An equation has been suggested which correlate the NMR and refractometry results to evaluate the stability constant of electron donor acceptor complexes. Using this equation the stability constant of complexation between carbon tetrachloride and toluene in cyclohexane has been studied by refractometry and NMR spectroscopy.    

Background: The main drawbacks of zirconia are its high refractive index and opacity. This study aimed to assess the effect of sintering temperature on the translucency of Ivoclar e. max ZirCAD (IEZ), and White Peaks Symphony (WPS) zirconia blocks. Materials and Methods: In this in vitro experimental study, 30 IEZ and 30 WPS zirconia blocks measuring 10 mm × 10 mm × 1 mm were prepared and underwent sintering in three subgroups at 1440°, C, 1500°, C, and 1530°, C. The specimens were then photographed against a black and a white background with a standard digital camera. The L*, a*, and b* color parameters were measured using Adobe Photoshop software, and translucency was calculated. Data were analyzed using one‑, way ANOVA and Tukey’, s test (P < 0. 05). Results: In both the IEZ and WPS groups, the maximum and minimum translucency parameters were recorded in 1530°, C and 1440°, C subgroups, respectively. The difference in the mean translucency was significant among the three subgroups of each zirconia group (P < 0. 001). The mean translucency of WPS zirconia was significantly higher than that of IEZ zirconia (P < 0. 01), and maximum difference was noted at 1500°, C sintering temperature. Conclusion: Increasing the sintering temperature from 1440°, C to 1530°, C can significantly increase the translucency of IEZ and WPS zirconia blocks, and can be considered to improve the quality of zirconia restorations.

Background: Accumulation of pleural and peritoneal fluid is seen in some diseases. In order to diagnose the disease and start the treatment, one of the most important actions will be to differentiate between exudates and transudates. The objective of this study was to determine the diagnostic value of measuring the specific gravity of the fluid through refractometer and strip in differentiation of exudates from transudates. Methods: The serum of patients was evaluated for protein, LDH, cholesterol, bilirubin and albumin. The fluid was evaluated for the number of white blood cells, protein, LDH, cholesterol, bilirubin and albumin. Then the fluids were divided into exduate and transudate categories based on Light and Gradient criteria. Finally, the specific gravity of the fluids was measured by refractometer, Erma, Japan and Medi-Test Combi II. The categorized fluids were compared with Gold Standards (final diagnosis) so that the sensitivity and specificity of Light and Gradient criteria in the transudate-exudate differentiation were specified. Results: In comparison with Light criteria, the cut off level of 1022 specific gravity measured by refractometer for pleural effusion has sensitivity, specificity of 92. 1%, 68. 1%respectively. In evaluation of peritoneal fluid considering cut off point 1023, measured by refractometer has reliable sensitivity 92. 4%, specificity 70. 4 compared with standard gradient method. Conclusion: Differentiating transudate from exudates by measuring its special gravity by refractometer will have acceptable sensitivity and specificity, and when rapidity is necessary or access to lab equipment is limited, this method could be used.

Vinylpyrrolidone-vinyl acetate (VP-VA) hydrophobically associating water-soluble copolymers were synthesized by free radical copolymerization. The effects of hydrophobic content and temperature on the viscosity and refractive index behaviour were investigated in detail. The critical concentration C* of the hydrophobically associating water-soluble copolymers was studied in the static state and in flowing solution by refractometry and viscosimetry, respectively. A dramatic decrease in solution viscosity of P(VP-VA) copolymers is observed with increasing the VA content at all temperatures. Also as the VA content in the copolymer increased, the solution refractive index of the copolymer decreased. The lowering in viscosity and refractive index reflects the contraction of the polymer coil because of intramolecular hydrophobic interactions. Variation of the dynamic and static critical concentration as a function of the temperature for P(VP-VA) copolymer in water has been investigated. The critical concentrations are lower when determined by refractive index measurements in the static state compared to the critical concentrations determined in the dynamic state using viscometer.