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H Kunieda

Publications and source records attributed to H Kunieda.

10 recordsLinked to original sources
PubMed2000

Formation of Cubic-Phase Microemulsions with Anionic and Cationic Surfactants at Equal Amounts of Oil and Water.

The formation and microstructure of cubic phases were investigated in anionic and cationic surfactant-containing systems at 25 degrees C. In the system sodium dodecyl sulfate(SDS)-dodecyltrimethylammonium bromide(DTAB)-water, mixing of two surfactants shows the phase transition hexagonal phase (H(1))-->surfactant precipitate, accompanied by an obvious decrease in the cross-sectional area per surfactant in the rod micelles of the hexagonal liquid crystal. In the mixed systems brine(A)-dodecane(B)-SDS(C)-DTAB(D)-hexanol(E), the isotropic discontinuous cubic phase is formed from the H(1) phase at a low cationic surfactant weight fraction, Y=D/(C+D), and from the lamellar phase at high Y upon dilution with equal amounts of oil and brine, respectively. The minimum surfactant concentration to form the cubic phase decreases with increases both in cationic surfactant weight fraction Y from 0 to 0.30 and in hexanol weight fraction, W(1)=E/(C+D+E), accordingly. The maximum solubilization for oil of the cubic phase reaches 43 wt% at 14 wt% of mixed surfactants and alcohol. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

Effect of Added Salts or Polyols on the Cloud Point and the Liquid-Crystalline Structures of Polyoxyethylene-Modified Silicone.

The effect of added salts (NaCl, Na(2)SO(4), and NaSCN) or polyols (glycerin (Gly), 1,3-butanediol (1,3-BD), ethylene glycol (EG), and polyethylene glycol (PEG400)) on the hexagonal liquid-crystalline structure of polyoxyethylene-modified silicone was investigated by means of small angle X-ray scattering (SAXS). The effective cross-sectional area of the lipophilic part of the aggregate, a(s), in the hexagonal phase decreases upon the addition of salts, on one hand, lowering the cloud point in the dilute aqueous siloxane surfactant solutions. On the other hand, if added salt raises the cloud point, the a(s) increases. Similar results were obtained in the case of the addition of polyols. Since the a(s) mainly depends on the EO chain length, the above results are direct evidence that the hydration or dehydration of the EO chain is affected by these additives. The static fluorescence probe method was applied to the Gly and 1,3-BD systems using 8-anilino-1-naphthalene-sulfonic acid, ANS, to know the change in hydration of the EO chains. In the Gly system, the hydration of the EO chain monotonically decreases whereas 1,3-BD first increases the hydration and then decreases it at high 1,3-BD content. These results are very consistent with the SAXS and cloud temperature results. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

Iron K Line Variability in the Low-Luminosity Active Galactic Nucleus NGC 4579.

We present results of new ASCA observations of the low-luminosity active galactic nucleus (LLAGN) NGC 4579 obtained on 1998 December 18 and 28, and we report on the detection of variability of an iron K emission line. The X-ray luminosities in the 2-10 keV band for the two observations are nearly identical (LX approximately 2x1041 ergs s(-1)), but they are approximately 35% larger than that measured in 1995 July by Terashima et al. An Fe K emission line is detected at 6.39+/-0.09 keV (source rest frame), which is lower than the line energy 6.73+0.13-0.12 keV in the 1995 observation. If we fit the Fe lines with a blend of two Gaussians centered at 6.39 and 6.73 keV, the intensity of the 6.7 keV line decreases, while the intensity of the 6.4 keV line increases, within an interval of 3.5 yr. This variability rules out thermal plasmas in the host galaxy as the origin of the ionized Fe line in this LLAGN. The detection and variability of the 6.4 keV line indicates that cold matter subtends a large solid angle viewed from the nucleus and that it is located within approximately 1 pc from the nucleus. It could be identified with an optically thick standard accretion disk. If this is the case, a standard accretion disk is present at the Eddington ratio of Lbol/LEdd approximately 2x10-3. A broad disk-line profile is not clearly seen, and the structure of the innermost part of accretion disk remains unclear.

Journal Article↗
PubMed2000

Cubic-Phase-Based Concentrated Emulsions.

The effect of different types of added oil on the formation of a discontinuous micellar-type cubic phase was investigated in water-polyoxyethylene dodecyl ether (C(12)EO(25)) systems by phase study and small-angle X-ray scattering. The thermal stability of the cubic phase increases upon addition of oil, especially short-chain hydrocarbons. However, in the heptane system, the maximum melting temperature of the cubic phase is lower than that for decane due to the formation of a different liquid crystal phase. The effect of polyols on C(12)EO(25) cubic phases was also investigated. It was found that the thermal stability of the cubic phase decreases with polyol concentration. The destabilizing effect becomes large as the polyol molecule penetrates further into the surfactant palisade layer. Although the solubilization of oil in the cubic phase is very low, a large amount of excess oil can be incorporated and a transparent cubic-phase-based concentrated emulsion is formed. The transparency is attributed to the very small difference in the refractive indices between the cubic and excess-oil phases. Copyright 2000 Academic Press.

Journal Article↗
PubMed1999

Effect of Types of Perfume Compounds on the Hydrophile-Lipophile Balance Temperature.

The effect of added perfume compounds (d-limonene (LN), alpha-hexylcinnamic aldehyde (HCA), beta-ionone (IN), benzyl acetate (BA), linalool (LL), geraniol (GL), eugenol (EL), and cis-3-hexenol (HL)) on the three-phase behavior was investigated in water/octaethylene glycol dodecyl ether (C(12)EO(8))/perfume compound systems. The HLB (hydrophile-lipophile balance) temperatures are considerably lower than those of saturated hydrocarbon systems and are in the order LN > HCA > IN > BA > LL > GL > EL > HL. It is considered that the perfume molecules tend to be solubilized in the vicinity of the interface of the water-hydrocarbon moieties of the surfactant or the surfactant palisade layer. To confirm this, the location of the solubilized perfume compound in aggregates of liquid crystals was investigated by small-angle X-ray scattering (SAXS). In the LN, HCA, IN, BA, LL, and GL systems, the hexagonal liquid crystalline phase changes to lamellar liquid crystals on addition of each perfume compound, whereas the hexagonal liquid crystalline phase is directly changed to a reverse micellar solution phase in the EL and HL systems. The effective cross-sectional area per surfactant molecule, a(s), was calculated by using interlayer spacing measured by SAXS. Perfume compounds, which reduce the HLB temperature greatly, tend to penetrate into the surfactant palisade layer and increase a(s). Thus, the perfume molecules change the surfactant curvature from positive to negative. The more the perfume compound penetrates into the palisade layer, the lower the HLB temperature becomes. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Mixing Effect of Polyoxyethylene-Type Nonionic Surfactants on the Liquid Crystalline Structures.

An effective cross-sectional area per surfactant molecule at hydrophobic interfaces of aggregates, a(S), in hexagonal (H(1)) and lamellar (L(alpha)) liquid crystals was calculated in homogeneous and mixed polyoxyethylene dodecyl ether systems as a function of polyoxyethylene (EO) chain length by means of small-angle X-ray scattering. The a(S) increases with increasing the EO chain length. The a(S) in the mixed surfactant system is considerably smaller than that in the single surfactant system, even if the average EO chain length is the same. The reduction of a(S) is larger than that predicted by ideal mixing of the surfactants. Moreover, if the EO chain lengths of the surfactants are more separated, the a(S) is smaller. The shapes of surfactant self-organizing structures may be governed by the balance of the attractive and the repulsive forces acting at the hydrophobic interfaces of the aggregates. According to this consideration, the mixing effect of surfactants with the different EO chain lengths on the a(S) in the L(alpha) phase was discussed. It is considered that the surfactant molecules are tightly packed in the aggregates since the reduction in repulsion force takes place in the excess EO chain part of the hydrophilic surfactant longer than the short EO chain of the lipophilic one. The lower surface tensions and the better stability of macroemulsions and the large solubilizing capacity of microemulsions result from the mixing effect. Copyright 1999 Academic Press.

Journal Article↗
PubMed1997

Effect of Temperature on the Phase Behavior of Ionic-Nonionic Microemulsions

Microemulsions are formed over a wide range of temperatures in brine/sodium dodecyl sulfate/polyoxyethylene dodecyl ether (C12EO2 or C12EO3)/decane systems. In a dilute region, lamellar liquid crystal is present instead of bicontinuous microemulsion at the composition at which the HLB of the mixed surfactant is optimum in the given system. The monomeric solubilities of C12EO2 or C12EO3 in oil and the mixing fraction of C12EO2 or C12EO3 in the mixed surfactant layer were determined using the geometrical relation of three-phase tie triangle containing the liquid crystal phase in the composition tetrahedron and were compared at 35 and 60°C. The change in the HLB composition with temperature is well described by increasing the monomeric solubility and decreasing the mixing fraction of nonionic surfactant in the surfactant layer. As a result, temperature-insensitive microemulsions are formed in the SDS-C12EO3 system. Copyright 1997 Academic Press. Copyright 1997Academic Press

Journal Article↗
PubMed1997

Phase Behavior of a Water/Nonionic Surfactant/Oil Ternary System in the Presence of Polymer Oil

The effect of a polymer oil, polydimethyl siloxane, on the phase behavior of the water/C12EO6/isopropyl myristate (IPM) system has been studied. Since the polymer oil is completely soluble in IPM, it was dissolved in IPM and the solutions were used as the oil phase to study its effect. The presence of polymer increases the hydrophobic nature of IPM and thereby decreases the solubilization of oil into the surfactant phase (microemulsion). Moreover, at a certain range of silicone oil concentration in the IPM, a four-phase body consisting of excess water, excess oil, and two surfactant phases is formed within the ternary system. The two surfactant phases are designated as D (with bicontinuous type of structure) and D' (with L3 type of structure). Careful phase behavioral studies revealed that, with increasing silicone oil concentration, a three-phase region containing water phase, D' phase, and an oil-rich D phase develops within the system and this region overlaps with the normal three-phase region of the system containing the water, D, and oil phases to give a four-phase body. The order of various phases from top to bottom in the four-phase body is oil, D, D', and water.

Journal Article↗
PubMed1995

[Clinical evaluation of FemoStop in arrest of hemorrhage of the femoral artery].

A new device, FemoStop, in which the compression bag is replaced with a translucent one made of polyethylene for easy inspection, was used in 74 patients (76 examinations) who underwent angiography, including the setting of indwelling catheters in 10 patients, to obtain an easy and reliable maneuver for arresting hemorrhage at the puncture site. No failure in arrest of hemorrhage was recognized, and complications such as hematoma and re-bleeding were nonexistent. The doctor's time required for the arrest of hemorrhage was less than 5 minutes. On the other hand, in a beginner using the conventional manual compression method in 74 patients (74 examinations), the rate of failing to arrest hemorrhage was 5/74 cases, small hematoma was seen in three cases, re-bleeding occurred in one, and the time required for arrest was about 20 minutes. In conclusion, FemoStop was clinically useful for beginners.

Adolescent↗