A high-speed magnetic tweezer beyond 10,000 frames per second

Bob M. Lansdorp, Shawn J. Tabrizi, Andrew Dittmore, and Omar A. Saleh

The magnetic tweezer is a single-molecule instrument that can apply a constant force to a biomolecule over a range of extensions, and is therefore an ideal tool to study biomolecules and their interactions. However, the video-based tracking inherent to most magnetic single-molecule instruments has traditionally limited the instrumental resolution to a few nanometers, above the length scale of single DNA base-pairs. Here we have introduced superluminescent diode illumination and high-speed camera detection to the magnetic tweezer, with graphics processing unit-accelerated particle tracking for high-speed analysis of video files. (Click on the link to read more).

Rev. Sci. Instrum. 84, 044301 (2013)

Flow bioreactor design for quantitative measurements over endothelial cells using micro-particle image velocimetry

Chia Min Leong, Abram Voorhees, Gary B. Nackman, and Timothy Wei

Mechanotransduction in endothelial cells (ECs) is a highly complex process through which cells respond to changes in hemodynamic loading by generating biochemical signals involving gene and protein expression. To study the effects of mechanical loading on ECs in a controlled fashion, different in vitro devices have been designed to simulate or replicate various aspects of these physiological phenomena. This paper describes the design, use, and validation of a flow chamber which allows for spatially and temporally resolved micro-particle image velocimetry measurements of endothelial surface topography and stresses over living ECs immersed in pulsatile flow.(Click on the link to read more).

Rev. Sci. Instrum. 84, 045109 (2013)

Creation of quantum-degenerate gases of ytterbium in a compact 2D-/3D-magneto-optical trap setup

Sören Dörscher, Alexander Thobe, Bastian Hundt, André Kochanke, Rodolphe Le Targat, Patrick Windpassinger, Christoph Becker, and Klaus Sengstock

We report on the first experimental setup based on a 2D-/3D-magneto-optical trap (MOT) scheme to create both Bose-Einstein condensates and degenerate Fermi gases of several ytterbium isotopes. Our setup does not require a Zeeman slower and offers the flexibility to simultaneously produce ultracold samples of other atomic species.(Click on the link to read more).

Rev. Sci. Instrum. 84, 043109 (2013)

Ultrafast ultrasonic imaging coupled to rheometry: Principle and illustration

Thomas Gallot, Christophe Perge, Vincent Grenard, Marc-Antoine Fardin, Nicolas Taberlet, and Sébastien Manneville

We describe a technique coupling standard rheology and ultrasonic imaging with promising applications to characterization of soft materials under shear. Plane wave imaging using an ultrafast scanner allows to follow the local dynamics of fluids sheared between two concentric cylinders with frame rates as high as 10 000 images per second, while simultaneously monitoring the shear rate, shear stress, and viscosity as a function of time.(Click on the link to read more).

Rev. Sci. Instrum. 84, 045107 (2013)

Production of large volume, strongly magnetized laser-produced plasmas by use of pulsed external magnetic fields

B. Albertazzi, J. Béard, A. Ciardi, T. Vinci, J. Albrecht, J. Billette, T. Burris-Mog, S. N. Chen, D. Da Silva, S. Dittrich, T. Herrmannsdörfer, B. Hirardin, F. Kroll, M. Nakatsutsumi, S. Nitsche, C. Riconda, L. Romagnagni, H.-P. Schlenvoigt, S. Simond, E. Veuillot, T. E. Cowan, O. Portugall, H. Pépin, and J. Fuchs

The production of strongly magnetized laser plasmas, of interest for laboratory astrophysics and inertial confinement fusion studies, is presented. This is achieved by coupling a 16 kV pulse-power system, which generates a magnetic field by means of a split coil, with the ELFIE laser facility at Ecole Polytechnique. (Click on the link to read more).

Rev. Sci. Instrum. 84, 043505 (2013)

Note: Rapid offset reduction of impedance bridges taking into account instrumental damping and phase shifting

C. M. van der Wel, R. J. Kortschot, I. A. Bakelaar, B. H. Erné, and B. W. M. Kuipers

The sensitivity of an imperfectly balanced impedance bridge is limited by the remaining offset voltage. Here, we present a procedure for offset reduction in impedance measurements using a lock-in amplifier, by applying a complex compensating voltage external to the bridge. This procedure takes into account instrumental damping and phase shifting, which generally occur at the high end of the operational frequency range. (Click on the link to read more).

Rev. Sci. Instrum. 84, 036109 (2013)

Invited Review Article: Large ring lasers for rotation sensing

Karl Ulrich Schreiber and Jon-Paul R. Wells

Over the last two decades a series of large ring laser gyroscopes have been built having an unparalleled scale factor. These upscaled devices have improved the sensitivity and stability for rotation rate measurements by six orders of magnitude when compared to previous commercial developments. This progress has made possible entirely new applications of ring laser gyroscopes in the fields of geophysics, geodesy, and seismology. Ring lasers are currently the only viable measurement technology, which is directly referenced to the instantaneous rotation axis of the Earth. The sensor technology is rapidly developing. This is evidenced by the first experimentally viable proposals to make terrestrial tests of general relativistic effects such as the frame dragging of the rotating Earth.

Rev. Sci. Instrum. 84, 041101 (2013)