998 resultados para Whitehall II


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The effect of aqueous pyridine on a hapten—antihapten system was investigated by the quantitative precipitin reaction and by the membrane filtration method. It was found that dilute solutions of pyridine inhibited the reaction between isopentenyladenosine and its antiserum. Other solvents examined were less effective. The effect of pyridine was reversible at concentrations where complete inhibition occurred, thus indicating its use for the dissociation of antigen—antibody complexes. The inhibitory effect of pyridine was exploited in a single-step purification method for anti—isopentenyladenosine and antideoxy-adenylate antibodies. In addition, generally applicable methods for linking nucleosides and nucleotides to aminoethyl-Sepharose are described.

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In an earlier paper (Part I) we described the construction of Hermite code for multiple grey-level pictures using the concepts of vector spaces over Galois Fields. In this paper a new algebra is worked out for Hermite codes to devise algorithms for various transformations such as translation, reflection, rotation, expansion and replication of the original picture. Also other operations such as concatenation, complementation, superposition, Jordan-sum and selective segmentation are considered. It is shown that the Hermite code of a picture is very powerful and serves as a mathematical signature of the picture. The Hermite code will have extensive applications in picture processing, pattern recognition and artificial intelligence.

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The nitrosation of monophenylamido substututed quadridentate Schiff base complexes of copper(II) are observed to adopt N-bonded isonitroso coordination whereas the phenylisocyanation of the corresponding mononitrosated quadridentate complexes are found to prefer O-bonded isonitroso coordination.

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Sustainable management of native pastures requires an understanding of what the bounds of pasture composition, cover and soil surface condition are for healthy pastoral landscapes to persist. A survey of 107 Aristida/Bothriochloa pasture sites in inland central Queensland was conducted. The sites were chosen for their current diversity of tree cover, apparent pasture condition and soil type to assist in setting more objective bounds on condition ‘states’ in such pastures. Assessors’ estimates of pasture condition were strongly correlated with herbage mass (r = 0.57) and projected ground cover (r = 0. 58), and moderately correlated with pasture crown cover (r = 0.35) and tree basal area (r = 0.32). Pasture condition was not correlated with pasture plant density or the frequency of simple guilds of pasture species. The soil type of Aristida/Bothriochloa pasture communities was generally hard-setting, low in cryptogam cover but moderately covered with litter and projected ground cover (30–50%). There was no correlation between projected ground cover of pasture and estimated ground-level cover of plant crowns. Tree basal area was correlated with broad categories of soil type, probably because greater tree clearing has occurred on the more fertile, heavy-textured clay soils. Of the main perennial grasses, some showed strong soil preferences, for example Tripogon loliiformis for hard-setting soils and Dichanthium sericeum for clays. Common species, such as Chrysopogon fallax and Heteropogon contortus, had no strong soil preference. Wiregrasses (Aristida spp.) tended to be uncommon at both ends of the estimated pasture condition scale whereas H. contortus was far more common in pastures in good condition. Sedges (Cyperaceae) were common on all soil types and for all pasture condition ratings. Plants identified as increaser species were Tragus australianus, daisies (Asteraceae) and potentially toxic herbaceous legumes such as Indigofera spp. and Crotalaria spp. Pasture condition could not be reliably predicted based on the abundance of a single species or taxon but there may be scope for using integrated data for four to five ecologically contrasting plants such as Themeda triandra with daisies, T. loliiformis and flannel weeds (Malvaceae).

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In semi-arid sub-tropical areas, a number of studies concerning no-till (NT) farming systems have demonstrated advantages in economic, environmental and soil quality aspects over conventional tillage (CT). However, adoption of continuous NT has contributed to the build-up of herbicide resistant weed populations, increased incidence of soil- and stubble-borne diseases, and stratification of nutrients and organic carbon near the soil surface. Some farmers often resort to an occasional strategic tillage (ST) to manage these problems of NT systems. However, farmers who practice strict NT systems are concerned that even one-time tillage may undo positive soil condition benefits of NT farming systems. We reviewed the pros and cons of the use of occasional ST in NT farming systems. Impacts of occasional ST on agronomy, soil and environment are site-specific and depend on many interacting soil, climatic and management conditions. Most studies conducted in North America and Europe suggest that introducing occasional ST in continuous NT farming systems could improve productivity and profitability in the short term; however in the long-term, the impact is negligible or may be negative. The short term impacts immediately following occasional ST on soil and environment include reduced protective cover, soil loss by erosion, increased runoff, loss of C and water, and reduced microbial activity with little or no detrimental impact in the long-term. A potential negative effect immediately following ST would be reduced plant available water which may result in unreliability of crop sowing in variable seasons. The occurrence of rainfall between the ST and sowing or immediately after the sowing is necessary to replenish soil water lost from the seed zone. Timing of ST is likely to be critical and must be balanced with optimising soil water prior to seeding. The impact of occasional ST varies with the tillage implement used; for example, inversion tillage using mouldboard tillage results in greater impacts as compared to chisel or disc. Opportunities for future research on occasional ST with the most commonly used implements such as tine and/or disc in Australia’s northern grains-growing region are presented in the context of agronomy, soil and the environment.

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Metal complexes of thiazoles have been studied in recent years[I-3] because of their biochemical importance[4,5]. However, data on metal complexes of thiazole derivatives containing another coordinating function are limited[2]. We have synthesized and examined the donor characteristics of a new ligand, 2-thioacetamide thiazole (TATZ)(I) towards chlorides and bromides of Zn(II), Cd(II), Hg(II) and Cu(I). The presence of four potential donor atoms and extensive charge delocalization should render TATZ a versatile ligand.

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The effect of age of the larvae on the manifestation of the "Sappe" disease of the silkworm by oral inoculation of different pathogens, viz., Aerobacter cloacae, Pseudomonas boreopolis, Escherichia freundii, Achromobacter delmarvae, A. Superficialis, Pseudomonas ovalis, and Staphylococcus albus was tested. It was found that the reaction of the larva to the pathogen was influenced by its age. Some, e.g., Escherichia freundii, were more lethal when introduced at early stages whereas certain others, e.g., Aerobacter cloacae and Staphylococcus albus, caused maximum damage when invading older larvae. Irrespective of the age of infection, death of the worms mainly occurred during molting and before spinning. The studies also indicated that growth and mortality of the larvae were affected differentially by the pathogens.

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(I): M r = 258.34, triclinic, Pi, a = 9.810 (3), b=9.635(3), e=15.015(4)A, a=79.11(2), #= 102.38 (3), y = 107.76 (3) o, V= 1308.5 A 3, Z = 4, Din= 1.318 (3) (by flotation in KI solution), D x = 1.311 g cm -3, Cu Ka, 2 = 1.5418/~, g = 20-05 cm -1, F(000) = 544, T---- 293 K, R = 0.074 for 2663 reflections. (II): M r = 284.43, monoclinic, P2~/c, a= 17.029 (5), b=6.706 (5), c= 14.629 (4), t= 113.55 (2) ° , V=1531.4A 3, Z=4, Dm=1.230(5) (by flotation in KI solution), Dx= 1.234gem -3, Mo Ka, 2 = 0.7107 A, g = 1.63 cm-1; F(000) = 608, T= 293 K, R = 0.062 for 855 reflections. The orientation of the C=S chromophores in the crystal lattice and their reactivity in the crystalline state are discussed. The C--S bonds are much shorter than the normal bond length [1.605 (4) (I), 1.665 (8) A (II) cf. 1.71 A].

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(I): Mr=274"39, orthorhombic, Pbca, a = 7.443 (1), b= 32.691 (3), c= 11.828 (2)A, V= 2877.98A 3, Z=8, Din= 1.216 (flotation in KI), D x = 1.266 g cm -3, /~(Cu Ka, 2 = 1.5418 A) = 17.55 cm -1, F(000) = li52.0, T= 293 K, R = 6.8%, 1378 significant reflections. (II): M r = 248.35, orthorhombic, P212~21, a = 5.873 (3), b = 13.677 (3), c = 15-668 (5) A, V = 1260.14 A 3, Z = 4, D,n = 1.297 (flotation in KI), Dx= 1.308 g cm -a, /t(CuKa, 2=1.5418 A) = 19.55 cm -~, F(000) = 520.0, T= 293 K, R = 6.9%, 751 significant reflections. Crystals of (I) and (II) undergo photo-oxidation in the crystallinestate. In (I) the dihedral angle between the phenyl rings of the biphenyl moiety is 46 (1) °. The C=S bond length is 1.611(5) A in (I) and 1.630 (9)/~ in (II). The correlation between molecular packing and reactivity is discussed.

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Syntheses and structural characterization of Ni(II) chelates of a new series of symmetric and unsymmetric tetradentate linear ligands are described. Preparative routes involve either the direct reaction between a metal complex and arene diazonium diazonium salts or a simple metal incorporation into the independently synthesized ligands. Recent X-ray structure determination of 4,9-dimethyl-5,8-diazadodeca-4,8-diene-2,11-dione-3,10-di(4′-methyl phenyl) hydrazonatonickel(II) complex reveals the geometry around the Ni(II) to be very close to square planar. The expected distortion because of the disposition of bulky aromatic groups on the neighbouring nitrogens is minimized by their projection in the opposite directions from the plane. PMP, IR and electronic spectral data for the complexes are quite in agreement with this structure.

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Three-component metal-inorganic assembly of a Co(II) network representing the first example of a 3D coordination polymer containing a hydrazine bridging ligand, has been synthesized and characterized.

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Eight Cylindropuntia species have naturalised in Australia and pose serious economic, environmental and social impacts. Two biotypes of Dactylopius tomentosus have been used as bio-control agents to control different Cylindropuntia species. The host range of four additional biotypes of Dactylopius tomentosus from southern USA was investigated. Feeding and development were restricted to the genus Cylindropuntia. However, they showed differences in specificity within this genus and some biotypes discriminated between the provenances of C. rosea and C. tunicata. Efficacy trials were conducted to determine whether populations of each biotype could be sustained on the naturalised Cylindropuntia species and if these populations could retard the growth or kill these plants. The acanthocarpa biotype offers potential control of C. rosea (Lorne Station), while the cylindropuntia sp. biotype shows great potential to control C. rosea (Grawin). The cylindropuntia sp. biotype also had a high impact on C. kleiniae and C. imbricata, and a moderate impact on C. leptocaulis and C. prolifera. The acanthocarpa X echinocarpa biotype had its greatest impact on C. tunicata (Grawin), killing this plant in 18 weeks. A fourth biotype, leptocaulis, was damaging to some species, but was less effective than the other biotypes. Cylindropuntia spinosior is the only naturalised species in Australia where no effective biocontrol agent has been found.

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