785 research outputs found

    Near Zone: Basic scattering code user's manual with space station applications

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    The Electromagnetic Code - Basic Scattering Code, Version 3, is a user oriented computer code to analyze near and far zone patterns of antennas in the presence of scattering structures, to provide coupling between antennas in a complex environment, and to determine radiation hazard calculations at UHF and above. The analysis is based on uniform asymptotic techniques formulated in terms of the Uniform Geometrical Theory of Diffraction (UTD). Complicated structures can be simulated by arbitrarily oriented flat plates and an infinite ground plane that can be perfectly conducting or dielectric. Also, perfectly conducting finite elliptic cylinder, elliptic cone frustum sections, and finite composite ellipsoids can be used to model the superstructure of a ship, the body of a truck, and airplane, a satellite, etc. This manual gives special consideration to space station modeling applications. This is a user manual designed to give an overall view of the operation of the computer code, to instruct a user in how to model structures, and to show the validity of the code by comparing various computed results against measured and alternative calculations such as method of moments whenever available

    Clownfishes evolution below and above the species level.

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    The difference between rapid morphological evolutionary changes observed in populations and the long periods of stasis detected in the fossil record has raised a decade-long debate about the exact role played by intraspecific mechanisms at the interspecific level. Although they represent different scales of the same evolutionary process, micro- and macroevolution are rarely studied together and few empirical studies have compared the rates of evolution and the selective pressures between both scales. Here, we analyse morphological, genetic and ecological traits in clownfishes at different evolutionary scales and demonstrate that the tempo of molecular and morphological evolution at the species level can be, to some extent, predicted from parameters estimated below the species level, such as the effective population size or the rate of evolution within populations. We also show that similar codons in the gene of the rhodopsin RH1, a light-sensitive receptor protein, are under positive selection at the intra and interspecific scales, suggesting that similar selective pressures are acting at both levels

    Genetic variability, heritability and genetic advance studies in top- cross and three-way cross maize (Zea mays L) hybrids

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    Understanding the genetic variability, heritability and genetic advance of traits in any plant population is an im- portant pre-requisite for selection program. This study was designed to assess the magnitude of genetic variabili- ty, heritability and genetic advance of traits in top-cross and three-way cross maize (Zea mays L) hybrids evaluated at three locations in South-Western Nigeria. The trial consisted of ten genotypes each of top-cross and three-way cross hybrids arranged in randomized complete block design with three replications. Data on grain yield and other desirable traits across the three locations were used to estimate the genetic variability parameters, heritability and genetic advance (GA). Highly significant (P ≤ 0.01) differences were detected within each hybrid class for all the traits. Traits evaluated in this study exhibited different levels of variability, heritability and genetic advance between the two hybrid classes. Low to moderate phenotypic coefficient of variation (PCV) and genotypic coefficient of variation (GCV) were recorded. Also, low to very high heritability and low to high GA values were recorded for all the traits measured in the top-cross hybrids, whereas the three-way cross hybrids exhibited low to moderately high heritability estimates and low to moderate GA values. Grain yield and field weight showed moderate GCV, moderately high heritability and high GA values in top-cross hybrids. These characters exhibited moderate GCV but low heritability and GA values in three-way hybrids. More characters in top-cross hybrids revealed sufficient amount of variability than in three-way cross hybrids, thus offer scope for genetic improvement through selection

    On the Effect of Asymmetrical Trait Inheritance on Models of Trait Evolution.

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    Current phylogenetic comparative methods modeling quantitative trait evolution generally assume that, during speciation, phenotypes are inherited identically between the two daughter species. This, however, neglects the fact that species consist of a set of individuals, each bearing its own trait value. Indeed, because descendent populations after speciation are samples of a parent population, we can expect their mean phenotypes to randomly differ from one another potentially generating a "jump" of mean phenotypes due to asymmetrical trait inheritance at cladogenesis. Here, we aim to clarify the effect of asymmetrical trait inheritance at speciation on macroevolutionary analyses, focusing on model testing and parameter estimation using some of the most common models of quantitative trait evolution. We developed an individual-based simulation framework in which the evolution of phenotypes is determined by trait changes at the individual level accumulating across generations, and cladogenesis occurs then by separation of subsets of the individuals into new lineages. Through simulations, we assess the magnitude of phenotypic jumps at cladogenesis under different modes of trait inheritance at speciation. We show that even small jumps can strongly alter both the results of model selection and parameter estimations, potentially affecting the biological interpretation of the estimated mode of evolution of a trait. Our results call for caution when interpreting analyses of trait evolution, while highlighting the importance of testing a wide range of alternative models. In the light of our findings, we propose that future methodological advances in comparative methods should more explicitly model the intraspecific variability around species mean phenotypes and how it is inherited at speciation

    Publisher Correction: The impact of endothermy on the climatic niche evolution and the distribution of vertebrate diversity.

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    In the version of this Article originally published, in Fig. 3a the first boundary was incorrectly labelled the "K/T boundary"; it should have read the "K/Pg boundary". The two equations in the main text were incorrectly omitted from the HTML. In the description of the posterior distribution of an ancestral state, the normal distribution was incorrectly described as being "assigned as prior to the node value"; it should have read "assigned as calibration to the node value". In the associated equation (the second equation in the text), the denominator of the last term was incorrectly given as "Node prior"; it should have read "Node calibration". In the same equation, the numerator of the third term on the right-hand side of the equation contained incorrect superscript notation on the x and this is shown in the full equation in the notice below.In the Acknowledgements, the following two sentences were incorrectly omitted: "The authors thank the Vital-IT facilities of the Swiss Institute of Bioinformatics for the computational support" and "This work was funded by the University of Lausanne and the Swiss National Science Foundation (CRSIII3-147630) to N.S." In the Author contributions section, the first sentence was incorrectly given as "J.R. designed the study. J.R., N.S. and D. Silvestro designed the methodology and ran the analyses"; it should have read "J.R., D.S. and N.S. designed the study and the methodology". In the Supplementary Information, all three instances of the word "prior" were incorrect and should have read "calibration".These errors have now been corrected in all versions of the Article

    Fossil data support a pre-Cretaceous origin of flowering plants

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    Data and scripts associated with the paper. Updated version of the code will be available here: https://github.com/dsilvestro/rootBB

    Characterization of Colletotrichum strains associated with olive anthracnose in Sicily

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    Anthracnose caused by Colletotrichum spp. is the most damaging olive fruit disease in many countries, including Italy. This disease has been sporadically detected in Sicily, but new agronomic practices can increase risk of olive anthracnose in this region. An etiological study of the disease focused on local olive cultivars growing at the International Olive Germplasm Collection (IOGC) in Villa Zagaria, Enna, Sicily has been undertaken. During 2018 and 2019, 137 Colletotrichum strains were isolated from olives. Colony morphology, conidium characteristics, and multilocus sequence analyses aided identification of three species: C. acutatum (affecting 70% of symptomatic olives), C. gloeosporioides, and C. cigarro. Three C. acutatum strains (B1316, P77, and P185), and one stram of each C. gloeosporioides (C2.1) and C. cigarro (Perg6B) were evaluated for pathogenicity on olive fruits from 11 Sicilian cultivars, known for their high-quality oil. Differences in virulence were detected among strains and their pathogenicity to the cultivars. The C. acutatum isolates were more virulent than those of C. gloeosporioides or C. cigarro. The Sicilian olive cultivars Cavaliera, Carolea, Calatina, and Nocellara del Belice were the most susceptible to the pathogen, while the cultivars Biancolilla and Nocellara Etnea were the most tolerant. Cultivar response under field conditions showed that anthracnose severity and fruit-rot incidence were positively correlated. This is the first report of C. acutatum and C. cigarro affecting olive trees in Sicily. Control measures for anthracnose depend on accurate characterization of the etiological agents and host cultivar resistance

    Human-machine interface for two-dimensional steering control with the auricular muscles

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    Human-machine interfaces (HMIs) can be used to decode a user's motor intention to control an external device. People that suffer from motor disabilities, such as spinal cord injury, can benefit from the uses of these interfaces. While many solutions can be found in this direction, there is still room for improvement both from a decoding, hardware, and subject-motor learning perspective. Here we show, in a series of experiments with non-disabled participants, a novel decoding and training paradigm allowing naïve participants to use their auricular muscles (AM) to control two degrees of freedom with a virtual cursor. AMs are particularly interesting because they are vestigial muscles and are often preserved after neurological diseases. Our method relies on the use of surface electromyographic records and the use of contraction levels of both AMs to modulate the velocity and direction of a cursor in a two-dimensional paradigm. We used a locking mechanism to fix the current position of each axis separately to enable the user to stop the cursor at a certain location. A five-session training procedure (20–30 min per session) with a 2D center-out task was performed by five volunteers. All participants increased their success rate (Initial: 52.78 ± 5.56%; Final: 72.22 ± 6.67%; median ± median absolute deviation) and their trajectory performances throughout the training. We implemented a dual task with visual distractors to assess the mental challenge of controlling while executing another task; our results suggest that the participants could perform the task in cognitively demanding conditions (success rate of 66.67 ± 5.56%). Finally, using the Nasa Task Load Index questionnaire, we found that participants reported lower mental demand and effort in the last two sessions. To summarize, all subjects could learn to control the movement of a cursor with two degrees of freedom using their AM, with a low impact on the cognitive load. Our study is a first step in developing AM-based decoders for HMIs for people with motor disabilities, such as spinal cord injury

    Using salinity to improve nutritional and market value of strawberries

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    Plants respond to salinity by producing antioxidants and osmolytes; some of these are nutritionally useful to humans (e.g. phenolics), or may improve the sensory quality of produce (e.g. sugars). For the current study, strawberries were irrigated with 0, 10, 20 or 40 mM NaCl, and the responses in antioxidants, phenolics, and flavour attributes were measured. A linear positive relationship was observed between salt stress and antioxidant concentrations, and the DPPH antioxidant assay responded more clearly than the FRAP assay. Phenolics were increased with statistical significance by salinity at all treatment levels, although trends differed between total phenolics and the subclasses anthocyanins and total flavonoids. It was seen that mild salinity (10 mM) with a low impact on yield could be used to increase antioxidants (6-10% above control) and total phenolics (11-16% above control). However differences between cultivars outweighed differences due to salinity in treatments below 20 mM NaCl. We found that sugars in strawberries (unlike other fruits) weren’t increased by salinity treatment. The lack of sugar increase can be explained by suggesting that organic acids are more important osmolytes than sugars for strawberries under salinity. However it was also determined that the failure of strawberries to increase their soluble sugars during salt stress can be explained by the lean nutrient regimes used by researchers, which don’t represent commercial production practices. Practically, mild salinity (≤20 mM) can be used to increase strawberry fruit value, but should be combined with an appropriate nutrient regime to avoid harm to flavour quality. The varieties Elsanta and Elsinore are both suitable for salt treatment, but Elsanta is better for antioxidant and phenolic production, as well as being more salt tolerant
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