Velocity correlations in dense granular flows

Velocity fluctuations of grains flowing down a rough inclined plane are experimentally studied. The grains at the free surface exhibit fluctuating motions, which are correlated over few grains diameters. The characteristic correlation length is shown to depend on the inclination of the plane and not on the thickness of the flowing layer. This result strongly supports the idea that dense granular flows are controlled by a characteristic length larger than the particle diameter

Detectability of the First Cosmic Explosions

We present a fully self-consistent simulation of a synthetic survey of the furthermost cosmic explosions. The appearance of the first generation of stars (Population III) in the Universe represents a critical point during cosmic evolution, signaling the end of the dark ages, a period of absence of light sources. Despite their importance, there is no confirmed detection of Population III stars so far. A fraction of these primordial stars are expected to die as pair-instability supernovae (PISNe), and should be bright enough to be observed up to a few hundred million years after the big bang. While the quest for Population III stars continues, detailed theoretical models and computer simulations serve as a testbed for their observability. With the upcoming near-infrared missions, estimates of the feasibility of detecting PISNe are not only timely but imperative. To address this problem, we combine state-of-the-art cosmological and radiative simulations into a complete and self-consistent framework, which includes detailed features of the observational process. We show that a dedicated observational strategy using $\lesssim 8$ per cent of total allocation time of the James Webb Space Telescope mission can provide us up to $\sim 9-15$ detectable PISNe per year.Comment: 9 pages, 8 figures. Minor corrections added to match published versio

Helicity supersymmetry of dyons

The 'dyon' system of D'Hoker and Vinet consisting of a spin 1/2 particle with anomalous gyromagnetic ratio 4 in the combined field of a Dirac monopole plus a Coulomb plus a suitable $1/r^2$ potential (which arises in the long-range limit of a self-dual monopole) is studied following Biedenharn's approach to the Dirac-Coulomb problem: the explicit solution is obtained using the `Biedenharn-Temple operator', $\Gamma$, and the extra two-fold degeneracy is explained by the subtle supersymmetry generated by the 'Dyon Helicity' or generalized `Biedenharn-Johnson-Lippmann' operator ${\cal R}$. The new SUSY anticommutes with the chiral SUSY discussed previously.Comment: 14 pages, 2 figure

Insecticide Evaluations for Soybean Aphid Management: the Good, the Bad and Their Residual Times

Soybean, Glycine max (L.), grown in Iowa and most of the north-central region of the United States has historically used low amounts of insecticide. However, an invasive insect pest has threatened soybean production in Iowa, with the arrival of the soybean aphid (Aphis glycines Matsumura). The soybean aphid causes yield losses from direct plant feeding, and has been shown to transmit several plant viruses. In Iowa, soybean aphid colonize soybean fields beginning in June and has produced outbreaks in July and August capable of reducing yields by nearly 25% (Johnson 2006)