Initial Stages Of Decay Research Articles

Comparison of ROC Feature Selection Method for the Detection of Decay in Citrus Fruit Using Hyperspectral Images

Hyperspectral imaging systems allow to detect the initial stages of decay caused by fungi in citrus fruit automatically, instead of doing it manually under dangerous ultraviolet illumination, thus preventing the fungal infestation of other sound fruit and, consequently, the enormous economical losses generated. However, these systems present the disadvantage of generating a huge amount of data, which is necessary to select for achieving some result useful for the sector. There are numerous feature selection methods to reduce dimensionality of hyperspectral images. This work compares a feature selection method using the area under the receiver operating characteristic (ROC) curve with other common feature selection techniques, in order to select an optimal set of wavelengths effective in the detection of decay in a citrus fruit using hyperspectral images. This comparative study is done using images of mandarins with the pixels labelled in five different classes: two types of healthy skin, two types of decay and scars, ensuring that the ROC technique generally provides better results than the other methods.

Regional statistics in confined two-dimensional decaying turbulence

Two-dimensional decaying turbulence in a square container has been simulated using the lattice Boltzmann method. The probability density function (PDF) of the vorticity and the particle distribution functions have been determined at various regions of the domain. It is shown that, after the initial stage of decay, the regional area averaged enstrophy fluctuates strongly around a mean value in time. The ratio of the regional mean and the overall enstrophies increases monotonously with increasing distance from the wall. This function shows a similar shape to the axial mean velocity profile of turbulent channel flows. The PDF of the vorticity peaks at zero and is nearly symmetric considering the statistics in the overall domain. Approaching the wall, the PDFs become skewed owing to the boundary layer.

Study of the sorption-desorption properties of pine wood at the initial stage of decay by wood-rot fungi 10th EWLP, Stockholm, Sweden, August 25–28, 2008

Abstract Hot water extraction of pine wood was carried out after 10 days of exposure to brown-rot fungi (Gloeophyllum trabeum, Coniophora puteana and Poria placenta) and a white-rot fungus (Coriolus versicolor). The microstructure of the wood cell wall was analysed by the water vapour sorption method. The content and composition of monosaccharides in the extracts were determined by high performance liquid chromatography. Despite the absence of essential mass losses at the initial stage of the contact with the fungi, slight changes in the cell wall microstructure can be observed, namely, the hydrophobisation and the change in the character of porosity in the region of 1–10 nm pore sizes. After hot water treatment, the mass decreases considerably, i.e., to 25% for the control and brown-rot treated samples and more than 30% for the white-rot treated sample. The sorption-desorption isotherms for the washed control sample and brown-rot samples were not changed practically, but the isotherm was changed clearly in the case of the white-rot treated sample. The microstructure of the white-rot sample changed after hot water washing radically and was accompanied with the formation of wide mesopores in the range of 5–9 nm width.

Sterols and lignin in Eucalyptus globulus Labill. wood: Spatial distribution and fungal removal as revealed by microscopy and chemical analyses

Abstract Wood decay experiments were carried out aiming at the selective removal of lipophilic compounds with selected basidiomycetes isolated from Eucalyptus globulus plantations in Uruguay: Dendrophora albobadia, Lentinus tigrinus, Peniophora cinerea, Peniophora lycii, and Phanerochaete crassa. Localization and composition of lipophilic compounds and lignin of E. globulus were determined by gas chromatography-mass spectrometry, fluorescence microscopy using filipin staining, confocal laser scanning microscopy (CLSM), and low temperature scanning electron microscopy. Free and esterified sterols, mainly sitosterol, were the predominant lipophilic compounds in the control wood. Sterols were present in ray parenchyma cells, together with polyphenols, and in vessels. This confirms earlier observations indicating that these cell types are the principal source of lipophilic extractives involved in pitch problems during pulping and bleaching. Sterols are also present in the vestures of fiber and vessel pits. Different fungal degradation patterns of E. globulus wood were determined. P. lycii showed the highest specificity for lignin degradation during short incubation time together with considerable sterol removal capacity. Ray parenchyma cells and their lumen deposits were strongly degraded by P. lycii. Eucalypt lignin located in vessel walls and fiber cell corners was more resistant to fungal attack, as revealed by CLSM. The initial decay stage of L. tigrinus was restricted to vessels and tyloses where the sterol compounds were removed.

Decay resistance of wood treated with amino-silicone compounds

Abstract An amino-silicone (AS; amino-polydimethylsiloxane) micro-emulsion was tested for its suitability to preserve wood against basidiomycetes in a mini-block experiment and in a test according to the European standard (1996) EN 113. Decay resistance was assessed against the white rot fungi Trametes versicolor, Ceriporiopsis subvermispora, and Hypoxylon fragiforme, as well as the brown rot fungi Coniophora puteana, Antrodia vaillantii, Gloeophyllum trabeum and Serpula lacrymans. Pine sapwood and beech wood were treated with AS emulsions at solute concentration levels of 2%, 5% and 15%. The mini-blocks treated with 15% concentrations of AS resisted decay by T. versicolor and C. puteana over a long time (12 weeks), while samples treated with low and moderate concentrations underwent considerable mass losses. Accordingly, microscopic studies revealed a high degree of colonisation by the white rot fungus and loss of cell wall integrity (brown rot) in samples treated with 2% AS. At high AS content (15%), no or only initial stages of decay could be observed. In the European standard (1996) test EN 113, the mass loss in all fungal cultures except for the white rot ascomycete H. fragiforme was below 5%, when the samples were treated with 15% AS. The effect of low and moderate AS concentration on the decay resistance was dependent on the fungal strain. The mode of action of AS treatment against basidiomycete decay is discussed.

Decay-induced biomineralization of the saguaro cactus (Carnegiea gigantea)

The saguaro, Carnegiea gigantea (Englemann), is a columnar cactus that grows to 15 m tall and weighs up to several tons, of which 85 to 90% of the mass is water. Roughly 18% of the dry mass consists of the biomineral weddellite (CaC2O4·2H2O). The C in the weddellite derives from atmospheric CO2 via photosynthesis. A mature saguaro can contain on the order of 1 × 105 g of weddellite. The weddellite crystals occur as aggregates up to 1 mm wide. After the death of the saguaro, a series of minerals crystallize in the rotting flesh. These minerals form from elements released from the decay of the cactus by microorganisms and thus is a type of biologically induced mineralization. During the initial stages of decay, authigenic Mg- and Ca-bearing minerals crystallize from elements released by the putrefying flesh and include lansfordite (MgCO3·5H2O), nesquehonite (MgCO3·3H2O), several polymorphs of MgC2O4·2H2O including glushinskite, monohydrocalcite (CaCO3·H2O), calcite, vaterite, and several unidentified Mg-bearing phases. As the saguaro decays, the soft, water-rich pith shrinks, but the ribs and skin remain intact, producing warm, moist pockets within the dead saguaro. Abundant, glassy lansfordite crystals to 1 mm in diameter grow in these pockets during the cooler winter months. Further decay leaves a dried hollow shell covered by the saguaro skin, inside of which nesquehonite and monohydrocalcite crystallize. Lansfordite and nesquehonite are unstable in the desert and rapidly amorphize after exposure to the atmosphere. Magnesium oxalates are locally abundant in the decayed flesh and occur as crystals up to 1.5 mm in length. The common occurrence of fungal hyphae on the glushinskite suggests that it forms as a result of the reaction between oxalic acid released by fungi and the Mg-rich solutions of the rotting saguaro. During the final stages of decay, the pith consists of a pale-brown to tan-colored sand of weddellite and its transformation product monohydrocalcite. This sand lithifies to porous sponge-like masses during the final stages of saguaro decay. This monohydrocalcite further alters to calcite. The δ13CVPDB of the monohydrocalcite and calcite after weddellite range from −1.65 to + 0.76‰. The calcite is subsequently solubilized and remobilized, precipitating as caliche in the desert soil, or redistributed by wind. In arid environments, the desert fauna metabolize the atmospheric C bound in the organic matter to CO2. In contrast, decay of the saguaro adds atmospheric C to the soil as inorganic C via the transformation of the biomineral weddellite to calcite. In areas with high saguaro density, it is estimated that up to 2.4 g/m2/yr of calcite can be added to the desert from the decayed cacti. This inorganic C has geologically long soil residence times, thus effectively sequestering the atmospheric C.

Wood biodegradation and enzyme production by Ceriporiopsis subvermispora during solid-state fermentation of Eucalyptus grandis

The white-rot fungus Ceriporiopsis subvermispora grows on wood aggressively and is suitable for biopulping of both soft and hardwoods. This fungus is able to produce laccase and manganese peroxidase (MnP) isoenzymes, as well as hemicellulases and a poor complex of cellulases lacking in cellobiohydrolase activity. In the present work, C. subvermispora was grown on Eucalyptus grandis wood chips under solid-state fermentation. Wood weight loss ranged from 2.9 to 11.7% for biodegradation periods of 15–90 days. The highest lignin loss was 27 %, which was similar to the loss of polyoses (21.6%) after 90 days of treatment. Glucan loss started to be significant only after 60 days of biodegradation attaining a maximum of 7.3% after 90 days. Extractives removal was also significant, reaching 42% after 90 days. Holocellulose yields were almost unchanged over all the biodegradation periods. However, the holocellulose viscosities decreased as a function of the biodegradation time, especially after 30 days. The yields of alpha-cellulose decreased from 44 to 37% as a function of the biodegradation time, indicating that cellulose depolymerization took place even when the glucan losses were low. Some relevant hydrolytic and oxidative enzymes present in the culture extracts were studied. Xylanase was the main hydrolytic enzyme and the levels of peroxidase were lower than those of laccase. During the initial wood decay stages, there was not a direct correlation between the levels of enzymatic activities and the extent of losses of wood weight or components. This suggests that the mineralization of wood components might be limited by the non-diffusion of the enzymes into the wood cell walls at the initial decay stages.

Rollup region of a turbulent trailing vortex issued from a blade with flow separation

This paper presents the results of an experimental investigation on the near field of a tip vortex generated by a blade at moderate incidence. The experiments were conducted at Rea 15 000 and the boundary layer over the blade separated around midchord on the upper surface. Laser-Doppler measurements of the turbulent flow (Tua 1.5%) were performed at various stations downstream of the blade. The three components of the mean velocity field and turbulent attributes were quantified at cross-planes, characterizing both the blade wake and the tip vortex structure. This allowed the analysis of the rollup and initial stages of decay of the tip vortex in the light of known theories and models. The axial velocity defect at the center of the vortex core evolved as x ˇ1 log x, without displaying any significant outgrowth imposed by the separated flow upstream. Momentum balances were also carried out at a station downstream to the conclusion of vortex rollup. The approximate axisymmetry of the flow field in the trailing vortex was used to formulate the balances in a cylindrical coordinate system. Among other observations, it was seen that an adverse axial pressure gradient developed in the vortex core, which reinforced the tenacity of the axial velocity defect. In contrast, an area influenced by a favorable pressure gradient was found outside the core. ” 2000 Elsevier Science Inc. All rights reserved.

Initial stages in the decay of the amorphous phase in the bulk metallic glass Zr-Cu-Ti

Using methods of x-ray diffraction analysis, differential scanning calorimetry, dilatometry, and transmission electron microscopy, we have investigated the initial stages of decay of the amorphous phase in a bulk metallic glass based on zirconium. We found that crystallization of the bulk metallic glass proceeds in several stages, where in the first stage the bulk conversion effect is equal to more than 1.6%, or about 80% of the total bulk crystallization effect. We showed that the first stage of decay of the amorphous phase in the bulk metallic glass Zr29Ti11Cu60 leads to the formation of a nanocrystalline structure with a grain size of 1–5 nm. We have analyzed the change in the shape of the diffraction maximum during the formation of the very fine nanocrystalline structure.

A RHEED study of the transition from two-dimensional to three-dimensional growth in the InAs/GaAs system

A specially developed detection system and an analysis of RHEED diffraction patterns were used to investigate the dynamics of transition from two-dimensional to three-dimensional growth mechanism in the heteroepitaxial InAs/GaAs system. An analysis of the dynamics of the diffraction patterns was used for the first time to investigate the dynamics of formation of quantum dots. A time shift in the dynamic behavior of the diffracted intensity for diffraction patterns recorded at different angles was found. This shift is explained in terms of the size differences in the three-dimensional islands at the initial stage of decay of the pseudomorphic layer. InAs/GaAs quantum dots grown under certain conditions produce reflections at 45° relative to the principal reflections. This is evidence for the ordering of islands in the [001] and [010] crystallographic directions.

Vortex Evolution and Bound Pair Formation in Anisotropic Nonlinear Optical Media.

We present a theoretical and experimental study of the propagation, decay, and interaction of optical vortices in media with an anisotropic nonlocal nonlinearity. The initial stage of decay of a circular vortex is characterized by charge dependent rotation, and stretching of the vortex. Our results suggest that a compact vortex of unit topological charge cannot exist in such media, but that a counterrotating vortex pair can form a bound state. Some analogies and differences between optical vortices and the classical dynamics of vortices in an ideal fluid are described.

Decomposition of Eucalyptus globulus leaves and three native leaf species (Alnus glutinosa, Castanea sativa and Quercus faginea) in a Portuguese low order stream

Leaf decomposition of the exotic evergreen Eucalyptus globulus (eucalyptus), and three native deciduous tree species, Alnus glutinosa (alder), Castanea sativa (chestnut) and Quercus faginea (oak), was compared in a second order stream in Central Portugal. Changes in dry weight, nitrogen and polyphenolic compounds and microbial colonization were periodically assessed for three months. Negative exponential curves fit the leaf weight loss with time for all leaf species. Mass loss rate was in the order alder (K = 0.0161) > chestnut (K = 0.0079) > eucalyptus (K = 0.0068) > oak (K = 0.0037). Microbial colonization followed the same pattern as breakdown rates. Evidence of fungal colonization was observed in alder after 3 days in the stream, whereas it took 21 days in oak leaves to have fungal colonization. Fungal diversity was leaf species-dependent and increased with time. In all cases, percent nitrogen per unit leaf weight increased, at least, at the initial stages of decay while soluble polyphenolics (expressed as percentage per unit leaf weight) decreased rapidly in the first month of leaves immersion. Intrinsic factors such as nitrogen and polyphenolic content may explain differences in leaf decomposition. The possible incorporation of eucalyptus litter into secondary production in a reasonable time span is suggested, although community balance and structure might be affected by differences in allochthonous patterns determined by eucalyptus monocultures.

Ultrafast decay dynamics of luminescence in porous silicon.

Ultrafast decay dynamics of luminescent porous silicon has been studied with a picosecond-spectroscopic technique. We have observed that the surface structure of the Si microcrystals changes the picosecond carrier dynamics: picosecond luminescence decay becomes faster with increasing hydrogen termination on the surface of a Si microcrystal. We have also observed the redshift of the luminescence peak in the initial decay stage. This shift disappears with increasing hydrogen termination. These results suggest that there are two luminescent states in Si microcrystals: a weak luminescent quantum-confinement state (Si microcrystal core) and a strong luminescent surface state. Surface treatment by hydrogen termination on Si microcrystals influences the transfer rate between the two states and changes the origin of luminescence from the surface state to the quantum-confinement state.

Decay Potential of Hummock and Hollow Sphagnum peats at Different Depths in a Swedish Raised Bog

2 release from the most .recently deposited Sphagnum feat litter from the 2.5-5 cm depth layer was nearly tWice as high (0.66 mg CO2 g-l d- ) as that from older organic material from the 10--12.5 cm depth layer (0.35 mg CO2 g-l d1 ) under common conditions of temperature, moisture and aeration. No consistent differences in CO2 emission rates were detected among the four Sphagnum species for the shallow organic material tested. However, when deeper (50--100 cm) Sphag­ num-dominated peat samples were exposed to the same aerated conditions, peat formed by the hummock-forming species released CO2 at a slower rate (0.23 mg g-l d1 ) than the two hollow species (0.29 mg g-l d- 1). The results suggest that the amount of previous exposure of Sphagnum peat to decay processes may be more important than the species composition in determining subsequent rates of decay and carbon loss. The observed rates of CO2 emission were used to estimate the annual mass loss from aerobically decaying organic material under the thermal regime at the study site. Based on these estimates, Sphagnum litter loses about 5% of its dry mass annually during the initial stages of decay, but the decay rate decreases to 2-3% annually for deeper Sphagnum peat exposed to aerobic conditions.

Influence of pH on the growth and leaf-maceration ability of fungi involved in the decomposition of floating leaves of Nymphaea alba in an acid water

Summary: Ten species of fungi were isolated from floating leaves cut from plants of Nymphaea alba in various initial stages of decay, which were collected from an acidic moorland pool. None of the fungal species isolated belonged to the aquatic Hyphomycetes sensu Ingold or the aero-aquatic fungi sensu Van Beverwijk. Growth experiments were conducted with five of the species on media containing glucose, polysaccharide or isolated cell walls of N. alba, each at three pH values. The fungi investigated were capable of growth on a variety of structural polysaccharides, indicating their potential importance in leaf degradation. Low pH inhibited growth on media containing glucose, pectin or cell wall fraction. Utilization of carboxymethylcellulose and crystalline cellulose did not differ much within the pH range studied. The fungi isolated were grown on N. alba leaf strips at three pH values to study the influence of pH on leaf maceration. All the fungi investigated could develop at low pH (4·0), but maceration was only observed at pH 5·5 or 7·5. It is likely that inhibition of pectin degradation is an important factor causing suppression of leaf fragmentation at low pH. This may contribute to the inhibition of the decomposition of macrophyte remains in acid aquatic systems.

The taphonomy of birds

The taphonomy of birds can be investigated with actualistic studies complemented by reviewing Konversat Lagerstätten such as Messel, Green River and Solnhofen.Two field sites were chosen in southern Florida: 1, a freshwater (16–23 ppt salinity) environment in which biogenic carbonate muds were being deposited and 2, a marine (30–34 ppt salinity) environment in which pyritous carbonate muds were being deposited. Ninety-six specimens (36 genera, 40 species) were used in this study (these were obtained from a wildlife centre where they died of natural causes). Experiments were set up in both marine and freshwater sites in the following categories: large protected, unprotected; small protected, unprotected. Protected specimens were placed in metal cages coated with small mesh (1.5mm2) nylon netting.The specimens were allowed to degrade under natural conditions. The following variables were recorded daily over a seventy day period: air and water temperature, humidity, rainfall, wind and current speed and direction, salinity, dissolved oxygen content, pH, and water depth. Specimens from each of the eight categories were sampled at day 1, 4, 7, 11, 28, 56, and 70.Scavengers play a major role in the early taphonomic processes. Unprotected specimens were rapidly removed from the study area by large predators such as alligators (Alligator mississippiensis) and American crocodiles (Crocodylus actus), and Turkey vultures (Cathartes aura). Even protected specimens were prone to attack by more “intelligent” large scavengers such as racoons. Smaller predators include crayfish in the freshwater site and the carnivorous gastropods (Crown conch) in the marine environment. The Crown conch was observed to be a voracious feeder and large numbers rapidly strip all flesh from any carcass within reach of the bottom.Decay proceeds rapidly in the warm waters of the field sites. Within the carcasses temperatures approach optimum bacterial temperatures and large bacterial colonies form within muscle blocks after only one day. The initial decay of the muscle fibres is also rapid (one day) as the muscle myofibrils start to break into short lengths and the myoseptum starts to disintegrate, and has totally disappeared after seven to fourteen days (depending on the initial mass of the bird).From graphs showing plots of percentage weight loss (weight loss as a percentage of original weight) versus time decay can be seen to follow an exponential curve ie. most rapid decay occurs early (as soft tissues decay) then weight loss slows down (after 10 days for small specimens and 28 days for large specimens) as by this time nearly all but the most resistant soft tissues have decayed and the weight loss is due to the removal of skeletal matter to the sedimentary record. Feathers are resistant to the initial stages of decay and the primary and secondary feathers remain attached to the wing bones for up to twenty-eight days even when the soft tissues have been totally removed.The results of the decay experiments have provided directly comparable specimens to those that can be found within the fossil record. This comparison of fossil and modern analogues allows a series of taphonomic thresholds to be defined in the fossilisation of birds.

The early stages of building stone decay in an urban environment

Short term exposure (2 months) of small limestone samples in an urban environment coupled with subsequent SEM observations provides detailed evidence of the initial stages of decay. After 2 months, significant amounts of gypsum were found on stone samples which had been sheltered from rainfall. Samples which had been exposed to rainfall had negligible gypsum development, but showed considerable microscale evidence of dissolution. Clear differences emerged between the responses of the two different building stones used in the experiment, with Portland Stone having much greater amounts of gypsum after exposure than Monk's Park Stone.

Decomposition of leaf litter in karri ( Eucalyptus diversicolor) forest of varying age

Rates of weight loss and release of N, P, K, S, Ca, Mg, Na and Cl from decomposing leaf litter were measured in regrowth karri ( Eucalyptus diversicolor F. Muell.) forest aged 6, 9 and 40 years and in mature karri forest growing in south-western Australia. Decomposing leaf litter from the four sites lost 47–55% of original dry weight after exposure for 82 weeks on the forest floor. Rates of weight loss from leaf litter at the four sites varied in the order: mature<40-year-old=9-year-old=6-year-old-forest. A composite exponential function, with separate decay functions for labile and resistant litter components, explained 98–99% of the variation in mean dry weight loss in relation to time of exposure. Loss of labile litter components was rapid (half-lives 5–14 weeks). Loss of the resistant components was faster for litter from regrowth stands (half-lives 116–119 weeks) than for litter from mature forest (half-life 189 weeks). Slower rates of leaf litter decomposition together with increasing amounts of leaf and non-leaf (twigs, bark and fruit) litterfall as the stands mature indicate that the rate of accumulation of forest litter will be greater in mature forest than in regrowth stands. The order of element mobility in decomposing karri leaf litter (Na>Cl>K>S>Ca>N>P) was similar to that reported for other eucalyp litters. Nutrient content of fresh leaf litter, and rates of nutrient release during leaf litter decomposition, tended to be greater in the younger regrowth stands than in mature forest. Therefore, although the amounts of leaf litterfall were smaller in the younger stands, the amounts of nutrients released during the initial stages of decomposition were similar to, or greater than, the amounts released from decomposing leaf litter at the mature forest. However, since the proportion of non-leaf components in annual litterfall increases with age of the forest, total release of K, S, Ca, Mg and Na from all litter fractions is likely to be greater on older stands. Nitrogen and P occur at low concentrations in the major non-leaf litters and are imported into these tissues during decomposition. Therefore, in the initial stages of decay, immobilization of N and P will be greater in the litter layer of mature forest than in young regrowth stands.

Grid turbulence in air and water

An experimental comparison of grid turbulence performed in a wind tunnel and in a water tunnel is described. The measurements were made in the initial stage of decay with mesh Reynolds numbers ranging from 12 800 to 81 000. Hot-wire and hot-film instrumentation combining analog and digital computing methods were used to measure higher-order correlations of the longitudinal component of turbulent velocity and higher-order moments of longitudinal turbulent velocity gradients. A comparison of the latter is obtained for an increase in Reynolds number without having to alter the flow geometry. Apart from the intrinsic interest of such measurements in water, the results show the non-Gaussian character of the turbulent fluctuation and compare the behavior of higher-order moments of turbulent velocity gradients to theoretical considerations for the small scale turbulent structure.

Initial Stage of Decay of Electrical Resistance in Deformed Aluminum

Initial Stage of Decay of Electrical Resistance in Deformed Aluminum