On Myosin II dynamics in the presence of external loads

We address the controversial hot question concerning the validity of the loose coupling versus the lever-arm theories in the actomyosin dynamics by re-interpreting and extending the phenomenological washboard potential model proposed by some of us in a previous paper. In this new model a Brownian motion harnessing thermal energy is assumed to co-exist with the deterministic swing of the lever-arm, to yield an excellent fit of the set of data obtained by some of us on the sliding of Myosin II heads on immobilized actin filaments under various load conditions. Our theoretical arguments are complemented by accurate numerical simulations, and the robustness of the model is tested via different choices of parameters and potential profiles.Comment: 6 figures, 8 tables, to appear on Biosystem

Exploring the global scientific literature on urban metabolism

Urban ecosystems can be conceptualized like living organisms supported by material and energy flows that allow the generation of ecosystem structures and functions and the production of goods and services. Urban metabolism accounts for the flows of materials, energy, resources, food, and people in cities, providing a framework for the study of the interactions between natural and socio-economic systems. In this paper, the global scientific literature on urban metabolism was explored to identify knowledge gaps and emerging research areas over the last decades. A bibliometric network analysis was implemented to generate maps based on network data of scientific publications displaying relationships among scientific journals, researchers, countries, and keywords. The total number of publications on urban metabolism from 1990 to 2019 resulted in 498 documents. USA and China resulted the first countries publishing on urban metabolism while among the journals, the Journal of Industrial Ecology and Journal of Cleaner Production resulted the first in the ranking. The co-occurrence network map of keywords showed that, over the last decade, the main focus of research on urban metabolism has shifted from environmental issues to environmental accounting and socio-economic aspects. Considering the importance of urban systems for the achievement of local and global sustainability goals, it is likely that the scientific literature on urban metabolism will continue growing over the next years. Being cities characterized by complex relationships between natural and socio-economic systems, it is desirable that future studies will explore the multidimensional features of urban metabolism through multi-criteria assessment frameworks

Model-based aerodynamic-angle attitude control of an atmospheric entry capsule

The paper describes the attitude control system of a low lift-to-drag biconic atmospheric entry capsule based on the Embedded Model Control methodology. The control structure derives from the development of the attitude dynamics and kinematics written in terms of aerodynamic angles, instead of Euler/quaternion kinematics. A detailed development of the simplified set of equations linking the torques generated by the reaction control system with the time evolution of the aerodynamic angles is provided. The simplified set of equations becomes the core of the control algorithm. The bank angle dynamics is shown to be fourthorder and forced by yaw and roll torques. A dynamic dispatching technique is proposed for converting fourth-order dynamics into a pair of second order systems. Nonlinear dynamic inversion and active disturbance rejection are employed to handle gyroscopic torques, parametric errors and to compensate for angular variation of translational velocity. A bank reversal logic is designed to reduce the effect of bank reversals on the translational motion. The performance of the attitude control algorithm has been tested on a high fidelity simulator and relevant results are presented

Assessing natural capital value in the network of Italian marine protected areas: A comparative approach

Marine and coastal natural capital stocks provide a bundle of ecosystem services vital for human well-being. The biophysical and economic assessment of the value of natural capital stocks is much needed for achieving nature conservation goals, while ensuring the sustainable exploitation of marine resources. Marine Protected Areas (MPAs) are increasingly being established worldwide to protect and conserve natural capital stocks from anthropogenic threats. In this study, a biophysical and trophodynamic model based on the emergy accounting method was used to assess the value of natural capital for a set of Italian MPAs. In particular, the assessment focused on four main macro-habitats: 1) sciaphilic hard bottom (SHB), 2) photophilic hard bottom (PHB), 3) soft bottom (SB), and 4) Posidonia oceanica seagrass beds (PSB). The emergy method allowed the assessment of natural capital stocks in terms of direct and indirect solar energy flows invested by nature for their generation. The SHB habitat showed the highest emergy density value in most of the investigated MPAs, confirming the high convergence of input resource flows in the formation of this habitat. When considering extensive indicators, the contribution of the PSB habitat to the total value of natural capital was higher than other habitats in most MPAs. In addition, to facilitate the understanding of the results in socio-economic contexts, the biophysical values of natural capital stocks were converted into monetary units. The total value of natural capital in the investigated MPAs ranged from about 8 to 1163 M€. In conclusion, assessing the value of natural capital can support local managers and policy makers in charge for achieving nature conservation targets while ensuring the sustainable exploitation of natural resources

Wintertime transport processes in the Gulf of Naples investigated by HF radar measurements of surface currents

Transport processes play a fundamental role in regulating the water renewal in coastal systems. The Gulf of Naples (Southern Tyrrhenian Sea) is a highly urbanised area, receiving pollutant discharges and terrestrial inputs that may reside inside the basin. For this reason, understanding the processes governing coast-offshore transport is of paramount importance for the welfare of the ecosystem and the sustainable exploitation of environmental resources. In this work, we analyse the wind-driven transport over lags of three days in winter reconstructing the basin scale surface circulation by means of High-Frequency radars and evaluating its dependence on wind circulation. Simulations of particle exchange between a coastal and an offshore area have been carried out, outlining the strong relationship between particle fate and circulation structures. Results are interpreted in terms of residence times and possible aggregative areas in the Gulf of Naples

Trends and evolution in the concept of marine ecosystem services: An overview

The biotic and abiotic assets of the marine environment form the “marine natural capital” embedded in the global ocean. Marine natural capital provides the flow of “marine ecosystem services” that are directly used or enjoyed by people providing benefits to human well-being. They include provisioning services (e.g., food), regulation and maintenance services (e.g., carbon sequestration and storage, and coastal protection), and cultural services (e.g., tourism and recreational benefits). In recent decades, human activities have increased the pressures on marine ecosystems, often leading to ecosystem degradation and biodiversity loss and, in turn, affecting their ability to provide benefits to humans. Therefore, effective management strategies are crucial to the conservation of healthy and diverse marine ecosystems and to ensuring their long-term generation of goods and services. Biophysical, economic, and sociocultural assessments of marine ecosystem services are much needed to convey the importance of natural resources to managers and policy makers supporting the development and implementation of policies oriented for the sustainable management of marine resources. In addition, the accounting of marine ecosystem service values can be usefully complemented by their mapping to enable the identification of priority areas and management strategies and to facilitate science–policy dialogue. Given this premise, this study aims to review trends and evolution in the concept of marine ecosystem services. In particular, the global scientific literature on marine ecosystem services is explored by focusing on the following main aspects: the definition and classification of marine ecosystem services; their loss due to anthropogenic pressures, alternative assessment, and mapping approaches; and the inclusion of marine ecosystem services into policy and decision-making processes

Recovery of methamphetamine associated cardiomyopathy predicted by late gadolinium enhanced cardiovascular magnetic resonance

Methamphetamine is known to cause a cardiomyopathy which may be reversible with appropriate medical therapy and cessation of use. Late gadolinium enhancement cardiovascular magnetic resonance (CMR) has been shown to identify fibrosis in ischemic and non-ischemic cardiomyopathies. We present a case of severe methamphetamine-associated cardiomyopathy in which cardiac function recovered after 6 months. Evaluation by CMR using late gadolinium enhancement was notable for an absence of enhancement, suggesting an absence of irreversible myocyte injury and a good prognosis. CMR may be useful to predict recovery in toxin-associated non-ischemic cardiomyopathies

ORBIT AND FORMATION CONTROL FOR LOW-EARTH-ORBIT GRAVIMETRY DRAG-FREE SATELLITES

The paper outlines orbit and formation control of a long-distance (>100 km) two-satellite formation for the Earth gravity monitoring. Modeling and control design follows the Embedded Model Control methodology. We distinguishe be-tween orbit and formation control: orbit control applies to a single satellite and performs altitude control. Formation control is formulated as a control capable of altitude and distance control at the same time. The satellites being placed in a low Earth orbit, orbit and formation control employ the measurements of a global navigation system. Formation control is imposed by long-distance laser interferometry, which is the key instrument together with GOCE-class accelerometers for gravity measurement. Orbit and formation control are low-frequency control systems in charge of cancelling the bias and drift of the residual drag-free accelerations. Drag-free control is the core of orbit/formation control since it makes the formation to fly drag-free only subject to gravity. Drag-free is demanded by the low-Earth orbit and by the accelerometer systematic errors. Drag-free control being required to have a bandwidth close to 1 Hz, is designed as the inner loop of the formation control, but formation control must not destroy drag-free performance, which is obtained by restricting formation control to be effective only below orbital frequency. A control of this kind appears to be original: an appropriate orbit and formation dynamics is derived, discussed and compared with the classical Hill-Clohessy-Wiltshire equations. The derived dynamics is the first step to build the embedded model which is sampled at the orbit rate. Embedded model derivation is explained only for the orbit control, and briefly mentioned for the formation control. Control design is explained in some details, pointing out reference generation, state predictor, control law and main design steps. Simulated results are provided. Drag free results are compared to GOCE data