Tag Archives: Los Alamos National Laboratory

Nanoparticles and strange forces

An April 10, 2017 news item on Nanowerk announces work from the University of New Mexico (UNM), Note: A link has been removed,

A new scientific paper published, in part, by a University of New Mexico physicist is shedding light on a strange force impacting particles at the smallest level of the material world.

The discovery, published in Physical Review Letters (“Lateral Casimir Force on a Rotating Particle near a Planar Surface”), was made by an international team of researchers lead by UNM Assistant Professor Alejandro Manjavacas in the Department of Physics & Astronomy. Collaborators on the project include Francisco Rodríguez-Fortuño (King’s College London, U.K.), F. Javier García de Abajo (The Institute of Photonic Sciences, Spain) and Anatoly Zayats (King’s College London, U.K.).

An April 7,2017 UNM news release by Aaron Hill, which originated the news item, expands on the theme,

The findings relate to an area of theoretical nanophotonics and quantum theory known as the Casimir Effect, a measurable force that exists between objects inside a vacuum caused by the fluctuations of electromagnetic waves. When studied using classical physics, the vacuum would not produce any force on the objects. However, when looked at using quantum field theory, the vacuum is filled with photons, creating a small but potentially significant force on the objects.

“These studies are important because we are developing nanotechnologies where we’re getting into distances and sizes that are so small that these types of forces can dominate everything else,” said Manjavacas. “We know these Casimir forces exist, so, what we’re trying to do is figure out the overall impact they have very small particles.”

Manjavacas’ research expands on the Casimir effect by developing an analytical expression for the lateral Casimir force experienced by nanoparticles rotating near a flat surface.

Imagine a tiny sphere (nanoparticle) rotating over a surface. While the sphere slows down due to photons colliding with it, that rotation also causes the sphere to move in a lateral direction. In our physical world, friction between the sphere and the surface would be needed to achieve lateral movement. However, the nano-world does not follow the same set of rules, eliminating the need for contact between the sphere and the surface for movement to occur.

“The nanoparticle experiences a lateral force as if it were in contact with the surface, even though is actually separated from it,” said Manjavacas. “It’s a strange reaction but one that may prove to have significant impact for engineers.”

While the discovery may seem somewhat obscure, it is also extremely useful for researchers working in the always evolving nanotechnology industry. As part of their work, Manjavacas says they’ve also learned the direction of the force can be controlled by changing the distance between the particle and surface, an understanding that may help nanotech engineers develop better nanoscale objects for healthcare, computing or a variety of other areas.

For Manjavacas, the project and this latest publication are just another step forward in his research into these Casimir forces, which he has been studying throughout his scientific career. After receiving his Ph.D. from Complutense University of Madrid (UCM) in 2013, Manjavacas worked as a postdoctoral research fellow at Rice University before coming to UNM in 2015.

Currently, Manjavacas heads UNM’s Theoretical Nanophotonics research group, collaborating with scientists around the world and locally in New Mexico. In fact, Manjavacas credits Los Alamos National Laboratory Researcher Diego Dalvit, a leading expert on Casimir forces, for helping much of his work progress.

“If I had to name the person who knows the most about Casimir forces, I’d say it was him,” said Manjavacas. “He published a book that’s considered one of the big references on the topic. So, having him nearby and being able to collaborate with other UNM faculty is a big advantage for our research.”

Here’s a link to and a citation for the paper,

Lateral Casimir Force on a Rotating Particle near a Planar Surface by Alejandro Manjavacas, Francisco J. Rodríguez-Fortuño, F. Javier García de Abajo, and Anatoly V. Zayats. Phys. Rev. Lett. (Vol. 118, Iss. 13 — 31 March 2017) 118, 133605 DOI:https://doi.org/10.1103/PhysRevLett.118.133605 Published 31 March 2017

This paper is behind a paywall.

Seaweed supercapacitors

I like munching on seaweed from time to time but it seems that seaweed may be more than just a foodstuff according to an April 5, 2017 news item on Nanowerk,

Seaweed, the edible algae with a long history in some Asian cuisines, and which has also become part of the Western foodie culture, could turn out to be an essential ingredient in another trend: the development of more sustainable ways to power our devices. Researchers have made a seaweed-derived material to help boost the performance of superconductors, lithium-ion batteries and fuel cells.

The team will present the work today [April 5, 2017] at the 253rd National Meeting & Exposition of the American Chemical Society (ACS). ACS, the world’s largest scientific society, is holding the meeting here through Thursday. It features more than 14,000 presentations on a wide range of science topics.

An April 5, 2017 American Chemical Society news release on EurekAlert), which originated the news item, gives more details about the presentation,

“Carbon-based materials are the most versatile materials used in the field of energy storage and conversion,” Dongjiang Yang, Ph.D., says. “We wanted to produce carbon-based materials via a really ‘green’ pathway. Given the renewability of seaweed, we chose seaweed extract as a precursor and template to synthesize hierarchical porous carbon materials.” He explains that the project opens a new way to use earth-abundant materials to develop future high-performance, multifunctional carbon nanomaterials for energy storage and catalysis on a large scale.

Traditional carbon materials, such as graphite, have been essential to creating the current energy landscape. But to make the leap to the next generation of lithium-ion batteries and other storage devices, an even better material is needed, preferably one that can be sustainably sourced, Yang says.

With these factors in mind, Yang, who is currently at Qingdao University (China), turned to the ocean. Seaweed is an abundant algae that grows easily in salt water. While Yang was at Griffith University in Australia, he worked with colleagues at Qingdao University and at Los Alamos National Laboratory in the U.S. to make porous carbon nanofibers from seaweed extract. Chelating, or binding, metal ions such as cobalt to the alginate molecules resulted in nanofibers with an “egg-box” structure, with alginate units enveloping the metal ions. This architecture is key to the material’s stability and controllable synthesis, Yang says.

Testing showed that the seaweed-derived material had a large reversible capacity of 625 milliampere hours per gram (mAhg-1), which is considerably more than the 372 mAhg-1 capacity of traditional graphite anodes for lithium-ion batteries. This could help double the range of electric cars if the cathode material is of equal quality. The egg-box fibers also performed as well as commercial platinum-based catalysts used in fuel-cell technologies and with much better long-term stability. They also showed high capacitance as a superconductor material at 197 Farads per gram, which could be applied in zinc-air batteries and supercapacitors. The researchers published their initial results in ACS Central Science in 2015 and have since developed the materials further.

For example, building on the same egg-box structure, the researchers say they have suppressed defects in seaweed-based, lithium-ion battery cathodes that can block the movement of lithium ions and hinder battery performance. And recently, they have developed an approach using red algae-derived carrageenan and iron to make a porous sulfur-doped carbon aerogel with an ultra-high surface area. The structure could be a good candidate to use in lithium-sulfur batteries and supercapacitors.

More work is needed to commercialize the seaweed-based materials, however. Yang says currently more than 20,000 tons of alginate precursor can be extracted from seaweed per year for industrial use. But much more will be required to scale up production.

Here’s an image representing the research,

Scientists have created porous ‘egg-box’ structured nanofibers using seaweed extract. Credit: American Chemical Society

I’m not sure that looks like an egg-box but I’ll take their word for it.

Aliens wreak havoc on our personal electronics

The aliens in question are subatomic particles and the havoc they wreak is low-grade according to the scientist who was presenting on the topic at the AAAS (American Association for the Advancement of Science) 2017 Annual Meeting (Feb. 16 – 20, 2017) in Boston, Massachusetts. From a Feb. 17, 2017 news item on ScienceDaily,

You may not realize it but alien subatomic particles raining down from outer space are wreaking low-grade havoc on your smartphones, computers and other personal electronic devices.

When your computer crashes and you get the dreaded blue screen or your smartphone freezes and you have to go through the time-consuming process of a reset, most likely you blame the manufacturer: Microsoft or Apple or Samsung. In many instances, however, these operational failures may be caused by the impact of electrically charged particles generated by cosmic rays that originate outside the solar system.

“This is a really big problem, but it is mostly invisible to the public,” said Bharat Bhuva, professor of electrical engineering at Vanderbilt University, in a presentation on Friday, Feb. 17 at a session titled “Cloudy with a Chance of Solar Flares: Quantifying the Risk of Space Weather” at the annual meeting of the American Association for the Advancement of Science in Boston.

A Feb. 17, 2017 Vanderbilt University news release (also on EurekAlert), which originated the news item, expands on  the theme,

When cosmic rays traveling at fractions of the speed of light strike the Earth’s atmosphere they create cascades of secondary particles including energetic neutrons, muons, pions and alpha particles. Millions of these particles strike your body each second. Despite their numbers, this subatomic torrent is imperceptible and has no known harmful effects on living organisms. However, a fraction of these particles carry enough energy to interfere with the operation of microelectronic circuitry. When they interact with integrated circuits, they may alter individual bits of data stored in memory. This is called a single-event upset or SEU.

Since it is difficult to know when and where these particles will strike and they do not do any physical damage, the malfunctions they cause are very difficult to characterize. As a result, determining the prevalence of SEUs is not easy or straightforward. “When you have a single bit flip, it could have any number of causes. It could be a software bug or a hardware flaw, for example. The only way you can determine that it is a single-event upset is by eliminating all the other possible causes,” Bhuva explained.

There have been a number of incidents that illustrate how serious the problem can be, Bhuva reported. For example, in 2003 in the town of Schaerbeek, Belgium a bit flip in an electronic voting machine added 4,096 extra votes to one candidate. The error was only detected because it gave the candidate more votes than were possible and it was traced to a single bit flip in the machine’s register. In 2008, the avionics system of a Qantus passenger jet flying from Singapore to Perth appeared to suffer from a single-event upset that caused the autopilot to disengage. As a result, the aircraft dove 690 feet in only 23 seconds, injuring about a third of the passengers seriously enough to cause the aircraft to divert to the nearest airstrip. In addition, there have been a number of unexplained glitches in airline computers – some of which experts feel must have been caused by SEUs – that have resulted in cancellation of hundreds of flights resulting in significant economic losses.

An analysis of SEU failure rates for consumer electronic devices performed by Ritesh Mastipuram and Edwin Wee at Cypress Semiconductor on a previous generation of technology shows how prevalent the problem may be. Their results were published in 2004 in Electronic Design News and provided the following estimates:

  • A simple cell phone with 500 kilobytes of memory should only have one potential error every 28 years.
  • A router farm like those used by Internet providers with only 25 gigabytes of memory may experience one potential networking error that interrupts their operation every 17 hours.
  • A person flying in an airplane at 35,000 feet (where radiation levels are considerably higher than they are at sea level) who is working on a laptop with 500 kilobytes of memory may experience one potential error every five hours.

Bhuva is a member of Vanderbilt’s Radiation Effects Research Group, which was established in 1987 and is the largest academic program in the United States that studies the effects of radiation on electronic systems. The group’s primary focus was on military and space applications. Since 2001, the group has also been analyzing radiation effects on consumer electronics in the terrestrial environment. They have studied this phenomenon in the last eight generations of computer chip technology, including the current generation that uses 3D transistors (known as FinFET) that are only 16 nanometers in size. The 16-nanometer study was funded by a group of top microelectronics companies, including Altera, ARM, AMD, Broadcom, Cisco Systems, Marvell, MediaTek, Renesas, Qualcomm, Synopsys, and TSMC

“The semiconductor manufacturers are very concerned about this problem because it is getting more serious as the size of the transistors in computer chips shrink and the power and capacity of our digital systems increase,” Bhuva said. “In addition, microelectronic circuits are everywhere and our society is becoming increasingly dependent on them.”

To determine the rate of SEUs in 16-nanometer chips, the Vanderbilt researchers took samples of the integrated circuits to the Irradiation of Chips and Electronics (ICE) House at Los Alamos National Laboratory. There they exposed them to a neutron beam and analyzed how many SEUs the chips experienced. Experts measure the failure rate of microelectronic circuits in a unit called a FIT, which stands for failure in time. One FIT is one failure per transistor in one billion hours of operation. That may seem infinitesimal but it adds up extremely quickly with billions of transistors in many of our devices and billions of electronic systems in use today (the number of smartphones alone is in the billions). Most electronic components have failure rates measured in 100’s and 1,000’s of FITs.

chart

Trends in single event upset failure rates at the individual transistor, integrated circuit and system or device level for the three most recent manufacturing technologies. (Bharat Bhuva, Radiation Effects Research Group, Vanderbilt University)

“Our study confirms that this is a serious and growing problem,” said Bhuva.“This did not come as a surprise. Through our research on radiation effects on electronic circuits developed for military and space applications, we have been anticipating such effects on electronic systems operating in the terrestrial environment.”

Although the details of the Vanderbilt studies are proprietary, Bhuva described the general trend that they have found in the last three generations of integrated circuit technology: 28-nanometer, 20-nanometer and 16-nanometer.

As transistor sizes have shrunk, they have required less and less electrical charge to represent a logical bit. So the likelihood that one bit will “flip” from 0 to 1 (or 1 to 0) when struck by an energetic particle has been increasing. This has been partially offset by the fact that as the transistors have gotten smaller they have become smaller targets so the rate at which they are struck has decreased.

More significantly, the current generation of 16-nanometer circuits have a 3D architecture that replaced the previous 2D architecture and has proven to be significantly less susceptible to SEUs. Although this improvement has been offset by the increase in the number of transistors in each chip, the failure rate at the chip level has also dropped slightly. However, the increase in the total number of transistors being used in new electronic systems has meant that the SEU failure rate at the device level has continued to rise.

Unfortunately, it is not practical to simply shield microelectronics from these energetic particles. For example, it would take more than 10 feet of concrete to keep a circuit from being zapped by energetic neutrons. However, there are ways to design computer chips to dramatically reduce their vulnerability.

For cases where reliability is absolutely critical, you can simply design the processors in triplicate and have them vote. Bhuva pointed out: “The probability that SEUs will occur in two of the circuits at the same time is vanishingly small. So if two circuits produce the same result it should be correct.” This is the approach that NASA used to maximize the reliability of spacecraft computer systems.

The good news, Bhuva said, is that the aviation, medical equipment, IT, transportation, communications, financial and power industries are all aware of the problem and are taking steps to address it. “It is only the consumer electronics sector that has been lagging behind in addressing this problem.”

The engineer’s bottom line: “This is a major problem for industry and engineers, but it isn’t something that members of the general public need to worry much about.”

That’s fascinating and I hope the consumer electronics industry catches up with this ‘alien invasion’ issue. Finally, the ‘bit flips’ made me think of the 1956 movie ‘Invasion of the Body Snatchers‘.

Scaling up quantum dot, solar-powered windows

An Oct. 12, 2016 news item on phys.org announces that Los Alamos National Laboratory (US) may have taken a step towards scaling up quantum dot, solar-powered windows for industrial production (Note: A link has been removed),

In a paper this week for the journal Nature Energy, a Los Alamos National Laboratory research team demonstrates an important step in taking quantum dot, solar-powered windows from the laboratory to the construction site by proving that the technology can be scaled up from palm-sized demonstration models to windows large enough to put in and power a building.

“We are developing solar concentrators that will harvest sunlight from building windows and turn it into electricity, using quantum-dot based luminescent solar concentrators,” said lead scientist Victor Klimov. Klimov leads the Los Alamos Center for Advanced Solar Photophysics (CASP).

Los Alamos Center for Advanced Solar Photophysics researchers hold a large prototype solar window. From left to right: Jaehoon Lim, Kaifeng Wu, Victor Klimov, Hongbo Li.

Los Alamos Center for Advanced Solar Photophysics researchers hold a large prototype solar window. From left to right: Jaehoon Lim, Kaifeng Wu, Victor Klimov, Hongbo Li.

An Oct. 11, 2016 Los Alamos National Laboratory news release, which originated the news item, describes the work in more detail,

Luminescent solar concentrators (LSCs) are light-management devices that can serve as large-area sunlight collectors for photovoltaic cells. An LSC consists of a slab of transparent glass or plastic impregnated or coated with highly emissive fluorophores. After absorbing solar light shining onto a larger-area face of the slab, LSC fluorophores re-emit photons at a lower energy and these photons are guided by total internal reflection to the device edges where they are collected by photovoltaic cells.

At Los Alamos, researchers expand the options for energy production while minimizing the impact on the environment, supporting the Laboratory mission to strengthen energy security for the nation.

In the Nature Energy paper, the team reports on large LSC windows created using the “doctor-blade” technique for depositing thin layers of a dot/polymer composite on top of commercial large-area glass slabs. The “doctor-blade” technique comes from the world of printing and uses a blade to wipe excess liquid material such as ink from a surface, leaving a thin, highly uniform film behind. “The quantum dots used in LSC devices have been specially designed for the optimal performance as LSC fluorophores and to exhibit good compatibility with the polymer material that holds them on the surface of the window,” Klimov noted.

LSCs use colloidal quantum dots to collect light because they have properties such as widely tunable absorption and emission spectra, nearly 100 percent emission efficiencies, and high photostability (they don’t break down in sunlight).

If the cost of an LSC is much lower than that of a photovoltaic cell of comparable surface area and the LSC efficiency is sufficiently high, then it is possible to considerably reduce the cost of producing solar electricity, Klimov said. “Semitransparent LSCs can also enable new types of devices such as solar or photovoltaic windows that could turn presently passive building facades into power generation units.”

The quantum dots used in this study are semiconductor spheres with a core of one material and a shell of another. Their absorption and emission spectra can be tuned almost independently by varying the size and/or composition of the core and the shell. This allows the emission spectrum to be tuned by the parameters of the dot’s core to below the onset of strong optical absorption, which is itself tuned by the parameters of the dot’s shell. As a result, loss of light due to self-absorption is greatly reduced. “This tunability is the key property of these specially designed quantum dots that allows for record-size, high-performance LSC devices,” Klimov said.

The “LSC quantum dots” were synthesized by Jaehoon Lim (a postdoctoral research associate). Hongbo Li (postdoctoral research associate), and Kaifeng Wu (postdoctoral Director’s Fellow) developed the procedures for encapsulating quantum dots into polymer matrices and their deposition onto glass slabs by doctor-blading. Hyung-Jun Song (postdoctoral research associate) fabricated prototypes of complete LSC-solar-cell devices and characterized them.

Here’s a link to and a citation for the paper,

Doctor-blade deposition of quantum dots onto standard window glass for low-loss large-area luminescent solar concentrators by Hongbo Li, Kaifeng Wu, Jaehoon Lim, Hyung-Jun Song, & Victor I. Klimov. Nature Energy 1, Article number: 16157 (2016) doi:10.1038/nenergy.2016.157 Published online: 10 October 2016

This paper is behind a paywall.

arXiv which helped kickoff the open access movement contemplates its future

arXiv is hosted by Cornell University and lodges over a million scientific papers that are open to access by anyone. Here’s more from a July 22, 2016 news item on phys.org,

As the arXiv repository of scientific papers celebrates its 25th year as one of the scientific community’s most important means of communication, the site’s leadership is looking ahead to ensure it remains indispensable, robust and financially sustainable.

A July 21, 2016 Cornell University news release by Bill Steele, which originated the news item, provides more information about future plans and a brief history of the repository (Note: Links have been removed),

Changes and improvements are in store, many in response to suggestions received in a survey of nearly 37,000 users whose primary requests were for a more robust search engine and better facilities to share supplementary material, such as slides or code, that often accompanies scientific papers.

But even more important is to upgrade the underlying architecture of the system, much of it based on “old code,” said Oya Rieger, associate university librarian for digital scholarship and preservation services, who serves as arXiv’s program director. “We have to create a work plan to ensure that arXiv will serve for another 25 years,” she said. That will require recruiting additional programmers and finding additional sources of funding, she added.

The improvements will not change the site’s essential format or its core mission of free and open dissemination of the latest scientific research, Rieger said.

arXiv was created in 1991 by Paul Ginsparg, professor of physics and information science, when he was working at Los Alamos National Laboratory. It was then common practice for researchers to circulate “pre-prints” of their papers so that colleagues could have the advantage of knowing about their research in advance of publication in scientific journals. Ginsparg launched a service (originally running from a computer under his desk) to make the papers instantly available online.

Ginsparg brought the arXiv with him from Los Alamos when he joined the Cornell faculty in 2001. Since then, it has been managed by Cornell University Library, with Ginsparg as a member of its scientific advisory board.

In 2015, arXiv celebrated its millionth submission and saw 139 million downloads in that year alone.

Nearly 95 percent of respondents to the survey said they were satisfied with arXiv, many saying that rapid access to research results had made a difference in their careers, and applauding it as an advance in open access.

“We were amazed and heartened by the outpouring of responses representing users from a variety of countries, age groups and career stages. Their insight will help us as we refine a compelling and coherent vision for arXiv’s future,” Rieger said. “We’re continuing to explore current and emerging user needs and priorities. We hope to secure funding to revamp the service’s infrastructure and ensure that it will continue to serve as an important scientific venue for facilitating rapid dissemination of papers, which is arXiv’s core goal.”

Though some users suggested new or additional features, a majority of respondents emphasized that the clean, unencumbered nature of the site makes its use easy and efficient. “I sincerely wish academic journals could try to emulate the cleanness, convenience and user-friendly nature of the arXiv, and I hope the future of academic publishing looks more like what we’ve been able to enjoy in the arXiv,” one user wrote.

arXiv is supported by a global collective of nearly 200 libraries in 24 countries, and an ongoing grant from the Simons Foundation. In 2012, the site adopted a new funding model, in which it is collaboratively governed and supported by the research communities and institutions that benefit from it most directly.

Having a bee in my bonnet about overproduced websites (MIT [Massachusetts Institute of Technology], I’m looking at you), I can’t help but applaud this user and, of course, arXiv, “I sincerely wish academic journals could try to emulate the cleanness, convenience and user-friendly nature of the arXiv, and I hope the future of academic publishing looks more like what we’ve been able to enjoy in the arXiv, …”

For anyone interested in arXiv plans, there’s the arXiv Review Strategy here on Cornell University’s Confluence website.

Enzymatic fuel cells with ultrasmall gold nanocluster

Scientists at the US Department of Energy’s Los Alamos National Laboratory have developed a DNA-templated gold nanocluster (AuNC) for more efficient biofuel cell design (Note: A link has been removed). From a Sept. 24, 2015 news item on ScienceDaily,

With fossil-fuel sources dwindling, better biofuel cell design is a strong candidate in the energy field. In research published in the Journal of the American Chemical Society (“A Hybrid DNA-Templated Gold Nanocluster For Enhanced Enzymatic Reduction of Oxygen”), Los Alamos researchers and external collaborators synthesized and characterized a new DNA-templated gold nanocluster (AuNC) that could resolve a critical methodological barrier for efficient biofuel cell design.

Here’s an image illustrating the DNA-templated gold nanoclusters,

Caption: Gold nanoclusters (~1 nm) are efficient mediators of electron transfer between co-self-assembled enzymes and carbon nanotubes in an enzyme fuel cell. The efficient electron transfer from this quantized nano material minimizes the energy waste and improves the kinetics of the oxygen reduction reaction, toward a more efficient fuel cell cycle. Credit: Los Alamos National Laboratory

Caption: Gold nanoclusters (~1 nm) are efficient mediators of electron transfer between co-self-assembled enzymes and carbon nanotubes in an enzyme fuel cell. The efficient electron transfer from this quantized nano material minimizes the energy waste and improves the kinetics of the oxygen reduction reaction, toward a more efficient fuel cell cycle.
Credit: Los Alamos National Laboratory

A Sept. 24, 2015 Los Alamos National Laboratory news release, which originated the news item, provides more details,

“Enzymatic fuel cells and nanomaterials show great promise and as they can operate under environmentally benign neutral pH conditions, they are a greener alternative to existing alkaline or acidic fuel cells, making them the subject of worldwide research endeavors,” said Saumen Chakraborty, a scientist on the project. “Our work seeks to boost electron transfer efficiency, creating a potential candidate for the development of cathodes in enzymatic fuel cells.”

Ligands, molecules that bind to a central metal atom, are necessary to form stable nanoclusters. For this study, the researchers chose single-stranded DNA as the ligand, as DNA is a natural nanoscale material having high affinity for metal cations and can be used to assembly the cluster to other nanoscale material such as carbon nanotubes.

In enzymatic fuel cells, fuel is oxidized on the anode, while oxygen reduction reactions take place on the cathode, often using multi copper oxidases. Enzymatic fuel cell performance depends critically on how effectively the enzyme active sites can accept and donate electrons from the electrode by direct electron transfer (ET). However, the lack of effective ET between the enzyme active sites, which are usually buried ~10Å from their surface, and the electrode is a major barrier to their development. Therefore, effective mediators of this electron transfer are needed.

The team developed a new DNA-templated gold nanocluster (AuNC) that enhanced electron transfer. This novel role of the AuNC as enhancer of electron transfer at the enzyme-electrode interface could be effective for cathodes in enzymatic fuel cells, thus removing a critical methodological barrier for efficient biofuel cell design.

Possessing many unique properties due to their discrete electron state distributions, metal nanoclusters (<1.5 nm diameter; ~2-144 atoms of gold, silver, platinum, or copper) show application in many fields.

Hypothesizing that due to the ultra-small size (the clusters are ~7 atoms, ~0.9 nm in diameter), and unique electrochemical properties, the AuNC can facilitate electron transfer to an oxygen-reduction reaction enzyme-active site and therefore, lower the overpotential of the oxygen reaction. Overpotential is the extra amount of energy required to drive an electrochemical reaction.

Ideally, it is desirable that all electrochemical reactions have minimal to no overpotential, but in reality they all have some. Therefore, to design an efficient electrocatalyst (for reduction or oxidation) we want to design it so that the reaction can proceed with a minimal amount of extra, applied energy.

When self assembled with bilirubin oxidase and carbon nanotubes, the AuNC acts to enhance the electron transfer, and it lowers the overpotential of oxygen reduction by a significant ~15 mV (as opposed to ~1-2 mV observed using other types of mediators) compared to the enzyme alone. The AuNC also causes significant enhancement of electrocatalytic current densities. Proteins are electronically insulating (they are complex, greasy and large), so the use of carbon nanotubes helps the enzyme stick to the electrode as well as to facilitate electron transfer.

Although gold nanoclusters have been used in chemical catalysis, this is the first time that we demonstrate they can also act as electron relaying agents to enzymatic oxygen reduction reaction monitored by electrochemistry.

Finally, the presence of AuNC does not perturb the mechanism of enzymatic O2 reduction. Such unique application of AuNC as facilitator of ET by improving thermodynamics and kinetics of O2 reduction is unprecedented.

Here’s a link to and a citation for the paper,

A Hybrid DNA-Templated Gold Nanocluster For Enhanced Enzymatic Reduction of Oxygen by Saumen Chakraborty, Sofia Babanova, Reginaldo C. Rocha, Anil Desireddy, Kateryna Artyushkova, Amy E. Boncella, Plamen Atanassov, and Jennifer S. Martinez. J. Am. Chem. Soc., 2015, 137 (36), pp 11678–11687 DOI: 10.1021/jacs.5b05338 Publication Date (Web): August 19, 2015

Copyright © 2015 American Chemical Society

This paper is behind a paywall.

Crystalline cellulose nanofibers and biomass fuel

Perhaps one day the researchers who work with cellulose at the nanoscale will agree to some kind of terminology. Unfortunately, that day does not seem to be scheduled for the near future as per the latest research from Los Alamos National Laboratory and the Great Lakes Bioenergy Research Center (GLBRC) in the June 19, 2013 news item on ScienceDaily,

Improved methods for breaking down cellulose nanofibers are central to cost-effective biofuel production and the subject of new research from Los Alamos National Laboratory (LANL) and the Great Lakes Bioenergy Research Center (GLBRC). Scientists are investigating the unique properties of crystalline cellulose nanofibers to develop novel chemical pretreatments and designer enzymes for biofuel production from cellulosic — or non-food — plant derived biomass.

“Cellulose is laid out in plant cell walls as crystalline nanofibers, like steel reinforcements embedded in concrete columns,” says GLBRC’s Shishir Chundawat. “The key to cheaper biofuel production is to unravel these tightly packed nanofibers more efficiently into soluble sugars using fewer enzymes.”

The June 19, 2013 Los Alamos National Laboratory news release, which originated the news item, explains the new technique in more detail,

An article published this week in the Proceedings of the National Academy of Sciences suggests—counter-intuitively—that increased binding of enzymes to cellulose polymers doesn’t always lead to faster breakdown into simple sugars. In fact, Chundawat’s research team found that using novel biomass pretreatments to convert cellulose to a unique crystalline structure called cellulose III reduced native enzyme binding while increasing sugar yields by as much as five times.

The researchers had previously demonstrated that altering the crystal structure of native cellulose to cellulose III accelerates enzymatic deconstruction; however, the recent observation that cellulose III increased sugar yields with reduced levels of bound enzyme was unexpected. To explain this finding, Chundawat and a team of LANL researchers led by Gnana Gnanakaran and Anurag Sethi developed a mechanistic kinetic model indicating that the relationship between enzyme affinity for cellulose and catalytic efficiency is more complex than previously thought.

Cellulose III was found to have a less sticky surface that makes it harder for native enzymes to get stuck non-productively on it, unlike untreated cellulose surfaces. The model further predicts that the enhanced enzyme activity, despite reduced binding, is due to the relative ease with which enzymes are able to pull out individual cellulose III chains from the pretreated nanofiber surface and then break them apart into simple sugars.

“These findings are exciting because they may catalyze future development of novel engineered enzymes that are further tailored for conversion of cellulose III rich pretreated biomass to cheaper fuels and other useful compounds that are currently derived from non-renewable fossil fuels,” says Gnanakaran.

Here’s a link to and a citation for the published paper,

Increased enzyme binding to substrate is not necessary for more efficient cellulose hydrolysis by Dahai Gaoa, Shishir P. S. Chundawat, Anurag Sethic, Venkatesh Balana, S. Gnanakaranc, and Bruce E. Dalea. Published online before print June 19, 2013, doi: 10.1073/pnas.1213426110
PNAS June 19, 2013

There is open access to the article (I’m not sure if this is permanent or temporary).

As I hinted at the beginning of this piece, there are a number of terms used to describe cellulose at the nanoscale. For example, there’s nanocrystalline cellulose (NCC) which is also known as cellulose nanocrystals (CNC); this second term now seems to be preferred. My latest writing on nanocellulose, which seems to be a generic term covering all of the versions cellulose at the nanoscale is in a May 21, 2013 posting about some nanotoxicology studies and in a May 7, 2013 posting about a Saskatchewan-based (Canada) biorefinery (Blue Goose Biorefinery) and its production of CNC.

There are many more here on the topic and, if you’re interested, you may want to try CelluForce, FPInnovations, CNC, and/or NCC, as well as, nanocellulose or cellulose, as blog search terms.

Evelyn Fox Keller, Lee Smolin, or Kathleen M. Vogel may be speaking at a science event near you

More details are emerging about Evelyn Fox Keller’s April 2013 visit to western Canada (first mentioned in my Jan. 23, 2013 posting). Fox Keller is an eminent scholar as per this description, from my Oct. 29, 2012 posting about her talk in Halifax, Nova Scotia,

Before giving you details about where to go for a link [to her livestreamed Oct. 30, 2012 talk], here’s more about the talk and about Keller,

Fifty years ago, Thomas Kuhn irrevocably transformed our thinking about the sciences with the publication of The Structure of Scientific Revolutions. For all his success, debate about the adequacy and applicability of his formulation persists to this day. Are there scientific revolutions in biology? Molecular genetics, for example, is currently undergoing a major transformation in its understanding of what genes are and of what role they play in an organism’s development and evolution. Is this a revolution? More specifically, is this a revolution of the sort that Kuhn had in mind? How is language used? What implications can we draw from this?

Dr. Keller is the recipient of the prestigious MacArthur ‘Genius’ Award and author of many influential works on science, society and modern biology such as: A Feeling for the Organism: The Life and Work of Barbara McClintock (1983), Reflections on Gender and Science (1985), Secrets of Life, Secrets of Death: Essays on Language, Gender, and Science (1992), The Century of the Gene (2000), Making Sense of Life: Explaining Biological Development with Models, Metaphors and Machines (2002) and The Mirage of a Space Between Nature and Nurture (2010).

Keller Fox will be visiting the University of Calgary (Alberta) on April 1, the University of Alberta on April 2, and the University of British Columbia on April 4, 2013.  I’ve not found details about the University of Calgary visit but did find this for the University of Alberta visit (from the  Situating Science network node for the University of Alberta web page),

Tue., Apr. 2, 4:00 PM – , 6:00 PM

Dr. Keller visits U. Alberta as part of her travels as the Cluster Visiting Scholar.

Dr. Keller will speak at 4 pm in the Engineering and Technology Learning Centre, room 1-017d. There will be a reception directly after the talk.

PARADIGM SHIFTS AND REVOLUTIONS IN CONTEMPORARY BIOLOGY

Details about the visit to the University of  British Columbia are a little sparse, Situating Science network node for the University of British Columbia web page

Network Node:
University of British Columbia
Date:
Thu., Apr. 4, 5:00 PM – , 6:30 PM

What Kind of Divide Separates Biology from Culture?
Evelyn Fox Keller, History and Philosophy of Science, MIT
April 4 2013 5:00 – 6:30 pm, with reception to follow

Presented by Science and Society Series at Green College
Location: TBD

I did try to find more information about where and who might be allowed to attend her University of British Columbia (UBC) visit on the UBC site (Science and Technology Studies colloquium webpage, which lists her visit) and on their Green College site but no more details were available.

The Perimeter Institute in Waterloo, Ontario (the other side of Canada) has announced, with full details, an April 3, 2013 talk by Lee Smolin. Smolin moved to Canada in 2000 to become a founding member of the Perimeter Institute as per the biographical information attached to this event announcement. From their Mar. 13, 2013 announcement,

Time Reborn(Live webcast)

Wednesday, April 3 @ 7:00 pm
Mike Lazaridis Theatre of Ideas
Perimeter Institute, Waterloo

Lee Smolin
Perimeter Institute

What is time? Is our perception of time passing an illusion which hides a deeper, timeless reality? Or is it real, indeed, the most real aspect of our experience of the world? Einstein said that, “the distinction between past, present, and future is only a stubbornly persistent illusion,” and many contemporary theorists agree that time emerges from a more fundamental timeless quantum universe. But in recent cosmological speculation, this timeless picture of nature seems to have reached a dead end, populated by infinite numbers of imagined unobservable universes.

In this talk, Lee Smolin explains why he changed his mind about the nature of time and has embraced the view that time is real and everything else, including the laws of nature, evolves. In a world in which time is real, the future is open and there is an essential role for human agency and imagination in envisioning and shaping a good future. Read More

Win tickets to be part of the live audience at Perimeter Institute for Time Reborn.

Sign up to receive an email reminder to watch the live webcast of Time Reborn.

As a service to audience members,
Words Worth Books will be onsite at this event.

Thank you for your support!

There is no information about accessing the webcast in the announcement. I last mentioned Smolin (briefly) in a June 4, 2009 posting,

… a physicist at Canada’s Perimeter Institute, Lee Smolin who, based on his work with Roberto Mangabeira Unger, a Brazilian philospher, suggests that the timeless multiverse (beloved of physicists and science fiction writers) does not exist.

This last event with Kathleen Vogel takes place in Washington, DC. From the Mar. 13, 2013 Woodrow Wilson Center announcement,

Invitation from the Woodrow Wilson Center

and the Los Alamos National Laboratory

Book Discussion: Phantom Menace or Looming Danger?: A New Framework for Assessing Bioweapons Threats

Speaker: Kathleen M. Vogel, Ph.D.

Associate Professor, Department of Science & Technology Studies

Acting Director, Reppy Institute for Peace and Conflict Studies

Cornell University

Date/Time: Friday, March 22, 2013, noon to 1:30 p.m.

Location: 5th Floor Conference Room

Woodrow Wilson Center in the Ronald Reagan Building,

1300 Pennsylvania Ave., NW

(“Federal Triangle” stop on Blue/Orange Line)

Please RSVP (acceptances only) at iss@wilsoncenter.org

For directions see the map on the Center’s website at www.wilsoncenter.org/directions. Please bring a photo ID and allow additional time to pass through a security checkpoint.

This meeting is part of an ongoing series that provides a forum for policy specialists from Congress and the Executive, business, academia, and journalism to exchange information and share perspectives on current nonproliferation issues. Lunch will be served. Seating is limited.