17,520 research outputs found
Quasiperiodic Modulated-Spring Model
We study the classical vibration problem of a chain with spring constants
which are modulated in a quasiperiodic manner, {\it i. e.}, a model in which
the elastic energy is , where and is an irrational number. For
, it is shown analytically that the spectrum is absolutely
continuous, {\it i.e.}, all the eigen modes are extended. For ,
numerical scaling analysis shows that the spectrum is purely singular
continuous, {\it i.e.}, all the modes are critical.Comment: REV TeX fil
Magnetic Soret effect: Application of the ferrofluid dynamics theory
The ferrofluid dynamics theory is applied to thermodiffusive problems in
magnetic fluids in the presence of magnetic fields. The analytical form for the
magnetic part of the chemical potential and the most general expression of the
mass flux are given. By employing these results to experiments, global Soret
coefficients in agreement with measurements are determined. Also an estimate
for a hitherto unknown transport coefficient is made.Comment: 7 pages, 2 figure
Brief review on semileptonic B decays
We concisely review semileptonic B decays, focussing on recent progress on
both theoretical and experimental sides.Comment: 18 pages, 2 figures; version to be published in Mod. Phys. Lett.
The Reduction in Right Ventricular Longitudinal Contraction Parameters Is Not Accompanied by a Reduction in General Right Ventricular Performance During Aortic Valve Replacement:An Explorative Study
Objective: The aim of the present study was to identify whether the decrease of longitudinal parameters after cardiothoracic surgery (ie, tricuspid annular systolic plane excursion [TAPSE] and systolic excursion velocity [S']) is accompanied by a reduction in global right ventricular (RV) performance. Design: Prospective, observational study. Setting: Single-center explorative study in a tertiary teaching hospital. Participants: The study comprised 20 patients who underwent aortic valve replacement with or without coronary artery bypass grafting. Interventions: During cardiac surgery, simultaneous measurements of RV function were performed with a pulmonary artery catheter and transesophageal echocardiography. Measurements and Main Results: TAPSE and Sâ were reduced significantly directly after surgery compared with the time before surgery (TAPSE from 20.8 [16.6-23.4] mm to 9.1 [5.6-15.5] mm; p < 0.001 and Sâ from 8.7 [7.9-10.7] cm/s to 7.2 [5.7-8.6] cm/s; p = 0.041). However, the reduction in TAPSE and Sâ was not accompanied by a reduction in RV performance, as assessed with the TEE-derived myocardial performance index (MPI) and pulmonary artery catheterâderived RV ejection fraction (RVEF). Both remained statistically unaltered before and after the procedure (MPI from 0.52 [0.43-0.58] to 0.50 [0.42-0.88]; p = 0.278 and RVEF from 27% [22%-32%] to 26% [22%-28%]; p = 0.294). Conclusions: In the direct postoperative phase, the reduction of echocardiographic parameters of longitudinal RV contractility (TAPSE and Sâ) were not accompanied by a reduction in global RV performance, expressed as MPI and RVEF. Solely relying on a single RV parameter as a marker for global RV performance may not be adequate to assess the complex adaptation of the right ventricle to aortic valve replacement
The maternal brain: Regionâspecific patterns of brain aging are traceable decades after childbirth
Pregnancy involves maternal brain adaptations, but little is known about how parity influences women's brain aging trajectories later in life. In this study, we replicated previous findings showing less apparent brain aging in women with a history of childbirths, and identified regional brain aging patterns linked to parity in 19,787 middleâ and olderâaged women. Using novel applications of brainâage prediction methods, we found that a higher number of previous childbirths were linked to less apparent brain aging in striatal and limbic regions. The strongest effect was found in the accumbensâa key region in the mesolimbic reward system, which plays an important role in maternal behavior. While only prospective longitudinal studies would be conclusive, our findings indicate that subcortical brain modulations during pregnancy and postpartum may be traceable decades after childbirth
History of childbirths relates to region-specific brain aging patterns in middle and older-aged women
Pregnancy involves maternal brain adaptations, but little is known about how parity influences womenâs brain aging trajectories later in life. In this study, we replicated previous findings showing less apparent brain aging in women with a history of childbirths, and identified regional brain aging patterns linked to parity in 19,787 middle and older-aged women. Using novel applications of brain-age prediction methods, we found that a higher number of previous childbirths was linked to less apparent brain aging in striatal and limbic regions. The strongest effect was found in the accumbens â a key region in the mesolimbic reward system, which plays an important role in maternal behavior. While only prospective longitudinal studies would be conclusive, our findings indicate that subcortical brain modulations during pregnancy and postpartum may be traceable decades after childbirth
From asylum seekers centre to a job:the Dutch legislation and practice on labourmarket integration of refugees
Interstellar dust in the BOOMERanG maps
Interstellar dust (ISD) emission is present in the mm-wave maps obtained by the BOOMERanG experiment at intermediate and high Galactic latitudes. We find that, while being sub-dominant at the lower frequencies (90,150, 240 GHz), thermal emission from ISD is dominant at 410 GHz, and is well correlated with the IRAS map at 100 ”m. We find also that the angular power spectrum of ISD fluctuations at 410 GHz is a power law, and its level is negligible with respect to the angular power spectrum of the Cosmic Microwave Background (CMB) at 90 and 150 GHz
Seeds Buffering for Information Spreading Processes
Seeding strategies for influence maximization in social networks have been
studied for more than a decade. They have mainly relied on the activation of
all resources (seeds) simultaneously in the beginning; yet, it has been shown
that sequential seeding strategies are commonly better. This research focuses
on studying sequential seeding with buffering, which is an extension to basic
sequential seeding concept. The proposed method avoids choosing nodes that will
be activated through the natural diffusion process, which is leading to better
use of the budget for activating seed nodes in the social influence process.
This approach was compared with sequential seeding without buffering and single
stage seeding. The results on both real and artificial social networks confirm
that the buffer-based consecutive seeding is a good trade-off between the final
coverage and the time to reach it. It performs significantly better than its
rivals for a fixed budget. The gain is obtained by dynamic rankings and the
ability to detect network areas with nodes that are not yet activated and have
high potential of activating their neighbours.Comment: Jankowski, J., Br\'odka, P., Michalski, R., & Kazienko, P. (2017,
September). Seeds Buffering for Information Spreading Processes. In
International Conference on Social Informatics (pp. 628-641). Springe
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