Measuring Dissolved Methane in Aquatic Ecosystems Using An Optical Spectroscopy Gas Analyzer.

Measuring greenhouse gas (GHG) fluxes and pools in ecosystems are becoming increasingly common in ecological studies due to their relevance to climate change. With it, the need for analytical platforms adaptable to measuring different pools and fluxes within research groups also grows. This study aims to develop a procedure to use portable optical spectroscopy-based gas analyzers, originally designed and marketed for gas flux measurements, to measure GHG concentrations in aqueous samples. The protocol involves the traditional headspace equilibration technique followed by the injection of a headspace gas subsample into a chamber connected through a closed loop to the inlet and outlet ports of the gas analyzer. The chamber is fabricated from a generic mason jar and simple laboratory supplies, and it is an ideal solution for samples that may require pre-injection dilution. Methane concentrations measured with the chamber are tightly correlated (r2 > 0.98) with concentrations determined separately through gas chromatography-flame ionization detection (GC-FID) on subsamples from the same vials. The procedure is particularly relevant for field studies in remote areas where chromatography equipment and supplies are not readily available, offering a practical, cheaper, and more efficient solution for measuring methane and other dissolved greenhouse gas concentrations in aquatic systems.

Impacto del índice de masa corporal en la presión arterial medida con esfigmomanómetro de mercurio en niños y adolescentes con diabetes mellitus tipo 1 / The impact of body mass index on blood pressure measured with mercury sphygmomanometer in children and adolescents with type 1 diabetes mellitus

Resumen Introducción Los pacientes con diabetes mellitus tipo 1 (DM1) y sobrepeso tienen más riesgo de desarrollar cambios en la presión arterial (PA), y esto incrementa su morbilidad y mortalidad cardiovascular. En este estudio se determinó la relación entre la PA y el índice de masa corporal (IMC) y el promedio de las tres últimas mediciones de hemoglobina glucosilada (HbA1c) de pacientes con DM1. Métodos Estudio transversal analítico en niños y adolescentes con DM1 con más de un año de evolución. Las variables dependientes fueron la PA sistólica y diastólica medidas con esfigmomanómetro y las variables independientes, IMC y promedio de las últimas tres mediciones de la HbA1c. Se utilizó regresión lineal múltiple con intervalo de confianza del 95%. Resultados Se estudiaron 75 pacientes con DM1. La mediana del tiempo de evolución de la DM1 fue de 3.5 años (mínimo 1 año-máximo 14.8 años), el IMC 19.5 ± 3.1 kg/cm2 y la HbA1c 8.3 ± 2.4%. De los 75 pacientes, 66 presentaron PA < percentil 90 y 9 PA ≥ percentil 90 (12%). Se construyeron dos modelos de regresión lineal múltiple, con PA sistólica y diastólica como variables dependientes. Las posibles variables predictoras fueron sugeridas por el contexto teórico y el análisis estadístico. El IMC expresado en puntuación zeta (zIMC) fue predictor para PA sistólica/diastólica. Los modelos sugirieron que a cada incremento de unidad del zIMC corresponde un aumento de 5.1 y 3.6 mmHg de PA sistólica y diastólica, respectivamente. Conclusiones Se observó una correlación positiva de la PA sistólica y la diastólica con el zIMC.

Abstract Background Patients with type 1 diabetes mellitus (T1DM) and overweight have more risk to develop changes in blood pressure that increase cardiovascular morbidity and mortality. In this study, the relationship between blood pressure (BP) with the body mass index (BMI) and the average of the last three measurements of glycated hemoglobin (HbA1c) in patients with T1DM was determined. Methods A cross-sectional analytical study was conducted in children and adolescents with T1DM with over a year since diagnosis. The dependent variables were systolic and diastolic BP, measured with a mercury sphygmomanometer. The independent variables were BMI and average of the last three measurements of HbA1. A linear regression with a 95% confidence interval was used. Results Seventy-five patients with T1DM were studied. The median of disease duration was 3.5 years (min 1-max 14.8 years), BMI 19.5 ± 3.1 kg/cm2 and HbA1c 8.3 ± 2.4%. Sixty-six patients showed BP < percentile 90 and 9 BP ≥ percentile 90 (12%). Two models of linear regression were constructed, with systolic and diastolic BP as dependent variables. The possible predictor variables were suggested by theoretical context and statistical analysis. The predictive variable of high BP was zBMI (body mass index expressed in z-score) for systolic and diastolic BP. Also, the models suggested that for an increase of one unit of zBMI, corresponded a rise of 5.1 and 3.6 mmHg in systolic and diastolic BP, respectively. Conclusions A positive correlation between systolic and diastolic BP with zBMI was observed.