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MeV carbon ion implantation followed by thermal annealing in a hydrogen-containing atmosphere produces a layer of diamond nanocrystals within fused quartz (SiO2). Cathodoluminescence (CL) microanalysis in a scanning electron microscope has revealed at least three previously unreported low intensity CL emissions from carbon implanted and thermally annealed fused SiO2. The CL emissions are observed at 2.78 eV [full width at half maximum (FWHM) of 0.08 eV], ∼3 eV (FWHM of 0.4 eV), and 3.18 eV (FWHM of 0.11 eV). The peak widths and energies of these emissions are incompatible with any known defects associated with the silicon dioxide host lattice. Nondestructive depth resolved CL microanalysis investigations confirm that these CL emissions originate from the near-surface region, consistent with their association with the layer of diamond nanocrystals. [ABSTRACT FROM AUTHOR]

The junction-voltage temperature relationship of a laser diode is used to determine the temperature of the device in the range -20 to 120 °C. We consider changes that occur to this relationship when the diode is driven at its nominal operating current and above. It is found that estimates of the parameters that appear in a function fitted to the voltage-temperature data are sensitive to driving currents at and above the nominal operating current. Changes in parameter estimates are attributed to degradation due to surface recombination at facets occurring when the laser diode is overdriven. An indication of this degradation is the change in the ideality factor that occurs as the current to the device is raised. This work indicates that the temperature of the junction can be determined over the range -20 to 120 °C with a standard uncertainty of ≈0.5 °C. [ABSTRACT FROM AUTHOR]

Experimental studies of high-temperature phase relations in the Fe-rich region of Nd-Fe-Ti ternary alloy systems reveal three main phases, tetragonal, monoclinic and rhombohedral, at 1,100 degrees Celsius. The monoclinic and tetragonal phases display thermodynamic instability for cooling temperatures from 900 to 1,000 degrees Celsius. The compositions of the three phases are '1:12,' '3.29' and '2:17.'

Focuses on a study which investigated high-temperature phase relations in the iron-rich corner of the Nd-Fe-Ti ternary alloy. Experimental procedure; Results and discussion; Conclusion.

Raman and neutron experiments using specific isotope labeling were combined in order to study the dynamics and structure of L-alanine. Inelastic neutron and Raman scattering data of C(2)H(4)(ND(2))CO(2)D are discussed in relation to the doubling of the lattice parameter a observed by means of neutron powder diffraction in C(2)D(4) (NH(2))CO(2)H. The major changes accompanying the phase transition are found in the vibrational frequencies involving the torsional vibration tau(CO(2)(-)), which is clearly affected by the hydrogen bonds between the protons of the ammonium group and the oxygen atoms of the carboxylate group. At lower temperatures the rearrangement of identifiable hydrogen bonds induces changes in the bending vibration delta(ND(3)), confirming some orientational disorder.

This work reports neutron diffraction and incoherent neutron scattering experiments on N-methylacetamide (NMA), which can be considered the model building block for the peptide linkage of polypeptides and proteins. Using the neutron data, we have been able to associate the onset of a striking negative thermal expansion (NTE) along the a-axis with a dynamical transition around 230 K, consistent with our calorimetric experiments. Observation of the NTE raises the question of possible proton transfer in NMA, which, from our data alone, still cannot be settled. We can only speculate that intermolecular repulsive forces increase as the O...H distance decreases upon cooling, and that around 230 K the lattice relaxes without observation of an actual proton transfer. However, the existence of a nonharmonic potential, reflected by the behavior of the phonon vibrations together with the observation of NTE, could be justified by the "vibrational" polaron theory in which a dynamic localization of the vibrational energy is created by coupling an internal molecular mode to a lattice phonon. More generally, this work shows that neutron powder diffraction techniques can be very powerful for investigating structural deformations in small peptide systems.