Transitions in large eddy simulation of box turbulence

One promising decomposition of turbulent dynamics is that into building blocks such as equilibrium and periodic solutions and orbits connecting these. While the numerical approximation of such building blocks is feasible for flows in small domains and at low Reynolds numbers, computations in developed turbulence are currently out of reach because of the large number of degrees of freedom necessary to represent Navier-Stokes flow on all relevant spatial scales. We mitigate this problem by applying large eddy simulation (LES), which aims to model, rather than resolve, motion on scales below the filter length, which is fixed by a model parameter. By considering a periodic spatial domain, we avoid complications that arise in LES modelling in the presence of boundary layers. We consider the motion of an LES fluid subject to a constant body force of the Taylor-Green type as the separation between the forcing length scale and the filter length is increased. In particular, we discuss the transition from laminar to weakly turbulent motion, regulated by simple invariant solution, on a grid of $32^3$ points

Stabilization of exact coherent structures in two-dimensional turbulence using time-delayed feedback

This work is supported by EPSRC New Investigator Award EP/S037055/1, “Stabilisation of exact coherent structures in fluid turbulence.”Time-delayed feedback control, attributed to Pyragas [Phys. Lett. A 170, 421 (1992)], is a method known to stabilize periodic orbits in low-dimensional chaotic dynamical systems. A system of the form ẋ (t) = f (x) has an additional term G(x(t - T) - x(t)) introduced where G is some "gain matrix" and T a time delay. The form of the delay term is such that it will vanish for any orbit of period T, therefore making it also an orbit of the uncontrolled system. This noninvasive feature makes the method attractive for stabilizing exact coherent structures in fluid turbulence. Here we begin by validating the method for the basic flow in Kolmogorov flow; a two-dimensional incompressible Navier-Stokes flow with a sinusoidal body force. The linear predictions for stabilization are well captured by direct numerical simulation. By applying an adaptive method to adjust the streamwise translation of the delay, a known traveling wave solution is able to be stabilized up to relatively high Reynolds number. We discover that the famous "odd-number" limitation of this time-delayed feedback method can be overcome in the fluid problem by using the symmetries of the system. This leads to the discovery of eight additional exact coherent structures which can be stabilized with this approach. This means that certain unstable exact coherent structures can be obtained by simply time stepping a modified set of equations, thus circumventing the usual convergence algorithms.Publisher PDFPeer reviewe

Electrodeposition of Tungsten from Molten KF–KCl–WO3 and CsF–CsCl–WO3

Electrodeposition of W coatings in KF–KCl eutectic melts was investigated after adding 0.5–2.0 mol% of WO3 at 923 K. Cyclic voltammetry at a Ag electrode suggested that the electrodeposition of W from W(VI) ions proceeds from 1.65 V vs K+/K. Electrodeposition of the α-W phase was confirmed by X-ray diffractometry (XRD). The effects of current density and amount of WO3 on the morphology of W coatings were investigated by surface and cross-sectional scanning electron microscopy (SEM). The smoothest W coating with a thickness of ~15 μm was formed at 12.5 mA cm−2 and 2.0 mol% WO3 in KF–KCl eutectic melts. By increasing the charge density, a coating thickness of ~30 μm was attained; however, it significantly increased the surface roughness of the coating. The electrodeposition of W was also performed in CsF–CsCl eutectic melts at a lower temperature of 873 K to suppress the growth of crystal grains. XRD confirmed the existence of both α-W and β-W phases in the W coatings deposited in the CsF–CsCl eutectic melts. SEM analyses revealed the successful formation of dense and smooth W coatings with ~30 μm thickness in the CsF–CsCl eutectic melts

Electrodeposition of Tungsten from Molten KF–KCl–WO₃ and CsF–CsCl–WO₃

PRiME 2020, Honolulu, USA, October 4-9, 2020.The electrodeposition of W films was investigated in KF–KCl eutectic melts after adding 0.5–2.0 mol% of WO₃ at 923 K. Cyclic voltammetry at a Ag electrode suggested that the electrodeposition of W from W(VI) ions proceeds from 1.65 V vs. K/K. Electrodeposition of α-W was confirmed by XRD analysis. The effect of current density and added amount of WO₃ on the morphology of W films was investigated by surface and cross-sectional SEM, which indicated that the best W film having thickness of ca. 15 μm was obtained at 12.5 mA cm⁻² and 2.0 mol% of WO₃. Although the film thickness was increased to ca. 30 μm by increasing the charge density, the surface roughness was significantly increased. To suppress the growth of crystal grains, electrodeposition of W was also investigated in CsF–CsCl eutectic melts at lower temperature of 873 K. The XRD confirmed the existences of both α-W and β-W in the W films. The SEM observations revealed that dense and smooth W films having thickness of ca. 30 μm was successfully obtained

Widely Extended [OIII] 88 um Line Emission around the 30 Doradus Region Revealed with AKARI FIS-FTS

We present the distribution map of the far-infrared [OIII] 88um line emission around the 30 Doradus (30 Dor) region in the Large Magellanic Cloud obtained with the Fourier Transform Spectrometer of the Far-Infrared Surveyor onboard AKARI. The map reveals that the [OIII] emission is widely distributed by more than 10' around the super star cluster R136, implying that the 30 Dor region is affluent with interstellar radiation field hard enough to ionize O^{2+}. The observed [OIII] line intensities are as high as (1-2) x 10^{-6} W m^{-2} sr^{-1} on the peripheral regions 4'-5' away from the center of 30 Dor, which requires gas densities of 60-100 cm^{-3}. However the observed size of the distribution of the [OIII] emission is too large to be explained by massive stars in the 30 Dor region enshrouded by clouds with the constant gas density of 10^2 cm^{-3}. Therefore the surrounding structure is likely to be highly clumpy. We also find a global correlation between the [OIII] and the far-infrared continuum emission, suggesting that the gas and dust are well mixed in the highly-ionized region where the dust survives in clumpy dense clouds shielded from the energetic photons.Comment: 17 pages, 9 figures, accepted for publication in Publications of the Astronomical Society of Japan (PASJ

Association of serum brain-derived neurotrophic factor with hepatic enzymes, AST/ALT ratio, and FIB-4 index in middle-aged and older women

Substantial evidence suggests an important role of liver function in brain health. Liver function is clinically assessed by measuring the activity of hepatic enzymes in the peripheral blood. Brain-derived neurotrophic factor (BDNF) is an important regulator of brain function. Therefore, we hypothesized that blood BDNF levels are associated with liver function and fibrosis. To test this hypothesis, in this cross-sectional study, we investigated whether serum BDNF concentration is associated with liver enzyme activity, aspartate aminotransferase (AST)/ alanine aminotransferase (ALT) ratio, and fibrosis-4 (FIB-4) index in middle-aged and older women. We found that serum BDNF level showed a significant positive association with ALT and γ-glutamyltranspeptidase (GGT) activity and negative association with FIB-4 index, and a trend of negative association with the AST/ALT ratio after adjustment for age. Additionally, these associations remained statistically significant even after adjustment for body mass index (BMI) and fasting blood glucose level. These results demonstrate associations of serum BDNF levels with liver enzymes and hepatic fibrosis-related indices, which may underlie liver-brain interactions

The phenotype of infiltrating macrophages influences arteriosclerotic plaque vulnerability in the carotid artery

Background: Proinflammatory (M1) macrophages and anti-inflammatory (M2) macrophages have been identified in atherosclerotic plaques. While these macrophages have been speculated to be related to plaque vulnerability, there are limited studies investigating this relationship. Therefore, we examined the association between macrophage phenotype (M1 versus M2) and plaque vulnerability and clinical events. Methods: Patients undergoing carotid endarterectomy received an ultrasound of the carotid artery before surgery. Plaques were processed for analysis by immunohistochemistry, Western blotting, and real-time polymerase chain reaction studies. Medical history and clinical data were obtained from medical records. Results: Patients were divided into 2 groups: those suffering from acute ischemic attack (symptomatic, n = 31) and those that did not present with symptoms (asymptomatic, n = 34). Ultrasound analysis revealed that plaque vulnerability was greater in the symptomatic group (P= .033; Chi-square test). Immunohistochemistry revealed that plaques from the symptomatic group had a greater concentration of M1 macrophages (CD68-, CD11c-positive) while plaques from the asymptomatic group had more M2 macrophages (CD163-positive). This observation was confirmed by Western blotting. Characterization by real-time polymerase chain reaction studies revealed that plaques from the symptomatic group had increased expression of the M1 markers CD68 and CD11c, as well as monocyte chemoattractive protein-1, interleukin-6, and matrix metalloproteinase-9. In addition, more M1 macrophages expressed in unstable plaques were defined by ultrasound analysis, while more M2 macrophages were expressed in stable plaques. Conclusions: Our data show that M1 macrophage content of atherosclerotic plaques is associated with clinical incidence of ischemic stroke and increased inflammation or fibrinolysis. We also show the benefits of using ultrasound to evaluate vulnerability in the plaques

Significance of fully automated tests for the diagnosis of antiphospholipid syndrome

AbstractAntiphospholipid antibodies (aPLs) can vary both immunologically and functionally, thus it is important to effectively and correctly identify their presence when diagnosing antiphospholipid syndrome. Furthermore, since many immunological/functional tests are necessary to measure aPLs, complete examinations are often not performed in many cases due to significant burden on the testing departments. To address this issue, we measured aPLs defined according to the classification criteria (anticardiolipin antibody: aCL) IgG/IgM and anti-β2 glycoprotein I antibody (aβ2GPI) (IgG/IgM) as well as non-criteria antibodies (aCL IgA, aβ2GPI IgA and aβ2GPI domain I), in a cohort of 211 patients (61 APS, 140 disease controls and 10 healthy individuals). APLs were measured using a fully automated chemiluminescent immunoassay instrument (BIO-FLASH®/ACL AcuStar®) and with conventional ELISA tests. We demonstrated that both sensitivity and accuracy of diagnosis of aCL IgG and aβ2GPI IgG were high, in agreement with the past reports. When multiple aPLs were examined, the accuracy of diagnosis increased. The proportion of APS patients that were positive for 2 or more types of aPLs (47/61, 77%) was higher than that of patients with systemic lupus erythematosus (SLE)(3/37, 9%), those with non-SLE connective tissues diseases (1/53,2%), those with other diseases or healthy volunteers. Based on these findings, it was concluded that the fully automated chemiluminescent immunoassay instrument, which allows the simultaneous evaluation of many types of aPLs, offers clear advantages for a more complete, more rapid and less labor-intensive alternative to running multiple ELISA and could help in better diagnosis for suspected APS patients

Characterization of hiPSC-Derived Muscle Progenitors Reveals Distinctive Markers for Myogenic Cell Purification Toward Cell Therapy

骨格筋幹細胞を純化する方法を確立 --筋肉の細胞移植治療の実現に向けて--. 京都大学プレスリリース. 2021-04-02.Enhanced muscle regeneration using stem cells. 京都大学プレスリリース. 2021-04-02.The transplantation of muscle progenitor cells (MuPCs) differentiated from human induced pluripotent stem cells (hiPSCs) is a promising approach for treating skeletal muscle diseases such as Duchenne muscular dystrophy (DMD). However, proper purification of the MuPCs before transplantation is essential for clinical application. Here, by using MYF5 hiPSC reporter lines, we identified two markers for myogenic cell purification: CDH13, which purified most of the myogenic cells, and FGFR4, which purified a subset of MuPCs. Cells purified with each of the markers showed high efficiency for regeneration after transplantation and contributed to the restoration of dystrophin expression in DMD-immunodeficient model mice. Moreover, we found that MYF5 regulates CDH13 expression by binding to the promoter regions. These findings suggest that FGFR4 and CDH13 are strong candidates for the purification of hiPSC-derived MuPCs for therapeutical application