Artificial Chemistry

John von Neumann constructed several models (originally known as kinematic models ) with the goal of incorporating the logical core of self-production into the system. Others studied von Neumann s model and modified it, for example, Walter Fontana, who devised the AlChemy (Algorithmic Chemistry) system. This can be described as artificial chemistry, an evolution reactor in which the objects which react are not molecules but mathematical functions. 

The set of molecules S = si,. .. Si,. .. Sn, where n might be infinite, describes aU vahd molecules that may appear in an artificial chemistry. A molecule s representation is often referred to as its structure and is set in contrast to its function, which is given by the reaction rules R. The description of valid molecules and their structure is usually the first step in the definition of an AC. This step is analogous to the part of chemistry that describes what kind of atomic configurations form stable molecules and how these molecules appear. 

Artificial chemistry algorithms intend to mimic as close as possible a real chemistry process, by assigning kinetic coefficients, defining molecule representation and focusing on an efficient energy conservation state. 

A review of scientific work in artificial chemistry can be found in [7]. Chemical inspired paradigms can be differenced by their parameter representation, which can be explicit or impUdL A DNA based algorithm is applied in [8] to solve the small hitting set problon. This NP-complete problem takes exponential time to solve it and it was demonstrated that when using DNA-based supercomputing, only polynonfial time is needed to solve it. 

P. Dittrich, J. Ziegler, W. Banzhaf, Artificial chemistries-a review. Artif. Life 7, 225-275 (2001)... 

Dittrich et al. [1], described the basic terms to characterize and classify artificial chemistries. Given the statistical and qualitative features of the reaction laws and element/component representation, our proposed algorithm is an abstraction of the chemical reaction process and can be described as a constructive dynamical... 

In the Lattice Artificial Chemistry model and also in later extensions of the GARD model, formation of the membrane itself is explicitly included. In GARD every species Aj may, in principle, catalyze every possible reaction in which another species A is formed/decomposed, with a catalytic probability Pij. This / matrix defines the chemical structure of the (auto) catalytic networks. The role and formation of the amphiphilic assembly that becomes the enclosing membrane can be incorporated into the catalytic network by assuming that the same molecules that form the assembly are also responsible for the mutually catalytic functions. This is a model that contains similarities with the sulfide protocell systems discussed earlier. The results of numerical simulations based on extended GARD model versions demonstrated the spontaneous emergence of catalytical assemblies that tend to lie below the Morowitz boundary. 

In the previous sections we have analyzed computational models of artificial chemistry that indicate that, in principle, the chemistry can be designed so as to create an artificial catalytic system, that optimizes its selectivity by evolutionary adaptation. 

The many possible oxidation states of the actinides up to americium make the chemistry of their compounds rather extensive and complicated. Taking plutonium as an example, it exhibits oxidation states of -E 3, -E 4, +5 and -E 6, four being the most stable oxidation state. These states are all known in solution, for example Pu" as Pu ", and Pu as PuOj. PuOl" is analogous to UO , which is the stable uranium ion in solution. Each oxidation state is characterised by a different colour, for example PuOj is pink, but change of oxidation state and disproportionation can occur very readily between the various states. The chemistry in solution is also complicated by the ease of complex formation. However, plutonium can also form compounds such as oxides, carbides, nitrides and anhydrous halides which do not involve reactions in solution. Hence for example, it forms a violet fluoride, PuFj. and a brown fluoride. Pup4 a monoxide, PuO (probably an interstitial compound), and a stable dioxide, PUO2. The dioxide was the first compound of an artificial element to be separated in a weighable amount and the first to be identified by X-ray diffraction methods. 

In chemistry, chemical structures have to be represented in machine-readable form by scientific, artificial languages (see Figure 2-2). Four basic approaches are introduced in the following sections trivial nomenclature systematic nomenclature chemical notation and mathematical notation of chemical structures. 

R. K. Lindsay, B. G. Buchanan, E.A. Feigenbaum, J. Lederberg, Applications of Artificial Intelligence for Organic Chemistry, McGraw-Hill, New York, 1980. 

H. M. Cartwright, Applieation.s of Artificial Intelligence in Chemistry Oxford, Oxford (1993). 

As with the case of energy input, detergency generally reaches a plateau after a certain wash time as would be expected from a kinetic analysis. In a practical system, each of its numerous components has a different rate constant, hence its rate behavior generally does not exhibit any simple pattern. Many attempts have been made to fit soil removal (50) rates in practical systems to the usual rate equations of physical chemistry. The rate of soil removal in the Launder-Ometer could be reasonably well described by the equation of a first-order chemical reaction, ie, the rate was proportional to the amount of removable soil remaining on the fabric (51,52). In a study of soil removal rates from artificially soiled fabrics in the Terg-O-Tometer, the percent soil removal increased linearly with the log of cumulative wash time. 

This book presents a unified treatment of the chemistry of the elements. At present 112 elements are known, though not all occur in nature of the 92 elements from hydrogen to uranium all except technetium and promethium are found on earth and technetium has been detected in some stars. To these elements a further 20 have been added by artificial nuclear syntheses in the laboratory. Why are there only 90 elements in nature Why do they have their observed abundances and why do their individual isotopes occur with the particular relative abundances observed Indeed, we must also ask to what extent these isotopic abundances commonly vary in nature, thus causing variability in atomic weights and possibly jeopardizing the classical means of determining chemical composition and structure by chemical analysis. 

The insect s choice of food may be governed to a considerable extent, as ours is, by attractants and repellents. In many instances, the actual insecticidal action of plant extractives may be due primarily to an artificially high level of application, while, in fact, the parent plants are only repellent in the field. This repellency may appear to be resistance on the part of the plant, and the chemistry of such resistance factors has begun to receive much-needed attention. For example, Smissman and his coworkers have examined the chemical basis for the inherited resistance of some strains of corn to attack by the European corn borer. 6-Methoxybenzoxazolinone (X) was isolated (2, SO) and shown to be one of the principal resistance factors, and a number of synthetic analogs were found to... 

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