Solid Lid Research Articles

The Movement of CO2 Through the Frozen World of Sea Ice

Every winter, a frozen blanket known as sea ice completely covers the Arctic Ocean. For centuries, sea ice has been viewed as a solid lid on the ocean that acts as a boundary to block gases traveling between the ocean and the atmosphere. However, scientific discoveries over recent years have shown that sea ice is more like a sponge, a porous substance that is also home to microscopic life forms. The pores in sea ice are filled with very salty liquid called brine that is rich in carbon dioxide (CO2). These liquid pockets create a network of tubes or channels that move gases like CO2, similar to the way veins and arteries move blood in our bodies. In this article, you will discover how CO2 enters, exits, and is transformed in one of the harshest environments on Earth.

Conjunctival flora growth in intravitreal injection settings

Purpose: To study the conjunctival flora in patients undergoing repeated intravitreal injections. Methods: Prospective observational study. Patients undergoing intravitreal injections were randomized into two groups: 1) preparation with povidone-iodine 5% alone, or 2) preparation with povidone-iodine 5% with Maxitrol eye drops. Our standard injection technique included topical anesthesia, a solid bladed lid speculum, and commercially prepared topical povidone-iodine 5% applied for 2 minutes. Cultures were obtained from the conjunctival cul-de-sac on routine office visits prior to any preparation and immediately after injection. Results: A total of 110 Eyes of 86 patients were enrolled in the study. Fifty-five were irrigated with povidone-iodine 5% only, and 55 were irrigated with a combination of povidone-iodine 5% and Maxitrol drops. Compared with the povidone-iodine only group, the Maxitrol and povidone-iodine group did not lead to a statistically significant reduction in patients with positive cultures after injection, (p=0.19). The most common organism cultured was coagulase-negative staphylococcus; however, Enterococcus, Pseudomonas, Staphylococcus aureus, and Bacillus were also cultured. Thirtyseven percent of organisms were resistant to 4th generation quinolones. No cases of endophthalmitis were recognized. Of the positive cultures, 33% were resistant to over 4 antibiotics tested. Conclusion: In this routine clinical setting, conjunctival antisepsis was difficult to achieve despite the use of topical povidone-iodine with or without Maxitrol. No infectious complications were recognized.

Evaporative loss of moderately volatile metals from the superheated 1849 Ma Sudbury impact melt sheet inferred from stable Zn isotopes

The retention of moderately volatile elements on the growing Earth remains a major uncertainty in models of terrestrial accretion. Large impactors were the main carriers of accreted material but their mutual energetic collisions and impacts onto the Earth also caused chemical fractionation for which limited experimental data exist. The objective of this work was to study several moderately volatile elements in the third-largest impact basin preserved on Earth at Sudbury, Ontario. We conducted a new chemostratigraphic transect (n=41) of Zn isotope ratios and concentrations by analysing melt sheet and basin fill samples. The data were compared to common Pb, Cs, Cd and Sb concentration systematics. Within the crystallised melt sheet there are strong trends in the extent of moderately volatile element deficits, Zn isotope composition (δ66/64ZnJMC-L from 0.18 to 0.47‰) and initial Pb isotope composition. The combined evidence suggests that these trends reflect footwall contamination of a melt sheet that had experienced evaporative Zn-loss of up to 75–80%. Accounting for plausible isotopic signatures of target rocks, the maximum mass-dependent Zn isotope fractionation ε was 0.29 ± 0.04‰ (1 s.d.), which translates to modest fractionation factors α=0.99986 to 0.99975. This is comparable to melt fallout-glass and fused sands from nuclear detonation sites. We attribute the observed Zn loss and isotope fractionation to the formation of the impact melt. The rapid formation of a solid lid of breccias upon seawater ingress may have prevented stronger evaporative loss and isotope fractionation. Within the crater fill, there is an up-stratigraphy increase in Zn isotope variability (δ66/64ZnJMC-L from 0.29 to 1.05‰). Combined with evidence for biogenic reduced C, this suggests sedimentation of authigenic particulates within an enclosed crater sea.In the melt sheet, the Zn-Pb and Rb-Cs pairs experienced different extents of maximum evaporative loss (Pb up to 98.4% vs. Zn 78%; and Cs ∼90% vs. Rb ∼30%). The relative loss pattern could reflect evaporation from superheated silicate melt at ∼1,450°C and 1 atm. Loss from super-liquidus melts formed by bolide impacts could have been a significant process shaping the Earth's volatile and moderately volatile inventory.

On the effect of conducting lid for natural convection in a horizontal fluid layer

In this study, effect of conducting lid attached in the horizontal fluid layer for Rayleigh-Bénard natural convection was discussed. Geometry which was taken into account was horizontal layer of fluid with conducting lid at the bottom. Conducting lid was heated from the bottom wall and the thermal energy was transferred to fluid layer through the solid/fluid interface, and then was cooled down from above. Thermal conductivity ratio varied to investigate the thermal behavior at the solid/fluid interface. Periodic boundary conditions were employed in the horizontal direction to allow lateral freedom for the convection cells. Prior to investigate thermal behavior of fluid layer with conducting lid, pure Rayleigh-Bénard natural convection without conducting body was reproduced. From two-dimensional Rayleigh-Bénard natural convection, an extension of wavelength of circulating roll cell was examined. A two-dimensional solution was obtained using Chebyshev spectral multi-domain methodology for different Rayleigh number at which the thermal behavior was evolved from steady state to chaotic pattern. Three-dimensional pure Rayleigh-Bénard natural convection was calculated from relatively low Rayleigh number such as 4×103 in order to investigate an evolution of thermal plume undergoing a representative zig-zag instability. In order to compare thermal behavior of fluid layer between with- and without conducting lid, effective Rayleigh numbers, Raeff, was introduced and 106 was applied. A solid lid at the bottom affects the flow pattern in that the flow is restricted to increase the dimensionless thermal conductivity. For three-dimensional simulation, periodic boundary condition was also applied along the span-wise direction which was discretized through a Fourier serious expansion with a uniform mesh configuration. For high effective Rayleigh number, thermal flow field was captured by visualizing the three-dimensional vortical structure. The flow behavior at the provided effective Rayleigh number showed a coherent pattern regardless of the magnitude of the thermal conductivity ratio.

Thermal convection in a horizontal layer of fluid with conducting lid at bottom

This study of thermal convection uses the following geometry: a horizontal layer of fluid heated from below of solid lid at bottom and cooled from above. A variety range of thermal conductivity ratio, k is considered to investigate the interface temperature, θi between solid and fluid region. Periodic boundary conditions are employed in the horizontal direction to allow for lateral freedom for the convection cells. A two-dimensional solution for unsteady natural convection is obtained, using an accurate and efficient Chebyshev spectral multi-domain methodology, for different effective Rayleigh numbers, Raeff varying over the range of 104–107. A concept for the effective Rayleigh number is to take into account an effect of existence of solid lid. The solid lid at bottom affects the flow pattern that the flow is restricted to increase of dimensionless thermal conductivity. The root mean square of time- and surface-averaged interface temperature decreases as dimensionless thermal conductivity increases. That is, the lateral motion of circulating cell of flow is fixed to arbitrary position at which the minimum solid temperature is obtained. The analysis has been further extended to three-dimensional geometry with periodic boundary condition. The span-wise direction is discretized by Fourier serious expansion with uniform mesh configuration. The thermal flow field has been captured by visualizing three-dimensional vortical structure. The flow behavior at a provided effective Rayleigh number shows coherent pattern regardless of a magnitude of the thermal conductivity ratio.

Tidal resonance in icy satellites with subsurface oceans

AbstractTidal dissipation is a major heat source for the icy satellites of the giant planets. Several icy satellites likely possess a subsurface ocean underneath an ice shell. Previous studies of tidal dissipation on icy satellites, however, have either assumed a static ocean or ignored the effect of the ice lid on subsurface ocean dynamics. In this study, we examine inertial effects on tidal deformation of satellites with a dynamic ocean overlain by an ice lid based on viscoelasto‐gravitational theory. Although ocean dynamics is treated in a simplified fashion, we find a resonant configuration when the phase velocity of ocean gravity waves is similar to that of the tidal bulge. This condition is achieved when a subsurface ocean is thin (<1 km). The enhanced deformation (increased h2 and k2 Love numbers) near the resonant configuration would lead to enhanced tidal heating in the solid lid. A static ocean formulation gives an accurate result only if the ocean thickness is much larger than the resonant thickness. The resonant configuration strongly depends on the properties of the shell, demonstrating the importance of the presence of a shell on tidal dissipation.

Controlled hydrothermal growth of multi-length-scale ZnO nanowires using liquid masking layers

In this study, we demonstrate a method for creating multi-length-scale ZnO nanowires in a controllable manner on diverse planar and curvilinear substrates by introducing immiscible liquid masking layers (LMLs) above and beneath a nutrient solution used in hydrothermal growth. The confinement of volatile reactants by the LMLs stabilizes the pH, which is an important parameter in determining the shape of the nanowires, to enable growth in a stable manner. The conformal wettability of the LMLs provides freedom in the choice of target substrates and allows for the possibility of mounting spatially moving stages without the use of a specially designed solid lid. Selective growth within the growth zone defined by the LMLs in a dynamic- and/or static-mode can create various types of ZnO nanowires with gradual or terraced length profiles in two- or three-dimensional geometries. For a device application, we developed cylindrical photodetectors with the configuration of Cr/ZnO seed/ZnO nanowires/poly(3-hexylthiophene-2,5-diyl)/poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) to show the ability to spatially modulate the photo-sensitivity by controlled hydrothermal growth of diverse length scales of ZnO nanowires using the LML method.

Vibrations of a circular cylinder submerged in a fluid with a non-homogeneous upper boundary

Results of solving a linear problem on steady vibrations of a horizontal cylinder submerged in a fluid, whose upper boundary is partially closed by a solid lid, whereas the rest of the surface is free, are presented. Multipole and eigenfunction expansion methods are used. Reciprocity relations are derived. Added-mass and damping coefficients and the wave amplitudes on the free surface of the fluid are calculated.

Deuterium trapping in liquid lithium irradiated by deuterium plasma

Liquid lithium was irradiated by deuterium plasma to a low fluence of 10 22 –10 23 D/m 2 , cooled down to room temperature, and then slowly heated. The temperature and release rate were measured during heating. Two plateaus on the temperature–time dependence were observed at 180 °C and 660 °C. The first one corresponds to melting of Li and the second one – either to melting or to decomposition of solid LiD. Features of deuterium release in TDS were interpreted in terms of decomposition of lithium deuterides formed during plasma irradiation.

Deuterium release from lithium irradiated by deuterium plasma

Lithium targets are exposed to deuterium plasma with a fluence of 1022–1023 D/m2 and then heated at a rate of about 5°C/s up to 600°C. Intense deuterium release starts at 400°C. Based on the TDS measurements, it is assumed that deuterium in Li exists in two equilibrium phases: a solid solution and LiD precipitates that start to actively decompose above 400°C.

Kombiniertes Plattenepithelkarzinom und malignes Melanom des Lides

We present a case report of co-existent components of squamous cell carcinoma and malignant melanoma within a solid eyelid tumour in a 74-year-old male. The particular composite of these two malignancies in ocular adnexa is to the best of our knowledge reported for the first time. The histological findings exhibited a solid anterior lid tumour infiltrating the skin and surrounding conjunctiva, as well as the orbicular muscles. The hyper- and parakeratotic keratin-rich squamous cell carcinoma was cytokeratin AE1/AE3 positive, had a slight atypia but an obvious invasion in the depth. Between the squamous cell carcinoma cells were islands of HMB45 and Melan-A positive melanoma cells with slight pigmentation, which demonstrated not only subcutaneous but also intraepithelial invasion.

Numerical analysis of 3D vortical cavity flow

AbstractThe vortical flows of an incompressible fluid in a rectangular three‐dimensional container with a large spanwise aspect ratio driven by a moving solid lid are studied using a combined compact finite difference (CCD) scheme with high accuracy and high resolution. The study focuses on the change of the steady flow structures in the cavity with Reynolds numbers ranging from 100 to 850. The results of the flow in the cavity with a spanwise aspect ratio 6.55 show that several stable closed streamlines localized near the symmetric plane are found at Re ≥500, while a closed stable streamline is found near the side wall at Re ≤300. The change of the flow pattern present in this system affects the diffusion properties in the flow but seems to have no qualitative effect on the global flow properties which include energy dissipation in the cavity. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Isotopic Effects in Solid LiH and LiD at Very Low Temperature

The ground state of the ionic solids LiD and LiH is theoretically studied using the Variational Monte Carlo (VMC) method. Our main focus has been the calculation of relevant properties of the H− and D− ions using a fully quantum approach. In particular, we report results on their kinetic energies, mean-squared displacements, Einstein frequencies, radial distribution functions, and density profiles around the sites. The microscopic results obtained for both isotopes show corrections beyond trivial isotopic effects due to their quantum behavior. Finally, the VMC results are compared with predictions from self consistent average phonon (SCAP) theory at T = 0 K.

Large-Eddy Simulation of Coastal Upwelling Flow

Large-eddy simulations were carried out to study laboratory-scale realizations of coastal upwelling in an annular rotating tank with a sloping bottom. A two-layer stratified fluid was set into rigid body motion with the tank and then driven by the relative rotation of a solid top lid. The simulation code developed in this work was a three-dimensional incompressible Navier-Stokes solver using the message passing interface. The simulation runs were performed on a distributed memory massively parallel computer, namely, the IBM SP2. The simulation results were able to reveal the evolution of the complex upwelling structures in detail. The results were used to compare with and to complement two relevant series of coastal upwelling experiments. A Rayleigh-Taylor type of instability took place in the top inversion layer due to the unstable stratification after establishment of the upwelling front. The primary upwelling front was unstable to azimuthal perturbations and developed large amplitude baroclinic waves. The frontal wave structure consists of cyclone/anticyclone pairs. Whether cyclonic eddies containing the lower-layer fluid pinch off from the front depends on the θ* value. The non-dimensional parameter θ*=g′h 0/u * fλs, which was first introduced by Narimousa and Maxworthy, combines the effects of stratification, rotation and surface stress and can be used to characterize the upwelling flow field. Our studies show that the frontal instabilities are much more intense and the upwelling front itself displays strong unsteadiness and cyclonic eddies containing the lower-layer fluid pinch off from the front when θ* is significantly less than 5.8. For θ*=5.8, the frontal instabilities are less intense and no pinched-off process is observed. To separate these regimes, a critical value of θ* of about 5.4 is consistent with Narimousa and Maxworthy's results.

Nonlinear Propagation of Wave Packets for Near-Critical Wave Numbers in a Liquid that Is Piecewise Nonuniform with Depth

This is a study of the evolution of finite amplitude wave packets at the contact surface between a semi-infinite liquid medium and a liquid located above it near a solid lid. The limiting case of near-critical wave numbers for propagation of wave packets in the liquid system is discussed. Perturbation expansions are obtained for the deviation of the contact surface from its unperturbed position and for wave numbers near the critical value. This is compared with the solution for the analogous limiting cases of one or two semi-infinite liquids. A version in which the wave numbers are far from critical is examined.

The Bénard-Marangoni-Instability in small circular containers under microgravity: Experimental results

During the 12-minute microgravity-phase of the sounding rocket MAXUS 2 a 3.0-mm-thick layer of 10 cSt silicone oil was heated from below to generate the Bénard-Marangoni-Instability (BMI) due to surface tension forces in the free oil surface. The layer was partly covered with a solid lid from Polycarbonate (LEXAN) with circular openings with diameter D for a flat free oil surface with aspect ratio A= D/d= 1.0, 1.5, 2.0, 3.0, 4.0, 8.0, 10.0. The flow structure in these 7 “containers” with liquid lateral walls was visualized by aluminum flakes which orient parallel to the flow direction. The BMI was clearly observed under microgravity, and the onset of convection as function of A was measured and compared to theory and ground-based experiments, of which the latter suffer under the additional action of buoyancy. Beautiful and sharp convection patterns have been observed in the containers A = 4, 8, and 10. At the end of the microgravity time an instability of the boundary between two convection cells in the container with A= 4 was observed (switching between modes (2,1) and (1,1)).

Plastic flow produced by single ion impacts on metals

Single ion impacts have been observed using in situ transmission electron microscopy and video recording with a time resolution of 33 ms. Gold was irradiated at 50 K and room temperature. Single ion impacts produce holes, modify existing holes, and extrude material into the initial specimen hole and holes formed by other ion impacts. The same behavior is observed at both temperatures. At both temperatures, ion impacts result in craters and ejected material. Ion impacts produce more small craters than large ones for all ion masses, while heavier mass ions produce more and larger craters than lighter mass ions. This comparison is affected by the ion energy. As the energy of an ion is increased, the probability for deposition near the surface decreases and fewer craters are formed. For a given ion mass, crater production depends on the probability for displacement cascade production in the near surface region. Craters and holes are stable at room temperature, however, ion impacts near an existing crater may cause flow of material into the crater either reshaping or annihilating it. Holes and craters result from the explosive outflow of material from the molten zone of near-surface cascades. The outflow may take the form of molten material, a solid lid or an ejected particle. The surface is a major perturbation on displacement cascades resulting from ion impacts.

SiC formation and influence on the morphology of polycrystalline silicon thin films on graphite substrates produced by zone melting recrystallization

Polycrystalline silicon thin films for photovoltaic applications are produced by a zone melting recrystallization process by means of a line electron beam. During this process carbon atoms of the graphite substrate dissolve in the silicon melt. Because of the high temperatures in the molten silicon, molecular silicon carbide is formed. It crystallizes at the melt interfaces to the vacuum and the graphite substrate by a heterogeneous nucleation. Cubic SiC crystals ( β-SiC) grow up to sizes of 700 nm. The morphology of the silicon layer is significantly influenced by the crystals at the Si–vacuum interface, since they assemble in a net-like structure. In this solid lid cracks may form followed by a deformation of the surface (clod shape). Utilizing this effect e.g. the surface roughness of the polycrystalline silicon thin film can be reduced and favorable conditions are obtained for a succeeding liquid phase epitaxy process (LPE) to grow the active layer of the cell.

Two-dimensional problem of a uniform flow of a two-layer fluid of finite depth past a circular cylinder

The linear steady problem of an irrotational uniform flow past a horizontal circular cylinder located in the upper or in the lower layer of a two-layer fluid is solved by the multipole-expansion method. The flow is perpendicular to the axis of the cylinder. The fluid is assumed to be inviscid and incompressible, and the flow in each layer is assumed to be potential. The upper layer can be bounded by a free surface or a solid lid, and the lower layer by a rigid horizontal bottom.

SiC formation and influence on the morphology of polycrystalline silicon thin films on graphite substrates produced by zone melting recrystallization

Polycrystalline silicon thin films for photovoltaic applications are produced by a zone melting recrystallization process by means of a line electron beam. During this process carbon atoms of the graphite substrate dissolve in the silicon melt. Because of the high temperatures in the molten silicon, molecular silicon carbide is formed. It crystallizes at the melt interfaces to the vacuum and the graphite substrate by a heterogeneous nucleation. Cubic SiC crystals ( β-SiC) grow up to sizes of 700 nm. The morphology of the silicon layer is significantly influenced by the crystals at the Si–vacuum interface, since they assemble in a net-like structure. In this solid lid cracks may form followed by a deformation of the surface (clod shape). Utilizing this effect e.g. the surface roughness of the polycrystalline silicon thin film can be reduced and favorable conditions are obtained for a succeeding liquid phase epitaxy process (LPE) to grow the active layer of the cell.