The Bousfield lattice of a triangulated category and stratification

For a tensor triangulated category which is well generated in the sense of Neeman, it is shown that the collection of Bousfield classes forms a set. This set has a natural structure of a complete lattice which is then studied, using the notions of stratification and support.     

Evidence of a canted magnetic state in self-doped LaMnO(3+δ) (δ?=?0.04): a magnetocaloric study

We report a detailed investigation of the magnetocaloric properties of self-doped polycrystalline LaMnO(3+δ) with δ?=?0.04. Due to the self-doping effect, the system exhibits a magnetic transition from a paramagnetic to ferromagnetic-like canted magnetic state (CMS) at ～120?K, which is associated with an appreciably large magnetocaloric effect (MCE). The CMS is an inhomogeneous magnetic phase developing due to a steady growth of antiferromagnetic correlation in its predominant ferromagnetic state below ～120?K. The stabilization of CMS in this material is concluded from a comprehensive analysis of magnetocaloric data using Landau theory, which is in excellent agreement with our neutron diffraction study. The magnetic entropy change versus temperature curves for different applied fields collapse into a single curve, revealing a universal behavior of MCE. Our studies suggest that investigation of MCE is an effective technique to acquire fundamental understanding about the basic magnetic structure of a system with complex competing interactions.     

Tuning of tetrahedrality in a silicon potential yields a series of monatomic (metal-like) glass formers of very high fragility

We obtain monatomic glass formers in simulations by modifying the tetrahedral character in a silicon potential to explore a triple point zone between potentials favoring diamond (dc) and bcc crystals. dc crystallization is always preceded by a polyamorphic transformation of the liquid, and is frustrated when the Kauzmann temperature of the high temperature liquid intersects the liquid-liquid coexistence line. The glass forming liquids are extraordinarily fragile. Our results suggest that Si and Ge liquids may be vitrified at a pressure close to the diamond-beta-tin-liquid triple point.     

Integrated investigation of the Li<Subscript>4</Subscript>Ti<Subscript>5</Subscript>O<Subscript>12</Subscript> phase stability

The Li₄Ti₅O₁₂ is applied in lithium ion batteries as anode material, which can be synthesized by various synthesis techniques. In this study, the molten salt synthesis technique at low temperatures, i.e. 350 °C, was applied to synthesize Li₄Ti₅O₁₂. Surprisingly, the Li₄Ti₅O₁₂ was not formed according to XRD analysis, which raised question about the stability range of Li₄Ti₅O₁₂. To investigate the stability of Li₄Ti₅O₁₂ at low temperatures, the high-temperature calcined Li₄Ti₅O₁₂ powder was equilibrated in the LiCl-KCl eutectic salt at 350 °C. The result of experiment revealed that the Li₄Ti₅O₁₂ is not decomposed. Results of ab initio calculations also indicated that the Li₄Ti₅O₁₂ phase is a stable phase at 0 K. The products of molten salt synthesis technique were then annealed at 900 °C, which resulted in the Li₄Ti₅O₁₂ formation. It was concluded that the Li₄Ti₅O₁₂ is a stable phase at low temperatures and the reasons for not forming the Li₄Ti₅O₁₂ by molten salt technique at low temperature are possibly related to activation energy and kinetic barriers. The Li₄Ti₅O₁₂ formation energy is also very small, due to the results of ab initio calculations.     

Complementarity in atomic (finite-level quantum) systems: an information-theoretic approach

We develop an information theoretic interpretation of the number-phase complementarity in atomic systems, where phase is treated as a continuous positive operator valued measure (POVM). The relevant uncertainty principle is obtained as an upper bound on a sum of knowledge of these two observables for the case of two-level systems. A tighter bound characterizing the uncertainty relation is obtained numerically in terms of a weighted knowledge sum involving these variables. We point out that complementarity in these systems departs from mutual unbiasededness in two significant ways: first, the maximum knowledge of a POVM variable is less than log (dimension) bits; second, surprisingly, for higher dimensional systems, the unbiasedness may not be mutual but unidirectional in that phase remains unbiased with respect to number states, but not vice versa. Finally, we study the effect of non-dissipative and dissipative noise on these complementary variables for a single-qubit system.     

Ion atmosphere relaxation controlled electron transfers in cobaltocenium polyether molten salts

A room-temperature redox molten salt for the study of electron transfers in semisolid media, based on combining bis(cyclopentadienyl)cobalt with oligomeric polyether counterions, [Cp2Co](MePEG350SO3), is reported. The transport properties of the new molten salt can be varied (plasticized) by varying the polyether content. The charge transport rate during voltammetric reduction of the ionically conductive [Cp2Co](MePEG350SO3) molten salt exceeds the actual physical diffusivity of [Cp2Co]+ because of rapid [Cp2Co](+/0) electron self-exchanges. The measured [Cp2Co](+/0) electron self-exchange rate constants (k(EX)) are proportional to the diffusion coefficients (D(CION)) of the counterions in the melt. The electron-transfer activation barrier energies are also close to those of ionic diffusion but are larger than those derived from optical intervalent charge-transfer results. Additionally, the [Cp2Co](+/0) rate constant results are close to those of dissimilar redox moieties in molten salts where D(CION) values are similar. All of these characteristics are consistent with the rates of electron transfers of [Cp2Co](+/0) (and the other donor-acceptor pairs) being controlled not by the intrinsic electron-transfer rates but by the rate of relaxation of the ion atmosphere around the reacting pair. In the low driving force regime of mixed-valent concentration gradients, the ion atmosphere relaxation is competitive with electron transfer. The results support the generality of the recently proposed model of ionic atmosphere relaxation control of electron transfers in ionically conductive, semisolid materials.     

Interaction of Cd and Zn with biologically important ligands characterized using solid-state NMR and ab initio calculations

For the first time, coordination geometry and structure of metal binding sites in biologically relevant systems are studied using chemical shift parameters obtained from solid-state NMR experiments and quantum chemical calculations. It is also the first extensive report looking at metal-imidazole interaction in the solid state. The principal values of the (113)Cd chemical shift anisotropy (CSA) tensor in crystalline cadmium histidinate and two different cadmium formates (hydrate and anhydrate) were experimentally measured to understand the effect of coordination number and geometry on (113)Cd CSA. Further, (13)C and (15)N chemical shifts have also been experimentally determined to examine the influence of cadmium on the chemical shifts of (15)N and (13)C nuclei present near the metal site in the cadmium-histidine complex. These values were then compared with the chemical shift values obtained from the isostructural bis(histidinato)zinc(II) complex as well as from the unbound histidine. The results show that the isotropic chemical shift values of the carboxyl carbons shift downfield and those of amino and imidazolic nitrogens shift upfield in the metal (Zn,Cd)-histidine complexes relative to the values of the unbound histidine sample. These shifts are in correspondence with the anticipated values based on the crystal structure. Ab initio calculations on the cadmium histidinate molecule show good agreement with the (113)Cd CSA tensors determined from solid-state NMR experiments on powder samples. (15)N chemical shifts for other model complexes, namely, zinc glycinate and zinc hexaimidazole chloride, are also considered to comprehend the effect of zinc binding on (15)N chemical shifts.