Review of Recent Developments in the Random-Field Ising Model

A lot of progress has been made recently in our understanding of the random-field Ising model thanks to large-scale numerical simulations. In particular, it has been shown that, contrary to previous statements: the critical exponents for different probability distributions of the random fields and for diluted antiferromagnets in a field are the same. Therefore, critical universality, which is a perturbative renormalization-group prediction, holds beyond the validity regime of perturbation theory. Most notably, dimensional reduction is restored at five dimensions, i.e., the exponents of the random-field Ising model at five dimensions and those of the pure Ising ferromagnet at three dimensions are the same.     

Stability of interfaces in a random environment. A rigorous renormalization group analysis of a hierarchical model

We study a hierarchical model of domain walls in aD-dimensional bond disordered Ising model at low temperatures. Using a renormalization group method inspired by the work of Bricmont and Kupiainen for the random field Ising model, we prove the existence of rigid interfaces at low enough temperatures in dimensionsD>3.     

Evaporation and heat exchanges between the sea and the atmosphere in the Gulf of Trieste during 1988

Summary Daily mean values of meteo-oceanographic parameters are used to compute evaporation and heat fluxes between the sea and the atmosphere in the Gulf of Trieste during 1988. Incoming solar radiation, long-wave radiation, latent and sensible heat fluxes are considered in the total heat budget. The contribution of the single parameters entering each formula is examined and a comparison between the results from different evaporative formulae is performed. The total heat budget for the year considered gives a net loss of energy of 21 W/m² which must be supplied by the heat transported by marine currents. The balance is positive for the sea surface from April to July, negative for the remaining period. Long-wave radiation accounts for the 45% of the total heat loss, latent heat for 53% and sensible heat for 2%. Computed annual mean evaporation is 1058 mm, with high peaks of more than 15 mm/day during strong Bora wind events. Evaporation slightly prevails on precipitation giving a net water loss of 30 cm. A comparison with what is found in the literature shows these results representative of the entire North Adriatic Sea. They confirm that this basin represents a sink of heat whose role in the general Mediterranean circulation consists in trasforming surface warmer waters coming from South in denser ones.     

Spectroscopic study on nystatin conformational modifications generated by its interaction with the solvent

Conformational transformations of the tetraenic nystatin chromophore under the influence of solvents and UV irradiation have been studied by absorption, fluorescence and wide-line NMR spectroscopy.     

Gibbs states of the Hopfield model in the regime of perfect memory

Summary We study the thermodynamic properties of the Hopfield model of an autoassociative memory. IfN denotes the number of neurons andM (N) the number of stored patterns, we prove the following results: IfM/N 0 asN , then there exists an infinite number of infinite volume Gibbs measures for all temperaturesT<1 concentrated on spin configurations that have overlap with exactly one specific pattern. Moreover, the measures induced on the overlap parameters are Dirac measures concentrated on a single point and the Gibbs measures on spin configurations are products of Bernoulli measures. IfM/N , asN for small enough, we show that for temperaturesT smaller than someT()<1, the induced measures can have support only on a disjoint union of balls around the previous points, but we cannot construct the infinite volume measures through convergent sequences of measures.Work partially supported by the Commission of the European Communities under contract No. SC1-CT91-0695     

Kinetic resolution of racemic allylic alcohols via iridium-catalyzed asymmetric hydrogenation: scope,synthetic applications and insight into the origin of selectivity

Asymmetric hydrogenation is one of the most commonly used tools in organic synthesis, whereas, kinetic resolution via asymmetric hydrogenation is less developed. Herein, we describe the first iridium catalyzed kinetic resolution of a wide range of trisubstituted secondary and tertiary allylic alcohols. Large selectivity factors were observed in most cases (s up to 211), providing the unreacted starting materials in good yield with high levels of enantiopurity (ee up to >99%). The utility of this method is highlighted in the enantioselective formal synthesis of some bioactive natural products including pumiliotoxin A, inthomycin A and B. DFT studies and a selectivity model concerning the origin of selectivity are presented.

Asymmetric hydrogenation is one of the most commonly used tools in organic synthesis, whereas, kinetic resolution via asymmetric hydrogenation was less developed.     

Upper bound on the decay of correlations in the plane rotator model with long-range random interaction

We give an upper bound on the decay of correlation function for the plane rotator model with Hamiltonian $$ - \frac{1}{2}\mathop \sum \limits_{xy} \frac{{J_{xy} \cos (\theta _x - \theta _y )}}{{\| {x - y} \|^{({3 \mathord{\left/ {\vphantom {3 2}} \right. \kern-\nulldelimiterspace} 2} + \varepsilon )^d } }}$$ in dimensiond=1 andd=2 when (J _xy are independent random variables with mean zero.     

Theory of nanoscale atomic lithography. An ab initio study of the interaction of "cold" Cs atoms with organthiols self-assembled monolayers on Au(111)

This paper deals with the microscopic mechanism of nanolithography of self-assembled monolayers (SAM) of alkanethiol molecules on Au(111) induced by the exposure of the film to a beam of "cold" Cs atoms. Density functional theory calculations have been carried out to elucidate the mechanism of interaction of the Cs atoms with the SAM. We found that the film damage occurs in two steps: the Cs atom penetrates the SAM and at a distance of 10-12 Angstrom from the surface donates one electron to Au, forming a Cs(+) cation which binds strongly to the surface and interacts with the polar head of the SR molecule. The thermal energy released in this process largely exceeds the energy required to stimulate the desorption of RS-SR disulfide molecules from the Au surface with consequent damage of the film. No chemical interaction occurs between Cs or Cs(+) and the hydrocarbon chain of the thiol molecule.     

Kinetics of enzyme-catalyzed alcoholysis of soybean oil in n-hexane

This work investigated the production of fatty acid ethyl esters (FAEEs) from soybean oil using n-hexane as solvent and two commercial lipases as catalysts, Novozym 435 and Lipozyme IM. A Taguchi experimental design was adopted considering the variables temperature (35–65°C), addition of water (0–10 wt/wt%), enzyme (5–20 wt/wt%) concentration, and oil-to-ethanol molar ratio (1:3–1:10). It is shown that complete conversion in FAEE is achieved for some experimental conditions. The effects of process variables on reaction conversion and kinetics of the enzymatic reactions are presented for all experimental conditions investigated in the factorial design.     

Optimization of alkaline transesterification of soybean oil and castor oil for biodiesel production

This article reports experimental data on the production of fatty acid ethyl esters from refined and degummed soybean oil and castor oil using NaOH as catalyst. The variables investigated were temperature (30–70°C), reaction time (1–3 h), catalyst concentration (0.5–1.5 w/wt%), and oil-to-ethanol molar ratio (1:3–1:9). The effects of process variables on the reaction conversion as well as the optimum experimental conditions are presented. The results show that conversions >95% were achieved for all systems investigated. In general, an increase in reaction temperature, reaction time, and in oil-to-ethanol molar ratio led to an enhancement in reaction conversion, whereas an opposite trend was verified with respect to catalyst concentration.