284 research outputs found
Effect of the Dynamics of a Horizontally Wobbling Mass on Biped Walking Performance
We have developed biped robots with a passive dynamic walking mechanism. This
study proposes a compass model with a wobbling mass connected to the upper body
and oscillating in the horizontal direction to clarify the influence of the
horizontal dynamics of the upper body on bipedal walking. The limit cycles of
the model were numerically searched, and their stability and energy efficiency
was investigated. Several qualitatively different limit cycles were obtained
depending mainly on the spring constant that supports the wobbling mass.
Specific types of solutions decreased the stability while reducing the risk of
accidental falling and improving the energy efficiency. The obtained results
were attributed to the wobbling mass moving in the opposite direction to the
upper body, thereby preventing large changes in acceleration and deceleration
while walking. The relationship between the locomotion of the proposed model
and the actual biped robot and human gaits was investigated.Comment: 6 pages, 8 figures, accepted to IEEE International Conference on
Robotics and Automation (ICRA 2023
Synthesis of Allenyl Esters by Horner-Wadsworth-Emmons Reactions of Ketenes Mediated by i-PrMgBr
The synthesis of conjugated allenyl esters (trisubstituted allenes) was achieved by the Mg(II)-mediated Horner-Wadsworth-Emmons reaction of methyl bis(2,2,2-trifluoroethyl)phosphonoacetate with di-substituted ketenes. In addition, a novel access to α-fluorinated allenyl carboxamides (tetra-substituted allenes) is presented
Bounding of a two-legged robot using CPG-based controller inspired by a cheetah simple model
The 11th International Symposium on Adaptive Motion of Animals and Machines. Kobe University, Japan. 2023-06-06/09. Adaptive Motion of Animals and Machines Organizing Committee.Poster Session P
Local Simulations of the Magneto-rotational Instability in Core-Collapse Supernovae
Bearing in mind the application to core-collapse supernovae, we study
nonlinear properties of the magneto-rotational instability (MRI) by means of
three- dimensional simulations in the framework of a local shearing box
approximation. By changing systematically the shear rates that symbolize the
degree of differential rotation in nascent proto-neutron stars (PNSs), we
derive a scaling relation between the turbulent stress sustained by the MRI and
the shear- vorticity ratio. Our parametric survey shows a power-law scaling
between the turbulent stress () and the shear- vorticity
ratio () as with its index . The MRI-amplified magnetic energy has a similar scaling relative to
the turbulent stress, while the Maxwell stress has slightly smaller power-law
index (). By modeling the effect of viscous heating rates due to the
MRI turbulence, we show that the stronger magnetic fields or the larger shear
rates initially imposed lead to the higher dissipation rates. For a rapidly
rotating PNS with the spin period in milliseconds and with strong magnetic
fields of G, the energy dissipation rate is estimated to exceed
. Our results suggest that the conventional
magnetohydrodynamic (MHD) mechanism of core-collapse supernovae is likely to be
affected by the MRI-driven turbulence, which we speculate, on one hand, could
harm the MHD-driven explosions due to the dissipation of the shear rotational
energy at the PNS surface, on the other hand the energy deposition there might
be potentially favorable for the working of the neutrino-heating mechanism.Comment: 12 pages, 8 figures, Accepted for publication in Ap
Malignant Lymphoma with Severe Infiltrative Growth into Skeletal Muscles in WBN/Kob Rats
Although spontaneously occurring neoplasms have been reported repeatedly in F344, SD and
Wistar rats, which are commonly used strains for routine toxicologic and carcinogenicity
studies, there are only a few reports of malignant lymphoma or lymphatic leukemia except
for large granular lymphocytic leukemia (LGL) in F344 rats. Malignant lymphoma
(lymphosarcoma) is thought to be uncommon in F344 rats. The authors encountered malignant
lymphomas of the non-LGL leukemia type with characteristic pathologic features in WBN/Kob
rats. The mean age at onset of the disease in all 13 affected rats (8 males and 5 females)
was about 60 weeks. Common and characteristic clinical signs were abnormal gait with hind
limb paralysis. Macroscopically, the enlargement of the lymph nodes, spleen and liver was
slight to moderate. Scattered multiple white-to-gray nodules encompassed the aorta and
assumed a bead-like appearance near the thoracic and lumbar vertebrae.
Histopathologically, neoplastic proliferative changes were predominant in the bone marrow
tissue of the entire body, and many tumor cells infiltrated the spleen and several lymph
nodes. The most striking histological features were constant and severe infiltration of
tumor cells in the adipose tissue and skeletal muscle adjacent the thoracic and lumber
vertebrae. Immunohistochemically, all tumor cells were positive for B-cell markers (PAX-5,
CD79a and CD45) and negative for CD3. From the results of immunohistochemistry and
morphological examination, these tumors were diagnosed as malignant B-cell lymphomas
Abnormal Human Action Detection Based on GAN
One of the important roles of a camera surveillance system is to detect abnormal human actions or events. In this study, we propose a method of abnormal human actions/events detection method using Generative Adversarial Nets (GAN). In anomaly action detection, the main problem is that the image data of abnormal human actions is more difficult to obtain than normal human actions. To solve this difficulty, we use only normal human action data in the employed training network and those actions not recognized as normal are judged as abnormal. Experimental results show effectiveness of the proposed method.The 2021 International Conference on Artificial Life and Robotics (ICAROB 2021), January 21-24, 2021, Higashi-Hiroshima (ăȘăłă©ă€ăłéćŹă«ć€æŽ
Bipedal Robot Running: Human-like Actuation Timing Using Fast and Slow Adaptations
We have been developing human-sized biped robots based on passive dynamic
mechanisms. In human locomotion, the muscles activate at the same rate relative
to the gait cycle during running. To achieve adaptive running for robots, such
characteristics should be reproduced to yield the desired effect. In this
study, we designed a central pattern generator (CPG) involving fast and slow
adaptation to achieve human-like running using a simple spring-mass model and
our developed bipedal robot, which is equipped with actuators that imitate the
human musculoskeletal system. Our results demonstrate that fast and slow
adaptations can reproduce human-like running with a constant rate of muscle
firing relative to the gait cycle. Furthermore, the results suggest that the
CPG contributes to the adjustment of the muscle activation timing in human
running.Comment: 15 pages, 12 figures, submitted to Advanced Robotic
Facile Two-Step Synthesis of Methyl Bis(2,2,2-trifluoroethyl)phosphonoacetate by Exploiting GareggâSamuelsson Reaction Conditions
A facile two-step synthesis of methyl bis(2,2,2-trifluoroethyl)phosphonoacetate (StillâGennari reagent) has been developed by exploiting GareggâSamuelsson reaction conditions. Starting from trimethyl phosphonoacetate, StillâGennari reagent was prepared in 94% yield via methyl 2-{bis[(trimethylsilyl)oxy]phosphoryl}acetate intermediate. This synthetic procedure was also used to prepare some kinds of HornerâWadsworthâEmmons reagents and related compounds
Passive immunisation of goldfish with the serum of those surviving a Cyprinid herpesvirus 2 infection after high temperature water treatment
Herpesviral haematopoietic necrosis of goldfish caused by cyprinid herpesvirus 2 (CyHV-2) can be controlled by raising water temperature to a virus non-permissive temperature of 34â. Consequently, the goldfish can survive and acquire resistance to the disease; the underlying mechanism of acquired resistance, however, remains unclear. In this study, we investigated serological changes in the surviving goldfish, with a focus on their humoral immunity, and examined whether sera of the surviving goldfish conferred passive immunity to naive goldfish. Levels of the anti-CyHV-2 antibodies in 8 of the 9 survivors measured via ELISA were higher than those in control fish. Neutralising antibodies were detected in the sera of 2 survivors, but no direct correlation was observed between ELISA optical density value and neutralising antibody titer. Passive immunisation tests showed that recipients injected with the serum containing neutralising antibodies showed higher survival rates than the control group. The sera from 6 other survivors showed no effect on the recipient\u27s mortality regardless of anti-CyHV-2 antibody levels. These results suggest that neutralising antibodies can contribute to acquired immunity in survivors, and other protective factors, including cell-mediated immunity, may work in the survivors that show no detectable neutralising antibodies
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