A high-field magnetization study of a Nd(2)Fe(14)Si(3) single crystal.

Magnetization study of a single crystal of Nd(2)Fe(14)Si(3) (with the rhombohedral Th(2)Zn(17)-type structure) reveals that the compound is a ferromagnet with a spontaneous magnetic moment of 32.3µ(B) per formula unit (at T = 2 K) and a Curie temperature equal to 495 K. The easy-magnetization direction lies close to the b-axis, tilting slightly towards the c-axis. (The b-axis [120] is not a high-symmetry direction in the crystallographic class D(3d).) The observed strong magnetic anisotropy is attributed almost entirely to the Nd sublattice, as concluded from comparison with a Y(2)Fe(14)Si(3) single crystal. A magnetic field applied along the c-axis induces a first-order spin reorientation transition at B(FOMP) = 20 T. In the process of magnetization the Nd and Fe sublattices behave as essentially non-collinear. This is manifest particularly in the downward curvature of the first (pre-FOMP) stage of the magnetization curve. It is proposed to regard this curvature as a validity criterion for the single-sublattice approximation.

Experience in the surgical treatment of pheochromocytoma.

A report is presented on the experience gained in diagnosis and treatment of pheochromocytomas in a group of 41 patients, observed and treated in the surgical clinic of the University Hospital of Leyden. Two groups are distinguished: patients observed before and after 1969. Prior to that year, anti-adrenergic blockade with dibenzyline and propanolol was not available, so aortography was practically impossible in view of the danger of triggering a hyptertensive crisis. Since 1969, this blockade has been applied systematically, both for the aortography which is now a routine measure and for the operation. By using subtotal adrenergic blockade, the surgical treatment of pheochromocytomas may now be regarded as safe.

Mycotic iliac haemorrhage after removal of an infected renal allografts.

A case is presented in which after removal of an infected renal allograft because of rejection, mycotic bleeding from the iliac artery could not be treated by ligature of the artery in view of the resulting ischaemia ofthe leg as demonstrated by a trial occlusion. A successful solution to this problem is presented in which a 'gradual ligature' of the iliac artery was brought about using a slow compression instrument. The indications, technique and results in this case of mycotic iliac haemorrhage after transplantectomy are described.

Transition-metal-based magnetic refrigerants for room-temperature applications.

Magnetic refrigeration techniques based on the magnetocaloric effect (MCE) have recently been demonstrated as a promising alternative to conventional vapour-cycle refrigeration. In a material displaying the MCE, the alignment of randomly oriented magnetic moments by an external magnetic field results in heating. This heat can then be removed from the MCE material to the ambient atmosphere by heat transfer. If the magnetic field is subsequently turned off, the magnetic moments randomize again, which leads to cooling of the material below the ambient temperature. Here we report the discovery of a large magnetic entropy change in MnFeP0.45As0.55, a material that has a Curie temperature of about 300 K and which allows magnetic refrigeration at room temperature. The magnetic entropy changes reach values of 14.5 J K-1 kg-1 and 18 J K-1 kg-1 for field changes of 2 T and 5 T, respectively. The so-called giant-MCE material Gd5Ge2Si2 (ref. 2) displays similar entropy changes, but can only be used below room temperature. The refrigerant capacity of our material is also significantly greater than that of Gd (ref. 3). The large entropy change is attributed to a field-induced first-order phase transition enhancing the effect of the applied magnetic field.

Diagnosis, treatment and operative complications of carotid body tumours.

A series of 42 patients who were treated in the Surgical Clinic of the University of Leyden on suspicion of a carotid body tumour between 1958 and 1979 is reported. Thirty-four patients in this series were operated upon in the University Hospital Leyden. Only 6 per cent of the tumours were malignant according to the criteria of nuclear polymorphia and metastases. Local infiltration, either histological or clinical, has no correlation with later outcome. In 11 per cent of the patients, vascular complications occurred. The necessity of operative damage to the surrounding cranial nerves increased with the size of the tumour. In one case the cranial nerve lesion was accidental. No per- or postoperative mortality was seen in this series.