Design and fabrication of a window for the gas Cherenkov detector 3.

The gas Cherenkov detector 3 was designed at Los Alamos National Laboratory for use in inertial confinement fusion experiments at both the Omega Laser Facility and the National Ignition Facility. This instrument uses a low-Z gamma-to-electron convertor plate and high pressure gas to convert MeV gammas into UV/visible Cherenkov photons for fast optical detection. This is a follow-on diagnostic from previous versions, with two notable differences: the pressure of the gas is four times higher, and it allows the use of fluorinated gas, requiring metal seals. These changes force significant changes in the window component, having a unique set of requirements and footprint limitations. The selected solution for this component, a sapphire window brazed into a stainless steel flange housing, is described.

Differential pathways in oxy and deoxy HbC aggregation/crystallization.

CC individuals, homozygous for the expression of beta(C)-globin, and SC individuals expressing both beta(S) and beta(C)-globins, are known to form intraerythrocytic oxy hemoglobin tetragonal crystals with pathophysiologies specific to the phenotype. To date, the question remains as to why HbC forms in vivo crystals in the oxy state and not in the deoxy state. Our first approach is to study HbC crystallization in vitro, under non-physiological conditions. We present here a comparison of deoxy and oxy HbC crystal formation induced under conditions of concentrated phosphate buffer (2g% Hb, 1. 8M potassium phosphate buffer) and viewed by differential interference contrast microscopy. Oxy HbC formed isotropic amorphous aggregates with subsequent tetragonal crystal formation. Also observed, but less numerous, were twisted, macro-ribbons that appeared to evolve into crystals. Deoxy HbC also formed aggregates and twisted macro-ribbon forms similar to those seen in the oxy liganded state. However, in contrast to oxy HbC, deoxy HbC favored the formation of a greater morphologic variety of aggregates including polymeric unbranched fibers in radial arrays with dense centers, with infrequent crystal formation in close spatial relation to both the radial arrays and macroribbons. Unlike the oxy (R-state) tetragonal crystal, deoxy HbC formed flat, hexagonal crystals. These results suggest: (1) the Lys substitution at beta6 evokes a crystallization process dependent upon ligand state conformation [i. e., the R (oxy) or T (deoxy) allosteric conformation]; and (2) the oxy ligand state is thermodynamically driven to a limited number of aggregation pathways with a high propensity to form the tetragonal crystal structure. This is in contrast to the deoxy form of HbC that energetically equally favors multiple pathways of aggregation, not all of which might culminate in crystal formation.

Promoting widespread, durable service quality via interlocking contingencies.

Technologies for promoting quality of organizational services to the developmentally disabled have been evolving over the past several decades. Feedback reinforcement and, often, goal-setting, powerful change tools, generally are incorporated within behavioral interventions. Despite their promise, wide-scale application of these strategies often is impeded by natural and informal organizational contingencies. In an attempt to combat such impediments, a structure of interlocking contingencies was designed to train and support managers' provision of effective feedback to their subordinates, peers, and superiors. The system included formal scheduling of feedback, reinforcement and goal setting in a way that attempted to (a) minimize financial costs, time and effort; (b) empower participants by involving them in designing the specifics of the system; and (c) promote momentum by encouraging dense schedules of feedback. Within a period of less than 6 months, supervisors, managers, and professional specialists conducted brief audits and delivered nearly 9,000 written feedback reports to workers serving 129 clients, with the result that staff-client interactions and client engagement levels increased substantially. Future research should replicate these methods under more rigorous experimental conditions and formally assess some of the system's spillover into realms such as gains in clients' skill levels, and staff and public acceptance.

Gastric visualization and image quality in radionuclide bone scanning: concise communication.

In a 12-mo study period, there were 14 days identified when the stomach was visualized in routine bone imaging. On these days, 44% of the 110 patients imaged demonstrated this effect. Only the quality control, binding efficiency, and scan quality differed (p less than 0.005) when the study population was compared with a reference population of 162 patients. However, on the days when this effect was noted, there was a significant (p less than 0.001) linear correlation between the presence and degree of gastric visualization and the radiopharmaceutical incubation and quality control parameters. The study suggests a sporadic phenomenon that appears to result from partial oxidation of the agent during incubation, producing (a) different species of labeled diphosphonate that display altered affinity for bone (scan quality) and (b) free pertechnetate (gastric activity).