Time-domain Brillouin imaging of sound velocity and refractive index using automated angle scanning.

We present a picosecond optoacoustic technique for mapping both the longitudinal sound velocity v and the refractive index n in solids by automated measurement at multiple probe incidence angles in time-domain Brillouin scattering. Using a fused silica sample with a deposited titanium film as an optoacoustic transducer, we map v and n in the depth direction. Applications include the imaging of sound velocity and refractive index distributions in three dimensions in inhomogeneous samples such as biological cells.

Odontogenic Infection Pathway to the Parapharyngeal Space: CT Imaging Assessment.

Introduction: Parapharyngeal space infection may lead to severe and potentially life-threatening complications. The aim of this study was to assess the odontogenic infection pathway to the parapharyngeal space using CT imaging. Materials and Methods: Nineteen patients in mandibular odontogenic infections with abscess who underwent contrast-enhanced CT were evaluated in this study. We reviewed the location of abscess and spread of odontogenic infections to the different components of the buccal space, submandibular space, sublingual space, masticator space and parapharyngeal space using CT imaging. The location of abscess and spread of odontogenic infections were analyzed with the Pearson Chi-square test. Results: Regarding the odontogenic infection pathway to parapharyngeal space, the masticator space (100%) was the most frequent, followed by the buccal space (85.7%), submandibular space (85.7%) and sublingual space (57.1%), while those without parapharyngeal space, the submandibular space (83.3%) was the most frequent, followed by the buccal space (75.0%), masticator space (58.3%) and sublingual space (33.3%). The masticator space was significant space in patients with/without parapharyngeal space infection (P = 0.047). Conclusion: CT imaging could be an effective method in assessment of odontogenic infection pathway to the parapharyngeal space. The odontogenic infection in masticator space tends to display spread of parapharyngeal space.

Diagnosis of root fractures using cone-beam computed tomography: difference of vertical and horizontal root fracture.

OBJECTIVES: The aim of this study was to investigate the occurrence of vertical and horizontal root fractures using cone-beam computed tomography (CBCT). METHODS: We reviewed the CBCT images of 51 patients who were examined by CBCT for the diagnosis of root fracture. The occurrences of vertical and horizontal root fractures were investigated concerning the pulpal vitality and the kind of tooth, and analyzed by cross-tabulation. The fracture direction of vertical root fracture and the fracture angle were also investigated, and analyzed by cross-tabulation and Kruskal-Wallis test, respectively. RESULTS: The occurrence of vertical and horizontal root fractures was statistically significantly different between vital tooth and non-vital tooth (p = 0.044). The occurrence of vertical and horizontal root fractures was also different among anterior, premolar, and molar teeth (p = 0.004). The kind of tooth on traumatized tooth was only anterior teeth and the number was larger on horizontal root fracture. The occurrence of vertical and horizontal root fractures on non-traumatized tooth was different among the kind of tooth (p = 0.007), and the number of vertical root fracture was larger than that of horizontal root fracture on premolar teeth. Fracture direction was not different, but the fracture angle was different among the kind of tooth on vertical root fracture (p = 0.027). CONCLUSIONS: The results suggested that the number of vertical root fracture was larger on non-vital tooth and that of horizontal root fracture was larger on vital tooth. The number of vertical root fracture was larger on premolar teeth.

Forming temperature of ethylene vinyl acetate sheets for fabrication of vacuum-formed mouthguards.

BACKGROUND/AIMS: The appropriate heating temperature for the fabrication of mouthguards using ethylene vinyl acetate sheets is reported to be 80-120°C. However, the measurement side of the heating temperature has not been determined. The aim of this study was to investigate the influence of the measurement side of the heating temperature when fabricating mouthguards. MATERIALS AND METHODS: Mouthguard sheets of 3.8 mm ethylene vinyl acetate were vacuum-formed on working models until the sheet was heated to 120°C. The sheet temperature was measured at the upper side and the lower side. The thickness of the mouthguard was measured at the labial surface of the central incisor, and the buccal and occlusal surfaces of the first molar. The fit of the mouthguard was examined at the central incisor and the first molar by measuring the distance between the mouthguard and the cervical margin of the working model. Differences in the thickness and fit of the mouthguards were analyzed by two-way analysis of variance. RESULTS: Mouthguard thickness varied among the measured regions of the central incisors and first molars (P < .01). The thicknesses at the labial surface of the central incisor and buccal surface of the first molar were larger when the sheet temperature measured at the lower side was 120°C compared to when the sheet temperature measured at the upper side was 120°C (P < .01). The fit of the mouthguard was better when the sheet temperature measured at the lower side was 120°C (P < .05). CONCLUSIONS: The sheet temperature should be measured at the lower side of the sheet and it should be 120°C for fabricating mouthguards.

Flower-like surface modification of titania materials by lithium hydroxide solution.

Surface modification of titania materials to give flower-like structures has been achieved simply by the treatment in lithium hydroxide aqueous solution under mild conditions. The flower-like structured materials were characterized by X-ray diffraction, thermogravimetric analysis, and Raman scattering. The analyses indicate that the flower-like materials are composed of layered hydrous lithium titanate. It is suggested that the unique intercalation behavior of lithium ions into titania allows dissolution and re-precipitation of titania to form the flower-like structure. The obtained flower-like structure can be retained up to 700 °C, while the crystal phase transforms into Li(4)Ti(5)O(12).

Phase-shifting electron holography for atomic image reconstruction.

Phase-shifting electron holography was used to reconstruct the object-wave function of high-spatial-frequency specimens of HgCdTe, and the requirements for precise measurements were investigated. Fresnel fringes due to the electrostatic biprism caused serious calculation errors during the phase-shifting reconstruction. Uniform interference fringes, obtained by adjusting the biprism voltage to cancel out the Fresnel fringes, were needed to minimize these errors. High-resolution holograms of a HgCdTe single crystal were recorded with coarse interference fringes and a high visibility of 65% and then used to reconstruct the atomic-scale object wave. Although the spatial resolution (0.25 nm) of the transmission electron microscope was worse than the separation (0.16 nm) between Hg (or Cd) and Te columns, the crystal polarity was determined from the aberration-corrected object wave.

Sculpted substrates for SERS.

Sculpted SERS-active substrates are prepared by assembling a closed packed monolayer of uniform polystyrene colloidal particles (diameter 350 to 800 nm) onto an evaporated gold surface and then electrodepositing gold through this template to produce films with controlled thicknesses, measured as fractions of the sphere diameter, d. The resulting surfaces consist of a regular hexagonal array of interconnected spherical cross-section dishes. The role of localised plasmons in determining the SERS enhancement factor obtained for benzene thiol adsorbed onto the surfaces is then investigated by correlation of the UV-visible reflectance spectra, 400 to 900 nm, measured at the same positions on the substrate surfaces, with the SERS spectra. The results are interpreted in terms of the relative contributions of plasmons that are free to propagate across the top surface and those trapped within the dishes of the sculpted surface.

Strong coupling of light to flat metals via a buried nanovoid lattice: the interplay of localized and free plasmons.

We study the optical plasmonic properties of metal surfaces which have a periodic lattice of voids buried immediately beneath their flat upper surface. Light reflection spectra calculated in the framework of a self-consistent electromagnetic multiple-scattering layer-KKR approach exhibit two types of plasmon resonances originating from the excitation of different plasmon modes: surface plasmon-polaritons propagating on the planar surface of metal and Mie plasmons localized in the buried voids. Coupling between these two types of plasma oscillation leads to an enhancement of the surface plasmon-polariton resonances even for close-packed void lattices. Our theoretical model quantitatively agrees with experimental results, demonstrating that planar surfaces can exhibit strong plasmonic field enhancements.

Mie plasmon enhanced diffraction of light from nanoporous metal surfaces.

The diffractive properties of gold films with a periodic lattice of sub-micron voids beneath the surface are investigated. It has been shown that nanoporous metal surfaces exhibit frequency-selective non-dispersive diffraction enhanced by Mie plasmons in nanovoids, which leads to absolute angular tolerance of the diffracted beam intensity that can be useful for a variety of applications covering angle-tolerant optical filters, deflectors, absorbers, and beam splitters. Diffraction spectra are measured and calculated to support these conclusions, showing good qualitative agreement.

Angle-resolved surface-enhanced Raman scattering on metallic nanostructured plasmonic crystals.

Surface-enhanced Raman scattering is an ideal tool for identifying molecules from the "fingerprint" of their molecular bonds; unfortunately, this process lacks a full microscopic understanding and, practically, is plagued with irreproducibility. Using nanostructured metal surfaces, we demonstrate strong correlations between plasmon resonances and Raman enhancements. Evidence for simultaneous ingoing and outgoing resonances in wavelength and angle sheds new light on the Raman enhancement process, allowing optimization of a new generation of reproducible Raman substrates.