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May 23, 2008


I'll be away for SAP training, followed by vacation and a celebration of my son's marriage on May 31, 2008. My next blog article will be on Wednesday, June 4, 2008.

"SAP" is the generic name of a variety of database software products of SAP AG, headquartered in Walldorf, Germany. There is one philosophy in computer science that everything is a database; it's just the user interface that's different. Casual reflection on objects as diverse as documents, spreadsheets, and directories lends credence to this viewpoint.

SAP AG is the largest European software company, and the third largest software company in the world. It has more than 40,000 employees and an annual revenue of more than $10 billion. Surprisingly, SAP owes its existence to the US software industry. In the 1960s, Scientific Data Systems (SDS) developed a business software suite with help from MIT. SDS was sold to Xerox in 1969, and Xerox almost immediately began to exit the computer market [1]. Xerox gave the MIT/SDS/Xerox software to IBM to allow a port to IBM mainframes. IBM gave the software to a group of German IBM employees who founded what was to become SAP in 1972. IBM was given a share in the new company.

Any large technology organization must invest heavily in research and development, and SAP is no exception. SAP has research laboratories in Palo Alto (California, USA), Bangalore (India), Gurgaon (India), Ra'anana (Israel), Montreal (Canada), Shanghai (China), and Sofia (Bulgaria). SAP has competitors in this highly-lucrative software section, the most important of which is Oracle. Oracle has confronted SAP in the courts on more than one occasion, claiming theft of intellectual property and unfair competition [2].

When they hear "SAP," the general public is more likely to think of the Second Audio Program channel that's often used for simultaneous language translation (typically Spanish) of television programs.

1. One felicitous outcome of Xerox's exit from computing was the availability of surplus hardware of their Xerox 820 personal computer, two mainboards of which I purchased at the time to make my own desktop computers.
2. China Martens, "Update: Oracle sues SAP for corporate theft," (InfoWorld, March 22, 2007).

May 22, 2008

Droste Effect and Recursion

Sometimes specialization can go to silly extremes. At one time we designed an electronic instrument for use in our own laboratory. Since we were resource-limited at the time (when were we not?), we decided to have our corporate engineering department build the device. At the first planning meeting, the director of engineering said he would hire a "packaging engineer" to decide where to place the front panel controls. All this for a one-off unit that we would use for two or three years. Needless to say, the quotation for the work came back a little too expensive, and we built the circuitry ourselves. I used a ruler and a little common sense to position the front panel controls. Now, every time I read the word, "packaging," I'm reminded of this episode. I've just read an interesting story about consumer product packaging that references the Droste Effect. The Droste effect is interesting, since the same idea is incorporated into computer programming as recursive functions.

The Droste effect is when there's an image which includes a smaller version of itself. In consumer packaging, the image on the package would incorporate the package itself; for example, a person holding the package. Of course, this image-in-an-image has a smaller version of itself embedded in it, etc. Only the finite resolution of the printing process prevents an infinite regression. The effect is named after a brand of Dutch cocoa powder introduced more than a hundred years ago. An image on the cocoa powder package depicted a nurse holding a tray with a cup of hot chocolate and the cocoa powder package itself. Perhaps inspired by this package, M. C. Escher, who was Dutch, incorporated recursion into some of his images.

There are some examples of Droste effect packaging in your local (US) supermarket [1]:

Land O'Lakes Butter

Morton Salt

Cracker Jacks

Here's an extra credit problem. If an acceptable image requires a million atoms (1000 x 1000 pixel resolution), and the full-sized package (assume it's mostly carbon) weighs about 20 grams, how many Droste Effect packages are physically possible if subsequent images are one-tenth the mass of the previous images. The answer is in Ref. 2.

A classic, and simple, example of recursion in computing is calculation of the factorial of a positive integer n, as in the following example in C:

int fact(int n)
if (n == 1)
return 1;
return n * fact(n - 1);

The function fact() contains itself. Although recursion leads to a simpler source code representation, execution of a recursive function is typically slower than execution of non-recursive code. More examples are found in Ref. 3. Of course, recursion has its own joke. "In order to understand recursion, first you must understand recursion."

1. Randy Ludacer, "Droste Effect Packaging" (Beach Packaging Design, April 12, 2008).
2. Only eighteen are possible. There's the original image of 1024 atoms (1.67 moles of carbon atoms), plus eighteen powers of ten down to 106. The last of these eighteen does not have a contained image meeting our resolution requirement, so it doesn't count. This example highlights the fact that real life is different from the mathematical ideal.
3. Recursion (Computer Science), Wikipedia.

May 21, 2008

Highly Stable Carbon-Nitrogen Bonds

Carbon-nitrogen bonds are common in organic materials. The most common bond is the singly-bonded carbon-nitrogen present in amines. pyridine has nitrogen bonded to carbon with the same π-bond found in benzene. Double bonds between carbon and nitrogen are found in imines, and triply-bonded carbon-nitrogen is found in nitriles. As a rule-of-thumb, all these materials are unstable at high temperature in the presence of water or oxygen. There are notable exceptions, such as polyimide, but continuous operation of carbon-nitrogen materials at a temperature above about 450oC is not possible.

As reported in Science [1], a German research team has discovered that amorphous SiBNC ceramics, prepared by pyrolysis of a methylamine polymeric precursor, have considerable resistance against thermal degradation and oxidation. This research from the Max-Planck-Institute für Festkörperforschung (Stuttgart) is published in a recent issue of Angewandte Chemie International Edition [2]. Carbon, which is usually released from such materials during pyrolysis, seems to bond strongly with nitrogen in the SiBNC material. Isotopes of carbon (13C) and nitrogen (15N) were used to identify the species present and their arrangement using NMR. In this case, the rotational-echo double-resonance technique was used. The data indicate some degree of multiple bonds between carbon and nitrogen through π-overlap. The carbon-nitrogen bond remains intact at 1400oC.

Much more interesting than carbon-nitrogen is Carbon-Silicon, the name of the rock duo of which Mick Jones is a member. Those of you who are late for teleconferences will be interested to learn that Jones was dismissed from The Clash because he was late or absent from too many rehearsals and concerts.

1. Gilbert Chin and Jake Yeston, Editor's Choice, Science, vol. 320, no. 5874 (April 18, 2008), p. 290.
2. Yee Hwa Sehlleier, Aswin Verhoeven, and Martin Jansen, "Observation of Direct Bonds between Carbon and Nitrogen in Si-B-N-C Ceramic after Pyrolysis at 1400oC," Angewandte Chemie International Edition, vol. 47, no. 19 (April 1, 2008), pp. 3600-3602

May 20, 2008

DARPA at Fifty

The US Defense Advanced Research Projects Agency (DARPA) is fifty years old. DARPA began life in February, 1958, as the Advanced Research Projects Agency (ARPA). ARPA was a presumed response to the launching of the first artificial satellite, Sputnik 1, by the Soviet Union on October 4, 1957. DARPA's mission is the encouragement of R&D projects at the fringes of possibility in all science and technology fields to further US national security needs. Because of this mission, some DARPA projects sound more like science fiction than science, and it's interesting that many successful DARPA projects have enabled consumer devices. Some notable examples, compiled by New Scientist magazine, are as follow [1-2]:

• The internet - Begun as ARPANET in the 1960s. You're reading this blog because of a DARPA innovation.

• The Global Positioning System (GPS) - Gave US Navy ships 200 meter positioning accuracy in 1960, and it's now used routinely in many consumer products.

Speech recognition and Language Translation Software - Handheld language translation devices are being used in Iraq.

Stealth Aircraft - First fielded as the F-117 Nighthawk stealth fighter, stealth technology makes airspace safer for US military pilots.

Gallium Arsenide - An enabling material for high-speed computing and telecommunications funded by DARPA in the mid-1980s. There was so much money thrown at this, even I was involved with gallium arsenide in the 1980s [3].

There were, of course, some notable failures:

• The Hafnium Bomb - A supposed nuclear energy transition in an isotope of hafnium was predicted to produce a radiation outburst without creating any nuclear fallout.

• The Mechanical Elephant - DARPA tried to create a walking robot during the Vietnam War. The walking war machines (Walkers) in Star Wars Episode V: The Empire Strikes Back may have been inspired by this project.

• Telepathic Spies - Extrasensory Perception was a hot topic in the 1960s, and when DARPA believed that the Soviet Union was conducting serious research in this area, it established its own program in the 1970s. One object was "remote viewing" in which a person could view something without being physically present.

FutureMap - This was a futures market used to predict and prioritize possible terrorist attach scenarios. This program was killed on political grounds, since it was thought that placing bets on terrorist activities was not a proper way to spend government money.

Project Orion - Project Orion was a study to determine whether interplanetary spacecraft could be propelled by nuclear explosions. Freeman Dyson, was involved with this project. The Orion project was killed when it was determined to be illegal according to the Partial Test Ban Treaty of 1963.

New Scientist lists some current DARPA projects with potential [4]:

• Robot Cars - DARPA's Grand Challenge, reported in an earlier article (Portable Power Challenge, September 17, 2007), is designed to produce completely autonomous vehicles for both urban and wilderness environments.

• Super Soldier - DARPA has projects that would allow soldiers to scale walls without ropes or ladders; and other projects to provide a mechanical exoskeleton to increase the physical strength of soldiers.

• High Speed Underwater Transport - Supercavitation could allow torpedo-shaped vehicles to travel underwater at speeds approaching 100 knots.

Supersonic Unmanned Aerial Vehicle (UAV) - Switchblade is the name of a prototype supersonic UAV designed to reach Mach 2.

1. Duncan Graham-Rowe, "Fifty years of DARPA: A surprising history" (New Scientist, May 15, 2008)
2. Duncan Graham-Rowe, "Fifty years of DARPA: Hits, misses and ones to watch" (New Scientist, May 15, 2008)
3. Devlin M. Gualtieri, Edward Porbansky, and Mandayam C. Narasimban, "Non-contacting inductively coupled displacement sensor system for detecting levels of conductive, non-magnetic liquids, and method of detecting levels of such liquids," US Patent No. 4,912,407 (Mar 27, 1990).
4. Duncan Graham-Rowe, "Fifty years of DARPA: Hits, misses and ones to watch, part II" (New Scientist, May 15, 2008).

May 19, 2008


About thirty years ago there was a television commercial for Heinz ketchup. The commercial was just the image of an upturned bottle of ketchup showing how slowly it poured against the background music of Carly Simon's "Anticipation." The commercial was designed to illustrate one of the CTQs for ketchup; namely, thickness, more scientifically called viscosity. It's hard to get ketchup to flow through a small bottle opening, but everyone has discovered the trick of shaking the bottle before pouring. Shaking will temporarily reduce the bulk viscosity of the ketchup, which is an interesting phenomenon in its own right. Now, physicists have found that confinement of a fluid with low viscosity in a small, nanometer-scale, channel will cause the fluid to become more viscous. Just as curiously, shaking will reduced this scale-induced viscosity [1].

Quantum mechanics have realized for a century that confinement of a particle in a small region leads to properties quite different from those in the macroscopic world. A simple expression of this is the Heisenberg uncertainty principle, expressed in spatial variables as

Δp•Δx > h/4π

where x is the position of a particle, p is the particle's momentum, and h is the Planck constant (6.626071 x 10-34 J-sec). This equation states that confining a particle to a small space gives rise to an uncertainty in momentum. The size scale for such uncertainty is at sub-atomic dimension, so such an effect is not expected in nano-scale fluids. Instead, what happens in fluids is a result of the arrangement and rearrangement of fluid molecules. Shaking will "unstick" the molecules for a short time. Then they will rearrange themselves back into their desired lowest energy configuration after a time called the viscoelastic relaxation time.

Physicists at the Georgia Institute of Technology used atomic force microscopy (AFM) to measure the viscosity of films of silicone oil (octamethylcylotetrasiloxane) of various thickness. Vibrating the AFM tip while measuring the tip forces allowed the measurement of the viscoelastic modulus at different frequencies, the equivalent of shaking. They found that the viscoelastic relaxation times for confined silicone oil and water are orders of magnitude longer than the usual values. These measurements were for water layers only three molecules thick; that is, water films less than about a nanometer in thickness. Silicone oil films needed to be less than four nanometers to show the enhanced viscosity. Relaxation times for water were observed to be as slow as a tenth of a second, comparable to that for supercooled water at 170-210 K. This work was funded by the National Science Foundation and the U.S. Department of Energy, and it's published in the March 14 issue of Physical Review Letters [2].

1. Abby Vogel, "Atomic force microscopy reveals liquids adjust viscosity when confined, shaken" (Georgia Institute of Technology Press Release, April 29, 2008).
2. Tai-De Li and Elisa Riedo, "Nonlinear Viscoelastic Dynamics of Nanoconfined Wetting Liquids," Phys. Rev. Lett. vol. 100 (March 13, 2008), p. 106102.
3. Dilbert's Project Uncertainty Principle
4. Schrödinger's Fridge (Angryflower.com).

May 16, 2008

Cosmic Cut-Off

We live in a violent universe. We're immersed in a sea of speeding particles, called cosmic rays, some of which are so energetic that they move nearly at the speed of light. I discussed cosmic rays in a previous article (Faster than a Speeding Bullet, November 12, 2007). Cosmic rays are not just of academic interest, since they cause "soft errors" in computer memory chips at a rate of about one soft error each week for a typical 1 GB system [1]. Cosmic rays are mostly protons (90%), helium nuclei, also known as alpha particles, (9%) and electrons (1%). They've been detected to have energies up to about 1020 electron volts (eV), which is much higher energy than the 1013 eV produced in terrestrial particle accelerators. The source of cosmic rays has been conjectured to be massive black holes at the centers of some galaxies.

Is there a limit to the violence of the universe? In 1966, when I was just a freshman in college, Kenneth Greisen of Cornell University and Georgiy Zatsepin and Vadim Kuzmin, both of the Lebedev Institute of Physics (Moscow) predicted an upper limit of cosmic ray energy of about 6 x 1019 eV [3-4]. This prediction was based on the calculated interaction of the cosmic ray protons with the universal microwave background radiation. This limit is called the GZK cut-off after its originators. A few cosmic rays had been detected with an energy of 3 x 1020 eV, fairly close to the GZK cut-off, but not as many observations as you would like to establish a statistically firm limit. Particle physicists generally operate at a 95% (or two-sigma) confidence interval. Physicists were not too concerned with the discrepancy between the GZK calculation and the observed 3 x 1020 eV detected, since cosmic ray sources close to Earth would not have much time to interact with the microwave background before reaching Earth.

Now, a huge team of US physicists called the "High Resolution Fly's Eye Collaboration" has published a paper that confirms the GZK cut-off to five standard deviations, which is enough to take the wind out of any naysayer's sails. Their data, from a now decommissioned cosmic ray observatory at the US Army Dugway Proving Ground in Utah, show a sharp suppression at an energy at 6 x 1019 eV. They also observed an "ankle" in the cosmic-ray energy spectrum at 4 x 1018 eV. The "High-Res" detectors were telescopes that observed a large portion of the sky to detect the ultraviolet fluorescence of nitrogen molecules as they are excited by cosmic rays. The "Fly's Eye" name comes from the appearance of the telescopes, which have hemispheres covered in photomultiplier tubes that resemble a fly's compound eye.

1. This Blog: Fleeting Memory, September 28, 2006.
2. Philip Ball, "Fly's eye detector spies cosmic-ray cut-off," Nature, vol. 452, no. 7185 (March 20, 2008), p264f.
3. K. Greisen, "End to the Cosmic-Ray Spectrum?", Phys. Rev. Lett., vol. 16 (1966), p. 748ff.
4. G. T. Zatsepin and V. A. Kuzmin, JETP Lett. vol. 4 (1966), p. 78 ff.

May 15, 2008

Robert Rauschenberg

When I first started working at Allied Chemical (now Honeywell), a large, original, silk-screened print by Robert Rauschenberg hung in the lobby of the Nichols/Meyer Building in Morristown. This artwork incorporated several images of technology, including an astronaut in a space suit. In those days, corporations were proud to support the arts, but now they're more concerned with the bottom line. I don't know about the disposition of that artwork, but wherever it is, it's become more valuable. Robert Rauschenberg died this week at age 82 [1-2].

Rauschenberg's works appealed to me and to other scientists, since he often incorporated images of technology. I think this was true because Rauschenberg believed that technology was a part of popular culture, and his works contained many pop images. Several other artists appeal to scientists and engineers. Many of the drawings of Paul Klee, such as The Twittering Machine (1922), have a draughtsman quality to them, and many of Klee's other images are geometrical. Of course, there's the iconic M. C. Escher, whose works, exemplified by Sky and Water and Ascending and Descending, also resonate with the taste of scientists, engineers, and mathematicians.

The technology content in Rauschenberg's works is not surprising, since he studied pharmacology at the University of Texas (Austin) before serving in the US Navy during World War II. Rauschenberg saw his first art museum while stationed in San Diego, and he realized that it was possible to make a living as a painter. During his career, he innovated in the use of materials in his creations. In the early 1950s, he created silhouette negatives on blueprint paper that were published in Life magazine. One phase of his career, as exemplified by the aforementioned Allied Chemical print, involved the use of "found images," which were photographs from magazines rendered using a photographic silkscreen process. In 1966, Rauschenberg teamed with some engineers to found Experiments in Art and Technology (E.A.T.), an organization that encouraged collaborations between artists and engineers. There were many regional chapters of E.A.T in the late 1960s, and its influence extended for several decades.

Rauschenberg had even won a Grammy Award, that for the album design of a limited-edition album cover for the Talking Heads album, Speaking in Tongues.

1. Michael Kimmelman, "Robert Rauschenberg, American Artist, Dies at 82" (New York Times, May 14, 2008).
2. Robert Rauschenberg (UK Telegraph, May 13, 2008).
3. Robert Rauschenberg (October 22, 1925 - May 12, 2008) Wikipedia.

May 14, 2008


The three passive circuit elements, the resistor, capacitor and inductor, are well known to all electrical engineers and those of us who still remember what we learned in our undergraduate general physics course. "Passive" means that they perform their function without applied power, and this distinguishes them from such "active" elements such as amplifiers. Physicists love differential equations, so the way we express the function of these elements is by these three differential equations:

Resistor: ∂v = R·∂i
Capacitor: ∂q = C·∂v
Inductor: ∂φ = L·∂i

In these equations, v is the voltage, i is the current, φ is the magnetic flux; and R, C, and L are the resistance, capacitance and inductance.

In 1971, Leon Chua, famous for the eponymous chaotic oscillator circuit, reasoned from symmetry considerations that there should exist at least one additional passive circuit element, dubbed the memristor, which satisfies the following differential equation:

Memristor: ∂φ = M·∂q

"Memristor," of course, is a combined word for a "memory resistor," and M is the "memristance." A memristor acts like a resistor at any given instant, but its resistance depends on the charge that's flowed through it, just as the voltage on a capacitor depends on the charge it's accumulated. The dependence of resistance on charge is bipolar, so a flow in one direction subtracts from the flow in the other direction.

The memrsitor was just an hypothesis for 37 years, since no physical memrsitors had been produced. Most likely, no one was really trying to produce one, since electrical engineers were doing very nicely with the three known passive devices and an occasional amplifier. All this changed recently with the announcement by Hewlett Packard of a memristor device fabricated using (of course) nanotechnology [1-6]. Although this device behaves mathematically as a memristor, its action is via a chemical effect and not the faster, and more useful, electromagnetic effect of Chua's original proposal. The device functions through ionic migration in a 5 nm film of titanium dioxide sandwiched between electrodes. As electrical charge is accumulated in this film, it becomes charged with oxygen vacancies that increase its conductance. When too much charge has passed through the device, its action saturates, and it acts as a simple resistor. The conductance effect of vacancies in bulk titanium dioxide has been known for years, and it's used in some types of oxygen gas sensors.

The electrical properties of very thin oxides have potential application in solid state memory devices, so there has been much work in this area before the Hewlett Packard work [7]. Hewlett Packard, however, is the first to describe the memristor action. One advantage of the memristor is that it will retain its state upon power loss, so it's a convenient replacement for flash memory. HP is already using memristors in dense nanowire crossbar switches with 100 Gbit storage on a single chip. Because of the combined analog and memory nature of memristors, and their high circuit density, they could be used to create sophisticated neural networks.

1. R. Colin Johnson, "First proof of circuit theory's 'missing link'?", EETimes, May 5, 2008, pp. 1f.
2. Leon O. Chua, "Memristor" The Missing Circuit Element", IEEE Transactions on Circuit Theory, vol. CT-18, no. 5 (September 1971), pp. 507-519.
3. R. Colin Johnson, "'Missing link' memristor created: Rewrite the textbooks?" (EETimes, April 30, 2008).
4. Dmitri B. Strukov, Gregory S. Snider, Duncan R. Stewart, and R. Stanley Williams, "The missing memristor found," Nature, vol. 453 (1 May 2008), pp. 80-83.
5. HP Labs Proves Existence of New Basic Element for Electronic Circuits (HP Press Release, April 30, 2008).
6. Jamie Beckett, "Demystifying the memristor: Proof of fourth basic circuit element could transform computing," (HP Press Release, April, 2008).
7. A. Beck, J. G. Bednorz, Ch. Gerber, C. Rossel, and D. Widmer, "Reproducible switching effect in thin oxide films for memory applications," Appl. Phys. Lett., vol. 77 (2000), p. 139.

May 13, 2008

The Weatherman

There's an old complaint that everyone talks about the weather, but no one does anything about it. George Cressman, a former director of the US National Weather Service, tried to do something about the weather by changing weather forecasting from an art to a science through scientific computing. George Cressman (1919-2008) died last month at age 88 [1-2].

Before ubiquitous computing, weather forecasters would rely on historical observations to make (often wrong) predictions. The idea is very simple - If your current weather map resembles that for a certain day n, then the predicted weather would be that on day (n + 1). The advent of computing allowed mathematical models to be developed and verified for weather prediction. As Cressman said in his unpublished autobiography, "I spent my professional life in pursuit of two main objectives: to learn how to integrate six simultaneous, partial differential equations and to figure out what to do with the answers." [1]

George Cressman was born on Oct. 7, 1919. After receiving an undergraduate degree from Pennsylvania State University, he took a short course in meteorology at New York University and served as a weather forecaster for the Army. His travels brought him to Chicago, where he taught meteorology to military students and received a Ph.D. in meteorology from the University of Chicago in 1949. His adviser was Carl-Gustaf Rossby, who identified the jet stream and was among the first to apply fluid dynamics to weather forecasting. After his Ph.D., Cressman did meteorological studies as a civilian consultant for the US Air Force at Andrews Air Force Base, and he participated in meteorological studies for about a dozen above-ground nuclear tests in the 1950s. While with the Air Force, Cressman was involved in the creation of the Joint Numerical Weather Prediction Unit, which was founded in 1954, and he became its first director.

In these early days of scientific computing, Cressman used an IBM 701 computer to analyze data from weather stations around the world to derive the first computer-aided weather forecasts. In 1958, the Joint Numerical Weather Prediction Unit separated into military and civilian functions, and Cressman became director of the civilian organization which eventually assumed the name, National Weather Service. Under Cressman's leadership, about a hundred weather radar stations were added to the national network, as well as many branch offices of the Weather Service. Cressman's intent, which was fully realized, was to make weather forecasting more useful, including the capability for early warning for floods, hurricanes and tornadoes.

1. Bruce Weber, "George Cressman Dies at 88; Led Weather Service" (New York Times, May 10, 2008).
2. Matt Schudel, "George Cressman; Modernized Weather Service Forecasting" (Washington Post, May 9, 2008).

May 12, 2008

Sculpting Nanocircuits

As it has always been for semiconductor processing, the development of devices with smaller and smaller features depends on progress in fabrication tools. When I first entered industrial research, transistors with minimum feature size of a few micrometers were common in integrated circuits, and at that time they were hard to make, and hard to see. Optical lithography, both contact and projection type, were used to fabricate these using photoresist masking and etching. The limitation here was the wavelength of light used for patterning the photoresist and the UV transmittance of the mask materials. The limiting wavelength at that time was 365 nm, an intense UV line of mercury-xenon lamps. Over the years, there have been methods developed, such as optical proximity correction, that extend this minimum feature size to smaller dimension. The most successful optical lithographic technique, phase-shift masking, actually utilizes diffractive effects to produce sub-wavelength features. We can finally fabricate nanoscale devices, but to say these components are a little rough around the edges is an understatement. The device designers want linear, smooth features, and what they get is an approximation resulting from the limitations of the various feature-producing processes. Smooth lines are important for electronic circuits, since sharp features produce high electric fields that lead to dielectric breakdown between adjacent circuit elements.

Electrical engineering professor Stephen Chou of Princeton University and his student, Qiangfei Xia, have addressed this problem by development of a post-processing feature-refinement method [1]. Their process appears as a paper in a current issue of Nature Nanotechnology [2]. This process, which they call "self-perfection by liquefaction," reduces line-edge roughness, increases the sidewall slope, flattens the top surface, narrows the linewidth, and increases the height/width aspect ratio.

The process relies on surface tension effects. Selected areas of patterned materials are heated above their melting point by intense bursts of light from an excimer laser a few tenths of a microsecond in duration. Flattened top surfaces were obtained by contacting a transparent plate to the patterned wafers. The surface tension at the plate draws the material into an erect, flat-topped shape. Using this technique, the Princeton engineers were able to produce 70 nanometer wide chromium lines with five times better smoothness [3]. They were able also to reduce the width of silicon lines from 285 nm to 175 nm, while increasing their height from 50 nm to 90 nm. Their work was supported by DARPA and the Office of Naval Research.

1. Chandra Shekhar, "Melting defects could lead to smaller, more powerful microchips" (Princeton University Press Release, May 4, 2008).
2. Stephen Y. Chou1 and Qiangfei Xia, "Improved nanofabrication through guided transient liquefaction," Nature Nanotechnology, vol. 3, no. 5 (May 4, 2008), pp. 295-300.
3. Photomicrographs of example structures.

May 09, 2008

Mathematical Objects

One mathematics problem that's been debated for nearly three millennia doesn't involve equations or numbers, but rather the idea of equations and numbers. The question, simply stated, is whether mathematics is discovered or invented. I'm a member of the discovery camp, in whose company we find the ancient philosopher, Plato, and our contemporary mathematician, Roger Penrose. One argument that favors discovery is the existence of the constant, pi, the ratio of the circumference to the diameter of a circle. The number, pi, is part of many fundamental equations of physics, which indicates to me that pi has a physical reality independent of an observer.

There are some, however, who take the opposite view, saying that the idea that mathematics is discovered "has more in common with mystical religions than with modern science." This controversy is summarized nicely in a recent article in Science News reporting on a forthcoming issue of the European Mathematical Society Newsletter in which discovery vs invention will be debated [1]. Science News has a special place in my heart, since it reported on one of my papers in the mid-1970s [2].

The discovery camp of mathematicians cite their feeling that in doing mathematics they are "looking" for a solution they believe already exists; no one has found it yet. This idea, of course, presumes that the mathematics is "out there," somewhere, waiting to be discovered; that is, it has existence as a pure idea, an essentially Platonist concept. The invention camp places mathematics on the same footing as music, another intellectual product of human culture. Indeed, there has been considerable mixing of mathematical and musical ideas, as in the music of Bach. A recent paper in Science [3] is entitled, "Musical operations, such as transpositions, can be expressed as symmetries of n-dimensional space." Of course the argument can be made that music is also "discovered," but this seems to be a far weaker argument. Likewise, if mathematics is invented, why doesn't 2 + 2 = 5? The truth inherent in the equation, 2 + 2 = 4, and other, more elaborate equations, expresses the fundamental link between physics and mathematics. Very few would claim that the universe would cease to exist if we weren't here to observe it.

There are proponents of each viewpoint, and the debate will persist. The mathematician, Barry Mazur, writes that "If you engage in mathematics long enough, you bump into The Question, and it won't just go away. If we wish to pay homage to the passionately felt experience that makes it so wonderful to think mathematics, we had better pay attention to it." [4]

1. Julie Rehmeyer, "Still debating with Plato - Where do mathematical objects live?" (Science News Online, April 25, 2008).
2. P. Duffer, D.M. Gualtieri, and V.U.S. Rao, "Pronounced Isotope Effect in the Superconductivity of HfV2 Containing Hydrogen (Deuterium)," Phys. Rev. Lett. vol. 37 (1976), pp. 1410-1413.
3. Rachel Wells Hall, "Musical operations, such as transpositions, can be expressed as symmetries of n-dimensional space," Science, Vol. 320. no. 5874 (April 18, 2008), pp. 328-329.
4. B. Mazur, "Mathematical Platonism and its Opposites," European Mathematical Society Newsletter (to appear, June, 2008).
5. E. B. Davies, "Let Platonism Die," European Mathematical Society Newsletter (June, 2007, pp. 24f.).
6. R. Hersh, "On Platonism," European Mathematical Society Newsletter," European Mathematical Society Newsletter (to appear, June, 2008).
7. U. Persson, "On Platonism," European Mathematical Society Newsletter (link to preprint; to appear, June, 2008).

May 08, 2008

For Your Reading Pleasure

Although I read many journal and magazine articles, I rarely have time to read books, so I'm very selective about what books I buy. I typically buy books for which I've read a favorable book review, and there are many scientific magazines, such as Nature, Science, New Scientist and American Scientist, with frequent book reviews or annual book review issues. If the review is authored by someone who's prominent in his field, not only is the book review very informative, but the recommendation is well taken.

New Scientist magazine recently asked seventeen scientists what book most influenced their life; that is, their life-changing book. There were only four physical scientists and one mathematician in the group, which should tell you something about the niche position of physical scientists in the scientific community. Here are their choices [1].

Michio Kaku [2], theoretical physicist - Isaac Asimov, The Foundation trilogy. Kaku writes that this science fiction classic forced him to ask what "impossible" technologies may be possible in the far future. As Arthur C. Clarke said, "Any sufficiently advanced technology is indistinguishable from magic." We have only to look at the last hundred years to get an idea of what this means.

Sean Carroll [3], theoretical physicist - George Gamow, One, Two, Three... Infinity. Sean Carroll has gotten a lot of press lately. I think he's trying to position himself as the next Carl Sagan (although I thought Brian Greene has already taken that position). Carroll writes that he realized he wanted to be a scientist at age ten, and George Gamow's 1947 book made physics accessible to someone of that young age. Gamow explained modern physics and such mathematical staples as transfinite numbers with simple equations.

Peter Atkins, chemist - Milton Abramovich and Irene Stegun, Handbook of Mathematical Functions. I was somewhat excited when I first discovered the table of integrals in the CRC Handbook, but you need to be an unapologetic nerd to claim that a book of math functions changed your life. Atkins says that this would be his "desert island" book. Unlike a laptop computer, batteries are not required.

Lawrence Krauss [4], physicist - Steven Weinberg, The First Three Minutes. Krauss writes that this book was his first introduction to cosmology, it led him to establish himself in the field of particle astrophysics, and it taught him how to write about science for a general audience.

Marcus du Sautoy [5], mathematician - G. H. Hardy, A Mathematician's Apology. Marcus du Sautoy writes that he read this book as an early teen, and it showed him how exciting mathematics could be. It transformed his concept of mathematics from rote computation to the more interesting task of pattern searching. Hardy's book included two simple proofs that impressed the young du Sautoy, the infinity of prime numbers and the irrationality of the square root of two.

You are, of course, expecting me to reveal my own life-changing book, and I won't disappoint. It's The World of Mathematics [6], a four volume set of essays on mathematics edited by James R. Newman, an Hungarian-American mathematician and mathematical historian who was on the board of editors for Scientific American. Like Gamow's book, many of the essays made mathematics understandable to a teenager, and there were some essays that went into greater depth. I would read the copy at our local library during my high school years, and several years ago I happily purchased my own set at a used bookshop. A paperback reprint version is available, also [7].

1. Life-changing books: recommendations from 17 leading scientists (NewScientist.com news service, April 10, 2008).
2. Michio Kaku Web Site
3. Sean Carroll Web Site
4. Lawrence M. Krauss Web Site
5. Marcus du Sautoy Web Site.
6. James Newman, The World of Mathematics (hardbound, 1956), New York: Simon and Schuster, 2535 pages, Library of Congress Catalog Number 55-10060.
7. James Newman, The World of Mathematics (paperback reprint, 2003), New York: Dover, 2480 pages. ISBN 0-486-43268-8.

May 07, 2008


The US invented the internet, there's no question about that. However, the US has turned into a low-speed, high-priced toll road of the information superhighway. The 2008 International Broadband Rankings of the Information Technology and Innovation Foundation have been released, and the US is now ranked fifteenth in the world for broadband internet access, having fallen in the ranking every year since 2001 [1]. What's most interesting is that households in South Korea, the broadband leader, have a download speed ten times faster (49.5 Mbps) than US households at just 13% the cost. If you thought you were paying too much for your cable or fiberoptic internet connection, you're right. Here's the broadband ranking for the top twenty [2].

1) South Korea
2) Japan
3) Finland
4) Netherlands
5) France
6) Sweden
7) Denmark
8) Iceland
9) Norway
10) Switzerland
11) Canada
12) Australia
13) United Kingdom
14) Luxembourg
15) United States
16) Germany
17) Belgium
18) Portugal
19) New Zealand
20) Spain

So, the US is now behind such technology powerhouses as France, Iceland and Luxembourg? How did we get into such a sorry state; or why have we been leap-frogged by other countries? The Information Technology and Innovation Foundation cites several reasons. First, nations with a "broadband strategy" fare the best. For example, a corporate-government partnership is responsible for Japan's high rank. Second, government incentives are important. Sweden, which ranks high on the list, gave incentives for companies to connect rural areas of the country. Expressed as a percentage of GDP, these incentives are equivalent to a US expenditure of $30 billion. Third, competition is important. Competition, as we all know, is sorely lacking in US broadband, and we are offered internet service bundled with other services. The Information Technology and Innovation Foundation cites unbundling of networks as the key factor in national success. Fourth, broadband is important only if a household has a computer. Sweden has subsidized computer purchases, and ninety percent of Swedes have computers.

The bottom line is this. There's a huge economy revolving around internet transactions, applications and content. If your populace is left in a back alley of the internet superhighway, your economy will suffer.

1. U.S. Should Draft Comprehensive Strategy, Provide Incentives to Boost Broadband Access (Information Technology and Innovation Foundation Press Release, May 1, 2008).
2. 2008 International Broadband Rankings (PDF File, Information Technology and Innovation Foundation, May 1, 2008).

May 06, 2008

Plugging Holes in Barrier Materials

When you have an imperfect wall, such as a cellar wall with a hole in it, what do you do to stop water from flowing into your cellar? You plug the hole. This is an easier task than trying to build a perfect wall in the first place. That's the tactic that a team of scientists from Singapore's A*STAR Institute of Materials Research and Engineering (IMRE) used to fabricate barrier films having a low permeance to water and oxygen. Their motivation was the production of a barrier film for organic light-emitting and solar cell materials. These organic materials are notoriously sensitive to water and oxygen. A*STAR is Singapore's umbrella science and technology organization. A*STAR's mission includes support of technology industries, for which organic electronics materials are expected to have an increasing importance. Organic electronics are expected to achieve more than $20 billion in global annual sales within five years.

The Singapore barrier films are apparently a thousand times more effective than present barrier materials. They are such a good barrier that one aspect of the research program was the development of a capability to quantify their performance. The IMRE team developed techniques to measure moisture permeation of less than 10-8g/m2/day. Present barrier materials are typically made as laminates of alternating organic and inorganic materials. The essential idea is to stagger the location of pinholes to increase the difficulty of molecule motion, a quality called tortuosity. These standard laminates have a water permeance of about 10-3g/m2/day at 25oC and 90% relative humidity, whereas organic electronic devices require many orders of magnitude better protection than that.

The IMRE barrier films incorporate nanoparticles that plug the pinholes and other gaps in their barrier laminates. As a further benefit, the nanoparticles absorb and retain water and oxygen so that these molecules do not reach the protected organic electronics. Laminate stacks of just two or three films are required to achieve the desired barrier properties. When used as a protective barrier for the calcium electrode of an organic light-emitting diode, no change in device performance was found after 2300 hours at 60oC and 90% relative humidity. IMRE has licensed the technology to G24Innovations, a solar cell manufacturer located in Cardiff, Wales, The United Kingdom. G24 is producing solar cells via a roll-to-roll manufacturing process that is suitable for volume production.

1. Cathy Yarbrough, "Nanoengineered barrier invented to protect plastic electronics from water degradation" (Agency for Science, Technology and Research (A*STAR), Singapore, Press Release, April 29, 2008).

May 05, 2008

Four Hundred

This is article number 400 on my blog, which I started on August 10, 2006. The number 400 is interesting enough to have its own Wikipedia entry.

Mathematically, 400 is the square of twenty. It's also a Harshad number, since it's divisible by the sum of its digits. Harshad numbers were named by their originator from the Sanskrit word meaning "great joy." Mathematicians have different pleasure centers.

One of the more unusual uses of 400 is as the number of grads in a circle. This unit was invented to divide a right angle into 100 parts, which made some mathematical calculations easier in the days before hand calculators and computers.

Because of my classical education, when I hear four hundred, I think of The Four Hundred (οι τετρακοσιοι), who were the rulers of Athens for a few months during the Peloponnesian War (411 BC). One outcome of the war was the book, History of the Peloponnesian War, by Thucydides, who is considered to be the "father of scientific history." His history shows strict standards of evidence and cause-effect analysis.

All of us have seen the 404 error code ("Not Found") when we've mistyped an address for a web site, but there's a related "400" error ("Bad Request"). You get a 400 error if what you've typed contains the address of a server, but the server doesn't understand what you want, or it can't service you. This often happens when you're behind a proxy server that's restricting information flow.

What article about the number 400 would be complete without mention of the Forbes 400, the list of the world's wealthiest individuals [1]? At the last check, in September, 2007, you needed a net worth of at least $1.3 billion to make this list. The collective worth of these 400 people is more than $1.5 trillion. I'm happy to say that many of these individuals, such as Google founders Sergey Brin and Larry Page, made their money through technology they had a personal hand in creating.

1. Matthew Miller, "The Forbes 400" (Forbes, September 20, 2007).

May 02, 2008

The Die is Cast

A fair die should always show each of its six numbers with equal probability when thrown. Casino dice are manufactured to high geometrical tolerance from durable materials, and it has always been assumed that throwing many thousands of rolls on a planar surface would confirm this regularity. However, this hypothesis wasn't tested until 2001 [1], principally because no one was willing to throw a die a million times (a good job for an undergraduate or a summer intern?). It was then that a group of physicists from the Okanagan College, Kelowna, British Columbia, Canada, decided to build a robot to do just that. The robot rolled a die every two and a half seconds onto a smooth plexiglas surface. The die was automatically photographed, so human attention was not required. Although it was not explicitly stated, they likely used a pattern recognition algorithm to extract the die data from each roll.

After 640934 rolls, here's what they found.

• 1 = 106376 (0.165970287)
• 2 = 107061 (0.167039040)
• 3 = 106850 (0.166709833)
• 4 = 107200 (0.167255911)
• 5 = 107168 (0.167205984)
• 6 = 106279 (0.165818945)

They concluded that each face has a probability of occurrence of one-in-six (0.1667) to within plus or minus 0.0010. Low quality dice, as purchased in toy stores, were a different matter. One such die rolled 21543 times gave the following.

• 1 = 2895 (0.134382398)
• 2 = 4214 (0.195608782)
• 3 = 3389 (0.157313280)
• 4 = 3347 (0.155363691)
• 5 = 4383 (0.203453558)
• 6 = 3315 (0.153878290)

As for "loaded" dice, if the distance between the 1 and 6 face was shortened by only 3%, one or six occurred 6% more often.

"Alea iacta est" (The die is cast), is what Julius Caesar said on January 10, 49 BC, as he crossed the Rubicon river with his army into Italy to begin a long civil war with Pompey. He is actually quoted by the Roman historian Suetonius as saying "Iacta alea est," but since the other phase is grammatically preferred, it's the one adopted by Latin teachers and learned by their students. Caius Suetonius Tranquillus wrote not only history, but another book, unfortunately lost, called "Lives of Famous Whores," possibly sold as a supplement to Plutarch's Lives in the Roman book shops.

1. Dean Christie, Ryan Glasheen, Chris Hamilton, Masahiro Imoto, Philip Matthews, James Moffat, Thalat Monajemi, Daniel B. Murray, John Nelson and Arne Sturm, "Experimentally obtained statistics of dice rolls," 6th Experimental Chaos Conference (Potsdam, Germany, July 22-26, 2001).
2. SVETONI TRANQVILII VITA DIVI IVLI (Suetonius Tranquillus, "The Life of the Divine Julius." (in Latin)

May 01, 2008

Darwin Online

In a previous article (Mr. Darwin's Pin Money, February 9, 2007), I wrote about the financial status of scientists in Charles Darwin's age. At that time, science was considered to be more of a hobby than a livelihood, and scientists needed to have family resources, or they needed to earn their livelihood in other activities. Darwin first attempted a profession as a physician, and then as an Anglican parson. Fortunately, he was able to make a decent living as a scientific naturalist, and the course of science was changed as a result.

You can now examine all of Darwin's works online at no charge compliments of Cambridge University, which launched The Complete Work of Charles Darwin Online web site [1] with about 20,000 papers by Darwin or about Darwin [2-4]. These items range from tiny scraps of paper to the complete text of his famous 1859 book, On the Origin of Species through Natural Selection. There are 90,000 page images available on the web site, one of which is Darwin's 1842 outline of his species theory. The availability of page images of documents in Darwin's own hand shows the working of the scientific mind. In an interview [2], John van Wyhe, putative curator of the Darwin collection, said, "You notice that it's messy. That shows that it's a working document. Darwin has crossed things out, changed his ideas." The web site has been popular. On the official opening day, April 17, 2008, The Complete Work of Charles Darwin Online had seven million hits and a data transfer of 1.86 terabytes!

One interesting item is Darwin's seventeen page analysis, at the age of 29, of the pros and cons of marriage. He did the analysis upon speculation that he might marry Emma Wedgwood, the granddaughter of Josiah Wedgwood, the pottery manufacturer. Darwin listed items in two columns, Marry and Not Marry. Under the Marry column, Darwin listed the following:

• Children.
• Constant companion and friend in old age.
• Someone to take care of the house.
• Charms of music and female chit-chat ("These things good for one's health").

Perhaps not surprisingly for the Victorian Era in which he lived, there was no mention of sex, except as an afterword relating to better digestion! Under the Not Marry column, Darwin listed the following:

• A terrible loss of time.
• Cannot read in the evenings.
• Fatness and idleness.
• Conversation of clever men at club.
• Not forced to visit relatives, and to bend in every trifle.
• No one to care for one in old age.
• Freedom to go where one liked.
• The expense and anxiety of children.
• Quarrelling.
• Less money for books, etc.
• If many children, forced to gain one's bread.

One glance at this list indicates that the arguments against Darwin's marrying seem to outweigh the advantages of marrying, but Darwin concluded otherwise. Without marriage, Darwin saw that life would entail just work. "My God, it is intolerable to spend one's whole life, like a neuter bee, working, working, working, & nothing after all - No, no, won't do." Darwin proposed to Emma in November, 1838, and they were married on January 29, 1839. Just five days before their marriage ceremony, Darwin had been elected a Fellow of the Royal Society. Darwin and Emma had ten children, so his "digestion" must have been good. Some of Darwin's reservations about marriage were true, especially the one about "The expense and anxiety of children." Two of his children died as infants, one of whom was his daughter, Annie. The death of Annie, at age ten, left a deep scar on Darwin's psyche.

1. The Complete Work of Charles Darwin Online (University of Cambridge).
2. Darwin's Notes and Thoughts Go Online (National Public Radio Morning Edition, April 25, 2008).
3. Darwin's first draft goes online (BBC News Online, April 17, 2008).
4. Geoffrey Wansell, "Origin of the spouses: The private papers that reveal Darwin's inner turmoil over whether or not to marry" (Daily Mail (UK), April 17, 2008).