Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Approximability of Minimum AND-Circuits

Given a set of monomials, the Minimum AND-Circuit problem asks for a circuit that computes these monomials using AND-gates of fan-in two and being of minimum size. We prove that the problem is not polynomial time approximable within a factor of less than 1.0051 unless P = NP, even if the monomials are restricted to be of degree at most three. For the latter case, we devise several efficient approximation algorithms, yielding an approximation ratio of 1.278. For the general problem, we achieve an approximation ratio of d − 3/2, where d is the degree of the largest monomial. In addition, we prove that the problem is fixed parameter tractable with the number of monomials as parameter. Finally, we reveal connections between the Minimum AND-Circuit problem and several problems from different areas

Abstract congruence closure and specializations

We use the uniform framework of abstract congruence closure to study the congruence closure algorithms described by Nelson and Oppen [9], Downey, Sethi and Tarjan [7] and Shostak [11]. The descriptions thus obtained abstracts from certain implementation details while still allowing for comparison between these different algorithms. Experimental results are presented to illustrate the relative efficiency and explain differences in performance of these three algorithms. The transition rules for computation of abstract congruence closure are obtained from rules for standard completion enhanced with an extension rule that enlarges a given signature by new constants

Biochar Application To A Colombian Savanna Oxisol: Fate And Effect On Soil Fertility, Crop Production, Nutrient Leaching And Soil Hydrology Volume I

Biochar, or biomass-derived black carbon (BC), is being considered as a tool for improving soil fertility, crop yields and for C sequestration in the soil. Biochar has been widely shown to be beneficial in agriculture, but the mechanisms underlying such effects are often not clearly demonstrated. Similarly, the fate of biochar after deliberate soil application has rarely been studied in the field. Two field experiments were undertaken on an Oxisol of the oriental savanna region of Colombia: one to study the effect of biochar application on soil fertility, crop yields, nutrient leaching and soil hydrology, and another to observe the fate of soil-applied BC as well as nonBC through soil respiration, leaching and changes in soil C stocks. The application of 20 t ha-1 of biochar resulted in maize yield increases of 28, 30 and 140% in the second, third and fourth year after biochar application. These yield increases were associated with greater nutrient uptake by the crop where biochar had been applied. Leaching below the rooting zone was reduced by 17% for P, 19% for Sr, 8% for NO3-N, 23% for Ca, 28% for Mg, and 36% for K, over two years, with biochar application. Simultaneously, soil availability of Ca and Mg was also greater, although these were limiting for maize production. The retention of nutrients by biochar and greater pH thus resulted in reduced leaching and greater crop uptake, with the greatest effect observed with Ca and Mg. In this heavy clay soil, biochar application did not modify soil hydrological parameters. In a separate experiment using stable isotope techniques to attribute sample C to its source, the mean residence time of biochar applied at a rate of 23.2 t ha-1 was found to be ~600 years at 26 ?C. Losses by respiration amounted to 2.2% of BC applied, while losses by leaching amounted to less than 1%. Small amounts of BC migrated downward below the application depth. Black C application caused a 189% increase in above ground biomass, which quantitatively explains greater amounts of non-BC also being respired, leached and found as a soil C stock