X-ray scattering reveals ion clustering of dilute chromium species in molten chloride medium

Enhancing the solar energy storage and power delivery afforded by emerging molten salt-based technologies requires a fundamental understanding of the complex interplay between structure and dynamics of the ions in the high-temperature media. Here we report results from a comprehensive study integrating synchrotron X-ray scattering experiments, ab initio molecular dynamics simulations and rate theory concepts to investigate the behavior of dilute Cr³⁺ metal ions in a molten KCl–MgCl₂ salt. Our analysis of experimental results assisted by a hybrid transition state-Marcus theory model reveals unexpected clustering of chromium species leading to the formation of persistent octahedral Cr–Cr dimers in the high-temperature low Cr³⁺ concentration melt. Furthermore, our integrated approach shows that dynamical processes in the molten salt system are primarily governed by the charge density of the constituent ions, with Cr³⁺ exhibiting the slowest short-time dynamics. These findings challenge several assumptions regarding specific ionic interactions and transport in molten salts, where aggregation of dilute species is not statistically expected, particularly at high temperature.

Ion clustering of dilute chromium species was unexpectedly revealed in a high-temperature molten chloride salt, challenging several long-held assumptions regarding specific ionic interactions and transport in molten ionic media.     

Towards Integrated Facility-Wide Data Acquisition and Analysis at NSLS-II

The National Synchrotron Light Source II (NSLS-II) is the newest, highly optimized third-generation synchrotron facility in the world. NSLS-II accommodates a wide range of scientific research, from materials and energy science to biological applications, which take advantage of its unprecedented brightness, photon flux, and beam stability in infrared, soft and hard X-rays. New X-ray facilities like NSLS-II provide brighter beams than their predecessors, and new X-ray detectors have been built to take advantage of those higher-intensity beams. As a result, acquisition rates and detector sizes have dramatically increased. Both the raw volume of data to process and the metadata to organize it present new challenges. The technology to acquire, manage, and make full scientific use of this data is just emerging.     

Phase diagram of K(x)Fe(2-y)Se(2-z)S(z) and the suppression of its superconducting state by an Fe2-Se/S tetrahedron distortion

We report structurally tuned superconductivity in a K(x)Fe(2-y)Se(2-z)S(z) (0 ≤ z ≤ 2) phase diagram. Superconducting T(c) is suppressed as S is incorporated into the lattice, eventually vanishing at 80% of S. The magnetic and conductivity properties can be related to stoichiometry on a poorly occupied Fe1 site and the local environment of a nearly fully occupied Fe2 site. The decreasing T(c) coincides with the increasing Fe1 occupancy and the overall increase in Fe stoichiometry from z = 0 to z = 2. Our results indicate that the irregularity of the Fe2-Se/S tetrahedron is an important controlling parameter that can be used to tune the ground state in the new superconductor family.     

New In-Situ and Operando Facilities for Catalysis Science at NSLS-II: The Deployment of Real-Time,Chemical, and Structure-Sensitive X-ray Probes

The start of operations at the National Synchrotron Light Source II (NSLS-II) at Brookhaven National Laboratory heralded a new beginning for photon-science-based research capabilities in catalysis. This new facility builds on many years of pioneering work that was conducted at the NSLS synergistically by many scientists from academia, government labs, and industry. Over several decades, numerous discoveries in catalysis were driven through the emergence of an arsenal of tools at the NSLS that exploited the power of emerging X-ray methods encompassing scattering, spectroscopy, and imaging. In-situ and operando methodologies that coupled reactor environments directly with advanced analytical techniques paved a rapid path towards realizing an improved fundamental understanding at the frontiers of chemical science challenges of the day.     

Dynamic modelling of die melt temperature profile in polymer extrusion: Effects of process settings,screw geometry and material

Extrusion is one of the major methods for processing polymeric materials and the thermal homogeneity of the process output is a major concern for manufacture of high quality extruded products. Therefore, accurate process thermal monitoring and control are important for product quality control. However, most industrial extruders use single point thermocouples for the temperature monitoring/control although their measurements are highly affected by the barrel metal wall temperature. Currently, no industrially established thermal profile measurement technique is available. Furthermore, it has been shown that the melt temperature changes considerably with the die radial position and hence point/bulk measurements are not sufficient for monitoring and control of the temperature across the melt flow. The majority of process thermal control methods are based on linear models which are not capable of dealing with process nonlinearities. In this work, the die melt temperature profile of a single screw extruder was monitored by a thermocouple mesh technique. The data obtained was used to develop a novel approach of modelling the extruder die melt temperature profile under dynamic conditions (i.e. for predicting the die melt temperature profile in real-time). These newly proposed models were in good agreement with the measured unseen data. They were then used to explore the effects of process settings, material and screw geometry on the die melt temperature profile. The results showed that the process thermal homogeneity was affected in a complex manner by changing the process settings, screw geometry and material.     

Top‐down analysis of novel synthetic branched proteins

A strategy for top‐down analysis of branched proteins has been reported earlier, which relies on electron transfer dissociation assisted by collisional activation, and software designed for graphic interpretation of tandem mass spectra and adapted for branched proteins. In the present study, the strategy is applied to identify unknown and novel products of reactions in which rationally mutated proteoforms of Rub1 are used to probe the selectivity of E1 and E2 enzymes normally active in ubiquitination. To test and demonstrate this application, components and attachment sites of three branched dimers are deduced and the mutations are confirmed.