Monthly Archives: April 2010

Memristors and nuances in a classification tug-of-war; NRC of Canada insights; rapping scientists

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Interestingly, there’s an item posted with today’s (April 8, 2010) date on the Nanowerk website from HP Labs reiterating the ‘memristor as a fourth circuit element’ concept that Forrest H Bennett has convincingly argued against first in his comments to my original posting (April 5, 2010) and, at greater length, in yesterday’s (April 7, 2010) interview.

Oddly, the item on Nanowerk, which I’m assuming is a news release from HP Labs as no author is listed, mostly regurgitates the HP Labs work on the memristor.

HP Labs researchers have discovered that the “memristor“ – a resistor with memory that represents the fourth basic circuit element in electrical engineering – has more capabilities than was previously thought. In addition to being useful in storage devices, the memristor can perform logic, enabling computation to one day be performed in chips where data is stored, rather than on a specialized central processing unit.

In fact, much of what’s mentioned in the news release and in the accompanying video was discussed in 2008 when they first published their work. The new excitement has been generated by a team at the University of Michigan (see April 5, 2010 posting), led by Dr. Wei Lu, who’ve proved that synapses in biological organisms behave like memristors. This means that the speculations that the HP Lab folks made in 2008 about hardware that learns are more likely.

As for the ‘fourth circuit element’ mentioned in the item, this brings me to classification schemes. These sorts of discussions can seem picayune to people who are not directly involved but classification schemes have a huge impact on how we think about the world around us and the ways in which we interact with it. For example, we think of the tomato and treat it as if it’s a vegetable when in fact, it’s a fruit. When was the last time you had some tomatoes and ice cream?

Whether the memristor is thought of as a ‘fourth circuit element’ (as per HP Labs and Dr. Leon Chua [as of 2003]) or a member of an ‘infinite periodic table of circuit elements’ (as per Forrest H Bennett) will have an impact on how memristors and other as yet unknown elements are investigated and understood.

As someone who doesn’t understand the particulars especially well, I find Forrest’s approach the more flexible one and therefore preferable. Classification schemes or models that are rigid both buckle as new information is added and tend to constrain it. For example, the Dewey decimal classification scheme used in most public libraries has been buckling under the pressure of adding new categories since the 1950s, at least. It’s the reason most academic libraries use the more flexible Library of Congress classification scheme, although that scheme has its problems too.

One final note, it seems that HP Labs is supporting the notion of a ‘fourth circuit element’ being added to the previous three (capacitors, inductors, and resistors) and they have the resources to distribute their preferred notion far and wide and repeatedly. Or as Forrest put it in one of his comments, “This “4th circuit element” business is marketing spin from HP …”

National Research Council of Canada Insights

In the wake of John McDougall’s appointment as the new president of the Canada’s National Research Council (NRC), Rob Annan over at the Don’t Leave Canada Behind blog has written a very important (if Canadian science policy interests you) piece about NRC.  Rob traces the organization from its beginnings.  From the posting,

The NRC was founded more than 90 years ago to advise the government on matters related to science and technology. It evolved into a federal research laboratory with the construction of the Sussex Dr. labs in the 1930s, and was the focus of Canada’s research efforts during WWII. Post-war, the NRC expanded and was a major source of Canadian research success, with notable achievements like the invention of the pacemaker, development of Canola and the crash position indicator.

From the 1950s through the 1970s, NRC’s success, growth, and increasing complexity led to the creation of spin-off organizations. Atomic research went to the Atomic Energy of Canada, defense research went to the Defense Research Board. Medical research funding went to the Medical Research Council, later the CIHR. Lastly, support for academic research was passed to NSERC.

All of these organizations have grown and prospered. The NRC? Not so much.

He goes on to trace developments to the present day,

The NRC has research institutes in every province in the country, from the Herzberg Institute of Astrophysics in BC to the Institute for Ocean Technology in Newfoundland. A total of 26 institutes across the country, covering all aspects of science and technology, and employing more than 4,000 people. It’s a broad effort and employs a lot of great scientists.

But since the 1980s, the NRC has been without a strong sense of self. Is it a basic research organization or an applied research organization? Does it exist to perform independent, government-sponsored research, or does it provide research services in support of the private sector? Does it perform early-stage research and then partner with industry, or is it a fee-for-service research organization? The answer is yes.

I encourage you to read his posting as there’s more to his history and analysis and he goes on to make some suggestions. Please don’t forget to read the comments which offer additional insights.

Dave Bruggeman (at Pasco Phronesis) also mentions Rob’s NRC posting in the context of explaining that the current US National Research Council differs greatly from the Canadian one and warns against assuming that organizations with similar names are the same. You can go read Dave’s description of the US NRC here. This is a timely reminder as the ‘reinventing technology assessment’ webcast that the Project on Emerging Nanotechnologies is hosting later this month features a speaker from the US National Research Council.

Rapping biologists and physicists

While browsing on Dave’s (Pasco Phronesis) blog, I found an item that features two videos of scientists rapping. The first comes from some physicists and the second comes from biologists. I agree with Dave that the biologists have the edge since they rap in front of a live audience although both videos are quite entertaining.

Interview about memristors with Forrest H Bennett III

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In response to my posting about memristors the other day, Forrest Bennett made intriguing comments which I followed up with some questions that he has kindly taken the time to answer. I usually split the interviews over a few days but this time I think it’s best that the interview remain in one piece. First a few biographical details, then the Q & A. [Square brackets indicate a detail that I’ve added for clarification.]

Forrest H Bennett III is a senior research scientist at Genetic Programming, Inc. He has published 55 papers and a book, “Genetic Programming III: Darwinian Invention and Problem Solving”. He holds 7 patents in machine learning, automatic programming, analog circuit design, molecular mechanics, modular robotics, programmable smart membranes, reconfigurable hardware, and control systems.

Q & A

> 1.. Could you expand your comment [in response to my blog posting of April 5, 2010] that memristors have potential by indicating what those are?

The main potential of memristors is to replace current flash memory devices. Flash memory is used in almost all digital products: cell phones, cameras, camcorders, USB memory sticks, music players, ebooks, PDAs, and increasingly netbooks, notebooks, tablets, and servers. Flash memory is currently a $20 billion market and growing. Flash memory storage is preferred over hard disks because it is smaller, faster, lower powered, and inherently more reliable because it has no moving parts.

So there is a large and growing demand for inexpensive higher capacity flash memory. This requires chip makers to shrink these flash memory chips ever smaller and smaller. The problem is that this is getting quite challenging, and will become more so in the next few years.

Memristors could meet this demand for low-cost high-density memory. Memristors are inherently simple, small, fast, and low powered. Moreover, engineers at HP claim that they can construct memristor memories in 3D instead of just the 2D of current flash technology. Memristors are not exotic to manufacture, and hence could be quite inexpensive. In fact, current memristors are produced using standard chip production facilities, but not yet in sufficient quantities for productization.

There is also a lot of discussion recently about using memristors to build “neuromorphic” systems. Neuromorphic systems are supposed to work analogously to the way brains work. Memristors could be used to build neuromorphic systems that are smaller, faster, and cheaper than could be built using conventional digital technology. The reason that memristors are considered for this task is that mathematically they behave similarly to the synapses in neurons.

> 2.. Is the criterion (or one of them) for defining a new fourth element circuit that someone assigns a unique measurement for the element?

There isn’t really a rigorous way to define what a new circuit element would have to look like. But there are three arguments against the idea that a memristor is a 4th circuit element:

First, the weakest argument is that memristance is measured in the same units (ohms) as resistors, whereas the standard 3 circuit elements each have their own units of measure. This is a very simple and intuitive way to think about it, but it’s not a rigorous argument.

Second, a stronger argument is based on what we now know about memcapacitors and meminductors. Now you might be temped to regard memcapacitors and meminductors as the 5th and 6th new fundamental circuit elements, but nobody does. Why?

If you stand back and look at the actual behavior of these 6 circuit elements, it is very clear that they naturally fall into two groups. One group is the normal resistor, capacitor, and inductor. The other group contains the new memresistor, memcapacitor, and meminductor. There is no way to consider the memristor to be the 4th element of the first group. The unmistakable distinction between these two groups is that the first group are “linear” elements, and the second group are “nonlinear” elements. What does that mean?

In a linear element there is a very simple relationship between the inputs and the outputs. So if you double the input, it doubles the output. If you cut the input in half, it cuts the output in half.

But in a nonlinear element the relationship between the input and the output can be much more complex. In fact, nonlinear elements can have arbitrarily complex relationships between inputs and outputs.

The third and strongest argument against the 4th element idea actually comes from Chua’s own 2003 paper, “Nonlinear Circuit Foundations for Nanodevices”, which is a wonderful paper. It actually contains an idea even more exciting than the idea of a “4th element”. He shows an entire periodic table of circuit elements! Not only that, it’s an infinite periodic table of circuit elements! If you think he might just be pulling elements out of a hat, I must point out that he proves in this paper that all of these circuit elements are *required* if you want to be able to build all possible circuits.

Now if you look at this periodic table of circuit elements, you will see that they fall naturally into 4 classes. There is one class that contains both capacitors and memcapacitors, another class that contains inductors and meminductors, and another class that contains *both* resistors and memristors. That is the strongest argument against the “4th element” idea: Chua’s own paper puts resistors and memristors into the *same* class of elements.

You may have noticed that I mentioned only 3 of the 4 classes in the periodic table. That’s right, there *is* a 4th class of devices that you’ve never heard discussed, but it’s not memristors!

> Does Chua still theorize that the memristor is a fourth circuit element?

Yes, he is still sticking by that as of 2003 at least. If you want to call memristors the 4th, memcapacitors the 5th, meminductors the 6th, then you are forced keep going through the entire periodic table and talk about the 7th, 8th, and so on up to infinity. That’s fine. However, you can not say that a memristor is as different from a resistor as a capacitor is from an inductor – that’s not true. And you can see that it’s not true by looking at Chua’s own periodic table.

> 3.. In mentioning the memcapacitors and meminductors along with memristors, you suggest that all of them are non-linear “generalizations” and more accurately viewed as subsets rather than new categories. Could you explain the concept of a non-linear generalization in language that could be understood by a non-technical audience?

(See above explanation of linear vs nonlinear.)

Since a linear element is a very restricted special case, and a nonlinear element can be arbitrarily complex, that means that linear elements are subsets of nonlinear elements. Which means that nonlinear elements are generalizations of linear elements. (I think you said it backwards.) [Yes, I did.]

> 4.. Are there any analogies or metaphors that you could suggest that a writer (such as myself) could use when trying to explain memristors and such to a non-technical audience?

Electrical current is analogous to water flowing in a pipe. The diameter of the pipe acts like a resistor. If you make the pipe smaller, there is more resistance to the water flow. Similarly, if you make the electrical resistance larger, there is more resistance to electric current flow.

In our water example, the memristor is much like a pipe in that its size controls the resistance to the water flow. And both resistance and memristance are measured in ohms.

The difference with a memristor is that the more water that flows through the pipe, the bigger the pipe gets – so the resistance goes down. Then if you run the water through the memristor in the opposite direction, the pipe gets smaller and smaller, and the resistance goes up. So with a memristor, you can control how big the pipe is by which way you run the water through it, and by how long you run the water through it.

> 5. Is there anything you’d like to add?

So why are memristors useful? Sticking with our water analogy, I can make the pipe bigger or small depending on which way I run the water through it. And, when I turn off the water, the pipe stays at whatever size it’s at. So the pipe has a memory. This means that I can use it to store data. I can run water through it in one direction to make the pipe big, and treat the big pipe like a stored digital ONE. Or can run water through it in the other direction to make the pipe small, and treat the small pipe like stored digital ZERO. Presto! We have a digital storage device. It may not sound very exciting when described like this, but the excitement is about just how small, low powered, simple, and 3D these devices can be.

But memristors can store more than just ONEs and ZEROs. They can also store intermediate values between ONE and ZERO depending on how long and hard I push the water through the memristor. This is what makes a memristor useful in simulating a neural synapse.

Thank you Forrest for your memristor insights.

Bacterial nanobots build a pyramid; solar cell breakthrough in Quebec; global nano regulatory framework conference at Northeastern University; Robert Fulford talks about the poetry of nanotechnology

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Just when I was thinking that the Canadian nanotechnology scene was slowing down there’s this: A research team at the École Polytechnique de Montréal (Québec) has announced that they’ve trained bacteria to build structures shaped like pyramids. From the news item on Nanowerk,

Faster than lion tamers… More powerful than snake charmers… Make way for the bacteria trainers! Professor Sylvain Martel and his team at the École Polytechnique de Montréal NanoRobotics Laboratory have achieved a new world first: “training” living bacteria to build a nanopyramid.

These miniature construction workers are magnetotactic bacteria (MTB): they have their own internal compasses, allowing them to be pulled by magnetic fields. MTB possess flagella bundles enabling each individual to generate a thrust force of approximately 4 picoNewtons. Professor Martel’s team has succeeded in directing the motion of a group of such bacteria using computer-controlled magnetic fields. In an experiment conducted by Polytechnique researchers, the bacteria transported several epoxy nanobricks and assembled them into a step-pyramid structure, completing the task in just 15 minutes. The researchers have also managed to pilot a group of bacteria through the bloodstream of a rat using the same control apparatus.

Nanowerk also features a video of the magnetotactic bacteria at work.

Solar cell breakthrough?

More Canadian nano from Québec: a researcher (Professor Benoît Marsan) and his team at the Université du Québec à Montréal (UQAM) have provided solutions to two problems which have been inhibiting the development of the very promising Graetzel solar cell that was developed in the 1990s in Switzerland. From the news item on Nanowerk a description of the problems,

Most of the materials used to make this cell are low-cost, easy to manufacture and flexible, allowing them to be integrated into a wide variety of objects and materials. In theory, the Graetzel solar cell has tremendous possibilities. Unfortunately, despite the excellence of the concept, this type of cell has two major problems that have prevented its large-scale commercialisation:

– The electrolyte is: a) extremely corrosive, resulting in a lack of durability; b) densely coloured, preventing the efficient passage of light; and c) limits the device photovoltage to 0.7 volts.

– The cathode is covered with platinum, a material that is expensive, non-transparent and rare. Despite numerous attempts, until Professor Marsan’s recent contribution, no one had been able to find a satisfactory solution to these problem

Now a description of the solutions,

– For the electrolyte, entirely new molecules have been created in the laboratory whose concentration has been increased through the contribution of Professor Livain Breau, also of the Chemistry Department. The resulting liquid or gel is transparent and non-corrosive and can increase the photovoltage, thus improving the cell’s output and stability.

– For the cathode, the platinum can be replaced by cobalt sulphide, which is far less expensive. It is also more efficient, more stable and easier to produce in the laboratory.

More details about the work and publication of the study are at Nanowerk.

Northeastern University and nano regulatory frameworks

According to a news item on Azonano, Northeastern University’s (Boston, MA) School of Law will be hosting a two-day conference on international regulatory frameworks for nanotechnology.

Leading international experts on the global regulation of nanotechnologies, including scientists, lawyers, ethicists and officials from governments, industry stakeholders, and NGOs will join in a two-day conference May 7-8, 2010 at Northeastern University’s School of Law.

The conference will identify best practices that address the needs of industries, the public and regulators. Speakers include representatives from the U.S. Environmental Protection Agency, the Brazil Ministry of Science and Technology, the Korean government, the International Conference of Chemicals Management and National Science Foundation-funded university-industry collaborations.

I checked out the law school’s conference website and noted a pretty good range of speakers from Asia, Europe, and North and South America. It can’t have been easy pulling such a diverse group together. Unfortunately, I didn’t recognize names other than two Canadian ones: Dr. Mark Saner and Pat Roy Mooney.

Saner who’s from Carleton University (Ottawa, Ontario) co-wrote a paper cited by Peter Julian (Canadian Member of Parliament) as one of the materials he used for reference when drawing up his recently tabled bill on nanotechnology regulation. (You can see Julian’s list here.) Saner, when he worked with the Council of Canadian Academies, was charged with drawing together the expert panel that wrote the council’s paper on nanotechnology. That panel put together a report (Small is Different: A Science Perspective on the Regulatory Challenges of the Nanoscale) that does a thoughtful job of discussing nanotechnology, regulations, the precautionary principle, etc. and which you can find here. (As I recall I don’t agree with everything as written in the report but it is, as I noted, thoughtful.)

As for Pat Roy Mooney, he’s the executive director for the ETC Group which is a very well-known (to many scientists and businesses in the technology sectors) civil society group. There’s an Oct. 2009 interview with Mooney here where he discusses (in English) nanotechnology during a festival in Austria.

Robert Fulford and nanotechnology

Canadian journalist and author, Robert Fulford just penned an essay/article about nanotechnology for the National Post. From the article,

Fresh bulletins regularly bring news of startling developments in this era’s most surprising and perhaps most poetic form of science, nanotechnology, the study of the unthinkably small.

It’s a pleasure to read as a literary piece. Fulford mostly concerns himself with visions of what nanotechnology could accomplish and with a book (No small matter) by Felice Frankel and George Whitesides which I first saw mentioned by Andrew Maynard on his 2020 Science blog here.

The memristor rises; commercialization and academic research in the US; carbon nanotubes could be made safer than we thought

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In 2008, two memristor papers were published in Nature and Nature Nanotechnology, respectively. In the first (Nature, May 2008 [article still behind a paywall], a team at HP Labs claimed they had proved the existence of memristors (a fourth member of electrical engineering’s ‘Holy Trinity of the capacitor, resistor, and inductor’). In the second paper (Nature Nanotechnology, July 2008 [article still behind a paywall]) the team reported that they had achieved engineering control.

I mention this because (a) there’s some new excitement about memristors and (b) I love the story (you can read my summary of the 2008 story here on the Nanotech Mysteries wiki).

Unbeknownst to me in 2008, there was another team, located in Japan, whose work  on slime mould inspired research by a group at the University of California San Diego (UC San Diego)  which confirmed theorist Leon Chua’s (he first suggested memristors existed in 1971) intuition that biological organisms used memristive systems to learn. From an article (Synapse on a Chip) by Surf daddy Orca on the HPlus magazine site,

Experiments with slime molds in 2008 by Tetsu Saisuga at Hokkaido University in Sapporo sparked additional research at the University of California, San Diego by Max Di Ventra. Di Ventra was familiar with Chua’s work and built a memristive circuit that was able to learn and predict future signals. This ability turns out to be similar to the electrical activity involved in the ebb and flow of potassium and sodium ions across cellular membranes: synapses altering their response according to the frequency and strength of signals. New Scientist reports that Di Ventra’s work confirmed Chua’s suspicions that “synapses were memristors.” “The ion channel was the missing circuit element I was looking for,” says Chua, “and it already existed in nature.”

Fast forward to 2010 and a team at the University of Michigan led by Dr. Wei Lu showing how synapses behave like memristors (published in Nano Letters, DOI: 10.1021/nl904092h [article behind paywall]). (Fromthe  HPlus site article)

Scientific American describes a US military-funded project that is trying to use the memristor “to make neural computing a reality.” DARPA’s Systems of Neuromorphic Adaptive Plastic Scalable Electronics Program (SyNAPSE) is funded to create “electronic neuromorphic machine technology that is scalable to biological levels.”

I’m not sure if the research in Michigan and elsewhere is being funded by DARPA (the US Dept. of Defense’s Defense Advanced Research Project Agency) although it seems likely.

In the short term, scientists talk about energy savings (no need to reboot your computer when you turn it back on). In the longer term, they talk about hardware being able to learn. (Thanks to the Foresight Institute for the latest update on the memristor story and the pointer to HPlus.) Do visit the HPlus site as there are some videos of scientists talking about memristors and additional information (there’s yet another team working on research that is tangentially related).

Commercializing academic research in US

Thanks to Dave Bruggeman at the Pasco Phronesis blog who’s posted some information about a White House Request for Information (RFI) on commercializing academic research. This is of particular interest not just because of the discussion about innovation in Canada but also because the US National Nanotechnology Initiative’s report to PCAST (President’s Council of Advisors on Science and Technology, my comments about the webcast of the proceedings here). From the Pasco Phronesis posting about the NNI report,

While the report notes that the U.S. continues to have a strong nanotechnology sector and corresponding support from the government. However, as with most other economic and research sectors, the rest of the world is catching up, or spending enough to try and catch up to the United States.

According to the report, more attention needs to be paid to commercialization efforts (a concern not unique to nanotechnology).

I don’t know how long the White House’s RFI has been under development but it was made public at the end of March 2010 just weeks after the latest series of reports to PCAST. As for the RFI itself, from the Pasco Phronesis posting about it,

The RFI questions are organized around two basic concerns:

  • Seeking ideas for supporting the commercialization and diffusion of university research. This would include best practices, useful models, metrics (with evidence of their success), and suggested changes in federal policy and/or research funding. In addition, the RFI is interested in how commercialization ecosystems can be developed where none exist.
  • Collecting data on private proof of concept centers (POCCs). These entities seek to help get research over the so-called “Valley of Death” between demonstrable research idea and final commercial product. The RFI is looking for similar kinds of information as for commercialization in general: best practices, metrics, underlying conditions that facilitate such centers.

I find the news of this RFI a little surprising since I had the impression that commercialization of academic research in the US is far more advanced than it is here in Canada. Mind you, that impression is based on a conversation I had with a researcher a year ago who commented that his mentor at a US university rolled out more than 1 start up company every year. As I understand it researchers in Canada may start up one or two companies in their career but never a series of them.

Carbon nanotubes, is exposure ok?

There’s some new research which suggests that carbon nanotubes can be broken down by an enzyme. From the news item on Nanowerk,

A team of Swedish and American scientists has shown for the first time that carbon nanotubes can be broken down by an enzyme – myeloperoxidase (MPO) – found in white blood cells. Their discoveries are presented in Nature Nanotechnology (“Carbon nanotubes degraded by neutrophil myeloperoxidase induce less pulmonary inflammation”) and contradict what was previously believed, that carbon nanotubes are not broken down in the body or in nature. The scientists hope that this new understanding of how MPO converts carbon nanotubes into water and carbon dioxide can be of significance to medicine.

“Previous studies have shown that carbon nanotubes could be used for introducing drugs or other substances into human cells,” says Bengt Fadeel, associate professor at the Swedish medical university Karolinska Institutet. “The problem has been not knowing how to control the breakdown of the nanotubes, which can caused unwanted toxicity and tissue damage. Our study now shows how they can be broken down biologically into harmless components.”

I believe they tested single-walled carbon nanotubes (CNTs) only as the person who wrote the news release seems unaware that mutil-walled CNTs also exist. In any event, this could be very exciting if this research holds up under more testing.