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51.
Modern ideas regarding soil successions and heterogeneity of podsolic soils in the conditions of various biogeocenoses are considered. Functional interdependence between the given natural phenomena is shown. Within the frameworks of macrosuccession, there are adduced examples of soil successions of various genesis and scale. The analysis of such soil successions allows estimating simultaneously the spatiotemporal components of heterogeneity of soils. Windfall soil complexes are a good illustration of soil succession shown at various levels of the organization of a soil body.  相似文献   
52.
Sediment cores collected from several lakes in northern Canada have been analyzed for mercury and several other chemical contaminants. Sites ranged from the Experimental Lakes Area of northwestern Ontario, north to Cornwallis Island, and west to the southern Yukon. Cores were sliced at sites of collection and individual slices were freeze dried and analyzed for Pb-210 and Cs-137 to estimate average time intervals of deposition. The earliest date estimated by Pb-210 was about 1850, and mercury concentrations in some lakes were clearly increasing before then, assuming no vertical movements of mercury within the sediments. Extrapolation of dates downward to deeper slices, assuming a constant sedimentation rate, indicated that in some lakes mercury inputs increased slowly even in the 1500's, more rapidly after 1750, and more rapidly yet over the current century. These increases are interpreted as increased fluxes of mercury to the lakes as a result of long-range transport of atmospheric mercury, since there are no local industrial sources of mercury. Slices taken near the bottom of a core are taken to estimate the geological component while elevations in excess of that in surface slices are taken to represent contamination from fallout. This partitioning suggests that sediments in the eastern Northwest Territories are dominated by pollution, while those from the western Northwest Territories are influenced more by their geological settings. Two cores from Hudson Bay suggest that mercury is increasing there too, but has not yet exceeded geological sources. Mercury shows little or no tendency to decline in the most recent slices; indicating that inputs of mercury remain at or near their historical maxima. Given relatively high and continuing inputs of mercury to northern lakes it seems likely that some portion of that mercury may find its way into the food chain, hence the long-term prospect is for increasing levels of mercury in northern fish.  相似文献   
53.
The aim was to determine the inoculation density above which Scots pine (Pinus sylvestris) is overcome by the blue‐stain fungus Ophiostoma ips that is associated with the bark beetle Ips sexdentatus. In north‐western Spain, stems of 16 Scots pines were inoculated at various densities (0, 400, 800 or 1600 inoculi/m2) along circumferential 100 or 150 cm wide inoculation belts. Each inoculum consisted of a 5 mm diameter cylinder of malt extract agar colonized by the fungus. Three months later, all trees were harvested and trunk resinosis and foliage colour were visually assessed. The percentage of healthy, desiccated, resin soaked, and blue‐stained sapwood, as well as growth productivity indices, were calculated from stem disks cut from within the inoculated zone of each tree. Sapwood‐specific hydraulic conductivity (Ks) of each tree was measured in the middle of the inoculated zone. All parameters of tree vigour changed dramatically to the worse when inoculation densities were above 400 inoculi/m2, and foliage changed from green to yellow‐green or yellow when an inoculation density of 800 instead of 400 was used. The percentage loss of sapwood‐specific conductivity (PLC) increased from 30 to 90% and the percentage of healthy, conductive sapwood dropped from 85 to 35% at 800 inoculi/m2. No effect of the width of the inoculation belt was observed, and there was no relationship between tree productivity indices and the level of resistance. A non‐linear negative relationship was found between PLC and the percentage of healthy sapwood. It is concluded that tree resistance was overcome and that trees were going to die when the inoculation density was ≥800 inoculi/m2.  相似文献   
54.
Integral diffusion coefficients for K in two contrasting soils, containing different levels of exchangeable K, are calculated from measurements of diffusive flux to a hydrogen resin paper. The diffusion coefficients are larger, the higher the exchangeable K level or moisture content. Diffusive flux of K in these soils can be accounted for entirely by diffusion through the soil solution in the pores. Impedance factors calculated compare satisfactorily with values for similar soils reported by other workers. The concentration dependence of the diffusion coefficient is shown to be causally related to the nature of the sorption isotherm. A method for estimating the differential diffusion coefficient at any concentration is described. It can also be calculated from the slope of the sorption isotherm at the chosen concentration, if the value of the impedance factor at the relevant moisture content is known and if diffusion other than through solution only is negligible.  相似文献   
55.
1. Two experiments were conducted with 1056 1-d-old Cobb x Cobb feather-sexed broiler chicks, to determine the relative nicotinic acid biopotencies of nicotinic acid (NA) and nicotinamide (NAm). 2. Two methods were used: the slope-ratio technique and the broken-line model. 3. In experiment 1, using the slope-ratio technique, NAm was 0.82 as active as NA in promoting growth to 21 d of age. In experiment 2 NAm was 0.96 as bipotent as NA. 4. Applying the broken-line model to the body weight data at 21 d of age for both NA and NAm in experiment 1, it was found that NAm had approximately 0.82 NA activity. The same analysis applied to the data of experiment 2 indicated that the biopotency of NAm was 1.09. 5. A t-test of the slope-ratio values obtained in both experiments indicated that the average (0.89) was not significantly different from 1.0. 6. It was concluded that the relative biopotencies of NA and NAm in broiler chicks fed a maize-soyabean meal diet were similar.  相似文献   
56.
Specific contrast ultrasound is widely applied in diagnostic procedures on humans but remains underused in veterinary medicine. The objective of this study was to evaluate the use of microbubble-based contrast for rapid ultrasonographic diagnosis of thrombosis in small animals, using male New Zealand white rabbits (average weight about 3.5 kg) as a model. It was hypothesized that the use of microbubble-based contrast agents will result in a faster and more precise diagnosis in our model of thrombosis. A pro-coagulant environment had been previously established by combining endothelial denudation and external vessel wall damage. Visualization of thrombi was achieved by application of contrast microbubbles [sterically stabilized, phospholipid-based microbubbles filled with sulfur hexafluoride (SF6) gas] and ultrasonography. As a result, rapid and clear diagnosis of thrombi in aorta abdominalis was achieved within 10 to 30 s (mean: 17.3 s) by applying microbubbles as an ultrasound contrast medium. In the control group, diagnosis was not possible or took 90 to 180 s. Therefore, sterically stabilized microbubbles were found to be a suitable contrast agent for the rapid diagnosis of thrombi in an experimental model in rabbits. This contrast agent could be of practical importance in small animal practice for rapid diagnosis of thrombosis.  相似文献   
57.
Since cattle are widely infected by bovine viral diarrhea virus (BVDV) in India, we searched for pestivirus infection in yaks. Of 71 pure and crossbred yaks from Himalayan region, pestivirus antigen was detected by Ag-ELISA in three animals. Pestivirus in leukocyte and cell culture isolated virus samples originating from positive yaks was also confirmed by RT-PCR using panpestivirus specific primers selected from 5'-untranslated region (5' UTR). The 5' UTR, N(pro) and E2 regions were sequenced and used for genetic typing. Phylogenetic analysis revealed that pestiviruses detected in three Himalayan yaks were similar genetically, belonging to BVDV-1. Antigenic characterisation of yak pestivirus also confirmed the typing as BVDV-1. This is the first report on the identification of BVDV type 1 in yaks.  相似文献   
58.
The IgG index measures the intrathecal immunoglobulin production and it is a useful tool for diagnosis of inflammatory diseases involving the central nervous system. This index is based on the precise quantification of albumin and IgG in canine cerebrospinal fluid and serum. Here, we report the development of an indirect competitive ELISAs for the detection of both antigens. Thirty-two dogs were included in this study, divided into three experimental groups. Group A was composed of 22 healthy animals, as determined by standard clinical examination. In group B, six animals, presented neurological pathologies associated with endogenous IgG production and, in group C four animals presented neurological diseases or symptoms not associated with intrathecal IgG production. Cerebrospinal fluid and serum samples were obtained from these animals. As expected, by using the indirect ELISAs proposed here, the IgG indexes obtained in healthy animals (A) were 0.371+/-0.252 (SD). In B and C, the values (3.002+/-1.897; 0.36+/-0.306, respectively), were in agreement with the pathologic conditions of the individuals in each group. Thus, the immunometric competition ELISA methods proposed here allow the discrimination of abnormal intrathecal IgG production, in a variety of inflammatory pathologic conditions of the central nervous system.  相似文献   
59.
OBJECTIVE: To evaluate the pharmacokinetics of ophthalmic ciprofloxacin in the tear film of normal mesocephalic and brachycephalic dogs. ANIMALS STUDIED: Twenty mesocephalic dogs and 15 brachycephalic dogs. PROCEDURES: Thirty-five microliters of ciprofloxacin were placed on the cornea of both eyes of each dog. Five brachycephalic dogs were used twice. A tear-test strip placed in the ventral cul de sac for 30 s was used to obtain samples. The tear film of each eye was sampled once at eight time-points post administration, resulting in five samples at each time-point. Samples were evaluated using high performance liquid chromatography. Data from the two skull types were compared using the unpaired two-tailed t-test. RESULTS: The mean concentration of ciprofloxacin in the tears of mesocephalic dogs was 192.8 +/- 269.97, 140.6 +/- 91.06, 56.60 +/- 28.47, 13.6 +/- 6.3, 43.25 +/- 59.71, 16.6 +/- 10.62, 15.6 +/- 13.16 and 6.25 +/- 9.84 microg/g at 5, 10, 15, 30 min and 1, 2, 4 and 6 h, respectively. The mean concentration of ciprofloxacin in the tears of brachycephalic dogs was 272.6 +/- 106.21, 144.4 +/- 142.32, 131.2 +/- 147.07, 75 +/- 80.07, 40.8 +/- 30.35, 35 +/- 21.98, 52.75 +/- 51.87 and 8.6 +/- 12.10 microg/g at 5, 10, 15, 30 min and 1, 2, 4 and 6 h, respectively. There was no statistical difference in tear concentration at any time-point between skull types. CONCLUSIONS: Topical application of ciprofloxacin resulted in a mean tear concentration of ciprofloxacin that remained above the MIC(90) levels for most pathogenic bacteria for 6 h in normal mesocephalic and brachycephalic dogs.  相似文献   
60.
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