排序方式： 共有55条查询结果，搜索用时 46 毫秒
41.
S. Zaki Ph.D. S. Farag Ph.D. G. Abu Elreesh Ph.D. M. Elkady Ph.D. M. Nosier D. El Abd Ph.D. 《International Journal of Environmental Science and Technology》2011,8(4):831-840
The aim of this study was to look for high efficient bioflocculant-producing microorganisms. Among 36 bacterial colonies isolated from a crude petroleum oil sample, three of them as Bacillus subtilis and Pseudomonas spp. exhibited flocculation activity exceeding 90 % after 3 days of cultivation. They were identified by 16 S rDNA sequence analysis as Bacillus subtilis and Pseudomonas sp. Spectroscopic analysis of the polymers by nuclear magnetic resonance and fourier-transform infrared revealed that the polymers were glycoproteins. These polymers were soluble in water and insoluble in any organic solvents tested. The effects of bioflocculant dosage, temperature and pH on the flocculation activity were evaluated. The maximum bioflocculation activities were observed at an optimum bioflocculant dosage of 3.5 mg/L (strains Bacillus subtilis and Pseudomonas) and 5.0 mg/L (strain CPO14), respectively. In addition, these biopolymers were able to flocculate kaolin suspension (5 g/L) over a wide range of pH (pH 3–9) and temperature (5–50 °C) tested in the presence of CaCl2. The highest flocculation activities of strains CPO8, CPO13 and CPO14 were 96.03 %, 92.17 % and 97.59 %, respectively in the early stationary phase (at 24 h), while the cell production reached its maximum in the stationary phase (at 72 h). Their efficient flocculation capabilities suggest potential applications in industries. 相似文献
42.
Agricultural intensification has led to the extreme simplification of agricultural landscapes. The subsequent impoverishment of farmland plant communities can drive dramatic changes in the associated food webs of agricultural systems, with potential implications for vertebrate pest management. Weeds may provide alternative food sources for damaging species and thus contribute to reducing their damage, which is particularly desirable if the species is a valuable resource in its own right. Wild rabbits (Oryctolagus cuniculus) are a game species of great conservation value in the Iberian Peninsula that cause frequent damage to crops. Here we describe the dynamics of non-crop plant communities over an annual cycle in a semiarid Mediterranean agro-ecosystem, and discuss the potential linkages and implications for rabbit damage management. Overall, the availability of alternative food for rabbits was very low, especially in the most extensive habitat types, i.e. olive groves and vineyards. The seasonal pattern in plant productivity, which coincides with the phenology of rabbits in Mediterranean areas was only detectable in the less intensively managed habitat types. Scarce natural vegetation remnants retained the highest richness, diversity and plant cover, potentially acting as a refuge for both, plants and rabbits. Our results indicate that intensive management practices, through reducing alternative food sources for rabbits, are likely to promote conflict between hunters, farmers and conservationists in semiarid agro-ecosystems of Southern Spain. 相似文献
43.
From 2002 to 2010, the jumbo squid (Dosidicus gigas) has been regularly encountered in large numbers throughout the California Current System (CCS). This species, usually found in subtropical waters, could affect coastal pelagic ecosystems and fisheries as both predator and prey. Neither the abundance of jumbo squid nor the optimal ocean conditions in which they flourish are well known. To understand better the potential impacts of this species on both commercial fisheries and on food-web structure we collected nearly 900 specimens from waters of the CCS, covering over 20° of latitude, over a range of depths and seasons. We used demographic information (size, sex, and maturity state) and analyzed stomach contents using morphological and molecular methods to best understand the foraging ecology of this species in different habitats of the CCS. Squid were found to consume a broad array of prey. Prey in offshore waters generally reflected the forage base reported in previous studies (mainly mesopelagic fishes and squids), whereas in more coastal waters (shelf, shelf break and slope habitats) squid foraged on a much broader mix that included substantial numbers of coastal pelagic fishes (Pacific herring and northern anchovy, as well as osmerids and salmonids in northern waters) and groundfish (Pacific hake, several species of rockfish and flatfish). We propose a seasonal movement pattern, based on size and maturity distributions along with qualitative patterns of presence or absence, and discuss the relevance of both the movement and distribution of jumbo squid over space and time. We find that jumbo squid are a generalist predator, which feeds primarily on small, pelagic or mesopelagic micronekton but also on larger fishes when they are available. We also conclude that interactions with and potential impacts on ecosystems likely vary over space and time, in response to both seasonal movement patterns and highly variable year-to-year abundance of the squid themselves. 相似文献
44.
HWANG Jinik PARK So Yun SUH Sung-Suk PARK Mirye LEE Sukchan LEE Taek-Kyun 《海洋学报(英文版)》2016,35(8):44-50
Viral hemorrhagic septicemia virus (VHSV) and marine birnavirus (MABV) are the causative pathogens for some of the most explosive epidemics of emerging viral diseases in many Asian countries, leading to huge economic losses in aquaculture. Rapid molecular detection for surveillance or diagnosis has been a critical component in reducing the prevalence of pathogen infection. The loop-mediated isothermal amplification (LAMP) of DNA is currently one of the most commonly used molecular diagnostic tools, as it is simple, quick, and easy to amplify target DNA under isothermal conditions. In the present study, a novel and highly specific LAMP assay for the sensitive and rapid detection of VHSV and MABV infection in fish was developed. Using a set of synthesized primers matching a specific region of the genome, the efficiency and specificity of the LAMP assay were optimized in terms of the reaction temperature and DNA polymerase concentration, as they are the main determinants of the sensitivity and specificity of the LAMP assay. In particular, we demonstrated that our assay could be applied to efficient detection of VHSV and MABV infection in the wild fish, Paralichthys olivaceus. Our results demonstrate the simplicity and convenience of this method for the detection of viral infection in aquatic organisms. 相似文献
45.
《Marine Policy》2016
One of the main challenges of international environmental agreements is improving relevant policy actions to promote adequate environmental responses. To support the work of decision makers, recent studies have used environmental and social indicators to construct global and regional-scale indices. This study aimed to use the Ocean Health Index and the Management Ranking for Brazilian States to assess Brazil’s performance regarding the Aichi Biodiversity Targets (ABTs) for coastal and marine ecosystems. Thus, six ABTs were matched and their performance was evaluated. These ABTs focused on the following topics: pollution, fish and invertebrate stocks, pressures on coral, threatened species and their conservation, the contribution of biodiversity to carbon stocks and the national biodiversity strategy and action plan. However, although the indices used showed many pathways to explore how Brazil is performing, it is still complex to evaluate ABTs’ performance regarding coastal and marine ecosystems at a global and regional scale. 相似文献
46.
S. Zaki Ph.D. S. Farag Ph.D. 《International Journal of Environmental Science and Technology》2010,7(3):553-560
The biosorption of copper (II) from aqueous solution using different bacterial strains was studied. Copper-biosorbing bacteria were isolated from tannery effluent collected from Borg Al-Arab, Alexandria, Egypt. These isolates displayed different degrees of copper biosorption under aerobic conditions. Based on 16S rDNA gene sequence analysis, three of them (S2, S5 and S7) were identified as Chryseobacterium sp., Enterobacter sp. and Stenotrophomonas sp., respectively. Initial copper (II) ion concentrations from 25–250 mg/L at constant temperature 30 °C were studied. The residual copper (II) concentration and its toxicity effect in solution were determined using atomic absorption spectrophotometer and bioluminescent bioreporter. The bioluminescence inhibition of strain (S5) reached to 91.4 % as compared with the strain (S7) reached to 83.3 % at 225 mg/L of copper ion where the maximum biosorption efficiency for S5 and S7 were 71 % and 70.1 % correspondingly using atomic absorption. The bioluminescent bioreporter was proved to be fast and accurate technique for measurement the toxicity effect of residual copper (II) in solution. 相似文献
47.
D. Abd-El-haleem A. Amara S. Zaki A. Abulhamd G. Abulreesh 《International Journal of Environmental Science and Technology》2007,4(4):513-520
In the recent decade, biosynthesis of the degradable biopolymers polyhydroxyalkanotes in transgenic yeasts became an important research task. Most research strategies depend on either metabolic engineering or molecular approaches. In the present work, research compared PHA biosynthesis in two types of yeasts; Saccharomyces cerevisiae and a non-convenient Kloeckera spp. Yeast strains were equipped in their cytoplasm with the phaABCRe operon containing genes phbA, phbB and phbC of the PHA biosynthetic pathway of Ralstonia eutropha, which encode β-ketothiolase, NADPH-linked acetoacetyl-CoA reductase and PHA synthase, respectively. The transgenic strains Saccharomyces cerevisiae and Kloeckera sp. were able to produce PHA. The maximum content of the polymer detected in the recombinant strain INVSc1/PHA1 was 2.68 % and only poly-3-hydroxybutyrate (PHB) accumulated. However, the non-conventional transgenic strain KY1/PHA was able to accumulate as maximum of 7.06 % of the copolymer poly-(3-hydroxybutyrate-co-poly-3-hydroxyvalerate) (PHV). Western blot analysis confirmed expression of the phaABCRe operon in the transgenic yeast strains. The nature of the PHA thus produced by all tested strains was analyzed by 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. 相似文献
48.
Nicole Bethoux Monica Segovia Viviana Alvarez Jean-Yves Collot Philippe Charvis Audrey Gailler Tony Monfret 《Journal of South American Earth Sciences》2011,31(1):139-152
A seismic study of a segment of the convergent margin of Ecuador is presented. During the SISTEUR campaign a network of 24 Ocean Bottom Seismometers (OBS) was deployed on the Carnegie Ridge, one line along the main axes of the ridge and two lines across the strike of the edge of the ridge, during one month. This marine network was complemented with a land network of 20 stations distributed in two lines: one parallel to the margin and the other perpendicular to it.The seismic event recorded by these networks, were located using different crustal models defined from the wide-angle seismic data modeling. Relative location techniques were used to improve earthquake locations. Seismogram waveform modeling allowed us to constrain hypocentral location for events farther than ～50 km from the network. This modeling also provided additional information to constrain the focal mechanisms of these events. The upper limit of the Interplate Seismogenic Zone (ISZ) is estimated to be at a 10 km depth in the region. The background seismic activity of the upper plate provided new insights:1) A seismic cluster that reaches the base of the overriding plate is linked to the Jipijapa-Portoviejo fault. The reactivation of this Quaternary fault is confirmed by focal mechanisms that provide rupture planes parallel to its superficial projection (N10°–N25°).2) The focal mechanisms presented in this study are compatible with a homogeneous regional stress field corresponding to an E–W to ESE–WNW compression and an NNE–SSW extension. The presence of strike-slip deformation, with a reverse component, corresponds to the NNE escape of the North Andean Block. Normal faulting accommodating this movement suggests that this part of the North Andean Block cannot be considered as a rigid block. 相似文献
49.
《New Astronomy》2007,12(5):383-397
We illustrate the energy transfer during planetary flybys as a function of time using a number of flight mission examples. The energy transfer process is rather more complicated than a monotonic increase (or decrease) of energy with time. It exhibits temporary maxima and minima with time which then partially moderate before the asymptotic condition is obtained. The energy transfer to angular momentum is exhibited by an approximate Jacobi constant for the system.We demonstrate this with flybys that have shown unexplained behaviors: (i) the possible onset of the “Pioneer anomaly” with the gravity assist of Pioneer 11 by Saturn to hyperbolic orbit (as well as the Pioneer 10 hyperbolic gravity assist by Jupiter) and (ii) the Earth flyby anomalies of small increases in energy in the geocentric system (Galileo-I, NEAR, and Rosetta, in addition discussing the Cassini and Messenger flybys). Perhaps some small, as yet unrecognized effect in the energy-transfer process can shed light on these anomalies. 相似文献
50.
Physiological function emerges from complex biomolecular interactions (e.g., protein–protein) and control mechanisms that enable animals to respond and adapt to changes in their environment. Cell injury and pathology induced by pollutants and other stressors appears to involve the gradual and progressive dysfunction of complex biomolecular interactions, resulting in loss of integrated physiological interactions and homeostasis leading to a reduced capacity to respond effectively to stress. In order to determine whether complexity can be used as an indicator of health, the hypothesis that pathology involves a loss of biological complexity has been tested using a generic physiological interaction network. System complexity was evaluated using Eulerian cycles and connectedness (connectance%) for estimating topological complexity and application of network theory (i.e., analysis of scale-free networks and network diameter). The complexity of the whole system increases when sub-systems, such as detoxication and anti-oxidant protective processes, augmented autophagy, protein degradation and induction of stress proteins, are up-regulated and start to interact significantly as part of a response to low-level stress (i.e., biphasic or hormetic response). However, with increasing severity of stress, cell injury and higher-level functional impairment lead to physiological dysfunction and breakdown of the whole interaction network with consequent loss of complexity. In summary for the model described here, network and graph theory appear to provide a mathematical formalism that can facilitate the system-level interpretation of health and dysfunction in living cells. 相似文献