Evolution of the electronic structure of Be clusters

Using a modified symbiotic genetic algorithm approach and many-body interatomic potential derived from first principles, we have calculated equilibrium geometries and binding energies of the ground-state and low-lying isomers of Be clusters containing up to 41 atoms. Molecular-dynamics study was also carried out to study the frequency of occurrence of the various geometrical isomers as these clusters are annealed during the simulation process. For a selected group of these clusters, higher-energy isomers were more often found than their ground-statestructures due to large catchment areas. The accuracy of the above ground-stategeometries and their corresponding binding energies were verified by carrying out separate ab initio calculations based on molecular-orbital approach and density-functional theory with generalized gradient approximation for exchange and correlation. The atomic orbitals were represented by a Gaussian 6-311G** basis, and the geometry optimization was carried out using the GAUSSIAN 98 code without any symmetry constraint. While the ground-stategeometries and their corresponding binding energies obtained from ab initio calculations do not differ much from those obtained using the molecular-dynamics approach, the relative stability of the clusters and the energy gap between the highest occupied and the lowest unoccupied molecular orbitals show significant differences. The energy gaps, calculated using the density-functional theory, show distinct shell closure effects, namely, sharp drops in their values for Be clusters containing 2, 8, 20, 34, and 40 electrons. While these features may suggest that small Be clusters behave free-electron-like and, hence, are metallic, the evolution of the structure, binding energies, coordination numbers, and nearest-neighbor distances do not show any sign of convergence towards the bulk value. We also conclude that molecular-dynamics simulation based on many-body interatomic potentials may not always give the correct picture of the evolution of the structure and energetics of clusters although they may serve as a useful tool for obtaining starting geometries by efficiently searching a large part of the phase space

Gata is ubiquitously required for the earliest zygotic gene transcription in the ascidian embryo

In ascidian embryos, the earliest transcription from the zygotic genome begins between the 8-cell and 16-cell stages. Gata.a, a maternally expressed Gata transcription factor, activates target genes specifically in the animal hemisphere, whereas the complex of β-catenin and Tcf7 antagonizes the activity of Gata.a and activates target genes specifically in the vegetal hemisphere. Here, we show that genes zygotically expressed at the 16-cell stage have significantly more Gata motifs in their upstream regions. These genes included not only genes with animal hemisphere-specific expression but also genes with vegetal hemisphere-specific expression. On the basis of this finding, we performed knockdown experiments for Gata.a and reporter assays, and found that Gata.a is required for the expression of not only genes with animal hemisphere-specific expression, but also genes with vegetal hemisphere-specific expression. Our data indicated that weak Gata.a activity that cannot induce animal hemisphere-specific expression can allow β-catenin/Tcf7 targets to be expressed in the vegetal cells. Because genes zygotically expressed at the 32-cell stage also had significantly more Gata motifs in their upstream regions, Gata.a function may not be limited to the genes expressed specifically in the animal or vegetal hemispheres at the 16-cell stage, and Gata.a may play an important role in the earliest transcription of the zygotic genome

Person-centered dementia care during COVID-19: a qualitative case study of impact on and collaborations between caregivers

BackgroundLittle is known about the actual impact of COVID-19 on caregivers of older people with dementia and resultant collaborations among them to provide continued person-centered care while undertaking infection control measures. In this study, we explored the impact of providing dementia care during COVID-19 on caregivers involved in dementia care.MethodsThis is an exploratory qualitative case study. The participants were family members living with older people with dementia, care managers, and the medical and long-term care facility staff. Data were collected from 46 caregivers via face-to-face and semi-structured interviews and analyzed using thematic analysis.ResultsThe interviews identified 22 themes related to the impact of COVID-19 on different positions of the caregivers involved in dementia care and their collaboration, and we categorized them into six categories. The core themes were “re-acknowledgement of care priorities” and “rebuilding of relationships.” When caregivers’ perceptions were aligned in the decision-making processes regarding care priorities, “reaffirmation of trust” and “strengthening of intimate relationships” emerged as positive changes in their relationships. Furthermore, the differences in the ability of each caregiver to access and select correct and appropriate information about COVID-19, and the extent of infection spread in the region were related to “anxiety during COVID-19 pandemic” and caused a “gap in perception” regarding infection control.ConclusionsThe present study clarified that the process of aligning the perceptions of caregivers to the objectives and priorities of care for older people with dementia during COVID-19 pandemic strengthened the relationships among caregivers. The findings of this study are useful for caregivers involved in person-centered dementia care

High-energy-resolution XANES of layered oxides for sodium-ion battery

The 3d transition metal oxides with layered structures, Na x MO2 (M = Mn, Co), are promising cathode materials for Na-ion secondary batteries. Here, we investigate the electronic structure of the M of four layered oxides (Na0.91CoO2, Na0.66CoO2, Na1.00MnO2, and Na0.54MnO2) by means of high energy resolution fluorescence detected X-ray absorption near-edge structure, which utilizes the 1s core-hole lifetime-broadening reduction. The highly energy-resolved spectroscopy reveals a shoulder structure in the pre-edge regions of the Co K-edge spectra in Na0.91CoO2. The structure is ascribed to the transition to the Co 3d/4p states via slight hybridization with the Na 3s state