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This work fully characterizes fractal generation in the seeded Tile Automata model (seeded TA), a model similar to the abstract Tile Assembly model (aTAM) with the added ability for adjacent tiles to change states. Under these assumptions, we first show that all discrete self-similar fractals (DSSFs) with feasible generators are strictly buildable at scale 1 and temperature 1 in seeded TA. We then show that these results imply the existence of a single seeded TA system Γ that can strictly build any DSSF infinitely at scale 1 and temperature 1. 

Abstract Along the river–sea continuum, microorganisms are directionally dispersed by water flow while being exposed to strong environmental gradients. To compare the two assembly mechanisms that may strongly and differently influence metacommunity dynamics, namely homogenizing dispersal and heterogeneous selection, we characterized the total (16S rRNA gene) and putatively active (16S rRNA transcript) bacterial communities in the Pearl River–South China Sea Continuum, during the wet (summer) and dry (winter) seasons using high-throughput sequencing. Moreover, well-defined sampling was conducted by including freshwater, oligohaline, mesohaline, polyhaline, and marine habitats. We found that heterogeneous selection exceeded homogenizing dispersal in both the total and active fractions of bacterial communities in two seasons. However, homogeneous selection was prevalent (the dominant except in active bacterial communities during summer), which was primarily due to the bacterial communities’ tremendous diversity (associated with high rarity) and our specific sampling design. In either summer or winter seasons, homogeneous and heterogeneous selection showed higher relative importance in total and active communities, respectively, implying that the active bacteria were more responsive to environmental gradients than were the total bacteria. In summary, our findings provide insight into the assembly of bacterial communities in natural ecosystems with high spatial connectivity and environmental heterogeneity. 

The ability to detect whether a species (or dimension) is zero in Chemical Reaction Networks (CRN), Vector Addition Systems, or Petri Nets is known to increase the power of these models - making them capable of universal computation. While this ability may appear in many forms, such as extending the models to allow transitions to be inhibited, prioritized, or synchronized, we present an extension that directly performs this zero checking. We introduce a new void genesis CRN variant with a simple design that merely increments the count of a specific species when any other species' count goes to zero. As with previous extensions, we show that the model is Turing Universal. We then analyze several other studied CRN variants and show that they are all equivalent through a polynomial simulation with the void genesis model, which does not merely follow from Turing-universality. Thus, inhibitor species, reactions that occur at different rates, being allowed to run reactions in parallel, or even being allowed to continually add more volume to the CRN, does not add additional simulation power beyond simply detecting if a species count becomes zero. 

Four new blue light-emitting materials based on benzo[1,2-d:4,5-d′]bisoxazole (BBO) have been synthesized, characterized, and fabricated into organic light-emitting diode (OLED) devices. Using a combination of theoretical and experimental methods, we investigated the effect of conjugation by comparing bulky alkyl groups and planar aromatic groups along the 2,6-axis. Two of these molecules, PB2Cz and PB3Cz, are cross-conjugated cruciform-type BBOs with phenyl and carbazole groups along the 2,6 and 4,8 axes, respectively. The other two molecules, AB2Cz and AB3Cz, have extended conjugation via the carbazole groups along the 4,8-axis and bulky adamantyl groups along the 2,6-axis. Concurrently, we explored the effect of regioisomerism on optoelectronic and device properties arising from attaching carbazole at the 2- (2Cz) or 3- (3Cz) position along the 4,8-axis. The materials’ geometric and electronic properties were predicted using time-dependent density functional theory (TD-DFT) calculations at the mPW3PBE/SV level. The molecules’ photoluminescent properties were measured in solution and film states. The BBO molecules were used as dopants in mixed host/guest OLED devices, producing teal to deep blue emission. Specifically, the AB2Cz and AB3Cz, with adamantyl on the 2,6-axis, exhibit blue to deep-blue emissions of 414–422 nm (CIEx < 0.20, CIEy < 0.10). In comparison, PB2Cz and PB3Cz have slightly longer emission wavelengths of 472–476 nm (CIEx < 0.16, CIEy < 0.28) and high brightness of 2700–3500 cdm–2. The BBOs with 2Cz resulted in more efficient devices with EQEs of ∼2.8–3.2%, while the 3Cz BBOs had EQEs of ∼1.1–1.5%. This work provides insight into designing efficient, purely organic blue-fluorescent OLED materials based on the BBO moiety. 

Head impacts are a major concern in contact sports and sports with high-speed mobility due to the prevalence of head trauma events and their dire consequences. Surrogates of human heads are required in laboratory testing to safely explore the efficacy of impact-mitigating mechanisms. This work proposes using polymer additive manufacturing technologies to obtain a substitute for the human skull to be filled with a silicone-based brain surrogate. This assembly was instrumentalized with an Inertial Measurement Unit. Its performance was compared to a standard Hybrid III head form in validation tests using commercial headgear. The tests involved impact velocities in a range centered around 5 m/s. The results show a reasonable homology between the head substitutes, with a disparity in the impact response within 20% between the proposed surrogate and the standard head form. The head surrogate herein developed can be easily adapted to other morphologies and will significantly decrease the cost of the laboratory testing of head protection equipment, all while ensuring the safety of the testing process.