Color Dispersion Research Articles

MAKING THE MOST OF CHANGES IN PRINTING

IT’S BEEN YEARS since the old industrial town of Haverhill, Mass., could be called an economic engine. But the millions of dollars being spent there by Cabot Corp. are a sign that innovative chemistry can spur investment and create new jobs in the unlikeliest of places. Last month, Cabot announced plans to invest $10 million to double color dispersion capacity at its ink-jet printing colorants plant in Haverhill. Powered with chemistry invented by Cabot researcher James A. Belmont, the facility makes pigment dispersions that are helping usher in big changes in the home, office, and commercial printing markets. The Haverhill plant opened in 2001 in a former backpack factory. Today it employs close to 80 lab technicians, engineers, managers, and hourly workers. The expansion project should add another 15 full-time positions, says Fred von Gottberg, who heads both Cabot’s ink-jet business and its new business segment. Gottberg attributes the genesis of the ink-jet business to ...

NGC 2419: a large and extreme second generation in a currently undisturbed cluster

We analyse complementary HST and SUBARU data for the globular cluster NGC 2419. We make a detailed analysis of the horizontal branch (HB), that appears composed by two main groups of stars: the luminous blue HB stars ---that extend by evolution into the RR Lyrae and red HB region--- and a fainter, extremely blue population. We examine the possible models for this latter group and conclude that a plausible explanation is that they correspond to a significant (~30 %) extreme second generation with a strong helium enhancement (Y~0.4). We also show that the color dispersion of the red giant branch is consistent with this hypothesis, while the main sequence data are compatible with it, although the large observational error blurs the possible underlying splitting. While it is common to find an even larger (50 -- 80) percentage of second generation in a globular cluster, the presence of a substantial and extreme fraction of these stars in NGC 2419 might be surprising, as the cluster is at present well inside the radius beyond which the galactic tidal field would be dominant. If a similar situation had been present in the first stages of the cluster life, the cluster would have retained its initial mass, and the percentage of second generation stars should have been quite small (up to ~10 %). Such a large fraction of extreme second generation stars implies that the system must have been initially much more massive and in different dynamical conditions than today. We discuss this issue in the light of existing models of the formation of multiple populations in globular clusters.

The reddening law of type Ia supernovae: separating intrinsic variability from dust using equivalent widths

We employ 76 type Ia supernovae with optical spectrophotometry within 2.5 days of B-band maximum light obtained by the Nearby Supernova Factory to derive the impact of Si and Ca features on supernovae intrinsic luminosity and determine a dust reddening law. We use the equivalent width of Si II {\lambda}4131 in place of light curve stretch to account for first-order intrinsic luminosity variability. The resultant empirical spectral reddening law exhibits strong features associated with Ca II and Si II {\lambda}6355. After applying a correction based on the Ca II H&K equivalent width we find a reddening law consistent with a Cardelli extinction law. Using the same input data, we compare this result to synthetic rest-frame UBVRI-like photometry in order to mimic literature observations. After corrections for signatures correlated with Si II {\lambda}4131 and Ca II H&K equivalent widths, and introducing an empirical correlation between colors, we determine the dust component in each band. We find a value of the total-to-selective extinction ratio, RV = 2.8 \pm 0.3. This agrees with the Milky Way value, in contrast to the low RV values found in most previous analyses. This result suggests that the long-standing controversy in interpreting SN Ia colors and their compatibility with a classical extinction law, critical to their use as cosmological probes, can be explained by the treatment of the dispersion in colors, and by the variability of features apparent in SN Ia spectra.

The SAURON project - XVIII. The integrated UV-line-strength relations of early-type galaxies

Using far (FUV) and near (NUV) ultraviolet photometry from guest investigator programmes on the Galaxy Evolution Explorer (GALEX) satellite, optical photometry from the MDM Observatory and optical integral-field spectroscopy from SAURON, we explore the UV-linestrength relations of the 48 nearby early-type galaxies in the SAURON sample. Identical apertures are used for all quantities, avoiding aperture mismatch. We show that galaxies with purely old stellar populations show well-defined correlations of the integrated FUV-V and FUV-NUV colours with the integrated Mgb and Hbeta absorption linestrength indices, strongest for FUV-NUV. Correlations with the NUV-V colour, Fe5015 index and stellar velocity dispersion are much weaker. These correlations put stringent constraints on the origin of the UV-upturn phenomenon in early-type galaxies, and highlight its dependence on age and metallicity. In particular, despite recent debate, we recover the negative correlation between FUV-V colour and Mg linestrength originally publicised by Burstein et al. (1988), which we refer to as the "Burstein relation", suggesting a positive dependence of the UV-upturn on metallicity. We argue that the scatter in the correlations is real, and present mild evidence that a strong UV excess is preferentially present in slow-rotating galaxies. We also demonstrate that most outliers in the correlations are galaxies with current or recent star formation, some at very low levels. We believe that this sensitivity to weak star formation, afforded by the deep and varied data available for the SAURON sample, explains why our results are occasionally at odds with other recent but shallower surveys. This is supported by the analysis of a large, carefully-crafted sample of more distant early-type galaxies from the Sloan Digital Sky Survey (SDSS), more easily comparable with current and future large surveys.

DIFFERENTIAL MORPHOLOGY BETWEEN REST-FRAME OPTICAL AND ULTRAVIOLET EMISSION FROM 1.5 <z< 3 STAR-FORMING GALAXIES

We present the results of a comparative study of the rest-frame optical and rest-frame ultraviolet morphological properties of 117 star-forming galaxies (SFGs), including BX, BzK, and Lyman break galaxies with B<24.5, and 15 passive galaxies in the region covered by the Wide Field Camera 3 Early Release Science program. Using the internal color dispersion (ICD) diagnostic, we find that the morphological differences between the rest-frame optical and rest-frame UV light distributions in 1.4<z<2.9 SFGs are typically small (ICD~0.02). However, the majority are non-zero (56% at >3 sigma) and larger than we find in passive galaxies at 1.4<z<2, for which the weighted mean ICD is 0.013. The lack of morphological variation between individual rest-frame ultraviolet bandpasses in z~3.2 galaxies argues against large ICDs being caused by non-uniform dust distributions. Furthermore, the absence of a correlation between ICD and galaxy UV-optical color suggests that the non-zero ICDs in SFGs are produced by spatially distinct stellar populations with different ages. The SFGs with the largest ICDs (>~0.05) generally have complex morphologies that are both extended and asymmetric, suggesting that they are mergers-in-progress or very large galaxies in the act of formation. We also find a correlation between half-light radius and internal color dispersion, a fact that is not reflected by the difference in half-light radii between bandpasses. In general, we find that it is better to use diagnostics like the ICD to measure the morphological properties of the difference image than it is to measure the difference in morphological properties between bandpasses.

基于序列相息图的真彩色三维物体全息成像

We propose a computational method for generating sequential kinoforms of real-existing full-color threedimensional (3D) objects and realizing high-quality 3D imaging. The depth map and color information are obtained using non-contact full-color 3D measurement system based on binocular vision. The obtained full-color 3D data are decomposed into multiple slices with RGB channels. Sequential kinoforms of each channel are calculated and reconstructed using a Fresnel-diffraction-based algorithm called the dynamicpseudorandom-phase tomographic computer holography (DPP-TCH). Color dispersion introduced by different wavelengths is well compensated by zero-padding operation in the red and green channels of object slices. Numerical reconstruction results show that the speckle noise and color-dispersion are well suppressed and that high-quality full-color holographic 3D imaging is feasible. The method is useful for improving the 3D image quality in holographic displays with pixelated phase-type spatial light modulators (SLMs).

Adjusting a light dispersion model to fit measurements from vertebrate ocular media as well as ray-tracing in fish lenses

Color dispersion, i.e., the dependency of refractive index of any transparent material on the wavelength of light, has important consequences for the function of optical instruments and animal eyes. Using a multi-objective goal attainment optimization algorithm, a dispersion model was successfully fitted to measured refractive indices of various ocular media and the longitudinal chromatic aberration determined by laser-scanning in the crystalline lens of the African cichlid fish, Astatotilapia burtoni. The model describes the effects of color dispersion in fish lenses and may be applicable to the eyes of other vertebrates as well.

Luminous Red Galaxies at Redshifts, z=0.4-0.5

AbstractWe describe and analyze the color dispersion of LRG's at redshifts, z=0.4-0.5.

H I-SELECTED GALAXIES IN THE SLOAN DIGITAL SKY SURVEY. II. THE COLORS OF GAS-RICH GALAXIES

We utilize color information for an HI-selected sample of 195 galaxies to explore the star formation histories and physical conditions that produce the observed colors. We show that the HI selection creates a significant offset towards bluer colors that can be explained by enhanced recent bursts of star formation. There is also no obvious color bimodality, because the HI selection restricts the sample to bluer, actively star forming systems, diminishing the importance of the red sequence. Rising star formation rates are still required to explain the colors of galaxies bluer than g-r < 0.3. We also demonstrate that the colors of the bluest galaxies in our sample are dominated by emission lines and that stellar population synthesis models alone (without emission lines) are not adequate for reproducing many of the galaxy colors. These emission lines produce large changes in the r-i colors but leave the g-r color largely unchanged. In addition, we find an increase in the dispersion of galaxy colors at low masses that may be the result of a change in the star formation process in low-mass galaxies.

HYPERCOMPACT STELLAR SYSTEMS AROUND RECOILING SUPERMASSIVE BLACK HOLES

A supermassive black hole ejected from the center of a galaxy by gravitational wave recoil carries a retinue of bound stars - a "hypercompact stellar system" (HCSS). The numbers and properties of HCSSs contain information about the merger histories of galaxies, the late evolution of binary black holes, and the distribution of gravitational-wave kicks. We relate the structural properties of HCSSs to the properties of their host galaxies, in two regimes: collisional, i.e. short nuclear relaxation times; and collisionless, i.e. long nuclear relaxtion times. HCSSs are expected to be similar in size and luminosity to globular clustersbut in extreme cases their stellar mass can approach that of UCDs. However they differ from all other classes of compact stellar system in having very high internal velocities. We show that the kick velocity is encoded in the velocity dispersion of the bound stars. Given a large enough sample of HCSSs, the distribution of gravitational-wave kicks can therefore be empirically determined. We combine a hierarchical merger algorithm with stellar population models to compute the rate of production of HCSSs over time and the probability of observing HCSSs in the local universe as a function of their apparent magnitude, color, size and velocity dispersion, under two assumptions about the star formation history prior to the kick. We predict that roughly 100 should be detectable within 2 Mpc of the center of the Virgo cluster and that many of these should be bright enough that their high internal velocity dispersions could be measured with reasonable exposure times.

Miniature optical autofocus camera by micromachined fluoropolymer deformable mirror

Along with the progress of image sensors in recent years, fix-focus cameras on mobile electronic devices do not fulfill consumer needs. With the size of mobile devices getting smaller and smaller, the displacement-to-thickness ratio is getting larger, and that makes mechanical motor systems difficult to be packaged inside cameras to achieve autofocus function. We propose a design using micromachined fluoropolymer deformable mirrors rather than traditional mechanical motor. With low color dispersion and adjustable power range of 20-diopter, deformable mirrors can be integrated into optical module and are well suitable for miniature optical auto-focus camera.

An Asbestos Fiber Detection Technique Utilizing Image Processing Based on Dispersion Color

In an asbestos qualitative analysis, the major methods are X-ray diffraction analysis and visual observation by operators using a microscope. In particular, a major method of visual evaluation is dispersion staining. In the usual visual observation process, the operators check the asbestos fibers in the view of the microscope and count the number of asbestos fibers. The method presented here attempts to detect asbestos fibers in the images taken by a microscope. The dispersion staining method identifies asbestos fibers with color dispersion from an immersion liquid combined with polarization. The presented method employs color changes of asbestos fibers associated with polarization. Specifically, candidate asbestos fibers are identified using the changes of dispersion colors and also position-matching between two images. The performance of the method has been evaluated by comparing its results with the results obtained by a human expert.

The development of colour-encapsulated microspheres for novel colour cosmetics

In the present study, the preparation, characterization and colour retention properties of organic colour-loaded microspheres are described. The study aimed to produce shatter-resistant, low-bleeding polymeric microspheres with particle diameters of 20 µm containing 10–20% (w/w) of the Food, Drug, and Cosmetic grade colourants FD&C Blue No. 1 Al Lake, FD&C Yellow No. 5 Al Lake and D&C Red No. 36 by utilizing an aqueous-dispersed polymer water-in-oil (W/O) solvent evaporation process featuring styrene/acrylates-based copolymers. The influences of matrix polymeric components on the shape, integrity and dye retention of the microspheres were studied. Encapsulation matrices based on alkali soluble polymers yielded misshapen spheroids that were prone both to swelling and decreased dye retention in aqueous environments, as well as loss of shape at 70°C in cosmetic oils under shear. A resin supported emulsion (RSE)-based matrix, in comparison, yielded highly spherical microspheres resistant to shape deformation and swelling. Additions of up to 15% (w/w) of an alkali soluble polymer to the RSE system improved colour dispersion without detrimentally affecting the structural integrity of the microspheres while also slightly decreasing dye concentrations released into aqueous solutions. The in vitro dye release of the colour-loaded microspheres in a cosmetic-type water-in-silicone (W/Si) emulsion was evaluated and compared to the in vitro dye release studies in aqueous solutions. No direct correlations between the emulsion system and single-component aqueous solutions could be made. Dye-release levels evaluated from contacting the microspheres with a complex aqueous medium (CAM5), which incorporated ingredient classes typically encountered in the aqueous phase of an emulsion, were found to correlate to levels determined in the generic W/Si emulsion with a 93% linear regression between the data sets. This study demonstrates that the CAM5 protocol (or, alternatively, a CAM2.5 protocol) satisfactorily predicted that the commercial materials derived, in part, from this study (Ciba: ENCAPSULENCE™ Blue 1, ENCAPSULENCE™ Yellow 5 and ENCAPSULENCE™ Red 36) are well suited to retain their colour and shape in liquid cosmetic foundations.

The colour-lightcurve shape relation of type Ia supernovae and the reddening law

A study of the time sequence of optical colours of a large sample of nearby Type Ia supernovae (SNe Ia) is presented. We study the dependence of the colour time evolution with respect to the lightcurve shape, parametrized by the stretch factor. We fit the spectral template that minimizes the colour dispersion in SNe Ia, as measured through UBVRI photometry of near-by supernovae. A clear colour dependence upon lightcurve shape is found, with the narrower lightcurves being redder up to about one month past lightcurve maximum. We also derive an average reddening law, after correcting for lightcurve shape differences in intrinsic colour, that is well described by a Cardelli, Clayton & Mathis law with R_V=1.75 \pm 0.27 for 80 Type Ia supernovae with E(B-V) < 0.7 mag. A subset sample including 69 SNe with modest reddening, E(B-V)<0.25 mag, yields a significantly smaller value, R_V ~ 1, suggesting that the observed reddening of Type Ia supernovae may have a more complex origin, perhaps involving other processes beside extinction by interstellar dust in the host galaxy.

P‐185: Single Cell Gap Single Mode Transflective Liquid Crystal Display with High Optical Efficiency

AbstractA transflective liquid crystal display with single cell gap single mode structure is reported. Electrically controllable birefringence (ECB) mode is applied at both reflective (R) and transmissive (T) regions. with optimized orientation of only two compensation films, very high brightness is achieved for both R and T regions. At the same time, the dark state has nearly no color dispersion. High contrast ratio is achieved. Moreover, the electro‐optical characteristics of R and T regions match with each other well. The fabrication process is also very easy.

Color dispersion in two-dimensional phase array based on polymer-dispersed liquid crystal film

This work proposes a feasible method for fabricating a two-dimensional periodic structure with a sub-micrometer periodicity using a single laser beam, based on polymer-dispersed liquid crystal (PDLC) films. The resulting nano-PDLC morphology is highly symmetrical, and similar to that written using multi-beam interference. The increase in the electric-tunability of the optical behavior, including spatial diffraction and color dispersion, is examined. The color dispersion provides optical evidence of the periodic structure of the PDLC film.

Polymer Deformable Mirror for Optical Auto Focusing

A low-stress organic polymer membrane is proposed as a deformable mirror that can be incorporated into a cellular phone camera to achieve auto focusing without motor-type moving parts. It is demonstrated that our fabricated device has an optical power of 20 diopters and can switch focus in 14 ms. The surface roughness of the organic membrane is measured around 15 nm, less than λ/20 of the visible light. With curve fitting, we found that the actuated membrane is almost parabolic in shape, which leads to less aberration than spherical surfaces. It is suitable for reflective- optics systems. fulfill the two requirements of large refractive index contrast and small density difference. Another solution is the use of liquid crystal lenses (4), (5), but the incident light must be linearly polarized. It was also proposed in (6) and (7) to adopt deformable mirrors in a reflective optics configuration. Recently, reflective optics has attracted more attention as a means of achieving a long lightpath in thin products because of the folded light-path design. Deformable mirrors have an advantage of low color dispersion, but the optical power of silicon-based deformable mirrors (8) is relatively small. We propose an organic polymer deformable mirror which can be operated over a large optical power range of up to 20 diopters, which is one order of magnitude higher than the range of previously reported devices. Experimental results of its actuated shape and surface roughness will also be discussed.

The Cosmic Horseshoe: Discovery of an Einstein Ring around a Giant Luminous Red Galaxy

We report the discovery of an almost complete (~300°) Einstein ring of diameter 10'' in Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5). Spectroscopic data from the 6 m telescope of the Special Astrophysical Observatory reveal that the deflecting galaxy has a line-of-sight velocity dispersion in excess of 400 km s-1 and a redshift of 0.444, while the source is a star-forming galaxy with a redshift of 2.379. From its color, luminosity, and velocity dispersion, we argue that this is the most massive galaxy lens hitherto discovered.

Structure through colour: a pixel approach towards understanding galaxies

We present a study of pixel Colour Magnitude Diagrams (pCMDs) for a sample of 69 nearby galaxies chosen to span a wide range of Hubble types. Our goal is to determine how useful a pixel approach is for studying galaxies according to their stellar light distributions and content. The galaxy images were analysed on a pixel-by-pixel basis to reveal the structure of the individual pCMDs. We find that the average surface brightness (or projected mass density) in each pixel varies according to galaxy type. Early-type galaxies exihibit a clear ``prime sequence'' and some pCMDs of face-on spirals reveal ``inverse-L'' structures. We find that the colour dispersion at a given magnitude is found to be approximately constant in early-type galaxies but this quantity varies in the mid and late-types. We investigate individual galaxies and find that the pCMDs can be used to pick out morphological features. We discuss the discovery of ``Red Hooks'' in the pCMDs of six early-type galaxies and two spirals and postulate their origins. We develop quantitative methods to characterise the pCMDs, including measures of the blue-to-red light ratio and colour distributions of each galaxy and we organise these by morphological type. We compare the colours of the pixels in each galaxy with the stellar population models of Bruzual & Charlot (2003) to calculate star formation histories for each galaxy type and compare these to the stellar mass within each pixel. Maps of pixel stellar mass and mass-to-light ratio are compared to galaxy images. We apply the pCMD technique to three galaxies in the Hubble Ultra Deep Field to test the usefulness of the analysis at high redshift. We propose that these results can be used as part of a new system of automated classification of galaxies that can be applied at high redshift.

Colours of intermediate z bulges in Groth and GOODS-N

AbstractThe chronology of bulge and disk formation is a major unsolved issue in galaxy formation, which impacts on our global understanding of the Hubble sequence. We present colours of the nuclear regions of intermediate-redshift disk galaxies, with the aim of obtaining empirical information of ages of bulges at intermediate z. We work with a sample of 248 galaxies (123 inclined + 125 face-on) from the HST Groth Strip Survey (Groth et al. 1994) and another one with 404 objects (214 inclined + 190 face-on) from the HST GOODS-N field (Giavalisco et al. 2004), covering redshifts 0.1 &lt; z &lt; 1.3. Those samples are apparent-diameter limited at R &gt; 1.4″. We find that, as in the Local Universe, the minor axis color profiles are negative (bluer outward), and fairly gentle, indicating that bulge colours are not distinctly different from disk colours. We apply a conservative criterion to identify bulges and potential precursors of present-day bulges, based on nuclear excess surface brightness above the exponential profile of the outer parts. For galaxies with central brightness excesses, rest-frame colour distributions show a red sequence that confirms the finding of very red bulges by Koo et al. (2005), using independent methods. In contrast, galaxies without central brightness excesses show typical colours of star-forming populations. Clearly, something had truncated star formation in many high-density cores, already at z ~ 1. The truncation epoch is uncertain, 1.5 &lt; z &lt; 10. The colour-magnitude distribution of intermediate-z bulges shows more colour dispersion than that of bulges in the Local Universe. About 50% of bulges are as red as local bulges, while the remainder are significantly bluer, a possible sign of late bulge formation. We also find that bulge colours correlate with integrated galaxy colours and with their disk colours.