SEMCIÊNCIA

Error bars in experimental biology. Geoff Cumming, Fiona Fidler, David L Vaux Add to My Library ShareThis The Journal of Cell Biology (2007) Volume: 177, Issue: 1, Publisher: Rockefeller Univ Press, Pages: 7-11 PubMed ID: 17420288 Available from http://www.ncbi.nlm.nih.gov/ Tags basics error bars graphing methods standard deviation standard error statistics Abstract Error bars commonly appear in figures in publications, but experimental biologists are often unsure how they should be used and interpreted. In this article we illustrate some basic features of error bars and explain how they can help communicate data and assist correct interpretation. Error bars may show confidence intervals, standard errors, standard deviations, or other quantities. Different types of error bars give quite different information, and so figure legends must make clear what error bars represent. We suggest eight simple rules to assist with effective use and interpretation of error bars. Cuidado! O autor di

Through the Mendeley research network you can connect with other researchers in your field . This opens up a whole new avenue for knowledge discovery. You can view the most read authors, journals and papers in your field . You can explore by using tags associated with your research area. By navigating the web of knowledge available to you, you make some useful contacts along the way too. In addition to that, you can also view interesting statistics about your own digital library. Discover more papers linked to your research interests Collaborate with fellow researchers and share information, resources and experiences with shared and public collections . Your research team will have easy access to each others papers. Just create a group, invite your colleagues and drag and drop documents in there. This way you can keep on top of what they're reading and discover more about what interests you. Start collaborating with other researchers Mendeley Desktop is academic software ...

Scale-invariant transition probabilities in free word association trajectories Martin Elias Costa 1 * , Flavia Bonomo 2 and Mariano Sigman 1 1 Integrative Neuroscience Laboratory, Physics Department, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina 2 Computer Science Department, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina Free-word association has been used as a vehicle to understand the organization of human thoughts. The original studies relied mainly on qualitative assertions, yielding the widely intuitive notion that trajectories of word associations are structured, yet considerably more random than organized linguistic text. Here we set to determine a precise characterization of this space, generating a large number of word association trajectories in a web implemented game. We embedded the trajectories in the graph of word co-occurrences from a linguistic corpus. To constrain possible transport models we m

Legal esse negócio dos referees não ficarem anônimos no final... Scale-invariant transition probabilities in free word association trajectories Martin Elias Costa 1 * , Flavia Bonomo 2 and Mariano Sigman 1 1 Integrative Neuroscience Laboratory, Physics Department, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina 2 Computer Science Department, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina Free-word association has been used as a vehicle to understand the organization of human thoughts. The original studies relied mainly on qualitative assertions, yielding the widely intuitive notion that trajectories of word associations are structured, yet considerably more random than organized linguistic text. Here we set to determine a precise characterization of this space, generating a large number of word association trajectories in a web implemented game. We embedded the trajectories in the graph of word co-occurrences from

OK, OK, já comentei que a Política, assim como a Arte, não pode ser reduzida à Ciência. Mas isso não implica que não existam relações e influências. Por exemplo, a Política, e as políticas públicas, são muito influenciadas pelos cientistas sociais e economistas (mesmo que estes sejam considerados por alguns céticos como pseudocientistas). Na questão da origem e mecanismos de mudança da distribuição de renda, os físicos têm dado uma contribuição interessante. Basta fazer uma busca no ArXiv sobre whealth distribution. Aqui um exemplo interesante, do pesoal da UFRGS: Versão final e referência aqui . E aqui o artigo com o copyleft do ArXiv : The unfair consequences of equal opportunities: comparing exchange models of wealth distribution Authors: G. M. Caon, S. Goncalves, J. R. Iglesias (Submitted on 1 Nov 2006) Abstract: Simple agent based exchange models are a commonplace in the study of wealth distribution of artificial societies. Generally, each agent is characterized by its wealt

Dois artigos sobre a blogosfera encontrados hoje: Empirical analysis of online social networks in the age of Web 2.0 Physica A: Statistical Mechanics and its Applications Volume 387, Issues 2-3 , 15 January 2008, Pages 675-684 Feng Fu a , b , , Lianghuan Liu a , b and Long Wang , a , b , a Center for Systems and Control, College of Engineering, Peking University, Beijing 100871, China b Department of Industrial Engineering and Management, College of Engineering, Peking University, Beijing 100871, China Received 17 July 2007; revised 30 September 2007. Available online 9 October 2007. Abstract Today the World Wide Web is undergoing a subtle but profound shift to Web 2.0, to become more of a social web. The use of collaborative technologies such as blogs and social networking site (SNS) leads to instant online community in which people communicate rapidly and conveniently with each other. Moreover, there are growing interest and concern regarding the top

Acho que finalmente entendi o conceito Bayesiano de probabilidades. Antes tarde do que nunca! É claro que eu poderia ter aprendido isso muito antes, com o livro do Jaynes tão recomendado pelo Nestor Caticha. Acho que na verdade aprendi, depois esqueci, depois li de nôvo, depois esqueci de novo. “Apreender” é diferente de aprender. Acho que envolve uma mudança de Gestalt, uma espécie de momento de “iluminação”. Isso aconteceu devido a dois acidentes (na verdade três): a) estou sem internet em casa, ou seja, sem essa máquina de perder tempo; b) este computador tinha uma pasta com alguns artigos em pdf, entre eles o ótimo Lectures on probability, entropy and statistical mechanics de Ariel Caticha, que me fora mandado há um bom tempo atrás pelo Nestor; c) eu havia terminado o livro Artemis Fowl – Uma aventura no Ártico e estava sem nada para ler na noite de Natal (escreverei um post sobre isso outro dia). Além do conceito de probabilidade Bayesiano, foi muito esclarecedor a discussão sob

Isso parece ser interessante: Mathematical undecidability and quantum randomness Authors: Tomasz Paterek , Johannes Kofler , Robert Prevedel , Peter Klimek , Markus Aspelmeyer , Anton Zeilinger , Caslav Brukner (Submitted on 27 Nov 2008) Abstract: We propose a new link between mathematical undecidability and quantum physics. We demonstrate that the states of elementary quantum systems are capable of encoding mathematical axioms and show that quantum measurements are capable of revealing whether a given proposition is decidable or not within the axiomatic system. Whenever a mathematical proposition is undecidable within the axioms encoded in the state, the measurement associated with the proposition gives random outcomes. Our results support the view that quantum randomness is irreducible and a manifestation of mathematical undecidability. Comments: 9 pages, 4 figures Subjects: Quantum Physics (quant-ph) Cite as: arXiv:0811.4542v1 [quant-ph]

Uma referência para meu (possível) futuro estudante de mestrado... Cellular Automata with Symmetric Local Rules Authors: Vladimir V. Kornyak (Submitted on 11 May 2006 ( v1 ), last revised 18 Sep 2006 (this version, v2)) Abstract: The cellular automata with local permutation invariance are considered. We show that in the two-state case the set of such automata coincides with the generalized Game of Life family. We count the number of equivalence classes of the rules under consideration with respect to permutations of states. This reduced number of rules can be efficiently generated in many practical cases by our C program. Since a cellular automaton is a combination of a local rule and a lattice, we consider also maximally symmetric two-dimensional lattices. In addition, we present the results of compatibility analysis of several rules from the Life family. Comments: 11 pages, corrected to match published version Subjects: Mathematical Physics (math-ph); Cellular Automata and Lattice Ga

Neste paper muito interessante (e razoávelmente legível), consegui esclarecer uma dúvida que coloquei no fórum de Física da UFF : Gravity and its Mysteries: Some Thoughts and Speculations Authors: A. Zee (Submitted on 14 May 2008 ( v1 ), last revised 28 Jul 2008 (this version, v2)) Abstract: I gave a rambling talk about gravity and its many mysteries at Chen-Ning Yang's 85th Birthday Celebration held in November 2007. I don't have any answers. Gravity, knowing about everything, is the only interaction sensitive to a shift of the Lagrangian by an additive constant. In classical physics, additive constants do not affect the equation of motion. In quantum mechanics, experiments typically measure only energy differences Delta E and not the energies themselves. The Casimir effect measures the change in vacuum energy Delta E before and after the mirrors are introduced, not the vacuum energy itself (as is sometimes erroneously stated.) But gravity knows about the vacuum energy 1/2 h...

EDITORIAL To Share the fame in a fair way, h_m modifies h for multi-authored manuscripts Michael Schreiber 2008 New J. Phys. 10 040201 (9pp) doi: 10.1088/1367-2630/10/4/040201 Michael Schreiber Institut für Physik, Technische Universität Chemnitz, 09107 Chemnitz, Germany E-mail: schreiber@physik.tu-chemnitz.de Abstract. The h -index has been introduced by Hirsch as a useful measure to characterize the scientific output of a researcher. I suggest a simple modification in order to take multiple co-authorship appropriately into account, by counting each paper only fractionally according to (the inverse of) the number of authors. The resulting h m -indices for eight famous physicists lead to a different ranking from the original h -indices. Received 16 November 2007 Published 10 April 2008 OK, OK, ninguém disse que o h_I era perfeito , mas sim um degrau na busca de índices melhores. Agora já existem três tipos de índice h individuais ( existe um , não publicado, mas usado pelo site Pub

Da New Scientist (acho que foi o Mark Buchanan que escreveu): Recipes came about by evolution 22 March 2008 From New Scientist Print Edition COQ AU VIN and steak-and-kidney pudding may not bring to mind the principles of evolution. Yet evolutionary mechanisms may well be reflected in recipes for these tried-and-tested dishes. Physicist Antonio Roque of the University of São Paulo in Brazil and colleagues analysed thousands of recipes ( arxiv.org/abs/0802.4393v1 ) drawn from the French Larousse Gastronomique, the British New Penguin Cookery Book, three editions of the Brazilian Dona Benta spanning nearly 60 years, and a medieval cookbook. When they looked at how often ingredients appeared in recipes and ranked them accordingly, they saw a precise mathematical relationship across the board between an ingredient's position on the list and how commonly it was used. "There's a remarkable similarity," says Roque, "independent of culture and author." This similari...

Embora Frank Rosemblatt tenha publicado um report em 1957, o primeiro artigo sobre o Perceptron publicado em revistas científicas é de 1958, ou seja, exatamente há 50 anos. Para comemorar essa data, vou contar nos próximos posts algo sobre o Perceptron . Este site de livros raros onde encontrei o exemplar do Psychologial Review de 1958 é interessante. Da Wikipédia, a conferir mais tarde: More recently, interest in the perceptron learning algorithm has increased again after Freund and Schapire (1998) presented a voted formulation of the original algorithm (attaining large margin) and suggested that one can apply the kernel trick to it. The kernel-perceptron not only can handle nonlinearly separable data but can also go beyond vectors and classify instances having a relational representation (e.g. trees, graphs or sequences). Freund, Y. and Schapire, R. E. 1998. Large margin classification using the perceptron algorithm. In Proceedings of the 11th Annual Conference on Computational L

Ainda sobre o paper noticiado na Nature News . Para quem ficou com preguiça de ir até o ArXiv Blog , reproduzo aqui o post com o comentário respondendo à crítica (ou dúvida) feita, que por sinal também nos foi feita por Mark Buchanan, autor de Ubiquity , um livro que eu recomendo para todos os meus orientados. Food for thought March 4th, 2008 by KFC Evolution seems to crop up all over the place. In life, business, ideas. And now in recipes through the ages. Yup, that’s recipes. For food. Osame Kinouchi from the Universidade de São Paulo in Brazil and buddies, have studied the way in which ingredients used in recipes vary around the world and through the ages. And they’ve found, they say, evidence of evolution. The team studied the relationship betwen recipes and ingredients in four cookbooks: three editions of the Brazilian Dona Benta (1946, 1969 and 2004), the French Larousse Gastronomique , the British New Penguin Cookery Book , and the medieval Pleyn Delit . They took the recipe

Nosso paper sobre a evolução da culinária foi comentado na Nature News , em uma reportagem de Daniel Cressey. Se alguém quiser convidar alguém da equipe para dar seminários, estamos à disposição, desde que a pessoa pague o jantar... Na Nature News, Hervé This comenta nosso paper, fazendo a seguinte crítica: He notes that the paper also doesn't clearly define what an 'ingredient' is — is a carrot an ingredient, or is a chopped carrot one ingredient and grated carrot another, for instance? Posso contar que durante a pesquisa estivemos bem conscientes desse problema. O fato é que a classificação ou agrupamento dos ingredientes formam um dendrograma muito ramificado. Ou seja, devemos juntar "caldo de limão" e "limão" num mesmo rótulo? Vinho tinto, vinho rosé e vinho branco são ingredientes separados? Nossa opção foi seguir de forma mais fiel possível a opção dos autores dos livros, pois se fossemos introduzir nossa própria classificação, talvez ela fosse t...

The Nonequilibrium Nature of Culinary Evolution Osame Kinouchi , Rosa W. Diez-Garcia , Adriano J. Holanda , Pedro Zambianchi , Antonio C. Roque (Submitted on 29 Feb 2008) Abstract: Food is an essential part of civilization, with a scope that ranges from the biological to the economic and cultural levels. Here we study the statistics of ingredients and recipes taken from Brazilian, British, French, and Medieval cookbooks. We find universal distributions with scale invariant behavior. We propose a copy-mutate process to model culinary evolution that fits very well our empirical data. We find a cultural founder effect produced by the nonequilibrium dynamics of the model. Both the invariant and idiosyncratic aspects of culture are accounted by our model, which may have applications in other kinds of evolutionary processes. Comments: 15 pages, 5 figures, 1 table, submitted to Physical Review E Subjects: Physics and Society (physics.soc-ph) Cite as: arXiv:0802.4393v1 [physics.soc-ph] Submis

OK, OK, Maria Guimarães, você venceu (com seu voto de Minerva ): eu mudei meu voto na Roda da Ciência na última hora, para dar empate, mas não consegui escapar desse assunto (Mares da Terra) sobre os quais não entendo nada. Assim, para dar a minha contribuição deste mês, apenas dou o link aqui para uma busca que fiz com a palavra "Ocean" no http://www.arxiv.org/ , repositório de preprints de livre acesso que todo mundo conhece interessado em ciência conhece ou deveria conhecer. PS: Para eu me lembrar depois: o mito de Minerva é muito parecido com o de Ishtar. Minerva também é a deusa da guerra, ciência, poesia, tecnologia, invenção, medicina, conhecimento e comércio. Figura: Head of Minerva by Elihu Vedder , 1896.

Theory of collective firing induced by noise or diversity in excitable media C. J. Tessone , A. Scirè , R. Toral , and P. Colet --> Institut Mediterrani d'Estudis Avançats, IMEDEA (CSIC-UIB), Campus Universitat Illes Balears, E-07122 Palma de Mallorca, Spain (Received 20 June 2006; published 9 January 2007) Large variety of physical, chemical, and biological systems show excitable behavior, characterized by a nonlinear response under external perturbations: only perturbations exceeding a threshold induce a full system response (firing). It has been reported that in coupled excitable identical systems noise may induce the simultaneous firing of a macroscopic fraction of units. However, a comprehensive understanding of the role of noise and that of natural diversity present in realistic systems is still lacking. Here we develop a theory for the emergence of collective firings in nonidentical excitable systems subject to noise. Three different dynamical regimes arise: subthreshol...

Unifying Evolutionary and Network Dynamics Authors: Samarth Swarup , Les Gasser (Submitted on 13 Apr 2007) Abstract: Many important real-world networks manifest "small-world" properties such as scale-free degree distributions, small diameters, and clustering. The most common model of growth for these networks is "preferential attachment", where nodes acquire new links with probability proportional to the number of links they already have. We show that preferential attachment is a special case of the process of molecular evolution. We present a new single-parameter model of network growth that unifies varieties of preferential attachment with the quasispecies equation (which models molecular evolution), and also with the Erdos-Renyi random graph model. We suggest some properties of evolutionary models that might be applied to the study of networks. We also derive the form of the degree distribution resulting from our algorithm, and we show through simulations that th...