Vertical cut through a quadrupole magnet: Black: Field distribution at a fixed vertical distance to the midplane. Magenta: Electron trajectories for various initial coordinates. Credit: C. Rethfeldt/HZB

The design  of  advanced synchrotron radiation sources requires precise  algorithms  for the  simulation of electron trajectories in  complex magnetic fields. However, multi-parameter studies can  be very time consuming. Now, a team from HZB has developed a new algorithm which significantly reduces the computation time.  This approach is now published in the renowned journal “Physical Review Special Topics Accelerator & Beams”.

In a storage ring like BESSY II electrons circulate nearly with the speed of light passing complex magnetic structures. These magnets guide the electron beam and focus it on the ideal orbit. They are comparable to optical lenses which focus the light. To evaluate the stability of the electron trajectories in the magnetic fields, several thousands of turns need to be simulated.  After each revolution the trajectories are slightly different, passing the magnets at slightly different positions. These combined and complex orbit and field calculations require a precise algorithm which could easily result in time consuming simulations.

Already in 2011, a team out of the HZB undulator group and of the HZB-institute of accelerator physics has published  a first paper of a new simulation algorithm, which drastically speeds up the simulation time for trajectories in complex undulator fields. This simulation routine was implemented into the public domain code “elegant“ of the Advanced Photon source / Argonne, and it is available, worldwide.

Now, Malte Titze together with Johannes Bahrdt and Godehard Wüstefeld could extend this method to another important class of  three dimensional magnets: multipoles such as  quadrupoles or sextupoles.

“The paper demonstrates, that this method yields very precise results, particularly within the fast changing fringing fields of the magnets”, Malte Titze explains. He is now engaged in research activities at CERN. “Such simulation methods are of great  interest for future light sources, especially for diffraction limited storage rings, which may include combined function magnets and exhibit significant cross talking between neighboring magnets,” comments Johannes Bahrdt. “This is of clear relevance for a successor of BESSY II”. The scientists describe their methods in the renowned journal of “Physical Review Special Topics Accelerator & Beams."

Cray has signed a $36 million contract to upgrade and expand the Cray XC supercomputers and Cray Sonexion storage system at the European Centre for Medium-Range Weather Forecasts (ECMWF). When the project is completed, the enhanced systems will allow the world-class numerical weather prediction and research center to continue to drive improvements in its highly-complex models to provide more accurate weather forecasts.

In June 2013, Cray announced it was awarded a contract to provide ECMWF with two Cray XC30 supercomputers and a Cray Sonexion storage system. Under the terms of this new contract, Cray will expand and upgrade the supercomputers at ECMWF to Cray XC40 systems, which will include next-generation Intel Xeon processors. ECMWF will also receive additional Cray Sonexion 2000 scale-out Lustre storage, and a 32-node Cray XC40-AC system with the next-generation of the Intel Xeon Phi processor code-named “Knights Landing”.

Located in Reading in the United Kingdom, ECMWF is focused on thedevelopment and operation of global models and data assimilation systems for the dynamics, thermodynamics and composition of the Earth’s fluid envelope and interacting parts of the Earth system. An independent, intergovernmental organization supported by 34 nations, the center specializes in global numerical weather prediction up to a few weeks ahead. It also provides longer-range forecasts for up to a year ahead and runs the EU-funded Copernicus Atmosphere Monitoring and Climate Change Services.

“This upgrade will help us to improve the quality of the service we provide to our Member and Co-operating States,” said ECMWF Director of Research Erland Källén. “It will enable us to develop high-resolution ensemble forecasts that improve the prediction of severe weather events in themedium range, up to about two weeks ahead. It will also make it possible to introduce improved data assimilation methods, allowing us to use more of the available Earth system observations, and to produce more detailed and better-quality atmospheric composition forecasts as well as high-quality climate datasets (re-analyses).”

“We are very pleased that ECMWF has made the decision to upgrade its Cray systems, which will provide the organization’s researchers and scientists with even more powerful, computational tools for advancing global numerical weather prediction,” said Catalin Morosanu, Cray’s vice president of sales for Europe, Middle East and Africa (EMEA) region. “The ability to easily and cost effectively upgrade our systems is an important design element of Cray supercomputers. This allows our customers to have a lower total cost of ownership of their systems over time, and quickly be able to deploy the latest and most-advanced technologies. We are proud of our relationship with ECMWF and the amazing work they do, and we are excited our partnership will continue well into the future.”

Cray XC40 supercomputers are engineered to meet the performance challenges of today’s most demanding users. Special features of the Cray XC40 supercomputer include: the industry-leading Aries system interconnect; a Dragonfly network topology that frees applications from locality constraints; optional flash SSD enabled DataWarp applications I/O accelerator technology; innovative cooling systems to lower customers’ total cost of ownership; the next-generation of the scalable, high performance and tightly integrated Cray Linux Environment that supports a wide range of applications; Cray’s optimized programming environment for improved performance and programmability; and the ability to handle a wide variety of processor types, including Intel Xeon processors, Intel Xeon Phi coprocessors, and NVIDIA Tesla GPU accelerators.

The Cray Sonexion 2000 scale-out storage solution combines Cray’s Lustre expertise with a tightly integrated, unique design that allows for maximum scalability and performance. Management and operations are simplified through an appliance design with all storage components including software, storage and infrastructure.

Consisting of products and multiple years of service, the contract to upgrade and expand the Cray systems at ECMWF is valued at more than $36 million. System deliveries are expected in 2016.

On the top row are two images of a nanomesh bilayer of PDMS cylinders in which the top layer is perpendicular to the complex orientation of the bottom layer. The bottom images show well-ordered nanomesh patterns of PDMS cylinders. The images on the right show zoomed-in views of the images on the left.

Since the 1960s, computer chips have been built using a process called photolithography. But in the past five years, chip features have gotten smaller than the wavelength of light, which has required some ingenious modifications of photolithographic processes. Keeping up the rate of circuit miniaturization that we’ve come to expect — as predicted by Moore’s Law — will eventually require new manufacturing techniques.

Block copolymers, molecules that spontaneously self-assemble into useful shapes, are one promising alternative to photolithography. In a new paper in the journal Nature Communications, MIT researchers describe the first technique for stacking layers of block-copolymer wires such that the wires in one layer naturally orient themselves perpendicularly to those in the layer below.

The ability to easily produce such “mesh structures” could make self-assembly a much more practical way to manufacture memory, optical chips, and even future generations of computer processors.

“There is previous work on fabricating a mesh structure — for example our work,” says Amir Tavakkoli, a postdoc in MIT’s Research Laboratory of Electronics and one of three first authors on the new paper. “We used posts that we had fabricated by electron-beam lithography, which is time consuming. But here, we don’t use the electron-beam lithography. We use the first layer of block copolymer as a template to self-assemble another layer of block copolymer on top of it.”

Tavakkoli’s co-first-authors on the paper are Sam Nicaise, a graduate student in electrical engineering, and Karim Gadelrab, a graduate student in materials science and engineering. The senior authors are Alfredo Alexander-Katz, the Walter Henry Gale Associate Professor of Materials Science and Engineering; Caroline Ross, the Toyota Professor of Materials Science and Engineering; and Karl Berggren, a professor of electrical engineering.

Unhappy couples

Polymers are long molecules made from basic molecular units strung into chains. Plastics are polymers, and so are biological molecules like DNA and proteins. A copolymer is a polymer made by joining two different polymers.

In a block copolymer, the constituent polymers are chosen so that they’re chemically incompatible with each other. It’s their attempts to push away from each other — both within a single polymer chain and within a polymer film — that causes them to self-organize.

In the MIT researchers’ case, one of the constituent polymers is carbon-based, the other silicon-based. In their efforts to escape the carbon-based polymer, the silicon-based polymers fold in on themselves, forming cylinders with loops of silicon-based polymer on the inside and the other polymer bristling on the outside. When the cylinders are exposed to an oxygen plasma, the carbon-based polymer burns away and the silicon oxidizes, leaving glass-like cylinders attached to a base.

To assemble a second layer of cylinders, the researchers simply repeat the process, albeit using copolymers with slightly different chain lengths. The cylinders in the new layer naturally orient themselves perpendicularly to those in the first.

Chemically treating the surface on which the first group of cylinders are formed will cause them to line up in parallel rows. In that case, the second layer of cylinders will also form parallel rows, perpendicular to those in the first.

But if the cylinders in the bottom layer are allowed to form haphazardly, snaking out into elaborate, looping patterns, the cylinders in the second layer will maintain their relative orientation, creating their own elaborate, but perpendicular, patterns.

The orderly mesh structure is the one that has the most obvious applications, but the disorderly one is perhaps the more impressive technical feat. “That’s the one the materials scientists are excited about,” Nicaise says.

Whys and wherefores

Glass-like wires are not directly useful for electronic applications, but it might be possible to seed them with other types of molecules, which would make them electronically active, or to use them as a template for depositing other materials. The researchers hope that they can reproduce their results with more functional polymers. To that end, they had to theoretically characterize the process that yielded their results. “We use computer simulations to understand the key parameters controlling the polymer orientation,” Gadelrab says.

What they found was that the geometry of the cylinders in the bottom layer limited the possible orientations of the cylinders in the upper layer. If the walls of the lower cylinders are too steep to permit the upper cylinders from fitting in comfortably, the upper cylinders will try to find a different orientation.

It’s also important that the upper and lower layers have only weak chemical interactions. Otherwise, the upper cylinders will try to stack themselves on top of the lower ones like logs on a pile.

Both of these properties — cylinder geometry and chemical interaction — can be predicted from the physics of polymer molecules. So it should be possible to identify other polymers that will exhibit the same behavior.

According to Patrick Theofanis, an engineer at the chip manufacturer Intel, the nanocylinders themselves are less interesting than the spaces between them. “In general, the ability to pattern square holes is very useful for us,” he says.

“If you think of the back end of our chips, we have the back-end wiring, and then you have the interconnect layers between those back-end metal layers, and that’s where you’d like to be able to punch through holes and connect one layer to the next one. It’s an attractive technology because the aspect ratio is very tunable in the way that they’ve done their scheme.”

Improving computer literacy and building internet and communications technology (ICT) skills in Indigenous communities is more about understanding the opportunities rather than imposing "Western" style learning programs, according to a new study published in the International Journal of Social Media and Interactive Learning Environments. The paper's author Michelle Eady of the University of Wollongong, New South Wales, Australia, offers an 11-point plan to help those working with communities to adopt and engage with the Internet.

The internet represents an unprecedented opportunity for employment training and development across the globe. Unfortunately, there is a digital divide between the culture of the developed world underpinned by the technological nations of East Asia and people who live in indigenous communities, such as those in Australia, North America and elsewhere. Educators have attempted to close this gap by applying the same approaches used to bridge the digital divide in the wider communities of the USA and Europe.

Unfortunately, the educational methods of the West do not always translate well to indigenous communities, where they are not only perceived as imperialistic in some quarters but also fail to acknowledge important cultural differences. This is often compounded by the fact that many indigenous communities are disadvantaged by geographical barriers, government policies, language background, poverty, and health and technical insufficiencies, Eady reports. Eady has laid out eleven principles for working together with and assisting Indigenous communities to prepare and effectively and efficiently use ICT:

1 Develop an awareness and understanding of learners' profiles
2 Create opportunities for online learning communities
3 Ensure teaching materials have content relevant to the community
4 Support and enhance traditions and cultural diversity
5 Provide accessible, suitable and reliable technology
6 Make programs intergenerational and inclusive
7 Foster positive relationships, mentoring and support
8 Promote community-based learning
9 Encourage genuine government involvement and "bottom up" partnerships
10 Understand community goals, directions and development
11 Embrace Aboriginal ways of knowing and learning through Elder wisdom

There are many other considerations, but these principles based on research with specific Indigenous communities in Australia and experience in Canadian communities could be applicable to other communities abroad.

"[The research] literature has shown that the internet has substantial potential to deliver literacy, essential skills and tertiary training and education to Indigenous learners who live in remote and isolated communities, providing real-time interaction between instructors and learners," says Eady. She adds that the design-based principles outlined in her paper "provide sound guidelines for future research that engages Indigenous learners with learning opportunities involving computer technologies."

Daniel Elton and Marivi Fernandez-Serra used computer simulation models of water developed at Stony Brook’s Institute for Advanced Computational Science to discover its molecular properties are similar to ice.

The finding, published in Nature Communications, changes views on the molecular nature of water and its applications to climate research and uses in energy technology

For more than 100 years, scientists have debated what the underlying molecular structure of water is, and the common view held has been that H2O molecules are either “water-like” or “ice-like.” Now through supercomputer simulation conducted at the Institute for Advanced Computational Science (IACS) at Stony Brook University, researchers can illustrate that the structure and dynamics of hydrogen bonding in liquid water is more similar to ice than previously thought. The finding, published in Nature Communications, changes the common understanding of the molecular nature of water and has relevance to many fields, such as climate science and molecular biophysics, and technologies such as desalinization and water-based energy production.

In condensed matter physics, phonons are considered to be a solid-state phenomenon and can be visualized as collective vibrations that propagate through a material. More precisely, a phonon is the fundamental quantum mechanical unit of lattice vibration. Optical phonons are a type of phonon that interact with electromagnetic radiation. These can be visualized as peaks in the infrared absorption spectrum in ice.

In the paper, “The hydrogen-bond network of water supports propagating optical phonon-like modes,” lead author Daniel C. Elton, a PhD candidate, and Marivi Fernandez-Serra, PhD, Associate Professor, in the Department of Physics and Astronomy and IACS, show that propagating vibrations or phonons can exist in water, just as in ice.

“No microscopes can allow us to directly see the behavior of water molecules and their pattern of hydrogen bonding. Therefore by simulating liquid water using the fundamental laws of physics, the structure and motion of molecules in water can be analyzed in great detail beyond what microscopes can reveal of liquid water,” said Elton. “Our method involved both experimental data and extensive molecular dynamics simulations, and we found that the optical phonon coupling leads to similar absorption peaks also found in ice.”

The authors used a new high-powered supercomputer cluster at Stony Brook’s IACS to create the water dynamics simulations. By centering on water’s unique hydrogen bond network, they routinely demonstrated that optical phonon-like modes can propagate the hydrogen bond network, just as in ice. Unlike in ice, however, hydrogen bonds in water are constantly being broken and reformed, so the phonons only last for about one trillionth of a second yet can travel over long distances up to two nanometers.

“Our findings challenge older ideas about water dynamics, which characterized peaks in the absorption spectrum as being due to the vibrational motions of at most a few molecules,” said Professor Fernandez-Serra. “We found water peaks in spectra correspond to two different types of phonons, called longitudinal and transverse. The shifting of the position of the longitudinal and transverse peaks with temperature can be related to important structural changes in the hydrogen bond network, which provides a new window into how water’s structure changes with temperature.”

Additionally, by comparing several different simulation techniques, the authors also found that the current non-polarizable water models used in biophysics fail to capture the higher frequency optical phonons. This work builds on their previous work , which showed that polarizable models are more accurate than the more often used non-polarizable models.

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