The crystal structure of racemic afoxolaner has been solved and refined using synchrotron X-ray powder diffraction data and optimized using density functional theory techniques. Afoxolaner crystallizes in space group P21/a (#14) with a = 9.6014(6), b = 14.0100(11), c = 39.477(10) Å, β = 94.389(7)°, V = 5,294.7(17) Å3, and Z = 8 at 298 K. The crystal structure consists of layers of molecules parallel to the ab-plane. The boundaries of the layers are rich in halogens. Within the layers, there is parallel stacking of rings along both the a- and b-axes. Two classical N–H···O hydrogen bonds link the two independent molecules into dimers. The powder pattern has been submitted to the International Centre for Diffraction Data (ICDD®) for inclusion in the Powder Diffraction File™ (PDF®).

Isaac Newton spent some four decades researching “chymistry,” the early modern equivalent of our chemistry. Although his laboratory notebooks survive, his experimental goals remain obscure to the present day. Our work reveals that Newton was engaged in fruitful chemical research even by modern standards. Replication of his experiments, involving Newton’s “vitriol” (from his “liquor of antimony,” NH4Cl, HNO3, and Sb2S3) and verdigris (Cu(CH3COO)2), produced a variety of NH4+-, Cl−-, SO4−2-, NO3−-, and Cu-containing crystallization products. We analyzed these products using powder X-ray diffraction (XRD) (Cu Kα radiation) and Rietveld refinement, which revealed a complex mixture of (NH4)2Cu(SO4)2(H2O)6, NH4NO3, NH4Cl, (NH4)2CuCl4(H2O)2, and (NH4)[Cu(NH3)2Cl3]⋅2H2O. The XRD data also consistently showed a suite of peaks unmatched by any phase in the PDF-5 database. A crystal of the unknown product was analyzed using single-crystal X-ray methods (Mo Kα radiation), revealing a previously unknown compound, (NH4)2[Cu2Cl2(C2H3O2)4]·2NH4Cl, with space group Pmna and room-temperature unit-cell parameters of a = 14.550(3) Å, b = 8.850(1) Å, and c = 9.116(2) Å. The inclusion of this phase in the Rietveld refinements yielded a satisfactory fit. Our ongoing replications of Newton’s crystallization experiments reveal that his research produced a complex, unusual suite of phases, including the aforementioned previously unknown compound.

BaLa2Cu1−xBaxTi2O9 (x = 0.00, 0.15, and 0.30) ceramics were synthesized in polycrystalline form via the conventional solid-state reaction techniques in air. The crystal structure of the title compositions was characterized by room-temperature X-ray powder diffraction and analyzed using the Rietveld refinement method. All the compositions crystallize in the tetragonal symmetry of space group I4/mcm (No. 140) with cell volumes: 249.43(1) Å3 for x = 0.00, 249.42(1) Å3 for x = 0.15, and 250.05(1) Å3 for x = 0.30. The tilt system of the MO6 octahedra (M = Cu(Ba2)/Ti) corresponds to the notation a0a0c−. The MO6 octahedra share the corners via oxygen atoms in 3D. Along the c-axis, the octahedra are connected by O(1) atoms of (0, 0, 1/4) positions; while in the ab-plane, they are linked by O(2) atoms of (x, x + 1/2, 0) positions. The bond angle of M–O2–M is 168.6(7)° for x = 0.00, 168.6(6)° for x = 0.15, and 166.8(6)° for x = 0.30, whereas the bond angle of M–O1–M is constrained to be 180° by space group I4/mcm.

Linear Temporal Logic (LTL) offers a formal way of specifying complex objectives for Cyber-Physical Systems (CPS). In the presence of uncertain dynamics, the planning for an LTL objective can be solved by model-free reinforcement learning (RL). Surrogate rewards for LTL objectives are commonly utilized in model-free RL for LTL objectives. In a widely adopted surrogate reward approach, two discount factors are used to ensure that the expected return (i.e., the cumulative reward) approximates the satisfaction probability of the LTL objective. The expected return then can be estimated by methods using the Bellman updates such as RL. However, the uniqueness of the solution to the Bellman equation with two discount factors has not been explicitly discussed. We demonstrate, through an example, that when one of the discount factors is set to one, as allowed in many previous works, the Bellman equation may have multiple solutions, leading to an inaccurate evaluation of the expected return. To address this issue, we propose a condition that ensures the Bellman equation has the expected return as its unique solution. Specifically, we require that the solutions for states within rejecting bottom strongly connected components (BSCCs) be zero. We prove that this condition guarantees the uniqueness of the solution, first for recurrent states (i.e., states within a BSCC) and then for transient states. Finally, we numerically validate our results through case studies.

Neural network (NN)-based control policies have proven their advantages in cyber-physical systems (CPS). When an NN-based policy fails to fulfill a formal specification, engineers leverage NN repair algorithms to fix its behaviors. However, such repair techniques risk breaking the existing correct behaviors, losing not only correctness but also verifiability of initial state subsets. That is, the repair may introduce new risks, previously unaccounted for. In response, we formalize the problem of Repair with Preservation (RwP) and develop Incremental Simulated Annealing Repair (ISAR). ISAR is an NN repair algorithm that aims to preserve correctness and verifiability — while repairing as many failures as possible. Our algorithm leverages simulated annealing on a barriered energy function to safeguard the already-correct initial states while repairing as many additional ones as possible. Moreover, formal verification is utilized to guarantee the repair results. ISAR is compared to a reviewed set of state-of-the-art algorithms, including (1) reinforcement learning based techniques (STLGym and F-MDP), (2) supervised learning-based techniques (MIQP and minimally deviating repair), and (3) online shielding techniques (tube MPC shielding). Upon evaluation on two standard benchmarks, OpenAI Gym mountain car and an unmanned underwater vehicle, ISAR not only preserves correct behaviors from previously verified initial state regions, but also repairs 81.4% and 23.5% of broken state spaces in the two benchmarks. Moreover, the signal temporal logic (STL) robustness of the ISAR-repaired policies is higher than the baselines.

The crystal structure of a new form of racemic reboxetine mesylate has been solved and refined using synchrotron X-ray powder diffraction data and optimized using density functional theory techniques. Reboxetine mesylate crystallizes in space group P21/c (#14) with a = 14.3054(8), b = 18.0341(4), c = 16.7924(11) Å, β = 113.4470(17)°, V = 3,974.47(19) Å3, and Z = 8 at 298 K. The crystal structure consists of double columns of anions and cations along the a-axis. Strong N–H···O hydrogen bonds link the cations and anions into zig-zag chains along the a-axis. The powder pattern has been submitted to the International Centre for Diffraction Data (ICDD®) for inclusion in the Powder Diffraction File™ (PDF®).

The crystal structure of tafamidis has been independently resolved and refined using synchrotron X-ray powder diffraction data and optimized using density functional techniques. Tafamidis crystallizes in space group P21/c (#14) with a = 3.787093(6), b = 14.97910(4), c = 22.93751(7) Å, β = 90.92672(19)°, V = 1,301.012(4) Å3, and Z = 4 at 295 K. The crystal structure consists of stacks of molecules along the a-axis. The molecules are inclined to this axis; the mean plane is (−4, 2, 11). Strong centrosymmetric O–H⋅⋅⋅O hydrogen bonds exist between carboxylic acid groups. The molecules are linked along the b-axis by C–H⋅⋅⋅N hydrogen bonds. Two C–H⋅⋅⋅Cl hydrogen bonds also contribute to the lattice energy. The powder pattern has been submitted to the International Centre for Diffraction Data for inclusion in the Powder Diffraction File™ (PDF®).

The crystal structure of quizartinib hydrate has been solved and refined using synchrotron X-ray powder diffraction data and optimized using density functional theory techniques. Quizartinib hydrate crystallizes in space group P-1 (#2) with a = 13.9133(9), b = 17.877(3), c = 19.8459(30) Å, α = 115.080(5), β = 93.768(5), γ = 100.831(5)°, V = 4,332.1(6) Å3, and Z = 6 at 298 K. In the complex crystal structure, the molecules are generally oriented parallel to the (110) plane. Two of the independent molecules are linked into dimers by N–H···O or N–H···N hydrogen bonds. Each molecule exhibits a unique pattern of C–H···O, C–H···N, or C–H···S hydrogen bonds. The powder pattern has been submitted to ICDD for inclusion in the Powder Diffraction File™ (PDF®).

The crystal structure of cabotegravir has been solved and refined using synchrotron X-ray powder diffraction data and optimized using density functional theory techniques. Cabotegravir crystallizes in space group P21212 (#18) with a = 31.4706(11), b = 13.4934(3), c = 8.43811(12) Å, V = 3,583.201(18) Å3, and Z = 8 at 298 K. The crystal structure consists of stacks of roughly parallel molecules along the c-axis. The molecules form layers parallel to the bc-plane. O–H···O hydrogen bonds link one of the two independent molecules into chains along the b-axis. The powder pattern has been submitted to the International Centre for Diffraction Data (ICDD®) for inclusion in the Powder Diffraction File™ (PDF®).

Data mining for materials science and structure prediction is growing rapidly. Such an approach relies a lot on the available published and unpublished crystal structure. In this contribution, we are using the experimental pattern reported in the PDF entry 00-058-0728 for the experimental data used to solve the previously unreported crystal structure of RbCdVO4. Contrary to the reported literature, the title compound crystallizes in the monoclinic system P21 with Z = 4. The lattice parameters are a = 12.53678(16) Å, b = 5.82451(7) Å, c = 12.47733(17) Å, β = 105.6169(10)°, and V = 877.47(2) Å3. Its crystal structure type is new and quite complex as it exhibits 28 atoms in the asymmetric unit.

Many mission-critical systems today have stringent timing requirements. Especially for cyber-physical systems (CPS) that directly interact with real-world entities, violating correct timing may cause accidents, damage or endanger life, property or the environment. To ensure the timely execution of time-sensitive software, a suitable system architecture is essential. This paper proposes a novel conceptual system architecture based on well-established technologies, including transition systems, process algebras, Petri Nets and time-triggered communications (TTC). This architecture for time-sensitive software execution is described as a conceptual model backed by an extensive list of references and opens up several additional research topics. This paper focuses on the conceptual level and defers implementation issues to further research and subsequent publications.