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Francisco J Gea - One of the best experts on this subject based on the ideXlab platform.
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Cobweb disease on oyster culinary medicinal mushroom pleurotus ostreatus caused by the mycoparasite cladobotryum mycophilum
Journal of Plant Pathology, 2019Co-Authors: Francisco J Gea, Maria J Navarro, Laura M SuzAbstract:In autumn 2016, symptoms of Cobweb disease were observed on cultivated Pleurotus ostreatus crops in Spain. Based on morphological and genetic analyses, the causal agent of Cobweb was identified as Cladobotryum mycophilum. Two cropping trials, inoculated with C. mycophilum, were set up to evaluate the pathogenicity of this causal agent of Cobweb. Two different inoculation methods were used: (i) an agar plug was taken from the growing edge of a C. mycophilum isolate and placed in the centre of each hole in the block of P. ostreatus substrate (IP), and (ii) spraying each hole with a conidial suspension (ISC). In both trials, there were significant differences in disease incidence between the controls and the inoculated samples, but there were no significant differences between the two inoculation treatments. Between 75 and 87.5% of the blocks of the IP treatments and 100% of the blocks of the ISC treatments showed Cobweb symptoms. Cladobotryum mycophilum was consistently re-isolated from the inoculated blocks (100%). These findings suggest that C. mycophilum can equally cause Cobweb disease in A. bisporus, P. eryngii, and P. ostreatus mushroom crops.
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Cobweb a serious pathology in mushroom crops a review
Spanish Journal of Agricultural Research, 2017Co-Authors: Jaime Carrasco, M J Navarro, Francisco J GeaAbstract:Cobweb is a fungal disease of commercially cultivated mushrooms. Several members of the ascomycete genus Cladobotryum sp. have been reported as causal agents. White button mushroom is the most frequently cited host, but a wide range of cultivated edible mushrooms suffer Cobweb. The pathology causes production losses and reduces the crop surface available. The parasite produces a great number of harmful conidia that can be released easily and distributed throughout the mushroom farm to generate secondary points of infection. To prevent initial outbreaks, hygiene is of primary importance within the facilities dedicated to mushroom cultivation, while additional measures must be implemented to control and reduce Cobweb if there is an outbreak, including chemical and biological methods. This review summarizes and discusses the knowledge available on the historic occurrence of Cobweb and its impact on commercial mushroom crops worldwide. Causal agents, disease ecology, including the primary source of infection and the dispersal of harmful conidia are also reviewed. Finally, control treatments to prevent the disease from breaking out are discussed.
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incidence identification and pathogenicity of cladobotryum mycophilum causal agent of Cobweb disease on agaricus bisporus mushroom crops in spain
Annals of Applied Biology, 2016Co-Authors: Jaime Carrasco, M J Navarro, M Santos, Fernando Dianez, Francisco J GeaAbstract:Between 2008 and 2011, outbreaks of Cobweb were observed in commercial white button mushroom (Agaricus bisporus) crops in Castilla-La Mancha (Spain). In the last 3 years, the presence of the disease has notably increased resulting in serious economic losses. Based on morphological and genetic analyses, the casual agent of Cobweb was identified as Cladobotryum mycophilum. A. bisporus mushroom crops were surveyed over a 2-year period to estimate the incidence of Cobweb. The presence of the disease was detected in 32% of the mushroom crops observed, being of particular concern in autumn (44% of crops infected) and winter (37%). As regards the casing material, the percentage of crops affected by Cobweb was 34% in crops using mineral casing and 29% in those cased with a peat-based casing, with no statistical relationship between the casing and the presence of Cobweb. Two cropping trials inoculated with C. mycophilum were set up to evaluate the pathogenicity of the causal agent of Cobweb in three peat-based casings (C1, C2 and C3). The effect of Cobweb on mushroom productivity was evaluated by comparing mushroom production and the Cobweb patches detected in the casing soil. The decrease in total yield of mushrooms attributed to Cobweb reached 12.9% with C2, and the crop area colonised by Cobweb reached a final percentage of 36% with C3.
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first report of cladobotryum mycophilum causing Cobweb on cultivated king oyster mushroom in spain
Plant Disease, 2011Co-Authors: Francisco J Gea, M J Navarro, Laura M SuzAbstract:In 2010, symptoms of Cobweb were observed on cultivated king oyster mushroom (Pleurotus eryngii) in Castilla-La Mancha (Spain) affecting 16% of the blocks of substrate cultivated. Cobweb appeared at the end of the crop cycle, first as small, white patches on the casing soil, subsequently spreading to the nearest king oyster mushroom by means of a fine gray-white mycelium, and eventually sporulating to produce masses of dry spores. The mycelium can quickly cover pinheads, stalks, pileus, and gills, eventually resulting in decomposition of the entire fruit body. Infected tissues of P. eryngii were plated onto potato dextrose agar (PDA) and the parasitic fungus was isolated. Fungal colonies consisted of abundant and cottony aerial mycelium spreading rapidly on PDA and red pigment spreading in the agar. Conidiogenous cells were 24 to 35 μm long, 3.5 to 5 μm wide basally, and tapered slightly to the tip. Conidia were cylindrical to narrowly ellipsoidal, 17 to 25 (-28) × 8 to 10 μm, and zero to three septate. T...
Anne M F Moore - One of the best experts on this subject based on the ideXlab platform.
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material properties of Cobweb silk from the black widow spider latrodectus hesperus
International Journal of Biological Macromolecules, 1999Co-Authors: Anne M F Moore, Kimly TranAbstract:Abstract We present the material analysis of scaffolding silk from the Cobweb of the black widow spider Latrodectus hesperus. 30 strands were tested from the webs of nine spiders. Strands were stretched at 0.211 mm/s as force and extension were recorded. Cross-sectional area was measured under 1000× oil-immersion light microscopy. The stress–strain curve shows that Cobweb silk is a distinct material from other known spider silks. The average breaking point for this Cobweb silk is 1.1±0.5 GPa at 0.22±0.05 strain. All samples increased stiffness as they were stretched, but to different extents. Variation in stiffness might be due to differential crystallization or alignment of the silk proteins during stretching.
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short and long range order of the morphology of silk from latrodectus hesperus black widow as characterized by atomic force microscopy
International Journal of Biological Macromolecules, 1999Co-Authors: S A Gould, Anne M F Moore, Joseph C Spagna, K T Tran, Jason ShulmanAbstract:The surfaces of both stretched and unstretched silk threads from the Cobweb weaver, Latrodectus hesperus (Black Widow) have been examined by atomic force microscopy (AFM). AFM images of Cobweb scaffolding threads show both unordered and highly ordered regions. Two types of fibers within the threads were observed: thicker ( 300 nm in diameter) fibers oriented parallel to the thread axis and thinner (10‐100 nm) fibrils oriented across the thread axis. While regions which lacked parallel fibers or fibrils were observed on threads at all strain values, the probability of observing fibers and:or fibrils increased with strain. High-resolution AFM images show that with increasing strain, both mean fiber and fibril diameters decrease and that fibrils align themselves more closely with the thread axis. The observation of fibers and fibrils within the Cobweb threads has implications for current models of the secondary and tertiary structure and organization of spider silk. © 1999 Elsevier Science B.V. All rights reserved.
Zhizhong Tan - One of the best experts on this subject based on the ideXlab platform.
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recursion transform method to a non regular m n Cobweb with an arbitrary longitude
Scientific Reports, 2015Co-Authors: Zhizhong TanAbstract:A general Recursion-Transform method is put forward and is applied to resolving a difficult problem of the two-point resistance in a non-regular m × n Cobweb network with an arbitrary longitude (or call radial), which has never been solved before as the Green's function technique and the Laplacian matrix approach are difficult in this case. Looking for the explicit solutions of non-regular lattices is important but difficult, since the non-regular condition is like a wall or trap which affects the behavior of finite network. This paper gives several general formulae of the resistance between any two nodes in a non-regular Cobweb network in both finite and infinite cases by the R-T method which, is mainly composed of the characteristic roots, is simpler and can be easier to use in practice. As applications, several interesting results are deduced from a general formula, and a globe network is generalized.
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resistance and capacitance of 4 n Cobweb network and two conjectures
International Journal of Circuit Theory and Applications, 2015Co-Authors: Zhizhong Tan, Ling Zhou, Dafeng LuoAbstract:A classic problem in electric circuit theory studied by numerous authors over 160 years is the computation of the resistance between two nodes in a resistor network, yet some basic problem in m×n Cobweb network is still not solved ideally. The equivalent resistance and capacitance of 4×n Cobweb network are investigated in this paper. We built a quaternion matrix equation and proposed the method of matrix transformations in terms of the network analysis. We proposed a brief equivalent resistance formula and find that the equivalent resistance is expressed by coskπ/9 in a series of strict calculation. Meanwhile, an equivalent resistance of infinite networks is gained. Using the inverse mapping relation between capacitance parameters and resistance parameters, the equivalent capacitance formula is also given for the 4×n capacitance Cobweb network. By analyzing and comparing the equivalent resistances of the 1×n, 2×n, 3×n and 4×n Cobweb networks, two conjectures on the equivalent resistance and capacitance of the m×n Cobweb network are proposed. Copyright © 2013 John Wiley & Sons, Ltd.
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two point resistance of a Cobweb network with a 2r boundary
Communications in Theoretical Physics, 2015Co-Authors: Zhizhong Tan, Jinghuai FangAbstract:We consider the problem of the two-point resistance on an m × n Cobweb network with a 2r boundary, which has never been solved before. Up to now researchers just only solved the cases with free boundary or null resistor boundary. This paper gives the general formulae of the resistance between any two nodes in both finite and infinite cases using a method of direct summation pioneered by Tan [Z. Z. Tan, et al., J. Phys. A 46 (2013) 195202], which is simpler and can be easier to use in practice. This method contrasts the Green' function technique and the Laplacian matrix approach, which is difficult to apply to the geometry of a Cobweb with a 2r boundary. We deduce several interesting results according to our general formula. In the end we compare and illuminate our formulae with two examples. Our analysis gives the result directly as a single summation, and the result is mainly composed of the characteristic roots.
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two point resistance of a Cobweb network with a 2r boundary
arXiv: Statistical Mechanics, 2014Co-Authors: Zhizhong TanAbstract:We consider the problem of two point resistance on an $m times n$ Cobweb network with a 2r boundary which has never been solved before. Past efforts prior to 2014 researchers just only solved the cases with free boundary or null resistor boundary. This paper gives the general formulae of the resistance between any two nodes in both finite and infinite cases using a method of direct summation pioneered by Tan [Z.Z.Tan, et al, J. Phys. A 46, 195202 (2013)], which is simpler and can be easier to use in practice. This method contrasts the Greens function technique and the Laplacian matrix approach, which is difficult to apply to the geometry of a Cobweb with a 2r boundary. We deduced several interesting results according to our general formula. In the end we compare and illuminate our formulae with two examples. Our analysis gives the result directly as a single summation, and the result is mainly composed of the characteristic roots.
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proof and extension of the resistance formula for an m x n Cobweb network conjectured by tan zhou and yang
arXiv: Statistical Mechanics, 2013Co-Authors: J W Essam, Zhizhong TanAbstract:An m x n Cobweb network consists of n radial lines emanating from a center and connected by $m$ concentric n-sided polygons. A conjecture of Tan, Zhou and Yang for the resistance from center to perimeter of the Cobweb is proved by extending the method used by the above authors to derive formulae for m = 1, 2 and 3 and general n. The resistance of an m x (s+t+1) fan network from the apex to a point on the boundary distant s from the corner is also found.
Cars Hommes - One of the best experts on this subject based on the ideXlab platform.
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carl s nonlinear Cobweb
Journal of Economic Dynamics and Control, 2018Co-Authors: Cars HommesAbstract:Abstract This essay surveys some of my work on expectations, learning and bounded rationality within the classical Cobweb model following early inspiring ideas from Carl Chiarella. In particular, I focus on the role of nonlinear dynamics, learning and heterogeneity within the Cobweb framework and how price fluctuations in the Cobweb theory fit with observations of individual and aggregate behaviour from laboratory experiments with human subjects.
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production delay and belief distributions in a continuous time Cobweb model
Social Science Research Network, 2017Co-Authors: Cars HommesAbstract:This paper provides a unified analysis of the impacts of both production delay and agents' belief distributions on the aggregate price fluctuations in a general continuous-time Cobweb model. We find that the time inconsistence between demand and supply due to production delay inherently generates overshooting effect in price. Large production delays give rise to price fluctuations, even with small intensity of choice. By allowing producers to update their beliefs based on an large belief set, we show that different belief distributions lead to different price dynamics, and in turn, stable (unstable) prices are typically associated with stationary (nonstationary) belief distributions.
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behavioral rationality and heterogeneous expectations in complex economic systems
Cambridge Books, 2013Co-Authors: Cars HommesAbstract:1. Introduction 2. Bifurcations and chaos in 1-D systems 3. Bifurcations and strange attractors in 2-D systems 4. The nonlinear Cobweb model 5. The Cobweb model with heterogeneous expectations 6. An asset pricing model with heterogeneous beliefs 7. Empirical validation 8. Laboratory experiments.
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learning in Cobweb experiments
Macroeconomic Dynamics, 2007Co-Authors: Cars Hommes, Joep Sonnemans, Jan Tuinstra, H Van De VeldenAbstract:Different theories of expectation formation and learning usually yield different outcomes for realized market prices in dynamic models. The purpose of this paper is to investigate expectation formation and learning in a controlled experimental environment. Subjects are asked to predict the next period's aggregate price in a dynamic commodity market model with feedback from individual expectations. Subjects have no information about underlying market equilibrium equations, but can learn by observing past price realizations and predictions. We conduct a stable, an unstable, and a strongly unstable treatment. In the stable treatment, rational expectations (RE) yield a good description of observed aggregate price fluctuations: prices remain close to the RE steady state. In the unstable treatments, prices exhibit large fluctuations around the RE steady state. Although the sample mean of realized prices is close to the RE steady state, the amplitude of the price fluctuations as measured by the variance is significantly larger than the amplitude under RE, implying persistent excess volatility. However, agents' forecasts are boundedly rational in the sense that fluctuations in aggregate prices are unpredictable and exhibit no forecastable structure that could easily be exploited.
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heterogeneous beliefs and the non linear Cobweb model
Journal of Economic Dynamics and Control, 2000Co-Authors: Jacob K Goeree, Cars HommesAbstract:Abstract This paper generalizes the evolutionary Cobweb model with heterogeneous beliefs of Brock and Hommes (1997. Econometrica 65, 1059–1095), to the case of non-linear demand and supply. Agents choose between a simple, freely available prediction strategy such as naive expectations and a sophisticated, costly prediction strategy such as rational expectations, and update their beliefs according to an evolutionary ‘fitness’ measure such as past realized net profits. It is shown that, for generic non-linear, monotonic demand and supply curves, the evolutionary dynamics exhibits ‘rational routes to randomness’, that is, bifurcation routes to strange attractors occur when the traders’ sensitivity to differences in evolutionary fitness increases.
Fen Zheng - One of the best experts on this subject based on the ideXlab platform.
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frequency symmetry comparison of Cobweb like disk resonator gyroscope with ring like disk resonator gyroscope
IEEE Electron Device Letters, 2019Co-Authors: Bo Fan, Shuwen Guo, Mengmeng Cheng, Ming Zhou, Fen ZhengAbstract:Frequency symmetry of a Cobweb-like disk resonator gyroscope (CDRG) has been compared with a conventional ring-like disk resonant gyroscope (RDRG) in this letter to corroborate that linear beam structures have a better process tolerance than curved beam structures for micro-fabrication processes. The CDRG comprises multiple concentric Cobweb-like rings and each is formed by 16 identical straight beams joined end-to-end. It exhibits as-fabricated symmetric vibration behavior superior to RDRGs. To compare as-fabricated structural symmetry, CDRG and RDRG are placed side-by-side on the same wafer and simulated using COMSOL. A tested frequency split as low as 0.56 Hz is achieved for CDRG, and the average relative frequency split is 79.7 ppm, which is approximately seven times smaller than that of RDRG. Additionally, a temperature characteristics test demonstrates that the as-fabricated CDRG has excellent temperature stability, and the relative frequency split varied by 2.83 ppm in the temperature ranging from −20 °C to +80 °C. The proposed concept is verified by the simulation and experimental results.