Machines incorporating techniques from artificial intelligence and machine learning can work with human users on a moment-to-moment, real-time basis to generate creative outcomes, performances and artefacts. We define such systems collaborative, creative AI systems, and in this article, consider the theoretical and practical considerations needed for their design so as to support improvisation, performance and co-creation through real-time, sustained, moment-to-moment interaction. We begin by providing an overview of creative AI systems, examining strengths, opportunities and criticisms in order to draw out the key considerations when designing AI for human creative collaboration. We argue that the artistic goals and creative process should be first and foremost in any design. We then draw from a range of research that looks at human collaboration and teamwork, to examine features that support trust, cooperation, shared awareness and a shared information space. We highlight the importance of understanding the scope and perception of two-way communication between human and machine agents in order to support reflection on conflict, error, evaluation and flow. We conclude with a summary of the range of design challenges for building such systems in provoking, challenging and enhancing human creative activity through their creative agency.

The competitive adsorption of lung surfactant (LS) and albumin at the air-liquid interface and the ability of polyethylene glycol (PEG) to mediate LS adsorption are analyzed using pressure area isotherms and grazing incidence x-ray diffraction (GIXD). The addition of albumin drastically reduces the amount of LS on the interface and slightly increases the LS lattice spacing. The addition of PEG restores the characteristic LS peaks, yielding a slightly more compact lattice. The scattering results are consistent with recent work which proposed that albumin creates a physical barrier which eliminates LS adsorption and that PEG enhances LS adsorption but does not significantly change LS surface ordering.

Immobilization of adsorbed Cs+ and Sr2+ on a molybdenum-doped, hexagonal tungsten bronze (HTB)-polyacrylonitrile (PAN) composite adsorbent can be achieved by heating in air at temperatures in the range 600 – 1200 °C. Thermal treatment of the parent composite material at 800 – 1000 °C undergoes a ca. 60% reduction in volume and retains its spherical morphology. For materials prepared at 800 – 1200 °C the full complement of Cs+ and the majority of Sr2+ partition into HTB phases (A∼0.16-0.3MO3; A = Cs, Sr, Na; M = Mo,W), along with sodium cations. The presence of high concentrations of Na+ relative to either Cs+ or Sr2+ does not appear to interfere with the formation of the HTB phase. The fraction (f) of Cs+ and Sr2+ leached from the tungstate phase assemblages is better or comparable with cesium hollandite (Cs0.8Ba0.4Ti8O18; f = ca. 8 × 10−5; rate = <1.2 × 10−4 g m−2d−1) and strontium titanate (SrTiO3; f = 3.1 × 10−3; rate = 2.63 × 10−4 g m−2 day×1), respectively, using a modified PCT test. Furthermore, where aggressive leaching conditions are employed (0.1M HNO3; 150 oC; 4 days), the tungstate phase assemblages display leach resistance orders of magnitude better than the reference phases (Cs+ - f = ca. 5 × 10−3; rate = ca. 1.4 × 10−3 g m−2 day−1; Sr2+ - f = ca. 8 × 10−2; rate = ca. 2.5 × 10−2 g m−2 day−1).

Nd-bearing zirconolite was leached at 90°C for 157 days in 0.001M citric acid under single-pass-flow-through conditions (modified MCC-4 protocol). Three different flow rates were used, ranging in an order of magnitude from 10 mL per day to 100 mL per day, to determine the effect of the rate of leachant replenishment on the durability of the zirconolite. Results of previous studies on the role of complexing agents on the leaching behaviour of single-phase zirconolite have been included in the discussion.

The pH of the citric acid solution was adjusted to 5 using KOH, mimicking that of the water in the parallel tests, to avoid the influence of pH on chemical durability of the zirconolite.

Simulated groundwater containing 0.001M citric acid at 90°C led to congruency in elemental releases and a diminution of release rate with time of about an order of magnitude, reaching virtual constancy after about 50 to 60 days to a level of about 10−5 g m−2 day−1. The most significant finding was that the elemental release rates of Nd, Ti and Zr (and Ca and Al where detected) were similar for all flow rates. Clearly, varying flow rate by up to an order of magnitude had no effect on elemental releases i.e. there is no solubility limit control on releases at 0.001M citric acid concentration.

An important finding of previous studies using identical leaching protocols with 0.001M citric acid, and inferred in our latest investigations reported here, was that there is no secondary layer development at the surface of the zirconolite to affect leach rates. In contrast, parallel tests carried out in deionised water instead of citric acid showed that hydroxides form in situ on the zirconolite surface, effectively forming hydrolysed zirconolite. This controls further dissolution of the zirconolite matrix due to the solubility limit being reached with respect to the hydrolysed phases rather than with zirconolite. Complexation by citrate ions prevents such control by hydrolysed species on zirconolite solubility.

Even under the more aggressive conditions imposed in these studies (0.001M citric acid), and regardless of flow rate of the leachant, elemental releases from zirconolite are very low for a candidate wasteform and demonstrate its attributes as a ceramic-based wasteform for the containment of actinides.

Immobilization of adsorbed Cs+ and Sr2+ on a molybdenum-doped, hexagonal tungsten bronze (HTB)-polyacrylonitrile (PAN) composite adsorbent can be achieved by heating in air at temperatures in the range 600 - 1200 °C. Thermal treatment of the parent composite material at 800 – 1000 °C undergoes a ca. 60% reduction in volume and retains its spherical morphology. For materials prepared at 800 – 1200 °C the full complement of Cs+ and the majority of Sr2+ partition into HTB phases (A∼0.16-0.3MO3; A = Cs, Sr, Na; M = Mo,W), along with sodium cations. The presence of high concentrations of Na+ relative to either Cs+ or Sr2+ does not appear to interfere with the formation of the HTB phase. The fraction (f) of Cs+ and Sr2+ leached from the tungstate phase assemblages is better or comparable with cesium hollandite (Cs0.8Ba0.4Ti8O18; f = ca. 8 × 10−5; rate = <1.2 × 10−4 g m−2d−1) and strontium titanate (SrTiO3; f = 3.1 × 10−3; rate = 2.63 × 10−4 g m−2day−1), respectively, using a modified PCT test. Furthermore, where aggressive leaching conditions are employed (0.1M HNO3; 150 °C; 4 days), the tungstate phase assemblages display leach resistance orders of magnitude better than the reference phases (Cs+ - f = ca. 5 × 10−3; rate = ca. 1.4 × 10−3 g m−2day−1; Sr2+ - f = ca. 8 × 10−2; rate = ca. 2.5 × 10−2 g m−2day−1).

Geopolymers should be serious waste form candidates for intermediate level waste (ILW), insofar as they are more durable than Portland cement and can pass the PCT-B test for high-level waste. Thus an alkaline ILW could be considered to be satisfactorily immobilised in a geopolymer formulation. However a simulated Hanford tank waste was found to fail the PCT-B criterion even for a waste loading as low as 5 wt%, very probably due to the formation of a soluble sodium phosphate compound(s). This suggests that it could be worth developing a “mixed” GP waste form in which the amorphous material can immobilise cations and a zeolitic component to immobilise anions. The PCT -B test is demonstrably subject to significant saturation effects, especially for relatively soluble waste forms.