Emission wavelength tuning of fluorescence by fine structural control of optical metamaterials with Fano resonance.

We demonstrated fine emission wavelength tuning of quantum dot (QD) fluorescence by fine structural control of optical metamaterials with Fano resonance. An asymmetric-double-bar (ADB), which was composed of only two bars with slightly different bar lengths, was used to obtain Fano resonance in the optical region. By changing the short bar length of ADB structures with high dimensional accuracy in the order of 10 nm, resonant wavelengths of Fano resonance were controlled from 1296 to 1416 nm. Fluorescence of QDs embedded in a polymer layer on ADB metamaterials were modified due to coupling to Fano resonance and fine tuning from 1350 to 1376 nm was observed. Wavelength tuning of modified fluorescence was reproduced by analysis using absorption peaks of Fano resonance. Tuning range of modified fluorescence became narrow, which was interpreted by a simple Gaussian model and resulted from comparable FWHM in QD fluorescence and Fano resonant peaks. The results will help the design and fabrication of metamaterial devices with fluorophores such as light sources and biomarkers.

Are current case-finding methods under-diagnosing tuberculosis among women in Myanmar? An analysis of operational data from Yangon and the nationwide prevalence survey.

BACKGROUND: Although there is a large increase in investment for tuberculosis control in Myanmar, there are few operational analyses to inform policies. Only 34% of nationally reported cases are from women. In this study, we investigate sex differences in tuberculosis diagnoses in Myanmar in order to identify potential health systems barriers that may be driving lower tuberculosis case finding among women. METHODS: From October 2014 to March 2015, we systematically collected data on all new adult smear positive tuberculosis cases in ten township health centres across Yangon, the largest city in Myanmar, to produce an electronic tuberculosis database. We conducted a descriptive cross-sectional analysis of sex differences in tuberculosis diagnoses at the township health centres. We also analysed national prevalence survey data to calculate additional case finding in men and women by using sputum culture when smear microscopy was negative, and estimated the sex-specific impact of using a more sensitive diagnostic tool at township health centres. RESULTS: Overall, only 514 (30%) out of 1371 new smear positive tuberculosis patients diagnosed at the township health centres were female. The proportion of female patients varied by township (from 21% to 37%, p = 0.0172), month of diagnosis (37% in February 2015 and 23% in March 2015 p = 0.0004) and age group (26% in 25-64 years and 49% in 18-25 years, p < 0.0001). Smear microscopy grading of sputum specimens was not substantially different between sexes. The prevalence survey analysis indicated that the use of a more sensitive diagnostic tool could result in the proportion of females diagnosed at township health centres increasing to 36% from 30%. CONCLUSIONS: Our study, which is the first to systematically compile and analyse routine operational data from tuberculosis diagnostic centres in Myanmar, found that substantially fewer women than men were diagnosed in all study townships. The sex ratio of newly diagnosed cases varied by age group, month of diagnosis and township of diagnosis. Low sensitivity of tuberculosis diagnosis may lead to a potential under-diagnosis of tuberculosis among women.

Comb-drive tracking and focusing lens actuators integrated on a silicon-on-insulator wafer.

This paper reports integrated tracking (horizontal) and focusing (vertical) actuators using microelectromechanical (MEMS) technology for optical storage. The design, fabrication and characterization of the integrated tracking and focusing actuators are demonstrated. The integrated tracking and focusing lens actuators that consist of springs, a lens holder and comb-drive actuators are implemented to obtain the two-dimensional tuning effect of an objective lens. A two-mask process is used to define the actuators on a silicon-on-insulator (SOI) wafer. The DC displacements and the frequency responses are characterized by applying voltage to the micro lens actuators. Displacements are experimentally characterized with ± 24.6µm in tracking direction and 5.7µm in focusing direction. Moreover, the influences of the cross-axis coupling are measured and evaluated. This MEMS device which has a small form factor provides an excellent response time and size reduction. The minimization and integration of the lens actuators can offer low costs in assembly and expand the application area of the optical head.

A 100 nm thick InGaN/GaN multiple quantum-well column-crystallized thin film deposited on Si(111) substrate and its micromachining.

A 100 nm thick InGaN/GaN multiple quantum-well column-crystallized thin film was deposited on Si(111) substrate, with InN as the interlayer, by molecular beam epitaxy. The diameter of the column crystal is about 40 nm. Transmission electron microscopy images showed clear five-period well layers. Photoluminescence measurements demonstrated a wide emission wavelength from about 500 to 800 nm with the full width at half maximum of 107 nm at room temperature. An unusual photoluminescence peak position shift was observed from the optical measurement. The selected area electron diffraction image demonstrated the hexagonal wurtzite structure of the column crystal. A self-supported GaN-based active subwavelength grating was proposed, and the active subwavelength grating structure was fabricated from the InGaN/GaN quantum-well thin film by a Si micromachining process.

Group IVA phospholipase A2-mediated production of fibronectin by oxidized LDL in mesangial cells.

The deposition of atherogenic lipoproteins such as oxidized low-density lipoprotein (oxLDL) within the mesangium is involved in the overproduction of extracellular matrix proteins, a key event in the progression of glomerular diseases including glomerulosclerosis. To clarify the mechanisms underlying the oxLDL-induced production of extracellular matrix proteins, we examined the possible involvement of group IVA phospholipase A(2) (PLA(2)) using human mesangial cells and group IVA PLA(2)-deficient mouse mesangial cells. oxLDL accelerated the production of fibronectin and collagen (type IV), components of extracellular matrix proteins, with the preceding release of arachidonic acid. Methyl arachidonyl fluorophosphonate (MAFP), known as an inhibitor of group IVA PLA(2), markedly suppressed the oxLDL-induced production of fibronectin as well as the release of arachidonic acid, whereas it did not inhibit the production of collagen. The inhibitory effect of MAFP on the production of fibronectin was reversed by adding arachidonic acid and 12-hydroxyeicosatetraenoic acid. Furthermore, we found that in group IVA PLA(2)-deficient mouse mesangial cells, the production of fibronectin in response to oxLDL was weak as compared with that in wild-type cells. However, the production by oxLDL of collagen was not suppressed in the group IVA PLA(2)-deficient cells. These findings suggest that group IVA PLA(2) is involved in the production of fibronectin in oxLDL-stimulated mesangial cells.

Tunable wavelength filter through bending control asymmetric single-mode grating fiber.

A tunable wavelength filter based on an asymmetric single-mode grating fiber fabricated by anisotropic CF4 plasma etching is proposed. The reflection wavelength is shown to shift linearly with the degree of curvature of the bent fiber, affording a center wavelength shift of 3.5 nm at 1550 nm. In this region of wavelength shift, the rejection and half-power width of the measured spectra remain almost constant.

Spectral control of thermal emission by periodic microstructured surfaces in the near-infrared region.

Thermal emissive properties of microstructured surfaces are measured in the near-infrared region. Two-dimensional periodic microstructured surfaces with metal coatings are fabricated with Si anisotropic etching and laser ablation techniques. The structural periods of the samples are 2.0 and 1.5 microm. Clear selective-emission bands are observed experimentally. This selective emission is attributed to the resonance effect between the emissive field and the surface microstructures. In addition, numerical calculation computed with rigorous coupled-wave analysis (RCWA) is performed on the microstructured samples. The selective-emission peaks measured through experiments can be reproduced well by RCWA, and this result suggests strongly that the thermal radiation from periodic structures may have spatial coherence. It is confirmed that the surface microstructure can be applied to the control of spectral emission from high-temperature materials.

Local mechanical properties measured by atomic force microscopy for cultured bovine endothelial cells exposed to shear stress.

Morphology and mechanical properties of cultured endothelial cells were measured, using a novel atomic force microscope (AFM) system, developed in our laboratory, in conjunction with an inverted confocal laser scanning microscope. We used this system to examine endothelial cell both in static cultures and exposed to a shear stress of 2 Pa. Initially, the three-dimensional topography of a cell was measured by the AFM and a location was selected for the subsequent measurement of the mechanical response of the cell. The surface of statically cultured cell was smooth. The cell height was not altered by the exposed duration of shear stress. A relationship between external force, F, and the indentation depth, delta, was obtained for several different locations on a cell. This force-indentation response was modelled using a quadratic equation, F = adelta2 + bdelta, indicating that two parameters, a and b, will be constants which are representative of the mechanical response. Endothelial cells cultured at static conditions demonstrated a polygonal shape and less stiff mechanical characteristics around the nucleus compared to those at peripheral regions. The stiffness of the endothelial cells exposed to shear stress increased with the duration time of exposure. At 6-h exposures, the stiffness was higher at upstream side of the cell than the downstream side. However, after 24-h exposure, the stiffness was similar on both sides of the cell. These changes in the stiffness of endothelial cells when exposed to shear stress were suggested to correspond with the distribution of stress fibers in the cell.

Broadband antireflection gratings fabricated upon silicon substrates.

We fabricated a two-dimensional subwavelength structured (SWS) surface upon a crystal silicon substrate. The SWS surface was patterned by electron beam lithography and etched by an SF(6) fast atom beam. The SWS grating had a conical profile, the period was 150 nm, and the groove was approximately 350 nm deep. The reflectivity was examined at 2002500-nm wavelengths. At 400 nm the reflectivity decreased to 0.5% from the 54.7% of the silicon substrate. We also used HeNe laser light to examine the reflectivity as a function of the incident angle.

Bistability of a self-standing film caused by photothermal displacement.

We report on the bistability of a self-standing thin film caused by photothermal displacement. The sample consisted of a self-standing thin film placed in front of a mirror. By irradiating the self-standing thin film with continuous wave laser light, the self-standing thin film deflected with thermoelastic bending moment. Since a standing wave of the laser light was generated by the reflection of the mirror, the bending moment generated on the film was periodic along the optical axis. The displacement of the film was found to be bistable with the laser light intensity. Simultaneously, the light intensity reflected from the sample was also bistable. These phenomena are explained by the photothermal displacement of thin film in the standing wave of laser light.

Tautomeric phenomenon of a novel potent immunosuppressant (FK506) in solution. I. Isolation and structure determination of tautomeric compounds.

Tautomeric phenomenon was observed in the HPLC chromatogram obtained from a novel potent immunosuppressant, FK506, in ethanol solution. Two tautomeric compounds derived from FK506 were isolated and purified by HPLC. Their structures were elucidated by spectral analyses. The mechanisms for this tautomerization were also established based on the results of structure analysis.

Photothermoelastic evaluation for small mechanical structures.

We describe a photothermal technique for testing the mechanical properties of small mechanical structures. Irradiation with chopped laser light on platelike or beamlike structures produces flexural vibration caused by thermoelastic bending. By monitoring the vibration, we can develop useful techniques for evaluating thickness, size attachment, tension, and adhesion of small mechanical structures. The technique will be useful for inspecting small mechanical structures that are fabricated with lithographic processes for various high technology applications.

Moiré signals by the photoacoustic effect.

We report the detection of moiré displacement signals using the photoacoustic effect. By using the transmission and reflection (absorption) gratings with a 25microm pitch, the lateral displacement of the grating is detected from the photoacoustic signals. The probe-beam deflecton method and the microphone method are used for detecting the acoustic vibration and the acoustic pressure, respectively. The signals vary periodically as the pitch of the grating for the lateral displacement. The characteristics of the displacement signal are also examined by using the Fresnel diffraction theory.

Photothermal bending of a layered sample in plate form.

In this paper, we report a photothermal effect (drum effect) of the layered platelike sample. Irradiation of chopped laser light on the clamped plate produces flexural vibration from the thermoelastic bending if the plate is thin. The characteristics of thermoelastic bending of the layered plate are theoretically examined on the basis of the temperature moment caused by thermal wave propagation. It is shown that the layered structure of the platelike sample can be obtained from the amplitude and phase signals of the vibration. Hence this effect will be useful as a photothermal inspection technique for the layered plate. A comparison with the conventional photothermal signal is also presented for a layered sample.

Photothermoelastic probing for a clamped plate sample.

In this paper we report a photothermal probing technique for a clamped thin plate sample that uses thermoelastic bending. Irradiation of the modulated laser light focused on the clamped plate sample generates the flexural vibration caused by thermoelastic bending. By scaning with the focused beam and optically sensing the bending, the irregularity of the plate is detectable nondestructively as changes in amplitude and phase of the flexural vibration. Characteristics of thermoelastic bending are also examined from the viewpoint of bending hot spot theory.