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EI Rodriguez Martinez CI Barriga-Paulino MI Zapata CC Chinchilla AM López-Jiménez CM Gómez 《BMC neuroscience》2012,13(1):104-23
ABSTRACT: BACKGROUND: The peri-adolescent period is a crucial developmental moment of transition from childhood to emergent adulthood. The present report analyses the differences in Power Spectrum (PS) of the Electroencephalogram (EEG) between late childhood (24 children between 8 and 13 years old) and young adulthood (24 young adults between 18 and 23 years old). RESULTS: The narrow band analysis of the Electroencephalogram was computed in the frequency range of 0--20 Hz. The analysis of mean and variance suggested that six frequency ranges presented a different rate of maturation at these ages, namely: low delta, delta-theta, low alpha, high alpha, low beta and high beta. For most of these bands the maturation seems to occur later in anterior sites than posterior sites. Correlational analysis showed a lower pattern of correlation between different frequencies in children than in young adults, suggesting a certain asynchrony in the maturation of different rhythms. The topographical analysis revealed similar topographies of the different rhythms in children and young adults. Principal Component Analysis (PCA) demonstrated the same internal structure for the Electroencephalogram of both age groups. Principal Component Analysis allowed to separate four subcomponents in the alpha range. All these subcomponents peaked at a lower frequency in children than in young adults. CONCLUSIONS: The present approaches complement and solve some of the incertitudes when the classical brain broad rhythm analysis is applied. Children have a higher absolute power than young adults for frequency ranges between 0-20 Hz, the correlation of Power Spectrum (PS) with age and the variance age comparison showed that there are six ranges of frequencies that can distinguish the level of EEG maturation in children and adults. The establishment of maturational order of different frequencies and its possible maturational interdependence would require a complete series including all the different ages. 相似文献
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An integral equation formulation for buoyancy-driven convection problems is developed and illustrated. Buoyancy-driven convection in a bounded cylindrical geometry with a free surface is studied for a range of aspect ratios and Nusselt numbers. The critical Rayleigh number, the nature of the cellular motion, and the heat transfer enhancement are computed using linear theory. Green's functions are used to convert the linear problem into linear Fredholm integral equations. Theorems are proved which establish the properties of the eigenvalues and eigenfunctions of the linear integral operator which appears in these equations. 相似文献
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CM Thaker S Rayaprol Krushna Mavani DS Rana MS Sahasrabudhe SI Patil DG Kuberkar 《Pramana》2002,58(5-6):1035-1039
The effect of simultaneous substitution of a fluctuating cation and a divalent cation in LaMnO3 perovskite modifies the properties of the material to exhibit large valence colossal magnetoresistance (CMR) effect. A good
example of these properties is (La1−2x
Pr
x
Ca
x
)MnO3 (LPCMO) type CMR material. In this communication it is reported that, with the increase in x (for x=0.1, 0.15, 0.2), the T
c varies between 100 and 120 K with improvisation in metal-insulator transition. Interestingly, resistance increases with x from few hundred ohms to few kilo ohms with corresponding decrease in the unit cell volume. The results of the studies using
X-ray diffraction (XRD), electrical resistivity, magnetoresistance and ac susceptibility measurements on LPCMO samples for
understanding the structural, transport and magnetic properties are discussed in detail. 相似文献
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CM Silva MF Duarte ML Mira MH Florêncio K Versluis AJ Heck 《Rapid communications in mass spectrometry : RCM》1999,13(12):1098-1103
Fast atom bombardment, combined with high-energy collision-induced tandem mass spectrometry, has been used to investigate gas-phase metal-ion interactions with captopril, enalaprilat and lisinopril, all angiotensin-converting enzyme inhibitors.Suggestions for the location of metal-binding sites are presented. For captopril, metal binding occurs most likely at both the sulphur and the nitrogen atom. For enalaprilat and lisinopril, binding preferably occurs at the amine nitrogen. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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Pavot Kristian Juraj Bernát Ján Imrich Tatiana Bušová 《Chemistry of Heterocyclic Compounds》1995,31(10):1204-1207
9-Isothiocyanatoacridines containing a reactive NCS group, together with a biologically active acridine skeleton, were used for the synthesis of new acridine heterocycles. Their reactivity with aliphatic and aromatic amines as well as 15 amino acids was quantified by kinetic measurements. Sodium D-alkyl-N-(9-acridinyl)iminothiocarbonates obtained by addition of sodium alkoxides to the title compounds gave three types of products with organic halogen reagents. The reaction of above iminothiocarbonates with alkyl halides led to the fluorescent S-alkyl derivatives, whereas bromoacetyl bromide and alkyl bromoacetates afforded the 3-(9acridinyl)-1, 3-thiazolidine-2,4-diones and a new heterocycle, spiro[dihydroacridine-9(IOH), 4'-thiazoline], respectively.Department of Organic Chemistry, P. J. Safarik University, 04167 Kosice, Slovak Republic. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1376–1379, October, 1995. Original article submitted July 1, 1995 相似文献
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A.A. Kamel CM. Ma M.S. El-Aasser F.J. Micale J.W. Vanderhoff 《Journal of Dispersion Science and Technology》2013,34(2-3):315-330
The electrophoretic mobility behavior of well-characterized polystyrene latex particles, carrying one type of surface functional endgroups, has been studied as a function of pH. At low pH, the interaction of protons with the functional endgroups increased in the order: Hydroxyl > carboxyl > sulfate; at high pH the order of interaction was reversed; and at intermediate pH no interactions were observed. The particles of the polystyrene latexes in their different forms at the intermediate pH range, dispersed in deionized water, all exhibited the same mobility irrespective of the functional endgroup. The origin of charge in these systems is explained as being the result of either the preferential adsorption of hydroxyl ions or an electron - injection mechanism due to the overlap of local intrinsic molecular - ion states in polystyrene and water. At low concentrations of functional endgroups, the surface properties of the polystyrene latexes are largely dependent upon the hydrophobic nature of the surface. 相似文献
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Metal-dependent global folding and activity of the 8-17 DNAzyme studied by fluorescence resonance energy transfer 总被引:2,自引:0,他引:2
Kim HK Liu J Li J Nagraj N Li M Pavot CM Lu Y 《Journal of the American Chemical Society》2007,129(21):6896-6902
The 8-17 DNAzyme is a DNA metalloenzyme catalyzing RNA transesterification in the presence of divalent metal ions, with activity following the order Pb2+ > Zn2+ >Mg2+. Since the DNAzyme has been used as a metal ion sensor, its metal-induced global folding was studied by fluorescence resonance energy transfer (FRET) by labeling the three stems of the DNAzyme with the Cy3/Cy5 FRET pair two stems at a time in order to gain deeper insight into the role of different metal ions in its structure and function. FRET results indicated that, in the presence of Zn2+ and Mg2+, the DNAzyme folds into a compact structure, stem III approaching a configuration defined by stems I and II without changing the angle between stems I and II. Correlations between metal-induced folding and activity were also studied. For Zn2+ and Mg2+, the metal ion with higher affinity for the DNAzyme in global folding (Kd(Zn) = 52.6 microM and Kd(Mg) = 1.36 mM) also displays higher affinity in activity (Kd(Zn) = 1.15 mM and Kd(Mg) = 53 mM) under the same conditions. Global folding was saturated at much lower concentrations of Zn2+ and Mg2+ than the cleavage activities, indicating the global folding of the DNAzyme occurs before the cleavage activity for those metal ions. Surprisingly, no Pb2+-dependent global folding was observed. These results suggest that for Pb2+ global folding of the DNAzyme may not be a necessary step in its function, which may contribute to the DNAzyme having the highest activity in the presence of Pb2+. 相似文献