The aggregation of Fe3+ and their d-d radiative transitions in ZnSe:Fe3+ nanobelts by CVD growth.

Transition metal (TM) doped II-VI semiconductors have attracted great attention due to their luminescence and diluted magnetism. In this study, the Fe3+-doped ZnSe nanobelts (NBs) were grown by a facile CVD method. The surface morphology observed via SEM is smooth and clean and the elemental composition measured via EDS confirms that the Fe3+ ions were incorporated into ZnSe NBs successfully. The micro-Raman scattering spectra demonstrate that the as-prepared NBs have the zinc blende structure. Furthermore, the Raman spectra of the Fe3+-doped NBs were compared with those of pure and Fe2+-doped reference samples. The former with a higher signal-to-noise ratio, an enhanced 2LO mode, a stronger LO mode redshift and a larger intensity ratio of LO/TO mode as well as the lower acoustic phonon modes confirms the better crystallization and the stronger electron-phonon coupling on Fe3+-incorporation. The emission of single Fe3+ ion, assigned to the 4T1 → 6A1 transition, was observed at about 570 nm. Moreover, increasing the doping concentration of Fe3+ ions caused the formation of different Fe-Fe coupled pairs in the lattice, which emitted light at about 530-555 nm for an antiferromagnetic-coupled pair, possibly due to the stacking faults and at about 620-670 nm for a ferromagnetic-coupled pair.

Prediction of narrow N* and Λ* resonances with hidden charm above 4 GeV.

The interaction between various charmed mesons and charmed baryons is studied within the framework of the coupled-channel unitary approach with the local hidden gauge formalism. Several meson-baryon dynamically generated narrow N* and Λ* resonances with hidden charm are predicted with mass above 4 GeV and width smaller than 100 MeV. The predicted new resonances definitely cannot be accommodated by quark models with three constituent quarks and can be looked for in the forthcoming PANDA/FAIR experiments.

Anterior maxillary segmental distraction for correction of maxillary hypoplasia and dental crowding in cleft palate patients: a preliminary report.

To evaluate the feasibility of anterior maxillary segmental distraction (AMSD) to correct maxillary hypoplasia and severe dental crowding in cleft lip and palate (CLP) patients, 7 patients (average age 16.4 years) with maxillary hypoplasia, shortened maxillary dental arch length and severe anterior dental crowding secondary to CLP were selected for this study. After anterior maxillary segmental osteotomy, 3 patients were treated using bilateral internal distraction devices, and 4 patients were treated using rigid external distraction devices. Photographs and radiographs were taken to review the improvement in facial profile and occlusion after distraction. An average 10.25 mm anterior maxillary advancement was obtained in all patients after 10-23 days of distraction and 9-16 weeks of consolidation. The sella-nasion-point A (SNA) angle increased from 69.5 degrees to 79.6 degrees. Midface convexity was greatly improved and velopharyngeal competence was preserved. The maxillary dental arch length was greatly increased by 10.1 mm (P<0.01). Dental crowding and malocclusion were corrected by orthodontic treatment. These results show that AMSD can effectively correct the hypoplastic maxilla and severe dental crowding associated with CLP by increasing the midface convexity and dental arch length while preserving velopharyngeal function, and dental crowding can be corrected without requiring tooth extraction.

Tailoring optical transmission via the arrangement of compound subwavelength hole arrays.

The transmission properties of light through metal films with compound periodic subwavelength hole arrays is numerically investigated by using the finite-difference time-domain (FDTD) method. The sharp dips in the transmission bands, together with the suppression of surface Plasmon resonance (SPR) (0, 1) peak, are found when two square holes in every unit cell are arranged asymmetrically along the polarization direction of the incident light. However, the shape of transmission spectra is not sensitive to the symmetry if the holes are arranged perpendicular to the propagation direction of surface plasmon polaritons (SPPs). The physics origin of these phenomena is explained qualitatively by the phase resonance of SPPs.

Broadband coherent emission observed in polycrystalline CdSSe nanowires under high excitation.

Polycrystalline CdSSe nanowires were prepared with a low-temperature physical evaporation method. Structural analysis combining HRTEM with XRD demonstrate that these as-prepared wires have a hexagonal wurtzite structure with a polycrystalline nature. Locally excited optical measurements show that though these wires can still act as waveguide cavities, their polycrystalline nature will induce a significant redshift of the emitted light during its transportation along them. Power dependent photoluminescence measurement shows that these polycrystalline wires can achieve broadband coherent emission at the band-edge band under high excitation, which shows marked contrast with the much narrower and multimode spectra observed in the single-crystalline nanowires with the same elemental composition. Time-resolved photoluminescence further confirms the occurrence of coherent emission in these wires, which originates from the electron-hole plasma (EHP) recombination of high-density carriers generated under high excitation. These kinds of polycrystalline alloy nanowires with broadband coherent emission should have potential uses in nano-scaled wavelength tunable light-emitting devices.

A wide bandgap plasmonic Bragg reflector.

Surface plasmon polaritons (SPPs) Bragg reflector with more excellent optical properties are investigated numerically. By introducing a finite array of periodic grooves on the two surfaces of metal-insulator-metal (MIM) waveguide, we fulfill the periodical changes of effective refractive index, which leads to the photonic band gap (PBG). And it has been further widened by inserting a dielectric material with higher refractive index in the waveguide with narrow slit width. Finite difference time domain (FDTD) simulation confirms the widened bandgap. In addition, a SPP nanocavity is introduced by breaking the periodicity of our proposed structure.

Quantum size effect on surface photovoltage spectra: alpha-Fe(2)O(3) nanocrystals on the surface of monodispersed silica microsphere.

A new method for the preparation of Fe(2)O(3) nanoparticle/SiO(2) microsphere composites is described, in which fine alpha-Fe(2)O(3) nanocrystals were prepared by forced hydrolysis of FeCl(3) aqueous solution. The structure and optical spectra of these alpha-Fe(2)O(3) nanocrystals have been studied. Their visible optical absorption can be enhanced by their adsorptions on the surface of SiO(2) microspheres and thereafter simple packing of these microspheres to the aggregated structures. The size-dependent photogenerated surface photovoltage spectra (SPS) of these composites were studied, and quantum confinement effects of the SPS properties were observed. The transport of photoinduced charges between nanocrystals with intrinsic electronic nature of confined states accounts for this phenomenon. These results are helpful in understanding the relationship among d-d transition and charge-transfer transition in transition metal oxides and find applications in photovoltaic devices.

Mass and KLamda coupling of the N*(1535).

Using a resonance isobar model and an effective Lagrangian approach, from recent BES results on J/psi-->ppeta and psi-->pK+Lamda, we deduce the ratio between effective coupling constants of N*(1535) to KLamda and peta to be R=gN*(153)KLamda/gN*(1535)peta=1.3+/-0.3. With the previous known value of gN*(1535)peta, the obtained new value of gN*(1535)KLamda is shown to reproduce recent pp-->pK+Lamdanear-threshold cross section data as well. Taking into account this large N*KLamda coupling in the coupled channel Breit-Wigner formula for the N*(1535), its Breit-Wigner mass is found to be around 1400 MeV, much smaller than the previous value of about 1535 MeV obtained without including its coupling to KLamda. The implication on the nature of N*(1535) is discussed.

ss component of the proton and the strangeness magnetic moment.

A complete analysis is given of the implications of the empirical indications for a positive strangeness magnetic moment mu(s) of the proton on the possible configurations of the uudss component of the proton. A positive value for mu(s) is obtained in the ss configuration where the uuds subsystem is in an orbitally excited state with [4](FS)[22](F)[22](S) flavor-spin symmetry, which is likely to have the lowest energy. The configurations in which the s is orbitally excited, which include the conventional Kappa(+)lambda(0) configuration, with the exception of that in which the uuds component has spin 2, yield negative values for mu(s). The hidden strangeness analogues of recently proposed quark cluster models for the theta(+) pentaquark give differing signs for mu(s).

Characterization and third-order optical nonlinearities of uniform surface-modified CdS nanoparticles.

Size-controlled uniform surface-capped CdS nanoparticles were readily prepared by an improved inverse microemulsion technique using hexanethiol as co-surfactant. The third-order optical nonlinearities were studied for the first time by newly-developed Z-scan technique, from which the enhanced nonlinear optical responses were observed after heat-treatment.