53 research outputs found
Introduction to special section: Building complex and realistic geological models from sparse data
International audienceEarth scientists have always created spatial models of the subsurface. Before the dawn of computer-based modeling, earth models were simply drawn by hand on a piece of paper as cross section or plan views, sometimes utilizing the techniques of descriptive geometry. These hand-draw models are quick and easy to create; this is why we are still doing them on white boards, note books and sometimes even on napkins. They communicate ideas very well, but they are subjective and rarely constrained by data in a measurable way. As the number of observations grew with the advancement of data collections technologies, the possibility to use mathematical algorithms to do the modeling became a reality. These processes, first applied in 2D then in 3D, removed some of the subjectivity from the modeling. These processes work very well when the data density is high enough, meaning that models built with different mathematical methods are both realistic and similar one to another
Positive early-late life-history trait correlations in elephant seals
Correlations between early- and late-life performance are a major prediction of
life-history theory. Negative earlyâlate correlations can emerge because biological processes
are optimized for early but not late life (e.g., rapid development may accelerate the onset of
senescence; âdevelopmental theory of agingâ) or because allocation to early-life performance
comes at a cost in terms of late-life performance (as in the disposable soma theory). But variation
in genetic and environmental challenges that each individual has to cope with during early
life may also lead to positive earlyâlate life-history trait correlations (the âfixed heterogeneityâ
or âindividual qualityâ hypothesis). We analyzed individual life-history trajectories of 7,420
known-age female southern elephant seals (Mirounga leonina) monitored over 36 yr to determine
how actuarial senescence (a proxy for late-life performance) correlate with age at first
reproduction (a proxy for early-life performance). As some breeding events may not be
detected in this field study, we used a custom âmultieventâ hierarchical model to estimate the
age at first reproduction and correlate it to other life-history traits. The probability of first
reproduction was 0.34 at age 3, with most females breeding for the first time at age 4, and comparatively
few at older ages. Females with an early age of first reproduction outperformed
delayed breeders in all aspects we considered (survival, rate of senescence, net reproductive
output) but one: early breeders appeared to have an onset of actuarial senescence 1 yr earlier
compared to late breeders. Genetics and environmental conditions during early life likely
explain the positive correlation between early- and late-life performance. Our results provide
the first evidence of actuarial senescence in female southern elephant seals.The South African National Research Foundation (NRF)http://www.esajournals.org/loi/ecolam2022Mammal Research InstituteZoology and Entomolog
Breast cancer specialists' perspective on their role in their patients' return to work: A qualitative study
OBJECTIVES: This study aimed to explore the views of breast cancer (BC) specialists as to their role in the return-to-work (RTW) process of their BC patients. METHODS: A qualitative study using semi-structured interviews was conducted in a sample of 20 BC specialists selected according to age, gender, medical specialty (medical oncology, radiation oncology, gynecological surgery), and healthcare organization (regional cancer center, university or private hospital). All interviews were audiotaped and transcribed for qualitative thematic content analysis. RESULTS: BC specialists had heterogeneous representations and practices regarding their role in their patients` RTW process, ranging from non-involvement to frequent discussion. Most BC specialists had concerns regarding the ?right time and right way? to address patient`s RTW. They hardly mentioned workplace and job factors as potential barriers but rather stressed motivation. The main reported barriers to involvement in the RTW process were lack of time, lack of knowledge, lack of skills, and a professional attitude exclusively focused on cancer care issues. CONCLUSION: While our study showed varying representations and practices among BC specialists, participants consistently identified barriers in supporting BC survivors` RTW. The results will guide the development of an intervention to facilitate the role of BC specialists in the RTW process as part of a multicomponent intervention to facilitate BC survivors` RTW
Challenging claims in the study of migratory birds and climate change
Recent shifts in phenology in response to climate change are well established but often poorly understood. Many animals integrate climate change across a spatially and temporally dispersed annual life cycle, and effects are modulated by ecological interactions, evolutionary change and endogenous control mechanisms. Here we assess and discuss key statements emerging from the rapidly developing study of changing spring phenology in migratory birds. These well-studied organisms have been instrumental for understanding climate-change effects, but research is developing rapidly and there is a need to attack the big issues rather than risking affirmative science. Although we agree poorly on the support for most claims, agreement regarding the knowledge basis enables consensus regarding broad patterns and likely causes. Empirical data needed for disentangling mechanisms are still scarce, and consequences at a population level and on community composition remain unclear. With increasing knowledge, the overall support (âconsensus viewâ) for a claim increased and between-researcher variability in support (âexpert opinions') decreased, indicating the importance of assessing and communicating the knowledge basis. A proper integration across biological disciplines seems essential for the field's transition from affirming patterns to understanding mechanisms and making robust predictions regarding future consequences of shifting phenologies
Weighted transitivity scores that account for triadic edge similarity in undirected graphs
Abstract The graph transitivity measures the probability that adjacent vertices in a network are interconnected, thus revealing the existence of tightly connected neighborhoods playing a role in information and pathogen circulation. When the connections vary in strength, focusing on whether connections exist or not can be reductive. I score the weighted transitivity according to the similarity between the weights of the three possible links in each triad. I illustrate the biological relevance of that information with two reanalyses of animal contact networks. In the rhesus macaque Macaca mulatta , a species in which kin relationships strongly predict social relationships, the new metrics revealed striking similarities in the configuration of grooming networks in captive and free-ranging groups, but only as long as the matrilines were preserved. In the barnacle goose Branta leucopsis , in an experiment designed to test the long-term effect of the goslingsâ social environment, the new metrics uncovered an excess of weak triplets closed by strong links in males compared to females, and consistent with the triadic process underlying goose dominance relationships
Net relatedness index of mixed species flocks
Species richness, net relatedness index, see article for site names and definition
Lewis acid mediated cyclisation of methylenecyclopropane derivatives
This thesis is concerned with the synthesis, and cyclisation of compounds containing a methylenecyclopropane moiety. Special interest is given to the Lewis acid mediated cyclisation of methylenecyclopropyl ketones and ketals, which proceed with high yields of highly functionalised carbocycles.Chapter 1 discussed the synthesis and the cyclisation of methylenecyclopropyl ketones and aldehydes 122, which gave cyclised compounds 125 and 126. (Fig. 8562A).In addition, a rapid method for the preparation of precursors for the Lewis acid mediated cyclisation of methylenecyclopropane derivatives was developed with addition of methylenecyclopropyl cuprate to conjugated ketones.Chapter 2 focused on the cascade process of 1,2-disubstituted methylenecyclopropanes with first cyclisation induced by Lewis acid to give an allyl cation intermediate which can be trapped in a cycloaddition reaction.Chapter 3 also discussed the cyclisation of 1,1-disubsittuted methylenecyclopropane derivatives mediated by Lewis acid, especially the synthesis of spirocycle compounds.Chapter 4 discussed the effect of a silyl group on the cyclisation reaction. Ketone 300 gave, under treatment with Lewis acid, cyclised compounds 303 and 304 in very good yields, due presumably to the ability of silicon to stabilise ÎČ-carbocation intermediate 301. (Fig. 8562B).Chapter 5 is concerned with the development of a cascade process as the silicon atom can be used to transfer allyl and phenyl groups. (Fig. 8562C).Finally Chapter 6 is concerned with an attempt, which failed, to synthesise the natural product Norketoagarofuran.</p
Demographic response to perturbations: the role of compensatory density dependence in a North American duck under variable harvest regulations and changing habitat
CLIMATE CHANGES AND POST-NUPTIAL MIGRATION STRATEGY BY TWO REEDBED PASSERINES
International audienc
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