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An enzyme-linked immunosorbent assay for detecting antibodies to purified protein derivative was evaluated as a rapid method for serodiagnosis of childhood tuberculosis. Its specificity for IgG antibodies was 0.98 as determined in 55 sera from nontuberculous children who showed no significant effect of previous Bacillus Calmette-Guérin vaccination on the production of specific antibodies. Results were negative in 29 of 33 (87.9%) tuberculin-positive children and in 18 of 20 (90.0%) contacts, none of whom had evidence of tuberculosis. The sensitivity of this test was 0.51 as determined in 49 sera from bacteriologically confirmed cases; 17 of 27 smear positive cases and 8 of 22 children with positive cultures were detected. Results were positive in 32 of 114 (28.1%) patients with a diagnosis of tuberculosis not confirmed by microbiology. Consequently whereas a negative result does not rule out tuberculosis, a positive result is a strong indication of the disease. The IgM antibody determination yielded much less discriminative results.

In this paper we present recent achievements in the field of investigation of the local, electronic and magnetic structure of the matter under extreme conditions of pressure and temperature. These results were obtained thanks to the coupling of a compact laser heating system to the energy-dispersive XAS technique available on the ID24 beamline at the ESRF synchrotron. The examples chosen concern the melting and the liquid structure of 3d metals and alloys under high pressures (HPs) and the observation of temperature-induced spin crossover in FeCO3 at HP.

The Earth’s crust–mantle boundary, the Mohorovicic discontinuity, has been traditionally considered to be the interface between the magnetic crust and the non-magnetic mantle1. However, this assumption has been questioned by geophysical observations2,3 and by the identification of magnetic remanence in mantle xenoliths4, which suggest mantle magnetic sources. Owing to their high critical temperatures, iron oxides are the only potential sources of magnetic anomalies at mantle depths5. Haematite (α-Fe2O3) is the dominant iron oxide in subducted lithologies at depths of 300 to 600 kilometres, delineated by the thermal decomposition of magnetite and the crystallization of a high-pressure magnetite phase deeper than about 600 kilometres6. The lack of data on the magnetic properties of haematite at relevant pressure–temperature conditions, however, hinders the identification of magnetic boundaries within the mantle and their contribution to observed magnetic anomalies. Here we apply synchrotron Mossbauer source spectroscopy in laser-heated diamond anvil cells to investigate the magnetic transitions and critical temperatures in Fe2O3 polymorphs7 at pressures and temperatures of up to 90 gigapascals and 1,300 kelvin, respectively. Our results show that haematite remains magnetic at the depth of the transition zone in the Earth’s mantle in cold or very cold subduction geotherms, forming a frame of deep magnetized rocks in the West Pacific region. The deep magnetic sources spatially correlate with preferred paths of the Earth’s virtual geomagnetic poles during reversals8 that might not reflect the geometry of the transitional field. Rather, the paths might be an artefact caused by magnetized haematite-bearing rocks in cold subducting slabs at mid-transition zone depths. Such deep sources should be taken into account when carrying out inversions of the Earth’s geomagnetic data9, and especially in studies of planetary bodies that no longer have a dynamo10, such as Mars. Synchrotron Mossbauer source spectroscopy is used to reveal that haematite remains magnetic in cold subducting slabs at the depth of the transition zone in the Earth’s mantle, with implications for the locations of magnetic poles during inversions of the Earth’s magnetic field.