Cytokine profile in chronic cardiac failure

Elevated tumour necrosis factor alpha (TNF-alpha) has been demonstrated in chronic cardiac failure (CCF) and may relate to severity of CCF and development of cachexia. We measured TNF receptor p55 in addition to TNF-alpha in an attempt to improve the detection rate of TNF-alpha activation, and simultaneously measured interleukin 6 (IL-6), interleukin 8 (IL-8) and C-reactive protein. Thirty-four patients with CCF and 24 control subjects were studied. Only TNF receptor p55 [6.95 (0.77-42.3) vs. 5.52 (1.50-13.36) ng mL-1 (median (range)] and IL-6 [0.335 (0-9.79) vs. 0(0-14.71) pg mL-1) were significantly elevated in patients compared with control subjects (both P < 0.05). All inflammatory markers were more frequently elevated in patients, but none correlated with any of the clinical parameters studied. Reasons for inflammatory marker elevation in CCF are uncertain, but future studies should measure the p55 TNF receptor and IL-6 in addition to TNF-alpha, to improve detection of cytokine activity.     

High-speed creep effects in magnetic films

Creep measurements were made on single domain walls in thin magnetic films using high-speed pulses with variable rise and fall times (0.4 ns to>1 mus) and durations (<1 ns to 3 μs). Combinations of these pulses and dc fields were applied along the hard axis while simultaneously easy-axis dc fields were applied. The two basic measurements that were made were onset of creep and the distance the wall crept per pulse as a function of applied fields. Definite rise-time effects were found, the exact behavior depending on the domain wall structure. For Bloch walls, gyromagnetic effects of the total wall (similar to wall streaming) are present for rise timeslsim 20ns, whereas for longer rise times the Bloch to Néel wall transition appears to be responsible. For films thinner than 900 Å the existence of a cross-tie structure was found to be necessary for creep. For this wall structure the exact mechanism which causes creep enhancement for rise times <100 ns is unknown.     

A study of noncoherent rotational switching for thin magnetic films

Thin magnetic film switching was investigated for fields near those needed for pure rotation. Experimentally the films were switched using <0.4 ns rise time field pulses. The resulting flux changes were detected in the easy and hard direction with a response time of 0.6 ns. Measurements were made for pulses both longer and shorter than the magnetization switching times. By analyzing the voltage waveforms and flux changes, it was concluded that instabilities and rapid rearrangements of the magnetization can occur within a few nanoseconds, causing anomalous results during switching. Equations of existing quantitative switching models-pure rotation, spin-wave, and stripe domain-were solved with a digital computer. To better compare theory and experiment, the solutions were modified to account for the sense system's finite rise time. It was found that none of the existing models adequately described the switching processes for low amplitude magnetic fields. However, qualitatively, the stripe domain model best fit the experimental data.