Optical rotatory power of Ca,Sr(C,H,CO,), was accurately measured over a wide temperature range containing both paraelectric and ferroelectric states. The gyration tensor qS3 has been determined from the experimental data; for instance, qss = 2.131 x 10-6, paraelectric a t 20 "C, and 2.129 x lo-&, ferroelectric a t -20 "C (A = 546 nm). A theory of optical activity based upon Born's theory has been developed in order to apply it to the ferroelectricity. In the light of the theory the ferroelectric property of Ca,Sr(C,H,CO,),, is discussed, and it has been revealed that some change occurs around -64 "C in either antisymmetrical parts of interelectronic coupling tensor or shifts of the atoms responsible for its ferroelectricity.Nous avons mesure avec precision le pouvoir rotatoire de Ca,Sr(C,H,CO,), dans un large domaine de temperature comprenant 8, la fois les Btats para et ferroblectriques, et nous avons ainsi pu determiner le tenseur de gyration qm; par exemple, g, = 2,131 x dans la phase paraelectrique 8, 20 "C, et 2,129 x 10-5 dans la phase ferroelectrique 8, -20 "C, pour la longuer d'onde Iz = 646 nm. Nous avons developpb la theorie de Born de maniere 8, I'appliquer au cw de la ferro6lectricit8, et nous pouvons ainsi interpreter les rbsultats expbrimentaux. Nous sommes alors amenbs 8, supposer q'un changement doit intervenir aux environs de -64 "C, soit dans la partie antisymmbtrique du tenseur d'interactions entre electrons, soit dans le deplacement des atomes responsables de la ferroblectricitb.

Preoperative factors related to perceived leg length discrepancy (PLLD) after total hip arthroplasty (THA) are not well studied. This study aimed to examine the preoperative factors, including hip abductor modulus, related to PLLD one month after THA. Methods: The study included 73 patients diagnosed with osteoarthritis secondary to developmental dysplasia of the hip and a posterior approach to surgery. Multiple logistic regression analysis was performed using the presence or absence of PLLD as the dependent variable and preoperative hip abductor's modulus of elasticity, pain, hip abduction range of motion, hip abductor muscle strength and pelvic obliquity as the independent variable. Additionally, receiver operating characteristic curves were used for the extracted variables for calculating the cutoffs, sensitivity, specificity and area under the curve (AUC) to determine the presence or absence of PLLD. The significance level was set at p<0.05. Results: The hip abductor modulus (odds ratio=1.13; 95% confidence interval=1.06-1.21; p<0.001) was selected as a preoperative factor. The cutoff value to determine the presence or absence of a PLLD was 16.32 kPa. The sensitivity and specificity were 81.8% and 72.5%, respectively, and the AUC was 0.8137. Conclusion: The hip abductor muscle elastic modulus affected PLLD one month after THA. If the preoperative hip abductor elastic modulus is higher than the cutoff value, it may affect the appearance of PLLD at one month postoperatively.

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