SynopsisEffect of addition of salt on the viscometric behavior of the dilute or concentrated aqueous solution of hydroxypropyl cellulose (HPC) was determined by means of an Ubbelohde or a cone-plate viscometer. That effect on the turbidity of the dilute system was also determined. As salts, NaC1, LiCl, and thiourea were chosen. The turbidity and viscometric behavior for the dilute system, and the viscometric behavior for the concentrated system were greatly affected by salt type and concentration. With increasing NaCl or LiCl concentration, the cloud point decreased,[el showed a maximum, Huggins' constant k' showed a minimum, and the shear viscosity for concentrated isotropic solutions showed a maximum. The 45 wt % solution with no salt showed a viscometric behavior which was characteristic of lyotropic liquid crystals; however, with increasing NaCl concentration, a critical temperature at which the shear viscosity showed a maximum with respect to temperature shifted to lower temperature. This behavior was due to an increase in the turbidity, not due to a phase transformation. On the other hand, an addition of thiourea did not affect so greatly the turbidity and viscometric behavior as an addition of NaCl or LiCl did. We speculated different actions of NaCl and thiourea.

Efficient electroluminescence of silicon light emitting p-n diodes of different sizes and shapes is investigated at room temperature. High quantum efficiency of the diodes, a long linear dependence of the electroluminescence intensity on the diode current and a low energy shift of the emission line in electroluminescence spectra with increasing diode current are explained by the self-compression of the injected electron-hole plasma into dense electron-hole plasma drops. Experiments on space scanning of the electroluminescence intensity of the diodes support this conclusion. The plasma self-compression is explained by the existence of an attraction in electron-hole plasma compensating the plasma pressure. A decrease of the semiconductor energy gap due to local lattice overheating, produced by the plasma, and the exchange-correlation interaction could contribute to this attraction. The self-focusing of the injection current can accompany the plasma self-compression.