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When open-cut mines are eventually abandoned, they leave a large hole with sloping sides. The hole fills with rain water, and there is also contaminated run-off from surrounding land, that moves through the rock and eventually through the sloping sides of the abandoned mine. This paper considers a two-dimensional unsteady model motivated by this leaching flow through the rock and into the rain-water reservoir. The stability of the interface between the two fluids is analysed in the inviscid limit. A viscous Boussinesq model is also presented, and a closed-form solution is presented to this problem, after it has been linearized in a manner consistent with Boussinesq theory. That solution suggests that the interfacial zone is effectively neutrally stable as it evolves in time. However, an asymptotic theory in the interfacial region shows the interface to be unstable. In addition, the nonlinear Boussinesq model is solved using a spectral method. Interfacial travelling waves and roll-up are observed and discussed, and compared against the predictions of asymptotic Boussinesq theory.
Cardiac strangulation from epicardial pacemaker leads is a rare event that can be difficult to recognise and can cause serious complications such as cardiac failure or death. We describe a 3-year-old girl who received an epicardial pacing system as a neonate for complete congenital cardiac block and developed cardiac strangulation from the leads. The clinical presentation modes are reviewed and technical aspects for lead and generator positioning are discussed.
Pulmonary arterial and intracranial calcifications are rarely found in children. A female infant, the recipient of a twin–twin transfusion syndrome was found, by ultrasound and computed tomography, to have both pulmonary arterial and intracerebral calcification. A rare condition, termed idiopathic arterial calcification of infancy, is the likely cause. This condition carries a poor prognosis and is usually fatal.
A non-dysmorphic 10 month old female was discovered at surgery to have severe vasculopathy of both the systemic and pulmonary arteries. These findings were confirmed by pathologic examination. Followup angiography has confirmed multiple sites of vascular obstruction which appear to be worsening. Angioplasty has only partially relieved these obstructions. The pathology and possible etiology are reviewed.
It is uncommon for thrombus to form within the heart of neonates with congenital cardiac disease. We describe a newborn with coarctation of the aorta, in whom a left atrial thrombus was discovered on the second day of life, and was thought to have been present before birth.
The unguarded tricuspid valve is uncommon. We describe herein a fetus with a grossly dilated right ventricle and atrium, with severe tricuspid and pulmonary valvar regurgitation. The right ventricle was akinetic, and no tricuspid tissue or valvar apparatus was identified. Colour Doppler showed a highly unusual retrograde flow of blood through the right heart. The pregnancy was terminated, and necropsy examination confirmed the gross dilation of the right heart chambers, with severely dysplastic valvar tissue at the right atrioventricular junction effectively giving an unguarded orifice. There was no valvar displacement, and the left heart was normal. The fetus had a normal karyotype, albeit with absent kidneys.
Pulmonary atresia with intact ventricular septum has been described extensively, and it is recognized that associated abnormalities of the coronary arteries may cause ischemia. We describe a fetus, diagnosed antenatally as having pulmonary atresia with intact ventricular septum and severe hypoplasia of the right ventricle, who developed severe left ventricular dysfunction. We hypothesize that this is due to reduced coronary blood flow because of falling right ventricular volume in the presence of complete right ventricular coronary arterial dependence.
An acute injury to a coronary artery was recognized during the surgical construction of the Fontan circulation. Surgical manipulation of the site of injury was not successful in restoring normal myocardial blood flow. A stent was therefore placed intraoperatively under direct vision, with restoration of normal coronary arterial flow acutely and at short-term follow-up.
Anomalous splitting has been observed in the photoreflectance (PR) response of SI:GaAs in the vicinity of the exciton at 78 K. Recent photohiminescence (PL) measurements suggest the splitting is correlated with the EL2 content of the samples. Separation between the two peaks in PR measurements range from about 2 to 4 meV. A striking effect is that each peak is maximized by a different phase setting of the lock-in. The splitting is sample dependent and is also affected by several other factors including surface conditions, temperature, pump beam intensity and modulation frequency.
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