Dynamics of Water Movement near Boundaries of the Vadose Zone

Processes at boundaries of the unsaturated soil water zone were investigated: At the upper boundary evaporation at the soil-atmosphere interface, and at the lower boundary the dynamic capillary fringe. For studying the upper boundary, an evaporation experiment at the representative elementary volume (REV) scale was considered and modelled numerically. A model with a diffusive boundary layer and a 1D Richards' description including vapour transport fitted well to experimental data. It showed a boundary layer dominated regime in the wet range and a regime where dynamics is controlled by soil hydraulic properties in the dry range. The model could successfully be used to determine soil hydraulic properties from the corresponding evaporation experiment by inverse modelling using a Monte-Carlo Levenberg-Marquardt approach. For the lower boundary, light transmission and NIR imaging spectroscopy methods were developed and employed to measure the micro- and macroscopic water distribution in response to transient boundary conditions in a semi-2D sand medium in a Hele-Shaw cell with high temporal and spacial resolution. The analysis showed that coupled multi-phase and dynamic non-equillibrium effects are essential to understand water movement in dynamic capillary fringes, and sub-REV processes play an important role in the dynamics

Technical Note: Comparison of storage strategies of sea surface microlayer samples

The sea surface microlayer (SML) is an important biogeochemical system whose physico-chemical analysis often necessitates some degree of sample storage. However, many SML components degrade with time so the development of optimal storage protocols is paramount. We here briefly review some commonly used treatment and storage protocols. Using freshwater and saline SML samples from a river estuary, we investigated temporal changes in surfactant activity (SA) and the absorbance and fluorescence of chromophoric dissolved organic matter (CDOM) over four weeks, following selected sample treatment and storage protocols. Some variability in the effectiveness of individual protocols most likely reflects sample provenance. None of the various protocols examined performed any better than dark storage at 4 °C without pre-treatment. We therefore recommend storing samples refrigerated in the dark

A new method to determine multi-angular reflectance factor from lightweight multispectral cameras with sky sensor in a target-less workflow applicable to UAV

A new physically based method to estimate hemispheric-directional reflectance factor (HDRF) from lightweight multispectral cameras that have a downwelling irradiance sensor is presented. It combines radiometry with photogrammetric computer vision to derive geometrically and radiometrically accurate data purely from the images, without requiring reflectance targets or any other additional information apart from the imagery. The sky sensor orientation is initially computed using photogrammetric computer vision and revised with a non-linear regression comprising radiometric and photogrammetry-derived information. It works for both clear sky and overcast conditions. A ground-based test acquisition of a Spectralon target observed from different viewing directions and with different sun positions using a typical multispectral sensor configuration for clear sky and overcast showed that both the overall value and the directionality of the reflectance factor as reported in the literature were well retrieved. An RMSE of 3% for clear sky and up to 5% for overcast sky was observed

Surfactant control of gas transfer velocity along an offshore coastal transect: results from a laboratory gas exchange tank

Understanding the physical and biogeochemical controls of air–sea gas exchange is necessary for establishing biogeochemical models for predicting regional- and global-scale trace gas fluxes and feedbacks. To this end we report the results of experiments designed to constrain the effect of surfactants in the sea surface microlayer (SML) on the gas transfer velocity (<i>k</i>_w; cm h⁻¹), seasonally (2012–2013) along a 20 km coastal transect (North East UK). We measured total surfactant activity (SA), chromophoric dissolved organic matter (CDOM) and chlorophyll <i>a</i> (Chl <i>a</i>) in the SML and in sub-surface water (SSW) and we evaluated corresponding <i>k</i>_w values using a custom-designed air–sea gas exchange tank. Temporal SA variability exceeded its spatial variability. Overall, SA varied 5-fold between all samples (0.08 to 0.38 mg L⁻¹ T-X-100), being highest in the SML during summer. SML SA enrichment factors (EFs) relative to SSW were  ∼  1.0 to 1.9, except for two values (0.75; 0.89: February 2013). The range in corresponding <i>k</i>₆₆₀ (<i>k</i>_w for CO₂ in seawater at 20 °C) was 6.8 to 22.0 cm h⁻¹. The film factor <i>R</i>₆₆₀ (the ratio of <i>k</i>₆₆₀ for seawater to <i>k</i>₆₆₀ for “clean”, i.e. surfactant-free, laboratory water) was strongly correlated with SML SA (<i>r</i> ≥ 0.70, <i>p</i> ≤ 0.002, each <i>n</i> = 16). High SML SA typically corresponded to <i>k</i>₆₆₀ suppressions  ∼  14 to 51 % relative to clean laboratory water, highlighting strong spatiotemporal gradients in gas exchange due to varying surfactant in these coastal waters. Such variability should be taken account of when evaluating marine trace gas sources and sinks. Total CDOM absorbance (250 to 450 nm), the CDOM spectral slope ratio (<i>S</i>_R = <i>S</i>_{275 − 295}∕<i>S</i>_{350 − 400}), the 250 : 365 nm CDOM absorption ratio (<i>E</i>₂ : <i>E</i>₃), and Chl <i>a</i> all indicated spatial and temporal signals in the quantity and composition of organic matter in the SML and SSW. This prompts us to hypothesise that spatiotemporal variation in <i>R</i>₆₆₀ and its relationship with SA is a consequence of compositional differences in the surfactant fraction of the SML DOM pool that warrants further investigation

Contrasting sediment flux in Val Lumnezia (Graubünden, Eastern Swiss Alps), and implications for landscape development

This paper presents qualitative estimates of sediment discharge from opposite valley flanks in the S-N-oriented Val Lumnezia, eastern Swiss Alps, and relates inferred differences in sediment flux to the litho-tectonic architecture of bedrock. The valley flank on the western side hosts the deep-seated Lumnezia landslide where an area of ca. 30km2 has experienced slip rates of several centimetres per year, potentially resulting in high sediment discharge to the trunk stream (i.e. the Glogn River). High slip rates have resulted in topographic changes that are detectable on aerial photographs and measurable with geodetic tools. In contrast, a network of tributary channels dissects the valley flank on the eastern side. There, an area of approximately 18km2 corresponding to < 30% of the surface has experienced a change in the landscape mainly by rock avalanche and rock fall, and the magnitudes of changes are below the calibration limit of digital photogrammetry. We thus infer lower magnitudes of sediment discharge on the eastern tributaries than on the western valley side, where landsliding has been the predominant erosional process. These differences are interpreted to be controlled by the dip-slope situation of bedrock on the western side that favours down-slope slip of material. Morphometric investigations reveal that the western valley side is characterized by a low topographic roughness because this valley flank has not been dissected by a channel network. It appears that high sediment discharge of the Lumnezia landslide has inhibited the establishment of a stable channel network and has largely controlled the overall evolution of the landscape. This contrasts to the general notion that channelized processes exert the first-order control on landscape evolution and formation of relief and needs to be considered in future studies about landscape architecture, drainage network and sediment discharg

Relationships between landscape morphology, climate and surface erosion in northern Peru at 5°S latitude

The northern segment of the Peruvian Andes is affected by a twofold climate with measurable implications on landscapes and landscape dynamics. During ‘normal' or ‘neutral' years easterly winds bring rain from the Atlantic and the Amazon Basin to the Sierras, which results in a seasonal climate with rather low-intensity precipitations. In contrast, during the large-scale warm phase of the ENSO cycle, El Niños transfer moisture from the Pacific to the Peruvian coast by westerly winds and result in high-intensity precipitation. We investigate the effects of this twofold climate for the case of the Piura drainage basin at ca. 5°S latitude (northern Peru). In the headwaters that have been under the influence of the easterlies, the landscape is mantled by a thick regolith cover and dissected by a network of debris flow channels that are mostly covered by a thick layer of unconsolidated sediment. This implies that in the headwaters of the Piura River sediment discharge has been limited by the transport capacity of the sediment transfer system. In the lower segment that has been affected by high-intensity rainfall in relation to the westerlies (El Niños), the hillslopes are dissected by debris flow channels that expose the bedrock on the channel floor, implying a supply-limited sediment discharge. Interestingly, measurements at the Piura gauging station near the coast reveal that, during the last decades, sediment was transferred to the lower reaches only in response to the 1982-1983 and 1997-1998 El Niño periods. For the latter period, synthetic aperture radar (SAR) intensity images show that the locations of substantial erosion are mainly located in areas that were affected by higher-than-average precipitation rates. Most important, these locations are coupled with the network of debris flow channels. This implies that the seasonal easterlies are responsible for the production of sediment through weathering in the headwaters, and the highly episodic El Niños result in export of sediment through channelized sediment transport down to the coastal segment. Both systems overlap showing a partially coupled sediment production-delivery syste

Design and Characterization of Surface‐Crosslinked Gelatin Nanoparticles for the Delivery of Hydrophilic Macromolecular Drugs

For nanotechnology enabled delivery of hydrophilic protein‐based drugs, several polymer‐based carrier systems have been used in the past to protect the sensitive load and to facilitate cellular uptake and crossing of biological barriers. This study uses gelatin, a natural and biodegradable macromolecule, as carrier material which is approved for several applications. Nanoprecipitation is used to form nanoparticles and to maintain the physicochemical integrity of gelatin, hydrophilic crosslinkers, e.g., paraformaldehyde, glutaraldehyde, carbodiimide, and transglutaminase are employed. However, these crosslinkers diffuse homogenously into the carrier matrix also crosslinking the polymeric matrix with the entrapped protein‐based molecules thus rendering it inactive. Hence a hydrophobic zero‐length crosslinker, diisopropylcarbodiimide, is applied to avoid diffusion into the particles. This will provide an opportunity to encapsulate protein‐based drugs in the non‐crosslinked matrix. The hypothesis of surface crosslinking is proven by the extent of crosslinking and more importantly by encapsulation and the release of lysozyme as a model hydrophilic protein. Furthermore, essential process parameters are evaluated such as crosslinker concentration, crosslinking time and crosslinking reaction temperature with regard to the effect on particle size, size distribution and zeta‐potential of gelatin nanoparticles. The optimum formulation results in the production of gelatin nanoparticles with 200‐300 nm and a polydispersity index < 0.2

(Re)shaping Educational Research through ‘Programmification’: Institutional Expansion, Change, and Translation in Norway

Educational research in Norway has experienced unprecedented structural expansion as well as cognitive shifts over the past two decades, especially due to increased state investments and the strategic use of extensive and multi-year thematic programs to fund research projects. Applying a neo-institutionalist framework, we examine institutionalization dynamics in cultural-cognitive, normative, and regulative dimensions over the past two decades using interviews, research program calls, policy documents, and funding data. In the cultural-cognitive dimension, we find references to the knowledge society, the importance of evidence in policy-making, and ideas of quality, excellence, and relevance. In the normative dimension, we find the introduction of new professional and methodological standards, reflecting broader global patterns of academic and epistemic drift. In the regulative dimension, the strengthened role of both government and the Research Council of Norway is manifest in substantial growth in both funding and large-scale, long-term planning, including thematic choices—evidence of ‘programification’. The importance of external models has grown in an era of internationalization, yet translation occurs at every level of governance of educational research. This results in a specific Norwegian research model, guided by a mode of governance of programs, that maintains social values traditionally strong in Nordic societies

The Atlantic Ocean surface microlayer from 50°N to 50°S is ubiquitously enriched in surfactants at wind speeds up to 13 m s−1

We report the first measurements of surfactant activity (SA) in the sea surface microlayer (SML) and in subsurface waters (SSW) at the ocean basin scale, for two Atlantic Meridional Transect from cruises 50°N to 50°S during 2014 and 2015. Northern Hemisphere (NH) SA was significantly higher than Southern Hemisphere (SH) SA in the SML and in the SSW. SA enrichment factors (EF = SASML/SASSW) were also higher in the NH, for wind speeds up to ~13 m s−1, questioning a prior assertion that Atlantic Ocean wind speeds >12 m s−1 poleward of 30°N and 30°S would preclude high EFs and showing the SML to be self-sustaining with respect to SA. Our results imply that surfactants exert a control on air-sea CO2 exchange across the whole North Atlantic CO2 sink region and that the contribution made by high wind, high latitude oceans to air-sea gas exchange globally should be reexamined

Analysis of the EIAV Rev-Responsive Element (RRE) Reveals a Conserved RNA Motif Required for High Affinity Rev Binding in Both HIV-1 and EIAV

A cis-acting RNA regulatory element, the Rev-responsive element (RRE), has essential roles in replication of lentiviruses, including human immunodeficiency virus (HIV-1) and equine infection anemia virus (EIAV). The RRE binds the viral trans-acting regulatory protein, Rev, to mediate nucleocytoplasmic transport of incompletely spliced mRNAs encoding viral structural genes and genomic RNA. Because of its potential as a clinical target, RRE-Rev interactions have been well studied in HIV-1; however, detailed molecular structures of Rev-RRE complexes in other lentiviruses are still lacking. In this study, we investigate the secondary structure of the EIAV RRE and interrogate regulatory protein-RNA interactions in EIAV Rev-RRE complexes. Computational prediction and detailed chemical probing and footprinting experiments were used to determine the RNA secondary structure of EIAV RRE-1, a 555 nt region that provides RRE function in vivo. Chemical probing experiments confirmed the presence of several predicted loop and stem-loop structures, which are conserved among 140 EIAV sequence variants. Footprinting experiments revealed that Rev binding induces significant structural rearrangement in two conserved domains characterized by stable stem-loop structures. Rev binding region-1 (RBR-1) corresponds to a genetically-defined Rev binding region that overlaps exon 1 of the EIAV rev gene and contains an exonic splicing enhancer (ESE). RBR-2, characterized for the first time in this study, is required for high affinity binding of EIAV Rev to the RRE. RBR-2 contains an RNA structural motif that is also found within the high affinity Rev binding site in HIV-1 (stem-loop IIB), and within or near mapped RRE regions of four additional lentiviruses. The powerful integration of computational and experimental approaches in this study has generated a validated RNA secondary structure for the EIAV RRE and provided provocative evidence that high affinity Rev binding sites of HIV-1 and EIAV share a conserved RNA structural motif. The presence of this motif in phylogenetically divergent lentiviruses suggests that it may play a role in highly conserved interactions that could be targeted in novel anti-lentiviral therapies