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排序方式: 共有149条查询结果,搜索用时 15 毫秒
1.
Incorrect labelling of plants in trade and misidentification are widespread. Likewise, in trade numerous names are being used for the ornamental aquatic plant known as ‘Kariba weed’, but rarely the correct scientific name Salvinia molesta Mitch. For inspection services of EPPO member countries, correct identification of S. molesta has become important since the species was added to the EPPO A2 List and the List of Union concern in accordance with EU regulation 1143/2014 based on an EPPO Pest Risk Analysis (PRA) for the species. Inspections and a targetted survey of Salvinia plants in trade in the Netherlands were performed and additional material was obtained from wild sources in South Africa, Hungary and the United States. Specimen identification was verified by comparison with the herbarium collection at Naturalis Biodiversity Center in Leiden and with the sequences available in NCBI GenBank database. This paper provides the tools to correctly identity the relevant Salvinia species. 相似文献
2.
Christian B. Sekomo Egide Nkuranga Diederik P. L. Rousseau Piet N. L. Lens 《Water, air, and soil pollution》2011,214(1-4):321-333
The Nyabugogo natural wetland (Kigali City, Rwanda) receives all kinds of untreated wastewaters, including those from industrial areas. This study monitored heavy metal concentrations (Cd, Cr, Cu, Pb, and Zn) in all environmental compartments of the swamp: water and sediment, the dominant plant species Cyperus papyrus, and fish (Clarias sp. and Oreochromis sp.) and Oligochaetes. Cr, Cu, and Zn concentrations in the water were generally below the WHO (2008) drinking water standards, whereas Cd and Pb were consistently above these limits. Except Cd, all metal concentrations were below the threshold levels for irrigation. The highest metal accumulation occurred in the sediment with up to 4.2 mg/kg for Cd, 68 mg/kg for Cu, 58.3 mg/kg for Pb, and 188.0 mg/kg for Zn, followed by accumulation in the roots of C. papyrus with up to 4.2 mg/kg for Cd, 45.8 mg/kg for Cr, 29.7 mg/kg for Cu, and 56.1 mg/kg for Pb. Except Cu and Zn, other heavy metal (Cd, Cr, and Pb) concentrations were high in Clarias sp., Oreochromis sp., and Oligochaetes. Therefore, there is a human health concern for people using water and products from the swamp. 相似文献
3.
Daas PJ Grolle K Van Vliet T Schols HA De Jongh HH 《Journal of agricultural and food chemistry》2002,50(15):4282-4289
In this paper the determination of the physical/rheological characteristics is described for a series of commercial galactomannans of which the structural details have been reported previously. Both solubility of the galactomannans and rheological properties of galactomannan solutions and galactomannan/xanthan mixtures were determined. Using a statistical analysis approach an attempt was undertaken to recognize correlations between structural and rheological data. The best correlation found was between the abundance of galactose substituents at a regular distance (type of galactomannan) and the storage modulus (G') of mixed galactomannan/xanthan gels, underscoring the hypothesis that branching hinders the formation of a network with xanthan gum. Also, the G' for the group of locust bean gums correlated with the degree of blockiness, that is, the size and occurrence of nonsubstituted regions on the mannose backbone. In addition, galactomannans displayed an apparent decrease in gelling ability with increasing average molecular weight. That G' also relates to the type of galactomannan can therefore partly be attributed to differences in average molecular weight for the various galactomannan types. However, within the series of locust bean gums tested, also an increase of G' with molecular weight was observed. This can be explained by the decreasing number of loose ends of the polymers and the concomitant increasing efficiency in network participation with increasing molecular weight. 相似文献
4.
5.
For control and enforcement purposes, all fishing vessels operating in European waters are equipped with satellite-based Vessel Monitoring by Satellite systems (VMS) recording their position at regular time intervals. VMS data are increasingly used by scientists to study spatial and temporal patterns of fishing activity and thus fishing impact (e.g. surface of sea bed trawled during a fishing trip). However, due to their low resolution (2 h basis), these data may provide a biased perception of fishing impact. We present here a method aiming at interpolating vessel trajectories from VMS data points to obtain higher-resolution data on vessel trajectories which in turn should provide improved estimates of the spatial and temporal patterns of fishing activity and hence fishing impact. This method is based on a spline interpolation technique, the cubic Hermite spline (cHs), using position, heading and speed to interpolate the trawl track of a vessel between two succeeding VMS data points. To take uncertainty of the interpolated track into account, the method also determines a confidence interval, which represents the spatial distribution of vessel presence probability between two successive VMS positions. The cHs method was compared to the straight line interpolation technique using a reference data set with intervals of 6 min which was assumed to represent the real trawl tracks. The results showed that the cHs method approximates the real trawl track markedly better than a straight line interpolation. The cHs method should therefore be preferred to the conventional straight line approach to interpolate vessel tracks in studies aiming at estimating fishing impact from VMS data. 相似文献
6.
The anti-colonization effect of porcine plasma powder against experimentally induced postweaning diarrhoea and oedema disease in just weaned piglets was examined. Piglets were infected with an Escherichia coli strain expressing F18ac fimbriae and producing SLTIIv- and LT-toxins. Reduced fecal excretion of the challenge strain and protection against clinical symptoms was obtained by daily supplementation of the feed with either 90 or 45 g of plasma powder. However, the piglets receiving 90 g of plasma powder a day showed diarrhoea and reduced weight gain compared to the piglets receiving 45 g of plasma powder a day. The diarrhoea was attributed to biogenic amines released from excessive protein in the diet. 相似文献
7.
8.
Growth and photosynthetic performance were analyzed in alloplasmic tomato at a high- (25/17 °C; HTR) and low-temperature regime (12/6 °C; LTR) in order to establish the role of cytoplasmic variation on low-temperature tolerance of tomato (Lycopersicon esculentum Mill.). Four alloplasmic tomato lines, containing the nuclear genome of tomato and the plastome of L. hirsutum LA 1777 Humb. & Bonpl., an accession collected at high-altitude in Peru, were reciprocally crossed with 11 tomato entries
with a high inbreeding level and a wide genetic variation, resulting in a set of 44 reciprocal crosses. Irrespective of growth
temperature, alloplasmic families with alien chloroplasts of L. hirsutum (h) were on average characterized by a high shoot biomass, a large leaf area, and a low specific leaf area in comparison with
their euplasmic counterparts. These results do not directly point to an advantageous effect of h-chloroplasts on biomass accumulation at low temperature but rather towards a small general beneficial effect on growth and/or
distribution of assimilates. Significant chloroplast-related differences in photosynthetic performance, however, were not
detected at both temperature regimes, indicating that h-chloroplasts can properly function in a variable nuclear background of L. esculentum. It is concluded that chloroplast substitution is not an effective method for breeding tomato plants with improved low-temperature
tolerance.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
9.
Piet?C.?N.?GroenewaldEmail author Carin?S.?Viljoen 《Journal of Agricultural, Biological & Environmental Statistics》2003,8(1):75-83
This article aims to determine the effect of certain covariates, such as season of kidding, parity, and time of kidding on
the characteristics of the lactation curve of Saanen dairy goats. Characteristics investigated are peak milk yield, time of
peak milk yield, total milk production, persistency, and the relationship between fat and protein in milk composition, as
well as between lactation curves of the same animal in successive years. The analysis is carried out using a hierarchical
Bayesian approach, together with Wood’s model, to model lactation. Posterior distributions of quantities of interest are obtained
by means of the Markov chain Monte Carlo (MCMC) methods. These clearly illustrate the significant effect of especially parity,
but also season and time of kidding on the characteristics of the lactation curve. Total and peak milk yield increase with
increasing parity up to about the third or fourth parity, while peak yield is later for first than for later parities. The
analysis also enables estimation of lactation characteristics of untested animals, prediction of future characteristics and
identification of exceptional animals. 相似文献
10.
Between October 1996 and May 1997, 94 horses which were suspected of being infected with strongyles were examined clinically, and samples of faeces were examined for strongyle eggs and cyathostome larvae (L4) and adults. Blood samples were monitored for total protein, albumin and beta-globulins. In 28 of the horses (30 per cent) cyathostome L4 and adults were detected in the faeces, and were significantly associated with the horses' condition, the occurrence of diarrhoea, with lower concentrations of total protein and albumin, and with higher percentages of beta-globulin. Thirty-four of the horses (36 per cent) were excreting strongyle eggs, but in these animals the associations were with high concentrations of total protein and albumin, and lower percentages of beta-globulin. The results showed that during the winter, a horse in poor condition which has diarrhoea, an albumin concentration less than 20 g/litre, and a ratio of albumin:globulin less than 0.7 is very likely to be infected with L4 and adult stages of cyathostomes. 相似文献