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Limbless locomotors, from microscopic worms to macroscopic snakes, traverse complex, heterogeneous natural environments typically using undulatory body wave propagation. Theoretical and robophysical models typically emphasize body kinematics and active neural/electronic control. However, we contend that because such approaches often neglect the role of passive, mechanically controlled processes (i.e., those involving mechanical intelligence), they fail to reproduce the performance of even the simplest organisms. To discover principles of how mechanical intelligence aids limbless locomotion in heterogeneous terradynamic regimes, here we conduct a comparative study of locomotion in a model of heterogeneous terrain (lattices of rigid posts). We use a model biological system, the highly studied nematode worm C. elegans, and a novel robophysical device whose bilateral actuator morphology models that of limbless organisms across scales. The robot's kinematics quantitatively reproduce the performance of the nematodes with purely open-loop control; mechanical intelligence simplifies control of obstacle navigation and exploitation by reducing the need for active sensing and feedback. An active behavior observed in C. elegans, undulatory wave reversal upon head collisions, robustifies locomotion via exploitation of the systems' mechanical intelligence. Our study provides insights into how neurally simple limbless organisms like nematodes can leverage mechanical intelligence via appropriately tuned bilateral actuation to locomote in complex environments. These principles likely apply to neurally more sophisticated organisms and also provide a new design and control paradigm for limbless robots for applications like search and rescue and planetary exploration.

Contact planning is crucial in locomoting systems.Specifically, appropriate contact planning can enable versatile behaviors (e.g., sidewinding in limbless locomotors) and facilitate speed-dependent gait transitions (e.g., walk-trot-gallop in quadrupedal locomotors). The challenges of contact planning include determining not only the sequence by which contact is made and broken between the locomotor and the environments, but also the sequence of internal shape changes (e.g., body bending and limb shoulder joint oscillation). Most state-of-art contact planning algorithms focused on conventional robots (e.g.biped and quadruped) and conventional tasks (e.g. forward locomotion), and there is a lack of study on general contact planning in multi-legged robots. In this paper, we show that using geometric mechanics framework, we can obtain the global optimal contact sequence given the internal shape changes sequence. Therefore, we simplify the contact planning problem to a graph optimization problem to identify the internal shape changes. Taking advantages of the spatio-temporal symmetry in locomotion, we map the graph optimization problem to special cases of spin models, which allows us to obtain the global optima in polynomial time. We apply our approach to develop new forward and sidewinding behaviors in a hexapod and a 12-legged centipede. We verify our predictions using numerical and robophysical models, and obtain novel and effective locomotion behaviors., Comment: SI video: https://doi.org/10.5281/zenodo.7608693

The files contained here are samples of Matlab scripts used for video labelling and analysis, as well as videos generated by automated labelling of tunnels based on ant motion detection. These were used for the work detailed in the manuscript "Agitated ants: regulation and self-organization of incipient nest excavation via collisional cues" (doi 10.1098/rsif.2022.0597).

Diverse physical systems, from maritime to quantum mechanical, experience forces mediated by asymmetries in surrounding fields. Here we discover a new phenomenon in which a vertically oscillating, floating robot can be attracted to or repelled from a boundary via a complex interference of generated and reflected gravity-capillary (GC) waves, whose dynamics were studied by Hocking in the 1980s. Force measurements on the robot reveal that attraction increases as oscillation frequency increases or particle-boundary separation decreases. Reconstruction of Hocking wave dynamics rationalizes a field-based asymmetry in wave amplitudes near boundaries that drives robot motion.

We offer our opinion on the benefits of integration of insights from active matter physics with principles of regulatory interactions and control to develop a field we term ``smart matter". This field can provide insight into important principles in living systems as well as aid engineering of responsive, robust and functional collectives., Comment: opinion piece

Reorientation (turning in plane) plays a critical role for all robots in any field application, especially those that in confined spaces. While important, reorientation remains a relatively unstudied problem for robots, including limbless mechanisms, often called snake robots. Instead of looking at snakes, we take inspiration from observations of the turning behavior of tiny nematode worms C. elegans. Our previous work presented an in-place and in-plane turning gait for limbless robots, called an omega turn, and prescribed it using a novel two-wave template. In this work, we advance omega turn-inspired controllers in three aspects: 1) we use geometric methods to vary joint angle amplitudes and forward wave spatial frequency in our turning equation to establish a wide and precise amplitude modulation and frequency modulation on omega turn; 2) we use this new relationship to enable robots with fewer internal degrees of freedom (i.e., fewer joints in the body) to achieve desirable performance, and 3) we apply compliant control methods to this relationship to handle unmodelled effects in the environment. We experimentally validate our approach on a limbless robot that the omega turn can produce effective and robust turning motion in various types of environments, such as granular media and rock pile., Comment: Accepted to ICRA 2022

Poster created by students of The Island School semester research class of Spring 2013

Supplemental Material for Lipoprotein(a) in systemic lupus erythematosus is associated with history of proteinuria and reduced renal function by Caoilfhionn M Connolly, Jessica Li, Daniel Goldman, Andrea Fava, Laurence Magder, and Michelle Petri in Lupus

The design of amorphous entangled systems, specifically from soft and active materials, has the potential to open exciting new classes of active, shape-shifting, and task-capable 'smart' materials. However, the global emergent mechanics that arises from the local interactions of individual particles are not well understood. In this study, we examine the emergent properties of amorphous entangled systems in three different examples: an in-silico "smarticle" collection, its robophysical chain, and living entangled aggregate of worm blobs (L. variegatus). In simulations, we examine how material properties change for a collective composed of dynamic three-link robots. We compare three methods of controlling entanglement in a collective: externally oscillations, shape-changes, and internal oscillations. We find that large-amplitude changes of the particle's shape using the shape-change procedure produced the highest average number of entanglements, with respect to the aspect ratio (l/w), improving the tensile strength of the collective. We demonstrate application of these simulations in two experimental systems: robotic chains and entangled worm blobs. In the robophysical models, we find emergent auxeticity behavior upon straining the confined collective. And finally, we show how the individual worm activity in a blob can be controlled through the ambient dissolved oxygen in water, leading to complex emergent properties of the living entangled collective, such as solid-like entanglement and tumbling. Taken together, our work reveals principles by which future shape-modulating, potentially soft robotic systems may dynamically alter their material properties, advancing our understanding of living entangled materials, while inspiring new classes of synthetic emergent super-materials., Comment: 15 pages, 19 figures, W.S. and H.T. contributed equally to this work

Systems consisting of spheres rolling on elastic membranes have been used as educational tools to introduce a core conceptual idea of General Relativity (GR): how curvature guides the movement of matter. However, previous studies have revealed that such schemes cannot accurately represent relativistic dynamics in the laboratory. Dissipative forces cause the initially GR-like dynamics to be transient and consequently restrict experimental study to only the beginnings of trajectories; dominance of Earth's gravity forbids the difference between spatial and temporal spacetime curvatures. Here by developing a mapping between dynamics of a wheeled vehicle on a spandex membrane, we demonstrate that an active object that can prescribe its speed can not only obtain steady-state orbits, but also use the additional parameters such as speed to tune the orbits towards relativistic dynamics. Our mapping demonstrates how activity mixes space and time in a metric, shows how active particles do not necessarily follow geodesics in the real space but instead follow geodesics in a fiducial spacetime. The mapping further reveals how parameters such as the membrane elasticity and instantaneous speed allow programming a desired spacetime such as the Schwarzschild metric near a non-rotating black hole. Our mapping and framework point the way to the possibility to create a robophysical analog gravity system in the laboratory at low cost and provide insights into active matter in deformable environments and robot exploration in complex landscapes.

Although typically possessing four limbs and short bodies, lizards have evolved a diversity of body plans, from short-bodied and fully-limbed to elongate and nearly limbless. Such diversity in body morphology is hypothesized as adaptations to locomotion cluttered terrestrial environments, but the mode of propulsion -- e.g., the use of body and/or limbs to interact with the substrate -- and potential body/limb coordination remain unstudied. Here, we use biological experiments, a geometric theory of locomotion, and robophysical experiments to comparatively and systematically investigate such dynamics in a diverse sample of lizard morphologies. Locomotor field studies in short-limb, elongated lizards (Brachymeles) and laboratory studies of full-limbed lizards (Uma scoparia and Sceloporus olivaceus) and a limbless laterally undulating organism (Chionactis occipitalis) reveal that the body wave dynamics can be described by a combination of traveling and standing waves; the ratio of the amplitudes of these components is inversely related to limb length. We use geometric theory to analyze and explain the wave dynamics and body-leg coordination observations; the theory predicts that leg thrust modulates the body weight distribution and self-propulsion generation mechanism, which in turn facilitates the choice of body waves. We test our hypothesis in biological experiments by inducing the use of traveling wave in stereotyped lizards by modulating the ground penetration resistance, as well as in controlled non-biological experiments involving an undulating limbed robophysical model. Our models could be valuable in understanding functional constraints on the evolutionary process of elongation and limb reduction in lizards, as well as advancing robot designs.

Figure 1. Lower Ordovician time scale, stages and graptolite, conodont and chitinozoan zonal schemes. The leftmost column is the chronometric time scale from Goldman et al. (2020, in Gradstein et al. 2020). Zonations and correlations for graptolites are modified from the following (and references therein) — Goldman et al. (2020), Hererra Sánchez et al. (2019), Loydell (2012), Maletz (2021), Maletz and Ahlberg (2018), VandenBerg and Cooper (1992), Cooper and Sadler (2012), and Zalasiewicz et al. (2009); for conodonts modified from Goldman et al. (2020), Albanesi and Ortega (2016), Bergström and Wang (1995), Wang et al. (2018), Zhen et al. (2015, 2017, 2021); Zhen and Percival (2003) and Zhang et al. (2019); and for chitinozoans from Goldman et al. (2020), Nõlvak et al. (2006) and Paris et al. (2004). 1The South Gondwana graptolite zonation for the Lower Ordovician is adapted from Gutiérrez-Marco and Martin (2016).

Study of the locomotion of a centipede (L. forficatus) at the air-water interface reveals that it does not predominantly use its 14 leg pairs to locomote; unlike most swimmers which propagate head-to-tail body bending waves, this species propels via tail-to-head waves. Its low mass and body-fluid contact yield locomotion dynamics in which fluid wave drag forces dominate inertia. Microorganism-inspired wave drag resistive force theory captures swimming performance of the macroscale animal, motivating a control hypothesis for the animals self-propulsion body and limb kinematics.

Additional file 1: Supplementary Table S1. Characteristics of SLE patients and healthy controls. Supplementary Table S2. Correlation of salivary ANA and ANA isotypes with clinical parameters. Supplementary Figure S1. ROC analysis indicating the discriminatory potential of combined ANA isotypes in discriminating SLE (n=70) from HC (n=10). Sen., sensitivity; Spec., specificity; AUC = Area under (ROC) curve.

We report in experiment and simulation the spontaneous formation of dynamically bound pairs of shape changing smarticle robots undergoing locally repulsive collisions. Borrowing terminology from Conway's simulated Game of Life, these physical `gliders' robustly emerge from an ensemble of individually undulating three-link two-motor smarticles and can remain bound for hundreds of undulations and travel for multiple robot dimensions. Gliders occur in two distinct binding symmetries and form over a wide range of angular flapping extent. This parameter sets the maximal concavity which influences formation probability and translation characteristics. Analysis of dynamics in simulation reveals the mechanism of effective dynamical attraction -- a result of the emergent interplay of appropriately oriented and timed repulsive interactions.

Breznau, Rinke, and Wuttke, et al. attempted to test for uniformity in the way hypotheses were tested across multiple research groups. They appeared to find a great deal of discord between conclusions reached using the same hypothesis and data. Yet, what they really found is that scientists are not properly understanding what hypotheses are.

Additional file 1: Supplemental Table 1. SLE characteristics by cancer status. Supplemental Table 2. Laboratory parameters and serologies by cancer status. Supplemental Table 3. Drug exposure (ever use) by cancer status. Supplemental Table 4. Cancer sites observed in the Hopkins Lupus Cohort (N = 119 cancer cases).

1AbstractCOVID-19 has significantly changed our daily lives. Stay-at-home orders and forced closings of all non-essential businesses has had a significant impact on our economy. While it is important to ensure that the healthcare system is not overwhelmed, there are many questions that remain about the efficacy of extreme social distancing, and whether there are alternatives to mandatory lockdowns. This paper analyzes the utility of various levels of social distancing, and suggests an alternative approach using voluntary distancing informed by an infectious load index or ‘infection weather report.’

Google Trends offers researchers a glimpse inside the minds of a large group of people, all at once, and offers a very high resolution as well. As a result, trend data may be useful for identifying rapid changes in day to day psychological states and behaviors associated with the COVID-19 outbreak. This paper analyzes stress related search terms as well as food related search terms, and identifies changes in patterns for each that appear to be associated with the outbreak.

This call to research paper addresses some questions about intersex and differences in sexual development and issues with the binary sex modal, before constructing the idea of fluctuations in sexual modes and suggesting a few possible areas of research to better understand evolutionary dynamics of certain intersex states. While there are many conditions that fall under the category of intersex, this paper focuses on DSDs that have a significant genetic component rather than environmental component. The final part of the paper focuses on changes in selective pressures against intersex variations and high fertility rates, due to improved socioeconomic conditions and changes in infant and childhood mortality rates.

Measles cases are on the rise in the United States, and around the world. One of the major proposed contributing factors is changes in vaccination behavior. However, insufficient research on changes in measles vaccination in the United States exists. This paper seeks to improve our understanding on the topic.

(1) The measurements on H. violana sp. nov. are based on 331 specimens from two samples. (2) The vesicle size data are from 378 chitinozoan species, including type species of all 57 known genera and additional 321 species randomly selected from the literature. (3) A literature survey was conducted to obtain estimates of the CV of egg size of aquatic (mostly marine) invertebrates for comparison to our estimate of the CV in H. violana size. We attempted to obtain estimates from a broad range of species representing phylogenetic diversity at the Phylum, Class and Order levels. The criteria of CV data selecting are elucidated in detail.

OBJECTIVE: Retinoblastoma (Rb) protein is a nuclear protein with several important functions, including the ability to stabilize heterochromatin. Because antibodies against the nucleosome and chromatin are key in systemic lupus erythematosus (SLE), we sought to determine whether Rb was an autoantigen in SLE and to evaluate any associated clinical phenotypes. METHODS: Sera from 222 patients with SLE from the Hopkins longitudinal cohort were studied. Additional cohorts tested included sera from 100 patients with primary Sjögren syndrome (pSS) (disease controls) evaluated at the Johns Hopkins Jerome L. Greene Sjögren’s Center and sera from 36 healthy individuals. Anti-Rb antibodies were assayed by immunoprecipitation of (35)S-methionine-labeled Rb, which was generated by in vitro transcription/translation. Fisher’s exact test was used for the univariate analysis. Multivariable exact logistic regression was used to model for the presence of proteinuria in patients with SLE. RESULTS: Anti-Rb antibodies were present in 15 of 222 (6.8%) patients with SLE, in 3 of 100 patients with pSS (3%), and in 0 of 36 healthy individuals. Among patients with SLE, Rb antibodies were strongly negatively associated with proteinuria (P = 0.0031), renal involvement (odds ratio [OR] = 0.11; P = 0.01), and anemia (OR = 0.05; P < 0.0001) and were positively associated with stroke (OR = 7.65; P = 0.05). The negative association with lupus nephritis held true in multivariate models (adjusted OR = 0.11; P = 0.01). CONCLUSION: Anti-Rb antibodies are a novel specificity not previously described in SLE. These new data define a possible SLE subset that is protected against renal involvement, is positively associated with stroke, and is not associated with antiphospholipid antibodies.

The opposition to existing religions seems to have given rise to a new system of belief and culture. This system, referred to in this paper as Religious Rejectionism, has all the characteristics of a religion. The paper argues for the religious nature of Religious Rejectionism, and finishes by providing suggestions on future research of the topic.

There are many psychological and anthropological models of religion. However, in many cases, the models produced in psychological research are not compatible with those from anthropological research, and in some cases, these models contradict core anthropological concepts. This paper identifies apparent cognitive signatures of religious belief, and integrates them with Ninian Smart's seven dimensions of religion in order to construct a unified model of religion. This model defines religion as an integrated system of beliefs of a specific kind, and cultural elements considered to be common among the world's religions.

Various animals exhibit locomotive behaviors (like sprinting and hopping) involving transient bursts of actuation coupled to the ground through internal elastic elements. The performance of such maneuvers is subject to reaction forces on the feet from the environment. On substrates like dry granular media, the laws that govern these forces are not fully understood and can vary with foot size and shape, material compaction (measured by the volume fraction, f ) and kinematics of intrusion. To gain insight into how such interactions affect jumping on granular media, we study the performance of a self-actuated spring mass robot with a 7.62-cm flat circular foot. We compare performance between two jump strategies: a single-cycle sine-wave actuation (a “single jump”) and a counter-movement pull-up phase proceeded by a single jump (a “stutter jump”); both jump methods perform well on hard ground. We systematically vary F at fixed actuation parameters for both strategies, and find that both of these jumps perform similarly poorly in loose-packed granular media, reaching only 44% of the close-packed jump height. Introducing a delay time between the pull-up phase and the push-off phase of the stutter jump (the delayed stutter jump) results in significantly improved jump heights at low volume fraction, achieving 77% of the close packed height. A 1D simulation of the robot jumping on granular media reveals that the commonly used depth dependent and velocity dependent model of granular intrusion force is insufficient to reproduce experimental jump heights. To gain insight into the behavior of the granular media during these impulsive events, we image a foot through a transparent sidewall, recording high speed videos at different packing states (F = 0.58‑0.63). To monitor grain flow, we adapt particle image velocimetry techniques to perform a 2D particle tracking velocimetry analysis on these images. A region of grains moving with similar downward speed to the intruder emerges. Subsequently, we implement an added-mass model, an effect observed in fluids, to our granular jumping simulation and find agreement with experiment.

We study the V-shaped wake (Mach cone) formed by a cylindrical rod moving through a thin, vertically vibrated granular layer. The wake, analogous to a shock (hydraulic jump) in shallow water, appears for rod velocities v_R greater than a critical velocity c. We measure the half-angle, theta, of the wake as a function of v_R and layer depth, h. The angle satisfies the Mach relation, sin(theta)=c/v_R, where c=sqrt(gh), even for h as small as one particle diameter., Comment: 4 pages 4 figures

Our experiments and three-dimensional molecular dynamics simulations of particles confined to a vertical monolayer by closely spaced frictional walls (sidewalls) yield velocity distributions with non-Gaussian tails and a peak near zero velocity. Simulations with frictionless sidewalls are not peaked. Thus interactions between particles and their container are an important determinant of the shape of the distribution and should be considered when evaluating experiments on a tightly constrained monolayer of particles., Comment: 4 pages, 4 figures, Added reference, model explanation charified, other minor changes

This call to research paper addresses some questions about intersex and differences in sexual development and issues with the binary sex modal, before constructing the idea of fluctuations in sexual modes and suggesting a few possible areas of research to better understand evolutionary dynamics of certain intersex states. While there are many conditions that fall under the category of intersex, this paper focuses on the phenomenon of SRY gene translocations, including the possibility of seemingly endosex males whose SRY gene appears on the X chromosome rather than the Y chromosome.