Conservation Laws in Cellular Automata

If X is a discrete abelian group and B a finite set, then a cellular automaton (CA) is a continuous map F:B^X-->B^X that commutes with all X-shifts. If g is a real-valued function on B, then, for any b in B^X, we define G(b) to be the sum over all x in X of g(b_x) (if finite). We say g is `conserved' by F if G is constant under the action of F. We characterize such `conservation laws' in several ways, deriving both theoretical consequences and practical tests, and provide a method for constructing all one-dimensional CA exhibiting a given conservation law.Comment: 19 pages, LaTeX 2E with one (1) Encapsulated PostScript figure. To appear in Nonlinearity. (v2) minor changes/corrections; new references added to bibliograph

Evolutionary stability of bargaining and price posting: implications for formal and informal activities

In this paper we study the co-existence of two well known trading protocols, bargaining and price-posting. To do so we consider a frictional environment where buyers and sellers play price-posting and bargaining games infinitely many times. Sellers switch from one market to the other at a rate that is proportional to their payoff differentials. Given the different informational requirements associated with these two trading mechanisms, we examine their possible co-existence in the context of informal and formal markets. Other than having different trading protocols, we also consider other distinguishing features. We find a unique stable equilibrium where price-posting (formal markets) and bargaining (informal markets) co-exist. In a richer environment where both sellers and buyers can move across markets, we show that there exists a unique stable dynamic equilibrium where formal and informal activities also co-exist whenever sellers’ and buyers’ net costs of trading in the formal market have opposite signs

Prevalence of odometers in cellular automata

We consider left permutive cellular automata Φ with no memory and positive anticipation, defined on the space of all doubly infinite sequences with entries from a finite alphabet. For each such automaton that is not one-to-one, there is a dense set of points x such that Φ : cl{Φn(x) : n ≥ 0} → cl{Φn(x) : n ≥ 0} is topologically conjugate to an odometer, the "+1" map on the countable product of finite cyclic groups. This set is a dense Gδ subset of an appropriate subspace. We identify the odometer in several cases

LA TUTELA GIURIDICA DELLA FORMA ESPRESSIVA NELL'OPERA D'ARTE CONTEMPORANEA

ABSTRACT: il lavoro di ricerca intende indagare una specifica problematica che investe la disciplina autoriale (regolata dalla legge 22 aprile 1941, n. 633) nella tutela apprestata alle opere dell'arte contemporanea (ai sensi in particolare dell'art. 2, comma 1, numero 4 l.d.a.). In particolare si vuole analizzare l'adattabilit\ue0 della normativa a quelle particolari tipologie di lavori artistici che mutano sensibilmente rispetto al passato la nozione di "forma espressiva", ossia il modo sensibile con cui l'artista/autore esteriorizza la propria idea creativa al pubblico: si tratta nello specifico delle opere d\u2019arte immateriali e appropriative, intendendosi nel primo caso quelle che prescindono da una dimensione concreta per negazione stessa di una forma espressiva materiale e, nel secondo caso, quelle che invece assumono la medesima forma di opere d\u2019arte gi\ue0 tutelate, mutandone tuttavia il significato artistico. L\u2019analisi parte dall'assunto che il sistema di tutela autoriale italiano, pur prevedendo astrattamente la possibilit\ue0 di riconoscere protezione ad ogni opera dell'ingegno a carattere creativo "qualunque ne sia il modo o la forma di espressione" (art. 1, comma 1, l.d.a.), in realt\ue0 appare ancora fortemente ancorato ad una concezione materiale dell'opera d'arte, come dimostra una consolidato orientamento al riguardo. Il lavoro intende dunque valutare la possibilit\ue0 di ricomprendere nella previsione legislativa simili opere dell\u2019ingegno a carattere creativo e, qualora ci\uf2 risulti sostenibile, verificare in che modo ad esse si possano applicare gli istituti tradizionali del diritto civile e d'autore (su tutti la propriet\ue0 e la disciplina dei contratti) per la loro circolazione sul mercato.ABSTRACT: the dissertation aims at analyzing a specific problem that involves the authorial legislation (regulated by the Law April 22, 1941, n. 633) for what concerns the legal protection of contemporary art works (in application to art. 2, paragraph 1, number 4, L. 633/1941). In particular the thesis focuses on the adaptability of the legislation to those particular types of artistic works that change significantly the notion of "form of expression", which can be defined as the perceptible way in which the artist externalizes his own creative idea to the public: it\u2019s the case of not material and appropriation art. In the first case we have conceptual works of art completely without a material form of expression and, in the second case, those which take the same form of expression of an already protected work of art, but changing its artistic significance. Even if the italian authorial law seems to provide legal protection to any creative intellectual work "whatever is the mode or form of expression" (according to art. 1, paragraph 1, L. 633/1941), actually it still appears to be strongly anchored to a material conception of the work of art, as evidenced by a consolidated orientation about. The dissertation thus intended verify the possibility of including in the legislative provision even those works which are not incorporated in material mediums and, after that, check out how they can be applied to the traditional issues of civil and copyright law (especially property and contract law) in their commercial circulation on the economic market

Proteome readjustments in the apoplastic space of Arabidopsis thaliana ggt1 mutant leaves exposed to UV-B radiation

Ultraviolet-B radiation acts as an environmental stimulus, but in high doses it has detrimental effects on plant metabolism. Plasma membranes represent a major target for ROS generated by this harmful radiation. Oxidative reactions occurring in the apoplastic space are counteracted by antioxidative systems mainly involving ascorbate and, to some extent, glutathione. The occurrence of the latter and its exact role in the extracellular space are not well documented, however. In Arabidopsis thaliana, the gamma-glutamyl transferase isoform GGT1 bound to the cell wall takes part in the so-called gamma-glutamyl cycle for extracellular glutathione degradation and recovery, and may be implicated in redox sensing and balance. In this work, oxidative conditions were imposed with UV-B and studied in redox altered ggt1 mutants. The response of ggt1 knockout Arabidopsis leaves to UV-B radiation was assessed by investigating changes in extracellular glutathione and ascorbate content and their redox state, and in apoplastic protein composition. Our results show that, on UV-B exposure, soluble antioxidants respond to the oxidative conditions in both genotypes. Rearrangements occur in their apoplastic protein composition, suggesting an involvement of H2O2, which may ultimately act as a signal. Other important changes relating to hormonal effects, cell wall remodeling, and redox activities are discussed. We argue that oxidative stress conditions imposed by UV-B and disruption of the gamma-glutamyl cycle result in similar stress-induced responses, to some degree at least. Data are available via ProteomeXchange with identifier PXD001807

Control of wind-wave power on morphological shape of salt marsh margins

Salt marshes are among the most common morphological features found in tidal landscapes and provide ecosystem services of primary ecological and economic importance. However, the continued rise in relative sea level and increasing anthropogenic pressures threaten the sustainability of these environments. The alarmingly high rates of salt marsh loss observed worldwide, mainly dictated by the lateral erosion of their margins, call for new insights into the mutual feedbacks among physical, biological, and morphological processes that take place at the critical interface between salt marshes and the adjoining tidal flats. We combined field measurements, remote sensing data, and numerical modeling to investigate the interplays between wind waves and the morphology, ecology, and planform evolution of salt marsh margins in the Venice Lagoon of Italy. Our results confirm the existence of a positive linear relationship between incoming wave power density and rates of salt marsh lateral retreat. In addition, we show that lateral erosion significantly decreases when halophytic vegetation colonizes the marsh margins, and that different erosion rates in vegetated margins are associated with different halophytes. High marsh cliffs and smooth shorelines are expected along rapidly eroding margins, whereas erosion rates are reduced in gently sloped, irregular edges facing shallow tidal flats that are typically exposed to low wind-energy conditions. By highlighting the relationships between the dynamics and functional forms of salt marsh margins, our results represent a critical step to address issues related to conservation and restoration of salt marsh ecosystems, especially in the face of changing environmental forcings