Isotopic composition of tropospheric and soil N2O from successive depths of agricultural plots with contrasting crops and nitrogen amendments

Agricultural soils are the dominant contributor to increases in atmospheric nitrous oxide (N2O). Few studies have investigated the natural N and O isotopic composition of soil N2O. We collected soil gas samples using horizontal sampling tubes installed at successive depths under five contrasting agricultural crops (e.g., unamended alfalfa, fertilized cereal), and tropospheric air samples. Mean d 15N and d 18O values of soil N2O ranged from -28.0 to +8.9‰, and from +29.0 to +53.6‰. The mean d 15N and d 18O values of tropospheric N2O were +4.6 ± 0.7‰ and +48.3 ± 0.2‰, respectively. In general, d values were lowest at depth, they were negatively correlated to soil [N2O], and d 15N was positively correlated to d 18O for every treatment on all sampling dates. N2O from the different agricultural treatments had distinct d 15N and d 18O values that varied among sampling dates. Fertilized treatments had soil N2O with low d values, but the unamended alfalfa yielded N2O with the lowest d values. Diffusion was not the predominant process controlling N2O concentration profiles. Based on isotopic and concentration data, it appears that soil N2O was consumed, as it moved from deeper to shallower soil layers. To better assess the main process(es) controlling N2O within a soil profile, we propose a conceptual model that integrates data on net N2O production or consumption and isotopic data. The direct local impact of agricultural N2O on the isotopic composition of tropospheric N2O was recorded by a shift toward lower d values of locally measured tropospheric N2O on a day with very high soil N2O emissions.

Approaching near-capacity on a multi-antenna channel using successive decoding and interference cancellation receivers

In this paper, we address the problem of designing multirate codes for a multiple-input and multiple-output (MIMO) system by restricting the receiver to be a successive decoding and interference cancellation type, when each of the antennas is encoded independently. Furthermore, it is assumed that the receiver knows the instantaneous fading channel states but the transmitter does not have access to them. It is well known that, in theory, minimum-mean-square error (MMSE) based successive decoding of multiple access (in multi-user communications) and MIMO channels achieves the total channel capacity. However, for this scheme to perform optimally, the optimal rates of each antenna (per-antenna rates) must be known at the transmitter. We show that the optimal per-antenna rates at the transmitter can be estimated using only the statistical characteristics of the MIMO channel in time-varying Rayleigh MIMO channel environments. Based on the results, multirate codes are designed using punctured turbo codes for a horizontal coded MIMO system. Simulation results show performances within about one to two dBs of MIMO channel capacity.

The Maturation of Agile Software Development Principles and Practice: Observations on Successive Industrial Studies in 2010 and 2012

The agile model of software development has been mainstream for several years, and is now in a phase where its principles and practices are maturing. The purpose of this paper is to describe the results of an industry survey aimed at understanding how maturation is progressing. The survey was taken across 40 software development companies in Northern Ireland at the beginning of 2012. The paper describes the design of the survey and examines maturity by comparing the results obtained in 2012 with those from a study of agile adoption in the same region in 2010. Both surveys aimed to achieve comprehensive coverage of a single area rather than rely on a voluntary sample. The main outcome from the work is a collection of ‘insights’ into the nature and practice of agile development, the main two of which are reported in this paper.

Enabling Complexity-Performance Trade-Offs for Successive Cancellation Decoding of Polar Codes

Polar codes are one of the most recent advancements in coding theory and they have attracted significant interest. While they are provably capacity achieving over various channels, they have seen limited practical applications. Unfortunately, the successive nature of successive cancellation based decoders hinders fine-grained adaptation of the decoding complexity to design constraints and operating conditions. In this paper, we propose a systematic method for enabling complexity-performance trade-offs by constructing polar codes based on an optimization problem which minimizes the complexity under a suitably defined mutual information based performance constraint. Moreover, a low-complexity greedy algorithm is proposed in order to solve the optimization problem efficiently for very large code lengths.

Characterisation and evaluation of novel surfactant bacterial anti-adherent coatings for endotracheal tubes designed for the prevention of ventilator-associated pneumonia.

It is accepted that ventilator-associated pneumonia is a frequent cause of morbidity and mortality in intensive care patients. This study describes the physicochemical properties of novel surfactant coatings of the endotracheal tube and the resistance to microbial adherence of surfactant coated endotracheal tube polyvinylchloride (PVC). Organic solutions of surfactants containing a range of ratios of cholesterol and lecithin (0:100, 25:75, 50:50, 75:25, dissolved in dichloromethane) were prepared and coated onto endotracheal tube PVC using a multiple dip-coating process. Using modulated temperature differential scanning calorimetry it was confirmed that the binary surfactant systems existed as physical mixtures. The surface properties of both surfactant-coated and uncoated PVC, following treatment with either pooled human saliva or phosphate-buffered saline (PBS), were characterised using dynamic contact angle analysis. Following treatment with saliva, the contact angles of PVC decreased; however, those of the coated biomaterials were unaffected, indicating different rates and extents of macromolecular adsorption from saliva onto the coated and uncoated PVC. The advancing and receding contact angles of the surfactant-coated PVC were unaffected by sonication, thereby providing evidence of the durability of the coatings. The cell surface hydrophobicity and zeta potentials of isolates of Staphylococcus aureus and Pseudomonas aeruginosa, following treatment with either saliva or PBS, and their adherence to uncoated and surfactant-coated PVC (that had been pre-treated with saliva) were examined. Adherence of S. aureus and Ps. aeruginosa to surfactant-coated PVC at each successive time period (0.5, 1, 2, 4, 8 h) was significantly lower than to uncoated PVC, the extent of the reduction frequently exceeding 90%. Interestingly, the microbial anti-adherent properties of the coatings were dependent on the lecithin content. Based on the impressive microbial anti-adherence properties and durability of the surfactant coating on PVC following dip coatings, it is proposed that these systems may usefully reduce the incidence of ventilator-associated pneumonia when employed as luminal coatings of the endotracheal tube.

Genealogies of Partition: History, History-Writing and 'The Troubles' in Ireland

Contemporary political disputes have a long history of expression and contestation through the genre of history-writing in Ireland. The role of history writing and political science writing during the nearly 40 years of the so-called 'Troubles' has been no exception to this. Battles between competing versions of what the conflict 'is about', mediated through academic and popular texts have themselves in turn become constitutive of it. This builds upon centuries of the representation of the complicated politics of this island as 'an issue' in British domestic politics - first 'the Catholic question', then 'the Irish question'. The location of political power outside the island for centuries has created successive battles for the representation of sectional interests in a metropolitan centre. The skills of propaganda, history writing, newspaper writing have consequently been deployed at a remarkable level of skill and intensity. In the recent period one of the consequences of this has been the removal from the debate of the actuality of partition; this builds upon a particular historical representation of partition as an historical inevitability. To seek to restore partition to the debate is not to call for its undoing but to recognise that seeking to circumvent debates about its origins in the key period of democratisation in Irish politics (1880-1920) has been counter-productive. This essay examines the genealogies of partition in Irish and international contexts in the light of these battles for representation, and aims to return a lost dimension to the debate about the so-called 'Troubles'in Ireland. The genealogy of partition is the issue that has been marginalised in academic study and this has affected both policy and politics.

Scheduling and Platforming Trains at Busy Complex Stations

We consider the problem of train planning or scheduling for large, busy, complex train stations, which are common in Europe and elsewhere, though not in North America. We develop the constraints and objectives for this problem, but these are too computationally complex to solve by standard combinatorial search or integer programming methods. Also, the problem is somewhat political in nature, that is, it does not have a clear objective function because it involves multiple train operators with conflicting interests. We therefore develop scheduling heuristics analogous to those successfully adopted by train planners using ''manual'' methods. We tested the model and algorithms by applying to a typical large station that exhibits most of the complexities found in practice. The results compare well with those found by traditional methods, and take account of cost and preference trade-offs not handled by those methods. With successive refinements, the algorithm eventually took only a few seconds to run, the time depending on the version of the algorithm and the scheduling problem. The scheduling models and algorithms developed and tested here can be used on their own, or as key components for a more general system for train scheduling for a rail line or network.Train scheduling for a busy station includes ensuring that there are no conflicts between several hundred trains per day going in and out of the station on intersecting paths from multiple in-lines and out-lines to multiple platforms, while ensuring that each train is allowed at least its minimum required headways, dwell time, turnaround time and trip time. This has to be done while minimizing (costs of) deviations from desired times, platforms or lines, allowing for conflicts due to through-platforms, dead-end platforms, multiple sub-platforms, and possible constraints due to infrastructure, safety or business policy.

Distribution-based adaptive bounding genetic algorithm for continuous optimisation problems

A new search-space-updating technique for genetic algorithms is proposed for continuous optimisation problems. Other than gradually reducing the search space during the evolution process with a fixed reduction rate set ‘a priori’, the upper and the lower boundaries for each variable in the objective function are dynamically adjusted based on its distribution statistics. To test the effectiveness, the technique is applied to a number of benchmark optimisation problems in comparison with three other techniques, namely the genetic algorithms with parameter space size adjustment (GAPSSA) technique [A.B. Djurišic, Elite genetic algorithms with adaptive mutations for solving continuous optimization problems – application to modeling of the optical constants of solids, Optics Communications 151 (1998) 147–159], successive zooming genetic algorithm (SZGA) [Y. Kwon, S. Kwon, S. Jin, J. Kim, Convergence enhanced genetic algorithm with successive zooming method for solving continuous optimization problems, Computers and Structures 81 (2003) 1715–1725] and a simple GA. The tests show that for well-posed problems, existing search space updating techniques perform well in terms of convergence speed and solution precision however, for some ill-posed problems these techniques are statistically inferior to a simple GA. All the tests show that the proposed new search space update technique is statistically superior to its counterparts.

Coexistence among native and introduced freshwater amphipods (Crustacea); habitat utilization patterns in littoral habitats

Studies of biological invasions predominantly stress threats to biodiversity through the elimination and replacement of native species. However, we must realise that resident communities may often be capable of integrating invaders, leading to patterns of coexistence. Within the past ninety years, three freshwater amphipod species have invaded Northern Ireland the North American Gammarus tigrinus and Crangonyx pseudogracilis, plus the European G. pulex. These species have come into contact with the ubiquitous native species, G. duebeni celticus. This study examined spatiotemporal patterns of stability of single and mixed species assemblages in an invaded lake. Lough Beg and its associated rivers were surveyed in summer 1994 and winter 1995, and a selection of stations re-sampled in summer one and five years later. All possible combinations of the four amphipod species were found. Although species presence/absence was stable between seasons at the scale of the whole lough, it was extremely fluid at the scale of individual sites, 82% of which changed in species composition between seasons. Overall mean amphipod abundance was similar across 5 distinguishable habitat types, but there were differences in species compositions among these habitats. In addition, although co-occurrences of Gammarus species did not differ from random, there was a strong negative association between Gammarus spp. and C. pseudogracilis. This latter pattern was at least in part generated by the better tolerance of C. pseudogracilis to lower water quality. A review of previous studies indicates that the exclusion of C. pseudogracilis by Gammarus species from high water quality areas is likely to involve biotic interaction. Thus, overall, co-existence of the four species, which is clearly dynamic and scale-dependent, appears promoted by spatial and temporal habitat heterogeneity. However, biotic interactions may also play a role in local exclusions. Since the three introduced species have not eliminated the native species, and each successive invasion has not replaced the previous invader, this study demonstrates that freshwater invaders may integrate with native communities leading to coexistence and increased species diversity.

High-resolution organellar genome analysis of Triticum and Aegilops sheds new light on cytoplasm evolution in wheat

We have utilised polymorphic chloroplast microsatellites to analyse cytoplasmic relationships between accessions in the genera Triticum and Aegilops. Sequencing of PCR products revealed point mutations and insertions/deletions in addition to the standard repeat length expansion/contraction which most likely represent ancient synapomorphies. Phylogenetic analyses revealed three distinct groups of accessions. One of these contained all the non-Aegilops speltoides S-type cytoplasm species, another comprised almost exclusively A, C, D, M, N, T and U cytoplasm-type accessions and the third contained the polyploid Triticum species and all the Ae. speltoides accessions, further confirming that Ae. speltoides or a closely related but now extinct species was the original B-genome donor of cultivated polyploid wheat. Successive decreases in levels of genetic diversity due to domestication were also observed. Finally, we highlight the importance of elucidating longer-term evolutionary processes operating at microsatellite repeat loci.

Role of peripheral afference during acquisition of a complex coordination task

It has long been supposed that the interference observed in certain patterns of coordination is mediated, at least in part, by peripheral afference from the moving limbs. We manipulated the level of afferent input, arising from movement of the opposite limb, during the acquisition of a complex coordination task. Participants learned to generate flexion and extension movements of the right wrist, of 75degrees amplitude, that were a quarter cycle out of phase with a 1-Hz sinusoidal visual reference signal. On separate trials, the left wrist either was at rest, or was moved passively by a torque motor through 50degrees, 75degrees or 100degrees, in synchrony with the reference signal. Five acquisition sessions were conducted on successive days. A retention session was conducted I week later. Performance was initially superior when the opposite limb was moved passively than when it was static. The amplitude and frequency of active movement were lower in the static condition than in the driven conditions and the variation in the relative phase relation across trials was greater than in the driven conditions. In addition, the variability of amplitude, frequency and the relative phase relation during each trial was greater when the opposite limb was static than when driven. Similar effects were expressed in electromyograms. The most marked and consistent differences in the accuracy and consistency of performance (defined in terms of relative phase) were between the static condition and the condition in which the left wrist was moved through 50degrees. These outcomes were exhibited most prominently during initial exposure to the task. Increases in task performance during the acquisition period, as assessed by a number of kinematic variables, were generally well described by power functions. In addition, the recruitment of extensor carpi radialis (ECR), and the degree of co-contraction of flexor carpi radialis and ECR, decreased during acquisition. Our results indicate that, in an appropriate task context, afferent feedback from the opposite limb, even when out of phase with the focal movement, may have a positive influence upon the stability of coordination.

Penetration of human skin by the cercariae of Schistosoma mansoni: an investigation of the effect of multiple cercarial applications.

It has previously been postulated that L-arginine emitted by penetrating Schistosoma mansoni cercariae serves as an intraspecific signal guiding other cercariae to the penetration site. It was suggested that penetrating in groups offers a selective advantage. If this hypothesis is correct and group penetration at one site on the host offers an advantage, it would follow that at such a site, successive groups of cercariae would be able to penetrate skin in either greater numbers or at a faster rate. This prediction was tested by the use of an in vitro model of cercarial penetration based on the Franz cell and using human skin. It was demonstrated that there was no increase in the percentage of cercariae able to penetrate the skin with subsequent exposures. Consequently, it seems unlikely that the release of L-arginine by cercariae during penetration could have evolved as a specific orientation system based on a selective advantage offered by group penetration.