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Observations aboard Cosmos satellites discovered trapped anomalous cosmic rays (ACRs), tracked the variation in their intensity in 1986-1988, and measured their fluence, spectrum, and composition at solar minimum in the previous solar cycle. The MAST instrument aboard the SAMPEX satellite has observed trapped anomalous cosmic rays in the present solar cycle, confirmed the general features of the Cosmos data, and provided the first detailed observations of trapped ACRs. In this paper we apply theoretical modeling of trapped ACRs, which is shown to provide a reasonably good description of both the Cosmos and SAMPEX data, to calculate the integral linear-energy-transfer (LET) spectra due to trapped ACRs in typical low-Earth orbits. We compare these calculations with the LET spectra produced by galactic cosmic rays (GCRs) and non-trapped ACRs in order to assess the relative radiation hazard posed by trapped ACRs.

The large solar energetic particle (SEP) events and simultaneous large geomagnetic disturbances observed during October 1989 posed a significant, rapidly evolving space radiation hazard. Using data from the GOES-7, NOAA-10, IMP-8 and LDEF satellites, we determined the geomagnetic transmission, heavy ion fluences, mean Fe ionic charge state, and effective radiation hazard observed in low Earth orbit (LEO) for these SEPs. We modeled the geomagnetic transmission by tracing particles through the combination of the internal International Geomagnetic Reference Field (IGRF) and the Tsyganenko (1989) magnetospheric field models, extending the modeling to large geomagnetic disturbances. We used our results to assess the radiation hazard such very large SEP events would pose in the anticipated 52 degrees inclination space station orbit.

We present data from the Lexan top stacks in the Heavy Ions In Space (HIIS) experiment which was flown for six years (April 1984-Jan 1990) onboard the LDEF spacecraft in 28.5 degrees orbit at about 476 km altitude. HIIS was built of passive (i.e. no timing resolution) plastic track detectors which collected particles continuously over the entire mission. In this paper we present data on low energy heavy ions (10 < or = Z, 20MeV/nuc < E < 200 MeV/nuc). These ions are far below the geomagnetic cutoff for fully ionized ions in the LDEF orbit even after taking into account the severe cutoff suppression caused by occasional large geomagnetic storms during the LDEF mission. Our preliminary results indicate an unusual elemental composition of trapped particles in the inner magnetosphere during the LDEF mission, including both trapped anomalous cosmic ray species (Ne, Ar) and other elements (such as Mg and Fe) which are not found in the anomalous component of cosmic rays. The origin of the non-anomalous species is not understood, but they may be associated with the solar energetic particle events and geomagnetic disturbances of 1989.

The treatment of late-stage African sleeping sickness in man is often complicated by a post-treatment reactive encephalopathy. The bases of this pathological reaction was investigated in a mouse model of African trypanosomiasis. Subcurative treatment with diminazene aceturate, which did not clear parasites from the central nervous system, resulted in a post-treatment meningoencephalitis similar to that seen in man. By contrast, a curative regimen of melaminylthioarsenite and 5-nitroimidazole, which cleared parasites from the central nervous system, did not cause any pathological reaction in the mice. This result indicates that subcurative treatment leads to the development of the post-treatment encephalopathy. Evidence that this may also be the case in man was provided by the detection of trypanosome DNA with the polymerase chain reaction in the brains of 9 patients who had died as the result of a post-treatment reaction. Our findings suggest that more aggressive treatment regimens, which ensure the elimination of trypanosomes from the central nervous system, may prevent post-treatment reactions in patients.

Of 66 patients with head injuries who had talked at some time after injury, 25% did not have intracranial haematoma at necropsy. Most of these had raised intracranial pressure (I.C.P.), and the commonest finding was local swelling related to contusions. Almost half of the non-haematoma cases had ischaemic or hypoxic brain damage, usually without contusions; 3 were children who had had status epilepticus. Fatality without raised I.C.P. was most often due to meningitis. In deteriorating patients without haematoma mortality and morbidity might be reduced by more diagnosis and treatment, particularly of raised I.C.P.

The incidence and distribution of ischaemic brain damage in a consecutive series of 151 patients who died as a result of a non-missile head injury in the Institute of Neurological Sciences was determined on the basis of a comprehensive neuropathological and neurohistological examination. Ischaemic damage was identified in 138 cases (91%) even after excluding cases who only had necrosis and infarction related to contusions or fat embolism, and infarction in the brain stem of the type conventionally associated with raised intracranial pressure. The ischaemic damage was assessed as severe in 37 (27%), moderately severe in 59 (43%) and mild in 42 (30%), and in the 138 cases with ischaemic brain damage it was found more frequently in the hippocampus (122 cases; 81%), and in the basal ganglia (119 cases; 79%) than in the cerebral cortex (70 cases; 46%) and in the cerebellum (67 cases; 44%). There were statistically significant correlations between ischaemic brain damage and either an episode of hypoxia or of raised intracranial pressure. From the nature of the brain damage it seems likely that much of it was due to a reduction in the cerebral perfusion pressure. This study has shown that ischaemic brain damage is common after head injury, that at least a proportion of it is probably avoidable, and that it is more important as a cause of mortality and morbidity after head injury than has been hitherto realised.

Antigens of Anaplasma centrale, Onderstepoort isolate, and A. marginale, Wacol isolate, were analysed by a Western blotting technique. Sera from A. centrale-infected calves reacted to 41- and 38-kDa antigens in A. centrale and a 41-kDa antigen in A. marginale. Serum collected during the primary reaction from an A. marginale-infected calf reacted only to the 41-kDa antigen of A. marginale; heterologous antibody response to the 41-kDa antigen of A. centrale did occur later during the infection, but remained markedly weaker than the homologous response. The serologic cross-reactivity to this 41-kDa Anaplasma antigen confirms that it is common to the genus and also that it is a heterogeneous complex.

Measurements of aortic length and circumference in 336 post-mortem specimens confirm earlier, neglected observations on the progressive increase in aortic size which occurs with advancing years. The increase is not related to atherosclerosis , or to hypertension and seems to be part of a true ageing process. The value of measurement of aortic size in body age determination merits exploration by forensic pathologists. Aortic calcification is found in raised and complicated atherosclerotic plaques and its prevalence and severity closely follows the accepted pattern of plaque severity, occurring earlier and more severely in men, in the abdominal aorta and in patients with overt vascular disease in other territories such as patients with cardiac infarcts. No association was found between the amount of calcification and the presence of hypertension, diabetes or neoplasia.

Among cosmic rays, the heavy nuclei ranging from carbon to iron provide the principal contribution to the dose equivalent. The LET-distributions and absorbed dose aid dose equivalent have been calculated and are presented as a function of shielding and tissue self-shielding. At solar minimum, outside the magnetosphere, the unshielded dose equivalent of nuclei with atomic number Z > or = 6 is about 47 rem/year. The contribution of the target nuclei adds 7 rem/year. With 4 g/cm2 aluminum shielding, and at a depth of 5 cm in a biological phantom of 30 cm diameter, the respective values are 11 and 10 rem/year. Corresponding dose rates for orbits with various inclinations are presented, as well as the LET distributions of various components of cosmic rays.

82 cases of diffuse axonal injury were found at necropsy in 635 patients with fatal nonmissile head injuries. 13 of these injuries were attributable to falls, and in all the patients fell from a considerable height. Diffuse axonal injury was not found in those with head injuries caused by a simple fall--ie, a fall from not more than the person's own height--but there was a statistically significant association between the presence of diffuse axonal injury and falls from a considerable height. These results indicate that diffuse axonal injury rarely, if ever, occurs as a result of a fall unless the patient has fallen some distance.