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Category Archives: Research

Microscope slide holder

A plate for holding 76 mm x 26 mm glass slides in the microscope. My first ever 'real' drawing with LibreCAD (that website has been down for two days now, so try also librecad on sourceforge). Drawing in PDF: chamber_holder Drawing in DXF: plate_v2.dxf

Lambda exonuclease video

The fourth paper from my thesis, entitled "Dual-trap optical tweezers with real-time force clamp control", has just been published online by Review of Scientific Instruments: http://link.aip.org/link/doi/10.1063/1.3615309 Here's a video from the paper. We are holding on to two micron sized plastic spheres with laser-beams (shown in the video as green/cyan cross-hairs). The lower beam/trap is [...]

Piled Higher'n Deeper

Finally got my PhD diploma yesterday. Yay! The thesis looks like this, and is available online.

Force-clamp feedback for optical tweezers

A ~16 um long DNA-molecule is tethered between optically trapped plastic beads. Beads are held by a stationary trap (lower blue cross-hairs) and a steerable trap (upper green cross-hairs). The graphs on the right show the measured force (red) and the force set-point (blue) (top), the distance between the traps (middle), and the force-extension curve [...]

Michelson interferometer

Tried this simple Michelson interferometer for measuring the error of a 100mm translation stage yesterday. The interferometer and stage are mounted to the same optical table, but there's still a fair amount of vibration of the measurement corner-cube which causes instability in the signal when the stage is not moving. Some sample data here: interf_data. One [...]

One More Feedback Paper

FPGA-based real-time position-clamp control in optical tweezers, The Sequel: doi:10.1063/1.3257693 (first part here)

Fluorescent DNA

Some very early testing of fluorescence imaging in our optical tweezers instrument. A 10 kb long piece of DNA (ca 3 um long when stretched) is held between two optically trapped microspheres. The DNA is coated with a fluorescent dye (SYBR-gold) which is exited by a 488 nm blue laser and the fluorescence signal is [...]

Colors

Fluorescent DNA

I'm testing an EMCCD camera. This is a video of fluorescently labeled DNA through a 100x epi-fluorescence microscope. Or you can try a slightly better quality wmv-download (82 Mb) Once we've had time to practice some more, it should look much cooler, something like these DNA-curtains, or DNA-ejection from bacteriophage lambda. But it's a start. Also [...]

Uniform random points in a circle using polar coordinates

I need this seldom enough to forget how it's done - but then it's annoying to have to think/google for the solution again when I do need it... So I'll document here. The task is to generate uniformly distributed numbers within a circle of radius R in the (x,y) plane. At first polar coordinates seems [...]