3D printing 18F radioactive phantoms for PET imaging

Purpose Phantoms are routinely used in molecular imaging to assess scanner performance. However, traditional phantoms with fillable shapes do not replicate human anatomy. 3D-printed phantoms have overcome this by creating phantoms which replicate human anatomy which can be filled with radioactive material. The problem with these is that small objects suffer to a greater extent than larger objects from the effects of inactive walls, and therefore, phantoms without these are desirable. The purpose of this study was to explore the feasibility of creating resin-based 3D-printed phantoms using 18F. Methods Radioactive resin was created using an emulsion of printer resin and 18F-FDG. A series of test objects were printed including twenty identical cylinders, ten spheres with increasing diameters (2 to 20 mm), and a double helix. Radioactive concentration uniformity, printing accuracy and the amount of leaching were assessed. Results Creating radioactive resin was simple and effective. The radioactive concentration was uniform among identical objects; the CoV of the signal was 0.7% using a gamma counter. The printed cylinders and spheres were found to be within 4% of the model dimensions. A double helix was successfully printed as a test for the printer and appeared as expected on the PET scanner. The amount of radioactivity leached into the water was measurable (0.72%) but not visible above background on the imaging. Conclusions Creating an 18F radioactive resin emulsion is a simple and effective way to create accurate and complex phantoms without inactive walls. This technique could be used to print clinically realistic phantoms. However, they are single use and cannot be made hollow without an exit hole. Also, there is a small amount of leaching of the radioactivity to take into consideration.

Investigation of Film Cooling Effectiveness of Dual-fanned Hole with Various Exit Widths

Film cooling effectiveness downstream of one row of holes of 30 degree inclination angle was measured by using a steady-state thermochromic liquid crystal technique at blowing ratios of 0.5, 1.0, 1.5 and 2.0, respectively. Three kinds of dual-fanned holes which have the same expanded entrance width and the different expanded exit widths were tested. The configuration of only expanded entrance, but cylindrical exit hole, was tested to examine the effect of the expanded entrance on film cooling performance. The numerical simulation for the three expanded exit configurations was carried out explaining the mechanism of film cooling by the flow and thermal field. The only expanded entrance has a weak influence on film cooling effectiveness. The ${W_o} = 1.5d$ configuration provides a lift of film cooling effectiveness compared to ${W_o} = 1.0d$ configuration. Film cooling effectiveness is not sensitive to the change of configurations from ${W_o} = 1.5d$ to ${W_o} = 2.0d$. Film cooling effectiveness for ${W_o} = 2.5d$ performs significantly better than the other configurations due to the presence of the anti-vortex. The effect of dual-fanned exit width on film cooling effectiveness is strongly dependent on the blowing ratios.

Friction Stir Spot Welding of AA2024-T3 with Modified Refill Technique

The quality of welded joints of FSSW is mainly dependent on the processing parameters while the main disadvantage of this process is the creation of an exit hole. Process parameters, namely tool dimensions, tool rotational speed, and stir time were changed and their impact on bond dimensions and weld strength was investigated using 2024-T3 Al Alloy. Macro- and microstructures of the welded samples were examined; shear fracture loads were measured and the optimum set of operation variables was determined. To decrease the exit hole of the first stage the present paper proposes a modified two-stage weld-refill process employing the same welding machine. In this work, this two-stage process was referred to as reversed friction stir spot welding (ReFSSW). In the second stage, a smaller pin was used and the shoulder diameter was designed such that to force the metal of the upper plate to flow towards the exit hole of the first stage decreasing its dimensions. The metal flow in the second stage was evaluated by examining the microstructure of the metal that filled the exit hole of the first stage. Thin stir zone was found around the pin of the second stage followed by thermomechanically affected zone consisting of grains elongated in the vertical direction. The proposed process resulted in smaller exit hole dimensions and consequently higher mechanical properties compared with the conventional single-stage FSSW.

A keeper of many crypts: a behaviour-manipulating parasite attacks a taxonomically diverse array of oak gall wasp species

Parasites of animals and plants can encounter trade-offs between their specificity to any single host and their fitness on alternative hosts. For parasites that manipulate their host's behaviour, the added complexity of that manipulation may further limit the parasite's host range. However, this is rarely tested. The recently described crypt-keeper wasp, Euderus set , changes the behaviour of the gall wasp Bassettia pallida such that B. pallida chews a significantly smaller exit hole in the side of its larval chamber and ‘plugs’ that hole with its head before dying. Euderus set benefits from this head plug, as it facilitates the escape of the parasitoid from the crypt after it completes development. Here, we find direct and indirect evidence that E. set attacks and manipulates the behaviour of at least six additional gall wasp species, and that these hosts are taxonomically diverse. Interestingly, each of E. set 's hosts has converged upon similarities in their extended phenotypes: the galls they induce on oaks share characters that may make them vulnerable to attack by E. set . The specialization required to behaviourally manipulate hosts may be less important in determining the range of hosts in this parasitoid system than other dimensions of the host–parasitoid interaction, like the host's physical defences.