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  • 1
    ISSN: 1573-5079
    Keywords: large subunit gene ; small subunit gene ; ribulose bisphosphate carboxylase/oxygenase ; cloning ; expression ; in vitro directed mutagenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The dominant natural form of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) is composed of large (L) 55-kDa and small (S) 15-kDa subunits. This enzyme (as the L8S8 form) is widely distributed among oxygenic photosynthetic species and among chemosynthetic bacteria. Another form lacking small subunits is found as an L2 dimer in Rhodospirillum rubrum or an L oligomer of uncertain aggregation state from Rhodopseudomonas spharoides. The present article reviews two basically different approaches in cloning the R. rubrum gene for RuBisCO. One results in high level expression of this gene product fused with a limited aminoterminal stretch of β-galactosidase and the other results in expression of wild-type enzyme in Escherichia coli. Also reviewed are a number of reports of cloning and assembly of the L8S8 enzyme in using E. coli L and S subunit genes from Anacystis nidulans, Anabaena 7120, Chromatium vinosum and Rps. sphaeroides. In vitro oligonucleotide-directed mutagenesis has been applied to the gene for RuBisCO from R. rubrum. In terms of contributing new information to our understanding of the catalytic mechanism for RuBisCO, the most significant replacement has been of lys 166 by a number of neutral amino acids or by arg or his. Results establish that lys 166 is a catalytically essential residue and illustrate the power of directed mutagenesis in understanding structure-function correlates for RuBisCO. Oligonucleotide-directed mutagenesis has also been applied to the first and second conserved regions of the S subunit gene for RuBisCO from A. nidulans. In the latter region, corresponding amino acid changes of trp 55 and trp 58 to phe, singly or together, had little or no effect upon enzyme activity. In contrast, mutagenesis in the first conserved region leading to the following pairs of substitutions: arg10 arg 11 to gly 10 gly11; thr14 phe 15 ser 16 to ala 14 phe 15 ala 16; ser 16 tyr 17 to ala 16 asp 17; or pro 19 pro 20 to ala 19 ala 20, are all deleterious. Advances are anticpated in the introduction and expression of interesting modifications of S (and L) subunit genes in plants. A new method of introducing and expressing foreign genes in isolated etiochloroplasts is identified.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5079
    Keywords: CO2/O2specificity factor ; mutagenesis ; rubisco small subunit ; tau
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Seven unique substitutions have been introduced by site-directed mutagenesis into the first conserved region of the small subunit of ribulose bisphosphate carboxylase/oxygenase from Anacystis nidulans 6301. After expression of each large, altered-small subunit gene tandem in Escherichia coli, two substitutions in the small subunit tyr17→asp17 (Y17D) and arg10→gly10 (R10G) result in little or no carboxylase activity. For the latter substitution, no L8S8enzyme complex could be detected suggesting that this mutation prevents assembly. Mutant enzymes containing the following substitutions R11G, T14A, S16A, Y17D and P19A have CO2/O2specificity factors (τ values) of 40, 35, 18, 39 and 44, respectively, compared with that of 44 for wild-type recombinant enzyme whereas P20A has full carboxylase activity and a τ value of 55.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2064
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary G.W. Brown, Yu.V. Prokhorov, L. Bondesson and others have developed characterization results for maximal invariant statistics. Such results show that it is possible to construct tests to distinguish between types of distributions. In this paper, these results are proved for a large number of cases that arise in particular in spatial statistics and directional statistics. The class of n-collected distributions, n≧3, is introduced. It is proved that if a distribution is n-collected then a sample of size n has sufficient information to distinguish the type of the distribution. In other words, the distribution of the maximal invariant characterizes type.
    Type of Medium: Electronic Resource
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  • 4
    Publication Date: 2017-01-04
    Description: Author Posting. © The Author(s), 2014. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Remote Sensing of Environment 159 (2015): 80-85, doi:10.1016/j.rse.2014.11.031.
    Description: Accuracy of digital elevation models (DEMs) often depends on how features of different spatial scales are represented. Scale dependence is particularly important in low gradient coastal environments where small vertical errors can affect large areas and where representation of fine scale topographic features can influence how DEMs are used for modeling inundation. It is commonly observed that different types of DEMs represent larger, coarse-scale topographic features similarly, but differ in how they represent smaller, finer-scale features. Spatial scale dependence of DEM accuracy can be quantified in terms of the correlation scale (λc); the spatial wavelength above which models agree with spectral coherency 〉 0.5 and below which they differ. We compare cross spectral analyses of the GDEM2 and SRTM global DEMs with 14,572 LiDAR derived elevations along transects in diverse coastal environments of New York City. Both global DEMs have positive bias relative to LiDAR ground elevations, but bias (μ) and uncertainty (σ) of GDEM2 (μ: 8.1 m; σ: 7.6 m) are significantly greater than those of SRTM (μ: 1.9 m; σ: 3.6 m). Cross-spectral coherency between GDEM2 and the LiDAR DEM begins to roll-off at scales of λ 〈 ~3 km, while coherency between SRTM and the LiDAR DEM begins to roll-off at scales of λ 〈 ~1 km. The correlation scale below which coherency with LiDAR attains a signal to noise ratio of 1 is ~1 km for GDEM2 and ~ 0.5 km for SRTM; closely matching the divergence scales where the surface roughness of the land cover exceeds the roughness of the underlying terrain.
    Description: This research was supported by the Office of Naval Research (grant N000-14-11-1-0653 to C.S.).
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: application/pdf
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Current views of mid-ocean ridges are strongly influenced by extensive mapping of the Mid-Atlantic Ridge and East Pacific Rise. The global picture of the mid-ocean ridge system, particularly in the sparsely surveyed Southern Oceans, is still based primarily on underway bathymetry profiles collected over the past 40 years. This study presents a quantitative analysis of global mid-ocean ridge morphology based on 156 of these underway bathymetric profiles, thereby allowing commonly recognized features such as axial valleys and axial ridges to be compared on a global basis. An Empirical Orthogonal Function (EOF) analysis is used to separate deterministic and stochastic components of axial morphology and to quantify the dependence of each on parameters such as spreading rate and axial depth. It is found that approximately 50 per cent of the variance in axial morphology may be described as a linear combination of five independent symmetric and anti-symmetric modes; the remainder is considered stochastic. Maximum axial valley relief decreases with spreading rate for rates less than 80 mm yr-1 while axial ridge relief remains relatively constant for all rates greater than 50 mm yr-1. The stochastic component of the axial morphology, referred to as bathymetric roughness, also decreases with spreading rate for rates less than 80 mm yr-1 and remains relatively constant at higher rates. Although both axial valley relief and bathymetric roughness near the ridge axis show a similar spreading rate dependence, they are weakly correlated at slow spreading centres. The distinct differences in morphologic variability of fast and slow spreading ridges may result from the episodicity of magmatic heat input which controls the lithospheric rheology at slow spreading ridges. These observations support the notion of a critical threshold separating two dynamically distinct modes of lithospheric accretion on mid-ocean ridges.
    Type of Medium: Electronic Resource
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  • 6
    Publication Date: 2017-03-07
    Description: Animals can be important in modulating ecosystem-level nutrient cycling, although their importance varies greatly among species and ecosystems. Nutrient cycling rates of individual animals represent valuable data for testing the predictions of important frameworks such as the Metabolic Theory of Ecology (MTE) and ecological stoichiometry (ES). They also represent an important set of functional traits that may reflect both environmental and phylogenetic influences. Over the past two decades, studies of animal-mediated nutrient cycling have increased dramatically, especially in aquatic ecosystems. Here we present a global compilation of aquatic animal nutrient excretion rates. The dataset includes 10,534 observations from freshwater and marine animals of N and/or P excretion rates. These observations represent 491 species, including most aquatic phyla. Coverage varies greatly among phyla and other taxonomic levels. The dataset includes information on animal body size, ambient temperature, taxonomic affiliations, and animal body N:P. This data set was used to test predictions of MTE and ES, as described in Vanni and McIntyre (2016; Ecology DOI: 10.1002/ecy.1582). This article is protected by copyright. All rights reserved.
    Print ISSN: 0012-9658
    Electronic ISSN: 1939-9170
    Topics: Biology
    Published by Wiley on behalf of The Ecological Society of America (ESA).
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  • 7
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    AGU (American Geological Union)
    In:  Journal of Geophysical Research - Solid Earth, 100 (B9). pp. 17931-17946.
    Publication Date: 2016-05-10
    Description: The evolution of ridge-hotspot systems is not well understood. In this investigation, satellite-derived marine gravity data are used in conjunction with underway bathymetric and magnetic anomaly profiles to investigate the nature of ridge-hotspot interaction at four sparsely explored systems in the Southern Ocean. These systems illustrate three different stages of ridge-hotspot interaction in which a migrating spreading center approaches a hotspot (Pacific-Antarctic/Louisville), passes over or is captured by the hotspot (Mid-Atlantic/Shona-Discovery), and ultimately migrates away from the hotspot (Southeast Indian/Kerguelen). All of these systems show some evidence of discrete ridge jumps in the direction of the hotspot as the spreading center attempts to relocate toward the hotspot by asymmetric spreading. Interestingly, these ridge jumps show no evidence of propagating offsets as have been seen on many other ridge-hotspot systems. A simple model predicts that typical plume excess temperatures can weaken the lithosphere sufficiently to promote asymmetric spreading and possibly allow a discrete ridge jump. The presence of previously uncharted, obliquely oriented aseismic ridges and gravity lineations between the ridge and the hotspot supports the notion of asthenospheric flux from the plume to the spreading center both before and after the time when the hotspot is ridge centered. The azimuths of the aseismic ridges cannot be explained by plate kinematics alone; they consistently extend from the ends toward the centers of the adjacent spreading segments suggesting some interaction between plume derived asthenospheric flux and local lithospheric structure. The features discussed here also indicate that the transfer of asthenospheric material from the plume to the spreading center is influenced by the local plate boundary configuration and interaction with transform offsets.
    Type: Article , PeerReviewed
    Format: text
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  • 8
    Publication Date: 2019-08-15
    Description: Characterization of urban radiance and reflectance is important for understanding the effects of solar energy flux on the urban environment as well as for satellite mapping of urban settlement patterns. Spectral mixture analyses of Landsat and Ikonos imagery suggest that the urban radiance field can very often be described with combinations of three or four spectral endmembers. Dimensionality estimates of Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) radiance measurements of urban areas reveal the existence of 30 to 60 spectral dimensions. The extent to which broadband imagery collected by operational satellites can represent the higher dimensional mixing space is a function of both the spatial and spectral resolution of the sensor. AVIRIS imagery offers the spatial and spectral resolution necessary to investigate the scale dependence of the spectral dimensionality. Dimensionality estimates derived from Minimum Noise Fraction (MNF) eigenvalue distributions show a distinct scale dependence for AVIRIS radiance measurements of Milpitas, California. Apparent dimensionality diminishes from almost 40 to less than 10 spectral dimensions between scales of 8000 m and 300 m. The 10 to 30 m scale of most features in urban mosaics results in substantial spectral mixing at the 20 m scale of high altitude AVIRIS pixels. Much of the variance at pixel scales is therefore likely to result from actual differences in surface reflectance at pixel scales. Spatial smoothing and spectral subsampling of AVIRIS spectra both result in substantial loss of information and reduction of apparent dimensionality, but the primary spectral endmembers in all cases are analogous to those found in global analyses of Landsat and Ikonos imagery of other urban areas.
    Keywords: Earth Resources and Remote Sensing
    Type: Proceedings of the Tenth JPL Airborne Earth Science Workshop; 375-385
    Format: text
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  • 9
    Publication Date: 2019-07-10
    Description: This paper presents a final technical report on a dedicated environmental remote sensing facility for the Columbia Earth Institute. The above-referenced award enabled the Lamont-Doherty Earth Observatory to establish a state-of-the-art remote sensing image analysis and data visualization facility to serve the research and educational needs of students and staff at Lamont and the Columbia Earth Institute.
    Keywords: Earth Resources and Remote Sensing
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  • 10
    Publication Date: 2019-07-12
    Description: Fast and slow spreading ridges have radically different morphologic and gravimetric characteristics. In this study, altimeter measurements from the Geosat Exact Repeat Mission are used to investigate spreading rate dependence of the ridge axis gravity field. Gravity roughness provides an estimate of the amplitude of the gravity anomaly and is robust to small errors in the location of the ridge axis. Gravity roughness as a weighted root mean square of the vertical deflection at 438 ridge crossings on the mid-ocean ridge system is computed. Ridge axis gravity anomalies show a decrease in amplitude with increasing spreading rate up to an intermediate rate of about 60-80 mm/yr and almost no change at higher rates; overall the roughness decreases by a factor of 10 between the lowest and highest rates. In addition to the amplitude decrease, the range of roughness values observed at a given spreading rate shows a similar order of magnitude decrease with transition between 60 and 80 mm/yr. The transition of ridge axis gravity is most apparent at three relatively unexplored locations on the Southeast Indian Ridge and the Pacific-Antarctic Rise; on these intermediate rate ridges the transition occurs abruptly across transform faults.
    Keywords: OCEANOGRAPHY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 97; B3 M; 3235-324
    Format: text
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