Phenomenology of ferromagnetism. I. Effects of magnetostatics onsusceptibility

Magnetic measurements, with particular emphasis on finite cylinders of iron in the form of whiskers, are interpreted with regard to magnetostatic effects. Demagnetizing fields are calculated using various degrees of approximation. In the cases considered the magnetostatic effects are dominant over other contributions to the micromagnetic energies. A particular approximation in which the demagnetizing field is assumed to be proportional to the second derivative of the magnetization is used to describe the sharp changes in response with field that occur near the Curie temperature     

Point singularities and magnetization reversal in ideally soft ferromagnetic cylinders

The principles of micromagnetics are used to describe the magnetization processes and magnetic configurations in a cylinder of finite length. The cylinder is of radius large compared to the exchange radius. Magnetostatic terms dominate in the limit that crystalline anisotropy is negligible. The exchange energy is minimized for boundary conditions primarily determined by magnetostatics. The point singularities required by topology are essential to understanding the process of magnetization. Complete reversal of magnetization is made possible by propagating point singularities down the axis of the cylinder. These propagating singularities arise from pair creation in a unit vector field.     

Three methods of oxytocin-induced parturition and their effects of foals

OBJECTIVE: To compare effects of 3 oxytocin-based induction techniques on fetal and neonatal foals. DESIGN: Prospective randomized controlled trial. ANIMALS: 16 pregnant mares. PROCEDURE: Parturition was induced in mares by use of 3 treatments: group 1, 75 U of oxytocin, IM; group 2, 15 U of oxytocin, IM, q 15 minutes, for a maximum of 75 U; group 3, 75 U of oxytocin in 1 L of 0.9% NaCl solution IV (1 U/min), for a maximum of 75 U. Blood gas values and indices of vitality were measured in foals, and variables describing parturition were measured in mares. RESULTS: Group-3 mares had a shorter interval from administration of oxytocin to rupture of the chorioallantois (OTCA) than group-2 mares. More foals were abnormal when the interval from oxytocin administration to delivery of the foal (OTDE) was > or = 60 minutes. Arterial blood gas values, measurements of vitality, and plasma cortisol concentrations did not differ among foals in various treatment groups. Increased interval for OTCA and OTDE resulted in higher neonatal PaCO2, and a longer interval for OTCA resulted in lower arterial pH. Time required for birth was shorter in mares with a dilated cervix. More abnormal foals than normal foals were delivered after premature placental separation or dystocia. Abnormal foals took longer to stand and suckle than normal foals. Interval from delivery to suckling was positively correlated with OTCA, OTDE, and PaCO2. CLINICAL IMPLICATIONS: Method of oxytocin-induced parturition did not impact neonatal outcome. Interval from induction until parturition, degree of cervical dilatation, and intrapartum complications influenced induction success.     

Supercomputers-perspectives on visualization

The role of visualization and its capabilities are discussed. The loss of information incurred in translating a three-dimensional scene into a two-dimensional image plane and ways of compensating for it are considered. The need for interactive capability is stressed. The dichotomy between the use of visualization for analysis and for communication is traced to the way the technology evolved. That is, historically, computer graphics has been used in two separate and quite different industries: for science and engineering, and for entertainment. The emergence of cross-fertilization between the two is examined. Future trends and challenges are discussed