Physics Commons^™

Bacterial Growth And Motility In Sub-Micron Constrictions, Jaan Männik, Rosalie Driessen, Peter Galajda, Juan E. Keymer, Cees Dekker

Jaan Männik

In many naturally occurring habitats, bacteria live in micrometer-size confined spaces. Although bacterial growth and motility in such constrictions is of great interest to fields as varied as soil microbiology, water purification, and biomedical research, quantitative studies of the effects of confinement on bacteria have been limited. Here, we establish how Gram-negative Escherichia coli and Gram-positive Bacillus subtilis bacteria can grow, move, and penetrate very narrow constrictions with a size comparable to or even smaller than their diameter. We show that peritrichously flagellated E. coli and B. subtilis are still motile in microfabricated channels where the width of the channel …

Chemically Induced Conductance Switching In Carbon Nanotube Circuits, Jaan Männik, Brett R. Goldsmith, Alexander Kane, Phillip G. Collins

Jaan Männik

The chemical reactivity of carbon nanotubes in H2SO4 is investigated using individual, single-walled carbon nanotubes (SWNTs) incorporated into electronic devices. Exploiting the device conductance as a sensitive indicator of chemical reactions, discrete oxidation and reduction events can be clearly observed. During oxidation, a SWNT opens circuits to a nanometer-scale tunnel junction with residual conduction similar to Frenkel-Poole charge emission. When electrochemically reduced, a SWNT returns to its original conductance. This redox cycle can be repeated many times, suggesting a novel chemical method of reversibly switching SWNT conductivity.

DOI: 10.1103/PhysRevLett.97.016601

Crossover From Kramers To Phase-Diffusion Switching In Moderately Damped Josephson Junctions, Jaan Männik, S. Li, W. Qiu, W. Chen, V. Patel, S. Han, J. E. Lukens

Jaan Männik

We have measured and propose a model for switching rates in a hysteretic dc superconducting quantum interference device (SQUID) in the regime where phase-diffusion processes start to occur. We show that the switching rates in this regime are smaller than the rates given by Kramers’ formula due to retrapping of the Josephson phase. The retrapping process, which is affected by the frequency dependent impedance of the environment of the dc SQUID, leads to a peaked second moment of the switching distribution as a function of temperature. The temperatures where the peaks occur are proportional to the critical current of the …

Effect Of Measurement On The Periodicity Of The Coulomb Staircase Of A Superconducting Box, Jaan Männik, J. E. Lukens

Jaan Männik

We report on the effect of the backaction of a single Cooper pair transistor electrometer (E) on the charge state of a superconducting box (B). The charge is e periodic in the gate bias of B when E is operated near voltages 2Δ/e or 4Δ/e. We show that this is due to quasiparticle poisoning of B at a rate proportional to the number of quasiparticle tunneling events in E per second. We are able to eliminate this backaction and recover 2e-charge periodicity using a new measurement method based on switching-current modulation of E.

URL: http://link.aps.org/doi/10.1103/PhysRevLett.92.057004

DOI: 10.1103/PhysRevLett.92.057004