A supershear transition mechanism for cracks   总被引：3，自引：0，他引：3  

Dunham EM  Favreau P  Carlson JM 《Science (New York, N.Y.)》2003,299(5612):1557-1559

Seismic data indicate that fault ruptures follow complicated paths with variable velocity because of inhomogeneities in initial stress or fracture energy. We report a phenomenon unique to three-dimensional cracks: Locally stronger fault sections, rather than slowing ruptures, drive them forward at velocities exceeding the shear wave speed. This supershear mechanism differentiates barrier and asperity models of fault heterogeneity, which previously have been regarded as indistinguishable. High strength barriers concentrate energy, producing potentially destructive pulses of strong ground motion.  相似文献   

Partitioning variation in Douglas-fir xylem properties among multiple scales via a Bayesian hierarchical model     

Dunham SM  Ganio LM  Gitelman AI  Lachenbruch B 《Tree physiology》2008,28(7):1017-1024

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Cathelicidins enhance protection of channel catfish,Ictalurus punctatus,and channel catfish ♀ × blue catfish,Ictalurus furcatus ♂ hybrid catfish against Edwarsiella ictaluri infection     

Rhoda Mae C. Simora  Shangjia Li  Nermeen Y. Abass  Jeffery S. Terhune  Rex A. Dunham 《Journal of fish diseases》2020,43(12):1553-1562

Cathelicidins are a class of antimicrobial peptides (AMPs) known to possess rapid and direct antimicrobial activities against a variety of microorganisms. Recently identified cathelicidins derived from alligator and sea snake were found to be more effective in inhibiting microbial growth than other AMPs previously characterized. The ability of these two cathelicidins along with the peptides, cecropin and pleurocidin, to protect channel catfish (Ictalurus punctatus, Rafinesque) and hybrid catfish (I. punctatus ♀ × blue catfish, Ictalurus furcatus, Valenciennes ♂) against Edwardsiella ictaluri, one of the most prevalent pathogens affecting commercial catfish industry, was investigated. Cathelicidin-injected fish (50 µg ml⁻¹ fish⁻¹) that were simultaneously challenged with E. ictaluri through bath immersion at a concentration of ~1 × 10⁶ CFU/ml had increased survival rates compared with other peptide treatments and the infected control. Bacterial numbers were also reduced in the liver and kidney of channel catfish and hybrid catfish in the cathelicidin treatments 24 hr post-infection. After 8 days of challenge, serum was collected to determine immune-related parameters such as bactericidal activity, lysozyme, serum protein, albumin and globulin. These immune-related parameters were significantly elevated in fish injected with the two cathelicidins as compared to other peptide treatments. These results indicate that cathelicidins derived from alligator and sea snake can stimulate immunity and enhance the resistance to E. ictaluri infection in channel catfish and hybrid catfish.  相似文献   

Instream cover and shade mediate avian predation on trout in semi‐natural streams          下载免费PDF全文

Brooke E. Penaluna  Jason B. Dunham  David L. G. Noakes 《Ecology of Freshwater Fish》2016,25(3):405-411

Piscivory by birds can be significant, particularly on fish in small streams and during seasonal low flow when available cover from predators can be limited. Yet, how varying amounts of cover may change the extent of predation mortality from avian predators on fish is not clear. We evaluated size‐selective survival of coastal cutthroat trout (Oncorhynchus clarkii clarkii) in replicated semi‐natural stream sections. These sections provided high (0.01 m² of cover per m² of stream) or low (0.002 m² of cover per m² of stream) levels of instream cover available to trout and were closed to emigration. Each fish was individually tagged, allowing us to track retention of individuals during the course of the 36‐day experiment, which we attributed to survival from predators, because fish had no other way to leave the streams. Although other avian predators may have been active in our system and not detected, the only predator observed was the belted kingfisher Megaceryle alcyon, which is known to prey heavily on fish. In both treatments, trout >20.4 cm were not preyed upon indicating an increased ability to prey upon on smaller individuals. Increased availability of cover improved survival of trout by 12% in high relative to low cover stream sections. Trout also survived better in stream sections with greater shade, a factor we could not control in our system. Collectively, these findings indicate that instream cover and shade from avian predators can play an important role in driving survival of fish in small streams or during periods of low flow.  相似文献   

Assessing reactivity in 3 breed of working dogs: Phenotypic determination and associated genotypes     

Karen L. Overall  Soraya Juarbe-Diaz  Donna J. Dyer  Melanie Lee Chang  Jennifer S. Yokoyama  Arthur E. Dunham 《Journal of Veterinary Behavior: Clinical Applications and Research》2009,4(6):249-250

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Genome-wide detection of polymorphisms at nucleotide resolution with a single DNA microarray     

Gresham D  Ruderfer DM  Pratt SC  Schacherer J  Dunham MJ  Botstein D  Kruglyak L 《Science (New York, N.Y.)》2006,311(5769):1932-1936

A central challenge of genomics is to detect, simply and inexpensively, all differences in sequence among the genomes of individual members of a species. We devised a system to detect all single-nucleotide differences between genomes with the use of data from a single hybridization to a whole-genome DNA microarray. This allowed us to detect a variety of spontaneous single-base pair substitutions, insertions, and deletions, and most (>90%) of the approximately 30,000 known single-nucleotide polymorphisms between two Saccharomyces cerevisiae strains. We applied this approach to elucidate the genetic basis of phenotypic variants and to identify the small number of single-base pair changes accumulated during experimental evolution of yeast.  相似文献   

Population decline of tsessebe antelope (Damaliscus lunatus lunatus) on a mixed cattle and wildlife ranch in Zimbabwe     

Kevin M. Dunham  E.F. Robertson 《Biological conservation》2003,113(1):111-124

The estimated number of tsessebes on a cattle and wildlife ranch in Zimbabwe decreased during 1995-1999 from 2209 to 435 animals. Existing records of rainfall, cattle management, wildlife numbers, captures, hunting and predation were analysed and, together with a demographic model and limited fieldwork, used to identify the probable cause of this decline. There was no convincing evidence that cheetah predation, excessive legal or illegal offtakes, a food shortage as a direct consequence of the 1994/1995 drought, or interspecific competition with wild herbivores were likely causes. After the 1991/1992 drought, tsessebe number was negatively correlated with cattle biomass, suggesting that cattle and tsessebe have competed for food since then. Two factors probably caused a long-lasting reduction in the dry-season availability of green grass leaf (the preferred food of tsessebe). First, drought and heavy grazing pressure by cattle may have shifted sward composition away from leafy grasses and towards grass species with small, wiry leaves. Secondly, while shrub encroachment has been occurring for decades, the 1991/1992 drought probably encouraged the establishment of another cohort of bushes, which now compete with grasses for soil moisture, reducing the water available for grass growth during the dry season. The competition between tsessebe and cattle was masked by significant cattle destocking during 1992-1995, but became apparent after 1995 when cattle numbers were increased. This competition was exaggerated by a general decline, since 1994, in rainfall during September-October, which further reduced the late dry season supply of green grass.  相似文献   

Rainfall and the decline of a rare antelope, the tsessebe (Damaliscus lunatus lunatus), in Kruger National Park, South Africa     

Kevin M. Dunham  E.F. Robertson 《Biological conservation》2004,117(1):83-94

The number of tsessebes in Kruger National Park, South Africa, increased during 1977-1985, but declined after 1986. We used tsessebe number and age structure to determine year-to-year variation in adult survival. Adult survival rate was positively correlated with dry-season rainfall (a measure of grass productivity during the dry season) and with the cumulative rainfall surplus. Juvenile survival rate (as indexed by the juvenile:female ratio) was also correlated with the cumulative rainfall surplus. Tsessebe feed in broad, grass-covered drainage lines within Colophospermum mopane shrubland on basaltic soils. Here drainage is slow and the cumulative rainfall surplus or deficit, relative to the mean annual rainfall, is an index of dry-season soil moisture, which, in turn, determines dry-season grass productivity and hence the food supply for tsessebe. Adult survival rate was density-dependent, indicating that there was intraspecific competition for food. When the relationships between survival rates and rainfall were used in a model of tsessebe population dynamics to predict juvenile and adult survival rates from the recorded annual and dry-season rainfalls, the modelled population changes were similar to those observed. We conclude that changes in tsessebe numbers probably resulted from rainfall-induced changes in food availability during the dry season, which caused adult survival to decline after 1986. The principal management implication is that the tsessebe decline can be reversed only by several successive years of above-average annual rainfall. The importance of green grass during the dry season as a key resource is emphasised, not only for tsessebe, but also for other African antelopes that graze selectively.  相似文献   

Onset and duration of action of lokivetmab in a canine model of IL-31 induced pruritus     

Timothy J. Fleck  Lori R. Norris  Sean Mahabir  Rodney R. Walters  Olivier Martinon  Steven A. Dunham  Andrea J. Gonzales 《Veterinary dermatology》2021,32(6):681-e182

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Renal dysplasia with multiple urogenital and large intestinal anomalies in a calf     

B M Dunham  W I Anderson  H Steinberg  J M King 《Veterinary pathology》1989,26(1):94-96

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