Decreasing Particle Diameter Research Articles

塩酸滴下法により調製したエッグシェルの吸着特性

Eggshell was treated by hydrogen chloride drop method, an d the adsorptions of water vapor and carbon dioxide were studied at the temperature of 20°C. The amounts of adsorption of both water and carbon dioxide increased with increase in calcium chloride content, and also increased with decrease in particle diameter. The amount of water adsorption was about 7-8 times that of carbon dioxide adsorption. SEM micrographs showed that spherical particles were obtained in samples containing 40 mol% of calcium chloride. It is concluded that eggshell treated by the hydrogen chloride drop method could be used for economical adsorption of water and carbon dioxide.

Mechanisms of Heat Transfer Augmentation around the Stagnation Point of an Impinging Air Jet Laden with Solid Particles. (Report 2. Effects of Thermal Properties of Laden Particles and Heat Transfer Surface on Heat Transfer Augmentation due to the Unsteady Heat Conduction).

In this paper, the authors studied heat transfer augmentation around the stagnation point of an impinging air jet laden with fine solid particles. Heat transfer around the stagnation point was measured for nine combinations of solid particles and the heat transfer surface material so as to examine the effects of the thermal properties of both laden particles and heat transfer surface on the heat transfer augmentation due to unsteady heat conduction between them. The contributions of unsteady heat conduction between the laden particles and heat transfer surfaces were separated from other heat transfer augmentation mechanisms by employing the separation technique reported in our previous paper. The results clearly showed that the contribution of unsteady heat conduction increases with increase of the product of heat capacity and thermal conductivity of the heat transfer surface material as well as of the laden particles. For a given combination of solid particles and heat transfer surface materials, the contribution of unsteady heat conduction is dominated primarily by the contacting frequency between the laden particles and heat transfer surface. This means that the heat transfer augmentation due to unsteady heat conduction becomes evident as the particle diameter decreases.

Differences in carbohydrate content of low density lipoproteins associated with low density lipoprotein subclass patterns

The neutral carbohydrate content of both the protein (apoB) and lipid fractions of low density lipoproteins (LDL) from subjects with a predominance of small, dense LDL (subclass pattern B) was found to be lower than in subjects with larger LDL (subclass pattern A): 45 +/- 12 versus 64 +/- 13 mg/g apoLDL, and 58 +/- 8 versus 71 +/- 8 mg/g apoLDL (P less than 0.0005 for both). Sialic acid content of LDL lipids, but not apoB, was also reduced in subclass pattern B. ApoB and glycolipid carbohydrate content of total LDL and LDL density subfractions declined with increasing LDL density and decreasing particle diameter. Moreover, in LDL subfractions from pattern B subjects, carbohydrate content of LDL apoB, but not LDL glycolipid, was significantly lower in comparison with particles of similar size from pattern A subjects. Thus, in LDL subclass pattern B, reductions in LDL carbohydrate content are associated both with reduced concentrations of larger carbohydrate-enriched LDL subclasses, and with reduced glycosylation of apoB in all LDL particles. LDL glycolipids may vary with overall lipid content of LDL particles, but variation in apoB glycosylation may indicate differences in pathways for LDL production, and reduced apoB glycosylation may reflect the altered metabolic state responsible for LDL subclass pattern B.

Origins of Marslike spectral and magnetic properties of a Hawaiian palagonitic soil

A palagonitic soil (HWMK1) from Mauna Kea, Hawaii, has Marslike spectral and magnetic properties. Reflectivity spectra of <20 μm size separates resemble spectra for Martian bright regions, and reflectivity spectra of coarser size separates have some spectral characteristics in common with spectra for Martian dark regions. The bulk soil is magnetic with a saturation magnetization of 0.98 A m2/kg of sample (∼10 A m2/kg of Fe) at 296 K. Petrographic observations show that the soil contains separate populations of black and orange tephra particles which are relatively unaltered fragments of tachylite (merocrystalline basalt) and extensively weathered (palagonitized) fragments of sideromelane (clear, brown basalt glass), respectively. Although both types of particles contain plagioclase and olivine microphenocrysts, their iron‐oxide mineralogies are substantially different, as documented by Mossbauer and static‐magnetic measurements. A strongly magnetic, opaque iron‐oxide (titanomagnetite) is associated with black particles and is responsible for the magnetic nature of the soil. A relatively weakly magnetic, superparamagnetic ferric‐oxide and minor hematite are associated with orange particles and are responsible for the color. The more highly weathered state (higher state of oxidation) of orange particles is a consequence of the faster weathering (palagonitization) rate for their sideromelane precursors than for tachylite. Increasing state of oxidation, decreasing saturation magnetization, and increasing near‐IR reflectivity with decreasing particle diameter of bulk soil are manifestations of the increasing proportions of palagonitic material as particle diameter decreases.

Alterations of intercellular junctions induced by hypoxia in canine myocardium

To delineate potential structural mechanisms of impaired cell coupling induced by hypoxia in canine myocardium, we characterized derangements in intercellular junctions and alterations in the space constant in strips of ventricular epimyocardium before and after selected intervals of hypoxia in vitro. Tissue samples were analyzed morphometrically with transmission and freeze-fracture electron microscopy. Space constants in control tissues averaged 1.61 +/- 0.47 mm (mean +/- SD). After 30 and 60 min of hypoxia, space constants declined by 0.24 +/- 0.22 and 0.32 +/- 0.17 mm, respectively (P less than 0.05 vs. control in each case). Impaired coupling was not reversible with reoxygenation. Focal pathological separation of intercalated disk membranes was observed after 30 min of hypoxia, but morphometric analysis demonstrated no reduction in gap junction surface density to account for uncoupling after 30 min of hypoxia. However, after 60 min of hypoxia, gap junction surface density was reduced by 45%. Quantitative analysis of freeze-fractured gap junction replicas after 30 min of hypoxia revealed a significant decrease in P-face particle diameter from 8.51 +/- 1.64 nm in control tissues to 7.25 +/- 1.33 nm (P less than 0.01) with no further change at 60 min. Thus impaired coupling at 30 min is likely related to a change in the gap junction particle. Further uncoupling after 60 min of hypoxia is likely related, in addition, to reduced gap junction surface density. These results suggest that alterations in P-face particles and gap junction surface density are important determinants of progressive cellular uncoupling induced by hypoxia.

Fat emulsion particle size: influence on the clearance rate and the tissue lipolytic activity

In lipid emulsions for parenteral use the mean particle diameter of the droplets in the 20% emulsions is larger than in the 10% emulsions. In long-chain triglyceride emulsions it is greater than in medium-chain triglyceride emulsions. As the particle diameter decreases, the total interfacial area increases, as does the lipoprotein lipase (LPL) and hepatic lipase (HL) activity. For a given quantity of triglycerides and phospholipids the lipolytic activity is proportional to the total interfacial area. A doubling of the phospholipid concentration is accompanied by a small reduction in the activity of both enzymes. In going from long-chain to medium-chain triglycerides, there is an acceleration in the clearance rate of infused lipid. For a similar emulsion, the clearance rate decreases as the particle size decreases. It seems plausible that the larger the mean droplet diameter, the greater the participation of the reticuloendothelial system in the clearance.

Evidence for pigmentary hematite on Mars based on optical, magnetic, and Mossbauer studies of superparamagnetic (nanocrystalline) hematite

Features attributed to ferric iron in remotely sensed spectral data of Mars and the magnetic nature of Martian soil at the Viking landing sites are consistent with the occurrence of hematite (α‐Fe2O3) as both superparamagnetic (nanocrystalline) hematite (sp‐Hm) and larger‐diameter hematite (bulk‐Hm) particles. These hematite particles most likely occur in pigmentary form, that is, as particles dispersed throughout the volume of a relatively spectrally neutral (silicate?) material. Likely physical forms of this pigmented volume include rocks, dust and soil particles, and coatings (weathering rinds) thereon. Accommodation of Martian data by hematite is a result of differences in optical and magnetic properties of sp‐Hm and bulk‐Hm particles. Optical, magnetic, and Mossbauer properties of sp‐Hm particles dispersed within particles of high‐area silica gel are reported in this study and compared to the corresponding properties of bulk‐Hm powders. Samples were prepared by calcining (∼550°C) powders of high‐area silica gel that had been impregnated with ferric nitrate solutions. The samples are classified according to type of Mossbauer spectrum observed at 293 K. (1) Type S + D samples, which by Mossbauer granulometry contain hematite particles both larger and smaller than 10(2) nm, are characterized by a hematite sextet plus superparamagnetic doublet. (Uncertainties are given in parentheses and refer to the final digit(s).) (2) Type D samples, which contain hematite particles smaller than 10(2) nm, are characterized by only a superparamagnetic doublet and so contain only sp‐Hm. The presence of larger particles in type S + D samples is consistent with X ray diffraction data; the diffraction patterns of type S + D samples are characterized by a few, broad hematite lines, and type D samples have no lines because the particles are too small to coherently scatter X rays. Measurements of internal field strengths (Hint) at 22 K for both type S + D and type D samples show that Hint is not constant but decreases with decreasing particle diameter from 54.0 T for bulk‐Hm to 46.6 T for 5.4‐nm sp‐Hm. This dependence implies that phase identifications based solely on comparisons to bulk values of Hint are equivocal when superparamagnetic particles are present. Sp‐Hm (<10‐nm diameter) is much more magnetic than bulk‐Hm; the saturation magnetization at 293 K for type D samples is 7(2) A m2/kg as compared to 0–0.5 A m2/kg for bulk‐Hm. Optical properties of type S + D samples are similar to those of bulk‐Hm; in particular, a well‐defined band minimum is present near 860 nm. Optical properties of type D samples, with only sp‐Hm at 293 K, are significantly different in that a step‐shaped feature instead of a well‐defined band is centered near 860 nm. The transition from well‐defined band to step‐shaped feature occurs at a hematite particle diameter of ∼10 nm. The position of the UV‐visible absorption edge and the absorption strength at 860 nm depend on the number density of sp‐Hm particles, the Fe2O3 concentration, and the physiochemical properties of the support material. For 7(2)‐nm sp‐Hm particles dispersed within silica gel particles (35‐ to 74‐μm powder with 6‐nm pore diameter) the absorption edge shifts toward the visible, and the absorption strength at 860 nm increases with increasing number density of the sp‐Hm particles. Visually, the color change is from nearly white to tan to dark red. Optical properties of samples containing 7(2)‐nm sp‐Hm particles are essentially independent of temperature between 173 and 293 K.

Semicontinuous emulsion polymerization of vinyl acetate. IV. Homopolymerization with poly(vinyl alcohol)

AbstractIn semicontinuous emulsion polymerization of vinyl acetate the system behaves as a flooded system in the first moment of the process. Then the polymerization rate becomes proportional to the introduced monomer. At moderate feed rate the polymerization rate is controlled by the addition rate. At a critical addition rate transition to a flooded system takes place. The conversion and particle diameter decrease with increasing stirring speed.

Fluidized Bed Combustion of High Ash Chars

Abstract The behavior of the fluidized bed combustion of high ash chars is analyzed by applying the two-phase theory, the gas (lowing in plug flow both in the emulsion and bubble phases. The ash is assumed to remain attached to the char particle and therefore the shrinking core model is considered. Combustion efficiency increases with bed temperature, excess air and ash content of char, as well as when the char mass flow rate and particle diameter decrease. The effect of excess air on the exit concentration is found to be related to the interphase mass transfer coefficient. The carbon monoxide concentration is reduced in the freeboard by two orders of magnitude due to its oxidation to carbon dioxide. These emissions are further reduced when preheated secondary air is introduced.

Development of an extremely high energy ball mill for solid state amorphizing transformations

In order to characterize the process of solid state amorphization by mechanical alloying, we have developed a rotating-arm ball mill that has a large grinding capacity, a range of rotating-arm velocities from 0 to 500 rev min −1, and peripheral equipment to measure the attrition temperature inside the tank and the torque applied to the rotating arm. For mechanically alloyed cobalt-rich alloys, the torque, P, increases with increasing rotational speed, R. For R between 80 and 300 rev min −1, which is a customarily used rotational speed, P = AR 0.3, where A is a constant. For R from 300 to 500 rev min −1, P = AR 1.6. The mechanical alloying of elemental crystalline powders of cobalt and zirconium using R = 450 rev min −1 was studied by monitoring the torque and the attrition temperature as a function of attrition time. The torque shows a peak at t ≈ 30 min. The attrition temperature shows a peak at t ≈ 1.5 h. This peak corresponds to an exothermic reaction in the powder and is identified with a solid state amorphizing transformation. For powders with average composition Co 85Zr 15, an increase in rotational speed from 300 to 450 rev min −1 leads to a reduction in the attrition time necessary to complete the amorphization from 8.5 to 3.5 h, and to a decrease in the average particle diameter from 37 to 7 μm.

Preparation and properties of sputter-deposited crystalline ultrafine particles

The composition and size dependence of the magnetic properties of crystalline Fe-Co and Ni ultrafine particles has been investigated. Samples were prepared by sputter deposition onto sputter-etched polyimide substrates. Little difference between the magnetic properties of crystalline and amorphous particles was found in Fe-rich alloys, but we found a greater influence of magnetocrystalline anisotropy in Co-rich alloys. When the particles are larger than 2500 Å, the samples have negative anisotropy Ku (easy direction parallel to the substrate plane). As the particle diameter decreases, Ku becomes positive, and the coercive field Hc increases from a few hundred oersteds to a maximum of more than 1000 Oe. Below a particle diameter of about 1000 Å, Ms , Ku, and Hc all drop rapidly toward zero, presumably due to the appearance of superparamagnetism. Annealing above about 200 °C leads to significant increases in Hc, Ku, and Ms, and also to significant changes in the line shapes of the x-ray diffraction patterns, as a result of stress relaxation. A low-temperature diffusion process leading to changes in the morphology of the subparticles may also be a cause of the increment of magnetic properties on annealing.

A wind tunnel study of the particle collection efficiency of an inverted frisbee used as a dust deposition gauge

The paper describes wind tunnel measurements of the performance of an inverted Frisbee used as a dust deposition gauge. Tests were conducted using glass spheres to simulate dust up to 183 μm in aerodynamic diameter over a range of wind speeds up to 10 m s −1. An overall figure for the collection efficiency of the Frisbee is around 50%. This is significantly better than for other gauges which are commonly in use for dustfall measurement. The collection efficiency fell with increasing wind speed and also with decreasing particle diameter down to a minimum at around 80–100 μm before rising again. This behaviour seems to be connected with a change in the main particle collection mechanism from deposition to turbulent diffusion. Some tests were performed to verify this finding by increasing the vertical components of turbulence over the gauge; this increased the collection efficiency and may be a useful method of improving performance in the field. A thin coating of liquid paraffin gives greater collection efficiencies at higher wind speeds due to a reduction in the blow-out of collected dust. The interference from the bottle mounted under the Frisbee for collecting excess rainfall was also investigated and found to be significant. Another gauge design was also investigated alongside the Frisbee. This was a snow collector designed originally for acid precipitation studies but which should also be a good dust collector. It proved to be so, though its collection efficiency was less than for a Frisbee.

Ａｌ‐Ｆｅ合金ガスアトマイズ粉末の特性とその高温加熱による変化

Properties of Ar gas atomized powders of Al-8mass%Fe alloy and its variation by annealing have been examined by means of scanning electron microscopy, transmission electron microscopy and hardness measurement. A cell structure having metastable phase AlmFe at its boundaries forms in particles in the size smaller than 105μm, besides a primary crystallized intermetallic compound Al3Fe predominantly exists in the particles larger than 105μm. The hardness of powders increases with decreasing particle diameter due to the refinement of cell structure. The annealing at temperature above 400°C accelerates the decomposition of cell structure and the formation of granular intermetallic compound, both of which result in the notable softening in the small size particles. AlmFe which has been at cell boun dariestransforms to Al3Fe by the annealing above 450°C. Even after high temperature annealing, large particles show only a slight decrease in hardness keeping low values due to a small change in the coarse structure.

Cell-to-cell communication in the heart: structure-function correlations.

The communicating cell junctions that ensure the electrical and diffusional continuity of the intracellular space in the heart fibres can be switched from their normal conducting, or opened state, to an exceptional non-conducting, or closed state. This electrical uncoupling is observed after cell injury in the presence of Ca2+ ions in the extracellular fluid, after metabolic inhibition and in the presence of aliphatic alcohols (C6 to C9). The correlations between electrical uncoupling and gap junction morphology in the heart are briefly reviewed. A decrease of the distance between P-face particles and between the E-face pits has been found in all investigations, but the functional significance of this observation is not understood at present. A quantitatively very similar decrease of the average particle diameter (about -0.7 nm) has been measured in glutaraldehyde-fixed sheep Purkinje fibres and in unfixed, quickly frozen rat auricles that had been electrically uncoupled by three different procedures. About half of this decrease was reversible on short-term electrical recoupling (within 20 min). It is concluded that a measurable decrease of the connexon diameter correlates with electrical uncoupling.

Calcium hydroxide and calcium carbonate particle size effects on reactivity with sulfur dioxide

The effect of in situ calcium hydroxide [Ca(OH 2)] and calcium carbonate (CaCO 3) sorbent particle size upon reactivity with 3000 ppm sulfur dioxide (SO 2) in an 1100°C drop-tube furnace was measured by on-line collection of the reacted sorbent with a particle cascade impactor. Significant agglomeration occurred for the hydroxides, while little was apparent for the carbonate. Reactivity of all sorbent particles increases as the measured particle diameter decreases such that conversion is inversely related to diameter to the 0.22–0.32 power. For these sorbents, Ca(OH) 2 particles had greater reactivity than the similarly sized CaCO 3 sorbent.

Sulfo cation-exchange resins as heterogeneous catalysts for the reaction of styrene with formaldehyde

1. Macroporous and gel sulfo cation-exchange resins are active catalysts for the condensation of styrene with formaldehyde. The product, 4-phenyl-1,3-dioxane was obtained in up to 97% yield. 2. The activity of macroporous sulfo cation-exchange resins increases with decreasing particle diameter but in the case of the gel samples, granule size has only a slight effect on the reaction rate. 3. The enhanced activity of sulfo cation-exchange resins is presumably a result of the high value of the acidity function Ho of the sulfonic acid groups of the cation-exchange resin.

The effect of particle size on fourier-transform infrared photoacoustic spectra

The effect of particle size on infrared photoacoustic spectra has been investigated by use of naturally occurring quartz. It is observed that the PAS peak intensities increase with a decrease in particle diameter and that the peak intensity ratios are not constant for particles of different diameters. When the particle diameter becomes smaller than the thermal diffusion length for a specific peak, a more dramatic increase in peak intensity is observed. It is also found that the PAS peak shape deteriorates with an increase in particle diameter. The effect of optical velocity of the interferometer on PAS peak intensities is also reported.

AEM analysis of solidification catalysts in atomized Fe-Ni

The liquid droplets produced by atomization processes are believed to undergo substantial supercooling during solidification, because the catalytic heterogeneities, for statistical reasons, tend to be isolated in the larger droplets. This supercooling can lead to the nucleation of metastable phases. As part of a study on the effect of liquid supercooling on nonequilibrium solidification, three binary Fe-Ni alloys have been produced by conventional argon atomization (Fe-20Ni, Fe-30Ni, and Fe-40Ni). The primary variables in these experiments are: i) the alloy composition; and ii) the powder particle diameter (inversely proportional to supercooling). Of particular interest in this system is the competitive nucleation kinetics between the stable fee and metastable bec phases. Bcc is expected to nucleate preferentially with decreasing %Ni and decreasing particle diameter.

The effect of particle size on peak intensities of FT—IR photoacoustic spectra

The effect of particle size on peak intensities of FT—IR photoacoustic spectra was investigated by use of naturally occurring quartz in our Laboratory. It is observed that the PAS peak intensities increases with a decrease in particle diameter and that the peak intensity ratios are not constant for particles of different diameters. The relations among particle size, peak intensity and thermal diffusion length are discussed.

Promotion and characterization of zeolitic catalysts used in the synthesis of hydrocarbons from syngas

Bifunctional metal-zeolite catalysts cobalt-ZSM-5 and cobalt-thoria-ZSM-5 have been examined for the conversion of synthesis gas (H 2/CO = 1) at 280 °C, 21 bar and WHSV = 0.77 g(g cat) −1 h −1 Thoria in amounts as low as 0.4 wt.% added to a cobalt-ZSM-5 with 9.0 wt.% cobalt caused a considerable increase in synthesis gas conversion and selectivity to gasolinerange hydrocarbons. Addition of thoria to the catalyst also resulted in a decrease of the aromatic fraction in the hydrocarbon product. Some Co-ThO 2-ZSM-B catalysts provided nearly 65 wt.% selectivity to gasolinerange product that contained 26 vol.% aromatics (alkylbenzenes). The selectivity to gasoline-range product exceeded the limit (48 wt.%) set by Schulz-Flory kinetics. Chemisorption and magnetization studies have been performed to determine metal particle size. Addition of thoria resulted in a decrease of the cobalt particle diameter from about 40 nm to 10 nm and caused an increase in CO/H adsorbed. The action of thoria as a promoter is possibly related to the presence of basic sites on its surface. Infrared studies have demonstrated a relative decrease in the number of Brönsted acid sites in ZSM-5 upon the addition of thoria, thus accounting for the decrease of the aromatic fraction in the liquid hydrocarbon product.