A bio-indicator for air pollution

Growth of lichens on trees: Bio-indicator for clean and contaminated air. Lichens are dual beings, developed from a symbiosis of algae and tiny fungi. Fungi and algae alone are dependent on moisture.

Rock from the depths of the earth

Basalt belongs to the group of igneous rocks. Igneous rocks are formed when hot liquid magma (lava) from the depths of the earth, is forced to the surface by volcanic forces and flows like a mudslide directly over the earth's surface, where it cools down and solidifies. Basalt is used in the road and hydraulic engineering in particular, as a result of its favorable mechanical properties.

Basalt as (geological) young volcanic rock, gets a fine-grained structure when cooling down relatively rapid. It is interspersed with small circular hollow vesicles. The color ranges from dark gray via gray-black to dark blue. Basalt is very solid and

Introduction to Darkfield illumination - Slider solution

For transparent samples in light microscopy, dark field illumination is a simple and affordable contrast method. The idea of this technique is to display and to emphasize border structures, means abrupt changes of the refractive index within the sample. Especially for single-celled organism in fresh or sweet water environments, with a refractive index close to water, this contrast method gives aesthetic and informative images.

Dark field emphasizes borders and isolated, single structures, flagella of protozoa and tiny particles. The comparison of a diatom sample in bright field and dark field clearly shows this:

How such an image is achieved? We need to eliminate the direct light which ordinarily passes the specimen and which is responsible for the bright background in bright field illumination. For objectives with a Numerical Aperture ≤ 0.65 this