Quantizing gravity and spacetime: Where do we stand ?

We review five possible solutions to the riddle posed by Quantum Gravity: (1) Gravity should stay as a classical theory (L. Rosenfeld); (2) Quantum Gravity requires a formalism which will take the human mind (or the intelligent observer) into account, resolving at the same time the riddle of the collapse of the wave function/state vector in Quantum Mechanics in general (Penrose); (3) Perturbative Quantization; (4) Hamiltonian Quantization (Dirac, Ashtekar); (5) String Theory. We also discuss the quantization of spacetime.     

Gravity from symmetry breakdown of a gauge affine theory

We construct a gauge field theory based on GA(4, ) space-time symmetry containing spinorial and tensorial (infinite-component) matter manifields. We break the dilation symmetry and thus trigger a spontaneous breaking of the SL(4, )/SO(1, 3), also generating Newton's constant. The resulting ‘large-scale” space-time (a compared to Planck length) is of Riemann-Cartan type and in the flat limit we recover special relativity.     

Foliar Delivery of siRNA Particles for Treating Viral Infections in Agricultural Grapevines

Grapevine leafroll disease (GLD) is a globally spreading viral infection that causes major economic losses by reducing crop yield, plant longevity, and berry quality, with no effective treatment. Grapevine leafroll associated virus-3 (GLRaV-3) is the most severe, prevalent GLD strain affecting wine production. Here, the ability of RNA interference (RNAi), a non-GMO gene-silencing pathway, to treat GLRaV-3 in infected Cabernet Sauvignon grapevines is evaluated. Lipid-modified polyethylenimine (lmPEI) is synthesized as the carrier for long double-stranded RNA (dsRNA, 250-bp-long) that targets RNA polymerase and coat protein is a gene target that are conserved in the GLRaV-3 genome. Self-assembled dsRNA–lmPEI particles, 220 nm in diameter, display inner ordered domains spaced 7.3 ± 2 nm from one another, correlating to lmPEI wrapping spirally around the dsRNA. The particles effectively protect RNA from degradation by ribonucleases and show to increase uptake rate into plant cells as a result of the lipid component comprising the RNA carrier. In three field experiments, a single dose of foliar sprayed treatment of the RNA-particles knocks down GLRaV-3 titer, and multiple doses of the treatment keep the viral titer at baseline and trigger recovery of the vine and berries. This study demonstrates RNAi as a promising platform for treating viral diseases in agriculture.     

Cold temperatures invert product ratios in Penning ionisation reactions with argon

In many chemical reactions with more than one possible outcome, the branching ratio, which is the ratio between the different reaction paths, is nearly constant over a wide range of collision energies. In barrierless systems governed by long-range interactions, however, the branching ratio is more sensitive to collision energy, and its dependence on it can be useful for better understanding the dynamics and reconstructing interaction potentials. Here we present the reaction rates of Penning and associative ionisation of metastable neon and helium with argon atoms. We obtain reaction rates in merge beam experiments, over a wide range of collision energies corresponding to that of room temperature, all the way down to a few millikelvins. We observe a change of two orders of magnitude in the branching ratio in the measured collision energy range and explain these changes using theoretical calculations.     

The effect of a mild base on curcumin in methanol and ethanol

Steady-state and time-resolved emission techniques were employed to study the effect of acetate, a mild base, on the luminescence of curcumin in methanol and ethanol. We found that the steady-state emission intensity as well as the average fluorescence decay time are reduced by a factor of 5 when the acetate concentration is raised to about 1.8 M. We attribute this large effect to an excited-state proton transfer (ESPT) from the acidic groups of curcumin to the acetate anion. We analyze the experimental data in terms of an ESPT reaction occurring between a photoacid and a base.     

Heaviness in toral rotations

We investigate the dimension of the set of points H(A, α) in the d-torus which have the property that their orbit under rotation by some α hits a fixed closed target A more often than expected for all finite initial portions of time. An upper bound for the lower Minkowski dimension of this set is found in terms of the upper Minkowski dimension of ∂A:

Maximal Crossed Product Orders Over Discrete Valuation Rings

The problem of determining when a (classical) crossed product T = S ^f ?G of a finite group G over a discrete valuation ring S is a maximal order, was answered in the 1960s for the case where S is tamely ramified over the subring of invariants S ^G . The answer was given in terms of the conductor subgroup (with respect to f) of the inertia. In this article we solve this problem in general when S/S ^G is residually separable. We show that the maximal order property entails a restrictive structure on the subcrossed product graded by the inertia subgroup. In particular, the inertia is abelian. Using this structure, one is able to extend the notion of the conductor. As in the tame case, the order of the conductor is equal to the number of maximal two-sided ideals of T and hence to the number of maximal orders containing T in its quotient ring. Consequently, T is a maximal order if and only if the conductor subgroup is trivial.