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  • 2000-2004  (68)
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  • 1
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    Water chemistry and iron speciation in samples taken during SWEDARP 97/98 campaign with S.A. Agulhas to the Southern Ocean (2004)
    PANGAEA
    In:  Supplement to: Croot, Peter L; Andersson, Karen; Öztürk, Murat; Turner, David R (2004): The distribution and speciation of iron along 6°E in the Southern Ocean. Deep Sea Research Part II: Topical Studies in Oceanography, 51(22-24), 2857-2879, https://doi.org/10.1016/j.dsr2.2003.10.012
    Details
    Publication Date: 2023-10-28
    Description: The distribution and speciation of iron was determined along a transect in the eastern Atlantic sector (6°E) of the Southern Ocean during a collaborative Scandinavian/South African Antarctic cruise conducted in late austral summer (December 1997/January 1998). Elevated concentrations of dissolved iron (〉0.4 nM) were found at 60°S in the vicinity of the Spring Ice Edge (SIE) in tandem with a phytoplankton bloom, chiefly dominated by Phaeocystis sp. This bloom had developed rapidly after the loss of the seasonal sea ice cover. The iron that fuelled this bloom was mostly likely derived from sea ice melt. In the Winter Ice Edge (WIE), around 55°S, dissolved iron concentrations were low (〈0.2 nM) and corresponded to lower biological productivity, biomass. In the Antarctic Polar Front, at approximately 50°S, a vertical profile of dissolved iron showed low concentrations (〈0.2 nM); however, a surface survey showed higher concentrations (1-3 nM), and considerable patchiness in this dynamic frontal region. The chemical speciation of iron was dominated by organic complexation throughout the study region. Organic iron-complexing ligands ([L]) ranged from 0.9 to 3.0 nM Fe equivalents, with complex stability log K'(FeL) = 21.4-23.5. Estimated concentrations of inorganic iron (Fe') ranged from 0.03 to 0.79 pM, with the highest values found in the Phaeocystis bloom in the SIE. A vertical profile of iron-complexing ligands in the WIE showed a maximum consistent with a biological source for ligand production and near surface minimum possibly consistent with loss via photodecomposition. This work further confirms the role iron that has in the Southern Ocean in limiting primary productivity.
    Keywords: Priority Programme 1158 Antarctic Research with Comparable Investigations in Arctic Sea Ice Areas; SPP1158
    Type: Dataset
    Format: application/zip, 5 datasets
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  • 2
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    Surface oceanographic data during cruise DI192 (2004)
    PANGAEA
    Details
    Publication Date: 2024-02-01
    Keywords: Biogeochemical Ocean Flux Study; BOFS; Carbon dioxide, partial pressure; Carbon dioxide, total; Chlorophyll a; CT; D192; DATE/TIME; DEPTH, water; DI192-track; Discovery (1962); Fluorescence; Irradiance, heat, flux density; JGOFS; Joint Global Ocean Flux Study; LATITUDE; LONGITUDE; Nitrate and Nitrite; Nitrite; Optical beam attenuation coefficient, water+particle sum; Oxygen; PAR scalar irradiance; Phosphate; Pressure, atmospheric; Salinity; Silicate; Temperature, air, dry bulb; Temperature, water; Underway cruise track measurements; Wind direction; Wind speed
    Type: Dataset
    Format: text/tab-separated-values, 145772 data points
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  • 3
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    Surface oceanographic data during cruise DI198 (2004)
    PANGAEA
    Details
    Publication Date: 2024-02-01
    Keywords: 74DI198_1; Biogeochemical Ocean Flux Study; BOFS; Carbon dioxide, partial pressure; Carbon dioxide, total; Chlorophyll a; CT; D198; DATE/TIME; Depth, bathymetric; DEPTH, water; DI198-track; Discovery (1962); Fluorescence; Irradiance, heat, flux density; JGOFS; Joint Global Ocean Flux Study; LATITUDE; LONGITUDE; Nitrate and Nitrite; Nitrite; Optical beam attenuation coefficient, water+particle sum; Oxygen; PAR vector irradiance; pH; Phosphate; Pressure, atmospheric; Radiance, total; Salinity; Silicate; Temperature, air, dry bulb; Temperature, air, wet bulb; Temperature, water; Underway cruise track measurements; UV AquaTracka Fluorometer, Chelsea Instruments; Wind direction; Wind speed
    Type: Dataset
    Format: text/tab-separated-values, 865847 data points
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  • 4
    Electronic Resource
    Electronic Resource
    Correlation of empirical magnetic susceptibility tensors and structure in low-spin haem proteins (2000)
    Springer
    European biophysics journal 29 (2000), S. 104-112 
    Details
    ISSN: 1432-1017
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Experimental magnetic susceptibility tensors are reported for eight haems c with bis-His coordination. These data, obtained by fitting the dipolar shifts of backbone protons in the tetrahaem cytochromes c 3 from Desulfovibrio vulgaris and D. gigas, are analysed together with published values for other haem proteins. The x and y axes are found to rotate in the opposite sense to the axial ligands and are also counter-rotated with respect to the frontier molecular orbitals of the haem. The magnetic z-axis is close to the normal to the haem plane in each case. The magnitudes of the magnetic anisotropies are used to derive crystal field parameters and the rhombic splitting, V, is correlated with the dihedral angle between the axial ligands. Hence, it is apparent that the axial ligands are the dominant factor in determining the variation in magnetic properties between haems, and it is confirmed that “high g max” EPR signals are a reliable indicator of near-perpendicular ligands. These results are in full agreement with the analysis of non-Curie effects and electronic structure in the His-Met coordinated cytochromes c and c 551. Collectively, they show that the orientations of axial ligands to the haem may be estimated from single-crystal EPR data, from 13C NMR shifts of the haem substituents, or from NMR dipolar shifts of the polypeptide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002490050255
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  • 5
    Electronic Resource
    Electronic Resource
    Customer-to-customer developments in (r)etailing: A case study of betting exchanges in the UK (2004)
    Bingley : Emerald
    Marketing intelligence & planning 22 (2004), S. 742-750 
    Details
    ISSN: 0263-4503
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Economics
    Notes: This article provides market intelligence, by way of a narrative case study, relating to online retailing in an unusual setting. While the transaction between business and customers is generally seen as very much the dominant element in such retailing, customer-to-customer interactions are generating important e-commerce niches. The case study presents an example, in the shape of "betting exchanges" in the UK, which allow customers to bet against each other rather than against the traditional betting shop. It briefly discusses some of the special challenges facing online retailers in general, outlines the size, structure and characteristics of the betting market, describes the emergence and operation of the betting exchanges, assesses their possible impacts on betting shops, and speculates about future developments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/02634500410568574
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  • 6
    Electronic Resource
    Electronic Resource
    An audio stream redirector for the Ethernet Speaker (2004)
    Bradford : Emerald
    Campus-wide information systems 21 (2004), S. 211-216 
    Details
    ISSN: 1065-0741
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Computer Science
    Notes: The authors have developed the "Ethernet Speaker" (ES), a network-enabled single board computer embedded into a conventional audio speaker. Audio streams are transmitted in the local area network using multicast packets, and the ES can select any one of them and play it back. A key requirement for the ES is that it must be capable of playing any type of audio stream, independent of the streaming protocol, or the encoding used. The authors achieved this by providing a streaming audio server built using the kernel-based audio stream redirector (ASR) in the OpenBSD kernel. The ASR accepts input from any of the existing audio file players, or streaming audio clients. Since all audio applications have to be able to use the system audio driver, this system can accommodate any protocol or file format, provided that there exists some compatible player running under OpenBSD. This paper discusses the design and implementation of the server as an ASR, the streaming protocol developed for this application, and the implementation of the client.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/10650740410567572
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  • 7
    Electronic Resource
    Electronic Resource
    Auto-transporter A protein of Neisseria meningitidis: a potent CD4+ T-cell and B-cell stimulating antigen detected by expression cloning (2000)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 37 (2000), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A meningococcal genomic expression library was screened for potent CD4+ T-cell antigens, using patients' peripheral blood lymphocytes (PBLs). One of the most promising positive clones was fully characterized. The recombinant meningococcal DNA contained a single, incomplete, open reading frame (ORF), which was fully reconstructed with reference to available genomic sequence data. The gene was designated autA (auto-transporter A) as its peptide sequence shares molecular characteristics of the auto-transporter family of proteins. Only a single copy of this gene was detected in the meningococcal, and none in the gonococcal, genomic sequence databases. The complete autA gene, when cloned into an expression vector, expressed a protein of approximately 68 kDa. Purified rAutA recalled strong secondary T-cell responses in PBLs of patients and some healthy donors, and induced strong primary T-cell responses in healthy donors. The human B-cell immunogenicity and cross-reactivity of AutA, purified under native conditions, was confirmed in dot immunoblot experiments. Immunoblots with rabbit polyclonal antibodies to rAutA demonstrated the conserved nature, antigenicity and cross-reactivity of AutA amongst meningococci of different serogroups and strains representing different hypervirulent lineages. AutA showed homology with another meningococcal and gonococcal ORF (designated AutB). AutB was cloned and expressed and used to raise an autB-specific antiserum. Immunoblot experiments indicated that AutB is not expressed in meningococci and does not cross-react with AutA. Thus, AutA, being a potent CD4+ T-cell and B-cell-stimulating antigen, which is highly conserved, deserves further investigation as a potential vaccine candidate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2000.02061.x
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  • 8
    Electronic Resource
    Electronic Resource
    A cross-biome comparison of daily light use efficiency for gross primary production (2003)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 9 (2003), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: Vegetation light use efficiency is a key physiological parameter at the canopy scale, and at the daily time step is a component of remote sensing algorithms for scaling gross primary production (GPP) and net primary production (NPP) over regional to global domains. For the purposes of calibrating and validating the light use efficiency (εg) algorithms, the components of εg– absorbed photosynthetically active radiation (APAR) and ecosystem GPP – must be measured in a variety of environments. Micrometeorological and mass flux measurements at eddy covariance flux towers can be used to estimate APAR and GPP, and the emerging network of flux tower sites offers the opportunity to investigate spatial and temporal patterns in εg at the daily time step. In this study, we examined the relationship of daily GPP to APAR, and relationships of εg to climatic variables, at four micrometeorological flux tower sites – an agricultural field, a tallgrass prairie, a deciduous forest, and a boreal forest. The relationship of GPP to APAR was close to linear at the tallgrass prairie site but more nearly hyperbolic at the other sites. The sites differed in the mean and range of daily εg, with higher values associated with the agricultural field than the boreal forest. εg decreased with increasing APAR at all sites, a function of mid-day saturation of GPP and higher εg under overcast conditions. εg was generally not well correlated with vapor pressure deficit or maximum daily temperature. At the agricultural site, a εg decline towards the end of the growing season was associated with a decrease in foliar nitrogen concentration. At the tallgrass prairie site, a decline in εg in August was associated with soil drought. These results support inclusion of parameters for cloudiness and the phenological status of the vegetation, as well as use of biome-specific parameterization, in operational εg algorithms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2486.2003.00573.x
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  • 9
    Electronic Resource
    Electronic Resource
    Alternative spatial resolutions and estimation of carbon flux over a managed forest landscape in Western Oregon (2000)
    Springer
    Landscape ecology 15 (2000), S. 441-452 
    Details
    ISSN: 1572-9761
    Keywords: carbon ; forest ; landscape scale ; net ecosystem production ; net primary production ; Oregon ; spatial resolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Spatially-distributed estimates of biologically-driven CO2 flux are of interest in relation to understanding the global carbon cycle. Global coverage by satellite sensors offers an opportunity to assess terrestrial carbon (C) flux using a variety of approaches and corresponding spatial resolutions. An important consideration in evaluating the approaches concerns the scale of the spatial heterogeneity in land cover over the domain being studied. In the Pacific Northwest region of the United States, forests are highly fragmented with respect to stand age class and hence C flux. In this study, the effects of spatial resolution on estimates of total annual net primary production (NPP) and net ecosystem production (NEP) for a 96 km2 area in the central Cascades Mountains of western Oregon were examined. The scaling approach was a simple `measure and multiply' algorithm. At the highest spatial resolution (25 m), a stand age map derived from Landsat Thematic Mapper imagery provided the area for each of six forest age classes. The products of area for each age class and its respective NPP or NEP were summed for the area wide estimates. In order to evaluate potential errors at coarser resolutions, the stand age map was resampled to grain sizes of 100, 250, 500 and 1000 m using a majority filter reclassification. Local variance in near-infrared (NIR) band digital number at successively coarser grain sizes was also examined to characterize the scale of the heterogeneity in the scene. For this managed forest landscape, proportional estimation error in land cover classification at the coarsest resolution varied from −1.0 to +0.6 depending on the initial representation and the spatial distribution of the age class. The overall accuracy of the 1000 m resolution map was 42% with respect to the 25 m map. Analysis of local variance in NIR digital number suggested a patch size on the order of 100–500 m on a side. Total estimated NPP was 12% lower and total estimated NEP was 4% lower at 1000 m compared to 25 m. Carbon flux estimates based on quantifying differences in total biomass stored on the landscape at two points in time might be affected more strongly by a coarse resolution analysis because the differences among classes in biomass are more extreme than the differences in C flux and because the additional steps in the flux algorithm would contribute to error propagation. Scaling exercises involving reclassification of fine scale imagery over a range of grain sizes may be a useful screening tool for stratifying regions of the terrestrial surface relative to optimizing the spatial resolution for C flux estimation purposes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008116300063
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  • 10
    Electronic Resource
    Electronic Resource
    Evaluation of the EVA descriptor for QSAR studies: 3. The use of a genetic algorithm to search for models with enhanced predictive properties (EVA_GA) (2000)
    Springer
    Journal of computer aided molecular design 14 (2000), S. 1-21 
    Details
    ISSN: 1573-4951
    Keywords: AM1 ; CoMFA ; GA ; MM3 ; molecular vibration ; variable modification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The EVA structural descriptor, based upon calculated fundamental molecular vibrational frequencies, has proved to be an effective descriptor for both QSAR and database similarity calculations. The descriptor is sensitive to 3D structure but has an advantage over field-based 3D-QSAR methods inasmuch as structural superposition is not required. The original technique involves a standardisation method wherein uniform Gaussians of fixed standard deviation (σ) are used to smear out frequencies projected onto a linear scale. The smearing function permits the overlap of proximal frequencies and thence the extraction of a fixed dimensional descriptor regardless of the number and precise values of the frequencies. It is proposed here that there exist optimal localised values of σ in different spectral regions; that is, the overlap of frequencies using uniform Gaussians may, at certain points in the spectrum, either be insufficient to pick up relationships where they exist or mix up information to such an extent that significant correlations are obscured by noise. A genetic algorithm is used to search for optimal localised σ values using crossvalidated PLS regression scores as the fitness score to be optimised. The resultant models were then validated against a previously unseen test set of compounds and through data scrambling. The performance of EVA_GA is compared to that of EVA and analogous CoMFA studies; in the latter case a brief evaluation is made of the effect of grid resolution upon the stability of CoMFA PLS scores particularly in relation to test set predictions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008180020974
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