Porque os dados nunca são brutos

sexta-feira, maio 22, 2020

Why Data Is Never Raw 

On the seductive myth of information free of human judgment

Source/Fonte: University of London

Nick Barrowman

A curious fact about our data-obsessed era is that we’re often not entirely sure what we even mean by “data”: Elementary particles of knowledge? Digital records? Pure information? Sometimes when we refer to “the data,” we mean the results of an analysis or the evidence concerning a certain question. On other occasions we intend “data” to signify something like “reliable evidence,” as in the saying “The plural of anecdote is not data.”

In everyday usage, the term “data” is associated with a jumble of notions about information, science, and knowledge. Countless reports marvel at the astonishing volumes of data being produced and manipulated, the efficiencies and new opportunities this has made possible, and the myriad ways in which society is changing as a result. We speak of “raw” data and laud it for its independence from human judgment. On this basis, “data-driven” (or “evidence-based”) decision-making is widely endorsed. Yet data’s purported freedom from human subjectivity also seems to allow us to invest it with agency: “Let the data speak for itself,” for “The data doesn’t lie.”

Out of this quizzical mix, it is perhaps unsurprising that near-magical thinking about data has emerged. In the 2015 book Digital Destiny: How the New Age of Data Will Transform the Way We Work, Live, and Communicate, Shawn DuBravac describes a collection of “properties of data” and expresses them in anthropomorphic terms. DuBravac, former chief economist at the Consumer Electronics Association and a self-styled futurist and “trendcaster,” claims that data “seeks permanence,” “wants to replicate,” “seeks instantaneity,” “wants to be understood,” and “seeks movement.”

Data is immediate.... When data comes into being, when it is first tracked, captured, or copied, it wants to immediately be utilized — to exert force and influence.... Data constantly moves toward efficiency. It removes barriers; it closes distances; it destroys the moments between recognition and understanding. Because data wants to be understood, it abhors friction.

This projection of human-like qualities onto data is ostensibly metaphorical, but it can muddle our thinking. It seems aimed at obscuring how intertwined is the production of data with human judgment, and the use of data with human agency. And once our agency has been obscured, it is not hard to imagine that data has a mind of its own, that to solve our great problems we have only to collect the data and set the computers running.

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Homoquiralidade: raios cósmicos podem ter deixado marcas indeléveis no início da vida

quinta-feira, maio 21, 2020

The Chiral Puzzle of Life
Noemie Globus1,2 and Roger D. Blandford3

Published 2020 May 20 • © 2020. The American Astronomical Society. All rights reserved.
The Astrophysical Journal Letters, Volume 895, Number 1

Published 2020 May 20 • © 2020. The American Astronomical Society. All rights reserved.

Author e-mails



Author affiliations

1 Center for Cosmology & Particle Physics, New York University, New York, NY 10003, USA

2 Center for Computational Astrophysics, Flatiron Institute, Simons Foundation, New York, NY 10003, USA

3 Kavli Institute for Particle Astrophysics & Cosmology, Stanford University, Stanford, CA 94305, USA

Received 2020 March 4, Accepted 2020 April 27, Published 2020 May 20

Citation Noemie Globus and Roger D. Blandford 2020 ApJL 895 L11

Keywords Astrobiology ; Cosmic rays


Biological molecules chose one of two structurally chiral systems which are related by reflection in a mirror. It is proposed that this choice was made, causally, by cosmic rays, which are known to play a major role in mutagenesis. It is shown that magnetically polarized cosmic rays that dominate at ground level today can impose a small, but persistent, chiral bias in the rate at which they induce structural changes in simple, chiral monomers that are the building blocks of biopolymers. A much larger effect should be present with helical biopolymers, in particular, those that may have been the progenitors of ribonucleic acid and deoxyribonucleic acid. It is shown that the interaction can be both electrostatic, just involving the molecular electric field, and electromagnetic, also involving a magnetic field. It is argued that this bias can lead to the emergence of a single, chiral life form over an evolutionary timescale. If this mechanism dominates, then the handedness of living systems should be universal. Experiments are proposed to assess the efficacy of this process.

Modelando o discurso científico

quarta-feira, maio 20, 2020

Modeling Scientific Discourse

Peter McBurney and Simon Parsons

Department of Computer Science
University of Liverpool
Liverpool L69 7ZF United Kingdom


The Problem Domain

We aim to build intelligent systems which can reason autonomously about the risk of carcinogenicity of chemicals, drawing on whatever theoretical or experimental evidence is available. In earlier work [14], reviewing the literature on methods of carcinogen risk assessment, we catalogued the different types of evidence adduced to support these claims, which may be in the form of: experimental results on tissue cultures, animals or human epidemiological studies; analytical comparisons with known carcinogens; or explication of biomedical causal pathways. Because the research which underpins conclusions in this domain is usually at the leadingedge of the scientific disciplines concerned, evidence from these different sources may be inconsistent or conflicting. Consequently, carcinogen risk assessment usually involves the comparison and resolution of multiple evidences and arguments for and against a particular scientific claim [23, 27].

To represent this domain in an intelligent system, therefore, we first require a philosophical model of scientific enquiry. Which philosophy of science is appropriate for such representation, and why? Next, having adopted such a conceptual model, we will need to formalize it. How can this be achieved? In particular, how may we represent the scientific uncertainty characteristic of knowledge in the carcinogen domain? These questions are the focus of this paper, which outlines our current thinking and approach.

O discurso evolutivo na obra Origem das Espécies é uma teleologia natural?

O discurso evolutivo na obra Origem das Espécies pode ser considerado uma teleologia natural?

Rafael Francisco Hiller - Unisinos

Heloisa Allgayer - Unisinos

Palavras-chave: Teleologia, Evolucionismo, Darwin


Neste artigo, iremos usar como aporte teórico a teoria da evolução desenvolvida na sexta edição da Origem das espécies de Charles Darwin, analisaremos a relação causal desenvolvida pelo autor na estruturação do argumento de seleção natural, a partir disso, será investigado possíveis traços teleológicos nas estratégicas argumentativas de Darwin. Como metodologia desse trabalho, serão examinados os capítulos que contém o principal arcabouço para a estruturação da hipótese de seleção natural, com base nisso, os elementos causais serão destacados, bem como serão elencados os possíveis traços de um discurso teleológico por parte de Darwin. A partir da análise que foi realizada é possível afirmar que discurso de Darwin possui pressupostos teleológicos no que se refere ao processo que leva a produção de novas formas orgânicas se mostra claramente na noção de mudanças que são produzidas como adaptações. A seleção natural, determina à preservação/extinção na natureza, possui a função de direcionamento do processo evolutivo, afim de que, surjam novas formas aperfeiçoadas. A partir disso, pode-se supor um princípio teleológico na estratégia argumentativa darwiniana, pois tem como causa final o surgimento de uma nova forma aperfeiçoada.

Palavras-chave: Teleologia; Evolucionismo; Darwin


Um bilhão de anos faltando no registro geológico: para onde podem ter ido?

segunda-feira, maio 18, 2020

Diachronous development of Great Unconformities before Neoproterozoic Snowball Earth

Rebecca M. Flowers, Francis A. Macdonald, View ORCID ProfileChristine S. Siddoway, and Rachel Havranek

PNAS May 12, 2020 117 (19) 10172-10180; first published April 27, 2020 https://doi.org/10.1073/pnas.1913131117 

Edited by Paul F. Hoffman, University of Victoria, Victoria, Canada, and approved March 6, 2020 (received for review July 30, 2019)


Erosion below the Great Unconformity has been interpreted as a global phenomenon associated with Snowball Earth. Geological relationships and thermochronologic data provide evidence that the bulk of erosion below the Great Unconformity in Colorado occurred prior to Cryogenian glaciation. We suggest that there are multiple, regionally diachronous Great Unconformities that are tectonic in origin.


The Great Unconformity marks a major gap in the continental geological record, separating Precambrian basement from Phanerozoic sedimentary rocks. However, the timing, magnitude, spatial heterogeneity, and causes of the erosional event(s) and/or depositional hiatus that lead to its development are unknown. We present field relationships from the 1.07-Ga Pikes Peak batholith in Colorado that constrain the position of Cryogenian and Cambrian paleosurfaces below the Great Unconformity. Tavakaiv sandstone injectites with an age of ≥676 ± 26 Ma cut Pikes Peak granite. Injection of quartzose sediment in bulbous bodies indicates near-surface conditions during emplacement. Fractured, weathered wall rock around Tavakaiv bodies and intensely altered basement fragments within unweathered injectites imply still earlier regolith development. These observations provide evidence that the granite was exhumed and resided at the surface prior to sand injection, likely before the 717-Ma Sturtian glaciation for the climate appropriate for regolith formation over an extensive region of the paleolandscape. The 510-Ma Sawatch sandstone directly overlies Tavakaiv-injected Pikes granite and drapes over core stones in Pikes regolith, consistent with limited erosion between 717 and 510 Ma. Zircon (U-Th)/He dates for basement below the Great Unconformity are 975 to 46 Ma and are consistent with exhumation by 717 Ma. Our results provide evidence that most erosion below the Great Unconformity in Colorado occurred before the first Neoproterozoic Snowball Earth and therefore cannot be a product of glacial erosion. We propose that multiple Great Unconformities developed diachronously and represent regional tectonic features rather than a synchronous global phenomenon.

Great Unconformity Snowball Earth thermochronology zircon (U-Th)/Heinjectites


↵1To whom correspondence may be addressed. Email: rebecca.flowers@colorado.edu.

Author contributions: R.M.F. and F.A.M. designed research; R.M.F., F.A.M., C.S.S., and R.H. performed research; and R.M.F., F.A.M., and C.S.S. wrote the paper.

Competing interest statement: P.F.H. and F.A.M. are coauthors on three papers, most recently in 2017.

This article is a PNAS Direct Submission.

This article contains supporting information online at https://www.pnas.org/lookup/suppl/doi:10.1073/pnas.1913131117/-/DCSupplemental.

Subscription or payment needed/Requer assinatura ou pagamento: PNAS


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Uma visão radical da evolução das organelas

segunda-feira, maio 04, 2020

Alternating terminal electron‐acceptors at the basis of symbiogenesis: How oxygen ignited eukaryotic evolution

Dave Speijer

First published:05 January 2017 https://doi.org/10.1002/bies.201600174


What kind of symbiosis between archaeon and bacterium gave rise to their eventual merger at the origin of the eukaryotes? I hypothesize that conditions favouring bacterial uptake were based on exchange of intermediate carbohydrate metabolites required by recurring changes in availability and use of the two different terminal electron chain acceptors, the bacterial one being oxygen. Oxygen won, and definitive loss of the archaeal membrane potential allowed permanent establishment of the bacterial partner as the proto‐mitochondrion, further metabolic integration and highly efficient ATP production. This represents initial symbiogenesis, when crucial eukaryotic traits arose in response to the archaeon‐bacterium merger. The attendant generation of internal reactive oxygen species (ROS) gave rise to a myriad of further eukaryotic adaptations, such as extreme mitochondrial genome reduction, nuclei, peroxisomes and meiotic sex. Eukaryotic origins could have started with shuffling intermediate metabolites as is still essential today.


Inferindo entropia a partir da estrutura

Inferring entropy from structure

Gil Ariel
Department of Mathematics, Bar-Ilan University, 52000 Ramat Gan, Israel

Haim Diamant
Raymond and Beverly Sackler School of Chemistry, Tel Aviv University, 69978 Tel Aviv, Israel


The thermodynamic definition of entropy can be extended to nonequilibrium systems based on its relation to information. To apply this definition in practice requires access to the physical system’s microstates, which may be prohibitively inefficient to sample or difficult to obtain experimentally. It is beneficial, therefore, to relate the entropy to other integrated properties which are accessible out of equilibrium. We focus on the structure factor, which describes the spatial correlations of density fluctuations and can be directly measured by scattering. The information gained by a given structure factor regarding an otherwise unknown system provides an upper bound for the system’s entropy. We prove that the maximum-entropy model corresponds to an equilibrium system with an effective pair-interaction. Approximate closed-form relations for the effective pair-potential and entropy in terms of the structure factor are obtained. The relations are used to estimate the entropy of an exactly solvable model and numerical examples of systems out of equilibrium, and the results are compared with other entropy-estimation methods. The focus is on low-dimensional examples, where our method, as well as a recently proposed compression-based one, can be tested against a rigorous direct-sampling technique. The entropy inferred from the structure factor is found to be consistent with the other methods, superior for larger system sizes, and accurate in identifying global transitions. Our approach allows for extensions of the theory to more complex systems and to higher-order correlations.


Mais uma hipótese sobre a origem da vida: de três funções privilegiadas a quatro pilares

sábado, maio 02, 2020

Defining Lyfe in the Universe: From Three Privileged Functions to Four Pillars

by Stuart Bartlett 1,2,* and Michael L. Wong 3,4
Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA

Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo 152-8550, Japan

Department of Astronomy and Astrobiology Program, University of Washington, Seattle, WA 98195, USA

NASA Nexus for Exoplanet System Science’s Virtual Planetary Laboratory, University of Washington, Seattle, WA 98195, USA

Author to whom correspondence should be addressed.

Received: 23 March 2020 / Revised: 12 April 2020 / Accepted: 13 April 2020 / Published: 16 April 2020

(This article belongs to the Special Issue Frontiers of Astrobiology)


Motivated by the need to paint a more general picture of what life is—and could be—with respect to the rest of the phenomena of the universe, we propose a new vocabulary for astrobiological research. Lyfe is defined as any system that fulfills all four processes of the living state, namely: dissipation, autocatalysis, homeostasis, and learning. Life is defined as the instance of lyfe that we are familiar with on Earth, one that uses a specific organometallic molecular toolbox to record information about its environment and achieve dynamical order by dissipating certain planetary disequilibria. This new classification system allows the astrobiological community to more clearly define the questions that propel their research—e.g., whether they are developing a historical narrative to explain the origin of life (on Earth), or a universal narrative for the emergence of lyfe, or whether they are seeking signs of life specifically, or lyfe at large across the universe. While the concept of “life as we don’t know it” is not new, the four pillars of lyfe offer a novel perspective on the living state that is indifferent to the particular components that might produce it. 

Keywords: definition of life; origin of life; astrobiology; mechanotroph