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101.
The study was performed on 16 Holstein‐Friesian calves divided into two groups of eight animals each. The first group was composed of calves whose mothers did not receive selenium supplements (Se0). The second group consisted of calves whose mothers were administered intramuscular injections of a selenium and vitamin E supplement containing 0.5 of sodium selenite/ml and 50 mg of tocopherol acetate/ml in a single dose of 30 ml (Se30) ml, 10 days before the expected parturition date (10 ± 2 days). The calves were fed 2.5 L of the mother's colostrum administered by stomach tube 2 hr after birth and another 2 L 6 hr after birth. Blood from all calves was collected 7 times from external jugular vein (day 0–before colostrum administration and on the 2nd, 3rd, 4th, 7th, 14th and 21st days of life) for analyses of selenium, ceruloplasmin, transferrin, lactoferrin, immunoglobulin G (IgG) concentrations and gamma‐glutamyl transferase (GGT) and lysozyme activity. Selenium concentration was significantly higher in calves whose mothers received selenium supplements than in the offspring of non‐supplemented cows until 72 hr after birth (p ≤ .05). Lysozyme and GGTP activity and IgG concentration were significantly higher in the S30 group during the entire experiment (p ≤ .05). Supplementation of selenium to the mothers did not influence the ceruloplasmin, lactoferrin and transferrin levels in calves. A single injection of a selenium supplement administered to cows during late pregnancy increases selenium levels in calves and enhances passive transfer from the mother to the offspring.  相似文献   
102.
Principal component analysis (PCA) was used to evaluate the results of standard fiber analyses, determinations of charge, electron spectroscopy for chemical analysis (ESCA) measurements, and selective staining of kraft fibers prebleached with oxygen, followed by hydrogen peroxide or ozone. The majority of data variance is explained by the lignin content in fibers and by polarity (hydrophilicity vs hydrophobicity) of functional groups. The lignin determination methods (kappa number, C1 (ESCA), selective staining) gave similar but not equal results, because they measure different parts of lignin. The determination methods of the charged groups (total charge, surface charge, C4 (ESCA), and hexenuronic acids) also gave similar but not equal results. The results of staining by using cationic dyes do not correlate with the quantity of anionic (mainly carboxylic) groups in fibers, regardless of whether the dyes are selective for lignin or hemicellulose. Hydrogen bonding and hydrophobic interactions seem to overrule ionic interactions between dyes and fibers. Therefore, the majority of bonds formed between fibers themselves, as well as between fibers and paper additives, can to a great extent be expected to have the character of hydrogen bonds.  相似文献   
103.
104.

Context

Urban environments create a wide range of habitats that harbour a great diversity of plant species, many of which are of alien origin. For future urban planning and management of the green areas within the city, understanding of the spatial distribution of invasive alien species is of great importance.

Objectives

Our main aim was to assess how availability of different ecosystem types within a city area, as well as several parameters describing urban structure interact in determining the cover and identity of invasive alien species.

Methods

We studied the distribution of chosen invasive plant species in a mid-sized city in the Czech Republic, central Europe, on a gradient of equal sized cells from the city centre to its outskirts.

Results

A great amount of variation was explained by spatial predictors but not shared with any measured variables. The species cover of invasive species decreased with increasing proportion of urban greenery and distance from the city centre, but increased with habitat richness; road margins, ruderal sites, and railway sites were richest in invasive species. In contrast, the total number of invasive species in cells significantly decreased with increasing distance from the city centre, but increased with habitat richness.

Conclusions

Our results suggest that different invasive species prefer habitats in the vicinity of the city centre and at its periphery and the spatial structure and habitat quality of the urban landscape needs to be taken into account, in efforts to manage alien plant species invasions in urban environments.
  相似文献   
105.
Increasing the amount of n‐3 PUFA in carp meat is one of the most important tasks in enhancing its overall quality. However, the relative influence of supplemental feed and natural feed on the FA profile of cultivated carp flesh is not well documented, making it difficult to choose the most efficient strategy. Carp diet composition and diet and flesh fatty acid profiles were simultaneously followed in order to determine the influence of pelleted feed compared to natural feed on fatty acid profiles of carp tissues. Pelleted feed clearly dominated over zooplankton and Chironomidae in the carp diet, producing carp tissue fatty acid profiles closely resembling those of pelleted feed. However, increase in the abundance of zooplankton over the course of the investigation resulting in concomitant increase of its proportion in feed bulk was in strong positive correlation with increase in n‐3 HUFA in the dorsal muscle. n‐3 PUFA enrichment of supplemental feed could be the dominant mechanism in production of carp meat rich in n‐3 PUFA. However, even a small increase in natural feed availability could significantly change the diet of common carp and result in considerable improvement of meat quality with regard to n‐3 HUFA content.  相似文献   
106.
Snow samples from 18 sites in Estonia were collected in February and March 1996 after 72–110 days of permanent snow cover. Three snow layers corresponding to different snow accumulation periods were separated in each sampling site. Snow water samples were analysed for sulphate (SO4 2-), nitrate (NO3 -), and chloride (Cl-) ions and elemental composition. Deposition fluxes of 27 chemical species were used for factor, cluster and correlation analysis. The effects of cement dust, oil shale fly ash, sulphur dioxide and chlorine from emissions of thermal power plants were distinguished. A large number of trace metals are strongly correlated with each other (R > 0.8) and with macro-components (except NO3 -), which refers to a common origin, identified as the mineral part of oil shale. Deposition fluxes of Ca, Mg, SO4 2- and a number of mineral components exceed near the power plants 1–2 decimal orders the background value. The deposition fluxes in forested sites are up to 2 times higher than in open land sites. This difference may be caused by more efficient turbulent transfer over rougher surface. It is suggested, that NO3 - and Zn originate mainly and Pb, Cd and Cu partially from non-local or diffuse sources (traffic, domestic heating, far transport). The results of this research could be used to evaluate the air pollution deposition models and for ecological impact estimations.  相似文献   
107.
This research investigated the influence of two flame retardant (FR) mixtures consisting melamine cyanurate (MeCy) and aluminum diethylphosphinate (AlPi), and MeCy and sodium aluminosilicate (SASi) at different weight ratios, on the flammability, thermal behavior and mechanical properties of polyamide 6 (PA6) composite yarns produced by meltspinning. The morphological and chemical properties of PA6/FR filaments were investigated by scanning electron microscopy and Fourier-transform infrared spectroscopy, flame retardancy by vertical burning test UL-94, thermal behavior by thermogravimetric and differential scanning calorimetric analyses, and mechanical properties by tensile tests. The results indicate that within the UL 94 V2 rating, the composite yarns differed significantly from each other in their burning and dripping behavior. The incorporation of both mixtures, MeCy+AlPi and MeCy+SASi, into the PA6/FR yarns significantly decreased the afterflame time relative to pristine PA6, confirming a lower production of flammable volatiles. This phenomenon was attributed mainly to MeCy, which caused an immediate extinguishment of the flame after the withdrawal of the igniting flame. Compared to one component MeCy, the incorporation of the MeCy+SASi mixture enhanced the thermooxidative stability of the PA6/FR yarns because of their additive effect at higher concentrations. In contrast, an antagonistic effect was obtained for the MeCy+AlPi mixture, irrespective of the concentration. Since the incorporation of MeCy+SASi did not drastically reduce the tensile properties of filaments, this mixture enables the production of the PA6/MeCy+SASi composite yarns with the enhanced flame retardancy and thermo-oxidative stability.  相似文献   
108.
The abundance and distribution of leptocephalus larvae of the European eel (Anguilla anguilla, Anguillidae) were examined using ten historic and recent Sargasso Sea expeditions that were selected on the basis of having the largest number of sampling stations and highest catches. The surveys cover the period 1920–2014. Station data were recalculated to the same unit of larval density per unit area, and the irregular station positions were transformed to a regular spatial grid to allow calculation of comparable measures of abundance of the youngest (0+) leptocephalus cohort. The result is that the mean and maximum densities of 0+ leptocephali after 2007 on average have decreased by 70%–80% from the densities during the period before the drastic decrease in glass eel recruitment, which started in the 1980s. This is of the same magnitude as the change in spawning stock, if the total continental commercial landings are used as a proxy. In the same period, the glass eel recruitment in Europe has decreased by more than 95%. The conclusion is that a major cause for the recruitment decrease may be an increased leptocephalus mortality during the oceanic phase or a large geographic shift in glass eel arrival. Combining the survey data, the spatial distribution of 0+ leptocephali was concentrated south of the northernmost front in the Subtropical Convergence Zone, but high densities were also found far south of the front in the western part of the distribution area and leptocephali were present also north of the average frontal position.  相似文献   
109.
Delphinidin has been found to possess DNA strand-breaking properties in cell culture. In the present study, we demonstrated that the extent of DNA damage by delphinidin is not affected by the expression of tyrosyl-DNA-phosphodiesterase 1, indicating that the induction of DNA strand breaks is not predominantly topoisomerase-mediated. However, the DNA-damaging properties of delphinidin were decreased by the addition of catalase to the cell culture medium, counteracting delphinidin-mediated hydrogen peroxide formation. Under these conditions, delphinidin showed clearly antioxidative properties in HT29 cells, preventing menadione-induced oxidative DNA damage. In contrast, in the absence of catalase, delphinidin lacked antioxidative properties. In conclusion, delphinidin acted as an effective antioxidant within intact cells if the formation of hydrogen peroxide was prevented. In the absence of catalase, the accumulated hydrogen peroxide appears to play a substantial role for the observed DNA-damaging properties of delphinidin and the apparent lack of antioxidative properties of this anthocyanidin.  相似文献   
110.
The multiple-stressor effects of air pollution, nutrient and water availability are the key issues of present forest ecosystem research. However, too little is known about the seasonal effect of pollutants on tree crown defoliation and their interaction with changes in climate. Therefore, data on seasonal variation in air pollution, including surface ozone, deposition of acidifying compounds and meteorological conditions, were tested against pine defoliation to identify the periods when the effect of the considered contaminants is most pronounced. The findings of the study revealed that a higher level of air concentrations of acidifying pollutants and their deposition was observed during the dormant period, with the exception of only ΣNH4+ air concentrations and their monthly deposition. An increase in precipitation over the vegetation period and mean monthly temperature from September to December, as well as a decrease in temperature and precipitation over the remaining months of the dormant period represented the climate change condition over the 14-year period in the observed region. Detected changes in the considered parameters during the dormant period were found to be most significant to changes in pine crown defoliation. Therefore, we concluded that climate changes, if they occur by the detected scenarios, should mitigate the negative effect of air pollutants and acid deposition on pine crown condition.  相似文献   
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