African Postharvest Losses Information System – a network for the estimation of cereal weight losses

Soaring food prices during 2007/2008, and the realisation that sporadic food shortages are likely to continue long into the future, has reawakened interest in the benefits of reducing food losses. As a means of making more accurate estimates of how much food is lost, the Joint Research Centre (European Commission) proposed the development of the African Postharvest Losses Information System (APhLIS) (http://www.phlosses.net). APhLIS estimates postharvest losses (PHLs) by cereal crop, by country and by province in East and Southern Africa. The system went live in March 2009 and combines a loss calculator, a free access database of key information, and a network of local experts who contribute the latest data and verify loss estimates. The loss calculator works of loss figures contributed from the literature and by local experts but also takes account of the prevailing climate, scale of farming (small/large), damp weather at harvest, larger grain borer (in the case of maize), proportion of grain held in farm sorage or marketed, and multiple harvests. Before the introduction of APhLIS, the origin and justification of PHL estimates were not well founded. Now PHL estimates are available that are • Transparent in the way they are calculated• Based on a complete screening of available research and literature• Contributed (in part) and verified by local experts• Based on the primary national unit (i.e. province not just country level, so estimates are more relevant)• Upgradeable as more (reliable) data become available, so that there is the opportunity for increasing accuracy in loss estimation over time.• Supported by a downloadable loss calculator that can be used to make loss calculations at ageographical scale below primary national unit.In the future, APhLIS may be expanded in technical scope (crops) and geographical range (countries) and used to help prioritize and justify loss reduction strategies including those for grain storage.Keywords: Weight loss, Loss calculator, Postharvest operations, Cereal suppl

Principles of Control for Decoherence-Free Subsystems

Decoherence-Free Subsystems (DFS) are a powerful means of protecting quantum information against noise with known symmetry properties. Although Hamiltonians theoretically exist that can implement a universal set of logic gates on DFS encoded qubits without ever leaving the protected subsystem, the natural Hamiltonians that are available in specific implementations do not necessarily have this property. Here we describe some of the principles that can be used in such cases to operate on encoded qubits without losing the protection offered by the DFS. In particular, we show how dynamical decoupling can be used to control decoherence during the unavoidable excursions outside of the DFS. By means of cumulant expansions, we show how the fidelity of quantum gates implemented by this method on a simple two-physical-qubit DFS depends on the correlation time of the noise responsible for decoherence. We further show by means of numerical simulations how our previously introduced "strongly modulating pulses" for NMR quantum information processing can permit high-fidelity operations on multiple DFS encoded qubits in practice, provided that the rate at which the system can be modulated is fast compared to the correlation time of the noise. The principles thereby illustrated are expected to be broadly applicable to many implementations of quantum information processors based on DFS encoded qubits.Comment: 12 pages, 7 figure

Braneworld inflation from an effective field theory after WMAP three-year data

In light of the results from the WMAP three-year sky survey, we study an inflationary model based on a single-field polynomial potential, with up to quartic terms in the inflaton field. Our analysis is performed in the context of the Randall-Sundrum II braneworld theory, and we consider both the high-energy and low-energy (i.e. the standard cosmology case) limits of the theory. We examine the parameter space of the model, which leads to both large-field and small-field inflationary type solutions. We conclude that small field inflation, for a potential with a negative mass square term, is in general favored by current bounds on the tensor-to-scalar perturbation ratio rs.Comment: 11 pages, 5 figures; references updated and a few comments added; final version to appear in Phys. Rev.

The role of serial European windstorm clustering for extreme seasonal losses as determined from multi-centennial simulations of high resolution global climate model data

Extratropical cyclones are the most damaging natural hazard to affect western Europe. Serial clustering occurs when many intense cyclones affect one specific geographic region in a short period of time which can potentially lead to very large seasonal losses. Previous studies have shown that intense cyclones may be more likely to cluster than less intense cyclones. We revisit this topic using a high resolution climate model with the aim to determine how important clustering is for windstorm related losses. The role of windstorm clustering is investigated using a quantifiable metric (storm severity index, SSI) that is based on near surface meteorological variables (10-metre wind speed) and is a good proxy for losses. The SSI is used to convert a wind footprint into losses for individual windstorms or seasons. 918 years of a present-day ensemble of coupled climate model simulations from the High-Resolution Global Environment Model (HiGEM) are compared to ERA-Interim re-analysis. HiGEM is able to successfully reproduce the wintertime North Atlantic/European circulation, and represent the large-scale circulation associated with the serial clustering of European windstorms. We use two measures to identify any changes in the contribution of clustering to the seasonal windstorm loss as a function of return period. Above a return period of 3 years, the accumulated seasonal loss from HiGEM is up to 20% larger than the accumulated seasonal loss from a set of random resamples of the HiGEM data. Seasonal losses are increased by 10-20% relative to randomised seasonal losses at a return period of 200 years. The contribution of the single largest event in a season to the accumulated seasonal loss does not change with return period, generally ranging between 25-50%. Given the realistic dynamical representation of cyclone clustering in HiGEM, and comparable statistics to ERA-Interim, we conclude that our estimation of clustering and its dependence on the return period will be useful for informing the development of risk models for European windstorms, particularly for longer return periods

Collineation group as a subgroup of the symmetric group

Let $\Psi$ be the projectivization (i.e., the set of one-dimensional vector subspaces) of a vector space of dimension $\ge 3$ over a field. Let $H$ be a closed (in the pointwise convergence topology) subgroup of the permutation group $\mathfrak{S}_{\Psi}$ of the set $\Psi$. Suppose that $H$ contains the projective group and an arbitrary self-bijection of $\Psi$ transforming a triple of collinear points to a non-collinear triple. It is well-known from \cite{KantorMcDonough} that if $\Psi$ is finite then $H$ contains the alternating subgroup $\mathfrak{A}_{\Psi}$ of $\mathfrak{S}_{\Psi}$. We show in Theorem \ref{density} below that $H=\mathfrak{S}_{\Psi}$, if $\Psi$ is infinite.Comment: 9 page

Functional Approach to Stochastic Inflation

We propose functional approach to the stochastic inflationary universe dynamics. It is based on path integral representation of the solution to the differential equation for the scalar field probability distribution. In the saddle-point approximation scalar field probability distributions of various type are derived and the statistics of the inflationary-history-dependent functionals is developed.Comment: 20 pages, Preprint BROWN-HET-960, uses phyzz

Experimental Implementation of Logical Bell State Encoding

Liquid phase NMR is a general purpose test-bed for developing methods of coherent control relevant to quantum information processing. Here we extend these studies to the coherent control of logical qubits and in particular to the unitary gates necessary to create entanglement between logical qubits. We report an experimental implementation of a conditional logical gate between two logical qubits that are each in decoherence free subspaces that protect the quantum information from fully correlated dephasing.Comment: 9 Pages, 5 Figure

How well are Tropical Cyclones represented in reanalysis data sets?

Tropical cyclones (TCs) are identified and tracked in six recent reanalysis data sets and compared with those from the IBTrACS best track archive. Results indicate that nearly every cyclone present in IBTrACS over the period 1979-2012 can be found in all six reanalyses using a tracking and matching approach. However, TC intensities are significantly under-represented in the reanalyses compared to the observations. Applying a typical objective TC identification scheme, it is found that the largest uncertainties in TC identification occur for the weaker storms; this is exacerbated by uncertainties in the observations for weak storms and lack of consistency in operational procedures. For example, it is unclear whether certain types of storms, such as tropical depressions, subtropical cyclones and monsoon depressions, are included in the best track data for all reporting agencies. There are definite improvements in how well TCs are represented in more recent, higher resolution reanalyses; in particular MERRA2 is comparable with the NCEP-CFSR and JRA55 reanalyses, which perform significantly better than the older MERRA reanalysis