This study deals with the faults’ detection and classification in AC transmission lines based on power spectral density (PSD), introducing PSD in time and frequency for analysing transient ...information under faulted conditions. The discrete wavelet transform is used for scaling current signals in time–frequency at different decomposition levels by approximation and detail coefficients. Then, a wavelet-covariance matrix is shaped with the aim to obtain its PSD, being this the key to detect and classifying faults. Results show that the proposed method attains the detection in a short time and the classification is accomplished via the Hellinger distance, whose straightforward implementation is carried out in this study. The classification process is compared adopting different classifiers to cope with a set of signals in a time frame. Finally, the proposal is extensively assessed using real and simulated signals stemming from multiple fault cases of radial and interconnected power grids.
The inhibitory activity of 34 natural products of various structural classes on hydroxyphenylpyruvate dioxygenase (HPPD), the target site for triketone herbicides, and the mode of interaction of ...selected natural products were investigated. Recombinant HPPD from arabidopsis is sensitive to several classes of natural compounds including, in decreasing order of sensitivity, triketones, benzoquinones, naphthoquinones and anthraquinones. The triketone natural products acted as competitive tight-binding inhibitors, whereas the benzoquinones and naphthoquinones did not appear to bind tightly to HPPD. While these natural products may not have optimal structural features required for in vivo herbicidal activity, the differences in their kinetic behavior suggest that novel classes of HPPD inhibitors may be developed based on their structural backbones.
Hydroxyphenylpyruvate dioxygenase is a target site for triketone herbicides. The inhibitory activity of 34 natural products of various structural classes on HPPD and the mode of interaction of selected natural products were investigated.
The chemical composition of the essential oil of kenaf (Hibiscus cannabinus) was examined by GC-MS. Fifty-eight components were characterized from H. cannabinus with (E)-phytol (28.16%), (Z)-phytol ...(8.02%), n-nonanal (5.70%), benzene acetaldehyde (4.39%), (E)-2-hexenal (3.10%), and 5-methylfurfural (3.00%) as the major constituents. The oil was phytotoxic to lettuce and bentgrass and had antifungal activity against Colletotrichum fragariae, Colletotrichum gloeosporioides, and Colletotrichum accutatum but exhibited little or no algicidal activity. Keywords: Kenaf; Hibiscus cannabinus; essential oil composition; fungi; algae; phytotoxicity; allelopathy
This paper assesses the coherency in power systems employing the affinity propagation (AP) algorithm with different distance metrics and quality measurements. This assessment allows determining the ...appropriate metric to cluster a frequency dataset that possesses coherent patterns. Thanks to the AP method does not require initialization for the number of clusters, its convergence characteristics guaranteed by the optimization process, and its capacity for using different distance metrics as input, the AP is adopted to identify and distinguish such coherent patterns that embody the collective motion of an operative area in a power system. The AP method is a data-driven method that uses an affinity matrix as input, i.e., the square matrix computed with pairwise distances. Since the distance function significantly impacts the quality of the resulting clustering, this contribution evaluates three different distance metrics, distance correlation, and the results are compared using four cluster indexes. The data collection is constituted by a set of frequency signals and the representative objects are the nodes identified as the center of each operative area. This contribution presents experimental results using simulated signals with added noise and real event signals captured by 94 PMUs. We found that our proposed strategy achieves highly competitive results for identifying coherent generator and non-generator buses in large-scale power systems.
The essential oil profile of maca (
Lepidium meyenii) obtained from Lima, Peru, was examined. Steam distillates of the aerial parts of
L. meyenii were continuously extracted with pentane and the ...pentane extracts analyzed by GC/MS. Retention indices and mass spectral data were used to identify 53 oil components. Phenyl acetonitrile (85.9%), benzaldehyde (3.1%), and 3-methoxyphenylacetonitrile (2.1%) were the major components of the steam distilled oil. The oil of
L. meyenii was tested for phytotoxic, cyanobactericidal, and antitermite activity. The oil was selectively toxic towards the cyanobacterium
Oscillatoria perornata compared to the green alga
Selenastrum capricornutum, with complete growth inhibition at 100 μg/ml. Mortality of the Formosan subterranean termite,
Coptotermes formosanus, was numerically, but not significantly, higher when held on filter paper treated with maca oil. At 1% (w/w), maca oil also appeared to act as a feeding deterrent to termites. Several minor components of the essential oil of maca including 3-methoxyphenylacetonitrile and benzylthiocyanate were significantly active against the Formosan termite. This is the first report on the essential oil composition of
L. meyenii.
Phenyl acetonitrile (85.9%), benzaldehyde (3.1%), and 3-methoxyphenylacetonitrile (2.1%) were the major components of the essential oil of
L. meyenii. Benzylthiocyanate and 3-methoxyphenylacetonitrile were significantly active against the Formosan termite.
Recent research of the Agricultural Research Service of USDA on the use of natural products to manage pests is summarized. Studies of the use of both phytochemicals and diatomaceous earth to manage ...insect pests are discussed. Chemically characterized compounds, such as a saponin from pepper (Capsicum frutescens L), benzaldehyde, chitosan and 2‐deoxy‐D‐glucose are being studied as natural fungicides. Resin glycosides for pathogen resistance in sweet potato and residues of semi‐tropical leguminous plants for nematode control are also under investigation. Bioassay‐guided isolation of compounds with potential use as herbicides or herbicide leads is underway at several locations. New natural phytotoxin molecular target sites (asparagine synthetase and fructose‐1,6‐bisphosphate aldolase) have been discovered. Weed control in sweet potato and rice by allelopathy is under investigation. Molecular approaches to enhance allelopathy in sorghum are also being undertaken. The genes for polyketide synthases involved in production of pesticidal polyketide compounds in fungi are found to provide clues for pesticide discovery. Gene expression profiles in response to fungicides and herbicides are being generated as tools to understand more fully the mode of action and to rapidly determine the molecular target site of new, natural fungicides and herbicides. Published in 2003 for SCI by John Wiley & Sons, Ltd.
The essential oil profile of Callicarpa americana was examined. Samples were collected from Lafayette county in north central Mississippi, and GC-MS data and retention indices were used to identify ...67 oil components. Humulene epoxide II (13.9%), α-humulene (10.0%), 7-epi-α-eudesmol (9.4%), β-pinene (8.8%), and 1-octen-3-ol (8.5%) were the major components of the steam-distilled oil. The oil was selectively toxic toward the cyanobacterium Oscillatoria perornata compared to Oscillatoria agardhii and the green alga Selenastrum capricornutum, with complete growth inhibition at 28.5 μg/mL. The oil was only mildly phytotoxic and antifungal. Keywords: Callicarpa americana; essential oil composition; fungi; algae; plant; bioactivity
Dehydrozaluzanin C, a natural sesquiterpene lactone, is a weak plant growth inhibitor with an
I
50 of about 0.5 mM for lettuce root growth. It also causes rapid plasma membrane leakage in cucumber ...cotyledon discs. Dehydrozaluzanin C is more active at 50 μM than the same concentration of the herbicide acifluorfen. Symptoms include plasmolysis and the disruption of membrane integrity is not light dependent. Reversal of its effects on root growth was obtained with treatment by various amino acids, with histidine and glycine providing ca. 40% reversion. The strong reversal effect obtained with reduced glutathione is due to cross-reactivity with DHZ and the formation of mono- and di-adducts. Photosynthetic, respiratory and mitotic processes, as well as NADH oxidase activity appear to be unaffected by this compound. Our results indicate that dehydrozaluzanin C exerts its effects on plants through two different mechanisms, only one of which is related to the disruption of plasma membrane function.
Volatile compounds were identified from unialgal continuous cultures of the cyanobacterium Oscillatoria perornata. Steam distillates of the unialgal cultures were continuously extracted with pentane, ...and the pentane extracts were analyzed by GC-MS. Retention indices and mass spectral data were used to identify 15 components. Relative amounts of individual components were expressed as percent peak area relative to total peak area. The main volatile components were heptadecane (57.0%), 2-methylisoborneol (29.4%), and benzaldehyde (1.2%). Together with the previously known 2-methylisoborneol, which is the major cause of the musty off-flavor problem in catfish farming operations in Mississippi, other components identified were dimethyl disulfide (1.0%), dimethyl trisulfide (0.5%), and benzothiazole (0.6%). These compounds and their organoleptic characteristics are discussed in relation to their possible contributions to cultured catfish off-flavor problems. Keywords: Blue-green algae; cyanobacteria; Oscillatoria perornata; catfish; Ictalurus punctatus; polysulfides; 2-methylisoborneol
The essential oil from the leaves of
Callicarpa japonica was analyzed by GC–MS, and 84 compounds were identified. The main constituents of the essential oil were spathulenol (18.1%), germacrene B ...(13.0%), bicyclogermacrene (11.0%), globulol (3.3%), viridiflorol (2.6%), α-guaiene (2.3%), and γ-elemene (2.0%). The essential oil constituents of
C. japonica were significantly different from those found in our previous work on
Callicarpa americana. The oil of
C. japonica was selectively phytotoxic to bentgrass compared to lettuce seeds, with 80–100% growth reduction observed at 0.3 mg/ml.
The main constituents of the essential oil of
Callicarpa japonica were spathulenol (18.1%), germacrene B (13.0%), and bicyclogermacrene (11.0%).
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