Effect of sodicity and salinity on disaggregation and tensile strength of an Alfisol under different cropping systems     

A. Rahman Barzegar  J. Malcolm Oades  Pichu Rengasamy  Lynne Giles 《Soil & Tillage Research》1994,32(4):329-345

The influence of electrolyte concentration (EC) and sodium adsorption ratio (SAR) on the tensile strength and aggregate stability via flocculation and dispersion behaviour of an Alfisol varying in organic carbon content due to different cropping systems was assessed using a split-split plot experiment involving eight soils, three levels of EC and seven levels of SAR.

Generally, at a given SAR value, mean weight diameter (MWD) increased with organic matter status of the soil in the following order: virgin pasture>wheat>wheat-fallow. As MWD decreased, the amount of dispersible clay increased at a given SAR indicating that more surfaces exposed due to slaking of aggregates led to more clay dispersion. Statistical analysis of changes in tensile strength with various factors showed that an increase in organic matter decreased the magnitude of changes in strength induced by sodicity because organic matter tends to increase aggregate stability (higher MWD). While individual soils had significant relationships between the tensile strength of the aggregates and the amount of spontaneously dispersible clay, this relationship was poor when the results of all soils were pooled together. The amounts of dispersible clay from dry aggregates were higher than from wet aggregates and dispersive breakdown of the aggregates of sodic soils occured irrespective of the mode of wetting. The most important factor in determining the soil strength was the amount of clay dispersed during wet-sieving analysis followed by MWD.  相似文献   

Effectiveness of five small Philippines’ coral reef reserves for fish populations depends on site-specific factors, particularly enforcement history     

Melita A. Samoilys  Keith M. Martin-Smith  Brian G. Giles  Erwin O. Brunio 《Biological conservation》2007,136(4):584-601

Community-managed, no-take marine reserves are increasingly promoted as a simple, precautionary measure to conserve biodiversity and sustain coral reef fisheries. However, we need to demonstrate the effects of such reserves to those affected by the loss of potential fishing grounds and the wider scientific community. We surveyed changes in fish communities in five small marine reserves in the central Philippines and three distant Control sites over seven years. We conducted underwater visual censuses of 53 fish families within the reserve (Inside), with a kilometre of the boundary (Outside) and at Control sites. We found significant differences between fish communities Inside and Outside the reserve only at the two sites with strictest compliance with fishing prohibition, while there were significant differences to distant Control sites in all cases. The strongest responses to reserve protection were found in predatory fishes (groupers and breams) and in butterflyfish. Other abundant fish families showed weak effects of protection. For all taxa analysed, we found significant effects of reserve Site and Site × Treatment interactions. The detection of fish responses to reserves is complicated by potential spillover effects, site-specific factors, particularly compliance, and the difficulty of identifying appropriate control areas.  相似文献   

Concurrent protozoal encephalitis and canine distemper virus infection in a raccoon (Procyon lotor).     

J D Thulin  D E Granstrom  H B Gelberg  D G Morton  R A French  R C Giles 《The Veterinary record》1992,130(8):162-164

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Immunohistochemical diagnosis of protozoan parasites in lesions of equine protozoal myeloencephalitis     

D E Granstrom  R C Giles  P A Tuttle  N M Williams  K B Poonacha  M B Petrites-Murphy  R R Tramontin  T W Swerczek  C B Hong  G B Rezabek 《Journal of veterinary diagnostic investigation》1991,3(1):75-77

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Complete heart block associated with vegetative endocarditis in a dog   总被引：1，自引：0，他引：1  

B T Robertson  H D Giles 《Journal of the American Veterinary Medical Association》1972,161(2):180-184

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Myeloproliferative disorder in a cat     

R C Giles  W C Buhles  C A Montgomery 《Journal of the American Veterinary Medical Association》1974,165(5):456-457

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Cryptosporidium parvum infection in orphan lambs on a farm open to the public     

Pritchard GC  Marshall JA  Giles M  Chalmers RM  Marshall RN 《The Veterinary record》2007,161(1):11-14

A longitudinal survey was undertaken on an open farm to investigate the occurrence of Cryptosporidium species infection in orphan lambs obtained from three local flocks. During an initial pilot study, Cryptosporidium oocysts were detected by a fluorescent antibody test (fat) in the faeces of two of 21 lambs aged between one and three weeks derived from one flock (flock A). Pooled pen samples of faeces were collected weekly from lambs derived from each flock; oocysts were detected by fat in 24 (49.0 per cent) of 49 samples from lambs from flock A, 18 (30.5 per cent) of 59 samples from lambs from flock B and 14 (29.8 per cent) of 47 samples from lambs from flock C. Oocyst counts of 1 x 10(3) to more than 2 x 10(6) per gram of faeces were detected in lambs up to 12 weeks old, with the peak counts occurring at six weeks of age in the lambs from flocks A and B and at four weeks of age in those from flock C. The oocysts were confirmed by molecular analysis as Cryptosporidium parvum. Virtually all the infections were subclinical.  相似文献   

Assessing the convergence of Markov Chain Monte Carlo methods: an example from evaluation of diagnostic tests in absence of a gold standard     

Toft N  Innocent GT  Gettinby G  Reid SW 《Preventive veterinary medicine》2007,79(2-4):244-256

The accessibility of Markov Chain Monte Carlo (MCMC) methods for statistical inference have improved with the advent of general purpose software. This enables researchers with limited statistical skills to perform Bayesian analysis. Using MCMC sampling to do statistical inference requires convergence of the MCMC chain to its stationary distribution. There is no certain way to prove convergence; it is only possible to ascertain when convergence definitely has not been achieved. These methods are rather subjective and not implemented as automatic safeguards in general MCMC software. This paper considers a pragmatic approach towards assessing the convergence of MCMC methods illustrated by a Bayesian analysis of the Hui–Walter model for evaluating diagnostic tests in the absence of a gold standard. The Hui–Walter model has two optimal solutions, a property which causes problems with convergence when the solutions are sufficiently close in the parameter space. Using simulated data we demonstrate tools to assess the convergence and mixing of MCMC chains using examples with and without convergence. Suggestions to remedy the situation when the MCMC sampler fails to converge are given. The epidemiological implications of the two solutions of the Hui–Walter model are discussed.  相似文献   

Calcium chelate is as effective as phosphite in controlling Phytophthora root rot in glasshouse trials     

Mohammed Y. Khdiar  Treena I. Burgess  Paul A. Barber  Giles E. St.J. Hardy 《Plant pathology》2023,72(1):112-119

Species in the genus Phytophthora cause significant economic losses in crops and damage to forests and natural ecosystems worldwide. Currently, phosphite is the most effective chemical for disease management, but excessive phosphite concentrations can result in phytotoxicity in plants and the development of tolerance by the pathogen. Two newly developed metal chelates and phosphite (alone and in combination) were tested for their in vitro and in planta efficacy against Phytophthora cinnamomi. In glasshouse trials, 0.25% and 0.5% of each chemical treatment (phosphite, Ca chelate, Zn chelate) and Ca chelate + phosphite were used as a foliar application on 3-month-old seedlings of Banksia grandis (experiment not repeated) and Eucalyptus marginata, prior to inoculation with P. cinnamomi. All noninoculated control plants remained healthy, while significant root damage and reduction of dry root weights were observed for inoculated untreated plants. Individually, phosphite and Ca chelate significantly reduced root lesion development of P. cinnamomi compared to the control, with Ca chelate attaining superior results to phosphite at the same concentration. In combination, Ca chelate + phosphite had the largest reduction in root lesion development in both plant species; however, this result has not yet been replicated but did reflect previous in vitro results. The Zn chelate applications were not effective. Ca chelate has the potential to be developed as a fungicide to control Phytophthora species.  相似文献   

Exophiala angulospora Causes Systemic Mycosis in Atlantic Halibut: a Case Report     

David P. Overy  Jan Giles  Stephanie Duffy  Mellisa Rommens  Gerald Johnson 《Journal of aquatic animal health》2015,27(1):12-19

Filamentous black yeasts from the genus Exophiala are ubiquitous, opportunistic pathogens causing both superficial and systemic mycoses in warm- and cold-blooded animals. Infections by black yeasts have been reported relatively frequently in a variety of captive and farmed freshwater and marine fishes. In November 2012, moribund and recently dead, farm-raised Atlantic Halibut Hippoglossus hippoglossus were necropsied to determine the cause of death. Histopathology revealed that three of seven fish were affected by a combination of an ascending trans-ductual granulomatous mycotic nephritis, necrotizing histiocytic encephalitis, and in one fish the addition of a fibrogranulomatous submucosal branchitis. Microbial cultures of kidney using selective mycotic media revealed pure growth of a black-pigmenting septated agent. Application of molecular and phenotypic taxonomy methodologies determined that all three isolates were genetically consistent with Exophiala angulospora. This is the first report of E. angulospora as the causal agent of systemic mycosis in Atlantic Halibut.

Received January 27, 2014; accepted July 23, 2014  相似文献