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

Uncontrollable uterine atony after replacement of uterine inversion managed by hysterectomy: a case report.

Background:Uterine inversion may cause massive hemorrhage, resulting in maternal deterioration and death. Replacement of the inverted uterus must be performed as soon as possible. As time passes, the inverted uterus becomes atonic and necrotic, and a surgical approach may be required.Case presentation:A 27-year-old Japanese woman was admitted to our hospital 4 hours postpartum with increased hemorrhage after the replacement of an inverted uterus. Recurrent inversion was diagnosed, and though the atonic uterus was replaced again by the Johnson maneuver, hemorrhage persisted. Balloon tamponade was not successful in stopping the hemorrhage, and uterine artery embolization was performed. Bleeding resumed the next day on removal of the balloon, and hysterectomy was performed. Massive hemorrhage, coagulopathy, and uterine necrosis caused uterine atony, and the reperfused blood flow on replacement of the ischemic uterus increased hemorrhage.Conclusions:Cases of uterine inversion with coagulopathy lasting for more than 4 hours may require a surgical intervention, and uterine replacement may have to be delayed until the maternal hemodynamic condition is stabilized. Uterine replacement under laparotomy may be also be considered due to the risk of increased hemorrhage