Agronomic efficiency of selected phosphorus fertilisers derived from secondary raw materials for European agriculture. A meta-analysis

International audiencePhosphorus (P) is a macronutrient essential for all living organisms. Food production has become highly dependent on mineral P-fertilisers derived from phosphate rock, a non-renewable and finite resource. Based on supply risk and economic importance for the European Union, phosphate rock and elemental P have been identified as critical raw materials. Moreover, P dissipation can lead to adverse impacts on the aquatic environment. The production and use of P-fertilisers derived from secondary raw materials could possibly contribute to a more sustainable agriculture in line with a circular economy. Biogenic and industrial resources and waste streams can be converted into value added materials, such as precipitated phosphate salts, thermal oxidation materials and derivates, and pyrolysis and gasification materials. A condition is, however, that the P must be recovered in a plant-available form and that the recovered P-fertiliser supports plant growth and nutrient uptake in European agroecosystems. Here, we review the agronomic efficiency of selected P-fertilisers derived from secondary raw materials by comparing plant responses relative to those after mined and synthetic P-fertiliser application in settings relevant for European agriculture, using meta-analyses. The major points are the following: (1) precipitated phosphate salts show similar agronomic efficiency to mined and synthetic P-fertilisers, with results that are consistent and generalisable across soil and crop types relevant for European agriculture; (2) thermal oxidation materials and derivates can deliver an effective alternative for mined and synthetic P-fertilisers, but the relative agronomic efficiency is dependent on the feedstock applied, possible post-combustion manufacturing processes, and the length of the plant growing season; (3) the agronomic efficiency of pyrolysis and gasification materials remains indeterminate due to a lack of available data for European settings. It is concluded that the agronomic efficiency of selected P-fertilisers derived from secondary raw materials supports their use in conventional and organic European agricultural sectors

See a Black Hole on a Shoestring

The modes of vibration of hanging and partially supported strings provide useful analogies to scalar fields travelling through spacetimes that admit conformally flat spatial sections. This wide class of spacetimes includes static, spherically symmetric spacetimes. The modes of a spacetime where the scale factor depends as a power-law on one of the coordinates provide a useful starting point and yield a new classification of these spacetimes on the basis of the shape of the string analogue. The family of corresponding strings follow a family of curves related to the cycloid, denoted here as hypercycloids (for reasons that will become apparent). Like the spacetimes that they emulate these strings exhibit horizons, typically at their bottommost points where the string tension vanishes; therefore, hanging strings may provide a new avenue for the exploration of the quantum mechanics of horizons.Comment: 5 pages, 1 figure, extensive changes to refect version accepted to PR

Phase synchronization from noisy univariate signals

We present methods for detecting phase synchronization of two unidirectionally coupled, self-sustained noisy oscillators from a signal of the driven oscillator alone. One method detects soft, another hard phase locking. Both are applied to the problem of detecting phase synchronization in von Karman vortex flow meters.Comment: 4 pages, 4 figure

The time resolution of the St. Petersburg paradox

A resolution of the St. Petersburg paradox is presented. In contrast to the standard resolution, utility is not required. Instead, the time-average performance of the lottery is computed. The final result can be phrased mathematically identically to Daniel Bernoulli's resolution, which uses logarithmic utility, but is derived using a conceptually different argument. The advantage of the time resolution is the elimination of arbitrary utility functions.Comment: 20 pages, 1 figur

Infrared spectroscopy of diatomic molecules - a fractional calculus approach

The eigenvalue spectrum of the fractional quantum harmonic oscillator is calculated numerically solving the fractional Schr\"odinger equation based on the Riemann and Caputo definition of a fractional derivative. The fractional approach allows a smooth transition between vibrational and rotational type spectra, which is shown to be an appropriate tool to analyze IR spectra of diatomic molecules.Comment: revised + extended version, 9 pages, 6 figure

Discretely guided electromagnetic effective medium

A material comprised of an array of subwavelength coaxial waveguides decomposes incident electromagnetic waves into spatially discrete wave components, propagates these components without frequency cut-off, and reassembles them on the far side of the material. The propagation of these wave components is fully controlled by the physical properties of the waveguides and their geometrical distribution in the array. This allows for an exceptional degree of control over the electromagnetic response of this effective medium, with numerous potential applications. With the development of nanoscale subwavelength coaxial waveguides, these applications (including metamaterial functionality) can be enabled in the visible frequency range

Controlling light-with-light without nonlinearity

According to Huygens' superposition principle, light beams traveling in a linear medium will pass though one another without mutual disturbance. Indeed, it is widely held that controlling light signals with light requires intense laser fields to facilitate beam interactions in nonlinear media, where the superposition principle can be broken. We demonstrate here that two coherent beams of light of arbitrarily low intensity can interact on a metamaterial layer of nanoscale thickness in such a way that one beam modulates the intensity of the other. We show that the interference of beams can eliminate the plasmonic Joule losses of light energy in the metamaterial or, in contrast, can lead to almost total absorbtion of light. Applications of this phenomenon may lie in ultrafast all-optical pulse-recovery devices, coherence filters and THz-bandwidth light-by-light modulators

Relationships between various characterisations of wave tails

One can define several properties of wave equations that correspond to the absence of tails in their solutions, the most common one by far being Huygens' principle. Not all of these definitions are equivalent, although they are sometimes assumed to be. We analyse this issue in detail for linear scalar waves, establishing some relationships between the various properties. Huygens' principle is almost always equivalent to the characteristic propagation property, and in two spacetime dimensions the latter is equivalent to the zeroth order progressing wave propagation property. Higher order progressing waves in general do have tails, and do not seem to admit a simple physical characterisation, but they are nevertheless useful because of their close association with exactly solvable two-dimensional equations.Comment: Plain TeX, 26 page