The problem of an inclined crack in an orthotropic strip

The elastostatic problem for an infinite orthotropic strip containing crack was considered. It was assumed that the orthogonal axes of material orthotropy may have an arbitrary angular orientation with respect to the orthogonal axes of geometric symmetry of the uncracked strip. The crack was located along an axis of orthotropy, hence, at an arbitrary angle with respect to the sides of the strip. The general problem was formulated in terms of a system of singular integral equations for arbitrary crack surface tractions. As examples Modes 1 and 2 stress intensity factors were calculated for the strip having an internal or an edge crack with various lengths and angular orientations

Stress intensity factors for an inclined crack in an orthotropic strip

The elastostatic problem for an infinite orthotropic strip containing a crack is considered. It is assumed that the orthogonal axes of material orthotropy may have an arbitrary angular orientation with respect to the orthogonal axes of geometric symmetry of the uncracked strip. The crack is located along an axis of orthotropy, hence at an arbitrary angle with respect to the sides of the strip. The general problem is formulated in terms of a system of singular integral equations for arbitrary crack surface tractions. As examples Modes I and II stress intensity factors are calculated for the strip having an internal or an edge crack with various lengths and angular orientations. In most calculations uniform tension or uniform bending away from the crack region is used as the external load. Limited results are also given for uniform normal or shear tractions on the crack surface

On a class of nonlocal nonlinear Schrödinger equations and wave collapse

A similar type of nonlocal nonlinear Schrödinger (NLS) system arises in both water waves and nonlinear optics. The nonlocality is due to a coupling between the first harmonic and a mean term. These systems are termed nonlinear Schrödinger with mean or NLSM systems. They were first derived in water waves by Benney-Roskes and later by Davey-Stewartson. Subsequently similar equations were derived and found to be fundamental systems in quadratically nonlinear optical media. Wave collapse can occur in these systems. The collapse structure and the role of the ground state in the collapse process are studied. There are similarities to the well-known collapse mechanism associated with classical NLS system. Numerical simulations show that NLSM collapse occurs with a quasi self-similar profile that is a modulation of the corresponding ground-state. Further, it is found that NLSM collapse can be arrested by adding small nonlinear saturation

Challenge-proven immediate type multiple local anesthetic hypersensitivity in a child.

Adverse reactions to local anesthetics (LA) are commonly reported in patients undergoing dental procedures and other minor surgical procedures. Most of these reactions, however, originate from psychosomatic, vasovagal or toxic conditions and are not immune-mediated. True immune-mediated reactions are considered extremely rare and are estimated to account for less than 1% of all adverse reactions to LA. On the other hand, almost all of the immune-mediated LA reactions that have been reported are related to adult patients. Here, however, we will present a pediatric case proven to be hypersensitive to two different amide-derivative LA's

Pentoxifylline does not prevent hypoxia/reoxygenation-induced necrotizing enterocolitis - An experimental study

WOS: 000222387700006PubMed ID: 15017117Hypoxia/reoxygenation (H/R)-induced intestinal injury plays a significant role in the development of necrotizing enterocolitis (NEC). We experimentally explored the effect of pentoxifylline (PTX) on an NEC model. Twenty-one newborn rabbits were divided into three groups: group 1 ( control), group 2 (H/R) and group 3 (H/R + PTX). Five minutes of reoxygenation following 5 min of hypoxia was performed three times a day during 3 days. Before each H/R procedure in the H/R + PTX group, the rabbits were treated with PTX 25 mg/kg intraperitoneally. Animals were sacrificed on the third day and ileum samples were taken for histopathological examination and biochemical enzyme studies [superoxide dismutase ( SOD), glutathione peroxidase (GPx), glutathione reductase (GR), and glutathione S-transferase (GST)]. There was a significant difference in the grade and number of the intestinal lesions between controls and the H/R and H/R + PTX groups (p 0.05). Significantly reduced GPx activity was found in the H/R and H/R + PTX groups compared with the controls (p 0.05). Ischemia/reperfusion injury was responsible for mediating hypoxia-induced intestinal necrosis in NEC and PTX pretreatment did not have a protective effect on NEC. Copyright (C) 2004 S. Karger AG, Basel

Pentoxifylline does not prevent hypoxia/reoxygenation-induced necrotizing enterocolitis: An experimental study

PubMed ID: 15017117Hypoxia/reoxygenation (H/R)-induced intestinal injury plays a significant role in the development of necrotizing enterocolitis (NEC). We experimentally explored the effect of pentoxifylline (PTX) on an NEC model. Twenty-one newborn rabbits were divided into three groups: group 1 (control), group 2 (H/R) and group 3 (H/R + PTX). Five minutes of reoxygenation following 5 min of hypoxia was performed three times a day during 3 days. Before each H/R procedure in the H/R + PTX group, the rabbits were treated with PTX 25 mg/kg intraperitoneally. Animals were sacrificed on the third day and ileum samples were taken for histopathological examination and biochemical enzyme studies [superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR), and glutathione S-transferase (GST)]. There was a significant difference in the grade and number of the intestinal lesions between controls and the H/R and H/R + PTX groups (p 0.05). Intestinal SOD, GR and GST activities in the H/R and H/R + PTX groups were significantly higher than in the control group (p 0.05). Significantly reduced GPx activity was found in the H/R and H/R + PTX groups compared with the controls (p 0.05). Ischemia/reperfusion injury was responsible for mediating hypoxia-induced intestinal necrosis in NEC and PTX pretreatment did not have a protective effect on NEC. Copyright © 2004 S. Karger AG, Basel