The evolution of insect metamorphosis is one of the most important sagas in animal history, transforming small, obscure soil arthropods into a dominant terrestrial group that has profoundly shaped ...the evolution of terrestrial life. The evolution of flight initiated the trajectory towards metamorphosis, favoring enhanced differences between juvenile and adult stages. The initial step modified postembryonic development, resulting in the nymph–adult differences characteristic of hemimetabolous species. The second step was to complete metamorphosis, holometaboly, and occurred by profoundly altering embryogenesis to produce a larval stage, the nymph becoming the pupa to accommodate the deferred development needed to make the adult. These changing life history patterns were intimately linked to two hormonal systems, the ecdysteroids and the juvenile hormones (JH), which function in both embryonic and postembryonic domains and control the stage-specifying genes Krüppel homolog 1 (Kr-h1), broad and E93. The ecdysteroids induce and direct molting through the ecdysone receptor (EcR), a nuclear hormone receptor with numerous targets including a conserved transcription factor network, the ‘Ashburner cascade’, which translates features of the ecdysteroid peak into the different phases of the molt. With the evolution of metamorphosis, ecdysteroids acquired a metamorphic function that exploited the repressor capacity of the unliganded EcR, making it a hormone-controlled gateway for the tissue development preceding metamorphosis. JH directs ecdysteroid action, controlling Kr-h1 expression which in turn regulates the other stage-specifying genes. JH appears in basal insect groups as their embryos shift from growth and patterning to differentiation. As a major portion of embryogenesis was deferred to postembryonic life with the evolution of holometaboly, JH also acquired a potent role in regulating postembryonic growth and development. Details of its involvement in broad expression and E93 suppression have been modified as life cycles became more complex and likely underlie some of the changes seen in the shift from incomplete to complete metamorphosis.
During their evolution insects progressed from direct development, through a simple metamorphosis of a nymph into an adult, and eventually to a complex metamorphosis with a specialized larval and pupal stage. In this review, Jim Truman takes a developmental perspective to understanding how this progression evolved.
Sense of agency refers to the feeling of control over actions and their consequences. In this article I summarize what we currently know about sense of agency; looking at how it is measured and what ...theories there are to explain it. I then explore some of the potential applications of this research, something that the sense of agency research field has been slow to identify and implement. This is a pressing concern given the increasing importance of 'research impact.'
Mass extinction at the Cretaceous–Paleogene (K-Pg) boundary coincides with the Chicxulub bolide impact and also falls within the broader time frame of Deccan trap emplacement. Critically, though, ...empirical evidence as to how either of these factors could have driven observed extinction patterns and carbon cycle perturbations is still lacking. Here, using boron isotopes in foraminifera, we document a geologically rapid surface-ocean pH drop following the Chicxulub impact, supporting impact-induced ocean acidification as amechanism for ecological collapse in the marine realm. Subsequently, surface water pH rebounded sharply with the extinction of marine calcifiers and the associated imbalance in the global carbon cycle. Our reconstructed water-column pH gradients, combined with Earth system modeling, indicate that a partial ∼50% reduction in global marine primary productivity is sufficient to explain observed marine carbon isotope patterns at the K-Pg, due to the underlying action of the solubility pump. While primary productivity recovered within a few tens of thousands of years, inefficiency in carbon export to the deep sea lasted much longer. This phased recovery scenario reconciles competing hypotheses previously put forward to explain the K-Pg carbon isotope records, and explains both spatially variable patterns of change in marine productivity across the event and a lack of extinction at the deep sea floor. In sum, we provide insights into the drivers of the last mass extinction, the recovery of marine carbon cycling in a postextinction world, and the way in which marine life imprints its isotopic signal onto the geological record.
Value at Risk (VaR) forecasts can be produced from conditional autoregressive VaR models, estimated using quantile regression. Quantile modeling avoids a distributional assumption, and allows the ...dynamics of the quantiles to differ for each probability level. However, by focusing on a quantile, these models provide no information regarding expected shortfall (ES), which is the expectation of the exceedances beyond the quantile. We introduce a method for predicting ES corresponding to VaR forecasts produced by quantile regression models. It is well known that quantile regression is equivalent to maximum likelihood based on an asymmetric Laplace (AL) density. We allow the density's scale to be time-varying, and show that it can be used to estimate conditional ES. This enables a joint model of conditional VaR and ES to be estimated by maximizing an AL log-likelihood. Although this estimation framework uses an AL density, it does not rely on an assumption for the returns distribution. We also use the AL log-likelihood for forecast evaluation, and show that it is strictly consistent for the joint evaluation of VaR and ES. Empirical illustration is provided using stock index data. Supplementary materials for this article are available online.
Background
Asthma is a common condition due to chronic inflammation of the lower respiratory tract. Chronic lower airway inflammation is known to be more common in individuals that also have ...inflammatory disorders of the upper airway. The scientific understanding of asthma continues to improve and it is important for providers who treat upper or lower airway inflammation to be familiar with asthma's definition and pathophysiology.
Methods
Articles were selected based on literature reviews through PubMed and personal knowledge of the author. The search selection was not standardized.
Results
Asthma is a heterogenic condition that is underdiagnosed and undertreated despite that the skills needed to diagnose it are readily attainable and effective treatments are available. Providers need a working understanding of asthma in order to be proficient at managing their patients with chronic nasal or sinus inflammation. This article provides a primer focusing on the current conception asthma in terms of definition, possible etiologies, inflammatory profile, pathophysiology, subtypes, and overlapping conditions.
Conclusion
Asthma is a chronic inflammatory disorder arising from not fully understood heterogenic gene‐environment interactions. It features variable airway obstruction and bronchial hyperresponsiveness. Clinically, asthmatics exhibit recurrent episodes of wheeze, cough, chest tightness, and shortness of breath.
Summary Background The oldest-old (those aged ≥80 years) are the most rapidly growing age group globally, and are most in need of health care and assistance. We aimed to assess changes in mortality, ...disability in activities of daily living, and physical and cognitive functioning among oldest-old individuals between 1998 and 2008. Methods We used data from the Chinese Longitudinal Healthy Longevity Study. Three pairs of cohorts aged 80–89 years, 90–99 years, and 100–105 years (in total, 19 528 oldest-old participants) were examined; the two cohorts in each pair were born 10 years apart, with the same age at the time of the assessment in the 1998 and 2008 surveys. Four health outcomes were investigated: annual death rate, Activities of Daily Living (ADL), physical performance in three tests and cognitive function measured by Mini-Mental State Examination (MMSE). We used different tests and multivariate regression analyses to examine the cohort differences. Findings Controlling for various confounding factors, we noted that annual mortality among oldest-old individuals was substantially reduced between 0·2% and 1·3% in 1998–2008 compared with individuals of the same age born 10 years previously, and that disability according to activities of daily living had significantly reduced annually between 0·8% and 2·8%. However, cognitive impairment in the later cohorts increased annually between 0·7% and 2·2% and objective physical performance capacity (standing up from a chair, picking up a book from the floor, and turning around 360°) decreased anually between 0·4% and 3·8%. We also noted that female mortality was substantially lower than male mortality among the oldest-old, but that women's functional capacities in activities of daily living, cognition, and physical performance were worse than their male counterparts. Interpretation Advances in medications, lifestyle, and socioeconomics might compress activities of daily living disability, that is, benefits of success, but lifespan extension might expand disability of physical and cognitive functioning as more frail, elderly individuals survive with health problems, that is, costs of success. Funding National Natural Science Foundation of China, National Institute on Aging/National Institutes of Health, United Nations Funds for Population Activities.
Perineuronal nets (PNNs) are extracellular matrix (ECM) chondroitin sulfate proteoglycan (CSPG)-containing structures that surround the soma and dendrites of various mammalian neuronal cell types. ...PNNs appear during development around the time that the critical periods for developmental plasticity end and are important for both their onset and closure. A similar structure - the perinodal ECM - surrounds the axonal nodes of Ranvier and appears as myelination is completed, acting as an ion-diffusion barrier that affects axonal conduction speed. Recent work has revealed the importance of PNNs in controlling plasticity in the CNS. Digestion, blocking or removal of PNNs influences functional recovery after a variety of CNS lesions. PNNs have further been shown to be involved in the regulation of memory and have been implicated in a number of psychiatric disorders.
Machine-learning models have demonstrated great success in learning complex patterns that enable them to make predictions about unobserved data. In addition to using models for prediction, the ...ability to interpret what a model has learned is receiving an increasing amount of attention. However, this increased focus has led to considerable confusion about the notion of interpretability. In particular, it is unclear how the wide array of proposed interpretation methods are related and what common concepts can be used to evaluate them. We aim to address these concerns by defining interpretability in the context of machine learning and introducing the predictive, descriptive, relevant (PDR) framework for discussing interpretations. The PDR framework provides 3 overarching desiderata for evaluation: predictive accuracy, descriptive accuracy, and relevancy, with relevancy judged relative to a human audience. Moreover, to help manage the deluge of interpretation methods, we introduce a categorization of existing techniques into model-based and post hoc categories, with subgroups including sparsity, modularity, and simulatability. To demonstrate how practitioners can use the PDR framework to evaluate and understand interpretations, we provide numerous real-world examples. These examples highlight the often underappreciated role played by human audiences in discussions of interpretability. Finally, based on our framework, we discuss limitations of existing methods and directions for future work. We hope that this work will provide a common vocabulary that will make it easier for both practitioners and researchers to discuss and choose from the full range of interpretation methods.
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