Unsteady forcing of turbulence by a randomly actuated impeller array

We investigate the unsteady forcing of turbulent flow in a well-stirred reactor using opposing arrays of pitched-blade impellers which randomly and independently reverse rotation. We systematically explore the dependence of the large-scale motions and the homogeneity and isotropy of the turbulence upon the forcing. We identify three dimensionless control parameters: the source fraction (the fraction of time spent in clockwise motion), the dimensionless forcing period and an impeller Reynolds number. We find the timescale of unsteady motion corresponds to the forcing period T, the average period of impeller reversal, independently of the impeller angular speed $$\varOmega$$ Ω and source fraction. As in jet-stirred tanks, unsteady forcing substantially increases the unsteady kinetic energy, energy dissipation, integral length scale and Taylor microscale Reynolds number ($$R_\lambda$$ R λ ) and improves the homogeneity and isotropy of the flow, provided the source fraction is chosen optimally and the forcing period is sufficiently large ($$\varOmega T > 10^3$$ Ω T > 10 3 ); impeller Reynolds number has a relatively small influence. The forcing period must be matched to angular speed: decreasing the forcing period below this threshold results in a less intense, more inhomogeneous turbulent flow. Spectra of two-point velocity increments demonstrate that unsteady energy injection is dominated by axial shear generated across impellers and becomes less prominent at smaller scales. However, even at $$R_\lambda \approx 354$$ R λ ≈ 354 , the signature of this unsteady forcing can still be detected in near-dissipation-range statistics. These observations provide insight into optimisation of forcing and the mechanism of energy transfer when using unsteady forcing to generate turbulence in confined vessels. Graphical abstract

Methodological Perspectives on the Study of the Health Effects of Unemployment – Reviewing the Mode of Unemployment, the Statistical Analysis Method and the Role of Confounding Factors

Introduction: Studying the relationship between unemployment and health raises many methodological challenges. In the current study, the aim was to evaluate how different ways of measuring unemployment and the choice of statistical model affects the effect estimate. Methods: The Northern Swedish cohort was used, and two follow-up surveys thereof from 1995 and 2007, as well as register data about unemployment. Self-reported current unemployment, self-reported accumulated unemployment and register-based accumulated unemployment were used to measure unemployment and its effect on self-reported health was evaluated. Analyses were conducted with G-computation, logistic regression and three estimators for the inverse probability weighting propensity scores, and 11 potentially confounding variables were part of the analyses. Results were presented with absolute differences in the proportion with poor self-reported health between unemployed and employed individuals for all estimators but logistic regression. Results: Of the initial 1083 pupils in the cohort, 488–693 individuals were defined as employed and 61–214 individuals were defined as unemployed in our different analyses. In the analyses, the deviation was large between the unemployment measures, with a difference of at least 2.5% in effect size when unemployed was compared with employed for the self-reported and register-based unemployment modes. The choice of statistical method only had a small influence on effect estimates and the deviation was in most cases lower than 1%. When models were compared based on the choice of potential confounders in the analytical model, the deviations were rarely above 0.6% when comparing models with 4 and 11 potential confounders. Our variable for health selection was the only one that strongly affected estimates when it was not part of the statistical model. Conclusions: Misspecifications of the statistical model or choice of analytical method might not matter much for effect estimates of the relationship between unemployment and health except for the inclusion of a variable measuring earlier health status before becoming unemployed. On the other hand, how unemployment is measured is highly important.

School Autonomy Policies Lead to Increases in Principal Autonomy and Job Satisfaction

We explore whether decentralization of decision-making influences school principals’ subjective experience of autonomy, job demands, burnout, and job satisfaction. Using six-years of longitudinal data, we used two Australian education reforms as a natural experiment of the effect of decentralization. Exploiting state-to-state variation in the policies, we used difference-in-differences models, finding that the decentralization policies had a small influence on increasing self-perceptions of autonomy without increasing job demands. We also found that the policies had a small positive effect on job satisfaction.

Black soldier fly (Hermetia illucens, L.) larvae for food and feed: modelling drying kinetics

Insects are a new alternative for food and feed and a solution for circular economy. Among the most promising insects, black soldier fly, mainly in the larvae phase, is a solution specially for feed, and in particular in its dried form. The aim of this work was to study the water loss transfer during convective drying of black soldier fly larvae (BSFL). The mass transfer model consisted of mass diffusion with two alternative boundary conditions (no external resistance and convection) and with/without shrinkage, applied with finite elements method, with a triangular mesh of 3,036 elements and a geometry reproducing the shape of the larvae. The moisture diffusion coefficient, estimated from the experimental data assuming an infinite slab, increased from 0.7002×10-10 m2/s at 60 °C to 2.792×10-10 m2/s at 90 °C, with an activation energy of 43.97 kJ/mol. The simulation predicted with detail the water content profile showing a quick water loss on the outer layers of the BSFL at the initial times. The evolution of the overall water content of BSFL during drying was better predicted for long times (when more than 80% of the moisture was removed) and at the highest temperature of 90 °C and showed that diffusion was the dominating mechanism, with small influence of the boundary conditions studied. Although shrinkage between 21 and 29% was considered, depending on the temperature, the inclusion of volume change in the model did not significantly improved the water content prediction.

Numerical Analysis of Friction Effects on Temperature and Phases within Forged Ti-6Al-4V Alloy Aeroengine Drum

Friction conditions significantly impact the temperature and phases of titanium forged parts, further directly affecting the microstructures and mechanical properties of final parts. In this paper, a 2D simplified finite element (FE) model combined with phase transition equations is developed to simulate a Ti-6Al-4V drum forging procedure. Then, friction effects on the temperature and phases of the forged drum are numerically analyzed and verified by experiments. The simulated results indicate that a reasonable range of friction factor is needed to obtain a relatively homogenous temperature distribution within the forged drum. Moreover, unlike its small influence on the α + β phase, improving friction obviously decreases the general levels of temperature and β phase and increases the homogeneities of α and β phases within the forged drum, which are associated with cooling rates and the heating effects of friction and deformation.

Crystal and molecular structures of some phosphane-substituted cymantrenes [(C5H4 X)Mn(CO)LL′] (X = H or Cl, L = CO, L′ = PPh3 or PCy3, and LL' = Ph2PCH2CH2PPh2)

UV irradiation of tetrahydrofuran solutions of [CpMn(CO)3] (Cp = π-C5H5 or π-C5H4Cl) in the presence of the phosphanes PPh3 or PCy3 (Cy = cyclohexyl) and Ph2PCH2CH2PPh2 yields the substitution products [CpMn(CO)2PR 3] (R = Ph or Cy) and [CpMn(CO)(Ph2PCH2CH2PPh2)], namely, dicarbonyl(η5-cyclopentadienyl)(triphenylphosphane-κP)manganese(I), [Mn(C5H5)(C18H15P)(CO)2], 1a, dicarbonyl(η5-1-chlorocyclopentadienyl)(triphenylphosphane-κP)manganese(I), [Mn(C5H4Cl)(C18H15P)(CO)2], 1b, dicarbonyl(η5-cyclopentadienyl)(tricyclohexylphosphane-κP)manganese(I), [Mn(C5H5)(C18H33P)(CO)2], 2a, dicarbonyl(η5-1-chlorocyclopentadienyl)(tricyclohexylphosphane-κP)manganese(I), [Mn(C5H4Cl)(C18H33P)(CO)2], 2b, carbonyl(η5-cyclopentadienyl)[1,2-bis(diphenylphosphanyl)ethane-κ2 P,P′]manganese(I), [Mn(C5H5)(C26H24P2)(CO)], 3a, and carbonyl(η5-1-chlorocyclopentadienyl)[1,2-bis(diphenylphosphanyl)ethane-κ2 P,P′]manganese(I), [Mn(C5H4Cl)(C26H24P2)(CO)], 3b, The crystal structure determinations show a very small influence of the chlorine substitution and a moderate influence of the phosphane substitution on the bond lengths. The PR 3 groups avoid being eclipsed with the C—Cl bonds. All the compounds employ weak C—H...O interactions for intermolecular association, which are enhanced by C—H...Cl contacts in the chlorinated products.

Binge-Swiping Through Politics

Social media has been used as a tool to spread political information since its creation, but its effectiveness has not been studied in depth. Older and wider known platforms such as Facebook, Twitter, Instagram, and Snapchat have been the focus of several academic studies, while newer platforms such as TikTok have been ignored. The guiding question of this study is, "does the social media platform TikTok inspire teenagers and young adults (13-20) to participate in political activities such as activism, voting, and educating themselves about political issues better than other social media platforms?" I hypothesized that TikTok usage would have a very strong correlation to political involvement of any kind. To answer the question, the study employed a mixed-method approach including a survey with 16 questions and an interview with TikTok content creators with 8 questions. The survey had 100 respondents and the interview had 6 respondents. This study found that TikTok had a stronger influence on teenage engagement in online political actions, especially learning about political issues. TikTok had a very small influence on teenage involvement in politics offline. Even though my hypothesis was only partially correct and TikTok doesn’t impact young people to vote as much as I expected, it still has a great value in society because it helps provide young people with the information they need to cast a well-informed ballot.

Influence of Y2O3 Content on Structural, Optical, Spectroscopic, and Laser Properties of Er3+, Yb3+ Co-Doped Phosphate Glasses

The influence of the addition of Y2O3 on the structural, spectroscopic, and laser properties of newly prepared Er, Yb-doped strontium-sodium phosphate glass was investigated. While the addition of Y2O3 has a small influence on the absorption spectra and fluorescence lifetime, it has a strong impact on the emission cross-section and on OH− content. The glasses were used as the active medium for diode-pumped laser emitting at 1556 nm. The increase in Y2O3 content leads to a significant 35% increase in laser slope efficiency up to 10.4%, but at the expense of the substantial reduction of the wavelength tunability from 82 to 54 nm.

Influence of microbiological culture results on antibiotic choices for veterans with hospital-acquired pneumonia and ventilator-associated pneumonia

Objective: We examined the impact of microbiological results from respiratory samples on choice of antibiotic therapy in patients treated for hospital-acquired pneumonia (HAP) or ventilator-associated pneumonia (VAP). Design: Four-year retrospective study. Setting: Veterans’ Health Administration (VHA). Patients: VHA patients hospitalized with HAP or VAP and with respiratory cultures between October 1, 2014, and September 30, 2018. Interventions: We compared patients with positive and negative respiratory culture results, assessing changes in antibiotic class and Antibiotic Spectrum Index (ASI) from the day of sample collection (day 0) through day 7. Results: Between October 1, 2014, and September 30, 2018, we identified 5,086 patients with HAP/VAP: 2,952 with positive culture results and 2,134 with negative culture results. All-cause 30-day mortality was 21% for both groups. The mean time from respiratory sample receipt in the laboratory to final respiratory culture result was longer for those with positive (2.9 ± 1.3 days) compared to negative results (2.5 ± 1.3 days; P < .001). The most common pathogens were Staphylococcus aureus and Pseudomonas aeruginosa. Vancomycin and β-lactam/β-lactamase inhibitors were the most commonly prescribed agents. The decrease in the median ASI from 13 to 8 between days 0 and 6 was similar among patients with positive and negative respiratory cultures. Patients with negative cultures were more likely to be off antibiotics from day 3 onward. Conclusions: The results of respiratory cultures had only a small influence on antibiotics used during the treatment of HAP/VAP. The decrease in ASI for both groups suggests the integration of antibiotic stewardship principles, including de-escalation, into the care of patients with HAP/VAP.

Genetic Factors of Predisposition and Clinical Characteristics of Rheumatoid Arthritis in Russian Patients

Rheumatoid arthritis (RA) is a multifactorial disease caused by a genetic predisposition and environmental factors. Predisposing alleles of various genes have a relatively small influence on the disease risk when they appear separately, but in combination, they predispose an individual to RA development. We genotyped 125 patients with RA including 60 SNPs and sequenced coding part of six genes by next-generation sequencing (NGS) technology on a target panel (IAD177464_185). According to our data, the alleles HLA-DRB1*04, HLA-DRB1*01, HLA-B*27, PTPN22 (rs2476601), TNF (rs1800629), TPMT (rs2842934), and IL4 (rs2243250), and genotypes HLA-DRB1*04:04, HLA-DRB1*01:16, PTPN22 (rs2476601), TPMT (rs2842934), were significantly associated with the RA development. Associations with clinical criteria (DAS28-CRP, HAQ-DI, and CDAI) and biochemical factors were investigated. We have shown that the PADI4 genotypes (rs11203367, rs2240340, rs11203366, and rs874881) are significantly associated with the baseline levels of DAS28-CRP, HAQ-DI, and CDAI; genotypes IL23R (rs7530511) and TNFRSF1A (rs748004, rs2228144) with the level of anti citrullinated peptide antibodies (ACPA); the genotypes DHODH (rs3213422) and MTHFR (rs180113) with the concentration of C-reactive protein (CRP); and the genotypes IL2RA (rs2104286), IRAK3 (rs11541076), and IL4R (rs1801275) with the level of rheumatoid factor (RF). Application of targeted NGS panel contributes to expanded genotyping to identify risk groups among the RA patients.