排序方式： 共有41条查询结果，搜索用时 15 毫秒
21.
Kouzayha A Al Iskandarani M Mokh S Rabaa AR Budzinski H Jaber F 《Journal of agricultural and food chemistry》2011,59(14):7592-7600
A fast and reliable method for the determination of polycyclic aromatic hydrocarbons (PAHs) in water samples by solid-phase extraction (SPE) using centrifugation has been developed and optimized. A silica-based C18 cartridge was used; parameters affecting the extraction procedure such as type and volume of the elution solvent, breakthrough volume of the percolated water sample, drying of the sorbent, and evaporation of the elute have been studied. The innovation of this work was the examination of the use of a centrifugation technique in both the drying and elution steps. When combined with centrifugation, the volume of the elution solvent was reduced to 1 mL and the time for sorbent drying decreased also to 10 min under vacuum. Under optimal conditions, recoveries for the 16 U.S. EPA PAHs were between 70 and 85% and the relative standard deviation varied between 1 and 14%. Surrogate standard recoveries were similarly between 61 and 94% with a relative standard deviation between 2 and 15%. The simplicity of the described method, use of less of organic solvent, short procedure time, and good recoveries demonstrate the advantages of this environmentally friendly approach for routine analysis of numerous samples. 相似文献
22.
Gopal Panthi Nasser A. M. Barakat Prabodh Risal Ayman Yousef Bishweshwar Pant Afeesh R. Unnithan Hak Yong Kim 《Fibers and Polymers》2013,14(5):718-723
Easy fabrication, porosity, good mechanical properties, and composition controllable of the electrospun nanofiber mat make this material a promising candidate for wound dressing applications. In the present study, nylon6/gelatin electrospun nanofiber mats are introduced as novel wound dressing materials. The introduced mats were synthesized by electrospinning of nylon6 and gelatin mixtures, three mats containing different gelatin content were prepared; 10, 20 and 30 wt%. Interestingly, addition of the gelatin did not affect the mechanical properties of the nylon 6, moreover the mat containing 10 wt% gelatin revealed higher mechanical properties due to formation of spider-net like structure from very thin nanofibers (～10 nm diameter) bonding the main nanofibers. Biologically study indicates that gelatin incorporation strongly enhances the bioactivity performance as increasing the gelatin content linearly increases the MC3T3-E1 cell attachment. Overall, the obtained results recommend exploiting the introduced mats as wound dressing material. 相似文献
23.
24.
Aissaoui Fatima Hedjal-Chebheb Mariam Soltani Abir Haouel-Hamdi Soumaya Talhi Oualid Ziani Borhane Eddine Chérif Mediouni-Ben Jemâa Jouda 《植物病害和植物保护杂志》2021,128(5):1167-1176
Journal of Plant Diseases and Protection - The aims of this work were to point out the seasonal variation in chemical composition and evaluate the insecticidal activities of Mentha spicata and... 相似文献
25.
M. N. Barakat 《Euphytica》1990,48(2):103-110
Summary Callus induction derived from root, hypocotyl and cotyledon explants were investigated for four cultivars of Trifolium alexandrinum L. The Murashige & Skoog (1962) medium containing 2.0 mg/L NAA and 0.5 mg/L BAP was able to induce callus from different explants. A wide range of culture media were tested to determine the morphogenetic potential of different callus types derived from different explant types. Shoot morphogenetic development was observed with the cultivars Sakha 4 and Giza 10. Cell suspension cultures were established from hypocotyl derived callus. Methods for isolation and culture of protoplasts from cotyledons are described. 相似文献
26.
M. N. Barakat 《Euphytica》1994,76(3):169-175
Summary Combining ability for six in vitro culture traits in wheat were studied in a 8×8 diallel cross (excluding reciprocals). Specific combining ability effects (sca) were significant for all six traits derived from immature embryos on two media protocols, whereas general combining ability (gca) variances were significant only for five of them. Furthermore, based on ratios obtained by comparing the ratio of K2 gca to K2 sca, sca was more important than gca for all six traits. Genetic correlations between shoot formation and other in vitro traits, except callus weight and root formation, were higher in magnitude than the corresponding phenotypic correlations estimates, indicating the importance of genetic effects. 相似文献
27.
To evaluate the chemical fingerprint of hydrocarbons in airborneorganic matter in the arid environment of Alexandria City, Egypt,the compositions of aliphatic and aromatic compounds were determined in suspended particulate material collected from a street undergoing heavy traffic in central Alexandria and in bulkdeposition samples collected from a site representing an area increasingly influenced by human and industrial activities. Qualitative and quantitative characterizations of individual compounds were based on gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS) analyses. More than 100 organic compounds are quantified in each sample, including n-alkanes, isoprenoids, polycyclic aromatic hydrocarbons(PAHs), sulfur-bearing heterocyclics, steranes/diasteranes, terpanes and aromatic steroids. The use of hydrocarbon profilesand ratios for identifying sources and processes is discussed.The molecular distribution of alkanes revealed that the mainsource of these compounds is from petroleum contamination withtrace input of vascular plant wax. The PAH profiles, especiallythe relative abundance of alkyl-PAHs and sulfur-containing heterocyclics, showed that PAHs are chiefly derived from trafficsources. The results further indicated that diesel vehicles aremore important PAH sources than gasoline vehicles. In addition,the source fingerprint of fossil fuel biomarkers such as steranes, terpanes and aromatic steroids agreed well with thefingerprint of unburned lubricating oil, which are probably contributed to vehicle exhaust emissions. 相似文献
28.
Osmotin and thaumatin from grape: a putative general defense mechanism against pathogenic fungi 总被引：1，自引：0，他引：1
Monteiro S Barakat M Piçarra-Pereira MA Teixeira AR Ferreira RB 《Phytopathology》2003,93(12):1505-1512
ABSTRACT Little information is available concerning the expression of pathogenesis-related (PR) proteins in grapevine (Vitis vinifera) and their effect properties on the major fungal pathogens of grape. A systematic study was performed on the effect of total or individual grape proteins on mycelial growth, spore germination, and germ tube growth of Uncinula necator, Phomopsis viticola, and Botrytis cinerea. Two proteins, identified as PR proteins by immunological methods and by N-terminal sequencing as osmotin and thaumatin-like protein, exhibited strong antifungal activities in vitro, blocking the growth of Phomopsis viticola and Botrytis cinerea mycelia. In addition, they inhibited spore germination and germ tube growth of U. necator, Phomopsis viticola, and Botrytis cinerea. The presence of both proteins displayed a synergistic effect. The expression of osmotin and thaumatin-like protein was induced in grapevine leaves and berries infected with U. necator and Phomopsis viticola. Thaumatin previously was thought to occur exclusively in berries. Immunoblot analyses revealed the accumulation of the two PR proteins in infected leaves and berries, supporting a role in vivo in increasing the resistance of grapevine to fungal attack. 相似文献
29.
Rana Roumieh Abir Barakat Nabila E Abdelmeguid Joly Ghanawi Imad Patrick Saoud 《Aquaculture Research》2013,44(11):1777-1790
Ammonia is a metabolite of aquatic organisms which might reach deleterious levels in intensive fish farms. The aim of the present study was to determine median lethal concentrations (96‐h LC50) of total ammonia nitrogen (TA‐N) on marbled spinefoot rabbitfish (Siganus rivulatus) and chronic effects of TA‐N on survival, growth and behaviour of juvenile rabbitfish over a 50 day period. In the first experiment, fish were exposed to 0, 2, 4, 6, 8, 10, 12, 14, 16, 18 and 20 mg L?1 TA‐N for 96 h and survival evaluated. In the second experiment, 12 fish were stocked per 50‐L tank and treated with one of 0, 2, 4, 6, 8, 10 and 12 mg L?1 TA‐N with three replicate tanks per treatment. Survival and growth were determined and histopathological alterations of gills due to chronic ammonia exposure were studied by light and electron microscopy. The 96‐h LC50 values were 16–18 mg L?1 TA‐N. In the chronic exposure experiment, fish reared in water with 0 mg L?1 TA‐N had 100% survival and had 50% weight increase in 50 days. Fish at 2 and 4 mg L?1 TA‐N all died whilst fish in 6, 8, 10 and 12 mg L?1 TA‐N survived and grew albeit less than in treatment 0 mg L?1. Gills from ammonia treated fish displayed severe histological and ultrastructural alterations including hyperplasia, hypertrophy and fusion of secondary lamellae, aneurysms and presence of pleomorphic altered cells. Chronic exposure to ammonia is deleterious to marbled spinefoot rabbitfish and low concentrations of ammonia appear to kill the fish in <50 days whilst fish can survive for more than 50 days at concentrations between 6 and 12 mg L?1 TA‐N. 相似文献
30.
AbstractSuccessful fruit fly control requires effective monitoring to make pest management decisions. Ceratitis capitata (Medfly) is typically monitored in Tunisia with parapheromone commercialised as trimedlure (TM). Chemical treatment is applied when the economic threshold (3 flies/trap/day) is reached. In this study, C. capitata populations in a commercial citrus orchard captured in McPhail traps baited with TM or enriched ginger oil (EGO) were compared over two seasons (2011 and 2012). Females of C. capitata were not attracted to TM or EGO. Trimedlure was significantly more attractive to C. capitata males than EGO under low and high population densities over sampling dates. The TM used in McPhail traps was adequate to attract male medflies in citrus orchards under a wide range of Medfly population levels. The use of the best attractant can help to make control decisions when population levels of flies are low, thus preventing unnecessary application of insecticides and/or other control methods. 相似文献