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排序方式: 共有90条查询结果,搜索用时 15 毫秒
1.
T. K. Kwei Kalle Levon Giuliana Tesoro Frank Liu Abraham Mey-Marom Surya Munukutla 《先进技术聚合物》1993,4(9):537-547
The synthesis of molecular composites where rigid polymer molecules are reinforcing elements in a thermoset bisimide matrix has been investigated. The approach has been designed to avoid phase separation by selecting systems where reaction of amine-terminated rigid and semiflexible oligomers with maleimide unsaturation occurs prior to crosslinking of the thermoset. This objective has been met for some compositions. The concentration and molecular weight of the rigid oligomers have been varied. The structure of the reinforcing polymer, the reactivity of the maleimide and the conditions for composite synthesis are variables of critical importance, and further work must determine the promise and limitations of this approach. 相似文献
2.
Levon A. Tavadyan Gegham Z. Sedrakyan Seyran H. Minasyan Frederick T. Greenaway John R.J. Sorenson 《Transition Metal Chemistry》2004,29(6):684-696
Bioactive copper(II), iron(III), and manganese(II) 3,5-di-i-propylsalicylate (3,5-DIPS) chelates were investigated in order to determine their ability to inhibit the free radical initiated chain reactions leading to the peroxidation of isopropylbenzene (i-PrPh) and ethylbenzene (EtPh). Quantitative kinetic studies of these chelates established the following order of anti-oxidant reactivities: manganese(II)-(3,5-DIPS)2>iron(III)(3,5-DIPS)3>copper(II)2(3,5-DIPS)4> > 3,5-DIPS acid. The mechanism of anti-oxidant reactivity of these three chelates is established as being due, in part, to their chain-breaking capacity resulting from the chemical reduction of the generated peroxyl radical to yield alkybenzenelhydroperoxides via reaction of the 3,5-DIPS ligand with the peroxyl radical. In the case of manganese(II)3,5-di-i-propylsalicylate, the central metalloelement also interacts with the peroxyl radical. The manganese(II)-(3,5-DIPS)2 and copper(II)2(3,5-DIPS)4 chelates were also found to exhibit alkylhydroperoxide pro-oxidative reactivity leading to the formation of the alkylbenzeneperoxyl radical. In addition, the manganese(II) atom underwent oxidation to manganese(III) with the formation of the alkylbenzenehydroperoxide or superoxide with air oxygen oxidation. Amyl acetate and dipropylamine (n-Pr2NH) were added to the reaction mixture to model the biochemical presence of ester or amine cellular components. Addition of amyl acetate to the reaction mixture increased the anti-oxidant reactivity of manganese(II)-(3,5-DIPS)2 while decreasing its pro-oxidant reactivity. The weaker anti-oxidant reactivites of iron(III)(3,5-DIPS)3 and copper(II)2(3,5-DIPS)4 were less affected by the addition of amyl acetate and the pro-oxidant reactivity of copper(II)2(3,5-DIPS)4 was not changed by the addition of amyl acetate, while the pro-oxidant property of iron(III)(3,5-DIPS)3 was eliminated. In contrast to 2,6-di-t-butyl-4-methylphenol, butylated hydroxy toluene (BHT), anti-oxidant reactivities of copper(II), iron(III), and manganese(II) 3,5-DIPS chelates were dramatically enhanced by the addition of n-Pr2NH to the reaction mixture. It is concluded that all three metalloelement chelates react with and remove alkylbenzeneperoxyl radicals and the hydroperoxyl radical. The manganese(II)-(3,5-DIPS)2 and copper(II)2(3,5-DIPS)4 chelates may also be useful in removing hydroperoxides in vivo. These reactivities, in addition to their established superoxide dismutase (SOD)-mimetic and catalase-mimetic reactivities, are suggested to possibly permit anti-oxidant and pro-oxidant reactivities in aqueous and organic cellular compartments. 相似文献
3.
Armen H. Poghosyan Levon H. Arsenyan Aram A. Shahinyan 《Colloid and polymer science》2014,292(12):3147-3156
In this study, we investigate micelle fission of long-chain alkyl sulfonate molecules using atomistic scale simulation. GROMACS software code with the united atom force field was applied. 0.5-μs parallel molecular dynamics simulation study was conducted for a surfactant/water system consisting of 192 sodium pentadecyl sulfonate and 40,553 water molecules. The large preassembled micelle was ruptured at Krafft above T?=?323-K temperature, and we track two ellipsoid-like micelles over the course of the production run. To estimate the micelle shape, we determined the principal moments of inertia and the eccentricity, which proved that the micelles have a pronounced prolate spheroid shape, which agrees well with our previous experimental data. The mechanism of micelle fission was explored in detail. The aggregation number, ionization degree, and other parameters obtained from simulation were consistent with existing experimental finding. The determined parameters in addition to simple visual inspection of trajectories revealed monomer-micelle exchange—with the estimated relaxation time τ 1?=?10??9s. We assume that the exchange process is conditioned by the unequal size of micelles leading to adjustment of aggregation number. 相似文献
4.
Levon H. Khachatrian 《Designs, Codes and Cryptography》1993,3(1):29-32
It is proven that the quadratic span of DeBruijn sequence of spann is at leastn+2, forn>3. 相似文献
5.
We call A ? $ \mathbb{E} $ n cone independent of B ? $ \mathbb{E} $ n , the euclidean n-space, if no a = (a 1,..., a n ) ∈ A equals a linear combination of B \ {a} with non-negative coefficients. If A is cone independent of A we call A a cone independent set. We begin the analysis of this concept for the sets P(n) = {A ? {0, 1} n ? $ \mathbb{E} $ n : A is cone independent} and their maximal cardinalities c(n) ? max{|A| : A ∈ P(n)}. We show that lim n → ∞ $ \frac{{c\left( n \right)}}{{2^n }} $ > $\frac{1}{2}$ , but can't decide whether the limit equals 1. Furthermore, for integers 1 < k < ? ≤ n we prove first results about c n (k, ?) ? max{|A| : A ∈ P n (k, ?)}, where P n (k, ?) = {A : A ? V n k and V n ? is cone independent of A} and V n k equals the set of binary sequences of length n and Hamming weight k. Finding c n (k, ?) is in general a very hard problem with relations to finding Turan numbers. 相似文献
6.
7.
O. A. Bezshyyko A. N. Vodin L. O. Golinka-Bezshyyko A. M. Dovbnya I. N. Kadenko A. O. Kivernyk A. A. Kovalenko V. A. Kushnir A. I. Levon V. V. Mitrochenko S. M. Olejnik G. E. Tuller 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(7):941-945
The isomer ratios for nuclei 104m,g Ag, 110m,g In, 108m,g In as products of the photonuclear reactions 107Ag(γ, 3n)104m,g Ag, 113In(γ, 3n)110m,g In, 109Ag(γ, 5n)104m,g Ag, 115In)(γ, 5n)110m,g In, 115In(γ, 7n)108m,g In are obtained. The Bremsstrahlung of electrons with energies within 32–84 MeV from the LU-40 linear accelerator was used for the irradiation of targets. The energy resolution and mean current of the electron beam were ~1% and 5 μA, respectively. The induced activity was used to obtain experimental isomer ratios. An HPGe spectrometer with an energy resolution of 1.9 keV for 60Co γ-line 1332 keV was used to acquire the instrumental γ-ray spectra of the activation products. A set of serial measurements with various acquisition times was performed. The cooling times varied from 5 seconds to several hours for Ag and up to tens of hours for In specimens. The obtained experimental isomer ratios are compared with the results from theoretical calculations. 相似文献
8.
9.
Ahlswede Rudolf Khachatrian Levon H. Mauduit C. Sárközy A. 《Periodica Mathematica Hungarica》2003,46(2):107-118
In earlier papers finite pseudorandom binary sequences were studied, quantitative measures of pseudorandomness of them were
introduced and studied, and large families of “good” pseudorandom sequences were constructed. In certain applications (cryptography)
it is not enough to know that a family of “good” pseudorandom binary sequences is large, it is a more important property if
it has a “rich”, “complex” structure. Correspondingly, the notion of “f-complexity” of a family of binary sequences is introduced. It is shown that the family of “good” pseudorandom binary sequences
constructed earlier is also of high f-complexity. Finally, the cardinality of the smallest family achieving a prescibed f-complexity and multiplicity is estimated.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
10.