New relations for scattering amplitudes in Yang-Mills theory at loop level

The calculation of scattering amplitudes in Yang-Mills theory at loop level is important for the analysis of background processes at particle colliders as well as our understanding of perturbation theory at the quantum level. We present tools to derive relations for especially one loop amplitudes, as well as several explicit examples for gauge theory coupled to a wide variety of matter. These tools originate in certain scaling behavior of permutation and cyclic sums of Yang-Mills tree amplitudes and loop integrands. In the latter case evidence exists for relations at all loop orders.Comment: 12 pages, 4 figures. v3: typos corrected, figures and clarifications adde

The Glenn Miller story

Der Film verfolgt das Leben des Jazzmusikers und späteren Bandleaders Glenn Miller. Zunächst wird er als armer Künstler dargestellt, der häufiger im Pfandleihhaus als auf der Bühne ist. Motiviert durch seinen Freund reist er nach New York, wo er ein Engagement am Broadway erhält. Auf dem Weg trifft er sich mit seiner unglücklich in einen anderen Mann verlobten Ex-Freundin, die er später nach New York holt und zügig und sehr zu ihrer Überraschung heiratet

Predicting the outcome of renal transplantation

ObjectiveRenal transplantation has dramatically improved the survival rate of hemodialysis patients. However, with a growing proportion of marginal organs and improved immunosuppression, it is necessary to verify that the established allocation system, mostly based on human leukocyte antigen matching, still meets today's needs. The authors turn to machine-learning techniques to predict, from donor-recipient data, the estimated glomerular filtration rate (eGFR) of the recipient 1 year after transplantation.DesignThe patient's eGFR was predicted using donor-recipient characteristics available at the time of transplantation. Donors' data were obtained from Eurotransplant's database, while recipients' details were retrieved from Charite Campus Virchow-Klinikum's database. A total of 707 renal transplantations from cadaveric donors were included.MeasurementsTwo separate datasets were created, taking features with <10% missing values for one and <50% missing values for the other. Four established regressors were run on both datasets, with and without feature selection.ResultsThe authors obtained a Pearson correlation coefficient between predicted and real eGFR (COR) of 0.48. The best model for the dataset was a Gaussian support vector machine with recursive feature elimination on the more inclusive dataset. All results are available at http://transplant.molgen.mpg.de/.LimitationsFor now, missing values in the data must be predicted and filled in. The performance is not as high as hoped, but the dataset seems to be the main cause.ConclusionsPredicting the outcome is possible with the dataset at hand (COR=0.48). Valuable features include age and creatinine levels of the donor, as well as sex and weight of the recipient

Gendering Peacebuilding in Post-conflict Northern Uganda

Approximately 1.8 million northern Ugandans were internally displaced during conflict between the Ugandan government and Lord’s Resistance Army (LRA) rebels (1987-2006). The ethnographic and qualitative research findings presented in this article illuminate the need to address structural violence, not just physical violence, in the aftermath of conflict, and to pay particular attention to how conflict and peacebuilding processes are gendered. Although gender-sensitive approaches to peacebuilding have increased in recent years, especially among scholars, in practice these processes often still fail to adequately address the myriad needs of survivors and to understand the complex interplay between gender, conflict, and post-conflict rebuilding. Instead, “gendered” peacebuilding efforts focus attention on physical sexual violence experienced by women during conflict as opposed to structural violence pervading conflict and the post-conflict period. For example, findings from research among Acholi and Langi, the two most prominent ethnic groups in northern Uganda, indicate that structural violence stemming from devastated economic livelihoods, poverty, ruptured sociocultural norms, and shifting gender roles exacerbate the effects of violent conflict and disproportionately affect women. Despite the prevalence of and participants’ concerns about structural violence, peacebuilders and policy-makers continue to emphasize and prioritize resolution of physical violence, such as rape. Based on primary research, this article explores the link between livelihood, peacebuilding efforts, and gender, and argues that gendering peacebuilding to address economic opportunity, land conflict, and other forms of pervasive structural violence is central to building sustainable peace in the region

A microRNA Imparts Robustness against Environmental Fluctuation during Development

The microRNA miR-7 is perfectly conserved from annelids to humans, and yet some of the genes that it regulates in Drosophila are not regulated in mammals. We have explored the role of lineage restricted targets, using Drosophila , in order to better understand the evolutionary significance of microRNA-target relationships. From studies of two well characterized developmental regulatory networks, we find that miR-7 functions in several interlocking feedback and feedforward loops, and propose that its role in these networks is to buffer them against perturbation. To directly demonstrate this function for miR-7, we subjected the networks to temperature fluctuation and found that miR-7 is essential for the maintenance of regulatory stability under conditions of environmental flux. We suggest that some conserved microRNAs like miR-7 may enter into novel genetic relationships to buffer developmental programs against variation and impart robustness to diverse regulatory networks

Coloration and the Evolution of Live Birth

Organisms have a finite amount of energy with which to invest in survival, growth, and reproduction. Reproductive strategies can range from those that require minimal energy to produce eggs (oviparity) that then develop unassisted, those that require some energy to produce eggs that then hatch internally (ovoviviparity), and those that require significant energy to fully develop internally before birth (viviparity). Females of species that invest large amounts of energy to give birth to live young (viviparous species) may thus have more to lose in choosing low-quality mates than females of species that lay eggs (oviparous species). These females may therefore invest more energy in choosing high-quality males, increasing the competition between males for mates selecting for males with traits that advertise quality. Female choosiness is known to lead to more male-male competition and thus larger males, as well as more colorful and more ornamented males. Thus, we used coloration and body size as a proxy for female mate choice to investigate the correlation between female choosiness and the evolution of viviparity. However, oviparity and viviparity are nearly ubiquitous in birds and mammals, respectively, making it difficult to resolve questions about the evolution of viviparity. Squamate reptiles (lizards and snakes) present a unique opportunity to assess the evolution of live birth because viviparity appears to have evolved multiple times within these groups. Using phylogenetically controlled methods and a well-resolved but diverse group of squamate reptiles, we assessed whether the evolution of viviparity led to more colorful males across 248 species. For a subset of individuals for which sexual size dimorphism was quantified, we also determined whether the evolution of viviparity impacted the degree of size dimorphism. Finally, we determined the average estimated length of time required for males to evolve ornaments and estimated the rate of evolution of coloration across reptiles. These data are important for understanding the evolution of color across multiple groups of animals, as well as for understanding the consequences of viviparity in endothermic groups such as mammals. For example, viviparous lineages have significantly higher speciation and extinction rates than oviparous lineages, and our study suggests that sexual selection for male colorfulness may be one of the drivers of these high rates