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Simon Fraser University – SCFC861Nanotechnology, The Next Big Idea: course Week 1

Yesterday (Oct. 23, 2014) I started teaching a course called, Nanotechnology: The Next Big Idea for Simon Fraser University’s (SFU) Continuing Studies programme and understand that students want a copy of the slides. Unfortunately, SFU does not have a system in place for continuing studies instructors to make their course materials available online to students, so, at the end of this post you will find a link to my Week One PowerPoint slides.

For those who may be mildly curious, here’s a description of the course and of what I was covering in the first week (from SFU’s course description webpage),

Nano what? Well, it’s the manipulation of matter on an atomic, molecular and supra-molecular scale. Considered obscure and still little understood by many outside the scientific community, even the term is contested. Is it nanoscience or nanotechnoogy? The answer is: it depends. It is epxected that nanotechnology will have a greater social impact than computers and the Internet.

We will explore the world of carbon nanotubes, graphene and other nanomaterials; the formal (government) and informatl (popular culture) discussions regarding risks and benefits; and Canada’s place in the international race underway to develop this emerging science and technology.

Week 1: Nanotechnology: The Nitty Gritty

What is nanotechnology? Even scientists have a problem explaining it especially since definitions for it are relatively new and still evolving. We will largely focus on the nature of carbon nanotubes, buckyballs, grapheme and silver/gold nanoparticles as a means of understanding “nanotech.”

Here’s the week 1 slide deck (revised to reflect the material covered during the class):

Week1_definitions and the nitty grittyR

Here are my ‘notes’ for yesterday’s class consisting largely of brief heads designed to remind me of the content to be found by clicking the link directly after the head.

Week1_definitons and nitty gritty

Happy Reading!

Getting up to the size of a dust speck, the first ‘large’ self-assembling DNA crystals

An Oct. 19, 2014 news item on ScienceDaily describes the latest developments in ‘DNA nanotechnology’ research at the Wyss Institute for Biologically Inspired Engineering at Harvard University,

DNA has garnered attention for its potential as a programmable material platform that could spawn entire new and revolutionary nanodevices in computer science, microscopy, biology, and more. Researchers have been working to master the ability to coax DNA molecules to self assemble into the precise shapes and sizes needed in order to fully realize these nanotechnology dreams.

For the last 20 years, scientists have tried to design large DNA crystals with precisely prescribed depth and complex features — a design quest just fulfilled by a team at Harvard’s Wyss Institute for Biologically Inspired Engineering. The team built 32 DNA crystals with precisely-defined depth and an assortment of sophisticated three-dimensional (3D) features, an advance reported in Nature Chemistry.

It seems a bit of a misleading for the Wyss Institute to state the ‘team built’ the DNA crystals as they are self-assembling according to this Oct. 19, 2014 Wyss Institute news release (also on EurekAlert), which originated the news item,

The team used their “DNA-brick self-assembly” method, which was first unveiled in a 2012 Science publication when they created more than 100 3D complex nanostructures about the size of viruses. The newly-achieved periodic crystal structures are more than 1000 times larger than those discrete DNA brick structures, sizing up closer to a speck of dust, which is actually quite large in the world of DNA nanotechnology.

“We are very pleased that our DNA brick approach has solved this challenge,” said senior author and Wyss Institute Core Faculty member Peng Yin, Ph.D., who is also an Associate Professor of Systems Biology at Harvard Medical School, “and we were actually surprised by how well it works.”

The news release goes on to describe some of the issues with other self-assembly methods along with more details about the ‘DNA brick’ approach,

Scientists have struggled to crystallize complex 3D DNA nanostructures using more conventional self-assembly methods. The risk of error tends to increase with the complexity of the structural repeating units and the size of the DNA crystal to be assembled.

The DNA brick method uses short, synthetic strands of DNA that work like interlocking Lego® bricks to build complex structures. Structures are first designed using a computer model of a molecular cube, which becomes a master canvas. Each brick is added or removed independently from the 3D master canvas to arrive at the desired shape – and then the design is put into action: the DNA strands that would match up to achieve the desired structure are mixed together and self assemble to achieve the designed crystal structures.

“Therein lies the key distinguishing feature of our design strategy—its modularity,” said co-lead author Yonggang Ke, Ph.D., formerly a Wyss Institute Postdoctoral Fellow and now an assistant professor at the Georgia Institute of Technology and Emory University. “The ability to simply add or remove pieces from the master canvas makes it easy to create virtually any design.”

The modularity also makes it relatively easy to precisely define the crystal depth. “This is the first time anyone has demonstrated the ability to rationally design crystal depth with nanometer precision, up to 80 nm in this study,” Ke said. In contrast, previous two-dimensional DNA lattices are typically single-layer structures with only 2 nm depth.

“DNA crystals are attractive for nanotechnology applications because they are comprised of repeating structural units that provide an ideal template for scalable design features”, said co-lead author graduate student Luvena Ong.

Furthermore, as part of this study the team demonstrated the ability to position gold nanoparticles into prescribed 2D architectures less than two nanometers apart from each other along the crystal structure – a critical feature for future quantum devices and a significant technical advance for their scalable production, said co-lead author Wei Sun, Ph.D., Wyss Institute Postdoctoral Fellow.

“My preconceived notions of the limitations of DNA have been consistently shattered by our new advances in DNA nanotechnology,” said William Shih, Ph.D., who is co-author of the study and a Wyss Institute Founding Core Faculty member, as well as Associate Professor in the Department of Biological Chemistry and Molecular Pharmacology at Harvard Medical School and the Department of Cancer Biology at the Dana-Farber Cancer Institute. “DNA nanotechnology now makes it possible for us to assemble, in a programmable way, prescribed structures rivaling the complexity of many molecular machines we see in Nature.”

“Peng’s team is using the DNA-brick self-assembly method to build the foundation for the new landscape of DNA nanotechnology at an impressive pace,” said Wyss Institute Founding Director Don Ingber, M.D., Ph.D. “What have been mere visions of how the DNA molecule could be used to advance everything from the semiconductor industry to biophysics are fast becoming realities.”

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

DNA brick crystals with prescribed depths by Yonggang Ke, Luvena L. Ong, Wei Sun, Jie Song, Mingdong Dong, William M. Shih, & Peng Yin. Nature Chemistry (2014) doi:10.1038/nchem.2083 Published online 19 October 2014

This paper is behind a paywall.

Simon Fraser University – Bioelectronics course: Week 6 (the end)

As I noted in my Oct. 7, 2014 posting, I changed up the order of the classes. Last night (Oct. 20, 2014)), I presented the Week 5 material for the last class  of Bioelectronics, Medical Imaging and Our Bodies (at Simon Fraser University in Vancouver, Canada). So, here’s a description of what I presented in this course’s last class,

Week 5 6: Reverse Engineering the Brain and Neuromorphic Engineering

New computer algorithms exploit supercomputing architectures in order to measure the connections between cortical and sub-cortical locations in the human body. While brain repair is one desired outcome, there is also a major interest in developing artificial brains. The boundary between machine and human is breaking down.

I also presented information about the ‘brain in a dish’ mentioned in the session on Growing Human Organs.

Here’s the final week’s slide deck,

Week 5_Reverse & Neuromorphic Engineering

As usual, here are my ‘notes’ for last night’s class consisting largely of brief heads designed to remind me of the content to be found by clicking the link directly after the head.

Week 5 Neuromorphic engineering and brain

Happy Reading! and one final note, I will be teaching a new six-week course at Simon Fraser University : Nanotechnology: The Next Big Idea.  It starts this week on Thursday, Oct. 23, 2014.

Nestling a two-element atomic chain inside a carbon nanotube

While there doesn’t seem to be a short-term application for this research from Japan, the idea of nestling a chain of two elements inside a carbon nanotube is intriguing, from an Oct. 16, 2014 news item on Nanowerk,

Kazutomo Suenaga of the Nanotube Research Center (NTRC) of the National Institute of Advanced Industrial Science and Technology (AIST) and Ryosuke Senga of the Nano-carbon Characterization Team, NTRC, AIST, have synthesized an atomic chain in which two elements are aligned alternately and have evaluated its physical properties on an atomic level.

An ionic crystalline atomic chain of cesium iodine (CsI) has been synthesized by aligning a cesium ion (Cs+), a cation and an iodine ion (I-), an anion, alternately by encapsulating CsI in the microscopic space inside a carbon nanotube. Furthermore, by using an advanced aberration-corrected electron microscope, the physical phenomena unique to the CsI atomic chain, such as the difference in dynamic behavior of its cations and anions, have been discovered. In addition, from theoretical calculation using density functional theory (DFT), this CsI atomic chain has been found to indicate different optical properties from a three-dimensional CsI crystal, and applications to new optical devices are anticipated.

An Oct. 16, 2014 National Institute of Advanced Industrial Science and Technology (AIST) press release, which originated the news item, situates the research within a social and historical context,

Social Background of Research

In the accelerating and ballooning information society, electronic devices used in computers and smartphones has constantly demanded higher performance and efficiency. The materials currently drawing expectations are low-dimensional materials with a single to few-atom width and thickness. Two-dimensional materials, typified by graphene, indicate unique physical characteristics not found in three-dimensional materials, such as its excellent electrical transport properties, and are being extensively researched.

An atomic chain, which has an even finer structure with a width of only one atom, has been predicted to display excellent electrical transport properties, like two-dimensional materials. Although expectations were higher than for two-dimensional materials from the viewpoint of integration, it had attracted little attention until now. This is because of the technological difficulties faced by the various processes of academic research from synthesis to analysis of atomic chains, and academic understanding has not progressed far (Fig. 1).

Figure 1
Figure 1 : Transition of target materials in material research

History of Research

AIST has been developing element analysis methods on a single-atom level to detect certain special structures including impurities, dopants and defects, that affect the properties of low-dimensional materials such as carbon nanotubes and graphene (AIST press releases on July 6, 2009, January 12, 2010, December 16, 2010 and July 9, 2012). In this research, efforts were made for the synthesis and analysis of the atomic chain, a low-dimensional material, using the accumulated technological expertise. This research has been supported by both the Strategic Basic Research Program of the Japan Science and Technology Agency (FY2012 to FY2016), and the Grants-in-aid for Scientific Research of the Japan Society for the Promotion of Science, “Development of elemental technology for the atomic-scale evaluation and application of low-dimensional materials using nano-space” (FY2014 to FY2016).

The press release also offers more details about the research and future applications,

Details of Research

The developed technology is the technology to expose carbon nanotubes, with a diameter of 1 nm or smaller, to CsI vapor to encapsulate CsI in the microscopic space inside the carbon nanotubes, to synthesize an atomic chain in which two elements, Cs and I, are aligned alternately. Furthermore, by combining aberration-corrected electron microscopy and an electronic spectroscopic technique known as electron energy-loss spectroscopy (EELS) detailed structural analysis of this atomic chain was conducted. In order to identify each atom aligned at a distance of 1 nm or less without destroying them, the accelerating voltage of the electron microscope was significantly lowered to 60 kV to reduce damage to the sample by electron beams, while maintaining sufficient spatial resolution of around 1 nm. Figure 2 indicates the smallest CsI crystal confirmed so far, and the CsI atomic chain synthesized in this research.

Figure 2
Figure 2 : Comparison of CsI atomic chain and CsI crystal
(Top: Actual annular dark-field images, Bottom: Corresponding models)

Figure 3 shows the annular dark-field (ADF) image of the CsI atomic chain and the element mapping for Cs and I, respectively, obtained by EELS. It can be seen that the two elements are aligned alternately. There has not been any report of this simple and ideal structure actually being produced and observed, and it can be said to be a fundamental, important finding in material science.

Normally, in an ADF image, those with larger atomic numbers appear brighter. However, in this CsI atomic chain, I (atomic number 53) appears brighter than Cs (atomic number 55). This is because Cs, being a cation, moves more actively (more accurately, the total amount of electrons scattered by the Cs atom is not very different from those of the I atom, but the electrons scattered by the moving Cs atom generate spatial expansion), indicating a difference in dynamic behavior of the cation and the anion that cannot occur in a large three-dimensional crystal. Locations where single Cs atom or I atom is absent, namely vacancies, were also found (Fig. 3, right).

The unique behavior and structure influence various physical properties. When optical absorption spectra were calculated using DFT, the response of the CsI atomic chain to light differed with the direction of incidence. Furthermore, it was found that in a CsI atomic chain with vacancies, the electron state of vacancy sites where the I atom is absent possess a donor level at which electrons were easily released, while vacancy sites where the Cs atom is absent possess a receptor level at which electrons were easily received. By making use of these physical properties, applications to new electro-optical devices, such as a micro-light source and an optical switch using light emission from a single vacancy in the CsI atomic chain, are conceivable. In addition, further research into combinations of other elements triggered by the present results may lead to the development of new materials and device applications. There are expectations for atomic chains to be the next-generation materials for devices in search of further miniaturization and integration.

Figure 3
Figure 3 : Synthesized CsI atomic chain, encapsulated in double-walled carbon nanotube
(From left: ADF image, element maps for Cs and I, model, ADF image of CsI atomic chains with vacancies)

Future Plans

Since the CsI atomic chain displays optical properties significantly different from large crystals that can be seen by the human eye, there are expectations for its application for new electro-optical devices such as a micro-light source and an optical switch using light emission from a single vacancy in the CsI atomic chain. The researchers will conduct experimental research in its application, focused on detailed study of its various physical properties, starting with its optical properties. In addition to CsI, efforts will also be made in the development of new materials that combine various elements, by applying this technology to other materials.

Furthermore, the mechanism of all adsorbents of radioactive substances (carbon nanotubes, zeolite, Prussian blue, etc.) currently being developed for commercial use are methods of encapsulating radioactive atoms inside microscopic space in the material. The researchers hope to utilize the knowledge of the behavior of the Cs atom in a microscopic space obtained in this research, to improve adsorption performance.

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

Atomic structure and dynamic behaviour of truly one-dimensional ionic chains inside ​carbon nanotubes by Ryosuke Senga, Hannu-Pekka Komsa, Zheng Liu, Kaori Hirose-Takai, Arkady V. Krasheninnikov, & Kazu Suenaga. Nature Materials (2014) doi:10.1038/nmat4069 Published online 14 September 2014

This paper is behind a paywall.

Simon Fraser University – Bioelectronics course: Week 5

Last night (Oct. 6, 2014) I changed it up and presented Week 6 of Bioelectronics, Medical Imaging and Our Bodies (at Simon Fraser University in Vancouver, Canada) instead of the previously planned week 5 topic on reverse engineering the brain and neuromorphic engineering, I wanted to encourage students to view a documentary available on Knowledge Network, How to Build a Beating Heart before it disappears from the Knowledge website on Oct. 14, 2014 and our week 6 class on ‘building organs’ wasn’t scheduled until the Monday (Oct. 20, 2014) after Thanksgiving weekend Oct. 11 – 13, 2014.

Last night’s class was on this topic:

Week 6 5: Growing Human Organs

While human organs are being grown or 3D-printed for transplant purposes, they are also being grown on chips for toxicology testing and, in a stunning turn of events, an August 2014 New York Times article described U.S. researchers who grew a “brain in a dish.”‘

Note 1: The ‘brain in a dish’ will be covered in what should have been the week 5 topic so you won’t find it in either the slide deck or the notes for last night’s class.

Note 2: I have kept week 6 in the file names for last night’s class materials (slide presentation and notes) on the assumption that at some point in the future I may go back to this material having forgotten that I switched the weeks around.

Here’s the slide deck for last night’s class:

Week 6_Growing Organs

As usual, here are my ‘notes’ for last night’s class consisting largely of brief heads designed to remind me of the content to be found by clicking the link directly after the head.

Week 6 Organ and human on a chip

Happy Reading!

Ingenuity Lab (Alberta, Canada) and The New Economy

Alberta’s Ingenuity Lab has won an award from the UK-based magazine, The New Economy. More details about the magazine and the award follow but, first, from an Oct. 1, 2014 Ingenuity Lab news release,

Ingenuity Lab, Alberta’s first nanotechnology accelerator, has been named ‘Best Nanotechnology Research Organization 2014′ by The New Economy magazine, just under two years after its inception.

The award, which was presented to Ingenuity Lab Director, Carlo Montemagno, PhD last month at the London Stock Exchange studios, honours those who are breaking new ground across technology, energy, business and strategy landscapes.

Here’s a Sept. 15, 2014 video of Montemagno with The New Economy interviewer, Jenny Hammond,

The New Economy has provided a transcription of the video on its Using science to address global challenges: Ingenuity Lab on its progressive approach webpage which also hosts the video. (This particular question and answer interested me most,)

The New Economy: Well what problems do these areas [mining, agriculture, energy and health] pose, and what breakthroughs have you made in these areas?

Carlo Montemagno: We have been able to mimic the way nature works in the production of matter. We look around and we see the original nanotechnology machines of grass and green things. What we’ve figured out how to do is, how do you extract out the metabolism that’s found in those plants and those animals, and impart them inside materials that we engineer and produce. So it’s not alive, but it has the same metabolic pathways. So now we can take just CO2 that’s been emitted from a source, sunlight or another light source, and convert it directly into valuated dropping chemicals. We’ve identified 72 different chemicals that we can produce. That means that we can take an emission which is implicated in global warming and all those other problems, and now instead of emitting it, we use that to provide new products for that drive, and hopefully we’ll drive a new economic sector, and it will be deployable globally.

The New Economy has posted, as of today Oct. 2, 2014, a more substantive description of the work for which the Ingenuity Labs are being honoured, Ingenuity Lab: fighting blindness, influenza and water pollution. This article provides a bit a of a contrast to the video as it makes no mention of mining or emissions.

For anyone interested in the magazine, there’s this on their Contact page,

The New Economy is published quarterly and provided to Finance Directors, Chief Financial Officers and their legal and strategic advisers, corporate treasurers and leading bankers, institutional investors and compliance officers, regulators, Ministers of Finance, Energy/Environment Ministries and their senior council. The New Economy’s remit is to engender financial investment and encourage discussion and debate of appropriate strategies for the promotion of global economic growth in a concise and constructive format.

The approach is to create thought leaders in chosen content areas and invite them to knowledge share, providing a platform which allows their analysis and experience to be seen by enterprise Financial Strategists, whilst their presence identifies their organisations as Market Leaders.

On checking the editorial staff and contributors list on the Contact page I recognized a name,

Executive Editor:
Michael McCaw

Senior Assignment Editor:
Eleni Chalkidou

Contributors:
Donna Dickenson, Esther Dyson, Mohamed A El-Erian, Jules Gray, Rita Lobo, Bjorn Lomborg, David Orrell, Matthew Timms, Claire Vanner [emphasis mine]

Certainly that name gives The New Economy some added cachet (from her Wikipedia entry; Note: Links and footnotes have been removed),

Esther Dyson (born 14 July 1951) is a former journalist and Wall Street technology analyst who is a leading angel investor, philanthropist, and commentator focused on breakthrough efficacy in healthcare, government transparency, digital technology, biotechnology, and space. She recently founded HICCup, which just launched its Way to Wellville contest of five places, five years, five metrics. Hiccup.co blog . Dyson is currently focusing her career on production of health and continues to invest in health and technology startups.

Returning to where this post started, the entire Ingenuity Labs news release about its 2014 award can be found here.

Simon Fraser University – Bioelectronics course: Week 4

Last night (Sept. 29, 2014) I presented Week 4 of Bioelectronics, Medical Imaging and Our Bodies (at Simon Fraser University in Vancouver, Canada),

Week 4: Peering into the Brain: Functional MRI and Neuroimaging

Functional magnetic resonance imaging (fMRI) works by detecting changes in blood oxygenation and flow that occur in response to neural activity. In parallel with fMRI, powerful techniques such as magnetic resonance imaging and others are being used to diagnose diseases such as Parkinson’s.

Here’s the week 4 slide deck. Note: I tried to correct typos but only found one and I’m sure I spotted two last night. So, I apologize for my typos. Thankfully, they don’t change the meaning of the text as can be the case.

Week 4_MRIs_brains

As usual, here are my ‘notes’ for week 4 which consist largely of brief heads designed to remind me of the content to be found by clicking the link directly after the head.

Week 4 Brain

Happy Reading!

Asthma on a chip

Harvard University’s Wyss Institute for Biologically Inspired Engineering has found a way to mimic the lung’s muscle action when an asthma attack is being experienced according to a Sept. 23, 2014 news item on Nanowerk,

The majority of drugs used to treat asthma today are the same ones that were used 50 years ago. New drugs are urgently needed to treat this chronic respiratory disease, which causes nearly 25 million people in the United States alone to wheeze, cough, and find it difficult at best to take a deep breath.

But finding new treatments is tough: asthma is a patient-specific disease, so what works for one person doesn’t necessarily work for another, and the animal models traditionally used to test new drug candidates often fail to mimic human responses–costing tremendous money and time.

Hope for healthier airways may be on the horizon thanks to a Harvard University team that has developed a human airway muscle-on-a-chip that could be used to test new drugs because it accurately mimics the way smooth muscle contracts in the human airway, under normal circumstances and when exposed to asthma triggers. [emphasis mine]

A Sept. 23, 2014 Wyss Institute news release (also on EurekAlert*), which originated the news item, provides more details about the technology and its advantages,

The chip, a soft polymer well that is mounted on a glass substrate, contains a planar array of microscale, engineered human airway muscles, designed to mimic the laminar structure of the muscular layers of the human airway.

To mimic a typical allergic asthma response, the team first introduced interleukin-13 (IL-13) to the chip. IL-13 is a natural protein often found in the airway of asthmatic patients that mediates the response of smooth muscle to an allergen.

Then they introduced acetylcholine, a neurotransmitter that causes smooth muscle to contract. Sure enough, the airway muscle on the chip hypercontracted – and the soft chip curled up – in response to higher doses of the neurotransmitter.

They achieved the reverse effect as well and triggered the muscle to relax using drugs called β-agonists, which are used in inhalers.

Significantly, they were able to measure the contractile stress of the muscle tissue as it responded to varying doses of the drugs, said lead author Alexander Peyton Nesmith, a Ph.D./M.D. student at Harvard SEAS and the University of Alabama at Birmingham. “Our chip offers a simple, reliable and direct way to measure human responses to an asthma trigger,” he said.

The team then investigated what happened on a cellular level in response to the IL-13 and confirmed, for example, that the smooth muscle cells grew larger in the presence of IL-13 over time – a structural hallmark of the airways in asthma patients as well. They also documented an increased alignment of actin fibers within smooth muscle cells, which is consistent with the muscle in the airway of asthma patients. Actin fibers are super-thin cellular components involved in muscle contraction.

Next they observed how IL-13 changes the expression of contractile proteins called RhoA proteins, which have been implicated in the asthmatic response, although the details of their activation and signaling have remained elusive. To do this they introduced a drug called HA1077, which is not currently used to treat asthmatic patients – but targets the RhoA pathway. It turns out that the drug made the asthmatic tissue on the chip less sensitive to the asthma trigger – and preliminary tests indicated that using a combined therapy of HA1077 plus a currently approved asthma drug worked better than the single drug alone.

“Asthma is one of the top reasons for trips to the emergency room – particularly for children, and a large segment of the asthmatic population doesn’t respond to currently available treatments,” said Wyss Institute Founding Director Don Ingber, M.D., Ph.D. “The airway muscle-on-a-chip provides an important and exciting new tool for discovering new therapeutic agents.”

The scientists have provided an illustration of healthy and asthmatic airways,

Schematic comparing a healthy airway (few immune cells, normal airway diameter) to an asthmatic airway (many immune cells, constricted airway). Credit: Harvard's Wyss Institute and Harvard SEAS [School of Engineering and Applied Sciences]

Schematic comparing a healthy airway (few immune cells, normal airway diameter) to an asthmatic airway (many immune cells, constricted airway). Credit: Harvard’s Wyss Institute and Harvard SEAS [School of Engineering and Applied Sciences]

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

Human airway musculature on a chip: an in vitro model of allergic asthmatic bronchoconstriction and bronchodilation by Alexander Peyton Nesmith, Ashutosh Agarwal, Megan Laura McCain and Kevin Kit Parker.Lab Chip, 2014,14, 3925-3936 DOI: 10.1039/C4LC00688G First published online 05 Aug 2014

This paper is open access provided you have registered yourself for free at the site.

* EurekAlert link added Sept. 24, 2014.

Simon Fraser University – Bioelectronics course: Week 3

We’re halfway through the course as of last night (Sept. 22, 2014) when I presented Week 3 of Bioelectronics, Medical Imaging and Our Bodies (at Simon Fraser University in Vancouver, Canada),

Week 3: X-Rays and CT Scans: Useful but Carcinogenic? + Monitoring Devices

Higher levels of X-ray exposure can increase the risk of mutation and cancer. Public demand for these tests is generally based on the belief that more testing is better without thought to any risks posed by the testing itself. What are the risks, costs and benefits?

Here’s the week 3 slide deck (Note 1: all the of the source materials are given although not necessarily where you might expect to see them; Note 2: I promised students I would check the date for a report cited for airport scanners and have confirmed it was published in 2013 as noted on the slide),

Week 3_CTs_Xrays

Also, here are my ‘notes’ for week 3 which consist largely of brief heads designed to remind me of the content to be found by clicking the link directly after the head.

Week 3 CTs Xrays and more

Happy reading!

New ‘Star of David’-shaped molecule from University of Manchester

It sounds like the scientists took their inspiration from Maurits Cornelius Escher (M. C. Escher) when they created their ‘Star of David’ molecule. From a Sept. 22, 2014 news item on Nanowerk,

Scientists at The University of Manchester have generated a new star-shaped molecule made up of interlocking rings, which is the most complex of its kind ever created.

Here’s a representation of the molecule,

Atoms in the Star of David molecule. Image credit: University of Manchester

Atoms in the Star of David molecule. Image credit: University of Manchester

Here’s a ‘star’ sculpture based on Escher’s work,

Sculpture of the small stellated dodecahedron that appears in Escher's Gravitation. It can be found in front of the "Mesa+" building on the Campus of the University of Twente.

Sculpture of the small stellated dodecahedron that appears in Escher’s Gravitation. It can be found in front of the “Mesa+” building on the Campus of the University of Twente (Netherlands)

If you get a chance to see the Escher ‘star’, you’ll be able to see more plainly how the planes of the ‘star’ interlock. (I had the opportunity when visiting the University of Twente in Oct. 2012.)

Getting back to Manchester, a Sept. 22, 2014 University of Manchester press release (also on EurekAlert but dated Sept. 21, 2014), which originated the news item, describes the decades-long effort to create this molecule and provides a few technical details,

Known as a ‘Star of David’ molecule, scientists have been trying to create one for over a quarter of a century and the team’s findings are published at 1800 London time / 1300 US Eastern Time on 21 September 2014 in the journal Nature Chemistry.

Consisting of two molecular triangles, entwined about each other three times into a hexagram, the structure’s interlocked molecules are tiny – each triangle is 114 atoms in length around the perimeter. The molecular triangles are threaded around each other at the same time that the triangles are formed, by a process called ‘self-assembly’, similar to how the DNA double helix is formed in biology.

The molecule was created at The University of Manchester by PhD student Alex Stephens.

Professor David Leigh, in Manchester’s School of Chemistry, said: “It was a great day when Alex finally got it in the lab.  In nature, biology already uses molecular chainmail to make the tough, light shells of certain viruses and now we are on the path towards being able to reproduce its remarkable properties.

“It’s the next step on the road to man-made molecular chainmail, which could lead to the development of new materials which are light, flexible and very strong.  Just as chainmail was a breakthrough over heavy suits of armour in medieval times, this could be a big step towards materials created using nanotechnology. I hope this will lead to many exciting developments in the future.”

The team’s next step will be to make larger, more elaborate, interlocked structures.

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

A Star of David catenane by David A. Leigh, Robin G. Pritchard, & Alexander J. Stephens. Nature Chemistry (2014) doi:10.1038/nchem.2056
Published online 21 September 2014

This paper is behind a paywall.