98 research outputs found
Turing machines can be efficiently simulated by the General Purpose Analog Computer
The Church-Turing thesis states that any sufficiently powerful computational
model which captures the notion of algorithm is computationally equivalent to
the Turing machine. This equivalence usually holds both at a computability
level and at a computational complexity level modulo polynomial reductions.
However, the situation is less clear in what concerns models of computation
using real numbers, and no analog of the Church-Turing thesis exists for this
case. Recently it was shown that some models of computation with real numbers
were equivalent from a computability perspective. In particular it was shown
that Shannon's General Purpose Analog Computer (GPAC) is equivalent to
Computable Analysis. However, little is known about what happens at a
computational complexity level. In this paper we shed some light on the
connections between this two models, from a computational complexity level, by
showing that, modulo polynomial reductions, computations of Turing machines can
be simulated by GPACs, without the need of using more (space) resources than
those used in the original Turing computation, as long as we are talking about
bounded computations. In other words, computations done by the GPAC are as
space-efficient as computations done in the context of Computable Analysis
Integrated Genomic Analysis of Diverse Induced Pluripotent Stem Cells from the Progenitor Cell Biology Consor tium
The rigorous characterization of distinct induced pluripotent stem cells (iPSC) derived from multiple reprogramming technologies,
somatic sources, and donors is required to understand potential sources of variability and downstream potential. To achieve this goal,
the Progenitor Cell Biology Consortium performed comprehensive experimental and genomic analyses of 58 iPSC from ten laboratories
generated using a variety of reprogramming genes, vectors, and cells. Associated global molecular characterization studies identified functionally
informative correlations in gene expression, DNA methylation, and/or copy-number variation among key developmental and
oncogenic regulators as a result of donor, sex, line stability, reprogramming technology, and cell of origin. Furthermore, X-chromosome
inactivation in PSC produced highly correlated differences in teratoma-lineage staining and regulator expression upon differentiation.
All experimental results, and raw, processed, and metadata from these analyses, including powerful tools, are interactively accessible
from a new online portal at https://www.synapse.org to serve as a reusable resource for the stem cell community
Structure of the parasite infracommunity of Sciades proops from the Japaratuba River Estuary, Sergipe, Brazil
Inhibition of dimethylarginine dimethylaminohydrolase (DDAH) and arginine deiminase (ADI) by pentafluorophenyl (PFP) sulfonates
Peer reviewe
Holocene fire and occupation in Amazonia: records from two lake districts
While large-scale pre-Columbian human occupation and ecological disturbance have been demonstrated close to major Amazonian waterways, less is known of sites in terra firme settings. Palaeoecological analyses of two lake districts in central and western Amazonia reveal long histories of occupation and land use. At both locations, human activity was centred on one of the lakes, while the others were either lightly used or unused. These analyses indicate that the scale of human impacts in these terra firme settings is localized and probably strongly influenced by the presence of a permanent open-water body. Evidence is found of forest clearance and cultivation of maize and manioc. These data are directly relevant to the resilience of Amazonian conservation, as they do not support the contention that all of Amazonia is a ‘built landscape’ and therefore a product of past human land use
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