scholarly journals Modulation of orthogonal body waves enables high maneuverability in sidewinding locomotion

2015 ◽  
Vol 112 (19) ◽  
pp. 6200-6205 ◽  
Author(s):  
Henry C. Astley ◽  
Chaohui Gong ◽  
Jin Dai ◽  
Matthew Travers ◽  
Miguel M. Serrano ◽  
...  
Keyword(s):  
Motor Pattern ◽  
Body Waves ◽  
Wave System ◽  
Single Plane ◽  
Snake Robot ◽  
Horizontal Wave ◽  
Terrestrial Environments ◽  
Wave Cycle ◽  
Crotalus Cerastes ◽  
High Degree

Many organisms move using traveling waves of body undulation, and most work has focused on single-plane undulations in fluids. Less attention has been paid to multiplane undulations, which are particularly important in terrestrial environments where vertical undulations can regulate substrate contact. A seemingly complex mode of snake locomotion, sidewinding, can be described by the superposition of two waves: horizontal and vertical body waves with a phase difference of ±90°. We demonstrate that the high maneuverability displayed by sidewinder rattlesnakes (Crotalus cerastes) emerges from the animal’s ability to independently modulate these waves. Sidewinder rattlesnakes used two distinct turning methods, which we term differential turning (26° change in orientation per wave cycle) and reversal turning (89°). Observations of the snakes suggested that during differential turning the animals imposed an amplitude modulation in the horizontal wave whereas in reversal turning they shifted the phase of the vertical wave by 180°. We tested these mechanisms using a multimodule snake robot as a physical model, successfully generating differential and reversal turning with performance comparable to that of the organisms. Further manipulations of the two-wave system revealed a third turning mode, frequency turning, not observed in biological snakes, which produced large (127°) in-place turns. The two-wave system thus functions as a template (a targeted motor pattern) that enables complex behaviors in a high-degree-of-freedom system to emerge from relatively simple modulations to a basic pattern. Our study reveals the utility of templates in understanding the control of biological movement as well as in developing control schemes for limbless robots.

Frequency modulation of body waves to improve performance of sidewinding robots

2021 ◽  
pp. 027836492110377
Author(s):  
Baxi Chong ◽  
Tianyu Wang ◽  
Jennifer M. Rieser ◽  
Bo Lin ◽  
Abdul Kaba ◽  
...  
Keyword(s):  
Center Of Mass ◽  
The Body ◽  
Body Waves ◽  
Contact Pattern ◽  
Body Frame ◽  
Improve Performance ◽  
Horizontal Wave ◽  
Terrestrial Environments ◽  
Unstable Oscillation ◽  
Locomotor Behaviors

Sidewinding is a form of locomotion executed by certain snakes and has been reconstructed in limbless robots; the gait is beneficial because it is effective in diverse terrestrial environments. Sidewinding gaits are generated by coordination of horizontal and vertical traveling waves of body undulation: the horizontal wave largely sets the direction of sidewinding with respect to the body frame while the vertical traveling wave largely determines the contact pattern between the body and the environment. When the locomotor’s center of mass leaves the supporting polygon formed by the contact pattern, undesirable locomotor behaviors (such as unwanted turning or unstable oscillation of the body) can occur. In this article, we develop an approach to generate desired translation and turning by modulating the vertical wave. These modulations alter the distribution of body–environment contact patches and can stabilize configurations that were previously statically unstable. The approach first identifies the spatial frequency of the vertical wave that statically stabilizes the locomotor for a given horizontal wave. Then, using geometric mechanics tools, we design the coordination between body waves that produces the desired translation or rotation. We demonstrate the effectiveness of our technique in numerical simulations and on experiments with a 16-joint limbless robot locomoting on flat hard ground. Our scheme broadens the range of movements and behaviors accessible to sidewinding locomotors at low speeds, which can lead to limbless systems capable of traversing diverse terrain stably and/or rapidly.

scholarly journals Snake Robot with Driving Assistant Mechanism

2020 ◽  
Vol 10 (21) ◽  
pp. 7478
Author(s):  
Junseong Bae ◽  
Myeongjin Kim ◽  
Bongsub Song ◽  
Maolin Jin ◽  
Dongwon Yun
Keyword(s):  
Dynamic Simulation ◽  
Degree Of Freedom ◽  
Rough Terrain ◽  
Snake Robot ◽  
Wide Range ◽  
Locomotion Speed ◽  
High Degree ◽  
Snake Robots

Snake robots are composed of multiple links and joints and have a high degree of freedom. They can perform various motions and can overcome various terrains. Snake robots need additional driving algorithms and sensors that acquire terrain data in order to overcome rough terrains such as grasslands and slopes. In this study, we propose a driving assistant mechanism (DAM), which assists locomotion without additional driving algorithms and sensors. In this paper, we confirmed that the DAM prevents a roll down on a slope and increases the locomotion speed through dynamic simulation and experiments. It was possible to overcome grasslands and a 27 degrees slope without using additional driving controllers. In conclusion, we expect that a snake robot can conduct a wide range of missions well, such as exploring disaster sites and rough terrain, by using the proposed mechanism.

scholarly journals A Key Motif in the Cholesterol-Dependent Cytolysins Reveals a Large Family of Related Proteins

mBio ◽  
2020 ◽  
Vol 11 (5) ◽  
Author(s):  
Jordan C. Evans ◽  
Bronte A. Johnstone ◽  
Sara L. Lawrence ◽  
Craig J. Morton ◽  
Michelle P. Christie ◽  
...  
Keyword(s):  
Large Family ◽  
Structural Similarity ◽  
Particle Analysis ◽  
Critical Component ◽  
Content Type ◽  
Conserved Motif ◽  
Forming Mechanism ◽  
Terrestrial Environments ◽  
Pore Complexes ◽  
High Degree

ABSTRACT The cholesterol-dependent cytolysins (CDCs) are bacterial, β-barrel, pore-forming toxins. A central enigma of the pore-forming mechanism is how completion of the prepore is sensed to initiate its conversion to the pore. We identified a motif that is conserved between the CDCs and a diverse family of nearly 300 uncharacterized proteins present in over 220 species that span at least 10 bacterial and 2 eukaryotic phyla. Except for this motif, these proteins exhibit little similarity to the CDCs at the primary structure level. Studies herein show this motif is a critical component of the sensor that initiates the prepore-to-pore transition in the CDCs. We further show by crystallography, single particle analysis, and biochemical studies of one of these CDC-like (CDCL) proteins from Elizabethkingia anophelis, a commensal of the malarial mosquito midgut, that a high degree of structural similarity exists between the CDC and CDCL monomer structures and both form large oligomeric pore complexes. Furthermore, the conserved motif in the E. anophelis CDCL crystal structure occupies a nearly identical position and makes similar contacts to those observed in the structure of the archetype CDC, perfringolysin O (PFO). This suggests a common function in the CDCs and CDCLs and may explain why only this motif is conserved in the CDCLs. Hence, these studies identify a critical component of the sensor involved in initiating the prepore-to-pore transition in the CDCs, which is conserved in a large and diverse group of distant relatives of the CDCs. IMPORTANCE The cholesterol-dependent cytolysins’ pore-forming mechanism relies on the ability to sense the completion of the oligomeric prepore structure and initiate the insertion of the β-barrel pore from the assembled prepore structure. These studies show that a conserved motif is an important component of the sensor that triggers the prepore-to-pore transition and that it is conserved in a large family of previously unidentified CDC-like proteins, the genes for which are present in a vast array of microbial species that span most terrestrial environments, as well as most animal and human microbiomes. These studies establish the foundation for future investigations that will probe the contribution of this large family of CDC-like proteins to microbial survival and human disease.

Flexibility of the axial central pattern generator network for locomotion in the salamander

2015 ◽  
Vol 113 (6) ◽  
pp. 1921-1940 ◽  
Author(s):  
D. Ryczko ◽  
J. Knüsel ◽  
A. Crespi ◽  
S. Lamarque ◽  
A. Mathou ◽  
...  
Keyword(s):  
Motor Coordination ◽  
Motor Nerve ◽  
Motor Pattern ◽  
Motor Patterns ◽  
Electrophysiological Recordings ◽  
Terrestrial Environments ◽  
Pleurodeles Waltlii ◽  
Locomotor Behaviors ◽  
Insight Into

In tetrapods, limb and axial movements are coordinated during locomotion. It is well established that inter- and intralimb coordination show considerable variations during ongoing locomotion. Much less is known about the flexibility of the axial musculoskeletal system during locomotion and the neural mechanisms involved. Here we examined this issue in the salamander Pleurodeles waltlii, which is capable of locomotion in both aquatic and terrestrial environments. Kinematics of the trunk and electromyograms from the mid-trunk epaxial myotomes were recorded during four locomotor behaviors in freely moving animals. A similar approach was used during rhythmic struggling movements since this would give some insight into the flexibility of the axial motor system. Our results show that each of the forms of locomotion and the struggling behavior is characterized by a distinct combination of mid-trunk motor patterns and cycle durations. Using in vitro electrophysiological recordings in isolated spinal cords, we observed that the spinal networks activated with bath-applied N-methyl-d-aspartate could generate these axial motor patterns. In these isolated spinal cord preparations, the limb motor nerve activities were coordinated with each mid-trunk motor pattern. Furthermore, isolated mid-trunk spinal cords and hemicords could generate the mid-trunk motor patterns. This indicates that each side of the cord comprises a network able to generate coordinated axial motor activity. The roles of descending and sensory inputs in the behavior-related changes in axial motor coordination are discussed.

The Problem of Air Flow Over Mountains: A Summary of Theoretical Studies

1948 ◽  
Vol 29 (1) ◽  
pp. 16-26 ◽  
Author(s):  
Paul Queney
Keyword(s):  
Wave Length ◽  
Potential Temperature ◽  
Vertical Plane ◽  
Critical Value ◽  
Mountain Range ◽  
Theoretical Problem ◽  
Wave System ◽  
Special Cases ◽  
Lee Waves ◽  
Horizontal Wave

The theoretical researches on the problem of the disturbance of an atmospheric current flowing over a mountain range, carried on during the last ten years, prove that most of the characteristic observed features can be explained, to a very large extent, by the hydrodynamical theory of internal, small adiabatic perturbations in a stratified rotating atmosphere. In the case of a uniform current of velocity u, in which the coefficient of vertical stability is also uniform (θ is the potential temperature, g the gravity, z the elevation), the perturbation pattern corresponding to a smooth, low, gently-sloping mountain range varies widely according to the half-width a of this mountain range:i) If a is comparable to the critical value (Ls/2π) = (u/s) ≈ 1 km, there is a system of short stationary lee waves, or gravity waves, with the wave length Ls.ii) If a is comparable to (Lf/2π) = (u/f) ≈ 100 km, where f is the Coriolis parameter, there is a complex system of gravity-inertia lee waves, with the horizontal wave length Lf at ground level, and the vertical wave length Ls in the vertical plane of the crest.iii) In the case of a westerly wind, if a is comparable to the third critical value , where β is the latitudinal variation of f, there is a system of long geostrophic lee waves, of the type studied by Rossby, with the horizontal wave length Lβ at ground level.iv) In the other cases, there are no lee waves, and the wave system is either missing (cases a ≪ (u/s) and ≫ (u/f)) or restricted to the vicinity of the vertical plane of the crest, with the wave length Ls (case (u/s) ≪ a ≪ (u/f). One of the effects of the tropopause, and of atmospheric discontinuities in general, is to produce eventually an additional system of waves on the upwind side of the mountain range, but these waves must be generally much smaller than the lee waves. Similar results are obtained for a plateau with smooth sides, and in the case of a more complex mountain profile the perturbation can be computed by superimposing elementary solutions. If the current is not uniform, if the ground deformation is steep, or if the perturbation is not adiabatic, the preceding results are not valid, and the solution of the theoretical problem has been obtained in only very special cases.

Gypsum-hosted endolithic communities of the Lake St. Martin impact structure, Manitoba, Canada: spectroscopic detectability and implications for Mars

2014 ◽  
Vol 13 (4) ◽  
pp. 366-377 ◽  
Author(s):  
T. Rhind ◽  
J. Ronholm ◽  
B. Berg ◽  
P. Mann ◽  
D. Applin ◽  
...  
Keyword(s):  
Microbial Community ◽  
Impact Crater ◽  
Organic Molecules ◽  
Soil Surface ◽  
Spectroscopic Technique ◽  
Community Members ◽  
Exterior Surface ◽  
Terrestrial Environments ◽  
High Degree ◽  
Endolithic Communities

AbstractThere is increasing evidence that Mars may have once been a habitable environment. Gypsum is targeted in the search for Martian biosignatures because it can host extensive cryptoendolithic communities in extreme terrestrial environments and is widespread on Mars. In this study the viability of using different spectroscopy-based techniques to identify the presence of gypsum endolithic communities was investigated by analysing various cryptoendoliths collected from the Lake St. Martin impact crater (LSM), a Mars analogue site found in Manitoba, Canada. Concurrently, the cryptoendolithic microbial community structure present was also analysed to aid in assigning spectroscopic features to microbial community members. Two main morphologies of endolithic communities were collected from gypsum deposits at LSM: true cryptoendolithic communities and annular deposits on partially buried boulders and cobbles <1 cm below the soil surface. Endolithic communities were found to be visibly present only in gypsum with a high degree of translucency and could occur as deep as 3 cm below the exterior surface. The bacterial community was dominated by a phylum (Chloroflexi) that has not been previously observed in gypsum endoliths. The exterior surfaces of gypsum boulders and cobbles are devoid of spectroscopic features attributable to organic molecules and detectable by reflectance, Raman, or ultraviolet-induced fluorescence spectroscopies. However, exposed interior surfaces show unique endolithic signatures detectable by each spectroscopic technique. This indicates that cryptoendolithic communities can be detected via spectroscopy-based techniques, provided they are either partially or fully exposed and enough photon–target interactions occur to enable detection.

scholarly journals Side-Impact Collision: Mechanics of Obstacle Negotiation in Sidewinding Snakes

2020 ◽  
Author(s):  
Henry C. Astley ◽  
Jennifer M. Rieser ◽  
Abdul Kaba ◽  
Veronica M. Paez ◽  
Ian Tomkinson ◽  
...  
Keyword(s):  
Natural Habitat ◽  
Body Waves ◽  
Side Impact ◽  
Behavioral Strategies ◽  
Cluttered Environments ◽  
Heterogeneous Habitats ◽  
Static Contact ◽  
Lateral Undulation ◽  
Crotalus Cerastes ◽  
And Control

AbstractSnakes excel at moving through cluttered environments, and heterogeneities can be used as propulsive contacts for snakes performing lateral undulation. However, sidewinding, often associated with sandy deserts, cuts a broad path through the environment that may increase the vulnerability to obstacles. Our prior work demonstrated that sidewinding can be represented as a pair of orthogonal body waves (vertical and horizontal) that can be independently modulated to achieve high maneuverability and incline ascent, suggesting that sidewinders may also use template modulations to negotiate obstacles. To test this hypothesis, we recorded overhead video of four sidewinder rattlesnakes (Crotalus cerastes) crossing a line of vertical pegs placed in the substrate. Snakes used three methods to traverse the obstacles: a Propagate Through behavior in which the lifted moving portion of the snake was deformed around the peg and dragged through as the snake continued sidewinding (115/160 runs), Reversal turns that reorient the snake entirely (35/160), or switching to Concertina locomotion (10/160). The Propagate-Through response was only used if the anterior-most region of static contact would propagate along a path anterior to the peg, or if a new region of static contact could be formed near the head to satisfy this condition; otherwise, snakes could only use Reversal Turns or switch to Concertina locomotion. Reversal Turns allowed the snake to re-orient and either escape without further peg contact or resorting to Propagate Through. We developed an algorithm to reproduce the Propagate Through behavior in a robotic model using a modulation of the two-wave template. This range of behavioral strategies provides sidewinders with a versatile range of options for effectively negotiating obstacles in their natural habitat, as well as provide insights into the design and control of robotic systems dealing with heterogeneous habitats.

Tissue section lifting for electron microscopy

1978 ◽  
Vol 36 (2) ◽  
pp. 86-87
Author(s):  
Adrian F. van Dellen
Keyword(s):  
Infectious Disease ◽  
Electron Microscopy ◽  
Tissue Culture ◽  
Organ System ◽  
Surrounding Tissue ◽  
Paraffin Sections ◽  
Surface Areas ◽  
Specific Determination ◽  
High Degree ◽  
Accuracy And Repeatability

The morphologic pathologist may require information on the ultrastructure of a non-specific lesion seen under the light microscope before he can make a specific determination. Such lesions, when caused by infectious disease agents, may be sparsely distributed in any organ system. Tissue culture systems, too, may only have widely dispersed foci suitable for ultrastructural study. In these situations, when only a few, small foci in large tissue areas are useful for electron microscopy, it is advantageous to employ a methodology which rapidly selects a single tissue focus that is expected to yield beneficial ultrastructural data from amongst the surrounding tissue. This is in essence what "LIFTING" accomplishes. We have developed LIFTING to a high degree of accuracy and repeatability utilizing the Microlift (Fig 1), and have successfully applied it to tissue culture monolayers, histologic paraffin sections, and tissue blocks with large surface areas that had been initially fixed for either light or electron microscopy.

Electron Microscopy in Molecular Biology

1967 ◽  
Vol 25 ◽  
pp. 2-3
Author(s):  
Cecil E. Hall
Keyword(s):  
Electron Microscopy ◽  
Molecular Biology ◽  
Noise Level ◽  
Molecular Structures ◽  
Material Structure ◽  
The Arts ◽  
Shadow Casting ◽  
Electron Image ◽  
High Degree ◽  
Very High

The visualization of organic macromolecules such as proteins, nucleic acids, viruses and virus components has reached its high degree of effectiveness owing to refinements and reliability of instruments and to the invention of methods for enhancing the structure of these materials within the electron image. The latter techniques have been most important because what can be seen depends upon the molecular and atomic character of the object as modified which is rarely evident in the pristine material. Structure may thus be displayed by the arts of positive and negative staining, shadow casting, replication and other techniques. Enhancement of contrast, which delineates bounds of isolated macromolecules has been effected progressively over the years as illustrated in Figs. 1, 2, 3 and 4 by these methods. We now look to the future wondering what other visions are waiting to be seen. The instrument designers will need to exact from the arts of fabrication the performance that theory has prescribed as well as methods for phase and interference contrast with explorations of the potentialities of very high and very low voltages. Chemistry must play an increasingly important part in future progress by providing specific stain molecules of high visibility, substrates of vanishing “noise” level and means for preservation of molecular structures that usually exist in a solvated condition.

A High Angle, Double Tilting Cold Stage for the AEI EM7

1974 ◽  
Vol 32 ◽  
pp. 450-451
Author(s):  
P.R. Swann ◽  
A.E. Lloyd
Keyword(s):  
Habit Plane ◽  
Temperature Control ◽  
Tilt Angle ◽  
Cooling System ◽  
Thermal Drift ◽  
High Angle ◽  
Cold Stage ◽  
High Degree ◽  
Better Than

Figure 1 shows the design of a specimen stage used for the in situ observation of phase transformations in the temperature range between ambient and −160°C. The design has the following features a high degree of specimen stability during tilting linear tilt actuation about two orthogonal axes for accurate control of tilt angle read-out high angle tilt range for stereo work and habit plane determination simple, robust construction temperature control of better than ±0.5°C minimum thermal drift and transmission of vibration from the cooling system.

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