Comparative Cross-sectional Study on Phasic Heart Rate Variability and Working Memory Among Young Adults.

Context: Heart rate variability (HRV) could be a promising early biomarker of cognitive impairment. A better understanding of reaction patterns between cardiovascular and cognitive functions can be helpful in predicting and preventing the manifestation of disease. Additionally, beneficial cardiovascular evidence for yoga is promising but lacks short-term (approximately one year) cross-sectional investigations. Objective: The study intended to investigate phasic HRV and its patterns of reaction in yoga practitioners and nonpractitioners, using rest and stress periods induced by cognitive tasks. Design: The research team designed a cross-sectional, controlled study. Setting: The study took place in the Cognitive Neuroscience Laboratory at Swami Vivekananda Yoga Anusandhana Samsthana (S-VYASA) in Bangalore, Karnataka, India. Participants: Participants were 84 healthy male volunteers, 42 in the yoga group, the intervention group, and 42 in the nonyoga group, the control group. Outcome Measures: Simultaneously the research team recorded both an autonomic measurement, an electrocardiogram (EKG), and a working memory (WM) task, the N-back task, to assess the effects of the two groups' reaction patterns on HRV and WM. The data included an average of a 5 min epoch for the baseline EKG and a 15 min epoch for the EKG during the N-back task. The research team recorded the HRV indices: (1) mean rhythm-to-rhythm (RR) intervals, (2) heart rate (HR), (3) standard deviation of RR intervals (STDRR), (4) root mean square of successive differences (RMSSD), (5) triangular interpolation of RR interval histogram (TINN), (6) percentage of successive normal sinus RR intervals >50 ms (pNN50), (7) number of adjacent N-N intervals over 50 ms (NN50), (8) low frequency (LF), (9) high frequency (HF), and (10) LF/HF ratio. The team compared the HRV indices to participants' reaction patterns while performing cognitive tasks. Results: In response to psychological stress, the yoga group had enhanced physiological activity, such as an increased cardiac activity, indicated during the task by a higher HR, NN50, and TINN and a lower RR, STDRR, pNN50, and RMSSD, indicating more flexibility. The control group had an increase only in HR and TINN and had a decreased RR. Simultaneously, the yoga group showed greater accuracy in the N-back task for WM compared to the control group. Conclusions: The study revealed significant differences in phasic HRV and WM performance among the groups. The yoga group had higher phasic HRV indices with higher cognitive performance than the control group. This is the first study that has attempted to show that the cross-sectional differences in HRV indices between yoga practitioners and nonpractitioners exist at an early stage of life, where no disease has yet manifested. The research team suggest that incorporating yoga into daily life at a young age may yield a healthy life.

Heartfulness Meditation Alters Electroencephalogram Oscillations: An Electroencephalogram Study.

Background: Heartfulness meditation (HM) has been shown to have positive impacts on cognition and well-being, which makes it important to look into the neurophysiological mechanisms underlying the phenomenon. Aim: A cross-sectional study was conducted on HM meditators and nonmeditators to assess frontal electrical activities of the brain and self-reported anxiety and mindfulness. Settings and Design: The present study employed a cross-sectional design. Methods: Sixty-one participants were recruited, 28 heartfulness meditators (average age male: 31.54 ± 4.2 years and female: 30.04 ± 7.1 years) and 33 nonmeditators (average age male: 25 ± 8.5 years and female: 23.45 ± 6.5 years). An electroencephalogram (EEG) was employed to assess brain activity during baseline (5 min), meditation (10 min), transmission (10 min) and post (5 min). Self-reported mindfulness and anxiety were also collected in the present study. The EEG power spectral density (PSD) and coherence were processed using MATLAB. The statistical analysis was performed using an independent sample t-test for trait mindfulness and anxiety, repeated measures analysis of variance (ANOVA) for state mindfulness and anxiety, and Two-way multivariate ANOVA for EEG spectral frequency and coherence. Results: The results showed higher state and trait mindfulness, P < 0.05 and P < 0.01, respectively, and lower state and trait anxiety, P < 0.05 and P < 0.05, respectively. The PSD outcomes showed higher theta (P < 0.001) and alpha (P < 0.01); lower beta (P < 0.001) and delta (P < 0.05) power in HM meditators compared to nonmeditators. Similarly, higher coherence was found in the theta (P < 0.01), alpha (P < 0.05), and beta (P < 0.01) bands in HM meditators. Conclusions: These findings suggest that HM practice may result in wakeful relaxation and internalized attention that can influence cognition and behavior.

Weak ferromagnetism and magnetoelectric coupling through the spin-lattice coupling in (1-x)Pb(Fe2/3W1/3)O3-(x)BiFeO3 (x = 0.1 and 0.4) solid solution.

We report on the structure, spin-lattice and magneto-electric coupling in (1-x)Pb(Fe2/3W1/3)O3-(x)BiFeO3(where x = 0.1 and 0.4) (PBFW) solid solution synthesized through two-step solid-state reaction method. The room temperature (RT) crystallographic studies were carried out using x-ray diffraction and neutron diffraction measurements which show a single-phase Pseudocubic crystal system with Pm-3m space group. Rietveld refinement was carried out to obtain the structural parameters using Fullprof software and the observed structural parameters are in good agreement with the previous reports. Temperature-dependent neutron diffraction measurements reveal the presence of commensurate G-type antiferromagnetic structure. The magnetic structure was analyzed using the propagation wave vector k ∼ (½ ½ ½) for both the solid solutions. The obtained lattice constants increase linearly and the magnetic moment decrease with temperature, which shows a remarkable anomaly around the magnetic (T N ∼ 405 K for x = 0.1 and 531 K for x = 0.4) transition temperatures. This anomaly clearly indicates the existence of spin-lattice and magnetoelectric coupling. The magnetic susceptibility (ZFC and FC at 500 Oe) and M-H hysteresis loop measurements show spontaneous magnetic moment due to the Fe3+-O2--Fe3+ superexchange interaction coexisting with the weak ferromagnetism. Bifurcation of ZFC and FC curve reveals the strong anisotropic nature. Astonishingly, magnetic measurements show the non-zero magnetic moment above T N and broadening of the magnetic transition indicates the presence of short-range uncompensated sublattice weak ferromagnetic clusters in the paramagnetic region. The Mossbauer spectroscopy and electron paramagnetic resonance studies exhibit the RT magnetically ordered system and confirm the +3 state of Fe along with the fraction of Fe2+ ions.

Unveiling the composite structures of emissive consolidated p-i-n junction nanocells for white light emission.

Hybrid organic-Red-Green-Blue (RGB) color quantum dots were incorporated into consolidated p(polymer)-i(RGB quantum dots)-n(small molecules) junction structures to fabricate a single active layer for a light emitting diode device for white electroluminescence. The semiconductor RGB quantum dots, as an intrinsic material, were electrostatically bonded between functional groups of the p-type polymer organic material core surface and the n-type small molecular organic material shell surface. The ZnCdSe/ZnS and CdSe/ZnS quantum dots distributed uniformly and isotropically surrounding the polymer core which in turn was surrounded by small molecular organic materials. In the present study, we have identified the mechanisms of chemical synthesis and interactions of the p-i-n junction nanocell structure through modeling studies by DFT calculations. We have also investigated optical, structural and electrical properties along with the carrier transport mechanism of the light emitting diodes which have a single active layer of consolidated p-i-n junction nanocells for white electroluminescence.

Emissive ZnO-graphene quantum dots for white-light-emitting diodes.

Hybrid nanostructures combining inorganic materials and graphene are being developed for applications such as fuel cells, batteries, photovoltaics and sensors. However, the absence of a bandgap in graphene has restricted the electrical and optical characteristics of these hybrids, particularly their emissive properties. Here, we use a simple solution method to prepare emissive hybrid quantum dots consisting of a ZnO core wrapped in a shell of single-layer graphene. We then use these quantum dots to make a white-light-emitting diode with a brightness of 798 cd m(-2). The strain introduced by curvature opens an electronic bandgap of 250 meV in the graphene, and two additional blue emission peaks are observed in the luminescent spectrum of the quantum dot. Density functional theory calculations reveal that these additional peaks result from a splitting of the lowest unoccupied orbitals of the graphene into three orbitals with distinct energy levels. White emission is achieved by combining the quantum dots with other emissive materials in a multilayer light-emitting diode.