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31.

Context

Arid rangelands have been severely degraded over the past century. Multi-temporal remote sensing techniques are ideally suited to detect significant changes in ecosystem state; however, considerable uncertainty exists regarding the effects of changing image resolution on their ability to detect ecologically meaningful change from satellite time-series.

Objectives

(1) Assess the effects of image resolution in detecting landscape spatial heterogeneity. (2) Compare and evaluate the efficacy of coarse (MODIS) and moderate (Landsat) resolution satellite time-series for detecting ecosystem change.

Methods

Using long-term (~12 year) vegetation monitoring data from grassland and shrubland sites in southern New Mexico, USA, we evaluated the effects of changing image support using MODIS (250-m) and Landsat (30-m) time-series in modeling and detecting significant changes in vegetation using time-series decomposition techniques.

Results

Within our study ecosystem, landscape-scale (>20-m) spatial heterogeneity was low, resulting in a similar ability to detect vegetation changes across both satellite sensors and levels of spatial image support. While both Landsat and MODIS imagery were effective in modeling temporal dynamics in vegetation structure and composition, MODIS was more strongly correlated to biomass due to its cleaner (i.e., fewer artifacts/data gaps) 16-day temporal signal.

Conclusions

The optimization of spatial/temporal scale is critical in ensuring adequate detection of change. While the results presented in this study are likely specific to arid shrub-grassland ecosystems, the approach presented here is generally applicable. Future analysis is needed in other ecosystems to assess how scaling relationships will change under different vegetation communities that range in their degree of landscape heterogeneity.
  相似文献   
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All the human and animal laboratory reports of zoonoses sent to Health Protection Scotland between 1993 and 2002 were identified. There were 24,946 reports from veterinary laboratories, and 94,718 (20 per cent) of the 468,214 reports from medical laboratories were considered to be zoonotic. The most common reports of zoonoses from people were Campylobacter, Salmonella, Cryptosporidium and Giardia species and Escherichia coli o157. The most common reports of zoonoses from animals were Salmonella, Cryptosporidium, Chlamydia and Campylobacter species and Mycobacterium avium paratuberculosis. For all the zoonoses in people, the National Health Service Board areas Borders, Dumfries and Galloway, Forth Valley, Grampian, Lanarkshire and Lothian had a higher than expected standardised incidence rate of infection, whereas Ayrshire and Arran, Fife, Greater Glasgow, Shetland, Tayside and Western Isles had a lower than expected rate. The organisms and diseases considered to be new and emerging were Rhodococcus species, Cyclospora cayetanensis, Leishmania species, Pneumocystis carinii (jiroveci) and bovine spongiform encephalopathy/variant Creutzfeldt-Jakob disease.  相似文献   
33.
PROBLEM: Chlamydophila felis is a common cause of conjunctivitis in cats and in some textbooks is listed as an important zoonotic pathogen. However, there are no published comprehensive reviews assessing the evidence supporting this. SEARCH AND ANALYSIS: Bibliographic databases and bibliographies of papers and textbooks were searched for all published cases of zoonotic disease associated with chlamydiosis in cats. All published case reports were reviewed to establish the quality of the evidence supporting the association between C. felis and zoonotic disease. RESULTS: There are only seven case reports, most of which were published before the development of assays capable of distinguishing C. felis from other chlamydial species, implicating this organism in zoonotic disease. None of the three cases of pneumonia and systemic disease described, two of which occurred in immunocompromised patients, can be unambiguously attributed to C. felis. Of the four cases of follicular keratoconjunctivitis described, only one, in an immunocompromised patient, could be unambiguously attributed to C. felis. CONCLUSION: While there is evidence that C. felis may occasionally cause keratoconjunctivitis in humans, there is little evidence to suggest it can cause serious systemic disease or pneumonia.  相似文献   
34.
The aim of this study was to establish whether enzootic pneumonia could be induced reliably in piglets by administering an aerosolised culture of Mycoplasma hyopneumoniae. Groups of five M hyopneumoniaefree Landrace x Large White piglets weaned at 11 to 14 days of age were exposed to aerosols of in vitro cultures of a virulent strain of M hyopneumoniae. In three separate trials, 14 of 15 pigs exposed to the bacteria developed pneumonia, but pigs exposed to the culture medium alone did not develop the disease. Lung pathology, both gross and histological, indicated acute disease. Ten of the pigs were tested for seroconversion by Western blot and they were all positive. The growth rates of the infected pigs were significantly reduced and the water consumption of the infected groups was also depressed. M hyopneumoniae was recovered from eight of the 15 infected pigs.  相似文献   
35.
The method currently used for testing potato tubers for viruses following harvest involves a growing‐on test. This takes up to 6 weeks to complete, and there is therefore a demand for more rapid test results. The sensitivity and reliability of direct tuber testing by DAS‐ELISA and real‐time RT‐PCR (TaqMan) were compared with the growing‐on test. In addition, the reliability of all three methods for the detection of Potato Y potyvirus (PVY) in tubers was compared over post‐harvest intervals of 6, 10, 14 and 18 weeks. The test material came from plots of tubers (cv. ‘Maris Piper’) containing a primary infection of strains PVYN and PVYO, following aphid transmission from marked infector plants grown during the 2003 season. Sample material was homogenized and divided, to provide comparative test material for detection of PVY by ELISA and real‐time RT‐PCR. Tuber eye‐plugs were then taken and subjected to the growing‐on test. The remainder of the tuber was also grown on and tested, to ensure infection was not missed as a consequence of an uneven distribution of virus throughout the tuber material. The results obtained using the two methods for direct testing of the tubers, and those results obtained from the traditional growing‐on test, are compared. The advantages and disadvantages of each method are discussed.  相似文献   
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Research was conducted to evaluate the sensitivity of Bos indicus and Bos taurus cattle to a tall fescue ergopeptine alkaloid by assessing vital sign responses. Eight Polled Hereford and seven Red Brahman steers received bolus i.v. injections of ergotamine tartrate and saline vehicle in a simple cross-over design. Physiological traits measured 30 min and immediately before and 30, 60, and 90 min after treatment were respiration rate, rectal temperature, skin temperature at the tailhead and tail tip, systolic and diastolic blood pressure, and heart rate. Blood samples were collected immediately before and 105 min after treatments to determine plasma prolactin and cortisol concentrations. Steers were fed a fescue-free diet in drylot. Ambient temperature and relative humidity averaged 31 degrees C and 55%, respectively, during data collection. No breed x treatment x time interactions were apparent for vital signs. The treatment x time interaction was significant (P < .05) for blood pressure and skin temperature. Ergotamine increased (P < .01) blood pressure and decreased (P < .01) skin temperature. The breed x treatment x time interactions were significant for prolactin (P < .1) and cortisol (P < .01). Ergotamine decreased plasma (P < .01) prolactin and increased (P < .01) cortisol concentrations in both breeds, despite some breed variation. Across all traits, Brahman and Hereford steers responded similarly to acute ergotamine exposure, indicating that the breeds are alike in acute sensitivity to a systemically administered ergopeptine alkaloid associated with fescue toxicosis.  相似文献   
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The Phanerozoic record of global sea-level change   总被引:5,自引:0,他引:5  
We review Phanerozoic sea-level changes [543 million years ago (Ma) to the present] on various time scales and present a new sea-level record for the past 100 million years (My). Long-term sea level peaked at 100 +/- 50 meters during the Cretaceous, implying that ocean-crust production rates were much lower than previously inferred. Sea level mirrors oxygen isotope variations, reflecting ice-volume change on the 10(4)- to 10(6)-year scale, but a link between oxygen isotope and sea level on the 10(7)-year scale must be due to temperature changes that we attribute to tectonically controlled carbon dioxide variations. Sea-level change has influenced phytoplankton evolution, ocean chemistry, and the loci of carbonate, organic carbon, and siliciclastic sediment burial. Over the past 100 My, sea-level changes reflect global climate evolution from a time of ephemeral Antarctic ice sheets (100 to 33 Ma), through a time of large ice sheets primarily in Antarctica (33 to 2.5 Ma), to a world with large Antarctic and large, variable Northern Hemisphere ice sheets (2.5 Ma to the present).  相似文献   
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