Biosourced, highly porous, carbon xerogel microspherest

The first tannin-based carbon xerogel microspheres were prepared and characterised. The materials were synthesised by inverse emulsion polymerisation in sunflower oil, based on the same formulation but using two main independent variables: stirring speed and surfactant amount. The resultant sol–gel spheres were then washed, dried in air, and pyrolysed. The effect of stirring speed and surfactant amount on carbon microsphere size distribution and porous texture was investigated in detail. Depending on the cases, ultramicroporous carbon microspheres with extremely narrow pore size distributions centred at 0.4–0.5 nm, zero mesoporosity, negligible macroporosity and median diameters close to 40 mm, could be obtained. These characteristics are typical of expensive commercial carbon molecular sieves, whereas the present materials were prepared with cheap and renewable precursors using a very simple method

Elective Cancer Surgery in COVID-19-Free Surgical Pathways During the SARS-CoV-2 Pandemic: An International, Multicenter, Comparative Cohort Study.

PURPOSE: As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19-free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS: This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19-free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS: Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19-free surgical pathways. Patients who underwent surgery within COVID-19-free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19-free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score-matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19-free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION: Within available resources, dedicated COVID-19-free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks

Elective cancer surgery in COVID-19-free surgical pathways during the SARS-CoV-2 pandemic: An international, multicenter, comparative cohort study

PURPOSE As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19–free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19–free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19–free surgical pathways. Patients who underwent surgery within COVID-19–free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19–free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score–matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19–free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION Within available resources, dedicated COVID-19–free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks

Mechanical properties of heat-treated organic foams

International audienceThe mechanical properties of a class of cellular material were measured. The composition of the material was progressively modified, while its pore structure was kept unchanged. Rigid foam, prepared from a thermoset resin, was gradually converted into reticulated vitreous carbon foam by pyrolysis at increasingly higher heat-treatment temperatures (HHT). The corresponding changes in the Young's modulus Y and the compressive strength sigma of the materials were measured over a wide range of porosities. The materials exhibit a percolation behavior with a zero percolation threshold. At very low densities the Young's modulus and the compressive strength appear to follow the power laws predicted by percolation theory near the percolation threshold. But, whereas the exponent tau associated with the power-law behavior of Y appears to vary significantly with the material's density and the HHT, the exponent associated with sigma does not change much. The possible cause of the apparent and surprising nonuniversality of tau is discussed in detail, in the light of the fact that only the materials' composition varies, not the structure of their pore space that could have caused the nonuniversality

Flammability assessment of tannin-based cellular materials

Fire retardance of highly porous tannin-based rigid foams formerly suggested as new, ecological, insulation materials, has been investigated in detail. For that purpose, one standard composition was tested using samples having five different bulk densities. Besides, for one given median density, three foams whose formulation has been modified by incorporation of boric and/or phosphoric acid were investigated as well. The parameters measured were the time to ignition, the critical heat flux for ignition and the heat release rate. All led to the conclusion that such foams present outstanding fire retardance. The tests were done blindly to avoid any interpretation bias. No significant differences could be observed when materials of standard composition but having different bulk densities were tested, or when testing modified foams. While modified foams showed slight differences, it was not possible to correlate these differences to higher fire performance

Acoustic properties of cellular vitreous carbon foams

International audienceThe present work deals with acoustic properties of highly porous rigid foams derived from flavonoid tannins. Such cellular solids derived from renewable resources were investigated before and after pyrolysis, the latter leading to cellular, vitreous, carbon foams. It is demonstrated here that these lightweight materials have a high air flow resistivity, which depends on the density of the foam. Vitreous carbon foams, especially, have rather low performances for sound absorption. Using a simple model, their sound absorption coefficients were predicted and found to be in very good agreement with measurements in all the investigated frequency range, 50-4300 Hz. However, we have shown that carbon foams are very appropriate materials to apply the double porosity concept since they can produce a high permeability contrast. This paper shows how vitreous carbon foams can become excellent sound-absorbing materials in a targeted frequency range by using the double porosity concept

Effect of sawdust as porosity agent on final properties of geopolymers

Abstract The geopolymers synthesis are based on geopolymerization, a sequence of reactions processed in an alkaline medium through oligomers providing a three-dimensional molecular structure. In this work, the polycondensation of metakaolin was performed with alkaline activators (NaOH and sodium silicate), wood sawdust and other additives. Two different compositions were evaluated after and before sintering at a high temperature (850 °C). The effect of sawdust addition and the thermal treatment of geopolymers were evaluated by scanning electronic microscopy, X-ray diffraction, mechanical properties, apparent density and porosity by different characterization techniques to guide of development of high porous and low-density materials for thermal and noise control application on building/home construction engineering applications

Biosourced, highly porous, carbon xerogel microspherest

The first tannin-based carbon xerogel microspheres were prepared and characterised. The materials were synthesised by inverse emulsion polymerisation in sunflower oil, based on the same formulation but using two main independent variables: stirring speed and surfactant amount. The resultant sol–gel spheres were then washed, dried in air, and pyrolysed. The effect of stirring speed and surfactant amount on carbon microsphere size distribution and porous texture was investigated in detail. Depending on the cases, ultramicroporous carbon microspheres with extremely narrow pore size distributions centred at 0.4–0.5 nm, zero mesoporosity, negligible macroporosity and median diameters close to 40 mm, could be obtained. These characteristics are typical of expensive commercial carbon molecular sieves, whereas the present materials were prepared with cheap and renewable precursors using a very simple method

Lignin-phenol-formaldehyde aerogels and cryogels

International audienceHighly porous organic aerogels have been prepared for the first time from a mixed lignin-phenol-form-aldehyde (LPF) resin. Six different P/L weight ratios and two (L + P)/F weight ratios have been tested, leading most of times to nice and reproducible hydrogels which were subsequently either supercritically of freeze-dried. A broad family of aerogels and cryogels, respectively, was thus obtained. These materials were thoroughly investigated in terms of porous structure, based on pycnometry, adsorption and electron microscopy studies. The pore-size distributions were found to depend strongly on the initial composition, but not on the method of drying. The thermal conductivity of aerogels and cryogels has been measured and found to be minimal in materials combining both high mesopore volume and ideal pore sizes