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Selected AbstractsEffects of pressure on the activity and spectroscopic properties of carboxyl proteinasesFEBS JOURNAL, Issue 3 2001Apparent correlation of pepstatin-insensitivity, pressure response The pressure dependence of the activity and spectroscopic properties of four carboxyl proteinases were investigated. Two were pepstatin-sensitive carboxyl proteinases (porcine pepsin and proteinase A from baker's yeast) and two were pepstatin-insensitive carboxyl proteinases (from Pseudomonas sp. 101 (pseudomonapepsin; PCP) and Xanthomonas sp. T-22 (xanthomonapepsin; XCP)). The specificity constant [kcat/Km(app)] of PCP and XCP for a synthetic peptide substrate showed only a slight decrease with increasing pressure, whereas pepsin and proteinase A showed substantial disactivation at higher pressures. The calculated apparent activation volume (,Vkcat/Km) was about 1, 3, 13, and 14 mL·mol,1 for PCP, XCP, pepsin, and proteinase A, respectively. The hydrolysis of acid-denatured myoglobin by the four carboxyl proteinases was only slightly affected by high pressure (except for proteinase A at 400 MPa), in contrast to the results for the peptide hydrolysis. In fact, PCP, XCP, and proteinase A actually showed slightly higher degradations of acid-denatured myoglobin at higher pressures. The residual activities of these enzymes after the incubation at high pressures implied a pressure-induced stabilization towards autolysis. The changes in the fourth derivative near-UV absorbance spectrum of the four enzymes in aqueous solution were measured at various pressures from 0.1 to 400 MPa. Upon an increase in pressure, the peaks from PCP and XCP red-shifted slightly, whereas pepsin and proteinase A blue-shifted substantially, thus indicating a more polar environment. The intrinsic fluorescence also decreased upon increasing pressure. However, the change for XCP was rather small, but the change for the other three was very large. The changes in the peak wavelength for pepsin and proteinase A were characteristic, and also indicated a more polar environment under high pressure. An analysis by the center of spectra mass (CSM) gave the ,G and ,V of transition as 9.8 kJ·mol,1 and ,24 mL·mol,1 (pepsin) and 11.7 kJ·mol,1 and ,43 mL·mol,1 (proteinase A), respectively, by assuming a simple two-state transition. The circular dichroism (CD) showed relatively small changes after 1-h incubations at 400 MPa, indicating that the secondary structures were largely maintained. [source] Selective Angle Electroluminescence of Light-Emitting Diodes based on Nanostructured ZnO/GaN HeterojunctionsADVANCED FUNCTIONAL MATERIALS, Issue 21 2009Hang-Kuei Fu Abstract Selective angle electroluminescence of violet light with a peak wavelength of 405,nm from light-emitting diodes based on nanostructured p-GaN/ZnO heterojunctions is reported. The fabrication of well-aligned nanobottles with excellent crystalline quality is achieved by chemical vapor deposition at temperatures as low as 450,°C with a specially designed upside-down arrangement of substrate configuration. Selective angle light sources are essential in our daily life. With the geometry of the nanobottle waveguides, it is very easy to realize such a practical application. Therefore, the discovery reported here should be very useful for the future development of many unique optoelectronic devices. [source] Rational Design of Charge-Neutral, Near-Infrared-Emitting Osmium(II) Complexes and OLED FabricationADVANCED FUNCTIONAL MATERIALS, Issue 16 2009Tsang-Chi Lee Abstract A new series of charge neutral Os(II) isoquinolyl triazolate complexes (1,4) with both trans and cis arrangement of phosphine donors are synthesized, and their structural, electrochemical and photophysical properties are established. In sharp contrast to the cis -arranged complexes 2,4, the trans derivative 1, which shows a planar arrangement of chromophoric N -substituted chelates, offers the most effective extended , -delocalization and hence the lowest excited state energy gap. These complexes exhibit phosphorescence with peak wavelengths ranging from 692,805,nm in degassed CH2Cl2 at room temperature. Near-infrared (NIR)-emitting electroluminescent devices employing 6,wt % of 1 (or 4) doped in Alq3 host material are successfully fabricated. The devices incorporating 1 as NIR phosphor exhibit fairly intense emission with a peak wavelength at 814,nm. Forward radiant emittance reaches as high as 65.02,µW,cm,2, and a peak EQE of ,1.5% with devices employing Alq3, TPBi and/or TAZ as electron-transporting/exciton-blocking layers. Upon switching to phosphor 4, the electroluminescence blue shifts to 718,nm, while the maximum EQE and radiance increase to 2.7% and 93.26 (,W,cm,2) respectively. Their performances are optimized upon using TAZ as the electron transporting and exciton-blocking material. The OLEDs characterized represent the only NIR-emitting devices fabricated using charge-neutral and volatile Os(II) phosphors via thermal vacuum deposition. [source] Color stability of frozen whole tilapia exposed to pre-mortem treatment with carbon monoxideJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 8 2008David Mantilla Abstract BACKGROUND: Color of muscle foods plays a major role in consumer perception of meat quality. Carbon monoxide (CO) has been successfully used for improving color of packaged meat and fish products. In this study, we wanted to investigate pre-mortem treatment of live tilapia using 100% CO for its ability to improve the color of frozen whole tilapia. We compared untreated and CO-treated whole, gutted tilapia, frozen for 2 and 4 months at , 20 °C. Frozen tilapia samples were thawed overnight at 4 °C, filleted and analyzed for their color, heme peak wavelength and CO concentration. RESULTS: Euthanasia using CO significantly increased redness (a* value) and lightness (L* value) of tilapia white and red muscle. Frozen storage significantly (P < 0.05) decreased redness of both CO-treated and untreated tilapia. However, even after 4 months of frozen storage, a*-value of CO-treated tilapia was similar to fresh untreated tilapia fillets. Heme peak wavelengths of CO-euthanized tilapia were higher than in untreated tilapia and there was no significant (P > 0.05) decrease in heme peak wavelengths of CO-treated tilapia white and red muscle during frozen storage. The CO content of frozen euthanized tilapia fillets was significantly (P > 0.05) higher than in untreated fillets. In general, red muscle tissue of euthanized tilapia had a higher concentration of CO than white muscle. CONCLUSION: Color stability of tilapia fillets was significantly improved by pre-mortem CO treatment. The color of CO-treated fillets was retained during frozen storage compared to untreated fillets. Hence, pre-mortem CO treatment could be used as a new method for improving color of tilapia. Copyright © 2008 Society of Chemical Industry [source] Evolution of the 3.3-,m emission feature in the Red RectangleMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2003In-Ok Song ABSTRACT Medium-resolution infrared spectroscopic observations of the biconical Red Rectangle nebula in the region of the 3.3-,m unidentified infrared (UIR) emission band are reported. The data were recorded at UKIRT using CGS4 and have allowed the peak wavelength, width, profile and intensity of the 3.3-,m feature to be investigated as a function of offset from the central star HD 44179. Analysis of the profile of the feature along the north-western bicone interface shows an evolution from Type 2 to Type 1 in the classification of Tokunaga et al. The 3.3-,m band recorded on-star shows a close fit to a Lorentzian profile, possibly suggesting a single class of carriers. Subtraction of the Lorentzian fit to the on-star spectrum from the spectrum at each offset reveals a new ,3.28'-,m emission feature that grows in intensity relative to the main 3.3-,m band as a function of distance from the central star. The 3.28-,m emission band at large offset appears to correspond well in wavelength and FWHM with an absorption feature seen towards the Galactic Centre. [source] Performance of high-power III-nitride light emitting diodesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2008G. Chen Abstract The performance of III-nitride based high-power light emitting diodes (LEDs) is reviewed. Direct color high-power LEDs with 1 × 1 mm2 chip size in commercial LUXEON® Rebel packages are shown to exhibit external quantum efficiencies at a drive current of 350 mA ranging from ,60% at a peak wavelength of ,420 nm to ,27% at ,525 nm. The short wavelength blue LED emits ,615 mW at 350 mA and >2 W at 1.5 A. The green LED emits ,110 lm at 350 mA and ,270 lm at 1.5 A. Phosphor-conversion white LEDs (1 × 1 mm2 chip size) are demonstrated that emit ,126 lm of white light when driven at 350 mA and 381 lm when driven at 1.5 A (Correlated Color Temperature, CCT , 4700 K). In a similar LED that employs a double heterostructure (DH) insign instead of a multi-quantum well (MQW) active region, the luminous flux increases to 435 lm (CCT , 5000 K) at 1.5 A drive current. Also discussed are experimental techniques that enable the separation of internal quantum efficiency and extraction efficiency. One technique derives the internal quantum efficiency from temperature and excitation-dependent photoluminescence measurements. A second technique relies on variable-temperature electroluminescence measurements and enables the estimation of the extraction efficiency. Both techniques are shown to yield consistent results and indicate that the internal quantum efficiency of short wavelength blue (, , 420 nm) high-power LEDs is as high as 71% even at a drive current of 350 mA. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Application of microsize light-emitting diode structure for monolithic optoelectronic integrated circuitsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2007S. Y. Moon Abstract A Si/III,V,N alloys/Si structure was grown on a Si substrate by solid-source molecular beam epitaxy (SSMBE) with an rf plasma nitrogen source and electron-beam (EB) evaporator. A two-dimensional (2D) growth mode was maintained during the growth of all layers. High-resolution X-ray diffraction (HRXRD) revealed that the structure had a small lattice mismatch to the Si substrate. InGaPN/GaPN double-heterostructure (DH) light-emitting diodes (LEDs) were fabricated on Si/III,V,N alloys/Si structure. The various sized LEDs were fabricated to put into the MOSFET for monolithic optoelectronic integrated circuits (OEIC). The luminescence properties of LEDs were evaluated by electroluminescence (EL). A double emission peak from all LED samples was observed at about 642 nm and 695 nm at room temperature (RT). As injection current increased, the emission peak wavelength changed from the peak wavelength of the InGaPN layer to that of the GaPN layer, likely due to carrier overflow of the active layer. A simplified fabrication process for the microsize LED of the unit circuit was proposed. The LEDs with emission areas from 5 × 5 ,m2 to 20 × 20 ,m2 were fabricated. The LED with an emission area of 5 × 5 ,m2 can be applied to an optical device of a monolithic OEIC. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Cathodoluminescence spectral mapping of III-nitride structuresPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2004R. W. Martin Abstract The application of cathodoluminescence spectral mapping to the characterisation of a range III-nitride semiconductor structures is described. Details are presented of the instrumentation developed to carry out such measurements using an electron probe micro-analyser. The spatial resolution of the luminescence data is ,100 nm. The technique is enhanced by the ability to simultaneously perform X-ray microanalysis and electron imaging. Results are presented from epitaxially laterally overgrown GaN and InGaN/GaN structures using both single-layer SiO2 and multilayer SiO2/ZrO2 masks. Effects of strain and microcavity formation are resolved. Application of the technique to InGaN epilayers shows spatially-dependent shifts in the peak wavelength of the luminescence spectrum which correlate directly with microscopic variations in the indium content. Regions emitting at lower energy and with decreased intensity are shown to have higher InN contents, mirroring equivalent macroscopic observations. Finally the spectral mapping technique is used to analyse the luminescence from micron-scale selectively grown III-N pyramids, indicating possible formation of quantum dots at the sharp tips. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] High efficiency violet to blue light emission in porous SiC produced by anodic methodPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2010T. Nishimura Abstract Porous fluorescent (f-) SiC containing N and B was produced by anodic oxidation. The average crystal size can be controlled by adding K2S2O8 as an oxidant to dilute HF solution during the anodic process. With the reduction of the average crystal size of the porous crystal, the PL peak wavelength becomes shorter, and its intensity increases. Such behavior can be explained by the quantum size effect of donor-acceptor-pair recombination. Finally, we confirmed the superior fluorescent property of blue light emission in porous f-SiC crystal (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Metallic nanoparticle array on GaN by microsphere lithographyPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2009Giuseppe Y. Mak Abstract The optical characteristics of GaN blue-light (peak wavelength at 440 nm) light-emitting diode (LED) under the effect of localized surface plasmon (LSP) have been studied. Hexagonal arrays of triangular metallic nanoparticles deposited through a self-assembled silica microsphere mask have been fabricated using vertical deposition. By comparing the PL spectra of samples coated with Au, Al and Ag nanoparticles, it is found that Ag nanoparticles offer the most pronounced PL enhancement. The resonance wavelength was determined from optical transmission and verified by theoretical calculations. These results provide a cost-effective solution for improving the efficiency of LEDs. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] M -plane InGaN/GaN light emitting diodes fabricated by MOCVD regrowth on c -plane patterned templatesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2008Christopher A. Schaake Abstract In this work we demonstrate a light emitting diode (LED) with m -plane quantum wells fabricated on a (000) template. N-polar, n-type GaN was grown by MOCVD on vicinal sapphire substrates. Stripes, measuring 500 nm wide, 500 nm tall and spaced 2 ,m apart, were etched parallel to the ,110, direction leading to sidewalls that are approximately {100}. Sputtered AlN was used as a regrowth mask on the c -plane surfaces. An active region consisting of 5 InGaN quantum wells and GaN barriers followed by p-type was grown. The regrowth occurred mostly on the exposed m -plane sidewalls, leading to lateral growth in the ,100, direction. The LED was processed using conventional methods. A thick metal contact was used to connect the p-regions together. Current vs. voltage measurements showed good rectifying behavior with a turn on of about 6 volts. On-wafer electroluminescence measurements revealed a peak wavelength of 422 nm. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Phasing power at the K absorption edge of organic arsenicACTA CRYSTALLOGRAPHICA SECTION D, Issue 5 2003Pascal Retailleau Single/multiple-wavelength anomalous dispersion (SAD/MAD) experiments were performed on a crystal of an organic arsenic derivative of hen egg-white lysozyme. A para -arsanilate compound used as a crystallizing reagent was incorporated into the ordered solvent region of the lysozyme molecule. Diffraction data were collected to high resolution (,2.0,Å) at three wavelengths around the K edge (1.04,Å) of arsenic at beamline BM30A, ESRF synchrotron. Anomalous Patterson maps clearly showed the main arsanilate site to be between three symmetry-related lysozyme molecules, at a location previously occupied by a para -toluenesulfonate anion. MAD phases at 2,Å derived using the program SHARP led to an electron-density map of sufficient quality to start manual building of the protein model. Amplitudes from a second crystal measured to a resolution of 1.8,Å at the peak wavelength revealed two additional heavy-atom sites, which reinforced the anomalous subset model and therefore dramatically improved the phasing power of the arsenic derivative. The subsequent solvent-flattened map was of such high accuracy that the program ARP/wARP was able to build a nearly complete model automatically. This work emphasizes the great potential of arsenic for de novo structure determination using anomalous dispersion methods. [source] Oxidation of PCE with a UV LED Photocatalytic ReactorCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 1 2005D. H. Chen Abstract This paper is the first to investigate photocatalysis using a cutting-edge and energy-efficient solid-state light source: Ultraviolet (UV) Light Emitting Diodes (LED's). UV LED's do not involve mercury vapor, can be driven with direct current (DC), and have a long lifetime of 100,000 hours. UV LED's with a peak wavelength of 375,nm were tested for perchloroethylene (PCE) photocatalytic oxidation over Degussa P,25 TiO2. At a UV light output of only 49,,W/cm2, the designed reactor delivers a PCE conversion of up to 43,%. If the UV LED price continues to drop, it is very likely that UV LED's will replace UV lamps as the favored light source in photocatalysis applications. [source] Rational Design of Charge-Neutral, Near-Infrared-Emitting Osmium(II) Complexes and OLED FabricationADVANCED FUNCTIONAL MATERIALS, Issue 16 2009Tsang-Chi Lee Abstract A new series of charge neutral Os(II) isoquinolyl triazolate complexes (1,4) with both trans and cis arrangement of phosphine donors are synthesized, and their structural, electrochemical and photophysical properties are established. In sharp contrast to the cis -arranged complexes 2,4, the trans derivative 1, which shows a planar arrangement of chromophoric N -substituted chelates, offers the most effective extended , -delocalization and hence the lowest excited state energy gap. These complexes exhibit phosphorescence with peak wavelengths ranging from 692,805,nm in degassed CH2Cl2 at room temperature. Near-infrared (NIR)-emitting electroluminescent devices employing 6,wt % of 1 (or 4) doped in Alq3 host material are successfully fabricated. The devices incorporating 1 as NIR phosphor exhibit fairly intense emission with a peak wavelength at 814,nm. Forward radiant emittance reaches as high as 65.02,µW,cm,2, and a peak EQE of ,1.5% with devices employing Alq3, TPBi and/or TAZ as electron-transporting/exciton-blocking layers. Upon switching to phosphor 4, the electroluminescence blue shifts to 718,nm, while the maximum EQE and radiance increase to 2.7% and 93.26 (,W,cm,2) respectively. Their performances are optimized upon using TAZ as the electron transporting and exciton-blocking material. The OLEDs characterized represent the only NIR-emitting devices fabricated using charge-neutral and volatile Os(II) phosphors via thermal vacuum deposition. [source] Detection of Fecal Contamination on Cantaloupes Using Hyperspectral Fluorescence ImageryJOURNAL OF FOOD SCIENCE, Issue 8 2005Angela M. Vargas ABSTRACT To determine whether detection of fecal contamination on cantaloupes is possible using fluorescence imaging, hyperspectral images of cantaloupes artificially contaminated with a range of diluted bovine feces were acquired from 425 to 774 nm in responses to ultraviolet-A (320 to 400 nm) excitation. Evaluation of images at emission peak wavelengths indicated that 675 nm exhibited the greatest contrast between feces contaminated and untreated surface areas. Two-band ratios compared with the single-band images enhanced the contrast between the feces contaminated spots and untreated cantaloupe surfaces. The 595/655-nm, 655/520-nm, and 555/655-nm ratio images provided relatively high detection rates ranging from 79% to 96% across all feces dilutions. However, both single band and ratio methods showed a number of false positives caused by such features as scarred tissues on cantaloupes. Principal component analysis (PCA) was performed using the entire hyperspectral images data; 2nd and 5th principal component (PC) image exhibited differential responses between feces spots and false positives. The combined use of the 2 PC images demonstrated the detection of feces spots (for example, minimum level of 16-,g/mL dry fecal matter) with minimal false positives. Based on the PC weighing coefficients, the dominant wavelengths were 465, 487, 531, 607, 643, and 688 nm. This research demonstrated the potential of multispectral-based fluorescence imaging for online applications for detection of fecal contamination on cantaloupes. [source] Color stability of frozen whole tilapia exposed to pre-mortem treatment with carbon monoxideJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 8 2008David Mantilla Abstract BACKGROUND: Color of muscle foods plays a major role in consumer perception of meat quality. Carbon monoxide (CO) has been successfully used for improving color of packaged meat and fish products. In this study, we wanted to investigate pre-mortem treatment of live tilapia using 100% CO for its ability to improve the color of frozen whole tilapia. We compared untreated and CO-treated whole, gutted tilapia, frozen for 2 and 4 months at , 20 °C. Frozen tilapia samples were thawed overnight at 4 °C, filleted and analyzed for their color, heme peak wavelength and CO concentration. RESULTS: Euthanasia using CO significantly increased redness (a* value) and lightness (L* value) of tilapia white and red muscle. Frozen storage significantly (P < 0.05) decreased redness of both CO-treated and untreated tilapia. However, even after 4 months of frozen storage, a*-value of CO-treated tilapia was similar to fresh untreated tilapia fillets. Heme peak wavelengths of CO-euthanized tilapia were higher than in untreated tilapia and there was no significant (P > 0.05) decrease in heme peak wavelengths of CO-treated tilapia white and red muscle during frozen storage. The CO content of frozen euthanized tilapia fillets was significantly (P > 0.05) higher than in untreated fillets. In general, red muscle tissue of euthanized tilapia had a higher concentration of CO than white muscle. CONCLUSION: Color stability of tilapia fillets was significantly improved by pre-mortem CO treatment. The color of CO-treated fillets was retained during frozen storage compared to untreated fillets. Hence, pre-mortem CO treatment could be used as a new method for improving color of tilapia. Copyright © 2008 Society of Chemical Industry [source] Thermal and nonthermal factors affecting the quantum efficiency of deep-ultraviolet light-emitting diodesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 12 2008H. Guo Abstract The optical characteristics of AlGaN-based multiple-quantum-well (MQW) light-emitting diodes (LEDs) with peak wavelengths ranging from 265,340 nm were characterized over a wide current range. It was found that thermal effects due to self-heating can be largely eliminated by pulsing the LEDs with a duty cycle below 0.2%. The current-induced energy shift up to 850 A/cm2 was negligible in the deep-UV LEDs, indicating the lack of localization effects. The quantum efficiency of the LEDs increased monotonically at low currents and attained a low saturated value at high currents. This is in contrast to the efficiency rolloff behavior of typical InGaN-based LEDs resulting from carrier delocalization at high injection levels. The efficiency saturation of the deep-UV LEDs suggests that defects play an important role in both carrier injection and recombination processes. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||