Magnet Safety Assessment for ITER

The ITER magnet system consists of structurally linked sets of toroidal (TF) and poloidal (PF) field coils, central solenoid (CS), and various support structures. The coils are superconducting, force flow Helium cooled with a Kapton-Glass-Epoxy multilayer insulation system. The stored magnetic energy is about 100GJ in the TF system and 20GJ in the PF-CS. Coils and structure are maintained at 4 K by enclosing them in a vacuum cryostat. The cryostat, comprising an outer envelope to the magnets, forms most of the second radioactivity confinement barrier. The inner primary barrier is formed by the vacuum vessel, its ports and their extensions. To keep the machine size within acceptable bounds, it is essential that the magnets are in close proximity to both of the nuclear confinement barriers. The objective of the magnet design is that, although local damage to one of the barriers may occur in very exceptional circumstances, large scale magnet structural or thermal failure leading to simultaneous breaching of both barriers is not credible. Magnet accidents fall into three categories: thermal (which includes arcing arising from insulation failure and local overheating due to discharge failure in the event of a superconductor quench), structural (which includes component mechanical failure arising from material inadequacies, design errors and exceptional force patterns arising from coil shorts or control failures), and fluid (Helium release due to cooling line failure). After a preliminary survey to select initial faults conceivable within the present design, these faults are systematically analyzed to provide an assessment of the damage potential. The results of this damage assessment together with an assessment of the reliability of the monitoring and protective systems, shows that the magnets can operate with the required safety condition.     

Sexual dimorphism of circulating somatotropin, insulin-like growth factor I and II, insulin-like growth factor binding proteins, and insulin: relationships to growth rate and carcass characteristics in growing lambs

The effects of sex and age on patterns of circulating somatotropin (ST) concentration and plasma IGF-I, IGF-II, insulin, and IGF binding protein-3 (IGFBP-3) were studied in ram, wether, and ewe lambs (n = 7 or 8) sampled at mean ages of 81 (I1) and 158 d (I2). Between 81 and 158 d of age, rams grew more rapidly than wethers (P < .01), and wethers grew more rapidly than ewes (P < .01). The sex differences in growth were reflected in empty body weight at slaughter: rams > wethers > ewes (P < .05). Mean plasma ST concentrations, ST pulse amplitude, and integrated plasma ST concentrations were greater (P < .05) in rams than in ewes at I1 and I2. Characteristics of the ST plasma profile in wethers were generally intermediate between those of rams and ewes. The interpulse interval was greater in ewes than in wethers at I2. The IGF-I and IGFBP-3 concentrations were greater in rams than in ewes at both sampling times. Plasma IGF-II was greater in ewes than in rams at I2. Mean plasma ST was approximately two thirds less at I2 than at I1 regardless of sex. Mean plasma ST and IGF-I at both ages were positively correlated with growth. Mean plasma ST at I2 was negatively correlated with fatness at slaughter. Sex and age significantly affected patterns of circulating ST and concentrations of IGF-I and IGFBP-3 in prepubertal growing lambs, under conditions for which growth rates and composition were also sexually dimorphic.     

The musculoskeletal management of children with cerebral palsy

Orthopedic management of children with cerebral palsy is best accomplished with a team approach, which generally is effective in the other neuromotor disabilities of childhood, such as myelomeningocele and muscle disease. Because contracture development is inevitable in growing children with spastic musculature or muscle imbalance and is a prime cause of musculoskeletal dysfunction, its control over time using therapy, bracing, and medication is essential. Problems such as severe contracture, joint deformity, and scoliosis interfere with the basic requirement of comfortable seating in children with quadriplegic involvement and frequently require surgery. In ambulatory children, the use of three-dimensional gait analysis has allowed multilevel surgery to be appropriately planned, minimizing exposure to surgery and therapy.     

Structure of very early protein folding intermediates: new insights through a variant of hydrogen exchange labelling

BACKGROUND: Hydrogen exchange labelling has been a key method in characterizing the structure of transient folding intermediates. In studies of several proteins, however, there has been clear spectroscopic evidence for partial folding of some kind at very early times, before any protection from exchange was measurable. These results, presumably a consequence of limited stability of specific backbone interactions, have made it difficult to assess the extent of native-like folding in the very early intermediates. We have used a variant of the labelling method to investigate marginally stable structures formed within the first few milliseconds of refolding of two such proteins, hen lysozyme and ubiquitin. RESULTS: In lysozyme, population of a subset of native-like secondary structures on this timescale is revealed, thus reconciling the exchange behaviour with circular dichroism measurements and confirming the significance of the rapidly formed embryonic structure as a foundation for the subsequent folding pathway. In the case of ubiquitin, by contrast, no significantly protective structure was detectable, suggesting that here secondary structural elements can be populated only marginally ahead of the major cooperative folding event; this was also supported by stopped-flow circular dichroism measurements. CONCLUSIONS: The hydrogen exchange approach can be extended to probe the formation of native-like structure formed in very early folding intermediates, even when the stability of specific interactions is marginal. In the case of lysozyme, this has provided a new window on an early stage of organization of the alpha-helical domain.     

Comparison of magnetic resonance volume flow rates, angiography, and carotid Dopplers. Preliminary results

BACKGROUND AND PURPOSE: We compared the results of conventional angiography, carotid Doppler, and magnetic resonance angiography volume flow rates to determine the clinical utility of volume flow rate assessment of blood flow to the anterior circulation in patients with carotid occlusive disease. METHODS: From 11 symptomatic patients, a total of 22 extracranial carotid arteries were studied with all three techniques. The studies were independently read, and regression analysis was used to compare the measurements. RESULTS: Carotid Doppler measurements of the distal extracranial carotid arteries were proportional to the inverse of the extracranial carotid volume flow rate (r = .53, R2 = 29%, P < .01), volume flow rates were proportional to the inverse of measured percent stenosis on angiography (r = .84, R2 = 71%, P < .01), and Dopplers were proportional to angiography (r = .94, R2 = 90%, P < .01). Symptomatic Doppler systolic velocity was significantly higher (P < .002), symptomatic measured stenosis was significantly higher (P < .002), and symptomatic volume flow rate was significantly lower (P < .01) than their respective asymptomatic-side values. These preliminary observations, however, may well change once a large data set, especially one in which more patients with high-grade carotid stenosis are included, is studied. CONCLUSIONS: Assessment of carotid volume flow rates by magnetic resonance angiography quantifies flow reduction secondary to atherosclerotic occlusive disease. The easily obtained flow data add both documentation of arterial flow characteristics related to internal carotid stenosis and information regarding the adequacy of collateral pathways.