Artículos con la etiqueta ‘biología’

Evolution: Life has Evolved to Evolve

Por • 10 feb, 2014 • Category: Leyes

Jim Shapiro synthesizes a great many observations about the mechanisms of evolution to reach the remarkable conclusion that large-scale modification, exchange, and rearrangement of the genome are common and should be viewed as fundamental features of life. In other words, the genome should be viewed not as mostly read-only with a few rare mutations, but rather as a fully-fledged read-write library of genetic functions under continuous revision. Revision of the genome occurs during cellular replication, during multicellular development, and during evolution of a population of individuals. DNA formatting controls the timing and location of genetic rearrangements, gene expression, and genetic repair. Each of these events is under the control of precise cellular circuits. Shapiro reviews the toolbox of natural genetic engineering that provides the functionalities necessary for efficient long-term genome restructuring.



Unconventional research in USSR and Russia: short overview

Por • 12 ene, 2014 • Category: Crítica

This work briefly surveys unconventional research in Russia from the end of the 19th until the beginning of the 21th centuries in areas related to generation and detection of a ‘high-penetrating’ emission of non-biological origin. The overview is based on open scientific and journalistic materials. The unique character of this research and its history, originating from governmental programs of the USSR, is shown. Relations to modern studies on biological effects of weak electromagnetic emission, several areas of bioinformatics and theories of physical vacuum are discussed.



Life Before Earth

Por • 26 dic, 2013 • Category: Ciencia y tecnología

An extrapolation of the genetic complexity of organisms to earlier times suggests that life began before the Earth was formed. Life may have started from systems with single heritable elements that are functionally equivalent to a nucleotide. The genetic complexity, roughly measured by the number of non-redundant functional nucleotides, is expected to have grown exponentially due to several positive feedback factors: gene cooperation, duplication of genes with their subsequent specialization, and emergence of novel functional niches associated with existing genes. Linear regression of genetic complexity on a log scale extrapolated back to just one base pair suggests the time of the origin of life 9.7 billion years ago. This cosmic time scale for the evolution of life has important consequences: life took ca. 5 billion years to reach the complexity of bacteria; the environments in which life originated and evolved to the prokaryote stage may have been quite different from those envisaged on Earth; there was no intelligent life in our universe prior to the origin of Earth, thus Earth could not have been deliberately seeded with life by intelligent aliens; Earth was seeded by panspermia; experimental replication of the origin of life from scratch may have to emulate many cumulative rare events; and the Drake equation for guesstimating the number of civilizations in the universe is likely wrong, as intelligent life has just begun appearing in our universe.



Is there enough fertile soil to feed a planet of growing cities?

Por • 19 ago, 2013 • Category: sociologia

We analyze a scaling law for the consumption of agricultural soil by the cities. The nonlinear depen- dence of the size of the city on the number of inhabitants gives rise to an equation for the population dynamics. We found the asymptotic limit of the solution for this equation, given by the carrying capacity in terms of number of inhabitants that can be fed. The carrying capacity as a function of the scaling law exponent is computed numerically, showing that the exponent must be very small to ensure a food sustainability. We suggest a bound for the value of this exponent and analyze the reliability of the scaling law for the major cities.



LT^2C^2: A language of thought with Turing-computable Kolmogorov complexity

Por • 9 mar, 2013 • Category: Opinion

Our setting leads to a Kolmogorov complexity function relative to LT^2C^2 which is computable in polynomial time, and it also induces a prediction algorithm in the spirit of Solomonoff’s inductive inference theory. We then prove the efficacy of this language by investigating regularities in strings produced by participants attempting to generate random strings. Participants had a profound understanding of randomness and hence avoided typical misconceptions such as exaggerating the number of alternations. We reasoned that remaining regularities would express the algorithmic nature of human thoughts, revealed in the form of specific patterns. Kolmogorov complexity relative to LT^2C^2 passed three expected tests examined here: 1) human sequences were less complex than control PRNG sequences, 2) human sequences were not stationary, showing decreasing values of complexity resulting from fatigue, 3) each individual showed traces of algorithmic stability since fitting of partial sequences was more effective to predict subsequent sequences than average fits. This work extends on previous efforts to combine notions of Kolmogorov complexity theory and algorithmic information theory to psychology



Extending physical chemistry to populations of living organisms. First step: measuring coupling strength

Por • 7 ene, 2013 • Category: Ambiente

For any system, whether physical or non-physical, knowledge of the form and strength of inter-individual interactions is a key-information. In an approach based on statistical physics one needs to know the interaction Hamiltonian. For non-physical systems, based on qualitative arguments similar to those used in physical chemistry, interaction strength gives useful clues about the macroscopic properties of the system. Even though our ultimate objective is the understanding of social phenomena, we found that systems composed of insects (or other living organisms) are of great convenience for investigating group effects. In this paper we show how to design experiments that enable us to estimate the strength of interaction in groups of insects. By repeating the same experiments with increasing numbers of insects, ranging from less than 10 to several hundreds, one is able to explore key-properties of the interaction. The data turn out to be consistent with a global correlation that is independent of distance (at least within a range of a few centimetres). Estimates of this average cross-correlation will be given for ants, beetles and fruit flies.



An information-processing approach to the origin of life

Por • 20 dic, 2012 • Category: Ambiente

“To a physicist or chemist life seems like ‘magic matter,’” Davies explained. “It behaves in extraordinary ways that are unmatched in any other complex physical or chemical system. Such lifelike properties include autonomy, adaptability and goal-oriented behavior — the ability to harness chemical reactions to enact a pre-programmed agenda, rather than being a slave to those reactions. “We believe the transition in the informational architecture of chemical networks is akin to a phase transition in physics, and we place special emphasis on the top-down information flow in which the system as a whole gains causal purchase over its components, This approach will reveal how the logical organization of biological replicators differs crucially from trivial replication associated with crystals (non-life). By addressing the causal role of information directly, many of the baffling qualities of life are explained.”



Predicting economic growth with classical physics and human biology

Por • 9 dic, 2012 • Category: Ambiente

We collect and analyze the data for working time, life expectancy, and the pair output and infrastructure of industrializing nations. During S-functional recovery from disaster the pair’s time shifts yield 25 years for the infrastructure’s physical lifetime. At G7 level the per capita outputs converge and the time shifts identify a heritable quantity with a reaction time of 62 years. It seems to control demand and the spare time required for enjoying G7 affluence. The sum of spare and working time is fixed by the universal flow of time. This yields analytic solutions for equilibrium, recovery, and long-term evolution for all six variables with biologically stabilized parameters.



Dynamical Diagnosis and Solutions for Resilient Natural and Social Systems

Por • 12 nov, 2012 • Category: Opinion

The concept of resilience embodies the quest towards the ability to sustain shocks, to suffer from these shocks as little as possible, for the shortest time possible, and to recover with the full functionalities that existed before the perturbation. We propose an operation definition of resilience, seeing it as a measure of stress that is complementary to the risk measures. Emphasis is put on the distinction between stressors (the forces acting on the system) and stress (the internal reaction of the system to the stressors). This allows us to elaborate a classification of stress measures and of the possible responses to stressors.



Information Theory of DNA Sequencing

Por • 4 abr, 2012 • Category: Ciencia y tecnología

DNA sequencing is the basic workhorse of modern day biology and medicine. Shotgun sequencing is the dominant technique used: many randomly located short fragments called reads are extracted from the DNA sequence, and these reads are assembled to reconstruct the original sequence. A basic question is: given a sequencing technology and the statistics of the DNA sequence, what is the minimum number of reads required for reliable reconstruction? This number provides a fundamental limit to the performance of any assembly algorithm. By drawing an analogy between the DNA sequencing problem and the classic communication problem, we formulate this question in terms of an information theoretic notion of sequencing capacity. This is the asymptotic ratio of the length of the DNA sequence to the minimum number of reads required to reconstruct it reliably. We compute the sequencing capacity explicitly for a simple statistical model of the DNA sequence and the read process. Using this framework, we also study the impact of noise in the read process on the sequencing capacity.