Larvicidal activity of natural and modified triterpenoids against Aedes aegypti (Diptera: Culicidae)          下载免费PDF全文

Gloria NS da Silva  Frances TT Trindade  Francine dos Santos  Grace Gosmann  Alexandre A e Silva  Simone CB Gnoatto 《Pest management science》2016,72(10):1883-1887

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Nitrifier dominance of Arctic soil nitrous oxide emissions arises due to fungal competition with denitrifiers for nitrate     

Steven D. Siciliano  Wai K. Ma  Richard E. Farrell 《Soil biology & biochemistry》2009,41(6):1104-1110

Arctic soils emit nitrous oxide, which is a potent greenhouse gas and also represents an important loss of nitrogen to oligotrophic Arctic ecosystems. However, little is known about the temperature sensitivity of nitrous oxide release in Arctic soils or the organisms mainly responsible for it. We investigated controls on nitrous oxide emissions in an Arctic soil across a typical temperature range (between 4 and 13 °C) on Truelove Lowland, Devon Island, Canada (75°40′N 84°35′W) at two different moisture contents. When fertilized with ammonia or nitrate, nitrous oxide emissions and temperature dependence of nitrous oxide emissions were insensitive to soil moisture content but linked to nitrification rates. Stable isotope analysis revealed that nitrous oxide was predominantly released by nitrifiers. However, nitrous oxide emissions were not linked to nitrifier prevalence with an insignificant (P < 0.219) increase in amoA genes and a (P < 0.01) decrease in archaeal nitrifiers. In contrast, denitrifier nosZ prevalence was 10,000 times greater than that of nitrifiers and was related to nitrous oxide emission potential when soils were fertilized with nitrate. Manipulating water-filled pore space should have changed the pattern of N₂O emissions. We used selective inhibitors to further explore why denitrification did not occur under field conditions when we manipulated water-filled pore space or when we used ¹⁵N analysis. When fungi were inhibited in the soil, nitrous oxide emissions from denitrifiers increased with no change in nitrous oxide released by nitrifiers. When fungi were active in the soil, there was little available nitrate but when fungi were inhibited, available soil nitrate increased over the incubation period. The dominance of nitrifiers in nitrous oxide emissions from Arctic soils under field conditions is linked to the competition for nitrate between fungi and denitrifiers.  相似文献   

Computed tomographic documentation of the natural progression of humeral intracondylar fissure in a cocker spaniel     

Farrell M  Trevail T  Marshall W  Yeadon R  Carmichael S 《Veterinary surgery : VS》2011,40(8):966-971

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女人三国     

TT  何龙 《今日农村》2008,(4)

4.0、3.0和2.0,她们之间本不应该有交点,但因为对网球的痴迷程度都是7.0,于是这三个在各自圈子里红得发烫的人,走到了一起。  相似文献   

Effect of planting stocktype and cultivation treatment on the establishment of Norway spruce on cutaway peatlands     

Florence Renou-Wilson  Michael Keane  E. P. Farrell 《New Forests》2008,36(3):307-330

In order to determine the effect of stocktype and cultivation treatment on the field performance (survival and growth) and physiological status of Picea abies in cutaway peatlands, small bare-root, large bare-root and containerised seedlings were planted in a deep ploughed and a control site. Survival after 2 years was good across all treatment (>90%) except for the large bare-root seedlings growing in the control site (84%). For all the morphological characteristics assessed in this study, there was no significant interaction between stocktype and cultivation treatment indicating that the growth response to site cultivation was not stocktype dependent. After two growing seasons, all Norway spruce seedlings performed better in the deep ploughed site and displayed also better nutritional and physiological status. Regardless of cultivation treatment, mean height, diameter and volume increment were significantly smaller for the large bare-root seedlings while the small bare-root seedlings displayed the greatest growth rates. In order to promote early height growth in container and small bare-root stock, large diameter is important. Other initial characteristics such as foliar nitrogen content may also have a strong influence on first year field performance. The physiological status of the seedlings during the first year after outplanting was assessed using chlorophyll fluorescence (CF) measurements. CF measurements detected a higher level of stress for the large-bare root stock (low Fv/Fm). On the other hand, small bare-root stock displayed highest maximum potential photochemical activity which corresponded to greatest growth rates. Container seedlings demonstrated higher capacity for photosynthetic electron transport during the first five months after planting suggesting that they recovered from planting stress quicker and optimised better light interception and utilization than bare-root stock. It can be concluded that intensive management systems including deployment of best-adapted stocktype and site cultivation can be used to enhance early height growth of Norway spruce on cutaway peatlands.  相似文献   

Increased pulmonary clearance of Serratia marcescens in calves given intravenous Freund's complete adjuvant   总被引：1，自引：0，他引：1  

H P Veit  R L Farrell 《The Cornell veterinarian》1984,74(3):269-281

Lung and alveolar macrophage studies were conducted following experimental immunostimulation of calves with Freund's complete adjuvant (FCA). Intravenous administration of FCA to calves 35 days before aerosol exposure to serratia marcescens resulted in a 53.1% reduction in the 2-hour pulmonary mean percent retention of the organism when compared to control calves. FCA treatment increased alveolar macrophage concentration (cells/g lung) by 30.9%. Lymphoid and granulomatous responses were increased in the lungs of treated calves.  相似文献   

Paralaryngeal accessory bronchial cyst as a cause of laryngeal haemiplegia in a horse.     

G M Baxter  D Allen  R L Farrell 《Equine veterinary journal》1992,24(1):67-69

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Acute inflammatory effects of intratracheally instilled Escherichia coli endotoxin and sonicated suspension of Haemophilus pleuropneumoniae in swine.   总被引：5，自引：1，他引：4       下载免费PDF全文

A D Liggett  L R Harrison    R L Farrell 《Canadian journal of veterinary research》1986,50(4):526-531

A single bolus of either Escherichia coli endotoxin, sonicated suspension of Haemophilus pleuropneumoniae, or pyrogen-free normal saline was intratracheally instilled in six week old specific-pathogen-free pigs. Pigs exposed to E. coli endotoxin developed fever, leukopenia followed by leukocytosis, and endotoxemia. Leukocytosis was the only clinical abnormality noted in pigs receiving the sonicated suspension of H. pleuropneumoniae. At one day postexposure, focal areas of atelectasis and consolidation were observed in the caudal lung lobes of animals receiving either E. coli endotoxin or the sonicated suspension of H. pleuropneumoniae. Lesions were characterized by a neutrophilic bronchitis and bronchiolitis with alveolitis in the surrounding tissue. Increased numbers of alveolar macrophages and evidence of phagocytosis were observed by light and electron microscopy. No clinical abnormalities or lesions were observed in animals receiving normal saline. Lesions typical of acute porcine Haemophilus pleuropneumonia were not produced by either E. coli endotoxin or sonicated suspension of H. pleuropneumoniae, indicating that multiple virulence factors are probably involved in lesion development.  相似文献   

Influence of food restriction during rearing on the body composition of layer-strain pullets and hens     

R J Johnson  R B Cumming  D J Farrell 《British poultry science》1985,26(3):335-348

The influence of two methods of food restriction during rearing on the body and liver composition of layer-type birds was investigated during and after restriction. In each of two experiments groups of birds were reared on one of three treatments: ad libitum food intake (A), time-limited food restriction (TR) or proportional food restriction (PR). All birds were fed ad libitum during the laying phase. In experiment 1, six birds from each treatment were selected at random for estimation of body and liver composition and killed at 70, 101, 162, 218 and 337 d of age. In experiment 2 four birds were selected from each treatment at 280 and 467 d of age. Body composition was predicted in experiment 2 at various times such as sexual maturity, using equations based on deuterium oxide dilution techniques. Body composition changes caused by food restriction were related to the length of restriction. Towards its end the major changes were: decreased body fat, increased total body water and increased water content of the fat-free mass for TR and PR birds compared to A birds. Some changes were not due to a reduced liveweight. Food restriction during rearing did not change body composition permanently, although predicted body fat at sexual maturity (experiment 2) was lower and protein content higher for TR and PR than for A birds. There was no demonstrable relationship between the body fat content predicted at sexual maturity and subsequent rate of lay (experiment 2).  相似文献   

A comparison of the energy and nitrogen metabolism of fed ducklings and chickens     

A. P. Siregar  D. J. Farrell 《British poultry science》1980,21(3):213-227

1. Energy measurements were made over 4 d on groups of three ducklings (aged from 5 to 22 d), and three broiler chickens (aged from 11 to 32 d) offered high‐ or low‐energy diets.

2. Food, metabolisable energy (ME) and water intakes were significantly higher for ducklings than for chickens. The ratio of water : food was 4.2 : 1 and 2.3 : 1 for ducklings and chickens, respectively. The food conversion ratio differed between diets but not species. Performance was generally better for both species on the high‐energy diet.

3. Heat production, energy, fat and protein retentions were higher for ducklings than chickens, and ducklings retained 0.44 of their energy as fat compared with 0.37 for chickens. Overall the ratio of protein (g) to fat (g) retention was 2.2 : 1 and 2.8 : 1 for ducklings and chickens respectively.

4. For ducklings, metabolisability of the high‐energy diet declined from 0.774 to 0.747, and to a lesser extent of the low‐energy diet, as they aged. There was no such decline for chickens. Net efficiency of utilisation of ME for gain was 0.64 for ducklings compared with 0.50 for chickens.

5. Fractional retention of dietary nitrogen (N) was 0.62 for ducklings and 0.55 for chickens. Gaseous ammonia‐N was 4.5 and 2.2%, respectively, of N retained.

6. In a second experiment groups of ducklings only, were offered high‐and low‐protein diets from 12 to 22 d of age. Comparisons among four diets showed that food and energy intake was lower on the low‐protein diet than on the other three. Energy retention on the high‐energy diet was greater (P<0.05) than on the other three diets.

7. It was concluded that a high‐energy diet is important for ducklings and chickens for maximum biological performance during the first 4 weeks of life.  相似文献