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Category: materials – Page 160

A multidisciplinary team of Indiana University researchers have discovered that the motion of chromatin, the material that DNA is made of, can help facilitate effective repair of DNA damage in the human nucleus — a finding that could lead to improved cancer diagnosis and treatment. Their findings were recently published in the Proceedings of the National Academy of Sciences.

DNA damage happens naturally in human body and most of the damage can be repaired by the cell itself. However, unsuccessful repair could lead to cancer.

“DNA in the nucleus is always moving, not static. The motion of its high-order complex, chromatin, has a direct role in influencing DNA repair,” said Jing Liu, an assistant professor of physics in the School of Science at IUPUI. “In yeast, past research shows that DNA damage promotes chromatin motion, and the high mobility of it also facilitates the DNA repair. However, in human cells this relationship is more complicated.”

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Astronomers may soon have the answer to what is perhaps the greatest mystery of modern science –is dark energy a uniform force across space and time, or has its strength evolved over eons?

The universe is not only expanding – it is accelerating outward, driven by what is commonly referred to as “dark energy.” The term is a poetic analogy to the label for dark matter, the mysterious material that dominates the matter in the Universe and that really is dark because it does not radiate light (it reveals itself via its gravitational influence on galaxies).

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A new technique makes it possible to capture videos of single atoms “swimming” at the interface between a solid and a liquid for the first time. The approach uses stacks of two-dimensional materials to trap the liquid, making it compatible with characterization techniques that usually require vacuum conditions. It could enable researchers to better understand how atoms behave at these interfaces, which play a crucial role in devices such as batteries, catalytic systems and separation membranes.

Several techniques exist to image single atoms, including scanning tunnelling microscopy (STM) and transmission electron microscopy (TEM). However, they involve exposing atoms on the surface of the sample to a high-vacuum environment, which can change the material’s structure. Techniques that do not require a vacuum, meanwhile, are either lower-resolution or only work for short time periods, meaning that the atoms’ motion cannot be captured on video.

Researchers led by materials scientists Sarah Haigh of the University of Manchester’s National Graphene Institute (NGI) have now developed a new approach that enables them to track the motion of single atoms on a surface when that surface is surrounded by liquid. They showed that the atoms behave very differently under these circumstances than they do in vacuum. “This is crucial,” explains Haigh, “since we want to understand atomic behaviour for realistic reaction/environmental conditions that the material will experience in use – for example, in a battery, supercapacitor and membrane reaction vessels.”

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Breakthroughs in modern microelectronics depend on understanding and manipulating the movement of electrons in metal. Reducing the thickness of metal sheets to the order of nanometers can enable exquisite control over how the metal’s electrons move. By doing so, one can impart properties that aren’t seen in bulk metals, such as ultrafast conduction of electricity. Now, researchers from Osaka University and collaborating partners have synthesized a novel class of nanostructured superlattices. This study enables an unusually high degree of control over the movement of electrons within metal semiconductors, which promises to enhance the functionality of everyday technologies.

Precisely tuning the architecture of metal nanosheets, and thus facilitating advanced microelectronic functionalities, remains an ongoing line of work worldwide. In fact, several Nobel prizes have been awarded on this topic. Researchers conventionally synthesize nanostructured superlattices—regularly alternating layers of metals, sandwiched together—from materials of the same dimension; for example, sandwiched 2D sheets. A key aspect of the present researchers’ work is its facile fabrication of hetero-dimensional superlattices; for example, 1D nanoparticle chains sandwiched within 2D nanosheets.

“Nanoscale hetero-dimensional superlattices are typically challenging to prepare, but can exhibit valuable physical properties, such as anisotropic electrical conductivity,” explains Yung-Chang Lin, senior author. “We developed a versatile means of preparing such structures, and in so doing we will inspire synthesis of a wide range of custom superstructures.”

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Thermoelectric devices convert thermal energy into electricity by generating a voltage from the difference in temperature between the hot and cold parts of a device.

To better understand how the conversion process occurs at the atomic scale, researchers used neutrons to study single crystals of tin sulfide and tin selenide. They measured changes that were dependent on temperature.

The measurements revealed a strong correlation between changes in the structure at certain temperatures and the frequency of atomic vibrations (phonons). This relationship affects how the materials conduct heat.

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An unusual protein structure known as a “rippled beta sheet,” first predicted in 1953, has now been created in the laboratory and characterized in detail using X-ray crystallography.

The new findings, published in July in Chemical Science, may enable the rational design of unique materials based on the rippled sheet architecture.

“Our study establishes the rippled beta sheet layer configuration as a motif with general features and opens the road to structure-based design of unique molecular architectures, with potential for materials development and ,” said Jevgenij Raskatov, associate professor of chemistry and biochemistry at UC Santa Cruz and corresponding author of the paper.

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A multidisciplinary team of Indiana University researchers have discovered that the motion of chromatin, the material that DNA is made of, can help facilitate effective repair of DNA damage in the human nucleus—a finding that could lead to improved cancer diagnosis and treatment. Their findings were recently published in the Proceedings of the National Academy of Sciences.

DNA damage happens naturally in and most of the damage can be repaired by the cell itself. However, unsuccessful repair could lead to cancer.

“DNA in the nucleus is always moving, not static. The motion of its high-order complex, chromatin, has a direct role in influencing DNA repair,” said Jing Liu, an assistant professor of physics in the School of Science at IUPUI. “In yeast, past research shows that DNA damage promotes chromatin motion, and the high mobility of it also facilitates the DNA repair. However, in human cells this relationship is more complicated.”

Read more | >

Atoms in magnetic materials are organized into regions called magnetic domains. Within each domain, the electrons have the same magnetic orientation. This means their spins point in the same direction. “Walls” separate the magnetic domains. One type of wall has spin rotations that are left-or right-handed, known as having chirality. When subjected to a magnetic field, chiral domain walls approach one another, shrinking the magnetic domains.

Researchers have developed a magnetic material whose thickness determines whether chiral domain walls have the same or alternating handedness. In the latter case, applying a leads to annihilation of colliding domain walls. The researchers combined and electron microscopy to characterize these internal, microscopic features, leading to better understanding of the magnetic behavior.

An emerging field of technology called spintronics involves processing and storing information by harnessing an electron’s spin instead of its charge. The ability to control this fundamental property could unlock new possibilities for developing electronic devices. Compared to current technology, these devices could store more information in less space and operate at higher speeds with less energy consumption.

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The discovery of high temperature superconductors in polyhydrides encourages searching for new types of hydrogen rich superconductors. Most of experimentally reported high Tc polyhydride superconductors are binary hydrides of main group elements, rare earth metals (La, Y etc.) or alkali earth metal (Ca).

Prof. Jin team at Institute of Physics of Chinese Academy of Sciences (IOPCAS) recently discovered new hafnium polyhydrides using synergetic techniques based on diamond anvil cell in combination with in situ laser heating during a search for new types of hydrogen rich superconducting materials.

“The hafnium polyhydrides are synthesized at 243GPa and 2000 K high pressure high temperature conditions and exhibits superconductivity with Tc ~83 K at 243GPa,” explained coauthor Xiancheng Wang who is a professor at IOPCAS. The upper critical field was estimated to be ~24 Tesla while the Ginzburg Landau superconducting coherent length obtained is ~37Å.

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Inserting any material into a special maze of mirrors and lenses can make it absorb light perfectly. This approach could be used to detect faint starlight or for charging faraway devices with lasers.

Ori Katz at the Hebrew University of Jerusalem in Israel and his colleagues created an almost perfect absorber of light by building an “anti-laser”.

In a laser, light bounces between mirrors until it becomes amplified enough to exit the device in a concentrated beam. In an “anti-laser”, says co-author Stefan Rotter at Vienna University of Technology in Austria, light enters the device then gets stuck in an inescapable series of bounces within it.

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