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Hydrocarbon pyrolysis is a complex chemical reaction system at extreme temperature and pressure conditions involving large numbers of chemical reactions and chemical species. Only two kinds of atoms are involved: carbons and hydrogens. Its effective description and predictions for new settings are challenging due to the complexity of the system and the high computational cost of generating data by molecular dynamics simulations. On the other hand, the ensemble of molecules present at any moment and the carbon skeletons of these molecules can be viewed as random graphs. Therefore, an adequate random graph model can predict molecular composition at a low computational cost. We propose a random graph model featuring disjoint loops and assortativity correction and a method for learning input distributions from molecular dynamics data. The model uses works of Karrer and Newman (2010) and Newman (2002) as building blocks. We demonstrate that the proposed model accurately predicts the size distribution for small molecules as well as the size distribution of the largest molecule in reaction systems at the pressure of 40.5 GPa, temperature range of 3200K-5000K, and H/C ratio range from 2.25 as in octane through 4 as in methane., Comment: 58 pages, 23 figures, 3 tables

We introduce the notion of Levenshtein graphs, an analog to Hamming graphs but using the edit distance instead of the Hamming distance; in particular, Levenshtein graphs allow for underlying strings (nodes) of different lengths. We characterize various properties of these graphs, including a necessary and sufficient condition for their geodesic distance to be identical to the edit distance, their automorphism group and determining number, and an upper bound on their metric dimension. Regarding the latter, we construct a resolving set composed of two-run strings and an algorithm that computes the edit distance between a string of length $k$ and any single-run or two-run string in $O(k)$ operations., Comment: 22 pages, 3 figures

The analysis of games and sports as complex systems can give insights into the dynamics of human competition, and has been proven useful in soccer, basketball, and other professional sports. In this paper we present a model for dodgeball, a popular sport in US schools, and analyze it using an ordinary differential equation (ODE) compartmental model and stochastic agent-based game simulations. The ODE model reveals a rich landscape with different game dynamics occurring depending on the strategies used by the teams, which can in some cases be mapped to scenarios in competitive species models. Stochastic agent-based game simulations confirm and complement the predictions of the deterministic ODE models. In some scenarios, game victory can be interpreted as a noise-driven escape from the basin of attraction of a stable fixed point, resulting in extremely long games when the number of players is large. Using the ODE and agent-based models, we construct a strategy to increase the probability of winning., Comment: Added Acknowledgments

Self-propelling organisms locomote via generation of patterns of self-deformation. Despite the diversity of body plans, internal actuation schemes and environments in limbless vertebrates and invertebrates, such organisms often use similar travelling waves of axial body bending for movement. Delineating how parameters (wave amplitudes, frequencies) lead to locomotor performance (e.g. speed, energy, turning capabilities) remains challenging. Here we show that a geometric framework that replaces laborious calculation with a diagrammatic scheme is well suited to discovery and comparison of optimal patterns of wave dynamics in diverse living systems. We focus on a regime of undulatory locomotion, that of highly damped environments, which is applicable not only to small organism movement in viscous fluids, but also larger animals moving in frictional fluids (sand) and on frictional ground. We find that the travelling wave dynamics used by mm-scale nematode worms and cm-scale desert dwelling snakes and lizards can be described by time series of the weights associated with two principal modes. The approximately circular closed path trajectories of mode weights in a self-deformation space enclose near-maximal surface integral (geometric phase) for organisms spanning two decades in body length. We hypothesize that such trajectories are targets of control (which we refer to as ``serpenoid templates"). Further, the geometric approach reveals how seemingly complex behaviors such as turning in worms and sidewinding snakes can be described as modulations of templates. Thus, the use of differential geometry in living systems can assist in the growth of comparative neuromechanics, allowing a common description of locomotion across taxa and providing hypotheses for function at lower levels of organization.

Natural and artificial self-propelled systems must manage environmental interactions during movement. Such interactions, which we refer to as active collisions, are fundamentally different from momentum-conserving interactions studied in classical physics, largely because the internal driving of the locomotor can lead to persistent contact with heterogeneities. Here, we experimentally and numerically study the effects of active collisions on a laterally-undulating sensory-deprived robophysical model, whose dynamics are applicable to self-propelled systems across length scales and environments. The robot moves via spatial undulation of body segments, with a nearly-linear center-of-geometry trajectory. Interactions with a single rigid post scatter the robot, and these deflections are proportional to the head-post contact duration. The distribution of scattering angles is smooth and strongly-peaked directly behind the post. Interactions with a single row of evenly-spaced posts (with inter-post spacing $d$) produce distributions reminiscent of far-field diffraction patterns: as $d$ decreases, distinct secondary peaks emerge as large deflections become more likely. Surprisingly, we find that the presence of multiple posts does not change the nature of individual collisions; instead, multi-modal scattering patterns arise from multiple posts altering the likelihood of individual collisions to occur. As $d$ decreases, collisions near the leading edges of the posts become more probable, and we find that these interactions are associated with larger deflections. Our results, which highlight the surprising dynamics that can occur during active collisions of self-propelled systems, can inform control principles for locomotors in complex terrain and facilitate design of task-capable active matter., Comment: 32 pages, 20 main figures, 8 supplemental figures

Based on a low temperature scanning tunneling microscopy study, we present a direct visualization of a cycloaddition reaction performed for some specific fluorinated maleimide molecules deposited on graphene. These studies showed that the cycloaddition reactions can be carried out on the basal plane of graphene, even when there are no pre-existing defects. In the course of covalently grafting the molecules to graphene, the sp2 conjugation of carbon atoms was broken and local sp3 bonds were created. The grafted molecules perturbed the graphene lattice, generating a standing-wave pattern with an anisotropy which was attributed to a (1,2) cycloaddition, as revealed by T-matrix approximation calculations. DFT calculations showed that while both (1,4) and (1,2) cycloaddition were possible on free standing graphene, only the (1,2) cycloaddition could be obtained for graphene on SiC(0001). Globally averaging spectroscopic techniques, XPS and ARPES, were used to determine the modification in the elemental composition of the samples induced by the reaction, indicating an opening of an electronic gap in graphene., Comment: 20 pages, 6 figures

Clinically significant attention problems among children present a significant obstacle to increasing student achievement. Computer-based attention training holds great promise as a way for schools to address this problem. The aim of this project is to evaluate the efficacy of two computer-based attention training systems in schools. One program uses neurofeedback (NFB) to train children with Attention-Deficit/Hyperactivity Disorder (ADHD) to focus on a task, and the other uses a Standard Computer Format (SCF) for cognitive retraining. The authors hypothesize that 1) both treatments will result in improvement in ADHD symptoms compared to a control condition; and 2) both treatments will result in improvement in academic outcomes compared to a control condition. This research is on-going and takes place in 19 elementary schools that accepted to participate in the project. The schools are part of two school systems in the greater Boston area. The authors' preliminary data from this four-year study evaluating the efficacy of two computer-based attention training systems in schools shows significant results as well as promising trends. As this is a preliminary analysis of preliminary data they have not addressed all of the study's aims and have not yet compared data between the three intervention groups. Teacher report of ADHD symptoms, math achievement by students, and objective classroom observations for their first wave were analyzed. The authors' preliminary data on these outcome measures suggest that computer-based attention training programs offered in an elementary school setting may be effective in reducing symptoms of ADHD and improved math achievement. (Contains 1 figure and 4 tables.)

The influence on learning of visuals accompanying self-paced text materials was investigated for students of varied reading comprehension ability levels. The use of varied degrees of realism and media presentation formats in facilitating learning on specific tasks was examined in order to clarify previous research, and to provide specific presentational guidelines for instructional designers considering a self-paced format. Programmed booklets with varied numbers of periodic review questions and answers and an additional audiotape were used to represent three levels of media presentation. Four levels of visual realism were studied: (1) no visuals; (2) line drawings; (3) shaded, detailed drawings; and (4) realistic pictures. Three levels of reading comprehension were identified for the 332 subjects. Visualization did not automatically result in improved achievement on different educational tasks for students of different reading comprehension abilities. The study demonstrated that individuals achieve at a different level of performance depending on the method of instructional presentation, the type of visuals accompanying printed instruction, and the level of reading comprehension. Further studies are necessary to provide the basis for detailed guidelines for developing self-paced visualized instruction. (LMM)

The purpose of this study was to evaluate the design and implementation of 10 neuropathology interactive videodisc instructional (IVI) modules used by Michigan State University undergraduate medical students in the College of Osteopathic Medicine and the College of Human Medicine. The modules were developed by Michigan State University personnel in HyperCard for Macintosh computers. The evaluation strategy incorporated a mixed method approach using qualitative and quantitative data to examine levels of student acceptance for the modules; ways in which IVI modules accommodate different learner styles; and to what extent the modules facilitate the attainment of higher level learning objectives. Students rated the units highly for learning effectiveness; many students reported group interaction as beneficial; and students expressed a desire for more IVI in the curriculum. The paper concludes with recommendations for future use of interactive videodisc technology in the teaching/learning process. (13 references) (Author)