Reconstruction of Current Flow and Imaging of Current-Limiting Defects in Polycrystalline Superconducting Films

Magneto-optical imaging was used to visualize the inhomogeneous penetration of magnetic flux into polycrystalline TlBa2Ca2Cu3Ox films with high critical current densities, to reconstruct the local two-dimensional supercurrent flow patterns and to correlate inhomogeneities in this flow with the local crystallographic misorientation. The films have almost perfect c-axis alignment and considerable local a- and b-axis texture because the grains tend to form colonies with only slightly misaligned a and b axes. Current flows freely over these low-angle grain boundaries but is strongly reduced at intermittent colony boundaries of high misorientation. The local (<10-micrometer scale) critical current density Jc varies widely, being up to 10 times as great as the transport Jc (scale of approximately 1 millimeter), which itself varies by a factor of about 5 in different sections of the film. The combined experiments show that the magnitude of the transport Jc is largely determined by a few high-angle boundaries.     

Dislocation-driven deformations in graphene

The movement of dislocations in a crystal is the key mechanism for plastic deformation in all materials. Studies of dislocations have focused on three-dimensional materials, and there is little experimental evidence regarding the dynamics of dislocations and their impact at the atomic level on the lattice structure of graphene. We studied the dynamics of dislocation pairs in graphene, recorded with single-atom sensitivity. We examined stepwise dislocation movement along the zig-zag lattice direction mediated either by a single bond rotation or through the loss of two carbon atoms. The strain fields were determined, showing how dislocations deform graphene by elongation and compression of C-C bonds, shear, and lattice rotations.     

In this issue – October 2010

Computed tomography diagnosis of brain infarction in dogs · Tibial tuberosity advancement in canine stifles · Holter monitoring in dogs with mitral valve disease · Staggers in horses grazing paspalum infected with Claviceps paspali · Distal luxation of the patella in a horse · Escherichia coli and Salmonella serotypes in sheep at slaughter · Alzheimer type II astrocytes in the brains of pigs with salt poisoning · Classification of infectious bronchitis viruses in poultry field specimens · Mortality events in sea-caged yellowtail kingfish     

In this issue – May 2010

Flea-associated infectious agents in cats in Eastern Australia · Complications of barium-impregnated polyethylene spheres · Reproductive efficiency of Thoroughbred and Standardbred horses · GPS tracking collars to monitor horses · Correction of vesicovaginal reflux in mares · Antibodies to Lawsonia intracellularis in Australian pig herds · Mucormycosis in the platypus · Panniculitis from Mycobacterium mageritense in a Tasmanian devil     

IN THIS ISSUE – June 2010

Surveillance for West Nile virus in Australia: role of the little raven · Fertility in mares after surgical correction of rectovaginal fistula · Development of method for serial blood sampling from conscious dogs · Specificity of a commercial snake venom detection kit in dog and cat urine · Femoral component failure in canine cemented total hip replacement · Hepatic myelolipoma incarcerated in a peritoneopericardial diaphragmatic hernia in a cat · Diclofenac sodium and flunixin meglumine with antibacterial treatment of respiratory disease of calves · Lead-free petrol reduces risk of acute lead poisoning in Australian cattle     

Congenital dyserythropoietic anaemia and dyskeratosis in Australian Poll Hereford calves

Congenital dyserythropoietic anaemia (CDA) is a heterogeneous group of rare genetic disorders that in humans is characterised by ineffective haematopoiesis with morphological abnormalities in erythroid precursor cells and secondary iron overload. In the 1990s, a syndrome of CDA with dyskeratosis and progressive alopecia was reported in Poll Hereford calves in Canada and the USA. We report the clinical and pathological findings in two Poll Hereford calves with this syndrome from separate properties in South Australia. The animals had a variably severe anaemia, associated with abnormal nucleated red blood cells in peripheral blood, and large numbers of rubricytes and metarubricytes with a characteristic nuclear ultrastructure in the bone marrow. Both calves were born with a wiry hair coat and a progressively ‘dirty‐faced’ appearance associated with hyperkeratosis and dyskeratosis (apoptosis).     

Equine anhidrosis: A review of pathophysiologic mechanisms

Anhidrosis is loss of the ability to sweat. The problem is seen in horses kept in a hot humid climate, and it may cause severe impairment of thermoregulation in the equine athlete. British Thoroughbreds imported to her tropical colonies are the earliest recorded cases, and since then the syndrome has come to be described as one of Thoroughbreds, usually performance athletes, undergoing acclimatization to heat and humidity. A recent epidemiologic study of cases in Florida has shown, however, that many different breeds, and long time inhabitants of a hot climate, may be affected. Equine sweat glands are of the apocrine type, and sweating is stimulated by direct local release of epinephrine from adrenergic nerve endings and by circulating epinephrine. Lack of sweating could be due to a number of possible flaws in a sequence from central nervous stimulation through sweat stimulation and secretion to delivery of sweat to the skin surface. The most likely possibilities are inadequate sweat gland response due to habituation of receptors to a high circulating level of epinephrine and occlusion of the sweat ducts by keratin plugs. Hormonal or metabolic imbalance may play a role both in the onset and secondary signs associated with anhidrosis.