bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modeling of Phosphate Ion Transfer to the Surface of Osteoblasts under Normal Gravity and Simulated Microgravity Conditions
Authors: MUKUNDAKRISHNAN KARTHIK , AYYASWAMY PORTONOVO S. , RISBUD MAKARAND , HU HOWARD H. , SHAPIRO IRVING M. 
Published: January 2005

Abstract:We have modeled the transport and accumulation of phosphate ions at the remodeling site of a trabecular bone consisting of osteoclasts and osteoblasts situated adjacent to each other in straining flows. Two such flows are considered; one corresponds to shear levels representative of trabecular bone conditions at normal gravity, the other corresponds to shear level that is representative of microgravity conditions. The latter is evaluated indirectly using a simulated microgravity environment prevailing in a rotating wall vessel bioreactor (RWV) designed by NASA. By solving the hydrodynamic equations governing the particle motion in a RWV using a direct numerical simulation (DNS) technique, the shear stress values on the surface of the microcarriers are found. In our present species transfer model, osteoclasts release phosphate ions (Pi) among other ions at bone resorption sites. Some of the ions so released are absorbed by the osteoblast, some accumulate at the osteoblast surface, and the remainder are advected away. The consumption of Pi by osteoblasts is assumed to follow Michaelis‐Menten (MM) kinetics aided by a NaPi cotransporter system. MM kinetics views the NaPi cotransporter as a system for transporting extracellular Pi into the osteoblast. Our results show, for the conditions investigated here, the net accumulation of phosphate ions at the osteoblast surface under simulated microgravity conditions is higher by as much as a factor of three. Such increased accumulation may lead to enhanced apoptosis and may help explain the increased bone loss observed under microgravity conditions.image
Ground‐Based Diffusion Experiments on Liquid Sn‐In Systems Using the Shear Cell Technique of the Satellite Mission Foton‐M1
Authors: SUZUKI SHINSUKE , KRAATZ KURT‐HELMUT , FROHBERG GÜNTER 
Published: January 2005

Abstract: This study reported in this paper was aimed at testing the shear cell that was developed for the satellite mission Foton‐M1 to measure diffusion coefficients in liquid metals under microgravity (μg)‐conditions. Thick Layer diffusion experiments were performed in the system Sn90In10 versus Sn under 1 g‐conditions. For this system several μg‐diffusion results are available as reference data. This combination provides a low, but sufficiently stable, density layering throughout the entire experiment, which is important to avoid buoyancy‐driven convection. The experimental results were corrected for the influences of the shear‐induced convection and mixing after the final shearing, both of which are typical for the shear cell technique. As the result, the reproducibility and the reliability of the diffusion coefficients in the ground‐based experiments were within the limits of error of μg‐data. Based on our results we discuss the necessary conditions to avoid buoyancy‐driven convection.
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Microgravity Experiments on Phase Change of Self‐Rewetting Fluids
Authors: ABE YOSHIYUKI , IWASAKI AKIRA , TANAKA KOTARO 
Published: January 2005

Abstract:A series of microgravity experiments on self‐rewetting fluids has been conducted at the 10‐second drop shaft of the Japan Microgravity Center (JAMIC). In all the experiments, 1.5 wt% of 1‐butanol aqueous solution were employed as a self‐rewetting fluid. The objective of the first experiment was to observe the boiling behavior of two‐dimensional adjacent dual vapor bubbles with the aid of a two‐wavelength interferometer and tracer particles. A significant difference was observed between a self‐rewetting fluid and a normal fluid (CFC‐113 in this experiment) in bubble interaction and flow developed along vapor/bubble interface. The second experiment focused on the flow at the bubble/heater contact area and around the three‐phase interline, visualized with tracer particles. Differing behavior among three fluids, 1‐butanol aqueous solution, CFC‐113, and ethanol aqueous solution, was observed. The last microgravity experiment was a demonstration of wickless heat pipes containing three different fluids as a working fluid, 1‐butanol aqueous solution, water, and ethanol aqueous solution. The temperature variation of working fluid in the heat pipe was monitored, and the liquid flow returning from the condensation region to the evaporation region was visualized by tracer particles. In addition to microgravity experiments, the performance of conventional heat pipes with 1‐butanol aqueous solution was evaluated on the ground, and compared with water heat pipes. Our preliminary results are presented.image
Experimental Study of a Constrained Vapor Bubble Fin Heat Exchanger in the Absence of External Natural Convection
Authors: BASU SUMITA , PLAWSKY JOEL L. , WAYNER PETER C. 
Published: January 2005

Abstract: In preparation for a microgravity flight experiment on the International Space Station, a constrained vapor bubble fin heat exchanger (CVB) was operated both in a vacuum chamber and in air on Earth to evaluate the effect of the absence of external natural convection. The long‐term objective is a general study of a high heat flux, low capillary pressure system with small viscous effects due to the relatively large 3 × 3 × 40 mm dimensions. The current CVB can be viewed as a large‐scale version of a micro heat pipe with a large Bond number in the Earth environment but a small Bond number in microgravity. The walls of the CVB are quartz, to allow for image analysis of naturally occurring interference fringes that give the pressure field for liquid flow. The research is synergistic in that the study requires a microgravity environment to obtain a low Bond number and the space program needs thermal control systems, like the CVB, with a large characteristic dimension. In the absence of natural convection, operation of the CVB may be dominated by external radiative losses from its quartz surface. Therefore, an understanding of radiation from the quartz cell is required. All radiative exchange with the surroundings occurs from the outer surface of the CVB when the temperature range renders the quartz walls of the CVB optically thick (λ > 4 microns). However, for electromagnetic radiation where λ < 2 microns, the walls are transparent. Experimental results obtained for a cell charged with pentane are compared with those obtained for a dry cell. A numerical model was developed that successfully simulated the behavior and performance of the device observed experimentally.
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Convection in Containerless Processing
Authors: HYERS ROBERT W. , MATSON DOUGLAS M. , KELTON KENNETH F. , ROGERS JAN R. 
Published: January 2005

Abstract: Different containerless processing techniques have different strengths and weaknesses. Applying more than one technique allows various parts of a problem to be solved separately. For two research projects, one on phase selection in steels and the other on nucleation and growth of quasicrystals, a combination of experiments using electrostatic levitation (ESL) and electromagnetic levitation (EML) is appropriate. In both experiments, convection is an important variable. The convective conditions achievable with each method are compared for two very different materials: a low‐viscosity, high‐temperature stainless steel, and a high‐viscosity, low‐temperature quasicrystal‐forming alloy. It is clear that the techniques are complementary when convection is a parameter to be explored in the experiments. For a number of reasons, including the sample size, temperature, and reactivity, direct measurement of the convective velocity is not feasible. Therefore, we must rely on computation techniques to estimate convection in these experiments. These models are an essential part of almost any microgravity investigation. The methods employed and results obtained for the projects levitation observation of dendrite evolution in steel ternary alloy rapid solidification (LODESTARS) and quasicrystalline undercooled alloys for space investigation (QUASI) are explained.
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Active Electrostatic Control of Liquid Bridge Dynamics and Stability
Authors: THIESSEN DAVID B. , WEI WEI , MARSTON PHILIP L. 
Published: January 2005

Abstract: Stabilization of cylindrical liquid bridges beyond the Rayleigh‐Plateau limit has been demonstrated in both Plateau‐tank experiments and in short‐duration low gravity on NASA KC‐135 aircraft using an active electrostatic control method. The method controls the (2,0) capillary mode using an optical modal‐amplitude detector and mode‐coupled electrostatic feedback stress. The application of mode‐coupled stresses to a liquid bridge is also a very useful way to study mode dynamics. A pure (2,0)‐mode oscillation can be excited by periodic forcing and then the forcing can be turned off to allow for a free decay from which the frequency and damping of the mode is measured. This can be done in the presence or absence of feedback control. Mode‐coupled feedback stress applied in proportion to modal amplitude with appropriate gain leads to stiffening of the mode allowing for stabilization beyond the Rayleigh‐Plateau limit. If the opposite sign of gain is applied the mode frequency is reduced. It has also been demonstrated that, by applying feedback in proportion to the modal velocity, the damping of the mode can be increased or decreased depending on the velocity gain. Thus, both the mode frequency and damping can be independently controlled at the same time and this has been demonstrated in Plateau‐tank experiments. The International Space Station (ISS) has its own modes of oscillation, some of which are in a low frequency range comparable to the (2,0)‐mode frequency of typical liquid bridges. In the event that a vibration mode of the ISS were close to the frequency of a capillary mode it would be possible, with active electrostatic control, to shift the capillary‐mode frequency away from that of the disturbance and simultaneously add artificial damping to further reduce the effect of the g‐jitter. In principle, this method could be applied to any fluid configuration with a free surface.
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A Microtexture Study of Palygorskite-Rich Sediments from the Hawthorne Formation, Southern Georgia, by Transmission Electron Microscopy and Atomic Force Microscopy
Authors: Krekeler Mark P. S. , Guggenheim Stephen , Rakovan John 
Published: January 2005

AbstractA microtexture analysis by TEM and AFM of palygorskite deposits from the Hawthorne Formation, southern Georgia is given. Palygorskite is the dominant mineral comprising an average of 65–70% of the sample volume with smaller volumes of smectite, illite and kaolinite. Morphologic observations indicate that the palygorskite formed in an unconfined environment, such as in the water column or in open-pore space. Some palygorskite textures appear to be secondary growths filling voids. An unusual texture is observed where smectite or illite-smectite (Reichweite, R = 0) form epitaxially on detrital illite and kaolinite particles. Oxides of Fe and Ti are common, and authigenic cassiterite is present but rare. Apatite is a common trace mineral in these sediments and occurs in a variety of textures. Apatite occurs as clusters which are believed to be small fecal pellets. These clusters have been partially dissolved and recrystallized and the crystals in the clusters are 50–100 µm in diameter. Other apatite crystals occur either as single crystals or in clusters that are not associated with fecal pellets.The textural data of this study suggest that there was an evolving and complex mineralogical and geochemical system during and after deposition of the palygorskite deposits in the Hawthorne. The epitaxial overgrowths of smectite on detrital illite and kaolinite particles indicate an intermittent stratified water column occurring in the system. Freshwater was introduced into the system from the northeast of the Apalachicola embayment and overrode more saline water in the southwest portion of the embayment. The results of this study are consistent with previous environmental interpretations and provide additional details.
Progressive Stages in the Formation of Kaolin Minerals of Different Morphologies in the Weathering of Plagioclase
Authors: Papoulis Dimitris , Tsolis-Katagas Panayota , Katagas Christos 
Published: January 2005

AbstractHalloysite and kaolinite occur in gneissic weathering profiles developed under a temperate climate in the Leucogia area of NE Greece. X-ray diffraction analyses of samples from three profiles of partially weathered gneisses have revealed that kaolinite becomes more abundant than halloysite with increasing intensity of the decomposition processes. To resolve the genetic relationship between halloysite and kaolinite, microtextures were examined by scanning electron microscopy using polished thin-sections and freshly exposed fracture surfaces, and their chemical compositions were determined using an analytical scanning electron microscope fitted with energy dispersive and wavelength dispersive spectrometers. Different morphological forms of halloysite and kaolinite were detected within the same rock mass. In the earliest stage of weathering, spheroidal aggregates consisting of microcrystalline halloysite are formed on the plagioclase surface. With progressive weathering, spheroidal halloysite converts to tubular halloysite. As weathering advances, tubular halloysite converts to platy halloysite, which in turn converts to kaolinite. Halloysite and kaolinite may coexist in the upper parts of the profiles. Electron microprobe analyses of spheroidal, tubular and platy halloysite and kaolinite show that the chemical composition of the various forms indicate a progressive Fe enrichment and Al depletion with advancing kaolinization, from VIFe0.08VIAl3.70 a.p.f.u. in spheroidal halloysite through VIFe0.29VIAl3.50 in platy halloysite to VIFe0.53VIAl3.32 in newly formed kaolinite. Final-stage, book-type kaolinite approaches its ideal chemical composition (VIFe0.04VIAl3.95). The mineralogy and composition of the kaolin minerals and the development of the various morphological forms of halloysite and kaolinite in different parts of the profiles are attributed to the chemistry of the ambient solutions. However, other physical and microenvironmental conditions (e.g. time and space available) also seem to have strong influence on the precipitation processes producing the morphological variations.
Weathering of Soils in Alpine Areas as Influenced by Climate and Parent Material
Authors: Egli Markus , Mirabella Aldo , Mancabelli Alessandro , Sartori Giacomo 
Published: January 2005

AbstractTwo soil sequences in northern Italy (Val di Fiemme and Val Genova) along an elevational gradient ranging from moderate (950 m a.s.l.) to high alpine (2440 m a.s.l.) climate zones were investigated with respect to element losses (Ca, Mg, K, Na, Fe, Al, Si, Mn) and development of clay minerals. Soils formed on paleo-rhyolitic parent material in Val di Fiemme and on tonalitic-granodioritic morainic material in Val Genova. All the soils have a similar age (∼12,000 y) and have been classified as Podzols. The soils are very acid and the pH values tend to increase with decreasing altitude. Podzolization processes were most intense in the range of the subalpine forest up to the timberline (1400–1900 m above sea-level (a.s.l.)). Element leaching was greatest in this range and weathering rates decrease with both higher and lower altitudes. Due to the different lithologies and precipitations between the two valleys, the total amount of chemical weathering was slightly different, although the same trends with altitude could be observed. Imogolite-type materials (ITM) are generally of minor importance. Greater concentrations of ITM were observed in the Bhs or Bs horizons of the Episkeleti-Entic Podzols at the lower altitudes. Iron eluviation was similar in all Podzols while larger amounts of eluviated Al were detected in Val Genova. The pattern of smectite distribution along the climosequences had similarities to the trend of cation losses. The largest amount of low-charge expandable minerals seems to exist in the range of the subalpine forest up to the timberline. The development of clay minerals with a smaller layer charge was more advanced in Podzols on rhyolitic material where smectite could be detected in the Bhs and Bs horizon. Parent material influenced chemical weathering in the soils along the two climosequences and essentially determined the degree of weathering and the formation of clay minerals.
Copper Sorption Mechanisms on Smectites
Authors: Strawn Daniel G. , Palmer Noel E. , Furnare Luca J. , Goodell Carmen , Amonette James E. , Kukkadapu Ravi K. 
Published: January 2005

AbstractDue to the importance of clay minerals in metal sorption, many studies have attempted to derive mechanistic models that describe adsorption processes. These models often include several different types of adsorption sites, including permanent charge sites and silanol and aluminol functional groups on the edges of clay minerals. To provide a basis for development of adsorption models it is critical that molecular-level studies be done to characterize sorption processes. In this study we conducted X-ray absorption fine structure (XAFS) and electron paramagnetic resonance (EPR) spectroscopic experiments on copper (II) sorbed on smectite clays using suspension pH and ionic strength as variables. At low ionic strength, results suggest that Cu is sorbing in the interlayers and maintains its hydration sphere. At high ionic strength, Cu atoms are excluded from the interlayer and sorb primarily on the silanol and aluminol functional groups of the montmorillonite or beidellite structures. Interpretation of the XAFS and EPR spectroscopy results provides evidence that multinuclear complexes are forming. Fitting of extended X-ray absorption fine structure spectra revealed that the Cu-Cu atoms in the multinuclear complexes are 2.65 Å apart, and have coordination numbers near one. This structural information suggests that small Cu dimers are sorbing on the surface. These complexes are consistent with observed sorption on mica and amorphous silicon dioxide, yet are inconsistent with previous spectroscopic results for Cu sorption on montmorillonite. The results reported in this paper provide mechanistic data that will be valuable for modeling surface interactions of Cu with clay minerals, and predicting the geochemical cycling of Cu in the environment.
Adsorption of Poly(Vinyl Alcohol) on Montmorillonite
Authors: de Bussetti Silvia G. , Ferreiro Eladio A. 
Published: January 2005

AbstractThe adsorption of poly(vinyl alcohol) (PVA) on montmorillonites saturated with calcium (Ca-Mt) and sodium (Na-Mt) as a function of the pH value and PVA concentration in aqueous solution was studied. Owing to the binding effect of the bivalent cation, the adsorption of PVA on Ca-Mt decreases as the pH of the suspension increases, whereas adsorption on Na-Mt is unaffected by the suspension pH. The adsorption maximum of PVA (pH 6) on Ca-Mt was 151.2 mg of PVA g−1 of clay, which is considerably lower than that on Na-Mt (496.2 mg g−1). These adsorption data coincide with the basal spacings obtained for the clays: 1.72 and 2.26 nm for Ca-Mt and Na-Mt, respectively. Sodium permits a greater separation between the clay laminae than calcium, but in both clays the presence of the polymer gives rise to a material in which PVA is intercalated between the laminae and is also adsorbed on the external surface. Adsorption is a slow process and is irreversible in both clays.
Sorption of Isoxaflutole and DKN on Organoclays
Authors: Carrizosa Maria Jose , Rice Pamela J. , Koskinen William C. , Carrizosa Ignacio , del Hermosin Maria Carmen 
Published: January 2005

AbstractSorption of the herbicide isoxaflutole and its main degradate, diketonitrile (DKN), to natural clays, SAz-1, SWy-2 and SHCa-1, and the organoclay derivatives (octadecylammonium (ODA) and hexadecyltrimethylammonium (HDTMA)) of these clays was investigated. Isoxaflutole hydrolysis to DKN was too rapid in aqueous solutions with organoclays to characterize sorption. No measurable DKN sorption was observed for the natural clays. Sorption of DKN was greater on organoclays with an interlayer paraffin-like complex that were prepared from the high-charge SAz-1 clay than on organoclays with a bilayer or monolayer interlayer complex prepared using lower-charge SWy-2 or SHCa-1 clays. Desorption isotherms indicated that sorption was irreversible. For SAz-1 with HDTMA at ∼100% of the clay CEC, the d001 values suggest that DKN enters the interlamellar space of the organoclay and dissociates into the anion. The DKN anion forms a very stable chelate complex with the residual cations and/or partially-coordinated structural cations. This strong interaction supports the irreversibility of the sorptive process.
Conformation of Surfactant Molecules in the Interlayer of Montmorillonite Studied by 13C MAS NMR
Authors: He Hongping , Frost Ray L. , Deng Feng , Zhu Jianxi , Wen Xiaoyan , Yuan Peng 
Published: January 2005

AbstractThe ordering conformation of surfactant molecules in intercalated montmorillonite prepared at various concentrations was investigated by 13C MAS NMR. The 13C MAS NMR study demonstrates the coexistence of ordered and disordered chain conformations. Two main resonance peaks are associated with the backbone alkyl chains: the resonance at 33 ppm corresponds to the ordered conformation (all-trans), and the resonance at 30 ppm corresponds to the disordered conformation (mixture of trans and gauche). Deconvolution of 13C MAS NMR spectra indicates that the ordering conformation of surfactant molecules within the gallery of montmorillonite depends very much on their orientation and packing density. When amine chains are oriented parallel to the silicate layers, the amount of all-trans conformer decreases with the increase of amine concentration. However, the amount of all-trans conformer increases with the increase of amine concentration when amine chains radiate from the silicate layers. Furthermore, 13C MAS NMR spectra show that the intercalated surfactant molecules in the clay minerals never attained the complete liquidlike or solidlike behavior.
Effect of the Tetrahedral Charge on the Order-Disorder of the cation Distribution in the Octahedral Sheet of Smectites and Illites by Computational Methods
Authors: Sainz-Díaz C. I. , Palin E. J. , Hernández-Laguna A. , Dove M. T. 
Published: January 2005

AbstractThe order-disorder behavior of the isomorphous cation substitution of the octahedral sheet of phyllosilicates was investigated by Monte Carlo simulations based only on atomistic models in some three-species systems Al/Fe/Mg including a wide range of different octahedral compositions that can be relevant to clay compositions found in nature, especially for smectites and illites. In many cases, phase transitions do not occur, in that long-range order is not attained, but most systems exhibit short-range order at low temperature. The ordering of the octahedral cations is highly dependent on the cation composition. Variations in the tetrahedral charge (smectite vs. illite) produce slight differences in the cation distribution and the short-range and long-range order of octahedral cations do not change drastically. The average size of Fe clusters and the long-range order of Fe are not larger in illites than in smectites as previous reports concluded, but the proportion of Fe3+ cations non-clustered is higher in smectites than in illites. This behavior supports the experimental behavior of the Fe effect on the Al-NMR signal, which is lower in illites than in smectites.