Impeded inverse energy transfer in the Charney--Hasegawa--Mima model of quasi-geostrophic flows

The behaviour of turbulent flows within the single-layer quasi-geostrophic (Charney-Hasegawa-Mima) model is shown to be strongly dependent on the Rossby deformation wavenumber lambda (or free-surface elasticity). Herein, we derive a bound oil the inverse energy transfer, specifically on the growth rate dl/dt of the characteristic length scale e representing the energy centroid. It is found that dl/dt = l(s) >> lambda(-1)) the inverse energy transfer is strongly impeded, in the sense that under the usual time scale no significant transfer of energy to larger scales occurs. The physical implication is that the elasticity of the free surface impedes turbulent energy transfer in wavenumber space, effectively rendering large-scale vortices long-lived and inactive. Results from numerical simulations of forced-dissipative turbulence confirm this prediction.Publisher PDFPeer reviewe

Revisiting Batchelor's theory of two-dimensional turbulence

Recent mathematical results have shown that a central assumption in the theory of two-dimensional turbulence proposed by Batchelor (Phys. Fluids, vol. 12, 1969, p. 233) is false. That theory, which predicts a X-2/3 k(-1) enstrophy spectrum in the inertial range of freely-decaying turbulence, and which has evidently been successful in describing certain aspects of numerical simulations at high Reynolds numbers Re, assumes that there is a finite, non-zero enstrophy dissipation X in the limit of infinite Re. This, however, is not true for flows having finite vorticity. The enstrophy dissipation in fact vanishes. We revisit Batchelor's theory and propose a simple modification of it to ensure vanishing X in the limit Re -> infinity. Our proposal is supported by high Reynolds number simulations which confirm that X decays like 1/ln Re, and which, following the time of peak enstrophy dissipation, exhibit enstrophy spectra containing an increasing proportion of the total enstrophy (omega(2))/2 in the inertial range as Re increases. Together with the mathematical analysis of vanishing X, these observations motivate a straightforward and, indeed, alarmingly simple modification of Batchelor's theory: just replace Batchelor's enstrophy spectrum X(2/3)k(-1) with (omega(2))k(-1)(In Re)(-1).Publisher PDFPeer reviewe

Logarithmic improvement of regularity criteria for the Navier-Stokes equations in terms of pressure

XY is partially supported by a grant from NSERC.In this article we prove a logarithmic improvement of regularity criteria in the multiplier spaces for the Cauchy problem of the incompressible Navier-Stokes equations in terms of pressure. This improves the main result in [S. Benbernou, A note on the regularity criterion in terms of pressure for the Navier-Stokes equations, Applied Mathematics Letters 22 (2009) 1438–1443].PostprintPeer reviewe

High school administrators' and teachers' perceptions of their educational action research skills

Educational action research has attracted significant attention from teacher-researchers and school administrators in recent years due to the method's effectiveness in teaching practices. Besides, educational action research skills are regarded as one of the essential aspects of doing action research. The present study aims to examine administrators' and teachers' perceptions of their educational action research skills; compare educational action research skills between the trained and the untrained groups and between the group that conducted the research and the group that did not. Quantitative research was used in this research. The study used the 11-item scale to survey 255 respondents (16 administrators and 239 teachers) from eleven high schools in Binh Duong province, Vietnam. The descriptive analysis was used to assess perceptions of high school administrators and teachers on their educational action research skills. Our results indicate that administrators and teachers assess their educational action research skills at very good. The trained group's educational action research skills are higher than the untrained group. Educational action research skills of the group conducted research are higher than the group that did not. The present findings provide more information on educational action research among administrators and teachers in Binh Duong province. Educational action research training programs, workshops, and educational policies should be implemented to reinforce and promote educational action research skills

Synthesis and Investigation of the Physical Properties of Lead-Free BCZT Ceramics

This work presents the structure, microstructure, and physical properties of low sintering temperature lead-free ceramics 0.52(Ba0.7Ca0.3)TiO3-0.48Ba(Zr0.2Ti0.8)O3 doped with nano-sized ZnO particles (noted as BCZT/x, x is the content of ZnO nanoparticles in wt.%, x = 0.00, 0.05, 0.10, 0.15, 0.20, and 0.25). The obtained results of Raman scattering and dielectric measurements have confirmed that Zn2+ has occupied B-site, to cause a deformation in the ABO3-type lattice of the BCZT/x specimens. The 0.15 wt.% ZnO-modified ceramic sintered at 1350°C exhibited excellent piezoelectric parameters: d33 = 420 pC/N, d31 = −174 pC/N, kp = 0.483, kt = 0.423, and k33 = 0.571. The obtained results indicate that the high-quality lead-free BCZT ceramic could be successfully synthesized at a low sintering temperature of 1350°C with an addition of appropriated amount of ZnO nanoparticles. This work also reports the influence of the sintering temperature on structure, microstructure, and piezoelectric properties of BCZT/0.15 compound. By rising sintering temperature, the piezoelectric behaviors were improved and rose up to the best parameters at a sintering temperature of 1450°C (d33 = 576 pC/N and kp = 0.55). The corresponding properties of undoped BCZT ceramics were investigated as a comparison. It also presented that the sintering behavior and piezo-parameters of doped BCZT samples are better than the undoped BCZT samples at each sintering temperature

High school administrators’ and teachers’ perspective of evaluation criteria for action research in the field of education

Action research becomes an appropriate and effective professional development method and strategy to promote inquiry knowledge and solve the problem that leads to action or change. Teachers participating in action research could gain a better insight into themselves as teachers, be motivated to continuous professional growth, and boost their self-confidence as professionals. The main objective here is to examine high-school administrators' and teachers' perceptions of the necessity of evaluation criteria for pedagogical action research. This research surveyed 255 respondents, including 16 administrators and 239 teachers from high-schools in Binh Duong province, Vietnam, with the 11-item questionnaire. The main finding indicated that all high-school administrators and teachers participating fully agree that novelty, effectiveness, and applicability are necessary criteria to evaluate quality of pedagogical action research in Vietnam. Our study contributes to the general discussion about necessary and appropriate criteria for evaluating the quality of pedagogical action research in Vietnam

Novel exopolysaccharide produced from fermented bamboo shoot-isolated Lactobacillus fermentum

This study aimed at providing a route towards the production of a novel exopolysaccharide (EPS) from fermented bamboo shoot-isolated Lactobacillus fermentum. A lactic acid bacteria strain, with high EPS production ability, was isolated from fermented bamboo shoots. This strain, R-49757, was identified in the BCCM/LMG Bacteria Collection, Ghent University, Belgium by the phenylalanyl-tRNA synthetase gene sequencing method, and it was named Lb. fermentum MC3. The molecular mass of the EPS measured via gel permeation chromatography was found to be 9.85 × 104 Da. Moreover, the monosaccharide composition in the EPS was analyzed by gas chromatography–mass spectrometry. Consequently, the EPS was discovered to be a heteropolysaccharide with the appearance of two main sugars—D-glucose and D-mannose—in the backbone. The results of one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance spectroscopy analyses prove the repeating unit of this polysaccharide to be [→6)-β-D-Glcp-(1→3)-β-D-Manp-(1→6)-β-D-Glcp-(1→]n, which appears to be a new EPS. The obtained results open up an avenue for the production of novel EPSs for biomedical applications

Decoding the capability of Lactobacillus plantarum W1 isolated from soybean whey in producing an exopolysaccharide

This study aims at producing exopolysaccharides (EPS) from a lactic acid bacterial strain. The soybean whey-isolated Lactobacillus plantarum W1 (EPS-W1), which belongs to genus Lactobacillus, is identified using the phenylalanyl-tRNA sequencing method. Of all the examined strains, R-49778 (as numbered by BCCM/LMG Bacteria Collection, Ghent University, Belgium) showed the highest capability of producing exopoly-saccharides. Structural characterization revealed a novel exopolysaccharide consisting of repeating units of -> 6)-D-Glcp-(1 ->; -> 3)-D-Manp-(1 ->; -> 3)-6-Glcp-(1 -> and a branch of -> 6)-D-Manp-(1 ->; -> 2)-D-Glcp-(1 ->. This discovery opens up avenues for the production of EPS for food industries, functional foods, and biomedical applications

Development of blood transfusion external quality assessment program at national scale

Introduction: External quality assessment is a crucial component in ensuring the quality of blood transfusion testing laboratories. Objectives: To develop a procedure for generating external quality assessment items for blood transfusion testing to evaluate participants' performance. Methods: Experimental research was conducted at Quality Control Center for Medical laboratory- University of Medicine and Pharmacy at Ho Chi Minh City, Vietnam. Three items, including red blood cell, serum, and atypical antibody serum samples, were assessed for homogeneity and stability; 5 assessment areas, including ABO grouping, Rh grouping, compatible cross matches, Coombs test, and screening of atypical antibodies, were utilized to evaluate the performance of 38 participants in the 2020-2021 period. Results: Red blood cell and serum samples maintained quality for a specific period at controlled temperatures, while serum samples with atypical antibodies showed stability at different temperatures. The participants demonstrated high satisfactory performance in ABO grouping, Rh grouping, Coombs test, and screening for atypical antibodies. However, the most unsatisfactory performance was reported in crossmatching, with 15% of participants unsatisfactory results. Conclusion: The procedure of production of proficiency testing items has been successfully developed, and its application at the national level is suggested to improve the quality of blood transfusion laboratories

Combination Antifungal Therapy for Cryptococcal Meningitis

Background Combination antifungal therapy (amphotericin B deoxycholate and flucytosine) is the recommended treatment for cryptococcal meningitis but has not been shown to reduce mortality, as compared with amphotericin B alone. We performed a randomized, controlled trial to determine whether combining flucytosine or high-dose fluconazole with high-dose amphotericin B improved survival at 14 and 70 days. Methods We conducted a randomized, three-group, open-label trial of induction therapy for cryptococcal meningitis in patients with human immunodeficiency virus infection. All patients received amphotericin B at a dose of 1 mg per kilogram of body weight per day; patients in group 1 were treated for 4 weeks, and those in groups 2 and 3 for 2 weeks. Patients in group 2 concurrently received flucytosine at a dose of 100 mg per kilogram per day for 2 weeks, and those in group 3 concurrently received fluconazole at a dose of 400 mg twice daily for 2 weeks. Results A total of 299 patients were enrolled. Fewer deaths occurred by days 14 and 70 among patients receiving amphotericin B and flucytosine than among those receiving amphotericin B alone (15 vs. 25 deaths by day 14; hazard ratio, 0.57; 95% confidence interval [CI], 0.30 to 1.08; unadjusted P=0.08; and 30 vs. 44 deaths by day 70; hazard ratio, 0.61; 95% CI, 0.39 to 0.97; unadjusted P=0.04). Combination therapy with fluconazole had no significant effect on survival, as compared with monotherapy (hazard ratio for death by 14 days, 0.78; 95% CI, 0.44 to 1.41; P=0.42; hazard ratio for death by 70 days, 0.71; 95% CI, 0.45 to 1.11; P=0.13). Amphotericin B plus flucytosine was associated with significantly increased rates of yeast clearance from cerebrospinal fluid (−0.42 log10 colony-forming units [CFU] per milliliter per day vs. −0.31 and −0.32 log10 CFU per milliliter per day in groups 1 and 3, respectively; P<0.001 for both comparisons). Rates of adverse events were similar in all groups, although neutropenia was more frequent in patients receiving a combination therapy. Conclusions Amphotericin B plus flucytosine, as compared with amphotericin B alone, is associated with improved survival among patients with cryptococcal meningitis. A survival benefit of amphotericin B plus fluconazole was not found