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Motivated by the recent discovery of a dispersive-to-nondispersive transition for linear waves in shear flows, we accurately explored the wavenumber-Reynolds number parameter map of the plane Poiseuille flow in the limit of least-damped waves. We have discovered the existence of regions of the map where the dispersion and propagation features vary significantly from their surroundings. These regions are nested in the dispersive, low-wavenumber part of the map. This complex dispersion scenario demonstrates the existence of linear dispersive focusing in wave envelopes evolving out of an initial, spatially localized, three-dimensional perturbation. An asymptotic wave packet's representation, based on the saddle-point method, allows to enlighten the nature of the packet's morphology, in particular, the arrow-shaped structure and spatial spreading rates. A correlation is also highlighted between the regions of largest dispersive focusing and the regions which are most subject to strong nonlinear coupling in observations. [ABSTRACT FROM AUTHOR]

It has been suggested that when fetal femur is insonated by the anterior approach of the fetal thigh the diaphysis appears rectilinear on the sonographic image, while lateral approach provides concave shape of the diaphysis. When the femur is approached laterally, the rounded upper-lateral extremity is probably not totally exposed to the ultrasound beam, which contributes to an underestimation of the real femur length. Retrospective analysis of sonographic images of fetal femur length measurement in consecutive examinations of women attending our centre for a routine ultrasound scan at 21-24 and 30-34 weeks between June 2017 and February 2018 was performed. [Extracted from the article]

This review summarizes the current state of research aiming at a description of the global heliosphere using both analytical and numerical modeling efforts, particularly in view of the overall plasma/neutral flow and magnetic field structure, and its relation to energetic neutral atoms. Being part of a larger volume on current heliospheric research, it also lays out a number of key concepts and describes several classic, though still relevant early works on the topic. Regarding numerical simulations, emphasis is put on magnetohydrodynamic (MHD), multi-fluid, kinetic-MHD, and hybrid modeling frameworks. Finally, open issues relating to the physical relevance of so-called "croissant" models of the heliosphere, as well as the general (dis)agreement of model predictions with observations are highlighted and critically discussed., (© The Author(s) 2022.)

Aim: To identify risk factors for maternity blues (MB) and to evaluate the impact of obstetric factors on MB prevalence., Materials and Methods: 194 mothers have completed the Edinburgh Postnatal Depression Scale (EPDS) 2 days after delivery. Bivariate and multivariate logistic regression models were used to identify the predictors of MB., Results: 57 women (29.4%) were positive at screening. Comparing the two groups, no statistically significant difference was found in age ( p  = .536), nationality ( p  = .065) and BMI before pregnancy ( p  = .224). Interestingly, no significant differences were highlighted in terms of assisted reproduction technology or spontaneous pregnancies and the presence of labor analgesia, while MB was significantly more frequent in case of cesarean section (CS) ( p  = .035). Statistical differences have been found in previous CS ( p  = .022), previous voluntary interruption of pregnancy ( p  = .021), number of previous pregnancies ( p  = .007), Apgar 5' ( p  = .026), lower level of education ( p  = .009), and previous postpartum depression (PPD) ( p  = .026). A logistic regression analysis was realized according to a multivariate model incorporating all the variables with a p -value ≤.25 in bivariate analysis. In the final model vaginal delivery (OR 0.451, 95% CI [0.224-0.911], p  = .026) resulted to be MB protective factor, while a lower level of education (OR 3.657, 95% CI [1.482-9.023], p  = .005) as well as previous PPD (OR 4.714, 95% CI [1.273-17.458], p  = .020) were identified as independent risk factors., Conclusion: This study showed that a lower education level and a previous PPD resulted to be important risk factors for MB development, while natural delivery was revealed as a protective factor. These results could be used to develop a better and more accurate prevention program after delivery.

The description of the local turbulent energy transfer and the high-resolution ion distributions measured by the Magnetospheric Multiscale mission together provide a formidable tool to explore the cross-scale connection between the fluid-scale energy cascade and plasma processes at subion scales. When the small-scale energy transfer is dominated by Alfvénic, correlated velocity, and magnetic field fluctuations, beams of accelerated particles are more likely observed. Here, for the first time, we report observations suggesting the nonlinear wave-particle interaction as one possible mechanism for the energy dissipation in space plasmas.

This study provides sufficient conditions for the temporal monotonic decay of enstrophy for two-dimensional perturbations traveling in the incompressible, viscous, plane Poiseuille, and Couette flows. Extension of Synge's procedure [J. L. Synge, Proc. Fifth Int. Congress Appl. Mech. 2, 326 (1938); Semicentenn. Publ. Am. Math. Soc. 2, 227 (1938)] to the initial-value problem allow us to find the region of the wave-number-Reynolds-number map where the enstrophy of any initial disturbance cannot grow. This region is wider than that of the kinetic energy. We also show that the parameter space is split into two regions with clearly distinct propagation and dispersion properties.

In this study we analyze the phase and group velocity of three-dimensional linear traveling waves in two sheared flows: the plane channel and the wake flows. This was carried out by varying the wave number over a large interval of values at a given Reynolds number inside the ranges 20-100, 1000-8000, for the wake and channel flow, respectively. Evidence is given about the possible presence of both dispersive and nondispersive effects which are associated with the long and short ranges of wavelength. We solved the Orr-Sommerfeld and Squire eigenvalue problem and observed the least stable mode. It is evident that, at low wave numbers, the least stable eigenmodes in the left branch of the spectrum behave in a dispersive manner. By contrast, if the wave number is above a specific threshold, a sharp dispersive-to-nondispersive transition can be observed. Beyond this transition, the dominant mode belongs to the right branch of the spectrum. The transient behavior of the phase velocity of small three-dimensional traveling waves was also considered. Having chosen the initial conditions, we then show that the shape of the transient highly depends on the transition wavelength threshold value. We show that the phase velocity can oscillate with a frequency which is equal to the frequency width of the eigenvalue spectrum. Furthermore, evidence of intermediate self-similarity is given for the perturbation field.