Pássaros extintos do Cretáceo voavam!!!

quarta-feira, novembro 14, 2018


The most complete enantiornithine from North America and a phylogenetic analysis of the Avisauridae

Jessie Atterholt1,2,3, J. Howard Hutchison1, Jingmai K. O’Connor4,5

November 13, 2018

Author and article information

1Department of Integrative Biology, University of California, Berkeley, CA, USA
2Raymond M. Alf Museum of Paleontology, Claremont, CA, USA
3Graduate College of Biomedical Sciences, Western University of Health Sciences, Pomona, CA, USA
4Key Laboratory of Vertebrate Evolution, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, People’s Republic of China
5CAS Center for Excellence in Life and Paleoenvironment, Beijing, People’s Republic of China 
Published2018-11-13Accepted2018-10-08Received2018-03-28 Academic EditorFabien Knoll Subject Areas Evolutionary Studies, Paleontology Keywords Enantiornithes, Evolution, Late Cretaceous, Fossil bird Copyright© 2018 Atterholt et al. Licence This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ) and either DOI or URL of the article must be cited. Cite this article Atterholt J, Hutchison JH, O’Connor JK. (2018) The most complete enantiornithine from North America and a phylogenetic analysis of the Avisauridae. PeerJ 6:e5910 https://doi.org/10.7717/peerj.5910

The authors have chosen to make the review history of this article public. 



A skeletal reconstruction of Mirarce eatoni showing preserved skeletal elements (white).

A skeletal reconstruction of Mirarce eatoni showing preserved skeletal elements (white).
Illustration: Scott Hartman.
Abstract

The most complete known North American enantiornithine was collected in 1992 but never formally described. The so-called “Kaiparowits avisaurid” remains one of the most exceptional Late Cretaceous enantiornithine fossils. We recognize this specimen as a new taxon, Mirarce eatoni (gen. et sp. nov.), and provide a complete anatomical description. We maintain that the specimen is referable to the Avisauridae, a clade previously only known in North America from isolated tarsometatarsi. Information from this specimen helps to clarify evolutionary trends within the Enantiornithes. Its large body size supports previously observed trends toward larger body mass in the Late Cretaceous. However, trends toward increased fusion of compound elements across the clade as a whole are weak compared to the Ornithuromorpha. The new specimen reveals for the first time the presence of remige papillae in the enantiornithines, indicating this feature was evolved in parallel to dromaeosaurids and derived ornithuromorphs. Although morphology of the pygostyle and (to a lesser degree) the coracoid and manus appear to remain fairly static during the 65 million years plus of enantiornithine evolution, by the end of the Mesozoic at least some enantiornithine birds had evolved several features convergent with the Neornithes including a deeply keeled sternum, a narrow furcula with a short hypocleidium, and ulnar quill knobs—all features that indicate refinement of the flight apparatus and increased aerial abilities. We conduct the first cladistic analysis to include all purported avisuarid enantiornithines, recovering an Avisauridae consisting of a dichotomy between North and South American taxa. Based on morphological observations and supported by cladistic analysis, we demonstrate Avisaurus to be paraphyletic and erect a new genus for “A. gloriae,” Gettyia gen. nov.

Cite this as Atterholt J, Hutchison JH, O’Connor JK. (2018) The most complete enantiornithine from North America and a phylogenetic analysis of the Avisauridae. PeerJ 6:e5910 https://doi.org/10.7717/peerj.5910  


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Nova teoria sobre a origem da água na Terra

Origin of Earth's Water: Chondritic Inheritance Plus Nebular Ingassing and Storage of Hydrogen in the Core

Jun Wu, Steven J. Desch, Laura Schaefer, Linda T. Elkins‐Tanton, Kaveh Pahlevan
Peter R. Buseck

First published: 09 October 2018 


Source/Fonte: NASA

Abstract

Recent developments in planet formation theory and measurements of low D/H in deep mantle material support a solar nebula source for some of Earth's hydrogen. Here we present a new model for the origin of Earth's water that considers both chondritic water and nebular ingassing of hydrogen. The largest embryo that formed Earth likely had a magma ocean while the solar nebula persisted and could have ingassed nebular gases. The model considers iron hydrogenation reactions during Earth's core formation as a mechanism for both sequestering hydrogen in the core and simultaneously fractionating hydrogen isotopes. By parameterizing the isotopic fractionation factor and initial bulk D/H ratio of Earth's chondritic material, we explore the combined effects of elemental dissolution and isotopic fractionation of hydrogen in iron. By fitting to the two key constraints (three oceans' worth of water in Earth's mantle and on its surface; and D/H in the bulk silicate Earth close to 150 × 10−6), the model searches for best solutions among ~10,000 different combinations of chondritic and nebular contributions. We find that ingassing of a small amount, typically >0–0.5 oceans of nebular hydrogen, is generally demanded, supplementing seven to eight oceans from chondritic contributions. About 60% of the total hydrogen enters the core, and attendant isotopic fractionation plausibly lowers the core's D/H to ~130 × 10−6. Crystallized magma ocean material may have D/H ≈ 110 × 10−6. These modeling results readily explain the low D/H in core‐mantle boundary material and account for Earth's inventory of solar neon and helium.

Plain Language Summary

People have long had curiosity in the origin of Earth's water (equivalently hydrogen). Solar nebula has been given the least attention among existing theories, although it was the predominating reservoir of hydrogen in our early solar system. Here we present a first model for Earth's water origin that quantifies contribution from the solar nebula in addition to that from chondrites, the primary building blocks of Earth. The model considers dissolution of nebular hydrogen into the early Earth's magma oceans and reaction between hydrogen and iron droplets within the magma ocean. Such processes not only delivered countless hydrogen atoms from the mantle to the core but also generated an appreciable difference in hydrogen isotopic composition (2H/1H ratio) between the mantle and core. Fitting the model to current knowledge about Earth's hydrogen produces best combinations of nebular and chondritic contributions to Earth's water. We find that nearly one out of every 100 water molecules on Earth came from the solar nebula. Our planet hides majority of its water inside, with roughly two oceans in the mantle and four to five oceans in the core. These results suggest inevitable formation of water on sufficiently large rocky planets in extrasolar systems.             

Conjectura e hipótese: a importância de verificações da realidade

segunda-feira, novembro 12, 2018

Conjecture and hypothesis: The importance of reality checks

David Deamer

Department of Biomolecular Engineering, University of California, Santa Cruz CA 95060, USA 

Corresponding author email

This article is part of the Thematic Series "From prebiotic chemistry to molecular evolution".

Guest Editor: L. Cronin 

Beilstein J. Org. Chem. 2017, 13, 620–624. doi:10.3762/bjoc.13.60 

Received 01 Jan 2017, Accepted 15 Mar 2017, Published 28 Mar 2017

Abstract

In origins of life research, it is important to understand the difference between conjecture and hypothesis. This commentary explores the difference and recommends alternative hypotheses as a way to advance our understanding of how life can begin on the Earth and other habitable planets. As an example of how this approach can be used, two conditions have been proposed for sites conducive to the origin of life: hydrothermal vents in salty seawater, and fresh water hydrothermal fields associated with volcanic landmasses. These are considered as alternative hypotheses and the accumulating weight of evidence for each site is described and analyzed.

Keywords: hydrothermal fields; hydrothermal vents; origin of life; polymerization by condensation; protocells

FREE PDF GRATIS: Beilstein J. Org. Chem.

A teoria neutra da evolução à luz da seleção natural

The Neutral Theory in Light of Natural Selection 

Andrew D Kern Matthew W Hahn

Molecular Biology and Evolution, Volume 35, Issue 6, 1 June 2018, Pages 1366–1371, https://doi.org/10.1093/molbev/msy092

Published: 02 May 2018


Abstract

In this perspective, we evaluate the explanatory power of the neutral theory of molecular evolution, 50 years after its introduction by Kimura. We argue that the neutral theory was supported by unreliable theoretical and empirical evidence from the beginning, and that in light of modern, genome-scale data, we can firmly reject its universality. The ubiquity of adaptive variation both within and between species means that a more comprehensive theory of molecular evolution must be sought.

Keywords natural selection, neutral theory, population genetics

Teóricos debatem quão ‘neutra’ é realmente a evolução

The neutral theory of molecular evolution proposed by Motoo Kimura has dominated the landscape of evolutionary theory for half a century, but it continues to face challenges.


Source/Fonte: Duong Thuy Nguyen for Quanta Magazine

When Charles Darwin articulated his theory of evolution by natural selection in On the Origin of Species in 1859, he focused on adaptations — the changes that enable organisms to survive in new or changing environments. Selection for favorable adaptations, he suggested, allowed ancient ancestral forms to gradually diversify into countless species.

That concept was so powerful that we might assume evolution is all about adaptation. So it can be surprising to learn that for half a century, a prevailing view in scholarly circles has been that it’s not.

Selection isn’t in doubt, but many scientists have argued that most evolutionary changes appear at the level of the genome and are essentially random and neutral. Adaptive changes groomed by natural selection might indeed sculpt a fin into a primitive foot, they said, but those changes make only a small contribution to the evolutionary process, in which the composition of DNA varies most often without any real consequences.

But now some scientists are pushing back against this idea, known as neutral theory, saying that genomes show much more evidence of evolved adaptation than the theory would dictate. This debate is important because it affects our understanding of the mechanisms that generate biodiversity, our inferences about how the sizes of natural populations have changed over time and our ability to reconstruct the evolutionary history of species (including our own). What lies in the future might be a new era that draws from the best of neutral theory while also recognizing the real, empirically supported influence of selection.

An “Appreciable Fraction” of Variation

Darwin’s core insight was that organisms with disadvantageous traits would slowly be weeded out through negative (or purifying) selection, while those with advantageous features would reproduce more often and pass those features on to the next generation (positive selection). Selection would help to spread and refine those valuable traits. For most of the first half of the 20th century, population geneticists largely attributed genetic differences between populations and species to adaptation through positive selection.





But in 1968, the famed population geneticist Motoo Kimura resisted the adaptationist perspective with his neutral theory of molecular evolution. In a nutshell, he argued that an “appreciable fraction” of the genetic variation within and between species is the result of genetic drift — that is, the effects of randomness in a finite population — rather than natural selection, and that most of these differences have no functional consequences for survival and reproduction.

The following year, the biologists Jack Lester King and Thomas Jukes published “Non-Darwinian Evolution,” an article that likewise emphasized the importance of random genetic changes in the course of evolution. A polarized debate subsequently emerged between the new neutralists and the more traditional adaptationists. Although everyone agreed that purifying selection would weed out deleterious mutations, the neutralists were convinced that genetic drift accounts for most differences between populations or species, whereas the adaptationists credited them to positive selection for adaptive traits.

Much of the debate has hinged on exactly what Kimura meant by “appreciable fraction” of genetic variation, according to Jeffrey Townsend, a biostatistician and professor of evolutionary biology at the Yale School of Public Health. “Is that 50 percent? Is it 5 percent, 0.5 percent? I don’t know,” he said. Because Kimura’s original statement of the theory was qualitative rather than quantitative, “his theory could not be invalidated by later data.”

Nevertheless, neutral theory was rapidly adopted by many biologists. This was partly a result of Kimura’s reputation as one of the most prominent theoretical population geneticists of the time, but it also helped that the mathematics of the theory was relatively simple and intuitive. “One of the reasons for the popularity of the neutral theory was that it made things a lot easier,” said Andrew Kern, a population geneticist now at the University of Oregon, who contributed an article with Matthew Hahn, a population geneticist at Indiana University, to a special issue of Molecular Biology and Evolution celebrating the 50th anniversary of neutral theory.

To apply a neutral model of evolution to a population, Hahn explained, you don’t have to know how strong selection is, how large the population is, whether mutations are dominant or recessive, or whether mutations interact with other mutations. In neutral theory, “all of those very hard parameters to estimate go away.”


...

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Interações ao redor do campo receptivo central medeiam a codificação de contraste espacial dependente do contexto na retina

quinta-feira, novembro 08, 2018

Receptive field center-surround interactions mediate context-dependent spatial contrast encoding in the retina

Maxwell H Turner, Gregory W Schwartz, Fred Rieke

University of Washington, United States; Northwestern University, United States

RESEARCH ARTICLE Sep 6, 2018


Abstract

Antagonistic receptive field surrounds are a near-universal property of early sensory processing. A key assumption in many models for retinal ganglion cell encoding is that receptive field surrounds are added only to the fully formed center signal. But anatomical and functional observations indicate that surrounds are added before the summation of signals across receptive field subunits that creates the center. Here, we show that this receptive field architecture has an important consequence for spatial contrast encoding in the macaque monkey retina: the surround can control sensitivity to fine spatial structure by changing the way the center integrates visual information over space. The impact of the surround is particularly prominent when center and surround signals are correlated, as they are in natural stimuli. This effect of the surround differs substantially from classic center-surround models and raises the possibility that the surround plays unappreciated roles in shaping ganglion cell sensitivity to natural inputs.


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Circuitos da retina: como nós vemos a floresta e as árvores

Retinal Circuits: How we see the forest and the trees

Jeffrey S Diamond 

National Institute of Neurological Disorders and Stroke, United States

INSIGHT Oct 12, 2018



Abstract

Signaling pathways in the retina help us see spatial detail in our visual world.

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Como as ideias viralizam na Academia

quarta-feira, novembro 07, 2018

Prestige drives epistemic inequality in the diffusion of scientific ideas

Allison C. Morgan, Dimitrios J. Economou, Samuel F. Way and Aaron Clausetile

EPJ Data Science20187:40


Received: 30 May 2018 Accepted: 7 October 2018 Published: 19 October 2018

Students attend a computer science class at CU Boulder. (Credit: Glenn Asakawa/CU Boulder)

Abstract

The spread of ideas in the scientific community is often viewed as a competition, in which good ideas spread further because of greater intrinsic fitness, and publication venue and citation counts correlate with importance and impact. However, relatively little is known about how structural factors influence the spread of ideas, and specifically how where an idea originates might influence how it spreads. Here, we investigate the role of faculty hiring networks, which embody the set of researcher transitions from doctoral to faculty institutions, in shaping the spread of ideas in computer science, and the importance of where in the network an idea originates. We consider comprehensive data on the hiring events of 5032 faculty at all 205 Ph.D.-granting departments of computer science in the U.S. and Canada, and on the timing and titles of 200,476 associated publications. Analyzing five popular research topics, we show empirically that faculty hiring can and does facilitate the spread of ideas in science. Having established such a mechanism, we then analyze its potential consequences using epidemic models to simulate the generic spread of research ideas and quantify the impact of where an idea originates on its longterm diffusion across the network. We find that research from prestigious institutions spreads more quickly and completely than work of similar quality originating from less prestigious institutions. Our analyses establish the theoretical trade-offs between university prestige and the quality of ideas necessary for efficient circulation. Our results establish faculty hiring as an underlying mechanism that drives the persistent epistemic advantage observed for elite institutions, and provide a theoretical lower bound for the impact of structural inequality in shaping the spread of ideas in science.

Keywords Social inequality Sociology of science Computational social science Faculty hiring networks Information diffusion 

FREE PDF: EPJ Data Science

Nosso cérebro é como 100 bilhões de minicomputadores todos funcionando sincronizados: mero acaso, fortuita necessidade ou design inteligente???

quinta-feira, outubro 18, 2018

Cell
Article| Volume 175, ISSUE 3, P643-651.e14, October 18, 2018


Enhanced Dendritic Compartmentalization in Human Cortical Neurons

Lou Beaulieu-Laroche, Enrique H.S. Toloza, Marie-Sophie van der Goes, Matthew P. Frosch, Sydney S. Cash, Mark T. Harnett5

Source/Fonte: New Scientist

Highlights

• Direct electrical recordings to compare human and rat cortical dendrites
• Longer human dendrites exhibit increased electrical compartmentalization
• Reduced ion channel densities in human dendrites
• Compartmentalization alters the input-output properties of human neurons

Summary

The biophysical features of neurons shape information processing in the brain. Cortical neurons are larger in humans than in other species, but it is unclear how their size affects synaptic integration. Here, we perform direct electrical recordings from human dendrites and report enhanced electrical compartmentalization in layer 5 pyramidal neurons. Compared to rat dendrites, distal human dendrites provide limited excitation to the soma, even in the presence of dendritic spikes. Human somas also exhibit less bursting due to reduced recruitment of dendritic electrogenesis. Finally, we find that decreased ion channel densities result in higher input resistance and underlie the lower coupling of human dendrites. We conclude that the increased length of human neurons alters their input-output properties, which will impact cortical computation.

FREE PDF GRATIS: Cell

Campanha de Bolsonaro aplica seu próprio viés político à educação???

terça-feira, outubro 16, 2018

“Quando você iguala ciência e ideologia, você anda para trás, ignora séculos de aprendizado”, diz Luiz Davidovich, presidente da Academia Brasileira de Ciências. “A teoria da evolução não é ideológica. É resultado de percepções científicas e foi testada ao longo do tempo.”

in Campanha de Bolsonaro aplica seu próprio viés político à educação.

Davidovich cometeu dois erros:

1. A teoria da evolução é sim ideológica - quem disse foi Darwin em uma de suas cartas que pelo menos ele tinha dado um chega pra lá no criacionismo; 
2. A teoria da evolução foi testada em nível microevolutivo, macroevolutivo, não! A descendência com modificação ao longo do tempo, por exemplo. Nunca explicaram a Explosão Cambriana. Quais são os mecanismos evolucionários? De A a Z? Qual a origem da informação genética? Por que do upgrade para a Síntese Evolutiva Ampliada/Estendida com aspectos neolamarckistas porque a Síntese Evolutiva Moderna já era em 1980 uma teoria científica falida que posava de ortodoxia científica somente nos livros-texto??? 

Sim, a teoria da evolução deve continuar sendo ensinada em nossas escolas, mas deve ser ensinada objetiva e honestamente considerando as evidências a favor e contra. Do jeito que a teoria da evolução é ensinada no Brasil, não é educação, mas doutrinação ideológica do materialismo filosófico que posa como se fosse ciência!

Como a geologia conta a história dos gargalos evolutivos e da vida na Terra

AstrobiologyVol. 18, No. 9 Hypothesis ArticlesFree Access
Geological and Geochemical Constraints on the Origin and Evolution of Life
Norman H. Sleep
Published Online:12 Sep 2018 https://doi.org/10.1089/ast.2017.1778
 
 Source/Fonte: Nature - NASA

Abstract

The traditional tree of life from molecular biology with last universal common ancestor (LUCA) branching into bacteria and archaea (though fuzzy) is likely formally valid enough to be a basis for discussion of geological processes on the early Earth. Biologists infer likely properties of nodal organisms within the tree and, hence, the environment they inhabited. Geologists both vet tenuous trees and putative origin of life scenarios for geological and ecological reasonability and conversely infer geological information from trees. The latter approach is valuable as geologists have only weakly constrained the time when the Earth became habitable and the later time when life actually existed to the long interval between ∼4.5 and ∼3.85 Ga where no intact surface rocks are known. With regard to vetting, origin and early evolution hypotheses from molecular biology have recently centered on serpentinite settings in marine and alternatively land settings that are exposed to ultraviolet sunlight. The existence of these niches on the Hadean Earth is virtually certain. With regard to inferring geological environment from genomics, nodes on the tree of life can arise from true bottlenecks implied by the marine serpentinite origin scenario and by asteroid impact. Innovation of a very useful trait through a threshold allows the successful organism to quickly become very abundant and later root a large clade. The origin of life itself, that is, the initial Darwinian ancestor, the bacterial and archaeal roots as free-living cellular organisms that independently escaped hydrothermal chimneys above marine serpentinite or alternatively from shallow pore-water environments on land, the Selabacteria root with anoxygenic photosynthesis, and the Terrabacteria root colonizing land are attractive examples that predate the geological record. Conversely, geological reasoning presents likely events for appraisal by biologists. Asteroid impacts may have produced bottlenecks by decimating life. Thermophile roots of bacteria and archaea as well as a thermophile LUCA are attractive.

FREE PDF GRATIS: Astrobiology
 

O problema cosmológico do lítio: uma das incógnitas na descrição atual do Big Bang

sexta-feira, outubro 12, 2018

7Be(n,p)7Li Reaction and the Cosmological Lithium Problem: Measurement of the Cross Section in a Wide Energy Range at n_TOF at CERN

L. Damone et al. (The n_TOF Collaboration [www.cern.ch/ntof])
Phys. Rev. Lett. 121, 042701 – Published 24 July 2018
Abstract
We report on the measurement of the 7Be(n,p)7Li cross section from thermal to approximately 325 keV neutron energy, performed in the high-flux experimental area (EAR2) of the n_TOF facility at CERN. This reaction plays a key role in the lithium yield of the big bang nucleosynthesis (BBN) for standard cosmology. The only two previous time-of-flight measurements performed on this reaction did not cover the energy window of interest for BBN, and they showed a large discrepancy between each other. The measurement was performed with a Si telescope and a high-purity sample produced by implantation of a 7Be ion beam at the ISOLDE facility at CERN. While a significantly higher cross section is found at low energy, relative to current evaluations, in the region of BBN interest, the present results are consistent with the values inferred from the time-reversal 7Li(p,n)7Be reaction, thus yielding only a relatively minor improvement on the so-called cosmological lithium problem. The relevance of these results on the near-threshold neutron production in the p+7Li reaction is also discussed.
  • Revised 9 May 2018
  • Received 16 March 2018
DOI: https://doi.org/10.1103/PhysRevLett.121.042701


Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

Published by the American Physical Society

Physics Subject Headings (PhySH) 

1. Research Areas

Big bang nucleosynthesis Nuclear reactions Nucleon induced nuclear reactions

Gravitation, Cosmology & Astrophysics Nuclear Physics
FREE PDF GRATIS: Phys Rev Let Sup Info

Being Modern - The Cultural Impact of Science in the Early Twentieth Century

quinta-feira, outubro 11, 2018

Being Modern: The Cultural Impact of Science in the Early Twentieth Century

Robert Bud, Paul Greenhalgh, Frank James and Morag Shiach | October 2018

Format: 234x156mm
 
Open Access PDF
ISBN: 978-1-78735-393-0
FREE
 
Hardback
ISBN: 978-1-78735-395-4
£50.00
 
Paperback
ISBN: 978-1-78735-394-7
£30.00
 
Pages: 438
About the book

In the early decades of the twentieth century, engagement with science was commonly used as an emblem of modernity. This phenomenon is now attracting increasing attention in different historical specialties. Being Modern builds on this recent scholarly interest to explore engagement with science across culture from the end of the nineteenth century to approximately 1940.

Addressing the breadth of cultural forms in Britain and the western world from the architecture of Le Corbusier to working class British science fiction, Being Modern paints a rich picture. Seventeen distinguished contributors from a range of fields including the cultural study of science and technology, art and architecture, English culture and literature examine the issues involved. The book will be a valuable resource for students, and a spur to scholars to further examination of culture as an interconnected web of which science was a critical part, and to supersede such tired formulations as 'Science and culture'.
About the editors

Robert Bud is Research Keeper at the Science Museum in London. His award-winning publications in the history of science include studies of biotechnology and scientific instruments. Paul Greenhalgh is Director of the Sainsbury Centre at the University of East Anglia, and Professor of Art History there. He has published extensively in the history of art, design, and the decorative arts in the early modern period. Frank James is Professor of History of Science at the Royal Institution and University College London. His research formerly centred on Faraday, but now focuses on Davy. Morag Shiach is Professor of Cultural History at Queen Mary University of London. She has published extensively on the cultural history of modernism and on modernism and labour. 

Table of contents Being Modern: Introduction
Robert Bud and Morag Shiach

Section 1: Science, modernity and culture

1 Multiple modernisms in concert: the sciences, technology and culture in Vienna around 1900
Mitchell G. Ash 

2 The cinematic sound of industrial modernity: first notes
Tim Boon

3 Woolf’s atom, Eliot’s catalyst and Richardson’s waves of light: science and modernism in 1919
Morag Shiach 

4 T.S. Eliot: modernist literature, disciplines and the systematic pursuit of knowledge
Kevin Brazil

Section 2: Tensions over science 

5 Modernity and the ambivalent significance of applied science: motors, wireless, telephones and poison gas
Robert Bud 

6 ‘The springtime of science’: modernity and the future and past of science
Frank A.J.L. James 

7 ‘Come on you demented modernists, let’s hear from you’: science fans as literary critics in the 1930s
Charlotte Sleigh

Section 3: Mathematics and physics 

8 Modern by numbers: modern mathematics as a model for literary modernism
Nina Engelhardt 

9 Sculpture in the Belle Epoque: mathematics, art and apparitions in school and gallery
Lewis Pyenson 

10 Architecture, science and purity
Judi Loach

11 A Portrait of the Scientist as a Young Ham: wireless, modernity and interwar nuclear physics
Jeff Hughes 

12 Whose modernism, whose speed? Designing mobility for the future, 1880s–1945
Ruth Oldenziel 

Section 4: Life, biology and the organicist metaphor 

13 Ludwig Koch’s birdsong on wartime BBC radio: knowledge, citizenship and solace
Michael Guida 

14 ‘More Modern than the Moderns’: performing cultural evolution in the Kibbo Kift Kindred
Annebella Pollen 

15 Organicism and the modern world: from A.N. Whitehead to Wyndham Lewis and D.H. Lawrence
Craig Gordon 

16 Liquid crystal as chemical form and model of thinking in Alfred Döblin’s modernist science
Esther Leslie 

17 ‘I am attracted to the natural order of things’: Le Corbusier’s rejection of the machine
Tim Benton 

Epilogue: Science after modernity
Frank A.J.L. James and Robert Bud

Select bibliography
Index 
 
FREE PDF GRATIS: UCL Press

Clusters de cromossomos ajudam a manter o genoma unido: mero acaso, fortuita necessidade ou design inteligente?

quarta-feira, outubro 10, 2018

A conserved function for pericentromeric satellite DNA

Madhav Jagannathan, Ryan Cummings, Yukiko M Yamashita

University of Michigan, United States

Research Article Mar 26, 2018 

Source/Fonte: The Scientist
 
Abstract


A universal and unquestioned characteristic of eukaryotic cells is that the genome is divided into multiple chromosomes and encapsulated in a single nucleus. However, the underlying mechanism to ensure such a configuration is unknown. Here, we provide evidence that pericentromeric satellite DNA, which is often regarded as junk, is a critical constituent of the chromosome, allowing the packaging of all chromosomes into a single nucleus. We show that the multi-AT-hook satellite DNA-binding proteins, Drosophila melanogaster D1 and mouse HMGA1, play an evolutionarily conserved role in bundling pericentromeric satellite DNA from heterologous chromosomes into ‘chromocenters’, a cytological association of pericentromeric heterochromatin. Defective chromocenter formation leads to micronuclei formation due to budding from the interphase nucleus, DNA damage and cell death. We propose that chromocenter and satellite DNA serve a fundamental role in encapsulating the full complement of the genome within a single nucleus, the universal characteristic of eukaryotic cells.  
 
eLife Digest


On Earth, life is divided into three domains. The smallest of these domains includes all the creatures, from sunflowers to yeasts to humans, that have the genetic information within their cells encased in a structure known as the nucleus. The genomes of these organisms are formed of long pieces of DNA, called chromosomes, which are packaged tightly and then unpackaged every time the cell divides. When a cell is not dividing, the chromosomes in the nucleus are loosely bundled up together.

It is well known that DNA is the blueprint for the building blocks of life, but actually most of the genetic information in a cell codes for nothing, and has unknown roles. An example of such ‘junk DNA’ is pericentrometric satellite DNA, small repetitive sequences found on all chromosomes.

However, new experiments by Jagannathan et al. show that, in the nucleus of animal cells, certain DNA binding proteins make chromosomes huddle together by attaching to multiple pericentrometric satellite DNA sequences on different chromosomes. In fact, if these proteins are removed from mice and fruit flies cells grown in the laboratory, the chromosomes cannot be clustered together. Instead, they ‘float away’, and the membranes of the nucleus get damaged, possibly buckling under the pressure of the unorganized DNA.

These events damage the genetic information, which can lead to the cell dying or forming tumors. ‘Junk DNA’ therefore appears to participate in fundamental cellular processes across species, a result that opens up several new lines of research.  
 
 
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Teoria das cordas: a energia escura é permitida mesmo?

de Sitter swampland conjecture and the Higgs potential

Frederik Denef, Arthur Hebecker, and Timm Wrase
Phys. Rev. D 98, 086004 – Published 2 October 2018
Abstract
According to a conjecture recently put forward in [1], the scalar potential V of any consistent theory of quantum gravity satisfies a bound |V|/VO(1). This forbids de Sitter solutions and supports quintessence models of cosmic acceleration. Here, we point out that in the simplest models incorporating the standard model in addition to quintessence, with the two sectors decoupled as suggested by observations, the proposed bound is violated by 50 orders of magnitude. However, a very specific coupling between quintessence and just the Higgs sector may still be allowed and consistent with the conjecture.
  • Received 7 August 2018
DOI: https://doi.org/10.1103/PhysRevD.98.086004

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.

Published by the American Physical Society

FREE PDF GRATIS: Phys Rev D

Existe um paradigma darwinista? Por uma ontologia histórica da teoria da evolução

terça-feira, outubro 09, 2018

Existe-t-il un paradigme darwinien? Pour une ontologie historique de la théorie de l’évolution
 
Nicola Bertoldi Université de Paris 1 - Panthéon Sorbonne
DOI: https://doi.org/10.20416/lsrsps.v5i1.8
 
Mots-clés: histoire et philosophie de la biologie, théorie de l’évolution, paradigme, Thomas Kuhn, ontologie historique 

Source/Fonte: New Scientist


Résumé

La théorie de Darwin est considérée par de nombreux historiens comme une véritable révolution scientifique, raison pour laquelle l’objectif de cet article est précisément de rendre compte des caractères révolutionnaires de cette théorie, dans le cadre d’une conception des révolutions scientifiques empruntée à l’œuvre de Thomas Kuhn. Cela implique, notamment, la définition d’un « paradigme darwinien », à la fois comme matrice disciplinaire et comme solution exemplaire à un problème donné. Dans un tel but, nous définirons la structure et le contenu de la théorie de Darwin, afin de mettre au jour la problématique qui pourrait être à la base d’un « paradigme darwinien », c’est-à-dire le problème de la complexité adaptative du vivant. Nous identifierons ensuite ce qui distinguerait ce paradigme des autres, si bien que le problème de la complexité ne saurait être posé et résolu que dans son cadre. Pour ce faire, nous nous concentrerons sur deux dichotomies : d’une part, celle entre fonctionnalisme et formalisme, d’autre part, celle entre naturalisme et idéalisme. En conclusion, nous mettrons au jour les limites de l’épistémologie kuhnienne pour l’analyse de la théorie de l’évolution, ce qui nous amènera à equisser les contours d’une approche alternative, que nous appellerons « ontologie historique ».
 
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Darwin, as teorias bem estabelecidas de padrões na evolução podem estar erradas

segunda-feira, outubro 01, 2018

History is written by the victors: The effect of the push of the past on the fossil record

Graham E. Budd Richard P. Mann

First published: 26 September 2018 https://doi.org/10.1111/evo.13593


Abstract

Survivorship biases can generate remarkable apparent rate heterogeneities through time in otherwise homogeneous birth‐death models of phylogenies. They are a potential explanation for many striking patterns seen in the fossil record and molecular phylogenies. One such bias is the “push of the past”: clades that survived a substantial length of time are likely to have experienced a high rate of early diversification. This creates the illusion of a secular rate slow‐down through time that is, rather, a reversion to the mean. An extra effect increasing early rates of lineage generation is also seen in large clades. These biases are important but relatively neglected influences on many aspects of diversification patterns in the fossil record and elsewhere, such as diversification spikes after mass extinctions and at the origins of clades; they also influence rates of fossilization, changes in rates of phenotypic evolution and even molecular clocks. These inevitable features of surviving and/or large clades should thus not be generalized to the diversification process as a whole without additional study of small and extinct clades, and raise questions about many of the traditional explanations of the patterns seen in the fossil record.

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Desvendando o mecanismo que protege o DNA replicado da degradação: mero acaso, fortuita necessidade ou design inteligente?

domingo, setembro 30, 2018

AND-1 fork protection function prevents fork resection and is essential for proliferation 
 

Takuya Abe, Ryotaro Kawasumi, Michele Giannattasio, Sabrina Dusi, Yui Yoshimoto, Keiji Miyata, Koyuki Umemura, Kouji Hirota & Dana Branzei

Nature Communications volume 9, Article number: 3091 (2018)

Abstract

AND-1/Ctf4 bridges the CMG helicase and DNA polymerase alpha, facilitating replication. Using an inducible degron system in avian cells, we find that AND-1 depletion is incompatible with proliferation, owing to cells accumulating in G2 with activated DNA damage checkpoint. Replication without AND-1 causes fork speed slow-down and accumulation of long single-stranded DNA (ssDNA) gaps at the replication fork junction, with these regions being converted to DNA double strand breaks (DSBs) in G2. Strikingly, resected forks and DNA damage accumulation in G2, but not fork slow-down, are reverted by treatment with mirin, an MRE11 nuclease inhibitor. Domain analysis of AND-1 further revealed that the HMG box is important for fast replication but not for proliferation, whereas conversely, the WD40 domain prevents fork resection and subsequent DSB-associated lethality. Thus, our findings uncover a fork protection function of AND-1/Ctf4 manifested via the WD40 domain that is essential for proliferation and averts genome instability.

Author information

Author notes

These authors contributed equally: Takuya Abe, Ryotaro Kawasumi.

Affiliations

IFOM, the FIRC Institute of Molecular Oncology, Via Adamello 16, 20139, Milan, Italy

Takuya Abe, Ryotaro Kawasumi, Michele Giannattasio, Sabrina Dusi & Dana Branzei

Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Minamiosawa 1-1, Hachioji-shi, Tokyo, 192-0397, Japan
Takuya Abe, Yui Yoshimoto, Keiji Miyata, Koyuki Umemura & Kouji Hirota

Dipartimento di Oncologia ed Emato-Oncologia, Università degli Studi di Milano, Milan, 20122, Italy
Michele Giannattasio

Istituto di Genetica Molecolare, Consiglio Nazionale delle Ricerche (IGM-CNR), Via Abbiategrasso 207, 27100, Pavia, Italy
Dana Branzei

Contributions

T.A., R.K., and D.B. designed the research; T.A. and R.K. performed the experiments; M.G. and S.D. performed TEM sample acquisition and analysis; Y.Y., K.M., K.U., and K.H. contributed to experiments on molecular combing and pulse field gel electrophoresis; T.A., R.K., and D.B analyzed the data; T.A. and R.K. made the figures; D.B. wrote the paper and all authors contributed suggestions. 

Competing interests

The authors declare no competing interests.
Corresponding author

Correspondence to Dana Branzei.

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