The foot is a limb that is not given much importance when compared to other vital organs such as the brain or heart. However, the foot is a very complex mechanical structure that is made of 26 bones, 33 joints, and more than 100 muscles and ligaments. About a quarter of the bones in the human body and about a fifth of the joints are found in our two feet. That is why Leonardo da Vinci described the human foot as an engineering and artistic masterpiece.

A healthy person takes about 5,000 steps a day. Given a life of eighty years, a person takes about 150 million steps throughout their life. Assuming that each step is 75 cm, a person walks about 110,000 kilometers throughout his life. This corresponds to walking around the equator about 3 times. Apart from that, a typical person stands for around 2-4 hours a day. During all these activities, the human foot carries the entire body’s weight. In standing position, body weight is supported by two feet while activities such as walking and running are done by only one foot for a certain period of time. While standing, the feet carry 100% of their body weight, while walking, this rate rises up to 150%. While walking, the foot that needs to be lifted from the ground approaches the ground again with an acceleration in the same direction as gravity. Therefore, the impact force at the moment the foot touches the ground corresponds to 150% of a person’s body weight. In cases of severe effects such as running and jumping, this force easily increases up to 5 times the body weight and up to 10 times in some people. For a person weighing 70 kilograms, this force can be 105 kg (or about 1050 Newton) in walking, and easily 350 kg (or about 3500 Newton) in running or jumping. Assuming that a person walking for an hour takes 5,000 steps, the foot pulls a total of about 500 tons of load (5,000 steps x 105 kg). In running, this figure will increase approximately three times.

The foot has been created with a wonderful mechanical and construction design that is able to consistently sustain such high loads. The bones and muscles of the foot add two different belt designs to it. One of them, the structure called the longitudinal belt starts from the heel bone (calcaneus) and ends with its metatarsal bones (Figure 1). Some researchers claim that the long arch is divided into two parts as the inner (medial arch) and the outer arch (lateral arch). However, both structures resemble bridges built in arches. The second arch on the foot is called the transverse arch. This belt is perpendicular to the long belt from the right side of the foot to the left side and is shorter in length (Figure 2).

Therefore, the foot is a marvelous structure consisting of roughly two arches. This structure of the foot can be compared to arch bridges or a dam. The arch structure is known as the strongest structure against steep loads in construction areas due to the robustness of the designs against compression forces in cases of vertical loading. Therefore, hydroelectric dams are constructed in the form of arches or arcs in order to make the most resistant model against hydrostatic pressure.

The arch structure of the foot is very flexible and can also move up and down like a car suspension and acts as a shock absorption. If there was no such structure on the foot, the impact forces during walking and running activities would be higher and cause chronic foot pain. The flatfoot complication is a result of a damage in the arch structure in the foot which comes from birth or develops afterwards. Flatfoot patients are often unable to perform long-term activities and experience foot pain as well as complications in other organs of the body.

Our feet’s arch structure is not the only factor involved in shock absorption that is designed against mechanical forces. The layer of fat on the bottom of the foot also contributes to this process. In a healthy person, this fat layer, which has a height of 2.5 cm under the heel, drops to 5-7 mm in the front part of the foot. It also helps to distribute the vertical and horizontal forces caused by standing or walking evenly on the sole of the foot. At the same time, it serves as a source of heat insulation and helps protect our feet from hot or cold surfaces. In some diseases such as diabetes, in which this fat layer melts or decreases, wounds called foot ulcers can develop because the shock absorption and load distribution get damaged. Mechanical pressure is calculated by dividing the amount of mechanical force by the surface area on which it is applied, meaning that smaller surfaces areas are subjected to more pressure. This is why very tiny needles, despite weighing almost nothing, can pierce our skin and cause pain. Similarly, damage to the fat layer under the foot causes the forces applied under the foot to act on a limited surface area. For example, the reduction of fat in the area just below the heads of the metatarsal bones reduces the “cushioning” effect in this area and causes a pressure in high values. This extra pressure can cause tissue damage along with the aforementioned foot ulcers.

Such a situation that will cause pain in a normal person cannot be felt by many diabetics. If diabetes is not well controlled, neuropathy or a “lack of feeling” may occur as a complication. Dead nerve cells become unable to feel pain which can result in people not knowing about harm that is being done to their body. Diabetic patients who develop neuropathy would not feel fatty layer damage and accompanying high pressure values whereas a typical person normally would. Untreated foot ulcers can become infected and can turn into gangrene. Since the gangrenous foot has to be cut, diabetes unfortunately causes a large number of amputations. Such amputations are sadly quite frequent throughout the world due to diabetic neuropathy. Dr. Paul Brand, who studied diabetic foot ulcers, defined pain as a gift from God that no one wanted. Sometimes, what we do not like might be better for us (Qur’an 2:216); likewise, pain can cause a lot of trouble to people but it can also alert us of dangers and harm to our bodies.

Thus, foot care is very important in diabetics. The following three actions are recommended to patients; daily inspection of the foot; daily washing; and control of the inside of the shoes. The pest, pebble, or similar hard object in the shoe that can be very harmful for diabetics with loss of sensation would be removed this way. On the other hand, when such a hard object remains in the shoes, patients may step on them repeatedly without feeling it which will likely lead to an ulcer case.

With its pain that works like a health alarm, extraordinary mechanical loads it carries, heat insulation and shock absorbing features, the human foot is a wonder of art that calls for contemplation.

If you heard that a very destructive creature was in your village, what would you expect this creature to look like? Perhaps a ferocious cat, or a colossal beast that was capable of leveling whole buildings? Such a creature does exist in Africa, except it is a single celled bacterium by the genus Trypanosome, a microscopic creature with the capacity to strike fear into the heart of virtually an entire continent. Living a segment of its life as a parasite in the bloodstream of humans and other mammals, Trypanosome can trigger a lethal neurological disorder in the circulatory system. It has also been found that it is the cause of a serious sleep disorder in humans. The disease can ruin a person’s circadian cycle, cause fevers, and changes in personality. Unfortunately, about 60 million people in 36 of the 52 countries in Africa are at constant risk.

Another significant role in the lifecycle of trypanosomiasis is the tsetse fly, the bacteria’s most common intermediate host, which transports the Trypanosome from one mammalian host to another. Trypanosomiasis is endemic in a large area of approximately 3.8 million sq. mi. in Africa, where both the parasitic disease and the tsetse fly coexist. Moreover, the danger is not limited to humans because it also affects many other mammal species, most notably livestock and horses. Malnutrition often follows as a direct consequence when large swaths of animals are killed by trypanosomiasis, as there will be less meat and dairy to consume.

The trypanosome parasite invites disease for the host mammal by collapsing or neutralizing its immune system. Let us first remember how the immune system works:

The immune system

Every living thing is provided with two things: food and protective systems. Immune system is one of these vital systems. Most immune systems across mammals function in similar ways; Antibodies are produced to destroy toxic substances and antigens on foreign bacteria, fungal cells, or the virus sheath invading the body. These antigens can be found on the infected foreign cells and have a unique shape and structure according to the organism that causes each disease. The immune system binds to the antigens of the foreign organism in the same manner as a key-lock system with its antibodies produced while fighting against the disease, thus neutralizes the invading organism.

Most of the antigens, which reveal the identity of a foreign being, are structures created of proteins, polysaccharides, or protein-based fats. Our immune system has the sensitivity and the capacity to produce an infinitely diverse variety that can discern even quite identical but foreign substances bearing antigenic properties for our body. To draw an analogy, a specific antibody can be produced for each speck of dust on Jupiter. Our immune system is blessed with the ability to synthesize appropriate antibodies by selecting proteins that differ in type or location of one amino acid.

The mechanism of binding of the antibody to the antigen is carried out with effective economy, because each type of antibody is produced specifically against a particular antigen. This mechanism works like a key-lock system, so the body recognizes its own cells and does not attack them. Each antibody produced in the immune system is created in a three-dimensional, one-to-one compatible structure with the antigen that causes it to be produced, and easily recognizes and locates it, binds as the key fits into the lock, and thus renders it harmless by disrupting the chemical structure of the antigen.

Trypanosome and the immune system

The case of trypanosome vs. the immune system is somewhat exceptional. The abovementioned almost universal immunity principle does not work against trypanosome. Even though parasites are constantly exposed to the mammalian immune system in the blood, they constantly change the antigen that forms the surface sheath. They thwart the host’s defense, as if rapidly changing their password so that it can never be guessed. Until the immune system produces new antibodies to bind to new antigens, some of the trypanosomes discard their sheaths and drape themselves in another one. If this condition persists, the immune system of the host cannot cope with the infection and may succumb to it.

This extraordinary phenomenon astonishes the scientific community and many scientists are investigating the molecular structure of antigen diversity extensively in African, European, and US laboratories. These parasites are only 0.015–0.030 mm in size, and its two most notorious species are Trypanosoma rhodesiense and Trypanosoma gambiense, which inflict serious damage on the human body.

Like many other parasitic species, the life cycle of trypanosomes is very complex. In each phase of this life journey, the parasite takes different forms and exhibits different characteristics in such an unusual way that generates curiosity. The life cycle can be summarized as follows: when the tsetse fly bites a disease-bearing mammal, the trypanosomes in the mammal’s blood are sucked up and settle in the middle intestine of the fly. They undergo a series of complex processes including several structural and biochemical changes. After about three weeks, the trypanosomes appear in the fly’s salivary glands in a disease-bearing form. Meanwhile, they are also draped in new surface sheaths.

When the secondary host fly bites a healthy person, the disease-causing trypanosomes enter the blood of the new host. In this new stopover, parasites are transformed into a form in which they can rapidly multiply. First, they wreak havoc in blood vessels and on lymph nodes, causing fever, marks and swelling in the body. At this stage, a constant struggle with the host’s immune system ensues. A likely invasion the patient’s central nervous system by the trypanosomes can cause intense drowsiness, coma, and eventually death.

In years of research on the trypanosomes, the thick surface sheath covering the cell membrane of the parasite was first described in 1965 by Keith Vickerman of the University of Glasgow. Shortly thereafter, different surface sheaths were discovered in different trypanosome clones. In 1968, Richard W. F. Page from the Molteno Parasitic Research Institute in Cambridge analyzed and decoded the isolated antigenic surface proteins from several clones, revealing that each clone had a biochemically different protein. The clarity of these differences suggests that each antigen is expressed by a different gene. In the 1970s, George Cross and his colleagues found evidence supporting Le Page’s proposal. These antigens are now called Variable Surface Glycoproteins (VSG). As a result of subsequent research, the picture became even more clear.

Once the infection has begun, antibodies are formed in the host’s immune system that bind to the variable surface glycoproteins that appear on the surface sheath of the invading parasites. These antibodies kill most of the initial trypanosomes. Yet interestingly, on a few remaining trypanosomes a new sheath to which antibodies cannot bind is built, and the trypanosomes evade the immune system’s grasp. The survivors induce a new population producing new variable surface glycoproteins. This time, the immune system produces new antibodies against these freshly constructed antigens. Meanwhile, the parasitic population grows. Newly produced antibodies are able to kill 99% of new parasites again. However, until that time, the parasitic group constituted by about 1% of the survivors has already changed its sheath. Hence, another population begins to multiply. This process of life being a struggle unfortunately continues until the host mammal dies.

The mechanisms of antigen diversity in trypanosomes are very complex and variable, and the total capacity to produce varieties is not clearly known. Recombinant DNA technology is used to investigate the structure of the genes for producing variable surface glycoproteins, the mechanism of cell membrane binding, and the selection and expression of one of the codes. In addition to the four licensed medicines produced for the treatment of parasitic diseases, new drugs are being developed.

It is astonishing that this tiny window of invisible dimensions has such a huge potential opening to different branches of science. Many such exceptional and precise situations exist in the universe that may showcase contradicting mechanisms with general principles and procedures. Sometimes we may wonder why God creates such harmful parasites. Since we do not know the performance at every point of an entire ecosystem with our insufficient scientific knowledge, limited sensory organs and temporary observation, we tend to see any seemingly harmful being as futile and devoid of wisdom and immediately raise our voices in protest. However, with new discoveries in science, thousands of wise meanings may be extracted from a creature we generally take for granted.

References

Lori Peacock, Simon Cook, Vanessa Ferris, Mick Bailey, Wendy Gibson (2012): The life cycle of Trypanosoma (Nannomonas) congolense in the tsetse fly, Parasites & Vectors, 5:109 www.parasitesandvectors.com/content/5/1/109.

Michael P Barrett, Richard J S Burchmore, August Stich, Julio O Lazzari, Alberto Carlos Frasch, Juan José Cazzulo, Sanjeev Krishna, (2003): The Trypanosomiases, The Lancet, Vol 362, November 1, Pages 1469-1475, www.thelancet.com.

www.cdc.gov/dpdx/trypanosomiasisafrican/index.html

The teeth of a tiny mollusk (Patella vulgata), which is a species of sea snails, have been found to be some of the strongest biomaterials in the world. Also known as limpets, these mollusks are a very small crustacean, often around 0.05-2 cm in size with a large cone shell and possess an incredibly complex system of teeth that dazzles the mind.

Research has revealed that the tensile strength of the sea snail’s teeth is higher than that of spider silk and is comparable to only the strongest commercial carbon fibers. It was found that the teeth of sea snails scraping algae off of rocks showed a tensile strength between 3 and 6.5 GPa (gigapascals). Spider silk roughly reaches a tensile strength of about only 1.3 Gpa. Scientists say that the snail’s teeth can even withstand the pressure that turns carbon into diamonds. Studies have determined that, to our current knowledge, there is no other material of this size (roughly 100 μm micrometers) with as much strength and durability.

This exceptional durability has led scientists to do research on the structure and functioning of these teeth, and the studies showed fascinating results.

The role of teeth in nutrition

Sea snails have a special tongue, called a radula, which they use to scrape off food from rocks. The most important feature of the radula is that it contains more than 100 rows of iron-mineral teeth. However, those used for food intake consist of only 10 rows on the outermost part of the teeth. During eating, a tremendous mechanism operates: the teeth are constantly repositioned according to their conditions of maturation and wear. Worn teeth are replaced by newly matured teeth over the course of 12 to 48 hours to ensure that fresh, sharp teeth are used instead of dulled ones.

This wonderful displacement system operates in a similar way to the movement mechanism on a conveyor belt where the teeth begin to grow primarily in the posterior part of the radula. Meanwhile, they are strengthened and matured by iron mineralization. When this mineralization is complete, they are moved towards the front of the radula. In this way, completely matured teeth are permanently retained at the far-front scraping area. During the scraping process, the matured teeth wear out at a rate equal to the growth rate. In the meantime, a new set of teeth begins to grow. By means of this magnificent cycle, new teeth are constantly created and matured so that there are no disruptions in nutrition.

Biomineralization

The structure of the sea snail’s teeth is also a masterpiece of material science. The dazzling durability of its structure provides optimum strength when scraping food off of rock surfaces.

Although the exact process of biomineralization of the teeth is not known, it is believed that it involves reactions of dissolution and re-precipitation. When the non-mineralized matrix is examined, well-arranged and densely packed chitin fibers are observed that are only a few nanometers apart. The matrix is a structure which keeps the reinforcing material together in layers that are composed of different materials. This organic matrix serves as a framework for crystallization in the structure of the teeth. In the mineralization system, the basic macromolecule α-chitin component is created first. The first mineral that then precipitates is the “goethite,” i.e. the aqueous iron-oxide mineral, which crystallizes parallel to the chitin fibers. These crystals are nucleated on the chitin fibers and formed between them by pushing and pulling the fibers. This way, crystals placed in order cause biomineralization of the structure.

It was found that 80% of the overall volume of the structure is composed of these crystals. The gap between the crystals and the chitin matrix is filled with amorphous silica (SiO₂). The iron contained in the aqueous iron-oxide mineral is the metal that constitutes the largest proportion of the composition. Other metals such as sodium, potassium, calcium, and copper are present in different proportions depending on the sea snail’s exact geographic location.

Critical factors in durability

The most important reason that the sea snail’s teeth have such high durability is because the fibers of the aqueous iron-oxide minerals in the teeth are nano-scale. This is due to the fact that materials of this size are not affected by the conditions that reduce strength.

Another critical durability factor is the small length of critical fibers. Critical fiber length is a parameter that defines the length of a material required to transfer strain from the matrix to the fibers at the time of external pressure. To achieve maximum strain, the length must be greater than the critical length. Materials with a large critical fiber length can hardly reinforce the matrix because most of the strain is not transferred to the fibers and remains on the matrix. On the contrary, materials with smaller critical lengths can transfer the strain on the matrix to the fibers. Therefore, they serve as an effective reinforcement for the matrix.

Fibers of aqueous iron-oxide minerals are of a critical length of 420 to 800 nanometers. This is much smaller than the length of the fibers in the teeth of about 3.1 µm (micrometers). This shows that nanofibers are an effective reinforcer for the matrix and contribute greatly to the ability of the teeth to bear loads.

Besides the structure and composition of the snail’s teeth, its morphological shape is also important in providing strength. It ensures that the strain is evenly distributed all over the tooth.

Modeling of biomaterials

All these studies indicate the presence of high-strength composites, which is when a material obtained by combining two or more materials with different physical characteristics, in nature.

Sea snail teeth, which have been created as a highly resistant and strong biomaterial, act as an inspiration for engineering and material science. Their characteristics, such as content and design, are expected to be modeled in areas that require durability and rigidity.

These marvelous systems found in the natural world, sometimes in creatures as tiny as a snail or mollusk, serve as a reminder that nature is filled with wonders for us to explore.

References

· Barber, Asa H., Dun Lu ve Nicola M. Pugno, Extreme Strength Observed in Limpet Teeth,  Journal of The Royal Society Interface, April 2015, DOI: 10.1098/rsif.2014.1326, PubMed.

· World’s Strongest Natural Material Discovered, How It Works, Imagine Publishing, No. 71, p. 11.

· en.wikipedia.org/wiki/Limpet
www.iflscience.com/plants-and-animals/worlds-strongest-natural-material-limpet-teeth/

· www.newworldencyclopedia.org/entry/Limpet

· Barber Asa H., Lu Dun and Pugno Nicola M. “Extreme strength observed in limpet teeth.” 12. J.R. Soc. Interface. http://doi.org/10.1098/rsif.2014.1326

“There was a footpath leading across the fields to New Southgate, and I used to go there alone to watch the sunset and contemplate suicide. I did not, however, commit suicide, because I wished to know more about mathematics.”
-Bertrand Russell, Nobel Laureate and Mathematician

It is mystical when you step outside on a snowy morning. Snowflakes are swirling around the vast sky and falling and blanketing the ground. If a snowflake lands on you, it is like a winter angel. There are no flowers around, for they cannot survive the cold; yet what lies before your eyes is an incredible beauty. And it’s remarkable, you come to realize, that no two snowflakes are alike. It is as if the uniqueness of a snowflake is controlled by a divine force. The individuality of a snowflake’s structure draws a parallel to human life. Like snowflakes, everyone has a unique story to tell.

I am not the only one who ponders about snowflakes; many mathematicians do the same. Actually, they think about the characteristics of snowflakes because they are particularly important for three basic mathematical principles: pattern, symmetry, and symmetry breaking.

A little-known scientist, Wilson Bentley, a.k.a. “the Snowflake Man” took pictures of snowflakes almost every day and observed them until he died. You can buy his book about his work on Amazon. If you wish to know why he did it, read about it at snowflakebentley.com.

“Under the microscope, I found that snowflakes were miracles of nature; and it seemed a shame that this beauty should not be seen and appreciated by others. Every crystal was a masterpiece of design and no one design was ever repeated. When a snowflake melted, that design was forever lost. That beauty was gone, without leaving any record behind.”
-Wilson Bentley

When I checked the Oxford dictionary, there were 3 definitions for the word “pattern.” Two of these definitions [listed below] are important for this article.

Pattern: 1. A repeated decorative design; 2. An example for others to follow.

When we check the pictures and delve deeper into each snowflake, we will see that the structures of the snowflakes are totally different. However, they have something in common: symmetry and a hexagonal structure.

These perfect ice crystals are genuine, even though it is hard to believe they are not fake.

When I take a close look at a snowflake, the beauty of the combination of ice molecules fascinates me every time; each flake is unique. However, uniqueness is not the point here. The things that make snowflakes important objects for mathematicians are their symmetry and their hexagonal structure. Math-loving people have a lot of interest in transformations. They love moving objects. And, surprisingly, if an object is symmetric, transformations are not even noticed by many.

To be more precise, when you have a hexagonal symmetric snowflake, or any other symmetrical object, when you rotate it in any direction, 60°, 120°, 180°, 240°, 300°, or 360°, people watching you wouldn’t realize it. If you check the images below, you will see rotated shapes but no difference. It appears to be the same shape in exactly the same place.

1- Counterclockwise rotation by 120°

2- Reflection through a vertical axis

3- Reflection axes of a snowflake[1]

Snowflakes also possess reflectional symmetry. If we stand in front of a mirror, our reflection looks exactly the same. Hence, if we put a mirror in the middle of a snowflake, there will be a reflection. For a snowflake, we can put a mirror 6 different ways. Thus, we can say that a snowflake has 12 symmetries: 6 from reflections, and 6 from rotations.[2]

Now we can define symmetry as a transformation that leaves things unchanged. We can also claim that a combination of any of the transformations will give us exactly the same shape. For instance, we can rotate our snowflake 60° two or three times in a row and flip it over, and it will remain unchanged.

At this point, you might ask the question: “You have all these fancy symmetries for this particular snowflake. But, does every snowflake possess the same symmetries?”

Snow is a molecular structure of an ice crystal. And ice is a structured substance. It is a different form of water. When the water cools down, the molecules move more slowly, and this begins to impact how the molecules line up. Hydrogen atoms of one water molecule bond with two oxygen atoms. As the water freezes, the molecules arrange into hexagonal patterns. They prefer to stay as far away from each other as possible, and that makes them take up more space. The large space affects density. The density of ice becomes less dense than water. This is why ice floats. Almost all other liquids have a higher density when they freeze.

When we examine an ice crystal carefully under normal conditions, we always see a combination of molecules with six-fold symmetry. Snowflake molecules make a honeycomb structure. This results in an inordinate amount of hexagonal symmetry in these molecular three-dimensional structures.

Okay, we saw the structure of a snowflake under normal conditions. But, what if we changed those conditions? Johannes Kepler answered this question after his experiments and wrote a book about snowflakes, particularly The Six-Cornered Snowflake.

There are two key elements which affect the structure of a snowflake: temperature and moisture. Each time the temperature or the amount of moisture change, the structure of a snowflake changes. If you check the snow crystal morphology diagram below, you will see that when the temperature nears 0° and humidity is high, the structure of a snowflake will be flowery. Flowery structures are called dendrites. When you make it a little bit colder, the structure will be fancy hexagonal plates. We can apply many combinations and get varying structures.

The Snow Crystal Morphology Diagram. Source: Snow Crystals – http://www.snowcrystals.com/science/science.html

Professor of physics Kenneth G. Libbrecht is the owner of the diagram below. In a PBS interview, he said, “It’s a mystery as to why snowflake shapes go from plates to columns to plates to columns as the temperature lowers. That’s one of the things I’ve been trying to understand. It has been a mystery for about 75 years, and it’s still unsolved.”[3]

The Shapes of Snowflakes | Source

In the end, although the structure of (almost) all snowflakes are the same, some of them are not completely hexagonal. For instance, there are some snowflakes that have tree structures. Some snowflakes have branches, and each branch has tiny branches.

But, why is the structure of some snowflakes not hexagonal?

So far, we have talked about pictures which were taken at a particular instant. We have seen the pictures of the motion of the snowflakes for the smallest amount of time that can be measured. However, a snowflake never stops spinning in the air. They tend to oscillate. That means the shape of the snowflake is changing all the time. But how? When you see a snowflake in the air, it changes its place after a second because it would be whirled about, and it will be under different conditions at that time. This process will occur up until the snowflake lands on the ground. We know from the diagram that the temperature and amount of moisture always affect the shape of a snowflake. While small-scale conditions are almost the same, on a larger-time scale, conditions will differ. And these differences will change every corner of a hexagonal snowflake, resulting in a different structure. This is the main reason behind the variety of snowflake structures and uniqueness.

In conclusion, we can say that a snowflake can preserve its six-fold symmetry at all times. I think we have another reason to love mathematics! I want to finish my piece with Hermann Hankel’s words:

“In most sciences one generation tears down what another has built, and what one has established another undoes. In mathematics alone, each generation adds a new story to the old structure.”

How can animals in the wild hunt during the night as if it were day? A remarkable biological feature acts as a pair of “natural” night vision goggles.

Animals can move and even hunt in the pitch-dark of the night. How do these animals see comfortably in the dark? How are their eyes different from ours?

Anatomically, the eye consists of three layers called the Tunica fibrosa (outer layer), the Tunica vasculosa (mid layer), and the Tunica nervosa (retina). The outer layer of the eye is composed of the sclera and cornea; the middle section of choroidea, corpus ciliare, and the iris; and the inner section of the retina.

Light rays reflected off objects first pass through the eye’s translucent layer (the cornea), then into the black round part located in the front of the eye (pupillae, or pupil), and later go through the lenses. The colored section around the pupil, covered by smooth muscles, is in charge of regulating the amount of light entering the eye. The real and inverted image of an object is projected on the retina by the refraction of light through the lens; the image is transmitted to the optical center of the brain as a result of nerve cell stimulation via the optical nerves. Sight happens as a result of these causal chains.

Now, there is a twist to all this: the optical center in the brain accepts spots that do not emit light as black. For humans, this means a loss of sight. Black objects are not visible because they absorb and keep all the light reaching them.

How could these animals, without night vision goggles, see in pitch blackness despite having the same optical mechanisms as humans?

The answer to this question was hidden in an anatomic structure (tapetum lucidum) located in the eyes of some vertebrates. This special structure, lacking in humans, monkeys, squirrels, birds, red kangaroos, and some other mammals, is found in equines, ruminants, and many carnivores. This structure is located in the cytoplasm of the choroidea layers in between the innermost light sensitive ocular layer and sclera, and it acts like a biological reflector. With its crystalline composition of varying colors from golden yellow to white, tapetum lucidum is a wonder of creation. The eyes of these animals shine when a light source is projected due to the aforementioned structure.

The primary task of this formation is to reflect the light which is projected to the rear section of the eye again without absorbing it. This happens due to the crystalline makeup. Thus, lower light levels are enhanced by the repeated reflection in the eye, and sight is enabled for animals. The second job of Tapetum lucidum is to elevate the sensitivity of the retina to light in order to transmit signals with no stimulation strength to the optical center.

This reminds us of night vision goggles. Night vision cameras are electro-optical devices that strengthen the light that is present. Light enters this device through the lens and hits the charged cathode, which has a lot of high energy. The energy load hits the phosphorous screen where the image is focused after passing through the vacuum inside the charger. The image is an enhanced picture on the phosphorous screen and it is not visible directly through the object. Tapetum lucidum however, is such an artistic work that it cannot even be compared with the night vision systems of technology. While the lifespan of a night vision system is only 2,500–4,000 hours (104–167 days), animals with Tapetum lucidum can benefit from this for a lifetime. The newest night vision systems, with a maximum optic range of 30-120 meters, cannot provide sight under light conditions one fourth of the moon’s illumination strength, whereas animals with Tapetum lucidum can see objects hundreds of meters away in much dimmer light.

This isn’t the only example of how masterfully and diverse eyes can be. Damseflies have over 30,000 simple eyes, called ommatids; eagles can see their prey from thousands of feet above them.

By the principle that “certain things are appreciated best in their absence,” if we imagine a dark night in which we are unable to see anything and cannot even step a foot safely, we can perhaps understand that Tapetum lucidum is a great blessing for these animals.

Reference

Veterinary Ophthalmology (2004) 7, 1,11–22. Comparative morphology of the tapetum lucidum (among selected species), F. J. Ollivier,* D. A. Samuelson, D. E. Brooks, P. A.Lewis, M. E. Kallberg and A. M. Komáromy.

The excellent nature of teeth comes from the microstructure of the material they are made of. They are not homogenous like cement used in construction work. It is composed of various different layers such as enamel, dentine, and cementum which are formed by enamel prisms and dentine tubules. This structure of the teeth is the source of inspiration for the produced restorations. Since an exact imitation is aimed, in addition to other properties, the microstructure of the teeth also needs to be imitated.

When the general structure of the teeth is investigated, it is observed that there are two major components: organic and inorganic structures. The filling material, referred to as composite, must be in the color of the tooth and must contain the same type of structure. The filling material in the composite increases the resistance of the restoration and has the same function of the mineral hydroxyapatite in the enamel. In the composite, resin matrix takes the place of the organic matrix in the enamel. Up to this point, everything seems fine but the images of scanning electron microscope (SEM) showing the cross sections portray the trivial difference between the composite and the natural tooth. The homogenous, ordinary appearance of the filling and the astonishingly embellished tooth are very easy to differentiate.

There are prerequisites that make tooth restoration successful. We can summarize these as esthetics, functionality, and phonation. These properties are affected with the loss of the tooth or the structure of the tooth. What follows is an analysis as to how and to what extent these properties can be replaced.

Esthetics in the dentistry means exact imitation of the tooth color. To be able to give a natural color to the filling or to the crown could be considered a miracle. It might sound like a very simple issue. However, this is probably the most challenging thing for dentists. If the color does not match, your restoration will look different and will easily be noticeable. Maybe it is my professional curiosity because while watching television I have a tendency to look at people’s teeth before I look anywhere else. From the most popular singers and actors to mighty and scholarly politicians, I can always recognize their prosthesis. Ironically, these people were spending their wealth on professional dentists who could not give their original teeth back to them. The color is not something that could be mixed up together by fulfilling only one of its features. The color comes into existence as a result of common features of many factors. A dentist’s only hope is one day using homogeneous clay typed structures squeezed from a tube.

The structure of the enamel and the dentine are deeply related with opacity and translucency, two important subjects of optics. That is why some parts of the tooth are translucent while the other parts are opaque. It is possible to restore it with a few optical tricks. The tooth is neither completely opaque nor translucent. For example, while the cutting edges of the tooth are translucent (especially the cutting edges of newly erupted milk teeth, they are almost glassy), the cervix of tooth, adjacent to gingiva, is opaque and dusky. Thus, in big restorations, we implant materials that reflect the light differently for every surface of the tooth. We try to compare and contrast to the original teeth by using optical tricks. However, a more important thing is the sustainability of this quality. Especially, for restorations made to anterior teeth, you can observe that the colors have become darker and have separated from adjacent tooth with a dusky-colored borderline. Indeed, it is evident that color harmony is not preserved properly.

We cannot expect to reach a result that is equivalent to the look and feel of natural teeth through esthetic restoration only. The mechanical properties of restoration must be similar to that of the natural teeth. The reaction of the teeth to a certain force is very important. Teeth are subjected to forces of different types and magnitudes throughout the day, and they are created so as to endure those forces. Any restoration must be as strong and durable as the natural teeth. A piece of filling that is placed into a tooth becomes a working part of the entire system. If it is not as resolute as the rest of the system, then it cannot integrate and may fall out. In this regard, the mechanical properties of the material for restoration are crucial. There are dozens of other aspects in which one can compare those properties with a natural tooth. Considering just a couple of the important properties such as hardness and flexibility is enough to show significant differences between natural teeth and restorative materials.

Both hardness and flexibility of a material are determined by certain characteristics and are all formulated in scientific terms. We can see the difference of natural teeth very easily by comparing the hardness and flexibility of the most commonly used composites in the fore teeth and that of hard tissues like enamel and dentine. There is yet another point not to be missed: What makes our teeth perfect is that they are both hard and flexible at the same time. We can see the big gap between real and artificial teeth when we compare the quantitative values of these mechanical properties.

Teeth, in addition to their superior mechanical features, impress us with their exceptional capacity to transmit the force they face. Teeth come in contact with their hard counterpart everyday while eating or otherwise. A casual observer might think that a tooth is directly attached to the chin bone. Let alone being attached, the tooth does not even touch the chin bone. It is tied to the chin bone with flexible strings. A fusion of the bone and teeth is out of the question. It’s as if a bucket is lowered in a well. Whenever we chew, the pressure endured by the teeth is transferred to the bone through these strings in the best manner. These periodontal ligaments serve as shock absorbers. It would be incomplete to explain force transfer in teeth with these strings. It is imperative to remember the structure called lines of forces located on the chin bone that are shaped in such a manner as to guide the force.

It is a noteworthy challenge to make restorations and to replace a tooth in every aspect. Man-made products or works of art cannot be completely imitated; experts at least could tell the differences right away. Could it then ever be possible to imitate an artwork of the Divine to the same degree of perfection in its authentic form?

Mehmet Yildiz is a Professor of operative dentistry at Ataturk University, Erzurum, Turkey.

The first is the preservation of characteristic, long term data imprints that describes the development of an organism in the stable DNA sequences.

Second is the storage of medium term epigenetically featured data that is carried a couple of generations further down the cellular level. Epigenetic information is not stored within nucleotide sequences but in the chemical modifications of these sequences (like the methylation of repeated strings of GC dinucleotide).

Third is the storage of data generated as a result of dynamic interactions between proteins, RNA and DNA in order to adapt to the events and changes during cellular life cycle in the form of nucleoprotein or DNA-protein complexes.

The data generation and storage capacity of DNA in three different hierarchical levels and time periods demonstrates that genome plays a plethora of roles in cellular activities and heredity. Formatting of genome for its generation and storage of data is carried out via DNA sequences of various features. Genomic system is composed of repeating DNA sequences. DNA sequences (satellite) function as a marker as they repeat numerous times in various frequencies. Genome includes genomic folders similar to that of computer systems. These genomic folders, also known as the epigenetic index of genomes, are responsible for the remodeling of chromatin and the coordinated control of genomic functions. Repeating DNA sequences play a critical role in replication of genome (making a copy of DNA), dispersal of copied DNA into daughter cells and construction of support systems that enable organization of chromatins.

It is possible to better understand genomic functions in relation to examples such as memory sticks and hard drives that are used in electronic information systems. The difference between a genome as a basic data-information storage medium from a hard disc is that it can be replicated as required by its nature and these replicas can be transferred to daughter cells. Following examples could be given to illustrate that a genome gains function only when it interacts with various data processing modules in the cell.

1. A copy of genome is produced by cellular DNA replication system
2. Correct localization of each genome copy towards daughter cells is only possible when chromosome segregation system works (the centrosomes and microtubules)
3. The central transcription system is responsible for the copy of data from DNA to RNA. Different gene expression patterns are developed via regulation of transcription time and level with the help of transcription factors and a web of cell signalization.

Very intricately organized genomic system structures are designed through the successive combination of protein encoding sequences, signals distributed in various places and repeating DNA sequences. Formatting of genome resembles formatting of computer programs. Various repeated serial commands of computer software are used to allocate addresses to files independent of the original data contained; different computer systems use different signals and structures to manage programs. In a similar fashion, diverse living species often utilize repeating DNA sequences and chromosomal structures to organize the encoded information and to format their genomes.

Diversity and variation of repeating DNA sequences are building blocks that are constructed into different genomic system structures. Genomes of different organisms bear characteristic system morphology just like computers with various operating systems and hardware. For instance, animal cells are created as a good model to take and incorporate foreign DNA into their genomes. Genetic data transfer among organisms of the same kind is referred to as “vertical gene transfer” whereas transfers between different species, genuses and classes are called “horizontal gene transfer.” Mobile DNA sequences like transposons are very effective horizontal gene transfer agents.

Cellular differentiation and morphogenesis (formation of tissue and organ from cell) is not programmed completely in the primary structure of the DNA sequence. Components of modular programs are encoded in a flexible way and a continuous renewed and recombined arrangement is enabled when needed.

The reason behind creation of different organisms from a single genome is this utilization of such genomic structure. Metamorphosis, that is the development of different organisms like invertebrates such as a caterpillar and a butterfly, is a good example of this feature.

Two organisms from the perspective of the same genomic protein and RNA codes can be considered as two different species. Different genomic structures and repetition of sequences among different organisms are distinctive criteria for the identification of species since these features can lead to mismatch of reproductive cells, different expression patterns of genetic code sequences, and may cause ecological diversity as well. That is why repeated DNA sequences are very important in studying parental relationships. Today, microsatellite DNA as repeated DNA sequences are used to configure biological relations among individuals in forensic sciences. Plant species vary in respect to the repeated sequences in centromeres in their chromosomes; these variations are used for identification of species. Main determinants of genomic system structure are diversity, frequency, and genomic localization of repeated DNA sequences. To explain this with examples, we could say that successively repeated sequences at centromeres, telomere repetitions and transcription, packing of chromatin, repeated sequences that are spread throughout genome in charge of cellular functions like nucleus localization are the main elements of the genome system structure. Genome is a single integrated system that is controlled closely and remotely via communication webs that use repeated sequences.

While explaining the Qur’anic concept of the Manifest Record (36:12) Bediuzzaman Said Nursi, the great renovator of Islamic thought in Turkey in the twentieth century, wrote that the Manifest Record expresses one aspect of Divine knowledge that is related “more to the past and future than to the present. It is a book of Divine Destiny that contains the origins, roots, and seeds of things, rather than their flourishing forms in their visible existence” (30th Word, Second Aim).

Inspired from this view, a seed can be considered as a tiny adorned form of Divinely creative command as programs and indexes and as a determinant for those programs and indexes in the organization of an entire tree. Since the Manifest Record book, as a title of Divine knowledge and command, observes the past and the future rather than the present, the genome of a grain or a seed acts like a library and an archive in which the future and past of an organism is written.

Sequences encoding different information in DNA

Different information types corresponding with various DNA sequences exist in the genome. These DNA sequences that were considered junk for a long time because they were not coding proteins, have in fact been found to be responsible for an amazing array of functions in genomic structure. Some of these sequences include:

1. Group determining sequences that enable coordinated or successive expression of genes,
2. Sequences acting as a marker in charge of initiation and termination during transcription of DNA to RNA ,
3. Signal sequences responsible for conversion of primary immature RNA, sequences into smaller functional RNA molecules,
4. Transcription control sequences that determine the expression frequency of genes,
5. Sequences that identify and mark the initiation regions for intensification and remodeling of chromatins,
6. Sequences that make binding regions which affect the relocation of genome in nucleus or nucleolus,
7. Sequences that target regions where covalent DNA modification (methylation) with functional groups like methyl takes place,
8. Sequences that control and identify the regions responsible for initiation of DNA replication,
9. Sequences that make the structures which enable completion of replication at terminal ends,
10. Sequences at the segregation points that enable equal distribution of copied DNA molecules into daughter cells and centromere sequences,
11. Sequences responsible for guidance during repair of DNA bound errors and damages,
12. Start point sequences used for repackaging of genomes,

Recurring sequences exist in the genomes of many organisms and shows great structural diversity. Recurring elements function as an initiator or terminator for heterochromatin regions. Furthermore they form an important scaffold and binding spots for folding of DNA structure. As if they carry out the job of an architectural mold in specific shaping of genome to be packed into a very limited area. The ratio of repeating sequences in genome (60-90%) is much more than sequences that are encoding proteins and RNA (10-40%). To explain it with an example, chromosomes in human genome are made up of packages of protein-DNA such as heterochromatin and euchromatin. Heterochromatin regions usually make up the regions with no transcription whereas euchromatin regions feature DNA transcription.

The ratio of protein encoding sequences to the entire human DNA is approximately 1.2%. Around 43% of euchromatin regions are composed of recurring and mobile DNA elements. 18% of heterochromatin region is also made of satellite (dense repeating sequences) and mobile DNA elements. Therefore almost 50% of human genomic DNA is composed of these repeating DNA sequences. In bacteria however, these only make up around 5-10% of the genome. These sequences were described as parasitic and junk individual DNA structures up until today and still continues to be described thus by many researchers and scientist. Nevertheless, even today, mobile DNA elements and repeating sequences are accepted as genomic parasites. Recent advances in the last ten years that have demonstrated this is not true, have instead revealed the vital importance of repeating sequences in genomic functions.

Repeating DNA sequences affect chromatin (dense pack of DNA and protein) structure in two ways. Irregular repeating DNA sequence copies contain binding regions for proteins that organize DNA. Heterochromatin (darker since it is densely packed chromatin) inhibits transcription and recombination, delays replication, and generally blocks the reading of information in DNA sequences that contain genetic coding. Heterochromatin regions are distributed throughout the chromosome. Because of this, presence of regions with coupled successive repeated sequences triggers heterochromatin formation.

In fruit flies, placement of protein encoding loci required for eye pigmentation near the heterochromatin blocks in centromeres (phenomenon of position effect) is provided via organization of chromosomes and thus, formation of phenotypic characters are inhibited. The “phenomenon of position effect” is convincing evidence that genome is a major system which is integrated with composition of partially repeating DNA sequences. When heterochromatin amount is increased in XYY male fruit flies, reorganized pigmentation of eye expression decreases. In XO males, when heterochromatin amount decreases, inhibition becomes severe. Changes in levels of protein which binds to special heterochromatin specific DNA regions generate opposite effects. Decrease in these proteins reduces or suppresses “phenomenon of position effect.” Surplus synthesis of these proteins also enriches this effect.

Repeating DNA sequences play an important role in the transfer of genome into daughter cells. For instance, they function in formation of the centromeres as chromosomal binding regions for microtubules, during gamete formation as linear terminals of chromosomes are replicated, and during chromosomal matching. Distribution of repeating sequences plays a major role in configuration of genomic functions. Each genome has genomic system structure that is shaped dependent on the amount of repeating DNA sequences to a major extent.

Going back to Nursi’s explanation of the Manifest Record, we can draw a parallelism between the book of the universe and the book of revelation, the first of which shows us that certain sequences in the genome are repeated for significance and necessity, just as many verses are repeated frequently in the Qur’an with nuances to refer to different meanings, benefits, and purposes, opening a wider space for many interpretations.

A genome is not only a book that contains protein and RNA codes, but also has a complex system structure with many functions for cellular vitality. The most needed sequences are those that are repeated more frequently. They are not pieces of junk DNA as predicted, they are jewels Divinely constructed.

References

• Shapiro J. A. 2001. “Genome Formatting for Computation and Function :Genome Organization and Reorganization in Evolution: Formatting for Computation and Function.” Presented at a symposium on “Contextualizing the Genome,” Ghent University, Belgium, November 25 – 28, 2001 (Ann. N.Y. Acad. Sci., in press)
• Shapiro, J.A. 2005. “A 21st century view of evolution: genome system architecture, repetitive DNA, and natural genetic engineering.” Gene 345, pp: 91–100.
• Shapiro J. A. and Sternberg R. V. 2005. “Why repetitive DNA is essential to genome function.” Biol. Rev., 80, pp. 1–24. Cambridge Philosophical Society.

Gómez-Valdés et al. Lack of Support for the Association between Facial Shape and Aggression: A Reappraisal Based on a Worldwide Population Genetics Perspective. PLoS ONE, 2013; 8 (1)

It is a common misconception that some people are profiled to be angry or aggressive because of their physical appearances, particularly their craniofacial shapes. In addition, there have been some studies suggesting that men with certain facial traits (round-shaped faces) are more likely to develop aggressive and unethical behavior. A new study using a sample of around 5000 individuals from 94 different countries has found no correlation between facial shape and aggressive/criminal behaviors. Researchers analyzed fWHRs (facial width-to-height ratio) and 2D/3D craniofacial landmark coordinates to estimate any possible correlation between skull shape and aggressive behaviors in men. First, they utilized the famous skull collection in Hallstatt/Austria to investigate any potential correlation between skull features and life history parameters of individuals, such as their overall fitness. Second, they analyzed the male prisoners convicted of crimes like inter-personal aggression (homicide, robbery etc.) from Mexico City Federal Penitentiary to see whether there is any relation between skull shape traits and aggressive crimes. Analyses of both databases have found no significant correlation between skull shape traits either with the fitness of males or with their aggressiveness. This study has very important social and political implications in today’s societies, as we unfortunately see many ethnical, racial and even physical prejudices. This comprehensive study has undoubtedly showed once more that physical traits cannot be a reliable predictor of complex human behaviors, which are mostly shaped by external factors such as education and socio-cultural practices.

Biggest Structure in the Universe Discovered

Clowe et al. A structure in the early Universe at z ∼ 1.3 that exceeds the homogeneity scale of the R-W concordance cosmology. Monthly Notices of the Royal Astronomical Society, January 11, 2013

Throughout history, mankind has been trying to answer the questions of “how big” or “how far,” when looking into the vast expanse of the universe. As new technologies are developed, bigger discoveries and consequently bigger numbers are brought to light. An international team of astronomers recently discovered a collection of 73 quasars which form a single structure; the largest structure ever observed in the entire universe. A quasar, short for quasi-stellar object, is the luminous center of a galaxy that surrounds a super massive black hole. The distance of these newly large quasar groups to the earth is about 9 billion light years (1 light year is approximately 9.5 trillion kilometers). The size of these structures is simply mind-blowing. Even if we have a spacecraft that travels at the speed of light, it would still take about 4 billion years to cross. If we put this overwhelming size into perspective, the Milky Way—earth’s home galaxy—is only about 100,000 light-years wide and our neighbor galaxy Andromeda is only 2.5 million light-years away from the Milky Way. So these quasars are 1600 times larger than the distance from the Milky Way to Andromeda. This discovery seriously challenges the size calculations based on the widely accepted Cosmological Principle which assumes that the universe is essentially homogeneous when viewed at a sufficiently large scale. Cosmological Principle predicts that there should not be any structure in the universe larger than 1.2 billion light-years. A four billion light-years wide structure would obviously be an outlier when compared to other structures in the universe and it might contradict with the homogeneity of the universe. However, scientists think that such contradiction would not necessarily falsify the Cosmological Principle originally established by Albert Einstein. It might only change the assumptions of the theory that define at which scale the universe can sufficiently be viewed.

More Twists on Double Helix

Biffi et al. Quantitative visualization of DNA G-quadruplex structures in human cells. Nature Chemistry, 20 January 2013.

About 60 years ago, on April 25th 1953, James Watson and Francis Crick published a one-page paper where they described the “double helix” structure of the DNA, the molecule that carries genetic information from parent to offspring. This discovery not only revolutionized the biological sciences and medicine but also dramatically changed the way we perceive life, nature and most importantly ourselves. Yet, new findings on DNA structure keep surprising us. Scientists from Cambridge University discovered the first quadruple helix—a four-stranded DNA structure in human cells which they named “G-quadruplex.” These structures were previously observed in test tubes but they were never found in cells. The building blocks of DNA molecules consist of four different bases: Adenine (A), Guanine (G), Cytosine (C) and Thymine (T). G-quadruplexes (G stands for Guanine) are formed by four guanine bases that forms a square DNA helix. Researchers found that these structures are enriched in rapidly-dividing cancer cells, specifically at the ends of chromosomes called telomeres. When researchers targeted and trapped these quadruple DNA structures with synthetic molecules, they found that DNA replication slows down and cell division is blocked. Researchers suspect that these quadruple DNA structures in telomeres of cancer cells could explain why cancer cells rapidly proliferate and divide. It is still not clear whether G-quadruplexes exist in healthy cells but targeting these structures in cancerous cells with pharmacology seems to be a promising method to stop the spread of cancer.

Carbon atom, which composes nearly 0.2% of the earth’s crust, has a very special place among elements. All living beings are formed from carbon-based compounds. In addition, 94% percent of compounds—that is, more than 4 million—contain carbon atoms. Certain carbon compounds form nearly 18% of the matter in living beings. The rest is mostly water. These compounds are used as building blocks in cell formation. Only carbon has the ability of compounding with other elements in sufficient variety and complexities in order to carry out the main functions that life is based on. As carbon atoms easily form chains by making chemical bonds, no other element is given such a quality. These chains formed in a line can separate into branches and can connect to form rings. These rings are actually polygons formed by three, four, five, six, or more carbon atoms. Due to this quality, carbon is the element that forms the basis of many things from the foods we eat, to the clothes we wear, from the fuels we use, to the furniture we have.

The heat level that makes carbon compounds possible is between -20 and +120 0C. Carbon compounds begin freezing at -20 0C and they begin breaking at 120 0C. In space, where extreme heat and freezing cold exists, the only heat range that makes carbon compounds possible is found on earth and this is a very sensitive heat range. Temperatures in our neighboring planets give a better idea: as hot as 450 0C in Venus, and as cold as -53 0C in Mars. Under these temperatures, it is impossible for carbon element to form compounds and thus living beings. Therefore, the earth is the only planet created with the suitable conditions that make life possible.

Crystal structures of carbon atom

Particular repeating arrangement of atoms in three dimensional space to form a certain geometric shape is known as a crystal structure.

Different crystal structures of the same substance are named “allotrope.” Carbon has three different allotropes found in nature: amorphous carbon (coal), graphite, diamond. In addition to these, an artificially produced allotrope is fullerene.

Amorphous carbon (coal)

Amorphous structure is one without a definite crystal structure; that is, one where atoms take their places in free order. A mass of carbon atoms of amorphous structure is known as coal. After plants die, they undergo chemical transformation with the activities of microorganisms. If dead plants collect in a suitable wetland and are buried into the ground with a geological process, the carbon amount in their body increases and they begin transforming into coal. Types of coal are categorized according to the carbon percentage they contain. Geologically, this transformation process takes a period of 15 to 345 million years. Coal is one of the most commonly used forms of energy.

Graphite

In graphite, carbon atoms are found in a hexagonal crystal structure. These sheets, resembling the surface of a honeycomb, pile up and form graphite. As the sheets are not connected with firm bonds, they easily shift when some force is applied. This is why graphite is used for eliminating friction at machine industry. The black substance in pencils is graphite hardened by adding some clay. Graphite can resist very high temperatures. Therefore it is used within the steel industry and melting metals. In addition, it is a very good conductor of electricity. For this reason, the brushes of the electric engines in household machines such as a washing machine and a vacuum cleaner are made of graphite. In recent years, graphite has been used as heat shields of space shuttles.

Diamond

Diamond is the hardest natural substance we know. In spite of being a transparent substance and having no color of its own, it can be found in pastel colors such as yellow, brown, or even dim black, owing to being mixed with other minerals. Diamond is a perfect electric isolator and is the substance with highest heat conductivity. For this reason, it can be cut without being deformed. In diamond, carbon atoms are found in a pattern to form a cubical crystal structure. Extraordinary resistance of carbon-carbon bond and its hard and integrated structure prevents its reacting with other things around. It burns at a heat of 850 0C. In a piece of diamond, there can be other atoms that cause impurity and decrease the value. In good quality natural diamonds, there is only 1 alien atom versus 100,000 carbon atoms. In addition to jewelry, diamonds are widely used at industrial products such as drills, glass cutters and the like. 75-80 % of diamond production is used in this industry.

Formation of coal, graphite, or diamond from carbon

Carbon based organic compounds were buried underground as a result of movements by the earth’s crust millions of years ago. Physical and chemical changes occurred with those organic masses through heat and pressure. Gradually, water, carbon dioxide, oxygen, and—in the highest phases—hydrogen leaves these masses. This organic matter called “turba” (first transforms into lignite, then to sub bituminous coal, then to bituminous coal, and then to anthracite). If the conditions allow, it transforms into graphite. Coal is the first type of substance formed by carbon atoms on their journey to become diamond. As lower values of heat, pressure, and time suffice for coal formation, graphite requires much higher values. Diamond is formed in the mantle layer of the earth at about 150-200 depth. This valuable substance is later carried to the surface of the earth by volcanic rocks such as lamproite and kimberlite. In order for diamond to form, an atmospheric pressure of 50,000 atm, 2,400 0C of heat, and a period of 3 billion years are required. Without this immense pressure and long time, the substance to be formed by carbon will simply be graphite. It is possible to transform graphite into diamond artificially; however, according to calculations, a minimum pressure of 10,000 atm is required. In 1955, for the first time artificial diamond was obtained under 100,000 atm, 2,500 0C heat, and by using chrome as catalyzer. However, the pieces of diamond obtained were small and black, most of them did not classify as jewels. In another attempt made in 1962, graphite turned into diamond under 200,000 atm, 5,000 0C heat, without using any catalyzer.

The similarity between carbon and human beings

As carbon atoms’ properties change according to the crystal structure, people’s lifestyle and view of life depends on the community they live in and their position in that community. In order to become diamond, the highest level of its kind, a person needs to undergo hard conditions. If carbon atoms were to say, “this is more than we can bear, we prefer easier conditions,” then they can be nothing more than graphite. If the conditions for graphite are avoided as well, then one cannot go beyond the level of coal. Diamonds are kept in safes and worn in most important occasions and graphite has different kinds of practical use as an industrial material. As for coal, it ends up in fire. The situation of human beings in a way resembles carbon atoms. Every person is made of the same elements biologically. Their value will naturally be different, according to the processes they underwent and the behaviors they presented. Some show patience in the face of misfortune, put their sincere trust in God, and become the diamonds of humanity. Some others, whom we can compare to graphite, attain a desirable level even if they cannot become diamonds. Those who choose to assume the lowliest form are likely to face a similar fate with the coal.

References

• H. W. Kroto, J. R. Heath, S. C. O’Brien, R. F. Curl ve R. E. Smalley. 1985. “C60: Buckminsterfullerene.” Nature 318. DOI:10.1038/318162a0.
• L. Vlasov, D. Trifonov. 2005. 107 Stories about Chemistry, TUBÝTAK., Ankara.

Octopuses are equipped with a very powerful sensing system in addition to their sharp vision. For example, an octopus whose vision is obstructed can sense the size of objects and the distance between them. Regulation and synchronization of vision is realized with internal and external movement of the lens contrary to human beings. When it faces a threat, the octopus releases dark blue-black ink and tries to repel its enemy. Immediately after the spray, its color changes and it carefully leaves that spot. The secretion glands found in the inner face of the bladder have been programmed to secrete ink the moment the animal becomes frightened. Another function of the ink is to blunt the attacking animal’s sense of smell. Even if the animal touches the octopus at this time, it cannot recognize it.

Another striking and important ability given to the octopus is its ability to camouflage. In some situations it tries to protect itself from danger by hiding itself with this capability. If it has not been able to find a suitable place to hide, the octopus swims among the corals and, taking on the color and shape of its surroundings with the help of color cells comprised of richly colored matter (chromatophores) found under the skin, it camouflages itself perfectly.

At first glance the suckers of an octopus are no different from suction cups vacuum pressed onto smooth surfaces. However, in reality this organ is more complex than it appears to be. This organ was not created just for the purpose of sticking on objects. By means of muscles unique to it, the octopus is able to make various maneuvers.

There are approximately 200-250 suckers in two lines on each arm of the octopus. This means there are approximately 2 thousand suckers on its eight arms. There are two small chambers on each sucker. The external chamber is called a cone and the internal one is called a pot. When it sights its prey, the muscles of the external cone take the shape of the surface of the prey and completely cover it. The muscles of the internal pot structure are full of water and, disconnected from the outside world, decrease the inner pressure. This difference from the outside pressure has the effect of a vacuum. The external muscle structure enables the octopus to turn from an erect or parallel angle by decreasing the pressure difference around the object and without destroying the functional structure of the sucker.

In addition to possessing the complex muscle structures explained above, the suckers have an amazing nerve system. The chemical receptors found on the edge of the suckers (chemo-receptors) give feedback regarding the taste of the object, and the pressure and position receptors give information regarding pressure and touch. The nerves of these receptors, gathered in a node, act as a tiny brain. The chain structure extending the length of the octopus’ arm connects the suckers and nodes and synchronizes them. This structure enables the animal to lift and raise its arms without need of a command from the main brain. How this amazing task is accomplished by the brain, arm and suckers is a subject that needs investigation.

Only considering its suckers, the octopus appears before us as a creature adorned with perfect artistry and special capabilities. The characteristics of these animals being in a wise and most appropriate form is one of the clearest proofs of the blessings and benefaction of a compassionate and merciful Creator.

Canoglu is a freelance writer from Turkey with a degree on zoology.