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51.
Bigović D Savikin K Janković T Menković N Zdunić G Stanojković T Djurić Z 《Natural product communications》2011,6(6):819-822
Flowers of Helichrysum plicatum were extracted under different experimental conditions, and their antioxidant activity was determined by DPPH radical scavenging assay. Extracts obtained with higher concentration of ethyl acetate (90% or 100%) were found to contain the greatest amount of total phenolics (> 250 mg gallic acid equivalents/g of dried extract), and high correlation between total phenolic content and antiradical activity was observed (r = -0.79). Based on the total phenolic content and antiradical activity, some extracts were selected for investigation of cytotoxic activity toward PC3, HeLa and K562 human cancer cell lines in vitro. All tested extracts exhibited moderate activity against HeLa cells (41.9-42.1 microg/mL), whereas the extract obtained with 100% ethyl acetate was the most active against K562 and PC3 cell lines (25.9 and 39.2 microg/mL, respectively). Statistical analysis revealed significant correlation between total phenolic content and cytotoxic activity against PC3 and K562 cells. HPLC identification of phenolic compounds from the extracts indicated the presence of apigenin, naringenin and kaempferol as free aglycones, and glycosides of apigenin, naringenin, quercetin and kaempferol. Among aglycones, kaempferol displayed moderate cytostatic activity against all cell lines (24.8-64.7 microM). 相似文献
52.
Dana Ortansa Dorohoi Carmen Felicia Dascalu Teodora Teslaru Livia Vicenta Gheorghies 《光谱学快报》2013,46(6):383-391
The visible electronic absorption spectra of two carbanion disubstituted cycloimmonium ylids having a 3-aryl-pyridazinium derivative as cation and a common disubstituted carbanion (-2,4,6-picryl-benzoyl) were studied in solvents with different physical and chemical properties. The visible electronic absorption band of 3-aryl-pyridazinium ylids is attributed to an electron charge transfer from the carbanion toward the heterocycle. The solvent effects on the visible electronic band of the studied ylids were described both by empirical parameters defined by Kosower and by using the theory of a dielectric homogeneous solution. Some remarks about the nature of the molecular interactions in the 3-aryl-phthalazinium-2,4,6-picryl-benzoyl methylid solutions are made in this paper on the basis of solvatochromic study. 相似文献
53.
In this paper we study the existence of solutions u ∈ \({{W}^{1,p}_{0}}\) (Ω) with △ p u ∈ L 2(Ω) for the Dirichlet problem 1 $$ \left\{ \begin{array} [c]{l}-\triangle_{p}u\left( x\right) \in-\partial{\Phi}\left( u\left( x\right) \right) +G\left( x,u\left( x\right) \right) ,x\in{\Omega},\\ u\mid_{\partial{\Omega}}=0, \end{array} \right. $$ where Ω ? R N is a bounded open set with boundary ?Ω, △ p stands for the p?Laplace differential operator, ?Φ denotes the subdifferential (in the sense of convex analysis) of a proper convex and lower semicontinuous function Φ and G : Ω × R → 2R is a multivalued map. We prove two existence results: the first one deals with the case where the multivalued map u ? G(x, u) is upper semicontinuous with closed convex values and the second one deals with the case when u ? G(x, u) is lower semicontinuous with closed (not necessarily convex) values. 相似文献
54.
Recursive matrix relations for kinematics and dynamics analysis of a three-prismatic-revolute-cylindrical (3-PRC) parallel
kinematic machine (PKM) are performed in this paper. Knowing the translational motion of the platform, we develop first the
inverse kinematical problem and determine the positions, velocities and accelerations of the robot’s elements. Further, the
inverse dynamic problem is solved using an approach based on the principle of virtual work and the results in the framework
of the Lagrange equations with their multipliers can be verified. Finally, compact matrix equations and graphs of simulation
for input force and power of each of three actuators are obtained. The investigation of the dynamics of this parallel mechanism
is made mainly to solve successfully the control of the motion of such robotic system. 相似文献
55.
Arrigo?CellinaEmail author Vasile?Staicu 《Calculus of Variations and Partial Differential Equations》2018,57(2):66
We consider the higher differentiability of a solution u to the problem of minimizing where \(\Lambda \) is of fast growth in the second variable, i.e., we assume that \(\Lambda (x,t)\) grows in t faster than \(t^N\), where N is the dimension of the space. We do not assume conditions limiting above the size of the second derivative of \(\Lambda \) with respect to t.
相似文献
$$\begin{aligned} \int _{\Omega }[\Lambda (x ,|\nabla v(x)|) +f(x)v(x)]dx \end{aligned}$$
56.
Chemical composition and antibacterial activity of selected essential oils and some of their main compounds 总被引:1,自引:0,他引:1
Wanner J Schmidt E Bail S Jirovetz L Buchbauer G Gochev V Girova T Atanasova T Stoyanova A 《Natural product communications》2010,5(9):1359-1364
The chemical composition of essential oils of cabreuva (Myrocarpus fastigiatus Allemao, Fabaceae) from Brazil, cedarwood (Juniperus ashei, Cupressaceae) from Texas, Juniper berries (Juniperus communis L., Cupressaceae) and myrrh (Commiphora myrrha (Nees) Engl., Burseraceae) were analyzed using GC/FID and GC/MS. The antimicrobial activity of these essential oils and some of their main compounds were tested against eleven different strains of Gram-positive and Gram-negative bacteria by using agar diffusion and agar serial dilution methods. Animal and plant pathogens, food poisoning and spoilage bacteria were selected. The volatile oils exhibited considerable inhibitory effects against all tested organisms, except Pseudomonas, using both test methods. Higher activity was observed against Gram-positive strains in comparison with Gram-negative bacteria. Cabreuva oil from Brazil showed similar results, but in comparison with the other oils tested, only when higher concentrations of oil were used. 相似文献
57.
Sergiu Aizicovici Vasile Staicu 《NoDEA : Nonlinear Differential Equations and Applications》2007,14(3-4):361-376
We prove the existence of integral solutions to the nonlocal Cauchy problem in a Banach space X, where is m-accretive and such that –A generates a compact semigroup, has nonempty, closed and convex values, and is strongly-weakly upper semicontinuous with respect to its second variable,
and . The case when A depends on time is also considered.
相似文献
58.
In this paper we consider a second order differential inclusion driven by the ordinary p-Laplacian, with a subdifferential term, a discontinuous perturbation and nonlinear boundary value conditions. Assuming the existence of an ordered pair of appropriately defined upper and lower solutions φ and ψ respectively, using truncations and penalization techniques and results from nonlinear and multivalued analysis, we prove the existence of solutions in the order interval [ψ,φ] and of extremal solutions in [ψ,φ]. We show that our problem incorporates the Dirichlet, Neumann and Sturm–Liouville problems. Moreover, we show that our method of proof also applies to the periodic problem. 相似文献
59.
A. Lucaciu M. V. Frontasyeva E. Steinnes Ye. N. Cheremisina C. Oprea T. B. Progulova L. Staicu L. Timofte 《Journal of Radioanalytical and Nuclear Chemistry》1999,240(2):457-458
This is the first systematic study of air pollution from heavy metals and other trace elements throughout several industrialized
areas and national parks of Eastern Romanian Carpathians using the moss biomonitoring technique. Samples ofHylocomium splendens collected at 120 sites were analyzed by epithermal neutron activation analysis at the pulsed fast reactor IBR-2 at JINR,
Dubna, for a wide range of elements including heavy metals and rare earths (Na, Mg, Al, Cl,K, Ca, Sc, V, Cr, Mn, Fe, Co, Ni
(by (n,p) reaction), Cu, Zn, As, Se, Br, Rb, Sr, Zr, Mo, Ag, Sn, Sb, I, Cs, Ba, La, Ce, Nd, Sm, Eu, Gd, Tb, Yb, Hf, Ta, W,
Au, Th, and U). Copper, lead and cadmium were determined by AAS. Certified Reference Standards of mosses produced for interlaboratory
comparisons in the European moss-survey 1995 were used to ensure the quality of the measurements. To present results in the
form of coloured contour maps the geographical information system GIS-INTEGRO was used. The regional extent of pollution with
specific metals was determined. Results reported are well consistent with those obtained in numerous recent projects carried
out in Germany, the Netherlands, Poland, Bulgaria and other countries. 相似文献
60.
The hydrodynamic behaviour of the magnetic liquid in a magnetic fluid rotary shaft seal can be described by a coupled system of nonlinear partial differential equations. A decoupling numerical solving strategy is proposed and applied to determine the flow in a magnetic fluid seal. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献