Monophasic Solution Research Articles

Direct imaging of surfactant micelles, vesicles, discs, and ripple phase structures by cryo-transmission electron microscopy

Surfactant microstructures in dilute aqueous solutions and dispersions—globular, swollen, and cylindrical or wormlike micelles, discoid and ripple phase structures, and uni- and multilamellar vesicles—can be seen at high resolution by cryo-transmission electron microscopy (cryo-TEM) of thin vitrified sample films. Sample films are prepared within a chamber where temperature and chemical activities of the surrounding vapor are controlled, thereby preventing evaporation and temperature changes that could alter the microstructure in the labile systems. The thin liquid films are quenched by rapidly plunging them into liquid ethane. The resulting vitrified samples are mounted into a cold-stage and transferred into a TEM for direct observation. Monophasic solutions of cetyltrimethylammonium bromide (CTAB) show globular micelles that swell with added toluene or styrene to form swollen micelles. Worm-like micelles form in CTABNaBr solutions. Dilute mixtures of dipalmitoylphosphatidylcholine (DPPC) and diheptanoylphosphatidylcholine (DHPC) show discoid structures above the main transition temperature of DPPC and A and A/2 ripple structures of the P β′ phase at temperatures below the main transition temperature. A new model is proposed for the A structure and the ripple structures are shown to exist as single bilayers. Biphasic dispersions of sodium 4-(1′-heptylnonyl)benzenesulfonate (SHBS) show spheroidal and tubular vesicles, and complex encapsulated vesicles and coiled tubules. Vesicle-like microstructures of SHBS persist at 90°C. At the relatively low SHBS concentrations studied there is no evidence of the constant spacing characteristic of the lamellar phase at higher concentrations, suggesting that the structures observed may result from unbinding fluctuations that disrupt lamellar phases.

The Reversible Proxibarbal‐Valofan Isomerisation. Part II. Kinetic studies in a biphasic octanol/water system

AbstractThe tautomerisation between proxibarbal (I) and the two diasterloisomers of valofan (IIX and IIY) was investigated at pH 7.4 in a biphasic octanol/H2O system. The rate constants of isomerisation and the equilibrium constants of (partition coefficients) were calculated by compartmental analysis. The rate constants of isomerisation were comparable with those determined in monophasic aqueous solutions, whereas at pH 7.4 and 37° the duration necessary for a global equilibrium to be reached was 4–6 times longer in the biphasic system. These reduced rates and the higher lipophilicity of IIX and IIY as compared to I may be of pharmacokinetic and pharmacodynamic significance. They may also have relevance for a number of drugs known or suspected to form lactonic or lactamic metabolites.

Formation of ordered phases of (hydroxypropyl)cellulose in miscible and immiscible isobutyric acid‐water mixtures

Abstract(Hydroxypropyl)cellulose (HPC) is known to form birefringent liquid‐crystalline phases at elevated polymer concentrations in either water or isobutyric acid (IBA). The HPC concentration at which the polymeric phase exhibits birefringence decreases as the IBA content in mixed H2O/IBA solvents decreases, even though the concentration ϕic for the formation of an ordered phase of HPC in water is greater than that in IBA. Water is a spectator component and apparently does not participate in the formation of a birefringent phase when IBA is present. A birefringent phase forms once the concentration of HPC in the solution omitting the H2O equals the ϕic of binary HPC/IBA solutions for temperatures from 23 to 95°C. The strong preferential affinity of HPC for IBA is visually evident as an HPC coagulate separates from dilute solution when the solvent mixture contains as little as 5% IBA. The coagulate dissolves to give a monophasic isotropic solution as the IBA content in the solvent is increased. A heterogeneous system in which a clear supernatant fluid covers a pearly white polymeric phase forms when the solvent mixture is immiscible and the HPC content is less than 50%. At high HPC content, the classical appearance associated with concentrated HPC solutions is seen. The optical and rheological properties of the heterogeneous systems are compared with those of homogeneous solutions at several HPC concentrations.

Successful non-surgical collection of ovine embryos

RNA sequencing (RNAseq) has divulged newer role of spermatozoal RNA in male fertility. This study aimed to evaluate different sperm purification and RNA extraction methods for long-read RNA sequencing of poly(A) transcriptome in goat spermatozoa. Sperm samples were purified by swim-up separation using different purification medium. Spermatozoal RNA was extracted by seven different methods with additional supplementation of reducing agents in lysis buffer. poly(A) selected RNA was used for cDNA library preparation and long-read RNAseq in Nanopore sequencer. Sperm purification by 1 h swim-up resulted in higher recovery (89.20 ± 1.15%), motility (82.33 ± 1.53%), viability (88.10 ± 5.03%) and plasma membrane integrity (71.33 ± 4.51%) in sperm TALP (sp-TL) medium. A monophasic solution of GITC with phenol and DTT resulted in the highest yield of large sized RNAs (3.89 ± 0.46 ng/million cells) suitable for long-read RNAseq of poly(A) transcripts. RNAseq resulted in reads of length, ranging from 500bp to 2 Kb. A total of 123 transcripts were identified in goat spermatozoa by de novo assembly and included sperm-specific transcripts such as CATSPERG, PRM2, CYLC2, SPATA6, PLCZ1 etc. This study is the first report of long-read RNAseq of poly(A) transcriptome in goat spermatozoa.

Characterization and performance of platinum-iridium reforming catalysts

Unsupported and ..gamma..-alumina-supported catalysts containing 0:1 to 64:1 iridium-platinum ratios were prepared and characterized by X-ray diffraction, Auger spectroscopy, and activity and selectivity tests for hexane and heptane reforming at 650/sup 0/K and 1 bar. Only monophasic solid solutions were observed. The surface concentration of iridium was low even at high bulk concentrations. The main effect of the iridium was suppression of the formation of carbonaceous deposits, possible by migration of deposited carbon atoms from platinum to iridium centers and their hydrogenation to methane. Under the mild reforming conditions used, no significant change in selectivity was observed with increasing iridium content, but at the higher pressures of industrial reforming when greater amounts of carbon deposit, the presence or iridium causes the known improvement of isomerization activity. Tests with acidic ..gamma..-alumina and with iridium/platinum on nonacidic ..cap alpha..-alumina confirmed the bifunctional character of the reforming catalysis, in which the alkane is dehydrogenated on a metal site, isomerized on an acidic site, and finally hydrogenated on a metal site.

銅合金の摩耗機構

Anti-friction property of alloy depends on the following factors.a) Adhesive property of sliding couple.b) Effects of oxide film and the other contaminations on preventing adhesion.c) Surface roughness and surface fitness between sliding surfaces.d) Shear strength and hardness of alloy.At the binary alloys of copper such as Cu-Zn, Cu-Sn, Cu-Al, Cu-Si etc., Cu-Zn is more adhesive than the other alloys. And the oxide film on the surface acts the part of inhibitant for adhesion, so the oxidized wear is apt to appear and wear loss is little. And then, mono-phase solid solution is easier to show oxidized wear than two-phase alloy. But when the condition of sliding is so severe that the underlying alloy is apt to flow, the oxide film of mono-phase alloy is easy to break and very large wear results.So anti-friction alloy should have some hard spots which prevent the flow of the softportion of structure in accordance with the severity of sliding condition.