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排序方式: 共有106条查询结果,搜索用时 46 毫秒
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Bouxsein NF Leal C McAllister CS Ewert KK Li Y Samuel CE Safinya CR 《Journal of the American Chemical Society》2011,133(19):7585-7595
We report the formation of liquid crystalline (LC) phases of short double-stranded DNA with nonpairing (nonsticky) overhangs, confined between two-dimensional (2D) lipid bilayers of cationic liposome-DNA complexes. In a landmark study (Science2007, 318, 1276), Nakata et al. reported on the discovery of strong end-to-end stacking interactions between short DNAs (sDNAs) with blunt ends, leading to the formation of 3D nematic (N) and columnar LC phases. Employing synchrotron small-angle X-ray scattering, we have studied the interplay between shape anisotropy-induced and DNA end-to-end interaction-induced N ordering for 11, 24, and 48 bp sDNA rods with single-stranded oligo-thymine (T) overhangs modulating the end-to-end interactions. For suppressed stacking interactions with 10-T overhangs, the volume fraction of sDNA at which the 2D isotropic (I)-to-N transition occurs for 24 and 48 bp sDNA rods depended on their length-to-width (L/D) shape anisotropy, qualitatively consistent with Onsager's theory for the entropic alignment of rigid rods. As the overhang length is reduced from 10 to 5 and 2 T for 24 and 48 bp sDNA, the N-to-I transition occurs at lower volume fractions, indicating the onset of some degree of end-to-end stacking interactions. The 11 bp sDNA rods with 5- and 10-T overhangs remain in the I phase, consistent with their small shape anisotropy (L/D ≈ 1.9) below the limit for Onsager LC ordering. Unexpectedly, in contrast to the behavior of 24 and 48 bp sDNA, the end-to-end interactions between 11 bp sDNA rods with 2-T overhangs set in dramatically, and a novel 2D columnar N phase (N(C)) with finite-length columns formed. The building blocks of this phase are comprised of 1D stacks of (on average) four 11 bp DNA-2T rods with an effective L(stacked)/D ≈ 8.2. Our findings have implications for the DNA-directed assembly of nanoparticles on 2D platforms via end-to-end interactions and in designing optimally packed LC phases of short anisotropic biomolecules (such as peptides and short-interfering RNAs) on nanoparticle membranes, which are used in gene silencing and chemical delivery. 相似文献
3.
Mohammad R. Torshizian Mohammad H. Kargarnovin Cyrus Nasirai 《Mechanics Research Communications》2011,38(3):164-169
In this paper, a two dimensional functionally graded material (2D-FGM) under an anti-plane load with an internal crack is considered. The crack is oriented in an arbitrary direction. The material properties are assumed to vary exponentially in two planar directions. The problem is analyzed and solved by two different methods namely Fourier integral transforms with singular integral equation technique, and then by the finite element method. The effects of crack orientation, material non-homogeneity, and other parameters on the value of stress intensity factor (SIF) are studied. Finally, the obtained results for Mode III stress intensity factor of different methods are compared. 相似文献
4.
Mischa Baier Nils H. Rustmeier Joachim Harr Norbert Cyrus Guido J. Reiss Andrea Grafmüller Brbel S. Blaum Thilo Stehle Laura Hartmann 《Macromolecular bioscience》2019,19(5)
Divalent precision glycooligomers terminating in N‐acetylneuraminic acid (Neu5Ac) or 3′‐sialyllactose (3′‐SL) with varying linkers between scaffold and the glycan portions are synthesized via solid phase synthesis for co‐crystallization studies with the sialic acid‐binding major capsid protein VP1 of human Trichodysplasia spinulosa‐associated Polyomavirus. High‐resolution crystal structures of complexes demonstrate that the compounds bind to VP1 depending on the favorable combination of carbohydrate ligand and linker. It is found that artificial linkers can replace portions of natural carbohydrate linkers as long as they meet certain requirements such as size or flexibility to optimize contact area between ligand and receptor binding sites. The obtained results will influence the design of future high affinity ligands based on the structures presented here, and they can serve as a blueprint to develop multivalent glycooligomers as inhibitors of viral adhesion. 相似文献
5.
The lattice Boltzmann method, an alternative approach to solving a fluid flow system, is used to analyze the dynamics of particles suspended in fluid. The interaction rule between the fluid and the suspended particles is developed for real suspensions where the particle boundaries are treated as no-slip impermeable surfaces. This method correctly and accurately determines the dynamics of single particles and multi-particles suspended in the fluid. With this method, computational time scales linearly with the number of suspensions,N, a significant advantage over other computational techniques which solve the continuum mechanics equations, where the computational time scales asN
3. Also, this method solves the full momentum equations, including the inertia terms, and therefore is not limited to low particle Reynolds number. 相似文献
6.
Mohammad Yeganeh Ghotbi 《Particuology》2012,10(4):492-496
Zinc hydroxide nitrate, an anionic exchanger layered material, undoped as well as doped with 2–10% nickel, was synthesized by using a pH-controlled precipitation method. The layered materials were then used to produce the undoped and nickel-doped zinc oxides by hydrothermal-treatment. X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy confirmed the formation of pure phase undoped and nickel-doped layered materials, as well as the products of the hydrothermal-treated materials, nanostructured zinc oxides. Optical studies of the nanostructured zinc oxides showed a decrease in band gap with increasing content of the doping agent, nickel. 相似文献
7.
Mohammadhassan Vasheghani Ehsan Marzbanrad Cyrus Zamani Mohamed Aminy Babak Raissi Toraj Ebadzadeh Hadi Barzegar-Bafrooei 《Heat and Mass Transfer》2011,47(11):1401-1405
Thermal conductivity of α-Al2O3 was measured using hot wire method. α-Al2O3 (20 nm in size) was synthesized by microwave method for which, the results were compared with commercially available γ-Al2O3. Thermal conductivity of nanofluids was investigated considering, it is dependency on Al2O3 phase. It was observed that by adding 3 wt% of nano γ-Al2O3 and α-Al2O3 to the engine oil, thermal conductivity increases by 37 and 31%, respectively. The corresponding viscosity increase for the
same amount of nano γ-Al2O3 and α-Al2O3 were 36 and 38%, respectively. It was concluded that the differences in thermal conductivity originate from higher specific
surface area of γ-Al2O3 compared to the α-Al2O3 which is the result of porosity difference, obtained during the synthesis process. 相似文献
8.
In this paper, homotopy perturbation method (HPM) and variational iteration method (VIM) are applied to solve nonlinear oscillator differential equations. Illustrative examples reveal that these methods are very effective and convenient for solving nonlinear differential equations. Moreover, the methods do not require linearization or small perturbation. Comparisons are also made between the exact solutions and the results of the homotopy perturbation method and variational iteration method in order to prove the precision of the results obtained from both methods mentioned. 相似文献
9.
Cyrus Parsi Aryana 《Complex Analysis and Operator Theory》2013,7(5):1513-1524
A direct calculation of the vector of Riemann constants corresponding to the marked double of a multiply connected planar region is given. The existence of eigenvalues of self-adjoint Toeplitz operators acting on Hardy spaces associated with non-negative representing measures on 1-holed planar regions is established in the case where there exists one bounded component in the complement of the essential range of the symbol $\phi $ of the operator. The analysis is done by using the zeros of translations of theta functions restricted to $\mathbb R $ in $\mathbb C $ . 相似文献
10.
H. Bararnia Abdoul R. Ghotbi G. Domairry 《Communications in Nonlinear Science & Numerical Simulation》2009,14(6):2689-2701
Homotopy analysis method (HAM) is employed to investigate the momentum, heat and mass transfer characteristics of MHD natural convection flow and heat generation fluid driven by a continuously moving permeable surface immersed in a fluid saturated porous medium. The solution is found to be dependent on several governing parameters, including the magnetic field strength parameter, Prandtl number, Darcy number, the dimensionless inertia coefficient, the dimensionless heat generation/absorption coefficient and the dimensionless suction/blowing coefficient. A parametric study of all governing parameters is carried out and representative results are illustrated to reveal a typical tendency of the solutions. Representative results are presented for velocity and temperature distributions as well as the local friction coefficient and local Nusselt number. Finally, a proper discussion is derived on the obtained results and some remarkable conclusions are mentioned. 相似文献