922017 research outputs found
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Perspective - Formate as a key intermediate in CCU
No full textReplacing fossil feedstocks for chemicals and polymers in the chemical industry is a key step towards a future circular society. Making use of CO2 as a starting material in Carbon Capture and Utilization (CCU) or Carbon Capture and Storage (CCS) processes presents a great opportunity. Unfortunately, converting CO2 is not easy - due to its stability and inherently low reactivity either high energy inputs or nifty catalytic systems are required for its conversion. An electrochemical cell using a gas-diffusion electrode to convert CO2 into formate is such a promising system. But making formate alone does not allow us to substitute many fossil carbon-fed processes. Oxalic acid on the other hand is a potential new platform chemical for material production as useful monomers such as glycolic acid can be derived from it. Fortunately, formate can be converted into oxalate (and subsequently oxalic acid) by coupling two formates in a formate to oxalate coupling reaction (FOCR). The FOCR is a reaction that has been studied for more than 175 years and has seen widespread industrial use in the past. In this work, we critically discuss the history of the FOCR, present the most recent advances and draw a perspective for its future. We provide an overview of all (side)products obtained in FOCR and examine the various reaction parameters and their ability to influence the reaction. To understand the reaction better and improve it in the future, we critically discuss the many mechanisms proposed for the various catalytic systems in the FOCR. At last, we explore the potential to introduce new catalytic and solvent systems or co-reactants to the FOCR to improve reaction performance and broaden the range of products from CO2 derived formate
Author response to letter regarding 'Skin and respiratory ill-health attributed to occupational face mask use'
No full textCorneal densitometry to assess the corneal cysteine deposits in patients with cystinosis
No full textAims: To assess the suitability of corneal densitometry measurements obtained with Scheimpflug imaging in estimating the corneal changes caused by cystine deposits in the cornea in patients with cystinosis.Methods: Scheimpflug imaging (Pentacam) was performed for 14 cystinosis patients and 16 age matched controls. Pentacam data was used for analysis of the corneal densitometry at different zones in the cornea for cystinosis patients and controls. The densitometry measurements were compared to the corneal crystal scores obtained from the slitlamp images for patients with cystinosis.Results: There was no statistically significant difference in keratometry measurements between the two groups (p>0.05). Corneal thickness was found to be significantly higher in the control group when compared to cystinosisgroup (p=0.0004). The Mean corneal densitometry was significantly higher in cystinosis patients when compared to the control group at most of the corneal layers and zones. The corneal densitometry readings for the right and left eyes showed moderate positive correlation with the corneal crystal score with a ceiling effect being reached at the maximum corneal crystal score of 3.Conclusion: Corneal densitometry obtained through Pentacam can be used as an objective estimate of the level of cystine crystals present in patients with cystinosis. The clinical estimate of corneal crystal score, although effective at low levels of crystal deposition, does not allow for accurate estimates of change when the level of crystal deposition is high leading to limited utility when assessing treatment effects. Hence, densitometry measurements can potentially be used to assess treatment efficacy of cystinosis treatments in clinical settings
Caries risk assessment related knowledge, attitude, and behaviors among Chinese dentists: A crosssectional survey
No full textObjectivesTo investigate caries risk assessment (CRA)-related knowledge, attitudes, and practices among dentists in China, to describe their subjective ratings of the significance of specific caries risk factors and to identify factors associated with the level of knowledge, attitudes, and use of CRA in routine clinical practice.Materials and MethodsA cross-sectional anonymous online questionnaire survey was performed. The questionnaire was distributed via WeChat (Tencent, Shenzhen, China) to practicing dentists between November 25 and December 25, 2021. For participant recruitment, we employed purposive and snowball sampling techniques. Data were collected using a specialized web-based survey tool (www.wjx.cn) and analyzed with descriptive statistics and regression analyses.ResultsA total of 826 valid questionnaires were collected. Only 292 (35.4%) respondents used CRA in routine practice, among whom a majority (243, 83.2%) did not use a specific CRA tool. The routine use of CRA was associated with the type of practicing office, attendance of caries-related lectures, the habit of reading caries-related literature, geographic location and the total knowledge score. The mean total knowledge score was 3.13 (score range: 0 to 6). Knowledge levels were related to several sociodemographic characteristics, including geographic location, the type of practicing office, attendance of caries-related lectures and the habit of reading caries-related literature. The risk factor deemed most important was “current oral hygiene”.ConclusionsCaries risk assessment has not widely entered clinical practice in China. The level of CRA-related knowledge among dentists was generally suboptimal
Grassland degradation-induced declines in soil fungal complexity reduce fungal community stability and ecosystem multifunctionality
No full textSoil microorganisms are major regulators of ecosystem functioning and are under threat from human-induced disturbances. Among these threats is grassland degradation, which is estimated to affect 49% of the grassland area worldwide, threatening biodiversity and ecosystem functioning. Yet, we currently lack an understanding of how grassland degradation influences belowground microbial communities, their stability, and functioning, and how effective restoration efforts are for the recovery of these important belowground properties. Here, we assessed soil fungal network complexity and a suite of ecosystem functions along a well-characterised gradient of grassland degradation and restoration on the Qinghai-Tibetan Plateau, and conducted an accompanying microcosm experiment designed to test the effects of complexity on stability in soil fungal communities. We found that with increasing levels of grassland degradation, soil fungal communities became less complex and were less compositionally stable when confronted with drought under laboratory conditions. Moreover, this degradation-induced reduction in fungal community complexity was associated with lower ecosystem multifunctionality. However, fungal communities and ecosystem multifunctionality failed to recover even after ten years of grassland restoration. Our results indicate that degradation-induced simplification of fungal communities can potentially impair fungal community stability and ecosystem multifunctionality, thereby highlighting the need to protect and restore healthy grasslands with complex belowground microbial communities
Valorization of Lignocellulose by Producing Polyhydroxyalkanoates Under Circular Bioeconomy Premises: Facts and Challenges
No full textIn light of the current concerns about environmental issues caused by the excessive use of fossil resources, more emphasis has been paid to the transition to a sustainable and circular economy. Bioplastics as eco-friendly products originating from biomass wastes have gained much attention to solve the problem of plastic pollution. Among them, polyhydroxyalkanoates (PHAs) are microbial polyesters produced using various feedstocks—renewable or recycled waste materials—contributing to a more sustainable commercial plastic life cycle by being a part of a circular bioeconomy. However, the scale-up of the PHAs process cost-effectively and sustainably remains challenging for large-scale industrial applications. This perspective article provides a comprehensive overview of the current insights into lignocellulosic biomass's role in achieving a circular bioeconomy. Emerging greener biomass conversion technologies are discussed to characterize energy demand, cost, and sustainability within biorefineries PHAs production. In addition, recent advances in synthetic biology and fermentation processes for PHAs production are discussed. Technological challenges, i.e., bioreactor set-up, downstream operation, and inconsistent properties to improve the sustainable production of PHAs and to help transfer this technology to real-world application, are also addressed
Vortex collision against static and spinning round cylinders: A lattice Boltzmann study
No full textIn this paper, the flow physics generated by the collision of a vortex dipole that moves against a spinning round cylinder is investigated numerically. Fluid dynamics is predicted by a combined central-moments-based lattice Boltzmann-immersed boundary method. First, the model is validated against well established consolidated benchmark problems, showing very high accuracy properties. Then, results from a comprehensive numerical campaign are presented. A wide set of values of the Reynolds number (Re) is investigated, ranging from 10 to 1000. The cylinder is forced to spin around its centre with different angular velocities, which are obtained by varying the spinning number(Sp) between 0 (corresponding to the static case) and 0.75. The generation of secondary vortices as a consequence of the impact is elucidated and linked to the time evolution of the kinetic energy, enstrophy and hydrodynamic forces. Interestingly, we find that the flow physics changes drastically when Re ≥ 250, independently from the value of Sp. Through a closer look at the vorticity field, we find that the impact creates two primary-secondary structures and a second impingement takes place when Re ≥ 250. Interestingly, the normalised drag force (𝐶𝑑) is found to constantly fluctuates around a mean value. Oscillations are due to the vorticity created by the rotation of the cylinder and are moreemphasised as Sp grows. Specifically, 𝐶𝑑 can achieve marked negative values as a consequence of thevelocity field created by the cylinder during its rotation.<br/
ESBMC-Solidity: An SMT-Based Model Checker for Solidity Smart Contracts
No full textSmart contracts written in Solidity are programs used in blockchain networks, such as Etherium, for performing transactions. However, as with any piece of software, they are prone to errors and may present vulnerabilities, which malicious attackers could then use. This paper proposes a solidity frontend for the efficient SMT-based context-bounded model checker (ESBMC), named ESBMC-Solidity, which provides a way of verifying such contracts with its framework. A benchmark suite with vulnerable smart contracts was also developed for evaluation and comparison with other verification tools. The experiments performed here showed that ESBMC-Solidity detected all vulnerabilities, was the fastest tool, and provided a counterexample for each benchmark. A demonstration is available at https://youtu.be/3UH8_1QAVN0
