No abstract

The shrinking/swelling behavior across the volume phase transition temperature, Tc, has been investigated for cylindrical gels made of poly(N-isopropylacrylamide-co-acrylic acid) (NIPA/AAc) and poly(N-isopropylacrylamide) (NIPA). NIPA/AAc gel shrank at Tc ) 43°C by quasistatic heating. On the other hand, the gel underwent a shrinking transition at a lower temperature, i.e., Tc ≈ 40°C, when a temperature jump was applied to the gel from 20°C. More interestingly, the shrinking process consisted of three stages: (i) a uniform shrinking stage where the gel diameter decreases exponentially, (ii) a plateau stage where the gel shrinks further from both ends of the cylinder while the middle (swollen) part remains in the swollen state, and (iii) a collapsing stage where the middle part of the gel shrinks linearly with time. This sequential process was found to be characteristic of weakly charged gels with a large aspect ratio. To the contrary, the swelling process was fitted with a single exponential function given by the Tanaka-Fillmore theory on gel swelling. This interesting shrinking behavior was discussed by comparing the results of swelling kinetics. In the case of NIPA homopolymer gel, the shrinking process was strongly decelerated due to phase separation, while the swelling process was well reproduced by the TanakaFillmore theory.

The equilibrium swelling ratios of temperature sensitive polymer gels have been studied as a function of the initial monomer concentration at preparation in both the swollen and the shrunken states. The linear swelling ratio, d/d0, was independent of the initial monomer concentration of N-isopropylacrylamide, C0, where d and d0 are the diameters of gels at observation and at preparation, respectively. On the other hand, d/d0 was proportional to C0 in the shrunken state. The swelling curves of gels with different C0's were successfully reproduced with a modified Flory-Rehner equation, where the effective cross-link density was modified to be proportional to C0 by taking account of the contribution of "excess cross-linking" by entanglement. Scaling rules for the polymer fractions were derived for both the swollen and the shrunken states; i.e., φsw ∼ C0 1 and φsh ∼ C0 0 , where φsw and φsh are the equilibrium volume fractions of the network at the swollen and shrunken phases, respectively.

EMB is a preferred surgical procedure for the repair of retinal detachment and macular hole closure in highly myopic eyes with posterior staphyloma.

Blue-on-yellow (B/Y) perimetry was performed on 31 patients with non-insulin-dependent diabetes mellitus to study the loss of sensitivity to short wavelengths. Of these patients, 21 were without retinopathy (NDR) and 10 had early background retinopathy (SDR). Eleven normal subjects served as controls. The results were compared to white-on-white (W/W) perimetry. Foveal sensitivity determined by B/Y and W/W perimetry showed no significant difference between NDR, SDR and normals. However, the mean sensitivity in the central 30-degree area and that in the upper half of the central 20- to 30-degree concentric circular field were significantly decreased in B/Y perimetry in SDR patients (p < 0.05, p < 0.01, respectively). No significant sensitivity loss was detected in the W/W test. We conclude that there is a blue cone system sensitivity loss in the central 30-degree area, particularly in the upper half of the visual field and the paracentral area in diabetic patients with early background retinopathy.