158 resultados para island fragmentation


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In this debate article, I am going to set out the case that sperm DNA fragmentation testing is essential in current day fertility management because-
• Our current semen analysis testing is unfit for purpose
• Sperm DNA damage testing has strong associations with every fertility check point
• Sperm DNA damage testing has strong associations with miscarriage
• Sperm DNA testing can explain ‘unexplained’ infertility
• There are reasons why sperm with poor DNA are successful in ICSI
• There are no non-invasive sperm function tests that provide the same information
• We need to take a fresh look at the ‘evidence’ against sperm DNA testing
• We have no reason to wait. There are benefits for clinics and couples alike.

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Earlier palynological studies of lake sediments from Easter Island suggest that the island underwent a recent and abrupt replacement of palm-dominated forests by grasslands, interpreted as a deforestation by indigenous people. However, the available evidence is inconclusive due to the existence of extended hiatuses and ambiguous chronological frameworks in most of the sedimentary sequences studied. This has given rise to an ongoing debate about the timing and causes of the assumed ecological degradation and cultural breakdown. Our multiproxy study of a core recovered from Lake Raraku highlights the vegetation dynamics and environmental shifts in the catchment and its surroundings during the late Holocene. The sequence contains shorter hiatuses than in previously recovered cores and provides a more continuous history of environmental changes. The results show a long, gradual and stepped landscape shift from palm-dominated forests to grasslands. This change started c. 450 BC and lasted about two thousand years. The presence of Verbena litoralis, a common weed, which is associated with human activities in the pollen record, the significant correlation between shifts in charcoal influx, and the dominant pollen types suggest human disturbance of the vegetation. Therefore, human settlement on the island occurred c. 450 BC, some 1500 years earlier than is assumed. Climate variability also exerted a major influence on environmental changes. Two sedimentary gaps in the record are interpreted as periods of droughts that could have prevented peat growth and favoured its erosion during the Medieval Climate Anomaly and the Little Ice Age, respectively. At c. AD 1200, the water table rose and the former Raraku mire turned into a shallow lake, suggesting higher precipitation/evaporation rates coeval with a cooler and wetter Pan-Pacific AD 1300 event. Pollen and diatom records show large vegetation changes due to human activities c. AD 1200. Other recent vegetation changes also due to human activities entail the introduction of taxa (e.g. Psidium guajava, Eucalyptus sp.) and the disappearance of indigenous plants such as Sophora toromiro during the two last centuries. Although the evidence is not conclusive, the American origin of V. litoralis re-opens the debate about the possible role of Amerindians in the human colonisation of Easter Island.

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The island of Mauritius offers the opportunity to study the poorly understood vegetation response to climate change on a small tropical oceanic island. A high-resolution pollen record from a 10 m long peat core from Kanaka Crater (560 m elevation, Mauritius, Indian Ocean) shows that vegetation shifted from a stable open wet forest Last Glacial state to a stable closed-stratified-tall-forest Holocene state. An ecological threshold was crossed at ∼11.5 cal ka BP, propelling the forest ecosystem into an unstable period lasting ∼4000 years. The shift between the two steady states involves a cascade of four abrupt (<150 years) forest transitions in which different tree species dominated the vegetation for a quasi-stable period of respectively ∼1900, ∼1100 and ∼900 years. We interpret the first forest transition as climate-driven, reflecting the response of a small low topography oceanic island where significant spatial biome migration is impossible. The three subsequent forest transitions are not evidently linked to climate events, and are suggested to be driven by internal forest dynamics. The cascade of four consecutive events of species turnover occurred at a remarkably fast rate compared to changes during the preceding and following periods, and might therefore be considered as a composite tipping point in the ecosystem. We hypothesize that wet gallery forest, spatially and temporally stabilized by the drainage system, served as a long lasting reservoir of biodiversity and facilitated a rapid exchange of species with the montane forests to allow for a rapid cascade of plant associations.

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The review essay opens with positive attributes of Ireland but then considers that the island has been subject to centuries of bitter dispute and unrest. The historical background to this is outlined, particularly the interactions between Ireland and its neighbouring island, Great Britain, which dominated Irish affairs. One policy adopted by the British was to encourage migration of Protestants into the largely Catholic island in the vain hope that this would reduce unrest. The
two islands were then united from 1801 as the United Kingdom of Great Britain and Ireland but demands from indigenous Irish Catholics for independence continued, resisted by the Protestant minority who wished to remain inside the UK. After the Great War a solution was imposed that granted most of Ireland independence but left the largely Protestant northeast corner within the UK as Northern Ireland. Reaction to and life with the Irish border are considered and the paper concludes with musings about its future.

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This study aimed to: (1) assess differences between two quantitative sampling methods of soil microarthropods (visual census vs. stone washing) in ice-free areas located along a latitudinal gradient (from 72 degrees 37'S to 74 degrees 42'S) in northern Victoria Land (Antarctica); (2) furnish preliminary results on the abundance and diversity of mites and springtails in the studied areas. Visual census yielded reliable density estimates for adult collembolans and larger prostigmatic mites but did not detect small species. The study updates the distribution of several mites, including the southernmost record of an Oribatida species at global scale. Species composition was correlated with latitude but the uneven abundance distribution and local high beta-diversity probably reflect habitat fragmentation and population isolation. Under this circumstance nested sampling design should be usefully employed. Priorities and suitable methods for studying terrestrial microarthropod communities in continental Antarctica are discussed.

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High power femtosecond laser pulses have unique properties that could lead to their application as ionization or activation sources in mass spectrometry. By concentrating many photons into pulse lengths approaching the timescales associated with atomic motion, very strong electric field strengths are generated, which can efficiently ionize and fragment molecules without the need for resonant absorption. However, the complex interaction between these pulses and biomolecular species is not well understood. To address this issue, we have studied the interaction of intense, femtosecond pulses with a number of amino acids and small peptides. Unlike previous studies, we have used neutral forms of these molecular targets, which allowed us to investigate dissociation of radical cations without the spectra being complicated by the action of mobile protons. We found fragmentation was dominated by fast, radical-initiated dissociation close to the charge site generated by the initial ionization or from subsequent ultrafast migration of this charge. Fragments with lower yields, which are useful for structural determinations, were also observed and attributed to radical migration caused by hydrogen atom transfer within the molecule.

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Bonanno, A., Gouder, T., Malone, C. A. T., and Stoddart, S. K. F. (1990). World Archaeology, 22 (2):pp. .

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Social policy and professional practice across the island of Ireland is dominated by the WHO (2002) definition of elder abuse and national and professional interpretations of what constitutes elder abuse. Top down, generalist knowledge of the abuse of older people have facilitated paternalistic and protectionist policies and services designed to protect older vulnerable adults across the Republic of Ireland (ROI) and Northern Ireland (NI). However a qualitative study involving 58 older people in six focus groups held across Ireland highlights an alternative understanding of elder abuse grounded in the subjective experiences of older people across urban and rural communities on the island. Indigenous ways of knowing offer a broader and more inclusive understanding of the experience of elder abuse (Lafferty 2012; Dow and Joosten 2012) together with opportunities for the prevention of ageism and the empowering of older people across the jurisdictions.

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