ABSTRACT This paper explores possible ways in which growth in Internet retailing (e‐retailing) may affect the spatial distribution of economic activities. After a brief overview of e‐retailing, a categorization of possible spatial impacts is introduced. These include impacts on the retail industry, such as substitution of e‐retail for brick‐and‐mortar retail, impacts on transportation, such as substitution of freight transportation for personal transportation in goods delivery, and pervasive impacts that affect the whole economy. The latter category includes uniform delivered pricing, spatial leveling of accessibility, and marketing strategies that target individuals rather than regions. The question of whether e‐retailing and brick‐and‐mortar retailing are truly substitutes is taken up in the next section, along with potential implications of multi‐channel retailing. The final section of the paper defines some critical research directions. 相似文献
1. Single strand conformation polymorphism analysis and DNA sequencing was performed in White Leghorn hens to explore the polymorphisms present in the promoter of the prolactin gene. The effects of different genotypes on egg production and quality traits were determined, and expression of the prolactin gene in different genotypes was quantified by real time-PCR.
2. Five genotypes and four alleles at each of two Fragments of the promoter were found, of which the FG genotype in Fragment 1 and the PQ genotype in Fragment 2 were the most predominant genotypes.
3. The genotypes of Fragment 1 had significant effects (P?0·05) on Haugh unit, albumen weight, albumen percentage and shell percentage at 40 weeks of age; egg weight and yolk index at 52 weeks of age; and egg weight at 64 weeks of age.
4. Prolactin expression in the genotypes of Fragment 1 differed significantly and GH genotyped birds had the highest level of expression. The genotypes of Fragment 2 did not show any significant differences of expression.
5. It was concluded that the prolactin gene promoter was highly polymorphic, and had significant effects on egg quality traits in White Leghorn hens. 相似文献
Filarial parasites, Litomosoides carinii and Setaria cervi, showed great susceptibility to the oxidants generated in vitro by the xanthine/xanthine-oxidase system. In order to counteract such injurious effects, both the filariids possessed an active antioxidant enzymes system. Superoxide dismutase, catalase and glutathione peroxidase were detected in appreciable amounts but glutathione reductase and glucose-6-phosphate dehydrogenase in very low quantities. The former three enzymes were also found to be released by the parasites into the ambient medium. The released enzymes may be responsible for scavenging the host-generated oxidants present in the immediate surroundings of the parasites and thereby enabling them to live comfortably in the host. This Institute-based antifilarial agent namely Compound 82/437 which is 2,2'-dicarbomethoxylamino-5,5'-dibenzimidazolylketone, markedly inhibited catalase and glutathione peroxidase of both L. carinii and S. cervi. The compound, therefore, appears to render the filariids prone to H2O2 toxicity leading to penultimate damage. 相似文献
Experiments were conducted to analyse the effect of 3-year-old grass plots, under a cut-and-carry system, on the yields of maize and groundnut crops, and at the same time to compare the relative importance of the water-stable aggregates and the nitrogen status of the soil. The N reserves, organic carbon and water-stable aggregate contents of soils were higher under grass plots than in the ploughed-up-fallow plots. Maize yields showed a close correlation with total soil N, mineralized N after incubation for 20 days, and water-stable aggregate contents; groundnut yields showed close correlation only with water-stable aggregates. The effects of the variations in soil N and in the water-stable aggregate content of the soil on the yields of maize and groundnuts were examined by multiple regression analysis of data from a large number of plots. 相似文献
A study on evapotranspiration from potato fields was conducted in the Lower Gangetic Plains of India. The input data required for the CROPWAT irrigation management model was collected, and evapotranspiration (ET) and irrigation water requirement (IWR) for potato crops were calculated using the model. Firstly, the CROPWAT model was validated by comparing simulated crop evapotranspiration (SET) with actual ET calculated through the field water balance method. Thereafter, SET and IWR for nine locations in the lower Gangetic plains of India were calculated for the period from 1996–1997 to 2008–2009, for the current situation (using 20-year-average weather data of the stations), and for elevated thermal conditions, i.e. considering 2 and 3 °C increases over the current temperature. The future change in IWR for potato up to 2050 was also calculated considering the projected climatic scenario generated by the PRECIS model. The CROPWAT calculated IWR values showed an increasing, though not statistically significant, trend in requirement of irrigation water for potato across the nine locations during the period from 1996–1997 to 2008–2009. At a temperature increase of 2 °C over normal, the mean SET of potato would increase by 0.06 mm per day and the average IWR would be 6.0 mm per season more. If the mean temperature would be 3 °C more than normal, the SET would be 0.16 mm day?1 higher and the IWR 16.6 mm. Also based on the projected climatic scenario generated by the PRECIS model, the future SET up to 2050 showed an increasing trend. The present study indicates increasing demand for irrigation water, which may significantly affect the agricultural scenario in the region. 相似文献
To see the deleterious effects of excess chromium (Cr) on carrot (Daucus carota L.) the cv. ‘Pusa Keshari’ was grown in refined sand under controlled glasshouse conditions with a complete nutrient solution (without Cr) for 48 days. On the 49th day, pots with two plants each were separated into three sets. One set served as a control. In each of the other two sets, Cr was supplied as dichromate at 0.1 and 0.5 mM to the basal nutrient solution. At 0.5 mM Cr toxicity symptoms appeared at d 52 (4 days after Cr supply) as reduction in growth and leaf size and loss of turgor. Old leaves became chlorotic and wilted. Chlorosis intensified and turned necrotic in another few days. These symptoms spread to next upper leaf. The development of chlorosis in leaves was delayed in plants receiving 0.1 mM Cr. At excess Cr (0.5 mM) in carrot, the biomass, concentration of chlorophylls a and b, iron (Fe), sulfur (S), and phosphorus (P) in shoots, and activity of catalase (CAT) in leaves decreased whereas the concentration of Cr and the activity of peroxidase (POX), superoxide dismutase (SOD), ribonuclease (RNAse), and acid phosphatase (A P) in leaves increased. 相似文献
Stage-specific haemagglutinating (HA) and precipitin antibodies (PA) to infective larvae (L3), adult worms and microfilariae (mf) have been demonstrated in sera of Mastomys natalensis during the course of Dipetalonema viteae infection using indirect haemagglutination (IHA) and Ouchterlony's gel-diffusion tests. L3-specific HA antibody titre was shown to be quite low and lasted for shorter period whereas adult-specific antibody response was significantly higher and persisted for longer duration (beyond day 240 post exposure). No precipitin antibody to L3 stage could be detected, however, significant adult-specific antibody was detected which ultimately tapered off by day 210 post exposure (p.e.). In contrast, mf-specific PA which appeared at the beginning of patency, never disappeared even at the late stage of infection. Mf-specific HA antibody appeared at early incubation period (day 15 p.e.) and after exhibiting two peaks, one in the midst of prepatent period (day 30 p.e.) and the other on day 180 p.e. persisted at low level during the late stage of infection when amicrofilaraemia developed. 相似文献