Analysis of chaotic dynamical systems with autoencoders.

We focus on chaotic dynamical systems and analyze their time series with the use of autoencoders, i.e., configurations of neural networks that map identical output to input. This analysis results in the determination of the latent space dimension of each system and thus determines the minimal number of nodes necessary to capture the essential information contained in the chaotic time series. The constructed chaotic autoencoders generate similar maximal Lyapunov exponents as the original chaotic systems and thus encompass their essential dynamical information.

Contraceptive knowledge, attitudes and use among women attending health clinics in St. Petersburg, Russian Federation.

PIP: This study describes women's knowledge, attitudes, and use of contraception in Russia. Data were obtained from a sample of 917 women attending 44 women's consulting centers in St. Petersburg during January 15-30, 1995. Findings indicate that 68% were married; 21% were single. 56.1% worked full-time, 7.2% worked part-time, and 9.4% were students. 50.9% reported having received sex education, of whom 73.8% learned about birth control methods and 70.7% learned about abortion. Over 90% of the entire sample knew about condoms, IUDs, and oral contraceptives. About 60-70% knew about rhythm, withdrawal, and female sterilization. 49-56% were aware of vaginal suppositories and vasectomy. Under 23% were aware of the diaphragm, sponge, jelly, and foam. People talked about family planning with doctors and partners. 58.7% preferred joint responsibility for family planning. 909 women responded to the question about the current method being used: 41% reported using condoms; 33.8%, IUDs; 32.8%, pills; 23.7%, the rhythm method; and 17.2%, withdrawal. Many women used multiple methods, but the questions did not clearly distinguish single from concurrent multiple method use or switching between a few methods. 20.6% report nonuse. 115 of 187 were pregnant or desiring a pregnancy. Nonusers were concerned about side effects. Method choice was based on effectiveness and ease of use. Few were dissatisfied with their method choice. About 75% reported method switching over time. Most of the 452 oral contraceptive users knew 2-3 side effects. 25.1% of the 319 condom users were usual users.^ieng