Tiltrotor research aircraft composite blade repairs: Lessons learned

The XV-15, N703NA Tiltrotor Research Aircraft located at the NASA Ames Research Center, Moffett Field, California, currently uses a set of composite rotor blades of complex shape known as the advanced technology blades (ATBs). The main structural element of the blades is a D-spar constructed of unidirectional, angled fiberglass/graphite, with the aft fairing portion of the blades constructed of a fiberglass cross-ply skin bonded to a Nomex honeycomb core. The blade tip is a removable laminate shell that fits over the outboard section of the spar structure, which contains a cavity to retain balance weights. Two types of tip shells are used for research. One is highly twisted (more than a conventional helicopter blade) and has a hollow core constructed of a thin Nomex-honeycomb-and-fiberglass-skin sandwich; the other is untwisted with a solid Nomex honeycomb core and a fiberglass cross-ply skin. During initial flight testing of the blades, a number of problems in the composite structure were encountered. These problems included debonding between the fiberglass skin and the honeycomb core, failure of the honeycomb core, failures in fiberglass splices, cracks in fiberglass blocks, misalignment of mated composite parts, and failures of retention of metal fasteners. Substantial time was spent in identifying and repairing these problems. Discussed here are the types of problems encountered, the inspection procedures used to identify each problem, the repairs performed on the damaged or flawed areas, the level of criticality of the problems, and the monitoring of repaired areas. It is hoped that this discussion will help designers, analysts, and experimenters in the future as the use of composites becomes more prevalent

The Structure of IR Luminous Galaxies at 100 Microns

We have observed twenty two galaxies at 100 microns with the Kuiper Airborne Observatory in order to determine the size of their FIR emitting regions. Most of these galaxies are luminous far-infrared sources, with L_FIR > 10^11 L_sun. This data constitutes the highest spatial resolution ever achieved on luminous galaxies in the far infrared. Our data includes direct measurements of the spatial structure of the sources, in which we look for departures from point source profiles. Additionally, comparison of our small beam 100 micron fluxes with the large beam IRAS fluxes shows how much flux falls beyond our detectors but within the IRAS beam. Several sources with point- like cores show evidence for such a net flux deficit. We clearly resolved six of these galaxies at 100 microns and have some evidence for extension in seven others. Those galaxies which we have resolved can have little of their 100 micron flux directly emitted by a point-like active galactic nucleus (AGN). Dust heated to ~40 K by recent bursts of non-nuclear star formation provides the best explanation for their extreme FIR luminosity. In a few cases, heating of an extended region by a compact central source is also a plausible option. Assuming the FIR emission we see is from dust, we also use the sizes we derive to find the dust temperatures and optical depths at 100 microns which we translate into an effective visual extinction through the galaxy. Our work shows that studies of the far infrared structure of luminous infrared galaxies is clearly within the capabilities of new generation far infrared instrumentation, such as SOFIA and SIRTF.Comment: 8 tables, 23 figure

Mutational Analysis of the Cyanobacterial Nitrogen Regulator PipX

PipX provides a functional link between the cyanobacterial global transcriptional regulator NtcA and the signal transduction protein PII, a protein found in all three domains of life as integrators of signals of the nitrogen and carbon balance. PipX, which is toxic in the absence of PII, can form alternative complexes with NtcA and PII and these interactions are respectively stimulated and inhibited by 2-oxoglutarate, providing a mechanism by which PII can modulate expression at the NtcA regulon. Structural information on PipX-NtcA complexes suggests that PipX coactivates NtcA controlled genes by stabilizing the active conformation of NtcA bound to 2-oxoglutarate and by possibly helping recruit RNA polymerase. To get insights into PipX functions, we perform here a mutational analysis of pipX informed by the structures of PipX-PII and PipX-NtcA complexes and evaluate the impact of point mutations on toxicity and gene expression. Two amino acid substitutions (Y32A and E4A) were of particular interest, since they increased PipX toxicity and activated NtcA dependent genes in vivo at lower 2-oxoglutarate levels than wild type PipX. While both mutations impaired complex formation with PII, only Y32A had a negative impact on PipX-NtcA interactions

Stroke related mortality at different altitudes: A 17-year nationwide population-based analysis from Ecuador

Worldwide, more than 5.7% of the population reside above 1,500m of elevation. It has been hypothesized that acute short-term hypoxia exposure could increase the risk of developing a stroke. Studies assessing the effect of altitude on stroke have provided conflicting results, some analyses suggest that long-term chronic exposure could be associated with reduced mortality and lower stroke incidence rates. An ecological analysis of all stroke hospital admissions, mortality rates and disability-adjusted life years in Ecuador was performed from 2001-2017. The cases and population at risk were categorized in low (<1,500m), moderate (1,500m -2,500m), high (2,500m -3,500m) and very high altitude (3,500-5,500m) according to the place of residence. The derived crude and direct standardized age-sex adjusted mortality and hospital admission rates were calculated. A total of 38,201 deaths and 75,893 stroke-related hospital admissions were reported. High altitude populations (HAP) had lower stroke mortality in men (OR: 0.91 [0.88 - 0.95]) and women (OR: 0.83 [0.79 - 0.86]). In addition, HAP had a significant lower risk of getting admitted to the hospital when compared with the low altitude group in men (OR: 0.55 [CI95% 0.54 - 0.56]) and women (OR: 0.65 [CI95% [0.64 - 0.66]). This is the first epidemiological study that aims to elucidate the association between stroke and altitude using four different elevation ranges. Our findings suggest that living at higher elevations offers a reduction or the risk of dying due to stroke as well as a reduction in the probability of being admitted to the hospital. Nevertheless, this protective factor has a stronger effect between 2,000m to 3,500 m

Most Networks in Wagner's Model Are Cycling

In this paper we study a model of gene networks introduced by Andreas Wagner in the 1990s that has been used extensively to study the evolution of mutational robustness. We investigate a range of model features and parameters and evaluate the extent to which they influence the probability that a random gene network will produce a fixed point steady state expression pattern. There are many different types of models used in the literature, (discrete/continuous, sparse/dense, small/large network) and we attempt to put some order into this diversity, motivated by the fact that many properties are qualitatively the same in all the models. Our main result is that random networks in all models give rise to cyclic behavior more often than fixed points. And although periodic orbits seem to dominate network dynamics, they are usually considered unstable and not allowed to survive in previous evolutionary studies. Defining stability as the probability of fixed points, we show that the stability distribution of these networks is highly robust to changes in its parameters. We also find sparser networks to be more stable, which may help to explain why they seem to be favored by evolution. We have unified several disconnected previous studies of this class of models under the framework of stability, in a way that had not been systematically explored before

Proteomic Comparison of Entamoeba histolytica and Entamoeba dispar and the Role of E. histolytica Alcohol Dehydrogenase 3 in Virulence

The protozoan intestinal parasite Entamoeba histolytica infects millions of people worldwide and is capable of causing amebic dysentery and amebic liver abscess. The closely related species Entamoeba dispar colonizes many more individuals, but this organism does not induce disease. To identify molecular differences between these two organisms that may account for their differential ability to cause disease in humans, we used two-dimensional gel-based (DIGE) proteomic analysis to compare whole cell lysates of E. histolytica and E. dispar. We observed 141 spots expressed at a substantially (>5-fold) higher level in E. histolytica HM-1∶IMSS than E. dispar and 189 spots showing the opposite pattern. Strikingly, 3 of 4 proteins consistently identified as different at a greater than 5-fold level between E. histolytica HM-1∶IMSS and E. dispar were identical to proteins recently identified as differentially expressed between E. histolytica HM-1∶IMSS and the reduced virulence strain E. histolytica Rahman. One of these was E. histolytica alcohol dehydrogenase 3 (EhADH3). We found that E. histolytica possesses a higher level of NADP-dependent alcohol dehydrogenase activity than E. dispar and that some EhADH3 can be localized to the surface of E. histolytica. Episomal overexpression of EhADH3 in E. histolytica trophozoites resulted in only subtle phenotypic differences in E. histolytica virulence in animal models of amebic colitis and amebic liver abscess, making it difficult to directly link EhADH3 levels to virulence differences between E. histolytica and less-pathogenic Entamoeba

Cytomegaloviral determinants of CD8+ T cell programming and RhCMV/SIV vaccine efficacy

Simian immunodeficiency virus (SIV) insert-expressing, 68–1 Rhesus Cytomegalovirus (RhCMV/SIV) vectors elicit major histocompatibility complex (MHC)-E- and -II-restricted, SIV-specific CD8(+) T cell responses, but the basis of these unconventional responses and their contribution to demonstrated vaccine efficacy against SIV challenge in the rhesus monkeys (RMs) has not been characterized. We show that these unconventional responses resulted from a chance genetic rearrangement in 68–1 RhCMV that abrogated the function of eight distinct immunomodulatory gene products encoded in two RhCMV genomic regions (Rh157.5/Rh157.4 and Rh158–161), revealing three patterns of unconventional response inhibition. Differential repair of these genes with either RhCMV-derived or orthologous human CMV (HCMV)-derived sequences (UL128/UL130; UL146/UL147) leads to either of two distinct CD8(+) T cell response types – MHC-Ia-restricted-only, or a mix of MHC-II- and MHC-Ia-restricted CD8(+) T cells. Response magnitude and functional differentiation are similar to RhCMV 68–1, but neither alternative response type mediated protection against SIV challenge. These findings implicate MHC-E-restricted CD8(+) T cell responses as mediators of anti-SIV efficacy and indicate that translation of RhCMV/SIV vector efficacy to humans will likely require deletion of all genes that inhibit these responses from the HCMV/HIV vector

Suppression and Regression of Choroidal Neovascularization in Mice by a Novel CCR2 Antagonist, INCB3344

PURPOSE: To investigate the effect of an intravitreally administered CCR2 antagonist, INCB3344, on a mouse model of choroidal neovascularization (CNV). METHODS: CNV was induced by laser photocoagulation on Day 0 in wild type mice. INCB3344 or vehicle was administered intravitreally immediately after laser application. On Day 14, CNV areas were measured on retinal pigment epithelium (RPE)-choroid flat mounts and histopathologic examination was performed on 7 µm-thick sections. Macrophage infiltration was evaluated by immunohistochemistry on RPE-choroid flat mounts and quantified by flow cytometry on Day 3. Expression of vascular endothelial growth factor (VEGF) protein in RPE-choroid tissue was examined by immunohistochemistry and ELISA, VEGF mRNA in sorted macrophages in RPE-choroid tissue was examine by real-time PCR and expression of phosphorylated extracellular signal-regulated kinase (p-ERK 1/2) in RPE-choroid tissue was measured by Western blot analysis on Day 3. We also evaluated the efficacy of intravitreal INCB3344 to spontaneous CNV detected in Cu, Zn-superoxide dismutase (SOD1) deficient mice. Changes in CNV size were assessed between pre- and 1week post-INCB3344 or vehicle administration in fundus photography and fluorescence angiography (FA). RESULTS: The mean CNV area in INCB3344-treated mice decreased by 42.4% compared with the vehicle-treated control mice (p<0.001). INCB3344 treatment significantly inhibited macrophage infiltration into the laser-irradiated area (p<0.001), and suppressed the expression of VEGF protein (p = 0.012), VEGF mRNA in infiltrating macrophages (p<0.001) and the phosphorylation of ERK1/2 (p<0.001). The area of spontaneous CNV in Sod1⁻/⁻ mice regressed by 70.35% in INCB3344-treated animals while no change was detected in vehicle-treated control mice (p<0.001). CONCLUSIONS: INCB3344 both inhibits newly forming CNV and regresses established CNV. Controlling inflammation by suppressing macrophage infiltration and angiogenic ability via the CCR-2/MCP-1 signal may be a useful therapeutic strategy for treating CNV associated with age-related macular degeneration

A 32-society investigation of the influence of perceived economic inequality on social class stereotyping

International audienceThere is a growing body of work suggesting that social class stereotypes are amplified when people perceive higher levels of economic inequality-that is, the wealthy are perceived as more competent and assertive and the poor as more incompetent and unassertive. The present study tested this prediction in 32 societies and also examines the role of wealth-based categorization in explaining this relationship. We found that people who perceived higher economic inequality were indeed more likely to consider wealth as a meaningful basis for categorization. Unexpectedly, however, higher levels of perceived inequality were associated with perceiving the wealthy as less competent and assertive and the poor as more competent and assertive. Unpacking this further, exploratory analyses showed that the observed tendency to stereotype the wealthy negatively only emerged in societies with lower social mobility and democracy and higher corruption. This points to the importance of understanding how socio-structural features that co-occur with economic inequality may shape perceptions of the wealthy and the poor

Elemental Composition of Natural Nanoparticles and Fine Colloids in European Forest Stream Waters and Their Role as Phosphorus Carriers

"This is the peer reviewed version of the following article: Gottselig, N., W. Amelung, J. W. Kirchner, R. Bol, W. Eugster, S. J. Granger, C. Hernández-Crespo, et al. 2017. Elemental Composition of Natural Nanoparticles and Fine Colloids in European Forest Stream Waters and Their Role as Phosphorus Carriers. Global Biogeochemical Cycles 31 (10). American Geophysical Union (AGU): 1592 1607. doi:10.1002/2017gb005657, which has been published in final form at https://doi.org/10.1002/2017GB005657. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving."[EN] Biogeochemical cycling of elements largely occurs in dissolved state, but many elements may also be bound to natural nanoparticles (NNP, 1-100 nm) and fine colloids (100-450 nm). We examined the hypothesis that the size and composition of stream water NNP and colloids vary systematically across Europe. To test this hypothesis, 96 stream water samples were simultaneously collected in 26 forested headwater catchments along two transects across Europe. Three size fractions (similar to 1-20 nm, >20-60 nm, and >60 nm) of NNP and fine colloids were identified with Field Flow Fractionation coupled to inductively coupled plasma mass spectrometry and an organic carbon detector. The results showed that NNP and fine colloids constituted between 2 +/- 5% (Si) and 53 +/- 21% (Fe; mean +/- SD) of total element concentrations, indicating a substantial contribution of particles to element transport in these European streams, especially for P and Fe. The particulate contents of Fe, Al, and organic C were correlated to their total element concentrations, but those of particulate Si, Mn, P, and Ca were not. The fine colloidal fractions >60 nm were dominated by clay minerals across all sites. The resulting element patterns of NNP <60 nm changed from North to South Europe from Fe-to Ca-dominated particles, along with associated changes in acidity, forest type, and dominant lithology.The authors gratefully acknowledge the assistance of the following people in locating suitable sampling sites, contacting site operators, performing the sampling, and providing data: A. Avila Castells (Autonomous University of Barcelona), R. Batalla (University of Lleida), P. Blomkvist (Swedish University of Agricultural Sciences), H. Bogena (Julich Research Center), A.K. Boulet (University of Aveiro), D. Estany (University of Lleida), F. Garnier (French National Institute of Agricultural Research), H.J. Hendricks-Franssen (Research Center Julich), L. JacksonBlake (James Hutton Institute, NIVA), T. Laurila (Finnish Meteorological Institute), A. Lindroth (Lund University), M.M. Monerris (Universitat Politecnica de Valencia), M. Ottosson Lofvenius (Swedish University of Agricultural Sciences), I. Taberman (Swedish University of Agricultural Sciences), F. Wendland (Research Center Julich), T. Zetterberg (Swedish University of Agricultural Sciences and The Swedish Environmental Research Institute, IVL) and further unnamed contributors. The Swedish Infrastructure for Ecosystem Science (SITES) and the Swedish Integrated Monitoring, the latter financed by the Swedish Environmental Protection Agency, and ICOS Sweden have supported sampling and provided data for the Swedish sites. J.J.K. gratefully acknowledges the support from CESAM (UID/AMB/50017/2013), funded by the FCT/MCTES (PIDDAC) with cofunding by FEDER through COMPETE. N.G. gratefully acknowledges all those who contributed to organizing and implementing the continental sampling. The raw data can be found at http://hdl.handle.net/2128/14937. This project was partly funded by the German Research Foundation (DFG KL2495/1-1).Gottselig, N.; Amelung, W.; Kirchner, J.; Bol, R.; Eugster, W.; Granger, S.; Hernández Crespo, C.... (2017). Elemental Composition of Natural Nanoparticles and Fine Colloids in European Forest Stream Waters and Their Role as Phosphorus Carriers. Global Biogeochemical Cycles. 31(10):1592-1607. https://doi.org/10.1002/2017GB005657S159216073110Baken, S., Moens, C., van der Grift, B., & Smolders, E. (2016). Phosphate binding by natural iron-rich colloids in streams. Water Research, 98, 326-333. doi:10.1016/j.watres.2016.04.032Baken, S., Regelink, I. C., Comans, R. N. J., Smolders, E., & Koopmans, G. F. (2016). Iron-rich colloids as carriers of phosphorus in streams: A field-flow fractionation study. Water Research, 99, 83-90. doi:10.1016/j.watres.2016.04.060Benedetti, M. F., Van Riemsdijk, W. H., Koopal, L. K., Kinniburgh, D. G., Gooddy, D. C., & Milne, C. J. (1996). Metal ion binding by natural organic matter: From the model to the field. Geochimica et Cosmochimica Acta, 60(14), 2503-2513. doi:10.1016/0016-7037(96)00113-5Binkley, D., Ice, G. G., Kaye, J., & Williams, C. A. (2004). NITROGEN AND PHOSPHORUS CONCENTRATIONS IN FOREST STREAMS OF THE UNITED STATES. Journal of the American Water Resources Association, 40(5), 1277-1291. doi:10.1111/j.1752-1688.2004.tb01586.xBishop, K., Buffam, I., Erlandsson, M., Fölster, J., Laudon, H., Seibert, J., & Temnerud, J. (2008). Aqua Incognita: the unknown headwaters. Hydrological Processes, 22(8), 1239-1242. doi:10.1002/hyp.7049Bol, R., Julich, D., Brödlin, D., Siemens, J., Kaiser, K., Dippold, M. A., … Hagedorn, F. (2016). Dissolved and colloidal phosphorus fluxes in forest ecosystems-an almost blind spot in ecosystem research. Journal of Plant Nutrition and Soil Science, 179(4), 425-438. doi:10.1002/jpln.201600079Buffle, J., & Leppard, G. G. (1995). Characterization of Aquatic Colloids and Macromolecules. 2. Key Role of Physical Structures on Analytical Results. Environmental Science & Technology, 29(9), 2176-2184. doi:10.1021/es00009a005Celi, L., & Barberis, E. (s. f.). Abiotic stabilization of organic phosphorus in the environment. Organic phosphorus in the environment, 113-132. doi:10.1079/9780851998220.0113Dahlqvist, R., Benedetti, M. F., Andersson, K., Turner, D., Larsson, T., Stolpe, B., & Ingri, J. (2004). Association of calcium with colloidal particles and speciation of calcium in the Kalix and Amazon rivers. Geochimica et Cosmochimica Acta, 68(20), 4059-4075. doi:10.1016/j.gca.2004.04.007Darch, T., Blackwell, M. S. A., Hawkins, J. M. B., Haygarth, P. M., & Chadwick, D. (2014). A Meta-Analysis of Organic and Inorganic Phosphorus in Organic Fertilizers, Soils, and Water: Implications for Water Quality. Critical Reviews in Environmental Science and Technology, 44(19), 2172-2202. doi:10.1080/10643389.2013.790752Dynesius, M., & Nilsson, C. (1994). Fragmentation and Flow Regulation of River Systems in the Northern Third of the World. Science, 266(5186), 753-762. doi:10.1126/science.266.5186.753Erickson, H. P. (2009). Size and Shape of Protein Molecules at the Nanometer Level Determined by Sedimentation, Gel Filtration, and Electron Microscopy. Biological Procedures Online, 11(1), 32-51. doi:10.1007/s12575-009-9008-xEspinosa, M., Turner, B. L., & Haygarth, P. M. (1999). Preconcentration and Separation of Trace Phosphorus Compounds in Soil Leachate. Journal of Environmental Quality, 28(5), 1497-1504. doi:10.2134/jeq1999.00472425002800050015xFernández-Martínez, M., Vicca, S., Janssens, I. A., Sardans, J., Luyssaert, S., Campioli, M., … Peñuelas, J. (2014). Nutrient availability as the key regulator of global forest carbon balance. Nature Climate Change, 4(6), 471-476. doi:10.1038/nclimate2177Giddings, J., Yang, F., & Myers, M. (1976). Flow-field-flow fractionation: a versatile new separation method. Science, 193(4259), 1244-1245. doi:10.1126/science.959835Gimbert, L. J., Andrew, K. N., Haygarth, P. M., & Worsfold, P. J. (2003). Environmental applications of flow field-flow fractionation (FIFFF). TrAC Trends in Analytical Chemistry, 22(9), 615-633. doi:10.1016/s0165-9936(03)01103-8Gottselig, N., Bol, R., Nischwitz, V., Vereecken, H., Amelung, W., & Klumpp, E. (2014). Distribution of Phosphorus-Containing Fine Colloids and Nanoparticles in Stream Water of a Forest Catchment. Vadose Zone Journal, 13(7), vzj2014.01.0005. doi:10.2136/vzj2014.01.0005Gottselig, N., Nischwitz, V., Meyn, T., Amelung, W., Bol, R., Halle, C., … Klumpp, E. (2017). Phosphorus Binding to Nanoparticles and Colloids in Forest Stream Waters. Vadose Zone Journal, 16(3), vzj2016.07.0064. doi:10.2136/vzj2016.07.0064Hagedorn , A. G. 2006 EG-Sicherheitsdatenblatt (Gemäß 2001/58/EG)Hart, B. T., Douglas, G. B., Beckett, R., Van Put, A., & Van Grieken, R. E. (1993). Characterization of colloidal and particulate matter transported by the magela creek system, Northern Australia. Hydrological Processes, 7(1), 105-118. doi:10.1002/hyp.3360070111Hassellöv, M., Lyvén, B., Haraldsson, C., & Sirinawin, W. (1999). Determination of Continuous Size and Trace Element Distribution of Colloidal Material in Natural Water by On-Line Coupling of Flow Field-Flow Fractionation with ICPMS. Analytical Chemistry, 71(16), 3497-3502. doi:10.1021/ac981455yHassellov, M., & von der Kammer, F. (2008). Iron Oxides as Geochemical Nanovectors for Metal Transport in Soil-River Systems. Elements, 4(6), 401-406. doi:10.2113/gselements.4.6.401Hens, M., & Merckx, R. (2001). Functional Characterization of Colloidal Phosphorus Species in the Soil Solution of Sandy Soils. Environmental Science & Technology, 35(3), 493-500. doi:10.1021/es0013576Hill, D. M., & Aplin, A. C. (2001). Role of colloids and fine particles in the transport of metals in rivers draining carbonate and silicate terrains. Limnology and Oceanography, 46(2), 331-344. doi:10.4319/lo.2001.46.2.0331Jarvie, H. P., Neal, C., Rowland, A. P., Neal, M., Morris, P. N., Lead, J. R., … Hockenhull, K. (2012). Role of riverine colloids in macronutrient and metal partitioning and transport, along an upland–lowland land-use continuum, under low-flow conditions. Science of The Total Environment, 434, 171-185. doi:10.1016/j.scitotenv.2011.11.061Jiang, X., Bol, R., Nischwitz, V., Siebers, N., Willbold, S., Vereecken, H., … Klumpp, E. (2015). Phosphorus Containing Water Dispersible Nanoparticles in Arable Soil. Journal of Environmental Quality, 44(6), 1772-1781. doi:10.2134/jeq2015.02.0085Kögel-Knabner, I., & Amelung, W. (2014). Dynamics, Chemistry, and Preservation of Organic Matter in Soils. Treatise on Geochemistry, 157-215. doi:10.1016/b978-0-08-095975-7.01012-3Krám, P., Hruška, J., & Shanley, J. B. (2012). Streamwater chemistry in three contrasting monolithologic Czech catchments. Applied Geochemistry, 27(9), 1854-1863. doi:10.1016/j.apgeochem.2012.02.020Lyvén, B., Hassellöv, M., Turner, D. R., Haraldsson, C., & Andersson, K. (2003). Competition between iron- and carbon-based colloidal carriers for trace metals in a freshwater assessed using flow field-flow fractionation coupled to ICPMS. Geochimica et Cosmochimica Acta, 67(20), 3791-3802. doi:10.1016/s0016-7037(03)00087-5Marschner, B., & Kalbitz, K. (2003). Controls of bioavailability and biodegradability of dissolved organic matter in soils. Geoderma, 113(3-4), 211-235. doi:10.1016/s0016-7061(02)00362-2Martin, J.-M., Dai, M.-H., & Cauwet, G. (1995). Significance of colloids in the biogeochemical cycling of organic carbon and trace metals in the Venice Lagoon (Italy). Limnology and Oceanography, 40(1), 119-131. doi:10.4319/lo.1995.40.1.0119Mattsson, T., Kortelainen, P., Laubel, A., Evans, D., Pujo-Pay, M., Räike, A., & Conan, P. (2009). Export of dissolved organic matter in relation to land use along a European climatic gradient. Science of The Total Environment, 407(6), 1967-1976. doi:10.1016/j.scitotenv.2008.11.014Missong, A., Bol, R., Willbold, S., Siemens, J., & Klumpp, E. (2016). Phosphorus forms in forest soil colloids as revealed by liquid-state31P-NMR. Journal of Plant Nutrition and Soil Science, 179(2), 159-167. doi:10.1002/jpln.201500119Montalvo, D., Degryse, F., & McLaughlin, M. J. (2015). Natural Colloidal P and Its Contribution to Plant P Uptake. Environmental Science & Technology, 49(6), 3427-3434. doi:10.1021/es504643fNeubauer, E., Köhler, S. J., von der Kammer, F., Laudon, H., & Hofmann, T. (2013). Effect of pH and Stream Order on Iron and Arsenic Speciation in Boreal Catchments. Environmental Science & Technology, 47(13), 7120-7128. doi:10.1021/es401193jNeubauer, E., v.d. Kammer, F., & Hofmann, T. (2011). Influence of carrier solution ionic strength and injected sample load on retention and recovery of natural nanoparticles using Flow Field-Flow Fractionation. Journal of Chromatography A, 1218(38), 6763-6773. doi:10.1016/j.chroma.2011.07.010Nischwitz, V., & Goenaga-Infante, H. (2012). Improved sample preparation and quality control for the characterisation of titanium dioxide nanoparticles in sunscreens using flow field flow fractionation on-line with inductively coupled plasma mass spectrometry. Journal of Analytical Atomic Spectrometry, 27(7), 1084. doi:10.1039/c2ja10387gRan, Y., Fu, J. ., Sheng, G. ., Beckett, R., & Hart, B. . (2000). Fractionation and composition of colloidal and suspended particulate materials in rivers. Chemosphere, 41(1-2), 33-43. doi:10.1016/s0045-6535(99)00387-2Regelink, I. C., Koopmans, G. F., van der Salm, C., Weng, L., & van Riemsdijk, W. H. (2013). Characterization of Colloidal Phosphorus Species in Drainage Waters from a Clay Soil Using Asymmetric Flow Field-Flow Fractionation. Journal of Environmental Quality, 42(2), 464-473. doi:10.2134/jeq2012.0322Regelink, I. C., Voegelin, A., Weng, L., Koopmans, G. F., & Comans, R. N. J. (2014). Characterization of Colloidal Fe from Soils Using Field-Flow Fractionation and Fe K-Edge X-ray Absorption Spectroscopy. Environmental Science & Technology, 48(8), 4307-4316. doi:10.1021/es405330xRegelink, I. C., Weng, L., & van Riemsdijk, W. H. (2011). The contribution of organic and mineral colloidal nanoparticles to element transport in a podzol soil. Applied Geochemistry, 26, S241-S244. doi:10.1016/j.apgeochem.2011.03.114RICHARDSON, C. J. (1985). Mechanisms Controlling Phosphorus Retention Capacity in Freshwater Wetlands. Science, 228(4706), 1424-1427. doi:10.1126/science.228.4706.1424Roth , C. 2011 Sicherheitsdatenblatt Gemäß Verordnung (EG) Nr. 1907/2006 RepSchmitt, D., Taylor, H. E., Aiken, G. R., Roth, D. A., & Frimmel, F. H. (2002). Influence of Natural Organic Matter on the Adsorption of Metal Ions onto Clay Minerals. Environmental Science & Technology, 36(13), 2932-2938. doi:10.1021/es010271pSix, J., Elliott, E. T., & Paustian, K. (1999). Aggregate and Soil Organic Matter Dynamics under Conventional and No-Tillage Systems. Soil Science Society of America Journal, 63(5), 1350-1358. doi:10.2136/sssaj1999.6351350xStolpe, B., Guo, L., Shiller, A. M., & Hassellöv, M. (2010). Size and composition of colloidal organic matter and trace elements in the Mississippi River, Pearl River and the northern Gulf of Mexico, as characterized by flow field-flow fractionation. Marine Chemistry, 118(3-4), 119-128. doi:10.1016/j.marchem.2009.11.007Tipping, E., & Hurley, M. . (1992). A unifying model of cation binding by humic substances. Geochimica et Cosmochimica Acta, 56(10), 3627-3641. doi:10.1016/0016-7037(92)90158-fTombácz, E., Libor, Z., Illés, E., Majzik, A., & Klumpp, E. (2004). The role of reactive surface sites and complexation by humic acids in the interaction of clay mineral and iron oxide particles. Organic Geochemistry, 35(3), 257-267. doi:10.1016/j.orggeochem.2003.11.002Trostle, K. D., Ray Runyon, J., Pohlmann, M. A., Redfield, S. E., Pelletier, J., McIntosh, J., & Chorover, J. (2016). Colloids and organic matter complexation control trace metal concentration-discharge relationships in Marshall Gulch stream waters. Water Resources Research, 52(10), 7931-7944. doi:10.1002/2016wr019072U.S. Department of Agriculture 1993 Soil survey manual, chapter 3. Selected chemical propertiesVitousek, P. (1982). Nutrient Cycling and Nutrient Use Efficiency. The American Naturalist, 119(4), 553-572. doi:10.1086/283931Wells, M. L., & Goldberg, E. D. (1991). Occurrence of small colloids in sea water. Nature, 353(6342), 342-344. doi:10.1038/353342a0Wen, L.-S., Santschi, P., Gill, G., & Paternostro, C. (1999). Estuarine trace metal distributions in Galveston Bay: importance of colloidal forms in the speciation of the dissolved phase. Marine Chemistry, 63(3-4), 185-212. doi:10.1016/s0304-4203(98)00062-0Zirkler, D., Lang, F., & Kaupenjohann, M. (2012). «Lost in filtration»—The separation of soil colloids from larger particles. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 399, 35-40. doi:10.1016/j.colsurfa.2012.02.02