53,884 results
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102. Commentary on Paper by Szent-Gyorgyi et al.
- Author
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Griffith, J. S.
- Published
- 1961
103. Comments on a Paper Dealing with Hydromagnetic Stability of a Plasma
- Author
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Slepian, Joseph
- Published
- 1962
104. Note on a Paper by Murnaghan
- Author
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Ibrahim, E. M.
- Published
- 1954
105. Summary of Results and Proofs on Fermat's Last Theorem (Fourth Paper)
- Author
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Vandiver, H. S.
- Published
- 1929
106. Remarks on Zwicky's Paper "On the Formation of Clusters of Nebulae and the Cosmological Time Scale"
- Author
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Vallarta, M. S.
- Published
- 1940
107. Fluid-driven origami-inspired artificial muscles.
- Author
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Li S, Vogt DM, Rus D, and Wood RJ
- Subjects
- Animals, Artificial Limbs, Biomechanical Phenomena, Biomimetics economics, Biomimetics methods, Humans, Hydrodynamics, Robotics economics, Muscle, Skeletal physiology, Paper, Robotics methods
- Abstract
Artificial muscles hold promise for safe and powerful actuation for myriad common machines and robots. However, the design, fabrication, and implementation of artificial muscles are often limited by their material costs, operating principle, scalability, and single-degree-of-freedom contractile actuation motions. Here we propose an architecture for fluid-driven origami-inspired artificial muscles. This concept requires only a compressible skeleton, a flexible skin, and a fluid medium. A mechanical model is developed to explain the interaction of the three components. A fabrication method is introduced to rapidly manufacture low-cost artificial muscles using various materials and at multiple scales. The artificial muscles can be programed to achieve multiaxial motions including contraction, bending, and torsion. These motions can be aggregated into systems with multiple degrees of freedom, which are able to produce controllable motions at different rates. Our artificial muscles can be driven by fluids at negative pressures (relative to ambient). This feature makes actuation safer than most other fluidic artificial muscles that operate with positive pressures. Experiments reveal that these muscles can contract over 90% of their initial lengths, generate stresses of ∼600 kPa, and produce peak power densities over 2 kW/kg-all equal to, or in excess of, natural muscle. This architecture for artificial muscles opens the door to rapid design and low-cost fabrication of actuation systems for numerous applications at multiple scales, ranging from miniature medical devices to wearable robotic exoskeletons to large deployable structures for space exploration., Competing Interests: The authors declare no conflict of interest., (Copyright © 2017 the Author(s). Published by PNAS.)
- Published
- 2017
- Full Text
- View/download PDF
108. Rapid prototyping of carbon-based chemiresistive gas sensors on paper
- Author
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Timothy M. Swager, Katherine A. Mirica, Jan M. Schnorr, Jonathan G. Weis, and Joseph M. Azzarelli
- Subjects
Rapid prototyping ,Paper ,Principal Component Analysis ,Multidisciplinary ,Fabrication ,Materials science ,Nanotubes, Carbon ,Nanotechnology ,Carbon nanotube ,Mechanical abrasion ,law.invention ,PNAS Plus ,law ,Mechanochemistry ,Microscopy, Electron, Scanning ,Graphite ,Gases ,Solubility ,Ball mill - Abstract
Chemically functionalized carbon nanotubes (CNTs) are promising materials for sensing of gases and volatile organic compounds. However, the poor solubility of carbon nanotubes hinders their chemical functionalization and the subsequent integration of these materials into devices. This manuscript describes a solvent-free procedure for rapid prototyping of selective chemiresistors from CNTs and graphite on the surface of paper. This procedure enables fabrication of functional gas sensors from commercially available starting materials in less than 15 min. The first step of this procedure involves the generation of solid composites of CNTs or graphite with small molecule selectors--designed to interact with specific classes of gaseous analytes--by solvent-free mechanical mixing in a ball mill and subsequent compression. The second step involves deposition of chemiresistive sensors by mechanical abrasion of these solid composites onto the surface of paper. Parallel fabrication of multiple chemiresistors from diverse composites rapidly generates cross-reactive arrays capable of sensing and differentiating gases and volatile organic compounds at part-per-million and part-per-thousand concentrations.
- Published
- 2013
109. Promote electroreduction of CO2 via catalyst valence state manipulation by surface-capping ligand.
- Author
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Yilin Zhao, Xiaoqing Liu, Jingyi Chen, Junmei Chen, Jiayi Chen, Lei Fan, Haozhou Yang, Shibo Xi, Lei Shen, and Lei Wang
- Subjects
PHASE transitions ,ELECTROLYTIC reduction ,CARBON monoxide poisoning ,CATALYSTS ,STANDARD hydrogen electrode ,CARBON paper ,ELECTROSPINNING - Abstract
Electrochemical CO
2 reduction provides a potential means for synthesizing value-added chemicals over the near equilibrium potential regime, i.e., formate production on Pd-based catalysts. However, the activity of Pd catalysts has been largely plagued by the potential-depended deactivation pathways (e.g., α-PdH to β-PdH phase transition, CO poisoning), limiting the formate production to a narrow potential window of 0 V to -0.25 V vs. reversible hydrogen electrode (RHE). Herein, we discovered that the Pd surface capped with polyvinylpyrrolidone (PVP) ligand exhibits effective resistance to the potential-depended deactivations and can catalyze formate production at a much extended potential window (beyond -0.7 V vs. RHE) with significantly improved activity (~14-times enhancement at -0.4 V vs. RHE) compared to that of the pristine Pd surface. Combined results from physical and electrochemical characterizations, kinetic analysis, and first-principle simulations suggest that the PVP capping ligand can effectively stabilize the high-valence-state Pd species (Pdδ+) resulted from the catalyst synthesis and pretreatments, and these Pdβ+ species are responsible for the inhibited phase transition from α-PdH to α-PdH, and the suppression of CO and H2 formation. The present study confers a desired catalyst design principle, introducing positive charges into Pd-based electrocatalyst to enable efficient and stable CO2 to formate conversion. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
110. Electrochemically active porous carbon nanospheres prepared by inhibition of pyrolytic condensation of polymers.
- Author
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Jaehyun Kim, Dayoung Lee, Cheolho Kim, Haeli Lee, Seungjun Baek, and Jun Hyuk Moon
- Subjects
CARBON-based materials ,POLYMERS ,CARBON paper ,CONDENSATION ,POROSITY ,ZINC oxide films - Abstract
Porous carbon is a pivotal material for electrochemical applications. The manufacture of porous carbon has relied on chemical treatments (etching or template) that require processing in all areas of the carbon/carbon precursor. We present a unique approach to preparing porous carbon nanospheres by inhibiting the pyrolytic condensation of polymers. Specifically, the porous carbon nanospheres are obtained by coating a thin film of ZnO on polystyrene spheres. The porosity of the porous carbon nanospheres is controlled by the thickness of the ZnO shell, achieving a BET-specific area of 1,124 m²/g with a specific volume of 1.09 cm³/g. We confirm that under the support force by the ZnO shell, a hierarchical pore structure in which small mesopores are connected by large mesopores is formed and that the pore-associated sp³ defects are enriched. These features allow full utilization of the surface area of the carbon pores. The electrochemical capacitive performance of porous carbon nanospheres was evaluated, achieving a high capacitance of 389 F/g at 1 A/g, capacitance retention of 71% at a 20-fold increase in current density, and stability up to 30,000 cycles. In particular, we achieve a specific area-normalized capacitance of 34.6 µF/cm², which overcomes the limitations of conventional carbon materials. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
111. Comparative analysis of constraints and caste differences in brain investment among social paper wasps
- Author
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Marie R. Clifford, Sean O'Donnell, and Yamile Molina
- Subjects
Paper wasp ,Multidisciplinary ,Sensory processing ,Ecology ,medicine.medical_treatment ,Wasps ,Brain ,Cognition ,Phylogenetic comparative methods ,Organ Size ,Biology ,Biological Sciences ,Investment (macroeconomics) ,Eusociality ,Biological Evolution ,Species Specificity ,Evolutionary biology ,Brain size ,Mushroom bodies ,medicine ,Animals ,Mushroom Bodies - Abstract
We compared species mean data on the size of functionally distinct brain regions to test the relative rates at which investment in higher-order cognitive processing (mushroom body calyces) versus peripheral sensory processing (optic and antennal lobes) increased with increasing brain size. Subjects were eusocial paper wasps from queen and worker castes of 10 species from different genera. Relative investment in central processing tissue increased with brain size at a higher rate than peripheral structure investment, demonstrating that tissue devoted to higher-order cognitive processing is more constrained by brain size. This pattern held for raw data and for phylogenetically independent contrasts. These findings suggest that there is a minimum necessary investment in peripheral sensory processing brain tissue, with little to gain from additional investment. In contrast, increased brain size provides opportunities to invest in additional higher-order cognitive processing tissue. Reproductive castes differed within species in brain tissue investment, with higher central-to-peripheral brain tissue ratios in queens than in workers. Coupled with previous findings that paper wasp queen, but not worker, brain architecture corresponds to ecological and social variation, queen brain evolution appears to be most strongly shaped by cognitive demands, such as social interactions. These evolutionary patterns of neural investment echo findings in other animal lineages and have important implications, given that a greater investment in higher-order processing has been shown to increase the prevalence of complex and flexible behaviors across the animal kingdom.
- Published
- 2011
112. Three-dimensional microfluidic devices fabricated in layered paper and tape
- Author
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Scott T. Phillips, George M. Whitesides, and Andres W. Martinez
- Subjects
Paper ,Applied Physical Sciences ,Multidisciplinary ,Computer science ,Microsystem ,Microfluidics ,Stacking ,Water ,Nanotechnology ,Bioactive paper ,Microfluidic Analytical Techniques ,Environmental Monitoring - Abstract
This article describes a method for fabricating 3D microfluidic devices by stacking layers of patterned paper and double-sided adhesive tape. Paper-based 3D microfluidic devices have capabilities in microfluidics that are difficult to achieve using conventional open-channel microsystems made from glass or polymers. In particular, 3D paper-based devices wick fluids and distribute microliter volumes of samples from single inlet points into arrays of detection zones (with numbers up to thousands). This capability makes it possible to carry out a range of new analytical protocols simply and inexpensively (all on a piece of paper) without external pumps. We demonstrate a prototype 3D device that tests 4 different samples for up to 4 different analytes and displays the results of the assays in a side-by-side configuration for easy comparison. Three-dimensional paper-based microfluidic devices are especially appropriate for use in distributed healthcare in the developing world and in environmental monitoring and water analysis.
- Published
- 2008
113. Deterministic and stochastic control of kirigami topology.
- Author
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Siheng Chen, Choi, Gary P. T., and Mahadevan, L.
- Subjects
- *
DEGREES of freedom , *PAPER arts , *TOPOLOGY , *PERCOLATION - Abstract
Kirigami, the creative art of paper cutting, is a promising paradigm for mechanical metamaterials. However, to make kirigami-inspired structures a reality requires controlling the topology of kirigami to achieve connectivity and rigidity. We address this question by deriving the maximum number of cuts (minimum number of links) that still allow us to preserve global rigidity and connectivity of the kirigami. A deterministic hierarchical construction method yields an efficient topological way to control both the number of connected pieces and the total degrees of freedom. A statistical approach to the control of rigidity and connectivity in kirigami with random cuts complements the deterministic pathway, and shows that both the number of connected pieces and the degrees of freedom show percolation transitions as a function of the density of cuts (links). Together, this provides a general framework for the control of rigidity and connectivity in planar kirigami. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
114. Evolution of restraint in a structured rock-paper-scissors community
- Author
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Joshua R. Nahum, Brittany N. Harding, and Benjamin Kerr
- Subjects
Consumption (economics) ,Multidisciplinary ,Natural selection ,Ecology ,media_common.quotation_subject ,Colloquium Papers ,Counterintuitive ,Competitor analysis ,Altruism ,Microeconomics ,Evolution, Molecular ,Economics ,Escherichia coli ,Biological dispersal ,Resource management ,Computer Simulation ,Selection, Genetic ,Set (psychology) ,media_common - Abstract
It is not immediately clear how costly behavior that benefits others evolves by natural selection. By saving on inherent costs, individuals that do not contribute socially have a selective advantage over altruists if both types receive equal benefits. Restrained consumption of a common resource is a form of altruism. The cost of this kind of prudent behavior is that restrained individuals give up resources to less-restrained individuals. The benefit of restraint is that better resource management may prolong the persistence of the group. One way to dodge the problem of defection is for altruists to interact disproportionately with other altruists. With limited dispersal, restrained individuals persist because of interaction with like types, whereas it is the unrestrained individuals that must face the negative long-term consequences of their rapacity. Here, we study the evolution of restraint in a community of three competitors exhibiting a nontransitive (rock–paper–scissors) relationship. The nontransitivity ensures a form of negative feedback, whereby improvement in growth of one competitor has the counterintuitive consequence of lowering the density of that improved player. This negative feedback generates detrimental long-term consequences for unrestrained growth. Using both computer simulations and evolution experiments with a nontransitive community of Escherichia coli , we find that restrained growth can evolve under conditions of limited dispersal in which negative feedback is present. This research, thus, highlights a set of ecological conditions sufficient for the evolution of one form of altruism.
- Published
- 2011
115. Showcasing advances and building community in modeling for sustainability.
- Author
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Selin, Noelle E., Giang, Amanda, and Clark, William C.
- Subjects
ECOLOGICAL regime shifts ,CLIMATE change & health ,PHOTOVOLTAIC power systems ,SYNTHETIC natural gas ,CARBON sequestration - Abstract
This document serves as an introduction to a special feature on modeling for sustainability. It showcases recent advances in sustainability science and the integration of modeling with theory and data-focused approaches. The papers in this feature highlight innovative modeling methods and their applications in fields such as air quality, water resources, and energy systems. The authors emphasize the importance of equitable distribution and consider distributional issues in modeling. They also discuss the different stages of modeling practice, including defining the purpose, selecting components, analyzing interactions, and assessing interventions. The document concludes by emphasizing the potential of modeling to contribute to long-term sustainability goals. Additionally, there is a list of references to various scientific articles and studies related to topics such as water management, climate change, energy transition, and sustainability. These articles cover a range of subjects including modeling and decision-making in watershed management, the nexus between water, land, food, and climate, the impact of climate oscillations on water supply planning, and the social aspects of the energy transition. These articles provide valuable insights and research findings for library patrons conducting research on these specific topics. [Extracted from the article]
- Published
- 2024
- Full Text
- View/download PDF
116. Flat teams drive scientific innovation.
- Author
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Fengli Xu, Lingfei Wu, and Evans, James
- Subjects
TEAMS in the workplace ,RESEARCH teams ,TRAINING of scientists ,ACQUISITION of data - Abstract
With teams growing in all areas of scientiic and scholarly research, we explore the relationship between team structure and the character of knowledge they produce. Drawing on 89,575 self-reports of team member research activity underlying scientiic publications, we show how individual activities cohere into broad roles of 1) leadership through the direction and presentation of research and 2) support through data collection, analysis, and discussion.he hidden hierarchy of a scientiic team is characterized by its lead (or L) ratio of members playing leadership roles to total team size.he L ratio is validated through correlation with imputed contributions to the speciic paper and to science as a whole, which we use to efectively extrapolate the L ratio for 16,397,750 papers where roles are not explicit. We ind that, relative to lat, egalitarian teams, tall, hierarchical teams produce less novelty and more often develop existing ideas, increase productivity for those on top and decrease it for those beneath, and increase shortterm citations but decrease long-term inluence.hese efects hold within person--the same person on the same-sized team produces science much more likely to disruptively innovate if they work on a lat, high-L-ratio team.hese results suggest the critical role lat teams play for sustainable scientiic advance and the training and advancement of scientists. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
117. Colloquium paper: reconstructing human evolution: achievements, challenges, and opportunities
- Author
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Bernard, Wood
- Subjects
Primates ,Fossils ,Colloquium Papers ,Animals ,Humans ,Hominidae ,Biological Evolution ,Phylogeny - Abstract
This contribution reviews the evidence that has resolved the branching structure of the higher primate part of the tree of life and the substantial body of fossil evidence for human evolution. It considers some of the problems faced by those who try to interpret the taxonomy and systematics of the human fossil record. How do you to tell an early human taxon from one in a closely related clade? How do you determine the number of taxa represented in the human clade? How can homoplasy be recognized and factored into attempts to recover phylogeny?
- Published
- 2010
118. Colloquium paper: bioenergetics, the origins of complexity, and the ascent of man
- Author
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Douglas C, Wallace
- Subjects
Cell Nucleus ,Colloquium Papers ,Mutation ,Electrochemistry ,Animals ,Humans ,DNA ,Selection, Genetic ,Energy Metabolism ,Biological Evolution ,Membrane Potentials ,Mitochondria - Abstract
Complex structures are generated and maintained through energy flux. Structures embody information, and biological information is stored in nucleic acids. The progressive increase in biological complexity over geologic time is thus the consequence of the information-generating power of energy flow plus the information-accumulating capacity of DNA, winnowed by natural selection. Consequently, the most important component of the biological environment is energy flow: the availability of calories and their use for growth, survival, and reproduction. Animals can exploit and adapt to available energy resources at three levels. They can evolve different anatomical forms through nuclear DNA (nDNA) mutations permitting exploitation of alternative energy reservoirs, resulting in new species. They can evolve modified bioenergetic physiologies within a species, primarily through the high mutation rate of mitochondrial DNA (mtDNA)–encoded bioenergetic genes, permitting adjustment to regional energetic environments. They can alter the epigenomic regulation of the thousands of dispersed bioenergetic genes via mitochondrially generated high-energy intermediates permitting individual accommodation to short-term environmental energetic fluctuations. Because medicine pertains to a single species, Homo sapiens, functional human variation often involves sequence changes in bioenergetic genes, most commonly mtDNA mutations, plus changes in the expression of bioenergetic genes mediated by the epigenome. Consequently, common nDNA polymorphisms in anatomical genes may represent only a fraction of the genetic variation associated with the common “complex” diseases, and the ascent of man has been the product of 3.5 billion years of information generation by energy flow, accumulated and preserved in DNA and edited by natural selection.
- Published
- 2010
119. Colloquium paper: the cognitive niche: coevolution of intelligence, sociality, and language
- Author
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Steven, Pinker
- Subjects
Male ,Genome, Human ,Colloquium Papers ,Intelligence ,Models, Theoretical ,Biological Evolution ,Cognition ,Species Specificity ,Animals ,Humans ,Female ,Cooperative Behavior ,Problem Solving ,Language - Abstract
Although Darwin insisted that human intelligence could be fully explained by the theory of evolution, the codiscoverer of natural selection, Alfred Russel Wallace, claimed that abstract intelligence was of no use to ancestral humans and could only be explained by intelligent design. Wallace's apparent paradox can be dissolved with two hypotheses about human cognition. One is that intelligence is an adaptation to a knowledge-using, socially interdependent lifestyle, the “cognitive niche.” This embraces the ability to overcome the evolutionary fixed defenses of plants and animals by applications of reasoning, including weapons, traps, coordinated driving of game, and detoxification of plants. Such reasoning exploits intuitive theories about different aspects of the world, such as objects, forces, paths, places, states, substances, and other people's beliefs and desires. The theory explains many zoologically unusual traits in Homo sapiens, including our complex toolkit, wide range of habitats and diets, extended childhoods and long lives, hypersociality, complex mating, division into cultures, and language (which multiplies the benefit of knowledge because know-how is useful not only for its practical benefits but as a trade good with others, enhancing the evolution of cooperation). The second hypothesis is that humans possess an ability of metaphorical abstraction, which allows them to coopt faculties that originally evolved for physical problem-solving and social coordination, apply them to abstract subject matter, and combine them productively. These abilities can help explain the emergence of abstract cognition without supernatural or exotic evolutionary forces and are in principle testable by analyses of statistical signs of selection in the human genome.
- Published
- 2010
120. Colloquium paper: adaptive specializations, social exchange, and the evolution of human intelligence
- Author
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Leda, Cosmides, H Clark, Barrett, and John, Tooby
- Subjects
Ethics ,Behavior ,Cognition ,Colloquium Papers ,Intelligence ,Humans ,Social Behavior ,Biological Evolution ,Models, Biological ,Algorithms - Abstract
Blank-slate theories of human intelligence propose that reasoning is carried out by general-purpose operations applied uniformly across contents. An evolutionary approach implies a radically different model of human intelligence. The task demands of different adaptive problems select for functionally specialized problem-solving strategies, unleashing massive increases in problem-solving power for ancestrally recurrent adaptive problems. Because exchange can evolve only if cooperators can detect cheaters, we hypothesized that the human mind would be equipped with a neurocognitive system specialized for reasoning about social exchange. Whereas humans perform poorly when asked to detect violations of most conditional rules, we predicted and found a dramatic spike in performance when the rule specifies an exchange and violations correspond to cheating. According to critics, people's uncanny accuracy at detecting violations of social exchange rules does not reflect a cheater detection mechanism, but extends instead to all rules regulating when actions are permitted (deontic conditionals). Here we report experimental tests that falsify these theories by demonstrating that deontic rules as a class do not elicit the search for violations. We show that the cheater detection system functions with pinpoint accuracy, searching for violations of social exchange rules only when these are likely to reveal the presence of someone who intends to cheat. It does not search for violations of social exchange rules when these are accidental, when they do not benefit the violator, or when the situation would make cheating difficult.
- Published
- 2010
121. Colloquium paper: genome-wide patterns of population structure and admixture among Hispanic/Latino populations
- Author
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Katarzyna, Bryc, Christopher, Velez, Tatiana, Karafet, Andres, Moreno-Estrada, Andy, Reynolds, Adam, Auton, Michael, Hammer, Carlos D, Bustamante, and Harry, Ostrer
- Subjects
Male ,Principal Component Analysis ,Genome, Human ,Colloquium Papers ,Chromosome Mapping ,Computational Biology ,Bayes Theorem ,Hispanic or Latino ,DNA, Mitochondrial ,United States ,Genetics, Population ,Sex Factors ,Cluster Analysis ,Humans ,Female ,Genome-Wide Association Study - Abstract
Hispanic/Latino populations possess a complex genetic structure that reflects recent admixture among and potentially ancient substructure within Native American, European, and West African source populations. Here, we quantify genome-wide patterns of SNP and haplotype variation among 100 individuals with ancestry from Ecuador, Colombia, Puerto Rico, and the Dominican Republic genotyped on the Illumina 610-Quad arrays and 112 Mexicans genotyped on Affymetrix 500K platform. Intersecting these data with previously collected high-density SNP data from 4,305 individuals, we use principal component analysis and clustering methods FRAPPE and STRUCTURE to investigate genome-wide patterns of African, European, and Native American population structure within and among Hispanic/Latino populations. Comparing autosomal, X and Y chromosome, and mtDNA variation, we find evidence of a significant sex bias in admixture proportions consistent with disproportionate contribution of European male and Native American female ancestry to present-day populations. We also find that patterns of linkage-disequilibria in admixed Hispanic/Latino populations are largely affected by the admixture dynamics of the populations, with faster decay of LD in populations of higher African ancestry. Finally, using the locus-specific ancestry inference method LAMP, we reconstruct fine-scale chromosomal patterns of admixture. We document moderate power to differentiate among potential subcontinental source populations within the Native American, European, and African segments of the admixed Hispanic/Latino genomes. Our results suggest future genome-wide association scans in Hispanic/Latino populations may require correction for local genomic ancestry at a subcontinental scale when associating differences in the genome with disease risk, progression, and drug efficacy, as well as for admixture mapping.
- Published
- 2010
122. Colloquium paper: phylogenomic evidence of adaptive evolution in the ancestry of humans
- Author
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Morris, Goodman and Kirstin N, Sterner
- Subjects
Phenotype ,Pan troglodytes ,Fossils ,Colloquium Papers ,Calibration ,Animals ,Brain ,Humans ,Models, Theoretical ,Biological Evolution ,Phylogeny - Abstract
In Charles Darwin’s tree model for life’s evolution, natural selection adaptively modifies newly arisen species as they branch apart from their common ancestor. In accord with this Darwinian concept, the phylogenomic approach to elucidating adaptive evolution in genes and genomes in the ancestry of modern humans requires a well supported and well sampled phylogeny that accurately places humans and other primates and mammals with respect to one another. For more than a century, first from the comparative immunological work of Nuttall on blood sera and now from comparative genomic studies, molecular findings have demonstrated the close kinship of humans to chimpanzees. The close genetic correspondence of chimpanzees to humans and the relative shortness of our evolutionary separation suggest that most distinctive features of the modern human phenotype had already evolved during our ancestry with chimpanzees. Thus, a phylogenomic assessment of being human should examine earlier stages of human ancestry as well as later stages. In addition, with the availability of a number of mammalian genomes, similarities in phenotype between distantly related taxa should be explored for evidence of convergent or parallel adaptive evolution. As an example, recent phylogenomic evidence has shown that adaptive evolution of aerobic energy metabolism genes may have helped shape such distinctive modern human features as long life spans and enlarged brains in the ancestries of both humans and elephants.
- Published
- 2010
123. Colloquium paper: a role for relaxed selection in the evolution of the language capacity
- Author
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Terrence W, Deacon
- Subjects
Models, Genetic ,Communication ,Colloquium Papers ,Animals ,Brain ,Humans ,Selection, Genetic ,Biological Evolution ,Models, Biological ,Epigenesis, Genetic ,Language - Abstract
Explaining the extravagant complexity of the human language and our competence to acquire it has long posed challenges for natural selection theory. To answer his critics, Darwin turned to sexual selection to account for the extreme development of language. Many contemporary evolutionary theorists have invoked incredibly lucky mutation or some variant of the assimilation of acquired behaviors to innate predispositions in an effort to explain it. Recent evodevo approaches have identified developmental processes that help to explain how complex functional synergies can evolve by Darwinian means. Interestingly, many of these developmental mechanisms bear a resemblance to aspects of Darwin's mechanism of natural selection, often differing only in one respect (e.g., form of duplication, kind of variation, competition/cooperation). A common feature is an interplay between processes of stabilizing selection and processes of relaxed selection at different levels of organism function. These may play important roles in the many levels of evolutionary process contributing to language. Surprisingly, the relaxation of selection at the organism level may have been a source of many complex synergistic features of the human language capacity, and may help explain why so much language information is “inherited” socially.
- Published
- 2010
124. A holistic picture of Austronesian migrations revealed by phylogeography of Pacific paper mulberry.
- Author
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Chi-Shan Chang, Hsiao-Lei Liu, Moncada, Ximena, Seelenfreund, Andrea, Seelenfreund, Daniela, and Kuo-Fang Chung
- Subjects
- *
BROUSSONETIA , *COMMENSALISM , *LAPITA culture , *HERBARIA , *PHYLOGEOGRAPHY - Abstract
The peopling of Remote Oceanic islands by Austronesian speakers is a fascinating and yet contentious part of human prehistory. Linguistic, archaeological, and genetic studies have shown the complex nature of the process in which different components that helped to shape Lapita culture in Near Oceania each have their own unique history. Important evidence points to Taiwan as an Austronesian ancestral homeland with a more distant origin in South China, whereas alternative models favor South China to North Vietnam or a Southeast Asian origin. We test these propositions by studying phylogeography of paper mulberry, a common East Asian tree species introduced and clonally propagated since prehistoric times across the Pacific for making barkcloth, a practical and symbolic component of Austronesian cultures. Using the hypervariable chloroplast sequences of 604 samples collected from East ndhF-rpl32 Asia, Southeast Asia, and Oceanic islands (including 19 historical herbarium specimens from Near and Remote Oceania), 48 haplotypes are detected and haplotype cp-17 is predominant in both Near and Remote Oceania. Because cp-17 has an unambiguous Taiwanese origin and cp-17-carrying Oceanic paper mulberries are clonally propagated, our data concur with expectations of Taiwan as the Austronesian homeland, providing circumstantial support for the "out of Taiwan" hypothesis. Our data also provide insights into the dispersal of paper mulberry from South China "into North Taiwan," the "out of South China-Indochina" expansion to New Guinea, and the geographic origins of post-European introductions of paper mulberry into Oceania. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
125. Colloquium papers: Numbering the hairs on our heads: the shared challenge and promise of phenomics
- Author
-
David, Houle
- Subjects
Phenotype ,Genotype ,Colloquium Papers ,Animals ,Genetic Variation ,Humans ,Selection, Genetic ,Biological Evolution - Abstract
Evolution and medicine share a dependence on the genotype–phenotype map. Although genotypes exist and are inherited in a discrete space convenient for many sorts of analyses, the causation of key phenomena such as natural selection and disease takes place in a continuous phenotype space whose relationship to the genotype space is only dimly grasped. Direct study of genotypes with minimal reference to phenotypes is clearly insufficient to elucidate these phenomena. Phenomics, the comprehensive study of phenotypes, is therefore essential to understanding biology. For all of the advances in knowledge that a genomic approach to biology has brought, awareness is growing that many phenotypes are highly polygenic and susceptible to genetic interactions. Prime examples are common human diseases. Phenomic thinking is starting to take hold and yield results that reveal why it is so critical. The dimensionality of phenotypic data are often extremely high, suggesting that attempts to characterize phenotypes with a few key measurements are unlikely to be completely successful. However, once phenotypic data are obtained, causation can turn out to be unexpectedly simple. Phenotypic data can be informative about the past history of selection and unexpectedly predictive of long-term evolution. Comprehensive efforts to increase the throughput and range of phenotyping are an urgent priority.
- Published
- 2009
126. Colloquium papers: Transfers and transitions: parent-offspring conflict, genomic imprinting, and the evolution of human life history
- Author
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David, Haig
- Subjects
Male ,Genomic Imprinting ,Child Development ,Colloquium Papers ,Puberty ,Humans ,Female ,Parent-Child Relations ,Child ,Adaptation, Physiological ,Biological Evolution - Abstract
Human offspring are weaned earlier than the offspring of other great apes but take longer to reach nutritional independence. An analysis of human disorders of imprinted genes suggests genes of paternal origin, expressed in infants, have been selected to favor more intense suckling than genes of maternal origin. The same analysis suggests that genes of maternal origin may favor slower childhood growth but earlier sexual maturation. These observations are consistent with a hypothesis in which slow maturation was an adaptation of offspring that reduced maternal fitness, whereas early weaning was an adaptation of mothers that reduced the fitness of individual offspring.
- Published
- 2009
127. Colloquium paper: three ambitious (and rather unorthodox) assignments for the field of biodiversity genetics
- Author
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John C, Avise
- Subjects
Species Specificity ,Colloquium Paper ,Animals ,Sequence Analysis, DNA ,Extinction, Biological ,Phylogeny - Abstract
The field of molecular genetics has many roles in biodiversity assessment and conservation. I summarize three of those standard roles and propose logical extensions of each. First, many biologists suppose that a comprehensive picture of the Tree of Life will soon emerge from multilocus DNA sequence data interpreted in concert with fossils and other evidence. If nonreticulate trees are indeed valid metaphors for life's history, then a well dated global phylogeny will offer an opportunity to erect a universally standardized scheme of biological classification. If life's history proves to be somewhat reticulate, a web-like phylogenetic pattern should become evident and will offer opportunities to reevaluate the fundamental nature of evolutionary processes. Second, extensive networks of wildlife sanctuaries offer some hope for shepherding appreciable biodiversity through the ongoing extinction crisis, and molecular genetics can assist in park design by helping to identify key species, historically important biotic areas, and biodiversity hotspots. An opportunity centers on the concept of Pleistocene Parks that could protect “legacy biotas” in much the same way that traditional national parks preserve special geological features and historical landmarks honor legacy events in human affairs. Third, genetic perspectives have become an integral part of many focused conservation efforts by unveiling ecological, behavioral, or evolutionary phenomena relevant to population management. They also can open opportunities to educate the public about the many intellectual gifts and aesthetic marvels of the natural world.
- Published
- 2008
128. Colloquium paper: patterns of biodiversity and endemism on Indo-West Pacific coral reefs
- Author
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Marjorie L, Reaka, Paula J, Rodgers, and Alexei U, Kudla
- Subjects
Greenhouse Effect ,Pacific Ocean ,Species Specificity ,Colloquium Paper ,Water Pollution ,Animals ,social sciences ,Anthozoa ,geographic locations - Abstract
Diversity of the primary groups of contemporary Indo-West Pacific coral reef organisms, including mantis shrimps (stomatopod crustaceans), peaks in the Indo-Australian Archipelago (IAA), reaches a lower peak in East Africa and Madagascar [Indian Ocean continental (IOC)], and declines in the central Indian Ocean (IO) and Central Pacific (CP). Percent endemism in stomatopods (highest in the IAA, high in the IOC, lower in regions adjacent to centers, and moderate in the CP) correlates positively with species diversity (this varies with scale) and inversely with species body size. Because it constrains reproductive traits and dispersal, body size is a reliable indicator of speciation and extinction potential in reef stomatopods and probably most marine organisms. Assemblages are dominated by small-sized species in the IAA and IOC. Both speciation and extinction likely are high, resulting in especially high endemism (small ranges reflect both originating and disappearing species) in these regions. Rates of speciation exceed extinction, yielding centers of diversity (especially in the IAA). Dispersal slows speciation and extinction in areas adjacent to these centers. Body size declines toward the CP, especially in atoll environments. Here the wheels of speciation and extinction again spin rapidly but in the opposite direction (extinction > speciation), yielding low diversity and moderate endemism. We conclude that life histories, dispersal, and speciation/extinction dynamics are primary agents that mold patterns of diversity and endemism. Historical factors, currents, productivity, and species diversity itself (through ecological interactions) also influence these patterns, in some cases by altering body size.
- Published
- 2008
129. Colloquium paper: extinction as the loss of evolutionary history
- Author
-
Douglas H, Erwin
- Subjects
Species Specificity ,Colloquium Paper ,Animals ,Plants ,Extinction, Biological ,human activities ,Biological Evolution - Abstract
Current plant and animal diversity preserves at most 1–2% of the species that have existed over the past 600 million years. But understanding the evolutionary impact of these extinctions requires a variety of metrics. The traditional measurement is loss of taxa (species or a higher category) but in the absence of phylogenetic information it is difficult to distinguish the evolutionary depth of different patterns of extinction: the same species loss can encompass very different losses of evolutionary history. Furthermore, both taxic and phylogenetic measures are poor metrics of morphologic disparity. Other measures of lost diversity include: functional diversity, architectural components, behavioral and social repertoires, and developmental strategies. The canonical five mass extinctions of the Phanerozoic reveals the loss of different, albeit sometimes overlapping, aspects of loss of evolutionary history. The end-Permian mass extinction (252 Ma) reduced all measures of diversity. The same was not true of other episodes, differences that may reflect their duration and structure. The construction of biodiversity reflects similarly uneven contributions to each of these metrics. Unraveling these contributions requires greater attention to feedbacks on biodiversity and the temporal variability in their contribution to evolutionary history. Taxic diversity increases after mass extinctions, but the response by other aspects of evolutionary history is less well studied. Earlier views of postextinction biotic recovery as the refilling of empty ecospace fail to capture the dynamics of this diversity increase.
- Published
- 2008
130. Colloquium paper: where does biodiversity go from here? A grim business-as-usual forecast and a hopeful portfolio of partial solutions
- Author
-
Paul R, Ehrlich and Robert M, Pringle
- Subjects
Greenhouse Effect ,Conservation of Natural Resources ,Species Specificity ,Colloquium Paper ,Animals ,Humans ,Extinction, Biological ,Forecasting - Abstract
The threats to the future of biodiversity are many and well known. They include habitat conversion, environmental toxification, climate change, and direct exploitation of wildlife, among others. Moreover, the projected addition of 2.6 billion people by mid-century will almost certainly have a greater environmental impact than that of the last 2.6 billion. Collectively, these trends portend a grim future for biodiversity under a business-as-usual scenario. These threats and their interactions are formidable, but we review seven strategies that, if implemented soundly and scaled up dramatically, would preserve a substantial portion of global biodiversity. These are actions to stabilize the human population and reduce its material consumption, the deployment of endowment funds and other strategies to ensure the efficacy and permanence of conservation areas, steps to make human-dominated landscapes hospitable to biodiversity, measures to account for the economic costs of habitat degradation, the ecological reclamation of degraded lands and repatriation of extirpated species, the education and empowerment of people in the rural tropics, and the fundamental transformation of human attitudes about nature. Like the carbon “stabilization wedges” outlined by Pacala and Socolow [Pacala S, Socolow R (2004) Stabilization wedges: Solving the climate problem for the next 50 years with current technologies. Science 305:968–972] (1), the science and technologies needed to effect this vision already exist. The remaining challenges are largely social, political, and economic. Although academic conservation biology still has an important role to play in developing technical tools and knowledge, success at this juncture hinges more on a massive mobilization of effort to do things that have traditionally been outside the scope of the discipline.
- Published
- 2008
131. Colloquium paper: species invasions and extinction: the future of native biodiversity on islands
- Author
-
Dov F, Sax and Steven D, Gaines
- Subjects
Geography ,Species Specificity ,Colloquium Paper ,fungi ,food and beverages ,Animals ,social sciences ,Extinction, Biological ,humanities - Abstract
Predation by exotic species has caused the extinction of many native animal species on islands, whereas competition from exotic plants has caused few native plant extinctions. Exotic plant addition to islands is highly nonrandom, with an almost perfect 1 to 1 match between the number of naturalized and native plant species on oceanic islands. Here, we evaluate several alternative implications of these findings. Does the consistency of increase in plant richness across islands imply that a saturation point in species richness has been reached? If not, should we expect total plant richness to continue to increase as new species are added? Finally, is the rarity of native plant extinctions to date a misleading measure of the impact of past invasions, one that hides an extinction debt that will be paid in the future? By analyzing historical records, we show that the number of naturalized plant species has increased linearly over time on many individual islands. Further, the mean ratio of naturalized to native plant species across islands has changed steadily for nearly two centuries. These patterns suggest that many more species will become naturalized on islands in the future. We also discuss how dynamics of invasion bear upon alternative saturation scenarios and the implications these scenarios have for the future retention or extinction of native plant species. Finally, we identify invasion-motivated research gaps (propagule pressure, time-lags to extinction, abundance shifts, and loss of area) that can aid in forecasting extinction and in developing a more comprehensive theory of species extinctions.
- Published
- 2008
132. Colloquium paper: ecological extinction and evolution in the brave new ocean
- Author
-
Jeremy B C, Jackson
- Subjects
Ecology ,Fossils ,Oceans and Seas ,Colloquium Paper ,fungi ,Animals ,Marine Biology ,Water Pollutants ,Extinction, Biological ,Biological Evolution - Abstract
The great mass extinctions of the fossil record were a major creative force that provided entirely new kinds of opportunities for the subsequent explosive evolution and diversification of surviving clades. Today, the synergistic effects of human impacts are laying the groundwork for a comparably great Anthropocene mass extinction in the oceans with unknown ecological and evolutionary consequences. Synergistic effects of habitat destruction, overfishing, introduced species, warming, acidification, toxins, and massive runoff of nutrients are transforming once complex ecosystems like coral reefs and kelp forests into monotonous level bottoms, transforming clear and productive coastal seas into anoxic dead zones, and transforming complex food webs topped by big animals into simplified, microbially dominated ecosystems with boom and bust cycles of toxic dinoflagellate blooms, jellyfish, and disease. Rates of change are increasingly fast and nonlinear with sudden phase shifts to novel alternative community states. We can only guess at the kinds of organisms that will benefit from this mayhem that is radically altering the selective seascape far beyond the consequences of fishing or warming alone. The prospects are especially bleak for animals and plants compared with metabolically flexible microbes and algae. Halting and ultimately reversing these trends will require rapid and fundamental changes in fisheries, agricultural practice, and the emissions of greenhouse gases on a global scale.
- Published
- 2008
133. Colloquium paper: engaging the public in biodiversity issues
- Author
-
Michael J. Novacek
- Subjects
Conservation of Natural Resources ,Multidisciplinary ,business.industry ,media_common.quotation_subject ,Global warming ,Environmental resource management ,Community Participation ,Environmental ethics ,Ecosystem services ,Pleasure ,Public interest ,Outreach ,Species Specificity ,Political science ,Colloquium Paper ,Overpopulation ,Terrorism ,Animals ,Letters ,business ,Family values ,Ecosystem ,media_common - Abstract
To engage people in biodiversity and other environmental issues, one must provide the opportunity for enhanced understanding that empowers individuals to make choices and take action based on sound science and reliable recommendations. To this end, we must acknowledge some real challenges. Recent surveys show that, despite growing public concern, environmental issues still rank below many other problems, such as terrorism, health care, the economy, and (in the U.S.) family values. Moreover, much of the recent upswing in interest in the environment is due to the marked shift in attention to global warming away from other environmental problems such as destruction of ecosystems, water pollution, overpopulation, and biodiversity loss. Such a change in public focus often comes with a tendency to decouple various environmental problems and ignore their synergistic effects. Exacerbating this problem are arguments from the media and other sources that discourage public interest in environmental topics by characterizing the science behind them as overly complex, immersed in debate and controversy, and detached from human interests. Educational programming, media, exhibitions, and other means of public outreach should build on the welcome increase in public interest in global warming by demonstrating the interplay of various environmental disruptions. In the case of biodiversity, the importance of species in providing ecosystem services, natural beauty and pleasure, and sustaining human lives is a message that requires constant attention and recrafting to impact diverse audiences.
- Published
- 2008
134. Chemically coupling SnO2 quantum dots and MXene for efficient CO2 electroreduction to formate and Zn–CO2 battery.
- Author
-
Lili Han, Xianyun Peng, Hsiao-Tsu Wang, Pengfei Ou, Yuying Mi, Chih-Wen Pao, Jigang Zhou, Jian Wang, Xijun Liu, Way-Faung Pong, Jun Song, Zhang Lin, Jun Luo, and Xin, Huolin L.
- Subjects
QUANTUM dots ,ELECTROLYTIC reduction ,CARBON paper ,OPEN-circuit voltage ,X-ray absorption ,X-ray microscopy ,PHOTOVOLTAIC power systems - Abstract
Electrochemical conversion of CO
2 into formate is a promising strategy for mitigating the energy and environmental crisis, but simultaneously achieving high selectivity and activity of electrocatalysts remains challenging. Here, we report low-dimensional SnO2 quantum dots chemically coupled with ultrathin Ti3 C2Tx MXene nanosheets (SnO2 / MXene) that boost the CO2 conversion. The coupling structure is well visualized and verified by high-resolution electron tomography together with nanoscale scanning transmission X-ray microscopy and ptychography imaging. The catalyst achieves a large partial current density of 257.8 mA cm-2 and high Faradaic efficiency of 94% for formate formation. Additionally, the SnO2 /MXene cathode shows excellent Zn–CO2 battery performance, with a maximum power density of 4.28 mW cm-2 , an open-circuit voltage of 0.83 V, and superior rechargeability of 60 h. In situ X-ray absorption spectroscopy analysis and first-principles calculations reveal that this remarkable performance is attributed to the unique and stable structure of the SnO2 /MXene, which can significantly reduce the reaction energy of CO2 hydrogenation to formate by increasing the surface coverage of adsorbed hydrogen. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
135. Nobel and novice: Author prominence affects peer review.
- Author
-
Huber, Jürgen, Inoua, Sabiou, Kerschbamer, Rudolf, König-Kersting, Christian, Palan, Stefan, and Smith, Vernon L.
- Subjects
REPORT writing ,ANONYMOUS authors ,NOBEL Prize winners ,RESEARCH personnel ,ATHLETIC trainers - Abstract
Peer review is a well-established cornerstone of the scientific process, yet it is not immune to biases like status bias, which we explore in this paper. Merton described this bias as prominent researchers getting disproportionately great credit for their contribution, while relatively unknown researchers get disproportionately little credit [R. K. Merton, Science 159, 56–63 (1968)]. We measured the extent of this bias in the peer-review process through a preregistered field experiment. We invited more than 3,300 researchers to review a finance research paper jointly written by a prominent author (a Nobel laureate) and by a relatively unknown author (an early career research associate), varying whether reviewers saw the prominent author’s name, an anonymized version of the paper, or the less-well-known author’s name. We found strong evidence for the status bias: More of the invited researchers accepted to review the paper when the prominent name was shown, and while only 23% recommended “reject” when the prominent researcher was the only author shown, 48% did so when the paper was anonymized, and 65% did when the little-known author was the only author shown. Our findings complement and extend earlier results on double-anonymized vs. singleanonymized review. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
136. Abstracts of Papers Presented at the Autumn Meeting of the National Academy of Sciences USA, Washington, D.C., 16 October 1972
- Author
-
Shockley, W. and Yew, Man-Li S.
- Published
- 1973
137. Note on Mr. King's Paper: "The Crystal Structure of Strontium"
- Author
-
Simon, F. and Vohsen, E.
- Published
- 1929
138. Reviewer bias in single- versus double-blind peer review.
- Author
-
Tomkins, Andrew, Min Zhang, and Heavlin, William D.
- Subjects
DATA mining ,COMPUTER science ,WEB search engines ,INFORMATION asymmetry ,COMPUTER systems - Abstract
Peer review may be "single-blind," in which reviewers are aware of the names and affiliations of paper authors, or "double-blind," in which this information is hidden. Noting that computer science research often appears first or exclusively in peer-reviewed conferences rather than journals, we study these two reviewing models in the context of the 10th Association for Computing Machinery International Conference on Web Search and Data Mining, a highly selective venue (15.6% acceptance rate) in which expert committee members review full-length submissions for acceptance. We present a controlled experiment in which four committee members review each paper. Two of these four reviewers are drawn from a pool of committee members with access to author information; the other two are drawn from a disjoint pool without such access. This information asymmetry persists through the process of bidding for papers, reviewing papers, and entering scores. Reviewers in the single-blind condition typically bid for 22% fewer papers and preferentially bid for papers from top universities and companies. Once papers are allocated to reviewers, single-blind reviewers are significantly more likely than their double-blind counterparts to recommend for acceptance papers from famous authors, top universities, and top companies. The estimated odds multipliers are tangible, at 1.63, 1.58, and 2.10, respectively. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
139. Machine learning meets physics: A two-way street.
- Author
-
Levine, Herbert and Yuhai Tu
- Subjects
MACHINE learning ,PHYSICS education ,ARTIFICIAL neural networks ,STATISTICAL learning ,BIOPHYSICS ,PHYSICAL sciences ,NEWTON'S laws of motion - Abstract
This document is a compilation of various scientific papers and preprints covering a wide range of topics, including protein folding, cell migration, machine learning, deep neural networks, neural scaling laws, representations and generalization in artificial and brain neural networks, and the neuron as a direct data-driven controller. The papers discuss different aspects of these subjects, providing a comprehensive overview of the current research in these fields. This document can be a valuable resource for library patrons conducting research on these topics, particularly in the fields of neuroscience and artificial intelligence. [Extracted from the article]
- Published
- 2024
- Full Text
- View/download PDF
140. How many scientific papers are not original?
- Author
-
Michael Lesk
- Subjects
Multidisciplinary ,Copying ,Computer science ,Physical Sciences ,Library science ,Editorial board ,Filter (software) - Abstract
Is plagiarism afflicting science? In PNAS, Citron and Ginsparg (1) count the number of authors who are submitting articles containing text already appearing elsewhere. They report disturbing numbers of authors resorting to copying, particularly in some countries where 15% of submissions are detected as containing duplicated material. I am on the editorial board of an Institute of Electrical and Electronic Engineers (IEEE) magazine, which also finds it useful to run all of the submissions through a plagiarism filter. What can be done about this?
- Published
- 2014
141. The simultaneous evolution of author and paper networks.
- Author
-
Börner, Katy, Maru, Jeegar T., and Goldstone, Robert L.
- Subjects
- *
SCIENTIFIC literature , *COMPUTERS , *INTELLECTUAL property , *STATICS , *ALGORITHMS , *RESEARCH - Abstract
There has been a long history of research into the structure and evolution of mankind's scientific endeavor. However, recent progress in applying the tools of science to understand science itself has been unprecedented because only recently has there been access to high-volume and high-quality data sets of scientific output (e.g., publications, patents, grants) and computers and algorithms capable of handling this enormous stream of data. This article reviews major work on models that aim to capture and recreate the structure and dynamics of scientific evolution. We then introduce a general process model that aim to capture and recreate the structure and dynamics of scientific evolution. We then introduce a general process model that simultaneously grows coauthor and paper citation networks. The statistical and dynamic property of the networks generated by this model are validated against a 20-year data set of article published in PNAS. Systematic deviations from a power law distribution of citations to papers are well fit by a model that incorporates a partitioning of authors and papers into topics, a bias for authors to cite recent papers, and a tendency for authors to cite papers cited by papers, and a tendency for authors to cite papers cited by papers that they have read. In this TARL Model (for topics, aging, and recursive linking), the number of topics is linearly related to the clustering coefficient of the simulated paper citation network. [ABSTRACT FROM AUTHOR]
- Published
- 2004
- Full Text
- View/download PDF
142. Crossmaps: Visualization of overlapping relationships in collections of journal papers.
- Author
-
Morris, Steven A. and Yen, Gary G.
- Subjects
- *
SCIENTIFIC literature , *SCIENCE , *RESEARCH , *PERIODICALS , *AUTHORS , *SCIENTISTS - Abstract
A crossmapping technique is introduced for visualizing multiple and overlapping relations among entity types in collections of journal articles. Groups of entities from So entity types are crossplotted to show correspondence of relations. For example, author collaboration groups are plotted on the x axis against groups of papers (research fronts) on the y axis. At the intersection of each pair of author group/Search front pairs a circular symbol is plotted whose size is proportional to the dumber of times that authors in the group appear as authors in pipers in the research front. Entity groups are found by agglomerative hierarchical clustering using conventional similarity measures. Crossmaps comprise a simple technique that is particularly suited to showing overlap in relations among entity groups. Particularly useful crossmaps are: research fronts against base reference clusters, research fronts against author collaboration groups, and research fronts against term co-occurrence clusters. When exploring the knowledge domain of a collection of journal papers, it is useful to have several crossmaps of different entity pairs, complemented by research front timelines and base reference cluster timelines. [ABSTRACT FROM AUTHOR]
- Published
- 2004
- Full Text
- View/download PDF
143. System transitions research and sustainable development: Challenges, progress, and prospects.
- Author
-
Geels, Frank W., Kern, Florian, and Clark, William C.
- Subjects
CAR sharing ,BICYCLE sharing programs ,FOOD prices ,SUSTAINABLE development ,RUSSIAN invasion of Ukraine, 2022- - Published
- 2023
- Full Text
- View/download PDF
144. Massive covidization of research citations and the citation elite.
- Author
-
Ioannidis, John P. A., Bendavid, Eran, Salholz-Hillel, Maia, Boyack, Kevin W., and Baas, Jeroen
- Subjects
COVID-19 pandemic ,SCIENCE publishing ,COVID-19 ,INTERNAL medicine - Abstract
Massive scientific productivity accompanied the COVID-19 pandemic. We evaluated the citation impact of COVID-19 publications relative to all scientific work published in 2020 to 2021 and assessed the impact on scientist citation profiles. Using Scopus data until August 1, 2021, COVID-19 items accounted for 4% of papers published, 20% of citations received to papers published in 2020 to 2021, and >30% of citations received in 36 of the 174 disciplines of science (up to 79.3% in general and internal medicine). Across science, 98 of the 100 most-cited papers published in 2020 to 2021 were related to COVID-19; 110 scientists received ≥10,000 citations for COVID-19 work, but none received ≥10,000 citations for non–COVID-19 work published in 2020 to 2021. For many scientists, citations to their COVID-19 work already accounted for more than half of their total career citation count. Overall, these data show a strong covidization of research citations across science, with major impact on shaping the citation elite. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
145. Digital printing of shape-morphing natural materials.
- Author
-
Ze Zhao, Kumar, Jatin, Youngkyu Hwang, Jingyu Deng, Bin Ibrahim, Mohammed Shahrudin, Changjin Huang, Suresh, Subra, and Nam-Joon Cho
- Subjects
DIGITAL printing ,FINITE element method - Abstract
We demonstrate how programmable shape evolution and deformation can be induced in plant-based natural materials through standard digital printing technologies. With nonallergenic pollen paper as the substrate material, we show how specific geometrical features and architectures can be custom designed through digital printing of patterns to modulate hygrophobicity, geometry, and complex shapes. These autonomously hygromorphing configurations can be "frozen" by postprocessing coatings to meet the needs of a wide spectrum of uses and applications. Through computational simulations involving the finite element method and accompanying experiments, we develop quantitative insights and a general framework for creating complex shapes in eco-friendly natural materials with potential sustainable applications for scalable manufacturing. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
146. A suggestion on improving mathematically heavy papers.
- Author
-
Kane A
- Subjects
- Biological Evolution, Communication Barriers, Ecology methods, Information Dissemination methods, Mathematics
- Published
- 2012
- Full Text
- View/download PDF
147. A co-opted steroid synthesis gene, maintained in sorghum but not maize, is associated with a divergence in leaf wax chemistry.
- Author
-
Busta, Lucas, Schmitz, Elizabeth, Kosma, Dylan K., Schnable, James C., and Cahoon, Edgar B.
- Subjects
STEROID synthesis ,SORGHUM ,GENES ,CORN ,PLANT-water relationships ,CARBON paper - Abstract
Virtually all land plants are coated in a cuticle, a waxy polyester that prevents nonstomatal water loss and is important for heat and drought tolerance. Here, we describe a likely genetic basis for a divergence in cuticular wax chemistry between Sorghum bicolor, a drought tolerant crop widely cultivated in hot climates, and its close relative Zea mays (maize). Combining chemical analyses, heterologous expression, and comparative genomics, we reveal that: 1) sorghum and maize leaf waxes are similar at the juvenile stage but, after the juvenile-to-adult transition, sorghum leaf waxes are rich in triterpenoids that are absent from maize; 2) biosynthesis of the majority of sorghum leaf triterpenoids is mediated by a gene that maize and sorghum both inherited from a common ancestor but that is only functionally maintained in sorghum; and 3) sorghum leaf triterpenoids accumulate in a spatial pattern that was previously shown to strengthen the cuticle and decrease water loss at high temperatures. These findings uncover the possibility for resurrection of a cuticular triterpenoid-synthesizing gene in maize that could create a more heat-tolerant water barrier on the plant's leaf surfaces. They also provide a fundamental understanding of sorghum leaf waxes that will inform efforts to divert surface carbon to intracellular storage for bioenergy and bioproduct innovations. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
148. Spatial evolutionary games with weak selection
- Author
-
Nanda, Mridu and Durrett, Richard
- Published
- 2017
149. Colloquium paper: human skin pigmentation as an adaptation to UV radiation.
- Author
-
Jablonski NG and Chaplin G
- Subjects
- Adaptation, Physiological, Biological Evolution, Female, Folic Acid metabolism, Genetic Variation, Geography, Humans, Male, Photolysis, Reactive Oxygen Species, Sunlight, Tetrahydrofolates chemistry, Ultraviolet Rays, Skin pathology, Skin radiation effects, Skin Pigmentation
- Abstract
Human skin pigmentation is the product of two clines produced by natural selection to adjust levels of constitutive pigmentation to levels of UV radiation (UVR). One cline was generated by high UVR near the equator and led to the evolution of dark, photoprotective, eumelanin-rich pigmentation. The other was produced by the requirement for UVB photons to sustain cutaneous photosynthesis of vitamin D(3) in low-UVB environments, and resulted in the evolution of depigmented skin. As hominins dispersed outside of the tropics, they experienced different intensities and seasonal mixtures of UVA and UVB. Extreme UVA throughout the year and two equinoctial peaks of UVB prevail within the tropics. Under these conditions, the primary selective pressure was to protect folate by maintaining dark pigmentation. Photolysis of folate and its main serum form of 5-methylhydrofolate is caused by UVR and by reactive oxygen species generated by UVA. Competition for folate between the needs for cell division, DNA repair, and melanogenesis is severe under stressful, high-UVR conditions and is exacerbated by dietary insufficiency. Outside of tropical latitudes, UVB levels are generally low and peak only once during the year. The populations exhibiting maximally depigmented skin are those inhabiting environments with the lowest annual and summer peak levels of UVB. Development of facultative pigmentation (tanning) was important to populations settling between roughly 23 degrees and 46 degrees , where levels of UVB varied strongly according to season. Depigmented and tannable skin evolved numerous times in hominin evolution via independent genetic pathways under positive selection.
- Published
- 2010
- Full Text
- View/download PDF
150. Colloquium paper: genome-wide patterns of population structure and admixture among Hispanic/Latino populations.
- Author
-
Bryc K, Velez C, Karafet T, Moreno-Estrada A, Reynolds A, Auton A, Hammer M, Bustamante CD, and Ostrer H
- Subjects
- Bayes Theorem, Chromosome Mapping, Cluster Analysis, Computational Biology methods, DNA, Mitochondrial genetics, Female, Genome-Wide Association Study, Hispanic or Latino, Humans, Male, Principal Component Analysis, Sex Factors, United States, Genetics, Population, Genome, Human
- Abstract
Hispanic/Latino populations possess a complex genetic structure that reflects recent admixture among and potentially ancient substructure within Native American, European, and West African source populations. Here, we quantify genome-wide patterns of SNP and haplotype variation among 100 individuals with ancestry from Ecuador, Colombia, Puerto Rico, and the Dominican Republic genotyped on the Illumina 610-Quad arrays and 112 Mexicans genotyped on Affymetrix 500K platform. Intersecting these data with previously collected high-density SNP data from 4,305 individuals, we use principal component analysis and clustering methods FRAPPE and STRUCTURE to investigate genome-wide patterns of African, European, and Native American population structure within and among Hispanic/Latino populations. Comparing autosomal, X and Y chromosome, and mtDNA variation, we find evidence of a significant sex bias in admixture proportions consistent with disproportionate contribution of European male and Native American female ancestry to present-day populations. We also find that patterns of linkage-disequilibria in admixed Hispanic/Latino populations are largely affected by the admixture dynamics of the populations, with faster decay of LD in populations of higher African ancestry. Finally, using the locus-specific ancestry inference method LAMP, we reconstruct fine-scale chromosomal patterns of admixture. We document moderate power to differentiate among potential subcontinental source populations within the Native American, European, and African segments of the admixed Hispanic/Latino genomes. Our results suggest future genome-wide association scans in Hispanic/Latino populations may require correction for local genomic ancestry at a subcontinental scale when associating differences in the genome with disease risk, progression, and drug efficacy, as well as for admixture mapping.
- Published
- 2010
- Full Text
- View/download PDF
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