A turbulent drag-reduction method employing synthetic jet sheets in a turbulent channel flow is investigated by direct numerical simulations. The jet sheets are wall-parallel and produced by periodic ...blowing and suction from pairs of thin slots aligned with the main streamwise flow. By varying the slot height and the jet-sheet angle with respect to the spanwise direction, drag-reduction margins between $10\,\%$ and $30\,\%$ are obtained for jet-sheet angles between $45 ^{\circ }$ and $75 ^{\circ }$, while a drag increase of almost 100 % is computed when the jet sheets are spanwise-oriented. When global skin-friction drag reduction occurs, the wall-shear stress near the jet-sheet exits increases during suction and decreases during blowing, while the velocity fluctuations weaken during suction and intensify during blowing. The global drag-reduction effect is produced by a finite counter flow induced by the nonlinear interaction between the jet-sheet flow and the main flow, although the turbulent intensity and Reynolds shear stresses increase. The power spent to generate the jet sheets is computed by modelling numerically the actuator underneath the channel flow as a piston oscillating sinusoidally along the spanwise direction in a round-shaped cavity from which the fluid is released into the channel through the cavity exits. A power balance leads to the computation of the efficiency of the actuator system, quantifying the portion of the piston power that is lost as internal power fluxes and heat transfer through the cavity walls. For the tested configurations, the power consumed by the piston to generate the jet sheets is larger than the power saved thanks to the drag reduction.
Abstract In this work, we present a new family of Zone Plates (ZPs) designed using the self-generating Kolakoski sequence. The focusing and imaging properties of these aperiodic diffractive lenses ...coined Kolakoski Zone Plates (KZPs) are extensively studied. It is shown that under monochromatic plane-wave illumination, a KZP produces two main foci of the same intensity along the axial axis. Moreover, one of the corresponding focal lengths is double the other, property correlated with the involved aperiodic sequence. This distinctive optical characteristic is experimentally confirmed. We have also obtained the first images provided by these bifocal new diffractive lenses.
Abstract
Shark fishing, driven by the fin trade, is the primary cause of global shark population declines. Here, we present a case study that exemplifies how industrial fisheries are likely depleting ...shark populations in the Eastern Tropical Pacific Ocean. In August 2017, the vessel Fu Yuan Yu Leng 999, of Chinese flag, was detained while crossing through the Galápagos Marine Reserve without authorization. This vessel contained 7639 sharks, representing one of the largest seizures recorded to date. Based on a sample of 929 individuals (12%), we found 12 shark species: 9 considered as Vulnerable or higher risk by the IUCN and 8 listed in CITES. Four species showed a higher proportion of immature than mature individuals, whereas size-distribution hints that at least some of the fishing ships associated with the operation may have been using purse-seine gear fishing equipment, which, for some species, goes against international conventions. Our data expose the magnitude of the threat that fishing industries and illegal trade represent to sharks in the Eastern Tropical Pacific Ocean.
The design and implementation of a multiplexed spiral phase mask in an experimental optical tweezers setup are presented. This diffractive optical element allows the generation of multiple concentric ...vortex beams with independent topological charges and without amplitude modulation. The generalization of the phase mask for multiple concentric vortices is also shown. The design for a phase mask of two multiplexed vortices with different topological charges is developed. We experimentally show the transfer of angular momentum to the optically trapped microparticles by enabling nearly independent orbiting dynamics around the optical axis within each vortex. The angular velocity of the confined particles versus the optical power in the focal region is also discussed for different combinations of topological charges.
Display omitted
•Design and implementation of a multiplexed spiral phase mask•Implementation of multiplexed vortex beam-based optical tweezers•Generation of concentric vortex beams with independent topological charges•The transfer of angular momentum to trapped microparticles within each vortex
Physics; Optics; Optical physics
Objectives
To examine the cross-sectional association between baseline depressive symptoms and the presence of type 2 diabetes (T2D), and its association with glycated hemoglobin (HbA1c) and other ...metabolic variables, and the prospective association of depressive symptoms and HbA1c after 1 year of follow-up.
Methods
n
= 6224 Mediterranean older adults with overweight/obesity and metabolic syndrome (48% females, mean age 64.9 ± 4.9 years) were evaluated in the framework of the PREDIMED-Plus study cohort. Depressive symptoms were assessed using the Beck Depression Inventory-II and HbA1c was used to measure metabolic control.
Results
The presence of T2D increased the likelihood of higher levels of depressive symptoms (
χ
2
= 15.84,
p
= 0.001). Polynomial contrast revealed a positive linear relationship (
χ
2
= 13.49,
p
= 0.001), the higher the depressive symptoms levels, the higher the prevalence of T2D. Longitudinal analyses showed that the higher baseline depressive symptoms levels, the higher the likelihood of being within the HbA1c ≥ 7% at 1-year level (Wald-
χ
2
= 24.06,
df
= 3,
p
< .001, for the full adjusted model). Additionally, depressive levels at baseline and duration of T2D predicted higher HbA1c and body mass index, and lower physical activity and adherence to Mediterranean Diet at 1 year of follow-up.
Conclusions
This study supports an association between T2D and the severity of depressive symptoms, suggesting a worse metabolic control from mild severity levels in the short–medium term, influenced by lifestyle habits related to diabetes care. Screening for depressive symptoms and a multidisciplinary integrative therapeutic approach should be ensured in patients with T2D.
In this work, we present a comparative analysis of different numerical methods to obtain the focusing properties of the zone plates based on Fibonacci and Cantor sequences. The Fresnel approximation ...was solved numerically in order to obtain the axial irradiance provided by these diffractive lenses. Two different methods were applied. The first one is based on numerical integration, specifically the Simpson integration method and the two-dimensional Gaussian quadrature. The second consisted in the implementation of the Fast Fourier Transform in both one and two dimensions. The axial irradiance of the lenses, the relative error with respect to the analytical solution, and the calculation time required by each method are analyzed and compared. From this analysis it was concluded that the Gauss method presents the best balance between accuracy and computation time. This analysis could be useful to decide the most convenient numerical method to be used for the study of more complex diffractive structures.
The rapid development of populations and the demand in the consumption of concrete is generating the need to produce larger quantities of cement, which brings with it negative effects for the ...environment. Approximately 0.87 kg of CO2 is produced by the manufacture of cement; In addition, the use of aggregates is generating great concern in the construction industry, due to the costs and the restriction of these. Similarly, the accumulation of construction and demolition waste (RCA) and rice husk ash (RHA) contribute to pollution. Therefore, the objective of this manuscript is to review the literature on the use of RCA and RHA for the elaboration of concrete. For this, indexed articles were used, between the years 2017-2021. The results showed that when 8% RHA is added, the concrete reaches a compressive strength of 70 MPa; as well as, the flexural strength of concrete by adding 50% RCA + 1.50% basalt microfibers was increased by 29.44%. On the other hand, when RHA is added by 15% it reaches a compressive strength of 48.8 MPa; in turn, the mechanical performance at bending with 10% seashell by fine aggregate and 20% RHA by cement, reached a resistance of 65 MPa. Concluding, that the behavior of concrete undoubtedly depends on the proportions of either RCA or RHA; however, the percentages must be no more than 8% and 15% respectively.
Acute lymphoblastic leukemia is the most important childhood cancer. Multidrug resistance is an important factor of poor prognosis. We present the P-glycoprotein (P-gp) activity in 2 patients with ...different outcomes. Both patients had B-cell acute lymphoblastic leukemia; they were responding properly to the treatment, but one of them had an increment in the P-gp activity that correlates with an increment in the disease manifestation, the patient had to be hospitalized and developed sepsis and subsequently died. P-gp levels were correlated with disease progression. P-gp activity needs to be evaluated during treatment to assess and prevent disease relapse or the patient´s death.
Spin-reorientation in DyGa Susilo, R.A.; Cadogan, J.M.; Muñoz-Pérez, S. ...
Journal of magnetism and magnetic materials,
09/2015, Letnik:
390
Journal Article
Recenzirano
We have used neutron powder diffraction to determine the magnetic structure of DyGa. This compound crystallises in the orthorhombic CrB-type structure with the Cmcm space group (#63) and the magnetic ...structure comprises ferromagnetic order of the Dy sublattice along the c-axis below TC=115K. Upon cooling below 25K, the Dy magnetic moments cant away from the c-axis towards the a-axis. At 3K, the Dy moment is 9.8(2) μB and the Dy magnetic moments point in the direction θ=22(2)°, ϕ=0° relative to the c-axis.
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