First Electrical Cable Built of a Single Molecule

BER1188B

- Can single molecules be deployed as reliable and effective conductors in the future electronic devices? Seeking the answer to this question we succeeded for the first time to create an electric cable from a single molecule in a systematic and reproducible way. The obtained wires are only 10 Ångstrom (1 nanometer) long, but they represent a prototypical example of a true molecular conductor clamped to the electrodes via the two well-defined “crocodile” clamps of atomic size. We create the wires by lifting one end of the single molecule lying on the atomically clean metal surface with the sharp metal tip vibrating with sub-Ångstom amplitudes. The vibrating tip on one hand plays a role of the second electric contact used for the conductance measurements at the same time it allows us to measure the stiffness of the wire thus controlling its conformation during the liftoff process.

Soda cans squeeze sound on tighter spots

LD13104


- On top of being convenient soda containers, cans are also good acoustic
resonators. Anyone can verify this by blowing air inside an empty can: an
almost pure tone can be heard. In this letter, we prove that a packed
bunch of soda cans behaves as a new sonic material with fascinating
properties. Subject to various tones, the ensemble of cans responds
collectively and creates complex sound patterns. Very interestingly, those
patterns oscillate on spatial dimensions of the order of a soda can, that
is, much smaller than the wavelength of the acoustic waves that excite
them. Generating broad spectrum sounds with low cost computer
loudspeakers, we demonstrate that 1 meter wavelength audible acoustic
waves can be squeezed thanks to the cans onto spots as tight as a few
centimetres. This experiment opens up the possibility to control acoustic
power or send audio messages on dimensions much smaller than the
wavelength. Our approach, evidenced with soda cans for the sake of
simplicity, is very general. It can be realized using many resonator and
is valid for acoustic and elastic waves at any frequency. We believe it
opens up exciting possibilities for the control of audible sound in new
exotic ways, but also more pragmatically for the design of smart sensors,
actuators and MEMS.

Stressed Workers Lead to Relaxed Colleagues

LC13228

- We study the nature of workplace stress from the aspects of human-human interactions. We investigated the distribution of Center for Epidemiological Studies Depression Scale scores, a measure of the degree of stress, in workplaces. We found that the degree of stress people experience when around other highly stressed people tends to be low, and vice versa. A simulation based on a model describing micro-level human-human interaction reproduced this observed phenomena and revealed that the energy state of a face-to-face communication network correlates with workplace stress macroscopically.

Bacteria Swim Faster in Groups

LD13593

- It is a well known fact that in nature many animals exhibit collective behaviours to move more efficiently and save energy. For example, birds fly in flocks when they migrate, fish swim together when they feed, and cyclists ride in a close group during a race to dramatically reduce drag. However, little is known about what happens when we consider collective behaviour in the microscopic world of bacteria. In particular, whether collective swimming is also the most efficient way of moving at the micro-scales, where viscous effects are dominant, is a question that until recently had no answer.

The mystery has been solved by researchers who investigated the collective swimming of bacteria. By measuring the three-dimensional velocity field, they discovered that by moving together bacteria can swim three times as fast, and that the mass transport in the suspension can be considerably improved.

Surprisingly, to achieve this enormous increase in speed, the bacteria used only a tiny amount of additional energy. The study was the first to discover that also for microorganisms collective swimming is the most energy-efficient way of moving and of absorbing oxygen and nutrients in nature.