An evaluation of the fatigue crack resistance of human dentin was conducted to identify the degree of degradation that arises with aging and the dependency on tubule orientation. Fatigue crack growth was achieved in specimens of coronal dentin through application of Mode I cyclic loading and over clinically relevant lengths (0 ≤ a ≤ 2 mm). The study considered two directions of cyclic crack gro...

Crack emerged in the late 1980s in Brazil. This emergence was a critical moment for public health; the growing AIDS epidemic led intravenous cocaine users to migrate toward crack use to avoid the use of injection drugs. At the same time, young consumers of marijuana also began using crack, largely due to market strategies in drug trafficking that led to a shortage of marijuana and the availabil...

BACKGROUND In Brazil, crack cocaine use remains a healthcare challenge due to the rapid onset of its pleasurable effects, its ability to induce craving and addiction, and the fact that it is easily accessible. Delayed action on the part of the Brazilian Government in addressing the drug problem has led users to develop their own strategies for surviving the effects of crack cocaine use, particu...

A permeable crack model is proposed to analyze crack growth in a piezoelectric ceramic. In this model, a permeable crack is modeled as a vanishing thin, finite dimension, rectangular slit with dielectric medium inside. A first-order approximation solution is derived in terms of the slit height, h0 . The main contribution of this paper is that the newly proposed permeable crack model reveals tha...

The mechanisms of fatigue-crack propagation are examined with particular emphasis on the similarities and differences between cyclic crack growth in ductile materials, such as metals, and corresponding behavior in brittle materials, such as intermetallics and ceramics. This is achieved by considering the process of fatiguecrack growth as a mutual competition between intrinsic mechanisms of crac...

Seasonal cracking of the soil matrix results in poor estimates of runoff and infiltration by simulation models due to the changing soil storage conditions. In this study, soil surface elevation changes were measured every two weeks and soil crack volume was calculated for a two-year period at the USDA-Agricultural Research Service, Riesel Y-2 watershed in central Texas. Soil anchors were placed...

An important task in mixed-mode fracture analysis and prediction is the simulation of crack growth under mixed-mode conditions. To complete such a task, one must have (a) a computer code capable of handling the kinematics of general crack growth and determining the stress and deformation states during crack growth, and (b) a fracture criterion that can properly predict the instant and direction...

In order to monitor the crack tip propagation of aluminum alloy, this study investigates the variation of the spectrum characteristics of a fiber Bragg grating (FBG), combined with an analysis of the spectrum simulation. The results identify the location of the subordinate peak as significantly associated with the strain distribution along the grating, corresponding to the different plastic zon...

In this paper, the stress intensity factor (SIF) variations along an arbitrarily developing crack front, the non-planar fatigue-crack growth patterns, and the fatigue life of a round bar with an initially straight-fronted surface crack, are studied by employing the 3D symmetric Galerkin boundary element method-finite element method (SGBEM-FEM) alternating method. Different loading cases, involv...

Recent reports suggest that brain-derived neurotrophic factor (BDNF) could be a biomarker for relapse, drug craving and withdrawal severity. In particular, elevated BDNF levels among former cocaine users have been associated with higher rates of relapse in 90 d. However, no data are available on BDNF levels at baseline and during crack cocaine withdrawal. This study evaluated BDNF among crack c...