Search

This study investigates the effects of CO2 curing on oriented cement-bonded boards. The boards comprised 35% and 45% (by mass) of strand-type particles of Eucalyptus spp. (8 × 2 × 0.1 cm) and 65% and 55% (by mass) of early high-strength Portland cement. To fabricate the boards, three layers of strands were arranged perpendicular to the previous layer, aiming for a target density of 1250 kg/m3, and the dimensions of the boards were 40 × 40 × 1 cm. The oriented cement-bonded boards underwent three different curing conditions: control, CO2 curing for 6 h, and 12 h, followed by curing in a saturated environment until the 28th day. The results indicated that CO2 curing increased the CaCO3 content in the boards, particularly when the curing period was longer (12 h). The physical and mechanical performance of the CO2-cured boards surpassed that of the control boards, with the modulus of rupture (MOR) increasing by 80% (6 h) and 84% (12 h) compared to the control. Scanning electron microscope investigations revealed that CO2 curing produced a denser matrix, leading to an improved bond between the strands and the matrix, resulting in enhanced technical performance. Based on these findings, this study suggests that CO2 curing can enhance the physical and mechanical properties of oriented cement-bonded boards, and a longer curing time (12 h) yielded superior performance. [ABSTRACT FROM AUTHOR]

The decarbonization of the economy, for which the contribution of power systems is significant, is a growing trend in Europe and in the world. In order to achieve the Paris Agreement's ambitious environmental goals, a substantial increase in the contribution of renewable sources to the energy generation mix is required. This trend brings about relevant challenges as the integration of this type of sources increases, namely in terms of the distribution system operation. In this paper, the challenges foreseen for future power systems are identified and the most effective approaches to deal with them are reviewed. The strategies include the development of Smart Grid technologies (meters, sensors, and actuators) coupled with computational intelligence that act as new sources of data, as well as the connection of distributed energy resources to distribution grids, encompassing the deployment of distributed generation and storage systems and the dissemination of electric vehicles. The impact of these changes in the distribution system as a whole is evaluated from a technical and environmental perspective. In addition, a review of management and control architectures designed for distribution systems is conducted. This article is categorized under:Energy Infrastructure > Systems and InfrastructureEnergy Infrastructure > Economics and Policy [ABSTRACT FROM AUTHOR]

Electrical distribution system operators (DSOs) are facing an increasing number of challenges, largely as a result of the growing integration of distributed energy resources (DERs), such as photovoltaic (PV) and wind power. Amid global climate change and other energy-related concerns, the transformation of electrical distribution systems (EDSs) will most likely go ahead by modernizing distribution grids so that more DERs can be accommodated. Therefore, new operational strategies that aim to increase the flexibility of EDSs must be thought of and developed. This action is indispensable so that EDSs can seamlessly accommodate large amounts of intermittent renewable power. One plausible strategy that is worth considering is operating distribution systems in a meshed topology. The aim of this work is, therefore, related to the prospects of gradually adopting such a strategy. The analysis includes the additional level of flexibility that can be provided by operating distribution grids in a meshed manner, and the utilization level of variable renewable power. The distribution operational problem is formulated as a mixed integer linear programming approach in a stochastic framework. Numerical results reveal the multi-faceted benefits of operating distribution grids in a meshed manner. Such an operation scheme adds considerable flexibility to the system and leads to a more efficient utilization of variable renewable energy source (RES)-based distributed generation. [ABSTRACT FROM AUTHOR]

Background. Malnutrition is a common feature in chronic renal failure and adversely affects patient morbidity and mortality. We here investigate the effects of nutritional status on the l-arginine–nitric oxide signaling pathway and platelet function in chronic renal failure patients on regular hemodialysis. Methods. Platelet aggregation was correlated with plasma amino acid profiles, l-arginine transport, and nitric oxide synthase (NOS) activity determined by conversion of l-[3H]-arginine to l-[3H]-citrulline and accumulation of intracellular cyclic guanosine monophospate (cGMP) in platelets from malnourished and well-nourished chronic renal failure patients on regular hemodialysis ( N= 78). Results. Transport of l-arginine (pmol/109cells/min) via y+ L system was increased in well-nourished (104 ± 15) compared to controls (57 ± 11) or malnourished chronic renal failure patients (55 ± 13). Basal NOS activity (pmol/108cells) was enhanced in well-nourished chronic renal failure patients (0.51 ± 0.01) compared to controls (0.18 ± 0.01) or malnourished chronic renal failure patients (0.08 ± 0.03). In addition, basal cGMP levels are elevated in platelets from well-nourished chronic renal failure compared to malnourished uremic patients. Platelet aggregation induced by collagen is impaired in well-nourished chronic renal failure patients compared to malnourished patients and controls. Plasma l-arginine levels are reduced in chronic renal failure patients and even lower in malnourished patients. Conclusion. Our findings provide the first evidence that l-arginine transport via the high affinity system y+ L and nitric oxide synthesis are only stimulated in platelets from well-nourished chronic renal failure patients, leading to impaired platelet aggregation. The absence of this adaptive response in the l-arginine–nitric oxide pathway in platelets from malnourished chronic renal failure patients may account for the enhanced occurrence of thrombotic events in these patients. [ABSTRACT FROM AUTHOR]