Shadowing effect: the game of who is taller

When sunlight falls on Earth, some shadowy areas do not receive it due to an elevated structure nearby. This causes the shadowy areas to have a different set of plants, which are usually shorter and smaller than the plants in the sunny areas. In brief, the shadowing effect is the input (here sunlight) reception behavior caused by height differences across a surface. The game here is that the taller ones grab more input than the shorter ones. In systems where the input is some kind of material falling on the surface, the most important outcome of the shadowing effect is slowly-rising columnar structures. The ultimate surface morphology depends heavily on the strength of the shadowing effect. Hills of snow following a heavy snow fall and forests with trees of various heights are examples of the shadowing effect.

Reemission effect: the game of reflections

When things bounce, they follow certain physical rules. When you throw something, it may stick or bounce depending on several factors. For instance, when the light falls onto a surface, some of it penetrates the surface and gets absorbed while the rest gets reflected. Reemission is another name for bouncing or reflection in physics, though the idea is not just equivalent angle reflection or equivalent reaction force bouncing.

Figure 1 illustrates the shadowing and reemission effects on a sample surface with hills. Falling particles will most often hit the hills first due to the shadowing effect. If the hill cannot grab the particle on the first hit, then the particle reemits, and it becomes possible for the particle to fall into a valley. In order for a particle to settle in a valley (e.g., particle B in Figure 1), it will have to go through a sequence of reemissions. Let’s say that a particle’s reemission probability (i.e., residual of the sticking coefficient) is p during a hit onto the surface. By simple math, if k reemissions are needed in order for a particle to settle in a valley point, then the probability of this valley point grabbing a particle is while it is for a hilltop under no shadow. In this very approximate model, k will be larger for a deeper valley point, thereby further reducing the grab probability. To get a quick sense of it, for p=0.5, the grab probability is 50% for a hilltop and 25%, 12.5%, and 6.25% for valley points with k=1, 2, and 3 respectively. Similarly, the parameter p represents the importance the of reemission effect in the growth of the surface. Higher p means more reemissions and a larger grab probability for valley points. That is, for p=0.9 (which means the material reemits 90% of the time), the grab probability is 10% for a hilltop; and 9%, 8.1%, and 7.3% for k=1, 2, and 3 respectively.

Intuitively, when the shadowing effect is dominant, the hills will grow larger and maybe merge with each other while sites at the valleys will remain short. The final surface will not be smooth but rough. Figure 2 shows this phenomenon on the macro scale for Tibetan forest growth under the shadowing effect, and Figure 3 shows it on the nano scale (1 nanometer corresponds to 1 billionth of a meter or about hundred thousand times smaller than the diameter of a human hair) for growth of nanostructures like nanorods (i.e., sticks at nanometer lengths). When the reemission effect is dominant, one can expect that the hills will get eliminated as the valleys will quickly grab the reemitted particles. In this case, the final surface will be smooth with evenly distributed growth.

Scientists have been using these effects to control the growth of the surface, especially recently for nanostructure growth. By changing the material characteristics (which affects the reemission probability) or the angle at which the atoms arrive at the surface (which affects shadowing), the scientist can control the dominance of the shadowing or reemission effects [3]. The final outcome of the nanostructures depends on other factors as well, such as (i) temperature of the substrate surface, (ii) energy of the particles, (iii) movement of the underlying substrate, and (iv) the initial pattern of the substrate as in Figure 3(b). By using a combination of these techniques, designers have been able to grow interesting structures such as nanosprings as shown in Fig. 3(b), or nanoballs as in Fig. 3(c). These nanostructures attracted the interest of researchers for various applications such as biosensors [4], engineering of light propagation [5], and microchip production [6].

A social perspective

It is not hard to see the role of shadowing and reemission effects on people and social growth as well. One typical tendency is that well-connected and well-known people or institutions are more likely to grab attention of newcomers to a society or a network. This phenomenon has been regularly observed in the growth of online social networks (e.g., Facebook) [3]. Similarly, wealthier people are more likely to receive a larger share of the aggregate social revenue, which yields a highly skewed wealth distribution. These social trends exist for valuable goods (i.e., “attention” in the former example and “money” in the latter) which have a high “sticking coefficient” and less reemission probability. A well-known phrase to describe this is “the rich get richer,” which Figure 3(a) clearly reveals, showing nanorod growth with a highly sticky material, silicon.

“Equal sharing” in societies is certainly achievable through a more dominant reemission effect. An analogy between reemissions and charity (or helping others) is plausible. Again, the social tendency has been to equally share (or reemit) items that are mostly commodity. Water, electricity, education, and health are examples of such commodities that people “reemit” in many societies, though even the water is not reemitted in some societies.

Conclusions

The interesting observation we would like the reader to recognize here is that shadowing and reemission effects take place at nano as well as at macro levels, and both play important roles in shaping formations or structures. Though these effects are mainly studied in physical structures, they certainly exist in unphysical structures such as societies. Sharing both physical wealth and knowledge is strongly advised for a strong community that lives in harmony. This is similar to the reemission effect during the growth of materials on the nano scale, in which reemission leads to smoother and denser films with structural integrity. On the other hand, when reemission is poor and the shadowing effect is dominant, it leads to isolated structures that look nicer but are structurally fragile (See Figure 3).

Dr. M. Yuksel is an Assistant Professor at the Computer Science and Engineering Department of the University of Nevada, Reno. Dr. T. Karabacak is an Assistant Professor at the Applied Science Department of the University of Arkansas at Litte Rock. Dr. H. Guclu is an Assistant Professor at the Biostatistics Department of the University of Pittsburgh.

References

1. T. Karabacak, H. Guclu, and M. Yuksel, “Network Behavior in Thin Film Growth Dynamics,” Physical Review B, 79(19), May 2009.
2. D. Winkler, “Patterns of forest distribution and the impact of fire and pastoralism in the forest region of Tibet,” In: G. Miehe and Y. L. Zhang, Editors, Environmental Changes in High Asia. Selbstverlag der Marburger Geographischen Gesellschaft, Marburg 135, pp. 201–227, 2000.
3. T. Karabacak, G.-C. Wang, and T.-M. Lu, “Physical self-assembly and the nucleation of 3D nanostructures by oblique angle deposition,” J. Vac. Sci. Technol. A 22, pp. 1778, 2004.
4. J.-X. Fu, A. Collins, and Y.-P. Zhao, “The optical properties and biosensor application of ultra thin Silver films prepared by oblique angle deposition,” J. Phys. Chem. C 112, pp. 16784–1679, 2008.
5. D.-X. Ye, Z.-P. Yang, A.S.P. Cang, J.Bur, S.Y. Lin, T.-M. Lu, R.Z. Wang, S. John, “Experimental realization of a well-controlled 3D silicon spiral photonic crystal,” J. Phys. D: Appl. Phys., 40, pp. 1, 2007.
6. P.-I. Wang, S. H. Lee, T. C. Parker, M. D. Frey, T. Karabacak, J.-Q. Lu, and T.-M. Lu, “Low temperature wafer bonding by copper nanorod array,”, Electrochem. and Solid State Lett., 12, pp. H138-H141, 2009.
7. R. Kumar, J. Novak, and A. Tomkins, “Structure and evolution of online social networks,” Proceedings of the 12th ACM SIGKDD International Conference on Knowledge Discovery and Data Mining, pp. 611-617, Philadelphia, PA, August 2006.

Nanoscience and nanotechnology started off in the early 1980s when scientists were able to detect materials on the nano-level through microscopic systems. This development enabled the synthesis of nano-level materials such as carbon nanotubes, nano crystals, and metal oxide nanoparticles. Nanotechnology is a type of technology, resulting from the research conducted on the atomic, molecular and macromolecular levels. A nanometer is one-billionth of a meter. Nano-level studies are conducted with materials whose sizes range between one to a hundred nanometers. Studies on the nano-level are conducted in the contemporary science fields such as chemistry, materials science, physics, biology, etc. One of the most compelling reasons that renders the research with nano-level materials so significant is that nanoparticles reflect a lot more different characteristics than when they do at the macro-level. Due to their small sizes, nanoparticles, especially those under 20 nm, have magnificent optical, magnetic, and chemical properties.[1] Nanoparticles include much more energy than the macro-level materials; this is because the ratio of the surface area of nanoparticles to their volume is much more bigger than the ratio in macro-level materials. A significant amount of energy is stored in nanoparticles as free surface energy. This energy revealed on the nano-level not only increases the reactivity of iron nanoparticles (the propensity to chemical reactivity), but also renders the magnetic qualities of materials quite differently than they would be at the macro-level.

Many types of nanoparticles are widely used in our daily lives. Iron, gold, silver and cadmium sulphide nanoparticles are some of the most commonly investigated nanoparticles. Yet iron nanoparticles receive special attention from scientists essentially in the field of biotechnology. Iron nanoparticles demonstrating different magnetic features have a wide range of use in fields, including but not limited to health care and electric/electronic industry. Owing to its magnetic feature, iron is also used in magnetic recording. The production of needle-shaped iron nanoparticles with high magnetic features has facilitated the manufacturing of mobile electronic devices with a high recording capacity. In this paper, we will focus on the use of iron nanoparticles’ contribution to the advances in the field of biotechnology, among numerous other contributions of iron nanoparticles in other fields.

Nanobiotechnology

Nanobiotechnology, among other fields of nanotechnology, is the field that focuses on biological systems. Nano-level devices designed to work with biosystems, nano-level cell biology, cell and nanoparticle interactions are some of the applications used in nanobiotechnology. Through those applications, biochemical processes and reactions in living beings can be scrutinized in great detail, which, in turn, enables scholars to come up with innovations in both diagnosis and treatment of various illnesses.

The following are the primary application areas of magnetic nanoparticles in the field of bionanotechnology: development of magnetic resonance imaging systems, and cancer research. Especially, iron oxides (magnetite, Fe3O4, maghemite, Fe2O3), owing to their cohesion with the chemical structure of biological systems, are prevalently used in biotechnology.

Magnetic Resonance Imaging (MRI)

MRI, mostly used in the medical field, is the method to monitor the internal structure of living mechanisms. Through the magnetic area and radio frequency waves, the image of a living tissue is formed. MRI is a complex system that produces images based on the intensity and movements of hydrogen atoms in the tissue. The MRI technique is used to diagnose almost all sorts of illnesses today. Yet it is most frequently used with illnesses pertaining to the central nervous system, brain and spinal cord. It has also been used to diagnose muscle-related and skeleton-related medical conditions, such as meniscus and herniated disc symptoms, as well as all types of neurological illnesses. MRI has not been found detrimental to any living organism thus far.

It is the paramagnetic ions such as gadolinium that are most frequently used as contrast enhancement agents in MRI applications. Although gadolinium has a high moment, this moment is too low compared to superparamagnetic materials. For this reason, superparamagnetic iron oxide nanoparticles are known to be more efficient MRI contrast enhancement agents. Known as such, those iron oxide nanoparticles are quite advantageous over gadolinium. Those nanoparticles can easily be functionalized to interact with biological samples. For example, superparamagnetic nanoparticles, which are not normally taken up by cells efficiently, can do so after being covered with another material (e.g. Dextran) that can ordinarily go into a cell. Thus, MR images of particular tissues could be obtained clearly, which enables us to make more accurate diagnoses and treatments.

Iron oxide nanoparticles are also deemed to be an efficient potential future method in cancer treatment. The results of several studies conducted to fulfill this goal are encouraging.

Iron oxide superparamagnetic nanoparticles are being tested as a method in hyperthermia treatment. Hyperthermia is defined as an abnormally high body temperature, and its treatment is carried out through the removal of certain tissues by increasing its temperature up to (42–46) 0C for 30 minutes. For instance, cancer infected liver tissues are exterminated through the hyperthermia method, which sends biologically activated iron oxide nanoparticles to those infected tissues. Moreover, none of the healthy tissues are damaged during this process. You may find more detailed information in references [1, 2, 4, 6] on how nanoparticles are aptly sent to the cancer infected tissues only while the surrounding healthy tissues remain unaffected by them. Hundreds of researchers carry out experiments and publish their findings on this topic everyday. Yet, further research needs to be done in order to reach solid conclusions.

Iron, which seems to carry greater potential significance than we previously thought, should receive much attention from scholars due to the fact that a chapter (surah) in the Holy Qur’an is entitled “Iron” (Hadeed). The question is, why was a 29-line chapter in the Qur’an is called (Iron) when the word “iron” was only mentioned once throughout the entire chapter.

The chapter “Iron” first begins by drawing the reader’s attention to the attributes and praised names of God. It invites people to believe in God and his messenger Muhammad (peace be upon him) by exalting God as the Almighty, Sovereign, Ruler, One whose existence is without a beginning and an end, Manifest and Hidden. Then, the chapter goes on to encourage believers to donate their wealth for the sake of God, for those who follow the word of God are rewarded with a place in Heaven. It also advises believers never to lose their ardor, while reminding them that even the earth will be resurrected after all has perished. And the wisdom behind the creation of iron is explained as such:

Assuredly We have sent Our Messengers with manifest truths (and clear proofs of their being Messengers), and We have sent down with them the Book and the Balance so that (relations among) humankind may live by equity. And We have sent down iron in [the essence] which is stern might and benefits for humankind, so that God may mark out those who help (the cause of) God and His Messengers, though they do not see Him. Surely God is All-Strong, All-Glorious with irresistible might. (57:25)

This particular verse includes several remarkable points. First, the very use of the phrase “sending down” for iron is so striking that it was also mentioned in [3, 5]. Another perplexing statement is, We sent down iron in [the essence] which is stern might and benefits for humankind, which might pave the way for thought-provoking venues regarding nanotechnology. The verse also indicates that which makes iron so special, its indiscernible or hidden qualities, rather than the outer surface of it. The specific reference to the “essence” of iron hints at this point. If the message of the verse had been related to the external qualities of iron, then the choice of the words would differ accordingly. Since the Qur’an is the word of God, there is wisdom behind the selection and sequencing of each word and letter. From this point of view, we can interpret that this verse informs us about the significance of the essence of iron on the nano level.

The significance of iron as stated in a single verse of the Qur’an has been briefly discussed. Numerous studies on the use of iron in nanotechnology seem to be on the horizon, which will only contribute to our admiration for the miracle of the Qur’an.

Kamil Ezgin is pursuing a PhD degree in chemistry in USA. For correspondence with the author kamilezgin@gmail.com.

References

1. Dale L. Huber. Synthesis, Properties, and Applications of Iron Nanoparticles, small, 2005, 1, No. 5, 482-501.
2. An-Hui Lu, E.L. Salabas, and Ferdi Schuth, Magnetic Nanoparticles: Synthesis, Protection, Functionalization, and Application, Angew. Chem. Int. Ed. 2007, 46, 1222-1244.
3. Edib Masûkî. “Enteresan Bir Tespit: Demirin Sakladiði Sir,” Sizinti, 1985, No. 73.
4. Peter Majewski and Benjamin Thierry. “Functionalized Magnetic Nanoparticles- Synthesis, Properties, and Bio-Applications,” Critical Reviews in Solid State and Materials Sciences, 2007, 32, 203-215.
5. http://www.mergeous.com/bullet.asp?tag=72
6. Volker Mailander and Katharina Landfester, “Interaction of Nanoparticles with Cells,” Biomacromolecules 2009, 10, 2379–2400.

Scientists were working on ways of obtaining complex micro or nano (a billionth of a meter) structures by using simple inorganic substances like silicon. Producing a micro-scale device such as a transistor required difficult and expensive processes such as cutting a silicon layer neatly. A species of sponge (tethya aurantia) has proved to be a model for a possible solution.

Like every other creature, sea sponges are given the ability to use chemical substances in the exact proportions they need to carry out their vital functions like an expert chemist. A sea sponge obtains siliceous acid from the water around it a few hundred meters under the sea. By a mechanism where chemical energy is used at high efficiency and silicatein enzyme functions as a catalyzer, this acid is transformed into silicon dioxide or silica, and perfect three-dimensional structures are built from it.

The most noteworthy aspect of this process is that there is no need for the poisonous chemicals or high temperatures scientists use to obtain complex inorganic structures. Sea sponges are granted the ability to build these complex structures far more effectively than the engineers who try to produce semi-conductive materials. When the outer tissue of a sponge is removed, the 2mm-long skeletal structure, which is thinner than human hair and which takes the form of glass needles, becomes visible.

Sponges fall into three categories with respect to the abundance of their cavities and the intricacy of the channels between them. Those with the maximum proportion of cavities and channels are the most desired ones. We can better understand how wonderful are the nano-scale structures within sponges by observing the relation between a sponge and water. When we dip a hand-size sponge in water and take it out, we see that it holds water equivalent to thousands of times more than its own weight. This is caused by the countless nano-cavities invisible to the naked eye within the body of the sponge. In these minute capillary distances, the adhesion and surface tension forces are given a dominant role between water and the substance of the sponge by the divine will. Sponges, which are classified as simple structured animals by some biologists, are granted some specialties to inspire us in making high technology products such as computer microchips and solar cells.

Daniel Morse and two of his colleagues from the University of California are working on some semi-conductive materials with amazing electronic features like turning daylight into electricity. The most important application field of this new technique will be more efficient photovoltaic solar cells. Presently, solar cells are produced under high temperatures and low pressure, which requires too much energy. However, the method taught to sea sponges is highly efficient and does not require high energy. Scientists have managed to produce simpler and cheaper solar cells by imitating sea sponges and using zinc oxide instead of silicon. This way the billion-dollar facilities where the semi conductive materials are produced can possibly be replaced by smaller units of production. The world of living beings has always opened doors to new horizons. Things we take for granted and to which we do not give much thought are waiting to be reflected upon and seen through the eye of wisdom.

References

• Paul Marks, Sea sponge leads way to cheaper solar cells, New Scientist, 24 March 2007, p. 32.

Particles that are the size of a nano (a billionth of a meter) are of great interest to science today. The most common saying in the engineering world is “the smaller the better,” and thus nanotechnology (technology of nano sizes) has become very popular in almost no time at all. Everybody is now trying to nanosize their ultrahigh technological instruments to catch up with ongoing nano-fashion. Taking this new technology into account, the use of the word “particles” instead of “atoms” that we encounter while reading about how the Law of Wisdom bestows important duties to inanimate and unconscious particles helps to unravel the mystery of how nanosized particles act under the Highest Command.3

As organisms made up of zillions of cells, we human beings are amazing biological systems. No moment passes without millions of reactions happening in our body. Most of them, indeed, all of them are being carried out by molecules, in particular supramolecular structures (also called enzymes) supplied with hands, arms or some other robotic units of several atoms. These are the actual “particles” on which the world is running.

The verse Not an atom’s weight of whatever there is in the Heavens or in the Earth escapes Him, nor is there anything smaller than that, or greater, but it is recorded in a Manifest Book2 has only clearly been understood since nanoscience has emerged. Some still interpret the meaning of zarrat (the original word used in Qur’an) as meaning atoms instead of particles, but it will not be long before they recognize that the actual work is being done by particles which are made up of molecules that consist of more than one atom, a state that is in agreement with Qur’an.

Zarrat are, first of all, the bricks used to build beings, worlds, and universes. They act in the name of the Glorious Creator, doing the work necessary for the continuity of systems. They work together as a team, in most cases without any trouble, demonstrating that the One Supreme Being is in command.

Secondly, the zarrat act as a multi-purpose cultivation field for all different crops, addressing the infinite treasury of His mercy and giving samples of His endless power.

The renewal of the zarrat each spring like an endless flood flowing through the world from the infinite treasury of His power, while preserving the property of being recyclable is a clear indication of the Absolute Commander.

Obviously, the so-called nanoscale sciences use these zarrat in action. Those particles work, doing whatever they have been told to do as they are obedient slaves of the Greatest King; however, some scientists fool themselves, assuming that each one of these particles is equipped with all-encompassing knowledge and power.

Above all else, the verse, “There is nothing that does not glorify Him with His praise, proclaiming that He is free from having any partners and all praise belongs to Him exclusively,”4 perfectly sums up the situation: the zarrat, the particles, have all been created to praise Him, the Creator, the Only Owner.

Notes

1. Nursi, Bediuzzaman Said, The Words, (translated by Sukran Vahide), Sozler Publications, 1998, page 570.
2. Qur’an, 34:3.
3. Nursi, ibid, 1998, page 580.
4. Qur’an, 17:44.