Scaling functions for nonequilibrium fluctuations: A picture gallery

The emergence of non-gaussian distributions for macroscopic quantities in nonequilibrium steady states is discussed with emphasis on the effective criticality and on the ensuing universality of distribution functions. The following problems are treated in more detail: nonequilibrium interface fluctuations (the problem of upper critical dimension of the Kardar-Parisi-Zhang equation), roughness of signals displaying Gaussian 1/f power spectra (the relationship to extreme-value statistics), effects of boundary conditions (randomness of the digits of pi).Comment: Invited contribution at SPIE conference on Fluctuations and Noise, Santa Fe, 2003; 9 pages, 6 figure

Large deviations in weakly interacting boundary driven lattice gases

One-dimensional, boundary-driven lattice gases with local interactions are studied in the weakly interacting limit. The density profiles and the correlation functions are calculated to first order in the interaction strength for zero-range and short-range processes differing only in the specifics of the detailed-balance dynamics. Furthermore, the effective free-energy (large-deviation function) and the integrated current distribution are also found to this order. From the former, we find that the boundary drive generates long-range correlations only for the short-range dynamics while the latter provides support to an additivity principle recently proposed by Bodineau and Derrida.Comment: 27 pages, 2 figure

Probability of the emergence of helical precipitation patterns in the wake of reaction-diffusion fronts

Helical and helicoidal precipitation patterns emerging in the wake of reaction-diffusion fronts are studied. In our experiments, these chiral structures arise with well-defined probabilities P_H controlled by conditions such as e.g., the initial concentration of the reagents. We develop a model which describes the observed experimental trends. The results suggest that P_H is determined by a delicate interplay among the time and length scales related to the front and to the unstable precipitation modes and, furthermore, the noise amplitude also plays a quantifiable role.Comment: 7 pages, 5 composite figure

Guiding-fields for phase-separation: Controlling Liesegang patterns

Liesegang patterns emerge from precipitation processes and may be used to build bulk structures at submicron lengthscales. Thus they have significant potential for technological applications provided adequate methods of control can be devised. Here we describe a simple, physically realizable pattern-control based on the notion of driven precipitation, meaning that the phase-separation is governed by a guiding field such as, for example, a temperature or a pH field. The phase-separation is modeled through a non-autonomous Cahn-Hilliard equation whose spinodal is determined by the evolving guiding field. Control over the dynamics of the spinodal gives control over the velocity of the instability front which separates the stable and unstable regions of the system. Since the wavelength of the pattern is largely determined by this velocity, the distance between successive precipitation bands becomes controllable. We demonstrate the above ideas by numerical studies of a 1D system with diffusive guiding field. We find that the results can be accurately described by employing a linear stability analysis (pulled-front theory) for determining the velocity -- local-wavelength relationship. From the perspective of the Liesegang theory, our results indicate that the so-called revert patterns may be naturally generated by diffusive guiding fields.Comment: Minor changes, to be published in Phys. Rev. E. 10 pages, 8 figure

WELT- UND HEIMENTWICKLUNGSTENDENZEN IM BODENSCHUTZ UND IN DER LANDWIRTSCHAFT ZWISCHEN STOCKHOLM UND RIO

Premda je u proteklih 20 godina između dviju svjetskih konferencija učinjeno mnogo u proizvodnji hrane i zaštiti okoliša, još uvijek ostaju brojne dileme o sudbini Zemlje i daljnjem razvoju čovječanstva na pragu trećeg milenija. U globalnim razmjerima to su ponovne prijetnje glađu zbog stalnog porasta stanovništva, povećanje temperature zraka zbog povećanih količina ugljičnog dioksida i drugih štetnih plinova, zatim prekomjerna sječa i sušenje šuma zbog kiselih kiša te erozija i zagađivanje tla i voda kemijskim polutantima, kao i napuštanjem posjeda i pretvorbom plodnih površina u građevinsko zemljište. Osim toga u članku se navode specifičnosti i potrebe poslijeratne obnove sela i poljoprivredne proizvodnje u Hrvatskoj.Although in the past 20 years from one world conference to the other much has been done in the production of foodstuffs and protection of environment, many dilemmas regarding the future of Earth and further development of mankind on the doorstep to the third millenium remain unsolved. Globally, they represent renewal of famine threats owing to the constant increase of the number of inhabitants, to increase of the temperature due to increase of the quantity of carbodioxide and other harmful gases, as well as to the over-large felling of the trees together with the dying of the forests under the impact of acid rains, and to the erosions and soil and water being polluted by chemical pollutants, then to individuals leaving the farms, on one side, and transformation of rich agricultural lands to building sites, on the other. The article also describes some specific features and needs of the post-war restauration of villages and of agricultural production in Croatia.Obwohl in den letzten 20 Jahren in der Nahrungsherstellung und im Umweltschutz viel getan worden ist, bleiben immer noch zahlreiche Dilemmas über das Schicksal der Erde und die Weiterentwicklung der Menschheit an der Schwelle des dritten Jahrtausends offen. Global betrachtet sind hier die wiederholten Hungerdrohungen wegen ständigen Bevölkerungszuwachses, die Erhöhung der Lufttemperatur wegen erhöhten Kohlendioxydgehalts und anderer schädlichen Gase, übermässiges Baumfällen und -trocknen wegen sauren Regens, Erosion und Boden- und Wasserverschmutzung durch chemische Verschmutzer, sowie Grundbesitzverlassen und die Umwandlung fruchtbarer Flächen in Baugrundstücke vorhanden. Ausserdem erwähnt der Artikel die Besonderheiten ind Ergebnisse des Nachkriegswiederaufbaus der ländlichen Gebiete und der landwirtschaftlichen Herstellung in Kroatien

BEDEUTUNG DES ERDBODENS IN NATUR- UND INAGROSYSTEMEN UND GEGENWÄRTIGE PROBLEMEMIT DESSEN BESCHÜTZUNG

U članku su iznijeta novija domaća i strana iskustva u zaštiti tla i okoliša. Pritom su korišteni i neobjavljeni podaci autora i suradnika izloženi u raspravama na radnim sastancima ili su pripremani za potrebe novog međunarodnog projekta "Dugoročni ambijentalni rizici za tla, podzemne vode i sedimente u slivnom području Dunava", koji pokreće Nizozemska fundacija za ekološki razvoj. Uvodno su obrazloženi globalni problemi proizvodnje hrane, definicija agroekosustava i njegova povezanost sa socijalnom ekologijom. Slijedi prikaz novih koncepcija o ulozi tla u prirodi i novih pojmova kao što su "kemijska vremenska bomba" i "ranjivost" tla, povezano sa spomenutim projektom. Potom se navode parametri i procjene dugoročnih rizika s primjerima acidifikacije tla, kontaminacije teškim metalima, polucije vode nitratima i fosfornim spojevima, te, ukratko, ostala oštećenja tla i terena u svijetu i kod nas. U završnom poglavlju ukazuje se na potrebu cjelovitog (holističkog) pristupa i tzv. "cross" disciplinskog istraživanja, zatim dugoročnih stacionarnih praćenja promjena u tlu i ostalim komponentama ekosustava regionalnog značaja, zajedno s akutnom potrebom formiranja odgovarajućih informacijskih sustava.The essay tells of new domestic and foreign achievements and experiences in protecting soils and environment. The unpublished data of the author and his assistants\u27 work are used here, but were also expressed during discussions at working meetings - they have been prepared for the international project "Long-term risks of environment on soils, underground waters and sediments in the Danube and its affluent area" which has been initiated by the Netherlands Foundation for Environmental Development. At the beginning of the essay, global problems of food production and definition of agricultural and ecological systems as well as the connection with the social ecology were introduced. Then, there followed a survey of new conceptions on the role of soil in nature, and new ideas on "the chemical time bomb" as well as on the "vulnerability" of soil in connection with the above mentioned project. Then, we continued with the enumeration of parameters and the estimation of long-term risks on the examples of acidification of soil, its contamination with heavy metals, of pollution of water by nitrates and phosphorous compounds, and finally the short survey of other damages on soils in areas and terrains in the world as in our country. The final chapter points to the necessary holistic approach and cross disciplinarian research work, to the long-term stationary surveying of soil changes and of other components of ecological system of local importance, and finally, an acute need to form appropriate data computer processing programs was stated.In dieser Darstellung sind neuere in- und ausländische Erfahrungen in Beschützung des Erdbodens und der Umwelt ausgelegt. Dabei hat man sich der noch nicht veröffentlichten Angaben des Autors und seiner Mitarbeiter bedient, die in Erörtungen während verschiedener Arbeitsversammlungen ausgelegt oder für Bedarfe des neuen internationalen, von einer holländischen Stiftung für ökologische Entwicklung inizierten Projektes namens "Langfristige Ambientgefahren für den Erdboden, für Unterwässer und für Sedimente im Donau-Zusammenflussgebiert" vorbereitet worden sind. Einleitend sind allgemeine Probleme der Nahrungsproduktion, Definition des Agrosystems und dessen Verknüpfung mit der Sozialökologie ausgelegt. Dann folgt eine Auslegung neuer Auffassung der Erdbodenrolle in der Natur neuer Begriffe, wie z.B. "chemische Zeitbombe" und "Verletztbarkeit" des Bodens in Verbindung mit dem erwähnten Projekt. Danach werden Parameter und Bewertung langfristiger Risikos angeführt mit Beispielen der Bodenazidifikation, Kontamination durch Schwermetalle, Wasserausscheidung durch Nitrate und Phosphorverbindungen und kurz: andere Erdboden- und Terainbeschädigungen in der Welt und bei uns. Im Abschlusskapitel wird auf den Bedarf einer gesamten (holistischen) Auffassung und der sgn. "cross" - Fachuntersuchungen hingewiesen, dann auf die langfristig stationierte Betrachtung der Bodenveränderungen und anderer EKO-System-Komponenten regionalen Charakters zusammen mit einem akuten Bedarf der Gestaltung entsprechender Informationssystemen