Terahertz emission from tubular pB(Zr,Ti)O3 nanostructures.

We report intense terahertz emission from lead zirconate titanate (PZT) tubular nanostructures, which have a wall thickness around 40 nm and protrude on n-type Si substrates. Such emission is totally absent in flat PZT films or bulk; hence the effect is attributed to the nanoscale geometry of the tubes. The terahertz radiation is emitted within 0.

(39)K NMR and EPR study of multiferroic K(3)Fe(5)F(15).

(39)K NMR spectra and relaxation times of polycrystalline K(3)Fe(5)F(15) have been used as a microscopic detector of the local magnetic fields at the magnetic transition at T(N) = 123 K. The NMR lineshape widens abruptly upon crossing T(N) due to the onset of internal magnetic fields, while we find no significant lineshift. The paraelectric to ferroelectric transition at T(c) = 490 K and the magnetic transition at T(N) have also been studied using X-band EPR (electron paramagnetic resonance).

Stability, thermal homolysis and intermediate phases of solid hydroazafullerene C59HN.

Density functional (DFT) calculations, high-temperature electron paramagnetic resonance (EPR) and transmission electron microscopy (TEM) results suggest that thermal homolysis of C59HN involves a remarkably stable intermediate C59N-C59HN* structure characterised by charge redistribution from a C59N* radical to a bonded C59HN.

An EPR method for probing surface magnetic fields, dipolar distances, and magnetization fluctuations in single molecule magnets.

We outline a spectroscopic method for probing the effective magnetic field B on the surface of crystals of the single molecule magnet (SMM) [(C6H15N3)6Fe8(mu3-O)2(mu2-OH)12]Br7(H2O)Br.H2O, (Fe8Br8). This technique utilizes the line shape changes in the EPR spectra of the organic radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) (g = 2.

Hydrophobic barrier in liposomes studied by FT-ESEEM.

An improvement of the electron spin echo envelope modulation technique (ESEEM) for studying the hydrophobic barrier in lipid membranes was proposed. Water penetration depth into the lipid bilayer composed of egg-phosphatidylcholine and dicetylphosphate was studied. For this purpose the stearic acid spin probes with nitroxide moiety at different positions on the acyl chain were dissolved in the bilayer of liposomes prepared in buffer solution with D2O.

A pulse EPR study of longitudinal relaxation of the stable radical in gamma-irradiated L-alanine.

The longitudinal relaxation rate of the first stable alanine radical, SAR1, was studied by employing pulse EPR technique over a wide temperature interval (5-290 K). The complex nonexponential recovery of the longitudinal magnetization in this temperature interval has been described with two characteristic relaxation times, 1/T*(1a) as the faster component and 1/T*(1b) as the slower component, respectively. It was shown that 1/T*(1a) is strongly affected by the CH(3) group dynamics of the SAR1 center.

In vitro permeability and scanning electron microscopy study of acid-etched and ground enamel surfaces protected with dental adhesive coating.

Clinical procedures, such as acid etching and reshaping of the teeth supporting removable partial dentures by grinding off some enamel surface, increase the permeability of dental enamel. Teeth take several months in vivo to partially recover from such damage. In the meantime, the tooth is more susceptible to carious decay.

The permeability of human cementum in vitro measured by electron paramagnetic resonance.

The structure and permeability of cementum are changed during the course of periodontal disease. In this study, the transport of water-soluble, spin-labelled molecules through cementum was studied by electron paramagnetic resonance (EPR). Cementum samples cut from different parts of the root were classified into four different groups: (A) samples exposed to the oral environment, (B) samples exposed to the periodontal-pocket environment; (C) samples cut from periodontally involved teeth but not exposed to saliva or periodontal pocket and (D) samples from sound young teeth extracted for orthodontic reasons.

1-370 GHz EPR linewidths for K3CrO8: a comprehensive test for the Anderson-Weiss model.

Electron paramagnetic resonance (EPR) measurements have been carried out over the frequency range of 1-370 GHz on single crystals of potassium peroxychromate (K3CrO8) with the view of examining the current models of exchange narrowing of EPR signals in solids. K3CrO8 has a simple (tetragonal) lattice structure, can be grown as single crystals pure or diluted with an isostructural diamagnetic host K3NbO8, and its paramagnetism can be described by a very simple (S = 12, I = 0) spin Hamiltonian. The measurements were made at various orientations of single crystals in the Zeeman field, with emphasis on the principal directions of the g-tensor.

Crystallite arrangement of hydroxyapatite microcrystals in human tooth cementum as revealed by electron paramagnetic resonance (EPR).

Human dental cementum was analyzed by electron paramagnetic resonance (EPR). The measured EPR powder spectra of gamma-irradiated cementum resembled those of gamma-irradiated enamel. Both spectra were characterized by the same line shapes and g values.

Determination of curing time in visible-light-cured composite resins of different thickness by electron paramagnetic resonance.

The irradiation time of a visible-light-activated composite necessary to achieve full polymerization throughout the material was studied. Curing-time dependence on the thickness of the material was also investigated. To monitor the visible light-activation effect, the free radical concentration was measured as a function of irradiation time.

Enhanced permeability of acid-etched or ground dental enamel.

Statement Of Problem: Acid etching creates retentive microcraters on enamel surfaces. Designing of a partial denture often involves reshaping the supporting and retentive teeth by grinding the enamel. Unfortunately, both these procedures damage the enamel surface.

Orientational and Magnetic Ordering of Buckyballs in TDAE-C60.

Spin ordering in the low-temperature magnetic phase is directly linked to the orientational ordering of C(60) molecules in organically doped fullerene derivatives. Electron spin resonance and alternating current susceptometry measurements on tetrakis(dimethylamino)ethylene-C(60) (TDAE-C(60)) (Curie temperature T(c) = 16 kelvin) show a direct coupling between spin and merohedral degrees of freedom. This coupling was experimentally demonstrated by showing that ordering the spins in the magnetic phase imprints a merohedral order on the solid or, conversely, that merohedrally ordering the C(60) molecules influences the spin order at low temperature.

Spontaneous Magnetic Ordering in the Fullerene Charge-Transfer Salt (TDAE)C60.

The zero-field muon spin relaxation technique has been used in the direct observation of spontaneous magnetic order below a Curie temperature (T(c)) of approximately 16.1 kelvin in the fullerene charge-transfer salt (tetrakisdimethylaminoethylene)C(60) [(TDAE)C(60)]. Coherent ordering of the electronic magnetic moments leads to a local field of 68(1) gauss at the muon site at 3.

The caries resistance of human teeth is determined by the spatial arrangement of hydroxyapatite microcrystals in the enamel.

Teeth from different people differ in their susceptibility to caries. The beginning and the development of tooth decay depend on the presence of bacterial plaque and on the structure of the tooth enamel. But it has not been established whether the organic or the inorganic component of the enamel (which is comprised principally of hydroxyapatite microcrystals organized in a firm matrix), is responsible for most of the resistance of teeth to caries.