Swelling of Crosslinked Polyelectrolytes Composed of Vinyl alcohol and Acrylic acid Units

Crosslinked copolymers of different polymer composition and density of crosslinking points were prepared by copolymerization of methylacrylate and vinylacetate in the presence of divinylbenzene as a crosslinking agent, the copolymers then being converted by saponification into polyelectrolytes containing carboxyl groups , along the chains. The degree of swelling of the sodium salts of these polyelectrolytes was measured in pure water. The osmotic coefficients in water were estimated from the degree of swelling in water, taking into consideration the effect of large deformation of the unit chains on the contractile pressure of the gel. The calculated values of the osmotic coefficient were very small and comparable to those previously found for the linear polyelectrolyte composed of the same components. The characteristic features of the results were discussed by considering the factors which may influence the activity of the counter-ions, such as the hydrolysis of the polyelectrolytes, the counter-ion fixation and the excluded volume effect of the macro-ions

Thermodynamic Study on Fusion, in Crystalline Polymer and Its Mixture with Diluent, based on Folded Chain Crystalline Model

In accordance with the regular folded chain crystallite model, an expression for the melting point depression of crystalline polymer in diluent was derived by extending the treatment given by Flory. The equation obtained is which reduces for very large x and considerably large ζ to where Tm⁰ is the melting point of the pure polymer of infinite fold length and chain length, Tm⁰(l) is tne melting point of the pure polymer of fold length l, Tm(l) is the melting point for the polymer of fold length l in the presence of diluent, ΔHᵤ is the heat of fusion per mole of repeating unit, Vᵤ and V₁ are the molar volumes of the polymer repeating unit and the diluent, respectively, x is the degree of polymerization, v₁ and v₂ are the volume fractions of the diluent and the polymer, respectively, ζ is the fold length in number of repeating units, σₑ is the end surface free energy per unit volume, Δhf is the heat of fusion per unit volume, and X₁ is the diluent-polymer interaction parameter. The model used here was discussed in relation to the fringed micelle model

Characterization of Polystyrene in Methyl Ethyl Ketone by Small-Angle X-Ray Scattering

Molecular and thermodynamic properties of polystyrene in methyl ethyl ketone were studied by a small-angle X-ray scattering with a Kratky camera. The molecular weight, radius of gyration, second virial coefficient, mass per unit length, hydrodynamic length, radius of gyration of cross section, persistence length, and radius of cross section were estimated. Some of these values were compared with the values determined by other methods. Both values agreed well each other

Effects of Cobalt-60 Gamma Radiation on Poly (vinyl alcohol) : II. Effects of Gamma Radiation on Water-Swollen Poly (vinyl alcohol) Films

Poly (vinyl alcohol) films swollen in water or swollen with adsorbed water vapor were irradiated with the dose up to 3.2×10⁷ γ in the presence of air. In these cases, gel formation occurred over a definite radiation dose. The active ends produced by main-chain fractures are assumed to be more capable of attacking other molecules at any point and joining to them, owing to the more mobile character of chains in the swollen films. On the assumption that the energy indirectly absorbed by the polymer depends on the water content in the swollen film, and that the free radicals produced from the water molecules do not directly contribute to the formation of linkage, theoretical calculation was performed for the case where the molecules are fractured by radiation and only a certain proportion e of the ends thus formed results in endinking and the remainder are stabilized and result in degradation. The experimental values of the radiation dose at gel point, the sol fraction, the average mole weight and the degree of swelling were compared with the theoretical relations. Assuning that the energy absorbed by the swollen film may entirely contribute to the polymer, we estimated the value of e at about 0.4 in the case of film swollen in water at 30°C

Chain Conformations of Polypeptide Copolymers

Chain conformations have been investigated theoretically by assuming Markoffian process for copolypeptides composed of two components of L-alanine, glycine, N-methyl glycine and N-methyl-L-alanine, for D.L-copolyalanine, and for D, L-copoly-N-methyl alanine. The characteristic ratio of these copolymers was plotted against the sequence probability that a residue is followed by a residue of the same kind. Some experimental results obtained for equimolar-D, L-copoly-γ-methyl glutamate are discussed with the aid of theoretical equation

Effects of Cobalt-60 Gamma Radiation on Poly (vinyl alcohol) : I. Effects of Gamma Radiation on Solid Poly (vinyl alcohol) Films

Solid films of the fractionated and unfractionated poly (vinyl alcohol) were cobalt-60 gamma irradiated both in the presence and absence of oxygen. The methods used to study the change in properties of the irradiated samples include intrinsic viscosity, swelling, solubility and density measurements. The changes of structure and the mechanism of reaction by the gamma radiation were quantitatively discussed in connection with the change in the molecular weight distribution. In our experimental condition of up to 5×10⁷ γ radiation dose, neither gel formation nor any difference dependent on the condition whether in the presence or the absence of oxygen was found. From the results obtained, we conclude that in the solid film, poly (vinyl alcohol) is dominantly degraded by random main-chain fracture throughout the crystalline and amorphous regions, although a small amount of endlinking may occur in the amorphous regions. Assuming the random main-chain fracture, the probability of a given main-chain bond being fractuated was estimated and it was found that the rate of degradation was propotional to the number of bond which was not fractured. The energy dissipation per chain fracture calculated was 38.7 e.v

The Lyman Continuum Escape Survey: Ionizing Radiation from [O III]-Strong Sources at a Redshift of 3.1

We present results from the LymAn Continuum Escape Survey (LACES), a Hubble Space Telescope (HST) program designed to characterize the ionizing radiation emerging from a sample of Lyman alpha emitting galaxies at redshift $z\simeq 3.1$. As many show intense [O III] emission characteristic of $z>6.5$ star-forming galaxies, they may represent valuable low redshift analogs of galaxies in the reionization era. Using HST Wide Field Camera 3 / UVIS $F336W$ to image Lyman continuum emission, we investigate the escape fraction of ionizing photons in this sample. For 61 sources, of which 77% are spectroscopically confirmed and 53 have measures of [O III] emission, we detect Lyman continuum leakage in 20%, a rate significantly higher than is seen in individual continuum-selected Lyman break galaxies. We estimate there is a 98% probability that $\leq 2$ of our detections could be affected by foreground contamination. Fitting multi-band spectral energy distributions (SEDs) to take account of the varying stellar populations, dust extinctions and metallicities, we derive individual Lyman continuum escape fractions corrected for foreground intergalactic absorption. We find escape fractions of 15 to 60% for individual objects, and infer an average 20% escape fraction by fitting composite SEDs for our detected samples. Surprisingly however, even a deep stack of those sources with no individual $F336W$ detections provides a stringent upper limit on the average escape fraction of less than 0.5%. We examine various correlations with source properties and discuss the implications in the context of the popular picture that cosmic reionization is driven by such compact, low metallicity star-forming galaxies.Comment: 26 pages, 16 figures, accepted for publication in Ap

Jugular Vein Technique for Serial Blood Sampling in the Hamster

The puncture is performed via the external jugular vein in hamster (100g) under appropriate anesthesia and will give 1 ml within 30 seconds with certainty and security. Blood volumes up to 1 ml have been obtained once a week for a period of 20 weeks