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91.
Moneeza Abbas Shabnum Shaheen Mahnoor Pervaiz Mehwish Jaffer Arfa Tahir 《Microscopy research and technique》2022,85(5):1808-1813
The main aim of this study was to explore the role of light microscopy in the identification of microalgae as a source of study. Three microalgal species (Nostoc, Anabaena, and Volvox) were identified by light. In this study, different parameters of the oil extraction process from algae biomass were studied. The samples of Nostoc, Anabaena, and Volvox were collected from the freshwater bodies in Lahore, and the samples were identified by light microscopy. Pretreatment of algae was done which includes harvesting, drying, and grinding. The sun drying of sample was done. Solvent extraction was done for the extraction of oil from algal cells. Solvent n-hexane and diethyl ether were used alone as well as in combination. Effects of n-hexane to oil ratio, size of algal biomass, and contact time on the percentage yield of extracted oil were studied and analyzed. It was concluded that maximum amount of oil was extracted from algae by using a greater ratio of solvent to algal biomass, maximum contact time, and smaller algal biomass size. The extracted oil yield was satisfactory, demonstrating the potential of microalgae for biodiesel production. It was discovered that if algal oil is subjected to transesterification, it can be turned into biodiesel, and light microscopy can be used to assess anatomical characteristics. However, more research will be required for transesterification. 相似文献
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Chih‐Yueh Ivan Liu Shaheen Mulani Kwok‐Kong Tony Mong 《Advanced Synthesis \u0026amp; Catalysis》2012,354(17):3299-3310
Based on the combined use of dimethylformamide (DMF) modulation and neighboring group participation, three iterative one‐pot α‐glycosylation methods, i.e., one‐pot (α,α)‐, one‐pot (β,α)‐, and one‐pot (α,β)‐glycosylations, were developed. These methods are applicable to a range of thioglycosyl donors, confer stereocontrol in α‐/β‐glycosidic bond formation, and thus provide for rapid access to oligosaccharides with various permutations of anomeric configurations. The utility of these one‐pot glycosylation methods is demonstrated in the synthesis of eight non‐natural and natural oligosaccharide targets, including the core 1 serine conjugate, core 8 serine conjugate, the D ‐Gal‐α(1→3)‐D ‐Glc‐α(1→3)‐L ‐Rha trisaccharide unit of the cell wall component in Streptococcus pneumoniae, and the D ‐Glc‐α(1→2)‐D ‐Glc‐α(1→3)‐D ‐Glc trisaccharide terminus of the N‐linked glycan precursor. Confirmation of the anomeric configurations of these oligosaccharides is evidenced by 1H, 13C, 13C‐non‐proton decoupling, and heteronuclear correlation 2D NMR experiments. Global deprotection of selected oligosaccharide targets is illustrated. 相似文献
94.
Matthew O. Reese Alexandre M. Nardes Benjamin L. Rupert Ross E. Larsen Dana C. Olson Matthew T. Lloyd Sean E. Shaheen David S. Ginley Garry Rumbles Nikos Kopidakis 《Advanced functional materials》2010,20(20):3476-3483
As organic photovoltaic efficiencies steadily improve, understanding degradation pathways becomes increasingly important. In this paper, the stability under prolonged illumination of a prototypical polymer:fullerene active layer is studied without the complications introduced by additional layers and interfaces in complete devices. Combining contactless photoconductivity with spectroscopy, structural characterization at the molecular and film level, and quantum chemical calculations, the mechanism of photoinduced degradation in bulk heterojunctions of poly (3‐hexylthiophene) (P3HT) and [6,6]‐phenyl C61‐butyric acid methyl ester (PCBM) is studied. Bare films are subjected to four conditions for 1000 h with either constant illumination or dark and either ambient or inert atmosphere. All samples are found to be intrinsically stable for 1000+ h under inert conditions, in contrast to complete devices. While PCBM stabilizes P3HT films exposed to air, its fullerene cage is found to undergo a series of oxidations that are responsible for the deterioration of the photoconductivity of the material. Quantum chemical calculations show that PCBM oxides have deeper LUMO levels than pristine PCBM and therefore act as traps for electrons in the PCBM domains. 相似文献
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Adel Shaheen Mohammad A. Haija Mariem Chamakh Ghada A. I. Assayed Fawzi Banat Ahmad I. Ayesh 《应用聚合物科学杂志》2020,137(24):48821
Polymer membranes of ferrites nanoparticles, glycerol, and poly(vinyl alcohol) (PVA) were fabricated using a solution casting method. Spinel ferrites nanoparticles, CuFe2O4 or ZnFe2O4, and glycerol were used as dopants to control the membranes' electrical conductivity. The morphology, composition, and interaction between PVA and the dopants were investigated byscanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), differentialscanning calorimeter (DSC), and thermal gravimetric analysis (TGA). Electrical characterization of the membranes was conducted by impedance spectroscopy using frequencies between 1 and 106 Hz and variable temperatures. The results revealed a negative temperature coefficient of the resistance of the membranes. Additionally, membranes with ZnFe2O4 nanoparticles exhibit higher electrical impedance than those with CuFe2O4 nanoparticles. Therefore, electrical conductivity could be controlled using a suitable dopant's composition and concentration. The membranes presented in this study exhibit semiconducting properties, thus, they have potentials to be utilized in multiple applications including the flexible organic-based device. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48821. 相似文献
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Ahmed B. Shaheen Abou-Zeid A. Abou-Zeid Ahmed I. El-Diwany 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1976,26(1):225-230
A simple synthetic medium was used in the fermentative production of puromycin to investigate the efficiencies of certain ingredients in stimulating the organism for higher yield. Addition of certain amino acids, especially L-histidine, L-glutamic acid, L-proline, L-aspartic acid, DL-methionine, L-leucine, β-alanine, L-isoleucine, DL-alanine, L-tyrosine and L-glycine, increased the antibiotic yield compared with the control. Lactic acid was more suitable for antibiotic production than the other organic acids used, i.e. maleic, acetic, malic, tartaric and fumaric acids. Addition of certain vitamins, namely cobalamin (vitamin B 12), nicotinic acid, vitamin B 1 and folic acid, did not markedly increase the antibiotic yield. Certain trace elements, such as zinc, copper, iron, manganese and cobalt, played an important role in the biosynthesis of puromycin by Streptomyces alboniger NRRL B-2403. The optimum concentrations of these trace elements were 0.2000, 0.0020, 0.0005, 0.3000, and 0.0050 g/litre respectively. The optimum concentration of K2HPO4 favouring bio-synthesis of puromycin was 1.5 g/litre. The amino acids formed in the microbial cells of Streptomyces alboniger NRRL B-2403 during the production of puromycin in the synthetic medium were determined quantitatively. Generally, all the amino acids recorded appeared in the microbial cells. 相似文献
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