2,318 research outputs found

    Transience and constancy of interactions in a plant-frugivore network

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    Plant-animal mutualistic interactions such as frugivory and seed dispersal display great variation in time due to fluctuations in fruit abundance, animal abundance, and behavior. In particular, some species participate in interactions with other species only transiently, while other species are active for longer periods of time. Species with a longer period of activity are able to interact with more species, and thus engage in constant participation in an interaction network. Species with high constancy would thus be expected to help maintain the biodiversity of a community; however, the manner in which constant species link to their partners may be critical to species coexistence. Because species that interact with many partners concurrently could create more competition compared to those species that interact sequentially with many partners, evaluating the concurrence in an interaction network sheds light on how the network can maintain biodiversity. In this study, we investigate how phenological patterns of fruit production and frugivore presence affect the temporal variation of a plant-frugivore network, and focus on the manner in which high degree species collect their interactions over time. We found a clear separation of activity periods: most species appeared only briefly and participated in relatively few interactions, or showed activity for longer time periods and participated in more interactions. Species that were active for longer time periods often shifted interactions, resulting in a sequential collection of their partners in time, rather than concurrence. For the seed dispersal mutualism in particular, sequential accumulation of partners may allow plant species more opportunities to disperse their seeds compared to concurrence. We suggest that for temporally and spatially heterogeneous landscapes, sequential accumulation of partners would serve to reduce competition and facilitate coexistence of species. Copyright © 2013 Yang et al

    What determines the temporal changes of species degree and strength in an oceanic island plant-disperser network?

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    Network models of frugivory and seed dispersal are usually static. To date, most studies on mutualistic networks assert that interaction properties such as species\u27 degree (k) and strength (s) are strongly influenced by species abundances. We evaluated how species\u27 degree and strength change as a function of temporal variation not only in species abundance, but also in species persistence (i.e., phenology length). In a two-year study, we collected community-wide data on seed dispersal by birds and examined the seasonal dynamics of the above-mentioned interaction properties. Our analyses revealed that species abundance is an important predictor for plant strength within a given sub-network. However, our analyses also reveal that species\u27 degree can often be best explained by the length of fruiting phenology (for plants degree) or by the number of fruiting species (for dispersers degree), which are factors that can be decoupled from the relative abundance of the species participating in the network. Moreover, our results suggest that generalist dispersers (when total study period is considered) act as temporal generalists, with degree constrained by the number of plant species displaying fruits in each span. Along with species identity, our findings underscore the need for a temporal perspective, given that seasonality is an inherent property of many mutualistic networks. © 2012 González-Castro et al

    Relative importance of phenotypic trait matching and species\u27 abundances in determining plant - Avian seed dispersal interactions in a small insular community

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    Network theory has provided a general way to understand mutualistic plant-animal interactions at the community level. However, the mechanisms responsible for interaction patterns remain controversial. In this study we use a combination of statistical models and probability matrices to evaluate the relative importance of species morphological and nutritional (phenotypic) traits and species abundance in determining interactions between fleshyfruited plants and birds that disperse their seeds. The models included variables associated with species abundance, a suite of variables associated with phenotypic traits (fruit diameter, bird bill width, fruit nutrient compounds), and the species identity of the avian disperser. Results show that both phenotypic traits and species abundance are important determinants of pairwise interactions. However, when considered separately, fruit diameter and bill width were more important in determining seed dispersal interactions. The effect of fruit compounds was less substantial and only important when considered together with abundance-related variables and/or the factor \u27animal species\u27. © The Authors 2014

    On-Surface Synthesis and Characterization of Triply Fused Porphyrin‚ÄďGraphene Nanoribbon Hybrids

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    This is the peer reviewed version of the following article: Angewandte Chemie - International Edition 59. 3 (2020): 1334-1339, which has been published in final form at https://doi.org/10.1002/anie.201913024. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived VersionsOn-surface synthesis offers a versatile approach to prepare novel carbon-based nanostructures that cannot be obtained by conventional solution chemistry. Graphene nanoribbons (GNRs) have potential for a variety of applications. A key issue for their application in molecular electronics is in the fine-tuning of their electronic properties through structural modifications, such as heteroatom doping or the incorporation of non-benzenoid rings. In this context, the covalent fusion of GNRs and porphyrins (Pors) is a highly appealing strategy. Herein we present the selective on-surface synthesis of a Por‚ÄďGNR hybrid, which consists of two Pors connected by a short GNR segment. The atomically precise structure of the Por‚ÄďGNR hybrid has been characterized by bond-resolved scanning tunneling microscopy (STM) and noncontact atomic force microscopy (nc-AFM). The electronic properties have been investigated by scanning tunneling spectroscopy (STS), in combination with DFT calculations, which reveals a low electronic gap of 0.4 eVFinancial support from Spanish MICINN (CTQ2017‚Äź85393‚ÄźP) is acknowledged. IMDEA Nanociencia acknowledges support from the ‚ÄúSevero Ochoa‚ÄĚ Programme for Centres of Excellence in R&D (MINECO, Grant SEV2016‚Äź0686). This work was supported by the Swiss National Science Foundation (200020_182015, IZLCZ2_170184) and the NCCR MARVEL funded by the Swiss National Science Foundation (51NF40‚Äź182892). Computational support from the Swiss Supercomputing Center (CSCS) under project ID s904 is gratefully acknowledged. Q.S. acknowledges the EMPAPOSTDOCS‚ÄźII programme under the Marie Sklodowska‚ÄźCurie grant agreement No 75436

    Iron Administration, Infection, and Anemia Management in CKD: Untangling the Effects of Intravenous Iron Therapy on Immunity and Infection Risk

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    dysfunction, increased exposure to infectious agents, loss of cutaneous barriers, comorbid conditions, and treatment-related factors (eg, hemodialysis and immunosuppressant therapy). Because iron plays a vital role in pathogen reproduction and host immunity, it is biologically plausible that intravenous iron therapy and/or iron deficiency influence infection risk in CKD. Available data from preclinical experiments, observational studies, and randomized controlled trials are summarized to explore the interplay between intravenous iron and infection risk among patients with CKD, particularly those receiving maintenance hemodialysis. The current evidence base, including data from a recent randomized controlled trial, suggests that proactive judicious use of intravenous iron (in a manner that minimizes the accumulation of non‚Äďtransferrin-bound iron) beneficially replaces iron stores while avoiding a clinically relevant effect on infection risk. In the absence of an urgent clinical need, intravenous iron therapy should be avoided in patients with active infection. Although serum ferritin concentration and transferrin saturation can help guide clinical decision making about intravenous iron therapy, definition of an optimal iron status and its precise determination in individual patients remain clinically challenging in CKD and warrant additional study

    Survey of Period Variations of Superhumps in SU UMa-Type Dwarf Novae

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    We systematically surveyed period variations of superhumps in SU UMa-type dwarf novae based on newly obtained data and past publications. In many systems, the evolution of superhump period are found to be composed of three distinct stages: early evolutionary stage with a longer superhump period, middle stage with systematically varying periods, final stage with a shorter, stable superhump period. During the middle stage, many systems with superhump periods less than 0.08 d show positive period derivatives. Contrary to the earlier claim, we found no clear evidence for variation of period derivatives between superoutburst of the same object. We present an interpretation that the lengthening of the superhump period is a result of outward propagation of the eccentricity wave and is limited by the radius near the tidal truncation. We interpret that late stage superhumps are rejuvenized excitation of 3:1 resonance when the superhumps in the outer disk is effectively quenched. Many of WZ Sge-type dwarf novae showed long-enduring superhumps during the post-superoutburst stage having periods longer than those during the main superoutburst. The period derivatives in WZ Sge-type dwarf novae are found to be strongly correlated with the fractional superhump excess, or consequently, mass ratio. WZ Sge-type dwarf novae with a long-lasting rebrightening or with multiple rebrightenings tend to have smaller period derivatives and are excellent candidate for the systems around or after the period minimum of evolution of cataclysmic variables (abridged).Comment: 239 pages, 225 figures, PASJ accepte

    Influence of Calendar Period on the Association Between BMI and Coronary Heart Disease: A Meta-Analysis of 31 Cohorts

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    Objective: The association between obesity and coronary heart disease (CHD) may have changed over time, for example due to improved pharmacological treatment of CHD risk factors. This meta-analysis of 31 prospective cohort studies explores the influence of calendar period on CHD risk associated with body mass index (BMI). Design and Methods: The relative risks (RRs) of CHD for a five-BMI-unit increment and BMI categories were pooled by means of random effects models. Meta-regression analysis was used to examine the influence of calendar period (>1985 v 1985) in univariate and multivariate analyses (including mean population age as a covariate). Results: The age, sex, and smoking adjusted RR (95% confidence intervals) of CHD for a five-BMI-unit increment was 1.28(1.22:1.34). For underweight, overweight and obesity, the RRs (compared to normal weight) were 1.11(0.91:1.36), 1.31(1.22:1.41), and 1.78(1.55:2.04), respectively. The univariate analysis indicated 31% (95%CI: 56:0) lower RR of CHD associated with a five-BMI-unit increment and a 51% (95%CI: 78: 14)) lower RR associated with obesity in studies starting after 1985 (n ¬ľ 15 and 10, respectively) compared to studies starting in or before 1985 (n ¬ľ 16 and 10). However, in the multivariate analysis, only mean population age was independently associated with the RRs for a five-BMI-unit increment and obesity ( 29(95%CI: 55: 5)) and 31(95%CI: 66:3), respectively) per 10-year increment in mean age). Conclusion: This study provides no consistent evidence for a difference in the association between BMI and CHD by calendar period. The mean population age seems to be the most important factor that modifies the association between the risk of CHD and BMI, in which the RR decreases with increasing age

    Pan-Cancer Analysis of lncRNA Regulation Supports Their Targeting of Cancer Genes in Each Tumor Context

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    Long noncoding RNAs (lncRNAs) are commonly dys-regulated in tumors, but only a handful are known toplay pathophysiological roles in cancer. We inferredlncRNAs that dysregulate cancer pathways, onco-genes, and tumor suppressors (cancer genes) bymodeling their effects on the activity of transcriptionfactors, RNA-binding proteins, and microRNAs in5,185 TCGA tumors and 1,019 ENCODE assays.Our predictions included hundreds of candidateonco- and tumor-suppressor lncRNAs (cancerlncRNAs) whose somatic alterations account for thedysregulation of dozens of cancer genes and path-ways in each of 14 tumor contexts. To demonstrateproof of concept, we showed that perturbations tar-geting OIP5-AS1 (an inferred tumor suppressor) andTUG1 and WT1-AS (inferred onco-lncRNAs) dysre-gulated cancer genes and altered proliferation ofbreast and gynecologic cancer cells. Our analysis in-dicates that, although most lncRNAs are dysregu-lated in a tumor-specific manner, some, includingOIP5-AS1, TUG1, NEAT1, MEG3, and TSIX, synergis-tically dysregulate cancer pathways in multiple tumorcontexts

    Genomic, Pathway Network, and Immunologic Features Distinguishing Squamous Carcinomas

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    This integrated, multiplatform PanCancer Atlas study co-mapped and identified distinguishing molecular features of squamous cell carcinomas (SCCs) from five sites associated with smokin
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