Fuel cells are very promising chemical energy conversion devices. Though the first fuel cell was made by William Grove in 1839, they’re just now being explored as a real energy alternative (1). Let’s take a look at how they work: in a fuel cell, electricity is generated by the reaction of hydrogen and oxygen, which forms water. They are similar to batteries and internal combustion engines (ICEs): just as in a combustion engine, where fuel is oxidized, the oxidization of hydrogen generates energy. They’ll work as long as fuel is provided.

Despite these similarities there are some differences that make fuel cells more attractive than batteries and ICEs. A fuel cell works more efficiently and quietly than engines do. When hydrogen is used as fuel, power and drinking water are produced as by-products (2). Having safe by-products answers our concerns regarding older power sources. A battery is dead if it is not re-chargeable; however a fuel cell can be continually reused.

Fuel cells are generally defined by the type of electrolyte used in the cell, and they operate at different temperatures. Alkaline fuel cells (AFCs), proton exchange membrane fuel cells (PEMFCs), and direct methanol fuel cells (DMFCs) are called low-temperature fuel cells. Phosphoric acid fuel cells (PAFCs) are an intermediate-temperature fuel cell. Molten carbonate fuel cells (MCFCs) and solid oxide fuel cells (SOFCs) are called high-temperature fuel cells (3, 4).

They have been mainly used for stationary, transportation, and portable applications. Since the need for electricity in daily life has dramatically increased, reliable and efficient power supplies have become necessary. Over 2,000 stationary fuel cell systems have been built in hotels, schools, and hospitals. Stationary power generation is considered more commercialized among the other fuel cell applications. Today, these systems have reached an efficiency of 40% when a hydrocarbon is used as fuel. Fuel cell systems are also used in telecommunication systems, and these cells provide power between 1 and 5 kW (5).

Fuel cells have been identified as the most probable alternative power source for transportation applications in place of internal combustion engines (ICEs). There are two distinct features of fuel cells that make them a better choice than ICEs. First, their carbon dioxide gas emissions are nearly zero. Second, fuel cells are much more efficient than ICEs – about two to three times (6). Ballard Power Systems have been developing zero-emission-vehicles by using PEMFCs, which have low operating temperatures and a higher power density.

NASA decided to use fuel cells on American spacecrafts in the 1960s. The advantage of using them in spacecraft was that while they were generating electric power, they produced drinkable water for the astronauts. A fuel cell was used as an integral part of the power supply PEMFCs (1kW) in the Gemini crafts and AFCs (1kW) in the Apollo crafts, both of which were a part of NASA’s human spaceflight programs (6).

Portable applications of fuel cells offer electrical power when reaching the electrical grid is not possible. When they are used as power sources outdoors, they help to avoid air and noise pollution (4). Because these portable fuel cells are lighter and more durable than batteries, they have been considered as alternative power sources for mobile phones, laptop computers, and some electronic devices (5). They are also used by the military in battle. A 4 kW PEM generator was built for the U.S. military by Intelligent Energy Ltd., out of Europe (7). Since direct methanol fuel cell systems are much lighter than the indirect systems, they are mostly used as portable power systems.

Although fuel cells have benefits when compared to other power sources, they are not widely used because of their high cost. In 2010, the Energy Information Administration released that the cost of fuel cells is $6.83 per installed watt, which is almost 7 times more expensive than a natural-gas turbine generator plant (8). In 2008, the Honda Clarity produced one of the first hydrogen-powered automobiles; these require very expensive catalysts: platinum (9). A catalyst makes the chemical reactions occur faster. Platinum is still the best catalyst, so this explains the prohibitive cost. A cheaper substitute for platinum is needed for use in automobiles. Another problem is that hydrogen is widely used as fuel for transportation applications. Until there is a sufficient hydrogen infrastructure, car manufacturers will find it hard to mass produce cars that use fuel cells.

Cetin is a freelance science writer.

References

1. Grove, W. R. (1839). On voltaic series and the combination of gases by platinum. Philosophical Magazine and Journal of Science, Series 3,14, 127-130.
2. Hoogers, G. (2003). Fuel Cell Technology Handbook. Boca Raton, FL: CRC Press.
3. Mekhilef, S., Saidur, R., Safari, A. (2012). Comparative study of different fuel cell technologies. Renewable and Sustainable Energy Reviews 16, 981-989.
4. Gencoglu, M. T., Ural, Z. (2009). Design of a PEM fuel cell system for residential application. International Journal of Hydrogen Energy 34, 5242-5248.
5. Andujar, J., Segura, F. (2009). Fuel cells: History and updating. A walk along two centuries. Renewable and Sustainable Energy Reviews 13, 2309-2322.
6. Iovine, John. “Fuel Cells.(composition, energy-generating processes and industry developments and innovations).” Poptronics. Poptronix, Inc. 2001. Retrieved May 17, 2012 from High Beam Research: http://www.highbeam.com/doc/1G1-69015426.html
7. Cowey, K., Green, K., Mepsted, G., Reeve, R. (2004). Portable and military fuel cells. Current Opinion in Solid State and Materials Science 8, 367-371.
8. Administration, U. E. (2010, November). Updated Capital Cost Estimates for Electricity Generation Plants. Retrieved from http://205.254.135.24/oiaf/beck_plantcosts.
9. Muller, R. A. (2012). Energy for Future Presidents: The Science Behind The Headlines. New York: W.W. Norton Company, Inc.

The fascinating aspect of these materials stems from the fact that when certain particles or devices are manufactured on the nanometer size region by means of special chemical and physical methods, they start showing distinct properties dependent on size, shape, and elemental compositions (such as huge amount of light absorption/emission, plasmonic resonance, high surface area, ability to convert light into heat, desirable magnetic properties, etc). Each of these features have found many applications in technology and they provide superior properties when compared to conventional materials. This article will not cover each technology based on nanomaterials but rather focus on the medical aspects and applications of nanotechnology and the direction it is heading.

Nano-medicine is a novel branch of nanotechnology seeking to deliver medically relevant drugs and imaging agents to the desired sites of the body. Biomedical imaging and drug delivery fields are benefitting from nanotechnology to a greater extent because not only do nanomaterials provide unprecedented results in diagnosis and therapies, considerable amounts of incentives in the form of governmental and private funding also drive topnotch institutions and scientists to study these materials around globe. For instance, iron oxide—when designed and manufactured on the nanometer order—can compete with, if not replace, most of the commercial magnetic resonance imaging (MRI) contrast agents due to some of its attributes, (i.e., being much more sensitive) requiring a less amount compared to other contrast agents, non-toxic to humans, and easy to manipulate in terms of its chemistry (1). Nanometer-sized spherical and rod-shaped Cadmium/Tellerium/Lead sulfides and selenides, also known as “Quantum Dots,” can absorb and emit light from ultra-violet (UV) to infrared region (IR) and this phenomenon could be utilized to construct biomedical sensors capable of detecting biologically relevant species (such as blood glucose, tumor markers, hormones, and etc.) with great accuracy and speed (2). Even by using multiple colors emitting “Quantum Dots,” one can, in principle, detect more than one biological entity simultaneously. Furthermore, their superior emissive properties could be harnessed to develop sensitive and selective fluorescence imaging techniques and assays which can lead to simple and early diagnosis of diseases. Gold nanorods, if irradiated with IR lasers, can generate extreme local temperatures in the surrounding medium owing to “plasmonic resonance of surface electrons,” and this feature could be directed to killing of localized tumor tissues known as “Photothermal Theraphy” (3).

Another class of nanomaterial called liposomes (4) can actually mimic lipid bilayer of the cell membrane which gives rise to a protective layer around organelles and nucleus, and maintains the transport of ions and molecules in and out of the cell. Synthetic liposomes, strikingly, can accommodate various cargoes extending from drugs to imaging agents in their inner cavity and render controlled release of its cargo as it circulates in the body, thereby providing longer bio-availability.

One of the most alluring uses of nanoparticle formulations in cancer therapy is their dimension. Certain sizes of nanoparticles can permeate into tumoral sites and be retained in that region longer than small particles or molecules. This extraordinary feature of nanoparticles, called “enhanced permeability and retention effect” (5), was utilized with liposomes to deliver chemotherapeutics to cancerous tissues effectively in a slow and controlled manner. In addition, chemical malleability of nanoparticles give rise to smart formulations which could respond to external stimuli in drug delivery applications. For example, the fact that cancer cells have lower pH values as compared to normal cells has been used to trigger release and delivery of drugs on site (6).

An alternative approach to conventional treatments is gene therapy in which the malfunctioning or mutant gene has been reintroduced into cells with a properly functioning one in order to restore the malady (7). Nanoparticles, especially polymeric counterparts, have shown promising results in encapsulating, carrying and delivering the gene of interest into desired cells.

Apart from synthetic nanoparticles, naturally occurring nanoparticles, have lately received great attention due to their unique structures and properties such as biocompatibility, uniform size, as well as suitability to chemical and genetic engineering. Plant and bacterial viruses, known as viral nanoparticles (8), have been tested for imaging and drug delivery applications, and because they infect only plants and bacteria, they are considered to be benign towards mammalians. Their inner and outer amino acids could be chemically modified with drugs and imaging modalities and cleverly engineered drug release mechanism could be invoked to operate upon external or internal stimulus.

Nanomaterials are, furthermore, suitable candidates for vaccine development. The immune system normally recognizes certain chemical groups on the surface of antigens (pathogens) and develops its defense mechanism based on this recognition. Multiple copies of these chemical groups could be chemically tailored around the surface of nanomaterial, and thereby could trigger the same immune response more efficiently (9).

The future of medicine will be shaped and enhanced through a targeted delivery of drugs and imaging contrasts into desired sites. Promisingly, nanoparticles will be able to assist in this regard to a considerable extent. Today’s cancer chemotherapy rely mostly on administering a variety of cancer drugs via intravenous (injecting through the vein) or oral means which delivers drugs to cancer cells as well as a considerable amount to healthy tissues which causes major side effects. In order to accumulate higher doses of drugs in tumor cells selectively and minimize nonspecific delivery, nanoparticles loaded with drugs and chemically decorated with “smart molecules” which have the ability to recognize cancer cells and specifically bind to them have been designed and tested successfully (10). These smart groups (organic molecules, antibodies, peptides and small molecules), surprisingly, have higher binding affinities toward some receptors over-expressed in cancer cells. Furthermore, encapsulation of drugs by nanomaterials provides a protective shell which prevents leakage of drugs to other sites.

An important drawback of cancer therapy is drug resistance in which cancer cells develop mechanisms to pump chemotherapeutics out of cells and decreases the efficacy of drugs. Nanoparticles, however, invalidate these resistance mechanisms by encapsulating drugs and should therefore not be exposed directly to surrounding cell environment. When nanoparticles reach the desired destination in the cell, an engineered mechanism or stimulus augment the release and drugs are expected to show their activity without any compromise (11).

It is fascinating to see how these small nanoparticles behave cleverly and orderly even though they look like inanimate and unconscious clusters of atoms. The extraordinary art, design and engineering witnessed in macro dimensions can also be seen in nano dimensions which means that a conscious and purposeful Hand of Power is present and visible in this nanoworld.

To sum up, nanomaterials could be ideal platforms for drug delivery and imaging applications and could complement the deficiencies in conventional therapies. Loading multiple copies of these entities into nanoparticles and devising clever mechanisms to target and deliver them into desired sites would be key elements in the nanomedicine of the future. We are living in a world where each of us has someone in our families or among our friends who are going through painful cancer treatments, which is a heart-rending and traumatic experience. Hopefully, nanomaterial-based therapies would give rise to solutions and success in battling against cancer. For in one prophetic tradition the Prophet Muhammad, peace be upon him, says: “O servants of God! Search for ways for treatment of illnesses. If God gives you ailments, for sure He bestows upon you cures for those.”

And why can’t this bestowal be in the nano form?

References

• Qiao RR, Yang CH, Gao MY. “Superparamagnetic iron oxide nanoparticles: from preparations to in vivo MRI applications” (vol 19, pg 6274, 2009). J Mater Chem 2009;19:9286-9286.
• Raymo FM, Yildiz I. “Luminescent chemosensors based on semiconductor quantum dots.” Phys Chem Chem Phys 2007;9:2036-2043.
• Giljohann DA, Seferos DS, Daniel WL, Massich MD, Patel PC, Mirkin CA. “Gold Nanoparticles for Biology and Medicine.” Angew Chem Int Edit 2010;49:3280-3294.
• Jesorka A, Orwar O. “Liposomes: Technologies and Analytical Applications.” Annu Rev Anal Chem 2008;1:801-832.
• Sancey L, Barbier E, Hirsjarvi S et al. “Enhanced Permeability and Retention (EPR) effect in tumors: characterization by MRI and fluorescence imaging.” B Cancer 2011;98:S67-S67.
• Hruby M, Konak C, Ulbrich K. “Polymeric micellar pH-sensitive drug delivery system for doxorubicin.” J Control Release 2005;103:137-148.
• Waehler R, Russell SJ, Curiel DT. “Engineering targeted viral vectors for gene therapy.” Nat Rev Genet 2007;8:573-587.
• Yildiz I, Shukla S, Steinmetz NF. “Applications of viral nanoparticles in medicine.” Curr Opin Biotech 2011;22:901-908.
• Peek LJ, Middaugh CR, Berkland C. “Nanotechnology in vaccine delivery.” Adv Drug Deliver Rev 2008;60:915-928.
• Ruoslahti E, Bhatia SN, Sailor MJ. “Targeting of drugs and nanoparticles to tumors.” J Cell Biol 2010;188:759-768.
• Liang XJ, Chen C, Zhao Y, Wang PC. “Circumventing tumor resistance to chemotherapy by nanotechnology.” Methods Mol Biol 2010;596:467-88.

A particularly interesting class of all these non-coding RNAs comprises riboswitches. Riboswitches are structured mRNA elements that regulate gene expression upon binding of a specific small metabolite. These biosensors were first discovered in 2002 in bacteria. Later, it was shown that plants, green algae and fungi also posses riboswitches. Although, only one type of riboswitch is found in plants and none has beeen detected in mammals yet, metabolite-sensing riboswitches are commonly used for the regulation of fundamental biochemical pathways in bacteria. Riboswitches help cells monitor the environmental conditions and determine if a compound is present at sufficient levels or not. Based on this decision, production, degradation or transport of the related metabolite is either turned on or off.

Architecture of a Riboswitch

A standard riboswitch is divided into two parts: a ligand-binding domain and a gene expression domain (Figure 1). Small molecular metabolites bind to the ligand-binding domain, which is called aptamer, of riboswitches with astonishing specificity. For instance, purine riboswitches differentiate guanine from adenine by at least 10,000-fold based on the identity of a single pyrimidine (thymine or cytosine) that binds to the ligand (1). When a ligand binds to aptamer, conformational changes of the RNA’s structure occur at the gene expression domain. Eventually, this leads to the modulation of gene expression. Some of the riboswitch mechanisms to regulate the expression of genes include formation of stem-loops, lollipop-like RNA structures, which lead to the blocking of transcription or translation, which are the processes where proteins are synthesized using the mature mRNA, self cleavage or mRNA destabilization (Figure 2).

Classes of Riboswitches

The numerous distinct classes of riboswitches discovered so far are differentiated by their ligands and remarkably, the same class of riboswitches can control gene expression through different mechanisms in various organisms. For example, a riboswitch that recognizes and binds thiamin pyrophosphate (TPP), a derivative of vitamin B1, is called as TPP riboswitch (2). In plant cells, when TPP levels are high, excess TPP binds to a TPP riboswitch located in one of the TPP biosynthesis genes. As a result of TPP binding, conformation of that RNA segment changes, which leads to the formation of an unstable mRNA product which degrades quickly. Although, a very little amount of stable mRNA is also produced, it is not enough for the protein synthesis of an important component of TPP biosynthesis. Therefore, TPP biosynthesis can not be completed and consequently TPP levels drop in the cell. On the other hand, when TPP levels are low in plants, more stable mRNA is formed because there is not enough TPP that can bind to the riboswitch and cause structural changes which will result in the formation of unstable mRNA. The stable mRNA produced in the absence of excess TPP is used for the protein biosynthesis of TPP metabolism successfully and thus TPP levels increase in the cell. Unlike plants in bacteria, when TPP concentration is high, riboswitches down-regulate expression of thiamin biosynthesis genes by either blocking the formation of any type of mRNA (both stable and unstable) or preventing the mRNA process rather than destabilizing the mRNA. Some of the other riboswitches that bind vitamin derived compounds are adenosylcobalamin, the coenzyme form of vitamin B12, and flavin mononucleotide, a biomolecule produced from vitamin B2, riboswitches. There are also riboswitches that can bind to amino acids such as lysine riboswitch. The cyclic diguanylate (c-di-GMP) riboswitch is the first known example of an RNA that binds a second messenger, which carries signals from receptors on the cell surface to target molecules inside the cell (3). Purine riboswitches selectively recognize guanine or adenine and regulate purine biosynthesis and transport, which is important for DNA/RNA synthesis. Another interesting type of riboswitch is the glmS riboswitch. It modulates gene expression by undergoing self-cleavage when there is a sufficient concentration of glucosamine-6-phosphate, an important amino sugar. The spectrum of ligands that can be recognized by riboswitches also includes a metal ion, as well. Mg(2+) riboswitches control Mg(2+) transportation when cells are grown in high Mg(2+) environments. In brief, the growing list of studies on riboswitches shows how novel mechanisms are which they use to regulate the gene expression of many fundamental metabolic pathways.

Applications for Riboswitches as drug targets and chemosensors

Riboswitches are powerful and essential components in all three domains of life which are bacteria, archaea (a group of single-celled microorganisms) and eukaryotes ( organisms whose cells contain complex structures inside membranes such as plants and fungi) functioning as intracellular biosensors and regulators. They regulate gene expression in a highly efficient, precise and fast way. Therefore, they can be engineered for various applications.

First of all, riboswitches are excellent candidates as drug targets since they control many important bacterial and fungal genes. Chemical analogs that mimic the actual ligands of the riboswitches can be designed to silence or regulate the expression of defective genes responsible for disease development or even kill certain bacterial pathogens by turning off the genes that are involved in fundamental metabolic pathways. A great example of this strategy is presented by the Breaker laboratory at Yale University. The Breaker group chose guanine-binding riboswitches as targets for the development of novel antibacterial compounds. They have designed several guanine analogues and tested their ability to be bound by the riboswitch and repress bacterial growth (4). They have been able to inhibit the bacterial growth by inducing guanine riboswitch action. Their approach could be used to discover new antibacterial compounds that specifically target other riboswitch classes.

In addition to being drug targets, riboswitches can open new frontiers in bioremediation, bionanotechnology, and synthetic biology. In 2007 Shana Topp and Justin P. Gallivan from Emory University demonstrated that Escherichia coli can be reprogrammed to detect, follow, and precisely localize to a completely new chemical signal by using a synthetic riboswitch (5). They suggest that the bacteria with synthetic or mutated riboswitches could be used to follow and degrade pollutants in soil or target small-molecule signals of disease. Overall, their work to equip the bacteria which can autonomously follow chemical signals, degrade, synthesize or release compounds can help scientists invent new technologies in bioremediation, drug transport, and synthetic biology.

Furthermore, riboswitches are ideal candidates for use in analytical devices and techniques. Their binding features make them suitable in all specific analytical applications in which selective recognition is required. Therefore, these powerful molecular tools can be utilized in analytical chemistry, molecular biology and biosensor technology (6).

As a result, living systems utilize riboswitches to detect the concentrations of small-molecule metabolites and to modulate the expression of related genes via numerous elegant mechanisms. The use of genetic engineering of riboswitches holds enormous potential for inventing new applications to sense and destroy pathogens, deliver drugs, perform bioremediation, detect chemicals and many others that might have significant impacts on our lives. It is also remarkable that only a couple of decades ago most of the non-coding RNAs were assumed to be useless, and are called junks since they do not provide any information for protein synthesis. Yet riboswitches by themselves are enough to prove that God has created everything with a purpose. He is All-Wise and he does nothing in vain. Riboswitches are not useless at all. They are such complex, and perfectly working systems that they can serve humanity as well-designed on/off switches in numerous applications.

Safiye Arslan is a research fellow in the area of biological chemistry and lives in Nevada.

References

1. Gilbert SD, Reyes FE, Edwards AL, Batey RT. 2009. Adaptive ligand binding by the purine riboswitch in the recognition of guanine and adenine analogs. Structure 17, 857-868

2. Wachter A, Tunc-Ozdemir M, Grove BC, Green PJ, Shintani DK, Breaker RR. 2007. Riboswitch control of gene expression in plants by splicing and alternative 3′ end processing of mRNAs. Plant Cell 19, 3437-3450.

3. Kulshina N, Baird NJ, Ferré-D’Amaré AR. 2009. Recognition of the bacterial second messenger cyclic diguanylate by its cognate riboswitch. Nature Structural & Molecular Biology 16, 1212-1217.

4. Kim JN, Blount KF, Puskarz I, Lim J, Link KH, Breaker RR. 2009. Design and antimicrobial action of purine analogues that bind Guanine riboswitches. ACS Chemical Biology 4, 915-927.

5. Topp S, Gallivan JP. 2007. Guiding bacteria with small molecules and RNA. Journal of the American Chemical Society 129, 6807-6811.

6. Mairal T, Ozalp VC, Lozano Sanchez P, Mir M, Katakis I, O’Sullivan CK. 2008. Aptamers: molecular tools for analytical applications. Analytical and Bioanalytical Chemistry 390, 989-1007.

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.

Educators who see the beauty at the center of mathematics and can make their students see it that way, are more likely to be able to get their students’ attention and teach them more effectively. Also, as well as facilitating the study of sophisticated mathematics, this puts mathematics in its proper place so as better to understand the value of what it has to say to human beings. To see the beauty and the pleasure in mathematics can change the negative attitudes of some students and help educators in teaching mathematics.

Often it seems that we pursue mathematics education from either a structural or an applications point of view. From a structural point of view, we insist on building up all of the tools one may need in a sequential, logical order, because an educator will need the students to know all of the smaller pieces before they can build any of the larger ideas. An analogy for this would be if we forced somebody to study all of the nails, screws, bolts, and tools to build a house before we let them even see the plans for the house. This is one of the main reasons that most people who study mathematics in their school years think that it is a pointless exercise in playing with formulas and has no significance in real life. For these people, mathematics might be helpful only in keeping track of their checkbooks after graduation. Some students think that they can calculate whatever they need using computers, but sometimes this is not very effective because students may not understand the logic behind the problems and the results do not mean anything to them or they are unable to detect errors.

The applications point of view leads to making up “word problems” that appear to be about the real world, but everyone knows that they are highly artificial. It also leads to focusing at higher levels on only the applications. Hence, for instance, in calculus we spend a lot of time plodding through various physical applications, without letting students see the bigger picture. Or we spend time in liberal arts mathematics talking about things such as modeling and linear programming, which yield great applications, but are generally tedious and do not give most students much appreciation for mathematics. If we see the beauty at the center of mathematics, as well as introducing ideas that may have application or may build some tools, we can bring students to have a much bigger picture of mathematics at a much earlier stage in their mathematical development.

Educators can include some fun topics in courses that they teach. For instance, they can encourage students to discover the amazing number patterns in nature, such as the Fibonacci sequence in pine cone spirals, pineapples, and cauliflowers, in which the number of pieces increases in the following manner: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89 … (add the last two numbers to get the next). Another example is the “golden ratio.” In mathematics and the arts, two quantities are in the golden ratio if the ratio between the sum of those quantities and the larger one is the same as the ratio between the larger one and the smaller. The golden ratio is a mathematical constant, approximately equal to 1.6180339887 and recent research shows that people think that the shapes and figures in this ratio are more interesting and aesthetically pleasing to the human eye.

Sometimes, even a small algebra trick can miraculously bring students to love mathematics and be more focused, and then more interested in the deeper aspects later on. Take a look at this symmetry:

1 x 1 = 1

11 x 11 = 121

111 x 111 = 12321

1111 x 1111 = 1234321

11111 x 11111 = 123454321

111111 x 111111 = 12345654321

1111111 x 1111111 = 1234567654321

11111111 x 11111111 = 123456787654321

111111111 x 111111111 = 12345678987654321.

Here are a few more examples showing the beauty of mathematics visually with numbers:

1 x 9 + 2 = 11

12 x 9 + 3 = 111

123 x 9 + 4 = 1111

1234 x 9 + 5 = 11111

12345 x 9 + 6 = 111111

123456 x 9 + 7 = 1111111

1234567 x 9 + 8 = 11111111

12345678 x 9 + 9 = 111111111

123456789 x 9 +10 = 1111111111

9 x 9 + 7 = 88

98 x 9 + 6 = 888

987 x 9 + 5 = 8888

9876 x 9 + 4 = 88888

98765 x 9 + 3 = 888888

987654 x 9 + 2 = 8888888

9876543 x 9 + 1 = 88888888

98765432 x 9 + 0 = 888888888.

Students’ minds can be broadened by seeing the surprising differences that arise when we move to non-Euclidean geometry. Fractal shape examples in nature, such as snow crystals, and things like the Mandelbrot set, which is a set of points in the complex plane the boundary of which forms a fractal, can be introduced with a background and give rise to amazingly beautiful images and ideas. Even such deep and thought-provoking ideas as these can be understood by students when they have curiosity, creativity, and an open mind.

All these examples and others like them can inspire people to see the beauty of mathematics and give them a better understanding and a sense of the expanse of mathematics. With a little more discovery of and exposure to the more beautiful aspects of mathematics, students are much less likely to feel any hatred for mathematics and may develop a much greater appreciation for the creation of the universe.

Ali Kemal Unver is a postdoctoral scholar at the University of California, Los Angeles.

Note

* The golden ratio can be derived by the quadratic formula, by starting with the first number as 1, then solving for the 2nd number x, where the ratio [x+1]/x = x/1 or (multiplying by x) yields: x+1 = x2, or a quadratic equation: x2-x-1=0. Then, by the quadratic formula, for positive x = [-b + sqrt(b2-4ac)]/2a with a=1, b=-1, c=-1, the solution for x is: [-(-1) + sqrt([-1]2 -4*1*-1)]/2*1 or [1 + sqrt(5) ]/2. See the second reference for details.

References

1. http://users.forthnet.gr/ath/kimon/
2. Green, Thomas M. “The Pentagram and the Golden Ratio.” http://www.contracosta.cc.ca.us/math/pentagrm.htm.

The Process of Discovery

Kamerlingh Omnes, a Dutch physicist dedicated to achieving ultracold refrigeration, opened this field in 1908 by liquefying helium at -452 F (4 K or -269 C).(1) This achievement enabled scientists to cool materials to very low temperatures and study their properties.

Scientists knew that a metal’s resistance fell as the temperature was lowered, but did not know what the limiting value would be when 0 K (the absolute minimum temperature) was approached. In 1911, Omnes began investigating the electrical properties of metals at very low temperatures. Many contemporaries, including Lord Kelvin, believed that resistance eventually would level off to a nonzero value. While passing a current through a very pure mercury wire whose temperature was being steadily lowered, Omnes noticed that its resistance vanished at 4.2K. He remarked: “Mercury passed into a new state, which on account of its extraordinary electrical properties may be called the superconducting state.” This marks the birth of superconductivity.

Scientific and commercial potentials were obvious. A resistance-free metal wire could carry current for a long time without any loss. Omnes tried to determine the amount of such a loss. After letting a superconducting loop run for a year, he determined that there was no significant current loss. He was awarded the Nobel Prize in 1913 for his discovery.

In 1933, Walter Meissner and Robert Ochsenfeld discovered that superconductors are both perfect conductors and perfect diamagnets, for magnetic fields cannot penetrate a superconductor’s interior. When a material is superconducting and a field is applied, the current flowing on the superconductor’s surface generates a magnetic field that cancels the applied field inside the superconductor (the Meissner effect). Since the magnetic field generated inside the superconductor opposes the applied field, superconductors are diamagnetic. This shielding of an applied magnetic field occurs only if the applied field is not very large. Superconductivity is destroyed at a certain point.

Theoretical Progress and Surprises

Theoretical progress was much slower, however, almost as if superconductivity had been discovered too early. The scientific community’s incomplete understanding of quantum mechanics made it impossible to understand the mechanism behind superconductivity. Some phenomenological theories were developed during the 1930s and 1940s, but a clearer picture only began to emerge in 1957.

Three American physicists, John Bardeen, Leon Cooper, and Robert Schriffer, used quantum field theory and many-body physics to develop the BCS theory, which explains superconductivity for elements and some alloys.(2) In essence, the theory states that a superconductor’s electrons condense into a quantum ground state and move together coherently. Pairs of electrons (Cooper pairs)-not single electrons-achieve current transfer. These physicists received the Noble Prize in 1972.

Another milestone came in 1962. Brian Josephson, a Cambridge University graduate student, predicted that an electrical current could flow between two superconductors separated by thin insulating barrier. He made a suitable device (the Josephson Junction) by inserting an insulating material between two superconductors. Sending current through one superconductor, he saw it pass through to the other one. Known as the Josephson effect, it is one of the most important components in superconducting electronics. Josephson was awarded a share of the Nobel Prize in 1973.

In 1986, Alex Miiller and Georg Bednorz of IBM Research Lab (Switzerland) synthesized a ceramic compound that superconducted at 30K (-243C), the highest superconductor temperature ever reached. This compound contained lanthanum, barium, copper, and oxygen. Scientists do not know why it super-conducts, for it insulates at high temperatures and conducts electricity very poorly before it superconducts. Bednorz and Miiller received the Noble Prize in 1987.

This discovery inspired many researchers to combine elements to achieve superconductivity at higher temperatures. In January 1987, researchers at the University of Alabama replaced the lanthanum in the Bednorz-Miiller compound with yttrium and reached a transition temperature (Tc) of 92K. As a result, the much cheaper liquid nitrogen could replace liquid helium as a coolant. By trial-and-error experimentation, a Tc of 138K was reached in a compound consisting of mercury, thallium, barium, calcium, copper, and oxygen.

These new materials all contain layered copper and oxygen planes with other elements in between the crystal structure. Superconductivity occurs on the planes, and the rest of the crystal serves as a charge reservoir. The magnetic field gradually penetrates these new materials (called High Tc superconductors), causing a mixed state between the normal state and the superconducting state.

In 1997, existing theories were shattered when an alloy of gold and indium was used as a superconductor and a magnet. This is expected to have an important effect on magnetic data storage.

The most recent surprise came in November 2000. About 10 years ago, scientists learned that carbon-60 could superconduct at near absolute zero. By expanding the lattice structure, a Tc of 52K was reached. About a month later, the same group reached a Tc of 90K. Many believe that this temperature could reach well over 100K. Carbon-60 is the only material that has reached such high Tcs without having copper and oxygen planes in its structure.

Applications

Superconductors do more than just conduct electricity. Other important functions are as follows:

• The Korean-developed SQUID (Superconducting QUantum Interference Device) can detect magnetic field changes that are 100 billion times smaller than Earth’s minute magnetic field, and uses the most fundamental properties of superconductors and quantum mechanics. Medical researchers use SQUIDs to study the human brain. Systems in which hundreds of SQUIDs are arranged in a helmet-like configuration containing liquid helium are commercially available. These systems detect the magnetic field produced by thousands of neurons. Although neurons produce huge fields when compared to the SQUID’s sensitivity, a magnetically shielded room is required to filter out fields produced by TVs, computers, cars, and so on. In these rooms, external stimulation applied to the patient’s brain enables specialists to locate tumors or other ill-functioning areas by mapping the brain’s functions. The human brain has two types of responses: stimulated and self-generated (spontaneous). By using the SQUID’s fast temporal response, one can locate non-invasively the epileptic loci, which causes some diseases. Alzheimer’s and Parkinson’s research also use SQUIDs at the detection level.

• Magnetic levitation became possible after scientists built superconducting magnets. Since superconductors have no resistance, a small voltage can generate huge currents and, therefore, magnetic fields large enough to float vehicles on these superconducting magnets with almost no friction. In 1999, a train in Japan reached a speed of 343 miles per hour. Japanese researchers are studying the possibility of a mag-lev linear motor car.

• Superconducting magnets have been used extensively in particle accelerators since 1987. Particle physics requires the acceleration of subatomic particles to speeds very close to the speed of light. This necessitates high magnetic fields that, in turn, need high currents-something for which superconductors are ideal. One event that made superconducting better known is probably the American Congress’ cancellation of the multi-billion Superconducting Super Collider (SSC) project in 1993. A European consortium is now pursuing this research field.

•Superconducting wires improve an electric generator’s efficiency by more than 99 percent. In addition, such generators are about half the size of conventional ones. General Electric estimates that there is a potential $20-30 billion global market for superconducting generators. Unfortunately, the high costs of cooling systems rules out using this technology to supply cities with electricity. But the moment sufficiently high Tcs are reached, superconductivity’s impact in this area will be immeasurable.

•Other applications are high-performance and high-capacity electronic filters (currently used in some cellular phone systems); a petaflop-computer (1,000 trillion floating point operations per second-1,000 times faster than today’s computers); mine and submarine detection (the U.S. Navy); and storing energy to enhance power stability (American Superconductor Corp.); satellites; telescopes and other light detection instruments; and Internet routers.

Footnotes

1. F (Fahrenheit): A temperature scale registering water’s freezing point as 32F and boiling point as 212 F at one atmosphere of pressure. K (Kelvin): A unit of absolute temperature equal to 1/273.16 of the absolute temperature of the water’s triple point; equal to one Celsius degree. C (Celsius): A temperature scale registering water’s freezing point as 0 C and boiling point as 100 C under normal atmospheric pressure.
2. Quantum field theory: A body of physical principles that accounts for subatomic phenomena. Quantum many-body physics: The branch of theoretical physics that studies the new collective phenomena or “elementary” constituents of a many-particle system and the underlying quantum mechanics that determines their behavior.

References 

• Clarke, J. “Superconductivity: A Macroscopic Quantum Phenomenon.” Beam Line 30, no. 2 (summer/fall 2000): 41-48.
• Dull, R. W. and H. R. Kerchner. “Applications of Superconductors.” A Teacher’s Guide to Superconductivity for High School Students (1994). Online at:
• www.ornl.gov/reports/m/ornlm3063r1/pt4.html.
• Gunnarsson, O. “C60: The Hole Story.” Nature 1408 (30 Nov. 2000): 528-29.
• http ://superconductors .org
• Tinkham, M. Introduction to Superconductivity. 2d ed. McGraw-Hill Higher Education: 1995.

Since the mid-1980s, there has been increasing interest in developing so-called “electronic noses” (e-noses), that is, electronic instruments that can detect and recognize simple and complex odors.1 And since the mid-1990s, nearly 20 years after the concept was originally published, the commercialization of e-noses has started to take place. The main reasons for this delay were the complex nature of the problem and the need for advanced technologies. However, the recent development of microsensor technology has led to low-cost integrated chemical sensors and application-specific microprocessing devices. This, coupled with our greater understanding of artificial intelligence, has allowed us to construct electronic instruments that perform in a manner similar to our own olfactory system.

E-noses are now being developed as systems for the automated detection and classification of odors, vapors, and gases. They are generally composed of a chemical sensing system (e.g., sensor array or spectrometer) and a pattern recognition system, such as an artificial neural network (ANN). At Pacific Northwest National Laboratory (PNNL), e-noses use ANN technology for the automated identification of volatile chemicals used in environmental and medical applications.2

The electronic nose works as follows. While a chemical vapor or odor is blown over a sensor array, sensor signals are digitized and fed into a computer. The ANN (implemented in software) then identifies the chemical. The benefits of e-noses include compactness, portability, real-time analysis, and automation.

FOOD INDUSTRY APPLICATIONS

Currently, the largest market for e-noses is the food industry. In some instances, e-noses can augment or replace panels of human experts and can reduce the amount of analytical chemistry performed in food production, especially when only qualitative results will do.

An electronic smelling device is a valuable tool for analyzing whether a product has gone bad. Potential applications of e-noses in the food industry are numerous: inspecting and grading food quality by odor; inspecting fish and beverage containers; controlling fermentation, automated flavoring, and microwave cooking; monitoring the ripening of cheese; verifying if orange juice is natural and/or fresh; testing plastic wrap for containing the odor of onions; and classifying grains and blueberry ripeness.

Using human odor panels to evaluate and control the quality of raw materials or finished products is extremely labor intensive, time consuming, expensive, and error prone. E-noses can quickly identify a characteristic odor classified as “good” or “bad” by the odor panel, thereby decreasing the workload, improving throughput, and reducing the cost of screening many samples at different stages of the manufacturing process. The system is applied easily to the manufacture and quality control of perfumes, cosmetics, and fine chemicals, as well as to packaging, monitoring environmental quality, the automotive industry, medical and diagnostic matters, and microbial classification.

ENVIRONMENTAL MONITORING

The PNNL is exploring the technologies required to perform cost-effective environmental restoration and waste management. This effort includes developing portable, inexpensive systems that can identify contaminants in the field in real time. Environmental applications of e-noses include identifying toxic wastes and household odors; analyzing fuel mixtures; detecting oil leaks; monitoring air quality, factory emissions, and hazardous chemicals; and testing ground water for odors.

MEDICAL APPLICATIONS

Since the sense of smell is important for physicians, an e-nose can be used as a diagnostic tool to examine bodily odors (e.g., breath, wounds, bodily fluids, etc.) and identify possible problems. Odors in the breath can indicate gastrointestinal, sinus, and liver problems, as well as infections and diabetes. Infected wounds and tissues emit distinctive odors, and odors coming from such bodily fluids as blood and urine can indicate liver and bladder problems. Currently, an e-nose for examining wound-related infections is being tested at South Manchester University Hospital.

In similar applications, ANNs have been used to track glucose levels in diabetics, determine ion levels in bodily fluids, and detect such pathological conditions as tuberculosis.

While the inclusion of visual, aural, and tactile senses into telepresent systems is widespread, the sense of smell has been largely ignored. PNNL recently proposed a more futuristic application of e-noses for telesurgery. In this application, an e-nose would identify odors in a remote surgical environment. These identified odors then would be transmitted electronically to another site, where an odor generation system would recreate them.

The next decade should see the cost of e-noses fall dramatically, with the result that they will be used not only in industry but also in everyday life. They can be used, for example, to detect tainted foods in the refrigerator, ensure clean clothes in the washing machine, detect poor air quality in the car, and perhaps even help us monitor our own health.

FOOTNOTES

1. J. W. Gardner and P. N. Bartlett, Electronic Noses (Oxford, UK: Oxford University Press, 1999).
2. http://www.ivanhoe.com/docs/backissues/electronicnose.html.

In recent years, we have realized that the world’s supplies of coal, gas and oil are limited. Nuclear power has been used as an alternative solution to fossil fuels. However, the use of nuclear power and fossil fuels incurred environmental problems so there is widespread public antipathy. As a result, the popularity of renewable energy has grown during the past twenty years. The World Energy Council estimated that renewable energy sources, such as solar, wind, hydro, wave and bio-mass, met 18% of the world’s energy needs in 1990 (World Energy Council, 1993). Their scenario is that the contribution from renewable energy could increase 30% by 2020.

One of the most promising of the renewable energy sources is the direct conversion of solar energy into electricity by photovoltaic generation. There are many reasons for growing popularity:

1. Photovoltaic generators do not pollute the air and do not leave waste products.

2. Photovoltaic generators are silent during operation.

3. They work effectively even in cloudy weather. They are more efficient at low temperatures.

4. As there are no moving parts, they work reliably for 20-30 years with little maintenance.

5. Solar energy is available everywhere so power can be generated anywhere it is needed. This makes photovoltaic generators attractive in the many places where there is no mains supply.

6. Photovoltaic generators can be planned and installed within a few months in contrast to conventional power stations which take at least five years to become operational.

7. Finally, photovoltaic generators can be located anywhere, such as in the roof or walls of an existing or already planned building, therefore they do no need to use up extra land.

The photovoltaic effect was first observed by Edmund Becquerel in 1839. Much later, in the 1930s, solid state researches developed the first photocells which were used in photographic exposure meters. In 1954, the Bell Telephone Laboratories made crystalline silicon solar cells with a conversion efficiency of 6% which was used in space programs. The market for photovoltaic modules has been growing steadily since; in 1991 it had reached about 50 MW per annum.

Solar Cell

The total radiant power from the sun falling on one square meter of a surface area can be as high as 1000W/m2 on a clear summer’s day and it can fall to 100W/m2 in cloudy conditions. In northern Europe, it seldom exceeds 850W/m2 (Treble F.C., 1993).

The inactive energy, solar energy, can be converted into electrical energy by solar cells. The absorption of light in semiconductors creates additional electrical charge carriers, both electrons and holes equally. If an electric field exists within the semiconductor, the negative electrons and positive holes move in opposite directions and this electrical charge separation results in the creation of a voltage. The movement of the electrical charges creates an electrical current and voltage so both current and voltage are generated simultaneously. This is the photovoltaic effect, the creation of a voltage by the action of light.

The basic way to establish an electric field in a semiconductor is to make a p-n junction. The electric field at the junction attracts electrons from the p-side and forces them to the n-side making it negatively charged. Similarly holes from the n-side are forced to the p-side, making this positively charged. Thus holes are creating a voltage. Figure 1 shows the basic features of a solar cell. The front contact grid is a thin metallic grid on the front surface and the back contact usually covers the whole of the back. This is called an n-on-p cell. Silicon is one of the popular semiconductor in the electronics industry so it is used for solar cells. Most commercial cells have a probable 20% efficiency which is the ratio of the maximum output power to the input power from the sun, but over 25% efficiency has been achieved in the laboratory. The theoretical limit for crystalline silicon cells is about 30% under 1000W/m2 irradiance and 25 °C operating temperature (Hill B., 1995). Solar cells which were made from gallium arsenate have achieved 34.2% efficiency.

Solar cells are fine objects which must be protected from any possible damage. The cells are usually connected in series, in parallel or a combination of both in order to produce necessary power and voltage. A photovoltaic module which is a collection of solar cells was bought about US$4/Wp (US$ per peak watt) in 1995. Modules must be capable of reliable operation for many years. The current target is a lifetimes of 30 years.

Photovoltaic applications

In 1994 the total world sales of photovoltaic modules reached 70 MWp per year. In recent years, photovoltaic modules have found many applications in various sectors. The main applications are given below:

1. Space applications: solar cells were first used to produce electricity for satellites in 1958. Since then, photovoltaic power generation has become an essential energy source in space. Solar cells can operate near or far from sun.

2. Telecommunication: transmitters and repeater stations are often located in distant places such us mountains, islands or deserts. Solar power has proved the cheapest and most reliable power for transmitters and repeater stations.

3. Electricity in villages: the majority of the population of the developing countries, approximately two billion people, live in small villages without electricity. As almost developing countries will find extending the mains grid to a few customers far removed from the mains supply lines too expensive, photovoltaic systems are the obvious, cheaper alternative. A small photovoltaic module with a battery can provide enough power for basic lighting, TV and a small refrigerator for a house. By 1993 more than 10,000 home systems had been installed in Indonesia. In addition, solar home systems had been installed in the Philippines, the Dominican Republic, Columbia, India, Kenya, Mexico, Morocco, Sri Lanka and Zimbabwe by 1993. The average price of a 50 Wp solar home system was about US$500 in 1993. Assume that a 50 Wp solar house system in future will cost about US$250, then 400 million solar home systems will be

installed in the world. The other applications of solar modules in villages are water pumping, irrigation, water purification, street lighting and TV receivers (Lysen E.H., 1994).

4. Grid connected buildings: the solar modules can be fixed on roofs or walls so no additional land is required. The most sensible use of photovoltaic cladding would be on commercial buildings because they need energy during working hours rather than at night. Photovoltaic cladding presently costs about 800m-2 in comparison with marble cladding cost around 1000m-2, granite cladding 800m-2. Photovoltaic cladding gives high-tech images for office blocks at lower cost than marble.

5. Central power stations: photovoltaic power stations have, so far, only been installed for purposes of research. Today, Austria, Germany, Italy, Spain and USA have small stations of this type.

The other applications of photovoltaic systems are pocket calculators, watches, clocks, torches, garden lights, portable radios, battery chargers for boats, caravans, electric cars, toys, railway signals, traffic warning lights, alarm systems, automatic weather stations, military equipment and so on.

Conclusion

The photovoltaic system cannot at present compete with mains electricity. However, early in the next century, when economies of scale are expected to bring about a reduction in manufacturing costs, solar power will be an important energy source.

References

• World Energy Council (1993) Energy for Tomorrow’s World, Kogan Page /St. Martin’s Press.
• Treble F. C. (1993) Solar Energy, The Solar Energy Society, Birmingham.
• Hill B. (1995) ‘Solar Power’, IEE Power Engineering Journal, (August 1995), pp. 175-80. Lysen E.H. (1994) ‘Photovolts for villages’, IEEE Spectrum, 31, (10), pp.34-9.

Two of the ways that people demonstrate their intelligence are communication and learning. Effective communication requires skills in the analysis of messages received and in the synthesis of messages transmitted. The ‘message’ may be a letter, an article, a poem, musical composition, painting, or indeed any other form of communication. In order to communicate effectively, one must be able to synthesize a message. To do that well needs the ability to make judgements about the level of sophistication of the recipient, careful use of the language of the communication and appropriate speed of presentation. Understanding a message also requires intelligence. A listener needs to know the meaning of most of the words being used and to have some knowledge of the context of the message.

The ability to learn and understand is considered by many as a vital component of intelligence and perhaps a definition of it.

‘Learning denotes the changes in a system that are adaptive in the sense that they enable the system to do the same task or tasks drawn from the same population more effectively the next time.’ ‘When a computer system improves its performance at a given task over time, without re-programming, it can be said to have learned something.’

There are many definitions for Artificial Intelligence or AI. One is: ‘the study of mental faculties that encompasses computational techniques for performing tasks which apparently require intelligence when performed by humans’. The term Artificial Intelligence was first used by John McCarthy in 1956. Since then, and especially in the last two decades, there has been a growing amount of research on AI. With many scientists, engineers and programmers either studying AI techniques or building AI systems or both, national and international organizations dedicated to AI have been formed and are growing. In the USA, for example, there is now an American Association for Artificial Intelligence. A number of AI applications in the medical and engineering fields have been successful and so established AI as a promising area of study with specialist sub-sectors, namely robotics, machine vision, natural language processing, machine learning, expert systems and neural networks.

Looked at closely, each of these sub-sectors turns out to be an attempt to imitate some human organs or faculties. Robotics, for example, aims to imitate what a human being can do using limbs, hands and feet, in co-ordination with the eye and brain-which is what ‘vision systems’ aims to copy. ‘Natural language processing’ is the development of systems that perform tasks using the kind of language that humans use in routine interactions. ‘Machine learning’ aims to make computers learn how to use computational techniques. An ‘expert system’ is built to house and sift large amounts of human knowledge in order to give advice in particular circumstances just as a human expert would do. And ‘neural networks’, as the name suggests, try to reproduce in part the human nervous system.

Even though there have been many successful applications devel

oped in these areas, AI, compared to human intelligence, is still in its infancy. Everyday observation shows that the modest brains of lower animals can perform tasks that are far beyond the range of even the largest and fastest modern electronic computers. Just imagine that any mosquito can fly around at great speed in unknown territory without bumping into objects blocking its path. And a frog’s tongue can catch these insects in full flight within a split second.

At present the number of processors which can be built for specialized parallel hardware is somewhere between 50,000 and 1 million. Compared to the number of neurones in the human brain this number is extremely small. The total number of neurones in the human central nervous system can only be estimated; some estimates put the number about 1011 combined with the average number of synapses per neurones this yields a total of about 1015 synaptic connections in the human brain, the majority of which are developed within a few months after birth.

Comparative facts like those show that there is a lot still to be learnt from human beings, animals and other creatures. When somebody looks at an intelligent system-say a vision system or an intelligent robot, they will remark that it is amazing. Indeed it is amazing to see a system correctly inspect and classify many products in the space of a second. Such systems are already installed and in operation on production lines and their performance is quite good. There are several expert systems in use in real world tasks. The importance of these systems derives from their artificial intelligence which in turn derives from human intelligence. A man-made system can be very smart and artificially very intelligent but no such system so far has been awarded a prize for its innovative abilities. It is the human being who made it who wins the prize. What is prized, what is of higher worth, is not the system but its maker or builder. What about the fantastic system that is a human being? Just as an AI system is strong evidence of the existence of its maker, namely, a human being, so too human beings and other natural systems are more and stronger evidence for the existence of their Maker. To make an artificial intelligence one must first have natural or real intelligence. That means the Maker of human beings and all other creatures has a supernatural power over all of them. Just as no one could say that AI systems build themselves, it should be impossible to say the same for human beings and other creatures. This supernatural power is the All-Mighty Creator. As we have seen, it is not the system but its maker that is prized and respected. Self-evidently, the One who created human intelligence is to be prized and respected more than anything or anyone else. God says in the Qur’an: ‘We have indeed created man in the best of moulds’ (95.3). As we believe that there is definitely a maker of an AI system, why should it be hard to believe that there is a Maker of human being?

References

• CHARNIAK, E. and McDERMOTT, D., (1985) Introduction to Artificial Intelligence, Addison-Wesley Publishing Company.
• HANCOX, P.J., MILLS, W.J. and REID, B. (1990)
• Artificial Intelligence/Expert Systems, Ergosyst Associates, London.
• MULLER, B. and REINHARDT, J. (1990) Neural Networks. An Introduction, Springer Verlag.
• FORSYTH, R. and RADA, R. (1986) Machine Learning:
• Applications in Expert Systems and Information Retrieval, Ellis Horwoood, Chichester.