17 research outputs found
Topology-Based MPC for Automatic Footstep Placement and Contact Surface Selection
State-of-the-art approaches to footstep planning assume reduced-order
dynamics when solving the combinatorial problem of selecting contact surfaces
in real time. However, in exchange for computational efficiency, these
approaches ignore joint torque limits and limb dynamics. In this work, we
address these limitations by presenting a topology-based approach that
enables~\gls{mpc} to simultaneously plan full-body motions, torque commands,
footstep placements, and contact surfaces in real time. To determine if a
robot's foot is inside a contact surface, we borrow the winding number concept
from topology. We then use this winding number and potential field to create a
contact-surface penalty function. By using this penalty function,~\gls{mpc} can
select a contact surface from all candidate surfaces in the vicinity and
determine footstep placements within it. We demonstrate the benefits of our
approach by showing the impact of considering full-body dynamics, which
includes joint torque limits and limb dynamics, on the selection of footstep
placements and contact surfaces. Furthermore, we validate the feasibility of
deploying our topology-based approach in an~\gls{mpc} scheme and explore its
potential capabilities through a series of experimental and simulation trials.Comment: 7 pages, 6 figure
Rapid Turnover of Cortical NCAM1 Regulates Synaptic Reorganization after Peripheral Nerve Injury
Peripheral nerve injury can induce pathological conditions that lead to persistent sensitized nociception. Although there is evidence that plastic changes in the cortex contribute to this process, the underlying molecular mechanisms are unclear. Here, we find that activation of the anterior cingulate cortex (ACC) induced by peripheral nerve injury increases the turnover of specific synaptic proteins in a persistent manner. We demonstrate that neural cell adhesion molecule 1 (NCAM1) is one of the molecules involved and show that it mediates spine reorganization and contributes to the behavioral sensitization. We show striking parallels in the underlying mechanism with the maintenance of NMDA-receptor- and protein-synthesis-dependent long-term potentiation (LTP) in the ACC. Our results, therefore, demonstrate a synaptic mechanism for cortical reorganization and suggest potential avenues for neuropathic pain treatment
Haptic cues in bimanual cooperative transport of large objects
As the interest in, and demand for, personal and service robots increase, research studies in human-robot interaction, especially involving physical contact between robots and humans, have become increasingly important. As an example of physical human-robot interaction (pHRI) research, cooperative object transport has been substantially investigated by many researchers. However, there is a gap in studies on bimanual cooperative object transport, a carrying mode essential for transport of large objects.
This research investigated human-human haptic interaction during cooperative bimanual transport of a large object. Eight pairs of human subjects, leader and follower dyads, were instructed to carry a large object with both hands and move cooperatively in the anteroposterior direction. The study focused on two haptic cues, the average rate of change of force (ARCF), and the interaction duration () employed by leaders and followers during the initiation phase of object transports. A custom-designed frame mounted with a load cell and an accelerometer was built to measure haptic interaction and transport movement in the anteroposterior direction. The experimental data showed that the leaders employed a repetitive ARCF during the initiation phase across trials. The other haptic cue for followers to respond to the leader’s initiation was also found to be repetitive. Modeling of the above-mentioned findings was conducted. The impedance model of a human arm during the initiation phase of bimanual cooperative transport was computed from the experimental data. Next, the expected interaction duration () computed by inputting the average rate of change of force to the impedance model was compared to the average value of the actual interaction duration () collected through the human-human study. The comparison showed that was larger than but in a comparable range. The findings of the human-human bimanual cooperative object transport study and subsequent modeling provide a basis for future development of a controller for human-robot cooperative transport of a large object.Applied Science, Faculty ofMechanical Engineering, Department ofGraduat
Photosensitizer-Trapped Gold Nanocluster for Dual Light-Responsive Phototherapy
Photoresponsive nanomaterials have recently received great attention in the field of cancer therapy. Here, we report a photosensitizer-trapped gold nanocluster that can facilitate dual light-responsive cancer therapy. We utilized methylene blue (MB) as a model photosensitizer, gold nanocluster as a model photothermal agent, and a polymerized DNA as the backbone of the nanocluster. We synthesized MB-intercalated gold DNA nanocluster (GMDN) via reduction and clustering of gold ions on a template consisting of MB-intercalated long DNA. Upon GMDN treatment, cancer cells revealed clear cellular uptake of MB and gold clusters; following dual light irradiation (660 nm/808 nm), the cells showed reactive oxygen species generation and increased temperature. Significantly higher cancer cell death was observed in cells treated with GMDN and dual irradiation compared with non-irradiated or single light-irradiated cells. Mice systemically injected with GMDN showed enhanced tumor accumulation compared to that of free MB and exhibited increased temperature upon near infrared irradiation of the tumor site. Tumor growth was almost completely inhibited in GMDN-treated tumor-bearing mice after dual light irradiation, and the survival rate of this group was 100% over more than 60 days. These findings suggest that GMDN could potentially function as an effective phototherapeutic for the treatment of cancer disease
Agile Maneuvers in Legged Robots: a Predictive Control Approach
Planning and execution of agile locomotion maneuvers have been a longstanding
challenge in legged robotics. It requires to derive motion plans and local
feedback policies in real-time to handle the nonholonomy of the kinetic
momenta. To achieve so, we propose a hybrid predictive controller that
considers the robot's actuation limits and full-body dynamics. It combines the
feedback policies with tactile information to locally predict future actions.
It converges within a few milliseconds thanks to a feasibility-driven approach.
Our predictive controller enables ANYmal robots to generate agile maneuvers in
realistic scenarios. A crucial element is to track the local feedback policies
as, in contrast to whole-body control, they achieve the desired angular
momentum. To the best of our knowledge, our predictive controller is the first
to handle actuation limits, generate agile locomotion maneuvers, and execute
optimal feedback policies for low level torque control without the use of a
separate whole-body controller.Comment: 20 pages, 16 figure
Bidirectional modulation of hyperalgesia via the specific control of excitatory and inhibitory neuronal activity in the ACC
Neurons in the anterior cingulate cortex (ACC) are assumed to play important roles in the perception of nociceptive signals and the associated emotional responses. However, the neuronal types within the ACC that mediate these functions are poorly understood. In the present study, we used optogenetic techniques to selectively modulate excitatory pyramidal neurons and inhibitory interneurons in the ACC and to assess their ability to modulate peripheral mechanical hypersensitivity in freely moving mice. We found that selective activation of pyramidal neurons rapidly and acutely reduced nociceptive thresholds and that this effect was occluded in animals made hypersensitive using Freund's Complete Adjuvant (CFA). Conversely, inhibition of ACC pyramidal neurons rapidly and acutely reduced hypersensitivity induced by CFA treatment. A similar analgesic effect was induced by activation of parvalbumin (PV) expressing interneurons, whereas activation of somatostatin (SOM) expressing interneurons had no effect on pain thresholds. Our results provide direct evidence of the pivotal role of ACC excitatory neurons, and their regulation by PV expressing interneurons, in nociception
Boletín de Segovia: Número 61 - 1925 mayo 22
Copia digital. Madrid : Ministerio de Cultura. Subdirección General de Coordinación Bibliotecaria, 200
Unexpected Size Effect Observed in ZnO-Au Composite Photocatalysts
Semiconductor-metal nanocomposites
prepared with well-defined gold nanoclusters, such as Au<sub>25</sub>, Au<sub>144</sub>, and Au<sub>807</sub>, showed size-dependent photocatalytic
activities for the reduction of nile blue and azobenzene. Whereas
the photoreduction of nile blue was directly related with the charge
separation and transfer rate from the photoexcited ZnO to gold nanoclusters,
the photoreaction of azobenzene showed unexpected size effect with
a clear threshold. Mechanistic investigations revealed that the photoreduction
of azobenzene proceeded via a proton-coupled electron transfer process.
The photocatalytic activity of the ZnO-Au nanocomposites was also
dependent on the excitation intensity, demonstrating that the multielectron/multiproton
process was controlled by the charge separation and transfer in the
nanocomposites
Evaluation of Engraftment of Superparamagnetic Iron Oxide-Labeled Mesenchymal Stem Cells Using Three-Dimensional Reconstruction of Magnetic Resonance Imaging in Photothrombotic Cerebral Infarction Models of Rats
Recent Progress of the PAL-XFEL
The X-ray free-electron laser of the Pohang Accelerator Laboratory (PAL-XFEL) was opened to users in 2017. Since then, significant progress has been made in PAL-XFEL operation and beamline experiments. This includes increasing the FEL pulse energy, increasing the FEL photon energy, generating self-seeding FEL, and trials of two-color operation. In the beamline, new instruments or endstations have been added or are being prepared. Overall, beamline operation has been stabilized since its initiation, which has enabled excellent scientific results through efficient user experiments. In this paper, we describe details of the recent progress of the PAL-XFEL