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371.
372.
李步青 《湖南环境生物职业技术学院学报》2007,13(1):30-32
利用电磁场软件模拟了行波管电磁线包磁场,以及在电磁线包磁场作用下电子注在慢波系统中的运动特性.模拟发现:随着边缘电子注入射慢波系统角度的增大,维持电子注在慢波系统内作螺旋运动所需的磁感应强度也增大;磁感应强度的大小主要影响慢波系统中心区域的电流密度,对边缘区域的影响很小;电子注主要其中于中心区域运动,其电流密度随半径增大呈指数减小.图4,表2,参5. 相似文献
373.
Hypnum cupressiforme epiphytic moss and tree bark (elm and holm oak) samples have been collected in three sites of the city of Florence in the period 1995-1998. Lead, zinc, copper, and cadmium were determined by differential pulse anodic stripping voltammetry (DPASV) in about 200 samples collected at different heights above ground. A new clean-up procedure by nitrogen jet has been followed and its efficiency has been also verified by electron microscopy (SEM and ESEM techniques). Lead median contents in moss and bark samples fall within the ranges of 0.052-0.86 and 0.20-1.30 μmoles g-1 (dry weight), resulting values for moss and bark are proportional to the vehicular traffic density. the increasing use of lead-free gasoline has not been followed by a decrease of lead moss concentration. 相似文献
374.
Richard D. Ashby Peter Cooke Daniel K. Y. Solaiman 《Journal of Polymers and the Environment》2007,15(3):179-187
Poly(hydroxyalkanoates) (PHAs) are a class of bacterially-derived polymers that are naturally biodegradable through the action
of extracellular depolymerase enzymes secreted by a number of different bacteria and fungi. In this paper we describe the
development of topographical imaging protocols (by both scanning electron microscopy; SEM, and confocal microscopy; CM) as
a means of monitoring the biodegradation of solution cast films of poly(3-hydroxybutanoate-co-3-hydroxyhexanoate) (P3HB/3HHx) and medium-chain-length (mcl-) PHA. Pseudomonas lemoignei and Comamonas P37C were used as sources for PHA depolymerase enzymes as these bacteria are known to degrade at least one of the polymers
in question. SEM revealed the bacterial colonization of the film surfaces while CM permitted the comparative assessment of
the roughness of the film surfaces upon exposure to the two bacterial strains. By dividing the total surface area of the film
(A′) by the total area of the scan (A) it was possible to monitor biodegradation by observing differences in the topography
of the film surface. Prior to inoculation, P3HB/3HHx films had an A′/A ratio of 1.06. A 24-h incubation with P. lemoignei increased the A′/A ratio to 1.47 while a 48- and 120-h incubation with Comamonas resulted in A′/A ratios of 1.16 and 1.33, respectively. These increases in the A′/A ratios over time demonstrated an increase
in the irregularity of the film surface, indicative of PHA polymer breakdown.
Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information
and does not imply recommendation or endorsement by the U.S. Department of Agriculture. 相似文献
375.
Shikha Raghuwanshi Tithi Agarwal Amit Yadav MGH Zaidi Yogesh Shouche Reeta Goel 《Chemistry and Ecology》2016,32(6):583-597
Bacterial strains with poly-3-hydroxybutyrate (PHB) degradation potential were isolated from waste yard soil samples of selected industrial sites in Uttarakhand, India, and two microbial consortia were developed, i.e. Consortium I comprises Pseudomonas sp. strain Rb10, Pseudomonas sp. strain Rb11 and Bacillus sp. strain Rb18, and Consortium II is composed of Lysinibacillus sp. strain Rb1, Pseudomonas sp. strain Rb13 and Pseudomonas sp. strain Rb19. The current study involved enrichment selection via liquid and semi-solid media, followed by isolation and screening of bacterial strains using PHB pellets and films. Furthermore, the identification and characterisation was done by triphasic approach. The utilisation of PHB by the characterised strains was confirmed by Fourier transform infrared spectroscopy and scanning electron microscopy. Moreover, the minimum inhibitory concentration of solubilised PHB was found to be 2.5?mg/mL, which was detected through ‘clear zone assay’. Further, the selection and biocompatibility testing of potential isolates were performed for the formation of bacterial consortia. Thus, the present work would provide direct and standardised protocol for screening and selection of potential microbiomes for biodegradation of polymers by overcoming the negative effect of organic solvents. Moreover, indigenously developed consortia would be evaluated for their in situ biodegradation potential against various bioplastic films. 相似文献
376.
Jiwan SINGH Yoon-Young CHANG Jae-Kyu YANG Seon-Hong KANG Janardhan Reddy KODURU 《Frontiers of Environmental Science & Engineering》2016,10(4):9
Phenol removal by n/m Fe in the presence of H2O2 was highly effective.
Increasing the amounts of n/m Fe and H2O2?increased the phenol removal rate.
Phenol removal was decreased with an increase in the concentration of phenol.
The natural pH (6.9) of the solution was highly effective for phenol removal.
The pseudo-first-order kinetics was best fitted for the degradation of phenol.
The study investigates the magnetic separation of Fe from automobile shredder residue (ASR) (<0.25 mm) and its application for phenol degradation in water. The magnetically separated Fe was subjected to an ultrasonically assisted acid treatment, and the degradation of phenol in an aqueous solution using nano/micro-size Fe (n/m Fe) was investigated in an effort to evaluate the possibility of utilizing n/m Fe to remove phenol from wastewater. The prepared n/m Fe was analyzed by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The effects of the dosages of n/mFe, pH, concentration of phenol and amount of H2O2 on phenol removal were evaluated. The results confirm that the phenol degradation rate was improved with an increase in the dosages of n/mFe and H2O2; however, the rate is reduced when the phenol concentration is higher. The degradation of phenol by n/mFe followed the pseudo-first-order kinetics. The value of the reaction rate constant (k) was increased as the amounts of n/m Fe and H2O2 increased. Conversely, the value of k was reduced when the concentration of phenol was increased. The probable mechanism behind the degradation of phenol by n/m Fe is the oxidation of phenol through hydroxyl radicals which are produced during the reaction between H2O2 and n/m Fe. 相似文献
377.
Jai Gopal Sharma 《毒物与环境化学》2013,95(2):367-371
Scanning electron microscopic (SEM) study of gills of Catla catla catla (17-day-old) exposed to UV-B radiation (145?µW?cm?2 at the water surface) for three different exposure times: 5, 10 and 15?min was conducted. Fish without UV-B exposure served as control. UV-B radiation damaged both gill filaments and lamellae. The intensity of damage was minimal in 5?min exposed fish, followed by 10?min exposed fish and maximal in 15?min. The gill epithelium was severely damaged in 15?min irradiated fish compared to control. Pavement cells (PVCs) were damaged and the numbers of microridges within PVCs decreased. The deep boundary of PVC was not clear. In some area of gill epithelium, PVCs were destroyed and mitochondrion-rich cells (MRCs) were exposed. The 5?min exposure reduced the number of microridges in the PVCs, but the boundary of PVCs was still visible. MRCs in the gill epithelium were not exposed in 5?min exposed fish. The damage to PVCs and subsequent exposure of MRCs in UV-B irradiated fish may hamper respiratory functions and disturb osmoregulation in catla. 相似文献
378.
Liver alterations were stereologically determined in five groups, each of 10 male and female Sprague–Dawley weanling rats fed PCB 105 (2,3,3′,4,4′-pentachlorobiphenyl) for 13 weeks at concentrations of 0.05, 0.5, 5, and 50?ppm mixed with corn oil. Animals from two groups receiving the oil in diets served as controls for each gender. A significant increase in mean volume fraction (VF) of smooth endoplasmic reticulum (SER) profiles was estimated in hepatocytes of female rats in 0.5, 5, and 50?ppm groups. A significant decrease in VF of mitochondria in female rats at 50?ppm was detected. In addition, a decrease in VF of lipid droplets was measured in female rats at 0.5, 5, and 50?ppm groups. No difference was found in VF of rough endoplasmic reticulum (RER) cisternae, and peroxisome profiles at any concentration of the PCB in either male or female animals as compared to baseline values from controls. A significant elevation of baseline VF for RER in female rats was detected in comparison with males. In the present study, no observable adverse effect level (NOAEL) for PCB 105 was estimated at <0.5?ppm for hepatocyte alterations in female Sprague–Dawley rats. 相似文献
379.
380.