A critical comparison of using a probabilistic weather generator versus a change factor approach: irrigation reservoir planning under climate change

In the UK, there is a growing interest in constructing on-farm irrigation reservoirs, however deciding the optimum reservoir capacity is not simple. There are two distinct approaches to generating the future daily weather datasets needed to calculate future irrigation need. The change factor approach perturbs the observed record using monthly change factors derived from downscaled climate models. This assumes that whilst the climate changes, the day-to-day climate variability itself is stationary. Problems may arise where the instrumental record is insufficient or particularly suspect. Alternatively, probabilistic weather generators can be used to identify options which are considered more robust to climate change uncertainty because they consider non-stationary climate variability. This paper explores the difference between using the change factor approach and a probabilistic weather generator for informing farm reservoir design at three sites in the UK. Decision outcomes obtained using the current normal practice of 80% probability of non-exceedance rule and simple economic optimisations are also compared. Decision outcomes obtained using the change factor approach and probabilistic weather generators are significantly different; whether these differences translate to real-world differences is discussed. This study also found that using the 80% probability of non-exceedance rule could potentially result in maladaptation

Irrigation demand modelling using the UKCP09 weather generator: lessons learned

The determination of irrigation demand is typically based on crop modelling using a long historic record of local daily weather data. However, there are rarely adequate weather station records near to given sites; often any local records cover a limited number of years, are incomplete, costly or are of poor quality. This paper examines whether version 1 of the UKCP09 weather generator can provide a simpler and effective method of calculating irrigation demand with sufficient accuracy for regulatory and design purposes. The irrigation demands at seven sites distributed around England were modelled using the UKCP09 baseline climatology and compared with results modelled using daily observed weather records. For the design dry year used for irrigation planning, the weather generator replicated the observed conditions with reasonable accuracy. The weather generator was however less successful at replicating extreme dry years. These results are encouraging but also provide a note of caution for the use of these generated datasets for studying current irrigation demand and by implication for modelling future needs under climate change. The study also demonstrated a simple sub-sampling approach for reducing the processing demands if using the dataset in more complex models, though this would not remove any underlying error

An Investigation of the Pederin Family: Total Synthesis of Theopederin D; Synthesis and Determination of the Relative and Absolute Configuration of Psymberic Acid

An investigation of the pederin family of natural products has led to the total synthesis of theopederin D, a synthesis of the C1-C6 portion of psymberin (psymberic acid), and the determination of the absolute configuration of C4 and C5 of this fragment.Highlights of our theopederin D synthesis include the use of an asymmetric ketene-aldehyde cycloaddition to synthesize the A ring (or pederic acid subunit), a 1,5-anti-boron mediated aldol to construct the C16-C17 bond with high a high level of diastereocontrol, formation of the C and D rings in a one-pot, six reaction sequence, selective differentiation of a tetrahydrofuranol in the presence of a tetrahydropyranol, and elaboration of the C ring using vinylation chemistry developed by Yamamoto and Rainier.The stereochemically labile B ring of theopederin D was constructed during the late stages of this synthesis using carbon-carbon bond activation via an Electron Transfer Initiated Cyclization (ETIC) method previously developed in the Floreancig research laboratories. This transformation proceeded under essentially neutral conditions and furnished the desired amidotrioxadecalin in high yield. The total synthesis of theopederin D was completed through coupling of pederic acid and an aminotrioxadecalin fragment using a modified diastereoselective strategy initially developed by Rawal.Our efforts toward the total synthesis of psymberin involved the synthesis of psymberic acid, as its absolute and relative stereochemistry was previously undefined. The use of readily available starting materials (D- or L-serine) and subsequent elaboration using syn or anti selective methallylation allowed for the efficient construction of all possible stereoisomers of psymberic acid. The absolute configuration of psymberic acid was determined through natural product and model system degradative studies, and analysis of the reaction products using a gas-chromatography/ mass spectrometry apparatus (GC-MS) outfitted with a chiral stationary phase

Decays of near BPS heterotic strings

The decay of highly excited massive string states in compactified heterotic string theories is discussed. We calculate the decay rate and spectrum of states carrying momentum and winding in the compactified direction. The longest lived states in the spectrum are near BPS states whose decay is dominated by a single decay channel of massless radiation which brings the state closer to being BPS.Comment: 28 pages, harvmac, 3 figure

The low energy expansion of the one-loop type II superstring amplitude

The one-loop four-graviton amplitude in either of the type II superstring theories is expanded in powers of the external momenta up to and including terms of order s^4 log s R^4, where R^4 denotes a specific contraction of four linearized Weyl tensors and s is a Mandelstam invariant. Terms in this series are obtained by integrating powers of the two-dimensional scalar field theory propagator over the toroidal world-sheet as well as the moduli of the torus. The values of these coefficients match expectations based on duality relations between string theory and eleven-dimensional supergravity.Comment: harvmac (b), 25 pages, 3 eps figures. v2: Factors of 2 corrected. Conclusion unchange

Non-renormalisation Conditions in Type II String Theory and Maximal Supergravity

This paper considers general features of the derivative expansion of Feynman diagram contributions to the four-graviton scattering amplitude in eleven-dimensional supergravity compactified on a two-torus. These are translated into statements about interactions of the form D^2k R^4 in type II superstring theories, assuming the standard M-theory/string theory duality relationships, which provide powerful constraints on the effective interactions. In the ten-dimensional IIA limit we find that there can be no perturbative contributions beyond k string loops (for k>0). Furthermore, the genus h=k contributions are determined exactly by the one-loop eleven-dimensional supergravity amplitude for all values of k. A plausible interpretation of these observations is that the sum of h-loop Feynman diagrams of maximally extended supergravity is less divergent than might be expected and could be ultraviolet finite in dimensions d < 4 + 6/h -- the same bound as for N=4 Yang--Mills.Comment: 30 pages, 4 figures. v3 Some rewording, typos corrected and some references added. v4: Abstract rephrased. More typos corrected. Version to be publishe

Germ cells of the centipede Strigamia maritima are specified early in embryonic development.

We provide the first systematic description of germ cell development with molecular markers in a myriapod, the centipede Strigamia maritima. By examining the expression of Strigamia vasa and nanos orthologues, we find that the primordial germ cells are specified from at least the blastoderm stage. This is a much earlier embryonic stage than previously described for centipedes, or any other member of the Myriapoda. Using these genes as markers, and taking advantage of the developmental synchrony of Strigamia embryos within single clutches, we are able to track the development of the germ cells throughout embryogenesis. We find that the germ cells accumulate at the blastopore; that the cells do not internalize through the hindgut, but rather through the closing blastopore; and that the cells undergo a long-range migration to the embryonic gonad. This is the first evidence for primordial germ cells displaying these behaviours in any myriapod. The myriapods are a phylogenetically important group in the arthropod radiation for which relatively little developmental data is currently available. Our study provides valuable comparative data that complements the growing number of studies in insects, crustaceans and chelicerates, and is important for the correct reconstruction of ancestral states and a fuller understanding of how germ cell development has evolved in different arthropod lineages.This is the final published version. It was originally published by Elsevier in Development Biology here: http://www.sciencedirect.com/science/article/pii/S0012160614002991. DOI: 10.1016/j.ydbio.2014.06.003

Active labour market policy in the UK : at a (local) crossroads?

Active labour market policy (ALMP) has developed into a widely used and seemingly embedded approach to addressing worklessness, both in the UK and internationally. But the future of UK ALMP looks far from certain. Some recent developments suggest demise and diminution. But at the same time there is also evidence of more positive points, including increasing recognition of the importance of employer involvement and activity a t local level. Possible future trajectories are considered in the light of emerging developments, and two potential scenarios for future UK ALMP are posited: ‘less support, more sticks’ and an ‘active local labour markets approach’

Some Systematics of the Coupling Constant Dependence of N=4 Yang-Mills

The operator, O_\tau, that generates infinitesimal changes of the coupling constant in N=4 Yang-Mills sits in the same supermultiplet as the superconformal currents. We show how superconformal current Ward identities determine a class of terms in the operator product expansion of O_\tau with any other operator. In certain cases, this leads to constraints on the coupling dependence of correlation functions in N=4 Yang-Mills. As an application, we demonstrate the exact non-renormalization of two and certain three-point correlation functions of BPS operators.Comment: 56 pages, LaTeX; amended and expanded arguments, added reference