OBJECTIVE To examine relationships between parenting behaviors, parent-child relationship, and moderating effects of age on youth substance use among a community sample of African-American mothers who use crack cocaine and their children (12-17 years). METHODS Maternal-child dyads (n = 208) were recruited through street outreach and snowball sampling and completed interviews about substance u...

in this paper, the crack detection and depth ratio estimation method are presented in beamlikestructures using elman networks. for this purpose, by using the frequencies of modes asinput, crack depth ratio of each element was detected as output. performance of the proposedmethod was evaluated by using three numerical scenarios of crack for fixed-simply supportedbeam consisting of a single crack...

introduction: the aim of this study was to investigate the scanning electron microscope (sem) analysis of tooth surface irradiated by different parameters of er:yag laser. methods: 15 caries-free extracted human third molars were used in this study. the teeth were put into 5 groups for laser irradiation as follows: group 1 (power: 2.5 w, energy: 250 mj); group 2(power: 3 w, energy: 300 mj); gro...

It is generally accepted that a certain change occurs in teeth containing a vital pulp as a response to such injuries as caries, attrition and abrasion. In these cases dentinal tubules are filled with gaseous substances. In ground sections the groups of dentinal tubules, appearing black in transmitted light, have been named dead tracts by FisH[1-3]. However, there are few reports on the observa...

An infinite elastic medium with a planar crack is considered. The crack is subjected to the pressure of fluid injected at a point on the crack surface. Description of the crack growth is based on the lubrication equation (balance of the injected fluid and the crack volume), the equation for crack opening caused by fluid pressure on the crack surface, the Poiseuille equation related local fluid ...

An assessment of the plasticity-induced crack-closure concept is made, in light of some of the questions that have been raised on the validity of the concept, and the assumptions that have been made concerning crack-tip damage below the crack-opening stress. The impact of using other crack-tip parameters, such as the cyclic crack-tip displacement, to model crack-growth rate behavior was studied...