A Tree-Loop Duality Relation at Two Loops and Beyond

The duality relation between one-loop integrals and phase-space integrals, developed in a previous work, is extended to higher-order loops. The duality relation is realized by a modification of the customary +i0 prescription of the Feynman propagators, which compensates for the absence of the multiple-cut contributions that appear in the Feynman tree theorem. We rederive the duality theorem at one-loop order in a form that is more suitable for its iterative extension to higher-loop orders. We explicitly show its application to two- and three-loop scalar master integrals, and we discuss the structure of the occurring cuts and the ensuing results in detail.Comment: 20 pages. Few typos corrected, some additional comments included, Appendix B and one reference added. Final version as published in JHE

Solving integral equations in η→3π\eta\to 3\pi

A dispersive analysis of $\eta\to 3\pi$ decays has been performed in the past by many authors. The numerical analysis of the pertinent integral equations is hampered by two technical difficulties: i) The angular averages of the amplitudes need to be performed along a complicated path in the complex plane. ii) The averaged amplitudes develop singularities along the path of integration in the dispersive representation of the full amplitudes. It is a delicate affair to handle these singularities properly, and independent checks of the obtained solutions are demanding and time consuming. In the present article, we propose a solution method that avoids these difficulties. It is based on a simple deformation of the path of integration in the dispersive representation (not in the angular average). Numerical solutions are then obtained rather straightforwardly. We expect that the method also works for $\omega\to 3\pi$.Comment: 11 pages, 10 Figures. Version accepted for publication in EPJC. The ancillary files contain an updated set of fundamental solutions. The numerical differences to the former set are tiny, see the READMEv2 file for detail

Tex19.1 Promotes Spo11-Dependent Meiotic Recombination in Mouse Spermatocytes

Meiosis relies on the SPO11 endonuclease to generate the recombinogenic DNA double strand breaks (DSBs) required for homologous chromosome synapsis and segregation. The number of meiotic DSBs needs to be sufficient to allow chromosomes to search for and find their homologs, but not excessive to the point of causing genome instability. Here we report that the mammal-specific gene Tex19.1 promotes Spo11-dependent recombination in mouse spermatocytes. We show that the chromosome asynapsis previously reported in Tex19.1-/- spermatocytes is preceded by reduced numbers of recombination foci in leptotene and zygotene. Tex19.1 is required for normal levels of early Spo11-dependent recombination foci during leptotene, but not for upstream events such as MEI4 foci formation or accumulation of H3K4me3 at recombination hotspots. Furthermore, we show that mice carrying mutations in Ubr2, which encodes an E3 ubiquitin ligase that interacts with TEX19.1, phenocopy the Tex19.1-/- recombination defects. These data suggest that Tex19.1 and Ubr2 are required for mouse spermatocytes to accumulate sufficient Spo11-dependent recombination to ensure that the homology search is consistently successful, and reveal a hitherto unknown genetic pathway promoting meiotic recombination in mammals

The Global Health System: Linking Knowledge with Action—Learning from Malaria

In the third in a series of articles on the changing nature of global health institutions, Gerald Keusch and colleagues examine institutional arrangements for malaria research

Laparoscopic management of appendicitis and symptomatic cholelithiasis during pregnancy

BACKGROUND: Laparoscopic surgery during pregnancy is a challenging procedure that most surgeons are reluctant to perform. The objective of this study was to evaluate whether laparoscopic appendectomy and cholecystectomy is safe in pregnant women. The management of these situations remains controversial. We report a single center study describing the successful management of 16 patients during pregnancy. METHODS: More than 3,356 laparoscopic procedures were performed in our institutions between May 1990 and June 2005. Sixteen of these patients were operated on in the second and third trimester between 22 and 32 weeks of estimated gestational age. We performed 11 laparoscopic appendectomies and 5 laparoscopic cholecystectomies. We also reviewed the management and operative technique used in these patients. RESULTS: In this study, the laparoscopic appendectomy or cholecystectomy was performed successfully in all patients. Three patients were in their second trimester, weeks 22, 23, and 25, and 13 were in the third trimester, weeks 27 (three patients), 28 (five patients), 31 (three patients), and 32 (two patients). No maternal or fetal morbidity occurred. Open laparoscopy was performed safely in all patients and all patients delivered healthy babies. CONCLUSION: From our experience laparoscopic management of appendicitis and biliary colic during pregnancy is safe, however the second trimester is preferable for laparoscopic cholecystectomy. Pregnancy is not a contraindication to the laparoscopic approach to appendicitis or symptomatic cholelithiasis. We believe that laparoscopic operations, when performed by experienced surgeons, are safe and even preferable for the mother and the fetu