19 research outputs found
Fiber optic sensors based on hybrid phenyl-silica xerogel films to detect n-hexane: determination of the isosteric enthalpy of adsorption
We investigated the response of three fiber optic sensing elements prepared at pH 10 from phenyltriethoxysilane (PhTEOS) and
tetraethylsilane (TEOS) mixtures with 30, 40, and 50% PhTEOS in the silicon precursor mixture. The sensing elements are referred
to as Ph30, Ph40 and Ph50, respectively. The films were synthesized by the sol–gel method and affixed to the end of optical fibers
by the dip-coating technique. Fourier transform infrared spectroscopy, N2 adsorption–desorption at 77 K and X-ray diffraction analysis
were used to characterize the xerogels. At a given pressure of n-hexane, the response of each sensing element decreased with
temperature, indicating an exothermic process that confirmed the role of adsorption in the overall performance of the sensing elements.
The isosteric adsorption enthalpies were obtained from the calibration curves at different temperatures. The magnitude of the
isosteric enthalpy of n-hexane increased with the relative response and reached a plateau that stabilized at approximately
−31 kJ mol−1 for Ph40 and Ph50 and at approximately −37 kJ mol−1 for Ph30. This indicates that the adsorbate–adsorbent interaction
was dominant at lower relative pressure and condensation of the adsorbate on the mesopores was dominant at higher relative
pressure.This work was supported by the Ministerio de Ciencia e Innovación (CTQ2009-07993). Paula Moriones is thankful to the Departamento de Industria y TecnologÃa, Comercio y Trabajo of the Navarre Government for fellowships (Ref. number 269/01/08)
Efectividad de distintos pretratamientos en el análisis granulométrico de tres suelos contrastantes de la Región Pampeana
Behrends Kraemer, Filipe. Universidad de Buenos Aires. Facultad de AgronomÃa. Departamento de IngenierÃa AgrÃcola y Uso de la Tierra. Cátedra de Manejo y Conservación de Suelos. Buenos Aires, Argentina.Fernández, Patricia. Universidad de Buenos Aires. Facultad de AgronomÃa. Departamento de IngenierÃa AgrÃcola y Uso de la Tierra. Cátedra de Manejo y Conservación de Suelos. Buenos Aires, Argentina.Ceddia, Marcos Bacis. Universidade Federal Rural de Rio de Janeiro.Departamento de Solo.s. Rio de Janeiro, Brasil.Chagas, Celio Ignacio. Universidad de Buenos Aires. Facultad de AgronomÃa. Departamento de IngenierÃa AgrÃcola y Uso de la Tierra. Cátedra de Manejo y Conservación de Suelos. Buenos Aires, Argentina.Morrás, Héctor José MarÃa. Instituto Nacional de TecnologÃa Agropecuaria (INTA). Instituto de Suelos (CIRN). Hurlingham, Buenos Aires, Argentina.163-172La granulometrÃa es una de las caracterÃsticas fundamentales del suelo, y su evaluación brinda información clave en la determinación de sus propiedades fÃsicas. Sin embargo, existen divergencias metodológicas en los procedimientos de dispersión del suelo y de eliminación de la materia orgánica (EMO). En este trabajo se evaluó la variación de la granulometrÃa en tres suelos pampeanos diferenciados en su textura, mineralogÃa y contenido de MO. Se pusieron a prueba dos procedimientos de EMO (calcinación a 430 ºC y oxidación por H2O2) y dos velocidades de agitación (90 y 150 rpm) en agitador recÃproco. Cuando la materia orgánica fue eliminada con agua oxigenada se obtuvo una mayor extracción de arcilla,independientemente de la velocidad de agitación. Sin embargo, en promedio, se encontraron contenidos más altos de arcillas con una mayor velocidad de agitación. En el suelo arenoso (Haplustol), la combinación calcinación y agitación 150 rpm presentó un desempeño estadÃsticamente similar al H2O2 y agitación 150 o 90 rpm. Por el contrario, para los suelos de textura fina evaluados en este trabajo (Argiudol y Hapludert) la utilización de la calcinación no serÃa conveniente ya que subestima el contenido de arcilla debido a una posible reorganización de las partÃculas de arcilla producida por el calor. Este trabajo destaca la importancia de las condiciones metodológicas en los resultados de la distribución granulométrica de los suelos, mientras que la evaluación de un mayor número de suelos y la evaluación de otros Ordenes es necesaria para lograr procedimientos adecuados para dicha determinación
Luminescence-based optical sensors fabricated by means of the layer-by-layer nano-assembly technique
Luminescence-based sensing applications range from agriculture to biology, including
medicine and environmental care, which indicates the importance of this technique as a detection tool.
Luminescent optical sensors are required to be highly stable, sensitive, and selective, three crucial
features that can be achieved by fabricating them by means of the layer-by-layer nano-assembly
technique. This method permits us to tailor the sensors0 properties at the nanometer scale, avoiding
luminophore aggregation and, hence, self-quenching, promoting the diffusion of the target analytes,
and building a barrier against the undesired molecules. These characteristics give rise to the
fabrication of custom-made sensors for each particular application.This work was supported by the Spanish State Research Agency (AEI) through the TEC2016-
79367-C2-2-R project and the European Regional Development Fund (ERDF-FEDER). Nerea de Acha would also
like to acknowledge her pre-doctoral fellowship (reference BES-2014-069692) funded by the Spanish Ministry of
Economy and Competitiveness through the TEC2013-43679-R project
Detection of ethanol in human breath using optical fiber long period grating coated with metal-organic frameworks
Trabajo presentado en la Eurosensors 2017 Conference. ParÃs, 3–6 de septiembre de 2017.An optical fiber sensor for ethanol detection in exhaled breath has been developed. It has been fabricated by functionalizing a Long Period Grating with a metal-organic framework, ZIF-8. The sensor’s response was tested by exposure to exhaled breath of a person before and after the ingestion of alcoholic drinks, showing a higher wavelength difference between the resonance bands in the second case. Further work will analyze cross-sensitivity towards temperature, relative humidity and carbon dioxide.The authors would like to acknowledge Spanish Ministry of Economy and Competitiveness for the financial support through TEC2016-78047-R project
Frequency, risk factors, and outcomes of hospital readmissions of COVID-19 patients
To determine the proportion of patients with COVID-19 who were readmitted to the hospital and the most common causes and the factors associated with readmission. Multicenter nationwide cohort study in Spain. Patients included in the study were admitted to 147 hospitals from March 1 to April 30, 2020. Readmission was defined as a new hospital admission during the 30 days after discharge. Emergency department visits after discharge were not considered readmission. During the study period 8392 patients were admitted to hospitals participating in the SEMI-COVID-19 network. 298 patients (4.2%) out of 7137 patients were readmitted after being discharged. 1541 (17.7%) died during the index admission and 35 died during hospital readmission (11.7%, p = 0.007). The median time from discharge to readmission was 7 days (IQR 3-15 days). The most frequent causes of hospital readmission were worsening of previous pneumonia (54%), bacterial infection (13%), venous thromboembolism (5%), and heart failure (5%). Age [odds ratio (OR): 1.02; 95% confident interval (95% CI): 1.01-1.03], age-adjusted Charlson comorbidity index score (OR: 1.13; 95% CI: 1.06-1.21), chronic obstructive pulmonary disease (OR: 1.84; 95% CI: 1.26-2.69), asthma (OR: 1.52; 95% CI: 1.04-2.22), hemoglobin level at admission (OR: 0.92; 95% CI: 0.86-0.99), ground-glass opacification at admission (OR: 0.86; 95% CI:0.76-0.98) and glucocorticoid treatment (OR: 1.29; 95% CI: 1.00-1.66) were independently associated with hospital readmission. The rate of readmission after hospital discharge for COVID-19 was low. Advanced age and comorbidity were associated with increased risk of readmission