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https://www.readbyqxmd.com/read/28211509/climbing-favours-the-tripod-gait-over-alternative-faster-insect-gaits
#1
Pavan Ramdya, Robin Thandiackal, Raphael Cherney, Thibault Asselborn, Richard Benton, Auke Jan Ijspeert, Dario Floreano
To escape danger or catch prey, running vertebrates rely on dynamic gaits with minimal ground contact. By contrast, most insects use a tripod gait that maintains at least three legs on the ground at any given time. One prevailing hypothesis for this difference in fast locomotor strategies is that tripod locomotion allows insects to rapidly navigate three-dimensional terrain. To test this, we computationally discovered fast locomotor gaits for a model based on Drosophila melanogaster. Indeed, the tripod gait emerges to the exclusion of many other possible gaits when optimizing fast upward climbing with leg adhesion...
February 17, 2017: Nature Communications
https://www.readbyqxmd.com/read/28183867/propulsion-in-hexapod-locomotion-how-do-desert-ants-traverse-slopes
#2
Toni Wöhrl, Lars Reinhardt, Reinhard Blickhan
The employment of an alternating tripod gait to traverse uneven terrains is a common characteristic shared among many hexapoda. Since this could be one specific cause for their ecological success, we examined the alternating tripod gait of the desert ant Cataglyphis fortis together with their ground reaction forces and weight-specific leg impulses for level locomotion and on moderate (±30°) and steep (±60°) slopes in order to understand mechanical functions of individual legs during inclined locomotion...
February 9, 2017: Journal of Experimental Biology
https://www.readbyqxmd.com/read/28157918/influence-of-axial-force-errors-on-the-deformation-of-the-4%C3%A2-%C3%A2-m-lightweight-mirror-and-its-correction
#3
Bin Lan, Xiaoxia Wu, Jianfeng Li, Ming Ming, Xiangyi Liu, Hongbo Yang
The lightweight primary mirror of the four meter Chinese telescope is supported axially by a passive hydraulic system, in parallel with an active system. The figure is sensitive to the errors in the axial forces, which can be effectively corrected using active optics. The squared RMS of this figure approximately follows the χ<sup>2</sup> distribution, as verified by Monte Carlo analysis. The probability distributions of the squared norm of the active-forces vector, of the squared norm of the leg-lengths vector in the hexapod platform, and of the squared RMS of the residual figure are discussed in terms of the bending modes obtained by singular-value decomposition of the influence matrix, the optical sensitivity matrix deduced through ray trace, and the Jacobian matrix of the hexapod platform...
January 20, 2017: Applied Optics
https://www.readbyqxmd.com/read/28148674/computer-hexapod-assisted-orthopaedic-surgery-provides-a-predictable-and-safe-method-of-femoral-deformity-correction
#4
A Hughes, N Heidari, S Mitchell, J Livingstone, M Jackson, R Atkins, F Monsell
AIMS: Computer hexapod assisted orthopaedic surgery (CHAOS), is a method to achieve the intra-operative correction of long bone deformities using a hexapod external fixator before definitive internal fixation with minimally invasive stabilisation techniques. The aims of this study were to determine the reliability of this method in a consecutive case series of patients undergoing femoral deformity correction, with a minimum six-month follow-up, to assess the complications and to define the ideal group of patients for whom this treatment is appropriate...
February 2017: Bone & Joint Journal
https://www.readbyqxmd.com/read/28110891/femoral-lengthening-in-children-and-adolescents
#5
REVIEW
Z Pejin
Current lengthening techniques are still based on the Ilizarov method and the concept of callotasis. Research and progress in medical devices have led to constant improvement in results. Hexapod fixators allow more precise correction of complex deformities, with shorter learning curve. Associating lengthening by external fixation (EF) to internal fixation (K-wire, intramedullary nail or locking plate) has reduced EF times and complications rates, while improving anatomic and functional results. Lengthening nails provides faster recovery of range of motion and return to activity during lengthening and consolidation, with better psychological tolerance...
January 16, 2017: Orthopaedics & Traumatology, Surgery & Research: OTSR
https://www.readbyqxmd.com/read/28046558/su-f-t-484-initial-evaluation-of-a-novel-6d-qa-phantom-hexacheck-for-daily-6d-couch-correction-assessment
#6
J E Roring, D Stanley, N Papanikolaou, A N Gutierrez
PURPOSE: Treatment couches with 6D correction capabilities have become a regular part of IGRT. While 6D couches have been shown to function mechanically well, phantoms for daily angular QA accuracy assessment have yet to be commercially available. Standard Imaging™ has developed a phantom designed for daily verification of pitch, roll, and yaw corrections. In this study, the mechanical integrity, reproducibility, and daily 6D correction stability of the phantom using both volumetric (Elekta- XVI kV-CBCT) and orthogonal kV (Brainlab ExacTrac) imaging was evaluated...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28028122/evolution-of-chemosensory-gene-families-in-arthropods-insight-from-the-first-inclusive-comparative-transcriptome-analysis-across-spider-appendages
#7
Joel Vizueta, Cristina Frías-López, Nuria Macías-Hernández, Miquel A Arnedo, Alejandro Sánchez-Gracia, Julio Rozas
Unlike hexapods and vertebrates, in chelicerates, knowledge of the specific molecules involved in chemoreception comes exclusively from the comparative analysis of genome sequences. Indeed, the genomes of mites, ticks and spiders contain several genes encoding homologs of some insect membrane receptors and small soluble chemosensory proteins. Here, we conducted for the first time a comprehensive comparative RNA-Seq analysis across different body structures of a chelicerate: the nocturnal wandering hunter spider Dysdera silvatica Schmidt 1981...
December 27, 2016: Genome Biology and Evolution
https://www.readbyqxmd.com/read/27989966/origin-and-evolution-of-the-panarthropod-head-a-palaeobiological-and-developmental-perspective
#8
Javier Ortega-Hernández, Ralf Janssen, Graham E Budd
The panarthropod head represents a complex body region that has evolved through the integration and functional specialization of the anterior appendage-bearing segments. Advances in the developmental biology of diverse extant organisms have led to a substantial clarity regarding the relationships of segmental homology between Onychophora (velvet worms), Tardigrada (water bears), and Euarthropoda (e.g. arachnids, myriapods, crustaceans, hexapods). The improved understanding of the segmental organization in panarthropods offers a novel perspective for interpreting the ubiquitous Cambrian fossil record of these successful animals...
December 17, 2016: Arthropod Structure & Development
https://www.readbyqxmd.com/read/27939714/the-rapidly-changing-landscape-of-insect-phylogenetics
#9
REVIEW
David R Maddison
Insect phylogenetics is being profoundly changed by many innovations. Although rapid developments in genomics have center stage, key progress has been made in phenomics, field and museum science, digital databases and pipelines, analytical tools, and the culture of science. The importance of these methodological and cultural changes to the pace of inference of the hexapod Tree of Life is discussed. The innovations have the potential, when synthesized and mobilized in ways as yet unforeseen, to shine light on the million or more clades in insects, and infer their composition with confidence...
December 2016: Current Opinion in Insect Science
https://www.readbyqxmd.com/read/27933259/deformity-correction-and-extremity-lengthening-in-the-lower-leg-comparison-of-clinical-outcomes-with-two-external-surgical-procedures
#10
Eugen Reitenbach, Robert Rödl, Georg Gosheger, Björn Vogt, Frank Schiedel
OBJECTIVE: Distraction osteogenesis is a method of stimulating the growth of new bone tissue in order to lengthen the extremities or bridge resected bone defects. In addition to the now-established intramedullary procedures, two different fixator systems are in use. The present study investigated the classical Ilizarov ring fixator (IRF) and a hexapod to assess the precision of lower-leg lengthening and complications classified using the Paley criteria for problems, obstacles, and complications...
2016: SpringerPlus
https://www.readbyqxmd.com/read/27914027/the-role-of-guided-growth-as-it-relates-to-limb-lengthening
#11
REVIEW
Peter M Stevens
For decades, the classic indication for limb lengthening has been reserved for anisomelia that was expected to reach or exceed 5 cm at maturity. Epiphysiodesis was reserved for discrepancies in the 2-5 cm range. With the increasing sophistication of fixators, including rail, hexapod, and hybrid, complex deformities may be corrected simultaneously while moderate to extreme lengthening is achieved. More recently, iterations of telescoping intramedullary rods have further strengthened our armamentarium. Meanwhile, permanent epiphysiodesis techniques, both open and percutaneous, have yielded to more versatile and reversible tethering of one (angle) or both (length) sides of a physis...
December 2016: Journal of Children's Orthopaedics
https://www.readbyqxmd.com/read/27896679/what-are-the-biomechanical-properties-of-the-taylor-spatial-frame%C3%A2
#12
Daniel J Henderson, Jeremy L Rushbrook, Paul J Harwood, Todd D Stewart
BACKGROUND: The Taylor Spatial Frame™ (TSF) is a versatile variant of the traditional Ilizarov circular fixator. Although in widespread use, little comparative data exist to quantify the biomechanical effect of substituting the tried-and-tested Ilizarov construct for the TSF hexapod system. QUESTIONS/PURPOSES: This study was designed to investigate the mechanical properties of the TSF system under physiologic loads, with and without the addition of a simulated bone model, with comparison to the standard Ilizarov frame...
November 28, 2016: Clinical Orthopaedics and related Research
https://www.readbyqxmd.com/read/27818969/surgical-treatment-of-neglected-clubfoot-using-external-fixator
#13
Rodrigo Mota Pacheco Fernandes, Maurilio Darcy Dos Santos Mendes, Renato Amorim, Marcus Aurélio Preti, Marcelo Back Sternick, Guilherme Pelosini Gaiarsa
The definition of neglected clubfoot (NC) includes a variable range of complex deformities of the foot that are refractory to conventional treatments or are treated inappropriately. Several etiologies may be related to this. The Ilizarov method has become established as a tool for treating these deformities. It minimizes soft-tissue damage through gradual correction of the deformity, with a high success rate in relation to achieving a plantigrade foot, with low incidence of recurrence. The indications for treatment include severe rigid deformities (Dimeglio III and IV), or adverse skin conditions...
September 2016: Revista Brasileira de Ortopedia
https://www.readbyqxmd.com/read/27802747/a-high-performance-wave-guide-cryogenic-thermal-break
#14
S J Melhuish, M A McCulloch, L Piccirillo, C Stott
We describe a high-performance wave guide cryogenic thermal break. This has been constructed both for Ka band, using WR28 wave guide, and Q band, using WR22 wave guide. The mechanical structure consists of a hexapod (Stewart platform) made from pultruded carbon fibre tubing. We present a tentative examination of the cryogenic Young's modulus of this material. The thermal conductivity is measured at temperatures above the range explored by Runyan and Jones, resulting in predicted conductive loads through our thermal breaks of 3...
October 2016: Review of Scientific Instruments
https://www.readbyqxmd.com/read/27755338/effectiveness-of-treatment-for-distal-tibial-nonunions-with-associated-complex-deformities-using-a-hexapod-external-fixator
#15
John E Arvesen, J Tracy Watson, Heidi Israel
OBJECTIVE: To determine the efficacy of a hexapod external fixator (TSF) and its ability to perform 6-axis correction in restoring deformities associated with distal tibial nonunions. DESIGN: Consecutive retrospective case review. SETTING: St. Louis University Hospital. Level 1 Trauma Center. PATIENTS/PARTICIPANTS: Thirty-seven patients with distal tibial nonunion with greater than 5 degrees of deformity in any plane...
February 2017: Journal of Orthopaedic Trauma
https://www.readbyqxmd.com/read/27714051/rational-design-of-pt-ni-co-ternary-alloy-nanoframe-crystals-as-highly-efficient-catalysts-toward-the-alkaline-hydrogen-evolution-reaction
#16
Aram Oh, Young Jin Sa, Hyeyoun Hwang, Hionsuck Baik, Jun Kim, Byeongyoon Kim, Sang Hoon Joo, Kwangyeol Lee
The rational design of highly efficient electrocatalysts for the hydrogen evolution reaction (HER) is of prime importance for establishing renewable and sustainable energy systems. The alkaline HER is particularly challenging as it involves a two-step reaction of water dissociation and hydrogen recombination, for which platinum-based binary catalysts have shown promising activity. In this work, we synthesized high performance platinum-nickel-cobalt alloy nanocatalysts for the alkaline HER through a simple synthetic route...
September 15, 2016: Nanoscale
https://www.readbyqxmd.com/read/27696666/wnt-repertoire-and-developmental-expression-patterns-in-the-crustacean-thamnocephalus-platyurus
#17
Savvas J Constantinou, Ryan M Pace, A J Stangl, Lisa M Nagy, Terri A Williams
Wnt genes are a family of conserved glycoprotein ligands that play a role in a wide variety of cell and developmental processes, from cell proliferation to axis elongation. There are 13 Wnt subfamilies found among metazoans. Eleven of these appear conserved in arthropods with a pattern of loss during evolution of as many as six subfamilies among hexapods. Here we report on Wnt genes in the branchiopod crustacean, Thamnocephalus platyurus, including the first documentation of the expression of the complete Wnt gene family in a crustacean...
December 2016: Evolution & Development
https://www.readbyqxmd.com/read/27663622/the-effect-of-six-degree-of-freedom-loading-sequence-on-the-in-vitro-compressive-properties-of-human-lumbar-spine-segments
#18
D B Amin, I M Lawless, D Sommerfeld, R M Stanley, B Ding, J J Costi
The complex, direction-dependent, poro-viscoelastic properties of the intervertebral disc (disc) suggest that investigations of the six degree of freedom (6DOF) behaviour may be susceptible to inter-test variation in mechanical response if the disc does not return to initial conditions between loading directions. No studies have quantified the effects of sequential multi-directional loading on the consistency of the compressive response of the disc throughout a 6DOF testing protocol. Therefore, the objective of this study was to determine the effect of 6DOF loading on the compressive properties (stiffness and phase angle) of human discs, as evaluated by a reference compression test performed after each single DOF test...
October 3, 2016: Journal of Biomechanics
https://www.readbyqxmd.com/read/27589766/trajectory-correction-and-locomotion-analysis-of-a-hexapod-walking-robot-with-semi-round-rigid-feet
#19
Yaguang Zhu, Bo Jin, Yongsheng Wu, Tong Guo, Xiangmo Zhao
Aimed at solving the misplaced body trajectory problem caused by the rolling of semi-round rigid feet when a robot is walking, a legged kinematic trajectory correction methodology based on the Least Squares Support Vector Machine (LS-SVM) is proposed. The concept of ideal foothold is put forward for the three-dimensional kinematic model modification of a robot leg, and the deviation value between the ideal foothold and real foothold is analyzed. The forward/inverse kinematic solutions between the ideal foothold and joint angular vectors are formulated and the problem of direct/inverse kinematic nonlinear mapping is solved by using the LS-SVM...
August 31, 2016: Sensors
https://www.readbyqxmd.com/read/27516737/design-of-spiking-central-pattern-generators-for-multiple-locomotion-gaits-in-hexapod-robots-by-christiansen-grammar-evolution
#20
Andres Espinal, Horacio Rostro-Gonzalez, Martin Carpio, Erick I Guerra-Hernandez, Manuel Ornelas-Rodriguez, Marco Sotelo-Figueroa
This paper presents a method to design Spiking Central Pattern Generators (SCPGs) to achieve locomotion at different frequencies on legged robots. It is validated through embedding its designs into a Field-Programmable Gate Array (FPGA) and implemented on a real hexapod robot. The SCPGs are automatically designed by means of a Christiansen Grammar Evolution (CGE)-based methodology. The CGE performs a solution for the configuration (synaptic weights and connections) for each neuron in the SCPG. This is carried out through the indirect representation of candidate solutions that evolve to replicate a specific spike train according to a locomotion pattern (gait) by measuring the similarity between the spike trains and the SPIKE distance to lead the search to a correct configuration...
2016: Frontiers in Neurorobotics
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