Coupling Between Thermal Oscillations in the Surface of a Micro-Cylinder and Vortex Shedding

his article studies the coupling between prescribed thermal oscillations in the surface of a micro-cylinder and vortex shedding. We deal with the unsteady, laminar, compressible flow regime where the aerodynamics forces have a periodic behavior. It is shown that appropriate spatial and time-dependent temperature oscillations on the surface of the micro-cylinder create a resonance that controls the amplitude and frequency of both lift and drag coefficients. In practice, what we study is a mechanism to modulate the amplitude and frequency of mechanical loads of aerodynamics origin in a micro-structure by using surface temperature fluctuations as the control parameter

Quantum spin pumping with adiabatically modulated magnetic barrier's

A quantum pump device involving magnetic barriers produced by the deposition of ferro magnetic stripes on hetero-structure's is investigated. The device for dc- transport does not provide spin-polarized currents, but in the adiabatic regime, when one modulates two independent parameters of this device, spin-up and spin-down electrons are driven in opposite directions, with the net result being that a finite net spin current is transported with negligible charge current. We also analyze our proposed device for inelastic-scattering and spin-orbit scattering. Strong spin-orbit scattering and more so inelastic scattering have a somewhat detrimental effect on spin/charge ratio especially in the strong pumping regime. Further we show our pump to be almost noiseless, implying an optimal quantum spin pump.Comment: 14 pages, 9 figures. Manuscript revised with additional new material on spin-orbit scattering and inelastic scattering. Further new additions on noiseless pumping and analytical results with distinction between weak and strong pumping regimes. Accepted for publication in Physical Review

Prevalence of burnout among psychiatrists: A systematic review and meta-analysis

Background: Burnout is a consequence of chronic occupational stress exposure. Psychiatrists are prone to burnout due to specific work-related factors. This study examined the burnout prevalence among psychiatrists. Methods: The study protocol was registered in PROSPERO (CRD42020204615). We searched MEDLINE, EMBASE, CENTRAL, PsycINFO, Web of Science, ClinicalTrials.gov, and OpenGrey for relevant publications. Random-effect meta-analysis was performed. We used subgroup analysis and meta-regression to reveal any association of geographical region, survey year, participants' age, gender, and response rate with burnout. Results: Thirty-six studies involving 5481 participants were included. The prevalence of overall burnout was 25.9% [11.1%–40.7%] as measured by a Maslach Burnout Inventory (MBI) and 50.3% [30.9%–69.8%] as measured by a Copenhagen Burnout Inventory (CBI). The pooled prevalence was 43.5% [27.9%–59%] for high emotional exhaustion (EE), 28.2% [17.5%–38.9%] for high depersonalization (DP), and 32.4% [3.4%–61.3%] for low personal accomplishment (PA). The mean scores of 22-item MBI subscales were 21.51 [18.64%–24.38%] for EE, 6.57 [5.53%–7.62%] for DP, and 31.83 [25.73%–37.94%] for PA. European psychiatrists revealed (p = 0.045) lower EE score (20.82; 95% CI 7.24–24.41) measured by 22-item MBI compared to their non-European colleagues (24.99; 95% CI 23.05–26.94). Other results include mean scores for 16-item MBI-General Survey, burnout rates, and scores in CBI subscales. Limitations: The main limitation was high heterogeneity in terms of statistics, screening methods, burnout definitions, and cut-off points utilized in included studies. Conclusions: Burnout is highly prevalent among psychiatrists. Future research should focus on finding consensus on burnout screening, longitudinal evaluation of psychiatrists' burnout predictors, and development of effective intervention strategies. © 2022 Elsevier B.V

Hydrolysis of Mg(BH4)2 and its coordination compounds as a way to obtain hydrogen

Three ligand-stabilized Mg(BH4)2–based complexes have been synthesized and evaluated as potential hydrogen storage media for portable fuel cell applications. The new borohydrides: Mg(BH4)2 × 0.5Et2O and Mg(BH4)2 × diglyme (diglyme – CH3O(CH2)2O(CH2)2OCH3) have been synthesized and examined by X-ray single crystal diffraction method. Hydrolysis reactions of the compounds liberate hydrogen in quantities ranging from 46 to 96% of the theoretical yield. The hydrolysis of Mg(BH4)2 and other borohydrides is also accompanied by the diborane formation. The amount of liberated diborane depends on the Mg-coordination environment. To explain this fact quantum-chemical calculations have been performed. It is shown that formation of Mg-O-Mg-bridges enables the side process of diborane generation. It means that the size and denticity of the ligand directly affects the amount of released diborane. In general, the larger the ligand and the higher its denticity, the smaller is amount of diborane produced. The new compound Mg(BH4)2 × diglyme decomposes without diborane formation that allows one to be considered as a new promising chemical hydrogen storage compound for the practical usage. © 2017 Elsevier B.V

Hydrolysis of Mg(BH4)2 and its coordination compounds as a way to obtain hydrogen

Three ligand-stabilized Mg(BH4)2–based complexes have been synthesized and evaluated as potential hydrogen storage media for portable fuel cell applications. The new borohydrides: Mg(BH4)2 × 0.5Et2O and Mg(BH4)2 × diglyme (diglyme – CH3O(CH2)2O(CH2)2OCH3) have been synthesized and examined by X-ray single crystal diffraction method. Hydrolysis reactions of the compounds liberate hydrogen in quantities ranging from 46 to 96% of the theoretical yield. The hydrolysis of Mg(BH4)2 and other borohydrides is also accompanied by the diborane formation. The amount of liberated diborane depends on the Mg-coordination environment. To explain this fact quantum-chemical calculations have been performed. It is shown that formation of Mg-O-Mg-bridges enables the side process of diborane generation. It means that the size and denticity of the ligand directly affects the amount of released diborane. In general, the larger the ligand and the higher its denticity, the smaller is amount of diborane produced. The new compound Mg(BH4)2 × diglyme decomposes without diborane formation that allows one to be considered as a new promising chemical hydrogen storage compound for the practical usage. © 2017 Elsevier B.V