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831.
Although the existence of robust inverted biomass pyramids (IBPs) seems paradoxical, they are well known to exist in planktonic communities, and have recently been discovered in pristine coral reefs and in a reef off the North Carolina coast. Understanding the underlying mechanisms which produce inverted biomass pyramids provides new ecological insights. Some ecologists hypothesize that “the high growth rate of prey and low death rate of predators” causes IBPs. However, we show this is not always the case (see Sections 3.1 and 4). We devise predator–prey models to describe three mechanisms that can lead to IBPs: (1) well-mixed populations with large prey turn-over rate, (2) well-mixed populations with prey immigration, and (3) non-mixed populations where the prey can hide in refuges. The three models are motivated by the three ecosystems where IBPs have been observed. We also devise three refuge mediated models, with explicit refuge size, which incorporate different prey responses in the refuge, and we discuss how these lead to IBPs. 相似文献
832.
Nath K Singh D Sharma YK 《Journal of environmental biology / Academy of Environmental Biology, India》2007,28(3):577-582
Under the reutilization and recycling strategy of industrial effluents, treated distillery and sugar factory mixed effluent was used in petridish culture experiments to investigate its effect on seed germination and seedling growth in wheat, garden pea, black gram and mustard. The seed germination and seedling growth were significantly reduced with increase in concentration of the effluent. The fresh matter was found significantly increased in barley (1.16 g per seedling in 25% dilution level of effluents in comparison to 0.93 in control), while other higher dilution levels reduce it. Wheat, garden pea, black gram, mustard invariably showed inhibition in fresh weight. Dry weight was found consistently reduced or unchanged in different treatments. Total chlorophyll contents in barley were significantly increased in different treatments (2.351 and 2.721 mg/g fresh weight of tissue at 25, 50% dilution levels in comparison to 1.781 of control) while in other crop it was reduced alloverthe treatments. Amylase activity in wheat, garden pea, black gram and mustard was reduced in all the treatments. Only in barley its level was enhanced from 0.76 to 0.85, 0.96, 0.81 in 25, 50, 75% dilution levels of the effluent mixture respectively Based on the data of different crops barley was found to be highly tolerant as the 25 and 50% dilution levels of combined effluents. It showed no change in germination %, while seedling growth was increased in lower dilution levels of combined effluent as compared to control Barley>garden pea>wheat>black gram>mustard gradually showed increased level of sensitivity respectively Most detrimental effects were seen in mustard. This toxicity might be due to excess of nutrients, beyond the limits of tolerance. Therefore, the higher concentration of mixed effluent was not advisable for irrigation purpose, however it could be used for irrigation purpose after proper treatment and dilution (one part treated effluent and five parts of available irrigation water), as this dilution level was found growth and yield promotory 相似文献
833.
Camptothecin (CPT), a broad spectrum antineoplastic agent, is known to induce oxidative stress and mitochondria are among the main sources of intracellular reactive oxygen species (ROS). We investigated the merit of vitamins E and C supplementation on CPT-induced mitochondrial alterations in vitro. Following treatment of isolated liver mitochondria with CPT, we assessed the mitochondrial membrane permeability transition (MPT), concentration of malondialdehyde, antioxidants and activities of the enzymes of the respiratory chain and Krebs cycle. Our results provide evidence that CPT caused mitochondrial swelling, increased lipid peroxidation and transition of mitochondrial permeability. The CPT lowered the levels of reduced mitochondrial thiols suggesting that thiol oxidation is the mechanism underlying CPT-induced MPT. Identical experiments were also performed after preincubating the mitochondria with vitamins E and C. It was found that vitamins E and C pretreatment inhibited the deleterious effects of CPT and loss of enzyme activity was restored by antioxidant supplementation. Our results suggest that the toxicity of CPT was mediated by an increase in ROS production by mitochondria. However, the addition of vitamins E or C ameliorated the oxidative stress. We propose that an attempt to counteract the deleterious consequences of chemotherapy with nutritional therapies may be a rational approach in superior patient care especially in a disease like cancer. 相似文献
834.
Potassium tetranitrodiammine cobaltate(III) K[Co(NH3)2(NO2)4] is a coordination complex having Co(III) as the central atom. Cobalt(III) compounds are being advocated for their anticarcinogenic potential. In the present study, we have for the first time evaluated this compound for its toxicity to rat RBC. The parameters studied include the effects of potassium tetranitrodiammine cobaltate(III) on GSH, GST, catalase, G6PD, acid phosphatase, GOT, and GPT. Scanning electron microscopy of RBCs of potassium tetranitrodiammine cobaltate(III) treated rats has also been carried out for evaluating its influence on the red cell morphology. The data showed that potassium tetranitrodiammine cobaltate(III) treatment causes marked biochemical changes in the rat RBCs along with changes in their shapes characterized by the formation of acanthocytes. The results thus suggest that acute administration of potassium tetranitrodiammine cobaltate(III) is potentially toxic to rat RBCs. 相似文献
835.
Yar tsa Gumba, the local name for Cordyceps sinensis, is an entomophilus fungus in the order Hypocreales and family Scolecosporaceae, found primarily in alpine and subalpine regions, from 3200 to 4000 m asl. The fungus is parasitic on caterpillars, primarily those in the genus Hepialus. Studies on Cordyceps sinensis indicate that the fungus may improve liver function, reduce cholesterol, adjust protein metabolism, inhibit lung carcinoma and treat aging disorders. In the last five years, since it was found in parts of Garhwal and Kumaun Himalaya, massive exploitation has occurred, leading to a drastic decrease in wild populations. This paper presents results of an exploration carried out on the fungus at several important sites, the mode of trafficking and suggested policy initiative for its sustainable exploitation. 相似文献
836.
In this study, we analysed the indigenous practices of agro-biodiversity, changing patterns of cropping systems and conservation of agriculturally important natural resources of rice–wheat-based agroecosystems. The research was carried out in three villages of Azamgarh district, eastern Uttar Pradesh, India. Participatory approaches and personal interviews were combined to collect the data from 180 farmers. The results indicated that resource-poor (RP) farmers, by applying traditional practices of natural resource conservation, outperform their rich (RR) counterparts in conserving agro-biodiversity. Increase in irrigation facilities, adoption of improved crop varieties, commercialisation of farming and socio-economic changes have threatened the agro-biodiversity and related natural resources of these agroecosystems. For most of the crops, the RP farmers had better production stability as compared to the RR ones because the former tend to apply more sustainable and ecologically sound indigenous practices. A negative growth rate was observed in the area/numbers and production of legumes, livestock, pasture lands and community forestry. Women, who are the local custodians of conserving indigenous biodiversity (uncultivated species) and crop varieties through localised knowledge and sociocultural institutions, had significantly higher knowledge on agro-biodiversity than men. We concluded that integration of farmers’ eco-friendly practices with formal science and policy-making in a participatory mode may enhance sustainability of functions of agroecosystem leading to the strengthening of adaptive practices in changing climate and socio-economic scenario. 相似文献
837.
Yunxue Xia Dong Qiu Zhong Lyv Jianshuai Zhang Narendra Singh Kaimin Shih Yuanyuan Tang 《Frontiers of Environmental Science & Engineering》2023,17(5):61
838.
The concentration of uranium has been assessed in drinking water samples collected from different locations in Bathinda district,
Punjab, India. The water samples are taken from hand pumps and tube wells. Uranium is determined using fission track technique.
Uranium concentration in the water samples varies from 2.23± 0.05 to 87.05± 0.29 μg/L. These values are compared with safe
limit values recommended for drinking water. The uranium concentration in almost all drinking water samples is found to be
more than the safe limit. Analysis of some heavy metals viz. Zn, Cd, Pb and Cu in water is made. The concentration of sodium,
potassium, calcium, magnesium, chlorine and total hardness along with the pH value and conductivity of the water samples are
measured. Some of the samples show stunningly high values of these parameters. 相似文献
839.
A. Pratheep Kumar Jitendra K. Pandey Bijendra Kumar R. P. Singh 《Journal of Polymers and the Environment》2006,14(2):203-212
Composites were prepared by two methods, (i) graft copolymerization (GFC) of isotactic polypropylene (PP) with maliec anhydride, (MAH) followed by esterification with coir fiber and (ii) by direct reactive mixing (DFC) of polypropylene (PP) and ethylene–propylene (EP) copolymers with MAH and peroxide with coir fiber. These composites, after molding in films (5×5 cm,
m thickness) were examined for susceptibility to biological attack by measuring the percentage weight loss in compost upto 6 months, periodically, and fungal colonization on surface of the samples, when kept as sole carbon source for the growth of Aspergillus niger in culture medium upto 40 days. Photodegradation was evaluated by monitoring the variations in FT-IR spectrum and crack formation after successive treatment with UV light (≥290 nm) for 0, 20, 50 and 100 h at 60°C in the presence of air. Specimens of virgin PP were taken as a reference during all period of photo and biodegradation studies. Significant changes were observed depending on the preparation methods during photodegradation and biodisintegration of composites. DFCs samples were disintegrated faster than GFCs during the composting whereas, in culture, GFCs were covered highly in well uniform way by fungi. It was observed that photo-oxidative ageing directly enhanced the biodegradability of composites as the increase in fungal growth rate and decrease in weight during composting were found. It was concluded that extent of compatibilization had a profound effect on photo-oxidation and biodisintegration of composite material; consequently ester bonds were main units during fungal consumption. Composition of monomers in copolymers was also showing significant effect on the degradability which decreased with increasing content of ethylene in ethylene–propylene (EP) copolymers. 相似文献
840.
Vishnu T. B. Singh Kh. Lakshman 《Journal of Material Cycles and Waste Management》2023,25(3):1519-1533
Journal of Material Cycles and Waste Management - In this study, the physical properties of modified asphalt binders and performance of asphalt mixes after the addition of different modifiers such... 相似文献