Showing papers by "Stefan Seeger published in 2017"

Catchment water storage variation with elevation

Abstract: One of the most important functions of catchments is the storage of water. Catchment storagebuffers meteorological extremes and interannual streamflow variability, controls the partitioningbetween evaporation and runoff, and influences transit times of water. Hydrogeological data toestimate storage are usually scarce and seldom available for a larger set of catchments. This studyfocused on storage in prealpine and alpine catchments, using a set of 21 Swiss catchments comprising different elevation ranges. Catchment storage comparisons depend on storage definitions.This study defines different types of storage including definitions of dynamic and mobile catchment storage. We then estimated dynamic storage using four methods, water balance analysis,streamflow recession analysis, calibration of a bucket‐type hydrological model Hydrologiska Byrans Vattenbalansavdelning model (HBV), and calibration of a transfer function hydrographseparation model using stable isotope observations. The HBV model allowed quantifying the contributions of snow, soil and groundwater storages compared to the dynamic catchment storage.With the transfer function hydrograph separation model both dynamic and mobile storage wasestimated. Dynamic storage of one catchment estimated by the four methods differed up toone order of magnitude. Nevertheless, the storage estimates ranked similarly among the 21catchments. The largest dynamic and mobile storage estimates were found in high‐elevationcatchments. Besides snow, groundwater contributed considerably to this larger storage.Generally, we found that with increasing elevation the relative contribution to the dynamic catchmentstorage increased for snow, decreased for soil, but remained similar for groundwater storage.

Sensitivity of young water fractions to hydro-climatic forcing and landscape properties across 22 Swiss catchments

Abstract: . The young water fraction Fyw , defined as the proportion of catchment outflow younger than approximately 2–3 months, can be estimated directly from the amplitudes of seasonal cycles of stable water isotopes in precipitation and streamflow. Thus, Fyw may be a useful metric in catchment inter-comparison studies that investigate landscape and hydro-climatic controls on streamflow generation. Here, we explore how Fyw varies with catchment characteristics and climatic forcing, using an extensive isotope data set from 22 small- to medium-sized (0.7–351 km 2 ) Swiss catchments. We find that flow-weighting the tracer concentrations in streamwater resulted in roughly 26 % larger young water fractions compared to the corresponding unweighted values, reflecting the fact that young water fractions tend to be larger when catchments are wet and discharge is correspondingly higher. However, flow-weighted and unweighted young water fractions are strongly correlated with each other among the catchments. They also correlate with terrain, soil, and land-use indices, as well as with mean precipitation and measures of hydrologic response. Within individual catchments, young water fractions increase with discharge, indicating an increase in the proportional contribution of faster flow paths at higher flows. We present a new method to quantify the discharge sensitivity of Fyw , which we estimate as the linear slope of the relationship between the young water fraction and flow. Among the 22 catchments, discharge sensitivities of Fyw are highly variable and only weakly correlated with Fyw itself, implying that these two measures reflect catchment behaviour differently. Based on strong correlations between the discharge sensitivity of Fyw and several catchment characteristics, we suggest that low discharge sensitivities imply greater persistence in the proportions of fast and slow runoff flow paths as catchment wetness changes. In contrast, high discharge sensitivities imply the activation of different dominant flow paths during precipitation events, such as when subsurface water tables rise into more permeable layers and/or the river network expands further into the landscape.

Directed in situ shaping of complex nano- and microstructures during chemical synthesis

Abstract: Chemical composition and shape determine the basic properties of any object. Commonly, chemical synthesis and shaping follow each other in a sequence, although their combination into a single process would be an elegant simplification. Here, a pathway of simultaneous synthesis and shaping as applied to polysiloxanes on the micro- and nanoscale is presented. Complex structures such as stars, chalices, helices, volcanoes, rods, or combinations thereof are obtained. Varying the shape-controlling reaction parameters including temperature, water saturation, and the type of substrate allows to direct the reaction toward specific structures. A general mechanism of growth is suggested and analytical evidence and thermodynamic calculations to support it are provided. An aqueous droplet in either gaseous atmosphere or in a liquid organic solvent serves as a spatially confined polymerization volume. By substituting the starting materials, germanium-based nanostructures are also obtained. This transferability marks this approach as a major step toward a generally applicable method of chemical synthesis including in situ shaping.

Health effects of laser printer emissions: a controlled exposure study.

Abstract: Ultrafine particles emitted from laser printers are suspected to elicit adverse health effects. We performed 75-minute exposures to emissions of laser printing devices (LPDs) in a standardized, randomized, cross-over manner in 23 healthy subjects, 14 mild, stable asthmatics, and 15 persons reporting symptoms associated with LPD emissions. Low-level exposures (LLE) ranged at the particle background (3000 cm-3 ) and high-level exposures (HLE) at 100 000 cm-3 . Examinations before and after exposures included spirometry, body plethysmography, transfer factors for CO and NO (TLCO, TLNO), bronchial and alveolar NO, cytokines in serum and nasal secretions (IL-1β, IL-5, IL-6, IL-8, GM-CSF, IFNγ, TNFα), serum ECP, and IgE. Across all participants, no statistically significant changes occurred for lung mechanics and NO. There was a decrease in volume-related TLNO that was more pronounced in HLE, but the difference to LLE was not significant. ECP and IgE increased in the same way after exposures. Nasal IL-6 showed a higher increase after LLE. There was no coherent pattern regarding the responses in the participant subgroups or single sets of variables. In conclusion, the experimental acute responses to short but very high-level LPD exposures were small and did not indicate clinically relevant effects compared to low particle number concentrations.

Functional Silver-Silicone-Nanofilament-Composite Material for Water Disinfection.

Abstract: The roughness of superhydrophobic silicone nanofilaments (SNFs) is exploited to enlarge the contact area of conventional filter material. As an efficient wetting of the filter material is crucial for water treatment, the wettability of SNFs is readily modified from superhydrophobic to hydrophilic during the functionalization process. SNFs are coated on glass beads and subsequently modified with biocidal silver nanoparticles (AgNPs). The enlarged surface area of SNFs allows a 30 times higher loading of AgNPs in comparison to glass beads without SNF coating. Thus, in column experiments, the AgNP-SNF-nanocomposite-modified glass beads exert superior antibacterial activity towards suspensions of E. coli K12 compared to AgNP functionalized glass beads without SNFs. Additionally, reusing the AgNP-SNF-nanocomposite-coated glass beads with fresh bacteria contaminated medium increases their efficacy and reduces the colony forming units by ≈6 log units. Thereby, the silver loss during percolation is below 0.1 μg mL−1. These results highlight, first, the potential of AgNP-SNF-nanocomposite-modified glass beads as an effective filter substrate for water disinfection, and second, the efficiency of SNF coating in increasing the contact area of conventional filter material.

A Facile, Sustainable Strategy towards the Preparation of Silicone Nanofilaments and Their Use as Antiwetting Coatings

Abstract: Synthesis of silicone nanofilaments (SNF) on substrates is a successful approach to fabricate superantiwetting surfaces. However, the yield of SNF is usually very low (<< 1 %). After coating reactions, excessive organosilane residues become wastes and are released to the environment. Here, we report a facile, sustainable, high yield strategy to prepare silicone nanofilament coatings by simply exposing trifunctional silane/toluene solution to air. When toluene is exposed to air with relative humidity between 30% and 45%, it can trap a suitable amount of water which enables fast and continuous growth of SNF on different substrates. This new finding not only simplifies the fabrication procedure but also enables the preparation of SNF coatings in a sustainable, high-yield manner. Such a novel technique allows the preparation of superhydrophobic samples on a large scale-hundreds of samples can be prepared in less than 1 day by simply using a mother solution containing a small amount of trifunctional silane.

Silicone Nanofilament-Supported Mixed Nickel-Metal Oxides for Alkaline Water Electrolysis

Abstract: Mixed transitionmetal nickel oxide materials (M-NiO; M=Co, Mn, Fe) supported on silicone nanofilaments (SNFs) were synthesized via precipitation reaction with urea. All materials were evaluated for their OER activity in 0.1 M KOH, of which the Fe-NiO/SNFs showed a notable improvement over NiO/SNFs and unsupported NiO. The results presented herein demonstrate the extension of our previously reported synthesis for NiO/SNFs to yield SNF-supported mixed transition metal-oxide materials. The versatility and scalability of the synthesis are particularly interesting for the facile preparation of three-dimensional, binderless electrodes for alkaline water electrolysis applications.

Supercritical angle Raman microscopy: a surface-sensitive nanoscale technique without field enhancement

Abstract: Raman scattering microscopy is a versatile tool for label-free imaging and molecular fingerprint analysis. Here, we provide the first demonstration that the selective collection of scattered signals exceeding the critical angle for total internal reflection enables surface-confined spontaneous Raman investigations at nanometre resolution. This high-axial selectivity leads to improved signal-to-background ratios, thus making this technique an excellent probe for surface-related molecular specimens. The richness of the spectroscopic information obtained through the supercritical angle Raman (SAR) collection path was proven by comparing its output with that of a parallel far-field collection path. Furthermore, we demonstrated that the proposed SAR technique is a versatile microscopy approach that can be used alone or in combination with amplified Raman modalities such as surface-enhanced resonance Raman scattering.

Liquid coating compositions for use in methods for forming a superhydrophobic, superoleophobic or superamphiphobic layer

Abstract: The present invention provides for method for forming a superhydrophobic, superoleophobic or superamphiphobic layer and imparting said property on a surface, comprising the steps of: a. preparing a liquid coating composition comprising a solvent and dispersed silicone nanoparticles, b. optionally priming the surface to form a primed surface on which a superhydrophobic, superoleophobic or superamphiphobic layer is to be formed, c. applying a layer of the liquid coating composition on the surface or primed surface on which the superhydrophobic, superoleophobic or superamphiphobic layer is to be formed, d. evaporating the solvent from the liquid coating composition to form a superhydrophobic, superoleophobic or superamphiphobic layer and impart said property on the surface or primed surface, wherein the dispersed silicone nanoparticles are formed by polymerization of at least one compound of formula I in an aprotic solvent comprising 5 to 500 ppm of water, RaSi(R1)n(X1)3-n (I) wherein Ra is a straight-chain or branched C(1-24) alkyl or alkenyl group, an aromatic group which is linked by a single covalent bond or linked by a straight-chain or branched alkylene unit having 1 to 8 carbon atoms, to the Si-atom, R1 a straight chain or a branched hydrocarbon radical having 1 to 6 carbon atoms, X1 is a hydrolysable group, which is one or more of a halogen or an alkoxy group, and n is 0 or 1, and preferably is 0.

A multifunctional plasma and deposition sensor for the characterization of plasma sources for film deposition and etching

Abstract: Our recently reported multifunctional plasma and deposition sensor [Welzel et al., Appl. Phys. Lett. 102, 211605 (2013)] was used for the characterization of two different plasma sources: a magnetron sputtering deposition source and an ion beam source. The multifunctional sensor, based on a conventional quartz crystal monitor (microbalance) for mass increase/decrease measurements, can measure quasi-simultaneously the deposition/etching flux, the energy flux, and the charged particle flux. By moving the sensor or the plasma source stepwise against each other, the lateral (radial) flux profiles of the different sources can be measured with a lateral resolution of about 8 mm, the diameter of aperture in front of the quartz crystal. It is demonstrated that this compact and simple multifunctional sensor is a versatile tool for the characterization of different kinds of plasma sources for deposition and etching purposes. By combining the different measured quantities, the ion-to-neutral ratio and the mean energy per deposited atom can be calculated, parameters that are essential for the characterization of plasma deposition and etch processes.Our recently reported multifunctional plasma and deposition sensor [Welzel et al., Appl. Phys. Lett. 102, 211605 (2013)] was used for the characterization of two different plasma sources: a magnetron sputtering deposition source and an ion beam source. The multifunctional sensor, based on a conventional quartz crystal monitor (microbalance) for mass increase/decrease measurements, can measure quasi-simultaneously the deposition/etching flux, the energy flux, and the charged particle flux. By moving the sensor or the plasma source stepwise against each other, the lateral (radial) flux profiles of the different sources can be measured with a lateral resolution of about 8 mm, the diameter of aperture in front of the quartz crystal. It is demonstrated that this compact and simple multifunctional sensor is a versatile tool for the characterization of different kinds of plasma sources for deposition and etching purposes. By combining the different measured quantities, the ion-to-neutral ratio and the mean energ...

Supercritical angle fluorescence as a tool to study the interaction between lipid bilayer and peptides

Abstract: The understanding of processes occurring at the interface between two media are of prior importance in various fields of research, from material sciences to biology. A custom-made microscope objective based on the supercritical angle technique was developed in our group, allowing to probe these interfacial events by carrying out surface-sensitive and low invasive spectroscopy of aqueous samples. A biological example of particular interest is the comprehension of neurodegenerative diseases which seem caused by the interaction of specific peptides with the membrane of the neurons. Taking advantage of our optical setup, we used supercritical angle fluorescence spectroscopy to specifically monitor the interaction between a supported lipid bilayer (SLB) and the Amyloid β peptide, notably responsible of the Alzheimer disease. Different forms of the peptide (40 and 42 amino acids composition) were tested and the interfacial fluorescence measured to get information about the lipid integrity and mobility. The adsorption of the peptide was also characterized in terms of kinetic and affinity.

Method and apparatus for the isolation and treatment of particulate targets

Abstract: A method of isolating and treating a particulate target using an apparatus comprising at least a capillary comprising a tip orifice and an internal cavity, said internal cavity comprising a treatment liquid, a positioning element capable of positioning the tip orifice of the capillary, a discharging/drawing element capable of causing a discharge of treatment liquid from the capillary as well as causing a drawing of treatment liquid into the capillary, said method comprising the steps of: a. locating the particulate target to be isolated and treated, b. positioning the tip orifice of the capillary such that the tip orifice of the capillary comes in proximity to the particulate target, using the positioning element, c. discharging a volume of treatment liquid such as to enclose the particulate target in the treatment liquid, d. drawing the particulate target enclosed in the treatment liquid into the internal cavity of the capillary, e. treating the particulate target within the internal cavity of the capillary comprising the treatment liquid.