Study of Johnsons Glacier (Livingston Island, Antarctica) by means of shallow ice cores and their tephra and by analysis of 137Cs content

With the aim of monitoring the dynamics of the Livingston Island ice cap, the Departament de Geodinàmica i Geofísica of the Universitat de Barcelona began yearly surveys in the austral summer of 1994-95 on Johnsons Glacier. During this field campaign 10 shallow ice cores were sampled with a manual ve rtical ice-core drilling machine. The objectives were: i) to detect the tephra layer accumulated on the glacier surface, attributed to the 1970 Deception Island pyroclastic eruption, today interstratified; ii) to verify wheter this layer might serve as a reference level; iii) to measure the 137Cs radio-isotope concentration accumulated in the 1965 snow stratum; iv) to use the isochrone layer as a mean of verifying the age of the 1970 tephra layer; and, v) to calculate both the equilibrium line of the glacier and average mass balance over the last 28 years (1965-1993). The stratigraphy of the cores, their cumulative density curves and the isothermal ice temperatures recorded confirm that Johnsons Glacier is a temperate glacier. Wind, solar radiation heating and liquid water are the main agents controlling the ve rtical and horizontal redistribution of the volcanic and cryoclastic particles that are sedimented and remain interstratified within the glacier. It is because of this redistribution that the 1970 tephra layer does not always serve as a very good reference level. The position of the equilibrium line altitude (ELA) in 1993, obtained by the 137Cs spectrometric analysis, varies from about 200 m a.s.l. to 250 m a.s.l. This indicates a rising trend in the equilibrium line altitude from the beginning of the 1970s to the present day. The varying slope orientation of Johnsons Glacier relative to the prevailing NE wind gives rise to large local differences in snow accumulation, which locally modifies the equilibrium line altitude. In the cores studied, 137Cs appears to be associated with the 1970 tephra layer. This indicates an intense ablation episode throughout the sampled area (at least up to 330 m a.s.l), which probably occurred synchronically to the 1970 tephra deposition or later. A rough estimate of the specific mass balance reveals a considerable accumulation gradient related to the increase with altitude

Sedimentology and Stratigraphy of the Pleisocene sediments in Lake Llauset (Southern Pyrenees, Spain) a first approach

The high alpine valleys in the Southem Pyrenees are characterised by a many small lakes and ponds. They occur above 2000 m and are said to have been formed by glacial erosion. The sediments in these basins should, therefore, contain stratigraphic information since deglaciation, at least. An interesting and may be one of the most important of these basins is Lake Llauset in the Alta Ribagorca. The Llauset basin has recently been developped for hydsopower production. In conection with the construction of the retaining wall at the "Riegel" the sedimentary filling of the lake basin could be investigated, and the first sedimentological and stratigraphical results are presented

Why Citrate Shapes Tetrahedral and Octahedral Colloidal Platinum Nanoparticles in Water

[EN] The performance of many advanced catalytic systems depends not only on the size and composition but also on the specific shape of the metal nanoparticles (NPs) from which they are assembled. In turn, the shape of colloidal NPs depends on the specific capping agent involved in their synthesis, though the mechanism is still poorly understood. Here, supported by electrochemical experiments, Fourier transform infrared spectra, and density functional theory calculations, on well-defined surfaces, we show how a specific capping agent determines the shape of colloidal NPs. Solvated citrate can become simultaneously adsorbed on the Pt(111) surface through three dehydrogenated carboxylic groups, with each one of them in bidentate configuration. On the other two basal planes, citrate can be adsorbed through only two of them. For this reason, under the synthesis conditions, citrate is more favorably adsorbed on the Pt(111) than on the other two basal planes of platinum. This adsorption behavior explains why colloidal platinum NPs of tetrahedral and octahedral shape are produced when citrate is used as the capping agent in water. The mechanism for citrate would also determine the shape of other pure face-centered cubic metals and can inspire the engineering of future capping agents.This work has been financially supported by the MCINN-FEDER (Spain) through project CTQ2016-76221-P.Gisbert-González, J.; Feliu, J.; Ferre Vilaplana, A.; Herrero, E. (2018). Why Citrate Shapes Tetrahedral and Octahedral Colloidal Platinum Nanoparticles in Water. The Journal of Physical Chemistry C. 122(33):19004-19014. https://doi.org/10.1021/acs.jpcc.8b05195S19004190141223

Evaluación y cartografía del riesgo de aludes en el camino PR-PNPE 21 de acceso a la Vega de Urriellu, Picos de Europa (Noroeste de España)

ABSTRACT: The growing interest in natural mountain areas related to winter recreation activities requires the elaboration of studies which quantify the risk of avalanches. In this work the main goal has been to assess the avalanche hazard and associate risk from an Avalanche Hazard Index (AHI) in one of the most popular mountain routes in Picos de Europa, the access walking track to Vega de Urriellu from Collado Pandébano, the PR-PNPE 21. Firstly, it has been necessary to locate and identify the avalanche path crossing the mountain route using different information: morphological, vegetation and historical. The frequency of the avalanches was estimated from the comparison of temporal sequences of aerial photographs, field observations, survey population and average slope of avalanche path. As regards to the risk assessment, several possible scenarios in relation to the variability of the data have been considered. The AHI obtained by this procedure is generally low for the entire winter season, moderate in certain situations when the factor exposure is high, and finally this Index is high at Easter due to the special visitors traffic. Also, information to the user is proposed as a means of mitigating risk.RESUMEN: El creciente interés en espacios naturales de áreas de montaña vinculado a actividades de ocio invernales hace conveniente la elaboración de estudios que evalúen cuantitativamente el riesgo de aludes. En el presente trabajo se han aplicado varias metodologías destinadas a localizar y delimitar las zonas de aludes y valorar el riesgo a partir de un Índice de Riesgo de Aludes (IRA) en una de las rutas de montaña más frecuentadas de los Picos de Europa, el camino de acceso a la Vega de Urriellu desde el Collado Pandébano, el PR?PNPE 21. Una vez definidas las zonas de aludes según criterios geomorfológicos, de vegetación e históricos se ha estimado la frecuencia de los aludes a partir de la observación de secuencias temporales de fotografías aéreas, observaciones de campo, encuesta a la población y pendiente media del recorrido de los aludes. En cuanto al cálculo del riesgo se han planteado varios escenarios probables en relación a la variabilidad de los datos tenidos en cuenta en el análisis del riesgo, obteniendo como resultado un IRA en general bajo para el conjunto de la temporada invernal, moderado en determinadas situaciones de exposición prolongada al peligro, y alto en la Semana Santa debido al especial tránsito de visitantes. Además, se propone la información al usuario como medida mitigadora del riesgo

Caída de bloques de hielo en los frentes del glaciar de casquete de la isla Livingston (Archipiélago de las Shetland del Sur). Detección por métodos sísmicos. Influencia de las variables ambientales

We used data from a seismic array to study the evolution of calving at Livingston Island. Starting with the idea that the flow is the main cause of calving, we examined the effect of temperature, tide, relative humidity and wind velocity on this phenomenon. Air temperature proved to be the most relevant parameter

Effectiveness of a telephone-based intervention for smoking cessation in patients with severe mental disorders : Study protocol for a randomized controlled trial

Background: Up to 75% of inpatients with mental disorders smoke, and their life expectancy is decreased by up to 25 years compared to the general population. Hospitalized patients without monitoring after discharge quickly return to prehospitalization levels of tobacco use. The aim of the 061 QuitMental study is to assess the effectiveness of a multicomponent and motivational telephone-based intervention to stop smoking through a quitline addressed to smokers discharged from mental health hospital wards. Methods: A pragmatic randomized controlled trial, single blinded, will include 2:1 allocation to the intervention group (IG) and the control group (CG). The IG will receive telephone assistance to quit smoking (including psychological and psychoeducational support, and pharmacological treatment advice if required) proactively for 12 months, and the CG will receive only brief advice after discharge. The sample size, calculated with an expected difference of 15 points on smoking abstinence between groups (IG, 20% and CG, 5%), α = 0.05, β = 0.10, and 20% loss, will be 334 participants (IG) and 176 participants (CG). Participants are adult smokers discharged from psychiatric units of five acute hospitals. Measurements include dependent variables (self-reported 7-day point prevalence smoking abstinence (carbon monoxide verified), duration of abstinence, number of quit attempts, motivation, and self-efficacy to quit) and independent variables (age, sex, and psychiatric diagnoses). In data analysis, IG and CG data will be compared at 48 h and 1, 6, and 12 months post discharge. Multivariate logistic regression (odds ratio; 95% confidence interval) of dependent variables adjusted for potential confounding variables will be performed. The number needed to treat to achieve one abstinence outcome will be calculated. We will compare the abstinence rate of enrolled patients between groups. Discussion: This trial evaluates an innovative format of a quitline for smokers with severe mental disorders regardless of their motivation to quit. If effective, the pragmatic nature of the study will permit transfer to routine clinical practice in the National Health System. Trial registration: ClinicalTrials.gov, NCT03230955. Registered on 24 July 2017

A long-term study of new particle formation in a coastal environment: Meteorology, gas phase and solar radiation implications

New particle formation (NPF) was investigated at a coastal background site in Southwest Spain over a four-year period using a Scanning Particle Mobility Sizer (SMPS). The goals of the study were to characterise the NPF and to investigate their relationship to meteorology, gas phase (O3, SO2, CO and NO2) and solar radiation (UVA, UVB and global). A methodology for identifying and classifying the NPF was implemented using the wind direction and modal concentrations as inputs. NPF events showed a frequency of 24% of the total days analyzed. The mean duration was 9.2±4.2 hours. Contrary to previous studies conducted in other locations, the NPF frequency reached its maximum during cold seasons for approximately 30% of the days. The lowest frequency took place in July with 10%, and the seasonal wind pattern was found to be the most important parameter influencing the NPF frequency. The mean formation rate was 2.2±1.7 cm-3 s-1, with a maximum in the spring and early autumn and a minimum during the summer and winter. The mean growth rate was 3.8±2.4 nm h-1 with higher values occurring from spring to autumn. The mean and seasonal formation and growth rates are in agreement with previous observations from continental sites in the Northern Hemisphere. NPF classification of different classes was conducted to explore the effect of synoptic and regional-scale patterns on NPF and growth. The results show that under a breeze regime, the temperature indirectly affects NPF events. Higher temperatures increase the strength of the breeze recirculation, favouring gas accumulation and subsequent NPF appearance. Additionally, the role of high relative humidity in inhibiting the NPF was evinced during synoptic scenarios. The remaining meteorological variables (RH), trace gases (CO and NO), solar radiation, PM10 and condensation sink, showed a moderate or high connection with both formation and growth rates.This work was partially supported by the Andalusian Regional Government through projects P10-RNM-6299 and P12-RNM-2409, the Spanish Ministry of Science and Technology (MINECO) through projects CGL2010-18782, CGL2011-24891/CLI, CGL2013-45410-R and the Complementary Action CGL2011-15008-E.European Union through the ACTRIS project (EU INFRA-2010-1.1.16-262254)

Quaternary Glacial Geology of the Alta Ribagorça Basin (Central Southern Pyrenees)

This paper is an abstract of the doctoral thesis presented by the autor at the University of Barcelona on September 1983. It constitutes a regional study about the Quatemary Glacial Geology in the Ribagorca high valleys. It is the first work in relation to the geomorphology, sedimentology and stratigraphy of the glacial and related deposits in this zone of the Pyrenees. Several formations of quatemary deposits have been studied in detail (mainly in Llauset Valley and in Taüll area); and the local quatemary stratigraphy is established and finally a correlation with some previously studied areas in the Pyrenees is attemped