2016, Şopu, D., Soyarslan, C., Sarac, B., Bargmann, S., Stoica, M., Eckert, J.

We investigate the influence of various critical structural aspects such as pore density, distribution, size and number on the deformation behavior of nanoporous Cu64 Zr36 glass. By using molecular dynamics and finite element simulations an effective strategy to control the strain localization in nanoporous heterostructures is provided. Depending on the pore distribution in the heterostructure, upon tensile loading the nanoporous glass showed a clear transition from a catastrophic fracture to localized deformation in one dominant shear band, and ultimately to homogeneous plastic flow mediated by a pattern of multiple shear bands. The change in the fracture mechanism from a shear band slip to necking-like homogeneous flow is quantitative interpreted by calculating the critical shear band length. Finally, we identify the most effective heterostructure with enhanced ductility as compared to the monolithic bulk metallic glass. The heterostructure with a fraction of pores of about 3% distributed in such a way that the pores do not align along the maximum shear stress direction shows higher plasticity while retaining almost the same strength as the monolithic glass. Our results provide clear evidence that the mechanical properties of nanoporous glassy materials can be tailored by carefully controlling the design parameters.

2016, de Kanter, Martinus, Meyer-Kirschner, Julian, Viell, Jörn, Mitsos, Alexander, Kather, Michael, Pich, Andrij, Janzen, Christoph

A novel probe head design is introduced, which enables in-line monitoring of particle sizes in undiluted stirred fluids using dynamic light scattering. The novel probe head separates a small sample volume of 0.65 ml from the bulk liquid by means of an impeller. In this sample volume, particle sizing is performed using a commercially available fiber-optical backscatter probe. While conventional light scattering measurements in stirred media fail due to the superposition of Brownian’ motion and forced convection, undistorted measurements are possible with the proposed probe head. One measurement takes approximately 30 s used for liquid exchange by rotation of the impeller and for collection of scattered light. The probe head is applied for in-line monitoring of the particle growth during microgel synthesis by precipitation polymerization in a one liter laboratory reactor. The in-line measurements are compared to off-line measurements and show a good agreement.

2017, Lautenbach, J., Höffner, J., Lübken, F.-J., Kopp, M., Gerding, M.

In the years from 2002 to 2012 potassium densities observations were performed in the mesopause region at Kühlungsborn using a potassium Doppler lidar. The 10-year diurnal data set comprises 5090 h of potassium number densities at 741 days with 25.2% under full daylight conditions. Potassium number densities show a clear semi-annual variation with two broad maxima reoccurring every year. The first maximum occurs in summer and lasts for about 4 months (May–August) with number densities up to 60 atoms/cc. The second maximum is observed from early December to late February with densities up to 30 atoms/cc. Both the peak density and the column density are higher at solstices than at equinoxes. The large data set shows little variation of the mean layer over the 10 years.

2017, Feng, Wuhu, Kaifler, Bernd, Marsh, Daniel R., Höffner, Josef, Hoppe, Ulf-Peter, Williams, Bifford P., Plane, John M.C.

We report measurements of atomic sodium, iron and temperature in the mesosphere and lower thermosphere (MLT) made by ground-based lidars at the ALOMAR observatory (69°N, 16°E) during a major sudden stratospheric warming (SSW) event that occurred in January 2009. The high resolution temporal observations allow the responses of the Na and Fe layers to the SSW at high northern latitudes to be investigated. A significant cooling with temperatures as low as 136 K around 90 km was observed on 22–23 January 2009, along with substantial depletions of the Na and Fe layers (an ~80% decrease in the column abundance with respect to the mean over the observation period). The Whole Atmosphere Community Climate Model (WACCM) incorporating the chemistry of Na, Fe, Mg and K, and nudged with reanalysis data below 60 km, captures well the timing of the SSW, although the extent of the cooling and consequently the depletion in the Na and Fe layers is slightly underestimated. The model also predicts that the perturbations to the metal layers would have been observable even at equatorial latitudes. The modelled Mg layer responds in a very similar way to Na and Fe, whereas the K layer is barely affected by the SSW because of the enhanced conversion of K+ ions to K atoms at the very low temperatures.

2015, Stoica, Mihai, Ramasamy, Parthiban, Kaban, Ivan, Scudino, Sergio, Nicoara, Mircea, Vaughan, Gavin B.M., Wright, Jonathan, Kumar, Ravi, Eckert, Jürgen

Fully amorphous rods with diameters up to 2 mm diameter were obtained upon 0.5 at.% Cu addition to the Fe36Co36B19.2Si4.8Nb4 bulk metallic glass. The Cu-added glass shows a very good thermal stability but, in comparison with the Cu-free base alloy, the entire crystallization behavior is drastically changed. Upon heating, the glassy (Fe36Co36B19.2Si4.8Nb4)99.5Cu0.5 samples show two glass transitions-like events, separated by an interval of more than 100 K, in between which a bcc-(Fe,Co) solid solution is formed. The soft magnetic properties are preserved upon Cu-addition and the samples show a saturation magnetization of 1.1 T combined with less than 2 A/m coercivity. The relaxation behavior prior to crystallization, as well as the crystallization behavior, were studied by time-resolved X-ray diffraction using synchrotron radiation. It was found that both glassy alloys behave similar at temperatures below the glass transition. Irreversible structural transformations take place when approaching the glass transition and in the supercooled liquid region.

2017, Costabel, Stephan, Siemon, Bernhard, Houben, Georg, Günther, Thomas

A multi-method geophysical survey, including helicopter-borne electromagnetics (HEM), transient electromagnetics (TEM), and magnetic resonance sounding (MRS), was conducted to investigate a freshwater lens on the North Sea island of Langeoog, Germany. The HEM survey covers the entire island and gives an overview of the extent of three freshwater lenses that reach depths of up to 45 m. Ground-based TEM and MRS were conducted particularly on the managed western lens to verify the HEM results and to complement the lithological information from existing boreholes. The results of HEM and TEM are in good agreement. Salt- and freshwater-bearing sediments can, as expected, clearly be distinguished due to their individual resistivity ranges. In the resistivity data, a large transition zone between fresh- and saltwater with a thickness of up to 20 m is identified, the existence of which is verified by borehole logging and sampling. Regarding lithological characterisation of the subsurface, the MRS method provides more accurate and reliable results than HEM and TEM. Using a lithological index derived from MRS water content and relaxation time, thin aquitard structures as well as fine and coarse sand aquifers can be distinguished. Complementing the existing borehole data with the lithology information estimated from MRS, we generate a map showing the occurrence of aquitard structures, which significantly improves the hydrogeological model of the island. Moreover, we demonstrate that the estimates of groundwater conductivity in the sand aquifers from geophysical data are in agreement with the fluid conductivity measured in the boreholes.

2017, Benze, Susanne, Gumbel, Jörg, Randall, Cora E., Karlsson, Bodil, Hultgren, Kristoffer, Lumpe, Jerry D., Baumgarten, Gerd

Combining limb and nadir satellite observations of Polar Mesospheric Clouds (PMCs) has long been recognized as problematic due to differences in observation geometry, scattering conditions, and retrieval approaches. This study offers a method of comparing PMC brightness observations from the nadir-viewing Aeronomy of Ice in the Mesosphere (AIM) Cloud Imaging and Particle Size (CIPS) instrument and the limb-viewing Odin Optical Spectrograph and InfraRed Imaging System (OSIRIS). OSIRIS and CIPS measurements are made comparable by defining a common volume for overlapping OSIRIS and CIPS observations for two northern hemisphere (NH) PMC seasons: NH08 and NH09. We define a scattering intensity quantity that is suitable for either nadir or limb observations and for different scattering conditions. A known CIPS bias is applied, differences in instrument sensitivity are analyzed and taken into account, and effects of cloud inhomogeneity and common volume definition on the comparison are discussed. Not accounting for instrument sensitivity differences or inhomogeneities in the PMC field, the mean relative difference in cloud brightness (CIPS - OSIRIS) is −102 ± 55%. The differences are largest for coincidences with very inhomogeneous clouds that are dominated by pixels that CIPS reports as non-cloud points. Removing these coincidences, the mean relative difference in cloud brightness reduces to −6 ± 14%. The correlation coefficient between the CIPS and OSIRIS measurements of PMC brightness variations in space and time is remarkably high, at 0.94. Overall, the comparison shows excellent agreement despite different retrieval approaches and observation geometries.

2016, Wende, K., Bekeschus, S., Schmidt, A., Jatsch, L., Hasse, S., Weltmann, K.D., Masur, K., von Woedtke, T.

Cold atmospheric pressure plasmas represent a favorable option for the treatment of heat sensitive materials and human or animal tissue. Beneficial effects have been documented in a variety of medical conditions, e.g., in the treatment of chronic wounds. It is assumed that the main mechanism of the plasma’s efficacy is mediated by a stimulating dissipation of energy via radiation and/or chemical energy. Although no evidence on undesired side effects of a plasma treatment has yet been presented, skepticism toward the safety of the exposure to plasma is present. However, only little data regarding the mutagenic potential of this new treatment option is available. Accordingly, we investigated the mutagenic potential of an argon plasma jet (kinpen) using different testing systems in accordance with ISO norms and multiple cell lines: a HPRT1 mutation assay, a micronucleus formation assay, and a colony formation assay. Moderate plasma treatment up to 180 s did not increase genotoxicity in any assay or cell type investigated. We conclude that treatment with the argon plasma jet kinpen did not display a mutagenic potential under the test conditions applied and may from this perspective be regarded as safe for the use in biomedical applications.

2015, Limbach, R., Winterstein-Beckmann, A., Dellith, J., Möncke, D., Wondraczek, L.

We provide a comprehensive description of the defect tolerance of sodium-borosilicate glasses upon sharp contact loading. This is motivated by the key role which is taken by this particular glass system in a wide variety of applications, ranging from electronic substrates, display covers and substrates for biomedical imaging and sensing to, e.g., radioactive waste vitrification. The present report covers the mechanical properties of glasses in the Na2O–B2O3–SiO2 ternary over the broad range of compositions from pure SiO2 to binary sodium-borates, and crossing the regions of various commercially relevant specialty borosilicate glasses, such as the multi-component Duran-, Pyrex- and BK7-type compositions and typical soda-lime silicate glasses, which are also included in this study. In terms of structure, the considered glasses may be separated into two groups, that is, one series which contains only bridging oxygen atoms, and another series which is designed with an increasing number of non-bridging oxygen ions. Elastic moduli, Poisson ratio, hardness as well as creep and crack resistance were evaluated, as well as the contribution of densification to the overall amount of indentation deformation. Correlations between the mechanical properties and structural characteristics of near- and mid-range order are discussed, from which we obtain a mechanistic view at the molecular reactions which govern the overall deformation reaction and, ultimately, contact cracking.

2016, Papendiek, Franka, Tartiu, Valentina E., Morone, Piergiuseppe, Venus, Joachim, Hönig, Anne

Fodder legumes play a major role in developing sustainable agricultural production systems and contain a range of compounds, which can be utilized to produce a wide spectrum of materials currently manufactured from petroleum-based sources. Hence, if associated with Green Biorefinery technology, the use of fodder legumes brings about significant advantages in terms of overall environmental sustainability. Since fodder legume production in Europe is currently very low, the objective of this study is to assess if a new value chain generated by Green Biorefineries can make fodder legume production profitable for farmers, and therewith increase cultivation numbers. We conducted a financial cost-benefit analysis of producing biomass from agricultural land in the federal state of Brandenburg (Germany) in three different production scenarios at two farm size levels. Costs, benefits, expected profits and risks between the scenarios were quantified. Fodder legume production for traditional fodder production was already able to increase the internal rate of return, while the production of feedstocks for Green Biorefineries, depending on prices paid for the legume juice showed an even higher profit potential. Therefore, in future agricultural production systems, fodder legumes should be part of crop rotations again.