Remoción de flúor en agua con zeolitas naturales mexicanas

96 páginas. Maestría en Ciencias e Ingeniería Ambientales.La problemática del flúor en México puede ser considerada crítica, puesto que no en todos los estados de México se han realizado estudios a las aguas subterráneas o pozos de donde es extraída el agua potable. Por lo anterior, el objetivo principal de éste trabajo fue evaluar la viabilidad del uso de las zeolitas naturales para la eliminación de fluoruros presentes en aguas subterráneas, que es destinada al consumo humano, así como, valorar el acondicionamiento de las zeolitas con soluciones de calcio, manganeso o hierro y su eficiencia como material adsorbente en dos sistemas de columna de lecho fijo, uno de flujo ascendente y otro de flujo descendente, proponer el tratamiento de acondicionamiento más adecuado a la zeolita en base a la eficacia, así como, designar los parámetros de operación, determinar la capacidad de adsorción de las zeolitas naturales y acondicionadas a través de isotermas de adsorción y proponer una alternativa para la disposición del residuo generado

Caracterización y acondicionamiento de zeolitas mexicanas con calcio para ser usados como materiales adsorbentes

En este trabajo se presenta la caracterización de zeolitas naturales mexicanas y su acondicionamiento con calcio para el proceso de adsorción usando cinco zeolitas naturales recolectadas en yacimientos de diferentes municipios del estado de Oaxaca, México. Los resultados de caracterización mostraron que las zeolitas tienen estructura tipo clinoptilolita y están presentes diferentes cationes en su estructura, las cuales fueron lavadas para eliminar impurezas e intercambiadas con solución de sodio 2 M y una de ellas se seleccionó para ser acondicionada con solución de calcio, para esta zeolita los resultados de caracterización por SEM/EDS, XRD y FTIR mostraron que la estructura tras el acondicionamiento no se modificó y que el contenido de calcio se vio incrementado.This work presents the characterization of Mexican natural zeolites and their conditioning with calcium for the adsorption process using five natural zeolites collected from different municipalities in the state of Oaxaca, Mexico. The characterization results showed that the zeolites have clinoptilolite type structure and different cations are present in their structure, which were washed to remove impurities and exchanged with 2 M sodium solution and one of them was selected to be conditioned with calcium solution, for this zeolite the characterization results by SEM / EDS, XRD and FTIR showed that the structure after the conditioning was not modified and that the calcium content was increased

An asymmetric BODIPY triad with panchromatic absorption for high-performance red-edge laser emission

© The Royal Society of Chemistry 2015. A rational design of an unprecedented asymmetric cassette triad based entirely on BODIPY chromophores allows efficient light harvesting over the UV-vis spectral region, leading to a bright and stable red-edge laser emission via efficient energy-transfer processes.Peer Reviewe

Zeolita natural tipo clinoptilolita acondicionada con hierro

En el suelo de la República Mexicana se encuentra una gran variedad de materiales zeolíticos, los cuales se consideran materiales locales de fácil adquisición y económicos que se han usado en un sinfín de aplicaciones, dadas las propiedades que tienen este tipo de materiales cristalinos. En el presente trabajo se presenta el acondicionamiento de dos zeolitas naturales mexicanas, tipo clinoptilolita de dos estados de la República Mexicana: Oaxaca y Guanajuato. Las zeolitas se acondicionaron con hierro por el método de precipitación-impregnación a partir de una solución de nitrato de hierro. Las zeolitas se caracterizaron por los métodos de Difracción de Rayos X (XRD), Microscopia Electrónica de Barrido (SEM), Análisis Químico Elemental (SEM/EDS), Espectroscopía Raman y Espectroscopía de Infrarrojo por Transformada de Fourier (FT-IR), y estos resultados mostraron que el acondicionamiento con hierro fue bueno para ambas zeolitas naturales. Dichos materiales se pretenden usar en un futuro, como adsorbentes de especies contaminantes en agua.On the floor of the Mexican Republic there is a great variety of zeolitic materials, which are considered easy-to-buy and cheap local materials that have been used in countless applications, given the properties of this type of crystalline materials. This paper presents the conditioning of a natural Mexican zeolite (clinoptilolite type) from two states of the Mexican Republic: Oaxaca and Guanajuato. The zeolite was conditioned with iron by the precipitation-impregnation method from an iron nitrate solution. The zeolites were characterized by the methods of X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Elemental Chemical Analysis (SEM/EDS), Raman Spectroscopy and Fourier Transformed Infrared Spectroscopy (FT-IR) and these results showed that iron conditioning was good for both natural zeolites. These materials are intended to be used in the future, as adsorbents of water-polluting species

Bis(haloBODIPYs) with Labile Helicity: Valuable Simple Organic Molecules That Enable Circularly Polarized Luminescence

Simple organic molecules (SOM) based on bis(haloBODIPY) are shown to enable circularly polarized luminescence (CPL), giving rise to a new structural design for technologically valuable CPL-SOMs. The established design comprises together synthetic accessibility, labile helicity, possibility of reversing the handedness of the circularly polarized emission, and reactive functional groups, making it unique and attractive as advantageous platform for the development of smart CPL-SOMs

The Effect of a Physical Activity Program on the Total Number of Primary Care Visits in Inactive Patients: A 15-Month Randomized Controlled Trial

Abstract Background: Effective promotion of exercise could result in substantial savings in healthcare cost expenses in terms of direct medical costs, such as the number of medical appointments. However, this is hampered by our limited knowledge of how to achieve sustained increases in physical activity. Objectives: To assess the effectiveness of a Primary Health Care (PHC) based physical activity program in reducing the total number of visits to the healthcare center among inactive patients, over a 15-month period. Research Design: Randomized controlled trial. Subjects: Three hundred and sixty-two (n = 362) inactive patients suffering from at least one chronic condition were included. One hundred and eighty-three patients (n = 183; mean (SD); 68.3 (8.8) years; 118 women) were randomly allocated to the physical activity program (IG). One hundred and seventy-nine patients (n = 179; 67.2 (9.1) years; 106 women) were allocated to the control group (CG). The IG went through a three-month standardized physical activity program led by physical activity specialists and linked to community resources. Measures: The total number of medical appointments to the PHC, during twelve months before and after the program, was registered. Self-reported health status (SF-12 version 2) was assessed at baseline (month 0), at the end of the intervention (month 3), and at 12 months follow-up after the end of the intervention (month 15). Results: The IG had a significantly reduced number of visits during the 12 months after the intervention: 14.8 (8.5). The CG remained about the same: 18.2 (11.1) (P = .002). Conclusions: Our findings indicate that a 3-month physical activity program linked to community resources is a shortduration, effective and sustainable intervention in inactive patients to decrease rates of PHC visits. Trial Registration: ClinicalTrials.gov NCT0071483

Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

The impact of surgical delay on resectability of colorectal cancer: An international prospective cohort study

AIM: The SARS-CoV-2 pandemic has provided a unique opportunity to explore the impact of surgical delays on cancer resectability. This study aimed to compare resectability for colorectal cancer patients undergoing delayed versus non-delayed surgery. METHODS: This was an international prospective cohort study of consecutive colorectal cancer patients with a decision for curative surgery (January-April 2020). Surgical delay was defined as an operation taking place more than 4 weeks after treatment decision, in a patient who did not receive neoadjuvant therapy. A subgroup analysis explored the effects of delay in elective patients only. The impact of longer delays was explored in a sensitivity analysis. The primary outcome was complete resection, defined as curative resection with an R0 margin. RESULTS: Overall, 5453 patients from 304 hospitals in 47 countries were included, of whom 6.6% (358/5453) did not receive their planned operation. Of the 4304 operated patients without neoadjuvant therapy, 40.5% (1744/4304) were delayed beyond 4 weeks. Delayed patients were more likely to be older, men, more comorbid, have higher body mass index and have rectal cancer and early stage disease. Delayed patients had higher unadjusted rates of complete resection (93.7% vs. 91.9%, P = 0.032) and lower rates of emergency surgery (4.5% vs. 22.5%, P < 0.001). After adjustment, delay was not associated with a lower rate of complete resection (OR 1.18, 95% CI 0.90-1.55, P = 0.224), which was consistent in elective patients only (OR 0.94, 95% CI 0.69-1.27, P = 0.672). Longer delays were not associated with poorer outcomes. CONCLUSION: One in 15 colorectal cancer patients did not receive their planned operation during the first wave of COVID-19. Surgical delay did not appear to compromise resectability, raising the hypothesis that any reduction in long-term survival attributable to delays is likely to be due to micro-metastatic disease

Evaluation of appendicitis risk prediction models in adults with suspected appendicitis

Background Appendicitis is the most common general surgical emergency worldwide, but its diagnosis remains challenging. The aim of this study was to determine whether existing risk prediction models can reliably identify patients presenting to hospital in the UK with acute right iliac fossa (RIF) pain who are at low risk of appendicitis. Methods A systematic search was completed to identify all existing appendicitis risk prediction models. Models were validated using UK data from an international prospective cohort study that captured consecutive patients aged 16–45 years presenting to hospital with acute RIF in March to June 2017. The main outcome was best achievable model specificity (proportion of patients who did not have appendicitis correctly classified as low risk) whilst maintaining a failure rate below 5 per cent (proportion of patients identified as low risk who actually had appendicitis). Results Some 5345 patients across 154 UK hospitals were identified, of which two‐thirds (3613 of 5345, 67·6 per cent) were women. Women were more than twice as likely to undergo surgery with removal of a histologically normal appendix (272 of 964, 28·2 per cent) than men (120 of 993, 12·1 per cent) (relative risk 2·33, 95 per cent c.i. 1·92 to 2·84; P < 0·001). Of 15 validated risk prediction models, the Adult Appendicitis Score performed best (cut‐off score 8 or less, specificity 63·1 per cent, failure rate 3·7 per cent). The Appendicitis Inflammatory Response Score performed best for men (cut‐off score 2 or less, specificity 24·7 per cent, failure rate 2·4 per cent). Conclusion Women in the UK had a disproportionate risk of admission without surgical intervention and had high rates of normal appendicectomy. Risk prediction models to support shared decision‐making by identifying adults in the UK at low risk of appendicitis were identified