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Recent advances in materials science and tissue engineering give the ability to create three-dimensional biocompatible ceramic scaffolds for bone repair. Applications include a variety of bone defects such as non-unions, replacing bone loss from trauma or disease, and maxillofacial reconstruction. An important, yet understudied, aspect of creating artificial bone requires knowledge of porosity. In this study, hydroxyapatite (HA) synthetic bone scaffolds were fabricated through an extrusion-based 3D printing technique called robocasting to characterize three modes of porosity distinguished by a range of pore diameter size: (i) ceramic pores (100nm – 2µm), (ii) intermediate pores (2µm – 70 µm), and (iii) structural pores (>70µm). Highly porous scaffolds were designed with a CAD software and printed with an ‘ink’ composed of a stable suspension of colloidal HA and some contained a fugitive pore former of poly(methyl methacrylate) (PMMA) particles between 20 and 65 microns. Porosity was characterized in two ways: (i) pure HA scaffolds were printed and sintered at 1200°C (highest sintering temperature), 1175°C, and 1150°C and, (ii) composite scaffolds were printed in HA/PMMA volumetric ratios of 95/5, 85/15, 75/25, 60/40, and 50/50 and were each sintered at 1200°C. As intuition would assume, the HA scaffolds showed a decrease in porosity as sintering temperature was increased and the HA/PMMA scaffolds showed an increase in porosity as the fugitive pore former volume fraction was increased. From this work, a method is established for creating a range of ceramic porosities due to sintering temperature, a range of intermediate porosities due to the volume fraction of fugitive pore former, and the ability to control structural porosity through CAD (this was only shown through the two scaffold models used and was not the focus of this study).

In situ microcosms of a planktonic community were exposed to the triazine herbicide simazine. Randomly selected sets of microcosms were collected and sampled each week for three weeks (plus Week 0). Samples of ambient water were collected each week for evaluation of enclosure effects. Physical and chemical parameters were measured per microcosm. Simazine was measured at Weeks 0 and 3 only. The following organisms were preserved and quantified: phytoplankton, bacteria, and zooplankton, including ciliates, copepod nauplii, cladocerans and rotifers. Simazine decreased dissolved oxygen and pH, but increased nitrate and ammonia concentrations compared to control microcosms. A temporary decrease in temperature occurred at Week 1. Phytoplankton were differentially affected by simazine. Sensitive taxa included Trachelomonas, Glenodinium, diatoms and several species of relatively minor significance. Dinobryon and miscellaneous coccoids were not significantly affected. Phytoplankton ≥9 um were more affected by simazine than phytoplankton

The isospin dependence of the nuclear interaction was probed using energy differences between analogue excited states across the A=74 isobaric triplet. The first spectroscopy of transitions between states in the proton-dripline nuclide, 74Sr was performed using the highly-selective recoil-beta tagging technique with the JUROGAM II + RITU + GREAT setup at the University of Jyvaskyla. Considerable experimental development was required to acheive the requisite level of sensitivity. This included the development of a phosphor-sandwich detector, a finely segmented doublesided silicon-strip detector (DSSD) and a charged-particle veto array (UoYtube). The 2+ to 0+ and 4+ to 2+ transitions were identified through a combination of time and energy gates, and the implementation of a charged-particle veto. A beta-decay half-life was also extracted, in good agreement with a complementary measurement performed at RIKEN. Comparison with Skyrme Hartree-Fock calculations indicates that 74Sr is approximately 1-MeV less bound than previously supposed, implying that both observed excited states are two-proton unbound. Through comparison with published data from the A=74 isobar, triplet-energy differences (TEDs) were determined, indicating a continued need for an additional isotensor, J=0, 100-keV isospin-nonconserving (INC) interaction component, consistent with that found to be required at lower masses. The implication of this result is that such an INC component is mandated across the nuclear landscape, regardless of local nuclear structure effects. Additionally, candidates for the beta-delayed proton decay of 73Sr via 73Rb to 72Kr were observed using the same experimental setup. The lowest energy proton detected is consistent with that which might be expected for the decay of the ground state in 73Rb, allowing for the first measurement of the proton separation energy, Sp. This value is of considerable astrophysical interest since 73Rb is considered to be a waiting point in the rp process.