INFLUENCE OF GLUTARALDEHYDE AND/OR OSMIUM TETROXIDE ON CELL VOLUME, ION CONTENT, MECHANICAL STABILITY, AND MEMBRANE PERMEABILITY OF EHRLICH ASCITES TUMOR CELLS

Effects of fixation with glutaraldehyde (GA), glutaraldehyde-osmium tetroxide (GA-OsO4), and osmium tetroxide (OsO4) on ion and ATP content, cell volume, vital dye staining, and stability to mechanical and thermal stress were studied in Ehrlich ascites tumor cells (EATC). Among variables investigated were fixation time, fixative concentration, temperature, osmolality of the fixative agent and buffer, total osmolality of the fixative solution, osmolality of the postfixation buffer, and time of postfixation treatment in buffer (Sutherland, R. M., et al. 1967. J. Cell Physiol. 69:185.). Rapid loss of potassium, exchangeable magnesium, and ATP, and increase of vital dye uptake and electrical conductivity occurred with all fixatives studied. These changes were virtually immediate with GA-OsO4 or OsO4 but slower with GA (in the latter case they were dependent on fixative temperature and concentration) (Foot, N. C. 1950. In McClung's Handbook of Microscopical Technique. 3rd edition. 564.). Total fixative osmolality had a marked effect on cell volume with OsO4 but little or no effect with GA or GA-OsO4. Osmolality of the buffer had a marked effect on cell volume with OsO4, whereas with GA or GA-OsO4 it was only significant at very hypotonic buffer osmolalities. Concentration of GA had no effect on cell volume. Osmolality of the postfixation buffer had little effect on cell volume, and duration of fixation or postfixation treatment had no effect with all fixatives. Freezing and thawing or centrifugal stress (up to 100,000 g) had little or no effect on cell volume after all fixatives studied. Mechanical stress obtained by sonication showed that OsO4 alone produced poor stabilization and that GA fixation alone produced the greatest stabilization. The results indicate that rapid membrane permeability changes of EATC follow fixative action. The results are consistent with known greater stabilizing effects of GA on model protein systems since cells were also rendered relatively stable to osmotic stress during fixation, an effect not noted with OsO4. After fixation with GA and/or OsO4 cells were stable to osmotic, thermal, or mechanical stress; this is inconsistent with several earlier reports that GA-fixed cells retain their osmotic properties

Discussion of a physical optics method and its application to absorbing smooth and slightly rough hexagonal prisms

Three different mathematical solutions of a physical optics model for far field diffraction by an aperture due to Karczewski and Wolf are discussed. Only one of them properly describes diffraction by an aperture and can, by applying Babinet's principle, be used to model diffraction by the corresponding plane obstacle, and by further approximation, diffraction by a particle. Studying absorbing scatterers allows a closer investigation of the external diffraction component because transmission is negligible. The physical optics model has been improved on two aspects: (i) To apply the diffraction model based on two-dimensional apertures more accurately to three-dimensional objects, a size parameter dependent volume obliquity factor is introduced, thus reducing the slightly overestimated side scattering computed for three-dimensional objects. (ii) To compensate simplifications in the underlying physical optics diffraction model for two-dimensional apertures [26] a size parameter dependent cross polarisation factor is implemented. It improves cross polarisation for diffraction and reflection by small particle facets. 2D patterns of P 11, –P 12/P 11 and P 22/P 11 and their azimuthal averages for slightly rough absorbing hexagonal prisms in fixed orientation are obtained and compared with results from the discrete dipole approximation. For particle orientations where shadowing is not negligible, improved phase functions are obtained by using a new method where the incident beam is divided into sub-beams with small triangular cross sections. The intersection points of the three sub-beam edges with the prism define the vertices of a triangle, which is treated by the beam tracer as an incidence-facing facet. This ensures that incident facing but shadowed crystal facets or regions thereof do not contribute to the phase functions. The method captures much of the fine detail contained in 2D scattering patterns obtained with DDA. This is important as speckle can be used for characterizing the size and roughness of small particles such as ice crystals.Peer reviewedFinal Accepted Versio

Traceable Coulomb Blockade Thermometry

We present a measurement and analysis scheme for determining traceable thermodynamic temperature at cryogenic temperatures using Coulomb blockade thermometry. The uncertainty of the electrical measurement is improved by utilizing two sampling digital voltmeters instead of the traditional lock-in technique. The remaining uncertainty is dominated by that of the numerical analysis of the measurement data. Two analysis methods are demonstrated: numerical fitting of the full conductance curve and measuring the height of the conductance dip. The complete uncertainty analysis shows that using either analysis method the relative combined standard uncertainty (k = 1) in determining the thermodynamic temperature in the temperature range from 20 mK to 200 mK is below 0.5 %. In this temperature range, both analysis methods produced temperature estimates that deviated from 0.39 % to 0.67 % from the reference temperatures provided by a superconducting reference point device calibrated against the Provisional Low Temperature Scale of 2000.Comment: 11 page

Laser processing of minerals common on asteroids

Asteroid mining and redirection are two trends that both can utilize lasers, one to drill and cut, the other to ablate and move. Yet little is known about what happens when a laser is used to process the types of materials we typically expect to find on most asteroids. To shed light on laser processing of asteroid material, we used a 300-W, pulsed Ytterbium fiber laser on samples of olivine, pyroxene, and serpentine, and studied the process with a high-speed camera and illumination laser at 10 000 frames per second. We also measure the sizes of the resulting holes using X-ray micro-tomography to find the pulse parameters which remove the largest amount of material using the least amount of energy. We find that at these power densities, all three minerals will melt and chaotically throw off spatter. Short, low-power pulses can efficiently produce thin, deep holes, and long, high-power pulses are more energy efficient at removing the most amount of material.Peer reviewe

Beam tracing with diffraction

Laurence Taylor, Evelyn Hesse, Z. Ulanowski, Paul H. Kaye, Antti Penttila, Timo Nousiainen, ‘Beam tracing with diffraction’, poster presented at the 15th Electromagnetic & Light Scattering Conference, Leipzig, Germany, 21-26 June, 2015.Non peer reviewe

Spherical shock experiments with Chelyabinsk meteorite: reflectance spectra changes with increasing shock

Spherical shock experiments produced gradual pressure changes from S4 level up to complete melting. At ~50 GPa peak pressure shock darkening of silicates is observed due to troilite melt penetrating silicate grains associated with reduction in intensity of silicate 1 and 2 µm absorptions. This process stops at higher pressures as partial melting of silicates along grain boundaries isolates troilite melt. Darkening occurs again upon material complete melting. In MIR region, spectral trends are similar, however the reststrahlen silicate bands are still resolved in shock-darkened or impact melt zone

Evaluating CENTURY and Yasso soil carbon models for CO2 emissions and organic carbon stocks of boreal forest soil with Bayesian multi-model inference

We can curb climate change by improved management decisions for the most important terrestrial carbon pool, soil organic carbon stock (SOC). However, we need to be confident we can obtain the correct representation of the simultanous effect of the input of plant litter, soil temperature and water (which could be altered by climate or management) on the decomposition of soil organic matter. In this research, we used regression and Bayesian statistics for testing process-based models (Yasso07, Yasso15 and CENTURY) with soil heterotrophic respiration (Rh) and SOC, measured at four sites in Finland during 2015 and 2016. We extracted climate modifiers for calibration with Rh. The Rh values of Yasso07, Yasso15 and CENTURY models estimated with default parameterization correlated with measured monthly heterotrophic respiration. Despite a significant correlation, models on average underestimated measured soil respiration by 43%. After the Bayesian calibration, the fitted climate modifier of the Yasso07 model outperformed the Yasso15 and CENTURY models. The Yasso07 model had smaller residual mean square errors and temperature and water functions with fewer, thus more efficient, parameters than the other models. After calibration, there was a small overestimate of Rh by the models that used monotonic moisture functions and a small generic underestimate in autumn. The mismatch between measured and modelled Rh indicates that the Yasso and CENTURY models should be improved by adjusting climate modifiers of decomposition or by accounting for missing controls in, for example, microbial growth.Peer reviewe

Greenhouse gas fluxes in a drained peatland forest during spring frost-thaw event

Peer reviewe

ASIME 2018 White Paper. In-Space Utilisation of Asteroids: Asteroid Composition -- Answers to Questions from the Asteroid Miners

In keeping with the Luxembourg government's initiative to support the future use of space resources, ASIME 2018 was held in Belval, Luxembourg on April 16-17, 2018. The goal of ASIME 2018: Asteroid Intersections with Mine Engineering, was to focus on asteroid composition for advancing the asteroid in-space resource utilisation domain. What do we know about asteroid composition from remote-sensing observations? What are the potential caveats in the interpretation of Earth-based spectral observations? What are the next steps to improve our knowledge on asteroid composition by means of ground-based and space-based observations and asteroid rendez-vous and sample return missions? How can asteroid mining companies use this knowledge? ASIME 2018 was a two-day workshop of almost 70 scientists and engineers in the context of the engineering needs of space missions with in-space asteroid utilisation. The 21 Questions from the asteroid mining companies were sorted into the four asteroid science themes: 1) Potential Targets, 2) Asteroid-Meteorite Links, 3) In-Situ Measurements and 4) Laboratory Measurements. The Answers to those Questions were provided by the scientists with their conference presentations and collected by A. Graps or edited directly into an open-access collaborative Google document or inserted by A. Graps using additional reference materials. During the ASIME 2018, first day and second day Wrap-Ups, the answers to the questions were discussed further. New readers to the asteroid mining topic may find the Conversation boxes and the Mission Design discussions especially interesting.Comment: Outcome from the ASIME 2018: Asteroid Intersections with Mine Engineering, Luxembourg. April 16-17, 2018. 65 Pages. arXiv admin note: substantial text overlap with arXiv:1612.0070