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1.
Arch. Soc. Esp. Oftalmol ; 99(3): 98-108, Mar. 2024. mapas, tab
Article in Spanish | IBECS | ID: ibc-231136

ABSTRACT

Antecedentes y objetivo: Las recomendaciones sobre el manejo general del glaucoma y el uso de cirugías mínimamente-invasivas y microincisionales en fases tempranas son limitadas. El objetivo de este estudio fue establecer un consenso sobre el manejo del glaucoma, centrándose en el implante XEN 45 (AbbVie Inc., North Chicago, IL, EE. UU.). Métodos: Se utilizó un método Delphi. El comité científico dirigió el estudio, identificó el panel de expertos y participó en la elaboración del cuestionario. Se invitó a 51 expertos a completar, en una escala Likert de 9 puntos, un cuestionario de 89 ítems que cubría 3 bloques temáticos. Se realizaron 2 rondas Delphi. Se logró consenso si≥66,6% de los expertos llegaron a un acuerdo o desacuerdo. Resultados: Los panelistas acordaron 84 ítems relacionados con la calidad de vida, el algoritmo terapéutico y el perfil del paciente, y el manejo quirúrgico pre y postoperatorio. Los panelistas consideraron el implante XEN idóneo para tratar el glaucoma en diferentes etapas y para diferentes perfiles de pacientes: pacientes jóvenes/ancianos/con comorbilidades-significativas, glaucoma-miópico, pacientes con fracaso quirúrgico previo y con postoperatorio complejo. El implante XEN se consideró un paso terapéutico previo a la cirugía filtrante clásica y una posible primera opción quirúrgica en pacientes ancianos con comorbilidades y presión intraocular descontrolada. El implante XEN permite al paciente retomar sus actividades diarias más rápidamente que las cirugías filtrantes convencionales y reducir y/o eliminar los tratamientos tópicos. Conclusiones: Este consenso según la metodología Delphi proporcionó una serie de recomendaciones generales para el tratamiento del glaucoma, incluidas aquellas relacionadas con la calidad de vida del paciente, el algoritmo terapéutico y el perfil del paciente, y específicas con respecto al uso del implante XEN.(AU)


Background and objective: Recommendations on general glaucoma management and the use of early minimally invasive and microincisional surgeries are limited. This study aimed to establish consensus regarding glaucoma management, focusing on the XEN-45 gel stent implant. Methods: A Delphi consensus-driven process was used. The scientific committee led the study, identified the expert panel, and participated in elaborating the questionnaire. Fifty-one panelists were invited to complete, on a nine-point Likert scale, an 89-item questionnaire covering three topic blocks. Two Delphi rounds were performed. Consensus was achieved if ≥66.6% of panelists reached agreement or disagreement. Results: Panelists agreed on 84 items related to the patients’ quality of life, the therapeutic algorithm and patient profile, and surgical and pre- and post-operative management. Panelists agreed on the suitability of XEN stent implants to treat glaucoma at different stages and for different patient profiles: young patients, elderly or with significant comorbidities, and with myopic glaucoma, patients who failed previous surgeries, and with previous poor post-operative experience. XEN surgery was considered a therapeutic step prior to classic filtering surgery and a possible first surgical option in elderly patients with comorbidities and uncontrolled intraocular pressure. XEN surgery allows the patient to return to routine daily activities faster than conventional filtering surgeries and to reduce and/or eliminate topical treatments. Conclusions: This Delphi-driven consensus resulted in a series of general recommendations for glaucoma management, including those related to patient quality of life, therapeutic algorithm, and patient profile, and specific ones regarding the use of XEN stent gel surgery.(AU)


Subject(s)
Humans , Male , Female , Delphi Technique , Glaucoma/surgery , Minimally Invasive Surgical Procedures , Algorithms , Ophthalmology
2.
Arch Soc Esp Oftalmol (Engl Ed) ; 99(3): 98-108, 2024 Mar.
Article in English | MEDLINE | ID: mdl-38216051

ABSTRACT

BACKGROUND AND OBJECTIVE: Recommendations on general glaucoma management and the use of early minimally invasive and microincisional surgeries are limited. This study aimed to establish consensus regarding glaucoma management, focusing on the XEN-45 gel stent implant. METHODS: A Delphi consensus-driven process was used. The scientific committee led the study, identified the expert panel, and participated in elaborating the questionnaire. Fifty-one panelists were invited to complete, on a nine-point Likert scale, an 89-item questionnaire covering three topic blocks. Two Delphi rounds were performed. Consensus was achieved if ≥66.6% of panelists reached agreement or disagreement. RESULTS: Panelists agreed on 84 items related to the patients' quality of life, the therapeutic algorithm and patient profile, and surgical and pre- and post-operative management. Panelists agreed on the suitability of XEN stent implants to treat glaucoma at different stages and for different patient profiles: young patients, elderly or with significant comorbidities, and with myopic glaucoma, patients who failed previous surgeries, and with previous poor post-operative experience. XEN surgery was considered a therapeutic step prior to classic filtering surgery and a possible first surgical option in elderly patients with comorbidities and uncontrolled intraocular pressure. XEN surgery allows the patient to return to routine daily activities faster than conventional filtering surgeries and to reduce and/or eliminate topical treatments. CONCLUSIONS: This Delphi-driven consensus resulted in a series of general recommendations for glaucoma management, including those related to patient quality of life, therapeutic algorithm, and patient profile, and specific ones regarding the use of XEN stent gel surgery.


Subject(s)
Glaucoma Drainage Implants , Glaucoma , Humans , Aged , Delphi Technique , Quality of Life , Treatment Outcome , Glaucoma/surgery
3.
Ultrasound Obstet Gynecol ; 63(3): 350-357, 2024 03.
Article in English | MEDLINE | ID: mdl-37774112

ABSTRACT

OBJECTIVE: Pre-eclampsia (PE) is a serious complication of pregnancy associated with maternal and fetal morbidity and mortality. As current prediction models have limitations and may not be applicable in resource-limited settings, we aimed to develop a machine-learning (ML) algorithm that offers a potential solution for developing accurate and efficient first-trimester prediction of PE. METHODS: We conducted a prospective cohort study in Mexico City, Mexico to develop a first-trimester prediction model for preterm PE (pPE) using ML. Maternal characteristics and locally derived multiples of the median (MoM) values for mean arterial pressure, uterine artery pulsatility index and serum placental growth factor were used for variable selection. The dataset was split into training, validation and test sets. An elastic-net method was employed for predictor selection, and model performance was evaluated using area under the receiver-operating-characteristics curve (AUC) and detection rates (DR) at 10% false-positive rates (FPR). RESULTS: The final analysis included 3050 pregnant women, of whom 124 (4.07%) developed PE. The ML model showed good performance, with AUCs of 0.897, 0.963 and 0.778 for pPE, early-onset PE (ePE) and any type of PE (all-PE), respectively. The DRs at 10% FPR were 76.5%, 88.2% and 50.1% for pPE, ePE and all-PE, respectively. CONCLUSIONS: Our ML model demonstrated high accuracy in predicting pPE and ePE using first-trimester maternal characteristics and locally derived MoM. The model may provide an efficient and accessible tool for early prediction of PE, facilitating timely intervention and improved maternal and fetal outcome. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.


Eficiencia de un enfoque de aprendizaje automático para la predicción de la preeclampsia en un país de ingresos medios OBJETIVO: La preeclampsia (PE) es una complicación grave del embarazo asociada a morbilidad y mortalidad materna y del feto. Dado que los modelos de predicción actuales tienen limitaciones y pueden no ser aplicables en situaciones con recursos limitados, se propuso desarrollar un algoritmo de aprendizaje automático (AA) que ofrezca una solución con potencial para desarrollar una predicción precisa y eficiente de la PE en el primer trimestre. MÉTODOS: Se realizó un estudio de cohorte prospectivo en Ciudad de México para desarrollar un modelo de predicción de la PE pretérmino (PEp) en el primer trimestre utilizando AA. Para la selección de variables se utilizaron las características maternas y los múltiplos de la mediana (MdM) obtenidos localmente para la presión arterial media, el índice de pulsatilidad de la arteria uterina y el factor de crecimiento placentario sérico. El conjunto de datos se dividió en subconjuntos de datos de entrenamiento, de validación y de test estadístico. Se empleó un método de red elástica para la selección de predictores, y el rendimiento del modelo se evaluó mediante el área bajo la curva de características operativas del receptor (ABC) y las tasas de detección (TD) con tasas de falsos positivos (TFP) del 10%. RESULTADOS: El análisis final incluyó a 3050 mujeres embarazadas, de las cuales 124 (4,07%) desarrollaron PE. El modelo de AA mostró una buena eficiencia, con un ABC de 0,897, 0,963 y 0,778 para la PEp, la PE de aparición temprana (PEat) y cualquier tipo de PE (todas las PE), respectivamente. Las TD con TFP del 10% fueron del 76,5%, 88,2% y 50,1% para la PEp, PEat y todas las PE, respectivamente. CONCLUSIONES: Nuestro modelo de AA demostró una alta precisión en la predicción de la PEp y la PEat utilizando características maternas del primer trimestre y MdM calculados localmente. El modelo puede proporcionar una herramienta eficiente y accesible para la predicción temprana de la PE, facilitando la intervención oportuna y la mejora de los resultados maternos y del feto.


Subject(s)
Pre-Eclampsia , Infant, Newborn , Pregnancy , Female , Humans , Pre-Eclampsia/diagnosis , Placenta Growth Factor , Prospective Studies , Biomarkers , Pregnancy Trimester, First
4.
Ecol Soc ; 28(3)2023 Sep.
Article in English | MEDLINE | ID: mdl-38179152

ABSTRACT

Despite the universally recognized importance of fostering trust and avoiding distrust in governance relationships, there remains considerable debate on core questions like the relation between (dis)trust and the evaluations of the characteristics that make a governance agent appear (un)worthy of trust. In particular, it remains unclear whether levels of (dis)trust simply follow levels of (dis)trustworthiness-such that building trust is primarily a question of increasing evidence of trustworthiness and avoiding evidence of distrustworthiness, or if their dynamics are more complicated. The current paper adds novel theory for thinking about the management of trust and distrust in the governance context through the application of principles borrowed from resilience theory. Specifically, we argue that trust and distrust exist as distinct, self-reinforcing (i.e., stable) states separated by a threshold. We then theorize as to the nature of the self-reinforcing processes and use qualitative data collected from and inductively coded in collaboration with Flint residents as part of a participatory process to look for evidence of our argument in a well-documented governance failure. We conclude by explaining how this novel perspective allows for clearer insight into the experience of this and other communities and speculate as to how it may help to better position governance actors to respond to future crises.

5.
Rev Sci Instrum ; 93(11): 113502, 2022 Nov 01.
Article in English | MEDLINE | ID: mdl-36461505

ABSTRACT

During inertial confinement fusion experiments at the National Ignition Facility (NIF), a capsule filled with deuterium and tritium (DT) gas, surrounded by a DT ice layer and a high-density carbon ablator, is driven to the temperature and densities required to initiate fusion. In the indirect method, 2 MJ of NIF laser light heats the inside of a gold hohlraum to a radiation temperature of 300 eV; thermal x rays from the hohlraum interior couple to the capsule and create a central hotspot at tens of millions degrees Kelvin and a density of 100-200 g/cm3. During the laser interaction with the gold wall, m-band x rays are produced at ∼2.5 keV; these can penetrate into the capsule and preheat the ablator and DT fuel. Preheat can impact instability growth rates in the ablation front and at the fuel-ablator interface. Monitoring the hohlraum x-ray spectrum throughout the implosion is, therefore, critical; for this purpose, a Multilayer Mirror (MLM) with flat response in the 2-4 keV range has been installed in the NIF 37° Dante calorimeter. Precision engineering and x-ray calibration of components mean the channel will report 2-4 keV spectral power with an uncertainty of ±8.7%.

6.
Rev Sci Instrum ; 92(2): 023516, 2021 Feb 01.
Article in English | MEDLINE | ID: mdl-33648072

ABSTRACT

Measurement of the neutron spectrum from inertial confinement fusion implosions is one of the primary diagnostics of implosion performance. Analysis of the spectrum gives access to quantities such as neutron yield, hot-spot velocity, apparent ion temperature, and compressed fuel ρr through measurement of the down-scatter ratio. On the National Ignition Facility, the neutron time-of-flight suite has been upgraded to include five independent, collimated lines of sight, each comprising a high dynamic range bibenzyl/diphenylacetylene-stilbene scintillator [R. Hatarik et al., Plasma Fusion Res. 9, 4404104 (2014)] and high-speed fused silica Cherenkov detectors [A. S. Moore et al., Rev. Sci. Instrum. 89, 10I120 (2018)].

8.
Cient. dent. (Ed. impr.) ; 16(2): 111-116, mayo-ago. 2019. ilus
Article in Spanish | IBECS | ID: ibc-183721

ABSTRACT

Introducción: La extracción de los terceros molares es una práctica habitual en la consulta odontológica. Es muy común la aparición postoperatoria de respuestas fisiológicas como el dolor, inflamación, hematomas y trismo, y cuyo tratamiento de elección sigue siendo la farmacología. La hiloterapia es un tratamiento alternativo complementario que forma parte de la medicina física terapéutica. Se trata de una unidad conectada a una máscara preformada de contorno facial que, mediante la reducción de la termperatura tisular de manera constante, persigue conseguir la disminución del flujo sanguíneo, la inflamación, el dolor y el edema. Caso clínico: Se presenta el caso clínico de una mujer de 22 años de edad, sin antecedentes médicos de interés, que acudió al Hospital Virgen de la Paloma por presentar dolor en el tercer molar inferior izquierdo. Una vez realizada la exploración clínica y radiológica de la paciente, se propuso como plan de tratamiento la extracción de los cuatro cordales, bajo anestesia general. Inmediatamente después de la cirugía se colocó a la paciente la máscara facial de Hilotherm(R), programada a una temperatura constante de 15ºC. Se revisó a las 24h y a los 8 días tras la intervención. Conclusiones: La terapia con la máscara facial Hilotherm(R) ha demostrado ser de utilidad en la disminución del dolor y la inflamación postoperatorios derivados de la extracción quirúrgica de los terceros molares, probablemente debido a la posibilidad de un control constante de la temperatura y a la mayor colaboración del paciente. No hay evidencia científica suficiente que respalde su posible participación en la reducción de hematomas. Asimismo, este sistema sugiere un aumento significativo de la calidad de vida de los pacientes, así como una buena aceptación por parte de éstos otorgando más comodidad y satisfacción


Introduction: The extraction of third molars is common practice in the dental practice. The postoperative appearance of physiological responses such as pain, inflammation, bruising and trismus is very common, for which the treatment of choice is still pharmacology. The hilotherapy is a complementary alternative treatment that is part of the therapeutic physical medicine which consists on a unit connected to a preformed face contour mask that, by constantly reducing tissue temperature, aims to achieve decreased blood flow, inflammation, pain and edema. Clinical case: A clinical case of a 22-year-old woman is presented, with no interesting medical record, who went to the Virgen de la Paloma Hospital with pain in the left lower third molar. Once the clinical and radiological examination of the patient had been carried out, a treatment plan for the extraction of the four wisdom teeth, under general anesthesia, was proposed. Immediately after the surgery, the patient was placed the facial mask of Hilotherm(R) on, programmed at a constant temperature of 15ºC. It was reviewed twice, 24h and 8 days after the intervention. Conclusions: Hilotherm(R) facial mask therapy has been shown to be useful in the reduction of postoperative pain and inflammation derived from the surgical extraction of third molars, probably due to the possibility of constant temperature control and greater patient collaboration. There is not enough scientific evidence to support its possible participation in the reduction of bruising. Likewise, this system suggests a significant increase in the quality of life of patients, as well as a good acceptance from patients, providing them with more comfort and satisfaction


Subject(s)
Humans , Female , Adult , Molar, Third/surgery , Edema/prevention & control , Pain, Postoperative/prevention & control , Cryotherapy/methods , Masks , Postoperative Complications/etiology , Postoperative Complications/prevention & control , Oral Surgical Procedures , Ecchymosis/prevention & control , Hematoma/prevention & control , Postoperative Care
9.
Rev Gastroenterol Mex (Engl Ed) ; 84(2): 220-240, 2019.
Article in English, Spanish | MEDLINE | ID: mdl-31014749

ABSTRACT

Since the publication of the 2008 guidelines on the diagnosis and treatment of diverticular disease of the colon by the Asociación Mexicana de Gastroenterología, significant advances have been made in the knowledge of that disease. A systematic review of articles published in the medical literature from January 2008 to July 2018 was carried out to revise and update the 2008 guidelines and provide new evidence-based recommendations. All high-quality articles in Spanish and English published within that time frame were included. The final versions of the 43 statements accepted in the three rounds of voting, utilizing the Delphi method, were written, and the quality of evidence and strength of the recommendations were established for each statement, utilizing the GRADE system. The present consensus contains new data on the definition, classification, epidemiology, pathophysiology, and risk factors of diverticular disease of the colon. Special emphasis is given to the usefulness of computed tomography and colonoscopy, as well as to the endoscopic methods for controlling bleeding. Outpatient treatment of uncomplicated diverticulitis is discussed, as well as the role of rifaximin and mesalazine in the management of complicated acute diverticulitis. Both its minimally invasive alternatives and surgical options are described, stressing their indications, limitations, and contraindications. The new statements provide guidelines based on updated scientific evidence. Each statement is discussed, and its quality of evidence and the strength of the recommendation are presented.


Subject(s)
Colonic Diseases/therapy , Diverticular Diseases/therapy , Consensus , Delphi Technique , Diverticulitis/therapy , Guidelines as Topic , Humans , Mexico
10.
Rev. gastroenterol. Méx ; 84(2): 220-240, April-June 2019.
Article in Spanish | LILACS, BIGG - GRADE guidelines | ID: biblio-1026189

ABSTRACT

Desde la publicación en 2008 de las guías de diagnóstico y tratamiento de la enfermedad diverticular del colon de la Asociación Mexicana de Gastroenterología ha habido avances significativos en el conocimiento de esta enfermedad. Se realizó una revisión sistemática de la literatura en PubMed de enero de 2008 a julio de 2018 con el fin de revisar y actualizar las guías 2008 y proporcionar nuevas recomendaciones basadas en la evidencia. Se incluyeron todas las publicaciones en español e inglés, de alta calidad. Se redactaron los enunciados, que fueron votados utilizando el método Delphi. Se estableció la calidad de la evidencia y la fuerza de las recomendaciones según el sistema GRADE para cada enunciado. Cuarenta y tres enunciados fueron finalmente votados y calificados. Se informan nuevos datos sobre definición, clasificación, epidemiología, fisiopatología y factores de riesgo. Se revisó con especial énfasis la utilidad de la tomografía computarizada y de la colonoscopia, así como los métodos endoscópicos para el control de la hemorragia. Se discutió sobre el tratamiento ambulatorio de la diverticulitis no complicada, el papel de la rifaximina y la mesalazina, en el manejo de la diverticulitis aguda complicada tanto en sus alternativas mínimamente invasivas hasta las opciones quirúrgicas con énfasis en sus indicaciones, limitaciones y contraindicaciones. Los nuevos enunciados proporcionan directrices basadas en la evidencia actualizada. Se presentan la discusión, el grado y la fuerza de la recomendación de cada uno de ellos.


Subject(s)
Humans , Colonic Diseases/diagnosis , Colonic Diseases/prevention & control , Diverticulitis/complications , Diverticulitis, Colonic/diagnosis , Diverticulum, Colon/therapy , Mexico
11.
Rev Sci Instrum ; 89(10): 10I146, 2018 Oct.
Article in English | MEDLINE | ID: mdl-30399731

ABSTRACT

The Cherenkov mechanism used in Gas Cherenkov Detectors (GCDs) is exceptionally fast. However, the temporal resolution of GCDs, such as the Gamma Reaction History diagnostic at the National Ignition Facility (NIF), has been limited by the current state-of-the-art photomultiplier tube technology to ∼100 ps. The soon-to-be deployed Pulse Dilation Photomultiplier Tube (PD-PMT) at NIF will allow for temporal resolution comparable to that of the gas cell or ∼10 ps. Enhanced resolution will contribute to the quest for ignition in a crucial way through precision measurements of reaction history and ablator areal density (ρR) history, leading to better constrained models. Features such as onset of alpha heating, shock reverberations, and burn truncation due to dynamically evolving failure modes may become visible for the first time. Test measurements of the PD-PMT at Atomic Weapons Establishment confirmed that design goals have been met. The PD-PMT provides dilation factors of 2 to 40× in 6 increments. The GCD-3 recently deployed at the NIF has been modified for coupling to a PD-PMT and will soon be making ultrafast measurements.

12.
Rev Sci Instrum ; 89(10): 10I148, 2018 Oct.
Article in English | MEDLINE | ID: mdl-30399772

ABSTRACT

Fusion reaction history and ablator areal density measurements for Inertial Confinement Fusion experiments at the National Ignition Facility are currently conducted using the Gamma Reaction History diagnostic (GRH_6m). Future Gas Cherenkov Detectors (GCDs) will ultimately provide ∼100x more sensitivity, reduce the effective temporal response from ∼100 to ∼10 ps, and lower the energy threshold from 2.9 to 1.8 MeV, relative to GRH_6m. The first phase toward next generation GCDs consisted of inserting the existing coaxial GCD-3 detector into a reentrant well which puts it within 4 m of the implosion. Reaction history and ablator gamma measurement results from this Phase I are discussed here. These results demonstrate viability for the follow-on Phases of (II) the use of a revolutionary new pulse-dilation photomultiplier tube to improve the effective measurement bandwidth by >10x relative to current PMT technology; and (III) the design of a NIF-specific "Super" GCD which will be informed by the assessment of the radiation background environment within the well described here.

16.
Rev Clin Esp (Barc) ; 217(8): 491, 2017 Nov.
Article in English, Spanish | MEDLINE | ID: mdl-28801134
17.
Genome Announc ; 5(8)2017 Feb 23.
Article in English | MEDLINE | ID: mdl-28232448

ABSTRACT

Here, we present the complete genome sequences of two Zika virus (ZIKV) strains, EcEs062_16 and EcEs089_16, isolated from the sera of febrile patients in Esmeraldas City, in the northern coastal province of Esmeraldas, Ecuador, in April 2016. These are the first complete ZIKV genomes to be reported from Ecuador.

18.
Mol Neurobiol ; 53(3): 1802-1807, 2016 Apr.
Article in English | MEDLINE | ID: mdl-25752997

ABSTRACT

Glioblastoma multiforme (GBM) is the most common brain tumor in adults. The role of high in normal-1 (HIN-1) as a potential biomarker in combating this disease is being described for the first time in this study. A combination of O6-methylguanine DNA methyltransferase (MGMT) and HIN-1 methylation could be a possible biomarker in therapy choice. Interestingly, survival data shows a similar trend for the methylation of MGMT and for unmethylation of HIN-1 and vice versa. Eighty-eight paraffin-embedded brain tumors were analyzed to screen methylation rates of different genes and evaluate the association between genes methylation and clinicopathologic variables. Our study is the first of its kind to indicate that MGMT and HIN-1 methylation status are inverted (97.7% of methylated ones) and could be new markers in the study of GBM prognosis, especially in the therapy selection.


Subject(s)
Brain Neoplasms/genetics , Brain Neoplasms/therapy , Cytokines/metabolism , Epigenesis, Genetic , Glioblastoma/genetics , Glioblastoma/therapy , Tumor Suppressor Proteins/metabolism , Adult , Aged , Aged, 80 and over , Biomarkers/metabolism , DNA Methylation/genetics , Female , Humans , Male , Middle Aged , Survival Analysis
19.
Water Sci Technol ; 72(6): 858-64, 2015.
Article in English | MEDLINE | ID: mdl-26360744

ABSTRACT

Sewage treatment with anammox could be implemented through a two-step reactor system, where the first reactor would be devoted to partial nitritation. A process design was sketched including control loops. The control strategy regulates the flow-rate of the rich ammonium sidestream produced after dewatering the digested sludge, to keep the ammonium concentration at a set point in the partial nitritation reactor by DOsing the SIde Stream (DOSIS). A second control loop manages the ammonium concentration set point based on the measurement of the total nitrogen in the partial nitritation reactor. A mathematical model was developed to assess the amount of sidestream required. Even in the case of a strong diurnal variability, simulations show how the control strategy is correctly performing, demonstrating the potential of the proposed technology.


Subject(s)
Bioreactors , Nitrogen/chemistry , Quaternary Ammonium Compounds , Sewage/chemistry , Waste Disposal, Fluid/methods
20.
J Environ Radioact ; 149: 36-42, 2015 Nov.
Article in English | MEDLINE | ID: mdl-26197347

ABSTRACT

Clay minerals are reputed sorbents for Cs-137 and can be used as a low-permeability material to prevent groundwater flow. Therefore, clay barriers are employed to seal Cs-137 polluted areas and nuclear waste repositories. This work is motivated by cases where groundwater flow cannot be impeded. A permeable and reactive barrier to retain Cs-137 was tested. The trapping mechanism is based on the sorption of cesium on illite-containing clay. The permeability of the reactive material is provided by mixing clay on a matrix of wood shavings. Column tests combined with reactive transport modeling were performed to check both reactivity and permeability. Hydraulic conductivity of the mixture (10(-4) m/s) was sufficient to ensure an adequate hydraulic performance of an eventual barrier excavated in most aquifers. A number of column experiments confirmed Cs retention under different flow rates and inflow solutions. A 1D reactive transport model based on a cation-exchange mechanism was built. It was calibrated with batch experiments for high concentrations of NH4+ and K+ (the main competitors of Cs in the exchange positions). The model predicted satisfactorily the results of the column experiments. Once validated, it was used to investigate the performance and duration of a 2 m thick barrier under different scenarios (flow, clay content, Cs-137 and K concentration).


Subject(s)
Aluminum Silicates/chemistry , Cesium Radioisotopes/chemistry , Environmental Restoration and Remediation/methods , Water Pollutants, Radioactive/chemistry , Water Pollution, Radioactive/prevention & control , Clay , Models, Theoretical , Permeability
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