Lítio e parâmetros orbitais em sistemas binários com componentes evoluídas

One of the best established properties of the single late type evolved stars is that their rotational velocity and lithium content decrease with effective temperature and age. Nevertheless, the root cause of this property, as well as the link between rotation and lithium abundance and, in particular, the effects of binarity on rotation and lithium content in binary systems with evolved component, are not yet completely established. How does the gravitational tides, in binary systems, affects rotational evolution and lithium dilution? Trying to answer these questions, we have carried out an observational survey, in the lithium region centered at the lithium I line A6707.81A, for a large sample of about 100 binary systems with evolved component along the spectral range F, G and K, with the CES spectrometer mounted at the CAT 1.44 m Telescope of the ESO, La Silla, Chile. By combining the abundances of lithium issued from these observations with rotational velocity and orbital parameters, we have found a number of important results. First of all, we confirm that in this class of binary systems rotation is effectively affected by tidal effects. Binary systems with orbital period lower than about 100 days and circular or nearly circular orbits, present rotational velocity enhanced in relation to the single giant stars and to the binary systems with an orbital period larger than 100 days. This is clearly the result of the synchonization between the rotational and orbital motions due to tidal effects. In addition, we have found that lithium abundances in binary systems with giant components present the same gradual decreasing with effective temperature, observed in the single giants of same luminosity class and spectral types. We have found no lithium-rich binary systems, in contrast with single giants. A remarkable result from the present study is the one showing that synchronized binary systems with giant component retains more of their original lithium than the unsynchronized systems. In fact, we have found a possible "inhibited zone", in which synchronized binary systems with giant component having lithium abundance lower than a threshold level should be unusual. Finally, the present study also shows that the binary systems with giant component presenting the highest lithium contents are those with the highest rotation rates

Investigação da influência do cochilo na aprendizagem escolar

There is a known positive effect of nocturnal sleep for brain plasticity and the consolidation of declarative and procedural memories, as well as for the facilitation of insight in problem solving. However, a possible pro-mnemonic effect of daytime naps after learning is yet to be properly characterized. The goal of this project was to evaluate the influence of daytime naps on learning among elementary and middleschool students, measuring the one-day (acute), and semester-long (chronic) effects of post-learning naps on performance. In the Acute Day-Nap condition, the elementary students were exposed to a class and then randomly divided into three groups: Nap (N), Game-based English Class (GBEC) and Traditional English Class (TEC). There were 2 multiple-choice follow-up tests to evaluate students performance in the short and long runs. In the short run, the N group outperformed the other two groups; and such tendency was maintained in the long run. In the chronic condition, the middle-school students were randomly separated into two groups: Nap (N) and Class (C) and were observed during one academic term. The N group had increased school performance in relation to the C group. In the statistical analyses, independent t-tests were applied considering the scores significant when p<0,05, expressed in terms of average ± average standard error. Results can be interpreted as an indication that a single daytime nap opportunity is not enough to ensure learning benefits. Therefore, more research is needed in order to advocate in favor of a daytime nap as a pedagogical means of promoting enhanced school performance

Influência de mudanças de fase no ciclo claro-escuro sobre o controle autonômico cardíaco de ratos

Introduction: The circadian system has neural projections for the Autonomic Nervous System (ANS), directly interfering with sympathetic-vagal modulation of the cardiovascular system. Disturbances in the circadian system, such as phase changes in light-dark cycle (LD), has been related to the risk of development of cardiovascular diseases due to increased sympathetic tone and reduction o Heart Rate Variability (HRV - RR intervals). Purpose: Investigate the interaction between Circadian Timing System and cardiac autonomic control in rats. Materials and methods: We used 18 Wistar rats (♀, age = 139.9 ± 32.1 days, weight = 219.5 ± 16.2 g), divided into three distinct groups: Control (CG), phase delay of 6h (GDe) and phase advance of 6h (GAd). Three animals were excluded during data collection (CG/GDe/GAd - n=5). Telemeters were surgically implanted in each animal for continuous acquisition of electrocardiographic (ECG) signals (duration of 21 days in the CG and 28 days in GDe/ GAd). A LD cycle was established 12h: 12h, beginning of light at18:00h and dark at 06:00h. The animals remained in the same CG LD cycle throughout the experimental period, while, on the 14th day of registration, the GDe and GAd underwent a delay and an advance in 6h, respectively. Throughout the experimental period, the locomotor activity (LA), the mean heart rate (mHR) and variables related to iRR [mean RR (mRR), SDNN, RMSSD, LF, HF and LF/ HF ratio ] were recorded. All data were analyzed in blocks of 3 and 7 days, for the presence of circadian rhythm, values of Cosinor - mesor, amplitude and acrophase (paired t test), phase relationship, differences between light and dark (t test independent), averages every 30 minutes along each time series (two-way ANOVA with post hoc Bonferroni). The data block B1,M1 and M2 in CG served as benchmarks for comparisons between series of analysis of the GAT/GAV. Results: We observed circadian rhythmicity in the variables LA, mRR and mFC(p<0.01). mRR and mFC showed phase relationship with the LA in all three groups, being less stable in GAd. In the CG, no significant differences between blocks were found in any of the analyzes(p>0.05). Among the 7 day blocks, there was a significant reduction in mRR(p=0.04) and mFC(p=0.03) in GDe and significant reduction in HF mean(p=0.02) in GAd; and between 3 day blocks, a significant increase of LF/HF(p= 0.04) in the GDe; besides mRR(p=0.03), SDNN(p=0.04), RMSSD (p=0.04), LF (p=0.01) and HF(p=0.02) significant increase in the GAd. It was found that the differences between the means of the mRR, LA and mFC in light and dark phases were not significant after phase changes in some of the blocks/moments (GDe and GAd). No significant results were found when comparing rhythmic variables means every 30 minutes over the blocks, except for a significant decrease in mRR at the middle of the dark phase (B2) and the start of light phase (B3) - (p<0.01). Conclusion: phase advances and delays (6h) altered cardiac autonomic control in the experimental groups by temporarily HRV decrease. Phase advances apparently had greater negative interference in this process, in relation to the phase delays.