Despite its tendency to produce hypotension, propofol is used widely to induce general anesthesia and to facilitate endotracheal intubation in critically ill patients. Both dose reduction and routine co-administration of vasopressors have been used to offset this unfavorable hemodynamic effect in this subset of individuals. There are potential problems associated with each of these corrective measures, however, and criticism of other intravenous hypnotics used for this purpose—particularly etomidate—may be unwarranted. Choice of the appropriate pharmacology to induce anesthesia to assist with intubation should likely be based on individual clinical assessment, together with an understanding of the drug profile and realistic adverse effects.
Selective hydrogenative depolymerization of polyesters to diols is regarded as a promising strategy for plastics upcycling. However, many catalysts documented in literature still involve harsh reaction conditions, such as high temperature and high H2 pressure. In this work, we present a PN3-ruthenium complex catalyzed polyesters upcycling into various highly value-added diols under mild reaction conditions using H2 as a hydrogen source. It is worth noting that PLA depolymerizes into 1,2-propanediol under 1 MPa hydrogen pressure at ambient temperature within 2 h; the conditions are much milder than those of previous reports. Aromatic polyester PET degradation needs harsher reaction conditions (80 °C, 4 MPa, 3 h). The different reaction conditions enable direct separation of the degradation products of PLA and PET mixture via sequential depolymerization, as well as mixing them with polyolefins (PE, PP, PS). More strikingly, this catalyst is also effective for the catalytic hydrogenation of polyesters in the presence of ethanol to afford various diols, avoiding the use of harsh reaction conditions and an expensive autoclave.
A fishway can assist fish species in overcoming barriers to migration, which depends on the eco-hydraulic characteristics of the fishway. Based on the tail fish benefiting when at the rear of a school than when at the front, and taking into account most anadromous fish species being characterized by egg-shaped morphology, the turbulent characteristics of an egg-shaped orifice fishway were experimentally studied in a fishway flume, a comparison with a rectangular orifice fishway with the same aspect ratio was made. The results showed that the maximum longitudinal velocity for the egg-shaped orifice decays faster than that for the rectangular one, the longitudinal velocity profile exhibits two peak values, while the corresponding velocity distribution for the rectangular orifice only reveals one peak, peak values of turbulence intensity on the different horizontal plane of egg-shaped orifice occur in the orifice edges, the larger turbulence intensities still exists in the central besides the edges for the rectangular orifice, Reynolds stress reaches peak value at the orifice edges, Auto-correlation coefficient of longitudinal velocity within orifice region is of small amplitude and short period relative to the outside the orifice region, microscale eddies within the orifice region were larger than those outside, mean scale of eddy is of larger variation and shorter period, and develops outside the orifice region, frequency-spectrum of velocity fluctuation exhibits dominant frequency in the low-frequency domain.
Besides the coarse and medium grain size distribution, the matrix components play a central role in the performance of refractory castables. Practical experience shows that the particle size distribution (PSD) and the specific surface area (SSA) of the ceramic matrix significantly influence processing, setting, and sintering behaviour. However, there is a lack of systematic studies on how changes in PSD or SSA affect castable properties. This study aims to address this gap by varying ceramic matrices to create model refractory castables with different matrix surface areas. Three dispersing agents with different mechanisms (electrosteric and steric) were used at graded concentrations. Results show that the SSA of the ceramic matrix has a significant influence on the rheological behaviour of refractory castables. A low SSA leads to shear thickening behaviour, a (very) low relative yield stress, and a high slump‑flow. Castables with an intermediate SSA and a multimodal composition show Bingham behaviour with a moderate relative yield stress and low relative viscosity, whereas a high SSA leads to shear thinning behaviour with a (very) high relative yield stress, (very) high relative viscosity, and a low slump-flow. Measurements of the dynamic viscosity of matrix suspensions at very low shear rates correlate with the rheological behaviour of fully composed refractory castables. Regression analysis using the Herschel‑Bulkley model successfully captures the observed qualitative relationships.
Carbon conversion technologies that transform carbon dioxide (CO2) into high-value chemicals are pivotal for achieving sustainability. Among these, enzyme-mediated CO2 fixation has recently gained increasing attention as a more sustainable and environmentally friendly alternative to traditional chemical methods, which typically require harsh conditions and impose significant environmental costs. Recent advances in computer-aided techniques have greatly facilitated the mechanistic understanding of CO2-fixing enzymes and accelerated the development of enzyme-catalyzed carboxylation strategies. This review highlights recent progress in enzyme-mediated CO2 fixation by categorizing key enzymes into four classes based on their cofactor or metal ion requirements: cofactor-independent enzymes, metal-dependent enzymes, nicotinamide adenine dinucleotide phosphate (NAD(P)H)-dependent enzymes, and prenylated flavin mononucleotide (prFMN)-dependent enzymes. We outline the basic principles and applications of molecular dynamics (MD) simulations and quantum mechanical (QM) calculations, which serve as essential tools for investigating enzyme conformational dynamics and reaction mechanisms. Through representative case studies, we demonstrate how computational analyses uncover catalytic features that enhance CO2 conversion efficiency. These insights underscore the critical role of computer-aided approaches in guiding the rational design and optimization of biocatalysts, thereby advancing the application of enzyme-based systems for CO2 fixation.
