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Category: chemistry – Page 189

First Light for a Next-Generation Light Source

X-ray free-electron lasers (XFELs) first came into existence two decades ago. They have since enabled pioneering experiments that “see” both the ultrafast and the ultrasmall. Existing devices typically generate short and intense x-ray pulses at a rate of around 100 x-ray pulses per second. But one of these facilities, the Linac Coherent Light Source (LCLS) at the SLAC National Accelerator Laboratory in California, is set to eclipse this pulse rate. The LCLS Collaboration has now announced “first light” for its upgraded machine, LCLS-II. When it is fully up and running, LCLS-II is expected to fire one million pulses per second, making it the world’s most powerful x-ray laser.

The LCLS-II upgrade signifies a quantum leap in the machine’s potential for discovery, says Robert Schoenlein, the LCLS’s deputy director for science. Now, rather than “demonstration” experiments on simple, model systems, scientists will be able to explore complex, real-world systems, he adds. For example, experimenters could peer into biological systems at ambient temperatures and physiological conditions, study photochemical systems and catalysts under the conditions in which they operate, and monitor nanoscale fluctuations of the electronic and magnetic correlations thought to govern the behavior of quantum materials.

The XFEL was first proposed in 1992 to tackle the challenge of building an x-ray laser. Conventional laser schemes excite large numbers of atoms into states from which they emit light. But excited states with energies corresponding to x-ray wavelengths are too short-lived to build up a sizeable excited-state population. XFELs instead rely on electrons traveling at relativistic speed through a periodic magnetic array called an undulator. Moving in a bunch, the electrons wiggle through the undulator, emitting x-ray radiation that interacts multiple times with the bunch and becomes amplified. The result is a bright x-ray beam with laser coherence.

Researchers make sand that flows uphill

Engineering researchers at Lehigh University have discovered that sand can actually flow uphill.

The team’s findings were published today in the journal Nature Communications. A corresponding video shows what happens when torque and an is applied to each grain—the grains flow uphill, up walls, and up and down stairs.

“After using equations that describe the flow of granular materials,” says James Gilchrist, the Ruth H. and Sam Madrid Professor of Chemical and Biomolecular Engineering in Lehigh’s P.C. Rossin College of Engineering and Applied Science and one of the authors of the paper, “we were able to conclusively show that these particles were indeed moving like a , except they were flowing uphill.”

Scientists design ultrastable, high-energy-density Zn–Mn battery

A research team led by Prof. Yan Lifeng from the University of Science and Technology of China (USTC) of the Chinese Academy of Sciences (CAS) has designed a water-based nanomicellar electrolyte by using methylurea (Mu). The results were published in the Journal of the American Chemical Society.

Aqueous zinc ion batteries (AZIBs) are competitive candidates for clean energy storage, but they are severely limited by the irreversible electrochemical reaction of the zinc anode. Therefore, it is a crucial issue to explore how to regulate the electrochemical performance of AZIBs through electrolyte design optimization.

In this paper, the researchers proposed a unique design of nanomicellar electrolyte, which comprises ZnSO4, MnSO4 and a high concentration of Mu molecules through a self-assembly strategy, where the aqueous-solvent environment is partitioned into hydrophilic and hydrophobic regions, and cations and anions are encapsulated into nanodomains.

Synthetic biology tool comprehensively reveals gene regulatory networks in E. coli

The intricate interplay of gene expression within living cells is akin to a well-orchestrated symphony, with each gene playing its part in perfect harmony to ensure cells function as they should. At the heart of this symphony are transcription factors (TFs), molecular maestros that regulate the expression of genes by binding to specific DNA sequences known as promoters.

Unlocking the secrets of these genome-scale requires a comprehensive collection of gene expression profiles, but measuring gene expression responses for every TF and pair has posed a formidable challenge due to the sheer number of potential combinations, even in relatively simple organisms such as bacteria.

To tackle this challenge, researchers led by Fuzhong Zhang, professor of energy, environmental & chemical engineering in the McKelvey School of Engineering at Washington University in St. Louis, developed a technique called pooled promoter responses to TF perturbation sequencing (PPTP-seq).

Excited-State (Anti)Aromaticity Explains Why Azulene Disobeys Kasha’s Rule

Fluorescence exclusively occurs from the lowest excited state of a given multiplicity according to Kasha’s rule. However, this rule is not obeyed by a handful of anti-Kasha fluorophores whose underlying mechanism is still understood merely on a phenomenological basis. This lack of understanding prevents the rational design and property-tuning of anti-Kasha fluorophores. Here, we propose a model explaining the photophysical properties of an archetypal anti-Kasha fluorophore, azulene, based on its ground-and excited-state (anti)aromaticity. We derived our model from a detailed analysis of the electronic structure of the ground singlet, first excited triplet, and quintet states and of the first and second excited singlet states using the perturbational molecular orbital theory and quantum-chemical aromaticity indices.

New recipes for origin of life may point way to distant, inhabited planets

Life on a faraway planet—if it’s out there—might not look anything like life on Earth. But there are only so many chemical ingredients in the universe’s pantry, and only so many ways to mix them. A team led by scientists at the University of Wisconsin–Madison has exploited those limitations to write a cookbook of hundreds of chemical recipes with the potential to give rise to life.

Their ingredient list could focus the search for life elsewhere in the universe by pointing out the most likely conditions—planetary versions of mixing techniques, oven temperatures and baking times—for the recipes to come together.

The process of progressing from basic to the complex cycles of cell metabolism and reproduction that define life, the researchers say, requires not only a simple beginning but also repetition.

World’s most powerful X-ray laser fired for the first time

With up to a million X-ray flashes a second, the laser will help study mechanisms in physics, chemistry, and biology.

The US Department of Energy’s (DOE) SLAC National Accelerator Laboratory has fired the first X-rays using the upgraded Linac Coherent Light Source (LCLS) X-ray free-electron laser (XFEL), a press release said. The upgraded version, dubbed LCLS-II, was built for $1.1 billion.

The SLAC National Accelerator Laboratory at Stanford has been building and operating powerful tools for advancing science for over six decades. The original LCLS was the world’s first XFEL, reaching its first light in April 2009.

Light-Triggered Particles Deliver Photoimmunotherapy for Cancer

More noninvasive cancer treatments are being made:

A research group from Japan Advanced Institute of Science and Technology (JAIST) developed light-activatable, liquid metal (LM) nanoparticles for cancer diagnosis and treatment via photoimmunotherapy. The LM nanoparticles can target and destroy cancer cells and can be fluorescently tagged to function as reporters to identify and eliminate tumors in vivo.

Gallium (Ga)-based LM nanoparticles are promising nanoscale materials for biomedical applications due to their physicochemical properties, including flexibility, easy surface modification, efficient photothermal conversion, and high biocompatibility.

Quantum computing offers new insight into photochemical processes

Quantum computing has provided new insights into a fundamental aspect of photochemical reactions that has previously proven difficult to study. The findings could improve scientists’ understanding of light-driven processes such as photosynthesis, smog formation and ozone destruction.

Photochemical processes occur when atomic nuclei and their electrons take on different configurations after absorbing a photon. Some of these reactions are guided by a quantum phenomenon called a conical intersection, where the potential energy surfaces that describe a molecule in its ground state and in its excited state converge. In these situations, quantum mechanical interference can prevent certain molecular transformations from taking place – a constraint known as a geometric phase. This limits the path that the reaction can take and affects the reaction outcome. The geometric phase has been known about since the 1950s, but due to the femtosecond timescales involved, it has never been directly observed in a molecular system.

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