It wasn’t…

Worse than that, in the third grade we had to learn about “conversion of units.” I figured it was good source of test problems. So I couldn’t escape from learning it. I admit it was difficult in the beginning. “The strange rule” said if we are to measure with a bigger scale, then we had to divide the number by ten and vice versa. Why was 120 cm equal to 1.2 m? If we knew that it was 120 already why did we bother to say it was also 1.2 in another unit? I got confused whether I should multiply the number by ten or divide by ten? (At least it was easy to multiply or divide by ten instead of another number, so I kept silent.)

In time, I realized that people used the unit to measure almost anything. Length is measured in meters, mass is in kilograms, time is in seconds. Wherever there was quantity, there was also a base-unit associated with it. Of course I never asked what a “second” was, because our teacher said everyone accepted this unit of time. Since it was a world-accepted “standard measure,” I subconsciously got the impression that the universe had a clock* and that people calibrated their time accordingly. In the same way, one kilogram was an absolute quantity in my mind by which every other mass can be measured.

As we grew up, more and more types of measures and units entered our lives: Volt, Joule, Ampere, Newton, and many others. Dealing with the “old” units of length and time was a piece of cake then. However, my faith in “standard measures” as universal remained unchanged until high school.

I was quite surprised in high school when our chemistry teacher told us that our very fundamental units of measures were actually not absolute. They were not fundamental in the sense that they, too, were defined in terms of other quantities. In fact, there is a history of “what to define as a unit” and “how to measure it.”

Let’s take time, for instance. We measure years by days and days by hours. Have we ever thought about why a year is 365 days and one day is 24 hours? Can’t we divide a year into 400 days or a day into 25 hours? Is this an artificial choice or a natural timing? It all depends on how we define a year and a day. We can identify a year by a full rotation of the earth around the sun. Also we can distinguish the beginning of day and night clearly. These are definite intervals of time dictated through our observations, and so there is not much choice other than setting one year at 365 days. Is there a similar fact behind the relation of day to hours? Not at all! It was in ancient Egypt, around 2000 BC, that days for the first time were sliced into 24 pieces of time. In the age of Babylonians, however, a day was designed to be 60 hours. Perhaps the reason for such division of the day (into 24 or 60) hours was that 24 or 60 are nice numbers which are divisible by many integers; the same reason why a full-angle is 360 degrees instead of 2π.

In the Middle Ages, for Muslims, measurement of astronomical phenomena was a very serious affair. They were very concerned about accurate timing. Determining the changing time of the five daily prayers and the beginning and ending of the month of Ramadan was more than a custom, it was a religious duty. And such calculations required high precision. This precision was exemplified in year 1000 AD by the Muslim scholar al-Biruni who gave the times of the new moons in terms of days, hours, minutes, seconds, thirds, and fourths after noon Sunday.

In the West, the first accurate time measurements were made by Roger Bacon in thirteenth century. In 1657, Christian Huygens invented the pendulum clock, which uses swinging weights to keep time. Later, Hyugens and William Clement refined the design so that clocks were accurate up to seconds. Another problem with older clocks was that although they worked fine in the local region, they lost accuracy at different parts of the globe and were thus unsuitable for navigation. The reason for the lack of accuracy was that earth’s rotation around the sun on its axis (which definitely affects the period of the pendulums) was not uniform. Several adjustments were made in the nineteenth century for better accuracy by improving the design to compensate for thermal expansion of the metal rods and air drag, which globalized the measurement of time. In 1956, the “second” was redefined in terms of the earth’s revolution around the sun, according to data gathered in year 1900. As the scientists were not completely satisfied, they re-defined the second (as the atomic second) a decade later. In 1967, the Thirteenth General Conference on Weights and Measures defined a second of atomic time in the International System of Units as:

The duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom.

Measuring the length was another important task for ancient peoples. Among the earlier civilizations, the most accurate system was developed by Indus Valley Civilization. While their contemporaries were using parts of the body for measurement, as early as 2600 BC, the Indus civilization had a much finer unit system that accounted even for millimeters. Most societies continued to use their own length scale until eighteenth century.

As early as seventeenth century, with the advances in the accurate measurement of time, pendulum motion was suggested to measure standard length. In the eighteenth century, there were two main approaches for measuring the standard unit of length. One suggested defining the meter as the length of a pendulum with a half-period of one second. The other suggested defining the meter as one ten-millionth of the length of the Earth’s meridian along a quadrant, which is the distance from the equator to the North Pole. In 1791, the French Academy of Sciences selected the choice based on the meridian. After several changes in the definition in 1960, the International Bureau of Weight and Measure organized the 11th CGPM (General Conference on Weights and Measure), during which the meter was redefined as 1,650,763.73 wavelengths of the orange-red emission line in the electromagnetic spectrum of the krypton-86 atom in a vacuum. The final decision came from the 17th CGPM as: “a meter is defined as 1/299,792,458 of a light-second.”

Figure 1. Historical International Prototype Meter bar, made of an alloy of platinum and iridium, was the standard from 1889 to 1960.

As for the measurement of mass, the situation is even more complicated since scientists cannot even agree on what mass is. There are mainly two different understandings of mass based on its features. One is called inertial mass (related to the quantity of a material); the other is gravitational mass (related to gravitational pull and acceleration). Whether these two concepts are equivalent or not is still in debate though in modern theories like Einstein’s general relativity, these two definitions are equivalent. We can, therefore, leave these philosophical discussions about the concept of mass to the scientists and go back to its measurement.

Just like the measurement of time and length, scientific mass measurement gained a boost after the French Revolution. At first, a gram, defined as the absolute mass of 1 cm3 of water at 0o C, was chosen as the standard. In 1799, scientists made a slight modification to the unit of mass by re-setting the definition at 4oC since it is the temperature at which water is most stable. Later, officials noticed that this unit was too small to be a standard of everyday commercial materials, which usually appear in large amounts. In 1889, the International Prototype Kilogram (IPK), made of an alloy of 90% platinum and 10% iridium (by weight), was designed to define the standard mass (Figure 2). After the first production, several more stable replicas of IPK have been produced to replace the older ones. Today every government who subscribes to this standard must have an exact copy of IPK, and these replicas must be returned to Paris periodically as they may get rusted or dirty with time.

Figure 2. Shown above is a computer-generated image of the International Prototype Kilogram (IPK). The IPK is made of a platinum-iridium alloy and is stored in a vault at the BIPM in Sèvres, France.

These facts may sound very odd to some, as it did to me when I first heard of them. I asked myself: If all these measures are defined in terms of something else, what is the point of defining them in the first place? For example, if we can agree to use the second as some interval of time, why do we bother to count the number of oscillations of Cesium. The answer is: We cannot agree unless we use a reference time which is geography-free, climate-free, and politics-free. Only then we will be sure that I, here in Western Pennsylvania, a person on the top of Everest, or a person in a submarine under the Pacific Ocean will call the same interval of time a “second.” In other words, the oscillation of the cesium isotope was believed to be free from all possible deficiencies that are results of physical location (Australia or America), environmental change (the Amazon Forests or the Sahara Desert), and politics.

In short, sand-clocks for measuring time (think of what kind of sand in what shape of glass tube) or the arm of a king as a length unit (imagine a king who seized the throne at 13 and died at 60), or weighing with iron cylinders (common in small grocery stores in some countries) is too unreliable, too unstable, too local, and of course, inaccurate to create a standard. Especially in this age of globalization, a consensus on measurement is absolutely necessary.

It seems a bit ironic that a simple-looking concept of science, measurement, could cause such controversy. A simple way to keep track of numbers that belong to different kind of quantities evolved into an area of serious research through time. Perhaps then, I should have not worried that much about my bad math grades on a subject which troubled the scientist themselves. After all, my grades were just my teacher’s own measurement.**

O. S. Caglayan has a PhD in mathematics. He is a freelance writer. He lives in Pittsburgh, Pennsylvania.

* This famous quotation attributed to Newton was opposed by Leibnizian view of time: “The universe is the clock.” The scientist as philosopher, Friedel Weinert, Springer; 1 edition (May 27, 2004)

** The author is indebted to his dear elementary school teacher Muazzez Ozalp for instilling in him the love of science.

References

1. G. J. Toomer. Ptolemey’s Almagest (Princeton, New Jersey: Princeton University Press, 1998)
2. The History of Time (Leofranc Holfrod-Strevens).
3. al-Biruni (1879). The chronology of ancient nations: an English version of the Arabic text “Vestiges of the Past”. London: W.H. Allen, 147-149. OCLC 9986841.
4. Matthew Bennett, Michael F. Schatz, Heidi Rockwood and Kurt Wiesenfeld, Proc. R. Soc. Lond. A 2002 458, 563-579.
5. Ian Whitelaw. A Measure of All Things: The Story of Man and Measurement, St. Martin’s Press, 2007.
6. http://physics.nist.gov/cuu/Units/meter.html
7. www.bipm.org/eng/home

Ramadan is a time of intensive worship and devotion to God, of reading the Qur’an and reflecting on its teachings, of comprehensive thanksgiving, giving to charity, practicing self-control and kindness, of training oneself to be a better person spiritually and improving relationships with others.

Fasting is not that difficult

To non-Muslims fasting in Ramadan may appear to be a time of hardship and deprivation, but that is not the experience of Muslims. There are at least five ameliorating factors that make fasting much easier than it appears. These are (1) the magic of intention, (2) the community spirit, (3) the ability of the human body to adapt, (4) social/cultural cooperation, and (5) divine help. The initial intention significantly reduces the perceived difficulty. Once one commits to fasting, it becomes much more doable and feasible. Knowing and seeing that fellow believers are fasting with you and sharing the early breakfast or the dinner with them strengthens the community spirit. Thirdly, the human body is amazingly adaptable. Within the first few days of fasting the body adapts to the new schedule and one does not feel hunger as one normally would. In communities where Muslims are a majority or a significant minority, there is assistance or cooperation offered to the fasters, such as flexible holidays and working hours. Finally, for any worshipper, there is divine help which eases the task once the worshipper has committed to doing it.

Over 500 million Muslims, from age 9 to 90 fast every year. Fasting does not prevent them from conducting their mundane work or business as usual. As a pillar of the religious life in Islam, fasting is probably the most practiced form of worship. Muslims think of Ramadan as a kind of tune-up for their spiritual lives.

The four dimensions of Ramadan

As the third “pillar,” or religious duty in Islam, fasting has many dimensions: The behavioral dimension, the religious dimension, the social dimension and the spiritual dimension.

The first is the obvious behavioral dimension. Fasting in Ramadan is a means of learning self-control. Due to a lack of preoccupation with the satisfaction of bodily appetites during the daylight hours when fasting, the spirit gains a measure of ascendancy. The soul is freed of the chains placed by carnal desires. Fasting provides a break in the cycle of rigid habits or overindulgence.

During fasting, not only the stomach, but also the tongue, eyes, ears, other limbs, and the heart and mind are equally obligated to be restrained. Just as we control our physical appetites, we also must control our negative emotions and actions. The Messenger of Islam, Muhammad, peace be upon him, expressed that fasting is not only restraining from food and drink, but that it also means refraining from impious acts. He said that if a person does not control their senses and behavior, then God does not require that person to refrain from eating. He added that if someone verbally abuses you, acts ignorantly towards you, or even hurts you, you should respond by only saying, “I am fasting; I am indeed fasting.” According to the masters of Sufism, the spiritual dimension of Islam, not only one’s organs, but also one’s thoughts and feelings need to be tightly controlled during this month.

As far as the social dimension is concerned, fasting is a way of experiencing hunger and developing sympathy for the less fortunate and thus learning thankfulness and appreciation for all of God’s bounties. Fasting increases people’s sympathy and compassion for those who have been deprived of their daily means of survival. Although everybody knows, in an abstract sense, that there are people who suffer from hunger and poverty around the world, this knowledge may not be great enough to have an impact on our daily behavior. During the fast of Ramadan, this knowledge is internalized, because we now not only know that there are hungry people, but we have a glimpse into their experience of hunger. This deeper, internalized knowledge helps us minimize wastefulness and to sincerely do our best to help those in need.

Ramadan is also a time of generosity. People are more generous, more cordial, and more ready than at other times of the year to do good and charitable work. Muslims often invite one another, friends and guests, Muslims and non-Muslims, in particular neighbors, regardless of creed, to share the evening meal and exchange gifts and best wishes.

Fasting establishes a continuity of practice with religions such as Judaism and Christianity, in which fasting is recognized as an important element of devotion to God. The very verse in the Qur’an that commands Muslims to fast reminds them of this connection: “O you who believe! Fasting is prescribed on you just as it was prescribed on the people before you.”

The spiritual dimension

In the spiritual dimension, fasting during Ramadan is an act of obedience. It leads to sincere thankfulness, which is the heart of worship. It also empowers our spiritual side over our physical tendencies. If we imagine our body as a vessel, such as a ship, our mind, heart and carnal desires are like hands that are trying to control this vessel. Fasting weakens the effect of the carnal self and strengthens the effects of the mind and the heart on the control of the body.

The experience of hunger in fasting breaks the illusory lordship of the carnal self, or ego, and, reminding the carnal self of its innate helplessness, convinces it that it is only a servant. Self consciousness, or the notion of “I,” is part of the “trust” that has been given to humans as the vicegerents of God on earth [The Qur’an, Ahzab 33:72]. “The All-Wise Creator entrusted each human being with an ego that has clues and examples that urge and enable them to recognize the truths about the attributes of the Lord of Creation and His essential qualities. Ego is the measure that makes known the qualities of His Lordship and the functions of His Divinity.” [Nursi, 2005, 552] Although God is closer to us than our jugular vein [The Qur’an], His names and attributes cannot be fully comprehended as they are infinite and we are finite, mortal, limited creatures. The virtual attributes that God gives us can serve as units of measure for comparison and for a better appreciation of God’s names and attributes.

It may be asked “Why did God make our ego a means to know His attributes and names?” Nursi answers this question as follows:

An absolute and all-encompassing entity has no limits or terms, and therefore cannot be shaped or formed, and cannot be determined in such a way that its essential nature can be comprehended. For example, light undetermined by darkness cannot be known or perceived. However, light can be determined if a real or hypothetical boundary line of darkness is drawn. In the same way, the Divine Attributes and Names (e.g., Knowledge, Power, Wisdom, and Compassion) cannot be determined, for they are all-encompassing and have no limits or like. Thus what they essentially are cannot be known or perceived. A hypothetical boundary is needed for them to become known.

In our case, this hypothetical boundary is our ego. Ego imagines within itself a fictitious lordship, power, and knowledge, and so posits a bounding line, hypothesizes a limit to the all-encompassing Attributes, and says: “This is mine, and the rest is His.” Ego thus makes a division. By means of the miniature measure it contains, ego slowly comes to understand the true nature of the Divine Attributes and Names.

Through this imagined lordship, ego can understand the Lordship of the Creator of the universe. By means of its own apparent ownership, it can understand the real Ownership of its Creator, saying: “As I am the owner of this house, the Creator is the Owner of this creation.” Through its partial knowledge, ego comes to understand His Absolute Knowledge. Through its defective, acquired art, it can intuit the Exalted Fashioner’s primary, originative art. For example, ego says: “I built and arranged this house, so there must be One Who made and arranged this universe.”

Ego contains thousands of states, attributes, and perceptions that, to some extent, disclose and make knowable the Divine Attributes and essential Qualities. It is like a measure, a mirror, or an instrument for seeing or finding out, an entity with an indicative function. [Nursi, 2005, 552]

It is not necessary for a unit of measure to actually exist; like hypothetical lines in geometry, a unit of measure may be formed by hypothesis and supposition. It is not necessary for its actual existence to be established by concrete knowledge and proofs. The self, however, sometimes forgets its true nature and imagines its “knowledge,” “power,” “ownership,” and “ability” to be real. When the self forgets its true nature and the purpose of these feelings, it becomes a seed that may grow into a tree of arrogance. Nursi points to the importance of fasting for keeping the self under control:

Fasting Ramadan breaks the carnal self’s illusory lordship and, reminding it that it is innately helpless, convinces it that it is a servant. As the carnal self does not like to recognize its Lord, it obstinately claims lordship even while suffering. Only hunger alters such a temperament. God’s Messenger relates that God Almighty asked the carnal self: “Who am I, and who are you?” It replied: “You are Yourself, and I am myself.” However much God tormented it and repeated His question, He received the same answer. But when He subjected it to hunger, it replied: “You are my All-Compassionate Lord; I am Your helpless servant.” [Nursi, 1995, 222-3]

Conclusion

Fasting in Ramadan may appear to be a difficult form of worship to those who have not experienced it. But there are many factors, some of which are listed above, that help the faithful to fulfill their commitment. Only God knows the true wisdom behind fasting, but we get a glimpse of it through the Qur’an, the prophetic tradition, and our personal experiences. Fasting is first a means of self-control, a way to increase in piety and find freedom from the tyranny of carnal desires. Secondly, fasting provides an opportunity for reflection, intense worship, and thankfulness. It enables members of the community to empathize with those who suffer from poverty and hunger. In the spiritual dimension, fasting leads to a sincere appreciation of God’s bounties and deep gratitude for the same, which is the essence of worship. Finally, the experience of hunger in fasting reminds the self of its true nature; that is its weaknesses and its dependence on the grace of God. It breaks the illusory lordship of the self and it reminds the carnal self of the purpose for its creation, which is faith, knowledge, worship, and love of God, as well as service for humanity.

Yuksel A. Aslandogan is the Vice President of Institute of Interfaith Dialog, Houston, Texas.

Muhammed Cetin is the editor and Publications Coordinator of IID, Institute of Interfaith Dialog.

References

• Nursi, S. The Words, The Light, Inc. NJ: 2005.
• Nursi, S. The Letters, Truestar, London: 1995.

New Findings in Biology

Olfaction was long considered a uniquely mammalian trait. Scientists have disproven this by showing that many intertebrates can smell. For example, birds were thought to be unable to smell, although they have nostrils in their bills. John Audubon, a famous nineteenth-century bird artist, reached this mistaken conclusion by observing vultures confronted with a covered and an uncovered animal corpse, he concluded that they could not smell. The minute weight of the birds’ olfactory bulb consolidated this widespread misconception. Recent research shows that birds use smell when finding and distinguishing food, choosing proper nesting sites and mates, and following avian navigation routes. Ken Stager, an orinthogist at Los Angeles County Natural History Museum, used turkey vultures to disprove Audubon’s vulture experiment. Marine biologist Betsy Bang, who measured the olfactory bulbs and tissues in the brains of 151 bird species, calculated the olfactory bulb’s mass as being between 3% to 37% of the brain’s entire mass. This shows that the ratio, and not the weight, determines a bird’s ability to smell.

Other examples are as follows:

•Pigeons perceive small amounts of odorants. If their olfactory bulbs are blocked, they become lost.

•Certain seabirds (e.g., white chinned petrels) are sensitive to the chemical emitted by their main food (plankton), and so follow an olfactory path over the sea.

•European starlings smell the best region for their nesting site.

•Chickens detect inedible bugs (e.g., bright-colored bad-tasting caterpillars) through smell and sight.

•Salmon return to their hatching sites years later by using the unique olfactory memory of these sites left in their brains.

Smelling is far more developed in mammals, especially dogs and cats, which can sense parts per billion or trillion and can identify millions of different odorants. Science would benefit greatly if such abilities could be reproduced in sensors. But first, how does the human nose smell?

Perceiving Odors

Scientists divide human olfaction into steps. First, a potential odorant emits an odor’s basic elements: volatile organic compounds (VOCs). We perceive an odor when molecules are transformed into an odor by binding the receptor proteins.(1) After binding with certain types of VOCs, these receptor proteins cause depolarization. The electrical charges produce unique signals, which the epithelium’s sensory cells transmit to our neural network (axons).

These signals then are carried to a cluster of neural networks in the brain (glomeruli).(2) Ultimately, the impulse reaches the hypothalamus and describes the scent through a process of classification and identification.

Quantifying Scents

Human odor panels or gas chromatography and mass spectroscopy (GC/MS) are used to identify odors. Such quantification is problematic, however, because it is hard to quantify the VOC’s perception in the nose as a unit of odor. Quantifying mass, volume, temperature, light intensity, and the molecular concentration of a soluble substance in a solution are reasonably objective and can be measured as a multiple of a standard unit.

But a standard olfactory measure does not exist, for it varies according to time and environment. Odor concentration is expressed as a multiple of a threshold: 50% of human “sniffers” must detect-not necessarily identify-it. This threshold is defined by the American Society for Testing and Materials (ASTM), and is accepted as the absolute threshold of odor perception. It takes 5 or 10 odor units for the human panel to identify the odor. GC/MS also can identify the odor’s chemical composition.

Electronic Nose

After developments in electronic sight and hearing, scientists sought similar progress in odor perception. Research began at the University of Warwick (Coventry, England) in the 1980s. Its participants coined the term “electronic nose,” now commonly known as “e-nose.”(3) Their progress made it a commercial commodity with many applications.

E-noses have moved from being metal oxide devices, to conducting polymers, and now to laptop-size or pocket-size odor sensors. The Swiss Federal Institute of Technology (Zurich) has made one the size of a wrist-watch. However, current e-nose use is largely restricted to labs and military applications. Scientists are trying to match or surpass the human sense of smell’s accuracy and sensitivity, after which they will work on surpassing that of the canine species.

Uses and Advantages

E-noses have a wide application in agriculture. Since they can detect minute differences, an e-nose using polymer materials can determine whether a tomato is sun-ripened, picked green, or internally damaged, and whether apple juice comes from a concentrate or is authentic but pasteurized.

Volunteers often test such products. But who wants to determine if corn oil is rancid or canola oil is oxidized? E-noses, having no such “qualms,” detect changed odors in oil samples and provide far more accurate reports.

In animal science and poultry, e-noses provide detailed reports about spoiled food. Judy Arnold, a microbiologist in Athens, GA, researches food quality for the Agricultural Research Service (ARS).

In 1998, researchers discovered that e-noses can detect gases produced by spoiled poultry products. They claim that an e-nose can determine freshness, period of time in a refrigerator, and the amount of fat in white meat. Such an objective evaluation benefits poultry farmers and producers by eliminating returns of “funny-smelling” poultry. E-noses also can detect meat’s decay rate and bacteria, overall quality and freshness, the composition of mixed meat-part products (e.g., processed meat), and how long a ham has been dry-cured. Given this, the e-nose’s ability to examine a bundle of scents makes it very useful. It can perform hundreds of preliminary assessments that would occupy a chemist for months.

The military uses e-noses to detect land mines and traces of chemical-biological weapons. This is important, for over 100 million land mines litter 62 war-torn countries. Although dog-sniffers are useful, this practice is inhumane (dogs are often injured) and impractical (they need lots of training).

E-noses also are better than metal detectors and ground-penetrating radar and infrared imaging-the former detects even tiny pieces of metal, whereas the latter often images pebbles. As e-noses can identify traces of TNT or similar explosives to the 100 parts per quadrillion level, their detection rate is far more accurate and efficient. Nomadics, a Still-water, OK-based company, produces a cigar-box-sized e-nose for this purpose. Tufts University produces an optical e-nose that is designed and functions much like a mammalian nose.

Environmentalists use e-noses to analyze air. For instance, e-noses can report the chemical makeup of odors emitted by a farm’s store of manure, detect the compounds causing that odor, help minimize leaks, and determine a new diet that will decrease such odors. With their ability to detect toxic VOCs and compounds leaking from a factory’s or waste site’s storage areas, e-noses will help environmentalists force industry to change its practices. The major difficulty here remains sampling, as concentrations vary with time and place.

Caltech has used Department of Defense funding to develop a device that identifies odors in seconds. Its 32 components swell like sponges when exposed to a particular vapor, and its resistance (hence conductivity) changes accordingly. As it can detect any type of odor, doctors at the Children’s Hospital in Los Angeles are studying medical applications. Currently, it is applied to patients’ breath to help diagnose upper respiratory infections.

The major advantages of e-noses over human noses in these areas are objectivity; ability to measure odors over long real-time periods; and immunity to fatigue, infection, mental state, hazardous material, and adaptation (gradual loss of sensitivity).

How E-noses Work

E-noses have three functional components: a sample handler, a gas sensor array, and a signal processing system. Its output identifies the odorant, estimates its concentration, and relates its characteristic properties. A sensor recognizes different types and concentrations of odors through its arrays, each of which has a different sensitivity. The resulting combination provides the response pattern that enables the e-nose to identify odorants.

In a typical e-nose, a vacuum pump pulls the first air sample into the tube housing the electronic sensor arrays. The air sampling unit exposes the odorant to the sensor, after which VOCs interact with the surface and the sensor’s active material until reaching a steady state. The sensor’s response is recorded and transmitted to the signal-processing unit. When completed, a washing gas cleanses the sensor. After the reference gas is applied to the unit, the sensor is ready to measure again.

E-nose Technologies

The sensor is the e-nose’s key element, and the sensor type is its defining characteristic. There are 5 types of e-nose sensors, as follows:

Optical sensors: Optical fiber sensors work through fluorescence and chemoluminescence. The tube’s glass fibers contain a thin encoated active material in their sides and at both ends. As VOCs interact with the organic matrix’s chemical dyes, the dye’s fluorescent emission changes the spectrum. These changes then are measured and recorded for different odorous particles.

Fiber arrays with different dye mixtures can be used as sensors. These are fabricated by dipcoating (binding a plastic solution to a substrate), micro electromechanical system (MEMS), and precision machining. The main advantage is that this adjustable tool can filter out noise. Also, since many dye forms are available in biological research, sensors are cheap and easy to fabricate. But the instrumentation control systems are complex, which adds to the cost, and have a limited lifetime due to photo bleaching (the sensing process slowly consumes the fluorescent dyes).

Optical sensors are sensitive and can measure low ppb (parts per billion); however, they are still in the researach stage of development.

Spectrometry-based Sensors: This group consists of a molecular spectrum-based gas chromatography (GC), an atomic mass spectrum-based mass spectrometry (MS), and a transmitted light spectrum-based light spectrum (LS). The first two can analyze the odor’s components accurately, which is a plus. However, their use of a vapor trap to increase concentration can alter the odor’s characteristics. LS devices do not consume the sample, but do require tunable quantum-well devices. GC and MS devices are commercially available, while LS devices are only at the research stage. All spectrometry-based sensors are fabricated by MEMS and precision machining, and can measure odors to a low ppb level.

The GC tube decomposes the odorant into its molecular constituents, and MS forms a mass spectrum for each peak. The spectra then is compared to a large precompiled database of spectral peaks to classify and identify odorants.

MOSFET (Metal-oxide-silicon field-effect-transistor): The basic principle here is capacitive charge coupling. In other words, VOCs react with the catalytic metal and thereby alter the device’s electrical properties. The device’s selectivity and sensitivity can be fine-tuned by varying the metal catalyst’s thickness and composition. MOSFETs are micro-fabricated and commercially available, but can measure only parts per million. They can be manufactured by electronic interface circuits, which minimizes batch-to-batch variation. However, the gas produced by the VOC-metal reaction must penetrate the MOSFET’s gate.

Conductivity Sensors: The sensor types used here are metal oxide or conducting polymer. Both operate on the principle of conductivity, for their resistance changes as they interact with VOCs. Metal oxide sensors are common, commercially available, inexpensive, and easy to produce (they are micro-fabricated). Their sensitivity ranges from 5-500 ppm. However, they only operate at high temperatures (200°C to 400°C).

In conducting polymer sensors, VOCs bond with the polymer backbone and change the polymer’s conductivity (resistance). They are micro-fabricated together with electroplating and screen printing, are commercially available, and can measure from .1 to 100 ppm. They operate at room temperature, yet are very sensitive to humidity. Moreover, it is hard to electropolymerize the active material, which makes batch-to-batch variation inevitable. Sometimes VOCs penetrate the polymer chain, which means that the sensor must be returned to its neutral and reference state-a very time-consuming process.

Piezoelectric Sensors: These devices, which measure any change in mass, come in two varieties: quartz crystal microbalance (QCM) and surface acoustic wave (SAW) devices.

QCM sensors have a resonating disk and metal electrodes on each side. While applying the gas sample to the resonator’s surface, the polymer surface absorbs VOCs from the environment. Thus its mass increases, which increases resonance frequency. As the U.S. Navy has long used QCMs, this technology is familiar, developed, and commercially available. A QCM sensor is fabricated by screen-printing, wire bonding, and MEMS. Althoug it can measure a 1.0 Ng mass change, its MEMS fabrication and interface electronics is a major disadvantages. QCM sensors are quite linear in mass changes, their sensitivity to temperature can be adjusted, and their response to water can vary for the material used.

MEMS techniques should be handled carefully, for the surface-to-volume ratio increases drastically as dimensions approach the micrometer levels. Measurement accuracy is lost when the increasing surface-to-volume ratio begins to degrade the signal-to-noise ratio. This problem occurs in most micro-fabricated devices. SAW devices have much higher frequencies. Since 3-D MEMS processing is unnecessary, SAW devices are cheaper. As with QCM devices, many polymer coatings are available. The differential devices can be quite sensitive. However, interface electronics require more complex electronics than those of conductivity sensors for both QCM and SAW sensors. Also, as the active membrane ages, resonance frequencies can drift and so must be detected for frequency by time. SAW devices are commercially available and sensitive to mass changes at the 1.0 pg level.

Pattern Recognition

Any e-nose’s primary task is to identify an odorant and perhaps measure its concentration. After the signal processing step comes the crucial step of pattern recognition: preprocessing, feature extraction, classification, and decision-making. A database of odors must be formed for comparison purposes.

Preprocessing accounts for sensor drifts and reduces sample-to-sample variation. This can be done by normalizing sensor response ranges, manipulating sensor baselines, and compressing sensor transients.

Feature extraction involves dimensionality reduction, a crucial step for statistical data analysis, since the database’s examples usually are subject to financial constraints. The higher dimensionality caused by sensor arrays is reduced to relevant pattern-recognition information and thus extracts only significant data. As most dimensions are correlated and dependent, it is better to reduce dimensionality to a few informative axes.

Feature extraction usually is accomplished by classical principal component analysis (PGA) or linear discriminant analysis (LDA). PCA is a linear transformation that finds the maximum variance projections and the most widely used technique for feature extraction. But as PCA ignores class labels, it is not an optimal technique for odor recognition.

LDA seeks to maximize the distance between class label examples and minimize the within distance, and thus is a more appropriate approach. LDA is also a linear transformation. For instance, LDA might better discriminate subtle but crucial odor projections, whereas PCA can remove the high variance random noise in a projection.(4)

The classification stage identifies odors. Classical classification techniques are KNN (k nearest neighbors), Bayesian classifiers, and ANN (artificial neural networks]. KNN with, say, 5 nearest points will find the 5 closest matches from the precompiled database. The closest match will be assigned as the tested material’s odorant class.

Bayesian classifiers first assign a posterior probability to the classes in the lower dimension and then pick the class that maximizes the predetermined probability distribution. ANN is closer to biological odor recognition. After being trained by the odor database, it is exposed to the unknown odorant in order to recognize the largest applicable response odorant class. The classifier estimates the class and places a confidence level on it.

In decision-making, risks and application-specific knowledge are considered in order to modify the classification. All decisions are reported-even a nonmatch.

Conclusion

As this article indicates, we can expect great progress in this area. And with each step forward, science and technology will continue to point toward the Greatest Artist’s most subtle designs and allow us to appreciate them better.

Footnotes

1. There are over 100 million receptor proteins of about 1,000 different types.
2. A human olfactory bulb contains approximately 2,000 glomeruli.
3. The terms “electronic nose” and “e-nose” are incorrect, for these devices cannot be considered “real” noses. The correct terminology should be “electronic arrays for chemical sensory and identification.” However, “e-nose” has gained wide acceptance in the literature since it first appeared during a 1991 NATO workshop in Reykjavik, Iceland.
4. Such nonlinear transformations as Sammon nonlinear maps and Kohonen self organizing maps also are used in feature extraction. These preserve the distance between pairs of examples when reducing dimensionality to 2 or 3.

References

• Baltes, Henry, Dirk Lange, and Andreas Koll. “The Electronic Nose in Lilliput.” IEEE Spectrum (Sept. 1998): 35-38.
• Barinaga, Marcia. “Salmon Follow Watery Odor Home.” Science 286 (22 Oct. 1999): 705-6.
• http://csmt.jpl.nasa.gov/enose.html.
• http://faculty.washington.edu/chudler/nosek.html.
• Malakoff, David. “Following the Scent of Avian Olfaction.” Science 286 (22 Oct. 1999): 704-5.
• Mamberts, Peter. “Seven-Transmembrane Proteins as Odorant and Chemosensory Receptors.” Science 286 (22 Oct. 1999): 707-10.
• Perkins, Sid. “Eau, Brother! Electronic Noses Provide a New Sense of the Future.” Science News 157 (19 Feb. 2000): 125-27.
• Schiffmann, Susan, and H. Troy Nagle. “The How and Why of Electronic Noses.” IEEE Spectrum (Sept. 1998): 22-32.
• Stern, Peter and Jean Marx. “Making Sense of Scents.” Science 286 (22 Oct. 1999): 703.
• Wolfgang, Gopel, and Tilo Weiss. “Design for Smelling.” IEEE Spectrum (Sept. 1998): 32-34.
• www.planetee.com/planetee/servlet/DisplayDocument?ArticleID=6899.
• www.sfn.org/briefings/smell.html.

always regard

whatever pleases and

displeases yourself as the measure.

Wish that others

may receive those things

that are most pleasing to you,

and do not forget that

whatever conduct displeases you

will displease others.

If you do this,

you will be safe

not only from misconduct

and bad behavior,

but also from hurting others.

Before proceeding to go into details relating to the subject of Divine Decree and Destiny, we had better give the translation of some relevant verses:

With Him are the keys of the Unseen. None but He knows them. He knows what is in the land and the sea. Not a leaf falls but He knows it, not a grain amid the darkness of the earth, naught of wet or dry but it is in a Manifest Book. (al-An’am, 6.59)

There is nothing hidden in the heaven or the earth but it is in a Manifest Book. (a1-Nanzl, 27.75) It is We Who bring the dead to life.

We record what they send (of their lives and conduct to the Hereafter) and what is left of them. All things we have kept in a Manifest Record. (Ya Sin, 36.12)

They say: ‘When (will) this promise (be fulfilled), if you are truthful?’ Say: ‘The knowledge is with God only, and I am but a plain warner.’ (al-Mulk, 67. 25-6)

Nay, but it is a glorious Qur’an. On a Preserved Tablet. (al Buruj, 85. 21-2)

In a sense, Decree and Destiny are of the same meaning, but in another, Destiny means pre-determination or pre-ordinance, while Decree means execution of this ordinance or putting it into effect.

To define more clearly and elaborately, Destiny means that from the microcosm (atoms) to the macrocosm (the universe as a whole), from particles to galaxies, God Almighty, Who knows everything down to the minutest and Whose Knowledge includes all space and time while Himself is absolutely beyond all time and space, gives existence in His Knowledge to all things or beings and assigns to each a certain shape, life-span, function or mission and certain particularities. This can be understood by an analogy-God’s is the highest comparison, and He is absolutely beyond all comparisons and different from whatever a man conceives of Him -with an author’s having the full and exact knowledge of the book he will write and arranging it in his mind in chapters, sections, paragraphs, sentences and words before writing it. In this sense, Destiny is almost identical with Divine Knowledge or Destiny is a title of Divine Knowledge, and is also called the Manifest Record or the Supreme Preserved Tablet.

Destiny also means that God makes everything according to a certain, particular measure and in exact balance. The Qur’an declares:

God knows what every female bears and what the wombs absorb and what they grow. And everything with Him is measured. (Al Ra’d, 13.8)

The sun and the moon are made punctual according to a calculation. The stars and the trees adore, in subservience to Him. And the sky He has uplifted; and He has set the balance, that you exceed not the balance, but observe the balance strictly, nor fall short thereof. (al-Rahman, 55. 5-9)

The exact balance and harmony in the universe clearly show the existence of Divine Destiny; that is, the universe, as a whole and with all the individual things or beings in it, which display an exact measure, balance, order and harmony, shows that everything is determined, measured, created and governed by God Almighty. Assertions like determinism, which is upheld by many, including even the supporters of the Marxist ideology, in explaining the order and operation of the universe including the human kingdom, are a tacit admission of Destiny, even though absolute determinism is incompatible with Islam in explaining the actions of man.

All seeds, fruit stones, measured and proportioned forms, and the extraordinary order and harmony of the universe, and its operation for billions of years without displaying the slightest breakdown or deviation in any part of it, all this demonstrates that everything takes place according to the absolute determination of God Almighty, Who is the All-Knowing and the All-Powerful. Each seed or fruit stone and even each ovum fertilized by a male sperm is like a case formed by Divine Power into which Divine Destiny has in-built the future life-history of a plant or an animal being. Divine Power employs atoms or particles according to the measure established by Divine Destiny as building blocks in growing the particular seed into the particular plant and the particular fertilized ovum into the particular being. This means that the future life-history of that plant or the animal being and the principles to govern its life are pre-recorded in the seed or the fertilized ovum as determining factors and processes.

Although the basic materials from which plants and animal beings, including human beings, are formed are the same, there is an almost infinite variety between species and individuals. The plants and animals that grow from the same constituent basic elements display such harmony and proportion, and yet such abundant diversity, that man cannot help but conclude that each of them is individually given its particular form and measure. It is Divine Destiny which establishes this measure.

A single seed displays Destiny in two ways: one by demonstrating the Manifest Record (Imamun Mubin), the other by displaying the Manifest Book (Kitabun Mubin). The Manifest Record is, as was pointed out above, another title for Divine Knowledge and Command, comprehensive of the universe both as a whole and with all its parts, big or small, and all the events in it. As everybody knows, the seed of a plant is also its ‘memory’. That is, a plant which grows from a seed also results in multiple seeds, in which the entire life-history of the plant have been recorded so that they can grow into new plants, which are almost identical with the original because plants do not have conscious spirits endowed with free will. Thus, besides demonstrating the Manifest Record and therefore Divine Destiny and Knowledge in which everything is present or exists with all its individualized particularities, a seed also indicates the Supreme Preserved Tablet (Lawhun Mahfuz) and corresponds to human memory in the human kingdom. By the way, since it indicates that the life-histories of creatures are recorded, a seed also points to afterlife.

The Manifest Book is another title for Divine Will and God’s creational and operational laws of the universe. If we call the Manifest Record Destiny Formal or Theoretical, the Manifest Book can be referred to as Destiny Actual. The future full- grown form of a plant or an animal being, which displays all the content of the seed or fertilized ovum, can be understood as its Destiny Actual.

In short, like seeds or plants or fertilized ovums and animal beings, everything in the universe clearly points to Divine Destiny, determining, judging, giving measure, particularizing and individualizing. True dreams which bring news of certain future events, are another, undeniable indication of Destiny or Divine ‘pre-determination’.

Question

Why is belief in Destiny included among the essentials of faith?

Answer

Because of self-conceit and the weakness of devotion, man tends to attribute to himself his accomplishments and good deeds and feels proud of himself. Whereas, as the Qur’an explicitly states, God creates you and what you do (al-Saffat, 37.96), it is the Divine Compassion which demands good deeds and the Power of the Lord which creates them. Whoever ponders over his life, he will realize and confess to himself that God has directed him to good acts, usually prevented him from doing wrong deeds and by endowing him with the sufficient capacity, power and means required for any accomplishment, favoured him with many accomplishments and good deeds. God guides man to good deeds and makes him succeed in willing and doing them, so the real cause of a man’s good deeds is the Divine Will. A man can possess and own them by means of faith and sincere devotion and by praying to God to be able to deserve them, consciously believing in the necessity of doing them and being pleased with what God has ordained for him. He can never be boastful of his good deeds and accomplishments and put on airs among people; what behoves him is to always be thankful to God and humble.

On the other hand, while attributing to himself his accomplishments and good deeds, man likes to absolve himself of his sins and misdeeds by ascribing them to Destiny. However, since God never likes a sin or wrong act, nor approves it, it is man himself who causes sins and commits them by his free will. Yet it is God Who creates sins (in the sense of enabling them to take place or giving them external existence) as well as good acts, simply because if He did not do so, the free will with which He has endowed man, would be annulled. Man wills to commit his sins. As was explained earlier, God calls man to good deeds, guides him to them and always inspires them in him, but man commits sins of his own free will and disobeys his Creator. Therefore, man is completely responsible for his sins and misdeeds. However, in order to protect himself against sins and the temptations of Satan and his carnal self, man must both try to remove his inclinations towards sins through repentance and asking forgiveness for them, and direct and exhort himself to do good deeds through prayer, devotion and trust in God.

In short, man has free will and is enjoined to follow the religious obligations and refrain from sins and wrong deeds. He cannot by any means ascribe his sins to God. Divine Destiny exists so that the believer does not grow proud of his good deeds by ascribing them to himself. Rather he must be thankful to God because of them. Man has free will so that the rebellious carnal self does not rid itself of the consequences of its sins by ascribing them to Destiny.

A second, important point to mention is that man usually complains about past events and the misfortunes that have struck him. Worse than that, he cannot save himself from falling into despair and abandoning himself to a dissipated life. He may even go so far as to complain against God. However, Destiny exists so that a man should relate past events and misfortunes to it in order not to be driven to despair and provide himself with relief, security and consolation. On the other hand, as will be discussed below, since Destiny does not exclude human free will, man is responsible for his future life and whatever he does consciously and intentionally.

In sum, whatever is (including misfortunes) should be considered in the light of Destiny, and what is to come, and sins and questions of responsibility, should be referred to human free will. In this way, the extremes of fatalism (jabr) and the denial of the role of Destiny in human actions (i’tizal, the view of the Mu’fazila) may be reconciled.