Közmenedzsment modellek alkalmazása az Európai Statisztikai Rendszer szervezeteinél

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The Problem of the "Prebiotic and Never Born Proteins"

It has been argued that the limited set of proteins used by life as we know it could not have arisen by the process of Darwinian selection from all possible proteins. This probabilistic argument has a number of implicit assumptions that may not be warranted. A variety of considerations are presented to show that the number of amino-acid sequences that need have been sampled during the evolution of proteins is far smaller than assumed by the argument.Comment: 14 Pages; International Journal of Astrobiology / FirstView Article / October 2012, pp 1

Chemical Transformations in Proto-Cytoplasmic Media. Phosphorus Coupling in the Silica Hydrogel Phase

It has been proposed that prebiotic chemical studies on the emergence of primitive life would be most relevant when performed in a hydrogel, rather than an aqueous, environment. In this paper we describe the ambient temperature coupling of phosphorus oxyacids [Pi] mediated by Fe(II) under aerobic conditions within a silica hydrogel (SHG) environment. We have chosen to examine SHGs as they have considerable geological precedence as key phases in silicification en route to rock formation. Following a description of the preparation and characterization studies on our SHG formulations, coupling experiments between Pi species are described across multiple permutations of (i) Pi compound; (ii) gel formulation; (iii) metal salt additive; and (iv) pH-modifying agent. The results suggest that successful Pi coupling, indicated by observation of pyrophosphate [PPi(V)] via 31P-NMR spectroscopy, takes place when the following components are present: (i) a mixture of mixture of Pi(III) and Pi(V) or pure PPi(III-V); (ii) Fe(II); (iii) acetic or formic acid (not hydrochloric acid); (iv) aerobic conditions or the presence of H2O2 as an oxidant; and (v) the presence of a gel system. On the basis of these, and aqueous control reactions, we suggest mechanistic possibilities

Computational and Proof Complexity of Partial String Avoidability

The partial string avoidability problem, also known as partial word avoidability, is stated as follows: given a finite set of strings with possible ``holes\u27\u27 (undefined symbols), determine whether there exists any two-sided infinite string containing no substrings from this set, assuming that a hole matches every symbol. The problem is known to be NP-hard and in PSPACE, and this paper establishes its PSPACE-completeness. Next, string avoidability over the binary alphabet is interpreted as a version of conjunctive normal form (CNF) satisfiability problem (SAT), with each clause having infinitely many shifted variants. Non-satisfiability of these formulas can be proved using variants of classical propositional proof systems, augmented with derivation rules for shifting constraints (such as clauses, inequalities, polynomials, etc). Two results on their proof complexity are established. First, there is a particular formula that has a short refutation in Resolution with shift, but requires classical proofs of exponential size (Resolution, Cutting Plane, Polynomial Calculus, etc.). At the same time, exponential lower bounds for shifted versions of classical proof systems are established

From Cosmos to Intelligent Life: The Four Ages of Astrobiology

The history of life on Earth and in other potential life-bearing planetary platforms is deeply linked to the history of the universe. Since life as we know it relies on chemical elements forged in dying heavy stars, the universe needs to be old enough for stars to form and evolve. Current cosmological theory indicates that the universe is 13.7$\pm 0.13$ billion years old and that the first stars formed hundreds of millions of years after the big bang. At least some stars formed with stable planetary systems wherein a set of biochemical reactions leading to life could have taken place. In this lecture, I argue that we can divide cosmological history into four ages, from the big bang to intelligent life. The Physical Age describes the origin of the universe, of matter, of cosmic nucleosynthesis, as well as the formation of the first stars and galaxies. The Chemical Age begun when heavy stars provided the raw ingredients for life through stellar nucleosynthesis and describes how heavier chemical elements collected in nascent planets and moons to give rise to prebiotic biomolecules. The Biological Age describes the origin of early life, its evolution through Darwinian natural selection, and the emergence of complex multicellular life forms. Finally, the Cognitive Age describes how complex life evolved into intelligent life capable of self-awareness and of developing technology through the directed manipulation of energy and materials. We conclude discussing whether we are the rule or the exception.Comment: 7 pages, Opening plenary talk delivered at the S\~ao Paulo Advanced School of Astrobiology, S\~ao Paulo, December 2011. In press, Int. J. Astrobio. Reference update