A concentration phenomenon for semilinear elliptic equations

For a domain \Omega\subset\dR^N we consider the equation -\Delta u + V(x)u = Q_n(x)\abs{u}^{p-2}u with zero Dirichlet boundary conditions and $p\in(2,2^*)$. Here $V\ge 0$ and $Q_n$ are bounded functions that are positive in a region contained in $\Omega$ and negative outside, and such that the sets $\{Q_n>0\}$ shrink to a point $x_0\in\Omega$ as $n\to\infty$. We show that if $u_n$ is a nontrivial solution corresponding to $Q_n$, then the sequence $(u_n)$ concentrates at $x_0$ with respect to the $H^1$ and certain $L^q$-norms. We also show that if the sets $\{Q_n>0\}$ shrink to two points and $u_n$ are ground state solutions, then they concentrate at one of these points

Validating performance of automotive materials at high strain rate for improved crash design

This paper investigates sources of performance variability in high velocity testing of automotive crash structures. Sources of variability, or so called noise factors, present in a testing environment, arise from uncertainty in structural properties, joints, boundary conditions and measurement system. A box structure, which is representative of a crash component, is designed and fabricated from a high strength Dual Phase sheet steel. Crush tests are conducted at low and high speed. Such tests intend to validate a component model and material strain rate sensitivity data determined from high speed tensile testing. To support experimental investigations, stochastic modeling is used to investigate the effect of noise factors on crash structure performance variability, and to identify suitable performance measures to validate a component model and material strain rate sensitivity data. The results of the project will enable the measurement of more reliable strain rate sensitivity data for improved crashworthiness predictions of automotive structures

Rapid metabolic pathway assembly and modification using serine integrase site-specific recombination

Synthetic biology requires effective methods to assemble DNA parts into devices and to modify these devices once made. Here we demonstrate a convenient rapid procedure for DNA fragment assembly using site-specific recombination by ϕC31 integrase. Using six orthogonal attP/attB recombination site pairs with different overlap sequences, we can assemble up to five DNA fragments in a defined order and insert them into a plasmid vector in a single recombination reaction. ϕC31 integrase-mediated assembly is highly efficient, allowing production of large libraries suitable for combinatorial gene assembly strategies. The resultant assemblies contain arrays of DNA cassettes separated by recombination sites, which can be used to manipulate the assembly by further recombination. We illustrate the utility of these procedures to (i) assemble functional metabolic pathways containing three, four or five genes; (ii) optimize productivity of two model metabolic pathways by combinatorial assembly with randomization of gene order or ribosome binding site strength; and (iii) modify an assembled metabolic pathway by gene replacement or addition

Monitoring Wind Turbine Loading Using Power Converter Signals

The ability to detect faults and predict loads on a wind turbine drivetrain's mechanical components cost-effectively is critical to making the cost of wind energy competitive. In order to investigate whether this is possible using the readily available power converter current signals, an existing permanent magnet synchronous generator based wind energy conversion system computer model was modified to include a grid-side converter (GSC) for an improved converter model and a gearbox. The GSC maintains a constant DC link voltage via vector control. The gearbox was modelled as a 3-mass model to allow faults to be included. Gusts and gearbox faults were introduced to investigate the ability of the machine side converter (MSC) current (I q) to detect and quantify loads on the mechanical components. In this model, gearbox faults were not detectable in the I q signal due to shaft stiffness and damping interaction. However, a model that predicts the load change on mechanical wind turbine components using I q was developed and verified using synthetic and real wind data

N, P and K budgets for crop rotations on nine organic farms in the UK

On organic farms, where the importation of materials to build/maintain soil fertility is restricted, it is important that a balance between inputs and outputs of nutrients is achieved to ensure both short-term productivity and long-term sustainability. This paper considers different approaches to nutrient budgeting on organic farms and evaluates the sources of bias in the measurements and/or estimates of the nutrient inputs and outputs. The paper collates 88 nutrient budgets compiled at the farm scale in 9 temperate countries. All the nitrogen (N) budgets showed an N surplus (average 83.2 kg N ha-1 year-1). The efficiency of N use, defined as outputs/inputs, was highest (0.9) and lowest (0.2) in arable and beef systems respectively. The phosphorus (P) and potassium (K) budgets showed both surpluses and deficits (average 3.6 kg P ha-1 year-1, 14.2 kg K ha-1 year-1) with horticultural systems showing large surpluses resulting from purchased manure. The estimation of N fixation and quantities of nutrients in purchased manures may introduce significant errors in nutrient budgets. Overall, the data illustrate the diversity of management systems in place on organic farms, and suggest that used together with soil analysis, nutrient budgets are a useful tool for improving the long-term sustainability of organic systems

Integrated weed management strategies for delaying herbicide resistance in wild oats

Les biotypes de folle avoine (Avena fatua) résistants aux herbicides infestent les principales régions céréalières de l'Ouest américain et de l'Ouest canadien. Cet article passe en revue les stratégies de lutte intégrée contre les mauvaises herbes qui peuvent être utilisées pour empêcher ou retarder le développement de la résistance aux herbicides chez la folle avoine. Une stratégie de lutte intégrée contre la folle avoine, destinée à retarder ou à empêcher le développement de la résistance, devrait être basée sur la prévention de l'introduction des grains de folle avoine dans le sol. Deux façons d'y arriver sont d'empêcher l'immigration de graines dans le champ à partir de sources externes, et de réduire ou éliminer la production de graines par la folle avoine déjà présente au champ. Il est de plus en plus évident que le recours à l'utilisation continuelle d'herbicides comme seul moyen de lutte contre les mauvaises herbes n'éliminera pas la folle avoine ni les autres graines de mauvaises herbes de la banque de graines du sol. Au contraire, tout porte à croire que cette pratique va sélectionner des biotypes résistants aux herbicides utilisés, particulièrement là où des herbicides ayant le même mode d'action sont utilisés de façon continue. Il est essentiel, cependant, que les herbicides soient considérés seulement comme une composante d'un système intégré global incluant la lutte culturale et d'autres stratégies de gestion, et que les principes agronomiques soient considérés lors du développement de ce système.Herbicide-resistant biotypes of wild oats (Avena fatua) infest most major cereal producing regions in the western United States and Canada. This paper reviews potential integrated weed management strategies that can be used to prevent or delay selection of herbicide-resistant wild oats plants. An integrated wild oats management strategy to delay or prevent the development of herbicide resistance should be based on preventing the movement of wild oats seed into the soil. Two ways to achieve this are by preventing the immigration of seed into the field from external sources, and by reducing or eliminating seed production by wild oats already in the field. It is becoming increasingly clear that reliance on continuous herbicide useas the sole means of weed control will fail to eliminate wild oats and other weed seed from the soil seedbank. On the contrary, evidence is mounting that this practice will select for biotypes that are resistant to the herbicides used, especially where herbicides of the same mode of action are used continuously. It is essential, therefore, that herbicides be considered as just one component of an overall integrated System together with cultural control and other management strategies, and that agronomic principles be considered when developing this System

System Resource Sharing for Synchronous Collaboration

We describe problems associated with accessing data resources external to the application, which we term externalities, in replicated synchronous collaborative applications (e.g., a multiuser text editor). Accessing externalities such as les, databases, network connections, environment variables and the system clock is not as straightforward in replicated collaborative software as in single-user applications and centralized collaborative systems. We describe ad hoc solutions that have been used previously. Our primary objection to the ad hoc solutions is that the developer must program dierent behavior into the dierent replicas of a multi-user application, which increases the cost and complexity of development. We introduce a novel general approach to accessing externalities uniformly in a replicated collaborative system. The approach uses a semi-replicated architecture where the actual externality resides at a single location and is accessed via replicated proxies. The proxies multiplex input to and output from the single instance of the externality. This approach facilitates the creation of replicated synchronous groupware in two ways: (1) developers use the same mechanisms as in traditional single-user applications (2) developers program all replicas to execute the same behavior. We describe a general design for proxied access to read{only, write{only and read{write externalities. We discuss the tradeos of this semi- replicated approach over full, literal replication and the class of applications to which this approach can be successfully applied. We also describe details of a prototype implementation of this approach within a replicated collaboration-transparency system, called Flexible JAMM (Java Applets Made Multi-user)

Reactive Inkjet Printing of Regenerated Silk Fibroin Films for Use as Dental Barrier Membranes

Current commercially available barrier membranes for oral surgery have yet to achieve a perfect design. Existing materials used are either non-resorbable and require a second surgery for their extraction, or alternatively are resorbable but suffer from poor structural integrity or degrade into acidic by-products. Silk has the potential to overcome these issues and has yet to be made into a commercially available dental barrier membrane. Reactive inkjet printing (RIJ) has recently been demonstrated to be a suitable method for assembling silk in its regenerated silk fibroin (RSF) form into different constructs. This paper will establish the properties of RSF solutions for RIJ and the suitability of RIJ for the construction of RSF barrier membranes. Printed RSF films were characterised by their crystallinity and surface properties, which were shown to be controllable via RIJ. RSF films degraded in either phosphate buffered saline or protease XIV solutions had degradation rates related to RSF crystallinity. RSF films were also printed with the inclusion of nano-hydroxyapatite (nHA). As reactive inkjet printing could control RSF crystallinity and hence its degradation rate, as well as offering the ability to incorporate bioactive nHA inclusions, reactive inkjet printing is deemed a suitable alternative method for RSF processing and the production of dental barrier membranes

Roche tomography of cataclysmic variables: I. artefacts and techniques

Roche tomography is a technique used for imaging the Roche-lobe filling secondary stars in cataclysmic variables (CVs). In order to interpret Roche tomograms correctly, one must determine whether features in the reconstruction are real, or due to statistical or systematic errors. We explore the effects of systematic errors using reconstructions of simulated datasets and show that systematic errors result in characteristic distortions of the final reconstructions that can be identified and corrected. In addition, we present a new method of estimating statistical errors on tomographic reconstructions using a Monte-Carlo bootstrapping algorithm and show this method to be much more reliable than Monte-Carlo methods which `jiggle' the data points in accordance with the size of their error bars.Comment: 11 pages, 8 figures. Accepted for publication in MNRA

Emotion: Appraisal-coping model for the "Cascades" problem

Modelling emotion has become a challenge nowadays. Therefore, several models have been produced in order to express human emotional activity. However, only a few of them are currently able to express the close relationship existing between emotion and cognition. An appraisal-coping model is presented here, with the aim to simulate the emotional impact caused by the evaluation of a particular situation (appraisal), along with the consequent cognitive reaction intended to face the situation (coping). This model is applied to the "Cascades" problem, a small arithmetical exercise designed for ten-year-old pupils. The goal is to create a model corresponding to a child's behaviour when solving the problem using his own strategies.Comment: 6 page