The well-known stability of the drift wave in a sheared slab geometry does not hold in the presence of dust particles. Due to the presence of dust particles, the magnetic shear damping is reduced ...drastically. As a result, collisionless drift modes become unstable under typical parameter regimes of tokamak. Consequently, drift wave must still be considered as an underlying dynamic of anomalous transport in tokamak edges, where dust particles are found to be abundant, the same physics is expected in the spacial environments as well.
By using the fundamental fluid equations of continuity and momentum transfer, we derive an eigenvalue equation for Rayleigh Taylor (RT) instability and solve the equation numerically. The result ...shows that the growth rate of the RT mode is considerably higher in a dusty plasma than in a pure plasma. This is a first step, but it shows quite unambiguously that the dust might have a crucial role in explaining the origin of the low-frequency fluctuations in the space, the origin of the low-frequency oscillations is not understood at present.
The friction and wear performance of pure poly (methyl methacrylate) (PMMA) and zirconium oxide (ZrO2) filled PMMA composites were realized under dry sliding conditions. Wear tests were carried out ...at room temperature under the loads of 5N, 10N and 20N at the sliding speed of 0.5m/s, 1.0m/s and 1.5m/s. The coefficients of friction of the composites were significantly influenced with ZrO2 content. Results for testing materials showed that the friction coefficient and the wear rate are sensitive to the applied loads and sliding speeds. The wear rates of the PMMA composite are changing between 3.01×10−7mm3/m and 5.50×10−6mm3/m, depending on ZrO2 additive percentage, applied load and sliding speeds. Increase in load value caused the increase in friction coefficient and wear rate.
The extent to which humans are modifying Earth's surface chemistry can be quantified by comparing total anthropogenic element fluxes with their natural counterparts (Klee and Graedel, 2004). We ...quantify anthropogenic mass transfer of 77 elements from mining, fossil fuel burning, biomass burning, construction activities, and human apportionment of terrestrial net primary productivity, and compare it to natural mass transfer from terrestrial and marine net primary productivity, riverine dissolved and suspended matter fluxes to the ocean, soil erosion, eolian dust, sea-salt spray, cosmic dust, volcanic emissions, and for helium, hydrodynamic escape from the Earth's atmosphere. We introduce an approach to correct for losses during industrial processing of elements belonging to geochemically coherent groups, and explicitly incorporate uncertainties of element mass fluxes through Monte Carlo simulations. We find that at the Earth's surface anthropogenic fluxes of iridium, osmium, helium, gold, ruthenium, antimony, platinum, palladium, rhenium, rhodium and chromium currently exceed natural fluxes. For these elements mining is the major factor of anthropogenic influence, whereas petroleum burning strongly influences the surficial cycle of rhenium. Our assessment indicates that if anthropogenic contributions to soil erosion and eolian dust are considered, anthropogenic fluxes of up to 62 elements surpass their corresponding natural fluxes.
The exploitation and design of metal‐free catalysts for chemical transformation is always a fascinating theme from the prospective of fundamental and applied research. In addition to their distinct ...advantages such as lower cost, higher biocompatibility and reliability and thus higher sustainability, metal‐free materials often unexpectedly render different reaction pathway or mechanism from conventional metal catalysts. As a consequence, metal‐free catalysts have revolutionized and expanded the platform of catalysis. Among them, carbons are a typical class of nonmetallic materials. To date, a series of elements (e. g., B, N, P or S) as heteroatom dopants have equipped pristine carbons with enhanced performance and even new chemical functionality. It was proposed to attribute to modulated electrical properties and surface physicochemical features originated from structural distortions and changes of charge densities. In this minireview, we overviewed the catalytic application of heteroatom‐doped carbocatalysts in oxidation, oxidative coupling, reduction and hydrogenation reactions with special emphasis on the role of heteroatoms and consequently enhanced performance. This minireview highlights the structure‐activity correlations, thereby directing the rational design of advanced metal‐free catalysts for organic synthesis. Some controversies about active sites and challenges in catalyst design are also discussed here.
No metal required: This Minireview summarizes the catalytic application of the metal‐free heteroatom‐doped carbocatalysts in oxidation, oxidative coupling, reduction and hydrogenation. The structure‐activity correlations obtained from extensive characterization and observed catalytic performance was highlighted, thereby providing guidance for the rational design of advanced catalysts for heterogeneous catalysis beyond electrochemistry.
Silicate and carbonate weathering reactions consume atmospheric CO2 depending on the type of weathering agents, namely carbonic (H2CO3), sulfuric (H2SO4), and nitric acids (HNO3), and have potential ...climate implications. However, the importance of HNO3 in weathering processes in the Himalayan glacierized basins has not been examined yet but is critical to better constrain the concomitant short (<103 years) and long‐term (>106 years) variability in the carbon cycle as it can drive negative feedback to a climate. By analyzing time‐series hydro‐geochemical data of proglacial meltwater in the Ganga headwaters of Central Himalaya, we demonstrate that the weathering rate of carbonate minerals is increased 1.06 times when the role of HNO3 is considered together with H2CO3 and H2SO4 in comparison to the role of H2CO3 and H2SO4. However, we also observe that the CO2 drawdown rate decreases 1.13 times and 1.06 times when the role of all three acids is considered in silicate and carbonate weathering reactions, respectively, compared to the CO2 drawdown rates linked to the role of H2CO3 and H2SO4. Moreover, the involvement of HNO3 in chemical weathering can reduce the inorganic global carbon sink by releasing CO2 into the ocean‐atmosphere system. We conclude that HNO3‐mediated chemical weathering reactions are important processes that alter the geologic carbon cycle of high‐altitude glacierized Himalayan catchments as well as on a global scale.
Key Points
H2SO4 and HNO3 acids can act as additional proton sources and influence the rates of chemical weathering and atmospheric CO2 consumption
Chemical weathering mediated by H2CO3, H2SO4, and HNO3 acids can enhance the rates of weathering but reduce the rates of CO2 drawdown
Sulfuric and nitric acid‐mediated chemical weathering reactions are important to better constrain geological carbon cycling
This research relied on afield experiment involving a real-world instance of corporate philanthropy to shed light on both the scope and limitations of the strategic returns to corporate social ...responsibility (CSR). In particular, the authors demonstrate that the impact of CSR in the real world is not only less pervasive than has been previously acknowledged but also more multifaceted than has been previously conceptualized. The findings indicated that contingent on CSR awareness, which was rather low, stakeholders did react positively to the focal company not only in the consumption domain but in the employment and investment domains as well. Stakeholder attributions regarding the genuineness of the company's motives moderated these effects. PUBLICATION ABSTRACT
For diagnostic purposes, the nine symptoms that compose the DSM-5 criteria for major depressive disorder (MDD) are assumed to be interchangeable indicators of one underlying disorder, implying that ...they should all have similar risk factors. The present study investigates this hypothesis, using a population cohort that shifts from low to elevated depression levels.
We assessed the nine DSM-5 MDD criterion symptoms (using the Patient Health Questionnaire; PHQ-9) and seven depression risk factors (personal and family MDD history, sex, childhood stress, neuroticism, work hours, and stressful life events) in a longitudinal study of medical interns prior to and throughout internship (n = 1289). We tested whether risk factors varied across symptoms, and whether a latent disease model could account for heterogeneity between symptoms.
All MDD symptoms increased significantly during residency training. Four risk factors predicted increases in unique subsets of PHQ-9 symptoms over time (depression history, childhood stress, sex, and stressful life events), whereas neuroticism and work hours predicted increases in all symptoms, albeit to varying magnitudes. MDD family history did not predict increases in any symptom. The strong heterogeneity of associations persisted after controlling for a latent depression factor.
The influence of risk factors varies substantially across DSM depression criterion symptoms. As symptoms are etiologically heterogeneous, considering individual symptoms in addition to depression diagnosis might offer important insights obfuscated by symptom sum scores.
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