Molecular Sieving Properties of Nanoporous Mixed-Linker ZIF-62: Associated Structural Changes upon Gas Adsorption Application

The evaluation of the flexibility in zeolitic imidazolate frameworks (ZIFs) has been very useful to understand their performance in gas adsorption and separation applications. Here, we have evaluated the adsorption properties of a nanoporous mixed-linker ZIF-62 using a combination of gas adsorption measurements, grand canonical Monte Carlo simulations, and synchrotron X-ray powder diffraction under operando conditions. While adsorption studies in nanoporous ZIF-62 at 77 K and atmospheric pressure predict a large O2/N2 separation ability, computational studies anticipate that the observed differences must be attributed to kinetic restrictions of N2 to access the internal porosity at cryogenic temperatures. Interestingly, upon a small increase in the adsorption temperature (90 K vs 77 K), both N2 and O2 are able to access the inner porous structure through the promotion of a phase transition (ca. 3.8% volume expansion) upon gas adsorption. This narrow phase (np) to expanded phase (ep) structural transition in ZIF-62 is completely suppressed above 150 K. Based on the excellent molecular sieve properties of nanoporous ZIF-62 for O2/N2 at cryogenic temperatures, we extended our study to the adsorption of linear and branched hydrocarbons. This study predicts the preferential adsorption of alkanes over alkenes in ZIF-62 for small hydrocarbons (C2), while in the case of C3 hydrocarbons and above, the adsorption process is mainly defined by kinetic restrictions.J.S.-A. acknowledges financial support from the MINECO (Projects MAT2016-80285-p and PID2019-108453GB-C21). The authors acknowledge ALBA for providing beamtime (Project No. 2019023264). Computational work was supported by the Cambridge High-Performance Computing Service, the Cambridge Service for Data-Driven Discovery (CSD3)

The Einstein Toolkit: A Community Computational Infrastructure for Relativistic Astrophysics

We describe the Einstein Toolkit, a community-driven, freely accessible computational infrastructure intended for use in numerical relativity, relativistic astrophysics, and other applications. The Toolkit, developed by a collaboration involving researchers from multiple institutions around the world, combines a core set of components needed to simulate astrophysical objects such as black holes, compact objects, and collapsing stars, as well as a full suite of analysis tools. The Einstein Toolkit is currently based on the Cactus Framework for high-performance computing and the Carpet adaptive mesh refinement driver. It implements spacetime evolution via the BSSN evolution system and general-relativistic hydrodynamics in a finite-volume discretization. The toolkit is under continuous development and contains many new code components that have been publicly released for the first time and are described in this article. We discuss the motivation behind the release of the toolkit, the philosophy underlying its development, and the goals of the project. A summary of the implemented numerical techniques is included, as are results of numerical test covering a variety of sample astrophysical problems.Comment: 62 pages, 20 figure

Perceptions of gender balance of IS journal editorial positions

An analysis of 18,854 editorial positions on IS journals was undertaken to examine the perceived gender balance of those positions as an indication of their contribution towards a positive role model for females considering an IS academic career. The nature and extent of perceived gender balance is examined in terms of overall composition of editorial positions, journal prestige and the specific area within IS covered by a journal. The results indicate that perceived gender balance of editorial positions reflects that of ICT academia generally, and that female representation appears to be concentrated in journals covering areas that are traditionally seen as female occupations, e.g., health, education, librarianship. As such, little or no encouragement is given to females considering an IS academic career.<br /

Multi-scale analysis of fretting fatigue in heterogeneous materials using computational homogenization

This paper deals with modeling of the phenomenon of fretting fatigue in heterogeneous materials using the multi-scale computational homogenization technique and finite element analysis (FEA). The heterogeneous material for the specimens consists of a single hole model (25% void/cell, 16% void/cell and 10% void/cell) and a four-hole model (25% void/cell). Using a representative volume element (RVE), we try to produce the equivalent homogenized properties and work on a homogeneous specimen for the study of fretting fatigue. Next, the fretting fatigue contact problem is performed for 3 new cases of models that consist of a homogeneous and a heterogeneous part (single hole cell) in the contact area. The aim is to analyze the normal and shear stresses of these models and compare them with the results of the corresponding heterogeneous models based on the Direct Numerical Simulation (DNS) method. Finally, by comparing the computational time and % deviations, we draw conclusions about the reliability and effectiveness of the proposed method