Imploding hydrogel shrinks objects to the nanoscale

14 Dec 2018 Belle Dumé

Complex structure prior to shrinking

A new 3D nanofabrication technique called Implosion Fabrication could be used to create a wide variety of nano- and microstructures not previously possible. The technique, which can print 3D objects of nearly any shape by patterning a polymer scaffold with a laser and then shrinking the structure to a thousandth of its original volume, might be used to make novel optical metamaterials and electronics devices.

Shrinking hydrogel scaffold

Most existing nanofabrication techniques are limited in what they can produce. Direct laser writing methods, for example, can produce 2D patterns but not 3D ones, which need to be built up a layer at a time – a process that is difficult and slow. Lithography, one of the oldest nanofabrication techniques, can again only print 2D layers on patterned surfaces.

Researchers led by Edward Boyden of the Massachusetts Institute of Technology have now put forward a new technique in which they use a laser to create patterns of reactive chemical groups inside a hydrogel scaffold. They then deposit material (which can be anything from quantum dots, a piece of DNA or gold nanoparticles) into the reactive groups in 3D. Finally, they dehydrate the gel (using an acid), which implodes the scaffold and the printed object it contains to a thousandth its original volume and form a nanoscale structure.

‘Stunning’ images of protoplanetary discs shed light on planet formation

15 Dec 2018

The young ones: images of 20 protoplanetary discs taken by ALMA (Courtesy: ALMA)

“Stunning” high-resolution images of 20 nearby protoplanetary discs have given astronomers a wealth of new information about how planets form around stars. Taken by the ALMA radio-telescope array in Chile, the images reveal that gas-giant planets ranging in size from Neptune to Saturn can form much faster than previously thought. A comprehensive study of the images also suggests that gas giants can be created much further from their host stars than had been expected. The observations also provide important clues about how Earth-like rocky planets are created.

While astronomers have yet to observe an exoplanet that is truly Earth-like, studying how exoplanetary systems form and evolve could provide important clues about how the Earth itself came into being. Armed with this knowledge, astronomers could work-out how many Earth-like exoplanets should be lurking nearby in the Milky Way.Over the past three decades, astronomers have catalogued nearly 4000 planets orbiting stars other than the Sun. These extra-solar planets – or exoplanets – include exotic objects such as “hot Jupiters” and “super Earths” and astronomers now know that exoplanetary systems exist in myriad forms – with some being very different to our familiar solar system.

Sticky dust

Systems of planets form from protoplanetary discs of gas and dust that surround young stars. The conventional model says that this process occurs slowly over many millions of years and in a hierarchical manner – with dust particles colliding and sticking together to create larger objects that then collide and stick together.

The ALMA survey was done by the DSHARP collaboration and was led by Sean Andrews at the Harvard-Smithsonian Center Astrophysics; Andrea Isella of Rice University; Laura Pérez of the University of Chile; and Cornelis Dullemond of Heidelberg University. Light from the host stars interacts with dust, causing it to glow with radio emissions. The team made systematic comparisons of the structures of 20 discs and were able to discern features as small as several astronomical units (1 AU is the distance between the Earth and Sun) in some of the discs.

Unseen planets

The team found that some structures such as concentric gaps and narrow rings are present in nearly all of the discs. Spiral and arc-like features were also spotted in some of the discs. They believe that some small-scale features are created by unseen gas-giant planets, and their existence in relatively young protoplanetary discs – some just one million years old – suggests that gas giants form much faster than previously thought.

“The most compelling interpretation of these highly diverse, small-scale features is that there are unseen planets interacting with the disc material,” explains Andrews.READ MORE

ALMA debuts its high-resolution results

Some of these features are very distant from the host stars, with the furthest being more than 100 AU away – about three times the distance between Neptune and the Sun. This suggests that some gas giants form in very large orbits, which was not expected before astronomers began observing protoplanetary discs.

The astronomers believe that protoplanetary disc structures could hold the answer to reconciling an apparent flaw in the hierarchical model of planet formation. In a smooth disc, once an object reaches about 1 km in diameter it is prone to being sucked into the star. This is not necessarily the case once the disc has become structured, and this could explain how rocky planets like Earth could form relatively close to stars. Planetary formation should also proceed more rapidly within a ring – where dust density is high — thus accelerating the planet-formation process.

The research is described in ten papers that have been accepted for publication in The Astrophysical Journal Letters.

D printing and genetic engineering bring biofilms to life

18 Dec 2018 Alexis Belessiotis-Richards

Design for a programmable and printable B. subtilis biofilm production platform. Credit: Chao Zhong

Bacterial biofilms could form the basis of a new biomaterial system with a range of tunable properties from fluorescence to tailored chemical activity. Work by a collaboration of researchers led by Chao Zhong at ShanghaiTech University has exploited the natural secretion of amyloid fibres from the bacterium bacillus subtilis for 3D printing to produce customized nanoscale biomaterials.

Material properties customized by genetic engineeringB. subtilis bacteria generate biofilms by secreting amyloid fibres via a tightly controlled cluster of genes known as the tapA-sipW-tasA operon. TapA nucleates the extracellular assembly of TasA proteins to create the amyloid nanofibres that give the biofilm its structural integrity. By genetically modifying the TasA protein, the researchers were able to introduce functional chemical groups onto the TasA fibres excreted by the bacteria. Hence, the bacterial films could be designed to act as functional living materials.

‘Pause’ in global warming was never real, scientists say

19 Dec 2018

(Courtesy: iStock/oonal)

Claims of a ‘pause’ in observed global temperature warming are comprehensively disproved in a pair of new studies published today.

An international team of climate researchers reviewed existing data and studies and reanalysed them. They concluded there has never been a statistically significant ‘pause’ in global warming. This conclusion holds whether considering the ‘pause’ as a change in the rate of warming in observations or as a mismatch in rate between observations and expectations from climate models.

Their papers are published today in Environmental Research Letters.

Doughnut waveguide preserves twisted light

19 Dec 2018

Twisted sisters: light with OAM values of +1 (top) and 0 (bottom) before (left) and after (centre) passing through the doughnut wave guide. The column on the right shows the inference of the two signals, confirming that helicity has been preserved. (Courtesy: Yuan Chen et al/Phys. Rev. Lett.)

A new waveguide that can transmit twisted light within a photonic chip has been unveiled in China. It was created by Xian-Min Jin at Shanghai Jiao Tong University and colleagues and allows twisted light to propagate without significant degradation to its helicity. The waveguide could lead to the development of new chips for optical and quantum computing.

An important challenge for those creating practical devices is that the effective index of refraction of a conventional solid wave guide is too low to allow the transmission of individual OAM states. Instead, states with similar OAM values will blur into each other.Characterized by its corkscrew-shaped wave fronts, twisted light carries orbital angular momentum (OAM) in a series of independent states. Each of these OAM states can be used to encode information, and this has already been used to boost the amount of data that can be transmitted using light. The quantum-mechanical nature of these states could also make twisted light useful for creating quantum computers.

Ion-based commercial quantum computer is a first

17 Dec 2018

Linear computation: montage of a photo of the chip containing the trapped ions and an image of the ions in a 1D array (Courtesy: Christopher Monroe)

The first commercial quantum computer that uses trapped ions for quantum bits (qubits) has been launched by the US-based start-up IonQ. The device is unlike other commercial systems, which use qubits made from superconducting circuits. The company is now working with a small number of users to improve the technology.

Over the past few years, quantum computing has gone from an enticing promise of vastly superior computing power to real devices that can do increasingly useful calculations. A modest number of commercial quantum computers have already been made by small companies such as Rigetti as well as tech giants such as IBM. What these systems all have in common are qubits made from superconducting circuits.

Deep learning enables automatic radiotherapy planning

14 Dec 2018

Dose distributions for a head-and-neck cancer patient: (left column) predicted plan; (centre) automatic generated plan; (right) voxel-by-voxel difference maps. (Courtesy: Med. Phys. 10.1002/mp.13271 © 2018 American Association of Physicists in Medicine)Dose distributions for a head-and-neck cancer patient. Left column: predicted plan; centre: automatic generated plan; right: voxel-by-voxel difference maps. (Courtesy: Med. Phys. 10.1002/mp.13271)

A multi-institutional team in Shanghai has developed an automated treatment planning system for intensity-modulated radiation therapy (IMRT) based on 3D dose prediction and dose distribution-based optimization. The researchers demonstrated that the deep-learning-based method shows promise for generating highly individualized radiotherapy plans optimized for precision and quality (Med. Phys. 10.1002/mp.13271).

Treatment planning software packages that use knowledge-based techniques to estimate dose–volume histogram (DVH) objectives are commercially available. But according to the authors, such methods do not provide reasonable estimates of patient-specific achievable dose distributions. They point out that because a large number of dose distributions satisfy the same DVH objectives, this may result in plans with acceptable DVH objectives but unacceptable dose distributions in some areas of clinical concern.

Lead author Jiawei Fan from Fudan University Shanghai Cancer Center and co-authors have presented a deep-learning method for 3D dose prediction for head-and-neck cancer treatments. The system provides estimates of DVH objectives, as well as giving voxel-level feedback to planners showing where the dose distribution could be improved.

To predict the achievable dose matrix for a given patient anatomy, the researchers developed a residual network-based framework trained to correlate voxel geometry to voxel dose. The input data for the network were acquired from individual trans-axial CT slices of the patient’s anatomy; the output was the dose matrix for each slice.

The model also included data from two additional images: an image of the planning target volume (PTV) describing its region, shape and size; and an image describing the shape, size and relative position of 12 organs-at-risk (OARs). These OARs included the brainstem, spinal cord, right and left parotid glands, right and left temporal lobes, right and left lenses, right and left optic nerves, chiasm and oral cavity.

Each training sample included one CT image, two delineation images and one dose distribution image. The researchers utilized data from 270 patients who underwent IMRT for head-and-neck cancers. They subdivided the dataset into a training set of 195 patients, a validation set of 25 patients and a testing set of 50 patients.

After training and testing their deep-learning model, the researchers compared the predicted dose distributions and DVH curves with results calculated by the treatment planning system. The results demonstrated that the deep-learning method could predict clinically acceptable dose distributions. Tests on a range of different prescription patterns with a large number of plans revealed that the automated plans were comparable to those that had been manually generated by dosimetrists.

The authors note that one distinctive feature of their method is its ability to obtain acceptable predictions for prescription doses that were not included in the training set. The model can also be used on patients with several PTVs that have different prescription doses.

The researchers are currently investigating the applicability of voxel-based dose prediction for other cancer cases. They are also working to improve the predicted results for small-volume OARs by using a training set with consistent clinical priorities and plan qualities to train the deep-learning network.

“The proposed automated treatment planning strategy opens up the possibility of a voxel-by-voxel cost optimization system and eliminates the need to convert a desired dose distribution to DVH values,” the authors conclude. “In the future, it would be a dramatic improvement if a physician’s clinical intent could be directly reflected in the target dose for each voxel through a treatment planning interface designed to make use of the predicted 3D dose distribution.”

Cynthia E Keen is a freelance journalist specializing in medicine and healthcare-related innovations

21/12/2018 FROM PHYSICSWORLD.COM

Deep-learning algorithm estimates gestational age from smartphone images

21 Dec 2018

An accurate estimate of a premature infant's gestational age is critical in post-delivery treatment plans to reduce the risk of neonatal deaths. (Courtesy: César Rincón/CC BY 2.0)

Prematurity is a significant cause of mortality in neonates. Knowledge of an infant’s gestational age is critical in post-delivery treatment plans to reduce neonatal deaths. In high-income countries, prenatal ultrasound scans – the ground truth measure – are the gold-standard method to track gestational aging, but in lower-income countries, access to ultrasound technology and medical experts is limited.

“If we could accurately estimate gestational age for newborns using simple, portable technology, we would be able to administer a proper post-treatment plan to reduce the risk of mortality in many under-serviced regions,” says Arjun Desai from Duke University, first-author on a new study into an automatic system for gestational aging.

OF PET/MRI reduces dose for breast cancer detection

20 Dec 2018

© 

AuntMinnieEurope.com

Clinicians can use as little as 10% of the conventional FDG dose and still produce diagnostic-quality images to detect breast cancer using a time-of-flight (TOF) imaging technique with PET/MRI, according to a study published in the December issue of the Journal of Nuclear Medicine.

Researchers from Switzerland, the US and Canada used five image reconstruction scenarios with varying amounts of FDG and found that TOF PET images with only 10% of the standard dose of the tracer were sufficiently adequate in terms of image quality, sharpness, noise and lesion detectability.

Concurrently, the reduced dose would bring the radiation burden for women with breast cancer to less than what they would receive from a single digital mammogram.

Pristine graphene produces giant photoresponse

19 Dec 2018 Belle Dumé

Intrinsic photoresponse in pristine graphene

Graphene is a sheet of carbon just one atom thick and has many unique properties, such as extraordinarily high electron mobility and high thermal conductivity. It can also, in principle, absorb light over all frequencies of the electromagnetic spectrum, which makes it ideal for use in photodetectors, biosensing and bioimaging applications, as well as in night vision devices. Now a team of researchers at the University of California at Riverside and the Massachusetts Institute of Technology (MIT) has discovered that pristine graphene can produce large amounts of photocurrent when illuminated with light if it is made into special, constricted, shapes. The unexpected thing about this photocurrent is that it occurs at graphene’s charge neutrality point – at which current flow is not expected at all. The new finding could be important for developing more efficient and ultrafast photodetectors and even improved light-harvesting devices like solar panels.

Robotics platform automates chemical synthesis

04 Dec 2018 Rebecca Fong

'Chemputer' brings universal complex molecular assembly a step closer. Credit: iStock Jorn-Pilon-Photography

A modular robotics system could take chemistry a step closer to the complete automation of organic synthesis. A team of researchers have developed the ‘Chemputer’, along with a general chemical programming language to automate the assembly of complex molecules, reported in Science. They demonstrated its ability to synthesize pharmaceutical compounds without human intervention.

The synthesis of complex organic molecules is one of the most labour-intensive branches of chemistry. Despite advances in automation, driven by the availability of digital labware, current technologies are limited to single classes of reactions. Now, Sebastian Steiner and co-workers from The University of Glasgow have come up with a generalized approach to digitizing synthesis in order to tackle this problem. Building on the experience of tens of thousands of chemists and hundreds of years of chemical literature, their advances could offer reliable access to complex molecules.

Twisted linkage geometries hint at new organic chemistry

20 Dec 2018 Anna Demming

Johannes Schönke and Eliot Fried created a variety of Möbius Kaleidocycles with different numbers of hinges from folded paper and 3D printed materials. Credit: OIST

Linkages are fundamental components to machines with moving parts. The term describes any assembly of rigid bodies connected by joints. From this vast catalogue of structures, the linkages that most often interest engineers are those with just one internal degree of freedom, meaning they can only change shape in one way, which allows greater mobility control.

Until recently only a few linkages met this requirement – scissorlike elements, the Sarrus linkage, the Bennett linkage, and the Bricard linkage. Now researchers at Okinawa Institute of Science and Technology in Japan have unearthed a whole new class of ring linkages with just one internal degree of freedom – Möbius Kaleidocycles. Reporting in the Proceedings of the National Academy of Sciences, they suggest that technological applications of their discovery may include robotics and “the design of new organic ring molecules with peculiar electronic properties”, as well as raising fundamental questions about geometry, topology, and the limitations of mobility for closed loop linkages.

Can ‘living well’ stop climate change?

20 Dec 2018

(Courtesy: iStock/momcilog)

Humanity has just 10 years to turn things around. The most recent IPCC report says that we need to reduce anthropogenic carbon dioxide emissions by 45% by 2030 or else be locked into a warming scenario that none of us wants to see. So, what to do? The answer, according to a new study, requires a fundamental change in society. It lies in satisfying human needs like happiness and health instead of focusing on economic growth.

“We need to start thinking, ‘is the carbon footprint that comes from different economic activities actually worth it in terms of societal outcomes?’,” says Gibran Vita from the Norwegian University of Science and Technology. “There is potential to live fulfilling lives with much less environmental impact.”

Tiny Casimir torque is measured at long last

20 Dec 2018

Torque wrench: artist’s impression of the Casimir torque (purple streaks) acting on two solids (blue) against a background of quantum fluctuations (silver spikes). (Courtesy: Jeremy Munday)

A very subtle macroscopic effect caused by quantum fluctuations has been observed more than four decades after it was predicted. The “Casimir torque”, which causes two optically anisotropic objects to rotate relative to one another, has been seen for the first time by physicists in the US, who say that the demonstration could lead to improvements in tiny electromechanical devices and liquid crystals.

But in 1972 American physicists Adrian Parsegian and George Weiss predicted that replacing the metal plates with optically anisotropic materials could also lead to a torque between the two objects. That is because the internal asymmetry of each plate would change the boundary conditions of the cavity when one is rotated relative to the other. The torque would arise spontaneously, causing a rotation that would stop when the cavity reaches its lowest energy state.Physicists know that quantum fluctuations in the vacuum can give rise to what is known as the Casimir force.

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Clinical proton system could enable small-animal studies

06 Dec 2018

The MEVION proton gantry, with the Monte Carlo model of the nozzle components, showing the range shifter plates, the adaptive aperture and (in yellow) a single CT slice of the mouse. (Courtesy: Isabel Almeida)

The MEVION proton gantry and the Monte Carlo model of the nozzle components, showing the range shifter plates, the adaptive aperture and (in yellow) a single CT slice of the mouse. (Courtesy: Isabel Almeida)Image-guided radiation delivery systems for pre-clinical animal research have been helping researchers throughout the world to make discoveries and advancements in cancer treatment. If state-of-the-art photon research platforms could be economically adapted for proton therapy, this could open up a completely new field in pre-clinical research.

Researchers at Maastricht University Medical Centre and MAASTRO Clinic have investigated the feasibility of using a compact clinical proton therapy system for pre-clinical research with millimetric beams. They determined that the MEVION S250i proton system with HYPERSCAN pencil-beam scanning technology and adaptive aperture-controlled collimation could be potentially be used for small-animal radiation research (Br. J. Radiol.10.1259/bjr.20180446).

Proton minibeams tackle aggressive brain tumours

13 Dec 2018 Tami Freeman

Irradiation with proton minibeams creates a highly heterogeneous dose distribution inside a rat’s head. (Courtesy: Sci. Reports 10.1038/s41598-018-34796-8/CC BY 4.0)

High-grade gliomas such as glioblastoma multiforme (GBM) pose one of the biggest challenges in clinical oncology. The gold standard treatment for these aggressive brain tumours — resection followed by radiotherapy and chemotherapy — is limited by high recurrence rates, therapy resistance and devastating side effects. One potential alternative could lie in proton minibeam radiation therapy (pMBRT).

Minibeam radiotherapy uses an array of parallel, submillimetre-sized radiation beams to deliver spatially fractionated dose. Proton minibeams have already demonstrated a remarkable reduction in neurotoxicity compared with standard proton therapy. Now, a French research collaboration has evaluated the outcomes of pMBRT in glioma-bearing rats (Sci. Reports 10.1038/s41598-018-34796-8).

Tripled climate cuts needed to fulfil pledge

30 Nov 2018

The world needs to cut greenhouse gases three times faster. Image by Thomas Hafeneth on Unsplash

The world is not yet living up to its undertaking to tackle global warming, and it will have to make tripled climate cuts − at least − if it is to do so, a report says.

The emissions gap − the difference between the global emissions of greenhouse gases scientists expect in 2030 and the level they need to be at to honour the world’s promises to cut them − is the largest ever.

The 2018 Emissions Gap Report is published by the UN Environment Programme (UNEP). While it is still possible to keep global warming below 2 °C, its authors say, the world’s current pace of action to cut emissions must triple for that to happen.

Elekta Unity receives 510(k) clearance

06 Dec 2018 Tami Freeman

The Elekta Unity MRI-guided radiotherapy system can now be implemented clinically in the US. (Courtesy: Elekta)

The Elekta Unity MRI-guided radiotherapy system has received 510(k) premarket notification from the US Food and Drug Administration, clearing the technology for commercial sales and clinical use in the US. Elekta Unity combines high-field 1.5 T MR imaging, precision radiation therapy and intelligent software, allowing clinicians to see what they treat in real time.

“Since receiving CE mark in June 2018, Elekta Unity has been transforming the care of cancer patients in Europe, and we are excited that this cutting-edge technology is now commercially available to US patients,” says Richard Hausmann, president and CEO of Elekta. “With Elekta Unity, it is now feasible to develop personalized, precision radiation therapy regimens that are optimized for safety and efficacy and make radiation therapy a viable treatment option for more patients.”

2018 Breakthrough of the Year: Hamish Johnston’s shortlist

06 Dec 2018 Hamish Johnston

The top five: (Courtesy: Keiichiro Imura, Noriaki K. Sato, and Tsutomu Ishimasa), (Courtesy: N R Fuller/National Science Foundation), (Courtesy: Jefferson Lab), (Courtesy: Shutterstock/Sam72), (Courtesy: Technical University of Vienna)

One of the highlights in the Physics World calendar is the annual announcement of our Breakthrough of the Year, which in recent years has been awarded to such landmark achievements as the first multimessenger observation of a neutron star merger, the detection of gravitational waves by the LIGO scientific collaboration, and the simultaneous quantum teleportation of two fundamental properties of the photon.

So, over the next few days, each of our online editors will select their own top five shortlists from the research they have covered in 2018. Their selections will be based on three criteria:It’s always hard to choose a single winner, and even to pick out the nine other scientific breakthroughs that make it into our Top 10, but this year we realized that we truly have an embarrassment of riches. That’s because three new expert editors have joined the Physics World team to expand our coverage of research fields that benefit from an interdisciplinary approach – medical physics and the biosciences; environment and energy; and materials science and technology – and we wanted to reflect that expanded scope in the 2018 award.

Twistronics pioneers win Physics World 2018 Breakthrough of the Year

13 Dec 2018 James Dacey

In this episode of Physics World Weekly we’re celebrating the Physics World 2018 Breakthrough of the Year. Announced today, the honour has gone to Pablo Jarillo-Herrero of the Massachusetts Institute of Technology (MIT) in the US and colleagues for making the discovery that led to the development of “twistronics”. The researchers discovered Mott insulator behaviour in pristine bilayer graphene when the orientation of the two layers were twisted by a specific angle.

Megawatt laser beacon could communicate with aliens

12 Nov 2018

On target: artist's impression of a laser beacon. (Courtesy: MIT News)

A bright laser beacon that announces our presence to extraterrestrial civilizations could soon be achievable, new research suggests. Calculations done by James Clark and Kerri Cahoy at the Massachusetts Institute of Technology suggest that current and near-future technologies could be used to produce light intense enough to be detectable to extrasolar astronomers as distant as 20,000 light-years away. The duo’s research also sheds light on how we could detect signs of intelligent life in star systems beyond our own.

NASA’s Insight mission successfully lands on Mars

26 Nov 2018 Michael Banks

Breaking ground: First image from NASA’s $800m Interior Exploration using Seismic Investigations, Geodesy and Heat Transport mission after it touched down on the Martian surface (Courtesy: NASA/JPL-Caltech)

The first probe to study the deep interior of Mars has successfully landed on the red planet. After spending over six months travelling around 550 million kilometres to Mars, NASA’s $800m Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) mission made a soft landing on the red planet in a flat region of the planet called Elysium Planitia. It will now spend the next couple of months deploying the craft’s instruments before studying Mars for at least two years.

Discovery of ‘magic-angle graphene’ that behaves like a high-temperature superconductor is Physics World 2018 Breakthrough of the Year

13 Dec 2018 Hamish Johnston

The Physics World 2018 Breakthrough of the Year goes to Pablo Jarillo-Herrero of the Massachusetts Institute of Technology (MIT) in the US and colleagues for making the discovery that led to the development of “twistronics”, which is a new and very promising technique for adjusting the electronic properties of graphene by rotating adjacent layers of the material. The technique was first used by the team to create “magic-angle graphene”, which behaves like a high-temperature superconductor. Nine other achievements are highly commended in the Top Ten Breakthroughs of 2018 and cover topics ranging from the first full body PET/CT scan to a zero-carbon aeroplane propelled by a jet of ions.

New twist: magic-angle bilayer graphene is the 2018 Breakthrough of the Year. (Courtesy: Pablo Jarillo-Herrero)

Graphene is a layer of carbon just one atom thick that has a honeycomb lattice. Bilayer graphene is a stack of two layers in which the two lattices are usually oriented in a specific way. Twistronics began when Jarillo-Herrero and colleagues discovered Mott insulator behaviour in pristine bilayer graphene when the orientation of the two layers were twisted by a magic angle.

The team, a collection of researchers from MIT, Harvard University and the National Institute of Materials Science (NIMS) in Japan, then showed that by adding electrons to the twisted bilayer using an applied electric field, they could make it superconducting.

The development of twistronics has already triggered several important follow-up discoveries in graphene research. Scientists at Columbia University devised a way to finely tune the angle between adjacent layers of 2D materials and thereby control the electronic properties. This highlights the potential for twistronics as an alternative paradigm for device engineering.

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X-ray scattering reveals plasmons in high-temperature superconductors

03 Nov 2018

Crystal structure of a high-temperature superconductor

US researchers studying high-temperature cuprate superconductors outside the superconducting regime have used cutting-edge X-ray scattering to detect long-predicted – but never previously observed – excitations called plasmons perpendicular to the material’s atomic planes. Researchers hope the findings may help theorists to understand these highly unusual materials better, and perhaps even guide the quest for room-temperature superconductors.

The cuprate superconductors are archetypal “strongly correlated” materials, which are difficult to describe using current approximate models. “In most theories we have today you try to catch the main interaction and treat the others as a small perturbation,” explains condensed matter physicist Wei-Sheng Lee of Stanford University in California, “But for these strongly correlated materials, all the interactions are equally important.”

The materials therefore baffle theoreticians. For example, whereas the established BCS theory of superconductivity predicts that the property should disappear above about 30 K, some cuprates remain superconducting at temperatures up to 130 K. Something seems to preserve the superconducting state at relatively high temperatures, but what it is remains unclear.

ΦΥΣΙΚΗ Β ΛΥΚΕΙΟΥ ΠΡΟΣΑΝΑΤΟΛΙΣΜΟΥ ΘΕΤΙΚΩΝ ΣΠΟΥΔΩΝ "ΚΑΤΑΣΤΑΤΙΚΗ ΕΞΙΣΩΣΗ ΤΩΝ ΙΔΑΝΙΚΩΝ ΑΕΡΙΩΝ"

ΦΥΣΙΚΗ Β ΛΥΚΕΙΟΥ ΠΡΟΣΑΝΑΤΟΛΙΣΜΟΥ ΘΕΤΙΚΩΝ ΣΠΟΥΔΩΝ "ΚΑΤΑΣΤΑΤΙΚΗ ΕΞΙΣΩΣΗ ΤΩΝ ΙΔΑΝΙΚΩΝ ΑΕΡΙΩΝ"

ΦΥΣΙΚΗ Β ΛΥΚΕΙΟΥ ΠΡΟΣΑΝΑΤΟΛΙΣΜΟΥ ΘΕΤΙΚΩΝ ΣΠΟΥΔΩΝ "ΟΙ ΝΟΜΟΙ ΤΩΝ ΑΕΡΙΩΝ ΚΑΙ Η ΚΥΚΛΙΚΗ ΜΕΤΑΒΟΛΗ"

ΦΥΣΙΚΗ Β ΛΥΚΕΙΟΥ ΠΡΟΣΑΝΑΤΟΛΙΣΜΟΥ ΘΕΤΙΚΩΝ ΣΠΟΥΔΩΝ "ΟΙ ΝΟΜΟΙ ΤΩΝ ΑΕΡΙΩΝ ΚΑΙ Η ΚΥΚΛΙΚΗ ΜΕΤΑΒΟΛΗ"

Raindrop formation in turbulent clouds is observed at long last

22 Nov 2018

Chance of showers: physicists have confirmed the role of turbulence in the creation of raindrops. (Courtesy: iStock/clickhere)

An aeroplane-mounted 3D imaging system has been used to show that turbulence causes water droplets in clouds to cluster together. The long-predicted effect has been confirmed by scientists in the US and Germany who found that droplets group together in clouds in ways that would not be expected if they were randomly distributed. The clustering may have an impact on rainfall, particularly in highly turbulent clouds, but the researchers say more data is needed to confirm this.

Scientists believe that turbulent flows within clouds help droplets cross the size-gap: the turbulent flows cause the mid-size droplets to cluster together, increasing the likelihood of them colliding and merging. “The prevailing theory is that naturally turbulent air motion within the cloud induces cloud particles to have some tendency to cluster,” explains Michael Larsen, a physicist at the College of Charleston in the US.Rain falls when gaseous water vapour in clouds condenses, forming tiny water droplets about 15 µm in diameter that must grow to about 100 µm before they fall as rain. Once the droplets reach around 40 µm in diameter they start to move down through the cloud and collide and merge with other droplets, increasing in size.

Climate impacts will seldom strike singly

22 Nov 2018

Namibia today: before long normally dry places will face drought, heatwave and wildfire. Image by Parsing Eye on Unsplash

By 2100, climate impacts will be felt by everyone and most people will experience at least three simultaneous hazards, inexorably made more hazardous by the build-up of greenhouse gases in the atmosphere.

And they could be the lucky ones: some people could be menaced by six different kinds of warming-related hazard simultaneously.

Camilo Mora of the University of Hawaii at Manoa and 22 colleagues report in Nature Climate Change that they read systematically through 3,280 peer-reviewed papers on the subject of climate change, and compiled a matrix of 467 ways in which 10 major climate hazards – floods, droughts, heat waves, fires and so on – and six aspects of human dependency (health, food, water, etc.) could affect humanity.

They did, they say, identify some positive or neutral effects, but the overwhelming majority of climate impacts would create problems for human communities and their economies.

Human bone growth is a thermodynamic process, reveals 3D printing study

22 Nov 2018

Crystal clear: transmission electron microscope image showing a blob of amorphous calcium phosphate that is beginning to crystallize at the bottom left. (Courtesy: Antiope Lotsari/Chalmers University of Technology)

Important insights into how human bones grow and crystallize on an atomic scale have been made by Martin Andersson and colleagues at Sweden’s Chalmers University of Technology. Inspired by their use of 3D printing to try to mimic bone structures, the team determined that bone development is a thermodynamic process, independent of other biological systems within the body. Their discovery could soon be used to develop treatments for bone-related diseases, and could also aid developments of more advanced prosthetic implants.

In our bones, new growth is initiated when spherical, disordered blobs of calcium phosphate are sent out from specialized cells to occupy the spaces in between strings of newly-formed collagen. When in place, these spheres transform from amorphous blobs into an orderly, crystalline substance known as apatite (see figure), which gives bone its unique mechanical properties. Exactly how this process plays out on a molecular scale had not been well understood.

Know your boundaries to progress materials science

22 Nov 2018 Anna Demming

A model guide: a technical note in Journal of Physics: Energy provides a guide for researchers to apply the latest tools for modelling energy materials and processes. Credit: Materials Design Group at Imperial College London

“We often focus on the bulk properties of materials for energy applications, such as light absorption for solar cells and ion diffusion rates for batteries, but the reality is that interfaces are critical,” says Aron Walsh, Professor of Materials at Imperial College London in the UK. His comments reflect a trend in energy materials research that is becoming increasingly focused at the boundaries, where one material ends and another begins.

According to Walsh the wealth of useful innovations for optimizing energy materials stemming from interface studies owes more to what is not known about these systems than what is. Identifying unexpected physical behaviour at the junction between compounds can provide insights into what might enhance or restrict the performance of a device.

Cosmic expansion rate remains a mystery despite new measurement

21 Nov 2018

Galaxy far away: an image taken by the Dark Energy Camera. (Courtesy: Fermilab)

A new value for the Hubble constant – the expansion rate of the universe — has been calculated by an international group of astrophysicists. The team used primordial distance scales to study more than 200 supernovae observed by telescopes in Chile and Australia. The new result agrees well with previous values of the constant obtained using a specific model of cosmic expansion, while disagreeing with more direct observations from the nearby universe – so exacerbating a long-running disagreement between cosmologists and astronomers.

The Hubble constant is calculated by looking at distant celestial objects and determining how fast they are moving away from Earth. A plot of the speeds of the objects versus their distance from Earth falls on a straight line, the slope of which is the Hubble constant.