Wednesday, 17 October 2018

Basics of Light Microscopy: Incident Light Microscopy for opaque samples (II) - Dark Field

In the first part of our Incident Light Microscopy post we already explained the double function of the microscope objective in this kind of application field.

Playing an essential part in the imaging process is the task of every microscope objective. The manufacturer pays a lot of attention and spends remarkable efforts in creating a glass hardware for reliable and “close-to-truth” image results.

In incident light applications, the objective is additionally part of the illumination system. The lamp house sends light horizontally through the illumination axis. A semi-transparent mirror with a 45° orientation deflects the light and sends it through the objective. After reflection from the specimen surface, the light brings back sample information to the eyepieces and/or camera.

For the Darkfield method in an Incident light setup, this description is also valid. We just should know one more fact about optical reflection: The angle of Incidence is equivalent to the angle of Reflection.

Thursday, 11 October 2018

Selecting the right microscope

BA Elite Series

Category: Advanced Transmitted Light Microscopes

Target specimen: Transparent samples (sections, smears, emulsions, water samples) from Biology & Medicine; rarely from Industry

Target customer: Lab technicians

This comparison is an approach for classifying different microscope models in a defined performance range. Here we are talking about Motic’s BA Elite series of Advanced Transmitted light microscopes, meant for routine work in university and biomedical lab. The comparison is meant to help you in finding a suitable solution for your lab.

The following chart is based on the specifications of the basic outfit for each model and its upgrade options. Our rating of the single specifications rests upon an individual understanding of the actual numerical values. This is a subjective rating, and we understand that each person might have its own opinion.

BA SERIES - Comparison Chart

Wednesday, 10 October 2018

We are not alone

In our body and on our skin live a lot of bacteria. On each human cell there are ten bacterial cells. This total of bacteria on and in our body is also called microbiome. Most of these are found in the large intestine: the intestinal flora. In an adult, the intestinal flora consists of 1014 (which are 100,000,000,000,000 bacteria). 99% thereof is strictly anaerobic.

These bacteria are useful:
  • The bacteria in the intestine treat indigestible vegetable food residues (fibers). This releases substances that stimulate the intestinal movement. 
  • In addition, the intestinal flora is important for the production of vitamin K. Vitamin K is absorbed into the blood through the intestinal mucosa. Vitamin K plays an important role in blood clotting. 
  • The entire intestinal wall is ‘occupied’ with bacteria. As long as there are enough good bacteria present in the intestinal flora, the bad ones have less chance to develop. 
  • In addition, there are many immune cells in your intestine. Your intestinal flora and your immune cells can affect each other. This interaction has an effect on your defense. For your immune system it is important to have many good bacteria in your intestines. 

Studying our intestinal flora has been very difficult until recently with classical culture and determination techniques. DNA research provided a solution and reading this from the DNA codes becomes faster and cheaper.
Because there are permanent bowel residents that are also easy to determine, like Escherichia coli and Streptococcus faecalis, these are used to detect contamination by feces. These bacteria are well recognizable in the pictures.

Source: Microbiology, Ine Wiersema
Prepared slide by Lieder

Tuesday, 2 October 2018

Seeing the effect of radiation damage

The rock matrix contains quartz, plagioclase feldspar, microcline feldspar and biotite mica. The greenish brown flake of biotite shown in the centre exhibits many dark brown circular features resembling cigarette-type burns. These features are known as pleochroic halos and are a diagnostic feature of biotite. These halos are interesting as they are isotropic compared to the surrounding material which is anisotropic. The halo in the centre of field shows a small brightly coloured crystal of zircon which causes the dark brown effect due to a process called metamictization. This process is the radioactive decay and destruction of the crystal structure surrounding the zircon and the affected area becomes amorphous and hence isotropic.

Zircon is a well-known mineral of many colours with a brilliant lustre with good hardness to make it a desirable gem. In its natural setting it contains slight traces of radioactive elements which cause metamictization. The level of radioactivity is so small and poses no risk when used in jewellery.

MOTIC equipment used: B1 Series microscope with attachable rotating stage and polarising/analyser accessories - Plan 4X achromatic objective with 10X WF 18mm eyepieces and Moticam X camera.