Search

Objective: Hypertension disrupts the bone integrity and its repair ability. This study explores the efficiency of a therapy based on the application of mesenchymal stem cells (MSCs) to repair bone defects of spontaneously hypertensive rats (SHR). Methods: First, we evaluated SHR in terms of bone morphometry and differentiation of MSCs into osteoblasts. Then, the effects of the interactions between MSCs from normotensive rats (NTR‐MSCs) cocultured with SHR (SHR‐MSCs) on the osteoblast differentiation of both cell populations were evaluated. Also, bone formation into calvarial defects of SHR treated with NTR‐MSCs was analyzed. Results: Hypertension induced bone loss evidenced by reduced bone morphometric parameters of femurs of SHR compared with NTR as well as decreased osteoblast differentiation of SHR‐MSCs compared with NTR‐MSCs. NTR‐MSCs partially restored the capacity of SHR‐MSCs to differentiate into osteoblasts, while SHR‐MSCs exhibited a slight negative effect on NTR‐MSCs. An enhanced bone repair was observed in defects treated with NTR‐MSCs compared with control, stressing this cell therapy efficacy even in bones damaged by hypertension. Conclusion: The use of MSCs derived from a heathy environment can be in the near future a smart approach to treat bone loss in the context of regenerative dentistry for oral rehabilitation of hypertensive patients. [ABSTRACT FROM AUTHOR]

Background/purpose – The study aimed to identify differences in the level of critical thinking dispositions of undergraduate students in Portugal according to their sociodemographic (gender, age) and academic (study field) characteristics. Materials/methods – A cross-sectional, descriptive correlational study was conducted with a convenience random sample of 1,017 students. Most of the participants were female (76.8%) and the average age of the respondents was 21.8 ± 4.22 years old. For data collection, the Critical Thinking Dispositions Scale (CTDS) was employed, which consists of 35 question items and was validated for the Portuguese population. In the statistical analysis, t-test, ANOVA, and hierarchical multiple regression model were used. Results – The students showed an average positive disposition for critical thinking (average CTDS score was 279.1 ± 27.1). The results demonstrated that gender, age, and field of study influenced the students’ dispositions for critical thinking. Older female students attending biomedicine courses had a higher disposition to think critically. Conclusion – Female students generally show higher critical thinking scores dispositions, regardless of the study field.

Motivated by the presence of a finite number of determining parameters (degrees of freedom) such as modes, nodes and local spatial averages for dissipative dynamical systems, we present here a continuous data assimilation algorithm for three-dimensional viscous hydrodynamic models. However, to validate the convergence of this algorithm our proofs require the existence of uniform global bounds on the gradients of the solutions of the underlying system in terms of certain combinations of the physical parameters (such as kinematic viscosity, the size of the domain and the forcing term). Therefore our proofs cannot be applied to the three-dimensional Navier-Stokes equations; instead we demonstrate the implementation of this algorithm, for instance, in the context of the three-dimensional Navier-Stokes-α equations. This algorithm consists of introducing a nudging process through a general type of approximation interpolation operator (which is constructed from observational measurements) that synchronizes the large spatial scales of the approximate solutions with those of unknown solutions of the Navier-Stokes-α equations corresponding to these measurements. Our main result provides conditions on the finite-dimensional spatial resolution of the collected data, sufficient to guarantee that the approximating solution, which is obtained from this collected data, converges to the unknown reference solution over time. These conditions are given in terms of the physical parameters.

The second-grade fluid equations are a model for viscoelastic fluids, with two parameters: α > 0, corresponding to the elastic response, and $${\nu > 0}$$ν>0, corresponding to viscosity. Formally setting these parameters to 0 reduces the equations to the incompressible Euler equations of ideal fluid flow. In this article we study the limits $${\alpha, \nu \to 0}$$α,ν→0 of solutions of the second-grade fluid system, in a smooth, bounded, two-dimensional domain with no-slip boundary conditions. This class of problems interpolates between the Euler-α model ($${\nu = 0}$$ν=0), for which the authors recently proved convergence to the solution of the incompressible Euler equations, and the Navier-Stokes case (α = 0), for which the vanishing viscosity limit is an important open problem. We prove three results. First, we establish convergence of the solutions of the second-grade model to those of the Euler equations provided $${\nu = \mathcal{O}(\alpha^2)}$$ν=O(α2), as α → 0, extending the main result in (Lopes Filho et al., Physica D 292(293):51–61, 2015). Second, we prove equivalence between convergence (of the second-grade fluid equations to the Euler equations) and vanishing of the energy dissipation in a suitably thin region near the boundary, in the asymptotic regime $${\nu = \mathcal{O}(\alpha^{6/5})}$$ν=O(α6/5), $${\nu/\alpha^{2} \to \infty}$$ν/α2→∞ as α → 0. This amounts to a convergence criterion similar to the well-known Kato criterion for the vanishing viscosity limit of the Navier-Stokes equations to the Euler equations. Finally, we obtain an extension of Kato’s classical criterion to the second-grade fluid model, valid if $${\alpha = \mathcal{O}(\nu^{3/2})}$$α=O(ν3/2), as $${\nu \to 0}$$ν→0. The proof of all these results relies on energy estimates and boundary correctors, following the original idea by Kato.

In this article we consider the Euler-α system as a regularization of the incompressible Euler equations in a smooth, two-dimensional, bounded domain. For the limiting Euler system we consider the usual non-penetration boundary condition, while, for the Euler-α regularization, we use velocity vanishing at the boundary. We also assume that the initial velocities for the Euler-α system approximate, in a suitable sense, as the regularization parameter α→0, the initial velocity for the limiting Euler system. For small values of α, this situation leads to a boundary layer, which is the main concern of this work. Our main result is that, under appropriate regularity assumptions, and despite the presence of this boundary layer, the solutions of the Euler-α system converge, as α→0, to the corresponding solution of the Euler equations, in L2 in space, uniformly in time. We also present an example involving parallel flows, in order to illustrate the indifference to the boundary layer of the α→0 limit, which underlies our work.

Helical symmetry is invariance under a one-dimensional group of rigid motions generated by a simultaneous rotation around a fixed axis and translation along the same axis. The key parameter in helical symmetry is the step or pitch, the magnitude of the translation after rotating one full turn around the symmetry axis. In this article we study the limits of three-dimensional helical viscous and inviscid incompressible flows in an infinite circular pipe, with respectively no-slip and no-penetration boundary conditions, as the step approaches infinity. We show that, as the step becomes large, the three-dimensional helical flow approaches a planar flow, which is governed by the so-called two-and-half Navier–Stokes and Euler equations, respectively.

Lei and Lin [Comm. Pure Appl. Math. 64 (2011), pp. 1297–1304] have recently given a proof of a global mild solution of the three-dimensional Navier-Stokes equations in function spaces based on the Wiener algebra. An alternative proof of existence of these solutions was then developed by Bae [Proc. Amer. Math. Soc. 143 (2015), pp. 2887–2892], and this new proof allowed for an estimate of the radius of analyticity of the solutions at positive times. We adapt the Bae proof to prove existence of the Lei-Lin solution in the spatially periodic setting, finding an improved bound for the radius of analyticity in this case. [ABSTRACT FROM AUTHOR]

This article explores connections and continuities between the Second World War and the early Cold War in three territories under European colonial rule in South China. It argues that the dismantling of French power in Guangzhouwan and the maintenance of British and Portuguese rule in Hong Kong and Macau owed as much to the specific wartime experience of these territories as to the convergence of competing post-war interests in China and Southeast Asia. Drawing on multilingual sources, this comparative study sheds new light on the challenges and opportunities posed by remnants of colonialism in South China for the Kuomintang, the CCP, and other actors in a context of Chinese Civil War, early Cold War and decolonisation. [ABSTRACT FROM AUTHOR]