20,275 research outputs found
Geometrical frustration in the spin liquid beta'-Me3EtSb[Pd(dmit)2]2 and the valence bond solid Me3EtP[Pd(dmit)2]2
We show that the electronic structures of the title compounds predicted by
density functional theory (DFT) are well described by tight binding models. We
determine the frustration ratio, J'/J, of the Heisenberg model on the
anisotropic triangular lattice, which describes the spin degrees of freedom in
the Mott insulating phase for a range of Pd(dmit)2 salts. All of the
antiferromagnetic materials studied have J'/J 0.9, consistent
with predictions for the Heisenberg model. All salts with 0.5 < J'/J < 0.9,
where many-body theories find a number of competing ground states, are known,
experimentally, to be charge ordered, valence bond solids or spin liquids.Comment: Accepted for publication in Phys. Rev. Lett. 4+11 pages, 3+15
figures, major rewrite, added calculations of Hubbard
Retrieval of episodic versus generic information: Does the order of recall affect the amount and accuracy of details reported by children about repeated events?
Children (N = 157) 4- to 8-years old participated 1 (single) or 4 times (repeated) in an interactive event. Across each condition, half were questioned a week later about the only or a specific occurrence of the event (Depth-first), and then about what usually happens. Half were prompted in the reverse order (Breadth-first). Children with repeated experience who first were asked about what usually happens reported more event-related information overall than those asked about an occurrence first. All children used episodic language when describing an occurrence; however children with repeated-event experience used episodic language less often when describing what usually happens than did those with single experience. Accuracy rates did not differ between conditions. Implications for theories of repeated-event memory are discussed
Dynamical reduction of the dimensionality of exchange interactions and the "spin-liquid" phase of -(BEDT-TTF)
We show that the anisotropy of the effective spin model for the dimer Mott
insulator phase of -(BEDT-TTF) salts is dramatically different
from that of the underlying tight-binding model. Intra-dimer quantum
interference results in a model of coupled spin chains, where frustrated
interchain interactions suppress long-range magnetic order. Thus, we argue, the
"spin liquid" phase observed in some of these materials is a remnant of the
Tomonaga-Luttinger physics of a single chain. This is consistent with previous
experiments and resolves some outstanding puzzles. An erratum [Phys. Rev. Lett.
120, 199901 (2018).] is added as an appendix.Comment: Accepted by PRL, 6 pages, 5 figure
Towards mechanomagnetics in elastic crystals: insights from [Cu(acac)]
We predict that the magnetic properties of \cuacac, an elastically flexible
crystal, change dramatically when the crystal is bent. We find that unbent
\cuacac\ is an almost perfect Tomonaga-Luttinger liquid. Broken-symmetry
density functional calculations reveal that the magnetic exchange interactions
along the chains is an order of magnitude larger than the interchain exchange.
The geometrically frustrated interchain interactions cannot magnetically order
the material at any experimentally accessible temperature. The ordering
temperature (), calculated from the chain random phase approximation,
increases by approximately 24 orders of magnitude when the material is bent. We
demonstrate that geometric frustration both suppresses and enhances the
sensitivity of to bending. In \cuacac, is extremely sensitive to
bending, but remains too low for practical applications, even when bent.
Partially frustrated materials could achieve the balance of high and good
sensitivity to bending required for practical applications of mechanomagnetic
elastic crystals
Children’s ability to recall unique aspects of one occurrence of a repeated event
Preschool and school-age children’s memory and source monitoring were investigated by questioning them about one occurrence of a repeated lab event (n = 39). Each of the four occurrences had the same structure, but with varying alternatives for the specific activities and items presented. Variable details had a different alternative each time; hi/lo details presented the identical alternative three times and changed once. New details were present in one occurrence only and thus had no alternatives. Children more often confused variable, lo, and new details across occurrences than hi details. The 4- to 5-year-oldchildren were less accurate than 7- to 8-year-old children at attributing details to the correct occurrence when specifically asked. Younger children rarely recalled new details spontaneously, whereas 50% of the older children did and were above chance at attributing them to their correct occurrence. Results are discussed with reference to script theory, fuzzy-trace theory and the source-monitoring framework
Mental context reinstatement reduces resistance to false suggestions after children have experienced a repeated event
When children allege repeated abuse, they are required to provide details about specific instances. This often results in children confusing details from different instances and so we examined whether ‘mental context reinstatement’ (MCR) could be used to improve children’s accuracy. Children (N = 120, 6-7-year olds) participated in 4 activities over a 2-week period and were interviewed about the last (4th) time with a standard recall or mental context reinstatement interview. They were then asked questions about specific details, and some questions contained false information. When interviewed again a day later, children in the MCR condition resisted false suggestions that were consistent with the event more than false suggestions that were inconsistent; in contrast, children in the standard interview condition were equally suggestible for both false detail types and showed a ‘yes bias’. The results suggest a practical way of eliciting more accurate information from child witnesses
GIBAGADINAMAAGOOM: AN OJIBWE DIGITAL ARCHIVE
Gibagadinamaagoom, (To Bring to Life, to Sanction, to Give Permission), will bring together a diverse array of partners to discuss how state-of-the-art digital technology can be employed to translate ancient and sophisticated systems of traditional Ojibwe knowledge. Discussions will address the challenging, vitally important questions concerning how to design a digital archive that can be accessed using multiple interfaces. Partners include educational (including tribal colleges) and cultural institutions, native Ojibwe scholars, digital media experts, and a distinguished advisory board. These collaborative partners are well positioned to develop one of the most culturally sensitive Native American archives ever built. This project will contribute significantly to how digital technology can be used to revise academic, museum, and library protocols regarding cultural sensitivity, and enhance teaching and learning with a commitment to honor the cultural sovereignty of the Ojibwe
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