105 research outputs found

    Late-Holocene vegetation and fire dynamics on the summits of the Guayana Highlands: the Uei-tepui palynological record.

    Get PDF
    The summits of the tepuis (sandstone table mountains of the Neotropical Guayana region¿Guayana Highlands, GH) have been considered valuable for palaeoecological studies due to their pristine nature, which emphasizes the role of natural (i.e. non-human) factors on ecological change. Anthropogenic fires, very frequent in the surrounding Gran Sabana (GS) uplands, have very rarely been documented in the GH, and are therefore not considered an important ecological factor in the high-tepui biome. This paper reports the palynological and charcoal results of a Late Holocene sequence from the summit of Uei-tepui (2104 m elevation), where extensive signs of fire were recently observed. Since ~2000 cal yr BP, the landscape of the study site has been dominated by meadowswith occasional shrubs and cloud forests,which underwent expansions and contractions driven by climate changes and fire. A major vegetation shift occurred in the mid-18th century, when a sustained increase in local fires favoured the expansion of the low and spreading Cyrilla racemiflora shrublands at the expense of meadows and forests. Uei-tepui firesmost probably were the result of human activities and reached the summit under study from the GS uplands through the vegetated slopes that characterize this tepui. The mostly anthropogenic nature of these fires, especially themore recent ones, is supported by the initial occurrence of wetter conditions, and by its coincidence with significant social changes in the GS indigenous populations, mainly the European contact. The emergence of fire as a disturbing agent of theGH biome highlights the need for an effective management plan in the GS uplands, where the vast majority of present-day fires originate, and designed in collaboration with the indigenous communities. Proactive conservationmeasures are considered even more important under future warming projections in the area

    Optical spectroscopy of Yb3+ centers in BaMgF4 ferroelectric crystal

    Full text link
    The following article appeared in Journal of Applied Physics 110.6 (2011): 063102 and may be found at http://scitation.aip.org/content/aip/journal/jap/110/6/10.1063/1.3638040We report on the optical characterization of Yb3+ doped BaMgF4+ nonlinear fluoride crystal grown by the Czochralski technique. Low temperature absorption spectroscopy reveals that Yb3+ incorporates into the matrix at four well differentiated centers. High resolution site selective experiments have been performed to determine the energy level schemes associated with the major Yb3+ centers detected in the system. The fluorescence decay times recorded at 10 K under selective excitation are analyzed for each Yb3+ center. The spectroscopic behavior of the codoped Yb3+:Na+:BaMgF4+ system has been also investigated. Codoping with Na+ eliminates two Yb3+ centers present in the singly doped Yb3+:BaMgF 4+ crystal. The charge compensation mechanisms and site location for Yb3+ in the fluoride matrix are discussedThis work has been supported by Spanish MICINN under Contract Nos. MAT2010-17443 and MAT2009-06580, Comunidad de Madrid under Grant No. PHAMA S2009/MAT-1756 and Universidad Autónoma de Madrid under Contract No. CCG10-UAM/MAT-5290

    Factors related to attitudes toward organ donation after death in the immigrant population in Spain

    Full text link
    The version posted must contain the text: This is the accepted version of the following article: [full citation], which has been published in final form at [Link to final article]Considering the relevance of the migratory processes in Western societies, the attitudes toward organ donation after death are analyzed bymeans of a survey applied to a representative random sample of the resident immigrant population in Spain, comprising 1202 subjects (estimated marginof error of ±2.88%, p = q, p < 0.05). Considered variables were disposition toward own organ donation, disposition toward deceased relatives donation in different situations, arguments against donation, socio-demographic indicators, religious beliefs, social integration, and information about organ donation and transplantation. Predisposition to donate varies strongly across geographical origin and religious beliefs and also shows relationships with additional socio-demographic, social integration, and informative variables. In turn, the relationship between religious beliefs and attitude toward donation varies as a function of the degreeof social integration. In Spain, the immigrant population is a heterogeneous collective that requires differential strategies to promote donation. Such strategies should be aimed at reinforcing the existing positive attitudes ofcitizens from West Europe and Latin America, and at familiarizing and informing about donation in citizens from the East, and at making specific efforts to break down the cultural and religious barriers toward donation in African citizens, with special emphasis on people of the Muslim faith

    Local environment of optically active Nd3 + ions in the ultratransparent BaMgF 4 ferroelectric crystal

    Full text link
    A comprehensive study of the site location of Nd3 + ions in the BaMgF 4 ultratransparent ferroelectric crystal is presented. By combining different low-temperature optical spectroscopies and electron paramagnetic resonance, the crystal field energy levels of Nd3 + ions and the gyromagnetic factors are experimentally determined. These results are employed to perform the crystal field analysis of Nd3 + ions considering a Cs point symmetry. The crystal field calculation yields a small root-mean-square deviation of 18 cm -1 and reveals a large crystal field strength (621 cm -1), verifying the assignment of the Ba2 + cationic site as the location for Nd3 + ions in this fluoride host. The results suggest a slight displacement of Nd3 + from the barium regular site with a rearrangement of the fluorine ions around it. The work gives a deep insight into the properties of the Nd3 +-doped BaMgF 4 crystal, a ferroelectric widely ultra-transparent material with potential applications as optical device operating in the Vacuum Ultraviolet-Ultraviolet and midinfrared spectral regionsThis work has been supported by the Spanish Ministry of Science under projects MAT2010-17443, MAT2010-21270-C04-02, Consolider-Ingenio MALTA CSD 2007-0045, and Comunidad Autonoma de Madrid under Grant 2009/MAT-175

    Europium doped-double sodium bismuth molybdate nanoparticles as contrast agents for luminescence bioimaging and X-ray computed tomography

    Get PDF
    A one-pot method for the synthesis of uniform Eu3+-doped NaBi(MoO4)2 nanoparticles with an ellipsoidal shape and tetragonal crystal structure functionalized with polyacrylic acid is reported for the first time in the literature. The method is based on a homogeneous precipitation reaction from solutions in an ethylene glycol/water medium containing appropriate bismuth, sodium, and molybdate precursors and polyacrylic acid. The luminescence properties (excitation and emission spectra and luminescence lifetime) of such nanoparticles are evaluated for different Eu3+ doping levels, finding an intense red emission for all synthesized samples. The X-ray attenuation properties of the nanoparticles have been also analyzed, which were found to be better than those of a commercially computed tomography contrast agent (iohexol). The dispersibility of the nanoparticles in a physiological medium was also analyzed, finding that they could be well dispersed in a 2-N-morpholinoethanesulfonic acid monohydrate medium (pH = 6.5). Finally, the cell viability of such a phosphor has been analyzed using MIA-PaCa-2 cells and its in vivo toxicity has been evaluated using the nematode Caenorhabditis elegans model finding no significant toxicity in both cases up to a nanoparticle concentration of 100 μg mL−1, which is within the range required for most in vivo applications. The developed Eu3+-doped NaBi(MoO4)2 nanoparticles are, therefore, excellent candidates for their use as bimodal probes for luminescence imaging and X-ray computed tomography

    Content Analysis of Digital Media Coverage of the Human Papillomavirus Vaccine School-Entry Requirement Policy in Puerto Rico

    Get PDF
    BACKGROUND: In August 2018, Puerto Rico (PR) became the 4th state or territory in the United States to adopt a human papillomavirus (HPV) vaccine school-entry requirement, for students 11-12 years old. Evidence suggests that the content of media coverage may impact people\u27s perception of HPV vaccine and their willingness to vaccinate. This study aimed to analyze the content of digital news coverage related to the implementation of the policy in PR. METHODS: A content review was conducted of digital media published from January 2017 through December 2018. The content reviewed was carried out in two steps: 1) creating a matrix to summarize each article\u27s content about the policy and 2) qualitative analysis using a grounded theory approach. RESULTS: The search resulted in 34 articles obtained from 17 online local and international news outlets that reported the policy\u27s implementation. Analyses showed that 61% of the news articles did not mention the number of required doses, and 79% discussed the new policy concerning cancer prevention. In 2017, news coverage focused mostly on describing the policy, while 2018 coverage focused on controversies surrounding the implementation. Neutral emergent codes included: 1) Description of the policy; 2) Information about HPV related cancers; and 3) General information about HPV vaccine. Negative emergent codes included: 1) infringement to patient and parental autonomy; 2) Hesitancy from the political sector, and 3) Hesitancy from groups and coalitions. Positive content included: 1) knowledge and acceptance of HPV vaccine for cancer prevention; 2) importance of education and protective sexual behaviors; and 3) new vaccination law proposal. CONCLUSIONS: Most of the media coverage in PR was neutral and included limited information related to the vaccine, HPV, and HPV-related cancers. Neutral and negative themes could influence public concerns regarding the new policy, as well as HPV vaccination rates in PR

    Detection of freeze injury in oranges using magnetic resonance imaging under motion conditions

    Full text link
    Magnetic resonance imaging (MRI) is applied for on-line inspection of fruits. The aim of this work is to address the applicability of MRI for freeze injury detection in oranges directly on a distribution chain. Undamaged and damaged oranges are conveyed at 50 and 100 mm/s by a specially designed conveyor within a 4.7 T spectrometer obtaining fast low-angle shot images. An automatic segmentation algorithm is proposed that allows the discrimination between undamaged and damaged orange

    Civil Society, Everyday Life and the Possibilities for Development Studies

    Get PDF
    Civil society is one of the most contentious terms in political thought. There is considerable, and highly significant, difference between academic debate about the meaning of ‘civil society’ and the way the term is mobilized in international development discourse. In particular, narratives of civil society in international development are often dominated by reference to organizational descriptions and measurability. But I would like to suggest here that the term should be reclaimed as a way of giving meaning to the stories of the everyday lives of the people who create, shape and embody civil society. Used in this way, the idea of civil society can be understood as intersecting emotions, discourses and practices and can add to the body of scholarly work that nurtures and values everyday life as a lens through which to view wider social processes. Paying attention to the everyday life of civil society may have implications for that way the civil society is engaged with academically, and also has the potential to refresh how civil society is thought about in development practice

    Modeling Core Metabolism in Cancer Cells: Surveying the Topology Underlying the Warburg Effect

    Get PDF
    BACKGROUND: Alterations on glucose consumption and biosynthetic activity of amino acids, lipids and nucleotides are metabolic changes for sustaining cell proliferation in cancer cells. Irrevocable evidence of this fact is the Warburg effect which establishes that cancer cells prefers glycolysis over oxidative phosphorylation to generate ATP. Regulatory action over metabolic enzymes has opened a new window for designing more effective anti-cancer treatments. This enterprise is not trivial and the development of computational models that contribute to identifying potential enzymes for breaking the robustness of cancer cells is a priority. METHODOLOGY/PRINCIPAL FINDINGS: This work presents a constraint-base modeling of the most experimentally studied metabolic pathways supporting cancer cells: glycolysis, TCA cycle, pentose phosphate, glutaminolysis and oxidative phosphorylation. To evaluate its predictive capacities, a growth kinetics study for Hela cell lines was accomplished and qualitatively compared with in silico predictions. Furthermore, based on pure computational criteria, we concluded that a set of enzymes (such as lactate dehydrogenase and pyruvate dehydrogenase) perform a pivotal role in cancer cell growth, findings supported by an experimental counterpart. CONCLUSIONS/SIGNIFICANCE: Alterations on metabolic activity are crucial to initiate and sustain cancer phenotype. In this work, we analyzed the phenotype capacities emerged from a constructed metabolic network conformed by the most experimentally studied pathways sustaining cancer cell growth. Remarkably, in silico model was able to resemble the physiological conditions in cancer cells and successfully identified some enzymes currently studied by its therapeutic effect. Overall, we supplied evidence that constraint-based modeling constitutes a promising computational platform to: 1) integrate high throughput technology and establish a crosstalk between experimental validation and in silico prediction in cancer cell phenotype; 2) explore the fundamental metabolic mechanism that confers robustness in cancer; and 3) suggest new metabolic targets for anticancer treatments. All these issues being central to explore cancer cell metabolism from a systems biology perspective
    corecore