Materials Literature
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Positron lifetime spectroscopy was used to study native vacancy defects in semi-insulating silicon carbide. The material is shown to contain (i) vacancy clusters consisting of 4--5 missing atoms and (ii) Si vacancy related negatively charged defects. The total open volume bound to the clusters anticorrelates with the…
Electrostatics play a key role in biomolecular assembly. Oppositely charged biomolecules, for instance, can be coassembled into functional units, such as DNA and histone proteins into nucleosomes and actin-binding protein complexes into cytoskeleton components, at appropriate ionic conditions. These cationic-anionic c…
The superconductor Sr_2RuO_4 is widely believed to be a spin triplet system with a chiral order parameter analogous to the A phase of superfluid helium-3. The best evidence for this pairing state is that the Knight shift or spin susceptibility measured in neutron scattering is constant below T_c, unlike in a spin-sing…
Rare-gas solids (Ne, Ar, Kr, and Xe) under hydrostatic pressure up to 30 kbar have been studied by path-integral Monte Carlo simulations in the isothermal-isobaric ensemble. Results of these simulations have been compared with available experimental data and with those obtained from a quasiharmonic approximation (QHA)…
A new mechanism for ferromagnetism in CeRh_3B_2 is proposed on the basis of variational Monte Carlo results. In a one-dimensional Anderson lattice where each 4f electron hybridizes with a ligand orbital between neighboring Ce sites, ferromagnetism is stabilized due to a nearly flat band which is a mixture of conductio…
Natural sedimentation processes give rise to fine layers in shales. If these layers alternate between organic-rich and organic-poor sediments, then the contrast in dielectric properties gives rise to an effective birefringence as the presence of hydrocarbons suppresses the dielectric constant of the host rock. We have…
We study the cylinder to sphere morphological transition of diblock copolymers in aqueous solution with a hydrophobic block and a charged block. We find a metastable undulated cylinder configuration for a range of charge and salt concentrations which, nevertheless, occurs above the threshold where spheres are thermody…
Utilizing magnetic susceptibility, specific heat, thermal expansion and IR spectroscopy we provide experimental evidence that the two subsequent antiferromagnetic transitions in ZnCr_2S_4 at T_N1 = 15 K and T_N2= 8 K are accompanied by significant thermal and phonon anomalies. The anomaly at T_N2 reveals a strong temp…
We investigate the effect of surface anisotropy in a spherical many-spin magnetic nanoparticle. By computing minor loops, two-dimensional (2D) and 3D energyscape, and by investigating the behavior of the net magnetization, we show that in the case of not too strong surface anisotropy the behavior of the many-spin part…
Ferroelectric and dielectric properties of polydomain (twinned) single-crystalline $\mathrm{Pb}({\mathrm{Zr}}_{1\ensuremath{-}x}{\mathrm{Ti}}_{x}){\mathrm{O}}_{3}$ thin films are described with the aid of a nonlinear thermodynamic theory, which has been developed recently for epitaxial ferroelectric films with dense l…
Introductory Concepts. Forces and Energy in Atoms. Major Discoveries in Radiation Physics. Interactions. Radioactive Transformation. Naturally Occurring Radiation and Radioactivity. Interactions of Radiation with Matter. Radiation Shielding. Production of Activation Products. Nuclear Fission and Its Products. Nuclear…
Interesting electrical polarity in nanoclusters usually requires the polarizability to exceed the value R^3 of the classical sphere of radius R. We clarify how this occurs naturally in single electron quantum systems, and relate it to the giant polarizability of Na_14F_13, and to spontaneous dipole formation on niobiu…
We have performed orbital free ab initio molecular dynamics simulations in order to study the thermal behaviour of two open surfaces of solid metallic systems, namely the (110) face of fcc Al and the (10-10) face of hcp Mg. Our results reproduce qualitatively both the experimental measurements and previous ab initio c…
The temperature-dependent Raman spectra of orthorhombic $R\mathrm{Mn}{\mathrm{O}}_{3}$ $(R=\mathrm{Pr},\mathrm{Nd},\mathrm{Sm},\mathrm{Eu},\mathrm{Gd},\mathrm{Tb},\mathrm{Dy},\mathrm{Ho},\mathrm{Y})$ were studied in the $5--300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ temperature range. It was established that while the…
A new plasticizer for poly(L-lactide) (PLA)-poly(propylene glycol) (PPG) is proposed. The advantage of using PPG is that it does not crystallize, has low glass transition temperature, and is miscible with PLA. PLA was plasticized with PPGs with nominal Mw of 425 and 1000 g/mol. Poly(ethylene glycol) (PEG), long known…
Doping of nanocrystals is an important and very difficult task. "Self-purification" mechanisms are often claimed to make this task even more difficult, as the distance a defect or impurity must move to reach the surface of a nanocrystal is very small. We show that self-purification can be explained through energetic a…
This research was undertaken to test the feasibility of using the foam technology to separate polyphenols from fruit juices for use as functional food ingredients. The separation performance, expressed as enrichment ratio, selectivity and percentage recovery, was determined as a function of operating variables, namely…
Composite thin films of (C72H66N8O12S4)yLi2xMn1−xPS3 have been obtained through a solution approach by interacting the tosylate salt of the cationic water soluble 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)porphyrin (H2T4) and MnPS3 exfoliated in the presence of lithium ions. The thin films have been investigated thr…
Diffusion coefficients of limonene in various linear low-density polyethylene (LLDPE) and low-density polyethylene (LDPE) resins have been determined from sorption data using a thermogravimetric methodology. From these data, one can determine whether polymer synthesis parameters such as the choice of catalytic process…
We report for the first time the formation of a new phase in a supercooled liquid molecular compound 2-biphenylmethanol by differential scanning calorimetry and x-ray diffraction measurements. It is found that at a crossover temperature T c ∼1.2 T g within a supercooled liquid metastable clusters (nuclei) start to app…