D. E. Farrell

Efficacy of deferoxamine in preventing complications of iron overload in patients with thalassemia major

BACKGROUND To determine whether deferoxamine prevents the complications of transfusional iron overload in thalassemia major, we evaluated 59 patients (30 were female and 29 male; age range, 7 to 31 years) periodically for 4 to 10 years or until death. METHODS At each follow-up visit, we performed a detailed clinical and laboratory evaluation and measured hepatic iron stores with a noninvasive magnetic device. RESULTS The body iron burden as assessed by magnetic measurement of hepatic iron stores was closely correlated (R = 0.89, P < 0.001) with the ratio of cumulative transfusional iron load to cumulative deferoxamine use (expressed in millimoles of iron per kilogram of body weight, in relation to grams of deferoxamine per kilogram, transformed into the natural logarithm). Each increase of one unit in the natural logarithm of the ratio (transfusional iron load to deferoxamine use) was associated with an increased risk of impaired glucose tolerance (relative risk, 19.3; 95 percent confidence interval, 4.8 to 77.4), diabetes mellitus (relative risk, 9.2; 95 percent confidence interval, 1.8 to 47.7), cardiac disease (relative risk, 9.9; 95 percent confidence interval, 1.9 to 51.2), and death (relative risk, 12.6; 95 percent confidence interval, 2.4 to 65.4). All nine deaths during the study occurred among the 23 patients who had begun chelation therapy later and used less deferoxamine in relation to their transfusional iron load (P < 0.001). CONCLUSIONS The early use of deferoxamine in an amount proportional to the transfusional iron load reduces the body iron burden and helps protect against diabetes mellitus, cardiac disease, and early death in patients with thalassemia major.

Magnetic-susceptibility measurement of human iron stores.

We made direct noninvasive magnetic measurements of hepatic iron stores with a specially designed superconducting quantum-interference-device (SQUID) susceptometer in 20 normal subjects and in 110 patients with liver disease, iron deficiency, hereditary hemochromatosis, or transfusional iron overload. Magnetic in vivo measurements of liver non-heme iron were closely correlated with chemical in vitro measurements in liver-biopsy specimens (r = 0.98, P less than 10(-5) up to 115 mumol per gram of liver tissue (wet weight) or more. Magnetically determined storage-iron concentrations were below 6.0 mumol per gram in iron-deficient patients and normal men and premenopausal women, but they were raised (9.7 to 31.4 mumol) in 12 of 67 patients with liver disease and were greatly increased (22.9 to 117.7 mumol) in patients with untreated hereditary hemochromatosis or transfusional iron overload. Magnetic measurements of iron stores provide a new quantitative technique for early detection of hereditary hemochromatosis and for rapid evaluation of treatment regimens for transfusional iron overload.

A study of the auditory evoked magnetic field of the human brain.

Small but reproducible and consistent auditory evoked magnetic fields have been obtained for 6 male subjects. These fields exhibit features with a clear spatial symmetry which can be accounted for by assuming that their source consists of two vertically oriented neuronal complexes symmetrically located deep in the temporal lobes. This assignment, which is also consistent with the available electrical data, places the sources within the auditory cortex near the sylvian fissure. Our results suggest that auditory evoked magnetic fields may provide assistance in unravelling the source structure that produces the auditory evoked response, both electrical and magnetic.

Magnetic measurement of human iron stores

This paper provides a review of the principles and practice of biomagnetic susceptometry, with particular reference to magnetic susceptibility measurements of the human liver. A novel SQUID biomagnetic susceptometer is described consisting of a second-order gradiometer combined with a superconducting field coil assembly. We report the first clinical non-invasive diagnosis of liver iron overload achieved with this susceptometer at the Metropolitan General Hospital in Cleveland. Estimates are provided for the limiting resolution of the method. Ongoing efforts to apply the same principles to the determination of iron overload in the heart are briefly described. Our work represents the first clinical diagnostic procedure to utilize the recently developed superconducting technology of weak field measurement.

The series Bi2Sr2Can−1CunO2n+4 (1≤n≤5): Phase stability and superconducting properties

Abstract Phase relations at 850°C and 870°C, and melting transitions in air, oxygen, and helium have been studied for Bi2.1Sr1.9CuO6 and for the series Bi2Sr2Can−1CunO2n+4 for n=1, 2, 3, 4, 5 and ∞ (“CaCuO 2 ”) . Up to 870°C, the n=2 composition resides in the compatibility tetrahedron bounded by Bi2+x(Sr, Ca)3−yCu2O8, (Sr, Ca)14Cu24O41. Ca2CuO3, and a BiSrCaO phase. The n ≥ 3 compositions reside in the compatibility tetrahedron Bi2+x(Sr, Ca)3−yCu2O8(Sr, Ca)14Cu24O41 Ca2CuO3CuO up to 850°C. However, Bi2+x(Sr, Ca)4−yCu3O10 forms for n ≥ 3 after extended heating at 870°C. Bi2+xSr2−yCuO 6 (i.e. the Ca-free, very low-Tc phase) melts in air at 914°C, while the Bi2+x(Sr, Ca)3−yCu2O8 composition that coexists with (Sr, Ca)14Cu24O41 , Ca2CuO3, and CuO melts at 895°C. During melting, all of the compositions studied lose 1–2% by weight of oxygen from the reduction of copper.

Magnetic Study of the His-Purkinje Conduction System in Man

It has recently been suggested that depolarization of the entire His-Purkinje conduction system of the heart produces a characteristic waveform in the surface electrocardiogram. The magnetic probe offers a different and, in some respects, advantageous means of observing such waveforms, and extensive records of the surface magnetic field generated by the human heart have been obtained for four normal subjects. A first-order SQUID gradiometer was employed havinAthe lowest noise level yet reported in any biomagnetic study (6 X 10-15 T/√Hz). Using an on-line computer, 100 beat averages were taken at 49 positions over the chest on a 1 in square grid. The fields observed have a characteristic symmetry and provide support for the suggestion that events associated with depolarization of the conduction system may be observed at the surface of the torso.

High Tc screen-printed YBa2Cu3O7−x films: effect of the substrate material

Thick films of YBa2Cu3O7−x have been deposited on highly polished alumina, magnesia spinel, nickel aluminum titanate (Ni‐Al‐Ti), and barium tetratitanate (Ba‐Ti) substrates by the screen printing technique. They were baked at 1000 °C for 15 min, oxygen annealed at a lower temperature, and characterized by electrical resistivity measurements, x‐ray diffraction, and optical and scanning electron microscopy. Properties of the films were found to be highly sensitive to the choice of the substrate material. The film on Ba‐Ti turned green after firing, due to a reaction with the substrate and were insulating. A film on Ni‐Al‐Ti had a Tc  (onset) ∼95 K and lost 90% of its resistance by ∼75 K. However, even at 4 K it was not fully superconducting, possibly due to a reaction between the film and the substrate and interdiffusion of the reaction products. The film on alumina had Tc  (onset) ∼96 K, Tc  (zero) ∼66 K, and ΔTc  (10–90%) ∼10 K. Our best film was obtained on spinel and had Tc  (onset) ∼94 K, zero resistan...

Effect of fluoride doping on the transition temperature of YBa2Cu3O6.5+δ

The effect of fluoride doping on the superconducting transition temperature, Tc, of YBa2Cu3O6.5+δ has been investigated. Samples of nominal composition YBa2Cu3FxO6.5+δ−0.5x were synthesized where x was varied by two orders of magnitude from 0.0165 to 1.65. Tc systematically increased with x, reached a maximum of 93.4 K (midpoint) for x=0.066 and then dropped for higher concentrations. The sharpest transition, ΔTc(10–90%)=0.7±0.1 K, coincided with a maximum in Tc. From powder x‐ray diffraction measurements, samples with x≤0.066 were found to be single phase perovskite whereas those with x≥0.165 also contained BaF2, CuO, and an unknown phase. Although we find no evidence for the very high Tc’s reported by S. R. Ovshinsky, R. T. Young, D. D. Allred, G. DeMaggio, and G. A. Van der Leeden [Phys. Rev. Lett. 58, 2579 (1987)], our results do indicate that the effect of fluorine is qualitatively different from that produced by other dopants.

High T/sub c/ screen-printed YBa/sub 2/Cu/sub 3/O/sub 7-//sub x/ films: Effect of the substrate material

Thick films of YBa2Cu3O7−x have been deposited on highly polished alumina, magnesia spinel, nickel aluminum titanate (Ni‐Al‐Ti), and barium tetratitanate (Ba‐Ti) substrates by the screen printing technique. They were baked at 1000 °C for 15 min, oxygen annealed at a lower temperature, and characterized by electrical resistivity measurements, x‐ray diffraction, and optical and scanning electron microscopy. Properties of the films were found to be highly sensitive to the choice of the substrate material. The film on Ba‐Ti turned green after firing, due to a reaction with the substrate and were insulating. A film on Ni‐Al‐Ti had a Tc  (onset) ∼95 K and lost 90% of its resistance by ∼75 K. However, even at 4 K it was not fully superconducting, possibly due to a reaction between the film and the substrate and interdiffusion of the reaction products. The film on alumina had Tc  (onset) ∼96 K, Tc  (zero) ∼66 K, and ΔTc  (10–90%) ∼10 K. Our best film was obtained on spinel and had Tc  (onset) ∼94 K, zero resistan...

Glass‐derived superconducting ceramics with zero resistance at 107 K in the Bi1.5Pb0.5Sr2Ca2Cu3Ox system

A melt of composition Bi1.5Pb0.5Sr2Ca2Cu3Ox was fast quenched to form a glass. This was subsequently air annealed and the influence of annealing time and temperature on the formation of various crystalline phases was investigated. X‐ray powder diffraction indicated that none of the resulting samples were single phase. However, for an annealing temperature of 840 °C, the volume fraction of the high Tc phase (isostructural with Bi2 Sr2 Ca2 Cu3O10 ) increased with annealing time. A specimen annealed at this temperature for 243 h followed by slow cooling showed a sharp transition [ΔTc (10–90%) ∼2 K] and Tc (R=0)=107.2 K. To our knowledge, this is the highest Tc yet reported for any superconductor prepared via the glass route.