Search

Author(s): Ryota Kabe (corresponding author) [1, 2]; Chihaya Adachi (corresponding author) [1, 2, 3] Long persistent luminescence (LPL) materials--widely commercialized as 'glow-in-the-dark' paints--store excitation energy in excited states that slowly [...]

Described is the synthesis in water under ambient conditions of water-soluble, luminescent poly(acrylic acid)-encapsulated CdTe/CdS nanoparticles. Counterion-collapsed poly(acrylic acid) is used as a nanotemplate for the formation of the quantum dot core. Gram quantities of nanoparticles are easily obtained. Simply varying the amount of thioacetamide used in the synthesis can shift the emission wavelengths of the resulting nanoparticles from green to yellow to red. Key words: quantum dot, cadmium, luminescence, nanoparticle, nanotemplate. On decrit la synthese, en solution aqueuse dans des conditions ambiantes, de nanoparticules solubles dans l'eau et luminescentes de CdTe/CdS encapsule dans de l'acide polyacrylique. De l'acide polyacrylique a l'etat effondre obtenu par ajout de contre-ions est utilise comme nanogabarit pour la formation de points quantiques cceur. Des quantites de nanoparticules de l'ordre du gramme s'obtiennent facilement. La simple variation de la quantite de thioacetamide utilisee dans la synthese peut deplacer les longueurs d'onde d'emission des nanoparticules resultantes du vert au jaune et au rouge. [Traduit par la Redaction] Mots-cles: point quantique, cadmium, luminescence, nanoparticule, nanogabarit., Introduction Counterion condensation of polyelectrolytes has been a topic of research for 60 years. (1) The simplistic view is that in the absence of counterions, the polyelectrolyte exists as an [...]

A method is proposed for the luminescence determination of neptunium in natural waters with the removal of interfering iron. For the separation of iron ionic and colloidal species, solid-phase extraction with N-benzoyl-phenylhydroxylamine as a complexing reagent is used. The method makes possible the reduction of iron concentration in samples by more than two orders of magnitude without noticeable losses of neptunium and, therefore, the attainment of a detection limit for neptunium equal to its value in samples containing no iron. Keywords: luminescence, crystal phosphor, neptunium, iron DOI: 10.1134/S1061934813030076, Long-living isotopes of actinide elements are dangerous environmental pollutants. The known techniques of their analysis, i.e., α-spectrometry, neutron activation analysis, and mass spectrometry, necessitate complex sample pretreatment to remove interfering [...]

ZnO nanostructures of various morphologies and crystallinities were fabricated by thermal evaporation from Zn powder in a tube furnace in the presence of oxygen. It was found that the morphology of ZnO nanostructures was affected by synthesis parameters, such as growth temperature, carrier gas flow, and the presence of catalyst on the surface of the substrate. Representative ZnO nanostructures were studied by X-ray excited optical luminescence (XEOL) and cathodoluminescence (CL) methods. The luminescence from these samples exhibits a morphology dependence of the branching ratio of the near band gap (NBG) emission in the UV and defect emission in the green (GE). The appearance of the optical emission also depends on the excitation method. X-ray absorption near-edge structures (XANES) at the O K-edge and Zn L-edge are also presented and their implications discussed. Key words: ZnO nanostructures, XEOL, XANES, cathodoluminescence. Faisant appel a une methode d'evaporation thermique d'une poudre de Zn dans un four electrique a tube en presence d'oxygene, on a fabrique des nanostructures de ZnO de morphologies et de cristallinites diverses. On a trouve que la morphologie des nanostructures de ZnO est affectee par divers parametres de la synthese, telle la temperature de croissance, la vitesse d'ecoulement du gaz et la presence de catalyseur sur la surface du substrat. On a etudie les structures de nanostructures de ZnO representatives en faisant appel aux methodes de luminescence optique excitee par rayons-X (LOEX) et de cathodoluminescence (CL). La luminescence dans ces echantillons presente, dans l'UV, une relation entre la morphologie sur le rapport de ramification et l'emission de la bande interdite rapprochee (BIR) et l'emission de defaut dans le vert (EV). L'apparition d'une emission optique depend aussi de la methode d'excitation. On a aussi determine les structures d'absorption des rayons-X pres du seuil (' XANES ') au seuil K de l'oxygene et au seuil L du zinc et on discute de leurs implications. Mots-cles : nanostructures du ZnO, luminescence optique excitee par rayons X (LOEX), structures d'absorption des rayons X pres du seuil (<< XANES >>), cathodoluminescence. [Traduit par la Redaction], Introduction Zinc oxide, a versatile technological material for light emitting and photonic applications (e.g., solid-state lasers and LEDs), is a semiconductor with a wide band gap (~3.37 eV) and large [...]

The development of sensors for noninvasive determination of oxygen levels in live cells and tissues is critical for the understanding of cellular functions, as well as for monitoring the status of disease, such as cancer, and for predicting the efficacy of therapy. We describe such nontoxic, targeted, and ratiometric 30 nm oxygen nanosensors made of polyacrylamide hydrogel, near-infrared (NIR) luminescent dyes, and surface-conjugated tumor-specific peptides. They enabled noninvasive real-time monitoring of oxygen levels in live cancer cells under normal and hypoxic conditions. The required sensitivity, brightness, selectivity, and stability were achieved by tailoring the interaction between the nanomatrix and indicator dyes. The developed nanosensors may become useful for in vivo oxygen measurements. 10.1021/ac1015358

A luminescent photoelastic coating is a relatively new technique to measure full-field surface strain and determine principal strain directions that has many potential applications in engineering. Generally, luminescent photoelastic coating technology uses an in situ strain gage measurement to calibrate the detected optical response to maximum shear strain. This calibration requires the determination of two coating parameters: the polarization efficiency and the coating characteristic. A better understanding and modeling of these two parameters, particularly the polarization efficiency, will enable a simpler a priori calibration and greater measurement accuracy. This paper presents a factorial design experiment that assesses the effect of four factors on the optical strain response of an luminescent photoelastic coating. The factors examined were substrate reflectance, luminescent dye concentration, absorption dye concentration and cure time. Results show the polarization efficiency is strongly correlated with the emission anisotropy of the coating. When the polarization efficiency is modeled as the measured emission anisotropy, the two most significant factors are the substrate reflectance and the luminescent dye concentration. Absorption dye concentration and reflectance-luminescence interaction are minor but significant effects. The most significant tested factors in modeling the coating coefficient are absorption dye concentration and substrate reflectance. The resulting uncertainties for the polarization efficiency and coating characteristic are 1.3 and 3.7%, respectively. DOI: 10.2514/1.J050060

The luminescence of CdSe/ZnS QDs is quenched via electron transfer by hemin/G-quadruplex associated with the particles. This phenomenon is implemented to develop DNA sensors or aptasensers by tailoring hairpin-functionalized QDs that generate the hemin/G-quadruplex quenchers upon sensing of the respective analytes. 10.1021/ac101456x

Forster resonance energy transfer (FRET) with fluorescent proteins permits high spatial resolution imaging of protein-protein interactions in living cells. However, substantial non-FRET fluorescence background can obscure small FRET signals, making many potential interactions unobservable by conventional FRET techniques. Here we demonstrate time-resolved microscopy of luminescence resonance energy transfer (LRET) for live-cell imaging of protein-protein interactions. A luminescent terbium complex, TMP-Lumi4, was introduced into cultured cells using two methods: (i) osmotic lysis of pinocytic vesicles; and (ii) reversible membrane permeabilization with streptolysin O. Upon intracellular delivery, the complex was observed to bind specifically and stably to transgenitally expressed Escherichia coli dihydrofolate reductase (eDHFR) fusion proteins. LRET between the eDHFR-bound terbium complex and green fluorescent protein (GFP) was detected as long-lifetime, sensitized GFP emission. Background signals from cellular autofluorescence and directly excited GFP fluorescence were effectively eliminated by imposing a time delay (10 [micro]s) between excitation and detection. Background elimination made it possible to detect interactions between the first PDZ domain of ZO-1 (fused to eDHFR) and the C-terminal YV motif of claudin-1 (fused to GFP) in single microscope images at subsecond time scales. We observed a highly significant (P < [10.sup.-6]), six-fold difference between the mean, donor-normalized LRET signal from cells expressing interacting fusion proteins and from control cells expressing noninteracting mutants. The results show that time-resolved LRET microscopy with a selectively targeted, luminescent terbium protein label affords improved speed and sensitivity over conventional FRET methods for a variety of live-cell imaging and screening applications. cellular imaging | dihydrofolate reductase | Forster resonance energy transfer | lanthanide luminescence | protein labeling doi/ 10.1073/pnas.1002025107

Oriented assemblies of small crystals forming larger structures are common in nature and crucial for forthcoming technologies as they circumvent the difficulties of structural manipulation at microscopic scale. We have discovered two distinctive concentric assemblies of zinc oxide rods, wherein each rod has an intrinsically positive and a negative polar end induced by the noncentrosymmetric arrangement of Zn and O atoms. All the rods in a single assembly emanate out of a central core maintaining a single polar direction. Due to growth along the two polar surfaces with different atomic arrangements, these assemblies are distinct in their intrinsic properties and exhibit strong UV luminescence in the exterior of Zn-polar assemblies, unlike the O-polar assemblies. Although novel applications can be envisioned, these observations suggest that hierarchical organization with respect to internal asymmetry might be widespread in natural crystal assemblies. cathodoluminescence | crystal assembly doi/ 10.1073/pnas.1008240107

The effects of excitation wavelength on the optical properties (emission spectrum and quantum yield) of a luminescent solar concentrator (LSC) containing a fluorescent organic dye (Lumogen F Rot 305) are studied. Excitation at wavelengths on the long-wavelength edge of the absorption spectrum of the dye results in redshifted emission, but the quantum yield remains constant at 100%. The origin of this effect and its consequences are discussed. The extent of the long-wavelength tail of the absorption spectrum of the dye is determined and the importance in reabsorption losses is shown. The optical efficiencies and photon transport probabilities of LSCs containing either an organic dye or a rare-earth lanthanide complex are compared using ray-tracing simulations and experiment. The optical efficiency is shown to depend strongly on the Stokes shift of the fluorophore. The lanthanide complex, which has a very large Stokes shift, exhibits a higher optical efficiency than the dye (64% cf. 50%), despite its lower quantum yield (86% cf. 100%). [c] 2010 Optical Society of America OCIS codes: 260.2510, 300.6280, 250.5460, 350.6050.

Thin films of A1N doped with chromium were deposited on flat Si (100) substrates and optical fibers by rf magnetron sputtering, using 100-200 W rf power and 5-8 mTorr nitrogen. The thickness of the films on the flat silicon substrate was 400 nm and on optical fibers with 80 [micro]m and smaller diameters was up to 10 [micro]m. Surface characterization and luminescence properties were investigated to fabricate resonant laser cavities. X-ray diffraction and scanning electron microscope studies showed that films deposited on flat silicon were amorphous, while those deposited on the fibers show columnar growth and some gain structure, most probably due to a temperature rise at the substrate during deposition. Cathodoluminescence and photoluminescence of the as-deposited and thermally activated A1N:Cr films showed an emission peak at 702 nm as a result of the [sup.4][T.sub.2] [right arrow] [sup.4][A.sub.2] transition. OCIS codes: 160.4670, 160.3380, 160.5293, 180.5810, 240.0310, 240.6490.

We have developed a homogeneous assay method in which the lanthanide ion carrier and light absorbing components of a luminescent lanthanide chelate are separated in two distinct molecules that can together form a luminescent mixed chelate complex. The separated label moieties were conjugated to oligonucleotides which were used as probes to detect a complementary target DNA. The background signal of the assay was very low, indicating the signal was highly dependent on the hybridization of the two probes on adjacent positions on the target oligonucleotide. 10.1021/ac9020825

This study investigated the potential of shade-trees to improve lighting conditions in the indoor space of a standard classroom in the United Arab Emirates (UAE) using computer simulation with the Radiance program. Shade trees are defined as selected suitable types of trees using certain criteria (i.e. evergreen, proper canopy density, proper height, growth in extreme hot climate conditions, safe roots) based on literature survey and consultation with landscape experts. It focuses on analysis of illuminance levels at desk locations (task) inside a standard classroom oriented to the North, East, South, and West for the selected critical times that are relevant to the locality An initial group of simulation runs was done at the outset to choose proper tree spacing. The dependent variables are illuminance level and illuminance range resulted from manipulating two independent variables, shade tree type and orientation. The simulation runs includes a base case with no shade trees against other improvement cases with shade trees. The findings show the significance of the shade trees for improved lighting distribution and quality. This is evident in the reduction of illuminance ranges throughout the classroom as it is the case with the Neem shade trees at 2 m providing the lowest range from 125-570 Lux on front of the window and from 130-498 Lux on front of the wall. Yet, some reduction in the overall levels of illuminance is experienced (18-31% reduction for North orientation; 87-96% reduction for other orientations) and an increase in the estimated operating hours of electric lighting. Finally, some passive methods such as high strip windows and roof monitors were recommended to compensate for the illuminance reduction, rather than using electric lighting. Keywords: Daylight, Illuminance, Schools, Tree shading, Visual comfort, Introduction The UAE lies between latitudes 22[degrees]-26.5[degrees]N and longitudes 51[degrees]-56.5[degrees]E. Being on the Tropic of Cancer (24 deg N) results in the UAE region receiving among the highest annual rate [...]

Here we report a graphene oxide amplified electrogenerated chemiluminescence (ECL) of quantum dots (QDs) platform and its efficient selective sensing for antioxidants. Graphene oxide facilitated the CdTe [QDs.sup.**+] production and triggered [O.sub.2.sup.**-] generation. Then, a high yield of CdTe QDs* was formed due to the combination of CdTe [QDs.sup.**+] and [O.sub.2.sup.**-], leading to an ~5-fold ECL amplification. Glutathione is the most abundant cellular thiol-containing peptide, but its selective sensing is an intractable issue in analytical and biochemical communities because its detection is interfered with by some thiol-containing compounds. This platform showed a detection limit of 8.3 [micro]M (S/N = 3) for glutathione and a selective detection linear dependence from 24 to 214 [micro]M in the presence of 120 [micro]M cysteine and glutathione disulfide. This platform was also successfully used for real sample (eye drug containing glutathione) detection without any pretreatment with a wide linear range from 0.04 to 0.29 [micro]g [mL.sup.-1]. 10.1021/ac901935a

A capillary electrophoresis coupled with electrochemiluminescent detection system (CE-ECL) was developed for the detection of polymerase chain reaction (PCR) amplicons. The ECL luminophore, tris(1,10-phenanthroline) ruthenium(II) (Ru[(phen).sub.3.sup.2+]), was labeled to the PCR primers before amplification. Ru[(phen).sub.3.sup.2+] was then introduced to PCR amplicons by PCR amplification. Eventually, the PCR amplicons were separated and detected by the homemade CE-ECL system. The detection of a typical genetically modified organism (GMO), Roundup Ready Soy (RRS), was shown as an example to demonstrate the reliability of the proposed approach. Four pairs of primers were amplified by multiple PCR (MPCR) simultaneously, three of which were targeted on the specific sequence of exogenous genes of RRS, and another was targeted on the endogenous reference gene of soybean. Both the conditions for PCR amplification and CE-ECL separation and detection were investigated in detail. Results showed that, under the optimal conditions, the proposed method can accurately identifying RRS. The corresponding limit of detection (LOD) was below 0.01% with 35 PCR cycles. 10.1021/ac901510s

Outdoor lighting fixtures are used to illuminate surrounding streets, parking lots, walkways, and the landscape surrounding many buildings. Examples of these light fixtures are cobra head streetlights, Acorns and Colonials. These streetlights are typically designed to achieve illumination levels required by published design standards such as minimum illuminance levels on parking as well as pedestrian walkways. The light from poles close to buildings often spills off onto building facades. This influences the illumination of the facade and impacts on light trespass ordinances of some municipalities. This paper develops a method for studying such an effect and outlines ways to minimize the effect of outdoor lighting on facade illumination without compromising parking lot and walkway illumination. A comparison is made between various types of area and road light fixtures. Keywords: Area lighting, Facade lighting, Light trespass, Street lighting, Introduction Road and parking lot lighting are typically designed to satisfy published standards such as the ANSI/IESNA RP-8 (IESNA, 1999) and G-103 (IESNA, 2003). A summary of the recommended illuminance [...]

The ability of luminescent species in the near-field to both induce and couple to surface plasmons has been known for many years, with highly directional emission from films (Surface Plasmon Coupled Luminescence, SPCL) facilitating the development of sensitive near-field assay sensing platforms, to name but just one application. Because of the near-field nature of the effect, only luminescent species (fluorescence, chemiluminescence and phosphorescence) within a few hundred nanometers from the surface play a role in coupling, which in terms of biosensing, provides for limited penetration into optically dense media, such as in whole blood. Another attractive feature is the highly polarized and angular dependent emission which allows both fixed angle and wavelength dependent emission angles to be realized at high polarization ratios. In this paper, a generic procedure based on theoretical Fresnel calculations, which outlines the step-by-step selection of an appropriate metal for SPCL applications is presented. It is also shown that 11 different metals have differing properties in different spectral regions and offer either fixed angle or wavelength-dependent angular shifts in emission. In addition, it is shown that both chemiluminescence and phosphorescence can also be observed in a highly directional manner similar to coupled fluorescence.

We report the scintillation properties of the undoped and cerium-doped variations of LiGd[Cl.sub.4] and NaGd[Cl.sub.4]. Powder samples of these materials exhibit significant scintillation under X-rays. The samples were synthesized by solid-state methods from a 1:1 molar ratio of lithium or sodium chloride and gadolinium trichloride. Cerium trichloride was used as the dopant. The physical, optical, and scintillation properties of these materials were analyzed by powder X-ray diffraction, photoluminescence, X-ray excited luminescence, and pulsed X-ray luminosity measurements. Increases in light yields are observed as the concentration of cerium increases. The highest light yields occurred at 20% cerium doping for both compounds. At larger concentrations neither compound formed, indicating a breakdown of the lattice with the addition of large amounts of cerium cations. At 20% cerium, LiGd[Cl.sub.4] and NaGd[Cl.sub.4] display scintillation light 3.6 times and 2.2 times the light yield of the reference material, YAl[O.sub.3] :[Ce.sup.3+], respectively. Both emit in the ranges of 340-350 nm and 365-370 nm and display multiexponential decays with cerium-like decay components at 33 ns (LiGd[Cl.sub.4] : Ce) and 26 ns (NaGd[Cl.sub.4] : Ce). Index Terms--Cerium, decay time, gadolinium, luminescence, scintillators.

In this paper, homogeneous and dense silicon-based coatings have been deposited from hexamethyldisiloxane (HMDSO: [Si.sub.2]O[(C[H.sub.3]).sub.6]) on patterned silicium in a Townsend dielectric barrier discharge operating at atmospheric pressure. A brief description of the physical mechanisms ruling the step coverage is first described, followed by a description of the atmospheric pressure plasma process used. The step coverage is discussed with regard to the aspect ratio of the patterned wafers. Coatings deposited in and after the discharge region have also been characterized to understand the influence of plasma activation. In order to understand the experimental results, numerical simulations have been performed using a simplified reactive transport model. These results provide information and first general insight on the physical mechanisms ruling the conformity of silicon-based films deposited with this technique. Index Terms--Atmospheric pressure Townsend discharge (APTD), dielectric barrier discharge (DBD), glow discharges, plasma-enhanced chemical vapor deposition (PECVD), reactive transport modeling, silicon oxide, step coverage.

A scheme for a plasma-solution reactor on the basis of a glow discharge stabilized by a fast air flow is suggested as a novel water treatment technique. The discharge ignition voltage is about 2.7 kV, and the input power can be as low as 3 W. It is found that plasma is generated in pulsed mode where the duration of each individual pulse is 15-20 [micro]s. A maximal destruction rate of methylene blue dye of 3.27 x [10.sup.-9] mol/l x s has been received in an acidic medium at a discharge power level of 6 W. A comparison of the efficiency of plasma interaction in different solutions has been carried out. The chemical effectiveness of the plasma treatment decreases with an increase of solution pH. It is shown that the developed glow discharge two phase reactor can be effectively used for destruction of water pollutants. Index Terms--Atmospheric plasma, gas flow, glow discharge, water treatment.

The possibilities of obtaining large-volume non-self-sustained atmospheric pressure glow discharge with the help of the self-sustained normal dc glow discharge in helium are demonstrated. The latter plays the role of 'plasma electrode' for the main discharge in a neighboring chamber in the three-electrode configuration. Electrical parameters of the non-self-sustained discharge for different voltage sign combinations of electrodes are presented. Conditions of discharge transfer from one chamber section to another are under investigations. The spatial profiles of potential at different discharge currents are determined. It is shown that larger volumetric plasma can be generated in the anode-cathode-anode configuration. Index Terms--Atmospheric pressure glow discharges (APGDs), atmospheric pressure plasma, glow discharges, plasma generation, plasma measurements.

An atmospheric-pressure glow-discharge plasma jet driven by a transformer of 1 : 500 and an alternating current of 50 Hz is presented. Discharge characteristics are investigated by oscillograph observations, and it is verified no risk of arcing. The stable glow discharge is deemed to benefit from the transformer's inductance. The electric characteristics and the plasma parameters are studied. The jet is employed in C[O.sub.2] reforming of C[H.sub.4] to syngas ([H.sub.2], CO). It brings out higher conversion ability than other plasmas such as dielectric barrier discharge and corona discharge, which is due to its special design and special plasma characteristic. Index Terms--Atmospheric pressure, glow discharge, inductance, syngas.

Ricin is a family member of the lethal ribosome-inactivating proteins (RIP) found in plants. Ricin toxin A-chain (RTA) from castor beans catalyzes the hydrolytic depurination of a single base from a GAGA tetraloop of eukaryotic rRNA to release a single adenine from the sarcin-ricin loop (SRL). Protein synthesis is inhibited by loss of the elongation factor binding site resulting in cell death. We report a sensitive coupled assay for the measurement of adenine released from ribosomes or small stem-loop RNAs by RTA catalysis. Adenine phosphoribosyl transferase (APRTase) and pyruvate orthophosphate dikinase (PPDK) convert adenine to ATP for quantitation by firefly luciferase. The resulting AMP is cycled to ATP to give sustained luminescence proportional to adenine concentration. Subpicomole adenine quantitation permits the action of RTA on eukaryotic ribosomes to be followed in continuous, high-throughput assays. Facile analysis of RIP catalytic activity will have applications in plant toxin detection, inhibitor screens, mechanistic analysis of depurinating agents on oligonucleotides and intact ribosomes, and in cancer immunochemotherapy. Kinetic analysis of the catalytic action of RTA on rabbit reticulocyte 80S ribosomes establishes a catalytic efficiency of 2.6 x [10.sup.8] [M.sup.-1] [s.sup.-1], a diffusion limited reaction indicating catalytic perfection even with large reactants.

High-throughput screening of catalysts could dramatically improve performance and reduce costs in the discovery and study of various catalysts. Here we report a cataluminescence-based array imaging as a high-throughput screening technique in the combinatorial discovery of active catalysts for CO oxidation. This strategy is based on the fact that the CO oxidation generates cataluminescence emission on the surface of nanomaterials, whose intensity is correlated to the activity of the catalyst. To demonstrate the feasibility of the cataluminescence-based array imaging for high-throughput screening of catalysts, different nanosized metal catalysts supported on Ti[O.sub.2] nanoparticles were prepared. These catalysts include monometallic Au, Pt, and the bimetallic Au-Pt heteroaggregate catalysts, at total metal loadings of 0.5%, 1.0%, and 2.5%, and with atomic ratios of 1:1, 1:2, and 2:1 (Au/Pt). A 4 x 4 array was integrated by depositing these nanosized catalysts onto the ceramic chip, and the brightness of each spot in the image was recorded. The catalytic activities of those catalysts for the CO oxidation were evaluated parallelly by both the cataluminescence imaging and the gas chromatography method. The correlation coefficient is 0.914 for the two techniques, indicating that the cataluminescence imaging technique can be applied for the evaluation of the catalytic activities. Moreover, fast evaluation of multiple catalysts at a series of working temperature can be achieved by this cataluminescene-based array imaging. With the development of nanotechnology as well as the catalyst industry, the cataluminescence-based array imaging will address its importance in the high-throughput screening of catalysts.

Because of the ability to selectively reveal the objects of interest with subcellular resolution, fluorescence microscopy provides widespread applications from basic biological research to clinical diagnosis. However, challenges still remain in reducing the degree of photobleaching and increasing the contrast between signal and noise. Herein, we found that rare-earth nanophosphors exhibit a unique up-conversion luminescence mechanism and imaging modality and developed a new three-dimensional visualization method of laser scanning up-conversion luminescence microscopy (LSUCLM) with little photobleaching and no background fluorescence, by introducing a reverse excitation dichroic mirror and the confocal pinhole technique. Moreover, we demonstrated the up-conversion emission imaging of thin films containing embedded rare-earth nanophosphors and cells multilabeled with the nanophosphors and organic dyes. These data show that LSUCLM not only shares noninvasive benefits and deep penetration of two-photon microscopy but also offers some distinct advantages, such as little photobleaching of both organic dyes and rare-earth nanophosphors, no background fluorescence from either endogenous fluorophores or colabeled fluorescent probes, and excellent compatibility with conventional confocal microscopy.

Three experiments examined whether salient color singleton distractors automatically interfere with the detection singleton form targets in visual search (e.g., J. Theeuwes, 1992), or whether the degree of interference is top-down modulable. In Experiments 1 and 2, observers started with a pure block of trials, which contained either never a distractor or always a distractor (0% or 100% distractors)--varying the opportunity to learn distractor suppression. In the subsequent trial blocks, the proportion of distractors was systematically varied (within-subjects factor in Experiment 1, betweensubjects factor in Experiment 2)--varying the incentive to use distractor suppression. In Experiment 3, observers started with 100% distractors in the first block and were presented with 'rare' color or luminance distractors, in addition to 'frequent' color distractors, in the second block. The results revealed distractor interference to vary as a function of both the initial experience with distractors and the incentive to suppress them: the interference was larger without relevant practice and with a lesser incentive to apply suppression (Experiments 1-3). This set of findings suggests that distractor interference is top-down modulable. Keywords: attentional capture, singleton distractor interference, top-down modulation, cross-trial priming

Pressure sensitive paints (PSP) that measure the changes in air pressure have proved to be useful in the design of aircraft and other vehicles. In this study we incorporate highly luminescent divalent osmium complexes into PSP. The divalent osmium complexes were heptafluorobutyrate salts of [[Os[(N-N).sub.2](L-L)].sup.2+] or [[Os[(L-L).sub.2](N-N)].sup.2+], where N-N is a derivative of 1,10-phenanthroline, and L-L is a diphosphine or diarsine ligand. The complexes were dissolved into poly(1,1,1,3,3,3-hexafluoroisopropylmethacrylate-co-1H, 1H-dihydroperflurobutylmethacrylate) (FIB) at a concentration of 0.002 g of complex to 1.000 g of polymer. The luminescence of the coatings was tested for pressure sensitivity, temperature dependence, and photodegradation. The paints featured strong pressure response, and the temperature dependence of the luminescence was measured as low as -0.11% [degrees][C.sup.-1]. Several of the complexes exhibited little photodegradation upon prolonged exposure to 400 nm light. These attributes make the complexes very desirable luminescent dyes for PSP.

Polymer-supported luminescent metal complexes represent an important class of oxygen, pH, and ion sensors. The diffusion properties of the analyte into the sensing film are important for rational sensor and support design and development. We describe a technique using lifetime measurements in the frequency domain for determining the diffusion coefficient of hydrochloric acid through various polymeric pH sensor films. Two types of polymers are doped with [Ru[(4,7-diphenyl-1,10-phenanthroline).sub.2] (4,4'-dicarboxy-2,2'-bipyridine)][Cl.sub.2]. We monitor the phase shift of luminescence (from which we calculate the apparent lifetime, [[tau].sub.app]) versus time after applying a step increase in the aqueous HCl concentration at the surfaces of the film. We model the decrease in [[tau].sub.app] as a function of time using the diffusion coefficient of HCl in the polymer as the only adjustable parameter. The model accurately predicts the lifetime versus time curves, and the resulting diffusion coefficients are highly dependent on the polymer. Relative to bulk water, diffusion of protons within very hydrophilic hydrated D4 polymer (a polyethylene oxide cross-linked siloxane ring polymer) films is hindered ~4-fold, while within a more hydrophobic sol gel it is hindered by over 1 order of magnitude. The methodology is adaptable for measuring diffusion coefficients of a variety of analytes in different sensor films as long as the bound and unbound forms luminesce and the excited states have different lifetimes.

A sensing system based on the photoinduced electron transfer of quantum dots (QDs) was designed to measure the interaction of anticancer drug and DNA, taking mitoxantrone (MTX) as a model drug. MTX adsorbed on the surface of QDs can quench the photoluminescence (PL) of QDs through the photoinduced electron-transfer process; and then the addition of DNA will bring the restoration of QDs PL intensity, as DNA can bind with MTX and remove it from QDs. Sensitive detection of MTX with the detection limit of 10 nmol [L.sup.-1] and a linear detection range from 10 nmol [L.sup.-1] to 4.5 [micro]mol [L.sup.-1] was achieved. The dependence of PL intensity on DNA amount was successfully utilized to investigate the interactions between MTX and DNA. Both the binding constants and the sizes of binding site of MTX-DNA interactions were calculated based on the equations deduced for the PL recovery process. The binding constant obtained in our experiment was generally consistent with previous reports. The sensitive and speedy detection of MTX as well as the avoidance of modification or immobilization process made this system suitable and promising in the drug-DNA interaction studies.

The aim of this study was to examine [Gd.sub.2][O.sub.2]S:Eu (also known as GOS:Eu) powder scintillator under X-ray mammography imaging conditions. For this purpose, three scintillator screens with coating thicknesses of 33.1, 46.4 and 63.1 mg/[cm.sup.2] were prepared in our laboratory by sedimentation of [Gd.sub.2][O.sub.2]S:Eu powder. Light emission efficiency and optical emission spectra of the screens were measured under X-ray excitation using X-ray tube voltages (22-49 kVp) employed in mammography. Spectral compatibility with various optical photon detectors (photodiodes, photocathodes, charge coupled devices, films) and intrinsic conversion efficiency value (0.12) were determined by using emission spectrum data. In addition, parameters related to X-ray detection and energy absorption efficiency were calculated. [Gd.sub.2][O.sub.2]S:Eu showed peak emission in the wavelength range 620-630 nm. The 63.1 mg/[cm.sup.2] phosphor screen appeared with the maximum light emission efficiency. Due to its reddish emission spectrum, [Gd.sub.2][O.sub.2] S:Eu showed excellent compatibility with the sensitivity of many currently used photodetectors and could be considered for application in X-ray imaging especially in various digital detectors. Index Terms--[Gd.sub.2][O.sub.2] S:Eu, luminescence efficiency, matching factor powder phosphors.

We have constructed a variable spectral-width, wavelength-tunable light source using a non-fiber-coupled broadband superluminescent diode device with an optical feedback mechanism. As lasing occurs, a strong output light which is linearly polarized and monochromatic is obtained. The spectral width varies with the injection current and the optical feedback ratio. By incorporating a dispersing prism into the feedback branch, a wavelength-tunable, external-cavity-feedback laser source is achieved. The result is a convenient, inexpensive apparatus suitable for experiments in undergraduate optics courses.

Luminescence data offer delicate probes of changes in structure and local environment in insulating materials. Therefore they have long been employed in studies of imperfections and characterisation of lattice distortions. Luminescence techniques are inherently very sensitive so respond to small concentrations of intrinsic defects and impurities, and intentionally added probe ions, such as rare earth or chromium ions, are particularly effective at displaying responsive changes linked to modified structural environments. Parameters of interest are variations in luminescence efficiency, the details of the emission spectra, polarisation, temperature dependence and changes in excited state lifetimes. These are suitable properties to monitor variations in both short and long range lattice structure, composition, pressure and temperature. For modern photonic materials such probes are powerful tools to follow changes introduced by processing to make waveguides, surface layers and new materials. The use of different excitation conditions for the luminescence can resolve differences between near surface and bulk features. A less common approach is to use luminescence as a route to detect phase transitions. This is particularly valuable for rapid survey studies of new materials which are of relevance to modern optics. One of the more surprising results is the observation that phase changes of very small inclusions, such as phase precipitates or impurity nanoparticles, can totally dominate the luminescence response of the bulk material. Specific examples include the frequent observation of trapped nanoparticles of water, [N.sub.2], [O.sub.2] and C[O.sub.2]. Further, the excitation techniques, and ion implantation or surface stresses can all induce surface relaxations which, in materials such as SrTi[O.sub.3] or ZnO, result in phase changes propagating throughout the entire crystal. This review rapidly recalls the methods used in the older studies of imperfections and then uses a range of examples to show how luminescence studies can be effective in detecting and confirming the presence of phase transitions. Interestingly the examples include not only transparent insulating materials but also fullerenes and superconductors. Keywords: luminescence; phase transitions; imperfections

Monitoring of excitation activity of nerve cells is very useful for not only brain research but also assessment of the effects of various chemicals, including drugs and toxins.We previouslyreported anovelenzyme luminescence method for real-time monitoring of L-glutamate release from C6 glioma cells with high levels of sensitivity (approximately equal to] 10 nM) and temporal resolution (

This paper describes a global luminescent oil-film skin-friction meter that is particularly useful in global skin-friction diagnostics for complex flows. This method is developed based on the relationship between the oil-film thickness and luminescent intensity of an oil film doped with luminescent molecules. The projected thin oil-film equation is given in the image plane, which relates skin friction with the normalized luminescent intensity. A variational formulation with a smoothness constraint on skin friction is given, and the corresponding Euler-Langrage equations are solved to obtain a snapshot solution for a relative skin-friction field. Successive snapshot solutions are superposed to reconstruct a complete relative skin-friction field, and the corresponding absolute field can be further determined by in situ calibration. This method is examined through numerical simulation and experiments.

The unusual luminescence of particular varieties of natural pink calcite (CaC[O.sub.3]) samples was studied by laser-induced time-resolved luminescence spectroscopy at different temperatures. The luminescence is characterized by intense blue emission under shortwave UV lamp excitation with an extremely long decay time, accompanied by pink-orange luminescence under longwave UV excitation. Our investigation included optical absorption, natural thermostimulated luminescence (NTL) and Laser-Induced Breakdown Spectroscopy (LIBS) studies. Two luminescence centers were detected: (1) a narrow violet band, with [[lambda].sub.max] = 412 nm, [DELTA] = 45 nm, two decay components of [[tau].sub.1] = 5 ns and [[tau].sub.2] = 7.2 ms, accompanied by very long afterglow, and an orange emission band with [[lambda].sub.max] = 595 nm, [DELTA] = 90 nm, and [tau] = 5 ns. Both luminescence centers are thermally unstable with the blue emission disappearing after heating at 500 [degrees]C, and the orange emission disappearing after heating at different temperatures starting from 230 [degrees]C, although sometimes it is stable up to 500 [degrees]C in different samples. Both centers have spectral-kinetic properties very unusual for mineral luminescence, which in combination with extremely low impurity concentrations prevent their identification with specific impurity related emission. The most likely explanation of these observations may be the presence of radiation-induced luminescence centers. The long violet afterglow is evidently connected with trapped charge carrier liberation, with their subsequent migration through the valence band and ultimate recombination with a radiation-induced center responsible for the unusual violet luminescence. Keywords: Calcite, time-resolved luminescence, radiation-induced luminescence centers

The article presents the experimental and theoretical characterization of arrays of tapered super-luminescent diodes. Results suggest the achievement of output powers in excess of 2.7 W with 10 percent wall-plug (W-P) efficiency from antireflection (AR)-coated arrays of tapered super-luminescent diodes.

Following our previous studies, a further investigation on three long (2.5 x 2.5 x 20 [cm.sup.3]) LSO and LYSO crystal samples was carried out, and was compared to a long BGO sample of the same size. The optical and scintillation properties, including transmittance, photo-luminescence and excitation spectra, were measured. The result of light output and light response uniformity, measured by using both PMT and APD, are reported. Their applications in future high energy physics experiments are discussed. Index Terms--Crystal, light output, lutetium oxyorthosilicate, lutetium yttrium oxyorthosilicate, photo luminescence, radiation damage, scintillator, transmission.

The angular dependency of luminescence and lasing spectra for a planar layer of a dye-doped cholesteric liquid crystal (CLC) was measured by comparing its Bragg, as well as leaky modes. The results of the analysis showed that both the modes depend on the pump intensity and the shape and dimension of the transverse cross section of the excitation beam, though the leaky modes impose various limitations on the energy of the Bragg lasing modes.

The luminescence of [(Lu, Y).sub.2]Si[O.sub.5]: Ce (LYSO:Ce) and [Gd.sub.2]Si[O.sub.5]: Ce (GSO:Ce) crystals was studied for use in tomographic medical x-ray imaging. LYSO:Ce and GSO:Ce are high density (7.1 g/[cm.sup.3] and 6.71 g/[cm.sup.3] respectively), high atomic number (71 for Lu and 64 for Gd), non-hydroscopic, and short decay time (40 ns and 60 ns respectively) scintillators. Evaluation was performed by determining: 1) the luminescence efficiency (LE) (emitted fight energy flux over incident x-ray energy flux) in x-ray energies employed in general x-ray imaging (40-140 kVp) and in mammographic x-ray imaging (22-49 kVp), 2) the fight emission spectrum, determined at various x-ray energies (22-140 kVp), and 3) the spectral compatibility to optical photon detectors, incorporated in medical imaging systems. Both scintillation materials exhibited adequately high LE in the x-ray diagnostic energy range, with LYSO:Ce's LE being distinctively higher. LYSO:Ce and GSO:Ce were found most compatible with the S-20 photocathode (0.9 for both materials) and adequately compatible to the amorphous silicon photodiode (0.74 for both materials), incorporated in many digital x-ray detectors. Index Terms--Inorganic scintillators, luminescence efficiency, LYSO:Ce, matching factor, radiation detectors.

Numerous authors have utilised physical properties of Chinese loess and red clay deposits to develop apparently detailed and continuous past climate records from the Miocene into the Holocene. Many of these studies have further suggested that the principal climatic agent responsible for the aeolian emplacement and diagenesis of Chinese loess, the East Asian Monsoon, has fluctuated rapidly on millennial to sub-millennial timescales, in concert with dramatic changes in the North Atlantic (Dansgaard-Oeschger cycles and Heinrich events) and the Western Pacific (El Nino Southern Oscillation). Much of this evidence is based on reconstructions and age models that are tied to assumptions concerning the nature of loess sedimentation and diagenesis, for example, the belief that loess sedimentation can be viewed as essentially continuous. Some authors have however, cast doubt on these assumptions and suggest that the application of radiometric techniques may be required to determine their validity. Recent studies utilising Optically Stimulated Luminescence (OSL) methods have reinforced these doubts and here, OSL dates obtained at 10 cm intervals from three sites along a transect across the Chinese Loess Plateau have been used, in combination with climate proxy evidence, to test the existing assumptions that underpin many palaeoclimatic reconstructions from loess. In this way, the first time-continuous and independently dated late Quaternary climate reconstruction is developed from loess. The data indicate that sedimentation is episodic and that once emplaced, loess is prone to pedogenic disturbance, diagenetic modification and in some cases erosion. The relationships between proxies and sedimentation rates are also assessed and climatic interpretations based on different age models compared. The implications of these findings for reconstructions of climate from loess are explored and comparisons are made between the developed palaeoclimate records and evidence from ice and ocean cores. This exercise also highlights important information concerning the relative influence of forcing mechanisms behind East Asian Monsoon change over the late Quaternary. Keywords: luminescence dating; Chinese loess; Quaternary; East Asian Monsoon; sedimentation; diagenesis

The paper describes the development and characterization of analytical properties of quantum dot-based probes for enzymatic activity and for screening enzyme inhibitors. The luminescent probes are based on fluorescence resonance energy transfer (FRET) between luminescent quantum dots that serve as donors and rhodamine acceptors that are immobilized to the surface of the quantum dots through peptide linkers. Peptide-coated CdSe/ZnS quantum dots were prepared using a one-step ligand exchange process in which RGDC peptide molecules replace trio-ctylphosphine oxide (TOPO) molecules as the capping ligands of the quantum dots. The peptide molecules were bound to the surface of the CdSe/ZnS quantum dots through the thioi group of the peptide cysteine residue. The peptide-coated quantum dots were labeled with rhodamine to form the FRET probes. The emission quantum yield of the quantum dot FRET probes was 4-fold lower than the emission quantum yield of TOPO-capped quantum dots. However, the quantum dot FRET probes were sufficiently bright to enable quantitative enzyme and enzyme inhibition assays. The probes were used first to test the enzymatic activity of trypsin in solution based on FRET signal changes of the quantum dot-based enzymatic probes in the presence of proteolytic enzymes. For example, exposure of the quantum dot FRET probes to 500 [micro]g/mL trypsin for 15 min resulted in 60% increase in the photoluminescence of the quantum dots and a corresponding decrease in the emission of the rhodamine molecules. These changes resulted from the release of rhodamine molecules from the surface of the quantum dots due to enzymatic cleavage of the peptide molecules. The quantum dot FRET-based probes were used to monitor the enzymatic activity of trypsin and to screen trypsin inhibitors for their inhibition efficiency.

The possibility to evaluate simultaneously the total ionizing dose and the displacement damage dose using a single OSL integrated sensor is demonstrated. Results obtained during the real time monitoring of both proton and electron beams are presented. Index Terms--Dosimetry, electron, non-ionizing dose, optically stimulated luminescence, OSL, proton.

The luminescence of Perylene Orange and LDS821 in poly(methyl methacrylate) (PMMA) following a 532 nm irradiation yielded information on photodegradation and energy transfer. The irradiation of the Perylene Orange/LDS821/PMMA films resulted in (i) a maximum in the Perylene Orange fluorescence photodegradation profile and (ii) an enhancement of the LDS821 fluorescence relative to the LDS821/PMMA films. These results are attributed to an energy transfer from the Perylene Orange to the LDS821 with an energy transfer rate constant of 5.19 [+ or -] 0.75 (2[sigma]) x [10.sup.11] [M.sup.-1] [s.sup.-1] and a Forster critical radius of 65.7 [Angstrom]. Fluorescence half-quenching and time-resolved fluorescence measurements attributed energy transfer to the Forster energy transfer with minor contributions of radiative energy transfer. OCIS codes: 140.3580, 160.2540, 160.3380, 160.4890, 230.7390, 310.2790.

Aequorin bioluminescence is emitted as a rapidly decaying flash upon calcium binding. Random mutagenesis and functional screening were used to isolate aequorin mutants showing slow decay rate of luminescence. Calcium sensitivity curves were shifted in all mutants, and an intrinsic link between calcium sensitivity and decay rate was suggested by the position of all mutations in or near EF-hand calcium-binding sites. From these results, a low calcium affinity was assigned to the N-terminal EF hand and a high affinity to the C-terminal EF-hand pair. In WT aequorin, the increase of the decay rate with calcium occurred at constant total photon yield and thus determined a corresponding increase of light intensity. Increase of the decay rate was underlain by variations of a fast and a slow component and required the contribution of all three EF hands. Conversely, analyses of double EF-hand mutants suggested that single EF hands are sufficient to trigger luminescence at a slow rate. Finally, a model postulating that proportions of a fast and a slow light-emitting state depend on calcium concentration adequately described the calcium dependence of aequorin bioluminescence. Our results suggest that variations of luminescence kinetics, which depend on three EF hands endowed with different calcium affinities, critically determine the amplitude of aequorin responses to biological calcium signals. EF hand | kinetics | luminescence | photoprotein | transduction