WorldWideScience

Sample records for surface brightness gradient

  1. Abundance gradients in low surface brightness spirals: clues on the origin of common gradients in galactic discs

    Science.gov (United States)

    Bresolin, F.; Kennicutt, R. C.

    2015-12-01

    We acquired spectra of 141 H II regions in 10 late-type low surface brightness galaxies (LSBGs). The analysis of the chemical abundances obtained from the nebular emission lines shows that metallicity gradients are a common feature of LSBGs, contrary to previous claims concerning the absence of such gradients in this class of galaxies. The average slope, when expressed in units of the isophotal radius, is found to be significantly shallower in comparison to galaxies of high surface brightness. This result can be attributed to the reduced surface brightness range measured across their discs, when combined with a universal surface mass density-metallicity relation. With a similar argument we explain the common abundance gradient observed in high surface brightness galaxy (HSBG) discs and its approximate dispersion. This conclusion is reinforced by our result that LSBGs share the same common abundance gradient with HSBGs, when the slope is expressed in terms of the exponential disc scalelength.

  2. The GALEX/S4G Surface Brightness and Color Profiles Catalog. I. Surface Photometry and Color Gradients of Galaxies

    Science.gov (United States)

    Bouquin, Alexandre Y. K.; Gil de Paz, Armando; Muñoz-Mateos, Juan Carlos; Boissier, Samuel; Sheth, Kartik; Zaritsky, Dennis; Peletier, Reynier F.; Knapen, Johan H.; Gallego, Jesús

    2018-02-01

    We present new spatially resolved surface photometry in the far-ultraviolet (FUV) and near-ultraviolet (NUV) from images obtained by the Galaxy Evolution Explorer (GALEX) and IRAC1 (3.6 μm) photometry from the Spitzer Survey of Stellar Structure in Galaxies (S4G). We analyze the radial surface brightness profiles μ FUV, μ NUV, and μ [3.6], as well as the radial profiles of (FUV ‑ NUV), (NUV ‑ [3.6]), and (FUV ‑ [3.6]) colors in 1931 nearby galaxies (z measured scale length and central surface brightness values yield distributions of spin and circular velocity within a factor of two of those obtained via direct kinematic measurements. We find that at a surface brightness fainter than μ [3.6] = 20.89 mag arcsec‑2, or below 3 × 108 M ⊙ kpc‑2 in stellar mass surface density, the average specific star formation rate (sSFR) for star-forming and quiescent galaxies remains relatively flat with radius. However, a large fraction of GALEX Green Valley galaxies show a radial decrease in sSFR. This behavior suggests that an outside-in damping mechanism, possibly related to environmental effects, could be testimony of an early evolution of galaxies from the blue sequence of star-forming galaxies toward the red sequence of quiescent galaxies.

  3. SURFACE PHOTOMETRY OF LOW SURFACE BRIGHTNESS GALAXIES

    NARCIS (Netherlands)

    DEBLOK, WJG; VANDERHULST, JM; BOTHUN, GD

    1995-01-01

    Low surface brightness (LSB) galaxies are galaxies dominated by an exponential disc whose central surface brightness is much fainter than the value of mu(B)(0) = 21.65 +/- 0.30 mag arcsec(-2) found by Freeman. In this paper we present broadband photometry of a sample of 21 late-type LSB galaxies.

  4. Low surface brightness spiral galaxies

    International Nuclear Information System (INIS)

    Romanishin, W.

    1980-01-01

    This dissertation presents an observational overview of a sample of low surface brightness (LSB) spiral galaxies. The sample galaxies were chosen to have low surface brightness disks and indications of spiral structure visible on the Palomar Sky Survey. They are of sufficient angular size (diameter > 2.5 arcmin), to allow detailed surface photometry using Mayall 4-m prime focus plates. The major findings of this dissertation are: (1) The average disk central surface brightness of the LSB galaxies is 22.88 magnitude/arcsec 2 in the B passband. (2) From broadband color measurements of the old stellar population, we infer a low average stellar metallicity, on the order of 1/5 solar. (3) The spectra and optical colors of the HII regions in the LSB galaxies indicate a lack of hot ionizing stars compared to HII regions in other late-type galaxies. (4) The average surface mass density, measured within the radius containing half the total mass, is less than half that of a sample of normal late-type spirals. (5) The average LSB galaxy neutral hydrogen mass to blue luminosity ratio is about 0.6, significantly higher than in a sample of normal late-type galaxies. (6) We find no conclusive evidence of an abnormal mass-to-light ratio in the LSB galaxies. (7) Some of the LSB galaxies exhibit well-developed density wave patterns. (8) A very crude calculation shows the lower metallicity of the LSB galaxies compared with normal late-type spirals might be explained simply by the deficiency of massive stars in the LSB galaxies

  5. Does low surface brightness mean low density?

    NARCIS (Netherlands)

    deBlok, WJG; McGaugh, SS

    1996-01-01

    We compare the dynamical properties of two galaxies at identical positions on the Tully-Fisher relation, but with different surface brightnesses. We find that the low surface brightness galaxy UGC 128 has a higher mass-to-light ratio, and yet has lower mass densities than the high surface brightness

  6. The surface brightness of spiral galaxies

    International Nuclear Information System (INIS)

    Phillipps, S.; Disney, M.

    1983-01-01

    Correlations between optical surface brightness and the radio properties of spiral galaxies are investigated. It is found that galaxies with high surface brightness are more likely to be strong continuum radio sources and that galaxies with low surface brightness have high 21-cm line emission. (author)

  7. The lowest surface brightness disc galaxy known

    International Nuclear Information System (INIS)

    Davies, J.I.; Phillipps, S.; Disney, M.J.

    1988-01-01

    The discovery of a galaxy with a prominent bulge and a dominant extremely low surface brightness disc component is reported. The profile of this galaxy is very similar to the recently discovered giant low surface brightness galaxy Malin 1. The disc central surface brightness is found to be ∼ 26.4 Rμ, some 1.5 mag fainter than Malin 1 and thus by far the lowest yet observed. (author)

  8. Kinematics of giant low surface brightness galaxies

    NARCIS (Netherlands)

    Pickering, TE; Davies, JI; Impey, C; Phillipps, S

    1999-01-01

    High sensitivity H I observations now exist for six giant low surface brightness (LSB) disk galaxies including the two prototypes, Malin 1 (Bothun et al. 1987; Impey & Bothun 1989) and F568-6 (also known as Malin 2; Bothun et al. 1990). Their H I surface brightnesses are generally low, but

  9. Galaxy Selection and the Surface Brightness Distribution

    Science.gov (United States)

    McGaugh, Stacy S.; Bothun, Gregory D.; Schombert, James M.

    1995-08-01

    Optical surveys for galaxies are biased against the inclusion of low surface brightness (LSB) galaxies. Disney [Nature, 263,573(1976)] suggested that the constancy of disk central surface brightness noticed by Freeman [ApJ, 160,811(1970)] was not a physical result, but instead was an artifact of sample selection. Since LSB galaxies do exist, the pertinent and still controversial issue is if these newly discovered galaxies constitute a significant percentage of the general galaxy population. In this paper, we address this issue by determining the space density of galaxies as a function of disk central surface brightness. Using the physically reasonable assumption (which is motivated by the data) that central surface brightness is independent of disk scale length, we arrive at a distribution which is roughly flat (i.e., approximately equal numbers of galaxies at each surface brightness) faintwards of the Freeman (1970) value. Brightwards of this, we find a sharp decline in the distribution which is analogous to the turn down in the luminosity function at L^*^. An intrinsically sharply peaked "Freeman law" distribution can be completely ruled out, and no Gaussian distribution can fit the data. Low surface brightness galaxies (those with central surface brightness fainter than 22 B mag arcsec^-2^) comprise >~ 1/2 the general galaxy population, so a representative sample of galaxies at z = 0 does not really exist at present since past surveys have been insensitive to this component of the general galaxy population.

  10. The surface brightness of spiral galaxies

    International Nuclear Information System (INIS)

    Phillipps, S.; Disney, M.

    1983-01-01

    It is proposed that Freeman's discovery that the extrapolated central surface brightness of spiral galaxies is approximately constant can be simply explained if the galaxies contain a spheroidal component which dominates the light in their outer isophotes. Calculations of an effective central surface brightness indicate a wide spread of values. This requires either a wide spread in disc properties or significant spheroidal components or, most probably, both. (author)

  11. The surface brightness of spiral galaxies

    International Nuclear Information System (INIS)

    Disney, M.; Phillipps, S.

    1985-01-01

    The intrinsic surface brightness Ssub(e) of 500 disc galaxies (0<=T<=9) drawn from the Second Reference Catalogue is computed and it is shown that Ssub(e) does not correlate significantly with Msub(B), (B-V) or type. This is consistent with the notion that there is a heavy selection bias in favour of disc galaxies with that particular surface brightness which allows inclusion in the catalogue over the largest volume of space. (author)

  12. Dark Matter in Low Surface Brightness Galaxies

    NARCIS (Netherlands)

    Blok, W. J. G. de; McGaugh, S. S.

    1996-01-01

    Abstract: Low Surface Brightness (LSB) galaxies form a large population of disc galaxies that extend the Hubble sequence towards extreme late-types. They are only slowly evolving, and still in an early evolutionary state. The Tully-Fisher relation and rotation curves of LSB galaxies both show that

  13. Dark matter in low surface brightness galaxies

    NARCIS (Netherlands)

    de Blok, WJG; McGaugh, SS; Persic, M; Salucci, P

    1997-01-01

    Low Surface Brightness (LSB) galaxies form a large population of disc galaxies that extend the Hubble sequence towards extreme late-types. They are only slowly evolving, and still in an early evolutionary state. The Tully-Fisher relation and rotation curves of LSB galaxies both show that LSB

  14. Do Low Surface Brightness Galaxies Host Stellar Bars?

    International Nuclear Information System (INIS)

    Cervantes Sodi, Bernardo; Sánchez García, Osbaldo

    2017-01-01

    With the aim of assessing if low surface brightness galaxies host stellar bars and by studying the dependence of the occurrence of bars as a function of surface brightness, we use the Galaxy Zoo 2 data set to construct a large volume-limited sample of galaxies and then segregate these galaxies as having low or high surface brightness in terms of their central surface brightness. We find that the fraction of low surface brightness galaxies hosting strong bars is systematically lower than that found for high surface brightness galaxies. The dependence of the bar fraction on the central surface brightness is mostly driven by a correlation of the surface brightness with the spin and the gas richness of the galaxies, showing only a minor dependence on the surface brightness. We also find that the length of the bars is strongly dependent on the surface brightness, and although some of this dependence is attributed to the gas content, even at a fixed gas-to-stellar mass ratio, high surface brightness galaxies host longer bars than their low surface brightness counterparts, which we attribute to an anticorrelation of the surface brightness with the spin.

  15. The surface brightness of spiral galaxies: Pt. 4

    International Nuclear Information System (INIS)

    Phillipps, S.; Disney, M.; Ohio State Univ., Columbus

    1988-01-01

    Using measurements from IRAS correlations are found between optical surface brightness and both infrared-to-optical flux ratio and infrared colour temperature, in the sense that galaxies with high surface brightness have higher FIR emission and higher temperatures. (author)

  16. Estimation of the space density of low surface brightness galaxies

    NARCIS (Netherlands)

    Briggs, FH

    1997-01-01

    The space density of low surface brightness and tiny gas-rich dwarf galaxies are estimated for two recent catalogs: the Arecibo Survey of Northern Dwarf and Low Surface Brightness Galaxies and the Catalog of Low Surface Brightness Galaxies, List II. The goals are (1) to evaluate the additions to the

  17. Star formation and the surface brightness of spiral galaxies

    International Nuclear Information System (INIS)

    Phillipps, S.; Disney, M.

    1985-01-01

    The (blue) surface brightness of spiral galaxies is significantly correlated with their Hα linewidth. This can be most plausibly interpreted as a correlation of surface brightness with star formation rate. There is also a significant difference in surface brightness between galaxies forming stars in a grand design spiral pattern and those with floc star formation regions. (author)

  18. Giant Low Surface Brightness Galaxies: Evolution in Isolation M. Das

    Indian Academy of Sciences (India)

    galaxies: ISM—galaxies: spiral—cosmology: dark matter. 1. Introduction. Giant Low Surface Brightness (GLSB) galaxies are some of the largest spiral galax- ies in our nearby universe. However, for decades these galaxies remained undetected in galaxy surveys. This is because their optically dim stellar disks have a bright-.

  19. Low surface brightness galaxies in the Fornax Cluster: automated galaxy surface photometry

    International Nuclear Information System (INIS)

    Davies, J.I.; Phillipps, S.; Disney, M.J.

    1988-01-01

    A sample is presented of low surface brightness galaxies (with extrapolated central surface brightness fainter than 22.0 Bμ) in the Fornax Cluster region which has been measured by the APM machine. Photometric parameters, namely profile shape, scale length, central brightness and total magnitude, are derived for the sample galaxies and correlations between the parameters of low surface brightness dwarf galaxies are discussed, with particular reference to the selection limits. Contrary to previous authors we find no evidence for a luminosity-surface brightness correlation in the sense of lower surface brightness galaxies having lower luminosities and scale sizes. In fact, the present data suggest that it is the galaxies with the largest scale lengths which are more likely to be of very low surface brightness. In addition, the larger scale length galaxies occur preferentially towards the centre of the Cluster. (author)

  20. Surface brightness parameters as tests of galactic evolution

    International Nuclear Information System (INIS)

    Tinsley, B.M.

    1976-01-01

    It is shown that surface brightness parameters defined in terms of an isophotal radius are insensitive to galactic evolution, because the effects of luminosity evolution on the flux and isophotal radius almost cancel each other. Surface brightness parameters defined in terms of a metric radius are able to give fairly direct information on evolution, but only if the metric scale of each galaxy in the sample is determined by photometry of the galaxy itself. If, instead, a metric radius is estimated by means of a fiducial value of q 0 , the brightness-redshift relation yields only a function of both evoluting and the unknown cosmological model, which is very similar to the function obtained from the Hubble diagram

  1. Low surface brightness galaxies in the cluster A1367

    International Nuclear Information System (INIS)

    Davies, J.I.; Phillipps, S.; Disney, M.J.

    1989-01-01

    We have obtained deep CCD frames of apparently blank regions of sky in the hope of detecting very low surface brightness (LSB) objects in the cluster A1367. We discuss our data reduction, and image detection and selection techniques. If the galaxies detected are actually cluster members then they are dwarfs and the conclusions of a previous paper on the Fornax cluster are essentially confirmed. One area of variance is that the lowest surface brightness galaxies do not appear to be preferentially concentrated towards the cluster centre. This can be explained by there being a much larger density of dwarf galaxies over this bright galaxy-rich region of the universe. We find over our small area approximately four times as many LSB galaxies as would be expected from our Fornax data. We speculate on the possible origin and likely intensity of intergalactic light within clusters. (author)

  2. Giant Low Surface Brightness Galaxies: Evolution in Isolation M. Das

    Indian Academy of Sciences (India)

    are much lower than that of normal late type spirals (de Blok et al. 1996). The thinness of the HI distribution has ... 2000) but this is not suprising considering their low star forma- tion rates and low metallicities (Schombert ... normal galaxies in surface brightness and structure (Barth 2007). Galex UV obser- vations of the disks ...

  3. Distribution of surface brightness in Seyfert galaxies. III. Analysis of data

    International Nuclear Information System (INIS)

    Afanas'ev, V.L.; Doroshenko, V.T.; Terebizh, V.Yu.

    1987-01-01

    The observational data on the distribution of the surface brightness μ(r) in normal and Seyfert galaxies given in the first two parts of the study [1,2] are considered. The general form of μ(r) for r ≤ approximately equals 2 kpc is the same for the two groups of galaxies. The values of the parameters that characterize the central part of the spherical component are found, namely, the surface brightness μ 1 /sup (0)/, the brightness, the brightness gradient n 1 , and the color indices (U-B) 1 /sup (0)/ and (B-V) 1 /sup (0)/ at distance 1 kpc from the center. The range of variation of the basic parameters and the correlations of the parameters with each other and with the absolute magnitudes M/sub B//sup (0)/ of the galaxies find a natural explanation in the framework of the standard models of the spherical subsystems of galaxies. The relationships have approximately the same form for normal and Seyfert galaxies. The photometric characteristics of the central regions of Sy 1 and Sy 2 type galaxies are similar. The obtained results do not contradict the idea that all sufficiently bright spiral galaxies can pass through a Seyfert stage with a characteristic time of ∼10 8 yr

  4. The surface brightness of 1550 galaxies in Fornax: automated galaxy surface photometry: Pt. 2

    International Nuclear Information System (INIS)

    Phillipps, S.; Disney, M.J.; Kibblewhite, E.J.; Cawson, M.G.M.

    1987-01-01

    A survey of a complete sample of galaxies in the region of the Fornax cluster is presented. Measurements with the Automatic Plate Measuring machine are used to derive the observed distribution of galaxy surface brightness for 1550 objects. Corrections for surface brightness dependent selection effects are then made in order to estimate the true distribution. It is found that the sample (with 16.6 ≤ Msub(APM) ≤ 19.1) is divided into two distinct populations. The 'normal' galaxies with extrapolated central surface brightness Ssub(x) ≤ 22.5 Bμ form a uniformly distributed background of field galaxies. Low surface brightness galaxies (Ssub(x) ≥ 22.5 Bμ), on the other hand, are strongly clumped about the cluster centre. There appear to be few low surface brightness field galaxies. (author)

  5. Spectrophotometry of four galaxies of high surface brightness

    International Nuclear Information System (INIS)

    Arakelyan, M.A.; Magtesyap, A.P.

    1982-01-01

    Spectrophotometry of emission lines for the nuclei of galaxies of high surface brightness Nos 428, 449, 454 and 532 from the Arakelyan (1975) list is carried out. Clouds of ionized gas are detected at the distances of approximately 2 kpc from the nuclei of the two former galaxies. Besides there seems to be a cloud moving along the line of sight with velocity approximately 1500 km/s in the galaxy No. 449

  6. The distribution of star formation and metals in the low surface brightness galaxy UGC 628

    Science.gov (United States)

    Young, J. E.; Kuzio de Naray, Rachel; Wang, Sharon X.

    2015-09-01

    We introduce the MUSCEL Programme (MUltiwavelength observations of the Structure, Chemistry and Evolution of LSB galaxies), a project aimed at determining the star-formation histories of low surface brightness galaxies. MUSCEL utilizes ground-based optical spectra and space-based UV and IR photometry to fully constrain the star-formation histories of our targets with the aim of shedding light on the processes that led low surface brightness galaxies down a different evolutionary path from that followed by high surface brightness galaxies, such as our Milky Way. Here we present the spatially resolved optical spectra of UGC 628, observed with the VIRUS-P IFU at the 2.7-m Harlen J. Smith Telescope at the McDonald Observatory, and utilize emission-line diagnostics to determine the rate and distribution of star formation as well as the gas-phase metallicity and metallicity gradient. We find highly clustered star formation throughout UGC 628, excluding the core regions, and a log(O/H) metallicity around -4.2, with more metal-rich regions near the edges of the galactic disc. Based on the emission-line diagnostics alone, the current mode of star formation, slow and concentrated in the outer disc, appears to have dominated for quite some time, although there are clear signs of a much older stellar population formed in a more standard inside-out fashion.

  7. Recent developments in the application of rf superconductivity to high-brightness and high-gradient ion beam accelerators

    International Nuclear Information System (INIS)

    Delayen, J.R.; Bohn, C.L.; Kennedy, W.L.; Nichols, G.L.; Roche, C.T.; Sagalovsky, L.

    1991-01-01

    A development program is underway to apply rf superconductivity to the design of continuous-wave (cw) linear accelerators for high- brightness ion beams. Since the last workshop, considerable progress has been made both experimentally and theoretically toward this application. Recent tests of niobium resonators for ion acceleration have yielded average accelerating gradients as high as 18 MV/m. In an experiment with a radio-frequency quadrupole geometry, niobium was found to sustain cw peak surface electric fields as high as 128 MV/m over large (10 cm 2 ) surface areas. Theoretical studies of beam impingement and cumulative beam breakup have also yielded encouraging results. Consequently, a section of superconducting resonators and focusing elements has been designed for tests with high-current deuteron beams. In addition, considerable data pertaining to the rf properties of high-T c superconductors has been collected at rf-field amplitudes and frequencies of interest in connection with accelerator operation. This paper summarizes the recent progress and identifies current and future work in the areas of accelerator technology and superconducting materials which will build upon it

  8. Measurement of Sky Surface Brightness Fluctuations at λ=4 Microns

    Science.gov (United States)

    Xu, Jing; Bock, James J.; Ganga, Ken M.; Gorjian, Varoujan; Uemizu, Kazunori; Kawada, Mitsunobu; Lange, Andrew E.; Matsumoto, Toshio; Watabe, Toyoki

    2002-12-01

    We present a measurement of faint-source confusion in deep, wide-field 4 μm images. The 1.8d×1.8d images with 17" resolution are centered about the nearby edge-on spiral galaxies NGC 4565 and NGC 5907. After removing statistical noise and gain fluctuations in the focal plane array, we measure spatial fluctuations in the sky brightness to be δνIν=2.74+/-0.14 nW m-2 sr-1, approximately 1% of the diffuse background level observed in a single pixel. The brightness fluctuations are confirmed to be associated with the sky by subtracting sequential images of the same region. An autocorrelation analysis shows the fluctuations are well described by unresolved point sources. We see no evidence for surface brightness fluctuations on larger angular scales (2'S)=1.04+0.86-0.34 nW m-2 sr-1 to the cosmic infrared background, evaluated at S=4.0×10-8 nW m-2. From the fluctuation data we can determine the integrated source counts N(>S)=1.79+0.26-0.40×107 sr-1, evaluated at S=4.0×10-8 nW m-2. The observed fluctuations are consistent with reddened K-band galaxy number counts. The number counts of extracted point sources with flux νFν>6.3×10-7 nW m-2 are dominated by stars and agree well with the Galactic stellar model of Wright & Reese. Removing the stellar contribution from DIRBE maps with zodiacal subtraction results in a residual brightness of 14.0+/-2.6 (22.2+/-5.9) nW m-2 sr-1 at 3.5 (4.9) μm for the NGC 5907 field and 24.0+/-2.7 (36.8+/-6.0) nW m-2 sr-1 at 3.5 (4.9) μm for the NGC 4565 field. The NGC 5907 residuals are consistent with tentative detections of the infrared background reported by Dwek & Arendt, Wright & Reese, and Gorjian, Wright, & Chary.

  9. Bright patches on chernozems - from space to surface and soil properties

    Science.gov (United States)

    Smetanova, Anna; Burian, Libor; Holec, Juraj; Minár, Jozef

    2016-04-01

    located in areas with slope gradient between 3 and 6°, which is consider as the higher slope in this part of the hilly land. In 1949 the distribution of bright patches was more strongly related to higher slope gradient, the convex forms of profile curvature, and upslope position than in 2004. In the studied catchment, 34 soil profiles were described in the bright patches (identified in 2004), and 73% of them were situated on the convex forms of profile curvature. The most of the profiles were eroded (88%), the mean soil loss was 0.36 m (in the comparison with the reference soil profile), and in 55% of described soil profiles the entire mollic horizon was removed. The typical surface horizon contained 2.3% of humus and 21% of carbonates. The soil profiles were further compared with these situated in the areas neighbouring with the bright patches, and soil profiles on two valley cross-sections, in order to understand the soil redistribution in the catchment, and describe the differences between the bright and black patches in the chernozem landscape. This work was supported by the Slovak Research and Development Agency under the contract ESF-EC-0006-07 and APVV-0625-11; Anna Smetanová has received the support of the AgreenSkills fellowship (under grant agreement n°267196).

  10. Suzaku observations of low surface brightness cluster Abell 1631

    Science.gov (United States)

    Babazaki, Yasunori; Mitsuishi, Ikuyuki; Ota, Naomi; Sasaki, Shin; Böhringer, Hans; Chon, Gayoung; Pratt, Gabriel W.; Matsumoto, Hironori

    2018-04-01

    We present analysis results for a nearby galaxy cluster Abell 1631 at z = 0.046 using the X-ray observatory Suzaku. This cluster is categorized as a low X-ray surface brightness cluster. To study the dynamical state of the cluster, we conduct four-pointed Suzaku observations and investigate physical properties of the Mpc-scale hot gas associated with the A 1631 cluster for the first time. Unlike relaxed clusters, the X-ray image shows no strong peak at the center and an irregular morphology. We perform spectral analysis and investigate the radial profiles of the gas temperature, density, and entropy out to approximately 1.5 Mpc in the east, north, west, and south directions by combining with the XMM-Newton data archive. The measured gas density in the central region is relatively low (a few ×10-4 cm-3) at the given temperature (˜2.9 keV) compared with X-ray-selected clusters. The entropy profile and value within the central region (r < 0.1 r200) are found to be flatter and higher (≳400 keV cm2). The observed bolometric luminosity is approximately three times lower than that expected from the luminosity-temperature relation in previous studies of relaxed clusters. These features are also observed in another low surface brightness cluster, Abell 76. The spatial distributions of galaxies and the hot gas appear to be different. The X-ray luminosity is relatively lower than that expected from the velocity dispersion. A post-merger scenario may explain the observed results.

  11. Characterizing bars in low surface brightness disc galaxies

    Science.gov (United States)

    Peters, Wesley; Kuzio de Naray, Rachel

    2018-05-01

    In this paper, we use B-band, I-band, and 3.6 μm azimuthal light profiles of four low surface brightness galaxies (LSBs; UGC 628, F568-1, F568-3, F563-V2) to characterize three bar parameters: length, strength, and corotation radius. We employ three techniques to measure the radius of the bars, including a new method using the azimuthal light profiles. We find comparable bar radii between the I-band and 3.6 μm for all four galaxies when using our azimuthal light profile method, and that our bar lengths are comparable to those in high surface brightness galaxies (HSBs). In addition, we find the bar strengths for our galaxies to be smaller than those for HSBs. Finally, we use Fourier transforms of the B-band, I-band, and 3.6 μm images to characterize the bars as either `fast' or `slow' by measuring the corotation radius via phase profiles. When using the B- and I-band phase crossings, we find three of our galaxies have faster than expected relative bar pattern speeds for galaxies expected to be embedded in centrally dense cold dark matter haloes. When using the B-band and 3.6 μm phase crossings, we find more ambiguous results, although the relative bar pattern speeds are still faster than expected. Since we find a very slow bar in F563-V2, we are confident that we are able to differentiate between fast and slow bars. Finally, we find no relation between bar strength and relative bar pattern speed when comparing our LSBs to HSBs.

  12. Growth of fibroblasts and endothelial cells on wettability gradient surfaces

    NARCIS (Netherlands)

    Ruardy, TG; Moorlag, HE; Schakenraad, JM; VanderMei, HC; Busscher, HJ

    1997-01-01

    The growth, spreading, and shape of human skin fibroblasts (PK 84) and human umbilical cord endothelial cells on dichlorodimethylsilane (DDS) and dimethyloctadecylchlorosilane (DOGS) gradient surfaces were investigated in the presence of serum proteins. Gradient surfaces were prepared on glass using

  13. Bright galaxies in the Fornax cluster. Automated galaxy surface photometry: Pt. 7

    International Nuclear Information System (INIS)

    Disney, M.J.; Phillipps, S.; Davies, J.L.; Cawson, M.G.M.; Kibblewhite, E.J.

    1990-01-01

    We have determined surface-brightness profiles for all galaxies down to magnitude B = 16 in the central region of the Fornax cluster. Using existing redshift data, we have determined the distributions of surface brightness for both the whole sample and for cluster disc galaxies only. Although both distributions peak at extrapolated central surface brightness ∼ 21.7B mag/arcsec 2 (the canonical result), it is shown that they are, in fact, consistent with very broad distributions of disc central surface brightness once selection effects and the effects of bulge contamination of the profile are taken into account. (author)

  14. HI observations of low surface brightness galaxies : Probing low-density galaxies

    NARCIS (Netherlands)

    deBlok, WJG; McGaugh, SS; vanderHulst, JM

    1996-01-01

    We present Very Large Array (VLA) and Westerbork Synthesis Radio Telescope (WSRT) 21-cm HI observations of 19 late-type low surface brightness (LSB) galaxies. Our main findings are that these galaxies, as well as having low surface brightnesses, have low HI surface densities, about a factor of

  15. Testing the dark matter hypothesis with low surface brightness galaxies and other evidence

    NARCIS (Netherlands)

    McGaugh, SS; de Blok, WJG

    1998-01-01

    The severity of the mass discrepancy in spiral galaxies is strongly correlated with the central surface brightness of their disks. Progressively lower surface brightness galaxies have ever larger mass discrepancies. No other parameter (luminosity, size, velocity, morphology) is so well correlated

  16. Three gradients and the perception of flat and curved surfaces.

    Science.gov (United States)

    Cutting, J E; Millard, R T

    1984-06-01

    Researchers of visual perception have long been interested in the perceived slant of a surface and in the gradients that purportedly specify it. Slant is the angle between the line of sight and the tangent to the planar surface at any point, also called the surface normal. Gradients are the sources of information that grade, or change, with visual angle as one looks from one's feet upward to the horizon. The present article explores three gradients--perspective, compression, and density--and the phenomenal impression of flat and curved surfaces. The perspective gradient is measured at right angles to the axis of tilt at any point in the optic array; that is, when looking down a hallway at the tiles of a floor receding in the distance, perspective is measured by the x-axis width of each tile projected on the image plane orthogonal to the line of sight. The compression gradient is the ratio of y/x axis measures on the projected plane. The density gradient is measured by the number of tiles per unit solid visual angle. For flat surfaces and many others, perspective and compression gradients decrease with distance, and the density gradient increases. We discuss the manner in which these gradients change for various types of surfaces. Each gradient is founded on a different assumption about textures on the surfaces around us. In Experiment 1, viewers assessed the three-dimensional character of projections of flat and curved surfaces receding in the distance. They made pairwise judgments of preference and of dissimilarity among eight stimuli in each of four sets. The presence of each gradient was manipulated orthogonally such that each stimulus had zero, one, two, or three gradients appropriate for either a flat surface or a curved surface. Judgments were made were made for surfaces with both regularly shaped and irregularly shaped textures scattered on them. All viewer assessment were then scaled in one dimension. Multiple correlation and regression on the scale values

  17. An Anisotropic Ocean Surface Emissivity Model Based on WindSat Polarimetric Brightness Observations

    Science.gov (United States)

    Smith, D. F.; Gasiewski, A. J.; Sandeep, S.; Weber, B. L.

    2012-12-01

    The goal of this research has been to develop a standardized fast full-Stokes ocean surface emissivity model with Jacobian for a wind-driven ocean surface applicable at arbitrary microwave frequencies, polarizations, and incidence angles. The model is based on the Ohio State University (OSU) two-scale code for surface emission developed by Johnson (2006, IEEE TGRS, 44, 560) but modified as follows: (1) the Meissner-Wentz dielectric permittivity (2012, IEEE TGRS, 50, 3004) replaces the original permittivity, (2) the Elfouhaily sea surface spectrum (1997, JGR, 102, C7,15781) replaces the Durden-Vesecky spectrum (1985, IEEE TGRS, OE-10, 445), but the Durden-Vesecky angular spreading function is retained, (3) the high-frequency portion of the Elfouhaily spectrum is multiplied by the Pierson-Moskowitz shape spectrum to correct an error in the original paper, (4) the generalized Phillips-Kitaigorodskii equilibrium range parameter for short waves is modeled as a continuous function of the friction velocity at the water surface to eliminate a discontinuous jump in the original paper. A total of five physical tuning parameters were identified, including the spectral strength and the hydrodynamic modulation factor. The short wave part of the spectrum is also allowed to have an arbitrary ratio relative to the long wave part. The foam fraction is multiplied by a variable correction factor, and also modulated to allow an anisotropic foam fraction with more foam on the leeward side of a wave. The model is being tuned against multi-year sequences of WindSat and Special Sensor Microwave/Imager (SSMI) data as analyzed by Meissner and Wentz (2012, IEEE TGRS, 50, 3004) for up to four Stokes brightnesses and in all angular harmonics up to two in twenty five wind bins from 0.5-25.5 m/s and of 1 m/s width. As a result there are 40 brightnesses per wind bin, for a total of 1000 brightnesses used to constrain the modified model. A chi-squared tuning criterion based on error standard

  18. The effect of monomolecular surface films on the microwave brightness temperature of the sea surface

    Science.gov (United States)

    Alpers, W.; Blume, H.-J. C.; Garrett, W. D.; Huehnerfuss, H.

    1982-01-01

    It is pointed out that monomolecular surface films of biological origin are often encountered on the ocean surface, especially in coastal regions. The thicknesses of the monomolecular films are of the order of 3 x 10 to the -9th m. Huehnerfuss et al. (1978, 1981) have shown that monomolecular surface films damp surface waves quite strongly in the centimeter to decimeter wavelength regime. Other effects caused by films are related to the reduction of the gas exchange at the air-sea interface and the decrease of the wind stress. The present investigation is concerned with experiments which reveal an unexpectedly large response of the microwave brightness temperature to a monomolecular oleyl alcohol slick at 1.43 GHz. Brightness temperature is a function of the complex dielectric constant of thy upper layer of the ocean. During six overflights over an ocean area covered with an artificial monomolecular alcohol film, a large decrease of the brightness temperature at the L-band was measured, while at the S-band almost no decrease was observed.

  19. Aquarius L3 Polar-Gridded Weekly Brightness Temperature and Sea Surface Salinity V005

    Data.gov (United States)

    National Aeronautics and Space Administration — The data set consists of weekly gridded Level-3 products of Aquarius L-band radiometer brightness temperature (TB) observations and Sea Surface Salinity (SSS)...

  20. SMEX02 Landsat 5 and 7 Thematic Mapper Land Surface Brightness Temperatures

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set consists of land surface brightness temperatures (TBs) derived from Landsat 5 Thematic Mapper (TM) and Landsat 7 Enhanced Thematic Mapper+ (ETM+)...

  1. The visibility of galaxies as a function of central surface brightness

    International Nuclear Information System (INIS)

    Disney, M.; Phillipps, S.

    1983-01-01

    The likelihood of a galaxy with given intrinsic profile appearing in a photograph catalogue with limiting criteria on apparent magnitude and angular size will depend on the maximum distance at which such a galaxy can lie and still obey both criteria. It is demonstrated that the corresponding volume in which the galaxy will be visible is a sensitive function of the galaxy's central surface brightness as well as its absolute magnitude. Before the observed concentrations around preferred values of surface brightness can be regarded as real, it will be necessary to make allowance for this selection effect. (author)

  2. Detection of a bright feature on the surface of Betelgeuse

    Energy Technology Data Exchange (ETDEWEB)

    Buscher, D.F.; Baldwin, J.E.; Warner, P.J. (Mullard Radio Astronomy Observatory, Cambridge (UK). Cavendish Lab.); Haniff, C.A. (Palomar Observatory, Pasadena, CA (USA))

    1990-07-01

    We present high-resolution images of the M-supergiant Betelgeuse in 1989 February at wavelengths of 633, 700 and 710 nm, made using the non-redundant masking method. At all these wavelengths, there is unambiguous evidence for an asymmetric feature on the surface of the star, which contributes 10-15 per cent of the total observed flux. This might be due to a close companion passing in front of the stellar disc or, more likely, to large-scale convection in the stellar atmosphere. (author).

  3. B and R CCD surface photometry of selected low surface brightness galaxies in the region of the Fornax cluster

    International Nuclear Information System (INIS)

    Davies, J.I.; Phillipps, S.; Disney, M.J.

    1990-01-01

    The recent discoveries of large numbers of low surface brightness (LSB) galaxies in clusters and of the extreme LSB giant galaxy Malin 1 are changing our view of the galactic contents of the Universe. In this paper we describe B and R band CCD photometry of a sample of LSB galaxies previously identified from photographic plates of the Fornax cluster. This sample contains some of the lowest surface brightness galaxies known, one having the same central surface brightness as Main 1. The objects in this sample have a wide range of morphologies, and galaxies of similar appearance may have very different (B-R) colours. The range of (B-R) colours for this sample (almost all of which would have been described as dE from their B band morphology alone) is as large as that of the entire Hubble sequence. (author)

  4. Extinction in the Galaxy from surface brightnesses of ESO-LV galaxies : Testing "standard" extinction maps

    NARCIS (Netherlands)

    Choloniewski, J.; Valentijn, E. A.

    A new method for the determination of the extinction in the Galaxy is proposed. The method uses surface brightnesses of external galaxies in the B and R-bands. The observational data have been taken from the ESO-LV galaxy catalog. As a first application of our model we derive the ratio of R-band to

  5. Is there really a luminosity-surface brightness relation for dwarf galaxies?

    International Nuclear Information System (INIS)

    Phillipps, S.; Davies, J.I.; Disney, M.J.

    1988-01-01

    A simple test is used to argue that the luminosity-surface brightness correlation found by several authors in eye-selected samples of cluster dwarf galaxies is likely to be merely the result of selection effects. There are therefore likely to be many more dwarfs in clusters like Virgo than is generally assumed. (author)

  6. The nucleus of Comet Borrelly: A study of morphology and surface brightness

    Science.gov (United States)

    Oberst, J.; Howington-Kraus, E.; Kirk, R.; Soderblom, L.; Buratti, B.; Hicks, M.; Nelson, R.; Britt, D.

    2004-01-01

    Stereo images obtained during the DS1 flyby were analyzed to derive a topographic model for the nucleus of Comet 19P/Borrelly for morphologic and photometric studies. The elongated nucleus has an overall concave shape, resembling a peanut, with the lower end tilted towards the camera. The bimodal character of surface-slopes and curvatures support the idea that the nucleus is a gravitational aggregate, consisting of two fragments in contact. Our photometric modeling suggests that topographic shading effects on Borrelly's surface are very minor (the given resolution of the terrain model. Instead, albedo effects are thought to dominate Borrelly's large variations in surface brightness. With 90% of the visible surface having single scattering albedos between 0.008 and 0.024, Borrelly is confirmed to be among the darkest of the known Solar System objects. Photometrically corrected images emphasize that the nucleus has distinct, contiguous terrains covered with either bright or dark, smooth or mottled materials. Also, mapping of the changes in surface brightness with phase angle suggests that terrain roughness at subpixel scale is not uniform over the nucleus. High surface roughness is noted in particular near the transition between the upper and lower end of the nucleus, as well as near the presumed source region of Borrelly's main jets. Borrelly's surface is complex and characterized by distinct types of materials that have different compositional and/or physical properties. ?? 2003 Elsevier Inc. All rights reserved.

  7. Thermal measurements of dark and bright surface features on Vesta as derived from Dawn/VIR

    Science.gov (United States)

    Tosi, Federico; Capria, Maria Teresa; De Sanctis, M.C.; Combe, J.-Ph.; Zambon, F.; Nathues, A.; Schröder, S.E.; Li, J.-Y.; Palomba, E.; Longobardo, A.; Blewett, D.T.; Denevi, B.W.; Palmer, E.; Capaccioni, F.; Ammannito, E.; Titus, Timothy N.; Mittlefehldt, D.W.; Sunshine, J.M.; Russell, C.T.; Raymond, C.A.; Dawn/VIR Team,

    2014-01-01

    Remote sensing data acquired during Dawn’s orbital mission at Vesta showed several local concentrations of high-albedo (bright) and low-albedo (dark) material units, in addition to spectrally distinct meteorite impact ejecta. The thermal behavior of such areas seen at local scale (1-10 km) is related to physical properties that can provide information about the origin of those materials. We use Dawn’s Visible and InfraRed (VIR) mapping spectrometer hyperspectral data to retrieve surface temperatures and emissivities, with high accuracy as long as temperatures are greater than 220 K. Some of the dark and bright features were observed multiple times by VIR in the various mission phases at variable spatial resolution, illumination and observation angles, local solar time, and heliocentric distance. This work presents the first temperature maps and spectral emissivities of several kilometer-scale dark and bright material units on Vesta. Results retrieved from the infrared data acquired by VIR show that bright regions generally correspond to regions with lower temperature, while dark regions correspond to areas with higher temperature. During maximum daily insolation and in the range of heliocentric distances explored by Dawn, i.e. 2.23-2.54 AU, the warmest dark unit found on Vesta rises to a temperature of 273 K, while bright units observed under comparable conditions do not exceed 266 K. Similarly, dark units appear to have higher emissivity on average compared to bright units. Dark-material units show a weak anticorrelation between temperature and albedo, whereas the relation is stronger for bright material units observed under the same conditions. Individual features may show either evanescent or distinct margins in the thermal images, as a consequence of the cohesion of the surface material. Finally, for the two categories of dark and bright materials, we were able to highlight the influence of heliocentric distance on surface temperatures, and estimate an

  8. Analysis of Mass Profiles and Cooling Flows of Bright, Early-Type Galaxies AO2, AO3 and Surface Brightness Profiles and Energetics of Intracluster Gas in Cool Galaxy Clusters AO3

    Science.gov (United States)

    White, Raymond E., III

    1998-01-01

    This final report uses ROSAT observations to analyze two different studies. These studies are: Analysis of Mass Profiles and Cooling Flows of Bright, Early-Type Galaxies; and Surface Brightness Profiles and Energetics of Intracluster Gas in Cool Galaxy Clusters.

  9. Soil hydraulic parameters and surface soil moisture of a tilled bare soil plot inversely derived from l-band brightness temperatures

    KAUST Repository

    Dimitrov, Marin

    2014-01-01

    We coupled a radiative transfer model and a soil hydrologic model (HYDRUS 1D) with an optimization routine to derive soil hydraulic parameters, surface roughness, and soil moisture of a tilled bare soil plot using measured brightness temperatures at 1.4 GHz (L-band), rainfall, and potential soil evaporation. The robustness of the approach was evaluated using five 28-d data sets representing different meteorological conditions. We considered two soil hydraulic property models: the unimodal Mualem-van Genuchten and the bimodal model of Durner. Microwave radiative transfer was modeled by three different approaches: the Fresnel equation with depth-averaged dielectric permittivity of either 2-or 5-cm-thick surface layers and a coherent radiative transfer model (CRTM) that accounts for vertical gradients in dielectric permittivity. Brightness temperatures simulated by the CRTM and the 2-cm-layer Fresnel model fitted well to the measured ones. L-band brightness temperatures are therefore related to the dielectric permittivity and soil moisture in a 2-cm-thick surface layer. The surface roughness parameter that was derived from brightness temperatures using inverse modeling was similar to direct estimates from laser profiler measurements. The laboratory-derived water retention curve was bimodal and could be retrieved consistently for the different periods from brightness temperatures using inverse modeling. A unimodal soil hydraulic property function underestimated the hydraulic conductivity near saturation. Surface soil moisture contents simulated using retrieved soil hydraulic parameters were compared with in situ measurements. Depth-specific calibration relations were essential to derive soil moisture from near-surface installed sensors. © Soil Science Society of America 5585 Guilford Rd., Madison, WI 53711 USA.

  10. THE FAINT END OF THE LUMINOSITY FUNCTION AND LOW SURFACE BRIGHTNESS GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Geller, Margaret J.; Kurtz, Michael J.; Fabricant, Daniel G. [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States); Diaferio, Antonaldo [Dipartimento di Fisica Generale ' Amedeo Avogadro' , Universita degli Studi di Torino, via P. Giuria 1, 10125 Torino (Italy); Dell' Antonio, Ian P., E-mail: mgeller@cfa.harvard.edu, E-mail: mkurtz@cfa.harvard.edu, E-mail: dfabricant@cfa.harvard.edu, E-mail: adiaferio@cfa.harvard.edu, E-mail: ian@het.brown.edu [Department of Physics, Brown University, Box 1843, Providence, RI 02912 (United States)

    2012-04-15

    Smithsonian Hectospec Lensing Survey (SHELS) is a dense redshift survey covering a 4 deg{sup 2} region to a limiting R = 20.6. In the construction of the galaxy catalog and in the acquisition of spectroscopic targets, we paid careful attention to the survey completeness for lower surface brightness dwarf galaxies. Thus, although the survey covers a small area, it is a robust basis for computation of the slope of the faint end of the galaxy luminosity function to a limiting M{sub R} = -13.3 + 5log h. We calculate the faint-end slope in the R band for the subset of SHELS galaxies with redshifts in the range 0.02 {<=}z < 0.1, SHELS{sub 0.1}. This sample contains 532 galaxies with R < 20.6 and with a median surface brightness within the half-light radius of SB{sub 50,R} = 21.82 mag arcsec{sup -2}. We used this sample to make one of the few direct measurements of the dependence of the faint end of the galaxy luminosity function on surface brightness. For the sample as a whole the faint-end slope, {alpha} = -1.31 {+-} 0.04, is consistent with both the Blanton et al. analysis of the Sloan Digital Sky Survey and the Liu et al. analysis of the COSMOS field. This consistency is impressive given the very different approaches of these three surveys. A magnitude-limited sample of 135 galaxies with optical spectroscopic redshifts with mean half-light surface brightness, SB{sub 50,R} {>=} 22.5 mag arcsec{sup -2} is unique to SHELS{sub 0.1}. The faint-end slope is {alpha}{sub 22.5} = -1.52 {+-} 0.16. SHELS{sub 0.1} shows that lower surface brightness objects dominate the faint-end slope of the luminosity function in the field, underscoring the importance of surface brightness limits in evaluating measurements of the faint-end slope and its evolution.

  11. Identification of faint central stars in extended, low-surface-brightness planetary nebulae

    International Nuclear Information System (INIS)

    Kwitter, K.B.; Lydon, T.J.; Jacoby, G.H.

    1988-01-01

    As part of a larger program to study the properties of planetary nebula central stars, a search for faint central stars in extended, low-surface-brightness planetary nebulae using CCD imaging is performed. Of 25 target nebulae, central star candidates have been identified in 17, with certainties ranging from extremely probable to possible. Observed V values in the central star candidates extend to fainter than 23 mag. The identifications are presented along with the resulting photometric measurements. 24 references

  12. SURFACE BRIGHTNESS PROFILES OF DWARF GALAXIES. II. COLOR TRENDS AND MASS PROFILES

    Energy Technology Data Exchange (ETDEWEB)

    Herrmann, Kimberly A. [Penn State Mont Alto, 1 Campus Drive, Mont Alto, PA 17237 (United States); Hunter, Deidre A. [Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001 (United States); Elmegreen, Bruce G., E-mail: kah259@psu.edu, E-mail: dah@lowell.edu, E-mail: bge@us.ibm.com [IBM T. J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, NY 10598 (United States)

    2016-06-01

    In this second paper of a series, we explore the B  −  V , U  −  B , and FUV−NUV radial color trends from a multi-wavelength sample of 141 dwarf disk galaxies. Like spirals, dwarf galaxies have three types of radial surface brightness profiles: (I) single exponential throughout the observed extent (the minority), (II) down-bending (the majority), and (III) up-bending. We find that the colors of (1) Type I dwarfs generally become redder with increasing radius, unlike spirals which have a blueing trend that flattens beyond ∼1.5 disk scale lengths, (2) Type II dwarfs come in six different “flavors,” one of which mimics the “U” shape of spirals, and (3) Type III dwarfs have a stretched “S” shape where the central colors are flattish, become steeply redder toward the surface brightness break, then remain roughly constant beyond, which is similar to spiral Type III color profiles, but without the central outward bluing. Faint (−9 >  M{sub B}  > −14) Type II dwarfs tend to have continuously red or “U” shaped colors and steeper color slopes than bright (−14 >  M{sub B}  > −19) Type II dwarfs, which additionally have colors that become bluer or remain constant with increasing radius. Sm dwarfs and BCDs tend to have at least some blue and red radial color trend, respectively. Additionally, we determine stellar surface mass density (Σ) profiles and use them to show that the break in Σ generally remains in Type II dwarfs (unlike Type II spirals) but generally disappears in Type III dwarfs (unlike Type III spirals). Moreover, the break in Σ is strong, intermediate, and weak in faint dwarfs, bright dwarfs, and spirals, respectively, indicating that Σ may straighten with increasing galaxy mass. Finally, the average stellar surface mass density at the surface brightness break is roughly 1−2  M {sub ⊙} pc{sup −2} for Type II dwarfs but higher at 5.9  M {sub ⊙} pc{sup −2} or 27  M {sub ⊙} pc{sup −2} for

  13. Mercurian bright patches - Evidence for physio-chemical alteration of surface material

    Science.gov (United States)

    Dzurisin, D.

    1977-01-01

    Morphologically and photometrically anomalous patches of highly-reflective material exist inside several large Mercurian craters. Calculations assuming that the patches exhibit an average lunar photometric function yield normal albedos of .39-.45, roughly 60% higher than Aristarchus, the brightest feature on the moon. Color-ratio images derived from Mariner 10 imaging data indicate that bright patches are bluer than typical Mercurian surface material, and are surrounded by material redder than typical surface material. Local physio-chemical alteration along impact-induced fractures may have been involved in production of these uniquely Mercurian features.

  14. Diffusion and surface alloying of gradient nanostructured metals

    Directory of Open Access Journals (Sweden)

    Zhenbo Wang

    2017-03-01

    Full Text Available Gradient nanostructures (GNSs have been optimized in recent years for desired performance. The diffusion behavior in GNS metals is crucial for understanding the diffusion mechanism and relative characteristics of different interfaces that provide fundamental understanding for advancing the traditional surface alloying processes. In this paper, atomic diffusion, reactive diffusion, and surface alloying processes are reviewed for various metals with a preformed GNS surface layer. We emphasize the promoted atomic diffusion and reactive diffusion in the GNS surface layer that are related to a higher interfacial energy state with respect to those in relaxed coarse-grained samples. Accordingly, different surface alloying processes, such as nitriding and chromizing, have been modified significantly, and some diffusion-related properties have been enhanced. Finally, the perspectives on current research in this field are discussed.

  15. Tracing the stellar component of low surface brightness Milky Way dwarf galaxies to their outskirts. I. Sextans

    Science.gov (United States)

    Cicuéndez, L.; Battaglia, G.; Irwin, M.; Bermejo-Climent, J. R.; McMonigal, B.; Bate, N. F.; Lewis, G. F.; Conn, A. R.; de Boer, T. J. L.; Gallart, C.; Guglielmo, M.; Ibata, R.; McConnachie, A.; Tolstoy, E.; Fernando, N.

    2018-01-01

    Aims: We present results from deep and very spatially extended CTIO/DECam g and r photometry (reaching out to 2 mag below the oldest main-sequence turn-off and covering 20 deg2) around the Sextans dwarf spheroidal galaxy. We aim to use this dataset to study the structural properties of Sextans overall stellar population and its member stars in different evolutionary phases, as well as to search for possible signs of tidal disturbance from the Milky Way, which would indicate departure from dynamical equilibrium. Methods: We performed the most accurate and quantitative structural analysis to-date of Sextans' stellar components by applying Bayesian Monte Carlo Markov chain methods to the individual stars' positions. Surface density maps are built by statistically decontaminating the sample through a matched filter analysis of the colour-magnitude diagram, and then analysed for departures from axisymmetry. Results: Sextans is found to be significantly less spatially extended and more centrally concentrated than early studies suggested. No statistically significant distortions or signs of tidal disturbances were found down to a surface brightness limit of 31.8 mag/arcsec2 in V-band. We identify an overdensity in the central regions that may correspond to previously reported kinematic substructure(s). In agreement with previous findings, old and metal-poor stars such as Blue Horizontal Branch stars cover a much larger area than stars in other evolutionary phases, and bright Blue Stragglers (BSs) are less spatially extended than faint ones. However, the different spatial distribution of bright and faint BSs appears consistent with the general age and metallicity gradients found in Sextans' stellar component. This is compatible with Sextans BSs having formed by evolution of binaries and not necessarily due to the presence of a central disrupted globular cluster, as suggested in the literature. We provide structural parameters for the various populations analysed and make

  16. The IAC Stripe 82 Legacy Project: a wide-area survey for faint surface brightness astronomy

    Science.gov (United States)

    Fliri, Jürgen; Trujillo, Ignacio

    2016-02-01

    We present new deep co-adds of data taken within Stripe 82 of the Sloan Digital Sky Survey (SDSS), especially stacked to reach the faintest surface brightness limits of this data set. Stripe 82 covers 275 ° ^2 within -50° ≤ RA ≤ +60° and -1.25° ≤ Dec. ≤ +1.25°. We discuss the steps of our reduction which puts special emphasis on preserving the characteristics of the background (sky + diffuse light) in the input images using a non-aggressive sky subtraction strategy. Our reduction reaches a limit of ˜28.5 mag arcsec-2 (3σ, 10 × 10 arcsec2) in the r band. The effective surface brightness limit (50 per cent completeness for exponential light distribution) lies at ˜ 25.5 mag arcsec-2. For point sources, we reach 50 per cent completeness limits (3σ level) of (24.2, 25.2, 24.7, 24.3, 23.0) mag in (u, g, r, I, z). This is between 1.7 and 2.0 mag deeper than the single-epoch SDSS releases. The co-adds show point spread functions (PSFs) with median full width at half-maximum values ranging from 1 arcsec in I and z to 1.3 arcsec in the u band. The imaging data are made publicly available at http://www.iac.es/proyecto/stripe82. The release includes deep co-adds and representations of the PSF for each field. Additionally, we provide object catalogues with stars and galaxies confidently separated until g ˜ 23 mag. The IAC Stripe 82 co-adds offer a rather unique possibility to study the low surface brightness Universe, exemplified by the discovery of stellar streams around NGC 0426 and NGC 0936. We also discuss further science cases like stellar haloes and disc truncations, low surface brightness galaxies, the intracluster light in galaxy clusters and the diffuse emission of Galactic dust known as Galactic Cirrus.

  17. Exploring near Earth object’s activity with cubesats: low surface brightness

    Science.gov (United States)

    Fuentes, Cesar; Diaz, Marcos; Falcon, Claudio; Clerc, Marcel

    2015-11-01

    Ever smaller Near Earth Objects (NEOs) continue to be discovered, with most potentially hazardous ones already surveyed and ongoing plans for space missions to deflect and mine them in the near future. These transitional objects in relatively unstable orbits have recently experienced collisional or dynamical encounters that have sent them to Earth’s vicinity. Finding comet-like activity (sublimation and ejected dust) is necessary to understand their origin, recent history, and evolution. Mommert et al (2014) have recently discovered cometary activity on the third largest NEO (3552) Don Quixote using near-Infrared imaging from Spitzer/IRAC they detect both a coma and tail as extended emission they identify as CO2 ice sublimation. This activity has gone unnoticed due to either sporadic activity or the relatively low surface brightness in optical wavelengths of light reflecting off dust, 26 mag/arcsec2 which necessarily imposes an extreme bias against detection. We propose to find this activity directly in the optical by going above the atmosphere.We are developing a 6U Cubesat to carry a 20cm aperture telescope. The volume restrictions impose a deployment system design for the telescope. We will study the optimal mission and optical setup for our goals, including the feasibility of a novel coronagraph to increase the sensitivity. Detecting NEO activity requires stability and low instrumental noise over many hours. Atmosphere’s varying point spread function (PSF), coupled with the extended PSF of reflective telescopes, lead us to propose to develop the concept and technology to manage a refractive telescope in space with the potential inclusion of a coronagraph, optimized for detecting faint features near bright targets. The experiment considers targeting nearby NEOs and optimizing observations for low surface brightness.

  18. Motion of Drops on Surfaces with Wettability Gradients

    Science.gov (United States)

    Subramanian, R. Shankar; McLaughlin, John B.; Moumen, Nadjoua; Qian, Dongying

    2002-11-01

    A liquid drop present on a solid surface can move because of a gradient in wettability along the surface, as manifested by a gradient in the contact angle. The contact angle at a given point on the contact line between a solid and a liquid in a gaseous medium is the angle between the tangent planes to the liquid and the solid surfaces at that point and is measured within the liquid side, by convention. The motion of the drop occurs in the direction of increasing wettability. The cause of the motion is the net force exerted on the drop by the solid surface because of the variation of the contact angle around the periphery. This force causes acceleration of an initially stationary drop, and leads to its motion in the direction of decreasing contact angle. The nature of the motion is determined by the balance between the motivating force and the resisting hydrodynamic force from the solid surface and the surrounding gaseous medium. A wettability gradient can be chemically induced as shown by Chaudhury and Whitesides who provided unambiguous experimental evidence that drops can move in such gradients. The phenomenon can be important in heat transfer applications in low gravity, such as when condensation occurs on a surface. Daniel et al have demonstrated that the velocity of a drop on a surface due to a wettability gradient in the presence of condensation can be more than two orders of magnitude larger than that observed in the absence of condensation. In the present research program, we have begun to study the motion of a drop in a wettability gradient systematically using a model system. Our initial efforts will be restricted to a system in which no condensation occurs. The experiments are performed as follows. First, a rectangular strip of approximate dimensions 10 x 20 mm is cut out of a silicon wafer. The strip is cleaned thoroughly and its surface is exposed to the vapor from an alkylchlorosilane for a period lasting between one and two minutes inside a

  19. THE STABILITY OF LOW SURFACE BRIGHTNESS DISKS BASED ON MULTI-WAVELENGTH MODELING

    International Nuclear Information System (INIS)

    MacLachlan, J. M.; Wood, K.; Matthews, L. D.; Gallagher, J. S.

    2011-01-01

    To investigate the structure and composition of the dusty interstellar medium (ISM) of low surface brightness (LSB) disk galaxies, we have used multi-wavelength photometry to construct spectral energy distributions for three low-mass, edge-on LSB galaxies (V rot = 88-105 km s -1 ). We use Monte Carlo radiation transfer codes that include the effects of transiently heated small grains and polycyclic aromatic hydrocarbon molecules to model and interpret the data. We find that, unlike the high surface brightness galaxies previously modeled, the dust disks appear to have scale heights equal to or exceeding their stellar scale heights. This result supports the findings of previous studies that low-mass disk galaxies have dust scale heights comparable to their stellar scale heights and suggests that the cold ISM of low-mass, LSB disk galaxies may be stable against fragmentation and gravitational collapse. This may help to explain the lack of observed dust lanes in edge-on LSB galaxies and their low current star formation rates. Dust masses are found in the range (1.16-2.38) x 10 6 M sun , corresponding to face-on (edge-on), V-band, optical depths 0.034 ∼ face ∼ eq ∼< 1.99).

  20. The MESSIER surveyor: unveiling the ultra-low surface brightness universe

    Science.gov (United States)

    Valls-Gabaud, David; MESSIER Collaboration

    2017-03-01

    The MESSIER surveyor is a small mission designed at exploring the very low surface brightness universe. The satellite will drift-scan the entire sky in 6 filters covering the 200-1000 nm range, reaching unprecedented surface brightness levels of 34 and 37 mag arcsec-2 in the optical and UV, respectively. These levels are required to achieve the two main science goals of the mission: to critically test the ΛCDM paradigm of structure formation through (1) the detection and characterisation of ultra-faint dwarf galaxies, which are predicted to be extremely abundant around normal galaxies, but which remain elusive; and (2) tracing the cosmic web, which feeds dark matter and baryons into galactic haloes, and which may contain the reservoir of missing baryons at low redshifts. A large number of science cases, ranging from stellar mass loss episodes to intracluster light through fluctuations in the cosmological UV-optical background radiation are free by-products of the full-sky maps produced.

  1. Automated detection of very Low Surface Brightness galaxies in the Virgo Cluster

    Science.gov (United States)

    Prole, D. J.; Davies, J. I.; Keenan, O. C.; Davies, L. J. M.

    2018-04-01

    We report the automatic detection of a new sample of very low surface brightness (LSB) galaxies, likely members of the Virgo cluster. We introduce our new software, DeepScan, that has been designed specifically to detect extended LSB features automatically using the DBSCAN algorithm. We demonstrate the technique by applying it over a 5 degree2 portion of the Next-Generation Virgo Survey (NGVS) data to reveal 53 low surface brightness galaxies that are candidate cluster members based on their sizes and colours. 30 of these sources are new detections despite the region being searched specifically for LSB galaxies previously. Our final sample contains galaxies with 26.0 ≤ ⟨μe⟩ ≤ 28.5 and 19 ≤ mg ≤ 21, making them some of the faintest known in Virgo. The majority of them have colours consistent with the red sequence, and have a mean stellar mass of 106.3 ± 0.5M⊙ assuming cluster membership. After using ProFit to fit Sérsic profiles to our detections, none of the new sources have effective radii larger than 1.5 Kpc and do not meet the criteria for ultra-diffuse galaxy (UDG) classification, so we classify them as ultra-faint dwarfs.

  2. Characterizing developing adverse pressure gradient flows subject to surface roughness

    Science.gov (United States)

    Brzek, Brian; Chao, Donald; Turan, Özden; Castillo, Luciano

    2010-04-01

    An experimental study was conducted to examine the effects of surface roughness and adverse pressure gradient (APG) on the development of a turbulent boundary layer. Hot-wire anemometry measurements were carried out using single and X-wire probes in all regions of a developing APG flow in an open return wind tunnel test section. The same experimental conditions (i.e., T ∞, U ref, and C p) were maintained for smooth, k + = 0, and rough, k + = 41-60, surfaces with Reynolds number based on momentum thickness, 3,000 carefully designed such that the x-dependence in the flow field was known. Despite this fact, only a very small region of the boundary layer showed a balance of the various terms in the integrated boundary layer equation. The skin friction computed from this technique showed up to a 58% increase due to the surface roughness. Various equilibrium parameters were studied and the effect of roughness was investigated. The generated flow was not in equilibrium according to the Clauser (J Aero Sci 21:91-108, 1954) definition due to its developing nature. After a development region, the flow reached the equilibrium condition as defined by Castillo and George (2001), where Λ = const, is the pressure gradient parameter. Moreover, it was found that this equilibrium condition can be used to classify developing APG flows. Furthermore, the Zagarola and Smits (J Fluid Mech 373:33-79, 1998a) scaling of the mean velocity deficit, U ∞δ*/δ, can also be used as a criteria to classify developing APG flows which supports the equilibrium condition of Castillo and George (2001). With this information a ‘full APG region’ was defined.

  3. Retrieval of surface temperature by remote sensing. [of earth surface using brightness temperature of air pollutants

    Science.gov (United States)

    Gupta, S. K.; Tiwari, S. N.

    1976-01-01

    A simple procedure and computer program were developed for retrieving the surface temperature from the measurement of upwelling infrared radiance in a single spectral region in the atmosphere. The program evaluates the total upwelling radiance at any altitude in the region of the CO fundamental band (2070-2220 1/cm) for several values of surface temperature. Actual surface temperature is inferred by interpolation of the measured upwelling radiance between the computed values of radiance for the same altitude. Sensitivity calculations were made to determine the effect of uncertainty in various surface, atmospheric and experimental parameters on the inferred value of surface temperature. It is found that the uncertainties in water vapor concentration and surface emittance are the most important factors affecting the accuracy of the inferred value of surface temperature.

  4. Northern dwarf and low surface brightness galaxies. II - The Green Bank neutral hydrogen survey

    Science.gov (United States)

    Schneider, Stephen E.; Thuan, Trinh X.; Mangum, Jeffrey G.; Miller, John

    1992-01-01

    The paper reports neutral hydrogen observations of a large sample of dwarf and other low surface brightness galaxies. A detailed discussion and error analysis of the observations are presented, and spectra are displayed for 329 galaxies detected for the first time, or detected with substantially better signal-to-noise ratios than achieved previously. The positions on the sky of 667 galaxies meeting the present selection criteria north of delta = 38 deg are shown. The distribution of the redshifts of galaxies detected at Green Bank is illustrated. The Green Bank detections tapered off strongly below the median H I flux of 3.7 Jy km/s detected at Arecibo: only 12 percent of the Green Bank sample was detected with smaller fluxes.

  5. Creating gradient wetting surfaces via electroless displacement of zinc-coated carbon steel by nickel ions

    Science.gov (United States)

    Xu, Chang; Liu, Huicong; Liang, Weitao; Zhu, Liqun; Li, Weiping; Chen, Haining

    2018-03-01

    Gradient wetting surfaces are getting increasing attention due to their wide application in multiple fields such as droplet movement and biosorption. However, the fabrication processes of full gradient wetting surfaces are still complex and costly. In present work, a facile and low-cost chemical immersion method was used to create a full gradient wetting surface. By controlling the displacement time in Ni2+ solution, the prepared surfaces perform hydrophilic to superhydrophilic. After being modified by stearic acid, the gradient hydrophilic surfaces convert into hydrophobic. The surface morphology, composition, and wetting behaviors of the as-prepared surfaces were systematically studied and discussed. The gradient wetting property could be attributed to the change in microroughness and surface energy. In addition, these surfaces also exhibited excellent self-cleaning and wax prevention properties. Furthermore, high stability and corrosion resistance were also found for these surfaces, which further highlight their promising practical applications in many fields.

  6. Assimilation of SMOS Brightness Temperatures or Soil Moisture Retrievals into a Land Surface Model

    Science.gov (United States)

    De Lannoy, Gabrielle J. M.; Reichle, Rolf H.

    2016-01-01

    Three different data products from the Soil Moisture Ocean Salinity (SMOS) mission are assimilated separately into the Goddard Earth Observing System Model, version 5 (GEOS-5) to improve estimates of surface and root-zone soil moisture. The first product consists of multi-angle, dual-polarization brightness temperature (Tb) observations at the bottom of the atmosphere extracted from Level 1 data. The second product is a derived SMOS Tb product that mimics the data at a 40 degree incidence angle from the Soil Moisture Active Passive (SMAP) mission. The third product is the operational SMOS Level 2 surface soil moisture (SM) retrieval product. The assimilation system uses a spatially distributed ensemble Kalman filter (EnKF) with seasonally varying climatological bias mitigation for Tb assimilation, whereas a time-invariant cumulative density function matching is used for SM retrieval assimilation. All assimilation experiments improve the soil moisture estimates compared to model-only simulations in terms of unbiased root-mean-square differences and anomaly correlations during the period from 1 July 2010 to 1 May 2015 and for 187 sites across the US. Especially in areas where the satellite data are most sensitive to surface soil moisture, large skill improvements (e.g., an increase in the anomaly correlation by 0.1) are found in the surface soil moisture. The domain-average surface and root-zone skill metrics are similar among the various assimilation experiments, but large differences in skill are found locally. The observation-minus-forecast residuals and analysis increments reveal large differences in how the observations add value in the Tb and SM retrieval assimilation systems. The distinct patterns of these diagnostics in the two systems reflect observation and model errors patterns that are not well captured in the assigned EnKF error parameters. Consequently, a localized optimization of the EnKF error parameters is needed to further improve Tb or SM retrieval

  7. Complex Surface Concentration Gradients by Stenciled "Electro Click Chemistry"

    DEFF Research Database (Denmark)

    Hansen, Thomas Steen; Lind, Johan Ulrik; Daugaard, Anders Egede

    2010-01-01

    Complex one- or two-dimensional concentration gradients of alkynated molecules are produced on azidized conducting polymer substrates by stenciled "electro click chemistry". The latter describes the local electrochemical generation of catalytically active Cu(I) required to complete a "click...... reaction" between alkynes and azides at room temperature. A stencil on the counter electrode defines the shape and multiplicity of the gradient(s) on the conducting polymer substrate, while the specific reaction conditions control gradient steepness and the maximum concentration deposited. Biologically...

  8. Onion-like surface design of upconverting nanophosphors modified with polyethylenimine: shielding toxicity versus keeping brightness?

    Science.gov (United States)

    Guller, Anna; Nadort, Annemarie; Generalova, Alla; Kornienko, Inna; Petersen, Elena; Qian, Yi; Shekhter, Anatoly; Goldys, Ewa; Zvyagin, Andrei

    2016-12-01

    Background: Upconverting nanoparticles (UCNPs) represent a unique class of nanomaterials, able to convert infrared excitation light into long lifetime visible and infrared photoluminescence, within the "optical transparency window" of biological tissues. This makes UCNPs an attractive contrast agent for background-free bioimaging. However, assynthesized UCNPs are hydrophobic and need additional surface coating for stability in water-based solutions and further functionalization. Polyethylenimine (PEI), a polycationic amphiphilic polymer, is a well-known transfection agent for gene delivery and a popular material for UCNPs surface hydrophilization. Combining the functional properties of UCNPs and PEI is extremely useful for precise visualization of genetic manipulations and intracellular drug delivery. At the same time, PEI is toxic to cells, while the photoluminescent properties of UCNPs are very sensitive to surface chemistry and environment. Then, creation of hydrophilic, biocompatible and simultaneously bright UCNPs, modified by PEI (UCNP-PEI), is a challenging task. Objectives: To analyze the effects of multilayer shielding coatings on cytotoxicity, cellular uptake and photoluminescent properties of UCNP-PEI. Methods and results: UCNP-PEI were modified with additional two or three layers of various polymers and characterized by size, surface charge and photophysical properties. HaCaT keratinocytes were exposed to the particles for 24 or 120 h to study the cytotoxicity and cellular uptake. The results show that onion-like coatings of UCNP-PEI simultaneously decrease cytotoxicity and relative luminescence of the particles, depending on structure and method of formation of multilayer coating. Conclusions: Rational design of UCNP-PEI using extra coatings layers can help to keep acceptable levels of biocompatibility and photoluminescence intensity.

  9. Extinction in the Galaxy from Surface Brightnesses of ESO-LV Galaxies : Determination of A_R/A_B ratio

    NARCIS (Netherlands)

    Choloniewski, J.; Valentijn, E. A.

    A new method for the determination of the extinction in the Galaxy is proposed. The method uses surface brightnesses of external galaxies in the B and R-bands. The observational data have been taken from the ESO-LV galaxy catalog. As a first application of our model we derive the ratio of R-band to

  10. CONSTRAINING THE NFW POTENTIAL WITH OBSERVATIONS AND MODELING OF LOW SURFACE BRIGHTNESS GALAXY VELOCITY FIELDS

    International Nuclear Information System (INIS)

    Kuzio de Naray, Rachel; McGaugh, Stacy S.; Mihos, J. Christopher

    2009-01-01

    We model the Navarro-Frenk-White (NFW) potential to determine if, and under what conditions, the NFW halo appears consistent with the observed velocity fields of low surface brightness (LSB) galaxies. We present mock DensePak Integral Field Unit (IFU) velocity fields and rotation curves of axisymmetric and nonaxisymmetric potentials that are well matched to the spatial resolution and velocity range of our sample galaxies. We find that the DensePak IFU can accurately reconstruct the velocity field produced by an axisymmetric NFW potential and that a tilted-ring fitting program can successfully recover the corresponding NFW rotation curve. We also find that nonaxisymmetric potentials with fixed axis ratios change only the normalization of the mock velocity fields and rotation curves and not their shape. The shape of the modeled NFW rotation curves does not reproduce the data: these potentials are unable to simultaneously bring the mock data at both small and large radii into agreement with observations. Indeed, to match the slow rise of LSB galaxy rotation curves, a specific viewing angle of the nonaxisymmetric potential is required. For each of the simulated LSB galaxies, the observer's line of sight must be along the minor axis of the potential, an arrangement that is inconsistent with a random distribution of halo orientations on the sky.

  11. IRAS surface brightness maps of visible reflection nebulae: evidence for non-equilibrium infrared emission

    International Nuclear Information System (INIS)

    Castelaz, M.W.; Werner, M.W.; Sellgren, K.

    1986-01-01

    Surface brightness maps at 12, 25, 60, and 100 microns of 16 visible reflection nebulae were extracted from the Infrared Astronomy Satellite (IRAS) database. The maps were produced by coadding IRAS survey scans over areas centered on the illuminating stars, and have spatial resolutions of 0.9' x 4' at 12 and 25 microns, 1.8' x 4.5' at 60 microns, and 3.6' x 5' at 100 microns. Extended emission in the four IRAS bandpasses was detected in fourteen of the reflection nebulae. The IRAS data were used to measure the flux of the infrared emission associated with each source. The energy distributions show that the 12 micron flux is greater than the 25 micron flux in 11 of the nebulae, and the peak flux occurs in the 60 or 100 micron bandpass in all 16 nebular. The 60 and 100 micron flux can be approximated by blackbodies with temperatures between 30 and 50 K, consistent with temperatures expected from extrapolation of greybody fits to the 60 and 100 micron data. The excess 12 and 25 micron emission is attributed to a nonequilibrium process such as emission from thermal fluctuations of very small grains excited by single ultraviolet photons, or emission from polycyclic aromatic hydrocarbons (PAHs) excited by ultraviolet radiation. The common features of the energy distributions of the 16 reflection nebulae, also seen in the reflection nebulae associated with the Pleiades, suggest that PAHs or very small grains may be found in most reflection nebulae

  12. The Fornax Deep Survey with VST. III. Low surface brightness dwarfs and ultra diffuse galaxies in the center of the Fornax cluster

    NARCIS (Netherlands)

    Venhola, Aku; Peletier, Reynier; Laurikainen, Eija; Salo, Heikki; Lisker, Thorsten; Iodice, Enrichetta; Capaccioli, Massimo; Verdoes Kleijn, Gijs; Valentijn, Edwin; Mieske, Steffen; Hilker, Michael; Wittmann, Carolin; Van de Venn, Glenn; Grado, Aniello; Spavone, Marilena; Cantiello, Michele; Napolitano, Nicola; Paolillo, Maurizio; Falcón-Barroso, Jesus

    2017-01-01

    Context. Studies of low surface brightness (LSB) galaxies in nearby clusters have revealed a sub-population of extremely diffuse galaxies with central surface brightness of μ0,g' > 24 mag arcsec-2, total luminosity Mg' fainter than -16 mag and effective radius between 1.5 kpc 23 mag arcsec-2. We

  13. Photodetachment of negative ion in a gradient electric field near a metal surface

    International Nuclear Information System (INIS)

    Liu Tian-Qi; Wang De-Hua; Han Cai; Liu Jiang; Liang Dong-Qi; Xie Si-Cheng

    2012-01-01

    Based on closed-orbit theory, the photodetachment of H − in a gradient electric field near a metal surface is studied. It is demonstrated that the gradient electric field has a significant influence on the photodetachment of negative ions near a metal surface. With the increase of the gradient of the electric field, the oscillation in the photodetachment cross section becomes strengthened. Besides, in contrast to the photodetachment of H − near a metal surface in a uniform electric field, the oscillating amplitude and the oscillating region in the cross section of a gradient electric field also become enlarged. Therefore, we can use the gradient electric field to control the photodetachment of negative ions near a metal surface. We hope that our results will be useful for understanding the photodetachment of negative ions in the vicinity of surfaces, cavities, and ion traps. (atomic and molecular physics)

  14. Nocturnal variation of air-surface temperature gradients for typical urban and rural surfaces

    Science.gov (United States)

    Swaid, Hanna

    The nocturnal variation of the standard atmospheric air-ground surface temperature gradient under fair weather conditions is considered. A semi-analytical model in the form of an exponential response function is proposed and experimentally verified against field observations conducted by the author at Haifa ( ca 32°N) and by others at various geographical locations. The proposed model is intended to predict the sought gradient variation with the aid of an experimentally derived parameter (a time constant) which is directly proportional to the thermal inertia of the substrate matter beneath the surface in question. Among the impervious ground-cover types widely encountered in urban environments, concrete surfaces exhibit the highest time constant of about 10 h, while that of bare dry rural soil is 6.5 h. Turf and wet soil surfaces, common in rural environments, have time constants of 3.6 and 10.8 h, respectively. Applicability of the proposed model to the exterior surfaces of building-envelope elements is also discussed, as are the implications of the present findings regarding the causative factors of urban heat islands.

  15. Constrained numerical gradients and composite gradients: Practical tools for geometry optimization and potential energy surface navigation.

    Science.gov (United States)

    Stenrup, Michael; Lindh, Roland; Fdez Galván, Ignacio

    2015-08-15

    A method is proposed to easily reduce the number of energy evaluations required to compute numerical gradients when constraints are imposed on the system, especially in connection with rigid fragment optimization. The method is based on the separation of the coordinate space into a constrained and an unconstrained space, and the numerical differentiation is done exclusively in the unconstrained space. The decrease in the number of energy calculations can be very important if the system is significantly constrained. The performance of the method is tested on systems that can be considered as composed of several rigid groups or molecules, and the results show that the error with respect to conventional optimizations is of the order of the convergence criteria. Comparison with another method designed for rigid fragment optimization proves the present method to be competitive. The proposed method can also be applied to combine numerical and analytical gradients computed at different theory levels, allowing an unconstrained optimization with numerical differentiation restricted to the most significant degrees of freedom. This approach can be a practical alternative when analytical gradients are not available at the desired computational level and full numerical differentiation is not affordable. © 2015 Wiley Periodicals, Inc.

  16. Error sources in the retrieval of aerosol information over bright surfaces from satellite measurements in the oxygen A band

    Science.gov (United States)

    Nanda, Swadhin; de Graaf, Martin; Sneep, Maarten; de Haan, Johan F.; Stammes, Piet; Sanders, Abram F. J.; Tuinder, Olaf; Pepijn Veefkind, J.; Levelt, Pieternel F.

    2018-01-01

    Retrieving aerosol optical thickness and aerosol layer height over a bright surface from measured top-of-atmosphere reflectance spectrum in the oxygen A band is known to be challenging, often resulting in large errors. In certain atmospheric conditions and viewing geometries, a loss of sensitivity to aerosol optical thickness has been reported in the literature. This loss of sensitivity has been attributed to a phenomenon known as critical surface albedo regime, which is a range of surface albedos for which the top-of-atmosphere reflectance has minimal sensitivity to aerosol optical thickness. This paper extends the concept of critical surface albedo for aerosol layer height retrievals in the oxygen A band, and discusses its implications. The underlying physics are introduced by analysing the top-of-atmosphere reflectance spectrum as a sum of atmospheric path contribution and surface contribution, obtained using a radiative transfer model. Furthermore, error analysis of an aerosol layer height retrieval algorithm is conducted over dark and bright surfaces to show the dependence on surface reflectance. The analysis shows that the derivative with respect to aerosol layer height of the atmospheric path contribution to the top-of-atmosphere reflectance is opposite in sign to that of the surface contribution - an increase in surface brightness results in a decrease in information content. In the case of aerosol optical thickness, these derivatives are anti-correlated, leading to large retrieval errors in high surface albedo regimes. The consequence of this anti-correlation is demonstrated with measured spectra in the oxygen A band from the GOME-2 instrument on board the Metop-A satellite over the 2010 Russian wildfires incident.

  17. Link between convection and meridional gradient of sea surface ...

    Indian Academy of Sciences (India)

    . Resolution. URL. SST. TMI ... In this paper, we use satellite data for SST and rainfall to show that there exists a strong relationship between convec- tion and the meridional gradient of SST in the bay. We show that convection sets in within a ...

  18. Link between convection and meridional gradient of sea surface ...

    Indian Academy of Sciences (India)

    A sensitivity analysis showed that the corresponding threshold for was 29°C. We hypothesise that the excess heating (∼1° C above the threshold for deep convection)required in the northern bay to trigger convection is because this excess in SST is what is required to establish the critical SST gradient.

  19. Star formation and the interstellar medium in low surface brightness galaxies - I. Oxygen abundances and abundance gradients in low surface brightness disk galaxies

    NARCIS (Netherlands)

    de Blok, WJG; van der Hulst, JM

    We present measurements of the oxygen abundances in 64 HII regions in 12 LSB galaxies. We find that oxygen abundances are low. No regions with solar abundance have been found, and most have oxygen abundances similar to 0.5 to 0.1 solar. The oxygen abundance appears to be constant as a function of

  20. Star formation and the interstellar medium in low surface brightness galaxies; 1, Oxygen abundances and abundance gradients in low surface brightness disk galaxies

    NARCIS (Netherlands)

    Blok, W. J. G. de; Hulst, J. M. van der

    1998-01-01

    Submitted to: Astron. Astrophys. Abstract: We present measurements of the oxygen abundances in 64 HII regions in 12 LSB galaxies. We find that oxygen abundances are low. No regions with solar abundance have been found, and most have oxygen abundances $sim 0.5$ to 0.1 solar. The oxygen abundance

  1. Radial Wettable Gradient of Hot Surface to Control Droplets Movement in Directions

    Science.gov (United States)

    Feng, Shile; Wang, Sijie; Tao, Yuanhao; Shang, Weifeng; Deng, Siyan; Zheng, Yongmei; Hou, Yongping

    2015-01-01

    A radial wettable gradient was fabricated on the surface of graphite plate by a simple one-step anodic oxidation process. It was found that the direction and value of the wettable gradient could be easily controlled by adjusting current and oxidation time gradient. With the increase of surface temperature, droplets on surface not only exhibited the transition of boiling mode, but also showed the controlled radial spreading, evaporation and movement behaviors. These phenomena could be attributed to the cooperation of wettability force, hysteresis force and vapor pressure (Leidenfrost effect). Especially, the controlled radial convergence or divergence of droplets with high velocity were realized on the surfaces with either inside or outside radial gradient, which would have crucial applications in the design of microfluidic devices and the exploration of the biotechnology. PMID:25975722

  2. Gradient nanostructured surface of a Cu plate processed by incremental frictional sliding

    DEFF Research Database (Denmark)

    Hong, Chuanshi; Huang, Xiaoxu; Hansen, Niels

    2015-01-01

    The flat surface of a Cu plate was processed by incremental frictional sliding at liquid nitrogen temperature. The surface treatment results in a hardened gradient surface layer as thick as 1 mm in the Cu plate, which contains a nanostructured layer on the top with a boundary spacing of the order...

  3. Microstructural and hardness gradients in Cu processed by high pressure surface rolling

    DEFF Research Database (Denmark)

    He, Q. Y.; Zhu, X.-M.; Mei, Q. S.

    2017-01-01

    The surface of an annealed Cu plate was processed by a high pressure surface rolling (HPSR) process. It is found that the deformed surface layer in the Cu plate after HPSR can be as thick as 2 mm and is characterized by a gradient microstructure, with grain sizes varying from the nanoscale...

  4. The Next Generation Virgo Cluster Survey (NGVS). XVIII. Measurement and Calibration of Surface Brightness Fluctuation Distances for Bright Galaxies in Virgo (and Beyond)

    Science.gov (United States)

    Cantiello, Michele; Blakeslee, John P.; Ferrarese, Laura; Côté, Patrick; Roediger, Joel C.; Raimondo, Gabriella; Peng, Eric W.; Gwyn, Stephen; Durrell, Patrick R.; Cuillandre, Jean-Charles

    2018-04-01

    We describe a program to measure surface brightness fluctuation (SBF) distances to galaxies observed in the Next Generation Virgo Cluster Survey (NGVS), a photometric imaging survey covering 104 deg2 of the Virgo cluster in the u*, g, i, and z bandpasses with the Canada–France–Hawaii Telescope. We describe the selection of the sample galaxies, the procedures for measuring the apparent i-band SBF magnitude {\\overline{m}}i, and the calibration of the absolute Mibar as a function of observed stellar population properties. The multiband NGVS data set provides multiple options for calibrating the SBF distances, and we explore various calibrations involving individual color indices as well as combinations of two different colors. Within the color range of the present sample, the two-color calibrations do not significantly improve the scatter with respect to wide-baseline, single-color calibrations involving u*. We adopt the ({u}* -z) calibration as a reference for the present galaxy sample, with an observed scatter of 0.11 mag. For a few cases that lack good u* photometry, we use an alternative relation based on a combination of (g-i) and (g-z) colors, with only a slightly larger observed scatter of 0.12 mag. The agreement of our measurements with the best existing distance estimates provides confidence that our measurements are accurate. We present a preliminary catalog of distances for 89 galaxies brighter than B T ≈ 13.0 mag within the survey footprint, including members of the background M and W Clouds at roughly twice the distance of the main body of the Virgo cluster. The extension of the present work to fainter and bluer galaxies is in progress.

  5. Patterned gradient surface for spontaneous droplet transportation and water collection: simulation and experiment

    International Nuclear Information System (INIS)

    Tan, Xianhua; Zhu, Yiying; Shi, Tielin; Tang, Zirong; Liao, Guanglan

    2016-01-01

    We demonstrate spontaneous droplet transportation and water collection on wedge-shaped gradient surfaces consisting of alternating hydrophilic and hydrophobic regions. Droplets on the surfaces are modeled and simulated to analyze the Gibbs free energy and free energy gradient distributions. Big half-apex angle and great wettability difference result in considerable free energy gradient, corresponding to large driving force for spontaneous droplet transportation, thus causing the droplets to move towards the open end of the wedge-shaped hydrophilic regions, where the Gibbs free energy is low. Gradient surfaces are then fabricated and tested. Filmwise condensation begins on the hydrophilic regions, forming wedge-shaped tracks for water collection. Dropwise condensation occurs on the hydrophobic regions, where the droplet size distribution and departure diameters are controlled by the width of the regions. Condensate water from both the hydrophilic and hydrophobic regions are collected directionally to the open end of the wedge-shaped hydrophilic regions, agreeing with the simulations. Directional droplet transport and controllable departure diameters make the branched gradient surfaces more efficient than smooth surfaces for water collection, which proves that gradient surfaces are potential in water collection, microfluidic devices, anti-fogging and self-cleaning. (paper)

  6. Fabrication of a wettability-gradient surface on copper by screen-printing techniques

    Science.gov (United States)

    Huang, Ding-Jun; Leu, Tzong-Shyng

    2015-08-01

    In this study, a screen-printing technique is utilized to fabricate a wettability-gradient surface on a copper substrate. The pattern definitions on the copper surface were freely fabricated to define the regions with different wettabilities, for which the printing definition technique was developed as an alternative to the existing costly photolithography techniques. This fabrication process using screen printing in tandem with chemical modification methods can easily realize an excellent wettability-gradient surface with superhydrophobicity and superhydrophilicity. Surface analyses were performed to characterize conditions in some fabrication steps. A water droplet movement sequence is provided to clearly demonstrate the droplet-driving effectiveness of the fabricated gradient surface. The droplet-driving efficiency offers a promising solution for condensation heat transfer applications in the foreseeable future.

  7. Fast drop movements resulting from the phase change on a gradient surface.

    Science.gov (United States)

    Daniel, S; Chaudhury, M K; Chen, J C

    2001-01-26

    The movement of liquid drops on a surface with a radial surface tension gradient is described here. When saturated steam passes over a colder hydrophobic substrate, numerous water droplets nucleate and grow by coalescence with the surrounding drops. The merging droplets exhibit two-dimensional random motion somewhat like the Brownian movements of colloidal particles. When a surface tension gradient is designed into the substrate surface, the random movements of droplets are biased toward the more wettable side of the surface. Powered by the energies of coalescence and collimated by the forces of the chemical gradient, small drops (0.1 to 0.3 millimeter) display speeds that are hundreds to thousands of times faster than those of typical Marangoni flows. This effect has implications for passively enhancing heat transfer in heat exchangers and heat pipes.

  8. Surface tension gradient enhanced thin film flow for particle deposition

    Science.gov (United States)

    Gilchrist, James; Joshi, Kedar; Muangnapoh, Tanyakorn; Stever, Michael

    2015-11-01

    We investigate the effect of varying concentration in binary mixtures of water and ethanol as the suspending medium for micron-scale silica particles on convective deposition. By pulling a suspension along a substrate, a thin film is created that results in enhanced evaporation of the solvent and capillary forces that order particles trapped in the thin film. In pure water or pure ethanol, assembly and deposition is easily understood by a simply flux balance first developed by Dimitrov and Nagayama in 1996. In solvent mixtures having only a few percent of ethanol, Marangoni stresses from the concentration gradient set by unbalanced solvent evaporation dominates the thin film flow. The thin film profile is similar to that found in ``tears of wine'' where the particles are deposited in the thin film between the tears and the reservoir. A simple model describes the 10x increase of deposition speed found in forming well-ordered monolayers of particles. At higher ethanol concentrations, lateral instabilities also generated by Marangoni stresses cause nonuniform deposition in the form of complex streaks that mirror sediment deposits in larger scale flows. We acknowledge funding from the NSF Scalable Nanomanufacturing Program under grant No. 1120399.

  9. Near-surface thermal gradients and their effects on mid-infrared emission spectra of planetary surfaces

    Science.gov (United States)

    Henderson, B. G.; Jakosky, B. M.

    1994-01-01

    We model the heat transfer by radiation and conduction in the top few millimeters of a planetary surface to determine the magnitude of near-surface (approximately 100 micrometers) thermal gradients and their effects on mid-infrared emission spectra for a number of planetary environments. The model is one-dimensional and uses a finite difference scheme for approximately 10 micrometers layers. Calculations are peformed for samples heated at the base and from above by sunlight. Our results indicate that near-surface radiative cooling creates significant thermal gradients in the top few hundred microns of surfaces in which radiation is an importamnt heat transfer mechanism. The effect is maximized in evacuated, underdense particulate media with sufficiently high temperatures. Near-surface thermal gradients will be significant in fine-grained particulate surfaces on the Moon (40-60 K/100 micrometers) and Mercury (approximately 80 K/100 micrometers), increasing spectral contrast and creating emission maxima in the transparent regions of the spectra. They will be of lesser importance on the surface of Mars, with a maximum value of around 5 k/100 micrometers in areas of low thermal inertia, and will be negligible on planets with more substantial atmospheres (less than 1 K/100 micrometers). We conclude that the effects that thermal gradients have on mid-IR emission spectra are predictable and do not negate the utility of emission spectroscopy for remote determination of planetary surface composition.

  10. Orientations of Liquid Crystals in Contact with Surfaces that Present Continuous Gradients of Chemical Functionality

    International Nuclear Information System (INIS)

    Clare, B.; Efimenko, K.; Fischer, D.; Genzer, J.; Abbott, N.

    2006-01-01

    We report the formation of continuous spatial gradients in the density of grafted semifluorinated chains on silicon oxide surfaces by vapor-phase diffusion of semifluorinated silanes. We quantify the orientations of the nematic liquid crystal (LC) 4-cyano-4'-pentylbiphenyl on these surfaces as a function of local surface composition obtained by using NEXAFS. These measurements demonstrate that it is possible to obtain the full range of tilt angles of a LC on these surfaces. We also use the data provided by these gradient surfaces to test hypotheses regarding the nature of the interaction between the LC and surfaces that give rise to the range of tilted orientations of the LC. We conclude that the orientations of the LC are not determined solely by the density of grafted semifluorinated chains or by the density of residual hydroxyl groups presented at these surfaces following reactions with the silanes. Instead, our results raise the possibility that the tilt angles of the semifluorinated chains on these surfaces (which are a function of the density of the grafted chains) may influence the orientation of the LC. These results, when combined, demonstrate the potential utility of gradient surfaces for screening surface chemistries that achieve desired orientations of LCs as well as for rapidly assembling experimental data sets that can be used to test propositions regarding mechanisms of anchoring LCs at surfaces

  11. HerMES: A DEFICIT IN THE SURFACE BRIGHTNESS OF THE COSMIC INFRARED BACKGROUND DUE TO GALAXY CLUSTER GRAVITATIONAL LENSING

    International Nuclear Information System (INIS)

    Zemcov, M.; Cooray, A.; Bock, J.; Dowell, C. D.; Nguyen, H. T.; Blain, A.; Béthermin, M.; Clements, D. L.; Conley, A.; Glenn, J.; Conversi, L.; Farrah, D.; Oliver, S. J.; Roseboom, I. G.; Griffin, M.; Halpern, M.; Marsden, G.; Jullo, E.; Kneib, J.-P.; Richard, J.

    2013-01-01

    We have observed four massive galaxy clusters with the SPIRE instrument on the Herschel Space Observatory and measure a deficit of surface brightness within their central region after removing detected sources. We simulate the effects of instrumental sensitivity and resolution, the source population, and the lensing effect of the clusters to estimate the shape and amplitude of the deficit. The amplitude of the central deficit is a strong function of the surface density and flux distribution of the background sources. We find that for the current best fitting faint end number counts, and excellent lensing models, the most likely amplitude of the central deficit is the full intensity of the cosmic infrared background (CIB). Our measurement leads to a lower limit to the integrated total intensity of the CIB of I 250μm >0.69 -0.03 +0.03 (stat.) -0.06 +0.11 (sys.) MJy sr –1 , with more CIB possible from both low-redshift sources and from sources within the target clusters. It should be possible to observe this effect in existing high angular resolution data at other wavelengths where the CIB is bright, which would allow tests of models of the faint source component of the CIB.

  12. Modeling of surface effects in crystalline materials within the framework of gradient crystal plasticity

    Science.gov (United States)

    Peng, Xiang-Long; Husser, Edgar; Huang, Gan-Yun; Bargmann, Swantje

    2018-03-01

    A finite-deformation gradient crystal plasticity theory is developed, which takes into account the interaction between dislocations and surfaces. The model captures both energetic and dissipative effects for surfaces penetrable by dislocations. By taking advantage of the principle of virtual power, the surface microscopic boundary equations are obtained naturally. Surface equations govern surface yielding and hardening. A thin film under shear deformation serves as a benchmark problem for validation of the proposed model. It is found that both energetic and dissipative surface effects significantly affect the plastic behavior.

  13. Finite Element Analysis of Surface Residual Stress in Functionally Gradient Cemented Carbide Tool

    Science.gov (United States)

    Su, Chuangnan; Liu, Deshun; Tang, Siwen; Li, Pengnan; Qiu, Xinyi

    2018-03-01

    A component distribution model is proposed for three-component functionally gradient cemented carbide (FGCC) based on electron probe microanalysis results obtained for gradient layer thickness, microstructure, and elemental distribution. The residual surface stress of FGCC-T5 tools occurring during the fabrication process is analyzed using an ANSYS-implemented finite element method (FEM) and X-ray diffraction. A comparison of the experimental and calculated values verifies the feasibility of using FEM to analyze the residual surface stress in FGCC-T5 tools. The effects of the distribution index, geometrical shape, substrate thickness, gradient layer thickness, and position of the cobalt-rich layer on residual surface stress are studied in detail.

  14. Proposal of control system of surface brightness of rolled sheet in cold rolling. Reikan atsuen ni okeru ita hyomen kotaku no seigyo system no teian

    Energy Technology Data Exchange (ETDEWEB)

    Azushima, A.; Iyanagi, Y.; Degawa, H.; Noro, K. (Yokohama National Univ., Yokohama, (Japan). Faculty of Engineering Daido Chemical Industry Co. Ltd., Tokyo, (Japan))

    1990-04-01

    The relation was systematically examined between the surface quality of a rolled sheet in cold rolling and tribological factors (rolling speed, reduction, viscosity of lubricant, surface roughnesses of a roll and sheet). In the case where the surface roughnesses of rolls and sheets were smooth, the surface brightness decreased with an increase in rolling speed and viscosity, resulting in rough surfaces. The dependence of the rolling speed, viscosity and roughness on the brightness was equal to that on an oil film thickness, and the brightness of rolled sheets could be thus expressed as the function of only the oil film thickness. In the case those were rough, the roughness had a great influence on the surface quality of rolled sheets, and the brightness could be expressed as the function of the oil film thickness and roughnesses of rolls and sheets before rolling. Based on these relations, the system was proposed capable of estimating and controlling the brightness of rolled sheets from/by conditions before rolling. 13 refs., 16 figs., 1 tab.

  15. Engineering optical gradient force from coupled surface plasmon polariton modes in nanoscale plasmonic waveguides

    Science.gov (United States)

    Lu, Jiahui; Wang, Guanghui

    2016-11-01

    We explore the dispersion properties and optical gradient forces from mutual coupling of surface plasmon polariton (SPP) modes at two interfaces of nanoscale plasmonic waveguides with hyperbolic metamaterial cladding. With Maxwell’s equations and Maxwell stress tensor, we calculate and compare the dispersion relation and optical gradient force for symmetric and antisymmetric SPP modes in two kinds of nanoscale plasmonic waveguides. The numerical results show that the optical gradient force between two coupled hyperbolic metamaterial waveguides can be engineered flexibly by adjusting the waveguide structure parameters. Importantly, an alternative way to boost the optical gradient force is provided through engineering the hyperbolic metamaterial cladding of suitable orientation. These special optical properties will open the door for potential optomechanical applications, such as optical tweezers and actuators. Project supported by the National Natural Science Foundation of China (Grant No. 11474106) and the Natural Science Foundation of Guangdong Province, China (Grant No. 2016A030313439).

  16. The abundance properties of nearby late-type galaxies. II. The relation between abundance distributions and surface brightness profiles

    International Nuclear Information System (INIS)

    Pilyugin, L. S.; Grebel, E. K.; Zinchenko, I. A.; Kniazev, A. Y.

    2014-01-01

    The relations between oxygen abundance and disk surface brightness (OH–SB relation) in the infrared W1 band are examined for nearby late-type galaxies. The oxygen abundances were presented in Paper I. The photometric characteristics of the disks are inferred here using photometric maps from the literature through bulge-disk decomposition. We find evidence that the OH–SB relation is not unique but depends on the galactocentric distance r (taken as a fraction of the optical radius R 25 ) and on the properties of a galaxy: the disk scale length h and the morphological T-type. We suggest a general, four-dimensional OH–SB relation with the values r, h, and T as parameters. The parametric OH–SB relation reproduces the observed data better than a simple, one-parameter relation; the deviations resulting when using our parametric relation are smaller by a factor of ∼1.4 than that of the simple relation. The influence of the parameters on the OH–SB relation varies with galactocentric distance. The influence of the T-type on the OH–SB relation is negligible at the centers of galaxies and increases with galactocentric distance. In contrast, the influence of the disk scale length on the OH–SB relation is at a maximum at the centers of galaxies and decreases with galactocentric distance, disappearing at the optical edges of galaxies. Two-dimensional relations can be used to reproduce the observed data at the optical edges of the disks and at the centers of the disks. The disk scale length should be used as a second parameter in the OH–SB relation at the center of the disk while the morphological T-type should be used as a second parameter in the relation at optical edge of the disk. The relations between oxygen abundance and disk surface brightness in the optical B and infrared K bands at the center of the disk and at optical edge of the disk are also considered. The general properties of the abundance–surface brightness relations are similar for the three

  17. Calculation of Surface Tensions of Polar Mixtures with a Simplified Gradient Theory Model

    DEFF Research Database (Denmark)

    Zuo, You-Xiang; Stenby, Erling Halfdan

    1996-01-01

    Key Words: Thermodynamics, Simplified Gradient Theory, Surface Tension, Equation of state, Influence Parameter.In this work, assuming that the number densities of each component in a mixture across the interface between the coexisting vapor and liquid phases are linearly distributed, we developed...

  18. An Improved Local Gradient Method for Sea Surface Wind Direction Retrieval from SAR Imagery

    Directory of Open Access Journals (Sweden)

    Lizhang Zhou

    2017-06-01

    Full Text Available Sea surface wind affects the fluxes of energy, mass and momentum between the atmosphere and ocean, and therefore regional and global weather and climate. With various satellite microwave sensors, sea surface wind can be measured with large spatial coverage in almost all-weather conditions, day or night. Like any other remote sensing measurements, sea surface wind measurement is also indirect. Therefore, it is important to develop appropriate wind speed and direction retrieval models for different types of microwave instruments. In this paper, a new sea surface wind direction retrieval method from synthetic aperture radar (SAR imagery is developed. In the method, local gradients are computed in frequency domain by combining the operation of smoothing and computing local gradients in one step to simplify the process and avoid the difference approximation. This improved local gradients (ILG method is compared with the traditional two-dimensional fast Fourier transform (2D FFT method and local gradients (LG method, using interpolating wind directions from the European Centre for Medium-Range Weather Forecast (ECMWF reanalysis data and the Cross-Calibrated Multi-Platform (CCMP wind vector product. The sensitivities to the salt-and-pepper noise, the additive noise and the multiplicative noise are analyzed. The ILG method shows a better performance of retrieval wind directions than the other two methods.

  19. Capillary electrophoresis in a fused-silica capillary with surface roughness gradient

    Czech Academy of Sciences Publication Activity Database

    Horká, Marie; Šlais, Karel; Karásek, Pavel; Růžička, F.; Šalplachta, Jiří; Šesták, Jozef; Kahle, Vladislav; Roth, Michal

    2016-01-01

    Roč. 39, č. 19 (2016), s. 3827-3834 ISSN 1615-9306 R&D Projects: GA ČR(CZ) GA16-03749S; GA MZd(CZ) NV16-29916A Institutional support: RVO:68081715 Keywords : capillary electrophoresis * supercritical water * surface roughness gradient Subject RIV: CB - Analytical Chemistry , Separation Impact factor: 2.557, year: 2016

  20. Gradients of parameters of the real structure in steels surface layers after mechanical treatment

    Czech Academy of Sciences Publication Activity Database

    Drahokoupil, Jan; Čerňanský, Marian; Ganev, N.; Kolařík, K.; Pala, Z.

    2007-01-01

    Roč. 130, - (2007), s. 77-80 ISSN 1012-0394 Institutional research plan: CEZ:AV0Z10100520 Keywords : gradients * real structure * steels * surface Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.493, year: 2005

  1. Discovery of megaparsec-scale, low surface brightness nonthermal emission in merging galaxy clusters using the green bank telescope

    Energy Technology Data Exchange (ETDEWEB)

    Farnsworth, Damon; Rudnick, Lawrence [Minnesota Institute for Astrophysics, University of Minnesota, 116 Church Street S.E., Minneapolis, MN 55455 (United States); Brown, Shea [Department of Physics and Astronomy, University of Iowa, 203 Van Allen Hall, Iowa City, IA 52242 (United States); Brunetti, Gianfranco [INAF/Istituto di Radioastronomia, via Gobetti 101, I-40129 Bologna (Italy)

    2013-12-20

    We present results from a study of 12 X-ray bright clusters at 1.4 GHz with the 100 m Green Bank Telescope. After subtraction of point sources using existing interferometer data, we reach a median (best) 1σ rms sensitivity level of 0.01 (0.006) μJy arcsec{sup –2}, and find a significant excess of diffuse, low surface brightness emission in 11 of 12 Abell clusters observed. We also present initial results at 1.4 GHz of A2319 from the Very Large Array. In particular, we find: (1) four new detections of diffuse structures tentatively classified as two halos (A2065, A2069) and two relics (A2067, A2073); (2) the first detection of the radio halo in A2061 at 1.4 GHz, which qualifies this as a possible ultra-steep spectrum halo source with a synchrotron spectral index of α ∼ 1.8 between 327 MHz and 1.4 GHz; (3) a ∼2 Mpc radio halo in the sloshing, minor-merger cluster A2142; (4) a >2× increase of the giant radio halo extent and luminosity in the merging cluster A2319; (5) a ∼7× increase to the integrated radio flux and >4× increase to the observed extent of the peripheral radio relic in A1367 to ∼600 kpc, which we also observe to be polarized on a similar scale; (6) significant excess emission of ambiguous nature in three clusters with embedded tailed radio galaxies (A119, A400, A3744). Our radio halo detections agree with the well-known X-ray/radio luminosity correlation, but they are larger and fainter than current radio power correlation studies would predict. The corresponding volume-averaged synchrotron emissivities are 1-2 orders of magnitude below the characteristic value found in previous studies. Some of the halo-like detections may be some type of previously unseen, low surface brightness radio halo or blend of unresolved shock structures and sub-Mpc-scale turbulent regions associated with their respective cluster merging activity. Four of the five tentative halos contain one or more X-ray cold fronts, suggesting a possible connection between gas

  2. A study of the HI and optical properties of Low Surface Brightness galaxies: spirals, dwarfs and irregulars

    Science.gov (United States)

    Honey, M.; van Driel, W.; Das, M.; Martin, J.-M.

    2018-03-01

    We present a study of the HI and optical properties of nearby (z ≤ 0.1) Low Surface Brightness galaxies (LSBGs). We started with a literature sample of ˜900 LSBGs and divided them into three morphological classes: spirals, irregulars and dwarfs. Of these, we could use ˜490 LSBGs to study their HI and stellar masses, colours and colour magnitude diagrams, and local environment, compare them with normal, High Surface Brightness (HSB) galaxies and determine the differences between the three morphological classes. We found that LSB and HSB galaxies span a similar range in HI and stellar masses, and have a similar MHI/M⋆-M⋆ relationship. Among the LSBGs, as expected, the spirals have the highest average HI and stellar masses, both of about 109.8M⊙. The LSGBs' (g-r) integrated colour is nearly constant as function of HI mass for all classes. In the colour magnitude diagram, the spirals are spread over the red and blue regions whereas the irregulars and dwarfs are confined to the blue region. The spirals also exhibit a steeper slope in the MHI/M⋆-M⋆ plane. Within their local environment we confirmed that LSBGs are more isolated than HSB galaxies, and LSB spirals more isolated than irregulars and dwarfs. Kolmogorov-Smirnov statistical tests on the HI mass, stellar mass and number of neighbours indicates that the spirals are a statistically different population from the dwarfs and irregulars. This suggests that the spirals may have different formation and HI evolution than the dwarfs and irregulars.

  3. Highly surface functionalized carbon nano-onions for bright light bioimaging

    International Nuclear Information System (INIS)

    Frasconi, Marco; Maffeis, Viviana; Bartelmess, Juergen; Giordani, Silvia; Echegoyen, Luis

    2015-01-01

    Carbon-based nanomaterials functionalized with fluorescent and water-soluble groups have emerged as platforms for biological imaging because of their low toxicity and ability to be internalized by cells. The development of imaging probes based on carbon nanomaterials for biomedical studies requires the understanding of their biological response as well as the efficient and safety exposition of the nanomaterial to the cell compartment where it is designed to operate. Here, we present a fluorescent probe based on surface functionalized carbon nano-onions (CNOs) for biological imaging. The modification of CNOs by chemical oxidation of the defects on the outer shell of these carbon nanoparticles results in an extensive surface functionalization with carboxyl groups. We have obtained fluorescently labelled CNOs by a reaction involving the amide bond formation between fluoresceinamine and the carboxylic acids groups on the surface of the CNOs. The functionalized CNOs display high emission properties and dispersability in water due to the presence of high surface coverage of carboxylic acid groups that translate in an efficient fluorescent probe for in vitro imaging of HeLa cells, without significant cytotoxicity. The resulting nanomaterial represents a promising platform for biological imaging applications due to the high dispersability in water, its efficient internalization by cancer cells and localization in specific cell compartments. (paper)

  4. Self-propulsion of Leidenfrost droplets on micropillared hot surfaces with gradient wettability

    Science.gov (United States)

    Chen, Meng-yao; Jia, Zhi-hai; Zhang, Tao; Fei, Yuan-yuan

    2018-03-01

    Motion of matter requires application of asymmetric potential. In this work, we explored the self-propulsion of Leidenfrost droplet on hot micropillared surfaces with gradient wettability. The surface fabricated with micropillars displays unidirectional properties. It was found that Leidenfrost droplets on this surface self-propelled from the smaller superficial area of micropillars (SSAM) towards the larger superficial area of micropillars (LSAM). The self-propulsion mechanism is proposed based on the self-rotation of Leidenfrost droplets and the theoretical model is well matched with the experimental findings.

  5. Cost-Effective Fabrication of Wettability Gradient Copper Surface by Screen Printing and its Application to Condensation Heat Transfer

    Science.gov (United States)

    Leu, Tzong-Shyng; Huang, Hung-Ming; Huang, Ding-Jun

    2016-06-01

    In this paper, wettability gradient pattern is applied to condensation heat transfer on a copper tube surface. For this application, the vital issue is how to fabricate gradient patterns on a curve tube surface to accelerate the droplet collection efficiently. For this purpose, novel fabrication processes are developed to form wettability gradient patterns on a curve copper tube surface by using roller screen printing surface modification techniques. The roller screen printing surface modification techniques can easily realize wettability gradient surfaces with superhydrophobicity and superhydrophilicity on a copper tube surface. Experimental results show the droplet nucleation sites, movement and coalescence toward the collection areas can be effectively controlled which can assist in removing the condensation water from the surface. The effectiveness of droplet collection is appropriate for being applied to condensation heat transfer in the foreseeable future.

  6. Land surface phenology and land surface temperature changes along an urban-rural gradient in Yangtze River Delta, china.

    Science.gov (United States)

    Han, Guifeng; Xu, Jianhua

    2013-07-01

    Using SPOT/VGT NDVI time series images (2002-2009) and MODIS/LST images (2002-2009) smoothed by a Savitzky-Golay filter, the land surface phenology (LSP) and land surface temperature (LST), respectively, are extracted for six cities in the Yangtze River Delta, China, including Shanghai, Hangzhou, Nanjing, Changzhou, Wuxi, and Suzhou. The trends of the averaged LSP and LST are analyzed, and the relationship between these values is revealed along the urban-rural gradient. The results show that urbanization advances the start of the growing season, postpones the end of the growing season, prolongs the growing season length (GSL), and reduces the difference between maximal NDVI and minimal NDVI in a year (NDVIamp). More obvious changes occur in surface vegetation phenology as the urbanized area is approached. The LST drops monotonously and logarithmically along the urban-rural gradient. Urbanization generally affects the LSP of the surrounding vegetation within 6 km to the urban edge. Except for GSL, the difference in the LSP between urban and rural areas has a significant logarithmic relationship with the distance to the urban edge. In addition, there is a very strong linear relationship between the LSP and the LST along the urban-rural gradient, especially within 6 km to the urban edge. The correlations between LSP and gross domestic product and population density reveal that human activities have considerable influence on the land surface vegetation growth.

  7. Near-surface temperature gradients and their effects on thermal-infrared emission spectra of particulate planetary surfaces

    Science.gov (United States)

    Henderson, B. G.; Jakosky, B. M.

    1993-01-01

    The infrared energy emitted from a planetary surface is generated within a finite depth determined by the material's absorption skin depth. This parameter varies significantly with wavelength in the infrared but has an average value of around 50 microns for most geologic materials. In solid rock, heat transfer is efficient enough so that this 50 micron zone of the near surface from which the radiation emanates will be more or less isothermal. In particulate materials, however, heat transfer is more complicated and occurs via a combination of mechanisms, including solid conduction within grains and across grain contacts, conduction through the interstitial gas, and thermal radiation within individual particles and across the void spaces in between grains. On planets with substantial atmospheres, the gas component dominates the heat transfer and tends to mitigate near-surface thermal gradients. However, on airless bodies, the gas component is absent and heat transfer occurs via solid conductions and radiation. If the particles are small relative to the average absorption skin depth, then the top 50-100 microns or so of the surface will be cooled by radiation to space allowing the creation of significant near-surface thermal gradients. In those regions of the spectrum where the absorption coefficient is low, the emission will come from the deeper, warmer parts of the medium, whereas in regions of high absorption, the emission will emanate from shallower, cooler parts of the medium. The resulting emission spectrum will show non-compositional features as a result of the thermal structure in the material. We have modeled the heat transfer in a particulate medium in order to determine the magnitude of near-surface thermal gradients for surfaces on airless bodies and on Mars. We use the calculated thermal structure to determine the effects it has on the infrared emission spectrum of the surface.

  8. Instability of non-Newtonian jets with a surface tension gradient

    International Nuclear Information System (INIS)

    Gao Zhanjun

    2009-01-01

    In this paper we investigate the mechanisms of temporal instability of non-Newtonian liquid jets, more specifically viscoelastic liquid jets, with a surface tension gradient. The dispersion relation between the growth rate and the wave number for a viscoelastic liquid jet is derived. The effects of various parameters on the instability behavior are studied. A number of quantitative conclusions and sensitivities on the instability behavior of viscoelastic jets are investigated. The present work can provide a good foundation for further investigations of the instability and breakup of viscoelastic liquid jets in the situation where the surface tension gradient exists. The applications of such a phenomenon include a microfluidic inkjet printheads with thousands of nozzles that are thermally modulated near the nozzle orifice to produce steady steams of picoliter-sized droplets at kilo-Hertz frequency rates

  9. DGSAT: Dwarf Galaxy Survey with Amateur Telescopes. II. A catalogue of isolated nearby edge-on disk galaxies and the discovery of new low surface brightness systems

    Science.gov (United States)

    Henkel, C.; Javanmardi, B.; Martínez-Delgado, D.; Kroupa, P.; Teuwen, K.

    2017-07-01

    The connection between the bulge mass or bulge luminosity in disk galaxies and the number, spatial and phase space distribution of associated dwarf galaxies is a discriminator between cosmological simulations related to galaxy formation in cold dark matter and generalised gravity models. Here, a nearby sample of isolated Milky Way-class edge-on galaxies is introduced, to facilitate observational campaigns to detect the associated families of dwarf galaxies at low surface brightness. Three galaxy pairs with at least one of the targets being edge-on are also introduced. Approximately 60% of the catalogued isolated galaxies contain bulges of different size, while the remaining objects appear to be bulgeless. Deep images of NGC 3669 (small bulge, with NGC 3625 at the edge of the image) and NGC 7814 (prominent bulge), obtained with a 0.4 m aperture, are also presented, resulting in the discovery of two new dwarf galaxy candidates, NGC 3669-DGSAT-3 and NGC 7814-DGSAT-7. Eleven additional low surface brightness galaxies are identified, previously notified with low quality measurement flags in the Sloan Digital Sky Survey (SDSS). Integrated magnitudes, surface brightnesses, effective radii, Sersic indices, axis ratios, and projected distances to their putative major hosts are displayed. At least one of the galaxies, NGC 3625-DGSAT-4, belongs with a surface brightness of μr ≈ 26 mag arcsec-2 and effective radius >1.5 kpc to the class of ultra-diffuse galaxies (UDGs). NGC 3669-DGSAT-3, the galaxy with the lowest surface brightness in our sample, may also be an UDG.

  10. Microhardness changes gradient of the duplex stainless steel (DSS surface layer after dry turning

    Directory of Open Access Journals (Sweden)

    G. Krolczyk

    2014-10-01

    Full Text Available The article presents the gradient of microhardness changes as a function of the distance from the material surface after turning with a wedge provided with a coating with a ceramic intermediate layer. The investigation comprised the influence of cutting speed on surface integrity microhardness in dry machining. The tested material was duplex stainless steel (DSS with two-phase, ferritic-austenitic structure. The tests have been performed under production conditions during machining of parts for electric motors and deep-well pumps.

  11. A gradient surface produced by combined electroplating and incremental frictional sliding

    DEFF Research Database (Denmark)

    Yu, Tianbo; Hong, Chuanshi; Kitamura, K.

    2017-01-01

    A Cu plate was first electroplated with a Ni layer, with a thickness controlled to be between 1 and 2 mu m. The coated surface was then deformed by incremental frictional sliding with liquid nitrogen cooling. The combined treatment led to a multifunctional surface with a gradient in strain...... processed Cu plate without Ni coating, showing a strong effect of the coated layer on the deformation. The experimental results are followed by an analysis of strengthening mechanisms and a discussion of the applicability of the new technique for increasing the durability and lifetime of components exposed...

  12. An adaptive finite element method for simulating surface tension with the gradient theory of fluid interfaces

    KAUST Repository

    Kou, Jisheng

    2014-01-01

    The gradient theory for the surface tension of simple fluids and mixtures is rigorously analyzed based on mathematical theory. The finite element approximation of surface tension is developed and analyzed, and moreover, an adaptive finite element method based on a physical-based estimator is proposed and it can be coupled efficiently with Newton\\'s method as well. The numerical tests are carried out both to verify the proposed theory and to demonstrate the efficiency of the proposed method. © 2013 Elsevier B.V. All rights reserved.

  13. The faint end of the red sequence galaxy luminosity function: unveiling surface brightness selection effects with the CLASH clusters

    Science.gov (United States)

    Martinet, Nicolas; Durret, Florence; Adami, Christophe; Rudnick, Gregory

    2017-08-01

    Characterizing the evolution of the faint end of the cluster red sequence (RS) galaxy luminosity function (GLF) with redshift is a milestone in understanding galaxy evolution. However, the community is still divided in that respect, hesitating between an enrichment of the RS due to efficient quenching of blue galaxies from z 1 to present-day or a scenario in which the RS is built at a higher redshift and does not evolve afterwards. Recently, it has been proposed that surface brightness (SB) selection effects could possibly solve the literature disagreement, accounting for the diminishing RS faint population in ground-based observations. We investigate this hypothesis by comparing the RS GLFs of 16 CLASH clusters computed independently from ground-based Subaru/Suprime-Cam V and Ip or Ic images and space-based HST/ACS F606W and F814W images in the redshift range 0.187 ≤ z ≤ 0.686. We stack individual cluster GLFs in two redshift bins (0.187 ≤ z ≤ 0.399 and 0.400 ≤ z ≤ 0.686) and two mass (6 × 1014M⊙ ≤ M200Japan.

  14. THE CASE AGAINST WARM OR SELF-INTERACTING DARK MATTER AS EXPLANATIONS FOR CORES IN LOW SURFACE BRIGHTNESS GALAXIES

    International Nuclear Information System (INIS)

    Kuzio de Naray, Rachel; Martinez, Gregory D.; Bullock, James S.; Kaplinghat, Manoj

    2010-01-01

    Warm dark matter (WDM) and self-interacting dark matter (SIDM) are often motivated by the inferred cores in the dark matter halos of low surface brightness (LSB) galaxies. We test thermal WDM, non-thermal WDM, and SIDM using high-resolution rotation curves of nine LSB galaxies. We fit these dark matter models to the data and determine the halo core radii and central densities. While the minimum core size in WDM models is predicted to decrease with halo mass, we find that the inferred core radii increase with halo mass and also cannot be explained with a single value of the primordial phase-space density. Moreover, if the core size is set by WDM particle properties, then even the smallest cores we infer would require primordial phase-space density values that are orders of magnitude smaller than lower limits obtained from the Lyα forest power spectra. We also find that the dark matter halo core densities vary by a factor of about 30 from system to system while showing no systematic trend with the maximum rotation velocity of the galaxy. This strongly argues against the core size being directly set by large self-interactions (scattering or annihilation) of dark matter. We therefore conclude that the inferred cores do not provide motivation to prefer WDM or SIDM over other dark matter models.

  15. Mechanical Behavior of Ultrafine Gradient Grain Structures Produced via Ambient and Cryogenic Surface Mechanical Attrition Treatment in Iron

    Directory of Open Access Journals (Sweden)

    Heather A. Murdoch

    2015-06-01

    Full Text Available Ambient and cryogenic surface mechanical attrition treatments (SMAT are applied to bcc iron plate. Both processes result in significant surface grain refinement down to the ultrafine-grained regime; the cryogenic treatment results in a 45% greater grain size reduction. However, the refined region is shallower in the cryogenic SMAT process. The tensile ductility of the grain size gradient remains low (<10%, in line with the expected behavior of the refined surface grains. Good tensile ductility in a grain size gradient requires the continuation of the gradient into an undeformed region.

  16. Variability of water content useful in surface along a rainfall gradient Mediterranean

    International Nuclear Information System (INIS)

    Ruiz-Sinoga, J. D.; Martinez-Murillo, J. F.; Gabarron-Galeote, M. A.

    2009-01-01

    A climatic gradient was defined in South of spain with a great decreased of rainfall from West to East (>1,000 mm), which produces changes in vegetation and hydric resources. this study was carried out in five hill slopes under different climatic conditions and their aims were to analyze: the variability of available water along the gradient since 2002 to 2006, the key factors of it and the influence on the vegetal cover. Results showed that clay content had a great influence in the surface available water for plants, which did not decrease in the deerfield sites, where the amount of days with hydric deficient was lower. Relationships between vegetation and soil water were stronger in the more humid field sites, where existed a feedback between both properties. (Author) 4 refs.

  17. Inferring Land Surface Model Parameters for the Assimilation of Satellite-Based L-Band Brightness Temperature Observations into a Soil Moisture Analysis System

    Science.gov (United States)

    Reichle, Rolf H.; De Lannoy, Gabrielle J. M.

    2012-01-01

    The Soil Moisture and Ocean Salinity (SMOS) satellite mission provides global measurements of L-band brightness temperatures at horizontal and vertical polarization and a variety of incidence angles that are sensitive to moisture and temperature conditions in the top few centimeters of the soil. These L-band observations can therefore be assimilated into a land surface model to obtain surface and root zone soil moisture estimates. As part of the observation operator, such an assimilation system requires a radiative transfer model (RTM) that converts geophysical fields (including soil moisture and soil temperature) into modeled L-band brightness temperatures. At the global scale, the RTM parameters and the climatological soil moisture conditions are still poorly known. Using look-up tables from the literature to estimate the RTM parameters usually results in modeled L-band brightness temperatures that are strongly biased against the SMOS observations, with biases varying regionally and seasonally. Such biases must be addressed within the land data assimilation system. In this presentation, the estimation of the RTM parameters is discussed for the NASA GEOS-5 land data assimilation system, which is based on the ensemble Kalman filter (EnKF) and the Catchment land surface model. In the GEOS-5 land data assimilation system, soil moisture and brightness temperature biases are addressed in three stages. First, the global soil properties and soil hydraulic parameters that are used in the Catchment model were revised to minimize the bias in the modeled soil moisture, as verified against available in situ soil moisture measurements. Second, key parameters of the "tau-omega" RTM were calibrated prior to data assimilation using an objective function that minimizes the climatological differences between the modeled L-band brightness temperatures and the corresponding SMOS observations. Calibrated parameters include soil roughness parameters, vegetation structure parameters

  18. Functionalized PDMS with versatile and scalable surface roughness gradients for cell culture

    KAUST Repository

    Zhou, Bingpu

    2015-07-21

    This manuscript describes a simple and versatile approach to engineering surface roughness gradients via combination of microfluidics and photo-polymerization. Through UV-mediated polymerization, N-isopropylacrylamide with concentration gradients are successfully grafted onto PDMS surface, leading to diverse roughness degrees on the obtained PDMS substrate. Furthermore, the extent of surface roughness can be controllably regulated via tuning the flow rate ratio between the monomer solution and deionized water. Average roughness ranging from 8.050 nm to 151.68 nm has well been achieved in this work. Such PDMS samples are also demonstrated to be capable of working as supporting substrates for controlling cell adhesion or detachment. Due to the different degrees of surface roughness on a single substrate, our method provides an effective approach for designing advanced surafecs for cell culture. Finally, the thermosensitive property of N-isopropylacrylamide makes our sample furnish as another means for controlling the cell detachment from the substrates with correspondence to the surrounding temperature.

  19. Enabling HST UV Exploration of the Low Surface Brightness Universe: A Pilot Study with the WFC3 X Filter Set

    Science.gov (United States)

    Thilker, David

    2017-08-01

    We request 17 orbits to conduct a pilot study to examine the effectiveness of the WFC3/UVIS F300X filter for studying fundamental problems in star formation in the low density regime. In principle, the broader bandpass and higher throughput of F300X can halve the required observing time relative to F275W, the filter of choice for studying young stellar populations in nearby galaxies. Together with F475W and F600LP, this X filter set may be as effective as standard UVIS broadband filters for characterizing the physical properties of such populations. We will observe 5 low surface brightness targets with a range of properties to test potential issues with F300X: the red tail to 4000A and a red leak beyond, ghosts, and the wider bandpass. Masses and ages of massive stars, young star clusters, and clumps derived from photometry from the X filter set will be compared with corresponding measurements from standard filters. Beyond testing, our program will provide the first sample spanning a range of LSB galaxy properties for which HST UV imaging will be obtained, and a glimpse into the ensemble properties of the quanta of star formation in these strange environments. The increased observing efficiency would make more tractable programs which require several tens to hundreds of orbits to aggregate sufficient numbers of massive stars, young star clusters, and clumps to build statistical samples. We are hopeful that our pilot observations will broadly enable high-resolution UV imaging exploration of the low density frontier of star formation while HST is still in good health.

  20. Can AGN and galaxy clusters explain the surface brightness fluctuations of the cosmic X-ray background?

    Science.gov (United States)

    Kolodzig, Alexander; Gilfanov, Marat; Hütsi, Gert; Sunyaev, Rashid

    2017-04-01

    Fluctuations of the surface brightness of cosmic X-ray background (CXB) carry unique information about faint and low-luminosity source populations, which is inaccessible for conventional large-scale structure (LSS) studies based on resolved sources. We used XBOOTES (5ks deep Chandra X-ray Observatory ACIS-I maps of the ˜ 9 deg2 Bootes field of the NOAO Deep Wide-Field Survey) to conduct the most accurate measurement to date of the power spectrum of fluctuations of the unresolved CXB on the angular scales of 3 arcsec-17 arcmin. We find that at sub-arcmin angular scales, the power spectrum is consistent with the active galactic nucleus (AGN) shot noise, without much need for any significant contribution from their one-halo term. This is consistent with the theoretical expectation that low-luminosity AGN reside alone in their dark matter haloes. However, at larger angular scales, we detect a significant LSS signal above the AGN shot noise. Its power spectrum, obtained after subtracting the AGN shot noise, follows a power law with the slope of -0.8 ± 0.1 and its amplitude is much larger than what can be plausibly explained by the two-halo term of AGN. We demonstrate that the detected LSS signal is produced by unresolved clusters and groups of galaxies. For the flux limit of the XBOOTES survey, their flux-weighted mean redshift equals ˜ 0.3, and the mean temperature of their intracluster medium (ICM), ≈ 1.4 keV, corresponds to the mass of M500 ˜ 1013.5 M⊙. The power spectrum of CXB fluctuations carries information about the redshift distribution of these objects and the spatial structure of their ICM on the linear scales of up to ˜Mpc, I.e. of the order of the virial radius.

  1. Using Spherical-Harmonics Expansions for Optics Surface Reconstruction from Gradients

    Directory of Open Access Journals (Sweden)

    Juan Manuel Solano-Altamirano

    2017-11-01

    Full Text Available In this paper, we propose a new algorithm to reconstruct optics surfaces (aka wavefronts from gradients, defined on a circular domain, by means of the Spherical Harmonics. The experimental results indicate that this algorithm renders the same accuracy, compared to the reconstruction based on classical Zernike polynomials, using a smaller number of polynomial terms, which potentially speeds up the wavefront reconstruction. Additionally, we provide an open-source C++ library, released under the terms of the GNU General Public License version 2 (GPLv2, wherein several polynomial sets are coded. Therefore, this library constitutes a robust software alternative for wavefront reconstruction in a high energy laser field, optical surface reconstruction, and, more generally, in surface reconstruction from gradients. The library is a candidate for being integrated in control systems for optical devices, or similarly to be used in ad hoc simulations. Moreover, it has been developed with flexibility in mind, and, as such, the implementation includes the following features: (i a mock-up generator of various incident wavefronts, intended to simulate the wavefronts commonly encountered in the field of high-energy lasers production; (ii runtime selection of the library in charge of performing the algebraic computations; (iii a profiling mechanism to measure and compare the performance of different steps of the algorithms and/or third-party linear algebra libraries. Finally, the library can be easily extended to include additional dependencies, such as porting the algebraic operations to specific architectures, in order to exploit hardware acceleration features.

  2. Using Spherical-Harmonics Expansions for Optics Surface Reconstruction from Gradients.

    Science.gov (United States)

    Solano-Altamirano, Juan Manuel; Vázquez-Otero, Alejandro; Khikhlukha, Danila; Dormido, Raquel; Duro, Natividad

    2017-11-30

    In this paper, we propose a new algorithm to reconstruct optics surfaces (aka wavefronts) from gradients, defined on a circular domain, by means of the Spherical Harmonics. The experimental results indicate that this algorithm renders the same accuracy, compared to the reconstruction based on classical Zernike polynomials, using a smaller number of polynomial terms, which potentially speeds up the wavefront reconstruction. Additionally, we provide an open-source C++ library, released under the terms of the GNU General Public License version 2 (GPLv2), wherein several polynomial sets are coded. Therefore, this library constitutes a robust software alternative for wavefront reconstruction in a high energy laser field, optical surface reconstruction, and, more generally, in surface reconstruction from gradients. The library is a candidate for being integrated in control systems for optical devices, or similarly to be used in ad hoc simulations. Moreover, it has been developed with flexibility in mind, and, as such, the implementation includes the following features: (i) a mock-up generator of various incident wavefronts, intended to simulate the wavefronts commonly encountered in the field of high-energy lasers production; (ii) runtime selection of the library in charge of performing the algebraic computations; (iii) a profiling mechanism to measure and compare the performance of different steps of the algorithms and/or third-party linear algebra libraries. Finally, the library can be easily extended to include additional dependencies, such as porting the algebraic operations to specific architectures, in order to exploit hardware acceleration features.

  3. Effect of fast mold surface temperature evolution on iPP part morphology gradients

    Science.gov (United States)

    Liparoti, Sara; Sorrentino, Andrea; Guzman, Gustavo; Cakmak, Mukerrem; Titomanlio, Giuseppe

    2016-03-01

    The control of mold surface temperature is an important factor that affects the sample surface morphology as well as the structural gradients (orientation crystal size, and type) as well as cooling stresses. The frozen layer thickness formed during the filling stage also has a very significant effect on the flow resistance and thus on the resulting pressure drop and flow length in thin wall parts. The possibility to have a hot mold during filling and a quick cooling soon afterward is a significant process enhancement particularly for specialized applications such as micro injection molding and for the reproduction of micro structured surfaces. Up to now, several methods (electromagnetic, infrared, hot vapor fleshing etc,) were tried to achieve fast temperature evolution of the mold. Unfortunately, all these methods require a complex balance between thermal and mechanical problems, equipment cost, energy consumption, safety, molding cycle time and part quality achievable. In this work, a thin electrical resistance was designed and used to generate a fast and confined temperature variation on mold surface (by joule effect). Since the whole temperature evolution can take place in a few seconds, one can couple the advantages of a high surface temperature during filling with the advantages of a low mold temperature, fast cooling and low heating dissipation. Some experiments were performed with a commercial iPP resin. The effects of the surface temperature and of the heating time (under constant electric power) on surface finishing and on the final morphology (thickness and structure of the different layers) are explored and discussed.

  4. Temporal variation of coastal surface sediment bacterial communities along an environmental pollution gradient.

    Science.gov (United States)

    Thiyagarajan, V; Tsoi, M M Y; Zhang, W; Qian, P Y

    2010-07-01

    Terminal restriction fragment length polymorphism analysis (T-RFLP) was used to track the changes of bacterial community compositions (BCC) in coastal surface sediments along an environmental pollution gradient between 2004 and 2006. BCC in the chronically contaminated sites showed the largest deviation from those in the adjacent sites. Surprisingly, BCC at two contrasting environments (oceanic vs. river-influenced) were more similar. Unexpectedly, the BCC did not recover (when compared to oceanic control site) even after 5 years of pollution abatement initiatives in Victoria Harbour, Hong Kong. On the other hand, disposal of treated sewage for 5 years in one of the sites did not significantly affect the BCC. A striking seasonal variation in the BCC was observed at only the polluted sites. Although factors other than pollution gradients may explain the observed BCC patterns, the information presented here can be useful in predicting long-term effects of pollution on BCC. Furthermore, this study suggests that BCC analysis using T-RFLP is a faster, reliable and easier approach to monitor microbenthic community response to environmental pollution gradient in coastal sediments. 2010 Elsevier Ltd. All rights reserved.

  5. Atmospherically derived organic surface films along an urban-rural gradient.

    Science.gov (United States)

    Gingrich, S E; Diamond, M L; Stern, G A; McCarry, B E

    2001-10-15

    Atmospherically derived organic films have been found on an impervious surface along an urban-rural gradient in the Toronto, Ontario, Canada area. Film thickness and concentrations, expressed on an aerial basis, of sigman-alkanes, sigmaPCB, sigmaPAH, and sigmaOC (organochlorine) pesticides decrease along this gradient, coincident with lower atmospheric emissions (PCB and PAH) and less accumulation in thinner rural films (OC pesticides). For PCBs and some OC pesticides, patterns of chemical abundance also shift, indicating a "fresh" pattern near emission sources (downtown) versus aged patterns at rural locations that are indicative of atmospheric transport. Plant-derived n-alkane concentrations were greater at urban than rural sites, and we hypothesize greater urban plant wax production and erosion due to air pollution. As expected, along the urban-rural gradient the concentration of particle-phase PAH decreased more rapidly than that of gas-phase compounds, but unexpectedly the contribution of alkylated PAH increased from urban to rural locations. Distances over which concentrations decline by 63% vary from 50 km for persistent gas-phase compounds (e.g., P1,2CB) to 10-20 km for reactive gas-phase compounds (e.g., naphthalene, fluoranthene) to particle-phase compounds (e.g., P6-10CB, benzo[b]fluoranthene, benzo[e]pyrene).

  6. Velocity gradients in the Earth's upper mantle: insights from higher mode surface waves

    Science.gov (United States)

    Fishwick, Stewart; Maupin, Valerie; Afonso, Juan Carlos

    2016-04-01

    The majority of seismic tomographic models of the uppermost mantle beneath Precambrian regions show a positive velocity gradient from the Moho to depths of around 100 km. It is becoming increasingly well recognised that this gradient is not readily compatible with simple models of a craton with constant composition and a steady-state geotherm and more complex compositional variations are invoked to explain this feature. At these depths most of the models are dominated by data from fundamental mode surface waves, and the combination of the sensitivity kernels alongside the choice of model parameterisation means that the velocity gradient could be an artefact of the particular inversion. Indeed, recent work using thermodynamically consistent velocity models suggests that in some cases there is not a requirement of this style of gradient. We investigate this aspect of the mantle structure further by returning to the Sa phase. This phase can be considered as the build up of a wave packet due to the overlapping group velocities of higher modes at periods of around 8 - 30 s. Using the Australian shield as a test-case we compare waveforms built from three different styles of velocity model. Firstly, the 1D model AU3 (Gaherty & Jordan, 1995) which did incorporate the Sa phase as part of the waveform in their modelling. Secondly, recent tomographic models of the Australian continent are used, which include no a priori information from the phase. Thirdly, a thermodynamically consistent velocity model that fits the broad dispersion characteristics of the tomography is tested. Finally, these synthetic waveforms are compared to real data crossing the Australian shield. The results illustrate small, but clear, variations in waveform dependent on the velocity structure. Complicating factors in any analysis involve the importance of having good knowledge of the crustal structure and a very accurate source depth (particularly if this is similar to the average crustal thickness).

  7. Analysis of SMOS brightness temperature and vegetation optical depth data with coupled land surface and radiative transfer models in Southern Germany

    Directory of Open Access Journals (Sweden)

    F. Schlenz

    2012-10-01

    Full Text Available Soil Moisture and Ocean Salinity (SMOS L1c brightness temperature and L2 optical depth data are analysed with a coupled land surface (PROMET and radiative transfer model (L-MEB. The coupled models are validated with ground and airborne measurements under contrasting soil moisture, vegetation and land surface temperature conditions during the SMOS Validation Campaign in May and June 2010 in the SMOS test site Upper Danube Catchment in southern Germany. The brightness temperature root-mean-squared errors are between 6 K and 9 K. The L-MEB parameterisation is considered appropriate under local conditions even though it might possibly be further optimised. SMOS L1c brightness temperature data are processed and analysed in the Upper Danube Catchment using the coupled models in 2011 and during the SMOS Validation Campaign 2010 together with airborne L-band brightness temperature data. Only low to fair correlations are found for this comparison (R between 0.1–0.41. SMOS L1c brightness temperature data do not show the expected seasonal behaviour and are positively biased. It is concluded that RFI is responsible for a considerable part of the observed problems in the SMOS data products in the Upper Danube Catchment. This is consistent with the observed dry bias in the SMOS L2 soil moisture products which can also be related to RFI. It is confirmed that the brightness temperature data from the lower SMOS look angles and the horizontal polarisation are less reliable. This information could be used to improve the brightness temperature data filtering before the soil moisture retrieval. SMOS L2 optical depth values have been compared to modelled data and are not considered a reliable source of information about vegetation due to missing seasonal behaviour and a very high mean value. A fairly strong correlation between SMOS L2 soil moisture and optical depth was found (R = 0.65 even though the two variables are considered independent in the

  8. Continuous micro liquid delivery by evaporation on a gradient-capillary microstructure surface

    International Nuclear Information System (INIS)

    Du, Xiaoze; Zhao, T S; Luo, Jia

    2011-01-01

    An evaporation-based micropump is proposed and fabricated for delivering liquid with constant flow rates of ∼100 nl s −1 continuously. The liquid is pumped by the surface transpiration in a micro evaporator, which consists of a gradient-capillary surface by microfabricating micropost arrays. The micropost arrays are patterned such that the gaps between microposts reduce gradually away from the center microwell to the surface edge, by which a capillary force is formed to pull the liquid spreading on the evaporator surface. A simple analytical model is proposed to obtain the primary characteristics of the micropump, by which the influences of the contact angle of fluid on the flow rate and also the corresponding parameters during the operation of micropump are analyzed. The most striking feature of the micropump is that it can be precisely and simply controlled only by varying the surface wall temperature. The results indicate that a very linear relationship between the flow rate and solid wall temperature can be achieved by the present design. Quite consistent variation trend of the flow rate with wall temperature can be obtained between the experimental tests and theoretical analysis. The present micropump concept may be potentially used in delivering a precisely controlled, continuous flow rate for many new applications in the fields of biotechnology, environmental testing and instrumentation for analytical chemistry

  9. A Precise Distance to the Host Galaxy of the Binary Neutron Star Merger GW170817 Using Surface Brightness Fluctuations

    Science.gov (United States)

    Cantiello, Michele; Jensen, J. B.; Blakeslee, J. P.; Berger, E.; Levan, A. J.; Tanvir, N. R.; Raimondo, G.; Brocato, E.; Alexander, K. D.; Blanchard, P. K.; Branchesi, M.; Cano, Z.; Chornock, R.; Covino, S.; Cowperthwaite, P. S.; D’Avanzo, P.; Eftekhari, T.; Fong, W.; Fruchter, A. S.; Grado, A.; Hjorth, J.; Holz, D. E.; Lyman, J. D.; Mandel, I.; Margutti, R.; Nicholl, M.; Villar, V. A.; Williams, P. K. G.

    2018-02-01

    The joint detection of gravitational waves (GWs) and electromagnetic radiation from the binary neutron star (BNS) merger GW170817 has provided unprecedented insight into a wide range of physical processes: heavy element synthesis via the r-process; the production of relativistic ejecta; the equation of state of neutron stars and the nature of the merger remnant; the binary coalescence timescale; and a measurement of the Hubble constant via the “standard siren” technique. In detail, all of these results depend on the distance to the host galaxy of the merger event, NGC 4993. In this Letter we measure the surface brightness fluctuation (SBF) distance to NGC 4993 in the F110W and F160W passbands of the Wide Field Camera 3 Infrared Channel (WFC3/IR) on the Hubble Space Telescope (HST). For the preferred F110W passband we derive a distance modulus of (m-M) =33.05+/- 0.08+/- 0.10 mag, or a linear distance d = 40.7 ± 1.4 ± 1.9 Mpc (random and systematic errors, respectively); a virtually identical result is obtained from the F160W data. This is the most precise distance to NGC 4993 available to date. Combining our distance measurement with the corrected recession velocity of NGC 4993 implies a Hubble constant H 0 = 71.9 ± 7.1 km s‑1 Mpc‑1. A comparison of our result to the GW-inferred value of H 0 indicates a binary orbital inclination of i ≳ 137°. The SBF technique can be applied to early-type host galaxies of BNS mergers to ∼100 Mpc with HST and possibly as far as ∼300 Mpc with the James Webb Space Telescope, thereby helping to break the inherent distance-inclination degeneracy of the GW data at distances where many future BNS mergers are likely to be detected. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with Program #15329 (PI: E

  10. GALAXY HALO TRUNCATION AND GIANT ARC SURFACE BRIGHTNESS RECONSTRUCTION IN THE CLUSTER MACSJ1206.2-0847

    International Nuclear Information System (INIS)

    Eichner, Thomas; Seitz, Stella; Monna, Anna; Suyu, Sherry H.; Halkola, Aleksi; Umetsu, Keiichi; Zitrin, Adi; Coe, Dan; Postman, Marc; Koekemoer, Anton; Bradley, Larry; Rosati, Piero; Grillo, Claudio; Høst, Ole; Balestra, Italo; Zheng, Wei; Lemze, Doron; Broadhurst, Tom; Moustakas, Leonidas; Molino, Alberto

    2013-01-01

    In this work, we analyze the mass distribution of MACSJ1206.2-0847, particularly focusing on the halo properties of its cluster members. The cluster appears relaxed in its X-ray emission, but has a significant amount of intracluster light that is not centrally concentrated, suggesting that galaxy-scale interactions are still ongoing despite the overall relaxed state. The cluster lenses 12 background galaxies into multiple images and one galaxy at z = 1.033 into a giant arc and its counterimage. The multiple image positions and the surface brightness (SFB) distribution of the arc, which is bent around several cluster members, are sensitive to the cluster galaxy halo properties. We model the cluster mass distribution with a Navarro-Frenk-White profile and the galaxy halos with two parameters for the mass normalization and the extent of a reference halo assuming scalings with their observed near-infrared light. We match the multiple image positions at an rms level of 0.''85 and can reconstruct the SFB distribution of the arc in several filters to a remarkable accuracy based on this cluster model. The length scale where the enclosed galaxy halo mass is best constrained is about 5 effective radii—a scale in between those accessible to dynamical and field strong-lensing mass estimates on the one hand and galaxy-galaxy weak-lensing results on the other hand. The velocity dispersion and halo size of a galaxy with m 160W,AB = 19.2 and M B,Vega = –20.7 are σ = 150 km s –1 and r ≈ 26 ± 6 kpc, respectively, indicating that the halos of the cluster galaxies are tidally stripped. We also reconstruct the unlensed source, which is smaller by a factor of ∼5.8 in area, demonstrating the increase in morphological information due to lensing. We conclude that this galaxy likely has star-forming spiral arms with a red (older) central component

  11. Studying the ICM in clusters of galaxies via surface brightness fluctuations of the cosmic X-ray background

    Science.gov (United States)

    Kolodzig, Alexander; Gilfanov, Marat; Hütsi, Gert; Sunyaev, Rashid

    2018-02-01

    We study surface brightness fluctuations of the cosmic X-ray background (CXB) using Chandra data of XBOOTES. After masking out resolved sources we compute the power spectrum of fluctuations of the unresolved CXB for angular scales from {≈ } 2 arcsec to ≈3°. The non-trivial large-scale structure (LSS) signal dominates over the shot noise of unresolved point sources on angular scales above {˜ } 1 arcmin and is produced mainly by the intracluster medium (ICM) of unresolved clusters and groups of galaxies, as shown in our previous publication. The shot-noise-subtracted power spectrum of CXB fluctuations has a power-law shape with the slope of Γ = 0.96 ± 0.06. Their energy spectrum is well described by the redshifted emission spectrum of optically thin plasma with the best-fitting temperature of T ≈ 1.3 keV and the best-fitting redshift of z ≈ 0.40. These numbers are in good agreement with theoretical expectations based on the X-ray luminosity function and scaling relations of clusters. From these values we estimate the typical mass and luminosity of the objects responsible for CXB fluctuations, M500 ∼ 1013.6 M⊙ h-1 and L0.5-2.0 keV ∼ 1042.5 erg s-1. On the other hand, the flux-weighted mean temperature and redshift of resolved clusters are T ≈ 2.4 keV and z ≈ 0.23 confirming that fluctuations of unresolved CXB are caused by cooler (i.e. less massive) and more distant clusters, as expected. We show that the power spectrum shape is sensitive to the ICM structure all the way to the outskirts, out to ∼few × R500. We also searched for possible contribution of the warm-hot intergalactic medium (WHIM) to the observed CXB fluctuations. Our results underline the significant diagnostic potential of the CXB fluctuation analysis in studying the ICM structure in clusters.

  12. AirSWOT Measurements of Water Surface Elevations and Hydraulic Gradients over the Yukon Flats, Alaska

    Science.gov (United States)

    Pitcher, L. H.; Pavelsky, T.; Smith, L. C.; Moller, D.; Altenau, E. H.; Lion, C.; Bertram, M.; Cooley, S. W.

    2017-12-01

    AirSWOT is an airborne, Ka-band synthetic aperture radar interferometer (InSAR) intended to quantify surface water fluxes by mapping water surface elevations (WSE). AirSWOT will also serve as a calibration/validation tool for the Surface Water and Ocean Topography (SWOT) satellite mission (scheduled for launch in 2021). The hydrology objectives for AirSWOT and SWOT are to measure WSE with accuracies sufficient to estimate hydrologic fluxes in lakes, wetlands and rivers. However, current understanding of the performance of these related though not identical instruments when applied to complex river-lake-wetland fluvial environments remains predominantly theoretical. We present AirSWOT data acquired 15-June-2015 over the Yukon Flats, Alaska, USA, together with in situ field surveys, to assess the accuracy of AirSWOT WSE measurements in lakes and rivers. We use these data to demonstrate that AirSWOT can be used to estimate large-scale hydraulic gradients across wetland complexes. Finally, we present key lessons learned from this AirSWOT analysis for consideration in future campaigns, including: maximizing swath overlap for spatial averaging to minimize uncertainty as well as orienting flight paths parallel to river flow directions to reduce along track aircraft drift for neighboring flight paths. We conclude that spatially dense AirSWOT measurements of river and lake WSEs can improve geospatial understanding of surface water hydrology and fluvial processes.

  13. Surface Approximation using Growing Self-Organizing Nets and Gradient Information

    Directory of Open Access Journals (Sweden)

    Jorge Rivera-Rovelo

    2007-01-01

    Full Text Available In this paper we show how to improve the performance of two self-organizing neural networks used to approximate the shape of a 2D or 3D object by incorporating gradient information in the adaptation stage. The methods are based on the growing versions of the Kohonen's map and the neural gas network. Also, we show that in the adaptation stage the network utilizes efficient transformations, expressed as versors in the conformal geometric algebra framework, which build the shape of the object independent of its position in space (coordinate free. Our algorithms were tested with several images, including medical images (CT and MR images. We include also some examples for the case of 3D surface estimation.

  14. Surface modification and its role in the preparation of FeSi gradient alloys with good magnetic property and ductility

    Science.gov (United States)

    Yu, Haiyuan; Bi, Xiaofang

    2018-04-01

    Realization of the effective Si penetration at a lower processing temperature is a challenge, but of significance in reducing the strict requirements for the equipment and realizing cost-cutting in production. In this work, we have modified the surface microstructure of Fe-3 wt%Si alloy by using surface mechanical attrition treatment. The modified surface microstructure is characteristic of nanocrystalline, which is found to significantly enhance the efficiency of subsequent Si penetration into the alloy, and successively leading to the decrease of penetration temperature up to 200 °C. As a consequence, the Si gradient distribution across thickness can be readily controlled by changing penetration time, and FeSi alloys with various gradients are prepared by chemical vapor deposition along with subsequent annealing process. The dependence of magnetic and mechanical properties on Si gradient for demonstrates that the increase of Si gradient reduces core losses, especially at higher frequencies, and meanwhile improves ductility of FeSi alloys as well. The mechanism underlying the effect of Si gradient is clarified by combining magnetostriction measurement and domain structure observations. This work provides a facile and effective way for achieving gradient FeSi alloys with good magnetic property and ductility.

  15. Variability of water content useful in surface along a rainfall gradient Mediterranean; Variabilidad de la disposibilidad hidrica superficial para la vegetacion a lo largo de un gradiente pluviometrico

    Energy Technology Data Exchange (ETDEWEB)

    Ruiz-Sinoga, J. D.; Martinez-Murillo, J. F.; Gabarron-Galeote, M. A.

    2009-07-01

    A climatic gradient was defined in South of spain with a great decreased of rainfall from West to East (>1,000 mm), which produces changes in vegetation and hydric resources. this study was carried out in five hill slopes under different climatic conditions and their aims were to analyze: the variability of available water along the gradient since 2002 to 2006, the key factors of it and the influence on the vegetal cover. Results showed that clay content had a great influence in the surface available water for plants, which did not decrease in the deerfield sites, where the amount of days with hydric deficient was lower. Relationships between vegetation and soil water were stronger in the more humid field sites, where existed a feedback between both properties. (Author) 4 refs.

  16. Evapotranspiration and surface energy balance across an agricultural-urban landscape gradient in Southern California, USA.

    Science.gov (United States)

    Shiflett, S. A.; Anderson, R. G.; Jenerette, D.

    2014-12-01

    Urbanization substantially affects energy, surface and air temperature, and hydrology due to extensive modifications in land surface properties such as vegetation, albedo, thermal capacity and soil moisture. The magnitude and direction of these alterations depends heavily on the type of urbanization that occurs. We investigated energy balance variation in a local network of agricultural and urban ecosystems using the eddy covariance method to better understand how vegetation fraction and degree of urbanization affects energy exchanges between the land surface and the atmosphere. We deployed eddy flux systems within a well-irrigated, agricultural citrus orchard, a moderately developed urban zone with a substantial amount of local vegetative cover, and an intensely developed urban zone with minimal vegetative cover and increased impervious surfaces relative to the other two sites. Latent energy (LE) fluxes in the agricultural area ranged from 7.9 ± 1.4 W m-2 (nighttime) to 168.7 ± 6.2 W m-2 (daytime) compared to 10.2 ± 3.5 W m-2 and 40.6 ± 4.1 W m-2, respectively, for the moderately developed urban area. Sensible energy (H) fluxes ranged from -9.1 ± 1.0 W m-2 (nighttime) to 119 ± 7.0 W m-2 (daytime) in the agricultural area compared to 9.6 ± 2.6 W m-2 and 134 ± 6.0 W m-2, respectively, for the moderately developed urban zone. Daytime LE is reduced with increasing urbanization; however, daily cycles of LE are less recognizable in urban areas compared to distinct daily cycles obtained above a mature citrus crop. In contrast, both daytime and nighttime H increases with increasing degree of urbanization. Reduction in vegetation and increases in impervious surfaces along an urbanization gradient leads to alterations in energy balance, which are associated with microclimate and water use changes.

  17. Variable but persistent coexistence of Prochlorococcus ecotypes along temperature gradients in the ocean's surface mixed layer.

    Science.gov (United States)

    Chandler, Jeremy W; Lin, Yajuan; Gainer, P Jackson; Post, Anton F; Johnson, Zackary I; Zinser, Erik R

    2016-04-01

    The vast majority of the phytoplankton communities in surface mixed layer of the oligotrophic ocean are numerically dominated by one of two ecotypes of Prochlorococcus, eMIT9312 or eMED4. In this study, we surveyed large latitudinal transects in the Atlantic and Pacific Ocean to determine if these ecotypes discretely partition the surface mixed layer niche, or if populations exist as a continuum along key environmental gradients, particularly temperature. Transitions of dominance occurred at approximately 19-21°C, with the eMED4 ecotype dominating the colder, and eMIT9312 ecotype dominating the warmer regions. Within these zones of regional dominance, however, the minority ecotype was not competed to extinction. Rather, a robust log-linear relationship between ecotype ratio and temperature characterized this stabilized coexistence: for every 2.5°C increase in temperature, the eMIT9312:eMED4 ratio increased by an order of magnitude. This relationship was observed in both quantitative polymerase chain reaction and in pyrosequencing assays. Water column stratification also contributed to the ecotype ratio along the basin-scale transects, but to a lesser extent. Finally, instances where the ratio of the eMED4 and eMIT9312 abundances did not correlate well with temperature were identified. Such occurrences are likely due to changes in water temperatures outpacing changes in community structure. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

  18. Theory of activated glassy relaxation, mobility gradients, surface diffusion, and vitrification in free standing thin films

    International Nuclear Information System (INIS)

    Mirigian, Stephen; Schweizer, Kenneth S.

    2015-01-01

    We have constructed a quantitative, force level, statistical mechanical theory for how confinement in free standing thin films introduces a spatial mobility gradient of the alpha relaxation time as a function of temperature, film thickness, and location in the film. The crucial idea is that relaxation speeds up due to the reduction of both near-surface barriers associated with the loss of neighbors in the local cage and the spatial cutoff and dynamical softening near the vapor interface of the spatially longer range collective elasticity cost for large amplitude hopping. These two effects are fundamentally coupled. Quantitative predictions are made for how an apparent glass temperature depends on the film thickness and experimental probe technique, the emergence of a two-step decay and mobile layers in time domain measurements, signatures of confinement in frequency-domain dielectric loss experiments, the dependence of film-averaged relaxation times and dynamic fragility on temperature and film thickness, surface diffusion, and the relationship between kinetic experiments and pseudo-thermodynamic measurements such as ellipsometry

  19. Theory of activated glassy relaxation, mobility gradients, surface diffusion, and vitrification in free standing thin films

    Energy Technology Data Exchange (ETDEWEB)

    Mirigian, Stephen, E-mail: kschweiz@illinois.edu, E-mail: smirigian@gmail.com; Schweizer, Kenneth S., E-mail: kschweiz@illinois.edu, E-mail: smirigian@gmail.com [Departments of Materials Science and Chemistry, University of Illinois, Urbana, Illinois 61801 (United States)

    2015-12-28

    We have constructed a quantitative, force level, statistical mechanical theory for how confinement in free standing thin films introduces a spatial mobility gradient of the alpha relaxation time as a function of temperature, film thickness, and location in the film. The crucial idea is that relaxation speeds up due to the reduction of both near-surface barriers associated with the loss of neighbors in the local cage and the spatial cutoff and dynamical softening near the vapor interface of the spatially longer range collective elasticity cost for large amplitude hopping. These two effects are fundamentally coupled. Quantitative predictions are made for how an apparent glass temperature depends on the film thickness and experimental probe technique, the emergence of a two-step decay and mobile layers in time domain measurements, signatures of confinement in frequency-domain dielectric loss experiments, the dependence of film-averaged relaxation times and dynamic fragility on temperature and film thickness, surface diffusion, and the relationship between kinetic experiments and pseudo-thermodynamic measurements such as ellipsometry.

  20. Multifactor analysis and simulation of the surface runoff and soil infiltration at different slope gradients

    Science.gov (United States)

    Huang, J.; Kang, Q.; Yang, J. X.; Jin, P. W.

    2017-08-01

    The surface runoff and soil infiltration exert significant influence on soil erosion. The effects of slope gradient/length (SG/SL), individual rainfall amount/intensity (IRA/IRI), vegetation cover (VC) and antecedent soil moisture (ASM) on the runoff depth (RD) and soil infiltration (INF) were evaluated in a series of natural rainfall experiments in the South of China. RD is found to correlate positively with IRA, IRI, and ASM factors and negatively with SG and VC. RD decreased followed by its increase with SG and ASM, it increased with a further decrease with SL, exhibited a linear growth with IRA and IRI, and exponential drop with VC. Meanwhile, INF exhibits a positive correlation with SL, IRA and IRI and VC, and a negative one with SG and ASM. INF was going up and then down with SG, linearly rising with SL, IRA and IRI, increasing by a logit function with VC, and linearly falling with ASM. The VC level above 60% can effectively lower the surface runoff and significantly enhance soil infiltration. Two RD and INF prediction models, accounting for the above six factors, were constructed using the multiple nonlinear regression method. The verification of those models disclosed a high Nash-Sutcliffe coefficient and low root-mean-square error, demonstrating good predictability of both models.

  1. Color constancy in a scene with bright colors that do not have a fully natural surface appearance.

    Science.gov (United States)

    Fukuda, Kazuho; Uchikawa, Keiji

    2014-04-01

    Theoretical and experimental approaches have proposed that color constancy involves a correction related to some average of stimulation over the scene, and some of the studies showed that the average gives greater weight to surrounding bright colors. However, in a natural scene, high-luminance elements do not necessarily carry information about the scene illuminant when the luminance is too high for it to appear as a natural object color. The question is how a surrounding color's appearance mode influences its contribution to the degree of color constancy. Here the stimuli were simple geometric patterns, and the luminance of surrounding colors was tested over the range beyond the luminosity threshold. Observers performed perceptual achromatic setting on the test patch in order to measure the degree of color constancy and evaluated the surrounding bright colors' appearance mode. Broadly, our results support the assumption that the visual system counts only the colors in the object-color appearance for color constancy. However, detailed analysis indicated that surrounding colors without a fully natural object-color appearance had some sort of influence on color constancy. Consideration of this contribution of unnatural object color might be important for precise modeling of human color constancy.

  2. The role of the meridional sea surface temperature gradient in controlling the Caribbean low-level jet

    Science.gov (United States)

    Maldonado, Tito; Rutgersson, Anna; Caballero, Rodrigo; Pausata, Francesco S. R.; Alfaro, Eric; Amador, Jorge

    2017-06-01

    The Caribbean low-level jet (CLLJ) is an important modulator of regional climate, especially precipitation, in the Caribbean and Central America. Previous work has inferred, due to their semiannual cycle, an association between CLLJ strength and meridional sea surface temperature (SST) gradients in the Caribbean Sea, suggesting that the SST gradients may control the intensity and vertical shear of the CLLJ. In addition, both the horizontal and vertical structure of the jet have been related to topographic effects via interaction with the mountains in Northern South America (NSA), including funneling effects and changes in the meridional geopotential gradient. Here we test these hypotheses, using an atmospheric general circulation model to perform a set of sensitivity experiments to examine the impact of both SST gradients and topography on the CLLJ. In one sensitivity experiment, we remove the meridional SST gradient over the Caribbean Sea and in the other, we flatten the mountains over NSA. Our results show that the SST gradient and topography have little or no impact on the jet intensity, vertical, and horizontal wind shears, contrary to previous works. However, our findings do not discount a possible one-way coupling between the SST and the wind over the Caribbean Sea through friction force. We also examined an alternative approach based on barotropic instability to understand the CLLJ intensity, vertical, and horizontal wind shears. Our results show that the current hypothesis about the CLLJ must be reviewed in order to fully understand the atmospheric dynamics governing the Caribbean region.

  3. Controls on plant functional surface cover types along a precipitation gradient in the Negev Desert of Israel

    NARCIS (Netherlands)

    Buis, E.; Veldkamp, A.; Boeken, B.; Breemen, van N.

    2009-01-01

    We studied the controls on functional surface cover types in four catchments along a semi-arid to arid precipitation gradient in the northern Negev Desert of Israel. First, we selected four functional types, based on their unique water use and redistribution functionality: shrubs, Asphodelus

  4. Sea surface temperature control of taxon specific phytoplankton production along an oligotrophic gradient in the Mediterranean Sea

    NARCIS (Netherlands)

    van de Poll, W.H.V.; Boute, P.G.; Rozema, P.D.; Buma, A.; Kulk, G.; Rijkenberg, M.J.

    2015-01-01

    The current study aimed to assess changes in phytoplankton composition and productivity along an oligotrophic gradient in relation to changes in sea surface temperature (SST). Phytoplankton pigments, nutrients, and physical water column properties were studied along a longitudinal transect in the

  5. A three-colour graph as a complete topological invariant for gradient-like diffeomorphisms of surfaces

    International Nuclear Information System (INIS)

    Grines, V Z; Pochinka, O V; Kapkaeva, S Kh

    2014-01-01

    In a paper of Oshemkov and Sharko, three-colour graphs were used to make the topological equivalence of Morse-Smale flows on surfaces obtained by Peixoto more precise. In the present paper, in the language of three-colour graphs equipped with automorphisms, we obtain a complete (including realization) topological classification of gradient-like cascades on surfaces. Bibliography: 25 titles

  6. Population dynamics of two antilisterial cheese surface consortia revealed by temporal temperature gradient gel electrophoresis

    Directory of Open Access Journals (Sweden)

    Hasler Madlen

    2010-03-01

    Full Text Available Abstract Background Surface contamination of smear cheese by Listeria spp. is of major concern for the industry. Complex smear ecosystems have been shown to harbor antilisterial potential but the microorganisms and mechanisms involved in the inhibition mostly remain unclear, and are likely related to complex interactions than to production of single antimicrobial compounds. Bacterial biodiversity and population dynamics of complex smear ecosystems exhibiting antilisterial properties in situ were investigated by Temporal temperature gradient gel electrophoresis (TTGE, a culture independent technique, for two microbial consortia isolated from commercial Raclette type cheeses inoculated with defined commercial ripening cultures (F or produced with an old-young smearing process (M. Results TTGE revealed nine bacterial species common to both F and M consortia, but consortium F exhibited a higher diversity than consortium M, with thirteen and ten species, respectively. Population dynamics were studied after application of the consortia on fresh-produced Raclette cheeses. TTGE analyses revealed a similar sequential development of the nine species common to both consortia. Beside common cheese surface bacteria (Staphylococcus equorum, Corynebacterium spp., Brevibacterium linens, Microbacterium gubbeenense, Agrococcus casei, the two consortia contained marine lactic acid bacteria (Alkalibacterium kapii, Marinilactibacillus psychrotolerans that developed early in ripening (day 14 to 20, shortly after the growth of staphylococci (day 7. A decrease of Listeria counts was observed on cheese surface inoculated at day 7 with 0.1-1 × 102 CFU cm-2, when cheeses were smeared with consortium F or M. Listeria counts went below the detection limit of the method between day 14 and 28 and no subsequent regrowth was detected over 60 to 80 ripening days. In contrast, Listeria grew to high counts (105 CFU cm-2 on cheeses smeared with a defined surface culture

  7. Construction of wettability gradient surface on copper substrate by controlled hydrolysis of poly(methyl methacrylate–butyl acrylate) films

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yong, E-mail: Yong.Z@mail.scut.edu.cn [Guangzhou Panyu Polytechnic, Guangzhou 511483 (China); Cheng, Jiang; Yang, Zhuo-ru [School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640 (China)

    2014-10-01

    We report a gradient wettability surface on copper slide prepared by a simple controlled ester group hydrolysis procedure of poly(methyl methacrylate–butyl acrylate) [P (MMA-BA)] films coated on the copper substrate. In the method, sodium hydroxide solutions are selected to prepare surface gradient wettability on P (MMA-BA) films. The P (MMA-BA) copolymers with different MMA contents are first synthesized by a conventional free atom radical solution polymerization method. The transfer of surface chemical composition from the ester group to acid salt is achieved by hydrolysis in NaOH solution. The effects of different concentrations of NaOH solution and reaction times on the physicochemical properties of the resulting surfaces are studied. The field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) results show that the varying concentration along the substrate length is only attributed to the hydrolysis reaction of ester groups. The hydrolysis causes insignificant change on the morphology of the original film on the copper substrate. In addition, it is found that the MMA copolymer content has a significant influence on the concentration of ester groups on the outermost surface and thus important for forming the slope gradients.

  8. Evaluation of the flux gradient technique for measurement of ozone surface fluxes over snowpack at Summit, Greenland

    Directory of Open Access Journals (Sweden)

    F. Bocquet

    2011-10-01

    Full Text Available A multi-step procedure for investigating ozone surface fluxes over polar snow by the tower gradient method was developed and evaluated. These measurements were then used to obtain five months (April–August 2004 of turbulent ozone flux data at the Summit research camp located in the center of the Greenland ice shield. Turbulent fluxes were determined by the gradient method incorporating tower measurements of (a ozone gradients measured by commercial ultraviolet absorption analyzers, (b ambient temperature gradients using aspirated thermocouple sensors, and (c wind speed gradients determined by cup anemometers. All gradient instruments were regularly inter-compared by bringing sensors or inlets to the same measurement height. The developed protocol resulted in an uncertainty on the order of 0.1 ppbv for 30-min averaged ozone gradients that were used for the ozone flux calculations. This protocol facilitated a lower sensitivity threshold for the ozone flux determination of ∼8 × 10−3μg m−2 s−1, respectively ∼0.01 cm s−1 for the ozone deposition velocity for typical environmental conditions encountered at Summit. Uncertainty in the 30-min ozone exchange measurements (evaluated by the Monte Carlo statistical approach was on the order of 10−2 cm s−1. This uncertainty typically accounted to ~20–100% of the ozone exchange velocities that were determined. These measurements are among the most sensitive ozone deposition determinations reported to date. This flux experiment allowed for measurements of the relatively low ozone uptake rates encountered for polar snow, and thereby the study of their environmental and spring-versus-summer dependencies.

  9. Estimating Surface Downward Shortwave Radiation over China Based on the Gradient Boosting Decision Tree Method

    Directory of Open Access Journals (Sweden)

    Lu Yang

    2018-01-01

    Full Text Available Downward shortwave radiation (DSR is an essential parameter in the terrestrial radiation budget and a necessary input for models of land-surface processes. Although several radiation products using satellite observations have been released, coarse spatial resolution and low accuracy limited their application. It is important to develop robust and accurate retrieval methods with higher spatial resolution. Machine learning methods may be powerful candidates for estimating the DSR from remotely sensed data because of their ability to perform adaptive, nonlinear data fitting. In this study, the gradient boosting regression tree (GBRT was employed to retrieve DSR measurements with the ground observation data in China collected from the China Meteorological Administration (CMA Meteorological Information Center and the satellite observations from the Advanced Very High Resolution Radiometer (AVHRR at a spatial resolution of 5 km. The validation results of the DSR estimates based on the GBRT method in China at a daily time scale for clear sky conditions show an R2 value of 0.82 and a root mean square error (RMSE value of 27.71 W·m−2 (38.38%. These values are 0.64 and 42.97 W·m−2 (34.57%, respectively, for cloudy sky conditions. The monthly DSR estimates were also evaluated using ground measurements. The monthly DSR estimates have an overall R2 value of 0.92 and an RMSE of 15.40 W·m−2 (12.93%. Comparison of the DSR estimates with the reanalyzed and retrieved DSR measurements from satellite observations showed that the estimated DSR is reasonably accurate but has a higher spatial resolution. Moreover, the proposed GBRT method has good scalability and is easy to apply to other parameter inversion problems by changing the parameters and training data.

  10. Biological soil crust succession impact on soil moisture and temperature in the sub-surface along a rainfall gradient

    Science.gov (United States)

    Zaady, E.; Yizhaq, H.; Ashkenazy, Y.

    2012-04-01

    Biological soil crusts produce mucilage sheets of polysaccharides that cover the soil surface. This hydrophobic coating can seal the soil micro-pores and thus cause reduction of water permeability and may influence soil temperature. This study evaluates the impact of crust composition on sub-surface water and temperature over time. We hypothesized that the successional stages of biological soil crusts, affect soil moisture and temperature differently along a rainfall gradient throughout the year. Four experimental sites were established along a rainfall gradient in the western Negev Desert. At each site three treatments; crust removal, pure sand (moving dune) and natural crusted were monitored. Crust successional stage was measured by biophysiological and physical measurements, soil water permeability by field mini-Infiltrometer, soil moisture by neutron scattering probe and temperature by sensors, at different depths. Our main interim conclusions from the ongoing study along the rainfall gradient are: 1. the biogenic crust controls water infiltration into the soil in sand dunes, 2. infiltration was dependent on the composition of the biogenic crust. It was low for higher successional stage crusts composed of lichens and mosses and high with cyanobacterial crust. Thus, infiltration rate controlled by the crust is inverse to the rainfall gradient. Continuous disturbances to the crust increase infiltration rates, 3. despite the different rainfall amounts at the sites, soil moisture content below 50 cm is almost the same. We therefore predict that climate change in areas that are becoming dryer (desertification) will have a positive effect on soil water content and vice versa.

  11. The Impact of Reduced SST Gradients and MJO-like Tropical Variability on Surface Winds at Midlatitude Upwelling Sites

    Science.gov (United States)

    Arnold, N. P.; Tziperman, E.

    2012-12-01

    Sediment core data suggest that sea surface temperatures (SST) at present-day sites of wind-driven coastal upwelling were much warmer during the early Pliocene, and only cooled gradually over the last 3-4My. Several hypotheses have been advanced to explain the Pliocene warm anomalies, including a globally deeper thermocline and weaker upwelling-favorable winds, but it remains unclear if the SST anomalies reflect differences in upwelling intensity or in subsurface water properties. In this study we explore two factors which might affect the surface winds responsible for midlatitude upwelling: (1) differences in the large-scale SST distribution and their impact on the atmospheric general circulation, and (2) teleconnections from changes in tropical convective variability. We run the NCAR Community Atmosphere Model with a spectrum of meridional and zonal surface temperature gradients, ranging from a modern climatology to a low-gradient state reminiscent of the early Pliocene. A prescribed forcing is then added to the model to stimulate tropical convective variability based on the observed Madden-Julian Oscillation (MJO), which can impact midlatitude sites by exciting atmospheric Rossby waves. Quantitative metrics of along-shore wind stress at several midlatitude sediment core sites are presented as a function of the prescribed SST gradients and tropical forcing amplitude.

  12. Surface Modification of C17200 Copper-Beryllium Alloy by Plasma Nitriding of Cu-Ti Gradient Film

    Science.gov (United States)

    Zhu, Y. D.; Yan, M. F.; Zhang, Y. X.; Zhang, C. S.

    2018-03-01

    In the present work, a copper-titanium film of gradient composition was firstly fabricated by the dual magnetron sputtering through power control and plasma nitriding of the film was then conducted to modify C17200 Cu alloy. The results showed that the prepared gradient Cu-Ti film by magnetron sputtering was amorphous. After plasma nitriding at 650 °C, crystalline Cu-Ti intermetallics appeared in the multi-phase coating, including CuTi2, Cu3Ti, Cu3Ti2 and CuTi. Moreover, even though the plasma nitriding duration of the gradient Cu-Ti film was only 0.5 h, the mechanical properties of the modified Cu surface were obviously improved, with the surface hardness enhanced to be 417 HV0.01, the wear rate to be 0.32 × 10-14 m3/Nm and the friction coefficient to be 0.075 at the load of 10 N, which are all more excellent than the C17200 Cu alloy. In addition, the wear mechanism also changed from adhesion wear for C17200 Cu substrate to abrasive wear for the modified surface.

  13. An Hα Imaging Survey of the Low-surface-brightness Galaxies Selected from the Fall Sky Region of the 40% ALFALFA H I Survey

    Science.gov (United States)

    Lei, Feng-Jie; Wu, Hong; Du, Wei; Zhu, Yi-Nan; Lam, Man-I.; Zhou, Zhi-Min; He, Min; Jin, Jun-Jie; Cao, Tian-Wen; Zhao, Pin-Song; Yang, Fan; Wu, Chao-Jian; Li, Hong-Bin; Ren, Juan-Juan

    2018-03-01

    We present the observed Hα flux and derived star formation rates (SFRs) for a fall sample of low-surface-brightness galaxies (LSBGs). The sample is selected from the fall sky region of the 40% ALFALFA H I Survey–SDSS DR7 photometric data, and all the Hα images were obtained using the 2.16 m telescope, operated by the National Astronomy Observatories, Chinese Academy of Sciences. A total of 111 LSBGs were observed and Hα flux was measured in 92 of them. Though almost all the LSBGs in our sample are H I-rich, their SFRs, derived from the extinction and filter-transmission-corrected Hα flux, are less than 1 M ⊙ yr‑1. LSBGs and star-forming galaxies have similar H I surface densities, but LSBGs have much lower SFRs and SFR surface densities than star-forming galaxies. Our results show that LSBGs deviate from the Kennicutt–Schmidt law significantly, which indicates that they have low star formation efficiency. The SFRs of LSBGs are close to average SFRs in Hubble time and support previous arguments that most of the LSBGs are stable systems and they tend to seldom contain strong interactions or major mergers in their star formation histories.

  14. [The temperature and temperature gradients distribution in the rabbit body thermophysical model with evaporation of moisture from its surface].

    Science.gov (United States)

    Rumiantsev, G V

    2004-04-01

    On created in laboratory heat-physical model of a rabbit body reflecting basic heat-physical parameters of the body such as: weight, size of a relative surface, heat absorption and heat conduction, heat capacity etc., a change of radial distribution of temperature and size was found across a superficial layer of evaporation of water from its surface, that simulates sweating, with various ratio of environmental temperature and capacity of electrical heater simulating heat production in animal. The experiments have shown that with evaporation of moisture from a surface of model in all investigated cases, there is an increase of superficial layer of body of a temperature gradient and simultaneous decrease of temperature of a model inside and on the surface. It seems that, with evaporation of a moisture from a surface of a body, the size of a temperature gradient in a thin superficial layer dependent in our experiments on capacity for heat production and environmental temperature, is increased and can be used in a live organism for definition of change in general heat content of the body with the purpose of maintenance of its thermal balance with environment.

  15. Highly efficient separation of surfactant stabilized water-in-oil emulsion based on surface energy gradient and flame retardancy.

    Science.gov (United States)

    Long, Mengying; Peng, Shan; Deng, Wanshun; Miao, Xinrui; Wen, Ni; Zhou, Qiannan; Deng, Wenli

    2018-06-15

    Surface energy gradient would generate an imbalance force to drive tiny water droplets in dry air from the hydrophilic bumps to superhydrophobic domains, which has found on the Stenocara beetle's back. Inspired by this phenomenon, we introduced a pristine superhydrophilic filter paper on the lower surface energy superhydrophobic filter paper. ZnSn(OH) 6 particles and polydimethylsiloxane were mixed to prepare the superhydrophobic coating, and the coating was spray-coated on the poly(dialkyldimethylammonium chloride) covered filter paper to separate the span 80 stabilized water-in-isooctane emulsion. A pristine filter paper was added on the superhydrophobic filter paper to fabricate another membrane for separation. The results revealed that with a pristine filter paper, the membrane performed higher efficiency and more recyclability, and it could separate the emulsions with higher surfactant concentrations. The stabilized water droplets passed the superamphiphilic surface, and hindered by the superhydrophobic surface, generating a surface energy gradient for better separation. In addition, the superhydrophobic membrane could be protected from fire to some degree due to the introduced ZnSn(OH) 6 particles with excellent flame retardancy. This easy and efficient approach via simply bringing in pristine superhydrophilic membrane has great potential applications for water-in-oil emulsion separation or oil purification. Copyright © 2018 Elsevier Inc. All rights reserved.

  16. The orthogonal gradients method: A radial basis functions method for solving partial differential equations on arbitrary surfaces

    KAUST Repository

    Piret, Cécile

    2012-05-01

    Much work has been done on reconstructing arbitrary surfaces using the radial basis function (RBF) method, but one can hardly find any work done on the use of RBFs to solve partial differential equations (PDEs) on arbitrary surfaces. In this paper, we investigate methods to solve PDEs on arbitrary stationary surfaces embedded in . R3 using the RBF method. We present three RBF-based methods that easily discretize surface differential operators. We take advantage of the meshfree character of RBFs, which give us a high accuracy and the flexibility to represent the most complex geometries in any dimension. Two out of the three methods, which we call the orthogonal gradients (OGr) methods are the result of our work and are hereby presented for the first time. © 2012 Elsevier Inc.

  17. New Observations of C-band Brightness Temperatures and Ocean Surface Wind Speed and Rain Rate From the Hurricane Imaging Radiometer (HIRAD)

    Science.gov (United States)

    Miller, Timothy L.; James, M. W.; Roberts, J. B.; Buckley, C. D.; Biswas, S.; May, C.; Ruf, C. S.; Uhlhorn, E. W.; Atlas, R.; Black, P.; hide

    2012-01-01

    HIRAD flew on the WB-57 during NASA's GRIP (Genesis and Rapid Intensification Processes) campaign in August September of 2010. HIRAD is a new C-band radiometer using a synthetic thinned array radiometer (STAR) technology to obtain cross-track resolution of approximately 3 degrees, out to approximately 60 degrees to each side of nadir. By obtaining measurements of emissions at 4, 5, 6, and 6.6 GHz, observations of ocean surface wind speed and rain rate can be retrieved. This technique has been used for many years by precursor instruments, including the Stepped Frequency Microwave Radiometer (SFMR), which has been flying on the NOAA and USAF hurricane reconnaissance aircraft for several years to obtain observations within a single footprint at nadir angle. Results from the flights during the GRIP campaign will be shown, including images of brightness temperatures, wind speed, and rain rate. Comparisons will be made with observations from other instruments on the GRIP campaign, for which HIRAD observations are either directly comparable or are complementary. Features such as storm eye and eyewall, location of storm wind and rain maxima, and indications of dynamical features such as the merging of a weaker outer wind/rain maximum with the main vortex may be seen in the data. Potential impacts on operational ocean surface wind analyses and on numerical weather forecasts will also be discussed.

  18. Discordance gradient-surface dans le rétrécissement mitral: le ...

    African Journals Online (AJOL)

    Il s'agit d'une étude transversale monocentrique incluant tous les patients admis au service de Cardiologie du CHU Ibn Rochd de Casablanca pour un RM serré ou très serré, sur une période d'une année (Janvier 2014 à Décembre 2014). Nous avons analysés séparément deux groupes de patients : ceux avec un gradient ...

  19. The Surface Brightness-color Relations Based on Eclipsing Binary Stars: Toward Precision Better than 1% in Angular Diameter Predictions

    Energy Technology Data Exchange (ETDEWEB)

    Graczyk, Dariusz; Gieren, Wolfgang [Millennium Institute of Astrophysics (MAS) (Chile); Konorski, Piotr [Obserwatorium Astronomiczne, Uniwersytet Warszawski, Al. Ujazdowskie 4, 00-478, Warsaw (Poland); Pietrzyński, Grzegorz [Universidad de Concepción, Departamento de Astronomia, Casilla 160-C, Concepción (Chile); Storm, Jesper [Leibniz-Institut für Astrophysik Potsdam, An der Sternwarte 16, D-14482 Potsdam (Germany); Nardetto, Nicolas [Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, UMR7293, Nice (France); Gallenne, Alexandre [European Southern Observatory, Alonso de Córdova 3107, Casilla 19001, Santiago 19 (Chile); Maxted, Pierre F. L. [Astrophysics Group, Keele University, Staffordshire, ST5 5BG (United Kingdom); Kervella, Pierre [Unidad Mixta Internacional Franco-Chilena de Astronomía (CNRS UMI 3386), Departamento de Astronomía, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago (Chile); Kołaczkowski, Zbigniew, E-mail: darek@astro-udec.cl, E-mail: darek@ncac.torun.pl [Instytut Astronomiczny, Uniwersytet Wrocławski, Kopernika 11, 51-622 Wrocław (Poland)

    2017-03-01

    In this study we investigate the calibration of surface brightness–color (SBC) relations based solely on eclipsing binary stars. We selected a sample of 35 detached eclipsing binaries with trigonometric parallaxes from Gaia DR1 or Hipparcos whose absolute dimensions are known with an accuracy better than 3% and that lie within 0.3 kpc from the Sun. For the purpose of this study, we used mostly homogeneous optical and near-infrared photometry based on the Tycho-2 and 2MASS catalogs. We derived geometric angular diameters for all stars in our sample with a precision better than 10%, and for 11 of them with a precision better than 2%. The precision of individual angular diameters of the eclipsing binary components is currently limited by the precision of the geometric distances (∼5% on average). However, by using a subsample of systems with the best agreement between their geometric and photometric distances, we derived the precise SBC relations based only on eclipsing binary stars. These relations have precisions that are comparable to the best available SBC relations based on interferometric angular diameters, and they are fully consistent with them. With very precise Gaia parallaxes becoming available in the near future, angular diameters with a precision better than 1% will be abundant. At that point, the main uncertainty in the total error budget of the SBC relations will come from transformations between different photometric systems, disentangling of component magnitudes, and for hot OB stars, the main uncertainty will come from the interstellar extinction determination. We argue that all these issues can be overcome with modern high-quality data and conclude that a precision better than 1% is entirely feasible.

  20. High brightness electron accelerator

    International Nuclear Information System (INIS)

    Sheffield, R.L.; Carlsten, B.E.; Young, L.M.

    1994-01-01

    A compact high brightness linear accelerator is provided for use, e.g., in a free electron laser. The accelerator has a first plurality of accelerating cavities having end walls with four coupling slots for accelerating electrons to high velocities in the absence of quadrupole fields. A second plurality of cavities receives the high velocity electrons for further acceleration, where each of the second cavities has end walls with two coupling slots for acceleration in the absence of dipole fields. The accelerator also includes a first cavity with an extended length to provide for phase matching the electron beam along the accelerating cavities. A solenoid is provided about the photocathode that emits the electrons, where the solenoid is configured to provide a substantially uniform magnetic field over the photocathode surface to minimize emittance of the electrons as the electrons enter the first cavity. 5 figs

  1. Observations of C-Band Brightness Temperatures and Ocean Surface Wind Speed and Rain Rate from the Hurricane Imaging Radiometer (HIRAD) during GRIP and HS3

    Science.gov (United States)

    Miller, Timothy L.; James, M. W.; Roberts, J. B.; Jones, W. L.; Biswas, S.; Ruf, C. S.; Uhlhorn, E. W.; Atlas, R.; Black, P.; Albers, C.

    2013-01-01

    HIRAD flew on high-altitude aircraft over Earl and Karl during NASA s GRIP (Genesis and Rapid Intensification Processes) campaign in August - September of 2010, and at the time of this writing plans to fly over Atlantic tropical cyclones in September of 2012 as part of the Hurricane and Severe Storm Sentinel (HS3) mission. HIRAD is a new C-band radiometer using a synthetic thinned array radiometer (STAR) technology to obtain cross-track resolution of approximately 3 degrees, out to approximately 60 degrees to each side of nadir. By obtaining measurements of emissions at 4, 5, 6, and 6.6 GHz, observations of ocean surface wind speed and rain rate can be retrieved. This technique has been used for many years by precursor instruments, including the Stepped Frequency Microwave Radiometer (SFMR), which has been flying on the NOAA and USAF hurricane reconnaissance aircraft for several years to obtain observations within a single footprint at nadir angle. Results from the flights during the GRIP and HS3 campaigns will be shown, including images of brightness temperatures, wind speed, and rain rate. Comparisons will be made with observations from other instruments on the campaigns, for which HIRAD observations are either directly comparable or are complementary. Features such as storm eye and eye-wall, location of storm wind and rain maxima, and indications of dynamical features such as the merging of a weaker outer wind/rain maximum with the main vortex may be seen in the data. Potential impacts on operational ocean surface wind analyses and on numerical weather forecasts will also be discussed.

  2. Hurricane Imaging Radiometer (HIRAD) Observations of Brightness Temperatures and Ocean Surface Wind Speed and Rain Rate During NASA's GRIP and HS3 Campaigns

    Science.gov (United States)

    Miller, Timothy L.; James, M. W.; Roberts, J. B.; Jones, W. L.; Biswas, S.; Ruf, C. S.; Uhlhorn, E. W.; Atlas, R.; Black, P.; Albers, C.

    2012-01-01

    HIRAD flew on high-altitude aircraft over Earl and Karl during NASA s GRIP (Genesis and Rapid Intensification Processes) campaign in August - September of 2010, and plans to fly over Atlantic tropical cyclones in September of 2012 as part of the Hurricane and Severe Storm Sentinel (HS3) mission. HIRAD is a new C-band radiometer using a synthetic thinned array radiometer (STAR) technology to obtain spatial resolution of approximately 2 km, out to roughly 30 km each side of nadir. By obtaining measurements of emissions at 4, 5, 6, and 6.6 GHz, observations of ocean surface wind speed and rain rate can be retrieved. The physical retrieval technique has been used for many years by precursor instruments, including the Stepped Frequency Microwave Radiometer (SFMR), which has been flying on the NOAA and USAF hurricane reconnaissance aircraft for several years to obtain observations within a single footprint at nadir angle. Results from the flights during the GRIP and HS3 campaigns will be shown, including images of brightness temperatures, wind speed, and rain rate. Comparisons will be made with observations from other instruments on the campaigns, for which HIRAD observations are either directly comparable or are complementary. Features such as storm eye and eye-wall, location of storm wind and rain maxima, and indications of dynamical features such as the merging of a weaker outer wind/rain maximum with the main vortex may be seen in the data. Potential impacts on operational ocean surface wind analyses and on numerical weather forecasts will also be discussed.

  3. Influence of slight microstructural gradients on the surface properties of Ti6Al4V irradiated by UV

    International Nuclear Information System (INIS)

    Gallardo-Moreno, A.M.; Multigner, M.; Pacha-Olivenza, M.A.; Lieblich, M.; Jimenez, J.A.; Gonzalez-Carrasco, J.L.; Gonzalez-Martin, M.L.

    2009-01-01

    Ti6Al4V alloy is one of the most widely used materials for biomedical implants. Among its properties, it is remarkable the photoactivity displayed by its passive layer, which is mainly composed by titanium dioxide. However, variations in the processing conditions may yield to differences in the microstructure which can be reflected on the surface properties of the machined product. From contact angle measurements taken on different zones of samples removed from a commercial bar of Ti6Al4V, it has been shown that the modifications of the surface Gibbs energy suffered by the alloy under UV irradiation have a radial dependence. This behaviour is related to slight microstructural changes of the alloy, particularly with an increase in the volume fraction of the β-phase when moving to the interior of the sample, which alters the composition and/or microstructure of the passive layer along its radius. This study shows that gradients in the microstructure and physical properties are sample size dependent and are likely related to thermal gradients during processing.

  4. The influence of small-scale sea surface temperature gradients on surface vector winds and subsequent impacts on oceanic Ekman pumping

    Science.gov (United States)

    Hughes, Paul J.

    Satellite observations have revealed a small-scale (air--sea coupling in regions of strong sea surface temperature (SST) gradients (e.g., fronts, currents, eddies, and tropical instability waves), where the surface wind and wind stress are modified. Surface winds and wind stresses are persistently higher over the warm side of the SST front compared to the cool side, causing perturbations in the dynamically and thermodynamically curl and divergence fields. Capturing this small-scale SST--wind variability is important because it can significantly impact both local and remote (i.e., large scale) oceanic and atmospheric processes. The SST--wind relationship is not well represented in numerical weather prediction (NWP) and climate models, and the relative importance of the physical processes that are proposed to be responsible for this relationship is actively and vehemently debated. This study focuses on the physical mechanisms that are primarily responsible for the SST-induced changes in surface wind and wind stress, and on the physical implication on ocean forcing through Ekman pumping. The roles that SST-induced atmospheric baroclinicity and boundary-layer stability play in modifying the surface vector wind in regions of strong SST gradients are examined with an idealized model. Modeled changes in surface wind speed due to changes in atmospheric boundary-layer stability and baroclinicity are largely between -2.0 and 2.0 m s-1, which is consistent with past observational findings. The baroclinic-related changes in the surface vector wind are found to have a largely linear dependence on the SST gradient, whereas the stability-related changes are highly non-linear. The linearity of the baroclinic impacts matches that of the observed (satellite and in situ) SST--wind relationship. This result suggests that the baroclinic-related mechanism is the leading factor in driving the observed surface wind response to strong open ocean SST fronts on scales greater than 25 km

  5. The gradient structure of the NiTi surface layers subjected to tantalum ion beam alloying

    Science.gov (United States)

    Girsova, S. L.; Poletika, T. M.; Meisner, L. L.; Schmidt, E. Yu

    2017-05-01

    The NiTi shape memory alloy has been modified by ion implantation with Ta to improve the surface and biological properties. The elemental and phase composition and structure of the surface and near-surface layers of NiTi specimens after the Ta ion implantation with the fluency D = 3 × 1017 cm-2 and D = 6 × 1017 cm-2 are examined. The methods of Auger electron spectroscopy (AES), transmission electron microscopy (TEM), and electron dispersion analysis (EDS) are used. It is found that a nonuniform distribution of elements along the depth of the surface layer after the ion implantation of NiTi specimens, regardless of the regime, is accompanied by the formation of a number of sublayer structures.

  6. Gas density gradient for three dark interstellar clouds

    International Nuclear Information System (INIS)

    Fulkerson, S.A.; Clark, F.O.

    1984-01-01

    A grid of models has been constructed of the surface brightness of selected transitions of interstellar formal-dehyde for three interstellar clouds. The grid included radial gas density gradients over a considerable range from uniform to very steep. The model results were then compared to observations of the interstellar dark clouds B361, L183, and L134. In all three cases, the comparison indicates that the gas is centrally condensed and follows a gradient in density which closely approximates an inverse square law. This result offers a hint that the dust may be more centrally condensed than the gas in B361

  7. Coccolith distribution patterns in South Atlantic and Southern Ocean surface sediments in relation to environmental gradients

    DEFF Research Database (Denmark)

    Boeckel, B.; Baumann, K.-H.; Henrich, R.

    2006-01-01

    In this study, the coccolith compositions of 213 surface sediment samples from the South Atlantic and Southern Ocean were analysed with respect to the environmental parameters of the overlying surface waters. From this data set, the abundance patterns of the main species and their ecological...... seems to be associated with high temperatures and salinities under low-nutrient conditions. Based on the relative abundances of Calcidiscus leptoporus, F. profunda, Gladiolithus flabellatus, Helicosphaera spp., Umbilicosphaera foliosa, Umbilicosphaera sibogae and a group of subordinate subtropical...

  8. Surface profile gradient in amorphous Ta{sub 2}O{sub 5} semi conductive layers regulates nanoscale electric current stability

    Energy Technology Data Exchange (ETDEWEB)

    Cefalas, A.C., E-mail: ccefalas@eie.gr [National Hellenic Research Foundation, Theoretical and Physical Chemistry Institute, 48 Vassileos Constantinou Avenue, Athens 11635 (Greece); Kollia, Z.; Spyropoulos-Antonakakis, N.; Gavriil, V. [National Hellenic Research Foundation, Theoretical and Physical Chemistry Institute, 48 Vassileos Constantinou Avenue, Athens 11635 (Greece); Christofilos, D.; Kourouklis, G. [Physics Division, School of Technology, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece); Semashko, V.V.; Pavlov, V. [Kazan Federal University, Institute of Physics, 18 Kremljovskaja str., Kazan 420008 (Russian Federation); Sarantopoulou, E. [National Hellenic Research Foundation, Theoretical and Physical Chemistry Institute, 48 Vassileos Constantinou Avenue, Athens 11635 (Greece); Kazan Federal University, Institute of Physics, 18 Kremljovskaja str., Kazan 420008 (Russian Federation)

    2017-02-28

    Highlights: • The work links the surface morphology of amorphous semiconductors with both their electric-thermal properties and current stability at the nanoscale (<1 μm). • Measured high correlation value between surface morphological spatial gradient and conductive electron energy spatial gradient or thermal gradient. • Unidirectional current stability is associated with asymmetric nanodomains along nanosize conductive paths. • Bidirectional current stability is inherent with either long conductive paths or nanosize conductive paths along symmetric nanodomains. • Conclusion: Surface design improves current stability across nanoelectonic junctions. - Abstract: A link between the morphological characteristics and the electric properties of amorphous layers is established by means of atomic, conductive, electrostatic force and thermal scanning microscopy. Using amorphous Ta{sub 2}O{sub 5} (a-Ta{sub 2}O{sub 5}) semiconductive layer, it is found that surface profile gradients (morphological gradient), are highly correlated to both the electron energy gradient of trapped electrons in interactive Coulombic sites and the thermal gradient along conductive paths and thus thermal and electric properties are correlated with surface morphology at the nanoscale. Furthermore, morphological and electron energy gradients along opposite conductive paths of electrons intrinsically impose a current stability anisotropy. For either long conductive paths (L > 1 μm) or along symmetric nanodomains, current stability for both positive and negative currents i is demonstrated. On the contrary, for short conductive paths along non-symmetric nanodomains, the set of independent variables (L, i) is spanned by two current stability/intability loci. One locus specifies a stable state for negative currents, while the other locus also describes a stable state for positive currents.

  9. Color Gradients Within Globular Clusters: Restricted Numerical Simulation

    Directory of Open Access Journals (Sweden)

    Young-Jong Sohn

    1997-06-01

    Full Text Available The results of a restricted numerical simulation for the color gradients within globular clusters have been presented. The standard luminosity function of M3 and Salpeter's initial mass functions were used to generate model clusters as a fundamental population. Color gradients with the sample clusters for both King and power law cusp models of surface brightness distributions are discussed in the case of using the standard luminosity function. The dependence of color gradients on several parameters for the simulations with Salpeter's initial mass functions, such as slope of initial mass functions, cluster ages, metallicities, concentration parameters of King model, and slopes of power law, are also discussed. No significant radial color gradients are shown to the sample clusters which are regenerated by a random number generation technique with various parameters in both of King and power law cusp models of surface brightness distributions. Dynamical mass segregation and stellar evolution of horizontal branch stars and blue stragglers should be included for the general case of model simulations to show the observed radial color gradients within globular clusters.

  10. Automated Measurement for Sensitivity Analysis of Runoff-Sediment Load at Varying Surface Gradients

    Directory of Open Access Journals (Sweden)

    Imanogor P.A.

    2015-07-01

    Full Text Available Direct measurement of surface runoff is often associated with errors and inaccuracies which results to unreliable hydrological data. An automatic Runoff-meter using tipping buckets arrangement calibrated to tip 0.14 liter of runoff water per tip with an accuracy of ± 0.001 litre was used to measure surface runoff from a steel bounded soil tray of dimension (1200 mm X 900 mm X 260 mm filled with sand loamy to the depth of 130 mm and inclined at angle (0 0 , 5 0 ,12 0 and 15 0 horizontal to the instrument. The effect of varying angles of inclination on runoff intensity, sediment loss rate and sediment loss is significant at 5 % confidence level, while surface runoff is not significant at 5 % confidence level. Total highest sediment loss of 458.2 g and 313.4 g were observed at angle 15 0 and 12 0 respectively. Total surface runoff of 361.5 mm and 445.8 mm were generated at inclined angle of 0 0 and 5 0 , while at angle 12 0 and 15 0 , 564.3 mm and 590.0 mm of surface runoff were generated. In addition, runoff intensity and sediment loss rate were highest at angle 15 0 , while the lowest values of 1.5mm/min and 5.43 g/min were obtained at angle of inclination 5 0 . The results showed that strong relationship existed among the hydrological variables as a result of subjecting the steel bounded soil tray to different angles of inclination. Such results would provide useful data for the running of physics-based deterministic model of surface runoff and erosion which will be useful for the design of hydrological structures, land use planning and management.

  11. Burkina Faso - BRIGHT II

    Data.gov (United States)

    Millennium Challenge Corporation — Millennium Challenge Corporation hired Mathematica Policy Research to conduct an independent evaluation of the BRIGHT II program. The three main research questions...

  12. Vibration analysis of bonded double-FGM viscoelastic nanoplate systems based on a modified strain gradient theory incorporating surface effects

    Science.gov (United States)

    Jamalpoor, Ali; Kiani, Ali

    2017-03-01

    On the basis of the modified strain gradient theory, the present paper deals with the theoretical analysis of the free vibration of coupled double-FGM viscoelastic nanoplates by Kelvin-Voigt visco-Pasternak medium. To establish static equilibrium of atoms on the each nanoplate surface, the effects of the surface layers are considered. The properties of material in the thickness direction vary according to the power low distribution. Kirchhoff plate assumption and Hamilton's variational principle are employed to achieve the partial differential equations for three different cases of vibration (out-of-phase, in-phase, and one nanoplate of the system being stationary) and corresponding boundary conditions. Navier's approach which satisfies the simply supported boundary conditions applied to analytically investigate the size effect on the natural frequencies of double-FGM viscoelastic nanoplate systems. Numerical studies are carried out to illustrate the influence of viscoelastic damping structural of the nanoplates, damping coefficient of the visco-Pasternak medium, independent length scale parameter, aspect ratio, surface properties, and other factors on the frequency behavior system. Some numerical results of this research illustrate that the frequencies may increase or decrease with respect to the sign of the surface properties of FGMs.

  13. Macrobenthic species response surfaces along estuarine gradients: prediction by logistic regression

    NARCIS (Netherlands)

    Ysebaert, T.; Meire, P.; Herman, P.M.J.; Verbeek, H.

    2002-01-01

    This study aims at contributing to the development of statistical models to predict macrobenthic species response to environmental conditions in estuarine ecosystems. Ecological response surfaces are derived for 10 estuarine macrobenthic species. Logistic regression is applied on a large data set,

  14. Mapping surface flow in low gradient areas with thermal remote sensing

    DEFF Research Database (Denmark)

    Prinds, Christian; Petersen, Rasmus Jes; Greve, Mogens Humlekrog

    Thermal infrared (TIR) imagery has long been used for mapping groundwater-surface water interactions and mainly for locating areas of groundwater seepage in lakes and shorelines (Rundquist et al. 1985, Banks et al. 1996). In this study, we used the method for locating discharge from tile drains...

  15. Selection effects in the bivariate brightness distribution for spiral galaxies

    International Nuclear Information System (INIS)

    Phillipps, S.; Disney, M.

    1986-01-01

    The joint distribution of total luminosity and characteristic surface brightness (the bivariate brightness distribution) is investigated for a complete sample of spiral galaxies in the Virgo cluster. The influence of selection and physical limits of various kinds on the apparent distribution are detailed. While the distribution of surface brightness for bright galaxies may be genuinely fairly narrow, faint galaxies exist right across the (quite small) range of accessible surface brightnesses so no statement can be made about the true extent of the distribution. The lack of high surface brightness bright galaxies in the Virgo sample relative to an overall RC2 sample (mostly field galaxies) supports the contention that the star-formation rate is reduced in the inner region of the cluster for environmental reasons. (author)

  16. Spatial Gradients in Trace Metal Concentrations in the Surface Microlayer of the Mediterranean Sea

    Directory of Open Access Journals (Sweden)

    Antonio eTovar-Sanchez

    2014-12-01

    Full Text Available The relationship between dust deposition and surface water metal concentrations is poorly understood. Dissolution, solubility, and partitioning reactions of trace metals from dust particles are governed by complex chemical, biological, and physical processes occurring in the surface ocean. Despite that, the role of the sea surface microlayer (SML, a thin, but fundamental component modulating the air-sea exchange of materials has not been properly evaluated. Our study revealed that the SML of the Mediterranean Sea is enriched with bioactive trace metals (i.e., Cd, Co, Cu and Fe, ranging from 8 (for Cd to 1000 (for Fe times higher than the dissolved metal pool in the underlying water column. The highest enrichments were spatially correlated with the atmospheric deposition of mineral particles. Our mass balance results suggest that the SML in the Mediterranean Sea contains about 2 tonnes of Fe. However, we did not detect any trends between the concentrations of metals in SML with the subsurface water concentrations and biomass distributions. These findings suggest that future studies are needed to quantify the rate of metal exchange between the SML and the bioavailable pool and that the SML should be considered to better understand the effect of atmospheric inputs on the biogeochemistry of trace metals in the ocean.

  17. Determination of charged particles and their polarity in XLPE by temperature gradient thermally stimulated surface potential measurement

    International Nuclear Information System (INIS)

    Iwamoto, Mitsumasa; Kato, Keizo; Kook, Sang-Hoon; Hino, Taro

    1985-01-01

    By the thermally stimulated surface potential measurement with a temperature gradient in the insulator specimen, various information not possible by the uniform heating is obtained. Determination of polarity of the carriers is capable of providing a knowledge on space charge in power cables, for example. For the cross-linked polyethylene (XLPE) film as cable insulation, polarity of the carriers trapped in it was determined, thereby demonstrating effectiveness of the method. The determination of polarity of mobile ions forming polarization of the ion space charge was also studied. In the ion C-peak appearing in the thermally stimulated current are involved straight-polarity mobile ions, and in the trap D-peak, hole carriers. (Mori, K.)

  18. Efficient numerical methods for simulating surface tension of multi-component mixtures with the gradient theory of fluid interfaces

    KAUST Repository

    Kou, Jisheng

    2015-08-01

    Surface tension significantly impacts subsurface flow and transport, and it is the main cause of capillary effect, a major immiscible two-phase flow mechanism for systems with a strong wettability preference. In this paper, we consider the numerical simulation of the surface tension of multi-component mixtures with the gradient theory of fluid interfaces. Major numerical challenges include that the system of the Euler-Lagrange equations is solved on the infinite interval and the coefficient matrix is not positive definite. We construct a linear transformation to reduce the Euler-Lagrange equations, and naturally introduce a path function, which is proven to be a monotonic function of the spatial coordinate variable. By using the linear transformation and the path function, we overcome the above difficulties and develop the efficient methods for calculating the interface and its interior compositions. Moreover, the computation of the surface tension is also simplified. The proposed methods do not need to solve the differential equation system, and they are easy to be implemented in practical applications. Numerical examples are tested to verify the efficiency of the proposed methods. © 2014 Elsevier B.V.

  19. Wave propagation analysis of embedded nanoplates based on a nonlocal strain gradient-based surface piezoelectricity theory

    Science.gov (United States)

    Ebrahimi, Farzad; Dabbagh, Ali

    2017-11-01

    The present paper deals with the smart characteristics of waves propagating in a piezoelectric nanosize plate rested on an elastic medium whenever surface effects are included. A more realistic simulation about the elastic medium is presented by utilizing a three-parameter medium containing Winkler, Pasternak and damping coefficients. Furthermore, both of the decreasing and increasing impacts of small scale influences are covered in the framework of a nonlocal strain gradient theory (NSGT). The electric potential is approximated by a function possessing linear and trigonometric parts. Also, by developing the surface elasticity theory of Gurtin-Murdoch for piezoelectric solids, influences of surface layers are considered. Kinematic relations are derived employing the Kirchhoff plate theory. Afterwards, Hamilton's principle is introduced in order to achieve Euler-Lagrange equations of piezoelectric nanoplates. The final part consists of an analytical approach to obtain the wave frequency value. The accuracy of the presented model is verified by organizing a comparison of the presented results with previous ones. Finally, some parametric case studies are rendered to clarify the influence of different parameters such as wave number, nonlocal and length scale parameters, foundation parameters and applied voltage.

  20. Optically abrupt localized surface plasmon resonances in si nanowires by mitigation of carrier density gradients.

    Science.gov (United States)

    Chou, Li-Wei; Boyuk, Dmitriy S; Filler, Michael A

    2015-02-24

    Spatial control of carrier density is critical for engineering and exploring the interactions of localized surface plasmon resonances (LSPRs) in nanoscale semiconductors. Here, we couple in situ infrared spectral response measurements and discrete dipole approximation (DDA) calculations to show the impact of axially graded carrier density profiles on the optical properties of mid-infrared LSPRs supported by Si nanowires synthesized by the vapor-liquid-solid technique. The region immediately adjacent to each intentionally encoded resonator (i.e., doped segment) can exhibit residual carrier densities as high as 10(20) cm(-3), which strongly modifies both near- and far-field behavior. Lowering substrate temperature during the spacer segment growth reduces this residual carrier density and results in a spectral response that is indistinguishable from nanowires with ideal, atomically abrupt carrier density profiles. Our experiments have important implications for the control of near-field plasmonic phenomena in semiconductor nanowires, and demonstrate methods for determining and controlling axial dopant profile in these systems.

  1. Coupling of climate models and ice sheet models by surface mass balance gradients: application to the Greenland Ice Sheet

    Directory of Open Access Journals (Sweden)

    M. M. Helsen

    2012-03-01

    Full Text Available It is notoriously difficult to couple surface mass balance (SMB results from climate models to the changing geometry of an ice sheet model. This problem is traditionally avoided by using only accumulation from a climate model, and parameterizing the meltwater run-off as a function of temperature, which is often related to surface elevation (Hs. In this study, we propose a new strategy to calculate SMB, to allow a direct adjustment of SMB to a change in ice sheet topography and/or a change in climate forcing. This method is based on elevational gradients in the SMB field as computed by a regional climate model. Separate linear relations are derived for ablation and accumulation, using pairs of Hs and SMB within a minimum search radius. The continuously adjusting SMB forcing is consistent with climate model forcing fields, also for initially non-glaciated areas in the peripheral areas of an ice sheet. When applied to an asynchronous coupled ice sheet – climate model setup, this method circumvents traditional temperature lapse rate assumptions. Here we apply it to the Greenland Ice Sheet (GrIS. Experiments using both steady-state forcing and glacial-interglacial forcing result in realistic ice sheet reconstructions.

  2. The structure of bright zinc coatings

    Directory of Open Access Journals (Sweden)

    MIODRAG STOJANOVIC

    2000-11-01

    Full Text Available The structures of bright zinc coatings obtained from acid sulfate solutions in the presence of dextrin/salicyl aldehyde mixture were examined. It was shown by the STM technique that the surfaces of bright zinc coatings are covered by hexagonal zinc crystals, the tops of planes of which are flat and mutually parallel and which exhibit smoothness on the atomic level. X-Ray diffraction (XRD analysis of the bright zinc coatings showed that the zinc crystallites are oriented in the (110 plane only.

  3. ALMA Discovery of Solar Umbral Brightness Enhancement at λ = 3 mm

    Energy Technology Data Exchange (ETDEWEB)

    Iwai, Kazumasa [Institute for Space-Earth Environmental Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601 (Japan); Loukitcheva, Maria [Center for Solar-Terrestrial Research, New Jersey Institute of Technology, 323 Martin Luther King Boulevard, Newark, NJ 07102 (United States); Shimojo, Masumi [Chile Observatory, National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan); Solanki, Sami K. [Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, D-37073 Göttingen (Germany); White, Stephen M., E-mail: k.iwai@isee.nagoya-u.ac.jp [Space Vehicles Directorate, Air Force Research Laboratory, Albuquerque, NM (United States)

    2017-06-01

    We report the discovery of a brightness enhancement in the center of a large sunspot umbra at a wavelength of 3 mm using the Atacama Large Millimeter/sub-millimeter Array (ALMA). Sunspots are among the most prominent features on the solar surface, but many of their aspects are surprisingly poorly understood. We analyzed a λ = 3 mm (100 GHz) mosaic image obtained by ALMA that includes a large sunspot within the active region AR12470, on 2015 December 16. The 3 mm map has a 300″ × 300″ field of view and 4.″9 × 2.″2 spatial resolution, which is the highest spatial resolution map of an entire sunspot in this frequency range. We find a gradient of 3 mm brightness from a high value in the outer penumbra to a low value in the inner penumbra/outer umbra. Within the inner umbra, there is a marked increase in 3 mm brightness temperature, which we call an umbral brightness enhancement. This enhanced emission corresponds to a temperature excess of 800 K relative to the surrounding inner penumbral region and coincides with excess brightness in the 1330 and 1400 Å slit-jaw images of the Interface Region Imaging Spectrograph ( IRIS ), adjacent to a partial lightbridge. This λ = 3 mm brightness enhancement may be an intrinsic feature of the sunspot umbra at chromospheric heights, such as a manifestation of umbral flashes, or it could be related to a coronal plume, since the brightness enhancement was coincident with the footpoint of a coronal loop observed at 171 Å.

  4. Surface Gradient Integrated Profiler for X-ray and EUV Optics--Calibration of the rotational angle error of the rotary encoders

    International Nuclear Information System (INIS)

    Higashi, Yasuo; Kume, Tatsuya; Enami, Kazuhiro; Ueno, Kenji; Mori, Yuzo; Takaie, Yuichi; Endo, Katsuyoshi; Yamauchi, Kazuto; Yamamura, Kazuya; Sano, Yasuhisa

    2007-01-01

    A new ultraprecision profiler has been developed to measure for example asymmetric and aspheric profiles. The principle of our measuring method is that the normal vector at each point on the surface is determined by making the incident light beam on the mirror surface and the reflected beam at that point coincident. The gradient at each point is calculated from the normal vector, and the surface profile is then obtained by integrating the gradients. The measuring instrument was designed in accordance with the above principle for the measuring method and is called Surface Gradient Integrated Profiler (SGIP). In the design, four ultraprecision goniometers were applied to adjust the light axis for the normal vector measurement. These goniostages make it possible to attain an angular resolution of 0.018 μ radian by electrically dividing a pulse of the rotary encoder. The surface gradients are determined only by the rotational angle of goniometers. Thus in the measuring instrument, the most important factor is the accuracy of the normal vectors measured by the goniometers. To attain an accuracy of 0.1 μ radian, we developed a system for correcting the rotational angle error of the goniometers in which the trigonometric measuring method is utilized for geometrical angle determination

  5. BrightFocus Foundation

    Science.gov (United States)

    ... announcement by Bill Gates of his $50 million investment in the Dementia Discovery Fund. A charitable act ... under section 501(c)(3) of the Internal Revenue Code of the United States.Copyright 2017 BrightFocus ...

  6. Surface CO2 Exchange Dynamics across a Climatic Gradient in McKenzie Valley: Effect of Landforms, Climate and Permafrost

    Directory of Open Access Journals (Sweden)

    Natalia Startsev

    2016-11-01

    Full Text Available Northern regions are experiencing considerable climate change affecting the state of permafrost, peat accumulation rates, and the large pool of carbon (C stored in soil, thereby emphasizing the importance of monitoring surface C fluxes in different landform sites along a climate gradient. We studied surface net C exchange (NCE and ecosystem respiration (ER across different landforms (upland, peat plateau, collapse scar in mid-boreal to high subarctic ecoregions in the Mackenzie Valley of northwestern Canada for three years. NCE and ER were measured using automatic CO2 chambers (ADC, Bioscientific LTD., Herts, England, and soil respiration (SR was measured with solid state infrared CO2 sensors (Carbocaps, Vaisala, Vantaa, Finland using the concentration gradient technique. Both NCE and ER were primarily controlled by soil temperature in the upper horizons. In upland forest locations, ER varied from 583 to 214 g C·m−2·year−1 from mid-boreal to high subarctic zones, respectively. For the bog and peat plateau areas, ER was less than half that at the upland locations. Of SR, nearly 75% was generated in the upper 5 cm layer composed of live bryophytes and actively decomposing fibric material. Our results suggest that for the upland and bog locations, ER significantly exceeded NCE. Bryophyte NCE was greatest in continuously waterlogged collapsed areas and was negligible in other locations. Overall, upland forest sites were sources of CO2 (from 64 g·C·m−2·year−1 in the high subarctic to 588 g C·m−2·year−1 in mid-boreal zone; collapsed areas were sinks of C, especially in high subarctic (from 27 g·C·m−2 year−1 in mid-boreal to 86 g·C·m−2·year−1 in high subarctic and peat plateaus were minor sources (from 153 g·C·m−2·year−1 in mid-boreal to 6 g·C·m−2·year−1 in high subarctic. The results are important in understanding how different landforms are responding to climate change and would be useful in modeling the

  7. Irradiance gradients

    International Nuclear Information System (INIS)

    Ward, G.J.; Heckbert, P.S.; Technische Hogeschool Delft

    1992-04-01

    A new method for improving the accuracy of a diffuse interreflection calculation is introduced in a ray tracing context. The information from a hemispherical sampling of the luminous environment is interpreted in a new way to predict the change in irradiance as a function of position and surface orientation. The additional computation involved is modest and the benefit is substantial. An improved interpolation of irradiance resulting from the gradient calculation produces smoother, more accurate renderings. This result is achieved through better utilization of ray samples rather than additional samples or alternate sampling strategies. Thus, the technique is applicable to a variety of global illumination algorithms that use hemicubes or Monte Carlo sampling techniques

  8. The liner brightness temperature measurement by two channel optical pyrometer

    Science.gov (United States)

    Kulish, M. I.; Dudin, S. V.; Ushnurtsev, A. E.; Mintsev, V. B.

    2018-01-01

    Measurability of liner inner surface brightness temperature by two channel optical pyrometer is shown. Liner is compressed by detonation products in large-scale experiment. Absolute radiant intensity values were obtained by measuring optical system channel calibration involving tungsten and xenon radiation sources. Three ways of surface brightness temperature measurement are presented at wavelengths of 620 and 850 nm. Using the developed procedure copper and steel liners behavior (brightness temperature, average speed) under compression by detonation products are evaluated.

  9. Edge integration and the perception of brightness and darkness

    NARCIS (Netherlands)

    Vladusich, T.; Lucassen, M.P.; Cornelissen, F.W.

    2006-01-01

    How do induced brightness and darkness signals from local and remote surfaces interact to determine the final achromatic color percept of a target surface? An emerging theory of achromatic color perception posits that brightness and darkness percepts are computed by weighting and summing the

  10. Analysis of the geochemical gradient created by surface-groundwater interactions within riverbanks of the East River in Crested Butte, Colorado

    Science.gov (United States)

    Lunzer, J.; Williams, K. H.; Malenda, H. F.; Nararne-Sitchler, A.

    2016-12-01

    An improved understanding of the geochemical gradient created by the mixing of surface and groundwater of a river system will have considerable impact on our understanding of microorganisms, organic cycling and biogeochemical processes within these zones. In this study, the geochemical gradient in the hyporheic zone is described using a variety of geochemical properties. A system of shallow groundwater wells were installed in a series of transects along a stream bank. Each transect consists of several wells that progress away from the river bank in a perpendicular fashion. From these wells, temperature, conductivity and pH of water samples were obtained via hand pumping or bailing. These data show a clear geochemical gradient that displays a distinct zone in the subsurface where the geochemical conditions change from surface water dominated to groundwater dominated. For this study, the East River near Crested Butte, Colorado has been selected as the river of interest due the river being a relatively undisturbed floodplain. Additionally, the specific section chosen on the East River displays relatively high sinuosity meaning that these meandering sections will produce hyporheic zones that are more laterally expansive than what would be expected on a river of lower sinuosity. This increase in lateral extension of the hyporheic zone will make depicting the subtle changes in the geochemical gradient much easier than that of a river system in which the hyporheic zone is not as laterally extensive. Data has been and will be continued to be collected at different river discharges to evaluate the geochemical gradient at differing rates. Overall, this characterization of the geochemical gradient along stream banks will produce results that will aid in the further use of geochemical methods to classify and understand hyporheic exchange zones and the potential expansion of these techniques to river systems of differing geologic and geographic conditions.

  11. Monitoring of the spatio-temporal change in the interplate coupling at northeastern Japan subduction zone based on the spatial gradients of surface velocity field

    Science.gov (United States)

    Iinuma, Takeshi

    2018-04-01

    A monitoring method to grasp the spatio-temporal change in the interplate coupling in a subduction zone based on the spatial gradients of surface displacement rate fields is proposed. I estimated the spatio-temporal change in the interplate coupling along the plate boundary in northeastern (NE) Japan by applying the proposed method to the surface displacement rates based on global positioning system observations. The gradient of the surface velocities is calculated in each swath configured along the direction normal to the Japan Trench for time windows such as 0.5, 1, 2, 3 and 5 yr being shifted by one week during the period of 1997-2016. The gradient of the horizontal velocities is negative and has a large magnitude when the interplate coupling at the shallow part (less than approximately 50 km in depth) beneath the profile is strong, and the sign of the gradient of the vertical velocity is sensitive to the existence of the coupling at the deep part (greater than approximately 50 km in depth). The trench-parallel variation of the spatial gradients of a displacement rate field clearly corresponds to the trench-parallel variation of the amplitude of the interplate coupling on the plate interface, as well as the rupture areas of previous interplate earthquakes. Temporal changes in the trench-parallel variation of the spatial gradient of the displacement rate correspond to the strengthening or weakening of the interplate coupling. We can monitor the temporal change in the interplate coupling state by calculating the spatial gradients of the surface displacement rate field to some extent without performing inversion analyses with applying certain constraint conditions that sometimes cause over- and/or underestimation at areas of limited spatial resolution far from the observation network. The results of the calculation confirm known interplate events in the NE Japan subduction zone, such as the post-seismic slip of the 2003 M8.0 Tokachi-oki and 2005 M7.2 Miyagi

  12. High Brightness OLED Lighting

    Energy Technology Data Exchange (ETDEWEB)

    Spindler, Jeffrey [OLEDWorks LLC; Kondakova, Marina [OLEDWorks LLC; Boroson, Michael [OLEDWorks LLC; Hamer, John [OLEDWorks LLC

    2016-05-25

    In this work we describe the technology developments behind our current and future generations of high brightness OLED lighting panels. We have developed white and amber OLEDs with excellent performance based on the stacking approach. Current products achieve 40-60 lm/W, while future developments focus on achieving 80 lm/W or higher.

  13. Arsenic and metallic trace elements cycling in the surface water-groundwater-soil continuum down-gradient from a reclaimed mine area: Isotopic imprints

    Science.gov (United States)

    Khaska, Mahmoud; Le Gal La Salle, Corinne; Sassine, Lara; Cary, Lise; Bruguier, Olivier; Verdoux, Patrick

    2018-03-01

    One decade after closure of the Salsigne mine (SW France), As contamination persisted in surface water, groundwater and soil near and down-gradient from the reclaimed ore processing site (OPS). We assess the fate of As and other associated chalcophilic MTEs, and their transport in the surface-water/groundwater/soil continuum down-gradient from the reclaimed OPS, using Sr-isotopic fingerprinting. The Sr-isotope ratio was used as a tracer of transfer processes in this hydro-geosystem and was combined to sequential extraction of soil samples to evaluate the impact of contaminated soil on the underlying phreatic groundwater. The contrast in Sr isotope compositions of the different soil fractions reflects several Sr sources in the soil. In the complex hydro-geosystem around the OPS, the transport of As and MTEs is affected by a succession of factors, such as (1) Existence of a reducing zone in the aquifer below the reclaimed OPS, where groundwater shows relatively high As and MTEs contents, (2) Groundwater discharge into the stream near the reclaimed OPS causing an increase in As and MTE concentrations in surface water; (3) Partial co-precipitation of As with Fe-oxyhydroxides, contributing to some attenuation of As contents in surface water; (4) Infiltration of contaminated stream water into the unconfined aquifer down-gradient from the reclaimed OPS; (5) Accumulation of As and MTEs in soil irrigated with contaminated stream- and groundwater; (6) Release of As and MTEs from labile soil fractions to underlying the groundwater.

  14. THE ACS FORNAX CLUSTER SURVEY. IV. DEPROJECTION OF THE SURFACE BRIGHTNESS PROFILES OF EARLY-TYPE GALAXIES IN THE VIRGO AND FORNAX CLUSTERS: INVESTIGATING THE 'CORE/POWER-LAW DICHOTOMY'

    International Nuclear Information System (INIS)

    Glass, Lisa; Ferrarese, Laura; Cote, Patrick; Blakeslee, John P.; Chen, Chin-Wei; Jordan, Andres; Infante, Leopoldo; Peng, Eric; Mei, Simona; Tonry, John L.; West, Michael J.

    2011-01-01

    Although early observations with the Hubble Space Telescope (HST) pointed to a sharp dichotomy among early-type galaxies in terms of the logarithmic slope γ' of their central surface brightness profiles, several studies in the past few years have called this finding into question. In particular, recent imaging surveys of 143 early-type galaxies belonging to the Virgo and Fornax Clusters using the Advanced Camera for Surveys (ACS) on board HST have not found a dichotomy in γ', but instead a systematic progression from central luminosity deficit to excess relative to the inward extrapolation of the best-fitting global Sersic model. Given that earlier studies also found that the dichotomy persisted when analyzing the deprojected density profile slopes, we investigate the distribution of the three-dimensional luminosity density profiles of the ACS Virgo and Fornax Cluster Survey galaxies. Having fitted the surface brightness profiles with modified Sersic models, we then deproject the galaxies using an Abel integral and measure the inner slopes γ 3D of the resulting luminosity density profiles at various fractions of the effective radius R e . We find no evidence of a dichotomy, but rather, a continuous variation in the central luminosity profiles as a function of galaxy magnitude. We introduce a parameter, Δ 3D , that measures the central deviation of the deprojected luminosity profiles from the global Sersic fit, showing that this parameter varies smoothly and systematically along the luminosity function.

  15. Brightness Alteration with Interweaving Contours

    Directory of Open Access Journals (Sweden)

    Sergio Roncato

    2012-12-01

    Full Text Available Chromatic induction is observed whenever the perceived colour of a target surface shifts towards the hue of a neighbouring surface. Some vivid manifestations may be seen in a white background where thin coloured lines have been drawn (assimilation or when lines of different colours are collinear (neon effect or adjacent (watercolour to each other. This study examines a particular colour induction that manifests in concomitance with an opposite effect of colour saturation (or anti-spread. The two phenomena can be observed when a repetitive pattern is drawn in which outline thin contours intercept wider contours or surfaces, colour spreading appear to fill the surface occupied by surfaces or thick lines whereas the background traversed by thin lines is seen as brighter or filled of a saturated white. These phenomena were first observed by Bozzi (1975 and Kanizsa (1979 in figural conditions that did not allow them to document their conjunction. Here we illustrate various manifestations of this twofold phenomenon and compare its effects with the known effects of brightness and colour induction. Some conjectures on the nature of these effects are discussed.

  16. Large Bright Ripples

    Science.gov (United States)

    2004-01-01

    3 February 2004 Wind is the chief agent of change on Mars today. Wind blows dust and it can move coarser sediment such as sand and silt. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows bright ripples or small dunes on the floors of troughs northeast of Isidis Planitia near 31.1oN, 244.6oW. The picture covers an area 3 km (1.9 mi) wide; sunlight illuminates the scene from the lower left.

  17. Observations of C-Band Brightness Temperature and Ocean Surface Wind Speed and Rain Rate in Hurricanes Earl And Karl (2010)

    Science.gov (United States)

    Miller, Timothy; James, Mark; Roberts, Brent J.; Biswax, Sayak; Uhlhorn, Eric; Black, Peter; Linwood Jones, W.; Johnson, Jimmy; Farrar, Spencer; Sahawneh, Saleem

    2012-01-01

    Ocean surface emission is affected by: a) Sea surface temperature. b) Wind speed (foam fraction). c) Salinity After production of calibrated Tb fields, geophysical fields wind speed and rain rate (or column) are retrieved. HIRAD utilizes NASA Instrument Incubator Technology: a) Provides unique observations of sea surface wind, temp and rain b) Advances understanding & prediction of hurricane intensity c) Expands Stepped Frequency Microwave Radiometer capabilities d) Uses synthetic thinned array and RFI mitigation technology of Lightweight Rain Radiometer (NASA Instrument Incubator) Passive Microwave C-Band Radiometer with Freq: 4, 5, 6 & 6.6 GHz: a) Version 1: H-pol for ocean wind speed, b) Version 2: dual ]pol for ocean wind vectors. Performance Characteristics: a) Earth Incidence angle: 0deg - 60deg, b) Spatial Resolution: 2-5 km, c) Swath: approx.70 km for 20 km altitude. Observational Goals: WS 10 - >85 m/s RR 5 - > 100 mm/hr.

  18. Bright point study

    International Nuclear Information System (INIS)

    Tang, F.; Harvey, K.; Bruner, M.; Kent, B.; Antonucci, E.

    1982-01-01

    Transition region and coronal observations of bright points by instruments aboard the Solar Maximum Mission and high resolution photospheric magnetograph observations on September 11, 1980 are presented. A total of 31 bipolar ephemeral regions were found in the photosphere from birth in 9.3 hours of combined magnetograph observations from three observatories. Two of the three ephemeral regions present in the field of view of the Ultraviolet Spectrometer-Polarimeter were observed in the C IV 1548 line. The unobserved ephemeral region was determined to be the shortest-lived (2.5 hr) and lowest in magnetic flux density (13G) of the three regions. The Flat Crystal Spectrometer observed only low level signals in the O VIII 18.969 A line, which were not statistically significant to be positively identified with any of the 16 ephemeral regions detected in the photosphere. In addition, the data indicate that at any given time there lacked a one-to-one correspondence between observable bright points and photospheric ephemeral regions, while more ephemeral regions were observed than their counterparts in the transition region and the corona

  19. On the theory and computation of surface tension: The elimination of parasitic currents through energy conservation in the second-gradient method

    International Nuclear Information System (INIS)

    Jamet, Didier; Torres, David; Brackbill, J.U.

    2002-01-01

    Errors in the computation of fluid flows with surface tension are examined. These errors cause large parasitic flows when the capillary number is large and have often been attributed to truncation error in underresolved interfacial regions. A study using the second-gradient method reveals that when truncation error is eliminated in the computation of energy exchanges between surface and kinetic energies so that energy is strictly conserved, the parasitic currents are reduced to round-off. The results are based on general thermodynamic arguments and can be used to guide improvements in other methods, such as the continuum-surface-force (CSF) method, which is commonly used with the volume-of-fluid (VOF) method

  20. Surface Tension of Binary Mixtures Including Polar Components Modeled by the Density Gradient Theory Combined with the PC-SAFT Equation of State

    Czech Academy of Sciences Publication Activity Database

    Vinš, Václav; Planková, Barbora; Hrubý, Jan

    2013-01-01

    Roč. 34, č. 5 (2013), s. 792-812 ISSN 0195-928X R&D Projects: GA AV ČR IAA200760905; GA ČR(CZ) GPP101/11/P046; GA ČR GA101/09/1633 Institutional research plan: CEZ:AV0Z20760514 Institutional support: RVO:61388998 Keywords : chemical polarity * gradient theory * surface tension Subject RIV: BJ - Thermodynamics Impact factor: 0.623, year: 2013 http://www.springerlink.com/openurl.asp?genre=article&id=doi:10.1007/s10765-012-1207-z

  1. High brightness electron sources

    Energy Technology Data Exchange (ETDEWEB)

    Sheffield, R.L.

    1995-07-01

    High energy physics accelerators and free electron lasers put increased demands on the electron beam sources. This paper describes the present research on attaining intense bright electron beams using photoinjectors. Recent results from the experimental programs will be given. The performance advantages and difficulties presently faced by researchers will be discussed, and the following topics will be covered. Progress has been made in photocathode materials, both in lifetime and quantum efficiency. Cesium telluride has demonstrated significantly longer lifetimes than cesium antimonide at 10{sup {minus}8} torr. However, the laser system is more difficult because cesium telluride requires quadrupled YLF instead of the doubled YLF required for cesium antimonide. The difficulty in using photoinjectors is primarily the drive laser, in particular the amplitude stability. Finally, emittance measurements of photoinjector systems can be complicated by the non-thermal nature of the electron beam. An example of the difficulty in measuring beam emittance is given.

  2. Estimation of gradients from scattered data

    Energy Technology Data Exchange (ETDEWEB)

    Stead, S.E.

    1984-01-01

    Many techniques for producing a surface from scattered data require gradients at the data points. Since only positional data are usually known, the gradients must be estimated before the surface can be computed. The quality of the surface depends on the estimated gradients; so it is important to compute accurate estimates.

  3. The nature of solar brightness variations

    Science.gov (United States)

    Shapiro, A. I.; Solanki, S. K.; Krivova, N. A.; Cameron, R. H.; Yeo, K. L.; Schmutz, W. K.

    2017-09-01

    Determining the sources of solar brightness variations1,2, often referred to as solar noise3, is important because solar noise limits the detection of solar oscillations3, is one of the drivers of the Earth's climate system4,5 and is a prototype of stellar variability6,7—an important limiting factor for the detection of extrasolar planets. Here, we model the magnetic contribution to solar brightness variability using high-cadence8,9 observations from the Solar Dynamics Observatory (SDO) and the Spectral And Total Irradiance REconstruction (SATIRE)10,11 model. The brightness variations caused by the constantly evolving cellular granulation pattern on the solar surface were computed with the Max Planck Institute for Solar System Research (MPS)/University of Chicago Radiative Magnetohydrodynamics (MURaM)12 code. We found that the surface magnetic field and granulation can together precisely explain solar noise (that is, solar variability excluding oscillations) on timescales from minutes to decades, accounting for all timescales that have so far been resolved or covered by irradiance measurements. We demonstrate that no other sources of variability are required to explain the data. Recent measurements of Sun-like stars by the COnvection ROtation and planetary Transits (CoRoT)13 and Kepler14 missions uncovered brightness variations similar to that of the Sun, but with a much wider variety of patterns15. Our finding that solar brightness variations can be replicated in detail with just two well-known sources will greatly simplify future modelling of existing CoRoT and Kepler as well as anticipated Transiting Exoplanet Survey Satellite16 and PLAnetary Transits and Oscillations of stars (PLATO)17 data.

  4. Comparison of distributed vortex receptivity coefficients at excitation of 3D TS-waves in presence and absence of surface waviness and pressure gradient

    Science.gov (United States)

    Borodulin, V. I.; Ivanov, A. V.; Kachanov, Y. S.; Mischenko, D. A.; Fedenkova, A. A.

    2016-10-01

    The paper is devoted to quantitative experimental investigation of effective mechanisms of excitation of 3D TS instability waves due to distributed boundary layer receptivity to free-stream vortices. Experiments carried out in a self-similar boundary layer with Hartree parameter βH = -0.115 and concentrated on studying two receptivity mechanisms connected with distributed scattering of 3D unsteady free-stream vortices both on the natural boundary layer nonuniformity (smooth surface) and on 2D surface nonuniformity (waviness). Obtained quantitative characteristics (distributed receptivity coefficients) are compared directly with those obtained in Blasius boundary layer. It is found that the adverse pressure gradient leads to reduction of efficiency of the vortex-roughness receptivity mechanism.

  5. Gradient Evolution of Body Colouration in Surface- and Cave-Dwelling Poecilia mexicana and the Role of Phenotype-Assortative Female Mate Choice

    Directory of Open Access Journals (Sweden)

    David Bierbach

    2013-01-01

    Full Text Available Ecological speciation assumes reproductive isolation to be the product of ecologically based divergent selection. Beside natural selection, sexual selection via phenotype-assortative mating is thought to promote reproductive isolation. Using the neotropical fish Poecilia mexicana from a system that has been described to undergo incipient ecological speciation in adjacent, but ecologically divergent habitats characterized by the presence or absence of toxic H2S and darkness in cave habitats, we demonstrate a gradual change in male body colouration along the gradient of light/darkness, including a reduction of ornaments that are under both inter- and intrasexual selection in surface populations. In dichotomous choice tests using video-animated stimuli, we found surface females to prefer males from their own population over the cave phenotype. However, female cave fish, observed on site via infrared techniques, preferred to associate with surface males rather than size-matched cave males, likely reflecting the female preference for better-nourished (in this case: surface males. Hence, divergent selection on body colouration indeed translates into phenotype-assortative mating in the surface ecotype, by selecting against potential migrant males. Female cave fish, by contrast, do not have a preference for the resident male phenotype, identifying natural selection against migrants imposed by the cave environment as the major driver of the observed reproductive isolation.

  6. Foveal to peripheral extrapolation of brightness within objects.

    Science.gov (United States)

    Toscani, Matteo; Gegenfurtner, Karl R; Valsecchi, Matteo

    2017-08-01

    Peripheral viewing is characterized by poor resolution and distortions as compared to central viewing; nevertheless, when we move our gaze around, the visual scene does not appear to change. One possible mechanism leading to perceptual uniformity would be that peripheral appearance is extrapolated based on foveal information. Here we investigate foveal-to-peripheral extrapolation in the case of the perceived brightness of an object's surface. While fixating a spot on the rendered object, observers were asked to adjust the brightness of a disc to match a peripherally viewed target area on the surface of the same object. Being forced to fixate a better illuminated point led to brighter matches as compared to fixating points in the shadow, indicating that foveal brightness information was extrapolated. When observers fixated additional points outside of the object on the scene's background, fixated brightness had no effect on the brightness match. Results indicate that our visual system uses the brightness of the foveally viewed surface area to estimate the brightness of areas in the periphery. However, this mechanism is selectively applied within an object's boundary.

  7. A comparison between evaporation ponds and evaporation surfaces as a source of the concentrated salt brine for salt gradient maintenance at Tajoura solar pond

    International Nuclear Information System (INIS)

    Ramadan, Abdulghani M.; Agha, Khairy R.; Abughres, M.

    2012-01-01

    One of the main problems that negatively affect the operation of salt gradient solar ponds and influence its thermal stability is the maintenance of salt gradient profile. Evaporation pond (EP) is designed to generate the salt which lost upward salt diffusion from the lower convective zone (LCZ) of the solar pond. Another attractive method is the evaporation surface facility (ES). Regions with moderate to high precipitation favor Evaporation Surface over Evaporation Ponds. Dry climates will generally favor Evaporation Ponds for the brine re-concentration. In previous studies [1-3], the authors have shown that the (EP) of Tajoura's Experimental Solar Pond (TESP) is under sized and can provide only about 30% of the salt required by a Salt Gradient Solar Pond (SGSP). The anticipated size of (EP) was estimated and presented in those studies under different design conditions, including Summer, Autumn and Spring designs, while the winter design was excluded due to the low rates of net evaporation during the winter season. In addition, the results presented were predicted for the first three years of operation. The daily variations of brine concentration in the (EP) of (TESP) and those based on different designs were predicted and discussed under different scenarios. The quantities of brine provided by the evaporation pond and that required by SGSP were predicted for both cases of surface water flushing (fresh water and sea-water) under the different design conditions as shown in Table 1. This paper investigates the differences between (EP) and (ES) both as a source for salt brine generation by evaporation. The effect of (EP) depth on the area ratio and daily variations of salt concentrations for three years of operation is shown. Results show that evaporation can be a reasonable method for salt brine generation. Reducing the depth of (EP) improves the capability of (EP) for brine re-concentration. It also increases the (EP) surface area for the same quantity of

  8. Chemical loading into surface water along a hydrological, biogeochemical, and land use gradient: A holistic watershed approach

    Science.gov (United States)

    Barber, L.B.; Murphy, S.F.; Verplanck, P.L.; Sandstrom, M.W.; Taylor, Howard E.; Furlong, E.T.

    2006-01-01

    Identifying the sources and impacts of organic and inorganic contaminants at the watershed scale is a complex challenge because of the multitude of processes occurring in time and space. Investigation of geochemical transformations requires a systematic evaluation of hydrologic, landscape, and anthropogenic factors. The 1160 km2 Boulder Creek Watershed in the Colorado Front Range encompasses a gradient of geology, ecotypes, climate, and urbanization. Streamflow originates primarily as snowmelt and shows substantial annual variation. Water samples were collected along a 70-km transect during spring-runoff and base-flow conditions, and analyzed for major elements, trace elements, bulk organics, organic wastewater contaminants (OWCs), and pesticides. Major-element and trace-element concentrations were low in the headwaters, increased through the urban corridor, and had a step increase downstream from the first major wastewater treatment plant (WWTP). Boron, gadolinium, and lithium were useful inorganic tracers of anthropogenic inputs. Effluent from the WWTP accounted for as much as 75% of the flow in Boulder Creek and was the largest chemical input. Under both hydrological conditions, OWCs and pesticides were detected in Boulder Creek downstream from the WWTP outfall as well as in the headwater region, and loads of anthropogenic-derived contaminants increased as basin population density increased. This report documents a suite of potential endocrine-disrupting chemicals in a reach of stream with native fish populations showing indication of endocrine disruption.

  9. Bright Streaks and Dark Fans

    Science.gov (United States)

    2007-01-01

    The south polar region of Mars is covered every year by a layer of carbon dioxide ice. In a region called the 'cryptic terrain,' the ice is translucent and sunlight can penetrate through the ice to warm the surface below. The ice layer sublimates (evaporates) from the bottom. The dark fans of dust seen in this image come from the surface below the layer of ice, carried to the top by gas venting from below. The translucent ice is 'visible' by virtue of the effect it has on the tone of the surface below, which would otherwise have the same color and reflectivity as the fans. Bright streaks in this image are fresh frost. The CRISM team has identified the composition of these streaks to be carbon dioxide. Observation Geometry Image PSP_003113_0940 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on 26-Mar-2007. The complete image is centered at -85.8 degrees latitude, 106.0 degrees East longitude. The range to the target site was 244.9 km (153.0 miles). At this distance the image scale is 49.0 cm/pixel (with 2 x 2 binning) so objects 147 cm across are resolved. The image shown here has been map-projected to 50 cm/pixel . The image was taken at a local Mars time of 06:20 PM and the scene is illuminated from the west with a solar incidence angle of 79 degrees, thus the sun was about 11 degrees above the horizon. At a solar longitude of 207.6 degrees, the season on Mars is Northern Autumn.

  10. Spatially resolved surface valence gradient and structural transformation of lithium transition metal oxides in lithium-ion batteries.

    Science.gov (United States)

    Liu, Hanshuo; Bugnet, Matthieu; Tessaro, Matteo Z; Harris, Kristopher J; Dunham, Mark J R; Jiang, Meng; Goward, Gillian R; Botton, Gianluigi A

    2016-10-26

    Layered lithium transition metal oxides are one of the most important types of cathode materials in lithium-ion batteries (LIBs) that possess high capacity and relatively low cost. Nevertheless, these layered cathode materials suffer structural changes during electrochemical cycling that could adversely affect the battery performance. Clear explanations of the cathode degradation process and its initiation, however, are still under debate and not yet fully understood. We herein systematically investigate the chemical evolution and structural transformation of the LiNi x Mn y Co 1-x-y O 2 (NMC) cathode material in order to understand the battery performance deterioration driven by the cathode degradation upon cycling. Using high-resolution electron energy loss spectroscopy (HR-EELS) we clarify the role of transition metals in the charge compensation mechanism, particularly the controversial Ni 2+ (active) and Co 3+ (stable) ions, at different states-of-charge (SOC) under 4.6 V operation voltage. The cathode evolution is studied in detail from the first-charge to long-term cycling using complementary diagnostic tools. With the bulk sensitive 7 Li nuclear magnetic resonance (NMR) measurements, we show that the local ordering of transition metal and Li layers (R3[combining macron]m structure) is well retained in the bulk material upon cycling. In complement to the bulk measurements, we locally probe the valence state distribution of cations and the surface structure of NMC particles using EELS and scanning transmission electron microscopy (STEM). The results reveal that the surface evolution of NMC is initiated in the first-charging step with a surface reduction layer formed at the particle surface. The NMC surface undergoes phase transformation from the layered structure to a poor electronic and ionic conducting transition-metal oxide rock-salt phase (R3[combining macron]m → Fm3[combining macron]m), accompanied by irreversible lithium and oxygen loss. In addition to

  11. An Ultraviolet/Optical Atlas of Bright Galaxies

    Science.gov (United States)

    Marcum, Pamela M.; O'Connell, Robert W.; Fanelli, Michael N.; Cornett, Robert H.; Waller, William H.; Bohlin, Ralph C.; Neff, Susan G.; Roberts, Morton S.; Smith, Andrew M.; Cheng, K.-P.; Collins, Nicholas R.; Hennessy, Gregory S.; Hill, Jesse K.; Hill, Robert S.; Hintzen, Paul; Landsman, Wayne B.; Ohl, Raymond G.; Parise, Ronald A.; Smith, Eric P.; Freedman, Wendy L.; Kuchinski, Leslie E.; Madore, Barry; Angione, Ronald; Palma, Christopher; Talbert, Freddie; Stecher, Theodore P.

    2001-02-01

    We present wide-field imagery and photometry of 43 selected nearby galaxies of all morphological types at ultraviolet and optical wavelengths. The ultraviolet (UV) images, in two broad bands at 1500 and 2500 Å, were obtained using the Ultraviolet Imaging Telescope (UIT) during the Astro-1 Spacelab mission. The UV images have ~3" resolution, and the comparison sets of ground-based CCD images (in one or more of B, V, R, and Hα) have pixel scales and fields of view closely matching the UV frames. The atlas consists of multiband images and plots of UV/optical surface brightness and color profiles. Other associated parameters, such as integrated photometry and half-light radii, are tabulated. In an appendix, we discuss the sensitivity of different wavebands to a galaxy's star formation history in the form of ``history weighting functions'' and emphasize the importance of UV observations as probes of evolution during the past 10-1000 Myr. We find that UV galaxy morphologies are usually significantly different from visible band morphologies as a consequence of spatially inhomogeneous stellar populations. Differences are quite pronounced for systems in the middle range of Hubble types, Sa through Sc, but less so for ellipticals or late-type disks. Normal ellipticals and large spiral bulges are fainter and more compact in the UV. However, they typically exhibit smooth UV profiles with far-UV/optical color gradients which are larger than any at optical/IR wavelengths. The far-UV light in these cases is probably produced by extreme horizontal branch stars and their descendants in the dominant, low-mass, metal-rich population. The cool stars in the large bulges of Sa and Sb spirals fade in the UV while hot OB stars in their disks brighten, such that their Hubble classifications become significantly later. In the far-UV, early-type spirals often appear as peculiar, ringlike systems. In some spiral disks, UV-bright structures closely outline the spiral pattern; in others, the

  12. Organochlorine pesticides and polychlorinated biphenyls along an east-to-west gradient in subtropical North Atlantic surface water.

    Science.gov (United States)

    Lammel, Gerhard; Spitzy, Alejandro; Audy, Ondřej; Beckmann, Sabine; Codling, Garry P; Kretzschmann, Lisett; Kukučka, Petr; Stemmler, Irene

    2017-04-01

    Despite the fact that most persistent toxic substances have hardly been primarily emitted for several decades, their concentrations are only slowly decreasing in the global oceans. Surface seawater samples were collected along a 38°-24° N/28°-67° W transect in the subtropical North Atlantic Ocean. While the concentration levels of hexachlorobenzene (2.1-6.1 pg L -1 ), dichlorodiphenyltrichloroethane (DDT, up to 2.1 pg L -1 ) and polychlorinated biphenyls (PCB, 10.8-24.9 pg L -1 ) were in the same range as observed earlier in the North Atlantic, hexachlorocyclohexane (HCH, 90-627 pg L -1 ) was found elevated, partly also relative to previous measurements in the same sea region. Hereby, the ratio α-HCH/γ-HCH was very low, 0.09-0.13. Chlordane and endosulfan were found in the range pollution patterns in surface seawaters seem to be determined by atmospheric and oceanic transport patterns, rather than by mixing and air-sea equilibrium. The comparison with global multicompartment chemistry-transport model predictions of surface seawater levels indicate underestimated degradation of PCBs and overestimated emissions of endosulfan.

  13. Effects of land use types on surface water quality across an anthropogenic disturbance gradient in the upper reach of the Hun River, Northeast China.

    Science.gov (United States)

    Wang, Ruizhao; Xu, Tianle; Yu, Lizhong; Zhu, Jiaojun; Li, Xiaoyu

    2013-05-01

    Surface water quality is vulnerable to pollution due to human activities. The upper reach of the Hun River is an important water source that supplies 52 % of the storage capacity of the Dahuofang Reservoir, the largest reservoir for drinking water in Northeast China, which is suffering from various human-induced changes in land use, including deforestation, reclamation/farming, urbanization and mine exploitation. To investigate the impacts of land use types on surface water quality across an anthropogenic disturbance gradient at a local scale, 11 physicochemical parameters (pH, dissolved oxygen [DO], turbidity, oxygen redox potential, conductivity, biochemical oxygen demand [BOD5], chemical oxygen demand [COD], total nitrogen [TN], total phosphorus [TP], NO(3)(-)N, and NH(4)(+)-N) of water from 12 sampling sites along the upper reach of the Hun River were monitored monthly during 2009-2010. The sampling sites were classified into four groups (natural, near-natural, more disturbed, and seriously disturbed). The water quality exhibited distinct spatial and temporal characteristics; conductivity, TN, and NO(3)(-)-N were identified as key parameters indicating the water quality variance. The forest and farmland cover types played significant roles in determining the surface water quality during the low-flow, high-flow, and mean-flow periods based on the results of a stepwise linear regression. These results may provide incentive for the local government to consider sustainable land use practices for water conservation.

  14. Microbial Community and Biochemical Dynamics of Biological Soil Crusts across a Gradient of Surface Coverage in the Central Mojave Desert

    Directory of Open Access Journals (Sweden)

    Rakesh Mogul

    2017-10-01

    Full Text Available In this study, we expand upon the biogeography of biological soil crusts (BSCs and provide molecular insights into the microbial community and biochemical dynamics along the vertical BSC column structure, and across a transect of increasing BSC surface coverage in the central Mojave Desert, CA, United States. Next generation sequencing reveals a bacterial community profile that is distinct among BSCs in the southwestern United States. Distribution of major phyla in the BSC topsoils included Cyanobacteria (33 ± 8%, Proteobacteria (26 ± 6%, and Chloroflexi (12 ± 4%, with Phormidium being the numerically dominant genus. Furthermore, BSC subsurfaces contained Proteobacteria (23 ± 5%, Actinobacteria (20 ± 5%, and Chloroflexi (18 ± 3%, with an unidentified genus from Chloroflexi (AKIW781, order being numerically dominant. Across the transect, changes in distribution at the phylum (p < 0.0439 and genus (p < 0.006 levels, including multiple biochemical and geochemical trends (p < 0.05, positively correlated with increasing BSC surface coverage. This included increases in (a Chloroflexi abundance, (b abundance and diversity of Cyanobacteria, (b OTU-level diversity in the topsoil, (c OTU-level differentiation between the topsoil and subsurface, (d intracellular ATP abundances and catalase activities, and (e enrichments in clay, silt, and varying elements, including S, Mn, Co, As, and Pb, in the BSC topsoils. In sum, these studies suggest that BSCs from regions of differing surface coverage represent early successional stages, which exhibit increasing bacterial diversity, metabolic activities, and capacity to restructure the soil. Further, these trends suggest that BSC successional maturation and colonization across the transect are inhibited by metals/metalloids such as B, Ca, Ti, Mn, Co, Ni, Mo, and Pb.

  15. Microbial Community and Biochemical Dynamics of Biological Soil Crusts across a Gradient of Surface Coverage in the Central Mojave Desert.

    Science.gov (United States)

    Mogul, Rakesh; Vaishampayan, Parag; Bashir, Mina; McKay, Chris P; Schubert, Keith; Bornaccorsi, Rosalba; Gomez, Ernesto; Tharayil, Sneha; Payton, Geoffrey; Capra, Juliana; Andaya, Jessica; Bacon, Leonard; Bargoma, Emily; Black, David; Boos, Katie; Brant, Michaela; Chabot, Michael; Chau, Danny; Cisneros, Jessica; Chu, Geoff; Curnutt, Jane; DiMizio, Jessica; Engelbrecht, Christian; Gott, Caroline; Harnoto, Raechel; Hovanesian, Ruben; Johnson, Shane; Lavergne, Britne; Martinez, Gabriel; Mans, Paul; Morales, Ernesto; Oei, Alex; Peplow, Gary; Piaget, Ryan; Ponce, Nicole; Renteria, Eduardo; Rodriguez, Veronica; Rodriguez, Joseph; Santander, Monica; Sarmiento, Khamille; Scheppelmann, Allison; Schroter, Gavin; Sexton, Devan; Stephenson, Jenin; Symer, Kristin; Russo-Tait, Tatiane; Weigel, Bill; Wilhelm, Mary B

    2017-01-01

    In this study, we expand upon the biogeography of biological soil crusts (BSCs) and provide molecular insights into the microbial community and biochemical dynamics along the vertical BSC column structure, and across a transect of increasing BSC surface coverage in the central Mojave Desert, CA, United States. Next generation sequencing reveals a bacterial community profile that is distinct among BSCs in the southwestern United States. Distribution of major phyla in the BSC topsoils included Cyanobacteria (33 ± 8%), Proteobacteria (26 ± 6%), and Chloroflexi (12 ± 4%), with Phormidium being the numerically dominant genus. Furthermore, BSC subsurfaces contained Proteobacteria (23 ± 5%), Actinobacteria (20 ± 5%), and Chloroflexi (18 ± 3%), with an unidentified genus from Chloroflexi (AKIW781, order) being numerically dominant. Across the transect, changes in distribution at the phylum ( p < 0.0439) and genus ( p < 0.006) levels, including multiple biochemical and geochemical trends ( p < 0.05), positively correlated with increasing BSC surface coverage. This included increases in (a) Chloroflexi abundance, (b) abundance and diversity of Cyanobacteria, (b) OTU-level diversity in the topsoil, (c) OTU-level differentiation between the topsoil and subsurface, (d) intracellular ATP abundances and catalase activities, and (e) enrichments in clay, silt, and varying elements, including S, Mn, Co, As, and Pb, in the BSC topsoils. In sum, these studies suggest that BSCs from regions of differing surface coverage represent early successional stages, which exhibit increasing bacterial diversity, metabolic activities, and capacity to restructure the soil. Further, these trends suggest that BSC successional maturation and colonization across the transect are inhibited by metals/metalloids such as B, Ca, Ti, Mn, Co, Ni, Mo, and Pb.

  16. Teradiode's high brightness semiconductor lasers

    Science.gov (United States)

    Huang, Robin K.; Chann, Bien; Burgess, James; Lochman, Bryan; Zhou, Wang; Cruz, Mike; Cook, Rob; Dugmore, Dan; Shattuck, Jeff; Tayebati, Parviz

    2016-03-01

    TeraDiode is manufacturing multi-kW-class ultra-high brightness fiber-coupled direct diode lasers for industrial applications. A fiber-coupled direct diode laser with a power level of 4,680 W from a 100 μm core diameter, record brightness levels for direct diode lasers. The fiber-coupled output corresponds to a Beam Parameter Product (BPP) of 3.5 mm-mrad and is the lowest BPP multi-kW-class direct diode laser yet reported. This laser is suitable for industrial materials processing applications, including sheet metal cutting and welding. This 4-kW fiber-coupled direct diode laser has comparable brightness to that of industrial fiber lasers and CO2 lasers, and is over 10x brighter than state-of-the-art direct diode lasers. We have also demonstrated novel high peak power lasers and high brightness Mid-Infrared Lasers.

  17. Relative significance of microtopography and vegetation as controls on surface water flow on a low-gradient floodplain

    Science.gov (United States)

    Choi, Jungyill; Harvey, Judson W.

    2014-01-01

    Surface water flow controls water velocities, water depths, and residence times, and influences sediment and nutrient transport and other ecological processes in shallow aquatic systems. Flow through wetlands is substantially influenced by drag on vegetation stems but is also affected by microtopography. Our goal was to use microtopography data directly in a widely used wetland model while retaining the advantages of the model’s one-dimensional structure. The base simulation with no explicit treatment of microtopography only performed well for a period of high water when vegetation dominated flow resistance. Extended simulations using microtopography can improve the fit to low-water conditions substantially. The best fit simulation had a flow conductance parameter that decreased in value by 70 % during dry season such that mcrotopographic features blocked 40 % of the cross sectional width for flow. Modeled surface water became ponded and flow ceased when 85 % of the cross sectional width became blocked by microtopographic features. We conclude that vegetation drag dominates wetland flow resistance at higher water levels and microtopography dominates at low water levels with the threshold delineated by the top of microtopographic features. Our results support the practicality of predicting flow on floodplains using relatively easily measured physical and biological variables.

  18. Bright new world

    Energy Technology Data Exchange (ETDEWEB)

    Kroó, Norbert; Rácz, Péter [Wigner Research Centre for Physics of the Hungarian Academy of Sciences, Institute for Solid State Physics and Optics, H-1525 Budapest, Pf. 49 (Hungary); Varró, Sándor [Wigner Research Centre for Physics of the Hungarian Academy of Sciences, Institute for Solid State Physics and Optics, H-1525 Budapest, Pf. 49 (Hungary); ELI-ALPS, ELI-Hu Nonprofit Kft., Dugonics tér 13, H-6720 Szeged (Hungary)

    2016-02-15

    Surface plasmons (SPOs) have been excited by intense femtosecond laser pulses on a gold film at room temperature and their near field has been analyzed by the intensity dependent response of an STM and by studying the spectra of multiplasmon emitted electrons. Around 80 GW/cm{sup 2} laser intensity, anomalies have been found in both cases, interpreted as the stepping in of electron pairing, transition to a diamagnetic state, and by anomalous Faraday rotation.

  19. The Los Alamos high-brightness photoinjector

    Energy Technology Data Exchange (ETDEWEB)

    O' Shea, P.G.

    1991-01-01

    For a number of years Los Alamos National Laboratory has been developing photocathode RF guns for high-brightness electron beam applications such as free-electron lasers (FELs). Previously thermionic high-voltage guns have been the source of choice for the electron accelerators used to drive FELs. The performance of such FELs is severely limited by the emittance growth produced by the subharmonic bunching process and also by the low peak current of the source. In a photoinjector, a laser driven photocathode is placed directly in a high-gradient RF accelerating cavity. A photocathode allows unsurpassed control over the current, and the spatial and temporal profile of the beam. In addition the electrodeless emission'' avoids many of the difficulties associated with multi-electrode guns, i.e. the electrons are accelerated very rapidly to relativistic energies, and there are no electrodes to distort the accelerating fields. For the past two years we have been integrating a photocathode into our existing FEL facility by replacing our thermionic gun and subharmonic bunchers with a high-gradient 1.3 GHz photoinjector. The photoinjector, which is approximately 0.6 m in length, produces 6 MeV, 300 A, 15 ps linac, and accelerated to a final energy of 40 MeV. We have recently begun lasing at wavelengths near 3 {mu}m. 16 refs., 2 figs., 5 tabs.

  20. Bright Light Treatment in Psychiatry

    Directory of Open Access Journals (Sweden)

    Pinar Guzel Ozdemir

    2017-06-01

    Full Text Available Bright light treatment is a treatment modality that leads elevation of mood due to attenuation in depressive symptoms, regulation in circadian rhythm activity, increase the effect of antidepressants and amelioration in sleep quality. Bright light treatment is considered among the first-line treatments for seasonal affective disorder because of high response rates. Additionally, bright light treatment being extended to other conditions, including non-seasonal mood disorders, Alzheimer's disease, circadian rhythm sleep disorders, eating disorders, attention deficit hyperactivity disorder and other behavioral syndromes is likely to have a far reached use. Side effects are often temporary and can generally be overcome by reducing exposure time. The central focus on this paper is to review the action mechanisms, efficacy, usage areas, the ways of administration and side effects of the light treatment. [Psikiyatride Guncel Yaklasimlar - Current Approaches in Psychiatry 2017; 9(2.000: 177-188

  1. Development of symmetric composition-gradient materials including hard particles in its surface layer; Hyosobu ni koshitsu ryushi wo fukumu taishogata sosei keisha zairyo no kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-03-01

    Development of new materials with both thermal resistance and thermal shock resistance was studied on the basis of symmetric ceramics/metal/ceramics gradient composition. Al2O3/TiC/Ni/TiC/Al2O3 was used as material model of basic composition, and the system was selected where WC-Co system alloy hard particles were dispersed into the Al2O3 ceramic surface layer. The layered material was sintered in N2 gas atmosphere by SHS/HIP method using exothermic caused by nitriding reaction. Since cracks were generated in some specimens of 5-layer structure, improved specimens of 7-layer structure were prepared. To examine the effect of a particle size on toughness, WC-Co system alloy specimens with different particle sizes were also prepared. As a result, no cracks were found, and residual stress and fracture toughness were affected by particle size. In addition, the following were studied: technique of mass production, observation of fine structures, analysis of thermal stress, thermal shock resistance, and friction and abrasion characteristics. 13 refs., 65 figs., 15 tabs.

  2. Wireless SAW Based Temperature Gradient Sensor Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Prime Photonics proposes design and development of a surface acoustic wave (SAW) based temperature gradient sensor for instrumentation of thermal protection systems...

  3. Variation reduction of brightness and pH of pulp sent to a paper mill

    Directory of Open Access Journals (Sweden)

    Napassavong Rojanarowan

    2015-03-01

    Full Text Available The variance of the brightness of pulp sent to the paper mill during the changing period of dry pulp grades affects the chemical control in the paper mill. This research aims to determine the mixing formula of pulp with different brightness from the EOP and D1 stages to handle this variation issue. This research uses response surface design with Central Composite Design type, regression technique and optimization technique to find the optimal setting of the mixing formula for each of the seven brightness levels to obtain the target brightness of 86% and the pH of 5.25. The mixing formulas are determined by the pulp mixing percentage and the sulfuric acid consumption. The experimental results reveal that when using higher EOP mixing ratio, the brightness decreases and the pH increases. Regarding the effect of the sulfuric acid, increasing the sulfuric acid makes the brightness and the pH decrease. After implementing the optimal formula in the production line, the mean of pulp brightness is closer to the target compared with the brightness before improvement and the brightness variation decreases without affecting the quality of other pulp grades, average of brightness decreased from 87.4% to 86.3% and standard deviation of brightness decreased from 1.09 to 0.46.

  4. Surface complexation modeling of groundwater arsenic mobility: Results of a forced gradient experiment in a Red River flood plain aquifer, Vietnam

    Science.gov (United States)

    Jessen, Søren; Postma, Dieke; Larsen, Flemming; Nhan, Pham Quy; Hoa, Le Quynh; Trang, Pham Thi Kim; Long, Tran Vu; Viet, Pham Hung; Jakobsen, Rasmus

    2012-12-01

    Three surface complexation models (SCMs) developed for, respectively, ferrihydrite, goethite and sorption data for a Pleistocene oxidized aquifer sediment from Bangladesh were used to explore the effect of multicomponent adsorption processes on As mobility in a reduced Holocene floodplain aquifer along the Red River, Vietnam. The SCMs for ferrihydrite and goethite yielded very different results. The ferrihydrite SCM favors As(III) over As(V) and has carbonate and silica species as the main competitors for surface sites. In contrast, the goethite SCM has a greater affinity for As(V) over As(III) while PO43- and Fe(II) form the predominant surface species. The SCM for Pleistocene aquifer sediment resembles most the goethite SCM but shows more Si sorption. Compiled As(III) adsorption data for Holocene sediment was also well described by the SCM determined for Pleistocene aquifer sediment, suggesting a comparable As(III) affinity of Holocene and Pleistocene aquifer sediments. A forced gradient field experiment was conducted in a bank aquifer adjacent to a tributary channel to the Red River, and the passage in the aquifer of mixed groundwater containing up to 74% channel water was observed. The concentrations of As (SCM correctly predicts desorption for As(III) but for Si and PO43- it predicts an increased adsorption instead of desorption. The goethite SCM correctly predicts desorption of both As(III) and PO43- but failed in the prediction of Si desorption. These results indicate that the prediction of As mobility, by using SCMs for synthetic Fe-oxides, will be strongly dependent on the model chosen. The SCM based on the Pleistocene aquifer sediment predicts the desorption of As(III), PO43- and Si quite superiorly, as compared to the SCMs for ferrihydrite and goethite, even though Si desorption is still somewhat under-predicted. The observation that a SCM calibrated on a different sediment can predict our field results so well suggests that sediment based SCMs may be a

  5. Helmholtz bright and boundary solitons

    International Nuclear Information System (INIS)

    Christian, J M; McDonald, G S; Chamorro-Posada, P

    2007-01-01

    We report, for the first time, exact analytical boundary solitons of a generalized cubic-quintic nonlinear Helmholtz (NLH) equation. These solutions have a linked-plateau topology that is distinct from conventional dark soliton solutions; their amplitude and intensity distributions are spatially delocalized and connect regions of finite and zero wave-field disturbances (suggesting also the classification as 'edge solitons'). Extensive numerical simulations compare the stability properties of recently derived Helmholtz bright solitons, for this type of polynomial nonlinearity, to those of the new boundary solitons. The latter are found to possess a remarkable stability characteristic, exhibiting robustness against perturbations that would otherwise lead to the destabilizing of their bright-soliton counterparts

  6. High brightness semiconductor lasers with reduced filamentation

    DEFF Research Database (Denmark)

    McInerney, John; O'Brien, Peter.; Skovgaard, Peter M. W.

    1999-01-01

    High brightness semiconductor lasers have applications in spectroscopy, fiber lasers, manufacturing and materials processing, medicine and free space communication or energy transfer. The main difficulty associated with high brightness is that, because of COD, high power requires a large aperture...

  7. 150 southern compact and bright-nucleus galaxies

    International Nuclear Information System (INIS)

    Fairall, A.P.

    1977-01-01

    Galaxies having regions of exceptionally high surface brightness have been selected from the ESO Quick Blue Survey and investigated by 'grating photography' -direct photography plus low-dispersion slitless spectroscopy. Two new Seyfert galaxies and a peculiar multiple system have been discovered. Differences in red continua are also noted. (author)

  8. Near-infrared photometry of bright elliptical galaxies

    NARCIS (Netherlands)

    Peletier, R. F.; Valentijn, E. A.; Jameson, R. F.

    High-quality visual-infrared color profiles have been determined for elliptical galaxies for the first time. Surface photometry in J and K is presented for 12 bright elliptical galaxies, and the results have been combined with CCD data in visual passbands. It is shown that the galaxies become bluer

  9. Next generation diode lasers with enhanced brightness

    Science.gov (United States)

    Ried, S.; Rauch, S.; Irmler, L.; Rikels, J.; Killi, A.; Papastathopoulos, E.; Sarailou, E.; Zimer, H.

    2018-02-01

    High-power diode lasers are nowadays well established manufacturing tools in high power materials processing, mainly for tactile welding, surface treatment and cladding applications. Typical beam parameter products (BPP) of such lasers range from 30 to 50 mm·mrad at several kilowatts of output power. TRUMPF offers a product line of diode lasers to its customers ranging from 150 W up to 6 kW of output power. These diode lasers combine high reliability with small footprint and high efficiency. However, up to now these lasers are limited in brightness due to the commonly used spatial and coarse spectral beam combining techniques. Recently diode lasers with enhanced brightness have been presented by use of dense wavelength multiplexing (DWM). In this paper we report on TRUMPF's diode lasers utilizing DWM. We demonstrate a 2 kW and a 4 kW system ideally suited for fine welding and scanner welding applications. The typical laser efficiency is in the range of 50%. The system offers plug and play exchange of the fiber beam delivery cable, multiple optical outputs and integrated cooling in a very compact package. An advanced control system offers flexible integration in any customer's shop floor environment and includes industry 4.0 capabilities (e.g. condition monitoring and predictive maintenance).

  10. High-brightness rf linear accelerators

    International Nuclear Information System (INIS)

    Jameson, R.A.

    1986-01-01

    The issue of high brightness and its ramifications in linacs driven by radio-frequency fields is discussed. A history of the RF linacs is reviewed briefly. Some current applications are then examined that are driving progress in RF linacs. The physics affecting the brightness of RF linacs is then discussed, followed by the economic feasibility of higher brightness machines

  11. Structure of bright-rimmed molecular clouds

    International Nuclear Information System (INIS)

    Wootten, A.; Sargent, A.; Knapp, G.; Huggins, P.J.

    1983-01-01

    Five bright-rimmed molecular clouds, NGC 1977, IC 1396, IC 1848 A, B35, and NGC 7822, have been mapped with 30'' resolution in the J = 2--1 lines of 12 co. For the first three, 13 CO maps have also been made. The spatial distributions of temperature, density, and molecular abundance in these clouds have been determined, particularly in the vicinity of the rims. In general, the gas densities increase close to the rims, but temperature enhancements occur over comparatively extended regions. Near the rims the gas kinematics is varied: velocity gradients are observed in several regions, and in IC 1396 line broadening is distinguishable. A detailed study of the excitation of 13 CO demonstrates that near the well-resolved rim in NGC 1977 where C I and carbon recombination lines have been observed, there is a definite decline in the CO abundance. These molecular clouds span a variety of stages of star formation, but in none does the interaction with the adjacent H II region appear to have substantially affected the course of the star-forming history of the cloud

  12. Bright Stuff on Ceres = Sulfates and Carbonates on CI Chondrites

    Science.gov (United States)

    Zolensky, Michael; Chan, Queenie H. S.; Gounelle, Matthieu; Fries, Marc

    2016-01-01

    Recent reports of the DAWN spacecraft's observations of the surface of Ceres indicate that there are bright areas, which can be explained by large amounts of the Mg sulfate hexahydrate (MgSO4•6(H2O)), although the identification appears tenuous. There are preliminary indications that water is being evolved from these bright areas, and some have inferred that these might be sites of contemporary hydro-volcanism. A heat source for such modern activity is not obvious, given the small size of Ceres, lack of any tidal forces from nearby giant planets, probable age and presumed bulk composition. We contend that observations of chondritic materials in the lab shed light on the nature of the bright spots on Ceres

  13. Coast-to-interior gradients and recent trends in physical and chemical properties of near-surface snow and firn in northwest Greenland

    Science.gov (United States)

    Wong, G. J.; Osterberg, E. C.; Hawley, R. L.; Caughey, S. K.; Courville, Z.; Howley, J.; Lutz, E.; Overly, T. B.

    2013-12-01

    The Greenland Ice Sheet (GIS), which holds enough ice to raise global sea levels by approximately 7 m, is a major driver of Arctic and global climate. Observations over the past two decades have documented changes including notable increases in ice discharge, significant warming in coastal regions, and expanded areal extent of annual surface melt (e.g., Rignot and Thomas, 2002; Mote, 2007; Hanna and others, 2008). In contrast, observations document little change in temperature or accumulation in the central regions of the ice sheet (Hanna and others, 2008, 2011). The 1120 km-long Greenland Inland Traverse (GrIT), between Thule Air Base in northwest Greenland and Summit Station in central Greenland, is a logistics traverse that follows a nearly identical route taken by Carl Benson and the US Army Snow, Ice and Permafrost Research Establishment (SIPRE) between 1952 and 1955 (Benson, 1962). Observations from the SIPRE and GrIT traverses provide two snapshots of surface conditions across the northwest region of the GIS separated by 56 years. Hawley and others (in review) observe an increase in snow accumulation rates along the GrIT traverse route based on internal reflecting horizons in radar data dated with firn cores, with larger accumulation increases observed in the coastal region near Thule. Here we expand upon the analysis of Hawley and others (in review) by determining coast-to-interior gradients in snow accumulation, density, hardness (Rammsonde), and snow chemistry using samples from 18 snow pits and 3 firn cores collected during the 2010 and 2011 GrIT traverses. Snow pit and firn core samples were analyzed for trace element (23Na, 24Mg, 27Al, 32S, 39K, 44Ca, 47Ti, 51V, 52Cr, 55Mn, 56Fe, 59Co, 63Cu, 66Zn, 75As, 88Sr, 111Cd, 133Cs, 138Ba, 139La, 140Ce, 141Pr, 208Pb, 209Bi, 238U) concentrations and stable water isotope ratios (δD, δ18O), and were dated by seasonal oscillations in chemical concentrations and isotope ratios. We compare the GrIT data to those of

  14. Temperature-gradient-induced

    Science.gov (United States)

    Park, Cheol; Glaser, Matt; Maclennan, Joe; Clark, Noel; Trittel, Torsten; Stannarius, Ralf

    Freely-suspended smectic films of sub-micrometer thickness and lateral extensions of several millimeters were used to study thermally driven migration and convection in the film plane. Film experiments were performed during the 6 minute microgravity phase of a TEXUS suborbital rocket flight (Texus 52, launched April 27, 2015). We have found an attraction of the smectic material towards the cold edge of the film in a temperature gradient, similar to the Soret effect. This process is reversed when this edge is heated up again. Thermal convection driven by two thermocontacts in the film is practically absent, even at temperature gradients up to 10 K/mm, with thermally driven convection only setting in when the hot post reaches the transition temperature to the nematic phase. The Observation and Analysis of Smectic Islands in Space (OASIS) flight hardware was launched on SpaceX-6 in April 2015 and experiments on smectic bubbles were carried out on the International Space Station using four different smectic A and C liquid crystal materials in separate sample chambers. We observed that smectic islands on the surface of the bubbles migrated towards the colder part of the bubble in a temperature gradient. This work was supported by NASA Grant No. NNX-13AQ81G, by the Soft Materials Research Center under NSF MRSEC Grants No. DMR-0820579 and No. DMR-1420736, and by DLR Grants 50WM1127 and 50WM1430.

  15. A Reconstruction of Sea Surface Temperature Gradients and an Assessment of the Suspected Presence of Continental Ice During the Cold Mid-Paleocene (61-57 Ma)

    Science.gov (United States)

    Bijl, P.; Cramwinckel, M.; Frieling, J.; Peterse, F.

    2016-12-01

    The early Eocene `hothouse' climate experienced paratropical vegetation on high latitudes and high (>1100 ppmv) atmospheric CO2 concentrations. It is generally considered as analogous to the endmember climate state should we use up all available fossil fuels. However, we do not know exactly through which processes this long-term warm episode came to be nor do we understand what the initial climate state was at the onset of this long-term climate. Deep-sea warming towards early Eocene hothouse conditions started in the mid-Paleocene, ending a 2 Myr time interval of relatively cold deep ocean temperatures. Reconstructed pCO2 concentrations of the mid-Paleocene seem to have been close to those of present-day, although data is scarce. The mid-Paleocene is notoriously sparsely represented in shelf sedimentary records, as most records show a conspicuous hiatus between 58 and 60 Mys. This gives the suggestion of a major global low in sea level, which is inconsistent with estimates of global ocean spreading rates, which suggest a relatively high sea level on long time scales for the Cretaceous-early Paleogene. The cold deep-sea temperatures, the conspicuously low sea level and low atmospheric CO2 during the mid-Paleocene have stimulated suggestions of the presence of major ice sheets on the poles, yet the absence of any trace for continental ice, either direct ice-proximal evidence or from benthic foraminiferal oxygen isotope records, calls the presence of such ice sheets into question. I will present a number of high resolution sea surface temperature records (based mostly on organic geochemical biomarker proxies) which start to reveal a latitudinal temperature gradient for the mid-Paleocene. Reconstructions come from shelf sediments from Tasmania, Australia, Tanzania, Tropical Atlantic Ocean, New Jersey). With these new records, I put Paleogene climate evolution into context. I will further present a review of shelf sedimentary records across the mid-paleocene to assess

  16. High-brightness electron injectors

    International Nuclear Information System (INIS)

    Sheffield, R.L.

    1987-01-01

    Free-electron laser (FEL) oscillators and synchrotron light sources require pulse trains of high peak brightness and, in some applications, high-average power. Recent developments in the technology of photoemissive and thermionic electron sources in rf cavities for electron-linac injector applications offer promising advances over conventional electron injectors. Reduced emittance growth in high peak-current electron injectors may be achieved by using high field strengths and by linearizing the radial component of the cavity electric field at the expense of lower shunt impedance

  17. Brightness of the photosphere and faculae at the limb based on eclipse observations

    Energy Technology Data Exchange (ETDEWEB)

    Akimov, L.A.; Belkina, I.L.; Dyatel, N.P.

    1982-05-01

    The absolute distributions of integral and surface brightness of the photospheric continuum (lambdaroughly-equal5870 A) and in faculae at the very limb are obtained from slitless spectrograms of the total solar eclipse of July 10, 1972. Several possible reasons for the brightness increase toward the limb in the distribution of photospheric surface brightness are discussed. The faculae showed high contrasts, up to 1.76 at a height of 200 km from the limb. A comparison of the times of local contacts observed and calculated with allowance for lunar relief showed that the active regions are at about 300 km above the photosphere. A schematic model of a facula is proposed.

  18. Aftereffect of Adaptation to Illusory Brightness

    Directory of Open Access Journals (Sweden)

    Xinguang Cao

    2011-05-01

    Full Text Available Several figures are known to induce illusory brightness. We tested whether adaptation to illusory brightness produced an aftereffect in brightness. After viewing a gray square area having illusory brightness (e.g., due to brightness contrast or illusory contours for ten seconds, the illusion-inducing surround vanished. After three seconds, subjects reported whether the square area was seen as brighter than, darker than, or the same brightness as a control gray square area. The luminance of the tested square area was physically unchanged. The results show that when the black surround inducing brightness contrast suddenly became gray (i.e., vanished, the center gray square tended to look darker than a control gray square. Similarly, after viewing a subjective square consisting of black-line terminations, the square area tended to look darker than the control even though the afterimage of the lines could not be seen. These results indicate that induced or illusory brightness causes an aftereffect in brightness regardless of the appearance of negative afterimages of the illusion-inducing components.

  19. Spectrophotometric study of five bright meteors

    International Nuclear Information System (INIS)

    Saidov, K.Kh.; Zolowa, O.F.

    1971-01-01

    The results of 200 spectrophotometric study of five bright meteors and indentification of spectral lines are given. Distribution of energy for different points of the paths of meteors is found. Masses of meteor particles are determined on the base of integrated curves of brightness

  20. LARGER PLANET RADII INFERRED FROM STELLAR ''FLICKER'' BRIGHTNESS VARIATIONS OF BRIGHT PLANET-HOST STARS

    International Nuclear Information System (INIS)

    Bastien, Fabienne A.; Stassun, Keivan G.; Pepper, Joshua

    2014-01-01

    Most extrasolar planets have been detected by their influence on their parent star, typically either gravitationally (the Doppler method) or by the small dip in brightness as the planet blocks a portion of the star (the transit method). Therefore, the accuracy with which we know the masses and radii of extrasolar planets depends directly on how well we know those of the stars, the latter usually determined from the measured stellar surface gravity, log g. Recent work has demonstrated that the short-timescale brightness variations ( f licker ) of stars can be used to measure log g to a high accuracy of ∼0.1-0.2 dex. Here, we use flicker measurements of 289 bright (Kepmag < 13) candidate planet-hosting stars with T eff = 4500-6650 K to re-assess the stellar parameters and determine the resulting impact on derived planet properties. This re-assessment reveals that for the brightest planet-host stars, Malmquist bias contaminates the stellar sample with evolved stars: nearly 50% of the bright planet-host stars are subgiants. As a result, the stellar radii, and hence the radii of the planets orbiting these stars, are on average 20%-30% larger than previous measurements had suggested

  1. Infrared-Bright Interacting Galaxies

    Science.gov (United States)

    Rojas Ruiz, Sofia; Murphy, Eric Joseph; Armus, Lee; Smith, John-David; Bradford, Charles Matt; Stierwalt, Sabrina

    2018-01-01

    We present the mid-infrared spectral mapping of eight LIRG-class interacting galaxies: NGC 6670, NGC 7592, IIZw 96, IIIZw 35, Arp 302, Arp 236, Arp 238, Arp 299. The properties of galaxy mergers, which are bright and can be studied at high resolutions at low-z, provide local analogs for sources that may be important contributors to the Far Infrared Background (FIRB.) In order to study star formation and the physical conditions in the gas and dust in our sample galaxies, we used the Spitzer InfraRed Spectrograph (IRS) to map the galaxies over the 5-35 μm window to trace the PAH, molecular hydrogen, and atomic fine structure line emission on scales of 1.4 – 5.3 kpc. Here we present the reduction for low and high-resolution data, and preliminary results in the analysis of fine structure line ratios and dust features in the two nuclei and interacting regions from one of our sample galaxies, NGC 6670.

  2. Extremely Low Passive Microwave Brightness Temperatures Due to Thunderstorms

    Science.gov (United States)

    Cecil, Daniel J.

    2015-01-01

    Extreme events by their nature fall outside the bounds of routine experience. With imperfect or ambiguous measuring systems, it is appropriate to question whether an unusual measurement represents an extreme event or is the result of instrument errors or other sources of noise. About three weeks after the Tropical Rainfall Measuring Mission (TRMM) satellite began collecting data in Dec 1997, a thunderstorm was observed over northern Argentina with 85 GHz brightness temperatures below 50 K and 37 GHz brightness temperatures below 70 K (Zipser et al. 2006). These values are well below what had previously been observed from satellite sensors with lower resolution. The 37 GHz brightness temperatures are also well below those measured by TRMM for any other storm in the subsequent 16 years. Without corroborating evidence, it would be natural to suspect a problem with the instrument, or perhaps an irregularity with the platform during the first weeks of the satellite mission. Automated quality control flags or other procedures in retrieval algorithms could treat these measurements as errors, because they fall outside the expected bounds. But the TRMM satellite also carries a radar and a lightning sensor, both confirming the presence of an intense thunderstorm. The radar recorded 40+ dBZ reflectivity up to about 19 km altitude. More than 200 lightning flashes per minute were recorded. That same storm's 19 GHz brightness temperatures below 150 K would normally be interpreted as the result of a low-emissivity water surface (e.g., a lake, or flood waters) if not for the simultaneous measurements of such intense convection. This paper will examine records from TRMM and related satellite sensors including SSMI, AMSR-E, and the new GMI to find the strongest signatures resulting from thunderstorms, and distinguishing those from sources of noise. The lowest brightness temperatures resulting from thunderstorms as seen by TRMM have been in Argentina in November and December. For

  3. Designers predict a bright future

    International Nuclear Information System (INIS)

    Statton, T.D.

    1996-01-01

    As power plant designers and builders, there is a bright future for the industry. The demand for electricity will continue to grow, and the need for new plants will increase accordingly. But companies that develop and supply these plants must adapt to new ways of doing business if they expect to see the dawn of this new age. Several factors will have a profound effect on the generation and use of electricity in future years. Instant communications now reach all corners of the globe, making people everywhere aspire to a higher standard of living. The economic surge needed to satisfy these appetites will, in turn, be fed by a network of suppliers who are themselves restructuring to serve global markets, unimpeded by past nationalistic barriers to trade. The strong correlation between economic progress and the growing demand for electricity is well recognized. A ready supply of affordable electricity is a necessary underpinning for any economic expansion. As economies advance and jobs increase, electric demand grows geometrically, fueled by an ever-improving quality of life. Coupled with increasing demand is the worldwide trend toward privatization of the generation industry. The reasons may vary in different parts of the world, but the effect is the same--companies are battling intensely for the right to build or purchase generating facilities. Those companies, like the industry they serve, are themselves in a period of transition. Once a closed, monopolistic group of owners in a predominantly services-based market, they are, thanks to competitive forces, being driven steadily toward a product-based structure

  4. Bright Sparks of Our Future!

    Science.gov (United States)

    Riordan, Naoimh

    2016-04-01

    My name is Naoimh Riordan and I am the Vice Principal of Rockboro Primary School in Cork City, South of Ireland. I am a full time class primary teacher and I teach 4th class, my students are aged between 9-10 years. My passion for education has developed over the years and grown towards STEM (Science, Technology, Engineering and Mathematics) subjects. I believe these subjects are the way forward for our future. My passion and beliefs are driven by the unique after school programme that I have developed. It is titled "Sparks" coming from the term Bright Sparks. "Sparks" is an after school programme with a difference where the STEM subjects are concentrated on through lessons such as Science, Veterinary Science Computer Animation /Coding, Eco engineering, Robotics, Magical Maths, Chess and Creative Writing. All these subjects are taught through activity based learning and are one-hour long each week for a ten-week term. "Sparks" is fully inclusive and non-selective which gives all students of any level of ability an opportunity to engage into these subjects. "Sparks" is open to all primary students in County Cork. The "Sparks" after school programme is taught by tutors from the different Universities and Colleges in Cork City. It works very well because the tutor brings their knowledge, skills and specialised equipment from their respective universities and in turn the tutor gains invaluable teaching practise, can trial a pilot programme in a chosen STEM subject and gain an insight into what works in the physical classroom.

  5. Constraints on Paleocene and Eocene Tropical Sea-Surface Temperatures and Meridional Temperature Gradients From Mg/Ca and Oxygen Isotope Ratios of Foraminifera in Sediments Recovered by the Ocean Drilling Program

    Science.gov (United States)

    Tripati, A.; Elderfield, H.; Wade, B.; Kelly, D. C.; Anderson, L. D.; Sindrey, C.

    2005-12-01

    Accurate reconstructions of tropical sea surface temperatures (SST) during the Paleocene and Eocene are needed to understand the contribution of greenhouse gases to past climate variability. When combined with constraints on high-latitude SST, tropical SST can be used to estimate past meridional temperature gradients. The traditional tool applied to reconstructing surface temperatures utilizes the temperature-dependant incorporation of oxygen isotopes into calcium carbonate. However, changes in the oxygen isotope composition of foraminiferal calcite also record variations in the isotopic composition of seawater, complicating temperature reconstructions. The magnesium to calcium (Mg/Ca) ratio of foraminiferal carbonate provides an alternative method for reconstructing temperatures in the past that is insensitive to variations in the oxygen isotopic composition of seawater. Here, we present constraints on tropical temperatures from Mg/Ca ratios of planktonic foraminifera in cores recovered by the Ocean Drilling Program during intervals characterized by large changes in atmospheric carbon dioxide levels, including the Paleocene-Eocene Thermal Maximum and the middle to late Eocene "greenhouse-icehouse" transition. Records are for mixed-layer dwellers belonging to the genus Morozovella and Acaranina, and for the thermocline dwelling taxa Subbotina. We combine these results with constraints on high-latitude SST from other proxies, including foraminiferal Mg/Ca and oxygen isotope ratios, to reconstruct changes in the pole-to-equator temperature gradient during these major climate transitions.

  6. Laser pulse shaping for high gradient accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Villa, F., E-mail: fabio.villa@lnf.infn.it [INFN-Laboratori Nazionali di Frascati, via E. Fermi 40, 00044 Frascati (Italy); Anania, M.P.; Bellaveglia, M. [INFN-Laboratori Nazionali di Frascati, via E. Fermi 40, 00044 Frascati (Italy); Bisesto, F. [INFN-Laboratori Nazionali di Frascati, via E. Fermi 40, 00044 Frascati (Italy); Università La Sapienza di Roma, Via A. Scarpa 14, Rome (Italy); Chiadroni, E. [INFN-Laboratori Nazionali di Frascati, via E. Fermi 40, 00044 Frascati (Italy); Cianchi, A. [INFN-Roma Tor Vergata and Università di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome (Italy); Curcio, A.; Galletti, M.; Di Giovenale, D.; Di Pirro, G.; Ferrario, M.; Gatti, G. [INFN-Laboratori Nazionali di Frascati, via E. Fermi 40, 00044 Frascati (Italy); Moreno, M.; Petrarca, M. [Università La Sapienza di Roma, Via A. Scarpa 14, Rome (Italy); Pompili, R.; Vaccarezza, C. [INFN-Laboratori Nazionali di Frascati, via E. Fermi 40, 00044 Frascati (Italy)

    2016-09-01

    In many high gradient accelerator schemes, i.e. with plasma or dielectric wakefield induced by particles, many electron pulses are required to drive the acceleration of one of them. Those electron bunches, that generally should have very short duration and low emittance, can be generated in photoinjectors driven by a train of laser pulses coming inside the same RF bucket. We present the system used to shape and characterize the laser pulses used in multibunch operations at Sparc-lab. Our system gives us control over the main parameter useful to produce a train of up to five high brightness bunches with tailored intensity and time distribution.

  7. Bright boys the making of information technology

    CERN Document Server

    Green, Tom

    2010-01-01

    Everything has a beginning. None was more profound-and quite as unexpected-than Information Technology. Here for the first time is the untold story of how our new age came to be and the bright boys who made it happen. What began on the bare floor of an old laundry building eventually grew to rival in size the Manhattan Project. The unexpected consequence of that journey was huge---what we now know as Information Technology. For sixty years the bright boys have been totally anonymous while their achievements have become a way of life for all of us. "Bright Boys" brings them home. By 1950 they'd

  8. Surface complexation modeling of groundwater arsenic mobility: Results of a forced gradient experiment in a Red River flood plain aquifer, Vietnam

    DEFF Research Database (Denmark)

    Jessen, Søren; Postma, Dieke; Larsen, Flemming

    2012-01-01

    Three surface complexation models (SCMs) developed for, respectively, ferrihydrite, goethite and sorption data for a Pleistocene oxidized aquifer sediment from Bangladesh were used to explore the effect of multicomponent adsorption processes on As mobility in a reduced Holocene floodplain aquifer...

  9. Automated Adaptive Brightness in Wireless Capsule Endoscopy Using Image Segmentation and Sigmoid Function.

    Science.gov (United States)

    Shrestha, Ravi; Mohammed, Shahed K; Hasan, Md Mehedi; Zhang, Xuechao; Wahid, Khan A

    2016-08-01

    Wireless capsule endoscopy (WCE) plays an important role in the diagnosis of gastrointestinal (GI) diseases by capturing images of human small intestine. Accurate diagnosis of endoscopic images depends heavily on the quality of captured images. Along with image and frame rate, brightness of the image is an important parameter that influences the image quality which leads to the design of an efficient illumination system. Such design involves the choice and placement of proper light source and its ability to illuminate GI surface with proper brightness. Light emitting diodes (LEDs) are normally used as sources where modulated pulses are used to control LED's brightness. In practice, instances like under- and over-illumination are very common in WCE, where the former provides dark images and the later provides bright images with high power consumption. In this paper, we propose a low-power and efficient illumination system that is based on an automated brightness algorithm. The scheme is adaptive in nature, i.e., the brightness level is controlled automatically in real-time while the images are being captured. The captured images are segmented into four equal regions and the brightness level of each region is calculated. Then an adaptive sigmoid function is used to find the optimized brightness level and accordingly a new value of duty cycle of the modulated pulse is generated to capture future images. The algorithm is fully implemented in a capsule prototype and tested with endoscopic images. Commercial capsules like Pillcam and Mirocam were also used in the experiment. The results show that the proposed algorithm works well in controlling the brightness level accordingly to the environmental condition, and as a result, good quality images are captured with an average of 40% brightness level that saves power consumption of the capsule.

  10. Brightness/darkness induction and the genesis of a contour

    Directory of Open Access Journals (Sweden)

    Sergio eRoncato

    2014-10-01

    Full Text Available Visual contours often result from the integration or interpolation of fragmented edges.The strength of the completion increases when the edges share the same contrast polarity (CP. Here we demonstrate that the appearance in the perceptual field of this integrated unit, or contour of invariant CP, is concomitant with a vivid brightness alteration of the surfaces at its opposite sides. To observe this effect requires some stratagems because the formation in the visual field of a contour of invariant CP normally engenders the formation of a second contour and then the rise of two streams of induction signals that interfere in different ways. Particular configurations have been introduced that allow us to observe the induction effects of one contour taken in isolation. I documented these effects by phenomenological observations and psychophysical measurement of the brightness alteration in relation to luminance contrast. When the edges of the same CP complete to form a contour, the background of homogeneous luminance appears to dim at one side and to brighten at the opposite side (in accord with the CP. The strength of the phenomenon is proportional to the local luminance contrast. This effect weakens or nulls when the contour of the invariant CP separates surfaces filled with different grey shades.These conflicting results stimulate a deeper exploration of the induction phenomena and their role in the computation of brightness contrast. An alternative perspective is offered to account for some brightness illusions and their relation to the phenomenal transparency. The main assumption asserts that, when in the same region induction signals of opposite CP overlap, the filling-in are blocked unless the image is stratified into different layers, one for each signal of the same polarity. Phenomenological observations document this solution by the visual system

  11. Nimbus-5 ESMR Polar Gridded Brightness Temperatures

    Data.gov (United States)

    National Aeronautics and Space Administration — The Nimbus-5 Electrically Scanning Microwave Radiometer (ESMR) data set consists of gridded brightness temperature arrays for the Arctic and Antarctic, spanning 11...

  12. Time-resolved brightness measurements by streaking

    Science.gov (United States)

    Torrance, Joshua S.; Speirs, Rory W.; McCulloch, Andrew J.; Scholten, Robert E.

    2018-03-01

    Brightness is a key figure of merit for charged particle beams, and time-resolved brightness measurements can elucidate the processes involved in beam creation and manipulation. Here we report on a simple, robust, and widely applicable method for the measurement of beam brightness with temporal resolution by streaking one-dimensional pepperpots, and demonstrate the technique to characterize electron bunches produced from a cold-atom electron source. We demonstrate brightness measurements with 145 ps temporal resolution and a minimum resolvable emittance of 40 nm rad. This technique provides an efficient method of exploring source parameters and will prove useful for examining the efficacy of techniques to counter space-charge expansion, a critical hurdle to achieving single-shot imaging of atomic scale targets.

  13. Observations and diagnostics in high brightness beams

    Energy Technology Data Exchange (ETDEWEB)

    Cianchi, A., E-mail: alessandro.cianchi@roma2.infn.it [University of Rome Tor Vergata and INFN-Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome (Italy); Anania, M.P.; Bisesto, F.; Castellano, M.; Chiadroni, E.; Pompili, R.; Shpakov, V. [INFN-LNF, Via Enrico Fermi 40, 00044 Frascati (Italy)

    2016-09-01

    The brightness is a figure of merit largely used in the light sources, like FEL (Free Electron Lasers), but it is also fundamental in several other applications, as for instance Compton backscattering sources, beam driven plasma accelerators and THz sources. Advanced diagnostics are essential tools in the development of high brightness beams. 6D electron beam diagnostics will be reviewed with emphasis on emittance measurement.

  14. Energy-exchange collisions of dark-bright-bright vector solitons.

    Science.gov (United States)

    Radhakrishnan, R; Manikandan, N; Aravinthan, K

    2015-12-01

    We find a dark component guiding the practically interesting bright-bright vector one-soliton to two different parametric domains giving rise to different physical situations by constructing a more general form of three-component dark-bright-bright mixed vector one-soliton solution of the generalized Manakov model with nine free real parameters. Moreover our main investigation of the collision dynamics of such mixed vector solitons by constructing the multisoliton solution of the generalized Manakov model with the help of Hirota technique reveals that the dark-bright-bright vector two-soliton supports energy-exchange collision dynamics. In particular the dark component preserves its initial form and the energy-exchange collision property of the bright-bright vector two-soliton solution of the Manakov model during collision. In addition the interactions between bound state dark-bright-bright vector solitons reveal oscillations in their amplitudes. A similar kind of breathing effect was also experimentally observed in the Bose-Einstein condensates. Some possible ways are theoretically suggested not only to control this breathing effect but also to manage the beating, bouncing, jumping, and attraction effects in the collision dynamics of dark-bright-bright vector solitons. The role of multiple free parameters in our solution is examined to define polarization vector, envelope speed, envelope width, envelope amplitude, grayness, and complex modulation of our solution. It is interesting to note that the polarization vector of our mixed vector one-soliton evolves in sphere or hyperboloid depending upon the initial parametric choices.

  15. A case study on large-scale dynamical influence on bright band using cloud radar during the Indian summer monsoon

    Science.gov (United States)

    Jha, Ambuj K.; Kalapureddy, M. C. R.; Devisetty, Hari Krishna; Deshpande, Sachin M.; Pandithurai, G.

    2018-02-01

    The present study is a first of its kind attempt in exploring the physical features (e.g., height, width, intensity, duration) of tropical Indian bright band using a Ka-band cloud radar under the influence of large-scale cyclonic circulation and attempts to explain the abrupt changes in bright band features, viz., rise in the bright band height by 430 m and deepening of the bright band by about 300 m observed at around 14:00 UTC on Sep 14, 2016, synoptically as well as locally. The study extends the utility of cloud radar to understand how the bright band features are associated with light precipitation, ranging from 0 to 1.5 mm/h. Our analysis of the precipitation event of Sep 14-15, 2016 shows that the bright band above (below) 3.7 km, thickness less (more) than 300 m can potentially lead to light drizzle of 0-0.25 mm/h (drizzle/light rain) at the surface. It is also seen that the cloud radar may be suitable for bright band study within light drizzle limits than under higher rain conditions. Further, the study illustrates that the bright band features can be determined using the polarimetric capability of the cloud radar. It is shown that an LDR value of - 22 dB can be associated with the top height of bright band in the Ka-band observations which is useful in the extraction of the bright band top height and its width. This study is useful for understanding the bright band phenomenon and could be potentially useful in establishing the bright band-surface rain relationship through the perspective of a cloud radar, which would be helpful to enhance the cloud radar-based quantitative estimates of precipitation.

  16. Robust brightness enhancement across a luminance range of the glare illusion.

    Science.gov (United States)

    Tamura, Hideki; Nakauchi, Shigeki; Koida, Kowa

    2016-01-01

    The glare illusion refers to brightness enhancement and the perception of a self-luminous appearance that occurs when a central region is surrounded by a luminance gradient. The center region appears to be a light source, with its light dispersing into the surrounding region. If the luminous edge is critical for generating the illusion, modulating the perceived luminance of the image, and switching its appearance from luminous to nonluminous, would have a strong impact on lightness and brightness estimation. Here, we quantified the illusion in two ways, by assessing brightness enhancement and examining whether the center region appeared luminous. Thus, we could determine whether the two effects occurred jointly or independently. We examined a wide luminance range of center regions, from 0 to 200% relative to background. Brightness enhancement in the illusion was observed for a wide range of luminances (20% to 200% relative to background), while a luminous-white appearance was observed when the center region luminance was 145% of the background. These results exclude the possibility that brightness enhancement occurs because the stimuli appear self-luminous. We suggest that restoring the original image intensity precedes the perceptual process of lightness estimation.

  17. Producing a gradient-composition nanocrystalline structure on nitrided surfaces of invar-type Fe-Ni alloys using megaplastic deformation

    Science.gov (United States)

    Shabashov, V. A.; Borisov, S. V.; Litvinov, A. V.; Kataeva, N. V.; Afanas'ev, S. V.; Titova, S. G.

    2014-09-01

    A nanocrystalline Fe-Ni matrix strengthened by dispersed CrN and TiN nitrides has been produced on the ion-plasma-nitrided surfaces of the austenitic Fe-Ni38-Cr15 and Fe-Ni36-Ti4 alloys using cyclic "nitride dissolution-nitride precipitation" phase transformations induced by megaplastic deformation. The high-pressure torsion of the nitrided alloys has led to the dissolution of the CrN nitrides and Ni3Ti intermetallic compounds, which appeared in the matrix, in the surface layer and to the mechanical alloying of the nitrided subsurface layer and the unnitriderd bulk of the specimens. Subsequent annealing has resulted in the formation of secondary nitrides, which propagated to a depth substantially exceeding the thickness of the original nitrided layer.

  18. The Physics and Applications of High Brightness Electron Beams

    Science.gov (United States)

    Palumbo, Luigi; Rosenzweig, J.; Serafini, Luca

    2007-09-01

    brightness photoinjector / M. Ferrario, V. Fusco, M. Migliorati and L. Palumbo. Simulations of coherent synchroton radiation effects in electron machines / M. Migliorati, A, Schiavi and G. Dattoli. QFEL: A numerical code for multi-dimensional simulation of free electron lasers in the quantum regime / A. Schiavi ... [et al.]. First simulations results on laser pulse jitter and microbunching instability at Saprxino / M. Boscolo ... [et al.]. -- Working Group 4. Working group 4 summary: applications of high brightness beams to advanced accelerators and light sources / M. Uesaka and A. Rossi. Study of transverse effects in the production of X-rays with free-electron laser based on an optical ondulator / A. Bacci ... [et al.]. Channeling projects at LNF: from crystal undulators to capillary waveguides / S.B. Dabagov ... [et al.]. Mono-Energetic electron generation and plasma diagnosis experiments in a laser plasma cathode / K. Kinoshita ... [et al.]. A high-density electron beam and quad-scan measurements at Pleiades Thompson X-ray source / J.K. Lim ... [et al.]. Laser pulse circulation system for compact monochromatic tunable hard X-ray source / H. Ogino ... [et al.]. Limits on production of narrow band photons from inverse compton scattering / J. Rosenzweig and O. Williams. Preliminary results from the UCLA/SLAC ultra-high gradient Cerenkov wakefield accelerator experiment / M.C. Thompson ... [et al.]. Status of the polarized nonlinear inverse compton scattering experiment at UCLA / O. Williams... [et al.]. Coupling laser power into a slab-symmetric accelerator structure / R.B. Yoder and J.B. Rosenzweig.

  19. Colors and Photometry of Bright Materials on Vesta as Seen by the Dawn Framing Camera

    Science.gov (United States)

    Schroeder, S. E.; Li, J.-Y.; Mittlefehldt, D. W.; Pieters, C. M.; De Sanctis, M. C.; Hiesinger, H.; Blewett, D. T.; Russell, C. T.; Raymond, C. A.; Keller, H. U.; hide

    2012-01-01

    The Dawn spacecraft has been in orbit around the asteroid Vesta since July, 2011. The on-board Framing Camera has acquired thousands of high-resolution images of the regolith-covered surface through one clear and seven narrow-band filters in the visible and near-IR wavelength range. It has observed bright and dark materials that have a range of reflectance that is unusually wide for an asteroid. Material brighter than average is predominantly found on crater walls, and in ejecta surrounding caters in the southern hemisphere. Most likely, the brightest material identified on the Vesta surface so far is located on the inside of a crater at 64.27deg S, 1.54deg . The apparent brightness of a regolith is influenced by factors such as particle size, mineralogical composition, and viewing geometry. As such, the presence of bright material can indicate differences in lithology and/or degree of space weathering. We retrieve the spectral and photometric properties of various bright terrains from false-color images acquired in the High Altitude Mapping Orbit (HAMO). We find that most bright material has a deeper 1-m pyroxene band than average. However, the aforementioned brightest material appears to have a 1-m band that is actually less deep, a result that awaits confirmation by the on-board VIR spectrometer. This site may harbor a class of material unique for Vesta. We discuss the implications of our spectral findings for the origin of bright materials.

  20. Linkage between seasonal insolation gradient in the tropical northern hemisphere and the sea surface salinity of the equatorial Indian Ocean during the last glacial period

    Digital Repository Service at National Institute of Oceanography (India)

    Saraswat, R.; Nigam, R.; Mackensen, A.; Weldeab, S.

    oxygen isotopic composition to estimate the local seawater oxygen isotopic composition (δ18Osw-ivc). The change in δ18Osw-ivc relative to the present day value (∆δ18Osw-ivc) was then calculated by subtracting the modern surface seawater oxygen isotopic... the modern measurement (Fig. 5), match very well with the Levitus 7 annual SSS over the core site, showing values of 34.7 and 34.8, respectively. Delaygue et al (2001) also developed a seawater oxygen isotope/salinity relationship for the Bay of Bengal...

  1. Past 100 Ky surface salinity-gradient response in the eastern Arabian Sea to the summer monsoon variation recorded by delta super(18)O of G. sacculifer

    Digital Repository Service at National Institute of Oceanography (India)

    Chodankar, A.R.; Banakar, V.K.; Oba, T.

    stream_size 32493 stream_content_type text/plain stream_name Global_Planet_Change_47_135.pdf.txt stream_source_info Global_Planet_Change_47_135.pdf.txt Content-Encoding UTF-8 Content-Type text/plain; charset=UTF-8... variation in freshwater flux to the Bay of Bengal and hence summer monsoon intensity. The north–south contrast in the sea level corrected (residual)-y 18 O G. sacculifer can be interpreted as a measure of surface Global and Planetary Change 47 (2005) 135...

  2. Proxy magnetometry of the photosphere: why are G-band bright points so bright?

    NARCIS (Netherlands)

    Rutten, R.J.; Kiselman, Dan; Voort, Luc Rouppe van der; Plez, Bertrand

    2000-01-01

    We discuss the formation of G-band bright points in terms of standard uxtube modeling, in particular the 1D LTE models constructed by Solanki and coworkers. Combined with LTE spectral synthesis they explain observed G-band bright point contrasts quite well. The G-band contrast increase over the

  3. STARS4ALL Night Sky Brightness Photometer

    Directory of Open Access Journals (Sweden)

    Jaime Zamorano

    2017-06-01

    Full Text Available We present the main features of TESS-W, the first version of a series of inexpensive but reliable photometers that will be used to measure night sky brightness. The bandpass is extended to the red with respect of that of the Sky Quality Meter (SQM. TESS-W connects to a router via WIFI and it sends automatically the brightness values to a data repository using Internet of Things protocols. The device includes an infrared sensor to estimate the cloud coverage. It is designed for fixed stations to monitor the evolution of the sky brightness. The photometer could also be used in local mode connected to a computer or tablet to gather data from a moving vehicle. The photometer is being developed within STARS4ALL project, a collective awareness platform for promoting dark skies in Europe, funded by the EU. We intend to extend the existing professional networks to a citizen-based network of photometers. 

  4. Increasing the brightness of light sources

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Ling

    2006-11-16

    In this work the principle of light recycling is applied to artificial light sources in order to achieve brightness enhancement. Firstly, the feasibilities of increasing the brightness of light sources via light recycling are examined theoretically, based on the fundamental laws of thermodynamics including Kirchhoff's law on radiation, Planck's law, Lambert-Beer's law, the etendue conservation and the brightness theorem. From an experimental viewpoint, the radiation properties of three different kinds of light sources including short-arc lamps, incandescent lamps and LEDs characterized by their light-generating mechanisms are investigated. These three types of sources are used in light recycling experiments, for the purpose of 1. validating the intrinsic light recycling effect in light sources, e. g. the intrinsic light recycling effect in incandescent lamps stemming from the coiled filament structure. 2. acquiring the required parameters for establishing physical models, e.g. the emissivity/absorptivity of the short-arc lamps, the intrinsic reflectivity and the external quantum efficiency of LEDs. 3. laying the foundations for designing optics aimed at brightness enhancement according to the characteristics of the sources and applications. Based on the fundamental laws and experiments, two physical models for simulating the radiance distribution of light sources are established, one for thermal filament lamps, the other for luminescent sources, LEDs. As validation of the theoretical and experimental investigation of the light recycling effect, an optical device, the Carambola, is designed for achieving deterministic and multiple light recycling. The Carambola has the function of a concentrator. In order to achieve the maximum possible brightness enhancement with the Carambola, several combinations of sources and Carambolas are modelled in ray-tracing simulations. Sources with different light-emitting mechanisms and different radiation properties

  5. Influence of single-walled carbon nanotubes (< 0.001 wt %) and/or zwitter-ionic phospholipid (SOPC) surface layer on the behaviour of the gradient flexoelectric and surface induced polarization domains arising in a homeotropic E7 (a mixture of 5CB, 7CB, 8OCB and 5CT) nematic layer

    International Nuclear Information System (INIS)

    Hinov, H P; Pavlic, J I; Marinov, Y G; Petrov, A G; Sridevi, S; Rafailov, P M; Dettlaff-Weglikowska, U

    2010-01-01

    The influence has been studied of single-walled carbon nanotubes with a concentration between 0.0001 and 0.001 wt % and a dried zwitter-ionic phospholipid (SOPC: l-stearoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine) layer of thickness, smaller than 0.5 μm, deposited only on a half of one of the two glass plates, on the behaviour of the gradient flexoelectric and surface polarization induced domains arising in a homeotropic nematic E7 (a mixture of 5CB, 7CB, 8OCB and 5CT) layer. We have observed for the first time different polar on/off formation of the surface polarization induced domains in the region of the liquid crystal cell without surface deposited lipid SOPC layer. On the other hand, the SOPC layer strongly decreases the gradient of the electric field thus leading to less-pronounced flexoelectric domains. However, the SOPC layer does not influence the creation of surface polarization induced domains and of injection induced domains arising at voltages above 4V. Appropriate dynamic light transmitted curves have been recorded and typical microphotographs have been taken.

  6. Generalized dark-bright vector soliton solution to the mixed coupled nonlinear Schrödinger equations.

    Science.gov (United States)

    Manikandan, N; Radhakrishnan, R; Aravinthan, K

    2014-08-01

    We have constructed a dark-bright N-soliton solution with 4N+3 real parameters for the physically interesting system of mixed coupled nonlinear Schrödinger equations. Using this as well as an asymptotic analysis we have investigated the interaction between dark-bright vector solitons. Each colliding dark-bright one-soliton at the asymptotic limits includes more coupling parameters not only in the polarization vector but also in the amplitude part. Our present solution generalizes the dark-bright soliton in the literature with parametric constraints. By exploiting the role of such coupling parameters we are able to control certain interaction effects, namely beating, breathing, bouncing, attraction, jumping, etc., without affecting other soliton parameters. Particularly, the results of the interactions between the bound state dark-bright vector solitons reveal oscillations in their amplitudes under certain parametric choices. A similar kind of effect was also observed experimentally in the BECs. We have also characterized the solutions with complicated structure and nonobvious wrinkle to define polarization vector, envelope speed, envelope width, envelope amplitude, grayness, and complex modulation. It is interesting to identify that the polarization vector of the dark-bright one-soliton evolves on a spherical surface instead of a hyperboloid surface as in the bright-bright case of the mixed coupled nonlinear Schrödinger equations.

  7. Richard Bright and his neurological studies.

    Science.gov (United States)

    Pearce, J M S

    2009-01-01

    Richard Bright was one of the famous triumvirate of Guy's Hospital physicians in the Victorian era. Remembered for his account of glomerulonephritis (Bright's disease) he also made many important and original contributions to medicine and neurology. These included his work on cortical epileptogenesis, descriptions of simple partial (Jacksonian) seizures, infantile convulsions, and a variety of nervous diseases. Most notable were his reports of neurological studies including papers on traumatic tetanus, syringomyelia, arteries of the brain, contractures of spinal origin, tumours of the base of the brain, and narcolepsy. His career and these contributions are outlined. Copyright 2009 S. Karger AG, Basel.

  8. The Bright SHARC Survey: The Cluster Catalog

    OpenAIRE

    Romer, A. K; Nichol, R. C.; Holden, B. P.; Ulmer, M. P.; Pildis, R. A.; Merrelli, A. J.; Adami, C.; Burke, D. J.; Collins, C. A.; Metevier, A. J.; Kron, R. G.; Commons, K.

    1999-01-01

    We present the Bright SHARC (Serendipitous High-Redshift Archival ROSAT Cluster) Survey, which is an objective search for serendipitously detected extended X-ray sources in 460 deep ROSAT PSPC pointings. The Bright SHARC Survey covers an area of 178.6 deg2 and has yielded 374 extended sources. We discuss the X-ray data reduction, the candidate selection and present results from our on-going optical follow-up campaign. The optical follow-up concentrates on the brightest 94 of the 374 extended ...

  9. TIGER Burned Brightly in JAMIC

    Science.gov (United States)

    Olson, Sandra L.; Kashiwagi, Takashi

    2001-01-01

    The Transition From Ignition to Flame Growth Under External Radiation in 3D (TIGER- 3D) experiment, which is slated to fly aboard the International Space Station, conducted a series of highly successful tests in collaboration with the University of Hokkaido using Japan's 10-sec JAMIC drop tower. The tests were conducted to test engineering versions of advanced flight diagnostics such as an infrared camera for detailed surface temperature measurements and an infrared spectroscopic array for gas-phase species concentrations and temperatures based on detailed spectral emissions in the near infrared. Shown in the top figure is a visible light image and in the bottom figure is an infrared image at 3.8 mm obtained during the microgravity tests. The images show flames burning across cellulose samples against a slow wind of a few centimeters per second (wind is from right to left). These flow velocities are typical of spacecraft ventilation systems that provide fresh air for the astronauts. The samples are ignited across the center with a hot wire, and the flame is allowed to spread upwind and/or downwind. As these images show, the flames prefer to spread upwind, into the fresh air, which is the exact opposite of flames on Earth, which spread much faster downwind, or with the airflow, as in forest fires.

  10. Comparing MODIS and near-surface vegetation indexes for monitoring tropical dry forest phenology along a successional gradient using optical phenology towers

    Science.gov (United States)

    Rankine, C.; Sánchez-Azofeifa, G. A.; Guzmán, J. Antonio; Espirito-Santo, M. M.; Sharp, Iain

    2017-10-01

    Tropical dry forests (TDFs) present strong seasonal greenness signals ideal for tracking phenology and primary productivity using remote sensing techniques. The tightly synchronized relationship these ecosystems have with water availability offer a valuable natural experiment for observing the complex interactions between the atmosphere and the biosphere in the tropics. To investigate how well the MODIS vegetation indices (normalized difference vegetation index (NDVI) and the enhanced vegetation index (EVI)) represented the phenology of different successional stages of naturally regenerating TDFs, within a widely conserved forest fragment in the semi-arid southeast of Brazil, we installed several canopy towers with radiometric sensors to produce high temporal resolution near-surface vegetation greenness indices. Direct comparison of several years of ground measurements with a combined Aqua/Terra 8 day satellite product showed similar broad temporal trends, but MODIS often suffered from cloud contamination during the onset of the growing season and occasionally during the peak growing season. The strength of the in-situ and MODIS linear relationship was greater for NDVI than for EVI across sites but varied with forest stand age. Furthermore, we describe the onset dates and duration of canopy development phases for three years of in-situ monitoring. A seasonality analysis revealed significant discrepancies between tower and MODIS phenology transitions dates, with up to five weeks differences in growing season length estimation. Our results indicate that 8 and 16 day MODIS satellite vegetation monitoring products are suitable for tracking general patterns of tropical dry forest phenology in this region but are not temporally sufficient to characterize inter-annual differences in phenology phase onset dates or changes in productivity due to mid-season droughts. Such rapid transitions in canopy greenness are important indicators of climate change sensitivity of these

  11. Temperate forest impacts on maritime snowpacks across an elevation gradient: An assessment of the snow surface energy balance and airborne lidar derived forest structure

    Science.gov (United States)

    Roth, T. R.; Nolin, A. W.

    2016-12-01

    Temperate forests modify snow evolution patterns both spatially and temporally relative to open areas. Dense, warm forests both impede snow accumulation through increased canopy snow interception and increase sub-canopy longwave energy inputs onto the snow surface. These process modifications vary in magnitude and duration depending on climatic, topographic and forest characteristics. Here we present results from a four year study of paired forested and open sites at three elevations, Low - 1150 m, Mid - 1325 m and High - 1465 m. Snowpacks are deeper and last up to 3-4 weeks longer at the Low and Mid elevation Open sites relative to the adjacent Forest sites. Conversely, at the High Forest site, snow is retained 2-4 weeks longer than the Open site. This change in snowpack depth and persistence is attributed to deposition patterns at higher elevations and forest structure differences that alter the canopy interception efficiency and the sub-canopy energy balance. Canopy interception efficiency (CIE) in the Low and Mid Forest sites, over the duration of the study were 79% and 76% of the total event snowfall, whereas CIE was 31% at the High Forest site. Longwave radiation in forested environments is the primary energy component across each elevation band due to the warm winter environment and forest presence, accounting for 82%, 88%, and 59% of the energy balance at the Low, Mid, and High Forest sites, respectively. High wind speeds in the High elevation Open site significantly increases the turbulent energy and creates preferential snowfall deposition in the nearby Forest site. These results show the importance of understanding the effects of forest cover on sub-canopy snowpack evolution and highlight the need for improved forest cover model representation to accurately predict water resources in maritime forests.

  12. Substrate curvature gradient drives rapid droplet motion.

    Science.gov (United States)

    Lv, Cunjing; Chen, Chao; Chuang, Yin-Chuan; Tseng, Fan-Gang; Yin, Yajun; Grey, Francois; Zheng, Quanshui

    2014-07-11

    Making small liquid droplets move spontaneously on solid surfaces is a key challenge in lab-on-chip and heat exchanger technologies. Here, we report that a substrate curvature gradient can accelerate micro- and nanodroplets to high speeds on both hydrophilic and hydrophobic substrates. Experiments for microscale water droplets on tapered surfaces show a maximum speed of 0.42  m/s, 2 orders of magnitude higher than with a wettability gradient. We show that the total free energy and driving force exerted on a droplet are determined by the substrate curvature and substrate curvature gradient, respectively. Using molecular dynamics simulations, we predict nanoscale droplets moving spontaneously at over 100  m/s on tapered surfaces.

  13. Robust fitting of diurnal brightness temperature cycle

    CSIR Research Space (South Africa)

    Udahemuka, G

    2007-11-01

    Full Text Available . In this paper, diurnal brightness temperatures received from the METEOSAT Second Generation (MSG) satellite were interpolated for missing data based on a model, and a performance test was performed by comparing a new approach based on robust modelling...

  14. A Magnetic Bright Point Case Study

    Czech Academy of Sciences Publication Activity Database

    Utz, D.; Jurčák, Jan; Bellot Rubio, L.; del Toro Iniesta, J.C.; Thonhofer, S.; Hanslmeier, A.; Veronig, A.; Muller, R.; Lemmerer, B.

    2013-01-01

    Roč. 37, č. 2 (2013), s. 459-470 ISSN 1845-8319. [Hvar Astrophysical Colloquium /12./. Hvar, 03.09.2012-07.09.2012] R&D Projects: GA MŠk(CZ) MEB061109 Institutional support: RVO:67985815 Keywords : solar magnetic field * magnetic bright points * sunrise/IMaX Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  15. Microwave brightness temperature imaging and dielectric properties ...

    Indian Academy of Sciences (India)

    material collected by former Soviet Union robots and Apollo astronauts. With the completion of the first round of lunar exploration by human beings, the study of lunar microwave brightness tempe- rature was completely forgotten. Accompanied by a new upcoming era of lunar exploration and the development of science and ...

  16. Human CD56bright NK Cells

    DEFF Research Database (Denmark)

    Michel, Tatiana; Poli, Aurélie; Cuapio, Angelica

    2016-01-01

    Human NK cells can be subdivided into various subsets based on the relative expression of CD16 and CD56. In particular, CD56(bright)CD16(-/dim) NK cells are the focus of interest. They are considered efficient cytokine producers endowed with immunoregulatory properties, but they can also become...

  17. A Bright Future for Magnetic Resonance

    Indian Academy of Sciences (India)

    IAS Admin

    Does magnetic resonance have a bright future? Ever since magnetic resonance in condensed phase started in 1945, questions about its future prospects (or its imminent doom) have been asked time and again. Some, like Nicolaas Bloembergen, left the field at an early stage because they felt there was no hope to gather ...

  18. Simultaneous brightness contrast of foraging Papilio butterflies

    Science.gov (United States)

    Kinoshita, Michiyo; Takahashi, Yuki; Arikawa, Kentaro

    2012-01-01

    This study focuses on the sense of brightness in the foraging Japanese yellow swallowtail butterfly, Papilio xuthus. We presented two red discs of different intensity on a grey background to butterflies, and trained them to select one of the discs. They were successfully trained to select either a high intensity or a low intensity disc. The trained butterflies were tested on their ability to perceive brightness in two different protocols: (i) two orange discs of different intensity presented on the same intensity grey background and (ii) two orange discs of the same intensity separately presented on a grey background that was either higher or lower in intensity than the training background. The butterflies trained to high intensity red selected the orange disc of high intensity in protocol 1, and the disc on the background of low intensity grey in protocol 2. We obtained similar results in another set of experiments with purple discs instead of orange discs. The choices of the butterflies trained to low intensity red were opposite to those just described. Taken together, we conclude that Papilio has the ability to learn brightness and darkness of targets independent of colour, and that they have the so-called simultaneous brightness contrast. PMID:22179808

  19. Conservation of an ion beam brightness. Study of a non brightness disturbing lens

    International Nuclear Information System (INIS)

    Bernard, P.

    1966-11-01

    Experimental studies of ion sources prove that large initial brightnesses can be obtained by using the plasma expansion principle. However these brightnesses are usually spoiled by the beam focusing and accelerating systems. A high intensity focusing set up is first theoretically studied, then numerically determined by use of a 7094 IBM computer. Aberrations have been minimized. It has then been possible to construct a set up conserving the source initial brightness. For a 100 mA beam the focusing voltage is 150 kV, the beam study has been done for 350 keV beam final energy. Given is a discussion of results. (author) [fr

  20. Travelling gradient thermocouple calibration

    International Nuclear Information System (INIS)

    Broomfield, G.H.

    1975-01-01

    A short discussion of the origins of the thermocouple EMF is used to re-introduce the idea that the Peltier and Thompson effects are indistinguishable from one another. Thermocouples may be viewed as devices which generate an EMF at junctions or as integrators of EMF's developed in thermal gradients. The thermal gradient view is considered the more appropriate, because of its better accord with theory and behaviour, the correct approach to calibration, and investigation of service effects is immediately obvious. Inhomogeneities arise in thermocouples during manufacture and in service. The results of travelling gradient measurements are used to show that such effects are revealed with a resolution which depends on the length of the gradient although they may be masked during simple immersion calibration. Proposed tests on thermocouples irradiated in a nuclear reactor are discussed

  1. Gradient field microscopy of unstained specimens.

    Science.gov (United States)

    Kim, Taewoo; Sridharan, Shamira; Popescu, Gabriel

    2012-03-12

    We present a phase derivative microscopy technique referred to as gradient field microscopy (GFM), which provides the first-order derivatives of the phase associated with an optical field passing through a transparent specimen. GFM utilizes spatial light modulation at the Fourier plane of a bright field microscope to optically obtain the derivatives of the phase and increase the contrast of the final image. The controllable spatial modulation pattern allows us to obtain both one component of the field gradient (derivative along one direction) and the gradient intensity, which offers some advantages over the regular differential interference contrast (DIC) microscopy. Most importantly, unlike DIC, GFM does not use polarizing optics and, thus, it is applicable to birefringent samples. We demonstrate these features of GFM with studies of static and dynamic biological cells (HeLa cells and red blood cells). We show that GFM is capable of qualitatively providing information about cell membrane fluctuations. Specifically, we captured the disappearance of the bending mode of fluctuations in osmotically swollen red blood cells.

  2. Shape reconstruction from gradient data.

    Science.gov (United States)

    Ettl, Svenja; Kaminski, Jürgen; Knauer, Markus C; Häusler, Gerd

    2008-04-20

    We present a generalized method for reconstructing the shape of an object from measured gradient data. A certain class of optical sensors does not measure the shape of an object but rather its local slope. These sensors display several advantages, including high information efficiency, sensitivity, and robustness. For many applications, however, it is necessary to acquire the shape, which must be calculated from the slopes by numerical integration. Existing integration techniques show drawbacks that render them unusable in many cases. Our method is based on an approximation employing radial basis functions. It can be applied to irregularly sampled, noisy, and incomplete data, and it reconstructs surfaces both locally and globally with high accuracy.

  3. Gradient Alloy for Optical Packaging

    Data.gov (United States)

    National Aeronautics and Space Administration — Advances in additive manufacturing, such as Laser Engineered Net Shaping (LENS), enables the fabrication of compositionally gradient microstructures, i.e. gradient...

  4. Gold nanoclusters with bright near-infrared photoluminescence.

    Science.gov (United States)

    Pramanik, Goutam; Humpolickova, Jana; Valenta, Jan; Kundu, Paromita; Bals, Sara; Bour, Petr; Dracinsky, Martin; Cigler, Petr

    2018-02-22

    The increase in nonradiative pathways with decreasing emission energy reduces the luminescence quantum yield (QY) of near-infrared photoluminescent (NIR PL) metal nanoclusters. Efficient surface ligand chemistry can significantly improve the luminescence QY of NIR PL metal nanoclusters. In contrast to the widely reported but modestly effective thiolate ligand-to-metal core charge transfer, we show that metal-to-ligand charge transfer (MLCT) can be used to greatly enhance the luminescence QY of NIR PL gold nanoclusters (AuNCs). We synthesized water-soluble and colloidally stable NIR PL AuNCs with unprecedentedly high QY (∼25%) upon introduction of triphenylphosphonium moieties into the surface capping layer. By using a combination of spectroscopic and theoretical methods, we provide evidence for gold core-to-ligand charge transfer occurring in AuNCs. We envision that this work can stimulate the development of these unusually bright AuNCs for promising optoelectronic, bioimaging, and other applications.

  5. Circadian Phase-Shifting Effects of Bright Light, Exercise, and Bright Light + Exercise.

    Science.gov (United States)

    Youngstedt, Shawn D; Kline, Christopher E; Elliott, Jeffrey A; Zielinski, Mark R; Devlin, Tina M; Moore, Teresa A

    2016-02-26

    Limited research has compared the circadian phase-shifting effects of bright light and exercise and additive effects of these stimuli. The aim of this study was to compare the phase-delaying effects of late night bright light, late night exercise, and late evening bright light followed by early morning exercise. In a within-subjects, counterbalanced design, 6 young adults completed each of three 2.5-day protocols. Participants followed a 3-h ultra-short sleep-wake cycle, involving wakefulness in dim light for 2h, followed by attempted sleep in darkness for 1 h, repeated throughout each protocol. On night 2 of each protocol, participants received either (1) bright light alone (5,000 lux) from 2210-2340 h, (2) treadmill exercise alone from 2210-2340 h, or (3) bright light (2210-2340 h) followed by exercise from 0410-0540 h. Urine was collected every 90 min. Shifts in the 6-sulphatoxymelatonin (aMT6s) cosine acrophase from baseline to post-treatment were compared between treatments. Analyses revealed a significant additive phase-delaying effect of bright light + exercise (80.8 ± 11.6 [SD] min) compared with exercise alone (47.3 ± 21.6 min), and a similar phase delay following bright light alone (56.6 ± 15.2 min) and exercise alone administered for the same duration and at the same time of night. Thus, the data suggest that late night bright light followed by early morning exercise can have an additive circadian phase-shifting effect.

  6. X-ray surface brightness of Kepler's supernova remnant

    International Nuclear Information System (INIS)

    White, R.L.; Long, K.S.

    1983-01-01

    We have observed Kepler's supernova remnant (SNR) with the imaging instruments on board the Einstein Observatory. The 0.15-4.5 keV flux incident on the Earth is 1.2 x 10 - 10 ergs cm - 2 s - 1 ; the flux corrected for interstellar absorption is 3.4 x 10 - 10 ergs cm - 2 s - 1 (L/sub x/ = 1.0 x 10 36 ergs s - 1 at D = 5 kpc) if the absorbing column density is N/sub H/ = 2.8 x 10 21 cm - 2 . The remnant is circular and shows a strong shell which is at least 5 times brighter in the north than in the south. The X-ray observations do not unambiguously determine whether the remnant is in the adiabatic or the free expansion phase. If the remnant is in the adiabatic phase, the density of the interstellar medium (ISM) ( 2 /sub e/>/sup 1/2/) surrounding Kepler's SNR must be about 5 cm - 3 . If the remnant is in the free expansion phase, where most of the emission arises from shock-heated ejecta, the ISM density must still be relatively high, n/sub i/> or approx. =0.1 cm - 3 . Even if the ISM is very inhomogeneous, with very many small, dense clouds, we show that the mean density of the ISM must be greater than approx.0.1 cm - 3 . In any case, the density of the x-ray emitting gas must be high ( 2 /sub e/>/sup 1/2/ > or approx. =10 cm - 3 ), and the temperature must be fairly low (T/sub e/ 7 K). The relatively high ISM density which is required is surprising in view of Kepler's distance above the galactic plane, approx.600 pc. Possibly the ISM around Kepler's SNR and around other type i SNRs is dominated by the mass lost from the presupernova star

  7. Rediscovering the Giant Low Surface Brightness Spiral Galaxy Malin 1

    Science.gov (United States)

    Galaz, Gaspar

    2018-01-01

    I summarize the latest discoveries regarding this ramarkable diffuse and giant galaxy, the largest single spiral in the universe so far. I describe how the latest discoveries could have been done easily 20 years ago, but an incredible summation of facts and some astronomical sociology, keeped many of them undisclosed. I present the most conspicuous features of the giant spiral arms of Malin 1, including stellar density, colors, stellar populations and some modeling describing their past evolution to the current state. I conclude with pending issues regarding stellar formation in Malin 1, and the efforts to detect its elusive molecular gas.

  8. Giant Low Surface Brightness Galaxies: Evolution in Isolation

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... These galaxies have very massive dark matter halos that also contribute to their stability and lack of evolution. In this paper we briefly review the properties of this unique class of galaxies and conclude that both their isolation and their massive dark matter halos have led to the low star formation rates and ...

  9. Spectrophotometry of four galaxies of high surface brightness

    International Nuclear Information System (INIS)

    Arakelyan, M.A.; Magtesyan, A.P.

    1982-01-01

    Spectrophotometry has been performed for the emission lines in the nuclei of Arakelyan galaxies Nos. 428, 449, 454, 532. In the first two objects, H II clouds occur roughly-equal2 kpc out from the nucleus. No. 449 may contain another cloud moving at roughly-equal1500 km/sec radial velocity. radial

  10. Deep learning for galaxy surface brightness profile fitting

    Science.gov (United States)

    Tuccillo, D.; Huertas-Company, M.; Decencière, E.; Velasco-Forero, S.; Domínguez Sánchez, H.; Dimauro, P.

    2018-03-01

    Numerous ongoing and future large area surveys (e.g. Dark Energy Survey, EUCLID, Large Synoptic Survey Telescope, Wide Field Infrared Survey Telescope) will increase by several orders of magnitude the volume of data that can be exploited for galaxy morphology studies. The full potential of these surveys can be unlocked only with the development of automated, fast, and reliable analysis methods. In this paper, we present DeepLeGATo, a new method for 2-D photometric galaxy profile modelling, based on convolutional neural networks. Our code is trained and validated on analytic profiles (HST/CANDELS F160W filter) and it is able to retrieve the full set of parameters of one-component Sérsic models: total magnitude, effective radius, Sérsic index, and axis ratio. We show detailed comparisons between our code and GALFIT. On simulated data, our method is more accurate than GALFIT and ˜3000 time faster on GPU (˜50 times when running on the same CPU). On real data, DeepLeGATo trained on simulations behaves similarly to GALFIT on isolated galaxies. With a fast domain adaptation step made with the 0.1-0.8 per cent the size of the training set, our code is easily capable to reproduce the results obtained with GALFIT even on crowded regions. DeepLeGATo does not require any human intervention beyond the training step, rendering it much automated than traditional profiling methods. The development of this method for more complex models (two-component galaxies, variable point spread function, dense sky regions) could constitute a fundamental tool in the era of big data in astronomy.

  11. Velocity bunching of high-brightness electron beams

    Directory of Open Access Journals (Sweden)

    S. G. Anderson

    2005-01-01

    Full Text Available Velocity bunching has been recently proposed as a tool for compressing electron beam pulses in modern high brightness photoinjector sources. This tool is familiar from earlier schemes implemented for bunching dc electron sources, but presents peculiar challenges when applied to high current, low emittance beams from photoinjectors. The main difficulty foreseen is control of emittance oscillations in the beam in this scheme, which can be naturally considered as an extension of the emittance compensation process at moderate energies. This paper presents two scenarios in which velocity bunching, combined with emittance control, is to play a role in nascent projects. The first is termed ballistic bunching, where the changing of relative particle velocities and positions occur in distinct regions, a short high gradient linac, and a drift length. This scenario is discussed in the context of the proposed ORION photoinjector. Simulations are used to explore the relationship between the degree of bunching, and the emittance compensation process. Experimental measurements performed at the UCLA Neptune Laboratory of the surprisingly robust bunching process, as well as accompanying deleterious transverse effects, are presented. An unanticipated mechanism for emittance growth in bends for highly momentum chirped beam was identified and studied in these experiments. The second scenario may be designated as phase space rotation, and corresponds closely to the recent proposal of Ferrario and Serafini. Its implementation for the compression of the electron beam pulse length in the PLEIADES inverse Compton scattering (ICS experiment at LLNL is discussed. It is shown in simulations that optimum compression may be obtained by manipulation of the phases in low gradient traveling wave accelerator sections. Measurements of the bunching and emittance control achieved in such an implementation at PLEIADES, as well as aspects of the use of velocity-bunched beam directly

  12. TC4 AMPR BRIGHTNESS TEMPERATURE (TB) V1

    Data.gov (United States)

    National Aeronautics and Space Administration — The TC4 AMPR Brightness Temperature (TB) dataset consists of brightness temperature data from July 19, 2007 through August 8, 2007. The Tropical Composition, Cloud...

  13. Australia 31-GHz brightness temperature exceedance statistics

    Science.gov (United States)

    Gary, B. L.

    1988-01-01

    Water vapor radiometer measurements were made at DSS 43 during an 18 month period. Brightness temperatures at 31 GHz were subjected to a statistical analysis which included correction for the effects of occasional water on the radiometer radome. An exceedance plot was constructed, and the 1 percent exceedance statistics occurs at 120 K. The 5 percent exceedance statistics occurs at 70 K, compared with 75 K in Spain. These values are valid for all of the three month groupings that were studied.

  14. Extreme Ultraviolet Explorer Bright Source List

    Science.gov (United States)

    Malina, Roger F.; Marshall, Herman L.; Antia, Behram; Christian, Carol A.; Dobson, Carl A.; Finley, David S.; Fruscione, Antonella; Girouard, Forrest R.; Hawkins, Isabel; Jelinsky, Patrick

    1994-01-01

    Initial results from the analysis of the Extreme Ultraviolet Explorer (EUVE) all-sky survey (58-740 A) and deep survey (67-364 A) are presented through the EUVE Bright Source List (BSL). The BSL contains 356 confirmed extreme ultraviolet (EUV) point sources with supporting information, including positions, observed EUV count rates, and the identification of possible optical counterparts. One-hundred twenty-six sources have been detected longward of 200 A.

  15. High-brightness H/sup -/ accelerators

    International Nuclear Information System (INIS)

    Jameson, R.A.

    1987-01-01

    Neutral particle beam (NPB) devices based on high-brightness H/sup -/ accelerators are an important component of proposed strategic defense systems. The basic rational and R and D program are outlined and examples given of the underlying technology thrusts toward advanced systems. Much of the research accomplished in the past year is applicable to accelerator systems in general; some of these activities are discussed

  16. Measuring night sky brightness: methods and challenges

    Science.gov (United States)

    Hänel, Andreas; Posch, Thomas; Ribas, Salvador J.; Aubé, Martin; Duriscoe, Dan; Jechow, Andreas; Kollath, Zoltán; Lolkema, Dorien E.; Moore, Chadwick; Schmidt, Norbert; Spoelstra, Henk; Wuchterl, Günther; Kyba, Christopher C. M.

    2018-01-01

    Measuring the brightness of the night sky has become an increasingly important topic in recent years, as artificial lights and their scattering by the Earth's atmosphere continue spreading around the globe. Several instruments and techniques have been developed for this task. We give an overview of these, and discuss their strengths and limitations. The different quantities that can and should be derived when measuring the night sky brightness are discussed, as well as the procedures that have been and still need to be defined in this context. We conclude that in many situations, calibrated consumer digital cameras with fisheye lenses provide the best relation between ease-of-use and wealth of obtainable information on the night sky. While they do not obtain full spectral information, they are able to sample the complete sky in a period of minutes, with colour information in three bands. This is important, as given the current global changes in lamp spectra, changes in sky radiance observed only with single band devices may lead to incorrect conclusions regarding long term changes in sky brightness. The acquisition of all-sky information is desirable, as zenith-only information does not provide an adequate characterization of a site. Nevertheless, zenith-only single-band one-channel devices such as the "Sky Quality Meter" continue to be a viable option for long-term studies of night sky brightness and for studies conducted from a moving platform. Accurate interpretation of such data requires some understanding of the colour composition of the sky light. We recommend supplementing long-term time series derived with such devices with periodic all-sky sampling by a calibrated camera system and calibrated luxmeters or luminance meters.

  17. Companions of Bright Barred Shapley Ames Galaxies

    OpenAIRE

    Garcia-Barreto, J. Antonio; Carrillo, Rene; Vera-Villamizar, Nelson

    2003-01-01

    Companion galaxy environment for a subset of 78 bright and nearby barred galaxies from the Shapley Ames Catalog is presented. Among spiral barred galaxies there are Seyfert galaxies, galaxies with circumnuclear structures, galaxies not associated with any large scale galaxy cloud structure, galaxies with peculiar disk morphology (crooked arms) and galaxies with normal disk morphology; the list includes all Hubble types. The companion galaxy list includes number of companion galaxies within 20...

  18. Modular Zero Energy. BrightBuilt Home

    Energy Technology Data Exchange (ETDEWEB)

    Aldrich, Robb [Steven Winter Associates, Inc., Norwalk, CT (United States); Butterfield, Karla [Steven Winter Associates, Inc., Norwalk, CT (United States)

    2016-03-01

    With funding from the Building America Program, part of the U.S. Department of Energy Building Technologies Office, the Consortium for Advanced Residential Buildings (CARB) worked with BrightBuilt Home (BBH) to evaluate and optimize building systems. CARB’s work focused on a home built by Black Bros. Builders in Lincolnville, Maine (International Energy Conservation Code Climate Zone 6). As with most BBH projects to date, modular boxes were built by Keiser Homes in Oxford, Maine.

  19. The Bright SHARC Survey: The Cluster Catalog

    Science.gov (United States)

    Romer, A. K.; Nichol, R. C.; Holden, B. P.; Ulmer, M. P.; Pildis, R. A.; Merrelli, A. J.; Adami, C.; Burke, D. J.; Collins, C. A.; Metevier, A. J.; Kron, R. G.; Commons, K.

    2000-02-01

    We present the Bright SHARC (Serendipitous High-Redshift Archival ROSAT Cluster) Survey, which is an objective search for serendipitously detected extended X-ray sources in 460 deep ROSAT PSPC pointings. The Bright SHARC Survey covers an area of 178.6 deg2 and has yielded 374 extended sources. We discuss the X-ray data reduction, the candidate selection and present results from our on-going optical follow-up campaign. The optical follow-up concentrates on the brightest 94 of the 374 extended sources and is now 97% complete. We have identified 37 clusters of galaxies, for which we present redshifts and luminosities. The clusters span a redshift range of 0.0696Bright SHARC clusters have not been listed in any previously published catalog. We also report the discovery of three candidate ``fossil groups'' of the kind proposed by Ponman et al. Based on data taken at the European Southern Observatory, Kitt Peak National Observatory, Cerro Tololo Inter-American Observatory, Canada-France-Hawaii, and Apache Point Observatory.

  20. Possible Bright Starspots on TRAPPIST-1

    Science.gov (United States)

    Morris, Brett M.; Agol, Eric; Davenport, James R. A.; Hawley, Suzanne L.

    2018-04-01

    The M8V star TRAPPIST-1 hosts seven roughly Earth-sized planets and is a promising target for exoplanet characterization. Kepler/K2 Campaign 12 observations of TRAPPIST-1 in the optical show an apparent rotational modulation with a 3.3-day period, though that rotational signal is not readily detected in the Spitzer light curve at 4.5 μm. If the rotational modulation is due to starspots, persistent dark spots can be excluded from the lack of photometric variability in the Spitzer light curve. We construct a photometric model for rotational modulation due to photospheric bright spots on TRAPPIST-1 that is consistent with both the Kepler and Spitzer light curves. The maximum-likelihood model with three spots has typical spot sizes of R spot/R ⋆ ≈ 0.004 at temperature T spot ≳ 5300 ± 200 K. We also find that large flares are observed more often when the brightest spot is facing the observer, suggesting a correlation between the position of the bright spots and flare events. In addition, these flares may occur preferentially when the spots are increasing in brightness, which suggests that the 3.3-day periodicity may not be a rotational signal, but rather a characteristic timescale of active regions.

  1. Personal audio with a planar bright zone.

    Science.gov (United States)

    Coleman, Philip; Jackson, Philip J B; Olik, Marek; Pedersen, Jan Abildgaard

    2014-10-01

    Reproduction of multiple sound zones, in which personal audio programs may be consumed without the need for headphones, is an active topic in acoustical signal processing. Many approaches to sound zone reproduction do not consider control of the bright zone phase, which may lead to self-cancellation problems if the loudspeakers surround the zones. Conversely, control of the phase in a least-squares sense comes at a cost of decreased level difference between the zones and frequency range of cancellation. Single-zone approaches have considered plane wave reproduction by focusing the sound energy in to a point in the wavenumber domain. In this article, a planar bright zone is reproduced via planarity control, which constrains the bright zone energy to impinge from a narrow range of angles via projection in to a spatial domain. Simulation results using a circular array surrounding two zones show the method to produce superior contrast to the least-squares approach, and superior planarity to the contrast maximization approach. Practical performance measurements obtained in an acoustically treated room verify the conclusions drawn under free-field conditions.

  2. Brightness illusion in the guppy (Poecilia reticulata).

    Science.gov (United States)

    Agrillo, Christian; Miletto Petrazzini, Maria Elena; Bisazza, Angelo

    2016-02-01

    A long-standing debate surrounds the issue of whether human and nonhuman species share similar perceptual mechanisms. One experimental strategy to compare visual perception of vertebrates consists in assessing how animals react in the presence of visual illusions. To date, this methodological approach has been widely used with mammals and birds, while few studies have been reported in distantly related species, such as fish. In the present study we investigated whether fish perceive the brightness illusion, a well-known illusion occurring when 2 objects, identical in physical features, appear to be different in brightness. Twelve guppies (Poecilia reticulata) were initially trained to discriminate which rectangle was darker or lighter between 2 otherwise identical rectangles. Three different conditions were set up: neutral condition between rectangle and background (same background used for both darker and lighter rectangle); congruent condition (darker rectangle in a darker background and lighter rectangle in a lighter background); and incongruent condition (darker rectangle in a lighter background and lighter rectangle in a darker background). After reaching the learning criterion, guppies were presented with the illusory pattern: 2 identical rectangles inserted in 2 different backgrounds. Guppies previously trained to select the darker rectangle showed a significant choice of the rectangle that appears to be darker by human observers (and vice versa). The human-like performance exhibited in the presence of the illusory pattern suggests the existence of similar perceptual mechanisms between humans and fish to elaborate the brightness of objects. (c) 2016 APA, all rights reserved).

  3. Infrared image detail enhancement based on the gradient field specification.

    Science.gov (United States)

    Zhao, Wenda; Xu, Zhijun; Zhao, Jian; Zhao, Fan; Han, Xizhen

    2014-07-01

    Human vision is sensitive to the changes of local image details, which are actually image gradients. To enhance faint infrared image details, this article proposes a gradient field specification algorithm. First we define the image gradient field and gradient histogram. Then, by analyzing the characteristics of the gradient histogram, we construct a Gaussian function to obtain the gradient histogram specification and therefore obtain the transform gradient field. In addition, subhistogram equalization is proposed based on the histogram equalization to improve the contrast of infrared images. The experimental results show that the algorithm can effectively improve image contrast and enhance weak infrared image details and edges. As a result, it can give qualified image information for different applications of an infrared image. In addition, it can also be applied to enhance other types of images such as visible, medical, and lunar surface.

  4. Aqueous origins of bright salt deposits on Ceres

    Science.gov (United States)

    Zolotov, Mikhail Yu.

    2017-11-01

    Bright materials have been reported in association with impact craters on Ceres. The abundant Na2CO3 and some ammonium salts, NH4HCO3 and/or NH4Cl, were detected in bright deposits within Occator crater with Dawn near infrared spectroscopy. The composition and appearance of the salts suggest their aqueous mobilization and emplacement after formation of the crater. Here we consider origins of the bright deposits through calculation of speciation in the H-C-N-O-Na-Cl water-salt type system constrained by the mass balance of observed salts. Calculations of chemical equilibria show that initial solutions had the pH of ∼10. The temperature and salinity of solutions could have not exceeded ∼273 K and ∼100 g per kg H2O, respectively. Freezing models reveal an early precipitation of Na2CO3·10H2O followed by minor NaHCO3. Ammonium salts precipitate near eutectic from brines enriched in NH4+, Cl- and Na+. A late-stage precipitation of NaCl·2H2O is modeled for solution compositions with added NaCl. Calculated eutectics are above 247 K. The apparently unabundant ammonium and chloride salts in Occator's deposits imply a rapid emplacement without a compositional evolution of solution. Salty ice grains could have deposited from post-impact ballistic plumes formed through low-pressure boiling of subsurface solutions. Hydrated and ammonium salts are unstable at maximum temperatures of Ceres' surface and could decompose through space weathering. Occator's ice-free salt deposits formed through a post-depositional sublimation of ice followed by dehydration of Na2CO3·10H2O and NaHCO3 to Na2CO3. In other regions, excavated and exposed bright materials could be salts initially deposited from plumes and accumulated at depth via post-impact boiling. The lack of detection of sulfates and an elevated carbonate/chloride ratio in Ceres' materials suggest an involvement of compounds abundant in the outer solar system.

  5. Uniform gradient expansions

    Directory of Open Access Journals (Sweden)

    Massimo Giovannini

    2015-06-01

    Full Text Available Cosmological singularities are often discussed by means of a gradient expansion that can also describe, during a quasi-de Sitter phase, the progressive suppression of curvature inhomogeneities. While the inflationary event horizon is being formed the two mentioned regimes coexist and a uniform expansion can be conceived and applied to the evolution of spatial gradients across the protoinflationary boundary. It is argued that conventional arguments addressing the preinflationary initial conditions are necessary but generally not sufficient to guarantee a homogeneous onset of the conventional inflationary stage.

  6. Uniform gradient expansions

    CERN Document Server

    Giovannini, Massimo

    2015-01-01

    Cosmological singularities are often discussed by means of a gradient expansion that can also describe, during a quasi-de Sitter phase, the progressive suppression of curvature inhomogeneities. While the inflationary event horizon is being formed the two mentioned regimes coexist and a uniform expansion can be conceived and applied to the evolution of spatial gradients across the protoinflationary boundary. It is argued that conventional arguments addressing the preinflationary initial conditions are necessary but generally not sufficient to guarantee a homogeneous onset of the conventional inflationary stage.

  7. High gradient superconducting quadrupoles

    International Nuclear Information System (INIS)

    Lundy, R.A.; Brown, B.C.; Carson, J.A.; Fisk, H.E.; Hanft, R.H.; Mantsch, P.M.; McInturff, A.D.; Remsbottom, R.H.

    1987-07-01

    Prototype superconducting quadrupoles with a 5 cm aperture and gradient of 16 kG/cm have been built and tested as candidate magnets for the final focus at SLC. The magnets are made from NbTi Tevatron style cable with 10 inner and 14 outer turns per quadrant. Quench performance and multipole data are presented. Design and data for a low current, high gradient quadrupole, similar in cross section but wound with a cable consisting of five insulated conductors are also discussed

  8. Experimental results in superconducting niobium resonators for high-brightness ion beam acceleration

    International Nuclear Information System (INIS)

    Delayen, J.R.; Bohn, C.L.; Roche, C.T.

    1991-01-01

    Two niobium resonant cavities for high-brightness ion beam acceleration have been constructed and tested. The first was based on a coaxial quarter-wave geometry and was optimized for phase velocity β O = O.15. This cavity, which resonates at 400 MHz in the fundamental mode, operated at an average (wall-to-wall) accelerating gradient of 12.9 MV/m under continuous-wave (cw) fields. At this gradient, a cavity Q of 1.4x10 8 was measured. The second was based on a coaxial half-wave geometry and was optimized for β O = 0.12. This cavity, which resonates at 355 MHz in the fundamental mode, operated at an average accelerating gradient of 18.0 MV/m under cw fields. This is the highest average accelerating gradient achieved to date in low-velocity structures designed for cw operation. At this gradient, a cavity Q of 1.2 x 10 8 was measured

  9. 7 CFR 51.2000 - Clean and bright.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Clean and bright. 51.2000 Section 51.2000 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Standards for Grades of Filberts in the Shell 1 Definitions § 51.2000 Clean and bright. Clean and bright...

  10. Active Processes: Bright Streaks and Dark Fans

    Science.gov (United States)

    2007-01-01

    [figure removed for brevity, see original site] [figure removed for brevity, see original site] Figure 1Figure 2 In a region of the south pole known informally as 'Ithaca' numerous fans of dark frost form every spring. HiRISE collected a time lapse series of these images, starting at Ls = 185 and culminating at Ls = 294. 'Ls' is the way we measure time on Mars: at Ls = 180 the sun passes the equator on its way south; at Ls = 270 it reaches its maximum subsolar latitude and summer begins. In the earliest image (figure 1) fans are dark, but small narrow bright streaks can be detected. In the next image (figure 2), acquired at Ls = 187, just 106 hours later, dramatic differences are apparent. The dark fans are larger and the bright fans are more pronounced and easily detectable. The third image in the sequence shows no bright fans at all. We believe that the bright streaks are fine frost condensed from the gas exiting the vent. The conditions must be just right for the bright frost to condense. Observation Geometry Image PSP_002622_0945 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on 16-Feb-2007. The complete image is centered at -85.2 degrees latitude, 181.5 degrees East longitude. The range to the target site was 246.9 km (154.3 miles). At this distance the image scale is 49.4 cm/pixel (with 2 x 2 binning) so objects 148 cm across are resolved. The image shown here has been map-projected to 50 cm/pixel . The image was taken at a local Mars time of 05:46 PM and the scene is illuminated from the west with a solar incidence angle of 88 degrees, thus the sun was about 2 degrees above the horizon. At a solar longitude of 185.1 degrees, the season on Mars is Northern Autumn.

  11. Generating substrate bound functional chemokine gradients in vitro

    DEFF Research Database (Denmark)

    Hjortø, Gertrud Malene; Hansen, Morten; Larsen, Niels Bent

    2009-01-01

    Microcontact printing (mCP) is employed to generate discontinuous microscale gradients of active fractalkine, a chemokine expressed by endothelial cells near sites of inflammation where it is believed to form concentration gradients descending away from the inflamed area. In vivo, fractalkine is ...... surface-bound chemokines (haptotactic gradients). The use of a capture antibody facilitates control of the orientation of tagged molecules, thereby ensuring a high degree of bio-functionality through correct presentation and reduced protein denaturation....

  12. BRITE-Constellation: Nanosatellites for precision photometry of bright stars

    Science.gov (United States)

    Weiss, W. W.; Moffat, A. F. J.; Schwarzenberg-Czerny, A.; Koudelka, O. F.; Grant, C. C.; Zee, R. E.; Kuschnig, R.; Mochnacki, St.; Rucinski, S. M.; Matthews, J. M.; Orleański, P.; Pamyatnykh, A. A.; Pigulski, A.; Alves, J.; Guedel, M.; Handler, G.; Wade, G. A.; Scholtz, A. L.; Scholtz

    2014-02-01

    will be selected is shown in Fig. 1. This sample falls into two principal classes of stars: (1) Hot luminous H-burning stars (O to F stars). Analyses of OB star variability have the potential to help solve two outstanding problems: the sizes of convective (mixed) cores in massive stars and the influence of rapid rotation on their structure and evolution. (2) Cool luminous stars (AGB stars, cool giants and cool supergiants). Measurements of the time scales involved in surface granulation and differential rotation will constrain turbulent convection models. Mass loss from these stars (especially the massive supernova progenitors) is a major contributor to the evolution of the interstellar medium, so in a sense, this sample dominates cosmic ``ecology'' in terms of future generations of star formation. The massive stars are believed to share many characteristics of the lower mass range of the first generation of stars ever formed (although the original examples are of course long gone). BRITE observations will also be used to detect some Jupiter- and even Neptune-sized planets around bright host stars via transits, as expected on the basis of statistics from the Kepler exoplanet mission. Detecting planets around such very bright stars will greatly facilitate their subsequent characterization. BRITE will also use surface spots to investigate stellar rotation. The following Table summarizes launch and orbit parameters of BRITE-Constellation components. The full version of this paper describing in more detail BRITE-Constellation will be published separately in a journal. The symposium presentation is available at http://iaus301.astro.uni.wroc.pl/program.php

  13. Electromagnetically induced transparency control in terahertz metasurfaces based on bright-bright mode coupling

    Science.gov (United States)

    Yahiaoui, R.; Burrow, J. A.; Mekonen, S. M.; Sarangan, A.; Mathews, J.; Agha, I.; Searles, T. A.

    2018-04-01

    We demonstrate a classical analog of electromagnetically induced transparency (EIT) in a highly flexible planar terahertz metamaterial (MM) comprised of three-gap split-ring resonators. The keys to achieve EIT in this system are the frequency detuning and hybridization processes between two bright modes coexisting in the same unit cell as opposed to bright-dark modes. We present experimental verification of two bright modes coupling for a terahertz EIT-MM in the context of numerical results and theoretical analysis based on a coupled Lorentz oscillator model. In addition, a hybrid variation of the EIT-MM is proposed and implemented numerically to dynamically tune the EIT window by incorporating photosensitive silicon pads in the split gap region of the resonators. As a result, this hybrid MM enables the active optical control of a transition from the on state (EIT mode) to the off state (dipole mode).

  14. Large-area and bright pulsed electroluminescence in monolayer semiconductors

    KAUST Repository

    Lien, Der-Hsien

    2018-04-04

    Transition-metal dichalcogenide monolayers have naturally terminated surfaces and can exhibit a near-unity photoluminescence quantum yield in the presence of suitable defect passivation. To date, steady-state monolayer light-emitting devices suffer from Schottky contacts or require complex heterostructures. We demonstrate a transient-mode electroluminescent device based on transition-metal dichalcogenide monolayers (MoS, WS, MoSe, and WSe) to overcome these problems. Electroluminescence from this dopant-free two-terminal device is obtained by applying an AC voltage between the gate and the semiconductor. Notably, the electroluminescence intensity is weakly dependent on the Schottky barrier height or polarity of the contact. We fabricate a monolayer seven-segment display and achieve the first transparent and bright millimeter-scale light-emitting monolayer semiconductor device.

  15. Investigating the Bright End of LSST Photometry

    Science.gov (United States)

    Ojala, Elle; Pepper, Joshua; LSST Collaboration

    2018-01-01

    The Large Synoptic Survey Telescope (LSST) will begin operations in 2022, conducting a wide-field, synoptic multiband survey of the southern sky. Some fraction of objects at the bright end of the magnitude regime observed by LSST will overlap with other wide-sky surveys, allowing for calibration and cross-checking between surveys. The LSST is optimized for observations of very faint objects, so much of this data overlap will be comprised of saturated images. This project provides the first in-depth analysis of saturation in LSST images. Using the PhoSim package to create simulated LSST images, we evaluate saturation properties of several types of stars to determine the brightness limitations of LSST. We also collect metadata from many wide-field photometric surveys to provide cross-survey accounting and comparison. Additionally, we evaluate the accuracy of the PhoSim modeling parameters to determine the reliability of the software. These efforts will allow us to determine the expected useable data overlap between bright-end LSST images and faint-end images in other wide-sky surveys. Our next steps are developing methods to extract photometry from saturated images.This material is based upon work supported in part by the National Science Foundation through Cooperative Agreement 1258333 managed by the Association of Universities for Research in Astronomy (AURA), and the Department of Energy under Contract No. DE-AC02-76SF00515 with the SLAC National Accelerator Laboratory. Additional LSST funding comes from private donations, grants to universities, and in-kind support from LSSTC Institutional Members.Thanks to NSF grant PHY-135195 and the 2017 LSSTC Grant Award #2017-UG06 for making this project possible.

  16. An exceptionally bright, compact starburst nucleus

    Science.gov (United States)

    Margon, Bruce; Anderson, Scott F.; Mateo, Mario; Fich, Michel; Massey, Philip

    1988-01-01

    Observations are reported of a remarkably bright (V about 13) starburst nucleus, 0833 + 652, which has been detected at radio, infrared, optical, ultraviolet, and X-ray wavelengths. Despite an observed flux at each of these wavelengths which is comparable to that of NGC 7714, often considered the 'prototypical' example of the starburst phenomenon, 0833 + 652 appears to be a previously uncataloged object. Its ease of detectability throughout the electromagnetic spectrum should make it useful for a variety of problems in the study of compact emission-line galaxies.

  17. Structures and Strength of Gradient Nanostructures

    DEFF Research Database (Denmark)

    Hansen, Niels; Zhang, Xiaodan; Huang, Xiaoxu

    distance from the surface forming a gradient structure. In this study [2], by shot peening of a low carbon steel a gradient structure has been produced extending to about 1 mm below the surface. A number of strengthening mechanisms have been analyzed as a basis for a calculation of the stress and strain......A recent study [1] has shown that a microstructure can be refined to a record low of 5 nm and that dislocation glide is still a controlling mechanism at this length scale. The nanostructure was produced in Cu by applying a very high strain in friction. The stress and strain decrease with increasing...... as a function of the distance from the surface. The results are evaluated by a finite element investigation of shot peening....

  18. UBVR Imaging of UV Bright Interacting Galaxies

    Science.gov (United States)

    Nelson, C. H.; Weistrop, D.; Angione, R.; Cruzen, S.; Kaiser, M. E.

    1997-12-01

    Interacting galaxies are often found to contain UV-bright knots which are the sites of very recent or ongoing star-formation. To investigate the stellar populations of these complexes we have obtained UBVR images of several interacting or morphologically disturbed UV bright galaxies (NGC 3395/6, NGC 3991/4/5, NGC 4194, NGC 6090). Images of IRAS 15179+3956, an interacting galaxy in the Bootes Void, were also obtained. The images were made with the 2048x 2048 CCD camera on the 1-meter telescope at the Mount Laguna Observatory. Colors and magnitudes of star-forming regions in these objects will be presented and used to study how their properties change with age and position within each galaxy and how star-formation propagates through the system. This is part of an ongoing study of starburst galaxies that will include STIS (Space Telescope Imaging Spectrograph) longslit spectroscopy of a subset of these galaxies. Mount Laguna Observatory is operated jointly by San Diego State University and the University of Illinois. This research is supported in part by NASA under contract NAS 5-31231.

  19. Does Stevens's Power Law for Brightness Extend to Perceptual Brightness Averaging?

    Science.gov (United States)

    Bauer, Ben

    2009-01-01

    Stevens's power law ([Psi][infinity][Phi][beta]) captures the relationship between physical ([Phi]) and perceived ([Psi]) magnitude for many stimulus continua (e.g., luminance and brightness, weight and heaviness, area and size). The exponent ([beta]) indicates whether perceptual magnitude grows more slowly than physical magnitude ([beta] less…

  20. Brightness checkerboard lattice method for the calibration of the coaxial reverse Hartmann test

    Science.gov (United States)

    Li, Xinji; Hui, Mei; Li, Ning; Hu, Shinan; Liu, Ming; Kong, Lingqin; Dong, Liquan; Zhao, Yuejin

    2018-01-01

    The coaxial reverse Hartmann test (RHT) is widely used in the measurement of large aspheric surfaces as an auxiliary method for interference measurement, because of its large dynamic range, highly flexible test with low frequency of surface errors, and low cost. And the accuracy of the coaxial RHT depends on the calibration. However, the calibration process remains inefficient, and the signal-to-noise ratio limits the accuracy of the calibration. In this paper, brightness checkerboard lattices were used to replace the traditional dot matrix. The brightness checkerboard method can reduce the number of dot matrix projections in the calibration process, thus improving efficiency. An LCD screen displayed a brightness checkerboard lattice, in which the brighter checkerboard and the darker checkerboard alternately arranged. Based on the image on the detector, the relationship between the rays at certain angles and the photosensitive positions of the detector coordinates can be obtained. And a differential de-noising method can effectively reduce the impact of noise on the measurement results. Simulation and experimentation proved the feasibility of the method. Theoretical analysis and experimental results show that the efficiency of the brightness checkerboard lattices is about four times that of the traditional dot matrix, and the signal-to-noise ratio of the calibration is significantly improved.

  1. Substrate-Bound Protein Gradients to Study Haptotaxis

    Directory of Open Access Journals (Sweden)

    Sebastien G. Ricoult

    2015-03-01

    Full Text Available Cells navigate in response to inhomogeneous distributions of extracellular guidance cues. The cellular and molecular mechanisms underlying migration in response to gradients of chemical cues have been investigated for over a century. Following the introduction of micropipettes and more recently microfluidics for gradient generation, much attention and effort was devoted to study cellular chemotaxis, which is defined as guidance by gradients of chemical cues in solution. Haptotaxis, directional migration in response to gradients of substrate-bound cues, has received comparatively less attention; however it is increasingly clear that in vivo many physiologically relevant guidance proteins – including many secreted cues – are bound to cellular surfaces or incorporated into extracellular matrix and likely function via a haptotactic mechanism. Here, we review the history of haptotaxis. We examine the importance of the reference surface, the surface in contact with the cell that is not covered by the cue, which forms a gradient opposing the gradient of the protein cue and must be considered in experimental designs and interpretation of results. We review and compare microfluidics, contact-printing, light patterning and 3D fabrication to pattern substrate-bound protein gradients in vitro, and focus on their application to study axon guidance. The range of methods to create substrate-bound gradients discussed herein make possible systematic analyses of haptotactic mechanisms. Furthermore, understanding the fundamental mechanisms underlying cell motility will inform bioengineering approaches to program cell navigation and recover lost function.

  2. The LLNL/UCLA high gradient inverse free electron laser

    Energy Technology Data Exchange (ETDEWEB)

    Moody, J. T.; Musumeci, P.; Anderson, G.; Anderson, S.; Betts, S.; Fisher, S.; Gibson, D.; Tremaine, A.; Wu, S. [Department of Physics and Astronomy, UCLA, Los Angeles California, 90095 (United States); Lawrence Livermore National Laboratory (United States)

    2012-12-21

    We describe the Inverse Free Electron Accelerator currently under construction at Lawrence Livermore National Lab. Upon completion of this accelerator, high brightness electrons generated in the photoinjector blowout regime and accelerated to 50 MeV by S-band accelerating sections will interact with > 4 TW peak power Ti:Sapphire laser in a highly tapered 50 cm undulator and experience an acceleration gradient of > 200 MeV/m. We present the final design of the accelerator as well as the results of start-to-end simulations investigating preservation of beam quality and tolerances involved with this accelerator.

  3. Very-High-Brightness Picosecond Electron Source

    International Nuclear Information System (INIS)

    Bluem, H.

    2003-01-01

    Bright, RF photocathode electron guns are the source of choice for most high-performance research accelerator applications. Some of these applications are pushing the performance boundaries of the present state-of-the-art guns. Advanced Energy Systems is developing a novel photocathode RF gun that shows excellent promise for extending gun performance. Initial gun simulations with only a short booster accelerator easily break the benchmark emittance of one micron for 1 nC of bunch charge. The pulse length in these simulations is less than 2 ps. It is expected that with more detailed optimization studies, the performance can be further improved. The performance details of the gun will be presented. In addition, we will discuss the present design concept along with the status of the project

  4. Bioinspired bright noniridescent photonic melanin supraballs.

    Science.gov (United States)

    Xiao, Ming; Hu, Ziying; Wang, Zhao; Li, Yiwen; Tormo, Alejandro Diaz; Le Thomas, Nicolas; Wang, Boxiang; Gianneschi, Nathan C; Shawkey, Matthew D; Dhinojwala, Ali

    2017-09-01

    Structural colors enable the creation of a spectrum of nonfading colors without pigments, potentially replacing toxic metal oxides and conjugated organic pigments. However, significant challenges remain to achieve the contrast needed for a complete gamut of colors and a scalable process for industrial application. We demonstrate a feasible solution for producing structural colors inspired by bird feathers. We have designed core-shell nanoparticles using high-refractive index (RI) (~1.74) melanin cores and low-RI (~1.45) silica shells. The design of these nanoparticles was guided by finite-difference time-domain simulations. These nanoparticles were self-assembled using a one-pot reverse emulsion process, which resulted in bright and noniridescent supraballs. With the combination of only two ingredients, synthetic melanin and silica, we can generate a full spectrum of colors. These supraballs could be directly added to paints, plastics, and coatings and also used as ultraviolet-resistant inks or cosmetics.

  5. The Galactic metallicity gradient

    Science.gov (United States)

    Rolleston, W. R. J.; Smartt, S. J.; Dufton, P. L.; Ryans, R. S. I.

    2000-11-01

    We have previously published intermediate to high resolution spectroscopic observations of approximately 80 early B-type main-sequence stars situated in 19 Galactic open clusters/associations with Galactocentric distances distributed over 6Twarog et al. \\cite{twa97}). However, there is no evidence to suggest that our data would be better fitted with a two-zone model. Moreover, we observe a N/O gradient of -0.04+/-0.02 dex kpc-1 which is consistent with that found for other spiral galaxies (Vila-Costas & Edmunds \\cite{vil93}).

  6. [Translaminar Gradient and Glaucoma].

    Science.gov (United States)

    Čmelo, J

    2017-01-01

    The cribriform plate is a threshold of the intraocular pressure (VOT) and of the intracranial pressure (IKT). The difference between the VOT and IKT is referred to as translaminar gradient (TLG). The goal was to evaluate the Glaucoma progression (visual field, fundus examination, HRT) with / without topical anti-glaucomatous therapy) in relation to the TLG. the significance of TLG has been studied in two groups. I. Group: 57 patients diagnosed and treatment of Primary Open-Angle Glaucoma (PGOU), 10 patients with Ocular hypertension (OH), 7 patients with Normal-Tension Glaucoma (NTG), and 75 healthy without glaucoma. The examinations of TLG were carried out once and retrospectively. In II. group there were prospectively studied 14 patients with OH and 24 patients with newly detected PGOU without local therapy. The examinations were performed 4 times at intervals of 10 to 11 months. All tests included a basic eye examination, ORA tonometry, HRT examination, gonioscopy, Color Doppler sonography of blood vessels of the eye and orbit. Venous pulsation pressure (VPT) has been recorded by the Ophthalmodynamometer Meditron (D-ODM). In case of spontaneous retinal venous pulsation, VPT was considered as the same pressure as the VOT. The TLG was calculated with formula of Querfurth: ICT = 0.29 + 0.74 (VOT / PI (AO)). [PI(AO) - Pulsatility index of the Ophthalmic artery (AO)]. I. group: TLG was in the control group without Glaucoma: 12.2 ± 2.0 torr. The NTG group: 9.0 ± 1.70 mm Hg. PGOU: 11.1 ± 1.91 mm Hg. OH: 12.6 ± 0.85 mm Hg. IKT alone does not show a significant relationship to the presence of glaucoma, ocular hypertension. II. Group: The average TLG in Ocular Hypertension (14 patients) has been 3.8 ± 1.2 torr. 2 patients (OH) had TLG 10 torr. and 15 torr. After 4 years in one of them (TLG = 15 torr.) there was recorded Glaucoma progression. In the PGOU group before antiglaucoma therapy, TLG was 15.0 ± 4.8 torr for all patients. After setting up local anti

  7. Study of Three-Dimensional Image Brightness Loss in Stereoscopy

    Directory of Open Access Journals (Sweden)

    Hsing-Cheng Yu

    2015-10-01

    Full Text Available When viewing three-dimensional (3D images, whether in cinemas or on stereoscopic televisions, viewers experience the same problem of image brightness loss. This study aims to investigate image brightness loss in 3D displays, with the primary aim being to quantify the image brightness degradation in the 3D mode. A further aim is to determine the image brightness relationship to the corresponding two-dimensional (2D images in order to adjust the 3D-image brightness values. In addition, the photographic principle is used in this study to measure metering values by capturing 2D and 3D images on television screens. By analyzing these images with statistical product and service solutions (SPSS software, the image brightness values can be estimated using the statistical regression model, which can also indicate the impact of various environmental factors or hardware on the image brightness. In analysis of the experimental results, comparison of the image brightness between 2D and 3D images indicates 60.8% degradation in the 3D image brightness amplitude. The experimental values, from 52.4% to 69.2%, are within the 95% confidence interval

  8. CLPX-Satellite: AMSR-E Brightness Temperature Grids

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set includes Aqua Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E) passive microwave brightness temperatures gridded to the...

  9. Radiative transfer modeling of the brightness temperature signatures of firn aquifers

    Science.gov (United States)

    Bringer, A.; Miller, J.; Johnson, J. T.; Jezek, K. C.

    2017-12-01

    Firn aquifers represent an important component of the ice sheet and ice shelf system and contribute to meltwater-induced hydrofracture, ice flow, and mass balance change. A new technique has been developed for mapping those aquifers particularly in Greenland using the L-band microwave radiometer measurements of the SMAP and SMOS satellites. The method identifies likely firn aquifer regions using changes in their brightness temperatures over the course of one year. In particular, the brightness temperature at the aquifer location slowly decreases from summer to winter. Even though similar decreases in brightness temperatures can occur over more general surface melt areas, the associated changes in time in such cases occur more rapidly and can be easily distinguished from aquifer regions. In this preliminary study, we propose a simple description of firn aquifers to facilitate the use of models for their brightness temperature signatures. We assume that the firn in the presence of an aquifer can be modeled as a 2 or 3 layer medium depending on the season, each layer having a varying thickness and wetness. Thermal emission for the layered aquifer description is then computed using a simple "cloud" radiative transfer model. We compare the predicted brightness temperatures to L-Band SMAP observations, and are generally able to reproduce time variations of the brightness temperatures, although the initial model used is incapable of describing differences between brightness temperatures in horizontal and vertical polarizations. Additional modeling studies will be reported in the presentation based on the use of more advanced radiative emission models (both coherent and incoherent) and more detailed descriptions of the firn aquifer medium. The results of these analyses will provide further insight into the influence of firn geophysical parameters (density, grain size, temperature, layering, depth and volumetric fraction of liquid meltwater) on L-band brightness

  10. Review of new shapes for higher gradients

    International Nuclear Information System (INIS)

    Geng, R.L.

    2006-01-01

    High-gradient superconducting RF (SRF) cavities are needed for energy frontier superconducting accelerators. Progress has been made over the past decades and the accelerating gradient E acc has been increased from a few MV/m to ∼42 MV/m in SRF niobium cavities. The corresponding peak RF magnetic field H pk on the niobium cavity surface is approaching the intrinsic RF critical magnetic field H crit,RF , a hard physical limit at which superconductivity breaks down. Pushing the gradient envelope further by adopting new cavity shapes with a lower ratio of H pk /E acc has been recently proposed. For a reduced H pk /E acc , a higher ultimate E acc is sustained when H pk finally strikes H crit,RF . The new cavity geometry include the re-entrant shape conceived at Cornell University and the so-called 'Low-loss' shape proposed by a DESY/JLAB/KEK collaboration. Experimental work is being pursued at Cornell, KEK and JLAB. Results of single-cell cavities are encouraging. A record gradient of 47 MV/m was first demonstrated in a 1.3 GHz re-entrant niobium cavity at Cornell University. At the time of writing, a new record of 52 MV/m has been realized with another 1.3 GHz re-entrant cavity, designed and built at Cornell and processed and tested at KEK. Single-cell low-loss cavities have reached equally high gradients in the range of 45-51 MV/m at KEK and JLAB. Owing to their higher gradient potential and the encouraging single-cell cavity results, the new cavity shapes are becoming attractive for their possible use in the international linear collider (ILC). Experimental work on multi-cell niobium cavities of new shapes is currently under active exploration

  11. Charge gradient microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Roelofs, Andreas; Hong, Seungbum

    2018-02-06

    A method for rapid imaging of a material specimen includes positioning a tip to contact the material specimen, and applying a force to a surface of the material specimen via the tip. In addition, the method includes moving the tip across the surface of the material specimen while removing electrical charge therefrom, generating a signal produced by contact between the tip and the surface, and detecting, based on the data, the removed electrical charge induced through the tip during movement of the tip across the surface. The method further includes measuring the detected electrical charge.

  12. The impact of melt ponds on summertime microwave brightness temperatures and sea-ice concentrations

    DEFF Research Database (Denmark)

    Kern, Stefan; Rösel, Anja; Pedersen, Leif Toudal

    2016-01-01

    Sea-ice concentrations derived from satellite microwave brightness temperatures are less accurate during summer. In the Arctic Ocean the lack of accuracy is primarily caused by melt ponds, but also by changes in the properties of snow and the sea-ice surface itself. We investigate the sensitivity...... the variation of the sensitivity to the melt-pond fraction across the algorithms to a different sensitivity of the brightness temperatures to snow-property variations. We find an underestimation of the sea-ice concentration by between 14 % (Bootstrap_f) and 26 % (Bootstrap_p) for 100 % sea ice with a melt...... % sea-ice concentration. None of the algorithms investigated performs best based on our investigation of data from summer 2009. We suggest that those algorithms which are more sensitive to melt ponds could be optimized more easily because the influence of unknown snow and sea-ice surface property...

  13. A model for atmospheric brightness temperatures observed by the special sensor microwave imager (SSM/I)

    Science.gov (United States)

    Petty, Grant W.; Katsaros, Kristina B.

    1989-01-01

    A closed-form mathematical model for the atmospheric contribution to microwave the absorption and emission at the SSM/I frequencies is developed in order to improve quantitative interpretation of microwave imagery from the Special Sensor Microwave Imager (SSM/I). The model is intended to accurately predict upwelling and downwelling atmospheric brightness temperatures at SSM/I frequencies, as functions of eight input parameters: the zenith (nadir) angle, the integrated water vapor and vapor scale height, the integrated cloud water and cloud height, the effective surface temperature, atmospheric lapse rate, and surface pressure. It is shown that the model accurately reproduces clear-sky brightness temperatures computed by explicit integration of a large number of radiosonde soundings representing all maritime climate zones and seasons.

  14. Brightness of the photosphere and faculae at the limb according to eclipse observations

    Energy Technology Data Exchange (ETDEWEB)

    Akimov, L.A.; Belkina, I.L.; Dyatel, N.P. (Khar' kovskij Gosudarstvennyj Univ. (Ukrainian SSR). Astronomicheskaya Observatoriya)

    The absolute integrated and surface brightness distributions of the photospheric continuum (lambda approximately 5870 A) and faculae at the extreme limb are obtained from July 10, 1972 solar eclipse slitless spectrograms. Some possible reasons of the limb brightening in the surface brightness distributions of the photosphere are discussed. It is detected that facular contrasts have the high values, up to 1.76 for the height about 200 km. This fact shows that radiation and matter density changes depending on height in the upper atmosphere in a facula more quickly than outside the facula. The comparison of the observed moments of local contacts with the theoretical ones, based on the lunar limb relief data, has shown that the active regions are approximately 300 km higher than the photosphere. The schematic model of the photospheric faculae is given.

  15. Brightness of the photosphere and faculae at the limb according to eclipse observations

    International Nuclear Information System (INIS)

    Akimov, L.A.; Belkina, I.L.; Dyatel, N.P.

    1982-01-01

    The absolute integrated and surface brightness distributions of the photospheric continuum (lambda approximately 5870 A) and faculae at the extreme limb are obtained from July 10, 1972 solar eclipse slitless spectrograms. Some possible reasons of the limb brightening in the surface brightness distributions of the photosphere are discussed. It is detected that facular contrasts have the high values, up to 1.76 for the height about 200 km. This fact shows that radiation and matter density changes depending on height in the upper atmosphere in a facula more quickly than outside the facula. The comparison of the observed moments of local contacts with the theoretical ones, based on the lunar limb relief data, has shown that the active regions are approximately 300 km higher than the photosphere. The schematic model of the photospheric faculae is given

  16. Space charge and wake field analysis for a high brightness electron source

    International Nuclear Information System (INIS)

    Parsa, Z.

    1991-01-01

    We present a brief overview of the formalism used, and some simulation results for transverse and longitudinal motion of a bunch of particles moving through a cavity (e.g., the Brookhaven National Laboratory high brightness photocathode gun), including effects of the accelerating field, space charge forces (e.g., arising from the interaction of the cavity surface and the self field of the bunch). 3 refs., 12 figs

  17. Generalized conjugate gradient squared

    Energy Technology Data Exchange (ETDEWEB)

    Fokkema, D.R.; Sleijpen, G.L.G. [Utrecht Univ. (Netherlands)

    1994-12-31

    In order to solve non-symmetric linear systems of equations, the Conjugate Gradient Squared (CGS) is a well-known and widely used iterative method. In practice the method converges fast, often twice as fast as the Bi-Conjugate Gradient method. This is what you may expect, since CGS uses the square of the BiCG polynomial. However, CGS may suffer from its erratic convergence behavior. The method may diverge or the approximate solution may be inaccurate. BiCGSTAB uses the BiCG polynomial and a product of linear factors in an attempt to smoothen the convergence. In many cases, this has proven to be very effective. Unfortunately, the convergence of BiCGSTAB may stall when a linear factor (nearly) degenerates. BiCGstab({ell}) is designed to overcome this degeneration of linear factors. It generalizes BiCGSTAB and uses both the BiCG polynomial and a product of higher order factors. Still, CGS may converge faster than BiCGSTAB or BiCGstab({ell}). So instead of using a product of linear or higher order factors, it may be worthwhile to look for other polynomials. Since the BiCG polynomial is based on a three term recursion, a natural choice would be a polynomial based on another three term recursion. Possibly, a suitable choice of recursion coefficients would result in method that converges faster or as fast as CGS, but less erratic. It turns out that an algorithm for such a method can easily be formulated. One particular choice for the recursion coefficients leads to CGS. Therefore one could call this algorithm generalized CGS. Another choice for the recursion coefficients leads to BiCGSTAB. It is therefore possible to mix linear factors and some polynomial based on a three term recursion. This way one may get the best of both worlds. The authors will report on their findings.

  18. A new perspective on the infrared brightness temperature ...

    Indian Academy of Sciences (India)

    It is observed that Johnson SB function is the best continuous distribution function in explaining the histogram of infrared brightness temperatures of the convective clouds. The best fit is confirmed by Kolmogorov–Smirnov statistic. Johnson SB's distribution of histogram of infrared brightness temperatures clearly ...

  19. Spatial Model of Sky Brightness Magnitude in Langkawi Island, Malaysia

    Science.gov (United States)

    Redzuan Tahar, Mohammad; Kamarudin, Farahana; Umar, Roslan; Khairul Amri Kamarudin, Mohd; Sabri, Nor Hazmin; Ahmad, Karzaman; Rahim, Sobri Abdul; Sharul Aikal Baharim, Mohd

    2017-03-01

    Sky brightness is an essential topic in the field of astronomy, especially for optical astronomical observations that need very clear and dark sky conditions. This study presents the spatial model of sky brightness magnitude in Langkawi Island, Malaysia. Two types of Sky Quality Meter (SQM) manufactured by Unihedron are used to measure the sky brightness on a moonless night (or when the Moon is below the horizon), when the sky is cloudless and the locations are at least 100 m from the nearest light source. The selected locations are marked by their GPS coordinates. The sky brightness data obtained in this study were interpolated and analyzed using a Geographic Information System (GIS), thus producing a spatial model of sky brightness that clearly shows the dark and bright sky areas in Langkawi Island. Surprisingly, our results show the existence of a few dark sites nearby areas of high human activity. The sky brightness of 21.45 mag arcsec{}-2 in the Johnson-Cousins V-band, as the average of sky brightness equivalent to 2.8 × {10}-4{cd} {{{m}}}-2 over the entire island, is an indication that the island is, overall, still relatively dark. However, the amount of development taking place might reduce the number in the near future as the island is famous as a holiday destination.

  20. A new perspective on the infrared brightness temperature ...

    Indian Academy of Sciences (India)

    And Johnson SB parameters are observed to be best in discriminating the Johnson SB distribution of infrared brightness temperatures of deep convective systems for each season. Due to these properties of Johnson SB function, it can be utilized in the modelling of the histogram of infrared brightness temperature of deep ...

  1. The ASAS-SN bright supernova catalogue - III. 2016

    DEFF Research Database (Denmark)

    Holoien, T. W. -S.; Brown, J. S.; Stanek, K. Z.

    2017-01-01

    This catalogue summarizes information for all supernovae discovered by the All-Sky Automated Survey for SuperNovae (ASAS-SN) and all other bright (m(peak)d......This catalogue summarizes information for all supernovae discovered by the All-Sky Automated Survey for SuperNovae (ASAS-SN) and all other bright (m(peak)d...

  2. Henrietta Leavitt - A Bright Star of Astronomy; Resonance June 2001

    Indian Academy of Sciences (India)

    Leavitt discovered around a thousand variable stars in these clouds. Among these, she found 25. Cepheid variables in the small Magellanic cloud and noted that the period of these variable stars were correlated with the peak brightness. The brighter the star was, the longer it took to vary its brightness. In other words, the.

  3. Lamp spectrum and spatial brightness at photopic levels

    DEFF Research Database (Denmark)

    Fotios, Steve; Atli, Deniz; Cheal, Chris

    2015-01-01

    Light sources are available in a variety of spectral power distributions (SPDs) and this affects spatial brightness in a manner not predicted by quantities such as illuminance. Tuning light source SPD to better match the sensitivity of visual perception may allow the same spatial brightness but a...

  4. Intrinsic brightness temperatures of blazar jets at 15 GHz

    Directory of Open Access Journals (Sweden)

    Hovatta Talvikki

    2013-12-01

    Full Text Available We have developed a new Bayesian Markov Chain Monte Carlo method to deconvolve light curves of blazars into individual flares, including proper estimation of the fit errors. We use the method to fit 15GHzlight curves obtained within the OVRO 40-m blazar monitoring program where a large number of AGN have been monitored since 2008 in support of the Fermi Gamma-Ray Space Telescope mission. The time scales obtained from the fitted models are used to calculate the variability brightness temperature of the sources. Additionally, we have calculated brightness temperatures of a sample of these objects using Very Long Baseline Array data from the MOJAVE survey. Combining these two data sets enables us to study the intrinsic brightness temperature distribution in these blazars at 15 GHz. Our preliminary results indicate that the mean intrinsic brightness temperature in a sample of 14 sources is near the equipartition brightness temperature of ~ 1011K.

  5. Considerations of ion temperature gradient driven turbulence

    International Nuclear Information System (INIS)

    Cowley, S.C.; Kulsrud, R.M.

    1991-02-01

    The ion temperature gradient driven instability is considered in this paper. Physical pictures are presented to clarify the nature of the instability. The saturation of a single eddy is modeled by a simple nonlinear equation. We show that eddies which are elongated in the direction of the temperature gradient are the most unstable and have the highest saturation amplitudes. In a sheared magnetic field, such elongated eddies twist with the field lines. This structure is shown to be alternative to the usual Fourier mode picture in which the mode is localized around the surface where k parallel = 0. We show how these elongated twisting eddies, which are an integral part of the ''ballooning mode'' structure, could survive in a torus. The elongated eddies are shown to be unstable to secondary instabilities that are driven by the large gradients in the long eddy. We argue that this mechanism isotropizes ion temperature gradient turbulence. We further argue that the ''mixing length'' is set by this nonlinear process, not by a linear eigenmode width. 17 refs., 6 figs

  6. Bright visible light emission from graphene.

    Science.gov (United States)

    Kim, Young Duck; Kim, Hakseong; Cho, Yujin; Ryoo, Ji Hoon; Park, Cheol-Hwan; Kim, Pilkwang; Kim, Yong Seung; Lee, Sunwoo; Li, Yilei; Park, Seung-Nam; Yoo, Yong Shim; Yoon, Duhee; Dorgan, Vincent E; Pop, Eric; Heinz, Tony F; Hone, James; Chun, Seung-Hyun; Cheong, Hyeonsik; Lee, Sang Wook; Bae, Myung-Ho; Park, Yun Daniel

    2015-08-01

    Graphene and related two-dimensional materials are promising candidates for atomically thin, flexible and transparent optoelectronics. In particular, the strong light-matter interaction in graphene has allowed for the development of state-of-the-art photodetectors, optical modulators and plasmonic devices. In addition, electrically biased graphene on SiO2 substrates can be used as a low-efficiency emitter in the mid-infrared range. However, emission in the visible range has remained elusive. Here, we report the observation of bright visible light emission from electrically biased suspended graphene devices. In these devices, heat transport is greatly reduced. Hot electrons (∼2,800 K) therefore become spatially localized at the centre of the graphene layer, resulting in a 1,000-fold enhancement in thermal radiation efficiency. Moreover, strong optical interference between the suspended graphene and substrate can be used to tune the emission spectrum. We also demonstrate the scalability of this technique by realizing arrays of chemical-vapour-deposited graphene light emitters. These results pave the way towards the realization of commercially viable large-scale, atomically thin, flexible and transparent light emitters and displays with low operation voltage and graphene-based on-chip ultrafast optical communications.

  7. Dark Skies, Bright Kids Year 9

    Science.gov (United States)

    Burkhardt, Andrew Michael; Matthews, Allison M.; Johnson, Kelsey E.; Avilez, Ian; Beale, Luca; Bittle, Lauren E.; Bordenave, David; Finn, Molly; Firebaugh, Ariel; Hancock, Danielle; Hughes, Paul; Rochford Hayes, Christian; Lewis, Hannah; Linden, Sean; Liss, Sandra; Liu, Mengyao; McNair, Shunlante; Murphy, Edward; Prager, Brian; Pryal, Matthew; Richardson, Whitney; Song, Yiqing; Troup, Nicholas; Villadsen, Jackie; Wenger, Trey V.; Wilson, Robert Forrest

    2018-01-01

    We present updates from the ninth year of operation of Dark Skies, Bright Kids (DSBK) including new club content, continued assessments, and our seventh annual Star Party. DSBK is an entirely volunteer-run outreach organization based out of the Department of Astronomy at the University of Virginia. Our core mission is to enhance elementary science education and literacy in Virginia through fun, hands-on activities that introduce basic Astronomy concepts. DSBK’s most fundamental program is an 8-10 week long after-school Astronomy camp at surrounding local elementary schools, where each week introduces new concepts through interactive hands-on activities. Over the past two summers, we have traveled to four rural Virginia locations to bring week-long Astronomy camps to otherwise overlooked elementary school districts. These programs aim to inspire a curiosity for science and include inquiry based activities in topics ranging from the electromagnetic spectrum to the classification and evolution of galaxies. We strive to be self-reflective in our mission to inspire scientific curiosity in the minds of underserved demographics. In this effort, we continually assess the effectiveness of each activity through feedback in student-kept journal pages and observed excitement levels. This self-reflection has initiated the development of new curriculum. In addition, differing from our normal collaboration with local elementary schools, we have found great success partnering with local youth organizations, who may better represent DSBK's target demographics and have infrastructure to support incoming outreach groups.

  8. Featured Image: Bright Dots in a Sunspot

    Science.gov (United States)

    Kohler, Susanna

    2018-03-01

    This image of a sunspot, located in in NOAA AR 12227, was captured in December 2014 by the 0.5-meter Solar Optical Telescope on board the Hinode spacecraft. This image was processed by a team of scientists led by Rahul Yadav (Udaipur Solar Observatory, Physical Research Laboratory Dewali, India) in order to examine the properties of umbral dots: transient, bright features observed in the umbral region (the central, darkest part) of a sunspot. By exploring these dots, Yadav and collaborators learned how their properties relate to the large-scale properties of the sunspots in which they form for instance, how do the number, intensities, or filling factors of dots relate to the size of a sunspots umbra? To find out more about the authors results, check out the article below.Sunspot in NOAA AR 11921. Left: umbralpenumbral boundary. Center: the isolated umbra from the sunspot. Right: The umbra with locations of umbral dots indicated by yellow plus signs. [Adapted from Yadav et al. 2018]CitationRahul Yadav et al 2018 ApJ 855 8. doi:10.3847/1538-4357/aaaeba

  9. Intercomparisons of Nine Sky Brightness Detectors

    Directory of Open Access Journals (Sweden)

    Henk Spoelstra

    2011-10-01

    Full Text Available Nine Sky Quality Meters (SQMs have been intercompared during a night time measurement campaign held in the Netherlands in April 2011. Since then the nine SQMs have been distributed across the Netherlands and form the Dutch network for monitoring night sky brightness. The goal of the intercomparison was to infer mutual calibration factors and obtain insight into the variability of the SQMs under different meteorological situations. An ensemble average is built from the individual measurements and used as a reference to infer the mutual calibration factors. Data required additional synchronization prior to the calibration determination, because the effect of moving clouds combined with small misalignments emerges as time jitter in the measurements. Initial scatter of the individual instruments lies between ±14%. Individual night time sums range from −16% to +20%. Intercalibration reduces this to 0.5%, and −7% to +9%, respectively. During the campaign the smallest luminance measured was 0.657 ± 0.003 mcd/m2 on 12 April, and the largest value was 5.94 ± 0.03 mcd/m2 on 2 April. During both occurrences interfering circumstances like snow cover or moonlight were absent.

  10. Modular Zero Energy. BrightBuilt Home

    Energy Technology Data Exchange (ETDEWEB)

    Aldrich, Robb [Consortium for Advanced Residential Buildings (CARB), Norwalk, CT (United States). Steven Winters Associates, Inc.; Butterfield, Karla [Consortium for Advanced Residential Buildings (CARB), Norwalk, CT (United States). Steven Winters Associates, Inc.

    2016-03-01

    Kaplan Thompson Architects (KTA) has specialized in sustainable, energy-efficient buildings, and they have designed several custom, zero-energy homes in New England. These zero-energy projects have generally been high-end, custom homes with budgets that could accommodate advanced energy systems. In an attempt to make zero energy homes more affordable and accessible to a larger demographic, KTA explored modular construction as way to provide high-quality homes at lower costs. In the mid-2013, KTA formalized this concept when they launched BrightBuilt Home (BBH). The BBH mission is to offer a line of architect-designed, high-performance homes that are priced to offer substantial savings off the lifetime cost of a typical home and can be delivered in less time. For the past two years, CARB has worked with BBH and Keiser Homes (the primary modular manufacturer for BBH) to discuss challenges related to wall systems, HVAC, and quality control. In Spring of 2014, CARB and BBH began looking in detail on a home to be built in Lincolnville, ME by Black Bros. Builders. This report details the solution package specified for this modular plan and the challenges that arose during the project.

  11. A Systematic Review of Bright Light Therapy for Eating Disorders.

    Science.gov (United States)

    Beauchamp, Marshall T; Lundgren, Jennifer D

    2016-10-27

    Bright light therapy is a noninvasive biological intervention for disorders with nonnormative circadian features. Eating disorders, particularly those with binge-eating and night-eating features, have documented nonnormative circadian eating and mood patterns, suggesting that bright light therapy may be an efficacious stand-alone or adjunctive intervention. The purpose of this systematic literature review, using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, was (1) to evaluate the state of the empirical treatment outcome literature on bright light therapy for eating disorders and (2) to explore the timing of eating behavior, mood, and sleep-related symptom change so as to understand potential mechanisms of bright light therapy action in the context of eating disorder treatment. A comprehensive literature search using PsycInfo and PubMed/MEDLINE was conducted in April 2016 with no date restrictions to identify studies published using bright light therapy as a treatment for eating disorders. Keywords included combinations of terms describing disordered eating (eating disorder, anorexia nervosa, bulimia nervosa, binge eating, binge, eating behavior, eating, and night eating) and the use of bright light therapy (bright light therapy, light therapy, phototherapy). After excluding duplicates, 34 articles were reviewed for inclusion. 14 published studies of bright light therapy for eating disorders met inclusion criteria (included participants with an eating disorder/disordered-eating behaviors; presented as a case study, case series, open-label clinical trial, or randomized/nonrandomized controlled trial; written in English; and published and available by the time of manuscript review). Results suggest that bright light therapy is potentially effective at improving both disordered-eating behavior and mood acutely, although the timing of symptom response and the duration of treatment effects remain unknown. Future research should

  12. Gradient Boosting Machines, A Tutorial

    Directory of Open Access Journals (Sweden)

    Alexey eNatekin

    2013-12-01

    Full Text Available Gradient boosting machines are a family of powerful machine-learning techniques that have shown considerable success in a wide range of practical applications. They are highly customizable to the particular needs of the application, like being learned with respect to different loss functions. This article gives a tutorial introduction into the methodology of gradient boosting methods. A theoretical information is complemented with many descriptive examples and illustrations which cover all the stages of the gradient boosting model design. Considerations on handling the model complexity are discussed. A set of practical examples of gradient boosting applications are presented and comprehensively analyzed.

  13. HG2006 Workshop on High-Gradient Radio Frequency

    CERN Multimedia

    2006-01-01

    Meeting to be held at CERN on 25-27 September 2006 in Room 40/S2-B01 (Building 40). The objective of the workshop is to bring the high-gradient RF community together to present and discuss recent theoretical and experimental developments. Significant progress has recently been made in understanding the basic physics of rf breakdown and developing techniques for achieving higher gradients. This workshop should contribute to maintaining these efforts and to promoting contacts and collaboration. The scientific programme will be organized in half day sessions dedicated to: High-gradient rf experimental results Theory and computation High-gradient technology, materials and processing Specialized experiments on related high-gradient or high-power phenomenon like dc discharge and pulsed surface heating Reports from collaborations and projects. Each session will consist of selected presentations followed by a dedicated discussion. Information about the meeting and participant registration is available at http...

  14. Metallicity gradients in early-type galaxies

    Science.gov (United States)

    Schombert, James M.; Hanlan, Patricia C.; Barsony, Mary; Rakos, Karl D.

    1993-01-01

    A study of medium-to-bright early-type galaxies in six bandpasses from 3500 A to 2.2 microns is presented in order to quantify their colors and color gradients and relate these to metallicity and properties of the underlying stellar population. The Stromgren filter system chosen makes it possible to introduce a new calibration to the Mg(2) system from the present narrow-band v - y indices. A comparison is presented of narrow-band colors centered on particular spectral features vs a color dominated by the mean temperature of the giant branch (i.e., J - K) to test the effects of light vs heavy element abundances on knowledge of the total system metallicity, Z, and the effects of reddening. A good correlation is found between v - y and Mg(2); it provides a connection between one light element metallicity indicator (v - y centers on the CN blend) and another, Mg. The color-magnitude relations for all five optical and near-IR colors are shown. The strongest correlation exists for the metallicity colors, v - y and J - K.

  15. Denaturing gradient gel electrophoresis

    International Nuclear Information System (INIS)

    Kocherginskaya, S.A.; Cann, I.K.O.; Mackie, R.I.

    2005-01-01

    It is worthwhile considering that only some 30 species make up the bulk of the bacterial population in human faeces at any one time based on the classical cultivation-based approach. The situation in the rumen is similar. Thus, it is practical to focus on specific groups of interest within the complex community. These may be the predominant or the most active species, specific physiological groups or readily identifiable (genetic) clusters of phylogenetically related organisms. Several 16S rDNA fingerprinting techniques can be invaluable for selecting and monitoring sequences or phylogenetic groups of interest and are described below. Over the past few decades, considerable attention was focussed on the identification of pure cultures of microbes on the basis of genetic polymorphisms of DNA encoding rRNA such as ribotyping, amplified fragment length polymorphism and randomly amplified polymorphic DNA. However, many of these methods require prior cultivation and are less suitable for use in analysis of complex mixed populations although important in describing cultivated microbial diversity in molecular terms. Much less attention was given to molecular characterization of complex communities. In particular, research into diversity and community structure over time has been revolutionized by the advent of molecular fingerprinting techniques for complex communities. Denaturing or temperature gradient gel electrophoresis (DGGE/TGGE) methods have been successfully applied to the analysis of human, pig, cattle, dog and rodent intestinal populations

  16. The GPM Common Calibrated Brightness Temperature Product

    Science.gov (United States)

    Stout, J.; Chou, J.

    2010-12-01

    The Global Precipitation Measurement (GPM) project will provide a core satellite carrying the GPM Microwave Imager (GMI) and will use microwave observations from a constellation of other satellites. Each partner with a satellite in the constellation will have a calibration that meets their own requirements and will decide on the format to archive their brightness temperature (Tb) record in GPM. However, GPM multi-sensor precipitation algorithms need to input intercalibrated Tb's in order to avoid differences among sensors introducing artifacts into the longer term climate record of precipitation. The GPM Common Calibrated Brightness Temperature Product is intended to address this problem by providing intercalibrated Tb data, called "Tc" data, where the "c" stands for common. The precipitation algorithms require a Tc file format that is both generic and flexible enough to accommodate the different passive microwave instruments. The format provides detailed information on the processing history in order to allow future researchers to have a record of what was done. The format is simple, including the main items of scan time, latitude, longitude, incidence angle, sun glint angle, and Tc. It also provides a quality flag, spacecraft orientation, spacecraft location, orbit, and instrument scan type (cross-track or conical). Another simplification is to store data in real numbers, avoiding the ambiguity of scaled data. Finally, units and descriptions will be provided in the product. The format is built on the concept of a swath, which is a series of scans that have common geolocation and common scan geometry. Scan geometry includes pixels per scan, sensor orientation, scan type, and incidence angles. The format includes 3 space saving methods: first rounding variables written as floats to their needed accuracy to achieve good compression, second writing sun glint angle as a one byte variable, and third storing only unique incidence angles but allowing access via a mapping

  17. Dark Skies, Bright Kids: Year 2

    Science.gov (United States)

    Carlberg, Joleen K.; Johnson, K.; Lynch, R.; Walker, L.; Beaton, R.; Corby, J.; de Messieres, G.; Drosback, M.; Gugliucci, N.; Jackson, L.; Kingery, A.; Layman, S.; Murphy, E.; Richardson, W.; Ries, P.; Romero, C.; Sivakoff, G.; Sokal, K.; Trammell, G.; Whelan, D.; Yang, A.; Zasowski, G.

    2011-01-01

    The Dark Skies, Bright Kids (DSBK) outreach program brings astronomy education into local elementary schools in central Virginia's Southern Albemarle County through an after-school club. Taking advantage of the unusually dark night skies in the rural countryside, DSBK targets economically disadvantaged schools that tend to be underserved due to their rural locale. The goals of DSBK are to foster children's natural curiosity, demonstrate that science is a fun and creative process, challenge students' conceptions of what a scientist is and does, and teach some basic astronomy. Furthermore, DSBK works to assimilate families into students' education by holding family observing nights at the school. Now in its third semester, DSBK has successfully run programs at two schools with very diverse student populations. Working with these students has helped us to revise our activities and to create new ones. A by-product of our work has been the development of lesson plans, complete with learning goals and detailed instructions, that we make publically available on our website. This year we are expanding our repertoire with our new planetarium, which allows us to visualize topics in novel ways and supplements family observing on cloudy nights. The DSBK volunteers have also created a bilingual astronomy artbook --- designed, written, and illustrated by UVa students --- that we will publish and distribute to elementary schools in Virginia. Our book debuted at the last AAS winter meeting, and since then it has been extensively revised and updated with input from many individuals, including parents, professional educators, and a children's book author. Because the club is currently limited to serving a few elementary schools, this book will be part of our efforts to broaden our impact by bringing astronomy to schools we cannot go to ourselves and reaching out to Spanish-speaking communities at the same time.

  18. Dark Skies, Bright Kids! Year 3

    Science.gov (United States)

    Whelan, David G.; Johnson, K. E.; Barcos-Munoz, L. D.; Beaton, R. L.; Borish, J.; Corby, J. F.; Dorsey, G.; Gugliucci, N. E.; Prager, B. J.; Ries, P. A.; Romero, C. E.; Sokal, K. R.; Tang, X.; Walker, L. M.; Yang, A. J.; Zasowski, G.

    2012-01-01

    Dark Skies, Bright Kids! (DSBK) is a program that brings astronomy education to elementary schools throughout central Virginia. In a relaxed, out-of-classroom atmosphere, we are able to foster the innate curiosity that young students have about science and the world around them. We target schools that are under-served due to their rural locale or special needs students, demonstrating that science is a fun and creative process to a segment of the population that might not otherwise be exposed to astronomy. Families are included in the learning experience during semi-annual `star parties'. Since last January, we have expanded the breadth and depth of our educational capabilities. We have developed new programs for use in our digital planetarium. We held the first Central Virginia Star Party, providing an atmosphere where local children from multiple schools were able to share their love for astronomy. Local government and University officials were also invited so that they could experience our focused science outreach. Most recently, we have become part of Ivy Creek School's Club Day activities, bringing our program to a new segment of the elementary school system in Albemarle County: those that have `low-incidence' disabilities, requiring special attention. We continue to develop a curriculum for after-school programs that functions as either a series of one-time activities or several months of focused outreach at one school. Many of these activities are provided on our website, http://www.astro.virginia.edu/dsbk/, for the wider astronomical community, including the new planetarium work. We have extended our book project to include two bilingual astronomy books called `Snapshots of the Universe,' one in Spanish and English, the other in French and English. These books introduce young people to some of the many wonders of the Universe through art and captions developed by DSBK volunteers.

  19. Dark Skies, Bright Kids! Year 4

    Science.gov (United States)

    Sokal, Kimberly R.; Johnson, K. E.; Barcos-Munoz, L. D.; Beaton, R.; Borish, J.; Crawford, S. B.; Corby, J.; Damke, G.; Dean, J.; Dorsey, G.; Jackson, L.; Liss, S.; Oza, A.; Peacock, S.; Prager, B.; Romero, C.; Sivakoff, G. R.; Walker, L.; Whelan, D. G.; Zucker, C.

    2013-01-01

    Aiming to engage young children's natural excitement and curiosity, the outreach group Dark Skies, Bright Kids (DSBK) brings a hands-on approach to astronomy to elementary schools in Virginia. We hope to enhance children's view and understanding of science while exploring the Universe using fun activities. DSBK focuses on rural and underserved schools in Albemarle County and offers a semester-long astronomy club for third through fifth grade students. We believe regular interactions foster personal relationships between students and volunteers that encourage a life-long interest in science. In our fourth year of hosting clubs, we returned to Ivy Creek Elementary School, where we saw wonderful responses from a special group of students with `low-incidence' disabilities. DSBK has grown to realize a broader reach beyond local astronomy clubs; we hope to ignite a spark of interest in astronomy and science more widely- in more children, their families, and their teachers. We also hosted the Second Annual Central Virginia Star Party with an open invitation to the community to encourage families to enjoy astronomy together. Throughout the year, DSBK now holds 'one-off' programs (akin to astronomy field days) for elementary schools and children's groups throughout Virginia. Furthermore, we are in the final stages of a project to create two bilingual astronomy books called "Snapshots of the Universe", in Spanish and French with English translations. This art book will be made available online and we are working to get a copy in every elementary school in the state. DSBK has begun to reach out to elementary school teachers in order to provide them with useful and engaging classroom material. We have adapted our volunteer-created activities into useful and ready-to-use lessons, available online. After improvements based on research through interactions and feedback from teachers, we have explicitly identified the learning goals in terms of Virginia's Standards of Learning

  20. Optical microvariability of bright type 2 quasars

    Science.gov (United States)

    Polednikova, Jana; Ederoclite, Alessandro; Cepa, Jordi; de Diego Onsurbe, José Antonio; González-Serrano, José Ignacio

    2014-07-01

    We present results from a project focused on searching optical microvariabilty (also known as ``intra-night'' variability) in type 2 - obscured - quasars. Optical microvariability can be described as very small changes in the flux, typically in the order of hundredths of magnitude, which can be observed on timescales of hours. Such studies have been so far conducted for samples of blazars and type 1, unobscured, AGNs, where the optical microvariability was detected with success. We have focused on obscured targets which would pose a challenge to the AGN standard model. In the present work, however, we have observed a sample of three bright (g mag < 17) type 2 quasar, based on the catalog of type 2 quasars from SDSS of Reyes et al. (2008). The observations were carried out with the 1.5 meter telescope at San Pedro Martir observatory in Mexico. The sample was observed during an observation period of four days in Johnsons V filter, resulting in at least two continuous intervals of observations per target during the observational run. We have obtained differential light curves for our sources as well as for the comparison stars. They were analyzed using one-way analysis of variance statistical test (ANOVA), which has been repeatedly used in the past for studies of unobscured targets. Based on the results from the statistical analysis, we show that at least two out of three observed targets appear to be variable on time scales of hours. So far, this is the first study which confirmed existence of optical microvariability in type 2 quasars.

  1. High Brightness HDR Projection Using Dynamic Freeform Lensing

    KAUST Repository

    Damberg, Gerwin

    2016-05-03

    Cinema projectors need to compete with home theater displays in terms of image quality. High frame rate and spatial resolution as well as stereoscopic 3D are common features today, but even the most advanced cinema projectors lack in-scene contrast and, more important, high peak luminance, both of which are essential perceptual attributes of images appearing realistic. At the same time, HDR image statistics suggest that the average image intensity in a controlled ambient viewing environment such as the cinema can be as low as 1% for cinematic HDR content and not often higher than 18%, middle gray in photography. Traditional projection systems form images and colors by blocking the source light from a lamp, therefore attenuating between 99% and 82% of light, on average. This inefficient use of light poses significant challenges for achieving higher peak brightness levels. In this work, we propose a new projector architecture built around commercially available components, in which light can be steered to form images. The gain in system efficiency significantly reduces the total cost of ownership of a projector (fewer components and lower operating cost), and at the same time increases peak luminance and improves black level beyond what is practically achievable with incumbent projector technologies. At the heart of this computational display technology is a new projector hardware design using phase modulation in combination with a new optimization algorithm that is capable of on-the-fly computation of freeform lens surfaces. © 2016 ACM.

  2. Quantitative Brightness Analysis of Fluorescence Intensity Fluctuations in E. Coli.

    Directory of Open Access Journals (Sweden)

    Kwang-Ho Hur

    Full Text Available The brightness measured by fluorescence fluctuation spectroscopy specifies the average stoichiometry of a labeled protein in a sample. Here we extended brightness analysis, which has been mainly applied in eukaryotic cells, to prokaryotic cells with E. coli serving as a model system. The small size of the E. coli cell introduces unique challenges for applying brightness analysis that are addressed in this work. Photobleaching leads to a depletion of fluorophores and a reduction of the brightness of protein complexes. In addition, the E. coli cell and the point spread function of the instrument only partially overlap, which influences intensity fluctuations. To address these challenges we developed MSQ analysis, which is based on the mean Q-value of segmented photon count data, and combined it with the analysis of axial scans through the E. coli cell. The MSQ method recovers brightness, concentration, and diffusion time of soluble proteins in E. coli. We applied MSQ to measure the brightness of EGFP in E. coli and compared it to solution measurements. We further used MSQ analysis to determine the oligomeric state of nuclear transport factor 2 labeled with EGFP expressed in E. coli cells. The results obtained demonstrate the feasibility of quantifying the stoichiometry of proteins by brightness analysis in a prokaryotic cell.

  3. Migration of inclusions in solids in stress gradients

    International Nuclear Information System (INIS)

    Olander, D.R.

    1980-01-01

    A theoretical method of assessing the influence of stress and temperature gradients on the motion of inclusions in solids is developed. In nonuniform stress fields, the stress distribution on the surface of the cavity must be calculated and transformed to a potential gradient for driving a surface atom flux. The bubble migration velocity is the first Legendre coefficient of the surface flux. Higher order components represent distortion. The stress gradient effect appears only in small-magnitude terms in the surface chemical potential, specifically in the stress effect on the solid atomic volume and in the elastic energy density. The migration velocities of spherical and faceted bubbles in solids are computed and the extent of distortion of a spherical bubble is estimated. The role of vacancy exchange with the bulk solid on the migration velocity is assessed. (author)

  4. Characterization of gradient control systems

    NARCIS (Netherlands)

    Cortés, Jorge; van der Schaft, Arjan; Crouch, Peter E.

    2005-01-01

    Given a general nonlinear affine control system with outputs and a torsion-free affine connection defined on its state space, we investigate the gradient realization problem: we give necessary and sufficient conditions under which the control system can be written as a gradient control system

  5. Sobolev gradients and differential equations

    CERN Document Server

    Neuberger, J W

    2010-01-01

    A Sobolev gradient of a real-valued functional on a Hilbert space is a gradient of that functional taken relative to an underlying Sobolev norm. This book shows how descent methods using such gradients allow a unified treatment of a wide variety of problems in differential equations. For discrete versions of partial differential equations, corresponding Sobolev gradients are seen to be vastly more efficient than ordinary gradients. In fact, descent methods with these gradients generally scale linearly with the number of grid points, in sharp contrast with the use of ordinary gradients. Aside from the first edition of this work, this is the only known account of Sobolev gradients in book form. Most of the applications in this book have emerged since the first edition was published some twelve years ago. What remains of the first edition has been extensively revised. There are a number of plots of results from calculations and a sample MatLab code is included for a simple problem. Those working through a fair p...

  6. Color Gradient in the King Type Globular Cluster NGC 7089

    Directory of Open Access Journals (Sweden)

    Young-Jong Sohn

    1999-12-01

    Full Text Available We use BV CCD images to investigate the reality of the color gradient within a King type globular cluster NGC 7089. Surface photometry shows that there is a strong radial color gradient in the central region of the cluster in the sense of bluer center with the amplitude of -0.39 +/- 0.07 mag/arcsec2 in (B - V. In the outer region of the cluster, however, the radial color gradient shows a reverse case, i.e., redder toward the center. (B - V color profile which was derived from resolved stars in VGC 7089 field also shows a significant color gradient in the central region of the clusters, indicating that lights from the combination of red giant stars and blue horizontal branch stars cause the radial color gradient. Color gradient of the outer region of NGC 7089 may be due to the unresolved background of the cluster. Similar color gradients in the central area of clusters have been previously observed exserved exclusively in highly concentrated systems classified as post core collapse clusters. We caution, however, to confirm the reality of the color gradient from resolved stars, we need more accurate imaging data of the cluster with exceptional seeing condition because the effect of completeness correlates with local density of stars.

  7. Enhancement of the Accelerating Gradient in Superconducting Microwave Resonators

    Energy Technology Data Exchange (ETDEWEB)

    Checchin, Mattia [Fermilab; Grassellino, Anna [Fermilab; Martinello, Martina [IIT, Chicago; Posen, Sam [Fermilab; Romanenko, Alexander [Fermilab; Zasadzinski, John [IIT, Chicago (main)

    2017-05-01

    The accelerating gradient of superconducting resonators can be enhanced by engineering the thickness of a dirty layer grown at the cavity's rf surface. In this paper the description of the physics behind the accelerating gradient enhancement by meaning of the dirty layer is carried out by solving numerically the the Ginzburg-Landau (GL) equations for the layered system. The calculation shows that the presence of the dirty layer stabilizes the Meissner state up to the lower critical field of the bulk, increasing the maximum accelerating gradient.

  8. Development and characterization of 430L matrix composites gradient materials

    Directory of Open Access Journals (Sweden)

    Elisa Maria Ruiz-Navas

    2005-03-01

    Full Text Available This paper deals with a new concept that is Functionally Gradient Materials (FGM. The materials developed in this work are constituted by a 430L matrix core and composite materials with this matrix and gradient concentration with NbC reinforcement, from the core to the surface, through different steps. Composite powders of different content in NbC were produced through high energy milling in order to obtain the gradient composition. The morphology and microhardness of these powders were characterised and subsequently were processed through conventional P/M techniques, pressing and sintering. The materials obtained show improved wear behaviour.

  9. The geomagnetic field gradient tensor

    DEFF Research Database (Denmark)

    Kotsiaros, Stavros; Olsen, Nils

    2012-01-01

    We develop the general mathematical basis for space magnetic gradiometry in spherical coordinates. The magnetic gradient tensor is a second rank tensor consisting of 3 × 3 = 9 spatial derivatives. Since the geomagnetic field vector B is always solenoidal (∇ · B = 0) there are only eight independent...... tensor elements. Furthermore, in current free regions the magnetic gradient tensor becomes symmetric, further reducing the number of independent elements to five. In that case B is a Laplacian potential field and the gradient tensor can be expressed in series of spherical harmonics. We present properties...... of the magnetic gradient tensor and provide explicit expressions of its elements in terms of spherical harmonics. Finally we discuss the benefit of using gradient measurements for exploring the Earth’s magnetic field from space, in particular the advantage of the various tensor elements for a better determination...

  10. Colloidal attraction induced by a temperature gradient.

    Science.gov (United States)

    Di Leonardo, R; Ianni, F; Ruocco, G

    2009-04-21

    Colloidal crystals are of extreme importance for applied research and for fundamental studies in statistical mechanics. Long-range attractive interactions, such as capillary forces, can drive the spontaneous assembly of such mesoscopic ordered structures. However, long-range attractive forces are very rare in the colloidal realm. Here we report a novel strong, long-ranged attraction induced by a thermal gradient in the presence of a wall. By switching the thermal gradient on and off, we can rapidly and reversibly form stable hexagonal 2D crystals. We show that the observed attraction is hydrodynamic in nature and arises from thermally induced slip flow on particle surfaces. We used optical tweezers to measure the force law directly and compare it to an analytical prediction based on Stokes flow driven by Marangoni-like forces.

  11. Transport of nanoparticles in a temperature gradient

    Science.gov (United States)

    Putnam, Shawn; Cahill, David

    2006-03-01

    Thermodiffusion, mass transport in a temperature gradient, is commonly characterized by either the thermodiffusion coefficient DT or the Soret coefficient ST; e.g., at low particle concentration c, the particle flux of a colloidal suspension subjected to a temperature gradient ∇T is J=- cDT∇T-Dc∇c, where Dc is the diffusion coefficient and the Soret coefficient is ST= DT/Dc. We present our measured DT data for aqueous suspensions of charged polystyrene spheres, alumina nanoparticles, and globular proteins of lysozyme. Special emphasis is given to our published work on charged polystyrene spheres with different surface functionalities. For example, in solutions with large concentrations of monovalent salts, 100 mM, DT for 26 nm spheres with carboxyl functionality can be varied within the range -0.9 x10^- 7 cm^2 s-1 K-1 protein solutions of lysozyme.

  12. Assimilation of microwave brightness temperatures for soil moisture estimation using particle filter

    International Nuclear Information System (INIS)

    Bi, H Y; Ma, J W; Qin, S X; Zeng, J Y

    2014-01-01

    Soil moisture plays a significant role in global water cycles. Both model simulations and remote sensing observations have their limitations when estimating soil moisture on a large spatial scale. Data assimilation (DA) is a promising tool which can combine model dynamics and remote sensing observations to obtain more precise ground soil moisture distribution. Among various DA methods, the particle filter (PF) can be applied to non-linear and non-Gaussian systems, thus holding great potential for DA. In this study, a data assimilation scheme based on the residual resampling particle filter (RR-PF) was developed to assimilate microwave brightness temperatures into the macro-scale semi-distributed Variance Infiltration Capacity (VIC) Model to estimate surface soil moisture. A radiative transfer model (RTM) was used to link brightness temperatures with surface soil moisture. Finally, the data assimilation scheme was validated by experimental data obtained at Arizona during the Soil Moisture Experiment 2004 (SMEX04). The results show that the estimation accuracy of soil moisture can be improved significantly by RR-PF through assimilating microwave brightness temperatures into VIC model. Both the overall trends and specific values of the assimilation results are more consistent with ground observations compared with model simulation results

  13. ECR Ion Source for a High-Brightness Cyclotron

    Science.gov (United States)

    Comeaux, Justin; McIntyre, Peter; Assadi, Saeed

    2011-10-01

    New technology is being developed for high-brightness, high-current cyclotrons with performance benefits for accelerator-driven subcritical fission power, medical isotope production, and proton beam cancer therapy. This paper describes the design for a 65 kV electron cyclotron resonance (ECR) ion source that will provide high-brightness beam for injection into the cyclotron. The ion source is modeled closely upon the one that is used at the Paul Scherrer Institute. Modifications are being made to provide enhanced brightness and compatibility for higher-current operation.

  14. Modelling asteroid brightness variations. I - Numerical methods

    Science.gov (United States)

    Karttunen, H.

    1989-01-01

    A method for generating lightcurves of asteroid models is presented. The effects of the shape of the asteroid and the scattering law of a surface element are distinctly separable, being described by chosen functions that can easily be changed. The shape is specified by means of two functions that yield the length of the radius vector and the normal vector of the surface at a given point. The general shape must be convex, but spherical concavities producing macroscopic shadowing can also be modeled.

  15. Gradient zone boundary control in salt gradient solar ponds

    Energy Technology Data Exchange (ETDEWEB)

    Hull, John R. (Downers Grove, IL)

    1984-01-01

    A method and apparatus for suppressing zone boundary migration in a salt gradient solar pond includes extending perforated membranes across the pond at the boundaries, between the convective and non-convective zones, the perforations being small enough in size to prevent individual turbulence disturbances from penetrating the hole, but being large enough to allow easy molecular diffusion of salt thereby preventing the formation of convective zones in the gradient layer. The total area of the perforations is a sizable fraction of the membrane area to allow sufficient salt diffusion while preventing turbulent entrainment into the gradient zone.

  16. Analysis of a high brightness photo electron beam with self field and wake field effects

    International Nuclear Information System (INIS)

    Parsa, Z.

    1991-01-01

    High brightness sources are the basic ingredients in the new accelerator developments such as Free-Electron Laser experiments. The effects of the interactions between the highly charged particles and the fields in the accelerating structure, e.g. R.F., Space charge and Wake fields can be detrimental to the beam and the experiments. We present and discuss the formulation used, some simulation and results for the Brookhaven National Laboratory high brightness beam that illustrates effects of the accelerating field, space charge forces (e.g. due to self field of the bunch), and the wake field (e.g. arising from the interaction of the cavity surface and the self field of the bunch)

  17. High brightness diode lasers controlled by volume Bragg gratings

    Science.gov (United States)

    Glebov, Leonid

    2017-02-01

    Volume Bragg gratings (VBGs) recorded in photo-thermo-refractive (PTR) glass are holographic optical elements that are effective spectral and angular filters withstanding high power laser radiation. Reflecting VBGs are narrow-band spectral filters while transmitting VBGs are narrow-band angular filters. The use of these optical elements in external resonators of semiconductor lasers enables extremely resonant feedback that provides dramatic spectral and angular narrowing of laser diodes radiation without significant power and efficiency penalty. Spectral narrowing of laser diodes by reflecting VBGs demonstrated in wide spectral region from near UV to 3 μm. Commercially available VBGs have spectral width ranged from few nanometers to few tens of picometers. Efficient spectral locking was demonstrated for edge emitters (single diodes, bars, modules, and stacks), vertical cavity surface emitting lasers (VCSELs), grating coupled surface emitting lasers (GCSELs), and interband cascade lasers (ICLs). The use of multiplexed VBGs provides multiwavelength emission from a single emitter. Spectrally locked semiconductor lasers demonstrated CW power from milliwatts to a kilowatt. Angular narrowing by transmitting VBGs enables single transverse mode emission from wide aperture diode lasers having resonators with great Fresnel numbers. This feature provides close to diffraction limit divergence along a slow axis of wide stripe edge emitters. Radiation exchange between lasers by means of spatially profiled or multiplexed VBGs enables coherent combining of diode lasers. Sequence of VBGs or multiplexed VBGs enable spectral combining of spectrally narrowed diode lasers or laser modules. Thus the use of VBGs for diode lasers beam control provides dramatic increase of brightness.

  18. Discordance gradient-surface dans le rétrécissement mitral: le gradient moyen transmitral est-il un critère de sévérité ou un indice de tolérance du rétrécissement mitral serré?

    Science.gov (United States)

    Najih, Hayat; Arous, Salim; Laarje, Aziza; Baghdadi, Dalila; Benouna, Mohamed Ghali; Azzouzi, Leila; Habbal, Rachida

    2016-01-01

    Le rétrécissement mitral (RM) rhumatismal demeure une valvulopathie fréquente dans les pays en voie de développement. Cependant, les pays industrialisés ont vu l'émergence ces dernières années de nouvelles étiologies de RM; notamment l'origine médicamenteuse et/ou toxique responsable de valvulopathies restrictives aussi bien sténosantes que régurgitantes. Pour cette raison, l'évaluation échocardiographique du RM et surtout, la définition de critères objectifs pour conclure au caractère serré du RM reste toujours d'actualité. Les objectifs du travail sont: évaluer l'existence ou non d'une corrélation directe entre le gradient moyen transmitral (GMT) et la sévérité du RM chez les patients porteurs d'un RM serré ou très serré (critère primaire) et analyser les différents paramètres qui conditionnent le gradient moyen transmitral (GMT) (Critère secondaire). Il s'agit d'une étude transversale monocentrique incluant tous les patients admis au service de Cardiologie du CHU Ibn Rochd de Casablanca pour un RM serré ou très serré, sur une période d'une année (Janvier 2014 à Décembre 2014). Nous avons analysés séparément deux groupes de patients : ceux avec un gradient moyen transmitral10mmHg (groupe2). 50 patients porteurs d'un RM serré ou très serré ont été inclus. L'âge moyen de nos patients est de 41,7 ans avec prédominance féminine (sex ratio: 0,25). 64% de nos patients avaient un RM serré et 36% avaient un RM très serré. 52% (26 patients) avaient un GMT 10mmHg, ce qui suggère l'absence de corrélation directe entre la sévérité du RM et le GMT (coefficient de Pearson R: -0,137). Pour la dyspnée, 80% des patients du groupe 1 étaient dyspnéiques stade II de la NYHA et 70% des patients du groupe 2 étaient dyspnéiques stade III (41%) ou IV (29%) de la NYHA, ce qui signifie l'existence d'une corrélation significative entre le GMT et la sévérité de la dyspnée (R: 0,586 et p: 0,001). L'étude analytique de la fr

  19. Ultra High Brightness/Low Cost Fiber Coupled Packaging Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The focus of the proposed effort is maximizing the brightness of fiber coupled laser diode pump sources at a minimum cost. The specific innovation proposed is to...

  20. DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperatures

    Data.gov (United States)

    National Aeronautics and Space Administration — NSIDC produces daily gridded brightness temperature data from orbital swath data generated by the Special Sensor Microwave/Imager (SSM/I) aboard the Defense...

  1. Operational Bright-Band Snow Level Detection Using Doppler Radar

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — A method to detect the bright-band snow level from radar reflectivity and Doppler vertical velocity data collection with an atmospheric profiling Doppler radar. The...

  2. SMEX02 SSM/I Brightness Temperature Data, Iowa

    Data.gov (United States)

    National Aeronautics and Space Administration — The Special Sensor Microwave/Imager (SSM/I) is a seven-channel, four-frequency, linearly polarized passive microwave radiometric system. Data are brightness...

  3. Matter-wave bright solitons in effective bichromatic lattice potentials

    Indian Academy of Sciences (India)

    wave bright solitons in bichromatic lattice potentials are considered and their dynamics for different lattice environments are studied. ... Scientific Computing Laboratory, Institute of Physics Belgrade, Pregrevica 118, 11080 Belgrade, Serbia ...

  4. Millimeter-wave Imaging Radiometer Brightness Temperatures, Wakasa Bay, Japan

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set includes calibrated brightness temperatures measured over Wakasa Bay in the Sea of Japan in January and February 2003. The MIR was carried on a...

  5. CLEMENTINE LWIR BRIGHTNESS TEMPERATURE V1.0

    Data.gov (United States)

    National Aeronautics and Space Administration — This volume contains the archive of Lunar brightness temperature data derived from images acquired by the Clementine Long Wavelength Infrared (LWIR) camera. The LWIR...

  6. Nimbus-1/HRIR Level 1 Brightness Temperature V001

    Data.gov (United States)

    National Aeronautics and Space Administration — The Nimbus-1 High Resolution Infrared Radiometer (HRIR) Level 1 Brightness Temperature Data Product (HRIRN1L1) contains infrared radiances converted to equivalent...

  7. CLPX-Satellite: AVHRR/HRPT Brightness Temperatures and Reflectances

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set includes AVHRR/HRPT (Advanced Very High Resolution Radiometer/High Resolution Picture Transmission) brightness temperatures and reflectances over the...

  8. AMSR-E/Aqua Daily EASE-Grid Brightness Temperatures

    Data.gov (United States)

    National Aeronautics and Space Administration — This document pertains to two data sets: AMSR-E/Aqua Daily EASE-Grid Brightness Temperatures (NSIDC-0301) and AMSR-E/Aqua Daily Global Quarter-Degree Gridded...

  9. Nimbus-7 SMMR Pathfinder Daily EASE-Grid Brightness Temperatures

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set consists of brightness temperatures acquired from the Scanning Multichannel Microwave Radiometer (SMMR) on board the Nimbus-7 Pathfinder satellite. The...

  10. SMAPVEX12 PALS Brightness Temperature Data V001

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set contains brightness temperature data obtained by the Passive Active L-band System (PALS) microwave aircraft instrument as a part of the Soil Moisture...

  11. SMEX03 SSM/I Brightness Temperature Data, Brazil

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set provides brightness temperature data acquired during the Soil Moisture Experiment 2003 (SMEX03) by the Special Sensor Microwave/Imager (SSM/I). The...

  12. SMEX03 SSM/I Brightness Temperature Data, Alabama

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set provides brightness temperature data acquired during the Soil Moisture Experiment 2003 (SMEX03) by the Special Sensor Microwave/Imager (SSM/I). The...

  13. Nimbus-5 ESMR Polar Gridded Brightness Temperatures, Version 2

    Data.gov (United States)

    National Aeronautics and Space Administration — The Nimbus-5 Electrically Scanning Microwave Radiometer (ESMR) data set consists of gridded brightness temperature arrays for the Arctic and Antarctic, spanning 11...

  14. Identifying Bright X-Ray Beasts

    Science.gov (United States)

    Kohler, Susanna

    2017-10-01

    Ultraluminous X-ray sources (ULXs) are astronomical sources of X-rays that, while dimmer than active galactic nuclei, are nonetheless brighter than any known stellar process. What are these beasts and why do they shine so brightly?Exceeding the LimitFirst discovered in the 1980s, ULXs are rare sources that have nonetheless been found in all types of galaxies. Though the bright X-ray radiation seems likely to be coming from compact objects accreting gas, theres a problem with this theory: ULXs outshine the Eddington luminosity for stellar-mass compact objects. This means that a stellar-mass object couldnt emit this much radiation isotropically without blowing itself apart.There are two alternative explanations commonly proposed for ULXs:Rather than being accreting stellar-mass compact objects, they are accreting intermediate-mass black holes. A hypothetical black hole of 100 solar masses or more would have a much higher Eddington luminosity than a stellar-mass black hole, making the luminosities that we observe from ULXs feasible.An example of one of the common routes the authors find for a binary system to become a ULX. In this case, the binary begins as two main sequence stars. As one star evolves off the main sequence, the binary undergoes a common envelope phase and a stage of mass transfer. The star ends its life as a supernova, and the resulting neutron star then accretes matter from the main sequence star as a ULX. [Wiktorowicz et al. 2017]They are ordinary X-ray binaries (a stellar-mass compact object accreting matter from a companion star), but they are undergoing a short phase of extreme accretion. During this time, their emission is beamed into jets, making them appear brighter than the Eddington luminosity.Clues from a New DiscoveryA few years ago, a new discovery shed some light on ULXs: M82 X-2, a pulsing ULX. Two more pulsing ULXs have been discovered since then, demonstrating that at least some ULXs contain pulsars i.e., neutron stars as the

  15. The effect of bright lines in environmental risk communication

    International Nuclear Information System (INIS)

    Wilson, K.N.; Desvousges, W.H.; Smith, K.V.; Payne, J.

    1993-01-01

    Bright lines in environmental risk communication refer to the specific levels at which an environmental risk becomes a serious health threat and action should be taken to mitigate its effects. This study examined the effect of ''bright lines'' in risk communication by emphasizing the radon exposure threshold level of 4 picocuries per liter. Specifically, the authors developed a computer-assisted interview containing bright-line versions of risk information. The bright-line version contained a range of possible radon levels, the corresponding number of estimated lung cancer cases, the relative health risk from radon compared to other health risks, and the EPA guidelines for mitigating levels above 4 picocuries in the home. The non-bright line version was identical to the bright-line version, except it did not include the EPA's mitigation recommendations. Effect measures included respondents' change in perceived risk after reading their materials, intended testing behavior, and advice to their neighbor for a specified radon level either above or below the 4 picocury threshold level. This paper discusses broader policy implications for designing effective risk communication programs

  16. A Bright Future for Magnetic Resonance

    Indian Academy of Sciences (India)

    IAS Admin

    Think of natural product chemistry. Think of drug screening. Think of structural biology. Think of the localization of mental activity by functional MRI. Think of the mapping of nerve bundles by diffusion tensor imaging (DTI). Think of metabolomics. Think of reaction mechanisms. Think of homogenous catalysis. Think of surface ...

  17. Microwave brightness temperature imaging and dielectric properties ...

    Indian Academy of Sciences (India)

    when Neil Armstrong set his foot on the lunar surface at 02:56:15 UT on 21st July 1969. From then on, a great number of scientists from differ- ent disciplines were involved in the study of lunar material collected by former Soviet Union robots and Apollo astronauts. With the completion of the first round of lunar exploration by ...

  18. Beta and Gamma Gradients

    DEFF Research Database (Denmark)

    Løvborg, Leif; Gaffney, C. F.; Clark, P. A.

    1985-01-01

    Experimental and/or theoretical estimates are presented concerning, (i) attenuation within the sample of beta and gamma radiation from the soil, (ii) the gamma dose within the sample due to its own radioactivity, and (iii) the soil gamma dose in the proximity of boundaries between regions...... of differing radioactivity. It is confirmed that removal of the outer 2 mm of sample is adequate to remove influence from soil beta dose and estimates are made of the error introduced by non-removal. Other evaluations include variation of the soil gamma dose near the ground surface and it appears...

  19. Strain gradients in epitaxial ferroelectrics

    International Nuclear Information System (INIS)

    Catalan, G.; Noheda, B.; McAneney, J.; Sinnamon, L.J.; Gregg, J.M.

    2005-01-01

    X-ray analysis of ferroelectric thin layers of Ba 1/2 Sr 1/2 TiO 3 with different thicknesses reveals the presence of strain gradients across the films and allows us to propose a functional form for the internal strain profile. We use this to calculate the influence of strain gradient, through flexoelectric coupling, on the degradation of the ferroelectric properties of films with decreasing thickness, in excellent agreement with the observed behavior. This paper shows that strain relaxation can lead to smooth, continuous gradients across hundreds of nanometers, and it highlights the pressing need to avoid such strain gradients in order to obtain ferroelectric films with bulklike properties

  20. Gradient Index Optics at DARPA

    Science.gov (United States)

    2013-11-01

    sodium, is submerged into a bath of molten salt containing a different ion, such as lithium bromide. Ions from the salt bath diffuse into the glass...molecules, creating a gradient of index of refraction (Mohr et al. 1979). • Crystal growing. From a silver- chloride /sodium- chloride bath, starting with a...sodium chloride seed, a crystal is pulled that begins to deplete the sodium in the bath and starts to pull silver, forming a gradient (Houde-Walter

  1. Stochastic Gradient Monomial Gamma Sampler

    OpenAIRE

    Zhang, Yizhe; Chen, Changyou; Gan, Zhe; Henao, Ricardo; Carin, Lawrence

    2017-01-01

    Recent advances in stochastic gradient techniques have made it possible to estimate posterior distributions from large datasets via Markov Chain Monte Carlo (MCMC). However, when the target posterior is multimodal, mixing performance is often poor. This results in inadequate exploration of the posterior distribution. A framework is proposed to improve the sampling efficiency of stochastic gradient MCMC, based on Hamiltonian Monte Carlo. A generalized kinetic function is leveraged, delivering ...

  2. Bright soil units on Mars determined from ISM imaging spectrometer data

    Science.gov (United States)

    Murchie, Scott; Mustard, John

    1993-01-01

    The lithology of bright Martian soil provides evidence for chemical and physical processes that have modified the planet's surface. Data from the ISM imaging spectrometer, which observed much of the equatorial region at a spatial resolution of approximately 22 km, cover the NIR wavelength range critical to ascertaining the presence and abundance of Fe-containing phases, hydroxylated silicates, and H2O in the bright soil. ISM data previously have revealed spatial variations in depth of the 3.0-microns H2O absorption suggesting differences in water content, a weak absorption at 2.2 microns indicative of metal-OH in phyllosilicate, and variations in the 1-micron Fe absorption indicative of differences in Fe mineralogy. This paper summarizes first results of a systematic investigation of spectral heterogeneity in bright soils observed by ISM. At least seven 'units' with distinctive properties were discriminated. Comparison of their spatial distributions with Viking data shows that they generally correspond with previously recognized morphologic, color, and thermal features. These correspondences and the units' spectral attributes provide evidence for lithologic differences between the soils in different geologic settings.

  3. New head gradient coil design and construction techniques.

    Science.gov (United States)

    Handler, William B; Harris, Chad T; Scholl, Timothy J; Parker, Dennis L; Goodrich, K Craig; Dalrymple, Brian; Van Sass, Frank; Chronik, Blaine A

    2014-05-01

    To design and build a head insert gradient coil to use in conjunction with body gradients for superior imaging. The use of the boundary element method to solve for a gradient coil wire pattern on an arbitrary surface allowed us to incorporate engineering changes into the electromagnetic design of a gradient coil directly. Improved wire pattern design was combined with robust manufacturing techniques and novel cooling methods. The finished coil had an efficiency of 0.15 mT/m/A in all three axes and allowed the imaging region to extend across the entire head and upper part of the neck. The ability to adapt an electromagnetic design to necessary changes from an engineering perspective leads to superior coil performance. Copyright © 2013 Wiley Periodicals, Inc.

  4. Search for bright nearby M dwarfs with virtual observatory tools

    Energy Technology Data Exchange (ETDEWEB)

    Aberasturi, M.; Caballero, J. A.; Montesinos, B.; Gálvez-Ortiz, M. C.; Solano, E.; Martín, E. L. [Centro de Astrobiología (CSIC-INTA), Departamento de Astrofísica, P.O. Box 78, E-28691 Villanueva de la Cañada, Madrid (Spain)

    2014-08-01

    Using Virtual Observatory tools, we cross-matched the Carlsberg Meridian 14 and the 2MASS Point Source catalogs to select candidate nearby bright M dwarfs distributed over ∼25,000 deg{sup 2}. Here, we present reconnaissance low-resolution optical spectra for 27 candidates that were observed with the Intermediate Dispersion Spectrograph at the 2.5 m Isaac Newton Telescope (R≈ 1600). We derived spectral types from a new spectral index, R, which measures the ratio of fluxes at 7485-7015 Å and 7120-7150 Å. We also used VOSA, a Virtual Observatory tool for spectral energy distribution fitting, to derive effective temperatures and surface gravities for each candidate. The resulting 27 targets were M dwarfs brighter than J = 10.5 mag, 16 of which were completely new in the Northern hemisphere and 7 of which were located at less than 15 pc. For all of them, we also measured Hα and Na I pseudo-equivalent widths, determined photometric distances, and identified the most active stars. The targets with the weakest sodium absorption, namely, J0422+2439 (with X-ray and strong Hα emissions), J0435+2523, and J0439+2333, are new members in the young Taurus-Auriga star-forming region based on proper motion, spatial distribution, and location in the color-magnitude diagram, which reopens the discussion on the deficit of M2-4 Taurus stars. Finally, based on proper motion diagrams, we report on a new wide M dwarf binary system in the field, LSPM J0326+3929EW.

  5. Beam brightness calculation for analytical and empirical distribution functions

    International Nuclear Information System (INIS)

    Myers, T.J.; Boulais, K.A.; O, Y.S.; Rhee, M.J.

    1992-01-01

    The beam brightness, a figure of merit for a beam quality useful for high-current low-emittance beams, was introduced by van Steenbergen as B = I/V 4 , where I is the beam current and V 4 is the hypervolume in the four-dimensional trace space occupied by the beam particles. Customarily, the brightness is expressed in terms of the product of emittances ε x ε y as B = ηI/(π 2 ε x ε y ), where η is a form factor of order unity which depends on the precise definition of emittance and hypervolume. Recently, a refined definition of the beam brightness based on the arithmetic mean value defined in statistics is proposed. The beam brightness is defined as B triple-bond 4 > = I -1 ∫ ρ 4 2 dxdydx'dy', where I is the beam current given by I ∫ ρ 4 dxdydx'dy'. Note that in this definition, neither the hypervolume V 4 nor the emittance, are explicitly used; the brightness is determined solely by the distribution function. Brightnesses are unambiguously calculated and expressed analytically in terms of the respective beam current and effective emittance for a few commonly used distribution functions, including Maxwellian and water-bag distributions. Other distributions of arbitrary shape frequently encountered in actual experiments are treated numerically. The resulting brightnesses are expressed in the form B = ηI/(π 2 ε x ε y ), and η is found to be weakly dependent on the form of velocity distribution as well as spatial distribution

  6. Color and emotion: effects of hue, saturation, and brightness.

    Science.gov (United States)

    Wilms, Lisa; Oberfeld, Daniel

    2017-06-13

    Previous studies on emotional effects of color often failed to control all the three perceptual dimensions of color: hue, saturation, and brightness. Here, we presented a three-dimensional space of chromatic colors by independently varying hue (blue, green, red), saturation (low, medium, high), and brightness (dark, medium, bright) in a factorial design. The 27 chromatic colors, plus 3 brightness-matched achromatic colors, were presented via an LED display. Participants (N = 62) viewed each color for 30 s and then rated their current emotional state (valence and arousal). Skin conductance and heart rate were measured continuously. The emotion ratings showed that saturated and bright colors were associated with higher arousal. The hue also had a significant effect on arousal, which increased from blue and green to red. The ratings of valence were the highest for saturated and bright colors, and also depended on the hue. Several interaction effects of the three color dimensions were observed for both arousal and valence. For instance, the valence ratings were higher for blue than for the remaining hues, but only for highly saturated colors. Saturated and bright colors caused significantly stronger skin conductance responses. Achromatic colors resulted in a short-term deceleration in the heart rate, while chromatic colors caused an acceleration. The results confirm that color stimuli have effects on the emotional state of the observer. These effects are not only determined by the hue of a color, as is often assumed, but by all the three color dimensions as well as their interactions.

  7. Use of Ground Penetrating Radar to Study Gradient Media

    Science.gov (United States)

    Titov, A.

    2016-12-01

    Nowadays Ground Penetrating Radar (GPR) is often used to solve different problems of applied geophysics including the hydrological ones. This work was motivated by detection of weak reflections in the body of water observed during the surveys on the freshwater lakes using GPR. The same reflections were first analyzed by John Bradford in 2007. These reflections can arise from the thermal gradient layer or thermocline due to different dielectric permittivity of cold and warm water. We employed physical and mathematical modeling to identify the properties of such thermoclines. We have constructed a special GPR stand to study the gradient media in our laboratory. The stand consists of a water-filled plastic tank and plastic tubes, which gather the cold water under the warm water. Our stand allows for changing parameters of the gradient layer, such as limits of dielectric permittivity and the thickness of the gradient layer. GPR antenna was placed slightly under the water surface to remove the parasitic reflections. To visualize the thermal distribution, an infrared camera and thermal sensors were used. Analysis of the GPR traces after physical modeling, performed in the MATLAB environment, allows us to locate the weak reflection from the gradient layer. We observed that (i) the change of the gradient boundary values alters the amplitude of the signal, (ii) the arrival time of the impulse reflected from the gradient layer corresponds to the arrival time of the impulse reflected from the top boundary of this layer, and (iii) the shape of the signal reflected from the gradient layer coincides with the shape of the signal reflected from the non-gradient boundary between two bodies. The quantitative properties of thermocline can be determined using amplitude analysis of GPR signals. Finally, the developed methods were successfully applied to real field data.

  8. Growth and deformation structure of gradient and layer-gradient Ti-Al-Si-Cu-N coatings

    Energy Technology Data Exchange (ETDEWEB)

    Ovchinnikov, Stanislav V., E-mail: ovm@spti.tsu.ru; Pinzhin, Yurii P., E-mail: pinzhin@phys.tsu.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); Korotaev, Alexandr D., E-mail: korotaev@phys.tsu.ru [National Research Tomsk State University, Tomsk, 634050 (Russian Federation)

    2014-11-14

    The features of the growth structure and modification of gradient and layer-gradient Ti-Al-Si-Cu-N coatings in the areas of deformation and fracture during indentation and scratch testing were investigated using transmission and scanning electron microscopy methods. The influence of the concentration of alloying elements and displacement potential in the substrate on the secondary sputtering, phase composition and the level of combined torsion and bending of the crystal lattice of doped TiN were determined. It was found out that the size of the crystals in deformation location bands grows with deformation of gradient nanocrystal coatings. The article shows that layer-gradient coatings combining submicrocrystalline and nanocrystalline structures have the increased plasticity and fracture toughness due to enhanced density of interfaces and formation of the soft metal phase (Cu) in the surface layer.

  9. Growth and deformation structure of gradient and layer-gradient Ti-Al-Si-Cu-N coatings

    International Nuclear Information System (INIS)

    Ovchinnikov, Stanislav V.; Pinzhin, Yurii P.; Korotaev, Alexandr D.

    2014-01-01

    The features of the growth structure and modification of gradient and layer-gradient Ti-Al-Si-Cu-N coatings in the areas of deformation and fracture during indentation and scratch testing were investigated using transmission and scanning electron microscopy methods. The influence of the concentration of alloying elements and displacement potential in the substrate on the secondary sputtering, phase composition and the level of combined torsion and bending of the crystal lattice of doped TiN were determined. It was found out that the size of the crystals in deformation location bands grows with deformation of gradient nanocrystal coatings. The article shows that layer-gradient coatings combining submicrocrystalline and nanocrystalline structures have the increased plasticity and fracture toughness due to enhanced density of interfaces and formation of the soft metal phase (Cu) in the surface layer

  10. Spheroidal Integral Equations for Geodetic Inversion of Geopotential Gradients

    Science.gov (United States)

    Novák, Pavel; Šprlák, Michal

    2017-12-01

    The static Earth's gravitational field has traditionally been described in geodesy and geophysics by the gravitational potential (geopotential for short), a scalar function of 3-D position. Although not directly observable, geopotential functionals such as its first- and second-order gradients are routinely measured by ground, airborne and/or satellite sensors. In geodesy, these observables are often used for recovery of the static geopotential at some simple reference surface approximating the actual Earth's surface. A generalized mathematical model is represented by a surface integral equation which originates in solving Dirichlet's boundary-value problem of the potential theory defined for the harmonic geopotential, spheroidal boundary and globally distributed gradient data. The mathematical model can be used for combining various geopotential gradients without necessity of their re-sampling or prior continuation in space. The model extends the apparatus of integral equations which results from solving boundary-value problems of the potential theory to all geopotential gradients observed by current ground, airborne and satellite sensors. Differences between spherical and spheroidal formulations of integral kernel functions of Green's kind are investigated. Estimated differences reach relative values at the level of 3% which demonstrates the significance of spheroidal approximation for flattened bodies such as the Earth. The observation model can be used for combined inversion of currently available geopotential gradients while exploring their spectral and stochastic characteristics. The model would be even more relevant to gravitational field modelling of other bodies in space with more pronounced spheroidal geometry than that of the Earth.

  11. Spheroidal Integral Equations for Geodetic Inversion of Geopotential Gradients

    Science.gov (United States)

    Novák, Pavel; Šprlák, Michal

    2018-03-01

    The static Earth's gravitational field has traditionally been described in geodesy and geophysics by the gravitational potential (geopotential for short), a scalar function of 3-D position. Although not directly observable, geopotential functionals such as its first- and second-order gradients are routinely measured by ground, airborne and/or satellite sensors. In geodesy, these observables are often used for recovery of the static geopotential at some simple reference surface approximating the actual Earth's surface. A generalized mathematical model is represented by a surface integral equation which originates in solving Dirichlet's boundary-value problem of the potential theory defined for the harmonic geopotential, spheroidal boundary and globally distributed gradient data. The mathematical model can be used for combining various geopotential gradients without necessity of their re-sampling or prior continuation in space. The model extends the apparatus of integral equations which results from solving boundary-value problems of the potential theory to all geopotential gradients observed by current ground, airborne and satellite sensors. Differences between spherical and spheroidal formulations of integral kernel functions of Green's kind are investigated. Estimated differences reach relative values at the level of 3% which demonstrates the significance of spheroidal approximation for flattened bodies such as the Earth. The observation model can be used for combined inversion of currently available geopotential gradients while exploring their spectral and stochastic characteristics. The model would be even more relevant to gravitational field modelling of other bodies in space with more pronounced spheroidal geometry than that of the Earth.

  12. A neurodynamical model of brightness induction in v1.

    Directory of Open Access Journals (Sweden)

    Olivier Penacchio

    Full Text Available Brightness induction is the modulation of the perceived intensity of an area by the luminance of surrounding areas. Recent neurophysiological evidence suggests that brightness information might be explicitly represented in V1, in contrast to the more common assumption that the striate cortex is an area mostly responsive to sensory information. Here we investigate possible neural mechanisms that offer a plausible explanation for such phenomenon. To this end, a neurodynamical model which is based on neurophysiological evidence and focuses on the part of V1 responsible for contextual influences is presented. The proposed computational model successfully accounts for well known psychophysical effects for static contexts and also for brightness induction in dynamic contexts defined by modulating the luminance of surrounding areas. This work suggests that intra-cortical interactions in V1 could, at least partially, explain brightness induction effects and reveals how a common general architecture may account for several different fundamental processes, such as visual saliency and brightness induction, which emerge early in the visual processing pathway.

  13. First results from the high-brightness x-ray spectroscopy beamline at ALS

    Energy Technology Data Exchange (ETDEWEB)

    Perera, R.C.C.; Ng, W.; Jones, G. [Lawrence Berkeley National Lab., CA (United States)] [and others

    1997-04-01

    Beamline 9.3.1 at the Advanced Light Source (ALS) is a windowless beamline, covering the 1-6 keV photon-energy range, designed to achieve the goal of high brightness at the sample for use in the X-ray Atomic and Molecular Spectroscopy (XAMS) science, surface and interface science, biology and x-ray optical development programs at ALS. X-ray absorption and time of flight photo emission measurements in 2 - 5 keV photon energy in argon along with the flux, resolution, spot size and stability of the beamline will be discussed. Prospects for future XAMS measurements will also be presented.

  14. Selection of high-brightness, laser-driven cathodes for electron accelerators and FELS

    International Nuclear Information System (INIS)

    Oettinger, P.E.

    1987-01-01

    Very intense, low emittance pulsed beams of electrons can be generated from laser-driven cathodes either by thermionic- or photo-emission. Several hundreds of amperes of electrons per square centimeter were observed for pulse lengths up to 50 ns. A normalized beam brightness of 10 7 A/cm 2 /rad 2 has been measured. These beams can be emission-gated at the cathode surface by modulating the laser-beam. Such beam bunching will generate picosecond-to-microsecond-long pulses at the source. A variety of cathodes are described, and a method of selection for specific applications is presented

  15. Growth rate and surface morphology of 4H-SiC crystals grown from Si-Cr-C and Si-Cr-Al-C solutions under various temperature gradient conditions

    Science.gov (United States)

    Mitani, Takeshi; Komatsu, Naoyoshi; Takahashi, Tetsuo; Kato, Tomohisa; Fujii, Kuniharu; Ujihara, Toru; Matsumoto, Yuji; Kurashige, Kazuhisa; Okumura, Hajime

    2014-09-01

    The growth rate and surface morphology of 4H-SiC crystals prepared by solution growth with Si1-xCrx and Si1-x-yCrxAly (x=0.4, 0.5 and 0.6; y=0.04) solvents were investigated under various temperature conditions. The growth rate was examined as functions of the temperature difference between the growth surface and C source, the amount of supersaturated C and supersaturation at the growth surface. We found that generation of trench-like surface defects in 4H-SiC crystals was suppressed using Si1-x-yCrxAly solvents even under highly supersaturated conditions where the growth rate exceeded 760 μm/h. Conversely, trench-like defects were observed in crystals grown with Si1-xCrx solvents under all experimental conditions. Statistical observation of the macrostep structure showed that the macrostep height in crystals grown with Si1-x-yCrxAly solvents was maintained at lower levels than that obtained using Si1-xCrx solvents. Addition of Al prevents the macrosteps from developing into large steps, which are responsible for the generation of trench-like surface defects.

  16. Bright and Not-So-Bright Prospects for Women in Physics in China-Beijing

    Science.gov (United States)

    Wu, Ling-An; Yang, Zhongqin; Ma, Wanyun

    2009-04-01

    Science in China-Beijing is enjoying a healthy increase in funding year by year, so the prospects for physicists are also bright. However, employment discrimination against women, formerly unthinkable, is becoming more and more explicit as the country evolves toward a market economy. Some recruitment notices bluntly state that only men will be considered, or impose restrictions upon potential female candidates. Female associate professors in many institutions are forced to retire at age 55, compared with 60 for men. This double-pinching discrimination against both younger and older women threatens to lead to a "pincer" effect, more serious than the "scissors" effect. Indeed, the ratio of senior-level women physicists in general has dropped significantly in recent years in China. Ironically, the number of female students applying for graduate studies is on the rise, as it is becoming increasingly difficult for them to compete with men in the job market with just an undergraduate degree. The Chinese Physical Society has made certain efforts to promote the image of women physicists, but it will take time and effort to reverse the trend.

  17. A high brightness probe of polymer nanoparticles for biological imaging

    Science.gov (United States)

    Zhou, Sirong; Zhu, Jiarong; Li, Yaping; Feng, Liheng

    2018-03-01

    Conjugated polymer nanoparticles (CPNs) with high brightness in long wavelength region were prepared by the nano-precipitation method. Based on fluorescence resonance energy transfer (FRET) mechanism, the high brightness property of the CPNs was realized by four different emission polymers. Dynamic light scattering (DLS) and scanning electron microscopy (SEM) displayed that the CPNs possessed a spherical structure and an average diameter of 75 nm. Analysis assays showed that the CPNs had excellent biocompatibility, good photostability and low cytotoxicity. The CPNs were bio-modified with a cell penetrating peptide (Tat, a targeted element) through covalent link. Based on the entire wave fluorescence emission, the functionalized CPNs1-4 can meet multichannel and high throughput assays in cell and organ imaging. The contribution of the work lies in not only providing a new way to obtain a high brightness imaging probe in long wavelength region, but also using targeted cell and organ imaging.

  18. Polyacrylamide temperature gradient gel electrophoresis.

    Science.gov (United States)

    Viglasky, Viktor

    2013-01-01

    Temperature Gradient Gel Electrophoresis (TGGE) is a form of electrophoresis in which temperature gradient is used to denature molecules as they move through either acrylamide or agarose gel. TGGE can be applied to analyze DNA, RNA, protein-DNA complexes, and, less commonly, proteins. Separation of double-stranded DNA molecules during TGGE relies on temperature-dependent melting of the DNA duplex into two single-stranded DNA molecules. Therefore, the mobility of DNA reflects not only the size of the molecule but also its nucleotide composition, thereby allowing separation of DNA molecules of similar size with different sequences. Depending on the relative orientation of electric field and temperature gradient, TGGE can be performed in either a parallel or a perpendicular mode. The former is used to analyze multiple samples in the same gel, whereas the later allows detailed analysis of a single sample. This chapter is focused on analysis of DNA by polyacrylamide TGGE using the perpendicular mode.

  19. Effects of Bright Light Treatment on Psychomotor Speed in Athletes

    Directory of Open Access Journals (Sweden)

    Mikko Paavo Tulppo

    2014-05-01

    Full Text Available Purpose: A recent study suggests that transcranial brain targeted light treatment via ear canals may have physiological effects on brain function studied by functional magnetic resonance imaging (fMRI techniques in humans. We tested the hypothesis that bright light treatment could improve psychomotor speed in professional ice hockey players. Methods: Psychomotor speed tests with audio and visual warning signals were administered to a Finnish National Ice Hockey League team before and after 24 days of transcranial bright light or sham treatment. The treatments were given during seasonal darkness in the Oulu region (latitude 65 degrees north when the strain on the players was also very high (10 matches during 24 days. A daily 12-min dose of bright light or sham (n = 11 for both treatment was given every morning between 8–12 am at home with a transcranial bright light device. Mean reaction time and motor time were analyzed separately for both psychomotor tests. Analysis of variance for repeated measures adjusted for age was performed. Results: Time x group interaction for motor time with a visual warning signal was p = 0.024 after adjustment for age. In Bonferroni post-hoc analysis, motor time with a visual warning signal decreased in the bright light treatment group from 127 ± 43 to 94 ± 26 ms (p = 0.024 but did not change significantly in the sham group 121 ± 23 vs. 110 ± 32 ms (p = 0.308. Reaction time with a visual signal did not change in either group. Reaction or motor time with an audio warning signal did not change in either the treatment or sham group. Conclusion: Psychomotor speed, particularly motor time with a visual warning signal, improves after transcranial bright light treatment in professional ice-hockey players during the competition season in the dark time of the year.

  20. Computational Strain Gradient Crystal Plasticity

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Kysar, Jeffrey W.

    2011-01-01

    element solution method is presented, which delivers the slip-rate field and the velocity-field based on two minimum principles. Some plane deformation problems relevant for certain specific orientations of a face centered cubic crystal under plane loading conditions are studied, and effective in......A model for strain gradient crystal visco-plasticity is formulated along the lines proposed by Fleck andWillis (2009) for isotropic plasticity. Size-effects are included in the model due to the addition of gradient terms in both the free energy as well as through a dissipation potential. A finite...

  1. High-brightness displays in integrated weapon sight systems

    Science.gov (United States)

    Edwards, Tim; Hogan, Tim

    2014-06-01

    In the past several years Kopin has demonstrated the ability to provide ultra-high brightness, low power display solutions in VGA, SVGA, SXGA and 2k x 2k display formats. This paper will review various approaches for integrating high brightness overlay displays with existing direct view rifle sights and augmenting their precision aiming and targeting capability. Examples of overlay display systems solutions will be presented and discussed. This paper will review significant capability enhancements that are possible when augmenting the real-world as seen through a rifle sight with other soldier system equipment including laser range finders, ballistic computers and sensor systems.

  2. An adaptive brightness preserving bi-histogram equalization

    Science.gov (United States)

    Shen, Hongying; Sun, Shuifa; Lei, Bangjun; Zheng, Sheng

    2011-11-01

    Based on mean preserving bi-histogram equalization (BBHE), an adaptive image histogram equalization algorithm for contrast enhancement is proposed. The threshold is gotten with adaptive iterative steps and used to divide the original image into two sub-images. The proposed Iterative of Brightness Bi-Histogram Equalization overcomes the over-enhancement phenomenon in the conventional histogram equalization. The simulation results show that the algorithm can not only preserve the mean brightness, but also keep the enhancement image information effectively from visual perception, and get a better edge detection result.

  3. Photometric behavior of spectral parameters in Vesta dark and bright regions as inferred by the Dawn VIR spectrometer

    Science.gov (United States)

    Longobardo, Andrea; Palomba, Ernesto; Capaccioni, Fabrizio; De Sanctis, Maria Cristina; Tosi, Federico; Ammannito, Eleonora; Schröder, Stefan E.; Zambon, Francesca; Raymond, Carol A.; Russell, Christopher T.

    2014-09-01

    NASA’s Dawn spacecraft orbited Vesta for approximately one year, collecting thousands of hyperspectral images of its surface. The mission revealed that Vesta’s surface shows the largest variations in surface albedo on asteroids visited thus far, due to the presence of dark and bright materials at the local scale (i.e. 0.1-10 km). The aim of this work is to characterize the photometric properties of bright and dark regions, and thus derive and apply an empirical photometric correction to all the hyperspectral observations of Vesta. The very large dataset (i.e. more than 20 million spectra) provided by the VIR imaging spectrometer onboard Dawn enabled accurate statistical analysis of the spectral dataset, aimed at retrieving empirical relations between several spectral parameters (i.e. visible and infrared reflectance, band depths, band centers, Band Area Ratio) and the illumination/viewing angles. The derived relations made it possible to derive photometrically corrected maps of these spectral parameters and to infer information on the regolith shadowing effect in the Vestan dark and bright regions. As an additional analysis, we also evaluated the correlation between surface temperature and band center position. A general conclusion of this analysis is that, from a photometric point of view, the distinction between bright and dark material units lies mainly in the larger contribution due to multiple scattering in the bright units. We observed reflectance and band depth variations over Vesta’s entire surface, but these variations were much larger in the dark regions than in the bright ones. Band centers have been found to shift to longer wavelengths at increasing temperatures, with a trend that is the same observed for HED meteorites (Reddy et al. [2012]. Icarus 217, 153-158). Finally, the Band Area Ratio (i.e. the ratio between areas of the main pyroxene absorption bands located at 1.9 μm and at 0.9 μm, respectively) did not show any dependence on

  4. COLORS AND COLOR GRADIENTS IN BULGES OF GALAXIES

    NARCIS (Netherlands)

    BALCELLS, M; PELETIER, RF

    We have obtained surface photometry in U, B, R, and I for a complete optically selected sample of 45 early-type spiral galaxies, to investigate the colors and color gradients of spiral bulges. Color profiles in U-R, B-R, U-B, and R-I have been determined in wedges opening on the semiminor axes.

  5. Aeromagnetic gradient survey used in sandstone type uranium deposits prospecting

    International Nuclear Information System (INIS)

    Li Xiaolu; Chang Shushuai

    2014-01-01

    The principle, advantage and data processing of aeromagnetic gradient survey approach is introduced in this paper which was used in sandstone type uranium deposits prospecting to study the shallow surface faults, uranium ore-forming environment and depth of magnetic body, which proved to be a good results. (authors)

  6. Dynamic brightness induction causes flicker adaptation, but only along the edges: Evidence against the neural filling-in of brightness

    Science.gov (United States)

    Robinson, Alan E.; de Sa, Virginia R.

    2013-01-01

    Is brightness represented in a point-for-point neural map that is filled in from the response of small, contrast-sensitive edge detector cells? We tested for the presence of this filled-in map by adapting to illusory flicker caused by a dynamic brightness-induction stimulus. Thereafter flicker sensitivity was reduced when our test region was the same size as the induced region, but not for smaller, inset regions. This suggests induced brightness is represented by either small edge-selective cells with no filling-in stage, or by contrast-sensitive spatial filters at many different scales, but not by a population of filled-in neurons arranged in a point-for-point map. PMID:23729768

  7. THE PANCHROMATIC HUBBLE ANDROMEDA TREASURY. I. BRIGHT UV STARS IN THE BULGE OF M31

    International Nuclear Information System (INIS)

    Rosenfield, Philip; Johnson, L. Clifton; Dalcanton, Julianne J.; Williams, Benjamin F.; Gilbert, Karoline M.; Girardi, Léo; Bressan, Alessandro; Lang, Dustin; Guhathakurta, Puragra; Dorman, Claire E.; Howley, Kirsten M.; Lauer, Tod R.; Olsen, Knut A. G.; Bell, Eric F.; Bianchi, Luciana; Caldwell, Nelson; Dolphin, Andrew; Kalirai, Jason; Larsen, Søren S.; Rix, Hans-Walter

    2012-01-01

    As part of the Panchromatic Hubble Andromeda Treasury multi-cycle program, we observed a 12' × 6.'5 area of the bulge of M31 with the WFC3/UVIS filters F275W and F336W. From these data we have assembled a sample of ∼4000 UV-bright, old stars, vastly larger than previously available. We use updated Padova stellar evolutionary tracks to classify these hot stars into three classes: Post-AGB stars (P-AGB), Post-Early AGB (PE-AGB) stars, and AGB-manqué stars. P-AGB stars are the end result of the asymptotic giant branch (AGB) phase and are expected in a wide range of stellar populations, whereas PE-AGB and AGB-manqué (together referred to as the hot post-horizontal branch; HP-HB) stars are the result of insufficient envelope masses to allow a full AGB phase, and are expected to be particularly prominent at high helium or α abundances when the mass loss on the red giant branch is high. Our data support previous claims that most UV-bright sources in the bulge are likely hot (extreme) horizontal branch (EHB) stars and their progeny. We construct the first radial profiles of these stellar populations and show that they are highly centrally concentrated, even more so than the integrated UV or optical light. However, we find that this UV-bright population does not dominate the total UV luminosity at any radius, as we are detecting only the progeny of the EHB stars that are the likely source of the UV excess. We calculate that only a few percent of main-sequence stars in the central bulge can have gone through the HP-HB phase and that this percentage decreases strongly with distance from the center. We also find that the surface density of hot UV-bright stars has the same radial variation as that of low-mass X-ray binaries. We discuss age, metallicity, and abundance variations as possible explanations for the observed radial variation in the UV-bright population.

  8. Image defog algorithm based on open close filter and gradient domain recursive bilateral filter

    Science.gov (United States)

    Liu, Daqian; Liu, Wanjun; Zhao, Qingguo; Fei, Bowen

    2017-11-01

    To solve the problems of fuzzy details, color distortion, low brightness of the image obtained by the dark channel prior defog algorithm, an image defog algorithm based on open close filter and gradient domain recursive bilateral filter, referred to as OCRBF, was put forward. The algorithm named OCRBF firstly makes use of weighted quad tree to obtain more accurate the global atmospheric value, then exploits multiple-structure element morphological open and close filter towards the minimum channel map to obtain a rough scattering map by dark channel prior, makes use of variogram to correct the transmittance map,and uses gradient domain recursive bilateral filter for the smooth operation, finally gets recovery images by image degradation model, and makes contrast adjustment to get bright, clear and no fog image. A large number of experimental results show that the proposed defog method in this paper can be good to remove the fog , recover color and definition of the fog image containing close range image, image perspective, the image including the bright areas very well, compared with other image defog algorithms,obtain more clear and natural fog free images with details of higher visibility, what's more, the relationship between the time complexity of SIDA algorithm and the number of image pixels is a linear correlation.

  9. Compositional gradients in Gramineae genes

    DEFF Research Database (Denmark)

    Wong, Gane Ka-Shu; Wang, Jun; Tao, Lin

    2002-01-01

    In this study, we describe a property of Gramineae genes, and perhaps all monocot genes, that is not observed in eudicot genes. Along the direction of transcription, beginning at the junction of the 5'-UTR and the coding region, there are gradients in GC content, codon usage, and amino-acid usage...

  10. The bright optical afterglow of the long GRB 001007

    DEFF Research Database (Denmark)

    Ceron, J.M.C.; Castro-Tirado, A.J.; Gorosabel, J.

    2002-01-01

    We present optical follow up observations of the long GRB 001007 between 6.14 hours and similar to468 days after the event. An unusually bright optical afterglow (OA) was seen to decline following a steep power law decay with index alpha = -2.03 +/- 0.11, possibly indicating a break in the light ...

  11. Evaluation of brightness temperature from a forward model of ...

    Indian Academy of Sciences (India)

    Ground-based microwave radiometers are getting great attention in recent years due to their capability to profile the temperature and humidity at high temporal and vertical resolution in the lower troposphere. The process of retrieving these parameters from the measurements of radiometric brightness temperature.

  12. The "Brightness Rules" Alternative Conception for Light Bulb Circuits

    Science.gov (United States)

    Bryan, Joel A.; Stuessy, Carol

    2006-01-01

    An alternative conception for the observed differences in light bulb brightness was revealed during an unguided inquiry investigation in which prospective elementary teachers placed identical bulbs in series, parallel, and combination direct current circuits. Classroom observations, document analyses, and video and audio transcriptions led to the…

  13. High-brightness fiber-coupled pump laser development

    Science.gov (United States)

    Price, Kirk; Karlsen, Scott; Leisher, Paul; Martinsen, Robert

    2010-02-01

    We report on the continued development of high brightness laser diode modules at nLIGHT Photonics. These modules, based on nLIGHT's PearlTM product platform, demonstrate excellence in output power, brightness, wavelength stabilization, and long wavelength performance. This system, based on 14 single emitters, is designed to couple diode laser light into a 105 μm fiber at an excitation NA of under 0.14. We demonstrate over 100W of optical power at 9xx nm with a diode brightness exceeding 20 MW/cm2-str with an operating efficiency of approximately 50%. Additional results show over 70W of optical coupled at 8xx nm. Record brilliance at wavelengths 14xx nm and longer will also be demonstrated, with over 15 W of optical power with a beam quality of 7.5 mm-mrad. These results of high brightness, high efficiency, and wavelength stabilization demonstrate the pump technology required for next generation solid state and fiber lasers.

  14. Beyond the Kepler/K2 bright limit

    DEFF Research Database (Denmark)

    White, Tim; Pope, B. J. S.; Antoci, Victoria

    2017-01-01

    very bright stars for asteroseismology and to search for transiting exoplanets. We apply this method to the seven brightest stars in the Pleiades open cluster. Each star exhibits variability; six of the stars show what are most likely slowly pulsating B-star pulsations, with amplitudes ranging from 20...

  15. A new perspective on the infrared brightness temperature ...

    Indian Academy of Sciences (India)

    3Database & Web-based Software Division, Space Applications Centre, Ahmedabad 380 015, India. ∗ ... temperatures clearly discriminates the cloud pixels of deep convective and non-deep convective cases. It ... that Johnson SB distribution of infrared brightness temperatures for deep convective systems is differ-.

  16. Compact collimators for high brightness blue LEDs using dielectric multilayers

    NARCIS (Netherlands)

    Cornelissen, H.J.; Ma, H.; Ho, C.; Li, M.; Mu, C.

    2011-01-01

    A novel method is presented to inject the light of millimeter-sized high-brightness blue LEDs into light guides of submillimeter thickness. Use is made of an interference filter that is designed to pass only those modes that will propagate in the light guide by total internal reflection. Other modes

  17. Protocol of networks using energy sharing collisions of bright solitons

    Indian Academy of Sciences (India)

    physics pp. 1009–1021. Protocol of networks using energy sharing collisions of bright solitons. K NAKAMURA1,2, T KANNA3,∗ and K SAKKARAVARTHI3. 1Faculty of Physics ... solitonic collisions is expected and therefore multiple soliton dynamics leads to a triv- ..... One can obtain various choices of αk which satisfy eq.

  18. Bright and dark soliton solutions of the (3+ 1)-dimensional ...

    Indian Academy of Sciences (India)

    In this paper, we obtain the 1-soliton solutions of the (3 + 1)-dimensional generalized Kadomtsev–Petviashvili (gKP) equation and the generalized Benjamin equation. By using two solitary wave ansatz in terms of sech p and tanh p functions, we obtain exact analytical bright and dark soliton solutions for the considered ...

  19. The star-bright hour : [poems] / Betti Alver

    Index Scriptorium Estoniae

    Alver, Betti, 1906-1989

    2003-01-01

    Autori lühitutvustus lk. 231. Sisu: The star-bright hour ; The debt ; Not a dream ; Fog-bound ; Corals in an Ancient river ; Frou-frou 1-3. Orig.: Tähetund ; Vilepuhuja ; Võlg ; "Mitte viirastus, meelepett..." ; Udus ; Korallid Emajões ; Froufrou 1-3

  20. The star-bright hour : [luuletused] / Betti Alver

    Index Scriptorium Estoniae

    Alver, Betti, 1906-1989

    2006-01-01

    Sisu: The star-bright hour ; Not a dream ; The Piper ; Corals in an ancent river. Luuletused pärinevad kogumikust "Tuulelaeval valgusest on aerud = Windship with Oars of Light. (Tallinn : Huma, 2001). Orig.: Tähetund ; Mitte viirastus, meelepett ; Vilepuhuja ; Korallid Emajões

  1. Brightness perception in low resolution images of 3d textures

    NARCIS (Netherlands)

    Spreeuwers, Lieuwe Jan; van der Heijden, Ferdinand; Siteur, J.

    1996-01-01

    A first step towards the analysis of the appearance of 3 dimensional textures is presented in this paper. It is assumed that the scale of the texture is small relative to the resolution of the camera. Therefore, the texture itself is not distinguishable.However, the perceived brightness of the

  2. Fluorescence brightness and photostability of individual copper (I) oxide nanocubes.

    Science.gov (United States)

    Zohora, Nafisa; Kandjani, Ahmad Esmaielzadeh; Orth, Antony; Brown, Hannah M; Hutchinson, Mark R; Gibson, Brant C

    2017-12-04

    Conventional organic fluorophores lose their ability to fluoresce after repeated exposure to excitation light due to photobleaching. Therefore, research into emerging bright and photostable nanomaterials has become of great interest for a range of applications such as bio-imaging and tracking. Among these emerging fluorophores, metal oxide-based nanomaterials have attracted significant attention as a potential multifunctional material with photocatalytic and angeogenisis abilities in addition to fluorescnce applications. However, most of these applications are highly dependent on size, morphology, and chemo-physical properties of individual particles. In this manuscript, we present a method to study the intrinsic optical characteristics of individual copper (I) oxide (Cu 2 O) nanocubes. When excited at 520 nm using only 11 µW excitation power (1.7 W/cm2), individual nanocubes were observed to emit light with peak wavelengths ~760 nm which is conveniently within the near-infrared 1 (NIR1) biological window where tissue autofluorescence is minimal. Bright and photostable fluorescence was observed with intensities up to 487 K counts/s under constant illumination for at least 2 minutes with a brightness approximately four times higher than the autofluorescence from a fixed cumulus-oocyte complex. With near-IR emission, high fluorescence brightness, and outstanding photostability, Cu 2 O nanocubes are attractive candidates for long-term fluorescent bioimaging applications.

  3. Matter-wave bright solitons in effective bichromatic lattice potentials

    Indian Academy of Sciences (India)

    Matter-wave bright solitons in bichromatic lattice potentials are considered and their dynamics for different lattice environments are studied. Bichromatic potentials are created from superpositions of (i) two linear optical lattices and (ii) a linear and a nonlinear optical lattice. Effective potentials are found for the solitons in both ...

  4. The Skylab ten color photoelectric polarimeter. [sky brightness

    Science.gov (United States)

    Weinberg, J. L.; Hahn, R. C.; Sparrow, J. G.

    1975-01-01

    A 10-color photoelectric polarimeter was used during Skylab missions SL-2 and SL-3 to measure sky brightness and polarization associated with zodiacal light, background starlight, and the spacecraft corona. A description is given of the instrument and observing routines together with initial results on the spacecraft corona and polarization of the zodiacal light.

  5. Brightness calibrates particle size in single particle fluorescence imaging.

    Science.gov (United States)

    Liu, Zhihe; Sun, Zezhou; Di, Weihua; Qin, Weiping; Yuan, Zhen; Wu, Changfeng

    2015-04-01

    This Letter provides a novel approach to quantify the particle sizes of highly bright semiconductor polymer dots (Pdots) for single-particle imaging and photobleaching studies. A quadratic dependence of single-particle brightness on particle size was determined by single-particle fluorescence imaging and intensity statistics. In terms of the same imaging conditions, the particle diameter can be quantified by comparing the individual brightness intensity with associated calibration curve. Based on this sizing method, photobleaching trajectories and overall photon counts emitted by single particles were analyzed. It is found that photobleaching rate constants of different sized Pdots are not strongly dependent on particle diameter except the sparsely occurring fluorescence blinking in certain dim particles and the rapid photobleaching component in some bright particles. The overall photon counts increase with increasing particle diameter. However, those larger than 30 nm deviate away from the increasing tendency. These results reveal the significance of selecting appropriate Pdots (≤30  nm) for single-particle imaging and tracking applications.

  6. Bright infrared LEDs based on colloidal quantum-dots

    KAUST Repository

    Sun, Liangfeng

    2013-01-01

    Record-brightness infrared LEDs based on colloidal quantum-dots have been achieved through control of the spacing between adjacent quantum-dots. By tuning the size of quantum-dots, the emission wavelengths can be tuned between 900nm and 1650nm. © 2013 Materials Research Society.

  7. Optical variability of the medium-bright quasar sample

    International Nuclear Information System (INIS)

    Huang, K.; Mitchell, K.J.; Usher, P.D.

    1990-01-01

    A variability study of the 32-member Medium-Bright Quasar Sample is reported. It is found that the star US 1953 has undergone a noticeable variation in the course of 26 hr. Apparent variations in the extragalactic object US 3498 may be illusory, owing to its partially resolved appearance. No other evidence for variability was detected. 34 refs

  8. Brightness Rural Electrification Program: Renewable Energy in China

    Energy Technology Data Exchange (ETDEWEB)

    2004-04-01

    Fact sheet describes China's New Brightness Rural Electrification Program to provide electricity for 23 million people in remote areas of China using renewable energy such as wind energy and solar power (photovoltaics). Targets, results, and progress are described. Regions targeted are Inner Mongolia, Tibet, and Gansu.

  9. Soil Moisture Active/Passive (SMAP) Forward Brightness Temperature Simulator

    Science.gov (United States)

    Peng, Jinzheng; Peipmeier, Jeffrey; Kim, Edward

    2012-01-01

    The SMAP is one of four first-tier missions recommended by the US National Research Council's Committee on Earth Science and Applications from Space (Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond, Space Studies Board, National Academies Press, 2007) [1]. It is to measure the global soil moisture and freeze/thaw from space. One of the spaceborne instruments is an L-band radiometer with a shared single feedhorn and parabolic mesh reflector. While the radiometer measures the emission over a footprint of interest, unwanted emissions are also received by the antenna through the antenna sidelobes from the cosmic background and other error sources such as the Sun, the Moon and the galaxy. Their effects need to be considered accurately, and the analysis of the overall performance of the radiometer requires end-to-end performance simulation from Earth emission to antenna brightness temperature, such as the global simulation of L-band brightness temperature simulation over land and sea [2]. To assist with the SMAP radiometer level 1B algorithm development, the SMAP forward brightness temperature simulator is developed by adapting the Aquarius simulator [2] with necessary modifications. This poster presents the current status of the SMAP forward brightness simulator s development including incorporating the land microwave emission model and its input datasets, and a simplified atmospheric radiative transfer model. The latest simulation results are also presented to demonstrate the ability of supporting the SMAP L1B algorithm development.

  10. Response of noctilucent cloud brightness to daily solar variations

    Science.gov (United States)

    Dalin, P.; Pertsev, N.; Perminov, V.; Dubietis, A.; Zadorozhny, A.; Zalcik, M.; McEachran, I.; McEwan, T.; Černis, K.; Grønne, J.; Taustrup, T.; Hansen, O.; Andersen, H.; Melnikov, D.; Manevich, A.; Romejko, V.; Lifatova, D.

    2018-04-01

    For the first time, long-term data sets of ground-based observations of noctilucent clouds (NLC) around the globe have been analyzed in order to investigate a response of NLC to solar UV irradiance variability on a day-to-day scale. NLC brightness has been considered versus variations of solar Lyman-alpha flux. We have found that day-to-day solar variability, whose effect is generally masked in the natural NLC variability, has a statistically significant effect when considering large statistics for more than ten years. Average increase in day-to-day solar Lyman-α flux results in average decrease in day-to-day NLC brightness that can be explained by robust physical mechanisms taking place in the summer mesosphere. Average time lags between variations of Lyman-α flux and NLC brightness are short (0-3 days), suggesting a dominant role of direct solar heating and of the dynamical mechanism compared to photodissociation of water vapor by solar Lyman-α flux. All found regularities are consistent between various ground-based NLC data sets collected at different locations around the globe and for various time intervals. Signatures of a 27-day periodicity seem to be present in the NLC brightness for individual summertime intervals; however, this oscillation cannot be unambiguously retrieved due to inevitable periods of tropospheric cloudiness.

  11. Henrietta Leavitt–A Bright Star of Astronomy

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 6; Issue 6. Henrietta Leavitt – A Bright Star of Astronomy. Biman Nath. Article-in-a-Box Volume 6 Issue 6 June 2001 pp 2-3. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/006/06/0002-0003 ...

  12. Preparing Young Adolescents for a Bright Future--Right Now!

    Science.gov (United States)

    Deering, Paul D.; Martin, Kathryn L.; Buelow, Stephanie M.; Hoffman, Jennifer T.; Cameli, Sandy; Martin, Matt; Walker, Robert E.; O'Neill, Tara B.

    2016-01-01

    We must prepare young adolescents for a bright future by examining all of our educational practices in terms of their current and future relevance. The education we provide our students must prepare them to address enormously complex issues involving demographics and international relations, environmental and human health, and the development and…

  13. Surface cleanliness measurement procedure

    Science.gov (United States)

    Schroder, Mark Stewart; Woodmansee, Donald Ernest; Beadie, Douglas Frank

    2002-01-01

    A procedure and tools for quantifying surface cleanliness are described. Cleanliness of a target surface is quantified by wiping a prescribed area of the surface with a flexible, bright white cloth swatch, preferably mounted on a special tool. The cloth picks up a substantial amount of any particulate surface contamination. The amount of contamination is determined by measuring the reflectivity loss of the cloth before and after wiping on the contaminated system and comparing that loss to a previous calibration with similar contamination. In the alternative, a visual comparison of the contaminated cloth to a contamination key provides an indication of the surface cleanliness.

  14. Simulating the Near-Surface Environments of Solar System Bodies in the Laboratory

    Science.gov (United States)

    Donaldson Hanna, K. L.; Bowles, N. E.; Greenhagen, B. T.

    2016-12-01

    Thermal infrared (TIR) emissivity measurements are sensitive to a planetary body's near-surface (upper hundreds of microns) environment, porosity and particle size, which make the interpretation of thermal infrared remote sensing observations of planetary surfaces challenging. Thus, well-constrained laboratory TIR measurements of analogue samples for a range of particle sizes, porosities and near-surface environments are needed. Near-surface environments and porosities for a range of solar system bodies can be simulated using facilities within University of Oxford's Planetary Spectroscopy Facility (PSF). The Simulated Lunar Environment Chamber (SLEC) within Oxford's PSF is a vacuum chamber capable of simulating near-surface conditions for a range of solar system bodies by varying atmospheric pressure and incident solar irradiation. By varying the near-surface environment, the thermal gradient in the upper hundreds of microns of the sample is varied, which can affect the position and contrast of diagnostic features in TIR spectra. The atmospheric pressure inside the chamber is varied between 1000, 5 and < 10-4 mbar to simulate Earth, Mars and airless bodies (e.g. the Moon, Mars' moons and asteroids) conditions. The solar-like irradiation is varied by adjusting the power of the halogen lamp until the brightness temperature of the sample is similar to the brightness temperature of the simulated planetary body. Varying the sample packing in the sample cup simulates a range of near-surface porosities. Here we present laboratory emissivity spectra of a suite of well-characterized rock, soil and mineral samples (< 25 mm in particle size) measured under a range of simulated planetary conditions including Earth, Mars, Moon and asteroids. These well-controlled laboratory measurements enable the interpretation of remote sensing observations, which help in determining a planet's surface composition as well as the consolidated nature of its regolith.

  15. Simulating Near-Surface Environments of Solar System Bodies in the Laboratory

    Science.gov (United States)

    Donaldson Hanna, Kerri; Bowles, Neil

    2017-04-01

    Thermal infrared (TIR) emissivity measurements are sensitive to a planetary body's near-surface (upper hundreds of microns) environment, porosity and particle size, which make the interpretation of thermal infrared remote sensing observations of planetary surfaces challenging. Thus, well-constrained laboratory TIR measurements of analogue samples for a range of particle sizes, porosities and near-surface environments are needed. Near-surface environments and porosities for a range of solar system bodies can be simulated using facilities within University of Oxford's Planetary Spectroscopy Facility (PSF). The Simulated Lunar Environment Chamber (SLEC) within Oxford's PSF is a vacuum chamber capable of simulating near-surface conditions for a range of solar system bodies by varying atmospheric pressure and incident solar irradiation. By varying the near-surface environment, the thermal gradient in the upper hundreds of microns of the sample is varied, which can affect the position and contrast of diagnostic features in TIR spectra. The atmospheric pressure inside the chamber is varied between 1000, 5 and < 10-4 mbar to simulate Earth, Mars and airless bodies (e.g. the Moon, Mars' moons and asteroids) conditions. The solar-like irradiation is varied by adjusting the power of the halogen lamp until the brightness temperature of the sample is similar to the brightness temperature of the simulated planetary body. Varying the sample packing in the sample cup simulates a range of near-surface porosities. Here we present laboratory emissivity spectra of a suite of well-characterized rock, soil and mineral samples (< 25 microns in particle size) measured under a range of simulated planetary conditions including Earth, Mars, Moon and asteroids. These well-controlled laboratory measurements enable the interpretation of remote sensing observations, which help in determining a planet's surface composition as well as the consolidated nature of its regolith.

  16. Wind induced errors on retrieving SSS with SMOS brightness temperature

    Science.gov (United States)

    Yin, X.; Boutin, J.; Martin, N.; Vergely, J.; Spurgeon, P.

    2012-04-01

    is used with correcting sea surface current. We study also the method to retrieve SSS and wind speed with multi-bands brightness temperature (TB) by collocating SSMI multi-bands TB and SMOS L-band TB.

  17. Elemental gradients in macrophytes from a reactor effluent gradient

    International Nuclear Information System (INIS)

    Grace, J.B.; Tilly, L.J.

    1978-01-01

    The tissues of submersed macrophtes from along the thermal gradient were analyzed for phosphorus to determine whether any pattern correspondent to standing crop distributions could be detected. Although water concentrations of phosphorus showed no detectable relationship to the thermal effluent, tissue concentrations of this element in submersed macrophytes declined with distance from the effluent entry point. The occurrence of this concentration pattern suggests that phosphorus availability is greater near the discharge. Because phosphorus is the element most often determined to limit aquatic productivity, its greater availability may partially account for the apparent enhancement of macrophte growth near the thermal discharge. A patter of macrophyte abundance which indicated enchancement related to the discharge gradient in the reactor-cooling reservoir, Par Pond is reported. Correlative data tended to implicate light and temperature as important in influencing the differential abundance pattern

  18. Cell Growth on ("Janus") Density Gradients of Bifunctional Zeolite L Crystals.

    Science.gov (United States)

    Kehr, Nermin Seda; Motealleh, Andisheh; Schäfer, Andreas H

    2016-12-28

    Nanoparticle density gradients on surfaces have attracted interest as two-dimensional material surfaces that can mimic the complex nano-/microstructure of the native extracellular matrix, including its chemical and physical gradients, and can therefore be used to systematically study cell-material interactions. In this respect, we report the preparation of density gradients made of bifunctional zeolite L crystals on glass surfaces and the effects of the density gradient and biopolymer functionalization of zeolite L crystals on cell adhesion. We also describe how we created "Janus" density gradient surfaces by gradually depositing two different types of zeolite L crystals that were functionalized and loaded with different chemical groups and guest molecules onto the two distinct sides of the same glass substrate. Our results show that more cells adhered on the density gradient of biopolymer-coated zeolites than on uncoated ones. The number of adhered cells increased up to a certain surface coverage of the glass by the zeolite L crystals, but then it decreased beyond the zeolite density at which a higher surface coverage decreased fibroblast cell adhesion and spreading. Additionally, cell experiments showed that cells gradually internalized the guest-molecule-loaded zeolite L crystals from the underlying density gradient containing bifunctional zeolite L crystals.

  19. Diode lasers optimized in brightness for fiber laser pumping

    Science.gov (United States)

    Kelemen, M.; Gilly, J.; Friedmann, P.; Hilzensauer, S.; Ogrodowski, L.; Kissel, H.; Biesenbach, J.

    2018-02-01

    In diode laser applications for fiber laser pumping and fiber-coupled direct diode laser systems high brightness becomes essential in the last years. Fiber coupled modules benefit from continuous improvements of high-power diode lasers on chip level regarding output power, efficiency and beam characteristics resulting in record highbrightness values and increased pump power. To gain high brightness not only output power must be increased, but also near field widths and far field angles have to be below a certain value for higher power levels because brightness is proportional to output power divided by beam quality. While fast axis far fields typically show a current independent behaviour, for broadarea lasers far-fields in the slow axis suffer from a strong current and temperature dependence, limiting the brightness and therefore their use in fibre coupled modules. These limitations can be overcome by carefully optimizing chip temperature, thermal lensing and lateral mode structure by epitaxial and lateral resonator designs and processing. We present our latest results for InGaAs/AlGaAs broad-area single emitters with resonator lengths of 4mm emitting at 976nm and illustrate the improvements in beam quality over the last years. By optimizing the diode laser design a record value of the brightness for broad-area lasers with 4mm resonator length of 126 MW/cm2sr has been demonstrated with a maximum wall-plug efficiency of more than 70%. From these design also pump modules based on 9 mini-bars consisting of 5 emitters each have been realized with 360W pump power.

  20. Progress in extremely high brightness LED-based light sources

    Science.gov (United States)

    Hoelen, Christoph; Antonis, Piet; de Boer, Dick; Koole, Rolf; Kadijk, Simon; Li, Yun; Vanbroekhoven, Vincent; Van De Voorde, Patrick

    2017-09-01

    Although the maximum brightness of LEDs has been increasing continuously during the past decade, their luminance is still far from what is required for multiple applications that still rely on the high brightness of discharge lamps. In particular for high brightness applications with limited étendue, e.g. front projection, only very modest luminance values in the beam can be achieved with LEDs compared to systems based on discharge lamps or lasers. With dedicated architectures, phosphor-converted green LEDs for projection may achieve luminance values up to 200-300 Mnit. In this paper we report on the progress made in the development of light engines based on an elongated luminescent concentrator pumped by blue LEDs. This concept has recently been introduced to the market as ColorSpark High Lumen Density LED technology. These sources outperform the maximum brightness of LEDs by multiple factors. In LED front projection, green LEDs are the main limiting factor. With our green modules, we now have achieved peak luminance values of 2 Gnit, enabling LED-based projection systems with over 4000 ANSI lm. Extension of this concept to yellow and red light sources is presented. The light source efficiency has been increased considerably, reaching 45-60 lm/W for green under practical application conditions. The module architecture, beam shaping, and performance characteristics are reviewed, as well as system aspects. The performance increase, spectral range extensions, beam-shaping flexibility, and cost reductions realized with the new module architecture enable a breakthrough in LED-based projection systems and in a wide variety of other high brightness applications.

  1. On the model of type 1 supernova near brightness maximum

    International Nuclear Information System (INIS)

    Mustel', Eh.R.; Chugaj, N.N.

    1975-01-01

    Some photometric and spectrophotometric data about supernovae of 1 type CH-1 are analyzed. Colour /Tsub(c)/ and spectrophotmetric /T/ temperatures of SN1972-e compared. It has been concluded that at the maximum brightness tsub(m) and before the maximum Tsub(c) approximately TTsub(c) < T after the maximum brightness. A considerable deviation of Tsub(c) from T is connected with the significant role of metal lines in the attenuation of the short-wavelength region spectrum CH-1, which becomes essential when T < 10000 deg K. Behaviour of the radius of the photosphere Rp at CH-1 is investigated on the basis of the accepted dependence of T on time. It is shown that at the maximum brightness Rp, increases linearly at the rate of about 5000 km/sec, and reaches its highest value approximately in 30-35sup(d) after the maximum brightness tsub(m) and then rather quickly decreases. The rate of the expansion of the photosphere is twice lower than the mean expansion velocity of the shell CH-1. The initial moments of separation of these CH are -25sup(d) and -16sup(d) respectively (with respect to the maximum V) have been found using an extrapolation of the Rp(t) dependence for SN 1972-e and SN 1970-j. The role of the temperature dependence of non-transparency on the behavior of the photosphere Ch-1 is discussed. Bolomeic luminosity of CH-1 at the maximum brightness is investigated. Arguments supporting the conclusion that the bolometric maximum of CH-1 comes formerly to a visual one, are given

  2. Application of a coupled microwave, energy and water transfer model to relate passive microwave emission from bare soils to near-surface water content and evaporation

    Directory of Open Access Journals (Sweden)

    L. P. Simmonds

    1999-01-01

    Full Text Available The paper examines the stability of the relation between microwave emission from the soil and the average near-surface water content in the case of relatively smooth, bare soils, and then considers the extent to which microwave radiometry can be used to estimate the effective surface resistance to vapour transfer, which is also related to the near-surface water status. The analysis is based on the use of a model (MICRO-SWEAT which couples a microwave radiative transfer model with a SVAT scheme that describes the exchanges of water vapour, energy and sensible heat at the land surface. Verification of MICRO-SWEAT showed good agreement (about 3K RMSE between predicted L band (1.4 GHz brightness temperature over soils with contrasting texture during a multi-day drydown, and those measured using a truck-mounted radiometer. There was good agreement between the measured and predicted relations between the average water content of the upper 2 cm of the soil profile and the brightness temperature normalised with respect to the radiometric surface temperature. Some of the scatter in this relationship was attributable to diurnal variation in the magnitude of near-surface gradients in temperature and water content, and could be accounted for by using the physically-based simulation model. The influence of soil texture on this relationship was well-simulated using MICRO-SWEAT. The paper concludes by demonstrating how MICRO-SWEAT can be used to establish a relationship between the normalised brightness temperature and the surface resistance for use in the prediction of evaporation using the Penman-Montheith equation.

  3. INTEGRAL FIELD SPECTROSCOPY AND MULTI-WAVELENGTH IMAGING OF THE NEARBY SPIRAL GALAXY NGC 5668 : AN UNUSUAL FLATTENING IN METALLICITY GRADIENT

    International Nuclear Information System (INIS)

    Marino, R. A.; Gil de Paz, A.; Castillo-Morales, A.; Pérez-González, P. G.; Gallego, J.; Zamorano, J.; Muñoz-Mateos, J. C.; Sánchez, S. F.; Alonso-Herrero, A.; Boissier, S.

    2012-01-01

    We present an analysis of the full bidimensional optical spectral cube of the nearby spiral galaxy NGC 5668, observed with the Pmas fiber PAcK Integral Field Unit (IFU) at the Calar Alto observatory 3.5 m telescope. We make use of broadband imaging to provide further constraints on the evolutionary history of the galaxy. This data set will allow us to improve our understanding of the mechanisms that drive the evolution of disks. We investigated the properties of 62 H II regions and concentric rings in NGC 5668 and derived maps in ionized-gas attenuation and chemical (oxygen) abundances. We find that while inward of r ∼36'' ∼ 4.4 kpc ∼ 0.36 (D 25 /2) the derived O/H ratio follows the radial gradient typical of spiral galaxies, the abundance gradient beyond r ∼ 36'' flattens out. The analysis of the multi-wavelength surface brightness profiles of NGC 5668 is performed by fitting these profiles with those predicted by chemo-spectrophotometric evolutionary models of galaxy disks. From this, we infer a spin and circular velocity of λ = 0.053 and v c = 167 km s –1 , respectively. The metallicity gradient and rotation curve predicted by this best-fitting galaxy model nicely match the values derived from the IFU observations, especially within r ∼36''. The same is true for the colors despite some small offsets and a reddening in the bluest colors beyond that radius. On the other hand, deviations of some of these properties in the outer disk indicate that a secondary mechanism, possibly gas transfer induced by the presence of a young bar, must have played a role in shaping the recent chemical and star formation histories of NGC 5668.

  4. Preparation and characterization of gradient polymer films

    International Nuclear Information System (INIS)

    Smith, S.C.

    1987-01-01

    Gradient polymers are multicomponent polymers whose chemical constitution varies with depth in the sample. Although these polymers may possess unique mechanical, optical, and barrier properties they remain relatively unexplored. This work is a study of the preparation of gradient polymers by sequential exposure of films to a diffusing monomer followed by electron beam irradiation. Initial experiments involved immersion of poly(vinyl chloride) (PVC) films in styrene or n-butyl methacrylate (BMA) for various time periods followed by irradiation with 1 or 10 megarads of accelerated electrons. A significant amount of poly(n-butyl methacrylate) (PBMA) formed in PVC/BMA systems, but little polystyrene could be found in the PVC/styrene films. A second set of experiments involved immersion of PVC and polyethylene (PE) films in BMA for 20, 40, 60, and 720 minutes followed by irradiation with 10 megarads of electrons. These films were then characterized using optical microscopy, quantitative transmission Fourier transform infrared spectroscopy (FTIR), and a depth profiling procedure based on quantitative attenuated total reflection (ATR) FTIR. It was concluded that the mechanism of PBMA formation in the polyethylene films was a result of events immediately following irradiation. Atmospheric oxygen diffusing into irradiated films trapped free radicals at the film surfaces. This was followed by storage in an evacuated desiccator where unintentional exposure to BMA vapor took place. This BMA reacted with free radicals that remained within the film cores, polymerizing to PBMA

  5. Summary of the Argonne Workshop on High Gradient RF

    CERN Document Server

    Norem, J

    2004-01-01

    Workshop on High Gradient rf was held at Argonne from October 7 - 9, 2003. This workshop reviewed the problems encountered when a number of accelerator technologies approached the high gradient limits. The aim of the workshop was to involve materials scientists and try to look at trigger mechanisms and surface interactions, in addition to reviewing progress. Talks were presented on superconducting rf, progress with high and low frequency copper cavities, and dielectrics. The focus was on both experimental and theoretical aspects of the problem. The overall picture presented at the workshop will be summarized.

  6. Impact of Ozone Gradient on Grapevine Leaves

    Science.gov (United States)

    Alebic-Juretic, Ana; Bokan-Vucelic, Itana; Mifka, Boris; Zatezalo, Marija; Zubak, Velimir

    2017-04-01

    Due to complex orography and air mass circulation, the Rijeka Bay area is characterized by O3 gradient, with concentrations risen with the altitude (1). Therefore AOT40 values were often exceeded and should result in harmful effects on vegetation. Based on previous controlled experiments (2), we examined the possible effect of atmospheric ozone on grape leaves under natural O3 gradient. Grapevine leaves (2-5) were collected from May to September 2016 at two sampling points in the proximity of two AQM stations: Site 1 in the city centre (20m asl) and Site 2 (186m asl) in the suburban settlement. Subsequent to weighing and determination of surface area, the leaves (0,5 g) were extracted in 95% ethanol and analysed on chlorophyl a (Chla), chlorophyl b (Chlb) and carotene (Car) content by UV-VIS spectrometry on 3 wavelengths (664, 649, 470 nm) (3) In summer 2016 O3 gradient was not that pronounced as usual (1), but stil the concentrations differed by approx. 20%, exceeding national AOT40 value at both sites (22.360 and 28.061 μg m-3 h, respectively, at Sites 1 and 2). The concentrations of other pollutants were bellow limit values (LV). The Cha and Chb in a sample leaves collected at the end of May at Site 2 are equal to that with filtered O3 in control experiment (2), i.e. without damage caused by ozone, while the Car content is lower approx. 50% and is kept at the same level. The con-centrations of pigments obtained in July prooved the possible damage by O3, while in subsequent months could speed up natural ageing. This is the first evidence of O3 damage on plants in the Rijeka Bay area, in spite of weaker O3 gradient and lacking visible signs of damage. Preliminary results indicate the need for more frequent sampling, particularly in the period included in AOT40 (May-July). References: 1. Alebić-Juretić A (2012) Int J Remote Sensing, 33(2): 335-345 2. Britvec M, Reichenauer T, Soja G., Ljubešić N, Pećina M (2001) Biologia (Bratislava),56/4: 417-424 3. Sumanata

  7. Human impact gradient on mammalian biodiversity

    Directory of Open Access Journals (Sweden)

    Mariana Munguía

    2016-04-01

    Full Text Available Drastic changes have been caused by human influence in natural landscapes, which may exert an intensive effect on species loss. However, species loss from human pressure is not random but depends on a series of environmentally associated factors. Linking species traits to environmental attributes may allow us to detect the ecological impacts of habitat so that meaningful habitat degradation gradients can be identified. The relationships between environmental factors and species traits provide the basis for identifying those biological traits that make species more sensitive to disturbance. These relationships are also helpful to detect the geographic distribution of latent risk to reveal areas where biodiversity is threatened. Here, we identify a “Human Impact Gradient for Biodiversity (HIGB” based on a three-table ordination method (RLQ analysis and fourth-corner analysis to identify key species traits that are associated with environmental gradient. Species distribution and environmental geographic data were gathered nationwide to analyze 68 localities, which represent 27% of Mexico’s surface, including 211 species of mammals. Nine environmental variables (including biophysical, geophysical and land-use impacts were analyzed by using the Geographic Information System. Three types of species’ traits were evaluated: locomotion, trophic habit and body size. We identified a human impact gradient, which was mainly determined by the percentage of the area that was covered by seedlings, the plant richness, the understory coverage percentage and the human settlement index. The most important species traits that are associated with non-human-impacted sites were carnivores, frugivores–herbivores and a body size that was greater than 17.8 kg; 25 species were selected by the decision criteria framework for species that were sensitive to degradation based on ecological function information. Conversely, granivores, fossorial and semifossorial

  8. Vertebrate pressure-gradient receivers

    DEFF Research Database (Denmark)

    Christensen-Dalsgaard, Jakob

    2011-01-01

    The eardrums of all terrestrial vertebrates (tetrapods) are connected through Eustachian tubes or interaural canals. In some of the animals, these connections create pressure-gradient directionality, an enhanced directionality by interaction of sound arriving at both sides of the eardrum and stro......The eardrums of all terrestrial vertebrates (tetrapods) are connected through Eustachian tubes or interaural canals. In some of the animals, these connections create pressure-gradient directionality, an enhanced directionality by interaction of sound arriving at both sides of the eardrum....... Recent vertebrates form a continuum from perfect interaural transmission (0 dB in a certain frequency band) and pronounced eardrum directionality (30-40 dB) in the lizards, over somewhat attenuated transmission and limited directionality in birds and frogs, to the strongly attenuated interaural...

  9. Modeling of Diamond Field-Emitter-Arrays for high brightness photocathode applications

    Science.gov (United States)

    Kwan, Thomas; Huang, Chengkun; Piryatinski, Andrei; Lewellen, John; Nichols, Kimberly; Choi, Bo; Pavlenko, Vitaly; Shchegolkov, Dmitry; Nguyen, Dinh; Andrews, Heather; Simakov, Evgenya

    2017-10-01

    We propose to employ Diamond Field-Emitter-Arrays (DFEAs) as high-current-density ultra-low-emittance photocathodes for compact laser-driven dielectric accelerators capable of generating ultra-high brightness electron beams for advanced applications. We develop a semi-classical Monte-Carlo photoemission model for DFEAs that includes carriers' transport to the emitter surface and tunneling through the surface under external fields. The model accounts for the electronic structure size quantization affecting the transport and tunneling process within the sharp diamond tips. We compare this first principle model with other field emission models, such as the Child-Langmuir and Murphy-Good models. By further including effects of carrier photoexcitation, we perform simulations of the DFEAs' photoemission quantum yield and the emitted electron beam. Details of the theoretical model and validation against preliminary experimental data will be presented. Work ssupported by LDRD program at LANL.

  10. Dynamic pulsed-field-gradient NMR

    CERN Document Server

    Sørland, Geir Humborstad

    2014-01-01

    Dealing with the basics, theory and applications of dynamic pulsed-field-gradient NMR NMR (PFG NMR), this book describes the essential theory behind diffusion in heterogeneous media that can be combined with NMR measurements to extract important information of the system being investigated. This information could be the surface to volume ratio, droplet size distribution in emulsions, brine profiles, fat content in food stuff, permeability/connectivity in porous materials and medical applications currently being developed. Besides theory and applications it will provide the readers with background knowledge on the experimental set-ups, and most important, deal with the pitfalls that are numerously present in work with PFG-NMR. How to analyze the NMR data and some important basic knowledge on the hardware will be explained, too.

  11. Generation of metal composition gradients by means of bipolar electrodeposition

    International Nuclear Information System (INIS)

    Tisserant, Gwendoline; Fattah, Zahra; Ayela, Cédric; Roche, Jérome; Plano, Bernard; Zigah, Dodzi; Goudeau, Bertrand; Kuhn, Alexander; Bouffier, Laurent

    2015-01-01

    Highlights: • A bipolar electrochemistry approach for the preparation of surface gradients is reported. • Several metals are simultaneously deposited on a bipolar electrode. • The elemental composition and thickness of the deposit varies alongside the bipolar electrode. • The deposit affects the surface properties and exhibits a barcode feature. - Abstract: Bipolar electrochemistry is an unconventional technique that currently encounters a renewal of interest due to modern applications in the fields of analytical chemistry or materials science. The approach is particularly relevant for the preparation of asymmetric objects or surfaces such as Janus particles for example. Bipolar electrochemistry allows spatially controlled deposition of various layers from electroactive precursors, selectively at one side of a bipolar electrode. We report here the concomitant cathodic deposition of up to three different metals at the same time in a single experiment. The deposits were characterized by optical and electron microscopy imaging as well as profilometry and energy dispersive X-ray spectroscopy. As a result, the deposited layer is composed of several areas exhibiting both a composition and a thickness gradient. Such a variation directly modifies the optical and electronic properties alongside the surface and gives access to the design of composite surfaces exhibiting a visual gradient feature.

  12. Primordial vorticity and gradient expansion

    CERN Document Server

    Giovannini, Massimo

    2012-01-01

    The evolution equations of the vorticities of the electrons, ions and photons in a pre-decoupling plasma are derived, in a fully inhomogeneous geometry, by combining the general relativistic gradient expansion and the drift approximation within the Adler-Misner-Deser decomposition. The vorticity transfer between the different species is discussed in this novel framework and a set of general conservation laws, connecting the vorticities of the three-component plasma with the magnetic field intensity, is derived. After demonstrating that a source of large-scale vorticity resides in the spatial gradients of the geometry and of the electromagnetic sources, the total vorticity is estimated to lowest order in the spatial gradients and by enforcing the validity of the momentum constraint. By acknowledging the current bounds on the tensor to scalar ratio in the (minimal) tensor extension of the $\\Lambda$CDM paradigm the maximal comoving magnetic field induced by the total vorticity turns out to be, at most, of the or...

  13. Reaction Gradients Viewed Inside Single Photoactive Particles

    Science.gov (United States)

    Alpert, P.; Corral Arroyo, P.; Dou, J.; Kreiger, U.; Luo, B.; Peter, T.; Ammann, M.

    2017-12-01

    In terms of chemical selectivity and spatial resolution, a technique known as scanning transmission X-ray microscopy coupled to near-edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS) is unmatched and will remain so for years into the future. We present a recent development coupling STXM/NEXAFS to a custom-built photochemical environmental reactor in which aerosol particles reside allowing for in situ chemical imaging. A laboratory investigation of metal-organic complex photochemistry was conducted. Transition metals are of great importance to atmospheric chemistry and aerosol photochemical aging due to their ability to catalyze oxidation reactions. Aerosol particles composed of mixtures of citric acid and iron citrate were probed for their organic carbon composition and iron oxidation state under atmospherically relevant conditions. At 40% relative humidity, oxygen diffusion and reaction was severely limited. Fe was reoxidized in the first 200 nm of the particle surface leaving reduced iron in the core. Similar gradients were observed at 60% RH, however waiting approximately 2 hours in the dark resulted in a recovery of the initial Fe(III) concentration. We draw two main conclusions from our findings. Frist, the oxidation gradients must have been the result of anoxic conditions at the interior of aerosol particles. This was predicted using a newly developed model for molecular diffusion through multiple layers with a reaction framework describing the photochemical processing of the metal organic matrix. Second, the lifetime of organic radicals in an anoxic diffusion limited organic matrix must be considerably long ( hours) to completely reoxidize iron as they wait for molecular oxygen. Long radical lifetimes in viscous organic aerosol in turn, could create high radical concentrations or favor radical-radical reactions in particles typically not considered when oxygen is plentiful. Our results impact predictions of aerosol physiochemical properties, e

  14. SMOS CATDS Level 3 products, Soil Moisture and Brightness Temperature: Presentation and results

    Science.gov (United States)

    Berthon, Lucie; Mialon, Arnaud; Bitar, Ahmad Al; Cabot, François; Bircher, Simone; Jacquette, Elsa; Quesney, Arnaud; Kerr, Yann H.

    2013-04-01

    The ESA's (European Space Agency) SMOS (Soil Moisture and Ocean Salinity) mission, operating since November 2009, is the first satellite dedicated to measuring surface soil moisture and ocean salinity. The CNES (Centre National d'Etudes Spatiales) has developed the CATDS (Centre Aval de Traitement des Données SMOS) ground segment. It provides spatial and temporal synthesis products (referred to as Level 3) of soil moisture, which are now covering the whole SMOS operation period since January 2010. These products have different time resolutions: daily products, 3-day global products (insuring a complete coverage of the Earth's surface), 10-day composite products, and monthly averaged products. Moreover, a new product provides brightness temperatures at H and V polarizations which are computed at fixed incidence angles every 5 degrees. All the CATDS products are presented in the NetCDF format on the EASE grid (Equal Area Scalable Earth grid) with a spatial resolution of ~ 25*25 km². The soil moisture Level 3 algorithm is based on ESA's Level 2 retrieval scheme with the improvement of using several overpasses (3 at most) over a 7-day window. Using many revisits is expected to improve the quality of the retrieved soil moisture. This communication aims at presenting the CATDS soil moisture and brightness temperature products as well as other geophysical parameters retrieved on the side, such as the vegetation optical depth or the dielectric constant of the surface. Furthermore, we illustrate the validation of this database, including the comparison of the Level 3 soil moisture to in-situ measurements available from various sites (Australia, US, southwest of France, Spain, Denmark, West Africa, French Alps), spanning different surface conditions.

  15. Factors controlling cloud microphysics, precipitation rate, and brightness temperature of tropical convective and stratiform clouds

    Science.gov (United States)

    Hashino, T.; Casella, D.; Mugnai, A.; Sano, P.; Smith, E. A.; Tripoli, G.

    2008-12-01

    This paper discusses factors controlling cloud microphysics, precipitation rate and brightness temperature of tropical convective and stratiform clouds. Tropical convective and stratiform clouds are important in radiative forcing of climates and distribution of precipitation over the ocean. The possible effects of climate change on these clouds are still not well understood. Recent studies show that the higher CCN concentration in a convective cloud can lead to more vigorous updrafts and a higher evaporation/precipitation ratio. The stronger updraft often means stronger downdraft and gust fronts, which can trigger convection nearby. This implies that increases in CCN concentration can result in an increase in area coverage and persistence of tropical cirrus and stratiform clouds. The increased cloudiness would then be expected to lower sensible and latent heat flux from the ocean by lowering sea surface temperature, affecting the future development of convective clouds. The sea surface temperature may also change in a local area due to change of ocean circulation in climate change scenarios. Satellite remote sensing is a powerful tool to study tropical and global precipitation distribution. Many physically-based passive-microwave (MW) satellite precipitation algorithms make use of cloud radiation databases (CRDs), which typically consist of microphysical profiles from cloud resolving model (CRMs) and simulated MW brightness temperature (Tb). Thus, it is important to validate Tb simulated by a CRM against the observed Tb. Also, it is important to study how any changes in the tropical clouds due to aerosols and sea surface temperature translate into the precipitation and brightness temperature. The case study chosen is KWAJEX campaign that took place from 23 July to 14 September 1999. Authors have developed microphysical physical framework (Advanced Microphysics Prediction System) to predict ice particle properties explicitly in a CRM (University of Wisconsin

  16. Potential gradients in concrete caused by charge separations in a complex electrolyte

    Energy Technology Data Exchange (ETDEWEB)

    Myrdal, R. [Rescon AS, Sagstua (Norway)

    1997-12-01

    Assessments of the severity of corrosion from potentials mapping at the concrete surface are disturbed by potential gradients in the concrete. Experiments have been carried out with the purpose of determining the origin and magnitude of potential gradients associated with potential measurements at concrete surfaces. It has been found that charge separations leading to liquid junction potentials and streaming potentials contribute to a large degree. The magnitude of the measured potential gradients was sometimes more than 100 mV. Gradients up to 30 mV was observed between embedded reference electrodes as a result of water exposure at the concrete surface. A theoretical model of streamlining potentials in concrete is developed, based on the observed drift in surface potentials.

  17. Avoiding vacuum arcs in high gradient normal conducting RF structures

    CERN Document Server

    Sjøbæk, Kyrre Ness; Adli, Erik; Grudiev, Alexej; Wuensch, Walter

    In order to build the Compact LInear Collider (CLIC), accelerating structures reaching extremely high accelerating gradients are needed. Such structures have been built and tested using normal-conducting copper, powered by X-band RF power and reaching gradients of 100 MV/m and above. One phenomenon that must be avoided in order to reliably reach such gradients, is vacuum arcs or “breakdowns”. This can be accomplished by carefully designing the structure geometry such that high surface fields and large local power flows are avoided. The research presented in this thesis presents a method for optimizing the geometry of accelerating structures so that these breakdowns are made less likely, allowing the structure to operate reliably at high gradients. This was done primarily based on a phenomenological scaling model, which predicted the maximum gradient as a function of the break down rate, pulse length, and field distribution in the structure. The model is written in such a way that it allows direct comparis...

  18. Instabilities in power law gradient hardening materials

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Tvergaard, Viggo

    2005-01-01

    Tension and compression instabilities are investigated for specimens with dimensions in the micron range. A finite strain generalization of a higher order strain gradient plasticity theory is implemented in a finite element scheme capable of modeling power law hardening materials. Effects...... of gradient hardening are found to delay the onset of localization under plane strain tension, and significantly reduce strain gradients in the localized zone. For plane strain compression gradient hardening is found to increase the load-carrying capacity significantly....

  19. Organic matter geochemical signatures (TOC, TN, C/N ratio, δ13C and δ15N) of surface sediment from lakes distributed along a climatological gradient on the western side of the southern Andes.

    Science.gov (United States)

    Contreras, Sergio; Werne, Josef P; Araneda, A; Urrutia, R; Conejero, C A

    2018-07-15

    Paleolimnological studies in western South America, where meteorological stations are scarce, are critical to obtain more realistic and reliable regional reconstructions of past climate and environmental changes, including vegetation and water budget variability. However, climate and environmental geochemical indicators must be tested before they can be applied with confidence. Here we present a survey of lacustrine surface sediment (core top, 0 to ~1cm) biogeochemical proxies (total organic carbon [TOC], total nitrogen [TN], carbon/nitrogen ratio [C/N ratio] and bulk organic δ 13 C and total δ 15 N) from a suite of 72 lakes spanning the transition from a Mediterranean climate with a patchwork of cultivated vegetation, pastureland, and conifers in central Chile to a rainy temperate climate dominated by broadleaf deciduous and evergreen forest further south. Sedimentary data are compared to the latitudinal and orographic climatic trends of the region based on the climatology (precipitation and temperature) produced with Climate Forecast System Reanalysis (CFSR) data and the modern Southern Hemisphere Westerly Winds (SWW) location. The geochemical data show inflection points at ~42°S latitude and ~1500m elevation that are likely related to the northern limit of influence of the SWW and elevation of the snow line, respectively. Overall the organic proxies were able to mimic climatic trends (Mean Annual Precipitation [MAP] and temperature [MAT]), indicating that they are a useful tool to be included in paleoclimatological reconstruction of the region. Copyright © 2018 Elsevier B.V. All rights reserved.

  20. Snow specific surface area simulation using the one-layer snow model in the Canadian LAnd Surface Scheme (CLASS

    Directory of Open Access Journals (Sweden)

    A. Roy

    2013-06-01

    Full Text Available Snow grain size is a key parameter for modeling microwave snow emission properties and the surface energy balance because of its influence on the snow albedo, thermal conductivity and diffusivity. A model of the specific surface area (SSA of snow was implemented in the one-layer snow model in the Canadian LAnd Surface Scheme (CLASS version 3.4. This offline multilayer model (CLASS-SSA simulates the decrease of SSA based on snow age, snow temperature and the temperature gradient under dry snow conditions, while it considers the liquid water content of the snowpack for wet snow metamorphism. We compare the model with ground-based measurements from several sites (alpine, arctic and subarctic with different types of snow. The model provides simulated SSA in good agreement with measurements with an overall point-to-point comparison RMSE of 8.0 m2 kg–1, and a root mean square error (RMSE of 5.1 m2 kg–1 for the snowpack average SSA. The model, however, is limited under wet conditions due to the single-layer nature of the CLASS model, leading to a single liquid water content value for the whole snowpack. The SSA simulations are of great interest for satellite passive microwave brightness temperature assimilations, snow mass balance retrievals and surface energy balance calculations with associated climate feedbacks.

  1. Bright breathers in nonlinear left-handed metamaterial lattices

    Science.gov (United States)

    Koukouloyannis, V.; Kevrekidis, P. G.; Veldes, G. P.; Frantzeskakis, D. J.; DiMarzio, D.; Lan, X.; Radisic, V.

    2018-02-01

    In the present work, we examine a prototypical model for the formation of bright breathers in nonlinear left-handed metamaterial lattices. Utilizing the paradigm of nonlinear transmission lines, we build a relevant lattice and develop a quasi-continuum multiscale approximation that enables us to appreciate both the underlying linear dispersion relation and the potential for bifurcation of nonlinear states. We focus here, more specifically, on bright discrete breathers which bifurcate from the lower edge of the linear dispersion relation at wavenumber k=π . Guided by the multiscale analysis, we calculate numerically both the stable inter-site centered and the unstable site-centered members of the relevant family. We quantify the associated stability via Floquet analysis and the Peierls-Nabarro barrier of the energy difference between these branches. Finally, we explore the dynamical implications of these findings towards the potential mobility or lack thereof (pinning) of such breather solutions.

  2. Quantitative Image Restoration in Bright Field Optical Microscopy.

    Science.gov (United States)

    Gutiérrez-Medina, Braulio; Sánchez Miranda, Manuel de Jesús

    2017-11-07

    Bright field (BF) optical microscopy is regarded as a poor method to observe unstained biological samples due to intrinsic low image contrast. We introduce quantitative image restoration in bright field (QRBF), a digital image processing method that restores out-of-focus BF images of unstained cells. Our procedure is based on deconvolution, using a point spread function modeled from theory. By comparing with reference images of bacteria observed in fluorescence, we show that QRBF faithfully recovers shape and enables quantify size of individual cells, even from a single input image. We applied QRBF in a high-throughput image cytometer to assess shape changes in Escherichia coli during hyperosmotic shock, finding size heterogeneity. We demonstrate that QRBF is also applicable to eukaryotic cells (yeast). Altogether, digital restoration emerges as a straightforward alternative to methods designed to generate contrast in BF imaging for quantitative analysis. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  3. VLA observations of the Palomar bright quasar survey

    International Nuclear Information System (INIS)

    Shaffer, D.B.; Schmidt, M.

    1982-01-01

    The authors have optically surveyed some 10000 square degrees of the northern sky to search for bright quasars. Their final sample contains about 100 quasars. The B magnitudes of the sample range from 13.1 to 16.5, with most in the range 15.0-16.2. The redshifts range from 0.03 to over 2, considerably concentrated toward smaller values (median of 0.18). They observed 94 of these quasars with the partially complete VLA in November/December 1979, and detected radio emission from 27 of them, or 29%, to a limit of 1-2 mJy. It is concluded that bright quasars are definitely more likely to be detectable radio sources. (Auth.)

  4. Optical Observations of X-ray Bright, Optically Normal Galaxies

    Science.gov (United States)

    Sadun, Alberto C.; Aryan, N. S.; Ghosh, K. K.

    2007-05-01

    X-ray bright, optically normal galaxies (XBONGs) are galaxies that seem to have normal spectra and morphology, but are relatively bright x-ray sources. The large ratio of the x-ray to optical emission suggests that some activity, similar to that of active galactic nuclei (AGN), is occurring. Since the galaxies do not show any obvious sign of nuclear activity in their optical spectra, one possible explanation is that these galaxies do not have an optically thick accretion disk at small radii, as previously assumed. Previous data for NGC 7626 classifies it as an XBONG, and so we are studying optical features of this galaxy in order to determine better its features. After confirming an x-ray jet, we are now comparing this to optical features that we have found, including warped dust lanes and a possible optical jet.

  5. Improving the laser brightness of a commercial laser system

    Science.gov (United States)

    Naidoo, Darryl; Litvin, Igor; Forbes, Andrew

    2016-02-01

    We investigate the selection of a flat-top beam and a Gaussian beam inside a laser cavity on opposing mirrors. The concept is tested external to the laser cavity in a single pass and double pass regime where the latter mimics a single round trip in the laser. We implement this intra-cavity selection through the use of two 16 level diffractive optical elements. We consider a solid-state diode side-pumped laser resonator in a typical commercial laser configuration that consists of two planar mirrors where the DOEs are positioned at the mirrors. We out couple the Gaussian and flat-top distributions and we show that we improve the brightness of the laser with active mode control. We also demonstrate that the quality of the beam transformations determine the brightness improvement.

  6. Near-Real-Time DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperatures

    Data.gov (United States)

    National Aeronautics and Space Administration — The Near-Real-Time DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperature product provides near-real-time brightness temperatures for both the Northern and...

  7. Manakins can produce iridescent and bright feather colours without melanosomes.

    Science.gov (United States)

    Igic, Branislav; D'Alba, Liliana; Shawkey, Matthew D

    2016-06-15

    Males of many species often use colourful and conspicuous ornaments to attract females. Among these, male manakins (family: Pipridae) provide classic examples of sexual selection favouring the evolution of bright and colourful plumage coloration. The highly iridescent feather colours of birds are most commonly produced by the periodic arrangement of melanin-containing organelles (melanosomes) within barbules. Melanin increases the saturation of iridescent colours seen from optimal viewing angles by absorbing back-scattered light; however, this may reduce the wide-angle brightness of these signals, contributing to a dark background appearance. We examined the nanostructure of four manakin species (Lepidothrix isidorei, L. iris, L. nattereri and L. coeruleocapilla) to identify how they produce their bright plumage colours. Feather barbs of all four species were characterized by dense and fibrous internal spongy matrices that likely increase scattering of light within the barb. The iridescent, yet pale or whitish colours of L. iris and L. nattereri feathers were produced not by periodically arranged melanosomes within barbules, but by periodic matrices of air and β-keratin within barbs. Lepidothrix iris crown feathers were able to produce a dazzling display of colours with small shifts in viewing geometry, likely because of a periodic nanostructure, a flattened barb morphology and disorder at a microstructural level. We hypothesize that iridescent plumage ornaments of male L. iris and L. nattereri are under selection to increase brightness or luminance across wide viewing angles, which may potentially increase their detectability by females during dynamic and fast-paced courtship displays in dim light environments. © 2016. Published by The Company of Biologists Ltd.

  8. Thoughts About Nursing Curricula: Dark Clouds and Bright Lights.

    Science.gov (United States)

    Turkel, Marian C; Fawcett, Jacqueline; Amankwaa, Linda; Clarke, Pamela N; Dee, Vivien; Eustace, Rosemary; Hansell, Phyllis Shanley; Jones, Dorothy A; Smith, Marlaine C; Zahourek, Rothlyn

    2018-04-01

    In this essay, several nurse scholars who are particularly concerned about the contemporary state of nursing science present their concerns about the inclusion of nursing conceptual models and theories in the curricula of nursing programs (dark clouds) and ways in which the concerns have been addressed (bright lights). This essay is the second of two essays that were catalyzed by Barrett's paper, "Again, What Is Nursing Science?" The first essay was published in the previous issue of Nursing Science Quarterly.

  9. High-brightness switchable multiwavelength remote laser in air

    Energy Technology Data Exchange (ETDEWEB)

    Yao Jinping; Cheng Ya; Xu Zhizhan [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Zeng Bin; Li Guihua; Chu Wei; Ni Jielei; Zhang Haisu [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Graduate School of Chinese Academy of Sciences, Beijing 100080 (China); Xu Huailiang [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012 (China); Chin, See Leang [Center for Optics, Universite Laval, Quebec City, Quebec G1V 0A6 (Canada)

    2011-11-15

    We demonstrate a harmonic-seeded switchable multiwavelength laser in air driven by intense midinfrared femtosecond laser pulses, in which population inversion occurs at an ultrafast time scale (i.e., less than {approx}200 fs) owing to direct formation of excited molecular nitrogen ions by strong-field ionization of inner-valence electrons. The bright multiwavelength laser in air opens the perspective for remote detection of multiple pollutants based on nonlinear optical spectroscopy.

  10. Bright triplet excitons in caesium lead halide perovskites

    Science.gov (United States)

    Becker, Michael A.; Vaxenburg, Roman; Nedelcu, Georgian; Sercel, Peter C.; Shabaev, Andrew; Mehl, Michael J.; Michopoulos, John G.; Lambrakos, Samuel G.; Bernstein, Noam; Lyons, John L.; Stöferle, Thilo; Mahrt, Rainer F.; Kovalenko, Maksym V.; Norris, David J.; Rainò, Gabriele; Efros, Alexander L.

    2018-01-01

    Nanostructured semiconductors emit light from electronic states known as excitons. For organic materials, Hund’s rules state that the lowest-energy exciton is a poorly emitting triplet state. For inorganic semiconductors, similar rules predict an analogue of this triplet state known as the ‘dark exciton’. Because dark excitons release photons slowly, hindering emission from inorganic nanostructures, materials that disobey these rules have been sought. However, despite considerable experimental and theoretical efforts, no inorganic semiconductors have been identified in which the lowest exciton is bright. Here we show that the lowest exciton in caesium lead halide perovskites (CsPbX3, with X = Cl, Br or I) involves a highly emissive triplet state. We first use an effective-mass model and group theory to demonstrate the possibility of such a state existing, which can occur when the strong spin–orbit coupling in the conduction band of a perovskite is combined with the Rashba effect. We then apply our model to CsPbX3 nanocrystals, and measure size- and composition-dependent fluorescence at the single-nanocrystal level. The bright triplet character of the lowest exciton explains the anomalous photon-emission rates of these materials, which emit about 20 and 1,000 times faster than any other semiconductor nanocrystal at room and cryogenic temperatures, respectively. The existence of this bright triplet exciton is further confirmed by analysis of the fine structure in low-temperature fluorescence spectra. For semiconductor nanocrystals, which are already used in lighting, lasers and displays, these excitons could lead to materials with brighter emission. More generally, our results provide criteria for identifying other semiconductors that exhibit bright excitons, with potential implications for optoelectronic devices.

  11. Facilitating the Transition from Bright to Dim Environments

    Science.gov (United States)

    2016-03-04

    USAARL Report No. 2016-17 Facilitating the Transition from Bright to Dim Environments By David Walsh1, Morris R. Lattimore1, David L. Still1...constitute research as defined under the human subjects protection regulations , as it is not ’a systematic investigation, including research development...efficiently and rapidly transition from light to dark environments, then to function effectively. Second, to determine how best to facilitate Soldier

  12. GRB 990712 optical decay: indication of bright host galaxy.

    Science.gov (United States)

    Hjorth, J.; Courbin, F.; Cuadra, J.; Minniti, D.

    We have obtained a 5-min R-band exposure of the optical afterglow of GRB 990712 (Frontera, GCN #385; Bakos et al., GCN #387) with the ESO 3.5-m NTT on 16.403 July 1999 UT. We detect an unresolved (seeing FWHM = 1.8") object at RA (2000) = 22 31 53.03, Dec (2000) = -73 24 28.3 (with a positional uncertainty of +- 0.6" relative to the USNO-A2.0 system), consistent with the position of the bright decaying source discovered by Bakos et al. (IAUC 7225). We have tied our photometry to the PLANET photometric zeropoint (K. Sahu, personal communication) and find that the object has continued to fade to R = 21.48 +- 0.02 (systematic) +- 0.05 (random). The combined SAAO data (Bakos et al., IAUC 7225) and NTT data indicate that the light curve is leveling off relative to a power law decline. Assuming that the light curve can be modeled as the combined effects of a power law decline of the OT and a constant contribution from the host galaxy we find an OT decay slope of -0.81 (i.e. a rather slow decay) and a bright host galaxy with R = 22.0. Such a bright host galaxy would be consistent with its fairly low redshift (z = 0.43) and would possibly even account for the prominent emission lines seen in the VLT spectrum (Galama et al., GCN #388). We caution however that the hypothesis of a bright host galaxy is based on just a few data points. To test this hypothesis continued monitoring of the system is therefore urged. The NTT image and the R-band light curve are posted at http://www.astro.ku.dk/~jens/grb990712/ .

  13. Gradient remediability in linear distributed parabolic systems ...

    African Journals Online (AJOL)

    The aim of this paper is the introduction of a new concept that concerned the analysis of a large class of distributed parabolic systems. It is the general concept of gradient remediability. More precisely, we study with respect to the gradient observation, the existence of an input operator (gradient efficient actuators) ensuring ...

  14. An education gradient in health, a health gradient in education, or a confounded gradient in both?

    Science.gov (United States)

    Lynch, Jamie L; von Hippel, Paul T

    2016-04-01

    There is a positive gradient associating educational attainment with health, yet the explanation for this gradient is not clear. Does higher education improve health (causation)? Do the healthy become highly educated (selection)? Or do good health and high educational attainment both result from advantages established early in the life course (confounding)? This study evaluates these competing explanations by tracking changes in educational attainment and Self-rated Health (SRH) from age 15 to age 31 in the National Longitudinal Study of Youth, 1997 cohort. Ordinal logistic regression confirms that high-SRH adolescents are more likely to become highly educated. This is partly because adolescent SRH is associated with early advantages including adolescents' academic performance, college plans, and family background (confounding); however, net of these confounders adolescent SRH still predicts adult educational attainment (selection). Fixed-effects longitudinal regression shows that educational attainment has little causal effect on SRH at age 31. Completion of a high school diploma or associate's degree has no effect on SRH, while completion of a bachelor's or graduate degree have effects that, though significant, are quite small (less than 0.1 points on a 5-point scale). While it is possible that educational attainment would have greater effect on health at older ages, at age 31 what we see is a health gradient in education, shaped primarily by selection and confounding rather than by a causal effect of education on health. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. Factors limiting the operation of structures under high gradient

    International Nuclear Information System (INIS)

    Schriber, S.O.

    1986-01-01

    Factors limiting the operation of rf structures under high-gradient conditions are described. Included are recent rf measurements at laboratories in Europe, Asia, and North America and how these measurements relate to earlier data as exemplified by the use of the Kilpatrick criterion (Kp). Operation limitations will cover mechanical, geometry, thermal, and surface constraints and the associated impact on structure design, fabrication, and material selection. Generally, structures operating continuous wave (100% duty factor) appear to be limited to peak surface fields at about twice the Kilpatrick limit, whereas pulsed structures operating with pulse lengths less than a millisecond can attain peak surface fields five times the Kilpatrick limit

  16. SMOS brightness temperature assimilation into the Community Land Model

    Science.gov (United States)

    Rains, Dominik; Han, Xujun; Lievens, Hans; Montzka, Carsten; Verhoest, Niko E. C.

    2017-11-01

    SMOS (Soil Moisture and Ocean Salinity mission) brightness temperatures at a single incident angle are assimilated into the Community Land Model (CLM) across Australia to improve soil moisture simulations. Therefore, the data assimilation system DasPy is coupled to the local ensemble transform Kalman filter (LETKF) as well as to the Community Microwave Emission Model (CMEM). Brightness temperature climatologies are precomputed to enable the assimilation of brightness temperature anomalies, making use of 6 years of SMOS data (2010-2015). Mean correlation R with in situ measurements increases moderately from 0.61 to 0.68 (11 %) for upper soil layers if the root zone is included in the updates. A reduced improvement of 5 % is achieved if the assimilation is restricted to the upper soil layers. Root-zone simulations improve by 7 % when updating both the top layers and root zone, and by 4 % when only updating the top layers. Mean increments and increment standard deviations are compared for the experiments. The long-term assimilation impact is analysed by looking at a set of quantiles computed for soil moisture at each grid cell. Within hydrological monitoring systems, extreme dry or wet conditions are often defined via their relative occurrence, adding great importance to assimilation-induced quantile changes. Although still being limited now, longer L-band radiometer time series will become available and make model output improved by assimilating such data that are more usable for extreme event statistics.

  17. Bright Soil Churned by Spirit's Sol 1861 Drive

    Science.gov (United States)

    2009-01-01

    NASA's Mars Exploration Rover Spirit drove 22.7 meters (74 feet) toward the southwest on the 1,861st Martian day, or sol, of Spirit's mission on Mars (March 28, 2009). After the drive, the rover took this image with its front hazard-avoidance camera, looking back at the tracks from the drive. As usual since losing the use of its right-front wheel in 2006, Spirit drove backwards. The immobile right-front wheel churned up a long stripe of bright soil during this drive. Where Spirit has found such bright soil in the past, subsequent analysis of the composition found concentrations of sulfur or silica that testified to past action of water at the site. When members of the rover team saw the large quantity of bright soil exposed by the Sol 1861 drive, they quickly laid plans to investigate the composition with Spirit's alpha particle X-ray spectrometer. The Sol 1861 drive took the rover past the northwest corner of the low plateau called 'Home Plate,' making progress on a route around the western side of Home Plate. The edge of Home Plate forms the horizon on the right side of this image. Husband Hill is on the horizon on the left side. For scale, the parallel rover wheel tracks are about 1 meter (40 inches) apart. The rover's hazard-avoidance cameras take 'fisheye' wide-angle images.

  18. On correct evaluation techniques of brightness enhancement effect measurement data

    Science.gov (United States)

    Kukačka, Leoš; Dupuis, Pascal; Motomura, Hideki; Rozkovec, Jiří; Kolář, Milan; Zissis, Georges; Jinno, Masafumi

    2017-11-01

    This paper aims to establish confidence intervals of the quantification of brightness enhancement effects resulting from the use of pulsing bright light. It is found that the methods used so far may yield significant bias in the published results, overestimating or underestimating the enhancement effect. The authors propose to use a linear algebra method called the total least squares. Upon an example dataset, it is shown that this method does not yield biased results. The statistical significance of the results is also computed. It is concluded over an observation set that the currently used linear algebra methods present many patterns of noise sensitivity. Changing algorithm details leads to inconsistent results. It is thus recommended to use the method with the lowest noise sensitivity. Moreover, it is shown that this method also permits one to obtain an estimate of the confidence interval. This paper neither aims to publish results about a particular experiment nor to draw any particular conclusion about existence or nonexistence of the brightness enhancement effect.

  19. SMOS brightness temperature assimilation into the Community Land Model

    Directory of Open Access Journals (Sweden)

    D. Rains

    2017-11-01

    Full Text Available SMOS (Soil Moisture and Ocean Salinity mission brightness temperatures at a single incident angle are assimilated into the Community Land Model (CLM across Australia to improve soil moisture simulations. Therefore, the data assimilation system DasPy is coupled to the local ensemble transform Kalman filter (LETKF as well as to the Community Microwave Emission Model (CMEM. Brightness temperature climatologies are precomputed to enable the assimilation of brightness temperature anomalies, making use of 6 years of SMOS data (2010–2015. Mean correlation R with in situ measurements increases moderately from 0.61 to 0.68 (11 % for upper soil layers if the root zone is included in the updates. A reduced improvement of 5 % is achieved if the assimilation is restricted to the upper soil layers. Root-zone simulations improve by 7 % when updating both the top layers and root zone, and by 4 % when only updating the top layers. Mean increments and increment standard deviations are compared for the experiments. The long-term assimilation impact is analysed by looking at a set of quantiles computed for soil moisture at each grid cell. Within hydrological monitoring systems, extreme dry or wet conditions are often defined via their relative occurrence, adding great importance to assimilation-induced quantile changes. Although still being limited now, longer L-band radiometer time series will become available and make model output improved by assimilating such data that are more usable for extreme event statistics.

  20. An assessment of skin temperature gradients in a tropical primate using infrared thermography and subcutaneous implants.

    Science.gov (United States)

    Thompson, Cynthia L; Scheidel, Caleb; Glander, Kenneth E; Williams, Susan H; Vinyard, Christopher J

    2017-01-01

    Infrared thermography has become a useful tool to assess surface temperatures of animals for thermoregulatory research. However, surface temperatures are an endpoint along the body's core-shell temperature gradient. Skin and fur are the peripheral tissues most exposed to ambient thermal conditions and are known to serve as thermosensors that initiate thermoregulatory responses. Yet relatively little is known about how surface temperatures of wild mammals measured by infrared thermography relate to subcutaneous temperatures. Moreover, this relationship may differ with the degree that fur covers the body. To assess the relationship between temperatures and temperature gradients in peripheral tissues between furred and bare areas, we collected data from wild mantled howling monkeys (Alouatta palliata) in Costa Rica. We used infrared thermography to measure surface temperatures of the furred dorsum and bare facial areas of the body, recorded concurrent subcutaneous temperatures in the dorsum, and measured ambient thermal conditions via a weather station. Temperature gradients through cutaneous tissues (subcutaneous-surface temperature) and surface temperature gradients (surface-ambient temperature) were calculated. Our results indicate that there are differences in temperatures and temperature gradients in furred versus bare areas of mantled howlers. Under natural thermal conditions experienced by wild animals, the bare facial areas were warmer than temperatures in the furred dorsum, and cutaneous temperature gradients in the face were more variable than the dorsum, consistent with these bare areas acting as thermal windows. Cutaneous temperature gradients in the dorsum were more closely linked to subcutaneous temperatures, while facial temperature gradients were more heavily influenced by ambient conditions. These findings indicate that despite the insulative properties of fur, for mantled howling monkeys surface temperatures of furred areas still demonstrate a