Development and applications of the LFDFT: the non-empirical account of ligand field and the simulation of the f–d transitions by density functional theory

Ligand field density functional theory (LFDFT) is a methodology consisting of non-standard handling of DFT calculations and post-computation analysis, emulating the ligand field parameters in a non-empirical way. Recently, the procedure was extended for two-open-shell systems, with relevance for inter-shell transitions in lanthanides, of utmost importance in understanding the optical and magnetic properties of rare-earth materials. Here, we expand the model to the calculation of intensities of f → d transitions, enabling the simulation of spectral profiles. We focus on Eu²⁺-based systems: this lanthanide ion undergoes many dipole-allowed transitions from the initial 4f⁷(⁸S7/2) state to the final 4f⁶5d¹ ones, considering the free ion and doped materials. The relativistic calculations showed a good agreement with experimental data for a gaseous Eu²⁺ ion, producing reliable Slater–Condon and spin–orbit coupling parameters. The Eu²⁺ ion-doped fluorite-type lattices, CaF₂:Eu²⁺ and SrCl₂:Eu²⁺, in sites with octahedral symmetry, are studied in detail. The related Slater–Condon and spin–orbit coupling parameters from the doped materials are compared to those for the free ion, revealing small changes for the 4f shell side and relatively important shifts for those associated with the 5d shell. The ligand field scheme, in Wybourne parameterization, shows a good agreement with the phenomenological interpretation of the experiment. The non-empirical computed parameters are used to calculate the energy and intensity of the 4f⁷–4f⁶5d¹ transitions, rendering a realistic convoluted spectrum

Estimation of dynamic bivariate correlation using a weighted graph algorithm

© 2020 by the authors. Dynamic correlation is the correlation between two time series across time. Two approaches that currently exist in neuroscience literature for dynamic correlation estimation are the sliding window method and dynamic conditional correlation. In this paper, we first show the limitations of these two methods especially in the presence of extreme values. We present an alternate approach for dynamic correlation estimation based on a weighted graph and show using simulations and real data analyses the advantages of the new approach over the existing ones. We also provide some theoretical justifications and present a framework for quantifying uncertainty and testing hypotheses

Crystal Structure and Characterization of Neutral Cobalt(III) 2,3-pyridinedicarboxylate Complex

A new Co(III) complex [CoIII(2,3-pdcH)3(H2O)3] (2,3-pdcH – monoanion of 2,3-pyridinedicarboxylic acid) has been synthesized from Co(II) salt at room temperature by using nonhydrothermal method and (NH4)2S2O8 as oxidant. The influence of the type of Co(II) salt used to the synthesis of the final product was investigated. The complex was characterized by elemental analyses, IR and UV-VIS spectroscopy, single crystal X-Ray diffraction and thermogravimetric analyses. The complex crystallizes in the monoclinic space group P21/c. The crystal structure reveals a homoleptic complex with a distorted octahedral geometry, where the ligand acts as monodeprotonated N, O-chelating anion

Place fields and the cognitive map

The discovery of place cells by John O'Keefe in the early 1970s was a breakthrough not just for systems neuroscience, but also for psychology: place fields provided a clear neural substrate for the notion of a cognitive map, a construct devised to explain rat learning and spatial cognition. However, is the robust location-related firing of place cells still best conceptualised as a cognitive map? In this commentary, we reassess this view of hippocampus function in light of subsequent findings on place cells. We argue that as place fields encode local space, and as they are modulated by ongoing behavior, the representation they provide may be more cognitive than map-like

From Rapid Place Learning to Behavioral Performance: A Key Role for the Intermediate Hippocampus

Rapid place encoding by hippocampal neurons, as reflected by place-related firing, has been intensely studied, whereas the substrates that translate hippocampal place codes into behavior have received little attention. A key point relevant to this translation is that hippocampal organization is characterized by functional-anatomical gradients along the septotemporal axis: Whereas the ability of hippocampal neurons to encode accurate place information declines from the septal to temporal end, hippocampal connectivity to prefrontal and subcortical sites that might relate such place information to behavioral-control processes shows an opposite gradient. We examined in rats the impact of selective lesions to relevant parts of the hippocampus on behavioral tests requiring place learning (watermaze procedures) and on in vivo electrophysiological models of hippocampal encoding (long-term potentiation [LTP], place cells). We found that the intermediate hippocampus is necessary and largely sufficient for behavioral performance based on rapid place learning. In contrast, a residual septal pole of the hippocampus, although displaying intact electrophysiological indices of rapid information encoding (LTP, precise place-related firing, and rapid remapping), failed to sustain watermaze performance based on rapid place learning. These data highlight the important distinction between hippocampal encoding and the behavioral performance based on such encoding, and suggest that the intermediate hippocampus, where substrates of rapid accurate place encoding converge with links to behavioral control, is critical to translate rapid (one-trial) place learning into navigational performance

Place cells on a maze encode routes rather than destinations

Hippocampal place cells fire at different rates when a rodent runs through a given location on its way to different destinations. However, it is unclear whether such firing represents the animal's intended destination or the execution of a specific trajectory. To distinguish between these possibilities, Lister Hooded rats (n=8) were trained to navigate from a start box to three goal locations via four partially overlapping routes. Two of these led to the same goal location. Of the cells that fired on these two routes, 95.8% showed route-dependent firing (firing on only one route), whereas only two cells (4.2%) showed goal-dependent firing (firing similarly on both routes). In addition, route-dependent place cells over-represented the less discriminable routes, and place cells in general over-represented the start location. These results indicate that place cell firing on overlapping routes reflects the animal's route, not its goals, and that this firing may aid spatial discrimination

Understanding the oxidative dehydrogenation of ethyl lactate to ethyl pyruvate over vanadia/titania

We studied the vapour-phase oxidative dehydrogenation (ODH) of ethyl lactate with air to give ethyl pyruvate over V2O5/TiO2 catalysts in a fixed-bed reactor. The nature of the vanadia species is changed by varying the vanadium surface density, and the corresponding structure of the VOx species was determined by XRD, UV-vis spectroscopy, XPS and H2-TPR. Monomeric and isolated vanadia species dominate at lower vanadium surface densities. As the surface density increases, two-dimensional polyvanadates and bulk-like vanadia crystallites become predominant. The activity per vanadium decreases with increasing vanadium surface density, indicating that the monomeric VOx species is better for pyruvate production and that the V–O–Ti bonds play an important role in the ODH of ethyl lactate. This is also confirmed by the superior catalytic performance of V2O5/TiO2 compared to vanadium supported on MgO, Al2O3, ZrO2 and CeO2. In situ DRIFT spectroscopy coupled with mass analysis shows that the reaction can involve three possible adsorption modes of ethyl lactate on the V2O5/TiO2 surface. Under anaerobic conditions, 2-hydroxypropionate forms, giving ethyl acetate as the major product. Conversely, under aerobic conditions, oxygen that is chemisorbed on V2O5/TiO2 is active and easily replenished from the gas phase, converting the ethyl-propionate-2-oxide intermediate into ethyl pyruvate.WZ thanks the China Scholarship Council for a PhD fellowship. EVRF thanks Generalitat Valenciana (project PROMETEOII/2014/004) and Ministerio de Economía y Competitividad (Spain) for projects MAT2013-45008-P, MAT2016-81732-ERC and RYC-2012-11427. This work is part of the Sustainable Chemistry Research Priority Area of the UvA (http://suschem.uva.nl)

Attention Enhances the Retrieval and Stability of Visuospatial and Olfactory Representations in the Dorsal Hippocampus

Attention enhances the encoding and retrieval of olfactory and visuospatial representations by modulating place field stability, firing rate, and neuronal synchronization of pyramidal cells in the hippocampus