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11.
Simulating the influence of intensive management and annual weather fluctuations on tree growth requires a shorter time step than currently employed by most regional growth models. High-quality data sets are available for several plantation species in the Pacific Northwest region of the United States, but the growth periods ranged from 2 to 12 years in length. Measurement periods of varying length complicate efforts to fit growth models because observed growth rates must be interpolated to a common length growth period or those growth periods longer or shorter than the desired model time step must be discarded. A variation of the iterative technique suggested by Cao [Cao, Q.V., 2000. Prediction of annual diameter growth and survival for individual trees from periodic measurements. Forest Sci. 46, 127–131] was applied to estimate annualized diameter and height growth equations for pure plantations of Douglas-fir, western hemlock, and red alder. Using this technique, fits were significantly improved for all three species by embedding a multi-level nonlinear mixed-effects framework (likelihood ratio test: p < 0.0001). The final models were consistent with expected biological behavior of diameter and height growth over tree, stand, and site variables. The random effects showed some correlation with key physiographic variables such as slope and aspect for Douglas-fir and red alder, but these relationships were not observed for western hemlock. Further, the random effects were more correlated with physiographic variables than actual climate or soils information. Long-term simulations (12–16 years) on an independent dataset using these annualized equations showed that the multi-level mixed effects models were more accurate and precise than those fitted without random effects as mean square error (MSE) was reduced by 13 and 21% for diameter and height growth prediction, respectively. The level of prediction error was also smaller than an existing similar growth model with a longer time step (ORGANON v8) as the annualized equations reduced MSE by 17 and 38% for diameter and height growth prediction, respectively. These models will prove to be quite useful for understanding the interaction of weather and silviculture in the Pacific Northwest and refining the precision of future growth model projections.  相似文献   
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Clostridium (C.) difficile is a common cause of nosocomial diarrhea in horses. Vancomycin and metronidazole have been used as standard treatments but are only moderately effective, which highlights the need for a novel alternative therapy. In the current study, we prepared antiserum of equine origin against both C. difficile toxins A and B as well as whole-cell bacteria. The toxin-neutralizing activities of the antibodies were evaluated in vitro and the prophylactic effects of in vivo passive immunotherapy were demonstrated using a conventional mouse model. The data demonstrated that immunized horses generated antibodies against both toxins A and B that possessed toxin-neutralizing activity. Additionally, mice treated with the antiserum lost less weight without any sign of illness and regained weight back to a normal range more rapidly compared to the control group when challenged orally with 107 C. difficile spores 1 day after serum injection. These results indicate that intravenous delivery of hyperimmune serum can protect animals from C. difficile challenge in a dose-dependent manner. Hence, immunotherapy may be a promising prophylactic strategy for preventing C. difficile infection in horses.  相似文献   
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Conventional measurements of tree root biomass in tree-based intercropping (TBI) systems can be inadequate in capturing the heterogeneity of rooting patterns or can be highly destructive and non-repeatable. In this study, we estimated coarse root biomass using ground penetrating radar (GPR) of 25-year-old trees inclusive of five species (Populus deltoides × nigra clone DN-177, Juglans nigra L., Quercus rubra L., Picea abies L. Karst, and Thuja occidentalis L.) at a TBI site in Southern Ontario, Canada. Subsurface images generated by GPR were collected in grids (4.5 × 4.5 m) centred on tree stems. The predictive relationship developed between GPR signal response and root biomass was corrected for species effects prior to tree-scale estimates of belowground biomass. Accuracy of the tree-scale estimates was assessed by comparing coarse root biomass measured from complete excavations of the corresponding tree. The mean coarse root biomass estimated from GPR analysis was 54.1 ± 8.7 kg tree?1 (mean ± S.E.; n = 12), within 1 % of the mean coarse root biomass measured from excavation. Overall there was a root mean square error of 14.4 kg between measured and estimated biomass with no detectable bias despite variable conditions within the in-field and multi-species study. Root system C storage by species, calculated with species-specific root carbon concentrations, is estimated at 5.4 ± 0.7–34.8 ± 6.9 kg C tree?1 at this site. GPR is an effective tool for non-destructively predicting coarse root biomass in multi-species environments such as temperate TBI systems.  相似文献   
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CASE DESCRIPTION: A 9-year-old dog was evaluated for traumatic cervical myelopathy after a surgical attempt to realign and stabilize the C2 and C3 vertebrae. CLINICAL FINDINGS: The dog could not ventilate spontaneously and was tetraplegic; positive-pressure ventilation (PPV) was maintained. Myelography and computed tomography revealed spinal cord compression with subluxation of the C2 and C3 vertebrae and extrusion of the C2-3 intervertebral disk. TREATMENT AND OUTCOME: Surgically, the protruding disk material was removed and the vertebrae were realigned with screws and wire. For PPV, assist control ventilation in volume control mode and then in pressure control mode was used in the first 6 days; this was followed by synchronized intermittent mandatory ventilation until 33 days after the injury; then only continuous positive airway pressure was provided until the dog could breathe unassisted, 37 days after the injury. Physical therapy that included passive range of motion exercises, neuromuscular electrical stimulation, and functional weight-bearing positions was administered until the dog was discharged 46 days after injury; the dog was severely ataxic and tetraparetic but could walk. Therapy was continued at home, and 1 year later, the dog could run and had moderate ataxia and tetraparesis. CLINICAL RELEVANCE: Hypoventilation with tetraparesis in traumatic spinal cord injury can be successfully treated with PPV exceeding 30 days, surgery, and physical therapy.  相似文献   
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To develop a conceptual understanding of the interaction between tourists and bears, this study examined the responses of brown bears (Ursus arctos) to experimentally introduced tourism at Douglas River in south-central Alaska within the framework of current predator-prey theory. Factors eliciting displacement and the nutritional consequences of behavioral changes were measured. GPS collars were deployed to track temporal and spatial resource use and scan and focal observations were used to quantify foraging efficiency, vigilance behavior, and bear use of various food resources. Total food intake was quantified by combining data on food resource use based on GPS locations and foraging efficiency was measured using spotting scopes from long distances. Seasonal food availability and quality were monitored and utilized as co-variates in comparisons between pre-treatment and treatment years. Though the bear population exhibited significant behavioral differences between the presence and absence of humans, changes in behavior generally mediated effects on total food intake. Adult males at a salt marsh viewing area were the only sex/age class exhibiting reduced food intake resulting from a 15% decline in foraging time when viewers were present. Salmon intake did not differ between pre-treatment and treatment years despite a 10% decline in time spent fishing when viewers were present. The tightly controlled experimental bear-viewing introduced in this study allowed bears to evaluate predation risk associated with human activity and optimally respond to minimize costs due to changes in foraging activities.  相似文献   
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We demonstrate the assembly of biohybrid materials from engineered tissues and synthetic polymer thin films. The constructs were built by culturing neonatal rat ventricular cardiomyocytes on polydimethylsiloxane thin films micropatterned with extracellular matrix proteins to promote spatially ordered, two-dimensional myogenesis. The constructs, termed muscular thin films, adopted functional, three-dimensional conformations when released from a thermally sensitive polymer substrate and were designed to perform biomimetic tasks by varying tissue architecture, thin-film shape, and electrical-pacing protocol. These centimeter-scale constructs perform functions as diverse as gripping, pumping, walking, and swimming with fine spatial and temporal control and generating specific forces as high as 4 millinewtons per square millimeter.  相似文献   
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Domesticated nature: shaping landscapes and ecosystems for human welfare   总被引:2,自引:0,他引:2  
Like all species, humans have exercised their impulse to perpetuate and propagate themselves. In doing so, we have domesticated landscapes and ecosystems in ways that enhance our food supplies, reduce exposure to predators and natural dangers, and promote commerce. On average, the net benefits to humankind of domesticated nature have been positive. We have, of course, made mistakes, causing unforeseen changes in ecosystem attributes, while leaving few, if any, truly wild places on Earth. Going into the future, scientists can help humanity to domesticate nature more wisely by quantifying the tradeoffs among ecosystem services, such as how increasing the provision of one service may decrease ecosystem resilience and the provision of other services.  相似文献   
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