Exploding foil initiators (EFIs), also known as slapper initiators or detonators, offer clear safety and timing advantages over other means of initiating detonation in high explosives. This work outlines a new capability for imaging and reconstructing three-dimensional images of operating EFIs. Flyer size and intended velocity were chosen based on parameters of the imaging system. The EFI metal plasma and plastic flyer traveling at 2.5 km/s were imaged with short ∼80 ps pulses spaced 153.4 ns apart. A four-camera system acquired 4 images from successive x-ray pulses from each shot. The first frame was prior to bridge burst, the 2nd images the flyer about 0.16 mm above the surface but edges of the foil and/or flyer are still attached to the substrate. The 3rd frame captures the flyer in flight, while the 4th shows a completely detached flyer in a position that is typically beyond where slappers strike initiating explosives. Multiple acquisitions at different incident angles and advanced computed tomography reconstruction algorithms were used to produce a 3-dimensional image of the flyer at 0.16 and 0.53 mm above the surface. Both the x-ray images and the 3D reconstruction show a strong anisotropy in the shape of the flyer and underlying foil parallel vs. perpendicular to the initiating current and electrical contacts. These results provide detailed flyer morphology during the operation of the EFI.
As anatomic total shoulder arthroplasty (aTSA) and reverse total shoulder arthroplasty (rTSA) become increasingly common, differences between the 2 procedures are of importance. The purpose of this study was to determine differences in acute pain levels between patients undergoing aTSA and rTSA. Sixty patients undergoing aTSA or rTSA were assessed for participation. The primary outcome was postoperative daily visual analog scale scores, which were initially collected for 4 days postoperatively. Secondary outcomes included opioid consumption, length of stay, and complications. Comparisons between the 2 groups were assessed using a multivariable analysis, which controlled for sex, age, body mass index, and type of anesthetic. A total of 57 patients consented and were analyzed. No significant differences were found in postoperative visual analog scale scores in the first 4 days following surgery or at 1 year postoperatively. Patients undergoing aTSA had a higher mean opioid requirement in the first 4 hours postoperatively (1.0±0.7 vs 0.4±0.6 morphine milligram equivalents,
P
<.01). Forty percent of patients undergoing shoulder arthroplasty were prescribed narcotics within the 3 months prior to surgery. Patients who were prescribed narcotics prior to surgery were more likely to continue to require narcotics at extended time periods postoperatively. Patients undergoing aTSA required more opioid medication in the immediate postoperative period. However, after 4 hours postoperatively, no significant differences in pain scores or opioid consumption were found. These findings suggest that patients undergoing aTSA or rTSA have similar postoperative pain profiles. Patients who are prescribed narcotics before shoulder arthroplasty are at an increased risk for postoperative opioid demand. [
Orthopedics
. 2019; 42(2):e247–e252.]
A novel set of experiments and reactive flow modeling of pentaerythritol tetranitrate (PETN) is presented. Here, the specific phenomenon of shock to detonation transition is examined, where an initial, relatively weak shock is propagated into pressed PETN powder at 1.65 g/cm3 and the subsequent buildup to detonation is observed experimentally. These experiments, in conjunction with reactant and products’ equations of state, are utilized for building reactive flow models.
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