Wednesday, 28 May 2014

There is history in limestone

Limestone is a sedimentary rock, and along with shale, is one of the best preservers of fossils. Over time, sedimentary rock presses down around what were once living things to preserve the basic outline of their appearance and physical characteristics. Crack open a large piece of limestone or walk a beach covered with limestone rocks and you are almost guaranteed to find a fossil. If you don't find one, rest assured that they are there, lending the calcium carbonate from bones, exoskeletons and shells to the limestone itself.

Limestone forms when calcite from the water crystallizes or when fragments from coral and shells cement together. Limestone is a type of sedimentary rock that contains fossils in the form of sea creatures. Entire reef formations and communities of organisms are found preserved in limestone. The types of fossils found in limestone include coral, algae (see images), clams, brachiopods, bryozoa and crinoids. Most limestone forms in shallow tropical or subtropical seas. In some cases, fossils make up the entire structure of limestone.

Source: eHow

Thursday, 22 May 2014

Basics of Light Microscopy: Resolution & Magnification

The drum battle between Ginger Baker and Art Blakey on the occasion of the Olympic Games 1972 in Munich revealed a clear message: precision rules power. Transferred to the world of optics, this message means: resolution rules magnification.

Resolution may be defined as the ability of a reproducing system to separate individual signals, no matter what nature they are: e.g. optical or acoustical. The jazz drummer Art Blakey (like many jazz drummers) was able to accelerate his playing to the max: the audience was not able to separate individual beats on his drums, or, in other words, the resolution power of the human ear was not able to “resolve” single beats of his playing.

In widefield microscopy, resolution is understood as the ability of the microscope hardware, means optics, to separate individual events in a distance range down to roughly 220 microns. It is the objective which is the key element of any resolution calculation. Eyepieces and downstream digital cameras can only process the information flux which has entered the objective. The larger the opening angle of the objective, the more information is available for data processing.

The schoolbook tells us that the Numerical Aperture of an objective, indicated on the objective sleeve, is directly accessible for a calculation of the minimum distance which can be resolved. The following sequence of 20X lenses, starting from a Plan Achromat up to a Plan Apochromat, displays NAs from 0.40 up to 0.65, thus increasing resolving power.

The following formula has to be applied:

d min is the minimum distance which can be resolved, NA the numerical aperture of objective and condenser respectively. In an ideal case both angles are identical (NA is the sinus value of a half opening angle of the objective). So taking into consideration that the human eye is most sensible in the range of 550nm (green), for a 20X objective we may calculate as follows:

Plan Achromat 20X
d min = 550nm/2 x 0.40 = 688nm

Plan Fluorite 20X
d min = 550nm/2 x 0.50 = 550nm

Plan Apochromat 20X
d min = 550nm/2x 0.65 = 423nm

So the resolution power for a 20X objective will be maximum 423nm. Taking into consideration that the aperture diaphragm of a condenser will have to be closed for contrast reasons, this ideal calculation will not be verified. But it gives some idea about the limits of conventional light microscopy.

It may be worth to mention that the user can do a lot to maximize the image results. Any deviation from the standard cover slip thickness of 0.17mm, any overload of embedding media of the sample (which acts an additional cover slip), any grease or oil on the front lens of a dry objective will have a deep impact on the image result. 

The above images display a diatom, a monocellular alga, enclosed in a silica exoskeleton with tiny pores of specific size. The left image resolves perfectly the arrangement of the pores, while the right image with the same magnification power is not able to display details.

Conclusion: Resolution, not magnification is the key issue.

Wednesday, 14 May 2014

A blood serious affair!

Arteries are the blood vessels that deliver oxygen-rich blood from the heart to the tissues of the body. Each artery is a muscular tube lined by smooth tissue and has three layers:

  • The intima, the inner layer lined by a smooth tissue called endothelium
  • The media, a layer of muscle that lets arteries handle the high pressures from the heart
  • The adventitia, connective tissue anchoring arteries to nearby tissues

The largest artery is the aorta, the main high-pressure pipeline connected to the heart's left ventricle. The aorta branches into a network of smaller arteries that extend throughout the body. The arteries' smaller branches are called arterioles and capillaries. The pulmonary arteries carry oxygen-poor blood from the heart to the lungs under low pressure, making these arteries unique.

Arteriosclerosis is hardening and thickening of the walls of the arteries. Arteriosclerosis can occur because of fatty deposits on the inner lining of arteries (atherosclerosis), calcification of the wall of the arteries, or thickening of the muscular wall of the arteries from chronically elevated blood pressure. Atherosclerosis is a progressive disease that is characterized by a buildup of plaque within the arteries. Plaque is formed from fatty substances, cholesterol, cellular waste, calcium, and fibrin. Plaque may partially or totally block the blood's flow through an artery. Two things can happen: bleeding into the plaque, or formation of a clot on the surface of the plaque. If either of these happens and blocks the artery, a heart attack or stroke may result.

Sources: WebMD, Franklin Institute

Tuesday, 13 May 2014

How to clean your microscope

Do not disassemble your microscope

Disassembly may significantly affect the performance of the instrument, and may result in electric shock or injury and will void the terms of the warranty.
Never attempt to dismantle any parts other than the ones described below. If you notice any malfunction, contact your nearest Motic supplier.


Keeping the optics of your microscope clean is essential for obtaining clear images.
Choosing the best cleaning method depends on the nature of the optical surface and type of dirt.

Dirtiness on the image may be caused by the following variables:
  • Dirt on the outer or inner eyepiece lens.
  • Dirt on the front lens of the objective.
  • Dirt on the upper lens of the condenser.
  • Dirt on the surface of the sample slide glass.
  • Dirt on the upper lens of illuminator.
  • Dirt on other optical components of the microscope such as mirrors, lamps, filters, intermediate lenses …
In the case of microscopes with a camera attached to it:

  • Dirt on the camera adapter.
  • Dirt on the protection filter of the camera sensor.

For Eyepieces with reticules:

  • Dirt on the outer or inner reticle glass.

Dirt image | Clean image

Objectives are the optical component of the microscope that require the most maintenance. Because for their actual use, they can get dirty easily.

For objectives that work without oil (dry): The first step is to carefully unscrew the objective from the nosepiece.

In order to make things easier and safer, we can screw the objective on one of the objective cases supplied with microscope. By doing it this way, the objective will be in a stable position avoiding possible falls.

 1  We will proceed by cleaning it using pressurized dry air - or an air gun if available – and, if after this is done we still observe spots of dust or dirt,  2  we will clean them with a cotton swab dampened with a low graduation of alcohol 70% or with a mixture of alcohol and ether (ratio alcohol: 3 and ether: 7).  3  With a spiral movement (starting from the center of the lens) we will then clean the surface of the lens.  4  We will then dry its surface by using pressurized dry air and we will check that the lens is clean either with the help of a magnifying glass or by screwing the lens back on the revolving nosepiece of the microscope.

For objectives that work with immersion oil it is essential to clean them after each observation session. To clean it we will use a cleaning cloth for lenses slightly dampened with a low graduation of alcohol. We will proceed by cleaning the frontal objective lens (normally 100X-Oil or 50X-Oil). It is important to make a preventive maintenance also for those objectives that work at a very close distance to the sample. With this we mean the 40X and 60X objectives, which may accidentally get in contact with the immersion oil.
Users of inverted biological microscopes have to take special care with the objectives because they can get dirty with dust or liquid that spills from the sample/s. In this case we recommend you check the status of the objectives accurately at least once a week.

For optical components such as eyepieces, condensers, filters, etc. we recommend using the same cleaning method. First cleaning it with pressurized dry air, then cleaning it with a cotton swab or a cleaning cloth for lenses (slightly moistened with a low graduation of alcohol) and finally drying it with pressurized dry air.
Once the cleaning process is finalized if the image is still not clear, you can either contact us or you can contact your Motic supplier.

For users that have a digital camera mounted on the microscope and whom observe dirt on the digital image, it is important that the first step is to proceed with objectives maintenance, as explained above. If the dirt persist, we have to find out if it has to do with the microscope or the camera. To check this we simply have to loosen the adapter and rotate the camera. If the dirt rotates whilst turning it, then it means that it is in the microscope. If it does not rotate, then it is either in the adapter or in the protection filter of the sensor. If the dirt is on the surface lens of the adapter then you can use the same cleaning method that we have explained above, but if the dirt is in the protection filter of the sensor then use pressurized dry air only. If the dirt persist you can either contact us or you can contact your Motic supplier.


The mechanical components of the microscope require less maintenance than the optical components. Our first maintenance advice is to use the dust cover provided with the microscope, this way we will avoid the accumulation of dust on the microscope.

If we wish to clean the stand or the specimen holder, we will simply use a cleaning cloth moistened with soap diluted in distilled water. After this we will proceed in perfectly drying the entire surface of the microscope. You have to take special care with the electrical components of the microscope such as the ON / OFF switch, the dimmer, the lamp holder…
If there are grease stains we can use the same cloth moistened with a low graduation of alcohol.

If you face any problems related to the maintenance of your microscope, please contact us. Our technicians will gladly help you solve your maintenance issue/s.