Xenon and krypton have been implanted into muscovite mica at room temperature and at liquid nitrogen temperature. The behavior of the implanted Xe and Kr was followed by low-temperature transmission electron microscopy and energy dispersive x-ray analysis. An electron diffraction pattern of diffuse bands is observed at room temperature due to the presence of fluid rare gas and to noncrystalline mica. Visible cavities with diameters 10–300 nm formed in the Xe-implanted mica. Visible cavities in room-temperature Kr-implanted mica ranged from 5–50 nm in diameter. The gas pressures at room temperature in the cavities are estimated, assuming all of the implanted gas precipitated in cavities to be ∼10 MPa for Xe and ∼20 MPa for Kr. These pressures are considerably lower than found for rare gases implanted in metals and ceramics, but sufficient to liquefy the rare gases at room temperature. The Xe and Kr were observed by dark-field microscopy to form fcc crystalline solids within the cavities at temperatures below their triple points, with lattice parameters of a (xe) = 0.630 ± 0.0015 nm and a (Kr) = 0.565 ± 0.005 nm. The solid Xe within bubbles was unstable under the electron beam of the transmission electron microscope at temperatures above 80 K, while the solid Kr within bubbles was unstable at temperatures as low as 35 K. The crystalline mica matrix undergoes a transformation from a crystalline structure to an amorphous structure as a result of implantation.

The microstructure of a muscovite mica exposed to a rare gas ion beam has been studied by transmission electron microscopy. The investigation of damage without implantation was carried out using argon and helium ions of sufficient energy to traverse the 100–150 nm mica specimens. For 340 keV Ar++ irradiation, amorphization of mica occurred at a fluence as low as 3.5 × 1014 ions · cm−2, which corresponds to 0.29 dpa. Muscovite can be amorphized using 80 keV helium ions, but this requires a much higher fluence and damage production of 4.6 × 10−6 ions · cm−2 and 0.60 dpa, respectively. Since helium irradiation results principally in ionization energy loss, it indicates that amorphization of muscovite results mainly from nuclear interactions. Complete amorphization of muscovite mica is found to take place for all ions at approximately the same amount of nuclear energy transfer to energetic primary knock-on atoms, assuming a recoil energy greater than 500 eV. This suggests that amorphization occurs directly in dense displacement cascades. A significant amount of helium, 100 ppm, can be implanted into muscovite mica without destroying the crystal structure.

Helium and xenon gases implanted into muscovite micas increase the reversible thermal expansion perpendicular to the silicate layers by one or two orders of magnitude. The gas‐mica composite behaves like a gas within an elastic membrane, and this can be developed into a thermal actuator or heat sensor. Helium gas is implanted into muscovite mica to simulate the anomalous thermal expansion behavior of water in phlogopite. The implanted Xe gas has been studied by Rutherford backscattering and by counting and measuring gas bubble radii. Helium gas appears to diffuse out of the structure, since the anomalous thermal expansion decreases slowly over a period of several months. All of the implanted Xe is found to remain within the mica structure.

Natural phlogopite micas have anomalously high, yet reversible thermal expansion, over 100% at 600 degree(s)C, attributed to non-structural water entrapped between the silicate layers. Above 100 degree(s)C, the mica-water vapor composite expands like a gas in an elastic membrane, stable to repeated thermal cycling to over 600 degree(s)C. Muscovite mica-noble gas composites are prepared by implantation and are stable with time and temperature to 600 degree(s)C. The behavior of the implanted gas is studied by Rutherford backscattering and transmission electron microscopy. Helium diffuses out slowly over a period of six months. A capacitometer is required to measure the thermal expansion of implanted specimens less than 1 micrometers thick.

We present an original case of Marchiafava-Bignami disease in a 47-year-old left-handed alcoholic man. Computed tomography and magnetic resonance imaging demonstrated the typical lesion, a necrosis of the middle portion of the corpus callosum. Diagnosis may thus be established in the living. In our case, the course was not fatal, which, to our knowledge, has only been described in four other cases in the literature. Clinically, our patient demonstrated an interhemispheric disconnection syndrome. The striking feature is that some of the symptoms were on the side opposite of the one that has previously been described in the literature, eg, right-handed agraphia, while others were on the usual side, eg, left-handed anomia. We discuss cerebral dominance for speech and handedness in left-handers and come to the conclusion that our patient's clinical features can only be explained by right hemispheric dominance for handedness and bilateral hemispheric representation of speech.

Vertebral fractures, spontaneous or due to minor trauma are classical complications of osteoporosis. Fractures are often painful, requiring analgesia and immobilisation for some weeks; immobilisation, however, has a negative effect on mineralisation. In order to consolidate the collapsed vertebra and relieve symptoms, the authors have developed a new therapy, percutaneous in-trasomatic injection of acrylic cement, which was initially proposed for the cure of aggressive spinal angiomas. After percutaneous biopsy of the vertebra, a 10 gauge needle is inserted in its body and a mixture of tantalum powder and methyl-methacrylate (3–5 cc) paste is injected. Five patients with severe pain due to osteoporotic vertebral crush fracture syndrome were successfully treated by this method. The technique and results are detailed.

Lithium compounds are being considered as fusion reactor breeder blanket ceramics. The present studies will examine the stability of the Li-compounds to radiation damage effects, and to the formation of non-crystalline phases.

Diamond has long been regarded as relatively resistant to radiation, although it does undergo structural damage when bombarded by neutrons or ions. Diamond powders have been irradiated by various noble gas ions at 1–3 MeV energy and X-ray diffraction studies have shown that the lattice expansion of ion-irradiated diamond saturates with increasing ion fluence and ion mass consistent with an equilibrium between the rates of production and annealing of defects in the diamond crystal structure. Electron microscope studies show the diamond particles to undergo swelling with volume increase up to about 50%, although sharp edges and features on the particles remain. Raman spectroscopy demonstrates the presence of non-diamond carbon in ion-irradiated diamond. The microstructure of ion-irradiated diamond can be considered to be a mixture of two major components: one of strained diamond, containing very large numbers of vacancies and vacancy clusters, of overall low macroscopic density because of pores and voids, and the other of scattered non-diamond carbon, either amorphous or graphitic.

Selected phlogopite micas display anomalous reversible thermal expansion, as much as 300%, perpendicular to the cleavage planes, on heating up to 900-degrees-C. The vaporization of traces of occluded H2O accounts for an abrupt increase (almost-equal-to 100%) in volume at the boiling point of water, and above this onset temperature, the thermal expansion is quantitatively similar to that of an ideal gas. The onset temperature increases with applied pressure approximately as the vapour pressure of H2O. The formation at temperature of lenticular bubbles on dislocation networks can be observed by transmission electron microscopy.

Specimens of high-Tc superconductor YBa2Cu3Ox have been irradiated with Si ions (7 MeV) up to 10 ions/nm2. Monolayers of fine particles (less than 5 ω size) were prepared on metal plates and X-ray diffraction patterns were taken before and after the irradiations. Intensities of all diffraction peaks decrease continuously with increase in fluence with a damage cross section of 0.21 nm2 without observation of a critical or threshold fluence. A 50% loss in crystallinity is observed at ∼ 3.6 eV/atom (0.12 dpa) although the rate of amorphization may increase beyond a fluence of ∼ 4 ions/nm2. Bragg diffraction peaks have disappeared and amorphization is complete by ≈10 eV/atom (0.33 dpa). Peak positions shift toward lower 2θ values indicating lattice expansion contributed to by point defects. There is a gradual transformation from orthorhombic toward tetragonal structure with the b0 parameter changing very little. c0 increasing by ≈ 0.6%, and α0 also increasing by ≈ 1% to approach b0. The damage cross section of the tetragonal phase is larger than that of the orthorhombic phase.

One-hundred patients with unexplained cerebral ischaemic events were explored by two-dimensional echocardiography. Thirty-nine patients showed abnormalities considered causative of embolic stroke. The most frequent cardiopathy found was mitral valve prolapse (38.5 per cent). This study suggests that unexplained cerebral ischaemic events should be evaluated by two-dimensional echocardiography and that the most frequent source of emboli to be expected is mitral valve prolapse.

The mechanical surface properties of single crystal WC are known to be affected by N (100 keV) ion implantation of 2000 ions/m 2 , when surface embrittlement occurs. This is considered to be due to dense formations of dislocations which hinder their movement. The present studies concern the ability of the WC crystal structure to withstand radiation damage and to remain crystalline at high fluence. Irradiations of a monolayer of fine powders of WC (particle sizes less than 5 μ) have been carried out using Si (7 MeV) ions up to 10 ions/nm 2 . X-ray diffraction patterns have been observed before and after irradiation; the diffraction peaks are displaced indicating a maximum increase of more than 1.0% in volume of the unit cell, peak widths increase very slightly, and the peak intensities decrease slightly and then remain constant. Assuming the maximum lattice parameter changes are due to an equilibrium between the production and annealing of defects, the saturation density of defects is about 10 22 defects/cm 3 . There is no evidence for the formation of a non-crystalline condition.

The Unique Case Of A Transient Opsoclonus-Myoclonus Syndrome In A 32-Year-Old Woman With Serologically Confirmed Hepatitis A Infection Is Reported. The Oculographic Study Showed Multidirectional Eye Oscillations Which Had The Character Of Saccades. The Various Hypotheses Proposed In The Literature To Explain This Infrequent Syndrome Are Outlined And A New Way To Approach These Pathologic Eye Movements Is Suggested.

Ceramic powders can be prepared in a radiation damaged condition by bombardment with 1 to 4 MeV ions of Ne, Ar, Kr or Xe. The powder particle sizes are chosen to correspond to the ion beam penetration but are found to be considerably greater than the calculated ion ranges for powders becoming metamict. A monolayer of powder particles of sizes up to about 5 μm is sedimented onto long strips of metal foil with an area density of about 1 mg-cm-2. The ion beam is rastered to irradiate an area as the foil rotates on a drum through the beam. Alternately, monolayers of powder particles can be prepared by the use of a very-thin layer of rubber cement. By these techniques, plates can be prepared for irradiation in the ion beam and also for direct insertion into an X-ray diffractometer. Gram amounts of irradiated material can be collected in a few hours for studies such as powder X-ray diffraction, SEM, Differential Scanning Calorimetry and density measurements. Thus, zircon ZrSiO4 becomes non-crystalline or metamict under ion bombardment with a damage cross-section DM = 0.33 nm-2 for Ar (3 MeV) ions; one gram can be rendered 50% non-crystalline after two hours of irradiation by a 6 μA ion beam.

Diamond, Si and Ge powders were irradiated by Ne, Ar, Kr and Xe (3 Mev) ions up to tluences ot ∼ 200 ions/nm2. As reported for fast-neutron irradiation, diamond undergoes structural damage with heavy ion bombardment. The (111) X-ray diffraction line was observed to broaden and shift toward lower angles; the lattice parameter expansions were correlated with the displacement damage component of the energy of the bombarding ions. The X-ray line shifts apparently approached asymptotically limiting values with increasing ion fluences (10–30 ion/nm2), consistent with a model involving dynamic equilibrium between production and radiation annealing of the defects. The saturation lattice parameter shifts increased with increasing ion mass. A volume increment per defect of (1.3 ± 0.2) × 10−3 nm3 was derived which is about 23% of the atomic volume. The X-ray diffraction lines of Ge did not shift or broaden significantly with ion irradiation but decreased in intensity with increasing ion fluence, consistent with the Morehead-Crowder model. The metamict damage cross-section of Ge to argon (3 MeV) ions is 0.35 ± 0.05 nm2- and 1.0 ± 0.2 nm2 for Kr (3 MeV) ions. The damaged Ge recovers completely after annealing for 30 min at 750 K in air. Silicon has a damage cross-section of 0.15 ± 0.10 nm2 for Kr (3 MeV) ions, and appears to undergo radiation annealing to a greater extent than Ge under the same conditions of irradiation.