In situ and tomographic observations of defect free channel formation in ion irradiated stainless steels.

The effects of heavy-ion irradiation on dislocation processes in stainless steels were investigated using in situ irradiation and deformation in the transmission electron microscope as well as post mortem electron tomography to retrieve information on the three-dimensional dislocation state. Irradiation-induced defects were found to pose a strong collective barrier to dislocation motion, leading to dislocation pileups forming in grain interiors and at grain boundaries. The passage of multiple dislocations along the same slip plane removes the irradiation defects and leads to the eventual formation of a defect-free channel. These channels are composed of densely tangled dislocation networks which line the channel-matrix walls as well as residual dislocation debris in the channel interiors. The structures of the dislocation tangles were found to be similar to those encountered in later stages of deformation in unirradiated materials, with the exception that they developed earlier in the deformation process and were confined to the defect free channels. Also, defect free channels were found to widen through both source widening as well as complex cross-slip mechanisms.

Recent advances in the study of structural materials compatibility with hydrogen.

Hydrogen is a ubiquitous element that enters materials from many different sources. It almost always has a deleterious effect on mechanical properties. In non-hydride-forming systems, research to date has identified hydrogen-enhanced localized plasticity and hydrogen-induced decohesion as two viable mechanisms for embrittlement. However, a fracture prediction methodology that associates macroscopic parameters with the degradation mechanisms at the microscale has not been established, as of yet. In this article, we report recent work on modeling and simulation of hydrogen-induced crack initiation and growth. Our goal is to develop methodologies to relate characteristics of the degradation mechanisms from microscopic observations and first-principles calculations with macroscopic indices of embrittlement. The approach we use involves finite element analysis of the coupled hydrogen transport problem with hydrogen-assisted elastoplastic deformation, thermodynamic theories of decohesion, and ab initio density functional theory calculations of the hydrogen effect on grain boundaries.

In situ TEM observation of the nucleation and growth of silver oxide nanoparticles.

The nucleation, growth, and coalescence of silver oxide nanoparticles have been investigated dynamically and at high spatial resolution by using the electron beam of a transmission electron microscope to stimulate and to observe the processes. Under the assumption the particles are hemispherical, the growth rate was found to be proportional to the square root of the electron irradiation time. This result suggests that the rate-limiting step is the attachment of atoms to the nanoparticles. Growth of the nanoparticles occurred by the addition of columns of atoms on {111} planes. Particle impingement resulted in interpenetration of the particles and, ultimately, the formation of a grain boundary.

Anetoderma of prematurity in association with electrocardiographic electrodes.

Anetoderma in premature infants is an uncommon lesion that may be associated with the use of various types of monitoring leads. In 2 infants multiple papules of anetoderma occurred on the forehead in association with the use of gel electrocardiographic electrodes. It is postulated that the cause of these papules was a local hypoxemia caused by pressure from the electrodes. Growth-restricted infants may be particularly predisposed to iatrogenic anetoderma.

Benign hypergammaglobulinaemic purpura of Waldenström associated with lymphoid interstitial pneumonitis.

A 31-year-old female is described who developed benign hypergammaglobulinaemic purpura and lymphoid interstitial pneumonitis concomitantly. High titre anti-nuclear antibodies were also noted. Several years previously, the patient had developed myasthenia gravis and multiple sclerosis. The present case is an example of multiple medical disorders characterized by immune dysregulation and represents the first reported associated of hypergammaglobulinaemic purpura with lymphoid interstitial pneumonitis.

Controlled environment transmission electron microscopy.

The design of a controlled environment electron microscope is described and examples are presented to demonstrate the information that can be obtained by studying gas-solid interactions in real time and at high spatial resolution.

Acquired ichthyosis in bone marrow transplant recipients.

BACKGROUND: Acquired ichthyosis (AI) has been described in a variety of clinical situations. We have observed cases of ichthyosis in bone marrow transplant recipients. OBJECTIVE: Our purpose was to characterize these changes clinically and histologically and to compare them with other cases of acquired ichthyosis. METHODS: Skin biopsy specimens were taken before transplantation and from affected areas after transplantation. RESULTS: AI was observed in four patients who had received a bone marrow transplant for leukemia. None of the patients had a previous personal or family history of ichthyosis. In all patients graft-versus-host disease developed after transplantation. The eruption clinically and histologically most closely resembled ichthyosis vulgaris. The ichthyotic changes appeared to be unrelated to specific drug therapy. CONCLUSION: AI is a previously unreported cutaneous complication of bone marrow transplantation. It may be related to graft-versus-host disease in these patients.

Pityriasis rosea-like eruption after bone marrow transplantation.

Bone marrow transplantation is associated with numerous cutaneous complications that may be related to the underlying (preexisting) disease, to pretransplant conditioning, to immunosuppression, to concomitant medication, or to graft-versus-host reaction. We describe four bone marrow transplant recipients with the clinical and histologic features of pityriasis rosea, a hitherto unreported association.

Scottish-English comparisons: a cautionary note on the census.

"This paper draws attention to the variation in Census Enumeration District size between Scotland and England and the implications for country-wide research. It also reflects on the varying definition of a room between the countries and over time."