997 resultados para 502


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There are essentially two different phenomenological models available to describe the interdiffusion process in binary systems in the olid state. The first of these, which is used more frequently, is based on the theory of flux partitioning. The second model, developed much more recently, uses the theory of dissociation and reaction. Although the theory of flux partitioning has been widely used, we found that this theory does not account for the mobility of both species and therefore is not suitable for use in most interdiffusion systems. We have first modified this theory to take into account the mobility of both species and then further extended it to develop relations or the integrated diffusion coefficient and the ratio of diffusivities of the species. The versatility of these two different models is examined in the Co-Si system with respect to different end-member compositions. From our analysis, we found that the applicability of the theory of flux partitioning is rather limited but the theory of dissociation and reaction can be used in any binary system.

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The crystal structures of copper acetate adducts with 1,4-diaza bicyclo [2.2.2.]octane and N,N-dimethyl formamide are shown to be dimeric with Cu---Cu distances of 2.633 Å and 2.616 Å respectively.

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Aulacopris mallhewsi sp. nov. is described from mountains behind Cape Tribulation in northern Queensland. Its nearest relatives are in southeastern Queensland. The species is the smallest in the genus and is flightless. Individuals engaged in ball making and ball rolling activities in the laboratory.

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Leaf carbon (C) content, leaf nitrogen (N) content, and C:N ratio are especially useful for understanding plant-herbivore interactions and may be important in developing control methods for the invasive riparian plant Arundo donax L. We measured C content, N content, C:N ratio, and chlorophyll index (SPAD 502 reading) for 768 leaves from A. donax collected over a five year period at several locations in California, Nevada, and Texas. Leaf N was more variable than leaf C, and thus we developed a linear regression equation for estimating A. donax leaf N from the leaf chlorophyll index (SPAD reading). When applied to two independent data sets, the equation (leaf N content % = -0.63 + 0.08 x SPAD) produced realistic estimates that matched seasonal and spatial trends reported from a natural A. donax population. Used in conjunction with the handheld SPAD 502 meter, the equation provides a rapid, non-destructive method for estimating A. donax leaf quality.

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To examine healthy slaughter-age cattle and sheep on-farm for the excretion of Salmonella serovars in faeces and to identify possible risk factors using a questionnaire. The study involved 215 herds and flocks in the four eastern states of Australia, 56 with prior history of salmonellosis. Production systems examined included pasture beef cattle, feedlot beef cattle, dairy cattle, prime lambs and mutton sheep and animals were all at slaughter age. From each herd or flock, 25 animals were sampled and the samples pooled for Salmonella culture. All Salmonella isolated were serotyped and any Salmonella Typhimurium isolates were phage typed. Questionnaires on each production system, prepared in Epi Info 6.04, were designed to identify risk factors associated with Salmonella spp excretion, with separate questionnaires designed for each production system. Salmonellae were identified in all production systems and were more commonly isolated from dairies and beef feedlots than other systems. Statistical analysis revealed that dairy cattle were significantly more likely to shed Salmonella in faeces than pasture beef cattle, mutton sheep and prime lambs (P < 0.05). A wide diversity of Salmonella serovars, all of which have been isolated from humans in Australia, was identified in both cattle and sheep. Analysis of the questionnaires showed access to new arrivals was a significant risk factor for Salmonella excretion on dairy properties. For beef feedlots, the presence of large numbers of flies in the feedlot pens or around stored manure were significant risk factors for Salmonella excretion. Dairy cattle pose the highest risk of all the slaughter-age animals tested. Some of the identified risk factors can be overcome by improved management practices, especially in relation to hygiene.

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In tropical forests, natural disturbance creates opportunities for species to claim previously utilized space and resources and is considered an important mechanism in the maintenance of species diversity. However, ecologists have long recognized that disturbance also promotes exotic plant invasions. Cyclones cause extensive defoliation, loss of major branches and multiple tree falls, resulting in a significantly more open canopy and increased light and heat levels in the understorey. The widespread and massive disturbance caused by cyclones provides ideal conditions for rapid recruitment and spread of invasive species. The ecological roles of invasive species in rainforest habitats following such a severe disturbance are poorly understood. Severe category 4 Cyclone Larry crossed the North Queensland coast in March 2006 causing massive disturbance to rainforest habitats from Tully to Cairns and west to the Atherton Tablelands. We established 10 plots in an area extensively damaged by this cyclone near El Arish in North Queensland. On each plot nine 2 × 2 m quadrats were established with three quadrats per plot in each of the following treatments: (i) complete debris removal down to the soil layer, (ii) removal of coarse woody debris only, and (iii) uncleared. We monitored recruitment, growth and mortality of all native and invasive species in the 90 quadrats every 3 months since the cyclone. Here we present the recruitment dynamics of invasive species across the study area in relation to the level of disturbance, the type of quadrat treatment, and the diversity and abundance of the native recruiting flora over the first 12 months post-cyclone. Our results suggest that invasive species will mostly comprise a transient component of the flora in the early stages of the successional response. However, some species may have longer-term effects on the successional trajectory of the rainforest and future forest composition and structure.

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The productivity of a fisheries resource can be quantified from estimates of recruitment, individual growth and natural and fisheries-related mortality, assuming the spatial extent of the resource has been quantified and there is minimal immigration or emigration. The sustainability of a fisheries resource is facilitated by management controls such as minimum and maximum size limits and total allowable catch. Minimum size limits are often set to allow individuals the opportunity to reproduce at least once before the chance of capture. Total allowable catches are a proportion of the population biomass, which is estimated based on known reproduction, recruitment, mortality and growth rates. In some fisheries, however, management actions are put in place without quantification of the resource through the stock assessment process. This occurs because species-specific information, for example individual growth, may not be available. In these circumstances, management actions need to be precautionary to protect against future resource collapse, but this often means that the resource is lightly exploited. Consequently, the productivity of the resource is not fully realised. Australia’s most valuable fisheries are invertebrate fisheries (Australian Department of Agriculture Fisheries and Forestry, 2008). For example, Australian fisheries (i.e. excluding aquaculture) production of crustaceans (largely prawns, rock lobster and crab) was 41,000 tonnes in 2006/7, worth $778 million. Production from mollusc (largely abalone, scallops, oysters and squid) fisheries was 39,000 tonnes, worth $502 million. Together, in 2006/7 crustacean and mollusc fisheries represented 58% of the total value of Australian wild fisheries production. Sustainable management of Australia’s invertebrate fisheries is frustrated by the lack of data on species-specific growth rates. This project investigated a new method to estimate age, and hence individual growth rates, in invertebrate fisheries species. The principle behind the new aging method was that telomeres (i.e. DNA end-caps of chromosomes) get shorter as an individual gets older. We studied commercial crustacean and molluscan species. A vertebrate fish species (silver perch, Bidyanus bidyanus) was used as a control to standardise our work against the literature. We found a clear relationship between telomere length and shell size for temperate abalone (Haliotis rubra). Further research is recommended before the method can be implemented to assist management of wildharvested abalone populations. Age needs to be substituted for shell size in the relationship and it needs to be studied for abalone from several regions. This project showed that telomere length declined with increasing age in Sydney rock oysters (Saccostrea glomerata) and was affected by regional variation. A relationship was not apparent between telomere length and age (or size as a surrogate for age) for crustacean species (school prawns, Metapenaeus macleayi; eastern rock lobster, Sagmariasus verreauxi; southern rock lobster, Jasus edwardsii; and spanner crabs, Ranina ranina). For school prawns, there was no difference between telomere length in males and females. Further research is recommended, however, as telomeric DNA from crustaceans was difficult to analyse using the terminal restriction fragment (TRF) assay. Telomere lengths of spanner crabs and lobsters were at the upper limit of resolution of the assay used and results were affected by degradation and possible contamination of telomeric DNA. It is possible that telomere length is an indicator of remaining lifespan in molluscan and crustacean individuals, as suggested for some vertebrate species (e.g. Monaghan, 2010). Among abalone of similar shell size and among lobster pueruli, there was evidence of individuals having significantly longer or shorter telomeres than the group average. At a population level, this may be a surrogate for estimates of future natural mortality, which may have usefulness in the management of those populations. The method used to assay telomere length (terminal restriction fragment assay) performed adequately for most species, but it was too expensive and time-consuming to be considered a useful tool for gathering information for fisheries management. Research on alternative methods is strongly recommended.

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Ones and Dilchert (2012) highlight the importance of examining workplace environmental sustainability at the interindividual (or between-person) and organizational levels. In this commentary, we aim to extend these authors’ framework by focusing on pro-environmental behaviors and their potential predictors at the intraindividual, or within-person, level. To this end, we will first describe the intraindividual perspective, its benefits, and the diary study methodology often used to operationalize this perspective. Secondly, we will share how the intraindividual perspective was useful in an empirical study we conducted on multilevel relationships among employees’ pro-environmental attitude, daily affect, and daily proenvironmental behaviors. Finally, we will discuss a number of possible limitations of the diary study methodology, ways to Correspondence concerning this article should be addressed to Megan J. Bissing-Olson. E-mail: m.bissing-olson@uq.edu.au Address: School of Psychology, The University of Queensland, Brisbane, Queensland 4072, Australia overcome them, and directions for future research.

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Objective To compare reproduction in extensively managed, tropically adapted beef cows that were either seropositive or seronegative to Neospora caninum. Design Longitudinal study of cows within management groups. Methods Compare pregnancy with weaning outcomes for 502 seropositive and 3255 seronegative cows in 25 management groups. Results We found N. caninum in all herds, with an average of 20% of 2640 tested animals seropositive within management group; prevalence varied between 0% and 94%. At 7 of 10 sites assessed, there was evidence of horizontal transmission of N. caninum. There was no overall difference in pregnancy rate (79% vs 75%; P > 0.05), reproductive wastage after confirmed pregnancy diagnosis (11% vs 10%; P > 0.05) or weaning rate (67% vs 68%; P > 0.05) between seronegative and seropositive cows, respectively. In one herd where a combination of risk factors for N. caninum was present, a significant reduction in pregnancy rate occurred after the 6 months mating (85% vs 69%; P < 0.05). The fetal and calf losses observed were lowest in south-east Queensland (4.3% of 117 pregnancies), highest in north-west Queensland (15.5% of 413 pregnancies) and intermediate in north-east Queensland (10.2% of 1625 pregnancies). Other infectious agents that are known to cause reproductive wastage were endemic in many herds, though none appeared to cause significant fetal or calf loss in this study. Conclusion Despite a high prevalence of N. caninum, there was no apparent effect on beef cattle reproduction, but there is potential to cause reproductive wastage if known risk factors to neosporosis are in effect.

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Nitrogen (N) is an essential nutrient in mango, influencing both productivity and fruit quality. In Australia, tree N is traditionally assessed once a year in the dormant pre-flowering stage by laboratory analysis of leaf N. This single assessment is insufficient to determine tree N status at all stages of the annual phenological cycle. Development of a field-based rapid N test would allow more frequent monitoring of tree N status and improved fertiliser management. This experiment examined the accuracy and useability of several devices used in other horticultural crops to rapidly assess mango leaf N in the field; the Konica Minolta 'SPAD-502 chlorophyll meter', Horiba 'Cardy Meter' and the Merck 'RQflex 10'. Regression and correlation analyses were used to determine the relationship between total leaf N and the measurements from the rapid test devices. The relationship between the chlorophyll index measured by the SPAD-502 meter and leaf N is highly significant at late fruit set (R 2=0.72, n=40) and post-harvest (R2=0.81, n=40) stages in the mango cultivar 'Kensington Pride' and significant (R2=0.51, n=40) at the flowering stage, indicating the device can be used to rapidly assess mango leaf N in the field. Correlation analysis indicated the relationship between petiole sap measured with the Cardy or Merck devices and leaf N is non-significant. © 2013 ISHS.

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Nitrogen (N) is an essential nutrient in mango, influencing both productivity and fruit quality. In Australian mango orchards, tree N is traditionally assessed once a year at the dormant pre-flowering stage using laboratory analysis of leaf N. This single assessment is insufficient to determine tree N status at all stages of the annual phenological cycle. Development of a field-based rapid N test would allow more frequent monitoring of tree N status and improved fertiliser management. These experiments examined the accuracy and useability of several devices used in other horticultural crops to rapidly assess mango leaf N in the field; the Konica Minolta 'SPAD-502 chlorophyll meter', Horiba 'Cardy Meter' and the Merck 'RQflex 10.' Regression and correlation analyses were used to determine the relationship between total leaf N and the measurements from the rapid test devices. The relationship between the chlorophyll index measured by the SPAD-502 meter and leaf N was highly significant at late fruit set (R 2=0.72, n=40) and post-harvest (R 2=0.81, n=40) stages and significant at the flowering stage (R 2=0.51, n=40) in the cultivar 'Kensington Pride', indicating the device can be used to rapidly assess mango leaf N in the field. Correlation analysis indicated the relationship between petiole sap measured with the Cardy or Merck devices and leaf N was non-significant.

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A non-linear model, construed as a generalized version of the models put forth earlier for the study of bi-state social interaction processes, is proposed in this study. The feasibility of deriving the dynamics of such processes is demonstrated by establishing equivalence between the non-linear model and a higher order linear model.

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M r=670.02, monoclinic, C2/c, a= 31.003(4), b=11.037(2), c=21.183(3)A, fl= 143.7 (1) °, V= 4291.2/k 3, D,n = 2.06, D x = 2.07Mgm -3, Z=8, MoKa, 2=0.7107/k, /~=7.45 mm -1, F(000) = 2560, T= 293 K, R = 0.061 for 1697 observed reflections. The bromphenol blue molecule consists essentially of three planar groupings: the sulfonphthalein ring system and two dibromophenol rings attached to the tetrahedral C atom of the five-membered ring of the sulfonphthalein system. The dibromophenol rings are inclined with resPect to each other at 73 ° whereas they make angles of 85 and 68 ° with respect to the sulfonphthalein system. The molecules aggregate into helical columns with the non-polar regions of the molecules in the interior and the polar regions on the surface. The columns are held together by a network of hydrogen bonds.

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A new 8-node serendipity quadrilateral plate bending element (MQP8) based on the Mindlin-Reissner theory for the analysis of thin and moderately thick plate bending problems using Integrated Force Method is presented in this paper. The performance of this new element (MQP8) is studied for accuracy and convergence by analyzing many standard benchmark plate bending problems. This new element MQP8 performs excellent in both thin and moderately thick plate bending situations. And also this element is free from spurious/zero energy modes and free from shear locking problem.

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Detailed investigations into the dielectric dispersion phenomenon in the giant dielectric constant material CaCu3Ti4O12 (CCTO) around room temperature revealed the existence of two successive dielectric relaxations. In the temperature domain, a new dielectric relaxation was clearly observed around 250K, in addition to the well-investigated dielectric relaxation close to 100K. The effect of sintering and doping (La3+) on the strength of these dielectric relaxations were studied in detail. The sintering temperature as well as its duration was found to have tremendous influence on the dielectric relaxation that was encountered around 250 K. This Maxwell-Wagner (M-W) type of relaxation was found to be originating from the surface layer containing the Cu-rich phase, which was ascribed to the difference in the oxygen content between the surface and the interior of the sample. Interestingly, this particular additional relaxation was not observed in La2/3Cu3Ti4O12, a low dielectric constant member of the CCTO family, in which the segregation of Cu-rich phase on the surface was absent. Indeed the correlation between the new relaxation and the presence of Cu-rich phase in CCTO ceramics was further corroborated by the absence of the same after removing the top and bottom layers. (C) 2007 Elsevier Ltd. All rights reserved.