A program that emits its own python source code when run, i.e. a Quine.

a="a= ;print a[0:2]+chr(34)+a+chr(34)+a[3:]#Another happy return!";print a[0:2]+chr(34)+a+chr(34)+a[3:]#Another happy return!

A version in particular for biologists with added emphasis on the cycle of life:

a="a= ;print a[0:2]+chr(34)+a+chr(34)+a[3:]#Keep studying the miracle of life!";print a[0:2]+chr(34)+a+chr(34)+a[3:]#Keep studying the miracle of life!

[News: Someone linked this text from the Open Source Toolkit: Hardware article collection and channel of PLoS. Thanks.]

I built my first fluorescent microscope. A Leitz Labovert became a surprisingly decent fluorescent microscope for DIY after spending about £100 and 3D printing a few custom parts. It is a simplified design with only a barrier and an excitation filter, LED illumination and no dichroic mirror.

The quality is sufficient for observing fluorescent yeast and in general fairly faint Drosophila embryos in low-to-midrange magnification.

Drosophila embryonic tracheal system, GFP-marked. Weak additional bright-field illumination for embryo outline.

Yeast with nuclear GFP marker.

Fluorescence is short wavelength light in, longer wavelength light out. In principle a fluorescent microscope needs only two parts: 1) a light source that emits light at the excitation, but not at the emission wavelengths of the sample, and 2) a barrier filter, which lets only the emitted longer wavelength light through, so it doesn’t drown out in the excitation light. There are a few details though, and I will start with the barrier filter.

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It maybe a less known fact that the lower cutoff of PCR cleanup and other DNA minipreps may be dialed in by appropriately diluting the binding buffer with water. PCR cleanup kits usually don’t bind fragments below 50-100 bp, depending on the manufacturer. Using water, dilution of the chaotropic salts in the binding buffer sets this limit higher. DNA smaller than the new limit runs through the coloumn, while higher MW DNA adsorbs as before. This can sometimes save the effort of gel purification. Continue reading →