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排序方式: 共有266条查询结果,搜索用时 15 毫秒
261.
S. Akbari N. Ghareghani G.B. Khosrovshahi A. Mahmoody 《Linear algebra and its applications》2009,430(11-12):3047-3052
For a graph G, a zero-sum flow is an assignment of non-zero real numbers on the edges of G such that the total sum of all edges incident with any vertex of G is zero. A zero-sum k-flow for a graph G is a zero-sum flow with labels from the set {±1,…,±(k-1)}. In this paper for a graph G, a necessary and sufficient condition for the existence of zero-sum flow is given. We conjecture that if G is a graph with a zero-sum flow, then G has a zero-sum 6-flow. It is shown that the conjecture is true for 2-edge connected bipartite graphs, and every r-regular graph with r even, r>2, or r=3. 相似文献
262.
R. Ghorbani-Vaghei M. Amiri N. Moshfeghifar H. Veisi S. Akbari Dadamahaleh 《Journal of the Iranian Chemical Society》2009,6(4):754-760
Poly(N,N′-dibromo-N-ethyl-benzene-1,3-disulfonamide) [PBBS] and N,N,N′,N′-tetrabromobenzene-1,3-disulfonamide [TBBDA] are effective catalysts for easy preparation of 1,1-diacetates from aldehydes and acetic anhydride, and for easy preparation of acetals using diols under microwave irradiation in the presence of SiO2. 相似文献
263.
Hadi Beitollahi Alireza Mohadesi Saeedeh Khalilizadeh Mahani Hassan Karimi-Maleh Ali Akbari 《Ionics》2012,18(7):703-710
A carbon paste electrode modified with 5-amino-3??,4??-dimethoxy-biphenyl-2-ol and carbon nanotubes was used for the sensitive voltammetric determination of norepinephrine (NE). The electrochemical response characteristics of the modified electrode toward NE, acetaminophen (AC), and folic acid (FA) were investigated by cyclic and square wave voltammetry (SWV). The results show an efficient catalytic activity of the electrode for the electrooxidation of NE, which leads to lowering its overpotential more than 160?mV. The modified electrode exhibits an efficient electron-mediating behavior together with well-separated oxidation peaks for NE, AC, and FA. Under the optimum pH of 7.0 in 0.1?M phosphate buffer solution, the SWV anodic peak current showed a linear relation vs. NE concentration in the range of 15.0 to 1,000.0???M with a detection limit of 8.0???M. 相似文献
264.
The heavy fermion metal CeB(6) exhibits a hidden order of the antiferroquadrupolar (AFQ) type below T(Q)=3.2 K and a subsequent antiferromagnetic (AFM) order at T(N)=2.3 K. It was interpreted as an ordering of the quadrupole and dipole moments of a Γ(8) quartet of localized Ce 4f(1) electrons. This established picture has been profoundly shaken by recent inelastic neutron scattering (G. Friemel et al., arXiv:1111.4151) that found the evolution of a feedback spin exciton resonance within the hidden order phase at the AFQ wave vector which is stabilized by the AFM order. We develop an alternative theory based on a fourfold degenerate Anderson lattice model, including both order parameters as particle-hole condensates of itinerant heavy quasiparticles. This explains in a natural way the appearance of the spin exciton resonance and the momentum dependence of its spectral weight, in particular, around the AFQ vector and its rapid disappearance in the disordered phase. Analogies to the feedback effect in unconventional heavy fermion superconductors are pointed out. 相似文献
265.
Neda Akbari Elham Assadpour Mohammad Saeed Kharazmi Seid Mahdi Jafari 《Molecules (Basel, Switzerland)》2022,27(18)
Vitamin B12 (VB12) is one of the essential vitamins for the body, which is sensitive to light, heat, oxidizing agents, and acidic and alkaline substances. Therefore, the encapsulation of VB12 can be one of the ways to protect it against processing and environmental conditions in food. In this work, the influence of pectin concentration (0.5–1% w/v), whey protein concentrate (WPC) level (4–8% w/v) and pH (3–9) on some properties of VB12-loaded pectin–WPC complex carriers was investigated by response surface methodology (RSM). The findings showed that under optimum conditions (1:6.47, pectin:WPC and pH = 6.6), the encapsulation efficiency (EE), stability, viscosity, particle size and solubility of complex carriers were 80.71%, 85.38%, 39.58 mPa·s, 7.07 µm and 65.86%, respectively. Additionally, the formation of complex coacervate was confirmed by Fourier-transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM). In addition, it was revealed that the most important factor in VB12 encapsulation was pH; at a pH < isoelectric point of WPC (pH = 3), in comparison with higher pH values (6 and 9), a stronger complex was formed between pectin and WPC, which led to an increase in EE, lightness parameter, particle size and water activity, as well as a decrease in the zeta-potential and porosity of complex carriers. 相似文献
266.
Fatemeh Zehtabi Hossein Montazerian Reihaneh Haghniaz Kaylee Tseng Neda Mohaghegh Kalpana Mandal Behnam Zamanian Mehmet Remzi Dokmeci Mohsen Akbari Alireza Hassani Najafabadi Han-Jun Kim Ali Khademhosseini 《Macromolecular bioscience》2023,23(1):2200333
Shear-thinning biomaterials (STBs) based on gelatin-silicate nanoplatelets (SNs) are emerging as an alternative to conventional coiling and clipping techniques in the treatment of vascular anomalies. Improvements in the cohesion of STB hydrogels pave the way toward their translational application in minimally invasive therapies such as endovascular embolization repair. In the present study, sodium phytate (Phyt) additives are used to tune the electrostatic network of SNs-gelatin STBs, thereby promoting their mechanical integrity and facilitating injectability through standard catheters. We show that an optimized amount of Phyt enhances storage modulus by approximately one order of magnitude and reduces injection force by ≈58% without compromising biocompatibility and hydrogel wet stability. The Phyt additives are found to decrease the immune responses induced by SNs. In vitro embolization experiments suggest a significantly lower rate of failure in Phyt-incorporated STBs than in control groups. Furthermore, the addition of Phyt leads to accelerated blood coagulation (reduces clotting time by ≈45% compared to controls) due to the contributions of negatively charged phosphate groups, which aid in the prolonged durability of STB in coagulopathic patients. Therefore, the proposed approach is an effective method for the design of robust and injectable STBs for minimally invasive treatment of vascular malformations. 相似文献