdialysis was used to measure dopamine efflux in the same brain regions. The effects of postnatal Mn exposure on nigrostriatal functioning were evaluated by assessing rotorod performance and amphetamine-induced stereotypy in adulthood. In terms of associative processes, both cocaine-induced conditioned place preference (CPP) and sucrose-reinforced operant responding were examined. Results showed that postnatal Mn exposure caused persistent declines in DAT protein expression and [3H]dopamine uptake in the striatum and nucleus accumbens, as well as long-term reductions in striatal dopamine efflux. Rotorod performance did not differ according to exposure condition, however Mn-exposed rats did exhibit substantially more amphetamine-induced stereotypy than vehicle controls. Mn exposure did not alter performance on any aspect of the CPP task (preference, extinction, or reinstatement testing), nor did Mn affect progressive ratio responding (a measure of motivation). Interestingly, acquisition of a fixed ratio task was impaired in Mn-exposed rats, suggesting a deficit in procedural learning. In sum, these results indicate that postnatal Mn exposure causes persistent declines in various indices of presynaptic dopaminergic functioning. Mn-induced alterations in striatal functioning may have long-term impact on associative and nonassociative behavior.

Preparation of mono- and diacylglycerols by enzymatic esterification of glycerol with conjugated linoleic acid in hexane.

Esterification of glycerol with conjugated linoleic acid (CLA) was carried out in hexane. Lipase from Rhizomucor miehei provided a high degree of esterification (80%) in 8 h at 50 degrees C when used at 15% (w/w) in a system containing a 1:2 molar ratio of glycerol to free fatty acids. Esterification levels >80% were obtained in 8 h at 40 degrees C with 15% (w/w) lipase from Candida antarctica at the same molar ratio of reactants. The extent of esterification of CLA was >90% after 4 h of reaction at 50 degrees C with a 5% (w/w) loading of either R. miehei or C. antarctica lipase, together with a 1:1 molar ratio of substrates. Both enzymes incorporated the original CLA as acylglycerol residues in primarily 1,3-diacylglycerol and 1-monoacylglycerol. The CLA-rich acylglycerols can be employed as emulsifiers or as substitutes for natural fats and oils.

Effect of larger ablation zone and transition zone on corneal optical aberrations after photorefractive keratectomy.

OBJECTIVE: To evaluate the effects of photorefractive keratectomy on corneal optical aberrations using a 5.5-mm optical zone and a 7.0-mm transition zone. METHODS: Videokeratographs of 72 eyes from 47 patients treated for low to moderate (1-9 diopters) myopia were obtained at the preoperative and 1-, 3-, 6-, 12-, and 18-month postoperative examinations. The videokeratoscopy data files were used to calculate the wavefront variance of the corneas for small (3-mm) and large (7-mm) pupils using a previously described method. RESULTS: In general, all optical aberrations decreased postoperatively for 3-mm pupils and increased for 7-mm pupils compared with preoperative values. For 3-mm pupils, the 2 common optical aberrations (comalike [S(3)] and spherical-like [S(4)]) decreased postoperatively and never returned to preoperative values. For 7-mm pupils, however, comalike aberrations increased slightly and spherical-like aberrations increased by nearly an order of magnitude during the postoperative period. Similarly, for 3-mm pupils, the higher order S(5) and S(6) aberrations decreased throughout the postoperative period, with S(6) values showing an approximately 23-fold reduction at 12 and 18 months. For 7-mm pupils, S(5) and S(6) aberrations increased slightly, more so for S(5) (approximately 3-fold) than for S(6). Total wavefront aberrations decreased an average of 2.3 times postoperatively for 3-mm pupils, and increased significantly (P<.05) at all postoperative examinations for 7-mm pupils. Opening the pupil from 3 mm to 7 mm before surgery produced a 14-fold increase in total aberrations, whereas this same change produced an average 113-fold increase after photorefractive keratectomy. CONCLUSIONS: Corneal optical aberrations after photorefractive keratectomy with a larger ablation zone and a transition zone are less pronounced and more physiologic than those associated with first-generation (5-mm) ablations with no transition zone. CLINICAL RELEVANCE: Evaluating the postoperative corneal aberration structure will help us devise ways to minimize the wavefront aberrations of the eye through the creation of an ideal corneal first surface, thereby improving visual results for patients undergoing excimer laser ablations for refractive correction.

Cd, Cu, Pb, and Zn coprecipitates in Fe oxide formed at different pH: aging effects on metal solubility and extractability by citrate.

Coprecipitates of heavy metals with Fe oxides may form in contaminated soil, water, and sediment systems, particularly when oxidation-reduction processes are occurring. Once formed, coprecipitates with ferrihydrite could limit heavy metal mobility, solubility, toxicity, and bioavailability in geochemical systems. In this study, Cd, Cu, Pb, and Zn were coprecipitated with Fe by titration to pHs 6 and 7. Metal solubility was monitored during the coprecipitation process to pH 7 and after aging of the product. In the coprecipitate formed at pH 6, metal solubility was determined after the system reached pH 6 and at subsequent time intervals. We also reacted the coprecipitates with citrate and evaluated potential metal availability at increased aging times. The pH of coprecipitate formation had little effect on the long-term solubility of Cu and Zn, whereas soluble Cd was greater in the coprecipitate formed at pH 6. Soluble percentages of metals were low at both pH 6 and 7 for Cu and Pb but averaged 1.5 to 3% for Zn and greater than 40% for Cd. Hysteresis was observed in the coprecipitation curves for Zn and Cd, revealing reduced solubility after adsorption or coprecipitation. Lead and Cu failed to show hysteresis, with strong retention in the solid phase at pH greater than 6. The citrate-extractable fraction was greatest for Cd and Zn, less for Cu, and least for Pb. Citrate-extractable metal was higher for the coprecipitate formed at pH 7 than at pH 6, suggesting increased potential availability from coprecipitates formed at higher pH.

Thermally induced changes in metal solubility of contaminated soils is linked to mineral recrystallization and organic matter transformations.

Soils are biogeochemical systems under continual modification by biological and chemical processes. Trace element solid-solution partitioning is thus influenced by long-term changes to these solid phases. We study Pb, Cd, Zn, and Cu solution speciation and solid-phase dynamics in two soils of volcanic origin (Te Akatea and Egmont, high in noncrystalline aluminosilicates), an oxisol from Brazil (Oxisol, high in oxides of Al and Fe), and several sludge-treated soils (labeled NYS soils, high in organic materials). Total soluble (by ICP) and labile (by ASV) concentrations of Pb, Cd, Zn, and Cu were determined after incubation of the soils for about 1.5 yr at room (23 degrees C) and elevated (70 degrees C) temperatures. Changes occurring to the solid phases were monitored by FTIR and extraction with oxalate and pyrophosphate. It is shown that induced hydrolysis or decomposition of organic materials in soils results in increases in both labile and total soluble concentrations of Pb, Cd, Cu, and Zn in solution. Labile and total soluble concentrations of Cu and Zn increase concomitantly with dissolved organic carbon (DOC); the nonlabile soluble fraction also increases with increasing DOC. Similarly, the concentration of Cd and Pb in solution increases with increasing DOC; however, most soluble Cd and Pb is asv-labile. Only in the Egmont soil (mineralogy dominated by proto-imogolite allophane) was reduced Pb solubility observed after prolonged equilibration and heating. Lead solubility increased after partial crystallization of amorphous minerals in the Te Akatea and the Oxisol. Thus, for most of the metal-soil systems studied, prolonged thermal treatment at 70 degrees C increased total soluble and asv-labile metals, suggesting that aging effects on metals in contaminated soils could release metals to labile forms in some cases.