Global Optimization Of Quasi-Monoenergetic Electron Beams From Laser Wakefield Accelerators

We globally optimize a terawatt-laser-driven wakefield accelerator by systematically varying laser and target parameters to achieve 100 MeV electrons, 10% energy spread, 100 pC charge, 4 mrad divergence and 10 mrad pointing fluctuation with similar to 100% reproducibility, thereby meeting conditions for producing similar to 10(6) 200 keV X-ray photons/pulse by inverse Compton scatter.Physic

Sex Ratio and Sexual Dimorphism in \u3ci\u3eFormica Exsectoides\u3c/i\u3e, the Allegheny Mound Ant (Hymenoptera: Formicidae)

We excavated 66 mounds from 6 populations of Formica exsectoides in Michigan jack pine, collecting sexual caste pupae for sex ratio estimates and measurement of dimorphism. Reproductive caste brood was present in only 37 ofthe 66 mounds, and presence of reproductive caste brood was associated with larger mound surface area. Females were heavier than males, but did not differ from males in energy density. Sexes did not differ in timing or rate of development. Sex ratio estimates based on individual mounds ranged from 1.0 (all male) to 0.08 (female·biased). Four of the six study populations were strongly male·biased, while sex ratio estimates for the remaining populations did not differ from equal investment. While this interpopulation variation may be caused by genetic factors, the equal investment populations were 10· cated in or near patches of clear·cut forest, suggesting that environmental impacts should be investigated

Determinations of |V_ub| and |V_cb| from measurements of B -> X_u,c\ell\nu differential decay rates

Methods are described in the framework of light-cone expansion which allow one to determine the Cabibbo-Kobayashi-Maskawa matrix elements |V_ub| and |V_cb| from measurements of the differential decay rates as a function of the scaling variables in the inclusive semileptonic decays of B mesons. By these model-independent methods the dominant hadronic uncertainties can be avoided and the B -> X_u\ell\nu decay can be very efficiently differentiated from the B -> X_c\ell\nu decay, which may lead to precise determinations of |V_ub| and |V_cb|.Comment: 11 pages, 2 figures, version as published in Mod. Phys. Lett. A, more discussion, references added, title chang

A semi-empirical stability criterion for real planetary systems

We test a crossing orbit stability criterion for eccentric planetary systems, based on Wisdom's criterion of first order mean motion resonance overlap (Wisdom, 1980). We show that this criterion fits the stability regions in real exoplanet systems quite well. In addition, we show that elliptical orbits can remain stable even for regions where the apocenter distance of the inner orbit is larger than the pericenter distance of the outer orbit, as long as the initial orbits are aligned. The analytical expressions provided here can be used to put rapid constraints on the stability zones of multi-planetary systems. As a byproduct of this research, we further show that the amplitude variations of the eccentricity can be used as a fast-computing stability indicator.Comment: 11 pages, 11 figures. MNRAS accepte