An intercomparison of CH3O2 measurements by Fluorescence Assay by Gas Expansion and Cavity Ring–Down Spectroscopy within HIRAC (Highly Instrumented Reactor for Atmospheric Chemistry)

Simultaneous measurements of CH3O2 radical concentrations have been performed using two different methods in the Leeds HIRAC (Highly Instrumented Reactor for Atmospheric Chemistry) chamber at 295 K and in 80 mbar of a mixture of 3 : 1 He : O2 and 100 mbar or 1000 mbar of synthetic air. The first detection method consisted of the indirect detection of CH3O2 using the conversion of CH3O2 into CH3O by excess NO with subsequent detection of CH3O by fluorescence assay by gas expansion (FAGE). The FAGE instrument was calibrated for CH3O2 in two ways. In the first method, a known concentration of CH3O2 was generated using the 185 nm photolysis of water vapour in synthetic air at atmospheric pressure followed by the conversion of the generated OH radicals to CH3O2 by reaction with CH4 / O2. This calibration can be used for experiments performed in HIRAC at 1000 mbar in air. In the second method, calibration was achieved by generating a near steady-state of CH3O2 and then switching off the photolysis lamps within HIRAC and monitoring the subsequent decay of CH3O2 which was controlled via its self-reaction, and analysing the decay using second order kinetics. This calibration could be used for experiments performed at all pressures. In the second detection method, CH3O2 has been measured directly using Cavity Ring-Down Spectroscopy (CRDS) using the absorption at 7487.98 cm-1 in the A <– X (ν12) band with the optical path along the ~1.4 m chamber diameter. Analysis of the second-order kinetic decays of CH3O2 by self-reaction monitored by CRDS has been used for the determination of the CH3O2 absorption cross section at 7487.98 cm-1, both at 100 mbar of air and at 80 mbar of a 3 : 1 He : O2 mixture, from which σCH3O2 = (1.49 ± 0.19) × 10–20 cm2 molecule-1 was determined for both pressures. The absorption spectrum of CH3O2 between 7486 and 7491 cm-1 did not change shape when the total pressure was increased to 1000 mbar, from which we determined that σCH3O2 is independent of pressure over the pressure range 100–1000 mbar in air. CH3O2 was generated in HIRAC using either the photolysis of Cl2 with UV black lamps in the presence of CH4 and O2 or the photolysis of acetone at 254 nm in the presence of O2. At 1000 mbar of synthetic air the correlation plot of [CH3O2]FAGE against [CH3O2]CRDS gave a gradient of 1.10 ± 0.02. At 100 mbar of synthetic air the gradient of the FAGE – CRDS correlation plot had a gradient of 1.06 ± 0.01 and at 80 mbar of 3 : 1 He : O2 mixture the correlation plot gradient was 0.91 ± 0.02. These results provide a validation of the FAGE method to determine concentrations of CH3O2

Considerations for designing and implementing combination HIV cure trials: findings from a qualitative in-depth interview study in the United States

Background: An increasing number of HIV cure trials involve combining multiple potentially curative interventions. Until now, considerations for designing and implementing complex combination HIV cure trials have not been thoroughly considered. Methods: We used a purposive method to select key informants for our study. Informants included biomedical HIV cure researchers, regulators, policy makers, bioethicists, and community members. We used in-depth interviews to generate ethical and practical considerations to guide the design and implementation of combination HIV cure research. We analyzed the qualitative data using conventional content analysis focused on inductive reasoning. Results: We interviewed 11 biomedical researchers, 4 community members, 2 regulators, 1 policy researcher, and 1 bioethicist. Informants generated considerations for designing and implementing combination interventions towards an HIV cure, focused on ethical aspects, as well as considerations to guide trial design, benefit/risk determinations, regulatory requirements, prioritization and sequencing and timing of interventions, among others. Informants also provided considerations related to combining specific HIV cure research modalities, such as broadly neutralizing antibodies (bNAbs), cell and gene modification products, latency-reversing agents and immune-based interventions. Finally, informants provided suggestions to ensure meaningful therapeutic improvements over standard antiretroviral therapy, overcome challenges of designing combination approaches, and engage communities around combination HIV cure research. Conclusion: The increasing number of combination HIV cure trials brings with them a host of ethical and practical challenges. We hope our paper will inform meaningful stakeholder dialogue around the use of combinatorial HIV cure research approaches. To protect the public trust in HIV cure research, considerations should be periodically revisited and updated with key stakeholder input as the science continues to advance

SISTEMA DE GESTIÓN AMBIENTAL PARA EL PROCESO PRODUCTIVO DE LA EMPRESA PASTAS CAPRI C.A

This study is framed in the form of special project supported by field research was descriptive in nature and intended to implement Environmental Management System based on ISO 14001:2004 / Cor.1 : 2009, Clause 4.1 General Requirements , 4.2 Environmental Policy 4.3 Planning 4.4 Implementation and Operation in the production process line Short Pasta company " PASTA CAPRI " C. A. The research was conducted in three phases : the first phase is diagnosed the need for implementation of the environmental management system , for which a checklist based on the clauses of ISO 14001 dichotomous questions was developed , validated by experts and applied to the study subjects , which were a total of five (5) participants. In the second phase the environmental management system was designed in response to the steps outlined in ISO 14001:2004 / Cor.1: 2009 standard and finally the third phase corresponded to the operational and technical validation of the environmental management system, for it a tool to study subjects was applied to meet compliance with the ISO 14001:2004 should / Cor.1: 2009 standard. The environmental management system allows the company to optimize its production process, improve the use of resources, improve efficiency, minimize the environmental impact of the company with their environment due to the reduction of pollutantsEl presente estudio se enmarcó en la modalidad de Proyecto Especial apoyado en una investigación de campo de naturaleza descriptiva y tuvo como propósito implantar Sistema de Gestión Ambiental basados en la norma ISO 14001:2004/Cor.1:2009, Subcláusula 4.1 Requisitos Generales, 4.2 Política Ambiental, 4.3 Planificación, 4.4 Implementación y Operación en el proceso productivo de la línea de Pastas Corta de la empresa “PASTAS CAPRI” C. A. La investigación se llevó a cabo en tres fases: en la primera fase se diagnosticó la necesidad de implementación del sistema de gestión ambiental, para lo cual se elaboró una lista de verificación basada en las cláusulas de la norma ISO 14001 con preguntas dicotómicas, validado por expertos y aplicado a los sujetos de estudio, que fueron un total de cinco (5) participantes. En la segunda fase se diseñó el sistema de gestión ambiental atendiendo a los pasos señalados en la norma ISO 14001:2004/Cor.1:2009 y por último la tercera fase correspondió a la validación operacional y técnica del sistema de gestión ambiental, para ello se aplicó un instrumento a los sujetos de estudio para conocer el cumplimiento de los debes de la norma ISO 14001:2004/Cor.1:2009. El sistema de gestión ambiental le permite a la empresa optimizar su proceso productivo, mejorar el uso de los recursos, mejora la eficiencia, minimizar el impacto ambiental de la empresa con su entorno debido a la disminución de elementos contaminantes

Very long optical path-length from a compact multi-pass cell

The multiple-pass optical cell is an important tool for laser absorption spectroscopy and its many applications. For most practical applications, such as trace-gas detection, a compact and robust design is essential. Here we report an investigation into a multi-pass cell design based on a pair of cylindrical mirrors, with a particular focus on achieving very long optical paths. We demonstrate a path-length of 50.31 m in a cell with 40 mm diameter mirrors spaced 88.9 mm apart - a 3-fold increase over the previously reported longest path-length obtained with this type of cell configuration. We characterize the mechanical stability of the cell and describe the practical conditions necessary to achieve very long path-lengths

Serum Renin and Major Adverse Kidney Events in Critically Ill Patients: A Multicenter Prospective Study

BACKGROUND: Preliminary studies have suggested that the renin-angiotensin system is activated in critical illness and associated with mortality and kidney outcomes. We sought to assess in a larger, multicenter study the relationship between serum renin and Major Adverse Kidney Events (MAKE) in intensive care unit (ICU) patients. METHODS: Prospective, multicenter study at two institutions of patients with and without acute kidney injury (AKI). Blood samples were collected for renin measurement a median of 2 days into the index ICU admission and 5-7 days later. The primary outcome was MAKE at hospital discharge, a composite of mortality, kidney replacement therapy, or reduced estimated glomerular filtration rate to ≤ 75% of baseline. RESULTS: Patients in the highest renin tertile were more severely ill overall, including more AKI, vasopressor-dependence, and severity of illness. MAKE were significantly greater in the highest renin tertile compared to the first and second tertiles. In multivariable logistic regression, this initial measurement of renin remained significantly associated with both MAKE as well as the individual component of mortality. The association of renin with MAKE in survivors was not statistically significant. Renin measurements at the second time point were also higher in patients with MAKE. The trajectory of the renin measurements between time 1 and 2 was distinct when comparing death versus survival, but not when comparing MAKE versus those without. CONCLUSIONS: In a broad cohort of critically ill patients, serum renin measured early in the ICU admission is associated with MAKE at discharge, particularly mortality

Validation of microscopic observation drug susceptibility testing for rapid, direct rifampicin and isoniazid drug susceptibility testing in patients receiving tuberculosis treatment.

Drug susceptibility testing (DST) is often needed in patients clinically failing tuberculosis (TB) therapy. Most studies of phenotypic direct drug susceptibility tests, such as microscopic observation drug susceptibility (MODS) tests, have been performed in patients not receiving TB treatment. The effect of ongoing TB treatment on the performance of MODS direct DST has not been previously explored, but patients failing such therapy constitute an important target group. The aim of this study was to determine the performance of MODS direct rifampicin and isoniazid DST in patients clinically failing first-line TB treatment, and to compare MODS direct DST with indirect proportion method DST. Sputa from 264 TB patients were cultured in parallel in Lowenstein-Jensen (LJ) and MODS assays; strains were tested for rifampicin and isoniazid susceptibility by the proportion method at the national reference laboratory. Ninety-three samples were culture-positive by LJ and MODS (concordance of 96%; kappa 0.92). With conventional MODS plate DST reading (performed on the same day as the sample is classified as culture-positive), the isoniazid DST concordance was 96.8% (kappa 0.89), and the concordance for rifampicin susceptibility testing was 92.6% (kappa 0.80). Reading of MODS DST plates 1 week after cultures had been determined to be culture-positive improved overall performance marginally-the isoniazid DST concordance was 95.7% (kappa 0.85); and the rifampicin DST concordance was 96.8% (kappa 0.91). Sensitivity for detection of multidrug-resistant TB was 95.8%. MODS testing provided reliable rifampicin and isoniazid DST results for samples obtained from patients receiving TB therapy. A modified DST reading schedule for such samples, with a final reading 1 week after a MODS culture turns positive, marginally improves the concordance with reference DST

About conditions of application of logistic regression

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado.El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado.Carta al EditorRevisión por pare

The spatial distribution of HO2in an atmospheric pressure plasma jet investigated by cavity ring-down spectroscopy

Cold atmospheric pressure plasma jets make important contributions to a range of fields, such as materials processing and plasma medicine. In order to optimise the effect of those plasma sources, a detailed understanding of the chemical reaction networks is pivotal. However, the small diameter of plasma jets makes diagnostics challenging. A promising approach to obtain absolute number densities is the utilisation of cavity-enhanced absorption spectroscopy methods, by which line-of-sight averaged densities are determined. Here, we present first measurements on how the spatial distribution of HO2 in the effluent of a cold atmospheric pressure plasma jet can be obtained by cavity ring-down spectroscopy in an efficient way. Instead of recording fully wavelength resolved spectra, we will demonstrate that it is sufficient to measure the absorption coefficient at two wavelengths, corresponding to the laser being on and off the molecular resonance. By sampling the effluent from the 1.6 mm diameter nozzle in the radial direction at various axial positions, we determined that the distances over which the HO2 density was distributed were (3.9 ± 0.5) mm and (6.7 ± 0.1) mm at a distance of 2 mm and 10 mm below the nozzle of the plasma jet, respectively. We performed an Abel inversion in order to obtain the spatial distribution of HO2 that is presented along the symmetry axis of the effluent. Based on that localised density, which was (4.8 ± 0.6) ⋅ 1014 cm-3 at the maximum, we will discuss the importance of the plasma zone for the production of HO2

An intercomparison of HO₂ measurements by fluorescence assay by gas expansion and cavity ring-down spectroscopy within HIRAC (Highly Instrumented Reactor for Atmospheric Chemistry)

The HO2 radical was monitored simultaneously using two independent techniques in the Leeds HIRAC atmospheric simulation chamber at room temperature and total pressures of 150 mbar and 1000 mbar of synthetic air. In the first method, HO2 was measured indirectly following sampling through a pinhole expansion to 3 mbar when sampling from 1000 mbar and 1 mbar when sampling from 150 mbar, with subsequent addition of NO to convert it to OH which was detected via laser-induced fluorescence spectroscopy using the FAGE (fluorescence assay by gas expansion) technique. The FAGE method is used widely to measure HO2 concentrations in the field, and was calibrated using the 185 nm photolysis of water vapour in synthetic air with a limit of detection at 1000 mbar of 1.6 × 106 molecule cm-3 for an averaging time of 30 s. In the second method, HO2 was measured directly and absolutely without the need for a calibration using Cavity Ring Down Spectroscopy (CRDS) with the optical path across the entire ~ 1.4 m width of the chamber, with excitation of the first O-H overtone at 1506.43 nm using a diode laser, and with a sensitivity determined from an Allan deviation plot of 3.0 × 108 and 1.5 109 molecule cm-3 at 150 mbar and 1000 mbar, respectively, for an averaging period of 30 s. HO2 was generated in HIRAC by the photolysis of Cl2 using black lamps in the presence of methanol in synthetic air and was monitored by FAGE and CRDS for ~ 5–10 minute periods with the lamps on and also during the HO2 decay after the lamps were switched off. At 1000 mbar total pressure the correlation plot of [HO2]FAGE versus [HO2]CRDS gave a gradient of 0.836 0.004 for HO2 concentrations in the range ~ 4–100 × 109 molecule cm-3 while at 150 mbar total pressure the corresponding gradient was 0.903 0.002 for HO2 concentrations in the range ~ 6–750 × 108 molecule cm-3 . For the period after the lamps were switched off, the second-order decay of the HO2 FAGE signal via its self-reaction was used to calculate the FAGE calibration constant for both 150 and 1000 mbar total pressure. This enabled a calibration of the FAGE method at 150 mbar, an independent measurement of the FAGE calibration at 1000 mbar, and an independent determination of the HO2 cross section at 1506.43 nm, HO2, at both pressures. For CRDS, the HO2 concentration obtained using HO2 determined using previous reported spectral data for HO2 and the kinetic decay of HO2 method agreed to within 20 and 12 % at 150 and 1000 mbar, respectively. For the FAGE method a very good agreement (difference within 8 %) has been obtained at 1000 mbar between the water vapour calibration method and the kinetic decay of the HO2 fluorescence signal method. This is the first intercomparison for HO2 between FAGE and CRDS methods, and the good agreement between HO2 concentrations measured using the indirect FAGE method and the direct CRDS method provides a validation for the FAGE method, which is used widely for field measurements of HO2 in the atmosphere