Clouds and aerosols in Puerto Rico ─ a new evaluation

The influence of aerosols, both natural and anthropogenic, remains a major area of uncertainty when predicting the properties and behaviour of clouds and their influence on climate. In an attempt to better understand warm cloud formation in a tropical marine environment, a period of intensive measurements took place in December 2004 in Puerto Rico, using some of the latest developments in online instrumentation such as aerosol mass spectrometers, cloud condensation nuclei counters and a hygroscopicity tandem differential mobility analyser. Simultaneous online measurements of aerosol size distributions, composition, hygroscopicity and optical properties were made near the lighthouse of Cape San Juan in the north-eastern corner of the island and at the top of East Peak mountain (1040 m a.s.l.), the two sites separated by 17 km. Additional measurements of the cloud droplet residual and interstitial aerosol properties were made at the mountain site, accompanied by measurements of cloud droplet size distributions, liquid water content and the chemical composition of cloud and rain water samples. <br><br> Both aerosol composition and cloud properties were found to be sensitive to wind sector. Air from the east-northeast (ENE) was mostly free of anthropogenic influences, the submicron fraction being mainly composed of non-sea salt sulphate, while that from the east-southeast (ESE) was found to be moderately influenced by populated islands upwind, adding smaller (&lt;100 nm), externally mixed, carbonaceous particles to the aerosol that increased the number concentrations by over a factor of 3. This change in composition was also accompanied with a reduction in the measured hygroscopicity and fractional cloud activation potential of the aerosol. At the mountain site, the average cloud droplet concentrations increased from 193 to 519 cm^&minus;3, median volume diameter decreased from 20 to 14 μm and the liquid water content increased from 0.24 to 0.31 g m^&minus;3 when the winds shifted from the ENE to ESE. Larger numbers of interstitial particles were recorded, most notably at sizes greater than 100 nm, which were absent during clean conditions. The average size of the residual particles and concentrations of cloudwater nitrate, sulphate and insoluble material increased during polluted conditions. <br><br> Previous studies in Puerto Rico had reported the presence of a significant non-anthropogenic organic fraction in the aerosols measured and concluded that this was a factor controlling the in situ cloud properties. However, this was not observed in our case. In contrast to the 1.00&plusmn;0.14 μg m^&minus;3 of organic carbon measured in 1992 and 1995, the organic matter measured in the current study of 0.17&plusmn;0.35 μg m^&minus;3 is many times lower, most of which can be attributed to anthropogenic sources. During clean conditions, the submicron aerosol was observed to be almost entirely inorganic, an observation supported by the hygroscopicity measurements. This suggests that organic aerosols from marine sources may not be completely ubiquitous (either spatially or temporally) in this environment and requires further investigation to quantify their true extent and implications, with more extensive, longer-term sampling in conjunction with wind field analyses

Monte Carlo simulation of kilovolt electron transport in solids

A Monte Carlo procedure to simulate the penetration and energy loss of low¿energy electron beams through solids is presented. Elastic collisions are described by using the method of partial waves for the screened Coulomb field of the nucleus. The atomic charge density is approximated by an analytical expression with parameters determined from the Dirac¿Hartree¿Fock¿Slater self¿consistent density obtained under Wigner¿Seitz boundary conditions in order to account for solid¿state effects; exchange effects are also accounted for by an energy¿dependent local correction. Elastic differential cross sections are then easily computed by combining the WKB and Born approximations to evaluate the phase shifts. Inelastic collisions are treated on the basis of a generalized oscillator strength model which gives inelastic mean free paths and stopping powers in good agreement with experimental data. This scattering model is accurate in the energy range from a few hundred eV up to about 50 keV. The reliability of the simulation method is analyzed by comparing simulation results and experimental data from backscattering and transmission measurements

Estrategias de estudio y trabajo en estudiantes universitarios de la UIB

El estudio se centra en el conocimiento de los procesos de aprendizaje que se desarrollan en la enseñanza superior, siendo su objetivo principal la evaluación de las estrategias de aprendizaje utilizadas por estudiantes universitarios a lo largo de su formación inicial. Responde a un diseño descriptivo-exploratorio, dirigido a las estrategias de estudio y trabajo de la población universitaria de la Universidad de las Islas Baleares (UIB). Para ello, se procedió a la elaboración de un cuestionario como instrumento de recogida de datos1 sobre estrategias de estudio y trabajo, categorizado en cuatro grupos de estrategias (disposicionales y de apoyo; de búsqueda, recogida y selección de información; de procesamiento y uso de información; metacognitivas, de regulación y control) y sus correspondientes subcategorías. Se trabajó con una muestra de 949 estudiantes de la UIB, clasificados por ámbitos disciplinares y estudios, agrupados en grandes dimensiones (sexo; estudios de ciclo corto y de ciclo largo; rama de estudios; dedicación al estudio y actividad laboral), aportando, para cada una de ellas los datos estadísticos en los que se constata una diferencia significativa.L’estudi està centrat en el coneixement dels processos d’aprenentatge que es desenvolupen a l’ensenyament superior, i el l’objectiu principal és l’avaluació de les estratègies d’aprenentatge utilitzades per estudiants universitaris al llarg de la seva formació inicial. Respon a un disseny descriptiu-exploratori, dirigit a les estratègies d’estudi i treball de la població universitària de la Universitat de les Illes Balears (UIB). En aquest sentit, es va confeccionar un qüestionari com a instrument de recollida de dades sobre estratègies d’estudi i treball, categoritzat en quatre grups d’estratègies (disposicionals i de suport; de cerca, recollida i selecció d’informació; de processament i ús d’informació; metacognitives, de regulació i control) i les subcategories corresponents. Es va treballar amb una mostra de 949 estudiants de la UIB, classificats per àmbits disciplinaris i estudis, agrupats en grans dimensions (sexe; estudis de cicle curt i de cicle llarg; branca d’estudis; dedicació a l’estudi i activitat laboral), que varen aportar, per a cadascuna, dades estadístiques en els quals es constata una diferència significativa.The study is focused on the knowledge of learning processes developed in Higher Education and the main objective is to assess the learning strategies of university students along their initial training. This is a response to a descriptive-exploratory design addressed to the learning and working strategies among the students of the University of the Balearic Islands (UIB). Regarding to this, a question paper was designed as a tool for the collection of data on the studying and working strategies sorted by four strategy groups (dispositional and backup groups; research, collection and selection of information; processing and use of information; metacognitive, regulation and control groups) with their respective subcategories. We took a sample of 949 students from the UIB, sorted by study and disciplinary areas, and we gathered them in larger-dimension groups (gender, shorter and longer degrees, field of study and commitment to studies and work). These groups provided, for each of the samples, statistical information in which an important difference is stated

Reassessing global change research priorities in mediterranean terrestrial ecosystems : how far have we come and where do we go from here?

Aim: Mediterranean terrestrial ecosystems serve as reference laboratories for the investigation of global change because of their transitional climate, the high spatiotemporal variability of their environmental conditions, a rich and unique biodiversity and a wide range of socio-economic conditions. As scientific development and environmental pressures increase, it is increasingly necessary to evaluate recent progress and to challenge research priorities in the face of global change. - Location: Mediterranean terrestrial ecosystems. - Methods: This article revisits the research priorities proposed in a 1998 assessment. - Results: A new set of research priorities is proposed: (1) to establish the role of the landscape mosaic on fire-spread; (2) to further research the combined effect of different drivers on pest expansion; (3) to address the interaction between drivers of global change and recent forest management practices; (4) to obtain more realistic information on the impacts of global change and ecosystem services; (5) to assess forest mortality events associated with climatic extremes; (6) to focus global change research on identifying and managing vulnerable areas; (7) to use the functional traits concept to study resilience after disturbance; (8) to study the relationship between genotypic and phenotypic diversity as a source of forest resilience; (9) to understand the balance between C storage and water resources; (10) to analyse the interplay between landscape-scale processes and biodiversity conservation; (11) to refine models by including interactions between drivers and socio-economic contexts; (12) to understand forest-atmosphere feedbacks; (13) to represent key mechanisms linking plant hydraulics with landscape hydrology. - Main conclusions:(1) The interactive nature of different global change drivers remains poorly understood. (2) There is a critical need for the rapid development of regional- and global-scale models that are more tightly connected with large-scale experiments, data networks and management practice. (3) More attention should be directed to drought-related forest decline and the current relevance of historical land use

Time to Switch to Second-line Antiretroviral Therapy in Children With Human Immunodeficiency Virus in Europe and Thailand.

Background: Data on durability of first-line antiretroviral therapy (ART) in children with human immunodeficiency virus (HIV) are limited. We assessed time to switch to second-line therapy in 16 European countries and Thailand. Methods: Children aged <18 years initiating combination ART (≥2 nucleoside reverse transcriptase inhibitors [NRTIs] plus nonnucleoside reverse transcriptase inhibitor [NNRTI] or boosted protease inhibitor [PI]) were included. Switch to second-line was defined as (i) change across drug class (PI to NNRTI or vice versa) or within PI class plus change of ≥1 NRTI; (ii) change from single to dual PI; or (iii) addition of a new drug class. Cumulative incidence of switch was calculated with death and loss to follow-up as competing risks. Results: Of 3668 children included, median age at ART initiation was 6.1 (interquartile range (IQR), 1.7-10.5) years. Initial regimens were 32% PI based, 34% nevirapine (NVP) based, and 33% efavirenz based. Median duration of follow-up was 5.4 (IQR, 2.9-8.3) years. Cumulative incidence of switch at 5 years was 21% (95% confidence interval, 20%-23%), with significant regional variations. Median time to switch was 30 (IQR, 16-58) months; two-thirds of switches were related to treatment failure. In multivariable analysis, older age, severe immunosuppression and higher viral load (VL) at ART start, and NVP-based initial regimens were associated with increased risk of switch. Conclusions: One in 5 children switched to a second-line regimen by 5 years of ART, with two-thirds failure related. Advanced HIV, older age, and NVP-based regimens were associated with increased risk of switch

Gastric stromal tumors: clinical presentation and surgical options Tumores estromales gástricos: formas de presentación y opciones quirúrgicas

Stromal tumors represent 1-3% of all primary gastric neoplasms. These tumors can occur at any age and display different clinical manifestations, but they rarely reach over 10 cm in size. Currently they are designed as gastrointestinal stromal tumors (GIST) but their classification is still controversial. Surgery is the treatment of choice, and the extension of surgical resection depends on the tumor size, neoplastic involvement of adjacent organs, and the presence of metastatic disease. In selected cases minimally invasive surgery can provide excellent results. We present four new patients with GIST who exemplify the different clinical forms of presentations of GISTs and their diverse treatment options.Los tumores estromales representan el 1-3% de las neoplasias gástricas primitivas. Se pueden presentar a cualquier edad, bajo muy diversas formas clínicas, siendo raro que alcancen un tamaño superior a los 10 cm. Estos raros tumores se encuadran en la actualidad dentro de los denominados tumores del estroma gastrointestinal (GIST´s) , cuya clasificación continúa siendo controvertida. La cirugía es el tratamiento de elección y su extensión viene determinada por el tamaño del tumor, la afectación de órganos vecinos y la presencia o no de metástasis. En casos seleccionados, la cirugía mínimamente invasiva puede llevarse a cabo con excelentes resultados. Presentamos cuatro casos que resumen las distintas formas de presentación clínica de estos tumores así como su manejo terapéutico

Use of wild-caught individuals as a key factor for success in vertebrate translocations

Success of vertebrate translocations is crucial to improve efficacy and efficiency of conservation actions but it is often difficult to assess because negative results (failed translocations) are seldom published. We developed surveys and sent them to heads of conservation services in three major Spanish Mediterranean regions. The purpose of our surveys was to determine which methodological factor, that could easily be implemented in practice, was more influential for translocation success. These factors included the origin of translocated individuals (captive or wild) and translocation effort (propagule size and program duration). After analyzing 83 programs, corresponding to 34 different vertebrate species, by means of generalized linear mixed modelling, we found that ‘origin’ was more relevant for translocation success than ‘effort’, although we could not rule out some role of translocation effort. Variance in success of translocation programs involving individuals from wild sources was smaller and consequently results more predictable. Origin interacted with taxa so that success was higher when using wild birds and especially wild fish and mammals, but not when releasing reptiles. Hence, we suggest that, for any given effort, translocation results will be better for most vertebrate taxa if individuals from wild sources are used. When this is not feasible, managers should release captive-reared individuals for a long number of years rather than a short number of years.A. M. A. was supported by a postdoctoral contract by Xunta de Galicia. L. R. received an ERASMUS scholarship during her stay at IMEDEA. We are also grateful to 'Programa de Investigación Competitiva del Sistema Universitario Gallego' reference GRC2014/050 from Xunta de Galicia for financing our project 'Grupo de Investigación en Biología Evolutiva (GIBE) de la Universidade da Coruña'.Peer Reviewe

Monte Carlo simulation of kilovolt electron transport in solids

A Monte Carlo procedure to simulate the penetration and energy loss of low¿energy electron beams through solids is presented. Elastic collisions are described by using the method of partial waves for the screened Coulomb field of the nucleus. The atomic charge density is approximated by an analytical expression with parameters determined from the Dirac¿Hartree¿Fock¿Slater self¿consistent density obtained under Wigner¿Seitz boundary conditions in order to account for solid¿state effects; exchange effects are also accounted for by an energy¿dependent local correction. Elastic differential cross sections are then easily computed by combining the WKB and Born approximations to evaluate the phase shifts. Inelastic collisions are treated on the basis of a generalized oscillator strength model which gives inelastic mean free paths and stopping powers in good agreement with experimental data. This scattering model is accurate in the energy range from a few hundred eV up to about 50 keV. The reliability of the simulation method is analyzed by comparing simulation results and experimental data from backscattering and transmission measurements