840 resultados para Ordination


Relevância:

20.00% 20.00%

Publicador:

Resumo:

Background and Aims: Success of invasive plant species is thought to be linked with their higher leaf carbon fixation strategy, enabling them to capture and utilize resources better than native species, and thus pre-empt and maintain space. However, these traits are not well-defined for invasive woody vines. Methods: In a glass house setting, experiments were conducted to examine how leaf carbon gain strategies differ between non-indigenous invasive and native woody vines of south-eastern Australia, by investigating their biomass gain, leaf structural, nutrient and physiological traits under changing light and moisture regimes. Key Results: Leaf construction cost (CC), calorific value and carbon : nitrogen (C : N) ratio were lower in the invasive group, while ash content, N, maximum photosynthesis, light-use efficiency, photosynthetic energyuse efficiency (PEUE) and specific leaf area (SLA) were higher in this group relative to the native group. Trait plasticity, relative growth rate (RGR), photosynthetic nitrogen-use efficiency and water-use efficiency did not differ significantly between the groups. However, across light resource, regression analyses indicated that at a common (same) leaf CC and PEUE, a higher biomass RGR resulted for the invasive group; also at a common SLA, a lower CC but higher N resulted for the invasive group. Overall, trait co-ordination (using pair-wise correlation analyses) was better in the invasive group. Ordination using 16 leaf traits indicated that the major axis of invasive-native dichotomy is primarily driven by SLA and CC (including its components and/or derivative of PEUE) and was significantly linked with RGR. Conclusions: These results demonstrated that while not all measures of leaf resource traits may differ between the two groups, the higher level of trait correlation and higher revenue returned (RGR) per unit of major resource need (CC) and use (PEUE) in the invasive group is in line with their rapid spread where introduced.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

In this paper, a new approach to enhance the transmission system distance relay co-ordination is presented. The approach depends on the apparent impedance loci seen by the distance relay during all possible disturbances. In a distance relay, the impedance loci seen at the relay location is obtained by extensive transient stability studies. Support vector machines (SVMs), a class of patterns classifiers are used in discriminating zone settings (zone-1, zone-2 and zone-3) using the signals to be used by the relay. Studies on a sample 9-bus are presented for illustrating the proposed scheme.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Children with developmental co-ordination disorder (DCD) face evident motor difficulties in activities of daily living (ADL). Assessment of their capacity in ADL is essential for diagnosis and intervention, in order to limit the daily consequences of the disorder. The aim of this study is to systematically review potential instruments for standardized and objective assessment of children's capacity in ADL, suited for children with DCD. As a first step, databases of MEDLINE, EMBASE, CINAHL and PsycINFO were searched to identify studies that described instruments with potential for assessment of capacity in ADL. Second, instruments were included for review when two independent reviewers agreed that the instruments: (1) are standardized and objective; (2) assess at activity level and comprise items that reflect ADL, and; (3) are applicable to school-aged children that can move independently. Out of 1507 publications, 66 publications were selected, describing 39 instruments. Seven of these instruments were found to fulfil the criteria and were included for review: the Bruininks-Oseretsky Test of Motor Performance-2 (BOT2); the Do-Eat (Do-Eat); the Movement Assessment Battery for Children-2 (MABC2); the school-Assessment of Motor and Process Skills (schoolAMPS); the Tuffts Assessment of Motor Performance (TAMP); the Test of Gross Motor Development (TGMD); and the Functional Independence Measure for Children (WeeFIM). As a third step, for the included instruments, suitability for children with DCD was discussed based on the ADL comprised, ecological validity and other psychometric properties. We concluded that current instruments do not provide comprehensive and ecologically valid assessment of capacity in ADL as required for children with DCD.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

A systematic study has been made of the crystal co-ordination of the barium ion in various compounds whose structures have been solved. Apart from the more common co-ordination polyhedra which are enumerated in text-books, a number of new polyhedra have been identified, particularly in cases where the co-ordination numbers are unusual, such as ten or eleven. According to the radius-ratio rule of Pauling, a co-ordination number of nine or ten is normally expected for the barium ion. The present investigations, however, reveal that it shows a variety of co-ordinations with ligancies from six up to twelve. Some of the factors that might possibly enter in explaining this wide range of co-ordination numbers are discussed. It appears as though the part played by the Ba2+ ion in deciding the structure is secondary, limiting itself only to occupying vacant spaces provided by other atoms in the crystal.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The reaction of imidazole (Him) with [Cu2(µ-O2CMe)4(H2O)2] in water–NaClO4 led to the formation of a polynuclear copper(II) complex, [Cu5(OH)2(H2O)(O2CMe)6(Him)4][ClO4]21, in which the pentanuclear units, showing four, five and six co-ordination geometries for the copper(II) centres and Cu Cu distances of 3.043(1), 3.178(1) and 3.578(1)Å, were linked by aqua bridges to give an intra-chain inter-unit Cu Cu separation of 4.507(1)Å.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

A tripod ligand possessing two pyridine moieties and a phenolato group as pendants forms a mononuclear complex with an axial copper(II)–phenolate co-ordination in a square-pyramidal environment.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

A novel ‘picket-fence’ porphyrin, 5,10,15,20-tetrakis[o-(tetrahydro-2-thenoylamino)phenyl]porphyrin (H2L) with ligating tetrahydrothiophene rings disposed perpendicular to the porphyrin plane has been synthesised. Its zinc(II) derivative, [ZnL], binds two silver(I) ions co-operatively with a dissociation constant of 4.8 × 10–8 dm3 mol–1. Time-resolved fluorescence lifetime measurements reveal the presence of intramolecular photoexcited electron transfer in this donor–acceptor system.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

In this paper, an approach to enhance the Extra High Voltage (EHV) Transmission system distance protection is presented. The scheme depends on the apparent impedance seen by the distance relay during the disturbance. In a distance relay,the impedance seen at the relay location is calculated from the fundamental frequency component of the voltage and current signals. Support Vector Machines (SVMs) are a new learning-byexample are employed in discriminating zone settings (Zone-1,Zone-2 and Zone-3) using the signals to be used by the relay.Studies on 265-bus system, an equivalent of practical Indian Western grid are presented for illustrating the proposed scheme.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

In this paper, knowledge-based approach using Support Vector Machines (SVMs) are used for estimating the coordinated zonal settings of a distance relay. The approach depends on the detailed simulation studies of apparent impedance loci as seen by distance relay during disturbance, considering various operating conditions including fault resistance. In a distance relay, the impedance loci given at the relay location is obtained from extensive transient stability studies. SVMs are used as a pattern classifier for obtaining distance relay co-ordination. The scheme utilizes the apparent impedance values observed during a fault as inputs. An improved performance with the use of SVMs, keeping the reach when faced with different fault conditions as well as system power flow changes, are illustrated with an equivalent 265 bus system of a practical Indian Western Grid.