Cardiac hemangioma of the right atrium in a neonate : fetal management and expedited surgical resection

Cardiac hemangioma is a rare tumor with a reported incidence of 1-2%. We describe the case of a neonate with a right atrial mass that was diagnosed prenatally. The fetus developed a supraventricular tachycardia and was delivered by cesarean section in the 35th week of gestation. The infant underwent surgery after 24 hours to remove the mass which was diagnosed as a cardiac capillary-cavernous hemangioma.peer-reviewe

Instabilities in the Flux Line Lattice of Anisotropic Superconductors

The stability of the flux line lattice has been investigated within anisotropic London theory. This is the first full-scale investigation of instabilities in the `chain' state. It has been found that the lattice is stable at large fields, but that instabilities occur as the field is reduced. The field at which these instabilities first arise, $b^*(\epsilon,\theta)$, depends on the anisotropy $\epsilon$ and the angle $\theta$ at which the lattice is tilted away from the $c$-axis. These instabilities initially occur at wavevector $k^*(\epsilon,\theta)$, and the component of $k^*$ along the average direction of the flux lines, $k_z$, is always finite. As the instability occurs at finite $k_z$ the dependence of the cutoff on $k_z$ is important, and we have used a cutoff suggested by Sudb\ospace and Brandt. The instabilities only occur for values of the anisotropy $\epsilon$ appropriate to a material like BSCCO, and not for anisotropies more appropriate to YBCO. The lower critical field $H_{c_1}(\phi)$ is calculated as a function of the angle $\phi$ at which the applied field is tilted away from the crystal axis. The presence of kinks in $H_{c_1}(\phi)$ is seen to be related to instabilities in the equilibrium flux line structure.Comment: Extensively revised paper, with modified analysis of elastic instabilities. Calculation of the lower critical field is included, and the presence of kinks in $H_{c_1}$ is seen to be related to the elastic instabilities. 29 pages including 16 figures, LaTeX with epsf styl

Soil conservation in Saskatchewan – a research perspective

Non-Peer ReviewedNext to the economic plight of agricultural producers, soil degradation is the most topical subject among agriculturalists today. Soil degradation involves the destruction of soil resources by erosion, organic matter loss, salinization and soil acidification; usually as a result of agricultural mismanagement. This paper has attempted to highlight some of the current areas of research that are specifically designed to address these problems and has suggested specific areas that the author believes require immediate attention. Summerfallowing has been, and still remains the major cause of soil degradation in Saskatchewan. Although farmers have made a significant effort to reduce this practice in recent years, we still have scenes remindful of the "Dirty Thirties" every few years. Thus we need to move to even more extended cropping systems. This can only be done by adopting new technology such as snow trapping in the Brown and Dark Brown Soil Zones, zero, and minimum tillage, chemical fallow where we must fallow, and so on. In the long run, the farmer will only adopt these changes if they are economical and not too risky; thus the need for an accelerated research effort to provide farmers with answers as soon as possible. Such government-funded programs as FarmLab and ERDA are steps in the right direction

Vortex microavalanches in superconducting Pb thin films

Local magnetization measurements on 100 nm type-II superconducting Pb thin films show that flux penetration changes qualitatively with temperature. Small flux jumps at the lowest temperatures gradually increase in size, then disappear near T = 0.7Tc. Comparison with other experiments suggests that the avalanches correspond to dendritic flux protrusions. Reproducibility of the first flux jumps in a decreasing magnetic field indicates a role for defect structure in determining avalanches. We also find a temperature-independent final magnetization after flux jumps, analogous to the angle of repose of a sandpile.Comment: 6 pages, 5 figure

Kinks in the Presence of Rapidly Varying Perturbations

Dynamics of sine-Gordon kinks in the presence of rapidly varying periodic perturbations of different physical origins is described analytically and numerically. The analytical approach is based on asymptotic expansions, and it allows to derive, in a rigorous way, an effective nonlinear equation for the slowly varying field component in any order of the asymptotic procedure as expansions in the small parameter $\omega^{-1}$, $\omega$ being the frequency of the rapidly varying ac driving force. Three physically important examples of such a dynamics, {\em i.e.}, kinks driven by a direct or parametric ac force, and kinks on rotating and oscillating background, are analysed in detail. It is shown that in the main order of the asymptotic procedure the effective equation for the slowly varying field component is {\em a renormalized sine-Gordon equation} in the case of the direct driving force or rotating (but phase-locked to an external ac force) background, and it is {\em the double sine-Gordon equation} for the parametric driving force. The properties of the kinks described by the renormalized nonlinear equations are analysed, and it is demonstrated analytically and numerically which kinds of physical phenomena may be expected in dealing with the renormalized, rather than the unrenormalized, nonlinear dynamics. In particular, we predict several qualitatively new effects which include, {\em e.g.}, the perturbation-inducedComment: New copy of the paper of the above title to replace the previous one, lost in the midst of the bulletin board. RevTeX 3.

The Potts Fully Frustrated model: Thermodynamics, percolation and dynamics in 2 dimensions

We consider a Potts model diluted by fully frustrated Ising spins. The model corresponds to a fully frustrated Potts model with variables having an integer absolute value and a sign. This model presents precursor phenomena of a glass transition in the high-temperature region. We show that the onset of these phenomena can be related to a thermodynamic transition. Furthermore this transition can be mapped onto a percolation transition. We numerically study the phase diagram in 2 dimensions (2D) for this model with frustration and {\em without} disorder and we compare it to the phase diagram of $i)$ the model with frustration {\em and} disorder and of $ii)$ the ferromagnetic model. Introducing a parameter that connects the three models, we generalize the exact expression of the ferromagnetic Potts transition temperature in 2D to the other cases. Finally, we estimate the dynamic critical exponents related to the Potts order parameter and to the energy.Comment: 10 pages, 10 figures, new result

Effect of nitrogen source on the growth and yield of cereals

Non-Peer Reviewe

Nitrate lost from various long-term fallow and continuous cropping rotations at Swift Current

Non-Peer Reviewe

Soil organic matter on the prairies – a dwindling resource

Non-Peer ReviewedEighteen prairie surface soils (representing cultivated and uncultivated coarse-, medium-, and fine-textured soils) from the Brown, Dark Brown, Thin Black, and Gray Soil Zones were analyzed for changes in total carbon, nitrogen, and potentially mineralizable nitrogen. The results show that organic matter losses are great, but loss of the potentially mineralizable nitrogen has been even greater due to cultivation. The significance of these findings is that more and more fallow soils are having to be fertilized with nitrogen

Influence of temperature, nitrogen fentilizer, and moisture stress on yield and protein content of Manitou spring wheat – a simulated dryland study

Non-Peer Reviewe