Experimental Investigation of Bubble Migration near Anisotropic Beams.

In order to resist bubble loading, anisotropic composite materials are the development direction of the future. The objective of this paper was to experimentally investigate the hydrodynamic performance of anisotropic laminate composite plates, with a focus on the effect of its anisotropic characteristics on single bubble migration. In these experiments, the bubble was generated in a transparent water tank filled with sufficiently degassed water by Joule heating at the connecting point of the electrodes through the discharge of a 6600 µF charge to 800 V, and a high-speed camera system with a recording speed of 40,000 frames per second was used to record the temporal evolution of bubble patterns and the dynamic responses of the laminated composite plates. The results are presented for two anisotropic cantilever composite beams with different ply angles, namely, 0° and 30°. Several variables, such as the shapes of the bubble, the curved trail of motion of the bubble center, bubble collapse time, and bubble initial standoff distances were extracted from the photographic images. The results showed that bubble migration near the 30° plate presents a curved bubble trail with an evident tilted angle during the collapse and rebound stages, which is very different from bubbles that all move vertically above the 0° plate. Furthermore, a characterization method for bubble migration was proposed to quantitatively describe the curved bubble trails and the deformation of the composite beams in temporal and spatial scales. This method shows that the curved bubble trails near the 30° plate are closely related to the dynamic response of composite beams, with a focus on the bending-twisting coupling effect.

Putative antirecombinase Srs2 DNA helicase promotes noncrossover homologous recombination avoiding loss of heterozygosity.

DNA damage alone or DNA replication fork arrest at damaged sites may induce DNA double-strand breaks and initiate homologous recombination. This event can result in a crossover with a homologous chromosome, causing loss of heterozygosity along the chromosome. It is known that Srs2 acts as an antirecombinase at the replication fork: it is recruited by the SUMO (a small ubiquitin-related modifier)-conjugated DNA-polymerase sliding clamp (PCNA) and interferes with Rad51/Rad52-mediated homologous recombination. Here, we report that Srs2 promotes another type of homologous recombination that produces noncrossover products only, in collaboration with PCNA and Rad51. Srs2 proteins lacking the Rad51-binding domain, PCNA-SUMO-binding motifs, or ATP hydrolysis-dependent DNA helicase activity reduce this noncrossover recombination. However, the removal of either the Rad51-binding domain or the PCNA-binding motif strongly increases crossovers. Srs2 gene mutations are epistatic to mutations in the PCNA modification-related genes encoding PCNA, Siz1 (a SUMO ligase) and Rad6 (a ubiquitin-conjugating protein). Knocking out RAD51 blocked this recombination but enhanced nonhomologous end-joining. We hypothesize that, during DNA double-strand break repair, Srs2 mediates collaboration between the Rad51 nucleofilament and PCNA-SUMO and directs the heteroduplex intermediate to DNA synthesis in a moving bubble. This Rad51/Rad52/Srs2/PCNA-mediated noncrossover pathway avoids both interchromosomal crossover and imprecise end-joining, two potential paths leading to loss of heterozygosity, and contributes to genome maintenance and human health.

La migración de la burbuja de aire postransferencia embrionaria es un evento al azar / Air bubble migration post embrionary tranferir is a random event

Demostrar que la migración de la burbuja de aire postransferencia embrionaria es un evento al azar que no depende de la posición del paciente. Estudio prospectivo multicéntrico. Se practicó transferencia embrionaria a 69 pacientes bajo guía ultrasonográfica. Se cargó el catéter de transferencia con una o dos burbujas junto con el medio conteniendo los embriones usando catéter de Frydman o catéter de Wallace y luego se les hizo seguimiento ecográfico en posición horizontal, 20-25 minutos más tarde y luego a los 90 minutos postransferencia en posición vertical para verificar movimiento y configuración de las burbujas. Centro Médico Docente La Trinidad, Caracas. Nortwestern University Feimberg School of medicine, Chicago, IL. EE.UU. En 50 (72,46 por ciento) de las pacientes se observó movimiento de las burbujas. En posición de pie se demostró una distribución al azar sin efecto visible de la gravedad. Las burbujas de aire se mueven y dividen frecuentemente posterior a la transferencia con la paciente en posición horizontal y de pie, lo que sugiere actividad contráctil uterina. No fue común observar movimiento de burbujas relacionada con la gravedad, lo que sugiere que el descanso horizontal postransferencia embrionaria puede ser innecesario.

To demonstrate that air bubble migration is a random event after embryo transfer regardless of the position of patient. Multicenter prospective study. Sixty nine embryo transfers were performed under ultrasound guidance. Transfer catheter was loaded with one or two air bubbles and medium containing embryos, either Wallace catheter or Frydman catheter were used, ultrasound tracking of air bubble was performed to verify movement and configuration inmediately, 20-25 minutes in horizontal position and 90 minutes on standing position after embryo transfer. Centro Medico Docente La Trinidad, Caracas. Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA. Movement was observed in 50 (72,46 percent) of the patients. Movement was not observed related to gravity while standing up. Air bubbles move and split frequently after embryo transfer with the patient in the horizontal position and on standing, suggestive of active uterine contractions. Gravity related bubble motion was uncommon, suggesting that horizontal rest post embryo transfer may be unnecessary.