Spatial Variability of Turbulent Mixing in the Abyssal Ocean   总被引：3，自引：0，他引：3  

KL Polzin  JM Toole  JR Ledwell  RW Schmitt 《Science (New York, N.Y.)》1997,276(5309):93-96

Ocean microstructure data show that turbulent mixing in the deep Brazil Basin of the South Atlantic Ocean is weak at all depths above smooth abyssal plains and the South American Continental Rise. The diapycnal diffusivity there was estimated to be less than or approximately equal to 0.1 x 10(-4) meters squared per second. In contrast, mixing rates are large throughout the water column above the rough Mid-Atlantic Ridge, and the diffusivity deduced for the bottom-most 150 meters exceeds 5 x 10(-4) meters squared per second. Such patterns in vertical mixing imply that abyssal circulations have complex spatial structures that are linked to the underlying bathymetry.  相似文献   

Endomycorrhizae in a newly cultivated acidic meadow: Effects of three years of barley cropping,tillage, lime,and phosphorus on root colonization and soil infectivity   总被引：2，自引：0，他引：2  

Chantal Hamel  Yolande Dalpé  Claude Lapierre  Régis R. Simard  Donald L. Smith 《Biology and Fertility of Soils》1996,21(3):160-165

The dynamics of mycorrhizae under disturbance created by crop production is not well understood. A 3-year experiment was undertaken on a nutrient-poor and acidic land that had last been cultivated in the early 1970s. We observed the effects of cropping spring barley (Hordeum vulgare L.) under four P-fertilizer levels and four levels of lime, in a minimum (rototillage), a reduced (chisel), or a conventional tillage system, on the mycorrhizal receptiveness of the host (maximum level of mycorrhizal colonization, as measured at harvest) and soil infectivity most probable number method. The host receptiveness decreased with time, while crop yields and soil infectivity increased simultaneously with time. Liming increased mycorrhizal colonization of barley roots and soil infectivity. P additions decreased root colonization but did not significantly affect the most probable number valuse. Slightly higher soil infectivity estimates were found under reduced tillage.  相似文献   

Water and Fertilizer Nitrogen Management to Minimize Nitrate Pollution from a Cropped Soil in Southwestern Quebec,Canada     

Elmi  Abdirashid A.  Madramootoo  C.  Egeh  Mohamud  Hamel  C. 《Water, air, and soil pollution》2004,151(1-4):117-134

Nitrate-N (NO₃ ^--N) pollution of water resources is a widely recognized problem. Water and nitrogen fertilizer are the two most important factors affecting NO₃ ^--N movement to surface and groundwater. Field trials were conducted from 1998 to 2000 growing seasons to investigate the combined impacts of water table management (WTM) and N fertilization rate on NO₃ ^--N concentration in the soil profile and in drain discharge. There were two water table treatments: free drainage (FD) with open drains at a 1.0 m depth from the soil surface and subirrigation (SI) with a target water table depth of 0.6 m below the soil surface, and two N fertilizer rates: 120 kg N ha^-1 (N₁₂₀) and 200 kg N ha^-1 (N₂₀₀) in a split-plot design. Compared to FD, SI reducedNO₃ ^--N concentration in the soil by up to 50% averaged over the two N rates. Concentrations of NO₃ ^--N in drainage water fromSI plots were lower than those from FD by 55 to 73%. These findings suggest that SI can be used as a means of reducing soil NO₃ ^--N pollution and drainage water NO₃ ^--N concentrations.  相似文献   

Factors associated with fusarium crown and root rot of asparagus outbreaks in quebec     

Hamel C  Vujanovic V  Nakano-Hylander A  Jeannotte R  St-Arnaud M 《Phytopathology》2005,95(8):867-873

ABSTRACT The Fusarium spp. causing Fusarium crown and root rot (FCRR) are ubiquitous and abundant in soils, but in contrast, disease expression is localized and sporadic. Previous studies have related FCRR infection to phenolic acids released by asparagus, to the repression of Mn-reducers in soil, and to various soil physicochemical conditions. Fifty commercial asparagus plantations were surveyed using an exploratory approach in order to pinpoint the ecological conditions associated with FCRR development. Twenty-eight variables were used to describe the soil environments of the asparagus crops as well as the influence of crop management practices used locally. The data set was analyzed both as a whole and parsed by main cultivars (Jersey Giant and Guelph Millenium). Both field conditions and percentage of field area affected by FCRR varied widely between asparagus plantations. Planting depth was positively correlated with percentage of field area affected by FCRR and, hence, deep planting may favor FCRR infection. Plantation age was positively correlated with percentage of field area affected by FCRR, while soil available Mn was inversely correlated. Most importantly, soil Mn availability decreased with increasing plantation age, supporting the hypothesis of an asparagusmediated negative impact on Mn-reducing bacteria and of the involvement of reduced Mn availability in FCRR development. Improving the availability of Mn could provide a solution to the problem of FCRR in asparagus plantations.  相似文献   

Two anatomic resources of canine pelvic limb muscles based on CT and MRI     

Sunico SK  Hamel C  Styner M  Robertson ID  Kornegay JN  Bettini C  Parks J  Wilber K  Smallwood JE  Thrall DE 《Veterinary radiology & ultrasound》2012,53(3):266-272

Advances in magnetic resonance (MR) imaging and three-dimensional (3D) modeling software provide the tools necessary to create sophisticated, interactive anatomic resources that can assist in the interpretation of MR images of extremities, and learning the structure and function of limb musculature. Modeling provides advantages over dissection or consultation of print atlases because of the associated speed, flexibility, 3D nature, and elimination of superimposed arrows and labels. Our goals were to create a diagnostic atlas of pelvic limb muscles that will facilitate interpretation of MR images of patients with muscle injury and to create a 3D model of the canine pelvic limb musculature to facilitate anatomic learning. To create these resources, we used structural segmentation of MR images, a process that groups image pixels into anatomically meaningful regions. The Diagnostic Atlas is an interactive, multiplanar, web-based MR atlas of the canine pelvic limb musculature that was created by manually segmenting clinically analogous MR sequences. Higher resolution volumetric MR and computed tomography (CT) data were segmented into separately labeled volumes of data and then transformed into a multilayered 3D computer model. The 3D Model serves as a resource for students of gross anatomy, encouraging integrative learning with its highly interactive and selective display capabilities. For clinicians, the 3D Model also serves to bridge the gap between topographic and tomographic anatomy, displaying both formats alongside, or even superimposed over each other. Both projects are hosted on an open-access website, http://3dvetanatomy.ncsu.edu/  相似文献   

Tick-borne fever caused by Anaplasma phagocytophilum in Germany: first laboratory confirmed case in a dairy cattle herd     

Nieder M  Silaghi C  Hamel D  Pfister K  Schmäschke R  Pfeffer M 《Tier?rztliche Praxis. Ausgabe G, Grosstiere/Nutztiere》2012,40(2):101-106

Four cows from North-West Germany have been diagnosed with tick-borne fever (TBF) based on the demonstration of morulae in neutrophilic granulocytes in their blood smears, positive signals in real-time PCR specific for Anaplasma phagocytophilum using DNA extracted from their buffy coats, and demonstration of specific antibodies in their sera using a commercially available immunofluorescence assay. Clinical findings included high fever, decreased milk production, lower limb edema with stiff walking, eye and nasal discharge, and depression. These signs developed about a week after the animals had been brought to the pasture for the first time in their life. All cows recovered after 5-15 days, although DNA of A.phagocytophilum could be detected by real-time PCR up to 6 weeks after onset of the disease. Considering the known prevalences of A.phagocytophilum in ticks in Germany and its detection in dogs and horses, we think that underdiagnosing of TBE in cattle is highly likely. Therefore TBF should be taken into account as differential diagnosis in case of high fever and/or a sudden decrease in milk production in pastured animals.  相似文献   

Aplysia gigantea toxicosis in 72 dogs in Western Australia     

RE Peacock  G Hosgood  KL Swindells  L Smart 《Australian veterinary journal》2013,91(7):292-295

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Eruption of first permanent incisors and live weight gain in grazing yearling Angora goats     

BA McGregor  KL Butler 《Australian veterinary journal》2013,91(5):179-184

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Rumination patterns,locomotion activity and milk yield for a dairy cow diagnosed with a left displaced abomasum     

S Talukder  KL Kerrisk  CEF Clark  SC Garcia  P Celi 《New Zealand veterinary journal》2013,61(3):180-181

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Oral vaccination of brushtail possums with BCG: Investigation into factors that may influence vaccine efficacy and determination of duration of protection     

BM Buddle  FE Aldwell  DL Keen  NA Parlane  KL Hamel  GW de Lisle 《New Zealand veterinary journal》2013,61(5):224-230

AIMS: To determine factors that may influence the efficacy of an oral pelleted vaccine containing Mycobacterium bovis bacille Calmette-Guérin (BCG) to induce protection of brushtail possums against tuberculosis. To determine the duration of protective immunity following oral administration of BCG.

METHODS: In Study 1, a group of possums (n=7) was immunised by feeding 10 pellets containing dead Pasteur BCG, followed 15 weeks later with a single pellet of live Pasteur BCG. At that time, four other groups of possums (n=7 per group) were given a single pellet of live Pasteur BCG orally, a single pellet of live Danish BCG orally, 10 pellets of live Pasteur BCG orally, or a subcutaneous injection of live Pasteur BCG. For the oral pelleted vaccines, BCG was formulated into a lipid matrix, and each pellet contained approximately 10⁷ colony forming units (cfu) of BCG, while the vaccine injected subcutaneously contained 10⁶ cfu of BCG. A sixth, non-vaccinated, group (n=7) served as a control. All possums were challenged by the aerosol route with a low dose of virulent M. bovis 7 weeks after vaccination, and killed 7–8 weeks after challenge. Protection against challenge with M. bovis was assessed from pathological and bacteriological findings.

In Study 2, lipid-formulated live Danish BCG was administered orally to three groups of possums (10–11 per group), and these possums were challenged with virulent M. bovis 8, 29 or 54 weeks later. The possums were killed 7 weeks after challenge, to assess protection in comparison to a non-vaccinated group.

RESULTS: The results from Study 1 showed that vaccine efficacy was not adversely affected by feeding dead BCG prior to live BCG. Feeding 10 vaccine pellets induced a level of protection similar to feeding a single pellet. Protection was similar when feeding possums a single pellet containing the Pasteur or Danish strains of BCG. All vaccinated groups had significantly reduced pathological changes or bacterial counts when compared to the non-vaccinated group. In Study 2, oral administration of Danish BCG induced protection against challenge with M. bovis, which persisted for at least 54 weeks after vaccination. Some protection was observed in possums challenged 54 weeks after vaccination, but this protection was significantly less than that observed in groups vaccinated 29 or 8 weeks prior to challenge. There was a strong relationship between the proportion of animals producing positive lymphocyte proliferation responses to M. bovis antigens and protection against challenge with M. bovis.

CONCLUSIONS: Factors considered potentially capable of interfering with vaccination, including feeding dead BCG to possums prior to feeding live BCG, feeding multiple doses of BCG at one time, and changing strains of BCG, were shown not to interfere with the acquisition of protective immune responses in possums. Protection against tuberculosis was undiminished up to 29 weeks after vaccination with BCG administered orally. It is concluded that vaccination of possums by feeding pellets containing BCG is a robust and efficient approach to enhance the resistance of these animals to tuberculosis.  相似文献