Secondary Radiation Influence on LSF Shapes in Radiography

A radiographic image is generated by both primary and secondary radiations. In a previous study [1, 2] the influence of secondary radiation on the generated image was shown for square based blocks of finite dimensions (few mean free paths). The response to a step change in the block’s thickness, varies drastically with the step location relative to the block’s edges [3]. However, even when the radiographed object is large and the step response is studied far off the object’s limits, the effect of the secondary radiation is still significant. This radiation distorts the “ideal” step response shape expected from the primary radiation

Receptor Heteromerization Expands the Repertoire of Cannabinoid Signaling in Rodent Neurons

A fundamental question in G protein coupled receptor biology is how a single ligand acting at a specific receptor is able to induce a range of signaling that results in a variety of physiological responses. We focused on Type 1 cannabinoid receptor (CB1R) as a model GPCR involved in a variety of processes spanning from analgesia and euphoria to neuronal development, survival and differentiation. We examined receptor dimerization as a possible mechanism underlying expanded signaling responses by a single ligand and focused on interactions between CB1R and delta opioid receptor (DOR). Using co-immunoprecipitation assays as well as analysis of changes in receptor subcellular localization upon co-expression, we show that CB1R and DOR form receptor heteromers. We find that heteromerization affects receptor signaling since the potency of the CB1R ligand to stimulate G-protein activity is increased in the absence of DOR, suggesting that the decrease in CB1R activity in the presence of DOR could, at least in part, be due to heteromerization. We also find that the decrease in activity is associated with enhanced PLC-dependent recruitment of arrestin3 to the CB1R-DOR complex, suggesting that interaction with DOR enhances arrestin-mediated CB1R desensitization. Additionally, presence of DOR facilitates signaling via a new CB1R-mediated anti-apoptotic pathway leading to enhanced neuronal survival. Taken together, these results support a role for CB1R-DOR heteromerization in diversification of endocannabinoid signaling and highlight the importance of heteromer-directed signal trafficking in enhancing the repertoire of GPCR signaling

Resolution Measurements of High Energy Radiography

The resolution of a film or film — screen combination is essential for characterizing the radiographic system. The conventional methods for measuring the resolution in radiography, based on the Image Quality Indicators (IQI) and Penetrameters, are not applicable for high energy radiation (in the MV range) due to the high penetration. In addition, the IQI and Penetrameters do not measure only the spatial resolution but rather an undefined combination of the spatial and thickness resolution. Another approach used for analyzing the film resolution is based on the measurement of the radiographic response to a step function input.</p

Secondary Radiation Influence on LSF Shapes in Radiography

A radiographic image is generated by both primary and secondary radiations. In a previous study [1, 2] the influence of secondary radiation on the generated image was shown for square based blocks of finite dimensions (few mean free paths). The response to a step change in the block’s thickness, varies drastically with the step location relative to the block’s edges [3]. However, even when the radiographed object is large and the step response is studied far off the object’s limits, the effect of the secondary radiation is still significant. This radiation distorts the “ideal” step response shape expected from the primary radiation.</p