Ecological Invasion, Roughened Fronts, and a Competitor's Extreme Advance: Integrating Stochastic Spatial-Growth Models

Both community ecology and conservation biology seek further understanding of factors governing the advance of an invasive species. We model biological invasion as an individual-based, stochastic process on a two-dimensional landscape. An ecologically superior invader and a resident species compete for space preemptively. Our general model includes the basic contact process and a variant of the Eden model as special cases. We employ the concept of a "roughened" front to quantify effects of discreteness and stochasticity on invasion; we emphasize the probability distribution of the front-runner's relative position. That is, we analyze the location of the most advanced invader as the extreme deviation about the front's mean position. We find that a class of models with different assumptions about neighborhood interactions exhibit universal characteristics. That is, key features of the invasion dynamics span a class of models, independently of locally detailed demographic rules. Our results integrate theories of invasive spatial growth and generate novel hypotheses linking habitat or landscape size (length of the invading front) to invasion velocity, and to the relative position of the most advanced invader.Comment: The original publication is available at www.springerlink.com/content/8528v8563r7u2742

Artificial neural network for prediction of the area under the disease progress curve of tomato late blight

ABSTRACT: Artificial neural networks (ANN) are computational models inspired by the neural systems of living beings capable of learning from examples and using them to solve problems such as non-linear prediction, and pattern recognition, in addition to several other applications. In this study, ANN were used to predict the value of the area under the disease progress curve (AUDPC) for the tomato late blight pathosystem. The AUDPC is widely used by epidemiologic studies of polycyclic diseases, especially those regarding quantitative resistance of genotypes. However, a series of six evaluations over time is necessary to obtain the final area value for this pathosystem. This study aimed to investigate the utilization of ANN to construct an AUDPC in the tomato late blight pathosystem, using a reduced number of severity evaluations. For this, four independent experiments were performed giving a total of 1836 plants infected with Phytophthora infestans pathogen. They were assessed every three days, comprised six opportunities and AUDPC calculations were performed by the conventional method. After the ANN were created it was possible to predict the AUDPC with correlations of 0.97 and 0.84 when compared to conventional methods, using 50 % and 67 % of the genotype evaluations, respectively. When using the ANN created in an experiment to predict the AUDPC of the other experiments the average correlation was 0.94, with two evaluations, 0.96, with three evaluations, between the predicted values of the ANN and they were observed in six evaluations. We present in this study a new paradigm for the use of AUDPC information in tomato experiments faced with P. infestans. This new proposed paradigm might be adapted to different pathosystems

Liver Impairment-The Potential Application of Volatile Organic Compounds in Hepatology

Liver diseases are currently diagnosed through liver biopsy. Its invasiveness, costs, and relatively low diagnostic accuracy require new techniques to be sought. Analysis of volatile organic compounds (VOCs) in human bio-matrices has received a lot of attention. It is known that a musty odour characterises liver impairment, resulting in the elucidation of volatile chemicals in the breath and other body fluids such as urine and stool, which may serve as biomarkers of a disease. Aims: This study aims to review all the studies found in the literature regarding VOCs in liver diseases, and to summarise all the identified compounds that could be used as diagnostic or prognostic biomarkers. The literature search was conducted on ScienceDirect and PubMed, and each eligible publication was qualitatively assessed by two independent evaluators using the SANRA critical appraisal tool. Results: In the search, 58 publications were found, and 28 were kept for inclusion: 23 were about VOCs in the breath, one in the bile, three in urine, and one in faeces. Each publication was graded from zero to ten. A graphical summary of the metabolic pathways showcasing the known liver disease-related VOCs and suggestions on how VOC analysis on liver impairment could be applied in clinical practice are given

Reduction of incidence and severity of Septoria lycopersici leaf spot of tomato with bacteria and yeasts Redução da incidência e severidade da mancha foliar do tomateiro causada por Septoria lycopersici com bacteria e leveduras

Septoria leaf spot, caused by Septoria lycopersici, is an important disease of tomato (Lycopersicon esculentum) which is mainly controlled by fungicide sprays. One of the alternatives to reduce fungicide applications is the use of leaf antagonists such as yeast and bacterium. This study was conducted from 1994 through 1995 in Auburn, AL, USA. The pathogen and one antagonist were isolated from field plants. In greenhouse, six yeast and one bacterial isolates were tested, in a set of seven experiments. The experiments were conducted in a completely randomized design with four to eight treatments and six replications. The antagonists (1-3 × 10(8) colony forming units ml-1) were inoculated 48h before the inoculation of the pathogen (1-2 × 10(5) conidia ml-1), under conditions of intermittent misting. The yeast isolate Y236 (Cryptococcus laurentii) and the bacterial isolate BTL (Pseudomonas putida) significantly (P <= 0.05) reduced the incidence or the severity of the disease in most experiments.<br>A mancha foliar causada pelo fungo Septoria lycopersici é uma doença no tomateiro (Lycopersicon esculentum), controlada basicamente pela aplicação de fungicidas. Uma das alternativas ao controle químico dessa enfermidade é a utilização de bactérias e leveduras antagonistas. Este estudo foi conduzido de 1994 a 1995 em Auburn, Alabama, EUA. O patógeno e um dos antagonistas foram isolados do filoplano de plantas de tomateiro infectadas pela doença em questão. Sete antagonistas (um isolado de bacteria e seis de leveduras) foram testados em uma série de sete experimentos conduzidos em casa de vegetação. Os experimentos foram conduzidos em um delineamento completamente casualizado com quatro a oito tratamentos e seis repetições. Em todos os experimentos, os antagonistas (1-3 × 10(8) unidades formadoras de colonia ml-1) foram inoculados 48h antes da inoculação com o patógeno (1-2 × 10(5) conidios ml-1), sob condições de nebulosidade intermitente. Entre os antagonistas testados, destacaram-se o isolado de levedura Y236 (Cryptococcus laurentii) e o isolado bacteriano BTL (Pseudomonas putida). Ambos os isolados reduziram significativamente (P <= 0.05) a incidência e a severidade da doença na maioria dos experimentos