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排序方式: 共有226条查询结果,搜索用时 15 毫秒
111.
Houmam A Muhammad H Koczkur KM 《Langmuir : the ACS journal of surfaces and colloids》2011,27(22):13544-13553
Long-range-ordered aromatic SAMs are formed on Au(111) using 4-nitrophenyl sulfenyl chloride as a precursor. Although the main structure is a √3 × √3 with a molecular density similar to that usually found for aliphatic SAMs, particular spots presenting specific shapes are also observed by STM. These include hexagons, partial hexagons, parallelograms, and zigzags resulting from specific arrangements of adsorbed molecules. These molecular arrangements are reversible as they form and dissociate or "vanish" in various areas on the surface. STM shows that these particular structures provide some order to their surrounding because areas void of these structures look less ordered. More interestingly, STM shows submolecular details of the molecules involved in forming these structures, hence providing direct experimental evidence for the ability of the STM to provide physical structure information of standing up SAMs. This is indeed a heavily debated question, and this work reports the first experimental example where submolecular physical structure is revealed by STM for standing-up SAMs. 相似文献
112.
Hamza Bouzid Mario Prosa Margherita Bolognesi Nadia Chehata Desta Gedefaw Cristiano Albonetti Mats R. Andersson Michele Muccini Abdelaziz Bouazizi Mirko Seri 《Journal of polymer science. Part A, Polymer chemistry》2019,57(4):487-494
High‐performance polymer solar cells (PSCs) are typically fabricated by spin coating in inert atmosphere from toxic halogenated solvents such as 1,2‐dichlorobenzene (o‐DCB) and chlorobenzene. This fabrication process is potentially hazardous for both the humans and the environment and dramatically impacts the possibility for the organic photovoltaic technology to be adopted at large scale. In this work, efficient PSCs blade coated in air using nonhalogenated 1,2,4‐trimethylbenzene (TMB) as processing solvent are demonstrated. The active layer, based on a previously synthesized benchmark polymer PFQ2T‐benzodithiophene blended with [6,6]‐phenyl‐C61‐butyric acid methyl ester (PC61BM), showed an enhanced solid‐state aggregation induced by the use of TMB. Compared to o‐DCB‐processed devices, the solar cells fabricated from TMB resulted 10% more efficient with a power conversion efficiency of 4.20%. Interestingly, the improved photovoltaic performance resulted from the combination of synergic effects promoted by a more favorable film morphology, such as high exciton dissociation efficiency and lower bimolecular recombinations resulting in higher charge collection efficiency at the electrodes. The positive effect of TMB, compared to that of commonly employed halogenated solvents, confirms the great potential of this approach for the development of efficient PSCs for practical applications with reduced environmental impact. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 487–494 相似文献
113.
Laurence Oswald Abdelaziz Al Ouahabi Chlo Laure Jean‐Arthur Amalian Laurence Charles Jean‐Franois Lutz 《Journal of polymer science. Part A, Polymer chemistry》2019,57(3):403-410
Soluble supports, with optimal molecular structures for iterative oligomer synthesis, were prepared by atom transfer radical copolymerization of styrene with Fmoc‐amino ethyl methacrylate. Size exclusion chromatography and nuclear magnetic resonance indicated formation of copolymers with controlled chain lengths, chain ends, dispersity, and comonomer compositions. These polymers were afterward subjected to two subsequent modifications steps: (a) the debromination of their ω‐chain ends via a tributyltin hydride treatment and (b) the removal of the Fmoc‐protecting groups in acidic conditions, thus leading to bromine‐free copolymers with a precise primary amine loading capacity. These universal amine‐containing precursors were then derived into a variety of functional supports. A glycine‐loaded Wang‐type soluble polystyrene support was prepared in two steps and tested for peptide synthesis as well as for the preparation of digital oligo(alkoxyamine amide)s. In both cases, it was possible to obtain uniform sequence‐defined oligomers as evidenced by electrospray ionization tandem mass spectrometry. However, each type of oligomer required specific experimental conditions and therefore soluble supports with an adapted loading capacity for optimal synthesis. Furthermore, the amine‐containing universal precursors were also transformed into soluble supports for iterative phosphoramidite chemistry. A support was specifically conceived for the iterative synthesis of abiotic digital oligo(phosphodiester)s and another one was designed for oligonucleotide synthesis. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 403–410 相似文献
114.
Yury Kolokolov Pavel Ustinov Najib Essounbouli Abdelaziz Hamzaoui 《Chaos, solitons, and fractals》2009,42(5):2635-2644
In this paper, a design method of pulse energy converter (PEC) controllers is proposed. This method develops a classical frequency domain design, based on the small signal modeling, by means of an addition of a nonlinear dynamics analysis stage. The main idea of the proposed method consists in fact that the PEC controller, designed with an application of the small signal modeling, is tuned after with taking into the consideration an essentially nonlinear nature of the PEC that makes it possible to avoid bifurcation phenomena in the PEC dynamics at the design stage (bifurcation-free design). Also application of the proposed method allows an improvement of the designed controller performance. The application of this bifurcation-free design method is demonstrated on an example of the controller design of direct current–direct current (DC–DC) buck converter with an input electromagnetic interference filter. 相似文献
115.
Dr. Emile R. Engel Dr. Abdelaziz Jouaiti Charl X. Bezuidenhout Prof. Mir Wais Hosseini Prof. Leonard J. Barbour 《Angewandte Chemie (International ed. in English)》2017,56(30):8874-8878
A non-interpenetrated metal–organic framework with a paddle-wheel secondary building unit has been activated by direct thermal evacuation, guest exchange with a volatile solvent, and supercritical CO2 drying. Conventional thermal activation yields a mixture of crystalline phases and some amorphous content. Exchange with a volatile solvent prior to vacuum activation produces a pure breathing phase with high sorption capacity, selectivity for CO2 over N2 and CH4, and substantial hysteresis. Supercritical drying can be used to access a guest-free open phase. Pressure-resolved differential scanning calorimetry was used to confirm and investigate a systematic loss of sorption capacity by the breathing phase as a function of successive cycles of sorption and desorption. A corresponding loss of sample integrity was not detectable by powder X-ray diffraction analysis. This may be an important factor to consider in cases where flexible MOFs are earmarked for industrial applications. 相似文献
116.
Abdelaziz Mestadi Magdeleine Normandin Dr. Jean-Robert Clermont Pierre Attané 《Rheologica Acta》1996,35(4):337-346
In this paper, we propose a numerical simulation of axisymmetric extensional experiments on a viscoelastic polydimethylsiloxane (PDMS) material, using a falling-weight extensional rheometer. The polymer behaviour is represented by a K-BKZ memory-integral constitutive equation, involving a damping function of the Wagner type. Under the assumption of a homogeneous flow zone in the sample, a numerical model is set up, using the stream-tube method and approximating functions. The governing equations of the problem, associated to a limited number of unknowns, are solved by means of the Levenberg-Marquardt optimization algorithm. The numerical results are found to be consistent with the experimental data and reveal the importance of the non-homogeneous flow zone, in relation to the estimation of the extensional strain rate. The calculations involve the sensitivity of the model on the fluid parameters and those concerning the size of the initial column of fluid. The limited computing (CPU) time of the code is also to be underlined. 相似文献
117.
118.
This research aims to highlight and examine an example of ecological complexity. By taking into account the interference between predator and prey, we introduce an ecological system with a general functional response. This model is perturbed by a novel class of fluctuations in the polynomial form. Analytically, we present an alternative method to obtain the acute threshold between stationarity and predator disappearance. Our analysis enriches and improves the work of Zhou et al. (2021) by unifying the criteria of said asymptotic characteristics. Numerically, we audit the accuracy of our threshold in three particular situations: linear, quadratic and cubic perturbations. We establish that the increasing order of disturbance has a passive influence on the extinction time of predators. This finding highlights that complex noise sources have a positive role in the transient dynamics of ecological systems. 相似文献
119.
Hassane Assaaoudi Mostafa Ijjaali Abdelaziz Ennaciri Ian S. Butler Janusz A. Kozinski 《Journal of chemical crystallography》2007,37(9):601-608
Abstract The cyclotriphosphate salt, ErNa3(P3O9)2 · 9H2O, has been characterized by single-crystal X-ray diffraction [hexagonal, space group , with unit cell parameters of a = b = 30.8451(14), c = 12.8063(8) ?; Z = 18]. The structure consists of alternating layers of [P3O9]3− groups, ErO8 dodecahedra, Na(1)O6 and Na(2)O7 polyhedra linked together by water molecules. The P3O9 rings are grouped along the c-axis in a P3O9–ErO8 arrangement thereby producing broad, hexagonal channels of diameter of 6.65 ? with a side dimension of 3.907 ?. The absence
of coincidences for the majority of the IR and Raman bands observed for the cyclotriphosphate salt is in accord with the centrosymmetric
structure of the material. The vibrational spectra have been interpreted on the basis of factor group effects.
Graphical abstract
We report the crystal structure and vibrational spectra of erbium trisodium bis(cyclotriphosphate)nanohydrate salt
ErNa
3
(P
3
O
9
)
2
·
9H
2
O
H. Assaaoudi, M. Ijjaali, A. Ennaciri, I. S. Butler* and J. A. Kozinski
Crystal structure and vibrational spectra of erbium trisodium bis(cyclotriphosphate) nonahydrate,ErNa3(P3O9)2 · 9H2O.
Projection of the coordination polyhedra of ErNa3(P3O9)2 · 9H2O down the c axis 相似文献
120.
Rodríguez de Castro Antonio Agnaou Mehrez Ahmadi-Sénichault Azita Omari Abdelaziz 《Transport in Porous Media》2019,130(3):799-818
Transport in Porous Media - With X-ray computed tomography still being flawed as a result of limitations in terms of spatial resolution and cost, toxic mercury intrusion porosimetry (MIP) is... 相似文献