Microlens array on flip-chip LED patterned with an ultraviolet micro-pixelated emitter

A direct-write lithographic technique for the fabrication of micro-lens arrays with an ultraviolet (UV) micro-light-emitting diode (LED) array serving as an exposure source is reported. Polymer microlens arrays of high optical quality have been fabricated on the sapphire side of a flip-chip truncated-conic (TC) LED. The properties of the lenses are evaluated by optical microscopy and atomic force microscopy. The determined focal length is close to the predicted value. The effects of microlens integration on the optical properties of the LED are investigated. © 2011 IEEE.published_or_final_versio

Angularly uniform white light-emitting diodes using an integrated reflector cup

We report on white light-emitting diodes (LEDs) with a truncated-conical (TC) geometry produced by laser micromachining. A blue LED was shaped into a circular disc with 50°-inclined sidewall using a modified laser micromachining setup. A layer of Al was coated onto the inclined sidewall and the bottom surface to form an integrated reflector. Due to the highly reflective mirror, laterally propagating photons are redirected into the upward direction, contributing to an increase of 21.7% of light intensity in the normal direction. With quantum dots applied to the surface, white light emission from this TC-LED structure demonstrated a 37% enhancement in color uniformity, compared with a conventional device. © 2010 IEEE.published_or_final_versio

Fiber-coupled light-emitting diode with a capillary-bonded hemispherical lens

A hemispherical lens capillary-bonded to an InGaN flip-chip light-emitting diode (LED) is demonstrated to efficiently couple light to a plastic optical fiber. The BK-7 hemispherical lens is bonded onto a circularly shaped LED chip with inclined sidewalls cut by laser-micromachining, so that lateral emissions are effectively suppressed. Capillary bonding minimizes air-gap between chip and lens enabling transmission of evanescent waves, thus maximizing overall optical transmission. With the lens attached, emission divergence from the assembly is significantly reduced, diverting rays into the acceptance cone of the fiber. Fiber coupling efficiency as high as 53.8% has been demonstrated. © 2011 IEEE.published_or_final_versio

Vertically mounted InGaN-on-Sapphire light-emitting diodes

An InGaN/GaN light-emitting diode (LED) chip mounted in a vertical configuration (vmLED) is demonstrated, exhibiting significant enhancement to light extraction, compared with a LED mounted in a conventional planar geometry. By flipping the chip orthogonally, two large illumination surfaces of the device are exposed for direct light extraction. Comparisons, through ray-trace modeling and experiment data with conventional surface-mounted LEDs, indicate that the vmLEDs achieve superior light extraction efficiency. A sapphire-prism-mounted vmLED is further proposed to improve heat sinking, which is well suited for higher current operations. © 2006 IEEE.published_or_final_versio

Improved interfacial and electrical properties of GaAs metal-oxdiesemiconductor capacitors with HfTiON as gate dialectric and TaON as Passivation interlayer

published_or_final_versio

Pixel-to-pixel fiber-coupled emissive micro-light-emitting diode arrays

We report on an integrated fiber-coupled bi-linear micro-light-emitting diode array, serving as a portable microdisplay system. The fiber bundle transforms the bi-linearly arranged optical signals from the emissive array into a 6-by-8 pixel microdisplay, offering a crisp and clear optical output. The pixel-to-pixel coupling arrangement ensures optical coupling efficiency. Due to the narrow acceptance cones of optical fibers, individual pixels can be well resolved with minimal crosstalk. The performance and functionality of this optical system is fully evaluated. A model to determine the fiber-coupling efficiency was constructed; it was found that the simulated results compare well with the measured data.published_or_final_versio

Relationship between gene co-expression and probe localization on microarray slides

BACKGROUND: Microarray technology allows simultaneous measurement of thousands of genes in a single experiment. This is a potentially useful tool for evaluating co-expression of genes and extraction of useful functional and chromosomal structural information about genes. RESULTS: In this work we studied the association between the co-expression of genes, their location on the chromosome and their location on the microarray slides by analyzing a number of eukaryotic expression datasets, derived from the S. cerevisiae, C. elegans, and D. melanogaster. We find that in several different yeast microarray experiments the distribution of the number of gene pairs with correlated expression profiles as a function of chromosomal spacing is peaked at short separations and has two superimposed periodicities. The longer periodicity has a spacing of 22 genes (~42 Kb), and the shorter periodicity is 2 genes (~4 Kb). CONCLUSION: The relative positioning of DNA probes on microarray slides and source plates introduces subtle but significant correlations between pairs of genes. Careful consideration of this spatial artifact is important for analysis of microarray expression data. It is particularly relevant to recent microarray analyses that suggest that co-expressed genes cluster along chromosomes or are spaced by multiples of a fixed number of genes along the chromosome

An introduction to Graph Data Management

A graph database is a database where the data structures for the schema and/or instances are modeled as a (labeled)(directed) graph or generalizations of it, and where querying is expressed by graph-oriented operations and type constructors. In this article we present the basic notions of graph databases, give an historical overview of its main development, and study the main current systems that implement them

Screening of antioxidant properties of the apple juice using the front-face synchronous fluorescence and chemometrics

Fluorescence spectroscopy is gaining increasing attention in food analysis due to its higher sensitivity and selectivity as compared to other spectroscopic techniques. Synchronous scanning fluorescence technique is particularly useful in studies of multi-fluorophoric food samples, providing a further improvement of selectivity by reduction in the spectral overlapping and suppressing light-scattering interferences. Presently, we study the feasibility of the prediction of the total phenolics, flavonoids, and antioxidant capacity using front-face synchronous fluorescence spectra of apple juices. Commercial apple juices from different product ranges were studied. Principal component analysis (PCA) applied to the unfolded synchronous fluorescence spectra was used to compare the fluorescence of the entire sample set. The regression analysis was performed using partial least squares (PLS1 and PLS2) methods on the unfolded total synchronous and on the single-offset synchronous fluorescence spectra. The best calibration models for all of the studied parameters were obtained using the PLS1 method for the single-offset synchronous spectra. The models for the prediction of the total flavonoid content had the best performance; the optimal model was obtained for the analysis of the synchronous fluorescence spectra at Delta lambda = 110 nm (R (2) = 0.870, residual predictive deviation (RPD) = 2.7). The optimal calibration models for the prediction of the total phenolic content (Delta lambda = 80 nm, R (2) = 0.766, RPD = 2.0) and the total antioxidant capacity (Delta lambda = 70 nm, R (2) = 0.787, RPD = 2.1) had only an approximate predictive ability. These results demonstrate that synchronous fluorescence could be a useful tool in fast semi-quantitative screening for the antioxidant properties of the apple juices.info:eu-repo/semantics/publishedVersio

Quasi-particle interference and superconducting gap in a high-temperature superconductor Ca2-xNaxCuO2Cl2

High-transition-temperature (high-Tc) superconductivity is ubiquitous in the cuprates containing CuO2 planes but each cuprate has its own character. The study of the material dependence of the d-wave superconducting gap (SG) should provide important insights into the mechanism of high-Tc. However, because of the 'pseudogap' phenomenon, it is often unclear whether the energy gaps observed by spectroscopic techniques really represent the SG. Here, we report spectroscopic imaging scanning tunneling microscopy (SI-STM) studies of nearly-optimally-doped Ca2-xNaxCuO2Cl2 (Na-CCOC) with Tc = 25 ~ 28 K. They enable us to observe the quasi-particle interference (QPI) effect in this material, through which unambiguous new information on the SG is obtained. The analysis of QPI in Na-CCOC reveals that the SG dispersion near the gap node is almost identical to that of Bi2Sr2CaCu2Oy (Bi2212) at the same doping level, while Tc of Bi2212 is 3 times higher than that of Na-CCOC. We also find that SG in Na-CCOC is confined in narrower energy and momentum ranges than Bi2212. This explains at least in part the remarkable material dependence of TcComment: 13pages, 4fig