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991.
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993.
Spatial data are increasing in size and complexity due to technological advances. For an analysis of a large and diverse spatial domain, simplifying assumptions such as stationarity are questionable and standard computational algorithms are inadequate. In this paper, we propose a computationally efficient method to estimate a nonstationary covariance function. We partition the spatial domain into a fine grid of subregions and assign each subregion its own set of spatial covariance parameters. This introduces a large number of parameters and to stabilize the procedure we impose a penalty to spatially smooth the estimates. By penalizing the absolute difference between parameters for adjacent subregions, the solution can be identical for adjacent subregions and thus the method identifies stationary subdomains. To apply the method to large datasets, we use a block composite likelihood which is natural in this setting because it also operates on a partition of the spatial domain. The method is applied to tropospheric ozone in the US, and we find that the spatial covariance on the west coast differs from the rest of the country.  相似文献   
994.
Mexican dwarf mistletoe (Arceuthobium vaginatum subsp. vaginatum, Viscaceae) is the most widespread and damaging parasitic plant in Mexico. It parasitizes 10 species of pines (Pinus spp., Pinaceae) as principal hosts, including Pinus cooperi, one of the economically most important pines in the state of Durango. As a case study, we used stem analysis to estimate the effects of Mexican dwarf mistletoe on volume and height growth of dwarf mistletoe‐infected Pcooperi in western Durango (Ejido El Brillante, Municipality Pueblo Nuevo). This case study sampled a total of 48 trees, 12 in each of four infection classes estimated using the 6‐class dwarf mistletoe rating system (DMR): uninfected (DMR 0), lightly infected (DMR 1–2), moderately infected (DMR 3–4) and severely infected (DMR 5–6). Significant reductions in both volume and height growth were found for moderately and severely infected trees when compared to uninfected trees. On average, reductions in volume growth and height growth were as high as 50% and 17%, respectively. The largest growth reductions were for moderately infected trees, but large growth reductions also occurred for severely infected trees. Because of the reduced growth associated with moderate to severe infection, Mexican dwarf mistletoe‐infested pine forests in Durango, where timber production is a high priority, should be managed using harvesting practices that reduce dwarf mistletoe infection, and thereby, increase forest productivity.  相似文献   
995.
996.
The well recognized cardiac effects of severe hyperkalemia include progressive rhythm and conduction disturbances such as bradycardia, spiked and narrow T waves, widening QRS complex, widening and flattening P wave, disappearance of the P wave, and cardiac arrest. Paradoxically, a heart rate greater than 200 beats/min may coexist with hyperkalemia in some cats. This report describes three cats with moderate to severe hyperkalemia and concurrent rapid heart rate. In each cat, the serum potassium (K(+)) concentration was > or =7.5 mEq/dl with a concurrent heart rate > 200 beats/min. In each cat, nine-lead electrocardiograms demonstrate an absence of P waves and a wide-complex tachycardia. Hyperkalemia should be considered in the differential diagnosis when a feline electrocardiogram demonstrates a wide-complex tachycardia without identifiable P waves.  相似文献   
997.
OBJECTIVE: To determine outcome of open toggle rod stabilization in dogs with luxation of the hip joint. Design-Retrospective case series. ANIMALS: 62 dogs. PROCEDURES: Information on signalment, surgical procedure, and postoperative care was obtained from the medical records. A questionnaire was sent to all owners to solicit follow-up information. RESULTS: The distribution for time between luxation and surgery was bimodal, with 24 (39%) dogs examined < or = 2 days after injury and 23 (37%) examined > 7 days after injury. Postoperative complications developed in 16 of the 62 (26%) dogs, with complications developing within 1 week after surgery in 10 of the 16. The most common complication was reluxation, which occurred in 7 dogs. Dogs in which surgery time was < 2 hours were significantly less likely to have a reluxation (2/40 [5%]) than were dogs in which surgery time was > or = 2 hours (5/22 [23%]). When asked to rate current limb function (0 = no lameness and 5 = non-weightbearing lame) a minimum of 6 months after surgery, 23 of 27 (85%) owners indicated a score of 0 or 1. CONCLUSIONS AND CLINICAL RELEVANCE: Results of the present study suggest that toggle rod stabilization is an effective treatment for hip joint luxation in dogs. However, complications, particularly reluxation, were common.  相似文献   
998.
The occurrence of chronic wasting disease (CWD) at the Toronto Zoo was investigated retrospectively, based on an examination of management, animal health, and postmortem records, and immunohistochemical studies. Records of animal movements, clinical signs, and postmortem findings were examined for all cervids 1973-2003. All available samples of fixed, wax-embedded lymphoid or central nervous system tissue from cervids that died at the Toronto Zoo from 1973 to 2003, > 12 months of age, were tested, using prion protein immunostaining. Chronic wasting disease prion antigen was detected in 8 of 105 animals tested: 7 mule deer and 1 black-tailed deer. The most likely method of introduction was the importation of CWD-infected animals from a zoo in the United States. Animal-to-animal contact and environmental contamination were the most likely methods of spread of CWD at the zoo. No mule deer left the Toronto Zoo site, and the last animal with CWD died in 1981. Historic findings and ongoing testing of cervids indicate that the Toronto Zoo collection has very low risk of currently being infected with CWD.  相似文献   
999.
Genetic parameters of litter traits and their relationships with farrowing kinetics traits were estimated in a Large White population to examine the impact of selection for litter size on perinatal mortality and one of its main determinants, farrowing kinetics. Data were collected on 2,947 farrowings from 1,267 sows between 1996 and 2004. Litter traits included the number born in total (NBT), number born alive (NBA), and the number (NSB) and proportion (PSB) of stillborn piglets. Four farrowing kinetics traits were considered: farrowing duration (FD), birth interval (BI = FD/NBT), heterogeneity of birth intervals (SDNB = SD of the number of piglets born each one-half hour), and birth assistance (BA) during the farrowing process. Genetic parameters were estimated using restricted maximum likelihood methodology. All traits were analyzed using a mixed linear animal model including year x month and parity as fixed effects; the additive genetic value of each animal and the sow permanent environment were treated as random effects. To normalize their distribution, kinetics traits were Box-Cox-transformed. Low heritability estimates were obtained for litter size and mortality traits, which was in agreement with literature results (i.e., 0.10 +/- 0.02, 0.08 +/- 0.02, 0.19 +/- 0.02, and 0.14 +/- 0.02 for NBT, NBA, NSB, and PSB, respectively). Heritability values were also low for kinetics traits: 0.10 +/- 0.02, 0.08 +/- 0.02, 0.01 +/- 0.01, and 0.05 +/- 0.03 for FD, BI, SDNB, and BA, respectively. The genetic correlation between NBT and NBA was strongly positive (ra = 0.90). On both phenotypic and genetic scales, NBT was positively associated with stillbirth (ra = 0.45 +/- 0.11, rp = 0.38 for NSB; ra = 0.46 +/- 0.13, rp = 0.17 for PSB). Conversely, NBA had low correlations with SB and PSB. Number born in total was moderately correlated to FD (ra = 0.34 +/- 0.15) and BI (ra = -0.37 +/- 0.15). A stronger relationship was found between NBA and BI (ra = -0.49 +/- 0.13), whereas the relationship with FD was lower (ra = 0.16 +/- 0.17). Moreover, FD was strongly correlated with stillbirth (ra = 0.42 +/- 0.12 with NSB), whereas BI was nearly independent of stillbirth. Contrary to selection on NBT, selection on NBA appears to be a good way to limit the negative side effects on stillbirth. Moreover, selection on NBA would lead to a small increase in FD and a faster and more regular birth process than would be obtained by selecting on NBT.  相似文献   
1000.
As the environment changes, will species be able to adapt? By conducting experiments in natural environments, biologists can study how evolutionary processes such as natural selection operate through time. We predicted that the introduction of a terrestrial predator would first select for longer-legged lizards, which are faster, but as the lizards shifted onto high twigs to avoid the predator, selection would reverse toward favoring the shorter-legged individuals better able to locomote there. Our experimental studies on 12 islets confirmed these predictions within a single generation, thus demonstrating the rapidity with which evolutionary forces can change during times of environmental flux.  相似文献   
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