3,045 research outputs found
Magnitude and Sign Correlations in Heartbeat Fluctuations
We propose an approach for analyzing signals with long-range correlations by
decomposing the signal increment series into magnitude and sign series and
analyzing their scaling properties. We show that signals with identical
long-range correlations can exhibit different time organization for the
magnitude and sign. We find that the magnitude series relates to the nonlinear
properties of the original time series, while the sign series relates to the
linear properties. We apply our approach to the heartbeat interval series and
find that the magnitude series is long-range correlated, while the sign series
is anticorrelated and that both magnitude and sign series may have clinical
applications.Comment: 4 pages,late
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Do Seasons Have an Influence on the Incidence of Depression? The Use of an Internet Search Engine Query Data as a Proxy of Human Affect
Background: Seasonal depression has generated considerable clinical interest in recent years. Despite a common belief that people in higher latitudes are more vulnerable to low mood during the winter, it has never been demonstrated that human's moods are subject to seasonal change on a global scale. The aim of this study was to investigate large-scale seasonal patterns of depression using Internet search query data as a signature and proxy of human affect. Methodology/Principal Findings: Our study was based on a publicly available search engine database, Google Insights for Search, which provides time series data of weekly search trends from January 1, 2004 to June 30, 2009. We applied an empirical mode decomposition method to isolate seasonal components of health-related search trends of depression in 54 geographic areas worldwide. We identified a seasonal trend of depression that was opposite between the northern and southern hemispheres; this trend was significantly correlated with seasonal oscillations of temperature (USA: r = −0.872, <0.001; Australia: r = −0.656, <0.001). Based on analyses of search trends over 54 geological locations worldwide, we found that the degree of correlation between searching for depression and temperature was latitude-dependent (northern hemisphere: r = −0.686; <0.001; southern hemisphere: r = 0.871; <0.0001). Conclusions/Significance: Our findings indicate that Internet searches for depression from people in higher latitudes are more vulnerable to seasonal change, whereas this phenomenon is obscured in tropical areas. This phenomenon exists universally across countries, regardless of language. This study provides novel, Internet-based evidence for the epidemiology of seasonal depression
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Free-living human cells reconfigure their chromosomes in the evolution back to uni-cellularity
Cells of multi-cellular organisms evolve toward uni-cellularity in the form of cancer and, if humans intervene, continue to evolve in cell culture. During this process, gene dosage relationships may evolve in novel ways to cope with the new environment and may regress back to the ancestral uni-cellular state. In this context, the evolution of sex chromosomes vis-a-vis autosomes is of particular interest. Here, we report the chromosomal evolution in ~ 600 cancer cell lines. Many of them jettisoned either Y or the inactive X; thus, free-living male and female cells converge by becoming ‘de-sexualized’. Surprisingly, the active X often doubled, accompanied by the addition of one haploid complement of autosomes, leading to an X:A ratio of 2:3 from the extant ratio of 1:2. Theoretical modeling of the frequency distribution of X:A karyotypes suggests that the 2:3 ratio confers a higher fitness and may reflect aspects of sex chromosome evolution
Antiarrhythmic effects of stimulating the left dorsal branch of the thoracic nerve in a canine model of paroxysmal atrial tachyarrhythmias
Background
Stellate ganglion nerve activity (SGNA) precedes paroxysmal atrial tachyarrhythmia (PAT) episodes in dogs with intermittent high-rate left atrial (LA) pacing. The left dorsal branch of the thoracic nerve (LDTN) contains sympathetic nerves originating from the stellate ganglia.
Objective
The purpose of this study was to test the hypothesis that high-frequency electrical stimulation of the LDTN can cause stellate ganglia damage and suppress PAT.
Methods
We performed chronic LDTN stimulation in 6 dogs with and 2 dogs without intermittent rapid LA pacing while monitoring SGNA.
Results
LDTN stimulation reduced average SGNA from 4.36 μV (95% confidence interval [CI] 4.10–4.62 μV) at baseline to 3.22 μV (95% CI 3.04–3.40 μV) after 2 weeks (P = .028) and completely suppressed all PAT episodes in all dogs studied. Tyrosine hydroxylase staining showed large damaged regions in both stellate ganglia, with increased percentages of tyrosine hydroxylase–negative cells. The terminal deoxynucleotidyl transferase dUTP nick end labeling assay showed that 23.36% (95% CI 18.74%–27.98%) of ganglion cells in the left stellate ganglia and 11.15% (95% CI 9.34%–12.96%) ganglion cells in the right stellate ganglia were positive, indicating extensive cell death. A reduction of both SGNA and heart rate was also observed in dogs with LDTN stimulation but without high-rate LA pacing. Histological studies in the latter 2 dogs confirmed the presence of extensive stellate ganglia damage, along with a high percentage of terminal deoxynucleotidyl transferase dUTP nick end labeling–positive cells.
Conclusion
LDTN stimulation damages both left stellate ganglia and right stellate ganglia, reduces left SGNA, and is antiarrhythmic in this canine model of PAT
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Clustering Heart Rate Dynamics Is Associated with β-Adrenergic Receptor Polymorphisms: Analysis by Information-Based Similarity Index
Background: Genetic polymorphisms in the gene encoding the β-adrenergic receptors (β -AR) have a pivotal role in the functions of the autonomic nervous system. Using heart rate variability (HRV) as an indicator of autonomic function, we present a bottom-up genotype–phenotype analysis to investigate the association between β -AR gene polymorphisms and heart rate dynamics. Methods: A total of 221 healthy Han Chinese adults (59 males and 162 females, aged 33.6610.8 years, range 19 to 63 years) were recruited and genotyped for three common β-AR polymorphisms: β-AR Ser49Gly, β-AR Arg16Gly and β-AR Gln27Glu. Each subject underwent two hours of electrocardiogram monitoring at rest. We applied an information-based similarity (IBS) index to measure the pairwise dissimilarity of heart rate dynamics among study subjects. Results: With the aid of agglomerative hierarchical cluster analysis, we categorized subjects into major clusters, which were found to have significantly different distributions of β-AR Arg16Gly genotype. Furthermore, the non-randomness index, a nonlinear HRV measure derived from the IBS method, was significantly lower in Arg16 homozygotes than in Gly16 carriers. The non-randomness index was negatively correlated with parasympathetic-related HRV variables and positively correlated with those HRV indices reflecting a sympathovagal shift toward sympathetic activity. Conclusions: We demonstrate a bottom-up categorization approach combining the IBS method and hierarchical cluster analysis to detect subgroups of subjects with HRV phenotypes associated with β-AR polymorphisms. Our results provide evidence that β-AR polymorphisms are significantly associated with the acceleration/deceleration pattern of heart rate oscillation, reflecting the underlying mode of autonomic nervous system control
Capacitive Spring Softening in Single-Walled Carbon Nanotube Nanoelectromechanical Resonators
We report the capacitive spring softening effect observed in single-walled
carbon nanotube (SWNT) nanoelectromechanical (NEM) resonators. The nanotube
resonators adopt dual-gate configuration with both bottom-gate and side-gate
capable of tuning the resonance frequency through capacitive coupling.
Interestingly, downward resonance frequency shifting is observed with
increasing side-gate voltage, which can be attributed to the capacitive
softening of spring constant. Furthermore, in-plane vibrational modes exhibit
much stronger spring softening effect than out-of-plan modes. Our dual-gate
design should enable the differentiation between these two types of vibrational
modes, and open up new possibility for nonlinear operation of nanotube
resonators.Comment: 12 pages/ 3 figure
Ganglionated plexi and ligament of Marshall ablation reduces atrial vulnerability and causes stellate ganglion remodeling in ambulatory dogs
Background
Simultaneous activation of the stellate ganglion (SGNA), the ligament of Marshall (LOM) and the ganglionated plexi (GP) often precedes the onset of paroxysmal atrial tachyarrhythmias (PAT).
Objective
To test the hypothesis that ablation of the LOM and the superior left GP (SLGP) reduces atrial vulnerability and results in remodeling of the stellate ganglion.
Methods
Nerve activity was correlated to PAT and ventricular rate (VR) at baseline, after ablation of the LOM and SLGP, and after AF. Neuronal cell death was assessed with Tyrosine hydroxylase (TH) and terminal deoxynucleotidyl transferase dUTP nick end label (TUNEL) staining.
Results
There were 4±2 PAT episodes per day in controls. None were observed in the ablation group; even though SGNA and VR increased from 2.2 μV (95% confidence interval (CI); 1.2 – 3.3 μV) and 80 bpm (CI 68 – 92 bpm) at baseline to 3.0 μV (CI 2.6 – 3.4 μV, p=0.046) and 90 bpm (CI 75 – 108 bpm, p=0.026) after ablation, and to 3.1 μV (CI 1.7 – 4.5 μV, p=0.116) and 95 bpm (CI 79 – 110 bpm, p=0.075) after AF. There was an increase in TH-negative cells in the ablation group and a 19.7% (CI, 8.6 – 30.8%) TUNEL-positive staining in both the left and right SG. None were observed in the control group.
Conclusion
LOM and SLGP ablation caused LSG remodeling and cell death. There was reduced correlation of the VR response and PAT to SGNA. These findings support the importance of SLGP and LOM in atrial arrhythmogenesis
Increased functional connectivity of the posterior cingulate cortex with the lateral orbitofrontal cortex in depression
To analyze the functioning of the posterior cingulate cortex (PCC) in depression, we performed the first fully voxel-level resting state functional-connectivity neuroimaging analysis of depression of the PCC, with 336 patients with major depressive disorder and 350 controls. Voxels in the PCC had significantly increased functional connectivity with the lateral orbitofrontal cortex, a region implicated in non-reward and which is thereby implicated in depression. In patients receiving medication, the functional connectivity between the lateral orbitofrontal cortex and PCC was decreased back towards that in the controls. In the 350 controls, it was shown that the PCC has high functional connectivity with the parahippocampal regions which are involved in memory. The findings support the theory that the non-reward system in the lateral orbitofrontal cortex has increased effects on memory systems, which contribute to the rumination about sad memories and events in depression. These new findings provide evidence that a key target to ameliorate depression is the lateral orbitofrontal cortex
Heavy quarkonium 2S states in light-front quark model
We study the charmonium 2S states and , and the bottomonium
2S states and , using the light-front quark model and the
2S state wave function of harmonic oscillator as the approximation of the 2S
quarkonium wave function. The decay constants, transition form factors and
masses of these mesons are calculated and compared with experimental data.
Predictions of quantities such as Br are made. The
2S wave function may help us learn more about the structure of these heavy
quarkonia.Comment: 5 latex pages, final version for journal publicatio
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