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991.
设计合成了两个系列20个含α-氨基酸的新型有机锗化合物, 对化合物进行了波谱表征, 用X射线衍射测定了化合物Ph3GeCH(Ph)CH2CONHCH(CH2COOC2H5)COOC2H5的晶体结构. 抗肿瘤实验结果表明, 这两个系列的化合物有一定的抗KB, HCT-8和Bel-7402活性. 相似文献
992.
The application of a multi-frequency laser source for the use in matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOFMS) is described. An elliptically polarized beam of a Nd:YAG laser emitting at 355 nm (200 mJ) is focused into a Raman shifter, filled with high pressure hydrogen. As a result, numerous Raman lasers (including vibrational and rotational Raman emissions for hydrogen; 4155 and 587 cm−1 shifts, respectively) were generated with a total power of ∼100 mJ. Using this multi-frequency laser as an ionization source, methionine enkephalin (MW 573.7), angiotensin I (MW 1296.5) and oxidized insulin chain B (MW 3495.9) were examined, as model compounds using α-cyano-4-hydroxycinnamic acid (CHCA), sinapinic acid (SA) and activated charcoal as the matrix, respectively. As a result, the S/N ratios were improved when the multi-frequency laser was used, compared to the single light source of the Nd:YAG laser (355 nm), irrespective of the type of matrix used. This is because the multi-frequency laser provides multi-line for absorption, where the traditional N2 laser only provides single wavelength (at 337 nm) for absorption. 相似文献
993.
A new transition metal-catalyzed formation of CF3-substituted α,β-unsaturated alkenes through the ylide intermediate from the reaction between methyl 3,3,3-trifluoro-2-diazopropionate 1 and aryl aldehydes has been developed. Further transformation of the alkene affords the α-trifluoromethyl substituted β-amino ester, a valuable intermediate in the synthesis of fluorine-containing amino acids with potential biological application. 相似文献
994.
Mariano Licciardi 《European Polymer Journal》2006,42(4):823-834
The non-viral gene vector properties of a protein-like polymer, the α,β-poly(N-2-hydroxyethyl)-d,l-aspartamide (PHEA) were investigated after its derivatization with 3-(carboxypropyl)trimethyl-ammonium chloride (CPTA) as molecule bearing cationic groups, in order to obtain stable polycations able to condense DNA. PHEA was firstly functionalized with hydrazide pendant groups by reaction with hydrazine monohydrate (HYD), obtaining the polyhydrazide α,β-poly(N-2-hydroxyethyl/carbazate)-d,l-aspartamide (PHEA-HYD). In this paper we reported that polymer functionalization degree can be easily modulated by varying reaction conditions, so allowing us to produce two PHEA derivatives at different molar percentage of hydrazide groups. Subsequently, condensation reaction of PHEA-HYD copolymers with CPTA yielded α,β-poly(N-2-hydroxyethyl)-N-carbazate[N′-(3-trimethylammonium chloride)propylhydrazide]-d,l-aspartamide (PHEA-HYD-CPTA) polycation derivatives. In vitro studies were carried out to evaluate polycations ability to complex DNA and to protect it from nuclease degradation. Obtained results demonstrated the good efficiency of our new PHEA-polycations derivatives, PHEA-HYD-CPTA, to complex and condense genomic material even at very low polycation/DNA weight ratio. 相似文献
995.
This article is concerned with the existence of solutions of boundary value problems for nonlinear second-order difference equations of the type , where δ>0 is the ratio of odd positive integers, {pn} and {qn} are real sequences. The authors apply the Linking Theorem and the Mountain Pass Lemma in the critical point theory and give some new results for the existence of solutions. 相似文献
996.
Until now the concept of a Soules basis matrix of sign patternN consisted of an orthogonal matrix R∈Rn,n, generated in a certain way from a positive n-vector, which has the property that for any diagonal matrix Λ = diag(λ1, … , λn), with λ1 ? ? ? λn ? 0, the symmetric matrix A = RΛRT has nonnegative entries only. In the present paper we introduce the notion of a pair of double Soules basis matrices of sign patternN which is a pair of matrices (P, Q), each in Rn,n, which are not necessarily orthogonal and which are generated in a certain way from two positive vectors, but such that PQT = I and such that for any of the aforementioned diagonal matrices Λ, the matrix A = PΛQT (also) has nonnegative entries only. We investigate the interesting properties which such matrices A have.As a preamble to the above investigation we show that the iterates, , generated in the course of the QR-algorithm when it is applied to A = RΛRT, where R is a Soules basis matrix of sign pattern N, are again symmetric matrices generated by the Soules basis matrices Rk of sign pattern N which are themselves modified as the algorithm progresses.Our work here extends earlier works by Soules and Elsner et al. 相似文献
997.
Precise Asymptotics in the Law of the Iterated Logarithm of Moving-Average Processes 总被引:1,自引:0,他引:1
Yun Xia LI Li Xin ZHANG 《数学学报(英文版)》2006,22(1):143-156
In this paper, we discuss the moving-average process Xk = ∑i=-∞ ^∞ ai+kεi, where {εi;-∞ 〈 i 〈 ∞} is a doubly infinite sequence of identically distributed ψ-mixing or negatively associated random variables with mean zeros and finite variances, {ai;-∞ 〈 i 〈 -∞) is an absolutely solutely summable sequence of real numbers. 相似文献
998.
We consider the stabilization of the wave equation with variable coefficients and a delay in the dissipative boundary feedback. By virtue of the Riemannian geometry methods, the energy-perturbed approach and the multiplier skills, we establish the uniform stability of the energy of the closed-loop system. 相似文献
999.
Desheng Shang 《Applied mathematics and computation》2010,217(4):1577-1583
In this paper, we employ the general integral method for traveling wave solutions of coupled nonlinear Klein-Gordon equations. Based on the idea of the exact Jacobi elliptic function, a simple and efficient method is proposed for obtaining exact solutions of nonlinear evolution equations. The solutions obtained include solitons, periodic solutions and Jacobi elliptic function solutions. 相似文献
1000.
A general form of Jordan-type double inequality for the generalized and normalized Bessel functions 总被引:1,自引:0,他引:1
Ling Zhu 《Applied mathematics and computation》2010,215(11):3802-3810
In this note, a general form of Jordan-type double inequality involving the generalized and normalized Bessel functions is presented, and then some recent results concerning generalized and sharp work of Jordan’s inequality are extended. At the same time, the applications of the results above give two new infinite series for sinx/x and sinhx/x. 相似文献