550-nm Band Research Articles

Effect of HPHT annealing in a medium with high hydrogen fugacity on the properties of plastically deformed brown IaAB diamond

To test the possibility of hydrogen diffusion into the dislocation core channels in plastically deformed type IaAB diamonds the diamond sample was annealed at 1500 °C and a pressure of 7.8 GPa for 21 h in a medium with high hydrogen fugacity. The band at 2860 cm−1 corresponding to the CH bonds stretching vibrations appeared in the infrared spectra. It is shown that the 550 nm band in the absorption spectra is due to the formation of complexes with charge transfer from W7 nitrogen centers to dangling bonds in the dislocation cores. Compensation of dangling bonds in dislocation cores with hydrogen led to the destruction of charge-transfer complexes, to a decrease in the intensity of the 550-nm band, and, as a consequence, to a decrease in the color of the diamond crystal.

Development of a multispectral stereo-camera system comparable to Hayabusa2 optical navigation camera (ONC-T) for observing samples returned from asteroid (162173) Ryugu

Hayabusa2 collected 5.4 g of samples from the asteroid (162173) Ryugu and brought them back to Earth. Obtaining multiband images of these samples with the spectral bands comparable to those used for remote-sensing observations is important for characterizing the collected samples and examining how representative the sample is compared with spacecraft observations of Ryugu as a whole. In this study, we constructed a multiband microscopic camera system that enables both visual multispectral imaging at 390 (ul), 475 (b), 550 (v), 590 (Na), 700 (w), and 850 nm (x), and three-dimensional (3D) shape reconstruction of individual grain samples based on stereo imaging. The imaging system yields the images of 4096 x 2160 pixels with the pixel resolution of 1.93 {\mu}m/pix and field of view of 7.9 x 4.2 mm. Our validation measurements demonstrate that our multispectral imaging system, which observes the samples with the spectral bands comparable to those on the telescopic optical navigation camera (ONC-T) on Hayabusa2, yields reflectance spectra with a relative error of 3% and a 3D model with an error of 5%. These results indicate that the multiband imaging system with a 3D shape reconstruction capability yields accurate spectral and shape data on the returned samples. Using this instrument, we conducted multispectral measurements of two Ryugu samples (grains in the dishes A3 and C1) acquired from two locations on the asteroid. The average spectra of the measured Ryugu samples were flat and consistent with the global averaged spectrum of Ryugu. The 550-nm band (v-band) reflectance of the returned grains in the dishes was 2.4% on average, higher than that of the global averaged spectrum of Ryugu observed with ONC-T. This apparent difference could be because the returned grains have greater specular reflectance.

Chameleon diamonds: Thermal processes governing luminescence and a model for the color change

To date, the eponymous color-changing behavior of chameleon diamonds lacks an explanation in terms of an identified diamond defect structure or process. Well known, however, is that this color-change is driven by the influence of both light and heat. In this paper, we present observations of how luminescence emission in chameleon diamonds responds to temperature changes and optical pumping. Fluorescence, phosphorescence, and thermoluminescence experiments on a suite of natural chameleon diamonds reveal that a specific emission band, peaking near 550nm, may be stimulated by several different mechanisms. We have observed thermal quenching of the 550nm emission band with an activation energy of 0.135eV. The 550nm band is also observed in phosphorescence and thermoluminescence. Thermoluminescence spectra suggest the presence of low lying acceptor states at 0.7eV above the valence band. When excited with 270nm light, we observe emission of light in two broad spectral bands peaking at 500 and 550nm. We suggest that the 550nm emission band results from donor—acceptor pair recombination (DAPR) from low lying acceptor states at ca. 0.7eV above the valence band and donor states approximately 2.5 to 2.7eV above the valence band. We do not identify the structure of these defects. We propose a speculative model of the physics of the color change from ‘yellow’ to ‘green’ which results from increased broad-band optical absorption in the near-IR to visible due to transitions from the valence band into un-ionized acceptor states available in the ‘green’ state of the chameleon diamond. We report near-IR absorption spectra confirming the increased absorption of light in the near-IR to visible in the ‘green’ when compared to the ‘yellow’ state with a threshold at ca. 0.65eV, supporting the proposed model.

Electroluminescence from SiNx layers doped with Ce3 + ions

Luminescent cerium doped silicon light emitting devices on indium tin oxide coated glass have been fabricated using plasma enhanced chemical vapour deposition and sputtering techniques. The electrical and electroluminescent properties of the devices have been investigated. The dominant conduction mechanism at high electric field is contributed to the Poole-Frenkel thermionic emission. The as deposited films emit a broad electroluminescence in the 500nm–800nm range. After laser annealing process, an additional 400nm–550nm band was observed. The EL spectra have been decomposed into two Gaussian bands at around 460nm and 650nm as a result of numerical fitting. The energy band centred at 460nm is attributed to the cerium doping of the film and the 650nm energy band is related to the luminescence from defect states in the SiNx lattice.

基于低单色像差离轴全息透镜的解复用器

A novel scheme is proposed, in which the aberrations in the off-axis holographic lenses used as demultiplexers are reduced to a low enough level for relatively small channel spacing. The scheme includes optimizing the recording and reconstruction geometries and collimating the reconstruction wave with a gradient-index lens. A demultiplexer operated in the 1 550-nm band with 5-nm channel spacing and ?\infty-dB crosstalk is obtained using the scheme. The channel spacing can be decreased to 2 nm by etching the cladding of the output fibers to a smaller size.

Postendocytic Sorting of Constitutively Internalized Dopamine Transporter in Cell Lines and Dopaminergic Neurons

The dopamine transporter (DAT) mediates reuptake of released dopamine and is the target for psychostimulants, such as cocaine and amphetamine. DAT undergoes marked constitutive endocytosis, but little is known about the fate and sorting of the endocytosed transporter. To study DAT sorting in cells lines, we fused the one-transmembrane segment protein Tac to DAT, thereby generating a transporter (TacDAT) with an extracellular antibody epitope suited for trafficking studies. TacDAT was functional and endocytosed constitutively in HEK293 cells. According to an ELISA-based assay, TacDAT intracellular accumulation was increased by the lysosomal protease inhibitor leupeptin and by monensin, an inhibitor of lysosomal degradation and recycling. Monensin also reduced TacDAT surface expression consistent with partial recycling. In both HEK293 cells and in the dopaminergic cell line 1Rb3An27, constitutively internalized TacDAT displayed primary co-localization with the late endosomal marker Rab7, less co-localization with the "short loop" recycling marker Rab4, and little co-localization with the marker of "long loop" recycling endosomes, Rab11. Removal by mutation of N-terminal ubiquitination sites did not affect this sorting pattern. The sorting pattern was distinct from a bona fide recycling membrane protein, the beta(2)-adrenergic receptor, that co-localized primarily with Rab11 and Rab4. Constitutively internalized wild type DAT probed with the fluorescently tagged cocaine analogue JHC 1-64, exhibited the same co-localization pattern as TacDAT in 1Rb3An27 cells and in cultured midbrain dopaminergic neurons. We conclude that DAT is constitutively internalized and sorted in a ubiquitination-independent manner to late endosomes/lysosomes and in part to a Rab4 positive short loop recycling pathway.

Gαi and Gβγ Jointly Regulate the Conformations of a Gβγ Effector, the Neuronal G Protein-activated K+ Channel (GIRK)

Stable complexes among G proteins and effectors are an emerging concept in cell signaling. The prototypical G betagamma effector G protein-activated K(+) channel (GIRK; Kir3) physically interacts with G betagamma but also with G alpha(i/o). Whether and how G alpha(i/o) subunits regulate GIRK in vivo is unclear. We studied triple interactions among GIRK subunits 1 and 2, G alpha(i3) and G betagamma. We used in vitro protein interaction assays and in vivo intramolecular Förster resonance energy transfer (i-FRET) between fluorophores attached to N and C termini of either GIRK1 or GIRK2 subunit. We demonstrate, for the first time, that G betagamma and G alpha(i3) distinctly and interdependently alter the conformational states of the heterotetrameric GIRK1/2 channel. Biochemical experiments show that G betagamma greatly enhances the binding of GIRK1 subunit to G alpha(i3)(GDP) and, unexpectedly, to G alpha(i3)(GTP). i-FRET showed that both G alpha(i3) and G betagamma induced distinct conformational changes in GIRK1 and GIRK2. Moreover, GIRK1 and GIRK2 subunits assumed unique, distinct conformations when coexpressed with a "constitutively active" G alpha(i3) mutant and G betagamma together. These conformations differ from those assumed by GIRK1 or GIRK2 after separate coexpression of either G alpha(i3) or G betagamma. Both biochemical and i-FRET data suggest that GIRK acts as the nucleator of the GIRK-G alpha-G betagamma signaling complex and mediates allosteric interactions between G alpha(i)(GTP) and G betagamma. Our findings imply that G alpha(i/o) and the G alpha(i) betagamma heterotrimer can regulate a G betagamma effector both before and after activation by neurotransmitters.

In situ measurement of absorption and emission cross sections in Er/sup 3+/-doped waveguides for transitions involving thermalized states

An application to transitions involving thermalized states of a procedure based on the McCumber theory to determine emission and absorption cross sections in waveguides from transversal fluorescence spectra is presented. The procedure is tested in Er-doped Ti:LiNbO/sub 3/ waveguides to provide accurate cross-section values for the recently attractive 550-nm band. We also study the excited-state absorption transition around 860 nm and present, to our knowledge, the first published cross-section values for this transition.

40-mW 100°C maximum temperature operation of 655-nm band InGaP-InGaAlP strained multiple-quantum-well laser diodes

High-power and high-temperature operation of 40 mW at 100/spl deg/C has been realized in 655-nm band multiple-quantum-well (MQW) laser diodes. Both low threshold current density and low optical power density have been achieved by optimizing InGaP-InGaAlP strained MQW separate-confinement heterostructure, high doping for acceptors in p-cladding layer and adopting low-optical-loss high-reflectivity-coating at the rear facet. Fundamental-transverse-mode operation, up to 70 mW, was obtained. High-frequency and large-intensity modulation characteristics above 1 GHz were demonstrated. The relative intensity noise values were as low as -135 dB/Hz under an optical feedback with high-frequency modulation. Stable operation of 30 mW at 70/spl deg/C over 1000 h was accomplished.

Confocal scanning microspectrofluorometry reveals specific anthracyline accumulation in cytoplasmic organelles of multidrug-resistant cancer cells.

We used confocal microspectrofluorometry to investigate intracellular distribution of pirarubicin or THP-DOX in parental K562, CEM, and LR73 tumor cells and their corresponding multidrug-resistant (MDR) strains. Each spectrum of a recorded image was considered as a combination of cell autofluorescence and fluorescence of the drug. In the cytoplasm of parental K562, CEM, and LR73 cells, THP-DOX fluorescence emission profile was similar to that of free drug in aqueous buffer. The (I550nm/I600nm) ratio was 0. 50 +/- 0.1. However, in the cytoplasm of resistant cells the 550-nm band profile was modified. The I550nm/I600nm ratio was 0.85 +/- 0.2 in MDR K562 cells, which is significantly different from the ratio in sensitive cells (p<0.01). This appeared first to correspond to accumulation and self-oligomerization of THP-DOX in cytoplasmic organelles of MDR cells. Transfection of LR73 cells with the mdr1 gene conferred this characteristic on the resistant LR73R cells. Bodipy-ceramide, a trans-Golgi probe, was co-localized with the typical fluorescence emission peak at 550 nm observed in the cytoplasm of MDR cells. This organelle has been shown to be more acidic in MDR cells. Moreover, this specific pattern was similar to that observed when anthracycline is complexed with sphingomyelin. The typical fluorescence emission peak at 550 nm decreased in MDR cells incubated simultaneously in the presence of the drug and quinine, verapamil, or S9788. Growth inhibitory effect and nuclear accumulation of THP-DOX data obtained on LR73R and LR73D cell lines showed that only during reversion of resistance by verapamil and S9788 was an increase of nuclear THP-DOX accumulation observed. Our data suggest that characteristics of molecular environment, such as higher pH gradient or lipid structures, would be potential mechanisms of multidrug-resistance via the sequestration of anthracyclines.

High-reflectance Waters of Possible Coccolithophore Blooms in NW Pacific : Analysis of 1979-86 Nimbus-7/CZCS Data Set

The temporal and spatial distribution patterns of coccolithophore-like high reflectance waters in the north-western Pacific (20°N-50°N, 120°E-180°E) during 1979-86 were determined from a Nimbus-7/CZCS data set of 1940 atmospherically-corrected and quality-checked scenes. The analysis was conducted by computer classification based on the satellite-derived sub-surface reflectance at 443nm and 550nm bands, with the aid of empirical screening to exclude cloud-contaminated pixels as well as areas of high suspended solid concentration. In 22 scenes within the data set, high reflectance waters were observed in the area ranging from 35°N to 50°N, especially in the off Hokkaido/Sanriku area from May to September. The locations of the high reflectance water appearance indicate tendency to shift northward over the period. Although the distribution pattern may be affected by the non-uniform sampling of cloud-free satellite observation, the whole analysis shows that there is little possibility to observe high reflectance waters in other regions, including Japan Sea and the Sea of Okhotsk.

Purification and characterization of nitrous oxide reductase from Pseudomonas aeruginosa strain P2

Nitrous oxide reductase, which catalyzes the reduction of N2O to N2, was purified in a largely oxidized form from Pseudomonas aeruginosa strain P2 by a simple anaerobic procedure to yield an enzyme with a peptide purity of 95-98%. For the native (dimeric) enzyme, Mr = 120,000 and for the denatured subunit, Mr = 73,000. The enzyme contained four Cu atoms/subunit, was purple in color, and exhibited a broad absorption band at 550 nm with an extinction coefficient of about 11,000 M-1 x cm-1 referenced to the dimer. It was nearly inactive as prepared but could be activated by incubation with 2-(N-cyclohexylamino)ethane sulfonate buffer, pH 10, to specific activities as high as 27 mumol of N2O x min-1 x mg-1.Km for N2O and benzyl viologen radical cation was about 2 and 4 microM, respectively, both before and after enzyme activation. Activation increased the t1/2 for turnover-dependent inactivation from about 30 s to 5-10 min. Reduction of the enzyme by dithionite was kinetically biphasic and resulted in the loss of the 550-nm band and ultimate appearance of a 670-nm band. Isoelectric focusing revealed five components with pI values from 5.2 to 5.7. The pI values did not change following activation. The copper CD spectrum of the enzyme as prepared was different from that for the activated enzyme, whereas those for the enzyme after exposure to air and the activated enzyme were similar. Because the activated enzyme is a mixture of activated and inactive species, the specific activity of the activated species must be substantially greater than the observed value. Molecular heterogeneity may also explain the decreased optical absorbance and CD amplitude that resulted from the activation process. The data overall reinforce the view that the absorption spectrum of nitrous oxide reductase is not a good predictor of absolute activity.

Use of visible spectral displacement method to determine the concentration of surfactants in aqueous solution

A substitution method in which phenolphthalein is displaced from the β-cyclodextrin cavity by the hydrocarbon moiety of a surfactant is used to determine the concentration of the surfactant. The 1:1 complex of phenolphthalein with β-cyclodextrin has an absorbance practically equal to zero in the region of the 550-nm band of the basic form of phenolphthalein. When solute molecules containing an alkyl moiety displace some of the phenolphthalein at a pH of approximately 10.5, the absorbance at 550 nm is significantly increased and serve as a direct measure of the concentration of the solute. The method is useful in determining concentrations of surfactants such as sodium dodecyl sulfate and N, N-dimethyl- N-dodecylamine oxide, which do not contain chromophores.

Optical properties of theTl0(1) center in KCl

We report both experimental and theoretical studies of the ${\mathrm{Tl}}^{0}$(1) center in KCl, a center consisting of a neutral Tl atom perturbed by the field of an adjacent anion vacancy. Absorption bands peaking at 1040, 720, 550, and 340 nm are all shown to belong to the ${\mathrm{Tl}}^{0}$(1) center. The relatively weak ($f\ensuremath{\lesssim}0.01$) bands at 1040 and 720 nm correspond to absorptions terminating on the crystal-field-split components of the ${6}^{2}{P}_{\frac{3}{2}}$ level, while the stronger band at 550 nm corresponds to transition to a state derived largely from ${7}^{2}{S}_{\frac{1}{2}}$. The sole luminescence band is the laser-active band having 1.6-\ensuremath{\mu}sec decay time and peaking at 1520 nm. The model presented here can account for the transition energies of the $6p$ manifold, including the Stokes shift between absorption (at 1040 nm) and luminescence, as well as the polarization properties and relative oscillator strengths of the 1040-, 720-, and 550-nm bands.