Research summary: A substantial and burgeoning body of research has described the influence of platform-mediated networks in a wide variety of settings, whereby users and complementors desire ...compatibility on a common platform. In this review, we outline extant views of these dynamics from the industrial organization (IO) economics, technology management, and strategic management perspectives. Using this review as a foundation, we propose a future research agenda in this domain that focuses the on the relative influence of network effects and platform quality in competitive outcomes, drivers of indirect network effects, the nature and attributes of complementors, and leveraging complementor dynamics for competitive advantage. Managerial summary: In many industries, such as social networks and video games, consumers place greater value on products with a large network of other users and a large variety of complementary products. Such "network effects" offer lucrative opportunities for firms that can leverage these dynamics to create dominant technology platforms. This article reviews current perspectives on network effects and the emergence of platforms, and offers several areas of future consideration for optimal strategies in these settings.
Metazoan MicroRNAs Bartel, David P.
Cell,
03/2018, Letnik:
173, Številka:
1
Journal Article
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MicroRNAs (miRNAs) are ∼22 nt RNAs that direct posttranscriptional repression of mRNA targets in diverse eukaryotic lineages. In humans and other mammals, these small RNAs help sculpt the expression ...of most mRNAs. This article reviews advances in our understanding of the defining features of metazoan miRNAs and their biogenesis, genomics, and evolution. It then reviews how metazoan miRNAs are regulated, how they recognize and cause repression of their targets, and the biological functions of this repression, with a compilation of knockout phenotypes that shows that important biological functions have been identified for most of the broadly conserved miRNAs of mammals.
MicroRNAs are pervasive sculptors of gene expression in animals. This review describes these small regulatory RNAs and their biogenesis, regulation, target recognition, mechanism of action, evolution, and biological functions.
Long intervening noncoding RNAs (lincRNAs) are transcribed from thousands of loci in mammalian genomes and might play widespread roles in gene regulation and other cellular processes. This Review ...outlines the emerging understanding of lincRNAs in vertebrate animals, with emphases on how they are being identified and current conclusions and questions regarding their genomics, evolution and mechanisms of action.
Discrete optimization problems are everywhere, from traditional operations research planning (scheduling, facility location and network design); to computer science databases; to advertising issues ...in viral marketing. Yet most such problems are NP-hard; unless P = NP, there are no efficient algorithms to find optimal solutions. This book shows how to design approximation algorithms: efficient algorithms that find provably near-optimal solutions. The book is organized around central algorithmic techniques for designing approximation algorithms, including greedy and local search algorithms, dynamic programming, linear and semidefinite programming, and randomization. Each chapter in the first section is devoted to a single algorithmic technique applied to several different problems, with more sophisticated treatment in the second section. The book also covers methods for proving that optimization problems are hard to approximate. Designed as a textbook for graduate-level algorithm courses, it will also serve as a reference for researchers interested in the heuristic solution of discrete optimization problems.
Combining nuclear (nuDNA) and mitochondrial DNA (mtDNA) markers has improved the power of molecular data to test phylogenetic and phylogeographic hypotheses and has highlighted the limitations of ...studies using only mtDNA markers. In fact, in the past decade, many conflicting geographic patterns between mitochondrial and nuclear genetic markers have been identified (i.e. mito‐nuclear discordance). Our goals in this synthesis are to: (i) review known cases of mito‐nuclear discordance in animal systems, (ii) to summarize the biogeographic patterns in each instance and (iii) to identify common drivers of discordance in various groups. In total, we identified 126 cases in animal systems with strong evidence of discordance between the biogeographic patterns obtained from mitochondrial DNA and those observed in the nuclear genome. In most cases, these patterns are attributed to adaptive introgression of mtDNA, demographic disparities and sex‐biased asymmetries, with some studies also implicating hybrid zone movement, human introductions and Wolbachia infection in insects. We also discuss situations where divergent mtDNA clades seem to have arisen in the absence of geographic isolation. For those cases where foreign mtDNA haplotypes are found deep within the range of a second taxon, data suggest that those mtDNA haplotypes are more likely to be at a high frequency and are commonly driven by sex‐biased asymmetries and/or adaptive introgression. In addition, we discuss the problems with inferring the processes causing discordance from biogeographic patterns that are common in many studies. In many cases, authors presented more than one explanation for discordant patterns in a given system, which indicates that likely more data are required. Ideally, to resolve this issue, we see important future work shifting focus from documenting the prevalence of mito‐nuclear discordance towards testing hypotheses regarding the drivers of discordance. Indeed, there is great potential for certain cases of mitochondrial introgression to become important natural systems within which to test the effect of different mitochondrial genotypes on whole‐animal phenotypes.
Vaccine nationalism's politics Fidler, David P
Science (American Association for the Advancement of Science),
2020-Aug-14, 2020-08-14, 20200814, Letnik:
369, Številka:
6505
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Before coronavirus disease 2019 (COVID-19) struck, cooperation on global health—especially for pandemic preparedness and response—would, we told ourselves, enhance national security, support economic ...wealth, protect human rights, and facilitate humanitarian assistance around the world. However, the politics of the coronavirus catastrophe do not reflect such national interests or international solidarity. “Vaccine nationalism” is more evidence that efforts to elevate health cooperation—and the sciences that inform it—have produced more rhetoric than political roots within countries and the international community.
For more than 70 years, the promise of noninvasive neuromodulation using focused ultrasound has been growing while diagnostic ultrasound established itself as a foundation of clinical imaging. ...Significant technical challenges have been overcome to allow transcranial focused ultrasound to deliver spatially restricted energy into the nervous system at a wide range of intensities. High-intensity focused ultrasound produces reliable permanent lesions within the brain, and low-intensity focused ultrasound has been reported to both excite and inhibit neural activity reversibly. Despite intense interest in this promising new platform for noninvasive, highly focused neuromodulation, the underlying mechanism remains elusive, though recent studies provide further insight. Despite the barriers, the potential of focused ultrasound to deliver a range of permanent and reversible neuromodulation with seamless translation from bench to the bedside warrants unparalleled attention and scientific investment. Focused ultrasound boasts a number of key features such as multimodal compatibility, submillimeter steerable focusing, multifocal, high temporal resolution, coregistration, and the ability to monitor delivered therapy and temperatures in real time. Despite the technical complexity, the future of noninvasive focused ultrasound for neuromodulation as a neuroscience and clinical platform remains bright.
The rational design of well-defined, first-row transition metal complexes that can activate dioxygen has been a challenging goal for the synthetic inorganic chemist. The activation of O2 is important ...in part because of its central role in the functioning of metalloenzymes, which utilize O2 to perform a number of challenging reactions including the highly selective oxidation of various substrates. There is also great interest in utilizing O2, an abundant and environmentally benign oxidant, in synthetic catalytic oxidation systems. This Perspective brings together recent examples of biomimetic Fe and Mn complexes that can activate O2 in heme or nonheme-type ligand environments. The use of oxidants such as hypervalent iodine (e.g., ArIO), peracids (e.g., m-CPBA), peroxides (e.g., H2O2) or even superoxide is a popular choice for accessing well-characterized metal–superoxo, metal–peroxo, or metal–oxo species, but the instances of biomimetic Fe/Mn complexes that react with dioxygen to yield such observable metal–oxygen species are surprisingly few. This Perspective focuses on mononuclear Fe and Mn complexes that exhibit reactivity with O2 and lead to spectroscopically observable metal–oxygen species, and/or oxidize biologically relevant substrates. Analysis of these examples reveals that solvent, spin state, redox potential, external co-reductants, and ligand architecture can all play important roles in the O2 activation process.
Crop diseases are a major threat to food security, but their rapid identification remains difficult in many parts of the world due to the lack of the necessary infrastructure. The combination of ...increasing global smartphone penetration and recent advances in computer vision made possible by deep learning has paved the way for smartphone-assisted disease diagnosis. Using a public dataset of 54,306 images of diseased and healthy plant leaves collected under controlled conditions, we train a deep convolutional neural network to identify 14 crop species and 26 diseases (or absence thereof). The trained model achieves an accuracy of 99.35% on a held-out test set, demonstrating the feasibility of this approach. Overall, the approach of training deep learning models on increasingly large and publicly available image datasets presents a clear path toward smartphone-assisted crop disease diagnosis on a massive global scale.
Combination of different satellite data will provide increased opportunities for more frequent cloud-free surface observations due to variable cloud cover at the different satellite overpass times ...and dates. Satellite data from the polar-orbiting Landsat-8 (launched 2013), Sentinel-2A (launched 2015) and Sentinel-2B (launched 2017) sensors offer 10 m to 30 m multi-spectral global coverage. Together, they advance the virtual constellation paradigm for mid-resolution land imaging. In this study, a global analysis of Landsat-8, Sentinel-2A and Sentinel-2B metadata obtained from the committee on Earth Observation Satellite (CEOS) Visualization Environment (COVE) tool for 2016 is presented. A global equal area projection grid defined every 0.05° is used considering each sensor and combined together. Histograms, maps and global summary statistics of the temporal revisit intervals (minimum, mean, and maximum) and the number of observations are reported. The temporal observation frequency improvements afforded by sensor combination are shown to be significant. In particular, considering Landsat-8, Sentinel-2A, and Sentinel-2B together will provide a global median average revisit interval of 2.9 days, and, over a year, a global median minimum revisit interval of 14 min (±1 min) and maximum revisit interval of 7.0 days.
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