Impact of the 2021 La Palma volcanic eruption on air quality: Insights from a multidisciplinary approach.

The La Palma 2021 volcanic eruption was the first subaerial eruption in a 50-year period in the Canary Islands (Spain), emitting ~1.8 Tg of sulphur dioxide (SO2) into the troposphere over nearly 3 months (19 September-13 December 2021), exceeding the total anthropogenic SO2 emitted from the 27 European Union countries in 2019. We conducted a comprehensive evaluation of the impact of the 2021 volcanic eruption on air quality (SO2, PM10 and PM2.5 concentrations) utilising a multidisciplinary approach, combining ground and satellite-based measurements with height-resolved aerosol and meteorological information. High concentrations of SO2, PM10 and PM2.5 were observed in La Palma (hourly mean SO2 up to ~2600 µg m-3 and also sporadically at ~140 km distance on the island of Tenerife (> 7700 µg m-3) in the free troposphere. PM10 and PM2.5 daily mean concentrations in La Palma peaked at ~380 and 60 µg m-3. Volcanic aerosols and desert dust both impacted the lower troposphere in a similar height range (~ 0-6 km) during the eruption, providing a unique opportunity to study the combined effect of both natural phenomena. The impact of the 2021 volcanic eruption on SO2 and PM concentrations was strongly influenced by the magnitude of the volcanic emissions, the injection height, the vertical stratification of the atmosphere and its seasonal dynamics. Mean daily SO2 concentrations increased during the eruption, from 38 µg m-3 (Phase I) to 92 µg m-3 (Phase II), showing an opposite temporal trend to mean daily SO2 emissions, which decreased from 34 kt (Phase I) to 7 kt (Phase II). The results of this study are relevant for emergency preparedness in all international areas at risk of volcanic eruptions; a multidisciplinary approach is key to understand the processes by which volcanic eruptions affect air quality and to mitigate and minimise impacts on the population.

Saharan Dust Events in the Dust Belt -Canary Islands- and the Observed Association with in-Hospital Mortality of Patients with Heart Failure.

Recent studies have found increases in the cardiovascular mortality rates during poor air quality events due to outbreaks of desert dust. In Tenerife, we collected (2014-2017) data in 829 patients admitted with a heart failure diagnosis in the Emergency Department of the University Hospital of the Canaries. In this region, concentrations of PM10 and PM2.5 are usually low (~20 and 10 µg/m3), but they increase to 360 and 115 µg/m3, respectively, during Saharan dust events. By using statistical tools (including multivariable logistic regressions), we compared in-hospital mortality of patients with heart failure and exposure to PM10 and PM2.5 during dust and no-dust events. We found that 86% of in-hospital heart failure mortality cases occurred during Saharan dust episodes that resulted in PM10 > 50 µg/m3 (interquartile range: 71-96 µg/m3). A multivariate analysis showed that, after adjusting for other covariates, exposure to Saharan dust events associated with PM10 > 50 µg/m3 was an independent predictor of heart failure in-hospital mortality (OR = 2.79, 95% CI (1.066-7.332), p = 0.03). In conclusion, this study demonstrates that exposure to high Saharan dust concentrations is independently associated with in-hospital mortality in patients with heart failure.

Straightening of light in a one dimensional dilute photonic crystal.

Light transport in a dilute photonic crystal is considered. The analytical expression for the transmission coefficient is derived. Straightening of light under certain conditions in a one-dimensional photonic crystal is predicted. Such behavior is caused by the formation of a localized state in transversal motion. The main contribution to the central diffracted wave transmission coefficient is due to states, that either close to the conductance band's bottom or deeply localized in the forbidden gap. Both these states suppress mobility in the transverse direction and force light to be straightened. Straightening of light in the optical region along with small reflection make these systems very promising for use in solar cells.

Impact of exposure of emergency patients with acute heart failure to atmospheric Saharan desert dust. / Impacto de la exposición a la calima del polvo del Sáhara en los pacientes con insuficiencia cardiaca aguda atendidos en un servicio de urgencias.

OBJECTIVES: To explore whether episodes of exposure to atmospheric Saharan dust is a risk factor for hospitalization in patients with acute heart failure (AHF) attended in a hospital emergency department (ED). METHODS: Single-center retrospective study of patients with AHF. The cohort was analyzed in 2 groups: ED patients hospitalized with AHF and patients discharged home from the ED. Air pollution on the 5 days leading to ED admission for AHF was recorded as the average concentration of breathable particulate matter with an aerodynamic diameter of no more than 10 µm (PM10) in the following ranges: fine PM (diameter less than 2.5 µm) or coarse PM (diameters between 2.5 and 10 µm). High Saharan dust pollution exposure was defined by mean daily PM10 concentrations between 50 and 200 µg/m3. Multivariable analysis was used to estimate risk for AHF in relation to PM10 exposure in the 5 days before the ED visit. RESULTS: A total of 1097 patients with AHF were treated in the ED; 318 of them (29%) were hospitalized and 779 (71%) were discharged home. Hospitalized patients were older, had more concomitant illnesses, and more episodes of exposure to Saharan dust (P < .0001). Multivariable analysis confirmed the association between Saharan dust exposure and hospital admission in these patients (odds ratio, 2.36; 95% CI, 1.21-4.58; P = .01). CONCLUSION: In the absence of prospective studies, the results of this series suggest that exposure to high levels of Saharan dust (PM10 concentrations between 50 and 200 µg/m3) may be a precipitating factor for hospitalization in AHF episodes.

OBJETIVO: Evaluar si la exposición a episodios de polvo sahariano predice los ingresos hospitalarios de los pacientes con insuficiencia cardiaca aguda (ICA) atendidos en un servicio de urgencias hospitalario (SUH). METODO: Estudio unicéntrico, de cohorte retrospectiva, de pacientes con ICA atendidos en un SUH. La población de estudio se dividió en 2 grupos: pacientes ingresados por ICA y pacientes con ICA dados de alta directa a domicilio desde el SUH. Se analizaron las concentraciones medias de material partículado (PMx) (respirables, diámetro aerodinámico, da< 10 µm), PM2,5 (finas, da <2,5 µm) y PM2,5-10 (gruesas, da 2,5-10 µm) desde el día de la llegada al SUH hasta 5 días previos. Se definió exposición intensa al polvo sahariano cuando las concentraciones medias diarias de PM10 estaban entre 50 y 200 µg/m3. La relación para estimar el riesgo de ingresar por ICA en función de la exposición de PMx durante los 5 días previos a su llegada a urgencias se analizó mediante análisis multivariable. RESULTADOS: Se incluyeron 1.097 pacientes con ICA, ingresaron 318 pacientes (29%), 779 (71%) se dieron de alta. Los pacientes ingresados por ICA tenían mayor edad, elevada comorbilidad y mayor proporción de pacientes expuestos a episodios intensos de polvo sahariano (p < 0,0001). En el análisis multivariable la exposición a episodios de polvo sahariano intensos se relacionó con el ingreso hospitalario en los pacientes con ICA (OR = 2,36; IC 95% 1,21-4,58; p = 0,01). CONCLUSIONES: En ausencia de estudios prospectivos, los resultados obtenidos de la serie analizada sugieren que la presencia de concentraciones elevadas de polvo sahariano (PM10: 50-200 µg/m3) puede constituir un factor precipitante de ingreso por ICA.

Impacto de la exposición a la calima del polvo del Sáhara en los pacientes con insuficiencia cardiaca aguda atendidos en un servicio de urgencias / Impact of exposure of emergency patients with acute heart failure to atmospheric Saharan desert dust

Objetivo: Evaluar si la exposición a episodios de polvo sahariano predice los ingresos hospitalarios de los pacientes con insuficiencia cardiaca aguda (ICA) atendidos en un servicio de urgencias hospitalario (SUH). Método: Estudio unicéntrico, de cohorte retrospectiva, de pacientes con ICA atendidos en un SUH. La población de estudio se dividió en 2 grupos: pacientes ingresados por ICA y pacientes con ICA dados de alta directa a domicilio desde el SUH. Se analizaron las concentraciones medias de material partículado (PMx) (respirables, diámetro aerodinámico, da < 10 µm), PM2,5 (finas, da < 2,5 µm) y PM2,5-10 (gruesas, da 2,5-10 µm) desde el día de la llegada al SUH hasta 5 días previos. Se definió exposición intensa al polvo sahariano cuando las concentraciones medias diarias de PM10 estaban entre 50 y 200 µg/m3. La relación para estimar el riesgo de ingresar por ICA en función de la exposición de PMx durante los 5 días previos a su llegada a urgencias se analizó mediante análisis multivariable. Resultados: Se incluyeron 1.097 pacientes con ICA, ingresaron 318 pacientes (29%), 779 (71%) se dieron de alta. Los pacientes ingresados por ICA tenían mayor edad, elevada comorbilidad y mayor proporción de pacientes expuestos a episodios intensos de polvo sahariano (p < 0,0001). En el análisis multivariable la exposición a episodios de polvo sahariano intensos se relacionó con el ingreso hospitalario en los pacientes con ICA (OR = 2,36; IC 95% 1,21-4,58; p = 0,01). Conclusiones: En ausencia de estudios prospectivos, los resultados obtenidos de la serie analizada sugieren que la presencia de concentraciones elevadas de polvo sahariano (PM10: 50-200 µg/m3) puede constituir un factor precipitante de ingreso por ICA

Objective: To explore whether episodes of exposure to atmospheric Saharan dust is a risk factor for hospitalization in patients with acute heart failure (AHF) attended in a hospital emergency department (ED). Methods: Single-center retrospective study of patients with AHF. The cohort was analyzed in 2 groups: ED patients hospitalized with AHF and patients discharged home from the ED. Air pollution on the 5 days leading to ED admission for AHF was recorded as the average concentration of breathable particulate matter with an aerodynamic diameter of no more than 10 µm (PM10) in the following ranges: fine PM (diameter less than 2.5 µm) or coarse PM (diameters between 2.5 and 10 µm). High Saharan dust pollution exposure was defined by mean daily PM10 concentrations between 50 and 200 µg/m3. Multivariable analysis was used to estimate risk for AHF in relation to PM10 exposure in the 5 days before the ED visit. Results: A total of 1097 patients with AHF were treated in the ED; 318 of them (29%) were hospitalized and 779 (71%) were discharged home. Hospitalized patients were older, had more concomitant illnesses, and more episodes of exposure to Saharan dust (P < .0001). Multivariable analysis confirmed the association between Saharan dust exposure and hospital admission in these patients (odds ratio, 2.36; 95% CI, 1.21-4.58; P = .01). Conclusions: In the absence of prospective studies, the results of this series suggest that exposure to high levels of Saharan dust (PM10 concentrations between 50 and 200 µg/m3) may be a precipitating factor for hospitalization in AHF episodes

Capsize of polarization in dilute photonic crystals.

We investigate, experimentally and theoretically, polarization rotation effects in dilute photonic crystals with transverse permittivity inhomogeneity perpendicular to the traveling direction of waves. A capsize, namely a drastic change of polarization to the perpendicular direction is observed in a one-dimensional photonic crystal in the frequency range 10 ÷ 140 GHz. To gain more insights into the rotational mechanism, we have developed a theoretical model of dilute photonic crystal, based on Maxwell's equations with a spatially dependent two dimensional inhomogeneous dielectric permittivity. We show that the polarization's rotation can be explained by an optical splitting parameter appearing naturally in Maxwell's equations for magnetic or electric fields components. This parameter is an optical analogous of Rashba like spin-orbit interaction parameter present in quantum waves, introduces a correction to the band structure of the two-dimensional Bloch states, creates the dynamical phase shift between the waves propagating in the orthogonal directions and finally leads to capsizing of the initial polarization. Excellent agreement between theory and experiment is found.

Soil dust aerosols and wind as predictors of seasonal meningitis incidence in Niger.

BACKGROUND: Epidemics of meningococcal meningitis are concentrated in sub-Saharan Africa during the dry season, a period when the region is affected by the Harmattan, a dry and dusty northeasterly trade wind blowing from the Sahara into the Gulf of Guinea. OBJECTIVES: We examined the potential of climate-based statistical forecasting models to predict seasonal incidence of meningitis in Niger at both the national and district levels. DATA AND METHODS: We used time series of meningitis incidence from 1986 through 2006 for 38 districts in Niger. We tested models based on data that would be readily available in an operational framework, such as climate and dust, population, and the incidence of early cases before the onset of the meningitis season in January-May. Incidence was used as a proxy for immunological state, susceptibility, and carriage in the population. We compared a range of negative binomial generalized linear models fitted to the meningitis data. RESULTS: At the national level, a model using early incidence in December and averaged November-December zonal wind provided the best fit (pseudo-R2 = 0.57), with zonal wind having the greatest impact. A model with surface dust concentration as a predictive variable performed indistinguishably well. At the district level, the best spatiotemporal model included zonal wind, dust concentration, early incidence in December, and population density (pseudo-R2 = 0.41). CONCLUSIONS: We showed that wind and dust information and incidence in the early dry season predict part of the year-to-year variability of the seasonal incidence of meningitis at both national and district levels in Niger. Models of this form could provide an early-season alert that wind, dust, and other conditions are potentially conducive to an epidemic.

Level statistics of disordered spin-1/2 systems and materials with localized Cooper pairs.

The origin of continuous energy spectra in large disordered interacting quantum systems is one of the key unsolved problems in quantum physics. Although small quantum systems with discrete energy levels are noiseless and stay coherent forever in the absence of any coupling to external world, most large-scale quantum systems are able to produce a thermal bath and excitation decay. This intrinsic decoherence is manifested by a broadening of energy levels, which aquire a finite width. The important question is: what is the driving force and the mechanism of transition(s) between these two types of many-body systems - with and without intrinsic decoherence? Here we address this question via the numerical study of energy-level statistics of a system of interacting spin-1/2 with random transverse fields. We present the first evidence for a well-defined quantum phase transition between domains of discrete and continous many-body spectra in such spin models, implying the appearance of novel insulating phases in the vicinity of the superconductor-insulator transition in InO(x) and similar materials.

Source areas and long-range transport of pollen from continental land to Tenerife (Canary Islands).

The Canary Islands, due to their geographical position, constitute an adequate site for the study of long-range pollen transport from the surrounding land masses. In this study, we analyzed airborne pollen counts at two sites: Santa Cruz de Tenerife (SCO), at sea level corresponding to the marine boundary layer (MBL), and Izaña at 2,367 m.a.s.l. corresponding to the free troposphere (FT), for the years 2006 and 2007. We used three approaches to describe pollen transport: (1) a classification of provenances with an ANOVA test to describe pollen count differences between sectors; (2) a study of special events of high pollen concentrations, taking into consideration the corresponding meteorological synoptic pattern responsible for transport and back trajectories; and (3) a source-receptor model applied to a selection of the pollen taxa to show pollen source areas. Our results indicate several extra-regional pollen transport episodes to Tenerife. The main provenances were: (1) the Mediterranean region, especially the southern Iberian Peninsula and Morocco, through the trade winds in the MBL. These episodes were characterized by the presence of pollen from trees (Casuarina, Olea, Quercus perennial and deciduous types) mixed with pollen from herbs (Artemisia, Chenopodiaceae/Amaranthaceae and Poaceae wild type). (2) The Saharan sector, through transport at the MBL level carrying pollen principally from herbs (Chenopodiaceae-Amaranthaceae, Cyperaceae and Poaceae wild type) and, in one case, Casuarina pollen, uplifted to the free troposphere. And (3) the Sahel, characterized by low pollen concentrations of Arecaceae, Chenopodiaceae-Amaranthaceae, Cyperaceae and Poaceae wild type in sporadic episodes. This research shows that sporadic events of long-range pollen transport need to be taken into consideration in Tenerife as possible responsible agents in respiratory allergy episodes. In particular, it is estimated that 89-97% of annual counts of the highly allergenous Olea originates from extra-regional sources in southern Iberia and northern Africa.

Atmospheric polycyclic aromatic hydrocarbons in remote European and Atlantic sites located above the boundary mixing layer.

BACKGROUND, AIM AND SCOPE: Ambient air concentrations of polycyclic aromatic hydrocarbons (PAH) were determined at five elevated mountain sites on the European continent and the Atlantic Ocean. All sites can be considered remote background areas since they are situated above the timberline and they lack local emission sources of these compounds. RESULTS AND DISCUSSION: Average gas phase concentrations of SigmaPAH were 165, 1,475, 1,553, 1,822 and 4,443 pg m(-3) for Tenerife, Pyrenees, Central Norway, Tyrolean Alps and High Tatras, respectively. Particulate phase concentrations were 55, 70, 383, 196 and 708 pg m(-3), respectively. The PAH profiles of samples from the different sites are very similar, being typical of PAH mixtures after long-range atmospheric transport. Part of the fluctuations in PAH concentrations are explained by the influence of temperature on the particulate/gas phase partitioning. CONCLUSION: The differences in PAH levels between sites, with the lowest concentrations found in Tenerife and the highest in the High Tatras, suggest the geographical influence of regional emissions on the sites, especially in the cold periods and for the sites in the eastern sector of the European continent. This is supported by air mass back-trajectories analysis for the samples on the different sites. The influence of the continent is not detectable in the case of the elevated site of Tenerife where the free troposphere has been sampled. The results in this study are consistent with the PAH levels found in soils and/or high mountain lake sediments from these areas.

Geochemical variations in aeolian mineral particles from the Sahara-Sahel Dust Corridor.

The Sahara-Sahel Dust Corridor runs from Chad to Mauritania and expels huge amounts of mineral aerosols into the Atlantic Ocean. Data on samples collected from Algeria, Chad, Niger, and Western Sahara illustrate how corridor dust mineralogy and chemistry relate to geological source and weathering/transport history. Dusts sourced directly from igneous and metamorphic massifs are geochemically immature, retaining soluble cations (e.g., K, Na, Rb, Sr) and accessory minerals containing HFSE (e.g., Zr, Hf, U, Th) and REE. In contrast, silicate dust chemistry in desert basins (e.g., Bodélé Depression) is influenced by a longer history of transport, physical winnowing (e.g., loss of Zr, Hf, Th), chemical leaching (e.g., loss of Na, K, Rb), and mixing with intrabasinal materials such as diatoms and evaporitic salts. Mineral aerosols blown along the corridor by the winter Harmattan winds mix these basinal and basement materials. Dusts blown into the corridor from sub-Saharan Africa during the summer monsoon source from deeply chemically weathered terrains and are therefore likely to be more kaolinitic and stripped of mobile elements (e.g., Na, K, Mg, Ca, LILE), but retain immobile and resistant elements (e.g., Zr, Hf, REE). Finally, dusts blown southwestwards into the corridor from along the Atlantic Coastal Basin will be enriched in carbonate from Mesozoic-Cenozoic marine limestones, depleted in Th, Nb, and Ta, and locally contaminated by uranium-bearing phosphate deposits.

Quantification of ozone uptake at the stand level in a Pinus canariensis forest in Tenerife, Canary Islands: an approach based on sap flow measurements.

Ozone uptake was studied in a pine forest in Tenerife, Canary Islands, an ecotone with strong seasonal changes in climate. Ambient ozone concentration showed a pronounced seasonal course with high concentrations during the dry and warm period and low concentrations during the wet and cold season. Ozone uptake by contrast showed no clear seasonal trend. This is because canopy conductance significantly decreased with soil water availability and vapour pressure deficit. Mean daily ozone uptake averaged 1.9 nmol m(-2) s(-1) during the wet and cold season, and 1.5 nmol m(-2) s(-1) during the warm and dry period. The corresponding daily mean ambient ozone concentrations were 42 and 51 nl l(-1), respectively. Thus we conclude that in Mediterranean type forest ecosystems the flux based approach is more capable for risk assessment than an external, concentration based approach.

Ecocardiografía transesofágica intraoperatoria durante cirugía no cardíaca / Ecocardiografía transesofágica intraoperatoria during not heart surgery

Introducción: La Sociedad Americana de Anestesiología (ASA) publicó guías para la realización de ecocardiografía transesofágica perioperatoria (ETE). Sin embargo su utilidad durante cirugías no cardiacas ha sido poco estudiada y claramente puede presentar beneficios por tratarse de un sistema de monitorización semiinvasivo que permite cambiar el manejo perioperatorio de pacientes complejos. Material y Métodos: Se estudiaron 175 pacientes adultos con transductor transesofágico multiplanar. Se evaluó utilidad de la técnica en cada paciente de acuerdo a cambios en el manejo perioperatorio dependientes de los hallazgos ecocardiográficos. Se clasificó a cada enfermo en uno de los siguientes 4 grupos de indicaciones: grupo 1 sin utilidad, grupo 2 cambio en manejo de volúmenes y drogas, grupo 3 cambio en manejo postoperatorio y grupo 4 sustituto catéter arteria pulmonar. Resultados: Un solo enfermo se catalogó en indicación 1 Los otros 174 (99 poe ciento) estuvieron distribuidos en grupo 2 y 77 casos (44 por ciento), grupo 3 y 44 enfermos (25 por ciento) y grupo 4 y 53 pacientes (30 por ciento) Conclusiones: La evaluación de ETE demuestra su alta utilidad, ya que implica cambios reales de diagnóstico y conducta en la mayoría de pacientes monitorizados durante cirugía no cardíaca incluidos en esta serie...

UV index experimental values during the years 2000 and 2001 from the Spanish broadband UV-B radiometric network.

An analysis is made of experimental ultraviolet erythemal solar radiation data measured during the years 2000 and 2001 by the Spanish UV-B radiation evaluation and prediction network. This network consists of 16 Robertson-Berger type pyranometers for evaluating solar erythemal radiation and five Brewer spectroradiometers for evaluating the stratospheric ozone. On the basis of these data the Ultraviolet Index (UVI) was evaluated for the measuring stations that are located either in coastal regions or in the more densely populated regions inland on the Iberian Peninsula. It has been checked that in most cases the maximum irradiance values corresponded to solar noon, although there were exceptions that could be explained by cloudiness. The maximum experimental values of the UVI were around 9 during the summer, though frequently passing this value at the inland measurement stations. The annual accumulated dose of irradiation on a horizontal plane has also been studied, as well as the evolution through the year in units of energy, standard erythemal doses and minimum erythemal doses, according to different phototypes.

Temperature and organic matter dependence of the distribution of organochlorine compounds in mountain soils from the subtropical Atlantic (Teide, Tenerife Island).

Surface soil samples from Teide mountain (Canary Islands) have been analyzed for polychlorobiphenyls (PCBs), DDTs, hexachlorocyclohexanes (HCHs), hexachlorobenzene (HCB), and pentachlorobenzene. The samples were situated between 10 and 3400 m above sea level being distributed below, at, and above the permanent inversion layer system characteristic of the subtropical Atlantic. All OC concentrations were, in general, low when compared with the data from urban, agricultural, or woodland soils reported elsewhere. Typical ranges were 0.04-9.2, 0.01-40, 0.001-1, or 0.01-3.2 ng x g(-1) dry weight for total PCBs, DDTs, HCHs, or HCB, respectively. These compounds exhibited a high dependence from the soil total organic carbon (TOC), showing high coefficients in the log(OC) versus log(TOC) correlations. The slopes of the curve fitted straight lines were, in turn, highly correlated to the log-transformed octanol-air coefficients of the compounds. This overall OC distribution points to steady-state conditions for the concentrations of these compounds in these mountain soils, in equilibrium with TOC. The equilibrium conditions are reached, despite the restrictions to convective air movement associated to the permanent atmospheric inversion layer at these latitudes. In addition, the log-transformed TOC-normalized concentrations of most PCBs, HCB, and pentachlorobenzene exhibit a good correlation with the reciprocal of average annual atmospheric temperatures also showing a temperature dependence for their distribution in the high mountain system. The calculated pseudo-enthalpies for this dependence, 120-160 kJ x mol(-1), exhibit higher values than those of octanol-air phase change calculated from laboratory experiments in previous studies, 66-93 kJ x mol(-1). The difference suggests a higher affinity of OC to soils than that corresponding to simple adsorption mechanisms.

Semivolatile organochlorine compounds in the free troposphere of the Northeastern Atlantic.

Polychlorobiphenyls (PCBs), hexachlorobenzene (HCB), hexachlorocyclohexanes, and DOTs were analyzed over 1 entire year period in the air of a high altitude remote site (2367 m above sea level) located in Teide (Tenerife, Canary Islands, 28 degrees N16 degrees W) in the Eastern North Atlantic region. Twenty samples were collected providing information on the concentrations of these semivolatile organochlorine compounds (SOCs) in the free troposphere since the stable and persistenttemperature inversion in the subtropics defines a clear separation from the marine boundary layer. More than 80% of total SOCs were in the gas phase. HCB was the individual SOC in higher concentration, 51 pg m(-3), well above than the other SOCs identified, 1-11 pg m(-3). Sum PCB concentrations were 78 pg m(-3). These concentrations range among the lowest described in atmospheric samples. The collected air originated from four main sectors, high and middle latitudes in the north Atlantic, Europe, and Africa, as determined from isentropic backward air mass trajectories. No significant differences were observed for the concentrations of these compounds between air masses showing a high uniform SOC composition of the free troposphere. Only the more volatile PCB congeners, #18 and #28, exhibited significant differences between air masses from northern and southern latitudes. A seasonal temperature dependence for the less volatile PCB congeners, five or more chlorine subtituents, was also observed. Free tropospheric concentrations of all SOCs except HCB were lower than those measured near sea level for reference. PCB concentrations at the two altitudes exhibited consistent differences according to degree of chlorination. The stronger decrease of the more volatile compounds with altitude might reflect higher photodegradation.

Lesión traumática de la aorta descendente por desaceleración / Traumatic injury of descending aorta by disacceleration

La mortalidad por accidentes en menores de 40 años ocupa un lugar prioritario en Chile. Los traumatismos de aorta torácica contribuyen en forma importante a la mortalidad y son rara vez diagnosticados. Presentamos nuestra experiencia con 5 casos operados de dislaceración traumática de aorta descendente. El diagnóstico se sospechó por un mediastino ancho a la Rx de tórax y se confirmó con TAC y angiografía en 3, sólo TAC en 1 y angiografía exclusiva en otro. Se intervienen entre 3 y 19 horas después del ingreso accediendo a la aorta descendente por toracotomía posterolateral izquierda con pinzamiento directo de la aorta en dos y con apoyo atrio-distal con bomba centrífuga en los otros 3. En todos se reemplazó el segmento lesionado con prótesis de Dacrón precoagulada. Un paciente fallece por isquemia visceral masiva y los otros 4 sobreviven. Todos los sobrevivientes se incorporan a una vida normal

Trasplante hepático en niños / Liver transplantation in children

Los trasplantes hepáticos constituyen el tratamiento más adecuado en gran número de pacientes con enfermedades crónicas y agudas terminales del hígado. La experiencia con este procedimiento es muy limitada en Chile. Se describen 11 niños que recibieron trasplantes hepáticos. La indicación más frecuente para hacerlo fue la atresia biliar. Se incluyeron receptores de alto riesgo como peso inferior a 10 kg, numerosas intervenciones quirúrgicas previas y hepatitis fulminante, pero no se registraron muertes intraoperatorias. En cuatro casos (36 por ciento) fue necesario hacer reducciones del hígado de los dadores para acomodarlos a receptores de bajo peso. Cinco receptores (45 por ciento) fueron tratados por rechazo agudo y no se han perdido injertos por causa inmunológica. Dos receptores fallecieron precozmente (uno por trombosis porta, otro por hipertensión intracraneana) y uno 15 meses después del trasplante por recidiva pulmonar y mediatínica de hepatoblastoma. La sobrevida actuarial es,hasta la fecha, 82 por ciento en un año. La serie demuestra que es posible realizar estos complejos procedimientos en el país, con similares resultados que en otros lugares del mundo

Disección aórtica / Aortic dissection

La disección aórtica es una emergencia médico-quirúrgica que implica un alto grado de sospecha clínica para echar a rodar un complejo algoritmo de estudio que permita certificar el diagnóstico y determinar si hay o no compromiso de la aorta ascendente. En las disecciones distales, el tratamiento médico se acepta como la mejor alternatva y en las proximales el tratamiento será operatorio. El enfermo debe ser seguido a permanencia con énfasis en el control de la presión arterial y el bloqueo beta-adrenérgico