The secret of a steady hand is tightening the right muscles.
Controlling the stiffness of some of our muscles lets us manage tricky feats of manipulation, such as keeping a screwdriver in a screw, researchers have found1. We tune the stiffness to oppose motions in the direction of instability, such as the sideways slips that would let the screwdriver slide out of the slot.
Although demanding on the brain, this is the most energy-efficient strategy, say Mitsuo Kawato of ATR Human Information Science Laboratories in Kyoto, Japan, and co-workers. Tightening all the muscles involved in a task reduces errors, but uses more energy. So the central nervous system learns from experience to contract only the muscles controlling motions in the direction of the most detrimental errors.
PHILIP BALL | Nature News Service
To show that the central nervous system uses stiffness changes - called impedance control - to regulate unstable manipulations, Kawatos team asked seated volunteers to make straight, horizontal arm movements from some starting position to a target position in front of them. If their movement strayed from a straight line, a robotic system attached to their forearm pushed them even further off course, forcing them to compensate.
Initially, the robot pushed subjects way off course. But after 100 or so trials, they learnt to counteract it, and most hit the target. By measuring the small deviations and the stabilizing forces the subjects arms exerted on the robotic system, the researchers estimated changes in muscle stiffness.
They found that the training runs taught subjects to tighten the muscles that control side-to-side movements more than those governing forward movements. In other words, the stiffening was tailored to resist the deflections that the robotic system produced. Muscles controlling backwards and forwards motions, which did not take the arm away from the intended path, stayed more loose.
PHILIP BALL | Nature News Service
A new method for the 3-D printing of living tissues
16.08.2017 | University of Oxford
Bergamotene - alluring and lethal for Manduca sexta
21.04.2017 | Max-Planck-Institut für chemische Ökologie
Controlling electronic current is essential to modern electronics, as data and signals are transferred by streams of electrons which are controlled at high speed. Demands on transmission speeds are also increasing as technology develops. Scientists from the Chair of Laser Physics and the Chair of Applied Physics at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have succeeded in switching on a current with a desired direction in graphene using a single laser pulse within a femtosecond ¬¬ – a femtosecond corresponds to the millionth part of a billionth of a second. This is more than a thousand times faster compared to the most efficient transistors today.
Graphene is up to the job
At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.
Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
26.09.2017 | Life Sciences
26.09.2017 | Physics and Astronomy
26.09.2017 | Information Technology