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1.
Effects of feed ration levels (RLs) and age on sensory characteristics, fillet lipid content (LC) and fatty acid composition (FA) of rainbow trout, Oncorhynchus mykiss (Walbaum), fillet were investigated in a longitudinal feeding experiment. Daily RLs were administered as a percentage of the ration size necessary for expected maximum growth (RL100). Fish on RL50, RL75, RL100 and RL200 were sampled at 1.4, 2.0 and 2.4 years of age. Analyses of LC and FA were carried out on a fillet cross-section. Sensory analyses were performed by an expert panel using ranking and conventional profiling. RL had no effect on the intensity of fresh smell or any sensory characteristic of taste or consistency of fish on RLs over 75%, irrespective of age; fish on RL50, however, scored significantly lower for fresh taste and firmness. Age had no effect on the intensity of total taste, whereas fresh taste increased and rancidity decreased with increasing age irrespective of RL. LC related strongly to RL and age, and increased up to 2.0 years of age. An increase in LC resulted in a higher level of monounsaturated FA and a lower level of polyunsaturated FA. A restriction to RL75 had no negative effects on sensory characteristics, LC or FA of the fillet. 相似文献
2.
The effects on a number of soil physical and aeration parameters of compaction during spring pre-sowing operations were measured on a clay soil (49% clay). A soil-tyre contact stress of 200 kPa was applied by tractor tyres.
Yield of an oat crop was reduced by 30% as a result of compaction. Total porosity of the soil was reduced by 6% v/v owing to loss of pores > 60 μm, and water retention was increased. The resultant decrease in air-filled porosity greatly reduced gas diffusion and air permeability coefficients of the soil, and, for a time, O2 content of the soil atmosphere was significantly lowered in the compacted treatment. Penetrometer resistance after sowing was 3.5 MPa in the control and 4.5 MPa in the compacted treatment; in the latter, root growth was inhibited until the soil dried and cracked. By the end of June, canopy temperature measurements indicated water stress in the oat crop on compacted soil but not in that on the control.
The results obtained indicated that air permeability, measured in the field, of 1 mm s−1 provides a satisfactory single value below which crop growth is likely to be reduced. 相似文献
Yield of an oat crop was reduced by 30% as a result of compaction. Total porosity of the soil was reduced by 6% v/v owing to loss of pores > 60 μm, and water retention was increased. The resultant decrease in air-filled porosity greatly reduced gas diffusion and air permeability coefficients of the soil, and, for a time, O
The results obtained indicated that air permeability, measured in the field, of 1 mm s
3.
Soil changes after traffic with a tracked and a wheeled forest machine: a case study on a silt loam in Sweden 总被引：2，自引：0，他引：2
Alterations to some soil physical parameters were evaluatedafter passes by a tracked forest machine and a wheeled one ofequal mass (about 20 000 kg). Measurements were made after arange of machine passes, with a maximum of eight. The measuredsoil physical parameters were dry bulk density, penetrationresistance, intrinsic air permeability, saturated hydraulicconductivity, porosity and pore-size distribution. Rut depthwas also measured. Although the wheeled machine caused deeper ruts than the trackedone, alterations caused by the two machines to the measuredsoil parameters were similar, except in the uppermost 5–10cm. The wheeled machine caused a decrease in bulk density at5 cm depth, whereas the tracked machine caused an increase,despite its lower ground pressure. 相似文献
4.
T. JOHANSSON 《Weed Research》1985,25(1):39-45
Stumps of birches (Betula spp.) and aspens (Populus tremula L.) in thinning stands and on clear-felled areas were injected with herbicides by a modified bolt gun. Herbicides were formed into tablets and placed in a wedge of nylon. The wedge was fixed in the stem with the tablet placed close to the cambium. The tablets dissolved inside the tree. Injection doses were one tablet per 2·5 or 5 cm stump diameter and were done about 5 cm below the cut surface of the stump. The injector worked adequately. Injected stumps of both species produced few and shorter suckers than untreated stumps. 相似文献
5.
The effects on soil aeration of varying both the intensity and quantity of water applied per irrigation were investigated in a field experiment on a clay soil. Soil physical and soil aeration parameters were measured before, and for up to 7 days after irrigation. Irrigation increased the volumetric water content of the surface layer by approximately 8% v/v. However, periods of waterlogging were short on this soil. Significant decreases in soil oxygen content in the days after irrigation were caused by increased soil and root respiration. In terms of subsequent crop growth, the practice of applying 30 mm irrigation water at an intensity of 5 mm h−1 was shown to be superior to irrigations providing half this quantity (15 mm) or double this intensity (10 mm h −1 ). The lower intensity irrigations decreased soil permeability by homogeneous wetting and swelling, and thus more of the water applied was recovered in the soil. Approximately one third of the water applied at the higher intensity was lost through cracks, and wetting of the soil was less uniform. 相似文献
6.
Abstract. Continuous visual observations of the signs of development of UDN in fish kept in aquaria were correlated with light microscopical, transmission and scanning electron microscopical results. The initial signs of the disease are circles of pathologically-changed epidermis. The tight junctions of the squamous cells within these mucus-free areas disintegrate resulting in the loss of the protective function of the zonula occludens. Subsequently, the intercellular spaces dilate and communicate with the exterior. Necrosis of the epidermal cells due to hydromineral disturbances occur simultaneously with fungal infections and marked responses of the melanophores. It is suggested that the fungal infections are triggered by metabolites of the necrotic epidermal cells. The epidermal cells are shed and the fungus determines the further course of the disease which terminates in large ulcers covered with fungal hyphae. No substantial evidence for the presence of a virus could be recorded at any stage of the disease. It is concluded that the disease is a squames and the fungus appears as an opportunist which causes the eventual death of the fish. 相似文献
7.
The chemical composition of needle and leaf litter from Scots pine, Norway spruce and white birch in Scandinavian forests 总被引：8，自引：0，他引：8
Needle litter from 14 stands of Scots pine (Pinus silvestris,L.), 13 stands of Norway spruce (Picea abies (L.) Karst.) andleaf litter from three stands of white birch (Betula pubescensEhrh.) were analysed for chemical composition. The concentrationsof the elements N, P, K, Ca, Mg and Mn as well as solid organiccomponents (lignin, cellulose and hemicelluloses) and solubleswere determined. When the average chemical compositions werecompared the Scots pine needle litter was clearly the most nutrient-poorlitter type. Of the solid organic-chemical components the ligninfraction dominated in the spruce and birch litter whereas thecellulose dominated in the pine needle litter. When Norway spruce and Scots pine were growing in adjacent standson soils with the same bedrock origin the spruce litter hadsignificantly higher concentrations of nutrients (N, P, K, Ca,Mg, Mn) than the pine needle litter. At sites where Norway spruceand white birch were growing in adjacent stands, the birch leaflitter had generally higher concentrations of nutrients. However, significant or nearly significant differences were onlyobtained for Mg (P = 0.002), K (P = 0.056) and N (P = 0.087),probably due to the few replicates of stands compared. Concerningorganic chemical components, the spruce needle litter had significantlyhigher concentrations of lignin and mannan than all the otherlitters and lower levels of ethanol-soluble substances, celluloseand galactan than the pine needle litter. Further, it had lowerconcentrations of water solubles, rhamnan and xylan than thebirch litter. No relationships were established between the nutrient statusof the conifer litters and the site index H100 (the dominantheight of the trees at a reference age of 100 years) of thestands. Concentrations of solid carbohydrates in the litterswere, however, positively correlated with site index (P <0.001). Further, the concentration of nitrogen in the pine needlelitter was negatively correlated with the latitude of the sites(P < 0.01). The influence of litter chemistry on the decompositionof litter and nutrient cycling of forests is discussed. 相似文献
8.
T. JOHANSSON 《Weed Research》1988,28(5):353-358
Ten-year-old birches (Betula spp.) and 15-year-old aspens (Populus tremula L.) in field were cut and treated by the 'selective cutter', which also wetted the mantle area of the stump. Twenty per cent glyphosate, applied at the rate of 0?38 ml per cm stump diameter and 10% imazapyr at 0?14 ml per cm stump diameter, effectively killed the stumps or prevented sprouting. The cutter worked adequately. 相似文献
9.
Daily returns of all hatchery- and naturally reared Baltic salmon, Salmo salar L., to the Umealven (Sweden) were examined for an 18-year period, 1974–1991. Returns of naturally reared fish to the Norrfors fish ladder were more abundant than returns of hatchery fish with little obvious trend since the mid-seventies. Arrival date and median return date to the Norrfors fish ladder were consistently different by rearing type and sex with no overall trend since 1974. Hatchery-reared fish passed through the ladder later than naturally reared fish of the same sex and size. Males migrated later than females of the same size and rearing type. Larger, and presumably older, fish migrated earlier than smaller fish. There was little trend in the timing of the run since 1974. There was no simple relationship with river flows or river temperatures to explain the variation in most characteristics of the run. Pre-midsummer mean river temperatures were negatively correlated with arrival date but this was only significant for hatchery-reared males. The fishery catch data in the estuary indicated that the proportion of hatchery-reared adults decreased between the Umeätilven estuary and the fish ladder. There is evidence that larger fish took longer to travel from the estuary to the fish ladder. 相似文献
10.
ABSTRACT This paper focuses upon the ways in which characteristics of regions in regards to knowledge sources, communication opportunities, and absorptive capacity influence the development of innovation ideas among existing and potential entrepreneurs. We formulate a model where entrepreneurs or innovating firms introduce new products in a quasi‐temporal setting. Market conditions are characterised by monopolistic competition between varieties belonging to the same product group, in which there is entry and exit of varieties. A stochastic process is assumed to generate new innovation ideas as time goes by, and a firm (entrepreneur) who receives such an idea has to transform the idea to an innovation, which in the model is specified as a particular variety combined with a specific destination market. The theoretical model is used as a reference when formulating two regression models, with which we estimate how a set of regional characteristics are associated with the likelihood of innovation ideas across Swedish local labour market regions. In one model, we examine the emergence of new export varieties, and in the second model, we investigate the appearance of new export firms. Results are consistent with the assumption that knowledge and information flows have a positive influence on the frequency of arrival of innovation ideas to firms. 相似文献