Multifractal Properties of Aperiodic Ising Model: role of geometric fluctuations

The role of the geometric fluctuations on the multifractal properties of the local magnetization of aperiodic ferromagnetic Ising models on hierachical lattices is investigated. The geometric fluctuations are introduced by generalized Fibonacci sequences. The local magnetization is evaluated via an exact recurrent procedure encompassing a real space renormalization group decimation. The symmetries of the local magnetization patterns induced by the aperiodic couplings is found to be strongly (weakly) different, with respect to the ones of the corresponding homogeneous systems, when the geometric fluctuations are relevant (irrelevant) to change the critical properties of the system. At the criticality, the measure defined by the local magnetization is found to exhibit a non-trivial F(alpha) spectra being shifted to higher values of alpha when relevant geometric fluctuations are considered. The critical exponents are found to be related with some special points of the F(alpha) function and agree with previous results obtained by the quite distinct transfer matrix approach.Comment: 10 pages, 7 figures, 3 Tables, 17 reference

Short Range Ising Spin Glasses: a critical exponent study

The critical properties of short-range Ising spin-glass models, defined on a diamond hierarchical lattice of graph fractal dimension $d_{f}=2.58$, 3, and 4, and scaling factor 2 are studied via a method based on the Migdal-Kadanoff renormalization-group scheme. The order parameter critical exponent $\beta$ is directly estimated from the data of the local Edwards- Anderson (EA) order parameter, obtained through an exact recursion procedure. The scaling of the EA order parameter, leading to estimates of the $\nu$ exponent of the correlation length is also performed. Four distinct initial distributions of the quenched coupling constants (Gaussian, bimodal, uniform and exponential) are considered. Deviations from a universal behaviour are observed and analysed in the framework of the renormalized flow in a two dimensional appropriate parameter space.Comment: 9 pages, 01 figure (ps

lessons from Brazilian air disasters

Purpose: The focus of this study was to analyze crisis management in a context of high-reliability organizations (HRO) evidenced in two cases of Brazilian air disasters. Aspects of human and technological natures were examined, addressing the complex sociotechnical system. Design/methodology/approach: This in-depth case study addressed the two most serious air disasters on Brazilian territory. The first case involved a midair collision between Gol Flight 1907 and the Legacy jet. In the second case, TAM flight 3054 had difficulty braking when landing at the airport and crashed into a building. Data were collected from official disaster documents. Findings: The results revealed that the management and operational activities aimed to maintain the necessary conditions that prioritize a high level of reliability. High reliability mainly involves concern over failure, reluctance to accept simplified interpretations, sensitivity to operations, commitment to resilience and detailed structure specifications. Practical implications: The implications are based on alerting highly reliable organizations, emphasizing the focus on managing more reliably, resiliently and conscientiously. Changes will be required in the operations of organizations seeking to learn to manage unexpected events and respond quickly to continually improve the responsiveness of their services. Originality/value: In the perspective of an intrinsic case study for crisis management in a context of HRO and disaster risk management, the originality of this study lies in its examination of the paradoxical nature of control within the systems of dangerous operations in complex organizations, as well as their contradictions in a high-reliability system.authorsversionpublishe

Physica A

p.2019-2024The proposal of this paper is to provide a simple angular random-walk model to build up polypeptide structures, which encompass properties of dihedral angles of folded proteins. From this model, structures will be built with lengths ranging from 125 up to 400 amino acids for the different fractions of secondary structure motifs, in which dihedral angles were randomly chosen according to narrow Gaussian probability distributions. In order to measure the fractal dimension of proteins three different cases were analyzed. The first contained α-helix structures only, the second β-strands structures and the third a mix of α-helices and β-sheets. The behavior of proteins with α-helix motifs are more compact than in other situations. The findings herein indicate that this model describes some structural properties of a protein and suggest that randomness is an essential ingredient but proteins are driven by narrow angular Gaussian probability distributions and not by random-walk processes

Dry Matter Yield and Nutritive Value of Coast-Cross N1 Preserved as Hay, Silage, and Haylage

Dry matter yield and nutritive value of coast-cross n° 1 (Cynodon dactylon (L.) Pers preserved as hay, silage and haylage were studied. The forage was harvested after 28, 35, 42 and 49 days of growth. Fertilization was completed with 400 kg/ha single superphosphate and 500 kg/ha 20-0-20 at the beginning of the experiment. The experimental design for dry matter yield (2 x 2 m plots) was a randomized block with four replications. Nutritive value was also analyzed in a randomized block design being the treatments arranged in a 3 x 4 factorial (three preservation methods and four ages). Dry matter yield increased linearly (P \u3c 0,05) with age, whilst crude protein content had an opposite effect. Dry matter content was not affected by age (P \u3e 0.05). Nutritive value of haylage was greater than those observed for hay and silage

Physica A

p.2682-2686We study the time series of the total energy of polypeptides and proteins. These time series were generated by molecular dynamics methods and analyzed by applying detrended fluctuation analysis to estimate the long-range power-law correlation, i.e. to measure scaling exponents α. Such exponents were calculated for all systems and their values follow environment conditions, i.e., they are temperature dependent and also, in a continuum medium approach, vary according to the dielectric constants (we simulated = 2 and = 80). The procedure was applied to investigate polyalanines, and other realistic models of proteins (Insect Defensin A and Hemoglobin). The present findings exhibit results that are consistent with previous ones obtained by other methodologies

Tricritical Points in the Sherrington-Kirkpatrick Model in the Presence of Discrete Random Fields

The infinite-range-interaction Ising spin glass is considered in the presence of an external random magnetic field following a trimodal (three-peak) distribution. The model is studied through the replica method and phase diagrams are obtained within the replica-symmetry approximation. It is shown that the border of the ferromagnetic phase may present first-order phase transitions, as well as tricritical points at finite temperatures. Analogous to what happens for the Ising ferromagnet under a trimodal random field, it is verified that the first-order phase transitions are directly related to the dilution in the fields (represented by $p_{0}$). The ferromagnetic boundary at zero temperature also exhibits an interesting behavior: for $0<p_{0}<p_{0}^{*} \approx 0.30856$, a single tricritical point occurs, whereas if $p_{0}>p_{0}^{*}$ the critical frontier is completely continuous; however, for $p_{0}=p_{0}^{*}$, a fourth-order critical point appears. The stability analysis of the replica-symmetric solution is performed and the regions of validity of such a solution are identified; in particular, the Almeida-Thouless line in the plane field versus temperature is shown to depend on the weight $p_{0}$.Comment: 23pages, 7 ps figure