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排序方式: 共有135条查询结果,搜索用时 15 毫秒
41.
42.
Rinkevicius Z Jha PC Oprea CI Vahtras O Agren H 《The Journal of chemical physics》2007,127(11):114101
This paper presents response theory based on a spin-restricted Kohn-Sham formalism for computation of time-dependent and time-independent nonlinear properties of molecules with a high spin ground state. The developed approach is capable to handle arbitrary perturbations and constitutes an efficient procedure for evaluation of electric, magnetic, and mixed properties. Apart from presenting the derivation of the proposed approach, we show results from illustrating calculations of static and dynamic hyperpolarizabilities of small Si(3n+1)H(6n+3) (n=0,1,2) clusters which mimic Si(111) surfaces with dangling bond defects. The results indicate that the first hyperpolarizability tensor components of Si(3n+1)H(6n+3) have an ordering compatible with the measurements of second harmonic generation in SiO2/Si(111) interfaces and, therefore, support the hypothesis that silicon surface defects with dangling bonds are responsible for this phenomenon. The results exhibit a strong dependence on the quality of basis set and exchange-correlation functional, showing that an appropriate set of diffuse functions is required for reliable predictions of the first hyperpolarizability of open-shell compounds. 相似文献
43.
Ioana Cristina Marinas Eliza Oprea Mihaela Buleandra Irinel Adriana Badea Bianca Maria Tihauan Luminita Marutescu Marin Angheloiu Elena Matei Mariana Carmen Chifiriuc 《Molecules (Basel, Switzerland)》2021,26(11)
The purpose of this paper was to characterize and investigate the antimicrobial potential of Amorpha fruticosa fruits essential oil (EO). The EO was extracted by hydrodistillation, analyzed by GC-MS, and then evaluated for its interaction with microbial and mammalian cells. The antimicrobial activity was assessed against bacterial and fungal strains, in a planktonic and adherent growth state, using qualitative and quantitative assays. The main components identified in A. fruticosa fruits EO were δ-cadinene, γ-muurolene, and α-muurolene. The Gram-positive strains proved to be more susceptible than Gram-negative bacteria and fungal strains. The EO exhibited good antibiofilm activity, inhibiting the microbial adherence to the inert (96-well plates and Foley catheter section) and cellular substrata. The flow cytometry analysis revealed as one of the possible mechanisms of antimicrobial action the alteration of cell membrane hydrophobicity. The cytotoxicity on the L929 cell line occurred at concentrations higher than 0.3 mg/mL. Taken together, our results demonstrate that A. fruticosa fruits EO contains active compounds with selective inhibitory effect on different microbial strains in planktonic and biofilm growth state, explained at least partially by the interference with microbial membranes due to their hydrophobic character. 相似文献
44.
Catalin Tanase Aurel Pui Adrian Oprea Karin Popa 《Journal of Radioanalytical and Nuclear Chemistry》2009,281(3):563-567
The present study follows the extent of translocation radioactivity from the substrates of the Crucea uranium mining area
to the macromycetes spontaneously occurred during June–October 2008. To this end, radioactivity measurements (gross α + β
and 137Cs) on both macromycetes and their substrates were made. The resultants obtained were confirmed by FT-IR spectroscopy, evidencing
the presence of characteristic bands around of 910 cm−1, corresponding to the asymmetric stretching vibration of the uranyl unit and to the interaction between the UO2
2+ ions and the group belonging to various cellular components. 相似文献
45.
Slater相变是一种由于反铁磁序形成而导致的金属—绝缘体相变.本文采用第一性原理密度泛函计算方法研究了两种Slater绝缘体材料NaOsO_3和Cd_2Os_2O_7的电子结构,进而研究了反铁磁序排列、自旋轨道耦合和电子关联对其电子结构以及相变性质的影响.研究结果表明,非磁相的NaOsO_3具有金属性;而G型线性反铁磁结构是驱动NaOsO_3发生Slater相变的磁基态.此外,研究结果表明,非磁相的焦绿石Cd_2Os_2O_7的能带结构在费米能级处是连续的,表现为金属性;并且带有磁阻挫的Cd_2Os_2O_7发生Slater相变的条件十分苛刻,只有在自旋轨道耦合和1.8 eV电子关联的共同作用下一种全进—全出非线性反铁磁结构才能使其发生Slater相变.说明全进—全出非线性反铁磁结构是使Cd_2Os_2O_7发生Slater相变的磁基态,而自旋轨道耦合和1.8 eV的电子关联在消除磁阻挫上起到了关键作用. 相似文献
46.
47.
Ross Geoghegan Andrew Nicas John Oprea 《Transactions of the American Mathematical Society》1996,348(5):2039-2062
Higher analogs of the Euler characteristic and Lefschetz number are introduced. It is shown that they possess a variety of properties generalizing known features of those classical invariants. Applications are then given. In particular, it is shown that the higher Euler characteristics are obstructions to homotopy properties such as the TNCZ condition, and to a manifold being homologically Kähler.
48.
L. M. Mosulishvili Ye. I. Kirkesali A. I. Belokobylsky A. I. Khizanishvili M. V. Frontasyeva S. F. Gundorina C. D. Oprea 《Journal of Radioanalytical and Nuclear Chemistry》2002,252(1):15-20
To evaluate the potentiality of the blue-green algae Spirulina platensis as a matrix for the production of Se-containing pharmaceuticals, the background levels of 31 major, minor and trace elements (Na, Mg, Al, Cl, K, Ca, Sc, V, Cr, Mn, Fe, Co, Ni using (n,p) reaction), As, Br, Zn, Rb, Mo, Ag, Sb, I, Ba, Sm, Tb, Tm, Hf, Ta, W, Au, Hg, Th were determined in Spirulina platensis biomass by means of epithermal neutron activation analysis. The possibility of the purpose-oriented incorporation of Se into Spirulina platensis biomass was demonstrated. The polynomial dependence of the Se accumulation on nutritional medium loading was revealed. The analytical technique used allows to control the amount of toxic elements in algae Spirulina platensis. Based on this study, a conclusion of the possibility to use Spirulina platensisas a matrix for the production of Se-containing pharmaceutical was drawn. 相似文献
49.
A. Pantelică C. Oprea M. Frontasyeva I. I. Georgescu E. Pincovschi L. Catană 《Journal of Radioanalytical and Nuclear Chemistry》2004,262(1):111-118
Instrumental neutron activation analysis (INAA) was used to determine various trace elements in crop vegetation (potato, carrot
and maize) grown around a phosphate fertilizer plant in Romania. INAA using long-lived radionuclides was applied at NIPNE
in Bucharest, and based on short-lived radionuclides at JINR in Dubna. The results for Na, Mg, Cl, K, Ca, Mn, Fe, Zn, As,
and Hg were compared with Romanian norms for the alimentary products, as well as with literature data. Concentration ratios
to control samples for both soil and crop as well as concentration factors of crop to host soil were assessed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
50.
Kurunczi L Seclaman E Oprea TI Crisan L Simon Z 《Journal of chemical information and modeling》2005,45(5):1275-1281
A homogeneous collection of 45 estrogen agonist derivatives with relative binding affinities measured to the estrogen receptor from Ratus norvegicus was used. The quantitative structure-activity relationships were derived using an improved minimal topologic difference (MTD) method in a partial least-squares (PLS) variant. The spatially assigned analysis of fragment properties can provide receptor site maps, within the limits of the existing series. A steric misfit was found for the steroidal position 2; benefic hydrophobic and van der Waals (enhanced by high polarizability) interactions were found for the 17alpha-CH=CH-X group. MTD-PLS mapping results are confirmed by the experimentally derived estradiol-estrogen receptor binding site contacts (based on X-ray crystallography). Our results suggest that this MTD-PLS method can yield useful results for interactions with receptors of unknown 3D structure and, generally, for the steric rigidity of receptor sites. 相似文献