Survey of Period Variations of Superhumps in SU UMa-Type Dwarf Novae

We systematically surveyed period variations of superhumps in SU UMa-type dwarf novae based on newly obtained data and past publications. In many systems, the evolution of superhump period are found to be composed of three distinct stages: early evolutionary stage with a longer superhump period, middle stage with systematically varying periods, final stage with a shorter, stable superhump period. During the middle stage, many systems with superhump periods less than 0.08 d show positive period derivatives. Contrary to the earlier claim, we found no clear evidence for variation of period derivatives between superoutburst of the same object. We present an interpretation that the lengthening of the superhump period is a result of outward propagation of the eccentricity wave and is limited by the radius near the tidal truncation. We interpret that late stage superhumps are rejuvenized excitation of 3:1 resonance when the superhumps in the outer disk is effectively quenched. Many of WZ Sge-type dwarf novae showed long-enduring superhumps during the post-superoutburst stage having periods longer than those during the main superoutburst. The period derivatives in WZ Sge-type dwarf novae are found to be strongly correlated with the fractional superhump excess, or consequently, mass ratio. WZ Sge-type dwarf novae with a long-lasting rebrightening or with multiple rebrightenings tend to have smaller period derivatives and are excellent candidate for the systems around or after the period minimum of evolution of cataclysmic variables (abridged).Comment: 239 pages, 225 figures, PASJ accepte

Estimation of Maximum Load for Pipes with Multiple Circumferential Flaws by Limit Load Analysis

ABSTRACT Fully plastic failure stress for a single circumferential flaw in a pipe is evaluated by the limit load criteria in accordance with Appendix C in the ASME Code Section XI and Appendix E-8 in the JSME S NA-1-2004. However, multiple flaws such as stress corrosion cracking are frequently detected in the same circumferential cross section in a pipe. Limit load analysis has been validated for pipes with multiple circumferential flaws. Quasi-static four-point bending tests were performed on Type 304 stainless steel pipes with single, double, or triple circumferential flaws. Maximum loads measured in these tests were estimated by limit load analysis for pipes with multiple circumferential flaws. All estimation results using flow stress defined by the JSME S NA-1-2008 are conservative compared to the test results. Estimation results using flow stresses obtained from tests for the pipe with a single flaw quantitatively agree with test results

A 19-Year Study of Dental Needlestick and Sharps Injuries in Japan

Background: Needlestick and sharps injuries (NSIs) are serious problems for dental health care workers (DHCWs) because they are at risk for occupational blood-borne infections. In this study, risk factors for NSIs in DHCWs at Tohoku University Hospital (TUH) in Japan over 19 years were analysed. Methods: NSI data of DHCWs at TUH from April 2002 to March 2020 were collected from the Exposure Prevention Information Network (EPINet) and statistically analysed. Results: A total of 195 NSIs occurred during the 19-year study period. Approximately 58.5% of NSIs occurred in DHCWs with less than 5 years of experience. Injection needles were the most frequent cause of NSIs (19.0%) followed by suture needles (13.3%) and ultrasonic scaler chips (12.8%). Needle injuries occurred mainly on the left hand, whereas ultrasonic scaler chip and bur injuries occurred on the right hand and other body parts whilst DHCWs were placing the instruments back on the dental unit hanging holder without removing the sharps. NSIs from other instruments primarily occurred on both hands and foot insteps during cleanup. No case of occupational blood-borne infection caused by NSIs was observed during the study period at TUH. Conclusions: NSIs occurred in DHCWs with less experience, and there were associations between the instruments, timing of use, and NSI site. EPINet was considered a valuable tool for monitoring NSIs in order to develop future strategies for minimising NSIs