阿拉斯加原油管道设计原则与特殊施工要点

阿拉斯加原油管道设计有传统埋设、特殊埋设和地上敷设.传统埋设的管顶埋深变化于0.9～2.7 m之间,特殊埋设则有降(保)温系统.地上敷设有桩基架设和高管堤.在该管道的设计与施工方案制定等方面,Alyeska管道公司随项目进展采用动态设计,不断完善施工方案,严格环保要求与设计安全相互促进,利用规范解决实际问题,工程师、环境专家和项目管理者密切合作,项目组织管理形式协调有序.从五个方面,重点阐述了Alyeska管道工程对中国寒区管道工程建设的借鉴意义.     

Familial episodic ataxia in lambs

Abstract

HISTORY: A similar episodic neurological disorder occurred in new born lambs on two unrelated properties involving disparate breeds of sheep. Because of the number of lambs born, cross-breeding and the fact it occurred in some mating groups and not others, a dominant mode of inheritance was, initially and separately, suspected in each case. The sires of affected lambs were apparently normal. Whereas one was New Zealand Romney, the other was a composite breed with East Friesian genetics, but both rams originated from the same source property. To investigate the pathogenesis of the disorder these two rams were acquired and mated with unrelated sheep, under experimental conditions in a more controlled environment.

CLINICAL FINDINGS: A proportion of lambs born to both sires exhibited a similar neurological disorder. Some lambs were noted to be abnormal at birth, both on home properties and in the experimental flock. They tended to adopt a head and neck extended posture and were slow to get to their feet and suckle when they then became more or less normal. When forced to move, they and other more robust lambs elicited an asymmetric gait, base-wide extensor hypertonia (hypometria) of thoracic limbs and flexor hypertonia (hypermetria) of pelvic limbs. In some there was nystagmus. After several metres of asymmetric ataxic gait they would fall to one side, sometimes adopting a sitting position. Recovery usually occurred in one to several minutes. As lambs aged, it became more difficult to elicit the episodes of dysfunction and by 6 months of age they appeared normal.

DIAGNOSIS: The disorder was diagnosed as a dominant familial episodic cerebellovestibular ataxia inherited as a dominant trait, with incomplete penetration of observed clinical signs and variable expressivity.

CLINICAL RELEVANCE: A proportion of affected lambs are likely to die in the neonatal period so the specific nature of the disorder may go unrecognised. Because of incomplete penetrance and varying expressivity, many of the lambs carrying this mutation will survive without showing clinical signs and may enter breeding flocks, where the disorder may be perpetuated and contribute to neonatal deaths.     

Long-acting selenium treatments for sheep

An intraruminal selenium (Se) pellet and a subcutaneous depot of barium selenate, equivalent to 1.6 mg Se/kg body weight, were each effective in maintaining increased blood Se concentrations for at least 200 weeks in ewes at pasture. These treatments given to the ewes 23 to 26 weeks before lambing increased the Se status of their lambs for 4 to 6 months.     

Duplication of the pale, soft, and exudative condition starting with normal postmortem pork

The objective of the current study was to create an in vitro model that duplicated the development of PSE pork. Postrigor pork chops with various pH values and normal color were vacuum-packaged, and heated at approximately 42 degrees C for various times (0, 15, 30, 60, 120, or 240 min), or heated to temperatures that occur early postmortem (34, 37, 39, or 42 degrees C for 60 or 120 min) in a water bath. Chops were cooled and allowed to bloom, after which changes in Minolta and Hunter color values were assessed, and purge loss was determined. Warming postrigor pork with normal color and pH to early postmortem body temperature for various times successfully duplicated the characteristics of PSE pork. After 60 to 120 min at 42 degrees C or above, chops with pH < 5.8 lightened until L values were similar to those typical of PSE pork (Minolta L = 61.0). Change in chop color depended on length of time the samples were warmed, as well as on pH. Below 34 degrees C, temperature had no (P > or = 0.28) effect on color (Minolta L, a, b, and Hunter L*, a*, b*); however, at higher temperatures, color change depended on pH and warming time. A comparison of the time and temperature relationships for changes in lightness and purge suggested that the mechanisms of the two processes are not identical. The similarities in the dynamic range of color change, change in absolute color values, and time frame for changes in vitro and in vivo suggest similarity of the processes creating PSE in a carcass and in the in vitro model.     

The association ofErwinia carotovora var.atroseptica andErwinia carotovora var.carotovora with insects in Colorado

Ten genera from 9 families of dipterous insects collected in the field in the San Luis Valley of Colorado were contaminated withErwinia carotovora var.atroseptica (Eca) andErwinia carotovora var.carotovora (Ecc).Erwinia-contaminated insects were collected from settling ponds near potato warehouses, potato cull piles on growers’ farms, municipal dumps, lettuce and potato fields. The percentage of contaminated insects reached 14.5% in early spring but decreased as the season progressed. Insects were more commonly contaminated withEca thanEcc early in the season. Later the proportion of contamination byEcc increased while that ofEca decreased. We suggest that insects may play a potentially important role in the epidemiology of potato blackleg especially in the reintroduction ofErwinia intoErwiniafree potato fields.     

Infectivity and persistence of an outbreak strain of Salmonella enterica serotype Typhimurium DT160 for house sparrows (Passer domesticus) in New Zealand

AIM: To examine the infective dose, incubation period and disease progression of an isolate of Salmonella enterica serotype Typhimurium definitive type 160 (DT160) originating from a naturally-infected house sparrow (Passer domesticus) during an outbreak of the disease in New Zealand.

METHODS: Thirty-six house sparrows captured from the wild and free of Salmonella spp were divided into six groups of six birds, housed individually, and inoculated orally with phosphate buffered saline (PBS) or 10¹, 10², 10³, 10⁵, 2 × 10⁸ colony forming units (cfu) of the outbreak strain of S. Typhimurium DT160. The birds were observed for 10 days for clinical signs and/or mortality, and faecal samples were collected to determine excretion of S. Typhimurium. The birds were eutha- nised 11 days post-inoculation (p.i.) and a wide range of tissue samples were collected for histopathological examination, and culture and typing of Salmonella spp. Macro-restriction profiling by pulsed-field gel electrophoresis (PFGE) using XbaI was performed for the epidemiological typing of S. Typhimurium DT160 isolates.

RESULTS: Mortality in house sparrows inoculated with S. Typhimurium DT160 was dose-dependent, and 2/6 birds inoculated with ¹⁰⁵ cfu and all six birds inoculated with 2 × 10⁸ cfu died during the study. Infected sparrows displayed few clinical signs, apart from diarrhoea and/or polyuria, fluffed plumage, and sitting on the floor of the cage. Faecal excretion of DT160 occurred briefly in two birds inoculated with 10² cfu and four birds inoculated with 10³ cfu, on most days in five birds inoculated with 10⁵ cfu, and continuously in six birds inoculated with 2 × 10⁸ cfu. DT160 was isolated from the livers of three birds which received 10³ cfu, five birds dosed with 10⁵ cfu, and all six birds given 2 × 10⁸ cfu. Following necropsy, histopathological lesions similar to those seen in the natural disease were observed in the liver or spleen of three birds which received 10³ cfu, and all birds dosed with ≥10⁵ cfu.

CONCLUSION: The results indicate that an isolate of S. Typhimurium DT60 originating from house sparrows in New Zealand is pathogenic to these birds and that the response is dose- dependent. The persistence and excretion of the pathogen may last for at least 10 days. This confirms that sparrows infected with DT160 could be a source of infection to humans and other in-contact animals.     

Glacial refugia: hotspots but not melting pots of genetic diversity

Glacial refuge areas are expected to harbor a large fraction of the intraspecific biodiversity of the temperate biota. To test this hypothesis, we studied chloroplast DNA variation in 22 widespread European trees and shrubs sampled in the same forests. Most species had genetically divergent populations in Mediterranean regions, especially those with low seed dispersal abilities. However, the genetically most diverse populations were not located in the south but at intermediate latitudes, a likely consequence of the admixture of divergent lineages colonizing the continent from separate refugia.     

Experimental Brucella abortus infection in pigs

Sixteen pigs inoculated by the intra-conjunctival, intravenous or subcutaneous routes with Brucella abortus Strain 544 developed a short-lived infection usually accompanied by conjunctival and vaginal excretion of the organism for up to 99 days post-inoculation. Serological tests performed by the agglutination, complement fixation, Rose Bengal plate, antiglobulin, immunodiffusion or ELISA procedures with B. abortus antigens disclosed wide variations in the antibody responses of individual animals. In some cases the serological tests were negative even though the animal was shown to be excreting B. abortus. The intradermal test for delayed hypersensitivity to Brucella antigens gave more consistent results, especially when supported by histological evaluation of the skin reactions.