Radiation-induced tensile stresses in fission-blanket components

A particle-beam fusion-fission hybrid reactor includes a surrounding blanket for energy production and for breeding fissile fuel. The blanket is subjected to radiation deposition pulses at the operating frequency of the fusion driver. A circulating coolant will remove heat from the blanket region. One-dimensional studies were made to examine possible configurations for the blanket elements. Depleted uranium solid plates, cylinders, and spheres were the initial choices. Depleted uranium solid plates, cylinders, and spheres were the initial choices. Uniform radiation deposition was assumed across the geometry, with the particular concern being the level of tension induced by the deposition pulse. The high tensions that appear in the solid cylindrical and spherical cases could be mitigated by the presence of hollow cores

THE GROWTH OF INHOMOGENEOUS THERMOPLASTIC SHEAR

On étudie la croissance catastrophique du cisaillement thermoplastique instable qui suit le passage d'une déformation homogène à une déformation hétérogène localisée dans le réseau de bandes de cisaillement. Des méthodes analytiques ou numériques approchées sont utilisées. Les calculs fournissent des expressions pour les largeurs, espacements, temps de croissance catastrophique des bandes de cisaillement ainsi que pour les vitesses de transfert de la contrainte entre les bandes de cisaillement. Les calculs sont appliqués à la localisation du cisaillement hétérogène observé dans la compression par choc soutenu de l'aluminium.The catastrophic growth of unstable thermoplastic shear following the transition from homogeneous deformation to heterogeneous localized deformation through distributed shear banding is studied through approximate analytic and computational methods. The calculations provide expressions for shear-band widths, spacing, catastrophic growth times and the rate of stress communication between shear bands. The calculations are applied to heterogeneous shear localization observed in the steady-wave shock compression of aluminum

WONDY V: a one-dimensional finite-difference wave-propagation code

WONDY V solves the finite difference analogs to the Lagrangian equations of motion in one spatial dimension (planar, cylindrical, or spherical). Simulations of explosive detonation, energy deposition, plate impact, and dynamic fracture are possible, using a variety of existing material models. In addition, WONDY has proven to be a powerful tool in the evaluation of new constitutive models. A preprocessor is available to allocate storage arrays commensurate with problem size, and automatic rezoning may be employed to improve resolution. This document provides a description of the equations solved, available material models, operating instructions, and sample problems

Shock phase transformation and release properties of aluminum nitride

À environ 22 GPa la structure du nitride d'aluminium change d'une structure hexagonale de wurtzite en une structure cubique de sel gemme. La phase se caractérise par un changement de volume d'environ 20% - non-récupérable. Nous avons étudié la manifestation de cet important changement de volume cors de la charge, au moyen de quatre expériences d'impact uniaxial. Nous avons effectué un relevé des vitesses de choc et d'échappement, à une pression d'impact de 40 GPa, y compris le développement du choc et de l'échappement, avec les distances de propagation. Grâce à une technique d'analyse numérique, nous avons déterminé les caractéristiques de fatigue et de tendance du nitride d'aluminium, y compris durant la phase de transformation.Aluminum nitride is characterized by a non-recoverable volume phase transformation from the wurtzite (hexagonal) to the rocksalt (cubic) structure that commences about 22 GPa, accompanied by a volume strain of about 20%. A study of the manifestation of this large volume change under shock loading was made with four uniaxial strain impact experiments. Particle velocity histories of the shock and release states were obtained corresponding to impact pressures of 40 GPa, including the evolution of the shock and release waves with propagation distance. Stress - strain features characterizing aluminum nitride, including the phase transformation, were determined with numerical analysis techniques

Sellar region atypical teratoid/rhabdoid tumors in adults: Clinicopathological characterization of five cases and review of the literature

Atypical teratoid/rhabdoid tumors (AT/RTs) are highly malignant CNS neoplasms that typically occur in children <2 years of age. These are characterized by high-grade histologic features and mutations of the INI1/SMARCB1 gene readily detected by loss of expression by immunohistochemistry. Among adults, the majority of AT/ RTs occurs in the cerebral hemispheres. A small number of adult AT/RTs involving the sellar and suprasellar region reported in the literature suggest a distinct clinical course for this group. Here, we describe detailed clinical and genetic characterization of 5 adult patients with AT/RTs involving the sellar and suprasellar region, and provide a review of the available clinical and genetic features of 22 previously reported cases in order to help increase our understanding of this unusual entity

Clusters of activated microglia in normal-appearing white matter show signs of innate immune activation

BACKGROUND: In brain tissues from multiple sclerosis (MS) patients, clusters of activated HLA-DR-expressing microglia, also referred to as preactive lesions, are located throughout the normal-appearing white matter. The aim of this study was to gain more insight into the frequency, distribution and cellular architecture of preactive lesions using a large cohort of well-characterized MS brain samples. METHODS: Here, we document the frequency of preactive lesions and their association with distinct white matter lesions in a cohort of 21 MS patients. Immunohistochemistry was used to gain further insight into the cellular and molecular composition of preactive lesions. RESULTS: Preactive lesions were observed in a majority of MS patients (67%) irrespective of disease duration, gender or subtype of disease. Microglial clusters were predominantly observed in the vicinity of active demyelinating lesions and are not associated with T cell infiltrates, axonal alterations, activated astrocytes or blood–brain barrier disruption. Microglia in preactive lesions consistently express interleukin-10 and TNF-α, but not interleukin-4, whereas matrix metalloproteases-2 and −9 are virtually absent in microglial nodules. Interestingly, key subunits of the free-radical-generating enzyme NADPH oxidase-2 were abundantly expressed in microglial clusters. CONCLUSIONS: The high frequency of preactive lesions suggests that it is unlikely that most of them will progress into full-blown demyelinating lesions. Preactive lesions are not associated with blood–brain barrier disruption, suggesting that an intrinsic trigger of innate immune activation, rather than extrinsic factors crossing a damaged blood–brain barrier, induces the formation of clusters of activated microglia