Electrical conductivity in the precambrian lithosphere of western canada   总被引：1，自引：0，他引：1  

DE Boerner  RD Kurtz  JA Craven  GM Ross  FW Jones  WJ Davis 《Science (New York, N.Y.)》1999,283(5402):668-670

The subcrustal lithosphere underlying the southern Archean Churchill Province (ACP) in western Canada is at least one order of magnitude more electrically conductive than the lithosphere beneath adjacent Paleoproterozoic crust. The measured electrical properties of the lithosphere underlying most of the Paleoproterozoic crust can be explained by the conductivity of olivine. Mantle xenolith and geological mapping evidence indicate that the lithosphere beneath the southern ACP was substantially modified as a result of being trapped between two nearly synchronous Paleoproterozoic subduction zones. Tectonically induced metasomatism thus may have enhanced the subcrustal lithosphere conductivity of the southern ACP.  相似文献   

Vibration damping of flax fibre-reinforced polypropylene composites     

Md Zillur Rahman  Krishnan Jayaraman  Brian Richard Mace 《Fibers and Polymers》2017,18(11):2187-2195

This work investigates the effects of fibre content and fibre orientation on the damping of flax fibre-reinforced polypropylene composites. Laminates of various fibre contents were manufactured by a vacuum bagging process; their dynamic behaviour were then found from the vibration measurements of beam test specimens using an impulse hammer technique to frequencies of 1 kHz. The frequency response of a sample was measured and the response at resonance was used to estimate the natural frequency and loss factor. The single-degree-of-freedom circle-fit method and the Newton’s divided differences formula were used to estimate the natural frequencies as well as the loss factors. The damping estimates were also investigated using a “carpet” plot. Experiments were subsequently conducted on a range of samples with different fibre volume fractions and orientations. The results show significant variations in natural frequencies and loss factors according to the variations in fibre orientation. Composites containing 45°, 60° and 90° fibre orientation exhibit approximately the same natural frequencies. Composites with differing fibre orientations exhibit different loss factors for the various modes of vibration, and the maximum loss factor is obtained for the case of 45° fibre orientation, with the loss factor generally lying in the range of 2-7 %. It was found that the loss factor increases with increasing frequency and decreases slightly with increasing fibre content. These outcomes indicate that flax fibre-reinforced composite could be a commercially viable material for applications in which noise and vibration are significant issues and where a significant amount of damping is required.  相似文献   

Farm management factors associated with bulk tank somatic cell count in Irish dairy herds     

PT Kelly  K O'Sullivan  DP Berry  SJ More  WJ Meaney  EJ O'Callaghan  B O'Brien 《Irish veterinary journal》2009,62(Z4):S45

The relationship between bulk tank somatic cell count (SCC) and farm management and infrastructure was examined using data from 398 randomly selected, yet representative, Irish dairy farms where the basal diet is grazed grass. Median bulk tank SCC for the farms was 282,887 cells/ml ranging from 82,209 to 773,028 cells/ml. Two questionnaires were administered through face-to-face contact with each farmer. Herd-level factors associated with bulk tank SCC were determined using linear models with annual somatic cell score (i.e., arithmetic mean of the natural logarithm of bulk tank SCC) included as the dependent variable. All herd level factors were analysed individually in separate regression models, which included an adjustment for geographical location of the farm; a multiple regression model was subsequently developed. Management practices associated with low SCC included the use of dry cow therapy, participation in a milk recording scheme and the use of teat disinfection post-milking. There was an association between low SCC and an increased level of hygiene and frequency of cleaning of the holding yard, passageways and cubicles. Herd management factors associated with bulk tank SCC in Irish grazing herds are generally in agreement with most previous studies from confinement systems of milk production.  相似文献   

Colossal Magnetoresistance Without Mn3+/Mn4+ Double Exchange in the Stoichiometric Pyrochlore Tl2Mn2O7     

MA Subramanian  BH Toby  AP Ramirez  WJ Marshall  AW Sleight  GH Kwei 《Science (New York, N.Y.)》1996,273(5271):81-84

Structural analysis from powder neutron and single-crystal x-ray diffraction data for a sample of the Tl2Mn2O7 pyrochlore, which exhibits colossal magnetoresistance (CMR), shows no deviations from ideal stoichiometry. This analysis gives an Mn-O distance of 1.90 angstroms, which is significantly shorter than the Mn-O distances (1.94 to 2.00 angstroms) observed in phases based on LaMnO3 perovskites that exhibit CMR. Both results in Tl2Mn2O7 indicate oxidation states very close to Tl23+Mn24+O7. Thus, Tl2Mn2O7 has neither mixed valence for a double-exchange magnetic interaction nor a Jahn-Teller cation such as Mn3+, both of which were thought to have an important function in CMR materials. An alternate mechanism for CMR in Tl2Mn2O7 based on magnetic ordering driven by superexchange and strong spin-fluctuation scattering above the Curie temperature is proposed here.  相似文献   

Applications of pedigree-based genome mapping in wheat and barley breeding programs   总被引：1，自引：0，他引：1  

Mandy Christopher  Emma Mace  David Jordan  David Rodgers  Paul McGowan  Ian Delacy  Phillip Banks  John Sheppard  David Butler  David Poulsen 《Euphytica》2007,154(3):307-316

The aim of the pedigree-based genome mapping project is to investigate and develop systems for implementing marker assisted selection to improve the efficiency of selection and increase the rate of genetic gain in breeding programs. Pedigree-based whole genome marker application provides a vehicle for incorporating marker technologies into applied breeding programs by bridging the gap between marker–trait association and marker implementation. We report on the development of protocols for implementation of pedigree-based whole genome marker analysis in breeding programs within the Australian northern winter cereals region. Examples of applications from the Queensland DPI&F wheat and barley breeding programs are provided, commenting on the use of microsatellites and other types of molecular markers for routine genomic analysis, the integration of genotypic, phenotypic and pedigree information for targeted wheat and barley lines, the genomic impacts of strong selection pressure in case study pedigrees, and directions for future pedigree-based marker development and analysis.  相似文献   

BOOK REVIEW     

WJ Pryor 《Australian veterinary journal》1991,68(6):219-219

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Injectable abamectin causes a delay in scarabaeine dung beetle egg-laying in cattle dung     

B. HOULDING  TJ RIDSDILL-SMITH  WJ BAILEY 《Australian veterinary journal》1991,68(5):185-186

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A lupinosis-associated myopathy in sheep and the effectiveness of treatments to prevent it     

JG ALLEN  P. STEELE  HG MASTERS  WJ LAMBE 《Australian veterinary journal》1992,69(4):75-81

A lupinosis-associated myopathy occurred in 26 of 48 sheep given a crude toxic extract of Phomopsis leptostromiformis, and in 18 of 34 sheep that grazed a toxic lupin stubble. Treatment with selenium or alpha-tocopherol alone neither prevented nor cured the myopathy, but selenium and alpha-tocopherol together may have been partially effective. Among the group of 48 intoxicated sheep, those with myopathy had a significantly lower mean terminal concentration of alpha-tocopherol in their livers than those with no myopathy. There was no relationship between the severity of liver injury and the occurrence of the myopathy. It was considered that this lupinosis-associated myopathy may have a similar pathogenesis to nutritional myopathy. Data on plasma creatine phosphokinase and erythrocyte glutathione peroxidase activities, plasma alpha-tocopherol concentrations and terminal tissue concentrations of selenium and alpha-tocopherol are presented.  相似文献   

Inhibitors of juvenile hormone biosynthesis in corpora allata of the cockroach Periplaneta americana (L.) in vitro     

Gerald T. Brooks  Grahame E. Pratt  David W. Mace  John A. Cocks 《Pest management science》1985,16(2):132-142

The spontaneous biosynthesis of methyl (2E,6E)-(10R)-10,11-epoxy-3,7,11-trimethyldodeca-2,6-dienoate (juvenile hormone III; JH III) in excised corpora allata of Periplaneta americana was inhibited by a number of synthetic prop-2-ynyl ethers and 1,3-benzodioxole derivatives. One structurally diverse group of compounds inhibited only the final biosynthetic enzyme methyl farnesoate epoxidase (EC.1.14.14.–) at low to moderate concentrations, but at higher concentrations, also inhibited methyl farnesoate (MF) formation, causing an accumulation of MF in the concentration range 10 to 100 μM. For a second, more limited, group of compounds, there was close congruence between the inhibition of JH III biosynthesis and that of total ester (MF plus JH III) biosynthesis over their effective inhibitory concentration ranges. In contrast to the first group, there was no accumulation of MF and these compounds evidently inhibited JH III biosynthesis, at the level of either farnesoic acid esterification by O-methyl transferase (EC.2.1.1.–), or at an earlier step in the biosynthetic pathway that remains to be elucidated.  相似文献   

The effect of 2,2-dimethylchromene derivatives and some other compounds on the development of Oncopeltus fasciatus (dallas) and Locusta migratoria migratorioides (R&F)     

Gerald T. Brooks  Anthony P. Ottridge  Richard C. Jennings  David W. Mace  B. Alan Alexander 《Pest management science》1985,16(6):571-588

As an adjunct to biochemical studies on the action of juvenile hormone antagonists (‘antijuvenile hormones’), a study has been made of the effects on insect development of 71 compounds based on the 2,2-dimethylchromene structure, and 30 other compounds, including especially chemicals containing acetylenic and 1,3-benzodioxole (methylenedioxyphenyl) groups, that were expected to inhibit microsomal mixed function oxidases. The ageratochromenes, 7-methoxy-2,2-dimethylchromene and 6,7-dimethoxy-2,2-dimethylchromene (precocene I and precocene II, respectively), were used for comparison. With the jar deposit method used for Oncopeltus fasciatus, and the topical application method used for Locusta migratoria, only derivatives of 2,2-dimethylchromene and 2-(3-methylbut-2-enyl)phenol, the alkene double bonds of which were activated by an alkoxy group, exhibited characteristic antijuvenile hormone actions. In the whole life-cycle exposure test on O. fasciatus, a number of other compounds had non-specific effects on development, especially at the fifth instar. Some of the compounds, including certain derivatives of 2,2-dimethylchromene with ester side-chains, had juvenile hormone agonist actions. The scope for structural optimization for antijuvenile hormone action in the 2,2-dimethylchromene series appears to be limited, and structure-activity relationships are obscured, especially for O. fasciatus, by an overlap between the prothetelic morphogenetic and lethal effects. The results are discussed in relation to the mode of action of the 2,2-dimethychromenes.  相似文献