Tag Archives: Switzerland

Attosecond science impacts femtochemistry

An Aug. 17, 2016 news item on Nanowerk reveals the latest about attoscience and femtochemistry (Note: A link has been removed),

Attosecond Science is a new exciting frontier in contemporary physics, aimed at time-resolving the motion of electrons in atoms, molecules and solids on their natural timescale. Electronic dynamics derives from the creation and evolution of coherence between different electronic states and proceeds on sub-femtosecond timescales. In contrast, chemical dynamics involves position changes of atomic centers and functional groups and typically proceeds on a slower, femtosecond timescale inherent to nuclear motion.

Nonetheless, there are exciting ways in which chemistry can hugely benefit from the technological developments pushed forward in the vibrant field of Attosecond Science. This was exploited in the work recently published by Lorenz Drescher and coworkers (“XUV transient absorption spectroscopy of iodomethane and iodobenzene photodissociation”).

An Aug. 17, 2016 (?) Forschungsverbund Berlin press release, which originated the news item, provides more detail about the work,

Attosecond pulses are generated in the process of High Harmonic Generation (HHG), in which infrared photons are upconverted to the extreme ultraviolet (XUV) frequency domain in a highly non-linear interaction of intense coherent light and matter. The short duration of attosecond pulses implies a frequency spectrum with photon energies spanning from a few electron volts (eV) to hundreds of eV. Such broad and continuous frequency spectra are ideally suited for core shell absorption measurements in molecules.

Core shell to valence shell transitions are a unique probe of molecular structure and dynamics. Core-to-valence transitions are element specific, due to the highly localized nature of core orbitals on specific atoms. On the other hand the intramolecular local environment of specific atomic sites is encoded, since an electron is lifted from a core orbital to a hole in the valence shell, affected by chemical bonding (…). Importantly, these transitions typically correspond to very short lifetimes of only a few femtoseconds. The use of ultrashort XUV pulses hence gives a new twist to the ultrafast studies of chemistry: It allows to probe chemical dynamics, initiated by a UV pump laser pulse, from the perspective of different reporter atoms within a molecule in an XUV transient absorption experiment. This is now beginning to be explored by a number of groups around the world.

In the experiment carried out by Drescher and coworkers at the MBI, photodissociation of iodomethane (CH3I) and iodobenzene (C6H5I) was studied with time-resolved XUV transient absorption spectroscopy at the iodine pre-N4,5 edge, using femtosecond UV pump pulses and XUV probe pulses from HHG (…). For both molecules the molecular core-to-valence absorption lines were found to fade immediately, within the pump-probe time-resolution. Absorption lines converging to the atomic iodine product however emerge promptly in CH3I but are time-delayed in C6H5I. In CH3I, we interpret this observation as the creation of an instantaneous new target state for XUV absorption by the UV pump pulse, which is then subject to relaxation of the excited valence shell as the molecule dissociates. This relaxation shows in a continuous shift in energy of the emerging atomic absorption lines in CH3I, which we measured in the experiment. In contrast, the delayed appearance of the absorption lines in C6H5I is indicative of a UV created vacancy, which within the molecule is initially spatially distant from the iodine reporter atom and has to first travel intramolecular before being observed. This behaviour is attributed to the dominant π → σ* UV excitation in iodobenzene, which involves the π orbital of the phenyl moiety.

While in the current work only a simplistic independent particle model was used to rationalize the observed experimental findings, MBI with its newly created theory department provides unique opportunities for joint experimental and theory studies on XUV transient absorption of photochemical processes. This will involve a new theoretical approach developed recently by researchers from MBI together with colleagues in Canada, the UK and Switzerland, which was recently submitted as a publication.

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

Communication: XUV transient absorption spectroscopy of iodomethane and iodobenzene photodissociation by L. Drescher, M. C. E. Galbraith, G. Reitsma, J. Dura, N. Zhavoronkov, S. Patchkovskii, M. J. J. Vrakking, and J. Mikosch. J. Chem. Phys. 145, 011101 (2016); http://dx.doi.org/10.1063/1.4955212

This paper appears to be open access.

Georgina Lohan, Bharti Kher, and Pablo Picasso: the beauty and the beastliness of art (in Vancouver)

Georgina Lohan

Vancouver (Canada) artist Georgina Lohan’s latest show was a departure of sorts. Better known for her tableware and jewelry, her art exhibit showcased ceramic sculptures ranging in height from 16 inches to over seven feet and incorporating concepts from biology, species evolution, mythology, philosophy, sociology, and archaeology to convey imagery associated with the primordial world.

Perhaps one of the most striking elements of Lohan’s work is its beauty. This is not a quality one often sees in contemporary art. If she were fish, Lohan could be seen as swimming against the tide.

Origins II 62" x 24" Porcelain, steel 2016

Origins II 62″ x 24″ Porcelain, steel 2016 Courtesy: Georgina Lohan

Within a context that encompasses beauty and the primordial ooze, she is representing many of the disturbing themes seen in contemporary art: fragmentation, loss, destruction, and, indirectly, war.

The artist deliberately exploits the structural fragility of her pieces (four of them had to be anchored to the walls of the gallery).  From Lohan’s own writings about the show,

The repetitive nature of loss and destruction when working with a fragile medium has consolidated my tactic of collage porcelain debris as well as a consideration of the fragment as signifier for a larger totality.

The heat of the kiln is equivalent to an acceleration of time. Gravity becomes a critical force at these high temperatures and strategies of support become more and more necessary the larger and heavier the pieces become. Glazes liquefy, boil and bubble before smoothing out, colour change, the work expands and shrinks, moving and changing it molecular structure, growing crystals and other phenomena. The results can unpredictable and there is a high level of risk, but there are also those alchemical moments when base metals have turned to gold.

Sadly, the show ended Aug. 11, 2016 but Lohan has plans for future shows. You can find out more at her website.

Bharti Kher

The Vancouver Art Gallery (VAG) is showcasing UK-born, New Delhi-based artist Bharti Kher in North America’s first 20 year retrospective of her work, titled ‘Matter’, from July 9, 2016 to Oct. 10, 2016.

I saw the show on a Tuesday (Aug. 16, 2016) which features entry by donation from 5 pm. Depending on how you feel about crowds, you may want to get there early for the lineup. (The Picasso show which is also happening is quite the attraction, more about Picasso: The Artist and His Muses later in this post.

There is a lot to this show so I’m concentrating on  elements of special interest to me: the goddess sculptures, the ‘fabric pieces’, and one of the bindi pieces.

The sculptures of the women incorporating animal pelts, fragile teacups, and/or antlers fascinated me. I was particularly intrigued by ‘And all the while the benevolent slept’ (2008).

Bharti Kher's And all the while the benevolent slept, 2008 Guillaume Ziccarelli

Bharti Kher’s And all the while the benevolent slept, 2008. Credit: Guillaume Ziccarelli

Here’s what Kher is doing with this goddess according to a June 28, 2016 VAG news release,

Through her use of a particular body type or character, Kher’s sculptures make reference to iconic figures from mythology and history. And all the while the benevolent slept (2008) references Chinnamasta, an Indian goddess Kali who, in traditional iconography, holds her own detached head in her hand, blood gushing from her neck, while she stands on top of a copulating couple. Through her self-sacrifice she awakens the awareness of spiritual energy while at the same time incarnating sexual energy

Kher’s ‘Chinnamasta’ stands on a tree stump and has branches growing out of her neck rather than pouring blood. For someone from a province where forestry is a major industry, this piece lends itself to a political/ecological reading, as well as, as a reading of the feminine which is so much a part of Kher’s work. The skull does not seem wholly human.

The artist does not explain the piece beyond noting its origins in traditional Indian iconography. Here’s more about Chinnamasta from its Wikipedia entry (Note: Links have been removed),

Chhinnamasta (Sanskrit: छिन्नमस्ता, Chinnamastā, “She whose head is severed”), often spelled Chinnamasta, and also called Chhinnamastika and Prachanda Chandika, is one of the Mahavidyas, ten Tantric goddesses and a ferocious aspect of Devi, the Hindu Divine Mother. Chhinnamasta can be easily identified by her unusual iconography. The nude self-decapitated goddess, usually standing or seated on a copulating couple, holds her own severed head in one hand, a scimitar in another. Three jets of blood spurt out of her bleeding neck and are drunk by her severed head and two attendants.

Chhinnamasta is a goddess of contradictions. She symbolises both aspects of Devi: a life-giver and a life-taker. She is considered both a symbol of sexual self-control and an embodiment of sexual energy, depending upon interpretation. She represents death, temporality, and destruction as well as life, immortality, and recreation. The goddess conveys spiritual self-realization and the awakening of the kundalini – spiritual energy. The legends of Chhinnamasta emphasise her self-sacrifice – sometimes coupled with a maternal element – sexual dominance, and self-destructive fury.

In reading more about Chinnamasta, the piece grows in intrigue.

Moving on to the ‘fabric pieces, there’s this from the June 28, 2016 VAG news release,

Bharti Kher’s furniture and sari sculptures speaks to socially constructed ideals of femininity and domesticity. Any utilitarian function has been rendered useless, and instead these pieces of furniture become proxies for a body. The sari-draped chairs in Absence (2011) introduces the possibility of domestic narratives filled with mothers, daughters, wives and lovers, whose bodiless garments preserve a former presence. In The day they met (2011), vibrant and richly patterned saris are decisively placed on a staircase, effectively embalming the ritual act of sari unwrapping.

Bharti Kerr, Absence, 2011, sari, resin, wooden chair. Private Collection Courtesy of the Artist and Galerie Peerotin, Photo Guillaume Ziccarelli

Bharti Kher, Absence, 2011, sari, resin, wooden chair. Private Collection Courtesy of the Artist and Galerie Peerotin, Photo Guillaume Ziccarelli

The saris appear on various pieces of furniture and sometimes appear as twisted, long rolls that could be said to resemble snakes. The fabrics are beautiful and they call to mind Lohan’s work and also ‘women’s work’.

Now for the bindis. For anyone not familiar with bindis, there’s this from its Wikipedia entry (Note: Links have been removed),

A bindi (Hindi: बिंदी, from Sanskrit bindu, meaning “point, drop, dot or small particle”) is a red dot worn on the center of the forehead, commonly by Hindu and Jain women. The word Bindu dates back to the hymn of creation known as Nasadiya Sukta in Rig Veda.[1] Bindu is considered the point at which creation begins and may become unity. It is also described as “the sacred symbol of the cosmos in its unmanifested state”.[2][3] Bindi is a bright dot of red colour applied in the center of the forehead close to the eyebrow worn in Indian Subcontinent (particularly amongst Hindus in India, Pakistan, Bangladesh, Nepal, and Sri Lanka)[2] and Southeast Asia among Bali and Javanese Hindus. Bindi in Hinduism, Buddhism, and Jainism is associated with Ajna Chakra and Bindu[4] is known as the third eye chakra. Bindu is the point or dot around which the mandala is created, representing the universe.[3][5] Bindi has historical and cultural presence in the region of Greater India.[6][7]

The first piece you see in the Matter show is Virus VII (2016). It is comprised of bindis, blues ones rather than the traditional red, painstakingly overlapped in a spiral that extends several feet in height and width and affixed to the wall. The piece is accompanied by a wooden box with a plaque and containing sheets of blue bindis,

Matter exhibition at Vancouver Art Gallery, July 9 - Oct. 10, 2016 Bharti Kher, Virus VII, 2016, Photo: Megan Hill-Carol Vancouver Art Gallery

Matter exhibition at Vancouver Art Gallery, July 9 – Oct. 10, 2016 Bharti Kher, Virus VII, 2016, Photo: Megan Hill-Carol Vancouver Art Gallery

It is a stunning piece that almost seems to vibrate and is a fitting and sensual entry to the show.

For an alternative experience of the Kher show, there’s Robin Laurence’s July 6, 2016 preview titled: Bharti Kher’s hybrid vision merges humans with animals to address politics, sociology, and love for the Georgia Straight. Unexpectedly (for me), the first piece she sees is the heart,

The first artwork visitors will see when they enter Bharti Kher’s thoughtful and provocative exhibition at the Vancouver Art Gallery is a life-size sculpture of the heart of a blue sperm whale. The largest creature that now exists on our planet, the blue whale possesses a heart that is also the biggest in the world—the size, the artist says, of a small car. Kher’s realistic, cast-resin depiction of the organ’s two massive chambers, enormous aorta, and branching blood vessels is a work of weird grandeur.

To some, it might suggest an environmental message, a monument to a creature slaughtered by the hundreds of thousands in the 19th century and threatened in our own age by pollution and rising ocean temperatures. The artist, however, says the work is about the nature of love, and its title, An Absence of Assignable Cause, evokes the irrationality of that most vaunted and lamented emotion.

“More things have been written about love and all the ways around it,” she says. “I thought it would be interesting to talk about it using an animal as a metaphor.”

Picasso: The Artist and His Muses

Never having been a big fan of Pablo Picasso’s, I wouldn’t have made a special effort to see the VAG’s Picasso: The Artist and His Muses exhibition (June 11 – Oct. 2, 2016) but since I was already on premise for the Kher exhibit, it seemed to foolish to pass up the opportunity.

The show focuses on six women, his relationship with them, and how his art was affected by those relationships.

His most widely known images of women are those with the distorted features and extra or missing eyes and ears such as this,

Pablo Picasso Bust of a Woman (Dora Maar), 1938 oil on canvas Hirshhorn Museum and Sculpture Garden, Gift of Joseph H. Hirshhorn, 1966 © Picasso Estate/SODRAC (2016) Photo: Cathy Carver

Pablo Picasso
Bust of a Woman (Dora Maar), 1938
oil on canvas
Hirshhorn Museum and Sculpture Garden, Gift of Joseph H. Hirshhorn, 1966
© Picasso Estate/SODRAC (2016)
Photo: Cathy Carver

These images have always left me cold. Seeing them in real life didn’t make that big a difference although I hadn’t fully appreciated their vibrancy having previously seen reproductions only. I did say I’m not a fan and that is especially true of the images of women most often seen. The surprise in this show, are the naturalistic studies where one can appreciate his extraordinary technique even if one is inclined to shun his distorted women.

I mention this show only because its subject, women, has been the direct and indirect focus of this commentary. For an even more jaundiced view of this show, you can read Robin Laurence’s June 10, 2016 preview of the VAG exhibition,

Muse is such a curiously antiquated term. Divine woman breathing inspiration into the mind of the creative male? Really? Still, Picasso: The Artist and His Muses has a more visitor-friendly sound to it than “Picasso and the Women He Fucked and Painted”. Not that visitor-friendly titles are a necessity where Pablo Picasso exhibitions are concerned.

The mere name of the man—easily the most famous artist of the 20th century, whose personal myth is built as much on his prodigious womanizing as on his protean art-making—guarantees attendance. Irrespective of what’s on view. Irrespective, too, of the challenges his work might pose to contemporary critics.

Organized with Art Centre Basel in Switzerland, the Vancouver Art Gallery’s big-draw summer show includes some 60 paintings, drawings, sculptures, and prints ranging across the years 1905 to 1971. Borrowed from an international array of public and private collections, it is the most ambitious exhibition of Picasso works ever shown in Western Canada.

I recommend reading both of Laurence’s pieces before going to the exhibit.

Final words

It seems when it comes to contemporary art, beauty is transgressive. The distortions with which Picasso experimented seem to have taken root and, like bamboo, taken over. So, an artist risks being shunned if his/her works are intrinsically beautiful (Lohan). Alternatively, an artist can include it by stealth (Kher) so viewers do not experience it as the primary impression.

All of these artists’ exhibitions have in one fashion or another focused on women. Lohan’s material of choice, porcelain, referenced women’s work indirectly and resonated in a fascinating way with Kher’s teacup bearing goddess. While Lohan and Kher are interested in women’s experiences (dressing/undressing and ornamentation (Kher), women’s roles in society (Lohan), meanwhile, Picasso seems to have considered women as raw material for his work.

Could your photo be a solar cell?

Scientists at Aalto University (Finland) have found a way to print photographs that produce energy (like a solar cell does) according to a July 25, 2016 news item on Nanowerk,

Solar cells have been manufactured already for a long from inexpensive materials with different printing techniques. Especially organic solar cells and dye-sensitized solar cells are suitable for printing.

“We wanted to take the idea of printed solar cells even further, and see if their materials could be inkjet-printed as pictures and text like traditional printing inks,” tells University Lecturer Janne Halme.

A semi-transparent dye-sensitized solar cell with inkjet-printed photovoltaic portraits of the Aalto researchers (Ghufran Hashmi, Merve Özkan, Janne Halme) and a QR code that links to the original research paper. Courtesy: Aalto University

A semi-transparent dye-sensitized solar cell with inkjet-printed photovoltaic portraits of the Aalto researchers (Ghufran Hashmi, Merve Özkan, Janne Halme) and a QR code that links to the original research paper. Courtesy: Aalto University

A July 26, 2016 Aalto University press release, which originated the news item, describes the innovation in more detail,

When light is absorbed in an ordinary ink, it generates heat. A photovoltaic ink, however, coverts part of that energy to electricity. The darker the color, the more electricity is produced, because the human eye is most sensitive to that part of the solar radiation spectrum which has highest energy density. The most efficient solar cell is therefore pitch-black.

The idea of a colorful, patterned solar cell is to combine also other properties that take advantage of light on the same surface, such as visual information and graphics.

– For example, installed on a sufficiently low-power electrical device, this kind of solar cell could be part of its visual design, and at the same time produce energy for its needs, ponders Halme.

With inkjet printing, the photovoltaic dye could be printed to a shape determined by a selected image file, and the darkness and transparency of the different parts of the image could be adjusted accurately.

– The inkjet-dyed solar cells were as efficient and durable as the corresponding solar cells prepared in a traditional way. They endured more than one thousand hours of continuous light and heat stress without any signs of performance degradation, says Postdoctoral Researcher Ghufran Hashmi.

The dye and electrolyte that turned out to be best were obtained from the research group in the Swiss École Polytechnique Fédérale de Lausanne, where Dr. Hashmi worked as a visiting researcher.

– The most challenging thing was to find suitable solvent for the dye and the right jetting parameters that gave precise and uniform print quality, tells Doctoral Candidate Merve Özkan.

This puts solar cells (pun alert) in a whole new light.

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

Dye-sensitized solar cells with inkjet-printed dyes by Syed Ghufran Hashmi, Merve Özkan, Janne Halme, Shaik Mohammed Zakeeruddin, Jouni Paltakari, Michael Grätzel, and Peter D. Lund. Energy Environ. Sci., 2016,9, 2453-2462 DOI: 10.1039/C6EE00826G First published online 09 Jun 2016

This paper is behind a paywall.

Osmotic power: electricity generated with water, salt and a 3-atoms-thick membrane


EPFL researchers have developed a system that generates electricity from osmosis with unparalleled efficiency. Their work, featured in “Nature”, uses seawater, fresh water, and a new type of membrane just three atoms thick.

A July 13, 2016 news item on Nanowerk highlights  research on osmotic power at École polytechnique fédérale de Lausanne (EPFL; Switzerland),

Proponents of clean energy will soon have a new source to add to their existing array of solar, wind, and hydropower: osmotic power. Or more specifically, energy generated by a natural phenomenon occurring when fresh water comes into contact with seawater through a membrane.

Researchers at EPFL’s Laboratory of Nanoscale Biology have developed an osmotic power generation system that delivers never-before-seen yields. Their innovation lies in a three atoms thick membrane used to separate the two fluids. …

A July 14, 2016 EPFL press release (also on EurekAlert but published July 13, 2016), which originated the news item, describes the research,

The concept is fairly simple. A semipermeable membrane separates two fluids with different salt concentrations. Salt ions travel through the membrane until the salt concentrations in the two fluids reach equilibrium. That phenomenon is precisely osmosis.

If the system is used with seawater and fresh water, salt ions in the seawater pass through the membrane into the fresh water until both fluids have the same salt concentration. And since an ion is simply an atom with an electrical charge, the movement of the salt ions can be harnessed to generate electricity.

A 3 atoms thick, selective membrane that does the job

EPFL’s system consists of two liquid-filled compartments separated by a thin membrane made of molybdenum disulfide. The membrane has a tiny hole, or nanopore, through which seawater ions pass into the fresh water until the two fluids’ salt concentrations are equal. As the ions pass through the nanopore, their electrons are transferred to an electrode – which is what is used to generate an electric current.

Thanks to its properties the membrane allows positively-charged ions to pass through, while pushing away most of the negatively-charged ones. That creates voltage between the two liquids as one builds up a positive charge and the other a negative charge. This voltage is what causes the current generated by the transfer of ions to flow.

“We had to first fabricate and then investigate the optimal size of the nanopore. If it’s too big, negative ions can pass through and the resulting voltage would be too low. If it’s too small, not enough ions can pass through and the current would be too weak,” said Jiandong Feng, lead author of the research.

What sets EPFL’s system apart is its membrane. In these types of systems, the current increases with a thinner membrane. And EPFL’s membrane is just a few atoms thick. The material it is made of – molybdenum disulfide – is ideal for generating an osmotic current. “This is the first time a two-dimensional material has been used for this type of application,” said Aleksandra Radenovic, head of the laboratory of Nanoscale Biology

Powering 50’000 energy-saving light bulbs with 1m2 membrane

The potential of the new system is huge. According to their calculations, a 1m2 membrane with 30% of its surface covered by nanopores should be able to produce 1MW of electricity – or enough to power 50,000 standard energy-saving light bulbs. And since molybdenum disulfide (MoS2) is easily found in nature or can be grown by chemical vapor deposition, the system could feasibly be ramped up for large-scale power generation. The major challenge in scaling-up this process is finding out how to make relatively uniform pores.

Until now, researchers have worked on a membrane with a single nanopore, in order to understand precisely what was going on. ” From an engineering perspective, single nanopore system is ideal to further our fundamental understanding of 8=-based processes and provide useful information for industry-level commercialization”, said Jiandong Feng.

The researchers were able to run a nanotransistor from the current generated by a single nanopore and thus demonstrated a self-powered nanosystem. Low-power single-layer MoS2 transistors were fabricated in collaboration with Andras Kis’ team at at EPFL, while molecular dynamics simulations were performed by collaborators at University of Illinois at Urbana–Champaign

Harnessing the potential of estuaries

EPFL’s research is part of a growing trend. For the past several years, scientists around the world have been developing systems that leverage osmotic power to create electricity. Pilot projects have sprung up in places such as Norway, the Netherlands, Japan, and the United States to generate energy at estuaries, where rivers flow into the sea. For now, the membranes used in most systems are organic and fragile, and deliver low yields. Some systems use the movement of water, rather than ions, to power turbines that in turn produce electricity.

Once the systems become more robust, osmotic power could play a major role in the generation of renewable energy. While solar panels require adequate sunlight and wind turbines adequate wind, osmotic energy can be produced just about any time of day or night – provided there’s an estuary nearby.

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

Single-layer MoS2 nanopores as nanopower generators by Jiandong Feng, Michael Graf, Ke Liu, Dmitry Ovchinnikov, Dumitru Dumcenco, Mohammad Heiranian, Vishal Nandigana, Narayana R. Aluru, Andras Kis, & Aleksandra Radenovic. Nature (2016)  doi:10.1038/nature18593 Published online 13 July 2016

This paper is behind a paywall.

Deep learning and some history from the Swiss National Science Foundation (SNSF)

A June 27, 2016 news item on phys.org provides a measured analysis of deep learning and its current state of development (from a Swiss perspective),

In March 2016, the world Go champion Lee Sedol lost 1-4 against the artificial intelligence AlphaGo. For many, this was yet another defeat for humanity at the hands of the machines. Indeed, the success of the AlphaGo software was forged in an area of artificial intelligence that has seen huge progress over the last decade. Deep learning, as it’s called, uses artificial neural networks to process algorithmic calculations. This software architecture therefore mimics biological neural networks.

Much of the progress in deep learning is thanks to the work of Jürgen Schmidhuber, director of the IDSIA (Istituto Dalle Molle di Studi sull’Intelligenza Artificiale) which is located in the suburbs of Lugano. The IDSIA doctoral student Shane Legg and a group of former colleagues went on to found DeepMind, the startup acquired by Google in early 2014 for USD 500 million. The DeepMind algorithms eventually wound up in AlphaGo.

“Schmidhuber is one of the best at deep learning,” says Boi Faltings of the EPFL Artificial Intelligence Lab. “He never let go of the need to keep working at it.” According to Stéphane Marchand-Maillet of the University of Geneva computing department, “he’s been in the race since the very beginning.”

A June 27, 2016 SNSF news release (first published as a story in Horizons no. 109 June 2016) by Fabien Goubet, which originated the news item, goes on to provide a brief history,

The real strength of deep learning is structural recognition, and winning at Go is just an illustration of this, albeit a rather resounding one. Elsewhere, and for some years now, we have seen it applied to an entire spectrum of areas, such as visual and vocal recognition, online translation tools and smartphone personal assistants. One underlying principle of machine learning is that algorithms must first be trained using copious examples. Naturally, this has been helped by the deluge of user-generated content spawned by smartphones and web 2.0, stretching from Facebook photo comments to official translations published on the Internet. By feeding a machine thousands of accurately tagged images of cats, for example, it learns first to recognise those cats and later any image of a cat, including those it hasn’t been fed.

Deep learning isn’t new; it just needed modern computers to come of age. As far back as the early 1950s, biologists tried to lay out formal principles to explain the working of the brain’s cells. In 1956, the psychologist Frank Rosenblatt of the New York State Aeronautical Laboratory published a numerical model based on these concepts, thereby creating the very first artificial neural network. Once integrated into a calculator, it learned to recognise rudimentary images.

“This network only contained eight neurones organised in a single layer. It could only recognise simple characters”, says Claude Touzet of the Adaptive and Integrative Neuroscience Laboratory of Aix-Marseille University. “It wasn’t until 1985 that we saw the second generation of artificial neural networks featuring multiple layers and much greater performance”. This breakthrough was made simultaneously by three researchers: Yann LeCun in Paris, Geoffrey Hinton in Toronto and Terrence Sejnowski in Baltimore.

Byte-size learning

In multilayer networks, each layer learns to recognise the precise visual characteristics of a shape. The deeper the layer, the more abstract the characteristics. With cat photos, the first layer analyses pixel colour, and the following layer recognises the general form of the cat. This structural design can support calculations being made upon thousands of layers, and it was this aspect of the architecture that gave rise to the name ‘deep learning’.

Marchand-Maillet explains: “Each artificial neurone is assigned an input value, which it computes using a mathematical function, only firing if the output exceeds a pre-defined threshold”. In this way, it reproduces the behaviour of real neurones, which only fire and transmit information when the input signal (the potential difference across the entire neural circuit) reaches a certain level. In the artificial model, the results of a single layer are weighted, added up and then sent as the input signal to the following layer, which processes that input using different functions, and so on and so forth.

For example, if a system is trained with great quantities of photos of apples and watermelons, it will progressively learn to distinguish them on the basis of diameter, says Marchand-Maillet. If it cannot decide (e.g., when processing a picture of a tiny watermelon), the subsequent layers take over by analysing the colours or textures of the fruit in the photo, and so on. In this way, every step in the process further refines the assessment.

Video games to the rescue

For decades, the frontier of computing held back more complex applications, even at the cutting edge. Industry walked away, and deep learning only survived thanks to the video games sector, which eventually began producing graphics chips, or GPUs, with an unprecedented power at accessible prices: up to 6 teraflops (i.e., 6 trillion calculations per second) for a few hundred dollars. “There’s no doubt that it was this calculating power that laid the ground for the quantum leap in deep learning”, says Touzet. GPUs are also very good at parallel calculations, a useful function for executing the innumerable simultaneous operations required by neural networks.
Although image analysis is getting great results, things are more complicated for sequential data objects such as natural spoken language and video footage. This has formed part of Schmidhuber’s work since 1989, and his response has been to develop recurrent neural networks in which neurones communicate with each other in loops, feeding processed data back into the initial layers.

Such sequential data analysis is highly dependent on context and precursory data. In Lugano, networks have been instructed to memorise the order of a chain of events. Long Short Term Memory (LSTM) networks can distinguish ‘boat’ from ‘float’ by recalling the sound that preceded ‘oat’ (i.e., either ‘b’ or ‘fl’). “Recurrent neural networks are more powerful than other approaches such as the Hidden Markov models”, says Schmidhuber, who also notes that Google Voice integrated LSTMs in 2015. “With looped networks, the number of layers is potentially infinite”, says Faltings [?].

For Schmidhuber, deep learning is just one aspect of artificial intelligence; the real thing will lead to “the most important change in the history of our civilisation”. But Marchand-Maillet sees deep learning as “a bit of hype, leading us to believe that artificial intelligence can learn anything provided there’s data. But it’s still an open question as to whether deep learning can really be applied to every last domain”.

It’s nice to get an historical perspective and eye-opening to realize that scientists have been working on these concepts since the 1950s.

Cleaning up nuclear waste gases with nanotechnology-enabled materials

Swiss and US scientists have developed a nanoporous crystal that could be used to clean up nuclear waste gases according to a June 13, 2016 news item on Nanowerk (Note: A link has been removed),

An international team of scientists at EPFL [École polytechnique fédérale de Lausanne in Switzerland] and the US have discovered a material that can clear out radioactive waste from nuclear plants more efficiently, cheaply, and safely than current methods.

Nuclear energy is one of the cheapest alternatives to carbon-based fossil fuels. But nuclear-fuel reprocessing plants generate waste gas that is currently too expensive and dangerous to deal with. Scanning hundreds of thousands of materials, scientists led by EPFL and their US colleagues have now discovered a material that can absorb nuclear waste gases much more efficiently, cheaply and safely. The work is published in Nature Communications (“Metal–organic framework with optimally selective xenon adsorption and separation”).

A June 14, 2016 EPFL press release (also on EurekAlert), which originated the news item, explains further,

Nuclear-fuel reprocessing plants generate volatile radionuclides such as xenon and krypton, which escape in the so-called “off-gas” of these facilities – the gases emitted as byproducts of the chemical process. Current ways of capturing and clearing out these gases involve distillation at very low temperatures, which is expensive in both terms of energy and capital costs, and poses a risk of explosion.

Scientists led by Berend Smit’s lab at EPFL (Sion) and colleagues in the US, have now identified a material that can be used as an efficient, cheaper, and safer alternative to separate xenon and krypton – and at room temperature. The material, abbreviated as SBMOF-1, is a nanoporous crystal and belongs a class of materials that are currently used to clear out CO2 emissions and other dangerous pollutants. These materials are also very versatile, and scientists can tweak them to self-assemble into ordered, pre-determined crystal structures. In this way, they can synthesize millions of tailor-made materials that can be optimized for gas storage separation, catalysis, chemical sensing and optics.

The scientists carried out high-throughput screening of large material databases of over 125,000 candidates. To do this, they used molecular simulations to find structures that can separate xenon and krypton, and under conditions that match those involved in reprocessing nuclear waste.

Because xenon has a much shorter half-life than krypton – a month versus a decade – the scientists had to find a material that would be selective for both but would capture them separately. As xenon is used in commercial lighting, propulsion, imaging, anesthesia and insulation, it can also be sold back into the chemical market to offset costs.

The scientists identified and confirmed that SBMOF-1 shows remarkable xenon capturing capacity and xenon/krypton selectivity under nuclear-plant conditions and at room temperature.

The US partners have also made an announcement with this June 13, 2016 Pacific Northwest National Laboratory (PNNL) news release (also on EurekAlert), Note: It is a little repetitive but there’s good additional information,

Researchers are investigating a new material that might help in nuclear fuel recycling and waste reduction by capturing certain gases released during reprocessing. Conventional technologies to remove these radioactive gases operate at extremely low, energy-intensive temperatures. By working at ambient temperature, the new material has the potential to save energy, make reprocessing cleaner and less expensive. The reclaimed materials can also be reused commercially.

Appearing in Nature Communications, the work is a collaboration between experimentalists and computer modelers exploring the characteristics of materials known as metal-organic frameworks.

“This is a great example of computer-inspired material discovery,” said materials scientist Praveen Thallapally of the Department of Energy’s Pacific Northwest National Laboratory. “Usually the experimental results are more realistic than computational ones. This time, the computer modeling showed us something the experiments weren’t telling us.”

Waste avoidance

Recycling nuclear fuel can reuse uranium and plutonium — the majority of the used fuel — that would otherwise be destined for waste. Researchers are exploring technologies that enable safe, efficient, and reliable recycling of nuclear fuel for use in the future.

A multi-institutional, international collaboration is studying materials to replace costly, inefficient recycling steps. One important step is collecting radioactive gases xenon and krypton, which arise during reprocessing. To capture xenon and krypton, conventional technologies use cryogenic methods in which entire gas streams are brought to a temperature far below where water freezes — such methods are energy intensive and expensive.

Thallapally, working with Maciej Haranczyk and Berend Smit of Lawrence Berkeley National Laboratory [LBNL] and others, has been studying materials called metal-organic frameworks, also known as MOFs, that could potentially trap xenon and krypton without having to use cryogenics.

These materials have tiny pores inside, so small that often only a single molecule can fit inside each pore. When one gas species has a higher affinity for the pore walls than other gas species, metal-organic frameworks can be used to separate gaseous mixtures by selectively adsorbing.

To find the best MOF for xenon and krypton separation, computational chemists led by Haranczyk and Smit screened 125,000 possible MOFs for their ability to trap the gases. Although these gases can come in radioactive varieties, they are part of a group of chemically inert elements called “noble gases.” The team used computing resources at NERSC, the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility at LBNL.

“Identifying the optimal material for a given process, out of thousands of possible structures, is a challenge due to the sheer number of materials. Given that the characterization of each material can take up to a few hours of simulations, the entire screening process may fill a supercomputer for weeks,” said Haranczyk. “Instead, we developed an approach to assess the performance of materials based on their easily computable characteristics. In this case, seven different characteristics were necessary for predicting how the materials behaved, and our team’s grad student Cory Simon’s application of machine learning techniques greatly sped up the material discovery process by eliminating those that didn’t meet the criteria.”

The team’s models identified the MOF that trapped xenon most selectively and had a pore size close to the size of a xenon atom — SBMOF-1, which they then tested in the lab at PNNL.

After optimizing the preparation of SBMOF-1, Thallapally and his team at PNNL tested the material by running a mixture of gases through it — including a non-radioactive form of xenon and krypton — and measuring what came out the other end. Oxygen, helium, nitrogen, krypton, and carbon dioxide all beat xenon out. This indicated that xenon becomes trapped within SBMOF-1’s pores until the gas saturates the material.

Other tests also showed that in the absence of xenon, SBMOF-1 captures krypton. During actual separations, then, operators would pass the gas streams through SBMOF-1 twice to capture both gases.

The team also tested SBMOF-1’s ability to hang onto xenon in conditions of high humidity. Humidity interferes with cryogenics, and gases must be dehydrated before putting them through the ultra-cold method, another time-consuming expense. SBMOF-1, however, performed quite admirably, retaining more than 85 percent of the amount of xenon in high humidity as it did in dry conditions.

The final step in collecting xenon or krypton gas would be to put the MOF material under a vacuum, which sucks the gas out of the molecular cages for safe storage. A last laboratory test examined how stable the material was by repeatedly filling it up with xenon gas and then vacuuming out the xenon. After 10 cycles of this, SBMOF-1 collected just as much xenon as the first cycle, indicating a high degree of stability for long-term use.

Thallapally attributes this stability to the manner in which SBMOF-1 interacts with xenon. Rather than chemical reactions between the molecular cages and the gases, the relationship is purely physical. The material can last a lot longer without constantly going through chemical reactions, he said.

A model finding

Although the researchers showed that SBMOF-1 is a good candidate for nuclear fuel reprocessing, getting these results wasn’t smooth sailing. In the lab, the researchers had followed a previously worked out protocol from Stony Brook University to prepare SBMOF-1. Part of that protocol requires them to “activate” SBMOF-1 by heating it up to 300 degrees Celsius, three times the temperature of boiling water.

Activation cleans out material left in the pores from MOF synthesis. Laboratory tests of the activated SBMOF-1, however, showed the material didn’t behave as well as it should, based on the computer modeling results.

The researchers at PNNL repeated the lab experiments. This time, however, they activated SBMOF-1 at a lower temperature, 100 degrees Celsius, or the actual temperature of boiling water. Subjecting the material to the same lab tests, the researchers found SBMOF-1 behaving as expected, and better than at the higher activation temperature.

But why? To figure out where the discrepancy came from, the researchers modeled what happened to SBMOF-1 at 300 degrees Celsius. Unexpectedly, the pores squeezed in on themselves.

“When we heated the crystal that high, atoms within the pore tilted and partially blocked the pores,” said Thallapally. “The xenon doesn’t fit.”

Armed with these new computational and experimental insights, the researchers can explore SBMOF-1 and other MOFs further for nuclear fuel recycling. These MOFs might also be able to capture other noble gases such as radon, a gas known to pool in some basements.

Researchers hailed from several other institutions as well as those listed earlier, including University of California, Berkeley, Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland, Brookhaven National Laboratory, and IMDEA Materials Institute in Spain. This work was supported by the [US] Department of Energy Offices of Nuclear Energy and Science.

Here’s an image the researchers have provided to illustrate their work,

Caption: The crystal structure of SBMOF-1 (green = Ca, yellow = S, red = O, gray = C, white = H). The light blue surface is a visualization of the one-dimensional channel that SBMOF-1 creates for the gas molecules to move through. The darker blue surface illustrates where a Xe atom sits in the pores of SBMOF-1 when it adsorbs. Credit: Berend Smit/EPFL/University of California Berkley

Caption: The crystal structure of SBMOF-1 (green = Ca, yellow = S, red = O, gray = C, white = H). The light blue surface is a visualization of the one-dimensional channel that SBMOF-1 creates for the gas molecules to move through. The darker blue surface illustrates where a Xe atom sits in the pores of SBMOF-1 when it adsorbs. Credit: Berend Smit/EPFL/University of California Berkley

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

Metal–organic framework with optimally selective xenon adsorption and separation by Debasis Banerjee, Cory M. Simon, Anna M. Plonka, Radha K. Motkuri, Jian Liu, Xianyin Chen, Berend Smit, John B. Parise, Maciej Haranczyk, & Praveen K. Thallapally. Nature Communications 7, Article number: ncomms11831  doi:10.1038/ncomms11831 Published 13 June 2016

This paper is open access.

Final comment, this is the second time in the last month I’ve stumbled across more positive approaches to nuclear energy. The first time was a talk (Why Nuclear Power is Necessary) held in Vancouver, Canada in May 2016 (details here). I’m not trying to suggest anything unduly sinister but it is interesting since most of my adult life nuclear power has been viewed with fear and suspicion.

More from PETA (People for the Ethical Treatment of Animals) about nanomaterials and lungs

Science progress by increments. First, there was this April 27, 2016 post featuring some recent work by the organization, People for the Ethical Treatment of Animals (PETA) focused on nanomaterials and lungs. Now approximately one month later, PETA announces a new paper on the topic according to a May 26, 2016 news item on phys.org,

A scientist from the PETA International Science Consortium Ltd. is the lead author of a review on pulmonary fibrosis that results from inhaling nanomaterials, which has been published in Archives of Toxicology. The coauthors are scientists from Health Canada, West Virginia University, and the University of Fribourg in Switzerland.

A May 26, 2016 PETA news release on EurekAlert, which originated the news item, provides more detail (Note: Links have been removed),

The increasing use of nanomaterials in consumer goods such as paint, building materials, and food products has increased the likelihood of human exposure. Inhalation is one of the most prominent routes by which exposure can occur, and because inhalation of nanomaterials may be linked to lung problems such as pulmonary fibrosis, testing is conducted to assess the safety of these materials.

The review is one part of the proceedings of a 2015 workshop [mentioned in my Sept. 3, 2015 posting] organized by the PETA International Science Consortium, at which scientists discussed recommendations for designing an in vitro approach to assessing the toxicity of nanomaterials in the human lung. The workshop also produced another report that was recently published in Archives of Toxicology (Clippinger et al. 2016) and a review published in Particle and Fibre Toxicology (Polk et al. 2016) [mentioned in my April 27, 2016 posting] on exposing nanomaterials to cells grown in vitro.

The expert recommendations proposed at the workshop are currently being used to develop an in vitro system to predict the development of lung fibrosis in humans, which is being funded by the Science Consortium.

“International experts who took part in last year’s workshop have advanced the understanding and application of non-animal methods of studying nanomaterial effects in the lung,” says Dr. Monita Sharma, nanotoxicology specialist at the Consortium and lead author of the review in Archives of Toxicology. “Good science is leading the way toward more humane testing of nanomaterials, which, in turn, will lead to better protection of human health.”

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

Predicting pulmonary fibrosis in humans after exposure to multi-walled carbon nanotubes (MWCNTs) by Monita Sharma, Jake Nikota, Sabina Halappanavar, Vincent Castranova, Barbara Rothen-Rutishauser, Amy J. Clippinger. Archives of Toxicology pp 1-18 DOI: 10.1007/s00204-016-1742-7 First online: 23 May 2016

This paper is behind a paywall.

Scented video games: a nanotechnology project in Europe

Ten years ago when I was working on a master’s degree (creative writing and new media), I was part of a group presentation on multimedia and to prepare started a conversation about scent as part of a multimedia experience. Our group leader was somewhat outraged. He’d led international multimedia projects and as far as he was concerned the ‘scent’ discussion was a waste of time when we were trying to prepare a major presentation.

He was right and wrong. I think you’re supposed to have these discussions when you’re learning and exploring ideas but, in 2006, there wasn’t much work of that type to discuss. It seems things may be changing according to a May 21, 2016 news item on Nanowerk (Note: A link has been removed),

Controlled odour emission could transform video games and television viewing experiences and benefit industries such as pest control and medicine [emphasis mine]. The NANOSMELL project aims to switch smells on and off by tagging artificial odorants with nanoparticles exposed to electromagnetic field.

I wonder if the medicinal possibilities include nanotechnology-enabled aroma therapy?

Getting back to the news, a May 10, 2016 European Commission press release, which originated the news item, expands on the theme,

The ‘smellyvision’ – a TV that offers olfactory as well as visual stimulation – has been a science fiction staple for years. However, realising this concept has proved difficult given the sheer complexity of how smell works and the technical challenges of emitting odours on demand.

NANOSMELL will specifically address these two challenges by developing artificial smells that can be switched on and off remotely. This would be achieved by tagging specific DNA-based artificial odorants – chemical compounds that give off smells – with nanoparticles that respond to external electromagnetic fields.

With the ability to remotely control these artificial odours, the project team would then be able to examine exactly how olfactory receptors respond. Sensory imaging to investigate the patterns of neural activity and behavioural tests will be carried out in animals.

The project would next apply artificial odorants to the human olfactory system and measure perceptions by switching artificial smells on and off. Researchers will also assess whether artificial odorants have a role to play in wound healing by placing olfactory receptors in skin.

The researchers aim to develop controllable odour-emitting components that will further understanding of smell and open the door to novel odour-emitting applications in fields ranging from entertainment to medicine.

Project details

  • Project acronym: NanoSmell
  • Participants: Israel (Coordinator), Spain, Germany, Switzerland
  • Project Reference N° 662629
  • Total cost: € 3 979 069
  • EU contribution: € 3 979 069
  • Duration:September 2015 – September 2019

You can find more information on the European Commission’s NANOSMELL project page.

Frankenstein and Switzerland in 2016

The Frankenstein Bicentennial celebration is in process as various events and projects are now being launched. In a Nov. 12, 2015 posting I made mention of the Frankenstein Bicentennial Project 1818-2018 at Arizona State University (ASU; scroll down about 15% of the way),

… the Transmedia Museum (Frankenstein Bicentennial Project 1818-2018).  This project is being hosted by Arizona State University. From the project homepage,

No work of literature has done more to shape the way people imagine science and its moral consequences than Frankenstein; or The Modern Prometheus, Mary Shelley’s enduring tale of creation and responsibility. The novel’s themes and tropes—such as the complex dynamic between creator and creation—continue to resonate with contemporary audiences. Frankenstein continues to influence the way we confront emerging technologies, conceptualize the process of scientific research, imagine the motivations and ethical struggles of scientists, and weigh the benefits of innovation with its unforeseen pitfalls.

The Frankenstein Bicentennial Project will infuse science and engineering endeavors with considerations of ethics. It will use the power of storytelling and art to shape processes of innovation and empower public appraisal of techno-scientific research and creation. It will offer humanists and artists a new set of concerns around research, public policy, and the ramifications of exploration and invention. And it will inspire new scientific and technological advances inspired by Shelley’s exploration of our inspiring and terrifying ability to bring new life into the world. Frankenstein represents a landmark fusion of science, ethics, and literary expression.

The bicentennial provides an opportunity for vivid reflection on how science is culturally framed and understood by the public, as well as our ethical limitations and responsibility for nurturing the products of our creativity. It is also a moment to unveil new scientific and technological marvels, especially in the areas of synthetic biology and artificial intelligence. Engaging with Frankenstein allows scholars and educators, artists and writers, and the public at large to consider the history of scientific invention, reflect on contemporary research, and question the future of our technological society. Acting as a network hub for the bicentennial celebration, ASU will encourage and coordinate collaboration across institutions and among diverse groups worldwide.

2016 Frankenstein events

Now, there’s an exhibition in Switzerland where Frankenstein was ‘born’ according to a May 12, 2016 news item on phys.org,

Frankenstein, the story of a scientist who brings to life a cadaver and causes his own downfall, has for two centuries given voice to anxiety surrounding the unrelenting advance of science.

To mark the 200 years since England’s Mary Shelley first imagined the ultimate horror story during a visit to a frigid, rain-drenched Switzerland, an exhibit opens in Geneva Friday called “Frankenstein, Creation of Darkness”.

In the dimly-lit, expansive basement at the Martin Bodmer Foundation, a long row of glass cases holds 15 hand-written, yellowed pages from a notebook where Shelley in 1816 wrote the first version of what is considered a masterpiece of romantic literature.

The idea for her “miserable monster” came when at just 18 she and her future husband, English poet Percy Bysshe Shelley, went to a summer home—the Villa Diodati—rented by literary great Lord Byron on the outskirts of Geneva.

The current private owners of the picturesque manor overlooking Lake Geneva will also open their lush gardens to guided tours during the nearby exhibit which runs to October 9 [May 13 – Oct. 9, 2016].

While the spot today is lovely, with pink and purple lilacs spilling from the terraces and gravel walkways winding through rose-covered arches, in the summer of 1816 the atmosphere was more somber.

A massive eruption from the Tambora volcano in Indonesia wreaked havoc with the global climate that year, and a weather report for Geneva in June on display at the exhibit mentions “not a single leaf” had yet appeared on the oak trees.

To pass the time, poet Lord Byron challenged the band of literary bohemians gathered at the villa to each invent a ghost story, resulting in several famous pieces of writing.

English doctor and author John Polidori came up with the idea for “The Vampyre”, which was published three years later and is considered to have pioneered the romantic vampyre genre, including works like Bram Stoker’s “Dracula”.

That book figures among a multitude of first editions at the Geneva exhibit, including three of Mary Shelley’s “Frankenstein, or the Modern Prometheus”—the most famous story to emerge from the competition.

Here’s a description of the exhibit, from the Martin Bodmer Foundation’s Frankenstein webpage,

To celebrate the 200th anniversary of the writing of this historically influential work of literature, the Martin Bodmer Foundation presents a major exhibition on the origins of Frankenstein, the perspectives it opens and the questions it raises.

A best seller since its first publication in 1818, Mary Shelley’s novel continues to demand attention. The questions it raises remain at the heart of literary and philosophical concerns: the ethics of science, climate change, the technologisation of the human body, the unconscious, human otherness, the plight of the homeless and the dispossessed.

The exposition Frankenstein: Creation of Darkness recreates the beginnings of the novel in its first manuscript and printed forms, along with paintings and engravings that evoke the world of 1816. A variety of literary and scientific works are presented as sources of the novel’s ideas. While exploring the novel’s origins, the exhibition also evokes the social and scientific themes of the novel that remain important in our own day.

For what it’s worth, I have come across analyses which suggest science and technology may not have been the primary concern at the time. There are interpretations which suggest issues around childbirth (very dangerous until modern times) and fear of disfigurement and disfigured individuals. What makes Frankenstein and the book so fascinating is how flexible interpretations can be. (For more about Frankenstein and flexibility, read Susan Tyler Hitchcock’s 2009 book, Frankenstein: a cultural history.)

There’s one more upcoming Frankenstein event, from The Frankenstein Bicentennial announcement webpage,

On June 14 and 15, 2016, the Brocher Foundation, Arizona State University, Duke University, and the University of Lausanne will host “Frankenstein’s Shadow,” a symposium in Geneva, Switzerland to commemorate the origin of Frankenstein and assess its influence in different times and cultures, particularly its resonance in debates about public policy governing biotechnology and medicine. These dates place the symposium almost exactly 200 years after Mary Shelley initially conceived the idea for Frankenstein on June 16, 1816, and in almost exactly the same geographical location on the shores of Lake Geneva.

If you’re interested in details such as the programme schedule, there’s this PDF,

Frankenstein¹s_ShadowConference

Enjoy!

Measuring the van der Waals forces between individual atoms for the first time

A May 13, 2016 news item on Nanowerk heralds the first time measuring the van der Waals forces between individual atoms,

Physicists at the Swiss Nanoscience Institute and the University of Basel have succeeded in measuring the very weak van der Waals forces between individual atoms for the first time. To do this, they fixed individual noble gas atoms within a molecular network and determined the interactions with a single xenon atom that they had positioned at the tip of an atomic force microscope. As expected, the forces varied according to the distance between the two atoms; but, in some cases, the forces were several times larger than theoretically calculated.

A May 13, 2016 University of Basel press release (also on EurekAlert), which originated the news item, provides an explanation of van der Waals forces (the most comprehensive I’ve seen) and technical details about how the research was conducted,

Van der Waals forces act between non-polar atoms and molecules. Although they are very weak in comparison to chemical bonds, they are hugely significant in nature. They play an important role in all processes relating to cohesion, adhesion, friction or condensation and are, for example, essential for a gecko’s climbing skills.

Van der Waals interactions arise due to a temporary redistribution of electrons in the atoms and molecules. This results in the occasional formation of dipoles, which in turn induce a redistribution of electrons in closely neighboring molecules. Due to the formation of dipoles, the two molecules experience a mutual attraction, which is referred to as a van der Waals interaction. This only exists temporarily but is repeatedly re-formed. The individual forces are the weakest binding forces that exist in nature, but they add up to reach magnitudes that we can perceive very clearly on the macroscopic scale – as in the example of the gecko.

Fixed within the nano-beaker

To measure the van der Waals forces, scientists in Basel used a low-temperature atomic force microscope with a single xenon atom on the tip. They then fixed the individual argon, krypton and xenon atoms in a molecular network. This network, which is self-organizing under certain experimental conditions, contains so-called nano-beakers of copper atoms in which the noble gas atoms are held in place like a bird egg. Only with this experimental set-up is it possible to measure the tiny forces between microscope tip and noble gas atom, as a pure metal surface would allow the noble gas atoms to slide around.

Compared with theory

The researchers compared the measured forces with calculated values and displayed them graphically. As expected from the theoretical calculations, the measured forces fell dramatically as the distance between the atoms increased. While there was good agreement between measured and calculated curve shapes for all of the noble gases analyzed, the absolute measured forces were larger than had been expected from calculations according to the standard model. Above all for xenon, the measured forces were larger than the calculated values by a factor of up to two.

The scientists are working on the assumption that, even in the noble gases, charge transfer occurs and therefore weak covalent bonds are occasionally formed, which would explain the higher values.

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

Van der Waals interactions and the limits of isolated atom models at interfaces by Shigeki Kawai, Adam S. Foster, Torbjörn Björkman, Sylwia Nowakowska, Jonas Björk, Filippo Federici Canova, Lutz H. Gade, Thomas A. Jung, & Ernst Meyer. Nature Communications 7, Article number: 11559  doi:10.1038/ncomms11559 Published 13 May 2016

This is an open access paper.