247 research outputs found
Nanostructured mixed transition metal oxides for high performance asymmetric supercapacitors: Facile synthetic strategy
No full textAbstract not availableSanaz Tajik, Deepak P. Dubal, Pedro Gomez-Romero, Amir Yadegari, Alimorad Rashidi, Bahram Nasernejad, Inamuddin, Abdullah M. Asir
Development of a smart plasma-treated nano-filter using carbon nitride nanostructures for oil–water emulsion separation: experimental and theoretical studies
No full textIn response to global concerns over oil and water separation, the research and development of super-wetting filters with high permeation flux has increased. In this study, an oxygen plasma treatment was applied to modify the surface of bulk-graphitic carbon nitride (b-CN) nanoparticles (g-C3N4) and carbon nitride nanosheet (CN-NS) coated stainless steel meshes to achieve highly efficient oil/water separation. The coated filters were characterized by X-ray diffraction, and several spectroscopy and microscopy techniques, in order to discern the structural changes, as well as the molecular changes, that is, the functional groups induced on the surface. Under 5 minutes of O2 plasma treatment, b-CN coated meshes achieve outstanding oil/water separation in concentrated mixtures, with an approximately 225-fold increase in permeate water flux of 34 394.9 L m−2 h−1 compared to untreated mesh. In contrast, the water separation flux changes slightly for CN-NS mesh using plasma treatment. The plasma-treated b-CN coated mesh also works efficiently for oil-in-water emulsions. By alternating plasma and heat treatments, the b-CN coated mesh can act as an intelligent filter, and switch between super-hydrophilicity and hydrophobicity. This occurs because the plasma and heat treatments induce the creation and loss of surface functional groups (mainly OH), respectively. Furthermore, by alternating plasma and heat treatments, it is possible to switch between super-hydrophobicity and initial water wettability of the coated mesh, enabling us to handle both options (water- and oil-removal) in one single separation device. Density Functional Theory (DFT) calculations reveal that the presence of the adsorbed OH, COOH, and NH2 groups induces the breaking of C-N bonds linking triazine rings on the surface of the C3N4 nanostructures. As a result of the defect created by the scission of the bond, one C atom and two N atoms of the triazine rings bonded to the functional groups protrude above the layer, and the vertical distances of the functional groups to the g-C3N4 layer increase substantially. The protruding functional groups then build a physical barrier preventing the approach of large hydrocarbon molecules to the surface of the filter, but allowing for water wetting
The Role of Allotropic Forms of Carbon-Based Nanostructures on Asphaltene Stability in Crude Oil Medium: Experimental and Computational Studies
No full textAsphaltene precipitation and deposition in various sections of the oil production system pose significant flow assurance challenges, leading to considerable economic implications. Previous studies highlight the significance of carbon-based nanostructures in inhibiting and managing asphaltene-related problems in the petroleum industry. However, the impact of different allotropic forms of carbon-based nanostructures on asphaltene formation and stability in crude oil has not yet been explored. Here, microscopy and asphaltene dispersant analyses are utilized to assess the effect of different allotropic forms of carbon-based nanostructures on asphaltene precipitation in crude oil. Also, density functional theory (DFT) and density functional tight binding (DFTB) methods are applied to describe the molecular behavior of the carbon nanostructures (CNSs) and asphaltene. Treatment of crude oil with 100 ppm of carbon-based nanostructures results in delay of asphaltene onset of precipitation from 23 vol % n-C-7 to 27, 36, and 41 vol % for graphene (G), carbon nanotubes (CNT), and fullerene-like carbon particles (FCP), respectively. The efficiency of the carbon-based nanostructures for postponement of asphaltene onset of precipitation (AOP) and reducing the size of asphaltene aggregates is in following decreasing order of FCP > CNTs > G. This performance of the carbon-based nanostructures is allocated to electron-cloud formation in the oil phase and strong pi-pi interactions between asphaltene molecules and the electron-cloud of aromatic rings of nanostructures. Higher efficiency of FCP compared to other nanostructures is described by the more effective surface geometry of FCP, which causes stronger pi-pi interactions between asphaltene aggregates and nanostructures. In contrast to various types of nanoparticles, carbon-based nanostructures, such as fullerene-like carbon particles and carbon nanotubes, effectively manage asphaltene precipitation and aggregation at low dosages of approximately 100 ppm or less. The minimum equilibrium distance for each carbon-based nanostructure is about 2.5 & Aring;, inferring the key role of the vdW forces in the stability of these complexes. DFTB modeling indicates that the binding energy values increase as the curvature of the carbon allotropes decreases
Book Extract: "Laughter in the Dark: Egypt to the Tune of Change" by Yasmine El Rashidi
No full textPRAISE FOR Laughter in the Dark
“Laughter in the Dark is a brilliantly composed portrait of Egypt’s answer to hip-hop—and how it functions as a musical genre, economic engine, and cultural force amid the restrictions of an increasingly authoritarian regime. Meticulously reported and elegantly written, it’s a must-read for any global citizen.” –ZACK O’MALLEY GREENBURG, author of Empire State of Mind: How Jay-Z Went From Street Corner to Corner Office
“In Laughter in the Dark, Yasmine El Rashidi provides a brisk, brilliant, and brave portrait of young Egyptians simmering under the weight of President Abdel Fattah El-Sisi’s repressive dictatorship and reveals the stark inequality between the rulers and the ruled.” –BASHARAT PEER, author of A Question of Order: India, Turkey, and the Return of Strongme
Experimental and Theoretical Studies toward Superior Anti-corrosive Nanocomposite Coatings of Aminosilane Wrapped Layer-by-Layer Graphene Oxide@MXene/Waterborne Epoxy
No full textHerein, layer-by-layer MXene/graphene oxide nanosheets wrapped with 3-aminopropyltriethoxy silane (abbreviated as F-GO@MXene) are proposed as an anti-corrosion promoter for waterborne epoxies. The GO@MXene nanohybrid is synthesized by a solvothermal reaction to produce a multi-layered 2D structure without defects. Then, the GO@MXene is modified by silane wrapping under a reflux reaction, in order to achieve chemical stability and to create active sites on the nanohybrid surface for reaction with the polymer matrix of the coating. The organic coating modified with 0.1 wt % F-GO@MXene has revealed superior corrosion protection efficiency than the organic coatings modified with either F-GO or F-MXene nanosheets. The impedance modulus at low frequency for the pure epoxy, epoxy/F-MXene, epoxy/F-GO, and epoxy/F-GO@MXene coatings is 4.17 x 10(5), 5.5 x 10(8), 4.46 x 10(8), and 1.14 x 10(10) Omega.cm(2) after 30 days of immersion in the corrosive media, respectively. The remarkable anti-corrosion property is assigned to the intense effect of the nanohybrid on the barrier performance, surface roughness, and adhesion strength of the epoxy coating. The complemental analysis based on first-principles density functional theory reveals that the adhesion strength related to the silane functional groups in its complexes follows the order F-GO@MXene > F-MXene > F-GO. The enhanced stabilization predicted on the GO@MXene nanohybrid ultimately stems from the combined role of the electrostatic and van der Waals forces, suggesting an increase in the penetration path of the corrosive media
Politics in an Arabian Oasis: the Rashidi tribal dynasty
No full textThis text is both a study of the relationships between tribes and state formation, and a political history of central Arabia. It deals with the Rashidi dynasty which in the 19th century emerged among the Shammar camel herders, made the oasis of Hail a capital rivalling Mecca and Medina in fame and prosperity, and attempted to unify central Arabia into a single polity. The author considers why at this particular moment the Shammar became susceptible to political centralization, the internal and external factors that contributed to the emergence of their dynasty, the changes in the political system and the factors which contributed to the subsequent instability and decline of the Shammar polity in the 20th century
Fame bias in editorial choice: Yes or No?
No full textRecently, Scientometrics has published a paper titled “Is there bias in editorial choice? Yes” (Moustafa 2015) in which some comments are given on our published paper in Nature titled “Is there fame bias in editorial choice?” (Mahian et al. 2015). Unfortunately, the author of above mentioned paper and many other readers might misunderstand the main aim of our correspondence. Here, we try to give some explanations to clarify the main goal of analysis presented in the paper
Is there fame bias in editorial choice?
No full textNature’s Correspondence items are reviewed only by the editors (see go.nature.com/cmchno). To investigate whether editorial bias towards internationally renowned correspondents might be at play in selecting candidates for publication, we analysed the scientific status
of Correspondence authors published in 2014.
We used the following pointers to gauge author reputation: faculty member in one of the world’s top 100 universities
(as listed in the Times Higher Education World University Rankings; see go.nature. com/bhgfxd); authorship of Nature or Science publications; high h index. We classed correspondents as established scholars if they fulfilled any or all of these criteria.
The number of letters published in Correspondence
in 2014 was 239, each with
one ‘corresponding author’ responsible for submission and communication with the editors. We found that 54% of these authors met some or all of our criteria. Some 13% of authors came from the developing world.
Within the limitations of our ‘fame factors’ (for example, some correspondents were well known but from outside academia)
and of sampling only the corresponding authors, we infer that scientific celebrity does not notably influence the selection of Correspondence for publication
Investigation of cation-assisted, chemically and thermally enhanced nitrogen-doped graphene nanofluid application as an efficient micro-emulsifier from EOR perspective
No full textAvailable online 8 December 2022Innovatively designed additives have been introduced in last decade to make EOR processes more efficient under challenging conditions. However, nitrogen-doped graphene (NDG) is not known as such a stable efficient method to be injected into reservoir under harsh thermodynamic condition. Some treatment has been applied to molecular structure of commonly used nitrogen-doped graphene aqueous solution for improvement of stability and quality of aqueous solution. These treatments involve both nano-structure and the aqueous carrier fluid properties. Nano-structure modification has been conducted in three successive steps: oxidation with acid vapor and modified Hummers method, citric acid polymerization and heat treatment that succeed in NDG functionalization with carboxyl and hydroxyl groups and structure enhancement in molecular scale. Existing free mono- and divalent cations in aqueous carrier phase improve the emulsification dominant mechanism from Pickering unstable emulsion toward more stable micro-emulsion mechanism which appeared to be superior to conventional emulsifiers used in EOR process because of improved solubility and more facile transport through porous media. Zeta potential of solution has increased from -30 to -12.2 mV highlighting more emulsion stability. The interfacial tension between aqueous fluid containing 500 ppm APH-NDG¹and free mono- and divalent cations and crude oil would be 50 % less in comparison to distilled water/crude oil IFT. Furthermore, APH-NDG, regardless of carrier aqueous type, causes a great decrease in contact angle and as a result, makes the rock surface become more water-wet.Amin Rezaei Namin, Mahyar Rajabi-Kochi, Alimorad Rashidi, Elham Yazdi, Mostafa Montazeri, Ali Asghar Gharesheikhlo
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