RESUMO
The complex {[Dy2(PDOA)3(H2O)6]·2H2O}n (1) (H2PDOA = 1,2-phenylenedioxydiacetic acid) was prepared from aqueous solution. Its crystal structure, built up of {-Dy-O-C-O-}n chains interlinked by PDOA ligands yielding a ladder-like arrangement, was determined at 173 K. 1 exhibits slow magnetic relaxation under a small magnetic field BDC = 0.2 T with two (LF and HF) relaxation channels. The LF relaxation time at BDC = 0.2 T and T = 1.85 K is as slow as τ(LF) = 46 ms whereas the HF channel is τ(HF) = 1.4 ms. The mole fraction of the LF species is xLF = 0.76 at 1.85 K and it escapes progressively on heating. In the dinuclear analogue [Dy2(PDOA)3(H2O)6]·3.5H2O (2) one PDOA ligand forms a bis(chelate) bridge between the two Dy(iii) atoms yielding a local structure analogous to that in 1; however its AC susceptibility data show slightly different quantitative characteristics of the single-molecule magnetic behaviour.
RESUMO
This study investigates the predictive value of child-related and environmental characteristics for early lexical development. The German productive vocabulary of 51 2-year-olds (27 girls), assessed via parental report, was analyzed taking children's gender, the type of early care they experienced, and their mono- versus bilingual language composition into consideration. The children were from an educationally homogeneous group of families and state-regulated daycare facilities with high structural quality. All investigated subgroups exhibited German vocabulary size within the expected normative range. Gender differences in vocabulary composition, but not in size, were observed. There were no general differences in vocabulary size or composition between the 2 care groups. An interaction between the predictors gender and care arrangement showed that girls without regular daycare experience before the age of 2 years had a somewhat larger vocabulary than all other investigated subgroups of children. The vocabulary size of the 2-year-old children in daycare correlated positively with the duration of their daycare experience prior to testing. The small subgroup of bilingual children investigated exhibited slightly lower but still normative German expressive vocabulary size and a different vocabulary composition compared to the monolingual children. This study expands current knowledge about relevant predictors of early vocabulary. It shows that in the absence of educational disadvantages the duration of early daycare experience of high structural quality is positively associated with vocabulary size but also points to the fact that environmental characteristics, such as type of care, might affect boys' and girls' early vocabulary in different ways.
RESUMO
OBJECTIVE: The present study aimed at examining the time course and topography of oscillatory brain activity and event-related potentials (ERPs) in response to laterally presented affective pictures. METHODS: Electroencephalography was recorded from 129 electrodes in 10 healthy university students during presentation of pictures from the international affective picture system. Frequency measures and ERPs were obtained for pleasant, neutral, and unpleasant pictures. RESULTS: In accordance with previous reports, a modulation of the late positive ERP wave at parietal recording sites was found as a function of emotional arousal. Early mid gamma band activity (GBA; 30-45 Hz) at 80 ms post-stimulus was enhanced in response to aversive stimuli only, whereas the higher GBA (46-65 Hz) at 500 ms showed an enhancement of arousing, compared to neutral pictures. ERP and late gamma effects showed a pronounced right-hemisphere preponderance, but differed in terms of topographical distribution. CONCLUSIONS: Late gamma activity may represent a correlate of widespread cortical networks processing different aspects of emotionally arousing visual objects. In contrast, differences between affective categories in early gamma activity might reflect fast detection of aversive stimulus features.