The maintenance of sex in bacteria is ensured by its potential to reload genes

Why sex is maintained in nature is a fundamental question in biology. Natural genetic transformation (NGT) is a sexual process by which bacteria actively take up exogenous DNA and use it to replace homologous chromosomal sequences. As it has been demonstrated, the role of NGT in repairing deleterious mutations under constant selection is insufficient for its survival, and the lack of other viable explanations have left no alternative except that DNA uptake provides nucleotides for food. Here we develop a novel simulation approach for the long-term dynamics of genome organization (involving the loss and acquisition of genes) in a bacterial species consisting of a large number of spatially distinct populations subject to independently fluctuating ecological conditions. Our results show that in the presence of weak inter-population migration NGT is able to subsist as a mechanism to reload locally lost, intermittently selected genes from the collective gene pool of the species through DNA uptake from migrants. Reloading genes and combining them with those in locally adapted genomes allow individual cells to re-adapt faster to environmental changes. The machinery of transformation survives under a wide range of model parameters readily encompassing real-world biological conditions. These findings imply that the primary role of NGT is not to serve the cell with food, but to provide homologous sequences for restoring genes that have disappeared from or become degraded in the local population.Comment: 16 pages with 3 color figures. Manuscript accepted for publication in Genetics (www.genetics.org

Computerized optimization of elastic booster autopilots. Volume 1: Technical manual

The philosophy and the mathematical basis of the nonlinear programming algorithm underlying the development of the COEBRA program were given. A User's Manual was given in a separate document. The purpose of this work was to convert the COEBRA program from the CDC 6400/6500 digital computer system to the UNIVAC 1108 at the George C. Marshall Space Flight Center and to provide an instruction manual on the use of the program

An Adaptive Identification and Prediction Algorithm for the Real-Time Forecasting of Hydrologic Time Series

In order to achieve the effective control of water resources systems, one must know the future behavior of the inputs to that particular system. Because of the uncertainties inherent in water resources processes, the prediction algorithm, to be constructed, should include stochastic elements, too. Moreover, the algorithm should be recursive to avoid cumbersome computations and to be able for real-time forecasting. In this paper we present a method which is applicable for both linear and nonlinear hydrologic systems having not completely time-invariant properties. The algorithms are based on the state space description of the processes involved and utilize the Kalman stochastic filtering technique. Due to the unknown nature of noise processes, the basic algorithms were changed to be adaptive. Using the algorithms the joint handling of water quantity and quality data becomes feasible

On the Optimal Adaptive Parameter Estimation Of Water Resources Control Systems

As water resource systems have grown larger and more complex, the importance of optimum operation of these systems has increased. Several IIASA papers have been published attacking these problems which are in essence, the problems of estimating/controlling the state of WR systems. J. Casti gave algorithms for the stochastic inflow-nonlinear objective reservoir control problem; A. Szollosi-Nagy outlined the closed-loop control of linear stochastic water quality systems with quadratic performance measure; and quite recently, K. Takeuchi dealt with the problem of typhoon forecasting using stochastic filtering techniques. There is at least one aspect which is common to these approaches, and that is the way they look at the dynamics of the water resource systems

A baromfi ágazat versenyképességének helyreállítása

A helyzetfelmérés eredményeként megállapítható, hogy a magyar baromfi ágazat legfÅ‘bb problémája a nemzetközi versenyképesség romlása. Ennek számos következménye lehet, ami közvetlenül vagy közvetve érinti a fenntarthatóság három pillérét, a gazdasági, társadalmi és természeti tényezÅ‘ket. Az elemzésben feltárt problémák ok-okozati kapcsolataiból egyértelműen kiderül, hogy mindezt az ágazat hazai és nemzetközi piaci kiszolgáltatottságának növekedése, valamint az ágazatban tapasztalható objektív versenyhátrányok megléte okozta. Ez utóbbi a versenytársakhoz képest tartósan alacsony jövedelmezÅ‘ségnek, a technológiai színvonalban tapasztalható lemaradásnak, a korszerű tudás, illetve az ágazati stratégia hiányának tulajdonítható. A fÅ‘bb problémakörökre összpontosítva az ágazat stratégiai célkitűzéseként megfogalmazható az újból versenyképes magyar baromfi ágazat, melyhez specifi kus célkitűzésként rendelhetÅ‘ az ágazat hazai és nemzetközi piaci kiszolgáltatottságának csökkentése, a jövedelem növelése, illetve a műszaki és technológiai fejlÅ‘dés. Véleményünk szerint a bemutatotthoz hasonló struktúrában, célirányosan, az egyes termékpályák szereplÅ‘inek bevonásával indokolt az állattenyésztési ágazatokat érintÅ‘ kérdések tisztázása és azok idÅ‘szakonkénti felülvizsgálata. Az adott ágazaton belüli problémák és azok közötti ok-okozati kapcsolatok feltárásával, majd az erre épülÅ‘ célstruktúra-célhierarchia felállításával cselekvési programok, elvégzendÅ‘ feladatok fogalmazhatók meg. Mindezen feladatok idÅ‘beli összehangolása, rendszerszemléletben való kezelése indokolja az ágazatokra lebontott, s ezen keresztül a teljes állattenyésztés stratégiai tervének kialakítását. Egyes tevékenységek kiemelése, megvalósítása a többi fi gyelembevétele nélkül rendkívüli veszélyeket rejt magában. --------------------- As a result of diagnosis it can be stated that deterioration of international competitiveness is the most important problem of the Hungarian poultry sector. This statement may have many consequences which directly or indirectly are connected with three aspects of sustainability: economic, social and natural factors. From causal relations of problems discovered in the analysis it has become unambiguosly clear that increasing domestic and international market defencelessness as well as objective competitive disadvantages were the causing factors in the sector. The mentioned disadvantages are due to low long-run profi tability and technology level lagging behind competitors as well as absence of modern knowledge and sector strategy. Concentrating on major problems, creating once more a competitive Hungarian poultry sector can be set as a strategic goal, while decreasing domestic and international market defencelessness, increasing profi t and technological improvement may serve as specifi c aims. Clearing and periodic reconsideration of problems of other livestock sectors can happen in a similar structure, purposefully, together with persons playing a part in product chains. By discovering causal relations of problems within a given sector and constructing a hierarchy of goals action programs and tasks to be completed can be formulated. Timely harmonisation of these tasks as well as treating them as a system justifi es creating strategic plans for sectors and the whole livestock production. Preferring some activities and implement them without any consideration to other ones is extremely dangerous.poultry sector, problem-tree, goal-structure, international competitiveness, market defencelessness, competitive disadvantages, Agribusiness, Livestock Production/Industries, Production Economics, baromfi ágazat, problémafa, célstruktúra, nemzetközi versenyképesség, versenyhátrányok,