Two-Loop Four-Graviton Scattering Amplitudes.

We present the analytic form of the two-loop four-graviton scattering amplitudes in Einstein gravity. To remove ultraviolet divergences we include counterterms quadratic and cubic in the Riemann curvature tensor. The two-loop numerical unitarity approach is used to deal with the challenging momentum dependence of the interactions. We exploit the algebraic properties of the integrand of the amplitude in order to reduce it to a minimal basis of Feynman integrals. Analytic expressions are obtained from numerical evaluations of the amplitude. Finally, we show that four-graviton scattering observables depend on fewer couplings than naïvely expected.

Two-Loop Four-Gluon Amplitudes from Numerical Unitarity.

We present the first numerical computation of two-loop amplitudes based on the unitarity method. As a proof of principle, we compute the four-gluon process in the leading-color approximation. We discuss the new method, analyze its numerical properties, and apply it to reconstruct the analytic form of the amplitudes. The numerical method is universal, and can be automated to provide multiscale two-loop computations for phenomenologically relevant signatures at hadron colliders.

Spontaneous pregnancy outcome after prenatal diagnosis of anencephaly.

Parents are usually told that many anencephalic offspring die in utero or soon after delivery, and many obstetricians offer elective termination of the pregnancy. Following the personal experience of the first author, a personal website was created with the intention of providing information and exchanging views with other parents confronted with a prenatal diagnosis of anencephaly. Data were collected from 211 pregnancies where the parents opted not to terminate pregnancy. These data revealed that polyhydramnios was a feature in 56 (26%) pregnancies, death in utero in 15 (7%) pregnancies, 72 (34%) babies were born prematurely (<37 weeks of gestation), 113 (53%) at term and 21 (10%) after 42 weeks. Stillbirth, presumably resulting from intrapartum death, occurred in 43 (20%) deliveries. One hundred and fifty-three (72%) of anencephalic offspring were liveborn, of those, 103 (67%) died within 24 hours but 6/211 survived 6 or more days (maximum 28 days). Continuation of pregnancy after a diagnosis of anencephaly is medically safe and should be considered as an option.

Anatomical localization of corticotropin-releasing activity in the human brain.

Corticotropin-releasing activity (CRa) and arginine-vasopressin (AVP) content were measured in seven human hypothalami. The hypothalami were obtained from routine autopsy of patients suffering from no obvious neuroendocrinological abnormality. Twelve distinct hypothalamic areas were dissected in the frozen state and extracted in aqueous solution. CRa was measured by a bioassay measuring the aCTH released by rat pituitary cells in vitro, and vasopressin by direct radioimmunoassay. CRa was detectable in almost every area with the highest values in the supraoptic, paraventricular and infundibular (arcuate) areas. Vasopressin concentrations were maximum in the supraoptic nucleus, followed by the paraventricular and infundibular nuclei. We conclude that: hypothalami obtained from routine autopsy at a general hospital can be used for consistent CRa and vasopressin assay. Vasopressin and CRa are similarly distributed in man and in the rat. In both species, high CRa, which is not explained by AVP, is found in the paraventricular nucleus. The infundibular (arcuate) nucleus seems to display non AVP-dependent CRa much greater in the human than in the rat.