Dissolved Organic Carbon Loading Stimulates Sediment Phosphorus Mobilization and Release: Preliminary Evidence From Xiangshan Port, East China Sea

Increasing concentrations of dissolved organic carbon (DOC) have been observed in coastal ecosystems worldwide over the past decade, and tight coupling of the carbon (C) and phosphorus (P) biogeochemical cycle has been recognized in aquatic ecosystems. However, there is still no consensus regarding the potential effects of DOC loading on sediment P release. In a 2-month mesocosm experiment, we tested the effects of DOC enrichment on sediment P release in six glass aquariums. Two treatments were set: Control (without sodium acetate (Na(CH3COO)) addition) and Na(CH3COO) addition (equivalent to 5 mg C L−1). The results showed the following: 1) DOC loading stimulated sediment P mobilization and release, as indicated by increases in the labile P recorded for 7-cm-deep sediment using diffusive gradients in thin films, the flux of P across the sediment–water interface, and the total P concentrations in the overlying water; and 2) stimulated alkaline phosphatase activity, increased P-solubilizing bacteria proportion, and decreased dissolved oxygen concentration were likely the primary mechanisms behind the DOC-stimulated sediment P mobilization and release. These results provide insight into the promotion of sediment P release induced by C addition. Further studies investigating the quantitative relationships between DOC loadings and P release are needed to fully elucidate the coupled roles of C and P, especially those based on large-scale field investigations with broader C forms and loadings.

How Subsistence Communities Reconfigure Livelihood Systems in Response to Climate Change: A Coupled-Systems Perspective

A defining societal challenge in the era of climate change is ensuring consumption adequacy in subsistence communities. To understand the intricacies of this challenge, we have conducted an ethnographic study of a low-income community that relies on subsistence fishing to maintain consumption adequacy. Based on our data analysis, we advance a conceptualization of subsistence livelihood systems that models the tight coupling among its three constituent subsystems: the market system, the social system, and the environmental system. These three subsystems are highly interdependent and operate in concert to maintain consumption adequacy. We then show how climate change-induced environmental disruptions threaten consumption adequacy by disequilibrating livelihood systems in subsistence settings, as well as unpack the self-directed adaptation and mitigation strategies employed by the community in response to the threat of consumption inadequacy. These response strategies create feedback loops to either preserve or attenuate the tight coupling among the three subsystems.

Structural Basis for Control of Bacterial RNA Polymerase Pausing by a Riboswitch and its Ligand

Folding of nascent transcripts can be modulated by the proximal RNA polymerase (RNAP) that carries out their transcription, and vice versa. A pause of RNAP during transcription of a preQ1 riboswitch (que-ePEC) is stabilized by a previously characterized template consensus sequence and the ligand-free conformation of the nascent RNA. Ligand binding to the riboswitch induces RNAP pause release and downstream transcription termination, however, the mechanism by which riboswitch folding modulates pausing is unclear. Here, we report single-particle cryo-electron microscopy reconstructions of que-ePEC in ligand-free and ligand-bound states. In the absence of preQ1, the RNA transcript is in an unexpected hyper-translocated state, preventing downstream nucleotide incorporation. Strikingly, upon ligand binding the riboswitch rotates around its helical axis, expanding the surrounding RNAP exit channel and repositioning the transcript for elongation. Our study reveals the tight coupling by which small nascent RNA structures and their ligands can functionally regulate the macromolecular transcription machinery.

Auditable Augmented/Mixed/Virtual Reality

Virtual, Augmented and Mixed Reality (XR) technologies are becoming increasingly pervasive. However, the contextual nature of XR, and its tight coupling of the digital and physical environments, brings real propensity for loss and harm. This means that auditability---the ability to inspect how a system operates---will be crucial for dealing with incidents as they occur, by providing the information enabling rectification, repair and recourse. However, supporting audit in XR brings considerations, as the process of capturing audit data itself has implications and challenges, both for the application (e.g., overheads) and more broadly. This paper explores the practicalities of auditing XR systems, characterises the tensions between audit and other considerations, and argues the need for flexible tools enabling the management of such. In doing so, we introduce Droiditor, a configurable open-source Android toolkit that enables the runtime capture of audit-relevant data from mobile applications. We use Droiditor as a means to indicate some potential implications of audit data capture, demonstrate how greater configurability can assist in managing audit-related concerns, and discuss the potential considerations that result. Given the societal demands for more transparent and accountable systems, our broader aim is to draw attention to auditability, highlighting tangible ways forward and areas for future work.

Mechanobiology of Microvascular Function and Structure in Health and Disease: Focus on the Coronary Circulation

The coronary microvasculature plays a key role in regulating the tight coupling between myocardial perfusion and myocardial oxygen demand across a wide range of cardiac activity. Short-term regulation of coronary blood flow in response to metabolic stimuli is achieved via adjustment of vascular diameter in different segments of the microvasculature in conjunction with mechanical forces eliciting myogenic and flow-mediated vasodilation. In contrast, chronic adjustments in flow regulation also involve microvascular structural modifications, termed remodeling. Vascular remodeling encompasses changes in microvascular diameter and/or density being largely modulated by mechanical forces acting on the endothelium and vascular smooth muscle cells. Whereas in recent years, substantial knowledge has been gathered regarding the molecular mechanisms controlling microvascular tone and how these are altered in various diseases, the structural adaptations in response to pathologic situations are less well understood. In this article, we review the factors involved in coronary microvascular functional and structural alterations in obstructive and non-obstructive coronary artery disease and the molecular mechanisms involved therein with a focus on mechanobiology. Cardiovascular risk factors including metabolic dysregulation, hypercholesterolemia, hypertension and aging have been shown to induce microvascular (endothelial) dysfunction and vascular remodeling. Additionally, alterations in biomechanical forces produced by a coronary artery stenosis are associated with microvascular functional and structural alterations. Future studies should be directed at further unraveling the mechanisms underlying the coronary microvascular functional and structural alterations in disease; a deeper understanding of these mechanisms is critical for the identification of potential new targets for the treatment of ischemic heart disease.

Rapid response of silicate weathering rates to climate change in the Himalaya

Chemical weathering of continental rocks plays a central role in regulating the carbon cycle and the Earth’s climate (Walker et al., 1981; Berner et al., 1983), accounting for nearly half the consumption of atmospheric carbon dioxide globally (Beaulieu et al., 2012). However, the role of climate variability on chemical weathering is still strongly debated. Here we focus on the Himalayan range and use the lithium isotopic composition of clays in fluvial terraces to show a tight coupling between climate change and chemical weathering over the past 40 ka. Between 25 and 10 ka ago, weathering rates decrease despite temperature increase and monsoon intensification. This suggests that at this timescale, temperature plays a secondary role compared to runoff and physical erosion, which inhibit chemical weathering by accel-erating sediment transport and act as fundamental controls in determining the feedback between chemical weathering and atmospheric carbon dioxide.

Bringing life to leadership: The emergence of principal leadership practice for educational success in low socio-economic schools

<p>The persistent educational achievement gap and historically haphazard nature of progress for students in impoverished contexts in New Zealand primary schools is a deep-seated problem needing urgent attention. This multifaceted and interconnected problem has no distinct origin and no clear solution and is continuing to harm individual and collective futures. This thesis explores principal leadership practice and how it intersects with the low socio-economic context, to improve outcomes for vulnerable students. Using a case study approach, two principals and their schools are holistically described using a theoretical framework grounded in complexity theory. Both the approach and theory uniquely explores principal practice as an individual and collective phenomenon, as a living, evolving network of self-organisation where both parts and wholes are significant, and as practice grounded in context. The theory also offers a unique way to arrange and interpret findings. The study findings identified local notions of educational success as a way of understanding the trajectory of the ecosystem whole. The broad principal leadership patterns of practice included: building the network; integrating multiple perspectives; facilitating cohesion; and confronting and addressing injustices. These patterns evidenced a tight coupling between theory and practice. In the spirit of complexity theory, principal leadership practice is additionally explained as a sum greater than its parts. The capability of the network is described through concepts of stability and flow and shows, that no matter how competent the principal leader and their network, the contribution to education reform grapples to be transformational. Recommendations are made for principal leaders, professional development providers, as well as the Ministry of Education and policymakers that offer hope and contribute to disrupting the current trajectory, so transformational change is more likely. Areas of instability and important leverage points, include professional learning and development, community-school connections and resourcing.</p>

Bringing life to leadership: The emergence of principal leadership practice for educational success in low socio-economic schools

<p>The persistent educational achievement gap and historically haphazard nature of progress for students in impoverished contexts in New Zealand primary schools is a deep-seated problem needing urgent attention. This multifaceted and interconnected problem has no distinct origin and no clear solution and is continuing to harm individual and collective futures. This thesis explores principal leadership practice and how it intersects with the low socio-economic context, to improve outcomes for vulnerable students. Using a case study approach, two principals and their schools are holistically described using a theoretical framework grounded in complexity theory. Both the approach and theory uniquely explores principal practice as an individual and collective phenomenon, as a living, evolving network of self-organisation where both parts and wholes are significant, and as practice grounded in context. The theory also offers a unique way to arrange and interpret findings. The study findings identified local notions of educational success as a way of understanding the trajectory of the ecosystem whole. The broad principal leadership patterns of practice included: building the network; integrating multiple perspectives; facilitating cohesion; and confronting and addressing injustices. These patterns evidenced a tight coupling between theory and practice. In the spirit of complexity theory, principal leadership practice is additionally explained as a sum greater than its parts. The capability of the network is described through concepts of stability and flow and shows, that no matter how competent the principal leader and their network, the contribution to education reform grapples to be transformational. Recommendations are made for principal leaders, professional development providers, as well as the Ministry of Education and policymakers that offer hope and contribute to disrupting the current trajectory, so transformational change is more likely. Areas of instability and important leverage points, include professional learning and development, community-school connections and resourcing.</p>

Identification of flux trade-offs in metabolic networks

Trade-offs are inherent to biochemical networks governing diverse cellular functions, from gene expression to metabolism. Yet, trade-offs between fluxes of biochemical reactions in a metabolic network have not been formally studied. Here, we introduce the concept of absolute flux trade-offs and devise a constraint-based approach, termed FluTO, to identify and enumerate flux trade-offs in a given genome-scale metabolic network. By employing the metabolic networks of Escherichia coli and Saccharomyces cerevisiae, we demonstrate that the flux trade-offs are specific to carbon sources provided but that reactions involved in the cofactor and prosthetic group biosynthesis are present in trade-offs across all carbon sources supporting growth. We also show that absolute flux trade-offs depend on the biomass reaction used to model the growth of Arabidopsis thaliana under different carbon and nitrogen conditions. The identified flux trade-offs reflect the tight coupling between nitrogen, carbon, and sulphur metabolisms in leaves of C3 plants. Altogether, FluTO provides the means to explore the space of alternative metabolic routes reflecting the constraints imposed by inherent flux trade-offs in large-scale metabolic networks.