Wednesday, 4 July 2018

Muscovite under polarization microscope

Muscovite has an anisotropic crystal structure, with two optical axis and a negative optical sign. The images and video taken with a polarization microscope with crossed polarizers and the Bertrand lens in place, are showing interference images (without lambda filter) in the plane perpendicular to the bisector between the two optical axes.To obtain these images, a thin slice of muscovite was split off from the crystal and taken for examination. Light entering this slice of crystal, produces the typical interference images for this type of crystal.

Click here for more information about Muscovite Mineral.

Monday, 2 July 2018

Basics of Light Microscopy: Incident Light Microscopy for opaque samples (I)

A closer look on Incident Light Microscopy reveals a new and noticeable fact. In a compound microscope for opaque samples, the objective plays two roles. First, like in a Transmitted light setup the objective is part of the imaging process. Quality and performance of the objective are essential elements to get reliable and “close-to-truth” results. 

Secondly, the objective additionally is part of the illumination system. Light from the lamp house passes the illumination axis and is deflected by a 45° orientated semi-transparent mirror. Sent through the objective, the light is reflected by the sample surface and brings back sample information to the eyepieces/camera. For a beginner it is difficult to accept that both illumination and imaging processes do not interfere visually. 

Monday, 18 June 2018

A pest on grapes

Uncinula necator or powdery mildew, a basidiomycete, is a pest on grapes. Its septate hyphae forms a mycelium on the surface of the leaves similar to a spider web. Special hyphal branches, the haustoria, penetrate the host cells to absorb food substances, thereby weakening the grape and reducing the harvest.

Wednesday, 6 June 2018

A medicinal parasite

Mistletoe (Viscum album), sinkers in host tissue, longitudinal.

The evergreen, spherical shrub of about 1 m in diameter grows on different trees. As a semi-parasite the mistletoe assimilates with its leaf green. The sinkers of the mistletoe penetrate deep into the wood body of the host plants and withdraw only water and mineral salts from the host, but this causes the part above the infestation site to suffer. The opposite, oblong-ovate leaves evaporate only a little water due to their leathery texture.

Wednesday, 16 May 2018

Computer chips out of sand

Sand is very rich in the element silicon. This substance can have a very pure grid form, which gives interesting electrical properties. Such a grid consists of almost only silicon atoms. Some of these atoms can be replaced by boron or phosphorus, resulting in semiconductors or transistors in the grid.

Wednesday, 2 May 2018

Just another worm

Tubifex tubifex, is a ringworm from the Tubificidae family. The scientific name of the species was first published for the first time in 1774 by Müller. It inhabits the sediments of lakes and rivers on several continents.

Wednesday, 18 April 2018

Cracks in the pipe

The cracks in the austenitic stainless steel sample on the picture below are most likely a case of Stress Corrosion Cracking (SCC). SCC is the cracking induced from the combined influence of tensile stress and a corrosive environment (such as chlorides). The impact of SCC on a material usually falls between dry cracking and the fatigue threshold of that material. The required tensile stresses may be in the form of directly applied stresses or in the form of residual stresses. The problem itself can be quite complex.

Thursday, 5 April 2018

Old but indispensable

A polarization microscope can be used to identify the mineralogical composition of geological materials in order to help reveal their origin and evolution. Some of the properties and techniques used include: refractive index, birefringence, Michel-Lévy interference color chart, extinction angle, conoscopic interference pattern (interference figure), Becke line test, wave plate etc.

Wednesday, 7 March 2018

Prehistoric nail imprints

On the images, a hand formed pottery fragment from the Michelsberg culture, Middle Neolithic period(4300 - 3500 BC) is shown. The Michelsberg culture is responsible for some of the oldest types of pottery in Europe, which is seen as a typical element of this culture. This pottery is generally found on hilltops, giving the impression of the presence of former fortified settlements. This impression is reinforced by findings of many waste pits with very different content and interruptions in the trenches that are interpreted as gates.

Thursday, 22 February 2018

About Polarization

Utilizing the polarization method in light microscopy reveals a specific kind of information about the sample. Applying this contrast method, we less often talk about structure size and shape, resolution power or even a specific staining. In case of transparent samples, polarization contrast in first instance has one subject in mind: the potential BIREFRINGENCE of the sample and its implications on a structural insight.

BIREFRINGENCE is a widespread phenomenon, found in nature as well as in man-made materials. Starch grains, fibers, crystals and minerals, plastic sheets and die cast components, the structural basis is always the same: embedded within an amorphous matrix, structures with an intrinsic geometric pattern cause an impact on the speed of light and its oscillating direction when sent through the sample.

Chemical cristals

Wednesday, 21 February 2018

A sponge a phoenix?

All sponges possess a remarkable ability to regenerate lost parts. A piece cut from the body of a sponge is capable of growing into a complete sponge. This power of regeneration helps the sponges to repair the damage caused in the harsh environment.

Wednesday, 7 February 2018

Transition of lava on Mount Etna

Limonite is a mineral consisting of various iron oxides. Limonite is yellow, ochre, brown or blackish colored by iron oxide.

Volcanic rock of Mount Etna can be transformed into Limonite, which is called like that because of its yellow brownish color. The Limonite is mainly produced by the oxidation of iron containing lava rocks by weathering, facilitated by splitting and pulverizing of the rock because of the penetration of the roots of vegetation enabling oxygen and humidity to enter.

Wednesday, 24 January 2018

Algae with an eye

Euglena species are often abundant in calm waters, where they can be present in such numbers, that the surface of ponds and ditches can have a green or red color.

Euglena is commonly studied in biology classes because it has both plant (it has chloroplasts and so can photosynthesize) and animal (it moves and can eat) characteristics. Depending on conditions, photosynthesis or eating can predominate. It is a single celled creature with a large flagellum (not visible in this video, see below) that lives in fresh water. It is generally elongate but can change its shape quite dramatically during so-called euglenoid movement. It swims using its flagellum and can orientate itself with respect to gravity and light.

Wednesday, 10 January 2018

Wood Collectors?

Wood Collectors primarily collect samples of plants from the group of seed plants, Spermatophytes. This can be either softwood (Gymnosperms) and hardwood (Angiosperms)

Wood however, is composed of various types of tissue, which wood collectors should be able to recognize and name in order to assign a particular species. Tissue which occurs abundantly in one species and is an important feature, can be completely absent in a different species. To see the right features, to name and describe them, is the most important for determination. The recognition of wood types can be done, among others, by the study of micro preparations.

Micro preparations of wood are thin slices of wood of 10-15 microns thick, cut into 3 planes:

a) In the transverse plane for example, the vessels, the distribution of vessels, the type and the distribution of the parenchyma (ground tissue), the number of rays per mm and the thickness of the fiber wall can be seen.