Structural and Electronic Rearrangements in Fe2S2, Fe3S4, and Fe4S4 Atomic Clusters under the Attack of NO, CO, and O2

Producción CientíficaWe report results, based on density functional theory–generalized gradient approximation calculations, that shed light on how NO, CO, and O2 interact with Fe2S2, Fe3S4, and Fe4S4 clusters and how they modify their structural and electronic properties. The interest in these small iron sulfide clusters comes from the fact that they are at the protein cores and that elucidating fundamental aspects of their interaction with those light molecules which are known to modify their functionality may help in understanding complex behaviors in biological systems. CO and NO are found to bind molecularly, leading to moderate relaxations in the clusters, but nevertheless to changes in the spin-polarized electronic structure and related properties. In contrast, dissociative chemisorption of O2 is much more stable than molecular adsorption, giving rise to significant structural distortions, particularly in Fe4S4 that splits into two Fe2S2 subclusters. As a consequence, oxygen tends to strongly reduce the spin polarization in Fe and to weaken the Fe–Fe interaction inducing antiparallel couplings that, in the case of Fe4S4, clearly arise from indirect Fe–Fe exchange coupling mediated by O. The three molecules (particularly CO) enhance the stability of the iron–sulfur clusters. This increase is noticeably more pronounced for Fe2S2 than for the other iron–sulfur clusters of different compositions, a result that correlates with the fact that in recent experiments of CO reaction with FemSm (m = 1–4), the Fe2S2CO product results as a prominent one.Junta de Castilla y León (Ref. project VA124G18)Ministerio de Economía, Industria y Competitividad (Project PGC2018-093745-B-I00) and FEDE

Building and Using Digital Libraries for ETDs

Despite the high value of electronic theses and dissertations (ETDs), the global collection has seen limited use. To extend such use, a new approach to building digital libraries (DLs) is needed. Fortunately, recent decades have seen that a vast amount of “gray literature” has become available through a diverse set of institutional repositories as well as regional and national libraries and archives. Most of the works in those collections include ETDs and are often freely available in keeping with the open-access movement, but such access is limited by the services of supporting information systems. As explained through a set of scenarios, ETDs can better meet the needs of diverse stakeholders if customer discovery methods are used to identify personas and user roles as well as their goals and tasks. Hence, DLs, with a rich collection of services, as well as newer, more advanced ones, can be organized so that those services, and expanded workflows building on them, can be adapted to meet personalized goals as well as traditional ones, such as discovery and exploration

Final proposal to encode the Cuneiform script in the SMP of the UCS

This is a proposal to encode the Phoenician script in the international character encoding standard Unicode. This script was published in Unicode Standard version 5.0 in July 2006. The Phoenician script is an historic script, used to represent texts in Paleo-Hebrew, Archaic Phoenician, Phoenician, Early Aramaic, Late Phoenician cursive, Phoenician papyri, Siloam Hebrew, Hebrew seals, Ammonite, Moabite, and Punic. Although some scholars today use Square Hebrew to transliterate Paleo-Hebrew, the Phoenician script was included in Unicode to be able to represent the historic script directly

The Effect of Improvements in Health and Longevity on Optimal Retirement and Saving

We develop a life-cycle model of optimal retirement and savings behavior under complete markets where retirement is caused by worsening health in old age. Our model explains the long-run decline in the age of retirement as an income level effect. We show that improvements in health and longevity tend to increase the desired retirement age, though less than proportionately, while, contrary to conventional views, reducing savings rates. The retirement age is not simply proportional to healthy life span because compound interest creates a wealth effect when lifespan increases, leading to more leisure (early retirement) and higher consumption (lower savings).

Non-exponential relaxation for anomalous diffusion

We study the relaxation process in normal and anomalous diffusion regimes for systems described by a generalized Langevin equation (GLE). We demonstrate the existence of a very general correlation function which describes the relaxation phenomena. Such function is even; therefore, it cannot be an exponential or a stretched exponential. However, for a proper choice of the parameters, those functions can be reproduced within certain intervals with good precision. We also show the passage from the non-Markovian to the Markovian behaviour in the normal diffusion regime. For times longer than the relaxation time, the correlation function for anomalous diffusion becomes a power law for broad-band noise.Comment: 6 pages, 2 figure