VIS-NIR/SWIR Spectral Properties of H2O Ice Depending on Particle Size and Surface Temperature

Laboratory measurements were performed to study the spectral signature of H2O ice between 0.4 and 4.2 µm depending on varying temperatures between 70 and 220 K. Spectral parameters of samples with particle sizes up to ~1360 µm, particle size mixtures, and different particle shapes were analyzed. The band depth (BD) of the major H2O-ice absorptions at 1.04, 1.25, 1.5, and 2 µm offers an excellent indicator for varying particle sizes in pure H2O ice. The spectral changes due to temperature rather, but not exclusively, affect the H2O-ice absorptions located at 1.31, 1.57, and 1.65 µm and the Fresnel reflection peaks at 3.1 and 3.2 µm, which strongly weaken with increasing temperature. As the BDs of the H2O-ice absorptions at 1.31, 1.57, and 1.65 µm increase, the band centers (BCs) of the H2O-ice absorptions at 1.25 and 1.5 µm slightly shift to shorter wavelengths. However, the BCs of the strong H2O-ice absorptions can also be affected by saturation in the case of large particles. The collected spectra provide a useful spectral library for future investigations of icy satellites such as Ganymede and Callisto, the major targets of ESA’s JUICE mission.

The Trend of Permeability of Loess in Yili, China, under Freeze–Thaw Cycles and Its Microscopic Mechanism

Loess landslides induced by the freeze–thaw effect frequently occur in Yili, China. Freeze–thaw cycles cause indelible changes in the soil microstructure, affecting its permeability. This study investigated the impacts of freeze–thaw cycles on the permeability of Yili loess using permeability tests on undisturbed (virgin, in situ) and remolded loess samples taken before and after freeze–thaw cycles. Scanning electron microscopy and nuclear magnetic resonance techniques were utilized to investigate the microscopic mechanism of the freeze–thaw process on the loess. Grey relation analysis (GRA) was employed to analyze the correlation between macroscopic permeability and microscopic parameters (maxi. radius, eccentricity, fractal dimension, directional probability entropy, and porosity). The results revealed that the permeability and all the microstructure parameters have roughly shown the same trend: “fluctuation–towards equilibrium–stability”. Firstly, the permeability coefficients of original and remolded loess experienced three and two peaked–trends, respectively, before 30 freeze–thaw cycles. The trends eventually stabilized within 30–60 freeze–thaw cycles. Increased number of freeze–thaw cycles disintegrated large particles in undisturbed loess into medium–sized particles, and particle shapes became more uncomplicated. Medium–sized particles in the remolded loess agglomerated to larger particles with more complex shapes. Furthermore, the overall porosity of the originally undisturbed loess decreased, and large and medium–sized pores transformed into small pores and micropores. In contrast, the overall porosity of remolded loess increased. Finally, the results revealed that permeability coefficients of the undisturbed and remolded loess became closely related with eccentricity and porosity, respectively. This study provides a reference for preventing and governing the loess landslides induced by the freeze–thaw cycles and permeability reduction in construction on loess in seasonally frozen areas in Yili.

Applied Geology of Wellington Rocks for Aggregate and Concrete

<p>This study was initiated to examine geological aspects of Wellington greywacke-suite rocks in relation to their end use as an engineering material - aggregate, particularly for concrete. An attempt has been made to map (at least in part), identify and categorise rocks for quarrying in the Wellington region, to evaluate and quantify their properties as aggregates and to appraise their qualities in concrete - in short to equate rock geology to aggregate and concrete performance as a tool for resource management. Study of bedding 1ed to a classification into three lithofacies and some 70 representative samples were examined petrographically. For engineering purposes, Wellington rocks may be divided into two categories, greywacke and argillite, each having separate and distinct mineralogies and chemistries which do not alter significantly between lithofacies. Greywacke is coarser and may be distinguished from argillite texturally at a mean grain size of 5 phi (0.031 mm). Rock properties, in particular strength, modulus, density, hardness and degradation tendencies, are linked directly or indirectly with mean grain size. Argillites, though more dense, are generally weaker, softer, less elastic and degrade more readily than greywackes, the latter property being readily assessed from a newly devised test based on the destruction of chlorite by hydrochloric acid. As aggregates, greywackes produce similar particle shapes irrespective of grading. Argillites, which are generally more angular, produce concretes which are more difficult to work. Physical properties of aggregate, inherently those of its parent rock, are reflected in concrete made from it. The possibility of laumontite promoting cement alkali-silicate reaction is obviated by the mode of occurrence of minerals within the rock. Although argillite aggregates are unsuitable in certain environments and return lower strength in concrete than do greywacke aggregates, they still have a place in low strength concrete applications.</p>

Applied Geology of Wellington Rocks for Aggregate and Concrete

<p>This study was initiated to examine geological aspects of Wellington greywacke-suite rocks in relation to their end use as an engineering material - aggregate, particularly for concrete. An attempt has been made to map (at least in part), identify and categorise rocks for quarrying in the Wellington region, to evaluate and quantify their properties as aggregates and to appraise their qualities in concrete - in short to equate rock geology to aggregate and concrete performance as a tool for resource management. Study of bedding 1ed to a classification into three lithofacies and some 70 representative samples were examined petrographically. For engineering purposes, Wellington rocks may be divided into two categories, greywacke and argillite, each having separate and distinct mineralogies and chemistries which do not alter significantly between lithofacies. Greywacke is coarser and may be distinguished from argillite texturally at a mean grain size of 5 phi (0.031 mm). Rock properties, in particular strength, modulus, density, hardness and degradation tendencies, are linked directly or indirectly with mean grain size. Argillites, though more dense, are generally weaker, softer, less elastic and degrade more readily than greywackes, the latter property being readily assessed from a newly devised test based on the destruction of chlorite by hydrochloric acid. As aggregates, greywackes produce similar particle shapes irrespective of grading. Argillites, which are generally more angular, produce concretes which are more difficult to work. Physical properties of aggregate, inherently those of its parent rock, are reflected in concrete made from it. The possibility of laumontite promoting cement alkali-silicate reaction is obviated by the mode of occurrence of minerals within the rock. Although argillite aggregates are unsuitable in certain environments and return lower strength in concrete than do greywacke aggregates, they still have a place in low strength concrete applications.</p>

Beyond Janus Geometry: Characterization of Flow Fields Around Nonspherical Photocatalytic Microswimmers

Catalytic microswimmers that move by a phoretic mechanism in response to a self-induced chemical gradient are often obtained by the design of spherical janus microparticles, which suffer from multi-step fabrication and low yields. Approaches such as irregular particle shapes, local excitation or intrinsic asymmetry are on the rise to facilitate manufacturing, but the effects on the generation of motion remain poorly understood. In this work, single crystalline BiVO4 microswimmers are presented that rely on a strict inherent asymmetry of charge-carrier distribution under illumination. The origin of the asymmetrical flow pattern is elucidated becauseof the high spatial resolution of measured flow fields around pinned BiVO4 colloids. As a result the flow from oxidative to reductive particle sides was confirmed. Distribution of oxidation and reduction reactions suggests a dominant self-electrophoretic motion mechanism with a source quadrupole as the origin of the induced flows. It is shown that the symmetry of the flow fields is broken by self-shadowing of the particles and synthetic surface defects that impact the photocatalytic activity of the microswimmers. The results demonstrate the complexity of symmetry breaking in nonspherical microswimmers and are leading the way towards understanding ofpropulsion mechanisms of phoretic colloids of various shapes.

Systematic morphological characterization of sub-visible particles generated from cardiovascular devices using dynamic image analysis

The assessment of particulate matter generated during a simulated use is requested by international standards for approval of cardiovascular devices. The particle suspension was generated during a simulated use test procedure of a commercially available coronary stent delivery system and analyzed by Dynamic image analysis (DIA) using FlowCAM 8000. Four parameters were analyzed: the diameter, the aspect ratio value, the circularity and the intensity. The results revealed that 53% of the particles were larger than 25 μm. The particle shapes were inhomogeneous with a wide ranging aspect ratio of 0.03 to 0.95. Around 83% had an intensity value of more than 140 grey scales and appeared translucent.

Comparative Study of Synthesis Parameters of Nanoporous Titania Particles to Improve Structural Properties and Photocatalytic Activity

Nanoporous materials have been widely used in many fields. However, their synthesis with uniform particle shapes, pore sizes, pore volumes, and surface areas remains a considerable challenge. Thus, choosing a suitable controllable method for synthesizing nanoporous materials is crucial to obtain appropriate properties. Herein, nanoporous titania particles (NPTPs) were prepared via the hydrothermal. This study investigated how the synthesis parameters such as the type of chelating agent, the hydrolysis method, and the drying technique affected the properties of NPTPs. The synthesis NPTPs were characterized by XRD, FESEM, and BET. The results demonstrated that when acetylacetone (ACAC) (as the chelating agent), the spray-hydrolysis (SH) method, and the freeze-drying (FD) technique were used, NPTPs achieved a more uniform particle shape, a smaller particle size, a larger pore size, a larger pore volume, and a higher surface area. Ultimately, the photocatalytic degradation (PCD) of methylene blue (MB) was examined using improved NPTPs.

The Degree of Linear Polarization for Suspended Particle Fields from Diverse Natural Waters

The Degree of Linear Polarization (DoLP) for unperturbed particle fields in waters from six diverse regions around the globe was measured with the custom Multi-Angle Scattering Optical Tool (MASCOT). DoLP here is defined as the ratio of two elements of Mueller scattering matrix, i.e., -M12/M11. Field sites covered inland waters, coastal oceans and open oceans, including both ocean color Case I and II water types. The angular shape of the measured particulate DoLP was analyzed in detail for each field site and for the ensemble average. Three parameters used to quantitatively characterize DoLP shape were the symmetry with respect to 90°, peak magnitude, and peak angle of measured DoLP angular curve. Vertical profiles of particulate DoLP were analyzed with maximum recorded depth of 111 m. Converse to Rayleigh scatterers, we found measured particulate DoLPs were not symmetric with respect to 90°. On average, DoLP peaks were shifted slightly toward larger angles, with most falling between estimated values of 90° and 95°. All particulate DoLP peak magnitudes generally varied within [0.6, 0.9]. Lorenz-Mie (homogeneous sphere) light scattering theory was used to construct a new inversion for bulk particulate refractive index from a lookup table based on DoLP and spectral attenuation measurements. We compared the Mie-DoLP-based particulate refractive index retrieval with the backscattering-based model from (Twardowski et al., J. Geophys. Res., 2001, 106(C7), 14,129–14,142). Particulate refractive index retrieved with the two models were in some cases comparable. At two of the six field sites we saw good agreement between the two models, whereas at another two field sites we observed large discrepancies between the two models. Further investigation on the choice of the modeled particle shapes and compositions may improve this retrieval approach. Results are compatible with previous studies on DoLPs in natural waters and comprehensive observations are provided on the particulate DoLP angular shape, vertical profile and global distributions that are important for future vector radiative transfer simulations. This study is relevant to future PACE polarimeters and associated remote retrieval of oceanic particle composition using polarimetry.

Influence of Pyrolysis Parameters Using Microwave toward Structural Properties of ZnO/CNS Intermediate and Application of ZnCr2O4/CNS Final Product for Dark Degradation of Pesticide in Wet Paddy Soil

Pesticide is a pollution problem in agriculture. The usage of ZnCr2O4/CNS and H2O2 as additive in liquid fertilizer has potency for catalytic pesticide degradation. Colloid condition is needed for easy spraying. Rice husk and sawdust were used as carbon precursor and ZnCl2 as activator. The biomass–ZnCl2 mixtures were pyrolyzed using microwave (400–800 W, 50 min). The products were dispersed in water by blending then evaporated to obtain ZnO/CNS. The composites were reacted with KOH, CrCl3·6H2O, more ZnCl2, and little water by microwave (600 W, 5 min). The ZnCr2O4/CNS and H2O2 were used for degradation of buthylphenylmethyl carbamate (BPMC) in wet deactivated paddy soil. TOC was measured using TOC meter. The FTIR spectra of the ZnO/CNS composites indicated the completed carbonization except at 800 W without ZnCl2. The X-ray diffractograms of the composites confirmed ZnO/CNS structure. SEM images showed irregular particle shapes for using both biomass. ZnCr2O4/CNS structure was confirmed by XRD as the final product with crystallite size of 74.99 nm. The sawdust produced more stable colloids of CNS and ZnO/CNS composite than the rice husk. The pyrolysis without ZnCl2 formed more stable colloid than with ZnCl2. The ZnCr2O4/CNS from sawdust gave better dark catalytic degradation of BPMC than from rice husk, i.e., 2.5 and 1.6 times larger for 400 and 800 W pyrolysis, respectively.