74 research outputs found
The anisotropic Ashkin-Teller model: a renormalization group study
The two-dimensional ferromagnetic anisotropic Ashkin-Teller model is
investigated through a real-space renormalization-group approach. The critical
frontier, separating five distinct phases, recover all the known exacts results
for the square lattice. The correlation length and crossover
critical exponents are also calculated. With the only exception of the
four-state Potts critical point, the entire phase diagram belongs to the Ising
universality class.Comment: 3 ps figures, accepted for publication in Physica
Universality and scaling study of the critical behavior of the two-dimensional Blume-Capel model in short-time dynamics
In this paper we study the short-time behavior of the Blume-Capel model at
the tricritical point as well as along the second order critical line. Dynamic
and static exponents are estimated by exploring scaling relations for the
magnetization and its moments at early stage of the dynamic evolution. Our
estimates for the dynamic exponents, at the tricritical point, are and .Comment: 12 pages, 9 figure
Short-Range Ising Spin Glass: Multifractal Properties
The multifractal properties of the Edwards-Anderson order parameter of the
short-range Ising spin glass model on d=3 diamond hierarchical lattices is
studied via an exact recursion procedure. The profiles of the local order
parameter are calculated and analysed within a range of temperatures close to
the critical point with four symmetric distributions of the coupling constants
(Gaussian, Bimodal, Uniform and Exponential). Unlike the pure case, the
multifractal analysis of these profiles reveals that a large spectrum of the
-H\"older exponent is required to describe the singularities of the
measure defined by the normalized local order parameter, at and below the
critical point. Minor changes in these spectra are observed for distinct
initial distributions of coupling constants, suggesting an universal spectra
behavior. For temperatures slightly above T_{c}, a dramatic change in the
function is found, signalizing the transition.Comment: 8 pages, LaTex, PostScript-figures included but also available upon
request. To be published in Physical Review E (01/March 97
Universal scaling behavior of non-equilibrium phase transitions
One of the most impressive features of continuous phase transitions is the
concept of universality, that allows to group the great variety of different
critical phenomena into a small number of universality classes. All systems
belonging to a given universality class have the same critical exponents, and
certain scaling functions become identical near the critical point. It is the
aim of this work to demonstrate the usefulness of universal scaling functions
for the analysis of non-equilibrium phase transitions. In order to limit the
coverage of this article, we focus on a particular class of non-equilibrium
critical phenomena, the so-called absorbing phase transitions. These phase
transitions arise from a competition of opposing processes, usually creation
and annihilation processes. The transition point separates an active phase and
an absorbing phase in which the dynamics is frozen. A systematic analysis of
universal scaling functions of absorbing phase transitions is presented,
including static, dynamical, and finite-size scaling measurements. As a result
a picture gallery of universal scaling functions is presented which allows to
identify and to distinguish universality classes.Comment: review article, 160 pages, 60 figures include
Update on detection, morphology and fragility in pili annulati in three kindreds.
BACKGROUND: Pili annulati is an inherited hair shaft abnormality with a wide range of clinical expression. OBJECTIVE: We have examined closely three kindreds to reveal levels and character of expression of the phenotype and supplement current literature on the threshold for detection and aspects of hair shaft fragility. PATIENTS AND METHODS: Eleven cases of pili annulati from three families were included in a clinical and morphological study. All cases were assessed clinically and by light and scanning electron microscopy (SEM) of hair shafts. In addition, transmission electron microscopy (TEM) (four patients) and amino acid analysis (three patients) were undertaken on clinically overt cases. Results Examination by light microscopy with a fluid mountant was more sensitive than clinical examination, increasing the detection rate by 120%. Microscopic examination revealed that the characteristic periodic bands become less frequent distally in the hair shaft. Microscopic features of weathering were found in two cases, adding pili annulati to the list of structural hair shaft dystrophies that may weaken hair and dispose to weathering. Amino acid analysis of the hair of three patients with pili annulati showed elevated lysine and decreased cystine content compared to 12 normal controls, consistent with the reduced threshold for weathering. CONCLUSION: Careful light microscopy with fluid-mounted hair is needed to detect subjects mildly affected by pili annulati. Expression of the phenotype varies widely between individuals, between hairs and within hairs of the same individual, where ageing of the hair diminishes detectable features
Cytokeratin expression in pili annulati hair follicles.
Pili annulati is a rare autosomal inherited hair shaft abnormality of unknown pathogenesis in which clinical examination reveals alternating light and dark bands leading to a shiny appearance of the hair due to cavities within the cortex of the hair shaft. This is the first investigation of the proposed cytokeratin defect in pili annulati hair follicles. Four cryopreserved pili annulati and four control scalp specimens were analysed using immunohistochemistry for different 'hard' trichocytic and 'soft' epithelial cytokeratins including K1, K6, K10, K14, K16, K17, K18, K19, Ha1 and Hb1. There was no difference in staining intensity and quality of staining pattern seen in pili annulati and control scalp specimens. These results suggest that pili annulati is not caused by a defect of the cytokeratins investigated in this study
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