Researchers find what makes chocolate melt in your mouth

Scientists use X-rays to see the true nature of chocolate.

The taste of a silky piece of rich chocolate is one of life’s great pleasures, and producing a smooth mouthfeel is an aspiration of every serious chocolatier.  The characteristics that truly set haute chocolate apart can be seen at the microscale thanks to recent, pivotal research performed by researchers from the University of Guelph at the Advanced Photon Source (APS) located at the U.S. Department of Energy’s (DOE) Argonne National Laboratory.

In a series of studies, University of Guelph researcher Fernanda Peyronel used a technique called ultra-small-angle x-ray scattering (USAXS) to investigate a property called fractal dimension, a particular feature of the geometric configuration of tiny particles of chocolate. “Basically, we’re trying to see whether these particles have a more open or a more closed structure and to correlate that to the mouthfeel experienced by consumers,” Peyronel said.

The USAXS technique allows scientists to resolve particles that range in size from a few hundred nanometers to around 10 micrometers — roughly the limit at which our taste buds can distinguish different textures. The beamline at the APS also accommodates detectors for small-angle x-ray scattering as well as large-angle x-ray scattering. These allow scientists to study their systems from less than a nanometer to around 10 micrometers.

>Read more on the APS at Argonne website

For superconductors, discovery comes from disorder

Discovered more than 100 years ago, superconductivity continues to captivate scientists who seek to develop components for highly efficient energy transmission, ultrafast electronics or quantum bits for next-generation computation.  However, determining what causes substances to become — or stop being — superconductors remains a central question in finding new candidates for this special class of materials.

In potential superconductors, there may be several ways electrons can arrange themselves. Some of these reinforce the superconducting effect, while others inhibit it. In a new study, scientists at the U.S. Department of Energy’s (DOE) Argonne National Laboratory have explained the ways in which two such arrangements compete with each other and ultimately affect the temperature at which a material becomes superconducting.

>Read more on the Advanced Photon Source at Argonne National Lab website

Image: This image shows the transition between Cooper pair density (indicated by blue dots) and charge density waves. Argonne scientists found that by introducing defects, they could disrupt charge density waves and increase superconductivity.
Credit:
Ellen Weiss / Argonne National Laboratory

Study offers new target for antibiotic resistant bacteria

As antibiotic resistance rises, the search for new antibiotic strategies has become imperative. In 2013, the Centers for Disease Control estimated that antibiotic resistant bacteria cause at least 2 million infections and 23,000 deaths a year in the U.S.; a recent report raised the likely mortality rate to 162,044.
New Cornell research on an enzyme in bacteria essential to making DNA offers a new pathway for targeting pathogens. In “Convergent Allostery in Ribonucleotide Reductase,” published June 14 in Nature Communications, researchers used the MacCHESS research stations at the Cornell High Energy Synchrotron Source (CHESS) to reveal an unexpected mechanism of activation and inactivation in the protein ribonucleotide reductase (RNR).

Understanding the “switch” that turns RNR off provides a possible means to shut off the reproduction of harmful bacteria.
RNRs take ribonucleotides, the building blocks of RNA, and convert them to deoxyribonucleotides, the building blocks of DNA. In all organisms, the regulation of RNRs involves complex mechanisms, and for good reason: These mechanisms prevent errors and dangerous mutations.

>Read more on the CHESS website

Image: William Thomas, a graduate student in the field of chemistry and chemical biology, collects data on ribonucleotide reductase.

17 meter long detector chamber delivered to CoSAXS

The experimental techniques used at the CoSAXS beamline will use a huge vacuum vessel with possibilities to accommodate two in-vacuum detectors in the SAXS/WAXS geometry.

A major milestone was reached for the CoSAXS project when this vessel was recently delivered, installed and tested.
The main method that will be used at the CoSAXS beamline is called Small Angle X-ray Scattering (SAXS). By detecting the scattered rays coming from the sample at shallow angles, less than 4° typically, it is possible to learn about the size, shape, and orientation of the small building blocks that make up different samples and how this structure gives these materials their properties. The materials to be studied can come from various sources and in diverse states, for example, plastics from packaging, food and how it is processed or proteins in solution which can be used as drugs.
The “co” in CoSAXS stands for coherence, a quality of the synchrotron light optimized at the MAX IV machine, that loosely could be translated as laser-likeness. In the specific case of X-ray Photon Correlation Spectroscopy (XPCS), it lets the researchers not only measure the structure of the building blocks in the sample but also their dynamics – how they change in time.

>Read more on the MAY IV Laboratory website

Coherent scattering imaging of skyrmions

Profiting from the coherence of synchrotron light, scientists have performed both reciprocal and real-space observations of magnetic skyrmion lattice deformation in a chiral magnet Co8Zn8Mn4.

The study of these materials is key for developing futures spintronic applications such as racetrack memory and logic devices.
The interplay between exchange interaction, antisymmetric Dzyaloshinskii-Moriya interaction, and magnetocrystalline anisotropy may cause incommensurate spin phases such as helical, conical, and Bloch-type skyrmion lattice states. The typical size of a magnetic skyrmion varies in a range from a few to a few hundred nanometers which makes them promising candidates for future spintronic applications such as skyrmion racetrack memory – with storage density higher than solid-state memory devices- and logic devices.
Coherent soft X-ray scattering and imaging are powerful tools to study the spin ordering in multicomponent magnetic compounds with element selectivity.
In this experiment, a skyrmion-hosting compound Co8Zn8Mn4 was investigated at cryogenic temperatures and applied high magnetic fields by a group of researchers from the Japanese RIKEN Center of Emergent Matter Science, National Institute for Materials Science, the Science and Technology Agency, University of Tokyo, the Institute of Materials Structure Science and Photon Factory, as well as from the ALBA Synchrotron.
 

Image: Coherent soft x-ray speckle patterns measured for Co8Zn8Mn4 sample at L3 absorption edge of Co at different temperatures 150 K, 120 K, 25 K (top panel, left to right) and applied field of 70 mT. White scale bar corresponds to 0.05 nm−1. Bottom panel shows micromagnetic simulations of the corresponding skyrmionic spin textures.

 

Superconductor exhibits “glassy” electronic phase

The study provides valuable insight into the nature of collective electron behaviors and how they relate to high-temperature superconductivity.

At extremely low temperatures, superconductors conduct electricity without resistance, a characteristic that’s already being used in cryogenically cooled power lines and quantum-computer prototypes. To apply this characteristic more widely, however, it’s necessary to raise the temperature at which materials become superconducting. Unfortunately, the exact mechanism by which this happens remains unclear.

Recently, scientists found that electrons in cuprate superconductors can self-organize into charge-density waves—periodic modulations in electron density that hinder the flow of electrons. As this effect is antagonistic to superconductivity, tremendous effort has been devoted to fully characterizing this charge-order phase and its interplay with high-temperature superconductivity.

>Read more on the Advanced Light Source at L. Berkeley Lab website

Image: At low doping levels, the charge correlations in the copper–oxide plane possess full rotational symmetry (Cinf) in reciprocal space (left), in marked contrast to all previous reports of bond-oriented charge order in cuprates. In real space (right), this corresponds to a “glassy” state with an apparent tendency to periodic ordering, but without any preference in orientation (scale bar ~5 unit cells).

New technique for two-dimensional material analysis

Discovery allows scientists to look at how 2D materials move with ultrafast precision.

Using a never-before-seen technique, scientists have found a new way to use some of the world’s most powerful X-rays to uncover how atoms move in a single atomic sheet at ultrafast speeds.

The study, led by researchers at the U.S. Department of Energy’s (DOE) Argonne National Laboratory and in collaboration with other institutions, including the University of Washington and DOE’s SLAC National Accelerator Laboratory, developed a new technique called ultrafast surface X-ray scattering. This technique revealed the changing structure of an atomically thin two-dimensional crystal after it was excited with an optical laser pulse.
>Read more on the Advanced Photon Source at Argonne website
>Another article is also available on the Linac Coheren Light Source at SLAC website

Image: An experimental station at SLACs Linac Coherent Light Source X-ray free-electron laser, where scientists used a new tool they developed to watch atoms move within a single atomic sheet.
Credit: SLAC National Accelerator Laboratory

Classic double-slit experiment in a new light

An international research team led by physicists from Collaborative Research Centre 1238, ‘Control and Dynamics of Quantum Materials’ at the University of Cologne has implemented a new variant of the basic double-slit experiment using resonant inelastic X-ray scattering at the European Synchrotron ESRF in Grenoble. This new variant offers a deeper understanding of the electronic structure of solids. Writing in Science Advances, the research group have now presented their results under the title ‘Resonant inelastic x-ray incarnation of Young’s double-slit experiment’.

The double-slit experiment is of fundamental importance in physics. More than 200 years ago, Thomas Young diffracted light at two adjacent slits, thus generating interference patterns (images based on superposition) behind this double slit. That way, he demonstrated the wave character of light. In the 20th century, scientists have shown that electrons or molecules scattered on a double slit show the same interference pattern, which contradicts the classical expectation of particle behaviour, but can be explained in quantum-mechanical wave-particle dualism. In contrast, the researchers in Cologne investigated an iridium oxide crystal (Ba3CeIr2O9) by means of resonant inelastic X-ray scattering (RIXS).

>Read more on the European Synchrotron website

Image: Beamline ID20, where the experiments took place.
Credit: P. Jayet.

Two more experiment stations start user operation

Facility double experiment capacity.

Two additional experiment stations—or instruments—have now started operation at European XFEL. The instruments for Small Quantum Systems (SQS) and Spectroscopy and Coherent Scattering (SCS) welcomed their first user groups for experiments last week and this week respectively. With the successful start of operation of the new instruments, European XFEL has now doubled its capacity to conduct research. With the first three groups coming to the new instruments in 2018, the total number of users who will have visited the facility in 2018 will reach over 500.
The two already operational instruments, SPB/SFX and FXE, have been used to examine biomolecules or biological processes and ultrafast reactions respectively since September 2017. In the future, two of the four now operational instruments will be run in parallel in twelve hour shifts. Two more instruments are scheduled to start user operation in the first half of 2019.

>Read more on the European XFEL website

Image: Scientists at the SQS instrument.
Credit: European XFEL / Jan Hosan

A shape-induced orientation phase within 3D nanocrystal solids

Designing nanocrystal (NC) materials aims at obtaining superlattices that mimic the atomic structure of crystalline solids. In such atomic systems, spatially anisotropic orbitals determine the crystalline lattice type. Similarly, in NC systems the building block anisotropy defines the order of the final solid: here, the NC shape governs the final superlattice structure. Yet, in contrast to atomic systems, NC shape-anisotropy induces not only positional, but also orientational order, ranging from full rotational disorder to a stable, fixed alignment of all NCs. This orientational relation is of special interest, as it determines to what extent atomically coherent connections between NCs are possible, thereby enabling complete wave function delocalization within the NC solid.
In addition to predicting the final NC orientation and position structure, the realization of NC materials demands a controllable fabrication process such that the designed order can be produced. Generally, such highly ordered NC superstructures are achieved through solvent evaporation induced self‐assembly on hard substrates. For applications where the 2D nature of this substrates process is limiting, nonsolvent into solvent diffusion, a technique commonly used to grow single crystals of dissolved molecules, is an attractive option. However, the precise influence of self-assembly parameters on the final superlattice outcome remains unknown. In this work, the researchers posed two closely related questions regarding the design of novel free-standing NC materials: (i) how can the NC self-assembly process be controlled to yield highly ordered free-standing supercrystals and (ii) what is the detailed positional and orientational order within the NC solid? A multidisciplinary team of collaborators, including the Austrian Small Angle X-ray Scattering (SAXS) beamline at Elettra, approached this challenge by a combined experimental and computational strategy.

>Read more on the Elettra Sincrotrone Trieste website

Image: Self‐assembly of 3D colloidal supercrystals built from faceted 20 nm Bi nanocrystals is studied by mens of in-situ synchrotron X‐ray scattering, combined with Monte Carlo simulations. 

Just like lego – studying flexible protein for drug delivery

Researchers from the Sapienza University of Rome and its spin-off company MoLiRom (Italy) are spending the weekend at the ESRF to study a protein that could potentially transport anticancer drugs.

Ferritin is a large spherical protein (20 times bigger than haemoglobin) that stores iron within its cavity in every organism. Just like a lego playset, Ferritin assembles and disassembles. It is also naturally targeted to cancer cells. These are the reasons why Ferritin is a great candidate as a drug-transport protein to fight cancer. An international team of scientists from “Sapienza” University of Rome and the SME MoLiRom (Italy) came to the ESRF to explore a special kind of ferritin that shows promising properties. “This is an archaebacterial ferritin that have transformed into a humanised ferritin to try to tackle cancer cells”, explains Matilde Trabuco, a scientist at the Italian SME MoLiRom.

The mechanism looks simple enough: “Ferritin has a natural attraction to cancer cells. If we encapsulate anti-cancer drugs inside it, it will act as a Trojan horse to go inside cells, then it will open up and deliver the drug”.

Ferritins have been widely used as scaffolds for drug-delivery and diagnostics due to their characteristic cage-like structure. Most ferritins are stable and disassemble only by a harsh pH jump that greatly limits the type of possible cargo. The humanised ferritin was engineered to combine assembly at milder conditions with specific targeting of human cancer cells.

 

>Read more on the European Synchrotron Website

 

Topological excitations emerge from a vibrating crystal lattice

It has long been known that the properties of materials are crucially dependent on the arrangement of the atoms that make up the material. For example, atoms that are further apart will tend to vibrate more slowly and propagate sound waves more slowly. Now, researchers from Brookhaven National Laboratory have used Sector 30 at the Advanced Photon Source (APS) to discover “topological” vibrations in iron silicide (FeSi). These topological vibration arise from a special symmetrical arrangement of the atoms in FeSi and endow the atomic vibrations with novel properties such as the potential to transmit sound waves along the edge of the materials without scattering and dissipation. Looking to the future one might envisage using these modes to transfer energy or information within technological devices.

In quantum mechanics, atomic motions in crystals are described in terms of vibrational modes called phonons. Similar to electrons moving in metals, phonons can also propagate through materials. The detailed properties of these excitations determine many of the thermal, mechanical and electronic properties of the material. In 2017, part of the current collaborative team from the Chinese Academy of Science, theoretically predicted the existence of the topological phonons in transition metal monosilicides. As shown in Fig.1, these topological phonons are formed by two Dirac-cones with different slopes and are protected by symmetry. Since the mathematical description of each Dirac-cone is intimately related to the famous Weyl-equation that was originally proposed in high-energy physics, these topological phonons are consequently called double-Weyl excitations.

>Read more on the Advanced Photon Source website

Image: (extract) Schematic view of the double-Weyl phonon dispersion. Full image here.
Credit: Brookhaven National Laboratory

Understanding how alkaline treatment affects bamboo

In China, bamboo is a symbol of longevity and vitality, able to survive the hardest natural conditions and remain green all year round. In a storm, bamboo stems bend but do not break, representing the qualities of durability, strength, flexibility and resilience1.

Bamboo is a traditional construction material in Asia. Its strength and flexibility arise from its hollow stems (‘culms’) made from distinct material components. The solid outer shell of the culm is made primarily from longitudinal fibres. A higher density at the outer wall makes it stronger than the inner regions, and results in remarkable stiffness and flexural strength. Running through the centre of bamboo stem are parenchyma cells that store and channel the plant’s nutrients.

At the micro-/nano-scale both the fibres and the matrix contain cellulose nano-fibrils of the same type. However, the structural arrangement of the two materials result in contrasting mechanical properties. Individual fibres may reach a strength of 900 MPa, whilst the matrix can only resist about 50 MPa. There is also a considerable difference in their elastic properties, with the fibres being much stiffer than the matrix.

Bamboo is often treated with alkaline solutions, to modify these properties. Alkaline treatments can turn this rapidly renewable and low-cost resource into soft textiles, and extract fibres to be used in composite materials or as biomass for fuel.

>Read more on the Diamond Light Source website

Image: Dr Enrico Salvati on the B16 beamline at Diamond.

X-ray laser opens new view on Alzheimer proteins

Graphene enables structural analysis of naturally occurring amyloids

A new experimental method permits the X-ray analysis of amyloids, a class of large, filamentous biomolecules which are an important hallmark of diseases such as Alzheimer’s and Parkinson’s. An international team of researchers headed by DESY scientists has used a powerful X-ray laser to gain insights into the structure of different amyloid samples. The X-ray scattering from amyloid fibrils give patterns somewhat similar to those obtained by Rosalind Franklin from DNA in 1952, which led to the discovery of the well-known structure, the double helix. The X-ray laser, trillions of times more intense than Franklin’s X-ray tube, opens up the ability to examine individual amyloid fibrils, the constituents of amyloid filaments. With such powerful X-ray beams any extraneous material can overwhelm the signal from the invisibly small fibril sample. Ultrathin carbon film – graphene – solved this problem to allow extremely sensitive patterns to be recorded. This marks an important step towards studying individual molecules using X-ray lasers, a goal that structural biologists have long been pursuing. The scientists present their new technique in the journal Nature Communications.

Amyloids are long, ordered strands of proteins which consist of thousands of identical subunits. While amyloids are believed to play a major role in the development of neurodegenerative diseases, recently more and more functional amyloid forms have been identified. “The ‘feel-good hormone’ endorphin, for example, can form amyloid fibrils in the pituitary gland. They dissolve into individual molecules when the acidity of their surroundings changes, after which these molecules can fulfil their purpose in the body,” explains DESY’s Carolin Seuring, a scientist at the Center for Free-Electron Laser Science (CFEL) and the principal author of the paper. “Other amyloid proteins, such as those found in post-mortem brains of patients suffering from Alzheimer’s, accumulate as amyloid fibrils in the brain, and cannot be broken down and therefore impair brain function in the long term.”

Image: On the ultra-thin, extremely regular layer of graphene, the fibrils align themselves in parallel in large domains. The intense X-ray light from the X-rax free-electron laser LCLS at the SLAC National Accelerator Center enabled the researchers to gain partial information about the fibril structure from ensembles of just a few fibrils.
Credit: Greg Stewart/SLAC National Accelerator Laboratory

A new Polarisation Analyser, and the benefits of 3D printing

The I16 beamline at Diamond is dedicated to the study of advanced materials using X-ray diffraction; part of this process is to use a device, known as a polarisation analyser (PA) that can analyse magnetic scattering from samples. Magnetic scattering is different to, and weaker than, normal X-ray scattering and analysis of the polarisation of this scattering can be used to gain insights into the magnetic properties of materials. Researchers can use this information to determine details of the 3D structure of the sample material.

The design of the PA includes an assembly of vacuum chambers, sets of slits to remove unwanted scattering and various detectors, arranged to rotate about different axes. Researchers use data collected from the detectors as they are moved and rotated to build up information on the polarisation of the scattering.

>Read more on the Diamond Light Source website

Image: extract of the polarisation analyser; to watch the video “The motion of the main axes of the polarisation analyser”, please have a look here.

 

Scientists use machine learning to speed discovery of metallic glass

In a new report, they combine artificial intelligence and accelerated experiments to discover potential alternatives to steel in a fraction of the time.

Blend two or three metals together and you get an alloy that usually looks and acts like a metal, with its atoms arranged in rigid geometric patterns.

But once in a while, under just the right conditions, you get something entirely new: a futuristic alloy called metallic glass that’s amorphous, with its atoms arranged every which way, much like the atoms of the glass in a window. Its glassy nature makes it stronger and lighter than today’s best steel, plus it stands up better to corrosion and wear.

Even though metallic glass shows a lot of promise as a protective coating and alternative to steel, only a few thousand of the millions of possible combinations of ingredients have been evaluated over the past 50 years, and only a handful developed to the point that they may become useful.

Now a group led by scientists at the Department of Energy’s SLAC National Accelerator Laboratory, the National Institute of Standards and Technology (NIST) and Northwestern University has reported a shortcut for discovering and improving metallic glass – and, by extension, other elusive materials – at a fraction of the time and cost.

>Read more on the SLAC website

Image: Fang Ren, who developed algorithms to analyze data on the fly while a postdoctoral scholar at SLAC, at a Stanford Synchrotron Radiation Lightsource beamline where the system has been put to use.
Credit: Dawn Harmer/SLAC National Accelerator Laboratory