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Khasa P.D. Sigler L. Chakravarty P. Dancik B.P. Erickson L. Mc Curdy D. 《New Forests》2001,22(3):179-197
The effect of three levels of fertilizer on thegrowth of three species of containerized-grownconifer seedlings (Pinus contorta, Picea glauca, and Picea mariana) and twospecies of bare-root conifer seedlings (Pinus sylvestris and Larix sibirica),and on the colonization of these seedlings bysix species of ectomycorrhizal fungi (Hebeloma longicaudum, Laccaria bicolor,Paxillus involutus, Pisolithustinctorius, Rhizopogon vinicolor andSuillus tomentosus), was studied. Thegrowth of the seedlings in both container-grownand bare-root nurseries increased as the levelsof fertilizer increased. For better seedlinggrowth and environmental quality it may be possible to reduce the level of fertilizers in commercial nurseries upto 33% by using selected mycorrhizal fungi.Ectomycorrhizal colonization in all seedlingswas not affected by fertilizer levels. Hebeloma longicaudum, L. bicolor, P.involutus, and P. tinctorius formedwell-developed ectomycorrhizae, whereasectomycorrhizal development by R.vinicolor and S. tomentosus was poor.Native mycorrhizal fungi colonizednon-inoculated control seedlings; however,their colonization was always lower than withinoculated fungi. 相似文献
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A series of miscible-displacement experiments was conducted to examine the impact of experiment conditions (detection limit, input pulse size, input concentration, pore-water velocity, contact time) on the performance of a mathematical solute transport model incorporating nonlinear, rate-limited sorption/desorption described by a continuous distribution reaction function. Effluent solute concentrations were monitored over a range of approximately seven orders of magnitude, allowing characterization of asymptotic tailing phenomenon. The model successfully simulated the extensive elution tailing observed for the measured data. Values for the mean desorption rate coefficient (ln k 2) and the variance of ln k 2 were obtained through calibration of the model to measured data. Similar parameter values were obtained for experiments with different input pulse size, input concentration, pore-water velocity, and contact time. This suggests that the model provided a robust representation of sorption–desorption for this system tested. The impact of analytical detection limit was examined by calibrating the model to subsets of the breakthrough curves wherein the extent of the elution tail was artificially reduced to mimic a poorer detection limit. The parameters varied as a function of the extent of elution tail used for the calibrations, indicating the importance of measuring as full an extent of the tail as possible. 相似文献
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Structures of free and inhibited human secretory phospholipase A2 from inflammatory exudate 总被引：5，自引：0，他引：5
D L Scott S P White J L Browning J J Rosa M H Gelb P B Sigler 《Science (New York, N.Y.)》1991,254(5034):1007-1010
Phospholipase A2 (PLA2) participates in a wide range of cellular processes including inflammation and transmembrane signaling. A human nonpancreatic secretory PLA2 (hnps-PLA2) has been identified that is found in high concentrations in the synovial fluid of patients with rheumatoid arthritis and in the plasma of patients with septic shock. This enzyme is secreted from certain cell types in response to the proinflammatory cytokines, tumor necrosis factor or interleukin-1. The crystal structures of the calcium-bound form of this enzyme have been determined at physiological pH both in the presence [2.1 angstrom (A) resolution] and absence (2.2 A resolution) of a transition-state analogue. Although the critical features that suggest the chemistry of catalysis are identical to those inferred from the crystal structures of other extracellular PLA2s, the shape of the hydrophobic channel of hnps-PLA2 is uniquely modulated by substrate binding. 相似文献
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Global economic activity is networked through cross‐national linkages between firm headquarters, branches, and subsidiaries. Brokerage emerges as a key territorial function of this network, with some places acting as gateways or intermediaries for flows of global knowledge, information, or trade. This function is particularly salient for small states and territories leveraging the benefits of borrowed size by offering global professional services, warehousing, logistics, shipping, and finance to wealthy nations or high net individuals. Nonetheless, to date our understanding of how small states and territories facilitate wealth accumulation is limited to broad concepts of their role as “gateways” or “brokers.” Drawing on a typology of brokerage and a network analysis applied to the ties between approximately 700,000 firm headquarter and subsidiary locations of 13 of the world's largest stock exchanges, we explore the brokerage role of small states and territories through case studies of Luxembourg, Singapore, Hong Kong, and Panama. Brokerage is found to play an important role in the economy of all four. We argue that each of these small states and territories is uniquely positioned as a broker in global corporate networks, but that this role differs according to geo‐economic and political positionality. 相似文献
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Johnson RS Sangster CR Sigler L Hambleton S Paré JA 《Australian veterinary journal》2011,89(12):515-519
Deep fungal dermatitis caused by the Chrysosporium anamorph of Nannizziopsis vriesii (CANV) was diagnosed in a group of coastal bearded dragons (Pogona barbata). The outbreak extended over a 6-month period, with four of six lizards from the same zoological outdoor enclosure succumbing to infection. A fifth case of dermatomycosis was identified in a pet lizard originally sourced from the wild. Diagnosis of infection with the CANV was based on similar clinical signs and histopathology in all animals and confirmed by culture and sequencing of the fungus from one animal. This is the first report of the CANV causing disease in a terrestrial reptile species in Australia and the first in the coastal bearded dragon. 相似文献
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Hall NH Conley K Berry C Farina L Sigler L Wellehan JF Roehrl MH Heard D 《Journal of zoo and wildlife medicine》2011,42(4):700-708
An 18-yr-old, male, albino, American alligator (Alligator mississippiensis) was evaluated for decreased appetite and abnormal buoyancy. Computed tomography (CT) of the coelomic cavity showed multifocal mineral and soft tissue attenuating pulmonary masses consistent with pulmonary fungal granulomas. Additionally, multifocal areas of generalized, severe emphysema and pulmonary and pleural thickening were identified. The alligator was euthanized and necropsy revealed severe fungal pneumonia associated with oxalosis. Metarhizium anisopliae var. anisopliae was cultured from lung tissue and exhibited oxalate crystal formation in vitro. Crystals were identified as calcium oxalate monohydrate by X-ray powder defractometry. Fungal identification was based on morphology, including tissue sporulation, and DNA sequence analysis. This organism is typically thought of as an entomopathogen. Clinical signs of fungal pneumonia in nonavian reptiles are often inapparent until the disease is at an advanced stage, making antemortem diagnosis challenging. This case demonstrates the value of CT for pulmonary assessment and diagnosis of fungal pneumonia in the American alligator. Fungal infection with associated oxalosis should not be presumed to be aspergillosis. 相似文献
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Crystal structure of cobra-venom phospholipase A2 in a complex with a transition-state analogue 总被引：6，自引：0，他引：6
S P White D L Scott Z Otwinowski M H Gelb P B Sigler 《Science (New York, N.Y.)》1990,250(4987):1560-1563
The crystal structure of a complex between a phosphonate transition-state analogue and the phospholipase A2 (PLA2) from Naja naja atra venom has been solved and refined to a resolution of 2.0 angstroms. The identical stereochemistry of the two complexes that comprise the crystal's asymmetric unit indicates both the manner in which the transition state is stabilized and how the hydrophobic fatty acyl chains of the substrate are accommodated by the enzyme during interfacial catalysis. The critical features that suggest the chemistry of binding and catalysis are the same as those seen in the crystal structure of a similar complex formed with the evolutionarily distant bee-venom PLA2. 相似文献
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Mads F Bertelsen Graham J Crawshaw Lynne Sigler Dale A Smith 《Journal of zoo and wildlife medicine》2005,36(1):82-87
The fungus Chrysosporium anamorph of Nannizziopsis vriesii was identified as the cause of fatal, multifocal, heterophilic dermatitis in four freshwater aquatic captive-bred tentacled snakes (Erpeton tentaculatum). Pale, 1- to 4-mm focal lesions involving individual scales, occurred primarily on the head and dorsum. Histology showed multifocal coagulation necrosis of the epidermis, with marked heterophilic infiltration without involvement of the underlying dermis. Septate, irregularly branched hyphae, and clusters of 4- to 8- by 2- to 3-microm rod-shaped cells (arthroconidia) were present within the lesions and in a superficial crust. Failure to maintain an acidic environment was likely a predisposing factor in the development of these lesions. 相似文献