8,965 research outputs found
Chiral Casimir Forces: Repulsive, Enhanced, Tunable
Both theoretical interest and practical significance attach to the sign and
strength of Casimir forces. A famous, discouraging no-go theorem states that
"The Casimir force between two bodies with reflection symmetry is always
attractive." Here we identify a loophole in the reasoning, and propose a
universal way to realize repulsive Casimir forces. We show that the sign and
strength of Casimir forces can be adjusted by inserting optically active or
gyrotropic media between bodies, and modulated by external fields.Comment: 12 pages, 6 figure
Axial Casimir Force
Quantum fluctuations in vacuum can exert a dissipative force on moving
objects, which is known as Casimir friction. Especially, a rotating particle in
the vacuum will eventually slow down due to the dissipative Casimir friction.
Here, we identify a dissipationless force by examining a rotating particle near
a bi-isotropic media that generally breaks parity symmetry or/and time-reversal
symmetry. The direction of the dissipationless vacuum force is always parallel
with the rotating axis of the particle. We therefore call this dissipationless
vacuum force the axial Casimir force.Comment: improved main text and appendice
Microfluidic polymerase chain reaction
We implement microfluidic technology to miniaturize a thermal cycling system for amplifying DNA fragments. By using a microfluidic thermal heat exchanger to cool a Peltier junction, we have demonstrated rapid heating and cooling of small volumes of solution. We use a miniature K-type thermocouple to provide a means for in situ sensing of the temperature inside the microrefrigeration system. By combining the thermocouple, two power supplies controlled by a relay system, and computer automation, we reproduce the function of a commercial polymerase chain reaction thermal cycler and demonstrate amplification of a DNA sample of about 1000 base pairs
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