The trimer-based spin liquid candidate Ba4NbIr3O12

Ba4NbIr3O12, a previously unreported material with a triangular planar geometry of Ir3O12 trimers, is described. Magnetic susceptibility measurements show no magnetic ordering down to 1.8 K despite the Curie-Weiss temperature of -13 K. The material has a very low effective magnetic moment of 0.80 {\mu}B/f.u. To look at the lower temperature behavior, the specific heat (Cp) was measured down to 0.35 K; it shows no indication of magnetic ordering and fitting a power law to Cp vs. T below 2 K yields the power {\alpha} = 3/4. Comparison to the previously unreported trimer compound made with the 4d element Rh in place of the 5d element Ir, Ba4NbRh3O12, is presented. The analysis suggests that Ba4NbIr3O12 is a candidate spin liquid material.Comment: 19 pages, 7 main figures, 2 SI figure

A model of inversion of DNA charge by a positive polymer: fractionization of the polymer charge

Charge inversion of a DNA double helix by an oppositely charged flexible polyelectrolyte (PE) is considered. We assume that, in the neutral state of the DNA-PE complex, each of the DNA charges is locally compensated by a PE charge. When an additional PE molecule is adsorbed by DNA, its charge gets fractionized into monomer charges of defects (tails and arches) on the background of the perfectly neutralized DNA. These charges spread all over the DNA eliminating the self-energy of PE. This fractionization mechanism leads to a substantial inversion of the DNA charge, a phenomenon which is widely used for gene delivery.Comment: 4 pages, 2 figures. Improved figures and various corrections to tex

Results of recent NASA studies on automatic spin prevention for fighter aircraft

A broad based research program was developed to eliminate or minimize inadvertent spins for advanced military aircraft. Recent piloted simulator studies and airplane flight tests have demonstrated that the automatic control systems in use on current fighters can be tailored to provide a high degree of spin resistance for some configurations without restrictions to maneuverability. Such systems result in greatly increased tactical effectiveness, safety, and pilot confidence

Failure Mechanism of True 2D Granular Flows

Most previous experimental investigations of two-dimensional (2D) granular column collapses have been conducted using three-dimensional (3D) granular materials in narrow horizontal channels (i.e., quasi-2D condition). Our recent research on 2D granular column collapses by using 2D granular materials (i.e., aluminum rods) has revealed results that differ markedly from those reported in the literature. We assume a 2D column with an initial height of h0 and initial width of d0, a defined as their ratio (a =h0/d0), a final height of h , and maximum run-out distance of d . The experimental data suggest that for the low a regime (a <0.65) the ratio of the final height to initial height is 1. However, for the high a regime (a >0.65), the ratio of a to (d-d0)/d0, h0/h , or d/d0 is expressed by power-law relations. In particular, the following power-function ratios (h0/h=1.42a^2/3 and d/d0=4.30a^0.72) are proposed for every a >0.65. In contrast, the ratio (d-d0)/d0=3.25a^0.96 only holds for 0.65< a1.5. In addition, the influence of ground contact surfaces (hard or soft beds) on the final run-out distance and destruction zone of the granular column under true 2D conditions is investigated.Comment: 8 page