Sedimentary molybdenum and uranium sequestration in a non-euxinic coastal setting: role of the sulfate-methane transition zone

Author(s):  
Sami Jokinen ◽  
Karoliina Koho ◽  
Joonas Virtasalo ◽  
Tom Jilbert

<p>Molybdenum (Mo) and uranium (U) contents in sedimentary records are commonly used to track past changes in seafloor oxygenation. However, inadequate understanding of Mo and U sequestration mechanisms in non-euxinic coastal areas limits their use as redox proxies in these settings. Because large areas of the coastal oceans are currently undergoing partial deoxygenation due to anthropogenic nutrient inputs and increased stratification, it is critical to improve our understanding of these proxies to allow robust assessment of the trajectory of environmental change. Here, we use a comprehensive set of sediment pore water and solid-phase analyses to deconvolve the mechanisms of authigenic Mo and U sequestration in a shallow non-euxinic coastal setting in the northern Baltic Sea. Despite the permanently oxic bottom waters in the area, eutrophication over the past decades has led to establishment of a shallow sulfate-methane transition zone (SMTZ) in the sediment, which is typical for human-impacted coastal settings on a trajectory towards hypoxia. Our results demonstrate remarkably synchronous patterns of Mo and U sequestration, whereby their authigenic uptake is largely predicated upon the depth and intensity of the SMTZ. Based on sequential extraction analyses, the authigenic Mo pool is dominated by refractory Fe-S phases such as pyrite and nanoscale FeMoS<sub>4</sub>, signaling that authigenic Mo uptake largely proceeds through the Fe-sulfide pathway. In addition, we observe a pool of extremely labile Mo deep within the SMTZ, potentially denoting a transient phase in authigenic Mo uptake and/or partial switch in the mode of sequestration to the organic matter pathway at low levels of dissolved iron. Authigenic U is largely hosted by acid-extractable and refractory phases, reflecting sequestration into poorly crystalline monomeric U(IV) and crystalline uraninite, respectively. Analogously to Mo, authigenic sequestration of U proceeds at two distinct fronts within the SMTZ, which are characterized by shifts in dissolved sulfide concentrations, providing strong evidence for a link between sulfide-producing processes and U reduction. Our results imply that both Mo and U have the potential to capture temporal shifts in bottom water oxygenation indirectly, through the connection between oxygenation and the depth of the SMTZ. Of the two elements, Mo appears a more viable redox proxy because of the substantially higher share of the authigenic pool. However, temporal resolution of these proxies is restricted by the relatively deep authigenic uptake within the sediment column and the integrated character of the signal caused by vertical migrations of the SMTZ. These findings set a framework for interpreting sedimentary Mo- and U-based paleoredox archives in other non-euxinic coastal settings.</p>

2017 ◽  
Vol 76 (4) ◽  
pp. 145-153 ◽  
Author(s):  
Jana Nikitin ◽  
Alexandra M. Freund

Abstract. Establishing new social relationships is important for mastering developmental transitions in young adulthood. In a 2-year longitudinal study with four measurement occasions (T1: n = 245, T2: n = 96, T3: n = 103, T4: n = 85), we investigated the role of social motives in college students’ mastery of the transition of moving out of the parental home, using loneliness as an indicator of poor adjustment to the transition. Students with strong social approach motivation reported stable and low levels of loneliness. In contrast, students with strong social avoidance motivation reported high levels of loneliness. However, this effect dissipated relatively quickly as most of the young adults adapted to the transition over a period of several weeks. The present study also provides evidence for an interaction between social approach and social avoidance motives: Social approach motives buffered the negative effect on social well-being of social avoidance motives. These results illustrate the importance of social approach and social avoidance motives and their interplay during developmental transitions.


2016 ◽  
Vol 37 (2) ◽  
pp. 96-104 ◽  
Author(s):  
Hasida Ben-Zur

Abstract. The current study investigated the associations of psychological resources, social comparisons, and temporal comparisons with general wellbeing. The sample included 142 community participants (47.9% men; age range 23–83 years), who compared themselves with others, and with their younger selves, on eight dimensions (e.g., physical health, resilience). They also completed questionnaires assessing psychological resources of mastery and self-esteem, and three components of subjective wellbeing: life satisfaction and negative and positive affect. The main results showed that high levels of psychological resources contributed to wellbeing, with self-enhancing social and temporal comparisons moderating the effects of resources on certain wellbeing components. Specifically, under low levels of mastery or self-esteem self-enhancing social or temporal comparisons were related to either higher life satisfaction or positive affect. The results highlight the role of resources and comparisons in promoting people’s wellbeing, and suggest that self-enhancing comparisons function as cognitive coping mechanisms when psychological resources are low.


Author(s):  
Donald Eugene Canfield

This chapter considers the aftermath of the great oxidation event (GOE). It suggests that there was a substantial rise in oxygen defining the GOE, which may, in turn have led to the Lomagundi isotope excursion, which was associated with high rates of organic matter burial and perhaps even higher concentrations of oxygen. This excursion was soon followed by a crash in oxygen to very low levels and a return to banded iron formation deposition. When the massive amounts of organic carbon buried during the excursion were brought into the weathering environment, they would have represented a huge oxygen sink, drawing down levels of atmospheric oxygen. There appeared to be a veritable seesaw in oxygen concentrations, apparently triggered initially by the GOE. The GOE did not produce enough oxygen to oxygenate the oceans. Dissolved iron was removed from the oceans not by reaction with oxygen but rather by reaction with sulfide. Thus, the deep oceans remained anoxic and became rich in sulfide, instead of becoming well oxygenated.


2020 ◽  
Vol 18 (1) ◽  
pp. 23-37
Author(s):  
Andreea Gheorghe ◽  
Oana Fodor ◽  
Anișoara Pavelea

This study explores the association between task conflict and team creativity and the role of group cognitive complexity (GCC) as a potential explanatory mechanism in a sample of 159 students organized in 49 groups. Moreover, we analyzed the moderating effect of collective emotional intelligence (CEI)in the relationship between task conflict and GCC.As hypothesized, we found that task conflict has a nonlinear relationship with GCC, but contrary to our expectations, it follows a U-shaped association, not an inversed U-shape. In addition,the moderating role of CEI was significant only at low levels. Contrary to our expectation, the mediating role of GCC did not receive empirical support. Theoretical and practical contributions are discussed.


Author(s):  
David L. Kirchman

Geomicrobiology, the marriage of geology and microbiology, is about the impact of microbes on Earth materials in terrestrial systems and sediments. Many geomicrobiological processes occur over long timescales. Even the slow growth and low activity of microbes, however, have big effects when added up over millennia. After reviewing the basics of bacteria–surface interactions, the chapter moves on to discussing biomineralization, which is the microbially mediated formation of solid minerals from soluble ions. The role of microbes can vary from merely providing passive surfaces for mineral formation, to active control of the entire precipitation process. The formation of carbonate-containing minerals by coccolithophorids and other marine organisms is especially important because of the role of these minerals in the carbon cycle. Iron minerals can be formed by chemolithoautotrophic bacteria, which gain a small amount of energy from iron oxidation. Similarly, manganese-rich minerals are formed during manganese oxidation, although how this reaction benefits microbes is unclear. These minerals and others give geologists and geomicrobiologists clues about early life on Earth. In addition to forming minerals, microbes help to dissolve them, a process called weathering. Microbes contribute to weathering and mineral dissolution through several mechanisms: production of protons (acidity) or hydroxides that dissolve minerals; production of ligands that chelate metals in minerals thereby breaking up the solid phase; and direct reduction of mineral-bound metals to more soluble forms. The chapter ends with some comments about the role of microbes in degrading oil and other fossil fuels.


Coatings ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 503
Author(s):  
Jaehyun Lee ◽  
Ehsan Esmaili ◽  
Giho Kang ◽  
Baekhoon Seong ◽  
Hosung Kang ◽  
...  

The dimple occurs by sudden pressure inversion at the droplet’s bottom interface when a droplet collides with the same liquid-phase or different solid-phase. The air film entrapped inside the dimple is a critical factor affecting the sequential dynamics after coalescence and causing defects like the pinhole. Meanwhile, in the coalescence dynamics of an electrified droplet, the droplet’s bottom interfaces change to a conical shape, and droplet contact the substrate directly without dimple formation. In this work, the mechanism for the dimple’s suppression (interfacial change to conical shape) was studied investigating the effect of electric pressure. The electric stress acting on a droplet interface shows the nonlinear electric pressure adding to the uniform droplet pressure. This electric stress locally deforms the droplet’s bottom interface to a conical shape and consequentially enables it to overcome the air pressure beneath the droplet. The electric pressure, calculated from numerical tracking for interface and electrostatic simulation, was at least 108 times bigger than the air pressure at the center of the coalescence. This work helps toward understanding the effect of electric stress on droplet coalescence and in the optimization of conditions in solution-based techniques like printing and coating.


Author(s):  
Haocheng Luo ◽  
Qingqi Liu ◽  
Chengfu Yu ◽  
Yangang Nie

Parental warmth plays an important role in the development of adolescents’ physical and mental health. There are numerous empirical studies indicating a relationship between parental warmth and prosocial behavior among adolescents, although the underlying mechanisms of this association remain unclear. Adopting a longitudinal design across two time points, the present study proposes a moderated mediation model to explore the mediating role of gratitude and the moderating role of the school climate between parental warmth and prosocial behavior. The sample consisted of 943 participants (483 boys and 451 girls) who participated in the second assessment and completed questionnaires assessing gratitude, school climate, and prosocial behavior in April 2019. Their parents participated in the first assessment and completed a questionnaire pertaining to parental warmth in October 2018. After controlling for the gender and age of the adolescents, the results showed that the positive association between parental warmth and prosocial behavior is mediated by gratitude, and school climate does play a moderating role in the second half of the mediating path. Specifically, the school climate can play a protective role in adolescents with low levels of gratitude. For adolescents with less gratitude, a strong school climate can promote more prosocial behaviors and can effectively alleviate the negative prediction of low levels of gratitude. This study provides a theoretical explanation for the generation of adolescents’ prosocial behavior and provides theoretical guidance for the interventions of schools and parents.


2021 ◽  
Vol 12 (8) ◽  
Author(s):  
David Della-Morte ◽  
Francesca Pacifici ◽  
Camillo Ricordi ◽  
Renato Massoud ◽  
Valentina Rovella ◽  
...  

AbstractThe pathophysiology of coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and especially of its complications is still not fully understood. In fact, a very high number of patients with COVID-19 die because of thromboembolic causes. A role of plasminogen, as precursor of fibrinolysis, has been hypothesized. In this study, we aimed to investigate the association between plasminogen levels and COVID-19-related outcomes in a population of 55 infected Caucasian patients (mean age: 69.8 ± 14.3, 41.8% female). Low levels of plasminogen were significantly associated with inflammatory markers (CRP, PCT, and IL-6), markers of coagulation (D-dimer, INR, and APTT), and markers of organ dysfunctions (high fasting blood glucose and decrease in the glomerular filtration rate). A multidimensional analysis model, including the correlation of the expression of coagulation with inflammatory parameters, indicated that plasminogen tended to cluster together with IL-6, hence suggesting a common pathway of activation during disease’s complication. Moreover, low levels of plasminogen strongly correlated with mortality in COVID-19 patients even after multiple adjustments for presence of confounding. These data suggest that plasminogen may play a pivotal role in controlling the complex mechanisms beyond the COVID-19 complications, and may be useful both as biomarker for prognosis and for therapeutic target against this extremely aggressive infection.


2021 ◽  
Vol 22 (14) ◽  
pp. 7360
Author(s):  
Angie De La Cruz ◽  
Aubrey Hargrave ◽  
Sri Magadi ◽  
Justin A. Courson ◽  
Paul T. Landry ◽  
...  

Platelet extravasation during inflammation is under-appreciated. In wild-type (WT) mice, a central corneal epithelial abrasion initiates neutrophil (PMN) and platelet extravasation from peripheral limbal venules. The same injury in mice expressing low levels of the β2-integrin, CD18 (CD18hypo mice) shows reduced platelet extravasation with PMN extravasation apparently unaffected. To better define the role of CD18 on platelet extravasation, we focused on two relevant cell types expressing CD18: PMNs and mast cells. Following corneal abrasion in WT mice, we observed not only extravasated PMNs and platelets but also extravasated erythrocytes (RBCs). Ultrastructural observations of engorged limbal venules showed platelets and RBCs passing through endothelial pores. In contrast, injured CD18hypo mice showed significantly less venule engorgement and markedly reduced platelet and RBC extravasation; mast cell degranulation was also reduced compared to WT mice. Corneal abrasion in mast cell-deficient (KitW-sh/W-sh) mice showed less venule engorgement, delayed PMN extravasation, reduced platelet and RBC extravasation and delayed wound healing compared to WT mice. Finally, antibody-induced depletion of circulating PMNs prior to corneal abrasion reduced mast cell degranulation, venule engorgement, and extravasation of PMNs, platelets, and RBCs. In summary, in the injured cornea, platelet and RBC extravasation depends on CD18, PMNs, and mast cell degranulation.


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